Low-frequency laboratory measurements of the elastic properties of sandstone flooded with supercritical CO2

2013 ◽  
Vol 53 (2) ◽  
pp. 484
Author(s):  
Vassili Mikhaltsevitch ◽  
Maxim Lebedev ◽  
Boris Gurevich
Keyword(s):  
Supercritical Co2 ◽  
Low Frequency ◽  
Bedding Plane ◽  
Residual Water ◽  
Laboratory Measurements ◽  
Elastic Parameters ◽  
Sandstone Sample ◽  
Confining Pressures ◽  
The Difference ◽  
Set Up

This extended abstract presents the results of the first low-frequency experiments conducted on a sandstone sample (Donnybrook, WA) flooded with supercritical CO2 (scCO2). The experiments investigated the effects of scCO2 injection on the elastic and anelastic properties of the rock. The sandstone sample (porosity—11.4%, permeability—0.28 mD) was cut in the direction orthogonal to a formation-bedding plane and tested in a Hoek's triaxial pressure cell equipped with the means for independent control of pore and confining pressures. The pore and confining pressures were set up at 10 and 31 MPa correspondingly. The low-frequency system and the pump comprising of scCO2 were held at a temperature of 42°C. Supercritical CO2 was injected into the sample preliminary saturated with distilled water. The amount of the residual water in the sample after the scCO2 injection was about 40% of pore volume. The elastic parameters obtained for the sample with scCO2 at frequencies from 0.1–100 Hz are very close to those for the dry sample. Some discrepancy in calculated acoustic velocities are caused by the difference in water and scCO2 densities. The measured extensional attenuation is larger when the sample is saturated with scCO2. The applicability of Gassmann's fluid substitution theory for the interpretation of obtained results was also tested during the experiments.

scholarly journals Laboratory Measurements of Light Scattering by Dust Particles

1996 ◽  
Vol 150 ◽  
pp. 409-413
Author(s):  
Patrick P. Combet ◽  
Philippe L. Lamy
Keyword(s):  
Light Scattering ◽  
Laser Beam ◽  
Mie Theory ◽  
Spherical Particles ◽  
Dust Particles ◽  
Laboratory Measurements ◽  
Scattering Function ◽  
Hene Laser ◽  
Set Up ◽  
Good Agreement

AbstractWe have set up an experimental device to optically study the scattering properties of dust particles. Measurements over the 8 — 174° interval of scattering angles are performed on a continuously flowing dust loaded jet illuminated by a polarized red HeNe laser beam. The scattering is averaged over the population of the dust particles in the jet, which can be determined independently, and give the “volume scattering function” for the two directions of polarization directly. While results for spherical particles are in good agreement with Mie theory, those for arbitrary particles show conspicuous deviations.

Experimental Investigation into Driver Behavior along Curved and Parallel Diverging Terminals of Exit Interchange Ramps

2021 ◽  
pp. 036119812199742
Author(s):  
Alberto Portera ◽  
Marco Bassani
Keyword(s):  
Design Stage ◽  
Lane Change ◽  
Age And Gender ◽  
Traffic Conditions ◽  
Current Design ◽  
The Difference ◽  
Safety Countermeasures ◽  
And Gender ◽  
Set Up ◽  
Curve Radius

Current design manuals provide guidance on how to design exit ramps to facilitate driving operations and minimize the incidence of crashes. They also suggest that interchanges should be built along straight roadway sections. These criteria may prove ineffective in situations where there is no alternative to terminals being located along curved motorway segments. The paper investigates driving behavior along parallel deceleration curved terminals, with attention paid to the difference in impact between terminals having a curvature which is the same sign as the motorway segment (i.e., continue design), and those having an opposite curvature (i.e., reverse design). A driving simulation study was set up to collect longitudinal and transversal driver behavioral data in response to experimental factor variations. Forty-eight drivers were stratified on the basis of age and gender, and asked to drive along three randomly assigned circuits with off-ramps obtained by combining experimental factors such as motorway mainline curve radius (2 values), terminal length (3), curve direction (2), and traffic conditions (2). The motorway radius was found to be significant for drivers’ preferred speed when approaching the terminal. Terminal length and traffic volume do not have a significant impact on either longitudinal or transversal driver outputs. However, the effect of curve direction was found to be significant, notably for reverse terminals which do not compel drivers to select appropriate speeds and lane change positions. This terminal type can give rise to critical driving situations that should be considered at the design stage to facilitate the adoption of appropriate safety countermeasures.

scholarly journals Analysis of Low-Frequency Mutations Associated with Drug Resistance to Raltegravir before Antiretroviral Treatment

2010 ◽  
Vol 55 (3) ◽  
pp. 1114-1119 ◽  
Author(s):  
Jia Liu ◽  
Michael D. Miller ◽  
Robert M. Danovich ◽  
Nathan Vandergrift ◽  
Fangping Cai ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Treatment Failure ◽  
Low Frequency ◽  
Hiv Treatment ◽  
Viral Population ◽  
Virologic Suppression ◽  
Resistance Mutations ◽  
The Difference ◽  
Allele Specific Sequencing ◽  
Hiv 1

ABSTRACTRaltegravir is highly efficacious in the treatment of HIV-1 infection. The prevalence and impact on virologic outcome of low-frequency resistant mutations among HIV-1-infected patients not previously treated with raltegravir have not been fully established. Samples from HIV treatment-experienced patients entering a clinical trial of raltegravir treatment were analyzed using a parallel allele-specific sequencing (PASS) assay that assessed six primary and six secondary integrase mutations. Patients who achieved and sustained virologic suppression (success patients,n= 36) and those who experienced virologic rebound (failure patients,n= 35) were compared. Patients who experienced treatment failure had twice as many raltegravir-associated resistance mutations prior to initiating treatment as those who achieved sustained virologic success, but the difference was not statistically significant. The frequency of nearly all detected resistance mutations was less than 1% of viral population, and the frequencies of mutations between the success and failure groups were similar. Expansion of pre-existing mutations (one primary and five secondary) was observed in 16 treatment failure patients in whom minority resistant mutations were detected at baseline, suggesting that they might play a role in the development of drug resistance. Two or more mutations were found in 13 patients (18.3%), but multiple mutations were not present in any single viral genome by linkage analysis. Our study demonstrates that low-frequency primary RAL-resistant mutations were uncommon, while minority secondary RAL-resistant mutations were more frequently detected in patients naïve to raltegravir. Additional studies in larger populations are warranted to fully understand the clinical implications of these mutations.

REFRACTION ARRIVALS THROUGH THIN HIGH‐VELOCITY LAYERS

Geophysics ◽  
1965 ◽  
Vol 30 (2) ◽  
pp. 204-212 ◽  
Author(s):  
J. H. Rosenbaum
Keyword(s):  
Exponential Decay ◽  
High Velocity ◽  
Elastic Layer ◽  
Approximate Formula ◽  
Asymptotic Theory ◽  
Surrounding Medium ◽  
Low Frequency ◽  
Horizontal Distance ◽  
Symmetric Mode ◽  
Elastic Parameters

The first significant refraction arrival through a thin high‐velocity elastic layer in an elastic medium has been investigated theoretically by means of an asymptotic theory. This first low‐frequency arrival is closely connected with the longitudinal plate wave in the thin layer. When the medium surrounding the layer is a fluid, the signal does not decay exponentially with horizontal distance; when the surrounding medium is a solid, the signal does decay exponentially. A very simple approximate formula for this exponential decay is presented and compared with numerical results of the more rigorous theory. The decay as well as the shape of the signal is dependent upon the contrast in elastic parameters between the plate and the surrounding medium. Higher‐frequency early arrivals, associated with the second symmetric mode, have also been investigated. They exhibit greater exponential decay with horizontal distance than the low‐frequency first arrivals.

Pump Performance Improvement by Restraining Back Flow in Screw-Type Centrifugal Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 755-762 ◽  
Author(s):  
Yasushi Tatebayashi ◽  
Kazuhiro Tanaka ◽  
Toshio Kobayashi
Keyword(s):  
Pressure Fluctuations ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Simple Method ◽  
Back Flow ◽  
Pump Performance ◽  
Impeller Outlet ◽  
Pump Head ◽  
The Difference ◽  
Set Up

The authors have been investigating the various characteristics of screw-type centrifugal pumps, such as pressure fluctuations in impellers, flow patterns in volute casings, and pump performance in air-water two-phase flow conditions. During these investigations, numerical results of our investigations made it clear that three back flow regions existed in this type of pump. Among these, the back flow from the volute casing toward the impeller outlet was the most influential on the pump performance. Thus the most important factor to achieve higher pump performance was to reduce the influence of this back flow. One simple method was proposed to obtain the restraint of back flow and so as to improve the pump performance. This method was to set up a ringlike wall at the suction cover casing between the impeller outlet and the volute casing. Its effects on the flow pattern and the pump performance have been discussed and clarified to compare the calculated results with experimental results done under two conditions, namely, one with and one without this ring-type wall. The influence of wall’s height on the pump head was investigated by numerical simulations. In addition, the difference due to the wall’s effect was clarified to compare its effects on two kinds of volute casing. From the results obtained it can be said that restraining the back flow of such pumps was very important to achieve higher pump performance. Furthermore, another method was suggested to restrain back flow effectively. This method was to attach a wall at the trailing edge of impeller. This method was very useful for avoiding the congestion of solids because this wall was smaller than that used in the first method. The influence of these factors on the pump performance was also discussed by comparing simulated calculations with actual experiments.

scholarly journals Meteorological conditions over Antarctic blue-ice areas and their influence on the local surface mass balance

2001 ◽  
Vol 47 (156) ◽  
pp. 37-50 ◽  
Author(s):  
Richard Bintanja ◽  
Carleen H. Reijmer
Keyword(s):  
Mass Balance ◽  
Low Frequency ◽  
Meteorological Conditions ◽  
Surface Mass Balance ◽  
Surface Mass ◽  
Wind Speeds ◽  
Dry Conditions ◽  
The Difference ◽  
Sublimation Rates ◽  
Different Characteristics

AbstractThis paper addresses the causes of the prevailing meteorological conditions observed over an Antarctic blue-ice area and their effect on the surface mass balance. Over blue-ice areas, net accumulation is zero and ablation occurs mainly through sublimation. Sublimation rates are much higher than over adjacent snowfields. The meteorological conditions favourable for high sublimation rates (warm, dry and gusty) are due to the specific orographic setting of this blue-ice area, with usually a steep upwind mountainous slope causing strong adiabatic heating. Diabatic warming due to radiation, and entrainment of warm air from aloft into the boundary layer augment the warming. The prevailing warm, dry conditions explain roughly 50% of the difference in sublimation, and the different characteristics of blue ice (mainly its lower albedo) the other 50%. Most of the annual sublimation (∼70%) takes place during the short summer (mainly in daytime), with winter ablation being restricted to occasional warm, dry föhn-like events. The additional moisture is effectively removed by entrainment and horizontal advection, which are maximum over the blue-ice area. Low-frequency turbulent motions induced by the upwind mountains enhance the vertical turbulent transports. Strong gusts and high peak wind speeds over blue-ice areas cause high potential snowdrift transports, which can easily remove the total precipitation, thereby maintaining zero accumulation.

Dynamics of Ferroelectric and Nematic Liquid Crystals Confined in Porous Matrices

1994 ◽  
Vol 366 ◽  
Author(s):  
Fouad M. Aliev
Keyword(s):  
Liquid Crystals ◽  
Heterogeneous Media ◽  
Volume Fraction ◽  
Low Frequency ◽  
Pore Wall ◽  
Polar Molecules ◽  
Average Pore ◽  
Surface Polarization ◽  
The Difference ◽  
Frequency Relaxation

ABSTRACTWe performed dielectric spectroscopy measurements to study dynamics of collective modes of ferroelectric (FLC) and molecular motion of nematic (NLC) liquid crystals with polar molecules confined in silica macroporous and microporous glasses with average pore sizes of 1000 Å (volume fraction of pores 40%) and 100 Å (27%) respectively. For FLC the Goldstone and the soft modes are found in macropores. The rotational viscosity associated with the soft mode is about 10 times higher in pores than in the bulk. These modes are not detected in micropores although low frequency relaxation is present. The last one probably is not connected with the nature of liquid crystal but is associated with surface polarization effects typical for two component heterogeneous media. The difference between the dynamics of orientational motion of the polar molecules of NLC in confined geometries and in the bulk is qualitatively determined by the total energy Fs of the interaction between molecules and the surface of the pore wall, which is found Fs ≈ 102erg/cm2.

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

Telemedicine in pediatric and perinatal cardiology: Economic evaluation of a service in English hospitals

2007 ◽  
Vol 23 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Robin Dowie ◽  
Hema Mistry ◽  
Tracey A. Young ◽  
Gwyn C. Weatherburn ◽  
Helena M. Gardiner ◽  
...  
Keyword(s):  
Older Children ◽  
Telemedicine Service ◽  
Clinical Events ◽  
District Hospitals ◽  
Nonsignificant Difference ◽  
Patient Groups ◽  
Women And Children ◽  
The Difference ◽  
Set Up ◽  
Mean Cost

Objectives:Pediatric cardiology has an expanding role in fetal and pediatric screening. The aims of this study were to observe how district hospitals use a pediatric telecardiology service, and to compare the costs and outcomes of patients referred to specialists by means of this service or conventionally.Methods:A telemedicine service was set up between a pediatric cardiac center in London and four district hospitals for referrals of second trimester women, newborn babies, and older children. Clinicians in each hospital decided on the role for their service. Clinical events were audited prospectively and costed, and patient surveys were conducted.Results:The hospitals differed in their selection of patient groups for the service. In all, 117 telemedicine patients were compared with 387 patients seen in London or in outreach clinics. Patients selected for telemedicine were generally healthier. For all patients, the mean cost for the initial consultation was £411 for tele-referrals and £277 for conventional referrals, a nonsignificant difference. Teleconsultations for women and children were significantly more expensive because of technology costs, whereas for babies, ambulance transfers were much more costly. After 6-months follow-up, the difference between referral methods for all patients was nonsignificant (telemedicine, £3,350; conventional referrals, £2,172), and nonsignificant within the patient groups.Conclusions:Telemedicine was perceived by cardiologists, district clinicians, and families as reliable and efficient. The equivocal 6-month cost results indicate that investment in the technology is warranted to enhance pediatric and perinatal cardiology services.

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