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The reconstruction of multipolar acoustic or electromagnetic sources from their far-field radiation patterns plays a crucial role in numerous practical applications. Most of the existing techniques for source reconstruction require dense multi-frequency data at the Nyquist sampling rate. Accessibility of only sparse data at a sub-sampled grid contributes to the null space of the inverse source-to-data operator, which causes significant imaging artifacts. For this purpose, additional knowledge about the source or regularization is required. In this article, we propose a novel two-stage strategy for multipolar source reconstruction from the sub-sampled sparse data that takes advantage of the sparsity of the sources in the physical domain. The data at the Nyquist sampling rate is recovered from sub-sampled data and then a conventional inversion algorithm is used to reconstruct sources. The data recovery problem is linked to a spectrum recovery problem for the signal with the finite rate of innovations (FIR) that is solved using an annihilating filter-based structured Hankel matrix completion approach (ALOHA). For an accurate reconstruction of multipolar sources, we employ a Fourier inversion algorithm. The suitability of the suggested approach for both noisy and noise-free measurements is supported by numerical evidence., 13 pages, 4 figures

This paper is devoted to a novel quantitative imaging scheme of identifying impenetrable obstacles in time-harmonic acoustic scattering from the associated far-field data. The proposed method consists of two phases. In the first phase, we determine the interior eigenvalues of the underlying unknown obstacle from the far-field data via the indicating behaviour of the linear sampling method. Then we further determine the associated interior eigenfunctions by solving a constrained optimization problem, again only involving the far-field data. In the second phase, we propose a novel iteration scheme of Newton's type to identify the boundary surface of the obstacle. By using the interior eigenfunctions determined in the first phase, we can avoid computing any direct scattering problem at each Newton's iteration. The proposed method is particularly valuable for recovering a sound-hard obstacle, where the Newton's formula involves the geometric quantities of the unknown boundary surface in a natural way. We provide rigorous theoretical justifications of the proposed method. Numerical experiments in both 2D and 3D are conducted, which confirm the promising features of the proposed imaging scheme. In particular, it can produce quantitative reconstructions of high accuracy in a very efficient manner., 19 pages

To make up for the defects of semanteme expression about linked data, this paper proposes a semanteme expressing method of associated entities based on relationship diagram so as to realize the machine expression and recognition of associated semanteme in relational databases. Starting with the structure and relationship of relational schema, this paper analyzes the rich semanteme of associated entities and presents the semanteme parsing method based on the traversal path as well as its formal expression; the analysis of instance database is also carried out. Studies show that this method can comprehensively parse and express the associated semanteme of entities. This work has reference significance for the research of intelligent semanteme synthesis and for semanteme-oriented intelligent query.

Aiming at the problem that the existing DC motor control and speed measurement cannot meet the needs of complex application scenarios, DC motor control scheme based on DSP TMS320VC5509A is proposed. The fixed frequency width modulation method is adopted to control the motor armature voltage to realize speed regulation. Experimental results show that the entire control system has high stability and accuracy, and can achieve stable regulation of the motor rotor speed.

This paper is concerned with the inverse electromagnetic scattering problem for anisotropic media. We use the interior resonant modes to develop an inverse scattering scheme for imaging the scatterer. The whole procedure consists of three phases. First, we determine the interior Maxwell transmission eigenvalues of the scatterer from a family of far-field data by the mechanism of the linear sampling method. Next, we determine the corresponding transmission eigenfunctions by solving a constrained optimization problem. Finally, based on both global and local geometric properties of the transmission eigenfunctions, we design an imaging functional which can be used to determine the shape of the medium scatterer. We provide rigorous theoretical basis for our method. Numerical experiments verify the effectiveness, better accuracy and super-resolution results of the proposed scheme., Comment: 22 pages

Transmission eigenfunctions are certain interior resonant modes that are of central importance to the wave scattering theory. In this paper, we present the discovery of novel global rigidity properties of the transmission eigenfunctions associated with the Maxwell system. It is shown that the transmission eigenfunctions carry the geometrical and topological information of the underlying domain. We present both analytical and numerical results of these intriguing rigidity properties. As an interesting application, we propose an illusion scheme of artificially generating a mirage image of any given optical object.

The analysis and interpretation of the Dachaidan area, Qaidam Basin, is difficult, owing to the co-location of two groups of thrust faults (N–E faults and N–W faults) there and the area’s complicated structural deformation history. To address this problem, field geological investigation, seismic study, well logging, and drilling data were used to identify the key fault systems and their distribution patterns through the area. By integrating surface and subsurface structural features and seismic and non-seismic data, we carried out studies using structural modeling and analysis of the Dachaidan area. Study results identified two systems of thrust faults (N–W faults and W–E faults). We found that these faults could be categorized into three systems: a basin-margin thrust system, an intro-basin thrust system, and an intro-basin compression and strike-slip fault system. These systems showed different features in different areas and zones. We also constructed interpretation models of different deformation mechanisms in the basin and on basin margins. Three tectonic systems (compression, extension, and strike-slip) were identified, which were further divided into eight structural domains. We also established structure coexistence and distribution patterns. The overall structural character of the area was summarized as the northern and southern parts belonging to different zones, with the western and eastern parts belonging to different systems. By analyzing the SW–NE tectonic evolution sections, we defined the back-propagation structural evolution sequences of thrust nappes (on the basin margin or in the basin) and back-thrust structures (in the basin) as well as their influence on the residual Mesozoic strata.

This paper is concerned with the elastic near cloaking for the Lam\'e system in three-dimensions using the notion of elastic scattering coefficients (ESC). Accordingly, the ESC of arbitrary three-dimensional objects are designed and some of their properties are discussed using elements of the elastic layer potential theory. Then, near-cloaking structures, coined as ESC-vanishing-structures, are constructed for the elastic cloaking at a fixed frequency or a band of frequencies. These multi-layered structures are designed so that their first few significant ESC vanish ahead of transformation-elastodynamics. The invisibility effect is achieved as the arbitrary elastic object inside the cloak has a near-zero scattering cross-section for a band of frequencies. The cloaking effect for the Lam\'e system is significantly enhanced by the proposed near-cloaking structures., Comment: 41 pages, 4 figures

We consider the inverse source problem of determining an acoustic source from multi-frequency phaseless far-field data. By supplementing some reference point sources to the inverse source model, we develop a novel strategy for recovering the phase information of far-field data. This reference source technique leads to an easy-to-implement phase retrieval formula. Mathematically, the stability of the phase retrieval approach is rigorously justified. Then we employ the Fourier method to deal with the multi-frequency inverse source problem with recovered phase information. Finally, some two and three dimensional numerical results are presented to demonstrate the viability and effectiveness of the proposed method.

The fatigue properties of 2024 aluminum alloy under the influence of TWIST on the aviation load spectrum were studied. The aircraft load spectrum was simplified, and the fatigue life of the aircraft was predicted by theoretical analysis, MATLAB program simulation and fatigue was test, and the failure mechanism was observed. The results show that the predicted values of fatigue life are 163800, 158280 and 134249 respectively. Aircraft cruise loads during actual gust load spectrum is simulated, the minimal fluctuation spectrum is ignored. The flight cycles are 92314 and 92321 times respectively. Crack initiation nucleation is originated in the test piece near the surface. Fatigue crack is propagated between intergranular and transcrystalline rupture. Instantaneous, rupture zone and crack propagation can be observed.

Based on the transformations of SJ-MSD (modified-signed digit) addition and the principle of SJ-MSD adder, the application of SJ-MSD adder of TOC to mean value filtering (ternary optical computer) is introduced. The realization of mean filtering processing is presented by reconfiguring SJ-MSD adders on TOP (ternary optical processor) in detail. Experiments show that the mean filter processing in TOC can be carried out successfully with a multiple of SJ-MSD parallel adders with large number of data bits. It also shows a great promise and advantages for the application of TOC in digital image processing and other respects.

By reuse the resource of existing cellular users, D2D (Device-to-Device) communication underlaying cellular network can improve the spectrum utilization rate and reduce the power consumption of mobile terminals. However, it will also bring interference to the existing cellular network. How to effectively restrain the interference caused by resource reuse has become the most important factor that affects the performance of multi-cell networks. In order to ensure the quality of service of D2D users and cellular users, this paper studies the power control and resource allocation scheme for D2D communication underlaying cellular communications. Specifically, based on multi-cell cellular network architecture, fractional frequency reuse is introduced to achieve resource partitioning and resource reuse between cellular users and D2D users. Based on the principle of maximizing the throughput of the whole system, the optimization objective is then established. Combined with the fractional power control and with the introduction of interference limits, we use the Lagrangian dual decomposition to solve the optimization objectives, and propose a dynamic power control strategy. Simulation results show that compared with the existing algorithms, the proposed scheme improves the performance of the overall system.

With the ever increasing number of user terminals and fast-growing demands for local service, D2D (Device-to-Device) relay communication technology is becoming essential to the next generation mobile networks, where an efficient relay selection scheme not only improves the system performance but also conserves energy consumption. Aiming at encouraging relay node to voluntarily forward data and regarding with relay node selection issue, this paper proposes an improved social-aware relay selection strategy. In particular, we introduce the concept of social threshold which is based on the knowledge of social relationship among mobile users. Then by exploiting optimal stopping theory, we further propose an optimal relay selection strategy on the basis of social threshold method. Simulation results indicate that the proposed algorithm is effective in reducing the number of probing times of candidate relays and improving the throughput gain of the system, which strikes a balance between energy consumption and system utility.

This paper is concerned with the mathematical design of a novel input/instruction device using a moving emitter. The emitter generates a point source and can be installed on a digit pen or worn on the finger of the human being who wants to interact/communicate with the computer. The input/instruction can be recognized by identifying the motion trajectory of the emitter performed by the human being from the collected wave field data. The identification process is modelled as an in- verse source problem where one intends to identify the trajectory of a moving point source. There are several salient features of our study which distinguish our result from the existing ones in the literature. First, the point source is moving in an inhomogeneous background medium, which models the human body. Second, the dynamical wave field data are collected in a limited aperture. Third, the recon- struction method is independent of the background medium, and it is totally direct without any matrix inversion. Hence, it is efficient and robust with respect to the measurement noise. Both theoretical justifications and computational experiments are presented to verify our novel findings., Comment: 20 pages, 7 figures