Abstract. In this paper, we consider an inverse electromagnetic medium scattering problem of reconstructing unknown objects from time-dependent boundary measurements. A novel time-domain direct sampling method is developed for determining the locations of unknown scatterers by using only a single incident source. Notably, our method imposes no restrictions on the waveform of the incident wave. Based on the Fourier–Laplace transform, we first establish the connection between the frequency-domain and the time-domain direct sampling method. Furthermore, we elucidate the mathematical mechanism of the imaging functional through the properties of modified Bessel functions. Theoretical justifications and stability analyses are provided to demonstrate the effectiveness of the proposed method. Finally, several numerical experiments are presented to illustrate the feasibility of our approach.

The reconstruction of multipolar acoustic or electromagnetic sources from their far-field signature plays a crucial role in numerous applications. Most of the existing techniques require dense multi-frequency data at the Nyquist sampling rate. The availability of 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 letter, we propose a novel two-stage strategy for multipolar source reconstruction from sub-sampled sparse data that takes advantage of the sparsity of the sources in the physical domain. The data at the Nyquist sampling rate isrecoveredfrom 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 thefinite rate of innovations(FIR) that is solved using anannihilating filter-based structured Hankel matrix completion approach(ALOHA). For an accurate reconstruction, a Fourier inversion algorithm is used. The suitability of the approach is supported by experiments.

We present the discovery of a novel and intriguing global geometric structure of the (interior) transmission eigenfunctions associated with the Helmholtz system. It is shown in generic scenarios that there always exists a sequence of transmission eigenfunctions with the corresponding eigenvalues going to infinity such that those eigenfunctions are localized around the boundary of the domain. We provide a comprehensive and rigorous justification in the case within the radial geometry, whereas for the nonradial case, we conduct extensive numerical experiments to quantitatively verify the localizing behaviors. The discovery provides a new perspective on wave localization. As significant applications, we develop a novel inverse scattering scheme that can produce super-resolution imaging effects and propose a method of generating the so-called pseudo surface plasmon resonant (PSPR) modes with a potential sensing application.

As a key feature of the next generation wireless networks (5G), heterogeneous networks (HetNets) architecture is embraced as the fundamental network technology to meet the immensely diverse service requirements and characteristics of various devices. By introducing underlaying device-to-device (D2D) communication into HetNets, it is possible to offload the unevenly distributed load from the overloaded macrocell to the uncongested femtocell in multitier HetNets. However, the performance of load balancing (LB) scheme heavily depends on the D2D relay selection method as well as the potential resource reuse interference brought by underlay D2D relaying. In order to improve resources utilization ratio and mitigate the resource reuse interference, an LB strategy based on D2D relaying is proposed. To accommodate more new users into the already overloaded macrocell, the macro user equipment with poor link quality will be first transferred into nearby uncongested femtocells by D2D relaying. Then, the released macrocell resource can be allocated to new users who cannot access femtocell due to location restriction. Furthermore, we also propose a two-stage relay selection and resource allocation scheme which not only minimizes the potential interference caused by resource reuse but also guarantees the transmission requirement of different users. Extensive simulation results demonstrate that by taking advantage of D2D relaying, the proposed LB algorithm can effectively adjust the unbalanced load between macrocell and femtocells, which achieves improved performance of the whole HetNets.

We herein try to schedule multiple AGVs (Automated Guided Vehicles) in real time with two-phase strategy in the flexible manufacturing workshops. This study considers the impact of running time, vehicle stopping and turning of AGVs, and deals with static workshop scheduling, real-time workshop scheduling with time-window based micro genetic algorithm. And we present a two-stage scheduling strategy for offline shortest path library generation and online optimal scheduling scheme generation. The preliminary experimental results showed the efficiency and stability of the proposed strategy and algorithm for Multiple AGVs system.