bluuebunny/crossref_metadata_2025 huggingface dataset:
Projective limits of finite decomposition systems
Authors: Feiste U.
Published: April 2007

Special finite topological decomposition systems were used to get compactifications of topological spaces in [6]. In this paper the notion of finite decomposition systems is applied for topological measure spaces. We get two canonical topological measure spaces X∞ and X∞d being projective limits of (discrete) finite decomposition systems for each topological measure space X = (X, O, A, P) and each net (Aα) α ϵ I of upward filtering finite σ‐algebras in A. X∞ is a compact topological measure space and the idea to construct is the same as used in [6]. The compactifications of [6] are cases of some special X∞. Further on we obtain that each measurable set of the remainder of X∞ has measure zero with respect to the limit measure P∞ (Theorem 1). X∞d is the STONE representation space X(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \cup \limits_{\alpha \in I} A\alpha $\end{document}) of \documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \cup \limits_{\alpha \in I} A\alpha $\end{document} Aα, hence a Boolean measure space with regular Borel measure. Some measure theoretical and topological relations between X, X(\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop \cup \limits_{\alpha \in I} A\alpha $\end{document}) and x(A) where x(A) is the Stone representation space of A, are given in Theorem 2. and 4. As a corollary from Theorem 2. we get a measure theoretical‐topological version to the Theorem of Alexandroff Hausdorff for compact T2 measure spaces x with regular Borel measure (Theorem 3.).
A Class of Spaces Containing all Connected and all Locally Connected Spaces
Authors: Kohli J. K.
Published: April 2007

A simultaneous generalization of connectedness and local connectedness, called sum connectedness, is introduced. The category of sum connected spaces forms the smallest co‐reflective subcategory of TOP containing all connected spaces. A product theorem, analogous to that for locally connected spaces, is proved for sum connected spaces and a necessary and sufficient condition for the STONE‐ČECH compactification of a TYCHONOFF space to be sum connected is obtained.
The Kernels of Skeletal Congruences on a Distributive Lattice
Authors: Cornish William H.
Published: April 2007

Let L be a distributive lattice with 0 and C(L) be its lattice of congruences. The skeleton, SC(L), of C(L) consists of all those congruences which are the pseudocomplements of members of C(L), and is a complete BOOLEan lattice. An ideal is the kernel of a skeletal congruence if and only if it is an intersection of relative annihilator ideals, i.e. ideals of the form j={x∈L: xΔr≤s} for suitable r, s∈L. The set KSC(L) of all such kernels forms an upper continuous distributive lattice and the map a ↦ (a={x∈L: x≤a} is a lower regular joindense embedding of L into KSC(L). The relationship between SC(L) and KSC(L) leads to numerous characterizations of disjunctive and generalized BOOLEan lattices. In particular, a distributive lattice L is disjunctive (generalized Boolean) if and only if the map Θ ↦ ker Θ is a lattice‐isomorphism of SC(L) onto KSC(L), whose inverse is the map J ↦ Θ (J)** (the map J ↦ Θ(J)). In addition, a study of KSC(L) leads to new simple proofs of results on the completions of special classes of lattices.
Discrete‐time GALERKIN Methods for Nonlinear Evolution Equations
Authors: Gröger Konrad
Published: April 2007

We consider a discrete‐time GALERKIN method for nonlinear evolution equations. We prove convergence properties of this method under various hypotheses. Moreover, we deal with iteration methods reducing the nonlinear GALERKIN equations to linear equations in finite dimensional spaces.
Linear integral equations of the third kind arising from neutron transport theory
Authors: Shulaia D.
Published: April 2007

The aim of this paper is to study, in the class of Hölder functions, linear integral equations with coefficients cos x having zeros in an interval under consideration. Using the theory of singular integral equations, necessary and sufficient conditions for the solvability of these equations under some assumptions on their kernels are given. The kernels of transport equations satisfy the required assumptions. Copyright © 2007 John Wiley & Sons, Ltd.
Wideband balun and vertical transition between microstrip and parallel‐strip transmission line
Authors: Kwon Do‐Hoon
Published: April 2007

A wideband vertical transition between microstrip and parallel‐strip transmission lines is presented. It performs as an unbalanced‐to‐balanced transformer as well. Its back‐to‐back configuration is fabricated, and the transition characteristics are measured. Measurement results reveal low insertion loss over wide frequency band. The performance of the microstrip transition is compared with those of the vertical transitions involving a coplanar waveguide and a conductor‐backed coplanar waveguide, and comments on the comparison results are provided. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1530–1532, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22482
Transmission through and wave guidance on metal plates perforated by periodic arrays of through‐holes of subwavelength coaxial cross‐section
Authors: Lomakin Vitaliy , Li Shuqing , Michielssen Eric
Published: April 2007

Perfect electrically conducting (PEC) plates perforated by doubly periodic arrays of through‐holes of subwavelength coaxial cross‐section permit enhanced transmission of plane waves and support surface wave guidance. The transmission enhancement is attributed to coupling of free‐space fields to TEM and TE11modal fields in holes and occurs via two distinct mechanisms. The first couples incident fields to local resonances (cavity modes) supported by individual holes. The second couples scattered fields (diffraction modes) to global resonances (surface waves). The surface waves arise due to strong interactions between the holes and can have a large propagation wavenumber. The presented PEC model is adequate in the microwave and terahertz regimes and insights into related wave phenomena at optical frequencies.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1554–1558, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22484
Axial mode helix antenna with exponential spacing
Authors: Chen Can‐Hui , Yung E.K.N. , Hu Bin‐Jie , Xie Sheng‐Li
Published: April 2007

A novel wideband CP helix antenna with exponential spacing is presented in this paper. Since traveling wave current over a wide range of frequencies has been excited, it possesses better performance. Both numerical results and experimental results show that the axial ratio bandwidth of the exponential spacing helix (ESH) antenna is 58.6% greater than that of the linear spacing helix (LSH) antenna in the same conditions. The characteristics of impedance, power gains, and radiation patterns for the ESH antenna are also investigated and compared with LSH antenna. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1525–1530, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22485
Optical properties of SIC/SIO2 composite thin film
Authors: Yi Jian , He XiaoDong , Sun Yue , Li Yao
Published: April 2007

SiC film was deposited by electron beam‐physical vapor deposition on thermal oxidized silicon substrates at 750°C, and SiC/SiO2 composite thin film was prepared. The obtained composite film was analyzed by Fourier‐transform infrared (FTIR) transmission and reflection spectroscopy, and the film reveals an amorphous structure and a high emissivity.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1551–1553, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22487
TEM horn antenna with an elliptic profile
Authors: Malherbe J. A. G , Barnes N.
Published: April 2007

A variety of profiles for the cross section of wideband TEM horns have been proposed, employing an optimal impedance function or exponential taper in order to minimize reflection losses. In this article, an elliptic longitudinal sectional profile, combined with an optimal impedance function, is proposed and evaluated.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1548–1551, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22488
A very compact dielectric waveguide directional coupler utilizing a double‐negative slab core
Authors: Huang Meng , Xu Shanjia
Published: April 2007

A novel dielectric waveguide directional coupler with a double‐negative slab lies in the coupling region is analyzed by the staircase approximation method, which combines the building block approach and multimode network theory with a rigorous mode‐matching procedure. Particular attention is directed toward the coupling characteristics under different structural and constitutive parameters of the coupler. Numerical results indicate that the transition and coupling length of the proposed coupler is only 70% and 42% of related lengths in the conventional coupler, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1545–1548, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22491
Reconfigurable multiwavelength erbium‐doped fiber laser using two multimode fiber Bragg gratings
Authors: Yan Jin‐Hua , Fu Hong‐Yan , He Sailing
Published: April 2007

A reconfigurable multiwavelength erbium‐doped fiber laser, using two multimode fiber Bragg gratings (MFBGs), is presented. Two MFBGs in L‐band are cascaded to form two overlapping resonant cavities. Various configurations of four‐, three‐, or two‐wavelength lasing are demonstrated experimentally by appropriately controlling the two polarization controllers inside the cavities. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1509–1511, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22493
Ultra‐wideband printed fork‐shaped monopole antenna with a band‐rejection characteristic
Authors: Liu Wen‐Chung , Chen Shu‐Ming
Published: April 2007

A novel ultra‐wideband design of a printed fork‐shaped monopole antenna with a band‐rejection characteristic is presented. The proposed antenna with a simpler structure has a larger impedance bandwidth, defined by voltage standing wave ratio ≤ 2, covering the range from 3.09 to 11 GHz, and a tunable cutoff band throughout adjustment of the centre strip length of the fork‐shaped monopole. Measured monopole‐like radiation patterns and in‐band antenna gains ≥ 2 dBi have also been obtained, simultaneously, with good agreement to the simulated results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1536–1538, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22495
Directional coupler for UHF mobile RFID reader
Authors: Jung Jin‐Wook , Nae Kwan‐Kyu , Thakur Jay Prakash , Cho Hong‐Gu , Park Jun‐Seok
Published: April 2007

In order to offer RFID services on mobile phones, the RFID reader must be embedded on the handset as a chip. However, the directional coupler was used as a ceramic passive component in conventional handsets. RFID system using an identical Tx/Rx carrier frequency has a significant volume limitation compared with active components. This article presents the directional coupler design for UHF RFID mobile reader using IPD (Integrated Passive Device) process. T and π‐type coupler with dimensions of 1.74 × 1.6 and 1.32 × 1.4 mm2 were assembled. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1501–1504, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22497
Measurement of a reciprocal four‐port transmission line structure using the 16‐term error model
Authors: Zhang Yun , Silvonen Kimmo , Zhu Ning H.
Published: April 2007

A new method to measure reciprocal four‐port structures, using a 16‐term error model, is presented. The measurement is based on 5 two‐port calibration standards connected to two of the ports, while the network analyzer is connected to the two remaining ports. Least‐squares‐fit data reduction techniques are used to lower error sensitivity. The effect of connectors is deembedded using closed‐form equations. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1511–1515, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22498
Design of triangular slot antenna for triple‐band (2.4/5.2/5.8 GHz) antenna with fork‐like tuning stub
Authors: Yoon J. H. , Han G. H. , Kim D. H. , Lee J. C. , Woo S. M. , Kim H. H.
Published: April 2007

A novel design for a triangular slot antenna with fork‐like tuning stub for 2.4/5.2/5.8 GHz triple‐band applications is presented in this article. The prototype consists of a triangular slot and a fork‐like tuning stub. The triangular slot is fed by a 50‐Ω microstrip line with a fork‐like tuning stub, which is printed on the opposite side of the microwave substrate. As seen in the experimental results, the impedance bandwidth (VSWR 1:2) of the proposed bandwidth is about 550 MHz for the 2.4‐GHz band and 1.736 GHz for the 5‐GHz band. This is a microstrip antenna for IEEE 802.11a/b wireless local area networks applications. Simulated and experimental results for the return loss, radiation patterns, and gains are presented and discussed.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1561–1565, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22499
A singular value decomposition based approach for far‐field reconstruction from irregularly spaced planar wide‐mesh scanning data
Authors: D'Agostino F. , Ferrara F. , Gennarelli C. , Guerriero R. , Migliozzi M. , Riccio G.
Published: April 2007

An efficient technique is developed in this article to evaluate the antenna far field from the knowledge of nonuniformly distributed near‐field data measured by a probe via a planar wide‐mesh scanning facility. To this end, the singular value decomposition method is properly applied to reconstruct the uniformly spaced samples, whose positions are fixed by a nonredundant sampling representation of the electromagnetic field. Then, the plane‐rectangular near‐field data needed to perform the classical probe compensated near‐field‐far‐field transformation are efficiently evaluated via an optimal sampling interpolation algorithm. Numerical tests, assessing the effectiveness and the stability of the far‐field reconstruction process, are reported. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1768–1772, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22502
Building a resonant cavity for the measurement of microwave dielectric permittivity of high loss materials
Authors: Rubinger C. P. L. , Costa L. C.
Published: April 2007

The design of a cavity resonator implies to solve the Maxwell equations inside that cavity, respecting the boundary conditions. As a consequence, the resonance frequencies appear as conditions in the solutions of the differential equation involved. The measurement of the complex permittivity, ϵ* = ϵ′‐iϵ″, can be made using the small perturbation theory. In this method, the resonance frequency and the quality factor of the cavity, with and without a sample, can be used to calculate the complex dielectric permittivity of the material. We measure the shift in the resonant frequency of the cavity, Δf, caused by the insertion of the sample inside the cavity, which can be related to the real part of the complex permittivity, ϵ′, and the change in the inverse of the quality factor of the cavity, Δ(1/Q), which can be related with the imaginary part, ϵ″. This is valid for very small perturbations of the electric field inside the cavity by the insertion of a sample. For materials with high losses, the perturbation can be very high, making impracticable the use of this technique. The solution is to use high volume cavities. In this work we report the design and the performance tests of a cavity to be used with high loss materials. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1687–1690, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22506
Two novel transmission lines with vertical conductors added to ground planes
Authors: Duyar Mehmet , Akan Volkan , Yazgan Erdem , Bayrak Mehmet
Published: April 2007

In this article, two different novel Coplanar Waveguides (CPW) structures have been proposed and analyzed. The CPW structures proposed provide flexibility for practical applications. For the analyses, conformal mapping techniques were employed. The closed form analytical expressions are generally suitable for usage in CAD‐oriented microwave circuit design. Both the structures have been simulated for quasi‐TEM mode in a 3D commercially available software. In addition, the results obtained in this work have been compared with the others available in the literature. Simulations and comparisons give support to the validity of the obtained analytical expressions in this study. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1653–1656, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22508
Use of genetic algorithms in linear and planar antenna array synthesis based on Schelkunoff method
Authors: Recioui A. , Azrar A.
Published: April 2007

Genetic algorithms coupled with the Schelkunoff synthesis method are used to synthesize equispaced linear and planar arrays. The purpose is to find the different excitation amplitudes and phases to achieve good matching between the desired and calculated radiation patterns. Examples which demonstrate the versatility of the approach presented in this article are considered for various patterns including the steered pattern case. The planar array is treated as a set of two separate linear arrays upon which Schelkunoff method is applied separately. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1619–1623, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22510
Dual‐frequency dual‐polarization antenna of high isolation with embedded mushroom‐like EBG cells
Authors: Lee Dong Hyun , Kim Jae Hee , Jang Jong Hun , Park Wee Sang
Published: April 2007

A dual‐frequency dual‐polarization (DFDP) antenna of high isolation between two ports with embedded 2 × 1 mushroom‐like electromagnetic bandgap (EBG) cells is presented. The equivalent circuit of a suspended microstrip line over 2 × 1 EBG cells is introduced. The numerical analysis from the equivalent circuit and measured results show that the microstrip line with embedded EBG cells has a distinctive and sharp rejection band that provides near 0 dB insertion loss outside the rejection band. By embedding the EBG cells under feedlines of a DFDP antenna, the isolation between two ports of the proposed antenna is enhanced by more than 20 dB, when compared with that of a conventional DFDP antenna. The proposed DFDP antenna is fabricated and measured. The simulated and measured results show a good agreement. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1764–1768, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22513
A novel design of a microstrip‐fed shorted square‐ring slot antenna for circular polarization
Authors: Chang Kow‐Ming , Lin Ren‐Jie , Deng I‐Chung , Ke Qing‐Xiang
Published: April 2007

The design of a circularly polarized slot antenna fed by a single microstrip line is presented. The circularly polarized radiation is achieved by means of using a shorted square‐ring slot. This proposed antenna has the fundamental resonant frequency of 2.4 GHz with the minimum return loss of −50.44 dB. The impedance bandwidth is 930 MHz or 38.7% referred to the resonant frequency, and it also has the 3‐dB axial‐ratio (AR) bandwidth of 310 MHz or 12.9% referred to the resonant frequency. In addition, this proposed antenna shows good performance of circular polarization (CP) radiation with the range of the lower 3‐dB AR value covering elevation angles between −40 to 40 degrees. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1684–1687 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22517
Circuit model and full wave analysis of a compact wideband quadrature hybrid
Authors: Jaiswal Adarsh K. , Kishk Ahmed A.
Published: April 2007

A printed, compact, and wideband quadrature hybrid is simulated and fabricated by utilizing the multi‐section technique for bandwidth enhancement and equivalent transmission line technique for size reduction. The compact quadrature hybrid has a size reduction of 50% as compared with the conventional quadrature hybrid. The compact hybrid achieves over 50% bandwidth at a centre frequency of 2 GHz. A circuit model and a full wave model are introduced and analyzed using Agilent Advanced design system. Excellent agreement between the simulated and the fabricated hybrid is achieved, which indicates that the circuit and full wave models are indeed a good representation of the fabricated compact wideband quadrature hybrid. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1650–1652, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22519
Design, realization, and test of a 900 MHz ceramic oscillator
Authors: Pisa Stefano , Piuzzi Emanuele , Tommasino Pasquale , Trifiletti Alessandro , Galli Alessandro , Giolo Giancarlo , Tafuto Antonio
Published: April 2007

The design of a 900 MHz ceramic oscillator, delivering a power of 10 dBm, has been carried out by using the negative‐resistance condition. A new procedure based on the Nyquist criterion, implemented within microwave CADs has been used to test the onset of oscillations at the desired frequency and the presence of spurious oscillation. An excellent agreement between nonlinear simulations and measurements performed on a prototype has been observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1713–1717, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22528
Study of the slow fading in indoor environment using parabolic equations
Authors: Magno Fátima N. B. , Souza João F. , Valente Zínia A. , Costa Jessé C. , Cavalcante Gervásio P. S.
Published: April 2007

This article compares slow fading component of the propagation loss calculated through parabolic wave equation and some models of the literature with results obtained during measurement campaign, in indoor environment. The frequency used was 850 MHz; a complex refractive index was considered. The implicit finite difference scheme of the Crank‐Nicolson type was applied in order to get the solution of the parabolic equation. The propagation was considered in 15° with direction paraxial. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1676–1679, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22530
A low noise 3.1 10.6 GHz pMOS distributed amplifier for ultra‐wideband applications
Authors: Wei Chien‐Cheng , Chiu Hsien‐Chin , Feng Wu‐Shiung
Published: April 2007

A low noise pMOS distributed amplifier for Ultra‐wideband (UWB) application is presented in this study. The amplifier is a two‐stage design fabricated in a standard 0.18‐μm CMOS process. The pMOS‐based distributed amplifier as input stage is used to achieve a better noise figure and a wider bandwidth; besides, the nMOS common‐source amplifier as output stage is applied to obtain sufficient gain over the band, respectively. The fully amplifier exhibits a power gain of 9 dB with a gain flatness of 0.8 dB, and noise figures are approximately lower than 5.3 dB from 3.1 to 10.6 GHz. The 1‐dB compression point and input third‐order intercept points are −8 dBm and 3.5 dBm with total power consumption of 22.5 mW, respectively. Experimental results indicate that the proposed architecture exhibits low noise and high gain performance for UWB applications. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1641–1644, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22532
Studies of small dualband annular‐ring slot antenna with a pair of implanted spur‐like slits
Authors: Sze Jia‐Yi , Hsu Chung‐I G. , Hsu Sheng‐Chin
Published: April 2007

In this article, a compact annular‐ring slot antenna for dualband operations is proposed and studied. A pair of spur‐like slits was implanted in the center patch of an annular‐ring slot antenna to excite two resonant modes with their resonant frequencies easily adjusted by changing the dimensions of these slits, resulting in a large range of dual‐frequency ratios (1.07–2.2). For the first excited resonant mode, the routes of the equivalent magnetic current distribution in the slot region can be lengthened by these slits. The resultant lowered first resonant‐band center frequency (from that of the unperturbed annular‐ring slot antenna) thus made the proposed antenna effectively miniaturized. The proposed antenna was found to have very good linearly polarized broadside radiation patterns and very low cross polarization levels in both operating bands.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1578–1581, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22536
Cylindrical double‐ridged waveguide as a basic unit of microwave heating applicators
Authors: Komarov Vyacheslav V. , Pchelnikov Yuriy N. , Yakovlev Vadim V.
Published: April 2007

This paper deals with a circular double‐ridged waveguide (CDRW) as a key element of traveling‐wave systems for microwave thermal processing. Approximate formulas for estimation of basic characteristics of CDRW partially filled with dielectric are derived with the use of the equivalent circuit technique. For accurate analysis, 3D FDTD models are developed and used for computation of coupling, electric field, and dissipated power in a coaxially excited five‐section CDRW applicator with three spherical loads. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1708–1713, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22539
QUASI‐static solutions of elliptical, cylindrical‐coupled parallel coplanar waveguide, and coupled parallel coplanar waveguide with finite ground planes
Authors: Duyar Mehmet , Akan Volkan , Yazgan Erdem , Bayrak Mehmet
Published: April 2007

This article presents the quasi‐static analyses of elliptical‐coupled parallel coplanar waveguide (ECP CPW), cylindrical‐coupled parallel coplanar waveguide (CCP CPW), and coupled parallel coplanar waveguide (CP CPW) with finite ground planes. Conformal‐mapping techniques have been used through the analyses. The obtained results show good agreement with IE3D electromagnetic‐circuit solver software's simulations for the planar case. In addition, the results have been compared with others available in the literature. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1702–1708, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22540
A new wideband three‐way power divider
Authors: Chen Guan‐Yu , Sun Jwo‐Shiun
Published: April 2007

A new three‐way power divider that provides equal power split over a wide bandwidth implemented on a single‐layer printed circuit board (PCB) is presented. It can be easily extended to an arbitrary number of output ports. The proposed power divider exhibits fairly good performance validated by measurement and simulation. Measured results show that the three output ports across the bandwidth from 1.8 to 10.5 GHz for 10 dB return loss are attainable. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1600–1603, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22547
A single‐feed wide‐ and dualband cavity‐backed slot antenna
Authors: Liu Yijun , Shen Zhongxiang , Chin H. C. , Lim W. L.
Published: April 2007

A compact design for a single‐feed cavity‐backed slot antenna is presented for operating at GSM (900 MHz) and DCS (1800 MHz). With the use of a carefully designed power distribution network, a single‐feed design is realized for a dual‐ and wideband slot antenna with high gain and good radiation patterns. Measured results show that the antenna has a wide bandwidth at both frequency bands and it exhibits high gain and good radiation patterns, which is desirable for many dualband applications.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1570–1572, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22549
Broadband dual‐frequency CPW‐FED antenna with a cross‐shaped feeding line for WLAN application
Authors: Liu Wen‐Chung
Published: April 2007

A novel and simple design of a coplanar waveguide‐fed planar monopole antenna with broadband dual‐frequency operation for wireless local area network (WLAN) application is proposed. Good impedance matching for dual‐resonance mode is obtained by feeding the radiating patch with a cross‐shaped strip line. Prototypes of the obtained design have been constructed and experimentally studied. The measured results explore broad dual‐frequency operation with (10 dB impedance bandwidths of 30%, ranging from 2.23 to 2.96 GHz, and 56.7%, ranging from 4.6 to 7.62 GHz, at bands of 2.43 and 5.33 GHz, respectively, which cover the 2.4/5.2/5.7 GHz WLAN operating bands, and show good agreement with the numerical prediction. Good monopole‐like radiation patterns and sufficient antenna gains over the operating bands have also been observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1739–1744, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22551
An ultra‐wideband stacked microstrip patch antenna
Authors: Ang Irene , Ooi B. L.
Published: April 2007

A novel ultra‐wideband (UWB) stacked microstrip patch antenna suitable for UWB application is presented in this article. This compact and planar proposed antenna is found to have a very broad impedance bandwidth as compared to the conventional electromagnetic coupled antenna. The proposed antenna is able to achieve an impedance bandwidth of about 101.8% for VSWR less than 2, centred at around 7 GHz. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1659–1665, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22555
Fractal‐shaped stepped‐impedance transformers for wideband application
Authors: Chen Wen‐Ling , Wang Guang‐Ming , Qi Yi‐Na , Liang Jian‐Gang
Published: April 2007

Microstrip stepped‐impedance transformers using a Sierpinski fractal shape are proposed for the first time. The proposed fractal‐shaped stepped‐impedance transformers can greatly enhance the operating frequency bandwidth. Bandwidth up to 44.0% and 73.9% (S11≤−30 dB) have been achieved by the presented two‐section and three‐section fractal‐shaped maximal flat stepped‐impedance transformers, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1628–1630, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22557
All‐optical logic or gate using two cascaded semiconductor optical amplifiers
Authors: Hamié Ali , Sharaiha Ammar , Guégan Mikael , Le Bihan Jean , Hamzé Adnan
Published: April 2007

A novel all‐optical logic OR gate based on cross‐gain modulation (XGM) using a two‐cascaded semiconductor optical amplifiers (SOAs) in a counterpropagating topology is presented. The attractive issue of the proposed method is that the logic OR gate can be obtained at a probe wavelength by taking advantage of the positive gain variation of one of the two used SOAs in the counterpropagating configuration. This reported feasibility study shows the all‐optical logic OR gate can be easily achieved with an extinction ratio higher than 7 dB.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1568–1570, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22560
Mechanism study of mechanical tuning in HTS filter application
Authors: Peng Huili , Zhang Xiaoping , Guo Xubo , Mu Lijuan , Wei Bin , Gao Baoxin , Cao Bisong
Published: April 2007

Mechanical tuning method using sapphire and copper rods for high temperature superconducting filters is presented. A three‐pole microstrip filter and a two‐pole patch filter were fabricated and tuned. Results show that the center frequency shifts toward lower end in dielectric tuning and toward either lower end or higher end in metallic tuning depending on the local electromagnetic field distribution.© 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1565–1568, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22561
Telomere length status of somatic cell sheep clones and their offspring
Authors: Alexander Basil , Coppola Gianfranco , Perrault Steven D. , Peura Teija T. , Betts Dean H. , King W. Allan
Published: April 2007

This study was carried out to determine the telomere length status of sheep clones and their offspring, and to examine telomere dynamics and chromosomal abnormalities in culture propagated donor cells. Skin samples were collected from somatic cell nuclear transfer‐derived sheep clones, and three of their progeny generated by natural mating. Samples were collected from control animals (n = 35), spanning in age from 1 month to 36 months of age. Genomic DNA was extracted from cell/tissue samples and their telomere lengths were assessed by terminal restriction fragment (TRF) analysis. Results revealed: that (a) sheep clones derived from cultured somatic cells have shortened telomere lengths compared to age‐matched controls; (b) the offspring derived from natural mating between clones had normal telomere lengths compared to their age‐matched counterparts; and donor cell cultures beyond 20 population doublings had significantly (P < 0.05) shortened telomeres and exhibited a higher numerical and structural chromosomal abnormalities. Mol. Reprod. Dev. 74: 1525–1537, 2007. © 2007 Wiley‐Liss, Inc.
Determining elastic constants of transversely isotropic rocks using Brazilian test and iterative procedure
Authors: Chou Yen‐Chin , Chen Chao‐Shi
Published: April 2007

The elastic constants of rocks are the basic parameters for rock mechanics, and play a very important role in engineering design. There are many laboratory methods to determine the elastic constants of transversely isotropic rocks, and the Brazilian test is a popular method. This paper presented a method combination of the Brazilian test, back calculation, and iterative procedure to evaluate the five independent elastic constants of transversely isotropic rocks in laboratory.
The strain data at the centre of discs were obtained using Brazilian test. The stresses at the centre of discs were computed using numerical programs. By using back calculation, the temporary elastic constants were computed after the stresses and stains were substituted into elastic mechanics equations. After iterative procedure, the convergent values of the elastic constants can be obtained. One numerical example and three experimental cases were proposed to show the applicability of this method. The convergent values of the five independent elastic constants can be obtained in no more than 10 iterative cycles. The results coming from numerical analysis method exhibited satisfactory outcome in accordance with those of generalized reduced gradient method. The merits of this method include convenient specimen preparation of the Brazilian test, simple iterative procedure, and readily available commercially numerical programs, so that this method can be easily popularized in research and engineering analysis. Copyright © 2007 John Wiley & Sons, Ltd.
The prevalence and risk factors of urinary incontinence and its influence on the quality of life among Egyptian women
Authors: El‐Azab Ahmed S. , Mohamed Eman M. , Sabra Hanaa I.
Published: April 2007

Aims

The exact magnitude of the problem of urinary incontinence (UI) in Egypt is not yet reported. We studied the prevalence and potential risk factors associated with UI among a group of Egyptian women as taken from a representative sample from the population.

Methods

Design: A cross‐sectional, community‐based study. Setting: Assiut, Upper Egypt, Egypt. Participants: women, aged 20 years and older, selected randomly from the population. Measurements: Participants completed a previously validated questionnaire; Urogenital Distress Inventory‐short form (UDI‐6).

Results

A total of 1,652 women were included. The prevalence of UI among our study subjects is 54.8%. Aging, low educational level, menopause, higher parity (>3), vaginal delivery, and previous multiple abortions (>3) were found to be significantly associated with UI. The prevalence of urge, stress and mixed incontinence, mutually exclusive of each other, was 15%, 14.8%, and 25%, respectively. The prevalence of severe incontinence is 8.4%. Regarding the quality of life, the most distressing issues for sufferers were their inability to pray (90%).

Conclusions

UI is quite common in Egypt and prevalence rates are higher when compared to other reports. Neurourol. Urodynam. 26:783–788, 2007. © 2007 Wiley‐Liss, Inc.
Elevating tensor rank increases anisotropy in brain areas associated with intra‐voxel orientational heterogeneity (IVOH): a generalised DTI (GDTI) study
Authors: Minati L. , Banasik T. , Brzezinski J. , Mandelli M.L. , Bizzi A. , Bruzzone M.G. , Konopka M. , Jasinski A.
Published: April 2007

Rank‐2 tensors are unable to represent multi‐modal diffusion associated with intra‐voxel orientational heterogeneity (IVOH), which occurs where axons are incoherently oriented, such as where bundles intersect or diverge. Under this condition, they are oblate or spheroidally shaped, resulting in artefactually low anisotropy, potentially masking reduced axonal density, myelinisation and integrity. Higher rank tensors can represent multi‐modal diffusion, and suitable metrics such as generalised anisotropy (GA) and scaled entropy (SE) have been introduced. The effect of tensor rank was studied through simulations, and analysing high angular resolution diffusion imaging (HARDI) data from two volunteers, fit with rank‐2, rank‐4 and rank‐6 tensors. The variation of GA and SE as a function of rank was investigated through difference maps and region of interest (ROI)‐based comparisons. Results were correlated with orientation distribution functions (ODF) reconstructed with q‐ball, and with colour‐maps of the principal and second eigenvectors. Simulations revealed that rank‐4 tensors are able to represent multi‐modal diffusion, and that increasing rank further has a minor effect on measurements. IVOH was detected in subcortical regions of the corona radiata, along the superior longitudinal fasciculus, in the radiations of the genu of the corpus callosum, in peritrigonal white matter and along the inferior fronto‐occipital and longitudinal fascicula. In these regions, elevating tensor rank increased anisotropy. This was also true for the corpus callosum, cingulum and anterior limb of the internal capsule, where increasing tensor rank resulted in patterns that, although mono‐modal, were more anisotropic. In these regions the second eigenvector was coherently oriented. As rank‐4 tensors have only 15 distinct elements, they can be determined without acquiring a large number of directions. By removing artefactual underestimation of anisotropy, their use may increase the sensitivity to pathological change. Copyright © 2007 John Wiley & Sons, Ltd.
Effects of AZD2171 and vandetanib (ZD6474, Zactima) on haemodynamic variables in an SW620 human colon tumour model: an investigation using dynamic contrast‐enhanced MRI and the rapid clearance blood pool contrast agent, P792 (gadomelitol)
Authors: Bradley D. P. , Tessier J. L. , Checkley D. , Kuribayashi H. , Waterton J. C. , Kendrew J. , Wedge S. R.
Published: April 2007

The effect of two novel therapeutic agents on tumour haemodynamics was investigated using a fast dynamic contrast‐enhanced (DCE)‐MRI protocol (0.5 s/image) sensitive to signal changes in both the vascular input function and tumour during the administration of the macromolecular rapid clearance blood pool agent (MM‐RCBPA), gadomelitol (P792, Vistarem). This enabled simultaneous measurement of the tumour blood flow per unit volume of tissue (F/VT, mL/s/mL), the fractional plasma volume (Vp, %), and the permeability surface area product per unit volume of tissue (PSρ, s−1) in subcutaneous SW620 human colorectal tumour xenografts grown in nude rats before and after (at 0 and 22 h; imaging at 24 h) acute treatment with AZD2171 (3 mg/kg) and vandetanib (ZD6474, Zactima; 50 mg/kg), which have inhibitory activity against vascular endothelial growth factor receptor‐2 (VEGFR‐2) tyrosine kinase. MRI was performed at 4.7 T using a single‐slice, modified, T1‐weighted, spoiled gradient‐echo technique. Both compounds reduced gadomelitol uptake into the tumour. AZD2171 and vandetanib, respectively, (a) greatly reduced PSρ to 19.7 ± 9.5% and 28.9 ± 14.1% of baseline (P = 0.007 and P = 0.02), (b) markedly reduced Vp to 31.2 ± 19.1% and 54.8 ± 21.2% of baseline (P = 0.015 and P = 0.09), and (c) had no significant effect on F/VT. There was no significant difference between groups treated with AZD2171 and vandetanib when each variable was compared. The reductions in PSρ and Vp are consistent with inhibition of VEGF signalling. AZD2171 (3 mg/kg) and vandetanib (50 mg/kg) were also found to produce a comparable chronic inhibition of SW620 tumour growth (89% for both). This study shows that DCE‐MRI using an MM‐RCPBA can be used to distinguish tumour vascular flow, volume, and permeability surface area product in a tumour model, and enables the acute effects of VEGF signalling inhibition to be examined in detail. Copyright © 2007 John Wiley & Sons, Ltd.
Viscoelasticity in polymers: Phenomenological to molecular mathematical modeling
Authors: Banks H.T. , Luke N.S. , Samuels J.R.
Published: April 2007

We report on two recent advances in the modeling of viscoelastic polymers: (i) a new constitutive model that combines the virtual stick‐slip continuum “molecular‐based” ideas of Johnson and Stacer with the Rouse bead chain ideas; (ii) a two‐dimensional version of a model that accounts for stenosis‐driven shear wave propagation in biotissue. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 817–831, 2007
Improving the performance of perfectly matched layers by means of hp‐adaptivity
Authors: Michler C. , Demkowicz L. , Kurtz J. , Pardo D.
Published: April 2007

We improve the performance of the Perfectly Matched Layer (PML) by using an automatic hp‐adaptive discretization. By means of hp‐adaptivity, we obtain a sequence of discrete solutions that converges exponentially to the continuum solution. Asymptotically, we thus recover the property of the PML of having a zero reflection coefficient for all angles of incidence and all frequencies on the continuum level. This allows us to minimize the reflections from the discrete PML to an arbitrary level of accuracy while retaining optimal computational efficiency. Since our hp‐adaptive scheme is automatic, no interaction with the user is required. This renders tedious parameter tuning of the PML obsolete. We demonstrate the improvement of the PML performance by hp‐adaptivity through numerical results for acoustic, elastodynamic, and electromagnetic wave‐propagation problems in the frequency domain and in different systems of coordinates. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 832–858, 2007
Modeling and numerical analysis of masonry structures
Authors: Ainsworth Mark , Mihai L. Angela
Published: April 2007

We model masonry structures as elastodynamic systems assembled from a large number of elastic bodies (bricks or stone‐blocks) in unilateral, frictional contact. The problem is formulated as a quasi‐variational inequality and discretised using piecewise polynomial finite elements in conjunction with an energy consistent time integration scheme. At each time‐step, the quasi‐variational inequality is reformulated as a nonlinear complementarity problem. An iterative splitting of the contact problem into normal contact and frictional contact, together with a primal‐dual active‐set method is employed to calculate deformations and openings in the model structures. Numerical results are presented to illustrate the efficiency of the resulting approach in predicting the mechanical behaviour of a bidimensional arch‐ring made of bricks, deformed due to body forces and surface tractions. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 798–816, 2007
Robust domain decomposition algorithms for multiscale PDEs
Authors: Graham I.G. , Scheichl R.
Published: April 2007

In this article, we describe a new class of domain decomposition preconditioners suitable for solving elliptic PDEs in highly fractured or heterogeneous media, such as arise in groundwater flow or oil recovery applications. Our methods employ novel coarsening operators, which are adapted to the heterogeneity of the media. In contrast to standard methods (based on piecewise polynomial coarsening), the new methods can achieve robustness with respect to coefficient discontinuities even when these are not resolved by a coarse mesh. This situation arises often in practical flow computation, in both the deterministic and (Monte‐Carlo simulated) stochastic cases. An example of a suitable coarsener is provided by multiscale finite elements. In this article, we explore the linear algebraic aspects of the multiscale algorithm, showing that it involves a blend of both classical overlapping Schwarz methods and nonoverlapping Schur methods. We also extend the algorithm and the theory from its additive variant to obtain new hybrid and deflation variants. Finally, we give extensive numerical experiments on a range of heterogeneous media problems illustrating the properties of the methods. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 859–878, 2007
Iteratively coupled mixed and Galerkin finite element methods for poro‐elasticity
Authors: Wheeler Mary F. , Gai Xiuli
Published: April 2007

We present a finite element formulation for coupled flow and geomechanics. We use mixed finite element spaces to approximate pressure and continuous Galerkin methods for displacements. In solving the coupled system, pressure and displacements can be solved either simultaneously in a fully coupled scheme or sequentially in a loosely coupled scheme. In this paper we formulate an iterative method where pressure and displacement solutions are staggered during a time step until a convergence tolerance is satisfied. A priori convergence results for the iterative coupling are also presented, along with a summary of the convergence results for the fully coupled scheme. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 785–797, 2007