涂层与基底的热膨胀系数差对垂直界面的微裂纹的影响

将陶瓷涂层/基体金属界面看作是在陶瓷基体中包含的圆柱形金属夹杂,在夹杂半径趋近于无穷大时的极限情形.给出了平面应变条件下圆形夹杂两侧的半裂纹的应力强度因子的解析表达式,让圆形夹杂的半径趋向无穷大,得到陶瓷涂层/基体金属界面的垂直微裂纹的有关结果.根据所得结果,分析了陶瓷涂层和金属材料的膨胀系数的差异对于其界面微开裂的影响,所得结论对于陶瓷涂层的设计和制备工艺等具有指导意义.     

蓄热体微纳米高辐射覆层对热风炉传热过程的影响

根据蓄热室内烟气与蓄热体的换热以及蓄热体的导热之间的能量平衡关系,建立了高炉热风炉蓄热室内部辐射与对流换热过程数学模型,并使用CFD软件对高炉热风炉蓄热室内部流动传热过程进行数值模拟.重点对石横特钢1080m3高炉3号热风炉(无覆层)和1号热风炉(有覆层)的烟气温度变化、热风温度变化、格子砖表面温度变化进行定量分析,并同现场热诊断结果进行比较.     

非调质钢中MnS分布对轧材横向塑性的影响

为了探究实际生产中非调质钢轧材横向塑性波动较大的原因,利用电子显微镜对比研究了连铸坯、轧材和拉伸试样断口中MnS夹杂物形貌及其演变行为,并对轧材横纵截面MnS夹杂物的尺寸、数量以及分布特征进行定量化表征,发现MnS夹杂物的分布特征是影响轧材横向塑性的关键。MnS夹杂物聚集分布,拉伸试样在受力过程中大量微裂纹在局部同时萌生,导致试样提前断裂,形成木质状的断口形貌,轧材表现出较差的横向塑性。当MnS夹杂物分布较为均匀时,拉伸试样受力相对均匀,应力集中小,轧材横向塑性较好。轧材中MnS夹杂物的分布行为主要取决于铸态下MnS夹杂物的形貌。减少铸态下II类树枝状MnS数量,是改善最终轧材横向塑性的关键。     

连续退火炉中保护气氛及结构特性对带钢冷却特性的影响

采用标准kε-紊流模型,对连续退火炉中快冷段局部带钢的二维非稳态温度场进行CFD模拟,模拟与实际结果吻合较好。研究结果表明:从温度均匀性和冷却速度来看,当氢气体积分数为30%时,冷却效果最佳;控制最优的冷却速度可以通过控制带钢初始温度、带钢与风箱间距和冷却气体喷出速度、冷却介质的含量等参数来实现。     

Direct Radiative Forcing of Anthropogenic Aerosols over Oceans from Satellite Observations

Anthropogenic aerosols play an important role in the atmospheric energy balance. Anthropogenic aerosol optical depth (AOD) and its accompanying shortwave radiative forcing (RF) are usually simulated by numerical models. Recently, with the development of space-borne instruments and sophisticated retrieval algorithms, it has become possible to estimate aerosol radiative forcing based on satellite observations. In this study, we have estimated shortwave direct radiative forcing due to anthropogenic aerosols over oceans in all-sky conditions by combining clouds and the Single Scanner Footprint data of the Clouds and Earth's Radiant Energy System (CERES/SSF) experiment, which provide measurements of upward shortwave fluxes at the top of atmosphere, with Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol and cloud products.We found that globally averaged aerosol radiative forcing over oceans in the clear-sky conditions and all-sky conditions were-1.03±0.48 W m-2 and -0.34±0.16 W m-2, respectively. Direct radiative forcing by anthropogenic aerosols shows large regional and seasonal variations. In some regions and in particular seasons, the magnitude of direct forcing by anthropogenic aerosols can be comparable to the forcing of greenhouse gases. However, it shows that aerosols caused the cooling effect, rather than warming effect from global scale, which is different from greenhouse gases.     

Effects of Electromagnetic Continuous Casting on Structures,Element Distributions and Mechanical Properties of Cu-Mg-Te-Y Alloys

New Cu-Mg-Te-Y alloys with high strength and high conductivity were prepared by electromagnetic continuous casting（EMCC）and direct chill casting（DC）.The structures,patterns of elements distributions and mechanical properties of the alloys were investigated.It was found that the equiaxed crystal zone was enlarged and the element Mg and Cu₂Te phase were well-distributed by medium-frequency electromagnetic field during continuous casting method.Moreover,the defects and casting impurities were significantly reduced with the addition of electromagnetic,leading to the improvement of the mechanical properties.     

高斯粗糙表面辐射特性的数值研究

采用时域有限差分法和近场-远场变换对两种不同材料的一维微尺度高斯粗糙表面辐射特性进行了数值模拟,并将计算结果与其他方法进行了对比分析.研究结果表明,对于理想导电材料表面,随着均方根粗糙度的增加,其双向反射率的尖峰值逐步减小并最终消失;随着均方根粗糙度与表面关联距离之比的增加,向后反射变得愈加明显;相同表面轮廓特征条件下,理想导电材料与硅粗糙表面的双向反射率的总体趋势相同但后者要远小于前者;随着入射角度的增大,理想导电材料粗糙表面的双向反射变得趋于像镜面反射.     

掺铕聚合物光纤的光辐射特性

制备了掺铕螯合物的阶跃型聚合物光纤。根据Judd-O fe lt(J-O)理论,从铕螯合物Eu(DBM)3掺杂的聚甲基丙烯酸甲酯(PMM A)的发射光谱获得了光学跃迁的J-O参数Ω2、Ω4(Ω2=15.71×1-0 20cm2,Ω4=0.24×10-20cm2)。用J-O参数计算了铕离子激发态(5D0)的辐射跃迁几率(513.97-s 1)和辐射寿命(1945.6μs),同时计算了5D0→7FJ跃迁的受激发射截面ijσ和荧光分支比,β分析表明,Eu(DBM)3掺杂的PMM A可望用于聚合物光纤放大器和激光器。     

Effects of Nonnormal Distributions on Highway Construction Acceptance Pay Factor Calculation

Percent within limits (PWL) is a commonly used quality control/quality assurance measure of highway pavement materials and construction, and it is a popular index for adjusting pay factors. However, PWL is based on the assumption of normal distribution of quality characteristics (e.g., concrete compressive strength and asphalt air voids). Skewness and kurtosis, which are common forms of statistical nonnormal distributions, can potentially bias the acceptance pay factor calculations. To examine this potential pay bias, simulations were performed to investigate the magnitude and the direction (overestimation or underestimation) of pay factor calculations. The study revealed that for both one-sided and two-sided specification limits, bias in pay factors not only did vary in magnitude but also reversed in direction over various ranges of PWL. These analyses showed that for a one-sided upper specification limit, on average, a positive skewness and kurtosis can underestimate the pay factor of an acceptable quality level population by 0.90%, and overestimates a rejectable quality level population by 3.8%. This leads to falsely penalizing acceptable products and rewarding bad products. The same was true for two-sided limits, which again varied based upon the percent of defective materials at the tails of the distribution. This is a very important issue because these biases in pay factors can easily upset the relative profit margins of the contractor. Furthermore, this may not be easily detectable without a detailed and sophisticated analysis as outlined in this paper. For multiple quality characteristics based pay factors, analyses showed that the combined magnitude of these biases was not linearly cumulative. Findings of the study indicate that bias in pay was higher for lots with fewer sublots and higher skewness and kurtosis.     

时效对TMC-2复合材料性能的影响

研究了时效制度对原位生成稀土钕氧化物颗粒增强Ti-6Al-4Sn-3.5Zr-0.5Mo复合材料（简称为TMC-2）棒材的组织和性能的影响，结果表明，采用直接时效处理可以获得比较高的室温拉伸强度和很低的650℃蠕变性能，而采用1030℃/0.5h/AC 800℃/0.5h/AC 时效的热处理制度，材料具有较好的拉伸，持久，蠕变和热稳定性等力学性能，时效温度升高，拉伸强度降低，而拉伸塑性，蠕变抗力和热稳定性有所改善。     

锆合金的织构及其对性能的影响

锆合金被广泛应用于核反应堆中，作为燃料元件的包壳材料或堆内结构部件，织构会影响其众多的应用性能，因此织构的研究及控制在锆合金的开发利用中具有重要作用。综述了，锆合金塑性变形的滑移和孪生系统；锆合金管板材的织构特点及控制方法；热轧温度对锆合金板材织构的影响以及退火处理锆合金织构的演化；并分别总结了织构与锆合金屈服强度、蠕变强度、碘致应力腐蚀开裂、氢化物取向分布以及辐照生长等性能的相互关系。