bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of optical fiber waveguides using the body of revolution version of the finite difference time domain method
Authors: Farahat Nader , Mittra Raj , Carrión José 
Published: November 2007

AbstractIn this paper we use the body of revolution (BOR) version of the finite difference time domain method to analyze axially‐symmetric dielectric waveguides including optical fibers. Because the BOR technique is two‐dimensional in nature, it is an efficient tool for analyzing the modes in optical fibers. In addition, the method is capable of dealing with individual modes propagating in the guide and this, in turn, facilitates the derivation of the dispersion diagrams for these modes without postprocessing. Dispersion diagrams of several modes of a dielectric guide, obtained by using the proposed technique show good agreement with the analytical results. Of course, the numerical technique is capable of handling dielectric guides with arbitrary radial profiles that are not readily amenable to analytical treatment. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 213–216, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23026
Dual‐frequency circularly polarized antenna
Authors: Beddeleem G. , Ribero J. M. , Kossiavas G. , Staraj R. , Fond E. 
Published: November 2007

AbstractSpatial communication systems need antennas circularly polarized. In this article, we propose a new compact dual‐frequency circularly polarized antenna. The two circular polarizations obtained in each frequency band are on opposite sense. This antenna is a patch of dimensions 36 × 36 mm2, printed on duroid substrate. Left hand circular polarization and right hand circular polarization maximum gains are 6.46 dB at the low frequency and 7.14 dB at the high frequency. Theoretical total efficiency is about 91% in the two bands. Parametric study shows that each frequency band can be controlled separately and that circular polarization can be maintained in each band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 177–180, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23028
Compact structure of UHF band RFID tag antenna mountable on metallic objects
Authors: Lee Byungje , Yu Byunggil 
Published: November 2007

AbstractA new type of a compact tag antenna, which can be effectively mounted on metallic objects, is proposed for UHF band RFID systems. The proposed antenna consists of a simple microstrip path and feed line, and it is fabricated on a very thin (1.6 mm) subtrate compared with previous works. The impedance of the proposed antenna can be easily adjusted to match the various impedance values of tag chips by simply changing the length of the feed line only. The antenna is analyzed by simulations by Ansoft HFSS software, and the measured results based on backscattering method are provided. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 232–234, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23031
Domain decomposition technique based on equivalent currents for moments method
Authors: Laviada Jaime , Pino Marcos R. , Las‐Heras Fernando 
Published: November 2007

AbstractThis article presents a technique based on domain decomposition applied to method of moments. Geometry is split in overlapped sections. Radiation due to other sections is considered as excitation to solve every section. This radiation is modeled by equivalent currents situated on surfaces at the beginning and end of every section. The aim of this method is to reduce the computational complexity of method of moments. Several examples with 2D corridors are shown and also some examples of converge failures. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 172–176, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23034
OBI reduction method using optical carrier suppression
Authors: Al‐Qdah M. T. , Abdul‐Rashid H. A. , Tayahi M. B. , Chuah H. T. , Abdullah M. K. 
Published: November 2007

AbstractOptical Beat Interference (OBI) can adversely affect passive optical networks that employs Multiple Optical Carrier Subcarrier Multiplexing (MOC‐SCM). The authors propose an OBI reduction method employing carrier suppressed MOC‐SCM system. A mathematical model is developed and an experiment is carried out to analyze the performance of the proposed system. The experimental results are in agreement with the mathematical model, which demonstrate an improvement of 27.8 dB in the carrier‐to‐interference ratio. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 256–259, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23037
Dual‐wavelength injection seeded Q‐switched fiber ring laser
Authors: Dragic Peter D. 
Published: November 2007

AbstractWe present a dual longitudinal mode narrow linewidth, injection‐seeded, Q‐switched fiber ring laser. Deeply modulated pulses near 1.55 μm with a modulation frequency that can be tuned continuously from DC to a demonstrated 25 GHz have been achieved. High peak powers are attained through the use of a reduced‐stimulated Brillouin scattering single‐clad erbium doped fiber. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 202–204, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23040
Reconfigurable microstrip rectangular loop antennas using RF MEMS switches
Authors: Zhou Lei , Sharma Satish K. , Kassegne Samuel K. 
Published: November 2007

AbstractIn this article, a low‐actuation voltage DC contact RF MEMS switch is developed for a reconfigurable microstrip rectangular loop antenna implementation providing frequency tunability. Electromechanical design optimization, microfabrication through the PolyMUMPS commercial process, and RF simulation is presented. The application of such RF MEMS switches to frequency‐tunable reconfigurable microstrip loop antennas is subsequently investigated by electromagnetic full wave analysis simulation tool. The physical perimeter of the loop antenna is electronically varied by controlling the ON/OFF states of the MEMS switches. The resonance frequency of the microstrip loop antenna is shown to be reconfigurable linearly by 56% with the linear change of the physical perimeter while the radiation pattern is almost invariant. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 252–256, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23042
Design of a novel compact antenna for a bluetooth LTCC module
Authors: Seo Donghyun , Jeon Seunggil , Kang Namkee , Ryu Join , Choi Jae‐Hoon 
Published: November 2007

AbstractA novel design concept for implementing an antenna on a compact LTCC module is proposed for a Bluetooth application. The integrated antenna consists of an LTCC module and a two‐layered radiating element, which occupies a volume of 5 mm × 6.3 mm × 0.8 mm. The antenna has a 7.5 dB return loss bandwidth of 100 MHz, from 2.39 to 2.49 GHz and has nearly omni‐directional radiation patterns with good antenna gain in spite of its small size. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 180–183, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23051
A compact wideband planar diversity antenna for mobile handsets
Authors: Liu Qingyuan , Du Zhengwei , Gong Ke , Feng Zhenghe 
Published: November 2007

AbstractA novel compact wideband printed diversity antenna for mobile handsets is presented. The antenna comprises two back‐to‐back G‐shaped monopoles placed symmetrically with respect to a T‐shaped and dual inverted‐L‐shaped ground plane. The measured results show that the proposed diversity antenna operates in a very wide bandwidth of 420 MHz starting from 1890 to 2310 MHz covering the UMTS band (1920–2170 MHz) with acceptable isolation. The antenna can provide pattern diversity to combat multipath fading. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 87–91, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23052
Analysis of the failure mechanism for a stable organic photovoltaic during 10 000 h of testing
Authors: Krebs Frederik C. , Norrman Kion 
Published: November 2007

AbstractThe degradation and failure mechanisms of a stable photovoltaic device comprising a bilayer heterojunction formed between poly(3‐carboxythiophene‐2,5‐diyl‐co‐thiophene‐2,5‐diyl) (P3CT) and Buckminsterfullerene (C60) sandwiched between indium tin oxide (ITO) and aluminium (Al) electrodes were elucidated by the time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analysis in conjunction with isotopic labelling using 18O2 after a total testing time of 13 000 h. This experiment allowed us to understand the chemistry that takes place in three dimensions during degradation and failure of the device under accelerated testing conditions. The cell was subjected to continuous illumination with an incident light intensity of 1000 W m−2 (AM1·5) at 72 ± 2°C under a vacuum of <10−6 mBar. During the illumination period, IV‐curves were recorded at regular intervals and the short circuit current of the device was monitored every 10 s for 10 760 h. The total illumination time was 12 200 h. During this period of time, the device performance degraded and the device was finally left in the dark at 25°C in an atmosphere where the oxygen had been replaced with the isotope 18O2. After 800 h in this atmosphere in the dark, the final IV‐curves in the dark and under illumination were recorded. The main purpose of this work was the analysis using TOF‐SIMS imaging and depth profiling of the degraded cell. The combined analyses correspond to the three‐dimensional chemical imaging of the device showing specifically where the oxygen had reacted during exposure. Several general findings were made that are applicable to similar devices. It was found that the oxygen diffuses into the device through the Al electrode in between the Al grains and through microscopic holes in the Al electrode. Once inside the device the oxygen diffuses in the lateral and vertical plane until the counter electrode is reached. C60 was found to be susceptible to the incorporation of 18O but P3CT was not under the conditions in question. The other prominent degradation pathway was found to be the diffusion of electrode materials into the device. Both electrode materials diffuse through the entire device to the counter electrode. Copyright © 2007 John Wiley & Sons, Ltd.
Efficiency potential of organic bulk heterojunction solar cells
Authors: Minnaert Ben , Burgelman Marc 
Published: November 2007

AbstractIn order for organic bulk heterojunction solar cells to compete with the traditional inorganic cells, power conversion efficiencies of more than 10% are desirable. Nowadays, efficiencies up to 5% are reached and the question about the limits for the attainable efficiency of organic cells arises. In this paper, we study the efficiency potential of organic bulk heterojunction solar cells. We make realistic assumptions to predict efficiencies obtainable in the near future, and calculate the upper‐limit. We study the influence of the difference between the lowest unoccupied molecular orbital (LUMO)‐energy levels of donor and acceptor, and the absorption window on the efficiency. Ideal material characteristics are obtained from these calculations, giving an idea how the ideal organic solar cell should look like. The calculations show that nowadays an efficiency of 5·8% for the single junction bulk heterojunction solar cell should be possible. Considering parameters which are credible to be achieved in the future, an organic solar cell of 15·2% is in reach, with an optimal bandgap of 1·5 eV for the absorber. We also consider the situation where both the n‐ and p‐type materials are absorbers. All calculations are not only done for a single junction cell, but also for tandem solar cells. For a tandem structure of organic cells, we find in a realistic scenario a maximum attainable efficiency of 10·1% and an efficiency of 23·2% in an optimistic scenario with optimal bandgaps Eg1 = 1·7 eV and Eg2 = 1·1 eV. Copyright © 2007 John Wiley & Sons, Ltd.
Fill factor as a probe of current‐matching for GaInP2/GaAs tandem cells in a concentrator system during outdoor operation
Authors: McMahon W. E. , Emery K. E. , Friedman D. J. , Ottoson L. , Young M. S. , Ward J. S. , Kramer C. M. , Duda A. , Kurtz Sarah 
Published: November 2007

AbstractDesigning a tandem solar cell for use in a concentrator system is challenging because: (a) the conditions are variable, so solar cells rarely operate under optimal conditions, and (b) the conditions are not controlled, so any design problems are difficult to characterize. Here, we show how the fill factor can be used as a diagnostic tool to either verify correct system design and operation or to help identify a problem. We give particular attention to the detection of spectral skewing by the concentrator optics, as this can reduce the performance of GaInP2/GaAs tandem cells and is difficult to characterize. The conclusions are equally valid for GaInP2/GaAs/Ge triple‐junction cells. Copyright © 2007 John Wiley & Sons, Ltd.
Analysis of tandem solar cell efficiencies under AM1.5G spectrum using a rapid flux calculation method
Authors: Bremner S. P. , Levy M. Y. , Honsberg C. B. 
Published: November 2007

AbstractWe report the use of a rapid flux calculation method using incomplete Riemann zeta functions as a replacement for the Bose–Einstein integral in detailed balance calculations to study the efficiency of tandem solar cell stacks under the terrestrial AM1.5G spectrum and under maximum concentration. The maximum limiting efficiency for unconstrained and constrained tandem stacks of up to eight solar cells, under the AM1.5G spectrum and maximum concentration, are presented. The results found agree well with previously published results with one exception highlighting the precautions necessary when calculating for devices under the AM1.5G spectrum. The band gap sensitivities of two tandem solar cell stack arrangements of current interest were also assessed. In the case of a three solar cell tandem stack the results show a large design space and illustrate that the constrained case is more sensitive to band gap variations. Finally, the effect of a non‐optimum uppermost band gap in a series constrained five solar cell tandem stack was investigated. The results indicate that a significant re‐design is only required when the uppermost band gap is greater than the optimum value with a relatively small effect on the limiting efficiency. It is concluded that this rapid flux calculation method is a powerful tool for the analysis of tandem solar cells and is particularly useful for the design of devices where optimum band gaps may not be available. Copyright © 2007 John Wiley & Sons, Ltd.
Experimental energy yield in 1·5 × and 2 × PV concentrators with conventional modules
Authors: García Miguel , Marroyo Luis , Lorenzo Eduardo , Pérez Miguel 
Published: November 2007

AbstractLow concentration devices along with standard (one sun) modules represent an attractive option to reduce the cost per kilowatt‐hour in photovoltaic installations. This paper deals with the energy gains obtained over a year by two of such devices: a 2 × V‐trough concentrator and a 1·5 × single flat mirror structure. The experiment was mounted on a two‐axis tracking system located in Arguedas (northern Spain). Due to various optical and electrical phenomena, the energy gain is notably lower than the geometrical concentration. We have conducted a theoretical analysis of these phenomena and quantified the energy loss associated with each. Daily and monthly energy gains show an influence of daylight clearness index on energy output. In view of this effect, and taking into account a possible increase in degradation of the photovoltaic modules due to high working temperatures and hot‐spots, the viability of these concentration devices is far from being clear. Copyright © 2007 John Wiley & Sons, Ltd.
Vitellogenin cleavage products as indicators for toxic stress in zebra fish embryos: A proteomic approach
Authors: Gündel Ulrike , Benndorf Dirk , von Bergen Martin , Altenburger Rolf , Küster Eberhard 
Published: November 2007

AbstractVitellogenins (Vtgs) are the major yolk proteins in all oviparous animals. Systematic and regulated processing of these during embryogenesis is crucial for embryonic development. In the present study, toxicant‐induced disturbance of Vtg degradation processes during Danio rerio (DR) embryogenesis was analysed to establish a sensitive tool for monitoring toxic stress at the molecular level. A 2‐DE‐based proteomic approach for whole DR embryos was established to study Vtg cleavage products (lipovitellin (Lv) derivatives). Ethanol was chosen as a positive control for a toxicity related change in the proteome of whole zebra fish embryos. Protein extracts from embryos treated with two ethanol concentrations, 0.5 and 2% v/v, showing either no or very strong visible effects, like absent heartbeat and blood circulation, were examined. Significant changes in the Lv pattern were detected for both conditions. The results are interpreted as scope for the use of the high abundant Lv derivatives as sensitive stress indicators in zebra fish embryos reflecting the overall fitness of the intact organisms.
Spatio‐temporal changes in germination and radical elongation of barley seeds tracked by proteome analysis of dissected embryo, aleurone layer, and endosperm tissues
Authors: Bønsager Birgit C. , Finnie Christine , Roepstorff Peter , Svensson Birte 
Published: November 2007

AbstractGermination of barley is accompanied by changes in water‐soluble seed proteins. 2‐DE was used to describe spatio‐temporal proteome differences in dissected seed tissues associated with germination and the subsequent radicle elongation. Protein identification by MS enabled assignment of proteins and functions to the seed embryo, aleurone, and endosperm. Abundance in 2‐DE patterns was monitored for 48 different proteins appearing in 79 gel spots at 8 time‐points up to 72 h post imbibition (PI). In embryo, a β‐type proteasome subunit and a heat shock protein 70 fragment were among the earliest proteins to appear (at 4 h PI). Other early changes were observed that affected spots containing desiccation stress‐associated late embryogenesis abundant and abscisic acid (ABA)‐induced proteins. From 12 h PI proteins characteristic for desiccation stress disappeared rapidly, as did a putative embryonic protein and an ABA‐induced protein, suggesting that these proteins are also involved in desiccation stress. Several redox‐related proteins differed in spatio‐temporal patterns at the end of germination and onset of radicle elongation. Notably, ascorbate peroxidase that was observed only in the embryo, increased in abundance at 36 h PI. The surprisingly early changes seen in the protein profiles already 4 h after imbibition indicate that germination is programmed during seed maturation.
Simulation of experimentally observed dilation phenomena during integral gas sorption in glassy polymers
Authors: Hölck Ole , Heuchel Matthias , Böhning Martin , Hofmann Dieter 
Published: November 2007

AbstractA molecular modeling investigation of dilation effects induced by sorbed gas molecules in two glassy polymers is presented. As experimental reference, integral sorption of CO2 and CH4 was measured for polysulfone (PSU) and a polyimide (6FDA‐TrMPD, PI4) at 308 K and a pressure of 10 bar. Simultaneously, the gas induced swelling effect was measured with a dilatometer based on a capacitive distance sensor recorded. The experimental evidence of the (on the observed time scale and concentration levels) elastic nature of the gas induced dilation is supported by the dilation and contraction behavior observed in molecular dynamics (MD) simulations of respective detailed atomistic packing models. These models were constructed in accordance with gas concentration levels obtained from the experimental sorption results. Quantitative deviations between simulated and measured dilations are discussed as a consequence of an anelastic response of the polymer matrix which is too fast to be resolved in the experiments whose kinetics is dominated by diffusional processes. In the simulation, the initial insertion of penetrant molecules into equilibrated packing models “circumvents” the slow diffusional process of the experiment and allows a reasonable representation of the dilation process as well as a closer investigation. Our simulation approach reveals a different behavior for PSU and PI4 on the corresponding time scale. Most likely, the different chain mobility of the two polymers is responsible for the respective response to the inserted amount of gas molecules which is discussed in terms of the different chain mobilities of the two polymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 59–71, 2008
Effect of diphenylsiloxane unit content on aggregation structure of poly(dimethylsiloxane‐co‐diphenylsiloxane)
Authors: Qu Liangliang , Huang Guangsu , Wang Qiang , Xie Zhijian 
Published: November 2007

AbstractA series of poly(dimethylsiloxane‐co‐diphenylsiloxane)s with different molar content of diphenylsiloxane unit (from 0.91 to 9.07 mol %) were synthesized and characterized by use of 1H NMR, gel permeation chromatography (GPC), the differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD). The presence of diphenylsiloxane unit results in a decrease in the “orderness” of the crystal phase and aggrandizement in degree of lattice distortion. By calculating the sequence length of dimethylsiloxane unit of the random copolymer, it can be concluded that the maximum average sequence length of dimethylsiloxane units required for the copolymer to be amorphous is 11, and increasing the dimethylsiloxane sequence length will favour crystallization. The reduction in sequence length of dimethylsiloxane unit leads to that the three‐dimensional crystal shape is destroyed and crystal shape transforms into two‐dimensional or one‐dimensional, and finally disappeared. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 72–79, 2008