Suchergebnisse

This PhD thesis is dedicated to the performance analysis of Cooperative Adaptive Cruise Control (CACC) system for intelligent vehicle platoon with the main aims of alleviating traffic congestion and improving traffic safety. At first, the Constant Time Headway (CTH) spacing policy for vehicle platoon is introduced. Based on this spacing policy, a novel decentralized Two-Vehicle-Ahead CACC (TVACACC) system is proposed, in which the desired acceleration of two front vehicles is taken into account. Then the string stability of the proposed system is theoretically analyzed. It is shown that by using the multiple wireless communication among vehicles, a better string stability is obtained compared to the conventional system. Vehicle platoon in Stop-and-Go scenario is simulated with both normal and degraded communication.Secondly, a graceful degradation technique for CACC was presented, as an alternative fallback strategy when wireless communication is lost or badly degraded. The proposed strategy, which is referred to DTVACACC, uses Kalman filter to estimate the preceding vehicle's current acceleration as a replacement of the desired acceleration. It is shown that the performance is maintained at a much higher level.Finally, a Reinforcement Learning (RL) approach of CACC system is proposed. The policy-gradient algorithm is introduced to achieve the longitudinal control. Then simulation has shown that this new RL approach results in efficient performance for CACC. ; Cette thèse est consacrée à l'analyse de performance de Régulateurs de Vitesse Adaptatifs Coopératifs(CACC) pour un train de véhicules intelligents afin de réduire la congestion du trafic et améliorer la sécurité routière.Premièrement, la politique d'espacement, à Intervalles Constants de Temps (CTH) est introduite. Basé sur cette politique d'espacement, un nouveau système décentralisé de Deux-Véhicules-Devant CACC (TVACACC) est proposé, dans lequel l'accélération souhaitée de deux véhicules précédents est prise en compte. Ensuite, la stabilité de la ...

This PhD thesis is dedicated to the performance analysis of Cooperative Adaptive Cruise Control (CACC) system for intelligent vehicle platoon with the main aims of alleviating traffic congestion and improving traffic safety. At first, the Constant Time Headway (CTH) spacing policy for vehicle platoon is introduced. Based on this spacing policy, a novel decentralized Two-Vehicle-Ahead CACC (TVACACC) system is proposed, in which the desired acceleration of two front vehicles is taken into account. Then the string stability of the proposed system is theoretically analyzed. It is shown that by using the multiple wireless communication among vehicles, a better string stability is obtained compared to the conventional system. Vehicle platoon in Stop-and-Go scenario is simulated with both normal and degraded communication.Secondly, a graceful degradation technique for CACC was presented, as an alternative fallback strategy when wireless communication is lost or badly degraded. The proposed strategy, which is referred to DTVACACC, uses Kalman filter to estimate the preceding vehicle's current acceleration as a replacement of the desired acceleration. It is shown that the performance is maintained at a much higher level.Finally, a Reinforcement Learning (RL) approach of CACC system is proposed. The policy-gradient algorithm is introduced to achieve the longitudinal control. Then simulation has shown that this new RL approach results in efficient performance for CACC. ; Cette thèse est consacrée à l'analyse de performance de Régulateurs de Vitesse Adaptatifs Coopératifs(CACC) pour un train de véhicules intelligents afin de réduire la congestion du trafic et améliorer la sécurité routière.Premièrement, la politique d'espacement, à Intervalles Constants de Temps (CTH) est introduite. Basé sur cette politique d'espacement, un nouveau système décentralisé de Deux-Véhicules-Devant CACC (TVACACC) est proposé, dans lequel l'accélération souhaitée de deux véhicules précédents est prise en compte. Ensuite, la stabilité de la ...

Venture culture is the result of environment, history, custom and system. From the view of history, the difference of venture culture between the south and the north is resulted by natural environment and cultural atmosphere, but nowadays, they are being gradually combined by the market economy. The government should constantly reform itself and promote this cultural innovation in the process of cultural. Key words: venture culture, difference, integration Résumé La culture d'entrprise est le fruit de l'environnement, de l'histoire, de l'habitude et de l'institution. Du point de vue historique, la culture d'entreprise du Sud est bien différente de celle du Nord à cause des différences de l'environnement naturel et humain. Actuellement, sous l'impulsion de la vague de l'économie de marché, ces deux cultures sont en train de se frotter et se mêler. Le gouvernement doit, au cours de cette reconstitution de la culture, ne cesser de se remodeler et promouvoir la création culturelle. Mots-clés: la culture d'entrprise, les différences, se mêler 摘 要 創業文化是環境、歷史、習慣和制度的產物。從歷史上看南北創業文化由於自然環境和人文環境的不同而具有較大差異,當今在市場經濟大潮的衝擊下二者正在磨合和交融。政府在這種文化重構的過程中應不斷地改造自身並促進這種文化創新。關鍵詞:創業文化;差異;交融

AbstractThis research explored why a routine government notice caused a series of unexpected public opinion crises. We used K‐means clustering and Baidu Application Programming Interface Gateway to analyse 12,478 comments from Sina Weibo on Chinese Ministry of Commerce's release to encourage people to stock up necessities. Results show that even government's routine notice releases are regular events with relatively low objective risk, but in practice, how the government releases information and makes clarification would significantly infect public risk perception and emotion. First, ambiguous government releases magnify existing risks, especially during sensitive times, and resulting in heightened uncertainty, public risk perception and spread of negative emotions, therefore, lead to heated public discussion. Second, timely and effective clarifications can lower public risk perception as well as lead to positive emotions, although public banter may come along and generate another round of online public opinion within a short time. Our work answers why regular events would cause unexpected public opinion from the perspective of government behaviour, illustrates the dynamic interaction between government and online public opinion and can inform public policy aimed at more efficient communication with the public.