The environmental air quality is one of the important problems of people′s concern. The study on human exposure to air pollutants provides an important basis for the nuprorement of human health effects. The question...The environmental air quality is one of the important problems of people′s concern. The study on human exposure to air pollutants provides an important basis for the nuprorement of human health effects. The questionnaire about time activity patterns includes questions about time spent in the houses, personal activities, indoor combustion sources, information about hobbies, (e.g. smoking), home repairing and decorating materials, and personal product use and so on. The questionnaire was conducted with 662 respondents over 16 years of age in Tianjin, China from fall 1995 to summer 1996. The results of the investigation show that 84% of people′s activities happen indoors, and 58% in family. The field researches of air pollutants monitoring of the most important air pollutants either indoors or outdoors, including carbon monoxide (CO), formaldehyde (HCHO), inhaled particulate (IR), and Benzpyrene(Bap), were carried out in winter and summer from 1995 to 1996. The results of the study on human exposure to four selected air pollutants show that indoor sources and their air pollution cause relatively high exposure in the total air pollution exposures. For example, only the exposure indoors at home is 71.0%,60.3%, 69.4% and 74.0% respectively for CO, HCHO, IR and Bap in the total air pollution exposure.展开更多
Emission of volatile organic compounds (VOCs) during drying of wood particles for particleboard manufacture, or for production of refined biofuels, is a potential environmental problem. The aim of this work is to stud...Emission of volatile organic compounds (VOCs) during drying of wood particles for particleboard manufacture, or for production of refined biofuels, is a potential environmental problem. The aim of this work is to study the emissions of VOCs during drying, and the influence on the emissions by different drying parameters.The experiments have mainly been done in a batch fluidized bed dryer, but measurements have also been done in a, pilot scale, continuous fluidized bed dryer. The parameters studied are air flow rate through the bed, air temperature, air dewpoint, and bed height. Since the present trend in biofuels and particle drying is towards very high dewpoints during drying, some measurements have been made at dewpoints up to 95℃, corresponding to a water content of 3.2 kg water per kilogram dry air. The emissions have been measured in two different ways,online during drying with a flame ionization detector and through wood analyses of the terpene content in the wood particles before and after drying. Substantial work has been made in developing the latter method as well as developing the drying equipment to be able to produce a wide range of conditions of the drying medium. It was shown that the VOCs emitted, during wood particle drying, mainly consist of terpenes. The behavior of the emissions was typical, at first contact with the drying gas a sharp peak in the release rate was detected. After that,the release rate stabilizes and declines slowly to a point where the material temperature increases and results in a second small peak in the release rate. Typically 80%-90% of the initial terpene content in the material was emitted during drying to low moisture content and it is not possible to significantly influence this release by changing the drying conditions. Up to 50% of the emitted terpenes are released during a very short period after contact with the drying medium. This fact could be utilized by employing a 2-step drying process. The fact that the VOC concentration in the inert gas gets much higher when drying at higher dewpoints could be taken into consideration when dealing with closed loop applications where the inert gas after the dryer is burnt.展开更多
The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results ...The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results showed that the average corrosion rate of copper exposed for one year was approximately 7.85μm/a,implying that Nansha Islands was classified as a corrosion category of CX.The structure and properties of the corrosion product layer generated on the front and back sides of the exposed sample differed significantly.The inner corrosion product layer(Cu2O)on the front side was relatively thick and dense,whereas the outer product layer(Cu2Cl(OH)3)was extremely thin.However,the outer product layer on the back side was thicker than the inner layer.Electrochemical measurements indicated that the protection afforded by the corrosion product layer on the front side was improved gradually,while that on the back side was deteriorated.展开更多
Coalfield fire is prevalent in the world. especially in China, but the main rea- son of the fire in the coalfield is not clarity. So it’s difficult to fight the coalfield fire. Based on the model of outcrop spontaneo...Coalfield fire is prevalent in the world. especially in China, but the main rea- son of the fire in the coalfield is not clarity. So it’s difficult to fight the coalfield fire. Based on the model of outcrop spontaneous combustion in coalfield, that when the fringe coal-rock is break up by the alternation air-temperature, the coal is oxygenated and heat is emitted. Then around coal-rock is heated and break up. The air-leakage conditions are changed and the convection of air in the coal-rock is come into being. The self-ignition process of fringe coal-crock is developed to the deeper coal seam. The oxi- dation and emitting heat mechanics process of coal, breakage and air-leakage mechan- ics process of the coal-rock in the coalfield are theoretically analyzed.展开更多
This study discusses a method of quantifying emissions from surface coal mining that has been trialled in Australia. The method is based on direct measurement of surface emissions from uncovered coal seams in mine pit...This study discusses a method of quantifying emissions from surface coal mining that has been trialled in Australia. The method is based on direct measurement of surface emissions from uncovered coal seams in mine pits, concurrent measurement of residual gas content of blasted coal in mine pits, and measurement of pre-mining gas content of the same seam from cores retrieved from exploration boreholes drilled away from active mining. The results from one of the mines studied are presented in this paper. In this mine,the pre-mining gas content of the target seam was measured using cores from an exploration borehole away from active mining. Gas content varied from 0.7 to 0.8 m3/t and gas composition varied from16% to 21% CH4(84–79% CO2). In-pit measurements included seam surface emissions and residual gas content of blasted and ripped coal. Residual gas content varied from 0.09 to 0.15 m3/t, less than twofold across the mine pit. Composition of the residual gas was in general 90% CO2and 10% CH4, with slight variation between samples. Coal seam surface emissions varied from 1.03 to 7.50 mL of CO2-e per minute and per square meter of the coal seam surface, a sevenfold variation across the mine pit.展开更多
The paper embarks to investigate the relationship between currency risk and stock prices of the oil and natural gas exploitation industry in the value-weighted Hushen-300 stock market, by applying the standard Capital...The paper embarks to investigate the relationship between currency risk and stock prices of the oil and natural gas exploitation industry in the value-weighted Hushen-300 stock market, by applying the standard Capital Asset Pricing Model (CAPM) and nonlinear exchange rate exposure model to the Renminbi against US dollar. The results show that the currency exposure does vary in the oil-gas stock prices throughout the bull and bear market. The study suggests that the models of the equilibrium exchange rate exposure must be extended to considering the nonlinear exchange rate exposure, the regime periods of bull and bear market, and the industry types that is sensitive to the currency exposures. The nonlinear dynamic relationship between the exchange rate changes and the Chinese energy stock prices throughout the bull and bear market add to the recent empirical evidences that foreign exchange markets and stock markets are closely correlated.展开更多
The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null positio...The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position,thereby affecting high-precision control and stability of the servo system.This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV.A numerical approach was employed to evaluate the effects,and then a mathematical model was established to obtain the variation law of leakage flow rate at null position.The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius,and is nonlinear as a quadratic concave function with annular clearance.The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable−nonlinear−linear trend.A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model,which agrees well with the conducted experimental study.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
The circle geometric constraint model (CGCM) was put forward for resolving the open-pit mine ore-matching problems (OMOMP). By adopting the approaches of graph theory, block model of blasted piles was abstracted i...The circle geometric constraint model (CGCM) was put forward for resolving the open-pit mine ore-matching problems (OMOMP). By adopting the approaches of graph theory, block model of blasted piles was abstracted into a set of nodes and directed edges, which were connected together with other nodes in the range of circle constraints, to describe the mining sequence. Also, the constructing method of CGCM was introduced in detail. The algorithm of CGCM has been realized in the DIM1NE system, and applied to a short-term (5 d) program calculation for ore-matching of a cement limestone mine in Hebei Province, China. The applications show that CGCM can well describe the mining sequence of ore blocks and its mining geometric constraints in the process of mining blasted piles. This model, which is applicable for resolving OMOMP under complicated geometric constraints with accurate results, provides effective ways to solve the problems of open-pit ore-matching.展开更多
This paper describes construction and characterization of a dew/frost -point generator developed at national institute for standards. It is intended to operate in the range from -50 ℃to 0 ℃. The air flows through a ...This paper describes construction and characterization of a dew/frost -point generator developed at national institute for standards. It is intended to operate in the range from -50 ℃to 0 ℃. The air flows through a saturator controlled by a regulated flow meter. The reference dew/frost -point temperature was measured by standard platinum resistance thermometer (SPRT) connected to a resistance bridge. A comparative study between the saturator temperature of the new generator measured by SPRT and the dew/frost-point temperature of a calibrated chilled-mirror hygrometer was conducted. It helped to determine the uncertainty of saturator; this uncertainty was found to be between ±0.06℃ to -4- 0.15℃ at confidence limit of 95%.Several experiments were carried out in the mentioned range. Obtained results gave the confidence that NIS generator could be used as a primary humid air generator.展开更多
The results obtained from the research on the behaviour of fences (solid and porous) in the protection against particulated material emission to the atmosphere from open storage piles,are presented. This research was ...The results obtained from the research on the behaviour of fences (solid and porous) in the protection against particulated material emission to the atmosphere from open storage piles,are presented. This research was carried out through computational fluid dynamics (CFD) simulation by software Ansys CFX-10.0 in 3D,with K-epsilon being considered in the turbulence model. The efficiency of the use of porous fences as a protection against the wind flow,which interacts with an open storage pile,is shown. The use of these fences (when porosity is ε=30%) allows the reduction of wind flow velocity which interacts with the pile in comparison with the case of no use of fences (when porosity is 100%). In addition,the use of porous fences makes the velocity vortex,which is formed between the solid fence (ε=0%) and the pile,disappear,reducing the particle emission to the atmosphere by 78%.展开更多
Dew and fog play major roles in providing the atmospheric moisture for plants and arthropods living in arid regions all over the world. Studies are needed to discriminate between dew and fog. A radiation system was de...Dew and fog play major roles in providing the atmospheric moisture for plants and arthropods living in arid regions all over the world. Studies are needed to discriminate between dew and fog. A radiation system was developed for measuring the incoming and outgoing solar (shortwave) radiation using two CM21 Kipp & Zonen pyranometers (one inverted), and the incoming (atmospheric) and outgoing (terrestrial) longwave radiation using two CG1 pyrgeometers in Logan (41047' N, 111~51' W, 1,460 m above mean sea level), Utah, USA, continuously since 1995. These instruments are ventilated with heated air to prevent precipitation of dew and frost on the sensors, which otherwise would disturb the measurements. Based upon these measurements and an algorithm, the cloud base height, the cloud base temperature and percent of cloudiness can be parameterized at local scale. A cloud base height around zero would indicate fog at the local scale. In 1999, Bowen ratio system was added to measure the evapotranspiration, dew and frost continuously throughout the year at the same location close to the radiation system. Combining these two systems (radiation and Bowen ratio) has yielded a reasonable approach to differentiate between the atmospheric moistures collected by dew and fog.展开更多
The occurrence of liquid condensation in natural gas accounts for new challenges during the interoperability between transmission networks,where condensation would lead to higher pressure drops,lower line capacity and...The occurrence of liquid condensation in natural gas accounts for new challenges during the interoperability between transmission networks,where condensation would lead to higher pressure drops,lower line capacity and may cause safety problem.A successful case of hydrocarbon dew point(HCDP)analysis is demonstrated during the mixing of natural gases in the transmission pipeline.Methods used to predict the HCDP are combined with equations of state(EOS)and characterization of C6+heavy components.Predictions are compared with measured HCDP with different concentrations of mixed gases at a wide range of pressure and temperature scopes.Software named"PipeGasAnalysis"is developed and helps to systematic analyze the condensation problem,which will provide the guidance for the design and operation of the network.展开更多
AIM: To investigate the effect of Bu-Zhong-Yi-Qi-Tang (Decoction for Reinforcing Middle Jiao and Replenishing Qi) on deficiency of N-glycan/nitric oxide (NO) and islet damage induced by injecting two medium doses of s...AIM: To investigate the effect of Bu-Zhong-Yi-Qi-Tang (Decoction for Reinforcing Middle Jiao and Replenishing Qi) on deficiency of N-glycan/nitric oxide (NO) and islet damage induced by injecting two medium doses of streptozotocin (STZ). METHODS: Diabetes was induced by intraperitoneal injection of STZ at 55 mg/kg on day 1 and day 8. Islet damage was evaluated using a scoring system. Nitrite, nitrate, α-mannosidase and amylase activities were measured by colorimetry. N-glycan patterns of amylase were determined with lectin [ConA, pisum sativum agglutinin (PSA), peanut agglutinin (PNA), and lens culinaris agglutinin (LCA)] affinity precipitation method. RESULTS: Severe islet necrosis and mild islet atrophy were observed in diabetic rats. The number and size ofislets, the activities of α-mannosidase, amylase and nitrite were decreased, while the binding of PNA and LCA to amylase was increased. All of which were improved after treatment with Bu-Zhong-Yi-Qi-Tang. Islet damage was significantly correlated with nitrite, nitrate, α-mannosidase, amylase and the binding of LCA, PNA, and PSA to amylase.CONCLUSION: STZ-induced islet damage is related to N-glycan deficiency in proteins by blocking α-mannosidase activity and no deficiency, accumulation of unfolded proteins, and endoplasmic reticulum stress and activation of cellular signals, all of which are improved after treatment with Bu-Zhong-YiQi-Tang.展开更多
Surface ozone(O_(3))poses significant threats to public health,agricultural crops,and plants in natural ecosystems.Global warming is likely to increase future O_(3)mainly by altering atmospheric photochemical reaction...Surface ozone(O_(3))poses significant threats to public health,agricultural crops,and plants in natural ecosystems.Global warming is likely to increase future O_(3)mainly by altering atmospheric photochemical reactions and enhancing biogenic volatile organic compound(BVOC)emissions.To assess the impacts of the future 1.5 K climate target on O_(3)concentrations and ecological O_(3)exposure in China,numerical simulations were conducted using the CMAQ(Community Multiscale Air Quality)model during April-October 2018.Ecological O_(3)exposure was estimated using six indices(i.e.,M7,M24,N100,SUM60,W126,and AOT40f).The results show that the temperature rise increases the MDA8 O_(3)(maximum daily eight-hour average O_(3))concentrations by∼3 ppb and the number of O_(3)exceedance days by 10-20 days in the North China Plain(NCP),Yangtze River Delta(YRD),and Sichuan Basin(SCB)regions.All O_(3)exposure indices show substantial increases.M24 and M7 in eastern and southern China will rise by 1-3 ppb and 2-4 ppb,respectively.N100 increases by more than 120 h in the surrounding regions of Beijing.SUM60 increases by greater than 9 ppm h^(−1),W126 increases by greater than 15 ppm h^(−1)in Shaanxi and SCB,and AOT40f increases by 6 ppm h^(−1)in NCP and SCB.The temperature increase also promotes atmospheric oxidation capacity(AOC)levels,with the higher AOC contributed by OH radicals in southern China but by NO_(3)radicals in northern China.The change in the reaction rate caused by the temperature increase has a greater influence on O_(3)exposure and AOC than the change in BVOC emissions.展开更多
For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air ...For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air leakage from the stand pipe into the cyclone was specially focused. A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage and inlet solid loading. The operate pressure, air leakage and inlet solid loading act as significant roles in cyclone pressure drop. The pressure drop increases with the increasing of pressure and decreases with the increasing of the flow rate of air leakage from the standpipe and with the increasing of the inlet solid loading.展开更多
Chronologies of glacial advances during the last glacial period in the Nyainqentanglha mountain range may provide constraints on the past climate in a transition zone of the Asian monsoon. We present 15 new Be exposur...Chronologies of glacial advances during the last glacial period in the Nyainqentanglha mountain range may provide constraints on the past climate in a transition zone of the Asian monsoon. We present 15 new Be exposure ages from two moraines in the Payuwang valley, on the north slope of the range. The inner moraine has exposure ages ranging from 18.0±1.7 to 30.6±2.8 ka (n=10), with a mean age of 23.8±4.0 ka, corresponding to the global Last Glacial Maximum (LGM). The outer moraine yields exposure ages ranging from 18.0±1.6 to 39.9±3.7 ka (n=5). Evidence for weathering leads us to view the oldest age as a mini mum age, placing moraine formation during MIS3. Chronologies from the last glacial period from south slope of the Nyainqentanglha support this interpretation. Thus, there appears to have been a local LGM (LLGM) during MIS3 and a more limited glacial advance during the global LGM. Glacial advances during MIS3 in the Nyainqentanglha may correlate with mil lennialscale climate change (Heinrich events).展开更多
文摘The environmental air quality is one of the important problems of people′s concern. The study on human exposure to air pollutants provides an important basis for the nuprorement of human health effects. The questionnaire about time activity patterns includes questions about time spent in the houses, personal activities, indoor combustion sources, information about hobbies, (e.g. smoking), home repairing and decorating materials, and personal product use and so on. The questionnaire was conducted with 662 respondents over 16 years of age in Tianjin, China from fall 1995 to summer 1996. The results of the investigation show that 84% of people′s activities happen indoors, and 58% in family. The field researches of air pollutants monitoring of the most important air pollutants either indoors or outdoors, including carbon monoxide (CO), formaldehyde (HCHO), inhaled particulate (IR), and Benzpyrene(Bap), were carried out in winter and summer from 1995 to 1996. The results of the study on human exposure to four selected air pollutants show that indoor sources and their air pollution cause relatively high exposure in the total air pollution exposures. For example, only the exposure indoors at home is 71.0%,60.3%, 69.4% and 74.0% respectively for CO, HCHO, IR and Bap in the total air pollution exposure.
文摘Emission of volatile organic compounds (VOCs) during drying of wood particles for particleboard manufacture, or for production of refined biofuels, is a potential environmental problem. The aim of this work is to study the emissions of VOCs during drying, and the influence on the emissions by different drying parameters.The experiments have mainly been done in a batch fluidized bed dryer, but measurements have also been done in a, pilot scale, continuous fluidized bed dryer. The parameters studied are air flow rate through the bed, air temperature, air dewpoint, and bed height. Since the present trend in biofuels and particle drying is towards very high dewpoints during drying, some measurements have been made at dewpoints up to 95℃, corresponding to a water content of 3.2 kg water per kilogram dry air. The emissions have been measured in two different ways,online during drying with a flame ionization detector and through wood analyses of the terpene content in the wood particles before and after drying. Substantial work has been made in developing the latter method as well as developing the drying equipment to be able to produce a wide range of conditions of the drying medium. It was shown that the VOCs emitted, during wood particle drying, mainly consist of terpenes. The behavior of the emissions was typical, at first contact with the drying gas a sharp peak in the release rate was detected. After that,the release rate stabilizes and declines slowly to a point where the material temperature increases and results in a second small peak in the release rate. Typically 80%-90% of the initial terpene content in the material was emitted during drying to low moisture content and it is not possible to significantly influence this release by changing the drying conditions. Up to 50% of the emitted terpenes are released during a very short period after contact with the drying medium. This fact could be utilized by employing a 2-step drying process. The fact that the VOC concentration in the inert gas gets much higher when drying at higher dewpoints could be taken into consideration when dealing with closed loop applications where the inert gas after the dryer is burnt.
基金The authors are grateful for the financial supports from National Natural Science Foundation of China(51671197)Strategic Priority Research Program of Chinese Academy of Sciences(13040502).
文摘The corrosion behavior of pure copper exposed to the atmosphere of Nansha Islands for 21 months was studied by mass loss method,composition analysis,morphology observation and electrochemical measurements.The results showed that the average corrosion rate of copper exposed for one year was approximately 7.85μm/a,implying that Nansha Islands was classified as a corrosion category of CX.The structure and properties of the corrosion product layer generated on the front and back sides of the exposed sample differed significantly.The inner corrosion product layer(Cu2O)on the front side was relatively thick and dense,whereas the outer product layer(Cu2Cl(OH)3)was extremely thin.However,the outer product layer on the back side was thicker than the inner layer.Electrochemical measurements indicated that the protection afforded by the corrosion product layer on the front side was improved gradually,while that on the back side was deteriorated.
基金Supported by National Natural Science Foundation of China (10102016) and National Natural Science Foundation of China (59974020)
文摘Coalfield fire is prevalent in the world. especially in China, but the main rea- son of the fire in the coalfield is not clarity. So it’s difficult to fight the coalfield fire. Based on the model of outcrop spontaneous combustion in coalfield, that when the fringe coal-rock is break up by the alternation air-temperature, the coal is oxygenated and heat is emitted. Then around coal-rock is heated and break up. The air-leakage conditions are changed and the convection of air in the coal-rock is come into being. The self-ignition process of fringe coal-crock is developed to the deeper coal seam. The oxi- dation and emitting heat mechanics process of coal, breakage and air-leakage mechan- ics process of the coal-rock in the coalfield are theoretically analyzed.
基金the CSIROthe Australian Coal Association Research Program
文摘This study discusses a method of quantifying emissions from surface coal mining that has been trialled in Australia. The method is based on direct measurement of surface emissions from uncovered coal seams in mine pits, concurrent measurement of residual gas content of blasted coal in mine pits, and measurement of pre-mining gas content of the same seam from cores retrieved from exploration boreholes drilled away from active mining. The results from one of the mines studied are presented in this paper. In this mine,the pre-mining gas content of the target seam was measured using cores from an exploration borehole away from active mining. Gas content varied from 0.7 to 0.8 m3/t and gas composition varied from16% to 21% CH4(84–79% CO2). In-pit measurements included seam surface emissions and residual gas content of blasted and ripped coal. Residual gas content varied from 0.09 to 0.15 m3/t, less than twofold across the mine pit. Composition of the residual gas was in general 90% CO2and 10% CH4, with slight variation between samples. Coal seam surface emissions varied from 1.03 to 7.50 mL of CO2-e per minute and per square meter of the coal seam surface, a sevenfold variation across the mine pit.
文摘The paper embarks to investigate the relationship between currency risk and stock prices of the oil and natural gas exploitation industry in the value-weighted Hushen-300 stock market, by applying the standard Capital Asset Pricing Model (CAPM) and nonlinear exchange rate exposure model to the Renminbi against US dollar. The results show that the currency exposure does vary in the oil-gas stock prices throughout the bull and bear market. The study suggests that the models of the equilibrium exchange rate exposure must be extended to considering the nonlinear exchange rate exposure, the regime periods of bull and bear market, and the industry types that is sensitive to the currency exposures. The nonlinear dynamic relationship between the exchange rate changes and the Chinese energy stock prices throughout the bull and bear market add to the recent empirical evidences that foreign exchange markets and stock markets are closely correlated.
基金Project(51705164)supported by the National Natural Science Foundation of China。
文摘The high-pressure electro-pneumatic servo valve(HESV)is a core element of the high-pressure pneumatic servo system.The annular clearance and the rounded corner of the spool-sleeve can cause the leakage at null position,thereby affecting high-precision control and stability of the servo system.This paper investigates the effects of the clearance structure on leakage behavior at null position of the HESV.A numerical approach was employed to evaluate the effects,and then a mathematical model was established to obtain the variation law of leakage flow rate at null position.The results indicate that the leakage flow rate at null position varies linearly with supply pressure and rounded corner radius,and is nonlinear as a quadratic concave function with annular clearance.The leakage flow rate of the annular clearance and the rounded corner varies with the valve opening in an invariable−nonlinear−linear trend.A test rig system of leakage behavior at null position of the HESV was built to confirm the validity of the numerical model,which agrees well with the conducted experimental study.
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.
基金Project(2011AA060407) supported by the National High Technology Research and Development Program of ChinaProject(51074073) supported by the National Natural Science Foundation of China
文摘The circle geometric constraint model (CGCM) was put forward for resolving the open-pit mine ore-matching problems (OMOMP). By adopting the approaches of graph theory, block model of blasted piles was abstracted into a set of nodes and directed edges, which were connected together with other nodes in the range of circle constraints, to describe the mining sequence. Also, the constructing method of CGCM was introduced in detail. The algorithm of CGCM has been realized in the DIM1NE system, and applied to a short-term (5 d) program calculation for ore-matching of a cement limestone mine in Hebei Province, China. The applications show that CGCM can well describe the mining sequence of ore blocks and its mining geometric constraints in the process of mining blasted piles. This model, which is applicable for resolving OMOMP under complicated geometric constraints with accurate results, provides effective ways to solve the problems of open-pit ore-matching.
文摘This paper describes construction and characterization of a dew/frost -point generator developed at national institute for standards. It is intended to operate in the range from -50 ℃to 0 ℃. The air flows through a saturator controlled by a regulated flow meter. The reference dew/frost -point temperature was measured by standard platinum resistance thermometer (SPRT) connected to a resistance bridge. A comparative study between the saturator temperature of the new generator measured by SPRT and the dew/frost-point temperature of a calibrated chilled-mirror hygrometer was conducted. It helped to determine the uncertainty of saturator; this uncertainty was found to be between ±0.06℃ to -4- 0.15℃ at confidence limit of 95%.Several experiments were carried out in the mentioned range. Obtained results gave the confidence that NIS generator could be used as a primary humid air generator.
基金the Spanish Ministry of Science and Education that granted these researches through the project CTM2005-00187/TECNO "Prediction Models and Prevention Systems in the Particle Atmospheric Pollution in an Industrial Environment" carried out at Oviedo University
文摘The results obtained from the research on the behaviour of fences (solid and porous) in the protection against particulated material emission to the atmosphere from open storage piles,are presented. This research was carried out through computational fluid dynamics (CFD) simulation by software Ansys CFX-10.0 in 3D,with K-epsilon being considered in the turbulence model. The efficiency of the use of porous fences as a protection against the wind flow,which interacts with an open storage pile,is shown. The use of these fences (when porosity is ε=30%) allows the reduction of wind flow velocity which interacts with the pile in comparison with the case of no use of fences (when porosity is 100%). In addition,the use of porous fences makes the velocity vortex,which is formed between the solid fence (ε=0%) and the pile,disappear,reducing the particle emission to the atmosphere by 78%.
文摘Dew and fog play major roles in providing the atmospheric moisture for plants and arthropods living in arid regions all over the world. Studies are needed to discriminate between dew and fog. A radiation system was developed for measuring the incoming and outgoing solar (shortwave) radiation using two CM21 Kipp & Zonen pyranometers (one inverted), and the incoming (atmospheric) and outgoing (terrestrial) longwave radiation using two CG1 pyrgeometers in Logan (41047' N, 111~51' W, 1,460 m above mean sea level), Utah, USA, continuously since 1995. These instruments are ventilated with heated air to prevent precipitation of dew and frost on the sensors, which otherwise would disturb the measurements. Based upon these measurements and an algorithm, the cloud base height, the cloud base temperature and percent of cloudiness can be parameterized at local scale. A cloud base height around zero would indicate fog at the local scale. In 1999, Bowen ratio system was added to measure the evapotranspiration, dew and frost continuously throughout the year at the same location close to the radiation system. Combining these two systems (radiation and Bowen ratio) has yielded a reasonable approach to differentiate between the atmospheric moistures collected by dew and fog.
基金Project(2011ZX05026-004-03)supported by the Key National Science and Technology Specific Program,ChinaProject(NCET-12-0969)supported by the Program for New Century Excellent Talents in University,China+1 种基金Project(51104167)supported by the National Natural Science Foundation of ChinaProject(BJ-2011-02)supported by the Research Funds of China University of Petroleum-Beijing
文摘The occurrence of liquid condensation in natural gas accounts for new challenges during the interoperability between transmission networks,where condensation would lead to higher pressure drops,lower line capacity and may cause safety problem.A successful case of hydrocarbon dew point(HCDP)analysis is demonstrated during the mixing of natural gases in the transmission pipeline.Methods used to predict the HCDP are combined with equations of state(EOS)and characterization of C6+heavy components.Predictions are compared with measured HCDP with different concentrations of mixed gases at a wide range of pressure and temperature scopes.Software named"PipeGasAnalysis"is developed and helps to systematic analyze the condensation problem,which will provide the guidance for the design and operation of the network.
基金Supported by The Project of Guangdong Science and Technology
文摘AIM: To investigate the effect of Bu-Zhong-Yi-Qi-Tang (Decoction for Reinforcing Middle Jiao and Replenishing Qi) on deficiency of N-glycan/nitric oxide (NO) and islet damage induced by injecting two medium doses of streptozotocin (STZ). METHODS: Diabetes was induced by intraperitoneal injection of STZ at 55 mg/kg on day 1 and day 8. Islet damage was evaluated using a scoring system. Nitrite, nitrate, α-mannosidase and amylase activities were measured by colorimetry. N-glycan patterns of amylase were determined with lectin [ConA, pisum sativum agglutinin (PSA), peanut agglutinin (PNA), and lens culinaris agglutinin (LCA)] affinity precipitation method. RESULTS: Severe islet necrosis and mild islet atrophy were observed in diabetic rats. The number and size ofislets, the activities of α-mannosidase, amylase and nitrite were decreased, while the binding of PNA and LCA to amylase was increased. All of which were improved after treatment with Bu-Zhong-Yi-Qi-Tang. Islet damage was significantly correlated with nitrite, nitrate, α-mannosidase, amylase and the binding of LCA, PNA, and PSA to amylase.CONCLUSION: STZ-induced islet damage is related to N-glycan deficiency in proteins by blocking α-mannosidase activity and no deficiency, accumulation of unfolded proteins, and endoplasmic reticulum stress and activation of cellular signals, all of which are improved after treatment with Bu-Zhong-YiQi-Tang.
基金supported by the National Natural Science Foundation of China[grant numbers 42277095 and 42021004].
文摘Surface ozone(O_(3))poses significant threats to public health,agricultural crops,and plants in natural ecosystems.Global warming is likely to increase future O_(3)mainly by altering atmospheric photochemical reactions and enhancing biogenic volatile organic compound(BVOC)emissions.To assess the impacts of the future 1.5 K climate target on O_(3)concentrations and ecological O_(3)exposure in China,numerical simulations were conducted using the CMAQ(Community Multiscale Air Quality)model during April-October 2018.Ecological O_(3)exposure was estimated using six indices(i.e.,M7,M24,N100,SUM60,W126,and AOT40f).The results show that the temperature rise increases the MDA8 O_(3)(maximum daily eight-hour average O_(3))concentrations by∼3 ppb and the number of O_(3)exceedance days by 10-20 days in the North China Plain(NCP),Yangtze River Delta(YRD),and Sichuan Basin(SCB)regions.All O_(3)exposure indices show substantial increases.M24 and M7 in eastern and southern China will rise by 1-3 ppb and 2-4 ppb,respectively.N100 increases by more than 120 h in the surrounding regions of Beijing.SUM60 increases by greater than 9 ppm h^(−1),W126 increases by greater than 15 ppm h^(−1)in Shaanxi and SCB,and AOT40f increases by 6 ppm h^(−1)in NCP and SCB.The temperature increase also promotes atmospheric oxidation capacity(AOC)levels,with the higher AOC contributed by OH radicals in southern China but by NO_(3)radicals in northern China.The change in the reaction rate caused by the temperature increase has a greater influence on O_(3)exposure and AOC than the change in BVOC emissions.
基金Financial support from The Ministry of Science and Technology of China (Contract No.2003AA529220)
文摘For the design of pressurized circulating fluidized beds, experiments were conducted in a small cyclone with 120 mm in diameter and 300 mm in height at high pressures and at atmospheric temperatures. Influence of air leakage from the stand pipe into the cyclone was specially focused. A semi-empirical model was developed for the prediction of the pressure drop of the cyclone separator at different operate pressures with the effect of air leakage and inlet solid loading. The operate pressure, air leakage and inlet solid loading act as significant roles in cyclone pressure drop. The pressure drop increases with the increasing of pressure and decreases with the increasing of the flow rate of air leakage from the standpipe and with the increasing of the inlet solid loading.
基金supported by National Natural Science Foundation of China(Key Program)(Grant No.41230523)Strategic Priority Research Program(B) of the Chinese Academy of Sciences(Grant No.XDB01020300)National Natural Science Foundation of China(General Program)(Grant No.40971017)
文摘Chronologies of glacial advances during the last glacial period in the Nyainqentanglha mountain range may provide constraints on the past climate in a transition zone of the Asian monsoon. We present 15 new Be exposure ages from two moraines in the Payuwang valley, on the north slope of the range. The inner moraine has exposure ages ranging from 18.0±1.7 to 30.6±2.8 ka (n=10), with a mean age of 23.8±4.0 ka, corresponding to the global Last Glacial Maximum (LGM). The outer moraine yields exposure ages ranging from 18.0±1.6 to 39.9±3.7 ka (n=5). Evidence for weathering leads us to view the oldest age as a mini mum age, placing moraine formation during MIS3. Chronologies from the last glacial period from south slope of the Nyainqentanglha support this interpretation. Thus, there appears to have been a local LGM (LLGM) during MIS3 and a more limited glacial advance during the global LGM. Glacial advances during MIS3 in the Nyainqentanglha may correlate with mil lennialscale climate change (Heinrich events).