众筹教育与高校美育课改革的契合及实现路径

众筹教育通过打造并完善教育资源共享平台,推动教育资源的虚拟重组、均衡发展,实现跨区域教育的协同发展,有助于实现知识增值的目标。众筹教育所具备的创意性筹资、柔性化生产、互动化交流、区域化共享等特征使其与当下的高校美育选修课教育体制改革的需求高度契合。从实现路径来看,众筹教育介入高校美育选修课改革可以从校内模拟众筹、区域内课程共享、完善教育资源共享平台3个层面逐步铺开,形成高校美育选修课线上与线下互动发展的新模式,为推动我国教育体制改革困局的破解提供思路。     

A delay-in-payment contract for Pareto improvement of a supply chain with stochastic demand

We consider a supply chain consisting of a single supplier and a single retailer with stochastic customer demand, which is operated over an infinite horizon. We propose a delay-in-payment contract to coordinate the supply chain. With this contract, the supplier allows the retailer to pay partial order cost at the ordering epoch, and to pay the remaining portion after a permissible number of periods. The system is formulated as a stochastic dynamic programming problem. It is shown that there exists a base-stock policy to be optimal. Compared with the traditional wholesale-price contract, the delay-in-payment contract with appropriate parameters can achieve a Pareto improvement (i.e., the performances of both the supplier and the retailer using the delay-in-payment contract are better than those using the wholesale-price contract). Numerical studies are performed to investigate both the effectiveness of the Pareto improvement, and the impact of the major parameters of the delay-in-payment contract on the system performance.     

水平井分段多簇压裂缝间干扰研究

水平井分段多簇压裂在现场得到了广泛运用，其压裂过程中普遍存在缝间干扰现象。缝间干扰有助于形成复 杂裂缝网络以提高储层导流能力，但是也会导致起裂困难，甚至形成砂堵。因此有必要对分段多簇压裂的缝间干扰问 题进行研究。对此，基于弹性力学建立了分析多簇裂缝诱导应力的数学模型，从起裂压力、裂缝宽度、簇间距等多方面 研究了缝间干扰对水平井分段多簇压裂施工的影响。模拟结果显示，诱导应力会导致起裂压力升高、裂缝变窄，严重 时将造成压裂施工失败。通过进行分析，给出了起裂过程及延伸过程中缝间干扰的影响关系。分析认为，利用缝间干 扰提高改造体积时应当控制簇间距防止对压裂施工造成负面影响。研究结论对优化水平井分段多簇压裂设计具有指 导意义。     

An M/G/1 clearing queueing system with setup time and multiple vacations for an unreliable server

This paper studies an M/G/1 clearing queueing system with setup time and multiple vacations, in which all present customers in the system are served simultaneously and breakdowns may occur in busy or setup period. We investigate the stationary distribution of system size and the Laplace–Stieltjes transform of sojourn time. In addition, various performance measures are discussed, such as the mean system size at arbitrary time and the mean length of a vacation circle. Moreover, a cost analysis is carried out for this queueing system. Numerical results are presented to study the sensitivity of the system parameters on the expected cost function and system performances.     

Why Frequency is Not Well Defined for Engineering Systems with Nonexponential Failure Times

Dr. Yellman proposes to define frequency as “a time‐rate of events of a specified type over a particular time interval.” We review why no definition of frequency, including this one, can satisfy both of two conditions: (1) the definition should agree with the ordinary meaning of frequency, such as that less frequent events are less likely to occur than more frequent events, over any particular time interval for which the frequencies of both are defined; and (2) the definition should be applicable not only to exponentially distributed times between (or until) events, but also to some nonexponential (e.g., uniformly distributed) times. We make the simple point that no definition can satisfy (1) and (2) by showing that any definition that determines which of any two uniformly distributed times has the higher “frequency” (or that determines that they have the same “frequency,” if neither is higher) must assign a higher frequency number to the distribution with the lower probability of occurrence over some time intervals. Dr. Yellman's proposed phrase, “time‐rate of events … over a particular time interval” is profoundly ambiguous in such cases, as the instantaneous failure rates vary over an infinitely wide range (e.g., from one to infinity), making it unclear which value is denoted by the phrase “time‐rate of events.”     

国际组织与成员国法律责任多重归属问题研究

国际组织和成员国的法律责任归属问题一直以来都是国际法争论的话题。政府间国际组织作为一类国际法主体,应独立承担法律责任。但在实践中,成员国在执行国际组织决议的过程中往往滥用国际组织法律人格,其行为不仅是国际组织法律人格的体现,还代表了自己的意志,造成法律责任归属不明。以此种争议情形为研究对象,结合1999年的使用武力合法性案,2007年欧洲人权法院的拜拉米案和萨拉马提(Behrami/Saramati)案、阿尔吉达(Al-Jedda)案以及2014年海牙法院关于斯雷布雷尼察(Srebrenica)诉荷兰案的相关判决,借鉴国外学者近几年的相关研究,认为应当坚持国际组织和成员国法律责任的多重归属。围绕责任多重归属原则的确立过程,通过对2011年《国际组织责任条款草案》相关条文的分析,明确了行为归属与责任归属的关系:只有确定行为归属之后,才能确定责任归属;为了最终确定责任的多重归属,提出以有效控制为标准认定行为归属,并明确这种有效控制是对具体行为的事实控制。     

论成品油定价机制中的有限规制：基于合谋的视角

利用单期静态博弈分析法、有限期动态博弈分析法和无限期动态博弈分析法对成品油定价机制中寡头厂商的合谋行为进行了分析。研究发现：两家寡头厂商在合谋条件下的收益均高于双方各自独立定产条件下的收益，因此，双方存在进行价格合谋的利益激励。基于此，我国成品油价格形成机制的改革可以考虑采用有限规制等手段。     

Model-based clustering of multivariate skew data with circular components and missing values

Motivated by classification issues that arise in marine studies, we propose a latent-class mixture model for the unsupervised classification of incomplete quadrivariate data with two linear and two circular components. The model integrates bivariate circular densities and bivariate skew normal densities to capture the association between toroidal clusters of bivariate circular observations and planar clusters of bivariate linear observations. Maximum-likelihood estimation of the model is facilitated by an expectation maximization (EM) algorithm that treats unknown class membership and missing values as different sources of incomplete information. The model is exploited on hourly observations of wind speed and direction and wave height and direction to identify a number of sea regimes, which represent specific distributional shapes that the data take under environmental latent conditions.     

Optimal hedging through limit orders

This article applies the methods of stochastic dynamic programming to a risk management problem, where an agent hedges her derivative position by submitting limit orders. Therefore, this model is the first, in the literature on optimal trading with limit orders, to handle a problem of hedging options or other derivatives. A hedging strategy is developed where both the size and the limit price of each order is optimally set.