A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to fur...A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.展开更多
Objective:Pelvic floor dysfunction is common among pregnant and postpartum women and significantly impacts quality of life.This study aims to translate the German Pelvic Floor Questionnaire for Pregnant and Postpartum...Objective:Pelvic floor dysfunction is common among pregnant and postpartum women and significantly impacts quality of life.This study aims to translate the German Pelvic Floor Questionnaire for Pregnant and Postpartum Women into Chinese and to evaluate its reliability and validity in the Chinese population.Methods:The questionnaire was translated using the Brislin model.A cross-sectional study was conducted among pregnant and postpartum women to assess the content validity,construct validity,Cronbach’sαcoefficient,test-retest reliability,and split-half reliability of the Chinese version.Results:A total of 72 women were included,with 6.9% being pregnant and 93.1% postpartum;the age was(32.3±3.6)years.The Chinese version of the questionnaire contains 4 dimensions and 45 items.The content validity index of individual items ranged from 0.833 to 1.000,with a scale-level content validity index of 0.977 and intraclass correlation coefficients(ICCs)exceeding 0.90.The overall Cronbach’s α coefficient was 0.891,with subscale coefficients ranging from 0.732 to 0.884(all ICCs>0.70).The testretest reliability of the total scale was 0.833,and for the 4 dimensions,bladder,bowel,prolapse,and sexual function,the values were 0.776,0.579,0.732,and 0.645,respectively.The split-half reliability was 0.74.Conclusion:The Chinese version of the questionnaire demonstrated good reliability and validity,indicating its applicability in assessing pelvic floor dysfunction and associated risk factors during pregnancy and postpartum.展开更多
A tracking stability control problem for the vertical electric stabilization system of moving tank based on adaptive robust servo control is addressed.This paper mainly focuses on two types of possibly fast timevaryin...A tracking stability control problem for the vertical electric stabilization system of moving tank based on adaptive robust servo control is addressed.This paper mainly focuses on two types of possibly fast timevarying but bounded uncertainty within the vertical electric stabilization system:model parameter uncertainty and uncertain nonlinearity.First,the vertical electric stabilization system is constructed as an uncertain nonlinear dynamic system that can reflect the practical mechanics transfer process of the system.Second,the dynamical equation in the form of state space is established by designing the angular tracking error.Third,the comprehensive parameter of system uncertainty is designed to estimate the most conservative effects of uncertainty.Finally,an adaptive robust servo control which can effectively handle the combined effects of complex nonlinearity and uncertainty is proposed.The feasibility of the proposed control strategy under the practical physical condition is validated through the tests on the experimental platform.This paper pioneers the introduction of the internal nonlinearity and uncertainty of the vertical electric stabilization system into the settlement of the tracking stability control problem,and validates the advanced servo control strategy through experiment for the first time.展开更多
In order to provide relay communication supports for future Chinese lunar exploration program,Queqiao-2 relay communication satellite was developed.Queqiao-2 can perform scientific observations with three kinds of sci...In order to provide relay communication supports for future Chinese lunar exploration program,Queqiao-2 relay communication satellite was developed.Queqiao-2 can perform scientific observations with three kinds of scientific instruments on board.The system design of Queqiao-2,including mission orbit and transfer orbit design,configuration and layout design,housekeeping and information flow design,power supply and distribution design,GNC and propulsion system design,communication links design,etc.,was accomplished through comprehensive tradeoff and evaluation on technical maturity,availability,schedule,cost,and so on.With a view to reducing development risk,both the platform and relay communication payloads were developed based on significant heritage from previous Queqiao relay satellite and other relevant spacecraft.Queqiao-2 features flexible system architecture to support multiple frequencies,modulations,data rates and software reconfigurations to meet new user requirements.Subsequent to a successful launch on March 20,2024,by means of 5 orbit maneuvers,Queqiao-2 was inserted into a highly elliptical frozen mission orbit around the moon with a 24h period on schedule.Following on-orbit tests and calibrations,Queqiao-2 has possessed the capacity to provide reliable relay communication services to multiple lunar exploration missions,as well as the capacity to perform scientific observations.Under the support of Queqiao-2,Chang′e-6 achieved its ambitious mission goal to collect and return samples from the moon′s mysterious far side.In the meanwhile,Queqiao-2 has also paved the way for the following Chinese lunar exploration missions including Chang′e-7 and Chang′e-8.The design life time of Queqiao-2 is more than 8 years.Benefit from flexibility and extensibility of relay communication system design,it is convenient to provide relay communication services for future lunar exploration missions of both China and other countries.In addition,innovative scientific observations would be performed during the period that no relay communication task is arranged.The system design of Queqiao-2 reflects the development philosophy of technical innovations and inheritance integration.Based on highly flexible and extensible system architecture,multiple and concurrent relay communication mission requirements can be met.It can provide strong supports for future lunar exploration missions.Successful launching,orbit entering and on-orbit tests of Queqiao-2 verified the correct design principle and versatility.By means of Queqiao-2,more innovative scientific outcomes are anticipated and lunar exploration activities can be facilitated.展开更多
To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dime...To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.展开更多
Technological trends in the automotive industry toward a software-defined and autonomous vehicle require a reassessment of today’s vehicle development process.The validation process soaringly shapes after starting wi...Technological trends in the automotive industry toward a software-defined and autonomous vehicle require a reassessment of today’s vehicle development process.The validation process soaringly shapes after starting with hardware-in-the-loop testing of control units and reproducing real-world maneuvers and physical interaction chains.Here,the road-to-rig approach offers a vast potential to reduce validation time and costs significantly.The present research study investigates the maneuver reproduction of drivability phenomena at a powertrain test bed.Although drivability phenomena occur in the frequency range of most up to 30∙Hz,the design and characteristics substantially impact the test setup’s validity.By utilization of modal analysis,the influence of the test bed on the mechanical characteristic is shown.Furthermore,the sensitivity of the natural modes of each component,from either specimen or test bed site,is determined.In contrast,the uncertainty of the deployed measurement equipment also affects the validity.Instead of an accuracy class indication,we apply the ISO/IEC Guide 98 to the measurement equipment and the test bed setup to increase the fidelity of the validation task.In conclusion,the present paper contributes to a traceable validity determination of the road-to-rig approach by providing objective metrics and methods.展开更多
Testing is a universal feature of social life.Throughout history people have been put to the test to prove their capabilities or to establish qualifications.Language tests play an important role in many people's l...Testing is a universal feature of social life.Throughout history people have been put to the test to prove their capabilities or to establish qualifications.Language tests play an important role in many people's lives,acting as gateways at important transitional moments in education.The college English test paper was reviewed and checked against the test specifications to see its content coverage and representative.To evaluate the test,this includes item analysis,descriptive statistics,validity,and what we see as the strong points and the weaknesses of the test based on the analysis and the testing conditions,both of which provided validity evidence.In order to gather details of the test items,item analysis was done to find out the difficulty and discrimination of each item and identify misfit items for further discussion.展开更多
IELTS conforms to the highest international standards of language assessment, testing four language skills-listening, reading, writing and speaking, which are equally weighted with scores reported on a 9-band scale of...IELTS conforms to the highest international standards of language assessment, testing four language skills-listening, reading, writing and speaking, which are equally weighted with scores reported on a 9-band scale of ability. Every candidate needs to take the same Listening and Speaking modules. The Speaking test of IELTS measures a candidate’s general proficiency in speaking in everyday situations via a structured, five-phase oral interview. As a performance test, the IELTS Speaking test has been one of the most important issues in the assessment of English proficiency. Assessment needs to be theory driven. For this reason, this paper will focus on validity, reliability and practicality of the IELTS Speaking test, qualities that affect assessment design.展开更多
This paper is concerned on the six qualities of language tests. They are: reliability, construct, validity, authenticity, interactiveness, impact and praticality. The six factors dependent on each other and are consid...This paper is concerned on the six qualities of language tests. They are: reliability, construct, validity, authenticity, interactiveness, impact and praticality. The six factors dependent on each other and are considered the essential basis for quality control of language tests.展开更多
The virtual enterprise will play a more and more im po rtant role in economy development. The virtual enterprise leader raises market a daptability and group cooperation ability through its dynamic management. Thus t ...The virtual enterprise will play a more and more im po rtant role in economy development. The virtual enterprise leader raises market a daptability and group cooperation ability through its dynamic management. Thus t he validity and efficiency of leader’s dynamic management determines the efficie ncy of the virtual enterprise operation, and the validity of the information flo w is one of the main factors. In this paper, the validity of the information flo w in the course of the leader’s dynamic management in the virtual enterprise is analyzed by using the economic searching theory and the information theory, and the possible ways to improve the validity and efficiency of leader’s dynamic man agement are indicated. Firstly, the basic concepts such as leader’s dynamic management, virtual enterpr ise, and its leader are defined. The dynamic management procedure for the virtua l enterprise leader is analyzed with the dynamic theory raised by Mowshowitz. Secondly, the model for the dynamic management of the virtual enterprise leader is constructed using multi-goal selection. The information flow validity for th e leader during the stages of the identification and the establishment is analyz ed with the economic searching theory and the information theory. Meanwhile, the value of the dynamic management policy is discussed with the information va lue theory. Finally, two ways to improve the validity of the information flow are obtained. The first way is to process the various kinds of information of the existing mem bers in the virtual enterprise for the future cooperative usage and to extend th e selective objects for the leader, and to make the detailed and clear mechanism of the object evaluation and selection (the market chance and the cooperative partner). The other way is to build the system of the effective transfer and process of the feedback information flow during the operation of the virtual ent erprise based on the information technology.展开更多
In order to present a new method for plugging channeling in oil field,the injection modes and validity period of foam system which plugged the formation water layer were studied by means of the experimental model whic...In order to present a new method for plugging channeling in oil field,the injection modes and validity period of foam system which plugged the formation water layer were studied by means of the experimental model which simulated the real conditions of oil wells existing channeling.Above all,the influence factors including reservoir pressure,permeability,oil saturation and gas-to-liquid ratio were studied through dynamic experiment.Then,in light of the technology characteristics of foam injection in oil field,the comparison between gas-liquid and liquid-gas injection modes was studied.The result shows that the gas-liquid injection mode can ensure the foam injectivity and plugging performance.The plugging validity of nitrogen foam injected into the formation water layer was evaluated in different plugging pressure gradients by the dynamic method which is more reasonable than the static evaluation method in laboratory.The research demonstrates that the plugging validity period of foam decreases with plugging pressure gradient increasing.If the plugging pressure gradient is 0.15 MPa/m,the validity period is 160 h.Finally,a empirical equation and a plate about the plugging validity and the plugging pressure gradient were obtained for forecasting the validity period of foam.展开更多
r-learning,which is based on e-learning and u-learning,is defined as a learning support system that intelligent robots serve verbal and nonverbal interactions on ubiquitous computing environment.In order to guarantee ...r-learning,which is based on e-learning and u-learning,is defined as a learning support system that intelligent robots serve verbal and nonverbal interactions on ubiquitous computing environment.In order to guarantee the advantages of r-learning contents with no limits of timc and place and with nonverbal interaction which are not in e-learning contents,in recent years,assessment criteria for r-learning contents are urgently rcquired.Therefore,the reliable and valid assessment criteria were developed for nonverbal interaction contents in r-learning,and its detailed research content is as follows.First,assessment criteria for nonverbal interaction in r-learning contents will be specified into gesture,facial expression,semi-verbal message,distance,physical contact and time.Second,the validity of the developed assessment criteria will be proved by statistics.Consequently,the assessment criteria for nonverbal interaction contents will be helpful when choosing the better r-learning content and producing the better r-learning content,and the reliability of school education is improved ultimately.展开更多
卫星海面高度异常产品再处理的研究多集中在欧洲和美国近海,中国近海尚未有过。在产生AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)全球0.25°多颗卫星海面高度异常产品时,只用了1/3~1/2的部分...卫星海面高度异常产品再处理的研究多集中在欧洲和美国近海,中国近海尚未有过。在产生AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)全球0.25°多颗卫星海面高度异常产品时,只用了1/3~1/2的部分沿轨资料,给区域海洋动力学研究造成了一定的限制。本研究尝试利用多颗卫星的所有沿轨资料及25个测潮站的观测资料,通过最优插值方法产生一份新的中国近海海面高度异常资料。新资料的空间分辨率仍为0.25°,但使用了来自3颗卫星(Jason-1、Jason-2、Cryo Sat-2)的所有沿轨资料及25个测潮站的观测资料。新资料的范围为10°S^50°N、90°~160°E。新资料与AVISO资料的对比分析表明新资料更接近沿轨海面高度异常观测,同时也更接近测潮站资料。与AVISO资料相比,新资料与沿轨海面高度异常观测的均方根误差降低了10.03%,与测潮站资料的均方根误差降低了9.6%。展开更多
In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a contro...In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear system.This structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.展开更多
基金Project(60873030) supported by the National Natural Science Foundation of China
文摘A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.
基金supported by the Natural Science Foundation of Hunan Province(2024JJ6626)the Hunan Provincial Key Laboratory of Regional Hereditary Birth Defects Prevention and Control(HPKL202320),China.
文摘Objective:Pelvic floor dysfunction is common among pregnant and postpartum women and significantly impacts quality of life.This study aims to translate the German Pelvic Floor Questionnaire for Pregnant and Postpartum Women into Chinese and to evaluate its reliability and validity in the Chinese population.Methods:The questionnaire was translated using the Brislin model.A cross-sectional study was conducted among pregnant and postpartum women to assess the content validity,construct validity,Cronbach’sαcoefficient,test-retest reliability,and split-half reliability of the Chinese version.Results:A total of 72 women were included,with 6.9% being pregnant and 93.1% postpartum;the age was(32.3±3.6)years.The Chinese version of the questionnaire contains 4 dimensions and 45 items.The content validity index of individual items ranged from 0.833 to 1.000,with a scale-level content validity index of 0.977 and intraclass correlation coefficients(ICCs)exceeding 0.90.The overall Cronbach’s α coefficient was 0.891,with subscale coefficients ranging from 0.732 to 0.884(all ICCs>0.70).The testretest reliability of the total scale was 0.833,and for the 4 dimensions,bladder,bowel,prolapse,and sexual function,the values were 0.776,0.579,0.732,and 0.645,respectively.The split-half reliability was 0.74.Conclusion:The Chinese version of the questionnaire demonstrated good reliability and validity,indicating its applicability in assessing pelvic floor dysfunction and associated risk factors during pregnancy and postpartum.
基金supported in part by the Nation Natural Science Foundation of China under Grant No.52175099China Postdoctoral Science Foundation under Grant No.2020M671494Jiangsu Planned Projects for Postdoctoral Research Funds under Grant No.2020Z179。
文摘A tracking stability control problem for the vertical electric stabilization system of moving tank based on adaptive robust servo control is addressed.This paper mainly focuses on two types of possibly fast timevarying but bounded uncertainty within the vertical electric stabilization system:model parameter uncertainty and uncertain nonlinearity.First,the vertical electric stabilization system is constructed as an uncertain nonlinear dynamic system that can reflect the practical mechanics transfer process of the system.Second,the dynamical equation in the form of state space is established by designing the angular tracking error.Third,the comprehensive parameter of system uncertainty is designed to estimate the most conservative effects of uncertainty.Finally,an adaptive robust servo control which can effectively handle the combined effects of complex nonlinearity and uncertainty is proposed.The feasibility of the proposed control strategy under the practical physical condition is validated through the tests on the experimental platform.This paper pioneers the introduction of the internal nonlinearity and uncertainty of the vertical electric stabilization system into the settlement of the tracking stability control problem,and validates the advanced servo control strategy through experiment for the first time.
文摘In order to provide relay communication supports for future Chinese lunar exploration program,Queqiao-2 relay communication satellite was developed.Queqiao-2 can perform scientific observations with three kinds of scientific instruments on board.The system design of Queqiao-2,including mission orbit and transfer orbit design,configuration and layout design,housekeeping and information flow design,power supply and distribution design,GNC and propulsion system design,communication links design,etc.,was accomplished through comprehensive tradeoff and evaluation on technical maturity,availability,schedule,cost,and so on.With a view to reducing development risk,both the platform and relay communication payloads were developed based on significant heritage from previous Queqiao relay satellite and other relevant spacecraft.Queqiao-2 features flexible system architecture to support multiple frequencies,modulations,data rates and software reconfigurations to meet new user requirements.Subsequent to a successful launch on March 20,2024,by means of 5 orbit maneuvers,Queqiao-2 was inserted into a highly elliptical frozen mission orbit around the moon with a 24h period on schedule.Following on-orbit tests and calibrations,Queqiao-2 has possessed the capacity to provide reliable relay communication services to multiple lunar exploration missions,as well as the capacity to perform scientific observations.Under the support of Queqiao-2,Chang′e-6 achieved its ambitious mission goal to collect and return samples from the moon′s mysterious far side.In the meanwhile,Queqiao-2 has also paved the way for the following Chinese lunar exploration missions including Chang′e-7 and Chang′e-8.The design life time of Queqiao-2 is more than 8 years.Benefit from flexibility and extensibility of relay communication system design,it is convenient to provide relay communication services for future lunar exploration missions of both China and other countries.In addition,innovative scientific observations would be performed during the period that no relay communication task is arranged.The system design of Queqiao-2 reflects the development philosophy of technical innovations and inheritance integration.Based on highly flexible and extensible system architecture,multiple and concurrent relay communication mission requirements can be met.It can provide strong supports for future lunar exploration missions.Successful launching,orbit entering and on-orbit tests of Queqiao-2 verified the correct design principle and versatility.By means of Queqiao-2,more innovative scientific outcomes are anticipated and lunar exploration activities can be facilitated.
文摘To accelerate the practicality of electromagnetic railguns,it is necessary to use a combination of threedimensional numerical simulation and experiments to study the mechanism of bore damage.In this paper,a three-dimensional numerical model of the augmented railgun with four parallel unconventional rails is introduced to simulate the internal ballistic process and realize the multi-physics field coupling calculation of the rail gun,and a test experiment of a medium-caliber electromagnetic launcher powered by pulse formation network(PFN)is carried out.Various test methods such as spectrometer,fiber grating and high-speed camera are used to test several parameters such as muzzle initial velocity,transient magnetic field strength and stress-strain of rail.Combining the simulation results and experimental data,the damage condition of the contact surface is analyzed.
文摘Technological trends in the automotive industry toward a software-defined and autonomous vehicle require a reassessment of today’s vehicle development process.The validation process soaringly shapes after starting with hardware-in-the-loop testing of control units and reproducing real-world maneuvers and physical interaction chains.Here,the road-to-rig approach offers a vast potential to reduce validation time and costs significantly.The present research study investigates the maneuver reproduction of drivability phenomena at a powertrain test bed.Although drivability phenomena occur in the frequency range of most up to 30∙Hz,the design and characteristics substantially impact the test setup’s validity.By utilization of modal analysis,the influence of the test bed on the mechanical characteristic is shown.Furthermore,the sensitivity of the natural modes of each component,from either specimen or test bed site,is determined.In contrast,the uncertainty of the deployed measurement equipment also affects the validity.Instead of an accuracy class indication,we apply the ISO/IEC Guide 98 to the measurement equipment and the test bed setup to increase the fidelity of the validation task.In conclusion,the present paper contributes to a traceable validity determination of the road-to-rig approach by providing objective metrics and methods.
文摘Testing is a universal feature of social life.Throughout history people have been put to the test to prove their capabilities or to establish qualifications.Language tests play an important role in many people's lives,acting as gateways at important transitional moments in education.The college English test paper was reviewed and checked against the test specifications to see its content coverage and representative.To evaluate the test,this includes item analysis,descriptive statistics,validity,and what we see as the strong points and the weaknesses of the test based on the analysis and the testing conditions,both of which provided validity evidence.In order to gather details of the test items,item analysis was done to find out the difficulty and discrimination of each item and identify misfit items for further discussion.
文摘IELTS conforms to the highest international standards of language assessment, testing four language skills-listening, reading, writing and speaking, which are equally weighted with scores reported on a 9-band scale of ability. Every candidate needs to take the same Listening and Speaking modules. The Speaking test of IELTS measures a candidate’s general proficiency in speaking in everyday situations via a structured, five-phase oral interview. As a performance test, the IELTS Speaking test has been one of the most important issues in the assessment of English proficiency. Assessment needs to be theory driven. For this reason, this paper will focus on validity, reliability and practicality of the IELTS Speaking test, qualities that affect assessment design.
文摘This paper is concerned on the six qualities of language tests. They are: reliability, construct, validity, authenticity, interactiveness, impact and praticality. The six factors dependent on each other and are considered the essential basis for quality control of language tests.
文摘The virtual enterprise will play a more and more im po rtant role in economy development. The virtual enterprise leader raises market a daptability and group cooperation ability through its dynamic management. Thus t he validity and efficiency of leader’s dynamic management determines the efficie ncy of the virtual enterprise operation, and the validity of the information flo w is one of the main factors. In this paper, the validity of the information flo w in the course of the leader’s dynamic management in the virtual enterprise is analyzed by using the economic searching theory and the information theory, and the possible ways to improve the validity and efficiency of leader’s dynamic man agement are indicated. Firstly, the basic concepts such as leader’s dynamic management, virtual enterpr ise, and its leader are defined. The dynamic management procedure for the virtua l enterprise leader is analyzed with the dynamic theory raised by Mowshowitz. Secondly, the model for the dynamic management of the virtual enterprise leader is constructed using multi-goal selection. The information flow validity for th e leader during the stages of the identification and the establishment is analyz ed with the economic searching theory and the information theory. Meanwhile, the value of the dynamic management policy is discussed with the information va lue theory. Finally, two ways to improve the validity of the information flow are obtained. The first way is to process the various kinds of information of the existing mem bers in the virtual enterprise for the future cooperative usage and to extend th e selective objects for the leader, and to make the detailed and clear mechanism of the object evaluation and selection (the market chance and the cooperative partner). The other way is to build the system of the effective transfer and process of the feedback information flow during the operation of the virtual ent erprise based on the information technology.
基金Project(2006CB705800)supported by the National Basic Research Program of China
文摘In order to present a new method for plugging channeling in oil field,the injection modes and validity period of foam system which plugged the formation water layer were studied by means of the experimental model which simulated the real conditions of oil wells existing channeling.Above all,the influence factors including reservoir pressure,permeability,oil saturation and gas-to-liquid ratio were studied through dynamic experiment.Then,in light of the technology characteristics of foam injection in oil field,the comparison between gas-liquid and liquid-gas injection modes was studied.The result shows that the gas-liquid injection mode can ensure the foam injectivity and plugging performance.The plugging validity of nitrogen foam injected into the formation water layer was evaluated in different plugging pressure gradients by the dynamic method which is more reasonable than the static evaluation method in laboratory.The research demonstrates that the plugging validity period of foam decreases with plugging pressure gradient increasing.If the plugging pressure gradient is 0.15 MPa/m,the validity period is 160 h.Finally,a empirical equation and a plate about the plugging validity and the plugging pressure gradient were obtained for forecasting the validity period of foam.
基金Project(2011)supported by the research grant of the Chungbuk National University,South Korea
文摘r-learning,which is based on e-learning and u-learning,is defined as a learning support system that intelligent robots serve verbal and nonverbal interactions on ubiquitous computing environment.In order to guarantee the advantages of r-learning contents with no limits of timc and place and with nonverbal interaction which are not in e-learning contents,in recent years,assessment criteria for r-learning contents are urgently rcquired.Therefore,the reliable and valid assessment criteria were developed for nonverbal interaction contents in r-learning,and its detailed research content is as follows.First,assessment criteria for nonverbal interaction in r-learning contents will be specified into gesture,facial expression,semi-verbal message,distance,physical contact and time.Second,the validity of the developed assessment criteria will be proved by statistics.Consequently,the assessment criteria for nonverbal interaction contents will be helpful when choosing the better r-learning content and producing the better r-learning content,and the reliability of school education is improved ultimately.
文摘卫星海面高度异常产品再处理的研究多集中在欧洲和美国近海,中国近海尚未有过。在产生AVISO(Archiving Validation and Interpolation of Satellite Oceanographic Data)全球0.25°多颗卫星海面高度异常产品时,只用了1/3~1/2的部分沿轨资料,给区域海洋动力学研究造成了一定的限制。本研究尝试利用多颗卫星的所有沿轨资料及25个测潮站的观测资料,通过最优插值方法产生一份新的中国近海海面高度异常资料。新资料的空间分辨率仍为0.25°,但使用了来自3颗卫星(Jason-1、Jason-2、Cryo Sat-2)的所有沿轨资料及25个测潮站的观测资料。新资料的范围为10°S^50°N、90°~160°E。新资料与AVISO资料的对比分析表明新资料更接近沿轨海面高度异常观测,同时也更接近测潮站资料。与AVISO资料相比,新资料与沿轨海面高度异常观测的均方根误差降低了10.03%,与测潮站资料的均方根误差降低了9.6%。
文摘In this paper, A fluid vector rudder flying-wing UAV is employed as the design object, so as to study the nonlinear design method and flight validation. For the maneuvering flight control, this paper presents a control structure. This control structure included the inner loop linearization decoupling methods to eliminate the known negative coupling and the outer loop backstepping methods for trajectory tracking control. The stability of the control structure has been proved in this paper. Compared with the traditional backstepping control method, this controller increases the inner loop decoupling structure and retains the aerodynamic damping term which makes the linearized system a weak nonlinear system.This structure can not only reduce the conservatism of the outer loop controller design, but also is convenient for engineering implementation. Simulation and flight validation results show that the proposed control scheme is effective.
