bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of SIW‐based planar integrated w‐band low‐phase noise Gunn harmonic oscillator
Authors: Liu Yong , Tang Xiaohong , Wu Tao 
Published: March 2011

AbstractBased on the substrate integrated waveguide (SIW) technology, the influence of SIW cavity on phase noise of W‐band oscillator is studied and a novel W‐band low phase noise GaAs Gunn planar harmonic oscillator is developed in this letter. The technique of harmonic extraction from Gunn diodes and the novel SIW cavity structure with short piston, which is introduced to study the influence of SIW cavity on phase noise of oscillator, are discussed in detail. Because of the high quality factor and planar structure of the SIW cavity resonator, the oscillator is characterized by some advantages such as low phase noise, small size, low cost and planar integration. The optimal phase noise is −105.81 dBc/Hz at 1 MHz offset 92.16 GHz carrier frequency and the measured output power is more than 6.2 dBm. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1239–1242, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26002
Effect of composited‐layer AlyGa1‐yN on performances of AlGaN/GaN HEMT with unintentionally doping barrier AlxGa1‐xN
Authors: Cheng Zhi‐qun , Hu Sha , Zhou Wei‐jian , Liu Jun 
Published: March 2011

AbstractA novel structure AxGa1‐xN/AlN/AlyGa1‐yN/GaN HEMT with composited‐layer and unintentionally doping barrier was designed for high linearity. The effect of two‐dimensional electron gas (2DEG) and electric field on device structure parameter is obtained from the self‐consistent solution basing on theory of semiconductor energy band and quantum well. Combining with results of theory analysis and TCAD software simulation results, the optimization structure Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT was proposed. And AxGa1‐xN/AlN/GaN HEMT without composited‐ layer and unintentionally doping barrier was designed together for comparison. Both devices with gate length of 0.3 μm and gate width of 200 μm were fabricated. Measured results show proposed AxGa1‐xN/AlN/AlyGa1‐yN/GaN HEMT has better performances of linearity, gain, and power added efficiency (PAE) than AxGa1‐xN/AlN/GaN HEMT. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1206–1209, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26004
Antenna representation in two‐port network scattering parameter
Authors: Prakoso Teguh , Ngah Razali , Ghassemlooy Zabih , Rahman Tharek Abdul 
Published: March 2011

AbstractThis paper proposes a representation of antenna in two‐port network s‐parameter, by exploiting the analogy between the antenna and a two‐port network, to produce a suitable method for evaluating antennas in system and circuit simulation. Complicated steps required by previous methods to determine an antenna‐specific equivalent‐circuit and its corresponding resistor, inductor, and capacitor values are avoided. Simulations results obtained for the circuit and system software confirms the validity of the proposed scheme. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1404–1409, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26005
Capacitance of a conductor‐backed coplanar waveguide with an upper shielding
Authors: Park Yong Bae , Park Geon Hye 
Published: March 2011

AbstractIn this letter, the capacitance of a conductor‐backed coplanar waveguide (CPW) with an upper shielding is investigated.An electrostatic boundary‐value problem of the conductor‐backed CPW with an upper shielding is solved using the Fourier transform, mode matching technique, and superposition. The capacitance of the conductor‐backed CPW is represented in a series and calculated in terms of the CPW geometry. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1364–1368, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26007
Optical carrier sinusoidal modulation suppressed by ultra‐long semiconductor optical amplifier gain saturation
Authors: Ribeiro Napoleão S. , Cavalcante André L. R. , Gallep Cristiano M. , Conforti Evandro 
Published: March 2011

AbstractThe amplitude modulated sinusoidal pattern over an optical carrier is suppressed by a deeply saturated ultra‐long semiconductor optical amplifier. The extinction‐ratio of the modulated signal is reduced from 16.8 to 3.9 dB at 15 GHz. The characterization of the amplitude modulation suppression is presented, with good results for broadband operation (15 nm at 1557 nm), high‐speed (up to 35 GHz) and high input extinction‐ratio (up to 16.8 dB). © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1286–1290, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26010
Polarization‐preserving evanescent‐mode filters
Authors: Yu Seng Yong , Bornemann Jens 
Published: March 2011

AbstractRectangular and circular waveguide evanescent‐mode filters with polarization‐preserving properties are presented. The filters are formed by inserting quadruple‐ridged resonators in a square or circular waveguide operated below cutoff. They are especially suited in applications requiring short and compact components. The numerical technique that facilitates eigenvalue and scattering parameter computations is verified against measurements. Basic design considerations are discussed, and structural dimensions are provided for two 9.5 GHz filters with 500 MHz bandwidth. Performances are validated by independent and commercially available electromagnetic software packages. Sensitivity issues for fabrication are addressed by a tolerance analysis. Fabrication accuracy is acceptable for operation in dual vertical and horizontal polarizations but is considerably more stringent for circularly polarized applications. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1435–1439, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26016
Microstrip‐fed polygon slot antenna design for WLAN applications
Authors: Sim Chow‐Yen‐Desmond , Cai Fu‐Ren 
Published: March 2011

AbstractA novel microstrip‐fed polygon slot antenna with dual‐band operation for WLAN (Wireless Local Area Network) applications in the 2.4/5.2/5.8 GHz bands is proposed. The polygon slot is formed by embedding two right‐angle triangular ground patches into both upper‐corners of the rectangular slot. To allow the excitation of three resonant modes located exactly around 2.4, 5.2, and 5.8 GHz bands, besides tuning the length of the hypotenuse of the triangular ground patches, an L‐shaped slit is also loaded into the rectangular radiating element. The design of this proposed antenna via simulation is illustrated in detail, and typical experiments were performed on the fabricated prototype. From the experimental results, the lower band measured along VSWR 2:1 operates from 2.36 to 2.63 GHz, while a broad upper band from 4.98 to 6.8 GHz is also observed. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1394–1398, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26018
A novel flexible GMRES with deflated restarted for efficient solution of electromagnetic problems
Authors: Hu X. Q. , Ding D. Z. , Chen R. S. 
Published: March 2011

AbstractTo iterative solve large dense complex linear systems arising from electric field integral equations formulation of electromagnetic scattering problems, multilevel fast multipole algorithm (MLFMA) is built to speed up the matrix‐vector product (MVP) operations. This article presents a novel flexible generalized minimum residual with deflated restarted (FGMRES‐DR), which can greatly improve the convergence of those large dense complex linear systems. Based on physical mechanism of the scattering problems, in inner iteration of FGMRES‐DR, an iterative solution of the near‐field matrix in MLFMA is adopted. In outer iteration, deflation method which is purely algebraic is used to eliminate the influence on convergence because of the smallest eigenvalues. Numerical experiments indicate that FGMRES‐DR is very effective and can reduce the number of MVP compared with the FGMRES in large‐scale electromagnetic problems. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1360–1364, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26019
Design of dual‐band colpitts VCO by switched negative resistance shaping
Authors: Chen Ying , Mouthaan Koen 
Published: March 2011

AbstractA switched negative resistance shaping technique is proposed to design a dual‐band Colpitts VCO.By making use of the Miller effect, the negative resistance of the Colpitts oscillator can be shaped with an additional switchable inductor‐capacitor (LC) resonator placed between the base and the collector of the bipolar transistor. The shaping of the negative resistance guarantees oscillation to start at only the selected resonant mode when a multimode resonator is used at the input of the Colpitts oscillator. Using the proposed technique, a dual‐band VCO is designed with center frequencies of 440 and 640 MHz. The measured continuous frequency tuning range is 15.8 and 16.3% for the lower band and the upper band, respectively. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1356–1360, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26020
Enhancement technique of insertion loss and linearity for PIN diode switches
Authors: Sun Pinping , Peng Liu , Upadhyaya Parag , Jeong Dong‐Ho , Heo Deukhyoun 
Published: March 2011

AbstractDesign and analysis of insertion loss and linearity enhancement technique for PIN diode RF switches are presented.Measurements show a 12.5% insertion loss improvement by optimizing anode‐to‐cathode distance, a 3.29% reduction of intrinsic resistance by choosing the octagonal shape over the square one, and a 1 dB P1dB improvement by using the new cathode biased technique. A low insertion loss and high isolation single‐pole double‐throw (SPDT) switch has been built with the proposed PIN diode. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1430–1435, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26022
Comparison of dynamic contrast‐enhanced MRI and dynamic contrast‐enhanced CT biomarkers in bladder cancer
Authors: Naish J. H. , McGrath D. M. , Bains L. J. , Passera K. , Roberts C. , Watson Y. , Cheung S. , Taylor M. B. , Logue J. P. , Buckley D. L. , Tessier J. , Young H. , Waterton J. C. , Parker G. J. M. 
Published: March 2011

AbstractDynamic contrast‐enhanced MRI (DCE‐MRI) is frequently used to provide response biomarkers in clinical trials of novel cancer therapeutics but assessment of their physiological accuracy is difficult. DCE‐CT provides an independent probe of similar pharmacokinetic processes and may be modeled in the same way as DCE‐MRI to provide purportedly equivalent physiological parameters. In this study, DCE‐MRI and DCE‐CT were directly compared in subjects with primary bladder cancer to assess the degree to which the model parameters report modeled physiology rather than artefacts of the measurement technique and to determine the interchangeability of the techniques in a clinical trial setting. The biomarker Ktrans obtained by fitting an extended version of the Kety model voxelwise to both DCE‐MRI and DCE‐CT data was in excellent agreement (mean across subjects was 0.085 ± 0.030 min−1 for DCE‐MRI and 0.087 ± 0.033 min−1 for DCE‐CT, intermodality coefficient of variation 9%). The parameter vp derived from DCE‐CT was significantly greater than that derived from DCE‐MRI (0.018 ± 0.006 compared to 0.009 ± 0.008, P = 0.0007) and ve was in reasonable agreement only for low values. The study provides evidence that the biomarker Ktrans is a robust parameter indicative of the underlying physiology and relatively independent of the method of measurement. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Fast bound pool fraction mapping using stimulated echoes
Authors: Soellinger M. , Langkammer C. , Seifert‐Held T. , Fazekas F. , Ropele S. 
Published: March 2011

AbstractMagnetization transfer imaging advanced to an indispensible tool for investigating white matter changes. Quantitative magnetization transfer imaging methods allow the determination of the bound pool fraction (BPF), which is thought to be directly linked to myelin integrity. Long acquisition times and high specific absorption rates are still inhibiting broad in vivo utilization of currently available BPF mapping techniques. Herewith, a stimulated echoes amplitude modulation‐based, single‐shot echo planar imaging technique for BPF and T1 quantification is presented at 3T. It allows whole brain mapping in 10–15 min and is low in specific absorption rates. The method was validated with different concentrations of bovine serum albumin (BSA) phantoms. Intra‐ and inter‐subject variability was assessed in vivo. Phantom measurements verified linearity between bovine serum albumin concentrations and measured BPF, which was independent of T1 variations. T1 values in the phantoms correlated well with values provided by standard T1 mapping methods. Intrasubject variability was minimal and mean regional BPFs of 10 volunteers (e.g., left frontal white matter = 0.135 ± 0.003, right frontal white matter = 0.129 ± 0.006) were in line with previously published data. Assessment of interhemispheric BPF differences revealed significantly higher BPF for the left brain hemisphere. To sum up, these results suggest the proposed method useful for cross‐sectional and longitudinal studies of white matter changes in the human brain. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.
Locating median paths on connected outerplanar graphs
Authors: Lari Isabella , Ricca Federica , Scozzari Andrea , Becker Ronald I. 
Published: March 2011

AbstractIn this article, we study the median path problem without length restrictions on the class of connected outerplanar graphs, assuming that weights equal to 1 are assigned to the edges of a graph G, and nonnegative weights are associated to its vertices. We provide an
$O(kn)$
time algorithm, where n is the number of vertices of G and k is the number of blocks in G. As a byproduct, when G is a biconnected outerplanar graph, we provide a linear time algorithm to find a median path between two fixed vertices of G without restrictions on the length. In the literature, we did not find polynomial time algorithms for this problem on such classes of graphs. © 2011 Wiley Periodicals, Inc. NETWORKS, 2011
Parametric maximum flow methods for minimax approximation of target quotas in biproportional apportionment
Authors: Serafini Paolo , Simeone Bruno 
Published: March 2011

AbstractIn this article, we study the biproportional apportionment problem, which deals with the assignment of seats to parties within regions. We consider the minimization of both the maximum absolute error and the maximum relative error of the apportioned seats with respect to target quotas. We show that this can be done polynomially through a reduction to a parametric maximum flow problem. Moreover, the maximum absolute error can be minimized in strongly polynomial time. More generally, our method can be used for computing
$\ell_{\infty}$
projections onto a flow polytope. We also address the issue of uniqueness of the solution, proposing a method based on finding unordered lexicographic minima. Our procedure is compared to other well‐known ones available in the literature. Finally we apply our procedures to the data of the 2008 Italian political elections, for which the procedure stated by the law produced an inconsistent assignment of seats. © 2011 Wiley Periodicals, Inc. NETWORKS, 2012
Application of response surface methodology to optimise ultrasonic‐assisted extraction of four chromones in Radix Saposhnikoviae
Authors: Li Wei , Wang Zi , Sun Yin‐shi , Chen Li , Han Li‐kun , Zheng Yi‐nan 
Published: March 2011

AbstractIntroduction – Radix Saposhnikoviae is one of the most famous Chinese herbal medicines with many pharmacological activities towards inflammatory symptoms and antioxidation. Chromones are considered as one of the effective components. It is important to find a reasonable method to extract the chromones in S. divaricata.Objective – To develop an ultrasonic‐assisted extraction (UAE) to extract chromones in Radix Saposhnikoviae and to optimise extraction conditions.Methodology – Four chromones (prim‐O‐glucosylcimifugin, cimifugin, 5‐O‐methylvisammioside and sec‐O‐glucosylhamaudol) were extracted by the UAE method combined with response surface methodology (RSM). Box–Behnken design (BBD) was applied to evaluate the effects of three independent variables (ethanol concentration, extraction time and extraction temperature) on the chromones yield of Radix Saposhnikoviae.Results – Correlation analysis of the mathematical‐regression model indicated that a quadratic polynomial model could be employed to optimise the extraction of chromones by UAE method. The optimal conditions to obtain the highest chromones yield of Radix Saposhnikoviae were a solvent of 75% ethanol, an extraction time of 48 min and an extraction temperature of 67°C.Conclusion – Under these optimal conditions, the experimental values agreed closely with the predicted values. The analysis of variance indicated a high goodness of model fit and the success of RSM method for optimising chromones extraction in Radix Saposhnikoviae. Copyright © 2011 John Wiley & Sons, Ltd.
Detection of High Levels of Pyrrolizidine‐N‐oxides in the Endangered Plant Cryptantha crassipes (Terlingua Creek Cat's‐eye) Using HPLC‐ESI‐MS
Authors: Williams Maria T. , Warnock Bonnie J. , Betz Joseph M. , Beck John J. , Gardner Dale R. , Lee Stephen T. , Molyneux Russell J. , Colegate Steven M. 
Published: March 2011

ABSTRACTIntroductionA previous investigation of pyrrolizidine alkaloids produced by nine species of Cryptantha identified at least two chemotypes within the genus. Other research has postulated that pyrrolizidine‐N‐oxide concentrations increase as the growing conditions become harsher, particularly with respect to water availability. Cryptantha crassipes is an endangered plant with a very limited distribution range within a dry, harsh Texan ecosystem.ObjectiveTo determine the pyrrolizidine alkaloid (and their N‐oxides) profile and concentrations in Cryptantha crassipes.MethodologyMethanolic extracts of Cryptantha crassipes were partitioned into dilute sulphuric acid and the alkaloids concentrated using strong cation exchange, solid‐phase extraction columns. Extracts were analysed using reversed‐phase high‐pressure liquid chromatography coupled to electrospray ionisation ion trap mass spectrometry.ResultsThe N‐oxides of lycopsamine and intermedine were the major pyrrolizidine alkaloids detected in Cryptantha crassipes. Smaller to trace amounts of other pyrrolizidine alkaloids observed were: the 7‐ and 3′‐acetylated derivatives and the 1,2‐dihydro analogs of lycopsamine‐N‐oxide and/or intermedine‐N‐oxide; a pair of unidentified N‐oxides, isobaric with lycopsamine‐N‐oxide; and the N‐oxides of leptanthine, echimiplatine, amabiline, echiumine and dihydroechiumine. Only trace amounts, if any, of the parent free base pyrrolizidine alkaloids were detected. The concentration of pyrrolizidine alkaloids was estimated to be 3–5% of the dry weight of milled leaves, or 10–50 times the levels previously reported for similar chemotypes.ConclusionsThe high levels of the N‐oxides of lycopsamine and intermedine establish the genus chemotype of the endangered Cryptantha crassipes and support earlier data linking high levels of N‐oxides to dry, harsh growing conditions. Copyright © 2011 John Wiley & Sons, Ltd.
Antifungal effect of chitosan on the growth of Aspergillus parasiticus and production of aflatoxin B1
Authors: Cota‐Arriola Octavio , Cortez‐Rocha Mario Onofre , Rosas‐Burgos Ema Carina , Burgos‐Hernández Armando , López‐Franco Yolanda Leticia , Plascencia‐Jatomea Maribel 
Published: March 2011

AbstractContamination of agricultural products by toxigenic fungi and the presence of mycotoxins cause serious economic damage, and toxic effects to humans and animals. In this study the effect of chitosan as a natural alternative for the control of the fungus Aspergillus parasiticus was evaluated. Chitosans were obtained from chitin previously extracted from shrimp heads using chemical (CS) and biological (CB) processes. The chitosan yields were 5.74 and 6.20% for CS and CB methods, respectively, with an amount of residual protein and ash below 1%, low molecular weight and degree of deacetylation of 80–82%. Chitosan showed fungistatic activity against A. parasiticus, with 6.71 and 10.66 g L−1 (CI50) of CS and CB, respectively, being required to delay fungal growth by 50% at 122 h. Chitosan (CI50) inhibited both radial growth up to 122 h, and germination of spores before 8 h higher than 50%. Chitosan also increased the average diameter of the spores and hyphae (P ≤ 0.05), reduced the septation process and increased the number of mitotic divisions of spores during germination. However, compared with control, chitosan decreased (P ≤ 0.05) aflatoxin B1 production at 8 days but increased (P ≤ 0.05) the total aflatoxins production by A. parasiticus. Copyright © 2011 Society of Chemical Industry
Fabrication of highly refractive, transparent BaTiO3/poly(methyl methacrylate) composite films with high permittivities
Authors: Nagao Daisuke , Kinoshita Takafumi , Watanabe Akira , Konno Mikio 
Published: March 2011

AbstractIncorporation of crystalline barium titanate (BT) nanoparticles into poly(methyl methacrylate) (PMMA) was carried out to prepare highly refractive polymer nanocomposite films that have transparency and high permittivities. The BT nanoparticles were prepared by hydrolysis of a barium/titanium complex alkoxide in 2‐methoxyethanol, then surface‐modified with a silane coupling agent (3‐methacryloxypropyltrimethoxysilane) to improve their affinity for PMMA. The incorporation of the surface‐modified nanoparticles into PMMA was performed up to a nanoparticle content almost equivalent to particle close‐packing state. The refractive index of the composite films increased with nanoparticle incorporation, keeping the relative transmittance normalized with PMMA film above 90%. A high refractive index of 1.82 was reached at a nanoparticle content of 53 vol% with a dielectric constant as high as 36 and a dissipation factor as low as 0.05. The results demonstrate that the crystalline BT nanoparticles are useful fillers for effectively increasing both refractive index and dielectric constant of polymer nanocomposites. Copyright © 2011 Society of Chemical Industry
Correlates of psychopathic personality traits in community couples
Authors: Savard Claudia , Sabourin Stéphane , Lussier Yvan 
Published: March 2011

ABSTRACTDrawing on a representative sample of 140 young couples, the study aimed to assess the distribution and correlates of psychopathic personality traits in a community sample. A related objective was to determine whether psychopathic traits contribute to men‐reported and women‐reported couple satisfaction, psychological aggression, neuroticism and psychological distress. Both partners completed self‐report measures of psychopathic traits, couple satisfaction, psychological aggression, neuroticism and psychological distress. Results for both men and women showed moderate or elevated psychopathic personality traits in a significant proportion of the sample. Actor–partner interdependence analyses (APIM) showed that global psychopathy significantly predicted couple satisfaction through an elevation of personal distress. APIM analyses for primary psychopathy showed the same pattern of results but only in men. Finally, there was a direct negative path from secondary psychopathy to couple satisfaction, but this association was partially mediated by personal distress and psychological aggression. Copyright © 2011 John Wiley & Sons, Ltd.