Über kapazitive Leitfähigkeit

Zusammenfassung Es zeigt sich, daß jeder Kondensator beim Anlegen einer elektrischen Spannung sich dieser gegenüber wie ein metallischer Leiter verhält, dessen Leitfähigkeit von der Kapazität, der Spannung und der zeitlichen Änderung beider Größen abhängt. Nach Ableitung eines allgemeinen Ausdruckes für die kapazitive Leitfähigkeit werden einige sich daraus ergebende Sonderfälle diskutiert. Im zweiten Teil der Arbeit wird die umgekehrte Problemstellung betrachtet.     

Robust adaptive beamforming for general-rank signal models

The performance of adaptive beamforming methods is known to degrade severely in the presence of even small mismatches between the actual and presumed array responses to the desired signal. Such mismatches may frequently occur in practical situations because of violation of underlying assumptions on the environment, sources, or sensor array. This is especially true when the desired signal components are present in the beamformer "training" data snapshots because in this case, the adaptive array performance is very sensitive to array and model imperfections. The similar phenomenon of performance degradation can occur even when the array response to the desired signal is known exactly, but the training sample size is small. We propose a new powerful approach to robust adaptive beamforming in the presence of unknown arbitrary-type mismatches of the desired signal array response. Our approach is developed for the most general case of an arbitrary dimension of the desired signal subspace and is applicable to both the rank-one (point source) and higher rank (scattered source/fluctuating wavefront) desired signal models. The proposed robust adaptive beamformers are based on explicit modeling of uncertainties in the desired signal array response and data covariance matrix as well as worst-case performance optimization. Simple closed-form solutions to the considered robust adaptive beamforming problems are derived. Our new beamformers have a computational complexity comparable with that of the traditional adaptive beamforming algorithms, while, at the same time, offer a significantly improved robustness and faster convergence rates.     

Basic processes in reading: Computation of abstract letter identities.

A speeded classification experiment examined the hypothesis that an early processing stage in reading involves the computation of abstract letter identities. When 20 undergraduates were asked to base their classification on physical criteria, letter strings that differed in case but shared the same letter identities (e.g., HILE/hile) were classified as "different" less efficiently than strings with a common phonological code but different spelling (e.g., HILE/hyle). Letter strings with a common phonological code but different spelling were classified as efficiently as letter strings without a common phonological code (e.g., HILE/hule). Results of the present experiment, along with other experimental findings and some neuropsychological observations, provide converging evidence for a representation and comparison process that is neither visual nor phonological but is based on abstract letter identities. It is suggested that the computation of abstract letter identities is a precursor to lexical access during reading. Implications for the interpretation of certain developmental reading difficulties are noted. (French abstract) (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A computer tool to support in design of industrial Ethernet

This paper presents a computer tool to support in the project and development of an industrial Ethernet network, verifying the physical layer (cables-resistance and capacitance, scan time, network power supply-POE’s concept ”Power Over Ethernet” and wireless), and occupation rate (amount of information transmitted to the network versus the controller network scan time). These functions are accomplished without a single physical element installed in the network, using only simulation. The computer tool has a software that presents a detailed vision of the network to the user, besides showing some possible problems in the network, and having an extremely friendly environment.     

The costs and benefits of undoing egocentric responsibility assessments in groups.

Individuals working in groups often egocentrically believe they have contributed more of the total work than is logically possible. Actively considering others' contributions effectively reduces these egocentric assessments, but this research suggests that undoing egocentric biases in groups may have some unexpected costs. Four experiments demonstrate that members who contributed much to the group outcome are actually less satisfied and less interested in future collaborations after considering others' contributions compared with those who contributed little. This was especially true in cooperative groups. Egocentric biases in responsibility allocation can create conflict, but this research suggests that undoing these biases can have some unfortunate consequences. Some members who look beyond their own perspective may not like what they see. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-fulfilling prophecy effects of mothers' beliefs on children's alcohol use: Accumulation, dissipation, and stability over time.

This research examined whether self-fulfilling prophecy effects accumulated, dissipated, or remained stable over time in terms of 2 complementary conceptual models. Analyses of longitudinal data from 2 samples of mother-child dyads (N?=487; N?=288) yielded 3 main findings. First, the degree to which mothers' inaccurate beliefs assessed at a single point in time predicted children's distal alcohol use did not differ from the degree to which they predicted children's proximal alcohol use, thereby supporting a pattern of stability for the samples on average. Second, mothers' inaccurate beliefs repeatedly assessed across time had additive self-fulfilling effects on their children's subsequent alcohol use assessed at a single later point in time. Third, these additive self-fulfilling effects served to exacerbate differences in the alcohol use of children who had been consistently exposed to unfavorable versus favorable beliefs year after year. The authors discuss these findings in terms of the link between self-fulfilling prophecies and social problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developing a More Rapid Test to Assess Sulfate Resistance of Hydraulic Cements

External sulfate attack of concrete is a major problem that can appear in regions where concrete is exposed to soil or water containing sulfates, leading to softening and cracking of the concrete. Therefore, it is important that materials selection and proportioning of concrete in susceptible regions be carefully considered to resist sulfate attack. American Society for Testing Materials (ASTM) limits the tricalcium aluminate phase in cements when sulfate exposure is of concern. The hydration products of tricalcium aluminate react with the sulfates resulting in expansion and cracking. While ASTM standard tests are available to determine the susceptibility of cements to sulfate attack, these tests require at least 6 months and often up to a year to perform; a delay that hinders development of new cements. This paper presents a new method for testing cement resistance to sulfate attack that is three to five times faster than the current ASTM tests. Development of the procedure was based upon insights on the degradation process by petrographic examination of sulfate-exposed specimens over time. Also key to the development was the use of smaller samples and tighter environmental control.     

A segmentation-based regularization term for image deconvolution.

This paper proposes a new and original inhomogeneous restoration (deconvolution) model under the Bayesian framework for observed images degraded by space-invariant blur and additive Gaussian noise. In this model, regularization is achieved during the iterative restoration process with a segmentation-based a priori term. This adaptive edge-preserving regularization term applies a local smoothness constraint to pre-estimated constant-valued regions of the target image. These constant-valued regions (the segmentation map) of the target image are obtained from a preliminary Wiener deconvolution estimate. In order to estimate reliable segmentation maps, we have also adopted a Bayesian Markovian framework in which the regularized segmentations are estimated in the maximum a posteriori (MAP) sense with the joint use of local Potts prior and appropriate Gaussian conditional luminance distributions. In order to make these segmentations unsupervised, these likelihood distributions are estimated in the maximum likelihood sense. To compute the MAP estimate associated to the restoration, we use a simple steepest descent procedure resulting in an efficient iterative process converging to a globally optimal restoration. The experiments reported in this paper demonstrate that the discussed method performs competitively and sometimes better than the best existing state-of-the-art methods in benchmark tests.