A new variational self-regular traction-BEM formulation for inter-element continuity of displacement derivatives

In this work, a non-symmetric variational approach is derived to enforce C ^1, continuity at inter-element nodes for the self-regular traction-BIE. This variational approach uses only Lagrangian C ⁰ elements. Two separate algorithms are derived. The first one enforces C ^1, continuity at smooth inter-element nodes, and the second enforces continuity of displacement derivatives in global coordinates at corner nodes, where C ^1, continuity cannot be enforced. The variational formulation for the traction-BIE is implemented in this work for two elastostatics problems with various discretizations and polynomial interpolants. Local and global measures of the discretization error are obtained by means of an error estimator recently derived by the authors. Comparisons are also made with the displacement-BIE, which does not require C ^1, continuity for the displacement. The lack of smoothness of the displacement derivatives at the inter-element nodes is shown to be an important source of both local and global error for the traction-BIE formulation, especially for quadratic elements. The accuracy of the boundary solution obtained from the traction-BIE improves significantly when C ^1, continuity is enforced where possible, i.e., at the smooth inter-element nodes only. The first author acknowledges the support received from CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico. The third author gratefully acknowledges support by the National Science Foundation (CTS-9983961). The fourth author acknowledges the support received from FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais.     

Super restricted edge connected Cartesian product graphs

An edge-cut F of a connected graph G is called a restricted edge-cut if G−F contains no isolated vertices. The minimum cardinality of all restricted edge-cuts is called the restricted edge-connectivity λ^′(G) of G. A graph G is said to be λ^′-optimal if λ^′(G)=ξ(G), where ξ(G) is the minimum edge-degree of G. A graph is said to be super-λ^′ if every minimum restricted edge-cut isolates an edge. This article gives a sufficient condition for Cartesian product graphs to be super-λ^′. Using this result, certain classes of networks which are recursively defined by the Cartesian product can be simply shown to be super-λ^′.     

How many servers are best in a dual-priority system?

We ask the question, “for minimizing mean response time (sojourn time), which is preferable: one fast server of speed 1, or k slow servers each of speed 1/k?” Our setting is the system with two priority classes of customers, high priority and low priority, where PH is a phase-type distribution. We find that multiple slow servers are often preferable, and we demonstrate exactly how many servers are preferable as a function of the load and service time distribution. In addition, we find that the optimal number of servers with respect to the high priority jobs may be very different from that preferred by low priority jobs, and we characterize these preferences. We also study the optimal number of servers with respect to overall mean response time, averaged over high and low priority jobs. Lastly, we ascertain the effect of the service demand variability of high priority jobs on low priority jobs.     

基于单片机STC89C52温湿度测控系统的设计

温湿度测控系统以单片机STC89C52为核心控制器,采用温湿度传感器SHT71为测量元件,由温湿度传感器、键盘、液晶显示、实时时钟电路、报警电路、执行电路、串口通讯电路等组成.详细介绍了硬件电路的设计,通过系统软件、硬件联机调试,实现了对环境温湿度的测量.实践证明,该系统电路简单、工作稳定、集成度高、调试方便、测量精度高,具有一定的实用价值,能达到对环境温湿度测量要求.     

活性炭纤维去除水中直接深蓝L-3RB及其再生研究

用红外及可见分子吸收光谱法研究了活性炭纤维(ACF)对直接深蓝L-3BR(DDB,C．I．Direct Blue 71)的吸收行为。用电化学法研究了DDB饱和吸附后ACF再生的可能性。发现ACF最佳吸附条件为pH=5;以2％NaCl％水溶液为支持电解液,用铜棒和石墨棒分别作阴极和阳极,阴极区ACF再生率达到95％,初步探讨了ACF对DDB的吸附和脱附DDB的机理。     

U71Mn和U75V钢轨钢疲劳短裂纹的扩展行为

在扫描电镜下对U71Mn和U75V钢轨钢的Ⅰ型低周疲劳加载和准静态加载下裂纹扩展的过程进行了观察.研究发现,从整体上看材料没有产生明显的宏观塑性变形,属准解理断裂.但从微观上看,裂纹的微观扩展路径曲折、不连续,常伴有分枝裂纹的形成.可观察到局部有韧窝、滑移线等典型的韧性断裂特征.尤其是U71Mn钢轨钢中还伴有局部的撕裂等更强烈的变形.钢轨钢U71Mn比U75V的抗疲劳裂纹扩展性能和韧性略优.     

烟草CYP71D亚家族的生物信息学分析

细胞色素P450（CYP450）是一类超基因家族编码的多功能氧化酶,在生物合成、代谢解毒及植物防御方面具有重要作用。其中CYP71D属于CYP450的一个亚家族,主要在次生代谢物合成和病虫害防御方面起作用。为了更好地了解烟草CYP71D亚家族基因特征和功能,本研究利用生物信息学分析手段及烟草转录组数据,对CYP71D亚家族基因的结构和表达等进行了分析。结果发现,在烟草中共有42个CYP71D亚家族成员,各成员在染色体上并非均匀分布,其氨基酸长度和等电点差异较大,但基因结构、保守结构域数目和分布高度一致;二级结构分析表明,烟草CYP71D亚家族成员具备P450蛋白特征结构域;基因表达模式分析显示,多数CYP71D基因在根、叶、花中特异表达,大部分基因参与了IAA激素、黑胫病、温度等逆境胁迫反应。这为烟草CYP71D亚家族基因功能的深入研究及烟草抗逆品种的培育奠定了基础。     

两种果酒酵母对杨梅果酒发酵及风味的影响

以东魁杨梅为原料,比较D254和71B两种酵母对杨梅果酒风味的影响,测定发酵过程中pH值、总酸、还原糖、可溶性固形物、酵母细胞数量、花青素含量等指标的变化,并采用气相色谱-质谱分析两种酵母发酵杨梅果酒香气成分。结果表明,用两种酵母发酵的杨梅果酒,其pH值、还原糖和可溶性固形物在发酵过程中的动态变化基本一致且最终含量无明显差异;71B发酵果酒的酵母数量、总酸含量和花青素含量高于D254;酒样中获得的果酒香气成分有较大差异,酵母D254和酵母71B发酵的杨梅果酒的主要香气成分中,醇类分别为71.64%和72.49%,酯类分别为10.34%和16.22%,酸类分别为9.02%和4.05%。与D254相比,酵母71B含有苯乙醇、十六酸乙酯和癸酸乙酯等具有特殊香气物质,香气更为浓郁。     

2017~2018年福建省0~5岁儿童出生队列肠道病毒71型疫苗接种率分析

目的分析2017~2018年福建省0~5岁儿童肠道病毒71型(enterovirus 71,EV71)疫苗的接种率。方法通过福建省免疫规划信息管理系统查询2017~2018年福建省0~5岁儿童EV71疫苗接种数据,应用Excel 2007软件对数据进行整理和统计分析。结果 2017~2018年福建省0~5岁儿童接种EV71疫苗950 598剂次。2017和2018年人均接种剂次分别为1 000. 71和1 812. 46剂次/万人,1岁组和2岁组为最高,3岁组次之,再次为6~12月龄组和4岁组,5岁组最低。2017和2018年全省全程接种率分别为4. 18%和8. 47%,各地市全程接种率为0. 70%~10. 46%和4. 62%~10. 96%;全省未全程接种与全程接种人数比值分别为1. 39和1. 14,各地区比值分别为1. 27~1. 85和1. 01~1. 21。结论目前福建省EV71疫苗接种率较低,需进一步提高,特别是6~12月龄儿童的接种率。应加强家长对手足口病(hand,foot and mouth disease,HFMD)认知及EV71疫苗安全性、保护力等方面的宣传教育,做好预防接种人员培训,严格执行接种程序,确保疫苗保护效果。     

重组人肠道病毒71型病毒样颗粒疫苗外源DNA残留量检测方法的建立

目的建立重组人肠道病毒71型(enterovirus 71,EV71)病毒样颗粒(virus-like particles,VLPs)疫苗原液中昆虫细胞宿主DNA残留的地高辛探针杂交检测方法。方法抽提昆虫细胞sf9基因组DNA,经分子筛纯化后作为阳性对照品;分别以1 000~5 000 bp和100~1 000 bp的基因组DNA超声随机小片段为模板,制备地高辛探针,与阳性对照进行杂交试验。同时验证方法的检测范围、灵敏度和特异性,并采用该方法对3批重组EV71 VLPs疫苗原液中宿主DNA残留量进行测定。结果纯化后DNA样品浓度为47. 5 ng/μL,A260/A280值为1. 86,可作为阳性对照。以100~1 000 bp DNA超声随机小片段作为模板,探针标记效率更高,杂交显色更清晰。该法检测范围为10 pg^10 ng,灵敏度达1 pg,特异性强。3批重组EV71 VLPs疫苗原液中每人份剂量的宿主细胞DNA残留均<50 pg。结论本实验建立的方法特异性强,灵敏度高,可用于重组EV71 VLPs疫苗制备过程中的原液检定及质量控制。