Journal articles on the topic 'Component life extension'
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1
Davidson, M. J., T. J. Jones, D. D. Rosard, and J. R. Scheibel. "Monitoring for Life Extension." Journal of Pressure Vessel Technology 107, no. 3 (August 1, 1985): 255–59. http://dx.doi.org/10.1115/1.3264444.
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Combustion Engineering is under contract to EPRI to develop, construct and implement into a utility boiler a prototype on-line Boiler Stress and Condition Analyzer. The objective of the program is to develop and to demonstrate the analyzer’s potential to optimize the life of critical boiler components. The analyzer has been designed to assist the operator to warn of damaging transients, to optimize boiler start-up/shutdown rates and to accumulate unit operation data for the calculation of component life expenditure. The analyzer has been installed on the 1000-MW oil-fired Consolidated Edison Ravenswood No. 30 unit. This paper will outline the overall program and highlight significant results to date.
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Nahm, Seung Hoon, Chang Min Suh, Min Woo Jung, Jong Yup Kim, and Chang Hwan Yang. "Application of Damage Tolerance Approach for Turbine Disk Life Extension." International Journal of Modern Physics B 17, no. 08n09 (April 10, 2003): 1916–21. http://dx.doi.org/10.1142/s0217979203019873.
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For gas turbine engines, the safe life methodology has historically been used for fatigue life management of failure critical engine components. The safe retirement limit is necessarily determined by a conservative life evaluation procedure, thereby many components which have a long residual life are discarded. The objective of this study is to introduce the damage tolerant design concept into the life management for aircraft engine component instead of conservative fatigue life methodology which has been used for both design and maintenance. The residual lives of turbine disk component under various temperatures and conditions using creep-fatigue crack initiation and growth data were estimated. As the result of analysis, it was confirmed that retirement for cause concept was applicable to the evaluation of residual life of retired turbine disk which had been designed based on the conventional fatigue life methodology.
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Bougaenko, S. E., E. Yu Rivkin, and B. S. Rodchenkov. "Strength Aspects of Safety and Life Extension of RBMK Reactors." Journal of Pressure Vessel Technology 113, no. 2 (May 1, 1991): 141–44. http://dx.doi.org/10.1115/1.2928738.
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RBMK channel power reactors belong to the one-loop boiling water reactors with graphite as a moderator. Equipment, pipelines and core elements are the main components of the coolant recirculation circuit. Analysis in terms of fracture mechanics shows that the circuit elements conform to the “leak-before-break” criterion, with the pipelines and equipment keeping their availability during the whole design operation period. The core is a critical component for the circuit availability.
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Tu, S.-T., and X. Ling. "Interpretation of damage mechanics behaviour of two-bar structures for the life extension of high-temperature components." Journal of Strain Analysis for Engineering Design 38, no. 2 (February 1, 2003): 125–32. http://dx.doi.org/10.1243/030932403321163659.
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The creep damage behaviour of two-bar structures of different dimensions and materials is studied in terms of continuum damage theory. The basic model is used to interpret the effectiveness of life extension measures for complicated structures. It is found that replacement of the more damaged component prior to rupture will result in an optimized life extension efficiency, depending on the geometric or material difference between the damaged and less damaged components. This has potential to provide guidance on the effectiveness of life extension repairs in high-temperature plants.
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Allen, T. R., J. I. Cole, E. A. Kenik, H. Tsai, S. Ukai, S. Mizuta, and T. Yoshitake. "Using fast reactor component evaluation for pressurized water reactor life extension." JOM 51, no. 10 (October 1999): 27–30. http://dx.doi.org/10.1007/s11837-999-0183-7.
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Carter, Jace A., and Tarun Goswami. "Probabilistic Risk Assessment for Life Extension of Turbine Engine Rotors." Metals 12, no. 8 (July 28, 2022): 1269. http://dx.doi.org/10.3390/met12081269.
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Maintaining the component service life beyond its historical limits requires the ability to accurately quantify component reliability and address the uncertainties in material responses. A probabilistic method for predicting the total fatigue life was developed and applied to determine the probability of failure of a Ti-6Al-4V turbine disk component. The total fatigue life incorporates a dual mechanism approach including the crack initiation life and propagation life while simultaneously determining the associated initial flaw sizes. A microstructure-based model was employed to address the uncertainties in material response and relate the crack initiation life with crack size. The propagation life was characterized using both small and large crack growth models to ensure accurate fatigue life prediction. Fatigue life predictions were found to correlate with experimental data at high stress levels. The risk assessment can be used to estimate the expected initial crack sizes from variability in material properties, which can further be used to establish an enhanced inspection planning.
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Woo, Chang Su, Wan Doo Kim, and Jae Do Kwon. "Fatigue Life Evaluation of Rubber Components for Automobile Vehicles." Key Engineering Materials 324-325 (November 2006): 181–84. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.181.
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The interest of the fatigue life for rubber components was increasing according to the extension of warranty period of the automotive components. In this study, the fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue tests. Finite element analysis of 3D dumbbell specimen and rubber component was performed based on a hyper-elastic material model determined from the mechanical tests. The Green-Lagrange strain at the critical location determined from the finite element analysis was used for evaluating the fatigue damage parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens and rubber component with different levels of maximum strain and various load. Fatigue life curves can be effectively represented by a following single function using the maximum Green-Lagrange strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the rubber component for automobile vehicle agreed fairly with the experimental fatigue lives.
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Aitken, R. R., D. P. W. Horrigan, and G. Moltschaniwskyj. "Life extension of impact damaged honeycomb sandwich panels." Aeronautical Journal 104, no. 1041 (November 2000): 509–16. http://dx.doi.org/10.1017/s0001924000017887.
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Abstract The assessment of damage due to impacts in composite sandwich panels and the component life reductions associated with such damage is becoming increasingly important within the aerospace industry. This study analyses minimum gauge, non-metallic honeycomb wing panels subject to impact damage. In all instances the damage is caused by ‘soft body’ impactors travelling at elevated velocities to simulate bird strike and other soft debris. The damage formed during these impacts is shown to be large in plan area but shallow and primarily causes crushing of the core in a thin layer. Loading of the panels after impact has been performed to determine the reduction in load carrying capacity and associated failure mechanisms. Damage due to soft body impact is shown to be very different to the classical rigid body impact upon which current repair schemes are based. As a result in many applications the use of current repair schemes may be inappropriate. The viability of new repair techniques is discussed with particular attention to the prevention of failure mechanisms due to loading after impact.
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Yi, Siliang, and Chih-Fu Wu. "Green-Extension Design—A New Strategy to Reduce the Environmental Pressure from the Existing Consumer Electronics." International Journal of Environmental Research and Public Health 18, no. 18 (September 12, 2021): 9596. http://dx.doi.org/10.3390/ijerph18189596.
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Existing electronic devices will quickly become e-waste when encountering technological iterations, which results in serious environmental and public health problems. Previous circular economy research has mainly focused on the development of new products with long life or recycling discarded products. This study firstly proposes the Green-Extension Design (GED) strategy for developing adaptable accessories that provide existing products with the ability to continue to work in a different context. Competitiveness was selected to evaluate the performance of GED, and three competitiveness components were derived through principal component analysis (PCA). Moreover, AHP (Analytic Hierarchy Process) was applied to define the weights of the three competitiveness components, and a GED model was established on the basis of production function. Furthermore, the calculation method for each competitiveness component was defined. The GED strategy is aimed at extending the life of existing products, as well as reducing resource waste and environmental pollution. The GED model based on competitiveness components can enable enterprises to design products of high competitiveness and obtain market share as a result.
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Lawand, Lydia, Khalil Al Handawi, Massimo Panarotto, Petter Andersson, Ola Isaksson, and Michael Kokkolaras. "A Lifecycle Cost-Driven System Dynamics Approach for Considering Additive Re-Manufacturing or Repair in Aero-Engine Component Design." Proceedings of the Design Society: International Conference on Engineering Design 1, no. 1 (July 2019): 1343–52. http://dx.doi.org/10.1017/dsi.2019.140.
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AbstractAero-engine component design decisions should consider re-manufacturing and/or repair strategies and their impact on lifecycle cost. Existing design approaches do not account for alternative production technologies such as the use of additive manufacturing in life extension processes. This paper presents a modeling and optimization methodology for examining the impact of design decisions in the early development stage on component lifecycle cost during the in-service phase while considering the potential use of additive manufacturing in life extension strategies. Specifically, a system dynamics model is developed to assess different end-of-life scenarios. Finally, an optimization problem is formulated and solved to minimize lifecycle cost with respect to design variables related to re-manufacturing.
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Wakiru, James, Liliane Pintelon, Peter N. Muchiri, and Peter K. Chemweno. "Integrated remanufacturing, maintenance and spares policies towards life extension of a multi-component system." Reliability Engineering & System Safety 215 (November 2021): 107872. http://dx.doi.org/10.1016/j.ress.2021.107872.
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Sitthipong, Siva, Prawit Towatana, Amnuay Sitticharoenchai, and Chaiyoot Meengam. "Life Extension of Propeller Shafts by Hardfacing Welding." Materials Science Forum 872 (September 2016): 62–66. http://dx.doi.org/10.4028/www.scientific.net/msf.872.62.
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At present the Cut-stern Kolek Boats of local fishermen at Kaoseng Community on the Coast of Songkhla Lake have a high rate of shaft failure. Consequently, the fishermen have spent lots of money on maintenance program of repairing shafts for a few years. Besides, the repairing cost, each time of the failure also causes water pollution from the leakage of grease. The incomplete transmission of power leads to engine overloading and fuel wasting. The investigation of the high failure rate of propeller shafts which were major machine component in power transmission illustrated the failure in normal fracture caused by the mechanisms of metal fatigue. Using the welding repair by shield metal arc welding process did not give the satisfied outcome because it created the short service life of reused propeller shafts after repairing. This research was aimed to study the metal fatigue behavior of long tail shafts in the Cut-stern Kolek boats and introduce the new method of welding repair process to prolong their service life. The experiment revealed that specimens resulted from the new welding repair process and the conventional one possessed different service life. The new process used the flux core which arc welding can prolong the service life of the shafts of boats more than 1.6 times of using the conventional method which is the electric welding by flux core arc welding. The research result will be extended to fishermen, in order to encourage them to become a part of sustainable inshore fisheries.
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Tu, Shan Tung. "Some Fundamental Aspects of Redesign and Remanufacture of High Temperature Components." Advanced Materials Research 44-46 (June 2008): 25–32. http://dx.doi.org/10.4028/www.scientific.net/amr.44-46.25.
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The impact of remanufacturing on the conservation of energy and resources has been well recognized during the last decade. When the relevant technologies are applied for high temperature components in power and process industries, a redesign of the component life should be required due to the time-dependent feature of high temperature failure. In order to provide some fundamentals for redesign and remanufacture of high temperature components, mechanical behavior of a two-bar structure with one bar being remanufactured is analyzed. An optimal repairing time is given. From the viewpoint of creep damage, various high temperature structures are analyzed by using damage coupled finite element method. Suggestions for life extension remanufacture are proposed for typical high temperature components.
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Lee, Young Shin, and Hyun Seung Lee. "Optimum Design for Life Extension on the End Coupling of Aluminum Hot Rolling Process." Advanced Materials Research 275 (July 2011): 125–28. http://dx.doi.org/10.4028/www.scientific.net/amr.275.125.
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The end coupling is the main component of the aluminum hot rolling process. The end coupling used for transmission of rotational power with heavy-duty load. Fracture of the end coupling causes serious economic injury because an end coupling is a very expensive component and takes a long time to repair. To prevent the destruction of the end coupling it is essential for mechanical life cycle to be known. In this paper, a parameter study on end coupling was performed in order to minimize maximum stress of an end coupling under static loads. To verify the interference of spindle assembly with modified end coupling, kinematic simulation was performed by applying the various combination type and dynamic boundary condition of the spindle assembly. The interference of an optimized model did not occur during combination process and driving process. As a result of an optimum design for life extension on end coupling, the maximum stress of end coupling was reduced about 26% compared with original model.
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Nemeth, N. N., L. M. Powers, L. A. Janosik, and J. P. Gyekenyesi. "Durability Evaluation of Ceramic Components Using CARES/LIFE." Journal of Engineering for Gas Turbines and Power 118, no. 1 (January 1, 1996): 150–58. http://dx.doi.org/10.1115/1.2816531.
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The computer program CARES/LIFE calculates the time-dependent reliability of monolithic ceramic components subjected to thermomechanical and/or proof test loading. This program is an extension of the CARES (Ceramics Analysis and Reliability Evaluation of Structures) computer program. CARES/LIFE accounts for the phenomenon of subcritical crack growth (SCG) by utilizing the power law, Paris law, or Walker equation. The two-parameter Weibull cumulative distribution function is used to characterize the variation in component strength. The effects of multiaxial stresses are modeled using either the principle of independent action (PIA), the Weibull normal stress averaging method (NSA), or the Batdorf theory. Inert strength and fatigue parameters are estimated from rupture strength data of naturally flawed specimens loaded in static, dynamic, or cyclic fatigue. Application of this design methodology is demonstrated using experimental data from alumina bar and disk flexure specimens, which exhibit SCG when exposed to water.
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Ainsworth, R. A., M. B. Ruggles, and Y. Takahashi. "Flaw Assessment Procedure for High-Temperature Reactor Components." Journal of Pressure Vessel Technology 114, no. 2 (May 1, 1992): 166–70. http://dx.doi.org/10.1115/1.2929024.
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An interim high-temperature flaw assessment procedure is described. This is a result of a collaborative effort between Electric Power Research Institute in the US, Central Research Institute of Electric Power Industry in Japan, and Nuclear Electric plc in the UK. The procedure addresses pre-existing defects subject to creep-fatigue loading conditions. Laws employed to calculate the crack growth per cycle are defined in terms of fracture mechanics parameters and constants related to the component material. The crack growth laws may be integrated to calculate the remaining life of a component or to predict the amount of crack extension in a given period. Fatigue and creep crack growth per cycle are calculated separately, and the total crack extension is taken as the simple sum of the two contributions. An interaction between the two propagation modes is accounted for in the material properties in the separate calculations. In producing the procedure, limitations of the approach have been identified. Some of these limitations are to be addressed in an extension of the current collaborative program.
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Polyanchikova, Mariya Y., Yuriy N. Polyanchikov, and Oleg A. Kursin. "Formation of Residual Stresses in the Internal Combustion Engine Sleeves after Abrasive Processing and Operation." Materials Science Forum 973 (November 2019): 65–68. http://dx.doi.org/10.4028/www.scientific.net/msf.973.65.
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The article presents the results of residual stresses measurements in the material of the internal combustion engine (ICE) sleeves. The studies have been carried out for new sleeves, sleeves after processing with diamond and single-component abrasive tools (SCAT) and sleeves that have exhausted their service life. The results of the research have established the fact that processing of the sleeves with a single-component abrasive tool substantially increases the values of internal residual compressive stresses, which contributes to the life extension of the engine in whole.
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Kim, Seohyun Chris, Derek K. O’Flaherty, Lijun Zhou, Victor S. Lelyveld, and Jack W. Szostak. "Inosine, but none of the 8-oxo-purines, is a plausible component of a primordial version of RNA." Proceedings of the National Academy of Sciences 115, no. 52 (December 3, 2018): 13318–23. http://dx.doi.org/10.1073/pnas.1814367115.
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The emergence of primordial RNA-based life would have required the abiotic synthesis of nucleotides, and their participation in nonenzymatic RNA replication. Although considerable progress has been made toward potentially prebiotic syntheses of the pyrimidine nucleotides (C and U) and their 2-thio variants, efficient routes to the canonical purine nucleotides (A and G) remain elusive. Reported syntheses are low yielding and generate a large number of undesired side products. Recently, a potentially prebiotic pathway to 8-oxo-adenosine and 8-oxo-inosine has been demonstrated, raising the question of the suitability of the 8-oxo-purines as substrates for prebiotic RNA replication. Here we show that the 8-oxo-purine nucleotides are poor substrates for nonenzymatic RNA primer extension, both as activated monomers and when present in the template strand; their presence at the end of a primer also strongly reduces the rate and fidelity of primer extension. To provide a proper comparison with 8-oxo-inosine, we also examined primer extension reactions with inosine, and found that inosine exhibits surprisingly rapid and accurate nonenzymatic RNA copying. We propose that inosine, which can be derived from adenosine by deamination, could have acted as a surrogate for G in the earliest stages of the emergence of life.
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Daniele, Joseph R., Ryo Higuchi-Sanabria, Jenni Durieux, Samira Monshietehadi, Vidhya Ramachandran, Sarah U. Tronnes, Naame Kelet, et al. "UPRER promotes lipophagy independent of chaperones to extend life span." Science Advances 6, no. 1 (January 2020): eaaz1441. http://dx.doi.org/10.1126/sciadv.aaz1441.
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Longevity is dictated by a combination of environmental and genetic factors. One of the key mechanisms to regulate life-span extension is the induction of protein chaperones for protein homeostasis. Ectopic activation of the unfolded protein response of the endoplasmic reticulum (UPRER) specifically in neurons is sufficient to enhance organismal stress resistance and extend life span. Here, we find that this activation not only promotes chaperones but also facilitates ER restructuring and ER function. This restructuring is concomitant with lipid depletion through lipophagy. Activation of lipophagy is distinct from chaperone induction and is required for the life-span extension found in this paradigm. Last, we find that overexpression of the lipophagy component, ehbp-1, is sufficient to deplete lipids, remodel ER, and promote life span. Therefore, UPR induction in neurons triggers two distinct programs in the periphery: the proteostasis arm through protein chaperones and metabolic changes through lipid depletion mediated by EH domain binding protein 1 (EHBP-1).
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Pichlmaier, Simon, Michael Kult, and Ulrich Wagner. "Extension of Energy and Transport Scenario Modelling to Include a Life Cycle Perspective." Future Transportation 1, no. 2 (July 22, 2021): 188–201. http://dx.doi.org/10.3390/futuretransp1020012.
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The paper outlines the methodology for the extension of the assessment of transport scenarios to include a life cycle perspective. When considering greenhouse gas emissions in the operational phase, the inclusion of the upstream chain increases emissions in conventional systems by only 17% to 19%. In transport systems that utilise a large share of electricity generated predominantly from renewable energies without direct emissions, this value can rise sharply. In the present case, up to 304%. The emissions currently associated with the production of the transport fleet correspond to 56 Mt CO2e and thus 22% of total emissions. In most scenarios, however, this value decreases more slowly than the operational emissions. This increases the share of emissions caused by production. Thus, the inclusion of life cycle emissions is an important component for assessing sustainability.
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Rosemeier, Malo, and Matthias Saathoff. "Assessment of a rotor blade extension retrofit as a supplement to the lifetime extension of wind turbines." Wind Energy Science 5, no. 3 (July 14, 2020): 897–909. http://dx.doi.org/10.5194/wes-5-897-2020.
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Abstract. The potential lifetime of wind turbine components is usually not fully utilized as the site conditions are less severe than assumed in the turbine design. Operators of wind farms can make use of the excess fatigue budget to increase the energy yield and thus decrease the levelized cost of energy (LCoE). To achieve this, the lifetime of the turbine can be extended until the fatigue budget is exhausted. Alternatively, a rotor blade extension (RBE) is an option to increase the energy yield of a wind turbine. An RBE increases the blade length and thus the swept area and the energy yield. An RBE also increases the loads on the turbine, however. Higher fatigue loads in turn reduce the fatigue budget of a turbine. This study investigates whether the use of an RBE is advantageous compared with a sole lifetime extension (LTE). As the use case, a commercial 1.5 MW turbine located in northern Germany was investigated. Aeroservoelastic multibody load simulations and simplified static load simulations were verified with each other. These simulations revealed the loads to determine the fatigue budget of the turbine components. Since the blade became the critical component when a certain RBE length was exceeded, the blade was subjected to a structural fatigue analysis. The fatigue analysis focused on the trailing-edge bond line which became critical when lead–lag loads increased with blade length. Finally, the energy production gains due to LTE and RBE were assessed. For the use case turbine, this study revealed an LTE of 8.7 years after a design life of 20 years with an additional energy yield of 43.5 %. Moreover, the extension of the 34 m blade with an RBE length of 0.8 m further increased the yield by 2.3 %.
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Kovacevic, Dragan, Slobodan Skundric, and Jelena Lukic. "Monitoring and diagnostics of power transformer insulation." Thermal Science 10, no. 4 (2006): 43–54. http://dx.doi.org/10.2298/tsci0604043k.
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Liberalization of the energy market drives utilities to a more cost-effective power system. Power transformers are the most complex, important, and critical components of the transition and distribution power systems. Insulation system is the key component of life extension, better availability and higher reliability of a transformer. In order to achieve both decreasing operational cost and reliable service condition-based maintenance is needed. Monitoring and diagnostics methods and techniques, for insulation condition assessment of power transformers, are described. Date base and knowledge rules diagnostics management system, in internet oriented environment, is outlined. .
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Garud, Y. S. "ROLE OF MECHANICS IN PLEX: A TECHNICAL PERSPECTIVE." Transactions of the Canadian Society for Mechanical Engineering 17, no. 2 (June 1993): 97–109. http://dx.doi.org/10.1139/tcsme-1993-0006.
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The mechanics of materials and structures plays an important role in majority of life prediction and structural integrity evaluations. In many industrial systems this role gets integrated with effects of service environment and material aging; corrosion, oxidation, and irradiation are examples of such effects which require an interdisciplinary approach. Degradation mechanisms related to these effects have been identified as potentially significant to plant life extension (PLEX). In-service inspection and component monitoring are some of the cost effective steps emphasized in the life extension works; usefulness of the results of these steps can be enhanced through the methods needed for the component condition assessment. These methods, therefore, demand an ever increasing accuracy and improvements requiring a better appreciation and integration of the mechanics. The above aspects of PLEX are critically examined in this paper with a review of key degradation mechanisms elucidating the role of mechanics. Current design basis and recent developments in the life prediction techniques are discussed identifying areas of further work. Stress corrosion cracking, corrosion fatigue, pressurized thermal shock, and long term material stability under thermal and irradiation aging are some of the phenomena emphasized in this work. The significance of mechanics in treating the sub-critical crack growth due to these phenomena is discussed. Also, from the point of view of final failure step, the role of impact energy and fracture toughness is examined with consideration of the time dependent changes in these properties. The additional objective of this presentation is to provide a perspective on the assessment of remaining life and safety margins with particular reference to the needs and challenges of the plant life extension.
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Venugopal, Arvinthan, Roslina Mohammad, Md Fuad Shah Koslan, Ashaari Shafie, Alizarin bin Ali, and Owi Eugene. "Crack Growth Prediction on Critical Component for Structure Life Extension of Royal Malaysian Air Force (RMAF) Sukhoi Su-30MKM." Metals 11, no. 9 (September 14, 2021): 1453. http://dx.doi.org/10.3390/met11091453.
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The critical aircraft structure, being the load-bearing members, is a vital component for any aircraft. The effect of fatigue loading, operating conditions, and environmental degradation has caused the structural integrity of the airframe to be assessed for its airworthiness requirement. Using the fatigue design concept of Safe Life, the RMAF adopts the Aircraft Structure Integrity Program (ASIP) to monitor the structural integrity of its critical components. RMAF has produced the task card using the engineering analysis concept on the aircraft’s critical structure. Various Computer-Aided Engineering (CAE) methods were used, and for this analysis, the Crack Growth Prediction method was used to determine the crack growth behavior and its ultimate failure point in case of any crack occurrences. Although there are six critical locations, the wing root is chosen since it has the highest possibility of fatigue failure. The analytical methods which were discussed are Crack Growth Analysis and Low Cycle Fatigue. For the numerical method, NX Nastran was used for the simulation of crack growth. The result from the crack growth analysis was validated with the numerical result. The conclusion is that, based on the fatigue life cycle, the wing root structure condition is not affected by severe damage, and its failure is approximately around 30 to 100 years for both the through hole and through side crack. Thus, its structural life can be extended. The research outcome will be on the extension of the structure life of the aircraft wing.
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Smeaton, Deborah, and Michael White. "The Growing Discontents of Older British Employees: Extended Working Life at Risk from Quality of Working Life." Social Policy and Society 15, no. 3 (July 14, 2015): 369–85. http://dx.doi.org/10.1017/s1474746415000366.
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A key component of sustainable welfare policy is the extension of working life (EWL). Currently this aim is chiefly pursued by financial policies, neglecting the potential role of quality of working life (QWL) in attracting people to remain employed. National survey data for Britain in the years 1992, 2006 and 2012 demonstrate deteriorating overall job attitude among older employees, following the changed competitive and technological conditions of the 1990s. The investigation goes on to diagnose aspects of the work situation implicated in adverse experience of work among older employees. Work demands and the nature of work emerge as key areas of discontent, with additional evidence of insecurity, and dissatisfaction with pensions, emerging over the recent recession. Policies potentially addressing QWL, with particular attention to the role of employers, are reviewed in the conclusion.
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Sopon, Mircea, Valentin Oleksik, Mihai Roman, Nicolae Cofaru, Mihaela Oleksik, Cosmin Mohor, Adrian Boicean, and Radu Fleaca. "Biomechanical Study of the Osteoporotic Spine Fracture: Optical Approach." Journal of Personalized Medicine 11, no. 9 (September 11, 2021): 907. http://dx.doi.org/10.3390/jpm11090907.
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Background and objectives: Osteoporotic spine fractures represent a significant factor for decreasing quality of life in the elderly female population. Understanding the mechanisms involved in producing these fractures can improve their prevention and treatment. This study presents a biomechanical method to produce a vertebral fracture, conducted on a human spine segment, observing the displacements and strains in the intervertebral disc, endplate, and vertebral body. Materials and Methods: We performed two tests, one corresponding to an extension loading, and the second to an axial loading. Results: The maximum displacement in the target vertebral body presented higher values in the case of the extension as compared to the axial strain where it mainly occurred after the fracture was produced. The strains occurred simultaneously on both discs. In the case of the axial strain, due to the occurrence of the fracture, the maximum value was recorded in the spine body, while in the case of the extensions, it occurred in the neural part of the upper disc. The advantage of this method was that the entire study was an experiment, using optical methods, increasing the precision of the material data input. Conclusions: The research method allowed recording in real time of a larger amount of data from the different components of the spine segment. If there was an extension component of the compression force at the moment of the initial loading, part of this load was absorbed by the posterior column with higher mechanical resistance. After the maximum capacity of the absorption was reached, in both situations the behavior was similar.
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Stevens, G. L., and S. Ranganath. "Use of On-Line Fatigue Monitoring of Nuclear Reactor Components as a Tool for Plant Life Extension." Journal of Pressure Vessel Technology 113, no. 3 (August 1, 1991): 349–57. http://dx.doi.org/10.1115/1.2928766.
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The application of an on-line fatigue monitoring system for tracking fatigue usage in operating power plants is described. The system, like several others which have been developed, uses the influence function approach, operates on a microcomputer, and determines component stresses using temperature, pressure, and flow rate data that are typically available from plant computers. Using plant-unique influence functions developed specifically for each component location, the system calculates stresses as a function of time and computes the fatigue usage. Stress values are calculated at time intervals defined by the user and the fatigue values are saved on files for use at a later time. The application of the GE Fatigue Monitoring System (GEFMS) to calculate fatigue usage in the feedwater nozzle of a GE Boiling Water Reactor is described in this paper. Stress predictions using GEFMS for a sample temperature transient show excellent agreement with results from finite element thermal and stress analysis performed on a mainframe computer. Fatigue usage calculations for a simulated 24-hr temperature record confirm that the system provides accurate results at a cost that is significantly lower than similar analysis done on mainframe computer systems. The system, which has been installed in a boiling water reactor plant, provides the technical basis to evaluate actual reactor conditions and justify plant life extension.
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Kashaev, Nikolai, Sergey Chupakhin, Volker Ventzke, Manfred Horstmann, Stefan Riekehr, Alessandro Barbini, Jorge F. dos Santos, Sören Keller, Benjamin Klusemann, and Norbert Huber. "Fatigue Life Extension of AA2024 Specimens and Integral Structures by Laser Shock Peening." MATEC Web of Conferences 165 (2018): 18001. http://dx.doi.org/10.1051/matecconf/201816518001.
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The goal of the present study is to understand the effects of laser shock peening (LSP)-induced residual stresses on the fatigue crack propagation (FCP) behaviour of the commonly used aircraft aluminium alloy AA2024 in T3 heat treatment condition. LSP treatment was performed using a pulsed Nd:YAG laser on compact tensile C(T)50-specimens with a thickness of 2.0 mm. LSP-treated specimens reveal a significant retardation of the fatigue crack propagation. The fatigue crack retardation effect can be correlated with the compressive residual stresses introduced by LSP throughout the entire specimen thickness. A possible application of the LSP process on a component like panel with three welded stringers representing a part of a fuselage structure was performed as well. The skin-stringer AA2024-AA7050 Tjoints were realised through stationary shoulder friction stir welding (SSFSW), a variant of the conventional friction stir welding process. In this relatively new process, the shoulder does not rotate and therefore does not contribute to the heat generation. Consequently, a reduced and more homogeneous heat input leads to a less affected microstructure and better mechanical properties. The efficiency of the LSP process has been demonstrated resulting in an increase of 200 – 400% in fatigue lifetime.
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Nikishkov, Yuri, Gennadiy Nikishkov, Guillaume Seon, Brian Shonkwiler, Andrew Makeev, Joseph D. Schaefer, and Brian Justusson. "Structures Technology for Component Damage and Failure Prediction." Journal of the American Helicopter Society 66, no. 3 (July 1, 2021): 1–16. http://dx.doi.org/10.4050/jahs.66.032006.
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Advanced structural analysis methods, known as progressive damage and failure analysis tools, are being developed to predict initiation and propagation of damage under repeated loading based on capturing individual and interacting damage modes. This work shows the ability of the progressive damage and failure analysis method implemented in CDMat software developed at the University of Texas Arlington Advanced Materials and Structures Lab to predict strength and fatigue failure of an advanced mechanically fastened aerospace structural joint, the common feature test component (CFTC)— representative of flight-critical structural attributes and failure modes—without a priori knowledge of the test result. The CFTC structural features include a composite tape skin, a composite fabric stiffener, and an aluminum rib applying pullthrough load through multiple countersunk bolts combined with the axial compression of skin and stiffener. Failure and damage predictions under static and constant-amplitude cyclic loading are compared with tests. Developed by Boeing under the Air Force Research Laboratory Composite Airframe Life Extension Program, the CFTC has been the most complex progressive damage and failure analysis validation article to date.
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Song, Gee Wook, Bum Shin Kim, and Jung Seob Hyun. "Life Prediction of High Pressure Steam Turbine Rotor." Key Engineering Materials 321-323 (October 2006): 707–10. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.707.
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The operation mode of thermal power plants has been changed from the base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient state, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in steam turbine and requires long outage for replacing the new one. For optimized power plant operation life and inspection management of rotor is necessary. It is known as general that start-up and shutdown operation greatly affect on steam turbine life. The start-up operation condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of main components life of steam turbine. The start-up stress of rotor which is directly related life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotation speed of itself. In this paper, the analysis method of start-up stress of rotor which considers simultaneously temperature and rotation speed transition is proposed, which includes a case study regarding 500MW fossil power plant steam turbine rotor. Also, the method of damage quantitative estimation of fatigue damage to operation condition is described. The method can be applied to find weak points to the fatigue damage. Using the method, total life consumption can be obtained, and can be also used for determining future operation mode and the life extension of old fossil power units.
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Vehniwal, Sanjamveer S., Raphael Ofoe, Samuel K. Asiedu, Jeff Hoyle, and Lord Abbey. "Extension of Cut Carnation Vase Life Using Compost Tea, Putrescine and Plant Extracts." Sustainable Agriculture Research 10, no. 1 (December 18, 2020): 32. http://dx.doi.org/10.5539/sar.v10n1p32.
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Cut flower vase life can be extended by various natural products, but their efficacy when mixed with compost tea is not reported. A study was performed to determine cut carnation (Dianthus caryophyllus cv. White Sim) vase life in 1 L of formulations (1) C3.5: 3.5% compost tea + 15 mg putrescine; (2) R5L10: C3.5 + 5 mL rosemary (Salvia rosmarinus) + 10 mL lemon (Citrus limon) extracts; (3) R10L10: C3.5 + 10 mL rosemary + 10 mL lemon extracts; (4) R5L20: C3.5 + 5 mL rosemary + 20 mL lemon extracts; (5) R10L20: C3.5 + 10 mL rosemary + 20 mL lemon extracts; (6) Chrysal: Floral Chrysal Clear (positive control); and (7) Dw: distilled water alone (negative control). The 15 mg putrescine significantly (P=0.002) reduced compost tea turbidity by 34%. The neutral pH of C3.5 and Dw did not change. However, pH increased by 24% in Chrysal and reduced by 39% in R5L10, R10L10 and R5L20 and by 54% in R10L20 on day 11. TDS and EC were highest in Chrysal from days 1 to 11. Petal discoloration, wilt, shrinkage and neck bend were delayed by C3.5 followed by Chrysal and then R5L10, but were accelerated by the other treatments. In conclusion, the cut carnation cv. White Sim longevity as influenced by variations in the vase solutions was Chrysal (14 days) > C3.5 (12.6 days) > R5L10 (10.7 days) but ≤ 9 days in the other treatments. These results were confirmed by a 2-D principal component analysis biplot. Future study will investigate microbial interaction.
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Ogita, Akira, Wakae Murata, Ken Yamauchi, Akiko Sakai, Yoshihiro Yamaguchi, Toshio Tanaka, and Ken-ichi Fujita. "Immature Pear Extract Constituents Exert Multifaceted Anti-aging Effects." Innovation in Aging 5, Supplement_1 (December 1, 2021): 679. http://dx.doi.org/10.1093/geroni/igab046.2556.
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Abstract Cellular senescence causes a gradual loss of physiological functions and induces chronic diseases, which negatively affect the quality of human life. Intervention in the cellular senescence process may reduce the incidence of these diseases while delaying the progression of age-related diseases, thereby prolonging human lifespan. In our previous study, we found that extending the chronological lifespan of budding yeast cells, a suitable cellular model for research on mammalian cells, could be achieved by adding immature pear extract (iPE). Moreover, at the 2020 GSA meeting, using a colony-counting method, we reported that both hydrophilic (WiPE) and hydrophobic (OiPE) iPE components exhibited a chronological lifespan prolongation on yeast cells. In this study, the expression of sirtuin-related genes, which regulate cellular senescence, was verified by quantitative real-time reverse-transcription polymerase chain reaction. Interestingly, sirtuin-related gene expression was significantly increased in the WiPE-treated cells only, and OiPE could extend the chronological lifespan of yeast cells through the mechanisms not involved in sirtuin-related gene expression. In general, hydrophobic and hydrophilic components exhibit different degradation and metabolism in cells. Since each component has a different strategy of absorption and excretion in the body, we hypothesize that iPE with multiple active components will have multifaceted effects on anti-aging. Our research on elucidating the mechanism of lifespan extension by OiPE and its application to mammalian cells is ongoing.
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Morancais, Amélie, Mathieu Fevre, Pascale Kanoute, Serge Kruch, and Manuel François. "Impact of Residual Stresses on the Fatigue Behavior of a Nickel-Based Superalloy." Materials Science Forum 768-769 (September 2013): 747–54. http://dx.doi.org/10.4028/www.scientific.net/msf.768-769.747.
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Aircraft engine components are subjected, voluntarily or not, to the influence of residual stresses (RS). These RS may evolve in service conditions and may have an influence on fatigue life of the component. This paper presents a method to take into account the RS and their relaxation in a finite element calculation to obtain the fatigue life. This method is applied to a representative high-pressure turbine disk specimen made of N18 Nickel-based superalloy. Firstly, residual stresses are measured using X-Ray diffraction technique on the surface and the thickness of specimens. The influence of different surface finishing processes on the intensity and distribution of RS is compared to as-received specimen. Then, using the experimental profile as an initial state, a fatigue life analysis is performed (on fatigue specimen) by applying a multiaxial extension of the Smith-Watson-Topper model. Numerical and experimental results are discussed in detail and it appears that residual compressive stresses have almost no influence for high strain range but they improve the fatigue life for lower ranges.
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LEE, HYUN-SEUNG, JANG-WON LEE, and YOUNG-SHIN LEE. "FATIGUE ANALYSIS ON THE END COUPLING OF THE ALUMINUM HOT ROLLING EQUIPMENT." International Journal of Modern Physics B 25, no. 31 (December 20, 2011): 4225–28. http://dx.doi.org/10.1142/s0217979211066635.
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The End Coupling is the main component of the aluminum hot rolling equipment. The End Coupling is used for transmission of rotational power with heavy-duty load. Fracture of the End Coupling causes serious economic losses because an End Coupling is a very expensive component and it takes a long time to repair it. Therefore, preventing the destruction of the End Coupling is essential for ensuring a long mechanical life cycle. In this paper, a parameter study on the End Coupling was performed in order to minimize maximum stress of the End Coupling under static loads. As a result of an optimum design for life extension on the End Coupling, the maximum stress of the modified End Coupling was lower than that of the initial model by 29%. The fatigue analysis for fatigue life prediction of the modified End Coupling was performed using the commercial finite element method. In the results of the fatigue life analysis, the safety factor of the modified End Coupling was 1.123. Therefore, it was demonstrated that the modified End Coupling has infinite life.
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Yang, Wenchao, Yuanyuan Tian, Mingfeng Han, and Xiaoqing Miao. "Longevity extension of worker honey bees (Apis mellifera) by royal jelly: optimal dose and active ingredient." PeerJ 5 (March 28, 2017): e3118. http://dx.doi.org/10.7717/peerj.3118.
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In the Western honey bee, Apis mellifera, queens and workers have different longevity although they share the same genome. Queens consume royal jelly (RJ) as the main food throughout their life, including as adults, but workers only eat worker jelly when they are larvae less than 3 days old. In order to explore the effect of RJ and the components affecting longevity of worker honey bees, we first determined the optimal dose for prolonging longevity of workers as 4% RJ in 50% sucrose solution, and developed a method of obtaining long lived workers. We then compared the effects of longevity extension by RJ 4% with bee-collected pollen from rapeseed (Brassica napus). Lastly, we determined that a water soluble RJ protein obtained by precipitation with 60% ammonium sulfate (RJP60) contained the main component for longevity extension after comparing the effects of RJ crude protein extract (RJCP), RJP30 (obtained by precipitation with 30% ammonium sulfate), and RJ ethanol extract (RJEE). Understanding what regulates worker longevity has potential to help increase colony productivity and improve crop pollination efficiency.
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Coles, Alasdair, Gavin Giovannoni, Thibault Moreau, Eva Havrdova, David Margolin, Linda Kasten, and Barry Singer. "ALEMTUZUMAB IMPROVES 3-YEAR QUALITY OF LIFE IN CARE-MS II." Journal of Neurology, Neurosurgery & Psychiatry 86, no. 11 (October 14, 2015): e4.9-e4. http://dx.doi.org/10.1136/jnnp-2015-312379.106.
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In the 2-year, phase 3 CARE–MS II study (NCT00548405) of relapsing-remitting multiple sclerosis (RRMS) patients with inadequate efficacy response to prior therapy, alemtuzumab demonstrated superior efficacy and quality-of-life (QoL) improvements versus subcutaneous interferon beta-1a, with manageable safety. Here, QoL outcomes are examined in alemtuzumab-treated patients at Year 3 in an ongoing extension study (NCT00930553). 393 of 435 alemtuzumab 12 mg-treated patients entered the extension study; 80 received as-needed alemtuzumab retreatment during Year 3. Mean Functional Assessment of multiple sclerosis total score (scale 0–176) improved from baseline to year 3 (119.1 vs 124.8; P<0.0001), with 5 of 6 subscales significantly improved. Mean Short-Form 36–Item survey physical and mental component summary scores (scale 1–100) rose from baseline to Year 3 (42.7 vs 44.7; P<0.0001, and 44.9 vs 46.5; P=0.042, respectively), with 6 of 8 subscales improved, and 82% and 73% of patients, respectively, having a stable or improved score at Year 3. EuroQol 5–dimensional visual analogue scale score improved from baseline to Year 3 (70.1 vs 73.0; P=0.0045). Overall sustained improvement in physical, mental, and emotional aspects of QoL were observed through 3 years in this population of alemtuzumab-treated RRMS patients, even though most patients received only 2 alemtuzumab treatment courses.
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Sigle, Steffen, Nadja Steblau, Wolfgang Wohlleben, and Günther Muth. "Polydiglycosylphosphate Transferase PdtA (SCO2578) of Streptomyces coelicolor A3(2) Is Crucial for Proper Sporulation and Apical Tip Extension under Stress Conditions." Applied and Environmental Microbiology 82, no. 18 (July 15, 2016): 5661–72. http://dx.doi.org/10.1128/aem.01425-16.
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ABSTRACTAlthough anionic glycopolymers are crucial components of the Gram-positive cell envelope, the relevance of anionic glycopolymers for vegetative growth and morphological differentiation ofStreptomyces coelicolorA3(2) is unknown. Here, we show that the LytR-CpsA-Psr (LCP) protein PdtA (SCO2578), a TagV-like glycopolymer transferase, has a dual function in theS. coelicolorA3(2) life cycle. Despite the presence of 10 additional LCP homologs, PdtA is crucial for proper sporulation. The integrity of the spore envelope was severely affected in apdtAdeletion mutant, resulting in 34% nonviable spores.pdtAdeletion caused a significant reduction in the polydiglycosylphosphate content of the spore envelope. Beyond that, apical tip extension and normal branching of vegetative mycelium were severely impaired on high-salt medium. This growth defect coincided with the mislocalization of peptidoglycan synthesis. Thus, PdtA itself or the polydiglycosylphosphate attached to the peptidoglycan by the glycopolymer transferase PdtA also has a crucial function in apical tip extension of vegetative hyphae under stress conditions.IMPORTANCEAnionic glycopolymers are underappreciated components of the Gram-positive cell envelope. They provide rigidity to the cell wall and position extracellular enzymes involved in peptidoglycan remodeling. AlthoughStreptomyces coelicolorA3(2), the model organism for bacterial antibiotic production, is known to produce two distinct cell wall-linked glycopolymers, teichulosonic acid and polydiglycosylphosphate, the role of these glycopolymers in theS. coelicolorA3(2) life cycle has not been addressed so far. This study reveals a crucial function of the anionic glycopolymer polydiglycosylphosphate for the growth and morphological differentiation ofS. coelicolorA3(2). Polydiglycosylphosphate is attached to the spore wall by the LytR-CpsA-Psr protein PdtA (SCO2578), a component of theStreptomycesspore wall-synthesizing complex (SSSC), to ensure the integrity of the spore envelope. Surprisingly, PdtA also has a crucial role in vegetative growth under stress conditions and is required for proper peptidoglycan incorporation during apical tip extension.
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Migranova, L., and M. Toksanbaeva. "Human Potential of the Population of Russian Regions: the Level and Dynamics of Development (Part Two)." Living Standards of the Population in the Regions of Russia 14, no. 3 (October 8, 2018): 59–72. http://dx.doi.org/10.19181/1999-9836-2018-10029.
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The Object of the Study. Human potential.The Subject of the Study. The level and dynamics of development of the human potential of the population of the RF subjects. The Purpose of the Study. Identifying differences in development of the human potential of the population of the RF subjects and opportunities for their reduction.The Main Provisions of the Article. Human potential and its development are considered article both as the purpose and the means of human progress reflecting extension of human opportunities including creative (resource) capabilities. Theoretical and instrumental interpretation of the main components of human potential based on its reproductive structure is analysed. The components include a demographic component, components of population health and education, and a sociocultural component. For estimation of human potential indicators for each of its component, as well as a methodology for both component-by-component and composite (aggregate of all components) calculations using the index method are proposed. The methodology is applied to all RF subjects using the Rosstat data for 2010 and 2015. On the basis of the obtained estimates the authors have identified the levels of human potential development in regions that enabling to range them by this level and analyze the direction of its changes in dynamics. Components have been found out a weak and strong impact on the composite estimates as well as specifics of this impact by groups of regions. It has been established that demographic and health components leave much to be desired, particularly in northern regions characterized by harsh natural climatic conditions of life in particular.In North Caucasus regions the problem of raising educational level of population has not lost its relevance. It is shown that despite the general growth in the level of human potential development in most subjects of the Russian Federation over the period in question it remains insufficient for implementing modernization processes in some regions.
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Salmas, Constantinos, Aris Giannakas, Petros Katapodis, Areti Leontiou, Dimitrios Moschovas, and Andreas Karydis-Messinis. "Development of ZnO/Na-Montmorillonite Hybrid Nanostructures Used for PVOH/ZnO/Na-Montmorillonite Active Packaging Films Preparation via a Melt-Extrusion Process." Nanomaterials 10, no. 6 (May 31, 2020): 1079. http://dx.doi.org/10.3390/nano10061079.
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Nowadays, the shelf-life extension of foods is a topic of major interest because of its environmental and economic benefits. For this purpose, various methods like deep-freezing, ultra-high-temperature pasteurization, drying methods, use of chemicals, controlled-atmosphere preservation, ionizing irradiation, and were investigated. During the last years, the smart packaging for foods using natural biodegradable components is of great interest because it provides positive environmental fingerprint and high shelf-life extension. In the present work, a new nanostructured composite material, the ZnO/Na-Montmorillonite hybrid, was developed. The high antimicrobial properties of the 3-D ZnO material in combination with the high barrier and strength properties of the 2-D Na-Montmorillonite material provided a high promising component for food smart packaging applications. As an extra innovation of this process, the ZnO nanorods coated the external surface of the Na-Montmorillonite and it was not intercalated into the clay as a pillaring material. This new material was incorporated with a 3% w/w composition with a biodegradable poly(vinyl)alcohol (PVOH) polymeric matrix which also exhibits antimicrobial activity. The final product was tested via XRD, FTIR, SEM, tensile test, water sorption, water vapor permeability, oxygen permeability UV–vis, and anti-microbial activity tests and it exhibited advanced mechanical and antimicrobial properties, especially for a ZnO/Na-Montmorillonite fraction of 4:1.
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Lucke, Ulrike, and Raphael Zender. "3D Interactions between Virtual Worlds and Real Life in an E-Learning Community." Advances in Human-Computer Interaction 2011 (2011): 1–11. http://dx.doi.org/10.1155/2011/684202.
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Virtual worlds became an appealing and fascinating component of today's internet. In particular, the number of educational providers that see a potential for E-Learning in such new platforms increases. Unfortunately, most of the environments and processes implemented up to now do not exceed a virtual modelling of real-world scenarios. In particular, this paper shows that Second Life can be more than just another learning platform. A flexible and bidirectional link between the reality and the virtual world enables synchronous and seamless interaction between users and devices across both worlds. The primary advantages of this interconnection are a spatial extension of face-to-face and online learning scenarios and a closer relationship between virtual learners and the real world.
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Khan, Muhammad Rehan, Stefania Volpe, Marika Valentino, Nicoletta Antonella Miele, Silvana Cavella, and Elena Torrieri. "Active Casein Coatings and Films for Perishable Foods: Structural Properties and Shelf-Life Extension." Coatings 11, no. 8 (July 28, 2021): 899. http://dx.doi.org/10.3390/coatings11080899.
Full textAbstract:
There is an urgent need to increase the food supplies to fulfil the demands of future generations as the population of the world is expected to grow beyond 10 billion by 2050. An essential component for ensuring global food security is to reduce food losses during the post-harvest stage. Active edible coatings and films are a promising sustainable preservation technology for shelf-life extension of food products by hindering decay kinetics of minimally processed fruits and vegetables (F&V), by restricting the mass transfer of moisture, aroma, or gases and carrying an active compound, such as an antioxidant or antimicrobial. Active protein-based coatings and films have the potential to extend the shelf-life of food products by decreasing their respiration rates, as they exhibit an excellent gas barrier and good mechanical properties as compared to other biopolymeric packaging. Among protein-based biopolymers, casein and its derivatives as packaging films have been extensively studied due to their low cost, complete biodegradability, and availability. Currently, there is no review study focusing on caseinate-based active coating and film, thus, this review aims to give insights on the composition, rheology, structure, and properties of caseinate-based formulations by critically discussing the results presented in the literature. A methodological approach was followed to obtain relevant literature to discuss the influence of additives on the shelf-life of F&V. Furthermore, changes in secondary structure of casein were observed after incorporation of bioactive compounds (i.e., phenolic acids). Likewise, there is a need to explore chemical interactions among bioactive compounds and biopolymer material by using in silico and laboratory trials as food additives have shown to influence the physicochemical properties of film and shelf-life of food products.
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Alassaf, Saleh H., Vladimir I. Savander, and Ahmed A. Hassan. "Use of erbium as a burnable absorber for the VVER reactor core life extension." Nuclear Energy and Technology 6, no. 4 (November 20, 2020): 275–79. http://dx.doi.org/10.3897/nucet.6.60563.
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The paper presents the results of a computational and theoretical analysis concerned with the use of erbium as a burnable absorber in VVER-type reactors. Partial refueling options for the reactor life extension to 18 and 24 months is considered, the refueling ratio being equal to three for the 18-month life and to two for the 24-month life. Erbium is expected to be present in all fuel elements in the FA with the same weight content. The influence of the erbium weight content on such neutronic characteristics of the reactor and fuel as burn-up, reactivity coefficients, residual volume of “liquid" control, and amounts of the liquid radioactive waste (LRW) formed was assessed. The calculations were performed using a simplified model of refueling without FA reshuffling. An infinite array of polycells consisting of FAs with different in-core times was considered. The escape of neutrons from the core was taken into account by selecting the critical value K∞ at the end of life. Erbium does not burn up in full for the lifetime which affects the fuel burn-up as compared with the liquid excessive reactivity compensation system. The reduction is 0.7% per 0.1% of the erbium weight load in the fuel elements. This, however, also reduces the maximum content of the boron absorber in the coolant and the LRW accumulation in the ratio of 5% per 0.1% of the erbium weight load. Erbium influences the spectral component of the coolant temperature reactivity coefficient which turns out to be negative even with its minor weight fraction in fuel elements, and a reduction in the boron absorber fraction leads to a positive value of the density reactivity coefficient. As a result, the overall coolant temperature reactivity coefficient has a negative value throughout the lifetime.
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Abdi, F., Y. Xue, M. Garg, B. Farahmand, J. Housner, and K. Nikbin. "An analysis approach toward FAA certification for damage tolerance of aircraft components." Aeronautical Journal 118, no. 1200 (February 2014): 181–96. http://dx.doi.org/10.1017/s0001924000009064.
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Abstract This paper presents a novel analysis approach by considering multiple crack interaction in achieving FAA certification for durability and damage tolerance of exterior attachment installations on an aircraft fuselage according to FAA policy on Certification by Analysis-Supported-by-Test (CAST). Durability and damage tolerance evaluation of an aircraft component requires assessment of damage initiation and fatigue crack propagations under service loading, which consists of complex loading types, paths and variable amplitudes. Both simulation and service experience showed that multiple cracks developed in the fuselage skin and doublers that are made of wrought aluminum alloys. Progressive failure analysis (PFA) tool was used to simulate the fatigue damage initiation life using a scale-down stress-life property. A virtual crack closure technique (VCCT) was implemented to evaluate fatigue crack growth with interactions between cracks from different parts in a component, which preserves conservativeness. The fatigue crack growth data is obtained uniquely from an analytical extension of fatigue crack growth data of thin aluminum sheet. Fatigue crack growth analysis showed that only a few initiated cracks propagated steadily before a crack became visible under inspection, which was validated by comparison to service history. Eventually one crack became dominate in the fracturing process thereby setting an inspection time. Analysis also showed that fatigue damage state in the components at the designed operational life will not exceed the static safety requirements. Therefore, FAA accepted the damage tolerance analysis and the aircraft retained certification with no need for repair.
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CHANG, SUNGHO, GEEWOOK SONG, BUMSHIN KIM, JUNGSEB HYUN, and JEONGSOO HA. "THE LIFE ASSESSMENT OF STEAM TURBINE ROTORS FOR FOSSIL POWER PLANTS." International Journal of Modern Physics B 20, no. 25n27 (October 30, 2006): 4371–76. http://dx.doi.org/10.1142/s0217979206041379.
Full textAbstract:
The operational mode of thermal power plants has been changed from base load to duty cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient states, for example, start up and stop, which results in thermal fatigue damage at the heavy section components. The rotor is the highest capital cost component in a steam turbine and requires long outage for replacing with a new one. For an optimized power plant operational life, inspection management of the rotor is necessary. It is known in general that the start-up and shutdown operations greatly affect the steam turbine life. The start-up operational condition is especially severe because of the rapid temperature and rotational speed increase, which causes damage and reduction of life of the main components life of the steam turbine. The start-up stress of a rotor which is directly related to life is composed of thermal and rotational stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is due to the rotational speed of the turbine. In this paper, the analysis method for the start-up stress of a rotor is proposed, which considers simultaneously temperature and rotational speed transition, and includes a case study regarding a 500MW fossil power plant steam turbine rotor. Also, the method of quantitative damage estimation for fatigue-creep damage to operational conditions, is described. The method can be applied to find weak points for fatigue-creep damage. Using the method, total life consumption can be obtained, and can be also be used for determining future operational modes and life extension of old fossil power units.
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Nimmegeers, Philippe, Alexej Parchomenko, Paul De Meulenaere, Dagmar R. D’hooge, Paul H. M. Van Steenberge, Helmut Rechberger, and Pieter Billen. "Extending Multilevel Statistical Entropy Analysis towards Plastic Recyclability Prediction." Sustainability 13, no. 6 (March 23, 2021): 3553. http://dx.doi.org/10.3390/su13063553.
Full textAbstract:
Multilevel statistical entropy analysis (SEA) is a method that has been recently proposed to evaluate circular economy strategies on the material, component and product levels to identify critical stages of resource and functionality losses. However, the comparison of technological alternatives may be difficult, and equal entropies do not necessarily correspond with equal recyclability. A coupling with energy consumption aspects is strongly recommended but largely lacking. The aim of this paper is to improve the multilevel SEA method to reliably assess the recyclability of plastics. Therefore, the multilevel SEA method is first applied to a conceptual case study of a fictitious bag filled with plastics, and the possibilities and limitations of the method are highlighted. Subsequently, it is proposed to extend the method with the computation of the relative decomposition energies of components and products. Finally, two recyclability metrics are proposed. A plastic waste collection bag filled with plastic bottles is used as a case study to illustrate the potential of the developed extended multilevel SEA method. The proposed extension allows us to estimate the recyclability of plastics. In future work, this method will be refined and other potential extensions will be studied together with applications to real-life plastic products and plastic waste streams.
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Goda, Akio, Shin Murata, Hideki Nakano, Kayoko Shiraiwa, Teppei Abiko, Koji Nonaka, Hiroaki Iwase, Kunihiko Anami, and Jun Horie. "Subjective and Objective Mental and Physical Functions Affect Subjective Cognitive Decline in Community-Dwelling Elderly Japanese People." Healthcare 8, no. 3 (September 18, 2020): 347. http://dx.doi.org/10.3390/healthcare8030347.
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Subjective cognitive decline (SCD) is complex and not well understood, especially among Japanese people. In the present study, we aimed to elucidate the relationships of subjective and objective mental and physical function with SCD among older community-dwelling Japanese adults. SCD was evaluated using the Kihon Checklist: Cognitive Function. Other parameters were evaluated using the Mini-Mental State Examination (MMSE) and the five-item version of the Geriatric Depression Scale (GDS-5), for an objective mental function other than SCD. A timed up-and-go test (TUG) and knee extension strength were used to test objective physical function, and the Mental Component Summary (MCS) and Physical Component Summary (PCS) in the Health-Related Quality of Life survey eight-item short form (SF-8) were used for subjective mental and physical functions. The results of the MMSE, GDS-5, TUG, knee extension strength, and MCS were significantly worse in the SCD group. In addition, logistic regression analysis showed that GDS-5 and MCS were associated with SCD onset. Depressive symptoms and decreased subjective mental function contribute to SCD among community-dwelling Japanese adults. These findings will be useful for planning dementia prevention and intervention programs for older Japanese adults.
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Chong, Megan K., Elizabeth R. Cebul, Karolina Mizeracka, and Maxwell G. Heiman. "Loss of the Extracellular Matrix Protein DIG-1 Causes Glial Fragmentation, Dendrite Breakage, and Dendrite Extension Defects." Journal of Developmental Biology 9, no. 4 (October 7, 2021): 42. http://dx.doi.org/10.3390/jdb9040042.
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The extracellular matrix (ECM) guides and constrains the shape of the nervous system. In C. elegans, DIG-1 is a giant ECM component that is required for fasciculation of sensory dendrites during development and for maintenance of axon positions throughout life. We identified four novel alleles of dig-1 in three independent screens for mutants affecting disparate aspects of neuronal and glial morphogenesis. First, we find that disruption of DIG-1 causes fragmentation of the amphid sheath glial cell in larvae and young adults. Second, it causes severing of the BAG sensory dendrite from its terminus at the nose tip, apparently due to breakage of the dendrite as animals reach adulthood. Third, it causes embryonic defects in dendrite fasciculation in inner labial (IL2) sensory neurons, as previously reported, as well as rare defects in IL2 dendrite extension that are enhanced by loss of the apical ECM component DYF-7, suggesting that apical and basolateral ECM contribute separately to dendrite extension. Our results highlight novel roles for DIG-1 in maintaining the cellular integrity of neurons and glia, possibly by creating a barrier between structures in the nervous system.
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Zhang, Hui, and Asok Ray. "Robust Damage-Mitigating Control of Mechanical Systems: Experimental Validation on a Test Apparatus." Journal of Dynamic Systems, Measurement, and Control 121, no. 3 (September 1, 1999): 377–85. http://dx.doi.org/10.1115/1.2802485.
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The goal of damage-mitigating control is to achieve high performance of operating machinery without overstraining the mechanical structures and the potential benefit is an increase in the component service life with no significant loss of performance. This paper presents the design of a test apparatus, the synthesis of a damage-mitigating control system, and the results of experimentation where the objective is to demonstrate the concept of fatigue damage reduction as an extension of multivariable robust feedback control. The test apparatus is built upon a three-degree-of-freedom, two-input three-output mechanical structure. The methodology of the damage-mitigating control synthesis is built upon the principles of: (i) frequency-domain identification of the plant dynamics and modeling of uncertainties in the state-space setting; and (ii) robust control based on the H∞ approach by taking both plant dynamic performance and material degradation of structural components into consideration. Case studies on the test apparatus indicate that fatigue life of specimens can be substantially extended with no appreciable degradation in the dynamic performance of the mechanical system.
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Marques, Ana C., Helena Dias, Sandro Matos, Bruno Sargaço, Ricardo Simoes, Aster De Schrijver, and João C. Bordado. "Polyurethane one-component foam formulation optimization for low free isocianate monomer content." Journal of Cellular Plastics 53, no. 2 (July 28, 2016): 167–79. http://dx.doi.org/10.1177/0021955x16639230.
Full textAbstract:
Recent changes in legislation have forced one-component foam producers to drop the amount of free monomeric isocyanate in their polyurethane systems. Also, it is required that commercial polyurethane aerosol cans exhibit at least one year of shelf life and polyurethane foams must be classified as B2 on the fire testing following DIN 4102. This paper reports on a systematic optimization study of polyurethane formulations dedicated to address these current industry requirements. A one-component foam system exhibiting simultaneously all of these parameters was achieved by reacting conventional diols, a relatively low-molecular weight monol (2-ethylhexanol), a flame retardant high-molecular weight monol (tris(bromoneopentyl)alcohol), a methylene diphenyl diisocyanate-based prepolymer (GreenAdduct 13), and a small amount of 2,4′-toluene diisocyanate. The use of monols allows producing prepolymers with low free methylene diphenyl diisocyanate by preventing chain extension and, therefore, avoiding extreme viscosity build-up. Toluene diisocyanate also promotes a lower viscosity inside the aerosol can, which enables the use of high enough quantities of high-molecular weight flame retardant monol to achieve a B2 fire test classification.
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Lichtenstein, Eric, Mareike Morat, Ralf Roth, Lars Donath, and Oliver Faude. "Agility-based exercise training compared to traditional strength and balance training in older adults: a pilot randomized trial." PeerJ 8 (April 14, 2020): e8781. http://dx.doi.org/10.7717/peerj.8781.
Full textAbstract:
Background In addition to generally high levels of physical activity, multi-component exercise training is recommended for the maintenance of health and fitness in older adults, including the prevention of falls and frailty. This training often encompasses serial sequencing of balance, strength, endurance and other types of exercise. Exercise training featuring integrative training of these components (i.e. agility training) has been proposed, as it more likely reflects real life challenges like stop-and-go patterns, cutting manoeuvers, turns and decision-making. In this study, we compared the efficacy of an agility-based training to the traditional strength and balance training approach with regard to selected risk factors for falls and frailty. Methods We trained twenty-seven community-dwelling healthy seniors (16♂; 11♀; age: 69.5 ± 5.3 y; BMI: 26.4 ± 3.7 kg/m2) for 8 weeks in a group setting with 3 sessions per week, each lasting 50 minutes. Participants were randomized into either the agility group (AGI; n = 12), that used the integrative multi-component training, or the traditional strength and balance group (TSB; n = 15). TSB performed balance and strength exercises separately, albeit within the same session. The training of both groups progressively increased in difficulty. Outcomes were static and dynamic balance (single leg eyes open stand, Y-balance test, reactive balance), lower limb (plantar flexion and dorsal extension) and trunk flexion and extension maximum strength and rate of torque development (RTD). In addition, we tested endurance by the six-minute walk test (6MWT). We calculated linear mixed effects models for between-groups comparisons as well as effect sizes (ES) with 95 % confidence intervals. Results Small ES in favor of AGI were found for plantar flexion strength (ES > 0.18[−0.27;0.89]) and RTD (ES > 0.43[−0.19;1.36]) as well as trunk extension RTD (ES = 0.35[−0.05;0.75]). No other parameters showed notable between group differences. Compliance was high in both groups (AGI: 90 ± 8% of sessions; TSB: 91 ± 7% of sessions). Discussion Agility-based exercise training seems at least as efficacious as traditional strength and balance training in affecting selected physical performance indicators among community-dwelling healthy seniors. In particular, lower limb and trunk extension explosive strength seem to benefit from the agility training.