A broadband tunable acoustic metasurface(BTAM)is conceived with Helmholtz resonators(HRs).The tunability of HRs’neck enables precise control over the phase shift of the unit cell.Through careful arrangement of unit c...A broadband tunable acoustic metasurface(BTAM)is conceived with Helmholtz resonators(HRs).The tunability of HRs’neck enables precise control over the phase shift of the unit cell.Through careful arrangement of unit cells,the BTAMs are engineered to exhibit various phase differences,thereby inducing anomalous reflections and acoustic focusing.Numerical simulations demonstrate the BTAM’s remarkable efficacy in manipulating the angle of reflection wave and achieving wave focusing across a broadband frequency range.Experimental investigations of the phase shift and anomalous reflection further validate the design of metasurface.This work contributes to the fields of broadband and tunable acoustic wave manipulation and provides a flexible and efficient approach for acoustic control devices.展开更多
In order to improve the steady and dynamic characteristic of the idle speed control and study the performance of the fuzzy control method for the idle speed control, a fuzzy control system is developed to control the ...In order to improve the steady and dynamic characteristic of the idle speed control and study the performance of the fuzzy control method for the idle speed control, a fuzzy control system is developed to control the idle speed of gasoline engine. The construction and working principle of the fuzzy controller are described, and the design procedure of the fuzzy controller is given in detail. The control parameters are determined by computer simulation. The simulation and experiments on the engine test bench show that the idle speed is controlled accurately both in stationary and in dynamic states, and the fuzzy control method is robust to the changes of engine parameters.展开更多
Objective To evaluate the fetal cardiac function in gestational diabetes mellitus （GDM） pregnancies under different maternal glycemic controls. Methods Forty four GDM mothers received 78 fetal echocardiographic eval...Objective To evaluate the fetal cardiac function in gestational diabetes mellitus （GDM） pregnancies under different maternal glycemic controls. Methods Forty four GDM mothers received 78 fetal echocardiographic evaluations at three gestational periods （〈28, 28-34 and ≥34 weeks） and were divided into poorly-（DM1） and well-（DM2） controlled groups according to their glycemic control at examination. Seventy uncomplicated mothers were selected as controls. Parameters of fetal cardiac anatomy and function were measured and analyzed. Results GDM fetuses＇ cardiac ventricular walls were thicker than controls＇, and the differences between DM1 and DM2 were not significant except for end-diastolic left ventricular walls. In both GDM groups, the aortic flow velocities increased earlier than pulmonary artery and DM1 fetuses changed earlier than DM2 ones. GDM fetuses＇ left atrial shortening fraction was smaller than the controls＇ in the period of ≥34 weeks and negatively correlated with thicknesses of left ventricular walls and interventricular septum in DM1 fetuses （r=-0.438 and -0.506）. The right ventricular diastolic function in DM1 and DM2 fetuses decreased after the period of 28-34 weeks and in the period of ≥34 weeks respectively. Tel index of both left and right ventricles increased in DM1 group after the period of 〈28 weeks and in DM2 group only in the period of ≥ 34 weeks, with no significant differences between DM1 and DM2 groups in this period. Conclusion Fetuses of GDM mothers showed cardiac function impairments. Good maternal glycemic control may delay the impairments, but cannot reduce the degree. Some cardiac changes in GDM fetuses were similar to those in pregestational diabetic pregnancies except for several parameters and their changing time.展开更多
Starting with the Ertan arch dam （240 m high, 3300 MW） in 2000, China successfully built a total of seven ultra-high arch dams over 200 m tall by the end of 2014. Among these, the ]inping 1 （305 m）, Xiaowan （294...Starting with the Ertan arch dam （240 m high, 3300 MW） in 2000, China successfully built a total of seven ultra-high arch dams over 200 m tall by the end of 2014. Among these, the ]inping 1 （305 m）, Xiaowan （294.5m）, and Xiluodu （285.5 m） arch dams have reached the 300 m height level （i.e., near or over 300 m）, making them the tallest arch dams in the world. The design and construction of these 300 m ultra-high arch dams posed significant challenges, due to high water pressures, high seismic de- sign criteria, and complex geological conditions. The engineering team successfully tackled these chal- lenges and made critical breakthroughs, especially in the area of safety control. In this paper, the author summarizes various key technological aspects involved in the design and construction of 300 m ultra- high arch dams, including the strength and stability of foundation rock, excavation of the dam base and surface treatment, dam shape optimization, safety design guidelines, seismic analysis and design, treatment of a complex foundation, concrete temperature control, and crack prevention. The experience gained from these projects should be valuable for future practitioners.展开更多
The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic an...The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic analysis of the martensite formation and microstructural control of high-Cr martensitic/ferritic steels are reviewed. A modular approach, incorporating Fisher partitioning nucleation and anisotropic growth for impingement, was proposed to describe the martensite formation kinetics under different cooling rates.The kinetic analysis suggested a thermal-activated growth feature occurring during the martensitic transformation of martensitic steels. The microstructure can be tuned by composition optimization and various combinations of heat treatment parameters(temperature, time, severe and minor deformation).For the application in power plant, the potential of boundary-design, refinement of original austenite grain size and the final martensitic lath, pinning effect of stable carbides, in improving the performances of martensitic/ferritic steels at elevated temperatures should be investigated more thoroughly.Furthermore, efforts should be made to explore the effects of retained austenite on the improvement of high-temperature creep strength. For the application of nuclear plants, attempts should also be made to produce Fe powders with uniformly distributed oxide particles by chemical reactions.展开更多
The existing hydraulic system always have problems of temperature rise,runningstability and anti-interference of the implementation components,reliability of hydrauliccomponents,maintenance difficulties,and other issu...The existing hydraulic system always have problems of temperature rise,runningstability and anti-interference of the implementation components,reliability of hydrauliccomponents,maintenance difficulties,and other issues.With high efficiency,energysaving,reliability,easy operating,stable running,anti-interference ability,and other advantages,the load-sensitive hydraulic system is more suitable for coal mine all-hydrauliccore rig.Therefore,for the technical development of the coal mine all-hydraulic core rig,the load-sensitive technology employed by the rig should be of great significance.展开更多
China is a country where 100% of the territory is located in a seismic zone. Most of the strong earthquakes are over prediction. Most fatalities are caused by structural collapse. Earthquakes not only cause severe dam...China is a country where 100% of the territory is located in a seismic zone. Most of the strong earthquakes are over prediction. Most fatalities are caused by structural collapse. Earthquakes not only cause severe damage to structures, but can also damage non-structural elements on and inside of facilities. This can halt city life, and disrupt hospitals, airports, bridges, power plants, and other infrastructure. Designers need to use new techniques to protect structures and facilities inside. Isolation, energy dissipation and, control systems are more and more widely used in recent years in China. Currently, there are nearly 6,500 structures with isolation and about 3,000 structures with passive energy dissipation or hybrid control in China. The mitigation techniques are applied to structures like residential buildings, large or complex structures, bridges, underwater tunnels, historical or cultural relic sites, and industrial facilities, and are used for retrofitting of existed structures. This paper introduces design rules and some new and innovative devices for seismic isolation, energy dissipation and hybrid control for civil and industrial structures. This paper also discusses the development trends for seismic resistance, seismic isolation, passive and active control techniques for the future in China and in the world.展开更多
This contribution deals with capture condition for interceptor missiles steered by aero-lift control system （ALCS） and attitude reaction-jet control system （ARCS）. With the guidance law derived from bounded differ...This contribution deals with capture condition for interceptor missiles steered by aero-lift control system （ALCS） and attitude reaction-jet control system （ARCS）. With the guidance law derived from bounded differential game formulation, existence condition of capture zone is studied for the case that the interceptor has advantage on maneuverability and disadvantage on agility. For the existence of the open capture zone, ARCS can only close after the engagement terminates. Moreover, ARCS also needs to contribute to maneuverability over the minimum required value. More fuel will be required if ARCS increases its contribution to maneuverability. The minimum required fuel occurs at the tangent point of two curves： the curve of critical parameters and a candidate constraint curve, which is also true even for the complex propellant constrain. The validity of these results is also demonstrated by simulations.展开更多
New solid backfill mining technology provides unique technical advantages for ‘‘three-under'' coal mining which refers to coal resources trapped under buildings, railways, and water bodies. This technology h...New solid backfill mining technology provides unique technical advantages for ‘‘three-under'' coal mining which refers to coal resources trapped under buildings, railways, and water bodies. This technology has a much higher recovery rate and can effectively control the surface subsidence. However, successful application of this technology depends heavily on geological conditions. To avoid the disadvantages associated with downward mining and overhead backfilling with this new technology, a new advanced solid backfill mining design with two pre-driving entries is proposed here to ensure the backfill effect. Taking Huayuan coal mine as an example, this paper tests the double gob-side entries retaining with no pillar left scheme and optimizes an integrated technology setup for backfill mining and gob-side entry retaining. Field applications show that the recovery rate increased from 40% for strip mining to 85% for backfill mining. Moreover, the new backfill technology allowed for better control over the surrounding rock deformation caused by the gob-side entry retaining effect and better control of ground subsidence as compared to strip mining.展开更多
This paper gives an overview of early development of nonlinear disturbance observer design technique and the disturbance observer based control （DOBC） design. Some critical points raised in the development of the me...This paper gives an overview of early development of nonlinear disturbance observer design technique and the disturbance observer based control （DOBC） design. Some critical points raised in the development of the methods have been reviewed and discussed which are still relevant for many researchers or practitioners who are interested in this method. The review is followed by the development of a new type of nonlinear PID controller for a robotic manipulator and its experimental tests. It is shown that, under a number of assumptions, the DOBC consisting of a predictive control method and a nonlinear disturbance observer could reduce to a nonlinear PID with special features. Experimental results show that, compared with the predictive control method, the developed controller significantly improves performance robustness against uncertainty and friction. This paper may trigger further research and interests in the development of DOBC and related methods, and building up more understanding between this group of control methods with comparable ones （particularly control methods with integral action）.展开更多
According to the phenomenon of "four more"and"four low "problems in the observation stations,the surface-based meteorological observing system can't adapt to the change of the adaptive observat...According to the phenomenon of "four more"and"four low "problems in the observation stations,the surface-based meteorological observing system can't adapt to the change of the adaptive observation equipment and reduce of business intensification. A station integrated system is proposed,w hich can be configured,connected and extended to all kinds of observation equipment. And the integrated processor is designed,supporting a variety of communication interface standards. Flexible configuration,connection and expansion betw een conventional and new type of meteorological observation equipment are supported. It is capable for online calibration and maintenance of observation equipment. The effectiveness of automatic observation equipment is totally achieved to provide basic information support for disaster prevention and mitigation and national economic development.展开更多
This work develops a new model to deal with the scenario that some companies can still run business even the surplus falls below zero temporarily. With such a scenario in mind, we allow the surplus process to continue...This work develops a new model to deal with the scenario that some companies can still run business even the surplus falls below zero temporarily. With such a scenario in mind, we allow the surplus process to continue in this negative-surplus period, during which capital injections will be ordered to assist in the stabilization of financial structure, until the financial status becomes severe enough to file bankruptcy. The capital injections will be modeled as impulse controls. By introducing the capital injections with time delays, optimal dividend payment and capital injection policies are considered. Using the dynamic programming approach, the value function obeys a quasi-variational inequality. With delays in capital injections, the company will be exposed to the risk of bankruptcy during the delay period. In addition, the optimal dividend payment and capital injection strategies should balance the expected cost of the possible capital injections and the time value of the delay periods. This gives rise to a stochastic control problem with mixed singular and delayed impulse controls. Under general assumptions, the lower capital injection barrier is determined, where bankruptcy occurs. The closed-form solution to the value function and corresponding optimal policies are obtained.展开更多
Objective:To systematically evaluate the clinical efficacy of acupuncture bloodletting therapy for herpes zoster.Methods:The computer searched the CNKI,WanFang,VIP,CBM,PubMed,and Cochrane Library databases.The time li...Objective:To systematically evaluate the clinical efficacy of acupuncture bloodletting therapy for herpes zoster.Methods:The computer searched the CNKI,WanFang,VIP,CBM,PubMed,and Cochrane Library databases.The time limit was from the establishment of the database to December 31,2019.Relevant literatures on randomized controlled trials of spinal bloodletting for shingles were retrieved.Data were extracted and quality evaluated based on the Cochrane bias risk assessment method.Meta analysis was performed using Rev Man5.3 and Stata15 statistical software.Results:(1)A total of 21 Chinese literatures were included,with a total of 1,533 patients;(2)Meta-analysis was performed using a fixed effect model,and the results showed that the total effective rate of the experimental group(OR=5.11,95%CI:(3.48,7.50),Z=8.33,P<0.00001)is better than the control group,the difference is statistically significant;(3)VAS score analysis using a random effects model(MD-2.23,95%CI(-2.46,-1.99),p<0.0001)(4)The incidence of sequela neuralgia was analyzed using a random effects model(OR=0.21,95%CI:(0.09,0.51),Z=3.48,P=0.0005).Conclusion:The effect of spinal bloodletting on the treatment of shingles and VAS scores,symptomatic relief,and the incidence of sequela neuralgia have advantages.展开更多
The cover beam refers to the load of the upper building structure in order to support, distribution and transmission, the beam can also be designed at the top of the vase pier. The construction quality of the cover be...The cover beam refers to the load of the upper building structure in order to support, distribution and transmission, the beam can also be designed at the top of the vase pier. The construction quality of the cover beam directly affects the quality of the bridge. In this paper, the construction process of a semi-inverted T-type invisible cover beam is combined with a project to summarize its construction technology. In order to control the construction quality of the cover beam, the reference basis is provided for the construction of half inverted T-shaped invisible cover beam in the future.展开更多
An inexpensive MC4044-based phase locked loop for constant speed control of a DC motor is discussed. It operates on a principle similar to that of a frequency synthesizer. The paper introduces the system configuration...An inexpensive MC4044-based phase locked loop for constant speed control of a DC motor is discussed. It operates on a principle similar to that of a frequency synthesizer. The paper introduces the system configuration with a detailed description of its operating principle, some practical design considerations are discussed with an experimental study to test the control performance of the newly designed system. The experimental result shows that the phase locked control system can regulate the speed of a DC torque motor with a precision up to 0.0022%(1).[展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11991030,11991031 and 12202054)Aeronautical Science Foundation(Grant No.ASFC20230042072010).
文摘A broadband tunable acoustic metasurface(BTAM)is conceived with Helmholtz resonators(HRs).The tunability of HRs’neck enables precise control over the phase shift of the unit cell.Through careful arrangement of unit cells,the BTAMs are engineered to exhibit various phase differences,thereby inducing anomalous reflections and acoustic focusing.Numerical simulations demonstrate the BTAM’s remarkable efficacy in manipulating the angle of reflection wave and achieving wave focusing across a broadband frequency range.Experimental investigations of the phase shift and anomalous reflection further validate the design of metasurface.This work contributes to the fields of broadband and tunable acoustic wave manipulation and provides a flexible and efficient approach for acoustic control devices.
文摘In order to improve the steady and dynamic characteristic of the idle speed control and study the performance of the fuzzy control method for the idle speed control, a fuzzy control system is developed to control the idle speed of gasoline engine. The construction and working principle of the fuzzy controller are described, and the design procedure of the fuzzy controller is given in detail. The control parameters are determined by computer simulation. The simulation and experiments on the engine test bench show that the idle speed is controlled accurately both in stationary and in dynamic states, and the fuzzy control method is robust to the changes of engine parameters.
基金supported by the National Natural Science Foundation of China (81001228)National High Technology Research and Development Program of China (863 Program)(2007AA02Z442)
文摘Objective To evaluate the fetal cardiac function in gestational diabetes mellitus （GDM） pregnancies under different maternal glycemic controls. Methods Forty four GDM mothers received 78 fetal echocardiographic evaluations at three gestational periods （〈28, 28-34 and ≥34 weeks） and were divided into poorly-（DM1） and well-（DM2） controlled groups according to their glycemic control at examination. Seventy uncomplicated mothers were selected as controls. Parameters of fetal cardiac anatomy and function were measured and analyzed. Results GDM fetuses＇ cardiac ventricular walls were thicker than controls＇, and the differences between DM1 and DM2 were not significant except for end-diastolic left ventricular walls. In both GDM groups, the aortic flow velocities increased earlier than pulmonary artery and DM1 fetuses changed earlier than DM2 ones. GDM fetuses＇ left atrial shortening fraction was smaller than the controls＇ in the period of ≥34 weeks and negatively correlated with thicknesses of left ventricular walls and interventricular septum in DM1 fetuses （r=-0.438 and -0.506）. The right ventricular diastolic function in DM1 and DM2 fetuses decreased after the period of 28-34 weeks and in the period of ≥34 weeks respectively. Tel index of both left and right ventricles increased in DM1 group after the period of 〈28 weeks and in DM2 group only in the period of ≥ 34 weeks, with no significant differences between DM1 and DM2 groups in this period. Conclusion Fetuses of GDM mothers showed cardiac function impairments. Good maternal glycemic control may delay the impairments, but cannot reduce the degree. Some cardiac changes in GDM fetuses were similar to those in pregestational diabetic pregnancies except for several parameters and their changing time.
文摘Starting with the Ertan arch dam （240 m high, 3300 MW） in 2000, China successfully built a total of seven ultra-high arch dams over 200 m tall by the end of 2014. Among these, the ]inping 1 （305 m）, Xiaowan （294.5m）, and Xiluodu （285.5 m） arch dams have reached the 300 m height level （i.e., near or over 300 m）, making them the tallest arch dams in the world. The design and construction of these 300 m ultra-high arch dams posed significant challenges, due to high water pressures, high seismic de- sign criteria, and complex geological conditions. The engineering team successfully tackled these chal- lenges and made critical breakthroughs, especially in the area of safety control. In this paper, the author summarizes various key technological aspects involved in the design and construction of 300 m ultra- high arch dams, including the strength and stability of foundation rock, excavation of the dam base and surface treatment, dam shape optimization, safety design guidelines, seismic analysis and design, treatment of a complex foundation, concrete temperature control, and crack prevention. The experience gained from these projects should be valuable for future practitioners.
基金the China National Funds for Distinguished Young Scientists (Grant No. 51325401)the International Thermonuclear Experimental Reactor (ITER) Program Special Project (Grant Nos. 2014GB125006 and 2015GB119001)+1 种基金the National High Technology Research and Development Program ("863" Program) of China (Granted No. SS2015AA042005)the National Natural Science Foundation of China (Grant No. 51474156)
文摘The martensitic/ferritic steels have been used as boiler and turbine materials in power plants, and also been selected as potential materials for structural materials in nuclear reactors. In this paper, the kinetic analysis of the martensite formation and microstructural control of high-Cr martensitic/ferritic steels are reviewed. A modular approach, incorporating Fisher partitioning nucleation and anisotropic growth for impingement, was proposed to describe the martensite formation kinetics under different cooling rates.The kinetic analysis suggested a thermal-activated growth feature occurring during the martensitic transformation of martensitic steels. The microstructure can be tuned by composition optimization and various combinations of heat treatment parameters(temperature, time, severe and minor deformation).For the application in power plant, the potential of boundary-design, refinement of original austenite grain size and the final martensitic lath, pinning effect of stable carbides, in improving the performances of martensitic/ferritic steels at elevated temperatures should be investigated more thoroughly.Furthermore, efforts should be made to explore the effects of retained austenite on the improvement of high-temperature creep strength. For the application of nuclear plants, attempts should also be made to produce Fe powders with uniformly distributed oxide particles by chemical reactions.
基金Supported by the Youth Innovation Fund of China Coal Research Institute(2007QN50)
文摘The existing hydraulic system always have problems of temperature rise,runningstability and anti-interference of the implementation components,reliability of hydrauliccomponents,maintenance difficulties,and other issues.With high efficiency,energysaving,reliability,easy operating,stable running,anti-interference ability,and other advantages,the load-sensitive hydraulic system is more suitable for coal mine all-hydrauliccore rig.Therefore,for the technical development of the coal mine all-hydraulic core rig,the load-sensitive technology employed by the rig should be of great significance.
文摘China is a country where 100% of the territory is located in a seismic zone. Most of the strong earthquakes are over prediction. Most fatalities are caused by structural collapse. Earthquakes not only cause severe damage to structures, but can also damage non-structural elements on and inside of facilities. This can halt city life, and disrupt hospitals, airports, bridges, power plants, and other infrastructure. Designers need to use new techniques to protect structures and facilities inside. Isolation, energy dissipation and, control systems are more and more widely used in recent years in China. Currently, there are nearly 6,500 structures with isolation and about 3,000 structures with passive energy dissipation or hybrid control in China. The mitigation techniques are applied to structures like residential buildings, large or complex structures, bridges, underwater tunnels, historical or cultural relic sites, and industrial facilities, and are used for retrofitting of existed structures. This paper introduces design rules and some new and innovative devices for seismic isolation, energy dissipation and hybrid control for civil and industrial structures. This paper also discusses the development trends for seismic resistance, seismic isolation, passive and active control techniques for the future in China and in the world.
文摘This contribution deals with capture condition for interceptor missiles steered by aero-lift control system （ALCS） and attitude reaction-jet control system （ARCS）. With the guidance law derived from bounded differential game formulation, existence condition of capture zone is studied for the case that the interceptor has advantage on maneuverability and disadvantage on agility. For the existence of the open capture zone, ARCS can only close after the engagement terminates. Moreover, ARCS also needs to contribute to maneuverability over the minimum required value. More fuel will be required if ARCS increases its contribution to maneuverability. The minimum required fuel occurs at the tangent point of two curves： the curve of critical parameters and a candidate constraint curve, which is also true even for the complex propellant constrain. The validity of these results is also demonstrated by simulations.
基金supported by the Fundamental Research Funds program for the Central Universities (No. 2014RC02)the Research Innovation Program for College Graduates of Jiangsu Province (No. CXLX13_951)Qing Lan Project
文摘New solid backfill mining technology provides unique technical advantages for ‘‘three-under'' coal mining which refers to coal resources trapped under buildings, railways, and water bodies. This technology has a much higher recovery rate and can effectively control the surface subsidence. However, successful application of this technology depends heavily on geological conditions. To avoid the disadvantages associated with downward mining and overhead backfilling with this new technology, a new advanced solid backfill mining design with two pre-driving entries is proposed here to ensure the backfill effect. Taking Huayuan coal mine as an example, this paper tests the double gob-side entries retaining with no pillar left scheme and optimizes an integrated technology setup for backfill mining and gob-side entry retaining. Field applications show that the recovery rate increased from 40% for strip mining to 85% for backfill mining. Moreover, the new backfill technology allowed for better control over the surrounding rock deformation caused by the gob-side entry retaining effect and better control of ground subsidence as compared to strip mining.
文摘This paper gives an overview of early development of nonlinear disturbance observer design technique and the disturbance observer based control （DOBC） design. Some critical points raised in the development of the methods have been reviewed and discussed which are still relevant for many researchers or practitioners who are interested in this method. The review is followed by the development of a new type of nonlinear PID controller for a robotic manipulator and its experimental tests. It is shown that, under a number of assumptions, the DOBC consisting of a predictive control method and a nonlinear disturbance observer could reduce to a nonlinear PID with special features. Experimental results show that, compared with the predictive control method, the developed controller significantly improves performance robustness against uncertainty and friction. This paper may trigger further research and interests in the development of DOBC and related methods, and building up more understanding between this group of control methods with comparable ones （particularly control methods with integral action）.
基金supported by Meteorological Industry Research Projects ( 2013 ) : Development and Application of Key Integration Technologies for Surface-based Meteorological Observation
文摘According to the phenomenon of "four more"and"four low "problems in the observation stations,the surface-based meteorological observing system can't adapt to the change of the adaptive observation equipment and reduce of business intensification. A station integrated system is proposed,w hich can be configured,connected and extended to all kinds of observation equipment. And the integrated processor is designed,supporting a variety of communication interface standards. Flexible configuration,connection and expansion betw een conventional and new type of meteorological observation equipment are supported. It is capable for online calibration and maintenance of observation equipment. The effectiveness of automatic observation equipment is totally achieved to provide basic information support for disaster prevention and mitigation and national economic development.
基金The research of Z. Jin was supported by the Faculty Research Grant of University of Melbourne, and the research of G. Yin was partially supported by the National Science Foundation （No. DMS-1207667）.
文摘This work develops a new model to deal with the scenario that some companies can still run business even the surplus falls below zero temporarily. With such a scenario in mind, we allow the surplus process to continue in this negative-surplus period, during which capital injections will be ordered to assist in the stabilization of financial structure, until the financial status becomes severe enough to file bankruptcy. The capital injections will be modeled as impulse controls. By introducing the capital injections with time delays, optimal dividend payment and capital injection policies are considered. Using the dynamic programming approach, the value function obeys a quasi-variational inequality. With delays in capital injections, the company will be exposed to the risk of bankruptcy during the delay period. In addition, the optimal dividend payment and capital injection strategies should balance the expected cost of the possible capital injections and the time value of the delay periods. This gives rise to a stochastic control problem with mixed singular and delayed impulse controls. Under general assumptions, the lower capital injection barrier is determined, where bankruptcy occurs. The closed-form solution to the value function and corresponding optimal policies are obtained.
基金National Key Research and Development Plan"Key Project of TCM Modernization Research"(No.2018YFC1705303)Science Foundation for Youth of National Natural Foundation of China(No.81704087)+1 种基金Innovation Talent Promotion Plan-Key Science and technology Innovation Team Plan(No.2017KCT-27)Key R&D project of Shaanxi Province(No.2018ZDXM-SF-010)
文摘Objective:To systematically evaluate the clinical efficacy of acupuncture bloodletting therapy for herpes zoster.Methods:The computer searched the CNKI,WanFang,VIP,CBM,PubMed,and Cochrane Library databases.The time limit was from the establishment of the database to December 31,2019.Relevant literatures on randomized controlled trials of spinal bloodletting for shingles were retrieved.Data were extracted and quality evaluated based on the Cochrane bias risk assessment method.Meta analysis was performed using Rev Man5.3 and Stata15 statistical software.Results:(1)A total of 21 Chinese literatures were included,with a total of 1,533 patients;(2)Meta-analysis was performed using a fixed effect model,and the results showed that the total effective rate of the experimental group(OR=5.11,95%CI:(3.48,7.50),Z=8.33,P<0.00001)is better than the control group,the difference is statistically significant;(3)VAS score analysis using a random effects model(MD-2.23,95%CI(-2.46,-1.99),p<0.0001)(4)The incidence of sequela neuralgia was analyzed using a random effects model(OR=0.21,95%CI:(0.09,0.51),Z=3.48,P=0.0005).Conclusion:The effect of spinal bloodletting on the treatment of shingles and VAS scores,symptomatic relief,and the incidence of sequela neuralgia have advantages.
文摘The cover beam refers to the load of the upper building structure in order to support, distribution and transmission, the beam can also be designed at the top of the vase pier. The construction quality of the cover beam directly affects the quality of the bridge. In this paper, the construction process of a semi-inverted T-type invisible cover beam is combined with a project to summarize its construction technology. In order to control the construction quality of the cover beam, the reference basis is provided for the construction of half inverted T-shaped invisible cover beam in the future.
文摘An inexpensive MC4044-based phase locked loop for constant speed control of a DC motor is discussed. It operates on a principle similar to that of a frequency synthesizer. The paper introduces the system configuration with a detailed description of its operating principle, some practical design considerations are discussed with an experimental study to test the control performance of the newly designed system. The experimental result shows that the phase locked control system can regulate the speed of a DC torque motor with a precision up to 0.0022%(1).[
