A network-aware framework for energy-efficient data acquisition in wireless sensor networks

Wireless sensor networks enable users to monitor the physical world at an extremely high fidelity. In order to collect the data generated by these tiny-scale devices, the data management community has proposed the utilization of declarative data-acquisition frameworks. While these frameworks have facilitated the energy-efficient retrieval of data from the physical environment, they were agnostic of the underlying network topology and also did not support advanced query processing semantics. In this paper we present KSpot+, a distributed network-aware framework that optimizes network efficiency by combining three components: (i) the tree balancing module, which balances the workload of each sensor node by constructing efficient network topologies; (ii) the workload balancing module, which minimizes data reception inefficiencies by synchronizing the sensor network activity intervals; and (iii) the query processing module, which supports advanced query processing semantics. In order to validate the efficiency of our approach, we have developed a prototype implementation of KSpot+ in nesC and JAVA. In our experimental evaluation, we thoroughly assess the performance of KSpot+ using real datasets and show that KSpot+ provides significant energy reductions under a variety of conditions, thus significantly prolonging the longevity of a WSN

A programmable VLSI filter architecture for application in real-time vision processing systems

An architecture is proposed for the realization of real-time edge-extraction filtering operation in an Address-Event-Representation (AER) vision system. Furthermore, the approach is valid for any 2D filtering operation as long as the convolutional kernel F(p,q) is decomposable into an x-axis and a y-axis component, i.e. F(p,q)=H(p)V(q), for some rotated coordinate system [p,q]. If it is possible to find a coordinate system [p,q], rotated with respect to the absolute coordinate system a certain angle, for which the above decomposition is possible, then the proposed architecture is able to perform the filtering operation for any angle we would like the kernel to be rotated. This is achieved by taking advantage of the AER and manipulating the addresses in real time. The proposed architecture, however, requires one approximation: the product operation between the horizontal component H(p) and vertical component V(q) should be able to be approximated by a signed minimum operation without significant performance degradation. It is shown that for edge-extraction applications this filter does not produce performance degradation. The proposed architecture is intended to be used in a complete vision system known as the Boundary-Contour-System and Feature-Contour-System Vision Model, proposed by Grossberg and collaborators. The present paper proposes the architecture, provides a circuit implementation using MOS transistors operated in weak inversion, and shows behavioral simulation results at the system level operation and electrical simulation and experimental results at the circuit level operation of some critical subcircuits

In-Situ Characterization of Carrier Mobility in Field Effect Transistors

The Field Effect Transistor (FET) is today the basic element of Very Large Scale Integrated (VLSI) digital systems. FETs are also used in analog circuits for high frequency (microwave) applications. Different types of FETs are the Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), the MEtal Semiconductor Field Effect Transistors (MESFETs) and the Modulation Doped Field Effect Transistors (MODFETs)

Very wide range tunable CMOS/bipolar current mirrors with voltage clamped input

In low power current mode signal processing circuits it is often necessary to use current mirrors to replicate and amplify/attenuate current signals and clamp the voltage of nodes with high parasitic capacitances so that the smallest currents do not introduce unacceptable delays. The use of tunable active-input current mirrors would meet both requirements. In conventional active-input current mirrors, stability compensation is required. Furthermore, once stabilized, the input current cannot be made arbitrarily small. In this paper we introduce two new active-input current mirrors that clamp their input node to a given voltage. One of them does not require compensation, while the other may under some circumstances. However, for both, the input current may take any value. The mirrors can operate with their transistors biased in strong inversion, weak inversion, or even as CMOS compatible lateral bipolar devices. If it is biased in weak inversion or as lateral bipolars, the current mirror gain can be tuned over a very wide range. According to the experimental measurements provided in this paper, the input current may spawn beyond nine decades and the current mirror gain can be tuned over 11 decades. As an application example, a sinusoidal gm-C-based VCO has been fabricated, whose oscillation frequency could be tuned for over seven decades, between 74 mHz and 1 MHz.Office of Naval Research (USA) N00014-95-1-040

Managing big data experiments on smartphones

The explosive number of smartphones with ever growing sensing and computing capabilities have brought a paradigm shift to many traditional domains of the computing field. Re-programming smartphones and instrumenting them for application testing and data gathering at scale is currently a tedious and time-consuming process that poses significant logistical challenges. Next generation smartphone applications are expected to be much larger-scale and complex, demanding that these undergo evaluation and testing under different real-world datasets, devices and conditions. In this paper, we present an architecture for managing such large-scale data management experiments on real smartphones. We particularly present the building blocks of our architecture that encompassed smartphone sensor data collected by the crowd and organized in our big data repository. The given datasets can then be replayed on our testbed comprising of real and simulated smartphones accessible to developers through a web-based interface. We present the applicability of our architecture through a case study that involves the evaluation of individual components that are part of a complex indoor positioning system for smartphones, coined Anyplace, which we have developed over the years. The given study shows how our architecture allows us to derive novel insights into the performance of our algorithms and applications, by simplifying the management of large-scale data on smartphones

Impact Ionization and Hot-Electron Injection Derived Consistently from Boltzmann Transport

We develop a quantitative model of the impact-ionizationand hot-electron–injection processes in MOS devices from first principles. We begin by modeling hot-electron transport in the drain-to-channel depletion region using the spatially varying Boltzmann transport equation, and we analytically find a self consistent distribution function in a two step process. From the electron distribution function, we calculate the probabilities of impact ionization and hot-electron injection as functions of channel current, drain voltage, and floating-gate voltage. We compare our analytical model results to measurements in long-channel devices. The model simultaneously fits both the hot-electron- injection and impact-ionization data. These analytical results yield an energydependent impact-ionization collision rate that is consistent with numerically calculated collision rates reported in the literature

An Ultra-Low-Power Micro-Optoelectromechanical Tilt Sensor

Published versio

Long-term dependence in exchange rates

The extent to which exchange rates of four major currencies against the Greek Drachma exhibit long-term dependence is investigated using a R/S analysis testing framework. We show that both classic R/S analysis and the modified R/S statistic if enhanced by bootstrapping techniques can be proven very reliable tools to this end. Our findings support persistence and long-term dependence with non-periodic cycles for the Deutsche Mark and the French Franc series. In addition a noisy chaos explanation is favored over fractional Brownian motion. On the contrary, the US Dollar and British Pound were found to exhibit a much more random behavior and lack of any long-term structure

Golf development in Cyprus and management: Linking the investment and operational concerns

Golfing tourism is considered as a growing sector. It may contribute towards the enrichment and diversification of the tourist product, the increase in visitors and expenditure, decrease of the seasonality problem etc. The new Cyprus Government policy to upgrade the image of Cyprus as a 'quality* destination will encourage private investment in new sectors like integrated golf courses. A cluster of existing and new developments will offer to golfers an irresistible challenge of new, different and varied courses, in an island that offers all- year round sunshine and a range of other facilities. This MSc Report is based on golf course development and the facet of investment and operational concerns for this kind of development. The several issues of the so called 'effective management' to create and sustain value for investors are presented in a sequence of seven chapters. These are as follows: Chapter 1 gives an overview of the topic, its methods of investigation and data collection. Chapter 2 introduces information on Cyprus in relation to geographical position, tourism and local market. Additionally, it briefly summarizes policies, provisions and restrictions in relation to golf course development. Chapter 3 gives an account of literature background on leisure integrated facilities provision and management and it highlights the need for a customer- focused approach. Chapter 4 focuses on market analysis. It discusses issues of supply and demand both local and external. Problem analysis is supported by a SWOT Analysis, which helps to focus on key areas that need to be taken into account in producing a marketing plan. Furthermore, there is a discussion of the case study analysis, based on local courses, as well as courses abroad to provide a means of comparison. Chapter 5 discusses the management profile of golf course development including issues of operation, course types, golf sale, marketing plans. Chapter 6 discusses development issues including development patterns and costs, as well as sustainability concerns. Chapter 7 outlines the conclusions and recommendations on the topic under research

The changing landscape of OSH regulation in the UK

This report presents key findings of a research project on the changing landscape of OSH regulation in the UK. Understanding the changing landscape of OSH regulation and standards and its implications are of central importance for ensuring that OSH outcomes are not compromised and the needs of different types of organisations are met. This project examined the landscape of OSH in the UK since its origin and in particular looked at how regulation of OSH has evolved over time. It considered both policy and practice issues as well as the role of key stakeholders in this process with a view to identify how the right balance can be achieved to promote health and safety going forward. To achieve its aims, a qualitative methodology was implemented in five stages: a. a literature and policy review, including a comparative analysis with other countries; b. case study analysis; c. stakeholder interviews, d. stakeholder workshops including focus groups; and e. research output synthesis