One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, the...One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.展开更多
growth in Africa, Ghana has been witnessing a surge in foreign direct investments. According to World Bank statistics, its economy grew by an average of 6 percent annually since 2005 before heading for an assessed 4.S...growth in Africa, Ghana has been witnessing a surge in foreign direct investments. According to World Bank statistics, its economy grew by an average of 6 percent annually since 2005 before heading for an assessed 4.S-percent growth this year. Foreign investments totaled over $12 billion from 1999 to 2009.展开更多
From September 13th-16th,2010,the Texworld show will be held at the Paris le Bourget exhibition centre.This show,735 weavers-which attests to the stability in the numbers of exhibitors
FOR 26-year-old Nigerian student Olufemi Lawal. China is home. He has set his heart on seeking employment in the country after completing his studies, but past regulations meant the inconvenience of leaving the countr...FOR 26-year-old Nigerian student Olufemi Lawal. China is home. He has set his heart on seeking employment in the country after completing his studies, but past regulations meant the inconvenience of leaving the country for a lengthy period before being able to return to job hunt.展开更多
Blesse D ncube knew there would be lucrative opportunities in learning Chinese.Therefore,the Zimbabwean chose to major in Chinese while doing her Bachelor of Arts and when she graduated in 2010,the 28-year-old found a...Blesse D ncube knew there would be lucrative opportunities in learning Chinese.Therefore,the Zimbabwean chose to major in Chinese while doing her Bachelor of Arts and when she graduated in 2010,the 28-year-old found a wealth of steady work in translation coming her way.展开更多
China’s Central Archives aspires to improve public access to information China is blessed with a long history,and for millenniums the people of China have used history as a mirror to learn from the past. An important...China’s Central Archives aspires to improve public access to information China is blessed with a long history,and for millenniums the people of China have used history as a mirror to learn from the past. An important part of the country’s history, all the archives of the Communist Party of China (CPC)展开更多
China’s art galleries,museums and libraries are to be made admission-free for the public In two years,Chinese citizens will not have to pay to enter public art galleries,the Ministry of Culture and the Ministry of Fi...China’s art galleries,museums and libraries are to be made admission-free for the public In two years,Chinese citizens will not have to pay to enter public art galleries,the Ministry of Culture and the Ministry of Finance jointly announced on February 10.展开更多
THE Lugu River is located at the eastern edge of the Qinghai-Tibet Plateau, within Ninglang County, Yunnan Province in southwestern China. This mysterious river, found 2,680 meters above sea level and covering an area...THE Lugu River is located at the eastern edge of the Qinghai-Tibet Plateau, within Ninglang County, Yunnan Province in southwestern China. This mysterious river, found 2,680 meters above sea level and covering an area of 50 square kilometers, is known as the "bright pearl of the plateau." The area around the Lugu River is not only beautiful but also known for its unique local ethnic customs of the Naxi, Lisu and Yi inhabitants.展开更多
To address the significant lifecycle degradation and inadequate state of charge(SOC)balance of electric vehicles(EVs)when mitigating wind power fluctuations,a dynamic grouping control strategy is proposed for EVs base...To address the significant lifecycle degradation and inadequate state of charge(SOC)balance of electric vehicles(EVs)when mitigating wind power fluctuations,a dynamic grouping control strategy is proposed for EVs based on an improved k-means algorithm.First,a swing door trending(SDT)algorithm based on compression result feedback was designed to extract the feature data points of wind power.The gating coefficient of the SDT was adjusted based on the compression ratio and deviation,enabling the acquisition of grid-connected wind power signals through linear interpolation.Second,a novel algorithm called IDOA-KM is proposed,which utilizes the Improved Dingo Optimization Algorithm(IDOA)to optimize the clustering centers of the k-means algorithm,aiming to address its dependence and sensitivity on the initial centers.The EVs were categorized into priority charging,standby,and priority discharging groups using the IDOA-KM.Finally,an two-layer power distribution scheme for EVs was devised.The upper layer determines the charging/discharging sequences of the three EV groups and their corresponding power signals.The lower layer allocates power signals to each EV based on the maximum charging/discharging power or SOC equalization principles.The simulation results demonstrate the effectiveness of the proposed control strategy in accurately tracking grid power signals,smoothing wind power fluctuations,mitigating EV degradation,and enhancing the SOC balance.展开更多
In order to study the dynamic response of the unmanned aerial vehicle cabin door opening and closing system under impact load conditions, considering the flexible treatment of mechanical components, and the system’s ...In order to study the dynamic response of the unmanned aerial vehicle cabin door opening and closing system under impact load conditions, considering the flexible treatment of mechanical components, and the system’s motion with different stiffness of energy-absorbing components, a rigid-flexible coupling model of the cabin door actuation system was established in LMS. Virtual. Motion. In Amesim, a control model of the motor was created. Through the Motion-Amesim co-simulation module, the dynamic module of the system was combined with the motor control module to complete the electromechanical coupling simulation and analyze the results. .展开更多
基金the financial support of the National Natural Science Foundation of China (No. 41121061)the National Basic Research Program (973) of China (Nos. 2012CB026101 and 2011CB013505)+1 种基金the Western Project Program of the Chinese Academy of Sciences (No. KZCX2-XB3-19)the Open Fund of State Key Laboratory of Frozen Soil Engineering (No. SKLFSE201209)
文摘One of the main construction problems in permafrost regions is protecting permafrost thermal stability. Although ventilating ducts and crushed-rock layers were successfully used in railway embankment construction, their effects might not meet large-width expressway requirements. The convection-intensifying composite embankment composed of perforated ventilation ducts and crushed-rock layers was numerically studied to investigate its cooling effects. Adopting a numerical model, the temperature fields for two kinds of composite embankment with and without air doors were analyzed considering air flow and heat transfer characteristics in porous media. The results show that wind velocity in the crushed-rock zone is intensified by the perforated ventilation duct. The underlying permafrost temperature obviously decreases, and the 0 °C isotherm position rises significantly due to composite embankment. The composite embankment with air doors is more effective than that without air doors. Therefore, the new convection-intensifying composite embankment is potentially a highly efficient cooling measure for construction in permafrost regions.
文摘growth in Africa, Ghana has been witnessing a surge in foreign direct investments. According to World Bank statistics, its economy grew by an average of 6 percent annually since 2005 before heading for an assessed 4.S-percent growth this year. Foreign investments totaled over $12 billion from 1999 to 2009.
文摘From September 13th-16th,2010,the Texworld show will be held at the Paris le Bourget exhibition centre.This show,735 weavers-which attests to the stability in the numbers of exhibitors
文摘FOR 26-year-old Nigerian student Olufemi Lawal. China is home. He has set his heart on seeking employment in the country after completing his studies, but past regulations meant the inconvenience of leaving the country for a lengthy period before being able to return to job hunt.
文摘Blesse D ncube knew there would be lucrative opportunities in learning Chinese.Therefore,the Zimbabwean chose to major in Chinese while doing her Bachelor of Arts and when she graduated in 2010,the 28-year-old found a wealth of steady work in translation coming her way.
文摘China’s Central Archives aspires to improve public access to information China is blessed with a long history,and for millenniums the people of China have used history as a mirror to learn from the past. An important part of the country’s history, all the archives of the Communist Party of China (CPC)
文摘China’s art galleries,museums and libraries are to be made admission-free for the public In two years,Chinese citizens will not have to pay to enter public art galleries,the Ministry of Culture and the Ministry of Finance jointly announced on February 10.
文摘THE Lugu River is located at the eastern edge of the Qinghai-Tibet Plateau, within Ninglang County, Yunnan Province in southwestern China. This mysterious river, found 2,680 meters above sea level and covering an area of 50 square kilometers, is known as the "bright pearl of the plateau." The area around the Lugu River is not only beautiful but also known for its unique local ethnic customs of the Naxi, Lisu and Yi inhabitants.
基金This study was supported by the National Key Research and Development Program of China(No.2018YFE0122200)National Natural Science Foundation of China(No.52077078)Fundamental Research Funds for the Central Universities(No.2020MS090).
文摘To address the significant lifecycle degradation and inadequate state of charge(SOC)balance of electric vehicles(EVs)when mitigating wind power fluctuations,a dynamic grouping control strategy is proposed for EVs based on an improved k-means algorithm.First,a swing door trending(SDT)algorithm based on compression result feedback was designed to extract the feature data points of wind power.The gating coefficient of the SDT was adjusted based on the compression ratio and deviation,enabling the acquisition of grid-connected wind power signals through linear interpolation.Second,a novel algorithm called IDOA-KM is proposed,which utilizes the Improved Dingo Optimization Algorithm(IDOA)to optimize the clustering centers of the k-means algorithm,aiming to address its dependence and sensitivity on the initial centers.The EVs were categorized into priority charging,standby,and priority discharging groups using the IDOA-KM.Finally,an two-layer power distribution scheme for EVs was devised.The upper layer determines the charging/discharging sequences of the three EV groups and their corresponding power signals.The lower layer allocates power signals to each EV based on the maximum charging/discharging power or SOC equalization principles.The simulation results demonstrate the effectiveness of the proposed control strategy in accurately tracking grid power signals,smoothing wind power fluctuations,mitigating EV degradation,and enhancing the SOC balance.
文摘In order to study the dynamic response of the unmanned aerial vehicle cabin door opening and closing system under impact load conditions, considering the flexible treatment of mechanical components, and the system’s motion with different stiffness of energy-absorbing components, a rigid-flexible coupling model of the cabin door actuation system was established in LMS. Virtual. Motion. In Amesim, a control model of the motor was created. Through the Motion-Amesim co-simulation module, the dynamic module of the system was combined with the motor control module to complete the electromechanical coupling simulation and analyze the results. .
