Benchmark experiment of large-angle scattering reaction cross section of iron at 14 MeV using two shadow bars – Comparison of experimental results with ENDF/B-VIII –

ABSTRACT

It is important to perform neutron transport simulations with accurate nuclear data in the neutronics design of a fusion reactor. However, absolute values of large-angle scattering cross sections vary among nuclear data libraries even for well-examined nuclide of iron. Benchmark experiments focusing on large-angle scattering cross sections were thus performed to confirm the correctness of nuclear data libraries. The series benchmark experiments were performed at a DT neutron source facility, OKTAVIAN of Osaka University, Japan, by the unique experimental system established by the authors’ group, which can extract only the contribution of large-angle scattering reactions. This system consists of two shadow bars, target plate (iron), and neutron detector (niobium). Two types of shadow bars were used and four irradiations were conducted for one experiment, so that contribution of room-return neutrons was effectively removed and only large-angle scattering neutrons were extracted from the measured four Nb reaction rates. The obtained experimental results were compared with calculations for five nuclear data libraries including JENDL-4.0, JEFF.-3.3, FENDL-3.1, ENDF/B- VII, and recently released ENDF/B-VIII. It was found from the comparison that ENDF/B-VIII showed the best result, though ENDF/B-VII showed overestimation and others are in large underestimation at 14 MeV.     

Compressive properties of pristine and SiC-Te-added MgB2 powders,green compacts and spark-plasma-sintered bulks

Pristine and (SiC+Te)-added MgB₂ powders, green and spark plasma sintered (SPS) compacts were investigated from the viewpoint of quasi-static and dynamic (Split-Hopkinson Pressure Bar, SHPB) compressive mechanical properties The amount of the additive (SiC+Te) was selected to be the optimum one for maximization of the superconducting functional parameters. Pristine and added MgB₂ show very similar compressive parameters (tan δ, fracture strength, Vickers hardness, others) and fragment size in the SHPB test. However, for the bulk SPSed samples the ratio of intergranular to transgranular fracturing changes, the first one being stronger in the added sample. This is reflected in the quasi-static K_IC that is higher for the added sample. Despite this result, sintered samples are brittle and have roughly similar fragmentation behavior as for brittle engineering ceramics. In the fragmentation process, the composite nature of our samples should be considered with a special focus on MgB₂ blocks (colonies) that show the major contribution to fracturing. The Glenn-Chudnovsky model of fracturing under dynamic load provides the closest values to our experimental fragment size data.     

防振条约束失效对蒸汽发生器传热管面内流弹失稳的影响研究

根据防振条布置以及面内支承连续失效个数，将防振条面内约束失效分析划分为多种工况，分析了不同工况下面内约束失效对传热管面内模态的影响，采用各位置阻尼在振型函数上进行加权平均的方法计算了各阶模态的阻尼比，进而研究了防振条面内不同约束对传热管面内流弹失稳的影响。分析结果表明，随着面内支承连续失效位置的增多，弯管段面内首阶模态频率不断降低，出现在弯管段的振型越加明显；弯管段面内首阶模态不一定是最大流弹失稳比值出现的模态，最大流弹失稳比值出现模态的振型几乎都出现在弯管段；随着面内支承连续失效位置的增多，面内流弹失稳比值不断增大，当连续3个及以上防振条面内约束失效时，将出现流弹失稳现象。     

基于MFSK的多载波水声通信系统及实验研究

本文在深入研究水声通信信道特性及多载波关键技术的基础上,设计并研制了基于M FSK的高速自适应多载波水声通信系统,并进行了湖上实验。理论分析、仿真及湖上试验结果表明:基于M FSK的多载波水声通信系统,多径抑制有效,对同步的精确度要求不高,性能稳健,更适合于恶劣水声通信环境下、中距离(10~30km)较高数据率多载波通信系统,易于工程实现,具有良好的应用前景。     

河口坝砂体储层非均质性及剩余油分布

运用非均质综合指数，以胜坨油田坨28断块沙二段8,9砂层组为例，对河口坝砂体储层的层间、层内、平面非均质性进行了定量表征，并分析了非均质性与剩余油分布之间的关系。认为河口坝储层层间非均质性弱，而层内、平面非均质性以中等-弱为主，非均质综合指数与含油饱和度有良好的对应关系，剩余油主要分布在非均质性中等的区域内。     

土壤冲击特性的实验研究

本文利用分离式Hopkinson压杆研究了土体在不同应变率条件下的冲击动态力学性能，发现土体有明显的应变率效应，与静载相比，冲击荷载下土的动强度和动模量均有很大的提高。     

On the determination of optimal transition profile of a stepped bar in tension or in torsion by BEM

The objective is to have uniformly distributed tangential stresses on the transition profile of a stepped bar subjected to tensile and torsional loading using an axisymmetric boundary element formulation. The transition curve is represented by the Langragian interpolation polynomial with progressive degrees to avoid shape distortion during the optimization procedure. The calculated result is compared with that obtained by fluid dynamics given in the literature. It is seen that the transition curve obtained in this paper is reasonable.     

先张法预应力桥梁板施工工艺及应用实例

结合太原市向阳店桥梁板施工实例，介绍了采用先张法进行预应力桥梁板施工的过程。阐述了桥梁板的施工工艺，该工艺实现了整体张拉、整体放张，使钢绞线逐根受力均匀，施工速度快，能保证梁端的质量。指出拉杆系统的使用，降低了成本，增加了效益。     

DDS+PLL系统的频谱分析

简要介绍了 ＤＤＳ＋ＰＬＬ频率合成的原理，分析了在 ＤＤＳ没有相位截断误差时，ＤＤＳ＋ＰＬＬ输出信号的杂散抑制度，并讨论了杂散抑制度与环路参数的关系。