The performance of closed reactor grade plutonium-thorium fuel cycles in reduced-moderation pressurised water reactors

The production of long-lived transuranic (TRU) waste is a major disadvantage of fission-based nuclear power. Previous work has indicated that TRU waste can be virtually eliminated in a pressurised water reactor (PWR) fuelled with a mixture of thorium and TRU waste, when all actinides are returned to the reactor after reprocessing. However, the optimal configuration for a fuel assembly operating this fuel cycle is likely to differ from the current configuration. In this paper, the differences in performance obtained in a reduced-moderation PWR operating this fuel cycle were investigated using WIMS. The chosen configuration allowed an increase of at least 20% in attainable burn-up for a given TRU enrichment. This will be especially important if the practical limit on TRU enrichment is low. The moderator reactivity coefficients limit the enrichment possible in the reactor, and this limit is particularly severe if a negative void coefficient is required for a fully voided core. Several strategies have been identified to mitigate this. Specifically, the control system should be designed to avoid a detrimental effect on moderator reactivity coefficients. The economic viability of this concept is likely to be dependent on the achievable thermal-hydraulic operating conditions. © 2012 Elsevier Ltd. All rights reserved.

延迟投饵对厚颌鲂仔鱼的影响

在室内养殖条件下,研究厚颌鲂仔鱼的摄食、耐饥饿和恢复生长能力。试验结果表明:(1)仔鱼在孵出后2～3d开口摄食,卵黄囊在之后的2d耗尽,饥饿仔鱼在12～13日龄达到不可逆点(PNR);(2)饥饿仔鱼的初次摄食率在卵黄囊耗尽时达到最高,保持在80%以上的时间为7d;(3)仔鱼在PNR后死亡率急剧增加,PNR后第3d仔鱼全部死亡;(4)经恢复生长试验,延迟3d投饵对仔鱼的存活率影响不大,延迟3～6d投饵对仔鱼全长生长影响不大。

垂直流人工湿地系统中不同组合填料净化能力研究

在较高水力负荷(1～2.5 m/d)下,选取沸石、无烟煤、蛭石、高炉钢渣、生物陶粒等5种填料,采用不同组合方式构建了4个模拟垂直流人工湿地并处理污水。结果表明:组合填料的种类、装填顺序和装填方式对净化效果产生了较大影响;与单一填料相比,4种组合填料对COD的平均去除率都有所提高,对BOD5的净化能力则略有降低;由上至下依次填充无烟煤、生物陶粒、沸石的组合填料具有较好的脱氮功能,对TN和NH4+-N的平均去除率分别达到85%和91%;由上至下依次填充无烟煤、蛭石、钢渣的组合填料具有较好的除磷功能,对TP和T

鳜肿瘤坏死因子相关的凋亡诱导配体Trail基因的原核表达

中国科学院“百人计划”项目([2005]192)资助

Change propagation analysis in complex technical systems

Understanding how and why changes propagate during engineering design is critical because most products and systems emerge from predecessors and not through clean sheet design. This paper applies change propagation analysis methods and extends prior reasoning through examination of a large data set from industry including 41,500 change requests, spanning 8 years during the design of a complex sensor system. Different methods are used to analyze the data and the results are compared to each other and evaluated in the context of previous findings. In particular the networks of connected parent, child and sibling changes are resolved over time and mapped to 46 subsystem areas. A normalized change propagation index (CPI) is then developed, showing the relative strength of each area on the absorber-multiplier spectrum between -1 and +1. Multipliers send out more changes than they receive and are good candidates for more focused change management. Another interesting finding is the quantitative confirmation of the "ripple" change pattern. Unlike the earlier prediction, however, it was found that the peak of cyclical change activity occurred late in the program driven by systems integration and functional testing. Patterns emerged from the data and offer clear implications for technical change management approaches in system design. Copyright © 2007 by ASME.

马口鱼和宽鳍(鱼巤)鳃上发现寄生桡足类一新种(杯口水蚤目,鳋科)(英文)

在湖北省丹江口水库的马口鱼和宽鳍(鱼巤)的鳃上发现的寄生桡足类1新种丹江鳋。形态观察的结果表明,丹江鳋与鳋属的其他种类有很多共同特征,尤其是与博氏鳋和膨大鳋。与其它所有鳋属种类不同的是丹江鳋的第2触肢内缘光滑无刺,及其楔形第2节的外缘呈明显的弧状。以核糖体内转录间隔区(ITS)为标记进行系统进化分析,结果表明,与膨大鳋相比,博氏鳋与丹江鳋的亲缘关系更近些。无论是形态还是系统进化分析的结果都支持丹江鳋为鳋属1个独立的新种。