Flexible simulation of competing risks data following prespecified subdistribution hazards

In recent years different approaches for the analysis of time-to-event data in the presence of competing risks, i.e. when subjects can fail from one of two or more mutually exclusive types of event, were introduced. Different approaches for the analysis of competing risks data, focusing either on cause-specific or subdistribution hazard rates, were presented in statistical literature. Many new approaches use complicated weighting techniques or resampling methods, not allowing an analytical evaluation of these methods. Simulation studies often replace analytical comparisons, since they can be performed more easily and allow investigation of non-standard scenarios. For adequate simulation studies the generation of appropriate random numbers is essential. We present an approach to generate competing risks data following flexible prespecified subdistribution hazards. Event times and types are simulated using possibly time-dependent cause-specific hazards, chosen in a way that the generated data will follow the desired subdistribution hazards or hazard ratios, respectively.     

Curation: a theoretical treatment

Curation is a key mechanism of sociality in a digital era. With an abundance of information, sifting, sorting, selecting, hiding, and standing out become laborious tasks. While researchers have diligently documented people’s curatorial strategies, digital curation remains undertheorized in its own right. I therefore theorize digital curation by disentangling productive curation from consumptive curation, addressing how people curate content that they share, and that which they consume. I embed these agentic curatorial practices within structural bounds, both social and technological. In doing so, I offer a basic theoretical model that captures a dynamic relationship between individual curators, their social networks, and technological design.     

超长钢板桩围堰合理内支撑施工方案

钢板桩围堰合理的内支撑施工方案对施工安全、工期长短、成本大小均有一定的影响。以阜阳至六安铁路颍河特大桥深水基础超长钢板桩围堰施工实践为例，通过建立钢板桩、内支撑和土层相互作用的三维整体有限元模型，根据封底混凝土施工时机的不同，选择4种施工方案，对超长钢板桩围堰内支撑施工方案进行了探讨。结果表明：封底混凝土施工越早，对围堰结构的整体安全越有利；实际采用的施工方案要根据桥址处工程地质条件，结合实际工程情况，经方案比选和分析论证以后确定。     

数字化生存的道德风险与信息崇拜的伦理考辨

当代人尤其是青年人面临诸多现实世界中自我难以解决的矛盾和困惑时,期许能在电子＂伊甸园＂中找回自我价值和精神皈依。然而,虚拟空间并非想象中的天堂,类似＂面具＂的交流形式遮蔽着许多本真的存在,消解了现实世界的核心价值;游离在虚拟和现实之间的自我与社会脱离;对网络的过渡依赖性导致人格的异化;方向感的迷茫和自我定位的偏差,使得价值追求从崇高滑向流俗甚至恶俗。数字化生存方式正颠覆着传统生活方式和现实生活世界的诸多价值标准,而信息崇拜的推波助澜,更使人们产生了一种莫名的幸福被剥夺的感觉。     

A new metamodel-based method for solving semi-expensive simulation optimization problems

In this article, a new algorithm for rather expensive simulation problems is presented, which consists of two phases. In the first phase, as a model-based algorithm, the simulation output is used directly in the optimization stage. In the second phase, the simulation model is replaced by a valid metamodel. In addition, a new optimization algorithm is presented. To evaluate the performance of the proposed algorithm, it is applied to the (s,S) inventory problem as well as to five test functions. Numerical results show that the proposed algorithm leads to better solutions with less computational time than the corresponding metamodel-based algorithm.     

Pricing arithmetic Asian option under a two-factor stochastic volatility model with jumps

This paper presents an efficient Monte Carlo simulation scheme based on the variance reduction methods to evaluate arithmetic average Asian options in the context of the double Heston's stochastic volatility model with jumps. This paper consists of two essential parts. The first part presents a new flexible stochastic volatility model, namely, the double Heston model with jumps. In the second part, by combining two variance reduction procedures via Monte Carlo simulation, we propose an efficient Monte Carlo simulation scheme for pricing arithmetic average Asian options under the double Heston model with jumps. Numerical results illustrate the efficiency of our method.     

Partial unit root and surplus-lag Granger causality testing: A Monte Carlo simulation study

Previous literature has shown that the addition of an untested surplus-lag Granger causality test can provide highly robust to stationary, non stationary, long memory, and structural break processes in the forcing variables. This study extends this approach to the partial unit root framework by simulation. Results show good size and power. Therefore, the surplus-lag approach is also robust to partial unit root processes.     

All pairwise comparisons of exponential location parameters under type i censoring — equal scale parameter case

In this paper, procedures for all pairwise comparisons of location parameters of negative exponential populations are developed when the common scale parameter is known or unknown using large sample distributional approximations of the relevant random variables. The small sample performance of these procedures are then examined using Monte Carlo simulation.     

新媒介背景的儿童类纸质媒体发展取向

数字媒介技术的革新加剧了“图像革命”，造成了人的思考能力的滑坡．这一影响加之于儿童则更加明显。儿童作为特殊且脆弱的社会群体，极易陷入新媒介所搅动的文化漩涡中，传统阅读这一儿童基础性认知技能遭遇到严峻考验。儿童类纸质媒体应充分发挥独有优势，与儿童类数字媒体展开错位竞争。从儿童文化内容的创作生产、儿童文化产品的销售渠道、儿童文化消费的最终实现三个层面完成自身的发展与跨越。     

基于ANSYS的压力容器表面凹坑缺陷安全评定分析

采用通用有限元程序ANSYS建立了移动式压力容器筒体外壁表面凹坑（轴向和周向）的有限元模型。结合筒体表面凹坑的应力理论计算，研究探讨了在恒定内压下，筒体表面凹坑缺陷处的应力分布与凹坑几何尺寸之间的关系。以第三强度理论作为仿真终止判据，获取凹坑各几何参量的阈值，利用MATLAB对阈值进行最小二乘拟合，绘制出凹坑缺陷的安全评估参考曲线。拟合结果表明：轴向和周向凹坑对筒体局部结构强度的影响不同，对应的安全评估参考曲线存在区别。