The case for technology in developing regions

Alongside good governance, technology is considered among the greatest enablers for improved quality of life. However, the majority of its benefits have been concentrated in industrialized nations and therefore limited to a fraction of the world's population. We believe that technology has a large role to play in developing regions, that "First World" technology to date has been a poor fit in these areas, and that there is thus a need for technology research for developing regions. Despite the relative infancy of technology studies in developing regions, anecdotal evidence suggests that access to technology has a beneficial economic impact. Cellular telephony is probably the most visible application, but there are many others, some of which we cover in this article. The World Bank's infoDev site catalogs hundreds of information and communications technologies (ICT) projects, albeit not all successful. Most of these projects use existing off-the-shelf technology designed for the industrialized world. Although it is clear that there are large differences in assumptions related to cost, power, and usage, there has been little work on how technology needs in developing regions differ from those of industrialized nations. We argue that Western market forces continue to meet the needs of developing regions accidentally at best.     

3D television: Developing a multi‐modal multi‐viewer TV system of the future

Abstract— Under the European Union funded Advanced Three‐dimensional Television System Technologies (ATTEST) project, De Montfort University (DMU) is developing a 3D display system targeted specifically at domestic television applications. This system uses a modified transmissive LCD panel together with novel backlighting and optics to project multiple viewing regions, or exit pupils, into the viewing space. These exit pupils are located in space using a head tracker. The display accommodates multiple viewers simultaneously and imposes no physical constraints, such as special eyewear. Viewers may move freely over a “typical” room‐sized area. The design of the backlighting facilitates many other display regimes beyond the “standard” 3DTV mode in which each viewer sees the same image pair.     

Online supervisor synthesis for partially observed discrete-eventsystems

A partial information supervisor that generates a class of closed controllable and observable sublanguages of a specified “legal” language is presented. This supervisor has the following features: 1) it can be implemented online (i.e., the disabled event set need only be computed once upon each event observation); 2) the computations of the disabled event set can be performed in O(mn) worst case complexity, where a is the number of states in the legal language generator and m is the number of events; 3) an online supervisor presented previously by Heymann and Lin (1993) is a special case of the new supervisor; and 4) all the languages generated by the new supervisor contain the supremal closed controllable and normal (supCCN) sublanguage of the legal language (in fact, they contain a language developed by Fa et al. (1993) that was shown to contain the supCCN sublanguage)     

Random field finite elements

The probabilistic finite element method (PFEM) is formulated for linear and non-linear continua with inhomogeneous random fields. Analogous to the discretization of the displacement field in finite element methods, the random field is also discretized. The formulation is simplified by transforming the correlated variables to a set of uncorrelated variables through an eigenvalue orthogonalization. Furthermore, it is shown that a reduced set of the uncorrelated variables is sufficient for the second-moment analysis. Based on the linear formulation of the PFEM, the method is then extended to transient analysis in non-linear continua. The accuracy and efficiency of the method is demonstrated by application to a one-dimensional, elastic/plastic wave propagation problem and a two-dimensional plane-stress beam bending problem. The moments calculated compare favourably with those obtained by Monte Carlo simulation. Also, the procedure is amenable to implementation in deterministic FEM based computer programs.     

VLSI systems for band matrix multiplication

We examine several VLSI architectures and compare these for their suitability for various forms of the band matrix multiplication problem. The following architectures are considered: chain, broadcast chain, mesh, broadcast mesh and hexagonally connected. The forms of the matrix multiplication problem that are considered are: band matrix × vector and band matrix × band matrix. Metrics to measure the utilization of resources (bandwidth and processors) are also proposed. An important feature of this paper is the inclusion of correctness proofs. These proofs are provided for selected designs and illustrate how VLSI designs may be proved correct using traditional mathematical tools.     

一种基于平衡微带耦合器的宽功率整流电路

在无线功率传输系统中,接收天线整流电路的传输效率受输入功率、频率及负载变化的影响,为此设计了一种带有平衡微带耦合器的整流电路。仿真结果表明,当输入功率在8~15 dBm范围内时,该电路转换效率超过70%,最高效率为80%;转换效率在频率为2.25~2.61 GHz范围内超过70%;在负载为150~1 600 Ω范围内超过60%。与普通整流电路相比,本文提出的整流电路能够在更宽的输入功率、频带及负载范围实现高效率传输。     

Generation and quenching of intensity pulsations in semiconductor lasers coupled to external cavities

The behavior of self-pulsing and nonpulsing lasers coupled to external cavities is investigated experimentally and theoretically. We investigate the dependence of the pulsation characteristics on the external cavity length using a saturable absorber model for self-pulsing lasers. It was found that quenching of self-pulsation occurs only for a certain limited range of external cavity length, and the frequencies of external-cavity induced pulsations lies within a certain range determined by the coupling coefficient. Small-signal analysis allows these ranges to be derived analytically. Hitherto, complex pulsation phenomena can be explained very intuitively by interpreting the combined laser-external cavity system as a microwave oscillator with a limited gain band and discrete mode structure.     

What is wrong with the existing reliability prediction methods?

Inaccurate reliability predictions could lead to disasters such as in the case of the U.S. Space Shuttle failure. The question is: ‘what is wrong with the existing reliability prediction methods?’ This paper examines the methods for predicting reliability of electronics. Based on information in the literature the measured vs predicted reliability could be as far apart as five to twenty times. Reliability calculated using the five most commonly used handbooks showed that there could be a 100 times variation. The root cause for the prediction inaccuracy is that many of the first-order effect factors are not explicitly included in the prediction methods. These factors include thermal cycling, temperature change rate, mechanical shock, vibration, power on/off, supplier quality difference, reliability improvement with respect to calendar years and ageing. As indicated in the data provided in this paper any one of these factors neglected could cause a variation in the predicted reliability by several times. The reliability vs ageing-hour curve showed that there was a 10 times change in reliability from 1000 ageing-hours to 10,000 ageing-hours. Therefore, in order to increase the accuracy of reliability prediction the factors must be incorporated into the prediction methods.