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1.
Ordinary and thermal diffusion of moisture in activated alumina are investigated using a new diffusion cell design and scheme of analysis reported earlier. The specific form of the mass flux equation has a pronounced effect on the magnitude of the associated thermal diffusion ratio. In the case of activated alumina-moist air, if a partial pressure gradient is used, then the thermal diffusion term is small if not zero.Free, Knudsen and surface diffusion all play a part in the diffusion through activated alumina. However, surface diffusion makes the major contribution and for this reason the model in this case can be simplified to a two parameter surface model.The activation energy for surface diffusion is constant and is approximately equal to the mean isosteric heat of absorption. In addition, mean pore radius, turtuosity, and other physical constants are computed from the least square fit of experimental data. Furthermore, the model is theoretically consistent over the entire concentration range (0≦ CA ≦ CAsat).A new fact about activated alumina (Grade F1) it that it does not transfer moisture in a nonisothermal condition so long as the partial pressures of moisture on the two sides of the pellet are the same. There appears to be no previous report of this fact in the periodical literature. 相似文献
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人畜饮用水中砷、氟、矿化度的超标,是影响三江源区饮水安全的因素之一。本文针对人畜饮水中砷、氟超标情况,引进F-Catch、As-Catch2高性能粒状吸附材料,进行技术开发,设计出JCD-砷(氟)吸附系统。这种吸附材料对氟、砷酸、亚砷酸具有很高的吸附能力,吸附能力是目前国内外砷、氟吸附剂吸附能力的6倍以上,能吸附大量0.01ppm以下低浓度的氟离子和砷酸、亚砷酸。将JCD-砷(氟)吸附系统与活性碳联用形成砷、氟水处理工艺流程,该工艺流程的处理能力可达到0.5m3/h,按照国家农村用水标准每人每天40L水,能够解决200人的安全饮用水,适合于农村人畜安全饮水的需求。并在项目区进行了试验示范,将含砷原水打入JCD-砷(氟)吸附系统,吸附系统中的功能材料As-Catch2与进水中的砷进行物化反应。再通过JCD-砷(氟)吸附系统中的As-Catch2层下方的30cm高度的多孔质活性炭滤层,利用活性炭具有的高效吸附作用,吸附水中的微污染物质,最终出水进入集水箱中,通过泵打入居民生活用水管道,进入用户家中得以安全使用。设备处理速率快、时间短,无需进行预处理,实现了砷、氟、磷等指标的同时去除,砷去除率达到100%,氟去除率达到85%以上,处理后的水质满足国家生活饮用水卫生标准,且系统不产生污泥,节省了污泥处理费用,设备结构简单、具有灵活的可变性、成本较低,自动化程度高、操作简单、易于管理,为三江源区人畜安全饮水提供了技术保障。 相似文献
3.
Mohamed A. Gadalla 《Journal of The Franklin Institute》2007,344(5):725-740
This paper presents a dynamic model to simulate the adsorption-desorption processes associated with intermittent heat pump systems. This simulation plays an important role in sizing the adsorption systems for various types of applications in the design stage. A mathematical model that is based on the control volume approach was first developed and then discretized using the finite difference implicit scheme. The equations for the conservation of mass, momentum, and energy in the bed were derived for high-pressure and low-pressure segments, including the adsorbate (refrigerant), the adsorbent (Linde 13X), and the vessel wall. A pseudo-homogeneous model for the compression system was adopted. The numerical results that describe the adsorption-desorption history were obtained. It was found that the amount of the refrigerant recovered in the desorption process at the end of the cyclic operation is smaller than the amount adsorbed during the adsorption process. This indicates that the time for the regeneration process should be longer than the time for the adsorption process in order to raise the sieve temperature. In order to compare the simulated results with experimental data, numerical values for the heat transfer coefficients were theoretically evaluated. To assure the stability of the simulated results, the incremental time of system operation is kept equal or less than the value obtained from the minimum stability requirement. The simulated results of the temperature distribution history during system operation are in good agreement with the conducted experimental results, which led to the conclusion that the model can be used as an effective tool during the design stage and for the system development. 相似文献
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通过探讨区域科技创新与生态环境优化的耦合协调机制，构建二者的综合评价指标体系，利用耦合协调度模型、探索性空间数据分析法以及空间计量模型，对2008—2017年我国30个省域科技创新与生态环境优化耦合协调发展程度、时空格局及驱动因素进行了分析。结果表明，我国各省域科技创新与生态环境优化水平，以及两者耦合协调度均呈现波动上升的趋势，区域间差距不断扩大。各省域两系统耦合协调度均值在0.299~0.654之间，大部分地区仍处于中度耦合协调阶段；整体显现出“东高、中平、西低”的空间格局，以及“高高—低低”集聚的空间关联性。产业结构生态化水平、市场竞争程度、政府科技创新支持、环境规制、区域城镇化率等因素对我国省域两系统耦合协调度均产生显著的正向影响及空间溢出效应，并表现出明显的区域异质性特征。据此，基于这些驱动因素的异质性影响，提出了促进区域两系统耦合协调发展的差异化政策建议。 相似文献
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Mohamad Sleiman Rachid Bouyekhf Adbellah El Moudni 《Journal of The Franklin Institute》2019,356(1):351-381
The paper explores the application of thermodynamic formalism to model and control transportation networks. Specifically, by considering the vehicles as the abstract energy supplied to the system, we show in certain circumstances that certain thermodynamic concepts such as temperature, thermal capacity and thermal equilibrium can have the corresponding notions in transportation context. In addition, despite the lack of a natural principle in transportation context that corresponds to the second law of thermodynamic as we will show, the most important thermodynamic notion, which is the entropy, can be also defined in order to measure the disorder of transportation systems. It is then shown that the state when all lanes have the same occupancy corresponds to the thermal equilibrium arising in isolated thermodynamic system. This equilibrium occupancy leads to a minimum entropy corresponding to a minimal disorder. Besides, by taking the transportation entropy as the storage function, a robust dissipativity based control strategy is presented to reduce the disorder and render the system better organized. Finally, an example is worked out to illustrate the results. 相似文献
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粤港澳大湾区城市热岛空间格局及影响因子多元建模 总被引：4，自引：0，他引：4
探究影响城市热岛空间格局的因子,及科学分析各因子的作用机制,对揭示城市热岛效应的机理有着重要意义。本文以粤港澳大湾区为研究区,综合利用数据空间化表达、空间叠置、地理探测器等方法,对影响城市热岛空间格局的因子开展研究,并构建地表温度与影响因子间的多元关系模型。结果表明,粤港澳大湾区的城市热岛强度等级呈现中间高四周低的空间分布格局,并在珠江入海口两岸形成半环状城市热岛带。本文选取的5种影响因子对城市热岛的空间格局皆具有较高的解释力,平均解释力排序为：单元人口密度（0.668）>建设用地面积占比（0.577）>单元路网密度（0.573）>植被面积占比（0.538）>水体面积占比（0.428）。所构建的多元关系模型,能较准确地反映城市热岛区域地表温度的分布状况,所拟合的地表温度结果与实际地表温度平均值的误差为0.34℃。 相似文献
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For the past three decades, Sanger’s method has been the primary DNA sequencing technology; however, inherent limitations in cost and complexity have limited its usage in personalized medicine and ecological studies. A new technology called “thermosequencing” can potentially reduce both the cost and complexity of DNA sequencing by using a microfluidic platform [Esfandyarpour, Pease, and Davis, J. Vac. Sci. Technol. B26, 661 (2008)]. To optimize the efficiency of the technology, finite element analysis was used to model the thermosequencing system by simulating the DNA incorporation reaction series and the resulting product concentration and heat production. Different models of the thermosequencing platform were created to simulate the effects of the materials surrounding the system, to optimize the geometry of the system, and to concentrate reaction heat into specific regions for detection in the real system. The resulting concentrations of reaction products were used to calibrate the reaction speed and to design the heat sensors in the thermosequencing technology. We recommend a modified gated structure for the microfluidic detection platform by using control valves and show how this new platform could dramatically improve the detection efficiency. 相似文献
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This paper presents the analysis and control of active magnetic bearing (AMB) systems with a flexible rotor. A sliding mode controller design scheme is proposed to compensate for the nonlinear effects of the AMB system. A nonlinear model of the AMB system with an electromagnetic actuator and a flexible rotor is proposed to facilitate the present system analysis and controller design. This nonlinear model takes into account the dynamics of the flexible rotor, the characteristics of the nonlinear electromagnetic suspended system, and the contact force between the auxiliary bearing and the shaft. This study also considers the auto-centering control of the AMB system when subjected to disturbances and variations in the system parameters. The numerical results show that the system exhibits a periodic motion and demonstrates high accuracy and robustness when operating under sliding mode control. 相似文献
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吸附法一直是处理磷废水的重要方法,被认为是能够很好地适用于宽浓度范围废水除磷的方法。本文采用三种金属氧化物作为吸附剂（活性氧化铝、水合氧化镧、新型稀土铈铁复合吸附剂）进行吸附除磷静态试验,考查在不同的条件下（吸附时间、温度、pH值）吸附剂对磷的吸附效果。本文为开发高效除磷吸附剂提供了有价值的参考依据,在防治水体富营养化方面具有广阔的前景。 相似文献
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钛白废水综合治理工艺作为一个系统工程构思,在明确钛白废水产生原因及主要污染因子后,首先提出钛白废水一次石粉中和,经压滤得到白石膏和FeSO4溶液,然后按FeSO4溶液浓度的高、低分别处理:高浓度FeSO4溶液用于制备铁红晶种;低浓度FeSO4溶液则进行二次石灰乳中和,经压滤得到红石膏和回收水。该方案不仅能较好地治理钛白废水,得到高价值副产品,而且治理成本低,使用设备简单。 相似文献
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基于DCC—MGARCH模型的中国A、B股市场相关性及其解释 总被引：2，自引：1，他引：1
金融资产相关性分析是现代金融学的重要基础,不论是投资组合的选择还是风险管理均涉及到相关性的估计和预测,寻求相关系数的可靠估计已成为众多研究者关注热点问题。本文利用Engle于2002年提出的DCC-MGARCH模型对我国沪深A、B股市场之间的相关性进行了动态考察,研究发现:沪深两市A、B股之间的相关系数总体为正,并具有明显的时变特征;1997年至2001年沪深A、B股市场的动态相关系数相对较小,波动性较大,2001之后两市A、B市场之间的动态相关系数明显增大,并且波动性减少,这表明沪深A、B市场之间的一体化程度正日趋增强,不过在处于相对高位之后,近几年来并没有呈现出进一步提高趋势;总体而言,A、B股市场动态相关系数还相对低,市场分割特征仍然明显。最后运用行为金融理论对A、B股市场的动态相关性的时变特征进行了分析和解释。 相似文献
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为量度区域虚拟水战略实施的适宜性以及虚拟水战略背景对区域经济社会生态等的影响程度,定义了区域虚拟水战略优势度概念,并分析了其影响因素,从水资源禀赋、非农水资源需求、水资源管理和农业发展现状4个方面构建了一个包含12个指标的综合定量评价体系,进而运用综合指数法对我国内陆31个省级行政区虚拟水战略优势度进行了定量评价。在评价结果基础上,将31个省(市、区)划分成高优势度组、较高优势度组、中等优势度组和低优势度组4种类型区,并给出每一类型组虚拟水战略背景下的农业发展、水资源规划管理和虚拟水研究等方面的差别性建议。从空间分布上来看,我国虚拟水战略优势度区域差异非常明显,呈现较为典型的“东部高、西部低”,“南部和北部高、中间低”的带状分布规律;从虚拟水战略优势度等级结构来看,基本呈现“中间多,两头少”的纺锤型分布规律。 相似文献
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无机磷在白浆土中的吸附与解吸机制 总被引：5，自引：0，他引：5
本文主要研究了土壤中铁铝氧化物对白浆土的表层和白浆层的磷酸盐吸附与解吸的影响以及在吸附和解吸过程中无机磷的释放和形态转化机理。研究结果表明,铁铝氧化物对磷的吸附和解吸都有影响,其中无定形铝的影响更大一些,而且铁铝氧化物对吸附的影响程度超过有机质。磷被白浆土吸附后,火部分转变成铝磷(Al-P)和铁磷(Fe-P)。相对来说,铝对磷的吸附在快反应阶段强于慢反应阶段,铁则相反。把吸磷后的样品恒温静置,则Al-P逐渐向Fe-P和Ca-P转化。吸附磷解吸时,也是以Al-P为主。Fe-P是较好的“速效磷源”,而Al-P既是较好的“速效磷源”,也是很好的“缓效磷源”。 相似文献
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青藏高原是世界上总辐射量最高的地区,也是全球超太阳常数的极值区域之一。此处形成了一个"嵌入"对流层中部大气的巨大的热源,可以伸展到自由大气,其超越了世界上任何超级城市群落所产生的中空热岛效应,对全球与区域大气环流系统变化的动力"驱动"产生了难以估计的效应。与地形热力过程季节变化密切相关的亚洲夏季风是世界上范围最广和强度最强的季风;从冬季到早春季节转换过程中,由于太阳辐射的影响造成青藏高原大地形感热的"快速响应"及其相对高值动态移动,在盛夏梅雨及其云降水带前沿线恰好停滞于中国"三阶梯"地形分布山地—平原过渡区。此现象表明,青藏高原可能扮演着夏季风过程陆地—海洋—大气相互作用的关键角色。中国区域低云量与总云量极值区均与青藏高原大江大河的源头(长江、澜沧江、雅鲁藏布江等)、中东部湖泊群与冰川集中区空间分布几乎吻合,这表明"亚洲水塔"形成的关键因素与"世界屋脊"特有的云降水结构不可分割。研究表明,青藏高原大气热源对局地与下游区域云降水过程水汽输送流型等均有显著影响。长江流域降水与全国低云量存在一个明显沿长江流域的带状高相关结构,充分表明长江流域降水与上游"亚洲水塔""热驱动"以及对流系统具有重要相关关系。从跨赤道经向环流的视角可发现,夏季南、北半球跨赤道气流低层强偏南、高层强偏北气流出现在东亚地区和北美区域两大地形对应的赤道区,这2个跨赤道极值区恰与青藏高原、落基山高原位置相对应。青藏高原纬向与经向环流圈结构与区域-全球大气环流相关机制,印证了"世界屋脊"隆起大地形的"热驱动"及其对流活动在全球能量、水分循环的作用。青藏高原特殊水汽三维结构分布和跨半球的纬向和经向大气垂直环流图表明青藏高原对全球尺度大气环流变化的贡献显著。文章进一步以东亚、全球水循环的视角,提出了青藏高原作为全球性大气"水塔"的观念,认为在高原地区一个水塔的"供水"和"蓄水"循环体系,特别是高原地表冰川、积雪和湖泊作为"蓄水池"系统,使得所有的河流可作为"输水管道",将"水塔"的水向周边区域输送出去,高层大气也提供向外输送的渠道。青藏高原特殊的跨半球大气水分循环可构建"世界水塔"与其周边地区独特的水文功能概念,综合描绘了青藏高原"世界水塔"及其地球上一个完整的行星尺度陆地—海洋—大气水分循环物理图像。 相似文献
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将经济、环境系统与水资源-能源-粮食系统相结合,以从三元到五元系统的绿色发展视角研究中国不同区域2005—2019年之间关于水资源-能源-粮食绿色发展综合指数的时空差异、耦合协调效应和空间效应。结果显示：（1）研究期内中国各省份五元系统绿色发展指数总体不高,发展趋势较为平稳,显示出明显的区域差异;（2）大部分省份的五元系统耦合协调度都在濒临失调与勉强协调区间,耦合协调度水平还比较低;（3）五元系统的耦合协调度在大多数年份内都呈现出显著正向的空间自相关,表现为正向的空间集聚现象;（4）耦合协调度的主要影响因素表现出明显的空间溢出。政府在政策制定过程中需要综合考虑各类资源与环境、经济系统的特性及其综合发展水平、各类系统间的耦合协调度,并考虑到每一个重要影响因素对耦合协调度空间上的直接效应和间接效应,以提升本区域和邻近区域整体绿色发展水平。 相似文献
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Definable surface chemistry is essential for many applications of microfluidic polymer systems. However, small cross-section channels with a high surface to volume ratio enhance passive adsorption of molecules that depletes active molecules in solution and contaminates the channel surface. Here, we present a one-step photochemical process to coat the inner surfaces of closed microfluidic channels with a nanometer thick layer of poly(ethylene glycol) (PEG), well known to strongly reduce non-specific adsorption, using only commercially available reagents in an aqueous environment. The coating consists of PEG diacrylate (PEGDA) covalently grafted to polymer surfaces via UV light activation of the water soluble photoinitiator benzoyl benzylamine, a benzophenone derivative. The PEGDA coating was shown to efficiently limit the adsorption of antibodies and other proteins to <5% of the adsorbed amount on uncoated polymer surfaces. The coating could also efficiently suppress the adhesion of mammalian cells as demonstrated using the HT-29 cancer cell line. In a subsequent equivalent process step, protein in aqueous solution could be anchored onto the PEGDA coating in spatially defined patterns with a resolution of <15 μm using an inverted microscope as a projection lithography system. Surface patterns of the cell binding protein fibronectin were photochemically defined inside a closed microfluidic device that was initially homogeneously coated by PEGDA. The resulting fibronectin patterns were shown to greatly improve cell adhesion compared to unexposed areas. This method opens for easy surface modification of closed microfluidic systems through combining a low protein binding PEG-based coating with spatially defined protein patterns of interest. 相似文献
18.
Krishna P. Singh 《Journal of The Franklin Institute》1976,302(2):195-205
From the standpoint of flow induced vibrations, U-bends of tubular heat exchangers constitute structurally one of the most vulnerable regions. The U-bends possess relatively low out-of-plane frequency enabling them to extract energy from the shell stream at low flow velocities. All published correlations in the literature imply the existence of a direct relationship between the flow velocities and the incidence of large ampitude tube vibrations. Hence it is important to determine the velocity profile in the U-bend region accurately. A method to obtain an engineering solution is proposed herein which may be utilized in conjunction with the available correlations to reliably predict the possibility of vibration. Determination of the flow profile may be further utilized to improve the estimates of shellside heat transfer coefficients. 相似文献
19.
作为中国农村广泛存在的公共设施,农田灌溉系统的有效治理对实现农业可持续发展,促进农业农村现代化具有重要意义。本文运用定性比较分析（QCA）方法探讨了资源禀赋、制度规则、社会文化、社会资本4个因素对农田灌溉系统治理绩效的协同影响,挖掘了农田灌溉系统治理绩效差异化的组态路径。研究发现：①单个独立因素并不能形成高与非高水平的农田灌溉系统治理绩效。②高水平农田灌溉系统治理绩效可归为文化主导下制度与社会资本驱动型、资源主导下文化与社会资本驱动型、制度主导下社会文化驱动型3大类路径;非高水平农田灌溉系统治理绩效有资源-文化抑制型、资源-制度-社会资本抑制型2条路径。③高与非高水平农田灌溉系统治理绩效路径存在非对称关系,不能简单运用高绩效原因的反面解释非高绩效;对比发现社会文化和社会资本对农田灌溉系统治理高与非高绩效的影响更普遍。④高水平农田灌溉系统治理绩效路径中激励制度与约束制度存在替代关系;社会文化、制度规则对资源禀赋存在替代作用,是克服资源禀赋约束,提高治理绩效的可行手段。研究结果不仅为多因素联动影响农村公共事物治理的研究提供新分析思路,还可为促进乡村振兴提供重要理论与实践参考。 相似文献
20.
本实验以水为工质，对截面尺寸为0.4mm×0.4mm水平布置的不锈钢矩形微槽内流动沸腾进行换热特性和可视化研究.质量流速范围为G＝62.5～187.5kg/m2s，进口温度分别为Tin＝30、45、 60°C.实验结果表明，在较低干度下，换热系数随着干度的增加而增加；干度较大时，换热系数保持不变直至换热恶化.质量流速的增加使换热系数有较大增加，进口温度的变化对换热系数几乎没有影响.可视化研究发现低壁面过热度时，有大量气泡产生；在本实验范围内，微槽内沸腾的流型主要有塞状流和环状流两种. 相似文献