基于轻水堆最佳估算系统分析程序RELAP/SCDAPSIM/MOD4.0,添加新的FLi Na K熔盐热物性参数和适用于熔盐的对流换热系数,开发了适用于FHR系统的热工水力分析程序RELAP5-FHR。通过FLi Na K高温熔盐实验回路对RELAP5-FHR程序进行实验验证。...基于轻水堆最佳估算系统分析程序RELAP/SCDAPSIM/MOD4.0,添加新的FLi Na K熔盐热物性参数和适用于熔盐的对流换热系数,开发了适用于FHR系统的热工水力分析程序RELAP5-FHR。通过FLi Na K高温熔盐实验回路对RELAP5-FHR程序进行实验验证。结果表明:RELAP5-FHR程序计算值与实验值吻合较好,验证了程序的适用性。展开更多
The thermal stability and fatigue resistance of piezoelectric ceramics are of great importance for industrialized application.In this study,the electrical properties of(0.99-x)(K0.48Na0.52)Nb0.975Sb0.025)O3-0.01CaZrO3...The thermal stability and fatigue resistance of piezoelectric ceramics are of great importance for industrialized application.In this study,the electrical properties of(0.99-x)(K0.48Na0.52)Nb0.975Sb0.025)O3-0.01CaZrO3-x(Bi0.5Na0.5)HfO3 ceramics are investigated.When x=0.03,the ceramics exhibit the optimal electrical properties at room temperature and high Curie temperature(Tc=253℃).In addition,the ceramic has outstanding thermal stability(d33≈301 pm/V at 160℃)and fatigue resistance(variation of Pr and d33~10 %after 10^4 electrical cycles).Subsequently,the defect configuration and crystal structure of the ceramics are studied by X-ray diffraction,temperature-dielectric property curves and impedance analysis.On one hand,the doping(Bio sNao.3)HfO3 makes the dielectric constant peaks flatten.On the other hand,the defect concentration and migration are obviously depressed in the doped ceramics.Both of them can enhance the piezoelectrical properties and improve the temperature and cycling reliabilities.The present study reveals that the good piezoelectric properties can be obtained in 0.96(K0.58Na0.52)(Nb0.975Sb.025)O3-0.01CaZrO3-0.03(Bi0.5Na0.5)HfO3 ceramics.展开更多
Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be he...Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be helpful for the better understanding of piezoelectric performance.In this work,the evolution of domain structure in large-d_(33)0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature was systematically investigated via comparing the various domain patterns that are obtained by acid-etching.It was found that domain structure changes greatly upon poling and varies largely with temperature.Complex domain patterns consisting of long narrow parallel stripes or herringbone structure separated by 180°domain boundaries are observed in the unpoled ceramics at room temperature.Domain patterns become less complicated upon poling,due to the collective polarization reversals of parallel-stripe domain clusters and banded fine-stripe domain segments.Parallel stripes and herringbone bands become much wider upon poling,as some narrow stripes and herringbone bands coalesce into broad ones,respectively.Hierarchical domain structure is commonly seen in the domain patterns acid-etched at room temperature,but is less frequently recognized at elevated temperatures.Schematic models of domain configurations were proposed to explain the domain structure and its evolution with poling.展开更多
The author presents an alternate proof of the Bismut-Zhang localization formula of ηinvariants, when the target manifold is a sphere, by using ideas of mod k index theory instead of the difficult analytic localizatio...The author presents an alternate proof of the Bismut-Zhang localization formula of ηinvariants, when the target manifold is a sphere, by using ideas of mod k index theory instead of the difficult analytic localization techniques of Bismut-Lebeau. As a consequence, it is shown that the R/Z part of the aualytically defined η invariant of Atiyah-Patodi-Singer for a Dirac operator on an odd dimensional closed spin manifold can be expressed purely geometrically through a stable Chern-Simons current on a higher dimensional sphere. As a preliminary application, the author discusses the relation with the Atiyah-Patodi-Singer R/Z index theorem for unitary flat vector bundles,and proves an R refinement in the case where the Dirac operator is replaced by the Signature operator.展开更多
文摘基于轻水堆最佳估算系统分析程序RELAP/SCDAPSIM/MOD4.0,添加新的FLi Na K熔盐热物性参数和适用于熔盐的对流换热系数,开发了适用于FHR系统的热工水力分析程序RELAP5-FHR。通过FLi Na K高温熔盐实验回路对RELAP5-FHR程序进行实验验证。结果表明:RELAP5-FHR程序计算值与实验值吻合较好,验证了程序的适用性。
基金Th e study was supported by National Natural Science Foundation of China(Grant Nos.51702119,51702122,and 51972146).
文摘The thermal stability and fatigue resistance of piezoelectric ceramics are of great importance for industrialized application.In this study,the electrical properties of(0.99-x)(K0.48Na0.52)Nb0.975Sb0.025)O3-0.01CaZrO3-x(Bi0.5Na0.5)HfO3 ceramics are investigated.When x=0.03,the ceramics exhibit the optimal electrical properties at room temperature and high Curie temperature(Tc=253℃).In addition,the ceramic has outstanding thermal stability(d33≈301 pm/V at 160℃)and fatigue resistance(variation of Pr and d33~10 %after 10^4 electrical cycles).Subsequently,the defect configuration and crystal structure of the ceramics are studied by X-ray diffraction,temperature-dielectric property curves and impedance analysis.On one hand,the doping(Bio sNao.3)HfO3 makes the dielectric constant peaks flatten.On the other hand,the defect concentration and migration are obviously depressed in the doped ceramics.Both of them can enhance the piezoelectrical properties and improve the temperature and cycling reliabilities.The present study reveals that the good piezoelectric properties can be obtained in 0.96(K0.58Na0.52)(Nb0.975Sb.025)O3-0.01CaZrO3-0.03(Bi0.5Na0.5)HfO3 ceramics.
基金financially supported by the National Natural Science Foundation of China(Grant No.51972196)Shandong Provincial Natural Science Foundation,China(Grants No.ZR2019MEM07).
文摘Domain structure often has significant influences on both piezoelectric properties and piezoelectric temperature stability of a ferroelectric ceramic.In-depth studies on the characters of domain structure should be helpful for the better understanding of piezoelectric performance.In this work,the evolution of domain structure in large-d_(33)0.96(K_(0.48)Na_(0.52))(Nb_(0.96)Sb_(0.04))O_(3)-0.04(Bi_(0.50)Na_(0.50))ZrO_(3) ceramics with poling and temperature was systematically investigated via comparing the various domain patterns that are obtained by acid-etching.It was found that domain structure changes greatly upon poling and varies largely with temperature.Complex domain patterns consisting of long narrow parallel stripes or herringbone structure separated by 180°domain boundaries are observed in the unpoled ceramics at room temperature.Domain patterns become less complicated upon poling,due to the collective polarization reversals of parallel-stripe domain clusters and banded fine-stripe domain segments.Parallel stripes and herringbone bands become much wider upon poling,as some narrow stripes and herringbone bands coalesce into broad ones,respectively.Hierarchical domain structure is commonly seen in the domain patterns acid-etched at room temperature,but is less frequently recognized at elevated temperatures.Schematic models of domain configurations were proposed to explain the domain structure and its evolution with poling.
基金Project supported by the Cheung-Kong Scholarshipthe Key Laboratory of Pure MathematicsCombinatorics of the Ministry of Education of Chinathe 973 Project of the Ministry of Science and Technology of China.
文摘The author presents an alternate proof of the Bismut-Zhang localization formula of ηinvariants, when the target manifold is a sphere, by using ideas of mod k index theory instead of the difficult analytic localization techniques of Bismut-Lebeau. As a consequence, it is shown that the R/Z part of the aualytically defined η invariant of Atiyah-Patodi-Singer for a Dirac operator on an odd dimensional closed spin manifold can be expressed purely geometrically through a stable Chern-Simons current on a higher dimensional sphere. As a preliminary application, the author discusses the relation with the Atiyah-Patodi-Singer R/Z index theorem for unitary flat vector bundles,and proves an R refinement in the case where the Dirac operator is replaced by the Signature operator.
