Dense-medium cyclones have been used for beneficiation of fine particles of coal. In this study, the usability of cyclones in the beneficiation of tailings of a coal preparation plant was investigated. For this purpos...Dense-medium cyclones have been used for beneficiation of fine particles of coal. In this study, the usability of cyclones in the beneficiation of tailings of a coal preparation plant was investigated. For this purpose, separation tests were conducted using spiral concentrator and heavy medium cyclones with the specific weight of medium 1.3-1.8 （g/cm^3） on different grading fractions of tailing in an industrial scale （the weight of tail sample was five tons）. Spiral concentrator was utilized to beneficiate particles smaller than 1 mm. In order to evaluate the efficiency of cyclones, sink and float experiments using a specific weight of 1.3, 1.5, 1.7 and 1.9 g/cm^3, were conducted on a pilot scale. Based on the obtained results, the recovery of floated materials in cyclones with the specific weight of 1.40, 1.47 and 1.55 g/cm^3 are 17.75%, 33.80%, and 50%, respectively. Also, the cut point （Pso）, which is the relative density at which particles report equally to the both products are 1.40, 1.67 and 1.86 g/cm^3. The probable errors of separation for defined specific weights for cyclones are 0.080, 0.085 and 0.030, respectively. Also, the coefficients of variation was calculated to be 0.20, 0.12 and 0.03. Finally, it could be said that the performance of a cyclone with a heavy medium of 1.40 g/cm^3 specific weight is desirable compared with other specific weights.展开更多
This paper, probing into heavy metal control in domestic rubbish by source screening and nutrient element analysis, revealed the feasibility of source control of heavy metals and the suitability of rubbish as turfgras...This paper, probing into heavy metal control in domestic rubbish by source screening and nutrient element analysis, revealed the feasibility of source control of heavy metals and the suitability of rubbish as turfgrass medium. Heavy metals in domestic rubbish were controlled by source screening before composting. The study consisted of a control with garden soil. The contents of main mineral elements and heavy metals in rubbish compost and control were determined by the method of ICP-AES. The results showed that heavy metal concentrations in rubbish were lower than those in garden soil, and little difference occurred between rubbish and garden soil in main mineral element concentrations. Based on this, it was concluded that rubbish compost was favorable for using as turfgrass medium and heavy metal control in rubbish by source screening was effective.展开更多
The relationship between Pb leaching concentration and the solution＇s pH with time was analyzed when cement in its solidified form was leached in an acid medium. The effects of the particle size of the solidified for...The relationship between Pb leaching concentration and the solution＇s pH with time was analyzed when cement in its solidified form was leached in an acid medium. The effects of the particle size of the solidified form, the cement adding method, and the hydration degree on Pb solidification were also investigated. The experimental results indicate that cement is quickly dissolved and hydrated in the acid medium, forming a C-S-H gel or silicic acid sol with good adsorption. When cement-Pb solidified form is leached in an acetate solution, the hydrated product erodes with time, so the Pb concentration increases slightly in the beginning. Then, some of the Pb ions are absorbed by the newly generated silicic acid sol, C-S-H. Others produce Pb（OH）2 precipitation for secondary solidification, leading to a gradual decrease in the Pb concentration in a leaching time of more than two hours. Moreover, the particle size of the solidified form has important effects on the Pb dissolution. When the amount of added cement is low, with a pH of less than 9.5, the solidification affects the sequence of the original cement powder, the cement hydrated powder, and the cement- Pb solidified form. When the added amount of cement increases with a pH of more than 11, the effect of adding methods on solidification decreases, and the solidified form is a little better than others.展开更多
A laboratory study was conducted to evaluate the effect of compost amendment on mobility and leaching potential of heavy metals, nitrogen （N） and phosphorus （P） from a peat-based commercial container medium contai...A laboratory study was conducted to evaluate the effect of compost amendment on mobility and leaching potential of heavy metals, nitrogen （N） and phosphorus （P） from a peat-based commercial container medium containing 700 g kg^-1 peat, 200 g kg^-1 perlite and 100 g kg^-1 vermiculite at varying amendment rates of compost （0, 0.25, 0.50, 0.75 and 1.00 L L^-1）. Increasing compost amendment significantly and linearly increased the pH （P 〈 0.01）, the total concentrations of organic carbon （P 〈 0.05）, copper （Cu） （P 〈 0.01）, cadmium （ca） （P 〈 0.01）, and lead （Pb） （P 〈 0.01）, and increased the bulk density （P 〈 0.01） of the medium. The electrical conductivity （EC）, and total N and P of the medium increased significantly （P 〈 0.01） and quadratically with increasing compost amendment. The relationship of the C/N ratio of the medium with the compost amendment rate was decreasing, significant （P 〈 0.01） and cubic, while that of the total Zn was increasing, significant （P 〈 0.01） and cubic. Extractable P, NO3-N, and NH4-N increased initially with an increasing compost amendment of up to 0.50 L L^-1 and then decreased with further increasing compost rate. Increasing compost rates resulted in a highly significant （P 〈 0.01） and linear increase in total Cd, Cu, and Pb, and a highly significant （P 〈 0.01） and cubic increase in total Zn in the medium. Increasing compost rates also significantly （P 〈 0.01） increased extractable Cu （linearly） and Zn （quadratically）, but significantly （P 〈 0.01） decreased extractable Pb （linearly）. There was no significant effect of compost amendment on the extractable Cd concentration in the medium. However, with increasing compost rates from 0.25 to 1.00 L L^-1, extractability of P, Cd, Cu, Pb and Zn （extractable concentration as a percent of total） was decreased, indicating that compost amendment could lower the leachability of these elements from the medium.展开更多
Predecessor rain events(PREs) in the Yangtze River Delta(YRD) region associated with the South China Sea and Northwest Pacific Ocean(SCS-WNPO) tropical cyclones(TCs) are investigated during the period from 2010 to 201...Predecessor rain events(PREs) in the Yangtze River Delta(YRD) region associated with the South China Sea and Northwest Pacific Ocean(SCS-WNPO) tropical cyclones(TCs) are investigated during the period from 2010 to 2019.Results indicate that approximately 10% of TCs making landfall in China produce PREs over the YRD region;however,they are seldom forecasted. PREs often occur over the YRD region when TCs begin to be active in the SCS-WNPO with westward paths, whilst the cold air is still existing or beginning to be present. PREs are more likely to peak in June and September. The distances between the PRE centers and the parent TC range from 900 to 1700 km. The median value of rain amounts and the median lifetime of PREs is approximately 200 mm and 24 h, respectively. Composite results suggest that PREs form in the equatorward jet-entrance region of the upper-level westerly jet(WJ), where a 925-hPa equivalent potential temperature ridge is located east of a 500-hPa trough. Deep moisture is transported from the TC vicinity to the remote PREs region. The ascent of this deep moist air in front of the 500-hPa trough and frontogenesis beneath the equatorward entrance region of the WJ is advantageous for the occurrence of PREs in the YRD region. The upper-level WJ may be affected by the subtropical high and westerly trough in the Northwest Pacific Ocean, and the occurrence of PREs may favor the maintenance of the upper-level WJ. The upper-level outflow of TCs in the SCS plays a secondary role.展开更多
1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the ...1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks展开更多
In this study,the Dynamical-Statistical-Analog Ensemble Forecast model(DSAEF_LTP model)for landfalling tropical cyclone(LTC)precipitation was employed to simulate the precipitation of 10 LTCs that occurred over China ...In this study,the Dynamical-Statistical-Analog Ensemble Forecast model(DSAEF_LTP model)for landfalling tropical cyclone(LTC)precipitation was employed to simulate the precipitation of 10 LTCs that occurred over China in 2018.With similarity region scheme(SRS)parameter values added and TC intensity introduced to the generalized initial value(GIV),four groups of precipitation simulation experiments were designed to verify the forecasting ability of the improved model for more TC samples.Results show that the simulation ability of the DSAEF_LTP model can be optimized regardless of whether adding SRS values only,or introducing TC intensity into GIV,while the experiment with both the two improvements shows a more prominent advantage in simulating the heavier precipitation of LTCs.Compared with four NWP models(i.e.,ECMWF,GFS,GRAPES and SMS-WARMS),the overall forecasting performance of the DSAEF_LTP model achieves a better result in simulating precipitation at the thresholds over 250 mm and performs slightly better than NWP models at the thresholds over 100 mm.展开更多
New design solutions have been proposed for a BRS-GPG type reactor circuit, which are different from transport and stationary low and medium-powered reactor installations cooled with heavy liquid-metal coolants, and w...New design solutions have been proposed for a BRS-GPG type reactor circuit, which are different from transport and stationary low and medium-powered reactor installations cooled with heavy liquid-metal coolants, and which correspond to the evolutionary development of such installations. While developing these solutions, the available experience in creating and operating So</span><span>viet pilot and commercial power plants cooled with lead-bismuth coolants</span><span> was used, including investigations, primarily experimental ones, carried out by team of authors in justification of a capacity range (50</span></span><span> </span><span>-</span><span> </span><span>250 MW) of low and medium-powered reactor plants with horizontal steam generators (BRS-</span><span> </span><span>GPG) proposed and elaborated at the NNSTU.展开更多
文摘Dense-medium cyclones have been used for beneficiation of fine particles of coal. In this study, the usability of cyclones in the beneficiation of tailings of a coal preparation plant was investigated. For this purpose, separation tests were conducted using spiral concentrator and heavy medium cyclones with the specific weight of medium 1.3-1.8 （g/cm^3） on different grading fractions of tailing in an industrial scale （the weight of tail sample was five tons）. Spiral concentrator was utilized to beneficiate particles smaller than 1 mm. In order to evaluate the efficiency of cyclones, sink and float experiments using a specific weight of 1.3, 1.5, 1.7 and 1.9 g/cm^3, were conducted on a pilot scale. Based on the obtained results, the recovery of floated materials in cyclones with the specific weight of 1.40, 1.47 and 1.55 g/cm^3 are 17.75%, 33.80%, and 50%, respectively. Also, the cut point （Pso）, which is the relative density at which particles report equally to the both products are 1.40, 1.67 and 1.86 g/cm^3. The probable errors of separation for defined specific weights for cyclones are 0.080, 0.085 and 0.030, respectively. Also, the coefficients of variation was calculated to be 0.20, 0.12 and 0.03. Finally, it could be said that the performance of a cyclone with a heavy medium of 1.40 g/cm^3 specific weight is desirable compared with other specific weights.
基金NationalNaturalScienceFoundation (59878033)Tianjin Science and Technology Developm entProgram (043100611).
文摘This paper, probing into heavy metal control in domestic rubbish by source screening and nutrient element analysis, revealed the feasibility of source control of heavy metals and the suitability of rubbish as turfgrass medium. Heavy metals in domestic rubbish were controlled by source screening before composting. The study consisted of a control with garden soil. The contents of main mineral elements and heavy metals in rubbish compost and control were determined by the method of ICP-AES. The results showed that heavy metal concentrations in rubbish were lower than those in garden soil, and little difference occurred between rubbish and garden soil in main mineral element concentrations. Based on this, it was concluded that rubbish compost was favorable for using as turfgrass medium and heavy metal control in rubbish by source screening was effective.
基金Found by the National High-tech Research and Development Program of China(No.SS2012AA062204)
文摘The relationship between Pb leaching concentration and the solution＇s pH with time was analyzed when cement in its solidified form was leached in an acid medium. The effects of the particle size of the solidified form, the cement adding method, and the hydration degree on Pb solidification were also investigated. The experimental results indicate that cement is quickly dissolved and hydrated in the acid medium, forming a C-S-H gel or silicic acid sol with good adsorption. When cement-Pb solidified form is leached in an acetate solution, the hydrated product erodes with time, so the Pb concentration increases slightly in the beginning. Then, some of the Pb ions are absorbed by the newly generated silicic acid sol, C-S-H. Others produce Pb（OH）2 precipitation for secondary solidification, leading to a gradual decrease in the Pb concentration in a leaching time of more than two hours. Moreover, the particle size of the solidified form has important effects on the Pb dissolution. When the amount of added cement is low, with a pH of less than 9.5, the solidification affects the sequence of the original cement powder, the cement hydrated powder, and the cement- Pb solidified form. When the added amount of cement increases with a pH of more than 11, the effect of adding methods on solidification decreases, and the solidified form is a little better than others.
文摘A laboratory study was conducted to evaluate the effect of compost amendment on mobility and leaching potential of heavy metals, nitrogen （N） and phosphorus （P） from a peat-based commercial container medium containing 700 g kg^-1 peat, 200 g kg^-1 perlite and 100 g kg^-1 vermiculite at varying amendment rates of compost （0, 0.25, 0.50, 0.75 and 1.00 L L^-1）. Increasing compost amendment significantly and linearly increased the pH （P 〈 0.01）, the total concentrations of organic carbon （P 〈 0.05）, copper （Cu） （P 〈 0.01）, cadmium （ca） （P 〈 0.01）, and lead （Pb） （P 〈 0.01）, and increased the bulk density （P 〈 0.01） of the medium. The electrical conductivity （EC）, and total N and P of the medium increased significantly （P 〈 0.01） and quadratically with increasing compost amendment. The relationship of the C/N ratio of the medium with the compost amendment rate was decreasing, significant （P 〈 0.01） and cubic, while that of the total Zn was increasing, significant （P 〈 0.01） and cubic. Extractable P, NO3-N, and NH4-N increased initially with an increasing compost amendment of up to 0.50 L L^-1 and then decreased with further increasing compost rate. Increasing compost rates resulted in a highly significant （P 〈 0.01） and linear increase in total Cd, Cu, and Pb, and a highly significant （P 〈 0.01） and cubic increase in total Zn in the medium. Increasing compost rates also significantly （P 〈 0.01） increased extractable Cu （linearly） and Zn （quadratically）, but significantly （P 〈 0.01） decreased extractable Pb （linearly）. There was no significant effect of compost amendment on the extractable Cd concentration in the medium. However, with increasing compost rates from 0.25 to 1.00 L L^-1, extractability of P, Cd, Cu, Pb and Zn （extractable concentration as a percent of total） was decreased, indicating that compost amendment could lower the leachability of these elements from the medium.
基金supported by the National Natural Science Foundation of China (Grant Nos. 42105004, 41930967, 42192554, and 42105011)the Natural Science Foundation of Zhejiang Province of China (Grant No. LQ20D050001)the Scientific Research Foundation of Hangzhou Normal University (Grant No. 2020QDL015)。
文摘Predecessor rain events(PREs) in the Yangtze River Delta(YRD) region associated with the South China Sea and Northwest Pacific Ocean(SCS-WNPO) tropical cyclones(TCs) are investigated during the period from 2010 to 2019.Results indicate that approximately 10% of TCs making landfall in China produce PREs over the YRD region;however,they are seldom forecasted. PREs often occur over the YRD region when TCs begin to be active in the SCS-WNPO with westward paths, whilst the cold air is still existing or beginning to be present. PREs are more likely to peak in June and September. The distances between the PRE centers and the parent TC range from 900 to 1700 km. The median value of rain amounts and the median lifetime of PREs is approximately 200 mm and 24 h, respectively. Composite results suggest that PREs form in the equatorward jet-entrance region of the upper-level westerly jet(WJ), where a 925-hPa equivalent potential temperature ridge is located east of a 500-hPa trough. Deep moisture is transported from the TC vicinity to the remote PREs region. The ascent of this deep moist air in front of the 500-hPa trough and frontogenesis beneath the equatorward entrance region of the WJ is advantageous for the occurrence of PREs in the YRD region. The upper-level WJ may be affected by the subtropical high and westerly trough in the Northwest Pacific Ocean, and the occurrence of PREs may favor the maintenance of the upper-level WJ. The upper-level outflow of TCs in the SCS plays a secondary role.
文摘1.IntroductionMedium Mn steel was developed be-cause the wear resistance of Hadfield steel(Mn13)is poor under low or medium im-pact and extrusion abrasion[1-4].In theforegoing investigations[2-4]we found thatwith the increase of C content,theneedle-like and network carbide in mediumMn steel increased(as shown in Fig.1(a)and(c)).Although its wear resistance was largelyimproved,its impact toughness was greatlydecreased.In order to increase toughness,along-term high temperature heat-treatmentwas needed.But the treatment caused cracks
基金National Key R&D Program of China(2019YFC1510205)National Natural Science Foundation of China(41675042)。
文摘In this study,the Dynamical-Statistical-Analog Ensemble Forecast model(DSAEF_LTP model)for landfalling tropical cyclone(LTC)precipitation was employed to simulate the precipitation of 10 LTCs that occurred over China in 2018.With similarity region scheme(SRS)parameter values added and TC intensity introduced to the generalized initial value(GIV),four groups of precipitation simulation experiments were designed to verify the forecasting ability of the improved model for more TC samples.Results show that the simulation ability of the DSAEF_LTP model can be optimized regardless of whether adding SRS values only,or introducing TC intensity into GIV,while the experiment with both the two improvements shows a more prominent advantage in simulating the heavier precipitation of LTCs.Compared with four NWP models(i.e.,ECMWF,GFS,GRAPES and SMS-WARMS),the overall forecasting performance of the DSAEF_LTP model achieves a better result in simulating precipitation at the thresholds over 250 mm and performs slightly better than NWP models at the thresholds over 100 mm.
文摘New design solutions have been proposed for a BRS-GPG type reactor circuit, which are different from transport and stationary low and medium-powered reactor installations cooled with heavy liquid-metal coolants, and which correspond to the evolutionary development of such installations. While developing these solutions, the available experience in creating and operating So</span><span>viet pilot and commercial power plants cooled with lead-bismuth coolants</span><span> was used, including investigations, primarily experimental ones, carried out by team of authors in justification of a capacity range (50</span></span><span> </span><span>-</span><span> </span><span>250 MW) of low and medium-powered reactor plants with horizontal steam generators (BRS-</span><span> </span><span>GPG) proposed and elaborated at the NNSTU.
基金supported by the National Natural Science Foundation of China(Nos.U1804146,51905153,52111530068)the Science and Technology Innovation Team of Henan University of Science and Technology,China(No.2015XTD006)Major Science and Technology Project of Henan Province,China(No.221100230200)。
