Visual Sample Plan (VSP) Models and Code Verification

VSP is an easy to use, visual and graphic software tool being developed to select the right number and location of environmental samples so that the results of statistical tests performed to provide input to environmental decisions have the required confidence and performance. It is a significant help for implementing the 6th and 7th steps of the Data Quality Objectives (DQO) planning process ("Specify Tolerable Limits on Decision Errors" and "Optimize the Design for Obtaining Data," respectively)

Proceedings of the 2nd Annual Workshop on Meteorological and Environmental Inputs to Aviation Systems

The proceedings of a workshop held at the University of Tennessee Space Institute, Tullahoma, Tennessee, March 28-30, 1978, are reported. The workshop was jointly sponsored by NASA, NOAA, FAA, and brought together many disciplines of the aviation communities in round table discussions. The major objectives of the workshop are to satisfy such needs of the sponsoring agencies as the expansion of our understanding and knowledge of the interactions of the atmosphere with aviation systems, as the better definition and implementation of services to operators, and as the collection and interpretation of data for establishing operational criteria, relating the total meteorological inputs from the atmospheric sciences to the needs of aviation communities

Verification of the Accuracy of Sample-Size Equation Calculations for Visual Sample Plan Version 0.9C

Visual Sample Plan (VSP) is a software tool being developed to facilitate the design of environmental sampling plans using a site-map visual interface, standard sample-size equations, a variety of sampling grids and random sampling plans, and graphs to visually depict the results to the user. This document provides comparisons between sample sizes calculated by VSP Version 0.9C, and sample sizes calculated by test code written in the S-Plus language. All sample sizes calculated by VSP matched the independently calculated sample sizes. Also the VSP implementation of the ELIGPRID-PC algorithm for hot spot probabilities is shown to match previous results for 100 standard test cases. The Conclusions and Limitations section of this document lists some aspects of VSP that were not tested by this suite of tests and recommends simulation-based enhancements for future versions of VSP

A framework for generating operational characteristic curves for semiconductor manufacturing systems using flexible and reusable discrete event simulations

This thesis proposes a framework for generating operating curves for semiconductor manufacturing facilities using a modular flexible discrete event simulation (DES) model embedded in an application that automates the design of experiments for the simulations. Typically, operating curves are generated using analytical queueing models that are difficult to implement and hence, can only be used for benchmarking purposes. Alternatively, DES models are more capable of capturing the complexities of a semiconductor manufacturing facility such as re-entrancy, rework and non-identical toolsets. However, traditional craft-based simulations require much time and resources. The proposed methodology aims to reduce this time by automatically calculating the parameters for experimentation and generating the simulation model. It proposes a novel method to more appropriately allocate simulation effort by selecting design points more relevant to the operating curve. The methodology was initially applied to a single toolset model and tested as a pilot case study using actual factory data. Overall, the resulting operating curves matched that of the actual data. Subsequently, the methodology was applied to a full semiconductor manufacturing facility, using datasets from the Semiconductor Wafer Manufacturing Data Format Specification. The automated framework was shown to generate the curves rapidly and comparisons against a number of queueing model equivalents showed that the DES curves were more accurate. The implications of this work mean that on deployment of the application, semiconductor manufacturers can quickly obtain an accurate operating curve of their factory that could be used to aid in capacity planning and enable better decision-making regarding allocation of resources

Time-dependent reliability analysis of corrosion-induced concrete cracking based on fracture mechanics criteria

Practical experience and observations suggest that corrosion affected reinforced concrete structures are more prone to cracking than other forms of structural deterioration. Around the world, maintenance and repairs resulting from premature concrete cracking and spalling are associated with very high running cost. Furthermore, the ever-increasing demand for greater load carrying capacity of existing reinforced concrete structure only exacerbate the issue. Consequently, this increases the probability of failure of corrosion-affected reinforced concrete structure. It is therefore vital to study corrosion-induced concrete cracking and to perform a service life prediction to avoid unwanted corrosion-induced failures and develop cost-effective methods for maintenance and rehabilitation of reinforced concrete structures. This research attempts to examine the process of concrete cracking and determine the critical crack depth at which a corrosion-induced crack becomes unstable and suddenly propagate to the concrete surface. In the analytical model, a model for corrosion-induced critical crack depth has been derived based on the concept of stress intensity factor. In the numerical model, an extended finite element method has been used to predict the concrete cover capacity based on a maximum principal stress fracture criterion. To validate the developed models, an accelerated corrosion experiment was conducted and the time to corrosion-induced cracking and the growth of crack width was measured. With the developed model, a time-dependent remaining service life prediction for corrosion-induced cracking in RC was conducted. It is concluded that the analytical method is one of the very few theoretical methods that can predict with reasonable accuracy corrosion-induced critical crack depth in reinforced concrete. It was also found that the extended finite element method can be used to model the concrete cover capacity which can then be used to predict the time to corrosion-induced concrete cracking.  It was also found that the porous zone in concrete can significantly affect the time to corrosion-induced cracking. It was also found that corrosion rate and concrete cover are the most influencing factors that will affect the remaining service life of corrosion affected reinforced concrete structures. With the developed models in this thesis, the information provided can help asset managers and engineers in making more inform decisions with regards to maintenance and rehabilitation strategies of corrosion affected reinforced concrete structures

Selection of Preservatives for Marine Structural Timbers in Herring Spawning Areas

INE/AUTC 12.2

The Second Joint NASA/FAA/DOD Conference on Aging Aircraft

The purpose of the Conference was to bring together world leaders in aviation safety research, aircraft design and manufacturing, fleet operation and aviation maintenance to disseminate information on current practices and advanced technologies that will assure the continued airworthiness of the aging aircraft in the military and commercial fleets. The Conference included reviews of current industry practices, assessments of future technology requirements, and status of aviation safety research. The Conference provided an opportunity for interactions among the key personnel in the research and technology development community, the original equipment manufacturers, commercial airline operators, military fleet operators, aviation maintenance, and aircraft certification and regulatory authorities. Conference participation was unrestricted and open to the international aviation community