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赵乃虎 《西安航空技术高等专科学校学报》2011,29(3):79-80
研究椭圆、双曲线、抛物线上三点构成直角三角形的充要条件,得到若干有益的结果。 相似文献
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Liu Jixue Tang Dengbin YangYingzhao 《中国航空学报》2007,20(4):313-319
The process of evolution, especially that of nonlinear evolution, of C-type instability of laminar-turbulent flow transition in nonparallel boundary layers are studied by means of a newly developed method called parabolic stability equations (PSE). Initial conditions, which are very important for the nonlinear problem, are investigated by computing initial solution of the harmonic waves, modifying the mean-flow-distortion, and giving initial value of TS wave and its subharmonic waves at initial station by solving linear PSE. A numerical method with high-order accuracy are developed in the text, the key normalization conditions in the PSE are satisfied, and nonlinear PSE are solved efficiently and implemented stably by the spatial marching. It has been shown that the computed process of nonlinear evolution of C-type instability in Blasius boundary layer is in good agreement with the experimental results. 相似文献
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数字相关法测时差的工程实现 总被引:1,自引:0,他引:1
时差测量精度是定位技术的关键指标。传统模拟法的时差测量精度随输入信号的沿宽加大而变坏(相同信噪比),当信号沿宽达到1500ns时,其时差测量精度已不能满足定位系统的要求。而数字相关法能适应不同沿宽的雷达信号时差的高精度测量。介绍了利用A/D、DSP和FPGA等器件搭建的硬件系统来实现数字相关法时差测量的方法。重点讨论了A/D采样模式、数字滤波、相关算法简化、插值技术及最终数据的统计处理。该方法具有一定的普遍适用性。 相似文献
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针对以落压比为横坐标,流量与效率为纵坐标,并按不同等转速线区分所表示的涡轮特性在涡轮处于临界状态时换算流量几乎保持不变,使得在航空发动机数学模型中应用该形式涡轮特性通过插值求解共同工作点时存在计算效率降低的不足,根据相似理论及等熵条件下涡轮膨胀功与落压比对应关系,推导了涡轮落压比、涡轮效率与涡轮当量功的关系,并结合抛物线插值方法给出了向以转速为横坐标,涡轮当量功与效率为纵坐标,并按不同等流量线区分所表示的涡轮特性转换方法。实例转换计算表明:采用所提出的转换计算方法,可有效解决以往涡轮特性插值流量基本不变的局限,并且两种格式的涡轮特性转换相对误差小于0.65%,满足工程要求。 相似文献
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Design and analysis of spiral bevel gears with seventh-order function of transmission error 总被引:2,自引:0,他引:2
This paper proposes a new approach to mial function of transmission error (TE) for spiral design and implement a seventh-order polyno- bevel gears with an aim to reduce the running vibration and noise of gear drive and improve the loaded distribution of the tooth. Based on the constraint conditions of predesigned seventh-order polynomial function curve and the theory of linear algebra, the polynomial coefficients of the seventh-order polynomial function of transmission error can be obtained. By applying a method named reverse tooth contact analysis, the modified roll coefficients as well as parts of machine-tool settings for the face-milling of spiral bevel gears can be individually determined. Therefore, a predesigned seventh-order polynomial function of transmission error for spiral bevel gears can be obtained by the modified roll with high-order coef- ficients, and comparisons of the seventh-order polynomial and parabolic functions of transmission error are also performed. The achievement of spiral bevel gears with the seventh-order function of transmission error can be accomplished on a universal Cartesian-type hypoid gear generator or a numerically controlled cradle-style hypoid gear generator due to its simple generating motion of axes of the cradle and the work piece. The results of a numerical example show that the bending stresses of the tooth of seventh-order are less than those of a parabolic one, while the contact stresses remain almost eouivalent. 相似文献