Two efficient methods for a multifrequency solution of the Helmholtz equation

Abstact In this paper, two efficient methods for the multifrequency analysis for the Helmholtz equation are compared. The first approach is based on the direct collocation method with a subsequent approximation of the matrix by the Adaptive Cross Approximation method. Using the so-called Fourier scheme, the elements of the matrices for a series of frequencies can be computed efficiently. In the second approach an indirect Galerkin type method with piecewise linear ansatz and test functions is combined with a special source simulation technique. This combination allows a rather accurate and systematic approximation of acoustical results in major parts of the considered frequency range, leading to a significant reduction of the computer time needed to calculate complete frequency spectra. A representative example demonstrates how the two proposed approaches can be used. Both procedures turn out to be very promising steps towards a more efficient calculation of complex sound radiation problems. Communicated by: O. Steinbach     

Development of FRACAS-CT module with FRAPCON4.0P01 for simulation of mechanical behaviors for accident-tolerant fuel cladding in a reactor

In order to evaluate the mechanical behaviors of accident-tolerant fuel (ATF) cladding under reactor conditions, a new analytical module, termed FRACAS-CT, was developed. A mechanical model of FRACAS-CT was formulated based on thick-wall theory to consider the multi-layered structure of ATF cladding. Two statuses of a pellet-cladding gap, that is, open and closed, were described by several boundary conditions of pressures, inside radial displacements, and axial strains of the multi-layered ATF cladding. The FRACAS-CT model was verified by comparison with an equivalent finite element (FE) model and was implemented into FRAPCON4.0P1 with consideration of creep and stress relaxation behaviors of the multi-layered ATF cladding. After the implementation, code verification work was performed, and finally, mechanical behaviors and fuel performance of the multi-layered ATF cladding were calculated under normal operating conditions. As a result, the implemented FRACAS-CT can simulate the mechanical response and fuel performance of the multi-layered ATF cladding.     

锆合金表面CrAl涂层的高温氧化与拉伸行为

为研究CrAl涂层的高温氧化和拉伸行为,提高锆合金的抗高温氧化性能,采用多弧离子镀技术在锆合金表面制备CrAl涂层。利用高温热处理炉在360~1160℃和860~1160℃下分别对原始锆合金和带CrAl涂层锆合金进行氧化测试,研究二者的氧化增重行为。采用扫描电镜（SEM）和X射线衍射（XRD）对氧化前后样品的微观形貌、成分与相结构进行系统表征分析。通过原位拉伸测试对原始锆合金和带CrAl涂层试样的力学性能进行研究。结果表明：CrAl涂层氧化时通过形成致密的Al₂O₃和Cr₂O₃氧化层,显著降低了氧化增重,在1060℃高温下基体未被明显氧化。原位拉伸时CrAl涂层直到4%应变时才出现少量微裂纹,显示出较好的塑性变形能力,样品断裂前未见涂层剥落。多弧离子镀制备的CrAl涂层表现出优异的抗氧化性能,涂层与锆合金具有较好的力学相容性,该涂层具有发展成为事故容错燃料（ATF）包壳涂层的潜力。     

汽车自动传动液防锈性能测定方法的研究——潮湿箱试验

在大量实验室研究工作基础上，阐明ＡＳＴＭＤ１７４８８３（１９９３）《潮湿箱中金属保护剂防锈性能测定法》是评定汽车自动传动液防锈性能较为科学而可行的方法。     

匹诺塞林对脑缺血再灌注内质网应激凋亡相关基因mRNA表达的影响

目的: 观察匹诺塞林对大鼠脑缺血再灌注急性期损伤内质网应激凋亡途径相关基因的调控作用。方法: 雄性SD大鼠50只，阻塞大脑中动脉建立脑缺血再灌注模型，随机分为假手术组、模型组、匹诺塞林1 mg/kg组、3 mg/kg组和10 mg/kg组，其中模型组及匹诺塞林各给药组，分别于大脑中动脉阻塞2 h后再灌注同时给药，6 h后取血并断头取脑，取缺血半暗带组织，实时荧光定量PCR（RT-PCR）法测定GRP78、CHOP、ATF4、XBP-1的mRNA变化。结果: 匹诺塞林能增加急性局灶性脑缺血再灌注GRP78 mRNA水平，其中匹诺塞林3 mg/kg、10 mg/组与模型组比较，差异有统计学意义（P<0.05或P<0.01）；匹诺塞林能降低内质网应激凋亡相关蛋白CHOP、ATF4，XBP-1 mRNA水平，与模型组相比，差异有统计学意义（P<0.05或P<0.01）。结论: 匹诺塞林能抗脑缺血再灌注损伤，其机制可能与保护内质网功能，减少GRP78、CHOP、ATF4及XBP-1相关基因表达有关。     

三维大地形下的飞行航迹优化仿真

三维大地形对空中飞行航迹有很大的影响,不同的飞行航迹在很大程度上影响空中交通流量(ATF).以最优飞行航迹为背景,增大空中交通流量为目的,介绍了三维大地形模型的生成方法和步骤,并模拟出真实环境下的三维大地形模型.针对飞行路径对飞行航迹的影响,在该模型上加入影响飞行的其他自然要素,如能见度、风向风速、降雨量、云底高等.将此虚拟的飞行环境中生成的飞行航迹优化,尽量避免自然因素对飞行航迹的影响,优化之后相同时间段内通过相同航域的飞机架数增加了,从而增大了空中交通流量.