Detoxification of water by semiconductor photocatalysis

An overview of the use of semiconductor photocatalysis for water purification is given. The basic principles of semiconductor photocatalysis are described along with the current understanding of the underlying reaction mechanism(s) and how it fits in with the major features of the observed Langmuir-Hinshelwood-type kinetics of pollutant destruction. These features are illustrated based on literature on the destruction of aqueous solutions of 4-chlorophenol as a pollutant, using titanium dioxide as the photocatalyst. The range of organic and inorganic pollutants that can be destroyed by semiconductor photocatalysis are reported and discussed. The basic considerations that need to be made when designing a reactor for semiconductor photocatalysis are considered. These include: the nature of the reactor glass, the type of illumination source, and the nature and type of semiconductor photocatalyst. The key basic photoreactor designs are reported and discussed, including external illumination, annular, and circular photoreactors. Actual designs that have been used for fixed and thin falling film semiconductor photocatalyst reactors are illustrated and their different features discussed. Basic non-concentrating and concentrating solar photoreactors for semiconductor photocatalysis are also reported. The design features of the major commercial photocatalytic reactor systems for water purification are reported and illustrated. Several case studies involving commercial photocatalytic reactors for water purification are reported. An attempt is made briefly to compare the efficacy of semiconductor photocatalysis for water purification with that of other, more popular and prevalent water purification processes. The future of semiconductor photocatalysis as a method of purifying water is considered

Chaebol, Financial Liberalization, and Economic Crisis: Transformation of Quasi-Internal Organization in Korea

This paper argues that the Korean governmentís policy with regard to financial deregulation and liberalization was endogenously determined, being largely influenced by the interest politics of perhaps the most powerful interest group in Korea, chaebol. It also argues that the cause of Koreaís financial crisis of 1997-98 cannot be analyzed without first examining the influence of chaebol on the post-1993 financial liberalization, which planted the seeds of the crisis. The paper concludes that financial liberalization undertaken in a haphazard manner, manipulated by a few dominant players in the economy runs into the danger of producing an outcome worse than before.Financial liberalization, The Asian crisis, Chaebol, Government intervention

Corporate Governance and Long Term Performance of the Business Groups: The Case of Chaebols in Korea

The existence of the business groups has been associated with market failure in emerging economies, and thus their performance has been argued and found to have declined with development of market institutions surrounding them. This paper takes up this issue of long-term performance of the business groups but argues that it has also to do with the internal problems, such as changes in the ownership and governance structure. It finds, with the Korea data and new method and theoretical grounds, that the relative performance of the business groups, the Chaebols, had consistently declined over the 1980s and 1990s although they were more efficient than the non-Chaebol firms during the early 1980s. The results are robust to different estimation methods, and also to controls for the possible survivorship bias, industry composition, and scale effects. The paper explains the performance change by examining the decrease of the shares held by the controlling families and the associated aggravation of the agency problem leading to unjustifiable expansion drives.Business groups, Long Term performance, Corporate Governance, Chaebols

Time Varying Coefficient: An Application of Flexible Least Squares to Cattle Captive Supply

Although conventional linear regression techniques assume time constancy of parameters time varying coefficient or the problem of structural instability in econometric relationships has been recognized by econometricians. In this study, time varying impact of captive supply on fed cattle cash market price is investigated via flexible least squares approach. Time path of flexible least squares coefficient estimate indicates an approximately four fold increase in price impact of captive supply over the sample period, but even this multiplied price impact is small compared to the effect of boxed beef price which shows negligible time variation. The time path also aids in identification of structural breaks in the price impact of captive supply.time varying coefficient, flexible least squares, structural break, captive supply, Research Methods/ Statistical Methods,