bluuebunny/crossref_metadata_2025 huggingface dataset:
28‐noded hexahedral isoparametric element for analysis of contact problems
Authors: Buczkowski Ryszard , Gabbert Ulrich
Published: January 2004

The previously introduced 21‐node three‐dimensional solid element (Commun. Numer. Meth. Engng 1998; 14: 681–692) fulfills the physical contact requirements properly. In dynamic explicit impact problems, however, due to non‐positive nodal masses on the contact face the 21‐node element must be used with care. To overcome this problem, a 28‐node transient element as a certain case of a degenerated 20‐node standard hexahedral element of the serendipity family is investigated. Construction of the shape functions of the transition element is described. This element is established by putting 16 nodes on the top or bottom face of the basic 20‐node solid element for an effective connection between contact region (28‐node elements) and rest of the structure (20‐node elements). Comparisons with results calculated for the 3D‐contact problem using the combination of the 21‐node and 20‐node elements prove high accuracy and overall superiority of the present method. Two numerical examples are selected to demonstrate applicability of the new element proposed. Copyright © 2004 John Wiley & Sons, Ltd.
A simple robust numerical integration algorithm for a power‐law visco‐plastic model under both high and low rate‐sensitivity
Authors: de Souza Neto E. A.
Published: January 2004

This note describes a simple and extremely robust algorithm for numerical integration of the power‐law‐type elasto‐viscoplastic constitutive model discussed by Perić (Int. J. Num. Meth. Eng. 1993; 36: 1365–1393). As the rate‐independent limit is approached with increasing exponents, the evolution equations of power‐law‐type models are known to become stiff. Under such conditions, the solution of the implicitly discretized viscoplastic evolution equation cannot be easily obtained by standard root‐finding algorithms. Here, a procedure which proves to be remarkably robust under stiff conditions is obtained by means of a simple logarithmic mapping of the basic backward Euler time‐discrete equation for the incremental plastic multiplier. The logarithm‐transformed equation is solved by the standard Newton–Raphson scheme combined with a simple bisection procedure which ensures that the iterative guesses for the equation unknown (the incremental equivalent plastic strain) remain within the domain where the transformed equation makes sense. The resulting implementation can handle small and large (up to order 106) power‐law exponents equally. This allows its effective use under any situation of practical interest, ranging from high rate‐sensitivity to virtually rate‐independent conditions. The robustness of the proposed scheme is demonstrated by numerical examples. Copyright © 2003 John Wiley & Sons, Ltd.
Energy release control for numerical simulations of failure in quasi‐brittle solids
Authors: Gutiérrez Miguel A.
Published: January 2004

A path‐following constraint is developed which is based on the energy release during failure. This makes it applicable to the simulation of quasi‐brittle materials when no previous knowledge is available on the failure behaviour of a body and, consequently, indirect displacement control methods like CMOD cannot be applied. The constraint is derived from the first principle of thermodynamics for a finite‐element discretization of a solid with a continuum damage model. The performance of the constraint is demonstrated by means of a bending test on a single‐edge‐notched beam. Copyright © 2003 John Wiley & Sons, Ltd.
Modelling infinite‐conductivity line sinks in the complex variable boundary‐element method
Authors: Sato Kozo
Published: January 2004

A numerical procedure for modelling infinite‐conductivity line sinks in the complex variable boundary‐element (BEM) method is outlined. Through a test problem, it is confirmed that the proposed model works and that an appropriate segmentation scheme is important for accurate computations. Copyright © 2003 John Wiley & Sons, Ltd.
A radial basis meshless method for solving inverse boundary value problems
Authors: Li Jichun
Published: January 2004

In this paper, we develop a new non‐iterative numerical method for solving inverse boundary value problems for linear elliptic equations of second order. Here we assume that the Dirichlet and Neumann boundary conditions are given only on part of the domain, we have to reconstruct the solution and its normal derivative on the unaccessible part of the domain, which is the well‐known ill‐posed Cauchy problem. We propose to solve such inverse problems directly by using the recently developed radial basis meshless method. Several numerical experiments are given to demonstrate the effectiveness and efficiency of the proposed method. Copyright © 2003 John Wiley & Sons, Ltd.
A note on integration schemes for the microplane model of the mechanical behaviour of concrete
Authors: Badel Pierre‐Bernard , Leblond Jean‐Baptiste
Published: January 2004

This paper discusses some aspects of the practical implementation of the very comprehensive ‘microplane’ model of the mechanical behaviour of concrete, proposed by Bažant and coworkers. This implementation involves numerical integration of some quantities over a hemisphere. The solution usually adopted is Gaussian integration with 21 or 28 points. However, Qiu and Crouch recently showed that this may be insufficient, and proposed to use more Gauss points. However, numerical experience shows that this strategy is relatively inefficient. Also, generating Gaussian integration schemes of high order on a hemisphere is a cumbersome task. An alternative integration scheme is proposed, which combines numerical efficiency and ease of automatic generation of more and more refined integration formulae. Copyright © 2004 John Wiley & Sons, Ltd.
Application of the additive Schwarz method to large scale Poisson problems
Authors: Singh K. M. , Williams J. J. R.
Published: January 2004

This paper presents an application of the additive Schwarz method to large scale Poisson problems on parallel computers. Domain decomposition in rectangular blocks with matching grids on a structured rectangular mesh has been used together with a stepwise approximation to approximate sloping sides and complicated geometric features. A seven‐point stencil based on central difference scheme has been used for the discretization of the Laplacian for both interior and boundary grid points, and this results in a symmetric linear algebraic system for any type of boundary conditions. The preconditioned conjugate gradient method has been used as an accelerator for the additive Schwarz method, and three different methods have been assessed for the solution of subdomain problems. Numerical experiments have been performed to determine the most suitable set of subdomain solvers and the optimal accuracy of subdomain solutions; to assess the effect of different decompositions of the problem domain; and to evaluate the parallel performance of the additive Schwarz preconditioner. Application to a practical problem involving complicated geometry is presented which establishes the efficiency and robustness of the method. Copyright © 2004 John Wiley & Sons, Ltd.
Combination of adaptive‐grid redistribution and embedding methods
Authors: Ameri M. , Shirani E.
Published: January 2004

The redistribution and embedding are two main adaptive‐grid methods. With use of initial structured grid, it is possible to combine these adaptive‐grid techniques. It means that before the grid becomes unstructured, we employ redistribution technique and then use embedding method. It is used to solve three model problems, transonic and supersonic inviscid flows in channels with circular arc bump and with convergent part. The Euler equations are integrated to steady state by an explicit, finite volume, Ni's Lax–Wendroff type. The combination of adaptive‐grid redistribution and embedding is complex, but it is shown in this paper that it is very efficient and worth to use it in large CPU time consuming problems. The results also show that the combination requires less grid points and therefore less memory space for prescribed accuracy. Copyright © 2004 John Wiley & Sons, Ltd.
Zero energy‐error mechanism of the combined hybrid method and improvement of Allman's membrane element with drilling d.o.f.'s
Authors: Zhou Tian‐Xiao , Xie Xiao‐Ping
Published: January 2004

By following the geometric point of view in mechanics combined with mathematical analysis, a novel expression of the combined hybrid variational principle is introduced to clarify its intrinsic mechanism of enhancing coarse‐mesh‐accuracy and stability of lower‐order displacement schemes. It is pointed out that the combined hybrid scheme achieving energy optimization leads to enhancement of accuracy at coarse meshes. By this mechanism's bringing to light the two factors (adding energy‐compatible bubbles and adjusting the combination parameter α) governing this enhancement, this paper presents a sound procedure for optimizing a combined hybrid scheme in a manner independent of the choice of assumed stresses. The effectiveness of the procedure is verified by improving Allman's membrane element with drilling d.o.f.'s. The numerical benchmark tests indicate that the combined hybrid counterpart of Allman's membrane element is capable of attaining the degree of accuracy of linear strain (i.e. 2‐order) element at coarse meshes without distortion. Copyright © 2004 John Wiley & Sons, Ltd.
Exact steady periodic water waves with vorticity
Authors: Constantin Adrian , Strauss Walter
Published: January 2004

We consider the classical water wave problem described by the Euler equations with a free surface under the influence of gravity over a flat bottom. We construct two‐dimensional inviscid periodic traveling waves with vorticity. They are symmetric waves whose profiles are monotone between each crest and trough. We use bifurcation and degree theory to construct a global connected set of such solutions. © 2003 Wiley Periodicals, Inc.
Exact and explicit expressions for the small‐signal dynamics and frequency response of switching converters
Authors: Ng S. W. , Lee Y. S.
Published: January 2004

In this paper, exact and explicit expressions for the dynamics and small‐signal responses of piecewise linear switching converters are derived. The results are very useful for the exact simulation and analysis of converter circuits. These expressions can also be used to develop simplified (approximate) models of converters for practical design purposes. An example is given to show that the well‐known state‐space averaging model is in fact the first‐order approximation of our exact model. Copyright © 2004 John Wiley & Sons, Ltd.
DAN directs endolymphatic sac and duct outgrowth in the avian inner ear
Authors: Gerlach‐Bank Lisa M. , Cleveland Amanda R. , Barald Kate F.
Published: January 2004

Bone morphogenetic proteins (BMPs) are expressed in the developing vertebrate inner ear and participate in inner ear axial patterning and the development of its sensory epithelium. BMP antagonists, such as noggin, chordin, gremlin, cerberus, and DAN (differential screening‐selected gene aberrative in neuroblastoma) inhibit BMP activity and establish morphogenetic gradients during the patterning of many developing tissues and organs. In this study, the role of the BMP antagonist DAN in inner ear development was investigated. DAN‐expressing cell pellets were implanted into the otocyst and the periotic mesenchyme to determine the effects of exogenous DAN on otic development. Similar to the effects on the inner ear seen after exposure of otocysts to the BMP4 antagonist noggin, semicircular canals were truncated or eliminated based upon the site of pellet implantation. Unique to the DAN implantations, however, were effects on the developing endolymphatic duct and sac. In DAN‐treated inner ears, endolymphatic ducts and sacs were merged with the crus or grew into the superior semicircular canal. Both the canal and endolymphatic duct and sac effects were rescued by joint implantation of BMP4‐expressing cells. Electroporation of DAN antisense morpholinos into the epithelium of stage 15–17 otocysts, blocking DAN protein synthesis, resulted in enlarged endolymphatic ducts and sacs as well as smaller semicircular canals in some cases. Taken together, these data suggest a role for DAN both in helping to regulate BMP activity spatially and temporally and in patterning and partitioning of the medial otic tissue between the endolymphatic duct/sac and medially derived inner ear structures. Developmental Dynamics 229:219–230, 2004. © 2003 Wiley‐Liss, Inc.
Endothelium‐specific Cre recombinase activity in flk‐1‐Cre transgenic mice
Authors: Licht Alexander H. , Raab Sabine , Hofmann Ursula , Breier Georg
Published: January 2004

The use of the Cre‐loxP recombination system allows the conditional inactivation of genes in mice. The availability of transgenic mice in which the Cre recombinase expression is highly cell type specific is a prerequisite to successfully use this system. We previously have characterized regulatory regions of the mouse flk‐1 gene sufficient for endothelial cell‐specific expression of the LacZ reporter gene in transgenic mice. These regions were fused to the Cre recombinase gene, and transgenic mouse lines were generated. In the resulting flk‐1‐Cre transgenic mice, specificity of Cre activity was determined by cross‐breeding with the reporter mouse lines Rosa26R or CAG‐CAT‐LacZ. We examined double‐transgenic mice at different stages of embryonic development (E9.5–E16.5) and organs of adult animals by LacZ staining. Strong endothelium‐specific staining of most vascular beds was observed in embryos older than E11.5 in one or E13.5 in a second line. In addition, the neovasculature of experimental BFS‐1 tumors expressed the transgene. These lines will be valuable for the conditional inactivation of floxed target genes in endothelial cells of the embryonic vascular system. Developmental Dynamics 229:312–318, 2004. © 2004 Wiley‐Liss, Inc.
Differentiation trapping screen in live culture for genes expressed in cardiovascular lineages
Authors: Chen Weisheng V. , Chen Zhi
Published: January 2004

We have developed a gene trap vector that transduces an EGFP‐neo fusion gene (Eno) to monitor the expression of trapped genes in living cells and embryos. Upon in vitro differentiation, most gene‐trapped embryonic stem (ES) cell clones exhibited detectable green fluorescence in various specialized cell types, which can be followed in the live culture in real time. Populations of ES cell‐derived cardiomyocytes, smooth muscle cells, vascular endothelial cells, and hematopoietic cells were readily recognized by their distinctive morphologies coupled with unique activities, allowing efficient screening for clones with trapped genes expressed in cardiovascular lineages. Applying G418 selection in parallel differentiation cultures further increased detection sensitivity and screening throughput by enriching reporter‐expressing cells with intensified green fluorescent protein signals. Sequence analyses and chimera studies demonstrated that the expression of trapped genes in vivo closely correlated with the observed lineage specificity in vitro. This provides a strategy to identify and mutate genes expressed in lineages of interest for further functional studies. Developmental Dynamics 229:319–327, 2004. © 2004 Wiley‐Liss, Inc.
Calcium transients regulate patterned actin assembly during myofibrillogenesis
Authors: Li Hongyan , Cook John D. , Terry Monica , Spitzer Nicholas C. , Ferrari Michael B.
Published: January 2004

The highly ordered arrangement of sarcomeric myosin during striated muscle development requires spontaneous calcium (Ca2+) transients. Here, we show that blocking transients also compromises patterned assembly of actin thin filaments, titin, and capZ. Because a conserved temporal assembly pattern has been described for these proteins, selective inhibitors of either thick or thin filament formation were used to determine their relative temporal interdependencies. For example, inhibition of myosin light chain kinase (MLCK) by application of a specific inhibitory peptide or phorbol myistate acetate (PMA) disrupts myosin assembly without significantly affecting formation of actin bands. The MLCK inhibitor ML‐7, however, disrupted actin as well as myosin. Surprisingly, agents that interfere with actin dynamics, such as cytochalasin D, produced only minor organizational disruptions in actin, capZ, and titin staining. However, cytochalasin D and other actin disrupting compounds significantly perturbed myosin organization. The results indicate that (1) Ca2+ transients regulate one or more of the earliest steps in sarcomere formation, (2) mature actin filaments can assemble independently of myosin band formation, and (3) myosin thick filament assembly is extremely sensitive to disruption of either the actin or titin filament systems. Developmental Dynamics 229:231–242, 2004. © 2003 Wiley‐Liss, Inc.
Long‐term culture of human embryonic stem cells in feeder‐free conditions
Authors: Rosler Elen S. , Fisk Gregory J. , Ares Ximena , Irving John , Miura Takumi , Rao Mahendra S. , Carpenter Melissa K.
Published: January 2004

We have demonstrated previously that human embryonic stem (hES) cells possess a characteristic morphologic, antigenic, and molecular profile that can be used to assess the state of ES cells (Carpenter et al., [2004] Dev Dyn 229:243–258). In this manuscript, we have examined the long‐term stability of three hES cell lines in feeder‐free culture. We demonstrate that the expression of antigens and transcription factors, telomerase activity, telomere length, and karyotype appear stable for all three hES cell lines after continuous culture for over 1 yr. All three lines retained pluripotent differentiation in vitro and in vivo. Although hES cell lines were remarkably stable over the period of analysis, a detailed quantitative analysis of antigen expression by flow cytometry and gene expression by microarray suggested that cell lines show subtle differences in the expression of small subsets of genes upon long‐term culture. Developmental Dynamics 229:259–274, 2004. © 2003 Wiley‐Liss, Inc.
Properties of four human embryonic stem cell lines maintained in a feeder‐free culture system
Authors: Carpenter Melissa K. , Rosler Elen S. , Fisk Gregory J. , Brandenberger Ralph , Ares Ximena , Miura Takumi , Lucero Mary , Rao Mahendra S.
Published: January 2004

Several laboratories have begun evaluating human ES (hES) cell lines; however, direct comparisons between different hES cell lines have not been performed. We have characterized the properties of four human cell lines maintained in feeder‐free culture conditions. Quantitative assessment of surface markers, microarray analysis of gene expression patterns, expression of SOX‐2, UTF‐1, Rex‐1, OCT3/4, CRIPTO, and telomerase activity demonstrated similar patterns in all hES cell lines examined. Undifferentiated hES cells do not respond to neurotransmitters such as acetylcholine, glutamate, and gamma‐aminobutyric acid. In addition, the undifferentiated hES cells possess gap junctions. Although similarities in marker expression were observed, allotyping showed that all four lines have a distinct HLA profile, predicting differences in transplantation responses. These data provide the first detailed comparison of different hES cell lines and demonstrate remarkable similarities among lines maintained in identical culture conditions. Developmental Dynamics 229:243–258, 2004. © 2003 Wiley‐Liss, Inc.
Zinc finger protein Zac1 is expressed in chondrogenic sites of the mouse
Authors: Tsuda Takeshi , Markova Dessislava , Wang Hui , Evangelisti Lucia , Pan Te‐Cheng , Chu Mon‐Li
Published: January 2004

Zac1 is a zinc finger transcription factor that elicits antiproliferative activity and is a potential tumor suppressor gene. Through a detailed spatiotemporal study by in situ hybridization of mouse embryos, we have found that Zac1 transcript is predominantly localized in developing chondrogenic tissue, in addition to the central nervous system as reported elsewhere. Zac1 is also expressed transiently in the myocardium, skeletal muscle, and basal aspect of the stratified embryonic epithelia. During cartilage development, the pattern of Zac1 expression is in close accordance with the distribution of type II collagen mRNA in mesenchymal condensation and prehypertrophic chondrocytes. In mouse ATDC5 cells undergoing in vitro chondrogenesis, the Zac1 mRNA is up‐regulated in parallel with genes expressed in precartilage but the Zac1 expression is low when type II collagen mRNA is markedly increased in differentiated cells. Together, these results suggest that Zac1 is a potential regulatory gene involved in chondrogenic differentiation. Developmental Dynamics 229:340–348, 2004. © 2004 Wiley‐Liss, Inc.
Survey of forkhead domain encoding genes in the Drosophila genome: Classification and embryonic expression patterns
Authors: Lee Hsiu‐Hsiang , Frasch Manfred
Published: January 2004

Genetic approaches in Drosophila led to the identification of Forkhead, the prototype of forkhead domain transcription factors that are now known to comprise an evolutionarily conserved family of proteins with essential roles in development and differentiation. Sequence analysis of the recently published genomic scaffold sequence from Drosophila melanogaster has allowed us to determine the presumably full complement of forkhead domain encoding genes in this species. We show herein that the Drosophila genome contains 17 forkhead domain encoding genes; 13 of these genes have orthologs in chordate species, and their products can be assigned to 10 of the 17 forkhead domain subclasses known from chordates. One Drosophila forkhead domain gene only has a Caenorhabditis elegans ortholog and may represent a subclass that is absent in chordates, while the remaining three cannot be classified. We present the mRNA expression patterns of seven previously uncharacterized members of this gene family and show that they are expressed in tissues from all three germ layers, including central and peripheral nervous system, epidermis, salivary gland primordia, endoderm, somatic mesoderm, and hemocyte progenitors. Furthermore, the expression patterns of two of these genes, fd19B and fd102C, suggest a role for them as gap genes during early embryonic head segmentation. Developmental Dynamics 229:357–366, 2004. © 2004 Wiley‐Liss, Inc.
Tracing of Xenopus tropicalis germ plasm and presumptive primordial germ cells with the Xenopus tropicalis DAZ‐like gene
Authors: Sekizaki Hiroyuki , Takahashi Shuji , Tanegashima Kousuke , Onuma Yasuko , Haramoto Yoshikazu , Asashima Makoto
Published: January 2004

A gamete is derived initially from a presumptive primordial germ cell (pPGC) and transmits genetic potential to the next generation. Xenopus tropicalis, which is a close relative of Xenopus laevis, has a diploid genome and advantages for genetic and genomic research; however, little is known about the developmental mechanism of its germinal lineage. Here, we identified the Xenopus tropicalis DAZ‐like gene (Xtdazl), which encodes RNA‐binding proteins homologous to Xdazl in Xenopus laevis and examined the expression patterns of Xtdazl transcripts during embryogenesis. In this work, we showed that Xtdazl mRNA was localized in the germ plasm and was expressed from the previtellogenic oocyte to early tadpole, in testis and ovary. The same localization patterns have been reported in Xenopus laevis germ plasm and pPGCs. These results indicate that Xtdazl mRNA is the first specific marker of germ plasm and pPGCs in Xenopus tropicalis and is very useful to trace Xenopus tropicalis pPGCs, including germ plasm until the early tadpole stage. Developmental Dynamics 229:367–372, 2004. © 2004 Wiley‐Liss, Inc.
Identification of a novel left–right asymmetrically expressed gene in the mouse belonging to the BPI/PLUNC superfamily
Authors: Hou Juan , Yashiro Kenta , Okazaki Yasushi , Saijoh Yukio , Hayashizaki Yoshihide , Hamada Hiroshi
Published: January 2004

In the process of left–right (L‐R) axis formation in the mouse, the node plays a critical role as a structure where the initial breaking of L‐R symmetry occurs. Here, we report on the gene LPlunc1, a member of BPI/PLUNC gene superfamily, which is asymmetrically expressed in the developing mouse node. LPlunc1 protein is secreted as a processed form of relative molecular mass 54K‐60K and shares sequence features with the other members of BPI/PLUNC superfamily, including the N‐terminal and C‐terminal homology domains, each of which is considered to form a lipid binding pocket. LPlunc1 is transiently expressed in the crown cells of the node asymmetrically. This expression pattern of Lplunc1 highly overlaps with that of Nodal, a major player during the L‐R formation. Interestingly, this asymmetric expression pattern is randomized in the iv mutant and reversed in the inv mutant, indicating that LPlunc1 is downstream of iv and inv. Our results suggest a link between lipid binding/transfer and the axis development. Developmental Dynamics 229:373–379, 2004. © 2004 Wiley‐Liss, Inc.
Calcineurin signaling in avian cardiovascular development
Authors: Liberatore Christine M. , Yutzey Katherine E.
Published: January 2004

Experiments were initiated in avian embryos to determine the embryonic expression of calcineurin protein phosphatase isoforms as well as to identify developmental processes affected by inhibition of calcineurin signal transduction. Chicken calcineurin A alpha (CnAα) and calcineurin A beta (CnAβ) are differentially expressed in the developing cardiovascular system, including primitive heart tube and valve primordia. Inhibition of calcineurin signaling by cyclosporin A (CsA) treatment in ovo resulted in distinct cardiovascular malformations, depending on the timing and localization of treatment. Initial formation of the heart tube was apparently normal in embryos treated with CsA from embryonic day (E)1 to E2, but hallmarks of heart failure were apparent with treatment from E2 to E3. Vascular defects were apparent in whole embryos treated on either day, but local administration of CsA directly to the forming vessels on E2 did not inhibit blood vessel formation. This observation supports an indirect effect of calcineurin inhibition on angiogenic remodeling as a result of compromised heart development. Together these studies are consistent with multiple roles for calcineurin signaling in the developing cardiovascular system. Developmental Dynamics 229:300–311, 2004.© 2003 Wiley‐Liss, Inc.
Early requirement for fgf8 function during hindbrain pattern formation in zebrafish
Authors: Wiellette Elizabeth L. , Sive Hazel
Published: January 2004

Fibroblast growth factor (FGF) signaling is required for normal development of the vertebrate brain, including the isthmus and caudal regions of the hindbrain. Recent work in zebrafish has identified a requirement for the combination of fgf3 and fgf8 functions in specification of rhombomeres 5 and 6 (r5, r6), when evaluated at mid‐ and late somitogenesis stages. However, when examined earlier in development, during early somitogenesis stages, FGF8 alone is required to initiate r5 and r6 development. Both a mutation in fgf8 and injection of fgf8‐targeted antisense morpholino‐modified oligonucleotides result in suppression of genes normally expressed in r5 and r6 by the one‐ to two‐somite stage. This expression recovers by the six‐somite stage, and we propose that this recovery is a response to activation of fgf3 and to delayed accumulation of fgf8. These data demonstrate an early, nonredundant requirement for fgf8 function in hindbrain patterning. Developmental Dynamics 229:393–399, 2004. © 2004 Wiley‐Liss, Inc.
Error patterns in word reading among primary school children: A cross‐orthographic study
Authors: Guron Louise Miller , Lundberg Ingvar
Published: January 2004

A comparative investigation of word reading efficiency indicates that different strategies may be used by English and Swedish early readers. In a first study, 328 native English speakers from UK Years 3 and 6 completed a pen‐and‐paper word recognition task (the Wordchains test). Results were analysed for frequency and type of errors committed. A sample of 123 chronological‐age‐matched Swedish children carried out the same task on a matched Swedish test. For a sub‐sample of 68 English/Swedish pairs matched on word recognition score and sex, significant differences were observed in a comparison of average and low scorers from the two language groups. The English children attempted more task items and committed more errors, while the Swedish group corrected their errors more, suggesting a difference in approach to the task. A second study of a larger Swedish sample (241 participants) found the same pattern of errors as Study 1. The implications of these findings are discussed in relation to the effects of orthographic depth and morphemic complexity. Copyright © 2004 John Wiley & Sons, Ltd.
Proposal of a shaped optical antenna realized as a lower‐order aspheric surface approximation
Authors: Uo Toyoaki , Toda Tomoaki , Takano Tadashi
Published: January 2004

Optical antennas used for point‐to‐point communication in optical intersatellite communication must have high aperture efficiency. By means of the reflector surface shaping method, it is possible to design an antenna with high aperture efficiency and low side lobes. However, the reflector surface becomes a nonspherical surface described by a higher‐order polynomial and is very susceptible to errors in the manufacturing process. This paper proposes a shaped optical antenna whose shaped surface is described without a higher‐order polynomial but with a nonspherical surface of the lowest order. The error characteristics are compared with those of the conventional shaped antenna. It is demonstrated that the proposed shaped optical antenna not only is more easily fabricated but also possesses almost identical error robustness to a nonshaped antenna. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 62–74, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10145
Application of modal polarization current model method to dielectric resonator antennas
Authors: Inoue Takashi , Inagaki Naoki , Kikuma Nobuyoshi
Published: January 2004

The polarization current model method (PCMM), a volume integral equation method, has been used for the analysis of electromagnetic field scattering by a dielectric body and of radiation from a dielectric body. The authors have proposed the total domain method of moments, namely, the mode expansion polarization current model method (M‐PCMM), in which the polarization current density is expanded in spherical wave functions, and have applied it to the analysis of dielectric body scattering. In the present paper, this M‐PCMM is applied to the analysis of dielectric resonator antennas (DRAs) in which a rectangular dielectric body is excited by a wire probe. The results are compared with the measured data. They are also compared with those obtained by Ansoft's HFSS, in which the finite element method is used for analysis by an approximation using a dielectric waveguide model. The three methods of analysis provide sufficient results for the resonant frequencies and the unloaded Qs. In addition, the M‐PCMM and HFSS provide results close to the measured values of the gain and the radiation efficiency. It is confirmed that a slight change of the spacing between the dielectric body and the external probe can affect the DRA characteristics significantly. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 42–51, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10152
Loss‐resilient layered multicast using forward error correction
Authors: Ichikawa Toshikazu , Asatani Koichi , Tominaga Hideyoshi
Published: January 2004

Rate control for multicasting is required for multipoint distribution of video over the Internet. In this paper, we focus on the video image quality during playback and propose layered multicast rate control using error correcting codes. First, we identify the severe degradation problem in the playback quality of the transmitted video due to packet losses resulting from congestion when transmitting high‐quality video using conventional techniques. To address this problem, we propose a method adopting the parity generated by the error correcting code in addition to the rate control in order to maintain the video image quality. We perform a simulation to show that the proposed method enables rate control that prevents the degradation in quality caused by congestion. Furthermore, we find the optimum block size of the error correcting code with respect to the control latency, and quantitatively evaluate the packet loss ratio and transmission efficiency with respect to the system scale and the transmission efficiency with respect to the layer increment ratio. We also develop a layer coding technique and study the optimum error correcting code in real‐time processing by the software and its implementability. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 29–41, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10156
An authentication architecture for collaboration among agents in ad hoc networks
Authors: Okataku Yasukuni , Yoshioka Nobukazu , Honiden Shinichi
Published: January 2004

This paper proposes an authentication architecture for collaboration among agents in a network environment without security assurance. The architecture requires that there should exist at least one secure node (oasis node). The oasis node generates the same number of authentication codes as the number of objects of authentication, using random numbers and agent information, and distributes the codes among the agents. The agents gather at the specified oasis node and obtain verification by the oasis node, based on the distributed random value and the authentication code. In the authentication architecture proposed in this paper, the random number and the authentication code are publicized information which can be compromised by eavesdropping. But the algorithm for generation and verification of the authentication code is not publicized. The architecture is suited for handling authentication processing in ad hoc collaboration among an unspecified number of agents. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 87(5): 11–19, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10165
Development of MIM/Ta2O5capacitor process for 0.10‐µm DRAM
Authors: Asano Isamu , Nakamura Yoshitaka , Hiratani Masahiko , Nabatame Toshihide , Iijima Shinpei , Saeki Tomonori , Futase Takuya , Yamomoto Satoshi , Saito Tatsuyuki , Sekiguchi Toshihiro
Published: January 2004

As the fabrication dimension becomes smaller, it becomes increasingly difficult to ensure storage capacitance for DRAM. For this reason, a capacitor process using high‐permittivity insulating films is strongly desired. In the research reported here, an MIM/tantalum pentoxide capacitor process is developed with ruthenium as an electrode material. The ruthenium CVD technique, the use of amorphous tantalum nitride as anti‐oxide barrier metal, and a contamination elimination process using periodic acid have been developed. By packaging as 0.13‐µm DRAM, capacitance performance equivalent to silica film is realized with a film thickness of 0.8 nm. The process is considered to be applicable to 0.10‐µm DRAM. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(2): 26–36, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10111
New delta arranged cell configuration of AC plasma display “DIA‐PDP” for high luminous efficiency and high resolution
Authors: Harada Shigeki , Yura Shinsuke , Morikawa Kazutoshi , Sano Ko
Published: January 2004

A new delta arranged cell‐configured AC plasma display (DIA‐PDP) was proposed, and a prototype 46‐inch diagonal panel was fabricated. The DIA‐PDP has two features. The first feature is an improved luminous efficiency. This is possible because nondischarge cells are formed in the panel and a black layer is formed on these cells. Since the light from the discharge cells does not reach the nondischarge cells, even if a black layer is provided on the nondischarge cells, the panel reflectance can be reduced without lowering the luminance. When compared under the condition of a constant set reflectivity, the luminous efficiency improves. A 33% improvement over the conventional ratio was verified for the 46‐inch panel. The second feature is improved vertical resolution. In the delta configuration, the subpixels are arranged at half the pitch of the scanning lines. By combining this configuration with an interlaced drive, the vertical resolution can be improved. To increase the size of a PDP using a lattice rib, we introduced a new rib forming technology and improved the exhaust conductance. Previously, the manufacturing steps increased to form the exhaust path in the lattice rib. In the new rib forming method, the exhaust conductance was successfully improved without increasing the number of manufacturing steps only for forming the crossing ribs in the nondischarge cells and by producing height differences caused by thermal shrinkage. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(2): 9–17, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10169
Practical speaker‐independent voice recognition using segmental features
Authors: Kimura Tatsuya , Ashida Akira , Niyada Katsuyuki
Published: January 2004

This paper reports a practical method that achieves speaker‐independent large‐vocabulary voice recognition with high accuracy and high noise immunity but with small computational complexity. The first feature of the method is that highly accurate recognition is realized by using an acoustic model in which the input consists of the segmental features formed by the analysis parameters of multiple frames. The second feature is that the likelihood corresponding to the output probability of each state of the acoustic model is calculated by a linear expression with the input parameter vector as the variable. The linear expression is derived from the equal‐covariance assumption. This linear expression reduces the computational complexity and the required memory capacity even if segmental features are used, without degrading recognition performance. The third feature is that a stable word spotting function detects correct solution candidates from the noise interval by including the idea of the a posteriori probability in the likelihood calculation. This word spotting function allows voice recognition which is robust to noise to be realized. The effectiveness of the proposed system was demonstrated in a recognition experiment with superimposed interior noise of a running vehicle. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(2): 73–81, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.10217
Selective image‐sharpness enhancement by coupled nonlinear reaction‐diffusion time‐evolution equations and its application to suppression of breathing distortions in moving pictures
Authors: Saito Takahiro , Satsumabayashi Jun , Komatsu Takashi
Published: January 2004

The authors describe a technique for selectively sharpening only edges that were blurred due to various causes without making interference factors such as random noise more conspicuous. The selective sharpening technique described in this paper is implemented as an iterative updating nonlinear algorithm obtained by discretizing a type of nonlinear reaction‐diffusion time‐evolution equations. The update terms of this algorithm consist of a quadratic nonlinear smoothing term, reaction term, and overshooting term. By performing quantitative evaluation experiments, the authors showed that the proposed technique has significantly better selective sharpness enhancement capabilities than existing sharpness enhancement techniques such as the peaking method. In addition, the authors introduced a processing parameter adaptive control method in the proposed technique and applied it to the suppression of breathing distortions in video sequences. Breathing distortions, which are video sequence distortions that often appear in old films, are time‐varying blurring distortions that occur due to temporal variations of the focus. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(5): 33–47, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10086
Software safety assessment based on a subordinated Markov chain model
Authors: Ito Masaki , Okamura Hiroyuki , Dohi Tadashi
Published: January 2004

Software safety can be defined as the property such that no situation inducing a hazard (dangerous condition) is created during the intended period under a specified environment when the software executes a predetermined function. In this paper, by considering the correlation in regard to the impact of software faults a new software safety assessment model based on a subordinated Markov chain is proposed. The goodness‐of‐fit is investigated for the software fault detection data observed in the actual test process, and we show the effectiveness of the proposed model in software safety evaluation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(5): 24–32, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10097
A generation method of orthogonal periodic complex number sequence sets with lowest peak of cross‐correlation for any period based on chirp sequences
Authors: Ohue Kenji
Published: January 2004

In this paper, we propose a new generation method of orthogonal periodic complex number sequence sets based on chirp sequences that can derive the orthogonal periodic complex number sequence set having the minimum cross‐correlation peak for any period. First, we use the Ohue–Okahisa Conjecture that is proven in a practical range related to the orthogonal periodic polyphase sequence obtained by taking the inverse discrete Fourier transform of a chirp sequence to derive the relationship between the period N having the minimum peak of the cross‐correlation and the chirp sequence parameter R, and clearly explain a generation method of an orthogonal periodic complex number sequence pair having the minimum cross‐correlation peak for any period. Next, we present a generation method of the orthogonal periodic complex number sequence set having the minimum cross‐correlation peak for any two sequences in the set. The dimension of this set is clearly equal to the minimum prime factor of the period N. Furthermore, we present a generation method of the orthogonal periodic polyphase sequence set having the minimum cross‐correlation peak for any period and show that the dimension of this set becomes a value 1 less than the minimum prime factor of period N. We show that this generation method can derive the orthogonal periodic complex number sequence set having the minimum cross‐correlation peak for periods that could not be generated by conventional techniques and can derive the orthogonal periodic polyphase sequence set demonstrated previously. Finally, we present a generation example of the orthogonal periodic sequence set having the minimum cross‐correlation peak and clearly show that the orthogonal periodic complex number sequence set and orthogonal periodic polyphase sequence set having the minimum cross‐correlation peak can be generated. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(5): 1–11, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10129
Effects of observation of robot–robot communication on human–robot communication
Authors: Kanda Takayuki , Ishiguro Hiroshi , Ono Tetsuo , Imai Michita , Nakatsu Ryohei
Published: January 2004

This paper proposes a human–robot communication system based on observations of robot–robot conversations to encourage humans to consider robots as natural targets for communication. In the proposed system, when nearby robots are communicating, voices and gestures are used to indicate that the robots are conversing with each other. When humans in the vicinity observe a robot building a relationship by interacting with another robot or the surrounding environment, they regard robots as equal targets for communication and build relationships with robots or carry out natural communications with robots. We used robots with sufficient body expression capabilities to actually implement a robot system that enabled communications according to robot–robot conversations or situations. This paper reports on a robot system that implements both of these kinds of robot–robot conversations and human–robot conversations and verifies the effects of the observation of robot–robot conversations through psychological experiments. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(5): 48–58, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10171
Texture mapping method from image streams captured by free camerawork
Authors: Sato Hiroyuki , Wu Weiguo , Yokoyama Atsushi , Akatsuka Takao
Published: January 2004

The authors propose a method to reproduce surface textures by mapping images used in shape restoration as textures when generating a three‐dimensional computer graphic image after restoring a three‐dimensional shape from multi‐viewpoint data of a real‐world model. In the past, an image used as a texture had to be captured under the same lighting conditions and at the same spatial resolution as its source. In this paper, the authors consider a method to select and correct an optimal image from among images captured using free camerawork, and then use it for mapping. In other words, the authors take into consideration the distance between the patch surface and points of capture, while at the same time comparing the orientation of the patch surfaces which comprise a three‐dimensional object and the orientation of the camera at the point from which it takes pictures. As a result, optimal pictures can be selected even when the distance to the subject or the position of the camera changes. In addition, by matching the pixel values distributed along the shared boundaries among adjacent patch surfaces, errors that may exist in the mapping between the patch surface and texture image can be corrected. Using their method, the authors perform verification experiments on a three‐dimensional shape obtained using the factorization method and achieve good results. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(5): 70–81, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10173