A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The eff...A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.展开更多
The compositional design of diffusion source plays a crucial role in improving magnetic properties of Nd-Fe-B magnet.In this work,Dy_(80)-_(x)Ce_(x)Al_(20)(x=0-50,in at%)alloy was employed as the diffusion source for ...The compositional design of diffusion source plays a crucial role in improving magnetic properties of Nd-Fe-B magnet.In this work,Dy_(80)-_(x)Ce_(x)Al_(20)(x=0-50,in at%)alloy was employed as the diffusion source for grain boundary diffusion.The results show that Dy-Ce co-diffusion can effectively enhance the infiltration ability of diffusion source.The maximum coercivity increment of up to 795 kA/m can be achieved when x=10 due to the deeper diffusion depth and higher Dy content in the shell,while a significant degradation of remanence is also exhibited due to the formation of a larger number of Dy-rich grains.Thus,Ce content is regulated to inhibit the deterioration of remanence.Increasing Ce content to above x=30,it is found that the formed CeFe_(2)phase near the surface can regulate the infiltration ability of diffusion source,reducing the area fraction of Dy-rich grain region that is detrimental to the rema-nence,and eventually,when x=50,the remanence is recovered to be comparable to that of as-prepared magnet,with a coercivity increment of 430 kA/m concurrently.This suggests that rationally designing the diffusion source composition enables the preparation of cost-effective magnets.展开更多
In this paper, the magnetic and transport properties in ABO3-type perovskite-like manganites as functions of the structure have been discussed from the viewpoints of A- and B-site doping, respectively. For the A-site ...In this paper, the magnetic and transport properties in ABO3-type perovskite-like manganites as functions of the structure have been discussed from the viewpoints of A- and B-site doping, respectively. For the A-site doping, two simple parameters, tolerance factor t and variance of the A-cation radius distribution s, can be used to characterize the magnetic/resistive phase diagram. For the B-site doping, the case is complicated due to the direct action to the center of double exchange. However, the dopant-size-induced local strain effect plays an important role in the physical properties besides the size mismatch between A- and B-site ions.展开更多
ZE20(Mg-2Zn-0.2Ce)^2 is a new wrought magnesium alloy with improved extrudability and mechanical properties[1].To understand the constitutive behavior and workability of this new alloy,Gleeble thermomechanical testing...ZE20(Mg-2Zn-0.2Ce)^2 is a new wrought magnesium alloy with improved extrudability and mechanical properties[1].To understand the constitutive behavior and workability of this new alloy,Gleeble thermomechanical testing has been carried out in this study.The flow stress behavior of ZE20 was investigated between 250℃–450℃ and 10^–3 s^–1–1.0 s^–1 in isothermal compression.Constitutive descriptions of the flow stress are provided.A new general approach at application of the extended Ludwik equation is demonstrated and was found to be more accurate than the hyperbolic sine Arrhenius model while having a similar number of model constants.Processing maps were developed based on the experimental results and are verified with microstructural investigation.A region of safe processing with non-basal texture and high activity of dynamic recrystallization(DRX)was found between 375℃ and 450℃,from 10^–1 s^–1 to 10^–2.5 s^–1.A region of potentially safe processing with annealing that is associated with shear band nucleation of non-basal grains was identified for temperatures as low as 300℃ and rates as high as 10^–1 s^–1.展开更多
BACKGROUND In our day-to-day practice,constipation is a common problem in the pediatric population and cause of frequent visit in outpatient and emergency department.But occult constipation(OC)remains as the most unad...BACKGROUND In our day-to-day practice,constipation is a common problem in the pediatric population and cause of frequent visit in outpatient and emergency department.But occult constipation(OC)remains as the most unaddressed problem.AIM To investigate the clinical profile of OC in children.METHODS It was a prospective observational study,done in Bangladesh from January 2022 to December 2024.It included all consecutive children diagnosed as OC and were treated accordingly.Before diagnosis,secondary causes of the presenting symptoms were excluded with appropriate investigations.They were followed up monthly for 4 months and treatment response were measured by improvement of symptoms.RESULTS A total of 404 children were included in this study with mean age group of 76.50±36.62 months,and male-female ratio of 1.67:1.The most common presenting complaint was abdominal pain(66%),followed by anorexia(49%),vomiting(24%),nausea(17%),frequent defecation with small volume stool(17%),altered bowel habit(16%),failure to thrive(14%)and recurrent helminthiasis(12%).Interestingly,2.5%children presented with persistent diarrhea.CONCLUSION Abdominal pain is the most common presentation of OC.When symptoms cannot be explained by other etiology,OC should be kept in mind.展开更多
Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modu...Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.展开更多
结合BaSi_2O_5及BSS助熔剂的添加技术,在不同料浆粒度、不同成型取向磁场、不同烧结工艺下制备了Ca永磁铁氧体,用压力试验机、永磁铁氧体测量仪、浮力法等对产品相关磁特性进行了检测,用X射线衍射仪分析样品的物相,用扫描电子显微镜观...结合BaSi_2O_5及BSS助熔剂的添加技术,在不同料浆粒度、不同成型取向磁场、不同烧结工艺下制备了Ca永磁铁氧体,用压力试验机、永磁铁氧体测量仪、浮力法等对产品相关磁特性进行了检测,用X射线衍射仪分析样品的物相,用扫描电子显微镜观察样品的断面形貌。结果表明:适量BaSi_2O_5与BSS助熔剂的复合掺杂促进了铁氧体晶粒的均匀生长,改善了产品的取向度,从而明显改善了产品的磁性能;对CaLa_(0.5)Fe1_(0.3)Co_(0.3)O_(19-δ)预烧料,细粉碎时添加0.4%的BaSi_2O_5、0.4%的助熔剂BSS,细粉碎平均粒度控制为0.70-0.75μm,成型取向磁场控制为产品HCJ值的3倍(即1245 k A/m),成型坯于1190℃并保温2 h,可获得Br为454 m T、HCJ为415 k A/m,M*为6280以上且承受负荷极限能力良好的永磁铁氧体。展开更多
基金Funded by the Xining Key R&D and Transformation Program(No.2024-Y-11)the Qinghai Province“Kunlun Talents-Highend Innovation and Entrepreneurship Talents”Top Talents。
文摘A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_(2),a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.
基金the National Natural Science Foundation of China(52161031,52361034)the 2023 Ganzhou"Leading the Charge with Open Competition"project+4 种基金the Key Project of Jiangxi Provincial Natural Science Foundation(20224ACB204005)the Jiangxi Provincial Natural Science Foundation(20224BAB214016)the National Key Research and Development Program of China(2022YFB3503400)the Major Science&Technology Specific Project of Jiangxi Province(20203ABC28W006)the Key Project of Science and Technology to Promote Mongolian Development(XM2021BT03)。
文摘The compositional design of diffusion source plays a crucial role in improving magnetic properties of Nd-Fe-B magnet.In this work,Dy_(80)-_(x)Ce_(x)Al_(20)(x=0-50,in at%)alloy was employed as the diffusion source for grain boundary diffusion.The results show that Dy-Ce co-diffusion can effectively enhance the infiltration ability of diffusion source.The maximum coercivity increment of up to 795 kA/m can be achieved when x=10 due to the deeper diffusion depth and higher Dy content in the shell,while a significant degradation of remanence is also exhibited due to the formation of a larger number of Dy-rich grains.Thus,Ce content is regulated to inhibit the deterioration of remanence.Increasing Ce content to above x=30,it is found that the formed CeFe_(2)phase near the surface can regulate the infiltration ability of diffusion source,reducing the area fraction of Dy-rich grain region that is detrimental to the rema-nence,and eventually,when x=50,the remanence is recovered to be comparable to that of as-prepared magnet,with a coercivity increment of 430 kA/m concurrently.This suggests that rationally designing the diffusion source composition enables the preparation of cost-effective magnets.
基金This work was supported by MOST of China (G19980613) NSFC (Nos. 29831010 & 20023005)+1 种基金 the Post-Doctoral Foundation of Chinathe Founder Foundation of PKU Corresponding author.
文摘In this paper, the magnetic and transport properties in ABO3-type perovskite-like manganites as functions of the structure have been discussed from the viewpoints of A- and B-site doping, respectively. For the A-site doping, two simple parameters, tolerance factor t and variance of the A-cation radius distribution s, can be used to characterize the magnetic/resistive phase diagram. For the B-site doping, the case is complicated due to the direct action to the center of double exchange. However, the dopant-size-induced local strain effect plays an important role in the physical properties besides the size mismatch between A- and B-site ions.
基金This work is partially supported by the United States Automotive Materials Partnership(USAMP).
文摘ZE20(Mg-2Zn-0.2Ce)^2 is a new wrought magnesium alloy with improved extrudability and mechanical properties[1].To understand the constitutive behavior and workability of this new alloy,Gleeble thermomechanical testing has been carried out in this study.The flow stress behavior of ZE20 was investigated between 250℃–450℃ and 10^–3 s^–1–1.0 s^–1 in isothermal compression.Constitutive descriptions of the flow stress are provided.A new general approach at application of the extended Ludwik equation is demonstrated and was found to be more accurate than the hyperbolic sine Arrhenius model while having a similar number of model constants.Processing maps were developed based on the experimental results and are verified with microstructural investigation.A region of safe processing with non-basal texture and high activity of dynamic recrystallization(DRX)was found between 375℃ and 450℃,from 10^–1 s^–1 to 10^–2.5 s^–1.A region of potentially safe processing with annealing that is associated with shear band nucleation of non-basal grains was identified for temperatures as low as 300℃ and rates as high as 10^–1 s^–1.
文摘BACKGROUND In our day-to-day practice,constipation is a common problem in the pediatric population and cause of frequent visit in outpatient and emergency department.But occult constipation(OC)remains as the most unaddressed problem.AIM To investigate the clinical profile of OC in children.METHODS It was a prospective observational study,done in Bangladesh from January 2022 to December 2024.It included all consecutive children diagnosed as OC and were treated accordingly.Before diagnosis,secondary causes of the presenting symptoms were excluded with appropriate investigations.They were followed up monthly for 4 months and treatment response were measured by improvement of symptoms.RESULTS A total of 404 children were included in this study with mean age group of 76.50±36.62 months,and male-female ratio of 1.67:1.The most common presenting complaint was abdominal pain(66%),followed by anorexia(49%),vomiting(24%),nausea(17%),frequent defecation with small volume stool(17%),altered bowel habit(16%),failure to thrive(14%)and recurrent helminthiasis(12%).Interestingly,2.5%children presented with persistent diarrhea.CONCLUSION Abdominal pain is the most common presentation of OC.When symptoms cannot be explained by other etiology,OC should be kept in mind.
基金financial support from the Chilean National Agency for Research and Development(ANID),National Doctorate No.21212028financial support from ANID,FONDECYT Regular Research Project No.1221793.
文摘Rubberized concrete is one of the most studied applications of discarded tires and offers a promising approach to developing materials with enhanced properties.The rubberized concrete mixture results in a reduced modulus of elasticity and a reduced compressive and tensile strength compared to traditional concrete.This study employs finite element simulations to investigate the elastic properties of rubberized mortar(RuM),considering the influence of inclusion stiffness and interfacial debonding.Different homogenization schemes,including Voigt,Reuss,and mean-field approaches,are implemented using DIGIMAT and ANSYS.Furthermore,the influence of the interfacial transition zone(ITZ)between mortar and rubber is analyzed by periodic homogenization.Subsequently,the influence of the ITZ is examined through a linear fracture analysis with the stress intensity factor as a key parameter,using the ANSYS SMART crack growth tool.Finally,a non-linear study in FEniCS is carried out to predict the strength of the composite material through a compression test.Comparisons with high density polyethylene(HDPE)and gravel inclusions show that increasing inclusion stiffness enhances compressive strength far more effectively than simply improving the mortar/rubber bond.Indeed,when the inclusions are much softer than the surrounding matrix,any benefit gained on the elastic modulus or strength from stronger interfacial adhesion becomes almost negligible.This study provide numerical evidence that tailoring the rubber’s intrinsic stiffness—not merely strengthening the rubber/mortar interface—is a decisive factor for improving the mechanical performance of RuM.
文摘结合BaSi_2O_5及BSS助熔剂的添加技术,在不同料浆粒度、不同成型取向磁场、不同烧结工艺下制备了Ca永磁铁氧体,用压力试验机、永磁铁氧体测量仪、浮力法等对产品相关磁特性进行了检测,用X射线衍射仪分析样品的物相,用扫描电子显微镜观察样品的断面形貌。结果表明:适量BaSi_2O_5与BSS助熔剂的复合掺杂促进了铁氧体晶粒的均匀生长,改善了产品的取向度,从而明显改善了产品的磁性能;对CaLa_(0.5)Fe1_(0.3)Co_(0.3)O_(19-δ)预烧料,细粉碎时添加0.4%的BaSi_2O_5、0.4%的助熔剂BSS,细粉碎平均粒度控制为0.70-0.75μm,成型取向磁场控制为产品HCJ值的3倍(即1245 k A/m),成型坯于1190℃并保温2 h,可获得Br为454 m T、HCJ为415 k A/m,M*为6280以上且承受负荷极限能力良好的永磁铁氧体。
