Currently,the investment of oil and gas industry is still facing an unfavorable environment,in which,instable factors,such as financial crisis,terrorist,religious conflicts and rigorous environmental regulations,keep ...Currently,the investment of oil and gas industry is still facing an unfavorable environment,in which,instable factors,such as financial crisis,terrorist,religious conflicts and rigorous environmental regulations,keep mucking up the business all around the world.Meanwhile,China’s rapid energy consumption growth boosted by a booming economy has put the country to rely heavily on exported oil.It is therefore extremely urgent to expand and diversify petroleum supply channel in consideration of the country’s energy security.As the world’s economy has been slowly recovering from the slump and展开更多
Although numerous studies have considered the two traditional operation strategies:following the electric load(FEL)and following the thermal load(FTL),for combined cooling,heating,and power(CCHP)systems in different c...Although numerous studies have considered the two traditional operation strategies:following the electric load(FEL)and following the thermal load(FTL),for combined cooling,heating,and power(CCHP)systems in different case studies,there are limited theoretical studies on the quantification methods to assess the feasibility of these two strategies in different load demands scenarios.Therefore,instead of a case study,we have undertaken a theoretical analysis of the suitable application scenarios for FEL and FTL strategies based on the energy-matching performance between systems'provision and users'demands.To compare the calculation models of energy saving rate(ESR)for FEL and FTL strategies in the left and right sub-regions of the energy-supply curve,a comprehensive parameter(^)that combines three inherently influential factors(off-design operation parameter,energy-matching parameter,and install capacity coefficient)is defined to determine the optimal installed capacity and feasibility of FEL or FTL strategies quantitatively.The results indicate that greater value of x contribute to a better energy saving performance,and FEL strategy shows better performance than FTL in most load demands scenarios,and the optimal installed capacity occurs when the load demand points were located in different regions of the energy-supply curve.Finally,taking a hotel in Beijing as an example,the value of the optimal install capacity coefficient is 0.845 and the FEL strategy is also suggested,and compared to the maximum install capacity,the average values of the ESR on a typical summer day,transition season,and winter can be enhanced by 3.9%,8.8%,and 1.89%,respectively.展开更多
Urban rail transit loops are essential in urban rail transit systems and transportation networks.However,precise requirements and reference standards for rail transit loop design have yet to be established.There are c...Urban rail transit loops are essential in urban rail transit systems and transportation networks.However,precise requirements and reference standards for rail transit loop design have yet to be established.There are certain areas for improvement in planning,construction,and operation.In the planning and design of urban rail transit loops,the scale of the city and the relationship between line operations should be considered to ensure that the line conforms to the city’s operating traffic conditions and can effectively cater to peak passenger flow requirements.This article presents strategies for planning,constructing,and operating urban rail transit loops,laying the foundation for the healthy operation of urban rail transit.展开更多
This paper explores the operational strategies of cross-border micro, small, and medium enterprises (MSMEs). Against the backdrop of globalization and digitalization, cross-border trade has become one of the important...This paper explores the operational strategies of cross-border micro, small, and medium enterprises (MSMEs). Against the backdrop of globalization and digitalization, cross-border trade has become one of the important pathways for many MSMEs to achieve growth and competitive advantage. Firstly, the paper outlines the concept and characteristics of cross-border MSMEs, as well as the analysis of their operational environment in the context of globalization, including political, economic, social, technological, environmental, and legal factors. Secondly, the paper proposes operational strategies for cross-border MSMEs, including international market selection and positioning, cross-border marketing strategies, supply chain management, cross-border financial management, and cross-border risk management. Finally, the paper summarizes the importance of effectively implementing these strategies for cross-border MSMEs to seize international market opportunities, reduce operational risks, and enhance competitiveness and profitability.展开更多
The skip-stop operation strategy (SOS) is rarely applied to Chinese urban rail transit networks because it is a simple scheme and a less universally popular transportation service. However, the SOS has performance a...The skip-stop operation strategy (SOS) is rarely applied to Chinese urban rail transit networks because it is a simple scheme and a less universally popular transportation service. However, the SOS has performance advantages, in that the total trip time can be reduced depending on the number of skipped stations, crowds of passengers can be rapidly evacuated at congested stations in peak periods, and the cost to transit companies is reduced. There is a contradiction between reducing the trip time under the SOS and increasing the passengers' waiting times under an all-stop scheme. Given this situation, the three objectives of our study were to minimize the waiting and trip times of all passengers and the travel times of trains. A comprehensive estimation model is presented for the SOS. The mechanism through which the trip time for all passengers is affected by the SOS is analyzed in detail. A 0-I integer programming formulation is established for the three objectives, and is solved using a tabu search algorithm. Finally, an example is presented to demonstrate that the estimation method for the SOS is capable of optimizing the timetable and operation schemes for a Chinese urban rail transit network.展开更多
A series-parallel hydraulic hybrid system applied to public buses is put torwaro, ano parameters of key components are analyzed and determined. Energy management strategy based on logic thresh- old is designed which i...A series-parallel hydraulic hybrid system applied to public buses is put torwaro, ano parameters of key components are analyzed and determined. Energy management strategy based on logic thresh- old is designed which is aimed at efficient operation of the overall system considering the operational characteristic of the components and taking the curves of engine, hydraulic pump/motor and hydrau- lic pump as the main design basis; regenerative control strategy which makes regenerative brake sys- tem and frictional brake system work harmoniously is designed to raise recovery rate of regenerative brake energy. System dynamic modeling and simulation results show that the energy control strategy designed here is able to adapt system to changes of working condition and switch the operating mode reasonably. The regenerative braking control strategy is effective in raising the utilization of energy and improving fuel economy.展开更多
An operation strategy of the electric vehicle (EV) battery charging and swapping station is proposed in the paper. The strategy is established based on comprehensively consideration of the EV charging behaviors and ...An operation strategy of the electric vehicle (EV) battery charging and swapping station is proposed in the paper. The strategy is established based on comprehensively consideration of the EV charging behaviors and the possible mutual actions between battery charging and swapping. Three energy management strategies can be used in the station: charging period shifting, energy exchange between EVs, and energy supporting from surplus swapping batteries. Then an optimization model which minimizes the total energy management costs of the station is built. The Monte Carlo simulation is applied to analyze the characteristics of the EV battery charging load, and a heuristic algorithm is used to solve the strategy providing the relevant information of EVs and the battery charging and swapping station. The operation strategy can efficiently reduce battery charging during the high electricity price periods and make more reasonable use of the resources. Simulations prove the feasibility and rationality of the strategy.展开更多
Gas turbine power units,as an effective way to cope with the severe challenge of renewable energy accommodation in power grids,arouse the interest of power enterprises in the deep peak-load regulation performance.Two ...Gas turbine power units,as an effective way to cope with the severe challenge of renewable energy accommodation in power grids,arouse the interest of power enterprises in the deep peak-load regulation performance.Two common alternative load-control strategies including constant turbine inlet temperature(TIT)and constant turbine exhaust temperature(TET)regulations were taken into consideration.To comparatively investigate the part-load performance under these strategies,both mathematical and physical models were set up successively to serve as a validation and complementary to each other.For the mathematical model of compressor with inlet guide vane(IGV),combustor and turbine,stage-stacking method based on blade average geometric parameter,energy conservation and turbine stage model were adopted respectively.For the physical model,design and off-design analysis were carried out based on GT PRO and THERMOFLEX respectively.The simulation result of mathematical model validated the reliability of the physical model.Based on this,the influence of ambient temperature and different load-regulating strategies on the off-design performance of gas turbine power units was studied in THERMOFLEX.The results in the case of a PG 9351FA gas turbine show that the ambient temperature has a great impact on system performance,i.e.,every 5℃ increase in the ambient temperature produces a reduction of 3.7%in the relative full-load output and 1.1%in the relative efficiency respectively;when the gas turbine operates under constant TIT strategy,TET starts to rise till it reaches the maximum allowable value with the load rate decreasing,and IGV keeps at the minimum angle with both TIT and TET decreasing when the load rate is lower than 65%;when the gas turbine operates under constant TET strategy,TIT drops slightly at load rate of above 60%while both TIT and TET evidently decrease below 60%load rate operating along the constant corrected speed line at the minimum allowable IGV opening;gas turbine effi-ciency is greatly affected by load rate and the performance degradation is more obvious especially in lower load rate regions;constant TET strategy is superior in the operating efficiency to constant TIT strategy under part-load conditions.展开更多
This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem...This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy.Based on the life cycle method,the configuration optimization under eight operation strategies is studied with the economy,energy,and environment indicators.The eight operation strategies include FEL,FEL-EC,FEL-TES,FEL-TES&EC,FTL,FTL-EC,FTL-TES,and FTL-TES&EC.The feasibility of each strategy is verified by taking a residential building cluster as an example.The indicators under the optimal configuration of each strategy are compared with that of the separate production(SP)system.The results showed that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy.The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer,and the results are just the opposite in winter.The initial annual investment of the PTST-CCHP system is higher than that of the SP system,but its economic performance is better than that of the SP system with the increase of life-cycle.展开更多
With the progress of new trends of society, gymnasium, the most important part in Chinese sports facility, can not only meet the needs of physical exercise of students, but also provide a favorable place for social we...With the progress of new trends of society, gymnasium, the most important part in Chinese sports facility, can not only meet the needs of physical exercise of students, but also provide a favorable place for social welfare development. But due to the influence of traditional management methods, some problems are still seen in the process of operation of university gymnasiums in china, which restricts the overall development of our country's sports enterprise. Therefore, this paper probes into the study on disadvantageous existed conditions and analyzes the operation strategies and management strategies of university gymnasiums on the basis of their characteristics and advantages.展开更多
To realize a better automatic train driving operation control strategy for urban rail trains,an automatic train driving method with improved DQN algorithm(classical deep reinforcement learning algorithm)is proposed as...To realize a better automatic train driving operation control strategy for urban rail trains,an automatic train driving method with improved DQN algorithm(classical deep reinforcement learning algorithm)is proposed as a research object.Firstly,the train control model is established by considering the train operation requirements.Secondly,the dueling network and DDQN ideas are introduced to prevent the value function overestimation problem.Finally,the priority experience playback and“restricted speed arrival time”are used to reduce the useless experience utilization.The experiments are carried out to verify the train operation strategy method by simulating the actual line conditions.From the experimental results,the train operation meets the ATO requirements,the energy consumption is 15.75%more energy-efficient than the actual operation,and the algorithm convergence speed is improved by about 37%.The improved DQN method not only enhances the efficiency of the algorithm but also forms a more effective operation strategy than the actual operation,thereby contributing meaningfully to the advancement of automatic train operation intelligence.展开更多
Present of wind power is sporadically and cannot be utilized as the only fundamental load of energy sources.This paper proposes a wind-solar hybrid energy storage system(HESS)to ensure a stable supply grid for a longe...Present of wind power is sporadically and cannot be utilized as the only fundamental load of energy sources.This paper proposes a wind-solar hybrid energy storage system(HESS)to ensure a stable supply grid for a longer period.A multi-objective genetic algorithm(MOGA)and state of charge(SOC)region division for the batteries are introduced to solve the objective function and configuration of the system capacity,respectively.MATLAB/Simulink was used for simulation test.The optimization results show that for a 0.5 MW wind power and 0.5 MW photovoltaic system,with a combination of a 300 Ah lithium battery,a 200 Ah lead-acid battery,and a water storage tank,the proposed strategy reduces the system construction cost by approximately 18,000 yuan.Additionally,the cycle count of the electrochemical energy storage systemincreases from4515 to 4660,while the depth of discharge decreases from 55.37%to 53.65%,achieving shallow charging and discharging,thereby extending battery life and reducing grid voltage fluctuations significantly.The proposed strategy is a guide for stabilizing the grid connection of wind and solar power generation,capability allocation,and energy management of energy conservation systems.展开更多
Background: Laparoscopic cholecystectomy (LC) remains the preferred me-thod for treating benign gallbladder diseases. However, clinical presentations of cholecystitis vary widely. For severely inflamed cases, LC can b...Background: Laparoscopic cholecystectomy (LC) remains the preferred me-thod for treating benign gallbladder diseases. However, clinical presentations of cholecystitis vary widely. For severely inflamed cases, LC can be challenging. Objectives: This study aimed to explore intraoperative strategies and postoperative management of complications during difficult LC to further enhance its safety. Methods: We retrospectively analyzed data from difficult LC procedures performed by the same expert at our hospital between January 2016 and December 2022. The surgical approach, handling methods, operative time, and postoperative complications were evaluated. Results: Utilizing techniques such as thin-layer progressive dissection, suction and blunt dissection, reverse resection, partial cystectomy, we successfully completed difficult LC in 278 cases. All surgeries were accomplished under laparoscopy. Five cases (0.72%) experienced bile leakage which was managed through drainage tube fistula formation before removal;there were no incidences of hemorrhage, abdominal infection, or biliary tract injury. Conclusion: Our series showed that difficult LC had high safety and low rates of conversion to open surgery and complications. The safety of complex gallbladder removal is related to the surgeon’s experience and proficiency in laparoscopic skills. Postoperative bile leakage can be effectively treated through drainage tube fistula formation.展开更多
The analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can assist in the designing,operating and optimizing pyrolysis processes.This work aims to utilize bot...The analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can assist in the designing,operating and optimizing pyrolysis processes.This work aims to utilize both experimental and modelling approaches to perform the analysis on three biomass feedstocks—wood sawdust,bamboo shred and Jatropha Curcas seed cake residue,and to provide insights for the design and operation of pyrolysis processes.For the experimental part,the study investigated the effect of heating rate,final pyrolysis temperature and sample size on pyrolysis using common thermal analysis techniques.For the modelling part,a transient mathematical model that integrates the feedstock characteristic from the experimental study was used to simulate the pyrolysis progress of selected biomass feedstock particles for reactor scenarios.The model composes of several sub-models that describe pyrolysis kinetic and heat flow,particle heat transfer,particle shrinking and reactor operation.With better understanding of the effects of process conditions and feedstock characteristics on pyrolysis through both experimental and modelling studies,this work discusses on the considerations of and interrelation between feedstock size,pyrolysis energy usage,processing time and product quality for the design and operation of pyrolysis processes.展开更多
Porter identifies high market share with cost leadership strategy which is based on the idea of competing on a price lower than that of the competition. However, in most consumer markets a business should serve the mi...Porter identifies high market share with cost leadership strategy which is based on the idea of competing on a price lower than that of the competition. However, in most consumer markets a business should serve the middle class by competing in the mid-price segment, offering quality better than that of the competition at a somewhat higher price. It is this path that can lead to market share leadership: a strategy that can be both profitable and sustainable. The U.S. men's shaving cream market consists of two major product-market segments: gel and foam. We test the hypothesis that the best-selling brand is very likely to be a member of the mid-price segment with a price tag that is higher than that of the nearest competition. This study is based on annual U.S. sales data for 2008 and 2007 from discount retail stores, food stores, and drug stores. We performed two separate analyses for 2008 and 2007, using cluster analysis as the main analytic tool. The results were remarkably consistent between the two years. In the gel segment--by far the most important--the price-quality segmentation analysis supported our hypothesis. An interesting finding is that, for both the gel and foam segments, we found the rank order correlation of brand unit price between 2007 and 2008 as highly significant. This means that in this market management considers the price of a brand as a strategic rather than a tactical variable. Although, technically the results for the foam segment were negative, this does not necessarily contradict our hypothesis. Finally, we discovered six strategic groups in the industry and have tried to articulate what their competitive strategy is.展开更多
Little by little, we are entering the new era, intelligent interfaces are absorbing us more and more every day, and artificial intelligence makes its presence in a stealthy way. Virtual humans that represent an evolut...Little by little, we are entering the new era, intelligent interfaces are absorbing us more and more every day, and artificial intelligence makes its presence in a stealthy way. Virtual humans that represent an evolution of autonomous virtual agents;they are computer programs and in the future capable of carrying out different activities in certain environments. They will give the illusion of being human;they will have a body, and they will be immersed in an environment. They will have a set of senses that will allow them: 1) Sensations and therefore associated expressions;2) Communication;3) Learning;4) Remembering events, among others. By integrating the above, they will have a personality and autonomy, so they will be able to plan with respect to objectives;allowing them to decide and take actions with their body, in other words, they will count on awareness. The applications will be focused on environments that they will inhabit, or as interfaces that will interact with other systems. The application domains will be multiple;one of them being education. This article shows the design of OANNA like an avatar with the role of pedagogical agent. It was modeled as an affective-cognitive structure related to the teaching-learning process linked to a pedagogical agent that represents the interface of an artilect. OANNA, has the necessary animations for intervention within the teaching-learning process.展开更多
Based on the development of modem logistics park in China, and with the thought of minimizing carbon emission, the development of Logistics Park was analyzed and the necessity of developing low carbon Logistics Park w...Based on the development of modem logistics park in China, and with the thought of minimizing carbon emission, the development of Logistics Park was analyzed and the necessity of developing low carbon Logistics Park was proposed. Low carbon emission in Logistics Park was planned. In the end, operation and implementation strategies of low carbon parks were put forward so as to create favorable environment for the re- alization of low carbon emission in Logistics Park.展开更多
The growth of international banks in China occurred after the "open-door" policy implemented. With the China accession to WTO, the effect of international banks to our economy and politics become more important. If ...The growth of international banks in China occurred after the "open-door" policy implemented. With the China accession to WTO, the effect of international banks to our economy and politics become more important. If international banks want to succeed in China over the next ten years so that the market as a whole develops and matures, they need the Chinese banks to be successful in their restructuring program. There is truly a win-win outcome here if all segments of the banking community recognize the benefit of improving the competitiveness of the Chinese banking industry as a whole. This article analyzes the pattern and strategy of expansion of international banks in China, for the purpose of showing some enlightenment to domestic banks.展开更多
The topic investigated competition in marketing as a survival yardstick for small and medium enterprises (SMEs) in Nigeria. The objectives addressed by this study were: (1) identifying different types and intensi...The topic investigated competition in marketing as a survival yardstick for small and medium enterprises (SMEs) in Nigeria. The objectives addressed by this study were: (1) identifying different types and intensity of competition that SMEs are exposed to along the life-cycle portfolio in Nigeria; (2) quantifying the strength of SMEs vis-a-vis some foreign enterprises in terms of market competition; and (3) proffering solutions on how best they could match competitively these foreign enterprises. Relevant models and theories were employed in literature to evolve detailed analysis of issues relating to the variables used in terms of competition in marketing and survival of juice-producing SMEs. Two hypotheses were investigated through the survey of 20 prominent Ikeja based SMEs using Cluster sampling, 5-points Likert summated rating scale was adopted, while Yard's formula with 95% confidence level and 5% error tolerance was used. Alternative form validity of the instrument was measured at 0.63 while its reliability was measured at Cronbach's alpha of 0.70. Pearson's product-moment correlation was used in testing hypothesis 1 while standard multiple regressions were used to test hypothesis 2. Findings revealed that there was strong relationship between survival of juice-producing SMEs with forms of competition on a firm's life-cycle; while competition had positive effects on survival components for the enterprises. It was concluded that since competition subsists in any firm's life-cycle, strategies to support operations for survival must be adopted. It was recommended that operators of SMEs have to monitor and manage competition as it affects their businesses positively and/or negatively.展开更多
文摘Currently,the investment of oil and gas industry is still facing an unfavorable environment,in which,instable factors,such as financial crisis,terrorist,religious conflicts and rigorous environmental regulations,keep mucking up the business all around the world.Meanwhile,China’s rapid energy consumption growth boosted by a booming economy has put the country to rely heavily on exported oil.It is therefore extremely urgent to expand and diversify petroleum supply channel in consideration of the country’s energy security.As the world’s economy has been slowly recovering from the slump and
基金This work was supported by the National K ey Research and Development Program of China(Grant No.2016 Y F B 0901405)the Science Fund for Creative Research Groups(No.51621062)the National Natural Science Foundation of China(Grant No.51806117,51236004).
文摘Although numerous studies have considered the two traditional operation strategies:following the electric load(FEL)and following the thermal load(FTL),for combined cooling,heating,and power(CCHP)systems in different case studies,there are limited theoretical studies on the quantification methods to assess the feasibility of these two strategies in different load demands scenarios.Therefore,instead of a case study,we have undertaken a theoretical analysis of the suitable application scenarios for FEL and FTL strategies based on the energy-matching performance between systems'provision and users'demands.To compare the calculation models of energy saving rate(ESR)for FEL and FTL strategies in the left and right sub-regions of the energy-supply curve,a comprehensive parameter(^)that combines three inherently influential factors(off-design operation parameter,energy-matching parameter,and install capacity coefficient)is defined to determine the optimal installed capacity and feasibility of FEL or FTL strategies quantitatively.The results indicate that greater value of x contribute to a better energy saving performance,and FEL strategy shows better performance than FTL in most load demands scenarios,and the optimal installed capacity occurs when the load demand points were located in different regions of the energy-supply curve.Finally,taking a hotel in Beijing as an example,the value of the optimal install capacity coefficient is 0.845 and the FEL strategy is also suggested,and compared to the maximum install capacity,the average values of the ESR on a typical summer day,transition season,and winter can be enhanced by 3.9%,8.8%,and 1.89%,respectively.
文摘Urban rail transit loops are essential in urban rail transit systems and transportation networks.However,precise requirements and reference standards for rail transit loop design have yet to be established.There are certain areas for improvement in planning,construction,and operation.In the planning and design of urban rail transit loops,the scale of the city and the relationship between line operations should be considered to ensure that the line conforms to the city’s operating traffic conditions and can effectively cater to peak passenger flow requirements.This article presents strategies for planning,constructing,and operating urban rail transit loops,laying the foundation for the healthy operation of urban rail transit.
文摘This paper explores the operational strategies of cross-border micro, small, and medium enterprises (MSMEs). Against the backdrop of globalization and digitalization, cross-border trade has become one of the important pathways for many MSMEs to achieve growth and competitive advantage. Firstly, the paper outlines the concept and characteristics of cross-border MSMEs, as well as the analysis of their operational environment in the context of globalization, including political, economic, social, technological, environmental, and legal factors. Secondly, the paper proposes operational strategies for cross-border MSMEs, including international market selection and positioning, cross-border marketing strategies, supply chain management, cross-border financial management, and cross-border risk management. Finally, the paper summarizes the importance of effectively implementing these strategies for cross-border MSMEs to seize international market opportunities, reduce operational risks, and enhance competitiveness and profitability.
基金financed by the National Basic Research Program of China, under project ID 2012CB725403
文摘The skip-stop operation strategy (SOS) is rarely applied to Chinese urban rail transit networks because it is a simple scheme and a less universally popular transportation service. However, the SOS has performance advantages, in that the total trip time can be reduced depending on the number of skipped stations, crowds of passengers can be rapidly evacuated at congested stations in peak periods, and the cost to transit companies is reduced. There is a contradiction between reducing the trip time under the SOS and increasing the passengers' waiting times under an all-stop scheme. Given this situation, the three objectives of our study were to minimize the waiting and trip times of all passengers and the travel times of trains. A comprehensive estimation model is presented for the SOS. The mechanism through which the trip time for all passengers is affected by the SOS is analyzed in detail. A 0-I integer programming formulation is established for the three objectives, and is solved using a tabu search algorithm. Finally, an example is presented to demonstrate that the estimation method for the SOS is capable of optimizing the timetable and operation schemes for a Chinese urban rail transit network.
基金Supported by the National Natural Science Foundation of China(No.50875054)Weihai Science and Technology Development Plan Project(No.2012DXGJ13)
文摘A series-parallel hydraulic hybrid system applied to public buses is put torwaro, ano parameters of key components are analyzed and determined. Energy management strategy based on logic thresh- old is designed which is aimed at efficient operation of the overall system considering the operational characteristic of the components and taking the curves of engine, hydraulic pump/motor and hydrau- lic pump as the main design basis; regenerative control strategy which makes regenerative brake sys- tem and frictional brake system work harmoniously is designed to raise recovery rate of regenerative brake energy. System dynamic modeling and simulation results show that the energy control strategy designed here is able to adapt system to changes of working condition and switch the operating mode reasonably. The regenerative braking control strategy is effective in raising the utilization of energy and improving fuel economy.
基金supported by the National Natural Science Foundation of China under Grant No.51007047
文摘An operation strategy of the electric vehicle (EV) battery charging and swapping station is proposed in the paper. The strategy is established based on comprehensively consideration of the EV charging behaviors and the possible mutual actions between battery charging and swapping. Three energy management strategies can be used in the station: charging period shifting, energy exchange between EVs, and energy supporting from surplus swapping batteries. Then an optimization model which minimizes the total energy management costs of the station is built. The Monte Carlo simulation is applied to analyze the characteristics of the EV battery charging load, and a heuristic algorithm is used to solve the strategy providing the relevant information of EVs and the battery charging and swapping station. The operation strategy can efficiently reduce battery charging during the high electricity price periods and make more reasonable use of the resources. Simulations prove the feasibility and rationality of the strategy.
基金This work was supported by Guangdong Province Key Laboratory of Efficient and Clean Energy Utilization(2013A061401005)by Guangdong Basic and Applied Basic Research Foundation(2020A1515011103)by research fund from Guangzhou Development Group Co.,Ltd.
文摘Gas turbine power units,as an effective way to cope with the severe challenge of renewable energy accommodation in power grids,arouse the interest of power enterprises in the deep peak-load regulation performance.Two common alternative load-control strategies including constant turbine inlet temperature(TIT)and constant turbine exhaust temperature(TET)regulations were taken into consideration.To comparatively investigate the part-load performance under these strategies,both mathematical and physical models were set up successively to serve as a validation and complementary to each other.For the mathematical model of compressor with inlet guide vane(IGV),combustor and turbine,stage-stacking method based on blade average geometric parameter,energy conservation and turbine stage model were adopted respectively.For the physical model,design and off-design analysis were carried out based on GT PRO and THERMOFLEX respectively.The simulation result of mathematical model validated the reliability of the physical model.Based on this,the influence of ambient temperature and different load-regulating strategies on the off-design performance of gas turbine power units was studied in THERMOFLEX.The results in the case of a PG 9351FA gas turbine show that the ambient temperature has a great impact on system performance,i.e.,every 5℃ increase in the ambient temperature produces a reduction of 3.7%in the relative full-load output and 1.1%in the relative efficiency respectively;when the gas turbine operates under constant TIT strategy,TET starts to rise till it reaches the maximum allowable value with the load rate decreasing,and IGV keeps at the minimum angle with both TIT and TET decreasing when the load rate is lower than 65%;when the gas turbine operates under constant TET strategy,TIT drops slightly at load rate of above 60%while both TIT and TET evidently decrease below 60%load rate operating along the constant corrected speed line at the minimum allowable IGV opening;gas turbine effi-ciency is greatly affected by load rate and the performance degradation is more obvious especially in lower load rate regions;constant TET strategy is superior in the operating efficiency to constant TIT strategy under part-load conditions.
基金supported by the National Natural Science Foundation of China(Grant No.51667013)the Research on Scheduling Control Technology of Photothermal Power Generation of The Power System with High Proportion New Energy on The Supply End(Grant No.SGGSKY00FJJS1900273).
文摘This paper proposed a new type of combined cooling heating and power(CCHP)system,including the parabolic trough solar thermal(PTST)power generation and gas turbine power generation.The thermal energy storage subsystem in the PTST unit provides both thermal energy and electrical energy.Based on the life cycle method,the configuration optimization under eight operation strategies is studied with the economy,energy,and environment indicators.The eight operation strategies include FEL,FEL-EC,FEL-TES,FEL-TES&EC,FTL,FTL-EC,FTL-TES,and FTL-TES&EC.The feasibility of each strategy is verified by taking a residential building cluster as an example.The indicators under the optimal configuration of each strategy are compared with that of the separate production(SP)system.The results showed that the PTST-CCHP system improves the environment and energy performance by changing the ratio of thermal energy and electric energy.The environment and energy indicators of FEL-TES&EC are superior to those of FTL-TES&EC in summer,and the results are just the opposite in winter.The initial annual investment of the PTST-CCHP system is higher than that of the SP system,but its economic performance is better than that of the SP system with the increase of life-cycle.
文摘With the progress of new trends of society, gymnasium, the most important part in Chinese sports facility, can not only meet the needs of physical exercise of students, but also provide a favorable place for social welfare development. But due to the influence of traditional management methods, some problems are still seen in the process of operation of university gymnasiums in china, which restricts the overall development of our country's sports enterprise. Therefore, this paper probes into the study on disadvantageous existed conditions and analyzes the operation strategies and management strategies of university gymnasiums on the basis of their characteristics and advantages.
文摘To realize a better automatic train driving operation control strategy for urban rail trains,an automatic train driving method with improved DQN algorithm(classical deep reinforcement learning algorithm)is proposed as a research object.Firstly,the train control model is established by considering the train operation requirements.Secondly,the dueling network and DDQN ideas are introduced to prevent the value function overestimation problem.Finally,the priority experience playback and“restricted speed arrival time”are used to reduce the useless experience utilization.The experiments are carried out to verify the train operation strategy method by simulating the actual line conditions.From the experimental results,the train operation meets the ATO requirements,the energy consumption is 15.75%more energy-efficient than the actual operation,and the algorithm convergence speed is improved by about 37%.The improved DQN method not only enhances the efficiency of the algorithm but also forms a more effective operation strategy than the actual operation,thereby contributing meaningfully to the advancement of automatic train operation intelligence.
基金supported by a Horizontal Project on the Development of a Hybrid Energy Storage Simulation Model for Wind Power Based on an RT-LAB Simulation System(PH2023000190)the Inner Mongolia Natural Science Foundation Project and the Optimization of Exergy Efficiency of a Hybrid Energy Storage System with Crossover Control for Wind Power(2023JQ04).
文摘Present of wind power is sporadically and cannot be utilized as the only fundamental load of energy sources.This paper proposes a wind-solar hybrid energy storage system(HESS)to ensure a stable supply grid for a longer period.A multi-objective genetic algorithm(MOGA)and state of charge(SOC)region division for the batteries are introduced to solve the objective function and configuration of the system capacity,respectively.MATLAB/Simulink was used for simulation test.The optimization results show that for a 0.5 MW wind power and 0.5 MW photovoltaic system,with a combination of a 300 Ah lithium battery,a 200 Ah lead-acid battery,and a water storage tank,the proposed strategy reduces the system construction cost by approximately 18,000 yuan.Additionally,the cycle count of the electrochemical energy storage systemincreases from4515 to 4660,while the depth of discharge decreases from 55.37%to 53.65%,achieving shallow charging and discharging,thereby extending battery life and reducing grid voltage fluctuations significantly.The proposed strategy is a guide for stabilizing the grid connection of wind and solar power generation,capability allocation,and energy management of energy conservation systems.
文摘Background: Laparoscopic cholecystectomy (LC) remains the preferred me-thod for treating benign gallbladder diseases. However, clinical presentations of cholecystitis vary widely. For severely inflamed cases, LC can be challenging. Objectives: This study aimed to explore intraoperative strategies and postoperative management of complications during difficult LC to further enhance its safety. Methods: We retrospectively analyzed data from difficult LC procedures performed by the same expert at our hospital between January 2016 and December 2022. The surgical approach, handling methods, operative time, and postoperative complications were evaluated. Results: Utilizing techniques such as thin-layer progressive dissection, suction and blunt dissection, reverse resection, partial cystectomy, we successfully completed difficult LC in 278 cases. All surgeries were accomplished under laparoscopy. Five cases (0.72%) experienced bile leakage which was managed through drainage tube fistula formation before removal;there were no incidences of hemorrhage, abdominal infection, or biliary tract injury. Conclusion: Our series showed that difficult LC had high safety and low rates of conversion to open surgery and complications. The safety of complex gallbladder removal is related to the surgeon’s experience and proficiency in laparoscopic skills. Postoperative bile leakage can be effectively treated through drainage tube fistula formation.
基金Supported by Hong Kong RGC research grant(613808,614307)Hong Kong PhD Fellowship Scheme for Oyedun Adetoyese Olajire(PF09-05997)the Global Power and Energy Company Limited
文摘The analysis on the feedstock pyrolysis characteristic and the impacts of process parameters on pyrolysis outcomes can assist in the designing,operating and optimizing pyrolysis processes.This work aims to utilize both experimental and modelling approaches to perform the analysis on three biomass feedstocks—wood sawdust,bamboo shred and Jatropha Curcas seed cake residue,and to provide insights for the design and operation of pyrolysis processes.For the experimental part,the study investigated the effect of heating rate,final pyrolysis temperature and sample size on pyrolysis using common thermal analysis techniques.For the modelling part,a transient mathematical model that integrates the feedstock characteristic from the experimental study was used to simulate the pyrolysis progress of selected biomass feedstock particles for reactor scenarios.The model composes of several sub-models that describe pyrolysis kinetic and heat flow,particle heat transfer,particle shrinking and reactor operation.With better understanding of the effects of process conditions and feedstock characteristics on pyrolysis through both experimental and modelling studies,this work discusses on the considerations of and interrelation between feedstock size,pyrolysis energy usage,processing time and product quality for the design and operation of pyrolysis processes.
文摘Porter identifies high market share with cost leadership strategy which is based on the idea of competing on a price lower than that of the competition. However, in most consumer markets a business should serve the middle class by competing in the mid-price segment, offering quality better than that of the competition at a somewhat higher price. It is this path that can lead to market share leadership: a strategy that can be both profitable and sustainable. The U.S. men's shaving cream market consists of two major product-market segments: gel and foam. We test the hypothesis that the best-selling brand is very likely to be a member of the mid-price segment with a price tag that is higher than that of the nearest competition. This study is based on annual U.S. sales data for 2008 and 2007 from discount retail stores, food stores, and drug stores. We performed two separate analyses for 2008 and 2007, using cluster analysis as the main analytic tool. The results were remarkably consistent between the two years. In the gel segment--by far the most important--the price-quality segmentation analysis supported our hypothesis. An interesting finding is that, for both the gel and foam segments, we found the rank order correlation of brand unit price between 2007 and 2008 as highly significant. This means that in this market management considers the price of a brand as a strategic rather than a tactical variable. Although, technically the results for the foam segment were negative, this does not necessarily contradict our hypothesis. Finally, we discovered six strategic groups in the industry and have tried to articulate what their competitive strategy is.
文摘Little by little, we are entering the new era, intelligent interfaces are absorbing us more and more every day, and artificial intelligence makes its presence in a stealthy way. Virtual humans that represent an evolution of autonomous virtual agents;they are computer programs and in the future capable of carrying out different activities in certain environments. They will give the illusion of being human;they will have a body, and they will be immersed in an environment. They will have a set of senses that will allow them: 1) Sensations and therefore associated expressions;2) Communication;3) Learning;4) Remembering events, among others. By integrating the above, they will have a personality and autonomy, so they will be able to plan with respect to objectives;allowing them to decide and take actions with their body, in other words, they will count on awareness. The applications will be focused on environments that they will inhabit, or as interfaces that will interact with other systems. The application domains will be multiple;one of them being education. This article shows the design of OANNA like an avatar with the role of pedagogical agent. It was modeled as an affective-cognitive structure related to the teaching-learning process linked to a pedagogical agent that represents the interface of an artilect. OANNA, has the necessary animations for intervention within the teaching-learning process.
基金Supported by Henan Science and Technology Program(102400440008)Henan Government Decision-making Research IFB Program (B667) .
文摘Based on the development of modem logistics park in China, and with the thought of minimizing carbon emission, the development of Logistics Park was analyzed and the necessity of developing low carbon Logistics Park was proposed. Low carbon emission in Logistics Park was planned. In the end, operation and implementation strategies of low carbon parks were put forward so as to create favorable environment for the re- alization of low carbon emission in Logistics Park.
文摘The growth of international banks in China occurred after the "open-door" policy implemented. With the China accession to WTO, the effect of international banks to our economy and politics become more important. If international banks want to succeed in China over the next ten years so that the market as a whole develops and matures, they need the Chinese banks to be successful in their restructuring program. There is truly a win-win outcome here if all segments of the banking community recognize the benefit of improving the competitiveness of the Chinese banking industry as a whole. This article analyzes the pattern and strategy of expansion of international banks in China, for the purpose of showing some enlightenment to domestic banks.
文摘The topic investigated competition in marketing as a survival yardstick for small and medium enterprises (SMEs) in Nigeria. The objectives addressed by this study were: (1) identifying different types and intensity of competition that SMEs are exposed to along the life-cycle portfolio in Nigeria; (2) quantifying the strength of SMEs vis-a-vis some foreign enterprises in terms of market competition; and (3) proffering solutions on how best they could match competitively these foreign enterprises. Relevant models and theories were employed in literature to evolve detailed analysis of issues relating to the variables used in terms of competition in marketing and survival of juice-producing SMEs. Two hypotheses were investigated through the survey of 20 prominent Ikeja based SMEs using Cluster sampling, 5-points Likert summated rating scale was adopted, while Yard's formula with 95% confidence level and 5% error tolerance was used. Alternative form validity of the instrument was measured at 0.63 while its reliability was measured at Cronbach's alpha of 0.70. Pearson's product-moment correlation was used in testing hypothesis 1 while standard multiple regressions were used to test hypothesis 2. Findings revealed that there was strong relationship between survival of juice-producing SMEs with forms of competition on a firm's life-cycle; while competition had positive effects on survival components for the enterprises. It was concluded that since competition subsists in any firm's life-cycle, strategies to support operations for survival must be adopted. It was recommended that operators of SMEs have to monitor and manage competition as it affects their businesses positively and/or negatively.