Mechanical properties of high gradient and hot isostatically pressed PWA 1480

This program has been designed to evaluate the potential benefits to alloy 1480 material properties due to high thermal gradient casting, hot isostatic pressing, and alternative heat treatment. Alloy 1480 castings have been obtained from vendors representing the extremes of commercial casting thermal gradients. Quantitative characterization of the dendrite arm spacing (DAS) and pore distributions has been conducted. A hot isostatic pressing (HIP) schedule, which avoids the many pitfalls of single crystal HIP has been devised for alloy 1480. In addition, an alternate heat treatment for alloy 1480 has been devised which provides benefits in mechanical properties. The standard gradient cast test material is being evaluated in the standard heat treat condition as a baseline and in the HIP plus alternate heat treated condition. The fhigh gradient cast material is being evaluated in alternate heat treat and HIP plus alternate heat treated conditions. Evaluations focus on demonstration of the benefits due to the applied processes, especially in the area of cyclic life

The influence of advanced processing on PWA 1480

High thermal gradient casting of PWA 1480 was evaluated as an avenue for reducing the size of casting porosity. Hot isostatic pressing (HIP) was also employed for the elimination of casting pores. An alternate to the standard PWA 1480 coating plus diffusion bonding aging heat treatment cycle was also evaluated for potential improvements in the properties of interest to the Space Shuttle Main Engine (SSME) application. Microstructural changes associated with the high thermal gradient casting process were quantified by measurement of the size and density of the casting porosity, the amount of retained casting eutectic, and dendrite arm spacings. The results of the advanced processing have shown an improvement in material microstructure due to high thermal gradient casting. Improved homogeneity of PWA 1480 is advantageous in providing an improved solution heat treatment window and, potentially, easier HIP. High thermal gradient casting improves fatigue life by reducing casting pore size. The alternate heat treatment improves the balance of strength and ductility which appears to improve low cycle fatigue life, but with a reduction in short time stress rupture life. Based upon these tests, hot isostatic pressing appears to afford further improvements in cyclic life, though additional evaluation is suggested. Development of the alternate heat treatment is not recommended due to the reduced stress rupture capability and the need to develop a new properties data base. High thermal gradient casting and HIP are recommended for application to single crystal castings

Endocrine and bone health in pediatric brain tumour survivors

In der vorliegenden Arbeit wurde im Rahmen der Querschnittsstudie „Untersuchungen zur Knochengesundheit bei Kindern und Jugendlichen nach onkologischer Erkrankung und Therapie“ die Kohorte der an einem Tumor des zentralen Nervensystems erkrankten Kinder untersucht. Für die Datenerhebung wurden die Kinder im laufenden Ambulanzbetrieb einer klinischen, laborchemischen und teilweise auch radiologischen Untersuchung unterzogen. Ergänzt wurden die Daten durch eine umfangreiche Aktenrecherche. Besonderes Merkmal der Studie ist die multifaktorielle Bewertung der Knochengesundheit. Vergleichbar gelagerte Studien zogen zumeist lediglich die Knochendichtemessung als Bewertungskriterium heran. Die gewonnenen Daten wurden gezielt in Hinblick auf die Knochengesundheit und den hormonellen Zustand der Patienten analysiert. Kinder, welche an einem Tumor des zentralen Nervensystems erkrankt sind, leiden häufiger unter Störungen des hormonellen Systems. Störungen des hormonellen Systems wiederum führen den Ergebnissen dieser Arbeit zufolge zu einer schlechteren Knochen- gesundheit. Daneben ergaben sich auch bisher nicht eindeutig beschriebene Hinweise auf eine Schädigung des Skelettsystems durch die Behandlung mit Vincristin. Somit ist eine engmaschige endokrinologische Nachsorge der Überlebenden einer kindlichen Hirntumorerkrankung sinnvoll und sollte noch verbessert werden, um den Anteil der nichtbehandelten Folgeerkrankungen weiter zu reduzieren

The Relevance of Sensory-based Intervention in Improving Occupational Performance in Pediatrics

The present capstone experience highlights sensory processing differences in relation to occupational performance. Current literature suggests varying evidence on sensory processing differences and effective interventions. This capstone utilizes GAS to measure progress toward functional goals with sensory-based intervention. Results indicate improvements for all five clients in at least one area after 5 to 8 sessions of sensory-based intervention. Improvements noted on GAS demonstrate the effectiveness of sensory-based intervention to address functional differences. The scope of practice for occupational therapy practitioners, therefore, includes sensory-based intervention to improve functional performance and well-being across several settings

Advanced single crystal for SSME turbopumps

The objective of this program was to evaluate the influence of high thermal gradient casting, hot isostatic pressing (HIP) and alternate heat treatments on the microstructure and mechanical properties of a single crystal nickel base superalloy. The alloy chosen for the study was PWA 1480, a well characterized, commercial alloy which had previously been chosen as a candidate for the Space Shuttle Main Engine high pressure turbopump turbine blades. Microstructural characterization evaluated the influence of casting thermal gradient on dendrite arm spacing, casting porosity distribution and alloy homogeneity. Hot isostatic pressing was evaluated as a means of eliminating porosity as a preferred fatigue crack initiation site. The alternate heat treatment was chosen to improve hydrogen environment embrittlement resistance and for potential fatigue life improvement. Mechanical property evaluation was aimed primarily at determining improvements in low cycle and high cycle fatigue life due to the advanced processing methods. Statistically significant numbers of tests were conducted to quantitatively demonstrate life differences. High thermal gradient casting improves as-cast homogeneity, which facilitates solution heat treatment of PWA 1480 and provides a decrease in internal pore size, leading to increases in low cycle and high cycle fatigue lives

Investigation of cleanliness verification techniques for rocket engine hardware

Oxidizer propellant systems for liquid-fueled rocket engines must meet stringent cleanliness requirements for particulate and nonvolatile residue. These requirements were established to limit residual contaminants which could block small orifices or ignite in the oxidizer system during engine operation. Limiting organic residues in high pressure oxygen systems is particularly important. The current method of cleanliness verification used by Rocketdyne requires an organic solvent flush of the critical hardware surfaces. The solvent is filtered and analyzed for particulate matter, followed by gravimetric determination of the nonvolatile residue (NVR) content of the filtered solvent. The organic solvents currently specified for use (1,1,1-trichloroethane and CFC-113) are ozone-depleting chemicals slated for elimination by December 1995. A test program is in progress to evaluate alternative methods for cleanliness verification that do not require the use of ozone-depleting chemicals and that minimize or eliminate the use of solvents regulated as hazardous air pollutants or smog precursors. Initial results from the laboratory test program to evaluate aqueous-based methods and organic solvent flush methods for NVR verification are provided and compared with results obtained using the current method. Evaluation of the alternative methods was conducted using a range of contaminants encountered in the manufacture of rocket engine hardware

Investigation of Cleanliness Verification Techniques for Rocket Engine Hardware

Oxidizer propellant systems for liquid-fueled rocket engines must meet stringent cleanliness requirements for particulate and nonvolatile residue. These requirements were established to limit residual contaminants which could block small orifices or ignite in the oxidizer system during engine operation. Limiting organic residues in high pressure oxygen systems, such as in the Space Shuttle Main Engine (SSME), is particularly important. The current method of cleanliness verification for the SSME uses an organic solvent flush of the critical hardware surfaces. The solvent is filtered and analyzed for particulate matter followed by gravimetric determination of the nonvolatile residue (NVR) content of the filtered solvent. The organic solvents currently specified for use (1, 1, 1-trichloroethane and CFC-113) are ozone-depleting chemicals slated for elimination by December 1995. A test program is in progress to evaluate alternative methods for cleanliness verification that do not require the use of ozone-depleting chemicals and that minimize or eliminate the use of solvents regulated as hazardous air pollutants or smog precursors. Initial results from the laboratory test program to evaluate aqueous-based methods and organic solvent flush methods for NVR verification are provided and compared with results obtained using the current method. Evaluation of the alternative methods was conducted using a range of contaminants encountered in the manufacture of rocket engine hardware

A Tale of Two Object Recognition Methods for Mobile Robots

This original publication is available at www.springerlink.comObject recognition is a key feature for building robots capable of moving and performing tasks in human environments. However, current object recognition research largely ignores the problems that the mobile robots context introduces. This work addresses the problem of applying these techniques to mobile robotics in a typical household scenario. We select two state-of-the-art object recognition methods, which are suitable to be adapted to mobile robots, and we evaluate them on a challenging dataset of typical household objects that caters to these requirements. The different advantages and drawbacks found for each method are highlighted, and some ideas for extending them are proposed. Evaluation is done comparing the number of detected objects and false positives for both approaches.This work has been partially funded by the FI grant and the BE grant from the AGAUR, the European Social Fund, the 2005/SGR/00093 project, supported by the Generalitat de Catalunya , the MIDCBR project grant TIN 200615140C0301, TIN 200615308C0202 and FEDER funds.Peer reviewe

Progress Towards III-V Photovoltaics on Flexible Substrates

Presented here is the recent progress of the NASA Glenn Research Center OMVPE group's efforts in the development of high efficiency thin-film polycrystalline III-V photovoltaics on optimum substrates. By using bulk polycrystalline germanium (Ge) films, devices of high efficiency and low mass will be developed and incorporated onto low-cost flexible substrates. Our progress towards the integration of high efficiency polycrystalline III-V devices and recrystallized Ge films on thin metal foils is discussed