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Cheng S.-F.,Chaoyang University of Technology | Huang C.-Y.,Ordnance Readiness Development Center | Tu Y.-T.,National Sun Yat - sen University
Environmental Technology | Year: 2011

Acid washing is a common method for soil remediation, but is not always efficient for chromium-contaminated soil. Both soil particle size and the forms of chromium existing in the soil affect the efficiency of soil washing. Laboratory batch and column dissolution experiments were conducted to determine the efficiencies of citric and hydrochloric acids as agents to extract chromium from soils contaminated with chromium. The effects of soil particle size and chromium fractionation on Cr leaching were also investigated. About 90% of chromium in the studied soil existed either in residual form or bound to iron and manganese oxides, and Cr fraction distributions were similar for all soil particle sizes. Almost all exchangeable and carbonate-bound chromium was removed by washing once with 0.5 M HCl, whereas organic chromium was more effectively removed by washing with citric acid rather than with HCl solution of the same concentration. For chromium fractions that were either bound to Fe-Mn oxides or existed as residual forms, the efficiencies of acid washing were usually 20% or less, except for 0.5 M HCl solution, which had much higher efficiencies. Separation of the soil sample by particle size before the separate washing of the soil fractions had little improvement on the chromium removal. © 2011 Taylor & Francis.

Yang S.-C.,National Defense University | Kuo S.-L.,Ordnance Readiness Development Center
Chung Cheng Ling Hsueh Pao/Journal of Chung Cheng Institute of Technology | Year: 2011

The theorem of software reliability models has been developed since 1970s. Many researchers have discussed about software reliability models, and have advocated some new models. Although the existing models have been possessed of mathematical methods and analytical processes, their assumptions and associated parameters are not practical and difficult to implement. Under the assumption of Nonhomogeneous Quasi-Renewal Weibull Process (NQRWP), this paper has presented a general software reliability model for practical applications. Changing the shape parameter of Weibull distribution and the software reliability growth parameter, this paper has categorized nine conditions of software failure behavior. The results can be applied to software failure simulation and prediction. Copyright © 2009 Chung Cheng Institute of Technology.

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