The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key ...The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.展开更多
For P91 steel weldment,performing post-weld heat treatment immediately after welding can enhance welding efficiency and reduce the risk of hydrogen-induced cracking.However,determining the post-weld cooling temperatur...For P91 steel weldment,performing post-weld heat treatment immediately after welding can enhance welding efficiency and reduce the risk of hydrogen-induced cracking.However,determining the post-weld cooling temperature(PWCT)is challenging due to potential impact on the mechanical properties of weldment after subsequent heat treatment.A systematic investigation is conducted to explore the effect of PWCT on the impact toughness of P91 steel welded joints.It has been demonstrated that the impact energy of the weld metal gradually increases from 40.2 to 49.5 J as the PWCT decreases from 300 to 100℃.Microstructural analysis reveals that PWCTs above 100℃ led to an increased dislocation density in the weld metal.Furthermore,in situ observations using a high-temperature confocal laser scanning microscope confirm that excessively high PWCTs result in the formation of untempered martensite after post-weld heat treatment.Such untempered martensites are identified as the primary cause of the reduced impact toughness in the weld metal.These findings underscore the importance of carefully controlling PWCT in welding procedures for P91 steel and similar grades.展开更多
The effect of cooling （laminar cooling） start temperature on the phase constitution was analyzed by quanti- tative metallography. The martensite/austenite （M/A） island distribution was fixed by colour metallograph...The effect of cooling （laminar cooling） start temperature on the phase constitution was analyzed by quanti- tative metallography. The martensite/austenite （M/A） island distribution was fixed by colour metallography. The strength and uniform elongation of the steels were tested with quasi-static tensile testing machine. The in-coordinate deformation of the soft and hard phases was analyzed using FEM. The results indicate that when the cooling start temperature is 690 ℃, the mechanical properties are the best, meeting the requirements of X80 high deformability pipeline steel.展开更多
Because of its advantages of light weight, high strength and convenient construction, steel structure has gradually become the first choice for large-span and high-rise structures. The use of high strength steel in bu...Because of its advantages of light weight, high strength and convenient construction, steel structure has gradually become the first choice for large-span and high-rise structures. The use of high strength steel in building engineering can reduce the section size of components and the weight of the structure, thus increasing the building area. But steel is not fire-resistant, when the temperature reaches 600<span style="white-space:nowrap;">°</span>C, steel loses most of the stiffness and strength. Therefore, it is of great significance to study the fire resistance of steel structures, and the mechanical properties of steel structures at high temperature are the foundation of the fire resistance research. The mechanical properties of steel after high temperature are the basis for the safety assessment of steel structure after fire. Therefore, this paper studies the mechanical properties of Q345 steel after high temperature cooling.展开更多
The use of cooled dialysate temperatures first came about in the early 1980s as a way to curb the incidence of intradialytic hypotension （IDH）. IDH was then, and it remains today, the most common complication affect...The use of cooled dialysate temperatures first came about in the early 1980s as a way to curb the incidence of intradialytic hypotension （IDH）. IDH was then, and it remains today, the most common complication affecting chronic hemodialysis patients. It decreases quality of life on dialysis and is an independent risk factor for mortality. Cooling dialysate was first employed as a technique to incite peripheral vasoconstriction on dialysis and in turn reduce the incidence of intradialytic hypotension. Although it has become a common practice amongst in-center hemodialysis units, cooled dialysate results in up to 70% of patients feeling cold while on dialysis and some even experience shivering. Over the years, various studies have been performed to evaluate the safety and effcacy of cooled dialysate in comparison to a standard, more thermoneutral dialysate temperature of 37℃. Although these studies are limited by small sample size, they are promising in many aspects. They demonstrated that cooled dialysis is safe and equally efficacious as thermoneutral dialysis. Although patients report feeling cold on dialysis, they also report increased energy and an improvement in their overall health following cooled dialysis. They established that cooling dialysate temperatures improves hemodynamic tolerability during and after hemodialysis, even in patients prone to IDH, and does so without adversely affecting dialysis adequacy. Cooled dialysis also reduces the incidence of IDH and has a protective effect over major organs including the heart and brain. Finally, it is an inexpensive measure that decreases economic burden by reducing necessary nursing intervention for issues that arise on hemodialysis such as IDH. Before cooled dialysate becomes standard of care for patients on chronic hemodialysis, larger studies with longer follow-up periods will need to take place to confrm the encouraging outcomes mentioned here.展开更多
Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. C...Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.展开更多
A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate...A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate： （1） the temperature field distribution of the thawing soil was not significantly influenced by the loading form under the tested loading conditions; similar results were obtained for samples at different dynamic loading frequencies and different dynamic loading ampli- tudes, which verified the independence of loading form and temperature field; （2） changed temperature field distributions were found in thawing soil with different cooling and thawing temperatures, and the cooling and thawing temperature of the samples were the main factors affecting their temperature distributions; （3） under the tested conditions, thawing set- tlements were little influenced by the thawing temperature and the dynamic loading frequency; and （4） a linear relation- ship existed between the thawing settlement and the cooling temperature, and a logarithmic function could be used to describe the relationship between the thawing settlement and the loading amplitude.展开更多
The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy st...The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at-20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.展开更多
By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanw...By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanwhile, the single sodium sulfate solution attack （SA） was also done as comparison. Micro-observations included the analysis of attack products by thermal analysis method and the determination of sulfate-ion content from surface to interior by chemical titrating method （modified barium sulfate gravimetric method）. Macro-observations mainly included the mechanical behaviors such as compressive strength, splitting strength. The experimental results indicate, in both cases, the main attack product is ettringite, only in the first layer of case SA some gypsum is checked; in case SA, the sulfate ions mainly concentrate in the surface layer, so the attack is relatively mild; but in case TW-SA, the repeated sub-high temperature/cooling by water promotes the sulfate ions diffusing inwards, which leads to obvious strength degradation.展开更多
Required by the supercritical carbon dioxide(s CO_(2))coal-fired power cycle,s CO_(2)entering a boiler has a high temperature and can cause overheating of tubes.To eliminate the pressure drop penalty effect,the s CO_(...Required by the supercritical carbon dioxide(s CO_(2))coal-fired power cycle,s CO_(2)entering a boiler has a high temperature and can cause overheating of tubes.To eliminate the pressure drop penalty effect,the s CO_(2)boiler consists of several modules,each having different heat flux received from the furnace side(q)and different CO_(2)temperature in the cooling wall tube(T_f).We aim to search for the best matching strategy coupling furnace side and tube side to obtain the lowest temperature of tubes.By theoretically analyzing the wall temperature influenced by q,T_f and a comprehensive thermal resistance C,two matching methods are introduced:the heat flux-temperature matching(HTM)which matches higher q with lower T_f,and the heat flux-heat flux matching(HHM)that matches higher q with higher allowable-heat-flux at the temperature limit of tubes.HTM is a conventional method but HHM is newly proposed here.We show that,if C is identical for different modules,the two methods coincide;otherwise,HHM is recommended.For a s CO_(2)boiler driving 1000 MWe power plant,smaller cooling wall temperatures are obtained by HHM than HTM.Based on HHM,the mid-partition wall,heat transfer enhancement,and downward flow are comprehensively used,decreasing the wall temperature significantly.展开更多
Typhoon Hato (2017) went through a rapid intensification (RI) process before making landfall in Zhuhai,Guangdong Province, as the observational data shows. Within 24 hours, its minimum sea level pressure deepened by35...Typhoon Hato (2017) went through a rapid intensification (RI) process before making landfall in Zhuhai,Guangdong Province, as the observational data shows. Within 24 hours, its minimum sea level pressure deepened by35hPa and its maximum sustained wind speed increased by 20m s-1. According to satellite observations, Hato encountered a large area of warm water and two warm core rings before the RI process, and the average sea surface temperature cooling (SSTC) induced by Hato was only around 0.73℃. Air-sea coupled simulations were implemented to investigate the specific impact of the warm water on its RI process. The results showed that the warm water played an important role by facilitating the RI process by around 20%. Sea surface temperature budget analysis showed that the SSTC induced by mixing mechanism was not obvious due to the warm water. Besides, the cold advection hardly caused any SSTC, either. Therefore, the SSTC induced by Hato was much weaker compared with that in general cases. The negative feedback between ocean and Hato was restrained and abundant heat and moisture were sufficiently supplied to Hato. The warm water helped heat flux increase by around 20%, too. Therefore, the warm water influenced the structure and the intensity of Hato. Although there might be other factors that also participated in the RI process, this study focused on air-sea interaction in tropical cyclone forecast and discussed the impact of warm water on the intensity and structure of a tropical cyclone.展开更多
Thermomechanical controlled processing （TMCP） of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechan...Thermomechanical controlled processing （TMCP） of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechanical properties of the steel was investigated. The results showed that the mechanical properties of the low carbon cold heading steel could be significantly improved by TMCP without heat treatment. The improvement of mechanical properties can be attributed mainly to the ferrite grain refinement due to low temperature rolling. In the experiments the better ultimate tensile strength and ductility are obtained by lowering finishing cooling temperature within the temperature range from 650 ℃ to 550 ℃ since the interlamellar space in pearlite colonies become smaller. Good mechanical properties can be obtained in a proper austenite condition and thermomechanical processing parameter. The ferrite morphology has a more pronounced effect on the mechanical behavior than refinement of the microstructure. It is possible to realize the replacement of medium-carbon by low-carbon for 490 MPa grade cold heading steel with TMCP.展开更多
The tendency of South China Sea throughflow (SCSTF) variation associated with the local monsoon system, and its impact on upper-layer thermal structure, are studied using the Simple Ocean Data Assimilation (SODA) data...The tendency of South China Sea throughflow (SCSTF) variation associated with the local monsoon system, and its impact on upper-layer thermal structure, are studied using the Simple Ocean Data Assimilation (SODA) dataset, combined with Ishii reanalysis data. Luzon Strait Transport (LST) is measured and used as an index for studying the SCSTF variation. Results show that LST had an increasing tendency over the last 50 years, mainly in summer and fall. The increasing tendency was 0.017 1 Sv/a in summer and 0.027 4 Sv/a in fall, as estimated by SODA, and 0.018 0Sv/a in summer and 0.018 9 Sv/a in fall, as estimated by "Island Rule" theory. LST increased by 0.53Sv in JJA (June-July-August) and 0.98Sv in SON (September-October-November) after climate shift, as inferred by SODA data. The average LST anomaly in JJA and SON is strongly related to the local monsoon system, especially to variability of the meridional wind stress anomaly after application of a 3-year running mean, with correlation coefficients 0.57 and 0.51, respectively. In addition to the basin-scale wind forcing, the local northeasterly wind stress anomaly in the SCS can push Pacific water entering the SCS more readily in JJA and SON after climate shift, and an SCSTF-associated cooling effect may favor subsurface cooling more frequently after climate shift.展开更多
The success of high temperature gas cooled reactor depends upon the safety and quality of the coated particle fuel. The understanding and evaluation of this fuel requires the development of an integrated mechanistic f...The success of high temperature gas cooled reactor depends upon the safety and quality of the coated particle fuel. The understanding and evaluation of this fuel requires the development of an integrated mechanistic fuel performance model that fully describes the mechanical and physicochemical behavior of the fuel particle under irradiation. In this paper, a review of the analytical capability of some of the existing computer codes for coated particle fuel was performed. These existing models and codes include FZJ model, JAERI model, Stress3 model, ATLAS model, PARFUME model and TIMCOAT model. The theoretic model, methodology, calculation parameters and benchmark of these codes were classified. Based on the failure mechanism of coated particle, the advantage and limits of the models were compared and discussed. The calculated results of the coated particles for China HTR-10 by using some existing code are shown. Finally, problems and challenges in fuel performance modeling were listed.展开更多
One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a sp...One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.展开更多
Online fuel pebble burnup measurement in a future high temperature gas cooling reactor is proposed for implementation through a high purity germanimn （HPGe） gamma spectrometer. By using KORIGEN software and MCNP Mon...Online fuel pebble burnup measurement in a future high temperature gas cooling reactor is proposed for implementation through a high purity germanimn （HPGe） gamma spectrometer. By using KORIGEN software and MCNP Monte Carlo simulations, the single pebble gamma radiations to be recorded in the detector are simulated under different, irradiation histories. A specially developed algorithm is applied to analyze the generated spectra to reconstruct the gamma activity of the ~arCs monitoring nuclide. It is demonstrated that by taking into account the intense interfering peaks, the 137Cs activity in the spent pebbles can be derived with a standard deviation of 3.0% （l（r）. The results support the feasibility of utilizing the HPGe spectrometry in the online determination of the pebble burimp in future modular pebble bed reactors.展开更多
Much more nuclear energy capacity is needed than currently installed to meet the demand of energy and the requirement on environment protection in the next decades. More stringent nuclear safety standards have to be e...Much more nuclear energy capacity is needed than currently installed to meet the demand of energy and the requirement on environment protection in the next decades. More stringent nuclear safety standards have to be established for future nuclear power plants.The philosophy of a catastrophe free nuclear technology is presented in this paper. The issue of afterheat removal of high temperature gas cooled reactors is handled.It is a striking inherent safety feature of the modular high temperature gas cooled reactor design that the afterheat removal takes place without any active core cooling systems.展开更多
The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effe...The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effects on the transmission heat through outer walls, ceiling and glazing windows. Good thermal isolation for buildings is important to reduce the transmitted heat and consumed power. The buildings models are constructed from common materials with 0 - 16 cm of thermal insulation thickness in the outer walls and ceilings, and double-layers glazing windows. The building heat loads were calculated for two types of walls and ceiling with and without thermal insulation. The cooling load temperature difference method, <em>CLTD</em>, was used to estimate the building heat load during a 24-hour each day throughout spring, summer, autumn and winter seasons. The annual cooling degree-day, <em>CDD</em> was used to estimate the optimal thermal insulation thickness and payback period with including the solar radiation effect on the outer walls surfaces. The average saved energy percentage in summer, spring, autumn and winter are 35.5%, 32.8%, 33.2% and 30.7% respectively, and average yearly saved energy is about of 33.5%. The optimal thermal insulation thickness was obtained between 7 - 12 cm and payback period of 20 - 30 month for some Egyptian Cities according to the Latitude and annual degree-days.展开更多
LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）Hxalloys were prepared by hydrogenation.Samples were annealed at 1343Kfor30-90 hto form the NaZn13 phase.La-rich andα-Fe secondary phases were also detected.Saturated hydr...LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）Hxalloys were prepared by hydrogenation.Samples were annealed at 1343Kfor30-90 hto form the NaZn13 phase.La-rich andα-Fe secondary phases were also detected.Saturated hydrogenation at 553 Kand 0.15 MPa of H_2 pressure for 5hwas employed to improve the Curie temperature of the alloys to 279 K.The maximum magnetic entropy change,relative cooling power,and adiabatic temperature change of LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x annealed at 1343 Kfor 90hafter hydrogen absorption are 6.38J/（kg·K）（magnetic changesμ0ΔH =1.65T）,100.1J/kg（μ0ΔH =1.65T）,and 2.2 K（μ0ΔH =1.48T）,respectively.Although the maximum magnetic entropy change of the LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys is lower than those of similar alloys with high purity raw materials,the relative cooling power is nearly the same.The effect of impurities of the raw materials used was also discussed.It is assumed that the impurity of 0.2wt.% Al is responsible for the reduced entropy change of the resulted alloys.The LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys prepared by this method could be a low cost alternative material for room temperature magnetic cooling applications.展开更多
The effects of sea surface temperature(SST)changes induced by tropical cyclone(TC)Bilis(0604)and its preceding TC,TC Ewiniar(0603),on the intensity of TC Bilis were investigated by using numerical experiments.The obse...The effects of sea surface temperature(SST)changes induced by tropical cyclone(TC)Bilis(0604)and its preceding TC,TC Ewiniar(0603),on the intensity of TC Bilis were investigated by using numerical experiments.The observed SST changes induced by TCs Ewiniar(0603)and Bilis(0604)were first separated by using the smooth filtering and cylindrical filtering methods.The maximum SST cooling induced by TC Ewiniar(0603)exceeded 3℃,and that induced by the two TCs,Ewiniar(0603)and Bilis(0604),exceeded 6℃.The simulation results show that the SST cooling induced by TC Ewiniar(0603)and by two TCs reduced the intensity of TC Bilis(0604)by 6.2 m s^(-1)and 7.6 m s^(-1)within 60 h,respectively.Without the SST cooling induced by TC Ewiniar(0603),TC Bilis(0604)could have developed into a typhoon.The cold wake induced by TC Ewiniar(0603)was an important factor in inhibiting the intensity of TC Bilis(0604).Based on the analysis of the physical processes of the simulation results,a schematic diagram of the effects of SST changes induced by TCs on the intensity of TC Bilis(0604)was presented.The SST cooling reduced the upward heat flux and moisture flux at the surface of TC mainly within a radius of two latitudes,which in turn decreased the conditional instability and atmospheric moisture in the lower layer of TC,followed by weakening in TC precipitation,TC warm core,the upward vertical velocity of TC,and the inward radial wind in the lower layer of TC.The intensity of TC Bilis(0604)decreased accordingly.展开更多
基金Project(2018XK2301) supported by the Change-Zhu-Tan National Independent Innavation Demonstration Zone Special Program,China。
文摘The ductile-to-brittle transition temperature(DBTT)of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics,where the start cooling temperature plays a key role.In this work,X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process.The quasi-polygonal ferrite(QF),granular bainite(GB),bainitic ferrite(BF)and martensite-austenite constituents were formed at the start cooling temperatures of 780℃(C1),740℃(C2)and 700℃(C3).As start cooling temperature decreased,the amount of GB decreased,the microstructure of QF and BF increased.Microstructure characteristics of the three samples,such as high-angle grain boundaries(HAGBs),MA constituents and crystallographic orientation,also varied with the start cooling temperatures.C2 sample had the lowest DBTT value(−86℃)for its highest fraction of HAGBs,highest content of<110>oriented grains and lowest content of<001>oriented grains parallel to TD.The high density of{332}<113>and low density of rotated cube{001}<110>textures also contributed to the best impact toughness of C2 sample.In addition,a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.
基金supported by the National Key R&D Program of China(No.2022YFE0123300)the National Natural Science Foundation of China(Nos.U20A20277 and 52474351)Major Project of Liaoning Province Innovation Consortium(No.2023JH1/11200012).
文摘For P91 steel weldment,performing post-weld heat treatment immediately after welding can enhance welding efficiency and reduce the risk of hydrogen-induced cracking.However,determining the post-weld cooling temperature(PWCT)is challenging due to potential impact on the mechanical properties of weldment after subsequent heat treatment.A systematic investigation is conducted to explore the effect of PWCT on the impact toughness of P91 steel welded joints.It has been demonstrated that the impact energy of the weld metal gradually increases from 40.2 to 49.5 J as the PWCT decreases from 300 to 100℃.Microstructural analysis reveals that PWCTs above 100℃ led to an increased dislocation density in the weld metal.Furthermore,in situ observations using a high-temperature confocal laser scanning microscope confirm that excessively high PWCTs result in the formation of untempered martensite after post-weld heat treatment.Such untempered martensites are identified as the primary cause of the reduced impact toughness in the weld metal.These findings underscore the importance of carefully controlling PWCT in welding procedures for P91 steel and similar grades.
文摘The effect of cooling （laminar cooling） start temperature on the phase constitution was analyzed by quanti- tative metallography. The martensite/austenite （M/A） island distribution was fixed by colour metallography. The strength and uniform elongation of the steels were tested with quasi-static tensile testing machine. The in-coordinate deformation of the soft and hard phases was analyzed using FEM. The results indicate that when the cooling start temperature is 690 ℃, the mechanical properties are the best, meeting the requirements of X80 high deformability pipeline steel.
文摘Because of its advantages of light weight, high strength and convenient construction, steel structure has gradually become the first choice for large-span and high-rise structures. The use of high strength steel in building engineering can reduce the section size of components and the weight of the structure, thus increasing the building area. But steel is not fire-resistant, when the temperature reaches 600<span style="white-space:nowrap;">°</span>C, steel loses most of the stiffness and strength. Therefore, it is of great significance to study the fire resistance of steel structures, and the mechanical properties of steel structures at high temperature are the foundation of the fire resistance research. The mechanical properties of steel after high temperature are the basis for the safety assessment of steel structure after fire. Therefore, this paper studies the mechanical properties of Q345 steel after high temperature cooling.
文摘The use of cooled dialysate temperatures first came about in the early 1980s as a way to curb the incidence of intradialytic hypotension （IDH）. IDH was then, and it remains today, the most common complication affecting chronic hemodialysis patients. It decreases quality of life on dialysis and is an independent risk factor for mortality. Cooling dialysate was first employed as a technique to incite peripheral vasoconstriction on dialysis and in turn reduce the incidence of intradialytic hypotension. Although it has become a common practice amongst in-center hemodialysis units, cooled dialysate results in up to 70% of patients feeling cold while on dialysis and some even experience shivering. Over the years, various studies have been performed to evaluate the safety and effcacy of cooled dialysate in comparison to a standard, more thermoneutral dialysate temperature of 37℃. Although these studies are limited by small sample size, they are promising in many aspects. They demonstrated that cooled dialysis is safe and equally efficacious as thermoneutral dialysis. Although patients report feeling cold on dialysis, they also report increased energy and an improvement in their overall health following cooled dialysis. They established that cooling dialysate temperatures improves hemodynamic tolerability during and after hemodialysis, even in patients prone to IDH, and does so without adversely affecting dialysis adequacy. Cooled dialysis also reduces the incidence of IDH and has a protective effect over major organs including the heart and brain. Finally, it is an inexpensive measure that decreases economic burden by reducing necessary nursing intervention for issues that arise on hemodialysis such as IDH. Before cooled dialysate becomes standard of care for patients on chronic hemodialysis, larger studies with longer follow-up periods will need to take place to confrm the encouraging outcomes mentioned here.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704031)the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China (Grant No. J0630313)+1 种基金the fundamental Research Fund for Physical and Mathematical of Lanzhou University (Grant No. Lzu05001)the Natural Science Foundation of Gansu,China (Grant No. 3ZS061-A25-035)
文摘Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.
基金provided by National Natural Science Foundation of China (NSFC) under Grant Nos.41001036 and 41171064
文摘A series of tests were conducted to analyze temperature field distribution and thawing settlement of a thawing soil under static and dynamic loading at various cooling and thawing temperatures. The results demonstrate： （1） the temperature field distribution of the thawing soil was not significantly influenced by the loading form under the tested loading conditions; similar results were obtained for samples at different dynamic loading frequencies and different dynamic loading ampli- tudes, which verified the independence of loading form and temperature field; （2） changed temperature field distributions were found in thawing soil with different cooling and thawing temperatures, and the cooling and thawing temperature of the samples were the main factors affecting their temperature distributions; （3） under the tested conditions, thawing set- tlements were little influenced by the thawing temperature and the dynamic loading frequency; and （4） a linear relation- ship existed between the thawing settlement and the cooling temperature, and a logarithmic function could be used to describe the relationship between the thawing settlement and the loading amplitude.
基金financially supported by the National Natural Science Foundation of China(Grant No.51904071)the Independent Project of State Key Laboratory of Rolling and Automation,Northeastern University(Grant No.ZZ202001)+1 种基金the Key Research and Development Program of Hebei Province of China(Grant No.18211019D)the Start-up Project of Doctor Scientific Research of Liaoning Province(Grant No.2020-BS-271)。
文摘The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at-20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.
基金Funded by the National Natural Science Foundation of China(No. 90715041)Outstanding Youth Science Fund of Henan Province(No.04120002300)
文摘By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanwhile, the single sodium sulfate solution attack （SA） was also done as comparison. Micro-observations included the analysis of attack products by thermal analysis method and the determination of sulfate-ion content from surface to interior by chemical titrating method （modified barium sulfate gravimetric method）. Macro-observations mainly included the mechanical behaviors such as compressive strength, splitting strength. The experimental results indicate, in both cases, the main attack product is ettringite, only in the first layer of case SA some gypsum is checked; in case SA, the sulfate ions mainly concentrate in the surface layer, so the attack is relatively mild; but in case TW-SA, the repeated sub-high temperature/cooling by water promotes the sulfate ions diffusing inwards, which leads to obvious strength degradation.
基金support of the National Key R&D Program of China(2017YFB0601801)the National Natural Science Foundation of China(No.51776064)。
文摘Required by the supercritical carbon dioxide(s CO_(2))coal-fired power cycle,s CO_(2)entering a boiler has a high temperature and can cause overheating of tubes.To eliminate the pressure drop penalty effect,the s CO_(2)boiler consists of several modules,each having different heat flux received from the furnace side(q)and different CO_(2)temperature in the cooling wall tube(T_f).We aim to search for the best matching strategy coupling furnace side and tube side to obtain the lowest temperature of tubes.By theoretically analyzing the wall temperature influenced by q,T_f and a comprehensive thermal resistance C,two matching methods are introduced:the heat flux-temperature matching(HTM)which matches higher q with lower T_f,and the heat flux-heat flux matching(HHM)that matches higher q with higher allowable-heat-flux at the temperature limit of tubes.HTM is a conventional method but HHM is newly proposed here.We show that,if C is identical for different modules,the two methods coincide;otherwise,HHM is recommended.For a s CO_(2)boiler driving 1000 MWe power plant,smaller cooling wall temperatures are obtained by HHM than HTM.Based on HHM,the mid-partition wall,heat transfer enhancement,and downward flow are comprehensively used,decreasing the wall temperature significantly.
基金National Basic R&D Project(973 Program)of China(2015CB452805)National Natural Science Foundation of China(61827901)+3 种基金National Key R&D Program of China(2017YFC1501602)Open Research Program of the State Key Laboratory of Severe Weather(2019LASW-A08)Basic Research Fund of CAMS(2016Z003,2018Y013)Program of the National Satellite Meteorological Centre(FY3(02P)-MAS-1803)。
文摘Typhoon Hato (2017) went through a rapid intensification (RI) process before making landfall in Zhuhai,Guangdong Province, as the observational data shows. Within 24 hours, its minimum sea level pressure deepened by35hPa and its maximum sustained wind speed increased by 20m s-1. According to satellite observations, Hato encountered a large area of warm water and two warm core rings before the RI process, and the average sea surface temperature cooling (SSTC) induced by Hato was only around 0.73℃. Air-sea coupled simulations were implemented to investigate the specific impact of the warm water on its RI process. The results showed that the warm water played an important role by facilitating the RI process by around 20%. Sea surface temperature budget analysis showed that the SSTC induced by mixing mechanism was not obvious due to the warm water. Besides, the cold advection hardly caused any SSTC, either. Therefore, the SSTC induced by Hato was much weaker compared with that in general cases. The negative feedback between ocean and Hato was restrained and abundant heat and moisture were sufficiently supplied to Hato. The warm water helped heat flux increase by around 20%, too. Therefore, the warm water influenced the structure and the intensity of Hato. Although there might be other factors that also participated in the RI process, this study focused on air-sea interaction in tropical cyclone forecast and discussed the impact of warm water on the intensity and structure of a tropical cyclone.
基金Sponsored by National Natural Science Foundation of China (50334010)Shenyang City Application Basic Research Project (1071198-1-00)
文摘Thermomechanical controlled processing （TMCP） of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechanical properties of the steel was investigated. The results showed that the mechanical properties of the low carbon cold heading steel could be significantly improved by TMCP without heat treatment. The improvement of mechanical properties can be attributed mainly to the ferrite grain refinement due to low temperature rolling. In the experiments the better ultimate tensile strength and ductility are obtained by lowering finishing cooling temperature within the temperature range from 650 ℃ to 550 ℃ since the interlamellar space in pearlite colonies become smaller. Good mechanical properties can be obtained in a proper austenite condition and thermomechanical processing parameter. The ferrite morphology has a more pronounced effect on the mechanical behavior than refinement of the microstructure. It is possible to realize the replacement of medium-carbon by low-carbon for 490 MPa grade cold heading steel with TMCP.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-Q11-02)the National Basic Research Program of China (973 Program) (Nos. 2011CB403503, 2011CB403504)+1 种基金the National Natural Science Foundation of China (No. 40806005)partially by a grant from the South China Sea Institute of Oceanology,Chinese Academy of Sciences (No. SQ200814)
文摘The tendency of South China Sea throughflow (SCSTF) variation associated with the local monsoon system, and its impact on upper-layer thermal structure, are studied using the Simple Ocean Data Assimilation (SODA) dataset, combined with Ishii reanalysis data. Luzon Strait Transport (LST) is measured and used as an index for studying the SCSTF variation. Results show that LST had an increasing tendency over the last 50 years, mainly in summer and fall. The increasing tendency was 0.017 1 Sv/a in summer and 0.027 4 Sv/a in fall, as estimated by SODA, and 0.018 0Sv/a in summer and 0.018 9 Sv/a in fall, as estimated by "Island Rule" theory. LST increased by 0.53Sv in JJA (June-July-August) and 0.98Sv in SON (September-October-November) after climate shift, as inferred by SODA data. The average LST anomaly in JJA and SON is strongly related to the local monsoon system, especially to variability of the meridional wind stress anomaly after application of a 3-year running mean, with correlation coefficients 0.57 and 0.51, respectively. In addition to the basin-scale wind forcing, the local northeasterly wind stress anomaly in the SCS can push Pacific water entering the SCS more readily in JJA and SON after climate shift, and an SCSTF-associated cooling effect may favor subsurface cooling more frequently after climate shift.
文摘The success of high temperature gas cooled reactor depends upon the safety and quality of the coated particle fuel. The understanding and evaluation of this fuel requires the development of an integrated mechanistic fuel performance model that fully describes the mechanical and physicochemical behavior of the fuel particle under irradiation. In this paper, a review of the analytical capability of some of the existing computer codes for coated particle fuel was performed. These existing models and codes include FZJ model, JAERI model, Stress3 model, ATLAS model, PARFUME model and TIMCOAT model. The theoretic model, methodology, calculation parameters and benchmark of these codes were classified. Based on the failure mechanism of coated particle, the advantage and limits of the models were compared and discussed. The calculated results of the coated particles for China HTR-10 by using some existing code are shown. Finally, problems and challenges in fuel performance modeling were listed.
基金National Natural Science Foundation of China(No.51345006)Specialized Research Fund for the Doctoral Program of Higher Education,China(No.20123719120004)
文摘One improved mixing-extruding machine was introduced as the second-generation product of the mixing-molding integrated technology. In the extruding system,the conventional single screw extruder was substituted by a special conical twin-screw extruder,resulting in stronger feeding ability,more stable extrusion pressure,and better quality of products. The integrated mathematical model of mixing-extruding process was also established by theoretical derivation and optimization according to the experimental results.Then its accuracy was verified by the influences of the pressure of floating weight and the cooling water temperature of extruder on the mixing-extruding integrated process. The results showed that the changes of both parameters could give rise to the fluctuation of the temperature and apparent viscosity of polyblends, thus further influencing the screw rotation speed.
基金Supported by National Science and Technology Major Project(ZX06901)National Natural Science Foundation of China(10975083,11079025)Tsinghua University Initiative Scientific Research Program
文摘Online fuel pebble burnup measurement in a future high temperature gas cooling reactor is proposed for implementation through a high purity germanimn （HPGe） gamma spectrometer. By using KORIGEN software and MCNP Monte Carlo simulations, the single pebble gamma radiations to be recorded in the detector are simulated under different, irradiation histories. A specially developed algorithm is applied to analyze the generated spectra to reconstruct the gamma activity of the ~arCs monitoring nuclide. It is demonstrated that by taking into account the intense interfering peaks, the 137Cs activity in the spent pebbles can be derived with a standard deviation of 3.0% （l（r）. The results support the feasibility of utilizing the HPGe spectrometry in the online determination of the pebble burimp in future modular pebble bed reactors.
文摘Much more nuclear energy capacity is needed than currently installed to meet the demand of energy and the requirement on environment protection in the next decades. More stringent nuclear safety standards have to be established for future nuclear power plants.The philosophy of a catastrophe free nuclear technology is presented in this paper. The issue of afterheat removal of high temperature gas cooled reactors is handled.It is a striking inherent safety feature of the modular high temperature gas cooled reactor design that the afterheat removal takes place without any active core cooling systems.
文摘The removal building heat load and electrical power consumption by air conditioning system are proportional to the outside conditions and solar radiation intensity. Building construction materials has substantial effects on the transmission heat through outer walls, ceiling and glazing windows. Good thermal isolation for buildings is important to reduce the transmitted heat and consumed power. The buildings models are constructed from common materials with 0 - 16 cm of thermal insulation thickness in the outer walls and ceilings, and double-layers glazing windows. The building heat loads were calculated for two types of walls and ceiling with and without thermal insulation. The cooling load temperature difference method, <em>CLTD</em>, was used to estimate the building heat load during a 24-hour each day throughout spring, summer, autumn and winter seasons. The annual cooling degree-day, <em>CDD</em> was used to estimate the optimal thermal insulation thickness and payback period with including the solar radiation effect on the outer walls surfaces. The average saved energy percentage in summer, spring, autumn and winter are 35.5%, 32.8%, 33.2% and 30.7% respectively, and average yearly saved energy is about of 33.5%. The optimal thermal insulation thickness was obtained between 7 - 12 cm and payback period of 20 - 30 month for some Egyptian Cities according to the Latitude and annual degree-days.
基金financially supported by Inner Mongolia Natural Science Foundation of China(2013MS0802)
文摘LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）Hxalloys were prepared by hydrogenation.Samples were annealed at 1343Kfor30-90 hto form the NaZn13 phase.La-rich andα-Fe secondary phases were also detected.Saturated hydrogenation at 553 Kand 0.15 MPa of H_2 pressure for 5hwas employed to improve the Curie temperature of the alloys to 279 K.The maximum magnetic entropy change,relative cooling power,and adiabatic temperature change of LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x annealed at 1343 Kfor 90hafter hydrogen absorption are 6.38J/（kg·K）（magnetic changesμ0ΔH =1.65T）,100.1J/kg（μ0ΔH =1.65T）,and 2.2 K（μ0ΔH =1.48T）,respectively.Although the maximum magnetic entropy change of the LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys is lower than those of similar alloys with high purity raw materials,the relative cooling power is nearly the same.The effect of impurities of the raw materials used was also discussed.It is assumed that the impurity of 0.2wt.% Al is responsible for the reduced entropy change of the resulted alloys.The LaFe_（11.39）Mn_（0.35）Si_（1.26）B_（0.1）H_x alloys prepared by this method could be a low cost alternative material for room temperature magnetic cooling applications.
基金National Natural Science Foundation of China(42275123)Guangdong Basic and Applied Basic Research Foundation(2024A1515010508)+2 种基金Guangdong Provincial Marine Meteorology Science Data Center(2024B1212070014)Innova-tion Team of Severe Weather Mechanism and Forecasting Technology in the South China Sea of Guangdong Meteorolo-gical Service(GRMCTD202201)Science and Technology Research Project of Guangdong Meteorological Service(GRMC2022M02)。
文摘The effects of sea surface temperature(SST)changes induced by tropical cyclone(TC)Bilis(0604)and its preceding TC,TC Ewiniar(0603),on the intensity of TC Bilis were investigated by using numerical experiments.The observed SST changes induced by TCs Ewiniar(0603)and Bilis(0604)were first separated by using the smooth filtering and cylindrical filtering methods.The maximum SST cooling induced by TC Ewiniar(0603)exceeded 3℃,and that induced by the two TCs,Ewiniar(0603)and Bilis(0604),exceeded 6℃.The simulation results show that the SST cooling induced by TC Ewiniar(0603)and by two TCs reduced the intensity of TC Bilis(0604)by 6.2 m s^(-1)and 7.6 m s^(-1)within 60 h,respectively.Without the SST cooling induced by TC Ewiniar(0603),TC Bilis(0604)could have developed into a typhoon.The cold wake induced by TC Ewiniar(0603)was an important factor in inhibiting the intensity of TC Bilis(0604).Based on the analysis of the physical processes of the simulation results,a schematic diagram of the effects of SST changes induced by TCs on the intensity of TC Bilis(0604)was presented.The SST cooling reduced the upward heat flux and moisture flux at the surface of TC mainly within a radius of two latitudes,which in turn decreased the conditional instability and atmospheric moisture in the lower layer of TC,followed by weakening in TC precipitation,TC warm core,the upward vertical velocity of TC,and the inward radial wind in the lower layer of TC.The intensity of TC Bilis(0604)decreased accordingly.
