Analytic Function Expansion Nodal (AFEN) Method in Hexagonal-Z Three-Dimensional Geometry for Neutron Diffusion Calculation

The analytic function expansion nodal (AFEN) method in hexagonal-z geometry is described focusing on its unique features, including the use of node-interface flux moments. Multigroup extension based on matrix function theory and coarse group rebalance (CGR) acceleration are also described. The COREDAX code implementing the AFEN method is verified testing on the VVER-440 benchmark problem, a “simplified” VVER-1000 benchmark problem, and the SNR-300 benchmark problem.     

黑龙江省第三积温带甜菜早播增产及其原理研究

本研究中,甜菜每早播10d,增加积温91．4～99．7℃,增加日照60—80h。4月15日早播甜菜的叶面积指数（IAI）、甜菜生长率（CGR）、叶生长率（CGRt）、根生长率（CGRr）等主要生理指标均明显地高于其它播期处理,其最大LAI达到5．57,LA14．3持续55d以上。4月15日早播甜菜产量达到66084kg／hm^2。分别较二、三、四播期处理增产9．8％、21．7％、33．0％,产量差异达1％极显著水准。在依安县甜菜每早播10d,增产9．2％～10．9％。4月15日至4月20日是依安县甜菜高产播期。     

Minimum delay algorithm based on time aggregated graph in DTN network

The DTN network has the characteristics of dynamic topology change,thus the routing algorithm of static network can not solve the routing problem of time-varying network,and can not support fast transmission of given tasks.The existing time-variant routing algorithm CGR (contact graph routing) uses the earliest contact to obtain the shortest path,but because of the influence of the order of the connectivity period,the CGR algorithm has low link utilization.To solve this problem,the method of finding the shortest path was proposed.Besides,in order to characterize the relation between the different connect periods of the same link,the time series of node cache was added to the time aggregated graph.Based on this,the end-to-end multi-path shortest delay routing algorithm for the known task requirements was proposed.Finally,the feasibility of the algorithm was proved by an example.     

镍基高温合金GH4049高温疲劳小裂纹扩展规律

对镍基高温合金GH4049在相同载荷、不同温度下疲劳小裂纹扩展规律进行了试验，利用复型技术和光学显微镜观测了裂纹尺寸演化全过程，发现小裂纹扩展速率的趋势是先快后慢，且温度升高，扩展速率反而下降。这与小裂纹的闭合效应有关，在700％小裂纹的氧化诱发闭合效应比650％时明显。     

Effect of corrosion potential on the corrosion fatigue crack growth behaviour of low-alloy steels in high-temperature water

The low-frequency corrosion fatigue (CF) crack growth behaviour of different low-alloy reactor pressure vessel steels was characterized under simulated boiling water reactor conditions by cyclic fatigue tests with pre-cracked fracture mechanics specimens. The experiments were performed in the temperature range of 240-288 °C with different loading parameters at different electrochemical corrosion potentials (ECPs). Modern high-temperature water loops, on-line crack growth monitoring (DCPD) and fractographical analysis by SEM were used to quantify the cracking response. In this paper the effect of ECP on the CF crack growth behaviour is discussed and compared with the crack growth model of General Electric (GE). The ECP mainly affected the transition from fast (‘high-sulphur’) to slow (‘low-sulphur’) CF crack growth, which appeared as critical frequencies ν_crit = f(ΔK, R, ECP) and ΔK-thresholds ΔK_EAC = f(ν, R, ECP) in the cycle-based form and as a critical air fatigue crack growth rate da/dt_Air,crit in the time-domain form. The critical crack growth rates, frequencies, and ΔK_EAC-thresholds were shifted to lower values with increasing ECP. The CF crack growth rates of all materials were conservatively covered by the ‘high-sulphur’ CF line of the GE-model for all investigated temperatures and frequencies. Under most system conditions, the model seems to reasonably well predict the experimentally observed parameter trends. Only under highly oxidizing conditions (ECP ? 0 mV_SHE) and slow strain rates/low loading frequencies the GE-model does not conservatively cover the experimentally gathered crack growth rate data. Based on the GE-model and the observed cracking behaviour a simple time-domain superposition-model could be used to develop improved reference CF crack growth curves for codes.     

空间延迟/中断容忍网络的接触图路由研究综述

基于覆盖协议和存储-携带-转发范式的延迟/中断容忍网络（delay/disruption tolerant network,简称DTN）被认为是应对空间环境挑战（如长延迟、间歇性连接等）的有效解决方案.接触图路由（contact graph routing,简称CGR）是一种利用空间DTN网络拓扑的先验知识来计算路径的动态路由算法.首先介绍了CGR的基本原理和算法过程,并给出了相关术语的定义及相应计算公式;然后,从路由环路避免、计算效率、路由准确性、拥塞控制、机会性扩展和异常处理方面总结了现有的CGR改进工作;接下来概述了已经进行的评估DTN协议栈和CGR适用性的代表性实测实验,并通过GEO/MEO/LEO卫星网络仿真实验,对比评估了CGR算法与多层卫星路由算法（multi-layered satellite routing algorithm,简称MLSR）的性能差异;最后给出了CGR的未来发展方向,包括扩展块CGR （CGR-extension block,简称CGR-EB）和缓存CGR （cache-CGR,简称C-CGR）整合、机会CGR、CGR向大型网络的扩展、服务质量保障CGR和接触计划描述方法改进等.     

基于连通图的天地一体化测控通信网络仿真

以GEO,MEO,LEO卫星构建的空间异构网络为对象,结合泛在网络的异构、自组织、自愈和协同等特性,介绍了天地一体化测控通信网络的概念,建立了基于“骨干、接入”模型的多层卫星网络,探索了卫星网络被分割(不连通)情况下的测控通信网络路由技术。最后,通过OPNET仿真软件对CGR(连通图)路由算法、random路由算法和flood路由算法在不同失效节点个数情况下的网络性能进行对比分析,结果表明采用连通图路由算法的网络具有更好的自愈和抗毁能力。     

疲劳保载时间与固溶处理对PMRené95合金高温裂纹扩展速率的影响

经不同固溶时效处理的PM René 95合金于650℃分别在蠕变、保载5和90 s疲劳载荷条件下进行了裂纹扩展速率实验.结果表明,相同热处理制度下,疲劳保载时间越长,裂纹扩展速率越高;相同载荷条件下,增加一次高温固溶并缓冷,有利于降低合金的裂纹扩展速率,且固溶温度越高裂纹扩展速率越低;1200℃一次固溶缓冷并于1160℃二次固溶热处理比1140℃一次固溶的裂纹扩展速率约降低一个数量级;基体晶粒尺寸适当加大,强化相粒子γ′c数量增加、形状趋于田字形,有利于降低裂纹扩展速率.     

DTN performance analysis of multi-asset Mars-Earth communications

The delay-/disruption-tolerant networking (DTN) architecture is considered the key enabling technology for future space communications, as confirmed by the current standardization within CCSDS and the experiments carried out onboard the International Space Station. Despite the scientific community efforts to analyze DTN architecture performance, most of the studies have focused on individual protocols, or have considered simple test cases, thus missing a whole system view. To bridge these research gaps, this paper presents a comprehensive analysis of DTN performance in Mars-Earth communications, considering a realistic and complex end-to-end scenario, where multiple assets and multiple data flows are involved, as envisioned for future space missions. To this end, a virtualized testbed based on ION software was used for an extensive emulation campaign, focusing particularly on Bundle and Licklider Protocol interaction with the CGR routing algorithm.     

划痕诱发的镍基合金应力腐蚀裂尖扩展驱动力分析

为了解表面划伤导致的不同氧化物形貌对镍基合金应力腐蚀(SCC)行为的影响,模拟了膜致应力下镍基合金划伤裂纹尖端的局部应力应变场。结果表明,楔形力是引发SCC裂纹扩展的主要驱动力。划痕裂纹前端的氧化物越厚,楔形力越大,并会增大SCC裂纹扩展速率。裂尖氧化物的形成导致了压应力、压应变和负的应变速率,并会阻碍半椭圆裂纹尖端上部和下部的SCC裂纹扩展。