bluuebunny/crossref_metadata_2025 huggingface dataset:
An efficient implementation of the PML for truncating FDTD domains
Authors: Ramadan Omar , Oztoprak Abdullah Y.
Published: December 2002

An efficient implementation of the perfectly matched layer (PML) is presented for truncating lossy and lossless finite‐difference time‐domain (FDTD) computational domains. The implementation is based on the stretched coordinate PML formulations and on the derivation of the wave equation in the PML region. Significant savings in computational time and memory storage requirements are achieved. In addition, the FDTD implementation of the new formulations is simpler than the conventional PML formulations. Two dimensional numerical tests have been carried out to validate the proposed formulations. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 55–60, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10669
DC‐2.1 GHz CMOS multiple feedback transimpedance amplifiers with high dynamic range and linearity
Authors: Chiang Ming‐Chou , Chen Ping‐Yu , Lu Shey‐Shi , Meng Chin‐Chun
Published: December 2002

A CMOS wideband transimpedance amplifier with multiple‐resistive feedback loops is reported for first time. This amplifier was fabricated by the 0.35‐μm CMOS process. Multiple‐feedback technique was used to achieve terminal impedance matching and wide bandwidth. The experimental results showed that a transimpedance gain of 51.7 dBΩ and a 3‐dB bandwidth of 2.1 GHz were obtained. High input P1dB of −5 dBm and input IP3 of 1 dBm were also measured. The high dynamic range and high linearity achieved were attributed to the multiple feedback technique used. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 60–61, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10670
A broadband cross‐shaped microstripline‐fed no‐offset ring slot antenna
Authors: Jang Yong‐Woong
Published: December 2002

A cross‐shaped microstrip‐fed ring slot antenna with large bandwidth is presented experimentally in this paper. The characteristics of the antenna are sensitive to the antenna design parameters. The VSWR, radiation pattern, and antenna gain of this configuration are presented. The measured bandwidth is approximately 77.766% (2.0 ≥ VSWR). © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 61–63, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10671
Analytical models of width‐limited microstrip lines
Authors: Svac̆ina Jir̆í
Published: December 2002

A set of closed form relations is proposed for the analysis of two types of width‐limited microstrip lines using a conformal mapping method. New closed‐form equations are derived for microstrip lines with rectangular and/or trapezoidal shaped dielectric substrates, and the computational results are compared with available data from other authors. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 63–65, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10672
Extended multiperiodic traveling wave model for the accurate analysis of the radiation performance of the Sierpinski fractal‐like multiband antenna
Authors: Soler Jordi , Puente Carles , Anguera Jaume
Published: December 2002

An extension of the Multiperiodic Traveling Wave Model to analyze the Sierpinski fractal‐like multiband antenna is presented. The novel extension improves the original model in the calculation of radiation patterns at the higher bands, which permit a better understanding of the radiation mechanism and also gives a complete description of the full radiation pattern. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 67–70, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10673
CPW‐FED rectangular microstrip ring antenna for suppression of parasitic backside radiation
Authors: Zhu Lei , Li Keren
Published: December 2002

A coplanar waveguide (CPW)‐fed rectangular microstrip ring antenna is proposed and developed for effective suppression of parasitic backside radiation, and is constructed on the basis of a simple slot‐to‐strip EM coupling principle. Due to the non‐radiative behavior of a CPW short‐end feeding block, this antenna allows us to realize an excellent unidirectional radiation pattern. With the use of our developed fullwave method of moments–short‐open calibration (MoM–SOC) technique, its electrical performance such as input impedance and radiation pattern are extensively investigated in theory. Obtained results demonstrate well that the front‐to‐back radiation ratio of our concern is consistently higher than 30 dB while its narrow bandwidth is incremented twice by simply widening its strip width. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 65–67, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10674
Multiprobe RLSA design for DBS reception
Authors: Sierra‐Castañer M. , Sierra‐Pérez M. , Vera‐Isasa M. , Fernández‐Jambrina J.L.
Published: December 2002

A synthesis method for circular‐polarization radial‐line slot antennas excited by four posts inside the radial line is presented. This excitation generates a rotational mode inside the waveguide, and the slots that radiate the field can be placed arranging concentric rings. The reflected field inside the radial line can be controlled. We present the design and a prototype model for this antenna that shows practical results. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 70–72, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10675
Chromatic dispersion effects in millimetre‐wave fibre‐optic links based on optically generated electrical modulation formats
Authors: Fuster J. M. , Roig J. C. , Candelas P. , Marti J.
Published: December 2002

The authors investigate the chromatic dispersion effects in millimeter‐wave upconverting fibre‐optic links employing EOM‐based photonic electrical QAM/PSK modulators. It is shown that, because the carrier suppression effect is mitigated in these links, a transmission system bandwidth wider than in the conventional case is achieved. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 72–74, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10676
Comment on “a PML‐FDTD formulation for the simulation of optical structures”
Authors: Ramadan Omar
Published: December 2002

The focus of this comment is to discuss an important point regarding the derivation of the wave equation in the perfectly matched layer (PML). It is demonstrated that the distance dependency of the PML conductivity profile should be taken into consideration when deriving the wave equation in the PML region. Significant improvements in the absorbing performance are achieved with a small number of PML layers. A numerical test is carried out in one dimension to validate the proposed formulations. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 74–76, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10677
Diplexing feed network for wideband dual‐frequency stacked microstrip patch antenna
Authors: de Haaij D. M. , Joubert J. , Odendaal J. W.
Published: December 2002

Simulated and measured results of a diplexing feed network for a wideband dual‐frequency stacked microstrip patch antenna are presented. The microstrip feed network is easy to design and consists of a T‐junction and a single decoupling resonator for each frequency band. The return loss in each of the frequency bands is better than 10 dB, over a better than 10% bandwidth. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 100–102, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10686
A high‐power amplifier using photonic bandgap and coplanar waveguide
Authors: Seo Chulhun
Published: December 2002

In this paper, an R‐band hybrid amplifier with a coplanar‐waveguide (CPW) and photonic‐bandgap (PBG) structure is designed and fabricated. We use PBG and CPW simultaneously in the amplifier to improve power‐added efficiency (PAE) and intermodulation distortion (IMD) in the R‐band. In this paper, the PBG structures are optimized to obtain a matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and IMD were improved by 15% and 4.5 dB, respectively, compared with a conventional amplifier. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 108–110, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10689
A C‐band ultra‐low‐power consumption HMIC amplifier for intelligent transportation system applications
Authors: Wen Guangjun , Law Choi Look , Shen Zhongxiang , Aditya Sheel , Li Chao
Published: December 2002

A multi‐stage hybrid integrated ultra‐low‐power‐consumption amplifier using a low‐cost silicon bipolar junction transistor for intelligent transportation system (ITS) applications is developed at 5.8 GHz. Under a low dc‐power bias of 3.0 V and 0.92 mA, the designed amplifier shows the state‐of‐the‐art performance with a gain of 32.5 dB, NF of 4.5 dB, input and output return loss of less than −10 dB, and a corresponding −1 dB compression point of −19.6 dBm at 5.8 GHz, achieving a gain‐to‐power‐consumption ratio of 11.78 dB/mW, which is the highest ever reported at C‐band. A design approach that can simultaneously provide high‐gain, low power consumption, low noise figure, and low return loss is presented in this paper. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 112–115, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10691
Research on the radiation characteristics of the reinforced leaky coaxial cable by FDTD and spatial harmonic expansion methods
Authors: Wang Jun Hong
Published: December 2002

An artificial closed cylindrical surface is placed around a reinforced leaky coaxial cable. The field inside the surface is calculated by the finite‐difference time‐domain (FDTD) method. The field outside is expanded by spatial harmonics. By matching the fields of the two regions at the artificial surface, equations for the unknown expansion coefficients are obtained. By solving these equations, the expansion coefficients and, therefore, the radiation field are obtained. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 142–145, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10701
Rigid‐plastic/rigid‐viscoplastic FE simulation using linear programming for metal forming
Authors: Xu Weili , Di Shenglin , Thomson Peter
Published: December 2002

For rigid‐plastic/rigid‐viscoplastic (RP/RVP) FE simulation in metal forming processes, the linear programming (LP) approach has many remarkable advantages, compared with a normal iterative solver. This approach is free from convergence problems and is convenient for dealing with contact surfaces, rigid zones, and friction forces. In this paper, a numerical model for axisymmetrical and plane‐strain analysis using RP/RVP and LP is proposed and applied to industrial metal forming. Numerical examples are provided to validate the accuracy and efficiency of the proposed method. Copyright © 2002 John Wiley & Sons, Ltd.
A vertex‐based finite volume method applied to non‐linear material problems in computational solid mechanics
Authors: Taylor G. A. , Bailey C. , Cross M.
Published: December 2002

A vertex‐based finite volume (FV) method is presented for the computational solution of quasi‐static solid mechanics problems involving material non‐linearity and infinitesimal strains. The problems are analysed numerically with fully unstructured meshes that consist of a variety of two‐ and three‐dimensional element types. A detailed comparison between the vertex‐based FV and the standard Galerkin FE methods is provided with regard to discretization, solution accuracy and computational efficiency. For some problem classes a direct equivalence of the two methods is demonstrated, both theoretically and numerically. However, for other problems some interesting advantages and disadvantages of the FV formulation over the Galerkin FE method are highlighted. Copyright © 2002 John Wiley & Sons, Ltd.
A numerical integration scheme for special finite elements for the Helmholtz equation
Authors: Bettess Peter , Shirron Joseph , Laghrouche Omar , Peseux Bernard , Sugimoto Rie , Trevelyan Jon
Published: December 2002

The theory for integrating the element matrices for rectangular, triangular and quadrilateral finite elements for the solution of the Helmholtz equation for very short waves is presented. A numerical integration scheme is developed. Samples of Maple and Fortran code for the evaluation of integration abscissæ and weights are made available. The results are compared with those obtained using large numbers of Gauss–Legendre integration points for a range of testing wave problems. The results demonstrate that the method gives correct results, which gives confidence in the procedures, and show that large savings in computation time can be achieved. Copyright © 2002 John Wiley & Sons, Ltd.
Sensitivity and optimization for shape and non‐linear boundary conditions in thermal boundary elements
Authors: Davey K. , Clark L. D.
Published: December 2002

This paper is concerned with the minimization of functionals of the form ∫Γ(b) f(h,T(b, h)) dΓ(b) where variation of the vector b modifies the shape of the domain Ω on which the potential problem, ∇2T=0, is defined. The vector h is dependent on non‐linear boundary conditions that are defined on the boundary Γ. The method proposed is founded on the material derivative adjoint variable method traditionally used for shape optimization. Attention is restricted to problems where the shape of Γ is described by a boundary element mesh, where nodal co‐ordinates are used in the definition of b.

Propositions are presented to show how design sensitivities for the modified functional ∫Γ(b) f(h,T (b, h)) dΓ(b) +∫Ω(b) λ(b, h) ∇2T(b, h) dΩ(b) can be derived more readily with knowledge of the form of the adjoint function λ determined via non‐shape variations. The methods developed in the paper are applied to a problem in pressure die casting, where the objective is the determination of cooling channel shapes for optimum cooling. The results of the method are shown to be highly convergent. Copyright © 2002 John Wiley & Sons, Ltd.
A comparison of transformation methods for evaluating two‐dimensional weakly singular integrals
Authors: Johnston Barbara M. , Johnston Peter R.
Published: December 2002

Accurate numerical evaluation of integrals arising in the boundary element method is fundamental to achieving useful results via this solution technique. In this paper, a number of techniques are considered to evaluate the weakly singular integrals which arise in the solution of Laplace's equation in three dimensions and Poisson's equation in two dimensions. Both are two‐dimensional weakly singular integrals and are evaluated using (in a product fashion) methods which have recently been used for evaluating one‐dimensional weakly singular integrals arising in the boundary element method.

The methods used are based on various polynomial transformations of conventional Gaussian quadrature points where the transformation polynomial has zero Jacobian at the singular point. Methods which split the region of integration into sub‐regions are considered as well as non‐splitting methods. In particular, the newly introduced and highly accurate generalized composite subtraction of singularity and non‐linear transformation approach (GSSNT) is applied to various two‐dimensional weakly singular integrals.

A study of the different methods reveals complex relationships between transformation orders, position of the singular point, integration kernel and basis function. It is concluded that the GSSNT method gives the best overall results for the two‐dimensional weakly singular integrals studied. Copyright © 2002 John Wiley & Sons, Ltd.
Structured extended finite element methods for solids defined by implicit surfaces
Authors: Belytschko Ted , Parimi Chandu , Moës Nicolas , Sukumar N. , Usui Shuji
Published: December 2002

A paradigm is developed for generating structured finite element models from solid models by means of implicit surface definitions. The implicit surfaces are defined by radial basis functions. Internal features, such as material interfaces, sliding interfaces and cracks are treated by enrichment techniques developed in the extended finite element method. Methods for integrating the weak form for such models are proposed. These methods simplify the generation of finite element models. Results presented for several examples show that the accuracy of this method is comparable to standard unstructured finite element methods. Copyright © 2002 John Wiley & Sons, Ltd.
Engineering new peptidic inhibitors from a natural chymotrypsin inhibitor
Authors: Mucsi Zoltán , Perczel András , Orosz György
Published: December 2002

Three model peptides of different sizes (17–24 amino acid residues), mimicking the chymotrypsin inhibitor SCGI (a peptide of 35 amino acid residues) isolated from Schistocerca gregaria were designed and prepared by convergent peptide synthesis. Selective formation of disulphide bridges in the closing step was achieved without selective protection of cysteine residues. The natural pattern of the two disulphide bridges was determined by 2D homonuclear 1H NMR techniques. All three model peptides were characterized by amino acid analysis, MS and CD spectra. Preliminary results revealed that the two smaller model peptides exhibit no inhibitory activity, whereas the larger one shows limited inhibition of chymotrypsin. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
A new peptidic protease inhibitor from Vicia faba seeds exhibits antifungal, HIV‐1 reverse transcriptase inhibiting and mitogenic activities
Authors: Ye X. Y. , Ng T. B.
Published: December 2002

A new trypsin–chymotrypsin inhibitor, with an N‐terminal sequence showing some differences from the previously reported trypsin–chymotrypsin inhibitor, was isolated from the broad bean Vicia faba. The inhibitor was a peptide with a molecular mass of 13 kDa. It was adsorbed on Affi‐gel blue gel and CM‐Sepharose. It exerted antifungal activity toward Mycosphaerella arachidicola and Physalospora piricola. In addition, the trypsin–chymotrypsin inhibitor elicited a mitogenic response from mouse splenocytes and inhibited the activity of human immunodeficiency virus‐1 reverse transcriptase. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Synthesis of Nα‐Boc‐Nε‐tetrabenzyl‐DTPA‐L‐lysine and Nα‐Fmoc‐Nε‐tetra‐t‐butyl‐DTPA‐L‐lysine, building blocks for solid phase synthesis of DTPA‐containing peptides
Authors: Davies John S. , Al‐Jamri Loai
Published: December 2002

Two building blocks, Boc‐Lys(Bn4‐DTPA)‐OH and Fmoc‐Lys($\hbox{Bu}^{\rm t}_{4}$‐DTPA)‐OH have been synthesized via the acylation of the ε‐amino group of Nα‐protected lysine, using suitably protected tetra‐esters of diethylene triamine pentaacetic acid (DTPA), a ligand with wide application as a chelating agent for complexing metal ions to peptides. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Electron paramagnetic resonance backbone dynamics studies on spin‐labelled neuropeptide Y analogues
Authors: Bettio Andrea , Gutewort Volker , Pöppl Andreas , Dinger Michaela C. , Zschörnig Olaf , Arnold Klaus , Toniolo Claudio , Beck‐Sickinger Annette G.
Published: December 2002

Neuropeptide Y (NPY) is one of the most abundant peptides in the central nervous system of mammalians. NPY acts by binding to at least five G‐protein coupled receptors (GPCRs) which have been named Y1, Y2, Y4, Y5 and Y6. Three spin‐labelled NPY analogues containing the nitroxide group of the amino acid TOAC (2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐amino‐4‐carboxylic acid) as a paramagnetic probe were synthesized by solid‐phase peptide synthesis. Synthetic problems owing to the sensitivity of nitroxide towards acidic and reducing conditions have been overcome by using a cleavage cocktail that contains anisole and cresol scavengers. Concerning the receptor binding preferences, the analogues [TOAC34]‐pNPY and [Ala31,TOAC32]‐pNPY showed a marked selectivity for the Y5 receptor, while [TOAC2]‐pNPY maintained a significant binding also to the Y2 receptor subtype. The modifications of the native peptide structure caused by the introduction of TOAC were examined by circular dichroism. In order to determine the rotational correlation time of the spin probes, electron paramagnetic resonance measurements were performed in solution and in the presence of liposomes. This allowed us to evaluate the backbone dynamics of the different parts of the NPY molecule in the free and membrane bound states. The results of these studies showed that NPY interacts with liposomes by using the C‐terminal α‐helix while the N‐terminal tail retains a flexibility that is comparable to that of the peptide in solution as already shown by NMR studies on DPC micelles. Furthermore, we demonstrated that TOAC‐labelling is a valuable tool to investigate changes in the backbone conformation and dynamics. This may be of major importance for peptides and small proteins when they bind to cell membranes. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Rabbit anti‐HMG‐17 antibodies recognize similar epitopes on the HMG‐17 molecule as lupus autoantibodies. Relation with histone H1 defined epitopes
Authors: Boumba Vassiliki A. , Seferiadis Konstantin
Published: December 2002

HMG‐17 is a nucleosomal protein which is an immune target of autoantibodies in systemic lupus erythematosus (SLE) and other autoimmune diseases. Autoantibody production in SLE is believed to result from autoantigen specific immune stimulation and subsequently, it is expected that antigenic determinants recognized by SLE autoantibodies and induced antibodies by immunization are quite similar. To examine this issue, rabbits were immunized with purified HMG‐17. The produced antiserum showed cross reactivity on blots and in inhibition ELISA with histone H1, even after its affinity purification with immobilized HMG‐17. Finally, purification of the antiserum over H1 absorbed on nitrocellulose membrane produced specific anti‐HMG‐17 antibodies in the supernatant and anti‐HMG‐17/H1 antibodies that were bound to H1. SLE sera positive for HMG‐17 had also cross reactivity with H1, and following the same procedure as before we received HMG‐17 specific SLE autoantibodies and anti‐HMG‐17/H1 autoantibodies. Using the multipin epitope mapping technology, 19 overlapping 15‐mer HMG‐17 peptides and six 15‐peptides, corresponding to known epitopes of histone H1, were synthesized. Four major epitopes were identified on the HMG‐17 molecule, reactive with induced anti‐HMG‐17 antibodies, and these were the same as major autoepitopes in SLE. The sequence 25–51 of HMG‐17, part of its DNA‐binding domain, was recognized by the anti‐HMG‐17/H1 antibodies that were bound to H1. These antibodies recognized also defined epitopes of H1. Our results show that SLE autoantibodies can be directed against the same or similar epitopes as do IgGs evoked during the active immunization of animals, and provide additional evidence that autosensitization with an autoantigen might be operative. The possibility that the same or similar epitopes are found on different molecules (in this study HMG‐17 and H1) supports the fact that there are rules by which nature selects the most dominant immunodeterminant to a given protein, which often represents functional or structural sites in the autoantigen. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd.
Construction of a paper reference system on the Web in XML
Authors: Takada Nobuhiko , Tamura Takeshi , Osawa Kazuhiko
Published: December 2002

As a replacement for the lecture‐driven teaching of the past, we are aiming to establish an individually initiated, efficient independent study environment using a computer network. This paper focuses in particular on the collection of Web information needed by researchers, based on efficient paper retrieval and collection Web sites using XML. XML can handle data on the Web more flexibly than the present HTML, and research into its practical applications is progressing rapidly. In the artificial intelligence field, ontology engineering for authoring tools to be used in creating teaching materials is under way. In this context, because XML has been defined by the W3C, it is an accessible standard, and application examples have appeared. However, few of them focus on retrieval. We describe a “paper retrieval system” for efficient retrieval, constructed only in HTML on the basis of XML, RDF, and XHTML. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 21–28, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10014
Routing and flow control by genetic algorithm for a flow model
Authors: Okuhara Koji , Tanaka Toshijiro , Ishii Hiroaki
Published: December 2002

In this paper, we propose an application of the genetic algorithm to adaptive routing and flow control in information networks. Although studies using a genetic algorithm have been made on routing or flow control individually, this study proposes a method which controls them simultaneously. We chose a flow model which can evaluate congestion by the traffic arrival rate in a link. By simulation, we show that the proposed network control method using the genetic algorithm is superior to the usual method which performs routing by the Dijkstra method and flow control by the gradient method. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 11–20, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10215
Pace‐the‐Scene Movie: A video‐based scene representation method for natural scenery
Authors: Kamei Katsuyuki , Seo Kazuo
Published: December 2002

This paper proposes Pace‐the‐Scene Movie, which is a video‐based scene reproduction method for natural scenery. To reproduce natural scenery, it was a problem to express the motion within the scenery and the user's walk‐through operation at the same time. The new method solves this problem. Its features include (1) replaying the source movie in order to represent the natural motion in the scenery, (2) correcting frames whenever required to realize walk‐through, and (3) skipping sequences appropriately. Errors in the presented images were also investigated, and the conditions for skipping sequences were deduced from the results. Further, a guideline for using multiple video streams is proposed. This method easily realizes reproduction of natural scenery with motion. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 1–10, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10338
Proposal of Dynamic Process Resolution Protocol making transparency of physical locations in closed communication group for intranet
Authors: Watanabe Akira , Ideguchi Tetsuo , Sasase Iwao
Published: December 2002

On an intranet, there is a need to form various kinds of closed communication groups that protect significant information in departmental and/or individual bases. To satisfy this need, encryption elements realizing closed communication groups require exact and complicated process information in which the processes of how to treat the received packets are specified. In general, this information is generated in a management server and downloaded to the encryption elements. However, by this method, the information must be regenerated and redownloaded to the encryption elements, every time the system configuration changes. In this paper, we propose the Dynamic Process Resolution Protocol, by which encryption elements generate the process information automatically from the logical definition of the closed communication groups for themselves, detecting the relationship of the locations among the encryption elements and the communication terminals. This method means that the function of generation of process information is split from the management server. This method imposes no work on the network manager when the system configuration changes if the logical definition does not change. Moreover, closed communication groups with free location are realized, that is, users who have the function of encryption elements can move anywhere in the intranet freely. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 29–44, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1182
Elevator group control system using multiagent system
Authors: Ogoshi Yasuhiro , Kimura Haruhiko , Hirose Sadaki , Osato Nobuyasu
Published: December 2002

In this study, the authors proposed an elevator group control system using multiagent system, and verified the efficiency of the system in areas characterized by concentration of large crowds of passengers on the main floor, for example, during morning rush‐hour traffic. Congestion on the main floor in heavy morning rush‐hour traffic areas was previously alleviated using specific traffic control systems providing so‐called morning rush‐hour operation by forced dispatching of multiple elevators to the main floor. However, since forced dispatching on the main floor affects areas other than the main floor and also the subsequent service on the main floor, it makes overall improvement of transportation efficiency a difficult task. There are published reports relating to morning rush‐hour operation, but these deal with centralized control based on overall monitoring and sending instruction commands. Thus, the problem is that if this control system stopped working, it caused overall malfunctioning. In addition, in a system based on overall monitoring and generating optimal control plan in accordance with the received information, it is not easy to generate design updates following a change in the system's design or environment. Therefore, in the current study the authors introduced a multiagent system with distributed processing, in which individual elevators make action decisions by independent learning process. The authors proposed an elevator group control system which uses simplified reasoning to provide for flexible response even in the case of a changed environment, such as when a part of the elevator group has stopped functioning. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 45–58, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1183
A polynomial time algorithm to infer sequential machines
Authors: Takahashi Katsuhiko , Fujiyoshi Akio , Kasai Takumi
Published: December 2002

In this paper, we will describe an algorithm which infers a Moore‐type sequential machine from examples of inputs and outputs of an unknown Moore‐type sequential machine. The hypothesis output by this inference algorithm is a nondeterministic Moore‐type sequential machine which does not conflict with the given examples of inputs and outputs; we will show that the update time of the hypothesis will become a polynomial time of the sum of the lengths of the examples of inputs and outputs. Moreover, we will show that this inference algorithm will identify the Moore‐type sequential machine in the limit by using the complete examples of inputs and outputs defined from the structures of the Moore‐type sequential machine. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 59–67, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1184
Acquisition of world images and self‐localization estimation using viewing image sequences
Authors: Madokoro Hirokazu , Sato Kazuhito , Ishii Masaki
Published: December 2002

We propose a method for robotic self‐localization estimation that can process position information without identifying special landmarks. This method, which combines viewpoint shifts with visual information about the environment, makes it possible for a robot to move both autonomously and purposefully. In our procedures, the robot surveys the landscape of an environment from multiple directions, obtaining self‐localization from a viewing image sequence. The robot is made aware of changes in the landscape via self‐organizing maps (SOM), which generate “concept patterns”. By making the SOM hierarchical, these concept patterns can be consolidated. This allows the robot to move both autonomously and purposefully in the environment toward a position by using previously collected information. By performing a travel experiment with the robot in an indoor environment, in which characteristic concept patterns recording topologies had been previously generated at various positions during a learning period, we confirmed that a correct self‐localization estimate can be generated from landscape changes detected via viewpoint shifts. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 68–78, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1185
Digital color imaging with color constancy
Authors: Takebe Keisuke , Ito Naoki , Nakauchi Shigeki , Usui Shiro
Published: December 2002

“Color constancy” which gives almost constant color perception of an object under illumination of various colors, is an important characteristic in identifying objects by our color vision. This paper proposes an algorithm to add color constancy to a digital camera, which reconstructs an image under arbitrary light conditions by using a pair of images (one with no additional light source, and the other with an additional light source) and estimating the color of the light source used. The results of images using a flash as an additional light source are presented. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 79–88, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002S/scj.1186
Moment calculation method for digital vision chip
Authors: Ishii Idaku , Komuro Takashi , Ishikawa Masatoshi
Published: December 2002

Recently, an interesting general‐purpose digital vision chip has been realized by integrating a photodetector (PD) and a processing element (PE) directly connected for each pixel on a single chip. This paper proposes bit plane (BP) feature decomposition as a realization of the idea of feature calculation that is suited to a massively parallel processing structure integrated on the digital vision chip. Moment calculation based on the method is discussed. An evaluation of the digital vision chip using the proposed calculation method is presented, and its effectiveness is demonstrated. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 89–97, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1187
Teleconference system composed of super‐high‐definition image system and B‐ISDN
Authors: Wada Minoru , Hashimoto Tsutomu , Matsumura Yasushi , Matsuda Tetsuya , Komori Masaru , Takahashi Takashi , Minato Kotaro , Tokutomi Yoshihiro , Takeda Hiroshi
Published: December 2002

This paper describes a system to carry out a medical conference between two remote places. Most kinds of medical images for a patient with circulatory‐organ disease are filed in a super‐high‐definition image system, and the quality of these images and the maneuverability of the system were evaluated by medical experts. The results show that the qualities of all of the images and the maneuverability of the system satisfy the medical requirements. Further, a wide‐band ISDN which has this system at two terminals in remote places has been constructed. The delay time, protocol analysis, and subjective evaluation of this system have been obtained, showing its good feasibility. © 2002 Wiley Periodicals, Inc. Syst Comp Jpn, 34(1): 98–110, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.1188
Comparison of tests for categorical data from a stratified cluster randomized trial
Authors: Dobbins Timothy A. , Simpson Judy M.
Published: December 2002

Two features commonly exhibited by randomized trials of health promotion interventions are cluster randomization and stratification. Ignoring correlations between individuals within clusters can lead to an inflated type I error rate and hence a P‐value which overstates the significance of the result. This paper compares several methods for analysing categorical data from a stratified cluster randomized trial. We propose an extension of a method from survey sampling that uses the design effect to reduce the effective sample size. We compare this with three methods from Zhang and Boos that extend the standard Cochran–Mantel–Haenszel (CMH) statistic by using appropriate covariance matrices, and with a bootstrap method. The comparison is based on empirical type I error rates from a simulation study, in which the number of clusters randomized is small, as in most public health intervention studies. The method that performs consistently well is one of the Zhang and Boos extensions of the standard CMH statistic. Copyright © 2002 John Wiley & Sons, Ltd.
A graphical sensitivity analysis for clinical trials with non‐ignorable missing binary outcome
Authors: Hollis Sally
Published: December 2002

Many clinical trials are analysed using an intention‐to‐treat (ITT) approach. A full application of the ITT approach is only possible when complete outcome data are available for all randomized subjects. In a recent survey of clinical trial reports including an ITT analysis, complete case analysis (excluding all patients with a missing response) was common. This does not comply with the basic principles of ITT since not all randomized subjects are included in the analysis. Analyses of data with missing values are based on untestable assumptions, and so sensitivity analysis presenting a range of estimates under alternative assumptions about the missing‐data mechanism is recommended. For binary outcome, extreme case analysis has been suggested as a simple form of sensitivity analysis, but this is rarely conclusive. A graphical sensitivity analysis is proposed which displays the results of all possible allocations of cases with missing binary outcome. Extension to allow binomial variation in outcome is also considered. The display is based on easily interpretable parameters and allows informal examination of the effects of varying prior beliefs. Copyright © 2002 John Wiley & Sons, Ltd.
A comparison of confidence interval methods for the intraclass correlation coefficient in cluster randomized trials
Authors: Ukoumunne Obioha C.
Published: December 2002

A Correction has been published for this article in Statistics in Medicine 23(18) 2004, 2935. This study compared different methods for assigning confidence intervals to the analysis of variance estimator of the intraclass correlation coefficient (ρ). The context of the comparison was the use of ρ to estimate the variance inflation factor when planning cluster randomized trials. The methods were compared using Monte Carlo simulations of unbalanced clustered data and data from a cluster randomized trial of an intervention to improve the management of asthma in a general practice setting. The coverage and precision of the intervals were compared for data with different numbers of clusters, mean numbers of subjects per cluster and underlying values of ρ. The performance of the methods was also compared for data with Normal and non‐Normally distributed cluster specific effects. Results of the simulations showed that methods based upon the variance ratio statistic provided greater coverage levels than those based upon large sample approximations to the standard error of ρ. Searle's method provided close to nominal coverage for data with Normally distributed random effects. Adjusted versions of Searle's method to allow for lack of balance in the data generally did not improve upon it either in terms of coverage or precision. Analyses of the trial data, however, showed that limits provided by Thomas and Hultquist's method may differ from those of the other variance ratio statistic methods when the arithmetic mean differs markedly from the harmonic mean cluster size. The simulation results demonstrated that marked non‐Normality in the cluster level random effects compromised the performance of all methods. Confidence intervals for the methods were generally wide relative to the underlying size of ρsuggesting that there may be great uncertainty associated with sample size calculations for cluster trials where large clusters are randomized. Data from cluster based studies with sample sizes much larger than those typical of cluster randomized trials are required to estimate ρ with a reasonable degree of precision. Copyright © 2002 John Wiley & Sons, Ltd.
A weighted Kaplan–Meier estimator for matched data with application to the comparison of chemotherapy and bone‐marrow transplant in leukaemia
Authors: Galimberti Stefania , Sasieni Peter , Valsecchi Maria Grazia
Published: December 2002

Studies on the comparison of transplantation with respect to standard therapy present a number of statistical challenges: they are usually not randomized, often retrospective (based on registry data) and the treatment assignment is time dependent (waiting time to transplant). Matching on known prognostic factors and waiting time to transplant can be used to select appropriate samples for the analysis. When a variable number of patients treated with conventional therapy matches each transplanted patient, the standard estimating and testing procedures need to be modified in order to account for the fact that matched data are highly stratified, with strata containing a few, possibly censored, observations. A weighted version of the Kaplan–Meier estimator, which accounts for a variable proportion of matching, is proposed and its statistical properties are studied. The problem of the comparison of the survival experience in the two treatment groups is also considered. Two tests, based on the distance between the survival estimates calculated at a prefixed time point, are examined and their behaviour is evaluated through simulations. The procedures proposed here are applied to data collected from an Italian study whose aim was the evaluation of bone marrow transplant, as compared to intensive chemotherapy, in the cure of paediatric acute lymphoblastic leukaemia. Copyright © 2002 John Wiley & Sons, Ltd.
Multicollinearity in prognostic factor analyses using the EORTC QLQ‐C30: identification and impact on model selection
Authors: Van Steen Kristel , Curran Desmond , Kramer Jocelyn , Molenberghs Geert , Van Vreckem Ann , Bottomley Andrew , Sylvester Richard
Published: December 2002

Clinical and quality of life (QL) variables from an EORTC clinical trial of first line chemotherapy in advanced breast cancer were used in a prognostic factor analysis of survival and response to chemotherapy. For response, different final multivariate models were obtained from forward and backward selection methods, suggesting a disconcerting instability. Quality of life was measured using the EORTC QLQ‐C30 questionnaire completed by patients. Subscales on the questionnaire are known to be highly correlated, and therefore it was hypothesized that multicollinearity contributed to model instability. A correlation matrix indicated that global QL was highly correlated with 7 out of 11 variables. In a first attempt to explore multicollinearity, we used global QL as dependent variable in a regression model with other QL subscales as predictors. Afterwards, standard diagnostic tests for multicollinearity were performed. An exploratory principal components analysis and factor analysis of the QL subscales identified at most three important components and indicated that inclusion of global QL made minimal difference to the loadings on each component, suggesting that it is redundant in the model. In a second approach, we advocate a bootstrap technique to assess the stability of the models. Based on these analyses and since global QL exacerbates problems of multicollinearity, we therefore recommend that global QL be excluded from prognostic factor analyses using the QLQ‐C30. The prognostic factor analysis was rerun without global QL in the model, and selected the same significant prognostic factors as before. Copyright © 2002 John Wiley & Sons, Ltd.
Use of the mean, hot deck and multiple imputation techniques to predict outcome in intensive care unit patients in Colombia
Authors: Pérez Adriana , Dennis Rodolfo J. , Gil Jacky F. A. , Rondón Martín A. , López Adriana
Published: December 2002

A cohort of intensive care unit (ICU) patients in 20 Colombian ICUs is used to describe the application of three imputation techniques: single, hot deck and multiple imputation. These strategies were used to impute the missing data in the variables used to construct APACHE II scores, a scoring system for the ICU patients that provides an unbiased standardized estimate of the probability of hospital death. Imputed APACHE II scores were then used in the APACHE II model to estimate adjusted hospital mortality rates. The area under the receiver operating characteristic (ROC) curve was used to compare imputation strategies with respect to predictive power. While statistically significant differences were found for the area under the ROC curve, these differences were not clinically significant. Copyright © 2002 John Wiley & Sons, Ltd.
Predicting time to prostate cancer recurrence based on joint models for non‐linear longitudinal biomarkers and event time outcomes
Authors: Pauler Donna K. , Finkelstein Dianne M.
Published: December 2002

Biological markers that are both sensitive and specific for tumour regrowth or metastasis are increasingly becoming available and routinely monitored during the regular follow‐up of patients treated for cancer. Obtained by a simple blood test, these markers provide an inexpensive non‐invasive means for the early detection of recurrence (or progression). Currently, the longitudinal behaviour of the marker is viewed as an indicator of early disease progression, and is applied by a physician in making clinical decisions. One marker that has been studied for use in both population screening for early disease and for detection of recurrence in prostate cancer patients is PSA. The elevation of PSA levels is known to precede clinically detectable recurrence by 2 to 5 years, and current clinical practice often relies partially on multiple recent rises in PSA to trigger a change in treatment. However, the longitudinal trajectory for individual markers is often non‐linear; in many cases there is a decline immediately following radiation therapy or surgery, a plateau during remission, followed by an exponential rise following the recurrence of the cancer. The aim of this article is to determine the multiple aspects of the longitudinal PSA biomarker trajectory that can be most sensitive for predicting time to clinical recurrence. Joint Bayesian models for the longitudinal measures and event times are utilized based on non‐linear hierarchical models, implied by unknown change‐points, for the longitudinal trajectories, and a Cox proportional hazard model for progression times, with functionals of the longitudinal parameters as covariates in the Cox model. Using Markov chain Monte Carlo sampling schemes, the joint model is fit to longitudinal PSA measures from 676 patients treated at Massachusetts General Hospital between the years 1988 and 1995 with follow‐up to 1999. Based on these data, predictive schemes for detecting cancer recurrence in new patients based on their longitudinal trajectory are derived. Copyright © 2002 John Wiley & Sons, Ltd.