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A study of the diffusion of sorbed water vapor through paper and regenerated cellulose filmsAhlen, Arne T. 01 January 1969 (has links)
No description available.
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The Effect of Employees¡¦ Job Satisfaction and Work Pressure on Turnover Intention¡XFinancial Industry and Non-financial Industry as Organizational VariableLo, Kuan-Tzu 10 May 2011 (has links)
This study was using a cross-level research framework and analysis of strategy to search the relationship between job satisfaction and turnover intention in non-financial sector and financial sector, and the effect in work pressure and the turnover intention.
This research was using the method of questionaire survey with hierarchical linear model analysis, reliability analysis and factor analysis. Analysis shows¡G
1.The higher job satisfaction, the lower turnover intention.
2.The higher work pressure, the higher turnover intention.
3. Industry category has mediating effects between job satisfaction and tornover intention.
4. Industry category does not have mediating effects between work pressure and tornover intention.
According to the results of research, providing business managers in different industry category to increase employees¡¦ job satisfaction to decrease turnover intention,and turnover behavior will reduce.
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Field application of an interpretation method of downhole temperature and pressure data for detecting water entry in horizontal/highly inclined gas wellsAchinivu, Ochi I. 15 May 2009 (has links)
In the oil and gas industry today, continuous wellbore data can be obtained with high
precision. This accurate and reliable downhole data acquisition is made possible by
advancements in permanent monitoring systems such as downhole pressure and
temperature gauges and fiber optic sensors. The monitoring instruments are increasingly
incorporated as part of the intelligent completion in oil wells where they provide
bottomhole temperature, pressure and sometimes volumetric flow rate along the
wellbore - offering the promise of revolutionary changes in the way these wells are
operated. However, to fully realize the value of these intelligent completions, there is a
need for a systematic data analysis process to interpret accurately and efficiently the raw
data being acquired. This process will improve our understanding of the reservoir and
production conditions and enable us make decisions for well control and well
performance optimization.
In this study, we evaluated the practical application of an interpretation model,
developed in a previous research work, to field data. To achieve the objectives, we developed a simple and detailed analysis procedure and built Excel user interface for
data entry, data update and data output, including diagnostic charts and graphs. By
applying our interpretation procedure to the acquired field data we predicted temperature
and pressure along the wellbore. Based on the predicted data, we used an inversion
method to infer the flow profile - demonstrating how the monitored raw downhole
temperature and pressure can be converted into useful knowledge of the phase flow
profiles and fluid entry along the wellbore. Finally, we illustrated the sensitivity of
reservoir parameters on accuracy of interpretation, and generated practical guidelines on
how to initialize the inverse process. Field production logging data were used for
validation and application purposes.
From the analysis, we obtained the production profile along the wellbore; the fluid
entry location i.e. the productive and non-productive locations along the wellbore; and
identified the fluid type i.e. gas or water being produced along the wellbore. These
results show that temperature and pressure profiles could provide sufficient information
for fluid identity and inflow distribution in gas wells.
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Investigation on the effects of ultra-high pressure and temperature on the rheological properties of oil-based drilling fluidsIbeh, Chijioke Stanley 15 May 2009 (has links)
Designing a fit-for-purpose drilling fluid for high-pressure, high-temperature (HP/HT)
operations is one of the greatest technological challenges facing the oil and gas industry
today. Typically, a drilling fluid is subjected to increasing temperature and pressure with
depth. While higher temperature decreases the drilling fluid’s viscosity due to thermal
expansion, increased pressure increases its viscosity by compression. Under these
extreme conditions, well control issues become more complicated and can easily be
masked by methane and hydrogen sulfide solubility in oil-base fluids frequently used in
HP/HT operations. Also current logging tools are at best not reliable since the
anticipated bottom-hole temperature is often well above their operating limit. The
Literature shows limited experimental data on drilling fluid properties beyond 350°F and
20,000 psig. The practice of extrapolation of fluid properties at some moderate level to
extreme-HP/HT (XHP/HT) conditions is obsolete and could result in significant
inaccuracies in hydraulics models.
This research is focused on developing a methodology for testing drilling fluids at
XHP/HT conditions using an automated viscometer. This state-of-the-art viscometer is
capable of accurately measuring drilling fluids properties up to 600°F and 40,000 psig. A
series of factorial experiments were performed on typical XHP/HT oil-based drilling
fluids to investigate their change in rheology at these extreme conditions (200 to 600°F and 15,000 to 40,000 psig). Detailed statistical analyses involving: analysis of variance,
hypothesis testing, evaluation of residuals and multiple linear regression are
implemented using data from the laboratory experiments.
I have developed the FluidStats program as an effective statistical tool for characterizing
drilling fluids at XHP/HT conditions using factorial experiments. Results from the
experiments show that different drilling fluids disintegrate at different temperatures
depending on their composition (i.e. weighting agent, additives, oil/water ratio etc). The
combined pressure-temperature effect on viscosity is complex. At high thresholds, the
temperature effect is observed to be more dominant while the pressure effect is more
pronounced at low temperatures.
This research is vital because statistics show that well control incident rates for non-
HP/HT wells range between 4% to 5% whereas for HP/HT wells, it is as high as 100%
to 200%. It is pertinent to note that over 50% of the world’s proven oil and gas reserves
lie below 14,000 ft subsea according to the Minerals Management Service (MMS). Thus
drilling in HP/HT environment is fast becoming a common place especially in the Gulf
of Mexico (GOM) where HP/HT resistant drilling fluids are increasingly being used to
ensure safe and successful operations.
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Stochastic modeling of the variation of velocity and permeability as a function of effective pressure using the Bed-of-Nails asperity-deformation modelGenova Barazarte, Ezequiel 15 May 2009 (has links)
The mechanical and transport properties of porous and cracked media, such as
velocity and permeability, are sensitive to the effects of effective pressure, which itself is
a function of the confining pressure and the pore-fluid pressure. The dependence of
permeability and velocity on effective pressure has previously been modeled using the
Bed-of-Nails asperity-deformation model. The main objective of this research was to
explore the sensitivity of the Bed-of-Nails and effective-pressure models to random,
Gaussian errors, by using an inverse approach. To achieve this, numerical modeling of
pre-existing velocity and permeability experimental data sets was done.
Extrapolation to 600 MPa was performed using an epidosite data set of
compressional velocity as a function of confining pressure, only using measurements in
the range 0-100 MPa. The results showed that, given sufficient data and considering
random error only, extrapolation can be done with a level of error of less than 1.5%.
Model error can also be significant in this type of exercise because it can give rise to
systematic misfit, although in this case it was shown that the effects of model error were
not considerable. Modeling the variation of compressional velocities as a function of confining and pore-fluid pressures in a deep-sea chalk showed that the best-fitting
asperity-deformation model is sensitive to the effective-pressure model.
Measurements of permeability in a Navajo-sandstone specimen as a function of
confining pressure were numerically modeled, and the results showed that measurements
made at low pressures, specifically near Pe = 0, are very important to constrain the
model. The same result was found in the case of permeability as a function of confining
and pore-fluid pressure in a Wilcox-shale where the lack of measurements near Pe = 0
caused the error in the model parameters to be overestimated. This occurs because the
rate of change of permeability as a function of effective pressure is very high at low
pressures. The lack of sufficient data near Pe = 0 overestimates the curvature matrix and,
therefore, the errors in the model parameters.
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Optimized Fan Control In Variable Air Volume HVAC Systems Using Static Pressure Resets: Strategy Selection and Savings AnalysisKimla, John 2009 December 1900 (has links)
The potential of static pressure reset (SPR) control to save fan energy in variable air
volume HVAC systems has been well documented. Current research has focused on the creation
of reset strategies depending on specific system features. As the commissioning process has
begun to require the prediction of savings, knowledge of the extent to which various SPR control
strategies impact fan energy has become increasingly important. This research aims to document
existing SPR control strategies and utilize building data and simulation to estimate fan energy
use.
A comprehensive review of the literature pertaining to SPR control was performed and
the results were organized into a top-down flow chart tool. Based on the type of feedback
available from a particular system, or lack thereof, this tool will facilitate the selection of a SPR
control strategy. A field experiment was conducted on a single duct variable air volume system
with fixed discharge air temperature and static pressure setpoints. Finally, an air-side model of
the experimental system was created using detailed building design information and calibrated
using field measurements. This model was used to estimate the fan energy required to supply
the trended airflow data using fixed static pressure (FSP) and SPR control based on zone
demand, system demand, and outside air temperature.
While utilizing trend data from November 1, 2008 to February 12, 2009, the FSP control
of the experimental system was used as the baseline for ranking the energy savings potential of
nine different forms of duct static pressure control. The highest savings (73-74%) were achieved
using zonal demand based SPR control. System demand based SPR control yielded savings
ranging from 59 to 76%, which increased when the duct sensor was positioned near the fan
discharge and under similar zone load conditions. The outside air temperature based SPR
control yielded savings of 65% since the experimental system supplied primarily perimeter
zones. Finally, increasing the FSP setpoint from 2 to 3 inWG increased fan energy by 45%,
while decreasing the setpoint from 2 to 1 inWG decreased fan energy by 41%.
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Characterization of the Influence of a Favorable Pressure Gradient on the Basic Structure of a Mach 5.0 High Reynolds Number Supersonic Turbulent Boundary LayerTichenor, Nathan R. 2010 August 1900 (has links)
High-speed high Reynolds number boundary layer flows with mechanical non-equilibrium effects have numerous practical applications; examples include access-to-space ascent, re-entry and descent, and military hypersonic systems. However, many of the basic turbulent flow processes in this regime are poorly understood and are beyond the realm of modern direct numerical simulations Previous studies have shown that curvature driven pressure gradients significantly alter the state of the turbulence in high-speed boundary layers; the turbulence levels have been shown to decrease by large amounts (up to 100 percent) and the Reynolds shear stress has been shown to change sign. However, most of our understanding is based on point measurement techniques such as hot-wire and Laser Doppler anemometry acquired at low to moderate supersonic Mach numbers (i.e., M = 2-3). After reviewing the available literature, the following scientific questions remain unanswered pertaining to the effect of favorable pressure gradients:
(1) How is state of the mean flow and turbulence statistics altered?
(2) How is the structure of wall turbulence; break-up, stretch or a combination?
(3) How are the Reynolds stress component production mechanisms altered?
(4) What is the effect of Mach number on the above processes?
To answer these questions and to enhance the current database, an experimental analysis was performed to provide high fidelity documentation of the mean and turbulent flow properties using two-dimensional particle image velocimetry (PIV) along with flow visualizations of a high speed (M4.88=), high Reynolds number (Re36,000θ≈) supersonic turbulent boundary layer with curvature-driven favorable pressure gradients (a nominally zero, a weak, and a strong favorable pressure gradient). From these data, detailed turbulence analyses were performed including calculating classical mean flow and turbulence statistics, examining turbulent stress production, and performing quadrant decomposition of the Reynolds stress for each pressure gradient case.
It was shown that the effect of curvature-driven favorable pressure gradients on the turbulent structure of a supersonic boundary layer was significant. For the strong pressure gradient model, the turbulent shear stress changed sign throughout the entire boundary layer; a phenomena was not observed to this magnitude in previous studies. Additionally, significant changes were seen in the turbulent structure of the boundary layer. It is believed that hairpin vortices organized within the boundary layer are stretched and then broken up over the favorable pressure gradient. Energy from these hairpin structures is transferred to smaller turbulent eddies as well as back into the mean flow creating a fuller mean velocity profile. It was determined that the effects of favorable pressure gradients on the basic structure of a turbulent Mach 5.0 boundary layer were significant, therefore increasing the complexity of computational modeling.
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Pressure Transient Analysis and Production Analysis for New Albany Shale Gas WellsSong, Bo 2010 August 1900 (has links)
Shale gas has become increasingly important to United States energy supply.
During recent decades, the mechanisms of shale gas storage and transport were gradually
recognized. Gas desorption was also realized and quantitatively described. Models and
approaches special for estimating rate decline and recovery of shale gas wells were
developed. As the strategy of the horizontal well with multiple transverse fractures
(MTFHW) was discovered and its significance to economic shale gas production was
understood, rate decline and pressure transient analysis models for this type of well were
developed to reveal the well behavior.
In this thesis, we considered a “Triple-porosity/Dual-permeability” model and
performed sensitivity studies to understand long term pressure drawdown behavior of
MTFHWs. A key observation from this study is that the early linear flow regime before
interfracture interference gives a relationship between summed fracture half-length and
permeability, from which we can estimate either when the other is known. We studied
the impact of gas desorption on the time when the pressure perturbation caused by
production from adjacent transference fractures (fracture interference time) and programmed an empirical method to calculate a time shift that can be used to qualify the
gas desorption impact on long term production behavior.
We focused on the field case Well A in New Albany Shale. We estimated the
EUR for 33 wells, including Well A, using an existing analysis approach. We applied a
unified BU-RNP method to process the one-year production/pressure transient data and
performed PTA to the resulting virtual constant-rate pressure drawdown. Production
analysis was performed meanwhile. Diagnosis plots for PTA and RNP analysis revealed
that only the early linear flow regime was visible in the data, and permeability was
estimated both from a model match and from the relationship between fracture halflength
and permeability. Considering gas desorption, the fracture interference will occur
only after several centuries. Based on this result, we recommend a well design strategy
to increase the gas recovery factor by decreasing the facture spacing. The higher EUR of
Well A compared to the vertical wells encourages drilling more MTFHWs in New
Albany Shale.
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Experimental Characterization and Molecular Study of Natural Gas MixturesCristancho Blanco, Diego Edison 2010 May 1900 (has links)
Natural Gas (NG) plays an important role in the energy demand in the United States and throughout the world. Its characteristics as a clean, versatile and a sustainable source of energy makes it an important alternative within the spectra of energy resources. Addressing industrial and academic needs in the natural gas research area requires an integrated plan of research among experimentation, modeling and simulation. In this work, high accuracy PpT data have been measured with a high pressure single sinker magnetic suspension densimeter. An entire uncertainty analysis of this apparatus reveals that the uncertainty of the density data is less that 0.05% across the entire ranges of temperature (200 to 500) K and pressure (up to 200 MPa). These characteristics make the PpT data measured in this study unique in the world. Additionally, both a low pressure (up to 35 MPa) and a high pressure (up to 200 MPa) isochoric apparatus have been developed during the execution of this project. These apparatuses, in conjunction with a recently improved isochoric technique, allow determination of the phase envelope for NG mixtures with an uncertainty of 0.45% in temperature, 0.05% in pressure and 0.12% in density. Additionally, an innovative technique, based upon Coherent Anti-Stokes Raman Scattering (CARS) and Gas Chromatography (GC), was proposed in this research to minimize the high uncertainty introduced by the composition analyses of NG mixtures. The collected set of P?T and saturation data are fundamental for thermodynamic formulations of these mixtures. A study at the molecular level has provided molecular data for a selected set of main constituents of natural gas. A 50-50% methane-ethane mixture was studied by molecular dynamics simulations. The result of this study showed that simulation time higher than 2 ns was necessary to obtain reasonable deviations for the density determinations when compared to accurate standards. Finally, this work proposed a new mixing rule to incorporate isomeric effects into cubic equations of state.
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Green Water Flow Kinematics and Impact Pressure on a Three Dimensional Model StructureAriyarathne, Hanchapola Appuhamilage Kusalika Suranjani 2011 August 1900 (has links)
Flow kinematics of green water due to plunging breaking waves interacting with a simplified, three-dimensional model structure was investigated in laboratory. Two breaking wave conditions were tested: one with waves impinging and breaking on the vertical wall of the model at the still water level and the other with waves impinging and breaking on the horizontal deck surface. The incoming wave parameters were selected similar to observed wave parameters for the maximum wave height for Hurricane Ivan based on Froude scaling. The Bubble Image Velocimetry (BIV) technique was used to measure the flow velocity. Measurements were taken on a vertical plane located at the center of the deck surface and a horizontal plane located slightly above the deck surface.
The evolution of green water flow kinematics in time and space is revealed in the study. The unsteady and non-uniform velocities were found to be quite different between the two wave conditions, even though the incoming waves are nearly identical. It was observed that the maximum velocity appears near the green water wave front and is 1.44C with C being the wave phase speed for the deck impingement case and 1.24C for wall impingement case. The velocity variations in the present study were compared with that in an earlier study using a two-dimensional model with the same wave condition as in the wall impingement condition. It was found that the magnitudes of the maximum vertical velocity is very different between these two models (1.7C in the 3D model versus 2.9C in the 2D model), whereas the magnitudes of the maximum horizontal velocity on the deck are very similar (1.2C in both 3D and 2D models).
The applicability of dam-break theory on green water velocity prediction for the three-dimensional model was also investigated. It was found that the dam-break theory works very well in terms of predicting the maximum velocity, which is also the front velocity, but not the spatial distribution of the velocity on the deck.
Furthermore, pressure measurements were performed at two vertical planes: one at the centre and the other at 0.05 m away from the centre. Ensemble averaged pressure variations were compared. Two types of pressure variations, impulsive type and non-impulsive type were observed. Impact pressure was successfully related to the pressure rising time. Void fraction was measured for few locations near the model front edge. Predictions of maximum impact pressure based on the measured pressure and flow velocity were investigated linking pressure with kinetic energy. Constant impact coefficient of 1.3 was found for wall impingement wave. However, for deck impingement wave, it was not possible to find a constant impact coefficient. It was also found that there is a linear relationship between the rising pressure gradient and the impact coefficient.
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