SDR走向军用领域

JTRS正致力于将可互换SDR(软件无线电)带入军用领域。但SDR对商业应用是否也是足够好的选择呢?SDR(软件无线电)并不是一种新技术。过去业界就已经尝试实现SDR,但都没有达到目标。最近激发起对SDR兴趣的是创新性软硬件技术的出现,这些技术能够以市场可承受的价格提供足够的灵活性、性能和功率效率。例如,宽带变换器现在可以工作在宽频率范围内,根据一种特定的位分辨率处理接收到的波形,而高频处理器可以直接与信号工作,从而省掉IF(中频)级,并降低成本。     

Scalar network analysers operating at Ka- and W-bands

Scalar network analysers measuring the amplitude of the reflection/transmission coefficients of waveguide structures have been realised at Ka- and W-bands. Their accuracy derived by using standard mismatches is excellent at Ka- band and fairly good at W-band. To our knowledge this is the first instance where the accuracy of measurements obtained from a scalar network analyser was checked over full waveguide bands with the aid of standard mismatches. The reported reflectometers are precursors of vector network analysers based on six-port reflectometers. Methods aimed at increasing the signal-to-noise ratio (SNR) of the measurements have been developed, while proposals for improving the dynamic range of these network analysers are put forward.     

PAC-learnability of probabilistic deterministic finite state automata in terms of variation distance

We consider the problem of PAC-learning distributions over strings, represented by probabilistic deterministic finite automata (PDFAs). PDFAs are a probabilistic model for the generation of strings of symbols, that have been used in the context of speech and handwriting recognition, and bioinformatics. Recent work on learning PDFAs from random examples has used the KL-divergence as the error measure; here we use the variation distance. We build on recent work by Clark and Thollard, and show that the use of the variation distance allows simplifications to be made to the algorithms, and also a strengthening of the results; in particular that using the variation distance, we obtain polynomial sample size bounds that are independent of the expected length of strings.     

Moving on and moving up: The experience of households who resell public sector dwellings

The long‐term consequences of the sale of public sector dwellings to sitting tenants are under‐researched; in particular, the experience of tenant purchasers in the housing market subsequent to purchase is little known. This paper reports research designed to fill this gap in knowledge. Over 200 tenants who had bought their dwelling from the Scottish Special Housing Association and subsequently resold on the open market were traced using the Register fo Sasines and the Land Register and interviewed. Most had made considerable capital gains on resale and had used some of the realised capital to trade up in the housing market. They were, on average, slightly more affluent and younger than sitting tenant purchasers generally; they represented a group of households who were privileged within the public sector through living as tenants in the best stock and who were enabled by the Right to Buy to convert that good luck into hard cash and move into mainstream owner occupation. This good luck compounded the advantaged position vis‐à‐vis other tenants that they enjoyed in the labour market.     

Impact of managed care on employment and training: A primer for survival.

Managed care has become the dominant economic force in health care delivery and has challenged many of professional psychology's training concepts and cherished attitudes. Organized psychology has not kept pace with the rapid industrialization of health care during the past decade and has been overlooked as a participant in health economic decisions. A number of changes need to be made in professional education and training if psychology is to be a major player in the new health systems. Additionally, professional psychologists must reexamine some of their most generally accepted attitudes and beliefs if they are to survive. These are described with a number of recommendations for the survival of an embattled profession. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An inverse method for determining elastic material properties and a material interface

A numerical procedure which integrates optimization, finite element analysis and automatic finite element mesh generation is developed for solving a two-dimensional inverse/parameter estimation problem in solid mechanics. The problem consists of determining the location and size of a circular inclusion in a finite matrix and the elastic material properties of the inclusion and the matrix. Traction and displacement boundary conditions sufficient for solving a direct problem are applied to the boundary of the domain. In addition, displacements are measured at discrete points on the part of the boundary where the tractions are prescribed. The inverse problem is solved using a modified Levenberg-Marquardt method to match the measured displacements to a finite element model solution which depends on the unknown parameters. Numerical experiments are presented to show how different factors in the problem and the solution procedure influence the accuracy of the estimated parameters.     

The Social Risk Hypothesis of Depressed Mood: Evolutionary, Psychosocial, and Neurobiological Perspectives.

The authors hypothesize that depressed states evolved to minimize risk in social interactions in which individuals perceive that the ratio of their social value to others, and their social burden on others, is at a critically low level. When this ratio reaches a point where social value and social burden are approaching equivalence, the individual is in danger of exclusion from social contexts that, over the course of evolution, have been critical to fitness. Many features of depressed states can be understood in relation to mechanisms that reduce social risk in such circumstances, including (a) hyper-sensitivity to signals of social threat from others, (b) sending signals to others that reduce social risks, and (c) inhibiting risk-seeking (e.g., confident, acquisitive) behaviors. These features are discussed in terms of psychosocial and neurobiological research on depressive phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multiple identity enactments and multiple personality disorder: A sociocognitive perspective.

People who enact multiple identities behave as if they possess 2 or more selves, each with its own characteristic moods, memories, and behavioral repertoire. Under different names, this phenomenon occurs in many cultures; in North American culture, it is frequently labeled multiple personality disorder (MPD). This article reviews experimental, cross-cultural, historical, and clinical findings concerning multiplicity and examines the implications of these findings for an understanding of MPD. Multiplicity is viewed from a sociocognitive perspective, and it is concluded that MPD, like other forms of multiplicity, is socially constructed. It is context bounded, goal-directed, social behavior geared to the expectations of significant others, and its characteristics have changed over time to meet changing expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)