Asymptotic Methods for Metal Oxide Semiconductor Field Effect Transistor Modeling

The behavior of metal oxide semiconductor field effect transistors (MOSFETs) with small aspect ratio and large doping levels is analyzed using formal perturbation techniques. Specifically, the influence of interface layers in the potential on the averaged channel conductivity is closely examined. The interface and internal layers that occur in the potential are resolved in the limit of large doping using the method of matched asymptotic expansions. This approach, together with other asymptotic techniques, provides both a pointwise description of the state variables as well as lumped current-voltage relations that vary uniformly across the various bias regimes. These current-voltage relations are derived for a variable doping model respresenting a particular class of devices

Evaluation of glare and lighting performance in nighttime highway construction projects

An increasing amount of highway repair and construction work is being performed during the off-peak nighttime hours. Nighttime construction is advocated as a way to mitigate the impact of construction operations on the traveling public, shorten the duration of construction operations, and reduce the potential for work zone accidents. However, the utilization and placement of lighting equipment to illuminate the work zone may cause harmful levels of glare for the traveling public. This type of nighttime glare needs to be controlled and minimized to ensure safety for the traveling public and construction workers. This research study focused on studying the veiling luminance ratio (glare) experienced by drive-by motorists in lanes adjacent to nighttime work zones. The major objectives of this study are to: (1) provide an in-depth comprehensive review of the latest literature on the causes of glare and the existing practices that can be used to quantify and control glare during nighttime highway construction; (2) identify practical factors that affect the measurement of veiling luminance ratio (glare) in and around nighttime work zones; (3) analyze and compare the levels of glare and lighting performance generated by typical lighting arrangements in nighttime highway construction; (4) evaluate the impact of lighting design parameters on glare and provide practical recommendations to reduce and control lighting glare in and around nighttime work zones; (5) develop a practical model that can be utilized by resident engineers and contractors to measure and quantify veiling luminance ratio (glare) experienced by drive-by motorists near nighttime highway construction sites; and (6) investigate and analyze existing recommendations on the maximum allowable levels of veiling luminance ratio (glare) that can be tolerated by nighttime drivers from similar lighting sources. In order to achieve these objectives, the study was conducted in four major tasks that focused on: (1) conducting a comprehensive literature review; (2) visiting and studying a number of nighttime highway construction projects; (3) conducting field studies to evaluate the performance of selected lighting arrangements; and (4) developing practical models to measure and control the levels of glare experienced by drive-by motorists in lanes adjacent to nighttime work zones. In the first task of the project, a comprehensive literature review was conducted to study the latest research and developments on veiling luminance ratio (glare) and its effects on drivers and construction workers during nighttime highway construction work. Sources of information included publications from professional societies, journal articles, on-line databases, and contacts from DOT???s. The review of the literature focused on: (1) lighting requirements for nighttime highway construction; (2) causes and sources of glare in nighttime work zones, including fixed roadway lighting, vehicles headlamps, and nighttime lighting equipment in the work zone; (3) the main types of glare which can be classified based on its source as either direct or reflected glare; and based on its impact as discomfort, disabling, or blinding glare; (4) available procedures to measure and quantify discomfort and disabling glare; (5) existing methods to quantify pavement/adaptation luminance which is essential in measuring discomfort and disabling glare; (6) available recommendations by State DOTs and professional organizations to control glare; and (7) existing guidelines and hardware for glare control. The second task involved site visits to a number of nighttime work zones to identify practical factors that affect the measurement of the veiling luminance ratio in nighttime construction sites. The site visits were conducted over a five-month period in order to gather data on the type of construction operations that are typically performed during nighttime hours, the type of lighting equipment used to illuminate the work area, and the levels of glare experienced by workers and motorists in and around the work zone. One of the main findings of these site visits was identifying a number of challenges and practical factors that significantly affect the measurement and quantification of the veiling luminance ratio (glare) in nighttime work zones. These practical factors were carefully considered during the development of the glare measurement model in this study to ensure its practicality and ease of use in nighttime work zones by resident engineers and contractors alike. Another important finding of the site visits was the observation that improper utilization and setup of construction lighting equipment may cause significant levels of glare for construction workers and drive-by motorists. In the third task, field experiments were conducted to study and evaluate the levels of lighting glare caused by commonly used lighting equipment in nighttime work zones. During these experiments, a total of 25 different lighting arrangements were tested over a period of 33 days from May 10, 2007 to June 12, 2007 at the Illinois Center for Transportation (ICT) in the University of Illinois at Urbana-Champaign. The objectives of these experiments were to: (1) analyze and compare the levels of glare and lighting performance generated by typical lighting arrangements in nighttime highway construction; and (2) provide practical recommendations for lighting arrangements to reduce and control lighting glare in and around nighttime work zones. The field tests were designed to evaluate the levels of glare and lighting performance generated by commonly used construction lighting equipment, including one balloon light, two balloon lights, three balloon lights, one light tower and one Nite Lite. The tests were also designed to study the impact of tested lighting parameters (i.e., type of light, height of light, aiming and rotation angles of light towers, and height of vehicle/observer) on the veiling luminance ratio experienced by drive-by motorists as well as their impact on the average horizontal illuminance and lighting uniformity ratio in the work area. Based on the findings from these tests, a number of practical recommendations were provided to control and reduce veiling luminance ratio/glare in and around nighttime work zones. The final (fourth) task of this study focused on the development of a practical model to measure and quantify veiling luminance ratio (glare) experienced by drive-by motorists in lanes adjacent to nighttime work zones. The model was designed to consider the practical factors that were identified during the site visits, including the need to provide a robust balance between practicality and accuracy to ensure that it can be efficiently and effectively used by resident engineers on nighttime highway construction sites. To ensure practicality, the model enables resident engineers to measure the required vertical illuminance data in safe locations inside the work zone while allowing the traffic in adjacent lanes to flow uninterrupted. These measurements can then be analyzed by newly developed regression models to accurately calculate the vertical illuminance values experienced by drivers from which the veiling luminance ratio (glare) can be derived. This task also analyzed existing recommendations on the maximum allowable levels of veiling luminance ratio (glare) that can be tolerated by nighttime drivers from various lighting sources, including roadway lighting, headlights of opposite traffic vehicles, and lighting equipment in nighttime work zones. The main research development of this study contribute to the advancement of current practice in highway construction and can lead to an increase in the safety of construction workers and the traveling public in and around the nighttime work zones. The outcome of this study will help in: (1) identifying practical factors and challenges that affect the measurements of glare in and around nighttime work zones; (2) evaluating and comparing the lighting performance and glare levels of typical construction lighting equipment that are commonly used in nighttime highway construction projects; (3) recommending practical lighting arrangements that generate acceptable levels of lighting glare for motorists and adequate levels of lighting performance for construction workers inside the work zone; (4) developing practical and safe model for measuring and quantifying the veiling luminance ratio experienced by drive-by motorists near nighttime highway construction sites; and (5) providing a baseline for Departments of Transportation (DOTs) to develop specifications and standards on how to control and quantify the levels of glare in nighttime highway construction projects

Design and Development of Experimental Setup of Hybrid PV/Thermal Collector

A portable Hybrid Photovoltaic/Thermal (PV/T) solar collector experimental apparatus was designed and developed. The purpose of this instructional experimental apparatus is to demonstrate solar energy applications. In this article, the authors present an experimental apparatus that will help undergraduate mechanical engineering students in understanding the basic heat transfer processes, and thermodynamics concepts and principles. This is achieved by utilising real life applications, such as using Hybrid Photovoltaic/Thermal solar collector to convert solar energy to both electrical and thermal energy. The article presents the details of the design and construction of the experimental apparatus, as well as testing procedures and sample results

Determination of unifloral honey volatiles from Centaurea iberica and Zizyphus spina-christi by Solid-Phase Microextraction and Gas Chromatography-Mass Spectrometry

The volatiles of two different unifloral Palestinian honeys from botanical species Centaurea iberica and Zizyphus spina-christi have been investigated for the first time. They were isolated, identified, and quantitatively analyzed using Headspace Solid-Phase Microextraction and Gas Chromatography Mass Spectrometry (HS-SPME-GCMS) methodology. The resulted total ion current (TIC) chromatographic profiles reflected the uniqueness of each type of honey and therefore the proposed procedure can be used to characterize each kind of honey by revealing the absence or presence of certain volatile constituents. A total of 18 compounds were seen in Centaurea iberica honey with phenylacetaldehyde, phenylethylalcohol, 2-ethyl hexanoic acid, 2,4,6-trimethylphenol and nonanoic acid as the principal components, whereas 25 compounds were seen in Zizyphus spinachristi honey with benzaldehyde, phenylacetaldehyde, phenylethylalcohol, benzeneacetonitrile, 2-ethyl hexanoic acid, octanoic acid, 2-methoxy-4-(1-propanol)-6-acetate phenol, nonanoic acid, decanoic acid, 1-hydroxy 2,4,6-trimethylbenzene, and 5-hydroxymethyl- 2-furaldehyde as the principal constituents. Ziziphus spina-christi honey was found to have two unequivocal potential markers: phenylacetonitrile and 5-hydroxymethyl-2-furancarboxaldehyde, while Centaurea Italica honey has only one representative floral origin marker compound: the 2,4,6-trimethylphenol

Grid Databases for Shared Image Analysis in the MammoGrid Project

The MammoGrid project aims to prove that Grid infrastructures can be used for collaborative clinical analysis of database-resident but geographically distributed medical images. This requires: a) the provision of a clinician-facing front-end workstation and b) the ability to service real-world clinician queries across a distributed and federated database. The MammoGrid project will prove the viability of the Grid by harnessing its power to enable radiologists from geographically dispersed hospitals to share standardized mammograms, to compare diagnoses (with and without computer aided detection of tumours) and to perform sophisticated epidemiological studies across national boundaries. This paper outlines the approach taken in MammoGrid to seamlessly connect radiologist workstations across a Grid using an "information infrastructure" and a DICOM-compliant object model residing in multiple distributed data stores in Italy and the UKComment: 10 pages, 5 figure

Prevalence of infraocclusion of primary molars determined using a new 2D image analysis methodology

The reported prevalence of infraocclusion varies widely, reflecting differences in definitions and measurement/scoring approaches.This study aimed to quantify the prevalence and extent of infraocclusion in singletons and twins during the late mixed dentition stage of dental development using a new diagnostic imaging method and objective criteria. The study also aimed to determine any associations between infraocclusion and sex, arch type, arch side and tooth type.Two samples were analysed; 1,454 panoramic radiographs of singletons and 270 dental models of twins. Both samples ranged in age from 8-11 years. Adobe Photoshop CS5 was used to measure the extent of infraocclusion. Repeatability tests showed systematic and random errors were small.The prevalence in the maxilla was low (<1%), whereas the prevalence in the mandible was 22% in the singleton sample and 32% in the twin sample. The primary mandibular first molar was affected more often than the second molar. There was no significant difference in the expression between sexes or sides.A new technique for measuring infraocclusion has been developed with high intra- and inter-operator reproducibility. This method should enhance early diagnosis of tooth developmental abnormalities and treatment planning during late mixed dentition stage of development.Ruba Odeh, Suzanna Mihailidis, Grant Townsend, Raija Lähdesmäki, Toby Hughes, and Alan Broo