bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gain clamped L‐band EDFA using a fiber Bragg grating in two stage configuration
Authors: Harun S. W. , Tamchek N. , Ahmad H. 
Published: April 2003

AbstractA gain clamping technique for the long‐wavelength‐band erbium‐doped fiber amplifier (L‐band EDFA) is presented. It uses two circulators and a fiber Bragg grating (FBG) to route a backward amplified spontaneous emission (ASE) from a second‐stage amplifier and launch it back into the first stage. The use of a broadband (BB) FBG has shown a better gain clamping effect, compared to a narrowband (NB) FBG. The amplifier gain for the BB FBG set up is clamped at 15.0 dB with a gain variation of less than 0.1 dB for an input power as high as −5 dBm. The use of a BB FBG has also flattened the gain spectrum. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 265–266, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10889
Novel periodically loaded ridged waveguide resonators
Authors: Goussetis George , Budimir Djuradj 
Published: April 2003

AbstractNovel periodically loaded E‐plane waveguide resonators are presented in this paper. The proposed resonators make use of the slow‐wave effect in order to achieve significantly increased loaded Q values for resonators of constant volume, as compared to their homogeneous counterparts, without introducing any complexity in the fabrication process. Numerical and experimental results are presented to validate the argument. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 266–268, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10890
Propagation of a femtosecond laser pulse through a dispersion‐free spatially‐chirped medium
Authors: Hovhannisyan D. L. , Stepanyan K. G. , Kalayjian Z. K. 
Published: April 2003

AbstractThe analytical solution of a wave equation that describes the propagation of a femtosecond laser pulse in a dispersion‐free finite‐length spatially chirped medium with 1D periodic inhomogeneity is presented. Such media are important to modern optics and are found in holograms, lasers, Bragg reflectors, compressors, and other applications. FDTD numerical modeling confirms the validity of our analytic results. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 269–273, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10891
Clock recovery from degraded signals at high repetition rates using a two‐ring injection mode‐locked fiber ring laser
Authors: Wang Zhaoxin , Wang Tong , Huo Li , Lou Caiyun , Gao Yizhi 
Published: April 2003

AbstractClock recovery from degraded signals at 10, 20, and 40 Gb/s data rates was achieved using a two‐ring injection mode‐locked fiber‐ring laser based on 10‐GHz bandwidth components. No pattern effect was observed in these experiments. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 273–276, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10892
An experimental implementation of resistive plates to enhance the performance of the mobile base station antennas
Authors: Chou Hsi‐Tseng , Wang Jing‐Song , Hsiao Yu‐Ting 
Published: April 2003

AbstractIn mobile communications, irregular handover and undesired interference, caused by wide inter‐sector coverage overlapping and the antenna's side‐lobe radiation, are improved by the application of resistive plates. This paper experimentally examines the characteristics of resistive plates and their design and implementation in order to reduce interference and enhance performance by guiding the power from overlapping regions to the main‐beam regions of each sector. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 276–280, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10893
Optimized grids for the wavelet‐analysis of generalized T‐junctions
Authors: Schneider Guido , Heyen Johann , Jacob Arne F. 
Published: April 2003

AbstractGeneralized microstrip T‐junctions are investigated by means of a method of moments (MoM) wavelet analysis. The focus is on the optimization of the grid for both efficiency and accuracy. Numerical results for different geometrical parameters show that, in contrast to simpler junctions, this grid has to be designed very carefully. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 280–282, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10894
Techniques to increase gain and impedance bandwidth of a cross‐aperture coupled patch antenna
Authors: Chung Kwok L. , Mohan Ananda S. 
Published: April 2003

AbstractA broadband high‐gain single‐feed cross‐aperture coupled patch antenna is presented in this paper. The measured results confirm that the antenna is capable of a 14.4% impedance bandwidth (VSWR ≤ 2), 3% of 3‐dB axial‐ratio bandwidth, and 17.4% of gain (>8 dBic) bandwidth with a mean gain level of 9.3 dBic. The techniques for obtaining high gain and broad impedance bandwidth as well as the effects on aperture size are discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 283–286, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10895
Linearity vs. Q‐factor of loads for RF amplifiers
Authors: Kim Jin‐pil , Park Seong‐su , Lee Sang‐gug 
Published: April 2003

AbstractThis paper analyzes and verifies that RF amplifier linearity as well as gain depend significantly on the quality of the output matching components or the loads (especially the inductor). Two amplifiers with off‐ and on‐chip matching circuits are built and compared. Measurement results show that a driver amplifier with off‐chip reactive output matching provides better linearity and gain of 3.6 dB and 1.6 dB, respectively, as compared to that of the amplifier with on‐chip matching. The amplifiers are implemented for 2.4‐GHz operation based on 0.35‐μm CMOS technology. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 286–288, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10896
Electrically tunable dispersion compensator based on nonlinearly chirped fiber Bragg grating
Authors: Yinying Zhang , Dexiang Wang , Enguang Dai , Deming Wu , Anshi Xu 
Published: April 2003

AbstractA new prototype of a compact and power‐efficient tunable dispersion compensator is demonstrated. To our acknowledge, this is the first time a tunable dispersion compensator using nonlinearly chirped fiber Bragg grating, coated with on‐fiber uniform metal heater, has been realized. A remarkable degree of dispersion tunability, as much as approximately 800 ps/nm, has been demonstrated. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 288–292, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10897
Numerical study of a Gaussian beam propagating in media with negative permittivity and permeability by using a bidirectional beam propagation method
Authors: Lu Jun , He Sailing 
Published: April 2003

AbstractGaussian beam propagation in structures containing meta‐materials with negative permittivity and negative permeability is numerically studied by using a bidirectional wide‐angle finite‐difference beam propagation method. Illustrative and quantitative views are given for various anomalous behaviors, such as the negative angle of refraction, beam refocusing, arbitrarily thin distributed Bragg reflector, and negative lateral shift of the reflected beam from a grounded slab, by a Gaussian beam propagating in some meta‐material structures. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 292–296, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10898
Almost uniformly excited arrays
Authors: Rodríguez J. A. , López P. , Ares F. , Moreno E. 
Published: April 2003

AbstractAntenna arrays with good performance that are uniformly excited except for the amplitudes and/or phases of a minority of elements can be synthesized using genetic algorithms. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 297–300, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10899
Wideband dielectric resonator‐loaded suspended microstrip patch antennas
Authors: Gupta Vijay , Sinha Sumit , Koul Shiban K. , Bhat Bharathi 
Published: April 2003

AbstractExperimental investigations of rectangular and circular suspended microstrip patch antennas with dielectric resonator loading at X‐band are reported. With loading, enhanced impedance bandwidth to about 18% is achieved in a single circular patch as compared to 13% for a single rectangular patch. In both cases, with loading, there is practically no change in the respective 3‐dB beam widths of the radiation patterns in E‐ and H‐planes. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 300–302, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10900
Application of the SN‐preconditioning method to the integral equations for a slot‐array antenna
Authors: Zhang Yu , Xie Yongjun , Liang Changhong 
Published: April 2003

AbstractIn this paper, a novel preconditioner scheme slot neighbour (SN) preconditioner is applied to dense matrix equations derived from integral equations for a slot‐array antenna in order to improve the convergence of iterative integral‐equation solvers, such as the conjugate‐gradient (CG) method. The preconditioner accounts for expansion‐function–testing‐function interactions in the vicinity of a given slot, requiring an order of Ns × Nb complexity for each Ns slot and each slot with Nb expansion unknowns. A typical slot‐array antenna is analyzed and good results demonstrate the validity of the proposed algorithms. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 302–305, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10901
Reduction of SAR in a human‐head model wrapped in clothing materials
Authors: Chen Hsing‐Yi , Shen Kun‐Yi 
Published: April 2003

AbstractAn analysis of clothing material for reducing RF energy absorption in a human‐head model has been studied using the finite‐difference time‐domain (FDTD) method. The local maximum specific absorption ratio (SAR) induced in the human head model is used for the evaluation of the clothing material's shielding effectiveness for EM exposure. It is found that clothing material with a dielectric constant close to that of human skin will induce higher RF energy absorption in the human‐head model. On the other hand, clothing material with a higher relative dielectric constant and permeability can greatly reduce RF energy absorption. If the clothing material is mixed with conducting materials or magnetic materials, a remarkable reduction of RF energy absorption in the human‐head model will be obtained. These preliminary results provide valuable knowledge to help in the manufacture of anti‐electromagnetic wave clothing. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 305–308, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10902
Cancellation of sub‐harmonic and second harmonic components to improve the linearity of a low‐power consumption LNA using SiGe HBT
Authors: Iturbide‐Sanchez Flavio , Jardon‐Aguilar Hildeberto , Tirado‐Mendez Jose Alfredo 
Published: April 2003

AbstractThree simple methods to improve the third‐order intercept point (IP3) of a low‐noise amplifier (LNA) for personal communication systems (PCS) applications or CDMA cellular handsets are introduced. Both simulations and results from previous works in the literature are compared in order to demonstrate the effectiveness of these methods in improving the performance of the LNA in terms of linearity when low‐bias voltage is used. The LNA was designed to operate at 1.9 GHz, using a silicon germanium (SiGe) heterojunction bipolar transistor (HBT) and 2.4 V bias voltage. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 308–311, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10903
A compact dual‐slot antenna for WLAN applications
Authors: Qing X. M. , Chia M. Y. W. 
Published: April 2003

AbstractThis paper proposes a novel compact dual‐slot antenna for 5‐GHz WLAN applications. The prototype comprises a rectangular slot, a H‐shaped slot, and an open‐circuited microstrip feed line. The simulation and experimental results indicate broad operating bandwidth from 4.9 GHz to 6.3 GHz at 10‐dB return loss and 3‐dBi gain. The proposed antenna is compact, easy to fabricate, and inexpensive, and it presents good broadband characteristics that cover all 5‐GHz WLAN bands. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 37: 311–313, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10904
Direct assessment of structural resistance against pressurized fracture
Authors: Bolzon G. , Cocchetti G. 
Published: April 2003

AbstractThe determination of the load bearing capacity of hydraulic structures such as dams, reservoirs and retaining walls requires the consideration of mixed‐mode fracture, possibly driven by the fluid pressure, in correspondence to artificial and natural joints (or cracks, in the latter case). A friction‐cohesive softening interface model with coupled degradation of normal and tangential strength is introduced here to account for the essential features of the joint behaviour; its predictive capability is assessed through extensive calculations. Alternative numerical techniques resting on the discrete‐crack approach are considered, focusing on simplified approaches for the direct appraisal of the structural resistance. Comparison is made with the results of evolutionary analyses, based on a priori piecewise linearization of the interface model and on ‘exact integration’. Copyright © 2003 John Wiley & Sons, Ltd.
Inter‐relations between experimental and computational aspects of slope stability analysis
Authors: Baker R. 
Published: April 2003

AbstractMost conventional slope stability calculations are based on the linear Mohr–Coulomb failure criterion. However, a substantial amount of experimental evidence suggests that failure criteria of many soils are not linear particularly in the range of small normal stresses. This departure from linearity is significant for slope stability calculations since for a wide range of practical stability problems, critical slip surfaces are shallow and normal stresses acting on such surfaces are small. There exists a technical difficulty in performing strength measurements in the range of small normal stresses relevant to such slope stability problems. As a result, in many practical situations strength measurements are performed at much larger normal stresses then those relevant for the stability problem under consideration. When this is the case, use of the Mohr–Coulomb criterion amounts to a linear extrapolation of experimental information (obtained at large normal stresses), into the range of small normal stresses, which is relevant to the problem. This extrapolation results with very significant overestimation of calculated safety factors in cases when there is large mismatch between experimental and relevant ranges of normal stresses. The present work delineates the extent of this problem and suggests a practical way to overcome it. Copyright © 2003 John Wiley & Sons, Ltd.
A micromechanical study of rolling and sliding contacts in assemblies of oval granules
Authors: Shodja Hossein M. , Nezami Erfan G. 
Published: April 2003

AbstractThe evolution of the microstructure of an assembly of cohesionless granular materials with associated pores, which carry the overall applied stresses through frictional contacts is a complex phenomenon. The macroscopic flow of such materials take place by the virtue of the relative rolling and sliding of the grains on the micro‐scale. A new discrete element method for biaxial compression simulations of random assemblies of oval particles with mixed sizes is introduced. During the course of deformation, the new positions of the grains are determined by employing the static equilibrium equations. A key aspect of the method is that, it is formulated for ellipse cross‐sectional particles, hence desirable inherent anisotropies are possible. A robust algorithm for the determination of the contact points between neighbouring grains is given. Employing the present methodology, many aspects of the behaviour of two‐dimensional assemblies of oval cross‐sectional rods have been successfully addressed. The effects of initial void ratio, interparticle friction angle, aspect ratio, and bedding angle on the rolling and sliding contacts are examined. The distribution of normals to the rolling and sliding contacts have different patterns and are concentrated along directions, which are approximately perpendicular to one another. On the other hand, the distribution of all contact normals (combined rolling and sliding) are close to that of rolling contacts, which confirm that rolling is the dominant mechanism. This phenomenon becomes more pronounced for higher intergranular friction angle. Characteristics of the rolling and sliding contacts are also discussed in the context of the force angle, which is the inclination of contact force with respect to the contact normal. Copyright © 2003 John Wiley & Sons, Ltd.
Capturing strain localization behind a geosynthetic‐reinforced soil wall
Authors: Lai Timothy Y. , Borja Ronaldo I. , Duvernay Blaise G. , Meehan Richard L. 
Published: April 2003

AbstractThis paper presents the results of finite element (FE) analyses of shear strain localization that occurred in cohesionless soils supported by a geosynthetic‐reinforced retaining wall. The innovative aspects of the analyses include capturing of the localized deformation and the accompanying collapse mechanism using a recently developed embedded strong discontinuity model. The case study analysed, reported in previous publications, consists of a 3.5‐m tall, full‐scale reinforced wall model deforming in plane strain and loaded by surcharge at the surface to failure. Results of the analysis suggest strain localization developing from the toe of the wall and propagating upward to the ground surface, forming a curved failure surface. This is in agreement with a well‐documented failure mechanism experienced by the physical wall model showing internal failure surfaces developing behind the wall as a result of the surface loading. Important features of the analyses include mesh sensitivity studies and a comparison of the localization properties predicted by different pre‐localization constitutive models, including a family of three‐invariant elastoplastic constitutive models appropriate for frictional/dilatant materials. Results of the analysis demonstrate the potential of the enhanced FE method for capturing a collapse mechanism characterized by the presence of a failure, or slip, surface through earthen materials. Copyright © 2003 John Wiley & Sons, Ltd.
A practical determination strategy of optimal threshold parameter for matrix compression in wavelet BEM
Authors: Koro Kazuhiro , Abe Kazuhisa 
Published: April 2003

AbstractA practical strategy is developed to determine the optimal threshold parameter for wavelet‐based boundary element (BE) analysis. The optimal parameter is determined so that the amount of storage (and computational work) is minimized without reducing the accuracy of the BE solution. In the present study, the Beylkin‐type truncation scheme is used in the matrix assembly. To avoid unnecessary integration concerning the truncated entries of a coefficient matrix, a priori estimation of the matrix entries is introduced and thus the truncated entries are determined twice: before and after matrix assembly. The optimal threshold parameter is set based on the equilibrium of the truncation and discretization errors. These errors are estimated in the residual sense. For Laplace problems the discretization error is, in particular, indicated with the potential's contribution ∥c∥ to the residual norm ∥R∥ used in error estimation for mesh adaptation. Since the normalized residual norm ∥c∥/∥u∥ (u: the potential components of BE solution) cannot be computed without main BE analysis, the discretization error is estimated by the approximate expression constructed through subsidiary BE calculation with smaller degree of freedom (DOF). The matrix compression using the proposed optimal threshold parameter enables us to generate a sparse matrix with O(N1+γ) (0≤γ<1) non‐zero entries. Although the quasi‐optimal memory requirements and complexity are not attained, the compression rate of a few per cent can be achieved for N∼1000. Copyright © 2003 John Wiley & Sons, Ltd.
A two‐grid method for expanded mixed finite‐element solution of semilinear reaction–diffusion equations
Authors: Chen Yanping , Huang Yunqing , Yu Dehao 
Published: April 2003

AbstractWe present a scheme for solving two‐dimensional semilinear reaction–diffusion equations using an expanded mixed finite element method. To linearize the mixed‐method equations, we use a two‐grid algorithm based on the Newton iteration method. The solution of a non‐linear system on the fine space is reduced to the solution of two small (one linear and one non‐linear) systems on the coarse space and a linear system on the fine space. It is shown that the coarse grid can be much coarser than the fine grid and achieve asymptotically optimal approximation as long as the mesh sizes satisfy H=O(h1/3). As a result, solving such a large class of non‐linear equation will not be much more difficult than solving one single linearized equation. Copyright © 2003 John Wiley & Sons, Ltd.
Explicit calculation of smoothed sensitivity coefficients for linear problems
Authors: Białecki R. A. , Divo E. , Kassab A. J. , Ait Maalem Lahcen R. 
Published: April 2003

AbstractA technique of explicit calculation of sensitivity coefficients based on the approximation of the retrieved function by a linear combination of trial functions of compact support is presented. The method is applicable to steady state and transient linear inverse problems where unknown distributions of boundary fluxes, temperatures, initial conditions or source terms are retrieved. The sensitivity coefficients are obtained by solving a sequence of boundary value problems with boundary conditions and source term being homogeneous except for one term. This inhomogeneous term is taken as subsequent trial functions. Depending on the type of the retrieved function, it may appear on boundary conditions (Dirichlet or Neumann), initial conditions or the source term. Commercial software and analytic techniques can be used to solve this sequence of boundary value problems producing the required sensitivity coefficients. The choice of the approximating functions guarantees a filtration of the high frequency errors. Several numerical examples are included where the sensitivity coefficients are used to retrieve the unknown values of boundary fluxes in transient state and volumetric sources. Analytic, boundary‐element and finite‐element techniques are employed in the study. Copyright © 2003 John Wiley & Sons, Ltd.