核事故应急决策中水体放射性核素扩散仿真分析

放射性核素浓度的确定是放射性事故应急救援和辐射防护等工作的基础和前提,是放射性事故应急救援的重要组成部分.在一维扩散模型的基础上,建立了放射性核素瞬时污染点源三维扩散模型、连续污染点源三维扩散模型、连续污染点源三维扩散稳态模型,并编写程序,实现了对放射性核素污染扩散的快速仿真分析,较好模拟了水体中放射性核素的扩散趋势.研究结果在核事故应急救援过程中,可为相关部门制定救援方案及应急决策提供科学依据.     

Preparation of Y-Ba-Cu-O film on metal substrate with buffer layers deposited by ion beam assisted deposition

Ion beam assisted pulsed laser deposition of biaxially aligned yttria-stabilized zirconia (YSZ) was used to produce a buffer layer for YBCO film on polycrystalline metallic substrate. The YSZ layers were biaxially aligned with (001) axis normal to the substrate. The minimum FWHM of (111) phi-scan of the YSZ was 19°, and the minimum FWHM of the rocking curve of YSZ was 4.5°. Highly c-axis oriented biaxially aligned YBCO thin films were epitaxially grown by laser ablation on these layers, with J_C(77K, 0T) = 2.1 × 10⁵ A/cm², . Project supported by the National Center for R&D on Superconductivity of China.     

Two heuristic solution concepts for the vehicle selection problem in line haul transports

In this article we will develop a mathematical model for a cost-efficient selection of vehicles with varying capacities for line haul transports with leasing options. For this integer optimization problem, which is a variant of the generalized assignment problem known as NP-hard, we will compare two heuristic solution concepts and try to answer the question in which cases a user should choose an exact or approximate solution concept depending on different data instances of the problem.