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1.
OH– and OD– defects are known to form rotational tunneling systems in KCl host crystals. We have studied the complex dielectric susceptibility of KCl doped with different concentrations of OH– and OD– in a wide range of frequencies and temperatures. Our main result is that there is a transition from coherent single ion tunneling at low defect concentration to an incoherent tunneling motion at high defect concentrations. In addition, we have studied the thermally activated motion of pairwise coupled hydroxide ions in an attempt to obtain information on the microscopic configurations of the different pairs contributing to the dielectric loss. PACS numbers: 61.72.Ji, 77.22-d, 78.30.Ly 相似文献
2.
We present an algorithmic approach to the design of low-power frequency-selective digital filters based on the concepts of adaptive filtering and approximate processing. The proposed approach uses a feedback mechanism in conjunction with well-known implementation structures for finite impulse response (FIR) and infinite impulse response (IIR) digital filters. Our algorithm is designed to reduce the total switched capacitance by dynamically varying the filter order based on signal statistics. A factor of 10 reduction in power consumption over fixed-order filters is demonstrated for the filtering of speech signals 相似文献
3.
The sodium dodecylsulphate (SDS) binding capacities of secalin, gliadin and gluten in the presence of a very low SDS concentration were determined and compared to the SDS binding capacities of bovine serum albumin (BSA), beta-lactoglobulin, ovalbumin und beta-casein. The SDS binding capacities of endosperm proteins determined in phosphate buffer (pH 6.0) are very low. Only 0.6 microgram .. 0.8 microgram SDS were bound to 500 micrograms of the proteins. This low SDS binding capacities do not correlate with the expected hydrophobicity of these proteins. In comparison, 500 micrograms of ovalbumin, beta-lactoglobulin and BSA each bind 0.5, 5.9 and 13.5 micrograms SDS, respectively. According to literature the SDS binding capacities of these proteins are in correlation with the surface hydrophobicity determined with cis-parinaric acid using the fluorescence probe method. The SDS binding capacities of endosperm proteins increased in the presence of 0.1 N acetic acid and consequently 6.2 micrograms .. 6.9 micrograms SDS were bound to 500 micrograms of the corresponding proteins. beta-casein described as a highly hydrophobic protein binds only 0.9 micrograms SDS to 500 micrograms of it in phosphate puffer (pH 6.0) and 1.2 micrograms SDS in 0.1 N acetic acid, respectively. 相似文献
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In order to overcome the limitations of previous columnar-to-equiaxed (CET) models, which neglect melt convection and the
movement of free equiaxed grains, this article presents a three-phase deterministic CET model. With appropriated multiphase
volume-averaging approaches, it is possible to account for nucleation and growth of equiaxed grains ahead of a growing columnar
front, the influence of melt convection, and grain sedimentation, and the occurrence of a CET in a casting of engineering
scale. Special modeling assumptions ensure that both CET mechanisms, namely, “hard” and “soft” blocking, are tackled. It is
highly recommended that both mechanisms should be considered, especially in the situation where grain sedimentation and melt
convection are present. Although the current model incorporates almost all the physical variables relevant to a CET event,
under special condition of a one-dimensional case, the model still reproduces the results of Hunt’s classical CET approach.
This article is based on a presentation made in the symposium entitled “Solidification Modeling and Microstructure Formation:
In Honor of Prof. John Hunt,” which occurred March 13–15, 2006, during the TMS Spring Meeting in San Antonio, Texas, under
the auspices of the TMS Materials Processing and Manufacturing Division, Solidification Committee. 相似文献
8.
Semiconductor laser amplifier as optical switching gate 总被引:3,自引:0,他引:3
Ehrhardt A. Eiselt M. Grossopf G. Kuller L. Ludwig R. Pieper W. Schnabel R. Weber H.G. 《Lightwave Technology, Journal of》1993,11(8):1287-1295
The properties of a semiconductor laser amplifier as optical switching gate are investigated. Particular attention is paid to gain, contrast ratio, and switching time of the device. These properties are studied experimentally and theoretically with respect to the injection current, optical input power, and cavity resonances. The experimental arrangements and the theoretical method are described. As an example of the various applications of semiconductor laser amplifier gates, packet switching experiments with self-routing, employing cascaded switching gates, are reported. In a theoretical analysis the restrictions that the properties of semiconductor laser amplifier gates impose on a larger switching system consisting of many such gates are investigated 相似文献
9.
Reinhold Ludwig Sergey Makarov Diran Apelian 《Journal of Nondestructive Evaluation》1998,17(3):153-166
This paper investigates electrostatic voltage distributions around a surface-breaking flaw due to an injected current of known
strength. The direct 3-D solution of the voltage behavior over the flawed surface is obtained numerically by the use of a
boundary integral formulation. A novel iteration method is applied to solve the resulting electrostatic integral equation
for the unknown surface voltage distribution. In addition to investigating the sensitivity of different flaw sizes to the
observed surface voltage distribution, important issues such as suitable probe spacing and current flow orientation are studied.
For sufficiently small surface-breaking flaws, a simple image source model is developed to evaluate the voltage response of
hairline cracks. The model is tested by comparing it with the developed numerical solution. Experiments aimed at establishing
the validity of the modeling approach show remarkable agreement with the theoretical model. 相似文献
10.
Linas Baltrunas Bernd Ludwig Stefan Peer Francesco Ricci 《Personal and Ubiquitous Computing》2012,16(5):507-526
In order to generate relevant recommendations, a context-aware recommender system (CARS) not only makes use of user preferences, but also exploits information about the specific contextual situation in which the recommended item will be consumed. For instance, when recommending a holiday destination, a CARS could take into account whether the trip will happen in summer or winter. It is unclear, however, which contextual factors are important and to which degree they influence user ratings. A large amount of data and complex context-aware predictive models must be exploited to understand these relationships. In this paper, we take a new approach for assessing and modeling the relationship between contextual factors and item ratings. Rather than using the traditional approach to data collection, where recommendations are rated with respect to real situations as participants go about their lives as normal, we simulate contextual situations to more easily capture data regarding how the context influences user ratings. To this end, we have designed a methodology whereby users are asked to judge whether a contextual factor (e.g., season) influences the rating given a certain contextual condition (e.g., season is summer). Based on the analyses of these data, we built a context-aware mobile recommender system that utilizes the contextual factors shown to be important. In a subsequent user evaluation, this system was preferred to a similar variant that did not exploit contextual information. 相似文献