bluuebunny/crossref_metadata_2025 huggingface dataset:
Experience with the antibiotic resistance analysis and DNA fingerprinting in tracking faecal pollution at two lake beaches
Authors: Edge T.A. , Hill S. , Stinson G. , Seto P. , Marsalek J.
Published: December 2007

Posting or closing of swimming beaches because of faecal contamination is a widespread problem reported in many locations. In a risk-based approach to this problem, the risk to swimmers' health is assessed by field monitoring of indicator bacteria and the associated risks are managed by source controls and other remedial measures. In risk assessment, great advances have been made in recent years with the introduction of microbial source tracking (MST) techniques. Two such techniques, antibiotic resistance analysis and DNA fingerprinting, were applied in a study of causes of faecal contamination at two lake beaches in Toronto, Ontario. Both methods identified bird faeces as the dominant sources of E. coli. Coping with this type of pollution presents a major environmental challenge.
Comparison of and uncertainties in raw sewage COD measurements by laboratory techniques and field UV-visible spectrometry
Authors: Bertrand-Krajewski J.-L. , Winkler S. , Saracevic E. , Torres A. , Schaar H.
Published: December 2007

A comprehensive investigation of the uncertainty of different COD analysis methods (DIN, small tube tests (STT) and UV-visible spectrometry methods) has been carried out on potassium hydrogen phthalate standard solutions and raw sewage samples from a large wastewater treatment plant. The UV-visible method allows estimating COD equivalent concentration from the measured absorption spectra by means of site specific regression and correlation functions. CODdin and CODstt methods showed equivalent global results but specific calibration relationships are necessary when high accuracy is required. The CODstt method is suitable for immediate COD analysis in the field. Sub-sampling is the main source of uncertainty. Spectrometry is able to estimate CODeq with an uncertainty of the same order of magnitude as the uncertainty in CODdin.
Role of colloids in heavy metal transfer through a retention-infiltration basin
Authors: Durin B. , Béchet B. , Legret M. , Le Cloirec P.
Published: December 2007

Runoff waters from a main bridge near Nantes (France), surface waters and pore waters in the infiltration basin collecting runoff were analysed after filtration and ultrafiltration to investigate the role of colloids in the transfer of trace metals (Zn, Cu and Pb) from the road to the groundwater. The role of the basin in mitigation of the variations of physico-chemical parameters and chemical elements concentrations was confirmed. An increase of mobile colloidal phase by comparison with runoff and high concentrations of trace metals were observed in pore waters of the sediment. Up to 100% of Pb and 60% of Cu and Zn may be associated to compounds having a molecular weight above 5 kDaltons. Principal component analysis outlined the variability of the influence of the physico-chemical parameters on trace metals concentrations for the different waters. Speciation calculations pointed out the potential precipitation of Fe and Al oxyhydroxides in all kind of waters.
Modelling as a tool when interpreting biodegradation of micro pollutants in activated sludge systems
Authors: Press-Kristensen K. , Lindblom E. , Henze M.
Published: December 2007

The aims of the present work were to improve the biodegradation of the endocrine disrupting micro pollutant, bisphenol A (BPA), used as model compound in an activated sludge system and to underline the importance of modelling the system. Previous results have shown that BPA mainly is degraded under aerobic conditions. Therefore the aerobic phase time in the BioDenitro process of the activated sludge system was increased from 50% to 70%. The hypothesis was that this would improve the biodegradation of BPA. Both the influent and the effluent concentrations of BPA in the experiment dropped significantly after increasing the aerobic time. From simulations with a growth-based biological/physical/chemical process model it was concluded that although the simulated effluent concentration of BPA was independent of the influent concentration at steady-state, the observed drop in effluent concentrations probably was caused by either a larger specific biomass to influent BPA ratio, improved biodegradation related to the increased aerobic phase time, or a combination of the two. Thereby it was not possibly to determine if the increase in aerobic phase time improved the biodegradation of BPA. The work underlines the importance of combining experimental results with modelling when interpreting results from biodegradation experiments with fluctuating influent concentrations of micro pollutants.
Screening health risk assessment of micropullutants for indirect potable reuse schemes: a three-tiered approach.
Authors: Rodriguez C. , Cook A. , Van Buynder P. , Devine B. , Weinstein P.
Published: December 2007

Indirect potable reuse schemes are an important consideration in the sustainable management of scarce water resources. However, communities still hold real concerns about the potential health risks of micropullutants in recycled water entering their potable water supply. Microfiltration or ultrafiltration followed by reverse osmosis is currently the standard treatment technology for potable use of recycled water. Nevertheless, membranes are not 100% efficient in the removal of trace organic contaminants and the potential health risks of these micropullutants need to be assessed. The aim of this paper is to present a three-tiered approach for the preliminary assessment of micropullutants in recycled water. A risk quotient is calculated by comparing measured concentrations against benchmark values. Tier 1 corresponds to regulated chemicals; the maximum contaminant level in drinking water is used as benchmark value. Tier 2 corresponds to unregulated chemicals with toxicity information; slope factors or risk specific doses are used to calculate benchmark values. Tier 3 corresponds to unregulated chemicals without toxicity information. The “Threshold of Toxicological Concern” concept is used to calculate benchmark values. The characterization of chemicals of concern following reverse osmosis in a water reclamation plant and the application of the three-tiered approach for the evaluation of the potential health risks is presented.
The Repression of IRS2 Gene by ATF3, a Stress-Inducible Gene, Contributes to Pancreatic β-Cell Apoptosis
Authors: Li Dan , Yin Xin , Zmuda Erik J. , Wolford Christopher C. , Dong Xiaocheng , White Morris F. , Hai Tsonwin
Published: December 2007

OBJECTIVE—β-Cell failure is an essential component of all types of diabetes, and the insulin receptor substrate 2 (IRS2) branch of signaling plays a key role in β-cell survival and function. We tested the hypothesis that activating transcription factor 3 (ATF3), a stress-inducible proapoptotic gene, downregulates the expression of IRS2 in β-cells.

RESEARCH DESIGN AND METHODS—We used both the gain- and loss-of-function approaches to test the effects of ATF3 on IRS2 gene expression. We also analyzed the binding of ATF3 to the IRS2 promoter by chromatin immunoprecipitation assay and the transcription of the IRS2 gene by polymerase II occupancy assay. Furthermore, we tested the ability of IRS2 to alleviate the proapoptotic effects of ATF3 in cultured β-cells and in transgenic mice using the rat insulin promoter to drive the transgenes.

RESULTS—Expression of ATF3 is sufficient to reduce IRS2 gene expression; in contrast, knockdown or knockout of ATF3 reduces the ability of stress signals to downregulate IRS2 expression. ATF3 binds to the IRS2 promoter in vivo, and the binding of ATF3 correlates with decreased IRS2 gene transcription. Functionally, expression of IRS2 protects β-cells from ATF3-induced apoptosis.

CONCLUSIONS—IRS2 is a target gene of ATF3, and its repression by ATF3 contributes, at least partly, to the apoptosis induced by ATF3. Because ATF3 is a stress-inducible gene, our work provides a direct link to explain how environmental stress factors can modulate IRS2 gene transcription.
Loss of Polymer-Modified Binder Durability with Oxidative Aging
Authors: Woo Won Jun , Hilbrich Jacob M. , Glover Charles J.
Published: December 2007

In recent years, there has been an increased use of polymers to modify asphalt binders, mainly to decrease pavement rutting but also to improve binder failure strain in direct tension. With binder oxidation, however, failure strain improvements (relative to the unmodified binder) disappear, and two mechanisms are suspected: polymer degradation and base binder embrittlement. The extent to which each of these mechanisms is responsible for loss of modified-binder performance is important and bears on maintenance treatments and recycling methodologies. Changes in styrene-butadiene-styrene (SBS) polymer-modified binder properties due to oxidation were analyzed by means of dynamic shear rheometry, ductility, force ductility, and gel permeation chromatograph. Previous literature reports using size exclusion chromatography showed that degradation of the molecular weight profile of SBS accompanied the loss of ductility in polymer-modified asphalt (PMA). Yet base binder embrittlement also occurred, as evidenced by ductility and force ductility. Testing aged PMA binders at higher temperatures to soften the base binder restored the polymer modulus to the force ductility measurements, as did blending with a softer deasphalted oil. The conclusion from these measurements is that the primary cause of PMA degradation with aging is base binder embrittlement rather than polymer degradation.
Comparison of Polyphosphoric Acid-Modified Asphalt Binders with Straight and Polymer-Modified Materials
Authors: Kodrat Irsan , Sohn Dave , Hesp Simon A. M.
Published: December 2007

This paper discusses the effects of polyphosphoric acid (PPA) modification on asphalt binders. Findings are compared with those for straight and polymer-modified materials of similar grades. The effect of PPA modification was investigated by means of conventional protocols as well as three new binder tests developed in Ontario, Canada. The compact tension test and the extended bending beam rheometer protocol were used to investigate low-temperature performance properties. The double edge-notched tension test was used to study the resistance to ductile failure. The brittle state fracture properties and the reversible aging processes were largely unaffected by PPA modification. However, changes in the low-temperature grade were considerable in some instances. While the essential work of fracture increases with the addition of PPA, the yield stress increases more rapidly in most binders and thus results in an overall drop in strain tolerance in the ductile state. Recent field experience in Ontario suggests that the use of PPA may either prevent or contribute to wheelpath cracking, depending on the formulation and concurrent use of polymer.
Comparative Laboratory Study of Sasobit and Aspha-Min Additives in Warm-Mix Asphalt
Authors: Wasiuddin Nazimuddin M. , Selvamohan Selvaratnam , Zaman Musharraf M. , Guegan Marie Louise Thérèse Anne
Published: December 2007

Warm-mix asphalt (WMA), which reduces the production temperatures (mixing and compaction) while maintaining the advantages of hot-mix asphalt (HMA), is becoming an attractive paving material. In this study, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives. For PG 64-22,2%, 3%, and 4% Sasobit additive reduced the mixing temperature of the pure binder from 163°C to 147°C (i.e., by 16°C). In case of the PG 70-28, the reductions are 10°C, 12°C and 13°C, respectively, for 2%, 3%, and 4% Sasobit additive. No significant decrease in mixing temperature by the Aspha-Min additive was observed in using the rotational viscometer. Evaluation of the binders on the basis of G*/sin(δ) demonstrates no negative effect on high-temperature grading due to high-temperature viscosity reduction. With the addition of 4% Sasobit additive, the high-temperature binder grading of PG 64 (actually PG 65) increases to PG 69, while 4% Sasobit additive improves the PG 70 (actually PG 75) to PG 80. No significant changes in grading were observed with the addition of the Aspha-Min additive. In fact, reduction in binder viscosity and improvement in binder grading without increasing the viscosity indicate two-way reductions (both direct and indirect) in production temperatures by the Sasobit additive. Finally, the Sasobit additive is found to decrease the asphalt pavement analyzer rut depths significantly, and these rut depths correlate well with the rutting factor G*/sin(δ). It was also observed that rutting potential decreases with decreasing mixing and compaction temperatures. Comparatively, a smaller reduction in rut depths was observed by adding the Aspha-Min additive.
Laboratory Investigations of Mechanical Performance of Foamed Bitumen Mixes that Use Half-Warm Aggregates
Authors: Gaudefroy Vincent , Olard François , Cazacliu Bogdan , de La Roche Chantal , Beduneau Etienne , Antoine Jean Pierre
Published: December 2007

For several years, as environmental criteria have become stricter and stricter, new moderated-temperature mixing technologies–warm or even half-warm (less than 100°C)–have appeared. This study, realized in Laboratoire Central des Ponts et Chaussées (LCPC) in Nantes, France, within the framework of the partnership between Eiffage Travaux Publics and LCPC, aimed at determining the influence of mixing parameters (such as temperature and initial water content of the mix aggregates) on the quality of mixing and the mechanical properties of the half-warm foamed bitumen mixes compared with the traditional cold-foamed bitumen mix and hot-mix asphalt, both of which acted as reference materials. It was also a way to understand better the role of water and its influence on asphalt quality. This study highlights the influence of the increase in the aggregate temperature to elaborate mix treated with foam bitumen. This coating process allows many benefits: an increase in coating quality, compactibility, and water resistance. As a consequence, mechanical performances are improved.
Evaluation of Heated Reclaimed Asphalt Pavement Material and Wax-Modified Asphalt for Use in Recycled Hot-Mix Asphalt
Authors: Mallick Rajib B. , Bradley Julie E. , Bradbury Richard L.
Published: December 2007

This study was performed to evaluate the use of heated-reclaimed asphalt pavement materials with emulsion and the use of hot-mix asphalt with wax (Sasobit) as base course materials. Mixes with lower-than-optimum and optimum emulsion content, as well as with heated-reclaimed asphalt pavement material and optimum emulsion content, were made; in addition, mixes with conventional asphalt binder and those with asphalt binder and Sasobit were produced at relatively lower temperatures. These mixes were tested for workability, and all but one were used for preparation of approximately 0.9- × 0.9- × 0.125-m slabs. The rates of densification during the compaction of these slabs were compared. Samples cored from the slabs were tested for stiffness and for dry and retained tensile strengths. The results showed that heating of reclaimed asphalt pavement material can improve the dispersion as well as the densification significantly. The use of asphalt binder was found to improve strength and stiffness, and the use of Sasobit helped to achieve almost similar workabilities and compactibilities at a lower temperature compared with those of hot-mix asphalt with neat asphalt binder. No significant difference was found between the modulus of the Sasobit and hot-mix asphalt samples. The dispersion of asphalt binder seemed to improve with the use of Sasobit at a lower mixing temperature. A field project is recommended for evaluating performance of emulsion mixes with heated reclaimed asphalt pavement materials and asphalt binder mixes with Sasobit.
Effect of Aggregate Degradation on Volumetric Properties of Georgia's Hot-Mix Asphalt
Authors: Lynn Todd , James Robert S. , Wu Peter Y. , Jared David M.
Published: December 2007

Various degrees of degradation of aggregate particles can occur in hot-mix asphalt (HMA) production during the mixing and compaction process. This breakdown may significantly increase the dust fraction of the aggregate gradation relative to that of laboratory specimens. This increased dust fraction could cause a loss of voids in the mineral aggregate (VMA) and air voids. After evaluation of 22 variations of HMA mixtures during production and construction, it was determined that aggregate degradation did result from plant mixing and field compaction activities. Aggregate degradation varied somewhat with respect to where the mixture was sampled within the production and construction processes. Aggregate degradation resulting from binder extraction that uses the ignition method, relative to the solvent extraction method, was also examined. Mixture volumetric properties (i.e., air voids and VMA) were significantly affected by aggregate degradation. On the basis of this study, before a volumetrics specification for mixture acceptance is investigated for future implementation in Georgia, a change in the Georgia Department of Transportation's mix design specification is recommended. The minimum VMA values for Superpave® mix design should be increased by 1% for all dense-graded mixes to compensate for the amount of aggregate degradation and loss of VMA during HMA production and construction. It is believed that this research-based policy change for mix design will better maintain the balance between proper durability and rut resistance of asphalt pavements in Georgia.
Mixed Traffic Flow in Anisotropic Continuum Model
Authors: Tang C. F. , Jiang R. , Wu Q. S. , Wiwatanapataphee B. , Wu Y. H.
Published: December 2007

An extended speed gradient model is developed to study the mixed traffic flow of two types of vehicles with different velocities and different lengths. Two new terms, representing the reaction of one type of vehicle to the other, are proposed and built into the dynamic speed evolution equations for fast cars and slow vehicles. With the developed model, the relation between the steady-state behavior of the mixed traffic flow system and two system parameters is analyzed, including the number density ratio R of the fast cars to the total vehicles and the vehicle length ratio α of the slow vehicle to the fast car. The formation and propagation of traffic jams, the dissolution process of the jams, and the local cluster effect of the mixed traffic system are also studied. The simulation results are reasonable and consistent with daily experience.
Experimental Features and Characteristics of Speed Dispersion in Urban Freeway Traffic
Authors: Wang Hao , Wang Wei , Chen Xuewu , Chen Jun , Li Jie
Published: December 2007

Characteristics of speed dispersion in urban freeway traffic are presented. Two definitions of speed dispersion are proposed: the standard deviation of the individual speeds and the average speed difference of two neighboring vehicles. On the basis of the definitions, traffic data obtained from two urban freeways in China are studied, and different characteristics of speed dispersion are found in four substates of traffic flow, which correspond to four regions in the empirical fundamental diagram. In the bunching state of congested traffic, the flow rate decreases with an increase in speed dispersion at a given mean speed. In the bunching state of fluid traffic, the speed dispersion of traffic flow is small, and in the free state of fluid traffic, speed dispersion is distributed in a disorderly manner in a wide range. Such phenomena are more remarkable under the definition of the average speed difference for speed dispersion. In addition, some possible explanations are presented for the characteristics of speed dispersion in each traffic substate. These speed dispersion studies provide a new approach for microscopic modeling and understanding of traffic flow characteristics.
Calibration of Microsimulation with Heuristic Optimization Methods
Authors: Ma Jingtao , Dong Hu , Zhang H. Michael
Published: December 2007

Model calibration is a crucial step in building a reliable microscopic traffic simulation application because it serves as the additional check to ensure that the model parameters accurately reflect the local driving environment so that decisions made on the basis of these results will not be misinformed decisions. Because of its stochastic nature and complexity, the calibration problem, usually formulated as an optimization problem, is often solved by using heuristic methods. To date, calibration is still a time-consuming task because many adopted methods require many simulation runs in search of an optimal solution. Moreover, many aspects of the calibration problem are not fully understood and need further investigation. In this study, another heuristics calibration algorithm is developed on the basis of the simultaneous perturbation stochastic approximation scheme and applied to calibration of several networks coded in Paramics. The results indicate that the new heuristic algorithm can reach the same level of accuracy with considerably fewer iterations and computer processor time than other heuristic algorithms such as genetic algorithms and the trial-and-error iterative adjustment algorithm. Applications of all three heuristic methods in a northern California network also reveal that some model parameters affect the simulation results more significantly than others. These findings can help modelers better choose calibration methods and fine-tune key parameters.
Random Utility Location, Production, and Exchange Choice; Additive Logit Model; and Spatial Choice Microsimulations
Authors: Abraham John E. , Hunt J. D.
Published: December 2007

A land use modeling system has been developed and applied on the basis of random utility theory. The system abstracts the decisions of the actors located in and traveling around a city or region as a series of logit models: (a) the choice of where to locate the home; (b) the choice of technology, lifestyle, or production option, being the choice of the quantities of “commodities” (consisting of goods, services, labor, and space categories) to consume or produce and hence what interactions will occur; and (c) the location of the “exchange” (transaction or interaction) for each commodity consumed or produced (i.e., for each interaction). These logit models can be combined in a nesting structure, but an additive logit formulation is required because the exchange choices are not mutually exclusive. The additive logit model, which is developed by combining the central limit theorem with random utility theory, can be applied to any choice situation in which several independent choices are conditional on a higher level choice. The resulting choice probabilities can be applied in an aggregate allocation system (as in software for the Production Exchange Consumption Allocation System, PECAS) and result in supply-and-demand equations for each commodity in each exchange that can be solved for a short-term equilibrium. In future research, microsimulation versions of the system could allow a fully integrated and dynamic representation of land use-transport interactions.
Application of Dynamic Value Pricing through Enhancements to TRANSIMS
Authors: Lee Kwang-Sub , Hobeika Antoine G.
Published: December 2007

In the past decade, transportation agencies have become increasingly interested in a high-occupancy toll (HOT) lane value pricing system, especially one with a dynamically varying toll system that depends on the congestion levels in the HOT lanes. HOT lane users are influenced by many factors, including toll prices, savings in time, and purpose of the trip. The current methodologies that forecast the demand for a HOT lane value pricing system are aggregate and do not consider individual traveler socioeconomic characteristics, particularly the value of time (VOT). This paper applies heterogeneous VOT for each individual into the generalized travel time function. This approach relaxes the conventional assumption of constant VOT. The generalized travel time function combined with VOT is used as a route choice for each traveler between the two choices (a toll lane versus a nontoll lane) in a HOT lane value pricing system. With this function, each driver is assigned to the network on the basis of a dynamic traffic assignment. This approach is implemented by using TRANSIMS on a large transportation network. TRANSIMS has a microscopic simulation model that enables the user to capture route choice behavior, including each traveler's response to dynamic tolls through heterogeneous VOT. To initiate this capability, TRANSIMS was enhanced to support dynamic toll pricing. It is now capable of presenting the 15-min dynamic toll rates. In addition, the impacts of various tolls on route choice can be analyzed on the basis of socioeconomic and trip characteristics of each traveler.
Event-Driven Queue-Based Traffic Flow Microsimulation
Authors: Charypar David , Axhausen Kay W. , Nagel Kai
Published: December 2007

Simulating traffic flow is an important problem in transport planning. The most popular simulation approaches for large-scale scenarios today are aggregated models. Unfortunately, these models lack temporal and spatial resolution. But microsimulations are interesting for traffic flow simulation, as they can accurately simulate features requiring both high temporal and high spatial resolution, including traffic jams and peak periods. However, most microscopic approaches involve high computational costs and expensive large computers to run them within a reasonable time. This work presents possibilities for reducing these costs by using a queue-based model and an event-driven approach jointly. The approach makes it possible to run large-scale scenarios with more than 1 million simulated person-days on networks with 10,000 links in less than 10 min on single CPU desktop computers present in most offices today.
Modeling Overlap in Multimodal Route Choice by Including Trip Part-Specific Path Size Factors
Authors: Hoogendoorn-Lanser Sascha , Bovy Piet
Published: December 2007

Overlap in route choice is a well-known problem in travel analysis. Because of overlap, alternatives are no longer independent (statistical effect), whereas little is unknown about how overlap may influence travelers' choice behavior. In this paper, route overlap is dealt with by considering multiple path size factors. Instead of a single path size factor for a complete route (called the basic path size factor), separate path size factors for subroutes are proposed to account for differences in valuation of the overlap between them. Three possible specifications of subroute path size factors are considered. To study the impact of separate path size factors for subroutes, path size logit models, including subroute path size factors, are analyzed and compared with estimation results obtained with multinomial logit, generalized nested logit, and basic path size logit models. It appears that including separate path size factors for subroutes significantly improves modeling performance. Furthermore, travelers appear to value overlap differently depending on when the overlap occurs during the trip. Overlap in the home end and the activity end of the trip are valued negatively, whereas overlap in the train line-haul part is valued positively, improving the trip's attractiveness. The similarity in changes in values for all parameter estimates indicates that the new path size specifications capture additional behavioral effects. The best specification of the subroute-specific path size factor is based on the length of the full route and the total number of full routes that share the overlapping legs.
Land Use Scenario DevelopeR
Authors: Gregor Brian
Published: December 2007

Land use models are generally recognized as useful tools for forecasting land use inputs to transportation models and for analyzing the land use effects of transportation projects. Unfortunately, the complexity of most land use models gets in the way of their widespread use by planning agencies. The Land Use Scenario DevelopeR (LUSDR) incorporates most of the land use behavior and policy sensitivity desired in a land use model, yet it has a simple structure and manageable data requirements. LUSDR operates at the level of individual households and employment establishments and microsimulates location decisions of land developments. The model produces a synthetic population of households with the attributes of size, workers, age of household head, income, dwelling tenure, and dwelling type. Households are packaged into residential developments. Employment is calculated from workers and allocated to economic sectors, employment establishments, and business developments (e.g., shopping centers, office parks). Residential and business developments are allocated to zones by an iterative process that identifies candidate zones on the basis of land availability and plan compatibility, chooses zones by using a location model and reconciles land supply and demand in each zone through a bidding process. The model is being used in a long-range land use visioning study in a small metropolitan planning organization and is planned for use in a number of applications in Oregon.
Aircraft Computers
Authors: Satterthwaite Charles P.
Published: December 2007

The aircraft industry and the computer industry are relative newcomers in two centuries of technical innovation. It is only natural that these powerful industries have merged to provide continuous improvements in capabilities and services for aircraft customers. Landau defines an aircraft as any structure or machine designed to travel through the air. He then defines a computer as a person who computes or a device used for computing. From these definitions, an aircraft computer is a device used on (or in association with) any air‐traveling machine or structures used to make computations. Computers can be found in every aspect of the aircraft industry. On the aircraft, there are computers for flight control and display, computers monitoring and regulating flight functions, computers recording and processing flight activities, computers providing passenger entertainment, and computers providing communication and navigation. Equally important are the ground‐based computers at airports, maintenance depots, and air traffic control stations that provide services for all aspects of flight.
Carry Logic
Authors: Lu Shih‐Lien , Ramachandran Ravichandran
Published: December 2007

Throughout this article, carry propagation with respect to fixed‐point binary addition will be discussed. As a multitude of 2‐input logic gates could be used to implement any algorithm, all measurements are made in terms of the number of 2‐input NAND gates throughout this study.
Cooperative Database Systems
Authors: Chu Wesley W.
Published: December 2007

Research in cooperative answering stems from three areas: natural language interface and dialogue systems, database systems, and logic programming and deductive database systems. The emphasis of this article is on cooperative databases. It covers such topics as presuppositions, misconceptions, intensional query answering, user modeling, query relaxation, and associative query answering.
Database Languages
Authors: Wang George (Taehyung) , Sheu Phillip C‐Y , Kitazawa Atsushi , Yamaguchi Hiroshi
Published: December 2007

A database management system (DBMS) consists of a collection of databases and a set of programs that enable users to create and maintain the data in the databases. The DBMS must provide an appropriate database language for each category of users such as database administrators (DBAs), database programmers, and end users. In general, a database management system provides two different types of languages: a data definition language (DDL) to specify database schema and a data manipulation language (DML) to retrieve, insert, delete, and modify data.
Dataflow Computers: Their History and Future
Authors: Hurson Ali R. , Kavi Krishna M.
Published: December 2007

The dataflow model of computation offers an attractive alternative to control‐flow in extracting parallelism from programs. The execution of a dataflow instruction is based on the availability of its operand(s); hence, the synchronization of parallel activities is implicit in the dataflow model. Instructions in dataflow model do not impose any constraints on sequencing except for the data dependencies in the program.

The elegant representation of concurrency in dataflow computation led to considerable interest in dataflow modes over the past three decades. These efforts have led to successively more elaborate architechtural implementations of the model. However, studies form past projects have revealed a number of inefficiencies in dataflow computing. Recent advances that may address these deficiencies have generated a renewed interest in dataflow. In this article we will survey the various issues and developments in dataflow computing.
Dimensionality Reduction
Authors: Dash Manoranjan , Liu Huan
Published: December 2007

Dimensionality reduction studies methods that effectively reduce data dimensionality for efficient data processing tasks such as pattern recognition, machine learning, text retrieval, and data mining. We introduce the field of dimensionality reduction by dividing it into two parts: feature extraction and feature selection. Feature extraction creates new features resulting from the combination of the original features; and feature selection produces a subset of the original features. Both attempt to reduce the dimensionality of a dataset to facilitate efficient data processing tasks. We introduce key concepts of feature extraction and feature selection, describe some basic methods, and illustrate their applications with some practical cases. Extensive research into dimensionality reduction has being carried out for many decades. Even today its demand is further increasing due to important high‐dimensional applications such as gene expression data, text categorization, and document indexing.
Distributed and Collaborative Development
Authors: Shim Hyong‐Sop , Prakash Atul , Lee Jang Ho
Published: December 2007

This article discusses key design concepts and research issues in CSCW, especially those relevant to providing awareness support for distributed software development, and provides a survey of CSCW systems and tools in this area. Common collaboration practices in open‐source development efforts we described and contrasted with those supported by specialized CSCW systems.
Home Computing Services
Authors: Mundorf Norbert , Kolbe Lutz
Published: December 2007

Driven by convergence, multimedia entertainment, price decline, and other factors, home computing services have emerged as an independent market from the corporate realm. This article describes the drivers behind this development. Using a framework, it structures the services in eight main categories. Applications, status quo, and trends are presented.
Instruction Sets
Authors: Gokhale Maya B. , Schlesinger Judith D.
Published: December 2007

Instruction sets began very simply and then became more complex as hardware gained complexity. By the 1980s, instruction sets had become sufficiently complex that a movement began to return to simpler instruction sets, albeit not the simplicity of the early machines. Reduced instruction set computers (RISC) architectures were introduced, in contrast to the complex instruction set computers (CISC) that were then in vogue. Another instruction set style, very long instruction word (VLIW), was also introduced in the 1980s as a means of increasing the parallelism within an instruction. Characteristics of each of these styles appear in modern instruction sets.

In addition to these
general‐purpose
ISAs, special‐purpose architectures, such as vector and parallel machines, and digital signal processors (DSPs), require ISAs that capture their unique capabilities.
Intelligent Agent
Authors: Zhang Chengqi , Zhang Zili
Published: December 2007

This article provides an insight for general readers on what intelligent agent is in the context of computer science and engineering. It describes the major developments that have led up to the current great interest in intelligent agents and then presents a brief discussion of the principal scientific and engineering issues in the field, which include the architecture of intelligent agents, communication languages for intelligent agents, and the methodologies and development tools for building intelligent agents. The typical applications and technological challenges for research and development over the next decade are also summarized.
Knowledge Acquisition
Authors: Kamel Magdi N.
Published: December 2007

Knowledge acquisition is the process by which problem‐solving expertise is obtained from some knowledge source, usually a domain expert. This knowledge can then be implemented into an expert system program that can provide expert assistance to nonexperts when and where a human expert is not available. Traditionally knowledge acquisition is accomplished through a series of long and intensive interviews between a knowledge engineer, who is a computer specialist, and a domain expert, who has superior knowledge in the domain of interest. The difficulty, time, and cost of manual knowledge acquisition, however, have stimulated research in developing machine learning approaches that autonomously acquire knowledge from data sources without the assistance of humans.

This article presents an in‐depth overview of knowledge acquisition by discussing the fundamental concepts of knowledge, types of knowledge, the process of knowledge acquisition, and knowledge acquisition methods. The article presents a classification that divides knowledge acquisition methods into three categories: manual methods, combined manual and automated methods, and automated methods. Manual methods discussed include interviews, task‐based methods, and expert self‐elicitation. Combined manual and automated methods discussed include expert‐driven and knowledge engineer‐driven approaches. Automated methods presented include learning by induction, neural networks, genetic algorithms, and analogical and case‐based reasoning. The article also addresses knowledge presentation and discusses eight of the most common representation methods: logic, production rules, frames, semantic networks, objects‐attributes‐value triplets, scripts, decision tables, and decision trees. The article concludes with a discussion of validation and verification of acquired knowledge.
Knowledge‐Based Computation
Authors: Leake David , Reichherzer Thomas
Published: December 2007

The knowledge‐based computation approach to artificial intelligence develops and studies intelligent systems that exploit explicitly represented knowledge. The approach addresses questions such as how knowledge should be represented in computational systems, what knowledge must be captured for a particular task and task domain, how knowledge should be organized, and how knowledge should be applied. This article introduces theoretical foundations for knowledge‐based computation, presents knowledge representation principles, and samples major approaches, trends, and opportunities for knowledge‐based computing.
Middleware for Distributed Systems
Authors: Schantz Richard E. , Schmidt Douglas C.
Published: December 2007

Improvements in hardware and networking technologies over the past decades have yielded dramatic increases in computer and communication capabilities. Despite these advances, the effort and cost required to develop, validate, port, and enhance software for distributed systems remained remarkably high. Much of the complexity and cost of building these systems can be alleviated by the use of highly flexible, efficient, dependable, and secure
middleware
, which is infrastructure software that resides between the applications and the underlying operating systems, networks, and hardware, specifically intended to provide a more appropriate platform for building and operating distributed systems. Middleware's primary roles are to (1) functionally bridge the gap between application programs and the lower‐level hardware and software infrastructure to coordinate how parts of applications are connected and how they interoperate and (2) provide reusable services that can be composed, configured, and deployed to create distributed systems rapidly and robustly by integrating components that may be developed by multiple technology suppliers.
Multicast Protocols and Algorithms
Authors: Polyzos George C. , Xylomenos George
Published: December 2007

Multicast refers to the transmission of data from one sender to an arbitrary set of receivers, a service useful for applications such as group conferencing, media distribution, and update of replicated databases. From an application viewpoint, the importance of multicast is that it allows adressing a set of receivers via a common identifier. From a network viewpoint, the importance of multicast is that when the transmission paths between the sender and the receivers share some links, multicast can conserve resources by only sending the data once over each such link. The most important issues raised by multicast are routing data to multiple destinations with minimal delay and/or duplication, handling feedback from possibly numerous receivers in a scalable manner, and providing appropriate quality of service for data delivery to each receiver.
Neural Controllers
Authors: Garg Devendra P. , Kumar Manish
Published: December 2007

Conventional control techiques such as DIP control, robust control, and optimal control have traditionally been used to control linear and nonlinear systems. These techniques are based on the model of the system, and their performance is largely dependent on the accuracy of the model. Modern control systems are charactgerized by their increassing complexity, nonlinearity, intelligence, enhanced ability to adapt and learn, and roubstness to uncertainty. Often, the dynamics of these systems are time‐delayed, ill‐defined, extremely nonlinear, and very complex, which makes it difficult to obtain an accurate analytical model of the system. This reality added to the uncertainties present in the environment and measurement devices, makes it particularly challenging to employ conventional techniques to control such systems. The ability of neural networks to handle nonlinear and ill‐defined problems, perform in the presence of noise and uncertainty, learn and adapt to changes in system parameters, and approximate functions and identify nonlinear systems have made them a popular choice for controlling such complex systems. Extensive research has been carried out over the last two decades for using neural networks to control nonlinear systems, and several neural network architectures have been proposed. This progress has led to a widespread application of neutral controllers in several of fields, such as the aerospace, communications, automated manufacturing, robotics, medical diagnosis systems, electric power systems, and process industries.
Class and Object
Authors: Dong Jing , Han Jianchao
Published: December 2007

Class and object are the fundamental concepts of object‐oriented technologies. All other concepts are based on them. In this article, the concepts of class and object are defined. Their relationships are also discussed. Class and object diagrams are presented for modeling static and dynamic structures of object‐oriented software systems.
Software Aging and Rejuvenation
Authors: Trivedi Kishor S. , Vaidyanathan Kalyanaraman
Published: December 2007

Several recent studies have established that most system outages are due to software faults. Given the ever‐increasing complexity of software and the well‐developed techniques and analysis for hardware reliability, this trend is not likely to change in the near future. In this article, we discuss the phenomenon of software aging and a preventive maintenance technique to deal with this problem called software rejuvenation. Stochastic models to evaluate the effectiveness of preventive maintenance in operational software systems and to determine optimal times to perform rejuvenation for different scenarios are described. We also present measurement‐based methodologies to detect software aging and estimate its effect on various system resources. These models are intended to help develop software rejuvenation policies. An automated online measurement‐based approach has been used in the software rejuvenation agent implemented in a major commercial server.
Video Conferencing and
IP
Telephony
Authors: Feng Wu‐chi
Published: December 2007

This chapter describes the areas of video conferencing and voice over IP telephony applications. The chapter is broken into three main components: digital media basics, managing interactive multimedia applications over networks, and multimedia networking issues for video conferencing and voice over IP. The digital media basics component will cover basic multimedia compression and streaming technologies. The managing interactive applications section will describe H.323 and SIP, two of the primary protocols deployed to enable video conferencing and voice over IP. Finally, we will describe some techniques that have been deployed to help in the adaptation of digital media to the available network resources on the Internet.
Autonomy‐Oriented Computing (
AOC
)
Authors: Liu Jiming , Jin Xiaolong , Tsui Kwok Ching
Published: December 2007

This article describes a new programming paradigm called
autonomy‐oriented computing
(AOC), which describes the construct of synthetic autonomy in locally interacting entities, and use the aggregated effects of entity interactions to generate desired global solutions or systems dynamics. The fundamental working mechanism of
self‐organization
that underlies the AOC paradigm offers the advantages of natural formulation as well as scalable performance to characterize complex systems or to computationally hard problems that are distributed and large scale in nature.
Rough Set Theory
Authors: Pawlak Zdzisław , Polkowski Lech , Skowron Andrzej
Published: December 2007

In this article, basic concepts and different areas of research in rough set theory are presented.
System Monitoring
Authors: Liu Yanhong A. , Tsai Jeffrey J. P.
Published: December 2007

System monitoring collects information about the behavior of a computer system while the system is running. This article examines components and techniques for system monitoring, monitoring principles, workload selection, and implementation.
Data Search Engine
Authors: Meng Weiyi , He Hai
Published: December 2007

This article provides an overview of the key technologies used to implement various types of search engines, including document search engines, database search engines, document metasearch engines, and database metasearch engines.
Decision Support Systems: Foundations and Variations
Authors: Holsapple Clyde W.
Published: December 2007

Now in their fourth decade, decision support systems have progressed to the point of being so diverse in nature and so widespread in everyday use that they are often taken for granted, not even being recognized for what they are. Yet, they have major positive impacts on both individuals and organizations. This article provides a foundation for understanding decision support systems. We examine why they exist, how they differ from other classes of software systems (e.g., management information systems), their basic architecture, and variations in their implementations and features. With this foundation, we can more fully grasp today's decision support options and be in a position to better appreciate the ever advancing frontier of decision support system research.