Casting properties of ASTM A128 Gr. E1 steel modified with Mn-alloying and titanium ladle treatment

This work aims to produce a high manganese steel with more refined austenite grains and better wear resistance without sacrificing the toughness and tensile properties by Mn alloying and Ti ladle treatment in comparision to ASTM A128 Gr. E1 steel (1.0C-13Mn) that is mostly used in the mining industry. The 1.0C-17Mn-xTi alloys (x=0, 0.05 and 0.1, in wt.%) were prepared. A relationship was established between the microstructures and mechanical properties of the as-cast and solution annealed alloys. Increasing Ti content increases the stable Ti(CN) phase on and beside the grain boundaries and decreases up to 37% the austenite grain size of the as-cast alloy with 0.10wt.% Ti. Correspondingly, after solution annealed, optimized titanium content (0.05wt.%) results in significant improvements in wear resistance, hardness, elongation, yield and tensile strengths by 44%, 31%, 30%, 8% and 12%, respectively, except 9% decrease in impact toughness compared to ASTM A 128 Gr. E1 steel without modification. These results show that 1.0C-17Mn-0.05Ti alloy can be used for parts exposed to high load wear and applied in conditions where relatively high tensile properties with sufficent ductility is needed.

     

Optimal Automatic Generation Control of Asynchronous Power Systems Using Output Feedback Control Strategy with Dynamic Participation of Wind Turbines

Abstract—This article presents the design of optimal output feedback automatic generation control regulators for an interconnected power system with dynamic participation of doubly fed induction generator based wind turbines. The power systems consist of plants with hydro-thermal turbines and are interconnected via parallel AC/DC links. Efforts have been made to propose optimal automatic generation control regulators based on feedback of output state variables, which are easily accessible and available for the measurement. The designed optimal output feedback automatic generation control regulators are implemented, and the system dynamic responses for various system states are obtained considering 1% load perturbation in one of the areas. The dynamic performance is compared with that obtained with optimal automatic generation control regulators designed using full state vector feedback. The pattern of closed-loop eigenvalues is also determined to test the system stability.     

Exploring the internationalization of Malaysian contractors: the international entrepreneurship dimension

The internationalization of construction companies is a subject of enduring interest among construction management scholars. The internationalization pattern of Malaysian contractors was explored, this time mainly using the international entrepreneurship body of literature as the theoretical basis. In doing so, the focus of the internationalization process was on the entrepreneurs or top management. Data were collected with a postal questionnaire survey and follow‐up semi‐structured interviews. The findings underscore the importance of the entrepreneurs’ decision in the surveyed firms’ internationalization trajectory. Top management’s perception of how their companies might benefit from internationalization was the highest ranked foreign market entry consideration. Top managements’ initial and subsequent motivation also fashioned their companies’ degree of internationalization and tactics for securing contracts. The characteristics of the entrepreneurs which drove their companies to internationalize were also captured. The international entrepreneurship domain continues to expand into previously uncharted areas. As such there is potential to uncover even more interesting findings from future research endeavours on international contractors using the international entrepreneurship approach.     

Effect of desensitizers on the microleakage of previously restored Class V resin composite restorations

Objectives: The aim of this in vitro study was to evaluate the effect of different desensitizers’ application on the microleakage of previously restored Class V composite resin restorations.

Materials and methods: Class V cavities were prepared on the buccal surfaces of 40 extracted human third molars. Forty box-shaped cavities were divided into four groups, based on the desensitizers used (n = 10). All teeth were restored with the same bonding agent and composite material. No desensitizer was applied in the control group. In the experimental groups, BisBlock, Gluma and Universal bonding agents were the desensitizers. The desensitizers were applied after completion of composite restorations according to manufacturers’ instructions. All specimens were then thermocycled at 5–55 °C, with a 10-s dwell time for 500 cycles. The samples were then immersed in 0.5% methylene blue dye for 24 h, sectioned into two equal halves, evaluated for microleakage using a stereomicroscope at 30× magnification and scored on a scale of 0–3. The data were analysed using the Kruskal–Wallis test at the significance level p < 0.05.

Results: There were no significant differences in microleakage after desensitizer application (p > 0.05). However, based on the obtained numerical values in our study, while the BisBlock and bonding groups showed lower microleakage at the occlusal margin, BisBlock, Gluma and bonding group showed lower microleakage at the gingival margin compared to the control group.

Conclusions: The application of desensitizers as a post-treatment option could be considered an advisable procedure to minimize microleakage.     

Investigation on the effect of spinning conditions on the properties of hollow fiber membrane for hemodialysis application

Polyethersulfone (PES) hollow fiber membranes were fabricated via the dry‐wet phase inversion spinning technique, aiming to produce an asymmetric, micro porous ultrafiltration hollow‐fiber specifically for hemodialysis membrane. The objective of this study is to investigate the effect of spinning conditions on the morphological and permeation properties of the fabricated membrane. Among the parameters that were studied in this work are air gap distance, dope extrusion rate, bore fluid flow rate, and the take‐up speed. The contact angle was measured to determine the hydrophilicity of the fibers. Membrane with sufficient hydrophilicity properties is desired for hemodialysis application to avoid fouling and increase its biocompatibility. The influences of the hollow fiber's morphology (i.e., diameter and wall thickness) on the performance of the membranes were evaluated by pure water flux and BSA rejection. The experimental results showed that the dope extrusion rate to bore fluid flow rate ratio should be maintained at 1:1 ratio to produce a perfectly rounded asymmetric hollow fiber membrane. Moreover, the flux of the hollow fiber spun at higher air gap distance had better flux than the one spun at lower air gap distance. Furthermore, spinning asymmetric hollow fiber membranes at high air gap distance helps to produce a thin and porous skin layer, leading to a better flux but a relatively low percentage of rejection for BSA separation. Findings from this study would serve as primary data which will be a useful guide for fabricating a high performance hemodialysis hollow fiber membrane. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43633.     

Identification of Bioactivity,Volatile and Fatty Acid Profile in Supercritical Fluid Extracts of Mexican arnica

Supercritical fluid extraction (SFE) is a sustainable technique used for the extraction of lipophilic metabolites such as pigments and fatty acids. Arnica plant is considered a potential candidate material with high antioxidant and antimicrobial activities. Therefore, in this study, a locally available Heterotheca inuloides, also known as Mexican arnica, was analyzed for the extraction of high-value compounds. Based on different pressure (P), temperature (T), and co-solvent (CoS), four treatments (T) were prepared. A maximum 7.13% yield was recovered from T2 (T = 60 °C, P = 10 MPa, CoS = 8 g/min), followed by 6.69% from T4 (T = 60 °C, P = 30 MPa, CoS = 4 g/min). Some bioactive sesquiterpenoids such as 7-hydroxycadalene, caryophyllene and δ-cadinene were identified in the extracts by GC/MS. The fatty acid profile revealed that the main components were palmitic acid (C16:0), followed by linoleic acid (C18:2ω6c), α-linolenic acid (C18:3ω3) and stearic acid (C18:0) differing in percent yield per treatment. Antibacterial activities were determined by the agar diffusion method, indicating that all the treatments exerted strong antibacterial activity against S. aureus, C. albicans, and E. coli strains. The antioxidant capacity of the extracts was also measured by three in vitro assays, DPPH, TEAC and FRAP, using Trolox as a standard. Results showed high antioxidant capacity enabling pharmaceutical applications of Mexican arnica.     

An interpretation of the changes in demographic behaviour at a sub-national level using spatial measures in post-socialist countries: A case study of the Czech Republic and Slovakia

The transformation of fertility and family behaviour in post-socialist countries was quick and the changes were striking. An account of the changes is the subject of dispute and the mechanisms have still not been explained in a fully satisfying manner. Relatively little attention has been paid to the changes in spatial aspects concerning the broadening of changes in family behaviour. The aim of this paper is to answer the question as to whether changes spread stochastically in post-socialist countries or if there are obvious spatial patterns. The study tries to answer the questions whether there are any cores of changes which may be understood as innovations, if there is any spatial clustering and if the extent is hierarchically arranged.     

Determination of rock type and moisture content in flysch using TLS intensity in the Elerji quarry (south-west Slovenia)

Bulletin of Engineering Geology and the Environment - Terrestrial laser scanning (TLS) was performed in tectonically undisturbed flysch in the Elerji quarry (south-west Slovenia), which represents...     

Understanding the Corrosion Inhibition Mechanism of Mild Steel in Hydrochloric Acid by a Triazole Derivative: A Combined Experimental and Theoretical Approach

Protection of Metals and Physical Chemistry of Surfaces - The effect of an heterocycle triazole, namely (1-(4-methoxyphenyl)-1H-1,2,3-triazol-4-yl)methanol (MTM) on the corrosion of mild steel in...