Effects of environmental factors on the adhesion and durability characteristics of epoxy-bonded concrete prisms

This work is concerned with the effects of environmental factors on the adhesion and durability characteristics of epoxy-bonded concrete prisms. The results indicate that the presence of liquid water at the interfacial zone during the epoxy injection process disrupts the initial bond configurations. The freezing and thawing up to about 40 cycles do not have a significant effect on the bond stability. An adequate degree of chemical stability is maintained in the bond line by the epoxy adhesives after 120 days of exposure to corrosive environments such as MgSO₄ and MgCl₂. However, there is a pronounced effect of these chemical substances on the concrete strength. The load-bearing capacity of epoxy-bonded concrete prisms decreases with increasing temperature. Despite this fact, the EP3-bonded concrete prisms give relatively high joint strengths at temperatures up to 100 °C.     

Denoising of arterial spin labeling data: wavelet-domain filtering compared with Gaussian smoothing

Purpose  

To investigate a wavelet-based filtering scheme for denoising of arterial spin labeling (ASL) data, potentially enabling reduction of the required number of averages and the acquisition time.     

Interface structure of diffusion bonded duplex stainless steel and medium carbon steel couple

Diffusion bonding of duplex stainless steel to medium carbon steel was carried out with different temperatures for sound bonds. In the bonding process, relatively intermediate temperatures such as 750, 800, 850 and 900 °C were used with a bonding time of 30 min. In this study, microstructural changes and mechanical properties in the interface region of duplex stainless steel and medium carbon steel couples were determined. The results showed that, in interface region, Cr₂₃C₆ was formed on the stainless steel side, while ferrite formation was observed on the carbon steel side as a result of mutual diffusion of C and Cr.     

A parametric study on the factors affecting the froth floatation of Jordanian tar sand utilizing a fluidized bed floatator

Different parameters affecting the behavior of froth flotation of Jordanian tar sand, obtained from the Dead Sea area, were studied. This study was performed in a modified fluidized bed floatator. The effects of the addition of a flotation agent, NaOH, temperature and flotation time on the beneficiation of bitumen in the froth were investigated. It was found that the beneficiation factor in the froth increased with the increase of temperature and flotation time. However, the amount of base (NaOH) and the flotation agent were found to have a negative effect on that factor. A regression model based on a full factorial experimental design results was obtained with a significant correlation coefficient. The optimum beneficiation factor was found to be 7.2 and the bitumen content in the froth was found to be 79% in the froth, which was obtained at 0.2 gNaOH/L, zero agent, 80 °C, and 30 min.     

Copolymerization of carbon monoxide with exo‐methylenecycloalkane and dienes: synthesis of functionalized aliphatic polyketones

Synthesis of functional aliphatic polyketones was achieved by co‐ and terpolymerization of the strained exo‐methylenecycloalkane, methylenecyclopropane (MCP), and also the dienes 1,5‐hexadiene, 1,7‐octadiene and 1,6‐heptadien‐4‐ol, with carbon monoxide and propene, using the dicationic palladium(II) phosphine complex [Pd(dppp) (NCCH₃)₂](BF₄)₂ (I) (dppp is 1,3‐bis(diphenyl‐phosphino)propane) as the catalyst precursor. The resulting MCP/CO copolymer contains both ring‐opened and cyclic microstructures. Ring‐opening copolymerization yields exo‐methylene functionalized polyketone. In contrast to hexadiene/carbon monoxide copolymer (Hx/CO), no ring structures were observed in the alternating octadiene/carbon monoxide (Oc/CO) and heptadien‐4‐ol/carbon monoxide (Hp‐ol/CO) copolymers. The remaining double bonds were left intact to yield polymers with olefinic functionalities in the side chains. © 2001 Society of Chemical Industry     

A study on performance and exhaust emissions of the steam injected DI diesel engine running with different diesel- conola oil methyl ester blends

Although biodiesels have low emission profiles, the main drawback of using biodiesel in diesel engines is higher NOx. Nowadays, the electronic controlled steam injection is a promising method for NOx control. This study investigates the effects of steam injection with diesel fuel-canola oil methyl ester (COME) blends on the performance and emissions characteristics of a direct injection (DI) single cylinder diesel engine. Steam is injected into the inlet manifold during inlet period. The combustion of diesel-COME blends has been modeled using two zone combustion model. The results have been compared with each other in terms of performance and emissions. The maximum increments in engine torque and power were measured as 2.5% for 10% COME (B10) at 1200 rpm, 2.8% for 20% COME (B20) at 2200 rpm. The effects of steam injection on performance and emissions of the diesel engine running with B10 and B20 COME blends were also investigated. Satisfaction improvements have been obtained with the combination of steam injection and COME blends. The maximum torque of the engine running with B10 and 10% steam ratio combination (B10 + S10) and B20 and 10% steam ratio combinations (B20 + S10) were found as 2.4% at 1400 rpm and 0.6% at 1400 rpm, respectively. Significant reduction has been observed in NOx emission with B10-S10 combination. The reduction rate in NOx emissions were 22% with B10-S10 and 18% with B20-S10 at 1200 rpm. The study showed that steam injection is an effective tool for controlling NOx emissions without performance degradation in the diesel engines fueled with COME blends.     

Interference analysis and capacity for forward link 3G CDMA network with adaptive antennas

In code division multiple access (CDMA) systems, the capacity of forward link (FL) communication to mobile receivers is limited primarily by co‐channel interference (CCI). Adaptive antenna arrays (AAAs) that use antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. For a 3G CDMA cellular network, where each BS equipped with an AAA serves mixture of voice and data users within its coverage, we study FL capacity and investigate the effects of different factors (array topology, multipath angle spread, data rate, and beamforming algorithm) on this capacity under Rayleigh fading channel. By modeling the instantaneous signal‐to‐interference power ratio received at the mobile, we derive the system outage equation that considers blocking of either desired voice or data user. Simulation results show that for the same element spacing and number of antenna elements per cell, the uniform circular array (UCA) topology results in larger capacity than the sectorized uniform linear array (ULA) topology does, and that a larger angle spread or data user rate reduces FL capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis,characterization, and thermal degradation kinetics of the copolymer poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate)

A copolymer of 4‐methoxybenzyl methacrylate and isobornyl methacrylate was synthesized by atom transfer radical polymerization. The structure of poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate) was confirmed by means of Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR techniques. The molecular weight distribution values of the copolymer were determined with gel permeation chromatography. The number‐average molecular weight and polydispersity index values of poly(4‐methoxybenzyl methacrylate‐co‐isobornyl methacrylate) were found to be 12,500 and 1.5, respectively. The kinetics of the thermal degradation of the copolymer was investigated with thermogravimetric analysis at different heating rates. The activation energy values obtained with the Kissinger, Flynn–Wall–Ozawa, and Tang methods were determined to be 166.38, 167.54, and 167.47 kJ/mol, respectively. Different integral and differential methods were used, and the results were compared with these values. Doyle approximation was also used for comparing the experimental results to master plots. An analysis of the experimental results suggested that the reaction mechanism was an R₁ deceleration type in the conversion range studied. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Surface Treatment of S355JR Carbon Steel Surfaces with ZrB<Subscript>2</Subscript> Nanocrystals by CO<Subscript>2</Subscript> Laser

To improve mechanical properties of S2355JR carbon steel, pre-synthesized ZrB₂ nanocrystals were used to coat the metal surface by laser cladding using 2000 W CO₂ laser. ZrB₂ nanocrystals were synthesized by mechanochemical process. The effect of laser power on the coating layers was examined for optimizing the most effective coating conditions. Microstructural studies were carried out using optical microscope, scanning electron microscope and X-ray diffraction to analyze phase structures of the coated layers. Mechanical characteristics of the laser coated layers were evaluated by studying microhardness, wear and scratch resistance properties. Maximum hardness of the coated layers was observed while cladding with 75 and 125 W laser powers, when other processing parameters and conditions were kept at optimum levels. EDS analysis of these laser cladded layers indicated the formation of complex boro-nitrides, nitrides and carbides of Zr and Fe that contributed to vast increase in hardness of the laser-clad coating on S2355JR steel. Depending upon the laser powers used, the thickness of the coated layers was found to be in the range of 15–37 µm. The wear and micro-scratch tests results revealed significant improvement in wear properties.     

Solution of Algebraic Lyapunov Equation on Positive-Definite Hermitian Matrices by Using Extended Hamiltonian Algorithm

This communique is opted to study the approximate solution of the Algebraic Lyapunov equation on the manifold of positive-definite Hermitian matrices. We choose the geodesic distance between -AHX - XA and P as the cost function, and put forward the Extended Hamiltonian algorithm (EHA) and Natural gradient algorithm (NGA) for the solution. Finally, several numerical experiments give you an idea about the effectiveness of the proposed algorithms. We also show the comparison between these two algorithms EHA and NGA. Obtained results are provided and analyzed graphically. We also conclude that the extended Hamiltonian algorithm has better convergence speed than the natural gradient algorithm, whereas the trajectory of the solution matrix is optimal in case of Natural gradient algorithm (NGA) as compared to Extended Hamiltonian Algorithm (EHA). The aim of this paper is to show that the Extended Hamiltonian algorithm (EHA) has superior convergence properties as compared to Natural gradient algorithm (NGA). Upto the best of author’s knowledge, no approximate solution of the Algebraic Lyapunov equation on the manifold of positive-definite Hermitian matrices is found so far in the literature.