Optical and electrical properties of zinc oxide films prepared by spray pyrolysis

Zinc oxide thin films were prepared on glass substrates from an aqueous solution of zinc acetate by spray pyrolysis. These films were characterized using X-ray diffraction, scanning electron microscopy and optical transmission. The films were highly transparent to the visible radiation and electrically conductive. Films deposited at optimum conditions exhibited a resistivity of 3·15×10⁻³ Ωm along with a transmittance of 98% at 550 nm.     

A flexible communications protocol for a distributed surveillance system

On-line surveillance for safety and security is a major requirement of public transport and other public places to address the modern demands of mobility in major urban areas and to effect improvements in quality of life and environment protection. The surveillance task is a complex one involving technology, management procedures and people. Visual surveillance based on Closed Circuit Television system is an important part of such systems, but visual processing is not sufficient and the geographical distribution of devices and management has to be taken into account. In this paper we present a surveillance architecture that reflects the distributed nature of the monitoring task and allows for distributed detection processes, not only dealing with visual processing but also with devices such as acoustic signature detection and mobile smart cards, actuators and a range of other possible sensors. The design uses ideas from control engineering and distributed communications networks resulting in a communications architecture based on CORBA and XML messaging. We have shown how to define a generic device/sensor model appropriate for the surveillance task and sufficiently flexible so as to allow for scalability, expansion and customisation of a practical surveillance task. The paper gives sufficient details on the protocols to show how intelligent detection modules can be integrated as part of this kind of system. The system components have been implemented and integrated in two major successful trials in metropolitan railway stations in London and in Paris, as part of a major EU-funded project (PRISMATICA).     

Unified overhead-aware schedulability analysis for slot-based task-splitting

Hard real- time multiprocessor scheduling has seen, in recent years, the flourishing of semi-partitioned scheduling algorithms. This category of scheduling schemes combines elements of partitioned and global scheduling for the purposes of achieving efficient utilization of the system’s processing resources with strong schedulability guarantees and with low dispatching overheads. The sub-class of slot-based “task-splitting” scheduling algorithms, in particular, offers very good trade-offs between schedulability guarantees (in the form of high utilization bounds) and the number of preemptions/migrations involved. However, so far there did not exist unified scheduling theory for such algorithms; each one was formulated in its own accompanying analysis. This article changes this fragmented landscape by formulating a more unified schedulability theory covering the two state-of-the-art slot-based semi-partitioned algorithms, S-EKG and NPS-F (both fixed job-priority based). This new theory is based on exact schedulability tests, thus also overcoming many sources of pessimism in existing analysis. In turn, since schedulability testing guides the task assignment under the schemes in consideration, we also formulate an improved task assignment procedure. As the other main contribution of this article, and as a response to the fact that many unrealistic assumptions, present in the original theory, tend to undermine the theoretical potential of such scheduling schemes, we identified and modelled into the new analysis all overheads incurred by the algorithms in consideration. The outcome is a new overhead-aware schedulability analysis that permits increased efficiency and reliability. The merits of this new theory are evaluated by an extensive set of experiments.     

On the structure of the privacy hierarchy

An N argument function f(x ₁,...,x _N ) is called t-private if a protocol for computing f exists so that no coalition of at most t parties can infer any additional information from the execution, other than the value of the function. The motivation of this work is to understand what levels of privacy are attainable. So far, only two levels of privacy are known for N argument functions which are defined over finite domains: functions that are N-private and functions that are (N – 1)/2-private but not N/2-private.In this work we show that the privacy hierarchy for N-argument functions which are defined over finite domains, has exactly (N + 1)/2 levels. We prove this by constructing, for any N/2 t N – 2, an N-argument function which is t-private but not (t + 1)-private.This research was supported by US-Israel Binational Science Foundation Grant 88-00282.     

Organizing drug injectors against AIDS: Preliminary data on behavioral outcomes.

Describes a project based on organizing drug injectors to change their subculture in ways that promote lower risk behaviors. Initial and follow-up interviews were conducted with 368 Ss. Findings indicate a decline in high-risk behaviors such as renting or borrowing used syringes and an increase in risk-reducing behaviors such as using new syringes and condoms. Almost half the Ss entered drug abuse treatment during the follow-up period; 60% taught others to use bleach to decontaminate injecting equipment. Risk reduction was greater among Ss who attended group meetings. Thus, organizing drug injectors is a feasible intervention that should be adopted elsewhere. Drug injectors can take on responsibility in combating AIDS. All evaluations of interventions should measure Ss' efforts to spread the message to others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Single,twin and triple buried heating pipes: on potential savings in heat losses and costs

In order to make district heating systems competitive in areas with single family houses or in other areas with low heat demands it is necessary to reduce the heat losses from the pipes. In recent years the twin pipe has become popular in the Nordic countries. In the article we describe how the heat loss and the heat loss coefficients can be calculated. We introduce the triple pipe with three media pipes (two supply pipes and one return pipe). The temperature dependency and the ageing of polyurethane insulation are briefly discussed. A comparison is made for different 80 mm distribution pipes and for different service pipes with respect to heat losses and to resources, i.e. materials needed for the casing and polyurethane insulation and the gravel in the excavations. For the distribution pipe we found that an egg‐shaped twin pipe can reduce the heat loss by 37% and the investments by 12% compared with a pair of single pipes. For the service pipes we found that the triple pipe reduces the heat loss by 45% compared with a common pair of single pipes and by 24% compared with circular twin pipes. The reduction in investment index is 21%. The article also addresses the question of the heat exchange between the two media pipes in a twin pipe. Copyright © 2005 John Wiley & Sons, Ltd.     

RVGEN: a tool for generation of random variates

A number of applications in simulation and software testing require random number generation, both uniform and non-uniform. Although libraries are available for random number generation, there is no user-friendly tool to enable the user to use and build random number generators. This paper presents the RVGEN tool, developed at TRDDC. Using the tool, the software developer can design a random number generator specific to a particular pattern. The tool takes specifications at a high level and also partly in C++, and generates C++ code for a number of user-friendly functions. These include setting and getting of random variate parameters, GUIs for inputting parameters, validation of parameters, parameter input and output from a file, generation of random variate class declarations, generation of seeds for multiple streams, and testing of the random variate generator. The tool provides a number of classical, general-purpose and empiric distributions by default.     

A matrix geometric representation for the queue length distribution of multitype semi-Markovian queues

In this paper we study a broad class of semi-Markovian queues introduced by Sengupta. This class contains many classical queues such as the GI/M/1 queue, SM/MAP/1 queue and others, as well as queues with correlated inter-arrival and service times. Queues belonging to this class are characterized by a set of matrices of size $m$ and Sengupta showed that its waiting time distribution can be represented as a phase-type distribution of order $m$. For the special case of the SM/MAP/1 queue without correlated service and inter-arrival times the queue length distribution was also shown to be phase-type of order $m$, but no derivation for the queue length was provided in the general case.This paper introduces an order $m^2$ phase-type representation $(\kappa ,K)$ for the queue length distribution in the general case and proves that the order $m^2$ of the distribution cannot be further reduced in general. A matrix geometric representation $(\kappa ,K,\nu )$ is also established for the number of type $\tau ?\{1,\dots ,m\}$ customers in the system, where a customer is of type $\tau$ if the phase in which it completes service belongs to $\tau$. We derive these results in both discrete and continuous time and also discuss the numerical procedure to compute $(\kappa ,K,\nu )$. When the arrivals have a Markovian structure, the numerical procedure is reduced to solving a Quasi–Birth–Death (for the discrete time case) or fluid queue (for the continuous time case).Finally, by combining a result of Sengupta and Ozawa, we provide a simple formula to compute the order $m$ phase-type representation of the waiting time in a MAP/MAP/1 queue without correlated service and inter-arrival times, using the $R$ matrix of a Quasi–Birth–Death Markov chain.