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  • 1
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The prediction of arctic ocean ice dynamics relies on a correct modelling of the stresses acting on the ice field, including the Coriolis effect, wind and current stresses and the ice interaction. Observations made in the past decade show significant ice interaction and flow patterns which can be consistently modeled with a plastic rheology. The main local physical process considered in these rheologies is the pressure ridging phenomenon. However recent arctic field work carried out in the marginal ice zone (less than 100 km from the edge of the ice field) shows the ice very near the edge to consist of a large number of discrete floes. While a plastic rheology may well have application under compact conditions in this region, under dispersed conditions the rheology may be different. In order to address this issue, in this work the ice floe collisions induced by ice deformation are analyzed. The internal kinematics as represented by the ice floe fluctuations is derived. Comparisons between the results and field data show excellent correlation. However, the theoretically predicted floe fluctuations are about one order of magnitude lower than the field measurements. Possibilities for this discrepancy are proposed and discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 771-778 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A microcomputer-based image processing system has been developed to use with solid-state nuclear track detectors for number counting, area measurement, and location identification. The image digitizer is designed to interface with a microcomputer and a standard black and white TV camera for data acquisition. A spatial dependent segmentation algorithm is proposed for track identification under nonuniform illumination and the low track-pixel population conditions. The system has been tested using Lexan samples irradiated by a Cf-252 spontaneous fission source. The counting accuracy is approximately 3% with a long term stability of 5%. Efficiency calibration was performed using samples with track densities up to 104/mm2. Results indicate that the proposed track identification scheme tends to reduce the track overlap effect and the system behaves as a nonparalyzable counting system. For track densities below 3000/mm2, either a paralyzable or a nonparalyzable counter model can be established with an accuracy better than 0.5%. For track densities below 1500/mm2, the track registration efficiency is in good agreement with manual counting results.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 1429-1432 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report a new type of normalization procedure for modulation spectroscopy experiments in order to obtain the relative change in the reflectance (transmittance) spectrum ΔR/R(ΔT/T). Our new technique utilizes a servomechanism driven variable neutral density filter which keeps the dc component of the signal from the detector constant by varying the intensity of the light striking the sample. This method is particularly useful for photoreflectance measurements which can have background problems due to scattered pump light and/or photoluminescence. Advantages for other modulation spectroscopies, particularly in the region of the fundamental band gap of semiconductors, also will be discussed.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report a modulation spectroscopy experiment on GaAs and Ga0.82Al0.18As at elevated temperatures. Using the contactless electromodulation method of photoreflectance, the direct gaps (E0) of these materials have been observed from 77 K to 600 °C. The latter temperature is comparable to molecular beam expitaxy, metalorganic chemical vapor deposition, growth temperatures, etc. Our results are at the highest temperature yet reported for E0 (GaAs) in a reflectance experiment and the first observation of E0 (Ga1−xAlxAs) at elevated temperatures. From the latter, the Varshni coefficients [Physica 34, 149 (1967)] for Ga0.82Al0.18As were determined.
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The amplitude of the photoreflectance (PR) spectra of the direct gap of semi-insulating GaAs has been studied as a function of pump chopping frequency (2–4000 Hz) and temperature (25–198 °C). We have been able to deduce a temperature-dependent trap time and hence trap activation energy of 0.70±0.05 eV. Our experiment demonstrates that PR can be used as a contactless method to study deep traps in semiconductors, analogous to deep level transient spectroscopy.
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  • 6
    ISSN: 1573-7195
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Resumé Les dépôts superficiels présentés par des stérilets en acier inoxydable retirés de l'utérus après une durée d'insertion variable ont été examinés au microscope électronique á balayage, et par analyse de rayons X en dispersion d'énergie, spectroscopie électronique d'Auger, spectroscopie des photoélectrons de rayons X, microscopie électronique à transmission et spectrophotométrie d'absorption atomique pour analyse micro-quantitative. Les résultats ont été comparés avec ceux obtenus avec les DIU au cuivre (TCu200) par les mêmes méthodes. Alors que les fils métalliques des DIU en acier inoxydable portés pendant 5 ans ne se sont pas modifiés de manière significative, les fils de cuivre présentaient différents degrés d'érosion après le même laps de temps. L'analyse montrait clairement des incrustations sur les fils métalliques des deux types de DIU. Les dépôts ont commencé sur les DIU au cuivre plus tôt que sur les DIU en acier inoxydable (respectivement, 27 jours et 3 mois après l'insertion). Ce processus a débuté après un laps de temps plus court que ne l'indiquaient les publications faites à cet égard. La quantité de dépôts a augmenté en fonction de la durée de l'insertion, mais on a pu constater d'importantes variations individuelles. L'analyse microscopique mentionnée ci-dessus a permis de montrer que le principal composant des dépôts sur les deux types de DIU était le calcium, présent sous sa forme cristallisée: le carbonate de calcium. Les substances liées aux cristaux de carbonate de calcium étaient très semblables aux composés organiques azotés. Nous pensons que le mécanisme régulant la formation de dépôts est semblable à celui des calculs. Cet article expose brièvement l'incidence de ces dépôts sur les complications d'une insertion de DIU-saignements utérins et grossesse accidentelle, question qui demande à être approfondie
    Abstract: Sumario Depósitos en la superficie de acero inoxidable en aparatos anticonceptivos extraídos del útero después de diferentes períodos de haber sido insertados, fueron examinados y analizados por medio de microscopía electrónica de barrido, de análisis de dispersión de energía de rayos X (XEDA), espectroscopía electrónica de Augar (AES), espectroscopía fotoelectrónica de rayos X (XPS), microscopía electrónica de transmisión y espectrofotometría atómica absortiva, a los efectos de análisis cuantitativo. Los datos obtenidos fueron comparados con aquellos pertenecientes a los DIU con cobre (TCu200) obtenidos por los mismos métodos. Las espirales de alambre de los DIU de acero inoxidable que permanecieronin situ durante 5 años no mostraron cambios evidentes pero las espirales de alambre de cobre mostraron diversos grados de erosión después del mismo período de tiempo. El análisis mostró claramente que las espirales de alambre en ambos tipos de DIU estaban incrustadas con depósitos. Los depósitos empezaron antes en los DIU con cobre que en los DIU de acero inoxidable (27 días y 3 meses respectivamente, después de la inserción). Este proceso empezó más temprano que lo que se había informado previamente en la literatura. La cantidad de depósitos aumentó con la duración de la inserción pero hubo grandes variantes individuales. Mediante el antes mencionado microanálisis, se encontró que el principal componente en los depósitos en ambos tipos de DIU era calcio que se presentaba en forma de carbonato de calcio. Las substancias adheridas a los cristales eran similares a las de compuestos de nitrógeno orgánico. Sugerimos que el mecanismo regulador de la formación de depósitos puede ser similar a la de los cálculos. La influencia de estos depósitos en complicaciones relacionadas con inserciones de DIU, tales como sangrado uterino y embarazo accidental, se discute brevemente en este artículo. El tema deberá ser estudiado en mayor detalle.
    Notes: Abstract Surface deposits on stainless steel contraceptive devices removed from the uterus after varying periods of insertion were examined and analyzed by means of scanning electron microscopy (SEM), X-ray energy dispersive analysis (XEDA), Augar electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and atomic absorption spectrophotometry for microquantitative analysis. The data obtained were compared with the data for copper-bearing IUDs (TCu200) obtained by the same method. The wire coils of stainless steel IUDs which had beenin situ for 5 years showed no obvious changes, but copper wire coils showed varying degrees of erosion after the same period of time. Analysis clearly showed that the wire coils of both types of IUD were encrusted with deposits. Deposition began earlier on copper-bearing IUDs than on stainless steel IUDs (27 days and 3 months after insertion, respectively). This process began earlier than has previously been reported in the literature. The amount of deposit increased with duration of insertion, but there were large individual variations. The microanalysis showed that the principal component of the deposit on both types of IUD was calcium, which was present in the crystal form of calcium carbonate. The substances attaching to the crystals were similar to the nitrogenous organic compounds. We suggest that the mechanism regulating the deposited formation may be similar to that of calculus. The influence of these deposits on complications relating to IUD insertion, such as uterine bleeding and accidental pregnancy, is briefly discussed in this article. The subject should be studied in greater detail.
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  • 7
    ISSN: 1573-2878
    Keywords: Efficient and weakly efficient solution ; Fréchet and Gateaux differentiability ; continuously nested approximations ; Brouwer and Leray-Schauder degrees ; Lebesgue measure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we discuss the optimality conditions for vector optimization problems. Properties of efficient and weakly efficient solutions are studied, and some new necessary conditions are obtained. Most of them are related to the mapping properties of the derivative operatorf′(x) of the objective functionf. Almost all of our results are based on the methods of functional analysis and the theory of degree.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 3233-3242 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents the results of a systematic and extensive investigation of polish-induced surface strain in 〈100〉 and 〈111〉 GaAs and InP using Raman scattering from the longitudinal optical (LO) phonon modes. By using various lines of an Ar-ion laser it was possible to accomplish nondestructive depth profiling. To account for the observed line-shape changes we have used a model which is based on the convolution of the penetration depth of the light and skin depth of the polish-induced surface strain. From such an analysis we have obtained the polish-induced surface strain, skin depth of the strain, and inhomogeneous broadening. For the 〈100〉 surface, the strain is about 2%–3% in both materials and the skin depth (100–500 A(ring)) is relatively independent of particle size. In contrast, for the 〈111〉 surface, the average surface strain is only about 0.6% for GaAs and 1.2% for InP and the skin depth is of the order the particle size. The dependence of the strain skin depth on polish time also has been studied. A qualitative argument based on polish-induced bond breaking is proposed to explain why surface strain for 〈111〉 is considerably less than for 〈100〉 and why the strain is compressive for both surfaces. Using a one-dimensional diffusion model, we can successfully explain the depth dependence of the polish-induced strain and the polish time dependence of the damage skin depth. This analysis yields a diffusion coefficient for the polish-induced strain for the two surfaces. Our diffusion model is consistent with the conventional model of chemomechanical polishing of compound semiconductors.
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