In this paper, a fast approach to generate time optimal and smooth trajectory has been developed and tested. Minimum time is critical for the productivity in industrial applications. Meanwhile, smooth trajectories bas...In this paper, a fast approach to generate time optimal and smooth trajectory has been developed and tested. Minimum time is critical for the productivity in industrial applications. Meanwhile, smooth trajectories based on cubic splines are desirable for their ability to limit vibrations and ensure the continuity of position, velocity and acceleration during the robot movement. The main feature of the approach is a satisfactory solution that can be obtained by a local modification process among each intermal between two consecutive via-points. An analytical formulation simplifies the approach to smooth trajectory and few,iterations are enough to determine the correct values. The approach can be applied in many robot manipulators which require high performance on time and smooth. The simulation and application of the approach on a palletizer robot are performed, and the experimental results provide evidence that the approach can realize the robot manipulators more efficiency and high smooth performance.展开更多
The time optimal problem for a two level quantum sys-tem is studied. We compare two different control strategies of bang-bang control and the geometric control, respectively, es-pecial y in the case of minimizing the ...The time optimal problem for a two level quantum sys-tem is studied. We compare two different control strategies of bang-bang control and the geometric control, respectively, es-pecial y in the case of minimizing the time of steering the state from North Pole to South Pole on the Bloch sphere with bounded control. The time performances are compared for different param-eters by the individual numerical simulation experiments, and the experimental results are analyzed. The results show that the ge-ometric control spends less time than the bang-bang control does.展开更多
Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for ...Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for impulse effects. Firstly, to address the inequality constraints,the penalty method is introduced. Then, a novel optimization strategy is developed, which only requires that the team objective function be strongly convex.展开更多
BACKGROUND Bile duct leaks(BDLs)are serious postsurgical adverse events.Typically,conservative management with ab-dominal drainage is the initial treatment option.However,prolonged abdominal drainage without improveme...BACKGROUND Bile duct leaks(BDLs)are serious postsurgical adverse events.Typically,conservative management with ab-dominal drainage is the initial treatment option.However,prolonged abdominal drainage without improvement can lead to biliary stricture and delay the optimal timing of endoscopic retrograde cholangiopancreatography(ERCP).AIM To identify the optimal timing for ERCP and the period during which clinical observation with conservative management is acceptable,balancing ERCP success and the risk of biliary strictures.METHODS We conducted a multicenter retrospective study involving 448 patients with BDLs between November 2002 and November 2022.The patients were divided into four groups based on the timing of ERCP:3 days,7 days,14 days,and 21 days.The primary outcome was clinical success,defined as the resolution of BDL and related symptoms within 6 months without additional percutaneous drainage,surgery,or death.The secondary outcome was incidence of biliary strictures.Univariate and multivariate logistic regression analyses were performed to identify factors associated with ERCP success and biliary stricture occurrence.RESULTS In a cohort of 448 consecutive patients diagnosed with BDLs,354 were excluded,leaving 94 patients who underwent ERCP.Clinical success was achieved in 84%of cases(79/94),with a median ERCP timing of 20 days(9.5-35.3 days).Biliary strictures were identified in 29(30.9%)patients.Performing ERCP within 3 weeks,compared to after 3 weeks,was associated with higher success rates[92.0%(46/50)vs 75.0%(33/44),P=0.032]and a lower incidence of biliary stricture incidence[18.0%(9/50)vs 45.5%(20/44),P=0.005].Subsequent multivariate analysis confirmed the association with higher success rates(odds ratio=4.168,P=0.045)and lower biliary stricture rates(odds ratio=0.256,P=0.007).CONCLUSION Performing ERCP for BDLs within 3 weeks may be associated with a higher success rate and a lower biliary stricture rate.If patients with BDLs do not respond to conservative treatment,ERCP is suggested to be performed within 3 weeks.展开更多
In this study,we construct a bi-level optimization model based on the Stackelberg game and propose a robust optimization algorithm for solving the bi-level model,assuming an actual situation with several participants ...In this study,we construct a bi-level optimization model based on the Stackelberg game and propose a robust optimization algorithm for solving the bi-level model,assuming an actual situation with several participants in energy trading.Firstly,the energy trading process is analyzed between each subject based on the establishment of the operation framework of multi-agent participation in energy trading.Secondly,the optimal operation model of each energy trading agent is established to develop a bi-level game model including each energy participant.Finally,a combination algorithm of improved robust optimization over time(ROOT)and CPLEX is proposed to solve the established game model.The experimental results indicate that under different fitness thresholds,the robust optimization results of the proposed algorithm are increased by 56.91%and 68.54%,respectively.The established bi-level game model effectively balances the benefits of different energy trading entities.The proposed algorithm proposed can increase the income of each participant in the game by an average of 8.59%.展开更多
As mobile edge computing continues to develop,the demand for resource-intensive applications is steadily increasing,placing a significant strain on edge nodes.These nodes are normally subject to various constraints,fo...As mobile edge computing continues to develop,the demand for resource-intensive applications is steadily increasing,placing a significant strain on edge nodes.These nodes are normally subject to various constraints,for instance,limited processing capability,a few energy sources,and erratic availability being some of the common ones.Correspondingly,these problems require an effective task allocation algorithmto optimize the resources through continued high system performance and dependability in dynamic environments.This paper proposes an improved Particle Swarm Optimization technique,known as IPSO,for multi-objective optimization in edge computing to overcome these issues.To this end,the IPSO algorithm tries to make a trade-off between two important objectives,which are energy consumption minimization and task execution time reduction.Because of global optimal position mutation and dynamic adjustment to inertia weight,the proposed optimization algorithm can effectively distribute tasks among edge nodes.As a result,it reduces the execution time of tasks and energy consumption.In comparative assessments carried out by IPSO with benchmark methods such as Energy-aware Double-fitness Particle Swarm Optimization(EADPSO)and ICBA,IPSO provides better results than these algorithms.For the maximum task size,when compared with the benchmark methods,IPSO reduces the execution time by 17.1%and energy consumption by 31.58%.These results allow the conclusion that IPSO is an efficient and scalable technique for task allocation at the edge environment.It provides peak efficiency while handling scarce resources and variable workloads.展开更多
In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to const...In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to constraints about the axis velocities and accelerations,when the tracking error satisfies a second order linear ordinary differential equation.Based on this simplification on the tracking error,the original feedrate generation problem is reduced to a new form which can be efficiently solved with linear programming algorithms.Simulation results are used to validate the methods.展开更多
We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum t...We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum time required to steer the system from an initial state to a specified final state.As applications the minimal time to implement Controlled-NOT gate,SWAP gate and Controlled-U gate is calculated in detail.The experimental realizations of these quantum gates are explicitly presented.展开更多
In this paper, we establish a bang-bang principle of time optimal controls for a controlled parabolic equation of fractional order evolved in a bounded domain Ω of R^n, with a controller w to be any given nonempty op...In this paper, we establish a bang-bang principle of time optimal controls for a controlled parabolic equation of fractional order evolved in a bounded domain Ω of R^n, with a controller w to be any given nonempty open subset of Ω. The problem is reduced to a new controllability property for this equation, i.e. the null controllability of the system at any given time T 〉 0 when the control is restricted to be active in ω× E, where E is any given subset of [0, T] with positive （Legesgue） measure. The desired controllability result is established by means of a sharp observability estimate on the eigenfunctions of the Dirichlet Laplacian due to Lebeau and Robbiano, and a delicate result in the measure theory due to Lions.展开更多
We present in this paper a survey of recent results on the relation between time and norm optimality for linear systems and the infinite dimensional version of Pontryagin＇s maximum principle. In particular, we discus...We present in this paper a survey of recent results on the relation between time and norm optimality for linear systems and the infinite dimensional version of Pontryagin＇s maximum principle. In particular, we discuss optimality （or nonoptimality） of singular controls satisfying the maximum principle and smoothness of the costate in function of smoothness of the target.展开更多
In this paper, a class of time optimal problem with impluse control is considered. Under certain conditions we prove that the optimal impluse control exists and its impluse number is finite. Moreover, it is proved tha...In this paper, a class of time optimal problem with impluse control is considered. Under certain conditions we prove that the optimal impluse control exists and its impluse number is finite. Moreover, it is proved that the minimum time function is locally Lipschitz continuous in its domain and is the unique viscosity solution of the corresponding Hamilton-Jacobi-Bellman system.展开更多
While many controlled irrigation and drainage techniques have been adopted in China, the environmental effects of these techniques require further investigation. This study was conducted to examine the changes of nitr...While many controlled irrigation and drainage techniques have been adopted in China, the environmental effects of these techniques require further investigation. This study was conducted to examine the changes of nitrogen and phosphorus of a flooded paddy water system after fertilizer application and at each growth stage so as to obtain the optimal drainage time at each growth stage. Four treatments with different water level management methods at each growth stage were conducted under the condition of ten-day continuous flooding. Results show that the ammonia nitrogen （ NH4-N ） concentration reached the peak value once the fertilizer was applied, and then decreased to a relatively low level seven to ten days later, and that the nitrate nitrogen （NO^-N） concentration gradually rose to its peak value, which appeared later in subsurface water than in surface water. Continuous flooding could effectively reduce the concentrations of NH^-N , NO3-N, and total phosphorus （TP） in surface water. However, the paddy water disturbance, in the process of soil surface adsorption and nitrification, caused NH]-N to be released and increased the concentrations of NH4-N and NO^-N in surface water. A multi-objective controlled drainage model based on environmental factors was established in order to obtain the optimal drainage time at each growth stage and better guide the drainage practices of farmers. The optimal times for surface drainage are the fourth, sixth, fifth, and sixth days after flooding at the tillering, jointing-booting, heading-flowering, and milking stages, respectively.展开更多
As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for ach...As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for achieving high controlling precision is to search for an appropriate time delay.This paper proposes a simple yet effective approach,based on incremental harmonic balance method,to determine the optimal time delay in the delayed feedback controller.The time delay is adjusted within the iterative scheme provided by the proposed method,and finally converges to the period of the target UPO.As long as the optimal time delay is fixed,moreover,the attained solution makes it quite convenient to analyze its stability according to the Floquet theory,which further provides the effective interval of the feedback gain.展开更多
By assay of accelerated aging germination, germination index, vigor index, seedling length, seedling weight, electric conductivity, dehydrogenase activity, ATP content and acid phosphoesterase activity during seed dev...By assay of accelerated aging germination, germination index, vigor index, seedling length, seedling weight, electric conductivity, dehydrogenase activity, ATP content and acid phosphoesterase activity during seed development of turf-type tall fescue, the seed vigor of tall fescue were studied. Combining with seed moisture content and yield, the optimal harvesting time of tall fescue was determined. The results indicated that the seed vigor increased continuously along with seed maturity, and the higher seed vigor was achieved at 19th day after perk anthesis and maintained continuously until 31st day after peak anthesis. At 25th day after peak anthesis, the highest yield of 3 533 kg ha-1 and the good quality of seeds of tall fescue were harvested with 32.19% moisture content. From 22nd to 31st day after peak anthesis, the seed yield of 3 300 kg ha-1 and the good quality seeds of tall fescue were harvested with 40 - 12. 43% moisture content, and the span was the optimal harvesting time.展开更多
Gestational diabetes mellitus(GDM)is a common pregnancy complication strongly associated with poor maternal-fetal outcomes.Its incidence and prevalence have been increasing in recent years.Women with GDM typically giv...Gestational diabetes mellitus(GDM)is a common pregnancy complication strongly associated with poor maternal-fetal outcomes.Its incidence and prevalence have been increasing in recent years.Women with GDM typically give birth through either vaginal delivery or cesarean section,and the maternal-fetal outcomes are related to several factors such as cervical level,fetal lung maturity,the level of glycemic control still present,and the mode of treatment for the condition.We categorized women with GDM based on the latter two factors.GDM that is managed without medication when it is responsive to nutrition-and exercise-based therapy is considered diet-and exercise-controlled GDM,or class A1 GDM,and GDM managed with medication to achieve adequate glycemic control is considered class A2 GDM.The remaining cases in which neither medical nor nutritional treatment can control glucose levels or patients who do not control their blood sugar are categorized as class A3 GDM.We investigated the optimal time of delivery for women with GDM according to the classification of the condition.This review aimed to address the benefits and harms of giving birth at different weeks of gestation for women with different classes of GDM and attempted to provide an analytical framework and clearer advice on the optimal time for labor.展开更多
In order to study the diurnal variation of soil CO2 effiux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO2 flux s...In order to study the diurnal variation of soil CO2 effiux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO2 flux system under five typical plant communi- ties （Suaeda glauca （Sg）, Chloris virgata （Cv）, Puecinellia distans （Pd）, Leymus chinensis （Lc） and Phragmites australis （Pa）） and an alkali-spot land （As） at the meadow steppe of western Songnen Plain. The results showed that the diurnal variation of soil CO2 effiux exhibited a single peak curve in the growing season. Diurnal maximum soil respiration （Rs） often appeared between 1 1：00 and 13：00, while the minimum occurred at 21：00-23：00 or before dawn. Air temperature near the soil surface （Ta） and soil temperature at 10 cm depth （Tlo） exerted dominant control on the diurnal variations of soil respiration. The time-windows 7：00-9：00 could be used as the optimal measuring time to represent the daily mean soil CO2 effiux at the Cv, Pd, Lc and Pa sites. The daily mean soil CO2 effiux was close to the soil COz effiux from 15：00 to 17：00 and the mean of 2 individual soil CO2 effiux from 15：00 to 19：00 at the As and Sg sites, respectively. During nocturnal hours, negative soil CO2 fluxes （CO2 downwards into the soil） were frequently observed at the As and Sg sites, the magnitude of the negative CO2 fluxes were 0.10-1.55 gmol/（m2.s） and 0.10-0.69 gmol/（m2.s）at the two sites. The results im- plied that alkaline soils could absorb CO2 under natural condition, which might have significant implications to the global carbon budget accounting.展开更多
In this paper, we consider a fully discrete finite element approximation for time fractional optimal control problems. The state and adjoint state are approximated by triangular linear fi nite elements in space and &l...In this paper, we consider a fully discrete finite element approximation for time fractional optimal control problems. The state and adjoint state are approximated by triangular linear fi nite elements in space and <em>L</em>1 scheme in time. The control is obtained by the variational discretization technique. The main purpose of this work is to derive the convergence and superconvergence. A numerical example is presented to validate our theoretical results.展开更多
Previous studies have demonstrated that differentiated neural stem cells （NSCs） are more suitable for transplantation than non-differentiated NSCs. In this study, NSCs were expanded in vitro for two passages, induce...Previous studies have demonstrated that differentiated neural stem cells （NSCs） are more suitable for transplantation than non-differentiated NSCs. In this study, NSCs were expanded in vitro for two passages, induced with retinoic acid to differentiate, and harvested between 1 6 days later. They were subsequently cultured in artificial cerebrospinal fluid for an additional 3 days, dudng which their growth and morphology was monitored. NSCs induced for 4 days exhibited a peak rate of cells differentiating into neurons and robust growth. Our results indicate that the optimal time point for transplanting NSCs is following a 4-day period of induced differentiation.展开更多
This paper has put forward a concept of optimal supporting time through analysing the influence of the supporting time in the heading face on the supporting result of surrounding rock.The method Of the optimal Support...This paper has put forward a concept of optimal supporting time through analysing the influence of the supporting time in the heading face on the supporting result of surrounding rock.The method Of the optimal Supporting time determined by graphical method is discussed, and the calculating formula for determining the optimal supporting time through the analysis method is derived.展开更多
文摘In this paper, a fast approach to generate time optimal and smooth trajectory has been developed and tested. Minimum time is critical for the productivity in industrial applications. Meanwhile, smooth trajectories based on cubic splines are desirable for their ability to limit vibrations and ensure the continuity of position, velocity and acceleration during the robot movement. The main feature of the approach is a satisfactory solution that can be obtained by a local modification process among each intermal between two consecutive via-points. An analytical formulation simplifies the approach to smooth trajectory and few,iterations are enough to determine the correct values. The approach can be applied in many robot manipulators which require high performance on time and smooth. The simulation and application of the approach on a palletizer robot are performed, and the experimental results provide evidence that the approach can realize the robot manipulators more efficiency and high smooth performance.
基金supported by the National Key Basic Research Program(2011CBA00200)the National Natural Science Foundation of China(61074050)
文摘The time optimal problem for a two level quantum sys-tem is studied. We compare two different control strategies of bang-bang control and the geometric control, respectively, es-pecial y in the case of minimizing the time of steering the state from North Pole to South Pole on the Bloch sphere with bounded control. The time performances are compared for different param-eters by the individual numerical simulation experiments, and the experimental results are analyzed. The results show that the ge-ometric control spends less time than the bang-bang control does.
基金supported in part by the National Natural Science Foundation of China(62276119)the Natural Science Foundation of Jiangsu Province(BK20241764)the Postgraduate Research & Practice Innovation Program of Jiangsu Province(KYCX22_2860)
文摘Dear Editor,This letter investigates predefined-time optimization problems(OPs) of multi-agent systems(MASs), where the agent of MASs is subject to inequality constraints, and the team objective function accounts for impulse effects. Firstly, to address the inequality constraints,the penalty method is introduced. Then, a novel optimization strategy is developed, which only requires that the team objective function be strongly convex.
基金Supported by the National Key Research and Development Program,China,No.2022YFC2503603.
文摘BACKGROUND Bile duct leaks(BDLs)are serious postsurgical adverse events.Typically,conservative management with ab-dominal drainage is the initial treatment option.However,prolonged abdominal drainage without improvement can lead to biliary stricture and delay the optimal timing of endoscopic retrograde cholangiopancreatography(ERCP).AIM To identify the optimal timing for ERCP and the period during which clinical observation with conservative management is acceptable,balancing ERCP success and the risk of biliary strictures.METHODS We conducted a multicenter retrospective study involving 448 patients with BDLs between November 2002 and November 2022.The patients were divided into four groups based on the timing of ERCP:3 days,7 days,14 days,and 21 days.The primary outcome was clinical success,defined as the resolution of BDL and related symptoms within 6 months without additional percutaneous drainage,surgery,or death.The secondary outcome was incidence of biliary strictures.Univariate and multivariate logistic regression analyses were performed to identify factors associated with ERCP success and biliary stricture occurrence.RESULTS In a cohort of 448 consecutive patients diagnosed with BDLs,354 were excluded,leaving 94 patients who underwent ERCP.Clinical success was achieved in 84%of cases(79/94),with a median ERCP timing of 20 days(9.5-35.3 days).Biliary strictures were identified in 29(30.9%)patients.Performing ERCP within 3 weeks,compared to after 3 weeks,was associated with higher success rates[92.0%(46/50)vs 75.0%(33/44),P=0.032]and a lower incidence of biliary stricture incidence[18.0%(9/50)vs 45.5%(20/44),P=0.005].Subsequent multivariate analysis confirmed the association with higher success rates(odds ratio=4.168,P=0.045)and lower biliary stricture rates(odds ratio=0.256,P=0.007).CONCLUSION Performing ERCP for BDLs within 3 weeks may be associated with a higher success rate and a lower biliary stricture rate.If patients with BDLs do not respond to conservative treatment,ERCP is suggested to be performed within 3 weeks.
基金supported by the National Nature Science Foundation of China(Nos.62063019)Natural Science Foundation of Gansu Province(22JR5RA241,2023CXZX-465).
文摘In this study,we construct a bi-level optimization model based on the Stackelberg game and propose a robust optimization algorithm for solving the bi-level model,assuming an actual situation with several participants in energy trading.Firstly,the energy trading process is analyzed between each subject based on the establishment of the operation framework of multi-agent participation in energy trading.Secondly,the optimal operation model of each energy trading agent is established to develop a bi-level game model including each energy participant.Finally,a combination algorithm of improved robust optimization over time(ROOT)and CPLEX is proposed to solve the established game model.The experimental results indicate that under different fitness thresholds,the robust optimization results of the proposed algorithm are increased by 56.91%and 68.54%,respectively.The established bi-level game model effectively balances the benefits of different energy trading entities.The proposed algorithm proposed can increase the income of each participant in the game by an average of 8.59%.
基金supported by the University Putra Malaysia and the Ministry of Higher Education Malaysia under grantNumber:(FRGS/1/2023/ICT11/UPM/02/3).
文摘As mobile edge computing continues to develop,the demand for resource-intensive applications is steadily increasing,placing a significant strain on edge nodes.These nodes are normally subject to various constraints,for instance,limited processing capability,a few energy sources,and erratic availability being some of the common ones.Correspondingly,these problems require an effective task allocation algorithmto optimize the resources through continued high system performance and dependability in dynamic environments.This paper proposes an improved Particle Swarm Optimization technique,known as IPSO,for multi-objective optimization in edge computing to overcome these issues.To this end,the IPSO algorithm tries to make a trade-off between two important objectives,which are energy consumption minimization and task execution time reduction.Because of global optimal position mutation and dynamic adjustment to inertia weight,the proposed optimization algorithm can effectively distribute tasks among edge nodes.As a result,it reduces the execution time of tasks and energy consumption.In comparative assessments carried out by IPSO with benchmark methods such as Energy-aware Double-fitness Particle Swarm Optimization(EADPSO)and ICBA,IPSO provides better results than these algorithms.For the maximum task size,when compared with the benchmark methods,IPSO reduces the execution time by 17.1%and energy consumption by 31.58%.These results allow the conclusion that IPSO is an efficient and scalable technique for task allocation at the edge environment.It provides peak efficiency while handling scarce resources and variable workloads.
基金partially supported by a National Key Basic Research Project of China under Grant No.2011CB302400the Natural Science Foundation of China under Grant No.60821002
文摘In this paper,the problem of time optimal feedrate generation under confined feedrate,axis accelerations,and axis tracking errors is considered.The main contribution is to reduce the tracking error constraint to constraints about the axis velocities and accelerations,when the tracking error satisfies a second order linear ordinary differential equation.Based on this simplification on the tracking error,the original feedrate generation problem is reduced to a new form which can be efficiently solved with linear programming algorithms.Simulation results are used to validate the methods.
基金supported by the National Natural Science Foundation of China(Grant No.11275131)the National Research Foundation for the Doctoral Program of Higher Education of China
文摘We study the optimal quantum control of heteronuclear two-qubit systems described by a Hamiltonian containing both nonlocal internal drift and local control terms.We derive an explicit formula to compute the minimum time required to steer the system from an initial state to a specified final state.As applications the minimal time to implement Controlled-NOT gate,SWAP gate and Controlled-U gate is calculated in detail.The experimental realizations of these quantum gates are explicitly presented.
基金Partially supported by National Natural Science Foundation of China (Grant No. 10525105)the NCET of China (Grant No. 04-0882)
文摘In this paper, we establish a bang-bang principle of time optimal controls for a controlled parabolic equation of fractional order evolved in a bounded domain Ω of R^n, with a controller w to be any given nonempty open subset of Ω. The problem is reduced to a new controllability property for this equation, i.e. the null controllability of the system at any given time T 〉 0 when the control is restricted to be active in ω× E, where E is any given subset of [0, T] with positive （Legesgue） measure. The desired controllability result is established by means of a sharp observability estimate on the eigenfunctions of the Dirichlet Laplacian due to Lebeau and Robbiano, and a delicate result in the measure theory due to Lions.
文摘We present in this paper a survey of recent results on the relation between time and norm optimality for linear systems and the infinite dimensional version of Pontryagin＇s maximum principle. In particular, we discuss optimality （or nonoptimality） of singular controls satisfying the maximum principle and smoothness of the costate in function of smoothness of the target.
文摘In this paper, a class of time optimal problem with impluse control is considered. Under certain conditions we prove that the optimal impluse control exists and its impluse number is finite. Moreover, it is proved that the minimum time function is locally Lipschitz continuous in its domain and is the unique viscosity solution of the corresponding Hamilton-Jacobi-Bellman system.
基金supported by the National Natural Science Foundation of China (Grant No. 50839002)the National Key Technologies R&D Program of China during the Eleventh Five-Year Plan Period (Grant No.2006BAD11B06)the Jiangsu Province Graduate Cultivation Innovative Project (Grant No.CXZZ11_0453)
文摘While many controlled irrigation and drainage techniques have been adopted in China, the environmental effects of these techniques require further investigation. This study was conducted to examine the changes of nitrogen and phosphorus of a flooded paddy water system after fertilizer application and at each growth stage so as to obtain the optimal drainage time at each growth stage. Four treatments with different water level management methods at each growth stage were conducted under the condition of ten-day continuous flooding. Results show that the ammonia nitrogen （ NH4-N ） concentration reached the peak value once the fertilizer was applied, and then decreased to a relatively low level seven to ten days later, and that the nitrate nitrogen （NO^-N） concentration gradually rose to its peak value, which appeared later in subsurface water than in surface water. Continuous flooding could effectively reduce the concentrations of NH^-N , NO3-N, and total phosphorus （TP） in surface water. However, the paddy water disturbance, in the process of soil surface adsorption and nitrification, caused NH]-N to be released and increased the concentrations of NH4-N and NO^-N in surface water. A multi-objective controlled drainage model based on environmental factors was established in order to obtain the optimal drainage time at each growth stage and better guide the drainage practices of farmers. The optimal times for surface drainage are the fourth, sixth, fifth, and sixth days after flooding at the tillering, jointing-booting, heading-flowering, and milking stages, respectively.
基金supported by the National Natural Science Foundation of China(Grants 11702333 and 11672337)Natural Science Foundation of Guangdong Province(Grant 2018B030311001).
文摘As a classical technique for chaos suppression,the time-delayed feedback controlling strategy has been widely developed by stabilizing unstable periodic orbits(UPOs)embedded in chaotic systems.A critical issue for achieving high controlling precision is to search for an appropriate time delay.This paper proposes a simple yet effective approach,based on incremental harmonic balance method,to determine the optimal time delay in the delayed feedback controller.The time delay is adjusted within the iterative scheme provided by the proposed method,and finally converges to the period of the target UPO.As long as the optimal time delay is fixed,moreover,the attained solution makes it quite convenient to analyze its stability according to the Floquet theory,which further provides the effective interval of the feedback gain.
基金The study was supported by“948”Project of the Ministry of Agriculture of China.
文摘By assay of accelerated aging germination, germination index, vigor index, seedling length, seedling weight, electric conductivity, dehydrogenase activity, ATP content and acid phosphoesterase activity during seed development of turf-type tall fescue, the seed vigor of tall fescue were studied. Combining with seed moisture content and yield, the optimal harvesting time of tall fescue was determined. The results indicated that the seed vigor increased continuously along with seed maturity, and the higher seed vigor was achieved at 19th day after perk anthesis and maintained continuously until 31st day after peak anthesis. At 25th day after peak anthesis, the highest yield of 3 533 kg ha-1 and the good quality of seeds of tall fescue were harvested with 32.19% moisture content. From 22nd to 31st day after peak anthesis, the seed yield of 3 300 kg ha-1 and the good quality seeds of tall fescue were harvested with 40 - 12. 43% moisture content, and the span was the optimal harvesting time.
基金Supported by National Natural Science Foundation of China,No. 82071679 and 82271721Basic and Clinical Cooperative Research Promotion Program of Anhui Medical University,No. 2019xkj T020
文摘Gestational diabetes mellitus(GDM)is a common pregnancy complication strongly associated with poor maternal-fetal outcomes.Its incidence and prevalence have been increasing in recent years.Women with GDM typically give birth through either vaginal delivery or cesarean section,and the maternal-fetal outcomes are related to several factors such as cervical level,fetal lung maturity,the level of glycemic control still present,and the mode of treatment for the condition.We categorized women with GDM based on the latter two factors.GDM that is managed without medication when it is responsive to nutrition-and exercise-based therapy is considered diet-and exercise-controlled GDM,or class A1 GDM,and GDM managed with medication to achieve adequate glycemic control is considered class A2 GDM.The remaining cases in which neither medical nor nutritional treatment can control glucose levels or patients who do not control their blood sugar are categorized as class A3 GDM.We investigated the optimal time of delivery for women with GDM according to the classification of the condition.This review aimed to address the benefits and harms of giving birth at different weeks of gestation for women with different classes of GDM and attempted to provide an analytical framework and clearer advice on the optimal time for labor.
基金Under the auspices of National Natural Science Foundation of China(No.41501090,41501105)Fundamental Research Funds for Central Universities(No.2412015KJ023)
文摘In order to study the diurnal variation of soil CO2 effiux from temperate meadow steppes in Northeast China, and determine the best time for observation, a field experiment was conducted with a LI-6400 soil CO2 flux system under five typical plant communi- ties （Suaeda glauca （Sg）, Chloris virgata （Cv）, Puecinellia distans （Pd）, Leymus chinensis （Lc） and Phragmites australis （Pa）） and an alkali-spot land （As） at the meadow steppe of western Songnen Plain. The results showed that the diurnal variation of soil CO2 effiux exhibited a single peak curve in the growing season. Diurnal maximum soil respiration （Rs） often appeared between 1 1：00 and 13：00, while the minimum occurred at 21：00-23：00 or before dawn. Air temperature near the soil surface （Ta） and soil temperature at 10 cm depth （Tlo） exerted dominant control on the diurnal variations of soil respiration. The time-windows 7：00-9：00 could be used as the optimal measuring time to represent the daily mean soil CO2 effiux at the Cv, Pd, Lc and Pa sites. The daily mean soil CO2 effiux was close to the soil COz effiux from 15：00 to 17：00 and the mean of 2 individual soil CO2 effiux from 15：00 to 19：00 at the As and Sg sites, respectively. During nocturnal hours, negative soil CO2 fluxes （CO2 downwards into the soil） were frequently observed at the As and Sg sites, the magnitude of the negative CO2 fluxes were 0.10-1.55 gmol/（m2.s） and 0.10-0.69 gmol/（m2.s）at the two sites. The results im- plied that alkaline soils could absorb CO2 under natural condition, which might have significant implications to the global carbon budget accounting.
文摘In this paper, we consider a fully discrete finite element approximation for time fractional optimal control problems. The state and adjoint state are approximated by triangular linear fi nite elements in space and <em>L</em>1 scheme in time. The control is obtained by the variational discretization technique. The main purpose of this work is to derive the convergence and superconvergence. A numerical example is presented to validate our theoretical results.
基金the National Natural Science Foundation of China, No. 30570628, 30770751
文摘Previous studies have demonstrated that differentiated neural stem cells （NSCs） are more suitable for transplantation than non-differentiated NSCs. In this study, NSCs were expanded in vitro for two passages, induced with retinoic acid to differentiate, and harvested between 1 6 days later. They were subsequently cultured in artificial cerebrospinal fluid for an additional 3 days, dudng which their growth and morphology was monitored. NSCs induced for 4 days exhibited a peak rate of cells differentiating into neurons and robust growth. Our results indicate that the optimal time point for transplanting NSCs is following a 4-day period of induced differentiation.
文摘This paper has put forward a concept of optimal supporting time through analysing the influence of the supporting time in the heading face on the supporting result of surrounding rock.The method Of the optimal Supporting time determined by graphical method is discussed, and the calculating formula for determining the optimal supporting time through the analysis method is derived.
