A Generalized Framework on Beamformer Design and CSI Acquisition for Single-Carrier Massive MIMO Systems in Millimeter Wave Channels

In this paper, we establish a general framework on the reduced dimensional channel state information (CSI) estimation and pre-beamformer design for frequency-selective massive multiple-input multiple-output MIMO systems employing single-carrier (SC) modulation in time division duplex (TDD) mode by exploiting the joint angle-delay domain channel sparsity in millimeter (mm) wave frequencies. First, based on a generic subspace projection taking the joint angle-delay power profile and user-grouping into account, the reduced rank minimum mean square error (RR-MMSE) instantaneous CSI estimator is derived for spatially correlated wideband MIMO channels. Second, the statistical pre-beamformer design is considered for frequency-selective SC massive MIMO channels. We examine the dimension reduction problem and subspace (beamspace) construction on which the RR-MMSE estimation can be realized as accurately as possible. Finally, a spatio-temporal domain correlator type reduced rank channel estimator, as an approximation of the RR-MMSE estimate, is obtained by carrying out least square (LS) estimation in a proper reduced dimensional beamspace. It is observed that the proposed techniques show remarkable robustness to the pilot interference (or contamination) with a significant reduction in pilot overhead

Beamspace Aware Adaptive Channel Estimation for Single-Carrier Time-varying Massive MIMO Channels

In this paper, the problem of sequential beam construction and adaptive channel estimation based on reduced rank (RR) Kalman filtering for frequency-selective massive multiple-input multiple-output (MIMO) systems employing single-carrier (SC) in time division duplex (TDD) mode are considered. In two-stage beamforming, a new algorithm for statistical pre-beamformer design is proposed for spatially correlated time-varying wideband MIMO channels under the assumption that the channel is a stationary Gauss-Markov random process. The proposed algorithm yields a nearly optimal pre-beamformer whose beam pattern is designed sequentially with low complexity by taking the user-grouping into account, and exploiting the properties of Kalman filtering and associated prediction error covariance matrices. The resulting design, based on the second order statistical properties of the channel, generates beamspace on which the RR Kalman estimator can be realized as accurately as possible. It is observed that the adaptive channel estimation technique together with the proposed sequential beamspace construction shows remarkable robustness to the pilot interference. This comes with significant reduction in both pilot overhead and dimension of the pre-beamformer lowering both hardware complexity and power consumption.Comment: 7 pages, 3 figures, accepted by IEEE ICC 2017 Wireless Communications Symposiu

Visual Feature Attribution using Wasserstein GANs

Attributing the pixels of an input image to a certain category is an important and well-studied problem in computer vision, with applications ranging from weakly supervised localisation to understanding hidden effects in the data. In recent years, approaches based on interpreting a previously trained neural network classifier have become the de facto state-of-the-art and are commonly used on medical as well as natural image datasets. In this paper, we discuss a limitation of these approaches which may lead to only a subset of the category specific features being detected. To address this problem we develop a novel feature attribution technique based on Wasserstein Generative Adversarial Networks (WGAN), which does not suffer from this limitation. We show that our proposed method performs substantially better than the state-of-the-art for visual attribution on a synthetic dataset and on real 3D neuroimaging data from patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). For AD patients the method produces compellingly realistic disease effect maps which are very close to the observed effects.Comment: Accepted to CVPR 201

Quantum Spin Lenses in Atomic Arrays

We propose and discuss `quantum spin lenses', where quantum states of delocalized spin excitations in an atomic medium are `focused' in space in a coherent quantum process down to (essentially) single atoms. These can be employed to create controlled interactions in a quantum light-matter interface, where photonic qubits stored in an atomic ensemble are mapped to a quantum register represented by single atoms. We propose Hamiltonians for quantum spin lenses as inhomogeneous spin models on lattices, which can be realized with Rydberg atoms in 1D, 2D and 3D, and with strings of trapped ions. We discuss both linear and non-linear quantum spin lenses: in a non-linear lens, repulsive spin-spin interactions lead to focusing dynamics conditional to the number of spin excitations. This allows the mapping of quantum superpositions of delocalized spin excitations to superpositions of spatial spin patterns, which can be addressed by light fields and manipulated. Finally, we propose multifocal quantum spin lenses as a way to generate and distribute entanglement between distant atoms in an atomic lattice array.Comment: 13 pages, 9 figure

Generating Employment For Turkey: Policy Alternatives In Comparison With Selected Countries

The main purpose of this paper is to provide some lessons for Turkey from the experiences of some selected countries that gained success in their fight against unemployment. In this respect, the experiences of selected countries; Ireland, Netherlands, United Kingdom and South Korea will be analyzed and the policy options for Turkey will be formed up. It is expected that the detailed analysis and comparison of the reforms in labor markets of these countries will put forward essential and applicable results. It is also supposed that our results will greatly contribute to the decrease in the unemployment level in Turkey, when applied. By doing so, this paper endeavors to get some meaningful policy findings for Turkey. In addition, it is believed that the comparison of the labor markets of these countries, the economic structures and labor markets of which are fairly different from each other will result in interesting findings

Precision of maxillo-mandibular registration with intraoral scanners in vitro

Purpose: To compare the precision of maxillo-mandibular registration and resulting full arch occlusion produced by three intraoral scanners in vitro. Methods: Six dental models (groups A–F) were scanned five times with intraoral scanners (CEREC, TRIOS, PLANMECA), producing both full arch and two buccal maxillo-mandibular scans. Total surface area of contact points (defined as regions within 0.1 mm and all mesh penetrations) was measured, and the distances between four pairs of key points were compared, each two in the posterior and anterior. Results: Total surface area of contact points varied significantly among scanners across all groups. CEREC produced the smallest contact surface areas (5.7–25.3 mm2), while PLANMECA tended to produce the largest areas in each group (22.2–60.2 mm2). Precision of scanners, as measured by the 95% CI range, varied from 0.1–0.9 mm for posterior key points. For anterior key points the 95% CI range was smaller, particularly when multiple posterior teeth were still present (0.04–0.42 mm). With progressive loss of posterior units (groups D–F), differences in the anterior occlusion among scanners became significant in five out of six groups (D–F left canines and D, F right canines, p < 0.05). Conclusions: Maxillo-mandibular registrations from three intraoral scanners created significantly different surface areas of occlusal contact. Posterior occlusions revealed lower precision for all scanners than anterior. CEREC tended towards incorrect posterior open bites, whilst TRIOS was most consistent in reproducing occluding units

The structure of vortical flow over a rounded broad-crested weir

Turbulent flow over a rounded broad-crested weir is investigated by means of detached eddy simulation (DES) and large eddy simulation (LES) with special emphasis on the interaction of coherent vortex structures with free-surface. In order to set up and validate the computational model, experimental studies were conducted in a laboratory flume using a moderately rounded broad-crested weir with a rounding ratio of R/P=0.15, where R is the radius of the upstream nose and P is the height of the weir. The simulated mean velocity, Reynolds stresses and free-surface profiles show good agreement with the experimental measurements. Spatial variation of the boundary layer on the crest is well captured using a dimensionless form of the Lamb vector divergence. Boundary layer shape factor calculated over the weir was found to be lie between 0.76 and 0.92. A horseshoe vortex system emanating from the bottom of the channel interacts with the free-surface at the entrance of the crest causing undulation on the free-surface. Unsteady characteristics of the flow are examined in terms of the power spectral density (PSD) of vortex-induced forces acting on the weir. It is found that a free-surface boundary layer develops from the undulation to the wall boundary layer on the crest. It was revealed from the simulations for various Reynolds numbers that the installation of an artificial pool upstream of the weir significantly modified vortex structures and reduced undulation effects by 86% according to a proposed undulation index.Comment: 30 pages, 20 figures and 4 table