bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wave propagation in metamaterial multi‐layered structures
Authors: Cory H. , Zach C. 
Published: February 2004

AbstractExpressions are given for the overall reflection and transmission coefficients of a multilayered structure consisting of metamaterial and dielectric slabs. Small‐reflection approximations are discussed. Two applications are proposed: anti‐reflection coatings and high‐reflection coatings. For the first application, a structure consisting of two slabs of the same width and opposite permittivities is studied. If the structure is placed between two semi‐infinite media of the same kind, the reflection vanish, while if these two media are different, the reflection depends only on their characteristics and on the angle of incidence. This device could be advantageously used as an antenna radome. For the second application, a structure consisting of a large number of identical pairs of slabs of high and low opposite permittivities and of the same widths, embedded in the same medium, is studied. This structure's transmittance variation with frequency shows no ripples, and has a large passband and a monotonous quasi‐symmetric rise to the right and to the left of the central frequency. The distinctive feature of these devices is the weakening of the influence of the frequency, the angle of incidence or the polarization on the propagation processes. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 460–465, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20005
Stepped impedance resonator bandpass filters using tapped‐line for controlling spurious response
Authors: Weng Min‐Hung , Chen Wu‐Nan , Huang Tsung‐Hui , Hung Cheng‐Yuan , Wu Hung‐Wei 
Published: February 2004

AbstractA stepped impedance resonator bandpass filter was designed and implemented, combining with the tapped‐line structure. The measured bandpass filters at the center frequency of 2.0 GHz has the characteristics: the insertion lossS21= −2.98 dB, BWR is 15.1%, and the transmission zeros occurred at 2.62 GHz with −48.5 dB. Especially, the wider rejection of −20 dB can be obtained form 2.4 to 8.2 GHz from the proper position of tapped‐line I/O. The designed filter shows the excellent abilities to shift and suppress the spurious response by properly designing the structure of the resonator. The proposed filter was designed and fabricated, and the performances closely matched the simulation results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 481–484, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20010
Finite‐element analysis of phased‐array antennas
Authors: Lou Zheng , Jin Jian‐Ming 
Published: February 2004

AbstractThe finite‐element method (FEM) is applied to the analysis of phased‐array antennas. Curvilinear tetrahedral elements are used for domain discretization and high‐order vector basis functions are used for field expansion. Periodic boundary and radiation conditions are enforced on a single unit cell in the infinite array. A waveguide port condition is also implemented to accurately model the field on the aperture of the coaxial line that provides excitation. The asymptotic waveform evaluation (AWE) technique is combined with the FEM to perform fast‐frequency and angular sweeps. The computed antenna parameters are compared with previously published results and good agreement is obtained. The effects of different feeding schemes on the array parameters are studied and compared. Frequency responses and scan performance of a flared‐notch antenna design are presented. Finally, a preliminary investigation is made on the validity of the infinite‐array approximation to the corresponding finite‐array problems. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 490–496, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20013
Magnetoplasmon dispersion on an n‐GaAs/dielectric interface at 77°K
Authors: Mok V. H. , Davis L. E. 
Published: February 2004

AbstractSurface magnetoplasmons on a single semiconductor–dielectric interface in a transverse static magnetic flux have been modelled. The dispersion diagrams exhibit nonreciprocal behaviour for the forward and reverse propagation as expected, but the effect of the permittivity of the dielectric is shown for the first time. The elliptical polarization of the electric field in both media, near the interface, above and below the EWR frequency, for both directions of propagation is computed. The results have implications for the development of miniature isolators and phase shifters at millimetric and submillimetric wavelengths. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 505–509, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20017
Compact dual‐band circularly polarized antenna for GPS/ETC operation on vehicles
Authors: Su Che‐Wei , Su Chih‐Ming , Wong Kin‐Lu 
Published: February 2004

AbstractA new integration design of two circularly polarized (CP) antennas for global positioning system (GPS) and electronic toll collection system (ETC) is presented. A probe‐fed corner‐truncated square microstrip antenna, which is a resonant‐type structure, is used for GPS operation at 1575 MHz. For achieving broadband CP operation in the 5800 MHz band (5725–5875 MHz) for ETC operation, a monopole‐fed CP loop antenna, which is a traveling‐wave‐type structure, is applied. The two antennas are integrated in a compact configuration in the proposed design and are suitable for GPS and ETC operations on vehicles. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 509–511, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20018
DC–12‐GHz 10‐dB gain shunt‐series shunt‐shunt wideband amplifiers by commercially available 0.35 μM SiGe HBT technology
Authors: Meng C. C. , Wu T. H. , Huang G. W. 
Published: February 2004

AbstractThe realization of wideband amplifiers with shunt‐series shunt‐shunt dual‐feedback configuration with commercially available 0.35‐μm SiGe BiCMOS technology is reported. The SiGe HBT used here has ft of 67 GHz and BVceo of 2.5 V. The experimental results show that power gain is 10 dB from DC to 12 GHz for a shunt‐series shunt‐shunt wideband amplifier, with the help of the emitter capacitive peaking technique. Input‐ and output‐return losses are better than 10 dB for the same frequency range. Noise figure increases from 8 to 12 dB for frequencies from 1 to 18 GHz. OP1dB and OIP3 are 0 dBm and 12 dBm at 1 GHz, respectively. Total current consumption is 11 mA at 3.3 V supply voltage. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 518–520, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20021
An enhanced cavity model for microstrip antennas
Authors: Gan Yeow‐Beng , Chua Chee‐Parng , Li Le‐Wei 
Published: February 2004

AbstractAn enhanced cavity model for analyzing microstrip patch antenna is presented. The predicted resonant frequency and resonant resistance of the antenna are in good agreement with measured data. Theoretical results of the enhanced model are also compared with some commonly used models to determine their range of validity. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 520–523, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20022
Looking for strengths in response to AIDS: individual, group and public authority roles in strategy
Authors: Curtis Donald 
Published: February 2004

AbstractThe HIV/AIDS pandemic is a challenge not only to medical understanding but also to understanding about how society works or can be made to work. New treatment regimes have to be matched with new social organisation. Caring and coping present society‐wide challenges and to the need to reinvent key social institutions in order to respond effectively. Existing studies demonstrate the vulnerability of modern, large‐scale state institutions to loss of knowledge, skill and competence in the face of high attrition rates in their pay role staff. Equally, family and kinship as well as other civil society institutions or ‘traditional’ social structures may be so disrupted by the loss of carers and providers that they cease to generate adequate levels of well‐being and security. The role of key individuals in providing public leadership is recognised but the significance of personal networks in communicating effective messages and mores is more difficult to pin down. Associations and mass movements have emerged that play a vital role in changing social attitudes and behaviour, and social institutions are adapting to the challenge. It appears that diverse social responses are essential, but, I argue, public policy thinking has a ‘centralist’, hierarchical, bias that discourages' sensible thinking about plural, diverse, strategies. This article seeks to develop a way of thinking about strategy, around the idea of institutional competence, to take account of, and be responsive to, diverse social forms and initiatives. Copyright © 2004 John Wiley & Sons, Ltd.
Thermotropic liquid crystalline poly (hydrazone–ether)s containing thiadiazole moiety in the main chain
Authors: Al‐Muaikel Nayef S 
Published: February 2004

AbstractA new homologous series of thermotropic liquid crystalline poly(hydrazone–ether)s based on the 1,3,4‐thiadiazole moiety in the main chain was synthesized by solution polycondensation of various diformyl‐α,ω‐diphenoxyalkanes with 2,5‐bis(mercaptoacetic hydrazide)‐1,3,4‐thiadiazole. The inherent viscosity of the polymers was prepared in the range of 0.39–0.76 dl g−1. The phase behaviour of these polymers was studied by differential scanning calorimetry, optical polarizing microscopy using a heated stage, and thermogravimetric analysis. Almost all the polymers exhibited thermotropic liquid crystalline properties. In most cases, the mesophase extends to 335 °C, where thermal decomposition prevents further observation. Methoxy substituents on the benzene ring of these polymers lower the transition temperature significantly. Copyright © 2004 Society of Chemical Industry
Swelling and elasticity of hydrogels based on poly(ethylene oxide) macroinimer
Authors: Melekaslan Demet , Kasapoglu Fatmanur , Ito Koichi , Yagci Yusuf , Okay Oguz 
Published: February 2004

AbstractA novel method for the preparation of hydrogels based on poly(ethylene oxide) (PEO) is presented. A PEO macroinimer possessing both polymerizable and radical generation sites was used to obtain hydrogels having dangling PEO chains. It was shown that PEO macroinimer acts during photopolymerization, both as a monomer and a crosslinker and thus, leads to the formation of hydrogels of various swelling capacities and moduli of elasticity. Copyright © 2004 Society of Chemical Industry
Synthesis of polyglactin by melt/solid polycondensation of glycolic/L‐lactic acids
Authors: Moon Sung‐Il , Deguchi Kenji , Miyamoto Masatoshi , Kimura Yoshiharu 
Published: February 2004

AbstractPolyglactin was successfully synthesized by the melt/solid polycondensation of a mixture of glycolic acid (GA) and L‐lactic acid (LA) mostly at a GA to LA monomer ratio of 90/10. In the polymerization procedure, a solid polycondensate was first prepared by melt‐polycondensation at 150–190 °C, mechanically crushed into particles of various sizes (150–180, 180–210, 210–250, 250–300 and 300–355 µm), and subjected to solid‐state post‐polycondensation at 170 °C for 10–20 h. The polyglactin finally obtained was a colourless solid. Catalyst screening revealed that the single use of methanesulfonic acid gave the highest molecular weight of the product. Starting from the crushed melt‐polycondensate with a diameter range of 180–250 µm, the highest number‐average molecular weight of attained was 80 000 Da. This process can afford a facile route to large‐scale synthesis of polyglactin with high molecular weight. Copyright © 2004 Society of Chemical Industry
Effects of tetramethylpolycarbonate‐block‐poly(styrene‐co‐acrylonitrile) copolymers containing various amounts of acrylonitrile on the interfacial properties of polycarbonate and poly(styrene‐co‐acrylonitrile) blends
Authors: Kim Y , Kim JH , Kim CK 
Published: February 2004

AbstractTetramethylpolycarbonate‐block‐poly(styrene‐co‐acrylonitrile) (TMPC‐block‐SAN) block copolymers containing various amounts of acrylonitrile (AN) were examined as compatibilizers for blends of polycarbonate (PC) with poly(styrene‐co‐acrylonitrile) (SAN) copolymers. To explore the effects of block copolymers on the compatibility of PC/SAN blends, the average diameter of the dispersed particles in the blend was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fibre retraction technique and an asymmetric double‐cantilever beam fracture test. Reduction in the average diameter of dispersed particles and effective improvement in the interfacial properties was observed by adding TMPC‐block‐SAN copolymers as compatibilizer of PC/SAN blend. TMPC‐block‐SAN copolymer was effective as a compatibilizer when the difference in the AN content of SAN copolymer and that of SAN block in TMPC‐block‐SAN copolymer was less than about 10 wt%. Copyright © 2004 Society of Chemical Industry
Statistical thermodynamics predictions of the solubility parameter
Authors: Utracki LA , Simha R 
Published: February 2004

AbstractThe Simha and Somcynsky (S‐S) lattice‐hole theory has been shown to represent accurately the pressure–volume–temperature (PVT) surface of chain molecular melts and their mixtures. The characteristic scaling parameters, P*, T* and V*, extracted from equation of state (eos) measurements, are known for a large number of polymers. On this basis it is possible to compute the configurational internal energy density and thus the solubility parameter δ as a function of temperature and pressure, δ = δ(T, P). In the first part of this paper it is shown that the theory leads to an energy approximately proportional to the first power of density, that is of the van der Waals type, as found for low molar mass fluids by Hildebrand. We continue with a computation of δ for a series of polymer melts at two levels of temperature, namely T = 25 °C and T = Tg + 300 K. Next, the results are compared with those listed in reference publications, all at ambient pressure. The theoretical values extrapolated from the melt to 25 °C were systematically higher than those listed. However, good correlation is obtained with the high‐temperature calculations for a large variety of polymers. Arguments for this low–high temperature correlation are presented in terms of corresponding levels of molecular mobility and packing in solution and in bulk. Copyright © 2004 Society of Chemical Industry
Oligomer and random copolymer layer in relation to enhancement of interfacial adhesion at polystyrene/poly(styrene‐co‐acrylonitrile) interface
Authors: Kim Hyun‐Joong , Rafailovich Miriam , Sokolov Jonathan 
Published: February 2004

AbstractThis study examines the interfacial adhesion between poly(styrene) (PS) and poly(styrene‐co‐acrylonitrile) (SAN) interfaces reinforced with poly(styrene‐co‐vinyl phenol) (PS‐ran‐PSPh) random copolymers using an asymmetric double‐cantilever beam (ADCB) test. The effects of oligomer and copolymer composition on interfacial adhesion were investigated. The results showed that the interfacial adhesion of the PS/SAN interface was increased significantly after removing the residual oligomer from the SAN. The interfacial adhesion was also measured for five‐purified SAN materials in the range 17–31 wt%. The highest level of PS/SAN adhesion was observed for 17% AN (acrylonitrile) materials. In addition, the interfacial adhesion of a mixture of diblock and random copolymer was measured in order to investigate which is the most effective method. The results showed that mixture systems are more cost‐effective with higher adhesion, which is independent of temperature. Atomic force microscopy showed that a single craze ahead of the crack is a possible failure mode during PS/SAN interface fracture. Copyright © 2004 Society of Chemical Industry
Effect of the thermal history of a rubber composite on the adhesion strength
Authors: Chung Kyung‐Ho , Im Wan‐Bin , Kaang Shinyoung , Yoon Tae‐Ho 
Published: February 2004

AbstractIn this study, the geometry of the tyre cord adhesion test (TCAT) was used to evaluate the adhesion strength between rubber and fibre. The activation energy (ΔE) of rubber compound used in this study was 72.43 kJ mol−1 and the difference of cure state between the inside and outside regions of the TCAT specimen with curing time was elucidated using the value of ΔE. The difference in cure state between the inside and outside regions of the TCAT specimen corresponded to the effect of 5.06 min of curing time. The cure state of the inside region of the TCAT specimen greatly affected the final adhesion strength and the results were confirmed by additional experiments. It was concluded that optimum adhesion between rubber and cord could not be obtained in a TCAT specimen unless the additional curing time to reach the optimum cure state of the inside region of the TCAT specimen was taken into account. Copyright © 2004 Society of Chemical Industry
Synthesis and characterization of block comb‐like copolymers P(A‐MPEO)‐block‐PSt
Authors: Li Yu‐Gang , Shi Peng‐Jie , Zhou Yunshen , Pan Cai‐Yuan 
Published: February 2004

AbstractAmphiphilic block comb‐shaped copolymers, poly[poly(ethylene oxide) methyl ether acrylate]‐block‐polystyrene [P(A‐MPEO)‐block‐PSt] with PSt as a handle, were successfully synthesized via a macromonomer technique. The reaction of MPEO with acryloyl chloride yielded a macromonomer, A‐MPEO. The macroinitiator PSt capped with the dithiobenzoate group (PSt‐SC(S)Ph) was prepared by reversible addition–fragmentation transfer (RAFT) polymerization of styrene in the presence of benzyl dithiobenzoate, and used as macroinitiator in the controlled radical block copolymerization of A‐MPEO at room temperature under 60Co irradiation. After the unreacted macromonomer A‐MPEO had been removed by washing with hot saturated saline water, block comb‐shaped copolymers were obtained. Their structure was characterized by 1H NMR spectroscopy and gel permeation chromatography. The phase transition and self‐assembling behaviour were investigated by atomic force microscope and differential scanning calorimetry. Copyright © 2004 Society of Chemical Industry
Optimal Representative Blocks for the Efficient Tracking of a Moving Object
Authors: Kim SangJoo , Kim WanCheol , Lee JangMyung 
Published: February 2004

AbstractOptimal representative blocks are proposed for an efficient tracking of a moving object and it is verified experimentally by using a mobile robot with a pan‐tilt camera. The key idea comes from the fact that when the image size of a moving object is shrunk in an image frame according to the distance between the camera of mobile robot and the moving object, the tracking performance of a moving object can be improved by shrinking the size of representative blocks according to the object image size. Motion estimation using edge detection (ED) and block‐matching algorithm (BMA) are often used in the case of moving object tracking by vision sensors. However, these methods often miss the real‐time vision data since these schemes suffer from the heavy computational load. To overcome this problem and to improve the tracking performance, the optimal representative block that can reduce a lot of data to be computed is defined and optimized by changing the size of the representative block according to the size of object in the image frame. The proposed algorithm is verified experimentally by using a mobile robot with a two degree‐of‐freedom active camera. © 2004 Wiley Periodicals, Inc.
A New Immune Genetic Algorithm and Its Application in Redundant Manipulator Path Planning
Authors: Luo Xiaoping , Wei Wei 
Published: February 2004

AbstractIn this paper, first the immune system is analyzed in a relatively deeper and all‐sided point of view reflecting the fresh research in biology. Second, based on the previous statements, a new optimization method, the immune genetic algorithm (IGA), is presented by simulating the behavior of the biological immune system and is proved to converge to the global optimum with probability 1. Third, a new method on the multi‐object optimization that is transformed into a single‐object one is proposed based on the joints' best compliance in the redundant robot path planning using IGA. Last, the experiment results show that the method of this article behaves more successfully. © 2004 Wiley Periodicals, Inc.
Ultrasonographic measurement of fetal nasal bone in a low‐risk population at 19–22 gestational weeks
Authors: Gámez F. , Ferreiro P. , Salmeán J. M. 
Published: February 2004

AbstractObjectiveTo determine the potential value of sonographic measurement of fetal nasal bone at 19–22 weeks' gestation in screening for trisomy 21 in a low‐risk population.MethodsThe fetal nasal bone was measured in a mid‐sagittal view in 2035 fetuses at 19–22 weeks' gestation. A reference range was constructed and the measurements in fetuses with trisomy 21 were compared to the normal group.ResultsThe fetal profile was successfully examined in 1913/2035 (94%) fetuses. The mean nasal bone length increased linearly with gestation from 6.2 mm at 19 weeks to 6.8 mm at 22 weeks. Nasal bone hypoplasia, defined by absence of the bone or a measurement below the 2.5th centile, was observed in 34/1899 (1.8%) chromosomally normal fetuses (1.8%), in 5/5 fetuses with trisomy 21 and in 0/9 fetuses with other chromosomal defects.ConclusionAt 19–22 weeks' gestation, nasal bone hypoplasia is observed in a high proportion of trisomy 21 fetuses and in less than 2% of chromosomally normal fetuses. Copyright © 2003 ISUOG. Published by John Wiley & Sons, Ltd.