有限元数值模拟方法在连轧管孔型设计中的应用

介绍了有限元法在连轧管孔型设计中的应用,分析了全浮芯棒连轧时金属流动特性,讨论了轧辊工作直径的确定方法.针对难轧钢种的钢管连轧,以减轻钢管内表裂纹缺陷为目标,借助于有限元数值模拟对连轧孔型进行了优化设计.试轧结果表明,新设计的孔型使T91钢管的内表缺陷大幅下降,经高压锅炉管精整线超声波探伤检验,合格率(绝对值)提高36.77%,对难轧钢种具有很强的适应性.     

Structure and Magnetic Properties of Nd(Fe,Mo) 12 N x Prepared by Mechanically Alloying

Ｂｅｃａｕｓｅｏｆｆｉｎｅｇｒａｉｎｓ,ｔｈｅｍａｇｎｅｔｓｐｒｅｐａｒｅｄｂｙｔｈｅｍｅｃｈａｎｉｃａｌａｌｏｙｉｎｇ（ＭＡ）ｔｅｃｈｎｉｑｕｅｈａｖｅｈｉｇｈｅｒｃｏｅｒｃｉｖｉｔｙｃｏｍｐａｒｅｄｗｉｔｈｔｈｏｓｅｐｒｅｐａｒｅｄｂｙｔｒａ...     

Modeling of diode-pumped actively Q-switched lasers

The intracavity photon density and initial population inversion density in the diode-pumped actively Q-switched laser rate equations are assumed to be Gaussian distributions. These space-dependent rate equations are solved numerically and a group of general curves are generated. By using these curves and the related formulas, the pulse parameters of an arbitrary actively Q-switched laser can be easily estimated and an optimally coupled Q-switched laser can be designed. A sample calculation for a Q-switched Nd³⁺:YVO₄ laser is presented to demonstrate the use of the curves and the related formulas     

基于情感层次理论中反思水平设计方法的研究

随着科技的进步和信息化时代的到来,产品设计的功能属性在当前的产品市场需求中被逐渐淡化,超出功能属性的是产品本身所延伸和发展出来的文化属性和审美属性.如今,在产品设计的领域中,情感化设计崭露头角,甚至成为了不可或缺的最核心的部分.本文将分层阐述情感化设计层次理论,并通过对几个设计案例的剖析来展现、表达反思水平的四种设计方...     

二冲程半直喷航空发动机喷油策略研究

基于自主研发的二冲程低压半直喷航空发动机及控制系统,开展喷油控制策略及对发动机性能影响规律的研究。结果表明：对于不同的发动机运行工况,需要采取不同的喷油策略组合。在起动和怠速工况,采用进气道喷射的独立供油方式;在部分负荷及高负荷工况,采用进气道喷射和缸内直喷协同供油方式,随着发动机直喷比例的提高,燃油消耗率相应减小;与采用进气道喷射供油相比较,采用低压半直喷供油可以获得较理想的燃油经济性。     

Spatio-Temporal Changes in Potential Evaporation Based on Entropy Across the Wei River Basin

The distribution of potential evaporation is highly unstable due to complex human activities and climate changes. Therefore, it is of great significance for further understanding hydrological cycle to estimate potential evaporation distribution. Reasonable regionalization of potential evaporation will help to improve the efficiency of irrigation and increase the ability of drought relief, which is of great importance to irrigation planning and management. Hence, the spatio-temporal changes in potential evaporation distribution at monthly and annual scales are investigated based on the modified Mann-Kendall trend test method and the entropy theory in the Wei River Basin. A nonparametric method as an attractive alternative to empirical and parametric approaches is proposed to calculate the univariate and bivariate probability distribution of potential evaporation. The directional information transfer index (DITI) is employed to estimate the similarity among the meteorological stations, and the k-means cluster analysis is used to classify the meteorological stations into several distribution zones with distinct features. Based on the monthly potential evaporation from 1960 to 2008 at 21 meteorological stations, the basin is ultimately classified into 8 zones with their own distinct spatio-temporal distribution features. In view of the distinct spatio-temporal distribution features, the DITI-based model combined with the nonparametric probability estimation method and the k-means cluster analysis offers a more precise classification of potential evaporation distribution zones.     

EPR核电机组部分冷却试验研究与风险识别

As the first reactor test of the European Pressurized Water Reactor (EPR) Units, partial cooldown test would cause enormous thermal shocks in the primary and secondary coolant circuits, which are not allowed to happen more than 15 times during the service life of a nuclear power station. In order to lower the risks in the test, studies are furthered on the control logic, theory, principles and the feasibility of the test, and the risks are summarized in 5 aspects. Meanwhile, comprehensive analysis is performed on partial cooldown test by simulations, and then the test method is optimized.The test succeeds at one time, and meets the nuclear safety requirements.     

Quantifying the Relative Contribution of Climate and Human Impacts on Runoff Change Based on the Budyko Hypothesis and SVM Model

The Wei River Basin (WRB), the largest tributary of the Yellow River in China, has experienced a noticeable decrease in annual runoff during the last 50 years. Quantifying the relative contributions of climate change and human activities on runoff changes is thus important for local water resources management and sustainable water resources utilizations. In this study, the heuristic segmentation method was first adopted to detect the change points of annual runoff at Linjiacun and Huaxian stations which lies in the middle and lower reaches of the basin, respectively. Then, the Budyko hypothesis and SVM-based model were applied to attribute the detected runoff changes to climate change and human activities. Results showed that: (1) two change points were detected for the annual runoff at the Linjiacun station (1971 and 1993), and Huaxian station (1969 and 1993); (2) based on the Budyko hypothesis, the relative contributions of climate change and human activities to runoff changes at Linjiacun and Huaxian stations are 42.2 %, 57.8 % and 30.5 %, 69.8 %, respectively, whilst those based on the SVM-based model are 45.3 %, 54.7 % and 34.7 %, 65.3 %, respectively. The high consistence between the two approaches indicates that human activities are the dominate factor on historical runoff changes in the WRB.     

二辊斜轧延伸9Cr-1Mo钢厚壁管内表裂纹形成倾向性模拟研究

借助于商用有限元软件MSC.SuperForm,对φ485 mm×73 mm大口径厚壁9Cr-1Mo钢管二辊斜轧延伸过程进行了3D热力耦合模拟;采用Oyane韧性断裂准则分析了轧件损伤场及钢管内表裂纹的倾向性,发现钢管内表邻近芯棒接触区存在破裂高危带。研究了轧辊入口锥角对轧件损伤场的影响,结果表明,轧辊入口锥角由3.0°增至5.0°时,轧件最大损伤特征由0.520 7降至0.3544,发生内表裂纹的倾向性降低。     

高温度稳定性烧结Nd-Fe-B研究进展

随着中国新能源汽车和国防军工等领域的发展,对钕铁硼磁体的温度稳定性提出了更高的要求.基于国内外研究进展,对钕铁硼温度稳定性研究的两个方向进行了综述,一是围绕提高钕铁硼最高使用温度的相关研究,对矫顽力、矫顽力温度系数、方形度和磁体最高使用温度内在关联进行了重点介绍;二是围绕降低钕铁硼磁体的剩磁温度系数的相关研究,就Co和...