Academic literature on the topic 'Quasi static cycle'
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Journal articles on the topic "Quasi static cycle"
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Luo, Yun Rong, Tao Zeng, and Lei Fu. "Investigation on the Influence of Fatigue Damage on the Mechanics Property of Anti-Seismic Steel HRB400E Reinforcing Steel Bars." Applied Mechanics and Materials 368-370 (August 2013): 1678–82. http://dx.doi.org/10.4028/www.scientific.net/amm.368-370.1678.
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Low cycle fatigue (LCF) experiments on anti-seismic steel HRB400E reinforcing steel bars under constant total strain (0.6%) control were conducted on a MTS 809 servo-hydraulic material testing machine. The specimens were then subjected to quasi-static tension until they ruptures on the machine. The mechanical properties such as cyclic stress-strain behaviour, quasi-static strength, and quasi-static ductility of the material at various levels of fatigue damage were investigated .The test results indicate that when compared to its virgin state, in a certain cycles (about 80% fatigue life) the cycle-dependent behaviors of the material can cause a slight change in the strength and ductility, and the ductility of the steel has an opposite trend to the strength. However, a significant decrease occurs to both the strength and the ductility as the cyclic cycles exceeds about 80% fatigue life.
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Roberts, T. M., T. G. Hughes, V. R. Dandamudi, and B. Bell. "Quasi-static and high cycle fatigue strength of brick masonry." Construction and Building Materials 20, no. 9 (2006): 603–14. http://dx.doi.org/10.1016/j.conbuildmat.2005.02.013.
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Lustig, Sahar, and David Elata. "Ambiguous definitions of the piezoelectric coupling factor." Journal of Intelligent Material Systems and Structures 31, no. 14 (2020): 1689–96. http://dx.doi.org/10.1177/1045389x20930104.
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When a piezoelectric material is subjected to a quasi-static electric (or mechanical) load, part of the input energy is converted to the mechanical (or electric) domain. The piezoelectric coupling factor k2 is defined as the ratio between the converted energy and the supplied energy. This factor is often considered as a measure of the transduction efficiency of the material. Another definition of the coupling factor is a non-dimensional ratio of material coefficients. To examine the compatibility between these two different definitions, we consider several quasi-static loading cycles of a simple one-dimensional problem. We show that in some specific cases, the two definitions are equivalent, but that in other cases they are incompatible. In addition, we show that in specific quasi-static loading cycles, the converted energy may be increased by a slight modification of the unloading part of the cycle.
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Voigt, Gerd-Hannes. "Quasi-static MHD processes in Earth's magnetosphere." Laser and Particle Beams 6, no. 3 (1988): 525–37. http://dx.doi.org/10.1017/s0263034600005449.
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The purpose of this paper is to demonstrate how the MHD equilibrium theory can be used to describe the global magnetic field configuration of Earth's magnetosphere and its time evolution under the influence of magnetospheric convection. The MHD equilibrium theory represents magneto-hydrodynamics in the slow-flow approximation. In this approximation time scales are long compared to typical Alfvén wave travel times, and plasma flow velocities are small compared to the Alfvén speed. Under those conditions, the inertial term ρ(dv/dt) in the MHD equation of motion is a small second order term which can be neglected. The MHD equilibrium theory is not a static theory, though, because time derivatives and flow velocities remain first order quantities in the continuity equation, in the thermodynamic equation of state, and in the induction equation. Therefore one can compute slowly time-dependent processes, such as magnetospheric convection, in terms of series of static equilibrium states. However, those series are not arbitrary; they are constrained by thermodynamic conditions according to which the magnetosphere evolves in time.It is an interesting question, whether or not the magnetosphere, driven by slow, lossless, adiabatic, earthward convection of magnetotail flux tubes, can reach a steady state. There exist magnetospheric equilibria in which magnetotail flux tubes satisfy the steady-state condition d/dt (Pρ−γ) = 0. Those configurations exhibit a deep magnetic field minimum in the equatorial plane, near the inner edge of the tail plasma sheet. The magnetosphere becomes tearing-mode unstable in the neighborhood of such a minimum, thus leading to periodic onsets of substorms in the inner plasma sheet. This explains why distinct magnetic field minima have not been observed in this region. Magnetic substorms seem to be an inevitable element of the global convection cycle which inhibit the establishment of an ultimate steady state.MHD equilibria discussed in this paper result from linear and non-linear solutions to the two-dimensional Grad-Shafranov equation for isotropic thermal plasma pressure.
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Tremblay, R., P. Bolduc, R. Neville, and R. DeVall. "Seismic testing and performance of buckling-restrained bracing systems." Canadian Journal of Civil Engineering 33, no. 2 (2006): 183–98. http://dx.doi.org/10.1139/l05-103.
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This paper describes a subassemblage seismic test program performed on six buckling-restrained braces (BRBs). Two different brace core segment lengths and two different buckling-restraining mechanisms were examined. The applied loading histories included a qualifying quasi-static cyclic test with stepwise incremental displacement amplitudes and a dynamically applied seismic loading. A test was also carried out on a conventional bracing member for comparison purposes. The concrete-filled tube specimens exhibited satisfactory performance under the quasi-static loading protocol, regardless of the length of the core segment. Strain hardening and frictional responses resulted in brace axial forces significantly exceeding the core yield capacity. The steel BRB system exhibited good performance under the quasi-static and dynamic loading sequences, provided that the clearance between the brace core and the buckling-restrained mechanism was kept to a minimum. The dynamic loading protocol was less severe for low-cycle fatigue than the quasi-static loading, but higher strain rates resulted in amplified yield resistance. The conventional bracing member withstood the entire quasi-static loading history but exhibited limited energy-dissipation capacity compared with the concrete-filled BRBs.Key words: concentrically braced steel frames, bracing members, buckling, energy dissipation, friction, yielding, fracture, seismic.
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Yang, Ke, Bo Wang, Jiawei Zhang, Zhe Li, and Boquan Liu. "Study on Quasi-Static Loading Protocols considering the Action Characteristics of Long-Period Ground Motions." Mathematical Problems in Engineering 2021 (February 5, 2021): 1–13. http://dx.doi.org/10.1155/2021/8863335.
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Due to abundant low-frequency components of long-period ground motions (LPGMs), long-period structures are susceptible to severe damage. The corresponding time-history displacement responses have significant “large-displacement” and “long-duration” characteristics. These action characteristics essentially reflect the different loading paths imposed on structures of LPGMs from ordinary ground motions (OGMs). Hence, revealing the influence mechanism of the action characteristics on the seismic performance of structural components is the key to investigating the influence of LPGMs on the whole structure. This paper presents a kind of quasi-static loading protocol considering the action characteristics of LPGMs. Firstly, nonlinear time-history analyses on structural systems subjected to 50 selected representative LPGMs were conducted. Inelastic cycles and corresponding amplitudes of time-history displacement responses under LPGMs were statistically analyzed through the rainflow method. Then, considering two of the most significant factors, structural period and target ductility, a prediction model of cycle number and cycle amplitude was obtained by regression. On this basis, the quasi-static loading protocol considering the action characteristics of LPGMs was developed. Proposed protocols can be directly applied to experimental investigations on the seismic performance for structural components under LPGMs.
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Luo, Bin, Benchun Duan, and Dunyu Liu. "3D Finite-Element Modeling of Dynamic Rupture and Aseismic Slip over Earthquake Cycles on Geometrically Complex Faults." Bulletin of the Seismological Society of America 110, no. 6 (2020): 2619–37. http://dx.doi.org/10.1785/0120200047.
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ABSTRACT We develop a new dynamic earthquake simulator to numerically simulate both spontaneous rupture and aseismic slip over earthquake cycles on geometrically complex fault systems governed by rate- and state-dependent friction. The method is based on the dynamic finite-element method (FEM) EQdyna, which is directly used in the simulator for modeling 3D spontaneous rupture. We apply an adaptive dynamic relaxation technique and a variable time stepping scheme to EQdyna to model the quasi-static processes of an earthquake cycle, including the postseismic, interseismic, and nucleation processes. Therefore, the dynamic and quasi-static processes of an earthquake cycle are modeled in one FEM framework. Tests on a vertical strike-slip fault verify the correctness of the dynamic simulator. We apply the simulator to thrust faults with various dipping angles, which can be considered as the simplest case of geometrically complex faults by breaking symmetry, compared with vertical faults, to examine effects of dipping fault geometry on earthquake cycle behaviors. We find that shallower dipping thrust faults produce larger seismic slip and longer recurrence time over earthquake cycles with the same rupture area. In addition, we find an empirically linear scaling relation between the recurrence interval (and the seismic moment) and the sinusoidal function of the dip angle. The dip-angle dependence is likely due to the free-surface effect, because of broken symmetry. These results suggest dynamic earthquake simulators that can handle nonvertical dipping fault geometry are needed for subduction-zone earthquake studies.
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Yeates, A. R., J. A. Constable, and P. C. H. Martens. "Solar Cycle Variation of Magnetic Flux Ropes in a Quasi-Static Coronal Evolution Model." Solar Physics 263, no. 1-2 (2010): 121–34. http://dx.doi.org/10.1007/s11207-010-9546-z.
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Daunys, Mykolas, Donata Putnaitė, and Žilvinas Bazaras. "PRINCIPLES FOR MODELLING TECHNOLOGICAL PROCESSES INVESTIGATION INTO THE STRENGTH AND DURABILITY OF AUTOMATIC COUPLER SA‐3 IN RAILWAY CARRIAGES." TRANSPORT 24, no. 2 (2009): 83–92. http://dx.doi.org/10.3846/1648-4142.2009.24.83-92.
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The paper presents the durability analysis of the automatic coupler in railway carriages. The loading of the automatic coupler predetermined by the weight of a train, train speed and railway relief is a time‐dependent variable. The finite element method was used for stress‐strain state calculation taking into account acting forces. In order to reduce stress concentration, the geometry of the automatic coupler's body was modified. Modelling results for different rounded radii demonstrated it was possible to reduce stress concentration up to 34%. Under maximum forces, plastic strain occurs in the automatic coupler's body. The calculation of strain and stress state in the body of the automatic coupler shows it is under a static, low and high cycle loading. Therefore, to calculate the durability of the automatic coupler, the dependencies for low cycle nonstationary stress limited loading has been proposed evaluating low cycle quasistatic and fatigue damages. In order to evaluate high cycle fatigue damage, a linear law for the summation of loading cycles has been suggested. For low cycle damage evaluation, the calculation method for the summation of fatigue and quasi‐static damages created at one loading cycle taking into account loading level and neglecting the sequence of cycles has been put forward. Thus, to calculate the automatic coupler for each specific case, it is necessary to determine the number of loading cycles at each loading level and to evaluate durability considering dependencies presented in this paper.
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Asran, Ahmed G., Hassan H. EL-Esnawi, and Sabry Elmorsy Fayed. "Experimental Investigation of RC Exterior Beam Column Connection with Eccentric Beam Subjected to Reversible Quasi Static Loads." Civil Engineering Journal 3, no. 4 (2017): 221–36. http://dx.doi.org/10.28991/cej-2017-00000088.
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Insufficiency of the Beam Column Joint (BCJ) caused structures failures particularly in case of the earthquakes. In most of the buildings, the beam center line was not aligned with the column center line. So, the effect of the eccentricity of the beam was studied in this article. Behaviour of reinforced concrete (RC) eccentric beam-column joint under reversible cyclic loading was investigated experimentally. The experimental program is one specimen. The specimen consisted of column and beam. The column divided into symmetry two parts (upper and lower parts). The beam fixed in middle of the column and it was free end. The main parameter was the effect of the eccentricity of the beam center line about the column center on behaviour of RC BCJ. The specimen was tested under reversible ten cycles. The horizontal displacement for the column and the vertical deflection at free end of the beam were recorded at each cycle. The crack pattern of the tested specimen was studied at every cycle in details. It was noticed that the eccentricity of the beam has concentrated more stresses on the joint side close to the eccentricity. The failure took place at the joint due to its weakness.
Dissertations / Theses on the topic "Quasi static cycle"
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Vasudevan, Satish. "AN INVESTIGATION OF QUASI-STATIC BEHAVIOR, HIGH CYCLE FATIGUE AND FINAL FRACTURE BEHAVIOR OFALUMINUM ALLOY 2024 AND ALUMINUM ALLOY 2219." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1193668130.
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Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2007.<br>"December, 2007." Title from electronic thesis title page (viewed 02/23/2008) Advisor, T. S. Srivatsan; Faculty readers, Craig Menzemer, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Kuruvilla, Mithun. "An understanding of the quasi-static behavior, high cycle fatigue and final fracture behavior of a titanium (Ti-4 Al-2.5 V-1.5 Fe-0.25 O₂) alloy." Akron, OH : University of Akron, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1217436482.
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Thesis (M.S.)--University of Akron, Dept. of Mechanical Engineering, 2008.<br>"August, 2008." Title from electronic thesis title page (viewed 01/13/2010) Advisor, T. S. Srivatsan; Faculty Readers, C. Menzemer, Anil Patnaik, Amit Prakash; Department Chair, Celal Batur; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Kuruvilla, Mithun. "An Understanding of the Quasi-static Behavior, High Cycle Fatigue and Final Fracture Behavior of a Titanium (Ti- 4 Al-2.5 V-1.5 Fe-0.25 O2) Alloy." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1217436482.
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Hoang, Minh Tam. "Frottement saccadé dans les matériaux granulaire modèles." Phd thesis, INSA de Lyon, 2011. http://tel.archives-ouvertes.fr/tel-00743550.
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Cette étude a pour objectifs la caractérisation expérimentale des frottements saccadés dans les matériaux granulaires modèles constitués des billes de verre monodisperses en compression triaxiale drainée et l'identification des paramètres de contrôle. Cinq paramètres macroscopiques caractérisent ces frottements saccadés : la chute de déviateur et la contraction volumique, l'intermittence de déformation axiale, le module d'Young et le coefficient de Poisson. Les frottements saccadés affectent simultanément le déviateur et la déformation volumique. Le comportement macroscopique est globalement contractant tandis que le matériau tend vers un état limite critique en grandes déformations, à la manière des sables lâches. Cependant il présente localement, dans les phases de blocage qui suivent immédiatement les ruptures temporaires, le comportement dilatant des sables denses, qui obéit à une relation contrainte-dilatance linéaire et unique. Les frottements saccadés disparaissent au-delà d'une vitesse critique d'écrasement axial, qui dépend de la contrainte de confinement et de la taille des grains. Le module d'Young dynamique par propagation d'ondes varie avec la contrainte de confinement selon une loi de puissance. Le module d'Young quasi-élastique au départ des phases de blocage est constant à l'intérieur du domaine élastique, de même que le coefficient de Poisson. Le suivi par granulométrie laser et par analyse d'images des matériaux après un ou plusieurs essais triaxiaux permet de suivre l'évolution de la taille moyenne et de la forme des grains. Tandis que les instabilités par saccade disparaissent suite à un certain nombre d'essais, on observe, simultanément à une légère diminution du volume moyen, l'apparition progressive de populations d'objets non sphériques par une fusion des grains analogue au frittage.
Book chapters on the topic "Quasi static cycle"
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Agata, Ryoichiro, Takane Hori, Sylvain D. Barbot, Mamoru Hyodo, and Tsuyoshi Ichimura. "Quasi-static Simulation Method of Earthquake Cycles Based on Viscoelastic Finite Element Modeling." In Mathematics for Industry. Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-6062-0_11.
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Barfusz, Oliver, Felix Hötte, Stefanie Reese, and Matthias Haupt. "Pseudo-transient 3D Conjugate Heat Transfer Simulation and Lifetime Prediction of a Rocket Combustion Chamber." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design. Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_17.
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Abstract Rocket engine nozzle structures typically fail after a few engine cycles due to the extreme thermomechanical loading near the nozzle throat. In order to obtain an accurate lifetime prediction and to increase the lifetime, a detailed understanding of the thermomechanical behavior and the acting loads is indispensable. The first part is devoted to a thermally coupled simulation (conjugate heat transfer) of a fatigue experiment. The simulation contains a thermal FEM model of the fatigue specimen structure, RANS simulations of nine cooling channel flows and a Flamelet-based RANS simulation of the hot gas flow. A pseudo-transient, implicit Dirichlet–Neumann scheme is utilized for the partitioned coupling. A comparison with the experiment shows a good agreement between the nodal temperatures and their corresponding thermocouple measurements. The second part consists of the lifetime prediction of the fatigue experiment utilizing a sequentially coupled thermomechanical analysis scheme. First, a transient thermal analysis is carried out to obtain the temperature field within the fatigue specimen. Afterwards, the computed temperature serves as input for a series of quasi-static mechanical analyses, in which a viscoplastic damage model is utilized. The evolution and progression of the damage variable within the regions of interest are thoroughly discussed. A comparison between simulation and experiment shows that the results are in good agreement. The crucial failure mode (doghouse effect) is captured very well.
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"Quasi-static tests on concrete encased composite columns." In Advances in Bridge Maintenance, Safety Management, and Life-Cycle Performance, Set of Book & CD-ROM. CRC Press, 2015. http://dx.doi.org/10.1201/b18175-353.
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Li, Q., Y. Wu, and Q. Wu. "Influence of quasi-static track deformations on the ride comfort of high speed trains." In Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations. CRC Press, 2021. http://dx.doi.org/10.1201/9780429279119-461.
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Swendsen, Robert H. "Thermodynamic Processes." In An Introduction to Statistical Mechanics and Thermodynamics. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198853237.003.0011.
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This chapter begins by defining terms critical to understanding thermodynamics: reversible, irreversible, and quasi-static. Because heat engines are central to thermodynamic principles, they are described in detail, along with their operation as refrigerators and heat pumps. Various expressions of efficiency for such engines lead to alternative expressions of the second law of thermodynamics. A Carnot cycle is discussed in detail as an example of an idealized heat engine with optimum efficiency. A special case, called negative temperatures, where temperatures actually exceed infinity, provides further insights. In this chapter we will discuss thermodynamic processes, which concern the consequences of thermodynamics for things that happen in the real world.
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"Eels at the Edge: Science, Status, and Conservation Concerns." In Eels at the Edge: Science, Status, and Conservation Concerns, edited by Giulio A. De Leo, Paco Melià, Marino Gatto, and Alain J. Crivelli. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781888569964.ch22.
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<em>Abstract.—</em>We critically review population dynamics models developed for <em>Anguilla </em>spp. eels. Despite the (quasi) panmictic nature of temperate eel species, most modeling effort has focused on subpopulations within specific brackish or inland water bodies. Models have been developed along three major lines: cohort approaches, input-output models that directly relate juvenile recruit abundance to migrating mature eels, and stage- or size-structured population models, or both, some of which explicitly account for the observed variability of eel life traits. More recently, attempts have been made to extend demographic analyses to the oceanic phase of the eel life cycle. We discuss eel population models in terms of mathematical complexity and usability, amount and quality of data required for calibration, realism in the description of life cycle and demographic parameters, potential for analyzing different fisheries management strategies, and inclusion of environmental and interindividual stochasticity and uncertainty in parameter estimation. While site-specific analyses are needed to understand eel life history in the continental phase, the generalized decline of eel recruitment requires a global assessment of metapopulation viability under different hypotheses and scenarios. Given the high number of unknowns and untested hypotheses, we emphasize the need to explicitly model uncertainty in parameter estimation and environmental and interindividual stochasticity (e.g., by using bootstrap techniques and Monte Carlo simulations). There is an urgent need for population models that can be used for conservation-based eel management in broad geographic areas where few data are available.
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McHugh, Maurice J., and Douglas G. Goodin. "Interdecadal-Scale Variability: An Assessment of LTER Climate Data." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0023.
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Interdecadal-scale climate variability must be considered when interpreting climatic trends at local, regional, or global scales. Significant amounts of variance are found at interdecadal timescales in many climate parameters of both “direct” data (e.g., precipitation and sea surface temperatures at specific locations) and “indirect” data through which the climate system operates (e.g., circulation indices such as the Pacific North American index [PNA] or the North Atlantic Oscillation index [NAO]). The aim of this study is to evaluate LTER climate data for evidence of interdecadal-scale variability, which may in turn be associated with interdecadal-scale fluctuations evident in ecological or biophysical data measured throughout the LTER site network. In their conceptualization of climatic variability, Marcus and Brazel (1984) describe four types of interannual climate variations: (1) Periodic variations around a stationary mean are well known to occur at short timescales, such as diurnal temperature changes or the annual cycle, but are difficult to resolve at decadal or longer timescales. (2) Discontinuities generated by sudden changes in the overall state of the climate system can reveal nonstationarity in the mean about which data vary in a periodic or quasi-periodic manner. These sudden alterations can result in periods perhaps characterized by prolonged drought or colder than normal temperatures. (3) The climate system may undergo trends such as periods of slowly increasing or decreasing precipitation or of warming or cooling until some new mean “steady” state is reached. (4) Climate data may exhibit increasing or decreasing variability about a specific mean value or steady state. Interdecadal contributions to climate variability can be described in terms of types 2 and 3 of Marcus and Brazel’s conceptual classification—discontinuities in the mean and trends in the data. Records of the Northern Hemisphere’s average land surface temperature show discontinuities in the mean state of the hemispheric temperature record in conjunction with obvious trends. Conceptually, it is hard to distinguish between these aspects of climate variability. Trends are an essential component of an alteration in the mean state of the temperature series, as they serve as a temporal linkage between the different mean states.
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Goodin, Douglas G., and Philip A. Fay. "Climate Variability in Tallgrass Prairie at Multiple Timescales: Konza Prairie Biological Station." In Climate Variability and Ecosystem Response in Long-Term Ecological Research Sites. Oxford University Press, 2003. http://dx.doi.org/10.1093/oso/9780195150599.003.0038.
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Climate is a fundamental driver of ecosystem structure and function (Prentice et al. 1992). Historically, North American grassland and forest biomes have fluctuated across the landscape in step with century- to millennialscale climate variability (Axelrod 1985; Ritchie 1986). Climate variability of at decadal scale, such as the severe drought of the 1930s in the Central Plains of North America, caused major shifts in grassland plant community composition (Weaver 1954, 1968). However, on a year-to-year basis, climate variability is more likely to affect net primary productivity (NPP; Briggs and Knapp 1995; Knapp et al. 1998; Briggs and Knapp 2001). This is especially true for grasslands, which have recently been shown to display greater variability in net primary production in response to climate variability than forest, desert, or arctic/alpine systems (Knapp and Smith 2001). Although the basic relationships among interannual variability in rainfall, temperature, and grassland NPP have been well studied (Sala et al. 1988; Knapp et al. 1998; Alward et al. 1999), the linkages to major causes of climate variability at quasi-quintennial (~5 years) or interdecadal (~10 year) timescales in the North American continental interior, such as solar activity cycles, the El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the North Pacific Index (NP), are less well understood. In this chapter, we will examine how interannual, quasi-quintennial, and interdecadal variation in annual precipitation and mean annual temperature at a tallgrass prairie site (Konza Prairie Biological Station) may be related to indexes of solar activity, ENSO, NAO, and NP, and in turn how these indexes may be related to aboveground net primary productivity (ANPP). Specifically, we present (1) period-spectrum analyses to characterize the predominant timescales of temperature and precipitation variability at Konza Prairie, (2) correlation analyses of quantitative indexes of the major atmospheric processes with Konza temperature and precipitation records, and (3) the implications of variation in major atmospheric processes for seasonal and interannual patterns of ANPP. The Konza Prairie Biological Station (KNZ), which lies in the Flint Hills (39º05' N, 96º35' W), is a 1.6-million-ha region spanning eastern Kansas from the Nebraska border to northeastern Oklahoma (figure 20.1). This region is the largest remaining tract of unbroken tallgrass prairie in North America (Samson and Knopf 1994) and falls in the more mesic eastern portion of the Central Plains grasslands.
Conference papers on the topic "Quasi static cycle"
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Fernandez, Rajan, and Keith Alexander. "An Experimental Investigation Assessing the Validity of Quasi-Static Calculations for an Oscillating Hydrofoil." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49440.
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Inspired by animals, flapping wing propulsion has been of interest since the early 1900s. Flapping hydrofoil propulsion has been attempted by designers of human powered watercraft because of the novelty and the apparent high theoretical efficiency, but with limited success. The earliest human powered hydrofoil, the Wasserlaufer, was invented by Julius Schuck in 1953. The first really successful human powered hydrofoil, the Trampofoil, was invented by Alexander Sahlin in 1998. While these craft function adequately the design data for flapping hydrofoils is inadequate or not available. This paper describes an experimental program and initial results for the required data. To design a vehicle with a lifting and thrusting oscillating hydrofoil the force that the hydrofoil will exert on the vehicle through its entire oscillating cycle must ideally be known. The force profiles could be estimated via quasi-static calculations based on steady flow lift and drag coefficients, but these often do not cover the full 360 degree range that can be required and there is doubt that the steady flow coefficients properly represent the dynamic situation of an oscillating hydrofoil. Hence a valuable process would be one that could determine dynamic drag and lift coefficient loops as function of the Strouhal number, heaving and pitching profiles. To work toward the collection of this information, experimental data is being recorded in a towing tank with an oscillating NACA4415 hydrofoil over a range of Strouhal numbers and types of oscillating profiles. While there are still some limitations to the experimental equipment preliminary experimental results show the limitations of using quasi-static calculations and go some way to providing the design data for the hydrofoil section tested. We conclude that quasi-static calculations based on the gliding coefficient curve for for an oscillating hydrofoil are only valid for very small Strouhal numbers (St≪0.05). We have shown that as the Strouhal number increases, the error in such calculations increases very rapidly. We also note that the lift coefficient of the hydrofoil has a strong dependence on the angle of attack and is not affected by the gliding stall.
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Schmitz, M. B., and G. Fitzky. "Surge Cycle of Turbochargers: Simulation and Comparison to Experiments." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53036.
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The turbocharger test facility can be operated in two different modes. In the first mode, the turbocharger turbine is driven by an external blower and a combustor. The compressor blows off through the chimney. In the second mode the turbocharger is operated similar to a gas turbine: the turbine drives the turbocharger compressor which pressurizes the combustion chamber. This study is focused on the surge cycle of the turbocharger for both operation modes of the test facility. The turbocharger has to withstand surge for all pressure ratios it is designed for without damaging the test rig. Especially for small compressors large plenum volumes can cause such damages. The dynamical model of the system is developed based on the work done by Greitzer [5], [6] and has been extended to the special requirements of the turbocharger test rig. For the components of the turbocharger a quasi-steady behavior with respect to the time scales of the surge cycle is assumed. Consequently, the experimentally obtained steady state characteristics for both compressor and turbine are applied to the model. In order to describe the compressor behavior for backflow conditions, the compressor map is extended for negative mass flow. The theoretical model is calibrated on experimental data. Thereafter the model is used to predict the surge cycle for different operation conditions. For the two operation modes, the blow-off and the recirculation operation, the time resolved values of static pressure and speed oscillation were recorded and compared to the theoretical predictions.
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Mankame, Nilesh D., and G. K. Ananthasuresh. "A Contact-Aided Compliant Mechanical Cycle-Doubler: Preliminary Analysis and Testing." In ASME 2004 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/detc2004-57541.
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The performance of a contact-aided compliant mechanism that functions as a cycle doubler is studied in this paper via nonlinear finite element simulations. The topology of this mechanism was obtained from a systematic synthesis procedure and is reported elsewhere. Although the design was obtained for a quasi-static specification, the kinematic characteristics of the design suggest its ability to function adequately at low to moderate frequencies. The scalability of the design and its single-piece construction enable fabrication using different materials at various length scales. Therefore, it is possible to choose a scale and material combination that yields the frequency doubling action for various input frequencies. Explicit dynamic nonlinear finite element simulations are used to verify the functionality of the design at two different length scales: macro (device footprint of 289 sq. cm) corresponding to an input frequency of 20 Hz and meso (device footprint of a square of 14.3 sq. cm) corresponding to an input frequency of 1 kHz. Experiments on a macro scale prototype are used to validate the FE simulations for low frequencies.
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Dooris, Andrew, Leigh Potter, and Paul Ares. "Determining Edge of Failure of a Spinal Wear Bearing." In ASME 2011 6th Frontiers in Biomedical Devices Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/biomed2011-66001.
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Mechanical test samples are often characterized using time-varying loads, either through slow monotonic changes in quasi-static testing, or through more rapid cyclic changes in dynamic testing. Spinal implant static and fatigue strengths are typically evaluated using such protocols, including such as standards ASTM F1717, ASTM F2077, and ASTM F2346. In contrast, wear tests such as ASTM F2423 and ASTM F2624 and ISO 18192-1, apply a single set of loading parameters over millions of cycles. These parameters are selected based on known, but limited, physiologic data. Wear tests however may be very sensitive to input parameters. Moreover, variations in surgical technique, patient anatomy, and pathology greatly alter the loading environment on the device. Wear tests ideally would evaluate the device under both the expected duty cycle as well as under varying test parameters.
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Skarke, Philipp, Shawn Midlam-Mohler, and Marcello Canova. "Waste Heat Recovery From Internal Combustion Engines: Feasibility Study on an Organic Rankine Cycle With Application to the Ohio State EcoCAR PHEV." In ASME 2012 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icef2012-92018.
Full textAbstract:
This paper presents a feasibility analysis on the application of Organic Rankine Cycles as a Waste Heat Recovery system for automotive internal combustion engines. The analysis is conducted considering the Ohio State University EcoCAR, a student prototype plug-in hybrid electric vehicle, as a case study for preliminary fuel economy evaluation. Starting from a energy-based powertrain simulation model validated on experimental data from the prototype vehicle, a first and second-law analysis was conducted to identify the potential for engine waste heat recovery, considering a variety of driving cycles and assuming the vehicle operating in charge-sustaining (HEV) mode. Then, a quasi-static thermodynamic model of an Organic Rankine Cycle (ORC) was designed, calibrated from data available in literature and optimized to fit the prototype vehicle. Simulations were then carried out to evaluate the amount of energy recovered by the ORC system, considering both urban and highway driving conditions. The results of the simulations show that a simple ORC system is able to recover up to 10% of the engine waste heat on highway driving conditions, corresponding to a potential 7% improvement in fuel consumption, with low penalization of the added weight to the vehicle electric range.
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Chen, Cheng, Amir Sharafi, Jason Flores, et al. "Design and Laboratory Validation of a Force-Amplified Piezoelectric Energy Harvesting Unit." In ASME 2020 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/detc2020-22117.
Full textAbstract:
Abstract In this paper, an innovative piezoelectric energy harvesting unit (PEHU) for the piezoelectric energy harvesting system (PEHS) from highway traffic is introduced. The proposed PEHU contains a non-linear force amplification mechanism, which substantially increases the electricity output of the PEHU in contrast to the conventional designs with direct loading to the piezoelectric stacks. Quasi-static laboratory tests have been performed to validate the design and the mathematical model. In a quasi-static load cycle of 1333N, a preloaded PEHU prototype is able to generate a voltage of 128V and a potential electric energy of 120mJ with a displacement as small as 2.54mm. The energy density that the PEHS can potentially deliver is estimated to be 8.64J/(m.pass.lane) and is the highest reported in the literature. This level of power generation suggests that the PEHU has a great potential for roadway energy harvesting.
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Vascellari, Michele, Re´my De´nos, and Rene´ Van den Braembussche. "Design of a Transonic High-Pressure Turbine Stage 2D Section With Reduced Rotor/Stator Interaction." In ASME Turbo Expo 2004: Power for Land, Sea, and Air. ASMEDC, 2004. http://dx.doi.org/10.1115/gt2004-53520.
Full textAbstract:
In transonic turbine stages, the exit static pressure field of the vane is highly non-uniform in the pitchwise direction. The rotor traverses periodically this non-uniform field and large static pressure fluctuations are observed around the rotor section. As a consequence the rotor blade is submitted to significant variations of its aerodynamic force. This contributes to the high cycle fatigue and may result in unexpected blade failure. In this paper an existing transonic turbine stage section is redesigned in the view of reducing the rotor stator interaction, and in particular the unsteady rotor blade forcing. The first step is the redesign of the stator blade profile to reduce the stator exit pitchwise static pressure gradient. For this purpose, a procedure using a genetic algorithm and an artificial neural network is used. Next, two new rotor profiles are designed and analysed with a quasi 3D Euler unsteady solver in order to investigate their receptivity to the shock interaction. One of the new profiles allows reducing the blade force variation by 50%.
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Kim, SooYong, SeungJoo Choe, Valeri P. Kovalevskiy, and Dong Hwa Kim. "Static and Dynamic Analysis of 2.5 MW Power Generation Gas Turbine Unit." In ASME Turbo Expo 2008: Power for Land, Sea, and Air. ASMEDC, 2008. http://dx.doi.org/10.1115/gt2008-50314.
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Development of a numerical mathematical model to calculate both the static and dynamic characteristics of a multi-shaft gas turbine consisting of a single combustion chamber with advanced cycle components such as intercooler and regenerator is presented in the paper. The numerical mathematical model is based on simplified assumptions such that quasi-static characteristic in turbo-machine and injector is used, pressure loss and heat transfer relation for static calculation neglecting fuel transport time delay can be employed. For study of static and dynamic regime, a control algorithm with following assumptions was made. When the inlet temperature of HPT exceeds the preset value, a signal to stop or open the fuel valve is issued and with a surge margin coefficient Ks&lt;1.1, signal to open the compressor anti surge valve with proportional deflection is issued. At Ks&lt;1.18 or as in starting, a maximum control signal will be issued. Static characteristic of the gas turbine engine in terms of rotation speed ω at ambient temperature of ta = 15°C is carried out. The rotation speed of power turbine is decreased from 20,000 to 4500 rpm, that means 4.4 times, whereas the rotation speed of gas generator is decreased only 2 ∼ 2.5 times. The air flow rate at this time decreased about 3 times. HPC had enough surge margins at all operation ranges. LPC starts to operate with the power turbine speed of 15,000 rpm (approximately 1 MW power output, that means, 40% of the nominal power) and reaches minimal permissible surge margin for safe operation bypassing the air through supercharging channel. Calculation of heat balance showed the difference did not exceed more than 0.06%, validating the accuracy of the applied method. The accuracy of each calculation is confirmed by monitoring mass and energy balance for different time steps of integration.
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Kim, Soo Yong, and Valeri P. Kovalevsky. "Investigation of a Nonlinear Numerical Mathematical Model of a Multi-Shaft Gas Turbine Unit." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38212.
Full textAbstract:
The development of numerical mathematical model to calculate both the static and dynamic characteristics of a multishaft gas turbine consisting of a single combustion chamber, including advanced cycle components such as intercooler and regenerator is presented in the paper. The mathematical model is based on the simplified assumptions that quasi-static characteristic of a turbo-machine and injector is used, total pressure loss and heat transfer relation for static calculation neglecting fuel transport time delay can be employed. The supercharger power has a cubical relation to its rotating velocity. The accuracy of each calculation is confirmed by monitoring mass and energy balances, and comparative calculations with different time steps of integration. The features of the studied gas turbine scheme are the starting device with compressed air bottles and injector supercharging air directly ahead of the combustion chamber. The start-up algorithms are reviewed at different geometrical characteristics of the injector and temperatures of ambient air.
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Sampathnarayanan, Balaji, Lorenzo Serrao, Simona Onori, Giorgio Rizzoni, and Steve Yurkovich. "Model Predictive Control as an Energy Management Strategy for Hybrid Electric Vehicles." In ASME 2009 Dynamic Systems and Control Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/dscc2009-2671.
Full textAbstract:
The energy management strategy in a hybrid electric vehicle is viewed as an optimal control problem and is solved using Model Predictve Control (MPC). The method is applied to a series hybrid electric vehicle, using a linearized model in state space formulation and a linear MPC algorithm, based on quadratic programming, to find a feasible suboptimal solution. The significance of the results lies in obtaining a real-time implementable control law. The MPC algorithm is applied using a quasi-static simulator developed in the MATLAB environment. The MPC solution is compared with the dynamic programming solution (offline optimization). The dynamic programming algorithm, which requires the entire driving cycle to be known a-priori, guarantees the optimality and is used here as the benchmark solution. The effect of the parameters of the MPC (length of prediction horizon, type of prediction) is also investigated.