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81.
In this paper we consider a wavelet algorithm for the piecewise constant collocation method applied to the boundary element solution of a first kind integral equation arising in acoustic scattering. The conventional stiffness matrix is transformed into the corresponding matrix with respect to wavelet bases, and it is approximated by a compressed matrix. Finally, the stiffness matrix is multiplied by diagonal preconditioners such that the resulting matrix of the system of linear equations is well conditioned and sparse. Using this matrix, the boundary integral equation can be solved effectively. 相似文献
82.
C. W. LEUNG Department of Mathematics The Chinese Universityof Hong Kong Shatin. N. T. Hong Kong China. 《数学年刊B辑(英文版)》1997,(1)
ASTRASSENLAWOFTHEITERATEDLOGARITHMFORPROCESSESWITHINDEPENDENTINCREMENTWangJiagangAbstractLetX={X(t),t0}beaproceswithindep... 相似文献
83.
Matthew J. Katz 《Computational Geometry》1997,8(6):299-316
We present a new data structure for a set of n convex simply-shaped fat objects in the plane, and use it to obtain efficient and rather simple solutions to several problems including (i) vertical ray shooting—preprocess a set of n non-intersecting convex simply-shaped flat objects in 3-space, whose xy-projections are fat, for efficient vertical ray shooting queries, (ii) point enclosure—preprocess a set C of n convex simply-shaped fat objects in the plane, so that the k objects containing a query point p can be reported efficiently, (iii) bounded-size range searching— preprocess a set C of n convex fat polygons, so that the k objects intersecting a “not-too-large” query polygon can be reported efficiently, and (iv) bounded-size segment shooting—preprocess a set C as in (iii), so that the first object (if exists) hit by a “not-too-long” oriented query segment can be found efficiently. For the first three problems we construct data structures of size O(λs(n)log3n), where s is the maximum number of intersections between the boundaries of the (xy-projections) of any pair of objects, and λs(n) is the maximum length of (n, s) Davenport-Schinzel sequences. The data structure for the fourth problem is of size O(λs(n)log2n). The query time in the first problem is O(log4n), the query time in the second and third problems is O(log3n + klog2n), and the query time in the fourth problem is O(log3n).
We also present a simple algorithm for computing a depth order for a set as in (i), that is based on the solution to the vertical ray shooting problem. (A depth order for , if exists, is a linear order of , such that, if K1, K2 and K1 lies vertically above K2, then K1 precedes K2.) Unlike the algorithm of Agarwal et al. (1995) that might output a false order when a depth order does not exist, the new algorithm is able to determine whether such an order exists, and it is often more efficient in practical situations than the former algorithm. 相似文献
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A. J. Parsons S. D. J. Inglethorpe D. J. Morgan A. C. Dunham 《Journal of Thermal Analysis and Calorimetry》1997,48(1):49-62
Using a system based on non-dispersive infrared (NDIR) detectors, evolved gas analysis (EGA) was able to identify and quantify the principal volatiles produced by heating powdered samples of UK brick clays. From these results, atmospheric emissions likely to result from brick production can be predicted. In addition, EGA results for extruded brick clay test pieces are significantly different from those of powdered samples. Within an extruded brick clay body, evolved gases are contained within a pore system and evolved gas-solid phase reactions also occur. This EGA study provides further evidence on the nature of firing reactions within brick clay bodies. The qualitative and quantitative influence of heating rate — a key process condition in brick manufacture — on gas release is also outlined.Dedicated to Dr. Robert Mackenzie on the occasion of his 75th birthday 相似文献
89.
R.C. Viscovini E.M. Telles A. Scalabrin D. Pereira 《Applied physics. B, Lasers and optics》1997,65(1):33-35
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared
absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength,
polarisation, optimum pressure of operation and precise offset measurements.
Received: 17 September 1996/Revised version: 18 November 1996 相似文献
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