Performance evaluation of power system stabilizers based on Population-Based Incremental Learning (PBIL) algorithm

This paper proposes a method of optimally tuning the parameters of power system stabilizers (PSSs) for a multi-machine power system using Population-Based Incremental Learning (PBIL). PBIL is a technique that combines aspects of GAs and competitive learning-based on Artificial Neural Network. The main features of PBIL are that it is simple, transparent, and robust with respect to problem representation. PBIL has no crossover operator, but works with a probability vector (PV). The probability vector is used to create better individuals through learning. Simulation results based on small and large disturbances show that overall, PBIL-PSS gives better performances than GA-PSS over the range of operating conditions considered.     

Hybrid sol gel coating: A solution to prevent interactions between plasticized poly(vinyl chloride) and injectable drugs?

During the infusion of drugs with medical devices in plasticized poly(vinyl chloride) (PVC) release of plasticizers in the injectable solution and/or sorption of drugs on PVC may occur. Thus, patient safety and/or effectiveness of his therapy may be altered. In this study, we assessed the efficiency of a sol gel hybrid coating in preventing plasticizers' release (di‐(2‐ethylhexyl) phthalate (DEHP)) from PVC matrix and drug sorption into PVC. Remaining concentrations of drugs and plasticizer's concentration released after migration tests were assessed by liquid chromatography. Migration processes were followed by Fourier Transform Infrared – Attenuated Total Reflectance (FTIR‐ATR) spectroscopy and PVC surface changes were characterized by scanning electron microscopy (SEM). An evaluation of the mechanical properties of both uncoated and coated polymer was done. The hybrid coating protects PVC from plasticizers leaching. Sorption of drugs tested is also limited. However, the protection against plasticized PVC interactions isn't optimal, probably due to a degradation of the layer, as shown on SEM microphotographs. Furthermore improvements might provide an efficient barrier to advert risks impaired to PVC interactions, to provide patient care safety. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40145.     

Overview of Concentrated Solar Power

CSP （concentrated solar power） has been viewed as the technology that if properly developed could lead to a large scale conversion of solar energy into electricity. CSP is a type of solar energy converter that is classified as thermal converter because the output power produced is a function of the operating temperature. The main components of a CSP plant are the solar field which is made up of the heliostat arrays, the receiver tower, the heat transfer fluid, the molten salt thermal energy storage tanks and the power conversion unit, which is made up of the turbine and the generator. The main advantage of CSP is that of a cheap thermal storage （i.e., molten salt storage） which makes it possible to dispatch power at a cost comparable to the grid electricity. Simulations run with the SAM （systems advisory model） developed by NREL （National Renewable Energy Laboratory） showed that CSP is capable of delivering electricity at the cost of 17UScents per kWh for the 30-year life of the plant. The main disadvantage of CSP however, is that of low efficiency （8%-16%）. There are ongoing research works to improve the efficiency of the CSP. One way to improve the efficiency is to increase the operating temperature of the system. In this paper, the authors discussed different modules of the CSP plant and suggested ways to improve on the conversion efficiencies of individual modules. Finally, an overall systems performance simulation is carried using SAM and the simulation results show that electricity can be produced using CSP at the cost of RI.05 per kWh.     

Vibration modeling of large repetitive sandwich structures with viscoelastic core

A double scale asymptotic method (DSAM) is proposed for vibration modeling of large repetitive sandwich structures with a viscoelastic core. The method decomposes the initial nonlinear vibration problem into two small linear ones. The first one is defined on few basic cells while the second is a differential global amplitude equation with complex coefficients. Their numerical computations permit determination of the damping properties as well as pass and stop bands avoiding the direct computation on the whole structure. Viscoelastic frequency dependent core with fractional and anelastic displacement field models are considered. The resulting nonclassical problems are solved by asymptotic numerical method coupled with automatic differentiation. Based on the presented method, a large reduction of the needed computational time and memory is obtained. The accuracy and efficiency of the proposed method are validated with comparisons to the direct simulations by discretization of the whole structure using asymptotic numerical method coupled with automatic differentiation.     

Characterization of particleboards of African mahogany sawdust made with tannic powders of Bridelia and African locust bean pods

European Journal of Wood and Wood Products - The purpose of this study was to valorize African mahogany wood, especially its residues (sawdust) from carpentry, in the manufacturing of...     

Design of H∞-PSS using numerator-denominatoruncertainty representation

This paper presents a new method of designing a robust H_∞-PSS to deal with some limitations of the existing H _∞-PSSs (standard H_∞-PSSs). These limitations include: (i) the inability to treat the system uncertainty when a stable nominal plant becomes an unstable perturbed plant; and (ii) the cancellation of the plant's poorly damped poles by the controller's zeros. The proposed multiple inputs single output controller for the excitation system is based on the “numerator-denominator” uncertainty representation which is not restricted in the modeling of uncertainty as compared to the standard additive or multiplicative uncertainty representation. Furthermore, the bilinear transformation has been used in the design to prevent the pole-zero cancellation of the poorly damped poles and to improve the control system performance. Simulation results have shown satisfactory performance of the proposed PSS for a wide range of operating conditions and good stability margin as compared to both the conventional PSS and the standard H_∞-PSS