bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Studies of Nitroxide‐Mediated Styrene Miniemulsion Polymerization – Opportunities for Process Improvement
Authors: Ma John W. , Cunningham Michael F. , McAuley Kim B. , Keoshkerian Barkev , Georges Michael K. 
Published: March 2003

AbstractModeling studies were performed to investigate how persulfate‐initiated nitroxide‐mediated styrene miniemulsion polymerizations are influenced by changes to the polymerization recipe. By manipulating the initial concentrations of potassium persulfate and nitroxide, and the aqueous phase volume, trends in the predicted polymerization time, number average molecular weight, polydispersity and degree of polymer livingness were identified that indicate operating conditions for improved process performance. Specifically, our model predicts the existence of experimental conditions that simultaneously minimize polymer polydispersity and maximize the livingness of the polymer. The mechanisms responsible for the predicted trends were identified from the predicted molecular weight distributions of the living and dead polymer chains.Predicted number MWDs at 20% monomer conversion for styrene NMMP systems employing various levels of [KPS]aq,0. Dormant KPS‐initiated polymer radicals.imagePredicted number MWDs at 20% monomer conversion for styrene NMMP systems employing various levels of [KPS]aq,0. Dormant KPS‐initiated polymer radicals.
Molecular Weight Development during Simultaneous Chain Scission, Long‐Chain Branching and Crosslinking, 2
Authors: Tobita Hidetaka 
Published: March 2003

AbstractThe matrix formula developed in Part 1 of this series is applied to describe the molecular weight development during free‐radical (co)polymerization. All of the required probabilistic parameters are expressed in terms of the kinetic rate constants and pertinent concentrations. In free‐radical polymerization, the primary chains are formed consecutively. The segments that constitute nonlinear polymer molecules are divided into N fractions on the basis of the birth conversion levels, and the weight‐average molecular weight of the whole reaction system is obtained by extrapolating N to infinity. Practically, such extrapolation can be conducted by using the calculated values for only three different N values with sufficient accuracy. In the context of the present theory, not only the full molecular weight distribution but also the polymer structure formed can be determined directly by using the Monte Carlo simulation method.
Calculated weight‐average chain length development.imageCalculated weight‐average chain length development.
Model Reduction in Emulsion Polymerization Using Hybrid First‐Principles/Artificial Neural Network Models
Authors: d'Anjou Alicia , Torrealdea F. Javier , Leiza José R. , Asua José M. , Arzamendi Gurutze 
Published: March 2003

AbstractA first‐principles mathematical model for emulsion polymerization was reduced by using a hybrid mathematical model composed by artificial neural networks (ANN) and material balances. The goal was to have an accurate model that may be integrated fast enough to be used for online optimization purposes. In the reduced model the polymerization rate and the instantaneous weight‐average molecular weight were calculated by means of artificial neural networks. These ANNs were incorporated to first‐principles material balances. The accuracy of the reduced model under a wide range of conditions was assessed. Savings in computer time were achieved by using the reduced model, which makes it suitable for online optimization purposes.
Effect of the temperature on the cumulative weight‐average molecular weight: first principles mathematical model (—); $\overline {{\rm M}_{{\rm w},{\rm inst}} }$(ANN2) and hybrid model predictions: (▵) 50 °C, (▪) 60 °C(training), (▿) 70 °C(validation), (•) 80 °C, (○) 90 °C.imageEffect of the temperature on the cumulative weight‐average molecular weight: first principles mathematical model (—); $\overline {{\rm M}_{{\rm w},{\rm inst}} }$(ANN2) and hybrid model predictions: (▵) 50 °C, (▪) 60 °C(training), (▿) 70 °C(validation), (•) 80 °C, (○) 90 °C.
RIS Models and Unperturbed Chain Properties of Polyesters Containing 1,3‐Cyclobutylene and 1,4‐Cyclohexylene Linkages
Authors: Sulatha Muralidharan S. , Natarajan Upendra 
Published: March 2003

AbstractPolyesters containing 1,3‐cyclobutylene and 1,4‐cyclohexylene linkages in the main chain are investigated using conformational energy calculations. Rotational isomeric state (RIS) models are developed for poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT), poly(1,4‐cyclohexylenedimethylene 2,5‐dimethylterephthalate) (DMPCT), poly(1,4‐cyclohexylenedimethylene 1,4‐cyclohexylenedicarboxylate) (PCC), and poly(2,2,4,4‐tetramethyl‐1,3‐cyclobutylene terephthalate) (CBDO). In DMPCT, the ester linkage prefers skewed conformations with respect to the phenyl group to relieve the steric strain caused by the methyl groups. The methyl groups on the cyclobutanediol moiety in CBDO restrict the rotational freedom about the oxycyclobutylene linkage. The unperturbed dimensions as described by characteristic ratio and persistence length are calculated for the trans and cis configurations of these polyesters. CBDO shows highly extended chain conformations among these polyesters indicating relative chain rigidity of the backbone. For DMPCT and PCC, in their trans configuration, the chain dimensions decrease with an increase in temperature while for their cis configurations, the chain dimensions increase with temperature, arising from basic differences in the fragment structures that control the competition of the relative populations as affected by temperature. Temperature has negligible influence on the unperturbed dimensions of both isomeric linkages of CBDO, while this is true for the trans configuration of PCT. The study shows that induction of cyclobutylene groups in the main chain results in a greater rigidity for homopolyesters than for chains with cyclohexylene groups.
Structure of the repeat units of polyesters in the planar trans configuration and the schematic of the RIS models with definition of geometrical parameters.imageStructure of the repeat units of polyesters in the planar trans configuration and the schematic of the RIS models with definition of geometrical parameters.
Organische Polymere als funktionelle Werkstoffe für chemische Sensoren
Authors: Kaden H. , Berthold M. , Jahn H. 
Published: March 2003

AbstractDie Funktion vieler chemischer Sensoren für Messungen in Flüssigkeiten und in Gasen bei Umgebungstemperatur beruht auf der Kombination eines Transducers mit organischen Membranen. Diese Membranen bestimmen wesentliche Sensoreigenschaften wie Selektivität und Ansprechverhalten. Außerdem schützen sie das Detektionssystem vor äußeren Einflüssen.Die Auswahl und Entwicklung von Polymermembranen ist deswegen ein wesentlicher Bestandteil der Sensorforschung und ‐entwicklung. Dabei sind elektrische, optische und biologische Eigenschaften der Polymere von Bedeutung. Es wird eine Übersicht über die in der Sensorik eingesetzten Materialien gegeben.Von besonderem Interesse für die Sensorforschung sind in letzter Zeit intrinsisch leitende Polymere (ILP), deren Eigenschaften neue Möglichkeiten der Sensorentwicklung eröffnet haben. Am Beispiel einer elektrochemischen pH‐Glaselektrode mit innerer Feststoffableitung wird gezeigt, dass Polypyrrol als Material für eine langzeitbeständige Potentialableitung und damit als Ersatz bisher ausschließlich verwendeter sog. elektrochemischer Elektroden 2. Art dienen kann. Praxiserprobungen bestätigen die Eignung dieses Polymermaterials. Aspekte des Transportmechanismus elektrischer Ladungen über die Grenzfläche ILP | Glas werden diskutiert.
Lenzing LYOCELL: Potentiale und Chancen einer neuen Fasergeneration
Authors: Harms H. 
Published: March 2003

AbstractCellulose ist der wichtigste „organische Konstruktions‐ und Funktionswerkstoff”︁ der Natur und weist dementspechend eine umfassenden Palette hervorragender und sehr spezifischer Eigenschaften auf. Diese Eigenschaften können für verschiedenste Produkte zugänglich gemacht und auch gezielt modifiziert werden, sobald es einem gelingt, die Cellulose in Lösung zu bringen und dann in der gewünschten Form auf geeignete Weise zu regenerieren. Die fortschreitende Entwicklung der neuen Lyocellfaser, das zunehmende Wissen um ihre Leistungsfähigkeit und die Möglichkeiten sie zu modifizieren, aber auch eine Reihe völlig „neuer Anwendungen”︁ des Lyocell Verfahrens für andere Produkte zeigen, daß die direkte Regeneration der Cellulose aus organischer Lösung eine völlig neue Nutzung ihres hervorragenden Eigenschaftspotentials ermöglicht. Lyocell öffnet also nicht nur die Chance für eine neue Generation cellulosischer Fasern ‐ auch für neue Einsatzgebiete ‐ sondern auch für eine Renaissance der Cellulose für unterschiedliche Produkte, bei denen sie einerseits in den letzten Jahrzehnten durch vollsynthetische Polymere substituiert wurde und bei denen andererseits völlig neue Anwendungen für dieses hervorragende Polymer erschlossen werden.
ABOUT THE CHARACTERIZATION OF THE MECHANICAL PROPERTIES OF NATURAL FIBRES
Authors: MIECK K.‐P. , REUSSMANN, T. , NECHWATAL A. 
Published: March 2003

AbstractAll composite models contain the E‐modulus or the tenacity of the reinforcing fibres. Therefore the exact measurement of the fibre properties is the essential prerequisite to achieve an agreement between the theoretical approaches and the practical results. Here some special problems in the fibre testing of natural fibres are discussed.
Chemische Zusammensetzung und Mikrostruktur polymerabgeleiteter Gläser und Keramiken im System Si–C–O. Teil 2: Charakterisierung der Gefügeausbildung mittels hochauflösender Durchstrahlungselektronenmikroskopie und Feinbereichsbeugung
Authors: Gegner J. 
Published: March 2003

AbstractFlüssige oder feste Siliconharze bilden die wirtschaftlich interessanteste Gruppe organischer Vorstufen zur pyrolytischen Herstellung von Glas‐ und Keramikwerkstoffen auf Siliziumbasis. Da dichte, maßstabile Bauteile kostengünstig durch Beimischung reaktiver Füllstoffpulver erreicht werden können, müssen chemische Zusammensetzung und Gefügeentwicklung der polymerabgeleiteten Rückstände während der thermischen Zersetzung genau bekannt sein. In der vorliegenden Arbeit werden deshalb die durch Pyrolyse des Modellprekursors Polymethylsiloxan bei Temperaturen von 525 bis 1550 °C hergestellten Gläser und Keramiken untersucht. Mittels analytischer Elektronenmikroskopie wurde in Teil 1 der Bindungszustand von Silizium im Nanometerbereich bestimmt und die Phasentrennung der metastabilen Si–C–O‐Matrix in SiO2, C und SiC nachgewiesen. Die in‐situ‐Kristallisation konnte durch Zugabe feinkörniger Pulver inerter Füllstoffe, wie Al2O3 oder SiC, wesentlich beschleunigt werden, was eine wirksame Prozesssteuerung ermöglicht. In Teil 2 wird die Mikrostruktur mittels hochauflösender Durchstrahlungselektronenmikroskopie und Feinbereichsbeugung charakterisiert. Es scheiden sich turbostratischer Kohlenstoff und kubisches β‐SiC als Kristallisationsprodukte aus. Diese Phasen sind in eine amorphe Matrix eingebettet. Inerte Füllstoffe senken die Kristallisationstemperatur um mehrere hundert °C. In diesem Fall wirkt das polymerabgeleitete Si–C–O‐Material als Bindemittel zwischen den Pulverteilchen. Reaktionsschichtbildung findet nicht statt. Bei den untersuchten Pyrolysebedingungen wurde keine Kristallisation von SiO2 beobachtet.
Planar waveguide add/drop wavelength filters based on segmented gratings
Authors: Tomljenovic‐Hanic S. , Love J. D. 
Published: March 2003

AbstractWe investigate the application of segmented reflection gratings in planar devices that can function as either a single‐ or two‐wavelength add/drop filter. The role of the segmented gratings is analogous to that of a blazed grating, but can provide a higher reflectivity level at the Bragg wavelength, eliminate back reflection into the fundamental mode, and provide arbitrarily close channel spacing in the two‐wavelength case. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 163–165, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10855
A wideband rectangular patch antenna with shorting pins
Authors: Chair R. , Mok W. C. , Luk K. M. , Lee K. F. 
Published: March 2003

AbstractThis paper presents a novel bandwidth enhancement technique by using shorting pins. A low‐profile rectangular‐shaped patch antenna with three shorting pins is presented. The impedance bandwidth of the proposed antenna achieves 33% (SWR < 2) while the overall thickness of the antenna is only 0.06λ0. The antenna has two close resonant bands. The lower resonant band has a conical radiation pattern with 4‐dBi maximum gain and the higher resonant band has a broadside radiation pattern with 8‐dBi maximum gain. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 165–167, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10856
Fast calculation of the propagation constants of leaky and Berenger modes of planar and circular dielectric waveguides terminated by a perfectly matched layer
Authors: Rogier Hendrik , Knockaert Luc , De Zutter Daniël 
Published: March 2003

AbstractA fast technique is proposed to determine the complex propagation constants of the leaky and Berenger modes of circular dielectric waveguides terminated by a perfectly matched layer (PML). The method relies on a coordinate transformation in the complex plane and uses the approximate analytical solutions of the dispersion relations as a first estimate. The efficiency of the technique is shown for a microstrip substrate and a VCSEL configuration, both terminated by a perfectly matched layer. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 167–171, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10857
Photonics true‐time delay using a tunable‐fiber laser source based on a high‐birefringence fiber‐loop‐mirror filter
Authors: Yang Jianliang , Tjin Swee Chuan , Ngo Nam Quoc 
Published: March 2003

AbstractA photonics true‐time‐delay (TDD) system using a chirped grating and a novel fiber‐ring laser is proposed and demonstrated. A high‐birefringence fiber‐loop mirror (HiBi‐FLM) is integrated in the laser cavity to act as a polarization‐independent wavelength filter. By properly adjusting the polarization controllers in the HiBi‐FLM, desirable lasing wavelength and number or wavelength spacing can be achieved. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 171–174, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10858
A wideband arrowhead planar monopole antenna for multi‐service mobile systems
Authors: Cabedo‐Fabrés M. , Nogueira Alejandro Valero , Bataller Miguel Ferrando 
Published: March 2003

AbstractA compact wideband arrowhead planar monopole antenna is obtained by trimming the lower edges of the triangular planar monopole. The shorted arrowhead monopole is very suitable for use in multi‐service wireless systems, yielding a measured bandwidth of 5:1 for VSWR < 2.1 while retaining good radiation characteristics. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 188–190, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10863
Experimental investigation of the performance of co‐ and counter‐pumped Raman fiber amplifiers
Authors: Xiangjun Xin , Chongxiu Yu , Jianhua Ren , Anjian Li , Qiang Wu , Yu Xin , Chuanlin Wang , Wenxiao Zheng , Shuangchen Ruan , Geguo Du , Xiaoqiang Yang , Gang Xin 
Published: March 2003

AbstractGain, gain saturation, optical signal‐to‐noise ratio (OSNR), and pump power conversion efficiency (PCE) of co‐ and counter‐pumped Raman fiber amplifiers (RFAs) are investigated and compared experimentally in this paper. Results show that obvious OSNR improvement can be achieved with co‐pumped RFAs. Compared with the counter‐pumped scheme, the co‐pumped solution has more severe gain saturation. PCE decreases as the input power increases for both pumping schemes, however, PCE decreases faster for the co‐pumped RFAs. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 190–194, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10864
Low‐pass impedance matching filters for packaged low‐cost laser diodes
Authors: Music H. , Alping A. , Johansson U. , Hedquist T. , Gevorgian Spartak 
Published: March 2003

AbstractA simple, cost‐effective, and compact passive matching network, in the form of a low‐pass filter, is developed for impedance matching of a commercially packaged laser diode with an optical connector. More than 15‐dB matching improvement is achieved at 1.8‐GHz frequency by using a small size (10.8 × 9.1 mm) three‐pole lumped element low‐pass LC filter. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 194–196, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10865
Angular spread at 2.1 GHz while entering tunnels
Authors: García‐Pardo José María Molina , Rodríguez José Victor Rodríguez , Juan‐Llácer Leandro 
Published: March 2003

AbstractPropagation characteristics while entering tunnels are analyzed by using a ray‐launching technique and the uniform theory of diffraction (UTD). RMS angular spread is studied and related to the “excitation zone.” This paper presents interesting differences in the behavior of this parameter and the RMS delay spread. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 196–198, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10866
Assessment of the GA‐based adaptive array control strategy: The case of stochastic life‐time co‐channel interferences
Authors: Donelli Massimo , Lommi Andrea , Massa Andrea , Sacchi Claudio 
Published: March 2003

AbstractIn this paper, the performances of an adaptive antenna array control strategy, based on an improved genetic algorithm, are evaluated in terms of signal‐to‐interference‐noise ratio (SINR). The working case considered deals with the presence of co‐channel interfering signals characterized by stochastic arrivals, phases, and lifetime. This scenario provides a reliable testing benchmark for such array control methodologies. The simulation results prove the robustness of the learned real‐time genetic algorithm (LRTGA) in the presence of non‐deterministic interferences as well. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 198–201, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10867
A new type of slow‐wave 1D PBG microstrip band‐pass filter
Authors: Nesic Dusan 
Published: March 2003

AbstractIn this paper, a new type of slow‐wave 1D PBG microstrip band‐pass filter with a half‐wavelength linear resonator is introduced. Reduction of the central frequency (slow‐wave effect) is over 50%, as compared to the conventional band‐pass filter of the same type. Additional coupling is over tuning narrow lines that can be used to regulate the filter's performance. In addition, it has very good S11 parameters and low losses in the band‐pass. Simulation and experimental results are in good agreement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 201–203, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10868
Lumped impedance matching using a hybrid genetic algorithm
Authors: du Plessis W. P. , Abrie P. L. D. 
Published: March 2003

AbstractA new impedance matching algorithm based on a hybrid genetic algorithm is presented. Unlike real‐frequency techniques, this new algorithm does not require ideal transformers, resonant sections are allowed, component ranges can be specified, and parasitic effects can be included. The results obtained are comparable to those obtained with the best published techniques. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 210–212, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10871
The effect of IP traffic burstiness on four‐wave mixing crosstalk in WDM networks
Authors: Tang Junhua , Zhang Liren , Siew Chee‐Kheong 
Published: March 2003

AbstractThe effect of bursty IP traffic on the statistics of four‐wave mixing in wavelength division multiplexing (WDM) networks is studied in terms of the distribution of the actual four‐wave mixing power under different IP traffic conditions. A novel approach for estimating the average four‐wave mixing power in WDM network with bursty IP traffic is presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 212–214, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10872
Microwave techniques for measurement of large‐structure vibration
Authors: Pieraccini Massimiliano , Luzi Guido , Mecatti Daniele , Gusella Vittorio , Atzeni Carlo 
Published: March 2003

AbstractIn this paper, the authors propose continuous‐wave single‐frequency (CW‐SF) and multi‐frequency (CW‐MF) microwave techniques for measurement of large‐structure vibration. Theoretical background and experimental results of tests on a vertical steel structure, subjected both to artificial solicitation through a vibrodyne and to wind, are reported. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 216–218, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10874
A robust and efficient method for obtaining the complex modes in inhomogeneously filled waveguides
Authors: Monsoriu Juan A. , Coves Angela , Gimeno Benito , Andres Miguel V. , Silvestre Enrique 
Published: March 2003

AbstractIn this paper, we present a computational simulation of the complex wave propagation in inhomogeneously filled waveguides with lossless and lossy dielectrics. We use a biorthonormal‐basis method as a numerical technique. The behavior of complex modes in different waveguides whose characterization with other methods involves some difficulties is analyzed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 218–222, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10875
Reducing resonant length of sidewall‐inclined slots in a rectangular waveguide
Authors: Heidari Abbas Ali , Forooraghi Keyvan , Hakkak Mohammad 
Published: March 2003

AbstractIn this paper, the admittance characteristics of a dielectric filled inclined slot in the narrow wall of a rectangular waveguide have been calculated. By enforcing the continuity of the tangential magnetic field through the slot aperture, an integral equation with the tangential electric field in the slot as the unknown is obtained. An entire domain method of moments (MoM) is used to solve the integral equation. Numerical results show that the slot can resonate without penetrating onto the top and bottom broad walls of the waveguide. It has also been shown that the resonant frequency (length) and the resonant conductance of the slot depend on the dielectric constant of the material filling the slot. The computed results are shown to be in good agreement with those obtained by HP‐HFSS. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 222–226, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10876
A microwave differentiator
Authors: Hsue Ching‐Wen , Kuan Ming‐Chih , Peng Chia‐Mei 
Published: March 2003

AbstractA wideband differentiator is implemented by using nonuniform transmission lines. To utilize the transfer function of a differentiator developed in a study of discrete signal processing (DSP), we formulate the scattering characteristics of equal‐length electrical transmission line sections in the Z domain. A uniform line shunted with a two‐section stub is obtained to emulate the transfer function of a stable second‐order recursive differentiator. A microstrip circuit is implemented to verify this novel method and experimental results are in good agreement with theoretical design parameters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 226–228, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10877