Sharif Digital Repository

Several methods have been proposed in data envelopment analysis (DEA) for measuring efficiency in problems with interval or ordinal data. In this study, we review the weaknesses and drawbacks of these methods and show how converting ordinal or interval data into precise data can lead to violations of established DEA axioms. One of the axioms violated by these conversion processes is the inclusion of observations axiom, which requires a consistent definition of the production possibility set. We describe the special properties of ordinal and interval data together with their effect on the DEA-based rankings using a theorem and an example. We also propose a new algorithm and apply random... 

In this paper, we propose an efficient secure data aggregation scheme for the smart grid, which supports both lossy and lossless data aggregation. In order to reduce the computational overhead of the control center, our proposed model includes a number of entities, called gateways, which act as intermediaries between the users and the control center. At the end of each measurement interval, each user generates a report which is encrypted using the Paillier cryptosystem and contains the user's consumption amount during the previous measurement interval as well as his or her prediction of consumption during another interval in the future. After receiving the user's reports, gateways perform...