Methods for incorporating imprecision in engineering design decision-making are briefly reviewed and compared. A tutorial is presented on the Method of Imprecision (MoI), a formal method, based on the mathematics of fuzzy sets, for representing and manipulating imprecision in engineering design. The results of a design cost estimation example, utilizing a new informal cost specification, are presented. The MoI can provide formal information upon which to base decisions during preliminary engineering design and can facilitate set-based concurrent design.

The dimensionality and complexity of typical multidisciplinary systems hinders the use of formal optimization techniques in application to this class of problems. The use of approximations to represent the system design metrics and constraints has become vital for achieving good performance in many multidisciplinary design optimization (MDO) algorithms. This paper reports resent research efforts on the use of variable fidelity response surface approximations (RSA) to drive the convergence of MDO problems using a trust region model management algorithm. The present study focuses on a comparative study of different response sampling strategies based on design of experiment (DOE) approaches within the disciplines to generate the zero order data to build the RSAs. Two MDO test problems that have complex coupling between disciplines are used to benchmark the performance of each sampling strategy. The results show that these types of variable fidelity RSAs can be eectively managed by the trust region model management strategy to drive convergence of MDO problems. It is observed that the efficiency of the optimization algorithm depends on the sampling strategy used. A comparison of the DOE approaches with those obtained using a optimization based sampling strategy (i.e., concurrent subspace optimization - CSSO) show the DOE methodologies to be competitive with the CSSO based sampling methodology in some cases. However, the CSSO based sampling strategy was found to be...

iii This document and the work it represents was impossible without the support of my wife Ginger. Often one needs non-technical advice to make clear what one is contemplating. Also one always needs a financial supporter. My thesis advisor Erik Antonsson helped focus many of my thoughts. In addition to providing me with technical assistance, he as well provided instruction on the process of conducting academic research, the communication of ideas both orally and written, and the approach to a developing field. I also owe much to my colleagues in the Engineering and Applied Science Division at Caltech. Their comments and advice maintained my comprehension and rigor. Andrew Lewis in particular provided me with invaluable support. Many of the technical proofs were impossible without him. This material and the work it represented were made possible, in part, by a fellowship from the AT&T-Bell Laboratories Ph.D. scholar program, sponsored by the AT&T foundation. Also, the National Science Foundation provided funding under a Presidential Young

Robustness is an important requirement for almost all kinds of products. In this article we show how evolutionary algorithms can be applied for robust design based on the approach of Taguchi. As an example we consider the design of multilayer optical coatings most frequently used for optical filters. 1 Introduction Robustness is an important requirement for almost all kinds of products, i.e. they should keep a good performance under varying conditions (temperature or humidity). Furthermore, the impact of wear, as well as manufacturing tolerances, should be limited as much as possible. Consequently, the production process itself as well as the environmental influences after the product is put to use have to be regarded during the product design. In this paper we focus on multilayer optical coatings (MOCs) as an example of how to achieve robust designs using evolutionary algorithms. MOCs are used to guarantee specific transmission and/or reflection characteristics of optical devices. Th...

We present an application of combinatorial designs and variance analysis to correlating events in the midst of multiple network faults. Network fault model is based on the probabilistic dependency graph that accounts for the uncertainty about the state of network elements. Orthogonal arrays help reduce the exponential number of failure configurations to a small subset on which further analysis is performed. The preliminary results show that statistical analysis can pinpoint the probable causes of the observed symptoms with high accuracy and significant level of confidence. An example demonstrates how multiple soft link failures are localized in MIL-STD 188-220's Datalink layer to explain the end-to-end connectivity problems in the network layer. This technique can be utilized for the networks operating in an unreliable environment such as wireless and/or military networks.

A design of experiments approach has been implemented using computational hypervelocity impact simulations to determine the most effective place to add mass to an existing metallic Thermal Protection System (TPS) to improve hypervelocity impact protection. Simulations were performed using axisymmetric models in CTH, a shock-physics code developed by Sandia National Laboratories, and validated by comparison with existing test data. The axisymmetric models were then used in a statistical sensitivity analysis to determine the influence of five design parameters on degree of hypervelocity particle dispersion. Several damage metrics were identified and evaluated. Damage metrics related to the extent of substructure damage were seen to produce misleading results, however damage metrics related to the degree of dispersion of the hypervelocity particle produced results that corresponded to physical intuition. Based on analysis of variance results it was concluded that the most effective way to increase hypervelocity impact resistance is to increase the thickness of the outer foil layer. Increasing the spacing between the outer surface and the substructure is also very effective at increasing dispersion.

A novel approach to the modeling and control of aerospace system design problems is presented. By integrating recent advances in probabilistic robust design and technology assessment methods with a traditional control system feedback architecture, the approach is intended to establish a unified structure for managing complex design problems under uncertainty. The notions of plant, state variables, feedback, and compensation are adapted from the realm of control theory to this new setting. A specific aspect of the paper addresses methods for categorizing and computing the plant's sensitivity to modeled uncertainty in the feedback system. An example problem is executed and described to illustrate probabilistic sensitivity analysis as well as one possible avenue for arriving at an optimal compensator. Since this topic is in the initial research stages, the near term challenges with regards to refining and improving the approach are identified throughout the paper. Two such challenges incl...

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Research article Using a water-immiscible ionic liquid to improve asymmetric reduction of 4-(trimethylsilyl)-3-butyn-2-one catalyzed by immobilized Candida parapsilosis CCTCC M203011 cells

This paper emphasizes the importance of teaching proper statistical design techniques in manufacturing engineering education. Metal cutting is chosen as an example area to outline the principles involved, and guidelines are provided to conduct and report experimental studies. INTRODUCTION A substantial portion of engineering research is experimental in nature. The validity of conclusions drawn from experimental research is significantly influenced by the conditions under which the experiment is conducted, and therefore careful thought has to be given to designing the experiment properly. Researchers in the social and life sciences have long realized the importance of this fact. However, it has been our experience that this is most often not the case in engineering. As an illustration, most graduate engineering curricula do not even require a course in experimental design. It is the intent of this paper to demonstrate the importance of teaching sound experimental design in manufacturi...