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
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
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
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
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
Ultrasonic attenuation spectroscopy （UAS） is an attractive process analytical technology （PAT） for on-line real-time characterisation of slurries for particle size distribution （PSD） estimation. It is however on...Ultrasonic attenuation spectroscopy （UAS） is an attractive process analytical technology （PAT） for on-line real-time characterisation of slurries for particle size distribution （PSD） estimation. It is however only applicable to relatively low solid concentrations since existing instrument process models still cannot fully take into account the phenomena of particle-particle interaction and multiple scattering, leading to errors in PSD estimation. This paper investigates an alternative use of the raw attenuation spectra for direct multivariate statistical process control （MSPC）. The UAS raw spectra were processed using principal component analysis. The selected principal components were used to derive two MSPC statistics, the Hotelling＇s T2 and square prediction error （SPE）. The method is illustrated and demonstrated by reference to a wet milling process for processinR nanoparticles.展开更多
We study the effect of state control on capital allocation and investment in China, where the government screens prospective stock issuers. We find that state firms are more likely to obtain government approval to con...We study the effect of state control on capital allocation and investment in China, where the government screens prospective stock issuers. We find that state firms are more likely to obtain government approval to conduct seasoned equity offerings than non-state firms. Further, non-state firms exhibit greater sensitivities of subsequent investment and stock performance to regulatory decisions on stock issuances than state firms. Our work suggests that state control of capital access distorts resource allocation and impedes the growth of non-state firms. We also provide robust evidence that financial constraints cause underinvestment.展开更多
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
随着风电渗透率的提高,双馈风电机组对电网频率的响应能力逐渐变弱,对于系统的频率稳定产生巨大影响。双馈风机单独调频能力不足以满足系统频率偏差要求,并且会产生弃风率高、能源利用率低的问题,为此将储能设备装设在双馈风机的并网侧...随着风电渗透率的提高,双馈风电机组对电网频率的响应能力逐渐变弱,对于系统的频率稳定产生巨大影响。双馈风机单独调频能力不足以满足系统频率偏差要求,并且会产生弃风率高、能源利用率低的问题,为此将储能设备装设在双馈风机的并网侧,组成风储联合系统共同参与系统一次调频。文中通过利用风机的转子动能以及储能设备出力共同承担一次调频功率需求,提出基于风机转子转速以及荷电状态(State of Charge,SOC)的变系数风储联合系统参与一次调频控制策略,双馈风机通过释放或吸收自身转子动能响应虚拟惯性环节,其通过自身转子转速来动态调整虚拟惯性系数,储能设备根据自身的荷电状态来动态调整虚拟下垂系数来参与频率响应的下垂环节。通过搭建仿真模型来比较阶跃负荷扰动以及连续负荷扰动情况下,变系数方法、定系数方法以及风电单独调频三种手段的调频效果,验证文中控制策略可以有效减小系统频率偏差,同时双馈风机能充分利用自身所蕴含的转子动能,储能设备也能平滑出力,缓解其过充过放的问题,延长使用寿命。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
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）.
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.
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.
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).[
文摘Ultrasonic attenuation spectroscopy （UAS） is an attractive process analytical technology （PAT） for on-line real-time characterisation of slurries for particle size distribution （PSD） estimation. It is however only applicable to relatively low solid concentrations since existing instrument process models still cannot fully take into account the phenomena of particle-particle interaction and multiple scattering, leading to errors in PSD estimation. This paper investigates an alternative use of the raw attenuation spectra for direct multivariate statistical process control （MSPC）. The UAS raw spectra were processed using principal component analysis. The selected principal components were used to derive two MSPC statistics, the Hotelling＇s T2 and square prediction error （SPE）. The method is illustrated and demonstrated by reference to a wet milling process for processinR nanoparticles.
基金the City University of Hong Kong (Grant No. 7200080)
文摘We study the effect of state control on capital allocation and investment in China, where the government screens prospective stock issuers. We find that state firms are more likely to obtain government approval to conduct seasoned equity offerings than non-state firms. Further, non-state firms exhibit greater sensitivities of subsequent investment and stock performance to regulatory decisions on stock issuances than state firms. Our work suggests that state control of capital access distorts resource allocation and impedes the growth of non-state firms. We also provide robust evidence that financial constraints cause underinvestment.
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.
文摘随着风电渗透率的提高,双馈风电机组对电网频率的响应能力逐渐变弱,对于系统的频率稳定产生巨大影响。双馈风机单独调频能力不足以满足系统频率偏差要求,并且会产生弃风率高、能源利用率低的问题,为此将储能设备装设在双馈风机的并网侧,组成风储联合系统共同参与系统一次调频。文中通过利用风机的转子动能以及储能设备出力共同承担一次调频功率需求,提出基于风机转子转速以及荷电状态(State of Charge,SOC)的变系数风储联合系统参与一次调频控制策略,双馈风机通过释放或吸收自身转子动能响应虚拟惯性环节,其通过自身转子转速来动态调整虚拟惯性系数,储能设备根据自身的荷电状态来动态调整虚拟下垂系数来参与频率响应的下垂环节。通过搭建仿真模型来比较阶跃负荷扰动以及连续负荷扰动情况下,变系数方法、定系数方法以及风电单独调频三种手段的调频效果,验证文中控制策略可以有效减小系统频率偏差,同时双馈风机能充分利用自身所蕴含的转子动能,储能设备也能平滑出力,缓解其过充过放的问题,延长使用寿命。
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.
