A comparison of optimization theories for energy conservation in heat exchanger groups

In general,thermal processes can be classified into two categories: heat-work conversion processes and heat transfer processes. Correspondingly,the optimization of thermal processes has to have two different criteria:the well known entropy generation minimization method and the recently proposed entransy dissipation maximization method. This study analyzes the thermal issues in a heat exchanger group,and optimizes the unit arrangements under different constraints based on a suitable optimization crite-rion. The result indicates that the principle of minimum entropy generation rate is valid for optimizing heat exchangers in a ther-modynamic cycle with given boundary temperatures. In contrast,the entransy dissipation maximization is more suitable in heat exchanger optimizations involving only heat transfer processes. Furthermore,the entropy generation rate induced by dumping used streams into ambient surroundings has to be taken into account,except for that originating from the hot and cold-ends of heat exchangers,when using the entropy generation minimization to optimize heat exchangers undergoing a thermodynamic cycle.     

Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

Variations in global atmospheric oscillations during the last millennium are simulated using the climate system model FGOALS_gl. The model was driven by reconstructions of both natural forcing (solar variability and volcanic aerosol) and anthropogenic forcing (greenhouse gases and sulfate aerosol). The model results are compared against proxy reconstruction data. The reconstructed North Atlantic Oscillation (NAO) was out of phase with the Pacific Decadal Oscillation (PDO) in the last millennium. During the ...     

论思维的复杂系统模型暨新一代专家系统的设想

在复杂系统研究思想指导下,构建了基于神经元网络结构的复杂系统思维模型,提出以网络节点表示概念,以网络连接表示命题,以网络回路实现知识表达,以网络节点间的时空动力学激发实现演绎推理等思维活动的理论新框架,并以此为基础对新一代专家系统进行了设计。     

聚苯胺修饰石墨烯纳米片的分散行为

针对氧化石墨(GO)用化学方法还原为石墨烯纳米片(GN)后极易再配列为类似石墨结构层状物的问题,本工作在GO还原过程中用聚苯胺(PANI)修饰石墨烯纳米片(P-GN),发现即使干燥后,P-GN仍可在N,N-二甲基甲酰胺(DMF)中呈分散状态稳定存在.     

不同恶化程度胃癌细胞系的细胞间隙连接通讯功能及Cx43表达的差异

以人正常胃黏膜上皮细胞系GES-1和不同恶化程度的人胃癌细胞系(低恶化AGS细胞系、中恶化SGC-7901细胞系、高恶化BGC-823细胞系)为研究对象,采用激光共聚焦显微镜的荧光漂白恢复技术及划痕标记荧光染料示踪技术研究不同恶化程度的胃癌细胞系细胞间隙连接通讯(Gap junctional intercellular communication,GJIC)功能的差异;采用荧光定量PCR技术和间接免疫荧光技术检测间隙连接蛋白(Connexin43,Cx43)基因在mRNA和蛋白水平的表达差异,探求其与胃癌恶性程度的相关性.结果表明,在正常胃细胞系和低、中及高恶化胃腺癌细胞系中,细胞间的GJIC功能随着恶性程度的升高而减弱(AGS、SGC-7901)或消失(BGC-823),且Cx43蛋白及mRNA的表达量随着恶性程度的升高而下调(AGS、SGC-7901)或缺失(BGC-823).这提示胃癌恶性程度与胃癌细胞的GJIC功能显著相关(P<0.05),GJIC在胃癌发生中起重要作用.     

联合摄影及斜点样方法的单株植物冠层结构参数测量(Ⅰ):冠层三维重建

联合摄影、三维立体体元模型及光线跟踪法开展了面向高精度总面积指数(plant area index,PAI)测量的冠层精细三维模型重建研究.研究发现,冠层背景及天气条件对冠层影像分类影响显著;相机外方位元素解算精度受控制点精度影响较大,但受控制点数目影响相对较小.合理的单位体元大小及分区大小组合对于冠层三维重建至关重要,任意单位体元大小及分区大小组合可引起冠层三维重建异常.与立体体元大小相比,分区大小对冠层三维重建影响更为显著.     

炼油厂废水库底泥中半挥发性有机污染物监测与评价

采用超声提取结合GC/MS测定了克拉玛依炼油厂污水库底质中的半挥发性有机物。选择16个多环芳烃作为加标物,测定超声提取法的回收率在65%94%。从底泥中检出62个色谱峰,能准确定性20个组分,主要包括9个多环芳烃、5个正构烷烃和3个酚类化合物。对缺少标准物的组分采用结构相似物进行定量,浓度范围在0.1259 ng/g。...     

瓦克曼的技术女性主义思想评析

朱迪·瓦克曼在批判并借鉴技术社会学和传统女性主义技术理论的基础上,提出了技术女性主义主张。这一思想的理论前提是对技术决定论和本质主义性别观的解构;实质在于强调技术与性别的相互形塑;目标是试图避免陷入技术恐惧与技术崇拜的困境,并消解性别身份差异性与政治立场统一性之间的冲突及其给女性主义政治实践带来的挑战。     

Genetic variants in novel pathways influence blood pressure and cardiovascular disease risk

Blood pressure is a heritable trait influenced by several biological pathways and responsive to environmental stimuli. Over one billion people worldwide have hypertension (≥140?mm?Hg systolic blood pressure or ≥90?mm?Hg diastolic blood pressure). Even small increments in blood pressure are associated with an increased risk of cardiovascular events. This genome-wide association study of systolic and diastolic blood pressure, which used a multi-stage design in 200,000 individuals of European descent, identified sixteen novel loci: six of these loci contain genes previously known or suspected to regulate blood pressure (GUCY1A3-GUCY1B3, NPR3-C5orf23, ADM, FURIN-FES, GOSR2, GNAS-EDN3); the other ten provide new clues to blood pressure physiology. A genetic risk score based on 29 genome-wide significant variants was associated with hypertension, left ventricular wall thickness, stroke and coronary artery disease, but not kidney disease or kidney function. We also observed associations with blood pressure in East Asian, South Asian and African ancestry individuals. Our findings provide new insights into the genetics and biology of blood pressure, and suggest potential novel therapeutic pathways for cardiovascular disease prevention.     

古代DNA 技术及其在家养动物驯化历史研究中的应用

家养动物始终伴随着人类文明的发生、发展, 其起源和驯化历史一直备受关注. 而在其 近万年的演化历史中, 家养和野生群体间可能发生基因互渗及替代, 因此基于现代物种DNA 信息进行的历史推断可能存在偏差. 近年来, 古代生物遗骸中的DNA (古代DNA)获取技术日 益成熟, 为这类研究开辟了新的途径. 本文总结了近年来古代DNA 技术研究进展, 点评了古 代生物遗骸DNA 的获取和鉴别方法、古代DNA 提取、扩增及测序技术的革新. 最后, 本文综 述了古代DNA 技术在猪、马、羊、狗等主要家养动物驯化历史研究中的应用进展, 为该技术 的进一步发展及应用提供有益的参考.