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排序方式: 共有113条查询结果,搜索用时 15 毫秒
1.
为验证航区风力达到7级时车辆不绑扎方案的可行性,开展了跟船实测最大横摇角等数据的工作,结合惯性力的计算方法,对装载车辆的安全性进行校核.结果表明:实际风力7级时,典型客滚船装载车辆不绑扎也不会滑移和倾覆;但当有涌浪等特殊海况时,横摇角超过10°时,不绑扎装载车辆不安全.根据校核结果,提出了简单实用、易于推广的车辆安全装载方法.  相似文献   
2.
A novel slotted helix slow-wave structure (SWS) is proposed to develop a high power, wide-bandwidth, and high reliability millimeter-wave traveling-wave tube (TWT). This novel structure, which has higher heat capacity than a conven- tional helix SWS, evolves from conventional helix SWS with three parallel rows of rectangular slots made in the outside of the helix tape. In this paper, the electromagnetic characteristics and the beam-wave interaction of this novel structure operating in the Ka-band are investigated. From our calculations, when the designed beam voltage and beam current are set to be 18.45 kV and 0.2 A, respectively, this novel circuit can produce over 700-W average output power in a frequency range from 27.5 GHz to 32.5 GHz, and the corresponding conversion efficiency values vary from 19% to 21.3%, and the maximum output power is 787 W at 30 GHz.  相似文献   
3.
吉川  徐进 《物理学报》2012,61(23):369-373
系统研究了点缺陷对晶体硅中氧沉淀生成的影响,及点缺陷和氧沉淀对重掺硼直拉硅单晶p/p+外延片中铜沉淀的影响.样品先在不同的气氛下进行1250℃/60 s快速热处理,随后在750℃/8 h+1050℃/16 h常规热处理过程中引入铜沾污.通过腐蚀结合光学显微镜研究发现,以O2作为保护气氛时,p+衬底中的沉淀密度较小,以Ar和N2作为保护气氛时,重掺硼p+衬底中生成了高密度的沉淀,且在上述所有样品的外延层中均无缺陷生成.研究认为,以O2作为保护气时引入的自间隙硅原子(SiI)可以抑制沉淀的形成,而以Ar和N2作为保护气氛时引入的空位则会促进沉淀的生成,这是导致此差异的主要原因.另外,研究还发现,p/p+外延结构能很好地吸除硅片中的铜杂质,从而保持了外延层的洁净.  相似文献   
4.
An open-styled dielectric-lined azimuthally periodic circular waveguide (ODLAP-CW) for a millimeter-wave traveling-wave tube (TWT) is proposed, which is a modified form of a dielectric-lined azimuthally periodic circular waveguide (DLAP-CW). The slow-wave characteristics of the open-styled DLAP-CW are studied by using the spatial harmonics method, which includes normalized phase velocity and interaction impedance. The complicated dispersion equations are numerically solved with MATLAB and the results are in good agreement with the simulation results obtained from HFSS. The influence of structural parameters on the RF properties is investigated based on our theory. The numerical results show that the optimal thickness of the metal rod can increase the interaction impedance, with the dielectric constant held fixed. Finally, the slow-wave characteristics and transmission properties of an open-styled structure are compared with those of the DLAP-CW. The results validate that the mode competition is eliminated in the improved structure with only a slight influence on the dispersion characteristics, which may significantly improve the stability of an open-styled DLAP-CW-based TWT, and the interaction efficiency is also improved.  相似文献   
5.
信曦  徐进  傅志中 《应用声学》2014,22(10):3285-32873296
为解决在不同光照环境下车牌的适应性定位问题,同时解决基于颜色定位的方法普遍存在的车身颜色与车牌颜色相近,以至于难以区分的问题,分析了不同光照下的车牌图像在HSV空间的分布特性与图像亮度等参数关系,结合车牌的混色分布特点、RGB与HSV空间变量转换关系,提出了一种可直接对RGB空间进行处理、能适应光照环境的快速车牌定位算法;实验结果表明,提出的定位算法对光照不足、环境光不均匀等复杂条件下获取的蓝白车牌图像具有很高的定位可靠性。  相似文献   
6.
In this paper, the synchronization of the fractional-order generalized augmented Lu¨ system is investigated. Based on the predictor–corrector method, we obtain phase portraits, bifurcation diagrams, Lyapunov exponent spectra, and Poincare′maps of the fractional-order system and find that a four-wing chaotic attractor exists in the system when the system parameters change within certain ranges. Further, by varying the system parameters, rich dynamical behaviors occur in the2.7-order system. According to the stability theory of a fractional-order linear system, and adopting the linearization by feedback method, we have designed a nonlinear feedback controller in our theoretical analysis to implement the synchronization of the drive system with the response system. In addition, the synchronization is also shown by an electronic circuit implementation for the 2.7-order system. The obtained experiment results accord with the theoretical analyses,which further demonstrate the feasibility and effectiveness of the proposed synchronization scheme.  相似文献   
7.
Wireless quantum communication networks transfer quantum state by teleportation. Existing research focuses on maximal entangled pairs. In this paper, we analyse the distributed wireless quantum communication networks with partially entangled pairs. A quantum routing scheme with multi-hop teleportation is proposed. With the proposed scheme, is not necessary for the quantum path to be consistent with the classical path. The quantum path and its associated classical path are established in a distributed way. Direct multi-hop teleportation is conducted on the selected path to transfer a quantum state from the source to the destination. Based on the feature of multi-hop teleportation using partially entangled pairs, if the node number of the quantum path is even, the destination node will add another teleportation at itself. We simulated the performance of distributed wireless quantum communication networks with a partially entangled state. The probability of transferring the quantum state successfully is statistically analyzed. Our work shows that multi-hop teleportation on distributed wireless quantum networks with partially entangled pairs is feasible,  相似文献   
8.
为研究Pd/Au纳米结构制备和电催化性能、控制粒子大小组分和自旋,用油浴热分解方法制备了核/壳纳米结构Pd/Au双金属合金纳米颗粒,采用PVP和多元醇作表面活性剂和稳定剂,依据溶液浓度、颗粒大小、吸附能控制晶相获得了均匀、一致的2层和3层Pd/Au纳米样品,并采用HAADF和HRTEM测试了纳米结构尺寸形貌,用EDS测试了成分分布,试验产物用TEM/XRD进行了表征,结果表明,Pd/Au具有面心立方八面体结构,与Au/Pd核壳不同,纳米Pd/Au具有活性、耐久性、电催化性和稳定性。  相似文献   
9.
一种基于信息理论的高动态范围图像评价方法   总被引:1,自引:0,他引:1  
高动态范围图像(high dynamic range image)指的是扩大了景物可分辨的光照范围的图像。在HDRI成像中动态范围是难以量化测量的,必须将对动态范围的计算转化为其它易于计算的像质评价函数。HDRI图像的像质评价和普通图像的像质评价存在着较大不同。比较了几种像质评价的方法后,提出了利用图像的熵作为标准进行高动态范围成像评价的方法。利用一种自然图像的概率模型对图像的熵与成像动态范围之间的关系进行了数值模拟,得到了具有普遍意义上的理想成像动态范围的计算公式,公式指出了对自然景物完善成像所需的最大动态范围;给出了图像熵与动态范围之间的关系。利用这种关系可以经由计算图像的熵来对系统的动态范围特性做出评价。这种评价方法在指导高动态范围成像系统的设计,以及高动态范围成像系统的测试中将发挥重要的作用。  相似文献   
10.
The transmissions of oxygen ions through Al2O3 nanocapillaries each 50 nm in diameter and 10 μm in length at a series of different tilt angles are measured,where the ions with energies ranging from 10 to 60 keV and charge states from 1 up to 6 are involved.The angular distribution and the transmission yields of transported ions are investigated.Our results indicate both the existence of a guiding effect when ions pass through the capillary and a significant dependence of the ion transmission on the energy and the charge state of the ions.The guiding effects are observed to be enhanced at lower projectile energies and higher charge states.Meanwhile,the results also exhibit that the transmission yields increase as the tilt angle decreases at a given energy and charge state.  相似文献   
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