Shooting at the poachers while the rhinos drown: Managing short‐ and long‐term threats to endangered wildlife in conservation reserves

This paper addresses management challenges associated with conserving endangered wildlife facing multiple threats from illegal poaching, habitat encroachment, and climate and land‐use change‐induced flooding. While poaching and encroachment challenges in conservation parks are of immediate nature, climate‐related risks exist in the long term. The park manager faces a utility function that includes as its arguments local community’s incomes, benefits to the larger society from preserving threatened species and the financial costs of monitoring and land‐use change efforts. Using the case of single‐horned rhinos in the Kaziranga National Park, India, an optimal mix of monitoring and land‐use changes is designed in presence of tradeoffs between short‐ and long‐term management efforts. As monitoring only addresses immediate challenges associated with poaching and encroachment, long‐term climatic risks remain ignored. Land‐use management offers risk‐protection as well as risk‐insurance benefits with respect to climate change‐induced flooding of the park. Recommendations for Resource Managers

• It is important to incorporate both short‐ and long‐term risks posed to endangered wildlife while investing in conservation efforts. There may exist a tradeoff between mitigating short‐ and long‐run risks due to financial and physical resource constraints. However, ignoring long‐term risks to wildlife habitats can jeopardize past conservation efforts.
• Land‐use management, both within and outside of conservation reserves, enhances resilience to climatic shocks through reducing flooding risks and must be an essential part of wildlife conservation efforts.
• Conservation efforts ignoring local community welfare considerations can become suboptimal as they lead to reduced cooperation and potential conflicts. When wildlife conservation efforts account for local community welfare implications, optimal management plans could result in lower species abundance in the short term. However, increasing the park size through additional land enrollment can mitigate some of this tradeoff.

     

ORGANIZED CRIMES AGAINST NATURE: ELEPHANTS IN SOUTHERN AFRICA

Poaching of elephants in Southern Africa is now dominated by international groups following a model of organized crime. This shift, from poaching conducted by small, local groups; with limited mobility, weapons, and technology, to individuals who organize, finance, equip, and transport well‐armed poaching units to previously scouted locations, has made the protection of elephants in Southern Africa much more difficult and dangerous. This paper develops a model of high‐tech criminal poaching. A poaching organization makes a decision on the number of “planned poaching expeditions.” If a poaching unit is intercepted the entire organization is destroyed, but is replaced by a new organization in the next year. The operating life of a poaching organization is a stochastic process, which in turn induces a stochastic evolution in the elephant population. Under plausible conditions, the number of planned poaching expeditions is highly sensitive to the probability of interception by anti‐poaching patrols, but is nonresponsive to reductions in the black‐market ivory price. Thereby it might be better to focus conservation efforts on increasing the probability of intercepting poaching units rather than trying to control black market ivory prices. A benchmark value of poaching expeditions is identified—above which elephants may slowly decline to extinction.     

SHARING THE BENEFITS OF COOPERATION IN HIGH SEAS FISHERIES: A CHARACTERISTIC FUNCTION GAME APPROACH

In the current paper we examine a game-theoretic setting in which three countries have established a regional organization for the conservation and management of straddling and highly migratory fish stocks. A characteristic function game approach is applied to describe the sharing of the surplus benefits from cooperation. We demonstrate that the nucleolus and the Shapley value give more of the benefits to the coalition with substantial bargaining power than does the Nash bargaining scheme. We also compare the results that are obtained by using the nucleolus and the Shapley value as solution concepts. The outcomes from these solution concepts depend on the relative efficiency of the most efficient coalition. Furthermore, the question of fair sharing of the benefits is considered in the context of straddling stocks.     

非线性耦合Schrdinger-KdV方程组的一个局部能量守恒格式

本文利用平均值离散梯度给出了一个构造哈密尔顿偏微分方程的局部能量守恒格式的系统方法.并用非线性耦合Schrdinger-KdV方程组加以说明.证明了格式满足离散的局部能量守恒律,在周期边界条件下,格式也保持离散整体能量及系统的其它两个不变量.最后数值实验验证了理论结果的正确性.     

基于模糊集理论的铁路建设项目融资方案综合后评价

铁路建设项目融资方案的优劣决定了项目建设的风险和效益.本文首次提出并明确了铁路建设项目融资方案后评价的概念,指出铁路建设项目融资方案后评价包括投入总资金后评价、资金结构后评价、融资成本后评价、融资风险后评价和资金使用计划后评价五项内容,给出了基于模糊集理论的铁路建设项目融资方案综合后评价的模糊综合评价模型,并通过实例验证了模型的实用性和可操作性,为后评价时点对已运营的铁路建设项目融资方案优劣评价提供了一种简单、科学的综合评价方法.     

Knowledge sharing in communities of practice: A game theoretic analysis

This research applies game theory to analyze the incentives of knowledge-sharing activities in various types of communities of practice (COPs), characterized by individual profiles and decision structures. Indeed, individual decision making results in the under-provision of knowledge; however, the benefit of knowledge sharing may be raised by IT investment and suitable incentive mechanisms we study here. In general conditions, improving communication and collaboration technologies should be prior to developing data mining technologies. However, when the number of community members is sufficiently small and the heterogeneity of the expected value of knowledge among community members is sufficiently large, developing data mining technologies should be considered more important than the other if most community members are low-type ones. On the other hand, based on a screening technique, we find that the benefit of knowledge sharing in the incomplete information setting can be the same as that in the complete information setting if the cost of more efficient community member is smaller than that of less efficient one.     

非定常对流扩散方程保正格式解的存在性

本文发展了非定常对流扩散方程的非线性保正格式.该格式为单元中心型有限体积格式,保持局部通量的守恒性,适用于任意星形多边形网格,本文证明了该离散格式解的存在性,并给出数值结果,表明该格式具有二阶精度.     

Secret Sharing Schemes with Detection of Cheaters for a General Access Structure

In a secret sharing scheme, some participants can lie about the value of their shares when reconstructing the secret in order to obtain some illicit benefit. We present in this paper two methods to modify any linear secret sharing scheme in order to obtain schemes that are unconditionally secure against that kind of attack. The schemes obtained by the first method are robust, that is, cheaters are detected with high probability even if they know the value of the secret. The second method provides secure schemes, in which cheaters that do not know the secret are detected with high probability. When applied to ideal linear secret sharing schemes, our methods provide robust and secure schemes whose relation between the probability of cheating and the information rate is almost optimal. Besides, those methods make it possible to construct robust and secure schemes for any access structure.     

ON THE CENTRAL RELAXING SCHEMES I:SINGLE CONSERVATION LAWS

1. IntroductionIn [6], Jin and adn constructed a class of uPWind relaxing schemes for nonlinearconservation lawswith initial data u(0, x) ~ "o(x), x ~ (xl, ...t -cd), by using the idea of the local relaxation approximation [2,3,6,10].The relaxing scheme is obtained in the following way: A linear hyperbolic systemwith a stiff source term is first constructed to approximate the original equation (1.1)with a small dissipative correction. Then this linear hyperbolic system is solved easilyby und…     

Detection of Cheaters in Vector Space Secret Sharing Schemes

A perfect secret sharing scheme is a method of distributing shares of a secret among a set P of participants in such a way that only qualified subsets of P can reconstruct the secret from their shares and non-qualified subsets have absolutely no information on the value of the secret. In a secret sharing scheme, some participants could lie about the value of their shares in order to obtain some illicit benefit. Therefore, the security against cheating is an important issue in the implementation of secret sharing schemes. Two new secret sharing schemes in which cheaters are detected with high probability are presented in this paper. The first one has information rate equal to 1/2 and can be implemented not only in threshold structures, but in a more general family of access structures. We prove that the information rate of this scheme is almost optimal among all schemes with the same security requirements. The second scheme we propose is a threshold scheme in which cheaters are detected with high probability even if they know the secret. The information rate is in this case 1/3 In both schemes, the probability of cheating successfully is a fixed value that is determined by the size of the secret.     

Secure collaborative supply chain planning and inverse optimization – The JELS model

It is a well-acknowledged fact that collaboration between different members of a supply chain yields a significant potential to increase overall supply chain performance. Sharing private information has been identified as prerequisite for collaboration and, at the same time, as one of its major obstacles. One potential avenue for overcoming this obstacle is Secure Multi-Party Computation (SMC). SMC is a cryptographic technique that enables the computation of any (well-defined) mathematical function by a number of parties without any party having to disclose its input to another party. In this paper, we show how SMC can be successfully employed to enable joint decision-making and benefit sharing in a simple supply chain setting. We develop secure protocols for implementing the well-known “Joint Economic Lot Size (JELS) Model” with benefit sharing in such a way that none of the parties involved has to disclose any private (cost and capacity) data. Thereupon, we show that although computation of the model’s outputs can be performed securely, the approach still faces practical limitations. These limitations are caused by the potential of “inverse optimization”, i.e., a party can infer another party’s private data from the output of a collaborative planning scheme even if the computation is performed in a secure fashion. We provide a detailed analysis of “inverse optimization” potentials and introduce the notion of “stochastic security”, a novel approach to assess the additional information a party may learn from joint computation and benefit sharing. Based on our definition of “stochastic security” we propose a stochastic benefit sharing rule, develop a secure protocol for this benefit sharing rule, and assess under which conditions stochastic benefit sharing can guarantee secure collaboration.     

MULTISYMPLECTIC FOURIER PSEUDOSPECTRAL METHOD FOR THE NONLINEAR SCHRODINGER EQUATIONS WITH WAVE OPERATOR

In this paper, the multisymplectic Fourier pseudospectral scheme for initial-boundary value problems of nonlinear SchrSdinger equations with wave operator is considered. We investigate the local and global conservation properties of the multisymplectic discretization based on Fourier pseudospectral approximations. The local and global spatial conservation of energy is proved. The error estimates of local energy conservation law are also derived. Numerical experiments are presented to verify the theoretical predications.     

微信社群互动行为对用户理财产品投资组合风险决策的影响

微信社群如何影响用户理财产品购买决策是当下金融产品营销的一个重要理论问题。本研究依据效价理论提出感知风险、感知收益与用户理财产品的投资组合风险决策的关系模型,并将用户的微信社群互动纳入模型。基于287个用户问卷数据,129个微信社群的互动行为数据,以及用户理财产品实际购买行为的数据分析,发现用户购买理财产品的投资组合风险决策受到其感知风险与感知收益的影响,而且微信社群的互动频率负向影响用户感知风险与用户投资组合风险决策之间的负向关系、微信社群的消极情绪会加强感知风险对用户投资组合风险决策的负向影响并削弱感知利益对于用户投资组合风险决策的正向影响。本研究扩展了有关用户理财产品决策影响因素的分析视角,并对理财产品的用户管理有借鉴价值。     

A virtual element method-based positivity-preserving conservative scheme for convection–diffusion problems on polygonal meshes

In this paper, we propose a positivity-preserving conservative scheme based on the virtual element method (VEM) to solve convection–diffusion problems on general meshes. As an extension of finite element methods to general polygonal elements, the VEM has many advantages such as substantial mathematical foundations, simplicity in implementation. However, it is neither positivity-preserving nor locally conservative. The purpose of this article is to develop a new scheme, which has the same accuracy as the VEM and preserves the positivity of the numerical solution and local conservation on primary grids. The first step is to calculate the cell-vertex values by the lowest-order VEM. Then, the nonlinear two-point flux approximations are utilized to obtain the nonnegativity of cell-centered values and the local conservation property. The new scheme inherits both advantages of the VEM and the nonlinear two-point flux approximations. Numerical results show that the new scheme can reach the optimal convergence order of the virtual element theory, that is, the second-order accuracy for the solution and the first-order accuracy for its gradient. Moreover, the obtained cell-centered values are nonnegative, which demonstrates the positivity-preserving property of our new scheme.     

Piecewise parabolic method on a local stencil for ideal magnetohydrodynamics

A numerical scheme based on the piecewise parabolic method on a local stencil (PPML) is proposed for solving the ideal magnetohydrodynamic (MHD) equations. The method makes use of the conservation of Riemann invariants along the characteristics of the MHD equations. As a result, a local stencil can be used to construct a numerical solution. This approach improves the dissipative properties of the numerical scheme and is convenient in the case of adaptive grids. The basic stages in the design of the scheme are illustrated in the two-dimensional case. The conservation of the solenoidal property of the magnetic field is discussed. The scheme is tested using several typical MHD problems.     

CONSERVATION OF THREE—POINT COMPACT SCHEMES ON SINGLE AND MULTIBLOCK PATCHED GRIDS FOR HYPERBOLIC PROBLEMS

For nonlinear hyperbloic problems,Conservation of the numerical scheme is important for convergence to the correct weak solutions.In this paper the the conservation of the well-known compact scheme up to fourth order of accuracy on a single and uniform grid is studied,and a conservative interface treatment is derived for compact schemes on patched grids .For a pure initial value problem,the compact scheme is shown to be equivalent to a scheme in the usual conservative form .For the case of a mixed initial boundary value problem,the compact scheme is conservative only if the rounding errors are small enough.For a pactched grid interface,a conservative interface condition useful for mesh fefiement and for parallel computation is derived and its order of local accuracy is analyzed.     

A CELL-CENTERED ALE METHOD WITH HLLC-2D RIEMANN SOLVER IN 2D CYLINDRICAL GEOMETRY

This paper presents a second-order direct arbitrary Lagrangian Eulerian (ALE) method for compressible flow in two-dimensional cylindrical geometry.This algorithm has half-face fluxes and a nodal velocity solver,which can ensure the compatibility between edge fluxes and the nodal flow intrinsically.In two-dimensional cylindrical geometry,the control vol-ume scheme and the area-weighted scheme are used respectively,which are distinguished by the discretizations for the source term in the momentum equation.The two-dimensional second-order extensions of these schemes are constructed by employing the monotone up-wind scheme of conservation law (MUSCL) on unstructured meshes.Numerical results are provided to assess the robustness and accuracy of these new schemes.     

均值-方差期望效用函数下的风险共担

借助Samuelson提出的风险汇合(Risk Adding)与风险分担(Risk Pooling)的概念,讨论了风险共担(Risk Sharing)机制产生的原理.在均值-方差效用函数下,给出了帕累托有效风险共担原则的具体形式,以及风险共担群体接纳新的个体,从而形成更大风险共担群体的条件.在此基础上,证明在均值-方差期望效用函数下,当考虑风险共担群体的形成条件以后,帕累托有效的风险共担原则等价于条件期望风险分配函数.从而在这一特殊效用函数下,建立了风险共担与风险分配函数之间的等价关系.     

非结构网格上一类满足局部极值原理的三阶精度有限体积方法

对二维标量双曲型守恒律方程,发展了一类满足局部极值原理的非结构网格有限体积格式.其构造思想是,以单调数值通量为基础,通过应用基于最小二乘法的二次重构和极值限制器,使数值解满足局部极值原理.为保证数值解在光滑区域达到三阶精度,该格式可结合局部光滑探测器使用.本文从理论上分析了格式的稳定性条件,数值实验验证了格式的精度和对间断的分辨能力.     

不可压饱和多孔弹性杆动力响应的多辛方法

研究了不可压饱和多孔弹性杆的一维动力响应问题.基于多孔介质理论,在流相和固相微观不可压、固相骨架小变形的假定下,建立了不可压流体饱和多孔弹性杆一维轴向动力响应的数学模型.利用Hamilton空间体系的多辛理论,构造了不可压饱和多孔弹性杆轴向振动方程的多辛形式及其多种局部守恒律.采用中点Box离散方法得到轴向振动方程的多辛离散格式和局部能量守恒律以及局部动量守恒律的离散格式;数值模拟了不可压饱和多孔弹性杆的轴向振动过程,记录了每一时间步的局部能量数值误差和局部动量数值误差.结果表明,已构造的多辛离散格式具有很高的精确性和较长时间的数值稳定性,这为解决饱和多孔介质的动力响应问题提供了新的途径.