基于盲数理论的河流水质未确知风险分析初探

基于未确知数学中有关盲数理论，对不确定性信息下河流水质风险分析问题进行了初步研究。在引入包含灰性，未确知性等不确定的水环境参量盲数的基础上，提出了水质风险分析的未确知风险概念及未确知风险测度，并建立了相应的表达形式和计算方法，实例研究表明，对水环境风险，尤其是非突发性水质风险所建模型具有很好的适用性。     

低渗透油藏开发效果综合评判体系新探讨

针对辽河油田低渗透油藏的特点,建立了低渗透注水油藏评价标准,将反映主观认知度的层次分析法和反映指标重要性的相似权二者结合起来,通过偏好系数确定出方案指标权重,然后用模糊综合评价模型和未确知测度模型对油藏开发效果进行评价。结果表明,开发效果等级处于较好以上储量占22％,虽然近4／5的储量开发效果处于中等以下的水平,但它们采出程度和含水相对较低,挖掘潜力较大。     

水资源系统分析中模糊隶属度与集对联系数的不确定性特征辨析

为探究模糊隶属度与集对联系数两种理论间的内在联系,分析了二者在概念、理论和适用性的异同,利用集对理论构造联系数模型与模糊数学思想构造隶属度函数,分别评价了黑龙江省水资源承载力现状。结果表明,集对理论与模糊数学理论在水资源系统分析中均有良好的效果。由于模糊性是排中率的破缺,模糊数学在不确定性的现状评价中更有优势;集对联系数可视为模糊隶属度的区间表达,可对评价对象进行简单分级,并能动态评价研究对象。     

灰色三角白化权集对分析模型在河流健康评价中的应用

鉴于河流健康状况评估中存在评价等级标准不确定性的问题,多方面考虑河流自然环境特征及社会服务功能等因素,构建河流健康评价指标体系,并基于传统SPA模型,以灰色聚类法中不同灰类的聚类系数代替对应的联系度分量,引入灰色三角白化权函数处理等级标准的不确定性信息,同时采用主客观相结合的组合赋权法确定指标权重,提出灰色三角白化权集对分析模型,将其应用于某河的健康状况评价中。结果表明,某河2014年健康等级为中等,与实际情况一致,可见改进后的模型能够更好地处理等级标准的不确定性信息;同时根据评价结果,该河流应加大水污染治理力度,加强河岸防洪工程建设,以改善河流水质状况和提高防洪能力。     

基于云模型和D-S证据理论的尾矿库失稳溃坝警情评价模型及应用

为实现对尾矿库失稳溃坝警情状态的系统评价,并考虑影响因素之间的不确定性、随机性和模糊性问题,将云模型和D-S证据理论相结合,构建了基于云模型和D-S证据理论的尾矿库失稳溃坝警情评价模型,即利用云模型实现对区间型数据的统一建模处理,再采用D-S证据理论对不同证据进行融合处理,得到最终的评价结果。实例应用表明,该模型评价结果与实际情况相符,在处理不确定性信息融合问题上有效、合理。     

基于过程机理的溃坝生命损失估算模型

针对溃坝造成大坝下游居民生命损失的问题,考虑溃坝洪水的发生过程,将溃坝前风险人口撤离率、溃坝后未撤离人口避难率、未避难人口死亡率及其他相关影响因素确定的修正系数这四项重要指标引入到溃坝生命损失估算过程中。根据我国已溃水库的相关资料,借鉴已有研究成果,着重分析了警报时间与撤离率、溃坝洪水严重性与避难率的关系曲线,并用模糊综合评价法确定生命损失的修正系数,最终得到系统的溃坝生命损失估算模型与方法。将该模型与方法应用于已溃大坝生命损失估算中,生命损失的平均相对误差绝对值为10.6%,通过与其他估算方法对比发现,该方法的计算结果更接近实际损失值。研究成果可为溃坝生命损失估算提供参考。     

基于组合赋权的模糊熵与灰色聚类-SPA水资源短缺风险二维综合评判模型及应用

水资源短缺风险评价存在诸多不确定因素,而传统灰色聚类评价法忽视了这一因素,且根据聚类系数最大原则确定评价等级降低了结果的可靠性。为此引入集对分析SPA理论,建立联系度分量与聚类系数的耦合关系,以兼顾评价中的确定性与不确定性信息;同时选用指数型白化函数,运用最小偏差组合赋权法确定各指标权重。此外,将模糊熵理论作为第二维评价体系来表征短缺风险的复杂度,建立基于组合赋权的模糊熵与灰色聚类-SPA二维综合评判模型,并应用于水资源短缺风险评价。评价结果与传统单一等级评价模式相比,可从等级与复杂度两个维度揭示短缺风险程度,更加直观合理,为相关评价研究提供了新思路。     

蒙特卡罗法求解湖库未确知水环境容量

针时未确知数学处理湖泊水库水环境系统众多不确定性信息中对未确知变量数、可能值区间分段数及采用的运算算子要求较高限制了未确知数学理论广泛应用的问题,提出用蒙特卡罗法模拟未确知数的可信度分布,根据满足可信度分布的未确知教试验值可直接进行未确知数运算.湖库水环境容量计算实例结果表明,该方案可行有效,计算结果可靠,对未确知数学在各学科领域广泛应用具有一定的推动价值.     

灰色三角白化权SPA模型在水资源脆弱性评价中的应用

鉴于水资源脆弱性评价等级标准中存在很多不确定性因素,从内部自然承载和外部压力驱动两个角度出发,构建水资源脆弱性综合评价指标体系,同时结合SPA和灰色聚类法理论,以灰色聚类系数代替对应的联系度分量,引入灰色三角白化权函数处理等级标准中的不确定性信息,并综合考虑主客观因素,计算指标权重,提出灰色三角白化权SPA模型,将其运用到某市的脆弱性综合评估中。评价结果显示,某市2014年评价等级为较不脆弱,与实际情况一致,可见优化后的模型能更好地处理等级标准中的不确定性信息;该市应在积极制定水资源管理条例,避免水资源量过度开采的同时,加大对河流水污染的治理强度,以改善水质,恢复良好的水生生态系统。     

基于未确知盲数的BP模型及其在年径流预测中的应用

针对未确知盲数可展现信息真实的数量及状态,将未确知盲数与BP网络耦合,提出了以未确知盲数为网络输入、预测对象为输出的BP模型,模型预测结果为具有置信度与置信区间的盲数,并将基于未确知盲数的BP模型用于年径流预测。结果表明,该模型有效,预测结果可供借鉴。     

不同糙面类型管道沿程阻力系数计算方法研究

在紊流过渡区,自然工业糙面与人工均匀糙面沿程阻力系数的变化规律差异明显,目前尚无适用于计算各类糙面沿程阻力系数的统一公式。在既有研究基础上,通过对人工均匀糙面沿程阻力系数变化曲线数字化,并引入壁面粗糙均匀度的概念,最终建立了适用于各类糙面及紊流各分区计算沿程阻力系数的统一公式。     

Effects of surface roughness of capillary wall on the profile of thin liquid film and evaporation heat transfer

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Possible transformations for natural convection on a vertical flat plate embedded in porous media with prescribed wall heat flux

This study derived the transformation of boundary layer equations for two-dimensional steady natural convection on a vertical wall embedded in porous media. Three different kinds of thermal boundary conditions are prescribed for wall heat flux: uniform distribution, power law variation, and exponential variation. The flow pattern contains three subregions based on the distance along the flat plate. When inertia resistance is ignored, similarity solution exists in case wall heat flux is in linear distribution. The known relationships of uniform wall temperature relative to wall heat flux variation and uniform wall heat flux relative to wall temperature variation in both cases of the pure fluid flow and the pure porous flow can all be obtained in the present transformation.     

Fractal analysis of polymer electrolyte fuel cell performance influenced by rough contact between microporous layer and catalyst layer

Improving the performance of fuel cell is a research focus. The rough interface between microporous layer (MPL) and catalyst layer (CL) which affects the performance of fuel cell has been simulated by W-M function. The relative heat resistance and the relative diffusivity of the rough contact surface to the perfect contact surface between MPL and CL had been calculated by Monte Carlo simulation. The results show that the relative thermal resistance and the relative diffusivity decrease with the increment of fractal dimension of rough surface. The research results have reference value for fuel cell design.     

基于RS-可拓云模型的水工隧洞围岩安全评价

为了提高水工隧洞施工安全评价结果的可靠性,选取岩石质量指标、湿抗压强度、完整性系数、结构面强度系数、地下水渗水量5个因素作为评价指标,运用改进重要度的粗糙集计算客观权重,选取可拓云模型充分考虑以往围岩评价过程中由于等级分界与数据获取存在的不确定性,构建了基于RS(粗糙集)-可拓云模型的水工隧洞围岩安全评价方法,并将该方法应用于某水工隧洞中的12段围岩中。结果表明,改进重要度的粗糙集计算的权重,既能满足所得权重的客观性,也能保证评估结果具有一定的解释性,基于RS-可拓云模型对于水工隧洞围岩安全等级的确定较为有效,通过该方法得出的隧洞围岩安全等级与实际情况一致。研究成果为水工隧洞围岩安全评价提供了一定的参考。     

A theoretical investigation of thermal contact conductance

The flow of heat between two nominally flat rough surfaces is considered. The variation of thermal conductance with applied load is determined for elastic and plastic modes of surface deformation.     

基于离散标准节理粗糙度系数曲线的粗糙单裂隙等效水力隙宽的确定

鉴于节理粗糙度、力学隙宽及迹线是影响确定粗糙单裂隙等效水力隙宽的三个关键因素,在既有研究的基础上,将光滑平行板和Barton提出的10条标准节理粗糙度系数曲线数字化,应用Fluent软件对不同节理粗糙度系数和不同力学隙宽模型进行数值模拟,探讨了节理粗糙度系数、力学隙宽、迹线与等效水力隙宽之间的关系。并与立方定理修正公式进行对比,结果表明等效水力隙宽随力学隙宽增大而线性增大,随节理粗糙度系数的增大而减小,并且考虑实际迹线情况的等效水力隙宽较不考虑的大。因此,在实际工程中,可采用所提出的拟合公式判断自然粗糙裂隙的渗透能力。     

Energy and exergy analyses of fabricated solar drying system with smooth and rough surfaces at different conditions: A case study

For this experimental work, the solar dryer system has been fabricated. Various experiments have been performed to evaluate the performance of the fabricated dryer system. Energy and exergy concepts have been used for the assessment. And comparative analyses have also been done with smooth and rough surfaces: Grade 150 and Grade 300. This experimental work has been concluded as the maximum collector (i.e., 74°C) and cabinet temperatures (i.e., 66°C) are attained at 13:00 p.m. with Grade 300 surface. Maximum moisture loss (i.e., 35 g) and percentage moisture loss (i.e., 7.53%) are recorded at 13:00 p.m. again with a rough surface. Minimum exergy destruction rate (i.e., 0.294 W) but minimum exergy efficiency (i.e., 20.82%) are found at 17:00 p.m. with a black painted surface, which is not an acceptable condition. Maximum energy efficiency (i.e., 35.98%) and heat removal factor (i.e., 0.56) are obtained at 13:00 p.m. with a rough surface. The best performance from the fabricated solar system is received between 12:00 and 14:00 p.m. This study recommends rough surfaces and 12:00–13:00 p.m. timings for the solar drying system as the performance of the system is better in terms of energy–exergy.     

An experimentally validated thermo-mechanical model for the prediction of thermal contact conductance

A predictive model for estimating thermal contact conductance between two nominally flat metallic rough surfaces has been developed and experimentally validated. The predictive model consists of two complementary parts, the first of which is a surface deformation analysis to calculate the actual area of contact for each contact spot, while the second accounts for the effects of constriction resistance and gas gap conductance between the contacting surfaces. A surface characterization technique is developed which generates an equivalent 3-D surface profile from multiple 2-D profiles and determines the unique wavelengths of importance for the surface deformation and constriction resistance models. For given surface profiles and material properties of two contacting surfaces, and a specified contact pressure, the surface characterization technique filters out non-essential wavelengths on the surface, after which the surface deformation analysis calculates the deformation and contact area of each contacting asperity by considering three different modes of deformation, namely, elastic, elastic–plastic, and plastic. The constriction resistance model is then used to calculate the constriction resistance for each contacting asperity based on the area of contact and radius of curvature of the asperity. The constriction resistance values for all the contacting asperities are then used to calculate the total thermal contact conductance. An experimental facility has also been constructed to measure thermal contact conductance of interfaces to verify the results of the predictive model. Good agreement has been found between the model predictions and experimental measurements, validating the modeling approach.     

Heat transfer enhancement of spray cooling with ammonia by microcavity surfaces

In the present work, spray cooling heat transfer performances with ammonia as coolant were experimentally investigated on three self-manufactured microcavity surfaces and the enhancement of heat transfer over that of flat surface was also examined. The experimental results showed that almost the same heat transfer performance was obtained at low surface superheats for different heat transfer surfaces due to the fact that the single phase convection dominated the heat transfer process. The microcavity surfaces exhibited uniform temperature distribution and higher heat transfer coefficient than that on the flat surface at high surface superheats once the heat transfer was dominated by the nucleate boiling. This was because that the capillary effect induced by the microcavity structure results in dramatic reduction in heat transfer resistance and then enhancement of the nucleate boiling. It was also found that the microcavity surface with the lowest Bo number of 0.1004 yielded the maximum heat transfer coefficient of 148,245 W/m²·K at the heat flux of 451 W/cm² as a result of the strongest capillary effect. In the meantime, low surface temperature of below 0 °C and uniform temperature distribution with deviation below ±1.5 °C at the heat flux of 420 W/cm² was simultaneously achieved.