Robust separation of topological in-plane and out-of-plane waves in a phononic crystal

Valley degree of freedom, associated with the valley topological phase, has propelled the advancement of the elastic waveguide by offering immunity to backscattering against bending and weak perturbations. Despite many attempts to manipulate the wave path and working frequency of the waveguide, internal characteristic of an elastic wave such as rich polarization has not yet been utilized with valley topological phases. Here, we introduce the rich polarization into the valley degree of freedom, to achieve topologically protected in-plane and out-of-plane mode separation of an elastic wave. Accidental degeneracy proves its real worth of decoupling the in-plane and out-of-plane polarized valley Hall phases. We further demonstrate independent and simultaneous control of in-plane and out-of-plane waves, with intact topological protection. The presenting procedure for designing the topologically protected wave separation based on accidental degeneracy will widen the valley topological physics in view of both generation mechanism and application areas.

High resolution bolt pre-load looseness monitoring using coda wave interferometry

This paper proposes a new concept, named the Detectable Resolution of Bolt Pre-load (DRBP), by using the coda wave interferometry (CWI) to quantitatively measure the pre-load looseness at a high resolution. Due to its characteristics of roughness, irregularity, and randomly distributed asperities, the contact surface of the bolted components can function as a natural interferometer to scatter the propagation waves. The multiply-scattered coda waves can amplify the slight changes in the travel path and show the visible perturbation in the time domain. By calculating the time-shifted correlation coefficient of coda waves before and after the slight pre-load looseness, the tiny pre-load changes can be clearly revealed. To evaluate the feasibility of the proposed method, a theoretical model considering the time shifts of coda waves and the variations of pre-load is established. Based on the acoustoelastic effect and the wave path summation theory of coda wave interferometry, the model shows that the time shifts of coda waves change linearly with the variations of pre-load. Verification experiments are conducted, and the results show that the R-square values of the fitting curves are larger than 0.9216. In addition, the proposed approach has the feature of high resolution. The ultimate pre-load resolution of the proposed approach is 0.331%, that is, when the variation of pre-load is larger than 0.331%, it can be detected. Therefore, theoretical analysis and experimental results prove that the CWI-based pre-load detection approach holds great potential for the detection of bolt pre-load looseness, especially during the initial stage.

An uplink power optimization solution for satellite HUBs station based on closed-loop control algorithm

In this paper, we present a power optimization solution based on the automatic power control method using a closed-loop algorithm for the uplink power control device (UPC) of the satellite communication HUB station. The results are evaluated by theoretical analysis and validated by simulation model on Matlab software, finally the model has also been used in the UPC device and tested in practice. The simulation process, and the test is carried out under the impact of varying rainfall on the wave path, the results are compared with the solutions that have been and are being used to demonstrate the effectiveness of the solution. This paper is the research product of the project "Researching, designing and manufacturing the uplink power controller military satellite communication system".

Determination of adjusted range corrections measured by electro-optical systems

Electromagnetic radiation used to determine ranges passes through media with different characteristics that affect the electromagnetic waves propagation speed and, accordingly, the accuracy of distance determination. The problem of the radio signal delay due to the influence of the atmosphere is an urgent problem, the solution of which is currently limited mainly to the calculation of range corrections using various atmospheric models. Depending on the required accuracy, the length of the measured line, the range of zenith distances, the availability of information about the state of the atmosphere, a flat, spherical, ellipsoidal model of atmospheres is used to determine the range corrections. In view of the fact that the parameters of the atmosphere characterizing its state along the electromagnetic wave path at the time of measurement, as a rule, are unknown, it becomes necessary to apply one or another hypothesis about the distribution of atmospheric parameters with height. In this paper, we propose a solution to the problem of determining corrections to the measured ranges from the known parameters of the atmosphere only at the initial and final points of the electromagnetic waves’ trajectory.

An efficient AIM for the scattering computation of the finite sparse array

Based on the traditional adaptive integral method(AIM), a fast method called array AIM is proposed to accelerate the scattering calculation of the finite periodic array and the sparse array. On one hand, this method could eliminate the idle grids through the utilization of 5-level block-Toeplitz matrix. Furthermore, the procedure of near correction is eliminated by applying the zeros shielding technique. On the other hand, the block Jacobi preconditioning technique is used to improve the iterative convergence, and the technique of wave path difference compensation is applied to accelerate the post-processing. The numerical results show that the proposed method not only possesses good accuracy, but also has much less cost both in time and memory, in comparison with the traditional AIM. Moreover, this method could be applied to solve the scattering problems for the finite periodic array, as well as the sparse array.

A Low-Profile and Beam-tilted Continuous Transverse Stub Array Antenna at W-band

This paper presents a low-profile, high gain, beam-tilted continuous transverse stub (CTS) array antenna at W-band. The antenna compromises 32 radiating slots and is fed by a parallel plate waveguide (PPW) network with a linear source generator. To deflect the outgoing beam, the principle of linear array scanning is adopted to design inverted T-type structure in each stub to introduce wave path difference. PPW network allows the antenna to obtain lower profile compared to other transmission lines. The design procedure, and the antenna characterization are described. The main beam of the antenna is titled 12 degree in H-plane. The simulation and measured results show that this antenna achieves peak gain of 32.4 dB and a 12 degree beam tilt angle at 99GHz. S11 parameters of the antenna is less than -10 dB in a broadband from 96 GHz to 103 GHz. This antenna has an advantage of miniaturization over other high-gain antenna solutions. The promising performance of this proposed CTS antenna reveals the possible candidate for Millimeter wave (MMW) telecommunication applications.

Acoustic Logging Methods in Fractured and Porous Formations

Formation fractures have significance effect on the permeability of rocks in oil and gas reservoirs. In real conditions, the opening of vertical fractures exceeds the opening of horizontal fractures and the permeability ofreservoirs in conditions of horizontal wells is higher than in vertical conditions. In the sonic log longitudinal waves, unlike the transverse waves, the attenuation rate strongly depends on the wave path direction. It is shown that themechanism of the attenuation of sound waves in porous rocks is represented by the scattering of "soft" microheterogeneousinclusions. For reservoir rocks with porosity (φ) of (10-20)%, the attenuation decrement is several times higher than the decrement of the other mechanisms.