bluuebunny/crossref_metadata_2025 huggingface dataset:
Design of conformal multiband antennas based on fractal concepts
Authors: Yeo Junho , Mittra Raj
Published: February 2003

In this paper we present some novel designs for conformal multiband antennas, based on fractal concepts, for application at three different frequencies. Although a whole host of conventional fractal type of monopole and dipole configurations have been designed in the past, they are not well suited for conformal applications. In this paper we describe a Sierpinski gasket type of fractal configuration, printed on a dielectric substrate backed by a ground plane, and propose a novel approach to enhancing its multiband performance, in terms of impedance matching characteristics as well as radiation patterns, at three operating frequencies. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 333–338, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10758
Detection of human respiration using square‐wave modulated electromagnetic impulses
Authors: Ong Keat G. , Dreschel William R. , Grimes Craig A.
Published: February 2003

A technique for monitoring human respiration utilizing square‐wave modulated electromagnetic impulses is presented. Lung volume changes associated with human respiration alter the time‐amplitude spectrum of a reflected electromagnetic impulse, while the Brillouin‐precursor associated with impulse propagation through dispersive media enables detection through otherwise opaque barriers. Results of numerical simulations and experiments are presented. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 339–343, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10759
A fast, high‐order quadrature sampled pre‐corrected fast‐Fourier transform for electromagnetic scattering
Authors: Gedney Stephen , Zhu Aiming , Tang Wee‐Hua , Liu Gang , Petre Peter
Published: February 2003

In this paper, a novel fast, high‐order solution procedure referred to as the quadrature sampled pre‐corrected fast‐Fourier transform (QS‐PCFFT) is presented. The method accelerates far‐interaction terms of an integral operator using the discontinuous FFT1, which combines Gaussian‐quadrature integration with the FFT. This method is applied to the locally corrected Nyström solution of electromagnetic scattering problems. It is shown that the QS‐PCFFT maintains high‐order convergence and scales asO(N) in memory andO(NlogN) in floating point operations. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 343–349, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10760
Multi‐frequency planar monopole antenna for GSM/DCS/PCS/WLAN operation
Authors: Teng Pey‐Ling , Chen Hong‐Twu , Wong Kin‐Lu
Published: February 2003

A novel planar monopole antenna capable of multi‐frequency operation at about 900, 1800, and 2450 MHz is presented. The monopole antenna occupies a small area of 6.5 × 50 mm2, and is easy to construct with low cost by printing on an FR4 substrate. The monopole antenna can be mounted perpendicularly to the system circuit board of a communication device so that a low profile to the system ground plane will result. In addition, the obtained impedance bandwidths of the proposed antenna at about 900, 1800, and 2450 MHz can cover the GSM (890–960 MHz), DCS (1710–1880 MHz), PCS (1850–1990 MHz), and WLAN (2400–2484 MHz) bands. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 350–352, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10761
Empirical relationship between δ and ferromagnetic resonance frequency in hexagonal ferrite‐based microwave absorbing paint
Authors: Meshram M. R. , Agrawal Nawal K. , Sinha Bharoti , Misra P. S.
Published: February 2003

This paper reports the development of an empirical relationship between δ andfrfor a Mn‐Ti‐substituted barium hexagonal ferrite‐based paint. The previously available empirical relation1is not valid beyond δ = 1.1, after which anomalous results are being obtained. An attempt has been made to overcome this limitation by preparing different samples of ferrite using δ = 1.6, 1.7, 1.8, 1.9, 2.7, and 3.1 and experimentally determining their respective complex permeability. A plot has been obtained between δ andfr(resonant frequency) and, using the curve fitting techniques, a best‐fitted curve was found. From this an empirical relation could easily be derived. This relation was found to be valid for a wide frequency range from 8 GHz to 18 GHz. Results show that a maximum absorption on the order of 8 dB can be obtained at the resonance frequency of the various samples, thus successfully validating the relation. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 352–355, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10762
A 2D near‐field microwave diversity imaging system in turntable mode
Authors: Ma Jinping , Che Wenquan , Mao Naihong
Published: February 2003

A novel near‐field microwave diversity imaging system in turntable mode is proposed theoretically. Based on the coherent spherical back‐projection principle, an imaging function used to describe the profile of object has been derived, in which frequency and angular diversity techniques are adopted. Imaging resolutions for both ideal and practical cases are discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 356–359, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10763
Accurate computation of vector potentials in lossy media
Authors: Chakraborty Swagato , Jandhyala Vikram
Published: February 2003

This paper presents an accurate formulation and integration scheme for computing vector potential interactions due to linear basis functions in lossy conducting media over wide frequency ranges. The emphasis is on an approach that is broadband and works both at high‐frequency surface impedance limits and at low‐frequency volumetric current flow limits. The method can be interpreted as a step towards a surface‐only formulation for an integral‐equation‐based broadband characterization. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 359–363, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10764
Design of steerable non‐uniform linear array geometry for side‐lobe reduction
Authors: Bae Ji‐Hoon , Kim Kyung‐Tae , Lee Joon‐Ho , Kim Hyo‐Tae , Choi Jae‐Ick
Published: February 2003

In this paper, we present a pattern synthesis method of non‐uniform linear array antennas for simultaneous reduction of the side‐lobe level and pattern distortion during beam steering. To achieve these two requirements, the positions of linear array elements are adjusted using the Gauss–Newton method. It is shown that the proposed method can significantly reduce pattern distortion as well as the side‐lobe level, although the beam direction is scanned. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 363–367, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10765
Accurate frequency domain modeling of LTCC solid‐gridded plane structures
Authors: Chen Guang , Jancura Andrej , Virga Kathleen L. , Winkler Gert , Prince John L.
Published: February 2003

This paper presents a modeling approach for solid‐gridded power‐ground plane structures in low‐temperature co‐fired ceramic (LTCC) modules. The approach uses a two‐dimensional transmission line approach and uses a new physical‐layout‐based cell‐dividing modeling method to expedite the simulation process. The approach is verified by comparing theS11parameters obtained from simulation and measurement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 367–371, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10766
An analysis of the kink phenomenon of scattering parameter S22 in RF power mosfets for system‐on‐chip (SOC) applications
Authors: Lin Yo‐Sheng , Lu Shey‐Shi
Published: February 2003

In this paper, the kink effect in scattering parameter S22 of RF power MOSFETs with drain‐to‐spacer offset is explained quantitatively for the first time. Our results show that for RF power MOSFETs the output impedance can be represented by a “shifted” series RC circuit at low frequencies and a “shifted” parallel RC circuit at high frequencies. The appearance of the kink point of S22 in a Smith chart is caused by this inherent ambivalent characteristic of the output impedance. It is found that an increase of drain‐to‐spacer offset enhances the kink effect. In addition, the kink effect in S22 of RF power MOSFETs can also be interpreted in terms of poles and zeros. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 371–376, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10767
Folded‐loop antennas for handset terminals at the 2.0‐GHz band
Authors: Adachi Takahiko , Hirata Akimasa , Shiozawa Toshiyuki
Published: February 2003

Folded‐loop antennas for mobile handsets are analyzed, taking into account the influence of the human body. Folding the loop antennas toward the back of a metallic box is found to reduce the peak SAR averaged over 1 g and 10 g of tissues by 30% to 60%, while the radiation characteristics are comparable with those of a monopole antenna. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 376–378, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10768
A combination of windowed plane wave spectrum (WPWS) and spectral transformation techniques for computing the radar scattering characteristics of thin conducting plates
Authors: Prakash V. V. S. , Mittra Raj
Published: February 2003

In this paper, the problem of scattering from finite perfectly conducting (PEC) plates has been analyzed by using the windowed plane wave spectrum (WPWS) technique, and the resultant solution is further refined via spectral transformation. The importance of windowing the spectrum of the induced current to improve the solution has been demonstrated. Numerical results have been presented to illustrate the accuracy of the technique via a comparison with those derived by using the method of moments analysis employing Rao, Wilton, and Glisson basis functions. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 378–381, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10769
Tapered meander slot antenna for dual band personal wireless communication systems
Authors: Allen Cuthbert M. , Elsherbeni Atef Z. , Smith Charles E. , Huang Chun‐Wen P. , Lee Kai‐Fong
Published: February 2003

A small size antenna is designed for dual‐band operation for personal wireless communication systems. The design is based on a tapered meander slot in a finite size ground plane, with a microstrip feed line at the opposite side of the dielectric substrate. The antenna supports 1800 MHz and 2400 MHz operations simultaneously with bandwidths of 130 MHz and 350 MHz, respectively. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 381–385, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10770
Electrically steerable cylindrical microstrip array antenna
Authors: Lee Choon Sae , Hsieh Tung‐Hung , Chen Pi‐Wei
Published: February 2003

A novel electronic beam steering is achieved by varying the amplitude of each radiating element in a microstrip array on a curved surface. PIN diodes are used to turn on the radiating patches facing in the intended direction while turning off all other patches. Since the amplitude‐varying antenna does not use expensive phase shifters, the resultant beam‐steering system is much less expensive than conventional phased‐array antennas. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 386–387, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10771
Modal dispersion curves of metal‐clad concave lens shaped waveguides and their comparative study
Authors: Kumar N. , Srivastava S. K. , Ojha S. P.
Published: February 2003

This paper presents a comparative study of dispersion characteristics of metal‐clad waveguides with concave‐lens‐like cross sections. Using the point‐matching method under weak‐guidance approximation, the modal characteristic equation is derived and the modal dispersion curves are obtained. The proposed waveguide may be conceived as a distortion of the square waveguide with a transverse compression at one pair of its parallel sides in order to become concave lens shaped. We find that, the effect of the concave lens shaped distortion is to shift the lowest cutoff value (Vc) towards a larger V value, and increases the number of modes. It is also observed that the lowest cutoff value increases gradually with the increase in the compression depth. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 388–392, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10772
Slot antenna with a tilted beam for satellite reception
Authors: Vera‐Isasa M. , Sierra‐Castañer M. , Sierra‐Pérez M.
Published: February 2003

A design method for DBS‐TV reception antennas with tilted beam using a radial feed line with a slot radiating array is proposed. A cylindrical TEM wave excites the slots and must be placed eccentrically in order to produce a tilted beam. The proposed design method allows us to obtain good results for tilt angles up to 10° as is demonstrated. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 392–394, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10773
Numerical assessment of multifrequency microwave radiometry for sensing malignant breast cancer tumors
Authors: El‐Shenawee Magda
Published: February 2003

A numerical study of microwave radiometry for malignant breast cancer tumors is presented. The numerical results show that the brightness temperature of malignant tumors exhibits a resonant behavior versus the frequency. The brightness magnitude decreases with the tumor burial depth, however, the resonance frequencies depend only on the tumor's size and material and are independent of the burial depth. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 394–398, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10774
New compact broadband phase shifters using coupled lines
Authors: Han Sang‐Min , Kwon Koo Hyung , Kim Young‐Sik
Published: February 2003

This 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

A 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

This 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

Design 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

This 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

High‐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

The 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

We 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

1H 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

1H 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

On 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

Penicillium 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

Unambiguous 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

The 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

Two 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

The 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

In‐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

A 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

This 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

A 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

This 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

In 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

Procedures 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.
Essential algorithms to minimize dynamic effects in using explicit codes for stamping process simulations
Authors: Hu Weilong
Published: February 2003

A key problem, when using dynamic codes to run the static or quasi‐static jobs, in particular, for a stamping process simulation attaching spring‐back calculation, is the dynamic effect. In order to minimize the dynamic effects, some kinds of loading algorithms should be performed. The enhancement of these is proposed in this paper, as well as making up for a deficiency that current damping models have when used to reduce the dynamic effects. Essential conditions that can be followed to generate an ideal loading curve are brought forward here including the starting and ending condition. A concerned model is recommended that satisfies all ideal requirements, which can be used directly for the stamping process simulation. Associated criteria and how to optimize the loading curves are also presented. Finally, a simple case has been done to describe its practical application in simulations. Meanwhile, several kinds of loading curves, which have been used commonly in the stamping process simulation, are selected to compare with the proposed loading curve. The different features of them are also discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Decentralisation in Africa: goals, dimensions, myths and challenges
Authors: Smoke Paul
Published: February 2003

Decentralisation is a complex and often somewhat elusive phenomenon. Many countries around the world have been attempting—for several reasons and with varying degrees of intention and success—to create or strengthen sub‐national governments in recent years. Africa is no exception to either the decentralisation trend or the reality of its complexity and diversity. Drawing selectively on the large academic and practitioner literature on decentralisation and the articles in this volume, this article briefly outlines a number of typical prominent goals of decentralisation. It then reviews some key dimensions of decentralisation—fiscal, institutional and political. These are too frequently treated separately by policy analysts and policy makers although they are inherently linked. Next, a few popular myths and misconceptions about decentralisation are explored. Finally, a number of common outstanding challenges for improving decentralisation and local government reform efforts in Africa are considered. Copyright © 2003 John Wiley & Sons, Ltd.
Fiscal decentralisation in Africa: a framework for considering reform
Authors: Prud'homme Rémy
Published: February 2003

This article argues that there is no simple (or even complex) uniform model for fiscal decentralisation in Africa. Each country has to devise its own strategy. The article proposes an analytical framework to help countries consider how to structure fiscal decentralisation. It presents briefly the main decentralisation instruments available—allocation of functions and revenues across the levels of government, development of intergovernmental transfers, institution of central monitoring and control mechanisms and the institution of electoral rules. It then examines the various objectives that will be served or impacted by these instruments, including economic efficiency, macro‐economic stability, interregional or interpersonal equity and political efficiency. Selected impacts are reviewed and illustrated to demonstrate how an understanding of these issues in each country is a prerequisite for designing appropriate decentralisation. Copyright © 2003 John Wiley & Sons, Ltd.
Sectoral decentralisation and intergovernmental arrangements in Africa
Authors: Andrews Matthew , Schroeder Larry
Published: February 2003

A critical issue in decentralisation is the assignment of services to sub‐national governments. This article examines normative arguments, legislated models and actual experiences of Sub‐Saharan service assignment in two key service sectors, primary health care and rural roads, each of which is a common target for decentralisation efforts and has substantially different characteristics. In analysing intergovernmental provision and production arrangements and the way in which different service components are organised in these sectors, it is apparent that legislated models of decentralisation are largely informed by normative theory. In both sectors, however, a disjoint is evident between what governments decentralise in a formal sense (i.e. in the law) and what they decentralise in an actual sense. This disjoint can be partially explained by normative arguments about the limits to decentralisation, for example, spillovers and economies of scale, but also result from the influence of factors such as intergovernmental and bureaucratic politics, local level capacity constraints and particular production issues associated with each service. Copyright © 2003 John Wiley & Sons, Ltd.
Local institutional and political structures and processes: recent experience in Africa
Authors: Olowu Dele
Published: February 2003

Democratic decentralisation is a stated goal of many African countries, but there are considerable institutional and political challenges involved in making it a reality. Even where official government decentralisation programmes are underway, many central agencies may be reluctant or unwilling to share significant powers with local governments. Overcoming local elite capture and generating genuine local participation can also be extremely difficult. This article reviews basic institutional and political mechanisms intended to facilitate effective decentralisation and intergovernmental fiscal relations, including legal, constitutional, fiscal and managerial reforms. It also explores the challenges of developing institutional mechanisms for hierarchical control and internal accountability which are potentially subject to considerable abuse. Particular attention is given to the development of external accountability through local elections, appropriately defined local government structures and operations, appropriately sized local government jurisdictions and various direct voice mechanisms that have been used to various degrees in Africa. Copyright © 2003 John Wiley & Sons, Ltd.
Democratic decentralisation of natural resources: institutional choice and discretionary power transfers in Sub‐Saharan Africa
Authors: Ribot Jesse C.
Published: February 2003

Decentralisation reforms are taking place across Africa. In decentralisation concerning natural resources, local institutions being chosen to receive powers and the degree and form of power transfers, however, do not establish conditions for more efficient or equitable use and management. A combination of locally accountable representation and discretionary powers are also needed. This combined condition is rarely established. Alternative local institutions are chosen even when democratic local bodies exist. This choice and the failure to transfer discretionary powers can undermine local democratic bodies and concentrate powers in the executive branch. The choices being made around natural resources appear to reflect a broad resistance of central governments to local democratisation and decentralisation of powers. Five measures may ameliorate the situation: (1) focus first on establishing democratic local government; (2) apply multiple accountability measures, in addition to elections, to support democratic local institutions; (3) engage local populations by transferring discretionary powers before transferring management burdens; (4) transfer powers before capacity building; and (5) shift from an oversight and management‐planing model to a minimum‐standards model in order to help create greater local autonomy nested within national objectives. Copyright © 2003 John Wiley & Sons, Ltd.
Local economic development: new generations of actors, policies and instruments for Africa
Authors: (Bert) Helmsing A. H. J.
Published: February 2003

As decentralisation advances, the question of local economic development acquires more significance. How can local governments and other local actors such as local producers and their associations, community based organisations, as well as NGOs and donors contribute to local economic development and poverty reduction? This article begins by examining how the context for local economic development has drastically changed. It stresses lack of demand and the absence of meso‐level institutions, i.e. institutions at the level of sector and area. Their absence deters investment responses by enterprises and households. In terms of local development initiatives, a distinction is made between community economic development and enterprise or business development. The first seeks to facilitate household economic diversification as an essential strategy of rural and urban livelihood; the second, enterprise development, seeks specialisation of the local economic base. These two lines are complemented by a third category, namely locality development, designed to create local public goods and positive externalities. The final section elaborates on the principal actors and their roles, stressing the importance of joint action and collective learning. Local governments have an important facilitating role, creating a favourable business environment and infrastructure conditions, and to contribute to convergence in decision‐making. Copyright © 2003 John Wiley & Sons, Ltd.