bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast FET and HEMT solvers for microwave CAD
Authors: Ladbrooke P. H. , Hill A. J. , Bridge J. P. 
Published: July 2007

AbstractMethods are discussed for forecasting, in a few seconds on a personal computer with a 486 processor, equivalent circuits and S‐parameters of a GaAs FET from a physical specification. By inverting the algorithms, similarly fast simulators can be devised to fit equivalent circuits to measured S‐parameters, in the process yielding information on the FET's material and structural dimensions. The practical value of such simulators is illustrated by FETs designed and implemented to have a noise figure and associated gain at 12 GHz comparable with commercial pseudomorphic HEMTs. © 1993 John Wiley & Sons, Inc.
Nonsymmetry of Z‐matrices for planar circuits as obtained by the contour integral method
Authors: Tsai C. M. , Gupta K. C. 
Published: July 2007

AbstractThis article points out the possibility of obtaining nonsymmetrical Z‐matrices when the contour integral method is used for analysis of a general‐shaped, two‐dimensional planar component even when the component is passive and reciprocal. The nonsymmetry is caused by dependence of the normal derivative of the Green's function on the geometry. This nonsymmetry may be reduced by increasing the number of sections on the contour or by selecting a Green's function such that its normal derivative on the contour is zero. © 1993 John Wiley & Sons, Inc.
A moment method formulation for slot‐coupled waveguide Tee‐junction
Authors: Wang Hanyang , Sangster A. J. 
Published: July 2007

AbstractA moment method analysis of an E‐plane waveguide Tee‐junction, in which the coupling element is an arbitrarily inclined slot, has been developed. Two cases are considered: namely, one in which the broad dimension of the coupled waveguide is transverse to the axis of the primary guide, and second, one in which the broad dimension of the coupled guide is axially directed. The computed results are shown to be in good agreement with network analyzer measurements on some typical cases. © 1993 John Wiley & Sons, Inc.
A new efficient CAD technique for inductive reactance coupled waveguide bandpass filters
Authors: Pramanick Protap , Bhartia Prakash 
Published: July 2007

AbstractThis article presents a computer‐aided synthesis technique for E‐plane and iris‐coupled waveguide bandpass filters. This technique uses fewer optimization variables than are required by the existing techniques. The designer begins with an accuratea prioriknowledge of the search direction and uses an efficient penalty function. The closed‐form expressions for waveguide discontinuities, for the initial computation of the K‐inverter values in the optimization procedure, greatly enhances the design speed. The technique has been implemented on a personal computer and has been found to be as accurate as the existing methods implemented on mainframe computers. Results are presented for several Ku and Ka‐band iris‐coupled and E‐plane filters. © 1993 John Wiley & Sons, Inc.
Analysis of waveguide directional filters by the moment method (invited article)
Authors: Seki Hajime 
Published: July 2007

AbstractAnalysis of a waveguide directional filter with N cavities is formulated in terms of the moment method. Electric fields on coupling apertures, being unknown, rigorously coupled integral equations, are established by using dyadic Green's functions. In this analysis, a virtual cavity technique is introduced as well as an approximate method to incorporate finite conductivity of cavity walls. Numerical results are also shown. © 1993 John Wiley & Sons, Inc.
Finite difference modeling of novel waveguiding structures for MMIC applications
Authors: Soghomonian Manook S. , Robertson Ian D. 
Published: July 2007

AbstractFinite difference schemes have been utilized to model the field profiles of several novel waveguiding structures, which support a quasi‐TEM class of propagation. From the electric field values the impedance, equivalent capacitance and attenuation of the structures are calculated. This article describes modification to existing guiding structures such as a conventional coplanar waveguiding structure, by inserting longitudinal and transverse dielectric stratifications, and describes the use of finite difference scheme to obtain their characteristics. © 1993 John Wiley & Sons. Inc.
CAD of two‐port Gap‐coupled rectangular microstrip patches and linear series‐fed arrays
Authors: Benalla Abdelaziz , Gupta K. C. 
Published: July 2007

AbstractA CAD approach based on the multiport network model (MNM) has been developed for the design/analysis of rectangular microstrip patches gap‐coupled to a microstrip feed line. Microstrip patches on thin substrates with and without a dielectric cover layer are considered. Results of the analysis for sample two‐port patches are compared with experimental and moment method results. The agreement validates the proposed model and the analysis procedure. Application of the MNM approach to CAD of linear series‐fed arrays of gap‐coupled rectangular microstrip patches is also discussed, © 1993 John Wiley & Sons, Inc.
Design of microstrip line‐fed patch arrays including mutual coupling
Authors: Yang Hung‐Yu David , Chen C. Harry , Castaneda Jesse A. , Wong William C. 
Published: July 2007

AbstractA computer‐aided design algorithm is developed to facilitate the design of E‐plane series‐fed patch arrays. A rigorous moment method is used to compute the impedance of and the currents on each patch element in the array. Mutual coupling between adjacent patch elements is included in the computation. Experimental validation of the algorithm is reported. The effects of fabrication tolerance, material parameter variations, and mutual coupling on the array performance are highlighted.
Moment method analysis of linearly tapered slot antennas
Authors: Köksal Adnan , Kauffman J. Frank 
Published: July 2007

AbstractAn accurate Method of Moments (MoM) model is developed and implemented for the analysis of the linearly tapered slot antenna (LTSA). The model employs an unequal size reactangular sectioning for conducting parts of the antenna. Piecewise sinusoidal basis functions are used for the expansion of conductor current. The effect of the dielectric is incorporated in the model by using equivalent volume polarization current density and solving the equivalent problem in free space. The feed section of the antenna including the micro‐stripline is handled rigorously in the MoM model by including slotline short‐circuit and microstripline currents among the unknowns. Comparison with measurements is made to demonstrate the validity of the model for both the air case and the dielectric case. Numerical results for the effect of the dielectric permittivity are presented.
Synthesis and performance of an active microstrip antenna
Authors: Fusco Vincent F. , Drew Stephen , McDowall D. Stewart 
Published: July 2007

AbstractThis article discusses the application of a synthesis method for, and the subsequent experimental characterization, of an active microstrip patch antenna. The active antenna incorporates a GaAs MESFET on the patch periphery and the circuit acts as a self‐oscillating radiating element. The MESFET and the antenna are mounted on the same side of the circuit, thereby preserving the conformal nature of the structure. The synthesis approach described is based on the method of harmonic balance and allows optimal FET terminations to be selected for a predefined, added power at a specified frequency of operation. Application of a time domain simulator is illustrated in order to demonstrate start‐up performance and limit cycle formation in the presence and absence of a frequency entrainment signal. The issue of stability of the active element is also addressed using a modified device/load line method. Theoretical and experimental results are presented for the external quality factor, locking power/phase variation, and power and frequency pushing characteristics of the active antenna. Finally, the effect on oscillator behavior of the mutual coupling between the microstrip patch and the active antenna distributed embedding elements is discussed.
Nuclear localization of valosin‐containing protein in normal muscle and muscle affected by inclusion‐body myositis
Authors: Greenberg Steven A. , Watts Giles D. , Kimonis Virginia E. , Amato Anthony A. , Pinkus Jack L. 
Published: July 2007

AbstractInclusion‐body myopathy with Paget's disease and frontotemporal dementia (IBMPFD) is a disease of muscle, bone, and brain that results from mutations in the gene encoding valosin‐containing protein (VCP). The mechanism of disease resulting from VCP mutations is unknown. Previous studies of VCP localization in normal human muscle samples have found a capillary and perinuclear distribution, but not a nuclear localization. Here we demonstrate that VCP is present in both myonuclei and endothelial cell nuclei in normal human muscle tissue. The immunodetection of VCP varies with acetone or paraformaldehyde fixation. Within the nucleus, VCP associates with the nucleolar protein fibrillarin and Werner syndrome protein (Wrnp) in normal and IBMPFD muscle. In patients with inclusion‐body myositis (IBM), normal nuclear localization is present and some rimmed vacuoles are lined with VCP. These findings suggest that impairment in the nuclear function of VCP might contribute to the muscle pathology occurring in IBMPFD. Muscle Nerve, 2007
Mechanisms of fatigue differ after low‐ and high‐force fatiguing contractions in men and women
Authors: Yoon Tejin , Schlinder Delap Bonnie , Griffith Erin E. , Hunter Sandra K. 
Published: July 2007

AbstractThe magnitude of failure in voluntary drive after fatiguing contractions of different intensities in men and women is not known. The purpose of this study was to compare the time to task failure and voluntary activation of men and women for a sustained isometric contraction performed at a low and high intensity with the elbow flexor muscles. Nine men and nine women sustained an isometric contraction at 20% and 80% of maximal voluntary contraction (MVC) force until task failure during separate sessions. The men had a shorter time to failure than women for the 20% but not the 80% MVC task. Voluntary activation was reduced to similar levels for the men and women at the end of the fatiguing contractions but was reduced less after the 80% MVC task than the 20% MVC contraction. Twitch amplitude was reduced similarly at task failure for both sexes and to similar levels at termination of the 20% and 80% MVC tasks. The rate of change in mean arterial pressure was the main predictor of time to failure for the low‐force sustained contraction. These results suggest that women experienced greater muscle perfusion, less peripheral fatigue, and a longer time to task failure than men during the low‐force fatiguing contraction. However, the low‐force task induced greater central fatigue than the high‐force contraction for both men and women. Thus, low‐force, long‐duration fatiguing contractions can be used in rehabilitation to induce significant fatigue within the central nervous system and potentially greater neural adaptations in men and women. Muscle Nerve, 2007
Quality of life in Swedish workers exposed to hand–arm vibration
Authors: Cederlund Ragnhild , Iwarsson Susanne , Lundborg Göran 
Published: July 2007

AbstractThe objective of the present study was to analyse whether differences existed among workers exposed to hand–arm vibration (HAV) with regard to quality of life (QoL) issues. One hundred and eight male workers from a heavy manufacturing plant, with and without HAV symptoms, and workers referred to a hand surgery department with severe HAV symptoms participated in the study. The participants attended a clinical interview, were given a physical examination of the hands and administered the Göteborg Quality of Life instrument and the Evaluation of Daily Activity Questionnaire (EDAQ). Results indicated that workers referred to a hand surgery department with more severe HAV symptoms described a lower quality of life, defined here as lower subjective well‐being, more symptoms of ill‐health and difficulties with activities of daily living (ADL), than workers with no HAV symptoms. Workers from a heavy manufacturing plant with HAV symptoms experienced more difficulties with ADL, especially while working outdoors in cold weather, than workers with no HAV symptoms. Limitations of the present study include the use of a subjective scale to describe HAV symptoms. Further research is recommended on a larger sample of workers at risk for HAV symptoms to develop preventative ergonomic strategies. Copyright © 2007 John Wiley & Sons, Ltd.
Biomimetic modification of chitosan with covalently grafted lactose and blended heparin for improvement of in vitro cellular interaction
Authors: Tan Huaping , Lao Lihong , Wu Jindan , Gong Yihong , Gao Changyou 
Published: July 2007

AbstractLactose‐ and heparin‐modified chitosan films were prepared and their physical and biological properties were compared with chitosan, chitosan‐g‐heparin, and chitosan‐g‐lactose films. Atomic force microscopy (AFM) measurement showed that all these films in the dry state were rather flat with a roughness smaller than 20 nm. While the chitosan‐g‐lactose/heparin and chitosan‐g‐lactose films have the highest swelling and weight loss ratios, the chitosan and chitosan‐g‐heparin films have the lowest. The chitosan‐g‐lactose/heparin film showed stronger ability to induce chondrocyte attachment, proliferation, viability, and glycosaminoglycan (GAG) secretion than that of the chitosan, chitosan‐g‐heparin, and chitosan‐g‐lactose films. Chondrocyte aggregates and nodules were observed on the chitosan‐g‐lactose/heparin and chitosan‐g‐lactose films, which still preserved viable metabolic ability. These results show that the lactose‐modified and heparin‐incorporated chitosan film can enhance the cell–biomaterial interaction synchronously. The resulting chitosan‐g‐lactose/heparin material is more bioactive that might be applicable as promising scaffold for chondrogenesis. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of pH on the drug release rate from a new polymer–drug conjugate system
Authors: Kenawy El‐Refaie , Abdel‐Hay Fouad , El‐Newehy Mohamed , Ottenbrite Raphael M 
Published: July 2007

AbstractThe corresponding N‐hydroximide and N‐methyl‐N‐hydroximide of poly[ethylene‐alt‐(maleic anhydride)] (weight average molecular weight (Mw) of 100–500 g mol−1) were prepared as a new oral drug delivery system. Syntheses of N‐hydroximide and N‐methylhydroxamic acid of poly[ethylene‐alt‐(maleic anhydride)] were carried out by chemical modification of polymer with hydroxylamine and N‐methylhydroxylamine, respectively, to give water‐soluble polymers. These activated polymers were immobilized with ketoprofen in the presence of dicyclohexylcarbodiimide to give the corresponding water‐insoluble ketoprofen conjugates. All products were characterized by elemental analysis as well as Fourier transform infrared and 1H NMR spectra. In vitro release of ketoprofen was studied by measuring UV absorption at λmax = 260 nm as a function of time. This study demonstrated the potential use of N‐hydroximide and N‐methyl‐N‐hydroxamic acid of poly[ethylene‐alt‐(maleic anhydride)] as a drug delivery system. Controlled release was studied at different pH values and at different temperatures. At physiological temperature, the amount of drug released increased with increasing pH. The copolymer‐drug adducts released the drug very slowly at the low pH found in the stomach thus protecting the drug from the action of high acid conditions and resident digestive enzymes. These N‐hydroxamic acid polymer‐drug conjugates were found to be potentially useful in the delivery of macromolecular drugs to targeted sites in the lower gastrointestinal tract and the colon area. Copyright © 2007 Society of Chemical Industry
Synthesis and properties of hyperbranched polyurethanes, hyperbranched polyurethane copolymers with and without ether and ester groups using blocked isocyanate monomers
Authors: Vanjinathan Mahalingam , Shanavas A. , Raghavan A. , Nasar A. Sultan 
Published: July 2007

AbstractStarting from 3,5‐diamino benzoic acid, 2‐hydroxy propyl[3,5‐bis{(benzoxycarbonyl)imino}]benzyl ether, an AB2‐type blocked isocyanate monomer with flexible ether group, and 2‐hydroxy propyl[3,5‐bis{(benzoxycarbonyl)imino}]benzoate, an AB2‐type blocked isocyanate monomer with ester group, were synthesized for the first time. Using the same starting compound, 3,5‐bis{(benzoxycarbonyl)imino}benzylalcohol, an AB2‐type blocked isocyanate monomer, was synthesized through a highly efficient short‐cut route. Step‐growth polymerization of these monomers at individually optimized experimental conditions results in the formation of hyperbranched polyurethanes with and without ether and ester groups. Copolymerizations of these monomers with functionally similar AB monomers were also carried out. The molecular weights of the polymers were determined using GPC and the values (Mw) were found to vary from 1.5 × 104 to 1.2 × 106. While hyperbranched polyurethanes having no ether or ester group were found to be thermally stable up to 217 °C, hyperbranched poly(ether–urethane)s and poly(ester–urethane)s were found to be thermally stable up to 245 and 300 °C, respectively. Glass transition temperature (Tg) of polyurethane was reduced significantly when introducing ether groups into the polymer chain, whereas Tg was not observed even up to 250 °C in the case of poly(ester–urethane). Hyperbranched polyurethanes derived from all the three different AB2 monomers were soluble in highly polar solvents and the copolymers showed improved solubility. Polyethylene glycol monomethyl ether of molecular weight 550 and decanol were used as end‐capping groups, which were seen to affect the thermal, solution, and solubility properties of polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3877–3893, 2007
Electrosyntheses of high‐quality polyphenanthrene in the electrolyte of boron trifluoride diethyl etherate containing trifluoroacetic acid
Authors: Nie Guangming , Han Xuejun , Zhang Shusheng , Wei Qingli 
Published: July 2007

AbstractA novel inherently conducting polymer, high‐quality polyphenanthrene (PPh) films were synthesized electrochemically by direct anodic oxidation of phenanthrene (Ph) in boron trifluoride diethyl etherate (BFEE) containing a certain amount of trifluoroacetic acid (TFA). The oxidation potential of Ph in this medium was measured to be only 0.63 V versus SCE, which was greatly lower than that determined in acetonitrile + 0.1 mol L−1 Bu4NBF4 (1.55 V vs. SCE). The electrolytes of BFEE containing TFA enable facile anodic oxidation of Ph monomer; however, similar oxidation using acetonitrile never produces such a polymeric material. PPh films obtained from this medium showed good redox activity and stability even in concentrated sulfuric acid. Dedoped PPh films were partly soluble in polar solvent such as CH2Cl2, acetone, tetrahydrofuran, and dimethyl sulfoxide. Fluorescent spectral studies indicate that PPh is a good blue‐light emitter. The structure and morphology of the polymer were studied by UV–vis spectroscopy, FTIR spectroscopy, 1H NMR spectroscopy, and scanning electron microscopy, respectively. The results of quantum chemistry calculations of Ph monomer and the spectroscopies of dedoped PPh indicated the polymerization mainly occurred at C(9) and C(10) positions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3929–3940, 2007
Effects of hydrogen in ethylene polymerization and oligomerization with magnesium chloride‐supported bis(imino)pyridyl iron catalysts
Authors: Huang Rubin , Koning Cor E. , Chadwick John C. 
Published: July 2007

AbstractThe effects of hydrogen in ethylene polymerization and oligomerization with different bis(imino)pyridyl iron(II) complexes immobilized on supports of type MgCl2/AlEtn(OEt)3–n have been investigated. Hydrogen has a significant activating effect on polymerization catalysts containing relatively bulky bis(imino)pyridyl ligands, but this is not the case in ethylene oligomerization with a catalyst containing relatively little steric bulk in the ligand. It was found that the presence of hydrogen in the latter system led to decreased activity and an overall increase rather than a decrease in product molecular weight, indicating deactivation of active species producing low molecular weight polymer and oligomer. Decreased formation of vinyl‐terminated oligomers in the presence of hydrogen can therefore contribute to the activating effect of hydrogen in ethylene polymerization with immobilized iron catalysts, if it is assumed that hydrogen activation is related to chain transfer after a 2,1‐insertion of a vinyl‐terminated oligomer into the growing polymer chain. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4054–4061, 2007
Impact Fragmentation of Metal Nanoparticle Agglomerates
Authors: Seipenbusch Martin , Toneva Petya , Peukert Wolfgang , Weber Alfred P. 
Published: July 2007

AbstractDeagglomeration experiments were performed with agglomerates of nanoparticles of Ni and Pt. The fragmentation was induced by high velocity impaction of the agglomerates in a single‐stage low pressure impactor and the fragmentation patterns were evaluated by TEM analysis. Weibull statistics are employed for a quantitative description of the fragmentation behavior. This study shows that for well‐defined interparticle contacts, the impact fragmentation technique combined with the evaluation according to Weibull statistics, allows the recovery of the expected size dependencies. For Pt and Ag, the adhesion force particle size dependency was dominated by van der Waals forces. In contrast, the adhesion force between Ni particles in the size range from 12–28 nm revealed a much stronger increase with particle size. This phenomenon may be attributed to permanent magnetic dipole moments which are also reflected in the chain‐like shape of the agglomerates. For nanoparticle agglomerates with less well‐defined contacts, such as those in industrial environments, the method provides a promising application to reveal the bond strength and cohesiveness of nanoparticle powders.
Improving the Robustness of Particle Size Analysis by Multivariate Statistical Process Control
Authors: Mattila Marko , Saloheimo Kari , Koskinen Kari 
Published: July 2007

AbstractThe robustness of online particle size analysis in wet processes is improved by applying data based modeling methods to the control of the sample preparation and measurement sequence of the particle size analyzer. The aim is to find a more accurate and reliable method of determining the end of the particle size integration period using multivariate statistical process control (MSPC).The studied approach is tested on analyzers installed at two mineral processing plant sites and validated using two validation tests. Research shows that the proposed method works with two very different slurry types. The main advantage of the adapted approach is that there are no adjustable parameters that have to be set by the user.