Locating a Biorefinery in Northern Spain: Decision Making and Economic Consequences

Biofuels are emerging as a prominent renewable and sustainable energy sources in developed countries. In this sense, this paper presents a case study in which a biorefinery has to be sited in Northern Spain. Thus, the strategic decision of locating such a facility is deeply investigated through strategic policy evaluation. Then, tactical decisions ranging from purchasing and transportation policies to storage protocols are carried out. Only local and limited biomass can be harvested for supplying the biorefinery through a heterogeneous vehicle fleet. Moreover two different and mutually exclusive storage strategies are evaluated: direct supply from crops to biorefinery and using intermediate-collectors. Additionally, crop exploitation factors and biorefinery sizes are used to generate several scenarios in which the strategic decision of location as well as all the tactic decisions are made. Some mixed integer linear programming models are proposed to figure out all relevant decision problems.The results suggest that the Northwest study area as the best option to locate the biorefinery and recommend the intermediate-collector storage strategy. Moreover, the key information about critical biomass, crops and times are also provided.     

施工企业人力资源管理现状探讨

人力资源是企业最宝贵的资源,也是企业的一种战略能动资源,这一点对于施工企业同样适用。在激烈的市场竞争环境下,人才是企业竞争的核心竞争力。对于施工企业特殊的工作环境、工作强度以及员工构成的特殊性,人力资源在确保实施建筑企业的经营战略中起扮演着关键的角色。     

Robust Markowitz mean‐variance portfolio selection under ambiguous covariance matrix

This paper studies a robust continuous‐time Markowitz portfolio selection problem where the model uncertainty affects the covariance matrix of multiple risky assets. This problem is formulated into a min–max mean‐variance problem over a set of nondominated probability measures that is solved by a McKean–Vlasov dynamic programming approach, which allows us to characterize the solution in terms of a Bellman–Isaacs equation in the Wasserstein space of probability measures. We provide explicit solutions for the optimal robust portfolio strategies and illustrate our results in the case of uncertain volatilities and ambiguous correlation between two risky assets. We then derive the robust efficient frontier in closed form, and obtain a lower bound for the Sharpe ratio of any robust efficient portfolio strategy. Finally, we compare the performance of Sharpe ratios for a robust investor and for an investor with a misspecified model.     

Hiring Older Employees: Do the Age Limits of Early Retirement and the Contribution Rates of Firms Matter?

We examine the effects of a Finnish pension reform on firms' incentives to hire older employees. The reform restricted the eligibility ages for early retirement and changed the size‐related contribution rates of firms. According to our theoretical model, the positive effect on the values of new hires extends to age groups younger than those directly affected by the reform, and the effects are strongest in the largest firms. These model predictions were confirmed in a difference‐in‐difference‐in‐differences analysis on the probability of the hiring of workers of different ages in firms of different sizes.     

我国中小企业成本管理中存在的问题及对策研究

本文对中小企业成本管理特点及目前所存在的问题进行了分析与总结,并就如何加强成本管理进行了对策研究。     

河北省着力改善两个环境面临的问题与对策建议

着力改善发展环境和生态环境具有十分重要的意义作用,目前河北省在着力改善两个环境的过程中存在一定的问题,需要采取措施积极解决。     

基于改进Dijkstra算法的最短路算法

Dijkstra算法是求解最短路径问题的经典算法。在现如今的城市交通网络中,经常需要寻求两个地点之间的最短距离,减少运输时间。本文将Dijkstra算法与C语言相结合,对Dijkstra算法进行改进,根据实际网络图的情况,建立了相应的数学模型,运用C语言编程,在给定的网络图中,实现了只需确定起始点和终点,就可以直接输出最短路径和最短距离的功能。在有多个相同最短路径的情况下,会将多个最短路径一起输出,在搜索到终点时,立即跳出,结束循环。在一般情况下,无需对所有点进行迭代,提高了效率。这种方法可以应用到现在的物流运输中,以此来节约时间,降低成本。     

再论我国公司法人格否认制度

10年前的2005年我国在新颁布的《公司法》中大胆的吸收了西方公司法中的一项重要制度，即公司法人格否认制度。该制度的产生是为了规避在股东有限责任的背景下股东滥用有限责任从而损害债权人的利益的问题。我国企业在进行了公司制的改革后，也同样存在着股东可能滥用有限责任的问题，因此在公司法中规定法人格否认是必须的。但是，从10来的司法实践来看，公司法人格否认制度还没有能够完全发挥其限制股东滥用有限责任，保护无辜债权人的立法目的。本文针对在司法实践中存在的问题，在理论上提出一些建议，以求进一步完善公司法人格否认制度。     

Robust consumption‐investment problem under CRRA and CARA utilities with time‐varying confidence sets

We consider a robust consumption‐investment problem under constant relative risk aversion and constant absolute risk aversion utilities. The time‐varying confidence sets are specified by Θ, a correspondence from [0, T] to the space of the Lévy triplets, and describe a priori drift, volatility, and jump information. For each possible measure, the log‐price processes of stocks are semimartingales, and the triplet of their differential characteristics is almost surely a measurable selector from the correspondence Θ. By proposing and investigating the global kernel, an optimal policy and a worst‐case measure are generated from a saddle point of the global kernel, and they constitute a saddle point of the objective function.     

Personalized goal-based investing via multi-stage stochastic goal programming

In this paper, we propose a goal-based investment model that is suitable for personalized wealth management. The model only requires a few intuitive inputs such as size of wealth, investment amount, and consumption goals from individual investors. In particular, a priority level can be assigned to each consumption goal and the model provides a holistic solution based on a sequential approach starting with the highest priority. This allows strict prioritization by maximizing the probability of achieving higher priority goals that are not affected by goals with lower priorities. Furthermore, the proposed model is formulated as a linear program that efficiently finds the optimal financial plan. With its simplicity, flexibility, and computational efficiency, the proposed goal-based investment model provides a new framework for automated investment management services.