A generalized Lloyd-type algorithm for adaptive transform coder design

In this paper, we establish a probabilistic framework for adaptive transform coding that leads to a generalized Lloyd type algorithm for transform coder design. Transform coders are often constructed by concatenating an ad hoc choice of transform with suboptimal bit allocation and quantizer design. Instead, we start from a probabilistic latent variable model in the form of a mixture of constrained Gaussian mixtures. From this model, we derive an transform coder design algorithm, which integrates optimization of all transform coder parameters. An essential part this algorithm is our introduction of a new transform basis-the coding optimal transform-which, unlike commonly used transforms, minimizes compression distortion. Adaptive transform coders can be effective for compressing databases of related imagery since the high overhead associated with these coders can be amortized over the entire database. For this work, we performed compression experiments on a database of synthetic aperture radar images. Our results show that adaptive coders improve compressed signal-to-noise ratio (SNR) by approximately 0.5 dB compared with global coders. Coders that incorporated the coding optimal transform had the best SNRs on the images used to develop the coder. However, coders that incorporated the discrete cosine transform generalized better to new images.     

集成产品数据管理软件PDM Works

当主流立体建模软件在上个世纪90年代中期面世的时候,它显著提高了时间和成本的效率,使得工程师工作效率更高.以前总是埋头在2D设计图中的设计团队现在能够在几个小时内完成设计,而且点击几下鼠标就能完成修改.更好的视图让他们能够从一开始就正确地设计一个产品,最大限度减少了后期装配的问题.他们还可以自动创建设计图,并且重复利用以前的设计,缩短新产品的设计时间.     

Fully automated on-wafer noise characterization of GaAs MESFETs andHEMTs

A technique is described that permits the rapid determination of all four noise parameters of a MESFET or HEMT at wafer level. The fully automated procedure, which has been implemented in the 2-8 GHz range, uses 16 accurately measured, very repeatable source impedance standards. The standards have been selected for optimum coverage of the input impedance plane to result in stable and rapidly convergent least-squares solutions for the minimum noise figure, optimum source impedance, and noise resistance of practical devices. The resultant system is very stable and produces accurate noise parameters for a wide range of devices     

Mercury diffusion in Hg1−xCdxTe

A radiotracer technique has been used to measure both mercury self-diffusion and surface concentration values in bulk and liquid phase epitaxy, LPE, grown Hg_1−xCd_xTe. A high resolution sectioning technique has allowed profiling of thin epitaxial layers in submicron steps. Hg_1-xCd_xTe samples with composition values betweenx _Cd= 0.16 and 0.23 were isothermally annealed in carefully controlled and monitored diffusion con-ditions. Mercury reservoirs containing Hg²⁰³ were used to provide vapour diffusion sources during closed tube isothermal anneals in the temperature range 300° C to 400° C. Evidence has been found which may indicate the presence of two components in the radio-tracer profiles for both bulk and epitaxially grown material. In some cases it was possible to estimate two diffusion coefficients,D ₁andD ₂, from the near surface and deeply penetrating components, respectively. Our results forD ₁andD ₂are compared with other work. For bulk material annealed at 400° C under a saturated mercury pressureD ₁= 2.0 x 10^-12cm²s^-1 andD ₂= 1.1 x 10^-11cm²s⁻¹. Diffusion coefficients at 310° C under saturated mercury pressure, have been measured in bulk and epitaxial material. Close agreement was found between these results with an average value ofD ₁= 1.4 x 10⁻¹³cm²s⁻¹. We believe this to be the first time radiotracer results for epitaxial material have been presented. We have collated diffusion data, as a function of reciprocal temperature, from several workers and suggest there is evidence for a change in the activation energy for mercury diffusion around 350° C. This may be due to a change in the dominant diffusion mechanism.     

Making research apply: High stakes public policy in a regulatory environment.

The experiences of 3 social psychologists asked to evaluate (and improve) a series of large-scale programs designed to change energy-related attitudes and behavior are described. The research generated significant change but also substantial conflict involving both the utility companies being evaluated and the state agency that commissioned the evaluation. This experience is reviewed with an eye to maximizing the usefulness of future efforts to apply social psychology in complex and potentially conflicted public policy arenas. The difference between influence and power models of applied research is discussed, and possible remedies are examined for social psychologists undertaking future research similar in scale, policy consequences, or potential controversy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Variability among males in sexually selected attributes.

Greater male than female variability is found in behavioral and morphological traits in animals. A theory that greater male variability is associated with variability in parental investment is described and contrasted with sexual strategies theory, which posits no sex differences in variability. Predictions from the theories were tested through meta-analyses of variance ratios for data sets involving sexually selected characteristics analyses (physical aggression and 5 aspects of mate choice) and 2 unlikely to have resulted from sexual selection (anger and self-esteem). Variation was significantly greater among men than women in 5 of the 6 former data sets and was similar for men and women in the latter 2 data sets, broadly supporting the predictions. A further analysis extends the theory to intellectual abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Direct measurement of base drift field in bipolar transistors

The authors have developed a method to measure an effective base drift field and the base transit-time reduction factor of bipolar transistors, by measuring the excess phase of the base transport factor. This technique relies on measuring small-signal characteristics of the transistor at a low frequency and following the phase of the transconductance at the frequency approaching and exceeding the unit current gain frequency (f_T). With this technique, the authors verify that the effective drift inside the base of Si bipolar transistors decreases with increased base implantation energy and thermal treatment. Such directly measured drift-dependent base transport provides additional insight for optimizing processing used in bipolar technology development     

On some Bayesian/regularization methods for image restoration

Methods are reviewed for choosing regularized restorations in image processing. In particular, a method developed by Galatsanos and Katsaggelos (see ibid., vol.1, p.322-336, 1992) is given a Bayesian interpretation and is compared with other Bayesian and non-Bayesian alternatives. A small illustrative example is provided and a complement is provided for the discussion of noise variance estimation of Galatsanos et al.