期刊文献+
共找到556,835篇文章
< 1 2 250 >
每页显示 20 50 100
基于实测数据的风电场风速-功率特性仿射建模方法
1
作者 邵振国 刘懿萱 张嫣 《电力自动化设备》 EI CSCD 北大核心 2019年第6期96-101,共6页
提出基于实测数据的风电场风速-功率曲线仿射建模方法。以预报误差、地形差异以及尾流效应影响因素作为噪声元,建立输入风速的仿射模型;将风电场功率实测数据划分为多个所属风速区间,求取各个风速区间的中心值,拟合仿射中心值曲线,进而... 提出基于实测数据的风电场风速-功率曲线仿射建模方法。以预报误差、地形差异以及尾流效应影响因素作为噪声元,建立输入风速的仿射模型;将风电场功率实测数据划分为多个所属风速区间,求取各个风速区间的中心值,拟合仿射中心值曲线,进而辨识风速-功率仿射模型中的噪声元系数。实测数据验证了所提方法的有效性。 展开更多
关键词 风电场 仿射模型 风速-功率曲线 建模 噪声元
考虑物理特征与行为因素的家庭用能特性建模
2
作者 葛少云 李吉峰 +2 位作者 刘洪 王亦然 张鹏 《电力自动化设备》 EI CSCD 北大核心 2019年第3期36-44,共9页
针对常规负荷建模与预测未考虑用户的行为特性,并且需要大量历史数据作为研究基础的问题,提出一种考虑物理特征与行为因素的家庭用能特性建模方法。以家庭能源中心作为研究对象,在介绍总体分析流程的同时,归纳外部需求、内部转换以及终... 针对常规负荷建模与预测未考虑用户的行为特性,并且需要大量历史数据作为研究基础的问题,提出一种考虑物理特征与行为因素的家庭用能特性建模方法。以家庭能源中心作为研究对象,在介绍总体分析流程的同时,归纳外部需求、内部转换以及终端能源负荷类型;考虑物理特征与行为因素,建立电器设备的用能模型,并提出模型扩展方法;在此基础上,通过非侵入式负荷分解与马尔可夫链相结合的方法分析模拟用户的用能行为。算例分析表明,所提方法具有独立刻画负荷肖像曲线的能力,不再依赖大量数据进行派生驱动。 展开更多
关键词 家庭用户 负荷预测 用能细节 马尔可夫链 建模
A Port-stream Based Equation Oriented Modelling of Complex Distillation Column: A Dividing Wall Column Case Study 预览
3
作者 R. Idris N. Harun M.R. Othman 《应用化学杂志》 2019年第2期9-21,共13页
Dividing wall column (DWC) offers higher degree of freedom in comparison with the conventional column. Furthermore, the different sections configurations within the column are highly interacting with several recycle l... Dividing wall column (DWC) offers higher degree of freedom in comparison with the conventional column. Furthermore, the different sections configurations within the column are highly interacting with several recycle loops. Facing with such complex unit operation, describing its behaviour encourages the focal point on the resolution of ideal modelling approaches. Equation oriented (EO) modelling of DWC has been studied by several researchers involving complex algorithm and methodology. In this work, a new approach for modelling of DWC is presented. The modelling methodology involves variables connectivity based on ports and streams that is admissible to equation-oriented flow sheet. To verify the functionality of the proposed method, the modelled DWC is validated with two case studies depicted from experimental literature data to separate alcohol mixture and fatty acid fractionation. The model development was performed in MOSAIC, a web-based modelling tool and run in gPROMS. The model shows good convergence and has less than 10% error when compared to the abovementioned case studies. To furthermore extend the model capability, relative gain array (RGA) analysis was conducted for the fatty acid fractionation to determine the best control configuration in DWC. Result shows that L-S-V and L-S-B configurations are the best control configurations. Our analysis also shows that reflux flowrate, side flowrate and vapor boilup are best to control distillate product, side product and bottom product respectively. 展开更多
关键词 Dividing Wall COLUMN Process MODELLING RELATIVE GAIN Array
在线阅读 下载PDF
Modelling of a Human Driver’s Interaction with Vehicle Automated Steering Using Cooperative Game Theory 预览
4
作者 Xiaoxiang Na David J.Cole 《自动化学报:英文版》 CSCD 2019年第5期1095-1107,共13页
The introduction of automated driving systems raised questions about how the human driver interacts with the automated system. Non-cooperative game theory is increasingly used for modelling and understanding such inte... The introduction of automated driving systems raised questions about how the human driver interacts with the automated system. Non-cooperative game theory is increasingly used for modelling and understanding such interaction, while its counterpart, cooperative game theory is rarely discussed for similar applications despite it may be potentially more suitable. This paper describes the modelling of a human driver’s steering interaction with an automated steering system using cooperative game theory. The distributed Model Predictive Control approach is adopted to derive the driver’s and the automated steering system’s strategies in a Pareto equilibrium sense, namely their cooperative Pareto steering strategies. Two separate numerical studies are carried out to study the influence of strategy parameters, and the influence of strategy types on the driver’s and the automated system’s steering performance. It is found that when a driver interacts with an automated steering system using a cooperative Pareto steering strategy, the driver can improve his/her performance in following a target path through increasing his/her effort in pursuing his/her own interest under the driver-automation cooperative control goal. It is also found that a driver’s adoption of cooperative Pareto steering strategy leads to a reinforcement in the driver’s steering angle control, compared to the driver’s adoption of non-cooperative Nash strategy. This in turn enables the vehicle to return from a lane-change maneuver to straight-line driving swifter. 展开更多
关键词 AUTOMATED driving system COOPERATIVE game theory DRIVER MODELLING
在线阅读 下载PDF
Plasma for cancer treatment: How can RONS penetrate through the cell membrane? Answers from computer modeling
5
作者 Annemie Bogaerts Maksudbek Yusupov +1 位作者 Jamoliddin Razzokov Jonas Van der Paal 《化学科学与工程前沿:英文版》 EI CAS CSCD 2019年第2期253-263,共11页
Plasma is gaining increasing interest for cancer treatment, but the underlying mechanisms are not yet fully understood. Using computer simulations at the molecular level, we try to gain better insight in how plasma-ge... Plasma is gaining increasing interest for cancer treatment, but the underlying mechanisms are not yet fully understood. Using computer simulations at the molecular level, we try to gain better insight in how plasma-generated reactive oxygen and nitrogen species (RONS) can penetrate through the cell membrane. Specifically, we compare the permeability of various (hydrophilic and hydrophobic) RONS across both oxidized and nonoxidized cell membranes. We also study pore formation, and how it is hampered by higher concentrations of cholesterol in the cell membrane, and we illustrate the much higher permeability of H2O2 through aquaporin channels. Both mechanisms may explain the selective cytotoxic effect of plasma towards cancer cells. Finally, we also discuss the synergistic effect of plasma-induced oxidation and electric fields towards pore formation. 展开更多
关键词 PLASMA MEDICINE cancer treatment computer MODELLING cell MEMBRANE REACTIVE oxygen and nitrogen species
Assessing the inter-annual variability of separation distances around odour sources to protect the residents from odour annoyance
6
作者 Marlon Brancher Martin Piringer +3 位作者 Davide Franco Paulo Belli Filho Henrique De Melo Lisboa Günther Schauberger 《环境科学学报:英文版》 SCIE EI CAS CSCD 2019年第5期11-24,共14页
In recent years, there has been a growing concern about potential impacts on public health and wellbeing due to exposure to environmental odour. Separation distances between odour-emitting sources and residential area... In recent years, there has been a growing concern about potential impacts on public health and wellbeing due to exposure to environmental odour. Separation distances between odour-emitting sources and residential areas can be calculated using dispersion models, as a means of protecting the neighbourhood from odour annoyance. This study investigates the suitability of using one single year of meteorological input data to calculate reliable direction-dependent separation distances. Accordingly, we assessed and quantified the inter-annual variability of separation distances at two sites with different meteorological conditions, one in Brazil and the other in Austria. A 5-year dataset of hourly meteorological observations was used for each site. Two odour impact criteria set in current regulations were selected to explore their effect on the separation distances. The coefficient of variation was used as a statistical measure to characterise the amount of annual variation. Overall,for all scenarios, the separation distances had a low degree of inter-annual variability(mean coefficient of variation values from 8% to 21%). Reasonable agreements from year to year were therefore observed at the two sites under investigation, showing that one year of meteorological data is a good compromise to achieve reliable accuracy. This finding can provide a more cost-effective solution to calculate separation distances in the vicinity of odour sources. 展开更多
关键词 Environmental odour Odour ANNOYANCE Impact assessment Dispersion modelling REGULATORY criteria SEPARATION distance
强潮环境下小型海岛海滩修复方案数值模拟研究 预览
7
作者 张振伟 刘建辉 +1 位作者 李兵 刘贞文 《福建师范大学学报:自然科学版》 CAS 北大核心 2019年第2期22-30,61共10页
应用FVCOM模型对强潮环境小型海岛(平潭大屿岛)周边海域开展了潮汐潮流数值模拟研究,结果表明大屿岛周围潮波为前进波,潮流与潮位变化同步,潮流在高潮(涨急)时由北向南流动,低潮(落急)时由南向北流动,且潮流流速较大.平潭大屿北侧海滩... 应用FVCOM模型对强潮环境小型海岛(平潭大屿岛)周边海域开展了潮汐潮流数值模拟研究,结果表明大屿岛周围潮波为前进波,潮流与潮位变化同步,潮流在高潮(涨急)时由北向南流动,低潮(落急)时由南向北流动,且潮流流速较大.平潭大屿北侧海滩属于典型的岬湾海滩,波浪作用为主要的动力因素,其南侧海滩在波浪和潮汐动力作用下形成的沙滩岸线与海流流向基本平行,潮流起到了一定的作用.针对平潭大屿岛两个沙滩不同的动力特性提出了相应的海滩修复方案,并应用XBEACH模型对强浪作用下海滩剖面演变进行了计算分析. 展开更多
关键词 海滩修复 强潮 波浪 数值模拟 无居民海岛
在线阅读 下载PDF
Boundary condition modelling and identification for cantilever-like structures using natural frequencies
8
作者 Wei LIU Zhichun YANG +1 位作者 Le WANG Ning GUO 《中国航空学报:英文版》 SCIE EI CAS CSCD 2019年第6期1451-1464,共14页
The actual boundary conditions of cantilever-like structures might be non-ideally clamped in engineering practice, and they can also vary with time due to damage or aging. Precise modelling of boundary conditions, in ... The actual boundary conditions of cantilever-like structures might be non-ideally clamped in engineering practice, and they can also vary with time due to damage or aging. Precise modelling of boundary conditions, in which both the boundary stiffness and the boundary mass should be modelled correctly, might be one of the most significant aspects in dynamic analysis and testing for such structures. However, only the boundary stiffness was considered in the most existing methods. In this paper, a boundary condition modelling and identification method for cantilever-like structures is proposed to precisely model both the boundary stiffness and the boundary mass using sensitivity analysis of natural frequencies. The boundary conditions of a cantilever-like structure can be parameterized by constant mass, constant rotational inertia,constant translational stiffness, and constant rotational stiffness. The relationship between natural frequencies and boundary parameters is deduced according to the vibration equation for the lateral vibration of a non-uniform beam. Then, an iterative identification formulation is established using the sensitivity analysis of natural frequencies with respect to the boundary parameters. The regularization technique is also used to solve the potential ill-posed problem in the identification procedure.Numerical simulations and experiments are performed to validate the feasibility and accuracy of the proposed method. Results show that the proposed method can be utilized to precisely model the boundary parameters of a cantilever-like structure. 展开更多
关键词 BOUNDARY CONDITION IDENTIFICATION BOUNDARY CONDITION MODELLING Iterative method Natural frequency Sensitivity analysis
基于Simulink的纯电动汽车纵向动力学模型研究 预览
9
作者 蔡建红 李守成 金国庆 《机械制造与自动化》 2019年第1期121-123,155共4页
随着现代汽车技术的发展,汽车系统也变得越来越复杂,建模已成为汽车电控系统开发过程中的重要流程。基于小型纯电动汽车平台,建立纯电动仿真模型。因为纯电动汽车与传统燃油汽车的主要差异集中在动力总成上,且其研发目的也更关注经济性... 随着现代汽车技术的发展,汽车系统也变得越来越复杂,建模已成为汽车电控系统开发过程中的重要流程。基于小型纯电动汽车平台,建立纯电动仿真模型。因为纯电动汽车与传统燃油汽车的主要差异集中在动力总成上,且其研发目的也更关注经济性,所以电动车的动力总成匹配、能量管理策略开发等工作也都是基于纵向动力学模型,基于策略模型的搭建并验证了整车性能。 展开更多
关键词 纯电动汽车 建模 纵向动力学 电池 电动机
在线阅读 下载PDF
魏晋南北朝时期“槅”考论 预览
10
作者 郭晓兰 《南方文物》 CSSCI 北大核心 2019年第1期184-190,共7页
槅是魏晋南北朝时期重要的饮食器具,也是当时墓葬中祭祀用具的一种。槅最迟产生于汉末,吴时得到推广,西晋人多使用长方形槅,至东晋及南朝传统的圆形槅占据主流,至南朝末年逐渐消失。槅流行的意义在于其首开食器内功能分区的先河,适应了... 槅是魏晋南北朝时期重要的饮食器具,也是当时墓葬中祭祀用具的一种。槅最迟产生于汉末,吴时得到推广,西晋人多使用长方形槅,至东晋及南朝传统的圆形槅占据主流,至南朝末年逐渐消失。槅流行的意义在于其首开食器内功能分区的先河,适应了一器多用的需要,并为隋唐及以后饮食器具的多样化打下了基础。 展开更多
关键词 造型 功能 出现背景
在线阅读 下载PDF
从郎之万方程出发建立多孔介质微观模型 预览
11
作者 张晓虎 李利峰 韩六平 《科学技术与工程》 北大核心 2019年第6期222-230,共9页
岩土类多孔介质宏观物理力学性质是岩土工程界关注的焦点,其关键是岩土类多孔介质本身复杂的微观结构。综述了当前多孔介质建模的研究现状,简要分析了各种模型建立方法的优势和劣势。针对多孔介质建模的复杂性,从随机动力学相分离过程... 岩土类多孔介质宏观物理力学性质是岩土工程界关注的焦点,其关键是岩土类多孔介质本身复杂的微观结构。综述了当前多孔介质建模的研究现状,简要分析了各种模型建立方法的优势和劣势。针对多孔介质建模的复杂性,从随机动力学相分离过程的朗之万方程出发,将多孔介质的形成过程看作是固相粒子和孔隙相粒子相互作用演化的结果,建立了构造随机多孔介质的微观生长模型。通过不断向空间播撒固相粒子和孔隙相粒子控制多孔介质的演化过程,同时计算了不同参数条件下演化过程中多孔介质孔隙率、欧拉数以及分形维数的变化趋势。由于考虑了固体相和空隙相粒子之间的相互作用力,模型生成的多孔介质与自然界真实的多孔介质更为接近,存在连通和不连通的孔隙结构,孔道迂回曲折。通过与真实样品微观结构的比对,验证了本模型的实用性、可行性。 展开更多
关键词 多孔介质 随机动力学 欧拉数 分形维数 SEM 模型
在线阅读 免费下载
第四次国际古气候模拟比较计划(PMIP4)概况与评述 预览
12
作者 郑伟鹏 满文敏 +1 位作者 孙咏 栾贻花 《气候变化研究进展》 CSCD 北大核心 2019年第5期510-518,共9页
古气候模拟比较计划(PMIP)是古气候数值模拟领域一项重大的国际合作研究计划,其主旨是为古气候模拟和模拟结果评估提供一个协调机制,理解过去气候变化的物理机制和气候反馈的重要作用,为未来气候预估提供科学依据。同时,通过对比分析验... 古气候模拟比较计划(PMIP)是古气候数值模拟领域一项重大的国际合作研究计划,其主旨是为古气候模拟和模拟结果评估提供一个协调机制,理解过去气候变化的物理机制和气候反馈的重要作用,为未来气候预估提供科学依据。同时,通过对比分析验证模式的模拟性能,探索其不确定性,促进耦合气候系统模式的发展。PMIP目前进行到第四阶段(PMIP4)。PMIP4进一步加强了与第六次国际耦合模式比较计划(CMIP6)的协作,选取了5组共同关注的PMIP4-CMIP6古气候模拟试验(中全新世、末次盛冰期、过去千年、末次间冰期和上新世暖期),考察气候系统对不同气候背景的综合响应。除此以外,PMIP4还设计了众多敏感性试验研究不同外强迫因子的影响。PMIP4模拟试验不仅为古气候研究提供大量的模拟数据,还将服务于CMIP6及其他众多模式比较计划。 展开更多
关键词 古气候 数值模拟 外强迫 中全新世 末次盛冰期
在线阅读 下载PDF
Numerical modelling of a low power non-transferred arc plasma reactor for methane conversion
13
作者 B I MIN D K DINH +2 位作者 D H LEE T H KIM S CHOI 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第6期29-37,共9页
Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane,which is the main component of shale gas,were simulated.The temperature... Thermal flow characteristics and the methane conversion reaction in a low power arc plasma reactor for efficient storage and transport of methane,which is the main component of shale gas,were simulated.The temperature and velocity distributions were calculated according to the type of discharge gases and arc current level by a self-developed magnetohydrodynamics (MHD)code and a commercial ANSYS-FLUENT code;the transport of chemical species was analyzed as including the chemical reactions of methane conversion.The simulated results were verified by the comparison of calculated and measured arc voltages with permissible low error as under 4%.Three C2 hydrocarbon gases with ethane (C2H6),ethylene (C2H4),and acetylene (C2H2)were selected as the converted species of methane from experimental data.The mass fraction of C2 hydrocarbons and hydrogen as the product of the conversion reaction at the reactor was also calculated.Those values show good agreement with the actual experimental results in that the major conversion reaction occurred in C2H2 and hydrogen,and the conversions to C2H6,C2H4,and hydrogen were minor reactions of methane pyrolysis conversion. 展开更多
关键词 numerical modelling non-transferred arc plasma METHANE chemical reaction
Roles of computational modelling in understanding p53 structure, biology, and its therapeutic targeting
14
作者 Yaw Sing Tan Yasmina Mhoumadi Chandra S. Verma 《分子细胞生物学报:英文版》 SCIE CAS CSCD 2019年第4期306-316,共11页
The transcription factor p53 plays pivotal roles in numerous biological processes, including the suppression of tumours. The rich availability of biophysical data aimed at understanding its structure–function relatio... The transcription factor p53 plays pivotal roles in numerous biological processes, including the suppression of tumours. The rich availability of biophysical data aimed at understanding its structure–function relationships since the 1990s has enabled the application of a variety of computational modelling techniques towards the establishment of mechanistic models. Together they have provided deep insights into the structure, mechanics, energetics, and dynamics of p53. In parallel, the observation that mutations in p53 or changes in its associated pathways characterize several human cancers has resulted in a race to develop therapeutic modulators of p53, some of which have entered clinical trials. This review describes how computational modelling has played key roles in understanding structural-dynamic aspects of p53, formulating hypotheses about domains that are beyond current experimental investigations, and the development of therapeutic molecules that target the p53 pathway. 展开更多
关键词 P53 STRUCTURE COMPUTATIONAL modelling THERAPEUTIC targeting
一种空气分级切向燃烧烟煤锅炉的燃尽特性
15
作者 刘福国 郭新根 +1 位作者 王守恩 崔福兴 《中国电机工程学报》 EI CSCD 北大核心 2019年第7期2113-2125,共13页
采用实炉试验和数值模拟研究一台空气分级低NO_x切向燃烧烟煤锅炉飞灰燃尽度随主燃烧区过剩空气系数的变化特性。结果表明,该锅炉在临界过剩空气系数为0.88时,主燃烧区出口处易燃小颗粒刚好消耗烟气中所有氧气,小颗粒快速燃烧形成的高... 采用实炉试验和数值模拟研究一台空气分级低NO_x切向燃烧烟煤锅炉飞灰燃尽度随主燃烧区过剩空气系数的变化特性。结果表明,该锅炉在临界过剩空气系数为0.88时,主燃烧区出口处易燃小颗粒刚好消耗烟气中所有氧气,小颗粒快速燃烧形成的高温烟气环境在缺氧量条件下对大颗粒燃烧未能起到促进作用,只增加主燃烧区辐射换热,降低SOFA风区烟气温度,而SOFA风区能提供富氧烟气环境。因此,在该临界过剩空气系数下,炉内温度场和氧量场协同性较差,不利于大颗粒的燃尽;降低主燃烧区过剩空气系数到临界值0.88以下,一部分小颗粒转移到SOFA风区,在富氧环境中小颗粒燃烧放热对烟温的提升促进大颗粒的燃尽,当主燃烧区过剩空气系数降低到0.71时,飞灰可燃物从1.89%下降到1.25%,在降低NO_x排放的同时,提高颗粒燃尽度。因此,对于空气分级低NO_x燃烧锅炉,运行时避开临界过剩空气系数对降低NO_x排放量和提高飞灰燃尽度有较为重要的意义。 展开更多
关键词 煤燃烧 低NO_x燃烧器 空气分级 燃尽 模型
Joint Loading Estimation Method for Horse Forelimb High Jerk Locomotion:Jumping
16
作者 Joanne Becker Mermoz Emmanuel Linares Jean-Marc 《仿生工程学报:英文版》 SCIE EI CSCD 2019年第4期674-685,共12页
Maximal local loads in animal joints are necessary to design bio-inspired mechanical joints.Many studies presented methods to determine joint reaction forces in humans and animals.However,many of these methods are inv... Maximal local loads in animal joints are necessary to design bio-inspired mechanical joints.Many studies presented methods to determine joint reaction forces in humans and animals.However,many of these methods are invasive,and no work has been published yet about the joint reaction forces in the horse forelimb during jumping.Non-invasive methods to measure the kinematics and ground reaction force of a horse forelimb were used in this work.A musculoskeletal model of horse forelimb was built with mechanical methods for the estimation of joint reaction forces.The entire forelimb was reconstructed by scanning real bones geometry with a 3D optical scanner and modeling all the muscles on a Computer Assisted Design(CAD)software.The model dynamics were simulated with OpenSim in order to estimate the joint loading.This study allows knowing an order of magnitude of the loads at the joints at jumping in order to determine latter the maximal joint contact loading values that will be a key at designing bio-inspired joints for mechanical assemblies. 展开更多
关键词 joint loading JUMPING KINEMATICS MODELLING OpenSim
Towards Energy Efficient Shape Rolling:Roll Pass Optimal Design and Case Studies
17
作者 Kan Huang Bin Huang +1 位作者 Lei Fu Kazem Abhary 《中国机械工程学报:英文版》 SCIE EI CAS CSCD 2019年第3期78-88,共11页
Shape rolling is widely employed in the production of long workpieces with appropriate cross-section profiles for other industrial applications. In the development of shape rolling systems, roll pass design (RPD) play... Shape rolling is widely employed in the production of long workpieces with appropriate cross-section profiles for other industrial applications. In the development of shape rolling systems, roll pass design (RPD) plays an essential role on the quality control of products, service life of rolls, productivity of rolling systems, as well as energy consumption of rolling operations. This study attempts to establish a generic strategy based on hybrid modeling and an improved genetic algorithm, to support the optimizations of RPD and shape rolling operations at a systematic perspective. Objectives include improving the quality and efficiency of RPD, reducing energy consumption of shape rolling, as well as releasing the demands on costly trails and expert knowledge in RPD. Hybrid modeling based on cross-disciplinary knowledge is developed to overcome the limitations of isolated single-disciplinary models. And conventional genetic algorithm is improved for the implementation of optimal design. Targeting to integrate empirical data and published reliable solutions into optimizations, a parameters estimation method is proposed to transfer the initially misaligned models into a uniform pattern. A tool based on the Matlab platform is developed to demonstrate the optimal design operations, with case studies involved to validate the proposed methodology. 展开更多
关键词 ROLL PASS OPTIMAL design Hybrid MODELLING GENETIC algorithm Parameters estimation
基于Stopwatch时间Petri网的柔性作业车间优先级调度研究 预览
18
作者 李雅琼 魏绍炎 潘春荣 《现代制造工程》 CSCD 北大核心 2019年第5期29-35,共7页
作业时间不确定的柔性作业车间调度问题由于其计算复杂性、约束条件数量以及工件加工优先级等限制,难以获得最优解。采用Stopwatch时间Petri网对区间柔性作业车间优先级调度问题进行建模,通过Stopwatch状态类可达性分析方法获得模型所... 作业时间不确定的柔性作业车间调度问题由于其计算复杂性、约束条件数量以及工件加工优先级等限制,难以获得最优解。采用Stopwatch时间Petri网对区间柔性作业车间优先级调度问题进行建模,通过Stopwatch状态类可达性分析方法获得模型所有可行变迁触发序列。为了准确执行变迁触发序列的时序分析,采取逆向分步法将此问题转化为线性规划问题,求出最小下界和最小上界的调度路径,进而获得基于优先级的最优调度方案。通过实验结果表明了模型的有效性,为区间柔性作业车间优先级调度提供了有效的模型支持。 展开更多
关键词 柔性作业车间调度 时间PETRI网 建模 时序分析
在线阅读 免费下载
Influence of bed elevation discordance on flow patterns and head losses in an open-channel confluence 预览
19
作者 Pedro Xavier Ramos Laurent Schindfessel +1 位作者 Joao Pedro Pego Tom De Mulder 《水科学与水工程:英文版》 EI CAS CSCD 2019年第3期235-243,共9页
Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized co... Confluences play a major role in the dynamics of networks of natural and man-made open channels, and field measurements on river confluences reveal that discordance in bed elevation is common.Studies of schematized confluences with a step at the interface between the tributary and the main channel bed reveal that bed elevation discordance is an important additional control for the confluence hydrodynamics.This study aimed to improve understanding of the influence of bed elevation discordance on the flow patterns and head losses in a right-angled confluence of an open channel with rectangular cross-sections.A large eddy simulation (LES)-based numerical model was set up and validated with experiments by others.Four configurations with different bed discordance ratios were investigated.The results confirm that, with increasing bed elevation discordance, the tributary streamlines at the confluence interface deviate less from the geometrical confluence angle, the extent of the recirculation zone (RZ) gets smaller, the ratio of the water depth upstream to that downstream of the confluence decreases, and the water level depression reduces.The bed elevation discordance also leads to the development of a large-scale structure in the lee of the step.Despite the appearance of the large-scale structure, the reduced extent of the RZ and associated changes in flow deflection/contraction reduce total head losses experienced by the main channel with an increase of the bed discordance ratio.It turns out that bed elevation discordance converts the lateral momentum from the tributary to streamwise momentum in the main channel more efficiently. 展开更多
关键词 Open channel CONFLUENCE BED ELEVATION DISCORDANCE Three-dimensional numerical MODELLING Large EDDY simulation Recirculation zone
在线阅读 下载PDF
Impact of recycling improvement on the life cycle of phosphorus
20
作者 Mohammad El Wali Saeed Rahimpour Golroudbary Andrzej Kraslawski 《中国化学工程学报:英文版》 SCIE EI CAS CSCD 2019年第5期1219-1229,共11页
Access to natural resources is increasingly more difficult and more costly, partly due to their economic significance and to continuous increase of their global consumption in the recent years. In the case of phosphor... Access to natural resources is increasingly more difficult and more costly, partly due to their economic significance and to continuous increase of their global consumption in the recent years. In the case of phosphorus (P), which is a critical raw material, geological distribution of its primary nonrenewable source (phosphate rock) is concentrated in particular regions leading to high supply risk of this raw material. In Europe (EU-28), where phosphate rock reserves are scarce, import of phosphorus has been the main source of supply. It means that Europe relies highly on the foreign exporters. From decision makers' perspective, recycling of phosphorus was taken into account as one of the possible solutions to decrease the dependence on imports and extraction of reserves. The question, however, is to what extent does the recycling of phosphorus help in reducing the reliance on typical supply resources? Hence, the main objective of this paper is to quantify the dynamic flow of phosphorus and show potential benefits of its recycling in Europe. This article presents a system dynamics model for representation of the element P flow and helps to quantify to what extent the recycled phosphorus could mitigate its criticality. Analysis of the results supports previous studies indicating the high reliance ofEU on P imports, estimating around 96% as the reliance percentage on imports. The results imply that improving P recycling has the potential to decrease the level of P imports to a certain extent, which may reach 79%. 展开更多
关键词 CRITICAL material PHOSPHORUS DYNAMIC MODELLING DYNAMIC simulation RECOVERY RECYCLING
上一页 1 2 250 下一页 到第
使用帮助 返回顶部 意见反馈