Uplink sum capacity evaluation of multi-user distributed antenna systems

This letter focuses on the simplified sum capacity evaluation for the uplink of a generalized multi-user distributed antenna system (DAS). Based on system scale-up, we derive a good approximation of the sum capacity by generalizing the results from random matrix theory. An iterative method is presented to calculate the unknown parameters in the approximation. The approximation is illustrated to be quite accurate and the iterative method is demonstrated to be quite efficient by Monte Carlo simulations.     

Improved performance of deep-blue polymer light-emitting diodes by one-step coating self-assembly hole injection/transport nanocomposites with both the optical and electrical optimization

In this study we demonstrate an easy solution-processed highly efficient deep-blue polymer light-emitting diode (PLED) via a simple one-step coating of self-assembly hole injection/transport nanocomposites to achieve both a finer hole ohmic contact and an increased light outcoupling, which is the first time report about both the optical and electrical optimization without necessitating changes in the design or structure of the wide bandgap deep-blue PLEDs themselves. The contact angle and surface energy measurement results demonstrate that triazine-based hole injection molecules can vertically migrate towards the bottom PEDOT:PSS layer to obtain a stable minimum of free energy, resulting in an optimal top-to-bottom HOMO energy level arrangement and an improved hole mobility in deep-blue PLEDs. The random surface nanostructure was formed on top of the hole bilayer, leading to the enhancement of light outcoupling verified by transmittance, transmittance haze and light extraction efficiency. Furthermore, in order to explore the reasons of the hole light scattering formation process, a transient drying monitoring technique is applied to track the drying process of the nanostructure films, revealing this approach effectiveness by easily modifying mixing ratios for obtaining different light outcoupling abilities.     

A novel strategy for rapid fabrication of continuous carbon fiber reinforced (TiZrHfNbTa)C high-entropy ceramic composites: High-entropy alloy in-situ reactive melt infiltration

For the first time, dense continuous carbon fiber (C_f) reinforced (TiZrHfNbTa)C high-entropy ceramic (C_f/HEC) composites were rapidly prepared via in-situ reactive melt infiltration (RMI). A TiZrHfNbTa high-entropy alloy served as the cation source and carbon in C_f reinforced carbon matrix (C_f/C) preforms served as the anion source, and a (TiZrHfNbTa)C high-entropy ceramic phase with a near equimolar ratio was successfully formed. The results revealed that most of the TiZrHfNbTa high-entropy alloy reacted with the carbon matrix, and the harvested C_f/HEC composites exhibited an excellent bending strength (612.6 MPa) and low ablation rates. High reaction rates caused by ultra-high temperature and homogeneous distribution of elements in the high-entropy TiZrHfNbTa alloy significantly reduced the difference in reactivity with C among Ti, Zr, Hf, Nb, and Ta are considered to be the reasons for successful formation of (TiZrHfNbTa)C high-entropy ceramic with a near equimolar ratio in C_f/HEC composites.     

Opportunistic channel selection approach under collision probability constraint in cognitive radio systems

In this work, we consider a cognitive radio system with multiple primary channels and one secondary user, and then we introduce a channel-usage pattern model and some basic concepts in this system. Based on this system model and the basic concepts, we propose two opportunistic channel selection algorithms to optimize the throughput of the secondary user: minimum collision rate channel selection algorithm and minimum handoff rate channel selection algorithm. According to the two algorithms, we, respectively, present the channel selection scheme based on minimum collision rate algorithm (CSS-MCRA) and the channel selection scheme based on minimum handoff rate algorithm (CSS-MHRA) under the constraint that the collision probability is bounded below collision tolerable level. Theoretical analysis and simulation results both show that, on one hand, both CSS-MCRA scheme and CSS-MHRA can follow the constraint of collision tolerable level; on the other hand, the performance of CSS-MCRA scheme is better than that of CSS-MHRA scheme if handoff latency is zero or very low, while the performance of CSS-MHRA scheme is better than that of CSS-MCRA scheme if handoff latency is long enough.     

Estimation of the epipole using optical flow at antipodal points

We present algorithms for estimating the epipole or direction of translation of a moving camera. We use constraints arising from two points that are antipodal on the image sphere in order to decouple rotation from translation. One pair of antipodal points constrains the epipole to lie on a plane, and two such pairs will correspondingly give two planes. The intersection of these two planes is an estimate of the epipole. This means we require image motion measurements at two pairs of antipodal points to obtain an estimate. Two classes of algorithms are possible and we present two simple yet extremely robust algorithms representative of each class. These are shown to have comparable accuracy with the state of the art when tested in simulation under noise and with real image sequences.     

Cloud service provisioning in two types of DCN with awareness of delay and link failure probability

Cloud service based on data center network (DCN) has become an attractive choice for various applications. Traditionally, multiple DCs are distributed at different nodes across a given optical network, and users access DCs through predefined routes (this architecture is named as Multiple Independent DCN, MI-DCN). However, as there exist transmission delay and failure probability on each link, such a network may not be a good choice for the service providers from the perspective of service reliability and cost. Therefore, we propose the idea of regrouping all the racks and distributing each rack group on a special node, where there exists a gateway (this architecture is named as Integrated Distributed DCN, ID-DCN). As each group can provide service independently, by properly grouping and routing, the whole network can work more efficiently with lower cost and higher reliability. In this paper, we study the service provision in the above two types of DCN. With the given failure probability and transmission delay on each link, we aim to minimize the total service cost and design the access routes for the demands originated from each node. To integrate the system cost, we introduce two cost scaling factors for delay and failure probability, which can be flexibly adjusted to control their relative importance (i.e., the weights). Based on mathematical approximation, a novel method is proposed to compute the failure probabilities of individual service paths. This translates our objective function into a linear expression. Then, we formulate two integer linear programs (ILP) to compare the solutions of the two scenarios. Via extensive numerical experiments, the performance of the two schemes is properly verified.     

Computed force and velocity control for spatial multi-DOF electro-hydraulic parallel manipulator

A novel dynamic trajectory tracking controller for spatial 6-DOF electro-hydraulic parallel manipulator considering system nonlinearity-computed force and velocity controller is proposed, with a view of improving the control performance with high computational efficiency of control algorithm. The dynamic model of electro-hydraulic parallel manipulator, both mechanical and hydraulic system, is described by using Kane and hydromechanics method. The requisite system states are estimated via forward kinematics based upon global Newton–Raphson with monotonic descent algorithms under the measured actuator position. The desired leg position and velocity required for the proposed controller are calculated by an analytical method corresponding to the desired generalized pose, and the desired driven force is computed with an effectively simplified inverse dynamics. Under feed-forward of the desired driven force and velocity, the computed force and velocity controller is developed with actual leg position as its feedback only, and the desired leg position, velocity and driven force as its input. The control performance of the proposed controller for multi-DOF parallel manipulator is evaluated in theory and experiment, especially for dynamic tracking performance. Experimental results show that the presented controller can greatly improve the dynamic trajectory tracking performance for high real time electro-hydraulic parallel manipulator.     

A key points-based blind watermarking approach for vector geo-spatial data

This paper presents a blind watermarking approach to protecting vector geo-spatial data from illegal use. By taking into account usability, invisibility, robustness, and blindness, the approach firstly determines three feature layers of the geo-spatial data and selects the key points from each layer as watermark embedding positions. Then it shuffles the watermark and embeds it in the least significant bits (LSBs) of the coordinates of the key points. A similar process for selecting the feature layers and the key points in the watermark embedding process is carried out to detect the watermark followed by obtaining the embedded watermark from the LSBs of the coordinates of the key points. Finally, the similarity degrees of three versions of the watermark from three feature layers are calculated to check if the data contains the watermark. Our experiments show that the method is rarely affected by data format change, random noise, similarity transformation of the data, and data editing.