bluuebunny/crossref_metadata_2025 huggingface dataset:
The catalytic pyrolysis of citric acid to itaconic and citraconic acids
Authors: Askew F. A. , Tawn A. R. H.
Published: July 2007

The yield of itaconic and citraconic acids obtained by laboratory‐scale pyrolysis of anhydrous citric acid can be markedly increased by various catalysts. The best catalyst of those examined was K2HPO4, which, at 5% of the citric acid used, increased the yield of mixed acids from 26% to 64% theoretical at 280°C. There is some indication that the relative proportion of citraconic and itaconic acids is influenced by the catalyst; AlPO3 yields a higher proportion of itaconic than K, HPO, but a lower total yield. Each positive catalyst appears to have a more or less strongly marked optimum temperature in the range 240–270deg;c. Increase in batch size, investigated using K2HPO4, was found to diminish the yield.
The examination of compositions prepared from polyvinyl chloride and related polymers
Authors: Haslam J. , Newlands G.
Published: July 2007

A method has been developed for the examination of compositions prepared from polyvinyl chloride and related polymers. Its purpose is to recover the polymer from the. composition by solution in tetrahydrofuran, followed by subsequent precipitation of the polymer with alcohol from the tetrahydrofuran solution.

Figures are given for the chlorine contents of polymers used in the preparation of compositions and of the corresponding polymers recovered from tetrahydrofuran solution; the influence of the test on the infra‐red spectra of the polymers is indicated.
The photocatalysed oxidation of polythene
Authors: Pross A. W. , Black R. M.
Published: July 2007

Polythene of molecular weight 11,000 to 22,000 on exposure to bright sunlight undergoes deterioration resulting in embrittlement and degradation of electrical and mechanical properties. Deterioration is thought to be due to photocatalysed oxidation and this per describes a study of deterioration by artificial ageing. Curves relating power factor to oxygen absorption arc shown. The ultra‐violet absorption spectrum shows that the attack is probably due to the presence of carbonyl groups as an impurity in the polythene.

The effect of antioxidant addition was followed by folding endurance tests. Infra‐red absorption spectra between 2.5μ. and 15μ. have been mapped before and after irradiation and the presence of hydroxyl, carbonyl and carboxyl groups established. The photochemical mechanism has been discussed and it is thought that the carbonyl groups are responsible for initiating the deterioration.
Hydrogenolysis of phenols in middle oils from coal hydro‐genation
Authors: Orchin Milton , Storch H. H.
Published: July 2007

When the middle oils obtained from the hydrogenation of coal were hydrogenated at 450° and 475° c. in a stainless‐steel autoclave in the absence of any added catalyst, very little of the phenolic material was convened to neutral products. Whereas the original material contained only 2·9%, phenols boiling below 230° c., the hydrogenated product (at 475° c.) contained 9·1% (based on the charge) phenols boiling below this temperature. When the phenolic fraction of the middle oil was isolated before hydrogenolysis and then treated, more conversion of high‐boiling to low‐boiling phenols occurred, but this was accompanied by elimination of oxygen and the production of about 20% neutral material.
Formaldehyde condensations with phenol and its homologues. V. The methylol compounds of 3 : 5‐dimethylphenol
Authors: Finn S. R. , Lewis G. J. , Megson N. J. L.
Published: July 2007

The structure of the monoalcohol of 3 : 5‐dimethylphenol, first made by von Auwers and believed to be a para‐substituted derivative, has now been confirmed. The synthesis of a new dialcohol, which has been characterized as an ortho‐ortho compound, is described. The effect of reaction conditions on the position of methylol substitution is discussed. It has been shown that during characterization of the monoalcohol, by pyrolysis with lime, methyl migration may occur.
Formaldehyde condensations with phenol and its homologues. VI. The trinuclear compound from p‐cresol
Authors: Finn S. H. , Lewis G. J.
Published: July 2007

It has been know since 1930 that a compound, m.p. 215° c., can be isolated from a p‐cresol‐formaldehyde resin made under acid conditions. The accepted structure of this compound was that of a linear molecule of three benzene rings linked by two methylene bridges. It was later suggested that the compound had a cyclic four‐ring structure, but evidence is now presented in support of the earlier trinuclear formulation. A new three‐ring compound, containing two chlorine atoms in place of two methyl groups, is also described.
Spectrophotometric determination of praseodymium, neo‐dymium and samarium
Authors: Wylie A. W.
Published: July 2007

The Beckman spectrophotometer (Model DU) has been used to determine the position and intensity of various absorption bands in aqueous solutions of several praseodymium, neodymium and samarium salts. The extinction coefficients of certain bands of these elements have been measured, and some factors influencing the bands have been investigated.
Unsaturation in petroleum as indicated by halogen addition methods
Authors: Winward A. , Garner F. H.
Published: July 2007

Straight‐run gas oils have appreciable bromine and iodine values but it is believed that no unsaturated hydrocarbons are present. The reaction with Hanus reagent, iodine bromide, is shown by analysis to be largely one of substitution and to be attributable to certain aromatic hydrocarbons distilling in the gas oil range. Of 23 hydrocarbons, including 17 aromatic hydrocarbons, the only hydrocarbons giving appreciable iodine values were mesitylene and isodurene which possess a 1: 3: 5‐trialkyl substituted aromatic ring: it is therefore probable that this structure is responsible for the apparent unsaturation of the higher‐boiling petroleum fractions.
LIMITS FOR THE PROPAGATION OF FLAME IN ACETALDEHYDE‐OXYGEN‐NITROGEN MIXTURES
Authors: White A. Creville , Joses Elwyn
Published: July 2007

In order to assess, and possibly find a method of reducing, the explosion huard in the manufacture of acetic acid from acetalde‐hyde, a knowledge was required of the range of acctaldehyde‐oxygen‐nitrogen mixtures capable of propapating flame under wrious conditions. The limits of inflammability in such mixtures were therefore determined for upward, horizontal and downward !lame‐propagation in glass tubes of I‐, 2‐ and 3‐in. diameter at room temperature and at soo C. The effect of contamination with carbon dioxide, acetylene and acetic acid was also examined, as well as that of using aluminium tubes in place of glass. The range of inflammability in the acetaldehydroxygen‐nitrogen system is exceptionally wide and offers little hope of eliminating explosion risks in the manufacture of acetic acid, the best safeguard being to minimize free space and place suitable guards at vulnerable points.

The results show that in acetaldehydc∼∼gen‐nitrogen mixmres, the lower limit is mainly a function of the acetaldehyde content, whereas the upper limit is mainly determined by the oxygen content; this suggests that the calorific value Of the gas is an important factor in limit propagation. Another important factor in the case of acetaldehyde is the apearancc of the ‘cool’ flame. This causes a marked extension of t!e upper limit, from which it is inferred that the products of ‘cool’ flame combustion are incompletly oxidized, the main constituent being possibly acetic acid.
SIZE DISTRIBUTIONS OF EMULSIONS
Authors: Jellinek H. H. G.
Published: July 2007

A systematic trcatmcnt of distribution functions of emulsions and thcir average quantitics is given. An equation derived by Rossi cxprcssing number‐sizc distributions of emulsions is discussed; additional distribution functions and average quantitics me dcrivcd for this case.
α‐monostearin and sodium stearate as emulsifying agents. III
Authors: Jellinek H. H. G. , Gordon A.
Published: July 2007

The action of sodium chloride, barium chloride, magnesium sulphate, aluminium sulphate, sodium nitrate and sodium sulphate on emulsions containing 1% (w/v) α‐monostearin in water‐white‐ oil and 0·5% (w/v) sodium stearate in water was investigated.

The phase separation curves for the emulsions containing the univalent salts were similar. The emulsions were of the O/W type; the oil separation became very rapid when a certain concentration of salt was reached.

The bi‐ and tervalent salts caused phase inversion of the emulsions and precipitation of (some of) the emulsifying agents.

The action of pH on the emulsions was also investigated. The stability of the emulsions decreased with decreasing pH values and the structure of the emulsions became complex; at higher PH values however, very mobile and stable O/W emulsions were obtained.
The insoluble matter of coal tar. VI. Oxidation of free carbon
Authors: Green S. J. , Thakur B.
Published: July 2007

Work on the oxidation of carbonaceous materials with alkaline potassium permanganate is briefly outlined and the experimental step‐wise oxidation of free carbon is described. The course of reaction as interpreted from these results is indicated. Bulk oxidation of free carbon and the nature of the products are reported. In the steam‐volatile fraction, formic, acetic and butyric acids have been identified. The water‐soluble non‐volatile acids and their methyl esters have been fractionated. Oxalic, succinic, phthalic, terephthalic and mellitic acids have been identified in the oxidation products. The major portion of the acids, however, was found to be more complex, probably having polynuclear structures.

Oxidation of C1 and C2 shows that C3 is more highly condensed than C2 and resembles graphite and coke in its properties.
The preparation of phosphotungstic acid and of sodium and barium phosphotungstates
Authors: Phillips M. A.
Published: July 2007

Methods of preparation are given for phosphotungstic acid, 3H2O.P2O5.24WO3, as distinct from the sodium salt, 3Na2O.P2O3, 24WO3.NH2O. The acid has an approximate solubility in water at room temperature of 5 parts in 1 part of water and the sodium salt has a solubility of approximately 1 in 1 part of water. The acid requires 1·12 c.c. 2N‐sodium hydroxide per g. to make it neutral to phenolphthalein whereas the latter requires 0·15 c.c. per g. The acid is a strong one and cannot be released from its sodium salt by hydrochloric or nitric acids, so that it must be prepared from barium phosphotungstate by use of sulphuric acid, taking advantage of the insolubility of barium sulphate. A preparation of barium phosphotungstate and of barium tungstate is included.
The chlorination of ethylene and propylene. I. The chlorination of ethylene
Authors: Galitzenstein E. , Woolf C.
Published: July 2007

The chlorination of ethylene in the liquid phase to form 1 : 2‐dichlorocthanc (ethylene dichloride), has been investigated in some detail, catalysts such as antimony trichloride and ferric chloride being employed, at temperatures between 4° and 44° c. The effect of excess of either reactant has been studied, and the use of mixtures of ethylene with methane tried.

The influence of sunlight and water in these reactions, and the formation of by‐products such as 1:1: 2‐trichloroethonc and β‐β′‐dichlorodiethyl ether, arc discussed.
The chlorination of ethylene dichloride
Authors: Galitzenstein E. , Woolf C.
Published: July 2007

The chlorination of ethylene dichloride to form mainly 1:1:2‐trichloroethane has been investigated. Various catalysts have been tried, but with most of those described in the literature, e.g. antimony chloride, the reaction is slow in the absence of light; in the presence of sunlight substitution is rapid. The use of aluminium chloride leads to the formation of tetrachloroethanes.

Smooth chlorination to trichloroethane is also possible by the use of sulphuryl chloride, with benzoyl peroxide as catalyst; the bulk of the sulphuryl chloride is recoverable with the aid of activated charcoal.
The dehydrochlorination of propylene dichloride
Authors: Galitzenstein E. , Woolf C.
Published: July 2007

The catalytic dehydrochlorination of propylene dichloride has been studied, with particular reference to the preparation of allyl chloride. Various solid catalysts have been tried, at temperatures between 200° and 450° c, but in every case mixtures of the three isomeric monochloropropenes have resulted. The most satisfactory performance was given by iodine at 450° c. which, at 0·5% concentration, gave 20°, conversion into mixed chloropropenes containing 31% allyl chloride. Side reactions were small, the yield of chloropropenes based on propylene dichloride consumed being 85·8°.
The corrosion of steel by sea salt of given moisture content
Authors: Duly S. J.
Published: July 2007

The moisture content of the residue obtained by evaporating sea water is shown here to be determined by the relative humidity of the air in which it is subsequently kept, provided that the storage temperature does not vary: samples of such sea salt corrode mild steel in proportion to their moisture contents. It follows that the extent of corrosion of mild steel by sea salt is governed by the relative humidity of the ambient air and that keeping the moisture content of the salt‐complex at 8% or less substantially prevents corrosion from this cause.
The effect on water vapour pressure of superimposed air pressure
Authors: Webster T. J.
Published: July 2007

In a compressed gas saturated with water vapour the vapour pressure of the water exceeds the normal value by an amount which is greater than can be predicted by Poynting's thermodynamic relationship. A quantitative knowledge of this behaviour is important in the design of equipment for drying compressed gases, particularly for drying by refrigeration, which is commonly used in the low‐temperature separation of air.

The equilibrium moisture‐content of compressed air at pressures from atmospheric to 200 atm, has been experimentally determined at temperatures between 15° c. and −35° c. It has been found that the vapour pressure of water and ice increases progressively as the total pressure on the system is increased and that the relative increase in vapour pressure at a particular pressure becomes grester as the temperature of the system is lowered. At a total pressure of 200 atm. and a temperature of −35° c. the water content of saturated air is more than three times the calculated value assuming the normal vapour pressure and 2.6 times that derived from Poynting's relationship.
The derivation of job designs
Authors: Clegg Chris W.
Published: July 2007

This paper presents a theoretical account of the derivation of job designs incorporating consideration of technology, structure and managerial control, viewed from an information processing perspective. A conceptual distinction is made between tasks and roles which has practical relevance in that organizations have independent choices regarding their design. These choices are underpinned by economic and psychological values as well as by managerial needs for control.

The paper argues that whilst options exist, organizations typically choose to simplify jobs, a strategy which may well be ineffective, especially under conditions of uncertainty. New, more complex job designs may be very difficult to implement for economic, psychological, managerial and political reasons. Research and development should now be directed towards a more detailed cognitive and social psychological understanding of the derivation and impact of job designs as well as towards study of the introduction and impact of new technology. These represent qualitative shifts in research emphasis.
The effects of perceived organizational support and perceived supervisor support on employee turnover
Authors: Maertz Carl P. , Griffeth Rodger W. , Campbell Nathanael S. , Allen David G.
Published: July 2007

This study examines mediated effects of perceived supervisor support (PSS) and perceived organizational support (POS) on turnover cognitions, and their interactive effects on turnover behavior in a sample of 225 social services workers. In this study, we address a seeming contradiction in current findings regarding support and attachments to managers versus attachments to the organization itself. The POS literature suggests fully mediated causal paths to turnover from POS and PSS, through affective commitment. Whereas, the commitment, LMX, and turnover literatures suggest alternative causal paths that imply broader effects for POS and PSS on turnover. Contrary to earlier POS literature, findings showed that PSS had independent effects on turnover cognitions not mediated through POS. Model tests also indicated that POS had significant effects on turnover mediated through normative commitment, as well as affective organizational commitment. Moreover, a new significant interactive relationship was discovered such that low PSS strengthened the negative relationship between POS and turnover, while high PSS weakened it. Implications for research and practice are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Quasi‐analytical static solution for the generalized boxed coplanar waveguide
Authors: Drake Enrique , Medina Francisco , Horno Manuel
Published: July 2007

A quasi‐analytical method for computing the quasi‐static‐TEM parameters of the generalized coplanar waveguide (GCPW) is reported. The structure is assumed to be enclosed in a rectangular frame and embedded in a layered medium. Essentially, the method is an analytically enhanced spectral domain formulation. Its application leads to virtually exact results in very short CPU times, making it suitable for CAD purposes. Although the method is somewhat more time consuming than conformal mapping approaches, it is a useful alternative because of its exactness and ability to deal with multilayer structures. © 1994 John Wiley & Sons, Inc.
Efficient analysis of passive microstrip elements in MMICs
Authors: Naishadham Krishna , Nuteson Todd W.
Published: July 2007

A new full‐wave, space‐domain moment method implementation is developed for the analysis and circuit‐characterization of passive microstrip elements (in an open environment) at microwave frequencies. The computational time and memory requirements are significantly reduced by filling the moment matrix efficiently utilizing closed‐form Green's functions and symmetries in the problem formulation, such that a circuit of moderate electrical size can be analyzed in reasonable time on a personal computer. © 1994 John Wiley & Sons. Inc.
Dielectric resonator antennas—a review and general design relations for resonant frequency and bandwidth
Authors: Mongia Rajesh K. , Bhartia Prakash
Published: July 2007

Open dielectric resonators (DRs) offer attractive features as antenna elements. These include their small size, mechanical simplicity, high radiation efficiency due to no inherent conductor loss, relatively large bandwidth, simple coupling schemes to nearly all commonly used transmission lines, and the advantage of obtaining different radiation characteristics using different modes of the resonator. In this article, we give a comprehensive review of the modes and the radiation characteristics of DRs of different shapes, such as cylindrical, cylindrical ring, spherical, and rectangular. Further, accurate closed form expressions are derived for the resonant frequencies, radiation Q‐factors, and the inside fields of a cylindrical DR. These design expressions are valid over a wide range of DR parameters. Finally, the techniques used to feed DR antennas are discussed. © 1994 John Wiley & Sons, Inc.
Application of fault modeling to continuous built‐in test (c‐BIT) for microwave and MMIC circuits
Authors: Rhodes David L. , Cummings Michael T. , Tempel George F.
Published: July 2007

A simulation‐before‐test method has been applied to the linear and nonlinear microwave built‐in test (BIT) problem. Fault simulation via a harmonic balance simulator is used to analyze and optimize BIT hardware placement based on figures of merit such as fault coverage, ambiguity size, and part isolation. Fault models for a prototype microwave mini‐system were developed along with models for the BIT hardware itself. The search method developed to automate the placement of BIT hardware is an essential design‐for‐test tool. The techniques developed were applied to an example system and results are given.
Three‐dimensional electromagnetic simulation of electronic circuits of general shape
Authors: Zheng Jian‐X.
Published: July 2007

A general purpose CAD tool, the IE3D electromagnetic simulator is presented in this article. The simulator is based on an integral equation, a method‐of‐moment formulation for a full‐wave solution of three‐dimensional (3D) arbitrarily shaped structures in microwave and millimeter‐wave integrated circuits (MMIC), high temperature superconductor (HTS) circuits, microstrip antennas, RF printed circuit boards (PCB), and high speed digital circuit packaging. The primary solution of the simulator is the current distribution on a metallic structure in an environment of multilayered substrates on infinitely extended ground plane. The circuit parameters of the structure in either S‐parameter form or RLC‐SPICE equivalent circuit form is extracted from the solved current distribution. The simulator consists of an MS‐Windows‐based layout editor, a schematic editor, an electromagnetic simulator, and a post processor. The simulator can perform stand‐alone electromagnetic simulation and optimization and mixed electromagnetic and nodal analysis. Simulation results for structures in various high frequency and high speed domains are presented and compared to measured results. © 1994 John Wiley & Sons, Inc.
Characteristics of rectangular dielectric waveguide with sinusoidally varying width
Authors: Mohammadi Abbas , Pramanick Protap
Published: July 2007

Wave propagation along a rectangular dielectric waveguide with slowly varying width has been studied using a transformed coordinate system and an effective cross‐section approach. The associated differential equation has been solved using numerical analysis and Hill's analysis. The computed results have been verified using the cascaded transmission line matrix analysis of the structure in the original coordinate system. The agreement is found to be excellent. Many properties of the modulated periodic structure, for example, the propagation constant, the phase and the group velocities, the axial dependence of theEy11mode. and the space harmonic, have been studied. The results and the method will be useful in computer‐aided design of dielectric waveguide phase shifters and filters. © 1995 John Wiley & Sons, Inc.
An accurate dispersion expression for shielded microstrip lines
Authors: Wells Garnet , Pramanick Protap
Published: July 2007

A closed‐form dispersion expression for shielded microstrip lines is presented here for the first time. The expression is valid for a wide range of frequencies, geometrical parameters, and substrate dielectric constants. Unlike previous expressions for open microstrip lines, the inflection frequency of the dispersion curve has been chosen to be a quadratic function of the frequency at which the quasi‐TEM mode of the microstrip couples strongly with the lowest order transverse electric mode of the equivalent parallel plate waveguide of the microstrip. Because this expression is accurate with respect to numerical techniques, it will be useful in time and frequency domain analyses of various shielded microstrip discontinuities, components, resonators, and VLSI packagings. Dispersion in open microstrip can be treated as a special case of this expression. © 1995 John Wiley & Sons, Inc.
Optimizing a microstrip bandpass filter using electromagnetics
Authors: Swanson Daniel G.
Published: July 2007

In this article, we will describe the design and optimization of a microstrip bandpass filter using an electromagnetic field‐solver as the analysis engine. The filter is analyzed and optimized using a cascade of field‐solver solutions. Convergence issues and proper mesh setup for the various subnetworks are discussed. And the necessary compromise between accuracy and solution time is also explored. © 1995 John Wiley & Sons, Inc.
Accurate design equations for covered microstrip coupled lines
Authors: Wan Changhua
Published: July 2007

Using the modified conformal mapping technique, closed‐form quasistatic design equations for covered microstrip slot/parallel‐coupled lines are derived in this article. They are found to be more accurate than the existing ones, when compared with the rigorous results by numerical methods. Specifically, the derived equations for the even‐mode properties of slot‐coupled lines and those for the odd‐mode properties of parallel‐coupled lines are extremely useful because the existing counterparts are either too rough or too inaccurate for use. In addition, two sets of available design equations for covered microstrip single line, which is equivalent to the covered microstrip slot‐coupled lines under odd‐mode excitations, are checked and recommendations are given.
An investigation on the effect of undercutting on the propagation parameters in single and coupled quasi‐TEM lines in a multilayered dielectric
Authors: Gentili Gian Guido
Published: July 2007

The effect of undercutting on the electrical parameters of general single and coupled quasi‐TEM lines in a multilayered dielectric is studied by an efficient quasistatic numerical method. Results are presented for characteristic impedance, propagation constant, and attenuation constant in single lines; two symmetrical coupled lines; and a four‐line system. In all cases studied a significant increase of losses has been observed.
Targeted ROTational magnetic resonance angiography (TROTA)
Authors: Goldfarb James W.
Published: July 2007

An MR angiographic method is presented in which a rotating 2D slice is centered on and targets a region or vessel of interest. Collecting a series of slices rotating about the center of the targeted region yields projection data sufficient for the calculation of 3D volumetric data of the region using conventional backprojection reconstruction techniques. These volumetric data depict the internal structure of the vessel and can be processed and displayed with multiplanar reformation, maximum intensity projections, and 3D rendering algorithms. The rotational angiographic acquisition preserves the high temporal resolution of 2D‐MR digital subtraction angiography with the added benefit of 3D reformatting and display. The method is explained in detail and results from phantom and human experiments are presented. Magn Reson Med, 2007. © 2007 Wiley‐Liss, Inc.
Estimating Ethernet Bridge Performance Requirements
Authors: Held Gilbert
Published: July 2007

In this article, we will examine the performance of an Ethernet Local Area Network (LAN) with the aid of a simple mathematical model, determine the utilization of an Ethernet LAN with frame length and frame rate monitoring equipment, and look at determining the bridge performance requirements for an Ethernet LAN.
Router Management—The SNMP Way
Authors: Morgenthal Steven , Henderson Frank
Published: July 2007

As LANS multiply across corporations, distributed processing has outgrown the ‘promising’ stage and has become an equal, both in scope of application and commercial potential, to the centralized computing approach.
Physical network management: An essential tool for managing growing networks
Authors: Upp Michael
Published: July 2007

Physical Network Management will not only be recognized as a new category of product, but will rise to the top as one of the key strategic issues for communications and network management.
Managing Image Files over the Network
Authors: Muller Nathan J.
Published: July 2007

Today's document‐imaging systems allow businesses and government agencies to move closer to a paperless office environment by providing the means to digitally store documents in massive image databases and manage their flow through various work processes. This method of document storage and management can solve many of the problems commonly experienced with paper files and help streamline business operations in the process.
Performance trending for management of packet‐switched networks
Authors: Sankar Ravi , Singh Ranvir
Published: July 2007

The objective in this paper is to develop and demonstrate the capability of applying modeling and simulation techniques to maintain the network integrity of a packet‐switched network. Here a new technique called performance trending is presented, in which key network parameters are monitored and network failure is predicted. A typical packet‐switched network is simulated to verify performance trending for network performance management.
Managing enterprise nets via the intelligent hub
Authors: Muller Nathan J.
Published: July 2007

Intelligent hubs provide the advantages of cable management, configuration flexibility, device control and interconnectivity with a variety of LAN media and carrier‐provided facilities and services.
Design and Analysis of Data Communication Systems
Authors: O'Clock George D. , Henderson Donald L.
Published: July 2007

A network can promote collaboration between many different and widely dispersed groups of workers. Expanding network capabilities and information flow throughout a business organization can help to improve quality, responsiveness, reaction time and, ultimately, sales and profits.
A study of FTP traffic: Estimation of the non‐optimality
Authors: Johannsen Thomas , Mansfield Glenn
Published: July 2007

File retrieval constitutes a major component of the traffic in the Internet. In the Internet the same file is in general offered by several servers and this redundancy gives rise to a lot of avoidable non‐optimality. In this work a study has been carried out to examine and estimate this non‐optimality.
HSSI Facilitates Bandwidth Allocation among Broadband Applications
Authors: Muller Nathan J.
Published: July 2007

The High Speed Serial Interface (HSSI) is a standard recommended by the Electronic Industries Association — Telecommunications Industry Association. It is designed to meet the growing demands of high‐speed data applications, eliminating the serial interface bottlenecks of V.35 and EIA‐422/499 when running applications over highspeed WANs.
An Optimal File Allocation Policy in a Networked Database Management System
Authors: Saha D. , Mukherjee A.
Published: July 2007

Optimal file allocation has been shown to be effective in reducing the average transaction processing time in a database system built upon a computer communications network. This paper investigates the use of a networked computing system to distribute files and to manage the system in an optimal fashion so as to minimize the sum of file storage and internode file transfer cost.
Cableless LANs: An emerging technology
Authors: McCarthy William R.
Published: July 2007

During the last year, the concept of Wireless Communications received enormous attention in the trade and financial journals worldwide. Unfortunately, as often occurs, everything from high‐performance LANs to cordless telephones is being lumped together, creating a great deal of confusion in the user community. So as not to add to that confusion, it should be made clear that this article deals exclusively with wireless systems for data communications.
Sidewinder: Defense in depth using type enforcement
Authors: Smith Richard E.
Published: July 2007

Sites use firewalls to defend against external attacks while providing necessary Internet services. Firewalls make a site safer: They present a smaller risk since they provide fewer services. However, most firewalls use standard computer operating systems. This can allow an attacker to overrun the firewall if a known security flaw is present. The Sidewinder(TM) firewall system overcomes this problem using type enforcement.

Network server applications operate in independently controlled compartments called domains, each granted specific permission to access particular types of files or communicate with other domains. If a server succumbs to an attack, type enforcement restricts the amount of damage an attacker can do. In particular, Sidewinder prevents an attack on an Internet server from accessing domains serving internal, protected networks. An attacker cannot overrun a Sidewinder because the type enforcement restrictions cannot be disabled while the system is handling network traffic.
High‐efficiency silicon solar cells: Full factor limitations and non‐ideal diode behaviour due to voltage‐dependent rear surface recombination velocity
Authors: Aberle Armin G. , Robinson Stephen J. , Wang Aihua , Zhao Jianhua , Wenham Stuart R. , Green Martin A.
Published: July 2007

Despite exceptionally high open‐circuit voltages, record high‐efficiency PERL (passivated emitter, rear locally diffused) silicon solar cells recently developed at the University of New South Wales demonstrate relatively low fill factors. This behaviour is shown to result from a surface recombination velocity at the rear Si‐SiO2 interface that increases with reducing voltage across the cell, leading to non‐ideal I‐V curves with high ideality factors (>1.3) near the maximum power point. When corrected for series resistance losses, the Air Mass 1.5 (AM1.5) fill factor of actual PERL cells is found to be limited to values below 82.9%, as opposed to the ideal theoretical limit of 85‐86% for silicon cells operating in low injection conditions. Relatively large series resistance losses (Rs > 0.35 ω cm2) further reduce this value to the experimentally observed fill factors below 81.4%.

Analysis of measured illuminated and dark I‐V characteristics of PERL cells reveals that the AM1.5 efficiency is mainly limited by recombination losses at the rear oxidized surface. Optimum PERL cell resistivity is about 2 ω cm. Owing to increased rear surface recombination velocity, lower resistivity material shows no advantage in open‐circuit voltage and suffers from short‐circuit current losses, while a strong reduction in the surface recombination velocity above the maximum power point results in smaller fill factors. High‐resistivity cells do show an improved short‐cuircuit current but suffer from voltage and fill factor losses.
A novel high open‐circuit voltagep‐nInP solar cell design
Authors: Kilmer Louis C. , Barnett Allen M.
Published: July 2007

The performance of InP solar cells has been limited by low open‐circuit voltages. While the reported short‐circuit current densities are approaching the theoretical limit, the open‐circuit voltages have yet to obtain what is expected from a semiconductor with a direct band gap of 1.35 eV. This work investigates the factors that determine the open‐circuit voltage and presents the design and fabrication of a novel high open‐circuit voltage p‐n InP solar cell. the key aspect of the novel design is a complete analysis of the top contact metallization effects on the reverse saturation current density and the open‐circuit voltage. the features of the design are not specific to InP solar cells but are applicable to other advanced material solar cells that require a thin emitter for an optimal design (those materials with a high absorption coefficient). By minimizing the reverse saturation current density, a high open‐circuit voltage and high efficiency may be obtained. In addition, a complete analysis of the solar cell modelling is provided, with comparisons to other published InP solar cell models and device results to juxtapose the key material and design parameter effects.
Grid‐support photovoltaics: Evaluation of criteria and methods to assess empirically the local and system benefits to electric utilities
Authors: Shugar Daniel S. , Hoff Thomas E.
Published: July 2007

In 1988, researchers at the Pacific Gas and Electric Company (PG&E) formulated the hypothesis that strategically sited photovoltaics (PV) could provide substantial local benefits to a utility's electrical transmission and distribution (T&D) system. Initial modelling of simulated data confirmed this hypothesis. These results indicated a need for empirical testing through operation of a commercial‐scale grid‐support PV plant within an appropriate utility T&D system. Towards this end, a comprehensive research plan was formulated to characterize and evaluate local and system benefits. Local benefits to be evaluated are: extended distribution transformer life, increased distribution planning area capacity, extended load tap changer life and maintenance intervals, reduced electrical line losses, improved system voltage, improved distribution system reliability and increased transmission system capacity. System benefits to be evaluated are: reduced system energy production costs, reduced requirements for additional generation capacity, reduced minimum load operation costs and reduced environmental impacts of fossil energy generation.

A 500 kW PV plant serving PG&E's Kerman Substation near Fresno, California, was selected and built as part of the Photovoltaics for Utility Scale Applications project. the plant began operating in April 1993, 6 months after construction was initiated, and evaluation of the benefits was initiated. Confirmation of the original hypothesis‐that strategically sited PV generation provides substantial benefits to selected T&D systems‐will demonstrate that PG&E and other utilities may be able to serve customers in a more cost‐effective and environmentally sensitive manner. In the process, utilities could provide new markets for PV and other modular generation technologies.
Decreased emitter sheet resistivity loss in high‐eficiency silicon solar cells
Authors: Aberle Armin G. , Wenham Stuart R. , Green Martin A. , Heiser Gernot
Published: July 2007

State‐of‐the‐art two‐dimensional (2D) numerical semiconductor device simulation tools are applied to bifacially contacted silicon solar cells of practical dimensions in order to investigate the 2D effects arising from ohmic voltage drops in cell emitters due to finite front metal grid line spacings. the 2D simulations show that for typical front finger spacings of high‐efficiency silicon solar cells the minority carrier flow in the base deviates strongly from the purely linear flow assumed by one‐dimensional (1D) theory. Compared to conventional 1D theory, this 2D effect results in reduced emitter sheet resistivity losses, an increased optimum front finger spacing and a reduced impact of finger spacing on cell efficiency. the 2D effects are of particular importance for concentrator solar cells.

The 2D simulations presented in this work considerably improve the general understanding of internal device physics of high‐efficiency silicon solar cells and reveal the limits of 1D models for the simulation of these devices.
Attaining a 30‐year photovoltaic system lifetime: The BOS issues
Authors: Durand Steven J.
Published: July 2007

Failures of power conditioning systems and balance of system (BOS) components have been responsible for the majority of system downtime in virtually all of the USA's large grid‐tied photovoltaic (PV) power plants. For these and future PV power plants, therefore, improvements in component reliability must be made before the design goal of a 30‐year system liftime can be attained. Advances in technology can increase reliability and still reduce costs of PV modules and power conditioning systems.

However, since BOS components come generally from mature technologies, increased reliability must be attained through the purchase of higher quality components.
Cost‐benefit analysis of high‐eficiency cast polycrystalline silicon solar cell sequences
Authors: Narayanan S. , Wohlgemuth J.
Published: July 2007

The incorporation of eficiency enhancement techniques and the use of high‐eficiency process sequences have led to the fabrication of polycrystalline silicon solar cells with efficiencies nearing 18% in the laboratory by various investigators. In this paper a number of cell process sequences used to fabricate high‐efficiency polycrystalline silicon solar cells are reviewed. A cost‐benefit analysis of the efficiency enhancement techniques was performed using the Interim Price Estimation Guidelines 2 model, developed by the Jet Propulsion Laboratory, Pasadena, USA. the figure of merit used to compare the sequences was that the cost of additional power, generated by the efficiency enhancement technique, should be less than the selling price of the product. Techniques like oxide passivation and emitter etch‐back, and sequences like the buried‐contact process, were found to be cost effective.
Solar cell efficiency tables (version 4)
Authors: Green Martin A. , Emery Keith
Published: July 2007

Updated tables showing the highest independently confirmed efficiencies for solar cells and modules are presented. Guidelines for inclusion of results into these tables are outlined and several new entries since January 1994 are briefly described.
A Ga0.51In0.49P/GaAs‐based photovoltaic converter for two‐directional optical power and data transmission
Authors: Vänttinen K. , Lammasniemi J. , Rakennus K. , Asonen H. , Jurva R. , Karioja P.
Published: July 2007

A GaAs‐based photovoltaic converter for optical‐to‐electrical power conversion and for data transmission was developed. the device structure is based on a modified GaAs solar cell structure having a lattice‐matched Ga0.51In0.49P window layer. the converter consists of an array of series‐connected photovoltaic cells. the input optical laser power is transmitted via a single optical multimode fibre and distributed homogeneously to the separate cells. One of the cells has separate connections for acting as a light‐emitting diode for data transmission in the opposite direction. the conversion eficiency of the individual cells was measured to be 49%, and the array conversion efficiency was 41%.
Thermophotovoltaics bibliography
Authors: Broman Lars
Published: July 2007

A bibliography containing 200 entries on thermophotovoltaic conversion of energy between 1960 and 1995 has been compiled. the entries are categorized with respect to type and contents.
Analysis and control of mismatch power loss in photovoltaic arrays
Authors: Roche David , Outhred Hugh , Kaye R. John
Published: July 2007

Connecting photovoltaic cells to form an array can cause problems when the characteristics of the cells are not matched. This problem, known as mismatch, can reduce the power output of the array and lead to cell degradation through localized heating of individual cells. Such problems can arise simply through the shading of a single cell. In this paper, which has a substantial tutorial content, three methods of reducing the effects of mismatch are investigated and compared; the use of integral bypass diodes (IBDs), series/paralleled circuit designs and reduced cell shunt resistance.

Experiments were performed on arrays incorporating cells with IBDs and their tolerance to shading was tested and compared to arrays with other cell designs. the potential benefits and costs of using IBDs are then assessed and conclusions drawn about the relative effectiveness of this strategy. the circuit design strategy known as series/paralleling is described and analysed and its effect on minimizing mismatch power loss is evaluated. Also, an expression for the optimum cell shunt resistance in a general shaded array is derived and the technique of reducing cell shunt resistance to minimize mismatch effects is assessed.
Photovoltaics in grid‐connected buildings: Energy flow and economic aspects
Authors: Caamaño E. , Lorenzo E.
Published: July 2007

Two main subjects must be considered in the analysis of a photovoltaic grid‐connected building. the first concerns the various energy flows, such as the hourly photovoltaic generation and the electricity consumption of the building, that determine the global energy balance, i.e. the extent to which the system will be able to supply the building's electricity consumption. This paper provides a simple method to estimate this behaviour. Secondly we must consider the long‐term cost of the system, a key aspect that depends on the economic scenario and can be made attractive given the appropriate policies (some examples are mentioned).
Bandgap engineering of amorphous semiconductors for solar cell applications
Authors: Bernhard N. , Bauer G. H. , Bloss W. H.
Published: July 2007

Different bandgap engineering approaches are discussed with respect to their application in thin‐film solar cells based on hydrogenated amorphous silicon (a‐Si: H) and its alloys with Ge or C. After a survey of the different approaches reported so far in the literature, the main emphasis will lie on the application of a‐Si: H/a‐Si1‐xCx:H multilayers for use in the p‐doped window layer, or a graded bandgap a‐Si1‐xCx:Hintrinsic layer with varying Ge content x. But also the possibility of using an a‐Si: H/a‐Si1‐xCx:H multilayer as the i‐layer will be addressed. Intrinsic films of both multilayers and graded bandgap material have been deposited in different series, varying electronic well and barrier widths in the first case, and the amount, form or local position of a change of the bandgap in the second case. Physical properties of both classes of materials have been investigated thoroughly. the results are discussed with respect to an application in amorphous thin‐film solar cells, also taking into account results from the literature about the implementation of these heterostructures in devices. Conclusions for the future perspectives of these approaches are drawn.
Experimental extraction of light confinement parameters for textured silicon wafers
Authors: Tobias I. , Rodriguez J. M. , Luque A.
Published: July 2007

A procedure for extracting the internal reflectivities and the mean tilt angle of light rays inside silicon wafers from reflectance measurements is presented. the procedure, based on a simple model of light confinement, is applied to silicon wafers textured with random pyramids. the results obtained are shown to be in good agreement with ray‐tracing calculations and theoretical estimates.

Se presenta un método para extraer, a partir de medidas de reflectancia, los valores de las reflectividades internas y del ángulo medio de inclinación de los rayos de luz en el interior de células solares. Este método está basado en un modelo sencillo del confinamiento interno de la luz y se aplica aqui a obleas de silicio con textura piramidal aleatoria. Los resultados obtenidos están de acuerdo con los calculados mediante trazado de rayos y con las estimaciones teóricas.
Performance analysis of photovoltaic pumping systems using switched reluctance motor drives
Authors: Metwally Hamid M. B. , Anis Wagdy R.
Published: July 2007

A photovoltaic (PV) pumping system using a switched reluctance motor (SRM) is investigated in this work. the motor is supplied by a DC voltage through a simple switching circuit. This drive circuit is much simpler than the normal DC/AC inverter required to supply an induction motor. the efficiency of the SRM is considerably higher than that of equivalent DC or induction motors. In addition, because of its simple construction, the SRM is cheaper than these conventional drives. These advantages give the proposed system higher efficiency and lower cost compared with other systems.

In this paper, which has a substantial tutorial content, a design example is studied in detail to explore the advantages of PV pumping systems based on the new drive. Study of the performance of the proposed system showed that the operating efficiency of the motor is about 85% during most of its working time. the matching efficiency between the PV array and the proposed system approaches 95%. the major part of the losses takes place in the pump and the riser pipes; this loss represents one‐third of the total available energy.