Localized Compressional Velocity Decrease Precursory to the Kalapana, Hawaii, Earthquake

Science ◽  
1978 ◽  
Vol 199 (4331) ◽  
pp. 882-885 ◽  
Author(s):  
A. C. JOHNSTON
Keyword(s):  
Compressional Velocity ◽  
Velocity Decrease

Coal strength and Young's modulus related to coal rank, compressional velocity and maceral composition

2013 ◽  
Vol 54 ◽  
pp. 129-135 ◽  
Author(s):  
Jienan Pan ◽  
Zhaoping Meng ◽  
Quanlin Hou ◽  
Yiwen Ju ◽  
Yunxing Cao
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Coal Rank ◽  
Compressional Velocity ◽  
Coal Strength

scholarly journals Wind Velocity Decreasing Effects of Windbreak Fence for Snowfall Measurement

2014 ◽  
Vol 2014 ◽  
pp. 1-20
Author(s):  
Ki-Pyo You ◽  
Young-Moon Kim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Velocity ◽  
Wind Tunnel Test ◽  
Field Measurements ◽  
Wind Flow ◽  
Dynamics Analysis ◽  
Computational Fluid Dynamics Analysis ◽  
Better Than ◽  
Velocity Decrease

Meteorological observatories use measuring boards on even ground in open areas to measure the amount of snowfall. In order to measure the amount of snowfall, areas unaffected by wind should be found. This study tried to determine the internal wind flow inside a windbreak fence, identifying an area unaffected by wind in order to measure the snowfall. We performed a computational fluid dynamics analysis and wind tunnel test, conducted field measurements of the type and height of the windbreak fence, and analyzed the wind flow inside the fence. The results showed that a double windbreak fence was better than a single windbreak fence for decreasing wind velocity. The double fence (width 4 m, height 60 cm, and fixed on the bottom) has the greatest wind velocity decrease rate at the central part of octagonal windbreak.

The Effect of Capillary Condensation on the Geomechanical and Acoustic Properties of Tight Formations: An Experimental Study

2021 ◽  
Author(s):  
Aamer Albannay ◽  
Binh Bui ◽  
Daisuke Katsuki
Keyword(s):  
Pore Pressure ◽  
Capillary Condensation ◽  
Pore Space ◽  
Dew Point ◽  
Acoustic Properties ◽  
Point Pressure ◽  
Tight Formations ◽  
Dew Point Pressure ◽  
Compressional Velocity

Abstract Capillary condensation is the condensation of the gas inside nano-pore space at a pressure lower than the bulk dew point pressure as the result of multilayer adsorption due to the high capillary pressure inside the small pore throat of unconventional rocks. The condensation of liquid in nano-pore space of rock changes its mechanical and acoustic properties. Acoustic properties variation due to capillary condensation provides us a tool to monitor phase change in reservoir as a result of nano-confinement as well as mapping the area where phase change occurs as well as characterize pore size distribution. This is particularly important for tight formations where confinement has a strong effect on phase behavior that is challenging to measure experimentally. Theoretical studies have examined the effects of capillary condensation; however, these findings have not been verified experimentally. The main objective of this study is to experimentally investigate the effect of capillary condensation on the mechanical and acoustic properties of shale samples. The mechanical and acoustic characterization of the samples was carried out experimentally using a state-of-the-art tri-axial facility at the Colorado School of Mines. The experimental set-up is capable of the simultaneous acquisition of coupled stress, strain, resistivity, acoustic and flow data. Carbon dioxide was used as the pore pressure fluid in these experiments. After a comprehensive characterization of shale samples, experiments were conducted by increasing the pore pressure until condensation occurs while monitoring the mechanical and acoustic properties of the sample to quantify the effect of capillary condensation on the mechanical and acoustic properties of the sample. Experimental data show a 5% increase in Young's Modulus as condensation occurs. This increase is attributed to the increase in pore stiffness as condensation occurs reinforcing the grain contact. An initial decrease in compressional velocity was observed as pore pressure increases before condensation occurs which is attributed to the expansion of the pore volume when pore pressure increases. After this initial decrease, compressional velocity slightly increases at a pressure around 750 - 800 psi which is close to the condensation pressure. We also observed a noticeable increase in shear velocity when capillary condensation occurs, this could be due to the immobility of the condensed liquid phase at the pore throats. The changes of geomechanical and acoustic signatures were observed at around 750 - 800 psi at 27°C, which is the dew point pressure of the fluid in the nano-pore space of the sample at this temperature. While the unconfined bulk dew point pressure of carbon dioxide at the same temperature is 977 psi. Hence, this study marks the first measurement of the dew point of fluid in nano-pore space and potentially leads to the construction of the phase envelope of fluid under confinement.

Differences in intersaccadic adaptation transfer between inward and outward adaptation

2011 ◽  
Vol 106 (3) ◽  
pp. 1399-1410 ◽  
Author(s):  
Fabian Schnier ◽  
Markus Lappe
Keyword(s):  
Peak Velocity ◽  
The Other ◽  
Saccade Target ◽  
Control Mechanisms ◽  
Saccadic Adaptation ◽  
Saccade Onset ◽  
Independent Parameters ◽  
Saccade Duration ◽  
Velocity Decrease

Saccadic adaptation is a mechanism to increase or decrease the amplitude gain of subsequent saccades, if a saccade is not on target. Recent research has shown that the mechanism of gain increasing, or outward adaptation, and the mechanism of gain decreasing, or inward adaptation, rely on partly different processes. We investigate how outward and inward adaptation of reactive saccades transfer to other types of saccades, namely scanning, overlap, memory-guided, and gap saccades. Previous research has shown that inward adaptation of reactive saccades transfers only partially to these other saccade types, suggesting differences in the control mechanisms between these saccade categories. We show that outward adaptation transfers stronger to scanning and overlap saccades than inward adaptation, and that the strength of transfer depends on the duration for which the saccade target is visible before saccade onset. Furthermore, we show that this transfer is mainly driven by an increase in saccade duration, which is apparent for all saccade categories. Inward adaptation, in contrast, is accompanied by a decrease in duration and in peak velocity, but only the peak velocity decrease transfers from reactive saccades to other saccade categories, i.e., saccadic duration remains constant or even increases for test saccades of the other categories. Our results, therefore, show that duration and peak velocity are independent parameters of saccadic adaptation and that they are differently involved in the transfer of adaptation between saccade categories. Furthermore, our results add evidence that inward and outward adaptation are different processes.

Preliminary interpretation of the first refraction arrivals in Gaspé from shots in Labrador and Quebec

1969 ◽  
Vol 6 (4) ◽  
pp. 771-774 ◽  
Author(s):  
Douglas S. Rankin ◽  
Ravi Ravindra ◽  
David Zwicker
Keyword(s):  
Upper Mantle ◽  
Arrival Time ◽  
The South ◽  
North Shore ◽  
The North ◽  
A Value ◽  
South Shore ◽  
Compressional Velocity ◽  
St Lawrence River

Previous work in the Gulf of St. Lawrence has yielded an unusually high upper-mantle compressional velocity. In the Gaspé area a more recent determination has yielded a value of 8.75 ± 0.20 km/s for an unreversed profile. The arrival time at a station on the north shore of the St. Lawrence River suggests that there is no major difference in velocity and depth relative to the south shore.

Sign in / Sign up

Export Citation Format

Share Document