Experimental Results. (experimental + results)

Distribution by Scientific Domains

Selected Abstracts

Investigation of the Start Transient in a Hall Thruster

H. Liu
Abstract A two dimensional axisymmetric fully kinetic Particle-in-Cell/Monte Carlo Collision (PIC-MCC) model is used to describe the ignition process in a Hall thruster. A current peak and latter the periodic oscillation of current and electric potential are found. The corresponding evolutions of plasma density, electric potential and atom density during the ignition process are introduced in the paper. In addition, influences of mass flow rate and discharge potential on current peak are modeled and analyzed. The simulated results are consistent with former experimental results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A practical 3D measurement system based on projection pattern control techniques

Genki Cho
Abstract Most of the recent 3D image measurement methods have employed certain pattern projection techniques because of their higher reliabilities. Especially, the intensity-modulated technique can detect more stripe addresses by a single projection and therefore is very much expected for its practical use in the near future. The traditional techniques of this type, however, have encountered several serious problems where 3D measurements are difficult in sensitivity, speed and accuracy or fatally impossible for unknown objects. In order to solve these problems, we propose an automatic control technique of angle and space frequency of projection pattern. Furthermore, for security of measurement accuracy and measurement speed, projection pattern intensity control technique and optimal intensity-modulation projection technique are adopted in the proposal measurement system. By using the proposed technique the automatic 3D measurement intended for the geostationary objects and the swaying objects were realized in experimental results. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(11): 34,41, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10147 [source]

Bilateral teleoperation under time-varying communication time delay considering contact with environment

Noriko Iiyama
Abstract With recent popularization of the Internet, bilateral control systems which are robust to fluctuant and unpredictable time delay are desirable. In such a situation, communication disturbance observer (CDOB) has been proposed as a control method for fluctuant and unpredictable time delay in bilateral teleoperation. It compensates time delay using disturbance observer by considering the effect of communication delay on the system as acceleration dimensional disturbance. Since this method cannot separate network disturbance from contact force exerted on a slave, force response of the slave transmitted to the master side is not precise. This paper presents a method for separating network disturbance from the contact force exerted on the slave. By producing the compensation value using separated network disturbance the force response value of the slave is transmitted to the master side more precisely. The validity of the proposed method is verified by experimental results. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(7): 38,46, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10051 [source]

Attitude control of planar end-effector and estimation of contact point using parallel mechanism

Ryogo Kubo
Abstract Recently, may robots have been utilized in unknown environment, for example, slave robots of teleoperation systems, walking robots and so on. They are called environment-adaptive robots. It is very important for the environment-adaptive robots to contact stably and to recognize unknown environment. In this paper, a compliance controller of attitude of a planar end-effector is proposed to achieve stable contact with unknown environment. The robot utilized in this research has parallel mechanism as a whole, since the planar end-effector is supported by three arms. With the assumption that only face-to-point contact exists between the end-effector and unknown environment, an estimation method of the contact point without sensors is also proposed. Moreover, excessive stress is not exerted on the robots and the environments by means of the controller we propose, when the contact point is estimated. Our new approach of contact motion can be widely applied to the robots using parallel mechanism. The validity of the proposed method is shown by the numerical and experimental results. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(3): 28, 36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10071 [source]

An Efficient Method for the Synthesis of Benzo[f]quinoline and Benzo[a]phenanthridine Derivatives Catalyzed by Iodine by a Three-Component Reaction of Arenecarbaldehyde, Naphthalen-2-amine, and Cyclic Ketone

Xiang-Shan Wang
Abstract A mild, efficient, and general method for the synthesis of benzo[f]quinoline and benzo[a]phenanthridine derivatives by a three-component reaction of arenecarbaldehyde, naphthalen-2-amine, and cyclic ketone using iodine as catalyst is described. A possible reaction mechanism for the formation of the product is proposed based on further experimental results.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Solid-State Structure and Tautomerism of 2-Aminotroponimines Studied by X-ray Crystallography and Multinuclear NMR Spectroscopy

Rosa M. Claramunt
Abstract Structural studies in the solid state by X-ray crystallography and by 13C and 15N CPMAS NMR spectroscopy carried out on a series of 2-aminotroponimine derivatives 2,5 has allowed to establish the existence of hydrogen bonding and to determine the most stable tautomer. Almost all the structures reflect the classical double-well potential function for the N,H···N hydrogen bonds. Only in the case of the compound N -(pyrrol-1-yl)-2-(pyrrol-1-ylamino)troponimine (5) the crystal structure shows two independent molecules, one with a classical hydrogen bond and another with either a single-well or a low-barrier hydrogen bond. The structure of this compound is discussed with the use of the solid-state NMR spectroscopic data. 2-Aminotropones, as intermediates to the 2-aminotroponimines, show the oxo-tautomer as the stable form. B3LYP/6-31G* calculations are used to rationalise the experimental results. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

The dynamic characteristics of a thermal control system using latent heat: Comparison between analytical and experimental results

Terushige Fujii
Abstract The two-phase flow thermal control system, using latent heat of the internal fluid, has received a great deal of research interest as a method for heat removal on the space station and the Space Solar Power System (SSPS). The system has a much lower weight than the single-phase flow, and the temperature can be accurately controlled by changing the saturated pressure inside the loop. To date, this system has not been put into practical use. Numerical analyses were therefore used to investigate the dynamic responses of the loop and to investigate the operational characteristics of the thermal control system. A simulation model was constructed, and the results of the numerical analysis were compared with the experimental results. Good agreement was obtained between analytical and experimental results. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(8): 564,578, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20090 [source]

Augmentation of boiling heat transfer from horizontal cylinder to liquid by movable particles

Yoshihiro Iida
Abstract This paper presents a series of experimental results on a passive augmentation technique of boiling heat transfer by supplying solid particles in liquid. A cylindrical heater 0.88 mm in diameter is placed in saturated water, in which a lot of mobile particles exist, and the nucleate and film boiling heat transfer characteristics are measured. Particle materials used were alumina, glass, and porous alumina, and the diameter ranged from 0.3 mm to 2.5 mm. Particles are fluidized by the occurrence of boiling without any additive power, and the heat transfer is augmented. The maximum augmentation ratio obtained in this experiment reaches about ten times the heat transfer coefficient obtained in liquid alone. The augmentation ratio is mainly affected by the particle material, diameter, and the height of the particle bed set at no boiling condition. The augmentation mechanism is discussed on the basis of the experimental results. © 2001 Scripta Technica, Heat Trans Asian Res, 31(1): 28,41, 2002 [source]

New aluminum-based ionic liquids: Synthesis, characterization, and theoretical study

Hossein Tavakol
Synthesis, characterization, spectral and molecular parameters of some new room-temperature ionic liquids (tetraalkylammonium bromotrichloro aluminum [R4N]+[AlCl3Br],) have been studied in the present study. All synthesized ionic liquids were characterized by IR, 1H, 13C, and 81Br-NMR. In addition, synthesized structures were optimized at the B3LYP/LANL2DZ level of theory and then the structures, molecular specifications, and infrared spectra of these were extracted using Gaussian 03 program. Theoretical data show good agreement with the experimental results. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:398,404, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20564 [source]

A practical approach for estimating illumination distribution from shadows using a single image

Taeone Kim
Abstract This article presents a practical method that estimates illumination distribution from shadows using only a single image. The shadows are assumed to be cast on a textured, Lambertian surface by an object of known shape. Previous methods for illumination estimation from shadows usually require that the reflectance property of the surface on which shadows are cast be constant or uniform, or need an additional image to cancel out the effects of varying albedo of the textured surface on illumination estimation. But, our method deals with an estimation problem for which surface albedo information is not available. In this case, the estimation problem corresponds to an underdetermined one. We show that the combination of regularization by correlation and some user-specified information can be a practical method for solving the underdetermined problem. In addition, as an optimization tool for solving the problem, we develop a constrained Non-Negative Quadratic Programming (NNQP) technique into which not only regularization but also multiple linear constraints induced by user-specified information are easily incorporated. We test and validate our method on both synthetic and real images and present some experimental results. © 2005 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 143,154, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.20047 [source]

Structure and hydrolysis of the heavy alkaline earth cations: Relativistic studies

Maria Barysz
Abstract The relativistic spin-averaged Douglas,Kroll theory at the level of the MP2 and CCSD(T) approximations has been applied to explain the hydrolysis trends for the Group 2 dications through the investigation of the structure and energetics of the model complexes with the water molecule. The parallel nonrelativistic calculations have been performed to show the possible role of the relativistic effect on the structure and hydrolysis of the heaviest metal cations. The calculated data are compared with the recent experimental results. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source]

Theoretical investigation of ion pair SN2 reactions of alkali isothiocyanates with alkyl halides.

Part 1.
Abstract The gas-phase ionic SN2 reactions NCS - + CH3F and ion pair SN2 reaction LiNCS + CH3F with inversion mechanism were investigated at the level of MP2(full)/6-311+G**//HF/6-311+G**. Both of them involve the reactants complex, inversion transition state, and products complex. There are two possible reaction pathways in the ionic SN2 reaction but four reaction pathways in the ion pair SN2 reaction. Our results indicate that the introduction of lithium significantly lower the reaction barrier and make the ion pair displacement reaction more facile. For both ionic and ion pair reaction, methyl thiocyanate is predicted to be the major product, but the latter is more selective. More-stable methyl isothiocyanate can be prepared by thermal rearrangement of methyl thiocyanate. The theoretical predictions are consistent with the known experimental results. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source]

Application of a genetic algorithm in an artificial neural network to calculate the resonant frequency of a tunable single-shorting-post rectangular-patch antenna

Shyam S. Pattnaik
Abstract In this article, an efficient application of a genetic algorithm (GA) in an artificial neural network (ANN) to calculate the resonant frequency of a coaxially-fed tunable rectangular microstrip-patch antenna is presented. For a normal feed-forward back-propagation algorithm, with a compromise between time and accuracy, it is difficult to train the network to achieve an acceptable error tolerance. The selection of suitable parameters of ANNs in a feed-forward network leads to a high number of man-hours necessary to train a network efficiently. However, in the present method, the GA is used to reduce the man-hours while training a neural network using the feed forward-back-propagation algorithm. It is seen that the training time has also been reduced to a great extent while giving high accuracy. The results are in very good agreement with the experimental results. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005. [source]

A theoretical investigation of the excited states of OCLO radical, cation, and anion using the CASSCF/CASPT2 method

Zi-Zhang Wei
Abstract Using the complete active space self-consistent field method with a large atomic natural orbital basis set, 10, 13, and 9 electronic states of the OClO radical, OClO+ cation, and OClO, anion were calculated, respectively. Taking the further correlation effects into account, the second-order perturbation (CASPT2) calculations were carried out for the energetic calibration. The photoelectron spectroscopy of the OClO radical and OClO, anion were extensively studied in the both case of the adiabatic and vertical ionization energies. The calculated results presented the relatively complete assignment of the photoelectron bands of the experiments for OClO and its anion. Furthermore, the Rydberg states of the OClO radical were investigated by using multiconfigurational CASPT2 (MS-CASPT2) theory under the basis set of large atomic natural orbital functions augmented with an adapted 1s1p1d Rydberg functions that have specially been built for this study. Sixteen Rydberg states were obtained and the results were consistent with the experimental results. © 2006 Wiley Periodicals, Inc. J Comput Chem 28: 467,477, 2007 [source]

Continuous process for production of hydrogenated nitrile butadiene rubber using a Kenics® KMX static mixer reactor

AICHE JOURNAL, Issue 11 2009
Chandra Mouli R. Madhuranthakam
Abstract A continuous process for hydrogenating nitrile butadiene rubber (NBR) was developed and its performance was experimentally investigated. A Kenics® KMX static mixer (SM) is used in the process as a gas,liquid reactor in which gaseous hydrogen reacts with NBR in an organic solution catalyzed by an organometallic complex such as an osmium complex catalyst. The Kenics® KMX SM was designed with 24 mixing elements with 3.81 cm diameter and arranged such that the angle between two neighboring elements is 90°. The internal structure of each element is open blade with the blades being convexly curved. The dimensions of the SM reactor are: 3.81 cm ID 80 S and 123 cm length and was operated cocurrently with vertical upflow. The NBR solutions of different concentrations (0.418 and 0.837 mol/L with respect to [CC]) were hydrogenated by using different concentrations of the osmium catalyst solution at various residence times. The reactions were conducted at a constant temperature of 138°C and at a constant pressure of 3.5 MPa. From the experimental results, it is observed that a conversion and/or degree of hydrogenation above 95% was achieved in a single pass from the designed continuous process. This is the first continuous process for HNBR production that gives conversions above 95% till date. Optimum catalyst concentration for a given mean residence time to achieve conversions above 95% were obtained. Finally, a mechanistic model for the SM reactor performance with respect to hydrogenation of NBR was proposed and validated with the obtained experimental results. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Investigation of reacting flow fields in miscible viscous fingering by a novel experimental method

AICHE JOURNAL, Issue 3 2009
Yuichiro Nagatsu
Abstract The reacting flow fields in reactive miscible viscous fingering in a Hele-Shaw cell studied by Nagatsu and Ueda had not been completely elucidated, mainly because one cannot exactly recognize where and when the reaction takes place in the reactive fingering pattern. We developed a novel experimental method that allowed us to identify the reaction region in the fingering pattern employed in the previous studies. The novel method involves switching of the less-viscous liquid injected in both the nonreactive and reactive experiments. By using the novel method, we succeeded in showing how the reaction region in the fingering pattern was affected by the initial reactant concentrations, the Péclet number, and time. We propose physical models of the reacting flow field in the cell's gap direction that can explain the obtained experimental results. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Two-phase flow in structured packings: Modeling and calculation on a macroscopic scale

AICHE JOURNAL, Issue 3 2008
B. Mahr
Abstract A model is presented that allows calculating the macroscopic flow field of counter-current two-phase flow in strongly anisotropic porous structures. It is applied to corrugated structured packings. All flow field variables and packing properties are averaged over the volume of an elementary cell. The anisotropic gas flow resistance is derived from measurements and from separate CFD calculations on 3D-X-ray CT scans. The liquid's flow resistance is calculated using an analytical model of liquid film flow on an inclined plate. Liquid flow along both preferential flow directions is represented by two separate phases, in order to consider horizontal forces despite their symmetry. Gas-liquid momentum transfer above the loading point is included. The macroscopic flow field is calculated for a 288 mm I.D. column containing four packing elements. Liquid spreading from a point source, for uniform irrigation, increased hold-up at the packing elements' joints and pressure drop are tested against experimental results. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source]

Dependence of axon initial segment formation on Na+ channel expression

Xiaorong Xu
Abstract Spinal motor neurons were isolated from embryonic rats, and grown in culture. By 2 days in vitro, the axon initial segment was characterized by colocalization and clustering of Na+ channels and ankyrinG. By 5 days, NrCAM, and neurofascin could also be detected at most initial segments. We sought to determine, as one important aim, whether Na+ channels themselves played an essential role in establishing this specialized axonal region. Small hairpin RNAs (shRNAs) were used to target multiple subtypes of Na+ channels for reduced expression by RNA interference. Transfection resulted in substantial knockdown of these channels within the cell body and also as clusters at initial segments. Furthermore, Na+ currents originating at the initial segment, and recorded under patch clamp, were strongly reduced by shRNA. Control shRNA against a nonmammalian protein was without effect. Most interestingly, targeting Na+ channels also blocked clustering of ankyrinG, NrCAM, and neurofascin at the initial segment, although these proteins were seen in the soma. Thus, both Na+ channels and ankyrinG are required for formation of this essential axonal domain. Knockdown of Na+ channels was somewhat less effective when introduced after the initial segments had formed. Disruption of actin polymerization by cytochalasin D resulted in multiple initial segments, each with clusters of both Na+ channels and ankyrinG. The results indicate that initial segment formation occurs as Na+ channels are transported into the nascent axon membrane, diffuse distally, and link to the cytoskeleton by ankyrinG. Subsequently, other components are added, and stability is increased. A computational model closely reproduced the experimental results. © 2005 Wiley-Liss, Inc. [source]

The third parameter in reactive barrier films

AICHE JOURNAL, Issue 2 2005
Eric E. Nuxoll
Abstract The lag time of a barrier film can be dramatically increased by the addition of sacrificial scavengers that consume solute before crossing the barrier. This increase in lag time is independent of the scavengers' reaction rate. This reaction rate does affect the amount of solute that crosses the membrane before steady state, a premature leakage that may render the barrier unsuitable regardless of its putative lag time and permeability. A third parameter is needed to characterize the barrier's transient behavior. Guided by experiments, we offer two candidate parameters for quantifying these changes. Correlations of these parameters are determined numerically and compared with experimental results. © 2005 American Institute of Chemical Engineers AIChE J, 51: 456,463, 2005 [source]

Synthesis and electroluminescent properties of fluorene-based copolymers containing electron-withdrawing thiazole derivatives

In Hwan Jung
Abstract We synthesized two fluorene-based copolymers poly[(2,5-bis(4-hexylthiophen-2-yl)thiazolo[5,4-day]thiazole-5,5,-diyl)-alt-(9,9,-dioctylfluorene-2,7-diyl)] (PF-TTZT), and poly[(5,5,-bis(4-hexylthiophen-2-yl)-2,2,-bithiazole-5,5,-diyl)-alt-(9,9,-dioctylfluorene-2,7-diyl)] (PF-TBTT), which contain the electron-withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF-TBTT are lower than those of PF-TTZT, and the bandgap of PF-TBTT is smaller than that of PF-TTZT. Thus the bithiazole moiety in PF-TBTT is more electron-withdrawing than the thiazolothiazole moiety in PF-TTZT. Light-emitting devices with indium tin oxide (ITO)/poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF-TBTT device was found to be almost three times better than that of the PF-TTZT device, which is because electron injection from the cathode to PF-TBTT is much easier than for PF-TTZT. We also investigated the planarity and frontier orbitals of the electron donor-acceptor (D-A) moieties with computational calculations using ab initio Hartree,Fock with the split-valence 6-31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron-withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7148,7161, 2008 [source]

Mode-locked Yb-doped large-mode-area photonic crystal fiber laser operating in the vicinity of zero cavity dispersion

Y.-J. Song
Abstract A passively mode-locked ytterbium-doped largemode-area photonic crystal fiber oscillator operating in the vicinity of zero cavity dispersion is demonstrated. The self-starting mode-locking operation is achieved by a high contrast saturable absorber mirror. Two mode-locking regimes with opposite signs of net cavity dispersion are investigated. At a net cavity dispersion of ,0.0035 ps2, the fiber laser directly generates 10-nJ laser pulses with an average power of 630 mW at 65.3 MHz repetition rate. The pulses can be dechirped to 78 fs by extracavity dispersion compensation. The pulse energy is scaled up to 18 nJ, yielding an average power of 1.2 W, when the cavity dispersion is set at 0.0035 ps2. In this regime, the laser output can be extracavitydechirped to 120 fs. Dynamics of pulse evolution in the fiber laser is illustrated by numerical simulation, which agrees well with experimental results. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Subtraction of scattering parameters for small-signal modulation characteristics of laser diode

S. J. Zhang
Abstract An extended subtraction method of scattering parameters for characterizing laser diode is proposed in this paper. The intrinsic response is extracted from the measured transmission coefficients of laser diode, and the parasitics of packaging network and laser chip are determined from the measured reflection coefficient of laser diode simultaneously. It is shown that the theories agree well with the experimental results. (© 2005 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source]

Analysis of wideband multilayer patch antenna with two parasitic elements

J. A. Ansari
Abstract The analysis of stacked patch antenna with two parasitic elements is presented. The antenna shows improved radiation and directivity by 6.57 dB when compared with single layer patch antenna. The bandwidth of the antenna is found to be dependent on various parameters such as h1, h2, and s. The proposed results are compared with the IE3D simulation and reported experimental results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1397,1401, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24378 [source]

Optical mm-wave generation based on phase modulation along with optical filtering

Jianxin Ma
Abstract We have investigated the generation and transmission of optical millimeter (mm)-wave signal based on optical phase modulator (PM) and fiber Bragg grating (FBG) filter. With an optimized modulation depth of PM and a higher carrier suppression ratio via a notch filter, the generated optical mm-wave can be transmitted over a long-distance without fading. We have also theoretically analyzed the impact of time shift on the eye closure of optical and electrical signal due to the fiber dispersion, which is well in accord with the experimental results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1787,1793, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22622 [source]

Transmission properties of two shifted magnetoinductive waveguides

A. Radkovskaya
Abstract Transmission properties of magnetoinductive waves propagating in two coupled one-dimensional metamaterial arrays are studied both experimentally and theoretically for the case when one of the arrays is shifted relative to the other one. Two different kinds of resonant metamaterial elements, split-pipe and spiral resonators, are investigated in the frequency bands centred at 46.2 and 586 MHz, respectively. It is shown that within a certain frequency range close to the resonant frequencies the transmission is strongly dependent on the shift. Theoretical calculations based on the impedance matrix show good agreement with the experimental results. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49:1054,1058, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22344 [source]

Microstrip dual-band bandpass filter using slow-wave resonators for WLAN applications

Xuehui Guan
Abstract A dual-band bandpass filter using microstrip slow-wave resonators is developed for wireless local area network applications. The fundamental and higher order resonant harmonics of a microstrip open-loop resonator are analyzed against the length of the loading open stub. Then a dual-band bandpass filters is designed in the form of slow-wave open-loop resonators. A zero-degree feed structure is employed to produce transmission zeros near the passband to increase the rate of attenuations, and a quarter-wavelength feed line for impedance matching is added to get desired external quality factor at the input and output. The theoretical analysis and design procedures are successfully verified by experimental results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 14,16, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22055 [source]

Full-wave analysis of a new designed wide band microstrip filter using the novel method of lines

Essam A. Hashish
Abstract A wide band small size microstrip filter is designed based on a full wave analysis achieved through a novel method of lines. Such a novel method enables the analysis of structures having either short or long interconnections between single discontinuities, and it reduces the discretization window through nonequidistant discretization. In the full-wave analysis, the scattering parameters of the designed filter are computed, leading to an achievement of a bandwidth up to 23%. The designed filter is fabricated and tested, where good agreement is found between the numerical and experimental results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 150,154, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22071 [source]

Remarks on "PAE improvement and compensation of small-signal gain drift due to temperature on power amplifiers through active biasing"

S. C. Bera
Abstract In the paper of German Torregrosa-Penalva et al. 1, a confusing result has been presented. The paper demonstrates the compensation of the small-signal gain drift with change of temperature and improvement of the FET amplifier's PAE using active biasing, which contradicts the previous published work and our experimental results. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 827,828, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21487 [source]

Impact of the delay ripple of cascaded gratings on dispersion compensation of long-haul fiber transmission systems

Tigang Ning
Abstract Delay ripples of chirped-fiber Bragg grating (CFBG), which can compensate 200-km-long fiber's dispersion, is detailedly analyzed. A numerical simulation of the delay ripple of cascaded gratings is done using Schrödinger's equation and is compared with an experiment using a 1000-km transmission system over G.652 fiber by five groups of CFBGs for dispersion compensation. The research shows that the system degradation depends on the delay-ripple period, which is 0.01,0.1 nm, and its amplitude. Fluctuation of the power penalty, which depends on the CFBG's ripple period when the source wavelength is changed ±20 GHz around the CFBG's center wavelength, is experimentally studied. The theoretical results agree well with the experimental results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 100,102, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20220 [source]

Dramatic spectral narrowing and broadband tuning from a self-injection-seeded diode laser

E. U. Rafailov
Abstract We demonstrate spectral narrowing with broadband tuning from a picosecond self-injection-seeded gain-switched diode laser. A narrowband spectral output was continuously tunable over a range of 44 nm from 1.538 to 1.582 ,m. We also observe a gain-switched hybrid-operation regime with elements of mode-locking. Our numerical simulations exhibit good agreement with the experimental results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 150,152, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20235 [source]