bluuebunny/crossref_metadata_2025 huggingface dataset:
Betriebsfestigkeit und Zuverlässigkeit von komplexen und intelligenten Strukturen
Authors: Hanselka H. , Sonsino C. M.
Published: September 2003

Die Betriebsfestigkeit und Zuverlässigkeit einer Konstruktion ist nur durch sorgfältige Bemessung zu erreichen. Dabei sind die aus den Einsatzprofilen stammenden unterschiedlichen Anforderungen an die Festigkeit der Bauteile zu berücksichtigen. Um einerseits alle Einflüsse aus Belastung, Werkstoff, Herstellungsprozess, örtlicher Geometrie zu erfassen und andererseits Forderungen bezüglich der Konkurrenzfähigkeit zu erfüllen, muss der Konstrukteur effiziente Methoden anwenden, mit denen Betriebsfestigkeit und Zuverlässigkeit gewährleistet werden.

Heute steht im Entwicklungsprozess einer Konstruktion die Verringerung der Markteinführungszeit im Vordergrund. Dies erfordert den vermehrten Einsatz numerischer Methoden (Simulation des dynamischen Systemverhaltens, der Bauteileigenschaften und der örtlichen Spannungen), um den Aufwand der experimentellen Vorgehensweise für Optimierung und Nachweis zu reduzieren.

In Zukunft werden immer mehr Konstruktionsteile von mechatronischen und sogar multifunktionalen Komponenten ersetzt. Kenntnisse des Systemverhaltens sowie der gegenseitigen Beeinflussung von elektronischer Steuerung und mechanischem Verhalten sind erforderlich, um die Zuverlässigkeit dieser Entwicklung zu bewerten.
Effects of Loading Waveform and Stress Field on High Temperature Fatigue Crack Growth of Alloy 718
Authors: Heuler P. , Affeldt E. , Wanhill R.J.H.
Published: September 2003

High temperature fatigue in nickel‐base superalloys for aero‐engine applications requires consideration of cycle‐ and time‐dependent phenomena. For waveforms with dwells and/or low frequencies crack growth rates may be significantly accelerated up to the point of fully time‐dependent crack growth. In the paper, the interaction of fatigue (cycle‐dependent) and dwell (time‐dependent) crack growth is addressed using a broad database for IN 718 tested at 600°C. Waveforms with dwells at as well as below maximum load levels are applied to standard CT and CC specimens and blunt notched specimens. It is demonstrated that both the level of dwells with respect to the maximum load level within a cycle as well as the specific conditions at the notch root considerably affect the significance of dwells for fatigue crack growth.
Betriebsfestigkeit und Äquivalentamplitude
Authors: Hänel B.
Published: September 2003

Der Betriebsfestigkeitsnachweis ist im Allgemeinen mit einem Spannungskollektiv durchzuführen. Bei Anwendung von Normkollektiven, Beanspruchungsgruppen oder Äquivalentamplituden ergeben sich Vereinfachungen, besonders im letzten Fall: Der Betriebsfestigkeitsnachweis hat dann die äußere Form eines Dauerfestigkeitsnachweises.

Rechnerisch ist das immer möglich, experimentell aber nur mit Einschränkungen.
Lebensdauervorhersage auf Basis von Finite Elemente Ergebnissen
Authors: Eichlseder W.
Published: September 2003

Unter dem Druck des Wettbewerbes werden möglichst kurze Produktentwicklungszeiten angestrebt, weshalb bereits im frühen Entwicklungsstadium Aussagen über die Lebensdauer und damit die Dimensionierung der Bauteile erforderlich werden. Da durch die häufig angestrebte Gewichtsoptimierung der Bauteile das Limit der Belastbarkeit so nah wie möglich erreicht werden soll, werden Simulationsmethoden sowohl im Berechnungs‐ als auch im Versuchsablauf verstärkt eingesetzt. Ausgehend von den Berechnungsergebnissen nach der Finte Elemente Methode werden zur Lebensdauervorhersage von Bauteilen örtliche Wöhlerlinien benötigt, die häufig aus Wöhlerlinien, ermittelt an Proben unter Laborbedingungen, abgeleitet werden müssen. Diese Übertragbarkeit von Proben‐ auf Bauteilwöhlerlinien wird für die Einflüsse durch Kerben, Größe und Gussgefüge exemplarisch aufgezeigt. Aufbauend auf diesen Wöhlerlinien, die für jede Stelle im Bauteil errechnet werden, kann unter Einbeziehung der lokalen Spannungen und Spannungsgradienten, ermittelt mit der Finite Elemente Methode, die Lebensdauer errechnet werden.
Prüftechnische Innovationen – Grundlage für Erfindungen in der Bauteilentwicklung
Authors: Hug J. , Runzer V.
Published: September 2003

In Clausthal‐Zellerfeld wurde bereits 1828 mit der ersten dynamischen Prüfmaschine der Welt der Grundstein für die Betriebsfestigkeit gelegt. Heute ist an dieser Stelle ein Kompetenzzentrum für Betriebsfestigkeit und dynamische Prüftechnik entstanden. Die Entwicklung neuer Prüfmaschinen und Prüfverfahren führt sehr oft zu Innovationen der zu prüfenden Bauteile und Systeme. Dies wird zunächst an Julius Albert's Kettenprüfmaschine, dann an aktuellen herausragenden Beispielen der Resonanzprüftechnik, wie dem Power Swing, dem Hochdruckprüfsystem bis 4000 bar und der Umlaufbiegeprüfsysteme der SincoTec GmbH veranschaulicht.
Datensammlung Betriebsfestigkeit – Zuverlässigkeit von Lebensdauerabschätzungen
Authors: Kotte K.L. , Eulitz K.‐G.
Published: September 2003

Nach der Wiedervereinigung Deutschlands initiierte Prof. Harald Zenner mehrere Forschungsvorhaben, die das Ziel verfolgten, das gesamtdeutsche Know‐How der Betriebsfestigkeit und den existierenden Fundus an Versuchsergebnissen aufzuarbeiten und damit für die weitere Nutzung zu sichern. In diesem Zusammenhang bearbeiteten das IMAB der TU Clausthal und das IFKM der TU Dresden gemeinsam zwei Vorhaben “Lebensdauervorhersage I und II”, die ihr Ergebnis zum einen in der Datensammlung Betriebsfestigkeit “DABEF”, zum anderen in einer sauberen statistischen Analyse zur Treffsicherheit der Lebensdauerabschätzungsverfahren hatten. Im Ergebnis dieser Untersuchungen wurden die Einflüsse des Klassierverfahrens von denen der Schadensakkumulation getrennt. Für die unterschiedlichen Berechnungsgruppen und Varianten der Miner‐Rechnung war es möglich, Anpassungsfaktoren für berechnete zulässige Beanspruchungen anzugeben. Die Datensammlung wurde inzwischen als wesentliche Basis für eine Habilitation sowie für mehrere Dissertationen und andere Forschungsarbeiten genutzt. Nicht zuletzt fanden die Ergebnisse der statistischen Analysen Eingang in die Richtlinie für den “Rechnerischen Festigkeitsnachweis” des FKM.
Betriebsfestigkeit + Funktion = Betriebsfunktionalität, Anforderungen an die Entwicklung von Fahrwerkbauteilen
Authors: Jung L. , Saathoff A. , Witt M.
Published: September 2003

Die Betriebsfestigkeit hat innerhalb der Fahrwerkentwicklung einen sehr hohen Stellenwert, da Fahrwerkbauteile in der Regel Sicherheitsbauteile sind. Die Festigkeit stellt jedoch nur einen Teilaspekt innerhalb der Entwicklungstätigkeit dar. Die übergeordnete Aufgabe in der Bauteilentwicklung ist die Sicherstellung der Funktionalität unter allen Betriebsbedingungen. Für die Bauteile Radlager, Gelenkwelle und Stabilisator werden beispielhaft die Entwicklungsanforderungen diskutiert.
Betriebsfestigkeit in der Fahrzeugentwicklung – von der Theorie zum Produkt
Authors: Jung T. , Liu J. , Maescher G. , Mauch H. , Stolze F.‐J.
Published: September 2003

Dargestellt wird die prinzipielle Vorgehensweise beim Nachweis der Betriebsfestigkeit in der Fahrzeugentwicklung: die Methoden, Lastannahme, Festigkeitsprüfung und die Vorschriften für die Freigabe und Qualitätssicherung. An praktischen Beispielen der Fahrzeugentwicklung aus Fahrwerk, Aggregat und Karosserie werden die Vorgehensweise und die verwendeten experimentellen und rechnerischen Simulationsmethoden erläutert.
Die Integration der Lebensdauerberechnung in den Fahrzeugentwicklungsprozess am Beispiel MIG‐geschweißter Bauteile aus Aluminium im Fahrwerksbereich
Authors: Brune M. , Oppermann H. , Chéreau S. , Pötter K.
Published: September 2003

Die Lebensdauerberechnung für metallische Bauteile ist in der Ergebnisqualität wesentlich von den notwendigen Inputgrößen abhängig. Hierzu gehören die Finite‐Elemente‐Vernetzung des Bauteilmodells, die Werkstoffkennwerte und die zugrunde‐gelegten Last‐Zeitfunktionen, durch die das Bauteil beansprucht wird. In dieser Arbeit wird am Beispiel eines liniengeschweißten Fahrwerkbauteils aus Aluminium der Einfluss der Finite‐Elemente‐Modellierung auf die Lebensdauerberechnung unter‐sucht. Besonderes Augenmerk wird hier auf die Schweißnahtmodellierung gelegt. Für die Berechnung der Lebensdauer kommt das Software‐Werkzeug FEMFAT der Firma “Engineering Center Steyr” zum Einsatz. Die Bewertung der Lebensdauer für die Schweißnähte basiert hier auf einem örtlichen Spannungskonzept. Im folgenden wird die Qualifizierung der Berechnung für den Produktiveinsatz anhand von BMW‐typischen Schweißnaht‐Wöhlerlinien beschrieben.
Verhalten von Magnesiumlegierungen für Anwendungen im Fahrzeugbau bei mechanisch‐elektrochemischer Komplexbeanspruchung: Einfluss passivierender Deckschichten und Mechanismen der lokalen Schädigung
Authors: Berger C. , Troßmann T. , Gugau M.
Published: September 2003

Für die Betriebssicherheit von Strukturbauteilen aus Magnesium ist es unerlässlich, dass alle maßgeblichen werkstofflichen, konstruktiven, fertigungsbedingten, betrieblichen und umgebungsbezogenen Einflussgrößen auf die Schwingfestigkeit bei der Bauteilauslegung berücksichtigt werden.

Magnesiumlegierungen sind aufgrund der hervorragenden Verhältnisse von Festigkeit und Steifigkeit zur Dichte von besonderem Interesse für Leichtbauanwendungen. Das Korrosionsverhalten von Magnesium wird anwendungsspezifisch von den gleichen Faktoren wie bei anderen metallischen Werkstoffen bestimmt. Einerseits weist der Werkstoff Magnesium eine gute Stabilität unter atmosphärischen Umgebungsbedingungen, in alkalischen Medien sowie in Fluss‐ und Chromsäure auf. Andererseits wird durch die generelle hohe elektrochemische Aktivität die Bedeutung spezifischer Einflussfaktoren sehr stark hervorgehoben. Dies betrifft insbesondere die Ausbildung und Beständigkeit der vor Korrosion schützenden Deckschichten.

Art, Zusammensetzung und Wirkung derartiger Schichten werden von folgenden Einflussfaktoren bestimmt: Legierungszusammensetzung, Passivierungsbedingungen, pH‐Wert, Elektrolytzusammensetzung sowie Art der Beaufschlagung und Temperatur.

Bei lokaler Schädigung dieser so genannten Passivschichten und Anwesenheit eines wässrigen Mediums ist eine Verminderung der Beanspruchbarkeit von Bauteilen aus Magnesium zu beobachten. Ein Ziel diese Untersuchungen ist die Klärung von Mechanismen der Deckschichtschädigung. Im Wesentlichen sind für alle metallischen Konstruktionswerkstoffe zwei Mechanismen der Schädigung von Relevanz: einerseits ist dies die Ausbildung von Gleitstufen bei mechanischer Beanspruchung und andererseits die selektive elektrochemische Aktivierung (z.B. durch chloridinduzierte Lochkorrosion).

Das Korrosionsverhalten hoch reiner Magnesiumlegierungen wurde in verschiedenen Lösungen (neutral, alkalisch, Wirkung spezifischer Anionen und Kationen) mit elektrochemischen Untersuchungsmethoden beschrieben. Die druckgegossenen Magnesiumlegierungen wurden wie hergestellt mit Gusshaut sowie mechanisch bearbeitet untersucht. Die Bewertung der erhaltenen Befunde verdeutlicht, dass in Abhängigkeit des Systems Legierung/Werkstoff‐ und Oberflächenzustand/Umgebungsbedingungen verschiedene Mechanismen der Schädigung der schützenden Deckschichten möglich sind. Weiterhin wird das Verhalten bei Schwingungsrisskorrosion wesentlich durch den Zustand der Bauteiloberfläche sowie die Prüfbedingungen beeinflusst.
Lebensdauerermittlung bei mehrachsigen wechselnden Beanspruchungen im niedrigen und hohen Temperaturbereich
Authors: Roos E. , Gengenbach T. , Rauch M. , Schemmel J.
Published: September 2003

Zur Berechnung der Dauerfestigkeit von Bauteilen aus duktilen Werkstoffen bei komplexer Schwingbeanspruchung stehen unterschiedliche Verfahren zur Verfügung. Hierbei wird im Wesentlichen zwischen den Festigkeitshypothesen der Integralen Anstrengung und denen der Kritischen Schnittebene unterschieden. Als typische Repräsentanten werden die Schubspannungsintensitätshypothese (SIH) sowie die Methode der kritischen Schnittebene (MKS) ausgewählt und für körperfeste und nicht körperfeste Hauptspannungsrichtungen gegenübergestellt. Für synchrone Beanspruchungen wird darüber hinaus das Berechnungsverfahren mit dem Anstrengungsverhältnis nach Bach verglichen.

Die Berechnungsmethodik wird deutlich komplexer, wenn zeitabhängige Werkstoffeigenschaften bei entsprechend hohen Temperaturen mit in die Betrachtung einbezogen werden müssen. Für diesen Fall wird die Anwendung von viskoplastischen Stoffgesetzen erforderlich, die eine Beschreibung von Kriechen und Ermüdung in Kombination ermöglichen. Am Beispiel eines modifizierten Werkstoffmodells nach Chaboche / Nouailhas wird die Berechnung mehrachsiger Kriechermüdungsversuche vorgestellt.
Singularity extraction technique for integral equation methods with higher order basis functions on plane triangles and tetrahedra
Authors: Järvenpää Seppo , Taskinen Matti , Ylä‐Oijala Pasi
Published: September 2003

A numerical solution of integral equations typically requires calculation of integrals with singular kernels. The integration of singular terms can be considered either by purely numerical techniques, e.g. Duffy's method, polar co‐ordinate transformation, or by singularity extraction. In the latter method the extracted singular integral is calculated in closed form and the remaining integral is calculated numerically. This method has been well established for linear and constant shape functions. In this paper we extend the method for polynomial shape functions of arbitrary order. We present recursive formulas by which we can extract any number of terms from the singular kernel defined by the fundamental solution of the Helmholtz equation, or its gradient, and integrate the extracted terms times a polynomial shape function in closed form over plane triangles or tetrahedra. The presented formulas generalize the singularity extraction technique for surface and volume integral equation methods with high‐order basis functions. Numerical experiments show that the developed method leads to a more accurate and robust integration scheme, and in many cases also a faster method than, for example, Duffy's transformation. Copyright © 2003 John Wiley & Sons, Ltd.
Quasi‐dual reciprocity boundary‐element method for incompressible flow: Application to the diffusive–advective equation
Authors: Loeffler C. F. , Mansur W. J.
Published: September 2003

This work presents a new boundary‐element method formulation called quasi‐dual reciprocity formulation for heat transfer problems, considering diffusive and advective terms. The present approach has some characteristics similar to those of the so‐called dual‐reciprocity formulation; however, the mathematical developments of the quasi‐dual reciprocity approach reduces approximation errors due to global domain interpolation. Some one‐ and two‐dimensional examples are presented, the results being compared against those obtained from analytical and dual‐reciprocity formulations. The method convergence is evaluated through analyses where the mesh is successively refined for various Peclet numbers, in order to assess the effect of the advective term. Copyright © 2003 John Wiley & Sons, Ltd.
Structural design optimization on thermally induced vibration
Authors: Chen Biaosong , Gu Yuanxian , Zhang Hongwu , Zhao Guozhong
Published: September 2003

The numerical method of design optimization for structural thermally induced vibration is originally studied in this paper and implemented in the software JIFEX. The direct and adjoint methods of sensitivity analysis for thermal‐induced vibration coupled with both linear and non‐linear transient heat conduction is firstly proposed. Based on the finite element method, the linear structural dynamics is treated simultaneously with linear and non‐linear transient heat conduction. In the heat conduction, the non‐linear factors include the radiation and temperature‐dependent materials. The sensitivity analysis of transient linear and non‐linear heat conduction is performed with the precise time integration method; and then, the sensitivity analysis of structural transient responses is performed by the Newmark method. Both the direct method and the adjoint method are employed to derive the sensitivity equations of thermal vibration. In the adjoint method, two adjoint vectors of structure and of heat conduction are used to derive the adjoint equations. The coupling effect of heat conduction on thermal vibration in the sensitivity analysis is particularly investigated. With the coupling sensitivity analysis, the optimization model is constructed and solved by the sequential linear programming or sequential quadratic programming algorithm. Numerical examples are given to validate the proposed methods and to demonstrate the importance of the coupled design optimization. Copyright © 2003 John Wiley & Sons, Ltd.
A posteriori error estimates and an adaptive scheme of least‐squares meshfree method
Authors: Park Sang‐Hoon , Kwon Kie‐Chan , Youn Sung‐Kie
Published: September 2003

A posteriori error estimates and an adaptive refinement scheme of first‐order least‐squares meshfree method (LSMFM) are presented. The error indicators are readily computed from the residual. For an elliptic problem, the error indicators are further improved by applying the Aubin–Nitsche method. It is demonstrated, through numerical examples, that the error indicators coherently reflect the actual error. In the proposed refinement scheme, Voronoi cells are used for inserting new nodes at appropriate positions. Numerical examples show that the adaptive first‐order LSMFM, which combines the proposed error indicators and nodal refinement scheme, is effectively applied to the localized problems such as the shock formation in fluid dynamics. Copyright © 2003 John Wiley & Sons, Ltd.
Near‐crack contour behaviour and extraction of log‐singular stress terms of the self‐regular traction boundary integral equation
Authors: Jorge Ariosto B. , Cruse Thomas A. , Fisher Timothy S.
Published: September 2003

This work contains an analytical study of the asymptotic near‐crack contour behaviour of stresses obtained from the self‐regular traction‐boundary integral equation (BIE), both in two and in three dimensions, and for various crack displacement modes. The flat crack case is chosen for detailed analysis of the singular stress for points approaching the crack contour. By imposing a condition of bounded stresses on the crack surface, the work shows that the boundary stresses on the crack are in fact zero for an unloaded crack, and the interior stresses reproduce the known inverse square root behaviour when the distance from the interior point to the crack contour approaches zero. The correct order of the stress singularity is obtained after the integrals for the self‐regular traction‐BIE formulation are evaluated analytically for the assumed displacement discontinuity model. Based on the analytic results, a new near‐crack contour self‐regular traction‐BIE is proposed for collocation points near the crack contour. In this new formulation, the asymptotic log‐singular stresses are identified and extracted from the BIE. Log‐singular stress terms are revealed for the free integrals written as contour integrals and for the self‐regularized integral with the integration region divided into sub‐regions. These terms are shown to cancel each other exactly when combined and can therefore be eliminated from the final BIE formulation. This work separates mathematical and physical singularities in a unique manner. Mathematical singularities are identified, and the singular information is all contained in the region near the crack contour. Copyright © 2003 John Wiley & Sons, Ltd.
On discontinuous Galerkin methods
Authors: Zienkiewicz O. C. , Taylor R. L. , Sherwin S. J. , Peiró J.
Published: September 2003

Discontinuous Galerkin methods have received considerable attention in recent years for problems in which advection and diffusion terms are present. Several alternatives for treating the diffusion and advective fluxes have been introduced. This report summarizes some of the methods that have been proposed.

Several numerical examples are included in the paper. These present discontinuous Galerkin solutions of one‐dimensional problems with a scalar variable. Results are presented for diffusion–reaction problems and advection–diffusion problems. We discuss the performance of various formulations with respect to accuracy as well as stability of the method. Copyright © 2003 John Wiley & Sons, Ltd.
Molecular orientation gradients in thermotropic liquid crystalline fiber
Authors: Taylor Jennifer E. , Romo‐Uribe Angel , Libera Matthew R.
Published: September 2003

The degree of molecular alignment averaged over meso‐length scale areas within thermotropic liquid crystalline polymer (LCP) fibers has been intensely studied over recent years. In this work, the degree of molecular orientation is found from spatially‐resolved electron diffraction of areas as small as 100 nm in diameter to relieve structural averaging of lower resolution techniques. This investigation reveals that the maximum degree of molecular alignment across a fiber 18 μm in diameter is approximately 1 μm from the fiber surface. Dark‐field imaging shows region with little crystallinity adjacent to the fiber surface. The banded structure, typical of TLCP fibers, is also less apparent in the surface region. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and functional properties of green fluorescent poly(methylmethacrylate) for use in liquid crystal systems
Authors: Grabchev Ivo , Chovelon Jean‐Marc
Published: September 2003

The copolymerization of six 4‐aminosubstituted‐1,8‐naphthalimide dyes comprising an allylic polymerizable group with methylmethacrylate has been investigated. The utility of the copolymers prepared as fluorescent component in polymer/liquid crystal systems has been examined. The photophysical and photochemical properties of the systems monomeric dye/liquid crystal and copolymer/liquid crystal have been also discussed. It has been shown that in a liquid crystal mixture 1,8‐naphthalimide dyes and respective copolymer/liquid crystals have yellow–green fluorescent color with good photostability. Copyright © 2003 John Wiley & Sons, Ltd.
UV curing behaviors and hydrophilic characteristics of UV curable waterborne hyperbranched aliphatic polyesters
Authors: Asif Anila , Huang Chengyu , Shi Wenfang
Published: September 2003

A series of waterborne hyperbranched polyesters (WBHPs) endcapped with methacrylic and salt‐like groups in different ratios have been investigated as UV curable resins. The kinetic studies of the drying step and UV curing were carried out by FT‐IR measurements. The drying of the film of 100 μm thickness was completed in less than 6 hr at 70°C or within 10 hr at 50°C in an oven. The influence of different photoinitiators and their concentrations, extent of unsaturation and acid content of WBHP on final unsaturation conversion was studied. The surface free energy is a critical character, which affects the surface properties of a cured film. So one method based on the measurement of contact angle of a pure liquid on a solid surface was applied to determine the polar and dispersive components of the surface energy of UV cured films. The investigations of surface energy of WBHPs illustrated that those with more acid content and thus higher polar component are more sensitive to water, while those containing less acid content and thus lower polar term are less water sensitive. Moreover, the UV cured films of WBHPs and their blends with commercial waterborne resins (trade name EB 210, EB 2002, EB 11 and IRR 160) have acceptable pendulum hardness varying from 55 to 180 sec. Copyright © 2003 John Wiley & Sons, Ltd.
Short communication the preparation of stable protected 3‐ethynylpyrrole suitable for electrochemical polymerization
Authors: Hlavatý Jaromír , Kubišta Jiří , Štícha Martin
Published: September 2003

Stable protected 3‐triisopropylsilylethynylpyrrole, 4b, was prepared in the yield 73% by first observed selective deprotection of double protected 1‐triisopropylsilyl‐3‐triisopropylsilylethynylpyrrole, 3b, which was obtained in the yield 44%. This deprotection in preference proceeds at the pyrrole nitrogen leaving the 3‐triisopropylsilylethynyl group intact. Due to its stability, ethynylpyrrole derivative 4b protected was like the first alkynyl pyrrole derivative electrochemically polymerized giving a black polypyrrole layer deposited on the platinum anode. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and characterization of cellulose resins
Authors: El‐Zawawy Waleed K. , Ibrahim Maha M.
Published: September 2003

A series of cellulose‐phenol‐formaldehyde (LCPF) and cellulose‐urea‐formaldehyde (CUF) resins were produced using banana waste. Detailed structure and quantitative information was provided by FT‐IR and mass spectroscopy. The main interests were the ability to use banana waste as a source of cellulose in the condensation reaction. Functionality of CPF and structure of CUF were investigated. Copyright © 2003 John Wiley & Sons, Ltd.
Anion exchange fibers for arsenate removal derived from a vinylbenzyl chloride precursor
Authors: Dominguez Lourdes , Economy James , Benak Kelly , Mangun Christian L.
Published: September 2003

The preparation of anionic exchange fibers (AEFs) is described utilizing an oligomer derived from vinylbenzyl chloride as the precursor coating on a glass fiber substrate. This approach permits a significant reduction in number of synthetic steps required for commercial beads, as well as eliminating the need for solvents prior to functionalization. The amination reaction time was also substantially reduced. These fibers were characterized through a variety of techniques such as scanning electron microscopy (SEM), analytical titration, and diffuse reflectance fourier transform infrared spectroscopy (DRIFTS) of the copolymer. With respect to ion exchange properties the fibers could be regenerated for over 20 cycles with no capacity loss or physical degradation of the coating. Particular emphasis was placed on establishing conditions for the removal of arsenate from water. The design and testing of AEF filters for breakthrough experiments were carried out and compared to commercially available beads. The results indicate that AEF have a significant kinetic advantage over the anionic exchange beads, which approaches an order of magnitude improvement in lowering effluent contaminants. Copyright © 2003 John Wiley & Sons, Ltd.
Flame retardancy and heat resistance of phenol‐biphenylene‐type epoxy resin compound modified with benzoguanamine
Authors: Iji Masatoshi , Kiuchi Yukihiro , Soyama Makoto
Published: September 2003

The flame retardancy and heat resistance of a phenol‐biphenylene‐type epoxy resin compound, which forms a self‐extinguishing network structure, were increased by the inclusion of a benzoguanamine‐modified phenol biphenylene resin. The benzoguanamine‐modified phenol biphenylene resin contains a benzoguanamine unit to release non‐flammable nitrogen substances during ignition and to increase the resin's reactivity toward epoxy resins, and biphenylene units to keep the resin's thermal degradation and water resistance. The addition of the benzoguanamine‐modified phenol biphenylene resin in the epoxy resin compound improved the epoxy resin compound's flame retardancy and heat resistance, and also increased its glass transition temperature while maintaining its water resistance and mechanical properties. Copyright © 2003 John Wiley & Sons, Ltd.
Morphology and degradation of biodegradable poly(L‐lactide‐co‐β‐malic acid)
Authors: He Bin , Bei Jianzhong , Wang Shenguo
Published: September 2003

Poly(L‐lactide‐co‐β‐malic acid) was obtained after the hydrogenolysis of the copolymer of L‐lactide (L‐LA) and β‐benzyl malate (MA). 1H‐NMR demonstrated that the composition of the copolymer was identical to the feeding dose. Thermal property study revealed the morphology of the copolymer could be changed from semi‐crystalline to amorphous with increasing hydrophilic β‐malic acid content. The copolymers with 8 and 13 mol% β‐malic acid content possessed enough mechanical property for fabricating cell scaffold. Degradation result demonstrated that most of the hydrophilic β‐malic acid units broke down from the copolymer within 1 week and the ester bond between L‐lactide and β‐malic acid hydrolyzed prior to the inner ester bond of poly(L‐lactide) (PLLA). Copyright © 2003 John Wiley & Sons, Ltd.
Direct current electric‐field induced scattering behavior in lyotropic liquid crystalline cell composed of carbazolyl groups pendant polypeptide and TNF
Authors: Naijo Yoshihisa , Fujisaki Eita , Tsunoda Makoto , Tanaka Toyohide , Kobayashi Norihisa
Published: September 2003

Polypeptide having carbazolyl groups (poly(γ‐[2‐(9‐carbazolyl)ethyl]‐L‐glutamate) (PCLG)) was synthesized in order to prepare a lyotropic liquid crystalline cell with higher mobility. This liquid crystal was revealed to show d.c. electric‐field induced scattering behavior, in which the transparent cell became scattered after applying d.c. bias voltage. This behavior was enhanced by adding small amounts of 2,4,7‐trinitrofluorenone (TNF) which is known to form charge transfer complex with carbazole. The transmittance varied from 90 to 20% under d.c. bias application. More than 150 turn‐on and off cycles were achieved in this cell without serious degradation. Copyright © 2003 John Wiley & Sons, Ltd.
Critical issues in the design of polycrystalline, thin‐film tandem solar cells
Authors: Coutts Timothy J. , Ward J. Scott , Young David L. , Emery Keith A. , Gessert Timothy A. , Noufi Rommel
Published: September 2003

We use an empirical technique for modeling the efficiency of thin‐film tandem solar cells and calculate an approximate upper limit on the range of performance of these hypothetical devices. This is shown to be approximately 28.2%, without losses due to inactive layers at the front of the device, or other parasitic sources. Reduction of the value of the reverse saturation current density by a factor of ten, increases the lossless efficiency by approximately 4% absolute. This change also greatly broadens the range of top and bottom cell bandgaps that would lead to efficiencies greater than 25%, the project goal. These observations emphasize the critical importance of focusing future research on gaining a thorough understanding of recombination losses.

We then calculate daily energy density outputs for various direct spectra, computed from meteorological data, and show that the optimum bandgap pairs are relatively insensitive to the detail of the spectral irradiance. We also show that the use of daily energy density output may be a more useful criterion than efficiency in designing tandem thin‐film solar cells. We compute contours of equal daily energy density output and show that the range of potentially suitable bandgap pairs is much larger than simple maximization of efficiency implies.

The simple parametric approach enables us to investigate the effect of partial loss of photons with energies less than that of the bandgap of the top cell, but greater than that of the bottom cell. These photons are essential to the project goal of 25% efficiency, which emphasizes the need to evaluate the optical properties in this wavelength range very carefully. We also discuss the reduction of the thickness, or the area, of the top cell. When the top subcell generates a greater current than the bottom subcell, either of these parameters may be reduced to enable current‐matching, and increased efficiencies, to be achieved. Again, this approach greatly extends the range of bandgaps that could lead to a 25% tandem thin‐film cell.

Next, we consider the case of concentrated sunlight and show that the optimum bandgap pairs decrease with concentration ratio. This is due to the atmospheric absorption bands. The efficiency increases by approximately 4% absolute per decade increase in concentration ratio.

Finally, we comment on some of the practical difficulties that can already be anticipated in constructing these devices. Published in 2003 by John Wiley & Sons, Ltd.
Corrosion effects in thin‐film photovoltaic modules
Authors: Carlson D. E. , Romero R. , Willing F. , Meakin D. , Gonzalez L. , Murphy R. , Moutinho H. R. , Al‐Jassim M.
Published: September 2003

Electrochemical corrosion effects can occur in thin‐film photovoltaic (PV) modules that are fabricated on tin‐oxide‐coated glass when operating at high voltages and at elevated temperatures in a humid climate. The current study shows that this corrosion is associated with a delamination of the tin oxide layer from the glass, which is caused by sodium accumulation near the interface between the tin oxide and the glass and by the ingression of moisture into the PV module from the edges. This corrosion in thin‐film PV modules can be significantly reduced by altering the growth conditions of the tin oxide or by using zinc oxide as a transparent conductive oxide electrode. Copyright © 2003 John Wiley & Sons, Ltd.
Characterization of optical collectors for concentration photovoltaic applications
Authors: Antón I. , Pachón D. , Sala G.
Published: September 2003

The design and characterization of the collector of a photovoltaic concentrator system is commonly carried out for a given receiver, the optical parameters of the collector being linked to it. This paper, which has substantial tutorial content, deals with the characterization of collectors for concentrator photovoltaic systems, independently of any receiver, and providing the necessary parameters for the design of a system. This strategy allows the parameters related to the collector and the receiver, which are usually manufactured by different industries, to be totally separated. It also allows the optical collectors coming from non‐photovoltaic industries to be evaluated. The information that the mirror and lens manufacturers should provide for a photovoltaic concentrator application can be summarized under three characteristics: overall optical efficiency; light distribution; and acceptance angle. Theory, equipment, and procedures to carry out the optical characterization of the collectors are explained. Copyright © 2003 John Wiley & Sons, Ltd.
International harmonization of grid connection guidelines: adequate requirements for the prevention of unintentional islanding
Authors: Woyte Achim , De Brabandere Karel , Van Dommelen Daniel , Belmans Ronnie , Nijs Johan
Published: September 2003

Islanding is still one of the major controversial subjects in the international harmonization of grid connection requirements for distributed generation, and particularly photovoltaics. As long as islanding is not intended in order to back up a loss of mains, it should be avoided. The present study reviews the theory of unintentional islanding and assesses the probability of occurrence of the phenomenon, based on previous studies and theoretical considerations. While islanding is virtually impossible if only a small number of distributed generation units is connected to a distribution grid, with higher distributed generation densities, the possibility of islanding becomes realistic. The risk associated with unintentional islanding is estimated, and adequate requirements for functional safety of protection devices are determined in order to ensure the necessary additional degree of safety to be introduced by an islanding prevention device. Finally, a fundamental set of requirements with regard to islanding, to be included in an international grid connection guideline, is derived from the study. Copyright © 2003 John Wiley & Sons, Ltd.
The Devensian periglacial record on Thanet, Kent, UK
Authors: Murton J. B. , Bateman M. D. , Baker C. A. , Knox R. , Whiteman C. A.
Published: September 2003

The Devensian periglacial record on Thanet, Kent, is traced from c. 88 to 74 ka and from c. 24 to 12 ka by optical luminescence dating of aeolian sand and silt in the periglacial stratigraphy. The record commences before 88 ka with valley cutting at Pegwell Bay. Valley filling had begun by c. 88 ka and continued to at least 74 ka, coinciding with a major episode of loess deposition in Europe. Permafrost aggradation commenced before c. 21 ka, brecciating near‐surface chalk by ice segregation in permafrost and the overlying active layer. Deposition of aeolian sand (coversand) occurred at c. 24–21 ka, correlating with the Older Coversand I in mainland Europe. Permafrost degradation commenced at c. 21 ka, probably due to climate warming during Greenland Interstadial 2. The resulting active‐layer deepening through ice‐rich permafrost initiated soft‐sediment deformation and formation of large‐scale patterned ground in an active layer c. 2 m deep. Renewed permafrost aggradation between c. 21.25 and 18 ka coincided with climate cooling during Greenland Stadial 2c and led to cryoturbation in a thinner active layer. Final permafrost degradation commenced no later than c. 14.7 ka, that is, the start of Greenland Interstadial 1e, and may have occurred to some extent during the climate warming associated with Greenland Stadial 2b (c. 19.5–16.9 ka). Renewed deposition of aeolian sand took place at c. 15.5 ka, coincident with loess deposition on Thanet. A final episode of aeolian sand deposition occurred at 12 ka, correlating with the Younger Coversand deposits that are widespread in northwest Europe and formed during Greenland Stadial 1. Copyright © 2003 John Wiley & Sons, Ltd.
The rock glaciers on Prins Karls Forland: corrections of surface displacement rates
Authors: Berthling Ivar , Etzelmüller Bernd , Eiken Trond , Sollid Johan Ludvig
Published: September 2003

The results from new global positioning system (GPS) surveys in 1998 and 2000 show, that errors exist in the results from terrestrial surveys in 1996. The published displacement values of Berthling et al. (1998) are too large. This note corrects these displacement values. Copyright © 2003 John Wiley & Sons, Ltd.
Massive ground ice body of glacial origin at Yugorski Peninsula, arctic Russia
Authors: Ingólfsson Ólafur , Lokrantz Hanna
Published: September 2003

A massive ground ice body at Cape Shpindler on Yugorski Peninsula, southern Kara Sea coast, Russia, was studied with regard to large‐scale internal structures, its stratigraphic context and contacts to surrounding sediments, in order to highlight its origin. The massive ground ice contains deformation structures and deformed sediment rafts that show a consistent direction of deforming force. It is bounded upwards with a sharp and unconformable thaw contact to overlying till. The stratigraphical and structural evidence suggests that the massive ground ice body is relict glacier ice. Examination of data from a separate study on ice crystallography and isotopic composition of the massive ice body does not contradict this conclusion. The isotope composition and profiles conform with what can be expected for deformed basal ice. The chronology for the Shpindler Cape sequence implies that the glacier ice might be older than 250 ka years. Consequently, permafrost has preserved the relict glacier ice for the duration of at least two interglacials (Eemian and Holocene), as well as several Saalian and Weichselian interstadials, illustrating the preservation potential of the permafrost. Copyright © 2003 John Wiley & Sons, Ltd.
Evidence for late‐Pleistocene permafrost in the New Jersey Pine Barrens (latitude 39°N), eastern USA
Authors: French Hugh M. , Demitroff Mark , Forman Steve L.
Published: September 2003

Relict sand wedges, up to 2.5 m deep and 0.4 m wide, are present in the Pine Barrens of southern New Jersey. They indicate the previous existence of permafrost. The wedges are composed predominantly of sand that shows evidence of wind transport and abrasion. Optically‐stimulated‐luminescence dating of infill material indicates that thermal‐contraction‐cracking and emplacement of the sand infill must have occurred during two separate periods during the Late Pleistocene. The most recent was in Late Wisconsinan times,∼15–18 ka. An earlier period of permafrost conditions is indicated by dates >55–65 ka. On both occasions, the Late‐Pleistocene ice sheets would have advanced as far south as northern New Jersey and strong winds would have occurred in the lower mid‐latitudes. The sandy soils of the Pine Barrens would have allowed the ice‐marginal periglacial zone to extend southwards into southern New Jersey. The sparse tundra vegetation on the sandy substrate, with its relatively high thermal conductivity, would have permitted deep frost penetration because the ‘thermal offset’ would have been minimized. A mean annual air temperature of between −3.0°C and −4.0°C is inferred. Permafrost was probably discontinuous and less than 10–15 m in thickness. Episodes of permafrost thaw are indicated by the widespread occurrence of deformed sediments (‘thermokarst involutions’) and by various small‐scale non‐diastrophic structures associated with bog ironstone beds. The presence of soil (ground) wedges in southern New Jersey and adjacent Delaware also suggest conditions of deep seasonal frost, probably when the most recent permafrost degraded. Copyright © 2003 John Wiley & Sons, Ltd.
Prediction of formation temperatures in permafrost regions from temperature logs in deep wells—field cases
Authors: Kutasov I. M. , Eppelbaum L. V.
Published: September 2003

Important data on the thermal regime of the Earth's interior come from temperature measurements in deep boreholes. Drilling greatly alters the temperature field of earth materials surrounding the wellbore. In permafrost regions, due to thawing of adjacent strata during drilling, representative data can be obtained only by repeated observations over a long period of time. In this paper we predict undisturbed formation temperatures (and geothermal gradients) from shut‐in temperature logs in deep wells. The main features of the method are: (1) in the permafrost section of the well, the starting point in the well thermal recovery is moved from the end of well completion to the moment of time when the refreezing of enclosing strata was completed; it takes into account the refreezing of thawed material in a temperature interval; and (2) below the permafrost base, the starting point in the well thermal recovery is moved from the end of well completion to the moment of time when the first shut‐in temperature log was taken. A generalized formula to process field data (for the well sections below and above the permafrost base) is presented. Temperature logs conducted in five wells verify the method. Copyright © 2003 John Wiley & Sons, Ltd.
Ground ice and soluble cations in near‐surface permafrost, Inuvik, Northwest Territories, Canada
Authors: Kokelj S. V. , Burn C. R.
Published: September 2003

The distribution of segregated ice and soluble ions in near‐surface permafrost were investigated in hummocky terrain near Inuvik, Northwest Territories. Soil water content profiles from analyses of drill cores indicate that ice‐poor permafrost developed beneath a permafrost table aggrading at approximately 4 cm/a, but an ice‐rich zone, 10 to 20 cm thick, was observed beneath a permafrost table that had remained stable for about a decade. Ice‐rich intervals 10 to 30 cm thick were observed immediately beneath both a thaw unconformity formed in 1981 and an older, deeper unconformity. In profile, the correspondence between zones of cation and ice enrichment suggests soluble materials were incorporated into permafrost during development of near‐surface aggradational ice. Moisture enrichment below an experimentally degrading permafrost table was negligible. Similar ice contents beneath the present permafrost table and the deep thaw unconformity, and the preservation of ice‐poor intervals immediately above the 1981 and deep thaw unconformities indicate limited vertical ice enrichment. The estimated rates of ice accumulation in two‐decade‐old permafrost are on the order of mm/a, but ice accumulation above older unconformities indicates that, in aggregate, these initial rates decrease with time. The ground ice and soluble cations sequestered in near‐surface permafrost comprise an important pool of water and nutrients that may be released into the active layer during periods of deeper thaw. Copyright © 2003 John Wiley & Sons, Ltd.
Capacity of model biobeds to retain and degrade mecoprop and isoproturon
Authors: Henriksen Vibeke V , Helweg Arne , Spliid Niels Henrik , Felding Gitte , Stenvang Lars
Published: September 2003

Biobeds are used to increase the adsorption and degradation of pesticide spillage on sites used for mixing and loading and for cleaning of sprayers. The adsorption and the rate of degradation of 14C‐labelled isoproturon and mecoprop (MCPP) at concentrations from 0.0005 to 25 000 mg kg−1 were determined in biobed soil. Further leaching of the two herbicides was determined in a model biobed with a surface area of 2 m2. The biobed material showed enhanced ability to adsorb the two herbicides. Kd was 5.2 litre kg−1 for isoproturon and 1.6 litre kg−1 for MCPP in biobed material, which is higher than in natural soil. In different experiments with natural soil, Kd ranges from 0.07 to 0.6 litre kg−1 for MCPP and from 1.5 to 4.6 litre kg−1 for isoproturon in soils with varying organic carbon content. Degradation of MCPP was rapid at concentrations from 0.0005 to 500 mg kg−1, delayed at 5000 mg kg−1, and very slow at 25 000 mg kg−1. For isoproturon, the relative degradation was most rapid at the lowest concentration and decreasing with increasing concentrations. After 120 days, between 55% and 8% 14C was evolved as 14CO2 at concentrations between 0.0005 and 25 000 mg kg−1. The rate of evolution of 14CO2 indicated that degradation rates at low concentrations were of first‐order and at higher concentrations of zero‐order. Leaching of MCPP and isoproturon was determined in a newly established model biobed during a 2‐year period. About 13% of applied MCPP and 1.4% of applied isoproturon leached out during the winter following the first autumn application (worst‐case scenario). Leaching was completely prevented when the biobed had a well‐developed grass cover and was covered during the winter. Copyright © 2003 Society of Chemical Industry
Effects of fludioxonil and pyrimethanil, two fungicides used against Botrytis cinerea, on carbohydrate physiology in Vitis vinifera L
Authors: Saladin Gaëlle , Magné Christian , Clément Christophe
Published: September 2003

In Vitis vinifera L, photosynthesis and photosynthate partitioning are affected in the presence of fludioxonil and pyrimethanil, two fungicides commonly used in vineyards against Botrytis cinerea Pers. However, the effects were found to be different according to the model studied: plantlets (cv Chardonnay) grown in vitro, fruiting cuttings (cv Chardonnay) and plants grown in vineyards (cvs Chardonnay, Pinot noir and Pinot Meunier). In the plantlets grown in vitro, both fungicides decreased gas exchanges, photosynthetic pigment and starch concentrations in the leaves, whereas soluble carbohydrates transiently accumulated, suggesting that plantlets mobilised starch in response to photosynthesis inhibition caused by fungicides. In the fruiting cuttings, the fungicides did not affect photosynthesis, although fludioxonil caused starch decrease in parallel with sucrose accumulation, suggesting that the fungicide effects were of lower intensity than in vitro. Conversely, in vineyard, the two fungicides stimulated photosynthesis and increased pigment concentrations in the three vine cultivars tested. In the meantime, glucose, fructose and starch levels of the leaves declined after fungicide exposure, whereas sucrose accumulated, indicating that sucrose synthesis increased in the leaves following the fungicide treatment. Among the three varieties, Chardonnay was the most sensitive to the fungicides as revealed by the intensity of the responses and the longer period for recovery. In vineyard, the results suggested that the two fungicides, in addition to inhibiting B cinerea development, had a beneficial effect on vine physiology through the stimulation of leaf carbon nutrition, which may further enable the plant to rapidly make use of its defence reactions. Copyright © 2003 Society of Chemical Industry