Uncoupled and coupled solutions of volume change problems in expansive soils

Lightly loaded structures constructed on expansive soils are often subjected to severe distress subsequent to construction, as a result of changes in the pore-water pressures in the soil. The structures most commonly damaged are roadways, airport runways, small buildings, irrigation canals, spillway structures and all near ground surface structures associated with infrastructure development. Changes in the pore-water pressure can occur as a result of variations in climate, change in depth to the water table, water uptake by vegetation, removal of vegetation or the excessive watering of a lawn. An analytical tool for the prediction of heave is extremely valuable to geotechnical engineers. There has been little advancement in the development of such a tool for solving engineering problems. There does not appear to be a computer program that has been written and widely accepted for solving this problem. It is important that such an analytical tool be developed and that it be developed for both one- and two-dimensional problems. The primary objective of this research study is to apply the general theory of consolidation/swelling for unsaturated soils to provide a reliable, practical technique for the prediction of one-, two- or three-dimensional volume change associated with unsaturated, expansive soils. The void ratio constitutive surface of an unsaturated, expansive soil was estimated from volume change indices obtained from conventional oedometer tests. Mathematical equations, which can be applied over a wide range of stress conditions, are proposed to describe the constitutive surfaces for both soil structure and water phase. The elastic parameter functions that are required for the volume change analysis are calculated from the constitutive surfaces with an assumed value of Poisson's ratio. The solutions to the volume change problems associated with an unsaturated, expansive soil are obtained using both an uncoupled and a coupled approach. In the uncoupled approach, the continuity equation for the water phase and the equilibrium equations are solved independently. Uncoupled solutions are obtained using a partial differential equation solver, called FlexPDE. In the coupled approach, the continuity equation and the equilibrium equations are solved simultaneously. Coupled solutions are obtained using a finite element program, called COUPSO. The examples presented in this study represent typical volume change problems that are often encountered in engineering practice (i.e., influence of vegetation on light engineering structures, water leakage under floor slab and infiltration of water from ground surface). The results of the analyses appeared to be reasonable and in accordance with anticipated behaviour. The research results also showed that the answers from uncoupled solutions compared well with those from the coupled solutions. It is suggested that uncoupled solutions are adequate for the analysis of most volume change predictions for unsaturated, expansive soils

Newton-Kantorovich Iterative Regularization for Nonlinear Ill-Posed Equations Involving Accretive Operators

The Newton-Kantorovich iterative regularization for nonlinear ill-posed equations involving monotone operators in Hilbert spaces is developed for the case of accretive operators in Banach spaces. An estimate for the convergence rates of the method is established.Розроблено ітераційну регулярнзацію Ньютона - Канторовича для нелінійних некоректних рівнянь з монотонним оператором у гільбертових просторах для випадку акретивного оператора в банахових просторах. Встановлено оцінки швидкостей збіжності методу

Isolation and identification of phenolic compounds from the leaf extract of Cassia alata L.

Cassia alata is one of the most important species of the genus Cassia which is rich in anthraquinones and polyphenols. This plant is used as a medicinal material of which the leaves are known to have laxative and antibiotic properties. In our study, the methanol leaf extract of C. alata showed a significant antibacterial activity against human pathogenic bacteria strains Staphylococcus aureus and Bacillus cereus. The organic layers such as n-hexane, ethyl acetate, and aqueous layers, were prepared by partitioning the methanol extract with n-hexane and ethyl acetate successively.  We successfully isolated and identified the structures of five compounds from C. alata leaves. Their structures were elucidated by MS and NMR spectroscopic methods as well as comparison with literature data. These compounds were determined to be methyl 2,4,6-trihydroxybenzoate (1), kaempferol (2), (-)epiafzelechin (3), kaempferol-3-O-glucoside (4) and kaempferol-3-O-gentiobioside (5). Keywords. Cassia alata L., epiafzelechin, kaempferol, kaempferol-3-O-glucoside, kaempferol-3-O-gentiobioside

Vietnamese rice exports: Do large destination markets stimulate?

What determines Vietnamese rice export flows? Data on rice export from Vietnam and its 124 destination markets in 2010 shows that high-income from agricultural sector of importing countries do not necessarily result in higher rice exports whereas exports tend to be higher to highly populated countries. In order to confirm the negative effect of the importing countries' GDP, We proceed to split the full sample into subsamples for Asian and non-Asian importing countries. While GDP covers the entire income of the whole economy, the value added agriculture performs better in determining the export pattern of firms operating in one sector. Specifically, distance in some cases encourages rice exports if destination markets are non-Asian countries implying a high export capacity of rice firms. For a heavy bulk good such as rice, the effect of landlocked dummy is far more sensitive to rice exports volume than exports value

Networks of Enterprises and Innovations: Evidence from SMEs in Vietnam

By using the latest dataset from the survey of SMEs conducted in Vietnam in 2011, we show that a firm both participating in a wider network of input suppliers, buyers, and associations of enterprises and conducting innovative activities in production has higher labor productivity than others, implying that networks of enterprises and innovation are complementary to each other in affecting performance of SMEs in Vietnam. We also find that supports of the government including providing better infrastructure to the SMEs and helping the SMEs to be formalized when being established are conducive to the development of the SMEs in Vietnam

Vietnamese rice exports: Do large destination markets stimulate?

What determines Vietnamese rice export flows? Data on rice export from Vietnam and its 124 destination markets in 2010 shows that high-income from agricultural sector of importing countries do not necessarily result in higher rice exports whereas exports tend to be higher to highly populated countries. In order to confirm the negative effect of the importing countries' GDP, We proceed to split the full sample into subsamples for Asian and non-Asian importing countries. While GDP covers the entire income of the whole economy, the value added agriculture performs better in determining the export pattern of firms operating in one sector. Specifically, distance in some cases encourages rice exports if destination markets are non-Asian countries implying a high export capacity of rice firms. For a heavy bulk good such as rice, the effect of landlocked dummy is far more sensitive to rice exports volume than exports value

Innovation and Performance of Enterprises: The Case of SMEs in Vietnam

Innovation is widely recognized as a key determinant of enterprise performance. It is, however, not clear how innovation affects performance of small-and-medium enterprises (SMEs) in transition economies. Based on data collected from surveys of SMEs in Vietnam from 2005 to 2011 this study shows that the human capital of owners/managers of SMEs, the quality of workers, and public physical infrastructure positively affect innovation and the performance of SMEs. More importantly, the study finds that innovation in products, production process, and marketing is a decisive factor for higher performance of SMEs in Vietnam

Vietnamese footwear export: The direction of trade and determinants of firms’ market penetration

We investigate determinants of firms’ direction of trade by using panel data of Vietnam’s footwear firms for the 2006-2010 period. Since no variance was found between firms, a pooled multinomial logit model is consequently preferable. Notably, the economies of scale show positive and significant effects for footwear firms serving the USA and EU markets. Although Vietnamese footwear firms are less likely to export to the ASEAN countries, they tend to focus on the diversification of products in this market. Both private and FDI firms are less likely to export to the EU compared with their counter parts owned by the State (SOEs). However, private firms outperform SOES in the U.S market