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A flowing afterglow source of NF(b¹(sigma)+): quenching rate constant measurementsLin, Daimay. January 1984 (has links)
Call number: LD2668 .T4 1984 L56 / Master of Science
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Numerical modelling of the insect respiratory system and gas flowSimelane, Simphiwe January 2015 (has links)
A thesis submitted in fulflment of the requirements
for the degree of Doctor of Philosophy
in the
School of Computer Science and Applied Mathematics. November 2015 / The understanding of
uid
ow at microscale geometrics is an increasingly important eld in
applied science and mechanics, especially in bioinspiration and biomimetics. These elds seek to
imitate processes and systems in biology to design improved e cient engineering devices. In this
thesis, inspired by the e ciency of the insect tracheal system in transporting respiratory gases
at microscale, mathematical models that both mimic and explain the gas exchange process are
developed. Models for the simultaneous movement of respiratory gases across the insect spiracle,
gas transfer from one respiratory chamber to the next, end di usion and tissue absorption at
the tracheole tips, and tracheal
uid transport are presented. Expressions for tracheal partial
pressures of the respiratory gases, rate of change of gas concentrations, rate of tracheal volume
change, spiracle behaviour on net gas
ow, cellular respiration and tissue absorption, and global
gas movement within the insect are presented as well.
Two versions of bioinspired pumping mechanism that is neither peristaltic nor belongs to
impedance mismatch class of pumping mechanism are then presented. A paradigm for se-
lectively pumping and controlling gases at the microscale in a complex network of channels is
presented. The study is inspired by the internal
ow distributions of respiratory gases produced
by rhythmic wall contractions in dung beetle tracheal networks. These networks have been
shown to e ciently manage
uid
ow compared to current produced micro
uidic devices. The
insect-like pumping models presented are expected to function e ciently in the microscale
ow
regime in a simple or complex network of channels. Results show the ability to induce a unidi-
rectional net
ow by using an inelastic channel with at least two moving contractions. These
results might help in explaining some of the physiological systems in insects and may help in
fabricating novel e cient micro
uidic devices.
In this study, both theoretical and the Di erential Transform Method are used to solve the
exible trachea with gas exchange problem as well as the 2D viscous
ow transport with or
without prescribed moving wall contractions problem. Both Lubrication theory and quasi-
steady approximations at low Reynolds number are used in the derivation of theoretical analysis.
ii
Moreover, an analytical investigation into the compressible gas
ow with slight rarefactions
through the insect trachea and tracheoles is undertaken, and a complete set of asymptotic
analytical solutions is presented. Then, estimation of the Reynolds and Mach numbers at the
channel terminal ends where the tracheoles directly deliver the respiratory gases to the cells
is obtained by comparing the magnitude of the di erent forces in the compressible gas
ow.
The 2D Navier-Stokes equations with a slip boundary condition are used to investigate the
compressibility and rare ed e ects in the respiratory channels.
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Computational modeling of Lorentz force induced mixing in alkali seeded diffusion flamesThompson, Jon Ira 21 November 1994 (has links)
Lorentz forces provide a unique method for the control and mixing of gas
flows without the physical intrusion of objects into the flow. Lorentz forces arise
when an electric current is passed through a volume in the presence of a magnetic
field. The interaction between the electric current and the electric and magnetic
fields produces a body force which affects the flow. These forces have been
investigated experimentally by other researchers and show promise as a way to
accelerate combustion in diffusion flames by increasing the mixing rate of fuel and
oxidant streams. Theoretical and numerical models were developed to gain insight
into this process.
Alkali metal seeding raises the electrical conductivity of a flame by two to
three orders of magnitude. This has two significant effects: the Lorentz force
becomes stronger for the same applied electric current and magnetic field, and the
alkali seed concentration becomes a dominant factor in determining electrical
conductivity of seeded gases. This makes electrical conductivity much easier to
predict, and so the Lorentz body force produced is easier to determine.
A theoretical basis for numerical modeling of reactive flows with variable
body forces has been developed. Many issues are important in simulating gas
flows. Conservation of chemical species must be carefully maintained. Mass
transport by gaseous diffusion, which limits combustion rates in a diffusion flame,
must be appropriately modeled. Viscous action is also important, since it promotes
mixing of the fuel and oxidant streams. Convective, conductive, and diffusive
transport of energy must be carefully treated since energy transport directly affects
the fluid flow.
A numerical model of an incompressible gas flow affected by Lorentz forces
was written and tested. Although assumptions made in the model, such as
isothermal conditions and uniform density, are not found in diffusion flames, the
numerical model predicts velocity vector patterns similar to those observed in actual
Lorentz force tests on diffusion flames.
A simulation code for compressible, reactive gas flows which include
Lorentz forces has also been written. Several parts of the model have been
validated, and the approach used appears likely to produce successful simulations.
Further validation studies will be required, however, before complete modeling of
the diffusion flame can proceed. / Graduation date: 1995
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PSPの低圧力域における基礎特性に関する研究新美, 智秀, NIIMI, Tomohide, 吉田, 昌記, YOSHIDA, Masaki, 近藤, 誠, KONDO, Makoto, 大島, 佑介, OSHIMA, Yusuke, 森, 英男, MORI, Hideo, 江上, 泰広, EGAMI, Yasuhiro, 浅井, 圭介, ASAI, Keisuke, 西出, 宏之, NISHIDE, Hiroyuki 12 1900 (has links)
No description available.
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CFD evaluation of pipeline gas stratification at low fluid flow due to temperature effectsBrar, Pardeep Singh 17 February 2005 (has links)
It has been found through experiments at Southwest Research Institute that temperature
differences between the gas and wall of the pipe through which the gas is flowing can
greatly influence the gas flow in the pipe line and give different velocity magnitudes at
the top and bottom half of the pipe. The effect on the flow is observed to worsen at low
fluid flow and high temperature differences. This effect has been observed by ultrasonic
flow meters which measure the chord average gas velocity at four heights across the pipe.
A significant variance in chord averaged velocities is apparent at these conditions. CFD
analysis was performed. Low flow velocities of 0.1524 m/sec, 0.3048 m/sec and 0.6096
m/sec and temperature differences of 5.5oK, 13.8oK and 27.7oK were considered. When
these conditions were imposed onto the three different geometries, it was seen that the
heating caused increased errors in the ultrasonic meter response. For the single elbow and
double elbow pipe configurations, the errors were below 0.5% for constant wall
temperature conditions but rose to 1% for sinusoid varying wall temperature conditions.
The error was seen to increase as the axial velocity became more stratified due to
momentum or temperature effects. The case of maximum error was noted for the double
elbow geometry with sinusoid wall temperature condition where a swirl type of flow was
noted to create localized velocity maxima at the center of the pipe. This part of the pipe
was barely touched by the ultrasonic meter acoustic path giving maximum error of 1.4%.
A thermal well was placed in the path of the gas flow in the pipe to observe the
temperature response on the surface of the thermal well. It was noted that the thermal
well surface temperature differed by 1.4% for most cases with gas velocity below 0.6096
m/sec.
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Gas flow sputtering of Cu(In,Ga)Se2 with extra selenium supplyTurunen, Marcus January 2015 (has links)
In this thesis CIGS absorber layers have been deposited by gas flow sputtering with an extra supply of selenium, a method that displays promise for large scale production because of its one-step sputtering route which deposits low energy particles in a high deposition rate. In this thesis a method was developed where selenium was added to the sputtering process inside the sputter chamber in a controllable manner and in larger amount than done in previous projects. A total of five samples were manufactured with altered evaporation temperatures and an extra supply of selenium which then were finalized to solar cells using the standard baseline process of the Ångström solar center. The characteristics of the CIGS layer and solar cells were analyzed by XRF, IV- and QE measurements. A cell with a conversion efficiency of 11.6 %, Jsc of 27.9 mA/cm2, Voc of 0.63 V and fill factor of 66.2 % was obtained on a 0.5 cm2 cell area without an antireflective coating. All samples contained cells with obtained efficiencies above 10 %, but over the whole samples the efficiencies varied considerably. The samples that were deposited with moderately large selenium evaporation provided the highest efficiencies with a relatively good homogeneity over the substrate. Results show a deficiency of copper in the CIGS films compared to the target composition. The copper content was lower than 70 % expressed in Cu/(Ga+In), which probably resulted in a low diffusion length for electrons, leading to limited cell efficiencies. Through the duration of the thesis issues that concerned the power supply- and the controls to the substrate heaters as well as the control of the evaporation temperature during the depositions arose that required problem solving and needs to be resolved for the future progression of this work. The conclusions drawn from this thesis are that it is possible to vary the temperature of the selenium source and thereby control the amount of selenium that evaporates during the deposition process even though there is a lot of additional heating in the sputter chamber from both the substrate heaters and the sputter source which could affect the ability to control the amount of selenium being evaporated. That the most likely reason for the limited efficiencies is due to the low copper content in the CIGS films and that a larger amount of evaporated selenium compared to previous work did not result in higher obtained efficiencies.
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Application of computational fluid dynamics to the analysis of inlet port design in internal combustion enginesChen, Anqi January 1994 (has links)
The present research describes an investigation of the flow through the inlet port and the cylinder of an internal combustion engine. The principal aim of the work is to interpret the effects of the port shape and valve lift on the engine's "breathing" characteristics, and to develop a better understanding of flow and turbulence behaviour through the use of Computational Fluid Dynamics (CFD), using a commercial available package STAR-CD. A complex computational mesh model was constructed, which presents the actual inlet port/cylinder assembly, including a curved port, a cylinder, moving valve and piston. Predictions have been carried out for both steady and transient flows. For steady flow, the influence of valve lift and port shape on discharge coefficient and the in-cylinder flow pattern has been examined. Surface static pressures predicted using the CFD code, providing a useful indicator of flow separation within the port/cylinder assembly, are presented and compared with experimental data. Details of velocity fields obtained by laser Doppler anemometry in a companion study at King's College London, using a steady flow bench test with a liquid working fluid for refractive index matching, compared favourably with the predicted data. For transient flow, the flow pattern changes and the turbulence field evolutions due to valve and piston movement are presented, and indicate the possible source of cyclic variability in an internal combustion engine.
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A three-dimensional direct simulation Monte Carlo methodology on unstructured Delaunay grids with applications to micro and nanoflowsChamberlin, Ryan Earl. January 2007 (has links)
Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: Nanoflow; microflow; unstructured; DSMC. Includes bibliographical references (leaves 171-178).
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CFD study of balcony spill plumes: focused on the balcony area /Ko, Yoon J. January 1900 (has links)
Thesis (M.App.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 144-146). Also available in electronic format on the Internet.
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Experimental study of pressure difference phenomena in rarefied gases /Huang, Chao-Ming, January 1996 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
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