Although scientists have performed many studies in the Taklimakan Desert, few of them have reported the blown sand motion along the southern edge of the Taklimakan Desert Highway, which differs significantly from the ...Although scientists have performed many studies in the Taklimakan Desert, few of them have reported the blown sand motion along the southern edge of the Taklimakan Desert Highway, which differs significantly from the northern region in terms of aeolian sand geomorphology and formation environment. Based on the field ob- servation data of airflow and aeolian sand transport, continuous monitoring data of erosional and depositional processes between 14 April 2009 and 9 April 2011 and data of surface sand grains from the classical section along the southern edge of the Taklimakan Desert Highway, this paper reported the blown sand motion within the sand-control system of the highway. The main results are as follows： 1） The existing sand-control system is highly effective in preventing and controlling desertification. Wind velocities within the sand-control system were ap- proximately 33%-100% of those for the same height above the mobile sand surface. Aeolian sand fluxes were approximately 0-31.21% of those of the mobile sand surface. Sand grains inside the system, with a mean diameter of 2.89 q）, were finer than those （2.15 q）） outside the system. In addition, wind velocities basically followed a loga- rithmic law, but the airflow along the classical section was mainly determined by topography and vegetation. 2） There were obvious erosional and depositional phenomena above the surface within the sand-control system, and these phenomena have very consistent patterns for all observation points in the two observed years. The total thicknesses of erosion and deposition ranged from 0.30 to 14.60 cm, with a mean value of 3.67 cm. In contrast, the deposition thicknesses were 1.90-22.10 cm, with a mean value of 7.59 cm, and the erosion thicknesses were 3.51-15.10 cm, with a mean value of 8.75 cm. The results will aid our understanding of blown sand within the sand-control system and provide a strong foundation for optimizing the sand-control system.展开更多
The Qinghai-Tibet Railway(QTR) passes through 281 km of sandy land, 11.07 km of which causes serious sand damage to the railway and thus, the control of blown sand is important for the safe operation of the railway. C...The Qinghai-Tibet Railway(QTR) passes through 281 km of sandy land, 11.07 km of which causes serious sand damage to the railway and thus, the control of blown sand is important for the safe operation of the railway. Construction of the railway and sand prevention system greatly changed the blown sand transport of the primary surface. Effective and feasible sand-control measures include stone checkerboard barriers(SCBs), sand fences(SFs), and gravel coverings. This study simulated the embankments, SCBs and SFs of the QTR in a wind tunnel, and analyzed their respective wind profile, sand deposition, and sand-blocking rate(SBR) in conjunction with field data, aiming at studying the influence of Golmud-Lhasa section of the QTR and sand prevention system on blown sand transport. The results of wind tunnel experiments showed that wind speed increased by 67.7%–77.3% at the upwind shoulder of the embankment and decreased by 50.0%–83.3% at upwind foot of embankment. Wind speed decreased by 50.0%–100.0% after passing through the first SF, and 72.2%–100.0% after the first row of stones within the first SCB grid. In the experiment of sand deposition, the higher the wind speed, the lower the SBR of SCB and SF. From field investigation, the amount of sand blocked by the four SFs decreased exponentially and its SBR was about 50.0%. By contrast, SCB could only block lower amounts of sand, but had a higher SBR(96.7%) than SF. Although, results show that SFs and SCBs along the Golmud-Lhasa section of the QTR provide an obvious sand blocking effect, they lead to the deposition of a large amount of sand, which forms artificial dunes and becomes a new source of sand damage.展开更多
The effects of lance height and bottom blown flowrate on the mixed time, the splashing amount, the penetrating depth, and the level fluctuation of an 85 t combined blown converter have been studied using a water model...The effects of lance height and bottom blown flowrate on the mixed time, the splashing amount, the penetrating depth, and the level fluctuation of an 85 t combined blown converter have been studied using a water model. The results show that the maximal stirring energy is provided to the bath at the top lance height of about 50-100 mm. When the top lance height is in the range ofg0- 110 mm, the splashing amount caused by the top jet can reach the maximal value. The appropriate operational parameters of Chongqing Iron and Steel Company （CISC） converter have been established that the top lance height is 1600-1760 mm and the bottom blowing flowrate is 240-480 Nm^3/h in the primary phase of a heat, 1100-1300 mm and 160-200 Nm^3/h in the second phase, and 1040-1120 mm and 200-350 Nm^3/h in the end phase. Also, the trial shows that the metallurgical result of the studied blow pattern is better than that of the former pattern. At the starting 3-4 min of a heat, the strong splashing is eliminated. 2008 University of Science and Technology Beijing. All rights reserved.展开更多
Approximately 331 million ha, one-third of China＇s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and the...Approximately 331 million ha, one-third of China＇s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and their risk governance of desertification and blown sand disaster in China were examined using satellite images, field photographs, field data and a literature review. The desiccated areas in Lop Nor and the lower Heihe River fluvial plain covered about 50,000 km2 and 40,000 km2, respectively. In Ejina, about 100 species of vegetation became extinct. The rate of wind erosion in China was between 1,000 tons/km2/year and 2,000 tons/km2/year. There were 12 sand deserts and sandy lands, occupying a total of 710,000 km2. Salinized soils occurred across 99.1 million ha. The two main sand and dust storm-prone areas in China were the Tarim Basin and its surroundings, and the Alxa Plateau and its surroundings. From 1981 to 2007, the annual average frequency of sand and dust storms varied from 1 d to 37 d with a general increase from southeast to northwest. Since 1978, China has implemented a number of ecological construction projects that have reduced desertification from 1999 to 2004 and from 2005 to 2009, and the number of dust and sand storm days from 9.3 d between 1954 and 1959 to 4.4 d between 2000 and 2007. The results could improve understanding of desertification and blown sand disasters in China and provide valuable experiences for global desertification control.展开更多
An improvement on the flow and mixing conditions in bottom blown ladles may be made by either shifting the nozzle from centre to off-centre or changing from one to two nozzles. Thus the shorter time for homogeneous mi...An improvement on the flow and mixing conditions in bottom blown ladles may be made by either shifting the nozzle from centre to off-centre or changing from one to two nozzles. Thus the shorter time for homogeneous mixing in ladle seems to be available.展开更多
In this paper, the radial temperature distributions of the blown CO2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO2 flows with different flow rates(50, 100 and ...In this paper, the radial temperature distributions of the blown CO2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO2 flows with different flow rates(50, 100 and 150 1 min^-1) were created to axially blow the arcs burning in a polymethyl methacrylate(PMMA) nozzle. Discharges with different arc currents(200 and 400A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the CⅡ 657.8 nm line was achieved by the Fowler–Milne method with the help of an oxygen atomic line of 777.2 nm.The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO2 flow rate was 50 1 min^-1, while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO2 flow rate was 150 1min^-1. The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO2 flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition,higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.展开更多
In this paper melt blown webs with different fiber dis-tributing density were simulated by the computer,and then their pore size distribution was calculated with the image analysis.Based on simulated fiber webs,the ef...In this paper melt blown webs with different fiber dis-tributing density were simulated by the computer,and then their pore size distribution was calculated with the image analysis.Based on simulated fiber webs,the effect of 10% big pores on the filtration properties was ana-lyzed theoretically.It is found that the pore radius be-comes smaller and its distribution becomes more uniformwith increasing line density,i.e.,the fiber distributing density.The flow proportion in these 10% big pores is linearly increased with increasing the standard展开更多
Field experiment was conducted to study the effect of applying organic matter in wind blown soil on microbial biomass and enzyme activity.The results showed that microbial biomass and enzyme activity keep dynamic chan...Field experiment was conducted to study the effect of applying organic matter in wind blown soil on microbial biomass and enzyme activity.The results showed that microbial biomass and enzyme activity keep dynamic changes during wheat growing season in wind blown soil,and reached the peak level in wheat booting stage.Compared with chemical fertilizer,all the other treatments could increase the microbial biomass in different degree,the same as catalsae and alkaline phosphatase activity,But urease activity was slightly difference from them.展开更多
Based on the processing experiment and sodium flame test this paper deals with the relationship between processing parameters, structure, and filtration property of melt blown fabric. Through the image analysis of Que...Based on the processing experiment and sodium flame test this paper deals with the relationship between processing parameters, structure, and filtration property of melt blown fabric. Through the image analysis of Questar micro-images in combination with the SEM observation and the measurement of some macrostructure indices, the relationship between the processing parameters and the structure especially the microstructure is emphasized Finally the effect of somestructure factors on filtration properties is discussed theoretically.展开更多
On March 2,the feasibility report of Sinopec Yizheng Chemical Fiber 4,000t Polypropylene Meltblown Nonwovens Project was formally completed.The project is expected to be completed in mid-April.By then,the daily output...On March 2,the feasibility report of Sinopec Yizheng Chemical Fiber 4,000t Polypropylene Meltblown Nonwovens Project was formally completed.The project is expected to be completed in mid-April.By then,the daily output of meltblown nonwovens can reach 12 tons,which can be used to process 12 million medical flat masks.展开更多
The Golmud-Korla Railway in the Gobi area faces operational challenges due to sand hazards,caused by strong and variable winds.This study addresses these challenges by conducting wind tunnel tests to evaluate the prot...The Golmud-Korla Railway in the Gobi area faces operational challenges due to sand hazards,caused by strong and variable winds.This study addresses these challenges by conducting wind tunnel tests to evaluate the protective benefits of High Density Polyethylene(HDPE)board sand fences,focusing on their orientation relative to various wind directions(referred to as'wind angle').This study found that the size of the low-velocity zone on the leeward side of the sand fences(LSF)expanded with an increase in the wind angle(WA).At 1H(the height of the sand fence)and 2H positions on the LSF,the wind speed profiles(WSP)exhibited a segmented logarithmic growth,constrained by Z=H at varying WAs.The efficacy of the sand fence in obstructing airflow escalated as WA increased.The size of the WA has a significant impact on the protective efficiency of HDPE board sand fences.Furthermore,compared to typical sandy surfaces,the rate of sand transport across the Gobi surface diminishes more slowly with height,attributed to the gravel's rebound effect.This phenomenon allows some sand particles to bypass the fences,rendering them less effective at blocking wind and trapping sand than in sandy environments.This paper offers scientific evidence supporting the practical use and enhancement of HDPE board sand fences in varied wind conditions.展开更多
Re puted as a wonderful achievement of the world's highway construction h istory, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea con...Re puted as a wonderful achievement of the world's highway construction h istory, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consist ing of crescent dunes, barchan chains, compound transverse dune ridges and co mplex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conductin g the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways in cluding mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress i n the control of sand drift damages in China and hold that the theoretica l research results and practices in the prevention of sand drift encr oachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectiv ely halt sand drift encroachment on the highway forever are the questions to be studied urgently.展开更多
基金supported by the National Natural Science Foundation of China (41271020, 41330746)CERS-China Equipment and Education Resources System (CERS-1-109)
文摘Although scientists have performed many studies in the Taklimakan Desert, few of them have reported the blown sand motion along the southern edge of the Taklimakan Desert Highway, which differs significantly from the northern region in terms of aeolian sand geomorphology and formation environment. Based on the field ob- servation data of airflow and aeolian sand transport, continuous monitoring data of erosional and depositional processes between 14 April 2009 and 9 April 2011 and data of surface sand grains from the classical section along the southern edge of the Taklimakan Desert Highway, this paper reported the blown sand motion within the sand-control system of the highway. The main results are as follows： 1） The existing sand-control system is highly effective in preventing and controlling desertification. Wind velocities within the sand-control system were ap- proximately 33%-100% of those for the same height above the mobile sand surface. Aeolian sand fluxes were approximately 0-31.21% of those of the mobile sand surface. Sand grains inside the system, with a mean diameter of 2.89 q）, were finer than those （2.15 q）） outside the system. In addition, wind velocities basically followed a loga- rithmic law, but the airflow along the classical section was mainly determined by topography and vegetation. 2） There were obvious erosional and depositional phenomena above the surface within the sand-control system, and these phenomena have very consistent patterns for all observation points in the two observed years. The total thicknesses of erosion and deposition ranged from 0.30 to 14.60 cm, with a mean value of 3.67 cm. In contrast, the deposition thicknesses were 1.90-22.10 cm, with a mean value of 7.59 cm, and the erosion thicknesses were 3.51-15.10 cm, with a mean value of 8.75 cm. The results will aid our understanding of blown sand within the sand-control system and provide a strong foundation for optimizing the sand-control system.
基金Under the auspices of National Natural Science Foundation of China(No.40930741)National Basic Research Program of China(No.2012CB026105)
文摘The Qinghai-Tibet Railway(QTR) passes through 281 km of sandy land, 11.07 km of which causes serious sand damage to the railway and thus, the control of blown sand is important for the safe operation of the railway. Construction of the railway and sand prevention system greatly changed the blown sand transport of the primary surface. Effective and feasible sand-control measures include stone checkerboard barriers(SCBs), sand fences(SFs), and gravel coverings. This study simulated the embankments, SCBs and SFs of the QTR in a wind tunnel, and analyzed their respective wind profile, sand deposition, and sand-blocking rate(SBR) in conjunction with field data, aiming at studying the influence of Golmud-Lhasa section of the QTR and sand prevention system on blown sand transport. The results of wind tunnel experiments showed that wind speed increased by 67.7%–77.3% at the upwind shoulder of the embankment and decreased by 50.0%–83.3% at upwind foot of embankment. Wind speed decreased by 50.0%–100.0% after passing through the first SF, and 72.2%–100.0% after the first row of stones within the first SCB grid. In the experiment of sand deposition, the higher the wind speed, the lower the SBR of SCB and SF. From field investigation, the amount of sand blocked by the four SFs decreased exponentially and its SBR was about 50.0%. By contrast, SCB could only block lower amounts of sand, but had a higher SBR(96.7%) than SF. Although, results show that SFs and SCBs along the Golmud-Lhasa section of the QTR provide an obvious sand blocking effect, they lead to the deposition of a large amount of sand, which forms artificial dunes and becomes a new source of sand damage.
文摘The effects of lance height and bottom blown flowrate on the mixed time, the splashing amount, the penetrating depth, and the level fluctuation of an 85 t combined blown converter have been studied using a water model. The results show that the maximal stirring energy is provided to the bath at the top lance height of about 50-100 mm. When the top lance height is in the range ofg0- 110 mm, the splashing amount caused by the top jet can reach the maximal value. The appropriate operational parameters of Chongqing Iron and Steel Company （CISC） converter have been established that the top lance height is 1600-1760 mm and the bottom blowing flowrate is 240-480 Nm^3/h in the primary phase of a heat, 1100-1300 mm and 160-200 Nm^3/h in the second phase, and 1040-1120 mm and 200-350 Nm^3/h in the end phase. Also, the trial shows that the metallurgical result of the studied blow pattern is better than that of the former pattern. At the starting 3-4 min of a heat, the strong splashing is eliminated. 2008 University of Science and Technology Beijing. All rights reserved.
文摘Approximately 331 million ha, one-third of China＇s total land, is prone to desertification processes, leading to natural disasters and economic losses. In this study, the situation, tendency, their influences and their risk governance of desertification and blown sand disaster in China were examined using satellite images, field photographs, field data and a literature review. The desiccated areas in Lop Nor and the lower Heihe River fluvial plain covered about 50,000 km2 and 40,000 km2, respectively. In Ejina, about 100 species of vegetation became extinct. The rate of wind erosion in China was between 1,000 tons/km2/year and 2,000 tons/km2/year. There were 12 sand deserts and sandy lands, occupying a total of 710,000 km2. Salinized soils occurred across 99.1 million ha. The two main sand and dust storm-prone areas in China were the Tarim Basin and its surroundings, and the Alxa Plateau and its surroundings. From 1981 to 2007, the annual average frequency of sand and dust storms varied from 1 d to 37 d with a general increase from southeast to northwest. Since 1978, China has implemented a number of ecological construction projects that have reduced desertification from 1999 to 2004 and from 2005 to 2009, and the number of dust and sand storm days from 9.3 d between 1954 and 1959 to 4.4 d between 2000 and 2007. The results could improve understanding of desertification and blown sand disasters in China and provide valuable experiences for global desertification control.
文摘An improvement on the flow and mixing conditions in bottom blown ladles may be made by either shifting the nozzle from centre to off-centre or changing from one to two nozzles. Thus the shorter time for homogeneous mixing in ladle seems to be available.
基金supported by National Natural Science Foundation of China (Nos. 51577145, 51707144 and 51877165)the Key Research and Development Program of Shaanxi Province (No. 2018ZDXM-GY-112)the State Key Laboratory of Electrical Insulation and Power Equipment (No. EIPE19302)
文摘In this paper, the radial temperature distributions of the blown CO2 arcs in a model gas circuit breaker were investigated by optical emission spectroscopy methods. The CO2 flows with different flow rates(50, 100 and 150 1 min^-1) were created to axially blow the arcs burning in a polymethyl methacrylate(PMMA) nozzle. Discharges with different arc currents(200 and 400A) were conducted in the experiment. The absolute intensity method was applied for a carbon ionic line of 657.8 nm to obtain the radial temperature profiles of the arc columns at a cross-section 1 mm above the nozzle. The calibration for the intensity of the CⅡ 657.8 nm line was achieved by the Fowler–Milne method with the help of an oxygen atomic line of 777.2 nm.The highest temperature obtained in the arc center was up to 19 900 K when the arc current was 400 A and the CO2 flow rate was 50 1 min^-1, while the lowest temperature in the arc center was about 15 900 K when the arc current was 200 A and the CO2 flow rate was 150 1min^-1. The results indicate that as the arc current increases, the temperature in the arc center would also increase apparently, and a larger gas flow rate would lead to a lower central temperature in general. It can also be found that the influence of the CO2 flow rate on the arc temperature was much less than that of the arc current under the present experimental conditions. In addition,higher temperature in the arc center would cause a sharper temperature decrease from the central region towards the edge.
文摘In this paper melt blown webs with different fiber dis-tributing density were simulated by the computer,and then their pore size distribution was calculated with the image analysis.Based on simulated fiber webs,the effect of 10% big pores on the filtration properties was ana-lyzed theoretically.It is found that the pore radius be-comes smaller and its distribution becomes more uniformwith increasing line density,i.e.,the fiber distributing density.The flow proportion in these 10% big pores is linearly increased with increasing the standard
基金Heilongjiang Province Science Plan Project( 960 67)
文摘Field experiment was conducted to study the effect of applying organic matter in wind blown soil on microbial biomass and enzyme activity.The results showed that microbial biomass and enzyme activity keep dynamic changes during wheat growing season in wind blown soil,and reached the peak level in wheat booting stage.Compared with chemical fertilizer,all the other treatments could increase the microbial biomass in different degree,the same as catalsae and alkaline phosphatase activity,But urease activity was slightly difference from them.
文摘Based on the processing experiment and sodium flame test this paper deals with the relationship between processing parameters, structure, and filtration property of melt blown fabric. Through the image analysis of Questar micro-images in combination with the SEM observation and the measurement of some macrostructure indices, the relationship between the processing parameters and the structure especially the microstructure is emphasized Finally the effect of somestructure factors on filtration properties is discussed theoretically.
文摘On March 2,the feasibility report of Sinopec Yizheng Chemical Fiber 4,000t Polypropylene Meltblown Nonwovens Project was formally completed.The project is expected to be completed in mid-April.By then,the daily output of meltblown nonwovens can reach 12 tons,which can be used to process 12 million medical flat masks.
基金financially supported by the National Natural Science Foundation of China (42461011, 42071014)the Fellowship of the China Postdoctoral Science Foundation (2021M703466)
文摘The Golmud-Korla Railway in the Gobi area faces operational challenges due to sand hazards,caused by strong and variable winds.This study addresses these challenges by conducting wind tunnel tests to evaluate the protective benefits of High Density Polyethylene(HDPE)board sand fences,focusing on their orientation relative to various wind directions(referred to as'wind angle').This study found that the size of the low-velocity zone on the leeward side of the sand fences(LSF)expanded with an increase in the wind angle(WA).At 1H(the height of the sand fence)and 2H positions on the LSF,the wind speed profiles(WSP)exhibited a segmented logarithmic growth,constrained by Z=H at varying WAs.The efficacy of the sand fence in obstructing airflow escalated as WA increased.The size of the WA has a significant impact on the protective efficiency of HDPE board sand fences.Furthermore,compared to typical sandy surfaces,the rate of sand transport across the Gobi surface diminishes more slowly with height,attributed to the gravel's rebound effect.This phenomenon allows some sand particles to bypass the fences,rendering them less effective at blocking wind and trapping sand than in sandy environments.This paper offers scientific evidence supporting the practical use and enhancement of HDPE board sand fences in varied wind conditions.
基金The National Key Project for Basic Research, No.G2000048705 Knowledge Innovation Project of the Cold and Arid Regions Environmental and Engineering Research Institute, CAS, No.CACX210093
文摘Re puted as a wonderful achievement of the world's highway construction h istory, the Taklimakan Desert highway is now facing serious sand drift encroachment problems due to its 447-km-long passage of sand sea consist ing of crescent dunes, barchan chains, compound transverse dune ridges and co mplex megadunes. To solve some technical problems in the protection of the highway from sand drift encroachment, desert experts have been conductin g the theoretical and applied studies on sand movement laws; causes, severities and time-space differentiation of sand drift damages; and control ways in cluding mechanical, chemical and biological measures. In this paper the authors give an overall summary on the research contents and recent progress i n the control of sand drift damages in China and hold that the theoretica l research results and practices in the prevention of sand drift encr oachment on the cross-desert highway represent a breakthrough and has an epoch-making significance. Since the construction of protective forest along the cross-desert highway requires large amount of ground water, what will be its environmental consequence and whether it can effectiv ely halt sand drift encroachment on the highway forever are the questions to be studied urgently.
