三维切口/裂纹结构的扩展边界元法分析

在线弹性理论中,三维 V 形切口/裂纹结构尖端区域存在多重应力奇异性,常规数值方法不易求解. 本文提出和建立了三维扩展边界元法 (XBEM),用于分析三维线弹性 V 形切口/裂纹结构完整的位移和应力场. 先将三维线弹性 V 形切口/裂纹结构分为尖端小扇形柱和挖去小扇形柱后的外围结构. 尖端小扇形柱内的位移函数采用自尖端径向距离 $r$ 的渐近级数展开式表达,其中尖端区域的应力奇异指数、位移和应力特征角函数通过插值矩阵法获得. 而级数展开式各项的幅值系数作为基本未知量. 挖去扇形域后的外围结构采用常规边界元法分析. 两者方程联立求解可获得三维 V 形切口/裂纹结构完整的位移和应力场,包括切口/裂纹尖端区域精细的应力场. 扩展边界元法具有半解析法特征,适用于一般三维 V 形切口/裂纹结构完整位移场和应力场的分析,其解可精细描述从尖端区域到整体结构区域的完整应力场. 作者研制了三维扩展边界元法程序,文中给出了两个算例,通过计算结果分析,表明了扩展边界元法求解三维 V 形切口/裂纹结构完整应力场的准确性和有效性.      

EAST PF8线圈氦管结构分析和疲劳试验

 为解决EAST PF8线圈氦管在与导体连接的焊缝位置出现的泄漏问题，分析了该氦管的载荷及边界条件，给出了4种载荷组合工况。建立PF8氦管的有限元模型，对4种工况进行了静力学分析。计算结果表明，热载荷和螺管固定支撑板G11变形是焊缝失效的主要原因。在4.5K下对PF8氦管样件进行了疲劳试验，结果表明氦管疲劳寿命超过2×10⁵次，满足使用要求。对PF8氦管进行了修复，使氦管与螺管固定支撑板G11板脱开，避免了额外载荷的作用，满足EAST使用要求。     

分析化学整体式电位滴定仪的自制研究

研制了整体式电位滴定仪,该滴定仪综合了加热、搅拌、酸度值测定、电位测定等功能,具有简便易操作、测试稳定、精准性和重复性高等优点,同时该仪器还可进一步应用于酸碱滴定、氧化还原滴定、络合滴定、沉淀反应、非水滴定等电位滴定的分析。从而增加了实验手段的多样化,提高了实验的趣味性和学生的积极性。     

PbICl precursor solutions for all solid-state PbS quantum-dot sensitized TiO2 nanorod array solar cells using successive ionic layer adsorption and reaction method

In this work, PbICl precursor solution in N,N-dimethylformamide was successfully applied to deposit PbS quantum-dots on TiO₂ nanorod arrays by successive ionic layer adsorption and reaction method (SILAR). The influence of PbI₂, PbBr₂, PbICl precursor solution on the morphology, crystal size and optical absorption of PbS quantum-dots was investigated and the photovoltaic performance of the corresponding solid-state PbS quantum-dot sensitized TiO₂ nanorod array solar cells with spiro-OMeTAD was evaluated. The average crystal sizes of PbS quantum-dots were 9.0 nm of PbI₂, 8.6 nm of PbBr₂ and 8.4 nm of PbICl and the photoelectric conversion efficiency of the corresponding solar cells achieved 2.63%, 3.00%, 3.45%. The result revealed that PbICl precursor solution was superior to PbBr₂ and PbI₂.     

车用散热器百叶窗翅片结构仿真优化

随着现代发动机技术的进步,发动机功率和性能的提升,也对发动机散热器提出了更高的要求。在兼备良好的散热性能和稳定性的同时,更要求散热器结构紧凑,以实现轻型化。通过对车用发动机管带式散热器的局部翅片和整体散热器进行三维建模,分析百叶窗翅片角度、翅片波距、翅片波高对空气侧压降影响,并对影响散热器散热性能主要因素进行分析。然后采用了多孔介质代替翅片的方法,模拟整体散热器的散热性能,并对比实验结果验证仿真模型准确性。最后拟合仿真数据的总传热系数和空气侧压降系数,建立粒子群算法优化数学模型。在不改变散热器外形尺寸和空气侧压降符合设计标准的情况下,优化散热器的翅片结构。翅片结构优化后,空气侧压降基本不变,散热量提升了11.6%。     

Preparation Bi2S3-TiO2 heterojunction/polymer ?ber composites and its photocatalytic degradation of methylene blue under Xe lamp irradiation

This paper presented the preparation of Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites and their performance of the degradation of methylene blue using Xe lamp irradiation. The polysulphone (PSU)/styrene-maleic anhydride copolymer (SMA) ?bers were prepared by electrospinning. Bismuth ions were introduced onto the surface of polymer ?ber by the coordinating of carboxyl of SMA, sul?de ions were incorporated to react with bismuth ions under hydrothermal condition. TiO₂ was deposited on the surface of the Bi₂S₃ by the reaction of titanium ions with urea also under hydrothermal condition. Scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM) images revealed that Bi₂S₃-TiO₂ heterojunction was uniformly distributed on the surface of PSU/SMA ?bers. The ultraviolet-visible absorption spectra (UV/VIS) showed that the Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites possess good visible-light response ability. The degradation rate of methylene blue in Bi₂S₃-TiO₂ heterojunction/polymer ?ber composites system was considerably higher than that of Degussa P25 or Bi₂S₃-TiO₂ heterojunction system under Xe lamp irradiation.     

Structures and photoelectrochemical performances of reduced TiO2 NTAs obtained by hydrogen thermal and electrochemical reduction methods

Journal of Solid State Electrochemistry - Reduced TiO2 nanotube arrays were obtained by hydrogen-thermal and electrochemical reduction methods respectively, and the photoelectrochemical...     

期末二次订购下风险规避且促销的收益共享契约协调研究

在期末二次订购下,利用CVaR准则考察收益共享下销售商风险规避且促销的决策问题,并得到一些有意义的管理启示。讨论了风险中性制造商在两生产模式下的生产决策。探讨了收益共享措施的协调问题,分析了各参数的关系,获得如下启示:销售商越是风险规避,首次订购量越少;制造商的首次生产量不一定是首次订购量,在有二次订货情况下可以投机生产来获得额外利润;在收益共享措施下,批发价固定,要风险态度不同的销售商订购等量的商品,风险规避度大的销售商,分享收益的比例小;如果制造商想要收益共享比例增大,那么首次批发价就要降低。     

New Quantum Codes Derived from Cyclic Codes

International Journal of Theoretical Physics - In this paper, we construct optimal or almost optimal dual-containing cyclic codes from cyclotomic classes of order r. Based on these cyclic codes...