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41.
We describe the formation of a narrow beam for intensity-modulated electromagnetic radiation propagating through highly scattering materials. We propose to use this beam to reconstruct images, similar to X-ray back-projection techniques. For sufficiently high modulation frequency, the photon density wave is primarily carried by photons that suffer small or no large-angle scattering, which gives rise to the beam’s narrow divergence. The beam-narrowing concept is supported by large-scale numerical simulations to examine the quality of the imaging. 相似文献
42.
In this paper, we give a new genus-3 topological recursion relation for Gromov-Witten invariants of compact symplectic manifolds.
This formula also applies to intersection numbers on moduli spaces of spin curves. A by-product of the proof of this formula
is a new relation in the tautological ring of the moduli space of 1-pointed genus-3 stable curves.
Research of the first author was partially supported by NSF grant DMS-0204824
Research of the second author was partially supported by NSF grant DMS-0505835 相似文献
43.
关于B值随机和的完全收敛性的进一步讨论 总被引:1,自引:0,他引:1
该文在深入揭示B值非随机和完全收敛性中的一系列等价关系的基础上,给出了随机和完全收敛的充分条件,改进和完善了有关文献中的既有成果,并对矩条件的必要性问题做了初步讨论. 相似文献
44.
Isabel Echeverria Ping-Chung Su Sindee L. Simon Donald J. Plazek 《Journal of Polymer Science.Polymer Physics》1995,33(17):2457-2468
Creep and differential scanning calorimetry (DSC) measurements have been used to study the physical aging behavior of a polyetherimide. Isothermal aging temperatures ranged from 160°C to Tg with aging times ranging from 10 min to 8 days. The only measurable effect of physical aging on the short-time creep curves is a shift of the creep compliance to longer times. Andrade plots of the compliance versus the cube root of time are linear at short times with the slope β decreasing with increasing aging time to a constant value once equilibrium is reached. Log β3 is related directly to the degree to which the creep curves shift to longer times with physical aging, and is used in this work as a measure of physical aging. A reduced curve of log β3 versus log aging time is obtained for the aging temperatures investigated by appropriate vertical and horizontal shifts. The enthalpy change during aging increases linearly with the logarithm of the aging time, ta, leveling off at equilibrium at values which increase with decreasing aging temperature. Hence, both nonequilibrium and equilibrium temperature shift factors can be calculated from the DSC data. Good agreement is observed between the equilibrium temperature shift factors obtained from the creep and DSC data. The temperature dependence of the nonequilibrium temperature shift factors is found to be an order of magnitude smaller than that of the equilibrium shift factors. The time scales to reach equilibrium for enthalpy and for mechanical measurements are found to be the same within experimental error. © 1995 John Wiley & Sons, Inc. 相似文献
45.
以废旧电熔锆刚玉为主要原料,采用合理的粒度级配,应用复合结合剂和外加剂以凝聚结合的方式研制成功具有高荷重软化温度、高强度、低气孔率、低烧结线变化的新型锆质不定形耐火材料。图4,表4,参3。 相似文献
46.
有序分组资料的线性趋势检验主要用于检验几个二项总体反应率的线性趋势;在医学与生物学中最典型的用途是研究剂量和反应的关系. 如果用Z检验来代替通常在本检验中所用的卡方检验,就可容易地导出本检验的确切概率计算方法,和其他2×C有序列联表有着相同的形式.本文给出了该检验的确切概率计算方法. 相似文献
47.
从校内“局域网”、社会“城域网”以及全球“因特网”三个方面探讨产学研结合立体网络的构建。联系工作实际,探索校企合作建设产学研基地和网络的有效途径。 相似文献
48.
扰动对天敌有多食性模型稳定性的影响 总被引:1,自引:0,他引:1
本文主要讨论了扰动对天敌具有多食性模型 x_1=x_1(r_1-a_1y), x_2=x_2(r_2-a_2y), y=y(-r_3+b_1x_1+b_2x_2)稳定性的影响。利用Liapunov函数得到了昆虫种类内部的密度制约,将促使昆虫与天敌系统进一步稳定化,进而得出同一食饵水平上的竞争是不稳定化的结论。其中后一种情况与J.M,Smith的结论完全一致。 相似文献
49.
浅论新时期高校学生思想政治工作 总被引:2,自引:1,他引:1
刘肃 《重庆三峡学院学报》2004,20(1):110-113
新的形势既为高校学生思想政治工作提供了难得的历史机遇,也提出了更高的要求和严峻的挑战.高校学生思想政治工作要与时俱进、开拓创新,找准新的切入点. 相似文献
50.
In this paper an extension of the (r|X
p
)-medianoid on networks introduced by Hakimi (1983) is studied. In this extension the customer considers not only the distance
but some characteristics of the facilities such as store size, quality of service and parking space. A new firm wants to establishr new facilities which have to compete with thep facilities that already exist in the market. The entry firm wants to find their locations and characteristics to maximize
profits. Three different customer choice rules (binary, partially binary and proportional preferences) are considered. Some
discretization results are obtained and a resolution procedure is proposed. The problem is solved combining a global search
algorithm based on a branch and bound procedure with some combinatorial heuristics (greedy, interchange, and tabu search).
Some computational experiences are presented.
Partially supported by Ministerio de Ciencia y Tecnología (Spain) and FEDER, grant BFM2002-04525-C02-01. 相似文献