基于蒙特卡罗模拟的项目费用风险分析方法——项目风险分析系列论文（一）

随着招投标项目竞争的日益剧烈,对于项目费用估算的准确性,以及费用不确定性风险分析的要求越来越高,采用概率费用分析的估算方法代替确定性费用估算的需求日益迫切。文章结合国外相关文献的成果,对采用蒙特卡罗模拟的费用风险分析方法、应具备的条件、需要注意的问题以及优势进行了探讨。     

Strain-rate dependence of low cycle fatigue behavior in a simulated BWR environment

The strain-rate dependence of low cycle fatigue behavior of ASTM A533B low-alloy steel was investigated in a simulated BWR environment. Fatigue resistance of the steel was found to be closely dependent on cyclic strain rate in high-temperature water. A tortuous cracking morphology was dominant at high strain rate and typical fan-like or quasi-cleavage cracking patterns were frequently observed on the corresponding fracture surface. An entirely straight cracking morphology, however, became dominant at low strain rate. Evidence of crack arrest was found on the fracture surface rather than fan-like or quasi-cleavage cracking patterns. The above cracking behavior in simulated BWR water may be attributed to a strain-rate-induced change in the dominant environmentally assisted cracking (EAC) mechanism from hydrogen-induced cracking to film-rupture/slip-dissolution-controlled cracking.     

基于EAC5000通信协议的电量数据远程通信系统

提出了基于EAC5000通信协议的电量数据采集系统,介绍了EAC5000通信协议在RS-485总线中的通信方式,阐述了针对RS-485总线信号的衰减、噪声干扰、浪涌干扰的解决方法,并结合工程实例说明了物理链路层、数据采集层、数据显示与应用层的实现方式及系统的软件设计思路.现场实践证明,该方案设计合理,系统运行稳定.     

硫酸壳聚糖体内抗肿瘤作用的实验研究

目的 研究硫酸壳聚糖的体内抗肿瘤作用。方法 用高、低(200 、100 mg/kg) 两个剂量的硫酸壳聚糖分别腹腔注射治疗肉瘤180(S180) 小鼠和艾氏腹水癌(EAC) 小鼠10 d, 然后测定其抑瘤率、重要器官的内脏指数和生命延长率, 同时设生理盐水组(空白对照组) 和氟尿嘧啶组(阳性对照组) 进行比较。结果 硫酸壳聚糖高、低剂量组和氟尿嘧啶组的抑瘤率分别为38.67 %、30.19 %和43.27 %,3 组的生命延长率分别为65.38 %、69.23 %和54.93 %。和生理盐水组、氟尿嘧啶组相比, 硫酸壳聚糖高、低剂量组的S180 小鼠的胸腺指数均有明显增加(P<0.05)。结论 硫酸壳聚糖能有效抑制S180小鼠肿瘤的生长和延长EAC 小鼠的生存时间, 其作用机制可能与其提高机体的免疫力有关。     

Stability-based minimization of load shedding in weakly interconnected systems for real-time applications

The transient stability of power systems is highly affected by the changes in the power generation and load levels. Due to the variability of the generating resources, the system stability can be provoked and the system stability limits can be reached as a result of certain sudden drop in the power generation. In these cases, the load shedding can act as an effective emergency corrective action for keeping system stability; however, over-shedding of loads results in severe economical as well as social security problems. Therefore, minimization of the load shedding required for the restoration of the system stability is one of the main objectives of this paper. Another critical issue related to successful load shedding is the fast assessment of the system stability, and the amount of the load shedding as well as the implementation of the load shedding corrective action. Therefore, this paper presents a fast method of stability assessment and load shedding requirements in the weakly interconnected power system. The method is an improved form of the extended equal area criterion (EEAC) where the required system equivalence is based on the availability of wide area monitoring (WAM) devices in modern power systems. The paper also investigates the impact of the implementation duration of the required load shedding. The results are verified through time domain simulations which confirm the accuracy of the presented method and its suitability for real-time applications.     

一个提供Overlay QOS的端到端接纳控制系统

叠置网络也必须与IP一样,为其扩展业务提供QOS支持。论文提出了一个提供OverlayQOS的端到端接纳控制系统———EAC接纳控制系统,并从叠置网的概念、叠置QOS节点的形成、EAC接纳控制技术、系统架构、模型实现和模拟性能评价等角度出发,对EAC接纳控制系统进行了较为全面的分析和阐述。     

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.     

腐植酸钠对生长猪免疫指标的影响

为了探讨腐植酸钠对生长猪免疫力的影响,选择24头体重为(26.18±1.32)kg的健康生长猪,随机分成2组,每组12头,一组设为试验组,另一组设为对照组。试验组连续灌喂10ml/kg的腐植酸钠(腐植酸钠总含量100mg/kg)10d后,测定T淋巴细胞Ea花环形成率和B淋巴细胞EAC花环形成率。结果表明:灌喂腐植酸钠的健康生长猪的Ea花环形成率明显高于对照组,差异显著(P<0.05);灌喂腐植酸钠的健康生长猪的EAC花环形成率明显高于对照组,差异极显著(P<0.01),表明灌喂腐植酸钠的生长猪机体的免疫水平明显提高。     

中草药饲料添加剂对奶牛Ea花环率和EAC花环率的影响

为了探讨中草药饲料添加剂对奶牛免疫水平的影响,选择健康奶牛20头作为试验对象,分为试验组和对照组,连续给药7d,测定奶牛的Ea花环形成率和EAC花环形成率。试验结果显示,试验组奶牛和对照组相比,Ea花环形成率和EAC花环形成率两项指标均有显著提高。     

To improve the quality of cluster ensembles by selecting a subset of base clusters

Conventional clustering ensemble algorithms employ a set of primary results; each result includes a set of clusters which are emerged from data. Given a large number of available clusters, one is faced with the following questions: (a) can we obtain the same quality of results with a smaller number of clusters instead of full ensemble? (b) If so, which subset of clusters is more efficient to be used in the ensemble? In this paper, these two questions are going to be answered. We explore a clustering ensemble approach combined with a cluster stability criterion as well as a dataset simplicity criterion to discover the finest subset of base clusters for each kind of datasets. Also, a novel method is proposed in order to accumulate the selected clusters and to extract final partitioning. Although it is expected that by reducing the size of ensemble the performance decreases, our experimental results show that our selecting mechanism generally lead to superior results.