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Experimental investigation of imbibition in oil-wet carbonates under low IFT conditions
Natural reservoir drives and waterflooding in naturally fractured carbonate reservoirs with an oil-wet matrix generate very low oil production. Surfactants enhance oil recovery in these reservoirs by altering wettability and reducing interfacial tension (IFT). The main purpose of this research was to determine how to scale up low IFT surfactant imbibition from the lab to fractured, oil-wet carbonate reservoirs. A series of imbibition experiments were conducted using cores with different horizontal (i.e. diameter) and vertical (i.e. height) dimensions. Their fractional oil recoveries (% OOIP) were systematically measured to better understand how to scale up the surfactant imbibition process. There was a particular need to perform experiments using cores with larger horizontal dimensions since almost all previous experiments in the literature used cores with a small diameter, typically 3.8 cm. The core diameters in this study varied from 3.8 to 20 cm. The traditional static imbibition experimental method was adapted and modified by periodically flushing out fluids surrounding the cores inside the cells to better estimate the oil recovery, including the significant amount of oil produced as an emulsion. The high performance surfactant formulations for the oils used on in this study were developed using microemulsion phase behavior tests. These surfactants gave ultra-low IFT (on the order of 0.001 dynes/cm) at optimal salinity and good aqueous stability. Although most of the experiments used ultra-low IFT formulations, experiments using higher IFT (on the order of 0.1 dynes/cm) formulations were also performed for comparison. Even for the higher IFT experiments, the capillary pressure is very small compared to gravity and viscous pressure gradients. In addition, experiments were done to understand the role of other variables on oil recovery, such as matrix permeability, surfactant and co-solvent concentrations, microemulsion viscosity, and oil viscosity. A simple analytical model was developed to predict the oil recovery as a function of vertical and horizontal fracture spacing, rock and fluid properties, and time. The model and experimental data are in good agreement considering the many simplifications made to derive the model. Both experimental data and the model showed that the oil recovery was lower for cores with larger horizontal and vertical dimensions. However, the decrease was not proportional to an increase in these dimensions. The scaling implied by the model is significantly different than the traditional scaling groups in the literature.Petroleum and Geosystems Engineerin
Accuracy of Commercially-Available Speech Recognition Systems in Identifying PIREP Terminology
Pilot Reports (PIREPs) are an important source of information that aids, other pilots, air traffic control, and operational aviation meteorologists in terms of forecasting and updating weather advisories such as SIGMETs. Pilots rely upon PIREPs so they can avoid hazardous weather and fly their aircraft in the safest manner possible. However, many PIREPs are not successfully submitted or transmitted to the many end users which impedes their ability to be used to keep the NAS safe. The National Transportation Safety Board (NTSB) made several recommendations for increasing the effectiveness and distribution of PIREPs, including receiving PIREPs from pilots directly and automatically (NTSB, 2017). We recruited eighty-four native-speaking participants to read a short, average, and long PIREP scripts in order to test the performance of various speech recognition systems (SRSs). The spoken PIREPs were transcribed by SRSs and compared to the original PIREP scripts. The words that were deleted, substituted, and inserted were identified and used to calculate the word error rate (WER) and word information loss (WIL). The WERs and WILs were separately analyzed with a repeated-measures marginal model to compare the accuracy between each of the SRSs. Also, the interaction between each SRS and gender was analyzed. The results demonstrated that Google, LilySpeech, and Transcribe had the same and superior performance when transcribing the average-length PIREPs than Braina and Dragon. All SRSs had equal performance at transcribing the short-length PIREPs. Dragon, Google, LilySpeech, and Transcribe had the same performance and superior when transcribing the long-length PIREPs than Braina. Additionally, we found that the short, average, and long-length transcriptions for all 5 commercial off-the-shelf (COTS) SRSs provided readable information for flight service stations (FSS) to enter valuable weather information into the PIREP system
The a priori Tan Theta Theorem for spectral subspaces
Let A be a self-adjoint operator on a separable Hilbert space H. Assume that
the spectrum of A consists of two disjoint components s_0 and s_1 such that the
set s_0 lies in a finite gap of the set s_1. Let V be a bounded self-adjoint
operator on H off-diagonal with respect to the partition spec(A)=s_0 \cup s_1.
It is known that if ||V||<\sqrt{2}d, where d=\dist(s_0,s_1), then the
perturbation V does not close the gaps between s_0 and s_1 and the spectrum of
the perturbed operator L=A+V consists of two isolated components s'_0 and s'_1
grown from s_0 and s_1, respectively. Furthermore, it is known that if V
satisfies the stronger bound ||V||< d then the following sharp norm estimate
holds: ||E_L(s'_0)-E_A(s_0)|| \leq sin(arctan(||V||/d)), where E_A(s_0) and
E_L(s'_0) are the spectral projections of A and L associated with the spectral
sets s_0 and s'_0, respectively. In the present work we prove that this
estimate remains valid and sharp also for d \leq ||V||< \sqrt{2}d, which
completely settles the issue.Comment: v3: some typos fixed; Examples adde
Static and dynamic traversable wormhole geometries satisfying the Ford-Roman constraints
It was shown by Ford and Roman in 1996 that quantum field theory severely
constrains wormhole geometries on a macroscopic scale. The first part of this
paper discusses a wide class of wormhole solutions that meet these constraints.
The type of shape function used is essentially generic. The constraints are
then discussed in conjunction with various redshift functions. Violations of
the weak energy condition and traversability criteria are also considered. The
second part of the paper analyzes analogous time-dependent (dynamic) wormholes
with the aid of differential forms. It is shown that a violation of the weak
energy condition is not likely to be avoidable even temporarily.Comment: 16 pages AMSTe
Visualisation of the local electrochemical activity of thermally-sprayed anti-corrosion coatings using scanning electrochemical microscopy
Scanning electrochemical microscopy was used to probe the local electrochemical activity of anti-corrosion coatings formed from Inconel 625, a Ni-Cr-Mo alloy commonly used in engineering applications. The coatings were formed using a high velocity oxygen fuel thermal spraying technique. Upon spraying onto mild steel substrates, clear splat boundaries were formed at the interface between droplets of the alloy as they cooled on the substrate surface. Scanning electrochemical microscopy in the feedback mode, employing ferrocenemethanol as redox mediator, was used to determine the local electrochemical activity of samples of the wrought alloy, the sintered alloy and the thermally-sprayed coating. Significantly, the wrought and sintered materials generally showed responses typical of those expected for a purely insulating material. However, feedback approach curve data showed that the electrochemical activity of the entire thermally-sprayed coating was higher than that of the bulk alloy. Local variations in the coating’s activity were then visualised using scanning electrochemical microscopy. These observations indicate that the spraying process increases the conductivity of Inconel 625 and that localised regions of increased electrochemical activity are generated throughout the material, which appear to be related to the splat boundaries formed during spraying
Global Monopole in Asymptotically dS/AdS Spacetime
In this paper, we investigate the global monopole in asymptotically dS/Ads
spacetime and find that the mass of the monopole in the asymptotically dS
spacetime could be positive if the cosmological constant is greater than a
critical value. This shows that the gravitational field of the global monopole
could be attractive or repulsive depending on the value of the cosmological
constant.Comment: 5 pages, 1 figure, to appear in Phys. Rev.
Resolution studies of cosmic-ray tracks in a TPC with GEM readout
A large volume TPC is a leading candidate for the central tracking detector
at a future high energy linear collider. To improve the resolution a new
readout based on micro-pattern gas detectors is being developed. Measurements
of the spatial resolution of cosmic-ray tracks in a GEM TPC are presented. We
find that the resolution suffers if the readout pads are too wide with respect
to the charge distribution at the readout plane due to insufficient charge
sharing. For narrow pads of 2 x 6 mm**2 we measure a resolution of 100
micometer at short drift distances in the absence of an axial magnetic field.
The dependence of the spatial resolution as a function of drift distance allows
the determination of the underlying electron statistics. Our results show that
the present technique uses about half the statistical power available from the
number of primary electrons. The track angle effect is observed as expected.Comment: 18 pages, 8 figures, version as published in Nucl. Inst. Met
Controlled Growth, Patterning and Placement of Carbon Nanotube Thin Films
Controlled growth, patterning and placement of carbon nanotube (CNT) thin
films for electronic applications are demonstrated. The density of CNT films is
controlled by optimizing the feed gas composition as well as the concentration
of growth catalyst in a chemical vapor deposition process. Densities of CNTs
ranging from 0.02 CNTs/{\mu}m^2 to 1.29 CNTs/{\mu}m^2 are obtained. The
resulting pristine CNT thin films are then successfully patterned using either
pre-growth or post-growth techniques. By developing a layered photoresist
process that is compatible with ferric nitrate catalyst, significant
improvements over popular pre-growth patterning methods are obtained.
Limitations of traditional post-growth patterning methods are circumvented by
selective transfer printing of CNTs with either thermoplastic or metallic
stamps. Resulting as-grown patterns of CNT thin films have edge roughness (< 1
{\mu}m) and resolution (< 5 {\mu}m) comparable to standard photolithography.
Bottom gate CNT thin film devices are fabricated with field-effect mobilities
up to 20 cm^2/Vs and on/off ratios of the order of 10^3. The patterning and
transfer printing methods discussed here have a potential to be generalized to
include other nanomaterials in new device configurations
A Performance Comparison Using HPC Benchmarks: Windows HPC Server 2008 and Red Hat Enterprise Linux 5
This document was developed with support from the National Science Foundation (NSF) under Grant No. 0910812 to Indiana University for ”FutureGrid: An Experimental, High-Performance Grid Test-bed.” Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.A collection of performance benchmarks have been run on an IBM System X iDataPlex cluster using two different operating systems. Windows HPC Server 2008 (WinHPC) and Red Hat Enterprise Linux v5.4 (RHEL5) are compared using SPEC MPI2007 v1.1, the High Performance Computing Challenge (HPCC) and National Science Foundation (NSF) acceptance test benchmark suites. Overall, we find the performance of WinHPC and RHEL5 to be equivalent but significant performance differences exist when analyzing specific applications. We focus on presenting the results from the application benchmarks and include the results of the HPCC microbenchmark for completeness
A Comparison of the LVDP and {\Lambda}CDM Cosmological Models
We compare the cosmological kinematics obtained via our law of linearly
varying deceleration parameter (LVDP) with the kinematics obtained in the
{\Lambda}CDM model. We show that the LVDP model is almost indistinguishable
from the {\Lambda}CDM model up to the near future of our universe as far as the
current observations are concerned, though their predictions differ
tremendously into the far future.Comment: 6 pages, 5 figures, 1 table, matches the version to be published in
International Journal of Theoretical Physic
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