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1
Halbe, Chaitanya Vishwajit. "Effects of Two-Phase Flow in a Multistage Centrifugal Compressor". Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73305.
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The performance of a vapor compression system is known to be affected by the ingestion of liquid droplets in the compressor. In these multiphase flows, the liquid and the vapor phase are tightly coupled. Therefore the interphase heat, mass and momentum transfer as well as droplet dynamics including droplet breakup and droplet-wall interactions play a vital role in governing these flows. Only thermodynamic analyses or two-dimensional mean-line calculations are not sufficient to gain an in-depth understanding of the complex multiphase flow field within the compressor. The objective of this research was to extend the current understanding of the operation of a multistage centrifugal compressor under two-phase flow conditions, by performing three-dimensional computational analysis.
In this work, two-phase flow of a single constituent (refrigerant R134a) through a two-stage, in-line centrifugal compressor was analyzed using CFD. The CFD model accounted for real gas behavior of the vapor phase. Novel user defined routines were implemented to ensure accurate calculations of interphase heat, mass and momentum transfer terms and to model droplet impact on the compressor surfaces. An erosion model was developed and implemented to locate the erosion "hot spots" and to estimate the amount of material eroded.
To understand the effects of increasing liquid carryover, the mass flow rate of the liquid phase was increased from 1% to 5% of the vapor mass flow rate. The influence of droplet size on the compressor performance was assessed by varying the droplet diameter at the inlet from 100 microns to 400 microns. The results of the two-phase flow simulations were compared with the simulation involving only the vapor phase.
Liquid carryover altered the flow field within the compressor, and as a result, both impellers were observed to operate at off-design conditions. This effect was more pronounced for the second impeller. The overall effects of liquid carryover were detrimental to the compressor performance. The erosion calculations showed maximum erosion potential on the blade and shroud of the first impeller.
The results from this investigation provided new and useful information that can be used to support improved design solutions.Ph. D.
2
Fiery, Michael Allen. "A form of two-phase sampling utilizing regression analysis". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4312.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains iv, 81 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 32).
3
Ninov, Valentin. "Two-dimensional zero-phase FIR filter design with nonuniform frequency sampling". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/MQ43655.pdf.
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ZHU, GUOHUA. "ASCERTAINMENT IN TWO-PHASE SAMPLING DESIGNS FOR SEGREGATION AND LINKAGE ANALYSIS". Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1112844349.
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Zhu, Guohua. "Ascertainment in two-phase sampling designs for segregation and linkage analysis /". Connect to text online, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1112844349.
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Thesis (Ph. D.)--Case Western Reserve University, 2005.[School of Medicine] Department of Epidemiology and Biostatistics. Includes bibliographical references. Available online via OhioLINK's ETD Center.
6
Nan, Bin. "Information bounds and efficient estimates for two-phase designs with lifetime data /". Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9587.
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Patel, Sonal. "Determination of Phase Equilibria and the Critical Point Using Two-Phase Molecular Dynamics Simulations with Monte Carlo Sampling". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3587.
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The two-phase MD technique employed in this work determines the liquid and vapor phase densities from a histogram of molecular densities within phase clusters in the simulation cell using a new Monte Carlo (MC) sampling method. These equilibrium densities are then fitted in conjunction with known critical-point scaling laws to obtain the critical temperature, and the critical density. This MC post-processing method was found to be more easily implemented in code, and it is efficient and easily applied to complex, structured molecules. This method has been successfully applied and benchmarked for a simple Lennard-Jones (LJ) fluid and a structured molecule, propane. Various degrees of internal flexibility in the propane models showed little effect on the coexisting densities far from critical point, but internal flexibility (angle bending and bond vibrations) seemed to affect the saturated liquid densities in the near-critical region, changing the critical temperature by approximately 20 K. Shorter cutoffs were also found to affect the phase dome and the location of the critical point. The developed MD+MC method was then used to test the efficacy of two all-atom, site-site pair potential models (with and without point charges) developed solely from the energy landscape obtained from high-level ab initio pair interactions for the first time. Both models produced equivalent phase domes and critical loci. The model's critical temperature for methanol is 77 K too high while that for 1-propanol is 80 K too low, but the critical densities are in good agreement. These differences are likely attributable to the lack of multi-body interactions in the true pair potential models used here. Lastly, the transferability of the ab initio potential model was evaluated by applying it to 1-pentanol. An attempt has been made to separate the errors due to transferability of the potential model from errors due to the use of a true-pair potential. The results suggested a good level of transferability for the site-site model. The lack of multi-body effects appears to be dominant weakness in using the generalized ab initio potential model for determination of the phase dome and critical properties of larger alcohols.
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Chatterjee, Nilanjan. "Semiparametric inference based on estimating equations in regression models for two phase outcome dependent sampling /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/8959.
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Ning, Shuluo. "Bayesian Degradation Analysis Considering Competing Risks and Residual-Life Prediction for Two-Phase Degradation". Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1339559200.
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Camci, Gulden. "Application Of Isokinetic Sampling Technique For Local Solid Densities In Upward Liquid-solid Flows Through An Annulus". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1089796/index.pdf.
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In this study, radial solid density distributions in upward flowing water-feldspar mixtures through a concentric annulus were investigated. Local solid density measurements were performed at a test cross-section in the fully developed flow region of a concentric annulus, which is a part of a closed-loop system consisting of a head tank, a variable speed slurry pump, an orificemeter, a heat exchanger, an annulus, a temperature probe, and a drain line. The solid particles with mean diameters of 72 and 138 
m at two different feed solid concentrations of 1 and 2 % v/v were used in the prepared slurries. The dependent variables being local solid density, local mixture velocity, and axial frictional pressure drop along the test-section, an experimental work was performed to obtain the radial solid density profiles and axial pressure gradients at different operating conditions. To determine the local solid densities, a sampling probe was used. At the beginning, this probe was used as a pitot tube to measure the local velocities in the test cross-section. Making use of these data, local solid densities were measured with the same probe under isokinetic and nonisokinetic conditions to compare both. For this purpose, an isokinetic sampling unit was designed and constructed to withdraw the samples under isokinetic flow conditions, at which the sampling velocity in the probe equated to the true flow velocity in the annulus very closely. The required constant back-pressure was supplied by pressurized N2 gas to equate these velocities to each other. The amounts of solids in the slurry samples collected at seven different radial locations in the test area under isokinetic and non-isokinetic conditions were determined by the gravimetric method. Local solid densities showed more uniform trends at the feed solid concentration of 1% v/v than those at 2% v/v. Increasing the feed solid concentration and particle size changed the shape of these profiles. The obtained local solid densities were generally higher near the outer wall than those near the inner wall
this result was consistent with the literature. As a general trend, local solid densities showed a decreasing trend at around a dimensionless radial distance of &
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=0.4, where the slurry velocity profile had its maximum value. It was observed that the two-phase axial frictional pressure gradients along the test section in the fully developed flow region increased with increasing feed solid concentration and the particle size at a constant slurry flow rate. Isokinetic sampling results showed that the local solid densities increased consistently with the increasing slurry velocity at all radial distances in the annular gap, while this trend was not observed clearly in the non-isokinetic measurements. Also the variations of the local solid densities along the radial distance were more obvious in the isokinetic results while these variations were obscured under nonisokinetic conditions by the experimental error at a higher level.
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Gao, Yong. "A Degradation-based Burn-in Optimization for Light Display Devices with Two-phase Degradation Patterns considering Warranty Durations and Measurement Errors". Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1509109739168013.
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Butkuvienė, Rita. "Baigtinės populiacijos parametrų įvertinių tikslumo tyrimas modeliuojant". Master's thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130617_111757-43302.
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Baigiamajame magistro darbe nagrinėjamas nuoseklusis ėmimas, priklausantis pozicinių imties planų su fiksuota rikiuojančio skirstinio forma klasei. Šio imties plano atveju gautos imties plano ir populiacijos elementų priklausymo imčiai tikimybių analizinės išraiškos. Remiantis entropija, nuoseklusis ėmimas yra lyginamas su tai pačiai klasei priklausančiais Pareto ir nuosekliuoju Puasono ėmimu. Nagrinėjamas ir dviejų fazių imties planas sluoksniavimui, taikant pirmosios fazės nuoseklųjį ėmimą. Baigtinėje populiacijoje apibrėžto tyrimo kintamojo reikšmių suma vertinama kvazi Horvico ir Tompsono įvertiniu. Modeliuojant tiriama, ar sumažėja įvertinio dispersija dėl antrosios fazės sluoksniavimo. Šiame tyrime naudojami Lietuvos gyventojų užimtumo statistinio tyrimo duomenys, vertinamas užimtųjų ir bedarbių skaičius, nedarbo lygis.The successive sampling design, belonging to the class of order sampling designs with fixed order distribution shape, is studied. Analytical expressions for design probability and element inclusion probability are obtained. Entropy is used to compare successive, Pareto and sequential Poisson sampling designs, belonging to the same class. Two-phase sampling design for stratification with the first-phase order sampling is also studied. The total of the study variable values, defined on a finite population, is estimated by a quasi-Horwitz-Thompson estimator. The behaviour of the variance estimator influenced by the second phase stratification is investigated by simulation. The study is carried out for estimates of the number of employed, unemployed and the unemployment rate using the Lithuanian Labor Force Survey data.
13
Prasser, Horst-Michael. "3. Workshop "Meßtechnik für stationäre und transiente Mehrphasenströmungen", 14. Oktober 1999 in Rossendorf". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-30118.
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Am 14. Oktober 1999 wurde in Rossendorf die dritte Veranstaltung in einer Serie von Workshops über Meßtechnik für stationäre und transiente Mehrphasenströmungen durchgeführt. Dieses Jahr kann auf auf 11 interessante Vorträge zurückgeblickt werden. Besonders hervorzuheben sind die beiden Hauptvorträge, die von Herrn Professor Hetsroni aus Haifa und Herrn Dr. Sengpiel aus Karlsruhe gehalten wurden. Erneut lag ein wichtiger Schwerpunkt auf Meßverfahren, die räumliche Verteilungen von Phasenanteilen und Geschwindigkeiten sowie die Größe von Partikeln bzw. Blasen der dispersen Phase zugänglich machen. So wurde über einen dreidimensional arbeitenden Röntgentomographen, ein Verfahren zur Messung von Geschwindigkeitsprofilen mit Gittersensoren und eine Methode zur simultanen Messung von Blasengrößen sowie Feldern von Gas- und Flüssigkeitsgeschwindigkeit mit einer optischen Partikelverfolgungstechnik vorgetragen. Daneben wurden interessante Entwicklungen auf dem Gebiet der lokalen Sonden vorgestellt, wie z.B. eine Elektrodiffusionssonde. Neue meßtechnische Ansätze waren ebenfalls vertreten; hervorzuheben ist der Versuch, die Methode der optischen Tomographie für die Untersuchung von Zweiphasenströmungen nutzbar zu machen. Der Tagungsband enthält die folgenden Beiträge: S. John, R. Wilfer, N. Räbiger, Universität Bremen, Messung hydrodynamischer Parameter in Mehrphasenströmungen bei hohen Dispersphasengehalten mit Hilfe der Elektrodiffusionsmeßtechnik E. Krepper, A. Aszodi, Forschungszentrum Rossendorf, Temperatur- und Dampfgehaltsverteilungen bei Sieden in seitlich beheizten Tanks D. Hoppe, Forschungszentrum Rossendorf, Ein akustisches Resonanzverfahren zur Klassifizierung von Füllständen W. Sengpiel, V. Heinzel, M. Simon, Forschungszentrum Karlsruhe, Messungen der Eigenschaften von kontinuierlicher und disperser Phase in Luft-Wasser-Blasenströmungen R. Eschrich, VDI, Die Probestromentnahme zur Bestimmung der dispersen Phase einer Zweiphasenströmung U. Hampel, TU Dresden, Optische Tomographie O. Borchers, C. Busch, G. Eigenberger, Universität Stuttgart, Analyse der Hydrodynamik in Blasenströmungen mit einer Bildverarbeitungsmethode C. Zippe, Forschungszentrum Rossendorf, Beobachtung der Wechselwirkung von Blasen mit Gittersensoren mit einer Hochgeschwindigkeits-Videokamera H.-M. Prasser, Forschungszentrum Rossendorf, Geschwindigkeits- und Durchflußmessung mit Gittersensoren
14
Prasser, Horst-Michael. "3. Workshop "Meßtechnik für stationäre und transiente Mehrphasenströmungen", 14. Oktober 1999 in Rossendorf". Forschungszentrum Rossendorf, 1999. https://hzdr.qucosa.de/id/qucosa%3A21838.
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Am 14. Oktober 1999 wurde in Rossendorf die dritte Veranstaltung in einer Serie von Workshops über Meßtechnik für stationäre und transiente Mehrphasenströmungen durchgeführt. Dieses Jahr kann auf auf 11 interessante Vorträge zurückgeblickt werden. Besonders hervorzuheben sind die beiden Hauptvorträge, die von Herrn Professor Hetsroni aus Haifa und Herrn Dr. Sengpiel aus Karlsruhe gehalten wurden. Erneut lag ein wichtiger Schwerpunkt auf Meßverfahren, die räumliche Verteilungen von Phasenanteilen und Geschwindigkeiten sowie die Größe von Partikeln bzw. Blasen der dispersen Phase zugänglich machen. So wurde über einen dreidimensional arbeitenden Röntgentomographen, ein Verfahren zur Messung von Geschwindigkeitsprofilen mit Gittersensoren und eine Methode zur simultanen Messung von Blasengrößen sowie Feldern von Gas- und Flüssigkeitsgeschwindigkeit mit einer optischen Partikelverfolgungstechnik vorgetragen. Daneben wurden interessante Entwicklungen auf dem Gebiet der lokalen Sonden vorgestellt, wie z.B. eine Elektrodiffusionssonde. Neue meßtechnische Ansätze waren ebenfalls vertreten; hervorzuheben ist der Versuch, die Methode der optischen Tomographie für die Untersuchung von Zweiphasenströmungen nutzbar zu machen. Der Tagungsband enthält die folgenden Beiträge: S. John, R. Wilfer, N. Räbiger, Universität Bremen, Messung hydrodynamischer Parameter in Mehrphasenströmungen bei hohen Dispersphasengehalten mit Hilfe der Elektrodiffusionsmeßtechnik E. Krepper, A. Aszodi, Forschungszentrum Rossendorf, Temperatur- und Dampfgehaltsverteilungen bei Sieden in seitlich beheizten Tanks D. Hoppe, Forschungszentrum Rossendorf, Ein akustisches Resonanzverfahren zur Klassifizierung von Füllständen W. Sengpiel, V. Heinzel, M. Simon, Forschungszentrum Karlsruhe, Messungen der Eigenschaften von kontinuierlicher und disperser Phase in Luft-Wasser-Blasenströmungen R. Eschrich, VDI, Die Probestromentnahme zur Bestimmung der dispersen Phase einer Zweiphasenströmung U. Hampel, TU Dresden, Optische Tomographie O. Borchers, C. Busch, G. Eigenberger, Universität Stuttgart, Analyse der Hydrodynamik in Blasenströmungen mit einer Bildverarbeitungsmethode C. Zippe, Forschungszentrum Rossendorf, Beobachtung der Wechselwirkung von Blasen mit Gittersensoren mit einer Hochgeschwindigkeits-Videokamera H.-M. Prasser, Forschungszentrum Rossendorf, Geschwindigkeits- und Durchflußmessung mit Gittersensoren
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陳振桐. "Bayesian Two-Phase Sampling". Thesis, 1997. http://ndltd.ncl.edu.tw/handle/91455459142790599271.
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Ling-YuHsu i 許伶伃. "Utilization of the Multivariate Analysis Techniques on Model-Based Two-Phase Sampling Selection". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/f4zmus.
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Risticevic, Sanja. "Solid phase microextraction coupled to comprehensive two-dimensional gas chromatography–time-of-flight mass spectrometry for metabolite profiling of apples: Potential of non-invasive in vivo sampling assay in characterization of metabolome". Thesis, 2012. http://hdl.handle.net/10012/7006.
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The objective of the current research project relies on implementation of solvent-free, green and environmentally friendly solid phase microextraction (SPME) sample preparation alternative in the area of complex sample characterization. The advantages that the technique offers in comparison to traditional methods of sample preparation including solvent-free implementation, short sample preparation times, small sample amount requirements, advanced automation capability and minimization of matrix effects are effectively employed during ex vivo and laboratory investigations of complex samples. More important, the underlying features of the technique including miniaturized format, nonexhaustive extraction recoveries and on-site compatibility were fully exploited in order to investigate the metabolome of biological systems directly on the site. Hence, in vivo SPME extraction format was employed in direct immersion SPME sampling of biological systems, hence eliminating the crucial prerequisites associated with multiple preparative steps and incorporation of metabolism quenching that are encountered during implementation of traditional sample preparation methods in global metabolite analysis. Furthermore, in vivo sampling format was hyphenated to comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GCxGC-ToFMS) for high-resolution sampling of volatile and semivolatile metabolites in ‘Honeycrisp’ apples.
The initial stages of the project involved evaluation of performance characteristics of commercial SPME extraction coatings in terms of extraction selectivity, extraction sensitivity and desorption efficiency by employing headspace SPME analysis of both aqueous standards spiked with representative volatile and semivolatile metabolites as well as the apple homogenate. DVB/CAR/PDMS coating was selected on the basis of optimum metabolite coverage and extraction sensitivity and was consequently employed during ex vivo and in vivo sampling assays corresponding to determination of volatile and semivolatile metabolites. The former extraction methodology incorporated appropriate sample preparation steps for quenching metabolic activity so that the relevant metabolome profile is not biased against unstable metabolites and those that are susceptible to inter-metabolite conversions which adversely impact preservation of metabolite identity. The two sample preparation assays were compared in terms of metabolite coverage and analytical precision in order to identify SPME route toward characterization of more representative metabolome and determination of instantaneous and more ‘true’ metabolism snapshoot. This is the first report illustrating the implementation of in vivo direct immersion SPME assay for non invasive determination of endogenous fruit metabolites whose profiles and contents are highly correlated to a multitude of influential fruit quality traits.
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Béliveau, Audrey. "Estimation simplifiée de la variance dans le cas de l’échantillonnage à deux phases". Thèse, 2011. http://hdl.handle.net/1866/6279.
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Dans ce mémoire, nous étudions le problème de l'estimation de la variance pour les estimateurs par double dilatation et de calage pour l'échantillonnage à deux phases. Nous proposons d'utiliser une décomposition de la variance différente de celle habituellement utilisée dans l'échantillonnage à deux phases, ce qui mène à un estimateur de la variance simplifié. Nous étudions les conditions sous lesquelles les estimateurs simplifiés de la variance sont valides. Pour ce faire, nous considérons les cas particuliers suivants : (1) plan de Poisson à la deuxième phase, (2) plan à deux degrés, (3) plan aléatoire simple sans remise aux deux phases, (4) plan aléatoire simple sans remise à la deuxième phase. Nous montrons qu'une condition cruciale pour la validité des estimateurs simplifiés sous les plans (1) et (2) consiste à ce que la fraction de sondage utilisée pour la première phase soit négligeable (ou petite). Nous montrons sous les plans (3) et (4) que, pour certains estimateurs de calage, l'estimateur simplifié de la variance est valide lorsque la fraction de sondage à la première phase est petite en autant que la taille échantillonnale soit suffisamment grande. De plus, nous montrons que les estimateurs simplifiés de la variance peuvent être obtenus de manière alternative en utilisant l'approche renversée (Fay, 1991 et Shao et Steel, 1999). Finalement, nous effectuons des études par simulation dans le but d'appuyer les résultats théoriques.In this thesis we study the problem of variance estimation for the double expansion estimator and the calibration estimators in the case of two-phase designs. We suggest to use a variance decomposition different from the one usually used in two-phase sampling, which leads to a simplified variance estimator. We look for the necessary conditions for the simplified variance estimators to be appropriate. In order to do so, we consider the following particular cases : (1) Poisson design at the second phase, (2) two-stage design, (3) simple random sampling at each phase, (4) simple random sampling at the second phase. We show that a crucial condition for the simplified variance estimator to be valid in cases (1) and (2) is that the first phase sampling fraction must be negligible (or small). We also show in cases (3) and (4) that the simplified variance estimator can be used with some calibration estimators when the first phase sampling fraction is negligible and the population size is large enough. Furthermore, we show that the simplified estimators can be obtained in an alternative way using the reversed approach (Fay, 1991 and Shao and Steel, 1999). Finally, we conduct some simulation studies in order to validate the theoretical results.