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Hopf bifurcation in a symmetric configuration of transmission lines

NONLINEAR ANALYSIS-REAL WORLD APPLICATIONS 2007年第4期8卷 1144-1170页

作者： Balanov, Zalman Krawcewicz, Wieslaw Ruan, Haibo Natanya Acad Coll Dept Math & Comp Sci IL-42365 Netanya Israel Univ Alberta Dept Math & Stat Sci Edmonton AB T6G 2G1 Canada

We apply the equivariant degree method to a Hopf bifurcation problem for a symmetric system of neutral functional differential equations, which reflects two symmetrically coupled configurations of the lossless transmission lines. The spectral information of the linearized system is extracted and translated into a bifurcation invariant, which carries structural information of the solution set. We calculate the values of the bifurcation invariant by following the standard computational scheme and using a specially developed Maple((c)) package. The computational results, as well as the minimal number of bifurcating branches and their least symmetries are summarized. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： BIFURCATION CENTROSYMMETRIC Power cables symmetric system Transmission Lines Invariant computational scheme

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A finite-volume solution with a bidirectional upwind difference scheme for the three-dimensional radiative transfer equation

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JOURNAL OF THE ATMOSPHERIC SCIENCES 2007年第11期64卷 4098-4112页

作者： Ishida, Haruma Asano, Shoji Tohoku Univ Grad Sch Sci Ctr Atmospher & Ocean Studies Sendai Miyagi 980 Japan

A new calculation scheme is proposed for the explicitly discretized solution of the three-dimensional (3D) radiation transfer equation (RTE) for inhomogeneous atmospheres. To separate the independent variables involved in the 3D RTE approach, the spherical harmonic series expansion was used to discretize the terms, depending on the direction of the radiance, and the finite-volume method was applied to discretize the terms, depending on the spatial coordinates. A bidirectional upwind difference scheme, which is a specialized scheme for the discretization of the partial differential terms in the spherical harmonic-transformed RTE, was developed to make the equation determinate. The 3D RTE can be formulated as a simultaneous linear equation, which is expressed in the form of a vector-matrix equation with a sparse matrix. The successive overrelaxation method was applied to solve this equation. Radiative transfer calculations of the solar radiation in two-dimensional cloud models have shown that this method can properly simulate the radiation field in inhomogeneous clouds. A comparison of the results obtained using this method with those using the Monte Carlo method shows reasonable agreement for the upward flux, the total downward flux, and the intensities of radiance.

关键词： CLOUD HORIZONTAL INHOMOGENEITY SHAPED OPTICAL MEDIA MARINE STRATOCUMULUS ATMOSPHERES CLIMATE FLUX Regenerative Turboprop Engine RADIATION FIELD Marine Stratocumulus difference scheme Bidirectional Climate computational scheme atmosphere Linear equation finite volume method transfer equation radiance Monte Carlo technique Radiative transfer equation

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Vibration analysis of drillstrings with self-excited stick-slip oscillations

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JOURNAL OF SOUND AND VIBRATION 2007年第3期299卷 540-558页

作者： Khulief, Y. A. Al-Sulaiman, F. A. Bashmal, S. King Fahd Univ Petr & Minerals Dept Mech Engn Dhahran 31261 Saudi Arabia

Drillstring vibration is one of the major causes for a deteriorated drilling performance. Field experience revealed that it is crucial to understand the complex vibrational mechanisms experienced by a drilling system in order to better control its functional operation and improve its performance. Sick slip oscillations due to contact between the drilling bit and formation is known to excite severe torsional and axial vibrations in the drillstring. A dynamic model of the drillstring including the drillpipes and drillcollars is formulated. The equation of motion of the rotating drillstring is derived using Lagrangian approach in conjunction with the finite element method. The model accounts for the torsional bending inertia coupling and the axial-bending geometric nonlinear coupling. In addition, the model accounts for the gyroscopic effect, the effect of the gravitational force field, and the stick slip interaction forces. Explicit expressions of the finite element coefficient matrices are derived using a consistent mass formulation. The generalized eigenvalue problem is solved to determine modal transformations, which are invoked to obtain the reduced-order modal form of the dynamic equations. The developed model is integrated into a computational scheme to calculate time-response of the drillstring system in the presence of stick-slip excitations. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： TORSIONAL VIBRATIONS DYNAMIC-ANALYSIS FRICTION SYSTEMS IMPACT MODEL TORSIONAL VIBRATION Dynamic analysis friction inertial coupling Vibration analysis Drill strings Function Operations stick-slip computational scheme

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On the calculation of Mossbauer isomer shift

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JOURNAL OF CHEMICAL PHYSICS 2007年第8期127卷 084101.1-084101.8页

作者： Filatov, Michael Univ Groningen Zernike Inst Adv Mat NL-9747 AG Groningen Netherlands

A quantum chemical computational scheme for the calculation of isomer shift in Mossbauer spectroscopy is suggested. Within the described scheme, the isomer shift is treated as a derivative of the total electronic energy with respect to the radius of a finite nucleus. The explicit use of a finite nucleus model in the calculations enables one to incorporate straightforwardly the effects of relativity and electron correlation. The results of benchmark calculations carried out for several iron complexes as well as for a number of atoms and atomic ions are presented and compared with the available experimental and theoretical data. (C) 2007 American Institute of Physics.

关键词： .isomer ssbauer spectroscopy electron correlation calculation of ssbauer computational scheme energy with respect nucleus model

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Amide IIR, VCD, and 2D IR spectra of polypeptide and ubiquitin: Numerical simulation studies

Amide IIR, VCD, and 2D IR spectra of polypeptide and ubiquit...

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Pacific Rim Conference on Lasers and Electro-Optics

作者： Choi, Jun-Ho Cho, Minhaeng Korea Univ Dept Chem Seoul South Korea

ISBN: (纸本)9781424411733

A computational scheme were established for numerical simulations of amide I IR absorption, vibrational circular dichroism (VCD), and 2D IR photon echo spectra of different secondary structure peptides and the protein ubiquitin in solution. We compared these simulated spectra with experiments and found good agreements between theory and experiments.

关键词： Polypeptides computational scheme numerical simulation Ubiquitins amides infrared spectra

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Analysis of the content of global ⁹⁰Sr in the water and bottom deposits of reservoirs

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ATOMIC ENERGY 2006年第6期100卷 447-456页

作者： Nosov, A. V. Chionov, V. G. Meshcheryakov, D. S. Kiselev, V. P. Kazakov, S. V. Bugaeva, L. G. nw.med.navy.mil Atomenergoproekt

A computational scheme, based on the systematic use of two models and permitting detailed (with different degrees of accuracy) estimation of the volume and specific activity of global-fallout Sr-90 in the water and bottom deposits of reservoirs, is proposed. As an example of the application of this approach, a comparison is made between the computational results and measurement data for reconstruction of the background contamination with global Sr-90 of Lakes Pes'vo and Udomlya - reservoirs for the Kalinin nuclear power plant. The computational results agree satisfactorily with the experimental data.

关键词： reservoirs computational scheme measurement data Reservoir waters

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Analyses on fluid flow and heat transfer inside Calandria vessel of CANDU-6 using CFD

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NUCLEAR ENGINEERING AND DESIGN 2006年第11期236卷 1155-1164页

作者： Kim, M Yu, SO Kim, HJ Korea Inst Nucl Safety Taejon 305338 South Korea

In a CANada Deuterium Uranium (CANDU) reactor, fuel channel integrity depends on the coolability of the moderator as an ultimate heat sink under transient conditions such as a loss of coolant accident (LOCA) with a coincidence of a loss of emergency core cooling (LOECC), as well as a normal operating condition. This study presents the assessments of moderator thermal-hydraulic characteristics in the normal operating condition and one transient condition for CANDU-6 reactors, using a general purpose three-dimensional computational fluid dynamics code. This study consists of two steps. First, an optimized calculation scheme is obtained by many-sided comparisons of the predicted results with the related experimental data, and by evaluating the fluid flow and temperature distributions. Then, in the second step, with the optimized scheme, the analyses for real CANDU-6 of normal operating condition and transition condition have been performed. The present model has successfully predicted the experimental results and also reasonably assessed the thermal-hydraulic characteristics of the real CANDU-6 with 380 fuel channels. Flow regime map with major parameters representing the flow pattern inside Calandria vessel has also proposed to be used as operational and/or regulatory guidelines. (C) 2005 Elsevier B.V. All rights reserved.

关键词： normal condition fluid flow Calandrias Heat transfer computational scheme FLOW PATTERNS Transient conditions heat sinks transition condition Experimental data pressure vessels moderators LOSS OF COOLANT Coincidence

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Identification of previously unrecognized antiestrogenic chemicals using a novel virtual screening approach

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CHEMICAL RESEARCH IN TOXICOLOGY 2006年第12期19卷 1595-1601页

作者： Wang, Ching Y. Ai, Ni Arora, Sonia Erenrich, Eric Nagarajan, Karthigeyan Zauhar, Randy Young, Douglas Welsh, William J. Univ Med & Dent New Jersey Robert Wood Johnson Med Sch Dept Pharmacol Piscataway NJ 08854 USA Univ Med & Dent New Jersey Inst Informat Piscataway NJ 08854 USA Univ Sci Philadelphia Dept Chem & Biochem Philadelphia PA 19104 USA US EPA Natl Risk Management Res Lab Cincinnati OH 45268 USA

The physiological roles of estrogen in sexual differentiation and development, female and male reproductive processes, and bone health are complex and diverse. Numerous natural and synthetic chemical compounds, commonly known as endocrine disrupting chemicals (EDCs), have been shown to alter the physiological effects of estrogen in humans and wildlife. As such, these EDCs may cause unanticipated and even undesirable effects. Large-scale in vitro and in vivo screening of chemicals to assess their estrogenic activity would demand a prodigious investment of time, labor, and money and would require animal testing on an unprecedented scale. Approaches in silico are increasingly recognized as playing a vital role in screening and prioritizing chemicals to extend limited resources available for experimental testing. Here. we evaluated a multistep procedure that is suitable for in silico (virtual) screening of large chemical databases to identify compounds exhibiting estrogenic activity. This procedure incorporates Shape Signatures, a novel computational tool that rapidly compares molecules on the basis of similarity in shape, polarity, and other bio-relevant properties. Using 4-hydroxy tamoxifen (4-OH TAM) and diethylstilbestrol (DES) as input queries, we employed this scheme to search a sample database of similar to 200 000 commercially available organic chemicals for matches (hits). Of the eight compounds identified computationally as potentially (anti)estrogenic, biological evaluation confirmed two as heretofore unknown estrogen antagonists. Subsequent radioligand binding assays confirmed that two of these three compounds exhibit antiestrogenic activities comparable to 4-OH TAM. Molecular modeling studies of these ligands docked inside the binding pocket of estrogen receptor alpha (ER alpha) elucidated key ligand-receptor interactions that corroborate these experimental findings. The present study demonstrates the utility of our computational scheme for this and related

关键词： Estrogens Estrogen Antagonists Estrogen Effect computational scheme Sex Differentiation Physiological aspects Sexual Development Virtual

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Automated calculation scheme for αⁿ contributions of QED to lepton g-2:: Generating renormalized amplitudes for diagrams without lepton loops

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NUCLEAR PHYSICS B 2006年第1-2期740卷 138-180页

作者： Aoyama, T Hayakawa, M Kinoshita, T Nio, M RIKEN Phys Theor Lab Wako Saitama 3510198 Japan Cornell Univ Lab Elementary Particle Phys Ithaca NY 14853 USA

Among 12 672 Feynman diagrams contributing to the electron anomalous magnetic moment at the tenth order, 6354 are the diagrams having no lepton loops, i.e., those of quenched type. Because the renormalization structure of these diagrams is very complicated, some automation scheme is inevitable to calculate them. We developed an algorithm to write down FORTRAN programs for numerical evaluation of these diagrams, where the necessary counterterms to subtract out ultraviolet subdivergence are generated according to Zimmermann's forest formula. Thus far we have evaluated crudely integrals of 2232 tenth-order vertex diagrams which require vertex renormalization only. Remaining 4122 diagrams, which have ultraviolet-divergent self-energy subdiagrams and infrared-divergent subdiagrams, are being evaluated by giving small mass lambda to photons to control the infrared problem. (c) 2006 Elsevier B.V. All rights reserved.

关键词： 8TH-ORDER MAGNETIC-MOMENT VACUUM POLARIZATION SUBDIAGRAMS PHOTON SCATTERING CONTRIBUTION ELECTRON G-2 2ND-ORDER GRAPHS VERTEX SCHOONSCHIP 4TH-ORDER VERTICES Feynman diagrams vertex head computational scheme Leptons

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Using spatial H₂ norm for sensor placement in parabolic partial differential equations

Using spatial <i>H</i><sub>2</sub> norm for sensor placement...

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American Control Conference 2006

作者： Armaou, Antonios Demetriou, Michael A. Penn State Univ Dept Chem Engn University Pk PA 16802 USA Worcester Polytech Inst Dept Mech Engn Worcester MA 01609 USA

ISBN: (纸本)1424402093

The issue of optimal sensor placement in the presence of disturbance is investigated for a class of transport-reaction processes, mathematically modeled by linear parabolic partial differential equations. Specifically, using modal decomposition to discretize the spatial coordinate, the optimal sensor location is computed through the solution of a nonlinear optimization problem in appropriate L-2 space. The notions of spatial and modal observability and robustness index are employed for the definition of the objective and constraint functionals. The formulated problem is subsequently solved using standard search algorithms. The proposed method is illustrated on a representative thermal diffusion process modeled by a one-dimensional parabolic PDE, where, in the presence of disturbances with known distribution, the optimal location of a single point sensor is computed.

关键词： computational scheme Improved filters Parabolic partial differential equations Sensor placement Spatial norms Spatial robustness Spillover effects

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