开发Java Web项目中发现服务之间的调用存在超时情况,由于涉及的处理逻辑全部是异步,引入定时重试的机制,重试工具选择了JDK自带的Scheduled Thread Pool Executor。当A服务依赖B服务,B服务由于在业务高峰期处理能力降低,导致大量A服务...开发Java Web项目中发现服务之间的调用存在超时情况,由于涉及的处理逻辑全部是异步,引入定时重试的机制,重试工具选择了JDK自带的Scheduled Thread Pool Executor。当A服务依赖B服务,B服务由于在业务高峰期处理能力降低,导致大量A服务过来的请求超时,A加入了超时重试机制,间隔时间根据重试次数的多少来决定,次数越多,两次重试之间间隔的时间越多,此时的业务高峰也会给A带来大量请求,大量的超时会导致重试队列迅速堆积,直到内存溢出。该文从线程池工作机制、Scheduled Thread Pool Executor实例的创建,获取重试任务的过程以及提交任务的过程角度分析,并通过源代码的剖析和测试工具My Eclipse进行演示测试内存泄露的情况,得出避免内存泄露的解决方案。展开更多
In order to provide the guideline for bus drivers to adjust speed to minimize scheduled deviation,the method for setting bus scheduled travel time is proposed. Firstly,multistate model is introduced to fit historical ...In order to provide the guideline for bus drivers to adjust speed to minimize scheduled deviation,the method for setting bus scheduled travel time is proposed. Firstly,multistate model is introduced to fit historical travel time data and identify different service states. Based on the calibrated travel time distribution parameters,an optimization model is proposed,followed by a Monte Carlo( MC) simulation based genetic algorithm( GA)procedure to obtain the optimal scheduled time. A case study from a fixed bus route from Shenzhen is used to demonstrate the model applicability. The sensitivity analysis is conducted to study the effects of parameters setting on optimal slack time for each segment. The results show that multistate model fits travel time under peak hours better than Lognormal distribution,and the length of scheduled travel time basically reflects travel time reliability.展开更多
Objective: To explore a new way for developing the human umbilical cord blood (CB) engraftment with high efficiency and in further understand the homing potentiality of hematopoietic stein/progenitor cells (HSC/HPC). ...Objective: To explore a new way for developing the human umbilical cord blood (CB) engraftment with high efficiency and in further understand the homing potentiality of hematopoietic stein/progenitor cells (HSC/HPC). Method: Sub-lethally irradiated severe combined immunodeficient (SCID) mice were transplanted i. v. with CB which was cryopre- served at - 80℃. Human cells in recipient mice were detected by flow cytometry and CFU-GM assay for each host organ. Results: In contrast with the single transplantation, scheduled engraftment of the identical numbers of CB cells resulted in an obvious increase of CD45+ and CD34+ cells produced in SCID mouse bone marrow (BM). While the donor cells were reduced by 5 times, the similar reconstitution of both hematopoietic fumctions and part of immunologic fumctions was ob- tained.Conclusion:Scheduled engraftment can improve repopulating of the HSC, which provides a novel way for clinical cord blood engraftment into adults.展开更多
Transmission line manipulations in a power system are necessary for the execution of preventative or corrective main- tenance in a network, thus ensuring the stability of the system. In this study, primal-dual interio...Transmission line manipulations in a power system are necessary for the execution of preventative or corrective main- tenance in a network, thus ensuring the stability of the system. In this study, primal-dual interior-point methods are used to minimize costs and losses in the generation and transmission of the predispatch active power flow in a hydroelectric system with previously scheduled line manipulations for preventative maintenance, over a period of twenty-four hours. The matrix structure of this problem and the modification that it imposes on the system is also broached in this study. From the computational standpoint, the effort required to solve a problem with or without line manipulations is similar, and the reasons for this are also discussed in this study. Computational results sustain our findings.展开更多
This paper proposes a gain scheduled control method for a doubly fed induction generator driven by a wind turbine. The purpose is to design a variable speed control system so as to extract the maximum power in the reg...This paper proposes a gain scheduled control method for a doubly fed induction generator driven by a wind turbine. The purpose is to design a variable speed control system so as to extract the maximum power in the region below the rated wind speed. Gain scheduled control approach is applied in order to achieve high performance over a wide range of wind speed. A double loop configuration is adopted. In the inner loop, the rotor speed is used as the scheduling parameter, while a function of wind and rotor speed is used as the scheduling parameter in the outer loop. It is verified in simulations that a high tracking performance has been achieved.展开更多
China will begin accrediting its own innovative products from this year. It plans to complete the Catalog of China's Independent Innovation Products by 2007 for future reference of government procurement. The ... China will begin accrediting its own innovative products from this year. It plans to complete the Catalog of China's Independent Innovation Products by 2007 for future reference of government procurement. The products in the catalog shall enjoy preferential policies.……展开更多
Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in t...Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in the project were given official notice that both sides should start to implement the contracts. "The move marked a significant step forward in the project’s construction," said Zeng Wenxing, General Manager of Ling’ ao Nuclear Power Co Ltd, set up in展开更多
A year from now, dam builders will have blocked the mighty Yangtze River at the Three Gorges, marking the start of the second phase of the gigantic water harnessing and developing scheme.
The oil and gas (O&G) industry on the Norwegian continental shelf (NCS) leads the world in terms of the number of subsea O&G installations. Ensuring the dependability of these assets is critical. Non-intrusive i...The oil and gas (O&G) industry on the Norwegian continental shelf (NCS) leads the world in terms of the number of subsea O&G installations. Ensuring the dependability of these assets is critical. Non-intrusive inspection, maintenance and repair (IMR) services are therefore needed to reduce risks. These services are planned and executed using a mono-hull offshore vessel complete with remotely operated vehicles (ROVs), a module handling system and an active heave compensated crane. Vessel time is shared between competing jobs, using a prioritized forward-looking schedule. Extension in planned job duration may have an impact on O&G production, service costs and health, safety, and environmental (HSE) risks. This paper maps factors influencing the job schedule efficiency. The influence factors are identified through reviews of literature as well as interviews with experts in one of the large IMR subsea service providers active on the Norwegian Continental Shelf. The findings show that the most obvious factors are weather disruption and water depth. Other factors include job complexity, job uncertainty, IMR equipment availability, as well as the mix of job complexity.展开更多
The Organizing Committee of the Wuhan Marathon announced on Feb.2 that the 2023 Wuhan Marathon will start at 7:30 a.m.on April 16 in front of Wuhan Science and Technology Museum.A total of 26,000 runners will take par...The Organizing Committee of the Wuhan Marathon announced on Feb.2 that the 2023 Wuhan Marathon will start at 7:30 a.m.on April 16 in front of Wuhan Science and Technology Museum.A total of 26,000 runners will take part in this year's event.It will be divided into three groups,specifically,the full marathon of 42.195 km for 8,000 runners,the half marathon of 21.0975 km for 10,000 runners,and the 13-km run for 8,000 people.展开更多
This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performanc...This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performance was attributed to multiple disturbances and uncertainties and the presence of hidden coupling terms,giving rise to a miss distance of greater than 20 m.To address these issues,the missile dynamics are decomposed into the angular rate dynamics as fast and the acceleration dynamics as slow subsystem using the singular perturbation theory to analyze a multi-time-scale property.Multifrequency extended state observers are then incorporated into the gain scheduling technique to attenuate disturbances,thus enhancing the control performance significantly.In the proposed engineering/practical design framework for missile autopilot,simple,conventional,and explicit tuning rules are provided.And the proposed control scheme can achieve input-to-state stability across the entire flight envelope under unknown but bounded disturbances.The advantages of the method over existing benchmark approaches are shown through nonlinear numerical simulations.This is supported by evidence from a new flight test result with a miss distance of only 2 m.展开更多
Introduction: The end of pregnancy is a high-risk period for both mother and foetus. Rigorous monitoring can prevent complications before delivery. Materials and Method: We conducted a descriptive cross-sectional obse...Introduction: The end of pregnancy is a high-risk period for both mother and foetus. Rigorous monitoring can prevent complications before delivery. Materials and Method: We conducted a descriptive cross-sectional observational study. It took place in the delivery room of the Teacher hospital Mother and Child of Jeanne Ebori Fondation from the 01 October 2020 to 01 October 2021. All patients followed at the Functional Investigation Centre (FIC) of the CHUMEFJE and who gave birth in that same hospital were included. Data were collected on the basis of pregnancy diaries, the fic register and delivery room registers. They were analysed using SPSS Statistical Software. Results: During the period of our study, 4086 parturients arrived in the delivery room. Of these, 150 were followed up at the FIC, giving a prevalence of 3.7%. The majority of parturients (48%) had only one prenatal contact. 6 (4%) patients underwent pelvic scans, and 4 (2.6%) presented with a narrowed pelvis. A vaginal delivery was performed in 80% of cases, and of the caesarean sections, 9 (30%) could be scheduled. The maternal prognosis was marred by one post-partum complication of hypertension, and newborns with poor adaptation to life outside the womb accounted for 3.3% of cases. Conclusion: The Functional Investigation Centre makes it possible to detect anomalies at the end of pregnancy with a view to better planning of delivery.展开更多
BEIJING,March 12(Xinhua)——China′s development of both 4⁃meter⁃diameter and 5⁃meter⁃diameter reusable rockets is being accelerated,with their inaugural flights scheduled for 2025 and 2026,respectively.The manufactur...BEIJING,March 12(Xinhua)——China′s development of both 4⁃meter⁃diameter and 5⁃meter⁃diameter reusable rockets is being accelerated,with their inaugural flights scheduled for 2025 and 2026,respectively.The manufacturing of these two new large reusable launching vehicle models is a response to growing demand in the commercial space market,said the China Aerospace Science and Technology Corporation.展开更多
Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintena...Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.展开更多
Systems with large operating regions and non-zero state target tracking have limited the industrial application of robust model predictive control (RMPC) with synthetic action. To overcome the problem, this paper pres...Systems with large operating regions and non-zero state target tracking have limited the industrial application of robust model predictive control (RMPC) with synthetic action. To overcome the problem, this paper presents a novel formulation of synthesizing scheduled RMPC for linear time varying (LTV) systems. Off-line, we compute the matrix that transforms target output into steady state first. Then a set of stabilizing state feedback laws which are corresponding to a set of estimated regions of stability covering the desired operating region are provided. On-line, these control laws are implemented as a single scheduled state feedback model predictive control (MPC) which switches between the set of local controllers and achieve the desired target at last. Finally, the algorithm is illustrated with an example.展开更多
Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the comple...Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the completion time,thus improving the loading and unloading efficiencies of automated container terminals.The proposed model integrated the two loading and unloading processes of“double-trolley quay crane+AGV+ARMG”and“single-trolley quay crane+container truck+ARMG”and then designed the simulated annealing particle swarm algorithm to solve the model.By comparing the results of the particle swarm algorithm and genetic algorithm,the algorithm designed in this paper could effectively improve the global and local space search capability of finding the optimal solution.Furthermore,the results showed that the proposed method of collaborative scheduling of multiple equipment resources in automated terminals considering hybrid processes effectively improved the loading and unloading efficiencies of automated container terminals.The findings of this study provide a reference for the improvement of loading and unloading processes as well as coordinated scheduling in automated terminals.展开更多
文摘开发Java Web项目中发现服务之间的调用存在超时情况,由于涉及的处理逻辑全部是异步,引入定时重试的机制,重试工具选择了JDK自带的Scheduled Thread Pool Executor。当A服务依赖B服务,B服务由于在业务高峰期处理能力降低,导致大量A服务过来的请求超时,A加入了超时重试机制,间隔时间根据重试次数的多少来决定,次数越多,两次重试之间间隔的时间越多,此时的业务高峰也会给A带来大量请求,大量的超时会导致重试队列迅速堆积,直到内存溢出。该文从线程池工作机制、Scheduled Thread Pool Executor实例的创建,获取重试任务的过程以及提交任务的过程角度分析,并通过源代码的剖析和测试工具My Eclipse进行演示测试内存泄露的情况,得出避免内存泄露的解决方案。
基金Sponsored by the National Natural Science Foundation of China(Grant No.71101109)Key Project of Shanghai Soft Science Research Program(Grant No.15692105400)Humanities and Social Sciences Program of the Ministry of Education,China(Grant No.15YJCZH148)
文摘In order to provide the guideline for bus drivers to adjust speed to minimize scheduled deviation,the method for setting bus scheduled travel time is proposed. Firstly,multistate model is introduced to fit historical travel time data and identify different service states. Based on the calibrated travel time distribution parameters,an optimization model is proposed,followed by a Monte Carlo( MC) simulation based genetic algorithm( GA)procedure to obtain the optimal scheduled time. A case study from a fixed bus route from Shenzhen is used to demonstrate the model applicability. The sensitivity analysis is conducted to study the effects of parameters setting on optimal slack time for each segment. The results show that multistate model fits travel time under peak hours better than Lognormal distribution,and the length of scheduled travel time basically reflects travel time reliability.
基金upported by National Natural Science Foundation of China, No. 39770329
文摘Objective: To explore a new way for developing the human umbilical cord blood (CB) engraftment with high efficiency and in further understand the homing potentiality of hematopoietic stein/progenitor cells (HSC/HPC). Method: Sub-lethally irradiated severe combined immunodeficient (SCID) mice were transplanted i. v. with CB which was cryopre- served at - 80℃. Human cells in recipient mice were detected by flow cytometry and CFU-GM assay for each host organ. Results: In contrast with the single transplantation, scheduled engraftment of the identical numbers of CB cells resulted in an obvious increase of CD45+ and CD34+ cells produced in SCID mouse bone marrow (BM). While the donor cells were reduced by 5 times, the similar reconstitution of both hematopoietic fumctions and part of immunologic fumctions was ob- tained.Conclusion:Scheduled engraftment can improve repopulating of the HSC, which provides a novel way for clinical cord blood engraftment into adults.
文摘Transmission line manipulations in a power system are necessary for the execution of preventative or corrective main- tenance in a network, thus ensuring the stability of the system. In this study, primal-dual interior-point methods are used to minimize costs and losses in the generation and transmission of the predispatch active power flow in a hydroelectric system with previously scheduled line manipulations for preventative maintenance, over a period of twenty-four hours. The matrix structure of this problem and the modification that it imposes on the system is also broached in this study. From the computational standpoint, the effort required to solve a problem with or without line manipulations is similar, and the reasons for this are also discussed in this study. Computational results sustain our findings.
文摘This paper proposes a gain scheduled control method for a doubly fed induction generator driven by a wind turbine. The purpose is to design a variable speed control system so as to extract the maximum power in the region below the rated wind speed. Gain scheduled control approach is applied in order to achieve high performance over a wide range of wind speed. A double loop configuration is adopted. In the inner loop, the rotor speed is used as the scheduling parameter, while a function of wind and rotor speed is used as the scheduling parameter in the outer loop. It is verified in simulations that a high tracking performance has been achieved.
文摘 China will begin accrediting its own innovative products from this year. It plans to complete the Catalog of China's Independent Innovation Products by 2007 for future reference of government procurement. The products in the catalog shall enjoy preferential policies.……
文摘Construction of Ling’ao Nuclear Power Plant in Guangdong Province, the country’s second-largest nuclear power project between 1996-2000, chalked up notable progress this year. On July, 15, all foreign suppliers in the project were given official notice that both sides should start to implement the contracts. "The move marked a significant step forward in the project’s construction," said Zeng Wenxing, General Manager of Ling’ ao Nuclear Power Co Ltd, set up in
文摘A year from now, dam builders will have blocked the mighty Yangtze River at the Three Gorges, marking the start of the second phase of the gigantic water harnessing and developing scheme.
文摘The oil and gas (O&G) industry on the Norwegian continental shelf (NCS) leads the world in terms of the number of subsea O&G installations. Ensuring the dependability of these assets is critical. Non-intrusive inspection, maintenance and repair (IMR) services are therefore needed to reduce risks. These services are planned and executed using a mono-hull offshore vessel complete with remotely operated vehicles (ROVs), a module handling system and an active heave compensated crane. Vessel time is shared between competing jobs, using a prioritized forward-looking schedule. Extension in planned job duration may have an impact on O&G production, service costs and health, safety, and environmental (HSE) risks. This paper maps factors influencing the job schedule efficiency. The influence factors are identified through reviews of literature as well as interviews with experts in one of the large IMR subsea service providers active on the Norwegian Continental Shelf. The findings show that the most obvious factors are weather disruption and water depth. Other factors include job complexity, job uncertainty, IMR equipment availability, as well as the mix of job complexity.
文摘The Organizing Committee of the Wuhan Marathon announced on Feb.2 that the 2023 Wuhan Marathon will start at 7:30 a.m.on April 16 in front of Wuhan Science and Technology Museum.A total of 26,000 runners will take part in this year's event.It will be divided into three groups,specifically,the full marathon of 42.195 km for 8,000 runners,the half marathon of 21.0975 km for 10,000 runners,and the 13-km run for 8,000 people.
基金the support of the National Natural Science Foundation of China(No.U21B6003)。
文摘This paper describes the design and implementation of a three-axis acceleration control autopilot for an asymmetric tail-controlled,skid-to-turn tactical missile.In an earlier flight test,degraded autopilot performance was attributed to multiple disturbances and uncertainties and the presence of hidden coupling terms,giving rise to a miss distance of greater than 20 m.To address these issues,the missile dynamics are decomposed into the angular rate dynamics as fast and the acceleration dynamics as slow subsystem using the singular perturbation theory to analyze a multi-time-scale property.Multifrequency extended state observers are then incorporated into the gain scheduling technique to attenuate disturbances,thus enhancing the control performance significantly.In the proposed engineering/practical design framework for missile autopilot,simple,conventional,and explicit tuning rules are provided.And the proposed control scheme can achieve input-to-state stability across the entire flight envelope under unknown but bounded disturbances.The advantages of the method over existing benchmark approaches are shown through nonlinear numerical simulations.This is supported by evidence from a new flight test result with a miss distance of only 2 m.
文摘Introduction: The end of pregnancy is a high-risk period for both mother and foetus. Rigorous monitoring can prevent complications before delivery. Materials and Method: We conducted a descriptive cross-sectional observational study. It took place in the delivery room of the Teacher hospital Mother and Child of Jeanne Ebori Fondation from the 01 October 2020 to 01 October 2021. All patients followed at the Functional Investigation Centre (FIC) of the CHUMEFJE and who gave birth in that same hospital were included. Data were collected on the basis of pregnancy diaries, the fic register and delivery room registers. They were analysed using SPSS Statistical Software. Results: During the period of our study, 4086 parturients arrived in the delivery room. Of these, 150 were followed up at the FIC, giving a prevalence of 3.7%. The majority of parturients (48%) had only one prenatal contact. 6 (4%) patients underwent pelvic scans, and 4 (2.6%) presented with a narrowed pelvis. A vaginal delivery was performed in 80% of cases, and of the caesarean sections, 9 (30%) could be scheduled. The maternal prognosis was marred by one post-partum complication of hypertension, and newborns with poor adaptation to life outside the womb accounted for 3.3% of cases. Conclusion: The Functional Investigation Centre makes it possible to detect anomalies at the end of pregnancy with a view to better planning of delivery.
文摘BEIJING,March 12(Xinhua)——China′s development of both 4⁃meter⁃diameter and 5⁃meter⁃diameter reusable rockets is being accelerated,with their inaugural flights scheduled for 2025 and 2026,respectively.The manufacturing of these two new large reusable launching vehicle models is a response to growing demand in the commercial space market,said the China Aerospace Science and Technology Corporation.
基金supported by the National Defence Preresearch Foundation of China(Nos.51327020105,51304010206)
文摘Servicing is applied periodically in practice with the aim of restoring the system state and prolonging the lifetime. It is generally seen as an imperfect maintenance action which has a chief influence on the maintenance strategy. In order to model the maintenance effect of servicing, this study analyzes the deterioration characteristics of system under scheduled servicing. And then the deterioration model is established from the failure mechanism by compound Poisson process. On the basis of the system damage value and failure mechanism, the failure rate refresh factor is proposed to describe the maintenance effect of servicing. A maintenance strategy is developed which combines the benefits of scheduled servicing and preventive maintenance. Then the optimization model is given to determine the optimal servicing period and preventive maintenance time, with an objective to minimize the system expected life-cycle cost per unit time and a constraint on system survival probability for the duration of mission time. Subject to mission time, it can control the ability of accomplishing the mission at any time so as to ensure the high dependability. An example of water pump rotor relating to scheduled servicing is introduced to illustrate the failure rate refresh factor and the proposed maintenance strategy. Compared with traditional methods, the numerical results show that the failure rate refresh factor can describe the maintenance effect of servicing more intuitively and objectively. It also demonstrates that this maintenance strategy can prolong the lifetime, reduce the total lifetime maintenance cost and guarantee the dependability of system.
文摘Systems with large operating regions and non-zero state target tracking have limited the industrial application of robust model predictive control (RMPC) with synthetic action. To overcome the problem, this paper presents a novel formulation of synthesizing scheduled RMPC for linear time varying (LTV) systems. Off-line, we compute the matrix that transforms target output into steady state first. Then a set of stabilizing state feedback laws which are corresponding to a set of estimated regions of stability covering the desired operating region are provided. On-line, these control laws are implemented as a single scheduled state feedback model predictive control (MPC) which switches between the set of local controllers and achieve the desired target at last. Finally, the algorithm is illustrated with an example.
基金supported by the National Key R&D Program of China(Grant No.2017YFC0805309)Natural Science Foundation of Fujian Province(Grant No.2021J01820)Department of Education of Fujian Province Project(Grant Nos.JAT190294 and JAT210230).
文摘Considering the uncertainty of the speed of horizontal transportation equipment,a cooperative scheduling model of multiple equipment resources in the automated container terminal was constructed to minimize the completion time,thus improving the loading and unloading efficiencies of automated container terminals.The proposed model integrated the two loading and unloading processes of“double-trolley quay crane+AGV+ARMG”and“single-trolley quay crane+container truck+ARMG”and then designed the simulated annealing particle swarm algorithm to solve the model.By comparing the results of the particle swarm algorithm and genetic algorithm,the algorithm designed in this paper could effectively improve the global and local space search capability of finding the optimal solution.Furthermore,the results showed that the proposed method of collaborative scheduling of multiple equipment resources in automated terminals considering hybrid processes effectively improved the loading and unloading efficiencies of automated container terminals.The findings of this study provide a reference for the improvement of loading and unloading processes as well as coordinated scheduling in automated terminals.