The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the de...The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the development block, this paper simulated and calculated the high concentration polymer flooding development case of the polymer flooding pilot test area through numerical simulation research, and selected the best case through the comparison of various development indicators. The simulation results showed that the larger the polymer dosage and the higher the concentration, the better the oil displacement effect. The best injection method in the construction process was the overall injection of high concentration polymer. The test area should implement high concentration polymer oil displacement as soon as possible. The research results provided theoretical guidance for the future development and management of the pilot area.展开更多
Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel.A closed-chamber distillation system,in which the pump is stopped and pressurein...Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel.A closed-chamber distillation system,in which the pump is stopped and pressureinduced salt distillation is performed,was arranged for fluoride salt treatment.A stair-step optimization process was demonstrated to improve the recovery efficiency by up to 99%.The pressure change curve was feasible for estimating the distillation process,and a method for displaying the pressure value online in order to determine the endpoint was also developed.The decontamination factor of Nd in the condensate salt was deduced to be greater than 100 with 1 wt%NdF3–FLiNaK distillation.The optimal conditions developed in this study showed a high recovery ratio for the fluoride carrier salt and a high separation efficiency for rare earth products.展开更多
Experiments were conducted to obtain the values of the Sauter bubble size, enrichment and recovery of bovine serum albumin （BSA） in a semi-batch col- umn fitted with a stainless steel sparger at elevated pressure. T...Experiments were conducted to obtain the values of the Sauter bubble size, enrichment and recovery of bovine serum albumin （BSA） in a semi-batch col- umn fitted with a stainless steel sparger at elevated pressure. The effects of Sur- face tension, surfactant concentration, foam/solution height ratio and air flow rate on the separation performance were investigated, and the results showed that good en- richments and recoveries can be achieved for bovine serum albumin operated at el- evated pressures. Especially the size of bubbles generated by the stainless steel sparger was smaller at higher pressures which is favorable to the foam separation process. Furthermore, the separation mechanism of bovine serum albumin operated at elevated pressure was also discussed.展开更多
This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the ...This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the brief history and basic procedures of LTCC.The framework of research on the drawing mechanism,basic concepts,and some theoretical models of LTCC are detailed in sect.research framework of top coal drawingmechanism.The authors note that theTop coal drawbody(TCD),Top coal boundary(TCB)and Top coal recovery ratio(TCRR)are key factors in the drawingmechanism.TheBody-boundary-ratio(BBR)research system has been the classic framework for research over the last 20 years.The modified Bergmark-Roos model,which considers the effects of the supporting rear canopy,flowing velocity of top coal,and its shape factor,is optimal for characterizing the TCD.A 3Dmodel to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed.In sect.physical testing and numerical simulation,the physical tests and numerical simulations in the literature are classified for ease of bibliographical review,and classic conclusions regarding the drawing mechanism of top coal are presented and discussedwith elaborate illustrations and descriptions.The deflection of the TCDis noted,and is caused by the shape of the rear canopy.The inclined coal seam always induces a largerTCD,and a deflection in theTCDhas also been observed in it.The effects of the drawing sequence and drawing interval on the TCRR are reviewed,where a long drawing interval is found to lead to significant loss of top coal.Its flowing behavior and velocity distribution are also presented.Sect.practical applications of drawingmechanisms forLTCCmines 4 summarizes over 10 cases where the TCRRof LTCCmines improved due to the guidance of the drawing mechanism.The final section provides a summary of the work here and some open questions.Prospective investigations are highlighted to give researchers guidance on promising issues in future research on LTCC.展开更多
A novel technology,modified roasting in CO-CO2 mixed gas and magnetic separation,was presented to recover iron from copper slag.The effects of various parameters such as dosage of flux(CaO),gas flowrate of CO and CO2,...A novel technology,modified roasting in CO-CO2 mixed gas and magnetic separation,was presented to recover iron from copper slag.The effects of various parameters such as dosage of flux(CaO),gas flowrate of CO and CO2,roasting temperature,roasting time,particle size of modified slag and magnetic flux density on the oxidized modification and magnetic separation were investigated by comparison of the X-ray diffraction patterns and iron recovery ratio.The optimum conditions for recovering iron by oxidizing roasting and magnetic separation are as follows:calcium oxide content of 25 wt.%,mixed gas flow rates of CO2 and CO of 180 and 20 mL/min,oxidizing roasting at 1323 K for 2 h,grinding the modified slag to 38.5-25.0μm and magnetic separation at 170 mT.The mineralogical and microstructural characteristics of modified slag revealed that the iron-bearing minerals in the copper slag were oxidized,the generated magnetite grew into large particles,and the silicate in copper slag was combined with calcium oxide to form calcium silicate.Finally,the iron-bearing concentrate with an iron grade of 54.79%and iron recovery ratio of 80.14%was effectively obtained.展开更多
In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus o...In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus of rupture （MOR） of poplar （Populus cathayana Rehd.） samples pretreated by 40-60% glycerin solutions and then compressed at 160℃ for 10-120 min. We analyzed the data statistically by using two-factor analysis of variance. The chemical compositions of thermal treated wood were also analyzed and compared with untreated control samples. The results showed that the compressive deformation of wood can be properly fixed by glycerin pretreatment. The recovery ratio of compressed wood decreased with prolonging compression time and increasing concent-ration of the glycerin solution. However, the mechanical properties of compressed wood decreased after a long time of compression. The optimal fixation of compressive deformation is to pretreat the wood by a solution of 50% glycerin and compression at 160℃ for 60 min. The analysis of chemical composition showed that glycerin displayed an accelerating effect on degradation of hemicelluloses and lignin during heat-treatment, which explains the main reason of the effect of acceleration of glycerin on deformation fixation of compressed wood.展开更多
The size distribution of the broken top coal blocks is an important factor,affecting the recovery ratio and the efficiency of drawing top coal in longwall top coal caving(LTCC)mining panel.The standard deviation of to...The size distribution of the broken top coal blocks is an important factor,affecting the recovery ratio and the efficiency of drawing top coal in longwall top coal caving(LTCC)mining panel.The standard deviation of top coal block size(dt)is one of the main parameters to reflect the size distribution of top coal.To find the effect of dt on the caving mechanism,this study simulates experiments with 9 different dt by using discrete element software PFC.The dt is divided into two stages:uniform distribution stage(UDS)whose dt is less than 0.1(Schemes 1–5),and nonuniform distribution stage(NDS)whose dt is more than 0.1(Schemes 6–9).This research mainly investigates the variation of recovery ratio,drawing body shape,boundary of top coal,and contact force between particles in the two stages,respectively.The results showed that with the increasing dt,the recovery ratio of the panel increases first and then decreases in UDS.It is the largest in Scheme 3,which mainly increases the drawing volume at the side of starting drawing end.However,the recovery ratio decreases first and then increases quickly in NDS,and it is the largest in Scheme 9,where the drawing volume at the side of finishing drawing end are relatively higher.In UDS,the major size of top coal is basically medium,while in NDS,the size varies from medium to small,and then to large,with a distinct difference in shape and volume of the drawing body.When the major size of top coal is medium and small,the cross-section width of the initial boundary of top coal at each height is relatively small.Conversely,when the top coal size is large,the initial boundary of top coal has a larger opening range,the rotating angle of lower boundary is relatively small in the normal drawing stage,which is conducive to the development of drawing body and reduces the residual top coal,and the maximum particle velocity and the particles movement angle are both larger.This study lays a foundation for the prediction of recovery ratio,and suggests that the uniform top coal is more manageable and has a larger recovery ratio.展开更多
To study the effects of CBM （coal bed methane） temperature-rising desorption, isothermal adsorption/desorption experiments on three ranks （anthracite, coking coal and lignite） of coal at different temperatures wer...To study the effects of CBM （coal bed methane） temperature-rising desorption, isothermal adsorption/desorption experiments on three ranks （anthracite, coking coal and lignite） of coal at different temperatures were designed based on the traditional CBM decompression desorption. The experimental results indicate that temperature-rising desorption is more effec- tive in high-rank coal, and ever-increasing temperature of high-rank coal reservoir can reduce the negative effects of coal ma- trix shrinkage in the process of production and improve the permeability of the coal reservoir as well. It is also revealed that the technique of temperature-rising desorption applied in higher-rank coal reservoir can enhance CBM recovery ratio. This study provided theoretical support for the application of temperature-rising desorption technique in practical discharging and mining projects, which can effectively tackle the gas production bottleneck problem.展开更多
Due to long-term water injection,often oilfields enter the so-called medium and high water cut stage,and it is difficult to achieve good oil recovery and water reduction through standard methods(single profile control...Due to long-term water injection,often oilfields enter the so-called medium and high water cut stage,and it is difficult to achieve good oil recovery and water reduction through standard methods(single profile control and flooding measures).Therefore,in this study,a novel method based on“plugging,profile control,and flooding”being implemented at the same time is proposed.To assess the performances of this approach,physical simulations,computer tomography,and nuclear magnetic resonance are used.The results show that the combination of a gel plugging agent,a polymer microsphere flooding agent,and a high-efficiency oil displacement agent leads to better results in terms of oil recovery with respect to the situation in which these approaches are used separately(the oil recovery is increased by 15.37%).Computer tomography scan results show that with the combined approach,a larger sweep volume and higher oil washing efficiency are obtained.The remaining oil in the cluster form can be recovered in the middle and low permeability layer,increasing the proportion of the columnar and blind end states of the oil.The nuclear magnetic resonance test results show that the combined“plugging,profile control,and flooding”treatment can also be used to control more effectively the dominant channels of the high permeability layer and further expand the recovery degree of the remaining oil in the pores of different sizes in the middle and low permeability layers.However,for the low permeability layer(permeability difference of 20),the benefits in terms of oil recovery are limited.展开更多
More and more oilfields are using acoustic technology to enhance oil recovery.In order to know the mechanism of acoustic oil recovery technology,the sound radiator of a new downhole vibration device is modeled and ana...More and more oilfields are using acoustic technology to enhance oil recovery.In order to know the mechanism of acoustic oil recovery technology,the sound radiator of a new downhole vibration device is modeled and analyzed.Based on the theoretical background,this paper firstly analyzes the acoustic mechanism for the oil reservoir and then makes a acoustic response analysis on the sound radiator model for frequency and time-domain investigation by using professional acoustic simulation softwareeLMS Virtual.lab Acoustics,finally calculates the acoustic transmission loss in the downhole oil reservoir.The research reveals that firstly,acoustic waves have influences on the oil&water fluidity in the oil reservoir,the oil pressure gradient and the interfacial tension of capillary;secondly,the acoustic radiation power and sound pressure of field point attain a peak on the natural frequency of the sound radiator;thirdly,with the acoustic impact,the sound pressure of oil reservoir would fluctuate so as to improve the oil recovery ratio;the last but not the least one is both the sound pressure of oil reservoir point and the transmission loss of rock have a positive correlation with the vibration frequency.Therefore,it is of great importance for the research of vibration frequency and structure optimization of sound radiator.展开更多
Reduction smelting of the bismuth oxide residue from pressure leaching of bismuth sulfide was investigated in the FeO-SiO_2-CaO ternary slag system.The results show that all the recovery ratios of Bi,Ag,Cu and Pb incr...Reduction smelting of the bismuth oxide residue from pressure leaching of bismuth sulfide was investigated in the FeO-SiO_2-CaO ternary slag system.The results show that all the recovery ratios of Bi,Ag,Cu and Pb increase with the increase of reductive coal proportion,reaction temperature and time,while too much reductive coal would help Fe enter metal phase;CaO/SiO_2and Fe O/SiO_2 of the chosen slag system should be 0.5-0.75 and 1.25-1.75,respectively,for the reason that the slag system has the optimum mobility and is beneficial for the recovery of metals.The corresponding optimum conditions are determined as follows:the added coal proportion is 7%of the leaching residue,CaO/SiO_2 mass ratio in the chosen slag system is 0.5 and FeO-SiO_2 is 1.5,the reaction temperature is 1300°C and the reaction time is 40 min.Under the above conditions,the recovery ratios of Bi,Ag,Cu and Pb are 99.6%,99.8%,97.0%and 97.3%,respectively.展开更多
The effects of quenching temperature on shape memory effect and microstructure of Fe 18Mn 5Si 8Cr 4Ni shape memory alloy have been studied. The results show that both the shape recovery ratio and the recovery stra...The effects of quenching temperature on shape memory effect and microstructure of Fe 18Mn 5Si 8Cr 4Ni shape memory alloy have been studied. The results show that both the shape recovery ratio and the recovery strain increased as quenching temperature increased, the amount of stress induced ε martensite in the process of cold work decreased with the increase of quenching temperature, the shape recovery ratio and the recovery strain reached maximum at 650℃, and then decreased rapidly with the further increase of quenching temperature,the stress induced ε martensite wholly disappeared at 1023K. But when the quenching temperature is higher than 1023K, the further increase of quenching temperature had little effect on shape recovery ratio, the amount and size of thermal induced ε martensite would increased with the further increase in quenching temperature. The shape memory effect can be improved by the moderate amount of pre exist ε martensite in the matrix before deforming.展开更多
The recovery ratio of top coal caving mining plays a key role in the development of this mining method. For the proposes to raise the recovery ratio and considering heading advance and roadway maintenance, a new metho...The recovery ratio of top coal caving mining plays a key role in the development of this mining method. For the proposes to raise the recovery ratio and considering heading advance and roadway maintenance, a new method of full seam mining for gently inclined thick coal seams is put forward on the basis of a theoretic research and engineering practice.展开更多
Iraq faces water scarcity due to a shortage of surface water resources. People in Safwan (Basrah, Iraq) and its environs use brackish groundwater as alternative resource. To improve water quality, small reverse osmosi...Iraq faces water scarcity due to a shortage of surface water resources. People in Safwan (Basrah, Iraq) and its environs use brackish groundwater as alternative resource. To improve water quality, small reverse osmosis (RO) plants have been established. The water selling price is (1.3 $/m<sup>3</sup>)* which does not cover the product cost which is (2.4 $/m<sup>3</sup>)*. Data were collected from eight plants, and a techno-economic assessment was conducted to explore the ideal cost. The known effective factored considered in this case, recovery ratio, temperature and total dissolved solids (TDS). From the other side, membrane replacement and energy cost were significantly effect, when their portions of the total production cost were 30.98%* and 48.38%* respectively as shown in Figure 10. In addition, software analysis was used to predict the scaling potential in raw water samples. Its results showed a high inorganic fouling (scaling) potential. Scaling has a permanent influence on operations and maintenance costs. These identified major cost influencers will be incorporated into the experimental design of the next phase of this ongoing research programme.展开更多
The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered ...The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.展开更多
Objective:To explore the influence of centrifugal parameters,centrifugal temperature,preparation equipment and anticoagulant on the manual preparation of platelet-rich plasma(PRP).Methods:Female ICR mice(n=36)were div...Objective:To explore the influence of centrifugal parameters,centrifugal temperature,preparation equipment and anticoagulant on the manual preparation of platelet-rich plasma(PRP).Methods:Female ICR mice(n=36)were divided into 4 groups according to four influencing factors of centrifugation parameters(centrifugation force and centrifugation time),centrifugation temperature,preparation device,and anticoagulant.The red blood cell concentration(RBC),white blood cell concentration(WBC)and platelet concentration(PLT)were detected by blood cell analyzer,and the platelet enrichment factor(PEF)and platelet recovery ratio(PRR)were calculated.Results:In the comparison of the calculation results of PLT,PEF and PRR in each group,the centrifugal parameters were higher at 300 g for 10 min and 1200 g for 15 min,which were 2600±201.55,3.68±1.29,61.60%±8.57%(P<0.05);When the centrifugal temperature was 4℃,the tunica albuginea was flatter and easier to be absorbed than the normal temperature,and the RBCs between the groups were 0.84±0.33 and 3.16±0.33,respectively,with significant difference.There was no significant difference among the three data groups of anticoagulants,and the choice of anticoagulants did not have too much influence.The quality of PRP obtained from the improved preparation device(anticoagulant+syringe)was significantly higher than that of the anticoagulant tube,and the results were 2568±124.52 and 3551.67±348.12,3.31±0.16 and 4.58±0.45,49.7%±2.41%and 68.74%±6.74%,respectively.Conclusion:High-quality platelet-rich plasma can be obtained by using an improved extraction device with any anticoagulant at 4℃and centrifugation parameters of 300 g for 10 min and 1200 g for 15 min.展开更多
To separate and concentrate NH4＋ and PO43 from the synthetic wastewater to the concentrated solution through a novel electrochemical reactor with circulated anode and cathode using the difference of the concentration...To separate and concentrate NH4＋ and PO43 from the synthetic wastewater to the concentrated solution through a novel electrochemical reactor with circulated anode and cathode using the difference of the concentration between electrode chamber and middle chamber.In recent years, the research on electrochemical processes have been focused on phosphate and ammonium removal and recovery. Among the wide range of possibilities with regards to electrochemical processes, capacitive deionization （CDI） saves the most energy while at the same time does not have continuity and selectivity. In this study, a new electrochemical reactor with electrolyte cyclic flowing in the electrode chambers was constructed to separate and concentrate phosphate and ammonium continuously and selectively from wastewater, based on the principle of CDI. At the concentration ratio of NaCI solution between the electrode chambers and the middle chamber （r） of 25 to 1, phosphate and ammonium in concentration level of domestic wastewater can be removed and recovered continuously and selectively as struvite. Long-term operation also indicated the ability to continuously repeat the reaction and verified sustained stability. Further, the selective recovery at the certain r could also be available to similar technologies for recovering other kinds of substances.展开更多
To enhance the friction performance of resin-based friction materials,five types of specimens with different polymer ether ketone(PEEK)contents were fabricated and their physiomechanical behaviours were tested and,the...To enhance the friction performance of resin-based friction materials,five types of specimens with different polymer ether ketone(PEEK)contents were fabricated and their physiomechanical behaviours were tested and,their tribological properties were investigated using a JF150F-II constant-speed tester.It was found that the addition of PEEK had a positive influence on the properties of the friction materials,and sample FM-3(the shorthand of‘Friction Materials-3’,containing 2 wt%PEEK)exhibited improved friction performance with a fade ratio and recovery ratio of 8.6%and 101.1%respectively.Among all samples,FM-4(the shorthand of‘Friction Materials-4’,con-taining 3 wt%PEEK)had the lowest specific wear rate with a value of 0.622×10^(−7)cm^(3)(N⋅m)^(−1)at 350℃.The PEEK can fill the microcracks in the composite at a high tem-perature and can also cover the hard abrasive particles to prevent them from directly damaging the composite.The findings from this study afford a foundation for studies to further improve the properties of resin-based friction materials.展开更多
Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its p...Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its potential value. The aim of this study was to investigate the correlation between ISI position and the outcome of surgical treatment for cervical spondylotic myelopathy （CSM） patients. Methods A retrospective study was conducted. Pre- and post-operative clinical status was evaluated by modified Japanese Orthopaedic Association （JOA） score. ISI was evaluated according to the T2-weighted sequences. The JOA score and the recovery ratios among patients with ISI in gray matter （group A）, in both gray and white matter （group B）, and ISI-negative group were compared. Results Totally 64 patients were enrolled in this retrospective study. Preoperative JOA score of ISI positive and negative group had significant difference, but the recovery ratios had no significant difference （the recovery ratios of the two groups in week 1, week 26, and week 104 were （21.54±14.65）%, （50.56±14.76）%, （59.23±13.08）% and （20.25±14.32）%, （54.46±3.16）% and （61.26±29.4）%, respectively; P 〉0.05）. The recovery ratios of negative group and group A in week 104 were superior to group B （the recovery ratios of negative group, group A, and group B in week 104 were （61.26±29.49）%, （65.35±11.36）%, and （50.33±10.20）%, respectively; P 〈0.05）. Conclusions Patients with ISI in the gray matter alone on T2-weighted MR images did not have significantly different surgical outcomes compared with those without ISI. Patients with ISI in both gray and white matter had surgical outcomes that were worse than those without ISI.展开更多
文摘The field test of high concentration polymer flooding has the characteristics of high cost, long cycle and irreversibility of the reservoir development process. In order to ensure the best development effect of the development block, this paper simulated and calculated the high concentration polymer flooding development case of the polymer flooding pilot test area through numerical simulation research, and selected the best case through the comparison of various development indicators. The simulation results showed that the larger the polymer dosage and the higher the concentration, the better the oil displacement effect. The best injection method in the construction process was the overall injection of high concentration polymer. The test area should implement high concentration polymer oil displacement as soon as possible. The research results provided theoretical guidance for the future development and management of the pilot area.
基金This work was financially supported by the National Natural Science Foundation of China(No.21771188)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA02030000)A study on some key issues regarding the Th-U fuel cycle was also funded(No.QYZDY-SSW-JSC016).
文摘Low-pressure distillation has been proposed as a suitable technique for the recovery of carrier salt from molten salt reactor spent fuel.A closed-chamber distillation system,in which the pump is stopped and pressureinduced salt distillation is performed,was arranged for fluoride salt treatment.A stair-step optimization process was demonstrated to improve the recovery efficiency by up to 99%.The pressure change curve was feasible for estimating the distillation process,and a method for displaying the pressure value online in order to determine the endpoint was also developed.The decontamination factor of Nd in the condensate salt was deduced to be greater than 100 with 1 wt%NdF3–FLiNaK distillation.The optimal conditions developed in this study showed a high recovery ratio for the fluoride carrier salt and a high separation efficiency for rare earth products.
文摘Experiments were conducted to obtain the values of the Sauter bubble size, enrichment and recovery of bovine serum albumin （BSA） in a semi-batch col- umn fitted with a stainless steel sparger at elevated pressure. The effects of Sur- face tension, surfactant concentration, foam/solution height ratio and air flow rate on the separation performance were investigated, and the results showed that good en- richments and recoveries can be achieved for bovine serum albumin operated at el- evated pressures. Especially the size of bubbles generated by the stainless steel sparger was smaller at higher pressures which is favorable to the foam separation process. Furthermore, the separation mechanism of bovine serum albumin operated at elevated pressure was also discussed.
基金This work is funded by the National Natural Science Foundation of China(Grant No.51934008,51674264 to Jiachen Wang,Grant No.51974320 to Shengli Yang)Fundamental Research Funds for the Central Universities(Grant No.06500182 to Zhengyang Song)Funds from State Key Laboratory of Coal Resources in Western China(SKLCRKF20-07 to Zhengyang Song).
文摘This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the brief history and basic procedures of LTCC.The framework of research on the drawing mechanism,basic concepts,and some theoretical models of LTCC are detailed in sect.research framework of top coal drawingmechanism.The authors note that theTop coal drawbody(TCD),Top coal boundary(TCB)and Top coal recovery ratio(TCRR)are key factors in the drawingmechanism.TheBody-boundary-ratio(BBR)research system has been the classic framework for research over the last 20 years.The modified Bergmark-Roos model,which considers the effects of the supporting rear canopy,flowing velocity of top coal,and its shape factor,is optimal for characterizing the TCD.A 3Dmodel to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed.In sect.physical testing and numerical simulation,the physical tests and numerical simulations in the literature are classified for ease of bibliographical review,and classic conclusions regarding the drawing mechanism of top coal are presented and discussedwith elaborate illustrations and descriptions.The deflection of the TCDis noted,and is caused by the shape of the rear canopy.The inclined coal seam always induces a largerTCD,and a deflection in theTCDhas also been observed in it.The effects of the drawing sequence and drawing interval on the TCRR are reviewed,where a long drawing interval is found to lead to significant loss of top coal.Its flowing behavior and velocity distribution are also presented.Sect.practical applications of drawingmechanisms forLTCCmines 4 summarizes over 10 cases where the TCRRof LTCCmines improved due to the guidance of the drawing mechanism.The final section provides a summary of the work here and some open questions.Prospective investigations are highlighted to give researchers guidance on promising issues in future research on LTCC.
基金The authors wish to express thanks to National Natural Science Foundation of China(Grant No.51774154)the Jiangxi Natural Science Foundation(Grant No.20151BAB206029)for the financial support for this research。
文摘A novel technology,modified roasting in CO-CO2 mixed gas and magnetic separation,was presented to recover iron from copper slag.The effects of various parameters such as dosage of flux(CaO),gas flowrate of CO and CO2,roasting temperature,roasting time,particle size of modified slag and magnetic flux density on the oxidized modification and magnetic separation were investigated by comparison of the X-ray diffraction patterns and iron recovery ratio.The optimum conditions for recovering iron by oxidizing roasting and magnetic separation are as follows:calcium oxide content of 25 wt.%,mixed gas flow rates of CO2 and CO of 180 and 20 mL/min,oxidizing roasting at 1323 K for 2 h,grinding the modified slag to 38.5-25.0μm and magnetic separation at 170 mT.The mineralogical and microstructural characteristics of modified slag revealed that the iron-bearing minerals in the copper slag were oxidized,the generated magnetite grew into large particles,and the silicate in copper slag was combined with calcium oxide to form calcium silicate.Finally,the iron-bearing concentrate with an iron grade of 54.79%and iron recovery ratio of 80.14%was effectively obtained.
基金supported by the National Natural Science Foundation of China (NSFC) (Grant No.30500386)
文摘In order to find an effective and environmentally friendly method to fix compressive deformation of wood, we determined or measured the recovery ratio, surface hardness, modulus of elasticity （MOE） and the modulus of rupture （MOR） of poplar （Populus cathayana Rehd.） samples pretreated by 40-60% glycerin solutions and then compressed at 160℃ for 10-120 min. We analyzed the data statistically by using two-factor analysis of variance. The chemical compositions of thermal treated wood were also analyzed and compared with untreated control samples. The results showed that the compressive deformation of wood can be properly fixed by glycerin pretreatment. The recovery ratio of compressed wood decreased with prolonging compression time and increasing concent-ration of the glycerin solution. However, the mechanical properties of compressed wood decreased after a long time of compression. The optimal fixation of compressive deformation is to pretreat the wood by a solution of 50% glycerin and compression at 160℃ for 60 min. The analysis of chemical composition showed that glycerin displayed an accelerating effect on degradation of hemicelluloses and lignin during heat-treatment, which explains the main reason of the effect of acceleration of glycerin on deformation fixation of compressed wood.
基金supported by the National Key R&D Plan of China,China(Grant No.2018YFC0604501)the Natural Science Foundation of China,China(Grant Nos.51934008,51674264,51904305)the Research Fund of the State Key Laboratory of Coal Resources and Safe Mining,CUMT,China(Grant No.SKLCRSM19KF023).
文摘The size distribution of the broken top coal blocks is an important factor,affecting the recovery ratio and the efficiency of drawing top coal in longwall top coal caving(LTCC)mining panel.The standard deviation of top coal block size(dt)is one of the main parameters to reflect the size distribution of top coal.To find the effect of dt on the caving mechanism,this study simulates experiments with 9 different dt by using discrete element software PFC.The dt is divided into two stages:uniform distribution stage(UDS)whose dt is less than 0.1(Schemes 1–5),and nonuniform distribution stage(NDS)whose dt is more than 0.1(Schemes 6–9).This research mainly investigates the variation of recovery ratio,drawing body shape,boundary of top coal,and contact force between particles in the two stages,respectively.The results showed that with the increasing dt,the recovery ratio of the panel increases first and then decreases in UDS.It is the largest in Scheme 3,which mainly increases the drawing volume at the side of starting drawing end.However,the recovery ratio decreases first and then increases quickly in NDS,and it is the largest in Scheme 9,where the drawing volume at the side of finishing drawing end are relatively higher.In UDS,the major size of top coal is basically medium,while in NDS,the size varies from medium to small,and then to large,with a distinct difference in shape and volume of the drawing body.When the major size of top coal is medium and small,the cross-section width of the initial boundary of top coal at each height is relatively small.Conversely,when the top coal size is large,the initial boundary of top coal has a larger opening range,the rotating angle of lower boundary is relatively small in the normal drawing stage,which is conducive to the development of drawing body and reduces the residual top coal,and the maximum particle velocity and the particles movement angle are both larger.This study lays a foundation for the prediction of recovery ratio,and suggests that the uniform top coal is more manageable and has a larger recovery ratio.
文摘To study the effects of CBM （coal bed methane） temperature-rising desorption, isothermal adsorption/desorption experiments on three ranks （anthracite, coking coal and lignite） of coal at different temperatures were designed based on the traditional CBM decompression desorption. The experimental results indicate that temperature-rising desorption is more effec- tive in high-rank coal, and ever-increasing temperature of high-rank coal reservoir can reduce the negative effects of coal ma- trix shrinkage in the process of production and improve the permeability of the coal reservoir as well. It is also revealed that the technique of temperature-rising desorption applied in higher-rank coal reservoir can enhance CBM recovery ratio. This study provided theoretical support for the application of temperature-rising desorption technique in practical discharging and mining projects, which can effectively tackle the gas production bottleneck problem.
基金The authors gratefully acknowledge the financial support from the National Science and Technology Major Special Project(2016ZX05058-003).
文摘Due to long-term water injection,often oilfields enter the so-called medium and high water cut stage,and it is difficult to achieve good oil recovery and water reduction through standard methods(single profile control and flooding measures).Therefore,in this study,a novel method based on“plugging,profile control,and flooding”being implemented at the same time is proposed.To assess the performances of this approach,physical simulations,computer tomography,and nuclear magnetic resonance are used.The results show that the combination of a gel plugging agent,a polymer microsphere flooding agent,and a high-efficiency oil displacement agent leads to better results in terms of oil recovery with respect to the situation in which these approaches are used separately(the oil recovery is increased by 15.37%).Computer tomography scan results show that with the combined approach,a larger sweep volume and higher oil washing efficiency are obtained.The remaining oil in the cluster form can be recovered in the middle and low permeability layer,increasing the proportion of the columnar and blind end states of the oil.The nuclear magnetic resonance test results show that the combined“plugging,profile control,and flooding”treatment can also be used to control more effectively the dominant channels of the high permeability layer and further expand the recovery degree of the remaining oil in the pores of different sizes in the middle and low permeability layers.However,for the low permeability layer(permeability difference of 20),the benefits in terms of oil recovery are limited.
基金Fund Project:The Graduate Fund of Southwest Petroleum University(CX2014SY02).
文摘More and more oilfields are using acoustic technology to enhance oil recovery.In order to know the mechanism of acoustic oil recovery technology,the sound radiator of a new downhole vibration device is modeled and analyzed.Based on the theoretical background,this paper firstly analyzes the acoustic mechanism for the oil reservoir and then makes a acoustic response analysis on the sound radiator model for frequency and time-domain investigation by using professional acoustic simulation softwareeLMS Virtual.lab Acoustics,finally calculates the acoustic transmission loss in the downhole oil reservoir.The research reveals that firstly,acoustic waves have influences on the oil&water fluidity in the oil reservoir,the oil pressure gradient and the interfacial tension of capillary;secondly,the acoustic radiation power and sound pressure of field point attain a peak on the natural frequency of the sound radiator;thirdly,with the acoustic impact,the sound pressure of oil reservoir would fluctuate so as to improve the oil recovery ratio;the last but not the least one is both the sound pressure of oil reservoir point and the transmission loss of rock have a positive correlation with the vibration frequency.Therefore,it is of great importance for the research of vibration frequency and structure optimization of sound radiator.
基金Project(134414) supported by the Postdoctoral Funded Program of Central South University,China
文摘Reduction smelting of the bismuth oxide residue from pressure leaching of bismuth sulfide was investigated in the FeO-SiO_2-CaO ternary slag system.The results show that all the recovery ratios of Bi,Ag,Cu and Pb increase with the increase of reductive coal proportion,reaction temperature and time,while too much reductive coal would help Fe enter metal phase;CaO/SiO_2and Fe O/SiO_2 of the chosen slag system should be 0.5-0.75 and 1.25-1.75,respectively,for the reason that the slag system has the optimum mobility and is beneficial for the recovery of metals.The corresponding optimum conditions are determined as follows:the added coal proportion is 7%of the leaching residue,CaO/SiO_2 mass ratio in the chosen slag system is 0.5 and FeO-SiO_2 is 1.5,the reaction temperature is 1300°C and the reaction time is 40 min.Under the above conditions,the recovery ratios of Bi,Ag,Cu and Pb are 99.6%,99.8%,97.0%and 97.3%,respectively.
文摘The effects of quenching temperature on shape memory effect and microstructure of Fe 18Mn 5Si 8Cr 4Ni shape memory alloy have been studied. The results show that both the shape recovery ratio and the recovery strain increased as quenching temperature increased, the amount of stress induced ε martensite in the process of cold work decreased with the increase of quenching temperature, the shape recovery ratio and the recovery strain reached maximum at 650℃, and then decreased rapidly with the further increase of quenching temperature,the stress induced ε martensite wholly disappeared at 1023K. But when the quenching temperature is higher than 1023K, the further increase of quenching temperature had little effect on shape recovery ratio, the amount and size of thermal induced ε martensite would increased with the further increase in quenching temperature. The shape memory effect can be improved by the moderate amount of pre exist ε martensite in the matrix before deforming.
基金TheNationalImportantTechniqueInnovationItem (No .[2 0 0 1] 411)
文摘The recovery ratio of top coal caving mining plays a key role in the development of this mining method. For the proposes to raise the recovery ratio and considering heading advance and roadway maintenance, a new method of full seam mining for gently inclined thick coal seams is put forward on the basis of a theoretic research and engineering practice.
文摘Iraq faces water scarcity due to a shortage of surface water resources. People in Safwan (Basrah, Iraq) and its environs use brackish groundwater as alternative resource. To improve water quality, small reverse osmosis (RO) plants have been established. The water selling price is (1.3 $/m<sup>3</sup>)* which does not cover the product cost which is (2.4 $/m<sup>3</sup>)*. Data were collected from eight plants, and a techno-economic assessment was conducted to explore the ideal cost. The known effective factored considered in this case, recovery ratio, temperature and total dissolved solids (TDS). From the other side, membrane replacement and energy cost were significantly effect, when their portions of the total production cost were 30.98%* and 48.38%* respectively as shown in Figure 10. In addition, software analysis was used to predict the scaling potential in raw water samples. Its results showed a high inorganic fouling (scaling) potential. Scaling has a permanent influence on operations and maintenance costs. These identified major cost influencers will be incorporated into the experimental design of the next phase of this ongoing research programme.
基金financially supported by the National Natural Science Foundation of China (No. 51474021)the Fundamental Research Funds for the Central Universities of China (No. FRF-SD-12-009A)
文摘The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.
文摘Objective:To explore the influence of centrifugal parameters,centrifugal temperature,preparation equipment and anticoagulant on the manual preparation of platelet-rich plasma(PRP).Methods:Female ICR mice(n=36)were divided into 4 groups according to four influencing factors of centrifugation parameters(centrifugation force and centrifugation time),centrifugation temperature,preparation device,and anticoagulant.The red blood cell concentration(RBC),white blood cell concentration(WBC)and platelet concentration(PLT)were detected by blood cell analyzer,and the platelet enrichment factor(PEF)and platelet recovery ratio(PRR)were calculated.Results:In the comparison of the calculation results of PLT,PEF and PRR in each group,the centrifugal parameters were higher at 300 g for 10 min and 1200 g for 15 min,which were 2600±201.55,3.68±1.29,61.60%±8.57%(P<0.05);When the centrifugal temperature was 4℃,the tunica albuginea was flatter and easier to be absorbed than the normal temperature,and the RBCs between the groups were 0.84±0.33 and 3.16±0.33,respectively,with significant difference.There was no significant difference among the three data groups of anticoagulants,and the choice of anticoagulants did not have too much influence.The quality of PRP obtained from the improved preparation device(anticoagulant+syringe)was significantly higher than that of the anticoagulant tube,and the results were 2568±124.52 and 3551.67±348.12,3.31±0.16 and 4.58±0.45,49.7%±2.41%and 68.74%±6.74%,respectively.Conclusion:High-quality platelet-rich plasma can be obtained by using an improved extraction device with any anticoagulant at 4℃and centrifugation parameters of 300 g for 10 min and 1200 g for 15 min.
基金This research was supported by the Key Program of the National Natural Science Foundation of China （Grant Nos. 51238004 ＆ 21521064）.
文摘To separate and concentrate NH4＋ and PO43 from the synthetic wastewater to the concentrated solution through a novel electrochemical reactor with circulated anode and cathode using the difference of the concentration between electrode chamber and middle chamber.In recent years, the research on electrochemical processes have been focused on phosphate and ammonium removal and recovery. Among the wide range of possibilities with regards to electrochemical processes, capacitive deionization （CDI） saves the most energy while at the same time does not have continuity and selectivity. In this study, a new electrochemical reactor with electrolyte cyclic flowing in the electrode chambers was constructed to separate and concentrate phosphate and ammonium continuously and selectively from wastewater, based on the principle of CDI. At the concentration ratio of NaCI solution between the electrode chambers and the middle chamber （r） of 25 to 1, phosphate and ammonium in concentration level of domestic wastewater can be removed and recovered continuously and selectively as struvite. Long-term operation also indicated the ability to continuously repeat the reaction and verified sustained stability. Further, the selective recovery at the certain r could also be available to similar technologies for recovering other kinds of substances.
基金Department of Science and Technology of Jilin Province,Grant/Award Number:20190302129GX。
文摘To enhance the friction performance of resin-based friction materials,five types of specimens with different polymer ether ketone(PEEK)contents were fabricated and their physiomechanical behaviours were tested and,their tribological properties were investigated using a JF150F-II constant-speed tester.It was found that the addition of PEEK had a positive influence on the properties of the friction materials,and sample FM-3(the shorthand of‘Friction Materials-3’,containing 2 wt%PEEK)exhibited improved friction performance with a fade ratio and recovery ratio of 8.6%and 101.1%respectively.Among all samples,FM-4(the shorthand of‘Friction Materials-4’,con-taining 3 wt%PEEK)had the lowest specific wear rate with a value of 0.622×10^(−7)cm^(3)(N⋅m)^(−1)at 350℃.The PEEK can fill the microcracks in the composite at a high tem-perature and can also cover the hard abrasive particles to prevent them from directly damaging the composite.The findings from this study afford a foundation for studies to further improve the properties of resin-based friction materials.
文摘Background Increased signal intensity （ISI） in the spinal cord on T2-weighted MR images has been reported in some previous researches, however no study focused on the position of the ISI in the spinal cord and its potential value. The aim of this study was to investigate the correlation between ISI position and the outcome of surgical treatment for cervical spondylotic myelopathy （CSM） patients. Methods A retrospective study was conducted. Pre- and post-operative clinical status was evaluated by modified Japanese Orthopaedic Association （JOA） score. ISI was evaluated according to the T2-weighted sequences. The JOA score and the recovery ratios among patients with ISI in gray matter （group A）, in both gray and white matter （group B）, and ISI-negative group were compared. Results Totally 64 patients were enrolled in this retrospective study. Preoperative JOA score of ISI positive and negative group had significant difference, but the recovery ratios had no significant difference （the recovery ratios of the two groups in week 1, week 26, and week 104 were （21.54±14.65）%, （50.56±14.76）%, （59.23±13.08）% and （20.25±14.32）%, （54.46±3.16）% and （61.26±29.4）%, respectively; P 〉0.05）. The recovery ratios of negative group and group A in week 104 were superior to group B （the recovery ratios of negative group, group A, and group B in week 104 were （61.26±29.49）%, （65.35±11.36）%, and （50.33±10.20）%, respectively; P 〈0.05）. Conclusions Patients with ISI in the gray matter alone on T2-weighted MR images did not have significantly different surgical outcomes compared with those without ISI. Patients with ISI in both gray and white matter had surgical outcomes that were worse than those without ISI.
