bluuebunny/crossref_metadata_2025_split huggingface dataset:
New compact broadband phase shifters using coupled lines
Authors: Han Sang‐Min , Kwon Koo Hyung , Kim Young‐Sik 
Published: February 2003

AbstractThis paper presents two types of phase shifters using parallel coupled lines as compact and broadband couplers. Phase shifts are enabled by varying the varactor capacitances or by switching the PIN diode ON/OFF. Both have shown about 40% bandwidth within ±3.5° phase error. While an adjustable phase control over 65° is obtained by the phase shifter with varactor diodes, 180° is yielded by that with PIN diodes. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 399–400, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10775
Optimization of a pyramidal fly‐eye diversity receiver for optical wireless systems under the influence of multipath dispersion and background noise
Authors: Al‐Ghamdi A. G. , Elmirghani J. M. H. 
Published: February 2003

AbstractA performance analysis of an indoor optical wireless communication system has been carried out for both a conventional hybrid system and a pyramidal fly‐eye diversity receiver with different fields of view. Novel results are presented for a hybrid system that employs a diversity technique, based on a triangular pyramidal receiver under various FOVs and in the presence of directive noise sources and multipath dispersion. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 401–406, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10776
Design of miniaturized planar cross‐coupled resonator filters
Authors: Ghanem Farid , Denidni Tayeb A. , Bosisio Renato‐G 
Published: February 2003

AbstractThis paper presents a new approach for the design of a miniature microstrip cross‐coupled resonator filter. This filter has been made more compact by using cross coupling between non‐adjacent resonators and inserting parallel‐coupled lines between the ends of each resonator that are designed for reduced size. The reduced‐size resonators are integrated within a compact design to provide a λ/2 by λ/8 six‐pole filter. A novel tuning technique is used to perform fine adjustments on filter response. Results are presented to evaluate filter performance. Very close agreement is obtained between numerical and measured performance of such filters. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 406–411, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10777
Printed antenna design for broadband waveguide‐based spatial power combiners
Authors: Lukic Milan V. , Yakovlev Alexander B. , Elsherbeni Atef Z. , Smith Charles E. , Steer Michael B. 
Published: February 2003

AbstractDesign of broadband printed antennas, including the finite arrays of interacting patch, U‐strip, U‐slot, and meander slot antennas, are presented for applications in waveguide‐based spatial power combiners operating at X‐band. The effect of several antenna design parameters on antenna bandwidth performance is investigated in this paper. The antenna designs presented show significant advantages in their scattering characteristics compared to rectangular patch and slot antennas traditionally used in spatial power combiners. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 411–415, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10778
A comparison between two high‐frequency techniques applied to the analysis of on‐board antennas
Authors: Conde Olga M. , Sáez de Adana Francisco , Cátedra Manuel F. 
Published: February 2003

AbstractThis paper contrasts the solutions given by the geometrical optics‐uniform theory of diffraction (GO‐UTD) and the physical optics‐stationary phase (PO‐SPM) methods when they are applied to the problem of analysis of on‐board antennas. Results for both approximations are given for antennas on board a satellite mock‐up. Advantages and drawbacks of both methods are shown. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 415–417, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10779
Non‐empirical calculations of NMR indirect carbon–carbon coupling constants: 3. Polyhedranes
Authors: Krivdin Leonid B. 
Published: February 2003

AbstractHigh‐level ab initio calculations of carbon–carbon coupling constants were carried out in tetrahedrane, prismane and cubane using the SOPPA (Second‐Order Polarization Propagator Approach) computational scheme, in good agreement with available experimental data. It was found that SOPPA performs perfectly well in combination with Dunning's correlation‐consistent basis sets augmented with inner core functions; however, no improvement was observed on adding tight s‐functions. The utmost importance of electronic correlation effects decreasing the total values of computed J(C,C) in the title compounds by a factor of ∼2.0–2.5 was found. Unknown values of J(C,C) in the title polyhedranes were predicted with high reliability and the latter were treated in terms of s‐characters of carbon–carbon bonds based on the additive scheme of coupling pathways. All three compounds under study showed decreased s‐characters of their carbon–carbon bonds, which is the result of their remarkable steric strain. Copyright © 2003 John Wiley & Sons, Ltd.
1H, 13C, 17O NMR and quantum‐chemical study of the stereochemistry of the sulfoxide and sulfone derivatives of 3‐arylidene‐1‐thioflavan‐4‐one epoxides
Authors: Kovács József , Tóth Gábor , Simon András , Lévai Albert , Koch Andreas , Kleinpeter Erich 
Published: February 2003

AbstractThe oxidation of the trans,cis‐(2) and trans,trans‐epoxides (3) of differently substituted (Z)‐3‐arylidene‐1‐thioflavan‐4‐ones (1) with dimethyldioxirane (DMD) yielded the appropriate sulfoxides (4, 5) and sulfones (6, 7). The structures were elucidated by the extensive application of one‐ and two‐dimensional 1H, 13C and 17O NMR spectroscopy. The conformational analysis was achieved by the application of 3J(C,H) coupling constants, NOESY responses and ab initio calculations. The preferred ground‐state conformers (twisted envelope‐A, twisted envelope‐B for 6 and twisted envelope‐A, envelope‐B for 7) were obtained as global minima of the theoretical ab initio MO study and also the examination of the 17O and 13C chemical shifts, calculated for the global minima structures of the sulfone isomers by the GIAO method. Analogous results, obtained for the sulfoxide isomers (4, 5), not only led to the preferred conformers but also gave evidence for the trans arrangement of the 2‐Ph group and the oxygen atom of the SO group. Chemical shift differences between the isomers, sulfoxides and sulfones were corroborated by ab initio calculations of the anisotropic effects of the oxirane ring and the SO and SO2 groups. Copyright © 2003 John Wiley & Sons, Ltd.
A new technique for differentiating between 2J(C,H) and 3/4J(C,H) connectivities
Authors: Sprang Thomas , Bigler Peter 
Published: February 2003

AbstractWe present a new pulse sequence that yields two simultaneously detected types of long‐range correlation spectra. The one spectrum is to show all nJ(C,H) connectivities and the other is to show exclusively 2J(C,H) connectivities. The method is demonstrated by using strychnine as a test sample. A comparison with HMBC shows that the 2J(C,H)/nJ(C,H) experiment supplies a nJ(C,H) spectrum that is of equal standard with regard to sensitivity and spectral information. The additional 2J(C,H) spectrum allows the disentanglement of 2J(C,H) and nJ(C,H) signals (n > 2) in HMBC type spectra, which greatly simplifies signal assignment and structure elucidation in general. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of 31P,31P coupling constants in cyclotriphosphazenes and their influence on 1H and 13C NMR spectra of phosphorus substituents
Authors: Vicente Virginie , Fruchier Alain , Cristau Henri‐Jean 
Published: February 2003

Abstract1H and 13C NMR spectra of symmetrically substituted cyclotriphosphazenes exhibit second‐order effects. The influence of the 31P,31P coupling constants between ring phosphorus atoms on these effects was studied. Some values of this coupling constant between phosphorus bearing identical substituents were measured using 13C satellites of the 31P signals or by introduction of a chiral substituent on the third phosphorus atom. Copyright © 2003 John Wiley & Sons, Ltd.
Complete 1H and 13C NMR chemical shift assignment of N1‐ and N3‐alkylnitrohistidines and of 1,4,6,7‐tetrahydroimidazo[4,5‐b]pyridines
Authors: Escolano Carmen , Kogan Marcelo J. , Rubiralta Mario , Giralt Ernest , Diez Anna 
Published: February 2003

Abstract1H and 13C NMR data for 13 nitrohistidine derivatives are reported, providing a diagnostic method for the elucidation of the N1‐(2) and the N3‐substituted (3) regioisomers. Spectral assignments of constrained surrogates of His (4) and of the His–Gly dipeptide (5 and 6) are also described. The structure of the compounds was confirmed by NOESY and heteronuclear (13C, 1H) short‐ and long‐range correlation experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Correlation between the reactivity and spectroscopic properties ofN‐substituted secondary thioamides. New intramolecular N···H+···N binding approach and proton complexes based on thioamide ligation
Authors: Spychała Jarosław 
Published: February 2003

AbstractOn the basis of a comparison of chemical shifts and wavenumbers of several secondary thioamides and amides having monocationic substituents attached to thiocarbamoyl or carbamoyl groups by a polymethylene chain, new intramolecular unconventional N···H+···N hydrogen bonding effects were discovered. It is argued that the CH2—N rotation is hindered and two+H···NHCH3non‐equivalent protons occur in a proton spectrum of hydrochloride1a(at 10.68 and 2.77 ppm, respectively) instead of two+NH2CH3protons. Presumably, the above steric factors inhibit the acidic hydrolysis of1a(stabilized by strong intramolecular N···H+···N hydrogen bonds) to an amide and prevent intramolecular cyclization of2a(stabilized by strong intramolecular neutral–neutral N···HN hydrogen bonds) to a cyclic amidine. Postulation of additional dihydrogen bond formation is helpful in understanding the spectroscopic differences of4and5. The above new bonding is also compared with intramolecular N···H—N+hydrogen bonds in primary amine salts7and8. In contrast to3, a cooperative hydrogen bonded system is observed in9and10. The weak hydrogen bonds in7–10facilitate the hydrolysis and cyclization reactions of secondary thioamides. The spectroscopic data for secondary (thio)amides are especially useful for characterizing the electronic situation at the (thio)carbamoyl nitrogen atoms and they are perfectly correlated with the reactivity. Examples of chelation of protons by thioamides (11and12), which contain strongly electron‐donating pyrimidine groups, are presented to show the contribution of dihydrogen bonding in the protonation reaction similar to1and4. Copyright © 2003 John Wiley & Sons, Ltd.
NMR study of a novel pentasaccharide isolated from Penicillium citrium
Authors: Yang Heejung , Kang Kyoung Rae , Lim Yoongho 
Published: February 2003

AbstractPenicillium citrium produces several fructose oligomers, namely kestose, neokestose, nystose, 1‐furanosylnystose and a novel pentasaccharide. The pentasaccharide consists of four fructoses and one glucose but its structure is different from that of 1‐furanosylnystose. Its complete structure was determined based on various two‐dimensional NMR experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Complete assignments of the 1H and 13C NMR spectra of 15 limonoids
Authors: Rodríguez Benjamín 
Published: February 2003

AbstractUnambiguous and complete assignments of 1H and 13C NMR chemical shifts for 15 limonoids, eight of them found in natural sources and seven other synthetic derivatives, are presented. The assignments are based on 2D shift‐correlated [1H,1H‐COSY, 1H,13C‐gHSQC‐1J(C,H), 1H,13C‐gHMBC‐nJ(C,H) (n = 2 and 3)] and NOE experiments. Copyright © 2003 John Wiley & Sons, Ltd.
Warifteine and methylwarifteine: 1H and 13C assignments by two‐dimensional NMR spectroscopy
Authors: Mukherjee Rabindranath , Keifer Paul A. 
Published: February 2003

AbstractThe identity and structures of warifteine and methylwarifteine, two tertiary bisbenzylisoquinoline alkaloids of an unusual type, were elucidated and verified by 2D NMR spectroscopy. Complete 1H and 13C NMR spectral assignments were obtained. Copyright © 2003 John Wiley & Sons, Ltd.
Complete 13C and 1H NMR spectral assignments of two isoflavones from the roots of Dalbergia horrida
Authors: Manoj C. Narayanan , Rao R. Priya , Sethuraman M. Gopalakrishnan , Nagarajan N. Shanmugam , Kaliaperumal Muralidharan 
Published: February 2003

AbstractTwo methoxylated isoflavones were isolated form the roots of Dalbergia horrida. These compounds show great promise as pharmaceutical agents. The 1H and 13C NMR spectra of the compounds were completely assigned by using a combination of 2D NMR experiments which included 1H–1H COSY, HMQC and HMBC studies. Copyright © 2003 John Wiley & Sons, Ltd.
NMR analysis of the O‐antigen polysaccharide from Escherichia coli strain F171
Authors: Fundin Johan , Weintraub Andrej , Xu Jian‐Guo , Widmalm Göran 
Published: February 2003

AbstractThe structure of the O‐antigen polysaccharide from Escherichia coli strain F171 has been determined. NMR analysis of the polysaccharide showed that it was composed of pentasaccharide repeating units. The 1H and 13C signals were assigned by 2D NMR techniques which revealed severe spectral overlap for key resonances at substitution positions. The structure of the repeating unit was deduced from 1H,13C HMBC and, in particular, by 1H,1H NOESY experiments as follows:

The structure is identical with that of the O‐antigen from Escherichia coli O25 previously determined by chemical degradation methods and the strain F171 should therefore belong to this serogroup. Copyright © 2003 John Wiley & Sons, Ltd.
Visualizing metabolic changes in breast‐cancer tissue using 1H‐NMR spectroscopy and self‐organizing maps
Authors: Beckonert Olaf , Monnerjahn Jürgen , Bonk Ulrich , Leibfritz Dieter 
Published: February 2003

AbstractIn‐vitro NMR spectroscopic examinations of tissue extracts can be combined with appropriate pattern‐recognition and visualization techniques in order to monitor characteristic metabolic differences between tissue classes. In the present study, such techniques are applied to a set of 88 breast‐tissue samples with the intention of identifying typical differences between various tissue classes. The set contains 49 breast‐tumor samples of various tumor grades and 39 samples of healthy tissue. The metabolite compositions of the tissue extracts were investigated using a dual extraction technique and high‐resolution 1H‐NMR spectroscopy. The spectra of the hydrophilic and the lipophilic compounds were assigned to three groups according to different malignancy grades of the respective tissue samples. The group characteristics were analyzed using the k‐nearest‐neighbor method and self‐organizing‐map visualizations. The results show an increase of UDP‐hexose, phosphocholine and phosphoethanolamine concentrations according to the tumor grade. Higher concentrations of taurine were detected in the malignant samples. Myo‐inositol and glucose content were elevated in control samples compared with malignant tissue. Both compounds also characterized different subgroups in the pool of unaffected tissue samples depending upon fat content or fibrosis. Several lipid metabolites showed a characteristic elevation with high malignancy. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical approximation of a thermally driven interface using finite elements
Authors: Zhao P. , Heinrich J. C. 
Published: February 2003

AbstractA two‐dimensional finite element model for dendritic solidification has been developed that is based on the direct solution of the energy equation over a fixed mesh. The model tracks the position of the sharp solid–liquid interface using a set of marker points placed on the interface. The simulations require calculation of the temperature gradients on both sides of the interface in the direction normal to it; at the interface the heat flux is discontinuous due to the release of latent heat during the solidification (melting) process. Two ways to calculate the temperature gradients at the interface, evaluating their interpolants at Gauss points, were proposed. Using known one‐ and two‐dimensional solutions to stable solidification problems (the Stefan problem), it was shown that the method converges with second‐order accuracy. When applied to the unstable solidification of a crystal into an undercooled liquid, it was found that the numerical solution is extremely sensitive to the mesh size and the type of approximation used to calculate the temperature gradients at the interface, i.e. different approximations and different meshes can yield different solutions. The cause of these difficulties is examined, the effect of different types of interpolation on the simulations is investigated, and the necessary criteria to ensure converged solutions are established. Copyright © 2003 John Wiley & Sons, Ltd.
Moving element method for train‐track dynamics
Authors: Koh C. G. , Ong J. S. Y. , Chua D. K. H. , Feng J. 
Published: February 2003

AbstractThis paper presents a new approach, called the moving element method, for the dynamic analysis of train‐track systems. By discretizing the rail beam on viscoelastic foundation into elements that ‘flow’ with the moving vehicle, the proposed method eliminates the need for keeping track of the vehicle position with respect to the track model. The governing equations are formulated in a co‐ordinate system travelling at a constant velocity, and a class of conceptual elements (as opposed to physical elements) are derived for the rail beams. In the numerical study, four cases of moving vehicle are presented taking into consideration the effects of moving load and rail corrugation. The method is shown to work for varying vehicle velocity and multiple contact points, and has several advantages over the finite element method. The numerical solutions compare favourably with the results obtained by alternative methods. Copyright © 2003 John Wiley & Sons, Ltd.
A class of parallel multiple‐front algorithms on subdomains
Authors: Bose A. , Carey G. F. , de Almeida V. F. 
Published: February 2003

AbstractA class of parallel multiple‐front solution algorithms is developed for solving linear systems arising from discretization of boundary value problems and evolution problems. The basic substructuring approach and frontal algorithm on each subdomain are first modified to ensure stable factorization in situations where ill‐conditioning may occur due to differing material properties or the use of high degree finite elements (p methods). Next, the method is implemented on distributed‐memory multiprocessor systems with the final reduced (small) Schur complement problem solved on a single processor. A novel algorithm that implements a recursive partitioning approach on the subdomain interfaces is then developed. Both algorithms are implemented and compared in a least‐squares finite‐element scheme for viscous incompressible flow computation using h‐ and p‐finite element schemes. Copyright © 2003 John Wiley & Sons, Ltd.
Automatic metric 3D surface mesh generation using subdivision surface geometrical model. Part 1: Construction of underlying geometrical model
Authors: Lee C. K. 
Published: February 2003

AbstractThis paper proposes a new automatic mesh generation algorithm for 3D surface mesh generation. The algorithm is based on the metric specification approach and can generate anisotropic meshes on 3D surfaces. It is based on a new geometrical model using the interpolating subdivision surface concept. By using the subdivision surface concept, the new mesh generator can generate finite element meshes to model a wide range of surfaces which may contain sharp features such as cusp points and crease lines. When comparing with other traditional algorithms which use analytical surface patches as the underlying geometrical model, the new mesh generation scheme can be used in applications such as large deformation or crack analyses in which the domains to be gridded are not well defined or involve changing boundaries. The presentation of the work is divided into two parts. In Part 1, a detailed description of the underlying geometrical model used will be given, while in Part 2, attention will be focused on the mesh generation algorithms and the performance of the mesh generator developed. Copyright © 2003 John Wiley & Sons, Ltd.
Automatic metric 3D surface mesh generation using subdivision surface geometrical model. Part 2: Mesh generation algorithm and examples
Authors: Lee C. K. 
Published: February 2003

AbstractIn this paper, a new metric advancing front surface mesh generation scheme is suggested. This new surface mesh generator is based on a new geometrical model employing the interpolating subdivision surface concept. The target surfaces to be meshed are represented implicitly by interpolating subdivision surfaces which allow the presence of various sharp and discontinuous features in the underlying geometrical model. While the main generation steps of the new generator are based on a robust metric surface triangulation kernel developed previously, a number of specially designed algorithms are developed in order to combine the existing metric advancing front algorithm with the new geometrical model. As a result, the application areas of the new mesh generator are largely extended and can be used to handle problems involving extensive changes in domain geometry. Numerical experience indicates that, by using the proposed mesh generation scheme, high quality surface meshes with rapid varying element size and anisotropic characteristics can be generated in a short time by using a low‐end PC. Finally, by using the pseudo‐curvature element‐size controlling metric to impose the curvature element‐size requirement in an implicit manner, the new mesh generation procedure can also generate finite element meshes with high fidelity to approximate the target surfaces accurately. Copyright © 2003 John Wiley & Sons, Ltd.
Plotting holographic interferograms for visualization of dynamic results from finite‐element calculations
Authors: Ragulskis M. , Palevicius A. , Ragulskis L. 
Published: February 2003

AbstractProcedures for plotting computer generated interferograms from the results of finite‐element analysis based on the principles of optical holography can provide a realistic view of dynamic processes taking place in the analysed structures. Such visualization is based on a solid physical background, does not require animation for representing dynamic processes, and is also important from the point of view of interpretation of experimental holograms.The numerical method for obtaining time‐averaged digital interferograms for structural dynamics applications is presented. Intensity mapping as well as the methods of digital stroboscopic analysis are used for plotting clearer images due to the fact that the intensity of higher interference bands decreases rapidly with the growth of vibration amplitudes. The digital time averaging of intermediate states of the moving surface together with varying direction of incident laser beam and estimation of diffuse and specular reflection phenomena enables the generation of realistic interferograms. Such a procedure is scalable in parallel computations and applicable to a wide variety of problems. Copyright © 2003 John Wiley & Sons, Ltd.