bluuebunny/crossref_metadata_2025 huggingface dataset:
The asymptotic behaviour of global smooth solutions to the multi‐dimensional hydrodynamic model for semiconductors
Authors: Hsiao Ling , Ju Qiangchang , Wang Shu
Published: September 2003

We establish the global existence of smooth solutions to the Cauchy problem for the multi‐dimensional hydrodynamic model for semiconductors, provided that the initial data are perturbations of a given stationary solutions, and prove that the resulting evolutionary solution converges asymptotically in time to the stationary solution exponentially fast. Copyright © 2003 John Wiley & Sons, Ltd.
Classical predator–prey system with infection of prey population—a mathematical model
Authors: Chattopadhyay J. , Pal S. , Abdllaoui A. El
Published: September 2003

The present paper deals with the problem of a classical predator–prey system with infection of prey population. A classical predator–prey system is split into three groups, namely susceptible prey, infected prey and predator. The relative removal rate of the susceptible prey due to infection is worked out. We observe the dynamical behaviour of this system around each of the equilibria and point out the exchange of stability. It is shown that local asymptotic stability of the system around the positive interior equilibrium ensures its global asymptotic stability. We prove that there is always a Hopf bifurcation for increasing transmission rate. To substantiate the analytical findings, numerical experiments have been carried out for hypothetical set of parameter values. Our analysis shows that there is a threshold level of infection below which all the three species will persist and above which the disease will be epidemic. Copyright © 2003 John Wiley & Sons, Ltd.
Uniform stabilization of a one‐dimensional hybrid thermo‐elastic structure
Authors: Dalsen Marié Grobbelaar‐Van
Published: September 2003

This paper is concerned with the stabilization of a one‐dimensional hybrid thermo‐elastic structure consisting of an extensible thermo‐elastic beam which is hinged at one end with a rigid body attached to its free end. The model takes account of the effect of stretching on bending and rotational inertia. The property of uniform stability of the energy associated with the model is asserted by constructing an appropriate Lyapunov functional for an abstract second order evolution problem. Critical use is made of a multiplier of an operator theoretic nature, which involves the fractional power A−1/2 of the bi‐harmonic operator pair A acting in the abstract evolution problem. An explicit decay rate of the energy is obtained. Copyright © 2003 John Wiley & Sons, Ltd.
Sound propagation in a channel with a discontinuity in the form of a semicircle
Authors: Weise Volkmar
Published: September 2003

For the description of wave propagation in ducts with variable cross‐sections it is necessary to determine reflection and transmission at the points of discontinuity in the cross‐sectional contour. Analytic solutions are well known for rectangular and circular duct cross‐sections with rotational symmetric arrangements. The aim of this paper is the description of sound propagation in cylindrical ducts with semicircular discontinuities and thus non‐rotationally symmetric discontinuities of the cross‐sectional contour. In particular, excitation with higher azimuthal and radial modes also will be included. This solution is achieved by using the orthogonality properties of the trigonometric and Bessel functions. Copyright © 2003 John Wiley & Sons, Ltd.
Homogenization of Maxwell's equations in dissipative bianisotropic media
Authors: Barbatis G. , Stratis I. G.
Published: September 2003

We study the periodic homogenization of Maxwell's equations for dissipative bianisotropic media in the time domain, both in R3 and in a bounded domain with the perfect conductor boundary condition. We consider both local with respect to time (optical response region) and non‐local in time (allowing dispersive effects) constitutive laws; in the non‐local case the explicit description of the homogenized coefficients is given in terms of the Laplace transform. The principal result of this work is the description of the asymptotic behaviour of the solutions of the considered problems as the period of the electromagnetic parameters tends to zero. Copyright © 2003 John Wiley & Sons, Ltd.
Design and characterization of low‐loss and low‐dispersion micromachined elevated CPW
Authors: Lee Sang‐No , Kim Yong‐Jun , Yook Jong‐Gwan
Published: September 2003

In this paper, the performance of a 10‐μm‐elevated low‐loss and low‐dispersion elevated coplanar waveguide (ECPW) is presented. It is shown that a wide range of characteristic impedances, encompassing the 40–100Ω range, is obtainable. A very low effective dielectric constant (close to 1) is predicted based on the 3D finite‐difference time‐domain (FDTD) method and confirmed by measurement. The overlapped configuration on standard silicon reveals the best performance, with a loss of about 0.2 dB/mm, which is much lower than that of a conventional CPW at 40 GHz. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 169–171, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11159
On the angular resolving powers of cross‐loop/monopole antenna arrays based on the music algorithm
Authors: Shi Xin‐Zhi , Wen Bi‐Yang , Wang Gaofeng , Wang Bing‐Zhong
Published: September 2003

To increase HF‐GWR portability, it is very desirable to use smaller antennas yet achieve higher angular resolving power. Based on the MUSIC algorithm, the angular resolving powers of various combined cross‐loop/monopole and monopole antenna arrays are studied with variations of target angles, signal‐to‐noise ratio, and sampling density. It is found that a combination of two cross‐loop/monopole antennas plus one monopole antenna gives the best performance. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 171–175, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11160
A broadband microstrip antenna: SGMFP antenna
Authors: Gao S. , Sambell A. , Korolkiewicz T. , Smith D.
Published: September 2003

A novel structure of broadband microstrip antennas, termed the SGMFP antenna, is proposed. It is consisted of a slot in the ground plane, a microstrip feedline supported on a substrate, a foam layer, and a patch. It can achieve broad bandwidth and high polarisation purity. By using a single patch, two design examples are provided, which achieves a bandwidth (S11 < −10 dB) of 23.7% and 20.3%, respectively. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 175–178, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11161
Broadband matching of stacked patch antennas using a single line‐transformer technique
Authors: Zentner Radovan , Bartolic Juraj , Zentner Ervin
Published: September 2003

This paper presents a synthesis of simple broadband matching networks consisting of a single line transformer. The procedure uses explicit, measured, or calculated input impedance values and finds characteristic impedance and length of line which match the load to the desired SWR. This kind of matching is especially useful for broadband stacked‐patch configurations, because here microstrip technology provides for arbitrary characteristic impedances of the transformer. The effectiveness of the procedure is demonstrated by examples of two different stacked patch configurations. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 178–183, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11162
Analysis of signal propagation on high‐speed planar interconnect systems based on full‐wave and macromodeling techniques
Authors: Liu En‐Xiao , Li Er‐Ping , Li Le‐Wei
Published: September 2003

An accurate and systematic approach for the analysis of signal propagation at high‐speed planar interconnect systems is proposed in this paper. The approach integrates a macromodeling technique based on the full‐wave time domain method and rational function approximation together with the SPICE circuit simulation. The admittance Y transfer function in the form of a set of discrete frequency sampling data is established by using the full‐wave finite‐difference time‐domain (FDTD) method, which characterizes the high‐speed planar interconnect subnetwork. Thereafter, the macromodel of the interconnect subnetwork is constructed through rational function approximation by using the Vector fitting method, which results in an accurate and robust solution for the overall problem. Subsequently, the resultant macromodel can be synthesised and converted to a SPICE‐compatible equivalent circuit. Therefore, the signal propagation analysis is finally facilitated and expedited by using the SPICE circuit simulator. Numerical experiments are presented in this paper to verify the accuracy and efficiency of the proposed method. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 183–187, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11163
Compact single‐level and multilevel folded‐line RF power dividers
Authors: Lim C. , Settaluri R. K. , Tripathi V. K. , Weisshaar A.
Published: September 2003

A new design methodology for compact single‐level and multilevel folded‐line radio frequency (RF) power dividers is presented. Simple design equations are developed for compact 3‐dB Wilkinson power dividers with single and cascaded folded‐line C‐sections. The new topologies show a reduction in footprint area to less than 40% of the conventional topology for single‐level compact designs and to less than 17% of the conventional topology for a multilevel compact design. The new compact designs are validated by full‐wave electromagnetic simulation as well as measurements. Excellent agreement is reported. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 187–189, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11164
Design improvements in distributed amplifiers for optical receiver front ends
Authors: Giannini F. , Limiti E. , Orengo G. , Serino A. , De Dominicis M.
Published: September 2003

This paper reports circuit design improvements with respect to classical distributed transimpedance amplifiers for optical receiver front ends to obtain the highest gain and bandwidth performances using a low‐cost MMIC technology. The design issues have been applied to the design of a front‐end amplifier for optical links up to 10 Gb/s, and an effective transimpedance gain of 48 dBΩ and a bandwidth from dc to 9 GHz are achieved. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 190–193, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11165
Examination of boundary conditions performance for estimating accuracy of MoM solutions on square plate benchmark geometry using triangle doublet basis functions
Authors: Bogdanov F. G. , Jobava R. G.
Published: September 2003

The boundary conditions performance (BCP) is shown to be an appropriate error criterion to estimate accuracy of method of moments (MoM) solutions on arbitrary structures, including open surfaces. A proper BCP error metric for electric field integral equations (EFIE) formulation is defined and applied for estimating accuracy on square plate benchmark geometry for triangle doublet basis functions. Comparison of BCP error with current and charge density distribution errors on the benchmark geometry is carried out based on the known benchmark solutions for the surface currents. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 193–196, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11166
Single‐voltage‐supply operation of Ga0.51In0.49P/AlGaAS/IN0.15Ga0.85As PHEMTS with high‐power density
Authors: Tu Hsing‐Yuan , Pan Hsuan‐Yu , Lu Shey‐Shi
Published: September 2003

A Ga0.51In0.49P/AlGaAs/In0.15Ga0.85As PHEMT with the highest power density among all single‐voltage‐supply operated devices, to our knowledge, was demonstrated for the first time. Operating at 1.8‐GHz under class‐A bias conditions, this FET shows 18.84‐dBm (382.8 mW/mm) saturated power and 17.25‐dBm (265.4 mW/mm) P1dB when the drain voltage is 3.6 V. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 196–199, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11167
Experimental demonstration of a direction‐of‐arrival estimation algorithm for millimeter‐wave switched‐beam array antennas
Authors: Sanchis P. , Polo V. , Herrera J. , Corral J. L. , Choi Moon‐Soon , Marti J.
Published: September 2003

In this paper, the experimental demonstration of a direction‐of‐arrival (DOA) estimation algorithm, based on power measurements and suitable for switched‐beam array antennas operating in the millimeter‐wave band, is reported. Simulation and experimental results for the proposed algorithm using a four‐element array antenna operating at 60 GHz have been obtained, showing excellent agreement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 199–201, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11168
60‐GHz radio‐on‐fiber distribution of 2 × 622 Mb/s WDM channels using remote photonic‐frequency upconversion
Authors: Seo Young‐Kwang , Seo Jun‐Hyuk , Choi Woo‐Young
Published: September 2003

A new distribution scheme of WDM channels in a 60‐GHz radio‐on‐fiber system is demonstrated by using the remote photonic‐frequency upconversion technique. The frequency upconversion of WDM data with 60‐GHz optical local‐oscillator signals is performed remotely at base stations with cross‐gain modulation in a semiconductor optical amplifier (SOA) and using square‐law photo detection of a photo‐diode (PD). © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 201–203, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11169
Dynamic behavior of MEM‐mirrors for tunable vertical cavity surface‐emitting lasers
Authors: Guan Yan , Matin M. A.
Published: September 2003

Tunable vertical cavity surface‐emitting lasers (VCSELs) are potentially useful for future optical networks. To date, the most successful mechanics to realize wavelength tunability in tunable VCSELs resides in MEM‐VCSELs via microelectromechanical (MEM) technology. The key parts to accomplish wavelength tuning in these MEM‐VCSELs are controllably movable top mirrors. We present dynamic problems in developing and characterizing these micromirrors. Simulation results of four different mirror shapes with different dimensions are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 203–207, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11170
Synthesis of impedance‐matching networks for RF‐power amplifier applications
Authors: Kim Nam‐Tae
Published: September 2003

The design of an RF‐power amplifier using the distributed network synthesis in order to achieve the required performance over an operating frequency range is presented. The transfer function of distributed matching circuits, which are useful for the design of RF‐power amplifiers, is derived using an equal ripple approximation. Element values of the network used to match device models are calculated in terms of minimum insertion losses and ripples for a specified network topology. To verify the performance of synthesized circuits, the results are applied to the design of an RF transistor power amplifier with an appropriate device‐modeling technique. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 207–211, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11171
A new dual‐band planar inverted‐F antenna for ISM‐band applications
Authors: Kim Sun K. , Park Jong K. , Choi Soek H. , Park Jae Y.
Published: September 2003

This paper proposes a new dual‐band planar inverted‐F antenna (PIFA) for ISM‐band applications. The proposed antenna is designed using the Microwave Studio Software of Computer Simulation Technology (CST). The measured results of the antenna are compared with the simulated results. The effects of antenna parameters such as the slit geometry and ground plane are studied. Both lower and upper frequency bands can be determined independently, which is very useful for the design of dual‐band antennas. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 211–214, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11172
A laminated ceramic bandpass filter realized using coupled stepped‐impedance resonators
Authors: Wang Xuedong , You Bin , Ji Wusheng , Li Ying
Published: September 2003

A tapped bandpass filter composed of two coupled stepped‐impedance resonators (SIRs) is proposed. The two resonators are arranged in different plane. The volume of proposed filter is about 60% of that of conventional filter. We investigate the filtering characteristics using both network analysis and experimentation. It is shown that this filter has a very sharp response below its passband. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 214–216, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11173
Rigorous modeling of arbitrary conformal microstrip filters and spiral inductors using the FDTD method
Authors: El Brak Mohamed , Essaaidi Mohamed
Published: September 2003

In this paper, a direct 3D finite‐difference time‐domain (FDTD) approach is implemented to investigate the electromagnetic behavior of arbitrary conformal microstrip filters and spiral inductors. To this end, the frequency dependence of the scattering‐matrix parameters of these microstrip circuit configurations has been studied in depth. The proposed model approaches the curved regions of the studied structures using a staircase discretization scheme. The obtained numerical results have been validated by comparisons with measured results in the literature, which considered extreme cases where the considered structures are planar. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 216–221, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11174
A novel time‐domain technique using wavelet‐like basis functions
Authors: Hutchcraft W. Elliott , Gordon Richard K.
Published: September 2003

A novel technique for the solution of electromagnetics problems in the time domain is proposed. In this technique, wavelet‐like functions are used as the basis set for the field components. The time‐domain algorithm is derived and examples using the technique are presented. Comparisons with analytic results and numerical results obtained using the finite‐difference time‐domain (FDTD) technique will be provided. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 221–226, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11175
Meta‐material surface design using the hierarchical genetic algorithm
Authors: Yuan Yuan , Chan Chi Hou , Man Kim Fung , Luk Kwai Man
Published: September 2003

In this paper, we design a meta‐material surface emulating a perfect magnetic conducting plane (PMC) using the hierarchical genetic algorithm (HGA). This is achieved by manipulating the unit‐cell geometry of frequency‐selective surface screens and the electrical properties of the supporting dielectric medium in the optimization process. The properties of the structure are evaluated using a method of moments (MoM)‐based electromagnetic solver. By virtue of the HGA, prior information of the number of FSS screens and dielectric layers is not required. The designed PMC is employed as a dipole‐antenna reflector for gain enhancement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 226–230, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11176
Influence of furniture on 60‐GHz radio propagation in a residential environment
Authors: Collonge S. , Zaharia G. , El Zein G.
Published: September 2003

At millimeter‐waves, home furniture's and objects' dimensions can be equal or superior to the wavelength. A comparison between propagation measurements conducted within a residential house for two configurations, furnished and empty, underscores the influence of the furniture on millimeter‐wave propagation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 230–233, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11177
Analysis of coplanar LiNbO3 waveguide structures applicable to electrooptic modulator with FDTD method
Authors: Lee Byungje , Byun Joonho , Kim Bok‐Ki
Published: September 2003

The 3D finite‐difference time‐domain (FDTD) method and the 2D quasi‐static formulation have been used to calculate the characteristic impedance and the microwave effective index of coplanar waveguide structures on lithium niobate (LiNbO3) single‐crystal substrates with a yttria‐stabilized zirconia (YSZ) or SiO2 buffer layer. The results shown can be a good source to predict the modulator characteristics. The effects of the thin buffer layer and anisotropy of the LiNbO3 crystal (x‐cut and z‐cut) are discussed. The comparison between the FDTD and quasi‐static results shows good agreement. In this paper, the efficient modeling technique of the FDTD method for the coplanar waveguide (CPW) structures based on an anisotropic substrate with a thin buffer layer is developed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 234–237, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11178
Compact multi‐layer diplexer for dual mode portable telephones
Authors: Lee Byoung Hwa
Published: September 2003

A new compact and effective lumped‐element diplexer structure targeted for low‐temperature co‐fired ceramic (LTCC) implementation that can exhibit high levels of isolation between low‐pass and high‐pass filters is proposed. Design equation formulations that take into account the isolation between the two filters are presented. As an example, a multilayer ceramic (MLC) chip diplexer in a dual‐mode portable telephone for 900‐MHz digital‐cellular and 1.9‐GHz personal communication systems is designed and fabricated. The simulated results are compared with the measured data and good agreement is reported. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 237–239, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11179
Fabry–Perot microcavity pressure sensor with a novel single deeply corrugated diaphragm
Authors: Wang W. J. , Lin R. M. , Ren Y. , Sun T. T. , Guo D. G.
Published: September 2003

A new Fabry–Perot (FP) microcavity structure with a novel single deeply corrugated diaphragm (SDCD) is presented for use in pressure sensing. Both analytical expression and finite‐element model (FEM) are used to evaluate the device's performance. The FP microcavity is fabricated on a single chip using both surface and bulk micromachining techniques. The results show that the signal averaging effect can substantially be reduced for the FP microcavity pressure sensor by the flatness‐enhancing diaphragm structure. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 240–243, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11180
Two‐dimensional photonic‐crystal microwave waveguide
Authors: Coves A. , San Blas A. A. , Gimeno B. , Díez A. , Andrés M. V. , Boria V. E.
Published: September 2003

This paper reports on the use of 2D photonic crystals to design microwave waveguides. The waveguide consists of a periodic arrangement of holes, with a square or rectangular cross section, that extends along the waveguide with a central defect defined by the absence of a hole. The theoretical analysis of such a structure is based on a biorthogonal‐basis method and provides a full‐vector description of the modes guided by the defect. Our results show that such a waveguide can be designed to support only one mode at any operating frequency. This mode is a polarization doublet whose dispersion is controlled by the geometrical parameters, thus permitting the design of a novel polarization‐maintaining waveguide. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 243–246, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11181
5‐GHz compact two‐element metal‐plate antenna for WLAN operation
Authors: Su Chih‐Ming , Chen Wen‐Shyang , Wong Kin‐Lu
Published: September 2003

A novel two‐element metal‐plate antenna arranged in a compact geometry and easily constructed from a single metal plate is presented. The antenna shows a high antenna‐gain level (> 4.0 dBi) and is suitable for WLAN operation in the 5.2/5.8‐GHz bands (5150–5350 MHz/5725–5875 MHz). The antenna‐gain level obtained can even be larger than 5.0 dBi for practical applications where the antenna is required to be placed in close proximity to a large metal plate, such as the metal plate or metal frame used to support the display of a laptop. Details of the proposed antenna design and obtained experimental results are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 246–249, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11182
Modelling of two new kinds of optical filters for use in WDM networks
Authors: de Moraes Sam Lara , Alves Cordeiro Albino Adriano , Carvalho Lustosa da Costa João Paulo , Rocco Giraldi Maria Thereza Miranda
Published: September 2003

In the present work, we model and analyze two new kind of optical filters. We also compare their responses. Both of them are based on fiber Bragg gratings (FBGs). The first filter analyzed and modeled is a comb filter based on an acousto‐optic modulator in a sinc‐sampled fiber Bragg grating. The second one is based on the operation of an FBG and two all‐fiber Fabry–Perot filters, which are connected by an optical circulator. These filters showed to be very attractive for use in wavelength division multiplexing (WDM) networks. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 249–253, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11183
Complex resonance of the circular‐arc dipole antenna
Authors: Leung K. W.
Published: September 2003

The complex resonance of the circular‐arc dipole antenna is studied theoretically. The Green's function technique is employed to formulate an integral equation for the dipole current, and the method of moments (MoM) is used to convert the equation into a matrix equation. An equation for the complex frequency is then obtained by enforcing the determinant of the impedance matrix to zero. From the complex frequency, the resonant frequency and Q factor of the circular‐arc dipole antenna are found. The effects of the arc radius, dipole length, and dipole radius on the complex frequency are investigated and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 253–256, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11184
Brain plasticity, learning, and developmental disabilities
Authors: Casey B.J.
Published: September 2003

This is a time of significant gains in methodological development for examining the developing human brain. New efforts are underway to unify the understanding of the development of brain anatomy with physiological, cellular and molecular processes that influence behavioral development. This special issue provides animal models of behavior and brain development, applications of noninvasive imaging and genetic methods to human brain development and behavior, and select reviews of how these models and methods have been applied to the examination of developmental disabilities. This issue reflects a sampling of current approaches to the study of brain plasticity, development and learning in typically and atypically developing humans and animals. MRDD Research Reviews 2003;9:133–134. © 2003 Wiley‐Liss, Inc.
Vocal learning in birds and humans
Authors: Wilbrecht Linda , Nottebohm Fernando
Published: September 2003

Vocal learning is the modification of vocal output by reference to auditory information. It allows for the imitation and improvisation of sounds that otherwise would not occur. The emergence of this skill may have been a primary step in the evolution of human language, but vocal learning is not unique to humans. It also occurs in songbirds, where its biology can be studied with greater ease. What follows is a review of some of the salient anatomical, developmental, and behavioral features of vocal learning, alongside parallels and differences between vocal learning in songbirds and humans. MRDD Research Reviews 2003;9:135–148. © 2003 Wiley‐Liss, Inc.
Early life influences on life‐long patterns of behavior and health
Authors: McEwen Bruce S.
Published: September 2003

The stability of a child's early life has profound effects on physical and mental health, and unstable parent‐child relationships, as well as abuse, can lead to behavioral disorders and increased mortality and morbidity from a wide variety of common diseases later in life. One common consequence, namely, depressive illness, is associated with chemical imbalances in the brain and hormonal dysregulation, constituting a form of allostatic load that alters interpretations of stimuli and influences, behavioral, and hormonal responses to potentially stressful situations. The brain not only encodes information and controls the behavioral responses but it is also changed structurally by those experiences. Structural changes in the hippocampus and amygdala, which are important brain structures for cognition and emotion, are representative of what may be occurring throughout the brain as a result of allostatic load resulting from the chronic stress of a disorder such as depression. Such structural changes include dendritic debranching and hypertrophy, cell proliferation, and synaptic remodeling; they are produced by the combined overactivity of stress hormones and endogenous neurotransmitters. These mediators are normally involved in adaptation, but can also promote damage when they are dysregulated and over‐active. They are very likely to be strongly biased by early life experiences. The findings from animal models thus provide a basis for understanding potential mechanisms of environmental and developmental determinants of individual differences in human stress reactivity, as well as anxiety, depression, and a host of related systemic disorders. There is an increasing amount of translational research that is beginning to tie the basic research to clinical outcomes of individuals exposed to abusive or inconsistent care‐giving in early life. A major goal of studies on this important topic is to define times in development and strategies for intervening to prevent or reverse the effects of adverse early life experiences. Although prevention is clearly the preferable route, some degree of reversal of psychopathology and pathophysiology caused by early life adversity appears to be an achievable goal. MRDD Research Reviews 2003;9:149–154. © 2003 Wiley‐Liss, Inc.
MRI‐based morphometric analysis of typical and atypical brain development
Authors: Kennedy David N. , Haselgrove Christian , McInerney Sean
Published: September 2003

The neuroinformatics landscape in which human brain morphometry occurs has advanced dramatically over the past few years. Rapid advancement in image acquisition methods, image analysis tools and interpretation of morphometric results make the study of in vivo anatomic analysis both challenging and rewarding. This has revolutionized our expectations for current and future diagnostic and investigative work with the developing brain. This paper will briefly cover the methods of morphometric analysis that available for neuroanatomic analysis, and tour some sample results from a prototype retrospective database of neuroanatomic volumetric information. From these observations, issues regarding the anatomic variability of developmental maturation of neuroanatomic structures in both typically and atypically developing populations can be discussed. MRDD Research Reviews 2003;9:155–160. © 2003 Wiley‐Liss, Inc.
Imaging the developing brain with fMRI
Authors: Davidson M.C. , Thomas K.M. , Casey B.J.
Published: September 2003

Advancements in magnetic imaging techniques have revolutionized our ability to study the developing human brain in vivo. The ability to noninvasively image both anatomy and function in healthy volunteers, including young children, has already enhanced our understanding of brain and behavior relations. The application of these techniques to developmental research offers the opportunity to further explore these relationships and allows us to ask questions about where, when and how cognitive abilities develop in relation to changes in underlying brain systems. It is also possible to explore the contributions of maturation versus learning in the development of these abilities through cross‐sectional and longitudinal research involving training and intervention procedures. Current imaging methodologies, in conjunction with new and rapidly evolving techniques, hold the promise of even greater insights into developmental issues in the near future. These methodologies and their application to development and learning are discussed in the current paper. MRDD Research Reviews 2003;9:161–167. © 2003 Wiley‐Liss, Inc.
Fiber tracking using magnetic resonance diffusion tensor imaging and its applications to human brain development
Authors: Watts Richard , Liston Conor , Niogi Sumit , Uluğ Aziz M.
Published: September 2003

Diffusion tensor imaging is unique in its ability to noninvasively visualize white matter fiber tracts in the human brain in vivo. Diffusion is the incoherent motion of water molecules on a microscopic scale. This motion is itself dependent on the micro‐structural environment that restricts the movement of the water molecules. In white matter fibers there is a pronounced directional dependence on diffusion. With white matter fiber tracking or tractography, projections among brain regions can be detected in the three‐dimensional diffusion tensor dataset according to the directionality of the fibers. Examples of developmental changes in diffusion, tracking of major fiber tracts, and examples of how diffusion tensor tractography and functional magnetic resonance imaging can be combined are provided. These techniques are complimentary and allow both the identification of the eloquent areas of the brain involved in specific functional tasks, and the connections between them. The noninvasive nature of magnetic resonance imaging will allow these techniques to be used in both longitudinal developmental and diagnostic studies. An overview of the technique and preliminary applications are presented, along with its current limitations. MRDD Research Reviews 2003;9:168–177. © 2003 Wiley‐Liss, Inc.
Synaptogenesis and heritable aspects of executive attention
Authors: Fossella John A. , Sommer Tobias , Fan Jin , Pfaff Don , Posner Michael I.
Published: September 2003

In humans, changes in brain structure and function can be measured non‐invasively during postnatal development. In animals, advanced optical imaging measures can track the formation of synapses during learning and behavior. With the recent progress in these technologies, it is appropriate to begin to assess how the physiological processes of synapse, circuit, and neural network formation relate to the process of cognitive development. Of particular interest is the development of executive function, which develops more gradually in humans. One approach that has shown promise is molecular genetics. The completion of the human genome project and the human genome diversity project make it straightforward to ask whether variation in a particular gene correlates with variation in behavior, brain structure, brain activity, or all of the above. Strategies that unify the wealth of biochemical knowledge pertaining to synapse formation with the functional measures of brain structure and activity may lead to new insights in developmental cognitive psychology. MRDD Research Reviews 2003;9:178–183. © 2003 Wiley‐Liss, Inc.
A review of the biological bases of ADHD: What have we learned from imaging studies?
Authors: Durston Sarah
Published: September 2003

Attention Deficit Hyperactivity Disorder (ADHD) is a common and impairing neuropsychiatric disorder with onset at preschool age. Although a significant amount of progress has been made investigating the neurobiology of this disorder, its precise etiology still remains unclear. Converging evidence from studies of the neuropharmacology, genetics, neuropsychology, and neuroimaging of ADHD imply the involvement of fronto‐striatal circuitry in ADHD. However, while it does appear that poor inhibitory control and the deficits in fronto‐striatal circuitry associated with it are central, there is evidence to suggest that more posterior cerebral areas are also implicated in this disorder. Anatomical studies suggest widespread reductions in volume throughout the cerebrum and cerebellum, while functional imaging studies suggest that affected individuals activate more diffuse areas than controls during the performance of cognitive tasks. The future impact of new MR imaging methodologies on the field is discussed. MRDD Research Reviews 2003;9:184–195. © 2003 Wiley‐Liss, Inc.
The development of reading impairment: A cognitive neuroscience model
Authors: McCandliss Bruce D. , Noble Kimberly G.
Published: September 2003

This review discusses recent cognitive neuroscience investigations into the biological bases of developmental dyslexia, a common disorder impacting approximately 5 to 17 percent of the population [Stanovich, 1986, Matthew effects in reading: Some consequences of individual differences in the acquisition of literacy. Reading Research Quarterly 21: 360–407]. Our aim is to summarize central findings from several lines of evidence that converge on pivotal aspects of the brain bases of developmental dyslexia. We highlight ways in which the approaches and methodologies of developmental cognitive neuroscience that are addressed in this special issue—including neuroimaging, human genetics, refinement of cognitive and biological phenotypes, neural plasticity and computational models—can be employed in uncovering the biological bases of this disorder. Taking a developmental perspective on the biological bases of dyslexia, we propose a simple cascading model for the developmental progression of this disorder, in which individual differences in brain areas associated with phonological processing influence the specialization of visual areas involved in the rapid processing of written words. We also discuss recent efforts to understand the impact of successful reading interventions in terms of changes within cortical circuits associated with reading ability. MRDD Research Reviews 2003;9:196–205. © 2003 Wiley‐Liss, Inc.
A systems neuroscience approach to autism: Biological, cognitive, and clinical perspectives
Authors: Eigsti Inge‐Marie , Shapiro Theodore
Published: September 2003

Autism is a behaviorally defined disorder characterized by a broad constellation of symptoms. Numerous studies directed to the biological substrate demonstrate clear effects of neurodevelopmental differences that will likely point to the etiology, course, and long‐term outcomes of the disorder. Consistently replicated research on the neural underpinnings of autism is reviewed. In general, results suggest several main conclusions: First, autism is a heterogeneous disorder and is likely to have multiple possible etiologies; second, structural brain studies have indicated a variety of diffuse anatomical differences, reflective of an early developmental change in the growth or pruning of neural tissue, rather than localized lesions; similarly, neurochemical studies suggest early, neuromodulatory discrepancies rather than gross or localized abnormalities; and finally, there are a number of limitations on studies of brain activity that to date preclude definitive answers to questions of how the brain functions differently in autism. The large number of active research programs investigating the cognitive neuroscience of autism spectrum disorders, in combination with the exciting development of new methodologies and tools in this area, indicates the drama and excitement of work in this area. MRDD Research Reviews 2003;9:206–216. © 2003 Wiley‐Liss, Inc.
Response of saturated porous media to cyclic thermal loading
Authors: Blond E. , Schmitt N. , Hild F.
Published: September 2003

The response of a semi‐infinite saturated porous medium subjected to a harmonic thermal loading on its free face is studied herein. The pressure diffusion equation that governs the fluctuation of the interstitial pressure is established. It allows us to obtain prevalent parameters, i.e. the thermal and fluid mass diffusivities and the coefficient of relative bulk variation. Closed‐form solutions of the maximum fluid pressure Pmax and its location xcr are derived. It is shown that the location xcr of Pmax is localized and depends on the diffusivity ratio and the frequency of the thermal loading while the magnitude of Pmax depends on the diffusivity ratio and the thermal amplitude. Master curves for xcr and Pmax versus diffusivity ratio are built. It follows that three regimes can be distinguished: namely, thin spalling, thick spalling or in‐depth cracking and no cracking. Copyright © 2003 John Wiley & Sons, Ltd.
A local identification technique for geotechnical and geophysical systems
Authors: Zeghal Mourad , Oskay Caglar
Published: September 2003

Geotechnical structures and natural soil deposits are massive multi‐phase particulate systems characterized by the development of localized response mechanisms under extreme loading conditions. Identification and analysis of such systems based on inverse boundary value problem formulations and sparse measurements are generally indeterminate. This paper presents an alternative local inverse problem technique. Point‐wise identification analyses of the constitutive behaviour of water‐saturated geotechnical and geophysical systems are performed using acceleration and pore pressure records provided by a cluster of closely spaced sensors. The developed novel technique does not require the availability of boundary condition measurements, or solution of an associated boundary value problem. The constitutive behaviour at a specific location of a soil‐system is analysed independently of adjacent response mechanisms or material properties. Numerical simulations and centrifuge tests of a soil‐retaining wall system are used to demonstrate the capabilities of the developed technique. Copyright © 2003 John Wiley & Sons, Ltd.
On the boundary conditions in slope stability analysis
Authors: Chugh Ashok K.
Published: September 2003

Boundary conditions can affect computed factor of safety results in two‐ and three‐dimensional stability analyses of slopes. Commonly used boundary conditions in two‐ and three‐dimensional slope stability analyses via limit‐equilibrium and continuum‐mechanics based solution procedures are described. A sample problem is included to illustrate the importance of boundary conditions in slope stability analyses. The sample problem is solved using two‐ and three‐dimensional numerical models commonly used in engineering practice. Copyright © 2003 John Wiley & Sons, Ltd.
A multi‐level parallelized substructuring‐frontal solution for coupled thermo/hydro/mechanical problems in unsaturated soil
Authors: Thomas H.R. , Yang H.T. , He Y. , Cleall P.J.
Published: September 2003

This paper proposes a multi‐level parallelized substructuring–frontal combined algorithm for the analysis of the problem of thermo/hydraulic/mechanical behaviour of unsaturated soil. Temperature, displacement, pore water pressure and pore air pressure are treated as the primary variables in a non‐linear analysis. Details are given firstly of the substructuring–frontal combined approach. The incorporation of the algorithm in a multi‐level parallel strategy is then discussed. The parallel processing can thus be carried out at different substructural levels. The method thus developed impacts, in a positive way, on both computer storage requirement and execution time. Copyright © 2003 John Wiley & Sons, Ltd.
Dynamic response of a soft soil layer to flow and periodical disturbance
Authors: Hsieh Ping‐Cheng
Published: September 2003

The dynamic response of a soft soil layer of finite thickness under the mutual effects of flow and periodical disturbance at the free surface is discussed in this work. The homogeneous water is governed by potential theory and the soil layer obeys Biot's theory of poroelasticity. The boundary‐value problem is solved by an analytical algorithm, in which the wave number is found first. Secondly, the closed form solutions are found by a two‐parameter perturbation method with the boundary‐layer correction. The results are also compared with those of the poroelastic soil layer of infinite thickness to show the impermeable rigid boundary effect. Copyright © 2003 John Wiley & Sons, Ltd.
Urinary incontinence across the lifespan
Authors: Miller Yvette D. , Brown Wendy J. , Russell Anne , Chiarelli Pauline
Published: September 2003

Aims

The objectives of the current study were (1) to measure type and severity of urinary leakage and (2) to investigate the association between these factors and age‐related life events and conditions in three groups of Australian women with a history of urinary leakage.

Methods

Five hundred participants were randomly selected from women in the young (aged 18–22 in 1996), mid‐age (45–50), and older (70–75) cohorts of the Australian Longitudinal Study of Women's Health (ALSWH) who had reported leaking urine in the 1996 baseline survey. Details about leaking urine (frequency, severity, situations) and associated factors (pregnancy, childbirth, body mass index [BMI]) were sought through self‐report mailed follow‐up surveys in 1999.

Results & Conclusions

Response rates were 50, 83, and 80% in the young, mid‐age, and older women, respectively. Most women confirmed that they had leaked urine in the past month, and the majority of these were cases of “mixed” incontinence. Incontinence severity tended to increase with BMI for women of all ages, and increased severity scores were associated with having urine that burns or stings. Additional independent risk factors for increasing incontinence severity were heavy smoking in young women, past or present use of hormone replacement therapy in older women, and BMI and history of hysterectomy in mid‐age women. Neurourol. Urodynam. 22:550–557, 2003. © 2003 Wiley‐Liss, Inc.