Dissertations / Theses on the topic 'High-stability'
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Kwasnicki, Wieslaw T. "High Speed Transient Stability, multiprocessing solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0024/NQ32881.pdf.
Full textYoung, David. "Hydrothermal stability of high silica zeolites." Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/9864.
Full textBonnaure, Laurent Paul. "Modelling high speed multistage compressor stability." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13046.
Full textEbrinc, Ali Aslan. "High Speed Viscous Plane Couette-poiseuille Flow Stability." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/3/12604769/index.pdf.
Full text#65533
s viscosity law are studied using a second-order finite difference scheme. The basic velocity and temperature distributions are perturbed by a small-amplitude normalmode disturbance. The small-amplitude disturbance equations are solved numerically using a global method using QZ algorithm to find all the eigenvalues at finite Reynolds numbers, and the incompressible limit of these equations is investigated for Couette-Poiseuille flow. It is found that the instabilities occur, although the corresponding growth rates are often small. Two families of wave modes, Mode I (odd modes) and Mode II (even modes), were found to be unstable at finite Reynolds numbers, where Mode II is the dominant instability among the unstable modes for plane Couette flow. The most unstable mode for plane Couette &
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Poiseuille flow is Mode 0, which is not a member of the even modes. Both even and odd modes are acoustic modes created by acoustic reflections between a will and a relative sonic line. The necessary condition for the existence of such acoustic wave modes is that there is a region of locally supersonic mean flow relative to the phase speed of the instability wave. The effects of viscosity and compressibility are also investigated and shown to have a stabilizing role in all cases studied. Couette-Poiseuille flow stability is investigated in case of a choked channel flow, where the maximum velocity in the channel corresponds to sonic velocity. Neutral stability contours were obtained for this flow as a function if the wave number,Reynolds number and the upper wall Mach number. The critical Reynolds number is found as 5718.338 for an upper wall Mach number of 0.0001, corresponding to the fully Poiseuille case.
Holmestad, Jon. "High-temperature stability of Al-Mg-Si alloys." Thesis, Norwegian University of Science and Technology, Department of Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6347.
Full textEbrinç, Ali Aslan. "High speed viscous plane couette-poiseuille flow stability." Ankara : METU, 2004. http://etd.lib.metu.edu.tr/upload/12604769/index.pdf.
Full textAng, Ing Chea. "Stability and quench protection of high-temperature superconductors." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35665.
Full textIncludes bibliographical references (leaves 83-84).
In the design and operation of a superconducting magnet, stability and protection are two key issues that determine the magnet's reliability and safe operation. Although the high-temperature superconductor (HTS) is considered much more stable than the low-temperature superconductor (LTS), it is susceptible to damage caused primarily by three events that can occur in large-scale "real" devices: 1) overheating; 2) high voltage; and, 3) overstressing. In this thesis, we have investigated the first two issues as well acoustic emission (AE) technique as a possible mean for an early detection of a quench. For most of the experimental work reported here, we used "pancake" coils wound with coated YBCO conductor, the HTS of choice by those currently developing HTS-based electric power devices, though, YBCO itself to date is still in the development phase. For protection against overheating, an HTS magnet assembled with pancake coils may be made self-protecting through speedy 2-D or even 3-D normal zone propagation (NZP) within its winding, aided by good thermally-diffusive turn-to-turn spacers.
(cont.) We have found experimentally that good thermal diffusivity alone, however, does not guarantee fast 2-D NZP: thermal contact resistance between winding layers plays a crucial role in NZP in the transverse direction. For high internal voltage, a small test "magnet" consisting of two pancake coils was studied to investigate the internal voltage distributions within the magnet when one of the pancakes was driven normal with a heater. Measured voltage distributions were compared with those of simulation. Finally, to complement standard resistive voltage technique, an acoustic emission (AE) technique was investigated for detection of a quench at an instance earlier than that possible with a resistive voltage technique. With improved understanding of these issues, we should be able to develop protection techniques that ensure reliable and safe operation of HTS devices.
by Ing Chea Ang.
S.M.
Xu, Jiapeng. "Stability of high temperature ceramics under corrosive environments." Thesis, Boston University, 2013. https://hdl.handle.net/2144/11090.
Full textCurrently, ceramics are being used under increasingly demanding environments. This research involves the study of high-temperature stability of ceramic materials in two diverse applications. The first application involves the use of ceramic materials in gas turbines. SiC/SiC ceramic matrix composites (CMCs) are increasingly being used in the hot-sections of gas turbines; and they are subject to recession of their surface if exposed to a flow of high-velocity water vapor, and to hot-corrosion when exposed to alkali salts. This research involves developing a hybrid system containing an environmental barrier coating (EBC) for protection of the CMC from chemical attack and a thermal barrier coating (TBC) that allows a steep temperature gradient across it to lower the temperature of the CMC for increased lifetimes. The EBC coating is a functionally graded mullite (3Al2O3•2SiO2) deposited by chemical vapor deposition (CVD), the TBC layer is yttria-stabilized zirconia (YSZ) deposited by air plasma spray (APS). The hybrid coating system demonstrated excellent physical and chemical stability under severe thermal shock and exposure to an aggressive hot-corrosion environment. Finite element modeling showed that through-thickness cracks reduce the tensile stresses in the TBC, but also reduce the beneficial compressive stresses in the EBC, and may actually lead to the propagation of the vertical cracks into the EBC. The second application involves the formation of solar-grade silicon by an inexpensive and environmentally friendly electrochemical process using an YSZ solid oxide membrane (SOM) at elevated temperature (~1100°C). The SOM membrane is exposed to a complex fluoride flux with dissolved silica, which is then electrochemically separated into silicon and oxygen. Membrane stability is crucial to ensure high efficiency and long-term performance of the SOM process. A failure model of the SOM membrane by the formation of "inner cracks" was studied, and attributed to yttrium depletion in the YSZ, which leads to phase transformation from the cubic to tetragonal phase. A series of systematic experiments were designed and performed to understand the synergistic roles of silica and YF3 in the flux in membrane degradation. It was shown that silica attacks the SOM membrane, while YF3 in the flux slows down the attack. The mechanism of the yttria depleted layer (YDL) formation was attributed to grain boundary attack by the silica in the flux, which was the rate-controlling step. This led to rapid ingress of the flux into this attacked grain boundaries, and the out diffusion of Y from the cubic YSZ grains to the grain boundary. This depletion of the Y from the cubic grains transformed them into tetragonal. Once all of the cubic grains in the YDL region converted to tetragonal YSZ grains, no further diffusion occurred. Based on the stability test results, a new flux design was proposed and tested. The flux composition did not attack the SOM membrane, and successful separation of silica in the flux to phase pure Si crystals was demonstrated without apparent damage to the SOM membrane, thereby demonstrating the viability of the Si-SOM process.
Thomas, Dirk. "Lateral Stability of High-Speed Trains at Unsteady Crosswind." Licentiate thesis, KTH, Aeronautical and Vehicle Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11377.
Full textCrosswind stability of rail vehicles has been a research area for several decades,mainly motivated by vehicle overturning accidents and higher speeds, but in recenttimes also by issues of lower energy consumption and track maintenance costsdemanding lower vehicle weights. During everyday operation, rail vehicles are subjectedto large lateral influences from track irregularities, track curves and crosswind,leading to large suspension deflections and increased crosswind sensitivity.Also unsteady crosswind like gusts calls for attention. Simulations of possible vehicleoverturning are necessary, but need to take large deflections and high shear inthe suspension into account. If delivering reasonable results, simulations representan important tool for overturning prediction of the vehicle.
In the present work, multibody simulations of a high-speed vehicle at large lateralinfluences from track curves and track irregularities have been carried out, using ahalf-vehicle model in 2D and a model of a whole vehicle in 3D. The vehicle modelsalso include different suspension models. Corresponding field measurements ofthe relative lateral and vertical deflections in the secondary suspension have beenperformed on a fast train and used for validation of the multibody simulations,resulting in good agreement between measurements and simulations.
The 3D vehicle model was further used to study the vehicle response to unsteadycrosswind during curve negotiation where aerodynamic loads obtained by unsteadyComputational Fluid Dynamics, namely Detached Eddy Simulations, representingthree types of gusts were used. In addition, the method of Quasi Transient GustModelling was evaluated in terms of overturning risk. Strong lateral and roll responsesof the vehicle and influences of the gust duration and the relative differencebetween mean and maximum wind speed were observed. Further, variations of suspensionand mass properties of the vehicle were performed to study the influenceon crosswind sensitivity. The position of the centre of mass of the carbody and thelateral bumpstop clearance showed significant influence on the crosswind stability.
Payeras, Antoni Mairata i. "Stability and oxidative reactivity of high-valent manganese complexes." Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428448.
Full textOrtega, Gómez Tino. "Stability analysis of the high performance light water reactor." Karlsruhe Forschungszentrum Karlsruhe, 2009. http://d-nb.info/994365624/34.
Full textVirgilio, Gianluca. "Is high-frequency trading a threat to financial stability?" Thesis, University of Hertfordshire, 2017. http://hdl.handle.net/2299/18841.
Full textTanvir, Tanvir. "Design and Stability Analysis of a High-Temperature SRAM." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1355516028.
Full textAgulov, A. V., V. A. Turchenko, S. A. Goncharova, U. V. Kudelin, A. A. Goncharov, A. I. Bazhin, and V. A. Stupak. "Thermal stability of film nanostructure of high-melting compounds." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20656.
Full textSchellenberg, Katja [Verfasser]. "A High-Throughput Analysis of Circadian Protein Stability / Katja Schellenberg." Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1048558614/34.
Full textErdmann, Natalie. "Identification of high-copy-number inhibitors of P1 plasmid stability." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ34055.pdf.
Full textMeegahapola, Lasantha. "Stability analysis and coordinated control strategies during high wind penetration." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534620.
Full textMummery, Gavin Thomas. "Developing a high-resolution bioengineering model for slope stability analysis." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435426.
Full textNelson, Joseph Richard. "Crystal structure prediction at high pressures : stability, superconductivity and superionicity." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268482.
Full textFréchette, Luc G. (Luc Guy). "Implications of stability modeling for high-speed axial compressor design." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10721.
Full textPosokhow, Bruno A. (Bruno Andre) 1975. "A study on the stability of a high speed compressor." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80618.
Full textMorrison, Sarah J., and Kaitlin M. Kratter. "ORBITAL STABILITY OF MULTI-PLANET SYSTEMS: BEHAVIOR AT HIGH MASSES." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621257.
Full textDhorajiwala, Husein, and Agnieszka Owczarczyk. "Global stability of high-rise buildings on foundation on piles." Thesis, KTH, Bro- och stålbyggnad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235317.
Full textI Sverige och andra länder är trenden att bygga högre alltmer populärt. Den globala stabiliteten hos höga byggnader är en viktig aspekt som måste beaktas vid byggnadens utformning. Den vanligaste grundläggningsmetoden i Sverige är grundläggning med pålar. Denna typ av grundläggning minskar den globala stabiliteten jämfört med grundläggning direkt på berggrunden. Att använda sneda pålar i grundläggningen är oundviklig för höghus, eftersom de är nödvändiga för att överföra horisontella laster till berggrunden. Syftet med detta examensarbete är att se hur grundläggning på pålar påverkar den globala stabiliteten och undersöka två enkla metoder för global stabilitet. I detta examensarbete undersöktes hur styvheten påverkar grundläggning med pålar med olika längder och lutningar, med hänseende på den globala stabiliteten. Pålcentrumets påverkan av rotation och den globala stabiliteten har även studerats. En metod som presenterades i examensarbetet är baserades på ekvivalent styvhet. Där utböjning på toppen av väggen togs för att beräkna böjstyvheten som reduceras på grund av grundläggning med pålar och ytterligare beräknades knäcklasten baserat på Eulers knäckning. I den andra metoden som föreslogs togs rotationen vid grundläggningsnivån med i beräkningen för att beräkna rotationsfjäderns styvhet och senare knäckningslasten på grund av kombinerad böjnings- och rotationsknäckning. Analysen genomfördes på en enkel tvådimensionell vägg och en tredimensionell byggnad som är stabiliserad av två torn. Tre olika konfigurationer av pålar undersöktes för enkel vägg och även för byggnaden Utredningen av examensarbetet visade att positionen av pålcentrum har en stor påverkan på den globala stabiliteten. Ju närmare pålcentrumet är till grundläggningsnivån desto bättre är den globala stabiliteten hos en konstruktion. Längden på pålarna har även en betydelse när det gäller stabiliteten. Ju längre pålarna är desto värre blir stabiliteten. Med längre pålar minskar den totala styvheten hos hela konstruktionen och därmed minskar även den globala stabiliteten. Utredningen visade även att metoden med rotation vid grundläggningsnivån gav mer noggrannare resultat än metoden för ekvivalent styvhet. Men för att kunna använda den förstnämnda metoden behöver man ha kännedom om vart pålcentrum ligger för konstruktionen och detta kan vara svårt att uppskatta. I en analys av en byggnad stabiliserad av två torn visades det att när pålarna är placerade långt från rotationscentrum av en konstruktion ökar den globala säkerheten och rotationsstyvheten. Det rekommenderas att använda sådan konfiguration av pålar att pålcentrum ligger på grundnivå för att öka den globala stabiliteten.
Moreu, Gamazo José M. (José María). "High-order tuners for convex optimization : stability and accelerated learning." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130859.
Full textCataloged from the official PDF version of thesis.
Includes bibliographical references (pages 131-132).
Iterative gradient-based algorithms have been increasingly applied for the training of a broad variety of machine learning models including large neural-nets. In particular, momentum-based methods, with accelerated learning guarantees, have received a lot of attention due to their provable guarantees of fast learning in certain classes of problems and multiple algorithms have been derived. However, properties for these methods hold true only for constant regressors. When time-varying regressors occur, which is commonplace in dynamic systems, many of these momentum-based methods cannot guarantee stability. Recently, a new High-order Tuner (HT) was developed and shown to have 1) stability and asymptotic convergence for time-varying regressors and 2) non-asymptotic accelerated learning guarantees for constant regressors. These results were derived for a linear regression framework producing a quadratic loss function. This thesis extends and discuss the results of this same HT for general smooth convex loss functions. Through the exploitation of convexity and smoothness definitions, we establish similar stability and asymptotic convergence guarantees. Additionally we conjecture that the HT has an accelerated convergence rate. Finally, we provide numerical simulations supporting the satisfactory behavior of the HT algorithm as well as the conjecture of accelerated learning.
by José M. Moreu Gamazo.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
Gonzalez-Torres, Juan Carlos. "Transient stability of high voltage AC-DC electric transmission systems." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS041.
Full textThe new policy frameworks adopted by national authorities has encouraged the large scale-integration of Renewable Energy Systems (RES) into bulk power systems. The large-scale integration of RES will have consequences on the electricity transmission system as it is conceived today, since the transmission of bulk power over long distances could lead the existing transmission systems to work close to their limits, thus decreasing their dynamic security margins. Therefore more complex transmissions systems are needed.Under this scenario, HVDC transmission systems raise as the most attractive solution for the reinforcement and improvement of existing AC networks, not only using point-to-point configurations, but also in a Multi-Terminal configuration. The introduction of HVDC transmission systems will eventually result in a hybrid high voltage AC/DC power system, which requires to be analyzed as a unique system in order to understand the interactions between the AC network and the DC grid.This thesis addresses the transient stability analysis of hybrid AC/DC electric transmission systems. More in particular, two questions sought to be investigated: What is the impact of a DC contingency on AC transient stability? How can we take advantage of the of DC transmission systems as control inputs in order to enhance AC transient stability?In the first part of this work, the mathematical models of the hybrid AC/DC grid are described as well as the necessary tools for the analysis of the system taking into account its nonlinear nature. Then, a thorough analysis of transient stability of the power system in the particular case of a DC fault and the execution of the corresponding protection strategies is done. As a complement, stability indicators and tools for sizing future MTDC grids in order to respect the constraints of existing protection strategies are proposed.The second part of the thesis addresses the control proposals for the modulation of power references of the HVDC transmission systems with the purpose of transient stability enhancement of the surrounding AC system. Firstly, we focus our study in the nonlinear control of point-to-point HVDC links in hybrid corridors. Fast power compensation, injection of damping power and injection of synchronizing power are identified as the mechanisms through which HVDC systems can improve stability margins.Finally, a control strategy for transient stability enhancement via active power injections of an MTDC grid is proposed. Using communication between the stations, the proposed decentralized control injects damping and synchronizing power between each pair of converters using only measurements at the converters level. The proposed implementation allows to fully use the available headroom of the converters by dealing with power limits in a decentralized way
Moser, David. "Stability of transition metal doped magnesium hydride high-pressure phases." Thesis, University of Salford, 2010. http://usir.salford.ac.uk/26827/.
Full textMunro, Keith Alistair. "High-pressure high-temperature behaviour of the lanthanide metals." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28881.
Full textColeman, Simon Anthony. "The aerodynamics of ground vehicles in cross winds." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278349.
Full textKinloch, Stephen Adam. "Interphase modification in TATB filled polymer bonded explosives." Thesis, Cranfield University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303329.
Full textHanan, Nathan, and David Nix. "Extending the Stability of Intravenous Ampicillin." The University of Arizona, 2012. http://hdl.handle.net/10150/614496.
Full textSpecific Aims: To assess the chemical stability of ampicillin for injection in normal saline at pH values ranging from 5 to 6. Methods: A stability-indicating high performance liquid chromatography (HPLC) method was developed and used to determine the stability of ampicillin for injection in normal saline following buffering with sodium acetate and acid adjustment with HCl at pH values of 5, 5.5, and 6. To confirm that the assay was stability-indicating, ampicillin trihydrate reference standard (1 mg/mL) was exposed to alkali, acid, and oxidative stress conditions and analyzed by HPLC for the presence of degradation products. Analysis was performed on a reverse-phase (C-18) column with a mobile phase consisting of water, acetonitrile, 1 M monobasic potassium phosphate, and 1 N acetic acid (909:80:10:1). Other HPLC parameters were: flow rate 1 mL/min; detection wavelength 254 nm; injection volume 20 µL; column temperature 30˚C. The method was evaluated for linearity, precision, and accuracy. The chemical stability of ampicillin for injection (18 mg/mL) in normal saline and sodium acetate (pH adjusted at values of 5, 5.5, and 6) was assessed at baseline (t=0), 7, 11, 17, 31, and 44 hours and compared to a control solution (no pH adjustment). Measurements at each time interval were performed in triplicate. Main Results: Ampicillin trihydrate reference standard (1 mg/mL) was adequately separated from degradation products following exposure to alkali, acid, and oxidative stress conditions. After 16 hours, a precipitate was observed in the solution at pH 6, and therefore stability is not reported. All other solutions (pH 5, pH 5.5, and control) were stable for at least 24 hours at room temperature and yielded t90 values of 110, 64.2, and 27.5 hours, respectively. Conclusions: Adjustment of intravenous ampicillin solutions to pH values of 5 or 5.5 significantly increased stability. Ampicillin appears to be most stable at a pH near its isoelectric point (pH 5).
Liu, Qiongxi. "An investigation of the stability of advanced carbon-based coatings under high temperature and high pressure." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7794/.
Full textEl, Chehaly Mohamed. "Power system stability analysis with a high penetration of distributed generation." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=92399.
Full textWith power systems operating near their loadability limits, voltage stability becomes an important issue. Many utilities have implemented long-term solutions to counter this problem, such as adding transmission lines and new power plants in order to improve the reliability of the power system. An alternative solution consists in increase of generation at the distribution level. This is also a way of meeting growing economical, technical and environmental constraints. The size, the technology and the placement of DG play an important role in the operation of distribution systems.
For long-term voltage stability analysis, bus-based voltage indices are implemented using Power-Voltage curves (PV curves) to analyze the contribution of DG. Large-penetration of DG also has an impact on the short-term stability (voltage stability and transient stability) of the system. Indices are developed to rank contingencies and show how different DG interconnections affect the system during faults. Time-domain simulations are used to perform those studies. For short-term voltage stability, voltage dips at load buses are monitored following a large disturbance. The maximum rotor speed deviations of centralized synchronous generators are used to study the transient stability of the overall system.
All of the indices defined above are tested on three commonly used test systems: the IEEE RTS-96 24-bus system, the IEEE 39-bus New England system and the IEEE 118 bus system. The studies conclude that, regardless of its technology, DG mostly improves the long-term voltage stability particularly when located in areas near large loads. With DG injecting reactive power, the voltage security margin is increased. Synchronous machine based DG has the greatest impact on the short-term stability when located near large centralized generators. For short-term voltage stability, the contribution of DG is most noticeable when it absorbs reactive power, thus lowering the voltage dips.
La pénétration de la production décentralisée (DG) ne cesse de croître dans les réseaux électriques. La structure des réseaux conventionnels est modifiée à cause de la présence des sources de puissance alternatives localisées au niveau de la distribution. La stabilité du système est donc étudiée afin de déterminer les conséquences de la grande pénétration de DG.
La stabilité de tension devient une préoccupation majeure de la plupart des utilités dont leur capacité de charge approche les limites. Plusieurs utilités ont mis en uvre des solutions à long terme pour contrer ce problème, telles que l'implémentation de nouvelles lignes de transmission et de nouvelles centrales électriques afin de garantir la fiabilité du réseau électrique. D'autres utilités ont opté à des solutions plus modernes telles que la production décentralisée qui satisfait les contraintes économiques, techniques et environnementales.
Concernant l'analyse de la stabilité de tension à long terme, des indices basés sur la tension sont implémentés à l'aide des courbes PV pour analyser la contribution de la DG. La haute pénétration de la DG a également un impact sur la stabilité à court terme du système. Les indices sont mis au point pour classifier les défauts et exposer les effets des différentes interconnexions de la DG sur le réseau. Ces études ont été performées à l'aide de plusieurs simulations. Concernant la stabilité de tension à court terme, les creux de tension qui apparaissent à la charge lors d'un défaut sont utilisés pour déterminer la stabilité du système. Les plus grands écarts de vitesse du rotor des générateurs synchrones centralisés aident à déterminer la stabilité transitoire du réseau.
Ces indices sont testés en utilisant trois réseaux électriques. Indépendamment de la technologie, les DGs améliorent la stabilité de tension à long terme quand elles sont situées proches des grosses charges. La stabilité de tension est augmentée lorsque les DG opèrent avec un facteur de puissance inductif. Les DGs basées sur des machines synchrones améliorent le plus la stabilité à court terme, lorsqu'elles sont situées proche des grands générateurs centralisés. Pour la stabilité de tension à court terme, la contribution de la DG est plus visible quand elle opère avec un facteur de puissance capacitif.
YANG, Demao. "Compression Stability of High Strength Steel Sections with Low Strain-Hardening." University of Sydney. School of Civil Engineering, 2003. http://hdl.handle.net/2123/561.
Full textLau, Ka. "Effects of biopolymer on stability mechanisms of aerated high-sugar confectionery." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426843.
Full textMcDowell, John Christopher. "Preparation characterisation and stability of selected high critical temperature ceramic superconductors." Thesis, University of Ulster, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260854.
Full textNorcio, Lawrence P. "Stability studies of coal liquid products using high performance liquid chromatography." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=984.
Full textTitle from document title page. Document formatted into pages; contains xi, 152 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 127-133).
Hu, Rui Ph D. Massachusetts Institute of Technology. "Stability analysis of natural circulation in BWRs at high pressure conditions." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/46431.
Full textIncludes bibliographical references (leaves 112-115).
At rated conditions, a natural circulation boiling water reactor (NCBWR) depends completely on buoyancy to remove heat from the reactor core. This raises the issue of potential unstable flow. oscillations. The objective of this work is to assess the characteristics of stability in a NCBWR at rated conditions, and the sensitivity to design and operating conditions in comparison to previous BWRs. Two kinds of instabilities, namely Ledinegg flow excursion and Density Wave Oscillations (DWO), have been studied. The DWO analyses were conducted for three oscillation modes: Single Channel thermal-hydraulic stability, coupled neutronics region-wide out-of-phase stability and core-wide in-phase stability. Using frequency domain methods, the three types of DWO stability characteristics of the NCBWR and their sensitivity to the operating parameters and design features have been determined. The characteristic equations are constructed from linearized equations, which are derived for small deviations around steady operating conditions. The Economic Simplified Boiling Water Reactor (ESBWR) is used in our analysis as a reference NCBWR design. It is found that the ESBWR can be stable with a large margin around the operating conditions by proper choice of the core inlet orifice scheme, and for appropriate power to flow ratios. In single channel stability analysis, neutronic feedback is neglected. Design features of the ESBWR, including shorter fuel bundle and use of part-length rods in the assemblies, tend to improve the thermal-hydraulic stability performance. However, the thermal-hydraulic stability margin is still lower than that of a typical BWR at rated conditions. In neutronic-coupled out-of-phase as well as in-phase stability analysis, the perturbation decay ratios for ESBWR at our assumed conditions are higher than that of a typical BWR (Peach Bottom 2) at rated conditions, due to its lower thermal-hydraulic stability margin and higher neutronic feedback.
(cont.) Nevertheless, the stability criteria are satisfied. To evaluate the NCBWR stability performance, comparison with BWR/Peach Bottom 2 at both the rated condition and maximum natural circulation condition has been conducted. Sensitivity studies are performed on the effects of design features and operating parameters, including chimney length, inlet orifice coefficient, power, flow rate, and axial power distribution, reactivity coefficients, fuel pellet-clad gap conductance. It can be concluded that the NCBWR and BWR stabilities are similarly sensitive to operating parameters.
by Rui Hu.
S.M.
Nelson, Weston McClain. "Spin Stability of Sounding Rocket Secondary Payloads Following High Velocity Ejections." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1961.
Full textSharma, Abhinav. "ESTIMATING THE EFFECTS OF BLASTING VIBRATIONS ON THE HIGH-WALL STABILITY." UKnowledge, 2017. https://uknowledge.uky.edu/mng_etds/38.
Full textYao, Yiying. "Thermal Stability of Al₂O₃/Silicone Composites as High-Temperature Encapsulants." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50593.
Full textPh. D.
Yakusheva, Anastasia A. "Devitrification Kinetics and Optical Stability of Optical Fibers at High Temperatures." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83487.
Full textMaster of Science
Sen, Shiladitya. "Engineering Proteins for Enhanced Stability using High-throughput and Combinatorial methods." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385987653.
Full textHamza, Haval Rawf. "The impacts of high-frequency trading on the financial markets’ stability." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1428416050.
Full textTamimi, Ala. "Voltage stability limits for weak power systems with high wind penetration." Diss., Kansas State University, 2011. http://hdl.handle.net/2097/13100.
Full textDepartment of Electrical and Computer Engineering
Anil Pahwa
Shelli K. Starrett
Analysis of power system voltage stability has practical value in increasing wind penetration levels. As wind penetration levels increase in power systems, voltage stability challenges arise due to locating wind resources far away from load centers. This dissertation presents several different voltage stability methods for sizing new wind farms. Power system wind penetration levels depend on the available voltage stability margins (VSMs) of the existing power system and system load characteristics. Three new iterative methods have been developed to maximize wind penetration level in weak power systems based on systems’ VSMs. The first two methods use an iterative approach for increasing the size of each wind farm until reaching the collapse point. Wind farms with less negative impact on system VSMs are sized larger than others. A third wind farm sizing method has been developed using modal analysis in conjunction with the traditional voltage stability method (Q-V method). Wind farms are placed at buses in the power system which have the lowest negative impact on voltage instability modes (strong wind injection buses). By placing the wind farms at the strongest wind injection buses, higher amounts of wind power can be injected into the power system. To further increase wind penetration in weak power systems, two additional techniques are introduced and applied to the western Kansas power system. The first technique uses modes of voltage instability to place voltage support equipment like static var compensators at locations in the power system where they provide the needed reactive power support for increasing levels of wind penetration. The second technique uses the fact that wind patterns at a wind farm site may rarely allow the wind farm to produce its maximum capacity during the peak loading hours. Wind farm maximum sizes can be increased above their maximum voltage stable size limit without driving the power system into becoming voltage unstable. Preventing voltage collapse for the additional increases in wind farm sizes is accomplished by disconnecting some wind turbines inside the wind farm during critical times to reduce its power output to a voltage stable level.
Garby, Romain. "Simulations of flame stabilization and stability in high-pressure propulsion systems." Phd thesis, Toulouse, INPT, 2013. http://oatao.univ-toulouse.fr/9706/1/garby.pdf.
Full textAndersson, Joel, and Ludvig Hagberg. "Stability Analysis of High Concrete Dams : Longtan Dam - a case study." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-67719.
Full textGrizio, Miranda. "Optimizing emulsion stability of high-oil pourable dressings using different stabilizers." Kansas State University, 2011. http://hdl.handle.net/2097/9202.
Full textDepartment of Food Science Institute
Fadi M. Aramouni
To find an optimal formulation of oil-in-water (O/W) emulsion pourable dressings containing 60% and 70% soybean oil, nine stabilizers common to the dressing industry were tested, each at three concentrations. The stabilizers tested were xanthan gum, propylene glycol alginate (PGA), a xanthan gum/guar gum/sodium alginate blend, a viscosifying modified corn starch, an emulsifying modified corn starch, microcrystalline cellulose (MCC), liquid salted egg yolks, liquid salted whole eggs, and dried egg whites (DEW). The emulsions were made with a laboratory high shear disperser and evaluated over 8 weeks by measurement of creaming in 100- mL graduated cylinders and by change in viscosity as measured by a Brookfield viscometer. The stabilizers and concentrations most effective at preventing separation and maintaining viscosity were MCC at 1%, 2%, and 3% in the 60% oil emulsion and 0.25% xanthan gum in the 70% oil emulsion. Average viscosities ranged from 3300 - 23,400 centipoise (cP). The emulsifying starch and dried egg whites were also effective at preventing creaming, but failed to maintain viscosity. The other ingredients showed some initial emulsion stability followed by either a gradual or sudden decrease in stabilization, as seen by decreasing viscosity and eventual separation.
Blank, V. D., A. N. Kirichenko, A. K. Aseev, V. N. Denisov, I. A. Perezhogin, B. A. Kulnitskiy, and A. A. Nuzhdin. "Influence of Shear Deformation on Carbon Onions Stability under High Pressure." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35018.
Full textOrtega, Gómez Tino [Verfasser]. "Stability analysis of the high performance light water reactor / Tino Ortega Gómez." Karlsruhe : Forschungszentrum Karlsruhe, 2009. http://d-nb.info/994365624/34.
Full textRojko, Roman. "New concepts for transverse beam stability in high-current heavy-ion synchrotrons." Phd thesis, Berlin : Dissertation.de, 2003. http://elib.tu-darmstadt.de/diss/000382.
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