Evaluation of plastering crew performance in building projects using data envelopment analysis

The research question addressed in this study was how the performance of construction crews working in a certain project or locality could be evaluated, ranked and improved. To develop and demonstrate the relevant framework, data envelopment analysis (DEA) was applied to establish the relative efficiency of plastering crews working in building projects located in different cities around Turkey. Data were collected from 40 crews of varying characteristics, and their technical efficiency scores were computed using the Banker, Charnes and Cooper (BCC) model, which is based on variable returns-to-scale (VRS). The model yields efficiency scores that range between 0 and 1, and a company or crew is considered efficient if its score is 1.0 (100%). Efficient and inefficient crews were identified and ranked on this basis in the study. Cross tabulation analyses were subsequently conducted to gain further insights into the relationships between the efficiency scores and input factors of numbers of skilled and unskilled laborers, daily labor unit costs, work hours, average age of crew members, total crew experience, plastering location, plastering technique, and plaster type. No discernible relationship could be identified between the efficiency scores and productivity outputs of the crews. It was found that plastering technique, plastering location, and total crew experience had a significant association with crew efficiency. Efficiency improvement strategies identified included training, hiring experienced plasterers, adopting more advanced plastering technology, implementing better jobsite management practices, and enhancing workers’ knowledge, skills and attitude towards productivity and quality. First published online: 25 Sep 201

Dietary L-arginine supplementation reduces Methotrexate-induced intestinal mucosal injury in rat

<p>Abstract</p> <p>Background</p> <p>Arginine (ARG) and nitric oxide maintain the mucosal integrity of the intestine in various intestinal disorders. In the present study, we evaluated the effects of oral ARG supplementation on intestinal structural changes, enterocyte proliferation and apoptosis following methotrexate (MTX)-induced intestinal damage in a rat.</p> <p>Methods</p> <p>Male rats were divided into four experimental groups: Control rats, CONTR-ARG rats, were treated with oral ARG given in drinking water 72 hours before and 72 hours following vehicle injection, MTX rats were treated with a single dose of methotrexate, and MTX-ARG rats were treated with oral ARG following injection of MTX. Intestinal mucosal damage, mucosal structural changes, enterocyte proliferation and enterocyte apoptosis were determined 72 hours following MTX injection. RT-PCR was used to determine bax and bcl-2 mRNA expression.</p> <p>Results</p> <p>MTX-ARG rats demonstrated greater jejunal and ileal bowel weight, greater ileal mucosal weight, greater ileal mucosal DNA and protein levels, greater villus height in jejunum and ileum and crypt depth in ileum, compared to MTX animals. A significant decrease in enterocyte apoptosis in the ileum of MTX-ARG rats (vs MTX) was accompanied by decreased bax mRNA and protein expression and increased bcl-2 protein levels.</p> <p>Conclusions</p> <p>Treatment with oral ARG prevents mucosal injury and improves intestinal recovery following MTX- injury in the rat.</p

Effect of curing time on selected properties of soil stabilized with fly ash, marble dust and waste sand for road sub-base materials

The properties of sub-base filling materials in highway construction are essential, as they can determine the performance of the road in service. Normally, the existing materials are removed and replaced with new materials that have adequate load-bearing capacity. Rising environmental concern and new environmental legislations have made construction professionals consider other methods. These methods include stabilizing the existing materials with other additives to improve their performance. Additives can be waste materials generated by different industries. In this work, the existing excavated soil is stabilized with waste materials. The wastes consisted of fly ash, marble dust and waste sand. The percentage addition of waste materials was 5%, 10%, 15% and 20% (by mass) of the existing soil. The soil/waste specimens were cured for 1, 7, 28, 56, 90 and 112 days before testing. Testing included the dry unit weight and unconfined compressive strength ( qu) as well as X-ray diffraction analysis and scanning electron microscopy observation. Also, the California Bearing Ratio values were obtained and are reported in this investigation. The results showed that the qu values increased with the increase in waste materials content. Also, there is tendency for the dry unit weight to increase with the increase in waste materials

Solid oxide-molten carbonate nano-composite fuel cells: Particle size effect

Varying the amount of specific interface area in the CeO2-Na2CO3 nanocomposite fuel cell electrolyte helped reveal the role of interfaces in ionic conductivity. We mixed ceria particles with micrometer or nanometer size distributions to obtain a specific surface area (SSA) in the composite from 47 m(2) g(-1) to 203 m(2) g(-1). Microstructural investigations of the nanocomposite showed that the Na2CO3 phase serves as the glue in the microstructure, while thermal analysis revealed a glass transition-like behavior at 350 degrees C. High SSA enhanced the ionic conductivity significantly at temperatures below 400 degrees C. Moreover, the activation energy for the Arrhenius conductivity (sigma T) of the composites was lower than that of the Na2CO3 phase. This difference in the activation energies is consistent with the calculated dissociation energy of the carbonate phase. The strong dependence of conductivity on the SSA, along with differences in the activation energies, suggests that the oxide surface acted as a dissociation agent for the carbonate phase. A model for the solid composite electrolyte is proposed: in the nanocomposite electrolyte, the oxide surface helps Na2CO3 dissociate, so that the "liberated" ions can move easily in the interaction region around the oxide particles, giving rise to high ionic conductivities. (C) 2014 Elsevier B.V. All rights reserved

Trends in Intragenerational Income Mobility in the Western States of Germany and the United States (1984 – 2006)

Using the Shorrocks R, we compare trends in intragenerational income mobility for the western states of Germany and the United States (1984 – 2006) and test the sensitivity of our results to the starting point and number of years considered. We find that our mobility estimates do not converge to a constant over time so the starting year chosen for the analysis matters. We conclude that income mobility declined in the western states of Germany over time and is now much closer to income mobility in the United States than was the case in the 1980s