bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parameter identification and optimal control of ground temperature
Authors: Kawahara Mutsuto , Sasaki Ken‐Ichi , Sano Yasuhiko 
Published: August 2005

AbstractTo avoid the use of pesticides on putting greens of golf courses, a temperature regulator system is strongly recommended nowadays in Japan. To maintain grass on the putting green without pesticide, the temperature of the ground should be controlled. This system consists of a cooling machine and buried pipes in the ground. The temperature of the water in the pipes cannot be regulated. In this paper, both identification and control problems are presented by the minimization technique and applied to a practical problem. To establish the system, it is important to obtain accurate parameters which are included in the governing equation. These parameters can be determined by parameter identification. The conjugate gradient method is used for the parameter identification procedure. The control problem aims to make the temperature at arbitrary points close to the objective temperature. The discrete‐time dynamic programming is used for the control procedure.
Turbulence models for unstructured finite element calculations
Authors: Marcum David L. , Weatherill Nigel P. 
Published: August 2005

AbstractAn unstructured finite element method is presented for calculation of turbulent flow fields about aerospace configurations. Algebraic, one‐equation, and two‐equation turbulence models are implemented and compared. A new procedure for implementing an unstructured algebraic model without an auxiliary structured grid is presented. The overall procedure is applied to simulation of flow about launch vehicle configurations. The turbulence models are evaluated for calculation of flow fields about a forebody with shock induced separation. For this case. the one‐equation model gives better predictions. An inviscid flow field about a complete launch vehicle with multiple boosters is also evaluated to demonstrate the overall procedure.
A general algorithm for compressible and incompressible flow—Part II. tests on the explicit form
Authors: Zienkiewicz O. C. , Morgan K. , Sai B. V. K. Satya , Codina R. , Vasquez M. 
Published: August 2005

AbstractThe algorithm introduced in Part I of this paper is applied in its explicit form to a variety of problems in order to demonstrate its wide range of applicability and excellent performance. Examples range from nearly incompressible, viscous, flows through transonic applications to high speed flows with shocks. In most examples linear triangular elements are used in the finite element approximation, but some use of quadratic approximation, again in triangles, indicates satisfactory performance even in the case of severe shocks.
Optimum aerodynamic shape design including mesh adaptivity
Authors: Bugeda Gabriel , Oñate Eugenio 
Published: August 2005

AbstractThis paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation of the sensitivities of the geometrical design parameters, the mesh, the flow variables and the error estimator to project the refinement parameters from one design to the next. This sensitivity analysis is described for the incompressible potential equations and the Euler equations. The efficiency of the proposed method is checked by means of two 2D inverse problems.
A split‐characteristic based finite element model for the shallow water equations
Authors: Zienkiewicz O. C. , Ortiz P. 
Published: August 2005

AbstractA new algorithm for the solution of the shallow water equations is introduced. The formulation is founded on a suitable operator‐splitting procedure for which a characteristic‐based rational form of including balancing dissipation terms is achieved.In the semi‐explicit form the method circumvents the requirement of a critical time step given in terms of the wave celerity, which is restrictive for the analysis of long‐wave propagation in shallow waters.In this work the robustness of the algorithm is illustrated for transient shallow water problems and for some supercritical flows, where the choice of an algorithm with optimal diffusion properties is manifest.
In vitro evaluation of biocompatibility of beta‐tricalcium phosphate‐reinforced high‐density polyethylene; an orthopedic composite
Authors: Homaeigohar S. SH. , Shokrgozar M. A. , Sadi A. Yari , Khavandi A. , Javadpour J. , Hosseinalipour M. 
Published: August 2005

AbstractBeta‐tricalcium phosphate‐reinforced high‐density polyethylene (β‐TCP/HDPE) is a new biomaterial which was made as a copy of bone composition with the aim of replacement of bony tissues. The composite samples were prepared using medical grade TCP powder and granular polyethylene. The raw materials were first compounded and the resulting composite preforms were compression molded into desired shape. The biocompatibility of composite samples with different volume fractions of TCP (20, 30, and 40 vol %) was assessed by proliferation, alkaline phosphatase (ALP), and cell adhesion assays using G‐292 osteoblast cells. Cell–material interaction on the surface of the composites was observed by scanning electron microscopy (SEM). The effect of β‐TCP/HDPE on the behavior of G‐292 cells was compared with those of a composite and a negative control samples. Results showed the composite samples had a higher proliferation rate of G‐292 cells in the presence of composite samples as compared to the composite control sample after 3, 7, and 14 days of incubation period. ALP production after incubation in the presence of composite samples was seen to peak on the day 7. The number of adhered cells on the composite samples was higher than the numbers adhered on composite and negative control samples after the above incubation periods. Morphology investigation of adhered cells by SEM indicated a normal morphology and also many of the cells were in the process of cell division. The above results indicate that β‐TCP/HDPE samples are biocompatible, nontoxic, and in some cases show an increase in the proliferation rate of the cells, ALP production, and cell adhesion as compared to the control counterparts. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
A discrete model of substitutional‐interstitial diffusion in the Czochralski growth of semiconductor crystals
Authors: Hearne M. T. , Rogers T. G. , Tuck B. 
Published: August 2005

AbstractA discrete model is developed to describe the diffusion of dopant/impurity in a single semiconductor crystal during Czochralski growth. The basic diffusion mechanism is assumed to be substitutional‐interstitial interchange for the impurity, together with self‐diffusion of the host atoms. In particular, the model incorporates the complicated conditions that result from the simultaneous growth and diffusion taking place at the crystal/melt interface. The high temperature dependence of the process is also taken into account, together with possible vacancy production to counteract vacancy depletion. The numerical model is explicit in time, and conditions for convergence and stability are considered. Results are presented for chromium doping of growing gallium arsenide crystals, and compared with published experimental data.
New one‐ and two‐dimensional algorithms for the transient simulation of semiconductor devices
Authors: Towers M. S. , McCowen A. 
Published: August 2005

AbstractOne‐ and two‐dimensional algorithms for the transient simulation of semiconductor devices are presented which incorporate a solenoidal total current. The paper includes results from one‐dimensional simulation of a p‐n junction, including forward‐to‐reverse bias switching and also switching and also switch‐on into high injection in an asymmetric structure. A discretization scheme for the two‐dimensional formulation is described with details on handling voltage driven terminals and the associated boundary conditions.
High‐frequency propagation on nonuniform multiconductor transmission lines in uniform media
Authors: Baum Carl E. 
Published: August 2005

AbstractThe asymptotic form, for high frequencies, of the equations of propagation on a nonuniform N‐conductor transmission line is considered. Under the assumption of perfect conditions in uniform, isotropic media, all N propagation velocities are the same, but the characteristic impedance matrix is allowed to vary with position along the line. Closed‐form solutions are obtained for some cases of interest.
Drift–diffusion versus energy model for millimetre‐wave impatt diodes modelling
Authors: Dalle C. , Rolland P. A. 
Published: August 2005

AbstractA new P–N junction device model is presented. It consists of two numerical unidimensional macroscopic models. The first is a drift–diffusion model. The second is an energy model accounting for the carrier energy relaxation effects. Because device optimization requires systematic investigations, the computing time is of paramount importance and, so an accurate comparison between these two models was undertaken under both static steady‐state and dynamic 94 GHz conditions in order to point out the relative interest of the energy model. This study is mainly devoted to silicon millimetre‐wave IMPATTs. This comparison has highlighted the superiority of the energy model for the description of low field transport phenomena. But as IMPATT RF properties are mainly governed by high field transport, the RF power levels predicted by the two models have been found to be similar. Moreover it has shown that the energy model tends to underestimate both the efficiency and the diode terminal negative resistance level. This parasitic effect is inherent to the description of the carrier generation process by impact ionization which in this model is assumed to be governed by the carrier energy.
An application of dyadics to the analysis of power transformers
Authors: Davies A. E. , Farrier D. R. , German D. M. 
Published: August 2005

AbstractA simulation of power transformers following switching operations is presented in which each core section is represented by a non‐linear inductance, the differential inductance being determined from the flux density in that section of the core. In analysing the resultant circuit model for the transformer it is shown that the circuit equations have dyadic properties which can be used to give a more efficient numerical solution.
Investigation on the power‐handling capacity of a class of E‐plane millimetre‐wave filters using finite element modelling
Authors: Ney Michel M. , Chénier Mario , Costache George I. 
Published: August 2005

AbstractAn approach, based on the finite element method (FEM), is used for evaluating the electromagnetic field distribution in a class of E‐plane metal insert filters, operating in the Ka‐band. Artificial boundary conditions are inserted directly in a functional, enabling a solution of the scalar wave equation by finite element method.The scattering parameters of the filter, the electromagnetic field and, therefore, the current distributions on the thin metal inserts are computed. Then, the power dissipated in the metallic septa, which is one of the major limitations for the maximum CW‐power that can be handled by these types of filter, is evaluated using a perturbational approach. Finally, the maximum field intensity is determined, allowing an estimate of the maximum peak power that these structures can handle.
Multigrid TLM for diffusion problems
Authors: Wong Chi Chung , Wong Wing Sun 
Published: August 2005

AbstractThe multigrid technique, which is mainly used in the finite difference method, is applied to the TLM (transmission‐line matrix or modeling) procedure. In the multigrid TLM, the field region is covered with sets of regular transmission‐line matrices of different mesh sizes. The finer grid pattern, which overlaps the coarser grid, fills the region with high field gradients. Data obtained in the coarser grid are transferred to the finer grid through an interpolation process and used as boundary conditions for the latter. The finer grid data are then transferred back to the coarser one, thus improving the coarse grid values. The method is applied to several diffusion problems and significant improvements in accuracy and efficiency are shown.
The modelling of EM leakage into advanced composite enclosures using the TLM technique
Authors: Mallik A. , Loller C. P. 
Published: August 2005

AbstractThe TLM technique has been enhanced to allow the accurate modelling of EM diffusion through advanced composite material shells. This is a significant development owing to the rapidly increasing use of conducting composite materials in aerospace vehicle design. The accurate EM modelling of this class of materials is important for correct design of vehicles with regard to electromagnetic compatibility (EMC).Existing 3‐D time‐domain TLM models a non‐perfectly conducting shell using a resistive sheet (or sheets) to simulate the surface. The results from this model are shown to be slightly inaccurate and require lengthy computer solution times. A separate 1‐D, frequency‐domain transmission‐line model has been developed elsewhere to better analyse the diffusion properties of composite materials. The incorporation of the results from this frequency domain code into the 3‐D time‐domain TLM algorithm is outlined.
Planar analysis of radial‐line power dividers
Authors: Bartolucci G. , Giannini F. , Paoloni C. 
Published: August 2005

AbstractThe resonant mode field expansion technique presented in previous papers to analyse one‐ or two‐port microstrip structures of different geometrical shapes is now applied to multiport radial lines. In particular, a radial‐linen‐way power divider is considered. This device allows, under certain hypotheses, an equiphase and equiamplitude splitting of an input signal. TheZmatrix formulation has been derived and utilized to obtain the scattering parameters for the circuit. The numerical results are in good agreement with both experimental and theoretical data presented in the literature. The low number of resonant modes required to obtain satisfactory numerical convergence allows a substantial reduction of the computing time with respect to other more complicated approaches.
Estimation of parameters in numerical modelling of non‐linear diffusion in semiconductors
Authors: Meere M. G. , King J. R. , Rogers T. G. 
Published: August 2005

AbstractA procedure is described for estimating various parameters governing the diffusion of impurities in semiconductors; these parameters are required for a number of explicit numerical models of non‐linear diffusion in III‐V crystals. The method is based on an analytical solution of the continuum equivalent of a discrete numerical model due to Zahari and Tuck and provides a systematic procedure for analysing experimental data to yield predictions for the coefficient of diffusion of the impurity, the coefficient of self‐diffusion of the host material, the bulk equilibrium vacancy concentration and, under conditions of “dissociation” pressure, the surface vacancy concentration. Application of the procedure to two sets of independent experimental data provided reasonably consistent values of the parameters.
The modelling of surface evolution during growth and erosion
Authors: Katardjiev I. V. , Carter G. , Nobes M. J. 
Published: August 2005

AbstractWhen the erosion or growth of a surface that occurs in semiconductor device processing can be considered as everywhere continuous in space and time, the equations of motion of the surface may be specified and determined numerically using a kinetic model of surface evolution. In this review the fundamental concepts of the kinematic model of surface evolution are discussed. Detailed consideration of the theory of characteristics reveals its limitations which are overcome by recent theoretical development based on the Huygens principle of wavefront reconstruction. Correct interpretation of the nature of the basic wavelet, coupled with contemporary ideas of surface and edge propagation, form the essence of a new numerical algorithm. Numerical analysis and consequent numerical procedures derived from the generalized kinematic model are presented. Examples of surface evolution, with particular reference to ion beam induced erosion are given to show the advantages and potential of the method as opposed to existing models and theoretical prediction.When evolution processes are discontinuous and localized, other approaches, particularly those that use numerical modelling, are required. Such approaches are also reviewed here.
A model for atomic mixing
Authors: Wadsworth M. , Armour D. G. , Badheka R. , Collins R. 
Published: August 2005

AbstractThis paper is concerned with the theoretical determination of the amount of atomic mixing which accompanies the erosion of a solid surface exposed to an energetic ion beam. The work is relevant to sputter depth profiling where such mixing complicates the deduction of the initial depth distributions from the measured ion yields.A mathematical model, which considers the effects of incident ion accumulation, ballistic relocation and diffusion is described. The governing integro‐differential equations are solved numerically.Results for a GaAs‐AlGaAs multi‐layer structure bombarded with O ions are compared with results obtained experimentally.
A hybrid moment‐ray‐mode method for wave scattering from an aperture coupled system
Authors: Lu I‐Tai , Ma Bai‐Lin 
Published: August 2005

AbstractWave scattering from an aperture coupled system is studied using a new method which combines the hybrid ray‐mode method and method of moments. The latter is used to formulate the coupling process and the former to provide the Green's function of a parallel plate waveguide. Following standard procedures of the method of moments, we first formulate a system equation for field distributions across the aperture. By expressing these unknown distributions in terms of appropriate basis functions and choosing appropriate weighting functions, the system equation is then reduced to a matrix equation which is solved numerically. In the system of equations, one needs to compute the Green's function of the waveguide for various arrangements of locations of source and receiver. The hybrid ray‐mode formulation is best suited for this purpose because it combines rays and modes self‐consistently to optimize the advantages of each. The efficiency of the ray‐mode Green's function makes use of the moment method practical in waveguides, and the flexibility of the moment method permits application of the Green's function considered to arbitrarily shaped and placed apertures. Numerical implementation illustrates these aspects.
Functional relaxations and spectral techniques in Computer‐Aided circuit analysis
Authors: Guarini Marcello W. , Palusinski Olgierd A. 
Published: August 2005

AbstractAnalysis of transients in integrated circuits is performed with the use of highly specialized computer programs. The transient responses are computed using time‐marching integration methods and require a substantial amount of computer time. A new method based on spectral analysis and waveform relaxation is proposed. The method results in a substantial saving in computing time without compromising the accuracy. A basic algorithm utilizing the spectral technique in a relaxation framework is described. A prototype simulator based on the algorithm was developed and used to simulate certain types of CMOS circuits. The results showed a significant time savings in comparison with the widely used circuit simulator ‘SPICE’. Example circuits and relevant results are provided.
Numerical solution of inhomogeneous and non‐linear ordinary differential equations using the TLM multicompartment model
Authors: Saleh A. H. M. , De Cogan D. 
Published: August 2005

AbstractThe paper presents a simple algorithm for solving a system of inhomogeneous high order differential equations with variable coefficients. The method also provides a numerical solution to non‐linear ordinary differential equations. The technique is based on reducing the high order equations into a system of first order rate equations. Through a simple translation process, the variables in the reduced set of equations are solved simultaneously by an iterative scheme using the TLM multicompartment model. The numerical technique is demonstrated by solving well‐known second order differential equations. The numerical solutions are compared with the analytical solutions to the differential equations.
Comparison between different formulations of the transverse resonance field‐matching technique for the three‐dimensional analysis of metal‐finned waveguide resonators
Authors: Bornemann Jens 
Published: August 2005

AbstractTwo different formulations of the transverse resonance field‐matching technique are applied to evaluate the modal spectrum of metal‐finned waveguide structures. In the theoretical treatment, Method 1 uses boundary conditions prior to interface relations and allows the number of expansion terms to be selected according to the dimensions of the cross‐section subregions. Method 2 imposes boundary and interface conditions in reversed order but requires the same number of expansion terms to be used in various subregions. The two procedures are then compared with respect to their influence on the modal scattering matrix computation of metal‐finned waveguide resonators. Method 2 shows excellent agreement with measurements, but it is restricted to configurations with relatively thin fins and moderate slot widths. Although Method 1 may be applied to more general structures, this procedure requires a higher computational effort and leads to slightly different results. However, it constitutes a powerful PC‐operational alternative whenever an extended precision compiler, as required for Method 2, is not available.
Numerical modelling of microwave detectors at high signal level
Authors: Wolski Mark R. , Ishii T. Koryu 
Published: August 2005

AbstractThe relationship between microwave power absorbed by a detector diode and the resulting detected voltage at high signal level is investigated. Experimental data is obtained from a zero‐biased diode mounted in a rectangular waveguide system operating at 9.5 GHz. The Alpa Industries Inc. 4561, 6724 and 6725 Schottky diodes and the M/A‐COM 1N23 Point Contact diode with 1 kω and 106 kω loads are examined. The P–V relationships are analysed by solving a system of non‐linear differential equations based on a lumped parameter model of the microwave system and diode.
Numerical modelling of hot electron transport in A graded heterojunction diode
Authors: Hjelmgren Hans , Snowden Christopher M. 
Published: August 2005

AbstractA detailed one‐dimensional energy transport model for unipolar GaAs/AlGaAs heterojunction structures is implemented, by extending the basic transport equations to include the energy balance equation for electrons. A non‐uniform grid‐mesh is used to obtain short simulation times, while the grid‐distance at the N–n++ interface is small, which is essential to obtain a low reverse current.
Hydrodynamic simulation of electron heating in conventional and lightly‐doped‐drain MOSFETs with application to substrate current calculation
Authors: Chai Kam‐Wing , Mawby P. A. , McCowen A. 
Published: August 2005

AbstractThis paper reviews the state of the art in hydrodynamic simulation of hot‐carrier transport in semiconductor devices with application to MOSFET substrate current calculation. Hydrodynamic equations for semiconductors and derived and discretized expressions of these equations for device simulation are presented. Special attention has been given to the discretization of the input power term that appears in the energy conservation equation. A new discretization method for the input power term, based on power generation consideration, is proposed. Energy‐based physical models for mobility and impact ionization are described for use in hydrodynamic simulation. Simulation results for both conventional and lightly‐doped‐drain MOSFETs are presented.