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91.
本文介绍了一种CMOS全片集成的功率放大器,满足802.15.4规范,并采用采用了中和电容技术。采用了一种新型的采用了数字接口的结构,可以使基带信号直接控制PA的输出功率,从而无需DAC。采用中和电容技术以提高反向隔离度。该芯片采用SMIC 0.18um工艺流片。 测试结果表明,在1dB压缩点处,本文所提出的功率放大器具有13.5dB的功率增益,最大3.48dBm的输出功率和35.1%的PAE。核心面积为0.73mm*0.55mm。 相似文献
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93.
平面钢闸门主梁的可靠度分析及概率设计 总被引:10,自引:2,他引:10
概率设计法在工程设计各领域中已逐步得到应用,而作为水工建筑物重要组成部分的水工金属结构,目前的设计方法是按现行的设计规范-《水利水电工程钢闸门设计规范》的许用应力法进行设计的。因此,水工金属结构的设计准则向概率设计法过渡已是大势所趋。现以平面闸门主梁为研究对象,对水工金属结构的概率设计问题进行了研究,建立了主梁的设计表达式并确定了各分项系数值;探讨了水工金属结构概率设计的一般方法。 相似文献
94.
95.
Dongpo Chen Lei Zhao Hongwei Diao Wenbin Zhang Ge Wang Wenjing Wang 《Journal of Materials Science: Materials in Electronics》2014,25(12):5322-5330
Four different low-temperature silver pastes were utilized to make metal grids by screen printing for silicon heterojunction solar cells. The rheological behaviors of the low-temperature silver pastes were characterized by viscosity test, thixotropy test, oscillatory stress sweep test and creep-recovery test. The correlationship between the screen-printing performance and the rheological properties was investigated. It was found that the shear thinning behavior and the thixotropy behavior of the silver pastes were desirable for the screen-printing process. An obvious viscoelastic behavior of the silver paste was also helpful for improving its printability. Further, good recovery and low creep and recovery compliances could minimize the printing defects and the tendencies to bleed out during the screen-printing, and thus increase the aspect ratio of the printed grids. 相似文献
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97.
This paper aims to find a reliable, collision-free path in a dynamic environment for highly maneuverable unmanned combat air vehicles (UCAVs). Given the real-time nature of the operational scenario, quick and adaptable reactions of UCAVs are necessary for updates in situational awareness. Therefore, we propose a three dimensional (3D) path planning approach based on the situational space to provide the tactical requirements of UCAVs for tracking targets and avoiding collisions. First, to ensure reliable nonlinear measurements, the interacting multiple model (IMM) algorithm based on a cubature Kalman filter (CKF) is chosen for the tracking and prediction algorithm. A constraint reference frame combining the kinematic model of constant acceleration (CA) is developed to solve the problem of arrival point generation. Second, by analyzing the relative motion between the UCAV and the moving objects, we define the situation space and give the corresponding calculation method. In tracking the moving target, the guidance vector contains the fusion information of displacement and velocity. At the same time, taking advantage of the one-step situation space as the judgment of the threat, we further plan the collision avoidance strategy. Third, as the safety in a practically reachable trajectory of the UCAV possesses the absolute priority, the collision avoidance acceleration accounts for this dominant factor in path planning. Simulations and experimental results prove that the proposed approach can plan a smooth and flyable path in 0.008 s under the premise of soft-landing target tracking. 相似文献
98.
Ning Ren He Yang Mei Zhan Zhi-Yong Zhang Hao-Min Jiang Ke-Shan Diao Xin-Ping Chen 《The International Journal of Advanced Manufacturing Technology》2013,69(1-4):181-195
The weld profiles, weld width, weld positions, and mechanical property changes in the weld and heat-affected zones (HAZ) are the most important parameters that influence the potential formability of the welded tube. To investigate the effect of weld characteristics on the forming behaviors of the welded tube, finite element models which consider the geometric profile and mechanical properties of the weld and HAZ are employed. The results show that (1) the mechanical constitutive relation of the weld region determined by the microhardness empirical formula obviously decreases the tangent strain, thickness strain, and cross-sectional deformation ΔD in the weld and HAZ as compared with that determined by the improved rule of mixtures, which is contrary to the hoop strain, and the predicted results determined by the improved rule of mixtures are much closer to the experimental ones; (2) different weld and HAZ widths determined by the microhardness profile and metallographic section have a little effect on the tangent strain, thickness strain, and ΔD distribution; (3) the implementation of weld profile and material properties decreases the wall variation of the weld region as the weld line locates on the outside and inside. On the contrary, both the weld profile and weld material properties increase the maximum ΔD. The sectorial weld profile has a stronger effect on the wall variation and maximum ΔD than the hourglass profile; and (4) the same weld and HAZ volume have a stronger effect on wall thinning and ΔD. 相似文献
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100.
R&D of the ground-coupled heat pump technology in China 总被引:1,自引:0,他引:1
Nairen Diao Ping Cui Junhong Liu Zhaohong Fang 《Frontiers of Energy and Power Engineering in China》2010,4(1):47-54
The ground-coupled heat pump (GCHP) systems have been identified as one of the best sustainable energy technologies for space
heating and cooling in residential and commercial buildings. In this paper, research on and development of the GCHP technology
in China are summarized. New models are presented for efficient thermal analysis of ground heat exchangers, of which one-
and two-dimensional solid cylindrical source models and their analytical solutions are devised to deal with pile ground heat
exchangers. Analytical solutions are also derived for vertical and inclined finite line source models as well as for a groundwater
advection model. Explicit solutions of a quasi-three-dimensional model can be used to better evaluate the thermal resistance
inside boreholes. Studies on hybrid GCHP systems and the thermal response test in China are also commented. 相似文献