Cosmological perturbation theory and the spherical collapse model — II. Non-Gaussian initial conditions

In Paper I of this series, we introduced the spherical collapse (SC) approximation in Lagrangian space as a way of estimating the cumulants ξ _J of density fluctuations in cosmological perturbation theory (PT). Within this approximation, the dynamics is decoupled from the statistics of the initial conditions, so we are able to present here the cumulants for generic non-Gaussian initial conditions, which can be estimated to arbitrary order including the smoothing effects. The SC model turns out to recover the exact leading-order non-linear contributions up to terms involving non-local integrals of the J -point functions. We argue that for the hierarchical ratios S _J , these non-local terms are subdominant and tend to compensate each other. The resulting predictions show a non-trivial time evolution that can be used to discriminate between models of structure formation. We compare these analytic results with non-Gaussian N -body simulations, which turn out to be in very good agreement up to scales where σ ≲ 1.     

Gravothermal catastrophe in anisotropic spherical systems

In this paper we investigate the gravothermal instability of spherical stellar systems endowed with a radially anisotropic velocity distribution. We focus our attention on the effects of anisotropy on the conditions for the onset of instability and in particular we study the dependence of the spatial structure of critical models on the amount of anisotropy present in a system. The investigation has been carried out by the method of linear series which has already been used in the past to study the gravothermal instability of isotropic systems._   We consider models described by King, Wilson and Woolley–Dickens distribution functions. In the case of King and Woolley–Dickens models, our results show that, for quite a wide range of the amount of anisotropy in the system, the critical value of the concentration of the system (defined as the ratio of the tidal to the King core radius of the system) is approximately constant and equal to the corresponding value for isotropic systems. Only for very anisotropic systems does the critical value of the concentration start to change and it decreases significantly as the anisotropy increases and penetrates the inner parts of the system. For Wilson models the decrease of the concentration of critical models is preceded by an intermediate regime in which critical concentration increases, reaches a maximum and then starts to decrease. The critical value of the central potential always decreases as the anisotropy increases.     

碳中和目标下中国燃煤电厂CCUS集群部署优化研究

燃煤电厂作为中国最大的CO₂排放源,是中国实现碳中和目标的关键点。CO₂捕集、利用与封存（CCUS）技术是目前煤电行业实现深度减排的唯一途径,碳约束情景下,CCUS技术将在实现煤电碳达峰、碳中和目标中发挥不可或缺的作用。研究中首先使用综合环境控制模型（IECM）对燃煤电厂捕集技术环节的成本构成和经济性进行核算,得到中国燃煤电厂逐厂CO₂捕集成本和捕集量;其次,基于地质利用封存潜力及分布特征,构建CCUS源汇匹配优化模型,得到碳中和目标下的煤电CCUS项目分阶段布局方案;最后,以优化基础设施建设并通过规模经济降低成本为前提,使用聚类分析方法对煤电CCUS项目集群进行识别,进一步构建改进成本最小生成树模型,得到CCUS项目集群最低成本CO₂输送管道网络的路线优化策略。研究表明：碳中和目标约束下,需要对总装机容量约为355 GW的300个燃煤电厂进行CCUS技术改造,2030—2060年间可实现累积减排190.11 亿t CO₂。煤电CCUS项目集群主要分布在华中、华北和西北地区,通过建立CCUS枢纽以实现CO₂运输基础设施共享,在松辽盆地、渤海湾盆地、苏北盆地和鄂尔多斯盆地优先开展CCUS早期集成示范项目,能显著降低运输成本,推动CCUS技术大规模、商业化发展。     

Detecting Randomness in Spatial Point Patterns: A “Stat-Geometrical” Alternative

There are several methods to test the hypothesis of complete spatial randomness of point patterns. This work involves a new geometrical-based strategy to detect spatial arrangements, which takes into account both Euclidean and angular distances, defining a triangle-based network. An asymptotic test based on the Kolmogorov–Smirnov statistic is proposed to accommodate this situation. To assess the usefulness of this method (Stat-Geo), simulations based on Monte Carlo procedures, conducted using SPLUS, give satisfactory results with a high degree of accuracy. As expected, the new technique proposed in this paper, performs better than traditional ones like distance-based or angle-based, since more information (combining distance and angle) is introduced in the decision-making system. This approach is a very simple way to offer high efficiency results for a low computational cost. Furthermore, this alternative method allows barycentric interpolation of the unsampled points into a two-dimensional simplex (triangular) framework.     

闽南和台湾海峡地区次天气尺度强降水云团的研究

利用数字化卫星云图和高空探测资料，对比分析两个发生在不同天气背景下的次天气尺度强降水去团的发生，发展及对台湾地区天气的影响，得到一些有意义的结果。     

Stellar variability in Trumpler 24. II

We present a second season of CCD time‐series observations of Trumpler 24 in Johnson B and V obtained in 2004. 18 new variable stars are found, 15 variables discovered in Paper I are discussed, and the variability class of 5 of them is given. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)