Two-Phase Bidirectional Dual-Relay Selection Strategy for Wireless Relay Networks

In this article, we introduce a new bi-directional dual-relay selection strategy with its bit error rate (BER) performance analysis. During the first step of the proposed strategy, two relays out of a set of N relay-nodes are selected in a way to optimize the system performance in terms of BER, based on the suggested algorithm which checks if the selected relays using the max-min criterion are the best ones. In the second step, the chosen relay-nodes perform an orthogonal space-time coding scheme using the two-phase relaying protocol to establish a bi-directional communication between the communicating terminals, leading to a significant improvement in the achievable coding and diversity gain. To further improve the overall system performance, the selected relay-nodes apply also a digital network coding scheme. Furthermore, this paper discusses the analytical approximation of the BER performance of the proposed strategy, where we prove that the analytical results match almost perfectly the simulated ones. Finally, our simulation results show that the proposed strategy outperforms the current state-of-the-art ones.     

A comparison of mixed integer programming formulations of the capacitated lot-sizing problem

We propose a novel mixed integer programming formulation for the capacitated lot-sizing problem with set-up times and set-up carryover. We compare our formulation to two earlier formulations, the Classical and Modified formulations, and a more recent formulation due to Suerie and Stadtler. Extensive computational experiments show that our formulation consistently outperforms the Classical and Modified formulations in terms of CPU time and solution quality. It is competitive with the Suerie–Stadtler (S&S) formulation, but outperforms all other formulations on the most challenging instances, those with low-capacity slack and a dense jobs matrix. We show that some of the differences in the performance of these various formulations arise from their different use of binary variables to represent production or set-up states. We also show that the LP relaxation of our Novel formulation provides a tighter lower bound than that of the Modified formulation. Our experiments demonstrate that, while the S&S formulation provides a much tighter LP bound, the Novel formulation is better able to exploit the intelligence of the CPLEX solution engine.     

A simple but sound approach for processing crystal growth kinetic data

The effects of common data smoothing techniques, on the estimating of the kinetic and thermodynamic parameters of the crystal growth process, were discussed in the light of birth and spread model. Adoption of the moving average, and filtration caused a noticeable misunderstanding of the real ruling growth mechanism, especially, during the early period of the crystal growth.In this work, a MATLAB routine was developed with standard, and reliable method to treat the prolonged concentration-time data sets, as obtained from continuous recording of refractometric °Brix readings of pure sucrose solutions in laboratory batch crystallization process. The method consists of finding the median of the residence time for every °Brix concentration, with and without interference of previous and post readings. In addition to 30% reduction in the evaluated interfacial free energies, up to 5-folds of increase in the estimates of the overall kinetic coefficients were reported using the common smoothing techniques instead of the proposed routine.     

Maximum power tracking for photovoltaic power system: Development and experimental comparison of two algorithms

This work presents an experimental comparison of two algorithms developed in order to maximize the output power from a photovoltaic (PV) system for the same given set of conditions. The maximum power point tracking (MPPT) methods proposed in this study are two extended algorithms: Perturb and Observe and Incremental Conductance. The numerical modelling of the PV system shows the MPPT interest and then the extended MPPT algorithms are highlighted. In this paper, a PV system based on a boost converter as MPPT device is considered. A programmable DC electronic load is fed by two identical PV systems in which the MPPT control converter algorithms are different. This experimental platform operates under the same conditions such as changing solar radiation and cell temperature. The experimental results obtained with a dSPACE controller board show the MPPT energy efficiency of the proposed algorithms.     

Is detailed progress monitoring possible without designated manual data collection?

The daily site report (DSR)—a common tool, which contains a lot of valuable data— is normally used for litigation purposes, i.e. claims and dispute resolution. All these valuable data are rarely used for the management and control of the ongoing project. The purpose of the current research is to develop a tool that uses data taken from a computerized DSR to generate monitoring and control information. We have developed a progress monitoring model, which uses data from a computerized DSR to generate information regarding the actual progress and then transfer it to the scheduling software. The model was developed and implemented in a concept proving prototype using Excel and MS Project. The operation and the usefulness of the prototype are demonstrated with a case study, synthetic, project. The results indicate that the DSR is a useful data collection tool for progress monitoring. The cost of the information generated from these data is low because no additional manual operations are required in order to collect the data.     

RF MEMS continuous reversible variable inductor based on a microfluidic network

In this work, RF MEMS continuous reversible variable inductor has been fabricated by using microelectronic technology and lamination process. We review, evaluate and compare this variable inductor with other work. The proposed inductor is a dual circular coil and has an inductance of few nH. The fundamental idea is to place a liquid droplet between the metal turns of a coil in order to modify the capacitive/resistive coupling between metal tracks and hence to change the stored magnetic energy. The SU-8 resin was used to realize the microfluidic channels and Au as metallic tracks. To prove the reversibility of the inductor, two cases were studied: filling and emptying of channels. The tuning range of the inductance is approximately 107 % at 1.6 GHz, making these devices very suitable as building blocks in many RF applications.     

Support Vector Regression control charts for multivariate nonlinear autocorrelated processes

Statistical process control charts are one of the most widely used techniques in industry and laboratories that allow monitoring of systems against faults. To control multivariate processes, most classical charts need to model process structure and assume that variables are linearly and independently distributed. This study proposes to use a nonparametric method named Support Vector Regression to construct several control charts that allow monitoring of multivariate nonlinear autocorrelated processes. Also although most statistical quality control techniques focused on detecting mean shifts, this research investigates detection of different parameter shifts. Based on simulation results, the study shows that, with a controlled robustness, the charts are able to detect the different applied disturbances. Moreover in comparison to Artificial Neural Networks control chart, the proposed charts are especially more effective in detecting faults affecting the process variance.     

Effectiveness of the earth tube heat exchanger system coupled to a space model in achieving thermal comfort in rural areas

The aim of this work is to investigate by modelling the possibility of reducing the operational energy of a typical house without negatively affecting its embodied energy. This is done through consideration of different building materials coupled with the use of an earth to air heat exchanger (EAHE) for fresh air supply and cooling. For known indoor and outdoor conditions and for given building materials (thermal capacity and conductance), a ventilation controller determines the amount of flow rate needed to temperate the indoor air temperature to achieve thermal comfort. Different wall configurations are assumed for each of the living zone and the bedroom zone of the apartment. It is found that the use of an optimal wall configuration in each zone coupled with the EAHE results in 76.7% energy savings compared with the reference case with conventional cooling.     

Contribution to the Fault Diagnosis of a Doubly Fed Induction Generator for a Closed-loop Controlled Wind Turbine System Associated with a Two-level Energy Storage System

—In this article, a contribution to the fault diagnosis of a doubly fed induction generator for a closed-loop controlled wind turbine system associated with a two-level energy storage system using an on-line fault diagnostic technique is proposed. This technique is proposed to detect the rotor fault in the doubly fed induction generator under non-stationary conditions based on the spectral analysis of stator currents of the doubly fed induction generator by an adaptive fast Fourier transform algorithm. Furthermore, to prevent system deterioration, a fractional-order controller with a simple design method is used for the control of the whole wind turbine system. The fractional-order controller ensures that the system is stable in both healthy and faulty conditions. Additionally, to improve the production capacity under wind speed fluctuations and grid demand changes, a two-level energy storage system consisting of a supercapacitor bank and lead-acid batteries is proposed. The obtained simulation results show that the objectives of the fault diagnosis procedure and control strategy are reached.