The Typical General Aviation Aircraft

NASA Technical Reports Server (NTRS)

Turnbull, Andrew

1999-01-01

The reliability of General Aviation aircraft is unknown. In order to "assist the development of future GA reliability and safety requirements", a reliability study needs to be performed. Before any studies on General Aviation aircraft reliability begins, a definition of a typical aircraft that encompasses most of the general aviation characteristics needs to be defined. In this report, not only is the typical general aviation aircraft defined for the purpose of the follow-on reliability study, but it is also separated, or "sifted" into several different categories where individual analysis can be performed on the reasonably independent systems. In this study, the typical General Aviation aircraft is a four-place, single engine piston, all aluminum fixed-wing certified aircraft with a fixed tricycle landing gear and a cable operated flight control system. The system breakdown of a GA aircraft "sifts" the aircraft systems and components into five categories: Powerplant, Airframe, Aircraft Control Systems, Cockpit Instrumentation Systems, and the Electrical Systems. This breakdown was performed along the lines of a failure of the system. Any component that caused a system to fail was considered a part of that system.

Parts and Components Reliability Assessment: A Cost Effective Approach

NASA Technical Reports Server (NTRS)

Lee, Lydia

2009-01-01

System reliability assessment is a methodology which incorporates reliability analyses performed at parts and components level such as Reliability Prediction, Failure Modes and Effects Analysis (FMEA) and Fault Tree Analysis (FTA) to assess risks, perform design tradeoffs, and therefore, to ensure effective productivity and/or mission success. The system reliability is used to optimize the product design to accommodate today?s mandated budget, manpower, and schedule constraints. Stand ard based reliability assessment is an effective approach consisting of reliability predictions together with other reliability analyses for electronic, electrical, and electro-mechanical (EEE) complex parts and components of large systems based on failure rate estimates published by the United States (U.S.) military or commercial standards and handbooks. Many of these standards are globally accepted and recognized. The reliability assessment is especially useful during the initial stages when the system design is still in the development and hard failure data is not yet available or manufacturers are not contractually obliged by their customers to publish the reliability estimates/predictions for their parts and components. This paper presents a methodology to assess system reliability using parts and components reliability estimates to ensure effective productivity and/or mission success in an efficient manner, low cost, and tight schedule.

Reliable Thermoelectric Module Design under Opposing Requirements from Structural and Thermoelectric Considerations

NASA Astrophysics Data System (ADS)

Karri, Naveen K.; Mo, Changki

2018-06-01

Structural reliability of thermoelectric generation (TEG) systems still remains an issue, especially for applications such as large-scale industrial or automobile exhaust heat recovery, in which TEG systems are subject to dynamic loads and thermal cycling. Traditional thermoelectric (TE) system design and optimization techniques, focused on performance alone, could result in designs that may fail during operation as the geometric requirements for optimal performance (especially the power) are often in conflict with the requirements for mechanical reliability. This study focused on reducing the thermomechanical stresses in a TEG system without compromising the optimized system performance. Finite element simulations were carried out to study the effect of TE element (leg) geometry such as leg length and cross-sectional shape under constrained material volume requirements. Results indicated that the element length has a major influence on the element stresses whereas regular cross-sectional shapes have minor influence. The impact of TE element stresses on the mechanical reliability is evaluated using brittle material failure theory based on Weibull analysis. An alternate couple configuration that relies on the industry practice of redundant element design is investigated. Results showed that the alternate configuration considerably reduced the TE element and metallization stresses, thereby enhancing the structural reliability, with little trade-off in the optimized performance. The proposed alternate configuration could serve as a potential design modification for improving the reliability of systems optimized for thermoelectric performance.

Photovoltaic performance and reliability workshop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kroposki, B

1996-10-01

This proceedings is the compilation of papers presented at the ninth PV Performance and Reliability Workshop held at the Sheraton Denver West Hotel on September 4--6, 1996. This years workshop included presentations from 25 speakers and had over 100 attendees. All of the presentations that were given are included in this proceedings. Topics of the papers included: defining service lifetime and developing models for PV module lifetime; examining and determining failure and degradation mechanisms in PV modules; combining IEEE/IEC/UL testing procedures; AC module performance and reliability testing; inverter reliability/qualification testing; standardization of utility interconnect requirements for PV systems; need activitiesmore » to separate variables by testing individual components of PV systems (e.g. cells, modules, batteries, inverters,charge controllers) for individual reliability and then test them in actual system configurations; more results reported from field experience on modules, inverters, batteries, and charge controllers from field deployed PV systems; and system certification and standardized testing for stand-alone and grid-tied systems.« less

Integration of tools for the Design and Assessment of High-Performance, Highly Reliable Computing Systems (DAHPHRS), phase 1

NASA Technical Reports Server (NTRS)

Scheper, C.; Baker, R.; Frank, G.; Yalamanchili, S.; Gray, G.

1992-01-01

Systems for Space Defense Initiative (SDI) space applications typically require both high performance and very high reliability. These requirements present the systems engineer evaluating such systems with the extremely difficult problem of conducting performance and reliability trade-offs over large design spaces. A controlled development process supported by appropriate automated tools must be used to assure that the system will meet design objectives. This report describes an investigation of methods, tools, and techniques necessary to support performance and reliability modeling for SDI systems development. Models of the JPL Hypercubes, the Encore Multimax, and the C.S. Draper Lab Fault-Tolerant Parallel Processor (FTPP) parallel-computing architectures using candidate SDI weapons-to-target assignment algorithms as workloads were built and analyzed as a means of identifying the necessary system models, how the models interact, and what experiments and analyses should be performed. As a result of this effort, weaknesses in the existing methods and tools were revealed and capabilities that will be required for both individual tools and an integrated toolset were identified.

Fix These First: How the World's Leading Companies Point the Way Toward High Reliability in the Military Health System.

PubMed

Beauvais, Brad; Richter, Jason; Brezinski, Paul

The 2014 Military Health System Review calls for healthcare system leaders to implement effective strategies used by other high-performing organizations. The authors state, " the [military health system] MHS can create an optimal healthcare environment that focuses on continuous quality improvement where every patient receives safe, high-quality care at all times" (Military Health System, 2014, p. 1). Although aspirational, the document does not specify how a highly reliable health system is developed or what systemic factors are necessary to sustain highly reliable performance. Our work seeks to address this gap and provide guidance to MHS leaders regarding how high-performing organizations develop exceptional levels of performance.The authors' expectation is that military medicine will draw on these lessons to enhance leadership, develop exceptional organizational cultures, onboard and engage employees, build customer loyalty, and improve quality of care. Leaders from other segments of the healthcare field likely will find this study valuable given the size of the military healthcare system (9.6 million beneficiaries), the United States' steady progression toward population-based health, and the increasing need for highly reliable systems and performance.

Sensitivity Analysis of ProSEDS (Propulsive Small Expendable Deployer System) Data Communication System

NASA Technical Reports Server (NTRS)

Park, Nohpill; Reagan, Shawn; Franks, Greg; Jones, William G.

1999-01-01

This paper discusses analytical approaches to evaluating performance of Spacecraft On-Board Computing systems, thereby ultimately achieving a reliable spacecraft data communications systems. The sensitivity analysis approach of memory system on the ProSEDS (Propulsive Small Expendable Deployer System) as a part of its data communication system will be investigated. Also, general issues and possible approaches to reliable Spacecraft On-Board Interconnection Network and Processor Array will be shown. The performance issues of a spacecraft on-board computing systems such as sensitivity, throughput, delay and reliability will be introduced and discussed.

Design and Analysis of a Flexible, Reliable Deep Space Life Support System

NASA Technical Reports Server (NTRS)

Jones, Harry W.

2012-01-01

This report describes a flexible, reliable, deep space life support system design approach that uses either storage or recycling or both together. The design goal is to provide the needed life support performance with the required ultra reliability for the minimum Equivalent System Mass (ESM). Recycling life support systems used with multiple redundancy can have sufficient reliability for deep space missions but they usually do not save mass compared to mixed storage and recycling systems. The best deep space life support system design uses water recycling with sufficient water storage to prevent loss of crew if recycling fails. Since the amount of water needed for crew survival is a small part of the total water requirement, the required amount of stored water is significantly less than the total to be consumed. Water recycling with water, oxygen, and carbon dioxide removal material storage can achieve the high reliability of full storage systems with only half the mass of full storage and with less mass than the highly redundant recycling systems needed to achieve acceptable reliability. Improved recycling systems with lower mass and higher reliability could perform better than systems using storage.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisner, R.; Melin, A.; Burress, T.

The objective of this project is to demonstrate improved reliability and increased performance made possible by deeply embedding instrumentation and controls (I&C) in nuclear power plant (NPP) components and systems. The project is employing a highly instrumented canned rotor, magnetic bearing, fluoride salt pump as its I&C technology demonstration platform. I&C is intimately part of the basic millisecond-by-millisecond functioning of the system; treating I&C as an integral part of the system design is innovative and will allow significant improvement in capabilities and performance. As systems become more complex and greater performance is required, traditional I&C design techniques become inadequate andmore » more advanced I&C needs to be applied. New I&C techniques enable optimal and reliable performance and tolerance of noise and uncertainties in the system rather than merely monitoring quasistable performance. Traditionally, I&C has been incorporated in NPP components after the design is nearly complete; adequate performance was obtained through over-design. By incorporating I&C at the beginning of the design phase, the control system can provide superior performance and reliability and enable designs that are otherwise impossible. This report describes the progress and status of the project and provides a conceptual design overview for the platform to demonstrate the performance and reliability improvements enabled by advanced embedded I&C.« less

System reliability approaches for advanced propulsion system structures

NASA Technical Reports Server (NTRS)

Cruse, T. A.; Mahadevan, S.

1991-01-01

This paper identifies significant issues that pertain to the estimation and use of system reliability in the design of advanced propulsion system structures. Linkages between the reliabilities of individual components and their effect on system design issues such as performance, cost, availability, and certification are examined. The need for system reliability computation to address the continuum nature of propulsion system structures and synergistic progressive damage modes has been highlighted. Available system reliability models are observed to apply only to discrete systems. Therefore a sequential structural reanalysis procedure is formulated to rigorously compute the conditional dependencies between various failure modes. The method is developed in a manner that supports both top-down and bottom-up analyses in system reliability.

The challenge of measuring emergency preparedness: integrating component metrics to build system-level measures for strategic national stockpile operations.

PubMed

Jackson, Brian A; Faith, Kay Sullivan

2013-02-01

Although significant progress has been made in measuring public health emergency preparedness, system-level performance measures are lacking. This report examines a potential approach to such measures for Strategic National Stockpile (SNS) operations. We adapted an engineering analytic technique used to assess the reliability of technological systems-failure mode and effects analysis-to assess preparedness. That technique, which includes systematic mapping of the response system and identification of possible breakdowns that affect performance, provides a path to use data from existing SNS assessment tools to estimate likely future performance of the system overall. Systems models of SNS operations were constructed and failure mode analyses were performed for each component. Linking data from existing assessments, including the technical assistance review and functional drills, to reliability assessment was demonstrated using publicly available information. The use of failure mode and effects estimates to assess overall response system reliability was demonstrated with a simple simulation example. Reliability analysis appears an attractive way to integrate information from the substantial investment in detailed assessments for stockpile delivery and dispensing to provide a view of likely future response performance.

Reliability model of a monopropellant auxiliary propulsion system

NASA Technical Reports Server (NTRS)

Greenberg, J. S.

1971-01-01

A mathematical model and associated computer code has been developed which computes the reliability of a monopropellant blowdown hydrazine spacecraft auxiliary propulsion system as a function of time. The propulsion system is used to adjust or modify the spacecraft orbit over an extended period of time. The multiple orbit corrections are the multiple objectives which the auxiliary propulsion system is designed to achieve. Thus the reliability model computes the probability of successfully accomplishing each of the desired orbit corrections. To accomplish this, the reliability model interfaces with a computer code that models the performance of a blowdown (unregulated) monopropellant auxiliary propulsion system. The computer code acts as a performance model and as such gives an accurate time history of the system operating parameters. The basic timing and status information is passed on to and utilized by the reliability model which establishes the probability of successfully accomplishing the orbit corrections.

Applicability and Limitations of Reliability Allocation Methods

NASA Technical Reports Server (NTRS)

Cruz, Jose A.

2016-01-01

Reliability allocation process may be described as the process of assigning reliability requirements to individual components within a system to attain the specified system reliability. For large systems, the allocation process is often performed at different stages of system design. The allocation process often begins at the conceptual stage. As the system design develops, more information about components and the operating environment becomes available, different allocation methods can be considered. Reliability allocation methods are usually divided into two categories: weighting factors and optimal reliability allocation. When properly applied, these methods can produce reasonable approximations. Reliability allocation techniques have limitations and implied assumptions that need to be understood by system engineers. Applying reliability allocation techniques without understanding their limitations and assumptions can produce unrealistic results. This report addresses weighting factors, optimal reliability allocation techniques, and identifies the applicability and limitations of each reliability allocation technique.

Reliability and coverage analysis of non-repairable fault-tolerant memory systems

NASA Technical Reports Server (NTRS)

Cox, G. W.; Carroll, B. D.

1976-01-01

A method was developed for the construction of probabilistic state-space models for nonrepairable systems. Models were developed for several systems which achieved reliability improvement by means of error-coding, modularized sparing, massive replication and other fault-tolerant techniques. From the models developed, sets of reliability and coverage equations for the systems were developed. Comparative analyses of the systems were performed using these equation sets. In addition, the effects of varying subunit reliabilities on system reliability and coverage were described. The results of these analyses indicated that a significant gain in system reliability may be achieved by use of combinations of modularized sparing, error coding, and software error control. For sufficiently reliable system subunits, this gain may far exceed the reliability gain achieved by use of massive replication techniques, yet result in a considerable saving in system cost.

A Simple and Reliable Method of Design for Standalone Photovoltaic Systems

NASA Astrophysics Data System (ADS)

Srinivasarao, Mantri; Sudha, K. Rama; Bhanu, C. V. K.

2017-06-01

Standalone photovoltaic (SAPV) systems are seen as a promoting method of electrifying areas of developing world that lack power grid infrastructure. Proliferations of these systems require a design procedure that is simple, reliable and exhibit good performance over its life time. The proposed methodology uses simple empirical formulae and easily available parameters to design SAPV systems, that is, array size with energy storage. After arriving at the different array size (area), performance curves are obtained for optimal design of SAPV system with high amount of reliability in terms of autonomy at a specified value of loss of load probability (LOLP). Based on the array to load ratio (ALR) and levelized energy cost (LEC) through life cycle cost (LCC) analysis, it is shown that the proposed methodology gives better performance, requires simple data and is more reliable when compared with conventional design using monthly average daily load and insolation.

General Aviation Aircraft Reliability Study

NASA Technical Reports Server (NTRS)

Pettit, Duane; Turnbull, Andrew; Roelant, Henk A. (Technical Monitor)

2001-01-01

This reliability study was performed in order to provide the aviation community with an estimate of Complex General Aviation (GA) Aircraft System reliability. To successfully improve the safety and reliability for the next generation of GA aircraft, a study of current GA aircraft attributes was prudent. This was accomplished by benchmarking the reliability of operational Complex GA Aircraft Systems. Specifically, Complex GA Aircraft System reliability was estimated using data obtained from the logbooks of a random sample of the Complex GA Aircraft population.

A reliability analysis tool for SpaceWire network

NASA Astrophysics Data System (ADS)

Zhou, Qiang; Zhu, Longjiang; Fei, Haidong; Wang, Xingyou

2017-04-01

A SpaceWire is a standard for on-board satellite networks as the basis for future data-handling architectures. It is becoming more and more popular in space applications due to its technical advantages, including reliability, low power and fault protection, etc. High reliability is the vital issue for spacecraft. Therefore, it is very important to analyze and improve the reliability performance of the SpaceWire network. This paper deals with the problem of reliability modeling and analysis with SpaceWire network. According to the function division of distributed network, a reliability analysis method based on a task is proposed, the reliability analysis of every task can lead to the system reliability matrix, the reliability result of the network system can be deduced by integrating these entire reliability indexes in the matrix. With the method, we develop a reliability analysis tool for SpaceWire Network based on VC, where the computation schemes for reliability matrix and the multi-path-task reliability are also implemented. By using this tool, we analyze several cases on typical architectures. And the analytic results indicate that redundancy architecture has better reliability performance than basic one. In practical, the dual redundancy scheme has been adopted for some key unit, to improve the reliability index of the system or task. Finally, this reliability analysis tool will has a directive influence on both task division and topology selection in the phase of SpaceWire network system design.

Reliability analysis of a phaser measurement unit using a generalized fuzzy lambda-tau(GFLT) technique.

PubMed

Komal

2018-05-01

Nowadays power consumption is increasing day-by-day. To fulfill failure free power requirement, planning and implementation of an effective and reliable power management system is essential. Phasor measurement unit(PMU) is one of the key device in wide area measurement and control systems. The reliable performance of PMU assures failure free power supply for any power system. So, the purpose of the present study is to analyse the reliability of a PMU used for controllability and observability of power systems utilizing available uncertain data. In this paper, a generalized fuzzy lambda-tau (GFLT) technique has been proposed for this purpose. In GFLT, system components' uncertain failure and repair rates are fuzzified using fuzzy numbers having different shapes such as triangular, normal, cauchy, sharp gamma and trapezoidal. To select a suitable fuzzy number for quantifying data uncertainty, system experts' opinion have been considered. The GFLT technique applies fault tree, lambda-tau method, fuzzified data using different membership functions, alpha-cut based fuzzy arithmetic operations to compute some important reliability indices. Furthermore, in this study ranking of critical components of the system using RAM-Index and sensitivity analysis have also been performed. The developed technique may be helpful to improve system performance significantly and can be applied to analyse fuzzy reliability of other engineering systems. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

System reliability, performance and trust in adaptable automation.

PubMed

Chavaillaz, Alain; Wastell, David; Sauer, Jürgen

2016-01-01

The present study examined the effects of reduced system reliability on operator performance and automation management in an adaptable automation environment. 39 operators were randomly assigned to one of three experimental groups: low (60%), medium (80%), and high (100%) reliability of automation support. The support system provided five incremental levels of automation which operators could freely select according to their needs. After 3 h of training on a simulated process control task (AutoCAMS) in which the automation worked infallibly, operator performance and automation management were measured during a 2.5-h testing session. Trust and workload were also assessed through questionnaires. Results showed that although reduced system reliability resulted in lower levels of trust towards automation, there were no corresponding differences in the operators' reliance on automation. While operators showed overall a noteworthy ability to cope with automation failure, there were, however, decrements in diagnostic speed and prospective memory with lower reliability. Copyright © 2015. Published by Elsevier Ltd.

MSFC Skylab airlock module, volume 2. [systems design and performance, systems support activity, and reliability and safety programs

NASA Technical Reports Server (NTRS)

1974-01-01

System design and performance of the Skylab Airlock Module and Payload Shroud are presented for the communication and caution and warning systems. Crew station and storage, crew trainers, experiments, ground support equipment, and system support activities are also reviewed. Other areas documented include the reliability and safety programs, test philosophy, engineering project management, and mission operations support.

Reliability analysis of a robotic system using hybridized technique

NASA Astrophysics Data System (ADS)

Kumar, Naveen; Komal; Lather, J. S.

2017-09-01

In this manuscript, the reliability of a robotic system has been analyzed using the available data (containing vagueness, uncertainty, etc). Quantification of involved uncertainties is done through data fuzzification using triangular fuzzy numbers with known spreads as suggested by system experts. With fuzzified data, if the existing fuzzy lambda-tau (FLT) technique is employed, then the computed reliability parameters have wide range of predictions. Therefore, decision-maker cannot suggest any specific and influential managerial strategy to prevent unexpected failures and consequently to improve complex system performance. To overcome this problem, the present study utilizes a hybridized technique. With this technique, fuzzy set theory is utilized to quantify uncertainties, fault tree is utilized for the system modeling, lambda-tau method is utilized to formulate mathematical expressions for failure/repair rates of the system, and genetic algorithm is utilized to solve established nonlinear programming problem. Different reliability parameters of a robotic system are computed and the results are compared with the existing technique. The components of the robotic system follow exponential distribution, i.e., constant. Sensitivity analysis is also performed and impact on system mean time between failures (MTBF) is addressed by varying other reliability parameters. Based on analysis some influential suggestions are given to improve the system performance.

Modeling and Simulation Reliable Spacecraft On-Board Computing

NASA Technical Reports Server (NTRS)

Park, Nohpill

1999-01-01

The proposed project will investigate modeling and simulation-driven testing and fault tolerance schemes for Spacecraft On-Board Computing, thereby achieving reliable spacecraft telecommunication. A spacecraft communication system has inherent capabilities of providing multipoint and broadcast transmission, connectivity between any two distant nodes within a wide-area coverage, quick network configuration /reconfiguration, rapid allocation of space segment capacity, and distance-insensitive cost. To realize the capabilities above mentioned, both the size and cost of the ground-station terminals have to be reduced by using reliable, high-throughput, fast and cost-effective on-board computing system which has been known to be a critical contributor to the overall performance of space mission deployment. Controlled vulnerability of mission data (measured in sensitivity), improved performance (measured in throughput and delay) and fault tolerance (measured in reliability) are some of the most important features of these systems. The system should be thoroughly tested and diagnosed before employing a fault tolerance into the system. Testing and fault tolerance strategies should be driven by accurate performance models (i.e. throughput, delay, reliability and sensitivity) to find an optimal solution in terms of reliability and cost. The modeling and simulation tools will be integrated with a system architecture module, a testing module and a module for fault tolerance all of which interacting through a centered graphical user interface.

Perform qualify reliability-power tests by shooting common mistakes: practical problems and standard answers per Telcordia/Bellcore requests

NASA Astrophysics Data System (ADS)

Yu, Zheng

2002-08-01

Facing the new demands of the optical fiber communications market, almost all the performance and reliability of optical network system are dependent on the qualification of the fiber optics components. So, how to comply with the system requirements, the Telcordia / Bellcore reliability and high-power testing has become the key issue for the fiber optics components manufacturers. The qualification of Telcordia / Bellcore reliability or high-power testing is a crucial issue for the manufacturers. It is relating to who is the outstanding one in the intense competition market. These testing also need maintenances and optimizations. Now, work on the reliability and high-power testing have become the new demands in the market. The way is needed to get the 'Triple-Win' goal expected by the component-makers, the reliability-testers and the system-users. To those who are meeting practical problems for the testing, there are following seven topics that deal with how to shoot the common mistakes to perform qualify reliability and high-power testing: ¸ Qualification maintenance requirements for the reliability testing ¸ Lots control for preparing the reliability testing ¸ Sampling select per the reliability testing ¸ Interim measurements during the reliability testing ¸ Basic referencing factors relating to the high-power testing ¸ Necessity of re-qualification testing for the changing of producing ¸ Understanding the similarity for product family by the definitions

Optimizing the Reliability and Performance of Service Composition Applications with Fault Tolerance in Wireless Sensor Networks

PubMed Central

Wu, Zhao; Xiong, Naixue; Huang, Yannong; Xu, Degang; Hu, Chunyang

2015-01-01

The services composition technology provides flexible methods for building service composition applications (SCAs) in wireless sensor networks (WSNs). The high reliability and high performance of SCAs help services composition technology promote the practical application of WSNs. The optimization methods for reliability and performance used for traditional software systems are mostly based on the instantiations of software components, which are inapplicable and inefficient in the ever-changing SCAs in WSNs. In this paper, we consider the SCAs with fault tolerance in WSNs. Based on a Universal Generating Function (UGF) we propose a reliability and performance model of SCAs in WSNs, which generalizes a redundancy optimization problem to a multi-state system. Based on this model, an efficient optimization algorithm for reliability and performance of SCAs in WSNs is developed based on a Genetic Algorithm (GA) to find the optimal structure of SCAs with fault-tolerance in WSNs. In order to examine the feasibility of our algorithm, we have evaluated the performance. Furthermore, the interrelationships between the reliability, performance and cost are investigated. In addition, a distinct approach to determine the most suitable parameters in the suggested algorithm is proposed. PMID:26561818

Reliability evaluation methodology for NASA applications

NASA Technical Reports Server (NTRS)

Taneja, Vidya S.

1992-01-01

Liquid rocket engine technology has been characterized by the development of complex systems containing large number of subsystems, components, and parts. The trend to even larger and more complex system is continuing. The liquid rocket engineers have been focusing mainly on performance driven designs to increase payload delivery of a launch vehicle for a given mission. In otherwords, although the failure of a single inexpensive part or component may cause the failure of the system, reliability in general has not been considered as one of the system parameters like cost or performance. Up till now, quantification of reliability has not been a consideration during system design and development in the liquid rocket industry. Engineers and managers have long been aware of the fact that the reliability of the system increases during development, but no serious attempts have been made to quantify reliability. As a result, a method to quantify reliability during design and development is needed. This includes application of probabilistic models which utilize both engineering analysis and test data. Classical methods require the use of operating data for reliability demonstration. In contrast, the method described in this paper is based on similarity, analysis, and testing combined with Bayesian statistical analysis.

Validation and Improvement of Reliability Methods for Air Force Building Systems

DTIC Science & Technology

focusing primarily on HVAC systems . This research used contingency analysis to assess the performance of each model for HVAC systems at six Air Force...probabilistic model produced inflated reliability calculations for HVAC systems . In light of these findings, this research employed a stochastic method, a...Nonhomogeneous Poisson Process (NHPP), in an attempt to produce accurate HVAC system reliability calculations. This effort ultimately concluded that

Laser System Reliability

DTIC Science & Technology

1977-03-01

system acquisition cycle since they provide necessary inputs to comparative analyses, cost/benefit trade -offs, and system simulations. In addition, the...Management Program from above performs the function of analyzing the system trade -offs with respect to reliability to determine a reliability goal...one encounters the problem of comparing present dollars with future dollars. In this analysis, we are trading off costs expended initially (or at

Thermal Protection for Mars Sample Return Earth Entry Vehicle: A Grand Challenge for Design Methodology and Reliability Verification

NASA Technical Reports Server (NTRS)

Venkatapathy, Ethiraj; Gage, Peter; Wright, Michael J.

2017-01-01

Mars Sample Return is our Grand Challenge for the coming decade. TPS (Thermal Protection System) nominal performance is not the key challenge. The main difficulty for designers is the need to verify unprecedented reliability for the entry system: current guidelines for prevention of backward contamination require that the probability of spores larger than 1 micron diameter escaping into the Earth environment be lower than 1 million for the entire system, and the allocation to TPS would be more stringent than that. For reference, the reliability allocation for Orion TPS is closer to 11000, and the demonstrated reliability for previous human Earth return systems was closer to 1100. Improving reliability by more than 3 orders of magnitude is a grand challenge indeed. The TPS community must embrace the possibility of new architectures that are focused on reliability above thermal performance and mass efficiency. MSR (Mars Sample Return) EEV (Earth Entry Vehicle) will be hit with MMOD (Micrometeoroid and Orbital Debris) prior to reentry. A chute-less aero-shell design which allows for self-righting shape was baselined in prior MSR studies, with the assumption that a passive system will maximize EEV robustness. Hence the aero-shell along with the TPS has to take ground impact and not break apart. System verification will require testing to establish ablative performance and thermal failure but also testing of damage from MMOD, and structural performance at ground impact. Mission requirements will demand analysis, testing and verification that are focused on establishing reliability of the design. In this proposed talk, we will focus on the grand challenge of MSR EEV TPS and the need for innovative approaches to address challenges in modeling, testing, manufacturing and verification.

Automation in visual inspection tasks: X-ray luggage screening supported by a system of direct, indirect or adaptable cueing with low and high system reliability.

PubMed

Chavaillaz, Alain; Schwaninger, Adrian; Michel, Stefan; Sauer, Juergen

2018-05-25

The present study evaluated three automation modes for improving performance in an X-ray luggage screening task. 140 participants were asked to detect the presence of prohibited items in X-ray images of cabin luggage. Twenty participants conducted this task without automatic support (control group), whereas the others worked with either indirect cues (system indicated the target presence without specifying its location), or direct cues (system pointed out the exact target location) or adaptable automation (participants could freely choose between no cue, direct and indirect cues). Furthermore, automatic support reliability was manipulated (low vs. high). The results showed a clear advantage for direct cues regarding detection performance and response time. No benefits were observed for adaptable automation. Finally, high automation reliability led to better performance and higher operator trust. The findings overall confirmed that automatic support systems for luggage screening should be designed such that they provide direct, highly reliable cues.

Factors which Limit the Value of Additional Redundancy in Human Rated Launch Vehicle Systems

NASA Technical Reports Server (NTRS)

Anderson, Joel M.; Stott, James E.; Ring, Robert W.; Hatfield, Spencer; Kaltz, Gregory M.

2008-01-01

The National Aeronautics and Space Administration (NASA) has embarked on an ambitious program to return humans to the moon and beyond. As NASA moves forward in the development and design of new launch vehicles for future space exploration, it must fully consider the implications that rule-based requirements of redundancy or fault tolerance have on system reliability/risk. These considerations include common cause failure, increased system complexity, combined serial and parallel configurations, and the impact of design features implemented to control premature activation. These factors and others must be considered in trade studies to support design decisions that balance safety, reliability, performance and system complexity to achieve a relatively simple, operable system that provides the safest and most reliable system within the specified performance requirements. This paper describes conditions under which additional functional redundancy can impede improved system reliability. Examples from current NASA programs including the Ares I Upper Stage will be shown.

Operator adaptation to changes in system reliability under adaptable automation.

PubMed

Chavaillaz, Alain; Sauer, Juergen

2017-09-01

This experiment examined how operators coped with a change in system reliability between training and testing. Forty participants were trained for 3 h on a complex process control simulation modelling six levels of automation (LOA). In training, participants either experienced a high- (100%) or low-reliability system (50%). The impact of training experience on operator behaviour was examined during a 2.5 h testing session, in which participants either experienced a high- (100%) or low-reliability system (60%). The results showed that most operators did not often switch between LOA. Most chose an LOA that relieved them of most tasks but maintained their decision authority. Training experience did not have a strong impact on the outcome measures (e.g. performance, complacency). Low system reliability led to decreased performance and self-confidence. Furthermore, complacency was observed under high system reliability. Overall, the findings suggest benefits of adaptable automation because it accommodates different operator preferences for LOA. Practitioner Summary: The present research shows that operators can adapt to changes in system reliability between training and testing sessions. Furthermore, it provides evidence that each operator has his/her preferred automation level. Since this preference varies strongly between operators, adaptable automation seems to be suitable to accommodate these large differences.

Reliability Issues in Stirling Radioisotope Power Systems

NASA Technical Reports Server (NTRS)

Schreiber, Jeffrey; Shah, Ashwin

2005-01-01

Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

Reliability Issues in Stirling Radioisotope Power Systems

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Schreiber, Jeffrey G.

2004-01-01

Stirling power conversion is a potential candidate for use in a Radioisotope Power System (RPS) for space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power and reduced requirement of radioactive material. Reliability of an RPS that utilizes Stirling power conversion technology is important in order to ascertain long term successful performance. Owing to long life time requirement (14 years), it is difficult to perform long-term tests that encompass all the uncertainties involved in the design variables of components and subsystems comprising the RPS. The requirement for uninterrupted performance reliability and related issues are discussed, and some of the critical areas of concern are identified. An overview of the current on-going efforts to understand component life, design variables at the component and system levels, and related sources and nature of uncertainties are also discussed. Current status of the 110 watt Stirling Radioisotope Generator (SRG110) reliability efforts is described. Additionally, an approach showing the use of past experience on other successfully used power systems to develop a reliability plan for the SRG110 design is outlined.

Model of load balancing using reliable algorithm with multi-agent system

NASA Astrophysics Data System (ADS)

Afriansyah, M. F.; Somantri, M.; Riyadi, M. A.

2017-04-01

Massive technology development is linear with the growth of internet users which increase network traffic activity. It also increases load of the system. The usage of reliable algorithm and mobile agent in distributed load balancing is a viable solution to handle the load issue on a large-scale system. Mobile agent works to collect resource information and can migrate according to given task. We propose reliable load balancing algorithm using least time first byte (LFB) combined with information from the mobile agent. In system overview, the methodology consisted of defining identification system, specification requirements, network topology and design system infrastructure. The simulation method for simulated system was using 1800 request for 10 s from the user to the server and taking the data for analysis. Software simulation was based on Apache Jmeter by observing response time and reliability of each server and then compared it with existing method. Results of performed simulation show that the LFB method with mobile agent can perform load balancing with efficient systems to all backend server without bottleneck, low risk of server overload, and reliable.

DATMAN: A reliability data analysis program using Bayesian updating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, M.; Feltus, M.A.

1996-12-31

Preventive maintenance (PM) techniques focus on the prevention of failures, in particular, system components that are important to plant functions. Reliability-centered maintenance (RCM) improves on the PM techniques by introducing a set of guidelines by which to evaluate the system functions. It also minimizes intrusive maintenance, labor, and equipment downtime without sacrificing system performance when its function is essential for plant safety. Both the PM and RCM approaches require that system reliability data be updated as more component failures and operation time are acquired. Systems reliability and the likelihood of component failures can be calculated by Bayesian statistical methods, whichmore » can update these data. The DATMAN computer code has been developed at Penn State to simplify the Bayesian analysis by performing tedious calculations needed for RCM reliability analysis. DATMAN reads data for updating, fits a distribution that best fits the data, and calculates component reliability. DATMAN provides a user-friendly interface menu that allows the user to choose from several common prior and posterior distributions, insert new failure data, and visually select the distribution that matches the data most accurately.« less

R&D of high reliable refrigeration system for superconducting generators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hosoya, T.; Shindo, S.; Yaguchi, H.

1996-12-31

Super-GM carries out R&D of 70 MW class superconducting generators (model machines), refrigeration system and superconducting wires to apply superconducting technology to electric power apparatuses. The helium refrigeration system for keeping field windings of superconducting generator (SCG) in cryogenic environment must meet the requirement of high reliability for uninterrupted long term operation of the SCG. In FY 1992, a high reliable conventional refrigeration system for the model machines was integrated by combining components such as compressor unit, higher temperature cold box and lower temperature cold box which were manufactured utilizing various fundamental technologies developed in early stage of the projectmore » since 1988. Since FY 1993, its performance tests have been carried out. It has been confirmed that its performance was fulfilled the development target of liquefaction capacity of 100 L/h and impurity removal in the helium gas to < 0.1 ppm. Furthermore, its operation method and performance were clarified to all different modes as how to control liquefaction rate and how to supply liquid helium from a dewar to the model machine. In addition, the authors have made performance tests and system performance analysis of oil free screw type and turbo type compressors which greatly improve reliability of conventional refrigeration systems. The operation performance and operational control method of the compressors has been clarified through the tests and analysis.« less

The development of a reliable amateur boxing performance analysis template.

PubMed

Thomson, Edward; Lamb, Kevin; Nicholas, Ceri

2013-01-01

The aim of this study was to devise a valid performance analysis system for the assessment of the movement characteristics associated with competitive amateur boxing and assess its reliability using analysts of varying experience of the sport and performance analysis. Key performance indicators to characterise the demands of an amateur contest (offensive, defensive and feinting) were developed and notated using a computerised notational analysis system. Data were subjected to intra- and inter-observer reliability assessment using median sign tests and calculating the proportion of agreement within predetermined limits of error. For all performance indicators, intra-observer reliability revealed non-significant differences between observations (P > 0.05) and high agreement was established (80-100%) regardless of whether exact or the reference value of ±1 was applied. Inter-observer reliability was less impressive for both analysts (amateur boxer and experienced analyst), with the proportion of agreement ranging from 33-100%. Nonetheless, there was no systematic bias between observations for any indicator (P > 0.05), and the proportion of agreement within the reference range (±1) was 100%. A reliable performance analysis template has been developed for the assessment of amateur boxing performance and is available for use by researchers, coaches and athletes to classify and quantify the movement characteristics of amateur boxing.

The reliability of WorkWell Systems Functional Capacity Evaluation: a systematic review

PubMed Central

2014-01-01

Background Functional capacity evaluation (FCE) determines a person’s ability to perform work-related tasks and is a major component of the rehabilitation process. The WorkWell Systems (WWS) FCE (formerly known as Isernhagen Work Systems FCE) is currently the most commonly used FCE tool in German rehabilitation centres. Our systematic review investigated the inter-rater, intra-rater and test-retest reliability of the WWS FCE. Methods We performed a systematic literature search of studies on the reliability of the WWS FCE and extracted item-specific measures of inter-rater, intra-rater and test-retest reliability from the identified studies. Intraclass correlation coefficients ≥ 0.75, percentages of agreement ≥ 80%, and kappa coefficients ≥ 0.60 were categorised as acceptable, otherwise they were considered non-acceptable. The extracted values were summarised for the five performance categories of the WWS FCE, and the results were classified as either consistent or inconsistent. Results From 11 identified studies, 150 item-specific reliability measures were extracted. 89% of the extracted inter-rater reliability measures, all of the intra-rater reliability measures and 96% of the test-retest reliability measures of the weight handling and strength tests had an acceptable level of reliability, compared to only 67% of the test-retest reliability measures of the posture/mobility tests and 56% of the test-retest reliability measures of the locomotion tests. Both of the extracted test-retest reliability measures of the balance test were acceptable. Conclusions Weight handling and strength tests were found to have consistently acceptable reliability. Further research is needed to explore the reliability of the other tests as inconsistent findings or a lack of data prevented definitive conclusions. PMID:24674029

System Analysis and Performance Benefits of an Optimized Rotorcraft Propulsion System

NASA Technical Reports Server (NTRS)

Bruckner, Robert J.

2007-01-01

The propulsion system of rotorcraft vehicles is the most critical system to the vehicle in terms of safety and performance. The propulsion system must provide both vertical lift and forward flight propulsion during the entire mission. Whereas propulsion is a critical element for all flight vehicles, it is particularly critical for rotorcraft due to their limited safe, un-powered landing capability. This unparalleled reliability requirement has led rotorcraft power plants down a certain evolutionary path in which the system looks and performs quite similarly to those of the 1960 s. By and large the advancements in rotorcraft propulsion have come in terms of safety and reliability and not in terms of performance. The concept of the optimized propulsion system is a means by which both reliability and performance can be improved for rotorcraft vehicles. The optimized rotorcraft propulsion system which couples an oil-free turboshaft engine to a highly loaded gearbox that provides axial load support for the power turbine can be designed with current laboratory proven technology. Such a system can provide up to 60% weight reduction of the propulsion system of rotorcraft vehicles. Several technical challenges are apparent at the conceptual design level and should be addressed with current research.

Dynamic decision-making for reliability and maintenance analysis of manufacturing systems based on failure effects

NASA Astrophysics Data System (ADS)

Zhang, Ding; Zhang, Yingjie

2017-09-01

A framework for reliability and maintenance analysis of job shop manufacturing systems is proposed in this paper. An efficient preventive maintenance (PM) policy in terms of failure effects analysis (FEA) is proposed. Subsequently, reliability evaluation and component importance measure based on FEA are performed under the PM policy. A job shop manufacturing system is applied to validate the reliability evaluation and dynamic maintenance policy. Obtained results are compared with existed methods and the effectiveness is validated. Some vague understandings for issues such as network modelling, vulnerabilities identification, the evaluation criteria of repairable systems, as well as PM policy during manufacturing system reliability analysis are elaborated. This framework can help for reliability optimisation and rational maintenance resources allocation of job shop manufacturing systems.

Analysis of travel time reliability on Indiana interstates.

DOT National Transportation Integrated Search

2009-09-15

Travel-time reliability is a key performance measure in any transportation system. It is a : measure of quality of travel time experienced by transportation system users and reflects the efficiency : of the transportation system to serve citizens, bu...

The implementation and use of Ada on distributed systems with high reliability requirements

NASA Technical Reports Server (NTRS)

Knight, J. C.

1988-01-01

The use and implementation of Ada were investigated in distributed environments in which reliability is the primary concern. In particular, the focus was on the possibility that a distributed system may be programmed entirely in Ada so that the individual tasks of the system are unconcerned with which processors are being executed, and that failures may occur in the software and underlying hardware. A secondary interest is in the performance of Ada systems and how that performance can be gauged reliably. Primary activities included: analysis of the original approach to recovery in distributed Ada programs using the Advanced Transport Operating System (ATOPS) example; review and assessment of the original approach which was found to be capable of improvement; development of a refined approach to recovery that was applied to the ATOPS example; and design and development of a performance assessment scheme for Ada programs based on a flexible user-driven benchmarking system.

Composing, Analyzing and Validating Software Models

NASA Astrophysics Data System (ADS)

Sheldon, Frederick T.

1998-10-01

This research has been conducted at the Computational Sciences Division of the Information Sciences Directorate at Ames Research Center (Automated Software Engineering Grp). The principle work this summer has been to review and refine the agenda that were carried forward from last summer. Formal specifications provide good support for designing a functionally correct system, however they are weak at incorporating non-functional performance requirements (like reliability). Techniques which utilize stochastic Petri nets (SPNs) are good for evaluating the performance and reliability for a system, but they may be too abstract and cumbersome from the stand point of specifying and evaluating functional behavior. Therefore, one major objective of this research is to provide an integrated approach to assist the user in specifying both functionality (qualitative: mutual exclusion and synchronization) and performance requirements (quantitative: reliability and execution deadlines). In this way, the merits of a powerful modeling technique for performability analysis (using SPNs) can be combined with a well-defined formal specification language. In doing so, we can come closer to providing a formal approach to designing a functionally correct system that meets reliability and performance goals.

Composing, Analyzing and Validating Software Models

NASA Technical Reports Server (NTRS)

Sheldon, Frederick T.

1998-01-01

This research has been conducted at the Computational Sciences Division of the Information Sciences Directorate at Ames Research Center (Automated Software Engineering Grp). The principle work this summer has been to review and refine the agenda that were carried forward from last summer. Formal specifications provide good support for designing a functionally correct system, however they are weak at incorporating non-functional performance requirements (like reliability). Techniques which utilize stochastic Petri nets (SPNs) are good for evaluating the performance and reliability for a system, but they may be too abstract and cumbersome from the stand point of specifying and evaluating functional behavior. Therefore, one major objective of this research is to provide an integrated approach to assist the user in specifying both functionality (qualitative: mutual exclusion and synchronization) and performance requirements (quantitative: reliability and execution deadlines). In this way, the merits of a powerful modeling technique for performability analysis (using SPNs) can be combined with a well-defined formal specification language. In doing so, we can come closer to providing a formal approach to designing a functionally correct system that meets reliability and performance goals.

Development and reliability of the rating of compensatory movements in upper limb prosthesis wearers during work-related tasks.

PubMed

van der Laan, Tallie M J; Postema, Sietke G; Reneman, Michiel F; Bongers, Raoul M; van der Sluis, Corry K

2018-02-10

Reliability study. Quantifying compensatory movements during work-related tasks may help to prevent musculoskeletal complaints in individuals with upper limb absence. (1) To develop a qualitative scoring system for rating compensatory shoulder and trunk movements in upper limb prosthesis wearers during the performance of functional capacity evaluation tests adjusted for use by 1-handed individuals (functional capacity evaluation-one handed [FCE-OH]); (2) to examine the interrater and intrarater reliability of the scoring system; and (3) to assess its feasibility. Movement patterns of 12 videotaped upper limb prosthesis wearers and 20 controls were analyzed. Compensatory movements were defined for each FCE-OH test, and a scoring system was developed, pilot tested, and adjusted. During reliability testing, 18 raters (12 FCE experts and 6 physiotherapists/gait analysts) scored videotapes of upper limb prosthesis wearers performing 4 FCE-OH tests 2 times (2 weeks apart). Agreement was expressed in % and kappa value. Feasibility (focus area's "acceptability", "demand," and "implementation") was determined by using a questionnaire. After 2 rounds of pilot testing and adjusting, reliability of a third version was tested. The interrater reliability for the first and second rating sessions were к = 0.54 (confidence interval [CI]: 0.52-0.57) and к = 0.64 (CI: 0.61-0.66), respectively. The intrarater reliability was к = 0.77 (CI: 0.72-0.82). The feasibility was good but could be improved by a training program. It seems possible to identify compensatory movements in upper limb prosthesis wearers during the performance of FCE-OH tests reliably by observation using the developed observational scoring system. Interrater reliability was satisfactory in most instances; intrarater reliability was good. Feasibility was established. Copyright © 2018 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Reliability-based optimization of an active vibration controller using evolutionary algorithms

NASA Astrophysics Data System (ADS)

Saraygord Afshari, Sajad; Pourtakdoust, Seid H.

2017-04-01

Many modern industrialized systems such as aircrafts, rotating turbines, satellite booms, etc. cannot perform their desired tasks accurately if their uninhibited structural vibrations are not controlled properly. Structural health monitoring and online reliability calculations are emerging new means to handle system imposed uncertainties. As stochastic forcing are unavoidable, in most engineering systems, it is often needed to take them into the account for the control design process. In this research, smart material technology is utilized for structural health monitoring and control in order to keep the system in a reliable performance range. In this regard, a reliability-based cost function is assigned for both controller gain optimization as well as sensor placement. The proposed scheme is implemented and verified for a wing section. Comparison of results for the frequency responses is considered to show potential applicability of the presented technique.

Reliability Assessment for COTS Components in Space Flight Applications

NASA Technical Reports Server (NTRS)

Krishnan, G. S.; Mazzuchi, Thomas A.

2001-01-01

Systems built for space flight applications usually demand very high degree of performance and a very high level of accuracy. Hence, the design engineers are often prone to selecting state-of-art technologies for inclusion in their system design. The shrinking budgets also necessitate use of COTS (Commercial Off-The-Shelf) components, which are construed as being less expensive. The performance and accuracy requirements for space flight applications are much more stringent than those for the commercial applications. The quantity of systems designed and developed for space applications are much lower in number than those produced for the commercial applications. With a given set of requirements, are these COTS components reliable? This paper presents a model for assessing the reliability of COTS components in space applications and the associated affect on the system reliability. We illustrate the method with a real application.

[Reliability of a positron emission tomography system (CTI:PT931/04-12)].

PubMed

Watanuki, Shoichi; Ishii, Keizo; Itoh, Masatoshi; Orihara, Hikonojyo

2002-05-01

The maintenance data of a PET system (PT931/04-12 CTI Inc.) was analyzed to evaluate its reliability. We examined whether the initial performance for the system resolution and efficiency is kept. The reliability of the PET system was evaluated from the value of MTTF (mean time to failure) and MTBF (mean time between failures) for each part of the system obtained from the maintenance data for 13 years. The initial performance was kept for the resolution, but the efficiency decreased to 72% of the initial value. The 83% of the troubles of the system was for detector block (DB) and DB control module (BC). The MTTF of DB and BC were 2,733 and 3,314 days, and the MTBF of DB and BC per detector ring were 38 and 114 days. The MTBF of the system was 23 days. We found seasonal dependence for the number of troubles of DB and BC. This means that the trouble may be related the humidity. The reliability of the PET system strongly depends on the MTBF of DB and BC. The improvement in quality of these parts and optimization of the environment in operation may increase the reliability of the PET system. For the popularization of PET, it is effective to evaluate the reliability of the system and to show it to the users.

A Design Heritage-Based Forecasting Methodology for Risk Informed Management of Advanced Systems

NASA Technical Reports Server (NTRS)

Maggio, Gaspare; Fragola, Joseph R.

1999-01-01

The development of next generation systems often carries with it the promise of improved performance, greater reliability, and reduced operational costs. These expectations arise from the use of novel designs, new materials, advanced integration and production technologies intended for functionality replacing the previous generation. However, the novelty of these nascent technologies is accompanied by lack of operational experience and, in many cases, no actual testing as well. Therefore some of the enthusiasm surrounding most new technologies may be due to inflated aspirations from lack of knowledge rather than actual future expectations. This paper proposes a design heritage approach for improved reliability forecasting of advanced system components. The basis of the design heritage approach is to relate advanced system components to similar designs currently in operation. The demonstrated performance of these components could then be used to forecast the expected performance and reliability of comparable advanced technology components. In this approach the greater the divergence of the advanced component designs from the current systems the higher the uncertainty that accompanies the associated failure estimates. Designers of advanced systems are faced with many difficult decisions. One of the most common and more difficult types of these decisions are those related to the choice between design alternatives. In the past decision-makers have found these decisions to be extremely difficult to make because they often involve the trade-off between a known performing fielded design and a promising paper design. When it comes to expected reliability performance the paper design always looks better because it is on paper and it addresses all the know failure modes of the fielded design. On the other hand there is a long, and sometimes very difficult road, between the promise of a paper design and its fulfillment; with the possibility that sometimes the reliability promise is not fulfilled at all. Decision makers in advanced technology areas have always known to discount the performance claims of a design to a degree in proportion to its stage of development, and at times have preferred the more mature design over the one of lesser maturity even with the latter promising substantially better performance once fielded. As with the broader measures of performance this has also been true for projected reliability performance. Paper estimates of potential advances in design reliability are to a degree uncertain in proportion to the maturity of the features being proposed to secure those advances. This is especially true when performance-enhancing features in other areas are also planned to be part of the development program.

Scaled CMOS Reliability and Considerations for Spacecraft Systems: Bottom-Up and Top-Down Perspective

NASA Technical Reports Server (NTRS)

White, Mark

2012-01-01

New space missions will increasingly rely on more advanced technologies because of system requirements for higher performance, particularly in instruments and high-speed processing. Component-level reliability challenges with scaled CMOS in spacecraft systems from a bottom-up perspective have been presented. Fundamental Front-end and Back-end processing reliability issues with more aggressively scaled parts have been discussed. Effective thermal management from system-level to the componentlevel (top-down) is a key element in overall design of reliable systems. Thermal management in space systems must consider a wide range of issues, including thermal loading of many different components, and frequent temperature cycling of some systems. Both perspectives (top-down and bottom-up) play a large role in robust, reliable spacecraft system design.

Reliability and Engineering | Photovoltaic Research | NREL

Science.gov Websites

-Time PV and Solar Resource Testing We study long-term performance, reliability, and failures of PV (NCPV) at NREL, we focus on photovoltaic (PV) reliability research and development (R&D) to improve PV technologies. We test modules and systems for long-term performance and stress them in the field

A Report on Simulation-Driven Reliability and Failure Analysis of Large-Scale Storage Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wan, Lipeng; Wang, Feiyi; Oral, H. Sarp

High-performance computing (HPC) storage systems provide data availability and reliability using various hardware and software fault tolerance techniques. Usually, reliability and availability are calculated at the subsystem or component level using limited metrics such as, mean time to failure (MTTF) or mean time to data loss (MTTDL). This often means settling on simple and disconnected failure models (such as exponential failure rate) to achieve tractable and close-formed solutions. However, such models have been shown to be insufficient in assessing end-to-end storage system reliability and availability. We propose a generic simulation framework aimed at analyzing the reliability and availability of storagemore » systems at scale, and investigating what-if scenarios. The framework is designed for an end-to-end storage system, accommodating the various components and subsystems, their interconnections, failure patterns and propagation, and performs dependency analysis to capture a wide-range of failure cases. We evaluate the framework against a large-scale storage system that is in production and analyze its failure projections toward and beyond the end of lifecycle. We also examine the potential operational impact by studying how different types of components affect the overall system reliability and availability, and present the preliminary results« less

The Role of Reliability, Vulnerability and Resilience in the Management of Water Quality Systems

NASA Astrophysics Data System (ADS)

Lence, B. J.; Maier, H. R.

2001-05-01

The risk based performance indicators reliability, vulnerability and resilience provide measures of the frequency, magnitude and duration of the failure of water resources systems, respectively. They have been applied primarily to water supply problems, including the assessment of the performance of reservoirs and water distribution systems. Applications to water quality case studies have been limited, although the need to consider the length and magnitude of violations of a particular water quality standard has been recognized for some time. In this research, the role of reliability, vulnerability and resilience in water quality management applications is investigated by examining their significance as performance measures for water quality systems and assessing their potential for assisting in decision making processes. The importance of each performance indicator is discussed and a framework for classifying such systems, based on the relative significance of each of these indicators, is introduced and illustrated qualitatively with various case studies. Quantitative examples drawn from both lake and river water quality modeling exercises are then provided.

Reliability and mass analysis of dynamic power conversion systems with parallel of standby redundancy

NASA Technical Reports Server (NTRS)

Juhasz, A. J.; Bloomfield, H. S.

1985-01-01

A combinatorial reliability approach is used to identify potential dynamic power conversion systems for space mission applications. A reliability and mass analysis is also performed, specifically for a 100 kWe nuclear Brayton power conversion system with parallel redundancy. Although this study is done for a reactor outlet temperature of 1100K, preliminary system mass estimates are also included for reactor outlet temperatures ranging up to 1500 K.

Statistical modeling of software reliability

NASA Technical Reports Server (NTRS)

Miller, Douglas R.

1992-01-01

This working paper discusses the statistical simulation part of a controlled software development experiment being conducted under the direction of the System Validation Methods Branch, Information Systems Division, NASA Langley Research Center. The experiment uses guidance and control software (GCS) aboard a fictitious planetary landing spacecraft: real-time control software operating on a transient mission. Software execution is simulated to study the statistical aspects of reliability and other failure characteristics of the software during development, testing, and random usage. Quantification of software reliability is a major goal. Various reliability concepts are discussed. Experiments are described for performing simulations and collecting appropriate simulated software performance and failure data. This data is then used to make statistical inferences about the quality of the software development and verification processes as well as inferences about the reliability of software versions and reliability growth under random testing and debugging.

Modeling of unit operating considerations in generating-capacity reliability evaluation. Volume 1. Mathematical models, computing methods, and results. Final report. [GENESIS, OPCON and OPPLAN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patton, A.D.; Ayoub, A.K.; Singh, C.

1982-07-01

Existing methods for generating capacity reliability evaluation do not explicitly recognize a number of operating considerations which may have important effects in system reliability performance. Thus, current methods may yield estimates of system reliability which differ appreciably from actual observed reliability. Further, current methods offer no means of accurately studying or evaluating alternatives which may differ in one or more operating considerations. Operating considerations which are considered to be important in generating capacity reliability evaluation include: unit duty cycles as influenced by load cycle shape, reliability performance of other units, unit commitment policy, and operating reserve policy; unit start-up failuresmore » distinct from unit running failures; unit start-up times; and unit outage postponability and the management of postponable outages. A detailed Monte Carlo simulation computer model called GENESIS and two analytical models called OPCON and OPPLAN have been developed which are capable of incorporating the effects of many operating considerations including those noted above. These computer models have been used to study a variety of actual and synthetic systems and are available from EPRI. The new models are shown to produce system reliability indices which differ appreciably from index values computed using traditional models which do not recognize operating considerations.« less

Reliability of intracerebral hemorrhage classification systems: A systematic review.

PubMed

Rannikmäe, Kristiina; Woodfield, Rebecca; Anderson, Craig S; Charidimou, Andreas; Chiewvit, Pipat; Greenberg, Steven M; Jeng, Jiann-Shing; Meretoja, Atte; Palm, Frederic; Putaala, Jukka; Rinkel, Gabriel Je; Rosand, Jonathan; Rost, Natalia S; Strbian, Daniel; Tatlisumak, Turgut; Tsai, Chung-Fen; Wermer, Marieke Jh; Werring, David; Yeh, Shin-Joe; Al-Shahi Salman, Rustam; Sudlow, Cathie Lm

2016-08-01

Accurately distinguishing non-traumatic intracerebral hemorrhage (ICH) subtypes is important since they may have different risk factors, causal pathways, management, and prognosis. We systematically assessed the inter- and intra-rater reliability of ICH classification systems. We sought all available reliability assessments of anatomical and mechanistic ICH classification systems from electronic databases and personal contacts until October 2014. We assessed included studies' characteristics, reporting quality and potential for bias; summarized reliability with kappa value forest plots; and performed meta-analyses of the proportion of cases classified into each subtype. We included 8 of 2152 studies identified. Inter- and intra-rater reliabilities were substantial to perfect for anatomical and mechanistic systems (inter-rater kappa values: anatomical 0.78-0.97 [six studies, 518 cases], mechanistic 0.89-0.93 [three studies, 510 cases]; intra-rater kappas: anatomical 0.80-1 [three studies, 137 cases], mechanistic 0.92-0.93 [two studies, 368 cases]). Reporting quality varied but no study fulfilled all criteria and none was free from potential bias. All reliability studies were performed with experienced raters in specialist centers. Proportions of ICH subtypes were largely consistent with previous reports suggesting that included studies are appropriately representative. Reliability of existing classification systems appears excellent but is unknown outside specialist centers with experienced raters. Future reliability comparisons should be facilitated by studies following recently published reporting guidelines. © 2016 World Stroke Organization.

Reliability of human-supervised formant-trajectory measurement for forensic voice comparison.

PubMed

Zhang, Cuiling; Morrison, Geoffrey Stewart; Ochoa, Felipe; Enzinger, Ewald

2013-01-01

Acoustic-phonetic approaches to forensic voice comparison often include human-supervised measurement of vowel formants, but the reliability of such measurements is a matter of concern. This study assesses the within- and between-supervisor variability of three sets of formant-trajectory measurements made by each of four human supervisors. It also assesses the validity and reliability of forensic-voice-comparison systems based on these measurements. Each supervisor's formant-trajectory system was fused with a baseline mel-frequency cepstral-coefficient system, and performance was assessed relative to the baseline system. Substantial improvements in validity were found for all supervisors' systems, but some supervisors' systems were more reliable than others.

Reliable High Performance Peta- and Exa-Scale Computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bronevetsky, G

2012-04-02

As supercomputers become larger and more powerful, they are growing increasingly complex. This is reflected both in the exponentially increasing numbers of components in HPC systems (LLNL is currently installing the 1.6 million core Sequoia system) as well as the wide variety of software and hardware components that a typical system includes. At this scale it becomes infeasible to make each component sufficiently reliable to prevent regular faults somewhere in the system or to account for all possible cross-component interactions. The resulting faults and instability cause HPC applications to crash, perform sub-optimally or even produce erroneous results. As supercomputers continuemore » to approach Exascale performance and full system reliability becomes prohibitively expensive, we will require novel techniques to bridge the gap between the lower reliability provided by hardware systems and users unchanging need for consistent performance and reliable results. Previous research on HPC system reliability has developed various techniques for tolerating and detecting various types of faults. However, these techniques have seen very limited real applicability because of our poor understanding of how real systems are affected by complex faults such as soft fault-induced bit flips or performance degradations. Prior work on such techniques has had very limited practical utility because it has generally focused on analyzing the behavior of entire software/hardware systems both during normal operation and in the face of faults. Because such behaviors are extremely complex, such studies have only produced coarse behavioral models of limited sets of software/hardware system stacks. Since this provides little insight into the many different system stacks and applications used in practice, this work has had little real-world impact. My project addresses this problem by developing a modular methodology to analyze the behavior of applications and systems during both normal and faulty operation. By synthesizing models of individual components into a whole-system behavior models my work is making it possible to automatically understand the behavior of arbitrary real-world systems to enable them to tolerate a wide range of system faults. My project is following a multi-pronged research strategy. Section II discusses my work on modeling the behavior of existing applications and systems. Section II.A discusses resilience in the face of soft faults and Section II.B looks at techniques to tolerate performance faults. Finally Section III presents an alternative approach that studies how a system should be designed from the ground up to make resilience natural and easy.« less

PV System 'Availability' as a Reliability Metric -- Improving Standards, Contract Language and Performance Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klise, Geoffrey T.; Hill, Roger; Walker, Andy

The use of the term 'availability' to describe a photovoltaic (PV) system and power plant has been fraught with confusion for many years. A term that is meant to describe equipment operational status is often omitted, misapplied or inaccurately combined with PV performance metrics due to attempts to measure performance and reliability through the lens of traditional power plant language. This paper discusses three areas where current research in standards, contract language and performance modeling is improving the way availability is used with regards to photovoltaic systems and power plants.

Redundancy management of inertial systems.

NASA Technical Reports Server (NTRS)

Mckern, R. A.; Musoff, H.

1973-01-01

The paper reviews developments in failure detection and isolation techniques applicable to gimballed and strapdown systems. It examines basic redundancy management goals of improved reliability, performance and logistic costs, and explores mechanizations available for both input and output data handling. The meaning of redundant system reliability in terms of available coverage, system MTBF, and mission time is presented and the practical hardware performance limitations of failure detection and isolation techniques are explored. Simulation results are presented illustrating implementation coverages attainable considering IMU performance models and mission detection threshold requirements. The implications of a complete GN&C redundancy management method on inertial techniques are also explored.

Analysis on Sealing Reliability of Bolted Joint Ball Head Component of Satellite Propulsion System

NASA Astrophysics Data System (ADS)

Guo, Tao; Fan, Yougao; Gao, Feng; Gu, Shixin; Wang, Wei

2018-01-01

Propulsion system is one of the important subsystems of satellite, and its performance directly affects the service life, attitude control and reliability of the satellite. The Paper analyzes the sealing principle of bolted joint ball head component of satellite propulsion system and discuss from the compatibility of hydrazine anhydrous and bolted joint ball head component, influence of ground environment on the sealing performance of bolted joint ball heads, and material failure caused by environment, showing that the sealing reliability of bolted joint ball head component is good and the influence of above three aspects on sealing of bolted joint ball head component can be ignored.

Performance and reliability of the NASA biomass production chamber

NASA Technical Reports Server (NTRS)

Fortson, R. E.; Sager, J. C.; Chetirkin, P. V.

1994-01-01

The Biomass Production Chamber (BPC) at the Kennedy Space Center is part of the Controlled Ecological Life Support System (CELSS) Breadboard Project. Plants are grown in a closed environment in an effort to quantify their contributions to the requirements for life support. Performance of this system is described. Also, in building this system, data from component and subsystem failures are being recorded. These data are used to identify problem areas in the design and implementation. The techniques used to measure the reliability will be useful in the design and construction of future CELSS. Possible methods for determining the reliability of a green plant, the primary component of CELSS, are discussed.

High Reliability Organizations in Education. Noteworthy Perspectives

ERIC Educational Resources Information Center

Eck, James H.; Bellamy, G. Thomas; Schaffer, Eugene; Stringfield, Sam; Reynolds, David

2011-01-01

The authors of this monograph assert that by assisting school systems to more closely resemble "high reliability" organizations (HROs) that already exist in other industries and benchmarking against top-performing education systems from around the globe, America's school systems can transform themselves from compliance-driven…

Large-scale-system effectiveness analysis. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patton, A.D.; Ayoub, A.K.; Foster, J.W.

1979-11-01

Objective of the research project has been the investigation and development of methods for calculating system reliability indices which have absolute, and measurable, significance to consumers. Such indices are a necessary prerequisite to any scheme for system optimization which includes the economic consequences of consumer service interruptions. A further area of investigation has been joint consideration of generation and transmission in reliability studies. Methods for finding or estimating the probability distributions of some measures of reliability performance have been developed. The application of modern Monte Carlo simulation methods to compute reliability indices in generating systems has been studied.

Advanced CHP Control Algorithms: Scope Specification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katipamula, Srinivas; Brambley, Michael R.

2006-04-28

The primary objective of this multiyear project is to develop algorithms for combined heat and power systems to ensure optimal performance, increase reliability, and lead to the goal of clean, efficient, reliable and affordable next generation energy systems.

System principles, mathematical models and methods to ensure high reliability of safety systems

NASA Astrophysics Data System (ADS)

Zaslavskyi, V.

2017-04-01

Modern safety and security systems are composed of a large number of various components designed for detection, localization, tracking, collecting, and processing of information from the systems of monitoring, telemetry, control, etc. They are required to be highly reliable in a view to correctly perform data aggregation, processing and analysis for subsequent decision making support. On design and construction phases of the manufacturing of such systems a various types of components (elements, devices, and subsystems) are considered and used to ensure high reliability of signals detection, noise isolation, and erroneous commands reduction. When generating design solutions for highly reliable systems a number of restrictions and conditions such as types of components and various constrains on resources should be considered. Various types of components perform identical functions; however, they are implemented using diverse principles, approaches and have distinct technical and economic indicators such as cost or power consumption. The systematic use of different component types increases the probability of tasks performing and eliminates the common cause failure. We consider type-variety principle as an engineering principle of system analysis, mathematical models based on this principle, and algorithms for solving optimization problems of highly reliable safety and security systems design. Mathematical models are formalized in a class of two-level discrete optimization problems of large dimension. The proposed approach, mathematical models, algorithms can be used for problem solving of optimal redundancy on the basis of a variety of methods and control devices for fault and defects detection in technical systems, telecommunication networks, and energy systems.

Analyzing Reliability and Performance Trade-Offs of HLS-Based Designs in SRAM-Based FPGAs Under Soft Errors

NASA Astrophysics Data System (ADS)

Tambara, Lucas Antunes; Tonfat, Jorge; Santos, André; Kastensmidt, Fernanda Lima; Medina, Nilberto H.; Added, Nemitala; Aguiar, Vitor A. P.; Aguirre, Fernando; Silveira, Marcilei A. G.

2017-02-01

The increasing system complexity of FPGA-based hardware designs and shortening of time-to-market have motivated the adoption of new designing methodologies focused on addressing the current need for high-performance circuits. High-Level Synthesis (HLS) tools can generate Register Transfer Level (RTL) designs from high-level software programming languages. These tools have evolved significantly in recent years, providing optimized RTL designs, which can serve the needs of safety-critical applications that require both high performance and high reliability levels. However, a reliability evaluation of HLS-based designs under soft errors has not yet been presented. In this work, the trade-offs of different HLS-based designs in terms of reliability, resource utilization, and performance are investigated by analyzing their behavior under soft errors and comparing them to a standard processor-based implementation in an SRAM-based FPGA. Results obtained from fault injection campaigns and radiation experiments show that it is possible to increase the performance of a processor-based system up to 5,000 times by changing its architecture with a small impact in the cross section (increasing up to 8 times), and still increasing the Mean Workload Between Failures (MWBF) of the system.

Reliability of Fault Tolerant Control Systems. Part 2

NASA Technical Reports Server (NTRS)

Wu, N. Eva

2000-01-01

This paper reports Part II of a two part effort that is intended to delineate the relationship between reliability and fault tolerant control in a quantitative manner. Reliability properties peculiar to fault-tolerant control systems are emphasized, such as the presence of analytic redundancy in high proportion, the dependence of failures on control performance, and high risks associated with decisions in redundancy management due to multiple sources of uncertainties and sometimes large processing requirements. As a consequence, coverage of failures through redundancy management can be severely limited. The paper proposes to formulate the fault tolerant control problem as an optimization problem that maximizes coverage of failures through redundancy management. Coverage modeling is attempted in a way that captures its dependence on the control performance and on the diagnostic resolution. Under the proposed redundancy management policy, it is shown that an enhanced overall system reliability can be achieved with a control law of a superior robustness, with an estimator of a higher resolution, and with a control performance requirement of a lesser stringency.

Effects of extended lay-off periods on performance and operator trust under adaptable automation.

PubMed

Chavaillaz, Alain; Wastell, David; Sauer, Jürgen

2016-03-01

Little is known about the long-term effects of system reliability when operators do not use a system during an extended lay-off period. To examine threats to skill maintenance, 28 participants operated twice a simulation of a complex process control system for 2.5 h, with an 8-month retention interval between sessions. Operators were provided with an adaptable support system, which operated at one of the following reliability levels: 60%, 80% or 100%. Results showed that performance, workload, and trust remained stable at the second testing session, but operators lost self-confidence in their system management abilities. Finally, the effects of system reliability observed at the first testing session were largely found again at the second session. The findings overall suggest that adaptable automation may be a promising means to support operators in maintaining their performance at the second testing session. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

RGCA: A Reliable GPU Cluster Architecture for Large-Scale Internet of Things Computing Based on Effective Performance-Energy Optimization

PubMed Central

Chen, Qingkui; Zhao, Deyu; Wang, Jingjuan

2017-01-01

This paper aims to develop a low-cost, high-performance and high-reliability computing system to process large-scale data using common data mining algorithms in the Internet of Things (IoT) computing environment. Considering the characteristics of IoT data processing, similar to mainstream high performance computing, we use a GPU (Graphics Processing Unit) cluster to achieve better IoT services. Firstly, we present an energy consumption calculation method (ECCM) based on WSNs. Then, using the CUDA (Compute Unified Device Architecture) Programming model, we propose a Two-level Parallel Optimization Model (TLPOM) which exploits reasonable resource planning and common compiler optimization techniques to obtain the best blocks and threads configuration considering the resource constraints of each node. The key to this part is dynamic coupling Thread-Level Parallelism (TLP) and Instruction-Level Parallelism (ILP) to improve the performance of the algorithms without additional energy consumption. Finally, combining the ECCM and the TLPOM, we use the Reliable GPU Cluster Architecture (RGCA) to obtain a high-reliability computing system considering the nodes’ diversity, algorithm characteristics, etc. The results show that the performance of the algorithms significantly increased by 34.1%, 33.96% and 24.07% for Fermi, Kepler and Maxwell on average with TLPOM and the RGCA ensures that our IoT computing system provides low-cost and high-reliability services. PMID:28777325

RGCA: A Reliable GPU Cluster Architecture for Large-Scale Internet of Things Computing Based on Effective Performance-Energy Optimization.

PubMed

Fang, Yuling; Chen, Qingkui; Xiong, Neal N; Zhao, Deyu; Wang, Jingjuan

2017-08-04

This paper aims to develop a low-cost, high-performance and high-reliability computing system to process large-scale data using common data mining algorithms in the Internet of Things (IoT) computing environment. Considering the characteristics of IoT data processing, similar to mainstream high performance computing, we use a GPU (Graphics Processing Unit) cluster to achieve better IoT services. Firstly, we present an energy consumption calculation method (ECCM) based on WSNs. Then, using the CUDA (Compute Unified Device Architecture) Programming model, we propose a Two-level Parallel Optimization Model (TLPOM) which exploits reasonable resource planning and common compiler optimization techniques to obtain the best blocks and threads configuration considering the resource constraints of each node. The key to this part is dynamic coupling Thread-Level Parallelism (TLP) and Instruction-Level Parallelism (ILP) to improve the performance of the algorithms without additional energy consumption. Finally, combining the ECCM and the TLPOM, we use the Reliable GPU Cluster Architecture (RGCA) to obtain a high-reliability computing system considering the nodes' diversity, algorithm characteristics, etc. The results show that the performance of the algorithms significantly increased by 34.1%, 33.96% and 24.07% for Fermi, Kepler and Maxwell on average with TLPOM and the RGCA ensures that our IoT computing system provides low-cost and high-reliability services.

Thermoelectric Outer Planets Spacecraft (TOPS)

NASA Technical Reports Server (NTRS)

1973-01-01

The research and advanced development work is reported on a ballistic-mode, outer planet spacecraft using radioisotope thermoelectric generator (RTG) power. The Thermoelectric Outer Planet Spacecraft (TOPS) project was established to provide the advanced systems technology that would allow the realistic estimates of performance, cost, reliability, and scheduling that are required for an actual flight mission. A system design of the complete RTG-powered outer planet spacecraft was made; major technical innovations of certain hardware elements were designed, developed, and tested; and reliability and quality assurance concepts were developed for long-life requirements. At the conclusion of its active phase, the TOPS Project reached its principal objectives: a development and experience base was established for project definition, and for estimating cost, performance, and reliability; an understanding of system and subsystem capabilities for successful outer planets missions was achieved. The system design answered long-life requirements with massive redundancy, controlled by on-board analysis of spacecraft performance data.

Reliability and Geographic Trends of 50,000 Photovoltaic Systems in the USA: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, D. C.; Kurtz, S. R.

2014-09-01

This paper presents performance and reliability data from nearly 50,000 photovoltaic (PV) systems totaling 1.7 gigawatts installed capacity in the USA from 2009 to 2012 and their geographic trends. About 90% of the normal systems and about 85% of all systems, including systems with known issues, performed to within 10% or better of expected performance. Although considerable uncertainty may exist due to the nature of the data, hotter climates appear to exhibit some degradation not seen in the more moderate climates. Special causes of underperformance and their impacts are delineated by reliability category. Hardware-related issues are dominated by inverter problemsmore » (totaling less than 0.5%) and underperforming modules (totaling less than 0.1%). Furthermore, many reliability categories show a significant decrease in occurrence from year 1 to subsequent years, emphasizing the need for higher-quality installations but also the need for improved standards development. The probability of PV system damage because of hail is below 0.05%. Singular weather events can have a significant impact such as a single lightning strike to a transformer or the impact of a hurricane. However, grid outages are more likely to have a significant impact than PV system damage when extreme weather events occur.« less

RELAV - RELIABILITY/AVAILABILITY ANALYSIS PROGRAM

NASA Technical Reports Server (NTRS)

Bowerman, P. N.

1994-01-01

RELAV (Reliability/Availability Analysis Program) is a comprehensive analytical tool to determine the reliability or availability of any general system which can be modeled as embedded k-out-of-n groups of items (components) and/or subgroups. Both ground and flight systems at NASA's Jet Propulsion Laboratory have utilized this program. RELAV can assess current system performance during the later testing phases of a system design, as well as model candidate designs/architectures or validate and form predictions during the early phases of a design. Systems are commonly modeled as System Block Diagrams (SBDs). RELAV calculates the success probability of each group of items and/or subgroups within the system assuming k-out-of-n operating rules apply for each group. The program operates on a folding basis; i.e. it works its way towards the system level from the most embedded level by folding related groups into single components. The entire folding process involves probabilities; therefore, availability problems are performed in terms of the probability of success, and reliability problems are performed for specific mission lengths. An enhanced cumulative binomial algorithm is used for groups where all probabilities are equal, while a fast algorithm based upon "Computing k-out-of-n System Reliability", Barlow & Heidtmann, IEEE TRANSACTIONS ON RELIABILITY, October 1984, is used for groups with unequal probabilities. Inputs to the program include a description of the system and any one of the following: 1) availabilities of the items, 2) mean time between failures and mean time to repairs for the items from which availabilities are calculated, 3) mean time between failures and mission length(s) from which reliabilities are calculated, or 4) failure rates and mission length(s) from which reliabilities are calculated. The results are probabilities of success of each group and the system in the given configuration. RELAV assumes exponential failure distributions for reliability calculations and infinite repair resources for availability calculations. No more than 967 items or groups can be modeled by RELAV. If larger problems can be broken into subsystems of 967 items or less, the subsystem results can be used as item inputs to a system problem. The calculated availabilities are steady-state values. Group results are presented in the order in which they were calculated (from the most embedded level out to the system level). This provides a good mechanism to perform trade studies. Starting from the system result and working backwards, the granularity gets finer; therefore, system elements that contribute most to system degradation are detected quickly. RELAV is a C-language program originally developed under the UNIX operating system on a MASSCOMP MC500 computer. It has been modified, as necessary, and ported to an IBM PC compatible with a math coprocessor. The current version of the program runs in the DOS environment and requires a Turbo C vers. 2.0 compiler. RELAV has a memory requirement of 103 KB and was developed in 1989. RELAV is a copyrighted work with all copyright vested in NASA.

Optimal Bi-Objective Redundancy Allocation for Systems Reliability and Risk Management.

PubMed

Govindan, Kannan; Jafarian, Ahmad; Azbari, Mostafa E; Choi, Tsan-Ming

2016-08-01

In the big data era, systems reliability is critical to effective systems risk management. In this paper, a novel multiobjective approach, with hybridization of a known algorithm called NSGA-II and an adaptive population-based simulated annealing (APBSA) method is developed to solve the systems reliability optimization problems. In the first step, to create a good algorithm, we use a coevolutionary strategy. Since the proposed algorithm is very sensitive to parameter values, the response surface method is employed to estimate the appropriate parameters of the algorithm. Moreover, to examine the performance of our proposed approach, several test problems are generated, and the proposed hybrid algorithm and other commonly known approaches (i.e., MOGA, NRGA, and NSGA-II) are compared with respect to four performance measures: 1) mean ideal distance; 2) diversification metric; 3) percentage of domination; and 4) data envelopment analysis. The computational studies have shown that the proposed algorithm is an effective approach for systems reliability and risk management.

Silicon Nanophotonics for Many-Core On-Chip Networks

NASA Astrophysics Data System (ADS)

Mohamed, Moustafa

Number of cores in many-core architectures are scaling to unprecedented levels requiring ever increasing communication capacity. Traditionally, architects follow the path of higher throughput at the expense of latency. This trend has evolved into being problematic for performance in many-core architectures. Moreover, the trends of power consumption is increasing with system scaling mandating nontraditional solutions. Nanophotonics can address these problems, offering benefits in the three frontiers of many-core processor design: Latency, bandwidth, and power. Nanophotonics leverage circuit-switching flow control allowing low latency; in addition, the power consumption of optical links is significantly lower compared to their electrical counterparts at intermediate and long links. Finally, through wave division multiplexing, we can keep the high bandwidth trends without sacrificing the throughput. This thesis focuses on realizing nanophotonics for communication in many-core architectures at different design levels considering reliability challenges that our fabrication and measurements reveal. First, we study how to design on-chip networks for low latency, low power, and high bandwidth by exploiting the full potential of nanophotonics. The design process considers device level limitations and capabilities on one hand, and system level demands in terms of power and performance on the other hand. The design involves the choice of devices, designing the optical link, the topology, the arbitration technique, and the routing mechanism. Next, we address the problem of reliability in on-chip networks. Reliability not only degrades performance but can block communication. Hence, we propose a reliability-aware design flow and present a reliability management technique based on this flow to address reliability in the system. In the proposed flow reliability is modeled and analyzed for at the device, architecture, and system level. Our reliability management technique is superior to existing solutions in terms of power and performance. In fact, our solution can scale to thousand core with low overhead.

Overview of RICOR's reliability theoretical analysis, accelerated life demonstration test results and verification by field data

NASA Astrophysics Data System (ADS)

Vainshtein, Igor; Baruch, Shlomi; Regev, Itai; Segal, Victor; Filis, Avishai; Riabzev, Sergey

2018-05-01

The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance systems, emphasizes the need for a highly reliable cryocooler having increased operational availability and optimized system's Integrated Logistic Support (ILS). In order to meet this need, RICOR developed linear and rotary cryocoolers which achieved successfully this goal. Cryocoolers MTTF was analyzed by theoretical reliability evaluation methods, demonstrated by normal and accelerated life tests at Cryocooler level and finally verified by field data analysis derived from Cryocoolers operating at system level. The following paper reviews theoretical reliability analysis methods together with analyzing reliability test results derived from standard and accelerated life demonstration tests performed at Ricor's advanced reliability laboratory. As a summary for the work process, reliability verification data will be presented as a feedback from fielded systems.

Different Approaches for Ensuring Performance/Reliability of Plastic Encapsulated Microcircuits (PEMs) in Space Applications

NASA Technical Reports Server (NTRS)

Gerke, R. David; Sandor, Mike; Agarwal, Shri; Moor, Andrew F.; Cooper, Kim A.

2000-01-01

Engineers within the commercial and aerospace industries are using trade-off and risk analysis to aid in reducing spacecraft system cost while increasing performance and maintaining high reliability. In many cases, Commercial Off-The-Shelf (COTS) components, which include Plastic Encapsulated Microcircuits (PEMs), are candidate packaging technologies for spacecrafts due to their lower cost, lower weight and enhanced functionality. Establishing and implementing a parts program that effectively and reliably makes use of these potentially less reliable, but state-of-the-art devices, has become a significant portion of the job for the parts engineer. Assembling a reliable high performance electronic system, which includes COTS components, requires that the end user assume a risk. To minimize the risk involved, companies have developed methodologies by which they use accelerated stress testing to assess the product and reduce the risk involved to the total system. Currently, there are no industry standard procedures for accomplishing this risk mitigation. This paper will present the approaches for reducing the risk of using PEMs devices in space flight systems as developed by two independent Laboratories. The JPL procedure involves primarily a tailored screening with accelerated stress philosophy while the APL procedure is primarily, a lot qualification procedure. Both Laboratories successfully have reduced the risk of using the particular devices for their respective systems and mission requirements.

Culture Representation in Human Reliability Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

David Gertman; Julie Marble; Steven Novack

Understanding human-system response is critical to being able to plan and predict mission success in the modern battlespace. Commonly, human reliability analysis has been used to predict failures of human performance in complex, critical systems. However, most human reliability methods fail to take culture into account. This paper takes an easily understood state of the art human reliability analysis method and extends that method to account for the influence of culture, including acceptance of new technology, upon performance. The cultural parameters used to modify the human reliability analysis were determined from two standard industry approaches to cultural assessment: Hofstede’s (1991)more » cultural factors and Davis’ (1989) technology acceptance model (TAM). The result is called the Culture Adjustment Method (CAM). An example is presented that (1) reviews human reliability assessment with and without cultural attributes for a Supervisory Control and Data Acquisition (SCADA) system attack, (2) demonstrates how country specific information can be used to increase the realism of HRA modeling, and (3) discusses the differences in human error probability estimates arising from cultural differences.« less

Performance and reliability of the NASA Biomass Production Chamber

NASA Technical Reports Server (NTRS)

Sager, J. C.; Chetirkin, P. V.

1994-01-01

The Biomass Production Chamber (BPC) at the Kennedy Space Center is part of the Controlled Ecological Life Support System (CELSS) Breadboard Project. Plants are grown in a closed environment in an effort to quantify their contributions to the requirements for life support. Performance of this system is described. Also, in building this system, data from component and subsystem failures are being recorded. These data are used to identify problem areas in the design and implementation. The techniques used to measure the reliability will be useful in the design and construction of future CELSS. Possible methods for determining the reliability of a green plant, the primary component of a CELSS, are discussed.

Performance of a system of reservoirs on futuristic front

NASA Astrophysics Data System (ADS)

Saha, Satabdi; Roy, Debasri; Mazumdar, Asis

2017-10-01

Application of simulation model HEC-5 to analyze the performance of the DVC Reservoir System (a multipurpose system with a network of five reservoirs and one barrage) on the river Damodar in Eastern India in meeting projected future demand as well as controlling flood for synthetically generated future scenario is addressed here with a view to develop an appropriate strategy for its operation. Thomas-Fiering model (based on Markov autoregressive model) has been adopted for generation of synthetic scenario (monthly streamflow series) and subsequently downscaling of modeled monthly streamflow to daily values was carried out. The performance of the system (analysed on seasonal basis) in terms of `Performance Indices' (viz., both quantity based reliability and time based reliability, mean daily deficit, average failure period, resilience and maximum vulnerability indices) for the projected scenario with enhanced demand turned out to be poor compared to that for historical scenario. However, judicious adoption of resource enhancement (marginal reallocation of reservoir storage capacity) and demand management strategy (curtailment of projected high water requirements and trading off between demands) was found to be a viable option for improvement of the performance of the reservoir system appreciably [improvement being (1-51 %), (2-35 %), (16-96 %), (25-50 %), (8-36 %) and (12-30 %) for the indices viz., quantity based reliability, time based reliability, mean daily deficit, average failure period, resilience and maximum vulnerability, respectively] compared to that with normal storage and projected demand. Again, 100 % reliability for flood control for current as well as future synthetically generated scenarios was noted. The results from the study would assist concerned authority in successful operation of reservoirs in the context of growing demand and dwindling resource.

Reliability Analysis of the Electrical Control System of Subsea Blowout Preventers Using Markov Models

PubMed Central

Liu, Zengkai; Liu, Yonghong; Cai, Baoping

2014-01-01

Reliability analysis of the electrical control system of a subsea blowout preventer (BOP) stack is carried out based on Markov method. For the subsea BOP electrical control system used in the current work, the 3-2-1-0 and 3-2-0 input voting schemes are available. The effects of the voting schemes on system performance are evaluated based on Markov models. In addition, the effects of failure rates of the modules and repair time on system reliability indices are also investigated. PMID:25409010

Effect of Sensors on the Reliability and Control Performance of Power Circuits in the Web of Things (WoT)

PubMed Central

Bae, Sungwoo; Kim, Myungchin

2016-01-01

In order to realize a true WoT environment, a reliable power circuit is required to ensure interconnections among a range of WoT devices. This paper presents research on sensors and their effects on the reliability and response characteristics of power circuits in WoT devices. The presented research can be used in various power circuit applications, such as energy harvesting interfaces, photovoltaic systems, and battery management systems for the WoT devices. As power circuits rely on the feedback from voltage/current sensors, the system performance is likely to be affected by the sensor failure rates, sensor dynamic characteristics, and their interface circuits. This study investigated how the operational availability of the power circuits is affected by the sensor failure rates by performing a quantitative reliability analysis. In the analysis process, this paper also includes the effects of various reconstruction and estimation techniques used in power processing circuits (e.g., energy harvesting circuits and photovoltaic systems). This paper also reports how the transient control performance of power circuits is affected by sensor interface circuits. With the frequency domain stability analysis and circuit simulation, it was verified that the interface circuit dynamics may affect the transient response characteristics of power circuits. The verification results in this paper showed that the reliability and control performance of the power circuits can be affected by the sensor types, fault tolerant approaches against sensor failures, and the response characteristics of the sensor interfaces. The analysis results were also verified by experiments using a power circuit prototype. PMID:27608020

Reliability estimation of a N- M-cold-standby redundancy system in a multicomponent stress-strength model with generalized half-logistic distribution

NASA Astrophysics Data System (ADS)

Liu, Yiming; Shi, Yimin; Bai, Xuchao; Zhan, Pei

2018-01-01

In this paper, we study the estimation for the reliability of a multicomponent system, named N- M-cold-standby redundancy system, based on progressive Type-II censoring sample. In the system, there are N subsystems consisting of M statistically independent distributed strength components, and only one of these subsystems works under the impact of stresses at a time and the others remain as standbys. Whenever the working subsystem fails, one from the standbys takes its place. The system fails when the entire subsystems fail. It is supposed that the underlying distributions of random strength and stress both belong to the generalized half-logistic distribution with different shape parameter. The reliability of the system is estimated by using both classical and Bayesian statistical inference. Uniformly minimum variance unbiased estimator and maximum likelihood estimator for the reliability of the system are derived. Under squared error loss function, the exact expression of the Bayes estimator for the reliability of the system is developed by using the Gauss hypergeometric function. The asymptotic confidence interval and corresponding coverage probabilities are derived based on both the Fisher and the observed information matrices. The approximate highest probability density credible interval is constructed by using Monte Carlo method. Monte Carlo simulations are performed to compare the performances of the proposed reliability estimators. A real data set is also analyzed for an illustration of the findings.

Development of modelling algorithm of technological systems by statistical tests

NASA Astrophysics Data System (ADS)

Shemshura, E. A.; Otrokov, A. V.; Chernyh, V. G.

2018-03-01

The paper tackles the problem of economic assessment of design efficiency regarding various technological systems at the stage of their operation. The modelling algorithm of a technological system was performed using statistical tests and with account of the reliability index allows estimating the level of machinery technical excellence and defining the efficiency of design reliability against its performance. Economic feasibility of its application shall be determined on the basis of service quality of a technological system with further forecasting of volumes and the range of spare parts supply.

Reliability models applicable to space telescope solar array assembly system

NASA Technical Reports Server (NTRS)

Patil, S. A.

1986-01-01

A complex system may consist of a number of subsystems with several components in series, parallel, or combination of both series and parallel. In order to predict how well the system will perform, it is necessary to know the reliabilities of the subsystems and the reliability of the whole system. The objective of the present study is to develop mathematical models of the reliability which are applicable to complex systems. The models are determined by assuming k failures out of n components in a subsystem. By taking k = 1 and k = n, these models reduce to parallel and series models; hence, the models can be specialized to parallel, series combination systems. The models are developed by assuming the failure rates of the components as functions of time and as such, can be applied to processes with or without aging effects. The reliability models are further specialized to Space Telescope Solar Arrray (STSA) System. The STSA consists of 20 identical solar panel assemblies (SPA's). The reliabilities of the SPA's are determined by the reliabilities of solar cell strings, interconnects, and diodes. The estimates of the reliability of the system for one to five years are calculated by using the reliability estimates of solar cells and interconnects given n ESA documents. Aging effects in relation to breaks in interconnects are discussed.

Climate and water resource change impacts and adaptation potential for US power supply

DOE PAGES

Miara, Ariel; Macknick, Jordan E.; Vorosmarty, Charles J.; ...

2017-10-30

Power plants that require cooling currently (2015) provide 85% of electricity generation in the United States. These facilities need large volumes of water and sufficiently cool temperatures for optimal operations, and projected climate conditions may lower their potential power output and affect reliability. We evaluate the performance of 1,080 thermoelectric plants across the contiguous US under future climates (2035-2064) and their collective performance at 19 North American Electric Reliability Corporation (NERC) sub-regions. Joint consideration of engineering interactions with climate, hydrology and environmental regulations reveals the region-specific performance of energy systems and the need for regional energy security and climate-water adaptationmore » strategies. Despite climate-water constraints on individual plants, the current power supply infrastructure shows potential for adaptation to future climates by capitalizing on the size of regional power systems, grid configuration and improvements in thermal efficiencies. Without placing climate-water impacts on individual plants in a broader power systems context, vulnerability assessments that aim to support adaptation and resilience strategies misgauge the extent to which regional energy systems are vulnerable. As a result, climate-water impacts can lower thermoelectric reserve margins, a measure of systems-level reliability, highlighting the need to integrate climate-water constraints on thermoelectric power supply into energy planning, risk assessments, and system reliability management.« less

Climate and water resource change impacts and adaptation potential for US power supply

NASA Astrophysics Data System (ADS)

Miara, Ariel; Macknick, Jordan E.; Vörösmarty, Charles J.; Tidwell, Vincent C.; Newmark, Robin; Fekete, Balazs

2017-11-01

Power plants that require cooling currently (2015) provide 85% of electricity generation in the United States. These facilities need large volumes of water and sufficiently cool temperatures for optimal operations, and projected climate conditions may lower their potential power output and affect reliability. We evaluate the performance of 1,080 thermoelectric plants across the contiguous US under future climates (2035-2064) and their collective performance at 19 North American Electric Reliability Corporation (NERC) sub-regions. Joint consideration of engineering interactions with climate, hydrology and environmental regulations reveals the region-specific performance of energy systems and the need for regional energy security and climate-water adaptation strategies. Despite climate-water constraints on individual plants, the current power supply infrastructure shows potential for adaptation to future climates by capitalizing on the size of regional power systems, grid configuration and improvements in thermal efficiencies. Without placing climate-water impacts on individual plants in a broader power systems context, vulnerability assessments that aim to support adaptation and resilience strategies misgauge the extent to which regional energy systems are vulnerable. Climate-water impacts can lower thermoelectric reserve margins, a measure of systems-level reliability, highlighting the need to integrate climate-water constraints on thermoelectric power supply into energy planning, risk assessments, and system reliability management.

Climate and water resource change impacts and adaptation potential for US power supply

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miara, Ariel; Macknick, Jordan E.; Vorosmarty, Charles J.

Power plants that require cooling currently (2015) provide 85% of electricity generation in the United States. These facilities need large volumes of water and sufficiently cool temperatures for optimal operations, and projected climate conditions may lower their potential power output and affect reliability. We evaluate the performance of 1,080 thermoelectric plants across the contiguous US under future climates (2035-2064) and their collective performance at 19 North American Electric Reliability Corporation (NERC) sub-regions. Joint consideration of engineering interactions with climate, hydrology and environmental regulations reveals the region-specific performance of energy systems and the need for regional energy security and climate-water adaptationmore » strategies. Despite climate-water constraints on individual plants, the current power supply infrastructure shows potential for adaptation to future climates by capitalizing on the size of regional power systems, grid configuration and improvements in thermal efficiencies. Without placing climate-water impacts on individual plants in a broader power systems context, vulnerability assessments that aim to support adaptation and resilience strategies misgauge the extent to which regional energy systems are vulnerable. As a result, climate-water impacts can lower thermoelectric reserve margins, a measure of systems-level reliability, highlighting the need to integrate climate-water constraints on thermoelectric power supply into energy planning, risk assessments, and system reliability management.« less

Projecting technology change to improve space technology planning and systems management

NASA Astrophysics Data System (ADS)

Walk, Steven Robert

2011-04-01

Projecting technology performance evolution has been improving over the years. Reliable quantitative forecasting methods have been developed that project the growth, diffusion, and performance of technology in time, including projecting technology substitutions, saturation levels, and performance improvements. These forecasts can be applied at the early stages of space technology planning to better predict available future technology performance, assure the successful selection of technology, and improve technology systems management strategy. Often what is published as a technology forecast is simply scenario planning, usually made by extrapolating current trends into the future, with perhaps some subjective insight added. Typically, the accuracy of such predictions falls rapidly with distance in time. Quantitative technology forecasting (QTF), on the other hand, includes the study of historic data to identify one of or a combination of several recognized universal technology diffusion or substitution patterns. In the same manner that quantitative models of physical phenomena provide excellent predictions of system behavior, so do QTF models provide reliable technological performance trajectories. In practice, a quantitative technology forecast is completed to ascertain with confidence when the projected performance of a technology or system of technologies will occur. Such projections provide reliable time-referenced information when considering cost and performance trade-offs in maintaining, replacing, or migrating a technology, component, or system. This paper introduces various quantitative technology forecasting techniques and illustrates their practical application in space technology and technology systems management.

Free-Mass and Interface Configurations of Hammering Mechanisms

NASA Technical Reports Server (NTRS)

Bao, Xiaoqi (Inventor); Sherrit, Stewart (Inventor); Badescu, Mircea (Inventor); Bar-Cohen, Yoseph (Inventor); Askins, Steve (Inventor); Ostlund, Patrick (Inventor)

2015-01-01

The design of the free-mass in an ultrasonic driller/corer (USDC) has been refined in order to improve the performance and operational reliability of the system. In one embodiment, the improvements in performance and operational reliability include decreasing the impact surface area of the free-mass to increase the transfer of impact energy from the piezoelectric transducer and reductions in the likelihood that the system will jam.

Standard Hardware Acquisition and Reliability Program's (SHARP's) efforts in incorporating fiber optic interconnects into standard electronic module (SEM) connectors

NASA Astrophysics Data System (ADS)

Riggs, William R.

1994-05-01

SHARP is a Navy wide logistics technology development effort aimed at reducing the acquisition costs, support costs, and risks of military electronic weapon systems while increasing the performance capability, reliability, maintainability, and readiness of these systems. Lower life cycle costs for electronic hardware are achieved through technology transition, standardization, and reliability enhancement to improve system affordability and availability as well as enhancing fleet modernization. Advanced technology is transferred into the fleet through hardware specifications for weapon system building blocks of standard electronic modules, standard power systems, and standard electronic systems. The product lines are all defined with respect to their size, weight, I/O, environmental performance, and operational performance. This method of defining the standard is very conducive to inserting new technologies into systems using the standard hardware. This is the approach taken thus far in inserting photonic technologies into SHARP hardware. All of the efforts have been related to module packaging; i.e. interconnects, component packaging, and module developments. Fiber optic interconnects are discussed in this paper.

Performance Analysis of Stirling Engine-Driven Vapor Compression Heat Pump System

NASA Astrophysics Data System (ADS)

Kagawa, Noboru

Stirling engine-driven vapor compression systems have many unique advantages including higher thermal efficiencies, preferable exhaust gas characteristics, multi-fuel usage, and low noise and vibration which can play an important role in alleviating environmental and energy problems. This paper introduces a design method for the systems based on reliable mathematical methods for Stirling and Rankin cycles using reliable thermophysical information for refrigerants. The model deals with a combination of a kinematic Stirling engine and a scroll compressor. Some experimental coefficients are used to formulate the model. The obtained results show the performance behavior in detail. The measured performance of the actual system coincides with the calculated results. Furthermore, the calculated results clarify the performance using alternative refrigerants for R-22.

Mechanical System Reliability and Cost Integration Using a Sequential Linear Approximation Method

NASA Technical Reports Server (NTRS)

Kowal, Michael T.

1997-01-01

The development of new products is dependent on product designs that incorporate high levels of reliability along with a design that meets predetermined levels of system cost. Additional constraints on the product include explicit and implicit performance requirements. Existing reliability and cost prediction methods result in no direct linkage between variables affecting these two dominant product attributes. A methodology to integrate reliability and cost estimates using a sequential linear approximation method is proposed. The sequential linear approximation method utilizes probability of failure sensitivities determined from probabilistic reliability methods as well a manufacturing cost sensitivities. The application of the sequential linear approximation method to a mechanical system is demonstrated.

Impact of distributed power electronics on the lifetime and reliability of PV systems: Impact of distributed power electronics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olalla, Carlos; Maksimovic, Dragan; Deline, Chris

Here, this paper quantifies the impact of distributed power electronics in photovoltaic (PV) systems in terms of end-of-life energy-capture performance and reliability. The analysis is based on simulations of PV installations over system lifetime at various degradation rates. It is shown how module-level or submodule-level power converters can mitigate variations in cell degradation over time, effectively increasing the system lifespan by 5-10 years compared with the nominal 25-year lifetime. An important aspect typically overlooked when characterizing such improvements is the reliability of distributed power electronics, as power converter failures may not only diminish energy yield improvements but also adversely affectmore » the overall system operation. Failure models are developed, and power electronics reliability is taken into account in this work, in order to provide a more comprehensive view of the opportunities and limitations offered by distributed power electronics in PV systems. Lastly, it is shown how a differential power-processing approach achieves the best mismatch mitigation performance and the least susceptibility to converter faults.« less

Impact of distributed power electronics on the lifetime and reliability of PV systems: Impact of distributed power electronics

DOE PAGES

Olalla, Carlos; Maksimovic, Dragan; Deline, Chris; ...

2017-04-26

Here, this paper quantifies the impact of distributed power electronics in photovoltaic (PV) systems in terms of end-of-life energy-capture performance and reliability. The analysis is based on simulations of PV installations over system lifetime at various degradation rates. It is shown how module-level or submodule-level power converters can mitigate variations in cell degradation over time, effectively increasing the system lifespan by 5-10 years compared with the nominal 25-year lifetime. An important aspect typically overlooked when characterizing such improvements is the reliability of distributed power electronics, as power converter failures may not only diminish energy yield improvements but also adversely affectmore » the overall system operation. Failure models are developed, and power electronics reliability is taken into account in this work, in order to provide a more comprehensive view of the opportunities and limitations offered by distributed power electronics in PV systems. Lastly, it is shown how a differential power-processing approach achieves the best mismatch mitigation performance and the least susceptibility to converter faults.« less

Team performance in networked supervisory control of unmanned air vehicles: effects of automation, working memory, and communication content.

PubMed

McKendrick, Ryan; Shaw, Tyler; de Visser, Ewart; Saqer, Haneen; Kidwell, Brian; Parasuraman, Raja

2014-05-01

Assess team performance within a net-worked supervisory control setting while manipulating automated decision aids and monitoring team communication and working memory ability. Networked systems such as multi-unmanned air vehicle (UAV) supervision have complex properties that make prediction of human-system performance difficult. Automated decision aid can provide valuable information to operators, individual abilities can limit or facilitate team performance, and team communication patterns can alter how effectively individuals work together. We hypothesized that reliable automation, higher working memory capacity, and increased communication rates of task-relevant information would offset performance decrements attributed to high task load. Two-person teams performed a simulated air defense task with two levels of task load and three levels of automated aid reliability. Teams communicated and received decision aid messages via chat window text messages. Task Load x Automation effects were significant across all performance measures. Reliable automation limited the decline in team performance with increasing task load. Average team spatial working memory was a stronger predictor than other measures of team working memory. Frequency of team rapport and enemy location communications positively related to team performance, and word count was negatively related to team performance. Reliable decision aiding mitigated team performance decline during increased task load during multi-UAV supervisory control. Team spatial working memory, communication of spatial information, and team rapport predicted team success. An automated decision aid can improve team performance under high task load. Assessment of spatial working memory and the communication of task-relevant information can help in operator and team selection in supervisory control systems.

Comparative research of redundant strap down inertial navigation system based on different configuration schemes

NASA Astrophysics Data System (ADS)

Yu, Yuting; Cheng, Ming

2018-05-01

Aiming at various configuration scheme and inertial measurement units of Strapdown Inertial Navigation System, selected tetrahedron skew configuration and coaxial orthogonal configuration by nine low cost IMU to build system. Calculation and simulation the performance index, reliability and fault diagnosis ability of the navigation system. Analysis shows that the reliability and reconfiguration scheme of skew configuration is superior to the orthogonal configuration scheme, while the performance index and fault diagnosis ability of the system are similar. The work in this paper provides a strong reference for the selection of engineering applications.

Reliability of Radioisotope Stirling Convertor Linear Alternator

NASA Technical Reports Server (NTRS)

Shah, Ashwin; Korovaichuk, Igor; Geng, Steven M.; Schreiber, Jeffrey G.

2006-01-01

Onboard radioisotope power systems being developed and planned for NASA s deep-space missions would require reliable design lifetimes of up to 14 years. Critical components and materials of Stirling convertors have been undergoing extensive testing and evaluation in support of a reliable performance for the specified life span. Of significant importance to the successful development of the Stirling convertor is the design of a lightweight and highly efficient linear alternator. Alternator performance could vary due to small deviations in the permanent magnet properties, operating temperature, and component geometries. Durability prediction and reliability of the alternator may be affected by these deviations from nominal design conditions. Therefore, it is important to evaluate the effect of these uncertainties in predicting the reliability of the linear alternator performance. This paper presents a study in which a reliability-based methodology is used to assess alternator performance. The response surface characterizing the induced open-circuit voltage performance is constructed using 3-D finite element magnetic analysis. Fast probability integration method is used to determine the probability of the desired performance and its sensitivity to the alternator design parameters.

Confirmatory Factor Analysis of the System for Evaluation of Teaching Qualities (SETQ) in Graduate Medical Training.

PubMed

Boerebach, Benjamin C M; Lombarts, Kiki M J M H; Arah, Onyebuchi A

2016-03-01

The System for Evaluation of Teaching Qualities (SETQ) was developed as a formative system for the continuous evaluation and development of physicians' teaching performance in graduate medical training. It has been seven years since the introduction and initial exploratory psychometric analysis of the SETQ questionnaires. This study investigates the validity and reliability of the SETQ questionnaires across hospitals and medical specialties using confirmatory factor analyses (CFAs), reliability analysis, and generalizability analysis. The SETQ questionnaires were tested in a sample of 3,025 physicians and 2,848 trainees in 46 hospitals. The CFA revealed acceptable fit of the data to the previously identified five-factor model. The high internal consistency estimates suggest satisfactory reliability of the subscales. These results provide robust evidence for the validity and reliability of the SETQ questionnaires for evaluating physicians' teaching performance. © The Author(s) 2014.

The reliability of an instrumented start block analysis system.

PubMed

Tor, Elaine; Pease, David L; Ball, Kevin A

2015-02-01

The swimming start is highly influential to overall competition performance. Therefore, it is paramount to develop reliable methods to perform accurate biomechanical analysis of start performance for training and research. The Wetplate Analysis System is a custom-made force plate system developed by the Australian Institute of Sport--Aquatic Testing, Training and Research Unit (AIS ATTRU). This sophisticated system combines both force data and 2D digitization to measure a number of kinetic and kinematic parameter values in an attempt to evaluate start performance. Fourteen elite swimmers performed two maximal effort dives (performance was defined as time from start signal to 15 m) over two separate testing sessions. Intraclass correlation coefficients (ICC) were used to determine each parameter's reliability. The kinetic parameters all had ICC greater than 0.9 except the time of peak vertical force (0.742). This may have been due to variations in movement initiation after the starting signal between trials. The kinematic and time parameters also had ICC greater than 0.9 apart from for the time of maximum depth (0.719). This parameter was lower due to the swimmers varying their depth between trials. Based on the high ICC scores for all parameters, the Wetplate Analysis System is suitable for biomechanical analysis of swimming starts.

Scheduling for energy and reliability management on multiprocessor real-time systems

NASA Astrophysics Data System (ADS)

Qi, Xuan

Scheduling algorithms for multiprocessor real-time systems have been studied for years with many well-recognized algorithms proposed. However, it is still an evolving research area and many problems remain open due to their intrinsic complexities. With the emergence of multicore processors, it is necessary to re-investigate the scheduling problems and design/develop efficient algorithms for better system utilization, low scheduling overhead, high energy efficiency, and better system reliability. Focusing cluster schedulings with optimal global schedulers, we study the utilization bound and scheduling overhead for a class of cluster-optimal schedulers. Then, taking energy/power consumption into consideration, we developed energy-efficient scheduling algorithms for real-time systems, especially for the proliferating embedded systems with limited energy budget. As the commonly deployed energy-saving technique (e.g. dynamic voltage frequency scaling (DVFS)) will significantly affect system reliability, we study schedulers that have intelligent mechanisms to recuperate system reliability to satisfy the quality assurance requirements. Extensive simulation is conducted to evaluate the performance of the proposed algorithms on reduction of scheduling overhead, energy saving, and reliability improvement. The simulation results show that the proposed reliability-aware power management schemes could preserve the system reliability while still achieving substantial energy saving.

Assessing segment- and corridor-based travel-time reliability on urban freeways tech transfer summary : tech transfer summary.

DOT National Transportation Integrated Search

2016-09-01

Travel time and travel-time reliability have been used as performance : measures to evaluate traffic system conditions and develop advanced : traveler information and traffic management systems. The objectives of this research were to: : - Quantify s...

Network reliability maximization for stochastic-flow network subject to correlated failures using genetic algorithm and tabu\\xA0search

NASA Astrophysics Data System (ADS)

Yeh, Cheng-Ta; Lin, Yi-Kuei; Yang, Jo-Yun

2018-07-01

Network reliability is an important performance index for many real-life systems, such as electric power systems, computer systems and transportation systems. These systems can be modelled as stochastic-flow networks (SFNs) composed of arcs and nodes. Most system supervisors respect the network reliability maximization by finding the optimal multi-state resource assignment, which is one resource to each arc. However, a disaster may cause correlated failures for the assigned resources, affecting the network reliability. This article focuses on determining the optimal resource assignment with maximal network reliability for SFNs. To solve the problem, this study proposes a hybrid algorithm integrating the genetic algorithm and tabu search to determine the optimal assignment, called the hybrid GA-TS algorithm (HGTA), and integrates minimal paths, recursive sum of disjoint products and the correlated binomial distribution to calculate network reliability. Several practical numerical experiments are adopted to demonstrate that HGTA has better computational quality than several popular soft computing algorithms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agalgaonkar, Yashodhan P.; Hammerstrom, Donald J.

The Pacific Northwest Smart Grid Demonstration (PNWSGD) was a smart grid technology performance evaluation project that included multiple U.S. states and cooperation from multiple electric utilities in the northwest region. One of the local objectives for the project was to achieve improved distribution system reliability. Toward this end, some PNWSGD utilities automated their distribution systems, including the application of fault detection, isolation, and restoration and advanced metering infrastructure. In light of this investment, a major challenge was to establish a correlation between implementation of these smart grid technologies and actual improvements of distribution system reliability. This paper proposes using Welch’smore » t-test to objectively determine and quantify whether distribution system reliability is improving over time. The proposed methodology is generic, and it can be implemented by any utility after calculation of the standard reliability indices. The effectiveness of the proposed hypothesis testing approach is demonstrated through comprehensive practical results. It is believed that wider adoption of the proposed approach can help utilities to evaluate a realistic long-term performance of smart grid technologies.« less

DG Planning with Amalgamation of Operational and Reliability Considerations

NASA Astrophysics Data System (ADS)

Battu, Neelakanteshwar Rao; Abhyankar, A. R.; Senroy, Nilanjan

2016-04-01

Distributed Generation has been playing a vital role in dealing issues related to distribution systems. This paper presents an approach which provides policy maker with a set of solutions for DG placement to optimize reliability and real power loss of the system. Optimal location of a Distributed Generator is evaluated based on performance indices derived for reliability index and real power loss. The proposed approach is applied on a 15-bus radial distribution system and a 18-bus radial distribution system with conventional and wind distributed generators individually.

Performance Issues for a Changing Electric Power Industry

EIA Publications

1995-01-01

Provides an overview of some of the factors affecting reliability within the electric bulk power system. Historical and projected data related to reliability issues are discussed on a national and regional basis. Current research on economic considerations associated with reliability levels is also reviewed.

Design and implementation of online automatic judging system

NASA Astrophysics Data System (ADS)

Liang, Haohui; Chen, Chaojie; Zhong, Xiuyu; Chen, Yuefeng

2017-06-01

For lower efficiency and poorer reliability in programming training and competition by currently artificial judgment, design an Online Automatic Judging (referred to as OAJ) System. The OAJ system including the sandbox judging side and Web side, realizes functions of automatically compiling and running the tested codes, and generating evaluation scores and corresponding reports. To prevent malicious codes from damaging system, the OAJ system utilizes sandbox, ensuring the safety of the system. The OAJ system uses thread pools to achieve parallel test, and adopt database optimization mechanism, such as horizontal split table, to improve the system performance and resources utilization rate. The test results show that the system has high performance, high reliability, high stability and excellent extensibility.

Numerical aerodynamic simulation facility. Preliminary study extension

NASA Technical Reports Server (NTRS)

1978-01-01

The production of an optimized design of key elements of the candidate facility was the primary objective of this report. This was accomplished by effort in the following tasks: (1) to further develop, optimize and describe the function description of the custom hardware; (2) to delineate trade off areas between performance, reliability, availability, serviceability, and programmability; (3) to develop metrics and models for validation of the candidate systems performance; (4) to conduct a functional simulation of the system design; (5) to perform a reliability analysis of the system design; and (6) to develop the software specifications to include a user level high level programming language, a correspondence between the programming language and instruction set and outline the operation system requirements.

Analyzing System on A Chip Single Event Upset Responses using Single Event Upset Data, Classical Reliability Models, and Space Environment Data

NASA Technical Reports Server (NTRS)

Berg, Melanie; LaBel, Kenneth; Campola, Michael; Xapsos, Michael

2017-01-01

We are investigating the application of classical reliability performance metrics combined with standard single event upset (SEU) analysis data. We expect to relate SEU behavior to system performance requirements. Our proposed methodology will provide better prediction of SEU responses in harsh radiation environments with confidence metrics. single event upset (SEU), single event effect (SEE), field programmable gate array devises (FPGAs)

Hawaii electric system reliability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva Monroy, Cesar Augusto; Loose, Verne William

2012-09-01

This report addresses Hawaii electric system reliability issues; greater emphasis is placed on short-term reliability but resource adequacy is reviewed in reference to electric consumers' views of reliability %E2%80%9Cworth%E2%80%9D and the reserve capacity required to deliver that value. The report begins with a description of the Hawaii electric system to the extent permitted by publicly available data. Electrical engineering literature in the area of electric reliability is researched and briefly reviewed. North American Electric Reliability Corporation standards and measures for generation and transmission are reviewed and identified as to their appropriateness for various portions of the electric grid and formore » application in Hawaii. Analysis of frequency data supplied by the State of Hawaii Public Utilities Commission is presented together with comparison and contrast of performance of each of the systems for two years, 2010 and 2011. Literature tracing the development of reliability economics is reviewed and referenced. A method is explained for integrating system cost with outage cost to determine the optimal resource adequacy given customers' views of the value contributed by reliable electric supply. The report concludes with findings and recommendations for reliability in the State of Hawaii.« less

Hawaii Electric System Reliability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loose, Verne William; Silva Monroy, Cesar Augusto

2012-08-01

This report addresses Hawaii electric system reliability issues; greater emphasis is placed on short-term reliability but resource adequacy is reviewed in reference to electric consumers’ views of reliability “worth” and the reserve capacity required to deliver that value. The report begins with a description of the Hawaii electric system to the extent permitted by publicly available data. Electrical engineering literature in the area of electric reliability is researched and briefly reviewed. North American Electric Reliability Corporation standards and measures for generation and transmission are reviewed and identified as to their appropriateness for various portions of the electric grid and formore » application in Hawaii. Analysis of frequency data supplied by the State of Hawaii Public Utilities Commission is presented together with comparison and contrast of performance of each of the systems for two years, 2010 and 2011. Literature tracing the development of reliability economics is reviewed and referenced. A method is explained for integrating system cost with outage cost to determine the optimal resource adequacy given customers’ views of the value contributed by reliable electric supply. The report concludes with findings and recommendations for reliability in the State of Hawaii.« less

Silicon Carbide (SiC) Device and Module Reliability, Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field

DTIC Science & Technology

2016-05-01

AFRL-RQ-WP-TR-2016-0108 SILICON CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled... Heat Input to an Acceleration Field Kirk L. Yerkes (AFRL/RQQI) and James D. Scofield (AFRL/RQQE) Flight Systems Integration Branch (AFRL/RQQI...CARBIDE (SiC) DEVICE AND MODULE RELIABILITY Performance of a Loop Heat Pipe Subjected to a Phase-Coupled Heat Input to an Acceleration Field 5a

Is laser speckle contrast analysis (LASCA) the new kid on the block in systemic sclerosis? A systematic literature review and pilot study to evaluate reliability of LASCA to measure peripheral blood perfusion in scleroderma patients.

PubMed

Cutolo, Maurizio; Vanhaecke, Amber; Ruaro, Barbara; Deschepper, Ellen; Ickinger, Claudia; Melsens, Karin; Piette, Yves; Trombetta, Amelia Chiara; De Keyser, Filip; Smith, Vanessa

2018-06-06

A reliable tool to evaluate flow is paramount in systemic sclerosis (SSc). We describe herein on the one hand a systematic literature review on the reliability of laser speckle contrast analysis (LASCA) to measure the peripheral blood perfusion (PBP) in SSc and perform an additional pilot study, investigating the intra- and inter-rater reliability of LASCA. A systematic search was performed in 3 electronic databases, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In the pilot study, 30 SSc patients and 30 healthy subjects (HS) underwent LASCA assessment. Intra-rater reliability was assessed by having a first anchor rater performing the measurements at 2 time-points and inter-rater reliability by having the anchor rater and a team of second raters performing the measurements in 15 SSc and 30 HS. The measurements were repeated with a second anchor rater in the other 15 SSc patients, as external validation. Only 1 of the 14 records of interest identified through the systematic search was included in the final analysis. In the additional pilot study: intra-class correlation coefficient (ICC) for intra-rater reliability of the first anchor rater was 0.95 in SSc and 0.93 in HS, the ICC for inter-rater reliability was 0.97 in SSc and 0.93 in HS. Intra- and inter-rater reliability of the second anchor rater was 0.78 and 0.87. The identified literature regarding the reliability of LASCA measurements reports good to excellent inter-rater agreement. This very pilot study could confirm the reliability of LASCA measurements with good to excellent inter-rater agreement and found additionally good to excellent intra-rater reliability. Furthermore, similar results were found in the external validation. Copyright © 2018. Published by Elsevier B.V.

Interrater reliability of a Pilates movement-based classification system.

PubMed

Yu, Kwan Kenny; Tulloch, Evelyn; Hendrick, Paul

2015-01-01

To determine the interrater reliability for identification of a specific movement pattern using a Pilates Classification system. Videos of 5 subjects performing specific movement tasks were sent to raters trained in the DMA-CP classification system. Ninety-six raters completed the survey. Interrater reliability for the detection of a directional bias was excellent (Pi = 0.92, and K(free) = 0.89). Interrater reliability for classifying an individual into a specific subgroup was moderate (Pi = 0.64, K(free) = 0.55) however raters who had completed levels 1-4 of the DMA-CP training and reported using the assessment daily demonstrated excellent reliability (Pi = 0.89 and K(free) = 0.87). The reliability of the classification system demonstrated almost perfect agreement in determining the existence of a specific movement pattern and classifying into a subgroup for experienced raters. There was a trend for greater reliability associated with increased levels of training and experience of the raters. Copyright © 2014 Elsevier Ltd. All rights reserved.

Performances and reliability predictions of optical data transmission links using a system simulator for aerospace applications

NASA Astrophysics Data System (ADS)

Bechou, L.; Deshayes, Y.; Aupetit-Berthelemot, C.; Guerin, A.; Tronche, C.

Space missions for Earth Observation are called upon to carry a growing number of instruments in their payload, whose performances are increasing. Future space systems are therefore intended to generate huge amounts of data and a key challenge in coming years will therefore lie in the ability to transmit that significant quantity of data to ground. Thus very high data rate Payload Telemetry (PLTM) systems will be required to face the demand of the future Earth Exploration Satellite Systems and reliability is one of the major concern of such systems. An attractive approach associated with the concept of predictive modeling consists in analyzing the impact of components malfunctioning on the optical link performances taking into account the network requirements and experimental degradation laws. Reliability estimation is traditionally based on life-testing and a basic approach is to use Telcordia requirements (468GR) for optical telecommunication applications. However, due to the various interactions between components, operating lifetime of a system cannot be taken as the lifetime of the less reliable component. In this paper, an original methodology is proposed to estimate reliability of an optical communication system by using a dedicated system simulator for predictive modeling and design for reliability. At first, we present frameworks of point-to-point optical communication systems for space applications where high data rate (or frequency bandwidth), lower cost or mass saving are needed. Optoelectronics devices used in these systems can be similar to those found in terrestrial optical network. Particularly we report simulation results of transmission performances after introduction of DFB Laser diode parameters variations versus time extrapolated from accelerated tests based on terrestrial or submarine telecommunications qualification standards. Simulations are performed to investigate and predict the consequence of degradations of the Laser diode (acting as a - requency carrier) on system performances (eye diagram, quality factor and BER). The studied link consists in 4× 2.5 Gbits/s WDM channels with direct modulation and equally spaced (0,8 nm) around the 1550 nm central wavelength. Results clearly show that variation of fundamental parameters such as bias current or central wavelength induces a penalization of dynamic performances of the complete WDM link. In addition different degradation kinetics of aged Laser diodes from a same batch have been implemented to build the final distribution of Q-factor and BER values after 25 years. When considering long optical distance, fiber attenuation, EDFA noise, dispersion, PMD, ... penalize network performances that can be compensated using Forward Error Correction (FEC) coding. Three methods have been investigated in the case of On-Off Keying (OOK) transmission over an unipolar optical channel corrupted by Gaussian noise. Such system simulations highlight the impact of component parameter degradations on the whole network performances allowing to optimize various time and cost consuming sensitivity analyses at the early stage of the system development. Thus the validity of failure criteria in relation with mission profiles can be evaluated representing a significant part of the general PDfR effort in particular for aerospace applications.

Difficult Decisions Made Easier

NASA Technical Reports Server (NTRS)

2006-01-01

NASA missions are extremely complex and prone to sudden, catastrophic failure if equipment falters or if an unforeseen event occurs. For these reasons, NASA trains to expect the unexpected. It tests its equipment and systems in extreme conditions, and it develops risk-analysis tests to foresee any possible problems. The Space Agency recently worked with an industry partner to develop reliability analysis software capable of modeling complex, highly dynamic systems, taking into account variations in input parameters and the evolution of the system over the course of a mission. The goal of this research was multifold. It included performance and risk analyses of complex, multiphase missions, like the insertion of the Mars Reconnaissance Orbiter; reliability analyses of systems with redundant and/or repairable components; optimization analyses of system configurations with respect to cost and reliability; and sensitivity analyses to identify optimal areas for uncertainty reduction or performance enhancement.

Failure Modes Effects and Criticality Analysis, an Underutilized Safety, Reliability, Project Management and Systems Engineering Tool

NASA Astrophysics Data System (ADS)

Mullin, Daniel Richard

2013-09-01

The majority of space programs whether manned or unmanned for science or exploration require that a Failure Modes Effects and Criticality Analysis (FMECA) be performed as part of their safety and reliability activities. This comes as no surprise given that FMECAs have been an integral part of the reliability engineer's toolkit since the 1950s. The reasons for performing a FMECA are well known including fleshing out system single point failures, system hazards and critical components and functions. However, in the author's ten years' experience as a space systems safety and reliability engineer, findings demonstrate that the FMECA is often performed as an afterthought, simply to meet contract deliverable requirements and is often started long after the system requirements allocation and preliminary design have been completed. There are also important qualitative and quantitative components often missing which can provide useful data to all of project stakeholders. These include; probability of occurrence, probability of detection, time to effect and time to detect and, finally, the Risk Priority Number. This is unfortunate as the FMECA is a powerful system design tool that when used effectively, can help optimize system function while minimizing the risk of failure. When performed as early as possible in conjunction with writing the top level system requirements, the FMECA can provide instant feedback on the viability of the requirements while providing a valuable sanity check early in the design process. It can indicate which areas of the system will require redundancy and which areas are inherently the most risky from the onset. Based on historical and practical examples, it is this author's contention that FMECAs are an immense source of important information for all involved stakeholders in a given project and can provide several benefits including, efficient project management with respect to cost and schedule, system engineering and requirements management, assembly integration and test (AI&T) and operations if applied early, performed to completion and updated along with system design.

Hybrid Power Management-Based Vehicle Architecture

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2011-01-01

Hybrid Power Management (HPM) is the integration of diverse, state-of-the-art power devices in an optimal configuration for space and terrestrial applications (s ee figure). The appropriate application and control of the various power devices significantly improves overall system performance and efficiency. The basic vehicle architecture consists of a primary power source, and possibly other power sources, that provides all power to a common energy storage system that is used to power the drive motors and vehicle accessory systems. This architecture also provides power as an emergency power system. Each component is independent, permitting it to be optimized for its intended purpose. The key element of HPM is the energy storage system. All generated power is sent to the energy storage system, and all loads derive their power from that system. This can significantly reduce the power requirement of the primary power source, while increasing the vehicle reliability. Ultracapacitors are ideal for an HPM-based energy storage system due to their exceptionally long cycle life, high reliability, high efficiency, high power density, and excellent low-temperature performance. Multiple power sources and multiple loads are easily incorporated into an HPM-based vehicle. A gas turbine is a good primary power source because of its high efficiency, high power density, long life, high reliability, and ability to operate on a wide range of fuels. An HPM controller maintains optimal control over each vehicle component. This flexible operating system can be applied to all vehicles to considerably improve vehicle efficiency, reliability, safety, security, and performance. The HPM-based vehicle architecture has many advantages over conventional vehicle architectures. Ultracapacitors have a much longer cycle life than batteries, which greatly improves system reliability, reduces life-of-system costs, and reduces environmental impact as ultracapacitors will probably never need to be replaced and disposed of. The environmentally safe ultracapacitor components reduce disposal concerns, and their recyclable nature reduces the environmental impact. High ultracapacitor power density provides high power during surges, and the ability to absorb high power during recharging. Ultracapacitors are extremely efficient in capturing recharging energy, are rugged, reliable, maintenance-free, have excellent lowtemperature characteristic, provide consistent performance over time, and promote safety as they can be left indefinitely in a safe, discharged state whereas batteries cannot.

Automated Portable Test System (APTS) - A performance envelope assessment tool

NASA Technical Reports Server (NTRS)

Kennedy, R. S.; Dunlap, W. P.; Jones, M. B.; Wilkes, R. L.; Bittner, A. C., Jr.

1985-01-01

The reliability and stability of microcomputer-based psychological tests are evaluated. The hardware, test programs, and system control of the Automated Portable Test System, which assesses human performance and subjective status, are described. Subjects were administered 11 pen-and-pencil and microcomputer-based tests for 10 sessions. The data reveal that nine of the 10 tests stabilized by the third administration; inertial correlations were high and consistent. It is noted that the microcomputer-based tests display good psychometric properties in terms of differential stability and reliability.

Reliability of a Test Battery Designed for Quickly and Safely Assessing Diverse Indices of Neuromuscular Function

NASA Technical Reports Server (NTRS)

Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason, R.; Buxton, Roxanne E.; Lawrence, Emily L.; Sinka, Joseph; Guilliams, Mark E.; Ploutz-Snyder, Lori L.; Bloomberg, Jacob J.

2010-01-01

Spaceflight affects nearly every physiological system. Spaceflight-induced alterations in physiological function translate to decrements in functional performance. Purpose: To develop a test battery for quickly and safely assessing diverse indices of neuromuscular performance. I. Quickly: Battery of tests can be completed in approx.30-40 min. II. Safely: a) No eccentric muscle actions or impact forces. b) Tests present little challenge to postural stability. III. Diverse indices: a) Strength: Excellent reliability (ICC = 0.99) b) Central activation: Very good reliability (ICC = 0.87) c) Power: Excellent reliability (ICC = 0.99) d) Endurance: Total work has excellent reliability (ICC = 0.99) e) Force steadiness: Poor reliability (ICC = 0.20 - 0.60) National

Space Vehicle Reliability Modeling in DIORAMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tornga, Shawn Robert

When modeling system performance of space based detection systems it is important to consider spacecraft reliability. As space vehicles age the components become prone to failure for a variety of reasons such as radiation damage. Additionally, some vehicles may lose the ability to maneuver once they exhaust fuel supplies. Typically failure is divided into two categories: engineering mistakes and technology surprise. This document will report on a method of simulating space vehicle reliability in the DIORAMA framework.

77 FR 53877 - Commission Information Collection Activities (FERC-715); Comment Request; Extension

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-04

...; A detailed description of the transmission planning reliability criteria used to evaluate system... reliability criteria are applied and the steps taken in performing transmission planning studies); and A... reliability criteria using its stated assessment practices. The FERC-715 enables the Commission to use the...

Thermocouples of tantalum and rhenium alloys for more stable vacuum-high temperature performance

NASA Technical Reports Server (NTRS)

Morris, J. F. (Inventor)

1977-01-01

Thermocouples of the present invention provide stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor wherein each metal of the sensor is selected from a group of metals comprising tantalum and rhenium and alloys containing only those two metals. The tantalum, rhenium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibilities and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys of the present invention result in improved emf, temperature properties and thermocouple hot junction performance. The thermocouples formed of the tantalum, rhenium alloys exhibit reliability and performance stability in systems involving high temperatures and vacuums and are adaptable to space propulsion and power systems and nuclear environments.

EFFECT OF LUBRICANT CONTAMINATION ON THE PERFORMANCE AND RELIABILITY OF HEAT PUMPS CHARGED WITH R-407C.

EPA Science Inventory

The report gives results of the development of new data that can be used to determine the effect of mineral oil contamination on the reliability of a heat pump system operating with a new hydrofluorocarbon mixture and polyol ester lubricant, to assess any performance degradation ...

A Passive System Reliability Analysis for a Station Blackout

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brunett, Acacia; Bucknor, Matthew; Grabaskas, David

2015-05-03

The latest iterations of advanced reactor designs have included increased reliance on passive safety systems to maintain plant integrity during unplanned sequences. While these systems are advantageous in reducing the reliance on human intervention and availability of power, the phenomenological foundations on which these systems are built require a novel approach to a reliability assessment. Passive systems possess the unique ability to fail functionally without failing physically, a result of their explicit dependency on existing boundary conditions that drive their operating mode and capacity. Argonne National Laboratory is performing ongoing analyses that demonstrate various methodologies for the characterization of passivemore » system reliability within a probabilistic framework. Two reliability analysis techniques are utilized in this work. The first approach, the Reliability Method for Passive Systems, provides a mechanistic technique employing deterministic models and conventional static event trees. The second approach, a simulation-based technique, utilizes discrete dynamic event trees to treat time- dependent phenomena during scenario evolution. For this demonstration analysis, both reliability assessment techniques are used to analyze an extended station blackout in a pool-type sodium fast reactor (SFR) coupled with a reactor cavity cooling system (RCCS). This work demonstrates the entire process of a passive system reliability analysis, including identification of important parameters and failure metrics, treatment of uncertainties and analysis of results.« less

Design-for-reliability (DfR) of aerospace electronics: Attributes and challenges

NASA Astrophysics Data System (ADS)

Bensoussan, A.; Suhir, E.

The next generation of multi-beam satellite systems that would be able to provide effective interactive communication services will have to operate within a highly flexible architecture. One option to develop such flexibility is to employ microwaves and/or optoelectronic components and to make them reliable. The use of optoelectronic devices, equipments and systems will result indeed in significant improvement in the state-of-the-art only provided that the new designs will suggest a novel and effective architecture that will combine the merits of good functional performance, satisfactory mechanical (structural) reliability and high cost effectiveness. The obvious challenge is the ability to design and fabricate equipment based on EEE components that would be able to successfully withstand harsh space environments for the entire duration of the mission. It is imperative that the major players in the space industry, such as manufacturers, industrial users, and space agencies, understand the importance and the limits of the achievable quality and reliability of optoelectronic devices operated in harsh environments. It is equally imperative that the physics of possible failures is well understood and, if necessary, minimized, and that adequate Quality Standards are developed and employed. The space community has to identify and to develop the strategic approach for validating optoelectronic products. This should be done with consideration of numerous intrinsic and extrinsic requirements for the systems' performance. When considering a particular next generation optoelectronic space system, the space community needs to address the following major issues: proof of concept for this system, proof of reliability and proof of performance. This should be done with taking into account the specifics of the anticipated application. High operational reliability cannot be left to the prognostics and health monitoring/management (PHM) effort and stage, no matter how important and - ffective such an effort might be. Reliability should be pursued at all the stages of the equipment lifetime: design, product development, manufacturing, burn-in testing and, of course, subsequent PHM after the space apparatus is launched and operated.

A Performance Appraisal System for School Principals.

ERIC Educational Resources Information Center

Knoop, Robert; Common, Ronald W.

The Performance Review, Analysis, and Improvement System for Educators (PRAISE) is a formative evaluation instrument designed to improve the performance of school principals. The system appears to be reliable and valid and is flexible enough to accommodate the needs of a variety of schools. Sample items and categories of the instrument include…

Estimation of reliable range of electron temperature measurements with sets of given optical bandpass filters for KSTAR Thomson scattering system based on synthetic Thomson data

NASA Astrophysics Data System (ADS)

Kim, K.-h.; Oh, T.-s.; Park, K.-r.; Lee, J. H.; Ghim, Y.-c.

2017-11-01

One factor determining the reliability of measurements of electron temperature using a Thomson scattering (TS) system is transmittance of the optical bandpass filters in polychromators. We investigate the system performance as a function of electron temperature to determine reliable range of measurements for a given set of the optical bandpass filters. We show that such a reliability, i.e., both bias and random errors, can be obtained by building a forward model of the KSTAR TS system to generate synthetic TS data with the prescribed electron temperature and density profiles. The prescribed profiles are compared with the estimated ones to quantify both bias and random errors.

Probabilistic Finite Element Analysis & Design Optimization for Structural Designs

NASA Astrophysics Data System (ADS)

Deivanayagam, Arumugam

This study focuses on implementing probabilistic nature of material properties (Kevlar® 49) to the existing deterministic finite element analysis (FEA) of fabric based engine containment system through Monte Carlo simulations (MCS) and implementation of probabilistic analysis in engineering designs through Reliability Based Design Optimization (RBDO). First, the emphasis is on experimental data analysis focusing on probabilistic distribution models which characterize the randomness associated with the experimental data. The material properties of Kevlar® 49 are modeled using experimental data analysis and implemented along with an existing spiral modeling scheme (SMS) and user defined constitutive model (UMAT) for fabric based engine containment simulations in LS-DYNA. MCS of the model are performed to observe the failure pattern and exit velocities of the models. Then the solutions are compared with NASA experimental tests and deterministic results. MCS with probabilistic material data give a good prospective on results rather than a single deterministic simulation results. The next part of research is to implement the probabilistic material properties in engineering designs. The main aim of structural design is to obtain optimal solutions. In any case, in a deterministic optimization problem even though the structures are cost effective, it becomes highly unreliable if the uncertainty that may be associated with the system (material properties, loading etc.) is not represented or considered in the solution process. Reliable and optimal solution can be obtained by performing reliability optimization along with the deterministic optimization, which is RBDO. In RBDO problem formulation, in addition to structural performance constraints, reliability constraints are also considered. This part of research starts with introduction to reliability analysis such as first order reliability analysis, second order reliability analysis followed by simulation technique that are performed to obtain probability of failure and reliability of structures. Next, decoupled RBDO procedure is proposed with a new reliability analysis formulation with sensitivity analysis, which is performed to remove the highly reliable constraints in the RBDO, thereby reducing the computational time and function evaluations. Followed by implementation of the reliability analysis concepts and RBDO in finite element 2D truss problems and a planar beam problem are presented and discussed.

Comprehensive Design Reliability Activities for Aerospace Propulsion Systems

NASA Technical Reports Server (NTRS)

Christenson, R. L.; Whitley, M. R.; Knight, K. C.

2000-01-01

This technical publication describes the methodology, model, software tool, input data, and analysis result that support aerospace design reliability studies. The focus of these activities is on propulsion systems mechanical design reliability. The goal of these activities is to support design from a reliability perspective. Paralleling performance analyses in schedule and method, this requires the proper use of metrics in a validated reliability model useful for design, sensitivity, and trade studies. Design reliability analysis in this view is one of several critical design functions. A design reliability method is detailed and two example analyses are provided-one qualitative and the other quantitative. The use of aerospace and commercial data sources for quantification is discussed and sources listed. A tool that was developed to support both types of analyses is presented. Finally, special topics discussed include the development of design criteria, issues of reliability quantification, quality control, and reliability verification.

Validity and Reliability of the 8-Item Work Limitations Questionnaire.

PubMed

Walker, Timothy J; Tullar, Jessica M; Diamond, Pamela M; Kohl, Harold W; Amick, Benjamin C

2017-12-01

Purpose To evaluate factorial validity, scale reliability, test-retest reliability, convergent validity, and discriminant validity of the 8-item Work Limitations Questionnaire (WLQ) among employees from a public university system. Methods A secondary analysis using de-identified data from employees who completed an annual Health Assessment between the years 2009-2015 tested research aims. Confirmatory factor analysis (CFA) (n = 10,165) tested the latent structure of the 8-item WLQ. Scale reliability was determined using a CFA-based approach while test-retest reliability was determined using the intraclass correlation coefficient. Convergent/discriminant validity was tested by evaluating relations between the 8-item WLQ with health/performance variables for convergent validity (health-related work performance, number of chronic conditions, and general health) and demographic variables for discriminant validity (gender and institution type). Results A 1-factor model with three correlated residuals demonstrated excellent model fit (CFI = 0.99, TLI = 0.99, RMSEA = 0.03, and SRMR = 0.01). The scale reliability was acceptable (0.69, 95% CI 0.68-0.70) and the test-retest reliability was very good (ICC = 0.78). Low-to-moderate associations were observed between the 8-item WLQ and the health/performance variables while weak associations were observed between the demographic variables. Conclusions The 8-item WLQ demonstrated sufficient reliability and validity among employees from a public university system. Results suggest the 8-item WLQ is a usable alternative for studies when the more comprehensive 25-item WLQ is not available.

Characterizing the reliability of a bioMEMS-based cantilever sensor

NASA Astrophysics Data System (ADS)

Bhalerao, Kaustubh D.

2004-12-01

The cantilever-based BioMEMS sensor represents one instance from many competing ideas of biosensor technology based on Micro Electro Mechanical Systems. The advancement of BioMEMS from laboratory-scale experiments to applications in the field will require standardization of their components and manufacturing procedures as well as frameworks to evaluate their performance. Reliability, the likelihood with which a system performs its intended task, is a compact mathematical description of its performance. The mathematical and statistical foundation of systems-reliability has been applied to the cantilever-based BioMEMS sensor. The sensor is designed to detect one aspect of human ovarian cancer, namely the over-expression of the folate receptor surface protein (FR-alpha). Even as the application chosen is clinically motivated, the objective of this study was to demonstrate the underlying systems-based methodology used to design, develop and evaluate the sensor. The framework development can be readily extended to other BioMEMS-based devices for disease detection and will have an impact in the rapidly growing $30 bn industry. The Unified Modeling Language (UML) is a systems-based framework for design and development of object-oriented information systems which has potential application for use in systems designed to interact with biological environments. The UML has been used to abstract and describe the application of the biosensor, to identify key components of the biosensor, and the technology needed to link them together in a coherent manner. The use of the framework is also demonstrated in computation of system reliability from first principles as a function of the structure and materials of the biosensor. The outcomes of applying the systems-based framework to the study are the following: (1) Characterizing the cantilever-based MEMS device for disease (cell) detection. (2) Development of a novel chemical interface between the analyte and the sensor that provides a degree of selectivity towards the disease. (3) Demonstrating the performance and measuring the reliability of the biosensor prototype, and (4) Identification of opportunities in technological development in order to further refine the proposed biosensor. Application of the methodology to design develop and evaluate the reliability of BioMEMS devices will be beneficial in the streamlining the growth of the BioMEMS industry, while providing a decision-support tool in comparing and adopting suitable technologies from available competing options.

Plastic packaged microcircuits: Quality, reliability, and cost issues

NASA Astrophysics Data System (ADS)

Pecht, Michael G.; Agarwal, Rakesh; Quearry, Dan

1993-12-01

Plastic encapsulated microcircuits (PEMs) find their main application in commercial and telecommunication electronics. The advantages of PEMs in cost, size, weight, performance, and market lead-time, have attracted 97% of the market share of worldwide microcircuit sales. However, PEMs have always been resisted in US Government and military applications due to the perception that PEM reliability is low. This paper surveys plastic packaging with respect to the issues of reliability, market lead-time, performance, cost, and weight as a means to guide part-selection and system-design.

Reliability of an x-ray system for calibrating and testing personal radiation dosimeters

NASA Astrophysics Data System (ADS)

Guimarães, M. C.; Silva, C. R. E.; Rosado, P. H. G.; Cunha, P. G.; Da Silva, T. A.

2018-03-01

Metrology laboratories are expected to maintain standardized radiation beams and traceable standard dosimeters to provide reliable calibrations or testing of detectors. Results of the characterization of an x-ray system for performing calibration and testing of radiation dosimeters used for individual monitoring are shown in this work.

Time-dependent Reliability of Dynamic Systems using Subset Simulation with Splitting over a Series of Correlated Time Intervals

DTIC Science & Technology

2013-08-01

cost due to potential warranty costs, repairs and loss of market share. Reliability is the probability that the system will perform its intended...MCMC and splitting sampling schemes. Our proposed SS/ STP method is presented in Section 4, including accuracy bounds and computational effort

A classification system for characterization of physical and non-physical work factors.

PubMed

Genaidy, A; Karwowski, W; Succop, P; Kwon, Y G; Alhemoud, A; Goyal, D

2000-01-01

A comprehensive evaluation of work-related performance factors is a prerequisite to developing integrated and long-term solutions to workplace performance improvement. This paper describes a work-factor classification system that categorizes the entire domain of workplace factors impacting performance. A questionnaire-based instrument was developed to implement this classification system in industry. Fifty jobs were evaluated in 4 different service and manufacturing companies using the proposed questionnaire-based instrument. The reliability coefficients obtained from the analyzed jobs were considered good (0.589 to 0.862). In general, the physical work factors resulted in higher reliability coefficients (0.847 to 0.862) than non-physical work factors (0.589 to 0.768).

Reliability and Validity of Finger Strength and Endurance Measurements in Rock Climbing

ERIC Educational Resources Information Center

Michailov, Michail Lubomirov; Baláš, Jirí; Tanev, Stoyan Kolev; Andonov, Hristo Stoyanov; Kodejška, Jan; Brown, Lee

2018-01-01

Purpose: An advanced system for the assessment of climbing-specific performance was developed and used to: (a) investigate the effect of arm fixation (AF) on construct validity evidence and reliability of climbing-specific finger-strength measurement; (b) assess reliability of finger-strength and endurance measurements; and (c) evaluate the…

Reliability Block Diagram (RBD) Analysis of NASA Dryden Flight Research Center (DFRC) Flight Termination System and Power Supply

NASA Technical Reports Server (NTRS)

Morehouse, Dennis V.

2006-01-01

In order to perform public risk analyses for vehicles containing Flight Termination Systems (FTS), it is necessary for the analyst to know the reliability of each of the components of the FTS. These systems are typically divided into two segments; a transmitter system and associated equipment, typically in a ground station or on a support aircraft, and a receiver system and associated equipment on the target vehicle. This analysis attempts to analyze the reliability of the NASA DFRC flight termination system ground transmitter segment for use in the larger risk analysis and to compare the results against two established Department of Defense availability standards for such equipment.

Development of a low risk augmentation system for an energy efficient transport having relaxed static stability

NASA Technical Reports Server (NTRS)

Sizlo, T. R.; Berg, R. A.; Gilles, D. L.

1979-01-01

An augmentation system for a 230 passenger, twin engine aircraft designed with a relaxation of conventional longitudinal static stability was developed. The design criteria are established and candidate augmentation system control laws and hardware architectures are formulated and evaluated with respect to reliability, flying qualities, and flight path tracking performance. The selected systems are shown to satisfy the interpreted regulatory safety and reliability requirements while maintaining the present DC 10 (study baseline) level of maintainability and reliability for the total flight control system. The impact of certification of the relaxed static stability augmentation concept is also estimated with regard to affected federal regulations, system validation plan, and typical development/installation costs.

Advanced Reactor PSA Methodologies for System Reliability Analysis and Source Term Assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grabaskas, D.; Brunett, A.; Passerini, S.

Beginning in 2015, a project was initiated to update and modernize the probabilistic safety assessment (PSA) of the GE-Hitachi PRISM sodium fast reactor. This project is a collaboration between GE-Hitachi and Argonne National Laboratory (Argonne), and funded in part by the U.S. Department of Energy. Specifically, the role of Argonne is to assess the reliability of passive safety systems, complete a mechanistic source term calculation, and provide component reliability estimates. The assessment of passive system reliability focused on the performance of the Reactor Vessel Auxiliary Cooling System (RVACS) and the inherent reactivity feedback mechanisms of the metal fuel core. Themore » mechanistic source term assessment attempted to provide a sequence specific source term evaluation to quantify offsite consequences. Lastly, the reliability assessment focused on components specific to the sodium fast reactor, including electromagnetic pumps, intermediate heat exchangers, the steam generator, and sodium valves and piping.« less

Integrating reliability and maintainability into a concurrent engineering environment

NASA Astrophysics Data System (ADS)

Phillips, Clifton B.; Peterson, Robert R.

1993-02-01

This paper describes the results of a reliability and maintainability study conducted at the University of California, San Diego and supported by private industry. Private industry thought the study was important and provided the university access to innovative tools under cooperative agreement. The current capability of reliability and maintainability tools and how they fit into the design process is investigated. The evolution of design methodologies leading up to today's capability is reviewed for ways to enhance the design process while keeping cost under control. A method for measuring the consequences of reliability and maintainability policy for design configurations in an electronic environment is provided. The interaction of selected modern computer tool sets is described for reliability, maintainability, operations, and other elements of the engineering design process. These tools provide a robust system evaluation capability that brings life cycle performance improvement information to engineers and their managers before systems are deployed, and allow them to monitor and track performance while it is in operation.

Sensor Systems for Prognostics and Health Management

PubMed Central

Cheng, Shunfeng; Azarian, Michael H.; Pecht, Michael G.

2010-01-01

Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM to monitor environmental, operational, and performance-related characteristics. The gathered data can be analyzed to assess product health and predict remaining life. In this paper, the considerations for sensor system selection for PHM applications, including the parameters to be measured, the performance needs, the electrical and physical attributes, reliability, and cost of the sensor system, are discussed. The state-of-the-art sensor systems for PHM and the emerging trends in technologies of sensor systems for PHM are presented. PMID:22219686

Sensor systems for prognostics and health management.

PubMed

Cheng, Shunfeng; Azarian, Michael H; Pecht, Michael G

2010-01-01

Prognostics and health management (PHM) is an enabling discipline consisting of technologies and methods to assess the reliability of a product in its actual life cycle conditions to determine the advent of failure and mitigate system risk. Sensor systems are needed for PHM to monitor environmental, operational, and performance-related characteristics. The gathered data can be analyzed to assess product health and predict remaining life. In this paper, the considerations for sensor system selection for PHM applications, including the parameters to be measured, the performance needs, the electrical and physical attributes, reliability, and cost of the sensor system, are discussed. The state-of-the-art sensor systems for PHM and the emerging trends in technologies of sensor systems for PHM are presented.

Protocol and Demonstrations of Probabilistic Reliability Assessment for Structural Health Monitoring Systems (Preprint)

DTIC Science & Technology

2011-11-01

assessment to quality of localization/characterization estimates. This protocol includes four critical components: (1) a procedure to identify the...critical factors impacting SHM system performance; (2) a multistage or hierarchical approach to SHM system validation; (3) a model -assisted evaluation...Lindgren, E. A ., Buynak, C. F., Steffes, G., Derriso, M., “ Model -assisted Probabilistic Reliability Assessment for Structural Health Monitoring

Performance and reliability enhancement of linear coolers

NASA Astrophysics Data System (ADS)

Mai, M.; Rühlich, I.; Schreiter, A.; Zehner, S.

2010-04-01

Highest efficiency states a crucial requirement for modern tactical IR cryocooling systems. For enhancement of overall efficiency, AIM cryocooler designs where reassessed considering all relevant loss mechanisms and associated components. Performed investigation was based on state-of-the-art simulation software featuring magnet circuitry analysis as well as computational fluid dynamics (CFD) to realistically replicate thermodynamic interactions. As a result, an improved design for AIM linear coolers could be derived. This paper gives an overview on performance enhancement activities and major results. An additional key-requirement for cryocoolers is reliability. In recent time, AIM has introduced linear coolers with full Flexure Bearing suspension on both ends of the driving mechanism incorporating Moving Magnet piston drive. In conjunction with a Pulse-Tube coldfinger these coolers are capable of meeting MTTF's (Mean Time To Failure) in excess of 50,000 hours offering superior reliability for space applications. Ongoing development also focuses on reliability enhancement, deriving space technology into tactical solutions combining both, excelling specific performance with space like reliability. Concerned publication will summarize the progress of this reliability program and give further prospect.

Intelligent pump test system based on virtual instrument

NASA Astrophysics Data System (ADS)

Ma, Jungong; Wang, Shifu; Wang, Zhanlin

2003-09-01

The intelligent pump system is the key component of the aircraft hydraulic system that can solve the problem, such as the temperature sharply increasing. As the performance of the intelligent pump directly determines that of the aircraft hydraulic system and seriously affects fly security and reliability. So it is important to test all kinds of performance parameters of intelligent pump during design and development, while the advanced, reliable and complete test equipments are the necessary instruments for achieving the goal. In this paper, the application of virtual instrument and computer network technology in aircraft intelligent pump test is presented. The composition of the hardware, software, hydraulic circuit in this system are designed and implemented.

Highlights of recent balance of system research and evaluation

NASA Astrophysics Data System (ADS)

Thomas, M. G.; Stevens, J. W.

The cost of most photovoltaic (PV) systems is more a function of the balance of system (BOS) components than the collectors. The exception to this rule is the grid-tied system whose cost is related more directly to the collectors, and secondarily to the inverter/controls. In fact, recent procurements throughout the country document that collector costs for roof-mounted, utility-tied systems (Russell, PV Systems Workshop, 7/94) represent 60% to 70% of the system cost. This contrasts with the current market for packaged stand-alone all PV or PV-hybrid systems where collectors represent only 25% to 35% of the total. Not only are the BOS components the cost drivers in the current cost-effective PV system market place, they are also the least reliable components. This paper discusses the impact that BOS issues have on component performance, system performance, and system cost and reliability. We will also look at recent recommended changes in system design based upon performance evaluations of fielded PV systems.

MEASUREMENT: ACCOUNTING FOR RELIABILITY IN PERFORMANCE ESTIMATES.

PubMed

Waterman, Brian; Sutter, Robert; Burroughs, Thomas; Dunagan, W Claiborne

2014-01-01

When evaluating physician performance measures, physician leaders are faced with the quandary of determining whether departures from expected physician performance measurements represent a true signal or random error. This uncertainty impedes the physician leader's ability and confidence to take appropriate performance improvement actions based on physician performance measurements. Incorporating reliability adjustment into physician performance measurement is a valuable way of reducing the impact of random error in the measurements, such as those caused by small sample sizes. Consequently, the physician executive has more confidence that the results represent true performance and is positioned to make better physician performance improvement decisions. Applying reliability adjustment to physician-level performance data is relatively new. As others have noted previously, it's important to keep in mind that reliability adjustment adds significant complexity to the production, interpretation and utilization of results. Furthermore, the methods explored in this case study only scratch the surface of the range of available Bayesian methods that can be used for reliability adjustment; further study is needed to test and compare these methods in practice and to examine important extensions for handling specialty-specific concerns (e.g., average case volumes, which have been shown to be important in cardiac surgery outcomes). Moreover, it's important to note that the provider group average as a basis for shrinkage is one of several possible choices that could be employed in practice and deserves further exploration in future research. With these caveats, our results demonstrate that incorporating reliability adjustment into physician performance measurements is feasible and can notably reduce the incidence of "real" signals relative to what one would expect to see using more traditional approaches. A physician leader who is interested in catalyzing performance improvement through focused, effective physician performance improvement is well advised to consider the value of incorporating reliability adjustments into their performance measurement system.

Model-centric distribution automation: Capacity, reliability, and efficiency

DOE PAGES

Onen, Ahmet; Jung, Jaesung; Dilek, Murat; ...

2016-02-26

A series of analyses along with field validations that evaluate efficiency, reliability, and capacity improvements of model-centric distribution automation are presented. With model-centric distribution automation, the same model is used from design to real-time control calculations. A 14-feeder system with 7 substations is considered. The analyses involve hourly time-varying loads and annual load growth factors. Phase balancing and capacitor redesign modifications are used to better prepare the system for distribution automation, where the designs are performed considering time-varying loads. Coordinated control of load tap changing transformers, line regulators, and switched capacitor banks is considered. In evaluating distribution automation versus traditionalmore » system design and operation, quasi-steady-state power flow analysis is used. In evaluating distribution automation performance for substation transformer failures, reconfiguration for restoration analysis is performed. In evaluating distribution automation for storm conditions, Monte Carlo simulations coupled with reconfiguration for restoration calculations are used. As a result, the evaluations demonstrate that model-centric distribution automation has positive effects on system efficiency, capacity, and reliability.« less

Model-centric distribution automation: Capacity, reliability, and efficiency

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onen, Ahmet; Jung, Jaesung; Dilek, Murat

A series of analyses along with field validations that evaluate efficiency, reliability, and capacity improvements of model-centric distribution automation are presented. With model-centric distribution automation, the same model is used from design to real-time control calculations. A 14-feeder system with 7 substations is considered. The analyses involve hourly time-varying loads and annual load growth factors. Phase balancing and capacitor redesign modifications are used to better prepare the system for distribution automation, where the designs are performed considering time-varying loads. Coordinated control of load tap changing transformers, line regulators, and switched capacitor banks is considered. In evaluating distribution automation versus traditionalmore » system design and operation, quasi-steady-state power flow analysis is used. In evaluating distribution automation performance for substation transformer failures, reconfiguration for restoration analysis is performed. In evaluating distribution automation for storm conditions, Monte Carlo simulations coupled with reconfiguration for restoration calculations are used. As a result, the evaluations demonstrate that model-centric distribution automation has positive effects on system efficiency, capacity, and reliability.« less

Reliability of System Identification Techniques to Assess Standing Balance in Healthy Elderly

PubMed Central

Maier, Andrea B.; Aarts, Ronald G. K. M.; van Gerven, Joop M. A.; Arendzen, J. Hans; Schouten, Alfred C.; Meskers, Carel G. M.; van der Kooij, Herman

2016-01-01

Objectives System identification techniques have the potential to assess the contribution of the underlying systems involved in standing balance by applying well-known disturbances. We investigated the reliability of standing balance parameters obtained with multivariate closed loop system identification techniques. Methods In twelve healthy elderly balance tests were performed twice a day during three days. Body sway was measured during two minutes of standing with eyes closed and the Balance test Room (BalRoom) was used to apply four disturbances simultaneously: two sensory disturbances, to the proprioceptive and the visual system, and two mechanical disturbances applied at the leg and trunk segment. Using system identification techniques, sensitivity functions of the sensory disturbances and the neuromuscular controller were estimated. Based on the generalizability theory (G theory), systematic errors and sources of variability were assessed using linear mixed models and reliability was assessed by computing indexes of dependability (ID), standard error of measurement (SEM) and minimal detectable change (MDC). Results A systematic error was found between the first and second trial in the sensitivity functions. No systematic error was found in the neuromuscular controller and body sway. The reliability of 15 of 25 parameters and body sway were moderate to excellent when the results of two trials on three days were averaged. To reach an excellent reliability on one day in 7 out of 25 parameters, it was predicted that at least seven trials must be averaged. Conclusion This study shows that system identification techniques are a promising method to assess the underlying systems involved in standing balance in elderly. However, most of the parameters do not appear to be reliable unless a large number of trials are collected across multiple days. To reach an excellent reliability in one third of the parameters, a training session for participants is needed and at least seven trials of two minutes must be performed on one day. PMID:26953694

A novel optimal configuration form redundant MEMS inertial sensors based on the orthogonal rotation method.

PubMed

Cheng, Jianhua; Dong, Jinlu; Landry, Rene; Chen, Daidai

2014-07-29

In order to improve the accuracy and reliability of micro-electro mechanical systems (MEMS) navigation systems, an orthogonal rotation method-based nine-gyro redundant MEMS configuration is presented. By analyzing the accuracy and reliability characteristics of an inertial navigation system (INS), criteria for redundant configuration design are introduced. Then the orthogonal rotation configuration is formed through a two-rotation of a set of orthogonal inertial sensors around a space vector. A feasible installation method is given for the real engineering realization of this proposed configuration. The performances of the novel configuration and another six configurations are comprehensively compared and analyzed. Simulation and experimentation are also conducted, and the results show that the orthogonal rotation configuration has the best reliability, accuracy and fault detection and isolation (FDI) performance when the number of gyros is nine.

Markov reward processes

NASA Technical Reports Server (NTRS)

Smith, R. M.

1991-01-01

Numerous applications in the area of computer system analysis can be effectively studied with Markov reward models. These models describe the behavior of the system with a continuous-time Markov chain, where a reward rate is associated with each state. In a reliability/availability model, upstates may have reward rate 1 and down states may have reward rate zero associated with them. In a queueing model, the number of jobs of certain type in a given state may be the reward rate attached to that state. In a combined model of performance and reliability, the reward rate of a state may be the computational capacity, or a related performance measure. Expected steady-state reward rate and expected instantaneous reward rate are clearly useful measures of the Markov reward model. More generally, the distribution of accumulated reward or time-averaged reward over a finite time interval may be determined from the solution of the Markov reward model. This information is of great practical significance in situations where the workload can be well characterized (deterministically, or by continuous functions e.g., distributions). The design process in the development of a computer system is an expensive and long term endeavor. For aerospace applications the reliability of the computer system is essential, as is the ability to complete critical workloads in a well defined real time interval. Consequently, effective modeling of such systems must take into account both performance and reliability. This fact motivates our use of Markov reward models to aid in the development and evaluation of fault tolerant computer systems.

Observer reliability of the Gross Motor Performance Measure and the Quality of Upper Extremity Skills Test, based on video recordings.

PubMed

Sorsdahl, Anne Brit; Moe-Nilssen, Rolf; Strand, Liv Inger

2008-02-01

The aim of this study was to examine observer reliability of the Gross Motor Performance Measure (GMPM) and the Quality of Upper Extremity Skills Test (QUEST) based on video clips. The tests were administered to 26 children with cerebral palsy (CP; 14 males, 12 females; range 2-13y, mean 7y 6mo), 24 with spastic CP, and two with dyskinesia. Respectively, five, six, five, four, and six children were classified in Gross Motor Function Classification System Levels I to V; and four, nine, five, five, and three children were classified in Manual Ability Classification System levels I to V. The children's performances were recorded and edited. Two experienced paediatric physical therapists assessed the children from watching the video clips. Intraobserver and interobserver reliability values of the total scores were mostly high, intraclass correlation coefficient (ICC)(1,1) varying from 0.69 to 0.97 with only one coefficient below 0.89. The ICCs of subscores varied from 0.36 to 0.95, finding'Alignment'and'Weight shift'in GMPM and'Protective extension'in QUEST highly reliable. The subscores'Dissociated movements'in GMPM and QUEST, and'Grasp'in QUEST were the least reliable, and recommendations are made to increase reliability of these subscores. Video scoring was time consuming, but was found to offer many advantages; the possibility to review performance, to use special trained observers for scoring and less demanding assessment for the children.

Photovoltaic-Powered Vaccine Refrigerator: Freezer Systems Field Test Results

NASA Technical Reports Server (NTRS)

Ratajczak, A. F.

1985-01-01

A project to develop and field test photovoltaic-powered refrigerator/freezers suitable for vaccine storage was undertaken. Three refrigerator/freezers were qualified; one by Solar Power Corp. and two by Solvolt. Follow-on contracts were awarded for 19 field test systems and for 10 field test systems. A total of 29 systems were installed in 24 countries between October 1981 and October 1984. The project, systems descriptions, installation experiences, performance data for the 22 systems for which field test data was reported, an operational reliability summary, and recommendations relative to system designs and future use of such systems are explained. Performance data indicate that the systems are highly reliable and are capable of maintaining proper vaccine storage temperatures in a wide range of climatological and user environments.

Summary of NASA Aerospace Flight Battery Systems Program activities

NASA Technical Reports Server (NTRS)

Manzo, Michelle; Odonnell, Patricia

1994-01-01

A summary of NASA Aerospace Flight Battery Systems Program Activities is presented. The NASA Aerospace Flight Battery Systems Program represents a unified NASA wide effort with the overall objective of providing NASA with the policy and posture which will increase the safety, performance, and reliability of space power systems. The specific objectives of the program are to: enhance cell/battery safety and reliability; maintain current battery technology; increase fundamental understanding of primary and secondary cells; provide a means to bring forth advanced technology for flight use; assist flight programs in minimizing battery technology related flight risks; and ensure that safe, reliable batteries are available for NASA's future missions.

Development of system reliability models for railway bridges.

DOT National Transportation Integrated Search

2012-07-01

Performance of the railway transportation network depends on the reliability of railway bridges, which can be affected by : various forms of deterioration and extreme environmental conditions. More than half of the railway bridges in US were : built ...

Numerical simulation of the cavitation characteristics of a mixed-flow pump

NASA Astrophysics Data System (ADS)

Chen, T.; Li, S. R.; Li, W. Z.; Liu, Y. L.; Wu, D. Z.; Wang, L. Q.

2013-12-01

As a kind of general equipment for fluid transportation, pumps were widely used in industry which includes many applications of high pressure, temperature and toxic fluids transportations. Performances of pumps affect the safety and reliability of the whole special equipment system. Cavitation in pumps cause the loss of performance and erosion of the blade, which could affect the running stability and reliability of the pump system. In this paper, a kind of numerical method for cavitaion performance prediction was presented. In order to investigate the accuracy of the method, CFD flow analysis and cavitation performance predictions of a mixed-flow pump were carried out. The numerical results were compared with the test results.

Optimizing preventive maintenance policy: A data-driven application for a light rail braking system.

PubMed

Corman, Francesco; Kraijema, Sander; Godjevac, Milinko; Lodewijks, Gabriel

2017-10-01

This article presents a case study determining the optimal preventive maintenance policy for a light rail rolling stock system in terms of reliability, availability, and maintenance costs. The maintenance policy defines one of the three predefined preventive maintenance actions at fixed time-based intervals for each of the subsystems of the braking system. Based on work, maintenance, and failure data, we model the reliability degradation of the system and its subsystems under the current maintenance policy by a Weibull distribution. We then analytically determine the relation between reliability, availability, and maintenance costs. We validate the model against recorded reliability and availability and get further insights by a dedicated sensitivity analysis. The model is then used in a sequential optimization framework determining preventive maintenance intervals to improve on the key performance indicators. We show the potential of data-driven modelling to determine optimal maintenance policy: same system availability and reliability can be achieved with 30% maintenance cost reduction, by prolonging the intervals and re-grouping maintenance actions.

Optimizing preventive maintenance policy: A data-driven application for a light rail braking system

PubMed Central

Corman, Francesco; Kraijema, Sander; Godjevac, Milinko; Lodewijks, Gabriel

2017-01-01

This article presents a case study determining the optimal preventive maintenance policy for a light rail rolling stock system in terms of reliability, availability, and maintenance costs. The maintenance policy defines one of the three predefined preventive maintenance actions at fixed time-based intervals for each of the subsystems of the braking system. Based on work, maintenance, and failure data, we model the reliability degradation of the system and its subsystems under the current maintenance policy by a Weibull distribution. We then analytically determine the relation between reliability, availability, and maintenance costs. We validate the model against recorded reliability and availability and get further insights by a dedicated sensitivity analysis. The model is then used in a sequential optimization framework determining preventive maintenance intervals to improve on the key performance indicators. We show the potential of data-driven modelling to determine optimal maintenance policy: same system availability and reliability can be achieved with 30% maintenance cost reduction, by prolonging the intervals and re-grouping maintenance actions. PMID:29278245

Agent autonomy approach to probabilistic physics-of-failure modeling of complex dynamic systems with interacting failure mechanisms

NASA Astrophysics Data System (ADS)

Gromek, Katherine Emily

A novel computational and inference framework of the physics-of-failure (PoF) reliability modeling for complex dynamic systems has been established in this research. The PoF-based reliability models are used to perform a real time simulation of system failure processes, so that the system level reliability modeling would constitute inferences from checking the status of component level reliability at any given time. The "agent autonomy" concept is applied as a solution method for the system-level probabilistic PoF-based (i.e. PPoF-based) modeling. This concept originated from artificial intelligence (AI) as a leading intelligent computational inference in modeling of multi agents systems (MAS). The concept of agent autonomy in the context of reliability modeling was first proposed by M. Azarkhail [1], where a fundamentally new idea of system representation by autonomous intelligent agents for the purpose of reliability modeling was introduced. Contribution of the current work lies in the further development of the agent anatomy concept, particularly the refined agent classification within the scope of the PoF-based system reliability modeling, new approaches to the learning and the autonomy properties of the intelligent agents, and modeling interacting failure mechanisms within the dynamic engineering system. The autonomous property of intelligent agents is defined as agent's ability to self-activate, deactivate or completely redefine their role in the analysis. This property of agents and the ability to model interacting failure mechanisms of the system elements makes the agent autonomy fundamentally different from all existing methods of probabilistic PoF-based reliability modeling. 1. Azarkhail, M., "Agent Autonomy Approach to Physics-Based Reliability Modeling of Structures and Mechanical Systems", PhD thesis, University of Maryland, College Park, 2007.

Evaluating the Performance of the IEEE Standard 1366 Method for Identifying Major Event Days

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eto, Joseph H.; LaCommare, Kristina Hamachi; Sohn, Michael D.

IEEE Standard 1366 offers a method for segmenting reliability performance data to isolate the effects of major events from the underlying year-to-year trends in reliability. Recent analysis by the IEEE Distribution Reliability Working Group (DRWG) has found that reliability performance of some utilities differs from the expectations that helped guide the development of the Standard 1366 method. This paper proposes quantitative metrics to evaluate the performance of the Standard 1366 method in identifying major events and in reducing year-to-year variability in utility reliability. The metrics are applied to a large sample of utility-reported reliability data to assess performance of themore » method with alternative specifications that have been considered by the DRWG. We find that none of the alternatives perform uniformly 'better' than the current Standard 1366 method. That is, none of the modifications uniformly lowers the year-to-year variability in System Average Interruption Duration Index without major events. Instead, for any given alternative, while it may lower the value of this metric for some utilities, it also increases it for other utilities (sometimes dramatically). Thus, we illustrate some of the trade-offs that must be considered in using the Standard 1366 method and highlight the usefulness of the metrics we have proposed in conducting these evaluations.« less

Development of custom measurement system for biomechanical evaluation of independent wheelchair transfers.

PubMed

Koontz, Alicia M; Lin, Yen-Sheng; Kankipati, Padmaja; Boninger, Michael L; Cooper, Rory A

2011-01-01

This study describes a new custom measurement system designed to investigate the biomechanics of sitting-pivot wheelchair transfers and assesses the reliability of selected biomechanical variables. Variables assessed include horizontal and vertical reaction forces underneath both hands and three-dimensional trunk, shoulder, and elbow range of motion. We examined the reliability of these measures between 5 consecutive transfer trials for 5 subjects with spinal cord injury and 12 nondisabled subjects while they performed a self-selected sitting pivot transfer from a wheelchair to a level bench. A majority of the biomechanical variables demonstrated moderate to excellent reliability (r > 0.6). The transfer measurement system recorded reliable and valid biomechanical data for future studies of sitting-pivot wheelchair transfers.We recommend a minimum of five transfer trials to obtain a reliable measure of transfer technique for future studies.

Reliability assessment of serviceability performance of braced retaining walls using a neural network approach

NASA Astrophysics Data System (ADS)

Goh, A. T. C.; Kulhawy, F. H.

2005-05-01

In urban environments, one major concern with deep excavations in soft clay is the potentially large ground deformations in and around the excavation. Excessive movements can damage adjacent buildings and utilities. There are many uncertainties associated with the calculation of the ultimate or serviceability performance of a braced excavation system. These include the variabilities of the loadings, geotechnical soil properties, and engineering and geometrical properties of the wall. A risk-based approach to serviceability performance failure is necessary to incorporate systematically the uncertainties associated with the various design parameters. This paper demonstrates the use of an integrated neural network-reliability method to assess the risk of serviceability failure through the calculation of the reliability index. By first performing a series of parametric studies using the finite element method and then approximating the non-linear limit state surface (the boundary separating the safe and failure domains) through a neural network model, the reliability index can be determined with the aid of a spreadsheet. Two illustrative examples are presented to show how the serviceability performance for braced excavation problems can be assessed using the reliability index.

Renewal of the Control System and Reliable Long Term Operation of the LHD Cryogenic System

NASA Astrophysics Data System (ADS)

Mito, T.; Iwamoto, A.; Oba, K.; Takami, S.; Moriuchi, S.; Imagawa, S.; Takahata, K.; Yamada, S.; Yanagi, N.; Hamaguchi, S.; Kishida, F.; Nakashima, T.

The Large Helical Device (LHD) is a heliotron-type fusion plasma experimental machine which consists of a fully superconducting magnet system cooled by a helium refrigerator having a total equivalent cooling capacity of 9.2 kW@4.4 K. Seventeenplasma experimental campaigns have been performed successfully since1997 with high reliability of 99%. However, sixteen years have passed from the beginning of the system operation. Improvements are being implementedto prevent serious failures and to pursue further reliability.The LHD cryogenic control system was designed and developed as an open system utilizing latest control equipment of VME controllers and UNIX workstations at the construction time. Howeverthe generation change of control equipment has been advanced. Down-sizing of control deviceshas beenplanned from VME controllers to compact PCI controllers in order to simplify the system configuration and to improve the system reliability. The new system is composed of compact PCI controller and remote I/O connected with EtherNet/IP. Making the system redundant becomes possible by doubling CPU, LAN, and remote I/O respectively. The smooth renewal of the LHD cryogenic controlsystem and the further improvement of the cryogenic system reliability are reported.

Automatic documentation system extension to multi-manufacturers' computers and to measure, improve, and predict software reliability

NASA Technical Reports Server (NTRS)

Simmons, D. B.

1975-01-01

The DOMONIC system has been modified to run on the Univac 1108 and the CDC 6600 as well as the IBM 370 computer system. The DOMONIC monitor system has been implemented to gather data which can be used to optimize the DOMONIC system and to predict the reliability of software developed using DOMONIC. The areas of quality metrics, error characterization, program complexity, program testing, validation and verification are analyzed. A software reliability model for estimating program completion levels and one on which to base system acceptance have been developed. The DAVE system which performs flow analysis and error detection has been converted from the University of Colorado CDC 6400/6600 computer to the IBM 360/370 computer system for use with the DOMONIC system.

The Reliability of Classification Decisions for the Furtado-Gallagher Computerized Observational Movement Pattern Assessment System--FG-COMPASS

ERIC Educational Resources Information Center

Furtado, Ovande, Jr.; Gallagher, Jere D.

2012-01-01

Mastery of fundamental movement skills (FMS) is an important factor in preventing weight gain and increasing physical activity. To master FMS, performance evaluation is necessary. In this study, we investigated the reliability of a new observational assessment tool. In Phase I, 110 video clips of children performing five locomotor, and six…

Three phase power conversion system for utility interconnected PV applications

NASA Astrophysics Data System (ADS)

Porter, David G.

1999-03-01

Omnion Power Engineering Corporation has developed a new three phase inverter that improves the cost, reliability, and performance of three phase utility interconnected photovoltaic inverters. The inverter uses a new, high manufacturing volume IGBT bridge that has better thermal performance than previous designs. A custom easily manufactured enclosure was designed. Controls were simplified to increase reliability while maintaining important user features.

Probabilistic assessment of dynamic system performance. Part 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belhadj, Mohamed

1993-01-01

Accurate prediction of dynamic system failure behavior can be important for the reliability and risk analyses of nuclear power plants, as well as for their backfitting to satisfy given constraints on overall system reliability, or optimization of system performance. Global analysis of dynamic systems through investigating the variations in the structure of the attractors of the system and the domains of attraction of these attractors as a function of the system parameters is also important for nuclear technology in order to understand the fault-tolerance as well as the safety margins of the system under consideration and to insure a safemore » operation of nuclear reactors. Such a global analysis would be particularly relevant to future reactors with inherent or passive safety features that are expected to rely on natural phenomena rather than active components to achieve and maintain safe shutdown. Conventionally, failure and global analysis of dynamic systems necessitate the utilization of different methodologies which have computational limitations on the system size that can be handled. Using a Chapman-Kolmogorov interpretation of system dynamics, a theoretical basis is developed that unifies these methodologies as special cases and which can be used for a comprehensive safety and reliability analysis of dynamic systems.« less

The reliability-quality relationship for quality systems and quality risk management.

PubMed

Claycamp, H Gregg; Rahaman, Faiad; Urban, Jason M

2012-01-01

Engineering reliability typically refers to the probability that a system, or any of its components, will perform a required function for a stated period of time and under specified operating conditions. As such, reliability is inextricably linked with time-dependent quality concepts, such as maintaining a state of control and predicting the chances of losses from failures for quality risk management. Two popular current good manufacturing practice (cGMP) and quality risk management tools, failure mode and effects analysis (FMEA) and root cause analysis (RCA) are examples of engineering reliability evaluations that link reliability with quality and risk. Current concepts in pharmaceutical quality and quality management systems call for more predictive systems for maintaining quality; yet, the current pharmaceutical manufacturing literature and guidelines are curiously silent on engineering quality. This commentary discusses the meaning of engineering reliability while linking the concept to quality systems and quality risk management. The essay also discusses the difference between engineering reliability and statistical (assay) reliability. The assurance of quality in a pharmaceutical product is no longer measured only "after the fact" of manufacturing. Rather, concepts of quality systems and quality risk management call for designing quality assurance into all stages of the pharmaceutical product life cycle. Interestingly, most assays for quality are essentially static and inform product quality over the life cycle only by being repeated over time. Engineering process reliability is the fundamental concept that is meant to anticipate quality failures over the life cycle of the product. Reliability is a well-developed theory and practice for other types of manufactured products and manufacturing processes. Thus, it is well known to be an appropriate index of manufactured product quality. This essay discusses the meaning of reliability and its linkages with quality systems and quality risk management.

Development of a nanosatellite de-orbiting system by reliability based design optimization

NASA Astrophysics Data System (ADS)

Nikbay, Melike; Acar, Pınar; Aslan, Alim Rüstem

2015-12-01

This paper presents design approaches to develop a reliable and efficient de-orbiting system for the 3USAT nanosatellite to provide a beneficial orbital decay process at the end of a mission. A de-orbiting system is initially designed by employing the aerodynamic drag augmentation principle where the structural constraints of the overall satellite system and the aerodynamic forces are taken into account. Next, an alternative de-orbiting system is designed with new considerations and further optimized using deterministic and reliability based design techniques. For the multi-objective design, the objectives are chosen to maximize the aerodynamic drag force through the maximization of the Kapton surface area while minimizing the de-orbiting system mass. The constraints are related in a deterministic manner to the required deployment force, the height of the solar panel hole and the deployment angle. The length and the number of layers of the deployable Kapton structure are used as optimization variables. In the second stage of this study, uncertainties related to both manufacturing and operating conditions of the deployable structure in space environment are considered. These uncertainties are then incorporated into the design process by using different probabilistic approaches such as Monte Carlo Simulation, the First-Order Reliability Method and the Second-Order Reliability Method. The reliability based design optimization seeks optimal solutions using the former design objectives and constraints with the inclusion of a reliability index. Finally, the de-orbiting system design alternatives generated by different approaches are investigated and the reliability based optimum design is found to yield the best solution since it significantly improves both system reliability and performance requirements.

Rooftop applications

NASA Technical Reports Server (NTRS)

Kern, E.

1982-01-01

Research on residential photovoltaic power systems based upon the experience of MIT-LL in implementing the DOE Residential Demonstration Project, especially the Northeast Residential Experiment Station (NE RES) is discussed. There is an immediate need for improved power-conditioner operational and reliability capabilities. Continuing evaluation of photovoltaic power systems is required to verify long-term performance, reliability, and utility interface effects. In the long term, the price of photovoltaic power systems must decrease, especially of modules.

Experimental and computational investigation of Morse taper conometric system reliability for the definition of fixed connections between dental implants and prostheses.

PubMed

Bressan, Eriberto; Lops, Diego; Tomasi, Cristiano; Ricci, Sara; Stocchero, Michele; Carniel, Emanuele Luigi

2014-07-01

Nowadays, dental implantology is a reliable technique for treatment of partially and completely edentulous patients. The achievement of stable dentition is ensured by implant-supported fixed dental prostheses. Morse taper conometric system may provide fixed retention between implants and dental prostheses. The aim of this study was to investigate retentive performance and mechanical strength of a Morse taper conometric system used as implant-supported fixed dental prostheses retention. Experimental and finite element investigations were performed. Experimental tests were achieved on a specific abutment-coping system, accounting for both cemented and non-cemented situations. The results from the experimental activities were processed to identify the mechanical behavior of the coping-abutment interface. Finally, the achieved information was applied to develop reliable finite element models of different abutment-coping systems. The analyses were developed accounting for different geometrical conformations of the abutment-coping system, such as different taper angle. The results showed that activation process, occurred through a suitable insertion force, could provide retentive performances equal to a cemented system without compromising the mechanical functionality of the system. These findings suggest that Morse taper conometrical system can provide a fixed connection between implants and dental prostheses if proper insertion force is applied. Activation process does not compromise the mechanical functionality of the system. © IMechE 2014.

Development of battery management system for nickel-metal hydride batteries in electric vehicle applications

NASA Astrophysics Data System (ADS)

Jung, Do Yang; Lee, Baek Haeng; Kim, Sun Wook

Electric vehicle (EV) performance is very dependent on traction batteries. For developing electric vehicles with high performance and good reliability, the traction batteries have to be managed to obtain maximum performance under various operating conditions. Enhancement of battery performance can be accomplished by implementing a battery management system (BMS) that plays an important role in optimizing the control mechanism of charge and discharge of the batteries as well as monitoring the battery status. In this study, a BMS has been developed for maximizing the use of Ni-MH batteries in electric vehicles. This system performs several tasks: the control of charging and discharging, overcharge and over-discharge protection, the calculation and display of state-of-charge (SOC), safety, and thermal management. The BMS is installed in and tested in a DEV5-5 electric vehicle developed by Daewoo Motor Co. and the Institute for Advanced Engineering in Korea. Eighteen modules of a Panasonic nickel-metal hydride (Ni-MH) battery, 12 V, 95 A h, are used in the DEV5-5. High accuracy within a range of 3% and good reliability are obtained. The BMS can also improve the performance and cycle-life of the Ni-MH battery peak, as well as the reliability and the safety of the electric vehicles.

Using benchmarks for radiation testing of microprocessors and FPGAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, Heather; Robinson, William H.; Rech, Paolo

Performance benchmarks have been used over the years to compare different systems. These benchmarks can be useful for researchers trying to determine how changes to the technology, architecture, or compiler affect the system's performance. No such standard exists for systems deployed into high radiation environments, making it difficult to assess whether changes in the fabrication process, circuitry, architecture, or software affect reliability or radiation sensitivity. In this paper, we propose a benchmark suite for high-reliability systems that is designed for field-programmable gate arrays and microprocessors. As a result, we describe the development process and report neutron test data for themore » hardware and software benchmarks.« less

Using benchmarks for radiation testing of microprocessors and FPGAs

DOE PAGES

Quinn, Heather; Robinson, William H.; Rech, Paolo; ...

2015-12-17

Performance benchmarks have been used over the years to compare different systems. These benchmarks can be useful for researchers trying to determine how changes to the technology, architecture, or compiler affect the system's performance. No such standard exists for systems deployed into high radiation environments, making it difficult to assess whether changes in the fabrication process, circuitry, architecture, or software affect reliability or radiation sensitivity. In this paper, we propose a benchmark suite for high-reliability systems that is designed for field-programmable gate arrays and microprocessors. As a result, we describe the development process and report neutron test data for themore » hardware and software benchmarks.« less

Assessing performance of an Electronic Health Record (EHR) using Cognitive Task Analysis.

PubMed

Saitwal, Himali; Feng, Xuan; Walji, Muhammad; Patel, Vimla; Zhang, Jiajie

2010-07-01

Many Electronic Health Record (EHR) systems fail to provide user-friendly interfaces due to the lack of systematic consideration of human-centered computing issues. Such interfaces can be improved to provide easy to use, easy to learn, and error-resistant EHR systems to the users. To evaluate the usability of an EHR system and suggest areas of improvement in the user interface. The user interface of the AHLTA (Armed Forces Health Longitudinal Technology Application) was analyzed using the Cognitive Task Analysis (CTA) method called GOMS (Goals, Operators, Methods, and Selection rules) and an associated technique called KLM (Keystroke Level Model). The GOMS method was used to evaluate the AHLTA user interface by classifying each step of a given task into Mental (Internal) or Physical (External) operators. This analysis was performed by two analysts independently and the inter-rater reliability was computed to verify the reliability of the GOMS method. Further evaluation was performed using KLM to estimate the execution time required to perform the given task through application of its standard set of operators. The results are based on the analysis of 14 prototypical tasks performed by AHLTA users. The results show that on average a user needs to go through 106 steps to complete a task. To perform all 14 tasks, they would spend about 22 min (independent of system response time) for data entry, of which 11 min are spent on more effortful mental operators. The inter-rater reliability analysis performed for all 14 tasks was 0.8 (kappa), indicating good reliability of the method. This paper empirically reveals and identifies the following finding related to the performance of AHLTA: (1) large number of average total steps to complete common tasks, (2) high average execution time and (3) large percentage of mental operators. The user interface can be improved by reducing (a) the total number of steps and (b) the percentage of mental effort, required for the tasks. 2010 Elsevier Ireland Ltd. All rights reserved.

A study on the real-time reliability of on-board equipment of train control system

NASA Astrophysics Data System (ADS)

Zhang, Yong; Li, Shiwei

2018-05-01

Real-time reliability evaluation is conducive to establishing a condition based maintenance system for the purpose of guaranteeing continuous train operation. According to the inherent characteristics of the on-board equipment, the connotation of reliability evaluation of on-board equipment is defined and the evaluation index of real-time reliability is provided in this paper. From the perspective of methodology and practical application, the real-time reliability of the on-board equipment is discussed in detail, and the method of evaluating the realtime reliability of on-board equipment at component level based on Hidden Markov Model (HMM) is proposed. In this method the performance degradation data is used directly to realize the accurate perception of the hidden state transition process of on-board equipment, which can achieve a better description of the real-time reliability of the equipment.

Bulk electric system reliability evaluation incorporating wind power and demand side management

NASA Astrophysics Data System (ADS)

Huang, Dange

Electric power systems are experiencing dramatic changes with respect to structure, operation and regulation and are facing increasing pressure due to environmental and societal constraints. Bulk electric system reliability is an important consideration in power system planning, design and operation particularly in the new competitive environment. A wide range of methods have been developed to perform bulk electric system reliability evaluation. Theoretically, sequential Monte Carlo simulation can include all aspects and contingencies in a power system and can be used to produce an informative set of reliability indices. It has become a practical and viable tool for large system reliability assessment technique due to the development of computing power and is used in the studies described in this thesis. The well-being approach used in this research provides the opportunity to integrate an accepted deterministic criterion into a probabilistic framework. This research work includes the investigation of important factors that impact bulk electric system adequacy evaluation and security constrained adequacy assessment using the well-being analysis framework. Load forecast uncertainty is an important consideration in an electrical power system. This research includes load forecast uncertainty considerations in bulk electric system reliability assessment and the effects on system, load point and well-being indices and reliability index probability distributions are examined. There has been increasing worldwide interest in the utilization of wind power as a renewable energy source over the last two decades due to enhanced public awareness of the environment. Increasing penetration of wind power has significant impacts on power system reliability, and security analyses become more uncertain due to the unpredictable nature of wind power. The effects of wind power additions in generating and bulk electric system reliability assessment considering site wind speed correlations and the interactive effects of wind power and load forecast uncertainty on system reliability are examined. The concept of the security cost associated with operating in the marginal state in the well-being framework is incorporated in the economic analyses associated with system expansion planning including wind power and load forecast uncertainty. Overall reliability cost/worth analyses including security cost concepts are applied to select an optimal wind power injection strategy in a bulk electric system. The effects of the various demand side management measures on system reliability are illustrated using the system, load point, and well-being indices, and the reliability index probability distributions. The reliability effects of demand side management procedures in a bulk electric system including wind power and load forecast uncertainty considerations are also investigated. The system reliability effects due to specific demand side management programs are quantified and examined in terms of their reliability benefits.

Digital Avionics Information System (DAIS): Reliability and Maintainability Model Users Guide. Final Report, May 1975-July 1977.

ERIC Educational Resources Information Center

Czuchry, Andrew J.; And Others

This report provides a complete guide to the stand alone mode operation of the reliability and maintenance (R&M) model, which was developed to facilitate the performance of design versus cost trade-offs within the digital avionics information system (DAIS) acquisition process. The features and structure of the model, its input data…

Waste Feed Delivery System Phase 1 Preliminary Reliability and Availability and Maintainability Analysis [SEC 1 and 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

CARLSON, A.B.

The document presents updated results of the preliminary reliability, availability, maintainability analysis performed for delivery of waste feed from tanks 241-AZ-101 and 241-AN-105 to British Nuclear Fuels Limited, inc. under the Tank Waste Remediation System Privatization Contract. The operational schedule delay risk is estimated and contributing factors are discussed.

Cascade Distiller System Performance Testing Interim Results

NASA Technical Reports Server (NTRS)

Callahan, Michael R.; Pensinger, Stuart; Sargusingh, Miriam J.

2014-01-01

The Cascade Distillation System (CDS) is a rotary distillation system with potential for greater reliability and lower energy costs than existing distillation systems. Based upon the results of the 2009 distillation comparison test (DCT) and recommendations of the expert panel, the Advanced Exploration Systems (AES) Water Recovery Project (WRP) project advanced the technology by increasing reliability of the system through redesign of bearing assemblies and improved rotor dynamics. In addition, the project improved the CDS power efficiency by optimizing the thermoelectric heat pump (TeHP) and heat exchanger design. Testing at the NASA-JSC Advanced Exploration System Water Laboratory (AES Water Lab) using a prototype Cascade Distillation Subsystem (CDS) wastewater processor (Honeywell d International, Torrance, Calif.) with test support equipment and control system developed by Johnson Space Center was performed to evaluate performance of the system with the upgrades as compared to previous system performance. The system was challenged with Solution 1 from the NASA Exploration Life Support (ELS) distillation comparison testing performed in 2009. Solution 1 consisted of a mixed stream containing human-generated urine and humidity condensate. A secondary objective of this testing is to evaluate the performance of the CDS as compared to the state of the art Distillation Assembly (DA) used in the ISS Urine Processor Assembly (UPA). This was done by challenging the system with ISS analog waste streams. This paper details the results of the AES WRP CDS performance testing.

Intra- and interobserver reliability of the Eaton classification for trapeziometacarpal arthritis: a systematic review.

PubMed

Berger, Aaron J; Momeni, Arash; Ladd, Amy L

2014-04-01

Trapeziometacarpal, or thumb carpometacarpal (CMC), arthritis is a common problem with a variety of treatment options. Although widely used, the Eaton radiographic staging system for CMC arthritis is of questionable clinical utility, as disease severity does not predictably correlate with symptoms or treatment recommendations. A possible reason for this is that the classification itself may not be reliable, but the literature on this has not, to our knowledge, been systematically reviewed. We therefore performed a systematic review to determine the intra- and interobserver reliability of the Eaton staging system. We systematically reviewed English-language studies published between 1973 and 2013 to assess the degree of intra- and interobserver reliability of the Eaton classification for determining the stage of trapeziometacarpal joint arthritis and pantrapezial arthritis based on plain radiographic imaging. Search engines included: PubMed, Scopus(®), and CINAHL. Four studies, which included a total of 163 patients, met our inclusion criteria and were evaluated. The level of evidence of the studies included in this analysis was determined using the Oxford Centre for Evidence Based Medicine Levels of Evidence Classification by two independent observers. A limited number of studies have been performed to assess intra- and interobserver reliability of the Eaton classification system. The four studies included were determined to be Level 3b. These studies collectively indicate that the Eaton classification demonstrates poor to fair interobserver reliability (kappa values: 0.11-0.56) and fair to moderate intraobserver reliability (kappa values: 0.54-0.657). Review of the literature demonstrates that radiographs assist in the assessment of CMC joint disease, but there is not a reliable system for classification of disease severity. Currently, diagnosis and treatment of thumb CMC arthritis are based on the surgeon's qualitative assessment combining history, physical examination, and radiographic evaluation. Inconsistent agreement using the current common radiographic classification system suggests a need for better radiographic tools to quantify disease severity.

Probabilistic resource allocation system with self-adaptive capability

NASA Technical Reports Server (NTRS)

Yufik, Yan M. (Inventor)

1996-01-01

A probabilistic resource allocation system is disclosed containing a low capacity computational module (Short Term Memory or STM) and a self-organizing associative network (Long Term Memory or LTM) where nodes represent elementary resources, terminal end nodes represent goals, and directed links represent the order of resource association in different allocation episodes. Goals and their priorities are indicated by the user, and allocation decisions are made in the STM, while candidate associations of resources are supplied by the LTM based on the association strength (reliability). Reliability values are automatically assigned to the network links based on the frequency and relative success of exercising those links in the previous allocation decisions. Accumulation of allocation history in the form of an associative network in the LTM reduces computational demands on subsequent allocations. For this purpose, the network automatically partitions itself into strongly associated high reliability packets, allowing fast approximate computation and display of allocation solutions satisfying the overall reliability and other user-imposed constraints. System performance improves in time due to modification of network parameters and partitioning criteria based on the performance feedback.

High-reliability release mechanism

NASA Technical Reports Server (NTRS)

Paradise, J. J.

1971-01-01

Release mechanism employing simple clevis fitting in combination with two pin-pullers achieves high reliability degree through active mechanical redundancy. Mechanism releases solar arrays. It is simple and inexpensive and performs effectively. It adapts to other release-system applications with variety of pin-puller devices.

Application of the Systematic Sensor Selection Strategy for Turbofan Engine Diagnostics

NASA Technical Reports Server (NTRS)

Sowers, T. Shane; Kopasakis, George; Simon, Donald L.

2008-01-01

The data acquired from available system sensors forms the foundation upon which any health management system is based, and the available sensor suite directly impacts the overall diagnostic performance that can be achieved. While additional sensors may provide improved fault diagnostic performance, there are other factors that also need to be considered such as instrumentation cost, weight, and reliability. A systematic sensor selection approach is desired to perform sensor selection from a holistic system-level perspective as opposed to performing decisions in an ad hoc or heuristic fashion. The Systematic Sensor Selection Strategy is a methodology that optimally selects a sensor suite from a pool of sensors based on the system fault diagnostic approach, with the ability of taking cost, weight, and reliability into consideration. This procedure was applied to a large commercial turbofan engine simulation. In this initial study, sensor suites tailored for improved diagnostic performance are constructed from a prescribed collection of candidate sensors. The diagnostic performance of the best performing sensor suites in terms of fault detection and identification are demonstrated, with a discussion of the results and implications for future research.

Application of the Systematic Sensor Selection Strategy for Turbofan Engine Diagnostics

NASA Technical Reports Server (NTRS)

Sowers, T. Shane; Kopasakis, George; Simon, Donald L.

2008-01-01

The data acquired from available system sensors forms the foundation upon which any health management system is based, and the available sensor suite directly impacts the overall diagnostic performance that can be achieved. While additional sensors may provide improved fault diagnostic performance there are other factors that also need to be considered such as instrumentation cost, weight, and reliability. A systematic sensor selection approach is desired to perform sensor selection from a holistic system-level perspective as opposed to performing decisions in an ad hoc or heuristic fashion. The Systematic Sensor Selection Strategy is a methodology that optimally selects a sensor suite from a pool of sensors based on the system fault diagnostic approach, with the ability of taking cost, weight and reliability into consideration. This procedure was applied to a large commercial turbofan engine simulation. In this initial study, sensor suites tailored for improved diagnostic performance are constructed from a prescribed collection of candidate sensors. The diagnostic performance of the best performing sensor suites in terms of fault detection and identification are demonstrated, with a discussion of the results and implications for future research.

Development of custom measurement system for biomechanical evaluation of independent wheelchair transfers

PubMed Central

Koontz, Alicia M.; Lin, Yen-Sheng; Kankipati, Padmaja; Boninger, Michael L.; Cooper, Rory A.

2017-01-01

This study describes a new custom measurement system designed to investigate the biomechanics of sitting-pivot wheelchair transfers and assesses the reliability of selected biomechanical variables. Variables assessed include horizontal and vertical reaction forces underneath both hands and three-dimensional trunk, shoulder, and elbow range of motion. We examined the reliability of these measures between 5 consecutive transfer trials for 5 subjects with spinal cord injury and 12 non-disabled subjects while they performed a self-selected sitting pivot transfer from a wheelchair to a level bench. A majority of the biomechanical variables demonstrated moderate to excellent reliability (r > 0.6). The transfer measurement system recorded reliable and valid biomechanical data for future studies of sitting-pivot wheelchair transfers. We recommend a minimum of five transfer trials to obtain a reliable measure of transfer technique for future studies. PMID:22068376

Reliability Impacts in Life Support Architecture and Technology Selection

NASA Technical Reports Server (NTRS)

Lange, Kevin E.; Anderson, Molly S.

2011-01-01

Equivalent System Mass (ESM) and reliability estimates were performed for different life support architectures based primarily on International Space Station (ISS) technologies. The analysis was applied to a hypothetical 1-year deep-space mission. High-level fault trees were initially developed relating loss of life support functionality to the Loss of Crew (LOC) top event. System reliability was then expressed as the complement (nonoccurrence) this event and was increased through the addition of redundancy and spares, which added to the ESM. The reliability analysis assumed constant failure rates and used current projected values of the Mean Time Between Failures (MTBF) from an ISS database where available. Results were obtained showing the dependence of ESM on system reliability for each architecture. Although the analysis employed numerous simplifications and many of the input parameters are considered to have high uncertainty, the results strongly suggest that achieving necessary reliabilities for deep-space missions will add substantially to the life support system mass. As a point of reference, the reliability for a single-string architecture using the most regenerative combination of ISS technologies without unscheduled replacement spares was estimated to be less than 1%. The results also demonstrate how adding technologies in a serial manner to increase system closure forces the reliability of other life support technologies to increase in order to meet the system reliability requirement. This increase in reliability results in increased mass for multiple technologies through the need for additional spares. Alternative parallel architecture approaches and approaches with the potential to do more with less are discussed. The tall poles in life support ESM are also reexamined in light of estimated reliability impacts.

Evaluating the Reliability of Emergency Response Systems for Large-Scale Incident Operations

PubMed Central

Jackson, Brian A.; Faith, Kay Sullivan; Willis, Henry H.

2012-01-01

Abstract The ability to measure emergency preparedness—to predict the likely performance of emergency response systems in future events—is critical for policy analysis in homeland security. Yet it remains difficult to know how prepared a response system is to deal with large-scale incidents, whether it be a natural disaster, terrorist attack, or industrial or transportation accident. This research draws on the fields of systems analysis and engineering to apply the concept of system reliability to the evaluation of emergency response systems. The authors describe a method for modeling an emergency response system; identifying how individual parts of the system might fail; and assessing the likelihood of each failure and the severity of its effects on the overall response effort. The authors walk the reader through two applications of this method: a simplified example in which responders must deliver medical treatment to a certain number of people in a specified time window, and a more complex scenario involving the release of chlorine gas. The authors also describe an exploratory analysis in which they parsed a set of after-action reports describing real-world incidents, to demonstrate how this method can be used to quantitatively analyze data on past response performance. The authors conclude with a discussion of how this method of measuring emergency response system reliability could inform policy discussion of emergency preparedness, how system reliability might be improved, and the costs of doing so. PMID:28083267

The Consequences of Using One Assessment System to Pursue Two Objectives

ERIC Educational Resources Information Center

Neal, Derek

2013-01-01

Education officials often use one assessment system both to create measures of student achievement and to create performance metrics for educators. However, modern standardized testing systems are not designed to produce performance metrics for teachers or principals. They are designed to produce reliable measures of individual student achievement…

Demonstrating the Safety and Reliability of a New System or Spacecraft: Incorporating Analyses and Reviews of the Design and Processing in Determining the Number of Tests to be Conducted

NASA Technical Reports Server (NTRS)

Vesely, William E.; Colon, Alfredo E.

2010-01-01

Design Safety/Reliability is associated with the probability of no failure-causing faults existing in a design. Confidence in the non-existence of failure-causing faults is increased by performing tests with no failure. Reliability-Growth testing requirements are based on initial assurance and fault detection probability. Using binomial tables generally gives too many required tests compared to reliability-growth requirements. Reliability-Growth testing requirements are based on reliability principles and factors and should be used.

System Risk Assessment and Allocation in Conceptual Design

NASA Technical Reports Server (NTRS)

Mahadevan, Sankaran; Smith, Natasha L.; Zang, Thomas A. (Technical Monitor)

2003-01-01

As aerospace systems continue to evolve in addressing newer challenges in air and space transportation, there exists a heightened priority for significant improvement in system performance, cost effectiveness, reliability, and safety. Tools, which synthesize multidisciplinary integration, probabilistic analysis, and optimization, are needed to facilitate design decisions allowing trade-offs between cost and reliability. This study investigates tools for probabilistic analysis and probabilistic optimization in the multidisciplinary design of aerospace systems. A probabilistic optimization methodology is demonstrated for the low-fidelity design of a reusable launch vehicle at two levels, a global geometry design and a local tank design. Probabilistic analysis is performed on a high fidelity analysis of a Navy missile system. Furthermore, decoupling strategies are introduced to reduce the computational effort required for multidisciplinary systems with feedback coupling.

Systems Integration Fact Sheet

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2016-06-01

This fact sheet is an overview of the Systems Integration subprogram at the U.S. Department of Energy SunShot Initiative. The Systems Integration subprogram enables the widespread deployment of safe, reliable, and cost-effective solar energy technologies by addressing the associated technical and non-technical challenges. These include timely and cost-effective interconnection procedures, optimal system planning, accurate prediction of solar resources, monitoring and control of solar power, maintaining grid reliability and stability, and many more. To address the challenges associated with interconnecting and integrating hundreds of gigawatts of solar power onto the electricity grid, the Systems Integration program funds research, development, and demonstrationmore » projects in four broad, interrelated focus areas: grid performance and reliability, dispatchability, power electronics, and communications.« less

Assessment of spare reliability for multi-state computer networks within tolerable packet unreliability

NASA Astrophysics Data System (ADS)

Lin, Yi-Kuei; Huang, Cheng-Fu

2015-04-01

From a quality of service viewpoint, the transmission packet unreliability and transmission time are both critical performance indicators in a computer system when assessing the Internet quality for supervisors and customers. A computer system is usually modelled as a network topology where each branch denotes a transmission medium and each vertex represents a station of servers. Almost every branch has multiple capacities/states due to failure, partial failure, maintenance, etc. This type of network is known as a multi-state computer network (MSCN). This paper proposes an efficient algorithm that computes the system reliability, i.e., the probability that a specified amount of data can be sent through k (k ≥ 2) disjoint minimal paths within both the tolerable packet unreliability and time threshold. Furthermore, two routing schemes are established in advance to indicate the main and spare minimal paths to increase the system reliability (referred to as spare reliability). Thus, the spare reliability can be readily computed according to the routing scheme.

Reliable high-power injection locked 6kHz 60W laser for ArF immersion lithography

NASA Astrophysics Data System (ADS)

Watanabe, Hidenori; Komae, Shigeo; Tanaka, Satoshi; Nohdomi, Ryoichi; Yamazaki, Taku; Nakarai, Hiroaki; Fujimoto, Junichi; Matsunaga, Takashi; Saito, Takashi; Kakizaki, Kouji; Mizoguchi, Hakaru

2007-03-01

Reliable high power 193nm ArF light source is desired for the successive growth of ArF-immersion technology for 45nm node generation. In 2006, Gigaphoton released GT60A, high power injection locked 6kHz/60W/0.5pm (E95) laser system, to meet the demands of semiconductor markets. In this paper, we report key technologies for reliable mass production GT laser systems and GT60A high durability performance test results up to 20 billion pulses.

UNIX-based operating systems robustness evaluation

NASA Technical Reports Server (NTRS)

Chang, Yu-Ming

1996-01-01

Robust operating systems are required for reliable computing. Techniques for robustness evaluation of operating systems not only enhance the understanding of the reliability of computer systems, but also provide valuable feed- back to system designers. This thesis presents results from robustness evaluation experiments on five UNIX-based operating systems, which include Digital Equipment's OSF/l, Hewlett Packard's HP-UX, Sun Microsystems' Solaris and SunOS, and Silicon Graphics' IRIX. Three sets of experiments were performed. The methodology for evaluation tested (1) the exception handling mechanism, (2) system resource management, and (3) system capacity under high workload stress. An exception generator was used to evaluate the exception handling mechanism of the operating systems. Results included exit status of the exception generator and the system state. Resource management techniques used by individual operating systems were tested using programs designed to usurp system resources such as physical memory and process slots. Finally, the workload stress testing evaluated the effect of the workload on system performance by running a synthetic workload and recording the response time of local and remote user requests. Moderate to severe performance degradations were observed on the systems under stress.

Performance Steel Castings

DTIC Science & Technology

2012-09-30

Development of Sand Properties 103 Advanced Modeling Dataset.. 105 High Strength Low Alloy (HSLA) Steels 107 Steel Casting and Engineering Support...to achieve the performance goals required for new systems. The dramatic reduction in weight and increase in capability will require high performance...for improved weapon system reliability. SFSA developed innovative casting design and manufacturing processes for high performance parts. SFSA is

A new communication protocol family for a distributed spacecraft control system

NASA Technical Reports Server (NTRS)

Baldi, Andrea; Pace, Marco

1994-01-01

In this paper we describe the concepts behind and architecture of a communication protocol family, which was designed to fulfill the communication requirements of ESOC's new distributed spacecraft control system SCOS 2. A distributed spacecraft control system needs a data delivery subsystem to be used for telemetry (TLM) distribution, telecommand (TLC) dispatch and inter-application communication, characterized by the following properties: reliability, so that any operational workstation is guaranteed to receive the data it needs to accomplish its role; efficiency, so that the telemetry distribution, even for missions with high telemetry rates, does not cause a degradation of the overall control system performance; scalability, so that the network is not the bottleneck both in terms of bandwidth and reconfiguration; flexibility, so that it can be efficiently used in many different situations. The new protocol family which satisfies the above requirements is built on top of widely used communication protocols (UDP and TCP), provides reliable point-to-point and broadcast communication (UDP+) and is implemented in C++. Reliability is achieved using a retransmission mechanism based on a sequence numbering scheme. Such a scheme allows to have cost-effective performances compared to the traditional protocols, because retransmission is only triggered by applications which explicitly need reliability. This flexibility enables applications with different profiles to take advantage of the available protocols, so that the best rate between sped and reliability can be achieved case by case.

Performance and Reliability Analysis of Water Distribution Systems under Cascading Failures and the Identification of Crucial Pipes

PubMed Central

Shuang, Qing; Zhang, Mingyuan; Yuan, Yongbo

2014-01-01

As a mean of supplying water, Water distribution system (WDS) is one of the most important complex infrastructures. The stability and reliability are critical for urban activities. WDSs can be characterized by networks of multiple nodes (e.g. reservoirs and junctions) and interconnected by physical links (e.g. pipes). Instead of analyzing highest failure rate or highest betweenness, reliability of WDS is evaluated by introducing hydraulic analysis and cascading failures (conductive failure pattern) from complex network. The crucial pipes are identified eventually. The proposed methodology is illustrated by an example. The results show that the demand multiplier has a great influence on the peak of reliability and the persistent time of the cascading failures in its propagation in WDS. The time period when the system has the highest reliability is when the demand multiplier is less than 1. There is a threshold of tolerance parameter exists. When the tolerance parameter is less than the threshold, the time period with the highest system reliability does not meet minimum value of demand multiplier. The results indicate that the system reliability should be evaluated with the properties of WDS and the characteristics of cascading failures, so as to improve its ability of resisting disasters. PMID:24551102

Constellation Ground Systems Launch Availability Analysis: Enhancing Highly Reliable Launch Systems Design

NASA Technical Reports Server (NTRS)

Gernand, Jeffrey L.; Gillespie, Amanda M.; Monaghan, Mark W.; Cummings, Nicholas H.

2010-01-01

Success of the Constellation Program's lunar architecture requires successfully launching two vehicles, Ares I/Orion and Ares V/Altair, in a very limited time period. The reliability and maintainability of flight vehicles and ground systems must deliver a high probability of successfully launching the second vehicle in order to avoid wasting the on-orbit asset launched by the first vehicle. The Ground Operations Project determined which ground subsystems had the potential to affect the probability of the second launch and allocated quantitative availability requirements to these subsystems. The Ground Operations Project also developed a methodology to estimate subsystem reliability, availability and maintainability to ensure that ground subsystems complied with allocated launch availability and maintainability requirements. The verification analysis developed quantitative estimates of subsystem availability based on design documentation; testing results, and other information. Where appropriate, actual performance history was used for legacy subsystems or comparative components that will support Constellation. The results of the verification analysis will be used to verify compliance with requirements and to highlight design or performance shortcomings for further decision-making. This case study will discuss the subsystem requirements allocation process, describe the ground systems methodology for completing quantitative reliability, availability and maintainability analysis, and present findings and observation based on analysis leading to the Ground Systems Preliminary Design Review milestone.

New understandings of failure modes in SSL luminaires

NASA Astrophysics Data System (ADS)

Shepherd, Sarah D.; Mills, Karmann C.; Yaga, Robert; Johnson, Cortina; Davis, J. Lynn

2014-09-01

As SSL products are being rapidly introduced into the market, there is a need to develop standard screening and testing protocols that can be performed quickly and provide data surrounding product lifetime and performance. These protocols, derived from standard industry tests, are known as ALTs (accelerated life tests) and can be performed in a timeframe of weeks to months instead of years. Accelerated testing utilizes a combination of elevated temperature and humidity conditions as well as electrical power cycling to control aging of the luminaires. In this study, we report on the findings of failure modes for two different luminaire products exposed to temperature-humidity ALTs. LEDs are typically considered the determining component for the rate of lumen depreciation. However, this study has shown that each luminaire component can independently or jointly influence system performance and reliability. Material choices, luminaire designs, and driver designs all have significant impacts on the system reliability of a product. From recent data, it is evident that the most common failure modes are not within the LED, but instead occur within resistors, capacitors, and other electrical components of the driver. Insights into failure modes and rates as a result of ALTs are reported with emphasis on component influence on overall system reliability.

Tightly-Coupled Integration of Multi-GNSS Single-Frequency RTK and MEMS-IMU for Enhanced Positioning Performance

PubMed Central

Li, Tuan; Zhang, Hongping; Niu, Xiaoji; Gao, Zhouzheng

2017-01-01

Dual-frequency Global Positioning System (GPS) Real-time Kinematics (RTK) has been proven in the past few years to be a reliable and efficient technique to obtain high accuracy positioning. However, there are still challenges for GPS single-frequency RTK, such as low reliability and ambiguity resolution (AR) success rate, especially in kinematic environments. Recently, multi-Global Navigation Satellite System (multi-GNSS) has been applied to enhance the RTK performance in terms of availability and reliability of AR. In order to further enhance the multi-GNSS single-frequency RTK performance in terms of reliability, continuity and accuracy, a low-cost micro-electro-mechanical system (MEMS) inertial measurement unit (IMU) is adopted in this contribution. We tightly integrate the single-frequency GPS/BeiDou/GLONASS and MEMS-IMU through the extended Kalman filter (EKF), which directly fuses the ambiguity-fixed double-differenced (DD) carrier phase observables and IMU data. A field vehicular test was carried out to evaluate the impacts of the multi-GNSS and IMU on the AR and positioning performance in different system configurations. Test results indicate that the empirical success rate of single-epoch AR for the tightly-coupled single-frequency multi-GNSS RTK/INS integration is over 99% even at an elevation cut-off angle of 40°, and the corresponding position time series is much more stable in comparison with the GPS solution. Besides, GNSS outage simulations show that continuous positioning with certain accuracy is possible due to the INS bridging capability when GNSS positioning is not available. PMID:29077070

Tightly-Coupled Integration of Multi-GNSS Single-Frequency RTK and MEMS-IMU for Enhanced Positioning Performance.

PubMed

Li, Tuan; Zhang, Hongping; Niu, Xiaoji; Gao, Zhouzheng

2017-10-27

Dual-frequency Global Positioning System (GPS) Real-time Kinematics (RTK) has been proven in the past few years to be a reliable and efficient technique to obtain high accuracy positioning. However, there are still challenges for GPS single-frequency RTK, such as low reliability and ambiguity resolution (AR) success rate, especially in kinematic environments. Recently, multi-Global Navigation Satellite System (multi-GNSS) has been applied to enhance the RTK performance in terms of availability and reliability of AR. In order to further enhance the multi-GNSS single-frequency RTK performance in terms of reliability, continuity and accuracy, a low-cost micro-electro-mechanical system (MEMS) inertial measurement unit (IMU) is adopted in this contribution. We tightly integrate the single-frequency GPS/BeiDou/GLONASS and MEMS-IMU through the extended Kalman filter (EKF), which directly fuses the ambiguity-fixed double-differenced (DD) carrier phase observables and IMU data. A field vehicular test was carried out to evaluate the impacts of the multi-GNSS and IMU on the AR and positioning performance in different system configurations. Test results indicate that the empirical success rate of single-epoch AR for the tightly-coupled single-frequency multi-GNSS RTK/INS integration is over 99% even at an elevation cut-off angle of 40°, and the corresponding position time series is much more stable in comparison with the GPS solution. Besides, GNSS outage simulations show that continuous positioning with certain accuracy is possible due to the INS bridging capability when GNSS positioning is not available.

Striped tertiary storage arrays

NASA Technical Reports Server (NTRS)

Drapeau, Ann L.

1993-01-01

Data stripping is a technique for increasing the throughput and reducing the response time of large access to a storage system. In striped magnetic or optical disk arrays, a single file is striped or interleaved across several disks; in a striped tape system, files are interleaved across tape cartridges. Because a striped file can be accessed by several disk drives or tape recorders in parallel, the sustained bandwidth to the file is greater than in non-striped systems, where access to the file are restricted to a single device. It is argued that applying striping to tertiary storage systems will provide needed performance and reliability benefits. The performance benefits of striping for applications using large tertiary storage systems is discussed. It will introduce commonly available tape drives and libraries, and discuss their performance limitations, especially focusing on the long latency of tape accesses. This section will also describe an event-driven tertiary storage array simulator that is being used to understand the best ways of configuring these storage arrays. The reliability problems of magnetic tape devices are discussed, and plans for modeling the overall reliability of striped tertiary storage arrays to identify the amount of error correction required are described. Finally, work being done by other members of the Sequoia group to address latency of accesses, optimizing tertiary storage arrays that perform mostly writes, and compression is discussed.

Distribution System Reliability Analysis for Smart Grid Applications

NASA Astrophysics Data System (ADS)

Aljohani, Tawfiq Masad

Reliability of power systems is a key aspect in modern power system planning, design, and operation. The ascendance of the smart grid concept has provided high hopes of developing an intelligent network that is capable of being a self-healing grid, offering the ability to overcome the interruption problems that face the utility and cost it tens of millions in repair and loss. To address its reliability concerns, the power utilities and interested parties have spent extensive amount of time and effort to analyze and study the reliability of the generation and transmission sectors of the power grid. Only recently has attention shifted to be focused on improving the reliability of the distribution network, the connection joint between the power providers and the consumers where most of the electricity problems occur. In this work, we will examine the effect of the smart grid applications in improving the reliability of the power distribution networks. The test system used in conducting this thesis is the IEEE 34 node test feeder, released in 2003 by the Distribution System Analysis Subcommittee of the IEEE Power Engineering Society. The objective is to analyze the feeder for the optimal placement of the automatic switching devices and quantify their proper installation based on the performance of the distribution system. The measures will be the changes in the reliability system indices including SAIDI, SAIFI, and EUE. The goal is to design and simulate the effect of the installation of the Distributed Generators (DGs) on the utility's distribution system and measure the potential improvement of its reliability. The software used in this work is DISREL, which is intelligent power distribution software that is developed by General Reliability Co.

Reliability of McConnell's classification of patellar orientation in symptomatic and asymptomatic subjects.

PubMed

Watson, C J; Propps, M; Galt, W; Redding, A; Dobbs, D

1999-07-01

Test-retest reliability study with blinded testers. To determine the intratester reliability of the McConnell classification system and to determine whether the intertester reliability of this system would be improved by one-on-one training of the testers, increasing the variability and numbers of subjects, blinding the testers to the absence or presence of patellofemoral pain syndrome, and adhering to the McConnell classification system as it is taught in the "McConnell Patellofemoral Treatment Plan" continuing education course. The McConnell classification system is currently used by physical therapy clinicians to quantify static patellar orientation. The measurements generated from this system purportedly guide the therapist in the application of patellofemoral tape and in assessment of the efficacy of treatment interventions on changing patellar orientation. Fifty-six subjects (age range, 21-65 years) provided a total of 101 knees for assessment. Seventy-six knees did not produce symptoms. A researcher who did not participate in the measuring process determined that 17 subjects had patellofemoral pain syndrome in 25 knees. Two testers concurrently measured static patellar orientation (anterior/posterior and medial/lateral tilt, medial/lateral glide, and patellar rotation) on subjects, using the McConnell classification system. Repeat measures were performed 3-7 days later. A kappa (kappa) statistic was used to assess the degree of agreement within each tester and between testers. The kappa coefficients for intratester reliability varied from -0.06 to 0.35. Intertester reliability ranged from -0.03 to 0.19. The McConnell classification system, in its current form, does not appear to be very reliable. Intratester reliability ranged from poor to fair, and intertester reliability was poor to slight. This system should not be used as a measurement tool or as a basis for treatment decisions.

Space Station Freedom power - A reliability, availability, and maintainability assessment of the proposed Space Station Freedom electric power system

NASA Technical Reports Server (NTRS)

Turnquist, S. R.; Twombly, M.; Hoffman, D.

1989-01-01

A preliminary reliability, availability, and maintainability (RAM) analysis of the proposed Space Station Freedom electric power system (EPS) was performed using the unit reliability, availability, and maintainability (UNIRAM) analysis methodology. Orbital replacement units (ORUs) having the most significant impact on EPS availability measures were identified. Also, the sensitivity of the EPS to variations in ORU RAM data was evaluated for each ORU. Estimates were made of average EPS power output levels and availability of power to the core area of the space station. The results of assessments of the availability of EPS power and power to load distribution points in the space stations are given. Some highlights of continuing studies being performed to understand EPS availability considerations are presented.

75 FR 53277 - Notice of Workshop on Polymers for Photovoltaic Systems

Federal Register 2010, 2011, 2012, 2013, 2014

2010-08-31

... photovoltaic systems; testing, performance, and reliability of polymers in photovoltaic systems; impact of... mentioned topics; presentation of a NIST- developed accelerated aging and service life prediction...

Evaluation of bus transit reliability in the District of Columbia.

DOT National Transportation Integrated Search

2013-11-01

Several performance metrics can be used to assess the reliability of a transit system. These include on-time arrivals, travel-time : adherence, run-time adherence, and customer satisfaction, among others. On-time arrival at bus stops is one of the pe...

ASDE-2 Reliability Improvement Study : Volume I. Operational Data and Modification Recommendations.

DOT National Transportation Integrated Search

1974-11-01

Eight airport sites and the FAA Oklahoma Depot were visited and surveys conducted to obtain reliability, maintainability and performance data on the ASDE-2 Radar System. The data was analyzed and recommendations for modification to the equipment made...

ASDE-2 Reliability Improvement Study : Volume II. Modulator, Receiver and Indicator Interface Recommendations

DOT National Transportation Integrated Search

1974-11-01

Eight airport sites and the FAA Oklahoma Depot were visited and surveys conducted to obtain reliability, maintainability and performance data on the ASDE-2 Radar System. The data was analyzed and recommendations for modification to the equipment made...

Aircraft Engine-Monitoring System And Display

NASA Technical Reports Server (NTRS)

Abbott, Terence S.; Person, Lee H., Jr.

1992-01-01

Proposed Engine Health Monitoring System and Display (EHMSD) provides enhanced means for pilot to control and monitor performances of engines. Processes raw sensor data into information meaningful to pilot. Provides graphical information about performance capabilities, current performance, and operational conditions in components or subsystems of engines. Provides means to control engine thrust directly and innovative means to monitor performance of engine system rapidly and reliably. Features reduce pilot workload and increase operational safety.

Towards New Metrics for High-Performance Computing Resilience

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hukerikar, Saurabh; Ashraf, Rizwan A; Engelmann, Christian

Ensuring the reliability of applications is becoming an increasingly important challenge as high-performance computing (HPC) systems experience an ever-growing number of faults, errors and failures. While the HPC community has made substantial progress in developing various resilience solutions, it continues to rely on platform-based metrics to quantify application resiliency improvements. The resilience of an HPC application is concerned with the reliability of the application outcome as well as the fault handling efficiency. To understand the scope of impact, effective coverage and performance efficiency of existing and emerging resilience solutions, there is a need for new metrics. In this paper, wemore » develop new ways to quantify resilience that consider both the reliability and the performance characteristics of the solutions from the perspective of HPC applications. As HPC systems continue to evolve in terms of scale and complexity, it is expected that applications will experience various types of faults, errors and failures, which will require applications to apply multiple resilience solutions across the system stack. The proposed metrics are intended to be useful for understanding the combined impact of these solutions on an application's ability to produce correct results and to evaluate their overall impact on an application's performance in the presence of various modes of faults.« less

Thermal Protection Materials and Systems: Past, Present, and Future

NASA Technical Reports Server (NTRS)

Johnson, Sylvia M.

2013-01-01

Thermal protection materials and systems (TPS) protect vehicles from the heat generated when entering a planetary atmosphere. NASA has developed many TPS systems over the years for vehicle ranging from planetary probes to crewed vehicles. The goal for all TPS is efficient and reliable performance. Efficient means using the right material for the environment and minimizing the mass of the heat shield without compromising safety. Efficiency is critical if the payload such as science experiments is to be maximized on a particular vehicle. Reliable means that we understand and can predict performance of the material. Although much characterization and testing of materials is performed to qualify and certify them for flight, it is not possible to completely recreate the reentry conditions in test facilities, and flight-testing

Increased Reliability of Gas Turbine Components by Robust Coatings Manufacturing

NASA Astrophysics Data System (ADS)

Sharma, A.; Dudykevych, T.; Sansom, D.; Subramanian, R.

2017-08-01

The expanding operational windows of the advanced gas turbine components demand increasing performance capability from protective coating systems. This demand has led to the development of novel multi-functional, multi-materials coating system architectures over the last years. In addition, the increasing dependency of components exposed to extreme environment on protective coatings results in more severe penalties, in case of a coating system failure. This emphasizes that reliability and consistency of protective coating systems are equally important to their superior performance. By means of examples, this paper describes the effects of scatter in the material properties resulting from manufacturing variations on coating life predictions. A strong foundation in process-property-performance correlations as well as regular monitoring and control of the coating process is essential for robust and well-controlled coating process. Proprietary and/or commercially available diagnostic tools can help in achieving these goals, but their usage in industrial setting is still limited. Various key contributors to process variability are briefly discussed along with the limitations of existing process and product control methods. Other aspects that are important for product reliability and consistency in serial manufacturing as well as advanced testing methodologies to simplify and enhance product inspection and improve objectivity are briefly described.

Toward extending the educational interpreter performance assessment to cued speech.

PubMed

Krause, Jean C; Kegl, Judy A; Schick, Brenda

2008-01-01

The Educational Interpreter Performance Assessment (EIPA) is as an important research tool for examining the quality of interpreters who use American Sign Language or a sign system in classroom settings, but it is not currently applicable to educational interpreters who use Cued Speech (CS). In order to determine the feasibility of extending the EIPA to include CS, a pilot EIPA test was developed and administered to 24 educational CS interpreters. Fifteen of the interpreters' performances were evaluated two to three times in order to assess reliability. Results show that the instrument has good construct validity and test-retest reliability. Although more interrater reliability data are needed, intrarater reliability was quite high (0.9), suggesting that the pilot test can be rated as reliably as signing versions of the EIPA. Notably, only 48% of interpreters who formally participated in pilot testing performed at a level that could be considered minimally acceptable. In light of similar performance levels previously reported for interpreters who sign (e.g., Schick, Williams, & Kupermintz, 2006), these results suggest that interpreting services for deaf and hard-of hearing students, regardless of the communication option used, are often inadequate and could seriously hinder access to the classroom environment.

Toward Extending the Educational Interpreter Performance Assessment to Cued Speech

PubMed Central

Krause, Jean C.; Kegl, Judy A.; Schick, Brenda

2008-01-01

The Educational Interpreter Performance Assessment (EIPA) is as an important research tool for examining the quality of interpreters who use American Sign Language or a sign system in classroom settings, but it is not currently applicable to educational interpreters who use Cued Speech (CS). In order to determine the feasibility of extending the EIPA to include CS, a pilot EIPA test was developed and administered to 24 educational CS interpreters. Fifteen of the interpreters’ performances were evaluated two to three times in order to assess reliability. Results show that the instrument has good construct validity and test–retest reliability. Although more interrater reliability data are needed, intrarater reliability was quite high (0.9), suggesting that the pilot test can be rated as reliably as signing versions of the EIPA. Notably, only 48% of interpreters who formally participated in pilot testing performed at a level that could be considered minimally acceptable. In light of similar performance levels previously reported for interpreters who sign (e.g., Schick, Williams, & Kupermintz, 2006), these results suggest that interpreting services for deaf and hard-of hearing students, regardless of the communication option used, are often inadequate and could seriously hinder access to the classroom environment. PMID:18042791

Federal Motor Carrier Safety Administration’s Advanced System Testing Utilizing a Data Acquisition System on the Highways (FAST DASH) Safety Technology Evaluation Project #2: Driver Monitoring Final Report.

DOT National Transportation Integrated Search

2016-12-01

An independent evaluation of a non-video-based onboard monitoring system (OBMS) was conducted. The objective was to determine if the OBMS system performed reliably, improved driving safety and performance, and improved fuel efficiency in a commercial...

Federal Motor Carrier Safety Administration’s advanced system testing utilizing a data acquisition system on the highways (FAST DASH) safety technology evaluation project #2 : driver monitoring, final report.

DOT National Transportation Integrated Search

2016-11-01

An independent evaluation of a non-video-based onboard monitoring system (OBMS) was conducted. The objective was to determine if the OBMS system performed reliably, improved driving safety and performance, and improved fuel efficiency in a commercial...

Technology Overview for Advanced Aircraft Armament System Program.

DTIC Science & Technology

1981-05-01

availability of methods or systems for improving stores and armament safety. Of particular importance are aspects of safety involving hazards analysis ...flutter virtually insensitive to inertia and center-of- gravity location of store - Simplifies and reduces analysis and testing required to flutter- clear...status. Nearly every existing reliability analysis and discipline that prom- ised a positive return on reliability performance was drawn out, dusted

Ku-band signal design study. [space shuttle orbiter data processing network

NASA Technical Reports Server (NTRS)

Rubin, I.

1978-01-01

Analytical tools, methods and techniques for assessing the design and performance of the space shuttle orbiter data processing system (DPS) are provided. The computer data processing network is evaluated in the key areas of queueing behavior synchronization and network reliability. The structure of the data processing network is described as well as the system operation principles and the network configuration. The characteristics of the computer systems are indicated. System reliability measures are defined and studied. System and network invulnerability measures are computed. Communication path and network failure analysis techniques are included.

Protocol for Reliability Assessment of Structural Health Monitoring Systems Incorporating Model-assisted Probability of Detection (MAPOD) Approach

DTIC Science & Technology

2011-09-01

a quality evaluation with limited data, a model -based assessment must be...that affect system performance, a multistage approach to system validation, a modeling and experimental methodology for efficiently addressing a ...affect system performance, a multistage approach to system validation, a modeling and experimental methodology for efficiently addressing a wide range

In Situ, On-Demand Lubrication System Developed for Space Mechanisms

NASA Technical Reports Server (NTRS)

Marchetti, Mario; Pepper, Stephen V.; Jansen, Mark J.; Predmore, Roamer E.

2003-01-01

Many moving mechanical assemblies (MMA) for space mechanisms rely on liquid lubricants to provide reliable, long-term performance. The proper performance of the MMA is critical in assuring a successful mission. Historically, mission lifetimes were short and MMA duty cycles were minimal. As mission lifetimes were extended, other components, such as batteries and computers, failed before lubricated systems. However, improvements in these ancillary systems over the last decade have left the tribological systems of the MMAs as the limiting factor in determining spacecraft reliability. Typically, MMAs are initially lubricated with a very small charge that is supposed to last the entire mission lifetime, often well in excess of 5 years. In many cases, the premature failure of a lubricated component can result in mission failure.

Reliability and economy -- Hydro electricity for Iran

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jahromi-Shirazi, M.J.; Zarbakhsh, M.H.

1998-12-31

Reliability is the probability that a device or system will perform its function adequately, for the period of time intended, under the operating conditions intended. Reliability and economy are two important factors in operating any system, especially in power generation. Due to the high rate in population growth in Iran, the experts have estimated that the demand for electricity will be about 63,000 MW in the next 25 years, the installed power is now about 26,000 MW. Therefore, the energy policy decision made in Iran is to go to power generation by hydroelectric plants because of reliability, availability of watermore » resources and the economics of hydroelectric power.« less

Reliability and Normative Data for the Dynamic Visual Acuity Test for Vestibular Screening.

PubMed

Riska, Kristal M; Hall, Courtney D

2016-06-01

The purpose of this study was to determine reliability of computerized dynamic visual acuity (DVA) testing and to determine reference values for younger and older adults. A primary function of the vestibular system is to maintain gaze stability during head motion. The DVA test quantifies gaze stabilization with the head moving versus stationary. Commercially available computerized systems allow clinicians to incorporate DVA into their assessment; however, information regarding reliability and normative values of these systems is sparse. Forty-six healthy adults, grouped by age, with normal vestibular function were recruited. Each participant completed computerized DVA testing including static visual acuity, minimum perception time, and DVA using the NeuroCom inVision System. Testing was performed by two examiners in the same session and then repeated at a follow-up session 3 to 14 days later. Intraclass correlation coefficients (ICCs) were used to determine inter-rater and test-retest reliability. ICCs for inter-rater reliability ranged from 0.323 to 0.937 and from 0.434 to 0.909 for horizontal and vertical head movements, respectively. ICCs for test-retest reliability ranged from 0.154 to 0.856 and from 0.377 to 0.9062 for horizontal and vertical head movements, respectively. Overall, raw scores (left/right DVA and up/down DVA) were more reliable than DVA loss scores. Reliability of a commercially available DVA system has poor-to-fair reliability for DVA loss scores. The use of a convergence paradigm and not incorporating the forced choice paradigm may contribute to poor reliability.

Upgrades to the International Space Station Water Recovery System

NASA Technical Reports Server (NTRS)

Kayatin, Matthew J.; Pruitt, Jennifer M.; Nur, Mononita; Takada, Kevin C.; Carter, Layne

2017-01-01

The International Space Station (ISS) Water Recovery System (WRS) includes the Water Processor Assembly (WPA) and the Urine Processor Assembly (UPA). The WRS produces potable water from a combination of crew urine (first processed through the UPA), crew latent, and Sabatier product water. Though the WRS has performed well since operations began in November 2008, several modifications have been identified to improve the overall system performance. These modifications aim to reduce resupply and improve overall system reliability, which is beneficial for the ongoing ISS mission as well as for future NASA manned missions. The following paper details efforts to improve the WPA through the use of reverse osmosis membrane technology to reduce the resupply mass of the WPA Multi-filtration Bed and improved catalyst for the WPA Catalytic Reactor to reduce the operational temperature and pressure. For the UPA, this paper discusses progress on various concepts for improving the reliability of the system, including the implementation of a more reliable drive belt, improved methods for managing condensate in the stationary bowl of the Distillation Assembly, and evaluating upgrades to the UPA vacuum pump.

Reliability and validity of CODA motion analysis system for measuring cervical range of motion in patients with cervical spondylosis and anterior cervical fusion.

PubMed

Gao, Zhongyang; Song, Hui; Ren, Fenggang; Li, Yuhuan; Wang, Dong; He, Xijing

2017-12-01

The aim of the present study was to evaluate the reliability of the Cartesian Optoelectronic Dynamic Anthropometer (CODA) motion system in measuring the cervical range of motion (ROM) and verify the construct validity of the CODA motion system. A total of 26 patients with cervical spondylosis and 22 patients with anterior cervical fusion were enrolled and the CODA motion analysis system was used to measure the three-dimensional cervical ROM. Intra- and inter-rater reliability was assessed by interclass correlation coefficients (ICCs), standard error of measurement (SEm), Limits of Agreements (LOA) and minimal detectable change (MDC). Independent samples t-tests were performed to examine the differences of cervical ROM between cervical spondylosis and anterior cervical fusion patients. The results revealed that in the cervical spondylosis group, the reliability was almost perfect (intra-rater reliability: ICC, 0.87-0.95; LOA, -12.86-13.70; SEm, 2.97-4.58; inter-rater reliability: ICC, 0.84-0.95; LOA, -13.09-13.48; SEm, 3.13-4.32). In the anterior cervical fusion group, the reliability was high (intra-rater reliability: ICC, 0.88-0.97; LOA, -10.65-11.08; SEm, 2.10-3.77; inter-rater reliability: ICC, 0.86-0.96; LOA, -10.91-13.66; SEm, 2.20-4.45). The cervical ROM in the cervical spondylosis group was significantly higher than that in the anterior cervical fusion group in all directions except for left rotation. In conclusion, the CODA motion analysis system is highly reliable in measuring cervical ROM and the construct validity was verified, as the system was sufficiently sensitive to distinguish between the cervical spondylosis and anterior cervical fusion groups based on their ROM.

Reliability and failure modes of narrow implant systems.

PubMed

Hirata, Ronaldo; Bonfante, Estevam A; Anchieta, Rodolfo B; Machado, Lucas S; Freitas, Gileade; Fardin, Vinicius P; Tovar, Nick; Coelho, Paulo G

2016-09-01

Narrow implants are indicated in areas of limited bone width or when grafting is nonviable. However, the reduction of implant diameter may compromise their performance. This study evaluated the reliability of several narrow implant systems under fatigue, after restored with single-unit crowns. Narrow implant systems were divided (n = 18 each), as follows: Astra (ASC); BioHorizons (BSC); Straumann Roxolid (SNC), Intra-Lock (IMC), and Intra-Lock one-piece abutment (ILO). Maxillary central incisor crowns were cemented and subjected to step-stress accelerated life testing in water. Use level probability Weibull curves and reliability for a mission of 100,000 cycles at 130- and 180-N loads (90 % two-sided confidence intervals) were calculated. Scanning electron microscopy was used for fractography. Reliability for 100,000 cycles at 130 N was ∼99 % in group ASC, ∼99 % in BSC, ∼96 % in SNC, ∼99 % in IMC, and ∼100 % in ILO. At 180 N, reliability of ∼34 % resulted for the ASC group, ∼91 % for BSC, ∼53 % for SNC, ∼70 % for IMC, and ∼99 % for ILO. Abutment screw fracture was the main failure mode for all groups. Reliability was not different between systems for 100,000 cycles at the 130-N load. A significant decrease was observed at the 180-N load for ASC, SNC, and IMC, whereas it was maintained for BSC and ILO. The investigated narrow implants presented mechanical performance under fatigue that suggests their safe use as single crowns in the anterior region.

Evaluation of ensemble forecast uncertainty using a new proper score: application to medium-range and seasonal forecasts

NASA Astrophysics Data System (ADS)

Christensen, Hannah; Moroz, Irene; Palmer, Tim

2015-04-01

Forecast verification is important across scientific disciplines as it provides a framework for evaluating the performance of a forecasting system. In the atmospheric sciences, probabilistic skill scores are often used for verification as they provide a way of unambiguously ranking the performance of different probabilistic forecasts. In order to be useful, a skill score must be proper -- it must encourage honesty in the forecaster, and reward forecasts which are reliable and which have good resolution. A new score, the Error-spread Score (ES), is proposed which is particularly suitable for evaluation of ensemble forecasts. It is formulated with respect to the moments of the forecast. The ES is confirmed to be a proper score, and is therefore sensitive to both resolution and reliability. The ES is tested on forecasts made using the Lorenz '96 system, and found to be useful for summarising the skill of the forecasts. The European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble prediction system (EPS) is evaluated using the ES. Its performance is compared to a perfect statistical probabilistic forecast -- the ECMWF high resolution deterministic forecast dressed with the observed error distribution. This generates a forecast that is perfectly reliable if considered over all time, but which does not vary from day to day with the predictability of the atmospheric flow. The ES distinguishes between the dynamically reliable EPS forecasts and the statically reliable dressed deterministic forecasts. Other skill scores are tested and found to be comparatively insensitive to this desirable forecast quality. The ES is used to evaluate seasonal range ensemble forecasts made with the ECMWF System 4. The ensemble forecasts are found to be skilful when compared with climatological or persistence forecasts, though this skill is dependent on region and time of year.

Advanced Launch System Multi-Path Redundant Avionics Architecture Analysis and Characterization

NASA Technical Reports Server (NTRS)

Baker, Robert L.

1993-01-01

The objective of the Multi-Path Redundant Avionics Suite (MPRAS) program is the development of a set of avionic architectural modules which will be applicable to the family of launch vehicles required to support the Advanced Launch System (ALS). To enable ALS cost/performance requirements to be met, the MPRAS must support autonomy, maintenance, and testability capabilities which exceed those present in conventional launch vehicles. The multi-path redundant or fault tolerance characteristics of the MPRAS are necessary to offset a reduction in avionics reliability due to the increased complexity needed to support these new cost reduction and performance capabilities and to meet avionics reliability requirements which will provide cost-effective reductions in overall ALS recurring costs. A complex, real-time distributed computing system is needed to meet the ALS avionics system requirements. General Dynamics, Boeing Aerospace, and C.S. Draper Laboratory have proposed system architectures as candidates for the ALS MPRAS. The purpose of this document is to report the results of independent performance and reliability characterization and assessment analyses of each proposed candidate architecture and qualitative assessments of testability, maintainability, and fault tolerance mechanisms. These independent analyses were conducted as part of the MPRAS Part 2 program and were carried under NASA Langley Research Contract NAS1-17964, Task Assignment 28.

Decentralized control

NASA Technical Reports Server (NTRS)

Steffen, Chris

1990-01-01

An overview of the time-delay problem and the reliability problem which arise in trying to perform robotic construction operations at a remote space location are presented. The effects of the time-delay upon the control system design will be itemized. A high level overview of a decentralized method of control which is expected to perform better than the centralized approach in solving the time-delay problem is given. The lower level, decentralized, autonomous, Troter Move-Bar algorithm is also presented (Troters are coordinated independent robots). The solution of the reliability problem is connected to adding redundancy to the system. One method of adding redundancy is given.

DPSSL and FL pumps based on 980-nm telecom pump laser technology: changing the industry

NASA Astrophysics Data System (ADS)

Lichtenstein, Norbert; Schmidt, Berthold E.; Fily, Arnaud; Weiss, Stefan; Arlt, Sebastian; Pawlik, Susanne; Sverdlov, Boris; Muller, Jurgen; Harder, Christoph S.

2004-06-01

Diode-pumped solid state laser (DPSSL) and fiber laser (FL) are believed to become the dominant systems of very high power lasers in the industrial environment. Today, ranging from 100 W to 5 - 10 kW in light output power, their field of applications spread from biomedical and sensoring to material processing. Key driver for the wide spread of such systems is a competitive ratio of cost, performance and reliability. Enabling high power, highly reliable broad-area laser diodes and laser diode bars with excellent performance at the relevant wavelengths can further optimize this ratio. In this communication we present, that this can be achieved by leveraging the tremendous improvements in reliability and performance together with the high volume, low cost manufacturing areas established during the "telecom-bubble." From today's generations of 980-nm narrow-stripe laser diodes 1.8 W of maximum CW output power can be obtained fulfilling the stringent telecom reliability at operating conditions. Single-emitter broad-area lasers deliver in excess of 11 W CW while from similar 940-nm laser bars more than 160 W output power (CW) can be obtained at 200 A. In addition, introducing telecom-grade AuSn-solder mounting technology on expansion matched subassemblies enables excellent reliability performance. Degradation rates of less than 1% over 1000 h at 60 A are observed for both 808-nm and 940-nm laser bars even under harsh intermittent operation conditions.

A flight test of laminar flow control leading-edge systems

NASA Technical Reports Server (NTRS)

Fischer, M. C.; Wright, A. S., Jr.; Wagner, R. D.

1983-01-01

NASA's program for development of a laminar flow technology base for application to commercial transports has made significant progress since its inception in 1976. Current efforts are focused on development of practical reliable systems for the leading-edge region where the most difficult problems in applying laminar flow exist. Practical solutions to these problems will remove many concerns about the ultimate practicality of laminar flow. To address these issues, two contractors performed studies, conducted development tests, and designed and fabricated fully functional leading-edge test articles for installation on the NASA JetStar aircraft. Systems evaluation and performance testing will be conducted to thoroughly evaluate all system capabilities and characteristics. A simulated airline service flight test program will be performed to obtain the operational sensitivity, maintenance, and reliability data needed to establish that practical solutions exist for the difficult leading-edge area of a future commercial transport employing laminar flow control.

High-reliability gas-turbine combined-cycle development program: Phase II. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hecht, K.G.; Sanderson, R.A.; Smith, M.J.

This three-volume report presents the results of Phase II of the multiphase EPRI-sponsored High-Reliability Gas Turbine Combined-Cycle Development Program whose goal is to achieve a highly reliable gas turbine combined-cycle power plant, available by the mid-1980s, which would be an economically attractive baseload generation alternative for the electric utility industry. The Phase II program objective was to prepare the preliminary design of this power plant. This volume presents information of the reliability, availability, and maintainability (RAM) analysis of a representative plant and the preliminary design of the gas turbine, the gas turbine ancillaries, and the balance of plant including themore » steam turbine generator. To achieve the program goals, a gas turbine was incorporated which combined proven reliability characteristics with improved performance features. This gas turbine, designated the V84.3, is the result of a cooperative effort between Kraftwerk Union AG and United Technologies Corporation. Gas turbines of similar design operating in Europe under baseload conditions have demonstrated mean time between failures in excess of 40,000 hours. The reliability characteristics of the gas turbine ancillaries and balance-of-plant equipment were improved through system simplification and component redundancy and by selection of component with inherent high reliability. A digital control system was included with logic, communications, sensor redundancy, and mandual backup. An independent condition monitoring and diagnostic system was also included. Program results provide the preliminary design of a gas turbine combined-cycle baseload power plant. This power plant has a predicted mean time between failure of nearly twice the 3000-hour EPRI goal. The cost of added reliability features is offset by improved performance, which results in a comparable specific cost and an 8% lower cost of electricity compared to present market offerings.« less

Power processing for electric propulsion

NASA Technical Reports Server (NTRS)

Finke, R. C.; Herron, B. G.; Gant, G. D.

1975-01-01

The inclusion of electric thruster systems in spacecraft design is considered. The propulsion requirements of such spacecraft dictate a wide range of thruster power levels and operational lifetimes, which must be matched by lightweight, efficient, and reliable thruster power processing systems. Electron bombardment ion thruster requirements are presented, and the performance characteristics of present power processing systems are reviewed. Design philosophies and alternatives in areas such as inverter type, arc protection, and control methods are discussed along with future performance potentials for meeting goals in the areas of power process or weight (10 kg/kW), efficiency (approaching 92 percent), reliability (0.96 for 15,000 hr), and thermal control capability (0.3 to 5 AU).

Application of reliability-centered-maintenance to BWR ECCS motor operator valve performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feltus, M.A.; Choi, Y.A.

1993-01-01

This paper describes the application of reliability-centered maintenance (RCM) methods to plant probabilistic risk assessment (PRA) and safety analyses for four boiling water reactor emergency core cooling systems (ECCSs): (1) high-pressure coolant injection (HPCI); (2) reactor core isolation cooling (RCIC); (3) residual heat removal (RHR); and (4) core spray systems. Reliability-centered maintenance is a system function-based technique for improving a preventive maintenance program that is applied on a component basis. Those components that truly affect plant function are identified, and maintenance tasks are focused on preventing their failures. The RCM evaluation establishes the relevant criteria that preserve system function somore » that an RCM-focused approach can be flexible and dynamic.« less

Performance assessment of the Gash Delta Spate Irrigation System, Sudan

NASA Astrophysics Data System (ADS)

Ghebreamlak, Araya Z.; Tanakamaru, Haruya; Tada, Akio; Adam, Bashir M. Ahmed; Elamin, Khalid A. E.

2018-02-01

The Gash Delta Spate Irrigation System (GDSIS), located in eastern Sudan with a net command area of 100 000 ha (an area currently equipped with irrigation structures), was established in 1924. The land is irrigated every 3 years (3-year rotation) or every 2 years (2-year rotation) so that about 33 000 or 50 000 ha respectively can be cultivated annually. This study deals with assessing the performance of the 3- and 2-year rotation systems using the Monte Carlo simulation. Reliability, which is a measure of how frequently the irrigation water supply satisfies the demand, and vulnerability, which is a measure of the magnitude of failure, were selected as the performance criteria. Combinations of five levels of intake ratio and five levels of irrigation efficiency for the irrigation water supply of each rotation system were analysed. Historical annual flow data of the Gash River for 107 years were fit to several frequency distributions. The Weibull distribution was the best on the basis of the Akaike information criteria and was used for simulating the ensembles of annual river flow. The reliabilities and vulnerabilities of both rotation systems were evaluated at typical values of intake ratio and irrigation efficiency. The results show that (i) the 3-year rotation is more reliable in water supply than the 2-year rotation, (ii) the vulnerability of the 3-year rotation is lower than that of the 2-year rotation and (iii) therefore the 3-year rotation is preferable in the GDSIS. The sensitivities of reliability and vulnerability to changes in intake ratio and irrigation efficiency were also examined.

48 CFR 32.1007 - Administration and payment of performance-based payments.

Code of Federal Regulations, 2010 CFR

2010-10-01

... contractor's experience, performance record, reliability, financial strength, and the adequacy of controls... of performance-based payments. 32.1007 Section 32.1007 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION GENERAL CONTRACTING REQUIREMENTS CONTRACT FINANCING Performance-Based Payments 32.1007...

Delirium diagnosis defined by cluster analysis of symptoms versus diagnosis by DSM and ICD criteria: diagnostic accuracy study.

PubMed

Sepulveda, Esteban; Franco, José G; Trzepacz, Paula T; Gaviria, Ana M; Meagher, David J; Palma, José; Viñuelas, Eva; Grau, Imma; Vilella, Elisabet; de Pablo, Joan

2016-05-26

Information on validity and reliability of delirium criteria is necessary for clinicians, researchers, and further developments of DSM or ICD. We compare four DSM and ICD delirium diagnostic criteria versions, which were developed by consensus of experts, with a phenomenology-based natural diagnosis delineated using cluster analysis of delirium features in a sample with a high prevalence of dementia. We also measured inter-rater reliability of each system when applied by two evaluators from distinct disciplines. Cross-sectional analysis of 200 consecutive patients admitted to a skilled nursing facility, independently assessed within 24-48 h after admission with the Delirium Rating Scale-Revised-98 (DRS-R98) and for DSM-III-R, DSM-IV, DSM-5, and ICD-10 criteria for delirium. Cluster analysis (CA) delineated natural delirium and nondelirium reference groups using DRS-R98 items and then diagnostic systems' performance were evaluated against the CA-defined groups using logistic regression and crosstabs for discriminant analysis (sensitivity, specificity, percentage of subjects correctly classified by each diagnostic system and their individual criteria, and performance for each system when excluding each individual criterion are reported). Kappa Index (K) was used to report inter-rater reliability for delirium diagnostic systems and their individual criteria. 117 (58.5 %) patients had preexisting dementia according to the Informant Questionnaire on Cognitive Decline in the Elderly. CA delineated 49 delirium subjects and 151 nondelirium. Against these CA groups, delirium diagnosis accuracy was highest using DSM-III-R (87.5 %) followed closely by DSM-IV (86.0 %), ICD-10 (85.5 %) and DSM-5 (84.5 %). ICD-10 had the highest specificity (96.0 %) but lowest sensitivity (53.1 %). DSM-III-R had the best sensitivity (81.6 %) and the best sensitivity-specificity balance. DSM-5 had the highest inter-rater reliability (K =0.73) while DSM-III-R criteria were the least reliable. Using our CA-defined, phenomenologically-based delirium designations as the reference standard, we found performance discordance among four diagnostic systems when tested in subjects where comorbid dementia was prevalent. The most complex diagnostic systems have higher accuracy and the newer DSM-5 have higher reliability. Our novel phenomenological approach to designing a delirium reference standard may be preferred to guide revisions of diagnostic systems in the future.

Reliability Analysis of Differential Relay as Main Protection Transformer Using Fuzzy Logic Algorithm

NASA Astrophysics Data System (ADS)

Mulyadi, Y.; Sucita, T.; Sumarto; Alpani, M.

2018-02-01

Electricity supply demand is increasing every year. It makes PT. PLN (Persero) is required to provide optimal customer service and satisfaction. Optimal service depends on the performance of the equipment of the power system owned, especially the transformer. Power transformer is an electrical equipment that transforms electricity from high voltage to low voltage or vice versa. However, in the electrical power system, is inseparable from interference included in the transformer. But, the disturbance can be minimized by the protection system. The main protection transformer is differential relays. Differential relays working system using Kirchoff law where inflows equal outflows. If there are excessive currents that interfere then the relays will work. But, the relay can also experience decreased performance. Therefore, this final project aims to analyze the reliability of the differential relay on the transformer in three different substations. Referring to the standard applied by the transmission line protection officer, the differential relay shall have slope characteristics of 30% in the first slope and 80% in the second slope when using two slopes and 80% when using one slope with an instant time and the corresponding ratio. So, the results obtained on the Siemens differential release have a reliable slope characteristic with a value of 30 on the fuzzy logic system. In a while, ABB a differential relay is only 80% reliable because two experiments are not reliable. For the time, all the differential relays are instant with a value of 0.06 on the fuzzy logic system. For ratios, the differential relays ABB have a better value than others brand with a value of 151 on the fuzzy logic system.

Markov modeling and reliability analysis of urea synthesis system of a fertilizer plant

NASA Astrophysics Data System (ADS)

Aggarwal, Anil Kr.; Kumar, Sanjeev; Singh, Vikram; Garg, Tarun Kr.

2015-12-01

This paper deals with the Markov modeling and reliability analysis of urea synthesis system of a fertilizer plant. This system was modeled using Markov birth-death process with the assumption that the failure and repair rates of each subsystem follow exponential distribution. The first-order Chapman-Kolmogorov differential equations are developed with the use of mnemonic rule and these equations are solved with Runga-Kutta fourth-order method. The long-run availability, reliability and mean time between failures are computed for various choices of failure and repair rates of subsystems of the system. The findings of the paper are discussed with the plant personnel to adopt and practice suitable maintenance policies/strategies to enhance the performance of the urea synthesis system of the fertilizer plant.

Generalized approach for identification and evaluation of technology-insertion options for military avionics systems

NASA Astrophysics Data System (ADS)

Harkness, Linda L.; Sjoberg, Eric S.

1996-06-01

The Georgia Tech Research Institute, sponsored by the Warner Robins Air Logistics Center, has developed an approach for efficiently postulating and evaluating methods for extending the life of radars and other avionics systems. The technique identified specific assemblies for potential replacement and evaluates the system level impact, including performance, reliability and life-cycle cost of each action. The initial impetus for this research was the increasing obsolescence of integrated circuits contained in the AN/APG-63 system. The operational life of military electronics is typically in excess of twenty years, which encompasses several generations of IC technology. GTRI has developed a systems approach to inserting modern technology components into older systems based upon identification of those functions which limit the system's performance or reliability and which are cost drivers. The presentation will discuss the above methodology and a technique for evaluating and ranking the different potential system upgrade options.

HRA Aerospace Challenges

NASA Technical Reports Server (NTRS)

DeMott, Diana

2013-01-01

Compared to equipment designed to perform the same function over and over, humans are just not as reliable. Computers and machines perform the same action in the same way repeatedly getting the same result, unless equipment fails or a human interferes. Humans who are supposed to perform the same actions repeatedly often perform them incorrectly due to a variety of issues including: stress, fatigue, illness, lack of training, distraction, acting at the wrong time, not acting when they should, not following procedures, misinterpreting information or inattention to detail. Why not use robots and automatic controls exclusively if human error is so common? In an emergency or off normal situation that the computer, robotic element, or automatic control system is not designed to respond to, the result is failure unless a human can intervene. The human in the loop may be more likely to cause an error, but is also more likely to catch the error and correct it. When it comes to unexpected situations, or performing multiple tasks outside the defined mission parameters, humans are the only viable alternative. Human Reliability Assessments (HRA) identifies ways to improve human performance and reliability and can lead to improvements in systems designed to interact with humans. Understanding the context of the situation that can lead to human errors, which include taking the wrong action, no action or making bad decisions provides additional information to mitigate risks. With improved human reliability comes reduced risk for the overall operation or project.

Automation reliability in unmanned aerial vehicle control: a reliance-compliance model of automation dependence in high workload.

PubMed

Dixon, Stephen R; Wickens, Christopher D

2006-01-01

Two experiments were conducted in which participants navigated a simulated unmanned aerial vehicle (UAV) through a series of mission legs while searching for targets and monitoring system parameters. The goal of the study was to highlight the qualitatively different effects of automation false alarms and misses as they relate to operator compliance and reliance, respectively. Background data suggest that automation false alarms cause reduced compliance, whereas misses cause reduced reliance. In two studies, 32 and 24 participants, including some licensed pilots, performed in-lab UAV simulations that presented the visual world and collected dependent measures. Results indicated that with the low-reliability aids, false alarms correlated with poorer performance in the system failure task, whereas misses correlated with poorer performance in the concurrent tasks. Compliance and reliance do appear to be affected by false alarms and misses, respectively, and are relatively independent of each other. Practical implications are that automated aids must be fairly reliable to provide global benefits and that false alarms and misses have qualitatively different effects on performance.

Reliable Decentralized Control of Fuzzy Discrete-Event Systems and a Test Algorithm.

PubMed

Liu, Fuchun; Dziong, Zbigniew

2013-02-01

A framework for decentralized control of fuzzy discrete-event systems (FDESs) has been recently presented to guarantee the achievement of a given specification under the joint control of all local fuzzy supervisors. As a continuation, this paper addresses the reliable decentralized control of FDESs in face of possible failures of some local fuzzy supervisors. Roughly speaking, for an FDES equipped with n local fuzzy supervisors, a decentralized supervisor is called k-reliable (1 ≤ k ≤ n) provided that the control performance will not be degraded even when n - k local fuzzy supervisors fail. A necessary and sufficient condition for the existence of k-reliable decentralized supervisors of FDESs is proposed by introducing the notions of M̃uc-controllability and k-reliable coobservability of fuzzy language. In particular, a polynomial-time algorithm to test the k-reliable coobservability is developed by a constructive methodology, which indicates that the existence of k-reliable decentralized supervisors of FDESs can be checked with a polynomial complexity.

Survey of aircraft electrical power systems

NASA Technical Reports Server (NTRS)

Lee, C. H.; Brandner, J. J.

1972-01-01

Areas investigated include: (1) load analysis; (2) power distribution, conversion techniques and generation; (3) design criteria and performance capabilities of hydraulic and pneumatic systems; (4) system control and protection methods; (5) component and heat transfer systems cooling; and (6) electrical system reliability.

Reliability and validity analysis of the open-source Chinese Foot and Ankle Outcome Score (FAOS).

PubMed

Ling, Samuel K K; Chan, Vincent; Ho, Karen; Ling, Fona; Lui, T H

2017-12-21

Develop the first reliable and validated open-source outcome scoring system in the Chinese language for foot and ankle problems. Translation of the English FAOS into Chinese following regular protocols. First, two forward-translations were created separately, these were then combined into a preliminary version by an expert committee, and was subsequently back-translated into English. The process was repeated until the original and back translations were congruent. This version was then field tested on actual patients who provided feedback for modification. The final Chinese FAOS version was then tested for reliability and validity. Reliability analysis was performed on 20 subjects while validity analysis was performed on 50 subjects. Tools used to validate the Chinese FAOS were the SF36 and Pain Numeric Rating Scale (NRS). Internal consistency between the FAOS subgroups was measured using Cronbach's alpha. Spearman's correlation was calculated between each subgroup in the FAOS, SF36 and NRS. The Chinese FAOS passed both reliability and validity testing; meaning it is reliable, internally consistent and correlates positively with the SF36 and the NRS. The Chinese FAOS is a free, open-source scoring system that can be used to provide a relatively standardised outcome measure for foot and ankle studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

Posturography using the Wii Balance Board™: A feasibility study with healthy adults and adults post-stroke.

PubMed

Llorens, Roberto; Latorre, Jorge; Noé, Enrique; Keshner, Emily A

2016-01-01

Posturography systems that incorporate force platforms are considered to assess balance and postural control with greater sensitivity and objectivity than conventional clinical tests. The Wii Balance Board (WBB) system has been shown to have similar performance characteristics as other force platforms, but with lower cost and size. To determine the validity and reliability of a freely available WBB-based posturography system that combined the WBB with several traditional balance assessments, and to assess the performance of a cohort of stroke individuals with respect to healthy individuals. Healthy subjects and individuals with stroke were recruited. Both groups were assessed using the WBB-based posturography system. Individuals with stroke were also assessed using a laboratory grade posturography system and a battery of clinical tests to determine the concurrent validity of the system. A group of subjects were assessed twice with the WBB-based system to determine its reliability. A total of 144 healthy individuals and 53 individuals with stroke participated in the study. Concurrent validity with another posturography system was moderate to high. Correlations with clinical scales were consistent with previous research. The reliability of the system was excellent in almost all measures. In addition, the system successfully characterized individuals with stroke with respect to the healthy population. The WBB-based posturography system exhibited excellent psychometric properties and sensitivity for identifying balance performance of individuals with stroke in comparison with healthy subjects, which supports feasibility of the system as a clinical tool. Copyright © 2015 Elsevier B.V. All rights reserved.

Reliability Assessment for Low-cost Unmanned Aerial Vehicles

NASA Astrophysics Data System (ADS)

Freeman, Paul Michael

Existing low-cost unmanned aerospace systems are unreliable, and engineers must blend reliability analysis with fault-tolerant control in novel ways. This dissertation introduces the University of Minnesota unmanned aerial vehicle flight research platform, a comprehensive simulation and flight test facility for reliability and fault-tolerance research. An industry-standard reliability assessment technique, the failure modes and effects analysis, is performed for an unmanned aircraft. Particular attention is afforded to the control surface and servo-actuation subsystem. Maintaining effector health is essential for safe flight; failures may lead to loss of control incidents. Failure likelihood, severity, and risk are qualitatively assessed for several effector failure modes. Design changes are recommended to improve aircraft reliability based on this analysis. Most notably, the control surfaces are split, providing independent actuation and dual-redundancy. The simulation models for control surface aerodynamic effects are updated to reflect the split surfaces using a first-principles geometric analysis. The failure modes and effects analysis is extended by using a high-fidelity nonlinear aircraft simulation. A trim state discovery is performed to identify the achievable steady, wings-level flight envelope of the healthy and damaged vehicle. Tolerance of elevator actuator failures is studied using familiar tools from linear systems analysis. This analysis reveals significant inherent performance limitations for candidate adaptive/reconfigurable control algorithms used for the vehicle. Moreover, it demonstrates how these tools can be applied in a design feedback loop to make safety-critical unmanned systems more reliable. Control surface impairments that do occur must be quickly and accurately detected. This dissertation also considers fault detection and identification for an unmanned aerial vehicle using model-based and model-free approaches and applies those algorithms to experimental faulted and unfaulted flight test data. Flight tests are conducted with actuator faults that affect the plant input and sensor faults that affect the vehicle state measurements. A model-based detection strategy is designed and uses robust linear filtering methods to reject exogenous disturbances, e.g. wind, while providing robustness to model variation. A data-driven algorithm is developed to operate exclusively on raw flight test data without physical model knowledge. The fault detection and identification performance of these complementary but different methods is compared. Together, enhanced reliability assessment and multi-pronged fault detection and identification techniques can help to bring about the next generation of reliable low-cost unmanned aircraft.

Enhanced Component Performance Study: Motor-Driven Pumps 1998–2014

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schroeder, John Alton

2016-02-01

This report presents an enhanced performance evaluation of motor-driven pumps at U.S. commercial nuclear power plants. The data used in this study are based on the operating experience failure reports from fiscal year 1998 through 2014 for the component reliability as reported in the Institute of Nuclear Power Operations (INPO) Consolidated Events Database (ICES). The motor-driven pump failure modes considered for standby systems are failure to start, failure to run less than or equal to one hour, and failure to run more than one hour; for normally running systems, the failure modes considered are failure to start and failure tomore » run. An eight hour unreliability estimate is also calculated and trended. The component reliability estimates and the reliability data are trended for the most recent 10-year period while yearly estimates for reliability are provided for the entire active period. Statistically significant increasing trends were identified in pump run hours per reactor year. Statistically significant decreasing trends were identified for standby systems industry-wide frequency of start demands, and run hours per reactor year for runs of less than or equal to one hour.« less

Memorial Hermann: high reliability from board to bedside.

PubMed

Shabot, M Michael; Monroe, Douglas; Inurria, Juan; Garbade, Debbi; France, Anne-Claire

2013-06-01

In 2006 the Memorial Hermann Health System (MHHS), which includes 12 hospitals, began applying principles embraced by high reliability organizations (HROs). Three factors support its HRO journey: (1) aligned organizational structure with transparent management systems and compressed reporting processes; (2) Robust Process Improvement (RPI) with high-reliability interventions; and (3) cultural establishment, sustainment, and evolution. The Quality and Safety strategic plan contains three domains, each with a specific set of measures that provide goals for performance: (1) "Clinical Excellence;" (2) "Do No Harm;" and (3) "Saving Lives," as measured by the Serious Safety Event rate. MHHS uses a uniform approach to performance improvement--RPI, which includes Six Sigma, Lean, and change management, to solve difficult safety and quality problems. The 9 acute care hospitals provide multiple opportunities to integrate high-reliability interventions and best practices across MHHS. For example, MHHS partnered with the Joint Commission Center for Transforming Healthcare in its inaugural project to establish reliable hand hygiene behaviors, which improved MHHS's average hand hygiene compliance rate from 44% to 92% currently. Soon after compliance exceeded 85% at all 12 hospitals, the average rate of central line-associated bloodstream and ventilator-associated pneumonias decreased to essentially zero. MHHS's size and diversity require a disciplined approach to performance improvement and systemwide achievement of measurable success. The most significant cultural change at MHHS has been the expectation for 100% compliance with evidence-based quality measures and 0% incidence of patient harm.

Design optimization of a fuzzy distributed generation (DG) system with multiple renewable energy sources

NASA Astrophysics Data System (ADS)

Ganesan, T.; Elamvazuthi, I.; Shaari, Ku Zilati Ku; Vasant, P.

2012-09-01

The global rise in energy demands brings major obstacles to many energy organizations in providing adequate energy supply. Hence, many techniques to generate cost effective, reliable and environmentally friendly alternative energy source are being explored. One such method is the integration of photovoltaic cells, wind turbine generators and fuel-based generators, included with storage batteries. This sort of power systems are known as distributed generation (DG) power system. However, the application of DG power systems raise certain issues such as cost effectiveness, environmental impact and reliability. The modelling as well as the optimization of this DG power system was successfully performed in the previous work using Particle Swarm Optimization (PSO). The central idea of that work was to minimize cost, minimize emissions and maximize reliability (multi-objective (MO) setting) with respect to the power balance and design requirements. In this work, we introduce a fuzzy model that takes into account the uncertain nature of certain variables in the DG system which are dependent on the weather conditions (such as; the insolation and wind speed profiles). The MO optimization in a fuzzy environment was performed by applying the Hopfield Recurrent Neural Network (HNN). Analysis on the optimized results was then carried out.

TRIDENT 1 third stage motor separation system

NASA Technical Reports Server (NTRS)

Welch, B. H.; Richter, B. J.; Sue, P.

1977-01-01

The third stage engine separation system has shown through test and analysis that it can effectively and reliably perform its function. The weight of the hardware associated with this system is well within the targeted value.

Automation in future air traffic management: effects of decision aid reliability on controller performance and mental workload.

PubMed

Metzger, Ulla; Parasuraman, Raja

2005-01-01

Future air traffic management concepts envisage shared decision-making responsibilities between controllers and pilots, necessitating that controllers be supported by automated decision aids. Even as automation tools are being introduced, however, their impact on the air traffic controller is not well understood. The present experiments examined the effects of an aircraft-to-aircraft conflict decision aid on performance and mental workload of experienced, full-performance level controllers in a simulated Free Flight environment. Performance was examined with both reliable (Experiment 1) and inaccurate automation (Experiment 2). The aid improved controller performance and reduced mental workload when it functioned reliably. However, detection of a particular conflict was better under manual conditions than under automated conditions when the automation was imperfect. Potential or actual applications of the results include the design of automation and procedures for future air traffic control systems.

Reliability Testing of NASA Piezocomposite Actuators

NASA Technical Reports Server (NTRS)

Wilkie, W.; High, J.; Bockman, J.

2002-01-01

NASA Langley Research Center has developed a low-cost piezocomposite actuator which has application for controlling vibrations in large inflatable smart space structures, space telescopes, and high performance aircraft. Tests show the NASA piezocomposite device is capable of producing large, directional, in-plane strains on the order of 2000 parts-per-million peak-to-peak, with no reduction in free-strain performance to 100 million electrical cycles. This paper describes methods, measurements, and preliminary results from our reliability evaluation of the device under externally applied mechanical loads and at various operational temperatures. Tests performed to date show no net reductions in actuation amplitude while the device was moderately loaded through 10 million electrical cycles. Tests were performed at both room temperature and at the maximum operational temperature of the epoxy resin system used in manufacture of the device. Initial indications are that actuator reliability is excellent, with no actuator failures or large net reduction in actuator performance.

Use of Model-Based Design Methods for Enhancing Resiliency Analysis of Unmanned Aerial Vehicles

NASA Astrophysics Data System (ADS)

Knox, Lenora A.

The most common traditional non-functional requirement analysis is reliability. With systems becoming more complex, networked, and adaptive to environmental uncertainties, system resiliency has recently become the non-functional requirement analysis of choice. Analysis of system resiliency has challenges; which include, defining resilience for domain areas, identifying resilience metrics, determining resilience modeling strategies, and understanding how to best integrate the concepts of risk and reliability into resiliency. Formal methods that integrate all of these concepts do not currently exist in specific domain areas. Leveraging RAMSoS, a model-based reliability analysis methodology for Systems of Systems (SoS), we propose an extension that accounts for resiliency analysis through evaluation of mission performance, risk, and cost using multi-criteria decision-making (MCDM) modeling and design trade study variability modeling evaluation techniques. This proposed methodology, coined RAMSoS-RESIL, is applied to a case study in the multi-agent unmanned aerial vehicle (UAV) domain to investigate the potential benefits of a mission architecture where functionality to complete a mission is disseminated across multiple UAVs (distributed) opposed to being contained in a single UAV (monolithic). The case study based research demonstrates proof of concept for the proposed model-based technique and provides sufficient preliminary evidence to conclude which architectural design (distributed vs. monolithic) is most resilient based on insight into mission resilience performance, risk, and cost in addition to the traditional analysis of reliability.

Research on the optimal structure configuration of dither RLG used in skewed redundant INS

NASA Astrophysics Data System (ADS)

Gao, Chunfeng; Wang, Qi; Wei, Guo; Long, Xingwu

2016-05-01

The actual combat effectiveness of weapon equipment is restricted by the performance of Inertial Navigation System (INS), especially in high reliability required situations such as fighter, satellite and submarine. Through the use of skewed sensor geometries, redundant technique has been applied to reduce the cost and improve the reliability of the INS. In this paper, the structure configuration and the inertial sensor characteristics of Skewed Redundant Strapdown Inertial Navigation System (SRSINS) using dithered Ring Laser Gyroscope (RLG) are analyzed. For the dither coupling effects of the dither gyro, the system measurement errors can be amplified either the individual gyro dither frequency is near one another or the structure of the SRSINS is unreasonable. Based on the characteristics of RLG, the research on coupled vibration of dithered RLG in SRSINS is carried out. On the principle of optimal navigation performance, optimal reliability and optimal cost-effectiveness, the comprehensive evaluation scheme of the inertial sensor configuration of SRINS is given.

Parallelized reliability estimation of reconfigurable computer networks

NASA Technical Reports Server (NTRS)

Nicol, David M.; Das, Subhendu; Palumbo, Dan

1990-01-01

A parallelized system, ASSURE, for computing the reliability of embedded avionics flight control systems which are able to reconfigure themselves in the event of failure is described. ASSURE accepts a grammar that describes a reliability semi-Markov state-space. From this it creates a parallel program that simultaneously generates and analyzes the state-space, placing upper and lower bounds on the probability of system failure. ASSURE is implemented on a 32-node Intel iPSC/860, and has achieved high processor efficiencies on real problems. Through a combination of improved algorithms, exploitation of parallelism, and use of an advanced microprocessor architecture, ASSURE has reduced the execution time on substantial problems by a factor of one thousand over previous workstation implementations. Furthermore, ASSURE's parallel execution rate on the iPSC/860 is an order of magnitude faster than its serial execution rate on a Cray-2 supercomputer. While dynamic load balancing is necessary for ASSURE's good performance, it is needed only infrequently; the particular method of load balancing used does not substantially affect performance.

Assessment of fatty degeneration of the gluteal muscles in patients with THA using MRI: reliability and accuracy of the Goutallier and quartile classification systems.

PubMed

Engelken, Florian; Wassilew, Georgi I; Köhlitz, Torsten; Brockhaus, Sebastian; Hamm, Bernd; Perka, Carsten; Diederichs, und Gerd

2014-01-01

The purpose of this study was to quantify the performance of the Goutallier classification for assessing fatty degeneration of the gluteus muscles from magnetic resonance (MR) images and to compare its performance to a newly proposed system. Eighty-four hips with clinical signs of gluteal insufficiency and 50 hips from asymptomatic controls were analyzed using a standard classification system (Goutallier) and a new scoring system (Quartile). Interobserver reliability and intraobserver repeatability were determined, and accuracy was assessed by comparing readers' scores with quantitative estimates of the proportion of intramuscular fat based on MR signal intensities (gold standard). The existing Goutallier classification system and the new Quartile system performed equally well in assessing fatty degeneration of the gluteus muscles, both showing excellent levels of interrater and intrarater agreement. While the Goutallier classification system has the advantage of being widely known, the benefit of the Quartile system is that it is based on more clearly defined grades of fatty degeneration. Copyright © 2014 Elsevier Inc. All rights reserved.

Closed-form solutions of performability. [in computer systems

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1982-01-01

It is noted that if computing system performance is degradable then system evaluation must deal simultaneously with aspects of both performance and reliability. One approach is the evaluation of a system's performability which, relative to a specified performance variable Y, generally requires solution of the probability distribution function of Y. The feasibility of closed-form solutions of performability when Y is continuous are examined. In particular, the modeling of a degradable buffer/multiprocessor system is considered whose performance Y is the (normalized) average throughput rate realized during a bounded interval of time. Employing an approximate decomposition of the model, it is shown that a closed-form solution can indeed be obtained.

The Shuttle processing contractors (SPC) reliability program at the Kennedy Space Center - The real world

NASA Astrophysics Data System (ADS)

McCrea, Terry

The Shuttle Processing Contract (SPC) workforce consists of Lockheed Space Operations Co. as prime contractor, with Grumman, Thiokol Corporation, and Johnson Controls World Services as subcontractors. During the design phase, reliability engineering is instrumental in influencing the development of systems that meet the Shuttle fail-safe program requirements. Reliability engineers accomplish this objective by performing FMEA (failure modes and effects analysis) to identify potential single failure points. When technology, time, or resources do not permit a redesign to eliminate a single failure point, the single failure point information is formatted into a change request and presented to senior management of SPC and NASA for risk acceptance. In parallel with the FMEA, safety engineering conducts a hazard analysis to assure that potential hazards to personnel are assessed. The combined effort (FMEA and hazard analysis) is published as a system assurance analysis. Special ground rules and techniques are developed to perform and present the analysis. The reliability program at KSC is vigorously pursued, and has been extremely successful. The ground support equipment and facilities used to launch and land the Space Shuttle maintain an excellent reliability record.

Anti-aliasing filter design on spaceborne digital receiver

NASA Astrophysics Data System (ADS)

Yu, Danru; Zhao, Chonghui

2009-12-01

In recent years, with the development of satellite observation technologies, more and more active remote sensing technologies are adopted in spaceborne system. The spaceborne precipitation radar will depend heavily on high performance digital processing to collect meaningful rain echo data. It will increase the complexity of the spaceborne system and need high-performance and reliable digital receiver. This paper analyzes the frequency aliasing in the intermediate frequency signal sampling of digital down conversion in spaceborne radar, and gives an effective digital filter. By analysis and calculation, we choose reasonable parameters of the half-band filters to suppress the frequency aliasing on DDC. Compared with traditional filter, the FPGA resources cost in our system are reduced by over 50%. This can effectively reduce the complexity in the spaceborne digital receiver and improve the reliability of system.

Upgrades to the ISS Water Recovery System

NASA Technical Reports Server (NTRS)

Kayatin, Matthew J.; Carter, Donald L.; Schunk, Richard G.; Pruitt, Jennifer M.

2016-01-01

The International Space Station Water Recovery System (WRS) is comprised of the Water Processor Assembly (WPA) and the Urine Processor Assembly (UPA). The WRS produces potable water from a combination of crew urine (first processed through the UPA), crew latent, and Sabatier product water. Though the WRS has performed well since operations began in November 2008, several modifications have been identified to improve the overall system performance. These modifications can reduce resupply and improve overall system reliability, which is beneficial for the ongoing ISS mission as well as for future NASA manned missions. The following paper details efforts to reduce the resupply mass of the WPA Multifiltration Bed, develop improved catalyst for the WPA Catalytic Reactor, evaluate optimum operation of UPA through parametric testing, and improve reliability of the UPA fluids pump and Distillation Assembly.

Reliability of the Cooking Task in adults with acquired brain injury.

PubMed

Poncet, Frédérique; Swaine, Bonnie; Taillefer, Chantal; Lamoureux, Julie; Pradat-Diehl, Pascale; Chevignard, Mathilde

2015-01-01

Acquired brain injury (ABI) often leads to deficits in executive functioning (EF) responsible for severe and long-standing disabilities in daily life activities. The Cooking Task is an ecological and valid test of EF involving multi-tasking in a real environment. Given its complex scoring system, it is important to establish the tool's reliability. The objective of the study was to examine the reliability of the Cooking Task (internal consistency, inter-rater and test-retest reliability). A total of 160 patients with ABI (113 men, mean age 37 years, SD = 14.3) were tested using the Cooking Task. For test-retest reliability, patients were assessed by the same rater on two occasions (mean interval 11 days) while two raters independently and simultaneously observed and scored patients' performances to estimate inter-rater reliability. Internal consistency was high for the global scale (Cronbach α = .74). Inter-rater reliability (n = 66) for total errors was also high (ICC = .93), however the test-retest reliability (n = 11) was poor (ICC = .36). In general the Cooking Task appears to be a reliable tool. The low test-retest results were expected given the importance of EF in the performance of novel tasks.

On reliable control system designs. Ph.D. Thesis; [actuators

NASA Technical Reports Server (NTRS)

Birdwell, J. D.

1978-01-01

A mathematical model for use in the design of reliable multivariable control systems is discussed with special emphasis on actuator failures and necessary actuator redundancy levels. The model consists of a linear time invariant discrete time dynamical system. Configuration changes in the system dynamics are governed by a Markov chain that includes transition probabilities from one configuration state to another. The performance index is a standard quadratic cost functional, over an infinite time interval. The actual system configuration can be deduced with a one step delay. The calculation of the optimal control law requires the solution of a set of highly coupled Riccati-like matrix difference equations. Results can be used for off-line studies relating the open loop dynamics, required performance, actuator mean time to failure, and functional or identical actuator redundancy, with and without feedback gain reconfiguration strategies.

Upgrades to the ISS Water Recovery System

NASA Technical Reports Server (NTRS)

Kayatin, Matthew; Takada, Kevin; Carter, Layne

2017-01-01

The ISS Water Recovery System (WRS) includes the Water Processor Assembly (WPA) and the Urine Processor Assembly (UPA). The WRS produces potable water from a combination of crew urine (first processed through the UPA), crew latent, and Sabatier product water. Though the WRS has performed well since operations began in November 2008, several modifications have been identified to improve the overall system performance. These modifications can reduce resupply and improve overall system reliability, which is beneficial for the ongoing ISS mission as well as for future NASA manned missions. The following paper details efforts to improve the WPA through the use of Reverse Osmosis technology to reduce the resupply mass of the WPA Multifiltration Bed and improved catalyst for the WPA Catalytic Reactor to reduce the operational temperature and pressure. For the UPA, this paper discusses progress on various concepts for improving the reliability of the UPA, including the implementation of a more reliable drive belt, improved methods for managing condensate in the stationary bowl of the Distillation Assembly, deleting the Separator Plumbing Assembly, and evaluating upgrades to the UPA vacuum pump.

Stability, reliability and cross-mode correlations of tests in a recommended 8-minute performance assessment battery

NASA Technical Reports Server (NTRS)

Wilkes, R. L.; Kennedy, R. S.; Dunlap, W. P.; Lane, N. E.

1986-01-01

A need exists for an automated performance test system to study drugs, agents, treatments, and stresses of interest to the aviation, space, and environmental medical community. The purpose of this present study is to evaluate tests for inclusion in the NASA-sponsored Automated Performance Test System (APTS). Twenty-one subjects were tested over 10 replications with tests previously identified as good candidates for repeated-measure research. The tests were concurrently administered in paper-and-pencil and microcomputer modes. Performance scores for the two modes were compared. Data from trials 1 to 10 were examined for indications of test stability and reliability. Nine of the ten APT system tests achieved stability. Reliabilities were generally high. Cross-correlation of microbased tests with traditional paper-and-pencil versions revealed similarity of content within tests in the different modes, and implied at least three cognition and two motor factors. This protable, inexpensive, rugged, computerized battery of tests is recommended for use in repeated-measures studies of environmental and drug effects on performance. Identification of other tests compatible with microcomputer testing and potentially capable of tapping previously unidentified factors is recommended. Documentation of APTS sensitivity to environmental agents is available for more than a dozen facilities and is reported briefly. Continuation of such validation remains critical in establishing the efficacy of APTS tests.

Analysis of strain gage reliability in F-100 jet engine testing at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Holanda, R.

1983-01-01

A reliability analysis was performed on 64 strain gage systems mounted on the 3 rotor stages of the fan of a YF-100 engine. The strain gages were used in a 65 hour fan flutter research program which included about 5 hours of blade flutter. The analysis was part of a reliability improvement program. Eighty-four percent of the strain gages survived the test and performed satisfactorily. A post test analysis determined most failure causes. Five failures were caused by open circuits, three failed gages showed elevated circuit resistance, and one gage circuit was grounded. One failure was undetermined.

Reliability based design optimization: Formulations and methodologies

NASA Astrophysics Data System (ADS)

Agarwal, Harish

Modern products ranging from simple components to complex systems should be designed to be optimal and reliable. The challenge of modern engineering is to ensure that manufacturing costs are reduced and design cycle times are minimized while achieving requirements for performance and reliability. If the market for the product is competitive, improved quality and reliability can generate very strong competitive advantages. Simulation based design plays an important role in designing almost any kind of automotive, aerospace, and consumer products under these competitive conditions. Single discipline simulations used for analysis are being coupled together to create complex coupled simulation tools. This investigation focuses on the development of efficient and robust methodologies for reliability based design optimization in a simulation based design environment. Original contributions of this research are the development of a novel efficient and robust unilevel methodology for reliability based design optimization, the development of an innovative decoupled reliability based design optimization methodology, the application of homotopy techniques in unilevel reliability based design optimization methodology, and the development of a new framework for reliability based design optimization under epistemic uncertainty. The unilevel methodology for reliability based design optimization is shown to be mathematically equivalent to the traditional nested formulation. Numerical test problems show that the unilevel methodology can reduce computational cost by at least 50% as compared to the nested approach. The decoupled reliability based design optimization methodology is an approximate technique to obtain consistent reliable designs at lesser computational expense. Test problems show that the methodology is computationally efficient compared to the nested approach. A framework for performing reliability based design optimization under epistemic uncertainty is also developed. A trust region managed sequential approximate optimization methodology is employed for this purpose. Results from numerical test studies indicate that the methodology can be used for performing design optimization under severe uncertainty.

Reliable and valid tools for measuring surgeons' teaching performance: residents' vs. self evaluation.

PubMed

Boerebach, Benjamin C M; Arah, Onyebuchi A; Busch, Olivier R C; Lombarts, Kiki M J M H

2012-01-01

In surgical education, there is a need for educational performance evaluation tools that yield reliable and valid data. This paper describes the development and validation of robust evaluation tools that provide surgeons with insight into their clinical teaching performance. We investigated (1) the reliability and validity of 2 tools for evaluating the teaching performance of attending surgeons in residency training programs, and (2) whether surgeons' self evaluation correlated with the residents' evaluation of those surgeons. We surveyed 343 surgeons and 320 residents as part of a multicenter prospective cohort study of faculty teaching performance in residency training programs. The reliability and validity of the SETQ (System for Evaluation Teaching Qualities) tools were studied using standard psychometric techniques. We then estimated the correlations between residents' and surgeons' evaluations. The response rate was 87% among surgeons and 84% among residents, yielding 2625 residents' evaluations and 302 self evaluations. The SETQ tools yielded reliable and valid data on 5 domains of surgical teaching performance, namely, learning climate, professional attitude towards residents, communication of goals, evaluation of residents, and feedback. The correlations between surgeons' self and residents' evaluations were low, with coefficients ranging from 0.03 for evaluation of residents to 0.18 for communication of goals. The SETQ tools for the evaluation of surgeons' teaching performance appear to yield reliable and valid data. The lack of strong correlations between surgeons' self and residents' evaluations suggest the need for using external feedback sources in informed self evaluation of surgeons. Copyright © 2012 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Taguchi Based Performance and Reliability Improvement of an Ion Chamber Amplifier for Enhanced Nuclear Reactor Safety

NASA Astrophysics Data System (ADS)

Kulkarni, R. D.; Agarwal, Vivek

2008-08-01

An ion chamber amplifier (ICA) is used as a safety device for neutronic power (flux) measurement in regulation and protection systems of nuclear reactors. Therefore, performance reliability of an ICA is an important issue. Appropriate quality engineering is essential to achieve a robust design and performance of the ICA circuit. It is observed that the low input bias current operational amplifiers used in the input stage of the ICA circuit are the most critical devices for proper functioning of the ICA. They are very sensitive to the gamma radiation present in their close vicinity. Therefore, the response of the ICA deteriorates with exposure to gamma radiation resulting in a decrease in the overall reliability, unless desired performance is ensured under all conditions. This paper presents a performance enhancement scheme for an ICA operated in the nuclear environment. The Taguchi method, which is a proven technique for reliability enhancement, has been used in this work. It is demonstrated that if a statistical, optimal design approach, like the Taguchi method is used, the cost of high quality and reliability may be brought down drastically. The complete methodology and statistical calculations involved are presented, as are the experimental and simulation results to arrive at a robust design of the ICA.

Validity and reliability of Optojump photoelectric cells for estimating vertical jump height.

PubMed

Glatthorn, Julia F; Gouge, Sylvain; Nussbaumer, Silvio; Stauffacher, Simone; Impellizzeri, Franco M; Maffiuletti, Nicola A

2011-02-01

Vertical jump is one of the most prevalent acts performed in several sport activities. It is therefore important to ensure that the measurements of vertical jump height made as a part of research or athlete support work have adequate validity and reliability. The aim of this study was to evaluate concurrent validity and reliability of the Optojump photocell system (Microgate, Bolzano, Italy) with force plate measurements for estimating vertical jump height. Twenty subjects were asked to perform maximal squat jumps and countermovement jumps, and flight time-derived jump heights obtained by the force plate were compared with those provided by Optojump, to examine its concurrent (criterion-related) validity (study 1). Twenty other subjects completed the same jump series on 2 different occasions (separated by 1 week), and jump heights of session 1 were compared with session 2, to investigate test-retest reliability of the Optojump system (study 2). Intraclass correlation coefficients (ICCs) for validity were very high (0.997-0.998), even if a systematic difference was consistently observed between force plate and Optojump (-1.06 cm; p < 0.001). Test-retest reliability of the Optojump system was excellent, with ICCs ranging from 0.982 to 0.989, low coefficients of variation (2.7%), and low random errors (±2.81 cm). The Optojump photocell system demonstrated strong concurrent validity and excellent test-retest reliability for the estimation of vertical jump height. We propose the following equation that allows force plate and Optojump results to be used interchangeably: force plate jump height (cm) = 1.02 × Optojump jump height + 0.29. In conclusion, the use of Optojump photoelectric cells is legitimate for field-based assessments of vertical jump height.

Operational present status and reliability analysis of the upgraded EAST cryogenic system

NASA Astrophysics Data System (ADS)

Zhou, Z. W.; Y Zhang, Q.; Lu, X. F.; Hu, L. B.; Zhu, P.

2017-12-01

Since the first commissioning in 2005, the cryogenic system for EAST (Experimental Advanced Superconducting Tokamak) has been cooled down and warmed up for thirteen experimental campaigns. In order to promote the refrigeration efficiencies and reliability, the EAST cryogenic system was upgraded gradually with new helium screw compressors and new dynamic gas bearing helium turbine expanders with eddy current brake to improve the original poor mechanical and operational performance from 2012 to 2015. Then the totally upgraded cryogenic system was put into operation in the eleventh cool-down experiment, and has been operated for the latest several experimental campaigns. The upgraded system has successfully coped with various normal operational modes during cool-down and 4.5 K steady-state operation under pulsed heat load from the tokamak as well as the abnormal fault modes including turbines protection stop. In this paper, the upgraded EAST cryogenic system including its functional analysis and new cryogenic control networks will be presented in detail. Also, its operational present status in the latest cool-down experiments will be presented and the system reliability will be analyzed, which shows a high reliability and low fault rate after upgrade. In the end, some future necessary work to meet the higher reliability requirement for future uninterrupted long-term experimental operation will also be proposed.

Intra- and inter-observer reliability of ten major histological scoring systems used for the evaluation of in vivo cartilage repair.

PubMed

Bonasia, Davide Edoardo; Marmotti, Antongiulio; Massa, Alessandro Domenico Felice; Ferro, Andrea; Blonna, Davide; Castoldi, Filippo; Rossi, Roberto

2015-09-01

In the last two decades, many surgical techniques have been described for articular cartilage repair. Reliable histological scoring systems are fundamental tools to evaluate new procedures. Several histological scoring systems have been described, and these can be divided in elementary and comprehensive scores, according to the number of sub-items. The aim of this study was to test the inter- and intra-observer reliability of ten main scores used for the histological evaluation of in vivo cartilage repair. The authors tested the starting hypothesis that elementary scores would show superior intra- and inter-observer reliability compared with comprehensive scores. Fifty histological sections obtained from the trochlea of New Zealand Rabbit and stained with Safranin-O fast green were used. The histological sections were analysed by 4 observers: 2 experienced in cartilage histology and 2 inexperienced. Histological evaluations were performed at time 1 and time 2, separated by a 30-day interval. The following scores were used: Mankin, O'Driscoll, Pineda, Wakitani, Fortier, Selleres, ICRS, ICRSII, Oswestry (OsScore) and modified O'Driscoll. Intra- and inter-observer reliability were evaluated for each score. In addition, the pavement-ceiling effect and the Bland-Altman Coefficient of Repeatability were then evaluated for each sub-item of every score. Intra-observer reliability was high for all observers in every score, even though the reliability was significantly lower for non-expert observers compared with expert counterparts. In terms of Coefficient of Repeatability, some scores performed better (O'Driscoll, Modified O'Driscoll and ICRSII) than others (Fortier, Seller). Inter-observer reliability was high for all observers in every score, but significantly lower for non-expert compared with expert observers. In expert hands, all the scores showed high intra- and inter-observer reliability, independently of the complexity. Although every score has advantages and disadvantages, ICRSII, O'Driscoll and Modified O'Driscoll scores should be preferred for the evaluation of in vivo cartilage repair in animal models.

Care 3 phase 2 report, maintenance manual

NASA Technical Reports Server (NTRS)

Bryant, L. A.; Stiffler, J. J.

1982-01-01

CARE 3 (Computer-Aided Reliability Estimation, version three) is a computer program designed to help estimate the reliability of complex, redundant systems. Although the program can model a wide variety of redundant structures, it was developed specifically for fault-tolerant avionics systems--systems distinguished by the need for extremely reliable performance since a system failure could well result in the loss of human life. It substantially generalizes the class of redundant configurations that could be accommodated, and includes a coverage model to determine the various coverage probabilities as a function of the applicable fault recovery mechanisms (detection delay, diagnostic scheduling interval, isolation and recovery delay, etc.). CARE 3 further generalizes the class of system structures that can be modeled and greatly expands the coverage model to take into account such effects as intermittent and transient faults, latent faults, error propagation, etc.

Measurement-based reliability/performability models

NASA Technical Reports Server (NTRS)

Hsueh, Mei-Chen

1987-01-01

Measurement-based models based on real error-data collected on a multiprocessor system are described. Model development from the raw error-data to the estimation of cumulative reward is also described. A workload/reliability model is developed based on low-level error and resource usage data collected on an IBM 3081 system during its normal operation in order to evaluate the resource usage/error/recovery process in a large mainframe system. Thus, both normal and erroneous behavior of the system are modeled. The results provide an understanding of the different types of errors and recovery processes. The measured data show that the holding times in key operational and error states are not simple exponentials and that a semi-Markov process is necessary to model the system behavior. A sensitivity analysis is performed to investigate the significance of using a semi-Markov process, as opposed to a Markov process, to model the measured system.

The Case for Modular Redundancy in Large-Scale High Performance Computing Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engelmann, Christian; Ong, Hong Hoe; Scott, Stephen L

2009-01-01

Recent investigations into resilience of large-scale high-performance computing (HPC) systems showed a continuous trend of decreasing reliability and availability. Newly installed systems have a lower mean-time to failure (MTTF) and a higher mean-time to recover (MTTR) than their predecessors. Modular redundancy is being used in many mission critical systems today to provide for resilience, such as for aerospace and command \\& control systems. The primary argument against modular redundancy for resilience in HPC has always been that the capability of a HPC system, and respective return on investment, would be significantly reduced. We argue that modular redundancy can significantly increasemore » compute node availability as it removes the impact of scale from single compute node MTTR. We further argue that single compute nodes can be much less reliable, and therefore less expensive, and still be highly available, if their MTTR/MTTF ratio is maintained.« less

Performance variation in motor imagery brain-computer interface: a brief review.

PubMed

Ahn, Minkyu; Jun, Sung Chan

2015-03-30

Brain-computer interface (BCI) technology has attracted significant attention over recent decades, and has made remarkable progress. However, BCI still faces a critical hurdle, in that performance varies greatly across and even within subjects, an obstacle that degrades the reliability of BCI systems. Understanding the causes of these problems is important if we are to create more stable systems. In this short review, we report the most recent studies and findings on performance variation, especially in motor imagery-based BCI, which has found that low-performance groups have a less-developed brain network that is incapable of motor imagery. Further, psychological and physiological states influence performance variation within subjects. We propose a possible strategic approach to deal with this variation, which may contribute to improving the reliability of BCI. In addition, the limitations of current work and opportunities for future studies are discussed. Copyright © 2015 Elsevier B.V. All rights reserved.

Reliability Considerations of ULP Scaled CMOS in Spacecraft Systems

NASA Technical Reports Server (NTRS)

White, Mark; MacNeal, Kristen; Cooper, Mark

2012-01-01

NASA, the aerospace community, and other high reliability (hi-rel) users of advanced microelectronic products face many challenges as technology continues to scale into the deep sub-micron region. Decreasing the feature size of CMOS devices not only allows more components to be placed on a single chip, but it increases performance by allowing faster switching (or clock) speeds with reduced power compared to larger scaled devices. Higher performance, and lower operating and stand-by power characteristics of Ultra-Low Power (ULP) microelectronics are not only desirable, but also necessary to meet low power consumption design goals of critical spacecraft systems. The integration of these components in such systems, however, must be balanced with the overall risk tolerance of the project.

Illustrated structural application of universal first-order reliability method

NASA Technical Reports Server (NTRS)

Verderaime, V.

1994-01-01

The general application of the proposed first-order reliability method was achieved through the universal normalization of engineering probability distribution data. The method superimposes prevailing deterministic techniques and practices on the first-order reliability method to surmount deficiencies of the deterministic method and provide benefits of reliability techniques and predictions. A reliability design factor is derived from the reliability criterion to satisfy a specified reliability and is analogous to the deterministic safety factor. Its application is numerically illustrated on several practical structural design and verification cases with interesting results and insights. Two concepts of reliability selection criteria are suggested. Though the method was developed to support affordable structures for access to space, the method should also be applicable for most high-performance air and surface transportation systems.

Stochastic modelling of the hydrologic operation of rainwater harvesting systems

NASA Astrophysics Data System (ADS)

Guo, Rui; Guo, Yiping

2018-07-01

Rainwater harvesting (RWH) systems are an effective low impact development practice that provides both water supply and runoff reduction benefits. A stochastic modelling approach is proposed in this paper to quantify the water supply reliability and stormwater capture efficiency of RWH systems. The input rainfall series is represented as a marked Poisson process and two typical water use patterns are analytically described. The stochastic mass balance equation is solved analytically, and based on this, explicit expressions relating system performance to system characteristics are derived. The performances of a wide variety of RWH systems located in five representative climatic regions of the United States are examined using the newly derived analytical equations. Close agreements between analytical and continuous simulation results are shown for all the compared cases. In addition, an analytical equation is obtained expressing the required storage size as a function of the desired water supply reliability, average water use rate, as well as rainfall and catchment characteristics. The equations developed herein constitute a convenient and effective tool for sizing RWH systems and evaluating their performances.

High-reliability computing for the smarter planet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, Heather M; Graham, Paul; Manuzzato, Andrea

2010-01-01

The geometric rate of improvement of transistor size and integrated circuit performance, known as Moore's Law, has been an engine of growth for our economy, enabling new products and services, creating new value and wealth, increasing safety, and removing menial tasks from our daily lives. Affordable, highly integrated components have enabled both life-saving technologies and rich entertainment applications. Anti-lock brakes, insulin monitors, and GPS-enabled emergency response systems save lives. Cell phones, internet appliances, virtual worlds, realistic video games, and mp3 players enrich our lives and connect us together. Over the past 40 years of silicon scaling, the increasing capabilities ofmore » inexpensive computation have transformed our society through automation and ubiquitous communications. In this paper, we will present the concept of the smarter planet, how reliability failures affect current systems, and methods that can be used to increase the reliable adoption of new automation in the future. We will illustrate these issues using a number of different electronic devices in a couple of different scenarios. Recently IBM has been presenting the idea of a 'smarter planet.' In smarter planet documents, IBM discusses increased computer automation of roadways, banking, healthcare, and infrastructure, as automation could create more efficient systems. A necessary component of the smarter planet concept is to ensure that these new systems have very high reliability. Even extremely rare reliability problems can easily escalate to problematic scenarios when implemented at very large scales. For life-critical systems, such as automobiles, infrastructure, medical implantables, and avionic systems, unmitigated failures could be dangerous. As more automation moves into these types of critical systems, reliability failures will need to be managed. As computer automation continues to increase in our society, the need for greater radiation reliability is necessary. Already critical infrastructure is failing too frequently. In this paper, we will introduce the Cross-Layer Reliability concept for designing more reliable computer systems.« less

Optimizing digital 8mm drive performance

NASA Technical Reports Server (NTRS)

Schadegg, Gerry

1993-01-01

The experience of attaching over 350,000 digital 8mm drives to 85-plus system platforms has uncovered many factors which can reduce cartridge capacity or drive throughput, reduce reliability, affect cartridge archivability and actually shorten drive life. Some are unique to an installation. Others result from how the system is set up to talk to the drive. Many stem from how applications use the drive, the work load that's present, the kind of media used and, very important, the kind of cleaning program in place. Digital 8mm drives record data at densities that rival those of disk technology. Even with technology this advanced, they are extremely robust and, given proper usage, care and media, should reward the user with a long productive life. The 8mm drive will give its best performance using high-quality 'data grade' media. Even though it costs more, good 'data grade' media can sustain the reliability and rigorous needs of a data storage environment and, with proper care, give users an archival life of 30 years or more. Various factors, taken individually, may not necessarily produce performance or reliability problems. Taken in combination, their effects can compound, resulting in rapid reductions in a drive's serviceable life, cartridge capacity, or drive performance. The key to managing media is determining the importance one places upon their recorded data and, subsequently, setting media usage guidelines that can deliver data reliability. Various options one can implement to optimize digital 8mm drive performance are explored.

A Method to Predict the Reliability of Military Ground Vehicles Using High Performance Computing

DTIC Science & Technology

2006-11-01

Krayterman U.S. Army RDECOM-TARDEC Warren, MI 48397 K.K. Choi, Ed Hardee University of Iowa Coralville , IA 52242 Byeng D. Youn Michigan...University of Iowa , performed an optimization of the design for an A-arm on a military ground vehicle (a Stryker), using no sources of uncertainty...LSF for the queueing system. 3.3 Reliability/Fatigue Analysis software We used several pieces of propriety code from the University of Iowa

Turbine Performance Optimization Task Status

NASA Technical Reports Server (NTRS)

Griffin, Lisa W.; Turner, James E. (Technical Monitor)

2001-01-01

Capability to optimize for turbine performance and accurately predict unsteady loads will allow for increased reliability, Isp, and thrust-to-weight. The development of a fast, accurate aerodynamic design, analysis, and optimization system is required.

High-reliability gas-turbine combined-cycle development program: Phase II, Volume 3. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hecht, K.G.; Sanderson, R.A.; Smith, M.J.

This three-volume report presents the results of Phase II of the multiphase EPRI-sponsored High-Reliability Gas Turbine Combined-Cycle Development Program whose goal is to achieve a highly reliable gas turbine combined-cycle power plant, available by the mid-1980s, which would be an economically attractive baseload generation alternative for the electric utility industry. The Phase II program objective was to prepare the preliminary design of this power plant. The power plant was addressed in three areas: (1) the gas turbine, (2) the gas turbine ancillaries, and (3) the balance of plant including the steam turbine generator. To achieve the program goals, a gasmore » turbine was incorporated which combined proven reliability characteristics with improved performance features. This gas turbine, designated the V84.3, is the result of a cooperative effort between Kraftwerk Union AG and United Technologies Corporation. Gas turbines of similar design operating in Europe under baseload conditions have demonstrated mean time between failures in excess of 40,000. The reliability characteristics of the gas turbine ancillaries and balance-of-plant equipment were improved through system simplification and component redundancy and by selection of component with inherent high reliability. A digital control system was included with logic, communications, sensor redundancy, and manual backup. An independent condition monitoring and diagnostic system was also included. Program results provide the preliminary design of a gas turbine combined-cycle baseload power plant. This power plant has a predicted mean time between failure of nearly twice the 3000-h EPRI goal. The cost of added reliability features is offset by improved performance, which results in a comparable specific cost and an 8% lower cost of electricty compared to present market offerings.« less

Rapid Modeling and Analysis Tools: Evolution, Status, Needs and Directions

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.; Stone, Thomas J.; Ransom, Jonathan B. (Technical Monitor)

2002-01-01

Advanced aerospace systems are becoming increasingly more complex, and customers are demanding lower cost, higher performance, and high reliability. Increased demands are placed on the design engineers to collaborate and integrate design needs and objectives early in the design process to minimize risks that may occur later in the design development stage. High performance systems require better understanding of system sensitivities much earlier in the design process to meet these goals. The knowledge, skills, intuition, and experience of an individual design engineer will need to be extended significantly for the next generation of aerospace system designs. Then a collaborative effort involving the designer, rapid and reliable analysis tools and virtual experts will result in advanced aerospace systems that are safe, reliable, and efficient. This paper discusses the evolution, status, needs and directions for rapid modeling and analysis tools for structural analysis. First, the evolution of computerized design and analysis tools is briefly described. Next, the status of representative design and analysis tools is described along with a brief statement on their functionality. Then technology advancements to achieve rapid modeling and analysis are identified. Finally, potential future directions including possible prototype configurations are proposed.

Validity and Reliability of Surface Electromyography Measurements from a Wearable Athlete Performance System

PubMed Central

Lynn, Scott K.; Watkins, Casey M.; Wong, Megan A.; Balfany, Katherine; Feeney, Daniel F.

2018-01-01

The Athos ® wearable system integrates surface electromyography (sEMG ) electrodes into the construction of compression athletic apparel. The Athos system reduces the complexity and increases the portability of collecting EMG data and provides processed data to the end user. The objective of the study was to determine the reliability and validity of Athos as compared with a research grade sEMG system. Twelve healthy subjects performed 7 trials on separate days (1 baseline trial and 6 repeated trials). In each trial subjects wore the wearable sEMG system and had a research grade sEMG system’s electrodes placed just distal on the same muscle, as close as possible to the wearable system’s electrodes. The muscles tested were the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF). All testing was done on an isokinetic dynamometer. Baseline testing involved performing isometric 1 repetition maximum tests for the knee extensors and flexors and three repetitions of concentric-concentric knee flexion and extension at MVC for each testing speed: 60, 180, and 300 deg/sec. Repeated trials 2-7 each comprised 9 sets where each set included three repetitions of concentric-concentric knee flexion-extension. Each repeated trial (2-7) comprised one set at each speed and percent MVC (50%, 75%, 100%) combination. The wearable system and research grade sEMG data were processed using the same methods and aligned in time. The amplitude metrics calculated from the sEMG for each repetition were the peak amplitude, sum of the linear envelope, and 95th percentile. Validity results comprise two main findings. First, there is not a significant effect of system (Athos or research grade system) on the repetition amplitude metrics (95%, peak, or sum). Second, the relationship between torque and sEMG is not significantly different between Athos and the research grade system. For reliability testing, the variation across trials and averaged across speeds was 0.8%, 7.3%, and 0.2% higher for Athos from BF, VL and VM, respectively. Also, using the standard deviation of the MVC normalized repetition amplitude, the research grade system showed 10.7% variability while Athos showed 12%. The wearable technology (Athos) provides sEMG measures that are consistent with controlled, research grade technologies and data collection procedures. Key points Surface EMG embedded into athletic garments (Athos) had similar validity and reliability when compared with a research grade system There was no difference in the torque-EMG relationship between the two systems No statistically significant difference in reliability across 6 trials between the two systems The validity and reliability of Athos demonstrates the potential for sEMG to be applied in dynamic rehabilitation and sports settings PMID:29769821

System Architectural Considerations on Reliable Guidance, Navigation, and Control (GN and C) for Constellation Program (CxP) Spacecraft

NASA Technical Reports Server (NTRS)

Dennehy, Cornelius J.

2010-01-01

This final report summarizes the results of a comparative assessment of the fault tolerance and reliability of different Guidance, Navigation and Control (GN&C) architectural approaches. This study was proactively performed by a combined Massachusetts Institute of Technology (MIT) and Draper Laboratory team as a GN&C "Discipline-Advancing" activity sponsored by the NASA Engineering and Safety Center (NESC). This systematic comparative assessment of GN&C system architectural approaches was undertaken as a fundamental step towards understanding the opportunities for, and limitations of, architecting highly reliable and fault tolerant GN&C systems composed of common avionic components. The primary goal of this study was to obtain architectural 'rules of thumb' that could positively influence future designs in the direction of an optimized (i.e., most reliable and cost-efficient) GN&C system. A secondary goal was to demonstrate the application and the utility of a systematic modeling approach that maps the entire possible architecture solution space.

Performance improvement on a MIMO radio-over-fiber system by probabilistic shaping

NASA Astrophysics Data System (ADS)

Kong, Miao; Yu, Jianjun

2018-01-01

As we know, probabilistic shaping (PS), as a typical one of modulation format optimization technologies, becomes a promising technology and attracts more and more attention, because of its higher transmission capacity and lower computation complexity. In this paper, we experimentally demonstrated a reliable 8 Gbaud-rate delivery of polarization multiplexed PS 16-QAM single carrier signal in a MIMO radio-over-fiber system with 20-km SMF-28 wire link and 2.5-m wireless link at 60 GHz. The BER performance of PS 16-QAM signals at different baud rate was also evaluated. What is more, PS 16-QAM was also experimentally compared with uniform 16-QAM, and it can be concluded that PS 16-QAM brings a better compromise between effectiveness and reliability performance and a higher capacity than uniform 16-QAM for the radio-over-fiber system.

Commercial Off-The-Shelf (COTS) Parts Risk and Reliability User and Application Guide

NASA Technical Reports Server (NTRS)

White, Mark

2017-01-01

All COTS parts are not created equal. Because they are not created equal, the notion that one can force the commercial industry to follow a set of military specifications and standards, along with the certifications, audits and qualification commitments that go with them, is unrealistic for the sale of a few parts. The part technologies that are Defense Logistics Agency (DLA) certified or Military Specification (MS) qualified, are several generations behind the state-of-the-art high-performance parts that are required for the compact, higher performing systems for the next generation of spacecraft and instruments. The majority of the part suppliers are focused on the portion of the market that is producing high-tech commercial products and systems. To that end, in order to compete in the high performance and leading edge advanced technological systems, an alternative approach to risk assessment and reliability prediction must be considered.

Final Report of the NASA Office of Safety and Mission Assurance Agile Benchmarking Team

NASA Technical Reports Server (NTRS)

Wetherholt, Martha

2016-01-01

To ensure that the NASA Safety and Mission Assurance (SMA) community remains in a position to perform reliable Software Assurance (SA) on NASAs critical software (SW) systems with the software industry rapidly transitioning from waterfall to Agile processes, Terry Wilcutt, Chief, Safety and Mission Assurance, Office of Safety and Mission Assurance (OSMA) established the Agile Benchmarking Team (ABT). The Team's tasks were: 1. Research background literature on current Agile processes, 2. Perform benchmark activities with other organizations that are involved in software Agile processes to determine best practices, 3. Collect information on Agile-developed systems to enable improvements to the current NASA standards and processes to enhance their ability to perform reliable software assurance on NASA Agile-developed systems, 4. Suggest additional guidance and recommendations for updates to those standards and processes, as needed. The ABT's findings and recommendations for software management, engineering and software assurance are addressed herein.

FOR Allocation to Distribution Systems based on Credible Improvement Potential (CIP)

NASA Astrophysics Data System (ADS)

Tiwary, Aditya; Arya, L. D.; Arya, Rajesh; Choube, S. C.

2017-02-01

This paper describes an algorithm for forced outage rate (FOR) allocation to each section of an electrical distribution system subject to satisfaction of reliability constraints at each load point. These constraints include threshold values of basic reliability indices, for example, failure rate, interruption duration and interruption duration per year at load points. Component improvement potential measure has been used for FOR allocation. Component with greatest magnitude of credible improvement potential (CIP) measure is selected for improving reliability performance. The approach adopted is a monovariable method where one component is selected for FOR allocation and in the next iteration another component is selected for FOR allocation based on the magnitude of CIP. The developed algorithm is implemented on sample radial distribution system.

Space station electrical power system availability study

NASA Technical Reports Server (NTRS)

Turnquist, Scott R.; Twombly, Mark A.

1988-01-01

ARINC Research Corporation performed a preliminary reliability, and maintainability (RAM) anlaysis of the NASA space station Electric Power Station (EPS). The analysis was performed using the ARINC Research developed UNIRAM RAM assessment methodology and software program. The analysis was performed in two phases: EPS modeling and EPS RAM assessment. The EPS was modeled in four parts: the insolar power generation system, the eclipse power generation system, the power management and distribution system (both ring and radial power distribution control unit (PDCU) architectures), and the power distribution to the inner keel PDCUs. The EPS RAM assessment was conducted in five steps: the use of UNIRAM to perform baseline EPS model analyses and to determine the orbital replacement unit (ORU) criticalities; the determination of EPS sensitivity to on-orbit spared of ORUs and the provision of an indication of which ORUs may need to be spared on-orbit; the determination of EPS sensitivity to changes in ORU reliability; the determination of the expected annual number of ORU failures; and the integration of the power generator system model results with the distribution system model results to assess the full EPS. Conclusions were drawn and recommendations were made.

Reliability Analysis of Sealing Structure of Electromechanical System Based on Kriging Model

NASA Astrophysics Data System (ADS)

Zhang, F.; Wang, Y. M.; Chen, R. W.; Deng, W. W.; Gao, Y.

2018-05-01

The sealing performance of aircraft electromechanical system has a great influence on flight safety, and the reliability of its typical seal structure is analyzed by researcher. In this paper, we regard reciprocating seal structure as a research object to study structural reliability. Having been based on the finite element numerical simulation method, the contact stress between the rubber sealing ring and the cylinder wall is calculated, and the relationship between the contact stress and the pressure of the hydraulic medium is built, and the friction force on different working conditions are compared. Through the co-simulation, the adaptive Kriging model obtained by EFF learning mechanism is used to describe the failure probability of the seal ring, so as to evaluate the reliability of the sealing structure. This article proposes a new idea of numerical evaluation for the reliability analysis of sealing structure, and also provides a theoretical basis for the optimal design of sealing structure.

48 CFR 242.7501 - Policy.

Code of Federal Regulations, 2010 CFR

2010-10-01

... DEFENSE CONTRACT MANAGEMENT CONTRACT ADMINISTRATION AND AUDIT SERVICES Contractor Accounting Systems and..., shall maintain an accounting system and related internal controls throughout contract performance which... accounting system and cost data are reliable; (c) Risk of misallocations and mischarges are minimized; and (d...

77 FR 26686 - Transmission Planning Reliability Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-07

... Normal (No Contingency) Conditions (Category A), TPL-002-1b--System Performance Following Loss of a... Reliability Standard should not allow an entity to plan for the loss of non-consequential firm load in the... approval of its proposal to revise and clarify footnote `b' ``in regard to load loss following a single...

Fault tree models for fault tolerant hypercube multiprocessors

NASA Technical Reports Server (NTRS)

Boyd, Mark A.; Tuazon, Jezus O.

1991-01-01

Three candidate fault tolerant hypercube architectures are modeled, their reliability analyses are compared, and the resulting implications of these methods of incorporating fault tolerance into hypercube multiprocessors are discussed. In the course of performing the reliability analyses, the use of HARP and fault trees in modeling sequence dependent system behaviors is demonstrated.

Reliability-Based Control Design for Uncertain Systems

NASA Technical Reports Server (NTRS)

Crespo, Luis G.; Kenny, Sean P.

2005-01-01

This paper presents a robust control design methodology for systems with probabilistic parametric uncertainty. Control design is carried out by solving a reliability-based multi-objective optimization problem where the probability of violating design requirements is minimized. Simultaneously, failure domains are optimally enlarged to enable global improvements in the closed-loop performance. To enable an efficient numerical implementation, a hybrid approach for estimating reliability metrics is developed. This approach, which integrates deterministic sampling and asymptotic approximations, greatly reduces the numerical burden associated with complex probabilistic computations without compromising the accuracy of the results. Examples using output-feedback and full-state feedback with state estimation are used to demonstrate the ideas proposed.

Management of ATM-based networks supporting multimedia medical information systems

NASA Astrophysics Data System (ADS)

Whitman, Robert A.; Blaine, G. James; Fritz, Kevin; Goodgold, Ken; Heisinger, Patrick

1997-05-01

Medical information systems are acquiring the ability to collect and deliver many different types of medical information. In support of the increased network demands necessitated by these expanded capabilities, asynchronous transfer mode (ATM) based networks are being deployed in medical care systems. While ATM supplies a much greater line rate than currently deployed networks, the management and standards surrounding ATM are yet to mature. This paper explores the management and control issues surrounding an ATM network supporting medical information systems, and examines how management impacts network performance and robustness. A multivendor ATM network at the BJC Health System/Washington University and the applications using the network are discussed. Performance information for specific applications is presented and analyzed. Network management's influence on application reliability is outlined. The information collected is used to show how ATM network standards and management tools influence network reliability and performance. Performance of current applications using the ATM network is discussed. Special attention is given to issues encountered in implementation of hypertext transfer protocol over ATM internet protocol (IP) communications. A classical IP ATM implementation yields greater than twenty percent higher network performance over LANE. Maximum performance for a host's suite of applications can be obtained by establishing multiple individually engineered IP links through its ATM network connection.

Reliability analysis in the Office of Safety, Environmental, and Mission Assurance (OSEMA)

NASA Astrophysics Data System (ADS)

Kauffmann, Paul J.

1994-12-01

The technical personnel in the SEMA office are working to provide the highest degree of value-added activities to their support of the NASA Langley Research Center mission. Management perceives that reliability analysis tools and an understanding of a comprehensive systems approach to reliability will be a foundation of this change process. Since the office is involved in a broad range of activities supporting space mission projects and operating activities (such as wind tunnels and facilities), it was not clear what reliability tools the office should be familiar with and how these tools could serve as a flexible knowledge base for organizational growth. Interviews and discussions with the office personnel (both technicians and engineers) revealed that job responsibilities ranged from incoming inspection to component or system analysis to safety and risk. It was apparent that a broad base in applied probability and reliability along with tools for practical application was required by the office. A series of ten class sessions with a duration of two hours each was organized and scheduled. Hand-out materials were developed and practical examples based on the type of work performed by the office personnel were included. Topics covered were: Reliability Systems - a broad system oriented approach to reliability; Probability Distributions - discrete and continuous distributions; Sampling and Confidence Intervals - random sampling and sampling plans; Data Analysis and Estimation - Model selection and parameter estimates; and Reliability Tools - block diagrams, fault trees, event trees, FMEA. In the future, this information will be used to review and assess existing equipment and processes from a reliability system perspective. An analysis of incoming materials sampling plans was also completed. This study looked at the issues associated with Mil Std 105 and changes for a zero defect acceptance sampling plan.

Reliability analysis in the Office of Safety, Environmental, and Mission Assurance (OSEMA)

NASA Technical Reports Server (NTRS)

Kauffmann, Paul J.

1994-01-01

The technical personnel in the SEMA office are working to provide the highest degree of value-added activities to their support of the NASA Langley Research Center mission. Management perceives that reliability analysis tools and an understanding of a comprehensive systems approach to reliability will be a foundation of this change process. Since the office is involved in a broad range of activities supporting space mission projects and operating activities (such as wind tunnels and facilities), it was not clear what reliability tools the office should be familiar with and how these tools could serve as a flexible knowledge base for organizational growth. Interviews and discussions with the office personnel (both technicians and engineers) revealed that job responsibilities ranged from incoming inspection to component or system analysis to safety and risk. It was apparent that a broad base in applied probability and reliability along with tools for practical application was required by the office. A series of ten class sessions with a duration of two hours each was organized and scheduled. Hand-out materials were developed and practical examples based on the type of work performed by the office personnel were included. Topics covered were: Reliability Systems - a broad system oriented approach to reliability; Probability Distributions - discrete and continuous distributions; Sampling and Confidence Intervals - random sampling and sampling plans; Data Analysis and Estimation - Model selection and parameter estimates; and Reliability Tools - block diagrams, fault trees, event trees, FMEA. In the future, this information will be used to review and assess existing equipment and processes from a reliability system perspective. An analysis of incoming materials sampling plans was also completed. This study looked at the issues associated with Mil Std 105 and changes for a zero defect acceptance sampling plan.

A rapid culture system uninfluenced by an inoculum effect increases reliability and convenience for drug susceptibility testing of Mycobacterium tuberculosis.

PubMed

Jung, Yong-Gyun; Kim, Hyejin; Lee, Sangyeop; Kim, Suyeoun; Jo, EunJi; Kim, Eun-Geun; Choi, Jungil; Kim, Hyun Jung; Yoo, Jungheon; Lee, Hye-Jeong; Kim, Haeun; Jung, Hyunju; Ryoo, Sungweon; Kwon, Sunghoon

2018-06-05

The Disc Agarose Channel (DAC) system utilizes microfluidics and imaging technologies and is fully automated and capable of tracking single cell growth to produce Mycobacterium tuberculosis (MTB) drug susceptibility testing (DST) results within 3~7 days. In particular, this system can be easily used to perform DSTs without the fastidious preparation of the inoculum of MTB cells. Inoculum effect is one of the major problems that causes DST errors. The DAC system was not influenced by the inoculum effect and produced reliable DST results. In this system, the minimum inhibitory concentration (MIC) values of the first-line drugs were consistent regardless of inoculum sizes ranging from ~10 3 to ~10 8 CFU/mL. The consistent MIC results enabled us to determine the critical concentrations for 12 anti-tuberculosis drugs. Based on the determined critical concentrations, further DSTs were performed with 254 MTB clinical isolates without measuring an inoculum size. There were high agreement rates (96.3%) between the DAC system and the absolute concentration method using Löwenstein-Jensen medium. According to these results, the DAC system is the first DST system that is not affected by the inoculum effect. It can thus increase reliability and convenience for DST of MTB. We expect that this system will be a potential substitute for conventional DST systems.

Patient-specific 3D models created by 3D imaging system or bi-planar imaging coupled with Moiré-Fringe projections: a comparative study of accuracy and reliability on spinal curvatures and vertebral rotation data.

PubMed

Hocquelet, Arnaud; Cornelis, François; Jirot, Anna; Castaings, Laurent; de Sèze, Mathieu; Hauger, Olivier

2016-10-01

The aim of this study is to compare the accuracy and reliability of spinal curvatures and vertebral rotation data based on patient-specific 3D models created by 3D imaging system or by bi-planar imaging coupled with Moiré-Fringe projections. Sixty-two consecutive patients from a single institution were prospectively included. For each patient, frontal and sagittal calibrated low-dose bi-planar X-rays were performed and coupled simultaneously with an optical Moiré back surface-based technology. The 3D reconstructions of spine and pelvis were performed independently by one radiologist and one technician in radiology using two different semi-automatic methods using 3D radio-imaging system (method 1) or bi-planar imaging coupled with Moiré projections (method 2). Both methods were compared using Bland-Altman analysis, and reliability using intraclass correlation coefficient (ICC). ICC showed good to very good agreement. Between the two techniques, the maximum 95 % prediction limits was -4.9° degrees for the measurements of spinal coronal curves and less than 5° for other parameters. Inter-rater reliability was excellent for all parameters across both methods, except for axial rotation with method 2 for which ICC was fair. Method 1 was faster for reconstruction time than method 2 for both readers (13.4 vs. 20.7 min and 10.6 vs. 13.9 min; p = 0.0001). While a lower accuracy was observed for the evaluation of the axial rotation, bi-planar imaging coupled with Moiré-Fringe projections may be an accurate and reliable tool to perform 3D reconstructions of the spine and pelvis.

Bridge reliability assessment based on the PDF of long-term monitored extreme strains

NASA Astrophysics Data System (ADS)

Jiao, Meiju; Sun, Limin

2011-04-01

Structural health monitoring (SHM) systems can provide valuable information for the evaluation of bridge performance. As the development and implementation of SHM technology in recent years, the data mining and use has received increasingly attention and interests in civil engineering. Based on the principle of probabilistic and statistics, a reliability approach provides a rational basis for analysis of the randomness in loads and their effects on structures. A novel approach combined SHM systems with reliability method to evaluate the reliability of a cable-stayed bridge instrumented with SHM systems was presented in this paper. In this study, the reliability of the steel girder of the cable-stayed bridge was denoted by failure probability directly instead of reliability index as commonly used. Under the assumption that the probability distributions of the resistance are independent to the responses of structures, a formulation of failure probability was deduced. Then, as a main factor in the formulation, the probability density function (PDF) of the strain at sensor locations based on the monitoring data was evaluated and verified. That Donghai Bridge was taken as an example for the application of the proposed approach followed. In the case study, 4 years' monitoring data since the operation of the SHM systems was processed, and the reliability assessment results were discussed. Finally, the sensitivity and accuracy of the novel approach compared with FORM was discussed.

An Investigation of the Generalizability of Medical School Grades.

PubMed

Kreiter, Clarence D; Ferguson, Kristi J

2016-01-01

Construct/Background: Medical school grades are currently unstandardized, and their level of reliability is unknown. This means their usefulness for reporting on student achievement is also not well documented. This study investigates grade reliability within 1 medical school. Generalizability analyses are conducted on grades awarded. Grades from didactic and clerkship-based courses were treated as 2 levels of a fixed facet within a univariate mixed model. Grades from within the 2 levels (didactic and clerkship) were also entered in a multivariate generalizability study. Grades from didactic courses were shown to produce a highly reliable mean score (G = .79) when averaged over as few as 5 courses. Although the universe score correlation between didactic and clerkship courses was high (r = .80), the clerkship courses required almost twice as many grades to reach a comparable level of reliability. When grades were converted to a Pass/Fail metric, almost all information contained in the grades was lost. Although it has been suggested that the imprecision of medical school grades precludes their use as a reliable indicator of student achievement, these results suggest otherwise. While it is true that a Pass/Fail system of grading provides very little information about a student's level of performance, a multi-tiered grading system was shown to be a highly reliable indicator of student achievement within the medical school. Although grades awarded during the first 2 didactic years appear to be more reliable than clerkship grades, both yield useful information about student performance within the medical college.

Reliability and Probabilistic Risk Assessment - How They Play Together

NASA Technical Reports Server (NTRS)

Safie, Fayssal; Stutts, Richard; Huang, Zhaofeng

2015-01-01

Since the Space Shuttle Challenger accident in 1986, NASA has extensively used probabilistic analysis methods to assess, understand, and communicate the risk of space launch vehicles. Probabilistic Risk Assessment (PRA), used in the nuclear industry, is one of the probabilistic analysis methods NASA utilizes to assess Loss of Mission (LOM) and Loss of Crew (LOC) risk for launch vehicles. PRA is a system scenario based risk assessment that uses a combination of fault trees, event trees, event sequence diagrams, and probability distributions to analyze the risk of a system, a process, or an activity. It is a process designed to answer three basic questions: 1) what can go wrong that would lead to loss or degraded performance (i.e., scenarios involving undesired consequences of interest), 2) how likely is it (probabilities), and 3) what is the severity of the degradation (consequences). Since the Challenger accident, PRA has been used in supporting decisions regarding safety upgrades for launch vehicles. Another area that was given a lot of emphasis at NASA after the Challenger accident is reliability engineering. Reliability engineering has been a critical design function at NASA since the early Apollo days. However, after the Challenger accident, quantitative reliability analysis and reliability predictions were given more scrutiny because of their importance in understanding failure mechanism and quantifying the probability of failure, which are key elements in resolving technical issues, performing design trades, and implementing design improvements. Although PRA and reliability are both probabilistic in nature and, in some cases, use the same tools, they are two different activities. Specifically, reliability engineering is a broad design discipline that deals with loss of function and helps understand failure mechanism and improve component and system design. PRA is a system scenario based risk assessment process intended to assess the risk scenarios that could lead to a major/top undesirable system event, and to identify those scenarios that are high-risk drivers. PRA output is critical to support risk informed decisions concerning system design. This paper describes the PRA process and the reliability engineering discipline in detail. It discusses their differences and similarities and how they work together as complementary analyses to support the design and risk assessment processes. Lessons learned, applications, and case studies in both areas are also discussed in the paper to demonstrate and explain these differences and similarities.

Closed circuit TV system automatically guides welding arc

NASA Technical Reports Server (NTRS)

Stephans, D. L.; Wall, W. A., Jr.

1968-01-01

Closed circuit television /CCTV/ system automatically guides a welding torch to position the welding arc accurately along weld seams. Digital counting and logic techniques incorporated in the control circuitry, ensure performance reliability.

Fatigue Reliability of Gas Turbine Engine Structures

NASA Technical Reports Server (NTRS)

Cruse, Thomas A.; Mahadevan, Sankaran; Tryon, Robert G.

1997-01-01

The results of an investigation are described for fatigue reliability in engine structures. The description consists of two parts. Part 1 is for method development. Part 2 is a specific case study. In Part 1, the essential concepts and practical approaches to damage tolerance design in the gas turbine industry are summarized. These have evolved over the years in response to flight safety certification requirements. The effect of Non-Destructive Evaluation (NDE) methods on these methods is also reviewed. Assessment methods based on probabilistic fracture mechanics, with regard to both crack initiation and crack growth, are outlined. Limit state modeling techniques from structural reliability theory are shown to be appropriate for application to this problem, for both individual failure mode and system-level assessment. In Part 2, the results of a case study for the high pressure turbine of a turboprop engine are described. The response surface approach is used to construct a fatigue performance function. This performance function is used with the First Order Reliability Method (FORM) to determine the probability of failure and the sensitivity of the fatigue life to the engine parameters for the first stage disk rim of the two stage turbine. A hybrid combination of regression and Monte Carlo simulation is to use incorporate time dependent random variables. System reliability is used to determine the system probability of failure, and the sensitivity of the system fatigue life to the engine parameters of the high pressure turbine. 'ne variation in the primary hot gas and secondary cooling air, the uncertainty of the complex mission loading, and the scatter in the material data are considered.

Constellation Ground Systems Launch Availability Analysis: Enhancing Highly Reliable Launch Systems Design

NASA Technical Reports Server (NTRS)

Gernand, Jeffrey L.; Gillespie, Amanda M.; Monaghan, Mark W.; Cummings, Nicholas H.

2010-01-01

Success of the Constellation Program's lunar architecture requires successfully launching two vehicles, Ares I/Orion and Ares V/Altair, within a very limited time period. The reliability and maintainability of flight vehicles and ground systems must deliver a high probability of successfully launching the second vehicle in order to avoid wasting the on-orbit asset launched by the first vehicle. The Ground Operations Project determined which ground subsystems had the potential to affect the probability of the second launch and allocated quantitative availability requirements to these subsystems. The Ground Operations Project also developed a methodology to estimate subsystem reliability, availability, and maintainability to ensure that ground subsystems complied with allocated launch availability and maintainability requirements. The verification analysis developed quantitative estimates of subsystem availability based on design documentation, testing results, and other information. Where appropriate, actual performance history was used to calculate failure rates for legacy subsystems or comparative components that will support Constellation. The results of the verification analysis will be used to assess compliance with requirements and to highlight design or performance shortcomings for further decision making. This case study will discuss the subsystem requirements allocation process, describe the ground systems methodology for completing quantitative reliability, availability, and maintainability analysis, and present findings and observation based on analysis leading to the Ground Operations Project Preliminary Design Review milestone.

IAPSA 2 small-scale system specification

NASA Technical Reports Server (NTRS)

Cohen, Gerald C.; Torkelson, Thomas C.

1990-01-01

The details of a hardware implementation of a representative small scale flight critical system is described using Advanced Information Processing System (AIPS) building block components and simulated sensor/actuator interfaces. The system was used to study application performance and reliability issues during both normal and faulted operation.

23 CFR 500.109 - CMS.

Code of Federal Regulations, 2011 CFR

2011-04-01

.... Congestion management means the application of strategies to improve system performance and reliability by... SYSTEMS Management Systems § 500.109 CMS. (a) For purposes of this part, congestion means the level at... management system or process is a systematic and regionally accepted approach for managing congestion that...

23 CFR 500.109 - CMS.

Code of Federal Regulations, 2010 CFR

2010-04-01

.... Congestion management means the application of strategies to improve system performance and reliability by... SYSTEMS Management Systems § 500.109 CMS. (a) For purposes of this part, congestion means the level at... management system or process is a systematic and regionally accepted approach for managing congestion that...

23 CFR 500.109 - CMS.

Code of Federal Regulations, 2013 CFR

2013-04-01

... SYSTEMS Management Systems § 500.109 CMS. (a) For purposes of this part, congestion means the level at.... Congestion management means the application of strategies to improve system performance and reliability by... management system or process is a systematic and regionally accepted approach for managing congestion that...

23 CFR 500.109 - CMS.

Code of Federal Regulations, 2014 CFR

2014-04-01

... SYSTEMS Management Systems § 500.109 CMS. (a) For purposes of this part, congestion means the level at.... Congestion management means the application of strategies to improve system performance and reliability by... management system or process is a systematic and regionally accepted approach for managing congestion that...

23 CFR 500.109 - CMS.

Code of Federal Regulations, 2012 CFR

2012-04-01

... SYSTEMS Management Systems § 500.109 CMS. (a) For purposes of this part, congestion means the level at.... Congestion management means the application of strategies to improve system performance and reliability by... management system or process is a systematic and regionally accepted approach for managing congestion that...

Miss-distance indicator for tank main guns

NASA Astrophysics Data System (ADS)

Bornstein, Jonathan A.; Hillis, David B.

1996-06-01

Tank main gun systems must possess extremely high levels of accuracy to perform successfully in battle. Under some circumstances, the first round fired in an engagement may miss the intended target, and it becomes necessary to rapidly correct fire. A breadboard automatic miss-distance indicator system was previously developed to assist in this process. The system, which would be mounted on a 'wingman' tank, consists of a charged-coupled device (CCD) camera and computer-based image-processing system, coupled with a separate infrared sensor to detect muzzle flash. For the system to be successfully employed with current generation tanks, it must be reliable, be relatively low cost, and respond rapidly maintaining current firing rates. Recently, the original indicator system was developed further in an effort to assist in achieving these goals. Efforts have focused primarily upon enhanced image-processing algorithms, both to improve system reliability and to reduce processing requirements. Intelligent application of newly refined trajectory models has permitted examination of reduced areas of interest and enhanced rejection of false alarms, significantly improving system performance.

Reliability analysis of the F-8 digital fly-by-wire system

NASA Technical Reports Server (NTRS)

Brock, L. D.; Goodman, H. A.

1981-01-01

The F-8 Digital Fly-by-Wire (DFBW) flight test program intended to provide the technology for advanced control systems, giving aircraft enhanced performance and operational capability is addressed. A detailed analysis of the experimental system was performed to estimated the probabilities of two significant safety critical events: (1) loss of primary flight control function, causing reversion to the analog bypass system; and (2) loss of the aircraft due to failure of the electronic flight control system. The analysis covers appraisal of risks due to random equipment failure, generic faults in design of the system or its software, and induced failure due to external events. A unique diagrammatic technique was developed which details the combinatorial reliability equations for the entire system, promotes understanding of system failure characteristics, and identifies the most likely failure modes. The technique provides a systematic method of applying basic probability equations and is augmented by a computer program written in a modular fashion that duplicates the structure of these equations.

System-wide versus component-specific trust using multiple aids.

PubMed

Keller, David; Rice, Stephen

2010-01-01

Previous research in operator trust toward automated aids has focused primarily on single aids. The current study focuses on how operator trust is affected by the presence of multiple aids. Two competing theories of multiple-trust are presented. A component-specific trust theory predicts that operators will differentially place their trust in automated aids that vary in reliability. A system-wide trust theory predicts that operators will treat multiple imperfect aids as one "system" and merge their trust across aids despite differences in the aids' reliability. A simulated flight task was used to test these theories, whereby operators performed a pursuit tracking task while concurrently monitoring multiple system gauges that were augmented with perfect or imperfect automated aids. The data revealed that a system-wide trust theory best predicted the data; operators merged their trust across both aids, behaving toward a perfectly reliable aid in the same manner as they did towards unreliable aids.

Developing and validating the Communication Function Classification System for individuals with cerebral palsy

PubMed Central

HIDECKER, MARY JO COOLEY; PANETH, NIGEL; ROSENBAUM, PETER L; KENT, RAYMOND D; LILLIE, JANET; EULENBERG, JOHN B; CHESTER, KEN; JOHNSON, BRENDA; MICHALSEN, LAUREN; EVATT, MORGAN; TAYLOR, KARA

2011-01-01

Aim The purpose of this study was to create and validate a Communication Function Classification System (CFCS) for children with cerebral palsy (CP) that can be used by a wide variety of individuals who are interested in CP. This paper reports the content validity, interrater reliability, and test–retest reliability of the CFCS for children with CP. Method An 11-member development team created comprehensive descriptions of the CFCS levels, and four nominal groups comprising 27 participants critiqued these levels. Within a Delphi survey, 112 participants commented on the clarity and usefulness of the CFCS. Interrater reliability was completed by 61 professionals and 68 parents/relatives who classified 69 children with CP aged 2 to 18 years. Test–retest reliability was completed by 48 professionals who allowed at least 2 weeks between classifications. The participants who assessed the CFCS were all relevant stakeholders: adults with CP, parents of children with CP, educators, occupational therapists, physical therapists, physicians, and speech–language pathologists. Results The interrater reliability of the CFCS was 0.66 between two professionals and 0.49 between a parent and a professional. Professional interrater reliability improved to 0.77 for classification of children older than 4 years. The test–retest reliability was 0.82. Interpretation The CFCS demonstrates content validity and shows very good test–retest reliability, good professional interrater reliability, and moderate parent–professional interrater reliability. Combining the CFCS with the Gross Motor Function Classification System and the Manual Ability Classification System contributes to a functional performance view of daily life for individuals with CP, in accordance with the World Health Organization’s International Classification of Functioning, Disability and Health. PMID:21707596

Reliability and Probabilistic Risk Assessment - How They Play Together

NASA Technical Reports Server (NTRS)

Safie, Fayssal M.; Stutts, Richard G.; Zhaofeng, Huang

2015-01-01

PRA methodology is one of the probabilistic analysis methods that NASA brought from the nuclear industry to assess the risk of LOM, LOV and LOC for launch vehicles. PRA is a system scenario based risk assessment that uses a combination of fault trees, event trees, event sequence diagrams, and probability and statistical data to analyze the risk of a system, a process, or an activity. It is a process designed to answer three basic questions: What can go wrong? How likely is it? What is the severity of the degradation? Since 1986, NASA, along with industry partners, has conducted a number of PRA studies to predict the overall launch vehicles risks. Planning Research Corporation conducted the first of these studies in 1988. In 1995, Science Applications International Corporation (SAIC) conducted a comprehensive PRA study. In July 1996, NASA conducted a two-year study (October 1996 - September 1998) to develop a model that provided the overall Space Shuttle risk and estimates of risk changes due to proposed Space Shuttle upgrades. After the Columbia accident, NASA conducted a PRA on the Shuttle External Tank (ET) foam. This study was the most focused and extensive risk assessment that NASA has conducted in recent years. It used a dynamic, physics-based, integrated system analysis approach to understand the integrated system risk due to ET foam loss in flight. Most recently, a PRA for Ares I launch vehicle has been performed in support of the Constellation program. Reliability, on the other hand, addresses the loss of functions. In a broader sense, reliability engineering is a discipline that involves the application of engineering principles to the design and processing of products, both hardware and software, for meeting product reliability requirements or goals. It is a very broad design-support discipline. It has important interfaces with many other engineering disciplines. Reliability as a figure of merit (i.e. the metric) is the probability that an item will perform its intended function(s) for a specified mission profile. In general, the reliability metric can be calculated through the analyses using reliability demonstration and reliability prediction methodologies. Reliability analysis is very critical for understanding component failure mechanisms and in identifying reliability critical design and process drivers. The following sections discuss the PRA process and reliability engineering in detail and provide an application where reliability analysis and PRA were jointly used in a complementary manner to support a Space Shuttle flight risk assessment.

Requirements for Successful Adoption of a Glucose Measurement System Into a Hospital POC Program.

PubMed

Füzéry, Anna K; Cembrowski, George S

2016-07-01

Widespread and successful implementation of any glucose measurement system in a hospital point-of-care (POC) program requires a number of features in addition to accurate and reliable analytical performance. Such features include, but are not limited to, a system's glucose-hematocrit dependence, durability, information technology capabilities, and battery capacity and battery life. While the study of Ottiger et al in this issue supports the analytical accuracy and reliability of Bayer's CONTOUR XT® blood glucose monitoring system, the suitability of other features of this system for a hospital POC program remains to be established. © 2016 Diabetes Technology Society.

NovoTTF™-100A System (Tumor Treating Fields) transducer array layout planning for glioblastoma: a NovoTAL™ system user study.

PubMed

Chaudhry, Aafia; Benson, Laura; Varshaver, Michael; Farber, Ori; Weinberg, Uri; Kirson, Eilon; Palti, Yoram

2015-11-11

Optune™, previously known as the NovoTTF-100A System™, generates Tumor Treating Fields (TTFields), an effective anti-mitotic therapy for glioblastoma. The system delivers intermediate frequency, alternating electric fields to the supratentorial brain. Patient therapy is personalized by configuring transducer array layout placement on the scalp to the tumor site using MRI measurements and the NovoTAL System. Transducer array layout mapping optimizes therapy by maximizing electric field intensity to the tumor site. This study evaluated physician performance in conducting transducer array layout mapping using the NovoTAL System compared with mapping performed by the Novocure in-house clinical team. Fourteen physicians (7 neuro-oncologists, 4 medical oncologists, and 3 neurosurgeons) evaluated five blinded cases of recurrent glioblastoma and performed head size and tumor location measurements using a standard Digital Imaging and Communications in Medicine reader. Concordance with Novocure measurement and intra- and inter-rater reliability were assessed using relevant correlation coefficients. The study criterion for success was a concordance correlation coefficient (CCC) >0.80. CCC for each physician versus Novocure on 20 MRI measurements was 0.96 (standard deviation, SD ± 0.03, range 0.90-1.00), indicating very high agreement between the two groups. Intra- and inter-rater reliability correlation coefficients were similarly high: 0.83 (SD ±0.15, range 0.54-1.00) and 0.80 (SD ±0.18, range 0.48-1.00), respectively. This user study demonstrated an excellent level of concordance between prescribing physicians and Novocure in-house clinical teams in performing transducer array layout planning. Intra-rater reliability was very high, indicating reproducible performance. Physicians prescribing TTFields, when trained on the NovoTAL System, can independently perform transducer array layout mapping required for the initiation and maintenance of patients on TTFields therapy.

Experimental optimization of the FireFly 600 photovoltaic off-grid system.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyson, William Earl; Orozco, Ron; Ralph, Mark E.

2003-10-01

A comprehensive evaluation and experimental optimization of the FireFly{trademark} 600 off-grid photovoltaic system manufactured by Energia Total, Ltd. was conducted at Sandia National Laboratories in May and June of 2001. This evaluation was conducted at the request of the manufacturer and addressed performance of individual system components, overall system functionality and performance, safety concerns, and compliance with applicable codes and standards. A primary goal of the effort was to identify areas for improvement in performance, reliability, and safety. New system test procedures were developed during the effort.

Reliable fusion of control and sensing in intelligent machines. Thesis

NASA Technical Reports Server (NTRS)

Mcinroy, John E.

1991-01-01

Although robotics research has produced a wealth of sophisticated control and sensing algorithms, very little research has been aimed at reliably combining these control and sensing strategies so that a specific task can be executed. To improve the reliability of robotic systems, analytic techniques are developed for calculating the probability that a particular combination of control and sensing algorithms will satisfy the required specifications. The probability can then be used to assess the reliability of the design. An entropy formulation is first used to quickly eliminate designs not capable of meeting the specifications. Next, a framework for analyzing reliability based on the first order second moment methods of structural engineering is proposed. To ensure performance over an interval of time, lower bounds on the reliability of meeting a set of quadratic specifications with a Gaussian discrete time invariant control system are derived. A case study analyzing visual positioning in robotic system is considered. The reliability of meeting timing and positioning specifications in the presence of camera pixel truncation, forward and inverse kinematic errors, and Gaussian joint measurement noise is determined. This information is used to select a visual sensing strategy, a kinematic algorithm, and a discrete compensator capable of accomplishing the desired task. Simulation results using PUMA 560 kinematic and dynamic characteristics are presented.

Effectiveness of glucose monitoring systems modified for the visually impaired.

PubMed

Bernbaum, M; Albert, S G; Brusca, S; McGinnis, J; Miller, D; Hoffmann, J W; Mooradian, A D

1993-10-01

To compare three glucose meters modified for use by individuals with diabetes and visual impairment regarding accuracy, precision, and clinical reliability. Ten subjects with diabetes and visual impairment performed self-monitoring of blood glucose using each of the three commercially available blood glucose meters modified for visually impaired users (the AccuChek Freedom [Boehringer Mannheim, Indianapolis, IN], the Diascan SVM [Home Diagnostics, Eatontown, NJ], and the One Touch [Lifescan, Milpitas, CA]). The meters were independently evaluated by a laboratory technologist for precision and accuracy determinations. Only two meters were acceptable with regard to laboratory precision (coefficient of variation < 10%)--the Accuchek and the One Touch. The Accuchek and the One Touch did not differ significantly with regard to laboratory estimates of accuracy. A great discrepancy of the clinical reliability results was observed between these two meters. The Accuchek maintained a high degree of reliability (y = 0.99X + 0.44, r = 0.97, P = 0.001). The visually impaired subjects were unable to perform reliable testing using the One Touch system because of a lack of appropriate tactile landmarks and auditory signals. In addition to laboratory assessments of glucose meters, monitoring systems designed for the visually impaired must include adequate tactile and audible feedback features to allow for the acquisition and placement of appropriate blood samples.

NASA trend analysis procedures

NASA Technical Reports Server (NTRS)

1993-01-01

This publication is primarily intended for use by NASA personnel engaged in managing or implementing trend analysis programs. 'Trend analysis' refers to the observation of current activity in the context of the past in order to infer the expected level of future activity. NASA trend analysis was divided into 5 categories: problem, performance, supportability, programmatic, and reliability. Problem trend analysis uncovers multiple occurrences of historical hardware or software problems or failures in order to focus future corrective action. Performance trend analysis observes changing levels of real-time or historical flight vehicle performance parameters such as temperatures, pressures, and flow rates as compared to specification or 'safe' limits. Supportability trend analysis assesses the adequacy of the spaceflight logistics system; example indicators are repair-turn-around time and parts stockage levels. Programmatic trend analysis uses quantitative indicators to evaluate the 'health' of NASA programs of all types. Finally, reliability trend analysis attempts to evaluate the growth of system reliability based on a decreasing rate of occurrence of hardware problems over time. Procedures for conducting all five types of trend analysis are provided in this publication, prepared through the joint efforts of the NASA Trend Analysis Working Group.

Design and performance of a no-single-failure control system for the mini-Brayton power conversion system. [for spacecraft power supplies

NASA Technical Reports Server (NTRS)

Brichenough, A. G.

1975-01-01

The control system consists of the ac-dc conversion, voltage regulation, speed regulation through parasitic load control, and overload control. A no-single-failure configuration was developed to attain the required reliability for a 10-year design life of unattended operation. The design principles, complete schematics, and performance are reported. Testing was performed on an alternator simulator pending construction of the actual Mini-Brayton alternator.

Towards early software reliability prediction for computer forensic tools (case study).

PubMed

Abu Talib, Manar

2016-01-01

Versatility, flexibility and robustness are essential requirements for software forensic tools. Researchers and practitioners need to put more effort into assessing this type of tool. A Markov model is a robust means for analyzing and anticipating the functioning of an advanced component based system. It is used, for instance, to analyze the reliability of the state machines of real time reactive systems. This research extends the architecture-based software reliability prediction model for computer forensic tools, which is based on Markov chains and COSMIC-FFP. Basically, every part of the computer forensic tool is linked to a discrete time Markov chain. If this can be done, then a probabilistic analysis by Markov chains can be performed to analyze the reliability of the components and of the whole tool. The purposes of the proposed reliability assessment method are to evaluate the tool's reliability in the early phases of its development, to improve the reliability assessment process for large computer forensic tools over time, and to compare alternative tool designs. The reliability analysis can assist designers in choosing the most reliable topology for the components, which can maximize the reliability of the tool and meet the expected reliability level specified by the end-user. The approach of assessing component-based tool reliability in the COSMIC-FFP context is illustrated with the Forensic Toolkit Imager case study.

Design Strategy for a Formally Verified Reliable Computing Platform

NASA Technical Reports Server (NTRS)

Butler, Ricky W.; Caldwell, James L.; DiVito, Ben L.

1991-01-01

This paper presents a high-level design for a reliable computing platform for real-time control applications. The design tradeoffs and analyses related to the development of a formally verified reliable computing platform are discussed. The design strategy advocated in this paper requires the use of techniques that can be completely characterized mathematically as opposed to more powerful or more flexible algorithms whose performance properties can only be analyzed by simulation and testing. The need for accurate reliability models that can be related to the behavior models is also stressed. Tradeoffs between reliability and voting complexity are explored. In particular, the transient recovery properties of the system are found to be fundamental to both the reliability analysis as well as the "correctness" models.

14 CFR 25.1435 - Hydraulic systems.

Code of Federal Regulations, 2013 CFR

2013-01-01

... on the hydraulic system(s), and/or subsystem(s) and elements, except that analysis may be used in place of or to supplement testing, where the analysis is shown to be reliable and appropriate. All... system(s), subsystem(s), or element(s) must be subjected to performance, fatigue, and endurance tests...

14 CFR 25.1435 - Hydraulic systems.

Code of Federal Regulations, 2011 CFR

2011-01-01

... on the hydraulic system(s), and/or subsystem(s) and elements, except that analysis may be used in place of or to supplement testing, where the analysis is shown to be reliable and appropriate. All... system(s), subsystem(s), or element(s) must be subjected to performance, fatigue, and endurance tests...

14 CFR 25.1435 - Hydraulic systems.

Code of Federal Regulations, 2014 CFR

2014-01-01

... on the hydraulic system(s), and/or subsystem(s) and elements, except that analysis may be used in place of or to supplement testing, where the analysis is shown to be reliable and appropriate. All... system(s), subsystem(s), or element(s) must be subjected to performance, fatigue, and endurance tests...

14 CFR 25.1435 - Hydraulic systems.

Code of Federal Regulations, 2012 CFR

2012-01-01

... on the hydraulic system(s), and/or subsystem(s) and elements, except that analysis may be used in place of or to supplement testing, where the analysis is shown to be reliable and appropriate. All... system(s), subsystem(s), or element(s) must be subjected to performance, fatigue, and endurance tests...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Arquit Niederberger, Anne

Abstract— Lighting systems have the ability to transform the economic and educational infrastructure of disadvantaged communities, and eradicating “light poverty” has become one of the primary goals of the International Year of Light 2015. Solid-state lighting (SSL) technology, based on light-emitting diode (LED) light sources, has emerged as the next generation of lighting technology, with a current global market penetration of roughly 5%. This paper will report on recent research on understanding SSL lighting system reliability (failure modes, environmental stressors, electrical power quality); discuss the implications of SSL technology reliability for providing lighting services; and suggest practical approaches to ensuremore » SSL reliability to benefit humanity. Among the key findings from this work is that LED sources can be extremely reliable, withstanding a broad range of environmental stresses without failure. Nonetheless, SSL lighting systems can have a negative impact on electrical power reliability, as well as on the affordability of lighting services, without attention to the quality of the accompanying power infrastructure. It is therefore critical to ensure that the performance of the power supply electronics used in lighting systems is matched to the quality of the power source, when evaluating energy efficient lighting choices.« less

Automation of reliability evaluation procedures through CARE - The computer-aided reliability estimation program.

NASA Technical Reports Server (NTRS)

Mathur, F. P.

1972-01-01

Description of an on-line interactive computer program called CARE (Computer-Aided Reliability Estimation) which can model self-repair and fault-tolerant organizations and perform certain other functions. Essentially CARE consists of a repository of mathematical equations defining the various basic redundancy schemes. These equations, under program control, are then interrelated to generate the desired mathematical model to fit the architecture of the system under evaluation. The mathematical model is then supplied with ground instances of its variables and is then evaluated to generate values for the reliability-theoretic functions applied to the model.

In-Use Performance Comparison of Hybrid Electric, CNG, and Diesel Buses at New York City Transit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barnitt, R. A.

2008-06-01

The National Renewable Energy Laboratory (NREL) evaluated the performance of diesel, compressed natural gas (CNG), and hybrid electric (equipped with BAE Systems? HybriDrive propulsion system) transit buses at New York City Transit (NYCT). CNG, Gen I and Gen II hybrid electric propulsion systems were compared on fuel economy, maintenance and operating costs per mile, and reliability.

Understanding the Reliability of Solder Joints Used in Advanced Structural and Electronics Applications: Part 2 - Reliability Performance.

DOE PAGES

Vianco, Paul T.

2017-03-01

Whether structural or electronic, all solder joints must provide the necessary level of reliability for the application. The Part 1 report examined the effects of filler metal properties and the soldering process on joint reliability. Filler metal solderability and mechanical properties, as well as the extents of base material dissolution and interface reaction that occur during the soldering process, were shown to affect reliability performance. The continuation of this discussion is presented in this Part 2 report, which highlights those factors that directly affect solder joint reliability. There is the growth of an intermetallic compound (IMC) reaction layer at themore » solder/base material interface by means of solid-state diffusion processes. In terms of mechanical response by the solder joint, fatigue remains as the foremost concern for long-term performance. Thermal mechanical fatigue (TMF), a form of low-cycle fatigue (LCF), occurs when temperature cycling is combined with mismatched values of the coefficient of thermal expansion (CTE) between materials comprising the solder joint “system.” Vibration environments give rise to high-cycle fatigue (HCF) degradation. Although accelerated aging studies provide valuable empirical data, too many variants of filler metals, base materials, joint geometries, and service environments are forcing design engineers to embrace computational modeling to predict the long-term reliability of solder joints.« less

Creation of the NaSCoRD Database

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denman, Matthew R.; Jankovsky, Zachary Kyle; Stuart, William

This report was written as part of a United States Department of Energy (DOE), Office of Nuclear Energy, Advanced Reactor Technologies program funded project to re-create the capabilities of the legacy Centralized Reliability Database Organization (CREDO) database. The CREDO database provided a record of component design and performance documentation across various systems that used sodium as a working fluid. Regaining this capability will allow the DOE complex and the domestic sodium reactor industry to better understand how previous systems were designed and built for use in improving the design and operations of future loops. The contents of this report include:more » overview of the current state of domestic sodium reliability databases; summary of the ongoing effort to improve, understand, and process the CREDO information; summary of the initial efforts to develop a unified sodium reliability database called the Sodium System Component Reliability Database (NaSCoRD); and explain both how potential users can access the domestic sodium reliability databases and the type of information that can be accessed from these databases.« less

Performance Analysis on Carrier Phase-Based Tightly-Coupled GPS/BDS/INS Integration in GNSS Degraded and Denied Environments

PubMed Central

Han, Houzeng; Wang, Jian; Wang, Jinling; Tan, Xinglong

2015-01-01

The integration of Global Navigation Satellite Systems (GNSS) carrier phases with Inertial Navigation System (INS) measurements is essential to provide accurate and continuous position, velocity and attitude information, however it is necessary to fix ambiguities rapidly and reliably to obtain high accuracy navigation solutions. In this paper, we present the notion of combining the Global Positioning System (GPS), the BeiDou Navigation Satellite System (BDS) and low-cost micro-electro-mechanical sensors (MEMS) inertial systems for reliable navigation. An adaptive multipath factor-based tightly-coupled (TC) GPS/BDS/INS integration algorithm is presented and the overall performance of the integrated system is illustrated. A twenty seven states TC GPS/BDS/INS model is adopted with an extended Kalman filter (EKF), which is carried out by directly fusing ambiguity fixed double-difference (DD) carrier phase measurements with the INS predicted pseudoranges to estimate the error states. The INS-aided integer ambiguity resolution (AR) strategy is developed by using a dynamic model, a two-step estimation procedure is applied with adaptively estimated covariance matrix to further improve the AR performance. A field vehicular test was carried out to demonstrate the positioning performance of the combined system. The results show the TC GPS/BDS/INS system significantly improves the single-epoch AR reliability as compared to that of GPS/BDS-only or single satellite navigation system integrated strategy, especially for high cut-off elevations. The AR performance is also significantly improved for the combined system with adaptive covariance matrix in the presence of low elevation multipath related to the GNSS-only case. A total of fifteen simulated outage tests also show that the time to relock of the GPS/BDS signals is shortened, which improves the system availability. The results also indicate that TC integration system achieves a few centimeters accuracy in positioning based on the comparison analysis and covariance analysis, even in harsh environments (e.g., in urban canyons), thus we can see the advantage of positioning at high cut-off elevations that the combined GPS/BDS brings. PMID:25875191

Performance analysis on carrier phase-based tightly-coupled GPS/BDS/INS integration in GNSS degraded and denied environments.

PubMed

Han, Houzeng; Wang, Jian; Wang, Jinling; Tan, Xinglong

2015-04-14

The integration of Global Navigation Satellite Systems (GNSS) carrier phases with Inertial Navigation System (INS) measurements is essential to provide accurate and continuous position, velocity and attitude information, however it is necessary to fix ambiguities rapidly and reliably to obtain high accuracy navigation solutions. In this paper, we present the notion of combining the Global Positioning System (GPS), the BeiDou Navigation Satellite System (BDS) and low-cost micro-electro-mechanical sensors (MEMS) inertial systems for reliable navigation. An adaptive multipath factor-based tightly-coupled (TC) GPS/BDS/INS integration algorithm is presented and the overall performance of the integrated system is illustrated. A twenty seven states TC GPS/BDS/INS model is adopted with an extended Kalman filter (EKF), which is carried out by directly fusing ambiguity fixed double-difference (DD) carrier phase measurements with the INS predicted pseudoranges to estimate the error states. The INS-aided integer ambiguity resolution (AR) strategy is developed by using a dynamic model, a two-step estimation procedure is applied with adaptively estimated covariance matrix to further improve the AR performance. A field vehicular test was carried out to demonstrate the positioning performance of the combined system. The results show the TC GPS/BDS/INS system significantly improves the single-epoch AR reliability as compared to that of GPS/BDS-only or single satellite navigation system integrated strategy, especially for high cut-off elevations. The AR performance is also significantly improved for the combined system with adaptive covariance matrix in the presence of low elevation multipath related to the GNSS-only case. A total of fifteen simulated outage tests also show that the time to relock of the GPS/BDS signals is shortened, which improves the system availability. The results also indicate that TC integration system achieves a few centimeters accuracy in positioning based on the comparison analysis and covariance analysis, even in harsh environments (e.g., in urban canyons), thus we can see the advantage of positioning at high cut-off elevations that the combined GPS/BDS brings.

Reliability and Productivity Modeling for the Optimization of Separated Spacecraft Interferometers

NASA Technical Reports Server (NTRS)

Kenny, Sean (Technical Monitor); Wertz, Julie

2002-01-01

As technological systems grow in capability, they also grow in complexity. Due to this complexity, it is no longer possible for a designer to use engineering judgement to identify the components that have the largest impact on system life cycle metrics, such as reliability, productivity, cost, and cost effectiveness. One way of identifying these key components is to build quantitative models and analysis tools that can be used to aid the designer in making high level architecture decisions. Once these key components have been identified, two main approaches to improving a system using these components exist: add redundancy or improve the reliability of the component. In reality, the most effective approach to almost any system will be some combination of these two approaches, in varying orders of magnitude for each component. Therefore, this research tries to answer the question of how to divide funds, between adding redundancy and improving the reliability of components, to most cost effectively improve the life cycle metrics of a system. While this question is relevant to any complex system, this research focuses on one type of system in particular: Separate Spacecraft Interferometers (SSI). Quantitative models are developed to analyze the key life cycle metrics of different SSI system architectures. Next, tools are developed to compare a given set of architectures in terms of total performance, by coupling different life cycle metrics together into one performance metric. Optimization tools, such as simulated annealing and genetic algorithms, are then used to search the entire design space to find the "optimal" architecture design. Sensitivity analysis tools have been developed to determine how sensitive the results of these analyses are to uncertain user defined parameters. Finally, several possibilities for the future work that could be done in this area of research are presented.

Reconfigurable Antenna and Cognitive Radio for Space Applications

NASA Technical Reports Server (NTRS)

Hwu, Shian U.

2012-01-01

This presentation briefly discusses a research effort on mitigation techniques of radio frequency interference (RFI) on communication systems for possible space applications. This problem is of considerable interest in the context of providing reliable communications to the space vehicle which might suffer severe performance degradation due to RFI sources such as visiting spacecrafts and various ground radar systems. This study proposes a communication system with Reconfigurable Antenna (RA) and Cognitive Radio (CR) to mitigate the RFI impact. A cognitive radio is an intelligent radio that is able to learn from the environment and adapt to the variations in its surrounding by adjusting the transmit power, carrier frequency, modulation strategy or transmission data rate. Therefore, the main objective of a cognitive radio system is to ensure highly reliable communication whenever and wherever needed. To match the intelligent adaptability of the cognitive radio, a reconfigurable antenna system will be required to ensure the system performance. The technical challenges in design such a system will be discussed in this presentation.

Implementation and Test of the Automatic Flight Dynamics Operations for Geostationary Satellite Mission

NASA Astrophysics Data System (ADS)

Park, Sangwook; Lee, Young-Ran; Hwang, Yoola; Javier Santiago Noguero Galilea

2009-12-01

This paper describes the Flight Dynamics Automation (FDA) system for COMS Flight Dynamics System (FDS) and its test result in terms of the performance of the automation jobs. FDA controls the flight dynamics functions such as orbit determination, orbit prediction, event prediction, and fuel accounting. The designed FDA is independent from the specific characteristics which are defined by spacecraft manufacturer or specific satellite missions. Therefore, FDA could easily links its autonomous job control functions to any satellite mission control system with some interface modification. By adding autonomous system along with flight dynamics system, it decreases the operator’s tedious and repeated jobs but increase the usability and reliability of the system. Therefore, FDA is used to improve the completeness of whole mission control system’s quality. The FDA is applied to the real flight dynamics system of a geostationary satellite, COMS and the experimental test is performed. The experimental result shows the stability and reliability of the mission control operations through the automatic job control.

RADC thermal guide for reliability engineers

NASA Astrophysics Data System (ADS)

Morrison, G. N.; Kallis, J. M.; Strattan, L. A.; Jones, I. R.; Lena, A. L.

1982-06-01

This guide was developed to provide a reliability engineer, who is not proficient in thermal design and analysis techniques, with the tools for managing and evaluating the thermal design and production of electronic equipment. It defines the requirements and tasks that should be addressed in system equipment specifications and statements of work, and describes how to evaluate performance.

Is Learner Self-Assessment Reliable and Valid in a Web-Based Portfolio Environment for High School Students?

ERIC Educational Resources Information Center

Chang, Chi-Cheng; Liang, Chaoyun; Chen, Yi-Hui

2013-01-01

This study explored the reliability and validity of Web-based portfolio self-assessment. Participants were 72 senior high school students enrolled in a computer application course. The students created learning portfolios, viewed peers' work, and performed self-assessment on the Web-based portfolio assessment system. The results indicated: 1)…

Reliability- and performance-based robust design optimization of MEMS structures considering technological uncertainties

NASA Astrophysics Data System (ADS)

Martowicz, Adam; Uhl, Tadeusz

2012-10-01

The paper discusses the applicability of a reliability- and performance-based multi-criteria robust design optimization technique for micro-electromechanical systems, considering their technological uncertainties. Nowadays, micro-devices are commonly applied systems, especially in the automotive industry, taking advantage of utilizing both the mechanical structure and electronic control circuit on one board. Their frequent use motivates the elaboration of virtual prototyping tools that can be applied in design optimization with the introduction of technological uncertainties and reliability. The authors present a procedure for the optimization of micro-devices, which is based on the theory of reliability-based robust design optimization. This takes into consideration the performance of a micro-device and its reliability assessed by means of uncertainty analysis. The procedure assumes that, for each checked design configuration, the assessment of uncertainty propagation is performed with the meta-modeling technique. The described procedure is illustrated with an example of the optimization carried out for a finite element model of a micro-mirror. The multi-physics approach allowed the introduction of several physical phenomena to correctly model the electrostatic actuation and the squeezing effect present between electrodes. The optimization was preceded by sensitivity analysis to establish the design and uncertain domains. The genetic algorithms fulfilled the defined optimization task effectively. The best discovered individuals are characterized by a minimized value of the multi-criteria objective function, simultaneously satisfying the constraint on material strength. The restriction of the maximum equivalent stresses was introduced with the conditionally formulated objective function with a penalty component. The yielded results were successfully verified with a global uniform search through the input design domain.

Probabilistic resource allocation system with self-adaptive capability

NASA Technical Reports Server (NTRS)

Yufik, Yan M. (Inventor)

1998-01-01

A probabilistic resource allocation system is disclosed containing a low capacity computational module (Short Term Memory or STM) and a self-organizing associative network (Long Term Memory or LTM) where nodes represent elementary resources, terminal end nodes represent goals, and weighted links represent the order of resource association in different allocation episodes. Goals and their priorities are indicated by the user, and allocation decisions are made in the STM, while candidate associations of resources are supplied by the LTM based on the association strength (reliability). Weights are automatically assigned to the network links based on the frequency and relative success of exercising those links in the previous allocation decisions. Accumulation of allocation history in the form of an associative network in the LTM reduces computational demands on subsequent allocations. For this purpose, the network automatically partitions itself into strongly associated high reliability packets, allowing fast approximate computation and display of allocation solutions satisfying the overall reliability and other user-imposed constraints. System performance improves in time due to modification of network parameters and partitioning criteria based on the performance feedback.

Benchmark analysis of forecasted seasonal temperature over different climatic areas

NASA Astrophysics Data System (ADS)

Giunta, G.; Salerno, R.; Ceppi, A.; Ercolani, G.; Mancini, M.

2015-12-01

From a long-term perspective, an improvement of seasonal forecasting, which is often exclusively based on climatology, could provide a new capability for the management of energy resources in a time scale of just a few months. This paper regards a benchmark analysis in relation to long-term temperature forecasts over Italy in the year 2010, comparing the eni-kassandra meteo forecast (e-kmf®) model, the Climate Forecast System-National Centers for Environmental Prediction (CFS-NCEP) model, and the climatological reference (based on 25-year data) with observations. Statistical indexes are used to understand the reliability of the prediction of 2-m monthly air temperatures with a perspective of 12 weeks ahead. The results show how the best performance is achieved by the e-kmf® system which improves the reliability for long-term forecasts compared to climatology and the CFS-NCEP model. By using the reliable high-performance forecast system, it is possible to optimize the natural gas portfolio and management operations, thereby obtaining a competitive advantage in the European energy market.

Structural design of high-performance capacitive accelerometers using parametric optimization with uncertainties

NASA Astrophysics Data System (ADS)

Teves, André da Costa; Lima, Cícero Ribeiro de; Passaro, Angelo; Silva, Emílio Carlos Nelli

2017-03-01

Electrostatic or capacitive accelerometers are among the highest volume microelectromechanical systems (MEMS) products nowadays. The design of such devices is a complex task, since they depend on many performance requirements, which are often conflicting. Therefore, optimization techniques are often used in the design stage of these MEMS devices. Because of problems with reliability, the technology of MEMS is not yet well established. Thus, in this work, size optimization is combined with the reliability-based design optimization (RBDO) method to improve the performance of accelerometers. To account for uncertainties in the dimensions and material properties of these devices, the first order reliability method is applied to calculate the probabilities involved in the RBDO formulation. Practical examples of bulk-type capacitive accelerometer designs are presented and discussed to evaluate the potential of the implemented RBDO solver.

Reliability of Long-Term Wave Conditions Predicted with Data Sets of Short Duration

DTIC Science & Technology

1985-03-01

the validity and reliability of predicted probable wave heights obtained from data of limited duration. BACKGROUND: The basic steps listed by...interest to perform the analysis outlined in steps 2 to 5, the prediction would only be reliable for up to a 3year return period. For a 5-year data set...for long-term hindcast data . The data retrieval and analysis program known as the Sea State Engineering Analysis System (SEAS) makes handling of the

Missile and Space Systems Reliability versus Cost Trade-Off Study

DTIC Science & Technology

1983-01-01

F00-1C09 Robert C. Schneider F00-1C09 V . PERFORMING ORGANIZATION NAME AM0 ADDRESS 16 PRGRAM ELEMENT. PROJECT. TASK BoeingAerosace CmpAnyA CA WORK UNIT...reliability problems, which has the - real bearing on program effectiveness. A well planned and funded reliability effort can prevent or ferret out...failure analysis, and the in- corporation and verification of design corrections to prevent recurrence of failures. 302.2.2 A TMJ test plan shall be

Reliability and Repetition Effect of the Center of Pressure and Kinematics Parameters That Characterize Trunk Postural Control During Unstable Sitting Test.

PubMed

Barbado, David; Moreside, Janice; Vera-Garcia, Francisco J

2017-03-01

Although unstable seat methodology has been used to assess trunk postural control, the reliability of the variables that characterize it remains unclear. To analyze reliability and learning effect of center of pressure (COP) and kinematic parameters that characterize trunk postural control performance in unstable seating. The relationships between kinematic and COP parameters also were explored. Test-retest reliability design. Biomechanics laboratory setting. Twenty-three healthy male subjects. Participants volunteered to perform 3 sessions at 1-week intervals, each consisting of five 70-second balancing trials. A force platform and a motion capture system were used to measure COP and pelvis, thorax, and spine displacements. Reliability was assessed through standard error of measurement (SEM) and intraclass correlation coefficients (ICC 2,1 ) using 3 methods: (1) comparing the last trial score of each day; (2) comparing the best trial score of each day; and (3) calculating the average of the three last trial scores of each day. Standard deviation and mean velocity were calculated to assess balance performance. Although analyses of variance showed some differences in balance performance between days, these differences were not significant between days 2 and 3. Best result and average methods showed the greatest reliability. Mean velocity of the COP showed high reliability (0.71 < ICC < 0.86; 10.3 < SEM < 13.0), whereas standard deviation only showed a low to moderate reliability (0.37 < ICC < 0.61; 14.5 < SEM < 23.0). Regarding the kinematic variables, only pelvis displacement mean velocity achieved a high reliability using the average method (0.62 < ICC < 0.83; 18.8 < SEM < 23.1). Correlations between COP and kinematics were high only for mean velocity (0.45

Parallelizing Timed Petri Net simulations

NASA Technical Reports Server (NTRS)

Nicol, David M.

1993-01-01

The possibility of using parallel processing to accelerate the simulation of Timed Petri Nets (TPN's) was studied. It was recognized that complex system development tools often transform system descriptions into TPN's or TPN-like models, which are then simulated to obtain information about system behavior. Viewed this way, it was important that the parallelization of TPN's be as automatic as possible, to admit the possibility of the parallelization being embedded in the system design tool. Later years of the grant were devoted to examining the problem of joint performance and reliability analysis, to explore whether both types of analysis could be accomplished within a single framework. In this final report, the results of our studies are summarized. We believe that the problem of parallelizing TPN's automatically for MIMD architectures has been almost completely solved for a large and important class of problems. Our initial investigations into joint performance/reliability analysis are two-fold; it was shown that Monte Carlo simulation, with importance sampling, offers promise of joint analysis in the context of a single tool, and methods for the parallel simulation of general Continuous Time Markov Chains, a model framework within which joint performance/reliability models can be cast, were developed. However, very much more work is needed to determine the scope and generality of these approaches. The results obtained in our two studies, future directions for this type of work, and a list of publications are included.

Loss of Load Probability Calculation for West Java Power System with Nuclear Power Plant Scenario

NASA Astrophysics Data System (ADS)

Azizah, I. D.; Abdullah, A. G.; Purnama, W.; Nandiyanto, A. B. D.; Shafii, M. A.

2017-03-01

Loss of Load Probability (LOLP) index showing the quality and performance of an electrical system. LOLP value is affected by load growth, the load duration curve, forced outage rate of the plant, number and capacity of generating units. This reliability index calculation begins with load forecasting to 2018 using multiple regression method. Scenario 1 with compositions of conventional plants produce the largest LOLP in 2017 amounted to 71.609 days / year. While the best reliability index generated in scenario 2 with the NPP amounted to 6.941 days / year in 2015. Improved reliability of systems using nuclear power more efficiently when compared to conventional plants because it also has advantages such as emission-free, inexpensive fuel costs, as well as high level of plant availability.

Closed-form solution of decomposable stochastic models

NASA Technical Reports Server (NTRS)

Sjogren, Jon A.

1990-01-01

Markov and semi-Markov processes are increasingly being used in the modeling of complex reconfigurable systems (fault tolerant computers). The estimation of the reliability (or some measure of performance) of the system reduces to solving the process for its state probabilities. Such a model may exhibit numerous states and complicated transition distributions, contributing to an expensive and numerically delicate solution procedure. Thus, when a system exhibits a decomposition property, either structurally (autonomous subsystems), or behaviorally (component failure versus reconfiguration), it is desirable to exploit this decomposition in the reliability calculation. In interesting cases there can be failure states which arise from non-failure states of the subsystems. Equations are presented which allow the computation of failure probabilities of the total (combined) model without requiring a complete solution of the combined model. This material is presented within the context of closed-form functional representation of probabilities as utilized in the Symbolic Hierarchical Automated Reliability and Performance Evaluator (SHARPE) tool. The techniques adopted enable one to compute such probability functions for a much wider class of systems at a reduced computational cost. Several examples show how the method is used, especially in enhancing the versatility of the SHARPE tool.

Integrated photovoltaic (PV) monitoring system

NASA Astrophysics Data System (ADS)

Mahinder Singh, Balbir Singh; Husain, NurSyahidah; Mohamed, Norani Muti

2012-09-01

The main aim of this research work is to design an accurate and reliable monitoring system to be integrated with solar electricity generating system. The performance monitoring system is required to ensure that the PVEGS is operating at an optimum level. The PV monitoring system is able to measure all the important parameters that determine an optimum performance. The measured values are recorded continuously, as the data acquisition system is connected to a computer, and data is stored at fixed intervals. The data can be locally used and can also be transmitted via internet. The data that appears directly on the local monitoring system is displayed via graphical user interface that was created by using Visual basic and Apache software was used for data transmission The accuracy and reliability of the developed monitoring system was tested against the data that captured simultaneously by using a standard power quality analyzer device. The high correlation which is 97% values indicates the level of accuracy of the monitoring system. The aim of leveraging on a system for continuous monitoring system is achieved, both locally, and can be viewed simultaneously at a remote system.

Investigation of the impact of main control room digitalization on operators cognitive reliability in nuclear power plants.

PubMed

Zhou, Yong; Mu, Haiying; Jiang, Jianjun; Zhang, Li

2012-01-01

Currently, there is a trend in nuclear power plants (NPPs) toward introducing digital and computer technologies into main control rooms (MCRs). Safe generation of electric power in NPPs requires reliable performance of cognitive tasks such as fault detection, diagnosis, and response planning. The digitalization of MCRs has dramatically changed the whole operating environment, and the ways operators interact with the plant systems. If the design and implementation of the digital technology is incompatible with operators' cognitive characteristics, it may have negative effects on operators' cognitive reliability. Firstly, on the basis of three essential prerequisites for successful cognitive tasks, a causal model is constructed to reveal the typical human performance issues arising from digitalization. The cognitive mechanisms which they impact cognitive reliability are analyzed in detail. Then, Bayesian inference is used to quantify and prioritize the influences of these factors. It suggests that interface management and unbalanced workload distribution have more significant impacts on operators' cognitive reliability.

20--500 watt AMTEC auxiliary electric power system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanenok, J.F. III; Sievers, R.K.

1996-12-31

Numerous design studies have been completed on Alkali Metal Thermal to Electric Converter (AMTEC) power systems for space applications demonstrating their substantial increase in performance. Recently design studies have been initiated to couple AMTEC power conversion with fossil fueled combustion systems. This paper describes the results of a Phase 1 SBIR effort to design an innovative, efficient, reliable, long life AMTEC Auxiliary Electric Power System (AEPS) for remote site applications (20--500 watts). The concept uses high voltage AMTEC cells, each containing 7 to 9 small electrolyte tubes, integrated with a combustor and recuperator. These multi-tube AMTEC cells are low cost,more » reliable, long life static converters. AMTEC technology is ideal for auxiliary electric power supplies that must operate reliably over a broad range of temperatures, fuel sources, power levels, and operational specifications. The simplicity, efficiency (20% systems) and modularity of this technology allow it to fill applications as varied as light-weight backpacks, remote site power supplies, and military base power. Phase 1 demonstrated the feasibility of a 20% system design, and showed that the development needs to focus on identifying long life AMTEC cell components, determining the AMTEC cell and system reliability, and demonstrating that a 20 watt AMTEC system is 3--5 times more efficient than existing systems for the same application.« less

Reliability of a standardized test in Swedish for evaluation of reading performance in healthy eyes. Interchart and test-retest analyses.

PubMed

Thaung, Jörgen; Olseke, Kjell; Ahl, Johan; Sjöstrand, Johan

2014-09-01

The purpose of our study was to establish a practical and quick test for assessing reading performance and to statistically analyse interchart and test-retest reliability of a new standardized Swedish reading chart system consisting of three charts constructed according to the principles available in the literature. Twenty-four subjects with healthy eyes, mean age 65 ± 10 years, were tested binocularly and the reading performance evaluated as reading acuity, critical print size and maximum reading speed. The test charts all consist of 12 short text sentences with a print size ranging from 0.9 to -0.2 logMAR in approximate steps of 0.1 logMAR. Two testing sessions, in two different groups (C1 and C2), were under strict control of luminance and lighting environment. Reading performance tests with chart T1, T2 and T3 were used for evaluation of interchart reliability and test data from a second session 1 month or more apart for the test-retest analysis. The testing of reading performance in adult observers with short sentences of continuous text was quick and practical. The agreement between the tests obtained with the three different test charts was high both within the same test session and at retest. This new Swedish variant of a standardized reading system based on short sentences and logarithmic progression of print size provides reliable measurements of reading performance and preliminary norms in an age group around 65 years. The reading test with three independent reading charts can be useful for clinical studies of reading ability before and after treatment. © 2013 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

The Effect of Power Protection Equipment on Explosion Hazards and on the Reliability of Power Supply to Longwall Systems

NASA Astrophysics Data System (ADS)

Boron, Sergiusz

2017-06-01

Operational safety of electrical machines and equipment depends, inter alia, on the hazards resulting from their use and on the scope of applied protective measures. The use of insufficient protection against existing hazards leads to reduced operational safety, particularly under fault conditions. On the other hand, excessive (in relation to existing hazards) level of protection may compromise the reliability of power supply. This paper analyses the explosion hazard created by earth faults in longwall power supply systems and evaluates existing protection equipment from the viewpoint of its protective performance, particularly in the context of explosion hazards, and also assesses its effect on the reliability of power supply.

Smart Water Conservation System for Irrigated Landscape. ESTCP Cost and Performance Report

DTIC Science & Technology

2016-10-01

water use by as much as 70% in support of meeting EO 13693. Additional performance objectives were to validate energy reduction, cost effectiveness ...Additional performance objectives were to validate energy reduction, cost effectiveness , and system reliability while maintaining satisfactory plant health...developments. The demonstration was conducted for two different climatic regions in the southwestern part of the United States (U.S.), where a typical

Reliability issues in active control of large flexible space structures

NASA Technical Reports Server (NTRS)

Vandervelde, W. E.

1986-01-01

Efforts in this reporting period were centered on four research tasks: design of failure detection filters for robust performance in the presence of modeling errors, design of generalized parity relations for robust performance in the presence of modeling errors, design of failure sensitive observers using the geometric system theory of Wonham, and computational techniques for evaluation of the performance of control systems with fault tolerance and redundancy management

Earth Observing System/Advanced Microwave Sounding Unit-A (EOS/AMSU-A): Reliability prediction report for module A1 (channels 3 through 15) and module A2 (channels 1 and 2)

NASA Technical Reports Server (NTRS)

Geimer, W.

1995-01-01

This report documents the final reliability prediction performed on the Earth Observing System/Advanced Microwave Sounding Unit-A (EOS/AMSU-A). The A1 Module contains Channels 3 through 15, and is referred to herein as 'EOS/AMSU-A1'. The A2 Module contains Channels 1 and 2, and is referred herein as 'EOS/AMSU-A2'. The 'specified' figures were obtained from Aerojet Reports 8897-1 and 9116-1. The predicted reliability figure for the EOS/AMSU-A1 meets the specified value and provides a Mean Time Between Failures (MTBF) of 74,390 hours. The predicted reliability figure for the EOS/AMSU-A2 meets the specified value and provides a MTBF of 193,110 hours.

Thermal Energy Storage using PCM for Solar Domestic Hot Water Systems: A Review

NASA Astrophysics Data System (ADS)

Khot, S. A.; Sane, N. K.; Gawali, B. S.

2012-06-01

Thermal energy storage using phase chase materials (PCM) has received considerable attention in the past two decades for time dependent energy source such as solar energy. From several experimental and theoretical analyses that have been made to assess the performance of thermal energy storage systems, it has been demonstrated that PCM-based systems are reliable and viable options. This paper covers such information on PCMs and PCM-based systems developed for the application of solar domestic hot water system. In addition, economic analysis of thermal storage system using PCM in comparison with conventional storage system helps to validate its commercial possibility. From the economic analysis, it is found that, PCM based solar domestic hot water system (SWHS) provides 23 % more cumulative and life cycle savings than conventional SWHS and will continue to perform efficiently even after 15 years due to application of non-metallic tank. Payback period of PCM-based system is also less compared to conventional system. In conclusion, PCM based solar water heating systems can meet the requirements of Indian climatic situation in a cost effective and reliable manner.

DESIGN INFORMATION ON FINE PORE AERATION SYSTEMS

EPA Science Inventory

Field studies were conducted over several years at municipal wastewater treatment plants employing line pore diffused aeration systems. These studies were designed to produce reliable information on the performance and operational requirements of fine pore devices under process ...

Design for Safety - The Ares Launch Vehicles Paradigm Change

NASA Technical Reports Server (NTRS)

Safie, Fayssal M.; Maggio, Gaspare

2010-01-01

The lessons learned from the S&MA early involvement in the Ares I launch vehicle design phases proved that performing an in-line function jointly with engineering is critical for S&MA to have an effective role in supporting the system, element, and component design. These lessons learned were used to effectively support the Ares V conceptual design phase and planning for post conceptual design phases. The Top level Conceptual LOM assessment for Ares V performed by the S&MA community jointly with the engineering Advanced Concept Office (ACO) was influential in the final selection of the Ares V system configuration. Post conceptual phase, extensive reliability effort should be planned to support future Heavy Lift Launch Vehicles (HLLV) design. In-depth reliability analysis involving the design, manufacturing, and system engineering communities is critical to understand design and process uncertainties and system integrated failures.

Joint System Prognostics For Increased Efficiency And Risk Mitigation In Advanced Nuclear Reactor Instrumentation and Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donald D. Dudenhoeffer; Tuan Q. Tran; Ronald L. Boring

2006-08-01

The science of prognostics is analogous to a doctor who, based on a set of symptoms and patient tests, assesses a probable cause, the risk to the patient, and a course of action for recovery. While traditional prognostics research has focused on the aspect of hydraulic and mechanical systems and associated failures, this project will take a joint view in focusing not only on the digital I&C aspect of reliability and risk, but also on the risks associated with the human element. Model development will not only include an approximation of the control system physical degradation but also on humanmore » performance degradation. Thus the goal of the prognostic system is to evaluate control room operation; to identify and potentially take action when performance degradation reduces plant efficiency, reliability or safety.« less

Effects of computing time delay on real-time control systems

NASA Technical Reports Server (NTRS)

Shin, Kang G.; Cui, Xianzhong

1988-01-01

The reliability of a real-time digital control system depends not only on the reliability of the hardware and software used, but also on the speed in executing control algorithms. The latter is due to the negative effects of computing time delay on control system performance. For a given sampling interval, the effects of computing time delay are classified into the delay problem and the loss problem. Analysis of these two problems is presented as a means of evaluating real-time control systems. As an example, both the self-tuning predicted (STP) control and Proportional-Integral-Derivative (PID) control are applied to the problem of tracking robot trajectories, and their respective effects of computing time delay on control performance are comparatively evaluated. For this example, the STP (PID) controller is shown to outperform the PID (STP) controller in coping with the delay (loss) problem.

Power processing for electric propulsion

NASA Technical Reports Server (NTRS)

Finke, R. C.; Herron, B. G.; Gant, G. D.

1975-01-01

The potential of achieving up to 30 per cent more spacecraft payload or 50 per cent more useful operating life by the use of electric propulsion in place of conventional cold gas or hydrazine systems in science, communications, and earth applications spacecraft is a compelling reason to consider the inclusion of electric thruster systems in new spacecraft design. The propulsion requirements of such spacecraft dictate a wide range of thruster power levels and operational lifetimes, which must be matched by lightweight, efficient, and reliable thruster power processing systems. This paper will present electron bombardment ion thruster requirements; review the performance characteristics of present power processing systems; discuss design philosophies and alternatives in areas such as inverter type, arc protection, and control methods; and project future performance potentials for meeting goals in the areas of power processor weight (10 kg/kW), efficiency (approaching 92 per cent), reliability (0.96 for 15,000 hr), and thermal control capability (0.3 to 5 AU).

Choosing an Optical Disc System: A Guide for Users and Resellers.

ERIC Educational Resources Information Center

Vane-Tempest, Stewart

1995-01-01

Presents a guide for selecting an optional disc system. Highlights include storage hierarchy; standards; data life cycles; security; implementing an optical jukebox system; optimizing the system; performance; quality and reliability; software; cost of online versus near-line; and growing opportunities. Sidebars provide additional information on…

Recent Photovoltaic Performance Data in the USA (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jordan, D.

2014-03-01

This paper presents performance data from nearly 50,000 Photovoltaic systems totaling 1.7 Gigawatts installed capacity in the USA from 2009 to 2012. 90% of the systems performed to within 10% or better of expected performance. Only 2-4% of the data indicate issues significantly affecting the system performance. Special causes of underperformance and their impacts are delineated by reliability category. Delays and interconnections dominate project-related issues particularly in the first year, but total less than 0.5% of all systems. Hardware-related issues are dominated by inverter problems totaling less than 0.4% and underperforming modules to less than 0.1%.

Reliability Assessment Approach for Stirling Convertors and Generators

NASA Technical Reports Server (NTRS)

Shah, Ashwin R.; Schreiber, Jeffrey G.; Zampino, Edward; Best, Timothy

2004-01-01

Stirling power conversion is being considered for use in a Radioisotope Power System for deep-space science missions because it offers a multifold increase in the conversion efficiency of heat to electric power. Quantifying the reliability of a Radioisotope Power System that utilizes Stirling power conversion technology is important in developing and demonstrating the capability for long-term success. A description of the Stirling power convertor is provided, along with a discussion about some of the key components. Ongoing efforts to understand component life, design variables at the component and system levels, related sources, and the nature of uncertainties is discussed. The requirement for reliability also is discussed, and some of the critical areas of concern are identified. A section on the objectives of the performance model development and a computation of reliability is included to highlight the goals of this effort. Also, a viable physics-based reliability plan to model the design-level variable uncertainties at the component and system levels is outlined, and potential benefits are elucidated. The plan involves the interaction of different disciplines, maintaining the physical and probabilistic correlations at all the levels, and a verification process based on rational short-term tests. In addition, both top-down and bottom-up coherency were maintained to follow the physics-based design process and mission requirements. The outlined reliability assessment approach provides guidelines to improve the design and identifies governing variables to achieve high reliability in the Stirling Radioisotope Generator design.

A reliable sewage quality abnormal event monitoring system.

PubMed

Li, Tianling; Winnel, Melissa; Lin, Hao; Panther, Jared; Liu, Chang; O'Halloran, Roger; Wang, Kewen; An, Taicheng; Wong, Po Keung; Zhang, Shanqing; Zhao, Huijun

2017-09-15

With closing water loop through purified recycled water, wastewater becomes a part of source water, requiring reliable wastewater quality monitoring system (WQMS) to manage wastewater source and mitigate potential health risks. However, the development of reliable WQMS is fatally constrained by severe contamination and biofouling of sensors due to the hostile analytical environment of wastewaters, especially raw sewages, that challenges the limit of existing sensing technologies. In this work, we report a technological solution to enable the development of WQMS for real-time abnormal event detection with high reliability and practicality. A vectored high flow hydrodynamic self-cleaning approach and a dual-sensor self-diagnostic concept are adopted for WQMS to effectively encounter vital sensor failing issues caused by contamination and biofouling and ensure the integrity of sensing data. The performance of the WQMS has been evaluated over a 3-year trial period at different sewage catchment sites across three Australian states. It has demonstrated that the developed WQMS is capable of continuously operating in raw sewage for a prolonged period up to 24 months without maintenance and failure, signifying the high reliability and practicality. The demonstrated WQMS capability to reliably acquire real-time wastewater quality information leaps forward the development of effective wastewater source management system. The reported self-cleaning and self-diagnostic concepts should be applicable to other online water quality monitoring systems, opening a new way to encounter the common reliability and stability issues caused by sensor contamination and biofouling. Copyright © 2017 Elsevier Ltd. All rights reserved.

Advanced flight control system study

NASA Technical Reports Server (NTRS)

Hartmann, G. L.; Wall, J. E., Jr.; Rang, E. R.; Lee, H. P.; Schulte, R. W.; Ng, W. K.

1982-01-01

A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts.

A dual-mode generalized likelihood ratio approach to self-reorganizing digital flight control system design

NASA Technical Reports Server (NTRS)

Bueno, R.; Chow, E.; Gershwin, S. B.; Willsky, A. S.

1975-01-01

The research is reported on the problems of failure detection and reliable system design for digital aircraft control systems. Failure modes, cross detection probability, wrong time detection, application of performance tools, and the GLR computer package are discussed.

Passive Thermal Management of Foil Bearings

NASA Technical Reports Server (NTRS)

Bruckner, Robert J. (Inventor)

2015-01-01

Systems and methods for passive thermal management of foil bearing systems are disclosed herein. The flow of the hydrodynamic film across the surface of bearing compliant foils may be disrupted to provide passive cooling and to improve the performance and reliability of the foil bearing system.

Comparing reliabilities of strip and conventional patch testing.

PubMed

Dickel, Heinrich; Geier, Johannes; Kreft, Burkhard; Pfützner, Wolfgang; Kuss, Oliver

2017-06-01

The standardized protocol for performing the strip patch test has proven to be valid, but evidence on its reliability is still missing. To estimate the parallel-test reliability of the strip patch test as compared with the conventional patch test. In this multicentre, prospective, randomized, investigator-blinded reliability study, 132 subjects were enrolled. Simultaneous duplicate strip and conventional patch tests were performed with the Finn Chambers ® on Scanpor ® tape test system and the patch test preparations nickel sulfate 5% pet., potassium dichromate 0.5% pet., and lanolin alcohol 30% pet. Reliability was estimated by the use of Cohen's kappa coefficient. Parallel-test reliability values of the three standard patch test preparations turned out to be acceptable, with slight advantages for the strip patch test. The differences in reliability were 9% (95%CI: -8% to 26%) for nickel sulfate and 23% (95%CI: -16% to 63%) for potassium dichromate, both favouring the strip patch test. The standardized strip patch test method for the detection of allergic contact sensitization in patients with suspected allergic contact dermatitis is reliable. Its application in routine clinical practice can be recommended, especially if the conventional patch test result is presumably false negative. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

FEMA and RAM Analysis for the Multi Canister Overpack (MCO) Handling Machine

DOE Office of Scientific and Technical Information (OSTI.GOV)

SWENSON, C.E.

2000-06-01

The Failure Modes and Effects Analysis and the Reliability, Availability, and Maintainability Analysis performed for the Multi-Canister Overpack Handling Machine (MHM) has shown that the current design provides for a safe system, but the reliability of the system (primarily due to the complexity of the interlocks and permissive controls) is relatively low. No specific failure modes were identified where significant consequences to the public occurred, or where significant impact to nearby workers should be expected. The overall reliability calculation for the MHM shows a 98.1 percent probability of operating for eight hours without failure, and an availability of the MHMmore » of 90 percent. The majority of the reliability issues are found in the interlocks and controls. The availability of appropriate spare parts and maintenance personnel, coupled with well written operating procedures, will play a more important role in successful mission completion for the MHM than other less complicated systems.« less

Reliability analysis of multicellular system architectures for low-cost satellites

NASA Astrophysics Data System (ADS)

Erlank, A. O.; Bridges, C. P.

2018-06-01

Multicellular system architectures are proposed as a solution to the problem of low reliability currently seen amongst small, low cost satellites. In a multicellular architecture, a set of independent k-out-of-n systems mimic the cells of a biological organism. In order to be beneficial, a multicellular architecture must provide more reliability per unit of overhead than traditional forms of redundancy. The overheads include power consumption, volume and mass. This paper describes the derivation of an analytical model for predicting a multicellular system's lifetime. The performance of such architectures is compared against that of several common forms of redundancy and proven to be beneficial under certain circumstances. In addition, the problem of peripheral interfaces and cross-strapping is investigated using a purpose-developed, multicellular simulation environment. Finally, two case studies are presented based on a prototype cell implementation, which demonstrate the feasibility of the proposed architecture.

Development and analysis of the Software Implemented Fault-Tolerance (SIFT) computer

NASA Technical Reports Server (NTRS)

Goldberg, J.; Kautz, W. H.; Melliar-Smith, P. M.; Green, M. W.; Levitt, K. N.; Schwartz, R. L.; Weinstock, C. B.

1984-01-01

SIFT (Software Implemented Fault Tolerance) is an experimental, fault-tolerant computer system designed to meet the extreme reliability requirements for safety-critical functions in advanced aircraft. Errors are masked by performing a majority voting operation over the results of identical computations, and faulty processors are removed from service by reassigning computations to the nonfaulty processors. This scheme has been implemented in a special architecture using a set of standard Bendix BDX930 processors, augmented by a special asynchronous-broadcast communication interface that provides direct, processor to processor communication among all processors. Fault isolation is accomplished in hardware; all other fault-tolerance functions, together with scheduling and synchronization are implemented exclusively by executive system software. The system reliability is predicted by a Markov model. Mathematical consistency of the system software with respect to the reliability model has been partially verified, using recently developed tools for machine-aided proof of program correctness.

The 20 GHz solid state transmitter design, impatt diode development and reliability assessment

NASA Technical Reports Server (NTRS)

Picone, S.; Cho, Y.; Asmus, J. R.

1984-01-01

A single drift gallium arsenide (GaAs) Schottky barrier IMPATT diode and related components were developed. The IMPATT diode reliability was assessed. A proof of concept solid state transmitter design and a technology assessment study were performed. The transmitter design utilizes technology which, upon implementation, will demonstrate readiness for development of a POC model within the 1982 time frame and will provide an information base for flight hardware capable of deployment in a 1985 to 1990 demonstrational 30/20 GHz satellite communication system. Life test data for Schottky barrier GaAs diodes and grown junction GaAs diodes are described. The results demonstrate the viability of GaAs IMPATTs as high performance, reliable RF power sources which, based on the recommendation made herein, will surpass device reliability requirements consistent with a ten year spaceborne solid state power amplifier mission.

Decision-theoretic methodology for reliability and risk allocation in nuclear power plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, N.Z.; Papazoglou, I.A.; Bari, R.A.

1985-01-01

This paper describes a methodology for allocating reliability and risk to various reactor systems, subsystems, components, operations, and structures in a consistent manner, based on a set of global safety criteria which are not rigid. The problem is formulated as a multiattribute decision analysis paradigm; the multiobjective optimization, which is performed on a PRA model and reliability cost functions, serves as the guiding principle for reliability and risk allocation. The concept of noninferiority is used in the multiobjective optimization problem. Finding the noninferior solution set is the main theme of the current approach. The assessment of the decision maker's preferencesmore » could then be performed more easily on the noninferior solution set. Some results of the methodology applications to a nontrivial risk model are provided and several outstanding issues such as generic allocation and preference assessment are discussed.« less

Balancing low cost with reliable operation in the rotordynamic design of the ALS Liquid Hydrogen Fuel Turbopump

NASA Technical Reports Server (NTRS)

Greenhill, L. M.

1990-01-01

The Air Force/NASA Advanced Launch System (ALS) Liquid Hydrogen Fuel Turbopump (FTP) has primary design goals of low cost and high reliability, with performance and weight having less importance. This approach is atypical compared with other rocket engine turbopump design efforts, such as on the Space Shuttle Main Engine (SSME), which emphasized high performance and low weight. Similar to the SSME turbopumps, the ALS FTP operates supercritically, which implies that stability and bearing loads strongly influence the design. In addition, the use of low cost/high reliability features in the ALS FTP such as hydrostatic bearings, relaxed seal clearances, and unshrouded turbine blades also have a negative influence on rotordynamics. This paper discusses the analysis conducted to achieve a balance between low cost and acceptable rotordynamic behavior, to ensure that the ALS FTP will operate reliably without subsynchronous instabilities or excessive bearing loads.

Sensor Selection and Optimization for Health Assessment of Aerospace Systems

NASA Technical Reports Server (NTRS)

Maul, William A.; Kopasakis, George; Santi, Louis M.; Sowers, Thomas S.; Chicatelli, Amy

2007-01-01

Aerospace systems are developed similarly to other large-scale systems through a series of reviews, where designs are modified as system requirements are refined. For space-based systems few are built and placed into service. These research vehicles have limited historical experience to draw from and formidable reliability and safety requirements, due to the remote and severe environment of space. Aeronautical systems have similar reliability and safety requirements, and while these systems may have historical information to access, commercial and military systems require longevity under a range of operational conditions and applied loads. Historically, the design of aerospace systems, particularly the selection of sensors, is based on the requirements for control and performance rather than on health assessment needs. Furthermore, the safety and reliability requirements are met through sensor suite augmentation in an ad hoc, heuristic manner, rather than any systematic approach. A review of the current sensor selection practice within and outside of the aerospace community was conducted and a sensor selection architecture is proposed that will provide a justifiable, dependable sensor suite to address system health assessment requirements.

Sensor Selection and Optimization for Health Assessment of Aerospace Systems

NASA Technical Reports Server (NTRS)

Maul, William A.; Kopasakis, George; Santi, Louis M.; Sowers, Thomas S.; Chicatelli, Amy

2008-01-01

Aerospace systems are developed similarly to other large-scale systems through a series of reviews, where designs are modified as system requirements are refined. For space-based systems few are built and placed into service these research vehicles have limited historical experience to draw from and formidable reliability and safety requirements, due to the remote and severe environment of space. Aeronautical systems have similar reliability and safety requirements, and while these systems may have historical information to access, commercial and military systems require longevity under a range of operational conditions and applied loads. Historically, the design of aerospace systems, particularly the selection of sensors, is based on the requirements for control and performance rather than on health assessment needs. Furthermore, the safety and reliability requirements are met through sensor suite augmentation in an ad hoc, heuristic manner, rather than any systematic approach. A review of the current sensor selection practice within and outside of the aerospace community was conducted and a sensor selection architecture is proposed that will provide a justifiable, defendable sensor suite to address system health assessment requirements.

Electrical insulation design requirements and reliability goals

NASA Astrophysics Data System (ADS)

Ross, R. G., Jr.

1983-11-01

The solar cells in a photovoltaic module which must be electrically isolated from module exterior surfaces to satisfy a variety of safety and operating considerations are discussed. The performance and reliability of the insulation system are examined. Technical requirements involve the capability of withstanding the differential voltage from the solar cells to the module frame. The maximum system voltage includes consideration of maximum open circuit array voltages achieved under low-temperature, high-irradiance conditions, and transient overvoltages due to system feedback of lightning transients. The latter is bounded by the characteristics of incorporated voltage limiting devices such as MOVs.

Performance and Reliability Optimization for Aerospace Systems subject to Uncertainty and Degradation

NASA Technical Reports Server (NTRS)

Miller, David W.; Uebelhart, Scott A.; Blaurock, Carl

2004-01-01

This report summarizes work performed by the Space Systems Laboratory (SSL) for NASA Langley Research Center in the field of performance optimization for systems subject to uncertainty. The objective of the research is to develop design methods and tools to the aerospace vehicle design process which take into account lifecycle uncertainties. It recognizes that uncertainty between the predictions of integrated models and data collected from the system in its operational environment is unavoidable. Given the presence of uncertainty, the goal of this work is to develop means of identifying critical sources of uncertainty, and to combine these with the analytical tools used with integrated modeling. In this manner, system uncertainty analysis becomes part of the design process, and can motivate redesign. The specific program objectives were: 1. To incorporate uncertainty modeling, propagation and analysis into the integrated (controls, structures, payloads, disturbances, etc.) design process to derive the error bars associated with performance predictions. 2. To apply modern optimization tools to guide in the expenditure of funds in a way that most cost-effectively improves the lifecycle productivity of the system by enhancing the subsystem reliability and redundancy. The results from the second program objective are described. This report describes the work and results for the first objective: uncertainty modeling, propagation, and synthesis with integrated modeling.

An integrated approach to system design, reliability, and diagnosis

NASA Technical Reports Server (NTRS)

Patterson-Hine, F. A.; Iverson, David L.

1990-01-01

The requirement for ultradependability of computer systems in future avionics and space applications necessitates a top-down, integrated systems engineering approach for design, implementation, testing, and operation. The functional analyses of hardware and software systems must be combined by models that are flexible enough to represent their interactions and behavior. The information contained in these models must be accessible throughout all phases of the system life cycle in order to maintain consistency and accuracy in design and operational decisions. One approach being taken by researchers at Ames Research Center is the creation of an object-oriented environment that integrates information about system components required in the reliability evaluation with behavioral information useful for diagnostic algorithms. Procedures have been developed at Ames that perform reliability evaluations during design and failure diagnoses during system operation. These procedures utilize information from a central source, structured as object-oriented fault trees. Fault trees were selected because they are a flexible model widely used in aerospace applications and because they give a concise, structured representation of system behavior. The utility of this integrated environment for aerospace applications in light of our experiences during its development and use is described. The techniques for reliability evaluation and failure diagnosis are discussed, and current extensions of the environment and areas requiring further development are summarized.

An integrated approach to system design, reliability, and diagnosis

NASA Astrophysics Data System (ADS)

Patterson-Hine, F. A.; Iverson, David L.

1990-12-01

The requirement for ultradependability of computer systems in future avionics and space applications necessitates a top-down, integrated systems engineering approach for design, implementation, testing, and operation. The functional analyses of hardware and software systems must be combined by models that are flexible enough to represent their interactions and behavior. The information contained in these models must be accessible throughout all phases of the system life cycle in order to maintain consistency and accuracy in design and operational decisions. One approach being taken by researchers at Ames Research Center is the creation of an object-oriented environment that integrates information about system components required in the reliability evaluation with behavioral information useful for diagnostic algorithms. Procedures have been developed at Ames that perform reliability evaluations during design and failure diagnoses during system operation. These procedures utilize information from a central source, structured as object-oriented fault trees. Fault trees were selected because they are a flexible model widely used in aerospace applications and because they give a concise, structured representation of system behavior. The utility of this integrated environment for aerospace applications in light of our experiences during its development and use is described. The techniques for reliability evaluation and failure diagnosis are discussed, and current extensions of the environment and areas requiring further development are summarized.

Probabilistic risk assessment for a loss of coolant accident in McMaster Nuclear Reactor and application of reliability physics model for modeling human reliability

NASA Astrophysics Data System (ADS)

Ha, Taesung

A probabilistic risk assessment (PRA) was conducted for a loss of coolant accident, (LOCA) in the McMaster Nuclear Reactor (MNR). A level 1 PRA was completed including event sequence modeling, system modeling, and quantification. To support the quantification of the accident sequence identified, data analysis using the Bayesian method and human reliability analysis (HRA) using the accident sequence evaluation procedure (ASEP) approach were performed. Since human performance in research reactors is significantly different from that in power reactors, a time-oriented HRA model (reliability physics model) was applied for the human error probability (HEP) estimation of the core relocation. This model is based on two competing random variables: phenomenological time and performance time. The response surface and direct Monte Carlo simulation with Latin Hypercube sampling were applied for estimating the phenomenological time, whereas the performance time was obtained from interviews with operators. An appropriate probability distribution for the phenomenological time was assigned by statistical goodness-of-fit tests. The human error probability (HEP) for the core relocation was estimated from these two competing quantities: phenomenological time and operators' performance time. The sensitivity of each probability distribution in human reliability estimation was investigated. In order to quantify the uncertainty in the predicted HEPs, a Bayesian approach was selected due to its capability of incorporating uncertainties in model itself and the parameters in that model. The HEP from the current time-oriented model was compared with that from the ASEP approach. Both results were used to evaluate the sensitivity of alternative huinan reliability modeling for the manual core relocation in the LOCA risk model. This exercise demonstrated the applicability of a reliability physics model supplemented with a. Bayesian approach for modeling human reliability and its potential usefulness of quantifying model uncertainty as sensitivity analysis in the PRA model.

Identification of emergent off-nominal operational requirements during conceptual architecting of the more electric aircraft

NASA Astrophysics Data System (ADS)

Armstrong, Michael James

Increases in power demands and changes in the design practices of overall equipment manufacturers has led to a new paradigm in vehicle systems definition. The development of unique power systems architectures is of increasing importance to overall platform feasibility and must be pursued early in the aircraft design process. Many vehicle systems architecture trades must be conducted concurrent to platform definition. With an increased complexity introduced during conceptual design, accurate predictions of unit level sizing requirements must be made. Architecture specific emergent requirements must be identified which arise due to the complex integrated effect of unit behaviors. Off-nominal operating scenarios present sizing critical requirements to the aircraft vehicle systems. These requirements are architecture specific and emergent. Standard heuristically defined failure mitigation is sufficient for sizing traditional and evolutionary architectures. However, architecture concepts which vary significantly in terms of structure and composition require that unique failure mitigation strategies be defined for accurate estimations of unit level requirements. Identifying of these off-nominal emergent operational requirements require extensions to traditional safety and reliability tools and the systematic identification of optimal performance degradation strategies. Discrete operational constraints posed by traditional Functional Hazard Assessment (FHA) are replaced by continuous relationships between function loss and operational hazard. These relationships pose the objective function for hazard minimization. Load shedding optimization is performed for all statistically significant failures by varying the allocation of functional capability throughout the vehicle systems architecture. Expressing hazards, and thereby, reliability requirements as continuous relationships with the magnitude and duration of functional failure requires augmentations to the traditional means for system safety assessment (SSA). The traditional two state and discrete system reliability assessment proves insufficient. Reliability is, therefore, handled in an analog fashion: as a function of magnitude of failure and failure duration. A series of metrics are introduced which characterize system performance in terms of analog hazard probabilities. These include analog and cumulative system and functional risk, hazard correlation, and extensions to the traditional component importance metrics. Continuous FHA, load shedding optimization, and analog SSA constitute the SONOMA process (Systematic Off-Nominal Requirements Analysis). Analog system safety metrics inform both architecture optimization (changes in unit level capability and reliability) and architecture augmentation (changes in architecture structure and composition). This process was applied for two vehicle systems concepts (conventional and 'more-electric') in terms of loss/hazard relationships with varying degrees of fidelity. Application of this process shows that the traditional assumptions regarding the structure of the function loss vs. hazard relationship apply undue design bias to functions and components during exploratory design. This bias is illustrated in terms of inaccurate estimations of the system and function level risk and unit level importance. It was also shown that off-nominal emergent requirements must be defined specific to each architecture concept. Quantitative comparisons of architecture specific off-nominal performance were obtained which provide evidence to the need for accurate definition of load shedding strategies during architecture exploratory design. Formally expressing performance degradation strategies in terms of the minimization of a continuous hazard space enhances the system architects ability to accurately predict sizing critical emergent requirements concurrent to architecture definition. Furthermore, the methods and frameworks generated here provide a structured and flexible means for eliciting these architecture specific requirements during the performance of architecture trades.

Validity and Reliability of Spine Rasterstereography in Patients With Adolescent Idiopathic Scoliosis.

PubMed

Tabard-Fougère, Anne; Bonnefoy-Mazure, Alice; Hanquinet, Sylviane; Lascombes, Pierre; Armand, Stéphane; Dayer, Romain

2017-01-15

Test-retest study. This study aimed to evaluate the validity and reliability of rasterstereography in patients with adolescent idiopathic scoliosis (AIS) with a major curve Cobb angle (CA) between 10° and 40° for frontal, sagittal, and transverse parameters. Previous studies evaluating the validity and reliability of rasterstereography concluded that this technique had good accuracy compared with radiographs and a high intra- and interday reliability in healthy volunteers. To the best of our knowledge, the validity and reliability have not been assessed in AIS patients. Thirty-five adolescents with AIS (male = 13) aged 13.1 ± 2.0 years were included. To evaluate the validity of the scoliosis angle (SA) provided by rasterstereography, a comparison (t test, Pearson correlation) was performed with the CA obtained using 2D EOS® radiography (XR). Three rasterstereographic repeated measurements were independently performed by two operators on the same day (interrater reliability) and again by the first operator 1 week later (intrarater reliability). The variables of interest were the SA, lumbar lordosis, and thoracic kyphosis angle, trunk length, pelvic obliquity, and maximum, root mean square and amplitude of vertebral rotations. The data analyses used intraclass correlation coefficients (ICCs). The CA and SA were strongly correlated (R = 0.70) and were nonsignificantly different (P = 0.60). The intrarater reliability (same day: ICC [1, 1], n = 35; 1 week later: ICC [1, 3], n = 28) and interrater reliability (ICC [3, 3], n = 16) were globally excellent (ICC > 0.75) except for the assessment of pelvic obliquity. This study showed that the rasterstereographic system allows for the evaluation of AIS patients with a good validity compared with XR with an overall excellent intra- and interrater reliability. Based on these results, this automatic, fast, and noninvasive system can be used for monitoring the evolution of AIS in growing patients instead of repetitive radiographs, thereby reducing radiation exposure and decreasing costs. 4.

Engine System Model Development for Nuclear Thermal Propulsion

NASA Technical Reports Server (NTRS)

Nelson, Karl W.; Simpson, Steven P.

2006-01-01

In order to design, analyze, and evaluate conceptual Nuclear Thermal Propulsion (NTP) engine systems, an improved NTP design and analysis tool has been developed. The NTP tool utilizes the Rocket Engine Transient Simulation (ROCETS) system tool and many of the routines from the Enabler reactor model found in Nuclear Engine System Simulation (NESS). Improved non-nuclear component models and an external shield model were added to the tool. With the addition of a nearly complete system reliability model, the tool will provide performance, sizing, and reliability data for NERVA-Derived NTP engine systems. A new detailed reactor model is also being developed and will replace Enabler. The new model will allow more flexibility in reactor geometry and include detailed thermal hydraulics and neutronics models. A description of the reactor, component, and reliability models is provided. Another key feature of the modeling process is the use of comprehensive spreadsheets for each engine case. The spreadsheets include individual worksheets for each subsystem with data, plots, and scaled figures, making the output very useful to each engineering discipline. Sample performance and sizing results with the Enabler reactor model are provided including sensitivities. Before selecting an engine design, all figures of merit must be considered including the overall impacts on the vehicle and mission. Evaluations based on key figures of merit of these results and results with the new reactor model will be performed. The impacts of clustering and external shielding will also be addressed. Over time, the reactor model will be upgraded to design and analyze other NTP concepts with CERMET and carbide fuel cores.

Stochastic modeling to identify requirements for centralized monitoring of distributed wastewater treatment.

PubMed

Hug, T; Maurer, M

2012-01-01

Distributed (decentralized) wastewater treatment can, in many situations, be a valuable alternative to a centralized sewer network and wastewater treatment plant. However, it is critical for its acceptance whether the same overall treatment performance can be achieved without on-site staff, and whether its performance can be measured. In this paper we argue and illustrate that the system performance depends not only on the design performance and reliability of the individual treatment units, but also significantly on the monitoring scheme, i.e. on the reliability of the process information. For this purpose, we present a simple model of a fleet of identical treatment units. Thereby, their performance depends on four stochastic variables: the reliability of the treatment unit, the respond time for the repair of failed units, the reliability of on-line sensors, and the frequency of routine inspections. The simulated scenarios show a significant difference between the true performance and the observations by the sensors and inspections. The results also illustrate the trade-off between investing in reactor and sensor technology and in human interventions in order to achieve a certain target performance. Modeling can quantify such effects and thereby support the identification of requirements for the centralized monitoring of distributed treatment units. The model approach is generic and can be extended and applied to various distributed wastewater treatment technologies and contexts.

Assess program: Interactive data management systems for airborne research

NASA Technical Reports Server (NTRS)

Munoz, R. M.; Reller, J. O., Jr.

1974-01-01

Two data systems were developed for use in airborne research. Both have distributed intelligence and are programmed for interactive support among computers and with human operators. The C-141 system (ADAMS) performs flight planning and telescope control functions in addition to its primary role of data acquisition; the CV-990 system (ADDAS) performs data management functions in support of many research experiments operating concurrently. Each system is arranged for maximum reliability in the first priority function, precision data acquisition.

State-of-the-Art for Small Satellite Propulsion Systems

NASA Technical Reports Server (NTRS)

Parker, Khary I.

2016-01-01

SmallSats are a low cost access to space with an increasing need for propulsion systems. NASA, and other organizations, will be using SmallSats that require propulsion systems to: a) Conduct high quality near and far reaching on-orbit research and b) Perform technology demonstrations. Increasing call for high reliability and high performing for SmallSat components. Many SmallSat propulsion technologies are currently under development: a) Systems at various levels of maturity and b) Wide variety of systems for many mission applications.

Advances in Flexible Hybrid Electronics Reliability

DTIC Science & Technology

2017-03-01

Advances in Flexible Hybrid Electronics Reliability Douglas R. Hackler, Richard L. Chaney, Brian N. Meek, Darrell E. Leber, Seth D. Leija, Kelly J...www.americansemi.com Abstract: Flexible Hybrid Electronics combine the best characteristics of printed electronics and silicon ICs to create high performance...presented for flexible hybrid electronics systems. Keywords: FleX; flexible; flexible hybrid electronics ; FHE; Silicon-on-Polymer Introduction

Performance and Reliability of Bonded Interfaces for High-temperature Packaging: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, Douglas J.

2017-10-19

As maximum device temperatures approach 200 °Celsius, continuous operation, sintered silver materials promise to maintain bonds at these high temperatures without excessive degradation rates. A detailed characterization of the thermal performance and reliability of sintered silver materials and processes has been initiated for the next year. Future steps in crack modeling include efforts to simulate crack propagation directly using the extended finite element method (X-FEM), a numerical technique that uses the partition of unity method for modeling discontinuities such as cracks in a system.

Rail Transit System Maintenance Practices for Automatic Fare Collection Equipment

DOT National Transportation Integrated Search

1984-05-01

A review of rail transit system maintenance practices for automatic fare collection (AFC) equipment was performed. This study supports an UMTA sponsored program to improve the reliability of AFC equipment. The maintenance practices of the transit sys...

Workshop on Microwave Power Transmission and Reception. Workshop Paper Summaries

NASA Technical Reports Server (NTRS)

1980-01-01

Microwave systems performance and phase control are discussed. Component design and reliability are highlighted. The power amplifiers, radiating elements, rectennas, and solid state configurations are described. The proper sizing of microwave transmission systems is also discussed.

Hybrid Power Management (HPM)

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2007-01-01

The NASA Glenn Research Center s Avionics, Power and Communications Branch of the Engineering and Systems Division initiated the Hybrid Power Management (HPM) Program for the GRC Technology Transfer and Partnership Office. HPM is the innovative integration of diverse, state-of-the-art power devices in an optimal configuration for space and terrestrial applications. The appropriate application and control of the various power devices significantly improves overall system performance and efficiency. The advanced power devices include ultracapacitors and fuel cells. HPM has extremely wide potential. Applications include power generation, transportation systems, biotechnology systems, and space power systems. HPM has the potential to significantly alleviate global energy concerns, improve the environment, and stimulate the economy. One of the unique power devices being utilized by HPM for energy storage is the ultracapacitor. An ultracapacitor is an electrochemical energy storage device, which has extremely high volumetric capacitance energy due to high surface area electrodes, and very small electrode separation. Ultracapacitors are a reliable, long life, maintenance free, energy storage system. This flexible operating system can be applied to all power systems to significantly improve system efficiency, reliability, and performance. There are many existing and conceptual applications of HPM.

An operating system for future aerospace vehicle computer systems

NASA Technical Reports Server (NTRS)

Foudriat, E. C.; Berman, W. J.; Will, R. W.; Bynum, W. L.

1984-01-01

The requirements for future aerospace vehicle computer operating systems are examined in this paper. The computer architecture is assumed to be distributed with a local area network connecting the nodes. Each node is assumed to provide a specific functionality. The network provides for communication so that the overall tasks of the vehicle are accomplished. The O/S structure is based upon the concept of objects. The mechanisms for integrating node unique objects with node common objects in order to implement both the autonomy and the cooperation between nodes is developed. The requirements for time critical performance and reliability and recovery are discussed. Time critical performance impacts all parts of the distributed operating system; e.g., its structure, the functional design of its objects, the language structure, etc. Throughout the paper the tradeoffs - concurrency, language structure, object recovery, binding, file structure, communication protocol, programmer freedom, etc. - are considered to arrive at a feasible, maximum performance design. Reliability of the network system is considered. A parallel multipath bus structure is proposed for the control of delivery time for time critical messages. The architecture also supports immediate recovery for the time critical message system after a communication failure.

Human reliability in petrochemical industry: an action research.

PubMed

Silva, João Alexandre Pinheiro; Camarotto, João Alberto

2012-01-01

This paper aims to identify conflicts and gaps between the operators' strategies and actions and the organizational managerial approach for human reliability. In order to achieve these goals, the research approach adopted encompasses literature review, mixing action research methodology and Ergonomic Workplace Analysis in field research. The result suggests that the studied company has a classical and mechanistic point of view focusing on error identification and building barriers through procedures, checklists and other prescription alternatives to improve performance in reliability area. However, it was evident the fundamental role of the worker as an agent of maintenance and construction of system reliability during the action research cycle.

A Delay-Aware and Reliable Data Aggregation for Cyber-Physical Sensing

PubMed Central

Zhang, Jinhuan; Long, Jun; Zhang, Chengyuan; Zhao, Guihu

2017-01-01

Physical information sensed by various sensors in a cyber-physical system should be collected for further operation. In many applications, data aggregation should take reliability and delay into consideration. To address these problems, a novel Tiered Structure Routing-based Delay-Aware and Reliable Data Aggregation scheme named TSR-DARDA for spherical physical objects is proposed. By dividing the spherical network constructed by dispersed sensor nodes into circular tiers with specifically designed widths and cells, TSTR-DARDA tries to enable as many nodes as possible to transmit data simultaneously. In order to ensure transmission reliability, lost packets are retransmitted. Moreover, to minimize the latency while maintaining reliability for data collection, in-network aggregation and broadcast techniques are adopted to deal with the transmission between data collecting nodes in the outer layer and their parent data collecting nodes in the inner layer. Thus, the optimization problem is transformed to minimize the delay under reliability constraints by controlling the system parameters. To demonstrate the effectiveness of the proposed scheme, we have conducted extensive theoretical analysis and comparisons to evaluate the performance of TSR-DARDA. The analysis and simulations show that TSR-DARDA leads to lower delay with reliability satisfaction. PMID:28218668

TRAMP; The next generation data acquisition for RTP

DOE Office of Scientific and Technical Information (OSTI.GOV)

van Haren, P.C.; Wijnoltz, F.

1992-04-01

The Rijnhuizen Tokamak Project RTP is a medium-sized tokamak experiment, which requires a very reliable data-acquisition system, due to its pulsed nature. Analyzing the limitations of an existing CAMAC-based data-acquisition system showed, that substantial increase of performance and flexibility could best be obtained by the construction of an entirely new system. This paper discusses this system, CALLED TRAMP (Transient Recorder and Amoeba Multi Processor), based on tailor-made transient recorders with a multiprocessor computer system in VME running Amoeba. The performance of TRAMP exceeds the performance of the CAMAC system by a factor of four. The plans to increase the flexibilitymore » and for a further increase of performance are presented.« less

A New Method for the Evaluation and Prediction of Base Stealing Performance.

PubMed

Bricker, Joshua C; Bailey, Christopher A; Driggers, Austin R; McInnis, Timothy C; Alami, Arya

2016-11-01

Bricker, JC, Bailey, CA, Driggers, AR, McInnis, TC, and Alami, A. A new method for the evaluation and prediction of base stealing performance. J Strength Cond Res 30(11): 3044-3050, 2016-The purposes of this study were to evaluate a new method using electronic timing gates to monitor base stealing performance in terms of reliability, differences between it and traditional stopwatch-collected times, and its ability to predict base stealing performance. Twenty-five healthy collegiate baseball players performed maximal effort base stealing trials with a right and left-handed pitcher. An infrared electronic timing system was used to calculate the reaction time (RT) and total time (TT), whereas coaches' times (CT) were recorded with digital stopwatches. Reliability of the TGM was evaluated with intraclass correlation coefficients (ICCs) and coefficient of variation (CV). Differences between the TGM and traditional CT were calculated with paired samples t tests Cohen's d effect size estimates. Base stealing performance predictability of the TGM was evaluated with Pearson's bivariate correlations. Acceptable relative reliability was observed (ICCs 0.74-0.84). Absolute reliability measures were acceptable for TT (CVs = 4.4-4.8%), but measures were elevated for RT (CVs = 32.3-35.5%). Statistical and practical differences were found between TT and CT (right p = 0.00, d = 1.28 and left p = 0.00, d = 1.49). The TGM TT seems to be a decent predictor of base stealing performance (r = -0.49 to -0.61). The authors recommend using the TGM used in this investigation for athlete monitoring because it was found to be reliable, seems to be more precise than traditional CT measured with a stopwatch, provides an additional variable of value (RT), and may predict future performance.

Improving the Defense Acquisition System and Reducing System Costs

DTIC Science & Technology

1981-03-30

The need for this specific commitment results from the competition among the conflicting objectives of high perform- ance, lower cost, shorter... conflict with initiatives to improve reliability and support. Whereas the fastest acquisition approach involves initiating production prxor to...their Individual thrusts result in confusion on the part of OASD who tries to implement conflicting programs, and of defense contractors performing

Discover CHP

EPA Pesticide Factsheets

Access information about how CHP systems work; their efficiency, environmental, economic, and reliability benefits; the cost and performance characteristics of CHP technologies; and how to calculate CHP efficiency emissions savings.

Feasibility model of a high reliability five-year tape transport, Volume 1. [development, performance, and test results

NASA Technical Reports Server (NTRS)

Eshleman, R. L.; Meyers, A. P.; Davidson, W. A.; Gortowski, R. C.; Anderson, M. E.

1973-01-01

The development, performance, and test results for the spaceborne magnetic tape transport are discussed. An analytical model of the tape transport was used to optimize its conceptual design. Each of the subsystems was subjected to reliability analyses which included structural integrity, maintenance of system performance within acceptable bounds, and avoidance of fatigue failure. These subsystems were also compared with each other in order to evaluate reliability characteristics. The transport uses no mechanical couplings. Four drive motors, one for each reel and one for each of two capstans, are used in a differential mode. There are two hybrid, spherical, cone tapered-crown rollers for tape guidance. Storage of the magnetic tape is provided by a reel assembly which includes the reel, a reel support structure and bearings, dust seals, and a dc drive motor. A summary of transport test results on tape guidance, flutter, and skew is provided.

Efficient reliability analysis of structures with the rotational quasi-symmetric point- and the maximum entropy methods

NASA Astrophysics Data System (ADS)

Xu, Jun; Dang, Chao; Kong, Fan

2017-10-01

This paper presents a new method for efficient structural reliability analysis. In this method, a rotational quasi-symmetric point method (RQ-SPM) is proposed for evaluating the fractional moments of the performance function. Then, the derivation of the performance function's probability density function (PDF) is carried out based on the maximum entropy method in which constraints are specified in terms of fractional moments. In this regard, the probability of failure can be obtained by a simple integral over the performance function's PDF. Six examples, including a finite element-based reliability analysis and a dynamic system with strong nonlinearity, are used to illustrate the efficacy of the proposed method. All the computed results are compared with those by Monte Carlo simulation (MCS). It is found that the proposed method can provide very accurate results with low computational effort.

A hierarchical approach to reliability modeling of fault-tolerant systems. M.S. Thesis

NASA Technical Reports Server (NTRS)

Gossman, W. E.

1986-01-01

A methodology for performing fault tolerant system reliability analysis is presented. The method decomposes a system into its subsystems, evaluates vent rates derived from the subsystem's conditional state probability vector and incorporates those results into a hierarchical Markov model of the system. This is done in a manner that addresses failure sequence dependence associated with the system's redundancy management strategy. The method is derived for application to a specific system definition. Results are presented that compare the hierarchical model's unreliability prediction to that of a more complicated tandard Markov model of the system. The results for the example given indicate that the hierarchical method predicts system unreliability to a desirable level of accuracy while achieving significant computational savings relative to component level Markov model of the system.

Evaluation of fault-tolerant parallel-processor architectures over long space missions

NASA Technical Reports Server (NTRS)

Johnson, Sally C.

1989-01-01

The impact of a five year space mission environment on fault-tolerant parallel processor architectures is examined. The target application is a Strategic Defense Initiative (SDI) satellite requiring 256 parallel processors to provide the computation throughput. The reliability requirements are that the system still be operational after five years with .99 probability and that the probability of system failure during one-half hour of full operation be less than 10(-7). The fault tolerance features an architecture must possess to meet these reliability requirements are presented, many potential architectures are briefly evaluated, and one candidate architecture, the Charles Stark Draper Laboratory's Fault-Tolerant Parallel Processor (FTPP) is evaluated in detail. A methodology for designing a preliminary system configuration to meet the reliability and performance requirements of the mission is then presented and demonstrated by designing an FTPP configuration.

Reliability assessment of fiber optic communication lines depending on external factors and diagnostic errors

NASA Astrophysics Data System (ADS)

Bogachkov, I. V.; Lutchenko, S. S.

2018-05-01

The article deals with the method for the assessment of the fiber optic communication lines (FOCL) reliability taking into account the effect of the optical fiber tension, the temperature influence and the built-in diagnostic equipment errors of the first kind. The reliability is assessed in terms of the availability factor using the theory of Markov chains and probabilistic mathematical modeling. To obtain a mathematical model, the following steps are performed: the FOCL state is defined and validated; the state graph and system transitions are described; the system transition of states that occur at a certain point is specified; the real and the observed time of system presence in the considered states are identified. According to the permissible value of the availability factor, it is possible to determine the limiting frequency of FOCL maintenance.

Reliability analysis of repairable systems using Petri nets and vague Lambda-Tau methodology.

PubMed

Garg, Harish

2013-01-01

The main objective of the paper is to developed a methodology, named as vague Lambda-Tau, for reliability analysis of repairable systems. Petri net tool is applied to represent the asynchronous and concurrent processing of the system instead of fault tree analysis. To enhance the relevance of the reliability study, vague set theory is used for representing the failure rate and repair times instead of classical(crisp) or fuzzy set theory because vague sets are characterized by a truth membership function and false membership functions (non-membership functions) so that sum of both values is less than 1. The proposed methodology involves qualitative modeling using PN and quantitative analysis using Lambda-Tau method of solution with the basic events represented by intuitionistic fuzzy numbers of triangular membership functions. Sensitivity analysis has also been performed and the effects on system MTBF are addressed. The methodology improves the shortcomings of the existing probabilistic approaches and gives a better understanding of the system behavior through its graphical representation. The washing unit of a paper mill situated in a northern part of India, producing approximately 200 ton of paper per day, has been considered to demonstrate the proposed approach. The results may be helpful for the plant personnel for analyzing the systems' behavior and to improve their performance by adopting suitable maintenance strategies. Copyright © 2012 ISA. Published by Elsevier Ltd. All rights reserved.

Optimized Biasing of Pump Laser Diodes in a Highly Reliable Metrology Source for Long-Duration Space Missions

NASA Technical Reports Server (NTRS)

Poberezhskiy, Ilya Y; Chang, Daniel H.; Erlig, Herman

2011-01-01

Optical metrology system reliability during a prolonged space mission is often limited by the reliability of pump laser diodes. We developed a metrology laser pump module architecture that meets NASA SIM Lite instrument optical power and reliability requirements by combining the outputs of multiple single-mode pump diodes in a low-loss, high port count fiber coupler. We describe Monte-Carlo simulations used to calculate the reliability of the laser pump module and introduce a combined laser farm aging parameter that serves as a load-sharing optimization metric. Employing these tools, we select pump module architecture, operating conditions, biasing approach and perform parameter sensitivity studies to investigate the robustness of the obtained solution.

WSN- and IOT-Based Smart Homes and Their Extension to Smart Buildings

PubMed Central

Ghayvat, Hemant; Mukhopadhyay, Subhas; Gui, Xiang; Suryadevara, Nagender

2015-01-01

Our research approach is to design and develop reliable, efficient, flexible, economical, real-time and realistic wellness sensor networks for smart home systems. The heterogeneous sensor and actuator nodes based on wireless networking technologies are deployed into the home environment. These nodes generate real-time data related to the object usage and movement inside the home, to forecast the wellness of an individual. Here, wellness stands for how efficiently someone stays fit in the home environment and performs his or her daily routine in order to live a long and healthy life. We initiate the research with the development of the smart home approach and implement it in different home conditions (different houses) to monitor the activity of an inhabitant for wellness detection. Additionally, our research extends the smart home system to smart buildings and models the design issues related to the smart building environment; these design issues are linked with system performance and reliability. This research paper also discusses and illustrates the possible mitigation to handle the ISM band interference and attenuation losses without compromising optimum system performance. PMID:25946630

WSN- and IOT-Based Smart Homes and Their Extension to Smart Buildings.

PubMed

Ghayvat, Hemant; Mukhopadhyay, Subhas; Gui, Xiang; Suryadevara, Nagender

2015-05-04

Our research approach is to design and develop reliable, efficient, flexible, economical, real-time and realistic wellness sensor networks for smart home systems. The heterogeneous sensor and actuator nodes based on wireless networking technologies are deployed into the home environment. These nodes generate real-time data related to the object usage and movement inside the home, to forecast the wellness of an individual. Here, wellness stands for how efficiently someone stays fit in the home environment and performs his or her daily routine in order to live a long and healthy life. We initiate the research with the development of the smart home approach and implement it in different home conditions (different houses) to monitor the activity of an inhabitant for wellness detection. Additionally, our research extends the smart home system to smart buildings and models the design issues related to the smart building environment; these design issues are linked with system performance and reliability. This research paper also discusses and illustrates the possible mitigation to handle the ISM band interference and attenuation losses without compromising optimum system performance.

Benefits of Imperfect Conflict Resolution Advisory Aids for Future Air Traffic Control.

PubMed

Trapsilawati, Fitri; Wickens, Christopher D; Qu, Xingda; Chen, Chun-Hsien

2016-11-01

The aim of this study was to examine the human-automation interaction issues and the interacting factors in the context of conflict detection and resolution advisory (CRA) systems. The issues of imperfect automation in air traffic control (ATC) have been well documented in previous studies, particularly in conflict-alerting systems. The extent to which the prior findings can be applied to an integrated conflict detection and resolution system in future ATC remains unknown. Twenty-four participants were evenly divided into two groups corresponding to a medium- and a high-traffic density condition, respectively. In each traffic density condition, participants were instructed to perform simulated ATC tasks under four automation conditions, including reliable, unreliable with short time allowance to secondary conflict (TAS), unreliable with long TAS, and manual conditions. Dependent variables accounted for conflict resolution performance, workload, situation awareness, and trust in and dependence on the CRA aid, respectively. Imposing the CRA automation did increase performance and reduce workload as compared with manual performance. The CRA aid did not decrease situation awareness. The benefits of the CRA aid were manifest even when it was imperfectly reliable and were apparent across traffic loads. In the unreliable blocks, trust in the CRA aid was degraded but dependence was not influenced, yet the performance was not adversely affected. The use of CRA aid would benefit ATC operations across traffic densities. CRA aid offers benefits across traffic densities, regardless of its imperfection, as long as its reliability level is set above the threshold of assistance, suggesting its application for future ATC. © 2016, Human Factors and Ergonomics Society.

Electric service reliability cost/worth assessment in a developing country

NASA Astrophysics Data System (ADS)

Pandey, Mohan Kumar

Considerable work has been done in developed countries to optimize the reliability of electric power systems on the basis of reliability cost versus reliability worth. This has yet to be considered in most developing countries, where development plans are still based on traditional deterministic measures. The difficulty with these criteria is that they cannot be used to evaluate the economic impacts of changing reliability levels on the utility and the customers, and therefore cannot lead to an optimum expansion plan for the system. The critical issue today faced by most developing countries is that the demand for electric power is high and growth in supply is constrained by technical, environmental, and most importantly by financial impediments. Many power projects are being canceled or postponed due to a lack of resources. The investment burden associated with the electric power sector has already led some developing countries into serious debt problems. This thesis focuses on power sector issues facing by developing countries and illustrates how a basic reliability cost/worth approach can be used in a developing country to determine appropriate planning criteria and justify future power projects by application to the Nepal Integrated Electric Power System (NPS). A reliability cost/worth based system evaluation framework is proposed in this thesis. Customer surveys conducted throughout Nepal using in-person interviews with approximately 2000 sample customers are presented. The survey results indicate that the interruption cost is dependent on both customer and interruption characteristics, and it varies from one location or region to another. Assessments at both the generation and composite system levels have been performed using the customer cost data and the developed NPS reliability database. The results clearly indicate the implications of service reliability to the electricity consumers of Nepal, and show that the reliability cost/worth evaluation is both possible and practical in a developing country. The average customer interruption costs of Rs 35/kWh at Hierarchical Level I and Rs 26/kWh at Hierarchical Level II evaluated in this research work led to an optimum reserve margin of 7.5%, which is considerably lower than the traditional reserve margin of 15% used in the NPS. A similar conclusion may result in other developing countries facing difficulties in power system expansion planning using the traditional approach. A new framework for system planning is therefore recommended for developing countries which would permit an objective review of the traditional system planning approach, and the evaluation of future power projects using a new approach based on fundamental principles of power system reliability and economics.

Inertial Measurement Units for Clinical Movement Analysis: Reliability and Concurrent Validity

PubMed Central

Nicholas, Kevin; Sparkes, Valerie; Sheeran, Liba; Davies, Jennifer L

2018-01-01

The aim of this study was to investigate the reliability and concurrent validity of a commercially available Xsens MVN BIOMECH inertial-sensor-based motion capture system during clinically relevant functional activities. A clinician with no prior experience of motion capture technologies and an experienced clinical movement scientist each assessed 26 healthy participants within each of two sessions using a camera-based motion capture system and the MVN BIOMECH system. Participants performed overground walking, squatting, and jumping. Sessions were separated by 4 ± 3 days. Reliability was evaluated using intraclass correlation coefficient and standard error of measurement, and validity was evaluated using the coefficient of multiple correlation and the linear fit method. Day-to-day reliability was generally fair-to-excellent in all three planes for hip, knee, and ankle joint angles in all three tasks. Within-day (between-rater) reliability was fair-to-excellent in all three planes during walking and squatting, and poor-to-high during jumping. Validity was excellent in the sagittal plane for hip, knee, and ankle joint angles in all three tasks and acceptable in frontal and transverse planes in squat and jump activity across joints. Our results suggest that the MVN BIOMECH system can be used by a clinician to quantify lower-limb joint angles in clinically relevant movements. PMID:29495600

A new scale for the assessment of performance and capacity of hand function in children with hemiplegic cerebral palsy: reliability and validity studies.

PubMed

Rosa-Rizzotto, M; Visonà Dalla Pozza, L; Corlatti, A; Luparia, A; Marchi, A; Molteni, F; Facchin, P; Pagliano, E; Fedrizzi, E

2014-10-01

In hemiplegic children, the recognition of the activity limitation pattern and the possibility of grading its severity are relevant for clinicians while planning interventions, monitoring results, predicting outcomes. Aim of the study is to examine the reliability and validity of Besta Scale, an instrument used to measure in hemiplegic children from 18 months to 12 years of age both grasp on request (capacity) and spontaneous use of upper limb (performance) in bimanual play activities and in ADL. Psychometric analysis of reliability and of validity of the Besta scale was performed. Outpatient study sample Reliability study: A sample of 39 patients was enrolled. The administration of Besta scale was video-recorded in a standardized manner. All videos were scored by 20 independent raters on subsequent viewing. 3 raters randomly selected from the 20-raters group rescored the same video two years later for intra-rater reliability. Intra and inter-rater reliability were calculated using Intraclass Correlation Coefficient (ICC) and Kendall's coefficient (K), respectively. Internal consistency reliability was assessed using Alpha's Chronbach coefficient. Validity study: a sample of 105 children was assessed 5 times (at t0 and 2, 3, 6 and 12 months later) by 20 independent raters. Each patient underwent at the same time to QUEST and Besta scale administration and assessment. Criterion validity was calculated using rho-Pearson coefficient. Reliability study: The inter-rater reliability calculated with Kendall's coefficient resulted moderate K=0.47. The intra-rater (or test-retest) reliability for 3 raters was excellent (ICC=0.927). The Cronbach's alpha for internal consistency was 0.972. Validity study: Besta scale showed a good criterion validity compared to QUEST increasing by age and severity of impairment. Rho Pearson's correlation coefficient r was 0.81 (P<0.0001). Limitations. Besta scales in infants finds hard to distinguish between mild to moderately impaired hand function. Besta scale scoring system is a valid and reliable tool, utilizable in a clinical setting to monitor evolution of unimanual and bimanual manipulation and to distinguish hand's capacity from performance.

48 CFR 215.404-71-2 - Performance risk.

Code of Federal Regulations, 2011 CFR

2011-10-01

... incentive range when contract performance includes the introduction of new, significant technological innovation. Use the technology incentive range only for the most innovative contract efforts. Innovation may... reliability, or reduced costs; or (B) New products or systems that contain significant technological advances...

Performability modeling with continuous accomplishment sets

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1979-01-01

A general modeling framework that permits the definition, formulation, and evaluation of performability is described. It is shown that performability relates directly to system effectiveness, and is a proper generalization of both performance and reliability. A hierarchical modeling scheme is used to formulate the capability function used to evaluate performability. The case in which performance variables take values in a continuous accomplishment set is treated explicitly.

[Examination of safety improvement by failure record analysis that uses reliability engineering].

PubMed

Kato, Kyoichi; Sato, Hisaya; Abe, Yoshihisa; Ishimori, Yoshiyuki; Hirano, Hiroshi; Higashimura, Kyoji; Amauchi, Hiroshi; Yanakita, Takashi; Kikuchi, Kei; Nakazawa, Yasuo

2010-08-20

How the maintenance checks of the medical treatment system, including start of work check and the ending check, was effective for preventive maintenance and the safety improvement was verified. In this research, date on the failure of devices in multiple facilities was collected, and the data of the trouble repair record was analyzed by the technique of reliability engineering. An analysis of data on the system (8 general systems, 6 Angio systems, 11 CT systems, 8 MRI systems, 8 RI systems, and the radiation therapy system 9) used in eight hospitals was performed. The data collection period assumed nine months from April to December 2008. Seven items were analyzed. (1) Mean time between failures (MTBF) (2) Mean time to repair (MTTR) (3) Mean down time (MDT) (4) Number found by check in morning (5) Failure generation time according to modality. The classification of the breakdowns per device, the incidence, and the tendency could be understood by introducing reliability engineering. Analysis, evaluation, and feedback on the failure generation history are useful to keep downtime to a minimum and to ensure safety.

Optimum random and age replacement policies for customer-demand multi-state system reliability under imperfect maintenance

NASA Astrophysics Data System (ADS)

Chen, Yen-Luan; Chang, Chin-Chih; Sheu, Dwan-Fang

2016-04-01

This paper proposes the generalised random and age replacement policies for a multi-state system composed of multi-state elements. The degradation of the multi-state element is assumed to follow the non-homogeneous continuous time Markov process which is a continuous time and discrete state process. A recursive approach is presented to efficiently compute the time-dependent state probability distribution of the multi-state element. The state and performance distribution of the entire multi-state system is evaluated via the combination of the stochastic process and the Lz-transform method. The concept of customer-centred reliability measure is developed based on the system performance and the customer demand. We develop the random and age replacement policies for an aging multi-state system subject to imperfect maintenance in a failure (or unacceptable) state. For each policy, the optimum replacement schedule which minimises the mean cost rate is derived analytically and discussed numerically.

Fatigue reliability of deck structures subjected to correlated crack growth

NASA Astrophysics Data System (ADS)

Feng, G. Q.; Garbatov, Y.; Guedes Soares, C.

2013-12-01

The objective of this work is to analyse fatigue reliability of deck structures subjected to correlated crack growth. The stress intensity factors of the correlated cracks are obtained by finite element analysis and based on which the geometry correction functions are derived. The Monte Carlo simulations are applied to predict the statistical descriptors of correlated cracks based on the Paris-Erdogan equation. A probabilistic model of crack growth as a function of time is used to analyse the fatigue reliability of deck structures accounting for the crack propagation correlation. A deck structure is modelled as a series system of stiffened panels, where a stiffened panel is regarded as a parallel system composed of plates and are longitudinal. It has been proven that the method developed here can be conveniently applied to perform the fatigue reliability assessment of structures subjected to correlated crack growth.

Design of low-cost general purpose microcontroller based neuromuscular stimulator.

PubMed

Koçer, S; Rahmi Canal, M; Güler, I

2000-04-01

In this study, a general purpose, low-cost, programmable, portable and high performance stimulator is designed and implemented. For this purpose, a microcontroller is used in the design of the stimulator. The duty cycle and amplitude of the designed system can be controlled using a keyboard. The performance test of the system has shown that the results are reliable. The overall system can be used as the neuromuscular stimulator under safe conditions.

Models and techniques for evaluating the effectiveness of aircraft computing systems

NASA Technical Reports Server (NTRS)

Meyer, J. F.

1977-01-01

Models, measures and techniques were developed for evaluating the effectiveness of aircraft computing systems. The concept of effectiveness involves aspects of system performance, reliability and worth. Specifically done was a detailed development of model hierarchy at mission, functional task, and computational task levels. An appropriate class of stochastic models was investigated which served as bottom level models in the hierarchial scheme. A unified measure of effectiveness called 'performability' was defined and formulated.

Exploiting New Data Sources to Quantify Arterial Congestion and Performance Measures.

DOT National Transportation Integrated Search

2017-01-01

Transit travel time, operating speed and reliability all influence service attractiveness, operating cost and system efficiency. These metrics have a long-term impact on system effectiveness through a change in ridership. As part of its bus dispatch ...

Statistical Analysis Tools for Learning in Engineering Laboratories.

ERIC Educational Resources Information Center

Maher, Carolyn A.

1990-01-01

Described are engineering programs that have used automated data acquisition systems to implement data collection and analyze experiments. Applications include a biochemical engineering laboratory, heat transfer performance, engineering materials testing, mechanical system reliability, statistical control laboratory, thermo-fluid laboratory, and a…

A highly reliable, autonomous data communication subsystem for an advanced information processing system

NASA Technical Reports Server (NTRS)

Nagle, Gail; Masotto, Thomas; Alger, Linda

1990-01-01

The need to meet the stringent performance and reliability requirements of advanced avionics systems has frequently led to implementations which are tailored to a specific application and are therefore difficult to modify or extend. Furthermore, many integrated flight critical systems are input/output intensive. By using a design methodology which customizes the input/output mechanism for each new application, the cost of implementing new systems becomes prohibitively expensive. One solution to this dilemma is to design computer systems and input/output subsystems which are general purpose, but which can be easily configured to support the needs of a specific application. The Advanced Information Processing System (AIPS), currently under development has these characteristics. The design and implementation of the prototype I/O communication system for AIPS is described. AIPS addresses reliability issues related to data communications by the use of reconfigurable I/O networks. When a fault or damage event occurs, communication is restored to functioning parts of the network and the failed or damage components are isolated. Performance issues are addressed by using a parallelized computer architecture which decouples Input/Output (I/O) redundancy management and I/O processing from the computational stream of an application. The autonomous nature of the system derives from the highly automated and independent manner in which I/O transactions are conducted for the application as well as from the fact that the hardware redundancy management is entirely transparent to the application.

Fuel Cell Balance-of-Plant Reliability Testbed Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sproat, Vern; LaHurd, Debbie

Reliability of the fuel cell system balance-of-plant (BoP) components is a critical factor that needs to be addressed prior to fuel cells becoming fully commercialized. Failure or performance degradation of BoP components has been identified as a life-limiting factor in fuel cell systems.1 The goal of this project is to develop a series of test beds that will test system components such as pumps, valves, sensors, fittings, etc., under operating conditions anticipated in real Polymer Electrolyte Membrane (PEM) fuel cell systems. Results will be made generally available to begin removing reliability as a roadblock to the growth of the PEMmore » fuel cell industry. Stark State College students participating in the project, in conjunction with their coursework, have been exposed to technical knowledge and training in the handling and maintenance of hydrogen, fuel cells and system components as well as component failure modes and mechanisms. Three test beds were constructed. Testing was completed on gas flow pumps, tubing, and pressure and temperature sensors and valves.« less

High rate concatenated coding systems using bandwidth efficient trellis inner codes

NASA Technical Reports Server (NTRS)

Deng, Robert H.; Costello, Daniel J., Jr.

1989-01-01

High-rate concatenated coding systems with bandwidth-efficient trellis inner codes and Reed-Solomon (RS) outer codes are investigated for application in high-speed satellite communication systems. Two concatenated coding schemes are proposed. In one the inner code is decoded with soft-decision Viterbi decoding, and the outer RS code performs error-correction-only decoding (decoding without side information). In the other, the inner code is decoded with a modified Viterbi algorithm, which produces reliability information along with the decoded output. In this algorithm, path metrics are used to estimate the entire information sequence, whereas branch metrics are used to provide reliability information on the decoded sequence. This information is used to erase unreliable bits in the decoded output. An errors-and-erasures RS decoder is then used for the outer code. The two schemes have been proposed for high-speed data communication on NASA satellite channels. The rates considered are at least double those used in current NASA systems, and the results indicate that high system reliability can still be achieved.

RICA: a reliable and image configurable arena for cyborg bumblebee based on CAN bus.

PubMed

Gong, Fan; Zheng, Nenggan; Xue, Lei; Xu, Kedi; Zheng, Xiaoxiang

2014-01-01

In this paper, we designed a reliable and image configurable flight arena, RICA, for developing cyborg bumblebees. To meet the spatial and temporal requirements of bumblebees, the Controller Area Network (CAN) bus is adopted to interconnect the LED display modules to ensure the reliability and real-time performance of the arena system. Easily-configurable interfaces on a desktop computer implemented by python scripts are provided to transmit the visual patterns to the LED distributor online and configure RICA dynamically. The new arena system will be a power tool to investigate the quantitative relationship between the visual inputs and induced flight behaviors and also will be helpful to the visual-motor research in other related fields.

Analysis of off-grid hybrid wind turbine/solar PV water pumping systems

USDA-ARS?s Scientific Manuscript database

While many remote water pumping systems exist (e.g. mechanical windmills, solar photovoltaic , wind-electric, diesel powered), very few combine both the wind and solar energy resources to possibly improve the reliability and the performance of the system. In this paper, off-grid wind turbine (WT) a...

A Framework For Fault Tolerance In Virtualized Servers

DTIC Science & Technology

2016-06-01

effects into the system. Decrease in performance, the expansion in the total system size and weight, and a hike in the system cost can be counted in... benefit also shines out in terms of reliability. 41 4. How Data Guard Synchronizes Standby Databases Primary and standby databases in Oracle Data

Use of Soft Computing Technologies for a Qualitative and Reliable Engine Control System for Propulsion Systems

NASA Technical Reports Server (NTRS)

Trevino, Luis; Brown, Terry; Crumbley, R. T. (Technical Monitor)

2001-01-01

The problem to be addressed in this paper is to explore how the use of Soft Computing Technologies (SCT) could be employed to improve overall vehicle system safety, reliability, and rocket engine performance by development of a qualitative and reliable engine control system (QRECS). Specifically, this will be addressed by enhancing rocket engine control using SCT, innovative data mining tools, and sound software engineering practices used in Marshall's Flight Software Group (FSG). The principle goals for addressing the issue of quality are to improve software management, software development time, software maintenance, processor execution, fault tolerance and mitigation, and nonlinear control in power level transitions. The intent is not to discuss any shortcomings of existing engine control methodologies, but to provide alternative design choices for control, implementation, performance, and sustaining engineering, all relative to addressing the issue of reliability. The approaches outlined in this paper will require knowledge in the fields of rocket engine propulsion (system level), software engineering for embedded flight software systems, and soft computing technologies (i.e., neural networks, fuzzy logic, data mining, and Bayesian belief networks); some of which are briefed in this paper. For this effort, the targeted demonstration rocket engine testbed is the MC-1 engine (formerly FASTRAC) which is simulated with hardware and software in the Marshall Avionics & Software Testbed (MAST) laboratory that currently resides at NASA's Marshall Space Flight Center, building 4476, and is managed by the Avionics Department. A brief plan of action for design, development, implementation, and testing a Phase One effort for QRECS is given, along with expected results. Phase One will focus on development of a Smart Start Engine Module and a Mainstage Engine Module for proper engine start and mainstage engine operations. The overall intent is to demonstrate that by employing soft computing technologies, the quality and reliability of the overall scheme to engine controller development is further improved and vehicle safety is further insured. The final product that this paper proposes is an approach to development of an alternative low cost engine controller that would be capable of performing in unique vision spacecraft vehicles requiring low cost advanced avionics architectures for autonomous operations from engine pre-start to engine shutdown.

Conceptual design of a piloted Mars sprint life support system

NASA Technical Reports Server (NTRS)

Cullingford, H. S.; Novara, M.

1988-01-01

This paper presents the conceptual design of a life support system sustaining a crew of six in a piloted Mars sprint. The requirements and constraints of the system are discussed along with its baseline performance parameters. An integrated operation is achieved with air, water, and waste processing and supplemental food production. The design philosophy includes maximized reliability considerations, regenerative operations, reduced expendables, and fresh harvest capability. The life support system performance will be described with characteristics of the associated physical-chemical subsystems and a greenhouse.

Measuring School Climate for Gauging Principal Performance: A Review of the Validity and Reliability of Publicly Accessible Measures. A Quality School Leadership Issue Brief

ERIC Educational Resources Information Center

Clifford, Matthew; Menon, Roshni; Gangi, Tracy; Condon, Christopher; Hornung, Katie

2012-01-01

This policy brief provides principal evaluation system designers information about the technical soundness and cost (i.e., time requirements) of publicly available school climate surveys. The authors focus on the technical soundness of school climate surveys because they believe that using validated and reliable surveys as an outcomes measure can…

Robert Tirawat | NREL

Science.gov Websites

-performance, high-reliability systems that use concentrated sunlight to generate power. Recently, Robert has been involved developing a high-efficiency solar selective absorber and anti-corrosion coatings

Ultrasound definition of tendon damage in patients with rheumatoid arthritis. Results of a OMERACT consensus-based ultrasound score focussing on the diagnostic reliability.

PubMed

Bruyn, George A W; Hanova, Petra; Iagnocco, Annamaria; d'Agostino, Maria-Antonietta; Möller, Ingrid; Terslev, Lene; Backhaus, Marina; Balint, Peter V; Filippucci, Emilio; Baudoin, Paul; van Vugt, Richard; Pineda, Carlos; Wakefield, Richard; Garrido, Jesus; Pecha, Ondrej; Naredo, Esperanza

2014-11-01

To develop the first ultrasound scoring system of tendon damage in rheumatoid arthritis (RA) and assess its intraobserver and interobserver reliability. We conducted a Delphi study on ultrasound-defined tendon damage and ultrasound scoring system of tendon damage in RA among 35 international rheumatologists with experience in musculoskeletal ultrasound. Twelve patients with RA were included and assessed twice by 12 rheumatologists-sonographers. Ultrasound examination for tendon damage in B mode of five wrist extensor compartments (extensor carpi radialis brevis and longus; extensor pollicis longus; extensor digitorum communis; extensor digiti minimi; extensor carpi ulnaris) and one ankle tendon (tibialis posterior) was performed blindly, independently and bilaterally in each patient. Intraobserver and interobserver reliability were calculated by κ coefficients. A three-grade semiquantitative scoring system was agreed for scoring tendon damage in B mode. The mean intraobserver reliability for tendon damage scoring was excellent (κ value 0.91). The mean interobserver reliability assessment showed good κ values (κ value 0.75). The most reliable were the extensor digiti minimi, the extensor carpi ulnaris, and the tibialis posterior tendons. An ultrasound reference image atlas of tenosynovitis and tendon damage was also developed. Ultrasound is a reproducible tool for evaluating tendon damage in RA. This study strongly supports a new reliable ultrasound scoring system for tendon damage. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Practical Framework: Implementing OEE Method in Manufacturing Process Environment

NASA Astrophysics Data System (ADS)

Maideen, N. C.; Sahudin, S.; Mohd Yahya, N. H.; Norliawati, A. O.

2016-02-01

Manufacturing process environment requires reliable machineries in order to be able to satisfy the market demand. Ideally, a reliable machine is expected to be operated and produce a quality product at its maximum designed capability. However, due to some reason, the machine usually unable to achieved the desired performance. Since the performance will affect the productivity of the system, a measurement technique should be applied. Overall Equipment Effectiveness (OEE) is a good method to measure the performance of the machine. The reliable result produced from OEE can then be used to propose a suitable corrective action. There are a lot of published paper mentioned about the purpose and benefit of OEE that covers what and why factors. However, the how factor not yet been revealed especially the implementation of OEE in manufacturing process environment. Thus, this paper presents a practical framework to implement OEE and a case study has been discussed to explain in detail each steps proposed. The proposed framework is beneficial to the engineer especially the beginner to start measure their machine performance and later improve the performance of the machine.

Medical reliable network using concatenated channel codes through GSM network.

PubMed

Ahmed, Emtithal; Kohno, Ryuji

2013-01-01

Although the 4(th) generation (4G) of global mobile communication network, i.e. Long Term Evolution (LTE) coexisting with the 3(rd) generation (3G) has successfully started; the 2(nd) generation (2G), i.e. Global System for Mobile communication (GSM) still playing an important role in many developing countries. Without any other reliable network infrastructure, GSM can be applied for tele-monitoring applications, where high mobility and low cost are necessary. A core objective of this paper is to introduce the design of a more reliable and dependable Medical Network Channel Code system (MNCC) through GSM Network. MNCC design based on simple concatenated channel code, which is cascade of an inner code (GSM) and an extra outer code (Convolution Code) in order to protect medical data more robust against channel errors than other data using the existing GSM network. In this paper, the MNCC system will provide Bit Error Rate (BER) equivalent to the BER for medical tele monitoring of physiological signals, which is 10(-5) or less. The performance of the MNCC has been proven and investigated using computer simulations under different channels condition such as, Additive White Gaussian Noise (AWGN), Rayleigh noise and burst noise. Generally the MNCC system has been providing better performance as compared to GSM.

Error control techniques for satellite and space communications

NASA Technical Reports Server (NTRS)

Costello, D. J., Jr.

1986-01-01

High rate concatenated coding systems with trellis inner codes and Reed-Solomon (RS) outer codes for application in satellite communication systems are considered. Two types of inner codes are studied: high rate punctured binary convolutional codes which result in overall effective information rates between 1/2 and 1 bit per channel use; and bandwidth efficient signal space trellis codes which can achieve overall effective information rates greater than 1 bit per channel use. Channel capacity calculations with and without side information performed for the concatenated coding system. Concatenated coding schemes are investigated. In Scheme 1, the inner code is decoded with the Viterbi algorithm and the outer RS code performs error-correction only (decoding without side information). In scheme 2, the inner code is decoded with a modified Viterbi algorithm which produces reliability information along with the decoded output. In this algorithm, path metrics are used to estimate the entire information sequence, while branch metrics are used to provide the reliability information on the decoded sequence. This information is used to erase unreliable bits in the decoded output. An errors-and-erasures RS decoder is then used for the outer code. These two schemes are proposed for use on NASA satellite channels. Results indicate that high system reliability can be achieved with little or no bandwidth expansion.

MoDOT pavement preservation research program volume III, development of pavement family and treatment performance models.

DOT National Transportation Integrated Search

2015-10-01

Pavement performance models describe the deterioration behavior of pavements. They are essential in a pavement management : system if the goal is to make more objective, reliable, and cost-effective decisions regarding the timing and nature of paveme...

Wireless and Powerless Sensing Node System Developed for Monitoring Motors.

PubMed

Lee, Dasheng

2008-08-27

Reliability and maintainability of tooling systems can be improved through condition monitoring of motors. However, it is difficult to deploy sensor nodes due to the harsh environment of industrial plants. Sensor cables are easily damaged, which renders the monitoring system deployed to assure the machine's reliability itself unreliable. A wireless and powerless sensing node integrated with a MEMS (Micro Electro-Mechanical System) sensor, a signal processor, a communication module, and a self-powered generator was developed in this study for implementation of an easily mounted network sensor for monitoring motors. A specially designed communication module transmits a sequence of electromagnetic (EM) pulses in response to the sensor signals. The EM pulses can penetrate through the machine's metal case and delivers signals from the sensor inside the motor to the external data acquisition center. By using induction power, which is generated by the motor's shaft rotation, the sensor node is self-sustaining; therefore, no power line is required. A monitoring system, equipped with novel sensing nodes, was constructed to test its performance. The test results illustrate that, the novel sensing node developed in this study can effectively enhance the reliability of the motor monitoring system and it is expected to be a valuable technology, which will be available to the plant for implementation in a reliable motor management program.

Wireless and Powerless Sensing Node System Developed for Monitoring Motors

PubMed Central

Lee, Dasheng

2008-01-01

Reliability and maintainability of tooling systems can be improved through condition monitoring of motors. However, it is difficult to deploy sensor nodes due to the harsh environment of industrial plants. Sensor cables are easily damaged, which renders the monitoring system deployed to assure the machine's reliability itself unreliable. A wireless and powerless sensing node integrated with a MEMS (Micro Electro-Mechanical System) sensor, a signal processor, a communication module, and a self-powered generator was developed in this study for implementation of an easily mounted network sensor for monitoring motors. A specially designed communication module transmits a sequence of electromagnetic (EM) pulses in response to the sensor signals. The EM pulses can penetrate through the machine's metal case and delivers signals from the sensor inside the motor to the external data acquisition center. By using induction power, which is generated by the motor's shaft rotation, the sensor node is self-sustaining; therefore, no power line is required. A monitoring system, equipped with novel sensing nodes, was constructed to test its performance. The test results illustrate that, the novel sensing node developed in this study can effectively enhance the reliability of the motor monitoring system and it is expected to be a valuable technology, which will be available to the plant for implementation in a reliable motor management program. PMID:27873798

Automation of diagnostic genetic testing: mutation detection by cyclic minisequencing.

PubMed

Alagrund, Katariina; Orpana, Arto K

2014-01-01

The rising role of nucleic acid testing in clinical decision making is creating a need for efficient and automated diagnostic nucleic acid test platforms. Clinical use of nucleic acid testing sets demands for shorter turnaround times (TATs), lower production costs and robust, reliable methods that can easily adopt new test panels and is able to run rare tests in random access principle. Here we present a novel home-brew laboratory automation platform for diagnostic mutation testing. This platform is based on the cyclic minisequecing (cMS) and two color near-infrared (NIR) detection. Pipetting is automated using Tecan Freedom EVO pipetting robots and all assays are performed in 384-well micro plate format. The automation platform includes a data processing system, controlling all procedures, and automated patient result reporting to the hospital information system. We have found automated cMS a reliable, inexpensive and robust method for nucleic acid testing for a wide variety of diagnostic tests. The platform is currently in clinical use for over 80 mutations or polymorphisms. Additionally to tests performed from blood samples, the system performs also epigenetic test for the methylation of the MGMT gene promoter, and companion diagnostic tests for analysis of KRAS and BRAF gene mutations from formalin fixed and paraffin embedded tumor samples. Automation of genetic test reporting is found reliable and efficient decreasing the work load of academic personnel.

Simulation of the Australian Mobilesat signalling scheme

NASA Technical Reports Server (NTRS)

Rahman, Mushfiqur

1990-01-01

The proposed Australian Mobilesat system will provide a range of circuit switched voice/data services using the B-series satellites. The reliability of the signalling scheme between the Network Management Station (NMS) and the mobile terminal (MT) is of critical importance to the performance of the overall system. Simulation results of the performance of the signalling scheme under various channel conditions and coding schemes are presented.

Technology verification phase. Dynamic isotope power system. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halsey, D.G.

1982-03-10

The Phase I requirements of the Kilowatt Isotope Power System (KIPS) program were to make a detailed Flight System Conceptual Design (FSCD) for an isotope fueled organic Rankine cycle power system and to build and test a Ground Demonstration System (GDS) which simulated as closely as possible the operational characteristics of the FSCD. The activities and results of Phase II, the Technology Verification Phase, of the program are reported. The objectives of this phase were to increase system efficiency to 18.1% by component development, to demonstrate system reliability by a 5000 h endurance test and to update the flight systemmore » design. During Phase II, system performance was improved from 15.1% to 16.6%, an endurance test of 2000 h was performed while the flight design analysis was limited to a study of the General Purpose Heat Source, a study of the regenerator manufacturing technique and analysis of the hardness of the system to a laser threat. It was concluded from these tests that the GDS is basically prototypic of a flight design; all components necessary for satisfactory operation were demonstrated successfully at the system level; over 11,000 total h of operation without any component failure attested to the inherent reliability of this type of system; and some further development is required, specifically in the area of performance. (LCL)« less

PERFORMANCE OF SOLAR HOT WATER COLLECTORS FOR ELECTRICITY PRODUCTION AND CLIMATE CONTROL

EPA Science Inventory

We will systematically evaluate commercially available solar thermal collectors and thermal storage systems for use in residential scale co-generative heat and electrical power systems. Currently, reliable data is unavailable over the range of conditions and installations thes...

RELIABILITY OF CONFOCAL MICROSCOPY SPECTRAL IMAGING SYSTEMS: USE OF MULTISPECTRAL BEADS

EPA Science Inventory

Background: There is a need for a standardized, impartial calibration, and validation protocol on confocal spectral imaging (CSI) microscope systems. To achieve this goal, it is necessary to have testing tools to provide a reproducible way to evaluate instrument performance. ...

Reliability-Based Model to Analyze the Performance and Cost of a Transit Fare Collection System.

DOT National Transportation Integrated Search

1985-06-01

The collection of transit system fares has become more sophisticated in recent years, with more flexible structures requiring more sophisticated fare collection equipment to process tickets and admit passengers. However, this new and complex equipmen...

The psychophysiological assessment method for pilot's professional reliability.

PubMed

Zhang, L M; Yu, L S; Wang, K N; Jing, B S; Fang, C

1997-05-01

Previous research has shown that a pilot's professional reliability depends on two relative factors: the pilot's functional state and the demands of task workload. The Psychophysiological Reserve Capacity (PRC) is defined as a pilot's ability to accomplish additive tasks without reducing the performance of the primary task (flight task). We hypothesized that the PRC was a mirror of the pilot's functional state. The purpose of this study was to probe the psychophysiological method for evaluating a pilot's professional reliability on a simulator. The PRC Comprehensive Evaluating System (PRCCES) which was used in the experiment included four subsystems: a) quantitative evaluation system for pilot's performance on simulator; b) secondary task display and quantitative estimating system; c) multiphysiological data monitoring and statistical system; and d) comprehensive evaluation system for pilot PRC. Two studies were performed. In study one, 63 healthy and 13 hospitalized pilots participated. Each pilot performed a double 180 degrees circuit flight program with and without secondary task (three digit operation). The operator performance, score of secondary task and cost of physiological effort were measured and compared by PRCCES in the two conditions. Then, each pilot's flight skill in training was subjectively scored by instructor pilot ratings. In study two, 7 healthy pilots volunteered to take part in the experiment on the effects of sleep deprivation on pilot's PRC. Each participant had PRC tested pre- and post-8 h sleep deprivation. The results show that the PRC values of a healthy pilot was positively correlated with abilities of flexibility, operating and correcting deviation, attention distribution, and accuracy of instrument flight in the air (r = 0.27-0.40, p < 0.05), and negatively correlated with emotional anxiety in flight (r = -0.40, p < 0.05). The values of PRC in healthy pilots (0.61 +/- 0.17) were significantly higher than that of hospitalized pilots (0.43 +/- 0.15) (p < 0.05). The PRC value after 8 h sleep loss (0.50 +/- 0.17) was significantly lower than those before sleep loss (0.70 +/- 0.15) (p < 0.05). We conclude that a pilot's PRC, which was closely related to flight ability and functional state, could partly represent the pilot's professional reliability. It is worthwhile to further research using a pilot's PRC as a predictor of mental workload in aircraft design.

Evaluation of the Performance of Routine Information System Management (PRISM) framework: evidence from Uganda.

PubMed

Hotchkiss, David R; Aqil, Anwer; Lippeveld, Theo; Mukooyo, Edward

2010-07-03

Sound policy, resource allocation and day-to-day management decisions in the health sector require timely information from routine health information systems (RHIS). In most low- and middle-income countries, the RHIS is viewed as being inadequate in providing quality data and continuous information that can be used to help improve health system performance. In addition, there is limited evidence on the effectiveness of RHIS strengthening interventions in improving data quality and use. The purpose of this study is to evaluate the usefulness of the newly developed Performance of Routine Information System Management (PRISM) framework, which consists of a conceptual framework and associated data collection and analysis tools to assess, design, strengthen and evaluate RHIS. The specific objectives of the study are: a) to assess the reliability and validity of the PRISM instruments and b) to assess the validity of the PRISM conceptual framework. Facility- and worker-level data were collected from 110 health care facilities in twelve districts in Uganda in 2004 and 2007 using records reviews, structured interviews and self-administered questionnaires. The analysis procedures include Cronbach's alpha to assess internal consistency of selected instruments, test-retest analysis to assess the reliability and sensitivity of the instruments, and bivariate and multivariate statistical techniques to assess validity of the PRISM instruments and conceptual framework. Cronbach's alpha analysis suggests high reliability (0.7 or greater) for the indices measuring a promotion of a culture of information, RHIS tasks self-efficacy and motivation. The study results also suggest that a promotion of a culture of information influences RHIS tasks self-efficacy, RHIS tasks competence and motivation, and that self-efficacy and the presence of RHIS staff have a direct influence on the use of RHIS information, a key aspect of RHIS performance. The study results provide some empirical support for the reliability and validity of the PRISM instruments and the validity of the PRISM conceptual framework, suggesting that the PRISM approach can be effectively used by RHIS policy makers and practitioners to assess the RHIS and evaluate RHIS strengthening interventions. However, additional studies with larger sample sizes are needed to further investigate the value of the PRISM instruments in exploring the linkages between RHIS data quality and use, and health systems performance.

A Comparison of a Brain-Based Adaptive System and a Manual Adaptable System for Invoking Automation

NASA Technical Reports Server (NTRS)

Bailey, Nathan R.; Scerbo, Mark W.; Freeman, Frederick G.; Mikulka, Peter J.; Scott, Lorissa A.

2004-01-01

Two experiments are presented that examine alternative methods for invoking automation. In each experiment, participants were asked to perform simultaneously a monitoring task and a resource management task as well as a tracking task that changed between automatic and manual modes. The monitoring task required participants to detect failures of an automated system to correct aberrant conditions under either high or low system reliability. Performance on each task was assessed as well as situation awareness and subjective workload. In the first experiment, half of the participants worked with a brain-based system that used their EEG signals to switch the tracking task between automatic and manual modes. The remaining participants were yoked to participants from the adaptive condition and received the same schedule of mode switches, but their EEG had no effect on the automation. Within each group, half of the participants were assigned to either the low or high reliability monitoring task. In addition, within each combination of automation invocation and system reliability, participants were separated into high and low complacency potential groups. The results revealed no significant effects of automation invocation on the performance measures; however, the high complacency individuals demonstrated better situation awareness when working with the adaptive automation system. The second experiment was the same as the first with one important exception. Automation was invoked manually. Thus, half of the participants pressed a button to invoke automation for 10 s. The remaining participants were yoked to participants from the adaptable condition and received the same schedule of mode switches, but they had no control over the automation. The results showed that participants who could invoke automation performed more poorly on the resource management task and reported higher levels of subjective workload. Further, those who invoked automation more frequently performed more poorly on the tracking task and reported higher levels of subjective workload. and the adaptable condition in the second experiment revealed only one significant difference: the subjective workload was higher in the adaptable condition. Overall, the results show that a brain-based, adaptive automation system may facilitate situation awareness for those individuals who are more complacent toward automation. By contrast, requiring operators to invoke automation manually may have some detrimental impact on performance but does appear to increases subjective workload relative to an adaptive system.

Spare a Little Change? Towards a 5-Nines Internet in 250 Lines of Code

DTIC Science & Technology

2011-05-01

NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Carnegie Mellon University,School of Computer Science,Pittsburgh,PA,15213 8. PERFORMING ...Std Z39-18 Keywords: Internet reliability, BGP performance , Quagga This document includes excerpts of the source code for the Linux operating system...Behavior and Performance . . . . . . . . . . . . . . . . . . . . . . . . . . .  .. Other Related Work

Reliable numerical computation in an optimal output-feedback design

NASA Technical Reports Server (NTRS)

Vansteenwyk, Brett; Ly, Uy-Loi

1991-01-01

A reliable algorithm is presented for the evaluation of a quadratic performance index and its gradients with respect to the controller design parameters. The algorithm is a part of a design algorithm for optimal linear dynamic output-feedback controller that minimizes a finite-time quadratic performance index. The numerical scheme is particularly robust when it is applied to the control-law synthesis for systems with densely packed modes and where there is a high likelihood of encountering degeneracies in the closed-loop eigensystem. This approach through the use of an accurate Pade series approximation does not require the closed-loop system matrix to be diagonalizable. The algorithm was included in a control design package for optimal robust low-order controllers. Usefulness of the proposed numerical algorithm was demonstrated using numerous practical design cases where degeneracies occur frequently in the closed-loop system under an arbitrary controller design initialization and during the numerical search.

The Effect of Incorrect Reliability Information on Expectations, Perceptions, and Use of Automation.

PubMed

Barg-Walkow, Laura H; Rogers, Wendy A

2016-03-01

We examined how providing artificially high or low statements about automation reliability affected expectations, perceptions, and use of automation over time. One common method of introducing automation is providing explicit statements about the automation's capabilities. Research is needed to understand how expectations from such introductions affect perceptions and use of automation. Explicit-statement introductions were manipulated to set higher-than (90%), same-as (75%), or lower-than (60%) levels of expectations in a dual-task scenario with 75% reliable automation. Two experiments were conducted to assess expectations, perceptions, compliance, reliance, and task performance over (a) 2 days and (b) 4 days. The baseline assessments showed initial expectations of automation reliability matched introduced levels of expectation. For the duration of each experiment, the lower-than groups' perceptions were lower than the actual automation reliability. However, the higher-than groups' perceptions were no different from actual automation reliability after Day 1 in either study. There were few differences between groups for automation use, which generally stayed the same or increased with experience using the system. Introductory statements describing artificially low automation reliability have a long-lasting impact on perceptions about automation performance. Statements including incorrect automation reliability do not appear to affect use of automation. Introductions should be designed according to desired outcomes for expectations, perceptions, and use of the automation. Low expectations have long-lasting effects. © 2015, Human Factors and Ergonomics Society.

Reliability enhancement of common module systems

NASA Astrophysics Data System (ADS)

Schellenberger, Gisbert; Ruehlich, Ingo; Korf, Herbert; Petrie, Juergen J.; Muenter, Rolf

2004-08-01

Several thousands of 1st Gen IR Systems operated by Integral Stirling Cooler HD1033 are still in service worldwide. Replacing the HD 1033 Stirling by a Linear Drive Cooler will result in a significant reliability enhancement of these IR system of about a factor of three. These attempts had been unsuccessful in the past due to excessive EMI noise induced by the linear cooler compressor. So a main goal for such a development is the elimination of various EMI distortions in the IR system by EMI filtering and shielding. Additionally, the synchronization of the cooler power to the predominant scanning frequency of the IR system significantly improves the image quality. Technical details of the solution, MTTF data and performance data are described in detail.

Distributed Ship Navigation Control System Based on Dual Network

NASA Astrophysics Data System (ADS)

Yao, Ying; Lv, Wu

2017-10-01

Navigation system is very important for ship’s normal running. There are a lot of devices and sensors in the navigation system to guarantee ship’s regular work. In the past, these devices and sensors were usually connected via CAN bus for high performance and reliability. However, as the development of related devices and sensors, the navigation system also needs the ability of high information throughput and remote data sharing. To meet these new requirements, we propose the communication method based on dual network which contains CAN bus and industrial Ethernet. Also, we import multiple distributed control terminals with cooperative strategy based on the idea of synchronizing the status by multicasting UDP message contained operation timestamp to make the system more efficient and reliable.

Coal-Powered Electric Generating Unit Efficiency and Reliability Dialogue: Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, Emmanuel

Coal continues to play a critical role in powering the Nation’s electricity generation, especially for baseload power plants. With aging coal generation assets facing decreased performance due to the state of the equipment, and with challenges exacerbated by the current market pressures on the coal sector, there are opportunities to advance early-stage technologies that can retrofit or replace equipment components. These changes will eventually result in significant improvements in plant performance once further developed and deployed by industry. Research and development in areas such as materials, fluid dynamics, fuel properties and preparation characteristics, and a new generation of plant controlsmore » can lead to new components and systems that can help improve the efficiency and reliability of coal-fired power plants significantly, allowing these assets to continue to provide baseload power. Coal stockpiles at electricity generation plants are typically large enough to provide 30 to 60 days of power prior to resupply—significantly enhancing the stability and reliability of the U.S. electricity sector. Falling prices for non-dispatchable renewable energy and mounting environmental regulations, among other factors, have stimulated efforts to improve the efficiency of these coal-fired electric generating units (EGUs). In addition, increased reliance on natural gas and non-dispatchable energy sources has spurred efforts to further increase the reliability of coal EGUs. The Coal Powered EGU Efficiency and Reliability Dialogue brought together stakeholders from across the coal EGU industry to discuss methods for improvement. Participants at the event reviewed performance-enhancing innovations in coal EGUs, discussed the potential for data-driven management practices to increase efficiency and reliability, investigated the impacts of regulatory compliance on coal EGU performance, and discussed upcoming challenges for the coal industry. This report documents the key findings and research suggestions discussed at the event. Discussions at the workshop will aid DOE in developing a set of distinct initiatives that can be pursued by government and industry to realize promising technological pursuits. DOE plans to use the results of the Dialogue coupled with ongoing technical analysis of efficiency opportunities within the coal-fired fleet, and additional studies to develop a comprehensive strategy for capitalizing on thermal efficiency improvements. Expected Power Plant Efficiency Improvements include developing cost-effective, efficient, and reliable technologies for boilers, turbines, and sensors and controls to improve the reliability and efficiency of existing coal-based power plants. The Office of Fossil Energy at DOE plans to work with industry to develop knowledge pertaining to advanced technologies and systems that industry can subsequently develop. These technologies and systems will increase reliability, add operational flexibility and improve efficiency, thereby providing more robust power generation infrastructure. The following table lists the research suggestions and questions for further investigation that were identified by participants in each session of the dialogue.« less

Robotic-Assisted Knee Arthroplasty: An Overview.

PubMed

van der List, Jelle P; Chawla, Harshvardhan; Pearle, Andrew D

2016-01-01

Unicompartmental knee arthroplasty and total knee arthroplasty are reliable treatment options for osteoarthritis. In order to improve survivorship rates, variables that are intraoperatively controlled by the orthopedic surgeon are being evaluated. These variables include lower leg alignment, soft tissue balance, joint line maintenance, and tibial and femoral component alignment, size, and fixation methods. Since tighter control of these factors is associated with improved outcomes of knee arthroplasty, several computer-assisted surgery systems have been developed. These systems differ in the number and type of variables they control. Robotic-assisted systems control these aforementioned variables and, in addition, aim to improve the surgical precision of the procedure. Robotic-assisted systems are active, semi-active, or passive, depending on how independently the systems perform maneuvers. Reviewing the robotic-assisted knee arthroplasty systems, it becomes clear that these systems can accurately and reliably control the aforementioned variables. Moreover, these systems are more accurate and reliable in controlling these variables when compared to the current gold standard of conventional manual surgery. At present, few studies have assessed the survivorship and functional outcomes of robotic-assisted surgery, and no sufficiently powered studies were identified that compared survivorship or functional outcomes between robotic-assisted and conventional knee arthroplasty. Although preliminary outcomes of robotic-assisted surgery look promising, more studies are necessary to assess if the increased accuracy and reliability in controlling the surgical variables leads to better outcomes of robotic-assisted knee arthroplasty.

Tackling the challenges of matching biomedical ontologies.

PubMed

Faria, Daniel; Pesquita, Catia; Mott, Isabela; Martins, Catarina; Couto, Francisco M; Cruz, Isabel F

2018-01-15

Biomedical ontologies pose several challenges to ontology matching due both to the complexity of the biomedical domain and to the characteristics of the ontologies themselves. The biomedical tracks in the Ontology Matching Evaluation Initiative (OAEI) have spurred the development of matching systems able to tackle these challenges, and benchmarked their general performance. In this study, we dissect the strategies employed by matching systems to tackle the challenges of matching biomedical ontologies and gauge the impact of the challenges themselves on matching performance, using the AgreementMakerLight (AML) system as the platform for this study. We demonstrate that the linear complexity of the hash-based searching strategy implemented by most state-of-the-art ontology matching systems is essential for matching large biomedical ontologies efficiently. We show that accounting for all lexical annotations (e.g., labels and synonyms) in biomedical ontologies leads to a substantial improvement in F-measure over using only the primary name, and that accounting for the reliability of different types of annotations generally also leads to a marked improvement. Finally, we show that cross-references are a reliable source of information and that, when using biomedical ontologies as background knowledge, it is generally more reliable to use them as mediators than to perform lexical expansion. We anticipate that translating traditional matching algorithms to the hash-based searching paradigm will be a critical direction for the future development of the field. Improving the evaluation carried out in the biomedical tracks of the OAEI will also be important, as without proper reference alignments there is only so much that can be ascertained about matching systems or strategies. Nevertheless, it is clear that, to tackle the various challenges posed by biomedical ontologies, ontology matching systems must be able to efficiently combine multiple strategies into a mature matching approach.

Lifetime predictions for dimmable two-channel drivers for color tuning luminaires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Lynn; Smith, Aaron; Clark, Terry

Two-channel tunable white lighting (TWL) systems represent the next wave of solid-state lighting (SSL) systems and promise flexibility in light environment while maintaining the high reliability and luminous efficacy expected with SSL devices. TWL systems utilize LED assemblies consisting of two different LED spectra (i.e., often a warm white assembly and a cool white assembly) that are integrated into modules. While these systems provide the ability to adjust the lighting spectrum to match the physiology needs of the task at hand, they also are a potentially more complex lighting system from a performance and reliability perspective. We report an initialmore » study on the reliability performance of such lighting systems including an examination of the lumen maintenance and chromaticity stability of warm white and cool white LED assemblies and the multi-channel driver that provides power to the assemblies. Accelerated stress tests including operational bake tests conducted at 75°C and 95°C were used to age the LED modules, while more aggressive temperature and humidity tests were used for the drivers in this study. Small differences in the performance between the two LED assemblies were found and can be attributed to the different phosphor chemistries. The lumen maintenances of both LED assemblies were excellent. The warm white LED assemblies were found to shift slightly in the green color direction over time while the cool white LED assemblies shifted slightly in the yellow color direction. The net result of these chromaticity shifts is a small, barely perceptible reduction in the tuning range after 6,000 hours of exposure to an accelerating elevated temperature of 75°C.« less

Crisis Reliability Indicators Supporting Emergency Services (CRISES): A Framework for Developing Performance Measures for Behavioral Health Crisis and Psychiatric Emergency Programs.

PubMed

Balfour, Margaret E; Tanner, Kathleen; Jurica, Paul J; Rhoads, Richard; Carson, Chris A

2016-01-01

Crisis and emergency psychiatric services are an integral part of the healthcare system, yet there are no standardized measures for programs providing these services. We developed the Crisis Reliability Indicators Supporting Emergency Services (CRISES) framework to create measures that inform internal performance improvement initiatives and allow comparison across programs. The framework consists of two components-the CRISES domains (timely, safe, accessible, least-restrictive, effective, consumer/family centered, and partnership) and the measures supporting each domain. The CRISES framework provides a foundation for development of standardized measures for the crisis field. This will become increasingly important as pay-for-performance initiatives expand with healthcare reform.

Small Business Innovations

NASA Technical Reports Server (NTRS)

1992-01-01

The purpose of QASE RT is to enable system analysts and software engineers to evaluate performance and reliability implications of design alternatives. The program resulted from two Small Business Innovation Research (SBIR) projects. After receiving a description of the system architecture and workload from the user, QASE RT translates the system description into simulation models and executes them. Simulation provides detailed performance evaluation. The results of the evaluations are service and response times, offered load and device utilizations and functional availability.

Metrics for the National SCADA Test Bed Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craig, Philip A.; Mortensen, J.; Dagle, Jeffery E.

2008-12-05

The U.S. Department of Energy Office of Electricity Delivery and Energy Reliability (DOE-OE) National SCADA Test Bed (NSTB) Program is providing valuable inputs into the electric industry by performing topical research and development (R&D) to secure next generation and legacy control systems. In addition, the program conducts vulnerability and risk analysis, develops tools, and performs industry liaison, outreach and awareness activities. These activities will enhance the secure and reliable delivery of energy for the United States. This report will describe metrics that could be utilized to provide feedback to help enhance the effectiveness of the NSTB Program.

Silicon nanowires reliability and robustness investigation using AFM-based techniques

NASA Astrophysics Data System (ADS)

Bieniek, Tomasz; Janczyk, Grzegorz; Janus, Paweł; Grabiec, Piotr; Nieprzecki, Marek; Wielgoszewski, Grzegorz; Moczała, Magdalena; Gotszalk, Teodor; Buitrago, Elizabeth; Badia, Montserrat F.; Ionescu, Adrian M.

2013-07-01

Silicon nanowires (SiNWs) have undergone intensive research for their application in novel integrated systems such as field effect transistor (FET) biosensors and mass sensing resonators profiting from large surface-to-volume ratios (nano dimensions). Such devices have been shown to have the potential for outstanding performances in terms of high sensitivity, selectivity through surface modification and unprecedented structural characteristics. This paper presents the results of mechanical characterization done for various types of suspended SiNWs arranged in a 3D array. The characterization has been performed using techniques based on atomic force microscopy (AFM). This investigation is a necessary prerequisite for the reliable and robust design of any biosensing system. This paper also describes the applied investigation methodology and reports measurement results aggregated during series of AFM-based tests.

Chris Deline | NREL

Science.gov Websites

., Meydbray, J., Donovan, M., and Forrest, J. 2014. Photovoltaic Shading Testbed for Module-Level Power Renewable Energy Laboratory (NREL) in Golden, Colorado, in the photovoltaic (PV) performance and reliability performance and stabilization, mismatch and partial shading in PV systems, and distributed power electronics

High-Performance Monitoring Architecture for Large-Scale Distributed Systems Using Event Filtering

NASA Technical Reports Server (NTRS)

Maly, K.

1998-01-01

Monitoring is an essential process to observe and improve the reliability and the performance of large-scale distributed (LSD) systems. In an LSD environment, a large number of events is generated by the system components during its execution or interaction with external objects (e.g. users or processes). Monitoring such events is necessary for observing the run-time behavior of LSD systems and providing status information required for debugging, tuning and managing such applications. However, correlated events are generated concurrently and could be distributed in various locations in the applications environment which complicates the management decisions process and thereby makes monitoring LSD systems an intricate task. We propose a scalable high-performance monitoring architecture for LSD systems to detect and classify interesting local and global events and disseminate the monitoring information to the corresponding end- points management applications such as debugging and reactive control tools to improve the application performance and reliability. A large volume of events may be generated due to the extensive demands of the monitoring applications and the high interaction of LSD systems. The monitoring architecture employs a high-performance event filtering mechanism to efficiently process the large volume of event traffic generated by LSD systems and minimize the intrusiveness of the monitoring process by reducing the event traffic flow in the system and distributing the monitoring computation. Our architecture also supports dynamic and flexible reconfiguration of the monitoring mechanism via its Instrumentation and subscription components. As a case study, we show how our monitoring architecture can be utilized to improve the reliability and the performance of the Interactive Remote Instruction (IRI) system which is a large-scale distributed system for collaborative distance learning. The filtering mechanism represents an Intrinsic component integrated with the monitoring architecture to reduce the volume of event traffic flow in the system, and thereby reduce the intrusiveness of the monitoring process. We are developing an event filtering architecture to efficiently process the large volume of event traffic generated by LSD systems (such as distributed interactive applications). This filtering architecture is used to monitor collaborative distance learning application for obtaining debugging and feedback information. Our architecture supports the dynamic (re)configuration and optimization of event filters in large-scale distributed systems. Our work represents a major contribution by (1) survey and evaluating existing event filtering mechanisms In supporting monitoring LSD systems and (2) devising an integrated scalable high- performance architecture of event filtering that spans several kev application domains, presenting techniques to improve the functionality, performance and scalability. This paper describes the primary characteristics and challenges of developing high-performance event filtering for monitoring LSD systems. We survey existing event filtering mechanisms and explain key characteristics for each technique. In addition, we discuss limitations with existing event filtering mechanisms and outline how our architecture will improve key aspects of event filtering.

Photovoltaic Reliability Group activities in USA and Brazil (Presentation Recording)

NASA Astrophysics Data System (ADS)

Dhere, Neelkanth G.; Cruz, Leila R. O.

2015-09-01

Recently prices of photovoltaic (PV) systems have been reduced considerably and may continue to be reduced making them attractive. If these systems provide electricity over the stipulated warranty period, it would be possible attain socket parity within the next few years. Current photovoltaic module qualifications tests help in minimizing infant mortality but do not guarantee useful lifetime over the warranty period. The PV Module Quality Assurance Task Force (PVQAT) is trying to formulate accelerated tests that will be useful towards achieving the ultimate goal of assuring useful lifetime over the warranty period as well as to assure manufacturing quality. Unfortunately, assuring the manufacturing quality may require 24/7 presence. Alternatively, collecting data on the performance of fielded systems would assist in assuring manufacturing quality. Here PV systems installed by home-owners and small businesses can constitute as an important untapped source of data. The volunteer group, PV - Reliable, Safe and Sustainable Quality! (PVRessQ!) is providing valuable service to small PV system owners. Photovoltaic Reliability Group (PVRG) is initiating activities in USA and Brazil to assist home owners and small businesses in monitoring photovoltaic (PV) module performance and enforcing warranty. It will work in collaboration with small PV system owners, consumer protection agencies. Brazil is endowed with excellent solar irradiance making it attractive for installation of PV systems. Participating owners of small PV systems would instruct inverter manufacturers to copy the daily e-mails to PVRG and as necessary, will authorize the PVRG to carry out review of PV systems. The presentation will consist of overall activities of PVRG in USA and Brazil.

Physical attraction to reliable, low variability nervous systems: Reaction time variability predicts attractiveness.

PubMed

Butler, Emily E; Saville, Christopher W N; Ward, Robert; Ramsey, Richard

2017-01-01

The human face cues a range of important fitness information, which guides mate selection towards desirable others. Given humans' high investment in the central nervous system (CNS), cues to CNS function should be especially important in social selection. We tested if facial attractiveness preferences are sensitive to the reliability of human nervous system function. Several decades of research suggest an operational measure for CNS reliability is reaction time variability, which is measured by standard deviation of reaction times across trials. Across two experiments, we show that low reaction time variability is associated with facial attractiveness. Moreover, variability in performance made a unique contribution to attractiveness judgements above and beyond both physical health and sex-typicality judgements, which have previously been associated with perceptions of attractiveness. In a third experiment, we empirically estimated the distribution of attractiveness preferences expected by chance and show that the size and direction of our results in Experiments 1 and 2 are statistically unlikely without reference to reaction time variability. We conclude that an operating characteristic of the human nervous system, reliability of information processing, is signalled to others through facial appearance. Copyright © 2016 Elsevier B.V. All rights reserved.

What's working, what's not: The monitoring and reporting system for Tasmania's national parks and reserves

Treesearch

Glenys Jones

2015-01-01

This paper describes the Australian State of Tasmania's management effectiveness Monitoring and Reporting System for national parks and reserves. This jurisdictional performance measurement system is designed to provide all interested parties with reliable factual information and measured evidence about reserve management achievements, progress and challenges. Key...

On Information Retrieval (IR) Systems: Revisiting Their Development, Evaluation Methodologies, and Assumptions (SIGs LAN, ED).

ERIC Educational Resources Information Center

Stirling, Keith

2000-01-01

Describes a session on information retrieval systems that planned to discuss relevance measures with Web-based information retrieval; retrieval system performance and evaluation; probabilistic independence of index terms; vector-based models; metalanguages and digital objects; how users assess the reliability, timeliness and bias of information;…

Reliability of sagittal plane hip, knee, and ankle joint angles from a single frame of video data using the GAITRite camera system.

PubMed

Ross, Sandy A; Rice, Clinton; Von Behren, Kristyn; Meyer, April; Alexander, Rachel; Murfin, Scott

2015-01-01

The purpose of this study was to establish intra-rater, intra-session, and inter-rater, reliability of sagittal plane hip, knee, and ankle angles with and without reflective markers using the GAITRite walkway and single video camera between student physical therapists and an experienced physical therapist. This study included thirty-two healthy participants age 20-59, stratified by age and gender. Participants performed three successful walks with and without markers applied to anatomical landmarks. GAITRite software was used to digitize sagittal hip, knee, and ankle angles at two phases of gait: (1) initial contact; and (2) mid-stance. Intra-rater reliability was more consistent for the experienced physical therapist, regardless of joint or phase of gait. Intra-session reliability was variable, the experienced physical therapist showed moderate to high reliability (intra-class correlation coefficient (ICC) = 0.50-0.89) and the student physical therapist showed very poor to high reliability (ICC = 0.07-0.85). Inter-rater reliability was highest during mid-stance at the knee with markers (ICC = 0.86) and lowest during mid-stance at the hip without markers (ICC = 0.25). Reliability of a single camera system, especially at the knee joint shows promise. Depending on the specific type of reliability, error can be attributed to the testers (e.g. lack of digitization practice and marker placement), participants (e.g. loose fitting clothing) and camera systems (e.g. frame rate and resolution). However, until the camera technology can be upgraded to a higher frame rate and resolution, and the software can be linked to the GAITRite walkway, the clinical utility for pre/post measures is limited.