The location of U-turn bays is an important consideration in indirect driveway left-turn treatments.In order to improve the performance of right-turns followed by U-turns（RTUTs）,this study evaluates the impacts of t...The location of U-turn bays is an important consideration in indirect driveway left-turn treatments.In order to improve the performance of right-turns followed by U-turns（RTUTs）,this study evaluates the impacts of the separation distances between driveway exits and downstream U-turn locations on the safety and operational performance of vehicles making RTUTs.Crash data are investigated at 179 selected roadway segments,and travel time data are measured using video cameras at 29 locations in the state of Florida,USA.Crash rate models and travel time models are developed based on data collected in the field.It is found that the separation distance between driveway exits and downstream U-turn locations significantly impacts the safety and operational performance of vehicles making right turns followed by U-turns.Based on the research results,the minimum and optimal separation distances between driveways and U-turn locations under different roadway conditions are determined to facilitate driver use of RTUTs.The results of this study can be used for future intersection improvement projects in China.展开更多
Periodic sentence is often identified as sentence with main clause as end-weight. In fact, this definition is so confusing that it causes the same confusion in practice. This paper aims at rethinking periodic sentence...Periodic sentence is often identified as sentence with main clause as end-weight. In fact, this definition is so confusing that it causes the same confusion in practice. This paper aims at rethinking periodic sentence and advocates the adoption of noble styles with periodic sentence as its chief representative.展开更多
Waste plastics mainly come from MSW and usually exist in the form of mixed plastics. During the co-pyrolysis process of mixed plastics, various plastic components have different physicochemical properties and reaction...Waste plastics mainly come from MSW and usually exist in the form of mixed plastics. During the co-pyrolysis process of mixed plastics, various plastic components have different physicochemical properties and reaction mechanisms. Considering the high viscosity and low thermal conductivity of molten plastics, a falling film pyrolysis reactor was selected to explore the rapid co-pyrolysis process of typical plastic components(PP, PE and PS).The oil and gas yields and the compositions of pyrolysis products of the three components under different ratios at pyrolysis temperatures were analyzed to explore the co-pyrolysis characteristics of PP, PE, and PS. The study is of great significance to the recycling of waste plastics.展开更多
When an oceanographic vessel is sailing, the currents near the surface of ship hull are rapid, making it hard to meet the environmental requirements of scientific observation equipment. To guarantee the installation s...When an oceanographic vessel is sailing, the currents near the surface of ship hull are rapid, making it hard to meet the environmental requirements of scientific observation equipment. To guarantee the installation space and environmental requirements of the observation equipment, the drop keel system was proposed for the first time for ocean-graphic ships at China, to avoid the traditional ＂rudder-shaft＂ type fin keel＇s disadvantage. The research study will examine the operational mechanism and functions of the drop keel system, the operating conditions of the fin keel to determine the driver method and its arrangement, and the locking method of the fin keel underwater. The research wilI also provide some general designs for analyzing the best plan for the drop keel system.展开更多
Molten plastics are characterised with high viscosity and low thermal conductivity. Applying falling film pyrolysis reactor to deal with waste plastics can not only improve heat transfer efficiency, but also solve the...Molten plastics are characterised with high viscosity and low thermal conductivity. Applying falling film pyrolysis reactor to deal with waste plastics can not only improve heat transfer efficiency, but also solve the flow problem. In this work, the pyrolysis process of molten polypropylene （PP） in a vertical falling film reactor is experimentally studied, and the influence of heating temperature on pyrolysis products is discussed. It has been found that with the temperature increases from 550 ℃ to 625 ℃, the yield of pyrolysis oil decreases from 74.4 wt% （ 4- 2.2 wt/%） to 53.5 wt% （± 1.3 wt%）. The major compositions of the pyrolysis oil are C9, C12 and C18, and β-scission reactions are predominant. The content of the light fraction C6-C12 of pyrolysis oil is 69.7 wt%. Compared with other pyrolysis reactors, the yield ofoil from vertical falling film pyrolysis reactor is slightly higher than that from tubular reactor, equal to that from rotary kiln reactor, and slightly lower than that in medium fluidised-bed reactor.展开更多
文摘The location of U-turn bays is an important consideration in indirect driveway left-turn treatments.In order to improve the performance of right-turns followed by U-turns（RTUTs）,this study evaluates the impacts of the separation distances between driveway exits and downstream U-turn locations on the safety and operational performance of vehicles making RTUTs.Crash data are investigated at 179 selected roadway segments,and travel time data are measured using video cameras at 29 locations in the state of Florida,USA.Crash rate models and travel time models are developed based on data collected in the field.It is found that the separation distance between driveway exits and downstream U-turn locations significantly impacts the safety and operational performance of vehicles making right turns followed by U-turns.Based on the research results,the minimum and optimal separation distances between driveways and U-turn locations under different roadway conditions are determined to facilitate driver use of RTUTs.The results of this study can be used for future intersection improvement projects in China.
文摘Periodic sentence is often identified as sentence with main clause as end-weight. In fact, this definition is so confusing that it causes the same confusion in practice. This paper aims at rethinking periodic sentence and advocates the adoption of noble styles with periodic sentence as its chief representative.
基金Supported by the National Natural Science Foundation of China(51503154,51776141)Major Projects of China Water Pollution Control and Treatment Science and Technology(2017ZX07202005)
文摘Waste plastics mainly come from MSW and usually exist in the form of mixed plastics. During the co-pyrolysis process of mixed plastics, various plastic components have different physicochemical properties and reaction mechanisms. Considering the high viscosity and low thermal conductivity of molten plastics, a falling film pyrolysis reactor was selected to explore the rapid co-pyrolysis process of typical plastic components(PP, PE and PS).The oil and gas yields and the compositions of pyrolysis products of the three components under different ratios at pyrolysis temperatures were analyzed to explore the co-pyrolysis characteristics of PP, PE, and PS. The study is of great significance to the recycling of waste plastics.
文摘When an oceanographic vessel is sailing, the currents near the surface of ship hull are rapid, making it hard to meet the environmental requirements of scientific observation equipment. To guarantee the installation space and environmental requirements of the observation equipment, the drop keel system was proposed for the first time for ocean-graphic ships at China, to avoid the traditional ＂rudder-shaft＂ type fin keel＇s disadvantage. The research study will examine the operational mechanism and functions of the drop keel system, the operating conditions of the fin keel to determine the driver method and its arrangement, and the locking method of the fin keel underwater. The research wilI also provide some general designs for analyzing the best plan for the drop keel system.
基金Supported by the National Natural Science Foundation of China(51503154)Major Projects of China Water Pollution Control and Treatment Science and Technology(2017ZX07202005)the Shanghai Municipal Science and Technology Commission Fund for improving the economy in the Yangtze River Delta region(12195811100)
文摘Molten plastics are characterised with high viscosity and low thermal conductivity. Applying falling film pyrolysis reactor to deal with waste plastics can not only improve heat transfer efficiency, but also solve the flow problem. In this work, the pyrolysis process of molten polypropylene （PP） in a vertical falling film reactor is experimentally studied, and the influence of heating temperature on pyrolysis products is discussed. It has been found that with the temperature increases from 550 ℃ to 625 ℃, the yield of pyrolysis oil decreases from 74.4 wt% （ 4- 2.2 wt/%） to 53.5 wt% （± 1.3 wt%）. The major compositions of the pyrolysis oil are C9, C12 and C18, and β-scission reactions are predominant. The content of the light fraction C6-C12 of pyrolysis oil is 69.7 wt%. Compared with other pyrolysis reactors, the yield ofoil from vertical falling film pyrolysis reactor is slightly higher than that from tubular reactor, equal to that from rotary kiln reactor, and slightly lower than that in medium fluidised-bed reactor.
