共查询到20条相似文献,搜索用时 62 毫秒
1.
尖轨在其周期性载荷作用下易发生断裂,引发列车事故。为对尖轨缺陷进行检测,文章基于磁致伸缩效应研制了导波检测系统,研究导波在尖轨中的传播特性、导波对尖轨附属件的检测能力以及缺陷的识别能力。采用ABAQUS/Explicit有限元方法研究了不同频率导波在尖轨中的传播特性。所研发的磁致伸缩导波检测系统在尖轨上的检测是可行有效的。使用导波检测系统在尖轨底面激励的水平剪切导波在基本轨和尖轨上可传播的有效距离至少为12 m,在空轨中至少能传播16 m。而且低频导波主要沿轨底传播,高频导波主要沿轨腰和轨头传播,多频导波结合能更加准确地对尖轨的检(监)测。 相似文献
2.
S. V. Loginov 《Technical Physics Letters》2003,29(6):447-449
A new approach to determining characteristics of a microsecond plasma opening switch at the moment of current interruption
is proposed. Dependences of the switch voltage and resistance on the current and geometric parameters are presented, and the
calculated values of the resistance are compared to the experimental data. 相似文献
3.
Terahertz wave switch based on silicon photonic crystals 总被引:5,自引:0,他引:5
A compact and integrated terahertz (THz) wave photonic crystal switch is proposed in silicon. The switch operates based on a dynamic shift of the photonic bandgap by using an external applied electric field. The plane wave expansion method and the finite-difference time-domain method are used to verify and analyze the characteristics of the proposed THz wave switch. Numerical simulation results show that the THz wave switch has a high extinction ratio of 29.9 dB. 相似文献
4.
Attard AE 《Applied optics》2003,42(15):2665-2673
In the present study, the bandwidth of a photonic switch described previously [Appl. Opt. 37,2296 (1998); 38, 3239 (1999)] is evaluated. First the optical bandwidth is evaluated for coupling between two fiber-core waveguides, in which the cores are embedded within the same cladding. Then the coupling bandwidth is determined for a fiber-core-to-slab-core waveguide, in which the cores are embedded within the same cladding. These bandwidths are then compared and contrasted with the bandwidths of the photonic switch, which consists of two fiber cores and a control waveguide. Two configurations of the photonic switch are considered: one in which the control waveguide is a fiber core and one in which the control waveguide is a slab core. For the photonic switch, the bandwidth characteristics are more complicated than for the coupled pairs, and these characteristics are discussed in detail. 相似文献
5.
《IEEE transactions on instrumentation and measurement》1977,26(2):105-109
This paper discusses characteristics and applications of an analog switch based upon the back-to-back connection of two light-emitter/phototransistor assemblies, with an original method of zeroing the offset voltage. The resulting device is thoroughly analyzed, and it is shown how this solid-state switch is comparable in accuracy with electromechanical relays, but it has much higher repetition-rate capabilities. Two applications are then introduced, namely an analog commutator and a low-level multiplexer, where the performances of the switch find their best exploitation. 相似文献
6.
The characteristics of a double teeth-shaped plasmonic optical switch are analyzed. Based on the metal–insulator–metal waveguide consisting of double rectangular teeth, a nanoscale liquid crystal optical switch is proposed and numerically simulated by using the finite difference time domain method with a perfectly matched layer absorbing boundary condition. It is found that the double teeth-shaped structure filled with liquid crystal can realize the function of a switch. The modulation depth of the double teeth-shaped structure is larger than 50?dB. 相似文献
7.
The author describes some advances in opening switch technology and their demonstration in the megampere advanced switch technology (MAST) hardware. After describing the MAST concept, he examines the efficiency, weight, and life characteristics of the switch. He concludes that the MAST switch demonstrates the feasibility of large-bore rapid-fire railgun systems based on inductive energy storage 相似文献
8.
A replicate/transfer switch compatible with the gap tolerant structure has been developed. The switch characteristics are superior to that of the existing switches both at the the 8-μm and 16-μm periods. The switch offers the advantages of good bias and phase margins, ease of fabrication, and reduced drive field requirements. In the 8-μm version the device requires a substantially lower drive field than the pickax design by virtue of reduced bubble-bubble interaction in the minor loops. 相似文献
9.
The chopper voltage regulators using a diode and an LC filter for output rectification and filtering are widely used in dc-to-dc conversion. Three possible configurations are 1) a series connection of the filter choke and switch with the load, 2) a series connection of the choke and the parallel connection of the switch with the load, and 3) a series connection of a chopper and the parallel connection of a choke with the load. Static characteristics of the regulators vary considerably among the aforementioned circuits. The output-to-input voltage ratios and the output characteristics of the circuits listed above are defined in the continuous and discontinuous current domains. An estimate and a comparison of the regulator performances are given. 相似文献
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论述了气隙式热开关的原理,结构形式及参数特性,讨论了它的结构尺寸对性能参数的影响。给出了导热管的直径,长度,壁厚与导通热导之间的关系曲线以及气体压强,外壳厚度与关断热导之间的关系曲线。建立了气隙式热开关的数学模型,求出了导通热流的瞬态响应特性,并给出了特性曲线有压力调节系统图。 相似文献
13.
A new control scheme of Class-E inverter for induction heating jar applications with clamped voltage characteristics using pulse frequency modulation (PFM) is introduced. To reduce the voltage stress of a switch, the proposed PFM control scheme does not need any auxiliary circuit. It can decrease the voltage stress of a switch through the modulation of switching frequency. The Class-E inverter using the proposed control scheme has the advantages of not only the same output power when it is compared with an active clamped class-E (ACCE) inverter, but also zero-voltage-switching, which are characteristics of conventional Class-E and ACCE inverter. The control principles of the proposed method are explained in detail and its validity is verified through experimental results 相似文献
14.
Xining Xu Chaoming Su Zujun Yu Hongmei Shi Liqiang Zhu Wen Gao 《Advanced Engineering Materials》2023,25(20):2300125
An approach to detect switch rail defect based on ultrasonic guided wave technology is studied. Eight typical cross-sections are chosen from the switch rail, and each cross-section's theoretical dispersion curves and wave structures are derived using the semianalytical finite-element method. The dispersion curve of eight sections has 262 modes at 60 kHz. Based on k-means clustering analysis algorithm, 25 kinds of classification results are obtained from 262 modes. According to the mean and variance of energy, an optimal set of modes with uniform amplitude over the entire section of the switch rail is selected. The optimal excitation point is determined based on the vibration energy. The defect echo signal is obtained by excitation of these guided wave modes. Field experiment results show that by comparing the sum of the differences between the collected and basic data and setting a certain threshold, the internal defect detection of the switch guide rail can be realized. The research results herein are valuable for analyzing the dispersion characteristics and realizing the nondestructive testing of the variable cross-section waveguide. 相似文献
15.
基于KB0系列产品的结构,以其动态数学模型为理论基础,设计一套基于单片机和高速图像处理技术的新型控制与保护开关动态测试系统。该系统可测试保护开关的铁芯及触头的位移,并在空载条件下验证了位移测试的准确性。开展了新型控制与保护开关闭合过程的动态特性研究,在不同的线圈工作电压、工作频率和合闸相角工况下,分别测试开关的闭合动作时间。研究了新型控制与保护开关闭合过程产生的触头弹跳现象,分析了一次弹跳和二次弹跳产生的原因,探究其与铁芯和触头闭合末速度的内在联系机理;通过试验结果的数据统计与图表分析,综合考虑动作时间、触头弹跳、铁芯末速度和触头末速度等特性参数,得出最佳合闸相角在30°左右。 相似文献
16.
A new concept for a highway switch, which can be used to connect different optical wavelength division multiplexing data highways for data exchange, is proposed and the system relevant properties are outlined. For the required add-drop filter elements we used ring resonators. Typical characteristics of channel bandwidth, channel spacing, free spectral range, amplification, and cross-talk behavior of a highway switch with double-cavity ring resonators are basically examined and to some extent compared with solutions that were obtained with standard single-ring resonators. A signal flow chart transformation for evaluating filter transfer functions is presented. 相似文献
17.
Effect of spectral correlations on spectral switches in the diffraction of partially coherent light 总被引:1,自引:0,他引:1
Pu J Nemoto S Lü B 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(10):1933-1939
The subject is the spectral characteristics of partially coherent light whose spectral degree of coherence satisfies or violates the scaling law in diffraction by a circular aperture. Three kinds of spectral correlations of the incident light are considered. It is shown that no matter whether the partially coherent light satisfies or violates the scaling law, a spectral switch defined as a rapid transition of spectral shifts is always found in the diffraction field. Different spectral correlations of the incident field in the aperture result in different points at which the spectral switch occurs. With an increment in the correlations, the position at which the spectral switch takes place moves toward the point at which the phase of the center frequency component omega0 becomes singular for illumination by spatially fully coherent light. For light that satisfies the scaling law, the spectral switch is attributed to the diffraction-induced spectral changes; for partially coherent light that violates the scaling law, the spectral switch is attributed to both the diffraction-induced spectral changes and the correlation-induced spectral changes. 相似文献
18.
Updesh Sharma Shankar Dutta 《Journal of Materials Science: Materials in Electronics》2014,25(12):5546-5551
This paper discussed about the effect of using high-k materials on scattering parameters of RFMEMS shunt switch. The effect of variation of dielectric constant (k: 3–70) of the dielectric layer of thickness 0.16 µm was studied first. In the upstate, no noticeable change is observed in insertion loss and return loss due to the variation of dielectric constants. In the down-state, both the isolation and return loss are found to be strongly dependent on the dielectric constants of the dielectric layer. Resonant frequency of the switch is decreasing exponentially with the increasing dielectric constant. In order to get resonant frequency of 35 GHz, optimum dielectric layer thicknesses for each dielectric constant are found by parametric analysis of the switch structure. With the optimum dielectric layer thicknesses, all the isolation and return loss behavior are found to be almost identical. However, now the up-state characteristics of the switch are found to be affected. Thus for Ka band applications, the insulating layer with dielectric constant 20–30, with corresponding layer thickness 0.4–0.6 μm, may be suitable for the RFMEMS switch applications. This will lead to return loss 8 dB, with insertion loss 1 dB in the upstate and return loss 1 db with isolation of ?50 dB at 35 GHz in the down state. Therefore, for the RFMEMS switch, one needs to select the dielectric layer in such a way that it makes a balance between all the scattering parameters. 相似文献
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Low-power all-optical switching with pharaonis phoborhodopsin (ppR) protein is demonstrated based on nonlinear excited-state absorption at different wavelengths. A modulating pulsed 532-nm laser beam is shown to switch the transmission of a continuous-wave signal light beam at: 1) 390 nm; 2) 500 nm; 3) 560 nm; and 4) 600 nm, respectively. Simulations based on the rate equation approach considering all seven states in the ppR photocycle are in good agreement with experimental results. It is shown that the switching characteristics at 560 and 600 nm, respectively, can exhibit negative to positive switching. The switching characteristics at 500 nm can be inverted by increasing the signal beam intensity. The profile of switched signal beam is also sensitive to the modulating pulse frequency and signal beam intensity and wavelength. The switching characteristics are also shown to be sensitive to the lifetimes of$mmb pbf pR_bf M$ and$mmb pbf pR_bf O$ intermediates. The results show the applicability of ppR as a low-power wavelength tunable all-optical switch. 相似文献