1,829 research outputs found

    Qualitative Reliability Issues for Solid and Liquid Wall Fusion Design

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    Papers presented at the IEEE 15th Symposium on Fusion Engineering by the Alcator C-MOD Group, October 1993

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    Technology Roadmap for the 21st Century Truck Program, a government-industry research partnership

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    Volume 2 – Conference: Wednesday, March 9

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    10. Internationales Fluidtechnisches Kolloquium:Group 1 | 2: Novel System Structures Group 3 | 5: Pumps Group 4: Thermal Behaviour Group 6: Industrial Hydraulic

    Preliminary Physics Motivation and Engineering Design Assessment of the National High Power Torus

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    The NASA SBIR product catalog

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    The purpose of this catalog is to assist small business firms in making the community aware of products emerging from their efforts in the Small Business Innovation Research (SBIR) program. It contains descriptions of some products that have advanced into Phase 3 and others that are identified as prospective products. Both lists of products in this catalog are based on information supplied by NASA SBIR contractors in responding to an invitation to be represented in this document. Generally, all products suggested by the small firms were included in order to meet the goals of information exchange for SBIR results. Of the 444 SBIR contractors NASA queried, 137 provided information on 219 products. The catalog presents the product information in the technology areas listed in the table of contents. Within each area, the products are listed in alphabetical order by product name and are given identifying numbers. Also included is an alphabetical listing of the companies that have products described. This listing cross-references the product list and provides information on the business activity of each firm. In addition, there are three indexes: one a list of firms by states, one that lists the products according to NASA Centers that managed the SBIR projects, and one that lists the products by the relevant Technical Topics utilized in NASA's annual program solicitation under which each SBIR project was selected

    Investigation of Novel Displacement-Controlled Hydraulic Architectures for Railway Construction and Maintenance Machines

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    This dissertation aims at showing how to transform hydraulic systems of railway multi-actuator machinery characterized by inefficient state-of-the-art systems into the 21st Century. Designing machines that are highly efficient, productive, reliable, and cost affordable represents the target of this research. In this regard, migrating from valve-controlled architectures to displacement-controlled layouts is the proper answer. Displacement-controlled systems remove the losses generated by flow throttling typical of conventional circuits, allow an easy implementation of energy recovery (e.g. during regenerative braking), and create the possibility for the use of hybrid systems capable of maximizing the downsizing of the combustion engine. One portion of the dissertation focuses on efficient propulsion systems suitable for railway construction and maintenance machines. Two non-hybrid architectures are first proposed, i.e. a novel layout grounded on two independent hydrostatic transmissions (HSTs) and two secondary controlled hydraulic motors (SCHMs) connected in parallel. Three suitable control strategies are developed according to the specific requirements for railway machines and dedicated controllers are implemented. Detailed analyses are conducted via high-fidelity virtual simulations involving accurate modeling of the rail/wheel interface. The performance of the propulsion systems is proven by acceptable velocity tracking, accurate stopping position, achieving regenerative braking, and the expected behavior of the slip coefficients on both axles. Energy efficiency is the main emphasis during representative working cycles, which shows that the independent HSTs are more efficient. They consume 6.6% less energy than the SCHMs working with variable-pressure and 12.8% less energy than the SCHMs controlled with constant-pressure. Additionally, two alternative hybrid propulsion systems are proposed and investigated. These architectures enable a 35% reduction of the baseline machine’s rated engine power without modifying the working hydraulics. Concerning the working hydraulics, the focus is to extend displacement-controlled technology to specific functions on railway construction and maintenance machines. Two specific examples of complete hydraulic circuits for the next generation tamper-liners are proposed. In particular, an innovative approach used to drive displacement-controlled dual function squeeze actuators is presented, implemented, and experimentally validated. This approach combines two functions into a unique actuator, namely squeezing the ballast and vibrating the tamping tools of the work-heads. This results in many advantages, such as variable amplitude and variable frequency of the tamping tools’ vibration, improved reliability of the tamping process, and energy efficient actuation. A motion of the squeeze actuator characterized by a vibration up to 45 Hz, i.e. the frequency used in state-of-the-art systems, is experimentally confirmed. In conclusion, this dissertation demonstrates that displacement-controlled actuation represents the correct solution for next-generation railway construction and maintenance machines

    A Bridge and Engine Room Staffing and Scheduling Model for Robust Mission Accomplishment in the Littoral Combat Ships

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    The Navy’s Littoral Combat Ships were designed to be relatively small surface vessels for operations near a littoral shore theater. These ships were envisioned to be highly automated, networked, agile, stealthy surface combatants capable of defeating anti-access and asymmetric threats in the littorals with minimum manpower. To date, however, some of these ships have experienced significant engineering and propulsion plant failures that impacted mission accomplishment and were attributable, at least in part, to under staffing and over scheduling the human component of the automation-human operational environment. The critical human components on the Littoral Combat Ship are bridge and engine room staffing. Since the engineering plant has been the source of most major failures to date, this project sought to develop an engine room staffing and scheduling model for the Littoral Combat Ship class given a stated set of minimum mission objectives when operating under normal conditions – called “Condition III Underway Steaming”, which is used as the basis for official Navy manning calculations, and to provide recommendations for improved automation-human modeling. A survey of the crew of several LCS ships was conducted and the results were analyzed using exploratory data analysis and multiple joint correspondence analysis. Results of the survey analysis were applied to the design of a joint physical-cognitive-automation workflow analysis of critical procedures and failure modes as they map to four dimensions: fatigue, watch and maintenance tasking, and automation-human interface. Workflow analysis results were then simulated in an IMPRINT model of a typical watch period, and the results were evaluated against the four dimensions of the survey. The project validated that the four dimensions analyzed are indeed worthy of consideration in manpower models, and that IMPRINT has the potential, with a few modifications, to model joint physical-cognitive-automation workflows as an improvement to the current manpower-only models used in Navy ship design by accounting for human factors
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