Collective Strategy Condensation: When Envy Splits Societies

Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed.     

Information percolation and cutoff for the random‐cluster model

We consider the random‐cluster model (RCM) on with parameters p∈(0,1) and q ≥ 1. This is a generalization of the standard bond percolation (with edges open independently with probability p) which is biased by a factor q raised to the number of connected components. We study the well‐known Fortuin‐Kasteleyn (FK)‐dynamics on this model where the update at an edge depends on the global geometry of the system unlike the Glauber heat‐bath dynamics for spin systems, and prove that for all small enough p (depending on the dimension) and any q>1, the FK‐dynamics exhibits the cutoff phenomenon at with a window size , where λ_∞ is the large n limit of the spectral gap of the process. Our proof extends the information percolation framework of Lubetzky and Sly to the RCM and also relies on the arguments of Blanca and Sinclair who proved a sharp mixing time bound for the planar version. A key aspect of our proof is the analysis of the effect of a sequence of dependent (across time) Bernoulli percolations extracted from the graphical construction of the dynamics, on how information propagates.     

一种基于序贯估计的直达声区水面舰船 被动测距方法 *

该文利用基于射线的盲解卷积方法，从直达声区的水面舰船噪声中提取出船和锚系于海底的垂直接收阵之间的时域信道响应，并利用直达波在不同阵元相对于参考阵元的到达时间差，通过序贯方法，利用射线模型和声速剖面信息，对水面舰船距接收阵的距离进行了估计。通过处理海深约为580 m的2016年美国圣巴巴拉海峡的实验数据，对1.6~3.5 km直达声区范围内Anna Maersk商船与垂直阵之间的距离进行了估计，验证了测距方法的有效性，并将结果与系统测量值和几何方法的估计值进行了比较。由于该方法不需要对海底参数进行估计，所以在海底参数未知时要优于传统匹配场方法；在声速剖面存在跃层且海底为多层分布的复杂信道条件下，该方法仍能对距离进行有效估计，且与测量值的相对误差在6%以内，小于几何方法的估计误差，测距结果精度较高。     

Methane dissolution inside bulk or porous-medium-confined water at near-hydrate equilibrium conditions

In this study, we perform a series of mass-balance-type calculations, in order to estimate the minimum volume of liquid water required to dissolve completely a single methane gas bubble, located inside different types of domains that are near or under hydrate equilibrium pressure/temperature conditions. We examine the case of methane bubble dissolution in the bulk, along with the cases of methane bubble dissolution within simple/regular networks of pores, where all pores have the same size. In our calculations, we consider experimental values for the equilibrium solubilities of methane in water, along the hydrate-forming line, as well as, values obtained from predictive tools that are based on different thermodynamic models. The effect of aqueous NaCl solutions on the results is also investigated. As a result of the relatively low solubility of methane in water, large volumes of water are required for complete dissolution of a methane bubble.     

The kinetics of solid-phase microextraction measured for freshly added and aged hydrophobic compounds in two different soils

The proper choice of exposure times is critical if the freely dissolved concentration of chemicals in soil porewater is to be measured via the equilibrium solid-phase microextraction (SPME) as the times to equilibrium may vary depending on compound and soil properties. To reveal the effects of compound hydrophobicity, ageing and soil organic matter content on times to equilibrium, the SPME uptake was measured for five freshly added and aged hydrophobic organic compounds (phenanthrene, pyrene, lindane, p,p′-DDT and polychlorinated biphenyl (PCB) 153) in two contrasted soils (arable and forest soil). The tested compound-soil systems behaved kinetically different. Longer equilibrium times were observed with increasing hydrophobicity of compounds for aged compared to freshly added chemicals and for the forest soil in comparison to the arable soil. The calculated soil–porewater partition coefficients (i.e. sorption coefficients, K_d) of chemicals differed between soil types mainly due to various organic carbon (OC) contents as evidenced by the comparable K_oc values (i.e. K_d values normalised to soil OC content). Similar K_oc values were also found with the various extent of ageing, indicating that both the freshly added and aged compounds linearly partitioned between the soil organic matter and porewater. Our results suggest that, for a respective compound, variations in equilibrium times may be expected depending upon the residence time and the organic matter content in soil where the longest equilibrium times seems to appear for a combination of aged compounds and high organic soils. With regard to this outcome, the effect of the level of sample depletion due to the SPME extraction (LD_SPME) on equilibrium times was assessed. At LDs_SPME of up to 10%, equilibrium times increases linearly with LDs_SPME for p,p′-DDT and PCB 153. For phenanthrene (LD_SPME<10%), and for lindane and pyrene (1.2% < LD_SPME > 40%), no clear relationships were observed.     

RIGID EQUILIBRIUM AS EXEMPLIFIED BY BIRDS STANDING ON A BRANCH1)

为了提高理论力学课堂的趣味性,本文以树枝上小鸟作为刚体平衡的例子,应用力的平行四边形法则、力的可传性、三力平衡汇交定理等基本原理分析了树枝上小鸟的双腿受力,以及啄木鸟尾巴在保持身体平衡中的作用,并讨论了小鸟不同姿态对其受力的影响,期望达到提高学习兴趣、寓教于乐、改善教学效果的目的。     

含参广义集值强向量平衡问题的稳定性

本文借助集合极限的性质和弱f-性假设证明了含参广义集值强向量平衡问题解集映射的下半连续性,其方法不同于最近文献(Zhao,2016和Meng,2018).此外,建立了含参广义集值强向量平衡问题解集连通性的充分条件,并举例验证了所得结果的正确性.本文得结果推广和改进了已有文献(Gong,2008,Xu,2009,Chen,2010,Xu,2013和Zhao,2013)中相应结果.     

生产率差异与企业对外直接投资进入模式选择

基于企业异质性视角,借鉴演化博弈理论探究企业通过OFDI“走出去”时的跨国并购方和标的方在全要素生产率上的差异对企业OFDI进入策略选择的影响机制。利用Hotelling模型构造资本密集型企业与劳动密集型企业OFDI进入策略选择博弈模型,讨论两类企业OFDI进入方式决策在并购双方生产率差异变化之下的变迁机理。研究发现:当并购方和被并购方生产率差异较小时,市场达到两类企业都倾向于跨国并购策略的演化稳定状态;当并购双方生产率差异较大时,企业的生产要素密集度及其结构对其OFDI进入模式决策具有重要的作用,知识或技术密集度较高的资本密集型企业与综合实力强势的部分劳动密集型企业采取跨国并购战略,而另一部分劳动密集型企业选择绿地新建方式进入国际市场。即企业OFDI进入策略选择因其所属的行业生产要素密集度及其结构不同而具有差异性。研究结论在一定程度上弥补了现有研究的不足,为以后的研究工作提供一定的理论参考。