bluuebunny/crossref_metadata_2025_split huggingface dataset:
A numerical study on the generation of impulsive noise by complex flows discharging from a muzzle
Authors: Bin Jonghoon , Kim Minwoo , Lee Soogab 
Published: March 2008

AbstractA numerical study on impulsive noise generation produced by complex flows discharging from a muzzle is achieved and the basic structures generating impulsive noise are analyzed. Complex flow features by a muzzle flow and noise generation mechanisms by several sources of noise are discussed from numerical simulations. Two‐dimensional axisymmetric Euler equations are used for governing equations. High‐order dispersion relation preserving finite difference method and an optimized four‐level marching method are used for spatial discretization and time integration, respectively. In order to show the capability of this method to capture blast waves and to examine the basic generation mechanism of acoustic waves from a muzzle, the interaction between a shock/blast wave and a vortex ring is implemented. From the numerical simulation of the 7.62‐mm NATO rifle G3 with a DM‐41 round in the near field, complex blast waves, jet flow, various vortices and their interaction phenomena are described and noise generation mechanism due to the interaction of complex flow structures is observed. The present results demonstrate that numerical simulation using computational aeroacoustic methods provides not only a reliable way to determine the blast wave dynamics of the muzzle flow but also allows an opportunity to study the physics and detailed mechanisms of the noise generation and propagation due to the interaction of complex flow structures generated from a muzzle system. Copyright © 2008 John Wiley & Sons, Ltd.
Optimal control problems with delays in state and control variables subject to mixed control–state constraints
Authors: Göllmann L. , Kern D. , Maurer H. 
Published: March 2008

AbstractOptimal control problems with delays in state and control variables are studied. Constraints are imposed as mixed control–state inequality constraints. Necessary optimality conditions in the form of Pontryagin's minimum principle are established. The proof proceeds by augmenting the delayed control problem to a nondelayed problem with mixed terminal boundary conditions to which Pontryagin's minimum principle is applicable. Discretization methods are discussed by which the delayed optimal control problem is transformed into a large‐scale nonlinear programming problem. It is shown that the Lagrange multipliers associated with the programming problem provide a consistent discretization of the advanced adjoint equation for the delayed control problem. An analytical example and numerical examples from chemical engineering and economics illustrate the results. Copyright © 2008 John Wiley & Sons, Ltd.
PROSPECT lost: when a pilot project does not look to learn
Authors: Mattingly Michael 
Published: March 2008

AbstractIf a development project is destined to reach only a selection of its intended beneficiaries or to give them only momentary or uncertain benefits, there is a strong rationale for making it instead a project of trials from which lessons can be taken for obtaining the impact that it may not otherwise have. Because the fundamental problems and opportunities of development are very complex by their nature, interventions that seek to test practice knowledge and to learn above all else may have the greatest potential for benefit in the long term. A project that wishes to create experience from which others can learn will engage in research, so it must be conceived, led and conducted as such. This means it must be designed with knowledge of research. It must be led with an appreciation and understanding of research method. Specific research activities must be conducted that produce knowledge and promote its up‐take, so that learning is a principle project outcome. The large urban anti‐poverty project, PROSPECT, conducted in Lusaka, Zambia, illustrates this argument. Copyright © 2008 John Wiley & Sons, Ltd.
New insights on the role of CXCR4 in cancer metastasis
Authors: Zlotnik A 
Published: March 2008

AbstractThe evolutionarily conserved chemokine superfamily encodes small peptide molecules that bind G‐protein‐coupled receptors. In humans, this superfamily includes at least 46 ligands and 18 receptors. In general, chemokines and their receptors form a chemotactic network that regulates the migration of cells to specific micro‐anatomical destinations within an organism in an organized and non‐random manner. Recent studies place chemokine‐chemokine receptor pairs at the centre of not only physiological cell migration, but also pathological processes such as metastasis. This mini review considers some recent data on how chemokines regulate tumour cells during metastasis. These observations suggest novel ways for pharmacological intervention. Copyright © 2008 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Fracture prediction in tough polyethylene pipes using measured craze strength
Authors: Davis P. , Burn S. , Gould S. 
Published: March 2008

AbstractIn this study, an empirical model is developed that predicts the time to failure for PE pipes under combined pressure and deflection loads. The time‐dependent craze strength of different PE materials is measured using the circumferentially deep‐notched tensile (CDNT) test. In agreement with previous research, results indicate that bimodal materials with comonomer side‐chain densities biased toward high‐molecular‐weight PE molecules exhibit significantly higher long‐term craze strengths. A comparison of currently available PE materials with CDNT samples taken from a PE pipe that failed by slow crack growth in service clearly indicates the superior performance of new‐generation materials. Using measured craze strength data from the CDNT test, a simplified model for predicting failure in buried PE pipes is developed. Extending previous research, the reference stress concept is used to calculate an equivalent craze stress for a pipe subjected to combined internal pressure and deflection loads. Good agreement is obtained between the model predictions and observed failure times in an experimental test‐bed study of pipes under in‐service loading conditions. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Semi‐empirical, squeeze flow and intermolecular diffusion model. I. Determination of model parameters
Authors: Grewell David , Benatar Avraham 
Published: March 2008

AbstractThis article reviews the development of molecular healing models that couple squeeze flow and intermolecular diffusion. Historically there are a few studies that combine these processes for fusion bonding of thermoplastic composites. The motivation of this work was to develop similar models for welding of polymer films and films to substrates. These models are theoretically developed and experimentally verified. It was found that the time dependence for squeeze flow is of the same order of magnitude as that for intermolecular diffusion, making models for these processes indistinguishable experimentally, and therefore, they were assumed to occur simultaneously. Furthermore, it was found that healing of the weld can be better defined as a function of time and temperature instead of temperature alone, as historically done for welding applications. Comparison of the weld strength predictions with experimental data for impulse welds showed that the developed models were able to predict weld strength over a wide range of parameters. In Part 2, moving heat source heat transfer models together with the coupled squeeze flow and intermolecular diffusion model are used to predict healing during laser microwelding. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Synthesis and photopolymerization kinetics of polymeric one‐component type II photoinitiator containing benzophenone moiety and tertiary amine
Authors: Xiao Pu , Wang Ying , Dai Mingzhi , Shi Suqing , Wu Gangqiang , Nie Jun 
Published: March 2008

AbstractA polymeric one‐component type II photoinitiator (PDABPP) based on 4,4′‐dihydroxybenzophenone (DHBP), acryloyl chloride, and piperazine was synthesized, and its structure was confirmed by GPC and 1H NMR. The photopolymerization kinetics of the photoinitiator was studied by real‐time infrared spectroscopy. It indicated that PDABPP was a more effective photoinitiator than that of benzophenone (BP)/triethylamine (TEA). The rate of polymerization and final conversion increased, and the induction period shortened with increase of PDABPP concentration, light intensity, and amine concentration. The kinetics of photopolymerization for tripropylene glycol diacrylate (TPGDA) incorporating PDABPP in the presence of different tertiary amines as the initiating system indicated that the PDABPP/TEA combination exhibited the highest polymerization rates among the PDABPP/amines combinations. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of weakly interacting nanofiller on the morphology and viscoelastic response of polyolefins
Authors: Kalfus Jan , Jancar Josef , Kucera Jaroslav 
Published: March 2008

AbstractEffect of silica nanofiller on the deformation response and morphology of low‐ and high‐density polyethylene (HDPE, LDPE) and isotactic polypropylene (PP) modified with fumed silica was investigated. The dynamic‐mechanical thermal spectroscopy, differential scanning calorimetry, optical microscopy, and density measurements were carried out to determine the temperature dependence of storage and loss moduli as well as nanocomposite morphology. It was demonstrated that the degree of matrix reinforcement is considerably affected by the extent of matrix crystallinity, especially, in the temperature range from (Tm–130°C) to Tm. Based on experimental evidence and literature review, it is proposed that this phenomenon may be attributed to the alpha‐mechanical relaxation process occurring above matrix Tg. As a result of adding silica into the melted matrix, mobility of chains in contact with silica particles became reduced. This caused substantial changes in morphology of these semicrystalline nanocomposites. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of PMMA addition on characterization and morphology of PVDF
Authors: Elashmawi I.S. , Hakeem N.A. 
Published: March 2008

AbstractPolyvinylidene fluoride and polymethylmethacrylate (PVDF/PMMA) films were blended with different concentrations by casting method. Structural, spectroscopic, and morphological characteristics of both the interface and the surface of the films have been investigated. The blends were characterized using X‐ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible, differential thermal analysis (DTA), and scanning electron microscopy (SEM). All measurements reveal that the blends take place based on the influence of PMMA content on PVDF. FTIR results indicate the possible interactions between carbonyl group of PMMA and CH2 groups of PVDF which indicates the formation of blends. Optical absorption spectra suggested the presence of an optical gap (Eg) which decreased with increasing PMMA content. UV/VIS spectra were characterized by a sharp edge and a window of wavelength range 290–350 nm for some blends. The optical window can be used as an optical sensor or band pass filter. The degree of crystallinity was found to decrease with increasing PMMA content, which was confirmed by XRD and DTA analysis. SEM micrograph shows spherulites which increase with the addition of PMMA and it becomes sharper and contains a longitudinal shape. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Novel phenylethynyl‐endcapped polyimide oligomers: Synthesis and characterization
Authors: Chen Jiansheng , Qu Ximing , Liu Jingang , Yang Haixia , Fan Lin , Yang Shiyong 
Published: March 2008

AbstractA series of novel phenylethynyl‐endcapped polyimide oligomers were prepared by polycondensation of an aromatic diamine mixture of 1,3‐bis(4‐aminophenoxy) benzene (1,3,4‐APB) and 3,4′‐oxydianiline (3,4′‐ODA) with different aromatic dianhydrides including 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐(hexafluoro isopropylidene)diphthalic anhydride (6FDA), 4,4′‐oxydiphthalic anhydride (ODPA), and 4,4′‐[2,2,2‐trifluoro‐1‐(3′,5′‐bis‐(trifluoro‐methyl)phenyl)ethylidene]diphthalic anhydride (9FDA) in the presence of 4‐phenyl‐ethynylaniline (PEA) as endcapping agent in aprotic solvent at elevated temperature. The chemical structures, thermal behavior, and melt rheological properties of the synthesized polyimide oligomers were investigated. Experimental results indicated that the fluorinated polyimide oligomers derived from 6FDA (PI‐2) and 9FDA (PI‐4) are amorphous solid resins and exhibited lower melt viscosities than those prepared from the unfluorinated aromatic dianhydrides such as BPDA and ODPA. The BPDA‐based polyimide oligomers with a molar ratio of 1,3,4‐APB/3,4′‐ODA = 50:50 (PI‐5) showed lower melt viscosity than those derived from a mixture of 1,3,4‐APB and 3,4′‐ODA with molar ratios of 75:25 and 100:0, respectively. In addition, the melt viscosity of the polyimide oligomers increased obviously with increasing of the polymer calculated molecular weights. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Flexural creep of all‐polypropylene composites: Model analysis
Authors: Banik K. , Karger‐Kocsis J. , Abraham T. 
Published: March 2008

AbstractIn this article, simple viscoelastic and empirical models are presented to predict and analyze the flexural creep behavior of all‐poly(propylene) (all‐PP) composites. Results of the successful application of these models to the actual creep behavior of unidirectional (UD) and cross‐ply (CP) all‐PP composites tested by short‐term flexural creep measurements over a temperature range of 20–80°C are presented. Analysis of the momentary creep behavior of all‐PP composites with different tape lay‐ups are made to understand their deformation mechanism. Further to the main theme of the article, an interesting discrepancy while predicting the long‐term creep behavior of these composites based on the time‐temperature superposition (TTS) principle and Findley power law model is visualized which has also been illustrated here. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Effect of orientation and crystallinity on the photodegradation of poly(ethylene terephthalate) fibers
Authors: Fashandi H. , Zadhoush A. , Haghighat M. 
Published: March 2008

AbstractIn this research, photodegradation of poly(ethylene terephthalate) (PET) fibers was investigated with emphasis on the morphological state of yarns. Two kinds of yarns, FDY (Fully Drawn Yarn) and POY (Partially Oriented Yarn), with different molecular orientation and crystallinity were applied in this research. FDY is spun in the same way as POY and subsequently drawn at high speed and then entangled before winding up. This sample has higher molecular orientation and crystallinity than the POY sample. Several analytical methods were applied in this study: viscometry, X‐ray diffraction, FTIR spectroscopy, UV–Visible spectrophotometry, and mechanical testing. Viscometry was used to determine molecular weight as a monitoring factor for degradation. X‐ray diagrams showed higher crystallinity for FDY samples during weathering process by irradiation. Results of mechanical testing indicated that the tenacity of the FDY fibers had less deterioration in comparison with the POY ones. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers
Numerical simulation of tunnel diodes for multi‐junction solar cells
Authors: Hermle M. , Létay G. , Philipps S. P. , Bett A. W. 
Published: March 2008

AbstractThis work presents efforts to simulate numerically the current voltage (IV) curve of a III–V based Esaki tunnel diode. Using a tunneling model, which takes into account the full nonlocality of the barrier, a good agreement between measured and simulated IV curves of a GaAs tunnel diode was achieved. The influence of a series resistance effect as well as the importance of trap assisted tunneling (TAT) could be shown. In addition, we present a two‐dimensional model of a III–V multi‐junction solar cell including the numerical model of the investigated Esaki tunnel diode. Copyright © 2008 John Wiley & Sons, Ltd.
Optical properties of TiO2 films made by air oxidation of Ti
Authors: Svitasheva S. N. , Gritsenko V. A. , Kolesov B. A. 
Published: March 2008

AbstractIn this work spectral behaviour of complex refractive index of thermal oxidized titanium films deposited onto Si (100) substrate were investigated by spectroscopic ellipsometry in the range of 1.5‐4.77 eV. The films were subjected to annealing in air at temperature 750 °C for 7 and 25 hours. As it follows from our studies, air oxidation of titanium resulted in coexisting of different phases in the film, and dependence of their optical and structural properties upon z‐coordinate (upon film depth). The spectral dependences of complex refractive index and the changing of film thickness due to cumulative annealing were determined from pseudodielectric function (PDF) ‐ ε(E) spectra, for which data acquisition was performed by Spectroscopic Phase Modulated Ellipsometer (SPME). Complicated phase composition of films was revealed by using multi‐layers conception of investigated film and applying oscillator's model and EMA approximation for description of spectral dependence of dielectric function of film or its separate layers. Raman spectra were used to distinguish phase components in the films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ellipsometric characterization of photo‐resist gratings using artificial neural network
Authors: Gereige I. , Robert S. , Stchakovsky M. , Jamon D. , Celle F. , Reynaud S. , Pommier J. C. , Jourlin Y. 
Published: March 2008

AbstractIn this work, we report on the control of patterned photoresist structures used as a mask in the photolithographic process. This control is crucial in order to detect any defect before the final etching step on the substrate or sublayer. Scatterometry is an optical method that has true potential for critical dimension and profile analysis.Spectroscopic ellipsometry is employed to measure the diffracted signature, and followed by a neural treatement to extract the geometrical parameters. Experimental results are validated on 2‐μm‐period gratings, with various geometrical profiles, transfered on a glass substrate. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ observation of photodoping phenomena in chalcogenide glass by spectroscopic ellipsometry
Authors: Murakami Y. , Wakaki M. , Kawabata S. 
Published: March 2008

AbstractAnormalous diffusion process of Ag into an As2S3 film induced by illumination of light with photon energy larger than optical gap was examined in‐situ by spectroscopic ellipsometry in the wavelength regions between 450 and 850 nm. Two steps of doping called as the first and second stage were derived through the analyses of the optical constants, which is difficult to obtain by the monochromatic ellipsometry. The features of photodoping were clearly observed through the analysis of the results of spectroscopic ellipsometry, which suggests the superiority of the method to treat for such complex phenomenon. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fréedericksz transition in homeotropically aligned liquid crystals: a photopolarimetric characterization
Authors: Vena C. , Versace C. , Strangi G. , D'Elia St. , Bartolino R. 
Published: March 2008

AbstractThis work is aimed to the photopolarimetric characterization of the disorder evolution occurring in homeotropically aligned nematic liquid crystal films during the Fréedericksz transition. This order‐disorder transition is studied by monitoring the depolarization effects of the transmitted light. Depolarization mainly occurs because light undergoes random and local phase displacements. The measurements reveal unexpected depolarization effects at the transition, which we interpret in terms of director field unhomogeneity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Real‐time spectroscopic ellipsometry for protein adsorption study and pH effect
Authors: Lousinian S. , Logothetidis S. 
Published: March 2008

AbstractCarbon based thin films, such as amorphous carbon (a‐C) and amorphous hydrogenated diamond‐like carbon (a‐C:H) are considered as excellent candidates for biomedical applications. Protein adsorption is an important aspect for the improvement of many applications, such as medical implants, biosensor design, etc. The density, orientation, and conformation of surface‐bound proteins are believed to be key factors in controlling subsequent cellular adhesion. Aim of this work is the study of the pH effect on fibrinogen adsorption on a haemocompatible a‐C:H thin film developed by rf reactive magnetron sputtering. For this purpose, Vis–UV Spectroscopic Ellipsometry (SE) has been used. It is a non destructive, surface sensitive technique, with the capability of performing real‐time measurements in air as well as in liquid environment, with great potential in biomedical studies. An appropriate ellipsometric model has been developed, in order to describe accurately the protein adsorption mechanisms in real‐time. SE results reveal the differences in the rate of fibrinogen thickness increase and transition rate of fibrinogen from liquid to adsorbed state. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Random errors and optimum estimation of measurements photometric ellipsometers
Authors: Dron O. S. 
Published: March 2008

AbstractA method of calculation of ellipsometric parameters, which allows to minimize random errors and simultaneously obtain their covariance matrix, is developed for photometric ellipsometry and polarimetry systems on the basis of Generalized least‐squares method (GLSM). As examples of application for rotating compensator ellipsometer the optimum value of retardation of the compensator equal to 132° is calculated, and also the technique of determination of the spectral range is offered. For shot‐noise limited systems the basic equation R = D (R)U is obtained, where R is the vector of measured parameters, D (R) is the covariance matrix of these parameters, and U is a constant vector describing the measuring system. All the results are applicable both for Stokes‐ and for Muller‐ellipsometry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Wide angle beam ellipsometry for extremely large samples
Authors: Major C. , Juhász G. , Horváth Z. , Polgar O. , Fried M. 
Published: March 2008

AbstractOur aim was to make possible to use ellipsometry for mapping purposes during one measuring cycle even on large wafers or panels (several dm2 area). The new technique (Patent pending: P0700366, 2007 [1]) (based on our wide‐angle beam ellipsometry solution) uses non‐collimated illumination with special mirror arrangement giving multiple‐angle‐of‐incidence information. The prototype uses a so called RGB‐laser (658, 532, 474 nm) as light source. The detection is almost without background. One rapid measuring cycle is enough to determine the polarization state at all the points inside the illuminated area. The collected data can be processed very fast providing nearly real‐time thicknesses and/or refractive index maps over a large (several dm2) area of the sample surface even in the case of multi‐layer samples. The method can be used for mapping (quality) control purposes in the case of large area solar cell table production lines even in vacuum chamber with 5‐10 mm lateral resolution. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)