Relevant bibliographies by topics / Steady and unsteady states

Academic literature on the topic 'Steady and unsteady states'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Steady and unsteady states"

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Ambike, Satyajit, Daniela Mattos, Vladimir M. Zatsiorsky, and Mark L. Latash. "Unsteady steady-states: central causes of unintentional force drift." Experimental Brain Research 234, no. 12 (August 19, 2016): 3597–611. http://dx.doi.org/10.1007/s00221-016-4757-7.

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Feng, J., and D. D. Joseph. "The unsteady motion of solid bodies in creeping flows." Journal of Fluid Mechanics 303 (November 25, 1995): 83–102. http://dx.doi.org/10.1017/s0022112095004186.

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In treating unsteady particle motions in creeping flows, a quasi-steady approximation is often used, which assumes that the particle's motion is so slow that it is composed of a series of steady states. In each of these states, the fluid is in a steady Stokes flow and the total force and torque on the particle are zero. This paper examines the validity of the quasi-steady method. For simple cases of sedimenting spheres, previous work has shown that neglecting the unsteady forces causes a cumulative error in the trajectory of the spheres. Here we will study the unsteady motion of solid bodies in several more complex flows: the rotation of an ellipsoid in a simple shear flow, the sedimentation of two elliptic cylinders and four circular cylinders in a quiescent fluid and the motion of an elliptic cylinder in a Poiseuille flow in a two-dimensional channel. The motion of the fluid is obtained by direct numerical simulation and the motion of the particles is determined by solving their equations of motion with solid inertia taken into account. Solutions with the unsteady inertia of the fluid included or neglected are compared with the quasi-steady solutions. For some flows, the effects of the solid inertia and the unsteady inertia of the fluid are importanty quantitatively but not qualitatively. In other cases, the character of the particles' motion is changed. In particular, the unsteady effects tend to suppress the periodic oscillations generated by the quasi-steady approximation. Thus, the results of quasi-steady calculatioins are never uniformly valid and can be completely misleading. The conditions under which the unsteady effects at small Reynolds numbers are important are explored and the implications for modelling of suspension flows are addressed.
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Kori, Hiroshi. "Slow Switching and Broken Cluster State in a Population of Neuronal Oscillators." International Journal of Modern Physics B 17, no. 22n24 (September 30, 2003): 4238–41. http://dx.doi.org/10.1142/s0217979203022246.

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We discuss a novel class of cluster states in globally coupled neuronal oscillators. It is well known that steady cluster states such as perfect synchrony and multi-cluster states arise in globally coupled oscillators. However, little has been discussed on unsteady cluster states which often arise in populations of neuronal oscillators. We show three types of unsteady cluster states, i.e. a pair of clusters involving slow switching, three clusters involving slow switching, and a broken single cluster. These states result from saddle connections between different cluster states, and typically arise near a bifurcation point where perfect synchrony loses its stability.
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de S. Teixeira, Renan, and Leonardo S. de B. Alves. "Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers." Theoretical and Computational Fluid Dynamics 31, no. 5-6 (March 7, 2017): 607–21. http://dx.doi.org/10.1007/s00162-017-0426-0.

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Dorney, D. J., and O. P. Sharma. "Evaluation of Flow Field Approximations for Transonic Compressor Stages." Journal of Turbomachinery 119, no. 3 (July 1, 1997): 445–51. http://dx.doi.org/10.1115/1.2841143.

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The flow through gas turbine compressors is often characterized by unsteady, transonic, and viscous phenomena. Accurately predicting the behavior of these complex multi-blade-row flows with unsteady rotor–stator interacting Navier–Stokes analyses can require enormous computer resources. In this investigation, several methods for predicting the flow field, losses, and performance quantities associated with axial compressor stages are presented. The methods studied include: (1) the unsteady fully coupled blade row technique, (2) the steady coupled blade row method, (3) the steady single blade row technique, and (4) the loosely coupled blade row method. The analyses have been evaluated in terms of accuracy and efficiency.
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Stoica, Adrian Mihail, and Marius Stoia-Djeska. "On a New Model Reduction Method for CFD Systems Used for Flow Control Design." Applied Mechanics and Materials 332 (July 2013): 9–14. http://dx.doi.org/10.4028/www.scientific.net/amm.332.9.

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The use of active control to get better characteristics of unsteady internal and external flows is the ultimate goal of the research presented in this paper. Usually, unsteady flows are calculated using Euler and/or Navier-Stokes solvers. The efficiency of numerical simulation of an unsteady flow dramatically increases if the unsteady solution is a small perturbation about a steady-state flow, due to disturbances occurring at the boundaries of the flow domain. The main difficulty related to the flow simulation is that any CFD (Computational Fluid Dynamics) technique generates discrete systems with a very large number of states. In order to design an efficient control, the flow solver must be not only accurate and numerically effective, but also it must have a low number of states. The aim of this paper is to present a new method for model reduction of CFD systems using representative governing equations. The focus is on descriptor type systems resulting from the spatial discretization of the CFD governing equations.
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Zhan, Tianyi, Fengze Sun, Chao Lv, Qian He, Xuan Wang, Kang Xu, Yaoli Zhang, and Liping Cai. "Evaluation of moisture diffusion in lignocellulosic biomass in steady and unsteady states by a dynamic vapor sorption apparatus." Holzforschung 73, no. 12 (November 26, 2019): 1113–19. http://dx.doi.org/10.1515/hf-2019-0063.

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Abstract To examine the methodology for determining the moisture diffusion behavior of lignocellulosic biomass in steady and unsteady states (two stages of a sorption isotherm), the diffusion coefficients in the steady and unsteady states (DSS and DUS) were investigated over a range of relative humidity (RH) from 10 to 90% using a dynamic vapor sorption (DVS) apparatus and a specifically designed cell kit. Thin samples with a thickness of 50 μm were prepared from three lignocellulosic biomasses, i.e. poplar, Chinese fir and moso bamboo. Based on Fick’s first and second laws, DSS and DUS were determined. An increase in DSS or DUS was observed with increasing equilibrium moisture content (EMC) or transient status, regardless of the lignocellulosic biomass species. The moisture-dependent DSS of poplar, Chinese fir and moso bamboo was similar to values previously reported. Chinese fir and moso bamboo exhibited the highest and the lowest DSS values, respectively, when the same EMCs were achieved. The results of this study revealed that DSS and DUS of lignocellulosic biomass (even with limited dimensions) could be determined during a sorption isotherm in a wide humidity range. Furthermore, the results are helpful for simulating moisture transport behaviors in the fields of drying, paper packaging and wooden building maintenance.
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Világi, František, Branislav Knížat, Róbert Olšiak, Marek Mlkvik, Peter Mlynár, František Ridzoň, and František Urban. "Simulation of Steady States of Helium Loop at Long Time Scenarios." MATEC Web of Conferences 328 (2020): 01009. http://dx.doi.org/10.1051/matecconf/202032801009.

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The natural circulation helium loop is an experimental facility designed for the research of the possibility of utilizing natural convection cooling for the case of decay heat removal from a fast nuclear reactor. This concept would bring an improved automated safety system for future nuclear power plants operating a gas-cooled reactor. The article presents a new possibility of direct use of energy conservation laws in a 1D simulation of natural circulation loops. The calculation is performed by a triple iteration process, nested into each other. The results of the calculations showed good agreement with the measurements at steady state. A calculation with the proposed model at unsteady state is not yet possible, especially because of the exclusion of heat accumulation into the material.
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Guan, Xiaofeng, M. S. High, and D. A. Tree. "Viscoelastic Effects in Modeling Web Handling Systems: Unsteady-State Analysis." Journal of Applied Mechanics 65, no. 1 (March 1, 1998): 234–41. http://dx.doi.org/10.1115/1.2789031.

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A model to predict the tension in open spans of web handling systems during transient operations has been developed. Governing equations were developed by using the White-Metzner equation to describe the material response in conjunction with mass and force balances. The governing equations were nondimensionalized and solved via the MacCormack predictor/corrector technique. Two dimensionless parameters emerged from the analysis, the Deborah number, De, and the ratio of the viscous stress to the steady state stress, N. The resulting model is the companion to a previously reported model for steady-state operations (Guan et al, 1995). The model was used to predict the behavior of a web handling system during start-up, transition between steady states, and a periodic disturbance. During start-up and transition, systems responded more rapidly at low De. The system response during a periodic disturbance was correlated to De, the frequency, and the magnitude of the disturbance.
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FOREST, M. GREGORY, and HONG ZHOU. "Unsteady analyses of thermal glass fibre drawing processes." European Journal of Applied Mathematics 12, no. 4 (August 2001): 479–96. http://dx.doi.org/10.1017/s0956792501004557.

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Fibre drawing is an important industrial process for synthetic polymers and optical communications. In the manufacture of optical fibres, precise diameter control is critical to waveguide performance, with tolerances in the submicron range that are met through feedback controls on processing conditions. Fluctuations arise from material non-uniformity plague synthetic polymers but not optical silicate fibres which are drawn from a pristine source. The steady drawing process for glass fibres is well-understood (e.g. [11, 12, 20]). The linearized stability of steady solutions, which characterize limits on draw speed versus processing and material properties, is well-understood (e.g. [9, 10, 11]). Feedback is inherently transient, whereby one adjusts processing conditions in real time based on observations of diameter variations. Our goal in this paper is to delineate the degree of sensitivity to transient fluctuations in processing boundary conditions, for thermal glass fibre steady states that are linearly stable. This is the relevant information for identifying potential sources of observed diameter fluctuation, and for designing the boundary controls necessary to alter existing diameter variations. To evaluate the time-dependent final diameter response to boundary fluctuations, we numerically solve the model nonlinear partial differential equations of thermal glass fibre processing. Our model simulations indicate a relative insensitivity to mechanical effects (such as take-up rates, feed-in rates), but strong sensitivity to thermal fluctuations, which typically form a basis for feedback control.
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Dissertations / Theses on the topic "Steady and unsteady states"

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Yassin, Menna. "Steady State Hydroplaning Risk Analysis and Evaluation of Unsteady State Effects." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7990.

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Hydroplaning is a major concern on high speed roadways during heavy rainfall events. Hydroplaning tools are widely used by designers to reduce their roadway’s hydroplaning potential, therefore reducing the possibilities of severe crashes. This dissertation presents two methodologies for improving the prediction of hydroplaning potential. The first phase focused on improving an existing widely used software called PAVDRN. Using multiple datasets from the Florida Department of Transportation, the author filtered the data using specific criteria to leave only truly dynamic hydroplaning crashes. The author then evaluated PAVDRN’s prediction capabilities and assessed its reliability in predicting a hydroplaning crash. Using past accident statistics, the author accounted for extraneous factors that are difficult to capture, such as driver behavior, and obtained probability factors for a more realistic estimate of hydroplaning risk on roadways. The second phase focused on improving the modeling technique used in hydroplaning prediction tools. Currently when assessing a roadway’s hydroplaning potential, the roadside drainage is not considered in the analysis. The author modeled a combined pavement-drainage system using a 1D/2D method to better capture the effects of roadside drainage, especially in the events of flooding. The methodology used in modeling successfully captures the backwater effects that are caused under critical flooding conditions. Lastly the author created a new tool (MY-PAVDTCH) to provide design engineers with updated waterfilm thickness values under roadside drainage flooded conditions.
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Zeiger, Matthew D. "The Dynamic Character of the Flow Over a 3.5 Caliber Tangent-Ogive Cylinder in Steady and Maneuvering States at High Incidence." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25150.

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Although complex, inconsistent and fickle, the time-averaged flow over a stationary slender forebody is generally well-understood. However, the nature of unsteady, time-varying flows over slender forebodies - whether due to the natural unsteadiness or forced maneuvering - is not well-understood. This body of work documents three experimental investigations into the unsteadiness of the flow over a 3.5 caliber tangent-ogive cylinder at high angles of incidence. The goal of the investigations is to characterize the natural and forced flow unsteadiness, using a variety of experimental tools. In the first investigation, flow data are collected over a stationary model in a water tunnel. Particle-Image Velocimetry (PIV) is employed to acquire time-dependent planes of velocity data with the model at several angles of attack. It is discovered that the asymmetric flow associated with the tangent-ogive forebody exhibits a large degree of unsteadiness, especially for data planes located far from the forebody tip. Vortex shedding of the type exhibited by a circular cylinder in crossflow is observed, but this shedding is skewed by the presence of the tip, the shedding process does not require equal periods of time from each side of the body, and this results in a time-averaged flowfield that is asymmetric, as expected. The rms values of the time-averaged velocity, as well as the turbulent kinetic energy and axial vorticity are calculated. In the second investigation, surface pressure data are acquired from several circumferential rings of pressure ports located on two models undergoing ramp coning motions in two different wind tunnel facilities. The surface pressure data are integrated to determine the sectional yaw forces. Coning motions were performed at several different reduced frequencies, and pneumatic control actuation from the nose was employed. The chosen control actuation method used a small mass flow rate ejected very close to the forebody tip, so as to leverage the inherent convective instability. The data resulting from these tests were analyzed in order to determine how the coning motions affect the distribution of surface pressure and yaw forces, how quickly the flow reacts to the motion, and the extent of control authority of the pneumatic actuation. It was discovered that the yaw forces increase in the direction of the motion for small reduced frequencies, but in the direction opposite to the motion for large reduced frequencies. The effects of the motion tend to dominate the control method, at least for the reduced frequencies and setup tested in the low-speed wind tunnel. The results from the high-speed testing with transitional separation give a preliminary indication that the control method could have sufficient control authority when the reduced frequencies are low. The third investigation involves tangent-ogive cylinder undergoing a pitching maneuver in a water tunnel. Laser-Doppler Velocimetry (LDV) is used in order to map out several planes of velocity data as the model is pitched. The LDV data is used to calculate vorticity and turbulent kinetic energy. Variables that are proportional to the flow asymmetry and proximity to the steady-state flow are defined. All of these variables are displayed as a function of time and space (where appropriate). The delay in the development of the asymmetry and the flow progression to the steady state are determined to be a function of pitch-axis location. The propagation velocity of the convective asymmetry is faster than expected, most likely because of the increased axial velocity in the vortex cores. Vortex breakdown of one of the vortices is observed, with loss of axial velocity and dilution of the vorticity over a large area. The cause of this phenomenon is not yet understood, but it is reminiscent of vortex breakdown over delta wings.
Ph. D.
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Grooms, Daniel Douglas. "Optimization of hybrid dynamic/steady-state processes using process integration." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1752.

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Mishra, Bikash. "Model development of a polymer electrolyte membrane fuel cell to predict steady and unsteady behavior." Diss., Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-08132008-103611.

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Hutton, Bridget Margaret. "Evaluation of a vibrating plate extraction column by application of steady state and unsteady state backflow models." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52262.

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Thesis (MScEng)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Liquid-liquid extraction is a branch of solvent extraction that employs addition of an immiscible solvent, as a separating agent, to a liquid feed. Various types of equipment can be used, however if the process requires more than three stages, typically an extraction column, operated in a countercurrent manner would be employed. In order to scale-up and design a commercial extraction column, it is necessary to quantify the extraction system hydrodynamics and mass transfer characteristics. The principal objectives of countercurrently operated extraction columns concern the mass transfer rate and permissible throughput. The performance of a countercurrent extraction column can be adversely affected by axial mixing, which disturbs countercurrent plug flow. Various methods have been devised whereby it is possible to evaluate the performance of a column extraction and scale it up to ensure that the commercial operation achieves the same separation achieved on a pilot scale. Classical axial dispersion models allow quantification of axial mixing and mass transfer rates. Two Backflow models were derived to describe the performance of a Vibrating Plate Extraction (VPE) Column, one for steady state and one for unsteady state operation. The steady state model consisted of a series of simultaneous equations, which were solved using the Excel solver function. The unsteady state model consisted of 54 ordinary differential equations, which were solved stagewise using a fourth order Runge Kutta procedure. The steady state model was based on a dissociation extraction process, whereby meta-cresol (mcresol) was separated from para-hydroxy-benzaldehyde (PHB). The process used the differing de-protonation constants of the two components and the fact that the solubility of the ionic species of each was low in the organic solvent. The extraction system was quantified using a combination of acid-base and extraction theory. Experimentally determined concentration profiles, measured along the length of the column, were force fitted to the model, thereby allowing determination of the model parameters. The mass transfer coefficients ranged between 0.0098 and 0.189 Imin, and it was found that backmixing of the dispersed phase was negligible, while that of the continuous phase was low (varying between 0 and 0.3). The unsteady state model, used to describe the dynamic response of a VPE, was based on a system whereby tert-butyl hydroquinone (TBHQ) was recovered from a purge stream. Conductivity measurements of the raffinate were used to determine the residence time distribution in the column, and hence allowed determination of the extent of axial mixing. It was preferable that the column be operated with minimum settler volumes, otherwise buffering in the settlers occurred, thereby masking axial mixing effects. This method did not facilitate accurate determination of backmixing, at least two other conductivity measurements in the column needed to be measured.
AFRIKAANSE OPSOMMING: Vloeistof-vloeistofekstraksie is 'n vertakking van oplosmiddelekstraksie wat gebruik maak van die toevoeging van 'n onmengbare oplosmiddel as 'n skeidingagent tot die vloeistofvoer. Verskeie tipes apparaat kan gebruik word, maar as die proses meer as drie stadia vereis, sal 'n ekstraksiekolom, in teenstroom bedryf, tipies gebruik word. Om dit moontlik te maak om 'n kommersiele ekstraksiekolom te skalleer en te bedryf, moet die ekstraksiesisteem se hidrodinamika en massa-oordragkarakteristieke gekwantifiseer word. Die hoof doelwitte van ekstraksiekolomme wat teenstroom bedryf word, gaan om die massa-oordrag en toelaatbare deurset. Die skeidingsdoeltreffendheid van 'n teenstroom ekstraksiekolom kan nadelig beinvloed word deur aksiale vermenging, wat teenstroom propvloei versteur. Verskeie metodes is voorgestel wat dit moontlik maak om die doeltreffendheid van 'n ekstraksiekolom te evalueer en te verseker dat dieselfde skeiding verkry word vir 'n kornmersiele aanleg as vir 'n loodsaanleg. Klassieke aksiale dispersiemodelle laat kwantitatiewe berekening van aksiale vermenging en massa-oordragtempos toe. Twee terugvloeimodelle is afgelei om die werksverrigting van 'n Vibrerende Plaat Ekstraksiekolom (VPE) te beskryf. Die gestadidge toestand model bestaan uit 'n stelsel gelyktydige vergelykings wat opgelos is d.m.v. Excel. Die ongestadige toestand model bestaan uit 54 gewone differensiaalvergelykings, wat stapsgewys opgelos is d.m.v. die vierde orde Runge-Kutta metode. Die gestadigde teostand model is gebaseer op 'n dissosiasie ekstraksieproses, waardeur m-kresol geskei is van p-hidroksiebensaldehied (PHB). Die proses maak gebruik van die verskillende protoneringskonstantes van die twee verbindings en die feit dat die oplosbaarheid van beide die ioniese spesies laag is in die organiese oplosmiddel. Die ekstraksiestelsel is gekwantifiseer deur gebruik te maak van 'n kombinasie van suur-basis- en ekstraksieteorie. Die model is gepas op eksperimenteel bepaalde konsentrasieprofiele, gemeet langs die lengte van die kolom. Die massa-oordragkoeffisiente het waardes aangeneem tussen 0.0098 en 0.189 Imin en daar is gevind dat die terugvermenging van die verspreide fase weglaatbaar was, terwyl die van die kontinue fase laag was (tussen 0 en 0.3). Die ongestadige toestand model wat gebruik is om die dinamiese respons van die VPE te beskryf, is gebaseer op 'n stelsel waar tert-butielhidrokinoon (TBHQ) herwin is vanuit 'n bloeistroom. Geleidingsmetings van die raffinaat is gebruik om die residensietydverspreiding in die kolom te bepaaI en het derhalwe toegelaat dat die mate van aksiale vermenging bepaaI kon word. Die kolom moet by voorkeur met minimale skeiervolumes bedryf word, anders is daar 'n buffereffek in die skeiers, wat die aksiale vermenging verskuiI. Hierdie metode Iaat nie die akkurate bepaling van terugvermenging toe nie en minstens twee ander geleidingsmetings in die kolom was benodig.
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McDougall, Steven Robert. "The application of network modelling techniques to steady-and-unsteady-state multiphase flow in porous media." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1406.

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Elsheikh, Mutasim Mohamed. "A Numerical and Experimental Investigation of Flow Induced Noise In Hydraulic Counterbalance Valves." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5683.

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The main objective of this study is to explore the complex fluid flow phenomena that result in the generation of a high frequency noise in counterbalance valves through an experimental and numerical investigation of the flow. Once the influence of the different components involved in noise generation is established, a secondary objective is the introduction of design modifications that eliminate the undesired effect without altering the operation envelope or the performance of the valve. A hydraulic test bench was used to carry out an experimental investigation of the noise generation process. A computer based data acquisition system was used to record pressure fluctuations, flowrates and hydraulic oil temperatures in a production valve under a variety of operational conditions. Extensive experimental measurements and numerical modeling lead to the hypothesis that noise generation is the result of an acoustic resonance triggered by shear layer instability at the valve inlet. The pressure gradients developed when the shear layer entrains the stagnant fluid in the valve main cavity cause the layer to become unstable and oscillate. The oscillation frequency will depend on a great number of factors such as valve geometry, pressure and velocity gradients and the density and viscosity of the fluid. It is postulated that the observed noise is generated when this frequency matches one of the resonant frequencies of the valve cavity. The proposed mechanism is theoretically poorly understood and well beyond simplified analysis, its accurate numerical simulation is computational very intensive requiring sophisticated CFD codes. The numerical investigation was carried out using STAR–CCM+, a commercially available CFD code featuring 3-D capabilities and sophisticated turbulence modeling. Streamline, pressure, velocity-vector and velocity-scalar plots were obtained for several valve configurations using steady and unsteady state flow simulations. An experimental and numerical analysis of an alternative valve geometry was carried out. Experimental results demonstrated a greatly reduced instability range. The numerical analysis of the unsteady behavior of the shear-layer streamlines for both valves yielded results that were compatible with the experimental work. The results of this investigation promise a great positive impact on the design of this type of hydraulic valves.
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Green, Henry Gregory. "Characteristics of steady and unsteady jets." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/38338.

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Abu-Khiran, E. "Steady and unsteady flow losses in automotive exhaust." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268980.

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Khezzar, Lyes. "Experiments with steady and unsteady confined turbulent flows." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/46926.

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Books on the topic "Steady and unsteady states"

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Weatherhead, Leslie Dixon. Steady in an unsteady world: Sermons. Edited by Odom Stephen A. Valley Forge, PA: Judson Press, 1986.

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Klinkner, Philip A. The Unsteady March. S.l: Free Press, 1998.

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Scott, Robert C. A method of predicting quasi-steady aerodynamics for flutter analysis of high speed vehicles using steady CFD calculations. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Jiang, Da-Quan, Min Qian, and Min-Ping Qian. Mathematical Theory of Nonequilibrium Steady States. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/b94615.

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Wilson, Gregory Jon. Computation of steady and unsteady shock-induced combustion over hypervelocity blunt bodies. Stanford, Conn: Stanford University, 1992.

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Hafez, M. M. Numerical algorithms for steady and unsteady incompressible Navier-Stokes equations: Final report. Davis, Calif: Dept. of Mechanical Engn., University of California, Davis, 1990.

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Duck, Peter W. Unsteady three-dimensional marginal separation, including breakdown. [Washington, D.C.]: NASA, 1990.

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Ground water modeling in multilayer aquifers: Steady flow. Chelsea, Mich: Lewis Publishers, 1990.

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Büyükalaca, Orhan. Studies of convective heat transfer to water in steady and unsteady pipe flow. Manchester: University of Manchester, 1993.

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Hounjet, M. H. L. ARSPNSC: A method to calculate subsonic steady and unsteady potential flow about complex configurations. Amsterdam: National Aerospace Laboratory, 1986.

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Book chapters on the topic "Steady and unsteady states"

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Kurz, H. D. "Technical Change, Growth and Distribution: A Steady-state Approach to ‘Unsteady’ Growth on Kaldorian Lines." In Nicholas Kaldor and Mainstream Economics, 421–48. London: Palgrave Macmillan UK, 1991. http://dx.doi.org/10.1007/978-1-349-10947-0_24.

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Lutscher, Frithjof. "Positive Steady States." In Interdisciplinary Applied Mathematics, 39–52. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-29294-2_4.

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Keizer, Joel. "Nonequilibrium Steady States." In Statistical Thermodynamics of Nonequilibrium Processes, 307–52. New York, NY: Springer New York, 1987. http://dx.doi.org/10.1007/978-1-4612-1054-2_7.

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Tulin, M. P., and R. Cointe. "Steady and Unsteady Spilling Breakers: Theory." In Nonlinear Water Waves, 159–67. Berlin, Heidelberg: Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83331-1_18.

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Munteanu, Ionuţ. "Stabilization of Unsteady States." In Progress in Nonlinear Differential Equations and Their Applications, 171–85. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-11099-4_8.

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Gil’, Michael I. "Existence of Steady States. Positive and Nontrivial Steady States." In Explicit Stability Conditions for Continuous Systems, 159–66. Berlin, Heidelberg: Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11311959_14.

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Smith, Frank T. "Break-up in Steady and Unsteady Separation." In Separated Flows and Jets, 25–37. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-84447-8_3.

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Dold, J. W., J. F. Clarke, and M. Short. "Steady and Unsteady Aspects of Detonation Initiation." In ICASE/LaRC Interdisciplinary Series in Science and Engineering, 493–512. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-1050-1_18.

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Hövel, Philipp. "Control of Steady States." In Springer Theses, 43–103. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14110-2_3.

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Marchisio, Mario Andrea. "Stability Analysis: Steady States." In Introduction in Synthetic Biology, 53–65. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-8752-3_5.

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Conference papers on the topic "Steady and unsteady states"

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Lück, Sebastian, Stefan Kuntzagk, Guido Doebbener, Andreas Kellersmann, Christoph Bode, and Jens Friedrichs. "Accuracy Assessment of Steady and Unsteady Multistage High Pressure Compressor Simulations." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91310.

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Abstract In this paper a comparison of the performance parameters and flow characteristics of a mature commercial high bypass engine’s 9-stages high pressure compressor (HPC) with steady-state mixing-plane (RANS) and unsteady RANS (URANS) CFD is carried out. The investigation is based on a numerical model of the CFM56-5C engine’s HPC which is installed on the Airbus A340-300 aircraft. The compressor under investigation features the so called 3D blading which is the first of two performance improvement packages available. An experimental engine of this type equipped with extensive additional instrumentation is in use by Lufthansa Technik to deliver detailed experimental data of the gas path. Experimental results have been discussed in previous works of the authors. In order to provide long-term forecasts of an engine’s state the aforementioned CFD model has been included into a multilevel engine model. To be able to evaluate the significance and applicability of the CFD results into such model, it is of great interest to which extent and level of detail it can deliver accurate performance predictions. From the comparison of both steady-state and unsteady simulation results it is found that overall compressor performance only differs negligibly while stage performance can differ significantly. It is depicted that among the stator vanes of the front stages local supersonic flow and flow separation can occur. These are not captured by the steady-state simulation to the same degree a time resolved simulation does. In rear stages differences fade and unsteady methods tend to predict better stage performance which may be due to favourable effects of rotor-stator interaction.
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Ibrahim, M. N. Mohamad, and L. F. Koederitz. "Two-Phase Steady-State and Unsteady-State Relative Permeability Prediction Models." In SPE Middle East Oil Show. Society of Petroleum Engineers, 2001. http://dx.doi.org/10.2118/68065-ms.

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Chatziioannou, Konstantinos, Vanessa Katsardi, Apostolos Koukouselis, and Euripidis Mistakidis. "Nonlinear Dynamic Response of a Compliant Tower Under the Effect of Steady and Unsteady Sea States." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62449.

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The purpose of this work is to highlight the importance of considering the actual nonlinear dynamic response for the analysis and design of fixed deep water platforms. The paper highlights the necessity of applying dynamic analysis through the comparison with the results obtained by the authors by applying static nonlinear analysis on the structure under examination. The example treated in the context of the present paper is a compliant tower, set-up in deep water. Nonlinearities are considered both for the calculation of the wave loadings and the structural analysis. The wave loading is based on linear random wave theory and comparisons are provided with the steady wave theories, Airy and Stokes 5th. The former solution is based on the most probable shape of a large linear wave on a given sea-state; the auto-correlation function of the underlying spectrum. On the other hand, in the field of structural analysis, two cases are considered for comparison, static analysis and time history dynamic analysis. For both types of analysis, two sub-cases are considered, a case in which geometric nonlinearity and nonlinearities related to the modelling of the soil are considered and a case in which the corresponding linear theories are employed (reference cases). The structural calculations were performed using the well-known structural analysis software SAP2000, which was enhanced by a special programming interface that was developed to calculate the wave loading and to directly apply the generated loads on the structural members. The results show that the consideration of the particle velocities associated with the linear random wave theory in the wave loading lead to significant differences with respect to the steady wave theories in terms of the displacements and stresses of the structure. Moreover, irrespectively of the adopted wave theory, the nonlinear analyses lead to significant discrepancies with respect to the linear ones. This is mainly associated with the nonlinear properties of the soil. Another source of discrepancies between the results of static and dynamic analyses stems from the change of the effective natural frequency of the structure when nonlinearities are considered.
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Copeland, Colin D., Ricardo Martinez-Botas, and Martin Seiler. "Comparison Between Steady and Unsteady Double-Entry Turbine Performance Using the Quasi-Steady Assumption." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59290.

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The experimental performance evaluation of a circumferentially divided, double-entry turbocharger turbine is presented in this paper with the aim of understanding the influence of pulsating flow. By maintaining a constant speed but varying the frequency of the pulses, the influence of frequency was shown to play an important role in the performance of the turbine. A trend of decreasing cycle-averaged efficiency at lower frequencies was measured. One of the principal objectives was to assess the degree to which the unsteady performance differs from the quasi-steady assumption. In order to make the steady-unsteady comparison for a multiple entry turbine, a wide set of steady equal and unequal admission flow conditions were tested. The steady state data was then interpolated as a function of three, non-dimensional parameters in order to allow a point-by-point comparison with the instantaneous unsteady operation. As an average, the quasi-steady assumption generally under-predicted the mass flow and efficiency loss through the turbine, albeit the differences were reduced as the frequency increased. Out-of-phase pulsations produced unsteady operating orbits that corresponded to a significant steady state, partial admission loss, and this was reflected as a drop in the quasi-steady efficiency. However, these differences between quasi-steady in-phase and out-of-phase predictions were not replicated in the measured results, suggesting that the unequal admission loss is not as significant in pulsating flow as it is in steady flow.
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Li, Huiying, Frank J. Kelecy, Aleksandra Egelja-Maruszewski, and Sergio A. Vasquez. "Advanced Computational Modeling of Steady and Unsteady Cavitating Flows." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67450.

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The numerical simulation of steady and unsteady cavitating flows presents unique challenges in the development of robust numerical methodologies. The major difficulties are associated with the large density variations due to the phase change processes, and the modeling of liquid-vapor mass transfer (along with potentially strong interfacial heat transfer). The multiphase cavitation modeling approach described in this paper has been found to be capable of addressing these issues in an accurate and robust fashion, and is therefore suitable for inclusion in an advanced general purpose CFD solver. In the present approach, cavitation can be modeled within the framework of either the multiphase mixture model or the Eulerian multifluid model. The governing equations are the mixture (mixture model) or phase (Eulerian multifluid model) momentum, energy, turbulence, and phase volume fraction equations. The liquid-vapor mass transfer (evaporation and condensation) is modeled using two baseline cavitation models: Schnerr-Sauer model, and Zwart-Gerber-Belamri model. An advanced numerical scheme has been developed for solving the model equations which can handle large liquid-vapor density ratios, provide for mass transfer source terms in phase volume equations, and address the coupling between the phase change rates and the pressure correction equation. In addition, the cavitation models have been extended to compressible multiphase liquid and vapor flow regimes, and to problems involving convective heat transfer. The numerical algorithm has been implemented in an advanced, general-purpose CFD code, FLUENT, and validations have been carried out for a range of steady-state and unsteady flows, including a 2D axisymmetric orifice, a 3D fuel injector, a radial liquid pump, and a vane pump. The results demonstrate that the cavitation models are able to correctly predict the location and size of vapor bubbles, pressure distributions, and bulk flow parameters. Tests also indicate that the present implementation is both fast and robust, as compared to previous approaches. For unsteady simulations, the method can employ large time steps (limited only by physical or mesh motion considerations), making it efficient for unsteady flows driven by either boundary conditions or mesh motion.
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Katunin, Yuri V., and Vladimir Ya Stenin. "The STG DICE Cell with the Decoder for Reading Data in Steady and Unsteady States for Hardened SRAM." In 2017 17th European Conference on Radiation and Its Effects on Components and Systems (RADECS). IEEE, 2017. http://dx.doi.org/10.1109/radecs.2017.8696115.

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Blocher, Michael, Markus May, and Harald Schoenenborn. "Dependency of Unsteady Time-Linearized Flutter Investigations on the Steady State Flow Field." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46500.

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The influence of the steady state flow solution on the aero-elastic stability behaviour of an annular compressor cascade shall be studied in order to determine sensitivities of the aero-dynamic damping with respect to characteristic flow parameters. In this context two different flow regimes — a subsonic and a transonic case — are subject to the analysis. The pressure distributions, steady as well as unsteady, on the blade surface of the NACA3506 profile are compared to experimental data that has been gained by the Institute of Aeroelasticity of the German Aerospace Center (DLR) during several wind tunnel tests at the annular compressor cascade facility RGP-400 of the Ecole Polytechnique Fe´de´rale de Lausanne (EPFL). Whereas a certain robustness of the unsteady CFD results can be stated for the subsonic flow regime, the transonic regime proves to be very sensitive with respect to the steady state solution.
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Schlamp, Stefan, Torsten Hofmann, Pascal Simon, and Bryan Hathorn. "Shock wave structure in dense nitrogen: Steady-state profile and unsteady processes." In 38th AIAA Thermophysics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2005. http://dx.doi.org/10.2514/6.2005-5212.

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Rushing, J. A., K. E. Newsham, P. M. Lasswell, J. C. Cox, and T. A. Blasingame. "Klinkenerg-Corrected Permeability Measurements in Tight Gas Sands: Steady-State Versus Unsteady-State Techniques." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 2004. http://dx.doi.org/10.2118/89867-ms.

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Peeters, Martin, and Mohamad Sleiman. "A Numerical Investigation of the Unsteady Flow in Centrifugal Stages." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0426.

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Computational Fluid Dynamics (CFD) has matured to the point where it can now be used effectively in impeller and diffuser design. The effective use of CFD for a complete centrifugal stage, however, still remains a challenge. The interaction between an impeller and its diffuser is not well understood and the level of modelling required to explain it is not really known. The goal of this paper is to present some results that can aid in this understanding. A numerical scheme is outlined that is capable of both steady and unsteady stage analysis. Results are presented for a stage consisting of an impeller and pipe diffuser using steady mixing plane analysis. Furthermore, unsteady results for a centrifugal stage consisting of an impeller and a vane diffuser are presented and compared to isolated steady analyses of each component. The results indicate that centrifugal stage performance is not well predicted using steady analysis. Differences in both the diffuser static pressure rise and the impeller pressure ratio are significant and it may be concluded that steady analysis is too unreliable for centrifugal stage predictions. Unsteady results also captured an important interaction phenomenon observed experimentally.
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Reports on the topic "Steady and unsteady states"

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Jameson, Antony, and Peter E. Vincent. High-Order Numerical Algorithms for Steady and Unsteady Simulation of Viscous Compressible Flow with Shocks. Fort Belvoir, VA: Defense Technical Information Center, June 2010. http://dx.doi.org/10.21236/ada563587.

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Benhabib, Jess, and Bálint Szőke. Optimal Positive Capital Taxes at Interior Steady States. Cambridge, MA: National Bureau of Economic Research, May 2019. http://dx.doi.org/10.3386/w25895.

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Bullard, James, and Steven H. Russell. Monetary Steady States in a Low Real Interest Rate Economy. Federal Reserve Bank of St. Louis, 1994. http://dx.doi.org/10.20955/wp.1994.012.

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Donnelly, Martin J., Stuart Jessup, and Ali Etebari. Measurement of Steady and Unsteady Duct Loads for Propeller 4381 at Crashback Conditions in the 36 in. Water Tunnel. Fort Belvoir, VA: Defense Technical Information Center, August 2010. http://dx.doi.org/10.21236/ada530416.

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Akkutlu, I. Yucel, and Yanis C. Yortsos. Non-Adiabatic Effects on Combustion Front Propagation in Porous Media: Multiplicity of Steady States. Office of Scientific and Technical Information (OSTI), March 2002. http://dx.doi.org/10.2172/792462.

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St. John, Haley, and Juliette Scantlebury. A 10-Year Review of Opioid-Related Deaths at West Tennessee Regional Forensic Center: 2007-2017. University of Tennessee Health Science Center, January 2021. http://dx.doi.org/10.21007/com.lsp.2019.0005.

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Prescription opioid deaths have tripled since 1999, and currently opioid overdose kills 115 Americans per day on average (1). Prior to 2014, prescription opioids have been the primary driver of opioid-related mortality. In recent years, the United States has seen a steady decline in the rate of opioid prescription. At the same time, there has been a significant increase in the number of deaths attributed to non-prescription opioids such as heroin, illicitly manufactured fentanyl, and fentanyl analogues. In 2017, among 70,237 drug overdose deaths nationally, 47,600 (67.8%) involved opioids, with increases across age groups, racial/ethnic groups, and county urbanization levels in multiple states (2). The opioid epidemic is especially profound in Tennessee, which had the 3rd highest opioid prescription rate in the country in 2017 and an opioid-related death rate of 19.3 deaths per 100,000 persons, compared to the national average of 14.6 (3). This retrospective study analyzes autopsy data from West Tennessee Regional Forensic Center (WTRFC) from 2007 to 2017 to gain a better understanding of the effects of the opioid epidemic on West Tennessee and the surrounding areas. Data from opioid-related accidents and suicides were analyzed in order to identify trends in race, age, gender, location, types of opioids, and drug combinations involved in opioid-related deaths.
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Kerber, Steve. Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction. UL Firefighter Safety Research Institute, December 2014. http://dx.doi.org/10.54206/102376/gieq2593.

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Under the United States Department of Homeland Security (DHS) Assistance to Firefighter Grant Program, Underwriters Laboratories examined fire service ventilation practices as well as the impact of changes in modern house geometries. There has been a steady change in the residential fire environment over the past several decades. These changes include larger homes, more open floor plans and volumes and increased synthetic fuel loads. This series of experiments examine this change in fire behavior and the impact on firefighter ventilation tactics. This fire research project developed the empirical data that is needed to quantify the fire behavior associated with these scenarios and result in immediately developing the necessary firefighting ventilation practices to reduce firefighter death and injury. Two houses were constructed in the large fire facility of Underwriters Laboratories in Northbrook, IL. The first of two houses constructed was a one-story, 1200 ft, 3 bedroom, bathroom house with 8 total rooms. The second house was a two-story 3200 ft, 4 bedroom, 2.5 bathroom house with 12 total rooms. The second house featured a modern open floor plan, two- story great room and open foyer. Fifteen experiments were conducted varying the ventilation locations and the number of ventilation openings. Ventilation scenarios included ventilating the front door only, opening the front door and a window near and remote from the seat of the fire, opening a window only and ventilating a higher opening in the two-story house. One scenario in each house was conducted in triplicate to examine repeatability. The results of these experiments provide knowledge for the fire service for them to examine their thought processes, standard operating procedures and training content. Several tactical considerations were developed utilizing the data from the experiments to provide specific examples of changes that can be adopted based on a departments current strategies and tactics.
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Zilberman, David, Amir Heiman, and B. McWilliams. Economics of Marketing and Diffusion of Agricultural Inputs. United States Department of Agriculture, November 2003. http://dx.doi.org/10.32747/2003.7586469.bard.

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Specific Research Objective. Develop a theory of technology adoption to analyze the role of promotional tools such as advertising, product sampling, demonstrations, money back guarantees and warranties in inducing technological change. Use this theory to develop criteria for assessing the optimal use of marketing activities in launching new agricultural input technologies. Apply the model to analyze existing patterns of marketing budget allocation among promotional tools for various agricultural input industries in the United States and Israel. Background to the Topic. Marketing tools (money-back guarantees [MBG] demonstration, free sampling and advertising) are used extensively to induce the adoption of agricultural inputs, but there is little understanding of their impacts on the diffusion of new technologies. The agricultural economic literature on technology adoption ignores marketing efforts by the private sector, which may result in misleading extension and technology transfer policies. There is a need to integrate marketing and economic approaches in analyzing technology adoption, especially in the area of agricultural inputs. Major Conclusion. Marketing tools play an important role in reducing uncertainties about product performance. They assist potential buyers to learn both about objective features, about a product, and about product fit to the buyer's need. Tools, such as MBGs and demonstration, provide different information about product fit but also require different degrees of cost for the consumer. In some situations they can be complimentary and optimal strategy combines the use of both. In other situations there will be substitution. Sampling is used to reduce the uncertainty about non-durable goods. An optimal level of informational tools declines throughout the life of a product but stays positive at a steady state. Implications. Recognizing the heterogeneity of consumers and the sources of their uncertainty about new technologies is crucial to develop a marketing strategy that will enhance the adoption of innovation. When fit uncertainty is high, allowing an MBG option, as well as a demonstration, may be an optimal strategy to enhance adoption.
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Kerber, Steve. Study of the Effectiveness of Fire Service Vertical Ventilation and Suppression Tactics in Single Family Homes. UL Firefighter Safety Research Institute, June 2013. http://dx.doi.org/10.54206/102376/iwzc6477.

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Under the United States Department of Homeland Security (DHS) Assistance to Firefighter Grant Program, Underwriters Laboratories examined fire service ventilation and suppression practices as well as the impact of changes in modern house geometries. There has been a steady change in the residential fire environment over the past several decades. These changes include larger homes, more open floor plans and volumes, and increased synthetic fuel loads. This investigation examined the influence of these changes to the fire behavior and subsequent impact on firefighter tactics relative to horizontal and vertical ventilation and suppression. It is anticipated that the results of this investigation will be incorporated into improved firefighting tactics and decision making to reduce firefighter injuries and fatalities. Vertical ventilation has been used successfully but also resulted in firefighter fatalities in the past, as it is not easily coordinated with suppression and other fire ground tasks such as horizontal ventilation. It is not straightforward for firefighters to train on the effects of vertical ventilation since fire service training structures and props do not allow for ventilation-limited fire conditions with representative fuel loads and floor plans that will be encountered on the fire ground. Thus, guidance on the effectiveness of vertical ventilation comes from experience gained during real incidents, but under many different fire ground conditions. This has made it difficult to develop comprehensive guidance on the coordination of vertical ventilation with other firefighter tactics, and how these tactics may influence the fire dynamics in the burning home. The purpose of this study was to improve the understanding of the fire dynamics associated with the use of vertical ventilation so that it may be more effectively deployed on the fire ground. Two houses were constructed in the large fire facility of Underwriters Laboratories in Northbrook, IL. The first house was a one-story house (1200 ft, three bedrooms, one bathroom) with a total of 8 rooms. The second house was a two-story house (3200 ft, four bedrooms, two and a half bathrooms) with a total of 12 rooms. The second house featured a modern open floor plan, two-story great room and open foyer. A total of seventeen experiments were conducted varying the ventilation locations and the number of ventilation openings. Ventilation scenarios included ventilating the front door and a window near the seat of the fire (with modern and legacy furnishings) to link to the previous research on horizontal ventilation, opening the front door and ventilating over the fire and remote from the fire. Additional experiments examined controlling the front door, making different sized ventilation holes in the roof and the impact of exterior hose streams. The results from the experiments led to identification of tactical considerations for the fire service to integrate into their education and fire ground strategies and tactics where applicable.
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DESIGN OF THE DEPLOYABLE-FOLDABLE ACTUATOR AND VIBRATION CONTROL DEVICE BASED ON THE SHAPE MEMORY ALLOYS WITH A TWO-WAY EFFECT. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.306.

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The paper aims at the design method of the space deployable-foldable actuator and vibration control device, and the selected material is the shape memory alloy. These devices can repeatedly adjust the deploy and fold states by changing the temperature, and also present a large energy dissipation to keep the stability of the structures in the vibration control. It can be observed that the fabricated two-way shape memory alloy actuator can present steady fold-deploy procedures more than five times, in which the recoverable rate is higher than 95.83%, and the required time in the complete deploying process is 15 s. Meanwhile, the vibration control device based on the shape memory alloys also gives an excellent performance, the lightweight device is only 315 g, and the vibration in the vertical direction can be limited to the millimeter-level (0.917 mm), it can also endure the repeated loadings in the applications and keep a good operating condition.
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