Bandwidth estimation for multimode optical fibers using the frequency correlation function of speckle patterns

In this paper we present a new method for estimating the bandwidth of multimode optical fibers based on the frequency correlation function of the speckle patterns generated by the interference of fiber modes. This technique, which does not require a pulse or signal generator, can be utilized to estimate the bandwidth of a multimode fiber using a relatively short length of fiber. By applying this method to a test fiber we obtained a bandwidth of approximately 36 MHz km which is in relatively good agreement with the approximately 44-MHz x km bandwidth measured by a conventional pulsed technique.     

Direct method for evaluation of bulk power system reliability Part 1: Theoretical foundation

The reliability of a bulk power system is defined as the probability of the set of states for which the DC load flow is satisfied with a particular demand and there is no line overload. A direct method to find such a set of working states, which does not require the solution of a load flow, is proposed. The method involves (i) replacing two sets, one defined by the constraints on line flows and the other by the constraints on phase angles, by two families of hyperboxes; and (ii) identifying the states for which there occur points in a pair of hyperboxes, one from each family, that satisfy the flow-angle relations. The theoretical foundation of the method is presented.     

Noise power spectra of optical two-beam interferometers induced by the laser phase noise

Dynamic range of many optical signal processing and sensing devices incorporating two-beam interferometers (such as Mach-Zehnder and Michelson interferometers) can be limited by random phase fluctuations of the optical source emission field. This paper is concerned with the intensity fluctuations, originating from the laser source phase noise, at the output of a two-beam interferometer. Closed-form theoretical expressions are presented for the autocovariance function, variance, and noise power spectral density of the instantaneous output intensity which are valid for any optical biasing phase and any source coherence time. Application of the results in the noise performance evaluation of optical devices incorporating two-beam interferometers will also be shown.     

Preoxidation treatment using HCl/HF vapor

Replacement of the conventional two-step sequence of aqueous HF dummy oxide strip and wet clean by a one-step vapor phase HCl/HF/H₂ O strip was investigated. Results indicated improvements in the electrical endurance of grown silicon dioxide and that the vapor mixture containing HCl was effective in reducing the detrimental effects caused by deliberately introduced contaminants. Compared with the conventional wet cleans, a 20% improvement in oxide lifetime was observed. Further improvements should be possible with proper optimization of the quantative composition or the constituents of the vapor     

A method for bulk power system reliability evaluation based on local coherency

The problem of bulk power system reliability evaluation is considered and a new solution approach is proposed. Bulk power system models are generally not coherent in the sense of reliability theory. Conditions are derived on network topology to guarantee coherency. Only parallel structure systems satisfy these conditions. Noncoherency of a power system may be the effect of only a subset of its transmission lines. Thus the concept of local coherency is introduced. A decomposition approach to bulk power system reliability evaluation based on the concept of local coherency is developed. Sufficient conditions for local coherency are derived.     

Optimizing blocking flow shop scheduling problem with total completion time criterion

The blocking flow shop scheduling problem has found many applications in manufacturing systems. There are a few exact methods for solving this problem with different criteria. In this paper, efforts will be made to optimize the total completion time criterion for this problem. We present two mixed binary integer programming models, one of which is based on the departure times of jobs from machines, and the other is based on the idle and blocking times of jobs. An initial upper bound generator and some lower bounds and dominance rules are also developed to be used in a branch and bound algorithm. The algorithm solves 17 instances of the Taillard's benchmark problem set in less than 20 min.     

A branch-and-bound algorithm for single machine scheduling with quadratic earliness and tardiness penalties

This paper considers the problem of scheduling a single machine, in which the objective function is to minimize the weighted quadratic earliness and tardiness penalties and no machine idle time is allowed. We develop a branch and bound algorithm involving the implementation of lower and upper bounding procedures as well as some dominance rules. The lower bound is designed based on a lagrangian relaxation method and the upper bound includes two phases, one for constructing initial schedules and the other for improving them. Computational experiments on a set of randomly generated instances show that one of the proposed heuristics, used as an upper bound, has an average gap less than 1.3% for instances optimally solved. The results indicate that both the lower and upper bounds are very tight and the branch-and-bound algorithm is the first algorithm that is able to optimally solve problems with up to 30 jobs in a reasonable amount of time.     

Rapid thermal multiprocessing for a programmable factory foradaptable manufacturing of ICs

This paper presents an overview of research at Stanford University on the development of concepts of a programmable factory, based on a new generation of flexible multifunctional equipment implemented in a smaller flexible factory. This approach is demonstrated through the development of a novel single wafer Rapid Thermal Multiprocessing (RTM) reactor with extensive integration of sensors, computers and related technology for specification, communication, execution, monitoring, control, and diagnosis to demonstrate the programmable nature of the RTM. The RTM combines rapid thermal processing and several other process environments in a single chamber, with applications for multilayer in-situ growth and deposition of dielectrics, semiconductors and metals. Because it is highly instrumented, the RTM is very flexible for in-situ multiprocessing, allowing rapid cycling of ambient gases, temperature, pressure, etc. It allows several processing steps to be executed sequentially in-situ, while providing sufficient flexibility to allow optimization of each processing step. This flexibility is partially the result of a new lamp system with three concentric rings each of which is independently and dynamically controlled to provide for better control over the spatial and temporal optical flux profile resulting in excellent temperature uniformity over a wide range of process conditions namely temperatures, pressures and gas flow rates. The lamp system has been optimally designed through the use of a newly developed thermal simulator. For equipment and process control, a variety of sensors for real-time measurements and a model based control system have been developed