Minhyun Kim

We consider the design of a hybrid multiple-input multiple-output (MIMO) processor consisting of a radio frequency (RF) beamformer and a baseband MIMO processor for millimeter-wave communications over multiuser interference channels. Sparse approximation problems are formulated to design hybrid MIMO processors approximating the minimum-mean-square-error transmit/receive processors in MIMO interference channels. They are solved by orthogonal-matching-pursuit-based algorithms that successively sel

Abstract We study robust regularity estimates for local minimizers of nonlocal functionals with non-standard growth of ( p , q )-type and for weak solutions to a related class of nonlocal equations. The main results of this paper are local boundedness and Hölder continuity of minimizers and weak solutions. Our approach is based on the study of corresponding De Giorgi classes.

Abstract We prove a full Harnack inequality for local minimizers, as well as weak solutions to nonlocal problems with non-standard growth. The main auxiliary results are local boundedness and a weak Harnack inequality for functions in a corresponding De Giorgi class. This paper builds upon a recent work on regularity estimates for such nonlocal problems by the same authors.

Abstract We study robust regularity estimates for a class of nonlinear integro-differential operators with anisotropic and singular kernels. In this paper, we prove a Sobolev-type inequality, a weak Harnack inequality, and a local Hölder estimate.

In this paper, we propose hybrid beamforming scheme for multi-user transmission in millimeter wave (mmWave) communications. The sum rate maximization problem considering limited feedback is formulated and solved by the joint scheduling and hybrid beamforming algorithm with two-stage channel state information (CSI) feedback framework. In the proposed scheme, the base station (BS) first narrows down the possible radio frequency (RF) beamforming vectors based on channel quality feedback and schedul

Perovskite oxides are promising candidates for chemiresistive-type gas sensors owing to their exceptional thermal and chemical stability during solid–gas reactions. However, perovskites suffer from critical issues such as low surface area and poor surface activity, which negatively influence the sensing characteristics. While metal nanoparticles can be incorporated in perovskites to improve their reactivity, the fundamental incompatibility between catalytic metals and perovskite oxides often lea

We consider channel estimation for massive multiple-input multiple-output (MIMO) systems operating in frequency division duplexing (FDD) mode. By exploiting the sparsity of significant propagation paths in massive MIMO channels, we develop a compressed sensing (CS) based channel estimator that can reduce the pilot overhead as compared with the conventional least squares (LS) and minimum mean square error (MMSE) estimators. The proposed scheme is based on the oblique matching pursuit (ObMP), an e

Abstract In this paper, we study local regularity properties of minimizers of nonlocal variational functionals with variable exponents and weak solutions to the corresponding Euler–Lagrange equations. We show that weak solutions are locally bounded when the variable exponent p is only assumed to be continuous and bounded. Furthermore, we prove that bounded weak solutions are locally Hölder continuous under some additional assumptions on p . On the one hand, the class of admissible exponents is a