Data Security in computer communication is becoming serious problem with developing computer network. This paper intended to design an encryption system to improve processing speed and to get higher degree of security by combining random number generation method, substitution method and Vernam's encryption method.

The study is to design optimal aircraft allocation model for sufficing the required level of damage, minimizing attrition cost when the aircrafts attack the enemy's fixed target. When friendly aircraft attacks enemy target, the aircraft will suffer the loss due to the enemy's anti-aircraft weapons and aircraft. For this study, it is required that the probability of target damage by the type of aircraft, level of target damage and attrition cost are computed for the application of this model.

Vehicle fleet planning problem is generic name given to a whole class of practical decision making problems which find the vehicle routes and schedules to accomplish the reqired service to customers using vehicles. In this paper the various problems are classified into the three groups according to their characteristics: (1) vehicle routing problems, (2) vehicle scheduling problems, and (3) vehicle routing and scheduling problems. The State of the art of each group is described and the future research directions are presented.

This paper is concerned with a standard size system and production proportion of combat boots. For the standard size system foot sizes of 327 soldiers were mesured by Martin type anthropometric equipment. 24 foot measurements were obtained on all individuals. The standard size system of which key measurements are foot length and joint girth are proposed on the basis of the statistically treated measurement data. The production (or purchasing) proportion of the proposed size system of combat boots are also proposed.

This thesis studies the estimation from interarrival and service time data of the mean number of customers in service at time t for an $M/G/{\infty}$ queue. The assumption is that the parametric form of the service time distribution is unknown and the empirical distribution of twe service time is used in the estimate the mean number of customers in service. In the case in which the customer arrival rate is known the distribution of the estimate is derived and an approximate normal confidence interval procedure is suggested. The use of the nonparametric methods, which are the jackknife and the bootstrap, to estimate variability and construct confidence intervals for the estimate is also studied both analytically and by simulation.