纵向非均质性对海上稠油油田水驱油开发效果的影响研究

为兼顾生产成本与开发效果,海上稠油油田开发大多采用多层合采,层内和层间的差异对水驱开发效果影响显著,针对纵向非均质严重的问题,基于不同渗透率级差、不同平均渗透率,建立了反韵律下9种非均质物理模型,研究层内和层间非均质性对海上稠油油田水驱开发效果的影响.研究结果表明:对于层内非均质模型,渗透率级差对开发效果影响更大,平均渗透率相近时,级差越大,层内非均质性越强,注入水沿高渗透层突进,油层下部驱替效果越差,采出程度越低;层内均质层间非均质时,级差越大采出程度越低,高渗层段注入水形成优势通道抑制低渗透层吸水,高渗透层最高采收率达77.4%,低渗层采收率可低至0.7%,使油层上下部驱替效果相差较大;层内和层间都非均质时,分层开采的开发效果好于多层合采,各层采收率变化幅度与分层开采时差异较大;利用综合影响因子表征层内和层间非均质性的综合影响,其值为0.08时对应采出程度为41.48%,综合影响因子越高,纵向非均质性越强,采出程度越低.     

Staggered solution of fluid-porous-media interaction using the method of local Lagrange multipliers

Surface interaction among non-overlapping bulk-fluid and porous-medium bodies occurs in different situations, e. g., the interaction of blood with a blood vessel wall, a body of water with an earth dam structure, or acoustic waves with acoustic panels used in soundproofing. These are multi-field phenomena, comprising various surface- and volume-coupling mechanisms that should be reflected in the corresponding mathematical models. These models, together with appropriate initial and boundary values, assemble a coupled problem, the solution of which reveals the behaviour of the system under external excitations. The solution is commonly done numerically, following a monolithic or a decoupled approach. Here, the focus is on the latter. To design an efficient decoupled scheme, different types of coupling within the problem are addressed. These are the volume coupling between the degrees of freedom (DOF) within each subdomain, and the surface coupling between the DOF on the common boundaries. In particular, the latter constrains the feasible space of the solution of the problem. In this regard, local Lagrange multipliers (LLM) are employed to reformulate the problem in an unconstrained form. Unlike other domain decomposition methods which are based on using global Lagrange multipliers, the LLM method yields a complete separation of the subdomains and, consequently, facilitates parallel solution of the sub-problems. Moreover, within the subdomains, the penalty method is used to decouple pressure from other DOF. This procedure, on the one hand, reduces the size of the problem that should be solved at the interface and, on the other hand, removes the burden of using mixed finite elements within the subsystems. In the next step, the stability behaviour of the resulting staggered approach is analysed, and the unconditional stability of the method is established. Finally, the method is employed to solve a benchmark example, and using the numerical results, the reliability of the outcomes of the stability analysis is investigated. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

基于模糊FNN-ELECTRE法的国有商业银行竞争力评价

随着金融业全方位开放,国有商业银行已成为国家经济命脉的核心,其竞争力强弱关系着国家经济的繁荣与衰退。本文基于模糊FNN-ELECTRE方法建立国有商业银行竞争力评价模型,以因素神经网络理论(FNN)与ELECTRE融合方法为基础,以现有商业银行竞争力评价指标为着眼,把国有商业银行竞争力的评价体系从现实竞争力和潜在竞争力两个因素抽取为一级指标,以规模、质量、业务结构、效率、成长性五个因素设为二级指标。从实证的角度对银行A、银行B、银行C、银行D、银行E五大国有银行进行分析验证,对其属性值进行和谐性与非和谐性检验得出,银行B竞争能力最强,银行E竞争能力最弱,五大国有银行均有改进空间。     

Analysis of an augmented mixed‐primal formulation for the stationary Boussinesq problem

In this article, we propose and analyze a new mixed variational formulation for the stationary Boussinesq problem. Our method, which uses a technique previously applied to the Navier–Stokes equations, is based first on the introduction of a modified pseudostress tensor depending nonlinearly on the velocity through the respective convective term. Next, the pressure is eliminated, and an augmented approach for the fluid flow, which incorporates Galerkin‐type terms arising from the constitutive and equilibrium equations, and from the Dirichlet boundary condition, is coupled with a primal‐mixed scheme for the main equation modeling the temperature. In this way, the only unknowns of the resulting formulation are given by the aforementioned nonlinear pseudostress, the velocity, the temperature, and the normal derivative of the latter on the boundary. An equivalent fixed‐point setting is then introduced and the corresponding classical Banach Theorem, combined with the Lax–Milgram Theorem and the Babu?ka–Brezzi theory, are applied to prove the unique solvability of the continuous problem. In turn, the Brouwer and the Banach fixed‐point theorems are used to establish existence and uniqueness of solution, respectively, of the associated Galerkin scheme. In particular, Raviart–Thomas spaces of order k for the pseudostress, continuous piecewise polynomials of degree ≤ k+1 for the velocity and the temperature, and piecewise polynomials of degree ≤ k for the boundary unknown become feasible choices. Finally, we derive optimal a priori error estimates, and provide several numerical results illustrating the good performance of the augmented mixed‐primal finite element method and confirming the theoretical rates of convergence. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 445–478, 2016     

O2O实体渠道与网络渠道价格差异的竞争分析

针对由O2O实体渠道和网络渠道集成的双渠道供应链,在Hotelling模型基础上先构建出消费者效用函数模型和需求函数模型,然后建立双渠道收益函数模型,并求解分析电子商务成熟度、购物成本、服务质量对两种渠道价格差异的影响.结果表明,电子商务成熟度超过一个临界值时,网络渠道价格将高于O2O实体渠道;网上购物成本越高,网络渠道价格低于O2O实体渠道;服务质量越高,利润越大.最后,将收集的相关指标数据进行假设检验和多元线性回归分析,实证结果与理论分析相符.因此,研究对分析这两种渠道的定价差异具有指导意义.     

T型微通道内液滴在幂律流体中运动机理的格子Boltzmann方法研究北大核心CSCD

采用非Newton不可压两相流格子Boltzmann模型研究了T型微通道内Newton液滴在非Newton幂律流体中的运动过程.研究了非Newton流体幂律指数n、主管道毛细数Ca、两相流量比Q、两相黏度比M以及主管道壁面润湿性θ对液滴在T型微通道内的形成尺寸、形成时间和变形参数(DI)的影响.研究结果表明:首先,主管道流体幂律指数n从0.4增加到1.6时,液滴的形成尺寸近似呈线性减小,而液滴的形成时间和变形参数先快速减小,然后缓慢减小;其次,黏度比对液滴形成尺寸、液滴形成以及变形参数的影响与幂律指数的影响基本一致;再者,随着Ca和主管道壁面润湿性的增加,形成液滴的尺寸近似呈线性减小,形成液滴的时间和变形参数先快速减小然后缓慢减小,且减小趋势随幂律指数的增加而减缓;最后,研究结果还表明主管道和子管道的流量比Q越大,液滴形成时间越长,液滴形成尺寸和变形参数越小.     

三种类型汽车的能耗和使用成本的建模研究

本文对电动,传统,混合动力三种类型汽车的能耗和使用成本问题进行了建模、求解及分析．首先定义了电动汽车的能量利用率ηE。根据能量守恒将所有电量转换成汽油消耗量,而传统车型则直接反映到汽油的消耗上,混合动力汽车则综合电动汽车和传统汽车的能耗模型,从而统一能耗水平评价标准．这样,我们就得到了三种不同类型车的能耗模型再进行模型求解以此来分析比较三种类型车哪一种节能效果好．对电动汽车来说,使用成本主要包括驾驶维护成本、报废处理成本,而对传统汽车来说,使用成本主要包括驾驶维护成本、报废处理成本、环境成本和其他成本,混合动力汽车则结合二者使用成本．因此,根据不同车型使用成本类型建立相应的数学模型,按照建立的公式,可以得到电动汽车的使用成本LCC1、传统汽车的使用成本LCC2和混合动力汽车的使用成本LCC3,从而进行模型求解．     

基于区间直觉模糊不确定语言的中小企业电子商务网站建设决策方法研究

阐述中小企业在整个国民经济中的重要地位,指出电子商务对于中小企业具有天然的适应性和可行的推广性.揭示研究对象中蕴含着广泛的模糊性,应用区间直觉模糊不确定语言的必要性.介绍区间直觉模糊不确定语言的基本概念、基本运算、算术平均和加权平均、距离、期望函数、精度函数、期望函数值、精度函数值以及对象比较方法等内容.提出区间直觉模糊不确定语言决策步骤:设定方案集、指标集、专家集,确定评判矩阵,确定指标权重,计算加权平均,计算期望函数、精度函数,期望函数值、精度函数值,进行排序.以盛东商贸有限公司电子商务网站设计方案测评为例,碍出方案3优于方案2优于方案5优于方案1优于方案4的结论.     

基于SVM的客车车型分类

通过支持向量机(SVM)对客车车型的长,宽,高,宽长比等7个特征进行特征选择,得到的准确率最高的子集是长、宽、高、宽长比、宽高比,以它作为样本特征进行分类.对客车的4类车型进行分类,每类车型选择80个样本,50个样本进行训练,30个样本进行预测,结果表明:对1类车型的分类准确率可达到100%,对2类和4类车型可达到96%以上,对3类车可达到93%以上.得到了比选用长、宽、高作为特征进行分类更优的结果.然后运用加入参数寻优的SVM对客车的4类车型进行分类,并加以比较.基于高斯函数的特性,两次用到SVM进行机器学习时,核函数均选用RBF核函数.     

Evaluation of the pliability and rigidity of nonbalanced monoclinic composites

Conclusions As the result of a change in the deformation characteristics of the elementary layers, which is asymmetric with respect to the middle plane of the composite, and caused by imperfections of technical character, aging, the effect of temperature, moisture content, corrosive media, and other factors, the balancing of the laminated polymeric composites is disturbed. Formulas were obtained for determining all the pliability and rigidity matrix components of a nonbalanced monoclinic composite from known deformation characteristics, volume, and order of packing of the elementary layers.Institute of Wood Cellulose Chemistry, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1030–1035, November–December, 1976.     

基于分层贝叶斯时空模型的雾霾天气过程计数分析

本文以北京市8个行政区(东城区、西城区、石景山区、海淀区、朝阳区、昌平区、顺义区、怀柔区)的PM2.5指数计算各区逐月雾霞天气过程计数频数为研究对象,选择考虑包括地表温度、相对湿度、平均风速、SO_2质量浓度和NO_2质量浓度在内的5个影响因素。本文定义雾霾天气过程,构建分层贝叶斯时空模型,在一个统计模型中对诸多影响因素进行分析,并从计数分析的角度对北京市雾霾天气现象的时空分布、影响因素进行深入讨论。通过分析得出,温度、湿度、污染物浓度对于雾霾天气过程发生具有促进作用,平均风速对于雾霾天气过程发生具有抑制作用。从时空角度分析,从时间维度上看雾霾天气过程的发生具有明显的季节性特征,冬季(1月、2月)以及3月雾霾天气过程发生次数最高,春季(4月、5月)发生次数最低,秋季发生次数略高于夏季。从空间维度上来看,中心城区(东城区、西城区、石景山、海淀区、朝阳区)雾霾天气过程发生次数明显高于郊区(顺义、昌平、怀柔),以东城区、西城区和朝阳区最为严重。     

环的(k,l,m,n)一根

Brown和McCoy在文[1]中建立了(F,Ω)-群的根理论,并由此考察了环的BrownMcCoy-根及其它一些根,根据这一方法,Szsz在文[2]中引进了环的(k,l,m,n)-根,其中k,l,m,n是任意的非负整数,并证明了环的Brown-McCoy根与(1,1,1,1)-根,(1,1     

An Experimental Comparison of MRP Purchase Discount Methods

This paper addresses the managerial issue of how best to order purchased materials in MRP environments when discounts are available from vendors. The least unit cost, least period cost, McLaren's order moment, revised part-period balancing, incremental part-period balancing, traditional discount order quantity, and an optimal algorithm are experimentally investigated under a variety of simulated scenarios. Other experimental factors include the coefficient of variation in demand, forecast uncertainty beyond the current period, the average time between orders, the ratio of the discount quantity to the EOQ, the attractiveness of the discount, the length of the planning horizon, inventory holding costs, and the autocorrelation of demand. All factors tested in this comprehensive experiment significantly affected the performance of the discount ordering procedures. Furthermore, the results from this study suggest that the least unit cost, McLaren's order moment, the traditional discount order quantity, and the optimal procedures significantly out-perform the others. A further choice among these alternative methods was found to be a function of the operating environment and limitations that may exist on available computing time.     

考虑双参照点和Choquet积分的新型研发机构绩效评估方法及应用

针对新型研发机构绩效评估值不确定、指标间存在关联、投资主体多元且有风险偏好、指标集权重未知等绩效问题,提出基于双参照点和Choquet积分的绩效评估方法。首先,结合新型研发机构的特点,构建绩效评估指标体系;其次,基于累积前景理论设计同行-期望双参照点;然后,构建指标间直接关联矩阵,依据K-可加模糊测度和平均边际贡献Banzhaf值优化求解指标集权重,代入Choquet积分方法和参照点权重公式计算各新型研发机构的综合绩效评估值,从而实现机构排序和问题分析。该方法考虑了新型研发机构的特点、数据不确定性、指标关联性、风险偏好性、权重未知性等因素,更加符合实际情况,案例验证了方法的有效性和实用性。     

Valuing the option to invest in an incomplete market

This paper considers the impact of entrepreneurial risk aversion and incompleteness on investment timing and the value of the option to invest. A risk averse entrepreneur faces the irreversible decision of when to pay a cost in order to receive a one-off investment payoff. The uncertainty associated with the investment payoff can be partly offset by hedging, but the remaining unhedgeable risk is idiosyncratic. Nested within our incomplete set-up is the complete model of McDonald and Siegel (Q J Econ 101:707–727, 1986) which assumes investment payoffs are perfectly spanned by traded assets. We find risk aversion and idiosyncratic risk erode option value and lower the investment threshold. Our main finding is that there is a parameter region within which the complete and incomplete models give differing investment signals. In this region, the option is never exercised (and investment never occurs) in the complete model, whereas the entrepreneur exercises the option in the incomplete setting. Strikingly, this parameter region corresponds to a negative implicit dividend yield on the payoff, and so this exercise behavior contrasts with conventional wisdom of Merton (Bell J Econ Manage 4:141–183, 1973) for complete markets. Finally, in this parameter region, increased volatility speeds-up investment and option values are not strictly convex in project value, in sharp contrast to the conclusion of standard real options models. The author thanks George Constantinides, Graham Davis, Jerome Detemple, Avinash Dixit, David Hobson, Stewart Hodges, Bart Lambrecht, Andrew Lyasoff, Robert McDonald, Pierre Mella-Barral, Jianjun Miao, Bob Nau (ES discussant), Gordon Sick, James Smith, Stathis Tompaidis, Elizabeth Whalley and Zvi Wiener for their comments. The author also thanks seminar participants at the University of Texas at Austin (2004), Kings College London, the Cornell Finance Workshop, the Oxford-Princeton Finance Workshop, the BIRS Finance Workshop (2004), the Eighth Annual Real Options conference, the Bachelier Finance Society Third World Congress (2004), Princeton University, Boston University, the Fields Institute Toronto, QMF 2004, Warwick Business School, and the Econometric Society Winter Meetings (2006). First version: July, 2004.     

基于电商平台的混合销售渠道对供应链决策的影响研究

考虑到电商平台对消费者强大的吸引力,本文建立了由供应商和平台商构成的基于电商平台混合销售的供应链模型。混合销售渠道包含直销和分销,其中平台商拥有电商平台,供应商通过电商平台进行直销,平台商分享一定的收益;而分销是指平台商从供应商处批发产品进行销售。分别建立了集中式和分散式决策模型,研究发现:随着消费者对分销渠道接受程度的提高,两种情形下直销渠道的零售价不变,分销渠道的零售价提高;分散式情形下的批发价、供应商和平台商的利润均提高;随着供应商分享收益比例的提高,两种渠道的零售价都降低,但批发价提高,供应商的利润提高,而平台商的利润下降,但供应链的总利润提高;研究得到了保证博弈双方都能从直销渠道中获利的收益分享比例范围。     

绿色产品定价与市场入侵研究:基于市场权力结构的视角

为研究绿色产品定价与市场入侵问题,针对由两个制造商和一个零售商组成的系统,构建了制造商主导、零售商主导以及供需双方均势等三种权力结构模型,分析了权力结构、消费者绿色偏好等因素对绿色产品定价和市场入侵的影响。研究发现:绿色产品入侵市场存在可行条件,并且绿色产品市场入侵会导致普通产品制造商的利润损失;市场入侵对零售商有利,说明零售商会有动机引入绿色产品;绿色产品入侵市场和市场权力结构均会影响各个企业最优定价策略,其中拥有主导权的企业会选择高价策略;权力结构会影响供需双方的利润分配,以及导致系统利润的损失。     

Personae at play. ‘Men of Mathematics’ in commentary

Mathematical writers, above all, Euclid, tend to present their theorems as decontextualized, abstract propositions, which has become the standard modus of textual presentation in theoretical mathematics. Mathematical commentators, however, provide their readers with personal names and historical facts in order to elucidate problems, provide contexts of discovery, or construct doxographies, among other things. Modern readers have used such information for the construction of histories of science. When we look at these passages, however, we see that personal names and information about mathematicians of the past can serve quite a range of different objectives, such as the strategic self-positioning of the commentator vis-à-vis the past or present of mathematics, the education of the reader, mathematical or moral, the construction of the history of the field, etc. Not only does the commentator present a persona of himself to the reader, he can also turn colleagues and predecessors into personae. This paper attempts to elucidate the practice, by offering four examples of such plays of and with personae, in Pappus, Eutocius, al-Nayrīzī, and Proclus.     

The role of sex chromosomes in evolution: A new concept

Sex differentiation allows us to check evolution innovations in the male genome before their transmission to the female one. This is possible under asynchronous evolution, since the male evolution precedes the female one. The asynchronicity means that there should be exclusively male genes, which present in the male genome but are absent from the female genome yet, and exclusively female genes, which the male genome has lost but which still exist in the female genome; this is also referred to as the genotypic sexual dimorphism. Treating the dimorphism as a consequence of the sexual dichronism, we are able to reveal the evolution roles of the sex chromosomes and suggest a new concept, which asserts that the Y-chromosome plays the role of a “gate” to feed the input information into, the role of the place where new genes are formed and verified, and the role of initiator, accelerator, and regulator of genotypic sexual dimorphism. On the other hand, the X-chromosome is treated as a “transport” which translocates new genes from the Y-chromosome to the autosomes, stabilizes and smoothens the sexual dimorphism, and stores old genes which have to be eliminated. The suggested concept gives a new understanding of the genesis, localization, and transferring of genes, as well as of the phenomena of chromosome inactivation, mobile genes, relation of the Y-chromosome to stresses, retroviruses, etc. Proceedings of the Seminar on Stability Problems for Stochastic Models, Hajdúszoboszló, Hungary, 1997, Part III.     

From convergence to divergence: the development of mathematical problem solving in research, curriculum, and classroom practice in Singapore

Following the movement of problem solving in the US and other parts of the world in the 1980s, problem solving became the central focus of Singapore’s national school mathematics curriculum in 1990 and thereafter the key theme in research and practice. Different from some other countries, this situation has largely not changed in Singapore mathematics education since then. However, within the domain of problem solving, mathematics educators in Singapore focused more on the fundamental knowledge, basic skills, and heuristics for problem solving till the mid 1990s. In particular, problem solving heuristics, especially the so-called “model method”, a term most widely used for problem solving, received much attention in syllabus, research, and classroom instruction. Since the late 1990s, following the national vision of “Thinking Schools, Learning Nation” and nurturing modern citizens with independent, critical, and creative thinking, Singapore mathematics educators’ attention has greatly expanded to the development of students’ higher-order thinking, self-reflection and self-regulation, alternative ways of assessment and instruction, among other aspects concerning problem solving. Researchers have also looked into the advantages and disadvantages of Singapore’s textbooks in representing problem solving, and the findings of these investigations have influenced the development of the latest school mathematics textbooks.