Optimal Design of Integrated Systems Health Management (ISHM) Systems for improving safety in NASA's Exploration Vehicles: A Two-Level Multidisciplinary Design Approach

In this paper, a two-level multidisciplinary design approach is described to optimize the effectiveness of ISHM s. At the top level, the overall safety of the mission consists of system-level variables, parameters, objectives, and constraints that are shared throughout the system and by all subsystems. Each subsystem level will then comprise of these shared values in addition to subsystem-specific variables, parameters, objectives and constraints. A hierarchical structure will be established to pass up or down shared values between the two levels with system-level and subsystem-level optimization routines

Using information Theory in Optimal Test Point Selection for Health Management in NASA's Exploration Vehicles

In this paper, we will present a new methodology that measures the "worth" of deploying an additional testing instrument (sensor) in terms of the amount of information that can be retrieved from such measurement. This quantity is obtained using a probabilistic model of RLV's that has been partially developed in the NASA Ames Research Center. A number of correlated attributes are identified and used to obtain the worth of deploying a sensor in a given test point from an information-theoretic viewpoint. Once the information-theoretic worth of sensors is formulated and incorporated into our general model for IHM performance, the problem can be formulated as a constrained optimization problem where reliability and operational safety of the system as a whole is considered. Although this research is conducted specifically for RLV's, the proposed methodology in its generic form can be easily extended to other domains of systems health monitoring

Event Detection in Aerospace Systems using Centralized Sensor Networks: A Comparative Study of Several Methodologies

Recent advances in micro electromechanical systems technology, digital electronics, and wireless communications have enabled development of low-cost, low-power, multifunctional miniature smart sensors. These sensors can be deployed throughout a region in an aerospace vehicle to build a network for measurement, detection and surveillance applications. Event detection using such centralized sensor networks is often regarded as one of the most promising health management technologies in aerospace applications where timely detection of local anomalies has a great impact on the safety of the mission. In this paper, we propose to conduct a qualitative comparison of several local event detection algorithms for centralized redundant sensor networks. The algorithms are compared with respect to their ability to locate and evaluate an event in the presence of noise and sensor failures for various node geometries and densities

An investigation of the efficacy of a water-cooled chill in improving the as-cast structure of the main bearing bulkhead in A319 engine blocks

In recent years, the automotive industry has been increasing the production of small, high-power gas engines as part of several strategies to achieve the new “Corporate Average Fuel Economy” (CAFE) standards, while at the same time meeting consumer demand for increased performance. This trend requires an improvement in the thermal and mechanical fatigue durability of the aluminium alloys used in the production of the cylinder heads and engine blocks in these engines. In the absence of modifying alloy chemistry, which potentially has significant implications for downstream operations such as heat treating and machining, one viable way to improve fatigue performance is to reduce the length-scales of the microstructural features arising from solidification that limit fatigue life. This, in turn, may be achieved by increasing the cooling rate during solidification (reducing the solidification time). Conventionally, solid chills are employed in industry to achieve this. A potential means of improving the efficacy of these chills is to incorporate water cooling. To assess the effectiveness of this method, a water-cooled chill was designed at UBC and installed in a bonded-sand engine block mould package (1/4 section). Twelve experiments were conducted with both a conventional solid chill and with a water-cooled chill (with and without a delay in water cooling). The moulds were instrumented with thermocouples to measure the evolution of temperature at key locations in the casting, and “Linear Variable Displacement Transducers” (LVDTs) to measure the gap size at the interface between the chill and the casting. A coupled thermal-stress mathematical model was developed in “ABAQUS 2016” to reproduce the experimental conditions and provide insight into interfacial heat transport and gap dynamics. Overall, the experimental and modelling results show the gap dynamics are complex and play a critical role in governing heat transport. If implemented carefully, the adoption of water-cooled chill technology has the potential to improve the cast microstructure, hence, increase the fatigue durability of the engine blocks.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat

Quantitative assessment of the effect of copper chills on casting/chill interface behavior and the microstructure of sand cast A319 alloy

Although the demand for A319 alloy has increased in recent years, thermal fatigue resistance of the alloy is still one of the most important challenges in engine applications, especially in the newer generation of engines in which cylinder spacing has been reduced. According to the previous studies there are several parameters that improve thermal fatigue resistance such as: low SDAS, fine grain size, low porosity level, and low intermetallic content. Cooling rate has a direct effect on the shape, size, and distribution of the microstructural phases, as well as on the scale of the dendrites, and pore size. High cooling rates can improve thermal fatigue resistance, as a result of fine microstructure and small pore size. On the other hand, thin sections of a mold may not properly fill and “Cold Shuts” may result, if high cooling rates are applied. One approach to balance these phenomena is to use a water-cooled chill where water cooling is activated part way through the casting sequence. This type of chill causes a lower cooling rate initially, when the filling procedure is occurring, and after filling, the cooling rate increases to reduce the microstructure size. The results show that this method has the potential to both avoid cold shuts and miss-runs and improve the cast microstructure farther into castings remote from the chill. A mathematical model has been developed in “ANSYS CFX 12.0” to evaluate the effectiveness of this concept quantitatively. The model simulates the behavior of the Casting/chill interface and also predicts the cooling rates resulting from different casting conditions when using solid chill and water-cooled chill.Applied Science, Faculty ofMaterials Engineering, Department ofGraduat

Selection of nurse’s role behaviors and identification of determinant factors in development of such roles

The purpose of this exploratory study was to determine the role behavior and the determinant factors influencing the achievement of such role behaviors by the B.S.N, graduates, May 1976, in the basic program of the University of British Columbia School of Nursing. Questions asked were: 1. What kind of role behaviors do University of British Columbia graduates have at the time of graduation, May 1976, and after three months employment in the hospital? 2. What are the determinant factors that influenced achievement of role behaviors of these B.S.N, graduates of the University of British Columbia School of Nursing? Marlene Kramer's Integrative Role Behavior scale and open-ended questionnaire were used to derive the information pertinent to the research problem. Kramer's Integrative Role Behavior scale was administered twice, once at graduation time, and the other three months after employment in the hospital. The open-ended questionnaire was administered after employment only. The study sample were 17 B.S.N.'s who were working in the hospitals throughout British Columbia and answered both sets of questionnaires at the two designated times. Analysis of the data included descriptive analysis, frequency tables, and the use of the T. test. The findings of the study showed that the University of British Columbia B.S.N.'s selected professional role behavior significantly higher at graduation time than upon employment. Besides, role behaviors appeared to be immediately responsive to exposure to the work system. The changes of role behavior upon employment were a higher selection of bureaucratic and integrative role behavior and lower selection of professional role behavior. The changes in selection of bureaucratic and integrative role behaviors were not statistically significant, but the trend of change was as literature suggested. The determinant factors in development of role behavior were mostly the result of ideal nursing education and actual work as a nurse following employment. In the educational setting instructors were instrumental in shaping the ideas of the nurse's role among B.S.N.'s. The study showed that these B.S.N.'s valued their education positively and their work settings (hospitals) negatively. The study suggests more extensive research on the problem. In the meantime, the three groups involved - i.e. nurse educators, nursing service administrators and B.S.N.'s involved - should share their frustrations and suggestions for better client care.Applied Science, Faculty ofNursing, School ofGraduat