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Simulated Results (simulated + result)
Selected AbstractsKinetic Study of the Oxidation of Catechols in the Presence of Some Aza-crown Ethers by Digital Simulation of Cyclic VoltammogramsELECTROANALYSIS, Issue 9 2009Davood Nematollahi Abstract The electrochemical oxidation of catechols (1) have been studied in the presence of diaza-18-crown-6 (DA18C6) (3a), diaza-15-crown-5 (DA15C5) (3b), and aza-15-crown-5 (A15C5) (3c) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled-potential coulometry. The results indicate the participation of electrochemically generated o -benzoquinones (2) in Michael-type reaction with aza-crown ethers (3) to form the corresponding new o -benzoquinone-aza-crown ether adducts (5). Based on ECE mechanism, the observed homogeneous rate constants (kobs) of the reaction of o -bezoquinones (2) with aza-crown ethers (3) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (kobs) was found to vary in the order DA18C6>DA15C5>A15C5. [source] Shrimp,a dynamic model of heavy-metal uptake in aquatic macrofaunaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2001Teresa Castro Simas Abstract A dynamic model for prediction of bioaccumulation in aquatic macrofauna is described. The model, entitled SHRIMP (Simulation of Heavy-metal Rate of Intake for Macrofaunal sPecies), consists of five coupled submodels, which simulate individual growth, population dynamics, metal transport in the abiotic part of the system, metal bioaccumulation at the organism level, and upscaling of individual contamination to the population scale. The sublethal effects of metal toxicity on individual and population levels are shown to act through the reduction of individual growth rates. The model was tested for cadmium and mercury using epibenthic crustacea from an estuarine system. Individual and population patterns of bioaccumulation were analyzed by comparing the simulated results of five different scenarios of dissolved metal concentrations. Model results suggest that the subtle effect of growth reduction due to metal toxicity is sufficient to cause a decrease on population numbers simply by affecting the growth of the mature females and males. [source] Simulating the spatial distribution of clay layer occurrence depth in alluvial soils with a Markov chain geostatistical approachENVIRONMETRICS, Issue 1 2010Weidong Li Abstract The spatial distribution information of clay layer occurrence depth (CLOD), particularly the spatial distribution maps of occurrence of clay layers at depths less than a certain threshold, in alluvial soils is crucial to designing appropriate plans and measures for precision agriculture and environmental management in alluvial plains. Markov chain geostatistics (MCG), which was proposed recently for simulating categorical spatial variables, can objectively decrease spatial uncertainty and consequently increase prediction accuracy in simulated results by using nonlinear estimators and incorporating various interclass relationships. In this paper, a MCG method was suggested to simulate the CLOD in a meso-scale alluvial soil area by encoding the continuous variable with several threshold values into binary variables (for single thresholds) or a multi-class variable (for all thresholds being considered together). Related optimal prediction maps, realization maps, and occurrence probability maps for all of these indicator-coded variables were generated. The simulated results displayed the spatial distribution characteristics of CLOD within different soil depths in the study area, which are not only helpful to understanding the spatial heterogeneity of clay layers in alluvial soils but also providing valuable quantitative information for precision agricultural management and environmental study. The study indicated that MCG could be a powerful method for simulating discretized continuous spatial variables. Copyright © 2009 John Wiley & Sons, Ltd. [source] Multicanier Modulation with Multistage Encoding/Decoding for a Nakagami Fading ChannelsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2000Lev Goldfeld The Multi Carrier Modulation (MCM) system with a multistage encoding/decoding scheme based on repetition and erasures-correcting decoding of block codes applied for a Nakagami fading channel is considered. Bit Error Rate (BER) as a function of Signal-to-Noise Ratio (SNR) has been found to agree well with the simulated results. It is shown that for low SNR the proposed system has a lower BER than both the MCM with Forward Error Correction (FEC) and MCM with optimal diversity reception and FEC. [source] Investigation of the Mekong River basin hydrology for 1980,2000 using the YHyMHYDROLOGICAL PROCESSES, Issue 9 2008Hapu Arachchige Prasantha Hapuarachchi Abstract This study investigates the Mekong River basin hydrology for the 1980,2000 period using a grid-based distributed hydrological model called Yamanashi Hydrological Model (YHyM). The performance of the model is evaluated using data observed at different locations and the results justify the physical soundness of the model. The seasonal variations of climatic and hydrological characteristics of the basin such as soil moisture, ground water saturation deficit, runoff, precipitation, evapotranspiration, etc. are analysed. On the basis of the simulated results, it is noticeable that there is no significant trend in the precipitation, discharge, or soil moisture state of the basin during the simulated period, though there are some seasonal variations which seem to be natural. However the analysis on the precipitation elasticity (E) of the river flow shows that the E values for all sub-basins are greater than unity, which indicates that x% change in annual precipitation can cause > x% change in annual river flow. Further the basin hydrological responses are analysed for a long term synthetically-induced drought the results of which show the significance of the base flow of the Mekong River basin. Copyright © 2008 John Wiley & Sons, Ltd. [source] Mobility of major ions and nutrients in the unsaturated zone during paddy cultivation: a field study and solute transport modelling approachHYDROLOGICAL PROCESSES, Issue 20 2007N. Rajmohan Abstract Study of the movement of water and solute within soil profiles is important for a number of reasons. Accumulation of prominent contaminants from agricultural chemicals in the unsaturated zone over the years is a major concern in many parts of the world. As a result, the unsaturated zone has been a subject of great research interest during the past decade. Hence, an intensive field study was conducted in a part of Palar and Cheyyar river basins to understand the variation of major ions and nutrients in the soil zone during paddy cultivation. The chloride and nitrate data were used to model the movement of these chemicals in the unsaturated zone using the HYDRUS-2D model. The field study shows that fertilizer application and irrigation return flow increases the major ions and nutrients concentration in the unsaturated zone. Further, the nutrient concentrations are regulated by plant uptake, fertilizer application and infiltration rate. Additionally, denitrification and soil mineralization processes also regulate the nitrogen concentration in the unsaturated zone. The solute transport modelling study concluded that the simulated results match reasonably with the observed trends. Simulated concentrations of chloride and nitrate for a 5-year period indicate that the concentrations of these ions fluctuate in a cyclic manner (from 60 to 68 mg l,1 and from 3·4 to 3·5 mg l,1 respectively in groundwater) with no upward and downward trend. The influence of excessive fertilizer application on groundwater was also modelled. The model predicts an increase of about 17 mg l,1 of chloride and 2·3 mg l,1 of nitrogen in the groundwater of this area when the application of fertilizers is doubled. The model indicates that the present level of use of agrochemicals is no threat to the groundwater quality. Copyright © 2007 John Wiley & Sons, Ltd. [source] Numerical simulation of the fracture process in cutting heterogeneous brittle materialINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2002H. Y. Liu Abstract The process of cutting homogeneous soft material has been investigated extensively. However, there are not so many studies on cutting heterogeneous brittle material. In this paper, R-T2D (Rock and Tool interaction), based on the rock failure process analysis model, is developed to simulate the fracture process in cutting heterogeneous brittle material. The simulated results reproduce the process involved in the fragmentation of rock or rock-like material under mechanical tools: the build-up of the stress field, the formation of the crushed zone, surface chipping, and the formation of the crater and subsurface cracks. Due to the inclusion of heterogeneity in the model, some new features in cutting brittle material are revealed. Firstly, macroscopic cracks sprout at the two edges of the cutter in a tensile mode. Then with the tensile cracks releasing the confining pressure, the rock in the initially high confining pressure zone is compressed into failure and the crushed zone gradually comes into being. The cracked zone near the crushed zone is always available, which makes the boundary of the crushed zone vague. Some cracks propagate to form chipping cracks and some dip into the rock to form subsurface cracks. The chipping cracks are mainly driven to propagate in a tensile mode or a mixed tensile and shear mode, following curvilinear paths, and finally intersect with the free surface to form chips. According to the simulated results, some qualitative and quantitative analyses are performed. It is found that the back rake angle of the cutter has an important effect on the cutting efficiency. Although the quantitative analysis needs more research work, it is not difficult to see the promise that the numerical method holds. It can be utilized to improve our understanding of tool,rock interaction and rock failure mechanisms under the action of mechanical tools, which, in turn, will be useful in assisting the design of fragmentation equipment and fragmentation operations. Copyright © 2002 John Wiley & Sons, Ltd. [source] A numerical method for the evaluation of non-linear transient moisture flow in cellulosic materialsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2006U. Nyman Abstract A numerical method for the transient moisture flow in porous cellulosic materials like paper and wood is presented. The derivation of the model is based on mass conservation for a mixture containing a vapour phase and an adsorbed water phase embedded in a porous solid material. The principle of virtual moisture concentrations in conjunction with a consistent linearization procedure is used to produce the iterative finite element equations. A monolithic solution strategy is chosen in order to solve the coupled non-symmetric equation system. A model for the development of higher order sorption hysteresis is also developed. The model is capable of describing cyclic hardening as well as cyclic softening of the equilibrium water concentration. The model is verified by comparison with the measured response to natural variations in temperature and humidity. A close agreement of the simulated results to measured data is found. Copyright © 2005 John Wiley & Sons, Ltd. [source] Finite-element analysis of a combined fine-blanking and extrusion processINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2006P. F. Zheng Abstract This paper presents the characteristics of the combined fine-blanking and extrusion process and gives a detailed analysis of the process with the finite-element method. To carry out the simulation step by step and avoid the tendency to diverge in the calculations, the remeshing, tracing and golden section methods were developed and introduced into the finite-element program. Different boundary conditions were used in the simulation; the mesh distortion, field of material flow, and the stress and strain distributions were obtained. From the simulated results, the deformation characteristics under different boundary conditions were revealed. An experiment was also carried out to verify the simulated results. A large strain analysis technique was chosen to determine the effective strain distribution based on the experiment. The effective strain distributions from the simulation are in accordance with the effective strain distributions and the hardness distributions from the experiment. Copyright © 2005 John Wiley & Sons, Ltd. [source] A DC stabilized log-domain nth-order multifunction filter based on the decomposition of nth-order HP filter function to FLF topologyINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 10 2009N. A. Shah Abstract The design of high-order log-domain filters can be easily accomplished by transposing already known linear-domain Gm -C filter topologies to their counterparts in the log-domain through the employment of a set of complementary operators. To achieve the Gm -C filter topologies, the multiple feedback approach is widely used due to its accrued advantages. In this paper a synthesis approach for the development of an nth-order multifunction log-domain filter comprising lowpass (LP), highpass (HP) and bandpass (BP) filter functions is proposed. The approach is based on the decomposition of nth-order HP filter function to follow-the-leader-feedback (FLF) topology. The design is simple and simultaneously achieves nearly all of the chief advantages. The design offers superior performance factors vis-à-vis the ones recently reported. To verify the high-order behavior of the topology, a 5th-order multifunction filter was designed and the achieved simulated results verify the theory. Copyright © 2008 John Wiley & Sons, Ltd. [source] Modelling of source-coupled logic gatesINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2002M. Alioto Abstract In this paper, the modelling of CMOS SCL gates is addressed. The topology both with and without output buffer is treated, and the noise margin as well as propagation delay performance are analytically derived, using standard BSIM3v3 model parameters. The propagation delay model of a single SCL gate is based on proper linearization of the circuit and the assumption of a single-pole behaviour. To generalize the results obtained to cascaded gates, the effect of the input rise time and the loading effect of an SCL gate are discussed. The expressions obtained are simple enough to be used for pencil-and-paper evaluations and are helpful from the early design phases, as they relate SCL gates performance to design and process parameters, allowing the designer to gain an intuitive understanding of performance dependence on design parameters and technology. The model has been validated by comparison with extensive simulations using a 0.35-µm CMOS process. The model agrees well with the simulated results, since in realistic cases the difference is less than 20% both for noise margin and delay. Therefore, the model proposed can be profitably used for pencil-and-paper evaluations and for computer-based timing analysis of complex SCL circuits. Copyright © 2002 John Wiley & Sons, Ltd. [source] Simulation of seasonal precipitation and raindays over Greece: a statistical downscaling technique based on artificial neural networks (ANNs)INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2007K. Tolika Abstract A statistical downscaling technique based on artificial neural network (ANN) was employed for the estimation of local changes on seasonal (winter, spring) precipitation and raindays for selected stations over Greece. Empirical transfer functions were derived between large-scale predictors from the NCEP/NCAR reanalysis and local rainfall parameters. Two sets of predictors were used: (1) the circulation-based 500 hPa and (2) its combination along with surface specific humidity and raw precipitation data (nonconventional predictor). The simulated time series were evaluated against observational data and the downscaling model was found efficient in generating winter and spring precipitation and raindays. The temporal evolution of the estimated variables was well captured, for both seasons. Generally, the use of the nonconventional predictors are attributed to the improvement of the simulated results. Subsequently, the present day and future changes on precipitation conditions were examined using large-scale data from the atmospheric general circulation model HadAM3P to the statistical model. The downscaled climate change signal for both precipitation and raindays, partly for winter and especially for spring, is similar to the signal from the HadAM3P direct output: a decrease of the parameters is predicted over the study area. However, the amplitude of the changes was different. Copyright © 2006 Royal Meteorological Society [source] A T-type fractal boundary single-feed circularly polarized microstrip antennaINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2009P. Nageswara Rao Abstract A single-feed T-type fractal boundary microstrip antenna is presented. It is established that a very good circular polarization is realizable with 3-dB axial ratio bandwidth of 1.27% at the center frequency of 2446 MHz by changing the electrical length in two directions of the square patch by using T-type fractal curve as boundary. Further it is shown that the surface area occupied by the antenna is reduced compared to the Euclidean shaped patch antenna without much degradation in gain of the antenna. Experimental results are compared with simulated results and a very good agreement is obtained. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009. [source] Robust fault estimation of uncertain systems using an LMI-based approachINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 18 2008Euripedes G. Nobrega Abstract General recent techniques in fault detection and isolation (FDI) are based on H, optimization methods to address the issue of robustness in the presence of disturbances, uncertainties and modeling errors. Recently developed linear matrix inequality (LMI) optimization methods are currently used to design controllers and filters, which present several advantages over the Riccati equation-based design methods. This article presents an LMI formulation to design full-order and reduced-order robust H, FDI filters to estimate the faulty input signals in the presence of uncertainty and model errors. Several cases are examined for nominal and uncertain plants, which consider a weight function for the disturbance and a reference model for the faults. The FDI LMI synthesis conditions are obtained based on the bounded real lemma for the nominal case and on a sufficient extension for the uncertain case. The conditions for the existence of a feasible solution form a convex problem for the full-order filter, which may be solved via recently developed LMI optimization techniques. For the reduced-order FDI filter, the inequalities include a non-convex constraint, and an alternating projections method is presented to address this case. The examples presented in this paper compare the simulated results of a structural model for the nominal and uncertain cases and show that a degree of conservatism exists in the robust fault estimation; however, more reliable solutions are achieved than the nominal design. Copyright © 2008 John Wiley & Sons, Ltd. [source] Exploratory second-order analyses for components and factorsJAPANESE PSYCHOLOGICAL RESEARCH, Issue 1 2002Haruhiko Ogasawara Abstract: Exploratory methods using second-order components and second-order common factors were proposed. The second-order components were obtained from the resolution of the correlation matrix of obliquely rotated first-order principal components. The standard errors of the estimates of the second-order component loadings were derived from an augmented information matrix with restrictions for the loadings and associated parameters. The second-order factor analysis proposed was similar to the classical method in that the factor correlations among the first-order factors were further resolved by the exploratory method of factor analysis. However, in this paper the second-order factor loadings were estimated by the generalized least squares using the asymptotic variance-covariance matrix for the first-order factor correlations. The asymptotic standard errors for the estimates of the second-order factor loadings were also derived. A numerical example was presented with simulated results. [source] IDEA: Interface dynamics and energetics algorithmJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2007D. Duca Abstract IDEA, interface dynamics and energetics algorithm, was implemented, in FORTRAN, under different operating systems to mimic dynamics and energetics of elementary events involved in interfacial processes. The code included a parallel elaboration scheme in which both the stochastic and the deterministic components, involved in the developed physical model, worked simultaneously. IDEA also embodied an optionally running VISUAL subroutine, showing the dynamic energy changes caused by the surface events, e.g., occurring at the gas-solid interface. Monte Carlo and ordinary differential equation system subroutines were employed in a synergistic way to drive the occurrence of the elementary events and to manage the implied energy flows, respectively. Biphase processes, namely isothermal and isobaric adsorption of carbon monoxide on nickel, palladium, and platinum surfaces, were first studied to test the capability of the code in modeling real frames. On the whole, the simulated results showed that IDEA could reproduce the inner characteristics of the studied systems and predict properties not yet experimentally investigated. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Adaptive steering control of a farm tractor with varying yaw rate propertiesJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 6-7 2009J. Benton Derrick This paper presents a novel application of a model reference adaptive control (MRAC) system to control the lateral position of a farm tractor tracking a straight path. Farm tractors can be configured with various implements, and the tractor yaw rate dynamics vary with each implement. It is desired that the lateral position response of the farm tractor remain consistent with respect to different implement configurations. Therefore, a MRAC system is implemented on the farm tractor to compensate for yaw rate plant variations by adapting the feed-forward yaw rate controller. Simulation results of the algorithm are shown that display poor performance due to neglected steering actuator dynamics and saturation. Modifications are made to the algorithm to account for the steering actuator properties, and more simulated results are presented that display ideal performance. Finally, the MRAC algorithm is implemented on a John Deere 8420 farm tractor, and experimental results are presented. © 2009 Wiley Periodicals, Inc. [source] Kinetic study of electrochemically induced Michael reactions of o -benzoquinones with 2-acetylcyclohexanone and 2-acetylcyclopentanoneJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2007Davood Nematollahi Abstract The reaction of electrochemically generated o -benzoquinones (2a-f) as Michael acceptors with 2-acetylcyclohexanone (ACH) and 2-acetylcyclopentanone (ACP), as nucleophiles has been studied in various pHs using cyclic voltammetry. The results indicate that the participation of o -benzoquinones (2a-f) in the Michael reaction with acetylcyclohexanone (ACH) to form the corresponding catechol derivatives (4a-f). Based on an EC mechanism, the homogeneous rate constants were estimated by comparing the experimental cyclic voltammetric responses with the digital simulated results. Copyright © 2007 John Wiley & Sons, Ltd. [source] Size-reduced defected ground microstrip directional couplerMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 9 2010Ashraf S. Mohra Abstract In this article, size reduction and harmonic suppression in coupled-lines microstrip directional couplers is attained using dumbbell, and reshaped dumbbell slots, as defected patterns, specifically placed under the metering position in the ground plane. Quantitative investigation of the performance of the directional coupler as controlled by the variations of the DGS rectangular slots height, DGS gap length, and the DGS reshaped rectangular slot height is presented. This concept is further illustrated experimentally for a 12 dB coupler realized on RT/Duroid 5880 substrate. The proposed DGS design confers size reduction because of the shift of the operating frequency to lower values. The measurements are in a good agreement with the simulated results and emphasize the size reduction and the harmonics suppression of the DGS coupled-lines microstrip directional coupler. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1933,1937, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25410 [source] Design of a planar ultra-wideband miniature monopole antenna for wireless USB dongle devicesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2010Yu-Chia Chang Abstract This article proposes a 3.1,5 GHz ultra-wideband antenna, defined by a ,10 dB return loss. The simplified planar antenna structures, compact size, and low profile make it profitable to the application of the embedded antenna in wireless universal serial bus dongle devices. The slit shape on the monopole radiator is tuned for miniature antenna size. A parasitic stub on the ground is adopted to increase antenna bandwidth for achieving 3.1,5 GHz impedance bandwidth. To reduce manufacturing cost and practical fabrication, we also propose a simplified rectangular antenna structure. It is found that wideband characteristics of the simplified rectangular structure antenna are similar to that of semicircular base structure. Finally, the antenna prototypes are fabricated and the antenna characteristics are measured. The radiation patterns are omnidirectional in azimuth cut. Moreover, the S -parameter of antenna characteristics has been measured. The consistency between the simulated results and the measurement results confirms the practicability of these techniques. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1013,1016, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25121 [source] Simulation and scale model measurement of a 600-GHz membrane-based twin slot antennaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2009W. Miao Abstract In this article, the input impedance (i.e., feed point impedance) of a 600-GHz membrane-based twin slot antenna for superconducting hot-electron-bolometer (HEB) mixers is investigated through numerical simulation and scale model measurement. The twin-slot antenna, with an RF choker filter included, was designed with the aid of Microwave Studio CST. A 200-times scale model of the designed twin slot antenna was fabricated to validate the simulated results. For the scale model measurement, de-embedding measurement technique was adopted to extract the input impedance of the twin slot antenna. The measured results are found in good agreement with the simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1452,1455, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24350 [source] Analysis of V-slot loaded patch for wide-band operationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008J. A. Ansari Abstract In this article, analysis of V-slot loaded patch antenna is proposed using equivalent circuit model. Such antenna provides a wide bandwidth which depends inversely on the base width and slot thickness. The proposed results are compared with experimental and simulated results which are in good agreements. Radiation pattern of the proposed antenna is in good agreement with the simulated results. This validates the accuracy of the proposed model. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3069,3075, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23891 [source] Properties of multiple gaps microstrip filter with fractal metallic patternsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2007Sheng Wang Abstract In this study, we demonstrate a multiple-gaps resonator filter, consisting of a multilayer structure with a fractal metallic pattern, that can tune the resonant frequencies of the multiple gaps. It is found that the resonant frequency of the gaps shifts to low frequencies with the increase of fractal patterns dimension. The experimental observations are in good agreement with the simulated results using the finite difference time domain method. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2726,2728, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22882 [source] Novel method for skirt response improvement of open-stub low-pass filterMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007Jan-Dong Tseng Abstract A direct circuit replacement method using interdigital low-pass structure directly replaced all open stubs of odd-order open-stub low-pass filter to achieve sharp skirt response. The characteristics of the interdigital structure are analyzed by lumped element equivalent circuits and investigated by full-wave electromagnetic simulator, IE3D. These simulated results were then applied as a guideline for the replacement. Two open-stub low-pass filters were designed by this method to enhance the skirt response near 3-dB cutoff frequency. The measured results show very good improvement on skirt response and the rejection level in stop band. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2434,2438, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22764 [source] Broad-band power divider based on radial waveguideMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2007Kaijun Song Abstract A broad-band power divider using coaxial probes and a radial waveguide is presented. The simple modeling of this power divider and design method based on equivalent circuits has been developed. A four-way radial waveguide power divider has been designed, fabricated, and measured. Close agreement is obtained between the measured results and the simulated results. The measured 15-dB return loss bandwidth of the broad-band multiple-port structure is demonstrated to be 81.5% and its 0.5-dB insertion loss bandwidth 84.6%. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 595,597, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22216 [source] Effective series-resistance model of spiral inductorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2005Heng-Ming Hsu Abstract A new resistance model, which considers both the metal-skin effect and eddy-current losses of rectangular spiral-inductor structures, is proposed. Specifically, a correction term is added to the in-series resistance model so as to more accurately model the high-frequency behavior of metal losses. The accuracy of this analytical model is validated by comparing its simulated results with the measured ones. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 46: 107,109, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20915 [source] Monte Carlo simulation of surface charge effects in T-branch nanojunctionsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008T. González Abstract We analyze the influence of the surface charge on the operation of ballistic T-branch junctions based on InAlAs/InGaAs layers by means of a semi-classical 2-D Monte Carlo simulator. A new self-consistent model in which the local value of the surface charge is dynamically adjusted depending on the surrounding carrier density is used in the calculations. The rectifying behaviour exhibited by these devices (down-bending shape of the output voltage VC as a function of the applied voltage VR = -VL =V) is found to be much influenced by the surface charge. A satisfactory agreement is achieved between simulated results and experimental measurements. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of loading rate on viscoplastic properties of polymer geosynthetics and its constitutive modelingPOLYMER ENGINEERING & SCIENCE, Issue 3 2010Fang-Le Peng On the basis of the special tensile test results under various loading histories, the rate-dependent behaviors of three polymer geosynthetics due to their viscous properties have been investigated. All the investigated polymer geosynthetics show significant loading rate effects, creep deformation, and stress relaxation. Except for the polyester geogrid showing the combined viscosity, all the investigated polymer geosynthetics exhibit the isotach viscosity. An elasto-viscoplastic constitutive model described in a nonlinear three-component model framework is developed to simulate the rate-dependent behaviors of polymer geosynthetics. The developed constitutive model is verified by comparing its simulated results with the experimental data of polymer geosynthetics presented in this study and those available from the literature. The comparison indicates that the developed model can reasonably interpret the rate-dependent behaviors of polymer geosynthetics under arbitrary loading histories, including the step-changed strain rate loading, creep, and stress relaxation applied during otherwise monotonic loading (ML). POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source] Protein probabilities in shotgun proteomics: Evaluating different estimation methods using a semi-random sampling modelPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 23 2006Xiaofang Xue Abstract The calculation of protein probabilities is one of the most intractable problems in large-scale proteomic research. Current available estimating methods, for example, ProteinProphet, PROT_PROBE, Poisson model and two-peptide hits, employ different models trying to resolve this problem. Until now, no efficient method is used for comparative evaluation of the above methods in large-scale datasets. In order to evaluate these various methods, we developed a semi-random sampling model to simulate large-scale proteomic data. In this model, the identified peptides were sampled from the designed proteins and their cross-correlation scores were simulated according to the results from reverse database searching. The simulated result of 18 control proteins was consistent with the experimental one, demonstrating the efficiency of our model. According to the simulated results of human liver sample, ProteinProphet returned slightly higher probabilities and lower specificity than real cases. PROT_PROBE was a more efficient method with higher specificity. Predicted results from a Poisson model roughly coincide with real datasets, and the method of two-peptide hits seems solid but imprecise. However, the probabilities of identified proteins are strongly correlated with several experimental factors including spectra number, database size and protein abundance distribution. [source] Transient simulation of a catalytic converter for a dual fuel engineTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2000Benlin Liu Abstract An experimental and modelling study was performed for a catalytic converter attached to a natural gas/diesel dual fuel engine. The catalytic converter was a ceramic monolith honeycomb substrate coated with a washcoat of catalyst. A multiple segmented design of converter was used. This paper describes the application of a one-dimensional finite element model for the transient and steady state operation of this converter. The model is a single channel model. The laminar flow was approximated using a dispersed plug flow model. The chemical kinetics were simulated using LHHW type expressions. Comparison of simulated results are made with experimental results for heating and cooling cycles that resulted from speed and load changes on the engine. These comparisons showed a maximum difference between experimental and predicted emission levels of about 10%. On a mené une étude expérimentale et réalisé la modération d'un convertisseur catalytique relié è un moteur è combustible double gaz naturel/diesel. Le convertisseur catalytique est un substrat de monolithes céramique en nid d'abeille enduit d'une couche de catalyseur. Une conception segmentée multiple a étée utilisée pour le convertisseur. On décrit dans cet article l'application d'un modèle d'éléments finis unidimensionnel pour un fonctionnement en régime transitoire et permanent du convertisseur. Ce modèle est un modèle à canal unique. L'écoulement laminaire a été approximé à l'aide d'un modèle à écoulement piston dispersé. La cinétique chimique a été simulée au moyen d'expressions de type LHHW. On effectue une comparaison entre les résultats simulés et les résultats expérimentaux pour les cycles de chauffe et de refroidissement qui résultent des changements de vitesse et de charge sur le moteur. Ces comparaisons montrent une différence maximum entre les taux d'émission expérimentaux et prédits d'environ 10%. [source] | ||||||||||||||||||||||||||||