Missouri University of Science and Technology

About: Missouri University of Science and Technology is a education organization based out in Rolla, Missouri, United States. It is known for research contribution in the topics: Control theory & Artificial neural network. The organization has 9380 authors who have published 21161 publications receiving 462544 citations. The organization is also known as: Missouri S&T & University of Missouri–Rolla.

A Comparison Study of Validity Indices on Swarm-Intelligence-Based Clustering

Abstract: Swarm intelligence has emerged as a worthwhile class of clustering methods due to its convenient implementation, parallel capability, ability to avoid local minima, and other advantages. In such applications, clustering validity indices usually operate as fitness functions to evaluate the qualities of the obtained clusters. However, as the validity indices are usually data dependent and are designed to address certain types of data, the selection of different indices as the fitness functions may critically affect cluster quality. Here, we compare the performances of eight well-known and widely used clustering validity indices, namely, the Calinski-Harabasz index, the CS index, the Davies-Bouldin index, the Dunn index with two of its generalized versions, the I index, and the silhouette statistic index, on both synthetic and real data sets in the framework of differential-evolution-particle-swarm-optimization (DEPSO)-based clustering. DEPSO is a hybrid evolutionary algorithm of the stochastic optimization approach (differential evolution) and the swarm intelligence method (particle swarm optimization) that further increases the search capability and achieves higher flexibility in exploring the problem space. According to the experimental results, we find that the silhouette statistic index stands out in most of the data sets that we examined. Meanwhile, we suggest that users reach their conclusions not just based on only one index, but after considering the results of several indices to achieve reliable clustering structures.

Mapping function to failure mode during component development

Abstract: When designing aerospace systems, it is essential to provide crucial failure information for failure prevention. Failure modes and effects types of analyses and prior engineering knowledge and experience are commonly used to determine the potential modes of failures a product might encounter during its lifetime. When new products are being considered and designed, this knowledge and information is expanded upon to help designers extrapolate based on their similarity with existing products and the potential design tradeoffs. In this work, we aim to enhance this process by providing design-aid tools which derive similarities between functionality and failure modes. Specifically, this paper presents the theoretical foundations of a matrix-based approach to derive similarities that exist between different failure modes, by mapping observed failure modes to the functionality of each component, and applies it to a simple design example. The function–failure mode method is proposed to design new products or redesign existing ones with solutions for functions that eliminate or reduce the potential of a failure mode.

New Techniques for Measuring Impedance Characteristics of Three-Phase AC Power Systems

Abstract: Naval ships as well as aerospace power systems are incorporating an increasing amount of power electronic switching sources and loads. Although these power-electronics-based components provide exceptional performance, they are prone to instability due to their constant power characteristics that lead to negative impedance. When designing these systems, integrators must consider the impedance versus frequency at a power system interface (which designates source and load). Stability criteria have been developed in terms of source and load impedance for both dc and ac power systems, and it is often helpful to have techniques for impedance measurement. For dc power systems, the measurement techniques have been well established. This paper suggests several methods for measuring ac impedance including utilization of power converters, wound-rotor induction machines, and chopper circuits. Simulation and laboratory results on an example ac power system demonstrate the effectiveness of the proposed methods.