The effect of the information delay, which was caused by thc naturc of the distance sensors and wireless communication systems, on the string stability of platoon of automated vehicles was studied. The longitudinal ve...The effect of the information delay, which was caused by thc naturc of the distance sensors and wireless communication systems, on the string stability of platoon of automated vehicles was studied. The longitudinal vehicle dynamics model was built by taking the information delay into consideration, and three typical information frameworks, i.e., leader-predecessor framework （LPF）, multiple-predecessors framework （MPF） and predecessor-successor framework （PSF）, were defined and their related spacing error dynamics models in frequency domain were proposed. The string stability of platoon of automated vehicles was analyzed for the LPF, MPF and PSF, respectively. Meanwhile, the related sufficient string stable conditions were also obtained. The results demonstrate that the string stability can be guaranteed tbr the LPF and PSF with considering the information delay, but the ranges of the control gains of the control laws are smaller than those without considering the information delay. For the MPF, the ＂weak＂ string stability, which can be guaranteed without considering the information delay, cannot be obtained with considering the information delay. The comparative simulations further demonstrate that the LPF shows better string stability, but the PSF shows better string scalable performance.展开更多
For the constant distance spacing policy,the existing researches of the string stability focus on the single-predecessor information framework（SPIF） and predecessor-successor information framework（PSIF）.The resear...For the constant distance spacing policy,the existing researches of the string stability focus on the single-predecessor information framework（SPIF） and predecessor-successor information framework（PSIF）.The research results demonstrated that the string stability could not be guaranteed with the SPIF,and then the PSIF was proposed to resolve this string instability.But the issue,whether the string stability can be guaranteed when applying the PSIF,is still controversial.Meanwhile,most of the previous researches on the string stability were conducted without consideration of the parasitic time delays and lags.In this paper,the practical longitudinal vehicle dynamics model is built with consideration of the parasitic time delays and lags existing in the actuators,sensors or the communication systems.Secondly,the detailed theoretical analysis of string stability in frequency domain is conducted to demonstrate that the classical linear control laws can not ensure the string stability when applying both the symmetrical PSIF（SPSIF） and asymmetrical PSIF（APSIF）.Thirdly,a control law,which adds the position and velocity information of the leading vehicle,is proposed to guarantee string stability for small/medium platoon,and the other control law,which adds the acceleration information of the controlled vehicle,is proposed to guarantee string stability for large platoon as well as small/medium platoon.Finally,the comparative simulation is conducted to confirm the conducted analysis and the proposed control laws.The conducted research completes the means to analyze the string stability in frequency domain,provides the parameters＇ reference for the design and implementation of the practical automatic following controllers,and improves the reliability and stability of the platoon of automatic vehicles.展开更多
To achieve sustainable development goals,georeferenced data and geographic information systems play a crucial role.Yet,the way in which these data and systems are summoned upon rests on positivist assumptions which ov...To achieve sustainable development goals,georeferenced data and geographic information systems play a crucial role.Yet,the way in which these data and systems are summoned upon rests on positivist assumptions which overlook both epistemological and ethical concerns.This is epitomized by the integrated geospatial information framework(IGIF)of the United Nations,which,from the perspective of sustainable development,aims to provide guidance for the management of geoinformation and related tools,considering these as mirrors of the physical world.In this respect,the article has three main goals.First,it delivers an epistemological and ethical critique of the IGIF,by highlighting its internal tensions.Second,it suggests how the IGIF and similar geoinformation initiatives can benefit from an ethical reflection that allows to conduct georeferenced practices in a fair(er)way.Third,it designs an ethics assessment list for self-evaluating the ethical robustness of geoinformation initiatives as ecosystems.展开更多
Purpose: The aim of this paper is to develop a standardized and reliable measurement tool for assessing information-seeking behavior of undergraduate students.Design/methodology/approach: Based on information literacy...Purpose: The aim of this paper is to develop a standardized and reliable measurement tool for assessing information-seeking behavior of undergraduate students.Design/methodology/approach: Based on information literacy and information-seeking behavior theories, expert advice and students' interview, items of undergraduates' informationseeking behavior indicators were selected. With the analysis of homogeneity reliability, item analysis and factor analysis, this study constructs an assessment system to evaluate reliability and validity of the scale.Findings: The information-seeking behavior scale for undergraduates has divided undergraduates' information-seeking behavior into seven dimensions, which include 46 items. The reliability analysis of Cronbach's α was 0.910, and the coefficient of split-half reliability was0.817. The results of factor analysis showed that Kaiser-Meyer-Olkin(KMO) was 0.864,which indicates 55.536% of the total variation could be explained by the above seven dimensions.Research limitations: Due to a small sample size and limited sample distribution, further research need be conducted in an expanded sample size in order to explore the application scope of this evaluation system; in addition, the stability of the scale also need be confirmed.Practical implications: The paper sets up an information-seeking behavior evaluation system for undergraduates and explores the characteristics of their information-seeking behavior.This study provides guidance for the development of future information literacy education and the improvement of the information literacy level of undergraduates.Originality/value: An information-seeking behavior scale for undergraduates has been developed, which comprehensively covers information need, information source, information evaluation, information retrieval, information management, information utilization and information morality. The scale is proved to have good reliability, validity, popularity anddiscrimination that it is qualified to be an assessment tool of information-seeking behavior for Chinese undergraduates.展开更多
Currently many enterprises have established some independent application systems such as CAD, CAPP, CAE and so on. Enterprise information integration makes these information islands connected, and thereby forms a unif...Currently many enterprises have established some independent application systems such as CAD, CAPP, CAE and so on. Enterprise information integration makes these information islands connected, and thereby forms a uniform enterprise-wide information environment. First this paper discusses the main research contents of enterprise integration. Then the author introduces an Internet-based configurable and open information integration framework, and presents a multi-tier integration architecture based on reusable component. Finally a development case of enterprise integration framework is introduced.展开更多
基金Project(20070006011) supported by the Doctoral Foundation of Ministry of Education of China
文摘The effect of the information delay, which was caused by thc naturc of the distance sensors and wireless communication systems, on the string stability of platoon of automated vehicles was studied. The longitudinal vehicle dynamics model was built by taking the information delay into consideration, and three typical information frameworks, i.e., leader-predecessor framework （LPF）, multiple-predecessors framework （MPF） and predecessor-successor framework （PSF）, were defined and their related spacing error dynamics models in frequency domain were proposed. The string stability of platoon of automated vehicles was analyzed for the LPF, MPF and PSF, respectively. Meanwhile, the related sufficient string stable conditions were also obtained. The results demonstrate that the string stability can be guaranteed tbr the LPF and PSF with considering the information delay, but the ranges of the control gains of the control laws are smaller than those without considering the information delay. For the MPF, the ＂weak＂ string stability, which can be guaranteed without considering the information delay, cannot be obtained with considering the information delay. The comparative simulations further demonstrate that the LPF shows better string stability, but the PSF shows better string scalable performance.
基金supported by Doctoral Foundation of Ministry of Education of China (Grant No.20070006011)
文摘For the constant distance spacing policy,the existing researches of the string stability focus on the single-predecessor information framework（SPIF） and predecessor-successor information framework（PSIF）.The research results demonstrated that the string stability could not be guaranteed with the SPIF,and then the PSIF was proposed to resolve this string instability.But the issue,whether the string stability can be guaranteed when applying the PSIF,is still controversial.Meanwhile,most of the previous researches on the string stability were conducted without consideration of the parasitic time delays and lags.In this paper,the practical longitudinal vehicle dynamics model is built with consideration of the parasitic time delays and lags existing in the actuators,sensors or the communication systems.Secondly,the detailed theoretical analysis of string stability in frequency domain is conducted to demonstrate that the classical linear control laws can not ensure the string stability when applying both the symmetrical PSIF（SPSIF） and asymmetrical PSIF（APSIF）.Thirdly,a control law,which adds the position and velocity information of the leading vehicle,is proposed to guarantee string stability for small/medium platoon,and the other control law,which adds the acceleration information of the controlled vehicle,is proposed to guarantee string stability for large platoon as well as small/medium platoon.Finally,the comparative simulation is conducted to confirm the conducted analysis and the proposed control laws.The conducted research completes the means to analyze the string stability in frequency domain,provides the parameters＇ reference for the design and implementation of the practical automatic following controllers,and improves the reliability and stability of the platoon of automatic vehicles.
文摘To achieve sustainable development goals,georeferenced data and geographic information systems play a crucial role.Yet,the way in which these data and systems are summoned upon rests on positivist assumptions which overlook both epistemological and ethical concerns.This is epitomized by the integrated geospatial information framework(IGIF)of the United Nations,which,from the perspective of sustainable development,aims to provide guidance for the management of geoinformation and related tools,considering these as mirrors of the physical world.In this respect,the article has three main goals.First,it delivers an epistemological and ethical critique of the IGIF,by highlighting its internal tensions.Second,it suggests how the IGIF and similar geoinformation initiatives can benefit from an ethical reflection that allows to conduct georeferenced practices in a fair(er)way.Third,it designs an ethics assessment list for self-evaluating the ethical robustness of geoinformation initiatives as ecosystems.
基金supported by the National Social Science Foundation of China(Grant No.:11BTQ044)the Innovative Training Program for College Students in Changsha University(Grant No:CW11255)
文摘Purpose: The aim of this paper is to develop a standardized and reliable measurement tool for assessing information-seeking behavior of undergraduate students.Design/methodology/approach: Based on information literacy and information-seeking behavior theories, expert advice and students' interview, items of undergraduates' informationseeking behavior indicators were selected. With the analysis of homogeneity reliability, item analysis and factor analysis, this study constructs an assessment system to evaluate reliability and validity of the scale.Findings: The information-seeking behavior scale for undergraduates has divided undergraduates' information-seeking behavior into seven dimensions, which include 46 items. The reliability analysis of Cronbach's α was 0.910, and the coefficient of split-half reliability was0.817. The results of factor analysis showed that Kaiser-Meyer-Olkin(KMO) was 0.864,which indicates 55.536% of the total variation could be explained by the above seven dimensions.Research limitations: Due to a small sample size and limited sample distribution, further research need be conducted in an expanded sample size in order to explore the application scope of this evaluation system; in addition, the stability of the scale also need be confirmed.Practical implications: The paper sets up an information-seeking behavior evaluation system for undergraduates and explores the characteristics of their information-seeking behavior.This study provides guidance for the development of future information literacy education and the improvement of the information literacy level of undergraduates.Originality/value: An information-seeking behavior scale for undergraduates has been developed, which comprehensively covers information need, information source, information evaluation, information retrieval, information management, information utilization and information morality. The scale is proved to have good reliability, validity, popularity anddiscrimination that it is qualified to be an assessment tool of information-seeking behavior for Chinese undergraduates.
文摘Currently many enterprises have established some independent application systems such as CAD, CAPP, CAE and so on. Enterprise information integration makes these information islands connected, and thereby forms a uniform enterprise-wide information environment. First this paper discusses the main research contents of enterprise integration. Then the author introduces an Internet-based configurable and open information integration framework, and presents a multi-tier integration architecture based on reusable component. Finally a development case of enterprise integration framework is introduced.
