This paper investigates the multiaxial fatigue life of the roller in rolling contact with wheels with respect to axis line deflection. The multiaxial fatigue criteria proposed by Wang and Brown, together with the raln...This paper investigates the multiaxial fatigue life of the roller in rolling contact with wheels with respect to axis line deflection. The multiaxial fatigue criteria proposed by Wang and Brown, together with the ralnflow counting method and Miner- Palmgren＇s rule, are applied to the cumulative damage estimation and life prediction. As the axis line deflection of overlong kilns generally results in asymmetric load distribution on each roller, the load ratio is introduced to describe the deflection for quantitative stress analyses. The stress analyses are performed within the finite element code ANSYS. The tangential friction stress is calculated in terms ：of the condition of the rolling contact area. By taking one roller as an example, the plotted fatigue life versus load ratio curve discovers how the axis line deflection affects the fatigue life. This study is significant to prevent the fatigue failure of the roller and can provide basis to adjust and optimize the axis line of the rotary kiln.展开更多
High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and eco...High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and economic operation of boiler. An on-line life monitoring model of high-temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wall metal temperature and working stress was measured by on-line monitoring, and with this model, the real-time calculation of the life expenditure of the heating surface tube bundles were realized. Based on the technique the on-line life monitoring and management system of high-temperature heating surface was developed for a 300 MW utility boiler. An effective device was thus suggested for the implementation of the safe operation and the condition-based maintenance of utility boilers.展开更多
Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service li...Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.展开更多
A series of improvements in prolonging the AOD refractory lining life in Baosteel are introduced and analyzed in this paper,including modification of the AOD shell shape, adjustment of the top slag components and sele...A series of improvements in prolonging the AOD refractory lining life in Baosteel are introduced and analyzed in this paper,including modification of the AOD shell shape, adjustment of the top slag components and selection of the side-blowing tuyeres. Firstly,the layout of side-blow tuyeres was altered with the angle between each two tuyeres being 22.5° instead of the original 18° ,and the connection of the outside steel shell in the side-blow area was modified from the former platform shape with great stress concentration into a new smooth circle shape. Secondly,the slag components were changed from the former CaO-FeO-SiO： system to the CaO-MgO-SiO2 system. Besides, the basicity of the top slag was kept higher than 1.8 ,and the MgO content in the slag was kept within the range of 8% - 12%. Finally,tuyeres with an inner diameter 13% smaller than that of the original tuyeres were used. Based on these research and optimization work,the thermodynamics and kinetics in the AOD refining bath has been improved markedly, and the campaign of the AOD has been prolonged from 45 heats at the beginning of its start-up to the current 185 heats. Meanwhile,the yield of chromium alloy and the decarburization efficiency have also been improved.展开更多
Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermitten...Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermittent operation, and different refining equipment on service life of ladle lining refractories were researched. The following conclusions are drawn ： （1） molten steel temperature rising, remaiaing time prolonging, slag oxidation ability enhancing, slag viscosity and basicity decreasing can aecelerate the corrosion of ladle lining ; （2） ultra-high temperature and vacuum treatment of ladle not only acceler- ate the fusion corrasion of ladle lining, but also make the carbon containing refractories react forming gases leading to more corrosion, so carbon containing refractories are not stdtable.for the smelting conditions of long term vacuum treatment and ultra-high temperature, especially carbon containing refractories added with conventional additives such as A1 and Si powders ; （ 3 ） argon blowing does not accelerate the corrosion of ladle lining obvioasly, but oxygen blowing does; （4） the corrosion degree of refractories varies with the refining equipment, and the service life of ladle lining decreases according to a certain proportion with the refining ratio increasing.展开更多
目的探讨高效on-line血液透析滤过（hemodiafiltration,HDF）联合血液透析（hemodialysis,HD）对维持性透析（maintenance hemodialysis,MHD）患者生存质量和长期生存率的影响。方法80例MHD患者分为高效on-line血液透析滤过联合血液透...目的探讨高效on-line血液透析滤过（hemodiafiltration,HDF）联合血液透析（hemodialysis,HD）对维持性透析（maintenance hemodialysis,MHD）患者生存质量和长期生存率的影响。方法80例MHD患者分为高效on-line血液透析滤过联合血液透析组（HDF＋HD组,50例）和常规血液透析组（HD组,30例）,观察比较两组入组时及治疗第3、6、12、36、60月患者的透析充分性、营养状态、生存质量和5年生存率。结果 HDF＋HD组尿素清除指数（urea clearance index,Kt/V）、血磷（phosphorus,Pi）、HCO_3-、β_2微球蛋白（β_2-microglobulin,β_2-MG）、C反应蛋白（c-reactive protein,CRP）、血清白蛋白（albumin,ALB）、主观综合营养评估（subjective global nutritional assessment,SGA）及SF-36健康调查简表（the MOS item short from health survey SF-36,SF-36）在治疗第12、36、60月时均较同期单纯HD组明显改善（Kt/V：t=2.604,P=0.011;t=2.600,P=0.011;t=2.598,P=0.011。Pi：t=-3.080,P=0.003;t=-3.172,P=0.002;t=-4.733,P〈0.001。HCO_3-：t=7.693,P〈0.001;t=12.917,P〈0.001;t=8.145,P〈0.001。β_2-MG：t=-20.369,P〈0.001;t=-21.205,P〈0.001;t=-23.658,P〈0.001。CRP：t=-12.983,P〈0.001;t=-19.689,P〈0.001;t=-17.395,P〈0.001。ALB：t=6.618,P〈0.001;t=7.688,P〈0.001;t=7.519,P〈0.001。SGA：t=7.104,P〈0.001;t=8.933,P〈0.001;t=6.381,P〈0.001。SF-36：t=17.366,P〈0.001;t=13.971,P〈0.001;t=11.748,P〈0.001）。Kaplan-Meier生存曲线显示,HDF＋HD组生存率较HD组高,差异有统计学意义（Log Rank检验,χ^2=3.917,P=0.048）。多因素分析结果提示SF-36与β_2-MG呈负相关（B=-0.352,P〈0.001）,与SGA呈正相关（B=0.772,P〈0.001）。结论与常规HD相比,高效on-line血液透析滤过联合血液透析能改善维持性透析患者的生存质量和长期生存率,增加中大分子毒素的清除和改善营养状态可能是改善生存质量的关键因素。展开更多
基金Project supported by the National High-Tech Research and Development Program of China (863Program) (No. 2007AA04Z415)the National Natural Science Foundation of China (No. 50675066)the Scientific Research Fund of Hunan Provincial Education Department (No. 09C407)
文摘This paper investigates the multiaxial fatigue life of the roller in rolling contact with wheels with respect to axis line deflection. The multiaxial fatigue criteria proposed by Wang and Brown, together with the ralnflow counting method and Miner- Palmgren＇s rule, are applied to the cumulative damage estimation and life prediction. As the axis line deflection of overlong kilns generally results in asymmetric load distribution on each roller, the load ratio is introduced to describe the deflection for quantitative stress analyses. The stress analyses are performed within the finite element code ANSYS. The tangential friction stress is calculated in terms ：of the condition of the rolling contact area. By taking one roller as an example, the plotted fatigue life versus load ratio curve discovers how the axis line deflection affects the fatigue life. This study is significant to prevent the fatigue failure of the roller and can provide basis to adjust and optimize the axis line of the rotary kiln.
文摘High-temperature heating surface such as superheater and reheater of large-sized utility boiler all experiences a relatively severe working conditions. The failure of boiler tubes will directly impact the safe and economic operation of boiler. An on-line life monitoring model of high-temperature heating surface was set up according to the well-known L-M formula of the creep damages. The tube wall metal temperature and working stress was measured by on-line monitoring, and with this model, the real-time calculation of the life expenditure of the heating surface tube bundles were realized. Based on the technique the on-line life monitoring and management system of high-temperature heating surface was developed for a 300 MW utility boiler. An effective device was thus suggested for the implementation of the safe operation and the condition-based maintenance of utility boilers.
基金Funded by the National Key Basic Research and Development Plans-973 Plans(2009CB623203)the Key Project of National Natural Science Foundation of China (50739001)+2 种基金the National Natural Science Foundation of China (50878109)the National Key Technology R & D Program (2007BAB27B03)the Education Ministry Doctor Foundation of China (20070429001)
文摘Qingdao Jiaozhou Bay subsea tunnel is the second self-built tunnel in China with the designed service life over 100 years.The durability of lining concrete are one of an important factors to determinate the service life of tunnel.Considering the main environmental loads and mechanical loads of subsea tunnel,the durability properties of lining concrete under combined action of compressive load and carbonation has been studied through the critical compressive load test,accelerated carbonation test,natural carbonation test and capillary suction test.The tests results show that critical compressive load apparently accelerates the carbonation and deteriorates the anti-permeability of concrete.Under the combined action of critical compressive load and carbonation,the durability of lining concrete decreases.Based on the carbonization life criteria and research results,for the high-performance concrete with proposed mix ratio,the predicted service life of lining concrete for Jiaozhou bay subsea tunnel is about 80 years which fails to reach the required service life.It is necessary to adopt other measurements simultaneously to improve the durability of lining concrete.
文摘A series of improvements in prolonging the AOD refractory lining life in Baosteel are introduced and analyzed in this paper,including modification of the AOD shell shape, adjustment of the top slag components and selection of the side-blowing tuyeres. Firstly,the layout of side-blow tuyeres was altered with the angle between each two tuyeres being 22.5° instead of the original 18° ,and the connection of the outside steel shell in the side-blow area was modified from the former platform shape with great stress concentration into a new smooth circle shape. Secondly,the slag components were changed from the former CaO-FeO-SiO： system to the CaO-MgO-SiO2 system. Besides, the basicity of the top slag was kept higher than 1.8 ,and the MgO content in the slag was kept within the range of 8% - 12%. Finally,tuyeres with an inner diameter 13% smaller than that of the original tuyeres were used. Based on these research and optimization work,the thermodynamics and kinetics in the AOD refining bath has been improved markedly, and the campaign of the AOD has been prolonged from 45 heats at the beginning of its start-up to the current 185 heats. Meanwhile,the yield of chromium alloy and the decarburization efficiency have also been improved.
文摘Effects of operation conditions such as ladle temperature, remining time of molten steel, slag basicity, slag oxidation, slag viscosity , vacuum treatment, ultra-high temperature, gas blowing and stirring, intermittent operation, and different refining equipment on service life of ladle lining refractories were researched. The following conclusions are drawn ： （1） molten steel temperature rising, remaiaing time prolonging, slag oxidation ability enhancing, slag viscosity and basicity decreasing can aecelerate the corrosion of ladle lining ; （2） ultra-high temperature and vacuum treatment of ladle not only acceler- ate the fusion corrasion of ladle lining, but also make the carbon containing refractories react forming gases leading to more corrosion, so carbon containing refractories are not stdtable.for the smelting conditions of long term vacuum treatment and ultra-high temperature, especially carbon containing refractories added with conventional additives such as A1 and Si powders ; （ 3 ） argon blowing does not accelerate the corrosion of ladle lining obvioasly, but oxygen blowing does; （4） the corrosion degree of refractories varies with the refining equipment, and the service life of ladle lining decreases according to a certain proportion with the refining ratio increasing.
文摘目的探讨高效on-line血液透析滤过（hemodiafiltration,HDF）联合血液透析（hemodialysis,HD）对维持性透析（maintenance hemodialysis,MHD）患者生存质量和长期生存率的影响。方法80例MHD患者分为高效on-line血液透析滤过联合血液透析组（HDF＋HD组,50例）和常规血液透析组（HD组,30例）,观察比较两组入组时及治疗第3、6、12、36、60月患者的透析充分性、营养状态、生存质量和5年生存率。结果 HDF＋HD组尿素清除指数（urea clearance index,Kt/V）、血磷（phosphorus,Pi）、HCO_3-、β_2微球蛋白（β_2-microglobulin,β_2-MG）、C反应蛋白（c-reactive protein,CRP）、血清白蛋白（albumin,ALB）、主观综合营养评估（subjective global nutritional assessment,SGA）及SF-36健康调查简表（the MOS item short from health survey SF-36,SF-36）在治疗第12、36、60月时均较同期单纯HD组明显改善（Kt/V：t=2.604,P=0.011;t=2.600,P=0.011;t=2.598,P=0.011。Pi：t=-3.080,P=0.003;t=-3.172,P=0.002;t=-4.733,P〈0.001。HCO_3-：t=7.693,P〈0.001;t=12.917,P〈0.001;t=8.145,P〈0.001。β_2-MG：t=-20.369,P〈0.001;t=-21.205,P〈0.001;t=-23.658,P〈0.001。CRP：t=-12.983,P〈0.001;t=-19.689,P〈0.001;t=-17.395,P〈0.001。ALB：t=6.618,P〈0.001;t=7.688,P〈0.001;t=7.519,P〈0.001。SGA：t=7.104,P〈0.001;t=8.933,P〈0.001;t=6.381,P〈0.001。SF-36：t=17.366,P〈0.001;t=13.971,P〈0.001;t=11.748,P〈0.001）。Kaplan-Meier生存曲线显示,HDF＋HD组生存率较HD组高,差异有统计学意义（Log Rank检验,χ^2=3.917,P=0.048）。多因素分析结果提示SF-36与β_2-MG呈负相关（B=-0.352,P〈0.001）,与SGA呈正相关（B=0.772,P〈0.001）。结论与常规HD相比,高效on-line血液透析滤过联合血液透析能改善维持性透析患者的生存质量和长期生存率,增加中大分子毒素的清除和改善营养状态可能是改善生存质量的关键因素。
