太阳能热光伏系统实验研究

对太阳能热光伏系统(STPV)进行了全面的实验研究,对系统组成装置即聚光器、辐射器、滤波器、电池、散热器等进行了合理的选型及加工;设计了系统中热光伏转换器的整体结构,并进行实验搭建,结合自动跟踪装置,对整个STPV系统进行了现场测试,分析了太阳能量密度对辐射器温度的影响,对不同辐射器入口条件下的温度分布进行了比较,并测量了不同辐射器温度下的电池输出特性;研究了散热器流速对电池温度及其输出功率的影响;讨论了实验测量值与理论解存在差异的原因。     

A Dynamic Memory Allocation Optimization Mechanism Based on Spark

Spark is a distributed data processing framework based on memory. Memory allocation is a focus question of Spark research. A good memory allocation scheme can effectively improve the efficiency of task execution and memory resource utilization of the Spark. Aiming at the memory allocation problem in the Spark2.x version, this paper optimizes the memory allocation strategy by analyzing the Spark memory model, the existing cache replacement algorithms and the memory allocation methods, which is on the basis of minimizing the storage area and allocating the execution area according to the demand. It mainly including two parts: cache replacement optimization and memory allocation optimization. Firstly, in the storage area, the cache replacement algorithm is optimized according to the characteristics of RDD Partition, which is combined with PCA dimension. In this section, the four features of RDD Partition are selected. When the RDD cache is replaced, only two most important features are selected by PCA dimension reduction method each time, thereby ensuring the generalization of the cache replacement strategy. Secondly, the memory allocation strategy of the execution area is optimized according to the memory requirement of Task and the memory space of storage area. In this paper, a series of experiments in Spark on Yarn mode are carried out to verify the effectiveness of the optimization algorithm and improve the cluster performance.     

Highly Enantioselective Phase‐Transfer Catalytic α‐Alkylation of α‐tert‐Butoxycarbonyllactams: Construction of β‐Quaternary Chiral Pyrrolidine and Piperidine Systems

A new enantioselective α‐alkylation of α‐tert‐butoxycarbonyllactams for the construction of β‐quaternary chiral pyrrolidine and piperidine core systems is reported. α‐Alkylations of N‐methyl‐α‐tert‐butoxycarbonylbutyrolactam and N‐diphenylmethyl‐α‐tert‐butoxycarbonylvalerolactam under phase‐transfer catalytic conditions (solid potassium hydroxide, toluene, −40 °C) in the presence of (S,S)‐3,4,5‐trifluorophenyl‐3,3′,5,5′‐tetrahydro‐2,6‐bis(3,4,5‐trifluorophenyl)‐4,4′‐spirobi[4H‐dinaphth[2,1‐c:1′,2′‐e]azepinium] bromide [(S,S)‐NAS Br] (5 mol%) afforded the corresponding α‐alkyl‐α‐tert‐butoxycarbonyllactams in very high chemical (up to 99%) and optical yields (up to 98% ee). Our new catalytic systems provide attractive synthetic methods for pyrrolidine‐ and piperidine‐based alkaloids and chiral intermediates with β‐quaternary carbon centers.     

Fine‐grained traffic classification based on functional separation

Current efforts to classify Internet traffic highlight accuracy. Previous studies have focused on the detection of major applications such as P2P and streaming applications. However, these applications can generate various types of traffic which are often considered as minor and ignorant traffic portions. As network applications become more complex, the price paid for not concentrating on minor traffic classes is in reduction of accuracy and completeness. In this context, we propose a fine‐grained traffic classification scheme and its detailed method, called functional separation. Our proposal can detect, according to functionalities, different types of traffic generated by a single application and should increase completeness by reducing the amount of undetected traffic. We verify our method with real‐world traffic. Our performance comparison against existing DPI‐based classification frameworks shows that the fine‐grained classification scheme achieves consistently higher accuracyand completeness. Copyright © 2013 John Wiley & Sons, Ltd.     

淡水湖泊沉积物污染评价方法比较——以北大港水库为例

为了比较沉积物污染的3种典型评价方法,对北大港水库内的11个采样点进行表层沉积物采样,并测定了样品的全盐量、有机质、全磷和全氮指标。根据测定得出的数据分别利用单因子指数法、内梅罗综合指数法和模糊数学综合评价法对沉积物污染状况进行评价,结果表明:水库中心的S1、S2和S3点为中度或重度污染,其余位于库周的采样点为未污染或轻度污染,总体上库心的沉积物污染比库周严重。结合北大港水库实例,比较3种评价方法的评价结果,得出结论:单因子指数法计算简便,但评价结果偏高;内梅罗综合指数法考虑了沉积物污染评价的综合性,但忽略了评价指标的权重影响;模糊数学综合评价法利用熵值赋权的方法确定指标权重,客观性与综合性较强,评价结果更接近实际情况。     

Novel Cinchona‐Aminobenzimidazole Bifunctional Organocatalysts

Efficient Cinchona‐derived chiral 2‐aminobenzimidazole catalysts were prepared by the coupling of 5,7‐bis(trifluoromethyl)‐2‐chlorobenzimidazole with C(9S)‐aminodihydroquinine or C(9R)‐aminodihydroquinidine and successively applied to the Michael addition of dimethyl malonate to nitroolefins as very efficient chiral Lewis acid bifunctional organocatalysts (up to >99% ee).     

The probiotic Lactobacillus rhamnosus BFE5264 and Lactobacillus plantarum NR74 promote cholesterol efflux and suppress inflammation in THP‐1 cells

BACKGROUND: The balance between the rate of cholesterol uptake/accumulation and the rate of cholesterol efflux is reflected in the amount of lipid accumulation in macrophages. Based upon the fact that liver X receptors (LXRs) play a role in cholesterol efflux, we studied the effects of probiotics on cholesterol efflux and anti‐inflammatory action in macrophages. We confirmed changes in LXR expression by treatment of LXR‐transfected CHO‐K1 cells with lactic acid bacteria (LAB), and co‐cultured THP‐1 cells with LAB to investigate changes in cholesterol efflux and inflammation. RESULTS: The experiment with CHO‐K1 cells showed upregulation of LXR‐β by LAB. Treatment of THP‐1 cells with LAB promoted LXR expression in THP‐1, which eventually led to significant upregulation of ABCA1 and ABCG1 expression. The treatment with live LAB also significantly promoted cholesterol efflux. LAB suppressed expression of interleukin (IL)‐1β and tumor necrosis factor (TNF)‐α, which resulted from activation of LXR. CONCLUSION: Our study shows that Lactobacillus rhamnosus BFE5264 and Lactobacillus plantarum NR74 activated LXR and induced cholesterol efflux by promoting expression of ABCA1 and ABCG1. Both strains also suppressed proinflammatory cytokines including IL‐1β and TNF‐α. This study could account for the observation that LAB may block foam cell formation by cholesterol efflux and immune modulation. © 2012 Society of Chemical Industry