Linear Pre-coding in MIMO–CDMA Relay Networks

Our aim in this paper is to define a novel beamforming approach in wireless multiple-input-multiple-output (MIMO) code-division-multiple-access (CDMA) relay networks, which involves communication between multiple source-destination pairs. It is assumed that full channel state information of source-relay and relay-destination channels are available. Our design consists of a two-step amplify-and-forward protocol. The first step includes signal transmission from the sources to the MIMO relay, and the second step contains transmitting a version of the linear precoded signal to the destinations. Beamforming is investigated only in MIMO-relay node to reduce end user’s hardware complexity and save the computational power. Accordingly, the optimization problem is defined to find the MIMO relay beamforming coefficients that minimize total relay transmit power by keeping the signal-to-interference-plus-noise ratio (SINR) of all destinations above a certain threshold value. It is shown that such optimization problem is a non-convex quadratically constrained quadratic programming, which is NP-hard in general. However, by relaxing this problem to a semi-definite programming problem, the problem can be solved efficiently. Simulation results verify the performance gain implied by MIMO–CDMA relay system compared to the non-CDMA coded system.     

Surface Runoff from Full-Scale Coal Combustion Product Pavements during Accelerated Loading

In this study, the release of metals and metalloids from full-scale portland cement concrete pavements containing coal combustion products (CCPs) was evaluated by laboratory leaching tests and accelerated loading of full-scale pavement sections under well-controlled conditions. An equivalent of 20 years of highway traffic loading was simulated at the OSU/OU Accelerated Pavement Load Facility (APLF). Three types of portland cement concrete driving surface layers were tested, including a control section [i.e., ordinary portland cement (PC) concrete] containing no fly ash and two sections in which fly ash was substituted for a fraction of the cement; i.e., 30% fly ash (FA30) and 50% fly ash (FA50). In general, the concentrations of minor and trace elements were higher in the toxicity characteristic leaching procedure (TCLP) leachates than in the leachates obtained from synthetic precipitation leaching procedure and ASTM leaching procedures. Importantly, none of the leachate concentrations exceeded the TCLP limits or primary drinking water standards. Surface runoff monitoring results showed the highest release rates of inorganic elements from the FA50 concrete pavement, whereas there were little differences in release rates between PC and FA30 concretes. The release of elements generally decreased with increasing pavement loading. Except for Cr, elements were released as particulates (>0.45?μm) rather than dissolved constituents. The incorporation of fly ash in the PC cement concrete pavements examined in this study resulted in little or no deleterious environmental impact from the leaching of inorganic elements over the lifetime of the pavement system.     

COMPUTATION OF BOUNDARY LAYER TRANSITION USING LOW-REYNOLDS-NUMBER TURBULENCE MODELS

A literature review shows that, for the commonly used turbulence models, the predicted location of boundary layer transition is very sensitive to the initial profiles of turbulence quantities and starting location of calculation. To eliminate these effects, two independent solution approaches are proposed: (1) to solve the boundary layer equations over a flat plate with the starting location of calculation very close to the leading edge of the plate, and (2) to solve the elliptic Navier-Stokes equations over the whole plate, including the leading edge and some region upstream of it. Computations show both approaches lead to identical results. Three well-known low-Reynolds-number (LRN) turbulence models are evaluated with respect to the transition on a flat plate. None of the models are able to predict the quantitative aspects of transition correctly without an ad hoc adjustment. A satisfactory new turbulence model is presented in a companion paper.     

Motion control of a magnetically levitated microrobot using magnetic flux measurement

Recent advancements in micro/nano domain technologies have led to a renewed interest in ultra-high resolution magnetic-based actuation mechanisms. This paper deals with the development of a novel research-made magnetic microrobotic station (MMS) with promising potential in biological/biomedical applications. The MMS consists of two separate basic components: a magnetic drive unit and a microrobot. The magnetic drive unit produces and regulates the magnetic field for non-contact propelling of the microrobot in an enclosed environment. Our previous research findings have reported that the MMS should be equipped with high accuracy laser sensors for the position determination of the microrobot in the workspace. However, the laser positioning techniques can be used only in highly transparent environments. This paper seeks to address microrobot position estimation in non-transparent environments. A novel technique based on real-time magnetic flux measurement has been proposed for position estimation of the microrobot in the case of the laser beam blockage. A combination of Hall-effect sensors is employed in the structure of the magnetic drive unit to find the microrobot’s position using the produced magnetic flux. The most effective installation position for the Hall-effect sensors has been determined based on the accuracy sensitivity of experimental measurements. We derived a mathematical function which relates Hall-effect sensors’ voltage output and the position of the microrobot. The motion control capability of the Hall-effect-based positioning method is experimentally verified in the horizontal axis, and it was demonstrated that the microrobot can be operated in most of the workspace range with an accuracy of 0.3?mm as the root-mean-square of the position error.     

Malicious inter-frame video tampering detection in MPEG videos using time and spatial domain analysis of quantization effects

In this paper, a new algorithm is proposed for forgery detection in MPEG videos using spatial and time domain analysis of quantization effect on DCT coefficients of I and residual errors of P frames. The proposed algorithm consists of three modules, including double compression detection, malicious tampering detection and decision fusion. Double compression detection module employs spatial domain analysis using first significant digit distribution of DCT coefficients in I frames to detect single and double compressed videos using an SVM classifier. Double compression does not necessarily imply the existence of malignant tampering in the video. Therefore, malicious tampering detection module utilizes time domain analysis of quantization effect on residual errors of P frames to identify malicious inter-frame forgery comprising frame insertion or deletion. Finally, decision fusion module is used to classify input videos into three categories, including single compressed videos, double compressed videos without malicious tampering and double compressed videos with malicious tampering. The experimental results and the comparison of the results of the proposed method with those of other methods show the efficiency of the proposed algorithm.     

Brad-OF: An Enhanced Energy-Aware Method for Parent Selection and Congestion Avoidance in RPL Protocol

The Internet of Things networks comprise a large number of resource-limited nodes, which often use multi-hop communications to transfer packets to the gateway. Thus, finding the proper forwarding path and managing limited resources have always been important. In this paper, the aim is to improve the approach of selecting the parent nodes to extend the network lifetime and also prevent congestion in nodes’ queues to prohibit network excessive traffic load. We address these issues in two ways. First, a linear combination equation is used to combine three crucial network metrics: ETX, delay, and node residual energy. Second, the “Node’s Traffic Intensity” metric is used to detect and prevent congestion in nodes’ queues. Results showed that by choosing appropriate nodes with higher battery-level for the paths toward the gateway and by avoiding numerous retransmissions, the nodes’ energy and network lifetime increased up to about 65%. Furthermore, by preventing congestion and queue overflow in network nodes, the amount of packet-loss decreased up to 81%. Also, through decreasing packet retransmissions and consequently increasing the number of original packets, the total number of sent original packets was improved. The proposed method is implemented and simulated by the NS-2.

     

A Worst-Case Robust Combination Method of Beam-Forming and Orthogonal Space–Time Block Coding

In this paper, a new robust multi-input multi-output system is proposed in a perturbed wireless channel which is to model imperfect channel information at the source side when beam-forming and orthogonal space–time block coding is utilized. The channel perturbation is bounded by a predefined variation based on worst-case robust design. Beam-forming is used to improve the performance of the system expressed by the upper bound of pairwise error probability of symbols. In this paper firstly, the maximum value of pairwise error probability is obtained in a closed form when channel perturbation is kept below a threshold. Then the beam-forming matrix is designed to minimize the pairwise error probability subject to a predefined maximum transmitting power. This approach provides near optimal results due to using the upper bound of pairwise error probability. It shows good performance based on the symbol error rate criterion compared with other existing methods of the multiple input multiple output system.     

A loss aware scalable topology for photonic on chip interconnection networks

The demand for robust computation systems has led to the increment of the number of processing cores in current chips. As the number of processing cores increases, current electrical communication means can introduce serious challenges in system performance due to the restrictions in power consumption and communication bandwidth. Contemporary progresses in silicon nano-photonic technology have provided a suitable platform for constructing photonic communication links as an alternative for overcoming such problems. Topology is one of the most significant characteristics of photonic interconnection networks. In this paper, we have introduced a novel topology, aiming to reduce insertion loss in photonic networks; detailed analysis of the proposed topology has also been provided based on synthetic and real application benchmarks using a cycle-accurate simulation environment. Results demonstrate that the proposed topology outperforms other considered topologies in terms of physical-layer parameters, such as insertion loss, and provides better scalability. Moreover, such improvement in physical-layer parameters has caused system performance parameters to improve significantly. For instance, the topology yields an improvement of at least 406 % in bandwidth, compared to the best case, when leveraging synthetic traffic patterns. Furthermore, when using scientific applications, execution time and energy efficiency are improved up to 85 % and 97 %, respectively.     

Microenergy harvesting applications for outdoor power equipment

An energy harvesting system designed in this paper is of electromagnetic linear-motion inertial type that is capable of converting kinetic energy into useful electrical energy. The harvester consists of moving magnet–iron poles enclosed by cylindrical coils and an iron stator, and two stationary magnets are placed at both end sides acting as spring. The developed energy harvester is to be used for outdoor power equipment such as lawnmower and snow blower. Preliminary vibrational analysis is conducted on the lawnmower and snow blower to determine its working frequency and the optimal point of vibration. It was determined that the lawnmower resonated at a frequency of 15 Hz while the snow blower resonated at 21 Hz. Two methods are used to tune the energy harvesting system. The first is changing the stationary magnet thickness while keeping the magnet air gap constant and second is changing the air gap while keeping the stationary magnet thickness constant. We found that it is optimal to change the air gap rather than the magnet thickness to change the natural frequency of the device. The energy harvesting system is tuned to work on a lawnmower where the natural frequency is 15 Hz. Natural frequency of 15 Hz is obtained when the magnet thickness is 9.525 mm and a gap of 70.75 mm, where the maximum power dissipated is 29 mW.