Geostochastic calculus

A stochastic calculus for a family of continuous measure-valued Markov processes is developed. Such processes arise naturally in the construction of stochastic models of spatially distributed populations. The stochastic calculus is a tool whereby a class of density-dependent models can be studied in terms of the multiplicative measure diffusion process. In this paper the stochastic integral is introduced in the space-time setting and a Cameron-Martin-Girsanov theorem is established.     

区域创新系统中知识扩散国外研究进展及未来展望

从区域创新系统知识扩散的影响因素、扩散途径、扩散特点入手,对1992年至2013年间国外区域创新系统有关知识扩散的研究进行了文献回顾,探讨了区域创新网络建设、区域创新系统政策研究等对知识扩散的作用,指出创新网络对知识扩散、政策工具运用对区域创新系统建设方面是西方学者关注重点,同时根据相关研究,提出区域创新系统中关于知识扩散方面未来的研究侧重点。     

索尔仁尼琴及其《古拉格群岛》的创作风格

作为20世纪引人注目的俄侨作家,索尔仁尼琴的作品以及传奇的一生越来越受到俄罗斯人民和世界各图文学家的关注,作家本人和他的作品因其复杂的经历而被赋予了神话般的色彩.这位富有人道主义精神的唯灵主义作家,对道德和真理的探求体现出俄罗斯文学的悠久传统,并将这种传统应用于小说<古拉格群岛>的创作中.作家在作品中以"写真实"的写作手法,以发散性的风格为读者展示出了一个鲜为人知的世界.     

产业共性技术扩散中政府作用最优力度分析——基于变换的Bass模型

基于一定理论假设将Bass模型中技术扩散的内部影响因素和外部影响因素分别与市场作用和政府作用对应起来,并着眼于政府作用对市场作用的“挤出”效应建立起政府作用与市场作用之间的函数关系,以此来对Bass模型进行变换,使其能刻画政府作用对产业共性技术扩散速度和时间路径的影响。基于变换的Bass模型,以最大化技术扩散速度为目标构建最优化问题以求得政府作用最优力度,由最优化问题可知政府作用对市场作用的“挤出”效应越大,最优政府作用力度就应该越小。还基于相关数据进行了数值模拟分析,并且验证了模型的有效性。研究认为:由于存在政府干预对市场作用的“挤出”效应,在促进产业共性技术扩散中需要把握最优的干预力度即政府作用最优力度,在量化政府作用和市场作用的基础上,求解出来的政府作用最优力度系数可为政府有效和适当干预技术扩散提供理论上的一个尺量。     

Locking the Wiener Process to its Level-Crossing Time

We consider the specific transformation of a Wiener process {X(t), t ≥ 0} in the presence of an absorbing barrier a that results when this process is “time-locked” with respect to its first passage time T _a through a criterion level a, and the evolution of X(t) is considered backwards (retrospectively) from T _a . Formally, we study the random variables defined by Y(t) ≡ X(T _a  ? t) and derive explicit results for their density and mean, and also for their asymptotic forms. We discuss how our results can aid interpretations of time series “response-locked” to their times of crossing a criterion level.     

Seroadaptive Strategies of Vancouver Gay and Bisexual Men in a Treatment as Prevention Environment

British Columbia’s treatment as prevention policy has provided free access to highly active antiretroviral therapy (HAART) to all HIV-positive provincial residents since 1996. One outcome is an increase in HIV-positive gay and bisexual men (GBM) with suppressed viral loads. Previous cross-sectional analyses indicated that some Vancouver GBM now recognize condomless anal sex with men on HAART who report a suppressed viral load as a seroadaptive strategy. To test the hypothesis that this new strategy, termed viral load sorting (VLS), is recognized and used among by GBM in the Momentum Health Study, we analyzed longitudinal data for HIV-negative/unknown (n = 556) and HIV-positive (n = 218) serostatus participants. Analyses indicated that both groups reported VLS, and that serostatus and Treatment Optimism Scale scores were significant determinants in frequency and use. Results exemplify the medicalization of sex and Rogers’ Diffusion Of Preventative Innovations Model, and they have important implications for HIV research and GBM sexual decision-making.     

The contagion of democracy through international networks

Work on democratization typically considers the diffusion of democracy through interstate partnerships. However, such partnerships constitute complex networks that scholars have yet to fully explore as vectors for the spread of democracy. We develop a network theory of democratization which characterizes these networks as epistemic communities that influence elites’ attitudes towards favorable regime types. Our theory predicts, and our empirical strategy confirms, that direct and indirect ties in the alliance network are vectors for democratization. In contrast to conventional wisdom, we find that direct influence is only transmitted through the defensive alliance network and find evidence of higher-order effects.     

Changes in Product Attributes and Costs as Drivers of New Product Diffusion and Substitution

Diffusion theory has typically focused on how communication, internal or external to a social system, leads to adoptions and diffusion of an innovation. We develop a diffusion and substitution model based on a somewhat different perspective. In some cases, progressive improvements in product attributes and/or continual cost reduction seem to be a key driver of the diffusion process. For example, after introduction of the 5.25‐inch disk drive, its capacity continually increased, and accordingly, so did customer willingness‐to‐pay. Our model is based on a linear reservation price framework, in which a product is described by its depth (defined as the difference between a product̂s maximum reservation price and its production cost), and its breadth (related to the slope of its reservation price curve), indicating how broadly it appeals across various customer segments. Because of changes in product depths and breadths over time, customers who previously preferred the old product may later prefer the new product, thus creating the diffusion process. While the Bass model describes diffusion as a function of the coefficients of innovation and imitation, in our model, it is described by the coefficients of depth and breadth (the rates of change in relative depth and breadth), along with an S‐coefficient that we associate with the technology S‐curve. We fit our model to data from the disk‐drive and the microprocessor industries.     

广告媒介下两种产品竞争与扩散模型的进一步研究

基于巴斯模型在非垄断情形下遇到的产品扩散问题,提出了在广告媒介下两种产品竞争与扩散模型,并对扩散过程作了进一步的研究,为预测和模拟动态市场结构演变提供了充分的理论依据。     

产业空间扩散的动力机理与长三角区域经济一体化

区域发展一体化,是指在一个主权国家的范围内,地域上较接近的省区之间、省内各地区之间、城市之间,通过合理的地域分工,推动区域协调发展的动态过程。从全国乃至全球范围来看,长江三角洲地区的发展走过的是一条从均衡走向不均衡的路径,这种不均衡正是区域先发地区向后发地区进行空间扩散的条件之一。长江三角洲区域经济发展的研究应从产业空间扩散基本理论框架入手。长江三角洲地区产业空间扩散的理论条件给产业在区域内部扩散创造了良好的制度保障。长江三角洲地区产业空间扩散的现实条件包括飞速发展的交通网络、广泛存在的劳动成本差距和不断推进的区域一体化等。