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991.
加工中心是高效自动化设备,为了充分利用机床的高效率、高精度、高自动化等特点,所以要考虑和了解影响加工中心加工精度的因素。 相似文献
992.
In this article ,we chiefly discuss optical part and photoelectrical part, and analyze the result data to make out the relationship between pinhole and special resolution and the influence of PMT on the result data. 相似文献
993.
An Iterative Procedure for Evaluating Digraph Competitions 总被引:1,自引:0,他引:1
A competition which is based on the results of (partial) pairwise comparisons can be modelled by means of a directed graph. Given initial weights on the nodes in such digraph competitions, we view the measurement of the importance (i.e., the cardinal ranking) of the nodes as an allocation problem where we redistribute the initial weights on the basis of insights from cooperative game theory. After describing the resulting procedure of redistributing the initial weights, an iterative process is described that repeats this procedure: at each step the allocation obtained in the previous step determines the new input weights. Existence and uniqueness of the limit is established for arbitrary digraphs. Applications to the evaluation of, e.g., sport competitions and paired comparison experiments are discussed. 相似文献
994.
Xiaofeng Ren 《Archive for Rational Mechanics and Analysis》1997,138(2):169-203
Multiple-layer solutions of the balanced bistable equation in infinite tubes are constructed via a variational method. I
start with a characterization of Palais-Smale sequences which easily gives some global minima in the desired function classes
as single layers. Assuming these minima are isolated as critical points, I paste them together to serve as an approximate
multiple-layer solution. If there were no exact solutions near the approximate one, the negative gradient flow of the energy
functional would significantly lower the energy. On the other hand, if the minima are kept far from each other, the energy
of a function near the approximate solution is not much less than that of the approximate solution. This contradiction proves
the existence of a solution.
(Accepted January 11, 1996) 相似文献
995.
René Lamour 《Numerische Mathematik》1991,59(1):815-829
Summary Consider a TPBVP for transferable nonlinear DAE's. In general the shooting equation has a singular Jacobian. A multiple shooting method which has a nonsingular Jacobian and also produces consistent initial values for the integration is presented. The estimation of the condition of the Jacobian shows the well-posedness of the method. Some illustrative examples are given 相似文献
996.
Synthetic saponites have been intercalated with hydroxyl aluminium oligomers and characterized with several techniques. The basal 001 peak of the pillared saponite (PS) is 1. 8 nm. The amount of the aluminium in the tctrahedral sheet is correlative with cross-linking density. The sheet-to-pillar linkage mode may be Si-O-AlpⅥ. The acid sites in pillared saponite may locate either at surface of clay or at that of pillar. The cumene conversion is relative to accessible acid sites on the surface of PS. The pillar density in the PS has an effect on the pore structure which is correlative with shape selectivity during the reaction between ethanol and ammonia. 相似文献
997.
ON THE EMPTY CONVEX PARTITION OF A FINITE SET IN THE PLANE 总被引:2,自引:0,他引:2
The authors discuss the partition of a finite set of points in the plane into empty convex polygons, and improve some upper bound and lower bound in the related enumeration problems. 相似文献
998.
999.
In studying the multiple scattering of acoustic waves by a half-space of distributed discrete scatterers, the quasicrystalline approximation(QCA) approach together with the hole correction (HC) or the pair distribution functions (PDF) have been used extensively, in which a system of simultaneous equations must be solved to determine the effective propagation constant and the expansion coefficients of the coherent exciting field. In this paper, we analyse the same problem under Foldy's approximation (EFA) by using the so-called modified T-matrix approach (MTMA) which was first proposed by Twersky. Two equations in a considerably simple and clear form are obtained for determining the effective propagation constant and the amplitude of the coherent transmitted field, as the scatterers are identical spheres. The numerical results in the low-frequency limit are also discussed in brief. 相似文献
1000.
The study of focused ion beam (FIB) milling for making etched facet and semiconductor/air distributed Bragg reflector (DBR) facets of AlGaInP-based red laser diodes (LD) is presented in this letter. For the Ga ion beam current of 100 pA at fixed accelerated voltage 30 kV, FIB milling rate of GaAs was found to be 0.46 μm3/nC. As a trade-off between high reflectivity and enough technical tolerance, the combination of third Bragg orders of semiconductor wall and air gap was chosen. The deeply etched mirror and distributed Bragg reflector facet consisting of pairs of semiconductor wall/air gap on laser diodes (LD) cavity facets with vertical sidewall on AlGaInP LDs were fabricated by focused Ga ion beam milling. Comparison of the AlGaInP LD with the mirrors between cleaved and FIB made facet was given and discussed. 相似文献