bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wideband circularly polarized single probe‐fed patch antenna
Authors: Ma Jinping , Kouki Ammar B. , Landry Rene 
Published: May 2012

AbstractA wideband circularly polarized single‐patch single probe‐fed patch antenna is investigated for applications of GPS L5, L2 and Galileo E5a, E5b bands. The wideband circular polarization (CP) is achieved by corner‐truncated square patch and insertion of a thick air layer between the radiating patch and the ground plane. A conducting circular disc is etched on the back side of the substrate to compensate the long inductive probe. The obtained 3‐dB axial ratio (AR) CP bandwidth for 25 and 28.5 mm air layer are 5.9% (71 MHz) and 6.4% (77 MHz), respectively. The later covers the all lower L bands of GPS and Galileo. The realized antenna gain reaches 6.45 dBi over the 3‐dB AR bandwidth. The measured and simulated results are in excellent agreement. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1803–1808, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26965
Small square monopole antenna having variable frequency band‐notch operation for UWB wireless communications
Authors: Ojaroudi Nasser , Ojaroudi Mohammad 
Published: May 2012

AbstractA novel printed monopole antenna for ultra wide band (UWB) applications with frequency band‐notch function is presented.By inserting a vertical H‐shaped slot in the ground plane, a new resonance at higher frequencies can be achieved and provides a wide usable fractional bandwidth of more than 110% (3–11.5 GHz). To generate frequency band‐stop performance, we use a horizontal H‐shaped parasitic structure in the ground plane, that with this design, a frequency notched band of 5.1–5.97 GHz has been obtained. Simulated and experimental results obtained for this antenna show that the proposed single band‐notch square monopole antenna has a good antenna gains and radiation behavior within the UWB frequency. The designed antenna has a small dimension of 12 × 18 mm2. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1994–1998, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26966
A multiband antenna with MIMO implementation for USB dongle size wireless devices
Authors: Kulkarni Anup N. , Sharma Satish K. 
Published: May 2012

AbstractA compact multiband antenna is proposed for future 4G Long‐Term Evolution (LTE) wireless devices of USB dongle. The antenna covers LTE band‐3 (1710–1880 MHz)/DCS1800 and LTE band‐7 (2500–2690 MHZ based on S11 = −6 dB matching criterion. Next the multiple‐input‐multiple‐output configuration of this antenna is investigated. Prototype antennas were fabricated and experimentally verified. Both measured and simulated results are presented. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1990–1994, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26967
Heterogeneous gigabit orthogonal frequency division multiplexing/radio over fiber transmissions of wired and wireless signals using a reflective semiconductor optical amplifier and single‐arm mach–zehnder modulator
Authors: Pham Dung Tien , Hong Moon‐Ki , Joo Jeong‐Min , Han Sang‐Kook 
Published: May 2012

AbstractWe propose and experimentally demonstrate a novel radio over fiber system that provides different gigabit orthogonal frequency division multiplexing (OFDM) signals transmission for wired and wireless networks using a conventional reflective semiconductor optical amplifier and a single‐arm Mach–Zehnder modulator (MZM). To halve sampling speed of electronics and to simplify a radio frequency front‐end design, the proposed scheme adopts Hermitian symmetry to generate the wireless signal. It was reported that using the proposed scheme, 5‐Gbps 16‐quadrature‐amplitude‐modulation‐OFDM wired and 1.17‐Gbps quadrature phase‐shift keying OFDM wireless signals were successfully transmitted through 23‐km standard single mode fiber link. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1954–1958, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26968
Behavior of several antenna topologies near the human head at the 2.4–2.5 GHz band
Authors: Anguera J. , Andújar A. , Picher C. , González L. , Puente C. , Kahng S. 
Published: May 2012

AbstractThe increasing growth of wireless devices operating at the 2.4–2.5 GHz band near the human head forces the antenna community to improve the robustness of the radiating system to the undesired effects caused by the proximity of the human head. In this sense, this study is focused on assessing the electromagnetic performance of several antenna topologies in the presence of the human head with the objective of determining the topology that maximizes the ratio between the radiated power in free space and the power absorbed by the human head. With this aim, the main antenna parameters [radiation efficiency, radiation patterns, and specific absorption rate (SAR)] of several antenna topologies (dipole, loop, slot, and microstrip patch) operating at the industrial, scientific, and medical 2.4–2.5 GHz band close to the human head are measured and compared. The experimental results demonstrate that the best performance is achieved by the microstrip patch antenna because it presents less human head absorption and less SAR, thus maximizing the radiated power. The study also states that the effect of the human head proximity over the radiation pattern increases the directivity in all cases under study except the patch case where the effect is negligible. Hence, it is possible to conclude that the microstrip patch is a good candidate for wireless devices operating close to the human head because it not only maximizes the ratio between the radiated power and the power absorbed by the human head but also contributes to reduce SAR. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1911–1916, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26970
Improved model of pseudopotentials for array elements
Authors: Psarros Ioannis , Kollia Vassiliki , Fikioris George 
Published: May 2012

AbstractA recent article has proposed a simplified model, based on the quantum‐mechanical concept of the pseudopotential, for certain types of array elements, particularly for short linear dipoles. A modification of that model that works for a large number of cases is presented here. The modification consists of replacing the complex pseudopotential parameter A by a properly defined real value of A, and is expected to greatly enable future analytical studies. The range of the dipoles' parameters for which the modified model is successful and carefully described. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1874–1879, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26971
New design of an ultra compact printed‐circuit antenna
Authors: Mahe Yann , Chousseaud Anne , Brunet Marc 
Published: May 2012

AbstractThis article presents the design of an ultra compact miniaturized antenna operating around 400 MHz (18 × 8 mm2 on FR4 substrate). Different kinds of miniaturization techniques have been developed. Results indicate that any arbitrary real input impedance can be obtained with S11 lower than −15 dB and quasi omnidirectional radiation pattern. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1783–1785, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26973
A compact broadband nonsynchronous noncommensurate impedance transformer
Authors: Zhurbenko Vitaliy , Kim Kseniya , Narenda Kumar 
Published: May 2012

AbstractNonsynchronous noncommensurate impedance transformers consist of a combination of high‐ and low‐impedance transmission lines. High‐impedance lines have narrow tracks in strip and microstrip technology, which allows for high flexibility and miniaturization of the layout in comparison to the traditional tapered line transformers. This flexibility of the broadband nonsynchronous noncommensurate impedance transformers is experimentally demonstrated in this article allowing the length reduction by almost three times. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1832–1835, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26975
Design of a fully integrated wideband six‐port network on a single layer microstrip substrate
Authors: Ibrahim Siti Zuraidah , Bialkowski Marek E. , Karim Mohd Nazri A. 
Published: May 2012

AbstractThe design of a novel wideband six‐port network on a single layer microstrip substrate is presented.Two different configurations of the single‐layer six‐port networks, one conventional and the other nonconventional, are designed, fabricated, and measured. The six‐port network based on the conventional configuration is formed by one Wilkinson divider and three couplers, with one unused port terminated with a coaxial match termination. The nonconventional six‐port network, proposed here, is constructed using a similar configuration except one of the couplers is replaced by a quadrature power divider eliminating the need for match termination. To obtain fully planar device with wideband operation, the six‐port networks use double‐stage Wilkinson dividers, disk type couplers, and a wireless via 90° phase shifter. Their performances are assessed via full‐wave electromagnetic simulations and measurements. Both the simulated and the measured results show a wide bandwidth of the two six‐port configurations in terms of amplitude and phase characteristics across the frequency band of 4.5–8.5 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1796–1803, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26976
Wide tuning range cmos millimeter‐wave vco using resistors‐added mosfet varactor
Authors: Chang Ho‐Jun , Kim Sung‐Jun , Lim Chang‐Woo , Yun Tae‐Yeoul 
Published: May 2012

AbstractThis article presents a CMOS millimeter‐wave voltage‐controlled oscillator (VCO), which provides a wide tuning range using a resistors‐added MOSFET varactor.Large resistors connected to the source and bulk allow a MOSFET varactor to lower minimum capacitance and to maintain maximum capacitance compared to a conventional MOSFET varactor. Thus, the total capacitance tuning range of the proposed varactor is expanded to ±46.1%, allowing a VCO with the new varactor to possess a frequency tuning range of 13.4% from 29.3 to 33.5 GHz. The measured phase noise is −97.8 dBc/Hz at a 1‐MHz offset at the center frequency of 31.3 GHz. The VCO in a 0.18‐μm standard CMOS process dissipates 12.6 mW from a 1.8‐V supply voltage. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1777–1783, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26983
An augmented Lagrangian algorithm for contact mechanics based on linear regression
Authors: Zavarise G. , De Lorenzis L. 
Published: May 2012

SUMMARYThe penalty method for the solution of contact problems yields an approximate satisfaction of the contact constraints. Augmentation schemes, which can be adopted to improve the solution, either include the contact forces as additional unknowns or are strongly affected by the penalty parameter and display a poor convergence rate. In a previous investigation, an unconventional augmentation scheme was proposed, on the basis of estimating the ‘exact’ values of the contact forces through linear interpolation of a database extracted by the previous converged states. An enhanced version of this method is proposed herein. With respect to the original method, the enhanced one eliminates some numerical problems and improves the regularity of the convergence path by carrying out the estimate through linear regression methods. The resulting convergence rate is superlinear, and the method is quite insensitive to the penalty parameter. The main underlying concept is that, within the iterative solution of a non‐linear problem, linear regression techniques may be used as a tool to ‘shoot’ faster to the final solution, on the basis of a set of intermediate data. The generality of this concept makes it potentially applicable to contact problems in more general settings, as well as to other categories of non‐linear problems. Copyright © 2012 John Wiley & Sons, Ltd.
Preparation and properties of fluorine‐containing polysiloxanes obtained via ring‐opening copolymerization of trifluoropropyltrimethylcyclotrisiloxane with cyclotetrasiloxane catalyzed by rare earth solid superacid SO$_{4}^{2-}$/TiO2/Ln3+
Authors: Yang Xiongfa , Shao Qian , Yang Linlin , Cao Cheng , Hua Xilin , Wu Lianbin , Lai Guoqiao 
Published: May 2012

AbstractTraditional catalysts such as (CH3)4NOH, NaOH, KOH, n‐BuLi and CF3SO3H can catalyze the copolymerization of trifluoropropyltrimethylcyclotrisiloxane with cyclotetrasiloxane to afford fluorine‐containing polysiloxanes. However, use of these catalysts poses significant difficulties in handling and separation. In this work, fluorine‐containing polysiloxanes were synthesized through a novel and environmentally friendly method: ring‐opening copolymerization of trifluoropropyltrimethylcyclotrisiloxane with cyclotetrasiloxane catalyzed by rare earth solid superacid SO$_{4}^{2-}$/TiO2/Ln3+. The effects of reaction conditions were examined in detail. The yield sequence of various rare earth catalysts is Nd ∼ La ∼ Y ∼ Sm > Gd, while the number‐average molecular weight sequence is Nd > La > Y > Sm > Gd. The optimum conditions for the ring‐opening copolymerization of trifluoropropyltrimethylcyclotrisiloxane with cyclotetrasiloxane are as follows: [Nd3+] = 0.05 mol L−1 and $[\hbox{SO}_{4}^{2-}] = 1.85$ mol L−1 in the immersing solution, SO$_{4}^{2-}$/TiO2/Nd3+ calcined at 500 °C and the copolymerization conducted at 80 °C for 40 min. Structures of resulting copolymers were characterized using size exclusion chromatography, 1H NMR spectroscopy, differential scanning calorimetry, thermogravimetric analysis and contact angle measurements. According to the copolymerization features, a cationic equilibrium reaction mechanism is proposed. Copyright © 2012 Society of Chemical Industry
Commercial biodegradable material for food contact: methodology for assessment of service life
Authors: Dopico‐García María Sonia , Ares‐Pernas Ana , González‐Rodríguez María Victoria , López‐Vilariño José Manuel , Abad‐López María José 
Published: May 2012

AbstractControl of the durability of commercial biodegradable materials when used as food packaging is relevant to guarantee the safety of food. The service life performance of a commercial material based on poly(lactic acid) was assessed through an aging test which mimics its real use (immersion in water at 40 °C for up to 6.5 months). The ability of different techniques for the evaluation of polymer decomposition was investigated and two types of degradation were shown, a reversible physical aging and a permanent deterioration due to hydrolysis. Physical aging was reflected in differential scanning calorimetry scans by increased glass transition temperature and corresponding enthalpy. A gradual decrease of crystallization temperature and increase of melting temperature and crystallinity were also observed. The progressive loss of mechanical properties reflected the sum of both types of degradation. Hardness, flexural modulus and flexural strength were more sensitive to deterioration than strain. The highest toughness of the material was achieved at two months. The cleavage of polymer chains and release of substances caused increased migration levels, especially marked for long time periods. Water uptake and migration levels followed a concordant pattern and experienced the highest increases. A simple protocol for quality control based on the obtained results is suggested. Copyright © 2012 Society of Chemical Industry
Tuning the sugar‐response of boronic acid block copolymers
Authors: Cambre Jennifer N. , Roy Debashish , Sumerlin Brent S. 
Published: May 2012

AbstractA detailed study of the pH‐ and sugar‐responsive behavior of poly(3‐acrylamidophenylboronic acid pinacol ester)‐b‐poly(N,N‐dimethylacrylamide) (PAPBAE‐b‐PDMA) block copolymers is presented. Reversible addition‐fragmentation chain transfer (RAFT) polymerization of the pinacol ester of 3‐acrylamidophenylboronic acid resulted in homopolymers with molecular weights between 12,000 and 37,000 g/mol. The resulting homopolymers were employed as macro‐chain transfer agents during the polymerization of N,N‐dimethylacrylamide (DMA). Successful chain extension and removal of the pinacol protecting groups to yield poly(3‐acrylamidophenylboronic acid)‐b‐PDMA (PAPBA‐b‐PDMA) with free boronic acid moieties resulted in pH‐ and sugar‐responsive block copolymers that were subsequently investigated for their behavior in aqueous solution. The PAPBA‐b‐PDMA block copolymers were capable of solution self‐assembly due to the PAPBA block being water‐insoluble below its pKa. The resulting aggregates were demonstrated to solubilize and release model hydrophobic compounds, as demonstrated by fluorescence studies. Dissociation of the aggregates was induced by raising the pH above the pKa of the boronic acid residues or by adding sugars capable of forming boronate esters. Aggregate size, dissociation kinetics, and the effect of various sugars were considered. The critical sugar concentration needed to induce aggregate dissociation was tuned by incorporation of hydrophilic DMA units within the PAPBA responsive segment to yield PDMA‐b‐poly(3‐acrylamidophenylboronic acid‐co‐DMA) block copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
A Simple Hydrothermal Method for the Growth of ZnO Crystals
Authors: Peng Yingzi , Huo Dexuan , Zheng Liang , Qian Zhenghong 
Published: May 2012

AbstractZnO microstructures have been grown from zinc chloride (ZnCl2) and ammonia solution at 100 °C for 1 – 24 hours. X‐ray diffraction, scanning electron microscope and field‐emission scanning microscope were utilized to investigate the structural properties and morphology of the ZnO crystals. Structural investigations show that phase‐pure hexagonal structure ZnO has been successfully synthesized, and the hexagonal structure ZnO can be achieved in solutions with an appropriate range of concentrations. Under our experimental conditions, several different morphologies of ZnO structures were obtained, including flower‐like and bar flower‐like. The relationship between the morphology and experimental conditions are discussed.
Experimental Study on Powder Flowability Using Vibration Shear Tube Method
Authors: Zainuddin Imran M. , Yasuda Masatoshi , Horio Takehiko , Matsusaka Shuji 
Published: May 2012

AbstractThe flowability of powders with different mass median diameters ranging from micrometers to nanometers was measured using the vibration shear tube method. In the measurement system used in this study, the powder was discharged through a narrow gap between a vibrating tube edge and a flat bottom surface, where each particle could experience high shear forces to overcome the adhesion and friction forces. The vibration amplitude was increased during the measurement, and the mass of particles discharged was measured at constant time intervals. From the relationship between the mass flow rate and the vibration acceleration, static and dynamic properties of the powders were evaluated using the critical vibration acceleration, characteristic mass flow rate, and gradient of mass flow rate. The correlation between the static and dynamic properties was studied in detail.
Influence of the annealing temperature on CuAlxGa1−xSe2 thin films obtained by selenization
Authors: López‐García J. , Guillén C. , Herrero J. 
Published: May 2012

AbstractCuAlxGa1−xSe2 (CAGS) is an attractive wide‐bandgap chalcopyrite for buffer and top cell in tandem solar cells avoiding the use of expensive In. Polycrystalline CAGS thin films with chalcopyrite structure and strongly oriented along the (112) plane have been obtained by a sequential process of vacuum evaporation and selenization, with different x values ranging from 0 to 1. The temperature of selenization has been varied between 450 and 550 °C and it has resulted on a critical parameter in the complete and homogeneous formation and crystalline quality of the CAGS thin films. The proportion of Al(x) also affects the temperature required for selenization. At least 500 °C is necessary to obtain complete formation of CAGS for x > 0.1 whereas for x ≤ 0.1 the formation takes place in a wide range of annealing temperatures. Resistivity, roughness, band gap energy, texture coefficient C112 and crystallite size tend to increase as the selenization or annealing temperature increases. CAGS thin film properties are optimized at 525 °C for high Al proportions for which some deterioration proceeded at higher temperatures whereas at low Al proportions, a similar behaviour for 525 and 550 °C is observed.
Nanostructured thin film silicon solar cells efficiency improvement using gold nanoparticles
Authors: Pudasaini Pushpa Raj , Ayon Arturo A. 
Published: May 2012

AbstractWe report the computational modeling of localized surface plasmon effects arising on gold (Au) nanoparticles deposited on silicon nanohole (SiNH) textured surface for thin film silicon solar cells application. Detailed balance analysis is carried out for the limiting efficiency of an optimized SiNH array textured surface in combination with the surface and bottom‐of‐a‐trench Au nanoparticle array described herein. We found that for the proposed geometry of the solar cell, the short circuit current density (JSC) and the power conversion efficiency (PCE) are 31.57 mA/cm2 and 25.42%, respectively, that compare favorably to the predicted JSC and PCE values of 25.45 mA/cm2 and 20.87% for an optimized SiNH textured surface without Au nanoparticles. We optimized the silicon dioxide/silicon nitride (SiO2/Si3N4) stack as a passivation layer, retaining the higher optical absorption. The scattering of incident radiation by the Au nanoparticles near their localized plasmon resonance is responsible for higher optical absorption and hence the higher predicted values for JSC and PCE.
Influence of pulsed laser annealing on the optical properties of ZnO nanorods
Authors: Lin T. N. , Huang C. P. , Shu G. W. , Shen J. L. , Hsiao C. S. , Chen S. Y. 
Published: May 2012

AbstractThe effect of pulsed laser annealing (PLA) on the photoluminescence (PL) properties of ZnO nanorods was investigated. As the fluence of pulsed laser increases, the UV PL in ZnO nanorods shows a general increasing trend, except at a range of fluences from 10 to 70 mJ/cm2. It is found that the treatment with the PLA at the fluence of 70 mJ/cm2 leads to a larger improvement of crystalline properties than that with rapid thermal annealing (RTA). The relationship between PL intensity and fluence of pulsed lasers can be well explained by a combination of the deterioration in surface crystallinity and the increased donor densities after PLA.
Effect of the pn junction engineering on Si microwire‐array solar cells
Authors: Dalmau Mallorquí A. , Epple F. M. , Fan D. , Demichel O. , Fontcuberta i Morral A. 
Published: May 2012

AbstractWe report on the impact of the doping concentration design on the performance of silicon microwire arrays as photovoltaic devices. We have fabricated arrays with different p‐ and n‐doping profiles and thicknesses, obtaining mean efficiencies as high as 9.7% under AM 1.5G solar illumination. The results reveal the importance of scaling the microwire diameter with the depletion width resulting from doping concentrations. The doping of the core should be kept low in order to reduce bulk recombination. Furthermore, the thickness of the n‐shell should be kept as thin as possible to limit the emitter losses.