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In order to solve the problems of low precision and long time of traditional transmission line fault region localization method, this paper proposes a transmission line fault region localization method based on wide area synchronous measurement technology. Set up a wide area synchronous measurement system and use the system to collect transmission line information. Based on the collected information, the transmission line state description matrix is constructed, and the diagonal elements in the state description matrix are modified according to the measurement points. After the modification, all the information is integrated to obtain the location results of the fault area. Experimental results show that the accuracy of fault location of transmission line is always maintained above 93%, and the average time of location is 0.46s, the practical application effect is good.

When using the artificial method to monitor the state of the transmission line grounding resistance, there will be the problem that the test time is too long to monitor the fault point in time. This paper proposes the method of the transmission line grounding resistance monitoring and fault state identification based on neural network. Using neural network, the fault points in the line decomposition section are determined, and the ground resistance is monitored in real time on the basis of the fault points. Analysis of the experimental results shows that the monitoring errors of the method in this paper are less than 0.1Ω, while the monitoring errors of the three pole phase method and clamp meter method in the resistance results are more than 1Ω, and the monitoring errors of clamp meter method are even as high as 6Ω at one time. Therefore, through the experimental comparison, we can know that the method in this paper is accurate in monitoring the grounding state of transmission lines, and can be used for online monitoring of tower grounding state.

Physical properties of J-carbon, J-silicon, and J-germanium (space group: P2/m) were studied by density functional theory calculations. J-germanium was found to be dynamically, mechanically and thermodynamically stable under ambient pressure. The bulk modulus B and the shear modulus G of J-germanium are 55 ​GPa and 41 ​GPa, respectively, slightly greater than those of P42/mnm Ge, hP12 Ge and oC12 Ge. J-carbon, J-silicon, and J-germanium exhibit a larger anisotropy in Young's modulus than do carbon, silicon, and germanium in the diamond phase and also exhibit larger anisotropy in bulk modulus and shear modulus than do the corresponding diamond phase allotropes. J-germanium is a quasi-direct band gap semiconductor material with the band gap of 0.943 ​eV that may be a candidate material for use in photovoltaic devices. The band gap and the minimum thermal conductivity κmin of J-carbon are both greater than those of diamond, and therefore, J-carbon may be a promising candidate material for deep ultraviolet photodetection.

Accommodation and convergence play critical roles in the natural process of depth perception, and the field of natural three-dimensional (3D) perception in stereo displays has been extensively explored. However, no prototypes of these natural 3D displays are suitable for wear due to the system size and weight. In addition, few of the researches have involved subjects with ametropia. We propose and develop an optical see-through head-mounted display (HMD) capable of diopter adjustment of both the virtual image and the real world scene. The prototype demonstrates a diagonal field of view (FOV) of 42o and an exit pupil diameter of 9 mm, and a diopter adjustment range of -5.5D to 0D. Depth adjustment of virtual image is demonstrated with experiments, the results show the HMD can be further used to investigate the accommodation and convergence cues in depth perception in AR environment, particularly for users with different degree of the ametropia.

The most common modulation transfer function (MTF) measurement equipment operates along a coaxial testing light path. It can be used to test several fields along one radial direction and is suitable for an optical system with rotational symmetry. However, off-axis optical systems need multidimensional adjustment and complex mechanical structures to measure the MTF of fields. In this paper, we propose a MTF testing module to address this issue by adding a rotatable mirror to redirect the light. The testing module greatly simplifies MTF measurement of off-axis imaging systems in both the process and mechanism. The figure error of the rotatable mirror is analyzed to ensure testing accuracy. MTF testing of a free-form surface prism using this novel method was successfully implemented and the results are presented. The method can be extended to the measurement of other parameters, such as the effective focal length.

It is difficult to design and fabricate a head-up display (HUD) with a large asymmetric field of view (FOV) while maintaining a good image quality. In this paper, we design and develop such a holographic HUD system. To improve luminance and enhance the environmental adaptability of the HUD, we use a liquid crystal display with high brightness as well as a holographic reflection element. The vertical FOV is tilted to an angle of −7°, which is consistent with the actual view of the pilot. The decentration and tilt of the optical relay system effectively compensate for the distortion and off-axis aberration due to the asymmetric FOV and tilted, curved combiner. The transition plates used in the mechanical structure significantly decrease the difficulty in fabrication and alignment, and virtual prototyping greatly reduces the risk and shortens the development cycle. Experimental results demonstrate that this prototype achieves a total FOV of 30° (horizontal) ×24° (vertical), a resolution of 1280×1024, and a 5% distortion.