Effects of grain size on phase transition behavior of nanocrystalline shape memory alloys

We report recent advances in the experimental and theoretical study of grain size(GS)effects on the thermal and mechanical properties of nanostructured NiTi polycrystalline shape memory alloy(SMA).It is shown that when GS<60 nm,the superelastic stress-strain hysteresis loop area(H)of the polycrystal decreases rapidly with GS and tends to vanish as GS approaches 10 nanometers.At the same time,the temperature dependence of the transition stress also decreases with GS and eventually approaches zero,leading to a wide superelastic temperature window and breakdown of the Clausius-Claperyon relationship.Rate dependence of the stress-strain responses is significantly reduced and the cyclic stability of the material is improved by the nanocrystallization.It is proposed that the emergence of such significant changes in the behavior of the material with GS reduction originate from the large increase in the area-to-volume ratios of the nanometer-thick interfaces(grain boundary and Austenite-Martensite(A-M)interface)in the polycrystal.In particular,with GS reduction,interfacial energy terms will gradually become dominant over the bulk energy of the crystallite,eventually bring fundamental changes in the phase transition responses of the material.Modelling strategy leading to the establishment of quantitative relationships among GS,grain boundary,A-M interfaces and the macroscopic responses of the material are outlined.     

Determination of optimum ejector operating pressures for anodic recirculation in SOFC systems

In this study, a numerical analysis of an ejector for micro combined heat and power system based on 18 kW Solid Oxide Fuel Cell (SOFC) using methane as fuel is presented. An ejector design, which reflects the real system conditions in the view of the flow characteristics, is provided and the ejector performance is numerically investigated for various methane pressure to exhaust pressure ratios and methane inlet temperatures. The results show that the fuel inlet temperature and the pressure ratio of the methane to exhaust significantly affect the steam to carbon ratio (STCR) and entrainment ratio. The higher pressure ratio and methane temperature allow a high entrainment ratio and STCR, but as pressure ratio and methane temperature increase, STCR and entrainment ratio remain unchanged after a specific value. 1140 different scenarios related with the inlet and outlet pressures of the ejector and methane temperature are created to determine the optimum operating conditions. The simulations show that the optimum methane inlet pressure is 7 bar and exhaust pressure is 1.159 bar for the ejector geometry of the interest. The entrainment ratio and STCR are determined as 2.05 and 0.92, respectively at this optimum scenario.     

Effects of coal properties on the production rate of combustion solid residue

The production rates of furnace bottom ash in a pulverized coal-fired power plant were monitored for a two-year period and its variations with respect to coal properties were analyzed. The power plant was originally designed to fire the coal sludge generated from a washing process; however, the coal sludge and its mixture with low-rank bituminous coal have been started to be used as the main fuel with time. The results of the hardgrove grindability measurements have shown that the grinding properties of sludge or its mixtures could not be predicted based on proximate analysis (moisture, ash, carbon and volatile contents); it could only be determined by experiments. The production rate of bottom ash in this particular power plant remained relatively insensitive to the high ash and moisture contents and could be estimated almost only by knowing the calorific value of the source coal. The evaluated dependency was linear.     

Development and characterization of polymer electrolyte membranes based on ionical cross-linked poly(1-vinyl-1,2,4 triazole) and poly(vinylphosphonic acid)

The fabrication, thermal and proton conducting properties of complex polymer electrolytes based on poly(vinylphosphonic acid) (VPA) and poly(1-vinyl-1,2,4-triazole) (PVTri) were investigated throughout this work. The membrane materials were produced by complexation of PVPA with PVTri at various concentrations to get PVTriP(VPA)_x where x designates the molar ratio of the polymer repeating units and varied from 0.25 to 4. The complexed structure of the polymers was confirmed by FT-IR spectroscopy. The TGA results verified that the presence of PVTri in the complex polymer electrolytes suppressed the formation of phosphonic acid anhydrides up to 150 °C. The DSC and SEM results demonstrated the homogeneity of the materials. Proton conductivity, activation energy and water/methanol uptake of these membranes were also measured. PVTriP(VPA)₂ showed a proton conductivity of 2.5 × 10⁻⁵ S cm⁻¹ at 180 °C in the anhydrous state. After humidification (RH = 50%), PVTri-P(VPA)₄ and PVTri-P(VPA)₂ showed respective proton conductivities of 0.008 and 0.022 S cm⁻¹ at 100 °C, where the conductivity of the latter is close to Nafion 117 at the same humidity level.     

The rheological behaviors and morphological characteristics of different food hydrocolloids ground to sub-micro particles: in terms of temperature and particle size

Temperature sweep tests and steady shear properties of five different food hydrocolloids (guar gum, xanthan gum, carboxymethylcellulose, pectin and carrageenan) in two different particle sizes groups have been determined at 25, 40, 60 and 80 °C in 1% aqueous solution. Also, the Scanning Electron Microscopy (SEM) images of gums were taken to investigate the morphological properties of the samples. The particle size and processing temperature significantly affected all rheological parameters of the hydrocolloid solutions. The flow behavior of the samples was fitted to Ostwald de Waele model (R²?=?0.959). The highest n value was recorded at 60 °C for all samples. The most drastic changes in consistency coefficient (K) values of the samples were observed in carrageenan solution and it was ranged from 0.013 to 1.774 Pa.sⁿ before the size reduction and from 0.007 to 0.337 Pa.sⁿ after the size reduction process. As the consistency coefficient (K) and apparent viscosity (η₅₀) decreased with the temperature, the flow behavior index increased in both group of samples. As a result, it was concluded that the increase in processing temperature and size reduction process caused a decrease in resistance of hydrocolloid solutions subjected to the deformation, which is a very important factor affecting the quality and good mouth-feel of products.     

Low Temperature Plasma for decontamination of E. coli in milk

Raw milk is a natural, highly nutritious product and a quick and easy supplement for human dietary requirements. Elimination of bacteria in milk has been a problem for decades and new methods with regards to non-thermal applications which do not harm the chemical composition of milk, are currently under investigation. The objective of the study was to determine the potential use of a novel, Low Temperature Plasma (LTP) system for its capability of killing Escherichia coli in milk with different fat contents. The time dependent effect of atmospheric corona discharge generated with 9kV of AC power supply on E. coli ATCC 25922 dispersed in whole, semi skimmed and skimmed milk was examined. Plasma was applied at time intervals of 0, 3, 6, 9, 12, 15 and 20min. A significant 54% reduction in the population of E. coli cells after only 3min was observed regardless of the fat content of the milk. The initial pre-plasma bacterial count of 7.78 Log CFU/ml in whole milk was decreased to 3.63 Log CFU/ml after 20min of plasma application. LTP did not cause any significant change to the pH and color values of raw milk samples. No viable cells were detected after one week examination in whole milk samples and remained so over the 6week storage period. The findings of this study show that the novel LTP system tested was able to significantly reduce E. coli in milk by more than a 3 fold log reduction without significantly affecting pH or color properties.     

An investigation about comfort and protection performances of disposable and reusable surgical gowns by objective and subjective measurements

This study was conducted to investigate comfort and microbial protection performances of two reusable and two disposable surgical gowns by subjective wear trials conducted on eight healthy Dentistry faculty students under environmental conditions suitable for a surgical operation. Protection performances of the gowns were tested by a modified bacterial resistance test. Physiological and psychological data were obtained during wear trials. All objective and subjective results were evaluated in the light of standard physical, mechanical, permeability, and resistance (thermal and water vapor) characteristics of the fabrics. According to the results, thermal comfort performance of the woven gown produced from microfiber polyester was the best according to subjective wear trial and microbial resistance test results. Disposable nonwoven gowns had lower comfort performances despite their higher permeability and lower resistance values. Moreover, chest skin temperature, arm microclimate temperature, and arm relative humidity are the physiological parameters significantly correlated with subjective comfort evaluation results.     

Characterization of interlaminar shear strength of laminated woven E‐glass/epoxy composites by four point bend shear test

An experimental and numerical investigation was performed to study the interlaminar shear response of laminated woven E‐glass/epoxy composites. The interlaminar shear strength results obtained from four point bend shear tests were compared with the results obtained from American Society for Testing and Materials (ASTM) test standards D2344 (short beam strength). The test results reveal that the four point bend interlaminar shear test results at a span to thickness ratio of 8 is higher than the short beam shear test results at a span to thickness ratio of 4. Numerical simulations were performed with ANSYS® software. The experimental results and the corresponding numerical results are in good agreement. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Comparative study of conducting polyaniline/copper and polyaniline/nickel composites in the presence of surfactants

Polyaniline/copper and polyaniline/nickel composites were synthesized in the presence and absence of surfactants using ammonium persulfate as an initiator. The structural and surface characteristics of the composites were studied and compared using different techniques. The interfacial interactions and thermal stability of the composites were characterized using X‐ray diffraction and thermogravimetric analysis. Surface properties were investigated using scanning electron microscopy and energy‐dispersed X‐ray spectroscopy. The results indicate significant changes in the morphological and physicochemical properties of the composites when incorporating surfactants. The surfactant‐induced surface characteristics also have an effect on conductivity. Copyright © 2010 Society of Chemical Industry     

Tomato powder impedes the development of azoxymethane‐induced colorectal cancer in rats through suppression of COX‐2 expression via NF‐κB and regulating Nrf2/HO‐1 pathway

Cancer is one of the leading causes of death worldwide. Since dietary factors have been connected to a reduced risk of a diversity of human cancers, in this study we investigated the effects of tomato powder (TP) on the development of azoxymethane (AOM)‐induced colorectal cancer in Wistar rats, and possible mechanism(s) by which TP shows its chemopreventive activity. Here we show that TP added to feed at 5% rate decreases the rate of aberrant crypt foci (ACF) and reduces the development of adenocarcinoma and growth of AOM‐induced colorectal cancer in rats. In addition, we demonstrate that TP supplementation shows its chemopreventive activities through inhibition of cyclooxygenase‐2 (COX‐2) expression via NF‐κB pathway and promotion of apoptosis, as well as regulating Nrf2/HO‐1 signaling pathway in colorectal tissue of AOM‐treated rats. Our findings identify an intimate connection between dietary supplementation of TP and the decreased risk of colorectal cancer in rats, and suggest that consumption of TP would be a natural candidate for the prevention of colorectal cancer in men.