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321.
用拦格朗日乘子法,利用向量分析的工具及巧妙的变换,对带磨擦约束的弹塑性接触问题的变分不等原理进行了严格的证明。 相似文献
322.
323.
刘景旺 《华北航天工业学院学报》2007,(1)
本文报导了通过结合自行制备的掺铈钒酸钇晶体(Ce3 :YVO4)荧光粉与InGaN/GaN蓝光发光二极管(LED)结合而得的白光发光二极管(W-LED)。在室温、正向电压3.5V、正向电流20mA时W-LED的CIE色坐标为(0.32,0.37),接近纯白色(0.33,0.33)。 相似文献
324.
针对相对疏松的铸造钛合金和相对密实的锻造钛合金的焊接问题,开展了两种状态的TC4钛合金电子束焊接工艺研究,对比了不同焊接参数对焊接质量的影响。研究结果表明,采用方波扫描可以较好地实现铸造钛合金与锻造钛合金的连接,焊缝成形良好,内部无缺陷;焊接接头力学性能分析表明,拉伸断裂位置全部在铸件母材区一侧。实焊结果证明,电子束焊接可以实现异种状态TC4钛合金焊接的工程化应用。 相似文献
325.
In 2012 we celebrate the 70th anniversary of the first successful rocket launch that reached a height of 84.5 km and had a speed of 4.824 km/h (5x sonic speed). This rocket flew 190 km to the target location. One of the masterminds of this launch was Walter Thiel, a German chemist and rocket engineer. Thiel was highly talented, during his education from primary school until diploma exams he always received a grade of A in his exams. He was called “the student with the 7 A grades”. In 1934 Thiel became Dr.-Ing. (chem.), with the highest possible honor (summa cum laude), when he was only 24 years old. He started to work for the rocket development department at Humboldt University, Berlin. Walter Dornberger asked him to leave the university research department and become head of rocket propulsion development in his team in Kummersdorf, near Berlin. Thiel's groundbreaking ideas for the rocket engine would lead to a significant reduction in material, weight and work processes, as well as a shortening in the length of the engine itself. Thiel and his team also defined the fuel itself and the best ratio of mixture between ethanol and liquid oxygen for the engine. In 1940 the propulsion team moved from Kummersdorf to Peenemünde after the launch sites were completed there. Thiel became deputy of Wernher von Braun at the R&D units. One of Thiel's team members was Konrad Dannenberg, who later became famous in the development of the Saturn program. On the night from August 17 to August 18, 1943, Thiel and his family (wife and two children) were killed during a Royal Air Force bombing raid (Operation Hydra). The Moon crater “Thiel” on the far side of the Moon is named after Walter Thiel. The research results of Walter Thiel had a strong impact on the United States' rocket program as well as the Russian rocket development program. 相似文献
326.
Simulation of asymmetric landing and typical ground maneuvers for large transport aircraft 总被引:6,自引:0,他引:6
Prashant Dilip Khapane 《Aerospace Science and Technology》2003,7(8):1708-619
It is important to determine static and dynamic ground loads for the aircraft ground maneuvers accurately in the design phase. Simulation of the important operational cases is a better way compared to the tests on real aircraft to investigate these loads at a reasonable cost. In this paper, the simulation of an asymmetric landing case and typical ground maneuvers for large transport aircraft is presented. The aircraft models are built in the multibody simulation tool SIMPACK. The tire model implemented in SIMPACK includes lateral dynamics of the tire. Cornering, braked runs and pushback are simulated as typical ground maneuvers. For simulation of braking, a simple but effective Antilock Braking System (ABS) algorithm is implemented. The article is based on the work done in cooperation between DLR and Airbus in the Flexible Aircraft 2 project. 相似文献
327.
Si对In718合金凝固过程及元素偏析的影响 总被引:2,自引:0,他引:2
本文研究了Si对In718合金凝固过程及元素偏析的影响。结果表明,当Si含量升高后,不仅在枝晶或Laves相中偏析程度加剧,而且在枝晶内的浓度也逐渐升高而达到显著水平。Si降低Nb在Laves相中的溶解度,因而促进Laves相的析出,提高Laves相吸收剩余液体的能力,缩小偏析区的面积。分析认为,过分降低Si含量对改善合金凝固组织及提高终凝温度的作用不大。 相似文献
328.
美国空军信息作战初探 总被引:3,自引:0,他引:3
在信息战条件下 ,美空军正大力发展全球定位系统 (GPS) ,充分利用C4ISR(指挥、控制、通信、计算机与情报、监视、侦察 )系统 ,关注信息网络和信息系统的安全 ,以提升空中平台的作战能力 ,最大限度地发挥武器系统及传统EW的效能 相似文献
329.
330.
In order to investigate the yielding behavior of the newly developed Ni 3 Al-based intermetallic alloy IC10, yield stresses have been measured in tension and compression with different orientations. The specimens were cut from a sheet with different angles inclined from the solidification direction. The inclined angles were taken to be 0 , 22.5 , 45 , 67.5 and 90 . All experiments were conducted at room temperature except for orientation 0 , whose deformation temperatures ranged from 298 to 1273 K. Experimental results show that the yield strength of alloy IC10 has the anomalous behavior which has been observed for other Ll 2 -long-range ordered intermetallic alloys, but it is less pronounced. The abnormalities show the following characteristics: (i) the yield strength increases as the temperature is raised below the peak temperature, (ii) yield strength anisotropy, (iii) tension/compression asymmetry. Compared to Ni 3 Al single crystals, the polycrystalline exhibits some different yielding behaviors which may be due to the high volume fraction of c phase. 相似文献