Dedication This dissertation is dedicated to my parents, my husband Liwen and my son Ethan. They have always been there for me. Their endless love and support kept me going for the whole idea of " Ph. D. " v Acknowledgements

We consider a PH/PH/1 queue in which a threshold policy determines the stage of the system. The arrival and service processes follow a Phase-Type (PH) distribution depending on the stage of the system. Each stage has both a lower and an upper threshold at which the stage of the system changes, and a new stage is chosen according to a prescribed distribution. The PH/PH/1 multi-threshold queue is...

1.1. Random walk in random potential. Let S = (S(n))n∈N0 be a nearestneighbor random walk on the lattice Zd, with start at the origin and drift h into the direction of the first axis. We suppose S being defined on a probability space (Ω,F , Ph), and we denote by Eh the associated expectation. Such a random process is characterized by the distributions of its finite-step sub-paths S[n] def = S(0...

Depending upon the contours, or profiles, of relationships between time and temperature applying (a) to the destruction of offensive organisms at constant temperature and (b) to the temperature change to which food is subjected, and depending upon the particular mathematical forms used to express these relationships, there are at-least two parameters associated with each relationship-a velocity...

The paper addresses control related design issues for neutralization plants. Mainly for control reasons, the neutralization is usually performed in several steps (mixing tanks) with gradual change in the concentration. The aim is to give recommendations for issues like tank sizes and number of tanks. Assuming strong acids and bases, we derive linearized relationships from the disturbance variab...