Codebook Based Minimum Subspace Distortion Hybrid Precoding for Millimeter Wave Systems

© 2018 IEEE. Hybrid precoding is adopted for millimeter wave (mmWave) communications to offer a good trade-off between hardware complexity and system performance. In this paper, we investigate a codebook based hybrid precoder for single-user mmWave systems with large antenna arrays. We exploit the sparse nature of mmWave channels to transform the hybrid precoding design problem into a vector space distortion optimization problem which is only related to the radio frequency (RF) precoder. A near optimal solution for the RF optimization problem is derived with the assumption of the perfect channel state information (CSI) at the transmitter, which is practically very difficult to obtain. To reduce the requirement of the CSI at the transmitter, we propose the codebook based minimum subspace distortion (MSD) hybrid precoding algorithm, which obtains CSI at the combiner side and returns the index of optimal RF codewords and the baseband precoder through a limited feedback channel. Simulation results are provided and validate the effectiveness of our proposed hybrid precoding algorithm

On resonant scatterers as a factor limiting carrier mobility in graphene

We show that graphene deposited on a substrate has a non-negligible density of atomic scale defects. This is evidenced by a previously unnoticed D peak in the Raman spectra with intensity of about 1% with respect to the G peak. We evaluated the effect of such impurities on electron transport by mimicking them with hydrogen adsorbates and measuring the induced changes in both mobility and Raman intensity. If the intervalley scatterers responsible for the D peak are monovalent, their concentration is sufficient to account for the limited mobilities achievable in graphene on a substrate.Comment: version 2: several comments are taken into account and refs adde

Temporal and spatial changes of water quality and management strategies of Dianchi Lake in southwest China

Temporal and spatial changes to the water quality of Dianchi Lake in southwest China were investigated using monthly monitoring data from 2005 to 2012. Dianchi Lake is divided into two parts, Caohai Lake and Waihai Lake, by a man-made dike. Caohai Lake lies at the north of Dianchi Lake, while Waihai Lake is the main water body of Dianchi Lake and accounts for 96.7% of the whole area of the lake. Based on the analysis of total phosphorus (TP), total nitrogen (TN), and chlorophyll <i>a</i> (Chl <i>a</i>) concentrations, it was determined that, in Caohai Lake, the annual concentrations of these variables ranged from 0.19–1.46 mg L⁻¹, 6.11–16.79 mg L⁻¹, 0.06–0.14 mg L⁻¹, respectively. In addition, the annual concentrations of TP, TN and Chl <i>a</i> in Waihai Lake ranged between 0.13 and 0.20 mg L⁻¹, 1.82 and 3.01 mg L⁻¹, and 0.04 and 0.09 mg L⁻¹, respectively. Cluster analysis (CA) classified the 10 monitoring sites into two clusters (cluster A and cluster B) based on similarities of water quality characteristics. Our data revealed that the current status of water quality within Caohai Lake was much worse than that of Waihai Lake. Water quality was seriously degraded during the economic boom near the period of the "Eleventh Five-Year Plan" (2005–2010), and gradually improved from 2010 to 2012 because of the "standard emission directive to industry". The main factors that influenced the spatial and temporal changes to water quality were natural factors including lake evolution and regional characteristic as well as human factors such as pollution load into the lake and management strategies that were already adopted. Some activities and regulations were implemented to enhance the lake environment by controlling wastewater emissions and establishing regulations to protect the lakes in the Yunnan Province. However, problems with institutional fragmentation (horizontal and vertical), simple treatment methods, low-intensity investment in pollution control, and lack of meaningful endogenous pollution control strategies were still present in the lake management strategy. To solve these problems, suitable control measures are needed, especially considering the current old-age status of Dianchi Lake. The fundamental improvement of the water quality within Caohai Lake was dependent on the measures taken in the upper reaches of the Caohai Watershed, including further recovery of submerged plants, resource utilization by floating plants and the reinforcement of sediment disposal. Management strategies for endogenous pollution in Waihai Lake were mainly dependent on restocking algae-eating fish and the ecological restoration of macrophytes. In this way, the swamping trend and the ageing process that is occurring in Dianchi Lake can be stunted. And the management strategies would be a contribution to the management of water conflicts between mankind and ecosystems in similar lakes

A new and simple water retention model for root-permeated soils

Vegetation can affect soil hydrology not only through evapotranspiration but also through changes in soil water retention curve (SWRC). Models that are able to predict root-induced change in SWRC are limited. Such models often contain many empirical parameters that are not easy to be obtained and calibrated. This letter proposes a new and simple model with only one root parameter, namely root volume ratio Rv, needed for predicting the SWRC of a root-permeated soil. The new model considers void ratio change through volume reduction of air void of soil due to the presence of roots. The modified void ratio of a root-permeated soil is then fed into a void-ratio-dependent SWRC model to predict any resultant change in SWRC. The performance of this new model is validated against three case studies. Good agreement between measurements and predictions is obtained, with discrepancies of degree of saturation &lt;13% for a given suction. </jats:p

Coherent versus Incoherent Light Scattering from a Quantum Dot

We analyze the light scattered by a single InAs quantum dot interacting with a resonant continuous-wave laser. High resolution spectra reveal clear distinctions between coherent and incoherent scattering, with the laser intensity spanning over four orders of magnitude. We find that the fraction of coherently scattered photons can approach unity under sufficiently weak or detuned excitation, ruling out pure dephasing as a relevant decoherence mechanism. We show how spectral diffusion shapes spectra, correlation functions, and phase-coherence, concealing the ideal radiatively-broadened two-level system described by Mollow.Comment: to appear in PRB 85, 23531

Performance of a Modified Rabbit Model of Abdominal Aortic Aneurysm Induced by Topical Application of Porcine Elastase: 5-Month Follow-up Study

AbstractObjectivesTo modify the method for creating an abdominal aortic aneurysm in rabbits, and to study its performance.Materials and methodsA total of 24 New Zealand white rabbits were induced topically with 10 μl of porcine elastase (0, 0.1, 5 and 10 units μl−1) to define the optimal concentration (groups A–D). Twelve aneurysms were induced with 10 units μl−1 of 10 μl elastase to serve as a follow-up group (group E) to serve as a follow-up. A 1.5-cm aortic segment was isolated and induced with elastase solution for 30 min.ResultsAll animals in groups D and E developed AAA by day 5. Aneurysms in Group E were stable over 100 days. Partial destruction to disappearance of elastic lamellae and smooth muscle cells (SMCs) was seen in elastase-treated animals by day 5. Regenerated elastin and proliferated SMCs were present in group E. Matrix metalloproteinases 2 and 9 and RAM11 showed strong expression in group D, but expression decreased in group E after day 15.ConclusionsThe rabbit AAA model induced via topical application of porcine elastase at 10 units μl−1 for 30 min appears easy and simple, with shorter induction and more rapid aortic dilation. The model is stable over 100 days and is useful to study the formation and progress of AAAs

A Unified Quantum NOT Gate

We study the feasibility of implementing a quantum NOT gate (approximate) when the quantum state lies between two latitudes on the Bloch's sphere and present an analytical formula for the optimized 1-to-$M$ quantum NOT gate. Our result generalizes previous results concerning quantum NOT gate for a quantum state distributed uniformly on the whole Bloch sphere as well as the phase covariant quantum state. We have also shown that such 1-to-$M$ optimized NOT gate can be implemented using a sequential generation scheme via matrix product states (MPS)

Non-minimal coupling of photons and axions

We establish a new self-consistent system of equations accounting for a non-minimal interaction of gravitational, electromagnetic and axion fields. The procedure is based on a non-minimal extension of the standard Einstein-Maxwell-axion action. The general properties of a ten-parameter family of non-minimal linear models are discussed. We apply this theory to the models with pp-wave symmetry and consider propagation of electromagnetic waves non-minimally coupled to the gravitational and axion fields. We focus on exact solutions of electrodynamic equations, which describe quasi-minimal and non-minimal optical activity induced by the axion field. We also discuss empirical constraints on coupling parameters from astrophysical birefringence and polarization rotation observations.Comment: 31 pages, 2 Tables; replaced with the final version published in Classical and Quantum Gravit

Surface energy engineering of graphene

Contact angle goniometry is conducted for epitaxial graphene on SiC. Although only a single layer of epitaxial graphene exists on SiC, the contact angle drastically changes from 69{\deg} on SiC substrates to 92{\deg} with graphene. It is found that there is no thickness dependence of the contact angle from the measurements of single, bi, and multi layer graphene and highly ordered pyrolytic graphite (HOPG). After graphene is treated with oxygen plasma, the level of damage is investigated by Raman spectroscopy and correlation between the level of disorder and wettability is reported. By using low power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices