Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticl...Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories： nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly sum marized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.展开更多
Surface accuracy directly affects the surface quality and performance of mechanical parts.Circular hole,especially spatial non-planar hole set is the typical feature and working surface of mechanical parts.Compared wi...Surface accuracy directly affects the surface quality and performance of mechanical parts.Circular hole,especially spatial non-planar hole set is the typical feature and working surface of mechanical parts.Compared with traditional machining methods,additive manufacturing(AM)technology can decrease the surface accuracy errors of circular holes during fabrication.However,an accuracy error may still exist on the surface of circular holes fabricated by AM due to the influence of staircase effect.This study proposes a surface accuracy optimization approach for mechanical parts with multiple circular holes for AM based on triangular fuzzy number(TFN).First,the feature lines on the manifold mesh are extracted using the dihedral angle method and normal tensor voting to detect the circular holes.Second,the optimal AM part build orientation is determined using the genetic algorithm to optimize the surface accuracy of the circular holes by minimizing the weighted volumetric error of the part.Third,the corresponding weights of the circular holes are calculated with the TFN analytic hierarchy process in accordance with the surface accuracy requirements.Lastly,an improved adaptive slicing algorithm is utilized to reduce the entire build time while maintaining the forming surface accuracy of the circular holes using digital twins via virtual printing.The effectiveness of the proposed approach is experimentally validated using two mechanical models.展开更多
目的:探讨射频消融减胎术(radio frequency ablation,RFA)对复杂性多胎妊娠的疗效。方法:回顾性分析2017年4月—2019年5月在武汉大学人民医院行RFA治疗的9例患者的临床资料,总结其临床疗效,包括流产、早产、足月产、活产、分娩方式和新...目的:探讨射频消融减胎术(radio frequency ablation,RFA)对复杂性多胎妊娠的疗效。方法:回顾性分析2017年4月—2019年5月在武汉大学人民医院行RFA治疗的9例患者的临床资料,总结其临床疗效,包括流产、早产、足月产、活产、分娩方式和新生儿体质量等。结果:9例患者中有2例是双绒毛膜三羊膜囊妊娠,有5例为单绒毛膜双羊膜囊双胎之一胎儿畸形行减胎术,1例为双胎输血综合征(twin-twin transfusion syndrome,TTTS)Ⅲ期减胎,1例为双胎之一选择性胎儿生长受限(selective fetal growth restriction,sFGR)Ⅱ型行选择性减胎术。9例患者均一次性RFA成功,手术成功率100%,均无手术并发症,仅1例于减胎术后2周流产,其余均获得活产。结论:RFA对复杂性多胎妊娠是一种安全有效且损伤小的宫内治疗方式,在临床上应该根据绒毛膜性及患者的意愿选择合适的减胎方式。展开更多
In-situ straining experiments in transmission electron microscopy were performed to investigate the propagation of crack,twinning and interaction of crack with twins. Lots of micro-twins were observed in the deformati...In-situ straining experiments in transmission electron microscopy were performed to investigate the propagation of crack,twinning and interaction of crack with twins. Lots of micro-twins were observed in the deformation band near the tip of crack. The stress is relaxed by the formation of micro-twins and the densely developed micro-twins prevent the growth of crack from the deformation band,subsequently the cracks extend into adjacent grains across grain boundaries,and grow along cleavage plane. Multiple twins are observed in hot-rolling AZ31 magnesium alloys,when cracks propagate into twins through twin grain boundaries(GBs),the direction of growth deviates. It is concluded that twins,especially multiple twins effectively baffle the development of crack.展开更多
文摘目的探讨在妊娠早期行多胎妊娠减胎术(multifetal pregnancy reduction,MFPR)是否影响体外受精-胚胎移植(In vitro fertilization and embryo transfer,IVF-ET)妊娠结局。方法选自2008年1月~2018年12月在焦作市妇幼保健院生殖中心接受IVF-ET助孕的患者,对移植后出现多胎妊娠并于妊娠6~8w在我中心行经阴道B超引导胚胎抽吸术的222例患者的病例资料进行回顾性分析,根据减胎术后保留单、双胎将患者分为减为单胎组和减为双胎组,并选择同期在我院生殖中心行IVF-ET助孕后单胎、双胎妊娠的222例患者为对照组(未减胎组)。首先比较组间患者的年龄,不孕年限、体重指数(body mass index,BMI=体重/身高2(kg/m^(2))、移植日子宫内膜厚度、早期流产率、晚期流产率、分娩孕周、早产率、新生儿出生体质量、小于胎龄儿(Small for gestation,SGA出生体重低于同胎龄应有体重第10百分位数以下)、妊娠并发症率(包括妊娠期糖尿病、妊娠期高血压病)及新生儿出生缺陷率等。其次比较伴单绒毛膜双胎三胎妊娠减单绒毛膜双胎之一(A组)与异卵三胎妊娠保留双胎(B组)组间妊娠结局。结果①单胎组:减为单胎组与单胎组间一般助孕情况、妊娠结局及并发症率组间比较均无差异(P>0.05)。②双胎组:减为双胎组SGA率较非减胎组高,且差异具有统计学意义(P<0.05)。③A组自发性减胎率(spontaneous pregnancy reduction,SPR)高于B组,且差异具有统计学意义(P<0.05)。结论①多胎妊娠在妊娠早期减为单胎可以获得与单胎妊娠相近似的妊娠结局,并降低多胎妊娠带来的严重母婴并发症发生率。②多胎妊娠在妊娠早期减为双胎后有增加子代SGA风险。③较伴单绒毛膜双胎三胎妊娠减单绒毛膜双胎之一虽然增加SPR风险,但剩余单绒毛膜单胎均可获得健康子代,因此在某些特定情况下伴单绒毛膜双胎三胎妊娠减单绒毛膜双胎之一是可行的。
文摘Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories： nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly sum marized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.
基金supported by the National Natural Science Foundation of China(Grant Nos.51775494,51821093,and 51935009)the National Key R&D Program of China(Grant No.2018YFB1700701)+1 种基金the Science and Technology Project of Zhejiang Province,China(Grant No.2019C01141)the Zhejiang Provincial Basic Public Welfare Research Project,China(Grant Nos.LGG18E050007 and LGG21E050020).
文摘Surface accuracy directly affects the surface quality and performance of mechanical parts.Circular hole,especially spatial non-planar hole set is the typical feature and working surface of mechanical parts.Compared with traditional machining methods,additive manufacturing(AM)technology can decrease the surface accuracy errors of circular holes during fabrication.However,an accuracy error may still exist on the surface of circular holes fabricated by AM due to the influence of staircase effect.This study proposes a surface accuracy optimization approach for mechanical parts with multiple circular holes for AM based on triangular fuzzy number(TFN).First,the feature lines on the manifold mesh are extracted using the dihedral angle method and normal tensor voting to detect the circular holes.Second,the optimal AM part build orientation is determined using the genetic algorithm to optimize the surface accuracy of the circular holes by minimizing the weighted volumetric error of the part.Third,the corresponding weights of the circular holes are calculated with the TFN analytic hierarchy process in accordance with the surface accuracy requirements.Lastly,an improved adaptive slicing algorithm is utilized to reduce the entire build time while maintaining the forming surface accuracy of the circular holes using digital twins via virtual printing.The effectiveness of the proposed approach is experimentally validated using two mechanical models.
基金Project(2006FJ4238) supported by the Research Fund for the Post-Doctoral Program of Hunan Province, China
文摘In-situ straining experiments in transmission electron microscopy were performed to investigate the propagation of crack,twinning and interaction of crack with twins. Lots of micro-twins were observed in the deformation band near the tip of crack. The stress is relaxed by the formation of micro-twins and the densely developed micro-twins prevent the growth of crack from the deformation band,subsequently the cracks extend into adjacent grains across grain boundaries,and grow along cleavage plane. Multiple twins are observed in hot-rolling AZ31 magnesium alloys,when cracks propagate into twins through twin grain boundaries(GBs),the direction of growth deviates. It is concluded that twins,especially multiple twins effectively baffle the development of crack.
