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Distribution by Scientific Domains

Information Science and Computing	40%
Chemistry	40%

Selected Abstracts

Dynamic performance of the beam position monitor support at the SSRF

JOURNAL OF SYNCHROTRON RADIATION, Issue 1 2009
Xiao Wang
Electron beam stability is very important for third-generation light sources, especially for the Shanghai Synchrotron Radiation Facility whose ground vibrations are much larger than those for other light sources. Beam position monitors (BPMs), used to monitor the position of the electron beam, require a greater stability than other mechanical structures. This paper concentrates on an investigation of the dynamic performance of the BPM support prototype. Modal and response analyses have been carried out by finite-element (FE) calculations and vibration measurements. Inconsistent results between calculation and measurement have motivated a change in the soft connections between the support and the ground from a ground bolt in the initial design to full grout. As a result the mechanical stability of the BPM support is greatly improved, showing an increase in the first eigenfrequency from 20.2,Hz to 50.2,Hz and a decrease in the ratio of the root-mean-square displacement (4,50,Hz) between the ground and the top of the support from 4.36 to 1.23 in the lateral direction. An example is given to show how FE analysis can guide the mechanical design and dynamic measurements (i.e. it is not just used as a verification method). Similar ideas can be applied to improve the stability of other mechanical structures. [source]

Fuzzy reasoning based on the extension principle,

INTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 4 2001
Yang Xu
According to the operation of decomposition (also known as representation theorem) (Negoita CV, Ralescu, DA. Kybernetes 1975;4:169,174) in fuzzy set theory, the whole fuzziness of an object can be characterized by a sequence of local crisp properties of that object. Hence, any fuzzy reasoning could also be implemented by using a similar idea, i.e., a sequence of precise reasoning. More precisely, we could translate a fuzzy relation "If A then B" of the Generalized Modus Ponens Rule (the most common and widely used interpretation of a fuzzy rule, A,,B, are fuzzy sets in a universe of discourse X, and of discourse Y, respectively) into a corresponding precise relation between a subset of P(X) and a subset of P(Y), and then extend this corresponding precise relation to two kinds of transformations between all L -type fuzzy subsets of X and those of Y by using Zadeh's extension principle, where L denotes a complete lattice. In this way, we provide an alternative approach to the existing compositional rule of inference, which performs fuzzy reasoning based on the extension principle. The approach does not depend on the choice of fuzzy implication operator nor on the choice of a t-norm. The detailed reasoning methods, applied in particular to the Generalized Modus Ponens and the Generalized Modus Tollens, are established and their properties are further investigated in this paper. © 2001 John Wiley & Sons, Inc. [source]

Numerical nonlinear observers using pseudo-Newton-type solvers

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 17 2008
Shigeru HanbaArticle first published online: 12 DEC 200
Abstract In constructing a globally convergent numerical nonlinear observer of Newton-type for a continuous-time nonlinear system, a globally convergent nonlinear equation solver with a guaranteed rate of convergence is necessary. In particular, the solver should be Jacobian free, because an analytic form of the state transition map of the nonlinear system is generally unavailable. In this paper, two Jacobian-free nonlinear equation solvers of pseudo-Newton type that fulfill these requirements are proposed. One of them is based on the finite difference approximation of the Jacobian with variable step size together with the line search. The other uses a similar idea, but the estimate of the Jacobian is mostly updated through a BFGS-type law. Then, by using these solvers, globally stable numerical nonlinear observers are constructed. Numerical results are included to illustrate the effectiveness of the proposed methods. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Stochastic search for isomers on a quantum mechanical surface

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2004
Martin Saunders
Abstract In studying molecules with unusual bonding and structures, it is desirable to be able to find all the isomers that are minima on the energy surface. A stochastic search procedure is described for seeking all the isomers on a surface defined by quantum mechanical calculations involving random kicks followed by optimization. It has been applied to searching for singlet structures for C6 using the restricted Hartree,Fock/6-311G basis set. In addition to the linear chain and ring previously investigated, 11 additional structures (A,K) were located at this level. These provide a basis for discussing qualitative bonding motifs for this carbon cluster. The application of a similar idea to searching for transition states is discussed. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 621,626, 2004 [source]

Affective Modelling: Profiling Geometrical Models with Human Emotional Responses

COMPUTER GRAPHICS FORUM, Issue 7 2009
Cheng-Hung Lo
Abstract In this paper, a novel concept, Affective Modelling, is introduced to encapsulate the idea of creating 3D models based on the emotional responses that they may invoke. Research on perceptually-related issues in Computer Graphics focuses mostly on the rendering aspect. Low-level perceptual criteria taken from established Psychology theories or identified by purposefully-designed experiments are utilised to reduce rendering effort or derive quality evaluation schemes. For modelling, similar ideas have been applied to optimise the level of geometrical details. High-level cognitive responses such as emotions/feelings are less addressed in graphics literatures. This paper investigates the possibility of incorporating emotional/affective factors for 3D model creations. Using a glasses frame model as our test case, we demonstrate a methodological framework to build the links between human emotional responses and geometrical features. We design and carry out a factorial experiment to systematically analyse how certain shape factors individually and interactively influence the viewer's impression of the shape of glasses frames. The findings serve as a basis for establishing computational models that facilitate emotionally-guided 3D modelling. [source]