Academic literature on the topic 'Dynamic coded redundancy'
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Journal articles on the topic "Dynamic coded redundancy"
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Xu, Kun, Zhiyong Du, and Bin Jiang. "Dynamic Coded Cooperation With Incremental Redundancy: Throughput and Diversity-Multiplexing Tradeoff Analysis." IEEE Communications Letters 24, no. 3 (March 2020): 506–9. http://dx.doi.org/10.1109/lcomm.2020.2969670.
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Péni, Tamás, Bálint Vanek, Zoltán Szabó, and József Bokor. "Supervisory Fault Tolerant Control of the GTM UAV Using LPV Methods." International Journal of Applied Mathematics and Computer Science 25, no. 1 (March 1, 2015): 117–31. http://dx.doi.org/10.1515/amcs-2015-0009.
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Abstract A multi-level reconfiguration framework is proposed for fault tolerant control of over-actuated aerial vehicles, where the levels indicate how much authority is given to the reconfiguration task. On the lowest, first level the fault is accommodated by modifying only the actuator/sensor configuration, so the fault remains hidden from the baseline controller. A dynamic reallocation scheme is applied on this level. The allocation mechanism exploits the actuator/sensor redundancy available on the aircraft. When the fault cannot be managed at the actuator/sensor level, the reconfiguration process has access to the baseline controller. Based on the LPV control framework, this is done by introducing fault-specific scheduling parameters. The baseline controller is designed to provide an acceptable performance level along all fault scenarios coded in these scheduling variables. The decision on which reconfiguration level has to be initiated in response to a fault is determined by a supervisor unit. The method is demonstrated on a full six-degrees-of-freedom nonlinear simulation model of the GTM UAV.
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Hoare, Johanna, Sarah Garnett, Louise Baur, Natalie Lister, and Hiba Jebeile. "A Novel Method to Determine a Custom Sample Size for Image-Based Instagram Content Analysis." Current Developments in Nutrition 6, Supplement_1 (June 2022): 768. http://dx.doi.org/10.1093/cdn/nzac063.010.
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Abstract Objectives Most Instagram users are young people, and social media is often used to search nutrition information. Health interventions aimed at young people should consider such information sources. Content analyses of Instagram images offer insights into types of content that may influence nutrition-related decision making and health behaviors. However, the number of analyzed images in existing studies has varied, and methods to determine data-specific sample sizes to reach saturation have not been explored. We aimed to develop a method to determine sample sizes for image-based content analyses on Instagram. We piloted the method and determined the reliability by identifying the saturation point for content categorized under two separate nutrition-related hashtags. Methods Instagram ‘top posts’ for a 21-year-old user were searched using hashtags ‘mindfuleating’ and ‘intuitiveeating’. 1200 images from each were extracted. Hashtag-specific coding frameworks were constructed inductively by two authors, initially coding the image- and text-based elements of the first 90 images collaboratively. Next, increments of 45 images were coded independently, then compared, solving disagreements by discussion. The process was repeated until saturation occurred when no new codes emerged. This was repeated seven weeks later to determine reliability. Results The coding frameworks constructed for #mindfuleating at first and second capture comprised 63 and 74 distinct codes, with saturation occurring at 360 and 405 images, respectively. The #intuitiveeating frameworks comprised 83 and 86 codes, with saturation at 450 and 495 images, respectively. The codes captured detailed pictorial content (e.g., ‘female’, ‘White’, ‘young adult’) and text (e.g., ‘nutrition information’, ‘relationship with food’). For both hashtags, the number of image-based codes decreased while text-based codes increased between coding. Conclusions Variations in coding frameworks and sample sizes over a short timeframe reflect the dynamic nature of Instagram content. Assessment of diet trends on social media requires accurate sampling to ensure nuances of a specific topic are captured, while research efficiency benefits from reduced data redundancy. Funding Sources NHMRC Peter Doherty Early Career Fellowship; Sydney Medical School Foundation, The University of Sydney.
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Nikulina, Olena, Valerii Severyn, and Vladyslav Sharov. "DEVELOPMENT OF A MODEL OF INTERFERENCE-RESISTANT DATA TRANSMISSION FOR INFORMATION TECHNOLOGY OF CONTROL OPTIMIZATION OF DYNAMIC SYSTEMS." Bulletin of National Technical University "KhPI". Series: System Analysis, Control and Information Technologies, no. 2 (8) (December 23, 2022): 57–62. http://dx.doi.org/10.20998/2079-0023.2022.02.09.
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For data transmission channels used in local control systems for various processes, simple and inexpensive methods are needed that will allow the necessary information to be transmitted without errors. Errors that occur in continuous communication channels are one of the main obstacles to the reliable transmission of information. As a result of the analysis of error statistics in discrete channels, it was concluded that single and double errors occur most often. The purpose of this article is to develop a model of interference-resistant data transmission for information technology optimization of control of dynamic systems. The analyzed causes of errors are signal attenuation, noise and various interferences. The resulting transmitted signal is determined by the combination of the useful signal and the interference signal. When considering discrete signals, several causes of errors are highlighted – edge distortions, pulse splitting, and others. Considered methods of combating obstacles: means of operational and preventive nature; means of increasing interference resistance during the transmission of single elements; use of feedback; adding redundancy to the code; tamper-proof coding. It is proposed to combat errors using tamper-resistant coding. Among the interference-resistant codes, redundant block separable systematic codes are selected, which are divided into cyclic codes and Hamming code. The basis of the interference-resistant coding model is the use of a systematic code - a cyclic code or a Hamming code followed by cascade coding. Since the coding model must be adaptively used in different systems, a necessary criterion of the model is its universality. The model should work in different systems without changing the encoding and decoding algorithms. Among the many types of interference-resistant codes, cascade codes are chosen for use. Widespread cascade codes are universal, easily scalable, work stably, have proven themselves well in world practice, therefore they are recommended for use in various information management systems. The implementation of the interference-resistant data transmission model is presented.
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Nikulina, Olena, Valerii Severyn, and Vladyslav Sharov. "SIMULATION AND ANALYSIS OF ENCODERS OF INTERFERENCE-RESISTANT CASCADE CODES FOR DYNAMIC SYSTEMS." Bulletin of National Technical University "KhPI". Series: System Analysis, Control and Information Technologies, no. 1 (9) (July 15, 2023): 64–69. http://dx.doi.org/10.20998/2079-0023.2023.01.10.
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For various channels of information transmission that can be used in local control systems of a wide range of processes, affordable, scalable, and inexpensive transmission methods are needed that allow the necessary information to be transmitted reliably without errors. Errors that occur in discrete, continuous communication channels are the main obstacle to the reliability of transmitted data. The main causes of errors are signal attenuation, noise and various interferences. As a result of the analysis of error statistics in discrete data transmission channels, it was concluded that single and double errors occur in the absolute majority of cases. It is proposed to combat errors by using tamper-resistant coding. Among the interference-resistant codes, redundant block-separated systematic codes are highlighted, among which is the Hamming code. The basis of the interference-resistant coding model is proposed to be the use of a systematic Hamming code followed by cascade coding by adding a parity check bit. The used model made it possible to deal with all the most likely cases of errors. Since this coding model must be flexibly used in different systems, a necessary criterion of the model is its universality. Therefore, the model was tested on a sample with code combinations of different numbers of bits. The purpose of this article is to analyze the dependence of the coding procedure execution time for encoders of different levels: a separate first-stage encoder, as well as a first-stage encoder with the addition of a second-stage encoder. Experiments were conducted with a large sample, which were subsequently analyzed and interpreted. Since the model proved to be flexible, simple, stable and effective as a result of experiments, and the process of combating interference by using cascade codes has proven itself well in world practice, it is recommended for use in various information management systems. The implementation of the coder for interference-resistant data transmission is given.
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Bao, Haizhou, Yiming Huo, Chuanhe Huang, Xiaodai Dong, and Wanyu Qiu. "Cluster-Based Cooperative Cache Deployment and Coded Delivery Strategy in C-V2X Networks." Wireless Communications and Mobile Computing 2021 (May 1, 2021): 1–19. http://dx.doi.org/10.1155/2021/8864004.
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Cellular vehicle-to-everything- (C-V2X-) based communications can support various content-oriented applications and have gained significant progress in recent years. However, the limited backhaul bandwidth and dynamic topology make it difficult to obtain the multimedia service with high-reliability and low-latency communication in C-V2X networks, which may degrade the quality of experience (QoE). In this paper, we propose a novel cluster-based cooperative cache deployment and coded delivery strategy for C-V2X networks to improve the cache hit ratio and response time, reduce the request-response delay, and improve the bandwidth efficiency. To begin with, we design an effective vehicle cluster method. Based on the constructed cluster, we propose a two-level cooperative cache deployment approach to cache the frequently requested files on the edge nodes, LTE evolved NodeB (eNodeB) and cluster head (CH), to maximize the overall cache hit ratio. Furthermore, we propose an effective coded delivery strategy to minimize the network load and the ratio of redundant files. Simulation results demonstrate that our proposed method can effectively reduce the average response delay and network load and improve both the hit ratio and the ratio of redundant files.
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Bayo, E., and M. A. Serna. "Penalty Formulations for the Dynamic Analysis of Elastic Mechanisms." Journal of Mechanisms, Transmissions, and Automation in Design 111, no. 3 (September 1, 1989): 321–27. http://dx.doi.org/10.1115/1.3259002.
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A series of penalty methods are presented for the dynamic analysis of flexible mechanisms. The proposed methods formulate the equations of motion with respect to a floating frame that follows the rigid body motion of the links. The constraint conditions are not appended to the Lagrange’s equations in the form of algebraic or differential constraints, but inserted in them by means of a penalty formulation, and therefore the number of equations of the system does not increase. Furthermore, the discretization of the equations using the finite element method leads to a system of ordinary differential equations that can be solved using standard numerical algorithms. The proposed methods are valid for three dimensional analysis and can be very easily implemented in existing codes. Furthermore, they can be used to model any type of constraint conditions, either holonomic or nonholonomic, and with any degree of redundancy. A series of mechanisms composed of elastic members are analyzed. The results demonstrate the capabilities of the proposed methods for simulation analysis.
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Koppala, Neelima, Nagarajan Ashok Kumar, Satyam Satyam, and Neeruganti Vikram Teja. "Proficient matrix codes for error detection and correctionin 8-port network on chip routers." Indonesian Journal of Electrical Engineering and Computer Science 29, no. 3 (March 1, 2023): 1336. http://dx.doi.org/10.11591/ijeecs.v29.i3.pp1336-1344.
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This paper verifies the applicability of the proposed code to dynamic Network on Chips that have variable faulty blocks with runtime suggesting an online error detection mechanism with adaptive routing algorithm that bypasses faulty components dynamically and the router architecture uses additional diagonal state indications for the reliable network on chip (NoC) operation. In NoC, the permanently faulty routers are disconnected to enable high runtime throughput as data packets are not lost due to self-loopback mechanism. The proposed proficient matrix codes use the capabilities of decimal matrix code technique with minimum check bits for maximum error correction capability. The proposed code is compared with existing codes such as decimal matrix codes, modified decimal matrix codes and parity matrix codes. The codes are developed in verilog hardware description language and simulated in the Xilinx ISE 14.5 tool. This proficient matrix code proves to be efficient for multiple adjacent error detection and correction with trade off in delay. Also 65% code rate is achieved with 22.73% less redundant bits that occupy less area by atleast 11.78%. The codes when used for increased data sizes like 8, 16, 32, and 64 bits, the power delay product decreased by atleast 1.74%.
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Reymarvelos M. Oros, Jonrick G. Escol, Ritz Crizelle M. Mabilen, Cyril Grace U. Rapista, Nin Christian G. Hufana, and Irish S. Tambis. "Progressive collapse and soil stress analyses of Manupali steel truss bridge in Lantapan, Bukidnon under hydraulic and traffic threats." World Journal of Advanced Research and Reviews 18, no. 1 (April 30, 2023): 738–57. http://dx.doi.org/10.30574/wjarr.2023.18.1.0634.
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Bridges designed to comply with current design codes may not provide enough strength to arrest a possible local failure following an abnormal event, thus leading to a progressive collapse. One may employ different approaches that vary according to linearity and dynamicity to analyze the potential of a structure to progressive collapse. Together with a prior risk assessment, this study analyzed the susceptibility of the Manupali steel truss bridge to progressive collapse using an adapted nonlinear static approach and assessed the bridge’s pile foundation capacity concerning changes in the imposed stresses caused by the dynamic effects of progressive collapse. Using P-Delta analysis in STAAD.Pro CONNECT Edition V22, this study determined that under its self-weight, the Manupali steel truss bridge is susceptible to progressive collapse, i.e., it is fracture critical. Nonetheless, being such does not mean the bridge is inherently unsafe, only that it lacks redundancy in the design. Furthermore, this study found that a collapse does not significantly detrimentally affect the foundation system except when the dynamic effect is so tremendous. With the results, this study recommends that the design of bridges should consider abnormal load cases to mitigate progressive collapse.
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El Allati, A., H. Amellal, and A. Meslouhi. "Improvement of quantum correlations by repetitive quantum error correction." International Journal of Quantum Information 17, no. 05 (August 2019): 1950044. http://dx.doi.org/10.1142/s0219749919500448.
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A quantum error-correcting code is established in entangled coherent states (CSs) with Markovian and non-Markovian environments. However, the dynamic behavior of these optical states is discussed in terms of quantum correlation measurements, entanglement and discord. By using the correcting codes, these correlations can be as robust as possible against environmental effects. As the number of redundant CSs increases due to the repetitive error correction, the probabilities of success also increase significantly. Based on different optical field parameters, the discord can withstand more than an entanglement. Furthermore, the behavior of quantum discord under decoherence may exhibit sudden death and sudden birth phenomena as functions of dimensionless parameters.
Dissertations / Theses on the topic "Dynamic coded redundancy"
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Badita, Ajay Kumar. "Design and Evaluation of Parallel Coded Systems." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5269.
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In this computer era, we all live in a place where the demand for data and computing is increasing day by day. Since the need for faster data retrieval and faster computation brings us a reliability as the solution, we need more more data storage points or computation units. Motivated by scalability, availability, and reliability, there has been a paradigm shift from centralized storage (computation) at a large supercomputer to distributed storage (computing) on a large cluster of regular servers to handle complex tasks. In distributed storage setting, a single file is divided into smaller number of subfiles, which are then stored across multiple nodes, and the file requests are handled by the storage cluster. Similarly, in dis- tributed compute setting, a single task is fragmented into a smaller number of subtasks, and processed by the compute cluster. File request time (task completion time) is limited by the slowest execution time of the parallel subtasks. The lagging subfile requests (subtasks) are referred to as stragglers, and they delay the entire file retrieval (task execution). Straggling servers is one of the challenges in distributed storage and compute systems.
Redundancy has emerged as a popular technique to mitigate the impact of stragglers. Redundant subfile requests (compute subtasks) can be sent to a larger set of storage (compute) nodes, such that a smaller subset suffices for the file (task) completion. This approach can be used for straggler mitigation in the face of uncertainty in file retrieval (task execution) times at the storage (compute) nodes. Coding theoretic techniques can be employed to systematically control the redundancy in storage and compute systems. The effective reliable strategies can be either replication coding or maximum distance separable (MDS) coding. Our work introduces new analytical bounds and approximation techniques for the latency-redundancy tradeoff for a range of system loads and a class of symmetric redundancy schemes, under the assumption of Poisson arrivals, exponential service-rates, and fork-join scheduling policy. The proposed approach can be employed to efficiently approximate the latency distribution of a queueing system at equilibrium. We also establish the stability region in terms of arrival rates for redundant systems with certain symmetries, which offers selection guidelines for design parameters to provide latency guarantees based on the proposed approximations.
We observe that redundancy can mitigate the impact of stragglers, however, it comes at the cost of additional server nodes working on redundant coded subfiles (subtasks). This cost can be measured by the amount of work done by all server nodes, called aggregate server utilization. In a proactive mitigation approach, we attempt to show that server utilization can be reduced by dynamic coded redundancy, where the number of redundant servers available to a file (task) changes with time. We are interested in dynamic coded redundancy for a single-file (single-compute task) with coded-subfiles (coded-subtasks). In dynamic coded redundancy, additional redundant coded subfiles (subtasks) are spawned on individual server nodes, adaptively over time. The instants at which coded subfiles (subtasks) are spawned are referred to as forking points. We are interested in optimal adaptive strategy such that a linear combination of the mean file retrieval time (mean task completion time) and the mean server utilization is minimized. Specifically, we address the following two interdependent questions: How should we select the forking points? How many coded subfiles (subtasks) should be initiated at each forking point? For this flexible forking strategy with multiple parameters, we analyze the mean of two performance metrics when the random service completion time at each node is independent and distributed identically (i.i.d.) to a shifted exponential. From this study, we find a tradeoff between the metrics which provides insights into the parameter choices. Experiments on Intel DevCloud illustrate that the shifted exponential distribution adequately captures the random coded subtask completion times, and our derived insights continue to hold.
Book chapters on the topic "Dynamic coded redundancy"
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Leydesdorff, Loet. "Evolutionary and Institutional Triple Helix Models." In Qualitative and Quantitative Analysis of Scientific and Scholarly Communication, 89–113. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-59951-5_5.
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AbstractThe institutional TH model focuses on relations of universities, industries, and governments in networks. Institutional arrangements develop over time along trajectories. The Triple-Helix metaphor of university-industry-government relations can also be elaborated into a neo-evolutionary model combining the vertical differentiation among the levels (in terms of relations, correlations, perspectives, and horizons of meaning) with the options for horizontal differentiation among the codes (e.g., markets, technologies, politics, etc., oper-ating in parallel). The neo-evolutionary model focuses on the interactions among selection mechanisms (markets, technologies, endowments) at the regime level. The historical and evolutionary dynamics feedback on each other. The relative weights of the historical versus evolutionary dynamics can be measured as a trade-off. Among three or more selection environments, synergy can be generated as redundancy on top of the aggregates of bilateral and unilateral contributions to the information flows. The number of new options available to an innovation system for realization may be as decisive for its survival more than the historical record of past performance.
Conference papers on the topic "Dynamic coded redundancy"
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Kucherov, N., V. Kuchukov, E. Golimblevskaia, N. Kuchukova, I. Vashchenko, and E. Kuchukova. "Efficient implementation of error correction codes in modular code." In 3rd International Workshop on Information, Computation, and Control Systems for Distributed Environments 2021. Crossref, 2021. http://dx.doi.org/10.47350/iccs-de.2021.09.
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The article develops an efficient implementation of an algorithm for detecting and correcting multivalued residual errors with a fixed number of calculations of the syndrome, regardless of the set of moduli size. Criteria for uniqueness are given that can be met by selecting moduli from a set of primes to satisfy the desired error correction capability. An extended version of the algorithm with an increase in the number of syndromes depending on the number of information moduli is proposed. It is proposed to remove the restriction imposed on the size of redundant moduli. Identifying the location of the error and finding the error vector requires only look-up tables and does not require arithmetic operations. In order to minimize the excess space, an extended algorithm is also proposed in which the number of syndromes and look-up tables increases with the number of information moduli, but the locations of errors can still be identified without requiring iterative computations. By using the approximate method, we have reduced the computational complexity of the algorithm for calculating the syndrome from quadratic to linear-logarithmic, depending on the number of bits in the dynamic range.
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Yu, Li, Jimin Xiao, and Tammam Tillo. "Dynamic redundancy allocation for video streaming using Sub-GOP based FEC code." In 2014 Visual Communications and Image Processing (VCIP). IEEE, 2014. http://dx.doi.org/10.1109/vcip.2014.7051620.
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Lee, Kyungwoo, Zino Benaissa, and Juan Rodriguez. "A dynamic tool for finding redundant computations in native code." In the 2008 international workshop. New York, New York, USA: ACM Press, 2008. http://dx.doi.org/10.1145/1401827.1401831.
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Kacewicz, Anna, and Stephen B. Wicker. "Optimizing redundancy using MDS codes and dynamic symbol allocation in mobile ad hoc networks." In 2008 42nd Annual Conference on Information Sciences and Systems (CISS). IEEE, 2008. http://dx.doi.org/10.1109/ciss.2008.4558682.
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Chakrabarti, Partha, and Manoj K. Maiti. "A Simple Time Domain Structural Redundancy Analysis Procedure for Semi-Submersibles." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29084.
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Offshore design codes like ABS and IMO require some level of redundancy in semi-submersible drilling vessels to withstand the loss of a slender bracing member without overall collapse of the structure, similar to fixed structures. Wave induced dynamic forces on semi-submersibles include hydrodynamic forces on ‘large body’, and inertia forces due to rigid body motions in six degrees of freedom. The amplitudes and phases of each component of the motion are important in defining the total force. Therefore, unlike static ‘pushover’ type analysis used in a relatively dynamically insensitive fixed jacket structure, semi-submersibles require nonlinear dynamic redundancy analysis in the time domain to determine the safety against collapse due to environmental loading. A simple time domain nonlinear analysis procedure is suggested in this study to capture the realistic behavior of the structure under wave loading. Dynamic loads are generated from hydrodynamic analysis of the floating body using a diffraction-radiation analysis program which assumes that the wave excitation is harmonic and so is the response. These loads are transferred to the structural analysis model. Each wave frequency is analyzed to produce a pair of loading conditions — ‘in-phase’ and ‘out of phase’. Combining these two components, a time history of the wave loading is created. In nonlinear structural analysis, first static loads are applied. Then wave load time history is applied for a few wave cycles in small increments. Results show that nonlinear analysis for one single cycle or two can usually predict the safety against collapse. If the analysis continues for a cycle or two, the structure passes the redundancy test. If it does not, the structure has a deficiency that needs to be addressed.
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Bettocchi, R., P. R. Spina, and P. M. Azzoni. "Fault Detection for Gas Turbine Sensors Using I/O Dynamic Linear Models: Methodology of Fault Code Generation." In ASME 1996 Turbo Asia Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-ta-002.
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This paper presents a methodology of sensor diagnosis which appears to be particularly suitable also for application in the field of small/medium power size industrial gas turbines. The methodology is based on the Analytical Redundancy technique and uses ARX (Auto Regressive with eXternal input) MISO (Multi-Input/Single-Output) linear dynamic models obtained from time series data of the gas turbine operating condition. The linear models allow the on-line calculation of some measurable parameter starting from the values of other measured parameters. The comparison between computed and measured values of the same parameters allows setting-up a vector of residuals which, if compared with the columns of the fault matrix, permits the identification of a possible sensor fault. The initial applications of the methodology to a single-shaft industrial gas turbine show an unambiguous and certain detection and isolation of fault in sensors used both in the measurement only and in feedback by the machine control system.
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Shilun, Zhao. "Dynamic Load Analysis of the Tower Structure of a Floating Wind Turbine Under Random Wind and Wave Excitation by Detuning Blade Pitch Controller Proportional Gains." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18405.
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Abstract This paper carried out coupled non-linear aero-hydro-servo-elastic simulations of a semisubmersible floating wind turbine under normal and severe sea states at various wind speeds. The NREL 5MW turbine was modeled by the SIMO-RIFLEX module in SESAM with hydrodynamic gathered by the WADAM code. A taut leg mooring system with redundancy was applied to account for the relatively shallow water site in the South China Sea. By detuning KP, the proportional gain coefficient of the blade-pitch controller, the platform motions and dynamic load effects on tower structure were investigated. It was found that the reduction of KP mitigates the load effects on tower top and base connections in certain load conditions. The motion performance of the platform was improved to some extent. The generator power output, as well as the fluctuation, were analyzed. Finally, suggestion on detailed blade pitch gains tuning according to specific wind speed and sea state was given.
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Sienicki, James J., and Plamen V. Petkov. "Passive Safety of the STAR-LM HLMC Natural Convection Reactor." In 10th International Conference on Nuclear Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/icone10-22290.
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The STAR-LM 300 to 400 MWt class modular, factory fabricated, fully transportable, proliferation resistant, autonomous, reactor system achieves passive safety by taking advantage of the intrinsic benefits of inert lead-bismuth eutectic heavy liquid metal coolant, 100+% natural circulation heat transport, a fast neutron spectrum core utilizing high thermal conductivity transuranic nitride fuel, redundant passive air cooling of the outside of the guard/containment vessel driven by natural circulation, and seismic isolation where required by site conditions. Postulated loss-of-heat sink without scram, overcooling without scram, and unprotected transient overpower accidents are analyzed for the 300 MWt STAR-LM design using a coupled thermal hydraulics-neutron kinetics plant dynamics analysis computer code. In all cases, STAR-LM is calculated to exhibit passive safety with peak cladding and coolant temperatures remaining within the existing database for lead-bismuth eutectic coolant and ferritic steel core materials.
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Zarzour, Mark, and John Vance. "Experimental Evaluation of a Metal Mesh Bearing Damper." In ASME 1999 International Gas Turbine and Aeroengine Congress and Exhibition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/99-gt-015.
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Metal mesh is a commercially available material used in many applications including seals, heat shields, filters, gaskets, aircraft engine mounts, and vibration absorbers. This material has been tested by the authors as a bearing damper in a rotordynamic test rig. The test facility was originally used to support the design of a turboprop engine, developing squirrel cages and squeeze film dampers for both the gas generator and power turbine rotors. To design the metal mesh damper, static stiffness and dynamic rap test measurements were first made on metal mesh samples in a specially designed nonrotating test fixture. These property tests were performed on samples of various densities and press fits. One sample was also tested in an Instron machine as an ancillary and redundant way to determine the stiffness. Using the stiffness test results and equations derived by a previous investigator, a spreadsheet program was written and used to size metal mesh donuts that have the radial stiffness value required to replace the squirrel cage in the power turbine. The squirrel cage and squeeze film bearing damper developed for the power turbine rotor was then replaced by a metal mesh donut sized by the computer code. Coast down tests were conducted through the first critical speed of the power turbine. The results of the metal mesh tests are compared with those obtained from previous testing with the squeeze film damper and Show that the metal mesh damper has the same damping as the squeeze film at room temperature but does not lose its damping at elevated temperatures up to 103 °C. Experiments were run under several different conditions, including balanced rotor, unbalanced rotor, heated metal mesh, and wet (with oil) metal mesh. The creep, or sag, of the metal mesh supporting the rotor weight was also measured over a period of several weeks and found to be very small. Based on these tests, metal mesh dampers appear to be a viable and attractive substitute for squeeze film dampers in gas turbine engines. The advantages shown by these tests include less variation of damping with temperature, ability to handle large rotor unbalance, and the ability (if required) to operate effectively in an oil free environment. Additional testing is required to determine the endurance properties, the effect of high impact or maneuver loads, and the ability to sustain blade loss loads (which squeeze films cannot handle).