共查询到20条相似文献,搜索用时 15 毫秒
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提出一种新型的内包层横截面边界为螺旋曲线的双包层光纤结构,并给出一种分析双包层光纤吸收效率的新方法:它以射线法为基础,采用概率理论计算出光纤内部传播的光线每次被内包层边界反射后能够被纤芯直接吸收的概率,并以此概率来衡量内包层横截面形状对光纤吸收效率的影响.最后用这种方法对螺旋型双包层光纤进行分析,得出它比一般缺陷型双包层光纤优异的结论. 相似文献
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Stretchable Capacitive Sensors of Torsion,Strain, and Touch Using Double Helix Liquid Metal Fibers 下载免费PDF全文
Christopher B. Cooper Kuralamudhan Arutselvan Ying Liu Daniel Armstrong Yiliang Lin Mohammad Rashed Khan Jan Genzer Michael D. Dickey 《Advanced functional materials》2017,27(20)
Soft and stretchable sensors have the potential to be incorporated into soft robotics and conformal electronics. Liquid metals represent a promising class of materials for creating these sensors because they can undergo large deformations while retaining electrical continuity. Incorporating liquid metal into hollow elastomeric capillaries results in fibers that can integrate with textiles, comply with complex surfaces, and be mass produced at high speeds. Liquid metal is injected into the core of hollow and extremely stretchable elastomeric fibers and the resulting fibers are intertwined into a helix to fabricate capacitive sensors of torsion, strain, and touch. Twisting or elongating the fibers changes the geometry and, thus, the capacitance between the fibers in a predictable way. These sensors offer a simple mechanism to measure torsion up to 800 rad m?1—two orders of magnitude higher than current torsion sensors. These intertwined fibers can also sense strain capacitively. In a complementary embodiment, the fibers are injected with different lengths of liquid metal to create sensors capable of distinguishing touch along the length of a small bundle of fibers via self‐capacitance. The three capacitive‐based modes of sensing described here may enable new sensing applications that employ the unique attributes of stretchable fibers. 相似文献
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《Microwave Theory and Techniques》1969,17(2):66-73
The propagation characteristics of leaky waves in a helix waveguide covered with a slitted cylinder are presented by a method of transverse network representation. The main interest is in helix waveguides with small pitch angles, characterized by a hybrid mode consisting of TE/sub 01/, and a small amount of TM/sub 01/ modes. The leaky wave discussed in this paper may then be regarded as a perturbation of the TM/sub 01/ wave by the slitted cylinder outside the helix. The radiation, metal, and dielectric losses are calculated numerically at a frequency of 50 GHz. The relation between the radiation loss and aperture angle of slit is very different from that of an ordinary leaky waveguide composed of a slitted cylinder without helix, especially when the distance between the helix and shield cylinder is about a quarter of the radial wavelength. The metal and dielectric losses are the same order as radiation loss, however the dielectric loss decreases as the power factor /spl epsiv/"/ /spl epsiv/' increases. The measured total attenuation constant averages about 5 dB/km, almost twice the theoretical value. 相似文献
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《Electron Devices, IEEE Transactions on》1962,9(1):69-75
In this paper the interaction between electron beams and coupled helices is studied and generalized to include the effects of 1) space chargeQC ; 2) finite circuit lossd ; 3) finite values of gain parameterC ; 4) an unrestricted coupling parameterk , and 5) the effect of having a large positive value of the velocity parameterb such that the propagation constants are purely imaginary. A general determinantal equation including all these factors is derived from the coupled-circuit equations and the stream equation. Curves of the propagation constants for a variety of operating parameters are shown. Attention is called to the fact that a region of growing wave is found for large positiveb for extremely tight coupling. The extent to which the "growing-wave island" is affected by the various operating parameters is also illustrated. Equations for the outer and inner helixr-f voltages are derived and from which curves of the propagatingr-f powers along the helices are computed and plotted. Positions for maximum transfer of energy between the helices can be deduced and the extent to which they are affected by the various Parameters is discussed. 相似文献
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介绍了一种小型化的UHF波段对讲机天线的设计方法。在设计过程中,采用ANSOFT公司的电磁仿真软件—HFSS对天线进行了理论求解和仿真计算,并通过理论与实验的方法来研究其性能。实验表明,测试结果与仿真结果吻合较好,并且此天线具有尺寸小、增益高、带宽宽(9.5%)、一致性好、成本低等的特点,可以投入批量生产。 相似文献
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Shunkang Liu 《Journal of Infrared, Millimeter and Terahertz Waves》2000,21(6):915-920
The characteristics of two kinds of bifilar helix circuit are discussed in this paper. One is alike wound bifilar helix and another is contrawound bifilar helix. Alike wound bifilar helix is often used in O-type backward wave tube (BWO). Owing to wider operating bandwidth, higher interaction impedance and large dimensions, the contrawound helix is suitable for broadband millimeter wave traveling wave tube (MMW TWT). 相似文献
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《Microwave Theory and Techniques》1979,27(10):860-863
Considered here is a planar structure comprising a pair of parallel arrays of periodically spaced conducting strips which conduct in different directions in the two arrays. The guiding properties of this planar structure are found to be similar, in one case, to those of circular tape helices. While in general, different dielectric media are assumed in the sandwiched and outer regions, the special cases studied are 1) the case in which air constitutes both the media, 2) the normal-helix case in which the inner medium is a solid dielectric and the outer medium is air, and 3) the "inverted-helix" case with the two media interchanged. 相似文献
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熊伟 《信息技术与信息化》2004,(3):60-61
本文介绍了流媒体的基本概念、Helix Producer的安装、如何使用Helix Producer编码流媒体以及什么是选择听众和编码作业. 相似文献
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A helical antenna with a high degree of polarisation purity for directions near endfire is described. The antenna structure was optimised by numerical analysis of its polarisation properties. Theoretical and experimental results are presented. 相似文献
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Lin Q Wang J Deng Z Ma G Jiang D Wang S Li F 《Applied Superconductivity, IEEE Transactions on》2010,20(1):8-13
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船载海事卫星(INMARSAT)通信天线波束宽度较窄,且在风浪下船体摇晃难以与低仰角处卫星进行通信。提出一种带有开槽巴伦的可调式自相移四臂螺旋天线,避免了馈电网络造成的横向面积过大等问题。天线长振子臂长度可微调,结合调整开槽巴伦上的移动环,可以局部改变天线通信频带。通过基于有限元算法的HFSS仿真和实验,得出该天线具有宽波束特性,3 dB 波瓣宽度约为165°。另外,可以实现左右圆极化互相转换,在较宽的角度下,天线轴比低于6 dB。该天线既可以作为海事卫星通信天线,又可以作为北斗、GPS 导航天线和测浪高所用的左旋圆极化天线。 相似文献
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The scattering of particles is described by multipole moments up to the electric quadrupole contribution. A method for the calculation of reflection and transmission from thin composite layers is derived. The approach uses periodic boundary conditions. The validity of the approach is checked by considering thin chiral layers composed of small metal helices. The investigations are performed in the frequency domain and include the resonance case 相似文献
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《Microwave Theory and Techniques》1983,31(1):73-76
A pair of unidirectionally conducting screens, conducting in different directions, constitute a planar helix. The planar helix is proposed as a slow-wave structure for application in a traveling-wave tube (TWT). Field theory is applied to analyze the behavior of the planar helix in the presence of a flat electron beans present between the two screens. Results indicate the presence of three modes, with one mode having a negative attenuation constant, as in the case of the usual helix-type TWT. Curves are shown for a typical proposed planar TWT. Also, the effect of beam current is indicated. 相似文献