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961.
资产优化中价值函数的一些基本性质 总被引:1,自引:0,他引:1
针对有交易费多种风险资产并存的市场情形,通过常系数投资消费模型中资产优化问题,利用随机分析方法和二阶椭圆变分方法,讨论了价值函数的一些基本性质,即价值函数的凹性、连续性和正则性,以及变分不等式的粘性解的存在性和唯一性。 相似文献
962.
Formalized study of self-assembly has led to the definition of the tile assembly model [Erik Winfree, Algorithmic self-assembly of DNA, Ph.D. Thesis, Caltech, Pasadena, CA, June 1998; Paul Rothemund, Erik Winfree, The program-size complexity of self-assembled squares, in: ACM Symposium on Theory of Computing, STOC02, Montreal, Quebec, Canada, 2001, pp. 459–468]. Research has identified two issues at the heart of self-assembling systems: the number of steps it takes for an assembly to complete, assuming maximum parallelism, and the minimal number of tiles necessary to assemble a shape. In this paper, I define the notion of a tile assembly system that computes a function, and tackle these issues for systems that compute the sum and product of two numbers. I demonstrate constructions of such systems with optimal Θ(1) distinct tile types and prove the assembly time is linear in the size of the input. 相似文献
963.
Surface tensions of the Sn–Ga–In ternary alloy are calculated from the surface tensions of the Sn–Ga, Ga–In and In–Sn sub-binary systems by using geometric models (the Kohler model and the Toop model), and a general solution model (the Chou model). The calculated results are in excellent agreement with the experimental data (except for the Kohler model), assuming an experimental accuracy of ±2.5%. At the same time, the surface tensions of the Sn–Ga–In ternary alloy at 773 K and their sub-binary systems are predicted on the basis of Butler’s equation, in combination with thermodynamic data, and different model parameters β equal to the ratio of the coordination number in the surface phase to that in the bulk phase. Different values of β have almost no influence on the surface tensions. The predicted results agree with the experimental data. Therefore, the resulting iso-surface tension curves for the Sn–Ga–In ternary alloy at 773 K, especially those calculated by using the Toop model, are reasonable. 相似文献
964.
PowerPoint电子讲义(下简称PPT)是如今学校课堂教学中非常常用的媒体形式和教学资源整合工具,许多学科教师的教学从某种程度上已十分依赖这一软件工具,但其对教学内容以页面为单位的呈现方式,却容易使学生在听讲过程中出现"迷航"现象.本文结合自身的教学实践,对PPT制作和使用中的"迷航"问题提出了几种解决策略和实用的建议. 相似文献
965.
针对并行设计中冲突协商策略的选取和优化解的非唯一性问题,给出了冲突的数学描述形式以及冲突原因的数学解释,证明了合作策略的优越性,研究了基于Nash定理的冲突协商解的存在性和唯一性,并给出一种协商模型以及具体应用实例. 相似文献
966.
溶液统计热力学模型的计算机模拟 总被引:2,自引:0,他引:2
溶液统计热力学中涉及到许多模型和抽象的概念,很难用传统的教学手段加以清晰地描述,成为教学中的难点。3DS MAX提供了能将这些概念和理论以三维空间清晰地叙述和形象地模拟的有力工具。本文利用3DS MAX动画制作技术(造型制作、材质设计、变色动画)模拟了S-正规溶液理论中二元理想固溶体的形成过程,并形象化地表达了二元理想固溶体中粒子在系统中NA+NB个晶格位上随机分布的构型数(混合位形配分函数)。充分发挥了3DS动画制作技术的优势,制作成高质量的溶液统计热力学MCAI课件,突破了教学中的难点。 相似文献
967.
根际环境因子对马铃薯块茎生长发育具有重要影响。马铃薯根际环境因子包括光照、温度、水分、空气、营养以及重力等,从生态学的角度综述了根际环境因子对马铃薯块茎生长发育的影响,并对存在的问题及其研究进展进行了讨论。 相似文献
968.
969.
Soil-water distribution in homogeneous soil profiles of Yolo clay loam and Yolo sand (Typic xerorthents) irrigated from a circular source of water, was measured several times after the initiation of irrigation. The effect of trickle discharge rates and soil type on the locations of the wetting front and soil-water distribution was considered. Soil-water tension and hydraulic conductivity, as functions of soil-water content, were also measured. The theories of time-dependent, linearized infiltration from a circular source and a finite-element solution of the two-dimensional transient soil-water equation were compared with the experimental results. In general, for both soils the computer horizontal and vertical advances of the wetting front were closely related to those observed. With both theories, a better prediction of the wetting front position for the clay loam soil than for the sandy soil is shown. The calculated and measured horizontal vertical advances did not agree over long periods of time. With the linearized solution, overestimated and underestimated vertical advances for the clay and sandy soils, respectively, were shown. The finite-element model approximate in a better way the vertical advances than the linearized solution, while an opposite tendency for the horizontal advances indicated, especially in sandy soil.Notation
k
constant (dK/d)
-
K
hydraulic conductivity
-
K
0
saturated hydraulic conductivity
-
J
0,J
1
Bessel functions of the first kind
-
h
soil water tension
-
q
Q/r
0
2
-
Q
discharge rate
-
r
cylindrical coordinate; also horizontal distance in soil surface
-
R
dimensionless quantity forr
-
r
0
constant pond radius
-
R
0
dimensionless quantity forr
0
-
t
time
-
T
dimensionless quantity fort
-
x, y
Cartesian coordinates
-
z
vertical coordinate; also vertical distance along thez axis chosen positively downward
-
Z
dimensionless quantity forz
-
empirical soil characteristic constant
-
dummy variable of integration
-
volumetric soil water content
-
matrix flux potential
-
dimensionless quantity for 相似文献
970.
E. J. Thrush G. Wale-Evans J. E. A. Whiteaway B. L. Lamb D. R. Wight N. G. Chew A. G. Cullis R. J. M. Griffiths 《Journal of Electronic Materials》1984,13(6):969-988
The composition profiles of GaAs/Ga1?xAlxAs heterostructures prepared in two different Metal-Organic Chemical Vapour Deposition (MOCVD) reactors have been studied. Transmission electron microscopy (TEM). and Auger and secondary ion mass spectrometry (SIMS) sputter profiling results are in good agreement and interface widths below 20 å have been achieved. Significant new results on transient phenomena have been obtained. showing that large and sometimes very sharp excursions in composition can be associated with valve switching actions. Direct evidence is presented that gas pressure or flow transients can occur during valve operations. and it is suggested that such instabilities are the cause of the effects observed. 相似文献