Air leakage may significantly affect the effectiveness of mine ventilation by in- creasing the cost of ventilation and arousing problems for ventilation management.Fur- thermore,air leakage may accelerate the process ...Air leakage may significantly affect the effectiveness of mine ventilation by in- creasing the cost of ventilation and arousing problems for ventilation management.Fur- thermore,air leakage may accelerate the process of coal spontaneous combustion and cause gas explosion,thus greatly threatens the safety of coal production.The estimation of air leakage,therefore,have great practical significance.For any ventilation system of coal mines,there is a defined pattern of pressure gradient which drived the mine air to flow in the network,drives possible air leakage to go shortcut as well.Air leakage may occur through ventilation structures such as ventilation doors and fractures of the surroun- dig coal and rock of airways.A concept and the relevent calculation method of the pres- sure gradient matrix was put forward to assist the analysis of potential air leakage routes. A simplified example was used to introduce the application principle of'pressure gradient matrix in identifying all the potential air leaking routes,which offers a deeper understand- ing over the ventilation system and the prevention of coal spontaneous combustion.展开更多
The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally invest...The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally investigated by using a high-speed camera, and a theoretical model of the average droplet size was established according to the unstable wave theory. The results demonstrated that gas velocity passing through the hole is the key factor affecting the spray angle, which increases gradually with an increase in the gas velocity. When the gas velocity exceeds 7.5 m/s, the spray angle becomes stable at around 55°. The average flow velocity of the liquid sheet at the spray-hole increases significantly with an increase in the gas velocity, and decreases slightly with an increase in the liquid flow rate; moreover, it increases from the bottom of spray hole upward to the top. The density of liquid drops distribution in the spray area can be described by the RosinRammler function. In addition, the liquid drops are mainly concentrated in the area of spray angle ranging from 20° to 40°, and they gradually become uniform with the increase in the gas velocity and the liquid flow rate. The average liquid drop size deceases with an increase in the gas velocity, and increases slightly with an increasing liquid flow rate. In the normal working range, the average liquid drop size is about 1.0 mm to 2.5 mm in diameter.展开更多
The typically sparse or lacking distribution of meteorological stations in mountainous areas inadequately resolves temperature elevation variability. This study presented the diurnal and seasonal variations of the ele...The typically sparse or lacking distribution of meteorological stations in mountainous areas inadequately resolves temperature elevation variability. This study presented the diurnal and seasonal variations of the elevation gradient of air temperature in the northern flank of the western Qinling Mountain range,which has not been thoroughly evaluated. The measurements were conducted at 9 different elevations between 1710 and 2500 m from August 2014 to August 2015 with HOBO Data loggers. The results showed that the annual temperature lapse rates(TLRs) for Tmean,Tmin and Tmax were 0.45?C/100 m,0.44?C/100 m and 0.40?C/100 m,respectively,which are substantially smaller than the often used value of 0.60°C/100 m to 0.65°C/100 m. The TLRs showed no obvious seasonal variations,except for the maximum temperature lapse rate,which was steeper in winter and shallower in spring. Additionally,the TLRs showed significant diurnal variations,with the steepest TLR in forenoon and the shallowest in early morning or late-afternoon,and the TLRs changed more severely during the daytime than night time. The accumulated temperature above 0°C,5°C and 10°C(AT0,AT5 and AT10) decreased at a lapse rate of 112.8?C days/100 m,104.5?C days/100 m and 137.0?C days/100 m,respectively. The monthly and annual mean diurnal range of temperatures(MDRT and ADRT) demonstrated unimodal curves along the elevation gradients,while the annual range of temperature(ART) showed no significant elevation differences. Our results strongly suggest that the extrapolated regional TLR may not be a good representative for an individual mountainside,in particular,where there are only sparse meteorological stations at high elevations.展开更多
The pattern that many ectotherms have smaller body sizes in coM environments follows the converse to Bergmann＇s rule and is most frequently found in lizards. Allen＇s rule predicts animals from warm climates usually ...The pattern that many ectotherms have smaller body sizes in coM environments follows the converse to Bergmann＇s rule and is most frequently found in lizards. Allen＇s rule predicts animals from warm climates usually have longer tails and limbs, while these traits tend to be shorter in individuals from cold climates. We examined body size variation in an endemic Chinese lizard Phrynocephalus theobaldi along a broad elevational gradient （3,600-5,000 m on the Qinghai-Tibetan Plateau）. Female body size showed a U-shaped cline, decreasing with increased elevation within the range 3,600-4,200 m, but increasing at eleva- tions 〉 4200 m. Male body size continued to increase with increasing elevations. Both sexes showed an increased pattern of ex- tremity length with elevation that does not conform to Allen＇s rule. Limb length and tail length increased along the elevational gradients. In terms of color pattern, an abdominal black speckled area appears at elevations 〉4,200 m. This trait increases in size with increased elevation. Unlike most studies, our results indicated that annual sunshine hours corresponding to the activity pe- riod of the lizards could play an important role on the positive body size cline in environments at very high elevations 〉 4200 m展开更多
基金the National Natural Science Foundation of China(50174045)the Natural Science Foundation of Shaanxi Province China(2006E205)
文摘Air leakage may significantly affect the effectiveness of mine ventilation by in- creasing the cost of ventilation and arousing problems for ventilation management.Fur- thermore,air leakage may accelerate the process of coal spontaneous combustion and cause gas explosion,thus greatly threatens the safety of coal production.The estimation of air leakage,therefore,have great practical significance.For any ventilation system of coal mines,there is a defined pattern of pressure gradient which drived the mine air to flow in the network,drives possible air leakage to go shortcut as well.Air leakage may occur through ventilation structures such as ventilation doors and fractures of the surroun- dig coal and rock of airways.A concept and the relevent calculation method of the pres- sure gradient matrix was put forward to assist the analysis of potential air leakage routes. A simplified example was used to introduce the application principle of'pressure gradient matrix in identifying all the potential air leaking routes,which offers a deeper understand- ing over the ventilation system and the prevention of coal spontaneous combustion.
基金supported by the Science and Technology Research and Development Plan of Hebei Province, China (12276710D)
文摘The spray behaviors of the combined trapezoid spray tray(CTST) have a significant effect on the gas-liquid interface. In this paper, the spray process of CTST in a column, 570 mm in diameter, was experimentally investigated by using a high-speed camera, and a theoretical model of the average droplet size was established according to the unstable wave theory. The results demonstrated that gas velocity passing through the hole is the key factor affecting the spray angle, which increases gradually with an increase in the gas velocity. When the gas velocity exceeds 7.5 m/s, the spray angle becomes stable at around 55°. The average flow velocity of the liquid sheet at the spray-hole increases significantly with an increase in the gas velocity, and decreases slightly with an increase in the liquid flow rate; moreover, it increases from the bottom of spray hole upward to the top. The density of liquid drops distribution in the spray area can be described by the RosinRammler function. In addition, the liquid drops are mainly concentrated in the area of spray angle ranging from 20° to 40°, and they gradually become uniform with the increase in the gas velocity and the liquid flow rate. The average liquid drop size deceases with an increase in the gas velocity, and increases slightly with an increasing liquid flow rate. In the normal working range, the average liquid drop size is about 1.0 mm to 2.5 mm in diameter.
基金funded by the Natural Science Foundation of China (Grant Nos.41630750,41271059)the National Key Basic Research Special Foundation of China (Grant No.2011FY110300)
文摘The typically sparse or lacking distribution of meteorological stations in mountainous areas inadequately resolves temperature elevation variability. This study presented the diurnal and seasonal variations of the elevation gradient of air temperature in the northern flank of the western Qinling Mountain range,which has not been thoroughly evaluated. The measurements were conducted at 9 different elevations between 1710 and 2500 m from August 2014 to August 2015 with HOBO Data loggers. The results showed that the annual temperature lapse rates(TLRs) for Tmean,Tmin and Tmax were 0.45?C/100 m,0.44?C/100 m and 0.40?C/100 m,respectively,which are substantially smaller than the often used value of 0.60°C/100 m to 0.65°C/100 m. The TLRs showed no obvious seasonal variations,except for the maximum temperature lapse rate,which was steeper in winter and shallower in spring. Additionally,the TLRs showed significant diurnal variations,with the steepest TLR in forenoon and the shallowest in early morning or late-afternoon,and the TLRs changed more severely during the daytime than night time. The accumulated temperature above 0°C,5°C and 10°C(AT0,AT5 and AT10) decreased at a lapse rate of 112.8?C days/100 m,104.5?C days/100 m and 137.0?C days/100 m,respectively. The monthly and annual mean diurnal range of temperatures(MDRT and ADRT) demonstrated unimodal curves along the elevation gradients,while the annual range of temperature(ART) showed no significant elevation differences. Our results strongly suggest that the extrapolated regional TLR may not be a good representative for an individual mountainside,in particular,where there are only sparse meteorological stations at high elevations.
基金Acknowledgments This work was supported by the National Natural Science Foundation of China （31372183, 31000950）. We thank the Chinese National Climate Data Center for his- torical climatic data, and the Tibetan government for permis- sion to collect specimens. We thank R. Brown, S. Mullin for their kind detailed reviews on the manuscript before submis- sion, and appreciate R. Brown for his extensive help in im- proving the language of the manuscript before publication. We also thank S. Meiri and another anonymous referee for their kind revisions or suggestions on our submitted manuscript.
文摘The pattern that many ectotherms have smaller body sizes in coM environments follows the converse to Bergmann＇s rule and is most frequently found in lizards. Allen＇s rule predicts animals from warm climates usually have longer tails and limbs, while these traits tend to be shorter in individuals from cold climates. We examined body size variation in an endemic Chinese lizard Phrynocephalus theobaldi along a broad elevational gradient （3,600-5,000 m on the Qinghai-Tibetan Plateau）. Female body size showed a U-shaped cline, decreasing with increased elevation within the range 3,600-4,200 m, but increasing at eleva- tions 〉 4200 m. Male body size continued to increase with increasing elevations. Both sexes showed an increased pattern of ex- tremity length with elevation that does not conform to Allen＇s rule. Limb length and tail length increased along the elevational gradients. In terms of color pattern, an abdominal black speckled area appears at elevations 〉4,200 m. This trait increases in size with increased elevation. Unlike most studies, our results indicated that annual sunshine hours corresponding to the activity pe- riod of the lizards could play an important role on the positive body size cline in environments at very high elevations 〉 4200 m
