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关键词： Sobolev equation   Finite difference   Local meshless method   RBF   LRBF-PUM   Error estimate   FINITE-ELEMENT-METHOD   DATA APPROXIMATION SCHEME   2-DIMENSIONAL SOBOLEV   NUMERICAL-SOLUTION   RBF PARTITION   INTERPOLATION   DIFFERENCE   MULTIQUADRICS   ALGORITHM   EFFICIENT  

摘要： This paper develops a numerical approach for finding the approximate solution of the Sobolev model. This model describes many natural processes, such as thermal conduction for different media and fluid evolution in soils and rocks. The proposed method approximates the unknown solution with the help of two main stages. At a first stage, the time discretization is performed by means of a second-order finite difference procedure. At a second stage, the space discretization is accomplished using the local radial basis function partition of unity collocation method based on the finite difference (LRBF-PUM-FD). The major disadvantage of global techniques is the high computational burden of solving large linear systems. The LRBF-PUM-FD significantly sparsifies the linear system and reduces the computational burden, while simultaneously maintaining a high accuracy level. The time-discrete formulation is studied in terms of the stability and convergence analysis via the energy method. Three examples are illustrated to verify the efficiency and accuracy of the method. (C) 2021 Elsevier Inc. All rights reserved.

关键词： Phosphoric acid fuel cell   Organic Rankine cycle   CCHP   Exergy efficiency   Thermal energy storage tank   Current density   PERFORMANCE ANALYSIS   THERMODYNAMIC ANALYSIS   STIRLING ENGINE   CCHP SYSTEM   OPTIMIZATION   DRIVEN   POLYGENERATION   REFRIGERATOR   GENERATION   RECOVERY  

摘要： In recent years, combined generation systems have become more popular due to their advantages such as high overall efficiency, low fuel consumption, low emissions and lower operating costs. Using fuel cell as prime mover with high efficiency and low pollution can be a solution to achieve higher efficiencies in the combined generation systems. In this study, performance of a novel combined cooling, heating and power system or trigeneration system with phosphoric acid fuel cell along with an organic Rankine cycle is conducted. The system includes a hydrogen storage tank, a phosphoric acid fuel cell, an afterburner, an organic Rankine cycle, a thermal energy storage tank, an absorption chiller, and heat exchangers. For recovery of the waste heat of phosphoric acid fuel cell, three heat recovery systems (the organic Rankine cycle, absorption chiller and, domestic hot water system) are proposed to meet the electricity, cooling and heating needs of a building. The use of heat storage tank and absorption chiller to use the waste heat of the fuel cell and utilize of organic Rankine cycle to supply some part of the power, in a new arrangement is one of the most important novelties of this study. The impacts of current density, operating pressure, and operating temperature of fuel cell on the performance of the trigeneration system are investigated from the perspectives of energy and exergy. The net electrical power of the trigeneration system is 432.8 kW, the cooling capacity is 17.5 kW, and the heating capacity is 90.7 kW, and the domestic hot water capacity is 128.5 kW. The results show increment of 57% in energy efficiency and 5.3% in exergy efficiency of the trigeneration system compared to the phosphoric acid fuel cell lonely. Also, with increasing the current density and operating temperature, energy and exergy efficiencies of the trigeneration system decrease, while increasing the operating pressure leads to rise of these parameters. Additionally, irreversibility of t

关键词： 基础教育课程改革   行动逻辑   类型学   课程治理机制  

摘要： 在我国新一轮基础教育课程改革持续深入推进的过程中,国家、地方和学校三个课程行动主体基于利益和价值的考量,受制于制度、资源、技术等因素影响,致使课程改革呈现出差异性与多样化的行动逻辑。根据课程行动主体间的共识度和协同度两个维度,构建创新扩散型、执行落差型、孤岛效应型和构建变通型四种课程改革实践样态的理想类型。基于基础教育课程改革类型学分析的上下联动机制、问题倒逼机制、试点推广机制与协同推进机制是课程改革的有效治理机制。

关键词： 果冻   来来往往   阳台  

摘要： “为什么翩翩这几天都不理我呢?”果冻趴在自家阳台上,看着远处来来往往的车辆,有些难过。“唉!”果冻又重重地叹了一口气。“小小年纪,叹什么气啊?”原来是爸爸走了过来。他看着愁眉苦脸的果冻,有些哭笑不得。

关键词： 道路桥梁   伸缩缝   施工技术  

摘要： 随着经济水平的不断增长,城市各项基础设施建设也在不断的完善,其中道路桥梁的建设也是人们关注的重中之重。在市政道路桥梁施工过程中,经常会出现各种各样的问题影响人们的正常出行,也会阻碍区域经济的快速发展,所以在市政道路工程建设过程中,应加大对各种施工技术的关注力度。因此在本文中,就针对伸缩缝施工技术进行探讨和分析。