A Mixed-Signal Approach Towards Linear and Efficient N-Way Doherty Amplifiers

A mixed-signal approach for the design and testing of high-performance N-way Doherty amplifiers is introduced. In support of this, an analysis of N-way power-combining networks is presented-in particular, their optimum design-by examining the relationship between the drive conditions of the active devices and input power. This analysis makes no prior assumption on the network topology and facilitates free-to-choose levels for the high-efficiency power back-off points. By comparing the results of this analysis with prior work, it is shown that very specific drive conditions apply to traditional three-way Doherty amplifier implementations to obtain simultaneously high-efficiency and high-linearity operation. To support these conclusions, a 15-W three-way Doherty amplifier was constructed using Philips GEN4 LDMOS devices featuring three separate inputs to independently drive the main and peaking devices. By testing this three-way amplifier with a custom-built measurement setup, capable of providing multiple digitally controlled coherent RF input signals with high spectral purity, a unique flexible amplifier concept is created resulting in a record-high efficiency for LDMOS-based Doherty amplifiers over a 12-dB back-off power range     

A survey on resource allocation in high performance distributed computing systems

An efficient resource allocation is a fundamental requirement in high performance computing (HPC) systems. Many projects are dedicated to large-scale distributed computing systems that have designed and developed resource allocation mechanisms with a variety of architectures and services. In our study, through analysis, a comprehensive survey for describing resource allocation in various HPCs is reported. The aim of the work is to aggregate under a joint framework, the existing solutions for HPC to provide a thorough analysis and characteristics of the resource management and allocation strategies. Resource allocation mechanisms and strategies play a vital role towards the performance improvement of all the HPCs classifications. Therefore, a comprehensive discussion of widely used resource allocation strategies deployed in HPC environment is required, which is one of the motivations of this survey. Moreover, we have classified the HPC systems into three broad categories, namely: (a) cluster, (b) grid, and (c) cloud systems and define the characteristics of each class by extracting sets of common attributes. All of the aforementioned systems are cataloged into pure software and hybrid/hardware solutions. The system classification is used to identify approaches followed by the implementation of existing resource allocation strategies that are widely presented in the literature.     

E-government and IT policy: Choices for government outreach and policy making

The conventional method for criminal investigation and trial of cases in the law courts in developing countries is usually slow. Consequently, the society is characterized by prolonged periods of detention of the suspects awaiting trial and congestion in the prisons and law courts. This paper attempts to describe the application of Artificial Intelligence (AI) in the investigation of crime. An Expert System (ES) is proposed which supports the storage and intelligent interactive processing of the knowledge acquired by study and experience of the human expert in the domain of criminal investigation, law and justice. One of the objectives of the study is to provide an intelligent computer‐based system which will enhance the efficient performance of the human expert in the domain of criminal investigation. The other objective is to provide a system for computer aided learning of criminal investigation.     

Assessing the effects of information and communication technologies on development

The idea of information and communication technology (ICT) being a “hammer” that can be applied to a wide variety of “nails” across different geographic locations, sectors, organizations, and contexts to improve efficiency and/or have a beneficial social impact has come under severe criticism, particularly in the realm of implementing socioeconomic development programs. Structuration theory remains one of the key metatheories that deconstruct the complexity of technology introductions in the context of organizational and behavioral change. In this study, we use a structurational lens to examine two pilot ICT implementations in the Indian microfinance sector, specifically exploring the interactions between the ICT intervention, the organizations and people implementing the change, and the structural and institutional context within which these projects were rolled out. We showcase how an “ICT for development” intervention is inherently a political process, involving choices around defining efficiency and targeting particular social welfare improvements, with varying repercussions for the involved microfinance institution and client. Where the client's context, constraints, and welfare are placed at the heart of the “efficiency” discussion during the technology's design and implementation, the development impact is seen to be far greater and more sustained. © 2009 Wiley Periodicals, Inc.     

Information systems as social systems: Implications for developing countries

Abstract

Computer‐based information systems should be conceptualised as social systems in which technology is only one of the dimensions. This broader perspective on information systems offers opportunities for a deeper understanding of their development and use. The social systems approach is illustrated in the paper by two research projects in the UK on the evaluation of information systems and information systems strategy formulation. The relevance of the UK research to a developing country context is discussed and it is argued that methodologies which aim to provide an understanding of the organisational, social and political context are highly suitable for organisations in developing countries. Some implications are drawn for research, education and practice related to information systems in developing countries.     

Statistical modeling of crack growth and reliability assessment of high-density polyethylene

In this work, a statistical evaluation of the crack-growth process in high-density polyethylene (HDPE) was carried out. The specimens were compression molded from virgin, molding-grade HDPE. Edgenotched specimens for replicate fatigue testing were prepared from compression-molded sheets. Fatigue test results were then analyzed, and it is shown that if the crack-growth process can be characterized as a random process following a power-law-type behavior, then the time to reach a critical crack length will be distributed according to an inverted lognormal model.     

New scale invariant template matching technique using hyper space image representation

A new approach for the template image matching is being presented. The method first converts the image into edges, then, the vital information of these edges has been presented as a set of vectors in a four dimensional hyper-space. A modified Radon Transform has been proposed to facilitate this vectorization process. All the above processing is being done offline for the main image of the area. The template image has also been vectorized in a same fashion in real time which is to be matched with the main image. A vector matching algorithm has been proposed to deliver match location with a very low computational cost. It works for a wide range of template scaling and noise conditions which were not there in the previous algorithms found in the literature.     

Acute upper limb ischemia resulting from cleidocranial dysostosis

A case is reported of a woman with an ischemic arm as a result of damage to the subclavian artery by the clavicular anomaly associated with cleidocranial dysostasis. Only one similar case has been reported previously.