Effect of boron compounds on fire protection properties of epoxy based intumescent coating

The aim of this study was to investigate the effect of boron compounds on fire protection properties of intumescent coating based on ammonium polyphosphate (APP). Three kinds of boron compounds namely boric acid (BA), zinc borate (ZB) and melamine borate (MB) were used. Total amount of flame retardant additive was kept constant at 30 wt%, and boron compounds were used at three concentrations of 1, 3 and 5 wt%. Thermogravimetric analysis (TGA), Attenuated total reflectance–Fourier transform infrared spectroscopy (ATR‐FTIR) and fire test were conducted for the determining the fire performance of intumescent coating. According to fire test results, BA and MB showed synergistic effect at 1 wt% loading. ZB showed antagonistic effect at all concentrations. Fire protection effect of intumescent coating decreased as the added amount of boron compound increased regardless of boron compound type because of suppression of intumescence. Copyright © 2016 John Wiley & Sons, Ltd.     

Impact of second harmonic injection on the linearity and linear gain of RF/microwave amplifiers

This article reviews the development and applications of harmonic injection technique. It discusses the impact of second harmonic injection on the linearity and linear gain of amplifiers. It reveals that amplifier characteristics and input drive level determine whether second harmonic injection enhances or reduces the linear gain of an amplifier. Furthermore, a method has been developed to predict this behaviour which can be used to identify amplifiers that are best suited to harmonic injection or build amplifiers that may particularly be used with harmonic injection. For experimental investigation, a second harmonic injected amplifier was used that employs a frequency-doubler. In laboratory experiments, third-order intermodulation distortion was suppressed by 18?dB at the expense of 0.7?dB linear gain whereas theoretical analysis has predicted that second harmonic injection could compromise the linear gain of the amplifier by up to 1.3?dB for 20?dB distortion suppression.     

A review: Exergy analysis of PEM and PEM fuel cell based CHP systems

In recent years, growing attention has been given to new alternative energy sources and exergy analysis since fossil fuels cause emissions that have some negative impacts on earth such as global warming, greenhouse effect etc. New power generation systems have been developed in order to reduce or eliminate these impacts as possible. So that, new alternative energy systems have been taken place instead of fossil fuel based systems with nearly zero emission levels. One of them is solid polymer electrolyte or proton exchange membrane (PEM) fuel cell. Although it has significant advantages, there are some disadvantages such as cost, and hydrogen is not a fuel that can be easily obtained. For these reasons, efficiency of a PEM fuel cell has a great significance. Energy efficiency of a system is the most important parameter for utilization. But, energy analysis does not always show the capacity to do work potential of energy of a system. Exergy analysis must be investigated for a system in order to see available work of the system. Because of disadvantages of the PEM fuel cell, exergy analysis has quite importance. In this paper PEM fuel cell and exergy analysis of PEM fuel cell are combined and investigated. A detailed review of the past and recent research activities has been documented. The review focuses on exergy analysis of both PEM fuel cells and PEM based combined heat and power (CHP) systems at different operating parameters. It is concluded that there are a lot of parameters which effects the exergy efficiencies of systems.     

Heat transfer analysis of parabolic trough solar receiver

Solar Parabolic Trough Collectors (PTCs) are currently used for the production of electricity and applications with relatively higher temperatures. A heat transfer fluid circulates through a metal tube (receiver) with an external selective surface that absorbs solar radiation reflected from the mirror surfaces of the PTC. In order to reduce the heat losses, the receiver is covered by an envelope and the enclosure is usually kept under vacuum pressure. The heat transfer and optical analysis of the PTC is essential to optimize and understand its performance under different operating conditions. In this paper a detailed one dimensional numerical heat transfer analysis of a PTC is performed. The receiver and envelope were divided into several segments and mass and energy balance were applied in each segment. Improvements either in the heat transfer correlations or radiative heat transfer analysis are presented as well. The partial differential equations were discretized and the nonlinear algebraic equations were solved simultaneously. Finally, to validate the numerical results, the model was compared with experimental data obtained from Sandia National Laboratory (SNL) and other one dimensional heat transfer models. Our results showed a better agreement with experimental data compared to other models.     

Fluid–structure interaction modeling of ringsail parachutes with disreefing and modified geometric porosity

Fluid?Cstructure interaction (FSI) modeling of parachutes poses a number of computational challenges. These include the lightness of the parachute canopy compared to the air masses involved in the parachute dynamics, in the case of ringsail parachutes the geometric porosity created by the construction of the canopy from ??rings?? and ??sails?? with hundreds of ??ring gaps?? and ??sail slits,?? in the case of parachute clusters the contact between the parachutes, and ??disreefing?? from one stage to another when the parachute is used in multiple stages. The Team for Advanced Flow Simulation and Modeling (T?AFSM) has been successfully addressing these computational challenges with the Stabilized Space?CTime FSI (SSTFSI) technique, which was developed and improved over the years by the T?AFSM and serves as the core numerical technology, and a number of special techniques developed in conjunction with the SSTFSI technique. The quasi-direct and direct coupling techniques developed by the T?AFSM, which are applicable to cases with nonmatching fluid and structure meshes at the interface, yield more robust algorithms for FSI computations where the structure is light. The special technique used in dealing with the geometric complexities of the rings and sails is the homogenized modeling of geometric porosity (HMGP), which was developed and improved in recent years by the T?AFSM. The surface-edge-node contact tracking (SENCT) technique was introduced by the T?AFSM as a contact algorithm where the objective is to prevent the structural surfaces from coming closer than a minimum distance in an FSI computation. The recently-introduced conservative version of the SENCT technique is more robust and is now an essential technology in the parachute cluster computations carried out by the T?AFSM. As an additional computational challenge, the parachute canopy might, by design, have some of its panels and sails removed. In FSI computation of parachutes with such ??modified geometric porosity,?? the flow through the ??windows?? created by the removal of the panels and the wider gaps created by the removal of the sails cannot be accurately modeled with the HMGP and needs to be actually resolved during the FSI computation. In this paper we focus on parachute disreefing, including the disreefing of parachute clusters, and parachutes with modified geometric porosity, including the reefed stages of such parachutes. We describe the additional special techniques we have developed to address the challenges involved and report FSI computations for parachutes and parachute clusters with disreefing and modified geometric porosity.     

Analysis of some fully-discrete algorithms for the one-dimensional heat equation

A fully discrete stability and accuracy analysis of some algorithms for the one-dimensional heat equation is presented. Results illustrate that 2-pass explicit schemes which simultaneously employ lumped and coupled capacity matrices are capable of improved performance over the standard 1-pass explicit scheme.     

Optimal deflection and stacking sequence prediction of curved composite structure using hybrid (FEM and soft computing) technique

Engineering with Computers - The bending deflections and the corresponding optimal fiber angle sequences of the subsequent layers have been predicted in this article using a hybrid technique. The...     

Thermodynamic analysis of a Proton Exchange Membrane fuel cell

In this study, energy and exergy analyses of a 1 kW Horizon H-1000 XP Proton Exchange Membrane (PEM) Fuel Cell has been investigated. A testing apparatus has been established to analyze the system efficiencies based on the first and second laws of thermodynamics. In this mechanism pure hydrogen has been directly used as a fuel in compressed gas formation. Purity of hydrogen was above 99.99%. The system performance was investigated through experimental studies on energy and parametric studies on exergy by changing the operating pressure and operation temperature. The results showed that the energy efficiency of PEM fuel cell is 45.58% for experimental study and 41.27% for parametric study at full load. Also, 2.25% and 4.2% performance improvements were obtained by changing the operating temperature ratio (T/T₀) from 1 to 1.2 and operating pressure ratio (P/P₀) from 1 to 2, respectively.     

Improving the dyeability of poly (lactic acid) fiber using octa (aminophenyl) POSS nanoparticle during melt spinning

Disperse dye structure affects the dyeability of poly (lactic acid) (PLA) fiber due to the low dyeing temperature and the short dyeing time. Thus, the dye uptake value of PLA fiber is low for some disperse dyes and needs to be improved. In this study, the dyeability of PLA fiber is improved with the addition of synthesized octa (aminophenyl) polyhedral oligomeric silsesquioxane (OAP-POSS) nanoparticle during the melt spinning process. The effects of dyeing conditions including dyeing temperature and time, OAP-POSS concentration, disperse dye types, and concentrations are investigated on the dyeability properties of PLA fiber samples. The tensile, thermal, and morphological properties of the fiber samples are also characterized by tensile testing, differential scanning calorimetry, scanning electron microscopy, and transmission electron microscopy. It is concluded that the percent crystallinity and the tensile strength of pure PLA fiber decrease as the added amount of OAP-POSS increases. According to the dyeing results, OAP-POSS, which behaves as a good sorbent for the disperse dyes used in this study, greatly improves the dyeability of PLA fiber, especially for disperse dyes with low dye uptake values.     

Drug/nondrug classification using Support Vector Machines with various feature selection strategies

In conjunction with the advance in computer technology, virtual screening of small molecules has been started to use in drug discovery. Since there are thousands of compounds in early-phase of drug discovery, a fast classification method, which can distinguish between active and inactive molecules, can be used for screening large compound collections. In this study, we used Support Vector Machines (SVM) for this type of classification task. SVM is a powerful classification tool that is becoming increasingly popular in various machine-learning applications. The data sets consist of 631 compounds for training set and 216 compounds for a separate test set. In data pre-processing step, the Pearson's correlation coefficient used as a filter to eliminate redundant features. After application of the correlation filter, a single SVM has been applied to this reduced data set. Moreover, we have investigated the performance of SVM with different feature selection strategies, including SVM–Recursive Feature Elimination, Wrapper Method and Subset Selection. All feature selection methods generally represent better performance than a single SVM while Subset Selection outperforms other feature selection methods. We have tested SVM as a classification tool in a real-life drug discovery problem and our results revealed that it could be a useful method for classification task in early-phase of drug discovery.