Nowadays,in order to expand the roof view to bring passengers closer to nature,more and more new energy vehicles are opting for canopy designs without sunshades.However,after removing traditional sunshades,new solutio...Nowadays,in order to expand the roof view to bring passengers closer to nature,more and more new energy vehicles are opting for canopy designs without sunshades.However,after removing traditional sunshades,new solutions must be sought to address issues such as heat insulation,glaring sunlight,and interior reflections from the roof glass during the summer months.This paper conducts an in-depth analysis of the technical advantages and shortcomings of sunshade-free canopy in terms of heat insulation and interior reflections during summer,from both theoretical analysis and experimental comparison perspectives,and proposes improvement strategies.The research results indicate that although the panoramic roof enhances the vehicle's interior view and technological appeal,it still has shortcomings in terms of heat insulation and the problem of interior reflections caused by direct sunlight.The proposed improvement strategies can effectively mitigate these issues,and offers consumers more comfortable and intelligent driving experiences.展开更多
With rapid development of unmanned aerial vehicles(UAVs), more and more UAVs access satellite networks for data transmission. To improve the spectral efficiency, non-orthogonal multiple access(NOMA) is adopted to inte...With rapid development of unmanned aerial vehicles(UAVs), more and more UAVs access satellite networks for data transmission. To improve the spectral efficiency, non-orthogonal multiple access(NOMA) is adopted to integrate UAVs into the satellite network, where multiple satellites cooperatively serve the UAVs and mobile terminal using the Ku-band and above. Taking into account the rain fading and the fading correlation, the outage performance is first analytically obtained for fixed power allocation and then efficiently calculated by the proposed power allocation algorithm to guarantee the user fairness. Simulation results verify the outage performance analysis and show the performance improvement of the proposed power allocation scheme.展开更多
The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO streng...The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China's 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.展开更多
To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the...To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the North China Plain,from 10 February to 6 March 2015.There were 20 days exceeding the threshold value of secondary Chinese Ambient Air Quality Standards for PM2.5(75 μg m-3,daily average over 24 h)during the study period.Five air pollution episodes were selected for investigation.During the pre-holiday pollution episode,NH^+_4,NO^-_3,and SO^(2-)_4 were more abundant,indicating that air pollution was caused by motor vehicle exhaust emissions and coal consumption under unfavorable meteorological conditions.During Chinese Lunar New Year's Eve,widespread use of fireworks resulted in extremely high aerosol concentrations.Firework displays caused increases in K+ and also enrichment of SO^(2-)_4 relative to NO^-_3.The holiday pollution episode was caused by regional transport,characterized by abundant SO^(2-)_4 and NH^+_4.In addition,the aging processes of the particles from fireworks discharge played an important role in the formation of NO-3and SO^(2-)_4.The Lantern Festival episode was characterized by a transition from the enrichment of K+ to secondary inorganic ions(NO^-_3,SO^(2-)_4,and NH^+_4).The results of this study are useful for a detailed understanding of the variation in atmospheric compositions and sources caused by anthropogenic activity,and highlight the importance of controlling intensive fireworks discharge.展开更多
A filtering algorithm and direction identification method are presented for the positioning system of the mid-speed maglev train. Considering the special structure of the mid-speed maglev train, the ground position es...A filtering algorithm and direction identification method are presented for the positioning system of the mid-speed maglev train. Considering the special structure of the mid-speed maglev train, the ground position estimation method is adopted for its traction system. As the train is running, the induction loop-cable receives the signal sent by the on-board antenna to detect the position and direction of the train. But the height of the on-board antenna relative to the loop-cable is highly vulnerable to the change of the suspension height and the magnetic field produced by the traction during traveling, which may lead to amplitude fluctuation of the received signal. Consequently, the position estimation may be inaccurate. Therefore, a discrete second-order nonlinear trackdifferentiator is proposed based on the boundary characteristic curves, and the new differentiator could also extract the running direction of the train for the traction system. The experimental results show that the tracking differentiator can effectively filter out the signal interference and can provide accurate direction signal.展开更多
According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was ...According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II,pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.展开更多
Along with the development of automatical truck dispatching in open pits, it is important to es-tablish general-gurpose criteria for truck dispatching optimization. The existing dispatching criteria are briefly introd...Along with the development of automatical truck dispatching in open pits, it is important to es-tablish general-gurpose criteria for truck dispatching optimization. The existing dispatching criteria are briefly introduced and optimal dispatching criteria for different haulage systems are recommended. Obvious economic results have been obtained from case studies applying the recommended dispatching criteria.展开更多
The development and experiment of a computer-controlled truck dispatching system in Surface mine is presented in this paper.It includes the system overall design, the system working mode design, the selection of the b...The development and experiment of a computer-controlled truck dispatching system in Surface mine is presented in this paper.It includes the system overall design, the system working mode design, the selection of the best truck travel path, the development of truck fleet programming, the development of database management system, and the development of truck real time dispatching, etc. The successful experiment is carried out in Huolinhe surface mine, and the satisfied results are obtained. Application of this system can improve the system production and the mine management. This system is the first one in our country at present.展开更多
Combination of a bus system and cable car system can reduce the overall congestion of traffic in urban areas, where surrounding hills or mountains hold larger settlements or tourist and recreational infrastructure. Wi...Combination of a bus system and cable car system can reduce the overall congestion of traffic in urban areas, where surrounding hills or mountains hold larger settlements or tourist and recreational infrastructure. With this kind of integration number of individual car trips can be significantly reduced. In this paper, the authors present an analysis of the pilot project implementation, which was held in Maribor. The authors conducted a limited test trial of two means of transportation, combining them into a single operating transport offer for inhabitants and tourists. Combined transport option proved to be a good starting point for reduction of traffic and parking congestion during winter tourist season and beyond. Method used in the research, in order to gain actual potential of integrating two systems and improving public transport offer, was establishment and implementation of the pilot project in Maribor during January 2011. Data was gathered through interviews of two interest groups. The first covered the users who were brought to the foothills of Pohorje's ski center by bus. The second covered the cable car users that were traveling to the top of Pohorje. For a limited time period, a trial principle of a single ticket was established, which gave ski-pass holders free bus ride on bus line No. 6. With the aim of reducing CO2, test drives of hybrid bus and compressed natural gas bus were conducted alongside many promotional activities with which users were informed of importance of environmentally friendly mobility options.展开更多
Open pit mining operations utilize large scale and expensive equipment. For the mines implementing shovel and truck operation system, trucks constitute a large portion of these equipment and are used for hauling the m...Open pit mining operations utilize large scale and expensive equipment. For the mines implementing shovel and truck operation system, trucks constitute a large portion of these equipment and are used for hauling the mined materials. In order to have sustainable and viable operation, these equipment need to be utilized efficiently with minimum operating cost. Maintenance cost is a significant proportion of the overall operating costs. The maintenance cost of a truck changes non-linearly depending on the type, age and truck types. A new approach based on stochastic integer programming (SIP) techniques is used for annually scheduling a fixed fleet of mining trucks in a given operation, over the life of mine (multi-year time horizon) to minimize maintenance cost. The maintenance cost data in mining usually has uncertainty caused from the variability of the operational conditions at mines. To estimate the cost, usually historic data from different operations for new mines, and/or the historic data at the operating mines are used. However, maintenance cost varies depending on road conditions, age of equipment and many other local conditions at an operation. Traditional models aim to estimate the maintenance cost as a deterministic single value and financial evaluations are based on the estimated value. However, it does not provide a confidence on the estimate. The proposed model in this study assumes the truck maintenance cost is a stochastic parameter due to the significant level of uncertainty in the data and schedules the available fleet to meet the annual production targets. The scheduling has been performed by applying both the proposed stochastic and deterministic approaches. The approach provides a distribution for the maintenance cost of the optimized equipment schedule minimizing the cost.展开更多
This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool. The results are summarized as follows: (1) A wave trai...This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool. The results are summarized as follows: (1) A wave train pattern (OKJ pattern) originating from the upstream areas of the Sea of Okhotsk to the subtropical regions could display its strong signal in early and middle summer. The OKJ pattern is clearly recognized in the first EOF component in Eurasia. (2) The other wave train pattern originating fi'om the Philippines via Japan to North America (the P-J pattern) shows quite strong signals in the whole summer. Although the P-J pattern is described as the second EOF component around the area from East Asia to Northeast Pacific Ocean, the variance contribution is the same as that of OKJ pattern in the first EOF component. (3) The composite analyses indicate that the OKJ and P-J wave trains could coexist to some extents.展开更多
On lunar exploration missions, the rovers which can move and explore directly are considered by various agency like NASA (National Aeronautics and Space Administration), JAXA (Japan Aerospace Exploration Agency), ...On lunar exploration missions, the rovers which can move and explore directly are considered by various agency like NASA (National Aeronautics and Space Administration), JAXA (Japan Aerospace Exploration Agency), ESA (European Space Agency). Lunar rovers are required to move on rough terrains such as craters and rear cliffs where it is scientifically very important to explore. However, there is a problem that the rovers have possibility of stack because of the lunar surface is covered with loose soil named Regolith. Therefore, this paper investigates a mechanism of kinetic behavior between the wheels of the exploration rovers and loose soil. And then, this paper proposed a flexible wheel to solve like that problems. The flexible wheel has the surface which can be changed flexibly toward rough terrain. Running experiments on loose soil which imitated regolith were carried out to observe the traversability of the flexible wheel using slip ratio. Traversality of flexible wheel was better than the circular rigid wheel. The authors believe that stress distribution is important. The stress distribution of the flexible wheels is horizontally long and stress value is small. However, the stress distribution can be changed by loaded more weight. Therefore, the relationship between the stress and the running performance was considered using this differential stress distribution. In experiments, the authors used the flexible wheel with simple structure (3 limbs). From these considerations, the relationship between the stress of the flexible wheel and the running performance was described.展开更多
It is known that the transport sector has a fundamental importance in the modem society, as the economic development is directly linked to mobility. Over the years, the transport became linked to different environment...It is known that the transport sector has a fundamental importance in the modem society, as the economic development is directly linked to mobility. Over the years, the transport became linked to different environmental problems, which can be detached greenhouse gases emissions in the atmosphere, where in recent decades can be perceived the intensification and targeting of efforts in research and development of new technologies to reduce the levels of greenhouse gases emissions in the atmosphere. In this context, it can be highlighted the modem systems of electronic engine management, new automotive catalysts and the use of renewable fuels which contribute to reducing the environmental impact. This research had, as its purpose, the analysis of fuels characteristics used for testing, comparative analysis of gas emissions from a motor vehicle running on ethanol or natural gas fuels according to NBR 6601 and conducting tests to estimate the maximum catalytic efficiency. For the implementation of trial, a flex vehicle was installed in a chassis dynamometer equipped with a gas analyzer, in order that before the completion of the urban driving cycle, were determined the content of hydrocarbons corrected, carbon monoxide corrected, carbon dioxide and oxygen present in gas emissions from the engine. The research concluded that: the performance analysis for characterization of fuel showed consistent with ANP specifications; after tests performances, it can be stated that natural gas fuel was the fuel which had the highest content of hydrocarbons and carbon monoxide corrected, while ethanol had the highest amount of carbon dioxide and oxygen residue present in gas emissions; before a comparative analysis, the vehicle catalyst showed the best performance for reducing the content of hydrocarbon corrected present in exhaustion gases when it worked with natural gas fuel and showed maximum efficiency of 100% to reduce the content of carbon monoxide corrected for both fuels. Before this, it can be stated that the vehicle catalyst showed satisfactory performance, achieving good reduction levels of greenhouse gases emissions.展开更多
The GF-3 satellite was successfully launched at 06:55 Beijing time on August10 using a LM-4C launch vehicle from the Taiyuan Satellite Launch Center.The launch was the 233rd flight of a LM family launch vehicle and t...The GF-3 satellite was successfully launched at 06:55 Beijing time on August10 using a LM-4C launch vehicle from the Taiyuan Satellite Launch Center.The launch was the 233rd flight of a LM family launch vehicle and the carrier rocket LM-4C was developed by the Shanghai Academy of Spaceflight Technology.展开更多
With the high focus on autonomous aerial refueling(AAR), it becomes increasingly urgent to design efficient methods or algorithms for solving the AAR problems in complicated aerial environments. A vision-based technol...With the high focus on autonomous aerial refueling(AAR), it becomes increasingly urgent to design efficient methods or algorithms for solving the AAR problems in complicated aerial environments. A vision-based technology for AAR is developed in this paper, and five monocular and binocular visual algorithms for pose estimation of the unmanned aerial vehicles(UAVs) are adopted and verified in this AAR system. The real-time on-board vision system is also designed for precise navigation in the UAVs docking phase. A series of out-door comparative experiments for different pose estimation algorithms are conducted to verify the feasibility and accuracy of the vision algorithms in AAR.展开更多
In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles(UAVs) in winds with constant speed and altitude is developed. Different to the widely considered line or orbit followin...In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles(UAVs) in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field(VF) strategy with the sliding mode control(SMC) method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm.展开更多
A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high...A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high-resolution paleoclimate record for eastern China during a time interval (from 54 000 to 19 000 aBP) of the last glaciation. The continuous record of oxygen-18 variations in the stalagmite, indicating a precipitation history of the East Asian monsoon, shows not only signals of the Heinrich events, but also the Dansgaard-Oeschger cycles which are first found in the last glacial climate record of the East Asian monsoon area. Although the stalagmite-based climatic signals match well with the GRIP ice core record, some differences between the two re-cords can be recognized: (1) The last glacial climate changes in eastern China exhibited a long-term remarkably cooling trend, superimposed on which were four successive Bond’s cycles illus-trated by the δ18O curve. This strong cooling tendency may be an effect of the strong summer mon-soon event during the MIS 3 over the Tibetan Plateau. (2) There exist some phase differences of 1000—2000 years between the cooling events in the stalagmite-based climate signal and the GRIP ice core record. Such differences should be further verified by calibrations of multiple dating meth-ods.展开更多
文摘Nowadays,in order to expand the roof view to bring passengers closer to nature,more and more new energy vehicles are opting for canopy designs without sunshades.However,after removing traditional sunshades,new solutions must be sought to address issues such as heat insulation,glaring sunlight,and interior reflections from the roof glass during the summer months.This paper conducts an in-depth analysis of the technical advantages and shortcomings of sunshade-free canopy in terms of heat insulation and interior reflections during summer,from both theoretical analysis and experimental comparison perspectives,and proposes improvement strategies.The research results indicate that although the panoramic roof enhances the vehicle's interior view and technological appeal,it still has shortcomings in terms of heat insulation and the problem of interior reflections caused by direct sunlight.The proposed improvement strategies can effectively mitigate these issues,and offers consumers more comfortable and intelligent driving experiences.
基金supported in part by the National Natural Science Foundation of China (No. 91638205, 91438206, 61771286, 61621091)
文摘With rapid development of unmanned aerial vehicles(UAVs), more and more UAVs access satellite networks for data transmission. To improve the spectral efficiency, non-orthogonal multiple access(NOMA) is adopted to integrate UAVs into the satellite network, where multiple satellites cooperatively serve the UAVs and mobile terminal using the Ku-band and above. Taking into account the rain fading and the fading correlation, the outage performance is first analytically obtained for fixed power allocation and then efficiently calculated by the proposed power allocation algorithm to guarantee the user fairness. Simulation results verify the outage performance analysis and show the performance improvement of the proposed power allocation scheme.
基金Joint Project of Natural Science Foundation of China and Yunnan Province (U0833602)
文摘The first two series(RMM1 and RMM2) of RMM Index(all-Season Real-time Multivariate MJO Index) are computed to obtain the interannual variation of the preceding winter(preceding December to current February) MJO strength,according to which active(or inactive) years of preceding winter MJO are divided.By utilizing the data provided by NCEP/NCAR,CMAP and China's 160 stations from 1979 to 2008,we studied the preceding winter MJO strength and discovered that the summer precipitation in the basin are of significantly negative correlation,i.e.when the preceding winter MJO is relatively active,the summer precipitation in the basin decreases,and vise verse.We also analyzed the causes.When the preceding winter MJO is relatively active,its release of potential heat facilities Inter-Tropical Convergence Zone(ITCZ) to strengthen and locate northward in winter and propagate northeastward.This abnormal situation lasts from winter to summer.In mid-May,ITCZ jumps northward to the South China Sea,the western Pacific subtropical high withdraws eastward,and the South China Sea summer monsoon sets off and strengthens.In summer,ITCZ propagates to South China Sea-subtropical western Pacific,the zonal circulation of subtropical Pacific strengthens,and a local meridional circulation of the South China Sea to the basin area forms,giving rise to the East Asia Pacific teleconnection wave-train.An East Asian monsoon trough and the Meiyu front show opposite features from south to north,the East Asian summer monsoon strengthens and advances northward.As a result,the summer monsoon is weakened as the basin is controlled by the subtropical high continually,with less rain in summer.On the contrary,when the preceding winter MJO is inactive,ITCZ weakens and is located southward,the subtropical high is located southward in summer,and the basin is in a region of ascending airflow with prevailing southwest wind.The East Asian monsoon trough and EASM weaken so that summer monsoon is reduced in the basin where precipitation increases.
基金supported by the Beijing Natural Science Foundation[grant number 8142034]Strategic Priority Research Program(B)of the Chinese Academy of Sciences[grant numbers XDB0502050 and XDB05030203]
文摘To better understand the characteristics of air quality and the relationship between the chemical composition evolution and source variation,an intensive atmospheric campaign was conducted in Tianjin,a megacity of the North China Plain,from 10 February to 6 March 2015.There were 20 days exceeding the threshold value of secondary Chinese Ambient Air Quality Standards for PM2.5(75 μg m-3,daily average over 24 h)during the study period.Five air pollution episodes were selected for investigation.During the pre-holiday pollution episode,NH^+_4,NO^-_3,and SO^(2-)_4 were more abundant,indicating that air pollution was caused by motor vehicle exhaust emissions and coal consumption under unfavorable meteorological conditions.During Chinese Lunar New Year's Eve,widespread use of fireworks resulted in extremely high aerosol concentrations.Firework displays caused increases in K+ and also enrichment of SO^(2-)_4 relative to NO^-_3.The holiday pollution episode was caused by regional transport,characterized by abundant SO^(2-)_4 and NH^+_4.In addition,the aging processes of the particles from fireworks discharge played an important role in the formation of NO-3and SO^(2-)_4.The Lantern Festival episode was characterized by a transition from the enrichment of K+ to secondary inorganic ions(NO^-_3,SO^(2-)_4,and NH^+_4).The results of this study are useful for a detailed understanding of the variation in atmospheric compositions and sources caused by anthropogenic activity,and highlight the importance of controlling intensive fireworks discharge.
基金Project(11226144) supported by the National Natural Science Foundation of China
文摘A filtering algorithm and direction identification method are presented for the positioning system of the mid-speed maglev train. Considering the special structure of the mid-speed maglev train, the ground position estimation method is adopted for its traction system. As the train is running, the induction loop-cable receives the signal sent by the on-board antenna to detect the position and direction of the train. But the height of the on-board antenna relative to the loop-cable is highly vulnerable to the change of the suspension height and the magnetic field produced by the traction during traveling, which may lead to amplitude fluctuation of the received signal. Consequently, the position estimation may be inaccurate. Therefore, a discrete second-order nonlinear trackdifferentiator is proposed based on the boundary characteristic curves, and the new differentiator could also extract the running direction of the train for the traction system. The experimental results show that the tracking differentiator can effectively filter out the signal interference and can provide accurate direction signal.
基金Project(U1134203)supported by the National Natural Science Foundation of China
文摘According to the analysis of the turbulent intensity level around the high-speed train, the maximum turbulent intensity ranges from 0.2 to 0.5 which belongs to high turbulent flow. The flow field distribution law was studied and eight types of flow regions were proposed. They are high pressure with air stagnant region, pressure decreasing with air accelerating region, low pressure with high air flow velocity region I, turbulent region, steady flow region, low pressure with high air flow velocity region II,pressure increasing with air decelerating region and wake region. The analysis of the vortex structure around the train shows that the vortex is mainly induced by structures with complex mutation and large curvature change. The head and rear of train, the underbody structure, the carriage connection section and the wake region are the main vortex generating sources while the train body with even cross-section has rare vortexes. The wake structure development law studied lays foundation for the train drag reduction.
文摘Along with the development of automatical truck dispatching in open pits, it is important to es-tablish general-gurpose criteria for truck dispatching optimization. The existing dispatching criteria are briefly introduced and optimal dispatching criteria for different haulage systems are recommended. Obvious economic results have been obtained from case studies applying the recommended dispatching criteria.
文摘The development and experiment of a computer-controlled truck dispatching system in Surface mine is presented in this paper.It includes the system overall design, the system working mode design, the selection of the best truck travel path, the development of truck fleet programming, the development of database management system, and the development of truck real time dispatching, etc. The successful experiment is carried out in Huolinhe surface mine, and the satisfied results are obtained. Application of this system can improve the system production and the mine management. This system is the first one in our country at present.
文摘Combination of a bus system and cable car system can reduce the overall congestion of traffic in urban areas, where surrounding hills or mountains hold larger settlements or tourist and recreational infrastructure. With this kind of integration number of individual car trips can be significantly reduced. In this paper, the authors present an analysis of the pilot project implementation, which was held in Maribor. The authors conducted a limited test trial of two means of transportation, combining them into a single operating transport offer for inhabitants and tourists. Combined transport option proved to be a good starting point for reduction of traffic and parking congestion during winter tourist season and beyond. Method used in the research, in order to gain actual potential of integrating two systems and improving public transport offer, was establishment and implementation of the pilot project in Maribor during January 2011. Data was gathered through interviews of two interest groups. The first covered the users who were brought to the foothills of Pohorje's ski center by bus. The second covered the cable car users that were traveling to the top of Pohorje. For a limited time period, a trial principle of a single ticket was established, which gave ski-pass holders free bus ride on bus line No. 6. With the aim of reducing CO2, test drives of hybrid bus and compressed natural gas bus were conducted alongside many promotional activities with which users were informed of importance of environmentally friendly mobility options.
文摘Open pit mining operations utilize large scale and expensive equipment. For the mines implementing shovel and truck operation system, trucks constitute a large portion of these equipment and are used for hauling the mined materials. In order to have sustainable and viable operation, these equipment need to be utilized efficiently with minimum operating cost. Maintenance cost is a significant proportion of the overall operating costs. The maintenance cost of a truck changes non-linearly depending on the type, age and truck types. A new approach based on stochastic integer programming (SIP) techniques is used for annually scheduling a fixed fleet of mining trucks in a given operation, over the life of mine (multi-year time horizon) to minimize maintenance cost. The maintenance cost data in mining usually has uncertainty caused from the variability of the operational conditions at mines. To estimate the cost, usually historic data from different operations for new mines, and/or the historic data at the operating mines are used. However, maintenance cost varies depending on road conditions, age of equipment and many other local conditions at an operation. Traditional models aim to estimate the maintenance cost as a deterministic single value and financial evaluations are based on the estimated value. However, it does not provide a confidence on the estimate. The proposed model in this study assumes the truck maintenance cost is a stochastic parameter due to the significant level of uncertainty in the data and schedules the available fleet to meet the annual production targets. The scheduling has been performed by applying both the proposed stochastic and deterministic approaches. The approach provides a distribution for the maintenance cost of the optimized equipment schedule minimizing the cost.
基金China-Japan intergovernmental cooperation program of the JICA (2009LASWZF04)Program of Ministry of Science and Technology of China (2009DFB20540)
文摘This study examines the wave trains at 500 hPa occurring in East Asian summer by using the Empirical Orthogonal Function (EOF) analysis as a diagnostic tool. The results are summarized as follows: (1) A wave train pattern (OKJ pattern) originating from the upstream areas of the Sea of Okhotsk to the subtropical regions could display its strong signal in early and middle summer. The OKJ pattern is clearly recognized in the first EOF component in Eurasia. (2) The other wave train pattern originating fi'om the Philippines via Japan to North America (the P-J pattern) shows quite strong signals in the whole summer. Although the P-J pattern is described as the second EOF component around the area from East Asia to Northeast Pacific Ocean, the variance contribution is the same as that of OKJ pattern in the first EOF component. (3) The composite analyses indicate that the OKJ and P-J wave trains could coexist to some extents.
文摘On lunar exploration missions, the rovers which can move and explore directly are considered by various agency like NASA (National Aeronautics and Space Administration), JAXA (Japan Aerospace Exploration Agency), ESA (European Space Agency). Lunar rovers are required to move on rough terrains such as craters and rear cliffs where it is scientifically very important to explore. However, there is a problem that the rovers have possibility of stack because of the lunar surface is covered with loose soil named Regolith. Therefore, this paper investigates a mechanism of kinetic behavior between the wheels of the exploration rovers and loose soil. And then, this paper proposed a flexible wheel to solve like that problems. The flexible wheel has the surface which can be changed flexibly toward rough terrain. Running experiments on loose soil which imitated regolith were carried out to observe the traversability of the flexible wheel using slip ratio. Traversality of flexible wheel was better than the circular rigid wheel. The authors believe that stress distribution is important. The stress distribution of the flexible wheels is horizontally long and stress value is small. However, the stress distribution can be changed by loaded more weight. Therefore, the relationship between the stress and the running performance was considered using this differential stress distribution. In experiments, the authors used the flexible wheel with simple structure (3 limbs). From these considerations, the relationship between the stress of the flexible wheel and the running performance was described.
文摘It is known that the transport sector has a fundamental importance in the modem society, as the economic development is directly linked to mobility. Over the years, the transport became linked to different environmental problems, which can be detached greenhouse gases emissions in the atmosphere, where in recent decades can be perceived the intensification and targeting of efforts in research and development of new technologies to reduce the levels of greenhouse gases emissions in the atmosphere. In this context, it can be highlighted the modem systems of electronic engine management, new automotive catalysts and the use of renewable fuels which contribute to reducing the environmental impact. This research had, as its purpose, the analysis of fuels characteristics used for testing, comparative analysis of gas emissions from a motor vehicle running on ethanol or natural gas fuels according to NBR 6601 and conducting tests to estimate the maximum catalytic efficiency. For the implementation of trial, a flex vehicle was installed in a chassis dynamometer equipped with a gas analyzer, in order that before the completion of the urban driving cycle, were determined the content of hydrocarbons corrected, carbon monoxide corrected, carbon dioxide and oxygen present in gas emissions from the engine. The research concluded that: the performance analysis for characterization of fuel showed consistent with ANP specifications; after tests performances, it can be stated that natural gas fuel was the fuel which had the highest content of hydrocarbons and carbon monoxide corrected, while ethanol had the highest amount of carbon dioxide and oxygen residue present in gas emissions; before a comparative analysis, the vehicle catalyst showed the best performance for reducing the content of hydrocarbon corrected present in exhaustion gases when it worked with natural gas fuel and showed maximum efficiency of 100% to reduce the content of carbon monoxide corrected for both fuels. Before this, it can be stated that the vehicle catalyst showed satisfactory performance, achieving good reduction levels of greenhouse gases emissions.
文摘The GF-3 satellite was successfully launched at 06:55 Beijing time on August10 using a LM-4C launch vehicle from the Taiyuan Satellite Launch Center.The launch was the 233rd flight of a LM family launch vehicle and the carrier rocket LM-4C was developed by the Shanghai Academy of Spaceflight Technology.
基金supported by the National Natural Science Foundation of China(Grant Nos.61425008,61333004&61273054)the Aeronautical Foundation of China(Grant No.2015ZA51013)
文摘With the high focus on autonomous aerial refueling(AAR), it becomes increasingly urgent to design efficient methods or algorithms for solving the AAR problems in complicated aerial environments. A vision-based technology for AAR is developed in this paper, and five monocular and binocular visual algorithms for pose estimation of the unmanned aerial vehicles(UAVs) are adopted and verified in this AAR system. The real-time on-board vision system is also designed for precise navigation in the UAVs docking phase. A series of out-door comparative experiments for different pose estimation algorithms are conducted to verify the feasibility and accuracy of the vision algorithms in AAR.
基金supported by the National Natural Science Foundation of China under Grant No.61403406
文摘In this paper, a curved path following control algorithm for miniature unmanned aerial vehicles(UAVs) in winds with constant speed and altitude is developed. Different to the widely considered line or orbit following, the curved path to be followed is defined in terms of the arc-length parameter, which can be straight lines, orbits, B-splines or any other curves provided that they are smooth. The proposed path following control algorithm, named by VF-SMC, is combining the vector field(VF) strategy with the sliding mode control(SMC) method. It is proven that the designed algorithm guarantees the tracking errors to be a bounded ball in the presence of winds, with the aid of the Lyapunov method and the BIBO stability. The algorithm is validated both in Matlab-based simulations and high-fidelity semi-physical simulations. In Matlab-based simulations, the proposed algorithm is verified for straight lines, orbits and B-splines to show its wide usage in different curves.The high-fidelity semi-physical simulation system is composed of actual autopilot controller, ground station and X-Plane flight simulator in-loop. In semi-physical simulations, the proposed algorithm is verified for B-spline path following under various gain parameters and wind conditions thoroughly.All experiments show the accuracy in curved path following and the excellent robustness to wind disturbances of the proposed algorithm.
基金the National Natural Science Foundation of China (Grant No.49972055). We thank Dr. Hai Cheng at Isotope Laboratory of Geology and Geophysics Department, Minnesota University, USA for his measurement of TIMS-U series dating.
文摘A 400-mm-long stalagmite from Tangshan Cave, Nanjing has beenanalyzed by a high-precision TIMS-U series dating method and also determined for oxygen and carbon stable isotopic compositions. The results provided a high-resolution paleoclimate record for eastern China during a time interval (from 54 000 to 19 000 aBP) of the last glaciation. The continuous record of oxygen-18 variations in the stalagmite, indicating a precipitation history of the East Asian monsoon, shows not only signals of the Heinrich events, but also the Dansgaard-Oeschger cycles which are first found in the last glacial climate record of the East Asian monsoon area. Although the stalagmite-based climatic signals match well with the GRIP ice core record, some differences between the two re-cords can be recognized: (1) The last glacial climate changes in eastern China exhibited a long-term remarkably cooling trend, superimposed on which were four successive Bond’s cycles illus-trated by the δ18O curve. This strong cooling tendency may be an effect of the strong summer mon-soon event during the MIS 3 over the Tibetan Plateau. (2) There exist some phase differences of 1000—2000 years between the cooling events in the stalagmite-based climate signal and the GRIP ice core record. Such differences should be further verified by calibrations of multiple dating meth-ods.