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排序方式: 共有401条查询结果,搜索用时 218 毫秒
41.
Osamu Moriue Masato Mikami Naoya Kojima Christian Eigenbrod 《Proceedings of the Combustion Institute》2005,30(2):1973-1980
Spontaneous ignition of single n-heptane droplets in a constant volume filled with air is numerically simulated with the spherical symmetry. The volume is closed against mass, species, and energy transfer. The numerical model is fully transient. It continues calculation even after the droplet has completely vaporized, and therefore can predict pre-vaporized ignition. Initial pressure and initial air temperature are fixed at 3 MPa and 773 K, respectively. The droplet is initially at room temperature, and its diameter is between 1 and 100 μm. When the overall equivalence ratio is fixed to be sufficiently large, there exists no ignition limit in terms of initial droplet diameter d0, and the ignition delay takes a minimum value at certain d0. In such a case, transition from the heterogeneous ignition to the homogeneous ignition with decreasing d0 is observed. When d0 is fixed to be so small that the ignition would not occur in an infinite volume of air, the ignition delay takes a minimum value at certain , which is less than unity. Two-stage ignition behavior is investigated with this model. Ignition delay of a cool flame has the dependence on d0 that is similar to that of ignition delay of a hot flame when is unity. When is almost zero, the ignition limit for cool flame in terms of d0 is not identified unlike that for hot flame. 相似文献
42.
In this paper, we introduce a new combinatorial invariant called q-binomial moment for q-ary constant weight codes. We derive a lower bound on the q-binomial moments and introduce a new combinatorial structure called generalized (s, t)-designs which could achieve the lower bounds. Moreover, we employ the q-binomial moments to study the undetected error probability of q-ary constant weight codes. A lower bound on the undetected error probability for q-ary constant weight codes is obtained. This lower bound extends and unifies the related results of Abdel-Ghaffar for q-ary codes and Xia-Fu-Ling for binary constant weight codes. Finally, some q-ary constant weight codes which achieve the lower bounds are found.
相似文献
43.
44.
毕延芳 《核聚变与等离子体物理》1985,(2)
聚变堆的纵场线圈通常采用无弯矩的恒张力线圈,即D形线圈,这是种尺寸巨大且场强高的纵场线圈,其受电磁力的作用机械支撑问題甚突出。 恒张力线圈的概念最初由File等人提出。最初的D形轮廓线(通常称为PrincetonD)是根据纵场场强与半径成反比(即B_θ∝1/R)的简化条件求解的,也就是假定整个环形纵场线圈沿环向连续均匀地分布。但实际上,纵场线圈总是做成分立的。因为诸如各种注入、加热和抽真空等通道需在线圈之间插入,目前的趋势是在满足等离子体外缘磁场纹波要 相似文献
45.
Luis J. Alí as Abdê nago Barros Aldir Brasil Jr. 《Proceedings of the American Mathematical Society》2005,133(3):875-884
Let be a compact hypersurface with constant mean curvature immersed into the unit Euclidean sphere . In this paper we derive a sharp upper bound for the first eigenvalue of the stability operator of in terms of the mean curvature and the length of the total umbilicity tensor of the hypersurface. Moreover, we prove that this bound is achieved only for the so-called -tori in , with . This extends to the case of constant mean curvature hypersurfaces previous results given by Wu (1993) and Perdomo (2002) for minimal hypersurfaces.
46.
In this paper, we give the equivalent PDEs for projectively flat Finsler metrics with constant flag curvature defined by a Euclidean metric and two 1-forms. Furthermore, we construct some classes of new projectively flat Finsler metrics with constant flag curvature by solving these equivalent PDEs. 相似文献
48.
Given a field F and integer n≥3, we introduce an invariant sn (F) which is defined by examining the vanishing of subspaces of alternating bilinear forms on 2-dimensional subspaces of vector spaces. This invariant arises when we calculate the largest dimension of a subspace of n?×?n skew-symmetric matrices over F which contains no elements of rank 2. We show how to calculate sn (F) for various families of field F, including finite fields. We also prove the existence of large subgroups of the commutator subgroup of certain p-groups of class 2 which contain no non-identity commutators. 相似文献
49.
50.
In this note we derive alternative weighting schemes that complement those of Färe and Zelenyuk (2003) for consistent aggregation of Farrell efficiencies when the technology exhibits (global) constant returns to scale. 相似文献