Metal Triflates Incorporated in Mesoporous Catalysts for Green Synthesis of Fine Chemicals

Strong Lewis acid SnTf-MCM-41 and SnTf-UVM-7 catalysts with unimodal and bimodal pore systems were prepared in a two-step synthesis in which the triflic acid (Tf) was incorporated into previously synthesized mesoporous tin-containing silicas. The Sn incorporation inside the pore walls was carried out through the Atrane method. The SnTf-UVM-7 catalysts were prepared by aggregating nanometric mesoporous particles defining a hierarchic textural-type additional pore system. Catalysts with different Si/Sn ratios in the range 21.8–50.8 for SnTf-MCM-41 and 18.4 for SnTf-UVM-7 were found to be efficient catalysts for the acylation of aromatics and heteroaromatics. Under microwave irradiation the reaction was possible even with acetic acid. The selectivity to the desired product (o-hydroxyacetophenone for phenol) or the unfavored three-substituted five ring heterocycles was dramatically increased under these conditions. The process is green, environmentally safe, and heterogeneous.     

Polymer negative birefringence films for compensation of twisted nematic devices

Compensation of the liquid crystal layer within twisted nematic displays operating in normally white and normally black modes was examined. Studies of commercially available compensation films allowed us to develop the optimum compensating configuration for normally white displays including negative C-plates, discotic splay layers and A-plates. The optimum compensation of the normally black display mode was achieved using a stack of A-plates. The compensation provides a wide viewing cone and no gray-scale inversion in the most important viewing directions for both optimized display types. The compensated devices exhibit an achromatic dark state.     

Ohmic‐assisted hydrodistillation of essential oils from Zataria multiflora Boiss (Shirazi thyme)

Ohmic‐assisted hydrodistillation (OAHD) is a combination of ohmic heating and distillation, and could be considered as a novel method for the extraction of essential oils. Major problems with traditional methods are long extraction time and lower purity of the extract. In this study, OAHD was applied as an economic and green technology for the extraction of essential oils from Zataria multiflora Boiss. (Shirazi thyme) aerial parts and the results were compared to those obtained from hydrodistillation (HD) as a conventional method. The results showed that OAHD method had the extraction time of 32.21 ± 2.59 min while this value was about 57.21 ± 2.33 min for hydrodistillation (HD). Scanning electron micrographs of thyme leaves showed a sudden eruption of essential oil glands and their surrounding area for OAHD samples. GC–MS analysis indicated that both methods of OAHD and HD can extract the same compounds.     

Numerical simulation of heat transfer and fluid flow of molten metal in MMA–St copolymer lost foam casting process

In this study, a computational fluid dynamics (CFD) code was developed to calculate the filling pattern using volume of fluid (VOF) algorithm with donor–acceptor method for free surface simulation. This algorithm has been modified to include the pressure of the gas produced from foam degradation. For this purpose a heat transfer model and 2D foam degradation model were developed. In heat transfer model, radiation and conduction between foam and molten metal; and convection between gas and molten metal were considered. In order to evaluate the results of simulation, a bench scale casting apparatus was assembled and the casting was conducted in a transparent mold. The effect of several parameters such as coating thickness, foam density and vacuum level on the gap temperature, gap pressure and filling speed was studied with the developed software. It was found that the simulated results are in good agreement with experimental results.     

Benefits valuation of potable water quality improvement in Malaysia: the case of Kajang Municipality

This article estimates the benefits of potable water quality improvements in Kajang Municipality in the state of Selangor, Malaysia, using the avertive cost method. Households were willing to pay MYR 322 annually to improve potable water quality. This represents about 80% of their average annual water bill. The present value of aggregate benefits over a period of 30 years at various social discount rates ranged from MYR 301 million to MYR 768 million. These estimates can be used as a reference for public investment criteria. The findings suggest that there is merit in an upward revision of water tariffs if they provide improvements in water quality.     

Artificial neural network application of modeling failure rate for Boeing 737 tires

This paper presents an application of artificial neural network (ANN) technique for conducting the reliability analysis of Boeing 737 tires. For this purpose, an ANN model utilizing the feed‐forward back‐propagation algorithm as a learning rule is developed. The inputs to the neural network are the flight operational time and the number of landings as independent variables and the output is the failure rate of the tires. Two years of data are used for failure rate prediction model and validation. Model validation, which reflects the suitability of the model for future predictions, is performed by comparing the predictions of the model with that of Weibull regression model. The results show that the failure rate predicted by the ANN is closer in agreement with the actual data than the failure rate predicted by the Weibull model. The present work also identifies some of the common tire failures and presents representative results based on the established model for the most frequently occurring tire failure. Copyright © 2010 John Wiley & Sons, Ltd.     

Job stress and job performance controversy revisited: An empirical examination in two countries.

This study examined the relationship between the measures of job stress and job performance among employees working in a large North American-based multinational corporation in Malaysia (N = 305) and Pakistan (N = 325). Data were collected by means of a structured questionnaire from employees on job stress and turnover intention. Job performance and absenteeism data were obtained from the company's records. In both countries, data were more supportive of the negative linear relationship between stress and performance than other types of relationships. Overall, 90% of comparisons supported the negative linear relationship, whereas a u-shaped/curvilinear relationship was supported in 10% of instances. Implications of the findings are discussed for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability and Erosion in Grassed Channels

Grass is a cost-effective form of erosion control. Since grass prevents erosion, the relationship between grass properties and erosion rate in grassed open channels is highlighted and analyzed within the context of channel stability. The deformation of grass caused by the flow’s momentum has been taken into consideration. Results are in good agreement with the available experimental erosion rate data for grassed channels. The purpose of this paper is to show that the amount of deformation of a grass channel lining due to flow can be used to estimate the erosion rate, and, as a result, lining deformation can be used as an indicator of channel stability. The method is simple enough to be useful for design.