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Suzhen Wang Shanshan Geng Zhanfeng Zhang Anshan Ye Keming Chen Zhaosheng Xu Huimin Luo Gangshan Wu Lina Xu Ning Cao 《计算机、材料和连续体（英文）》2019,61(2):739-757
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. 相似文献
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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。 相似文献
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目的 研究变位磁场强度对变位磁场作用下电弧熔积中电弧和熔池传热与流动的影响规律与机理。方法 基于流动动力学方程(麦克斯韦方程组、动量守恒方程、连续方程、能量守恒方程),建立了变位磁场作用下TIG电弧-熔池耦合的数值模型,对比分析了外加不同强度的变位磁场对电弧与熔池传热传质的影响规律与机理。结果 外加变位磁场使电弧发生偏移,电弧等离子体具有偏向一侧与旋转的流动趋势,熔池的整体形貌向x正方向与y负方向发生偏移,熔池除了具有中心向外流动趋势以外,还具有偏向一侧与围绕中心旋转的趋势。随着变位磁场强度的增大,电弧与熔池整体形貌偏移量增大且偏向一侧与围绕中心旋转的趋势增强。结论 外加变位磁场可使电弧发生偏移,且变位磁场强度增大,电弧与熔池整体形貌偏移量增大。 相似文献
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Yohan Park Young Ju Lee Suckchang Hong Mi‐hyun Kim Myungmo Lee Taek‐Soo Kim Jae Kyun Lee Sang‐sup Jew Hyeung‐geun Park 《Advanced Synthesis u0026amp; Catalysis》2011,353(18):3313-3318
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. 相似文献
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Byungchul Park Youngjoon Won JaeYoon Chung Myung‐sup Kim James Won‐Ki Hong 《International Journal of Network Management》2013,23(5):350-381
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. 相似文献
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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。 相似文献
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Hong‐sup Yoon Jae‐hyun Ju Ji‐eun Lee Hyun‐joon Park Jung‐min Lee Hyeun‐kil Shin Wilhelm Holzapfel Kun‐young Park Myoung‐Sool Do 《Journal of the science of food and agriculture》2013,93(4):781-787
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 相似文献
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针对排放酸性含铬废水所产生的环境污染问题,采用超声波辅助法制备纳米FeS,用于处理酸性含铬废水。通过正交试验确定了超声波辅助法制备纳米FeS的最佳制备条件,并讨论了反应时间、pH值和Cr(Ⅵ)初始浓度对纳米FeS处理酸性含铬废水的影响。结果表明：超声波辅助法制备纳米FeS的最佳制备条件为超声波频率40 kHz、超声波处理时间10 min、制备反应温度15 ℃,在此条件下Cr(Ⅵ)和总铬的去除率分别为81.03%、63.40%;当反应时间达到50 min后,纳米FeS对酸性含铬废水的处理效果趋于稳定,酸性条件能促进纳米FeS对Cr(Ⅵ)和总铬的去除;随着Cr(Ⅵ)初始浓度的升高,纳米FeS对Cr(Ⅵ)和总铬的单位去除量逐渐增大,当Cr(Ⅵ)初始浓度为300 mg/L时,Cr(Ⅵ)和总铬的单位去除量分别可达486.65和383.55 mg/g。可见,超声波制备的纳米FeS可以有效去除废水中的铬离子,为今后实际工程应用提供了一定的理论指导。 相似文献
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暂堵转向工艺是多簇射孔簇开启的有效方法,而投球器是实施暂堵转向工艺的关键设备之一。现有页岩气开发采用的液动旋塞投球器无法多次定量精准投球,无法满足当前现场需求。面对这个问题,研制了一种高压远程控制投球器,采用螺旋投球原理实现精确计数,采用侧装动力总成和分体式顶盖总成便于拆装,可实现140 MPa承压能力、多次精准投球、装球数量大,且操作简单。暂堵转向压裂用远程控制投球器经厂内和现场测试,完全满足140 MPa承压能力、多次精准投球、装球数量大。经过多次现场应用,验证了新型投球器具有密封可靠、精确投球、操作简单、运行安全可靠等优点,满足了国内超高压堵塞球分层压裂工况的使用要求,可全面替代现有的液动旋塞阀投球器。 相似文献
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Lei Zhang Myoung‐Mo Lee Soo‐Mi Lee Jihye Lee Maosheng Cheng Byeong‐Seon Jeong Hyeung‐geun Park Sang‐sup Jew 《Advanced Synthesis u0026amp; Catalysis》2009,351(18):3063-3066
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). 相似文献
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