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  • American Institute of Physics (AIP)  (9,330)
  • Annual Reviews  (508)
  • Munksgaard International Publishers  (76)
  • 1990-1994  (9,914)
  • 1970-1974
  • 1955-1959
  • 1991  (9,914)
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Publisher
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  • 1990-1994  (9,914)
  • 1970-1974
  • 1955-1959
Year
  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The present paper is part of a comprehensive study of dental conditions and attitudes in a Swedish county population aged 45–69 years. A questionnaire was mailed to 3000 randomly-sampled individuals. The response rate was 79.4% Part of the questionnaire contained questions about subjective need for implant treatment. The subjects were informed of the clinical procedures as well as of the fees for implant treatment in the Swedish insurance system. The subjects wearing removable dentures were asked if. instead of their removable denture(s), they wanted dental implants if such treatment was possible. Of those wearing removable partial dentures, 23% answered “yes”. The corresponding figure for subjects totally edentulous in one jaw was 17%; for subjects totally edentulous in both jaws 8%percnt;. The individuals who had reported missing teeth not replaced were asked if they wanted their missing teeth replaced by dental implants if such treatment were possible. The % answering “yes” was 21%. The subjects with all teeth remaining were hypothetically asked what kind of treatment they wanted if they would lose 1 or 2 of their teeth. The answer “dental implant” was given by 51%. Thus, subjective need for dental implants tended to decrease with poorer dental conditions. The major reason for not wanting dental implants was satisfaction with present dental conditions. Cost for treatment had some importance. while environmental and psychological factors showed only very limited influence.
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  • 2
    ISSN: 1600-0501
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: This investigation is the result of a multicenter research project between the Catholic University of Leuven and the University of Madrid with the purpose of studying histometrically and ultrastructurally periimplant marginal tissue reactions in medium-term Brånemark implants. 12 patients were selected and distributed according to predefined clinical and radiological parameters into a periimplant infection group (A) and a non-periimplant infection group (B). Biopsies were taken from these patients and analyzed by means of microscopy (LM), histometry (HM) and transmision electron microscopy (TEM). With LM group A showed pathological features consistent with an advanced gingivitis lesion, while group B showed signs of healthy gingiva in the connective tissue and vauolae formation in the epithelium. With HM, group A showed significantly higher transmigration of inflammatory cells in the epithelium than group B. In the connective tissue, group A showed a higher % of inflammatory infiltrate with significantly higher numbers of plasma cells and mononuclear cells than group B. With TEM, group A showed an ultrastructural picture consistent with plaque-induced periodontitis, while group B showed a rather healthy connective tissue and vacuolae formation in the epithelium. These results suggest that supra-crestal marginal tissues around osseointegrated implants react to plaque bacteria similarly to periodontal tissues around teeth by chronic inflammation.
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  • 3
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Acute responses to 65 min exposures to environmental tobacco smoke (ETS) were tested in 24 healthy non-asthmatic nonsmokers and 16 asthmatic nonsmokers, using an environmental chamber. Each subject was exposed to air (sham), and machine-generated cigarette smoke containing 17 ppm and 31 ppm carbon monoxide (CO). Nonasthmatic subjects exercised intermittently (mean respiratory minute volume (V̊E) of 44 l/min during each of two 15–min exercise bouts); asthmatic subjects remained at rest. After completion of the exposure, subjects made a 0–5 rating of the severity of symptoms, as well as rating the overall severity of exposure on a 0–100 scale. Both symptoms and exposure severity rating were significantly related to CO concentrations. Ratings for a given ETS exposure tended to be higher for asthmatic than for nonasthmatic subjects. Overall exposure severity rating was significantly (p 〈 0.05) related to four symptom scores for the asthmatics and three for the nonasthmatic subjects. Symptoms common to both groups included unpleasant odour, and nasal discharge; shortness of breath was unique for nonasthmatics and eye irritation for asthmatk subjects. Although the nonasthmatic subjects were exercising intermittently, and thus received both a higher respiratory exposure (calculated from a CO-based index of ETS concentration, V̊E, and time) and biological exposure (calculated independently using a rebreathing estimate of the increment in carboxyhemoglobin level), the asthmatic subjects appeared to be more adversely affected by the ETS exposures in terms of their subjective responses.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Thermal comfort measurements were taken in 17 enterprises at 129 work sites in shops, stores and offices. The measurements included air temperature, air velocity, relative humidity and radiant temperature asymmetry according to ISO 7726 and ISO 7730 standards. The workers also answered a questionnaire dealing with thermal comfort. Predicted mean vote (PMV) and the percentages of workers complaining of draught (“percentage dissatisfied”, PD) were determined and compared with the workers' assessments of thermal conditions. The estimations of air temperature were always too low, and the estimated PMV indicated that the thermal environment was too warm. The calculated PMVs were usually lower than the estimated ones. Most of the workers complained of draught, even though, according to the PD index, fewer than 17% of the workers should have felt discomfort due to draught. The radiant temperature asymmetry was always small and did not explain complaints of draught on the basis of the reference value. Judged by the present reference values, and the measurement of the thermal environment, the workers overestimated the sensation of thermal discomfort.
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  • 5
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The purpose of this study was to evaluate whether asthmatic reactions and changes in tear film quality could be provoked by exposing subjects to emissions from building materials in climate chambers. Twenty asthmatics and 5 healthy controls were exposed to (1) gypsum board hung with waterborne painted wallpaper; (2) rubber floor covering; (3) nylon carpet with rubber mat; (4) particle board coated with acid-curing paint; and (5) no test materials in climate chambers for 6 h. Participants recorded symptoms by filling in questionnaires, and clinical data were evaluated by lung function measurements at intervals of 30 min to 1h, and external eye examinations before and after exposure (appearance of foam at eyelid, semi-quantitative measurements of precorneal superficial lipid layer, break-up time and epithelial damage). There was agreement between a trained panel's evaluation of perceived air quality and the participants' opinion of indoor air quality. No correlation was found between lung function measurements and exposure to the materials. However, for all materials, statistically significant changes in tear film quality were observed to varying degrees. Lipophilic Volatile Organic Compounds (VOCs) may destabilize the lipid multilayer of the tear fluid, and this mechanism is suggested to be at least partly responsible for eye irritation.
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  • 6
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The emission of volatile organic compounds (VOCs) from five different waterborne paints was measured in small climatic chambers under standard conditions over a one-year period. The aims of the study were to evaluate the time emission profiles and to develop methods for comparison of different paints. The paints were applied to tin-plated steel sheets. VOCs were sampled on Tenax TA and analysed by thermal desorption and gas chromatography. The chamber concentrations increased rapidly during the first few hours and then decreased as the emission rates dropped. A model expression including an exponentially decreasing emission rate of the paint film, the air exchange rate, and a normalization of the film thickness was fitted to the concentration versus time data. The time required to reach a given emission rate was estimated and found suitable for comparison of the emission of VOCs from the paints. It was found that data sampled within three weeks or less may be sufficient to predict the emission of VOCs up to one year. Reduction of long-term emissions may be achieved most efficiently by (1) substituting a more -volatile VOC whose emission is controlled by evaporation for a less volatile VOC characterized by diffusion-controlled emission and (2) reducing the paint film thickness rather than reducing the initial VOC content of the paint.
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: A numerical model has been developed to investigate the contaminant removal and air freshness in a ventilated two-zone enclosure. The average contaminants and the distributions of air age in each zone under variable positions of door, supply and exhaust are compared. The correlation between the average contaminants and each of the main parameters, such as door location, supply and exhaust positions etc., are presented, and the average air ages in both zones are illustrated against door position. It is found that the average air age in the upstream zone is less affected by the door position than that in the downstream zone, and that the door position near the side-walls seems to give better air circulation. It is also concluded that the supply and door positions affect the concentration in the upstream zone significantly, while the exhaust location does not seem to influence the average concentration in either the upstream or the downstream zone.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The Zolder case was one of the six case studies on mould problems and sulface condensation, initiated within the International Energy Agency (IEA) Annex 14 on “Condensation and Energy”. This project, a joint research effort of Belgium, the Federal Republic of Germany, Italy, the Netherlands and the United Kingdom, was completed in March 1990.Complex relations bemeen mould, surface condensation, energy caservation and parameters such as the outdoor climate, the thermal quality of the building, the ventilation and the occupants' behaviour are explained, followed by an analysis of the Zolder-Lindeman case. This illustrates the extent to which mould may deteriorate the livability of a social housing estate. On three houses, different mitigation measures were evaluated before and after implementation: loft space insulation, inside insulation, double glazing outside insulation, natural ventilation, and demand controlled ventilation.The results for one of the three show that the severe mould problems resulted from the cambination of poor overall insulation quality and the impossibility of ventilating properly. A thermal retrofit, together with the installation of a natural ventilation system, proved to be successful.
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: This paper describes tests of thermal comfort and air distribution performance of two relatively new occupant-controlled localized ventilation (also called task ventilation) systems. The first is a raisd-floor distribution system providing air through grilles in the floor panels, and the second is a desk-mounted unit supplying conditioned air at desktop level. The tests were performed in a new controlled environment chamber (CEC) having unique capabilities for detailed studies of space conditioning and thermal comfort in office environments. Measurements were made in a mockup of a typical partitioned open-plan office, and the resulting temperature and air velocity distributions are reported for a variety of system- and locally controlled conditions. Comfort model predictions are presented to describe the degree of environmental control and range of occupant comfort levels produced in the workstations. The results are also compared to those produced by a conventional ceiling supply system.The tests investigated the effects of supply volume, supply location, supply vent orientation, supply/return temperature difference, heat load density, and workstation size and layout. Temperature differences in the range of 1–2.5°C were observed between adjacent workstations, and local air velocities in the vicinity of outlets could exceed 3 m/s. Such wide-ranging values could violate existing comfort standards (ASHRAE, 1981; ISO, 1984), if strictly interpreted. However since these systems put the local thermal conditions within the workstations under the direct control of their occupants, it is recommended that the standards grant exceptions to such systems.
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  • 11
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The main airflow and contaminant paths or the spatial distribution of the age of air (or contaminant) in a room are of great interest in estimating venrilation efficiency. A simple meusurement method is presented which consists of injecting one or more tracer gases at locations of interest and analysing the concentration at several other locations, carefully chosen for best accuracy.Response functions can be fitted to these measurements, which are the age of the tracers or of the air or the concentration of the tracers as a function of the location. The salient paths, such as the dead zones, are also determined from these functions.The paper presents the method, its application and validation in a well controlled test room.
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  • 12
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The influence of personal activity sources on exposure to indoor contaminants is defined and demonstrated using data from occupational and residential studies. The ratios of measurements from personal exposure monitors to those made by microenvironmental exposure monitors are summarized to be typically 3 to 10 for occupational settings and 1.2 to 3.3 for residential settings. The ratios are shown to be lognormally distributed, and dependent primarily on the proximity of the source to the receptors. Current models are reviewed for possible application to the prediction of indoor concentration gradients and future model development and validation studies are suggested.
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  • 13
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Two families of macroscopic adsorption models are formulated, based on fundamental principles of adsorption science and technology, that may be used for macroscopic (e.g., whole-building) contaminant dispersal analysis. The first family of adsorption models – the Equilibrium Adsorption (EA) Models – are based upon the simple requirement of adsorption equilibrium between adsorbent and room air. The second family – the Boundary Layer Diffusion Controlled Adsorption (BLDC) Models – add to the equilibrium requirement a boundary layer model for diffusion of the adsorbate from the room air to the adsorbent surface. Two members of each of these families are explicitly discussed, one based on the linear adsorption isotherm model and the other on the Langmuir isotherm model. The linear variants of each family are applied to model the adsorption dynamics of formaldehyde in gypsum wall board and compared to measured data. These applications and a more general consideration of the dynamic character of adsorption provided by these models indicate that simple physical adsorption and desorption transport processes h e the potential to significantly affect the dispersal of contaminants in buildings.
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  • 14
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The paper evaluates ocular manifestations as reported in two different questionnaires completed within one to Two weeks by 164 office workers in four town halls in Copenhagen. Among 14 previously investigated, these town halls constitute the two with the highest and the two with the lowest prevalence of the Sick Building Syndrome (defined as mucous membrane complaints such as eye, nose or throat irritation, and general symptoms such as headaches or fatigue several times a week). There was a highly significant rank correlation in each of the four town halls between the frequency of self-reported ocular manifestations in the two questionnaires. Furthermore, the eye complaints reported in both questionnaires were significantly correlated with an objective measure for eye dryness, investigated using a biomicroscope. By combining the two questionnaires it was possible to define subgroups using both frequency of eye complaints and consistency of reporting in the two questionnaires. The subgroup of 107 subjects with consistency in the frequency of their eye complaints in the two questionnaires showed a significantly higher correlation with the objective index than did the subjects with inconsistent reporting. Furthermore, with increased frequency of complaints and consistency of reporting, not only the prevalence of microscopically determined eye dryness, but also the number of up to 7 different eye symptoms per subject increased, and an increased percentage of these symptoms was found to be related to sensory reactions in the common chemical sense, which earlier has been postulated to be involved in the Sick Building Syndrome. In conclusion, the study shows that data from two different questionnaires on self-reported ocular manifestations associated with the Sick Building Syndrome are reproducible and associated with objective dryness in the eyes.
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  • 15
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Volatile organic compounds (VOC) in office buildings originate from multiple sources, such as outdoor air, building materials., occupants, office supplies, and office equipment. Many of the VOC found in office buildings are also present in environmental tobacco smoke (ETS), e.g., benzene, toluene, formaldehyde. Measurements made to date in office buildings have been interpreted by some to imply that the contributions of ETS to VOC exposures in office buildings are small. We have made a first order estimate of the contributions of ETS to VOC concentrations based on the VOC content of ETS and a time-dependent mass-balance model. Four different ventilation-infiltration scenarios were modelled for a typical office building.The results indicate that ETS can contribute significantly to total indoor levels of VOC in office buildings, even under moderate ventilation conditions. Ranges of concentrations for three of the four modelled scenarios substantially overlapped measured ranges of the compounds in office buildings. Average daytime concentrations of benzene from ETS, for example, for three of the four modelled scenarios, ranged from 2.7 to 6.2 μg m−3, compared to reported measurements of 1.4 to 8.1 μg m−3 for four office buildings. Under a “worst reasonable” case scenario, the average modelled ETS-contributed concentration of benzene was 33.9 μg m−3 for a 40-hour work week.
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  • 16
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: We have developed a new air sampler for collecting parriculate and gas phase polycyclic aromatic compounds (PAC). This sampler was designed to collect a 25 m3 volume of air at a constant sampling rate of 34 l/min over a 12-hour sampling penod. The 25 m3 sample volume is necessary to achieve the desired nglm3 detection limit for PAC. The 34 l/min sampling rate is estimated to cause less than a 5% reduction in the indoor contaminant concentrations. The sampler pump is a I/4 horsepower vacuum pump in an acoustically shielded fan-cooled enclosure and is relatively quiet. The pump draws air through a 47 mm teflon impregnated glass fibre filter for collection of particulate-phase PAC followed by a cartridge containing XAD-4 resin in front and back sections (2.5 g each) for collection of gas-phase PAC. In a pilot field study the mean breakthrough from the front sorbent section to the back section was less than 1% for each of 14 species of gas phase PAC except biphenyl which had a mean breakthrough of 3.7%. The pressure drop increase across the filter is linear up to a loading of 6 mg and causes less than a 10% reduction in the sample flow rate. The sampler was successfully demonstrated in a pilot field test with air temperatures as high as 30°C.
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  • 17
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: We model radon entry into basements using a previously developed three-dimensional steady-state finite difference model that has been modified in the following ways: first, cylindrical coordinates are used to take advantage of the symmetry of the problem in the horizontal plane, thereby increasing resolution and computing eficiency without signifiant loss of generality; second, the configuration of the basement has been made m e realistic by incorporating the concrete fmtm which sup ports the basement walls and floor; third, a quadratic relationship between the pressure and flow in the L-shaped gap between slab, footer, and wall has been employed; and fourth, the natural convection of the soil gas which follows from the heating of the basement in winter has been taken into account. The temperature field in the soil is determined fiom the equation of energy consmation, using the basement, surface, and deep-soil temperatures as boundary conditions. The pressure field is determined from Darcy's law and the equation of mass conservation (continuity), assuming that there is nofIow across any boundary except the soil surface (atmospheric pressure) and the opening in the basement shell (fixed pressure), Since the energy conservation equation includes both heat advection and conduction, the temperature and pressure equations must be coupled. After the pressure and temperature fields have been obtained, the velocity field is found fiom Darcy's h. Finally, the radon concentration field is found from the equation of mass-transport, assuming that diffusive entry through openings may be neglected. The convective radon entry rate through the opening or openings is then calculated. In this paper we describe the modified model, compare the predicted radon entry rates with and without the consideration of thermal convection, and compare the predicted rates with rates determined from data from seven houses in the Spokane River valley of Washington and Idaho. Although the predicted rate is much lower than the mean of the rates determined from measurements, er-TOTS in the measurement of soil permeability and variations in the permeability of the area immediately under the basement slab, which has a signifiant influence on the pressure field, can account for the range of entry rates inferredfiom the data.
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  • 18
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Airborne pollutants can cause failures in switching and computing equipment. This paper focuses on a subset of such pollutants - airborne fine panicles (〈 2.5 μm diameter). It begins by examining the extent to which different improvements in heating, ventilating and air conditioning (HVAC) systems reduce indoor concentrations of fine particles. For each modification, the consequent reduction in soiling rate is derived. The concomitant increase in operating costs is also calculated. These costs are then compared with the costs of failures in telephone switching offices, leading to estimates of failure rate reductions that would make improvements cost-effective. Finally, the reduction in failures required to offset the costs of the improvements are compared with documented differences in failure rates between unimproved and improved environments. This study suggests that, in many telephone switching offices, the added operating costs associated with more efficient building filters and continuous fan operation are more than offset by reductions in failure rates.
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  • 19
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: This publication summarizes field investigations and controlled experiments on the relation between low levels of indoor air pollution with volatile organic compounds (VOC) and human health and comfort. The Henle-Kock criteria from epidemiology are revised for the dose-response relation between VOC's and health as comfort effects and existing evidence for each criterion are discussed. A biological model for human responses is suggested, based on three mechanisms: sensory perception of the environment, weak inflammatory reactions, and environmental stress reactions. Further, the TVOC-indicator concept for exposure is discussed. The conclusion is that no experimental or field data contradict the proposed causality. On the contrary, evidence supports the suggested causality. The biological model, however, is not yet based on acceptable measures of the variables for exposures, co-variables or health effects. A tentative guideline for VOC's in non-industrial indoor environments is suggested. The no-effect level seems to be about 0.2 mg/m3. A multi-factorial exposure range may exist between 0.2 and 3 mg/m3. Above 3 mg/m3 discomfort is expected.
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  • 20
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Monitoring of human reactions to the emission of formaldehyde and volatile organic compounds (VOC) from four commonly used building materials was carried out. The building materials were: a painted gypsum board, a rubber floor, a nylon carpet, and a particle board with an acid-curing paint. The exposures were performed in climate chambers. The air quality was quantified on the decipol scale by a trained panel, measurements of formaldehyde and VOC being performed simultaneously. The irritating potency of the materials was measured by a mouse bioassay. The VOC measurements showed several malodorants and irritants. Some abundant VOC identified in the head-space analyses were absent in the climate chamber air. The rubber floor and the nylon carpet exhibited a marked increase in decipols compatible with a number of odorous VOC identified in the air. A high formaldehyde concentration (minimum 743μg/m3) was measured for the particle board coated with an acid-curing paint. This was not reflected by a corresponding relatively high decipol value but a long-lasting irritating potency was observed in the mouse bioassay. TVOC sampled on Tenax and expressed in mass per volume as well as in molar concentration, and decipol evaluation both have limitations and should be used with caution as indicators of (perceived) indoor air quality. Eye irritation expressed by means of the eye index reflecting the tear film quality index (comprised of break-up time, foam formation, thickness of the precorneal lipid layer of the tear film, and epithelial damage) was found to be insensitive to formaldehyde and a VOC mixture but sensitive to TVOC concentrations of 1–2 mg/m3. Lipophilic VOC may be the cause of reduced tear film quality by destabilization of the lipid multilayer of the tear film.
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  • 21
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The aim of the study was to compare the results of a self-administered questionnaire, designed to estimate the prevalence of the sick building syndrome, with an independent medical interview and clinical opinion. Six buildings were chosen for study from a sample of 47 with known measurements of the building symptom index. One building with a high and one with a low score was selected from each of three ventilation classes (natural ventilation, air-conditioning with induction units and air-conditioning with variable air volume systems). A stratified random sample of 160 workers in these buildings was studied. Each received, in random order, a self-administered questionnaire, and a medical opinion based on a free medical history. The doctor had no access to the self-administered questionnaire at the time. The average number of work-related symptoms per worker (the building symptom index), which is used to compare one building with another, showed a good agreement between the two methods. There were, however, consistent differences between the two assessments in individual symptoms. The self-administered questionnaire produced a higher prevalence of work-re-lated runny nose and flu-like symptoms, which were often regarded as being due to infections in the medical opinion. In individuals, work-related symptoms on the self-administered questionnaire were validated by the medical opinion in over 75% of cases for eye and throat symptoms, lethargy and headache. Only 31% of work-related runny nose and 21% of work-related flu-like symptoms were thought by the medical opinion to be work-related. The medical opinion identified an extra 5% of work-related symptoms that were missed on the self-administered questionnaire. The self-administered questionnaire therefore produced a satisfactory estimate of the building symptom index, removing the potential bias of an interviewer. The questions on ninny nose and flu-like symptoms would be improved by including only those that occurred more frequently. The building symptom index was calculated for the six buildings twice, with separate random samples of workers completing the questionnaire two years apart. The buildings were ranked in the same order (for the building symptom index) on both occasions, again confirming the validity of the self-administered questionnaire.
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  • 22
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Concern for the health risk of occupants in buildings containing asbestos fireproofing, acoustic materials or lagging, among other products, has led to several investigations of airborne asbestos concentrations in buildings and exposure assessments of occupants and maintenance personnel. The purpose of this paper is to summarize these results, to place in perspective exposure to occupants and maintenance personnel, and to estimate risks based on these exposures. Regulatory implications of these results are discussed. It is concluded that asbestos-in-air measurements carried out with the most appropriate methods in buildings with damaged or undamaged asbestos-containing materials consistently show extremely low concentrations comparable to those measured outdoors for fibers greater than 5 μm in length. Risks to occupants in such buildings are correspondingly very low. Potential exposures are higher to those performing building maintenance procedures that may disturb the asbestos-containing materials. Operations and maintenance procedures are effective in protecting maintenance personnel through engineering controls, work practices and personal protective devices, which are used to a greater or lesser extent depending on the specific activity.
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  • 23
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Field measurements of 21 volatile organic compounds (VOC) using diffusive samplers, formaldehyde, temperature, and humidity were performed from the time of building completion throughout the following one-year period in two new semi-detached twin apartments. One of these was occupied after six weeks. Headspace analyses from all building materials and products showed 120 different VOC. Formaldehyde concentrations were strongly seasonally dependent in the vacant apartment and increased to above 400 μg/m3 during the warm season. The formaldehyde concentration generally decreased in the occupied apartment but increased again during the fall season. VOC originating from building materials generally showed a decrease in emission, but strong seasonal variations were observed. It was shown that human activity introduces several VOC to the indoor environment. Storage of motorcycle parts in the crawl space of the occupied apartment resulted in migration and an infiltration of benzene and toluene into the apartment above and probably to a delayed peak concentration in the twin vacant apartment. Similarly, large VOC increases in one apartment were reflected by a later increase of the same VOC in the twin apartment. Hexanal increased during the warm season. TVOC, as the sum of 21 VOC, was generally approximately 50 % higher in the occupied apartment during the cold season. The results indicate the difficulties in interpreting long-term measurements. The “flushing period” recommended for this type of building has been estimated to be about 130 days.
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  • 24
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: A model based on heat diffusion through the skin is developed for the dynamic response of cutaneous thermo-receptors to temperature stimuli at the skin surface. It is applied to various neurophysiological experiments with good results. The model is then extended to sensation and a set of psychophysical experiments on human subjects is examined and compared with the model predictions. Altogether, in terms of both the neurophysiological response and the sensation response, this model gives good agreement with the experiments.
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  • 25
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The purpose of the study was to evaluate the occurrence of symptoms and the perception of poor indoor air quality among the occupants of houses and apartments with different ventilation systems. The study population consisted of the 473 occupants of 242 dwellings in the Helsinki metropolitan area who responded to a self-administered questionnaire (response rate 93.1%) after a two-week period of indoor air quality measurements. The symptoms of interest were those often related to poor indoor air quality including dryness or itching of the skin; dryness, irritation or itching of the eyes; nasal congestion (“blocked nose”) nasal dry-ness; nasal discharge (“runny nose”); sneezing; cough; breathlessness; headache or migraine; and lethargy, weakness or nausea. Perception of coldness; warm-ness; draught; dryness; stuffiness; and sufficiency of air exchange was also requested. The age-standardized period prevalences of the symptoms and complaints were systematically more common among the occupants of the apartments than those of the houses. The occupants of the houses with natural ventilation seemed to have more symptoms and complaints than those with balanced ventilation. However, in the apartments with balanced ventilation the occupants reported, in general, more symptoms and complaints than those with natural ventilation.
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  • 26
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: One of the objectives of EPA's indoor air quality (IAQ) program is to provide guidance on the impact of indoor sources on IAQ. A computer model, EXPOSURE, was developed to assist in this effort. EXPOSURE calculates pollutant concentration as a function of time for each room of the building. EXPOSURE includes effects of sources, sinks, room-to-room air movement, and air exchange with the outdoors. Several experiments designed to evaluate the impact of indoor sources on IAQ are described. Measured concentrations are compared with concentrations predicted by an IAQ model. The measured concentrations are in excellent agreement with the predictions. The model predictions and the experimental data demonstrate the importance of sinks in determining long-term IAQ.
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  • 27
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: It is well known that the inhabitants of dwellings use the room heating and ventilation to build up their own individual climatic zone in which they feel comfortable. To date individual measurements have been conducted to investigate these climatic zones, or line charts have been drawn up with a thermohygrograph in long-duration tests.Compared with the form of presentation used previously, the possibilities for evaluation have been substantially improved by the use of measured data-recording installations for the long-term investigation and presentation of results in the form of dots (temperature/humidity value pairs) in an h,x-diagram. The h,x-diagram is a type of psychrometric chart which is widely used in Germany. The advantage of this chart is that all thermodynamic properties of moist air can be determined without calculation. The dry bulb temperature, the wet bulb temperature, the dew point, the relative humidity, the humidity ratio, the specific enthalpy and the specific volume of moist air can be read directly from the diagram.
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  • 28
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The indoor air quality in several types of dwellings that were renovated to save energy for spatial heating has been investigated. Concentrations of pollutants were monitored in three rooms of inhabited houses. Data of the outside air and ventilation and infiltration were also collected. Relationships were established between observed concentrations and ventilation. In some cases concentrations show a good relationship with the calculated air change rate, in other cases this relationship was poor or absent.Elevated levels of pollutants could be related to sources in most cases. The ventilation behavior of the inhabitants has a major influence on the concentrations.From this and other studies it can be concluded that, in general, making dwellings more airtight leads to higher concentrations of pollutants. Deviations from health-related guidelines then become more likely.
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  • 29
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: Mechanical ventalation system performance involves the provision of adequate amuunts of outdoor air, uniform distribution of ventilation air within the occupied space, and the maintenance of thermal comfort. Standard measurement techniques exist to evaluate thermal comfort and air change rates in mechanically ventilated buildings; procedures to evaluate air distribution or ventilation effectiveness in the field are still being developed. This paper presents measuremetlts of air change rates and ventilation effectivenes in an office/library building in Washington, DC. The tracer gas decay technique was used to measure whole building air change rates. The air change rates during the measurement period were essentially constant at about 0.8 air changes per hour, somewhat below the design specification and above the minimum recmmmded in ASHRAE Standard 62-1989. Ventilation effectiveness was investigated at several locations within the building through the measurement of local tracer gas decay rate and mean local age of air. The ventilation effectiveness measurements serve as an investigation of the applicability of the m e a s u r r n procedures employed, providing insight into the measurement issue of establishing initial conditions, the spatial variation in test results within a building, and the repeatabildy between tests. The results of the ventilation effectiveness meusurements are consistent with good distrhtion of the outdoor air by the ventilation system and good mixing within the occupied space.
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  • 30
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: We studied the performance of a task ventilation system that permits occupants to control the flow rate and direction of air supplied to their work space through four floor-mounted supply grill. Air exited the room through a ceding-mounted return grill. To study air-flow patterns, we measured the age of air at multiple locations using a tracer gas stepup. To study the intra-room transport of tobacco smoke particles, cigarettes were smoked mechanically in one workstation and particle concentrations were measured at multiple locations. Our major findings were as follows: (1) deviations from uniform age of air, and uniform particle concentration, were generally less than 30 percent; (2)some supply air short-circuits to the return grill when directed toward the return with high velocity; (3) low supply velocities resulted in a floor-to-ceiling displacement flow; (4) directing the supply air toward the occupant, of partially toward the occupant, typically yielded an age of air at the occupant's breathing level that was 15 to 25 percent lower than the age at other breathing-level locations; (5) with low supply velocities und air directed toward the occupants, tobacco smoke particle concentrations in a ventilated non-smoking workstation were 50 percent of the chamber-average concentration.
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  • 31
    Electronic Resource
    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: This paper describes the techniques used within the ESPR/〉 system to represent and solve the heat and mass conservation equations relation to combined building and plant systems. In Particular, it describes the equation-sets used to represent inter-zonal (building) and inter-component (plant) fluid flow and the method used for the integration of the non-linear heat and muss frow equations. By means of a case study, the application in a real design context is demonstrated.
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  • 32
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    Electronic Resource
    Oxford, UK : Munksgaard International Publishers
    Indoor air 1 (1991), S. 0 
    ISSN: 1600-0668
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Medicine
    Notes: The interaction of indoor air pollutants with interior surfaces (i.e., sinks) is a well known, but poorly understood, phenomenon. Studies have shown that re-emissions of adsorbed organic vapours can contribute to elevated concentrations of organics in indoor environments. Research is being conducted in small environmental test chambers to develop data for predicting sink behaviour. This paper reports on the development of sink models based on fundamental mass transfer theory. The results of experiments conducted to determine the magnitude and rate of adsorption and desorption of vapour phase organic compounds for several materials are presented. Five materials were evaluated: carpet, painted wallboard, ceiling tile, window glass, and upholstery. Two organic compounds were tested with each material: tetrachloroethylene (a common cleaning solvent) and ethylbenzene (a common constituent of petroleum-based solvents widely used in consumer products). The results of the experimental work are presented showing the relevant sink effect parameters for each material tested and comparing the sorptive behaviour of the two organic compounds evaluated. An indoor air quality (IAQ) model was modified to incorporate adsorption and desorption sink rates. The model was used to predict the temporal history of the concentration of total vapour phase organics in a test house after application of a wood finishing product. The predicted results are presented and compared to measured values. Suggestions for further research on indoor sinks are presented.
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  • 33
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A quadrupole mass spectrometer (QMS) utilizing the second stable zone in Mathieu's stability diagram was developed. The system performance was experimentally compared with the conventional QMS using the first stable zone. The peak shapes obtained were sharper and the tail components arising from adjacent peaks were less than those of the conventional QMS, although the analyzable range was limited to lower mass and the attenuation in sensitivity was about 1/50. This improved QMS is usable in detecting very small peaks adjoining large ones.
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  • 34
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A versatile electron-impact time-of-flight mass spectrometer (EI-TOFMS) in a pulsed molecular beam has been constructed. The instrument contains a fast rise time, square pulse generator, biased at high voltage, which simplifies the implementation of EI-TOFMS. Power field effect transistors are used as the active switching element, which afford compact size and simplified circuit construction. The effect of the shape of the repelling pulse on the flight time and space focusing condition is estimated by numerical calculation. Preliminary test results are provided for pulsed molecular beams of ammonia and hydrogen iodide.
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  • 35
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The construction and the fundamental studies of a kilohertz-range flash x-ray generator having a triode in conjunction with an extremely hot cathode are described. This generator consisted of the following components: a constant-high voltage power supply, an energy storage condenser of 100 nF, a constant high-voltage power supply for regulating an initial grid voltage of −1.6 kV, a grid pulser, and an x-ray tube. The x-ray tube was of an enclosed-triode type and consisted of the following major parts: an anode rod made of copper, a plane anode tip (target) made of tungsten, a focusing electrode made of iron, a hot cathode (filament) made of tungsten, a grid made from tungsten wire, and a glass tube body. The energy storage condenser was charged from 50 to 70 kV, and the electric charges in the condenser were discharged repetitively to the x-ray tube by the grid electrode driven by the grid pulser. The temperature of the filament was about 2000 K, and the cathode current was primarily controlled by the grid voltage and its value was less than 1.2 A. The pulse widths were about 1 μs and the maximum repetitive frequency was about 2.0 kHz. The x-ray intensity was 19.7 nC/kg at 0.5 m per pulse with a peak grid voltage of 1.0 kV and a condenser charged voltage of 70 kV.
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  • 36
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A time-of-flight spectrometer has been specially designed for measuring the masses of ions produced by low-energy positrons interacting with organic molecules in a Penning trap. To make the flight times insensitive to the starting positions of the ions in the trap, acceleration was done using a potential that varied as the square of the distance of the ion from the detector. The containment of the positrons in the Penning trap for extended time periods effected very long collision paths between the positrons and the molecules. The entire length of the Penning trap source could be sampled. These features produced high sensitivity, enabling the measurement of ionization processes with small cross sections. The spectrometer is useful for mass spectrometry of ions produced by processes other than positron interaction. Both large and small volume sources can be accommodated.
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  • 37
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2138-2141 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spectroscopic plasma tomography measurement system has been developed and operated on a field-reversed configuration (FRC) plasma machine with the use of five photocollector arrays. Each photocollector array that is located azimuthally around the plasma column consists of ten optical fibers and a pinhole. Two-dimensional (2D) and time-resolved visible emission profiles can be reconstructed numerically from the fifty-channel projection data. The use of five multichannel visible monochromators makes it possible to obtain a result that has explicit physical meanings. A computer simulation has been performed to demonstrate the potential to reconstruct the 2D profile without the assumptions about plasma rotation or symmetry. The first experimental result for visible bremsstrahlung emission profiles of the FRC plasma is presented.
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  • 38
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high proton yield beam was produced in a semicylindrical multicusp plasma generator. The dimension of the cylinder is 34 cm in diameter and 129 cm in length, and the beam extraction area is 8 cm in width and 120 cm in length. A strongly linked magnetic field configuration was utilized to confine the primary electrons in the cylinder and prevent them from flowing into the beam extraction region. As a temporary test hydrogen ion beams were extracted from the central region of the plasma generator. Ion species in the beam were measured by a Doppler-shifted spectroscopy of Balmer-alpha light and found to be 95% at a beam current density of 175 mA/cm2 at the filling pressure of 0.4 Pa.
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  • 39
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2146-2153 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A ring of accurately placed and matched printed circuit coils is placed at the center of the DIII-D tokamak vacuum vessel, aligned magnetically with the toroidal field and used to measure the nonaxisymmetric magnetic field of each of the 18 poloidal field coils. [Toroidal and poloidal variations can be of mode n and m, respectively, with helical variations of form cos(nφ−mθ).] From the error fields, it is computed that the most irregular poloidal field coil is one of the outer vertical field coils having a shift of 1.9 ±0.2 cm (compared to a diameter of 482 cm), and having an ellipticity 1.0027. All the 18 poloidal field coils together make a resonant, helical, radial error field for m=2, n=1 of about 1.4 × 10−4 of the toroidal field.
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  • 40
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2154-2158 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact supersonic molecular beam source was developed that has a liquid nitrogen trap to cryogenically pump the gas and is small enough in size to install in conventional molecular beam epitaxy (MBE) systems. With the source, well-collimated molecular beams of N2O and NO2 whose flux densities are ∼1016 molecules cm−2 s−1 are generated. The effectiveness of the source was proved in the preparation of oxide superconducting thin films by MBE with an NO2 beam where as-grown superconducting films were obtained in high vacuum of ≤10−5 Pa.
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  • 41
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report an NMR probe that we use in ultra low temperature experiments in a top-loading dilution refrigerator. The probe is thermally anchored to the 1.2 K pumped 4He pot and is thermally isolated from the sample located inside a Kel-F cup containing liquid 3He. The probe is adapted from a standard double resonance probe, using air trimmer capacitors, a λ/4 cable, a homemade saddle coil, and metal film resistors. The double resonance design breaks the probe's tuning ranges into two bands. The high frequency band tunes from 100 to 150 MHz covering all the nuclei with large gyromagnetic ratios, 3H, 19F, 1H, 3He. The low frequency band tunes for 17 to 54 MHz covering all nuclei with gyromagnetic ratios between 133Cs and 119Sn. The air trimmer capacitors have an open structure that allows efficient pumping and the metal film resistors are used to reduce the Q of the probe. This probe has been successfully used for a wide range of nuclei including 1H, 19F, 3He, 119Sn, 117Sn, 115Sn, 11B, 13C, 29Si, 27Al, and 2H.
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  • 42
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2163-2166 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Important information about physical characteristics of clays can be inferred from the distribution of the orientations of straight lines in photographs of cross sections of its samples. This article describes the development of a semiautomated system for clay analysis that is based on the application of computer vision techniques. Due to the inherent complexity of these techniques, two strategies have been used in order to reduce the execution time: an effective technique, the binary Hough transform, is applied for detection of straight lines and the transputer is used to enhance the system processing power. The article includes the characterization of the clay analysis application, the description of the binary Hough transform for detection of straight line segments, the presentation of the semiautomated system, and a complete illustrative example.
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  • 43
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2205-2212 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A theoretical analysis of standing waves in a pipe with flow was conducted aimed toward the development of a flowmeter based on a measurement of phase difference between two points on the circumference of a pipe separated axially by an integral multiple of half sound wavelength. Effects of nonzero Mach number, variable ratios of upstream and downstream running waves, choice of location of the sensing pressure taps, and the incorrect spacings were examined numerically. Calculations were also made for steam flow where the maximum Mach number is much smaller than in cold air flows. For an industrial application where steam flow velocities are below 50 m/s, a very accurate sensor is shown to be possible. Experimental data were obtained by using an active aeroacoustic source over the range of 50 m/s to zero in an air flow. Experimental phase plots obtained from several coast-down tests have been compared with analytical results. The agreement with theory is excellent when the spacings are near Nλ/2 and the sensing locations are near the pressure antinodes. Otherwise, some zero shifts are introduced. Theory predicts that for steam flow much better results can be expected because the maximum Mach number is much smaller. Effects due to the (1−M2) factor would be imperceptible for steam flow.
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  • 44
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2218-2227 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Commercial carbon composition resistors have been used as gauges to make dynamic stress measurements in homogeneous and heterogeneous reactive and inert materials. Initial loading was provided by plane wave lenses or shaped charge jets. A series of gas gun and aquarium experiments has been conducted to characterize the behavior of the gauges. Calibrations up to about 14 GPa for nominal 470 Ω resistors and 17 GPa for nominal 4700 Ω resistors are presented. The accuracy of the carbon resistor gauges is limited by response time considerations when submicrosecond rise times are encountered, and there is hysteresis during release. The gauge-to-gauge reproducibility appears to be adequate, and they survive in situations where no other stress transducer has been successfully used, such as in reacting beds of large-particle gun propellants.
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  • 45
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel method and instrument capable of either monitoring continuously a condensation process or estimating the thickness of a liquid layer in the μm range are presented. The underlying physical principle is a variant of the photopyroelectric technique in which the changes in the thermal wave propagation due to the presence of the liquid layer are sensed by the pyroelectric sensor. The theoretical model developed supports the experimental results obtained.
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  • 46
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A modified centrifuge has been developed. There are four advantages to this apparatus: (i) The presence of centrifugal acceleration permits the formation of the boundary between the two phases of a fluid system more quickly after phase separation, especially for viscous fluids such as polymer blends. (ii) The rotor is able to accommodate three samples. (iii) The formation of homogeneous solutions in the one phase region can be achieved within the constant temperature rotor which can be controlled to ±0.003 °C up to ≈300 °C. (iv) The phase separation temperature can be measured as a function of centrifugal acceleration up to 1500 gravity. By using the centrifugal apparatus, the coexistence curves of polystyrene in methylcyclohexane were measured. The results in terms of critical exponents and preexponential factors were in excellent agreement with the best literature values and thus confirmed the reliability of our apparatus.
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  • 47
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The hardware and software designs for fast measurement of dielectric properties of different substances over a wide range of characteristic times (10−5–10−10 s) by means of time domain dielectric spectroscopy (TDS) are presented. The characteristic feature of the described installation is the nonuniform time sampling of measured signals, which enables one to cover a wide range of characteristic times with a single measurement. Comparative results for an aqueous solution of lysozyme obtained on the traditional apparatus and on the described one are presented.
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  • 48
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2266-2270 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we describe how nonlinear electrical transmission lines can be used to produce bursts of very short-time voltage pulses (solitons). The relevant parameters and relations for designing suitable transmission lines are given. The number of solitons and their amplitudes are given in a diagram as functions of the (normalized) amplitude and the width of the rectangular input pulse. Several examples of constructed transmission lines (including some very fast structures) are described and solitons produced by them are shown.
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  • 49
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article we describe a simple SQUID magnetometer system useful for the magnetic characterization of high temperature superconductors. The system employs a commercial rf SQUID probe with associated electronics located in a 4He gas exchange cryostat. The system is equipped with a copper coil dc magnet for fields up to 50 Gauss. The cryostat is surrounded by a μ-metal shield that keeps the remanent field to less than 20 mGauss. The apparatus has been used extensively to measure both the superconducting transition temperature and width as well as the relative quantities of magnetic flux expulsion and exclusion. It has therefore served as an important first step in the evaluation of sample quality.
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  • 50
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2281-2287 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A data acquisition system designed for magnetic resonance instrumentation is presented. Its performance may be suitable for a broad set of applications where repetitive and noisy signals must be time-averaged in order to increase the signal-to-noise ratio. The system is built from easily available, low cost parts on a standard board for the PC-AT (16-bit) bus. 12-bit data acquisition and 32-bit time averaging take place in the memory of the PC under control of its CPU. The sustained data rate, including on-line signal averaging, can be as high as 250 kHz (500 kHz with interlaced data acquisitions). Timing is accomplished by on-board software programmable hardware timers. The CPU is then free for other tasks during the time, if any, between acquisition scans. Thus on-line display of the time-averaged data and their FT spectrum may be performed without impairing the timing accuracy, which is limited by the 10-MHz board clock to 100 ns. All functions of the interface are controlled by machine-language routines, callable from within quickbasic programs.
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  • 51
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple and elegant technique is outlined in which a specially designed crucible may be used for noble metal evaporation in a pendant-drop type electron beam evaporator with virtually no modifications.
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  • 52
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel synchronous real-time analog sampling method for obtaining the sum and difference interferograms in double modulation Fourier transform infrared absorption experiments is described, and the application of this sampling methodology to polarization-modulation FTIR measurements of thin films at metal surfaces is demonstrated. A quadratic approximation of the background signal is used to calculate the difference interferogram. The demodulation of a test waveform with the real-time sampling electronics reveals how the bandwidth limitations of previous double modulation experiments on FTIR interferometers that employed lock-in amplifiers have been eliminated.
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  • 53
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An experimental apparatus designed to study structural and electronic properties of surfaces is described. Ultraviolet photoemission (UPS) and metastable deexcitation spectroscopies (MDS) have been implemented in order to obtain information on electronic states in the valence-band region with different surface sensitivity. The supersonic metastable beam source is fully described and characterized by time-of-flight measurements while the characteristics of the apparatus have been tested in the study of the Ag(110) surface, clean and following the dissociative chemisorption of oxygen. Exploiting the surface sensitivity of MDS, measurements as function of the oxygen coverage allow a direct correlation between work function increase and the population of the s-p bands of the substrate near the Fermi edge. Oxygen-induced states around 7.5 eV, difficult to observe in UPS because of strong contributions from the d bands of the substrate, are also detected.
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  • 54
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1438-1444 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An aperture-limited, differentially pumped environmental cell has been developed and installed in a JEOL 4000 EX electron microscope. With this environmental cell it is possible to observe, at high spatial resolution, the detailed changes in microstructure that occur during the interaction between a solid and a gaseous environment. The cell has been pressurized to 70 Torr with H2 gas for several hours with no adverse effects on the microscope performance. While the initial tests have been performed with hydrogen gas, the materials used to construct the environmental cell can tolerate corrosive environments. The key features of the environmental cell design along with the results from some applications are presented in this paper.
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  • 55
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A sensitive spectrometer, based on a dc superconducting quantum interference device, for the direct detection of low-frequency pulsed nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR), is described. The frequency response extends from about 10 to 200 kHz, and the recovery time after the magnetic pulse is removed is typically 50 μs. As examples, NMR spectra are shown from Pt and Cu metal powders in a magnetic field of 6 mT, and NQR spectra are shown from 2D in a tunneling methyl group and 14N in NH4ClO4.
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  • 56
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1445-1452 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe the design of a probe for dynamic-angle spinning (DAS) NMR experiments, comprised of a spinning cylindrical sample holder whose axis may be reoriented rapidly between discrete directions within the bore of a superconducting magnet. This allows the refocusing of nuclear spin magnetization that evolves under anisotropic interactions such as chemical shift anisotropy and quadrupolar coupling, providing high resolution NMR spectra for quadrupolar nuclei in solid materials. The probe includes an axial air delivery system to bearing and drive jets which support and spin a rotor containing the sample. Axis reorientation is accomplished with a pulley attached to the probehead and coupled to a stepping motor outside of the magnet. The choice of motor and gear ratio is based on an analysis of the moments of inertia of the motor and load, the desired angular resolution, and simplicity of design. Control of angular accuracy and precision are discussed, as well as the efficiency of radiofrequency irradiation and detection. High resolution DAS spectra of oxygen-17 and aluminum-27 nuclei in polycrystalline minerals illustrate the experimental capabilities.
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  • 57
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1464-1467 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Measurement of beam properties at the foci of high energy linacs is difficult due to the small size of the waists in proposed and existing accelerators (1 nm −2 μm). This article considers the use of bremsstrahlung radiation from thin foils to measure the size and phase space density these beams using nonimaging optics. The components of the system are described, and the ultimate resolution, evaluated theoretically for the case of the Final Focus Test Beam (FFTB) at Stanford Linear Accelerator Center, is a few nm.
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  • 58
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1468-1470 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A numerical method is presented of finding the rms width and the height of a Maxwellian transverse velocity distribution from an experimentally obtained beamlet profile formed by a finite-width slit. The results are also least-squares fit to polynomials that can be very conveniently used in actual data analyses.
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  • 59
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electrostatically guided positron beam which is variable in energy from 0 to 60 keV is described. A frozen inert gas (Ar, Kr, and Xe) is used as the positron moderator. The efficiency, ε, defined as the ratio of the number of slow positrons at the target to the number of positrons emitted by the source has been measured; the values obtained for Ar, Kr, and Xe were ε∼ 2.5×10−4, 1.6×10−4, and 1.1×10−4, respectively. We estimate a source/moderator efficiency of εm∼7.6×10−4, 4.7×10−4, and 3.0×10−4 for Ar, Kr, and Xe, respectively, which includes source effects, grid transmission, geometrical losses, and beam transport. These values are comparable to the best reported values for thin metal foil moderators. The measured εm is specific to the electrostatic system; significantly higher values for the same moderator should be attainable in magnetically guided beams, where higher transmission for moderators with large energy spreads is usually obtained.
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  • 60
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1471-1474 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A compact cylindrical reflection mirror analyzer for low energy ion scattering spectrometer has been designed and constructed to be used in a vacuum thin film deposition system for in situ analysis of fresh-deposited films. The design of the energy analyzer is similar to that of the ellipsoidal mirror analyzer, consisting of an electrostatic reflection mirror of the cylindrical sector type with a mean radius of curvature of 4.0 cm and a sector angle of 70°, a high pass energy filter, and two slits. The performance of this analyzer has been tested by the scattering of Li+ ions with energies of 606, 707, and 807 eV, respectively, on Al, Ti, Co, Cu, and stainless steel samples at angles from 125° to 155°. An average energy resolution of (1)/(56) has been obtained at an energy band of 10 eV and primary ion energy of 800 eV. Better resolution is expected with a narrower energy band and a higher primary energy. In situ monitoring of thin Cu film deposited on Si substrate in Ar+ ion sputtering process has been done to show the feasibility of this system.
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  • 61
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1489-1493 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Neutron source strength and yield from field-reversed configurations have been measured in the FRX-C/LSM magnetic compression experiment using plastic scintillators, indium activation samples, and moderated rhodium activation counters. The calibration of these neutron detectors is complicated by the changing shape and position of the plasma and by the presence of the massive aluminum compression coils. The overall uncertainty in the neutron measurements is estimated to be 45%.
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  • 62
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: High bandwidth capacitive probes are useful tools for potentials measurements in the tokamak scrape off layer. An improved capacitive divider probe design with very high frequency bandwidth is shown. The gain of this system is between 0 and −8 dB for frequencies from 0.1 Hz to more than 100 MHz, with the −3 dB point at approximately 40 MHz. The probe structure, circuits, performance, and experimental results from the Phaedrus-T tokamak are given.
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  • 63
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1475-1480 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A potential modulation differentiation technique which uses heterodyne modulation is presented. The second derivative I‘(V) of the collected current I(V) is obtained by modulating the voltage V using two synchronized signals with angular frequencies Kω0 and (K − 1)ω0, K(very-much-greater-than)1, and detecting the component of the collected current with angular frequency ω0. This technique eliminates problems caused by stray capacitively coupled signals and harmonic distortions produced by the signal generator and the preamplifiers. It can be applied to techniques in which the desired signal is the second derivative of the collected current, such as retarding field Auger electron spectroscopy, appearance potential spectroscopy, and work-function measurements. Auger spectra obtained using a multigrid retarding field analyzer and the proposed modulation technique show that only three grids are needed rather than the four grids required in the conventional experimental setup. Furthermore, there is no need for resonant filters or neutralization (bridge) amplifiers, and the high dynamic range commercial lock-in amplifier can be replaced by a circuit based on a single chip.
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  • 64
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron diffraction apparatus is described that has been designed specifically for use with molecular beams containing small particles in the nanometer size range. A novel electron detection system has been developed, using linear charge coupled device imagers, which allows rapid parallel measurement of the diffraction signal in a direct electron counting mode. The apparatus also features a 100 kV electron gun and electron optics derived from a Philips EM 300 electron microscope. Details of the apparatus are presented and measurement results on small silver particles in a beam of helium carrier gas are also given; these are interpreted using an icosahedral structure for the small particles.
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  • 65
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 1498-1503 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A sputtering source utilizing both microwave and dc planar magnetron plasmas is described. Microwave power is introduced into the plasma by a coaxial-type cavity. The magnetron target is placed on the open end of the inner conductor. This source produces a plasma which is well matched, stable, and can operate continuously at gas pressures from 3×10−4 to 2×10−2 Torr. Plasmas with densities greater than 1011 cm−3 are obtained at gas pressure of 10−4 Torr using a microwave power of 100 W. The deposition rate of Cu is more than 0.13 μm/min for an argon gas pressure of 3×10−4 Torr, and microwave and dc powers of 100 W, respectively. This new source has many potential uses such as sputtering, etching, and chemical vapor deposition.
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  • 66
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The presence of a high-frequency ((approximately-greater-than)6 MHz) oscillation in the discharge current and voltage of a plasma-focus device is found experimentally and is explained by using equivalent circuit analyses. The occurrence of such an oscillation is attributed to the excitation of the resonant oscillation in the discharge circuit. It is also shown that the high-frequency response of the driver circuit, which consists of a capacitor bank and cables, plays an important role in determining the high-frequency behavior of the discharge current and voltage.
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  • 67
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2008-2010 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and construction of a flange-mounted ultra-high vacuum compatible fatigue apparatus using a piezoelectric actuator is described. This apparatus is capable of operation under ambient pressures down to 10−9 Torr. Push-pull fatigue tests can be performed under load, total strain, and plastic strain control at frequencies up to 100 Hz. Control of the fatigue tests and data acquisition are done using standard fatigue control electronics and software.
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  • 68
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2011-2015 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An apparatus is described for the measurement of vapor pressures of low volatility solids and liquids by a static method in the range 10−2–100 mm Hg and 30 °C–300 °C. The method consists in inserting between the pressure gauge (here a capacitance manometer) and the product to be tested, a membrane that is maintained in equipressure by a suitable control loop. Experimental problems related to this arrangement are discussed. A test of the apparatus with a known product (benzoic acid) has been performed. The results have been found to be in good accordance with data found in the literature.
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  • 69
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2016-2018 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In order to automate the driving of terrestrial vehicles it is necessary to know at any time and with the highest accuracy the values of the speed of the vehicle and of the distance covered by the vehicle; it is also necessary to know the direction of the motion relative to the ground. These values must be measured in the real-time domain and this involves that contactless and very low time-constant sensors must be used. On the other hand, the applications concerned ask for a miniaturization of the whole measurement system. For these reasons, sensors using the Doppler effect in the microwave range are particularly well convenient to these applications. We developed an X band microwave Doppler cinemometer (MDC) with a printed antenna that is built using microstrip technology.
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