Geotechnical properties of red shale encountered in deep underground mining were characterized on both laboratory and field scale to reveal its unfavorably in geoenvironment.Its constituents,microstructure,strength pr...Geotechnical properties of red shale encountered in deep underground mining were characterized on both laboratory and field scale to reveal its unfavorably in geoenvironment.Its constituents,microstructure,strength properties and water-weakening properties were investigated.In situ stress environment and mining-induced fractured damage zone after excavation were studied to reveal the instability mechanism.The results show that red shale contains swelling and loose clayey minerals as interstitial filling material,producing low shear strength of microstructure and making it vulnerable to water.Macroscopically,a U-shaped curve of uniaxial compressive strength(UCS)exists with the increase of the angle between macro weakness plane and the horizon.However,its tensile strength reduced monotonically with this angle.While immersed in water for72h,its UCS reduced by91.9%comparing to the natural state.Field sonic tests reveal that an asymmetrical geometrical profile of fractured damage zone of gateroad was identified due to geological bedding plane and detailed gateroad layout with regards to the direction of major principle stress.Therefore,red shale is a kind of engineering soft rock.For ground control in underground mining or similar applications,water inflow within several hours of excavation must strictly be prevented and energy adsorbing rock bolt is recommended,especially in large deformation part of gateroad.展开更多
Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and disc...Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.展开更多
To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomo...To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomotive are established.The coupling vibration equations of axle hung motor and wheelset are derived.For the air braking,the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed.It can be found that if the ABSF is applied in the front wheelset,all the wheelsets move laterally in the same direction.Once the ABSF occurs in the middle or rear one,other wheelsets may move laterally towards the opposite direction.The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment.For the asymmetric braking,the free lateral gap of axle-box could increase the wheelset motion amplitude,but could not change the moving direction.In both the straight line and curve,the ABSF may lead to wheelset misaligning motion,intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state.Especially for the steering wheelsets,the asymmetric braking increases the wheelset attack angle significantly,which forms the worst braking condition.展开更多
Background Hypertension is a common chronic disease among older adults, and is associated with medical complications and mor- tality. This study aimed to examine the effects of social network characteristics on the pr...Background Hypertension is a common chronic disease among older adults, and is associated with medical complications and mor- tality. This study aimed to examine the effects of social network characteristics on the prevalence, awareness, and control of hypertension among older adults. Methods The Korean Social Life, Health, and Aging Project （KSHAP） interviewed 814 〉 60-year-old residents and their spouses from a rural township between December 2011 and March 2012 （response rate： 95%）. We evaluated the data from 595 partici- pants. Multivariate logistic regression models were used to assess the effects of network characteristics on hypertension. Results We ob- served strong sex-specific network effects on the prevalence, awareness, and control of hypertension. Among older women, network density was associated with hypertension awareness [odds ratio （OR）： 2.63, 95% confidence interval （CI）： 1.03 5.37J and control （OR： 1.72; 95% CI 0.94-3.13）. Among older men, large networks were associated with a lower prevalence of hypertension （OR： 0.75; 95% CI： 0.58-0.96）. Compared to older women, older men with coarse networks exhibited better hypertension awareness （OR： 0.37; 95% CI： 0.14-0.95） and control （OR： 0.42; 95% CI： 0.19-0.91 ）. Network size interacted with density for hypertension control （P = 0.051）, with controlled hyperten- sion being associated with large and course networks. Conclusions A large network was associated with a lower risk for hypertension, and a coarse network was associated with hypertension awareness and control among older men. Older women with dense networks were most likely to exhibit hypertension awareness and control.展开更多
HPP （high pressure processing） is one of the novel technologies to produce microbiologically safe food. HPP is a non-thermal food processing method, wherein the food is subjected to a very high pressure ranging betw...HPP （high pressure processing） is one of the novel technologies to produce microbiologically safe food. HPP is a non-thermal food processing method, wherein the food is subjected to a very high pressure ranging between 100-800 MPa in order to prevent undesirable chemical and microbiological reactions, and hence, prolong the shelf-life. HPP is also called as ＂high hydrostatic processing, ultra-high pressure processing or isostatic processing＂. In dairy products, HHP has the potential to modify the functional properties of proteins, polysaccharides and alter biochemical reactions without significantly affecting the nutritional and sensory properties. HPP treatment induces significant changes in milk components particularly in proteins （whey proteins and caseins）, as well as on their applicability in innovative dairy productions. HPP influences technological properties of various milk products such as firmness, water-holding capacity of the gel and network structure, cheese yield, rennet coagulation time and ripening.展开更多
In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slop...In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slope. Modulating the argument of current output from ONLLY testing equipment can make the relay protection device operate, thus, the data used for calculation would be obtained naturally after several trails. In order to make sure how effective that method could be, some experiment data is given as well.展开更多
When the underexpanded supersonic jet impinges on the obstacle, it is well known that the self-induced flow os- cillation occurs. This oscillation depends on the pressure ratio in the flowfield, the position of an obs...When the underexpanded supersonic jet impinges on the obstacle, it is well known that the self-induced flow os- cillation occurs. This oscillation depends on the pressure ratio in the flowfield, the position of an obstacle and is related with the noise problems of aeronautical and other industrial engineering. The characteristic and the mechanism of self-induced flow oscillation, have to be clarified to control various noise problems. But, it seems that the characteristics of the oscillated flowfield and the mechanism of an oscillation have to be more cleared to control the oscillation. This paper aims to clarify the effect of the pressure ratio and the obstacle position and the mechanism of self-induced flow oscillation by numerical analysis and experiment, when the underexpanded su- personic jet impinges on the cylindrical body. From the result of this study, it is clear that occurrence of the self-induced flow osciUation depends on the pressure balance in the flowfield.展开更多
基金Projects(51774058,51674047)supported by the National Natural Science Foundation of ChinaProjects(cstc2016jcyjA1861,cstc2018jcyjA3320)supported by Chongqing Basic Science and Cutting-edge Technology Special Projects,ChinaProject(2015M570607)supported by Postdoctoral Science Foundation of China
文摘Geotechnical properties of red shale encountered in deep underground mining were characterized on both laboratory and field scale to reveal its unfavorably in geoenvironment.Its constituents,microstructure,strength properties and water-weakening properties were investigated.In situ stress environment and mining-induced fractured damage zone after excavation were studied to reveal the instability mechanism.The results show that red shale contains swelling and loose clayey minerals as interstitial filling material,producing low shear strength of microstructure and making it vulnerable to water.Macroscopically,a U-shaped curve of uniaxial compressive strength(UCS)exists with the increase of the angle between macro weakness plane and the horizon.However,its tensile strength reduced monotonically with this angle.While immersed in water for72h,its UCS reduced by91.9%comparing to the natural state.Field sonic tests reveal that an asymmetrical geometrical profile of fractured damage zone of gateroad was identified due to geological bedding plane and detailed gateroad layout with regards to the direction of major principle stress.Therefore,red shale is a kind of engineering soft rock.For ground control in underground mining or similar applications,water inflow within several hours of excavation must strictly be prevented and energy adsorbing rock bolt is recommended,especially in large deformation part of gateroad.
文摘Using hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle as a simulation example, the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle were simulated and discussed with SIMULINK software and hydraulic control theory. The results show that the dynamic characteristics of hydraulic power steering system are improved obviously by using bladder accumulator, the hydraulic power steering system of model EIMCO 922 load-haul-dump vehicle generates vibration at the initial stage under the normal steering condition of pulse input, and its static response time is 0.25 s shorter than that without bladder accumulator. Under the normal steering working condition, the capacity of steering accumulator for absorbing pulse is directly proportional to the cross section area of connecting pipeline, and inversely proportional to the length of connecting pipeline. At the same time, the precharge pressure of nitrogen in steering accumulator should be 60%80% of the rated minimum working pressure of hydraulic power steering system. Under the abnormal steering working condition, the steering cylinder piston may obtain higher motion velocity, and the dynamic response velocity of hydraulic power steering system can be increased by reducing the pressure drop of hydraulic pipelines between the accumulator and steering cylinder and by increasing the rated pressure of hydraulic power steering system, but the dynamic characteristics of hydraulic power steering system in load-haul-dump vehicle have nothing to do with the precharge pressure of nitrogen in steering accumulator.
基金Projects(52072249,51605315)supported by the National Natural Science Foundation of ChinaProject(E2018210052)supported by the Natural Science Foundation of Hebei Province,ChinaProject(TPL1707)supported by the Open Funds for the State Key Laboratory of Traction Power,China。
文摘To research the influence of asymmetric brake shoe forces(ABSF)induced by braking failure on the dynamic performance of six-axle locomotive,the static equilibrium model of three-axle bogie and dynamic model for locomotive are established.The coupling vibration equations of axle hung motor and wheelset are derived.For the air braking,the influence mechanism of ABSF on the wheel-rail asymmetric motion and force characteristics are discussed.It can be found that if the ABSF is applied in the front wheelset,all the wheelsets move laterally in the same direction.Once the ABSF occurs in the middle or rear one,other wheelsets may move laterally towards the opposite direction.The motion amplitude and direction of all wheelsets strictly depend on the resultant moment of suspension yawing moment and brake shoe asymmetric moment.For the asymmetric braking,the free lateral gap of axle-box could increase the wheelset motion amplitude,but could not change the moving direction.In both the straight line and curve,the ABSF may lead to wheelset misaligning motion,intensify the wheel-rail lateral dynamic interaction and deteriorate wheel-rail contact state.Especially for the steering wheelsets,the asymmetric braking increases the wheelset attack angle significantly,which forms the worst braking condition.
文摘Background Hypertension is a common chronic disease among older adults, and is associated with medical complications and mor- tality. This study aimed to examine the effects of social network characteristics on the prevalence, awareness, and control of hypertension among older adults. Methods The Korean Social Life, Health, and Aging Project （KSHAP） interviewed 814 〉 60-year-old residents and their spouses from a rural township between December 2011 and March 2012 （response rate： 95%）. We evaluated the data from 595 partici- pants. Multivariate logistic regression models were used to assess the effects of network characteristics on hypertension. Results We ob- served strong sex-specific network effects on the prevalence, awareness, and control of hypertension. Among older women, network density was associated with hypertension awareness [odds ratio （OR）： 2.63, 95% confidence interval （CI）： 1.03 5.37J and control （OR： 1.72; 95% CI 0.94-3.13）. Among older men, large networks were associated with a lower prevalence of hypertension （OR： 0.75; 95% CI： 0.58-0.96）. Compared to older women, older men with coarse networks exhibited better hypertension awareness （OR： 0.37; 95% CI： 0.14-0.95） and control （OR： 0.42; 95% CI： 0.19-0.91 ）. Network size interacted with density for hypertension control （P = 0.051）, with controlled hyperten- sion being associated with large and course networks. Conclusions A large network was associated with a lower risk for hypertension, and a coarse network was associated with hypertension awareness and control among older men. Older women with dense networks were most likely to exhibit hypertension awareness and control.
文摘HPP （high pressure processing） is one of the novel technologies to produce microbiologically safe food. HPP is a non-thermal food processing method, wherein the food is subjected to a very high pressure ranging between 100-800 MPa in order to prevent undesirable chemical and microbiological reactions, and hence, prolong the shelf-life. HPP is also called as ＂high hydrostatic processing, ultra-high pressure processing or isostatic processing＂. In dairy products, HHP has the potential to modify the functional properties of proteins, polysaccharides and alter biochemical reactions without significantly affecting the nutritional and sensory properties. HPP treatment induces significant changes in milk components particularly in proteins （whey proteins and caseins）, as well as on their applicability in innovative dairy productions. HPP influences technological properties of various milk products such as firmness, water-holding capacity of the gel and network structure, cheese yield, rennet coagulation time and ripening.
文摘In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slope. Modulating the argument of current output from ONLLY testing equipment can make the relay protection device operate, thus, the data used for calculation would be obtained naturally after several trails. In order to make sure how effective that method could be, some experiment data is given as well.
文摘When the underexpanded supersonic jet impinges on the obstacle, it is well known that the self-induced flow os- cillation occurs. This oscillation depends on the pressure ratio in the flowfield, the position of an obstacle and is related with the noise problems of aeronautical and other industrial engineering. The characteristic and the mechanism of self-induced flow oscillation, have to be clarified to control various noise problems. But, it seems that the characteristics of the oscillated flowfield and the mechanism of an oscillation have to be more cleared to control the oscillation. This paper aims to clarify the effect of the pressure ratio and the obstacle position and the mechanism of self-induced flow oscillation by numerical analysis and experiment, when the underexpanded su- personic jet impinges on the cylindrical body. From the result of this study, it is clear that occurrence of the self-induced flow osciUation depends on the pressure balance in the flowfield.
