Adapting ADtrees for improved performance on large datasets with high-arity features

The ADtree, a data structure useful for caching sufficient statistics, has been successfully adapted to grow lazily when memory is limited and to update sequentially with an incrementally updated dataset. However, even these modified forms of the ADtree still exhibit inefficiencies in terms of both space usage and query time, particularly on datasets with very high dimensionality and with high-arity features. We propose four modifications to the ADtree, each of which can be used to improve size and query time under specific types of datasets and features. These modifications also provide an increased ability to precisely control how an ADtree is built and to tune its size given external memory or speed requirements.     

Silicon-on-Insulator Spectral Filters Fabricated With CMOS Technology

We give an overview of recent progress in passive spectral filters and demultiplexers based on silicon-on-insulator photonic wire waveguides: ring resonators, interferometers, arrayed waveguide gratings, and echelle diffraction gratings, all benefit from the high-index contrast possible with silicon photonics. We show how the current generation of devices has improved crosstalk levels, insertion loss, and uniformity due to an improved fabrication process based on 193 nm lithography.      

Evaluating expectations about negative emotional states of aggressive boys using Bayesian model selection.

Researchers often have expectations about the research outcomes in regard to inequality constraints between, e.g., group means. Consider the example of researchers who investigated the effects of inducing a negative emotional state in aggressive boys. It was expected that highly aggressive boys would, on average, score higher on aggressive responses toward other peers than moderately aggressive boys, who would in turn score higher than nonaggressive boys. In most cases, null hypothesis testing is used to evaluate such hypotheses. We show, however, that hypotheses formulated using inequality constraints between the group means are generally not evaluated properly. The wrong hypotheses are tested, i.e.. the null hypothesis that group means are equal. In this article, we propose an innovative solution to these above-mentioned issues using Bayesian model selection, which we illustrate using a case study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exact solutions to the modified 2D Burgers vortex equation: a general result for the unsteady case

Exact solutions to the unsteady modified 2D Burgers vortex equation are obtained for arbitrary forms of the flow parameter γ(t) via Fourier analysis. The result extends the available literature, where only very specific forms of the flow parameter γ(t) have been considered in the unsteady flow cases. One strength of the method is that we need not assume separable solutions.     

Zirconia-modified exfoliated graphite

Zirconia has been incorporated into exfoliated graphite (EG) through the anodic polarization in the natural graphite-ZrO(NO₃)₂-HNO₃-H₂O system, followed by flash heating. The thermal properties of the oxidized graphites employed as precursors to EG have been studied by thermogravimetry in combination with differential scanning calorimetry, and the distribution of ZrO₂ particles in the EG has been assessed by scanning and transmission electron microscopy. Conditions are described for the preparation of EG with bulk densities in the range 1.3–4.7 g/l and ZrO₂ contents in the range 4–34 wt %.     

Variational density matrix optimization using semidefinite programming

We discuss how semidefinite programming can be used to determine the second-order density matrix directly through a variational optimization. We show how the problem of characterizing a physical or N-representable density matrix leads to matrix-positivity constraints on the density matrix. We then formulate this in a standard semidefinite programming form, after which two interior point methods are discussed to solve the SDP. As an example we show the results of an application of the method on the isoelectronic series of Beryllium.     

A Revised Criterion for the Portevin–Le Chatelier Effect Based on the Strain-Rate Sensitivity of the Work-Hardening Rate

An improved analysis is presented of the stability of plastic deformation under conditions where dynamic strain aging (DSA) occurs, which leads to instabilities known as the Portevin–Le Chatelier (PLC) effect. It is shown that PLC instabilities can occur for conditions that are not covered by the currently prevailing criterion presented by Estrin and Kubin (1991), which focuses on a negative strain rate sensitivity of the flow stress, caused by interactions of solutes with thermally activated glide of mobile dislocations. The current analysis recognizes that the strain-rate sensitivity of the flow stress consists of two contributions, one associated with glide of mobile dislocations and the second with work hardening, related to storage of immobile dislocations. In this paper, an instability criterion is proposed that takes into account the possibility of a negative strain-rate sensitivity of the work-hardening rate, which is caused by diffusion of solutes to immobile dislocations. The latter contribution leads to an extended instability criterion. This criterion also provides an explanation for the existence of a critical strain above which instabilities occur. In this article, previously published tensile test data are used to show that a negative strain-rate sensitivity of the work-hardening rate, which influences significantly the occurrence of the PLC effect, can indeed occur under DSA conditions.     

A no-tension elastic–plastic model and optimized back-analysis technique for modeling nonlinear mechanical behavior of rock mass in tunneling

In this paper, we present a no-tension elastic–plastic model and an optimized back-analysis technique for stability analysis of underground tunnels. A set of constitutive equations is presented to simulate the no-tension behavior and plastic yielding of jointed rock masses which yield according to the Drucker–Prager yield criterion and permits no-tension. A nonlinear 2-D finite element model is consequently formulated for the prediction of the behavior of the excavated rock mass. As for the model parameters, the genetic algorithm technique is employed to find the optimal rock mass properties by minimizing the discrepancy between the predicted results and field measurement. The nonlinear finite element model coupling with the genetic algorithm optimized back-analysis technique is then applied to a synthetic example of a deep tunnel in yielding rock. The results show that the forward and back-analysis system is capable of estimating the model parameters with stable and good convergence and give reasonable predictions. Numerical experiments are also carried out to check the influences of position and numbers of measurements to the reliability of the back-analysis results. Furthermore, the sensitivity analysis of the genetic algorithms optimization procedure is discussed in terms of identification of geo-material properties.     

照明的明天：什么是热点

从社会、产品和应用的角度,举例说明未来数年照明的＂热点＂。从社会的角度,说明可持续发展以及相关节能产品和应用设计的持续重要性。要更加关注完全无废料的设计,即＂从摇篮到摇篮＂（from cradle to cradle）的设计。从产品的角度,说明固态将成为许多产品应用的标准。在固态照明方面,由于所提供的数据常常有误而令新用户不满,因此向固态照明转变的脚步会放缓。若有效控制固态照明中的眩光,须有新型的光学设计。目前的评价体系,是通过经验方法获得,完全不适用于固态照明环境,因此需要全新的眩光评价体系。普通室内照明的显色性和色表规格,过去以白炽灯为基准,现在须设定严格的新标准。在应用方面,若要达到非视觉生物效应,智能动态照明也要成为一种标准。我们将看到,为减少因生物钟失调而出现的问题,会广泛应用光学治疗。在固定路灯方面,随着汽车系统本身的发展,不会再优先考虑物体的能见度。我们需要的不再是路灯亮度概念,而是更加三维的概念。若综合考虑中间视觉的所有效果,路灯光源的最有效光谱应该偏暖白光。老年人会丧失短波长视觉能力,是其中的主要原因。     

Spacer defined FinFET: Active area patterning of sub-20 nm fins with high density

We present a method to obtain Si-fins with a critical dimension (CD) below 20 nm, separated by a minimum distance of 25 nm and connected by a common source/drain (S/D) pad. The method comprises of recursive spacer defined patterning to quadruple the line density of a 350 nm pitch resist pattern defined by 193 nm lithography. Spacer defined patterning is combined with resist based patterning to simultaneously define fins and S/D pads in a Silicon on Insulator (SOI) film. CD and Line Width Roughness (LWR) analysis was done on top down SEM images taken in a center die and in an edge die of a 200 mm wafer. The average CD is 17 nm in the center of the wafer and 18 nm at the edge. The LWR is 3 nm for both center and edge. Additional process steps to remove etch damage and round the top corner of the fin (i.e. oxidation followed by H₂ anneal) further reduce the CD to 13 nm.