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Boussinesq-equation and rans hybrid wave modelSitanggang, Khairil Irfan 15 May 2009 (has links)
This dissertation presents the development of a novel hybrid wave model, comprised
of the irrotational, 1-D horizontal Boussinesq and 2-D vertical turbulence-closed
Reynolds Averaged Navier-Stokes (RANS) wave models. The two constituents are
two-way coupled with the interface placed at a location where turbulence is relatively
small. Boundary conditions on the interfacing side of each model is provided by its
counterpart model through data exchange, requiring certain transformation due to
the difference in physical variables employed in both models. The model is intended
for large-scale wave simulation, accurate in both the nonbreaking and breaking zones
with relatively coarser grid in the former and finer in latter, and yet efficient.
Hybrid model tests against idealized solitary and standing wave motions and
wave-overtopping on structure exhibit satisfactory to very good agreement. Compared
with pure RANS simulations, the hybrid model saves computational time by
a factor proportional to the reduction in the size of the RANS domain. Also, a
large-scale tsunami simulation is provided for a numerical setup that is practically
unapproachable using RANS alone; not only does the hybrid model offer more rapid
simulation of relatively small-scale problems, it provides an opportunity to examine
very large total domains with the fine resolution typical of RANS simulations.
To allow for implementation on even larger domain with affordable CPU time, the hybrid model is parallelized to run on distributed memory machine. This is done
by parallelizing the RANS model while leaving the Boussinesq model serial. One
of the processors is responsible for both the sub-RANS and Boussinesq calculations.
ICCG(0) for solving the pressure equation is parallelized using the nonoverlappingdecomposition
technique, requiring more iterations than the serial one. Standing
wave and hypothetical tsunami simulations with 960×66 and 1000×100 grids, and
using 8 processors confirm model validity and computational efficiency of 82% and
65%.
Finally, the 2-D Boussinesq model is parallelized using domain decomposition
technique. The solution to the tridiagonal system arising in the model is calculated
as the sum of the homogeneous and particular solutions. Parallel model tests using
up to 32 processors exhibit model accuracy and efficiency of 80% for simulation with
500×500–2000×2000 grids.
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Development of design tool for statically equivalent deepwater mooring systemsUdoh, Ikpoto Enefiok 15 May 2009 (has links)
Verifying the design of floating structures adequately requires both numerical
simulations and model testing, a combination of which is referred to as the
hybrid method of design verification. The challenge in direct scaling of moorings
for model tests is the depth and spatial limitations in wave basins. It is therefore
important to design and build equivalent mooring systems to ensure that the
static properties (global restoring forces and global stiffness) of the prototype
floater are matched by those of the model in the wave basin prior to testing.
A fit-for-purpose numerical tool called STAMOORSYS is developed in this
research for the design of statically equivalent deepwater mooring systems. The
elastic catenary equations are derived and applied with efficient algorithm to
obtain local and global static equilibrium solutions. A unique design page in
STAMOORSYS is used to manually optimize the system properties in search of
a match in global restoring forces and global stiffness. Up to eight mooring lines
can be used in analyses and all lines have the same properties. STAMOORSYS
is validated for single-line mooring analysis using LINANL and Orcaflex, and for
global mooring analysis using MOORANL and Orcaflex. A statically equivalent
deepwater mooring system for a representative structure that could be tested in
the Offshore Technology Research Center at Texas A&M University is then
designed using STAMOORSYS and the results are discussed.
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Hybrid air foil bearing with external pressurizationPark, Soongook 15 May 2009 (has links)
Foil bearings are widely used for oil-free micro turbomachinery. One of the critical technical issues related to reliability of the foil bearings is a coating wear on the top foil and rotor during start/stops. Bearing cooling is also mandatory for certain applications because the foil bearings can generate significant amount of heat depending on operating conditions. Usually axial flow is used through the space between the top foil and bearing sleeve. In this thesis, a hybrid air foil bearing with external pressurization is introduced. The hybrid operation eliminates the coating wear during start-up/shut down, and also reduces drag torque during starts. Furthermore, this hybrid foil bearing does not need cooling system. An experimental test with a loaded bearing under hydrostatic mode demonstrates the high potential of hybrid air foil bearings. The load capacity of the hybrid foil bearing was measured at 20,000 rpm, and compared with that of hydrodynamic foil bearing. The hybrid foil bearing has much higher load capacity than the hydrodynamic foil bearing. The starting torque was also measured and compared with hydrodynamic bearing. A simple analytical model to calculate top foil deflection under hydrostatic pressurization has been developed. Predictions via orbit simulations indicate the hybrid air foil bearings can have a much higher critical speed and onset speed of instability than the hydrodynamic counter part. Major benefits of the hybrid foil bearings also include very low starting torque, reduced wear of the top foil and rotor, and very effective cooling capability by the pressurized air itself. This new concept of hybrid air foil bearings are expected to be widely applied to the oil free turbomachinery industry, especially for heavily loaded and/or high temperature applications.
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Synthesis and Characterization of Polyimide/Clay Hybrid CmpositesYuan, Chih-Hao 29 July 2002 (has links)
Abstract
Organically modified montmorillonite by a long chain alkylammonium surfactant was used to prepare polyimide/clay nanocomposites in this study. Several attempts were made in an effort to achieve fully exfoliated nanocomposites. These included the one-step method, two-step method and in-situ polymerization method. At the same time, the effects of polyimide structures and clay contents were studied. Two dianhydrides and two diamines were used to prepare polyimide/clay nanocomposites via the two-step method. The polyimide/clay nanocomposites with various clay contents from 1.5 ~ 10 wt % were prepared via the two-step method too. The structure of polyimides and the dispersion level of clay were identified by Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometry (XRD). Thermogravimetric analysis (TGA) was performed to demonstrate the thermal stability of the nanocomposites.
TGA and XRD results indicate the surfactants are intercalated into the layers of clay. FTIR results indicate the all polyimides in the nanocomposites are formed successfully. XRD results indicate the BPDA-ODA/clay nanocomposite within 3 % by weight of clay via the two-step method is shown to have the best dispersion level of clay. These results are consistent with observations from TGA. The temperature at 10 % by weight loss of the nanocomposite is 31 ¢J greater than that of pure BPDA-ODA. The formation mechanism of polyimide/clay nanocomposites via the two-step method can be described by three distinct steps. A polyamic acid/clay mixture with an exfoliated morphology is first formed. A portion of solvents and intercalated surfactants are then either degraded or expelled from the clay gallery under thermal imidization, resulting in a reduced gallery height of 1.32 nm. On the other hand, portion of the clay layers show an exfoliated morphology due to the effective surfactant and polyimide molecules. As a result, a partially exfoliated polyimide/clay nanocomposite is obtained.
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Evaluation of the heterotic potential of sorghum [Sorghum bicolor (L.) Moench] adapted to the southern Africa regionMpofu, Leo Thokoza 25 April 2007 (has links)
Sorghum [Sorghum bicolor (L.) Moench] production in Africa is widespread with low yields due to low inputs and the lack of sorghum hybrids. This situation has forced most of these farmers to grow maize hybrids since they are readily available in the seed market. Sorghum hybrids could be used if their potential was demonstrated. The objective of this study is to document the level of heterosis in Southern Africa sorghum germplasm. The performance of 52 F1 grain sorghum hybrids and their parental lines was evaluated in four environments. Measurements for grain yield, panicle exsertion, days to mid anthesis and plant height were analyzed to obtain estimates of high parent heterosis. High parent heterosis was observed to be 37.18% for yield, 82.77% for exsertion, -0.02% for days to mid anthesis and 23.7% for height. ICSR-939 and (87EON366*90EON328)-LD30 can be used as testers to develop more female lines for further hybrid seed production in breeding programs because they had the highest general combining ability. Protein content averaged 11.69%. ATx635 had significantly higher protein content than ATx631 (13.49% compared to 9.69%, respectively) and its hybrids had more protein than ATx631 hybrids (11.6% compared to 10.67% for ATx631). Mean heterosis for protein content was negative at -12.5%. This shows that hybrids had lower protein content than their parents since protein content is negatively correlated to grain yield (-0.35**). Starch content averaged 72.13% and ATx631 hybrids had more starch than ATx635 hybrids (73.16 compared to 72.37% respectively). Two hybrids, ATx.631/(87EON366*90EON328)-LD30 and ATx631/ ((TAM428*SV1)*CE151)-LD3 had the highest yields (5.04 t/ha and 4.93 t/ha, respectively). These hybrids also had small grains with good hardness and acceptable whiteness. They had good exsertion, flowered in good time and had acceptable plant heights. These two hybrids were compared to regional check varieties Macia and Tegemeo for all traits and they were either superior or within an acceptable range. These two hybrids are therefore recommended for release in the region. There is need therefore to start working on the various components of seed systems in the region so that seed of these two hybrids is made available to farmers who need the seed.
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Kinetics and dynamics study on the allosteric pathway of phosphofructokinase from Escherichia coliTie, Cuijuan 10 October 2008 (has links)
Phosphofructokinase from Escherichia coli (EcPFK) is allosterically regulated by MgADP and phosphoenolpyruvate (PEP), which act to activate or inhibit, respectively, by changing the substrate (Fru-6-P) affinity of the enzyme. Both ligands bind to the same allosteric site in EcPFK. Therefore, the questions we want to address are how these two molecules regulate EcPFK and how the allosteric signal is propagated throughout the enzyme. EcPFK has 28 potential site-site interactions. These interactions in turn derive from multiple copies of 6 potentially unique homotropic interactions and 4 potentially unique heterotropic interactions. Making hybrid tetramer of EcPFK is used to isolate a single heterotropic interaction. To improve the yield of the 1:3 hybrid, the in vivo hybrid formation method was developed. Four heterotropic interactions were isolated by this manner and re-evaluated. The same kinetics characteristics were obtained for each 1:3 hybrid from both the in vivo and in vitro method. To address the question of how the allosteric signal is transmitted throughout EcPFK, we identified residues (G184, Asp59 and S157) that are important for the allosteric regulation for both PEP inhibition and MgADP activation. The impact of each mutation on individual interaction is unique and also suggests that the structural basis for PEP inhibition is different from that for MgADP activation. Most importantly, since the sum of each heterotropic interaction with a modification in only one subunit is equal to the total heterotropic interaction with a modification in all four subunits, this result indicates that the heterotropic allosteric signal transmission is realized in a single subunit. The 23Ã heterotropic interaction, which contributes the most to the PEP inhibition, was chosen to study the dynamic properties. Fluorescence was used to study the dynamic perturbations of the 23Ã interaction upon ligand binding. Taking advantage of the hybrid formation strategy and the tryptophan-shift mutagenesis method, a tryptophan residue can be placed at different individual locations throughout the native subunit containing the 23Ã heterotropic interaction. The steady-state anisotropy and lifetime measurement at each tryptophan position indicate that the 23Ã allosteric interaction involves the perturbation of side-chain dynamics both near and quite far away from the respective ligand binding sites.
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A study in the process modeling of a fuel cell/microturbine hybrid system under ambient conditionsShelton, Michael S. January 1900 (has links)
Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains viii, 44 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 40-41).
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Hybrid logic and its proof-theory /Braüner, Torben. January 1900 (has links)
Doktordisputats, Roskilde universitet.
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Hybrid zone theory and empirical studies of behavior and population genetics of the field crickets Gryllus texensis and Gryllus rubensHiggins, Laura A., 1971- 06 July 2011 (has links)
Not available / text
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THE DESIGN OF A NEW SOLID STATE ELECTRONIC ITERATIVE DIFFERENTIAL ANALYZER MAKING MAXIMUM USE OF INTEGRATED CIRCUITSConant, Brian Kendall, 1937- January 1968 (has links)
No description available.
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