Suchergebnisse

Studies on furan resin as dune sand stabiliser are presented. Influence of acid catalysts, viz. phenol disulphonic acid, sulphuric acid, hydrochloric acid and phosphoric acid and other catalysts, viz. trichlorotoluene and benzoyl chloride along with promoters, zinc chloride and ferric chloride, on the strength of stabilised furan resin-sand specimens has been discussed. Optimisation studies on resin content, catalysts and promoters and curing conditions have revealed that maximum strength of 260 kg/cm/sup 2/ of the standard specimens made by compaction of coastal sand using furan resins (10 per cent), sulphuric acid (9N, 30 per cent) and a curing time of 2 hr at 40 degree Centigrade is higher than the 170 kg/cm/sup 2/ of specimens made of Rajasthan desert sand. Sandy patches stabilised by seepage technique recorded a maximum strength of 125 kg/cm/sup 2/. Physico-chemical characteristics of this system and effect of environment on stabilised specimens have also been studied and field trials conducted successfully. This resin-catalyst system would be extremely useful in humid and saline field (coastal) areas for different military applications.

The ability to collect and disseminate individually identifiable microdata is becoming increasingly important in a number of arenas. This is especially true in health care and national security, where this data is considered vital for a number of public health and safety initiatives. In some cases legislation has been used to establish some standards for limiting the collection of and access to such data. However, all such legislative efforts contain many provisions that allow for access to individually identifiable microdata without the consent of the data subject. Furthermore, although legislation is useful in that penalties are levied for violating the law, these penalties occur after an individual's privacy has been compromised. Such deterrent measures can only serve as disincentives and offer no true protection. This paper considers security issues involved in releasing microdata, including individual identifiers. The threats to the confidentiality of the data subjects come from the users possessing statistical information that relates the revealed microdata to suppressed confidential information. The general strategy is to recode the initial data, in which some subjects are "safe" and some are at risk, into a data set in which no subjects are at risk. We develop a technique that enables the release of individually identifiable microdata in a manner that maximizes the utility of the released data while providing preventive protection of confidential data. Extensive computational results show that the proposed method is practical and viable and that useful data can be released even when the level of risk in the data is high.