A strategy for the integration of production planning and scheduling in refineries is proposed. This strategy relies on rolling horizon strategy and a two-level decomposition strategy. This strategy involves an upper ...A strategy for the integration of production planning and scheduling in refineries is proposed. This strategy relies on rolling horizon strategy and a two-level decomposition strategy. This strategy involves an upper level multiperiod mixed integer linear programming (MILP) model and a lower level simulation system, which is extended from our previous framework for short-term scheduling problems [Luo, C.E, Rong, G, "Hierarchical apthis extended framework is to reduce the number of variables and the size of the optimization model and, to quickly find the optimal solution for the integrated planning/scheduling problem in refineries. Uncertainties are also considered in this article. An integrated robust optimization approach is introduced to cope with uncertain parameters with both continuous and discrete probability distribution.展开更多
Regarding the postulate of traffic infrastructure and vehicles, much attention should be given to the effect of road conditions on accidents. With large numbers of traffic accidents on Shenda Freeway, Liaoning Provinc...Regarding the postulate of traffic infrastructure and vehicles, much attention should be given to the effect of road conditions on accidents. With large numbers of traffic accidents on Shenda Freeway, Liaoning Province, Harbin City and others in P. R. China, parameters and the effect of accidents caused by horizontal alignment, vertical alignment, cross section and intersection are studied systematically The disciplinary analysis of these effects are presented in this paper. The viewpoint is acknowledged that high sub grade and steep slopes are against traffic safety, which is common and ignored in high-usage highways in China. Design parameters of the current design criteria and the corresponding countermeasures are suggested for safety on our highways.展开更多
Most of data distribution mechanism in Opportunistic Networks is derived by Epidemic data distribution,and Epidemic data distribution means that when each node meets another node,it may copy its own messages and trans...Most of data distribution mechanism in Opportunistic Networks is derived by Epidemic data distribution,and Epidemic data distribution means that when each node meets another node,it may copy its own messages and transfer to another node.On the one hand,the copies improve the forwarding rate,and reduce the transmission delay.However,on the other hand,energy consumption increases and network survival time is reduced because the copies consume transmission resource.Therefore,copy number should be under control.In this paper,we first introduce the existing routing strategy based on Epidemic briefly,and present the Epidemic routing protocol analysis model and copy control mechanism based on the limited Epidemic in Opportunistic Networks.Then based on the limited copies scheme(LCS),we propose an energy balance scheme(EBS),the results show that EBS can improve the network survival time.展开更多
Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay,Fujian Province,China. However,the cumulative pollution varies in different geographic locations and natural conditions...Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay,Fujian Province,China. However,the cumulative pollution varies in different geographic locations and natural conditions in the enclosed bay. In this study,hydrodynamic conditions,sediment characteristics,and aquaculture methods were recognized as the underlying causes of spatial heterogeneity in the distribution of nitrogen and phosphorous pollutants,the two major controlling factors of habitat degradation in the bay area. In order to achieve the goal of balancing nutrient inputs and outputs in Sansha Bay,we developed a feasible and practical zone restoration strategy for reasonable adjustment and arrangement of aquaculture species and production scale in accordance with varying hydrodynamic conditions and sediment characteristics in six sub-bay areas(sub-systems). The proposed zone restoration strategy lays a solid foundation for habitat restoration and management in Sansha Bay.展开更多
The European Directive 2010/31 claims that by 2020 only (nearly-) ZEB (zero-energy-buildings) may be built. To reach this goal, it is pertinent for buildings to be energetically optimized first. The remaining ener...The European Directive 2010/31 claims that by 2020 only (nearly-) ZEB (zero-energy-buildings) may be built. To reach this goal, it is pertinent for buildings to be energetically optimized first. The remaining energy demand must then be covered by on-site renewable energies (PV, geothermal, etc.). With the area of use (energy demand) and the size of the building envelope/estate (renewable energy supply) in competition with each other, the maximum number of building stories will be most likely limited. For 15 different climatic locations worldwide, the energy demand of optimised office rooms has been simulated and compared with the possible renewable energy production on site. For every location, a good correlation has been found between the simulated energy demand and data like heating and cooling degree hours. Correspondent linear equations are given here. As another result, the maximum numbers of possible stories for ZEBS have been derived, being between 3 and 10 depending on the location.展开更多
Organic Rankine Cycles(ORCs) are an effective way to produce electricity from low-grade heat sources, which cannot be effectively obtained using conventional high-temperature Rankine cycles. Due to the lack of availab...Organic Rankine Cycles(ORCs) are an effective way to produce electricity from low-grade heat sources, which cannot be effectively obtained using conventional high-temperature Rankine cycles. Due to the lack of available information regarding the real Organic Rankine Cycle units on industrial level, off-design simulation under diversified operating conditions plays a significant role for both the system performance prediction and control strategy design. This paper summarizes the theoretical basis, modeling approaches and tools for ORC off-design simulations. Firstly, a review was conducted on the individual state-of-the-art convective heat transfer correlations and void fraction models. Secondly, different kinds of modeling approaches and simulation tools were proposed, highlighting their relevant characteristics, and were categorized for their specific applications. Moreover, an in-depth analysis of technical challenges related to various applications and focusing on the model accuracy and complexity, computational efficiency, as well as the model compatibility were extensively described and discussed. Finally, the current research trends in this field and the development for further investigations were presented.展开更多
A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanc...A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.展开更多
In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,a...In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,are generally neglected.To solve this problem,this paper utilizes the frozen element permeability method to compute the armature self-and mutual-inductance,permanent magnet d-and q-axis flux varying with d-axis and q-axis current,then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively.Based on this model,the method for computing the performance of the generators is also proposed.Taking a 1.5-MW DDPMG as an example,the time-stepping finite element method(T-S FEM) is adopted to analyze the performance with no-load and loaded conditions,the results show a good agreement with the ones obtained by the improved model.Compared with the simplified model,it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.展开更多
基金Supported by the National Natural Science Foundation of China (60421002) and the National High Technology R&D Program of China (2007AA04Z191).
文摘A strategy for the integration of production planning and scheduling in refineries is proposed. This strategy relies on rolling horizon strategy and a two-level decomposition strategy. This strategy involves an upper level multiperiod mixed integer linear programming (MILP) model and a lower level simulation system, which is extended from our previous framework for short-term scheduling problems [Luo, C.E, Rong, G, "Hierarchical apthis extended framework is to reduce the number of variables and the size of the optimization model and, to quickly find the optimal solution for the integrated planning/scheduling problem in refineries. Uncertainties are also considered in this article. An integrated robust optimization approach is introduced to cope with uncertain parameters with both continuous and discrete probability distribution.
文摘Regarding the postulate of traffic infrastructure and vehicles, much attention should be given to the effect of road conditions on accidents. With large numbers of traffic accidents on Shenda Freeway, Liaoning Province, Harbin City and others in P. R. China, parameters and the effect of accidents caused by horizontal alignment, vertical alignment, cross section and intersection are studied systematically The disciplinary analysis of these effects are presented in this paper. The viewpoint is acknowledged that high sub grade and steep slopes are against traffic safety, which is common and ignored in high-usage highways in China. Design parameters of the current design criteria and the corresponding countermeasures are suggested for safety on our highways.
基金supported by the National Natural Science Foundation of China(61171097)Key Lab of Information Network Security, Ministry of Public Security(C14613)
文摘Most of data distribution mechanism in Opportunistic Networks is derived by Epidemic data distribution,and Epidemic data distribution means that when each node meets another node,it may copy its own messages and transfer to another node.On the one hand,the copies improve the forwarding rate,and reduce the transmission delay.However,on the other hand,energy consumption increases and network survival time is reduced because the copies consume transmission resource.Therefore,copy number should be under control.In this paper,we first introduce the existing routing strategy based on Epidemic briefly,and present the Epidemic routing protocol analysis model and copy control mechanism based on the limited Epidemic in Opportunistic Networks.Then based on the limited copies scheme(LCS),we propose an energy balance scheme(EBS),the results show that EBS can improve the network survival time.
基金Supported by the Projects of Public Science and Technology Research Funds of Ocean Sector of China(No.201205009)the National Natural Science Foundation of China(No.41201569)
文摘Unbalanced inputs and outputs of material are the root cause of habitat degradation in Sansha Bay,Fujian Province,China. However,the cumulative pollution varies in different geographic locations and natural conditions in the enclosed bay. In this study,hydrodynamic conditions,sediment characteristics,and aquaculture methods were recognized as the underlying causes of spatial heterogeneity in the distribution of nitrogen and phosphorous pollutants,the two major controlling factors of habitat degradation in the bay area. In order to achieve the goal of balancing nutrient inputs and outputs in Sansha Bay,we developed a feasible and practical zone restoration strategy for reasonable adjustment and arrangement of aquaculture species and production scale in accordance with varying hydrodynamic conditions and sediment characteristics in six sub-bay areas(sub-systems). The proposed zone restoration strategy lays a solid foundation for habitat restoration and management in Sansha Bay.
文摘The European Directive 2010/31 claims that by 2020 only (nearly-) ZEB (zero-energy-buildings) may be built. To reach this goal, it is pertinent for buildings to be energetically optimized first. The remaining energy demand must then be covered by on-site renewable energies (PV, geothermal, etc.). With the area of use (energy demand) and the size of the building envelope/estate (renewable energy supply) in competition with each other, the maximum number of building stories will be most likely limited. For 15 different climatic locations worldwide, the energy demand of optimised office rooms has been simulated and compared with the possible renewable energy production on site. For every location, a good correlation has been found between the simulated energy demand and data like heating and cooling degree hours. Correspondent linear equations are given here. As another result, the maximum numbers of possible stories for ZEBS have been derived, being between 3 and 10 depending on the location.
基金financially supported by the National Key Basic Research Program of China 973 Program(Grant No.2014CB249201)
文摘Organic Rankine Cycles(ORCs) are an effective way to produce electricity from low-grade heat sources, which cannot be effectively obtained using conventional high-temperature Rankine cycles. Due to the lack of available information regarding the real Organic Rankine Cycle units on industrial level, off-design simulation under diversified operating conditions plays a significant role for both the system performance prediction and control strategy design. This paper summarizes the theoretical basis, modeling approaches and tools for ORC off-design simulations. Firstly, a review was conducted on the individual state-of-the-art convective heat transfer correlations and void fraction models. Secondly, different kinds of modeling approaches and simulation tools were proposed, highlighting their relevant characteristics, and were categorized for their specific applications. Moreover, an in-depth analysis of technical challenges related to various applications and focusing on the model accuracy and complexity, computational efficiency, as well as the model compatibility were extensively described and discussed. Finally, the current research trends in this field and the development for further investigations were presented.
文摘A novel control strategy for the load converter supplying the unbalanced AC load in a DC isolated distribution system is presented. The control algorithm results in balanced and sinusoidal load voltages under unbalanced AC loading. The unbalanced load is characterized in the d-q-0 rotating coordinate based on symmetrical sequence components. Also, the mathematical model of the load converter in both a-b-c and d-q-0 coordinates is derived by using the average large signal model. Then, two control strategies for the load converter are presented. The first one uses the conventional d-q-0 controller to ensure the voltage and current regulation. The second one is a newly proposed control strategy based on the decomposition of the voltage and current into in-stantaneous positive, negative, and zero sequences. These three sequences are controlled independently in their own reference frames as DC signals. The performance of the load converter using these two control strategies is compared. Simulation results show the validity and capability of the newly proposed control strategy.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50977028,51077048)
文摘In some control strategies of the direct-rive permanent magnet generator(DDPMG),the mathematics model is excessively simplified and some complex nonlinear characteristics,such as core saturation and cross-saturation,are generally neglected.To solve this problem,this paper utilizes the frozen element permeability method to compute the armature self-and mutual-inductance,permanent magnet d-and q-axis flux varying with d-axis and q-axis current,then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively.Based on this model,the method for computing the performance of the generators is also proposed.Taking a 1.5-MW DDPMG as an example,the time-stepping finite element method(T-S FEM) is adopted to analyze the performance with no-load and loaded conditions,the results show a good agreement with the ones obtained by the improved model.Compared with the simplified model,it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.