scholarly journals The stability of source localization in a whole-head magnetoencephalography system demonstrated by auditory evoked field measurements

2011 ◽  
Vol 110 (7) ◽  
pp. 074702 ◽  
Author(s):  
Kuen-Lin Chen ◽  
Hong-Chang Yang ◽  
Sung-Ying Tsai ◽  
Yu-Wei Liu ◽  
Shu-Hsien Liao ◽  
...  
Keyword(s):  
Source Localization ◽  
Field Measurements ◽  
The Stability

Experiments on the stability and transition of wind-driven water surfaces

2001 ◽  
Vol 446 ◽  
pp. 25-65 ◽  
Author(s):  
FABRICE VERON ◽  
W. KENDALL MELVILLE
Keyword(s):  
Surface Current ◽  
Field Measurements ◽  
Surface Flow ◽  
Transition To Turbulence ◽  
Surface Velocity ◽  
Small Scale ◽  
Gas Transfer ◽  
Water Surfaces ◽  
Langmuir Circulations ◽  
The Stability

We present the results of laboratory and field measurements on the stability of wind-driven water surfaces. The laboratory measurements show that when exposed to an increasing wind starting from rest, surface current and wave generation is accompanied by a variety of phenomena that occur over comparable space and time scales. Of particular interest is the generation of small-scale, streamwise vortices, or Langmuir circulations, the clear influence of the circulations on the structure of the growing wave field, and the subsequent transition to turbulence of the surface flow. Following recent work by Melville, Shear & Veron (1998) and Veron & Melville (1999b), we show that the waves that are initially generated by the wind are then strongly modulated by the Langmuir circulations that follow. Direct measurements of the modulated wave variables are qualitatively consistent with geometrical optics and wave action conservation, but quantitative comparison remains elusive. Within the range of parameters of the experiments, both the surface waves and the Langmuir circulations first appear at constant Reynolds numbers of 370 ± 10 and 530 ± 20, respectively, based on the surface velocity and the depth of the laminar shear layer. The onset of the Langmuir circulations leads to a significant increase in the heat transfer across the surface. The field measurements in a boat basin display the same phenomena that are observed in the laboratory. The implications of the measurements for air–sea fluxes, especially heat and gas transfer, and sea-surface temperature, are discussed.

Influence of the groundwater on the stability of a clay bank in Baie James, Québec

1985 ◽  
Vol 22 (3) ◽  
pp. 409-413
Author(s):  
Peter Rosenberg ◽  
Jacques Provençal ◽  
Guy Lefebvre ◽  
J.-Jacques Paré
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Field Measurements ◽  
Failure Surface ◽  
Surface Failure ◽  
Failure Morphology ◽  
Critical Failure Surface ◽  
Groundwater Regime ◽  
The Stability ◽  
River Banks

The Rivière Broadback in northern Québec flows westward almost parallel to latitude 51 °N to discharge into Baie James at its southern end. Near the estuary the river banks are in clay. Surveys of the landsliding activity showed that many of the slides are superficial, with depths seldom greater than about 2 m, and are usually in the clay crust.Instrumentation revealed regional groundwater pattern close to the river banks that showed areas varying from those with significant underdrainage to those with hydrostatic pressure conditions. The stability of 26 m high river slopes inclined at 27° in an area of underdrainage was investigated.Triaxial testing on undisturbed tube samples was used to obtain the postpeak parameters. Stability analyses gave a factor of safety close to one for shallow failure surfaces. With underdrainage, the factor of safety for deep failure surfaces is appreciably higher. When hydrostatic pore pressure conditions are assumed, analysis gave a factor of safety for deep failure that was reduced by about 30%.The results of the analyses emphasize the relation between the morphology of the landslide activity and the groundwater regime. With underdrainage, effective stresses increase much faster with depth and the critical failure surface is always close to the surface, as confirmed by field observations. Key words: natural slope, clay, pore pressure, field measurements, stability failure surface, failure morphology.

scholarly journals Are the Hessdalen Lights a Reality, an Illusion, or a Mix of the Two ?

2021 ◽  
Vol 35 (3) ◽  
pp. 590-622
Author(s):  
Gianni Pascoli
Keyword(s):  
Field Measurements ◽  
Full Description ◽  
High Time Resolution ◽  
Full Understanding ◽  
Traversable Wormholes ◽  
Magnetic Field Measurements ◽  
The Stability ◽  
Atmospheric Phenomena ◽  
Theoretical Considerations ◽  
Recent Idea

The Hessdalen lights (HLs in the following) are luminous, floating,  more or less spherical atmospheric phenomena,  with a lifetime  of a few  seconds to sometimes several minutes. These phenomena are seen in the Hessdalen Valley in Norway for decades.  Unfortunately  a full understanding of these baffling events is still lacking in spite of solid  working  scientific   projects  intended  to explain them. This  paper  tries  to  improve  the  situation.  It raises the questions where the energy for the creation of the HLs  comes from, and what was  its nature : (geo) chemical, electric or still other ?   We propose a new  scenario for the Hessdalen lights. It exploits the recent idea of stable and traversable wormholes  whose the potential existence  is beginning to be  recognized in physics. Even though appearing highly  speculative, this hypothesis  has not been so far explored  elsewhere  while it could supply  a full  description  of the wholeness of the  phenomenon. On the other side  even if  the probability that a HL could indeed be a wormhole is may be low,  this question should not dismissed out of hand. These  theoretical considerations could  help to increase   knowledge and understanding  of  both  the HLs  and the wormholes, drawing mutual enrichment. In other words HLs  could betray the presence of hidden wormholes and we must not let slip through our fingers  this possibility even if it is very tiny.  In this framework we discuss of the stability, the energetics and the oversized dimension of the HLs. In physics the  final arbiter  is not the theory but the experiment. Thus some “simple” experiments are eventually  suggested  (high time resolution photometry and magnetic field measurements).  Eventually, if the process described is real and after mastering it,  there is a free and inexhaustible source of energy   that would be derived,  a tremendous breakthrough after which we could forget the controlled nuclear fusion. Regarding its structure, the paper is divided in four paragraphs 1, 2,3, 4 independent of each other.  Illustrative pictures help  to understand the text.  

scholarly journals Hydrological Behavior of an Infiltration-Induced Landslide in Colorado, USA

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Alexandra Wayllace ◽  
Barbara Thunder ◽  
Ning Lu ◽  
Aziz Khan ◽  
Jonathan W. Godt
Keyword(s):  
Groundwater Flow ◽  
Numerical Simulations ◽  
Water Table ◽  
Field Measurements ◽  
Early Summer ◽  
Horizontal Distance ◽  
Key Factor ◽  
Landslide Body ◽  
Active Landslide ◽  
The Stability

Infiltration-induced landslides are common in mountainous and hilly areas of the world. When they occur near transportation corridors, they can impact public safety, impede transport of goods and people, and damage transportation infrastructure. This work presents a study of the hydrological behavior and its effects on the stability of an active landslide located on an embankment along Interstate-70 west of the Eisenhower Tunnel in central Colorado, USA. Groundwater dynamics were monitored for three years; two piezometers were installed near the head of the slide and one piezometer was placed near the toe. The hydrological observations at this site are unusual in that water table positions beneath the westbound shoulder of the highway (upslope) varied twice as much as water table positions beneath the eastbound shoulder (downslope), only 30 m distant horizontally. To better understand the factors controlling these observed differences, observations of the stratigraphy and the geomorphology of the watershed beyond the landslide body were incorporated into a conceptual model tested using numerical simulations of two-dimensional, variably saturated groundwater flow. Results from the numerical simulations calibrated against field measurements and a seasonally varying stability analysis of the site show that the large observed differences in the water table positions over the short horizontal distance are likely due to a combination of (1) the large size of the watershed that allows a significant amount of infiltration of snowmelt into the hillslope, (2) the contrast of hydrological properties of soils in the watershed, and (3) the changes in steepness of the dip of the bedrock below the slide. These three factors control the direction, speed, and amount of groundwater flow traveling through the slope. It is also shown that the seasonal hydrology of the site is a key factor in the stability of the slope, where most of the observed displacement occurs during the early summer season. Variations in the water table level within a year resulting from low snow years compared to variations from high snow years can be as much as 100%. Finally, it is important to consider the large contributing area of the watershed when evaluating the hillslope hydrologic conditions and remediation options.

Analysis of progressive deformation of the Edmonton Convention Centre excavation

1987 ◽  
Vol 24 (3) ◽  
pp. 430-440 ◽  
Author(s):  
D. H. Chan ◽  
N. R. Morgenstern
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Strain Softening ◽  
Progressive Failure ◽  
Field Measurements ◽  
Shear Zones ◽  
Element Model ◽  
Progressive Deformation ◽  
Element Analysis ◽  
The Stability

A finite element analysis was performed of the deformations observed during the excavation of the Edmonton Convention Centre. Local geology in the Edmonton area consists of layers of shale with weak bentonite seams overlain by glacial deposits. The presence of the bentonite seams, which possess strain-softening characteristics, controls the stability of the excavation, which is located in a valley wall. To simulate the influence of the bentonite seams a strain-softening finite element model is used to estimate the amount of deformation in the foundation of the excavation. Field measurements indicated that localized progressive straining had occurred during the excavation process, and substantial heave of the foundation floor was observed. The finite element results show progressive deformation of the excavation and propagation of shear zones. Good agreement between the finite element results and the field observations is obtained. Key words: progressive failure, strain softening, finite element analysis, shear band, excavation stability.

Effect of Torsion on Stability, Dynamic Forces, and Vibration Characteristics in Drillstrings

1997 ◽  
Vol 119 (1) ◽  
pp. 11-19 ◽  
Author(s):  
M. A. Elsayed ◽  
D. W. Dareing ◽  
M. A. Vonderheide
Keyword(s):  
Field Measurements ◽  
Stability Diagram ◽  
Torsional Vibrations ◽  
Longitudinal Vibrations ◽  
Simulation Techniques ◽  
Time Simulation ◽  
Dynamic Forces ◽  
Analysis Of Stability ◽  
The Stability ◽  
Drilling Conditions

Traditionally, the analysis of stability in drillstrings is based on longitudinal vibrations only. However, field experience indicates the presence of torsional effects in the form of modulations in longitudinal vibrations. Moreover, torsional dynamic forces are significant and lead to joint problems during drilling. In this paper, we discuss the effect of torsional vibrations on the stability and both longitudinal and torsional forces in drillstrings. Using a model of a typical drillstring that incorporates both longitudinal and torsional multi-degree of freedom, we develop the equations governing displacements and forces at any joint. Using time simulation techniques, we obtain the stability diagram and calculate the dynamic forces at any joint as a function of time. We finally show the effect of torsion on the nature of vibrations through frequency analysis, a technique that is useful in the interpretation of field measurements under various drilling conditions.

scholarly journals Stability of Individuals during Urban Inundations: What Should We Learn from Field Observations?

Geosciences ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 341 ◽  
Author(s):  
Hubert Chanson ◽  
Richard Brown
Keyword(s):  
Real Life ◽  
Fluid Flows ◽  
Field Measurements ◽  
Topographic Effects ◽  
Hydrodynamic Instabilities ◽  
Flood Events ◽  
Flow Conditions ◽  
Life Impact ◽  
Flood Flows ◽  
The Stability

The flooding of urbanized areas constitutes a major hazard to populations and infrastructure. Flood flows during urban inundations have been studied only recently and the real-life impact of fluid flows on individuals is not well understood. The stability of individuals in floodwaters is re-assessed based upon the re-analysis of detailed field measurements during a major flood event. The results emphasized that hydrodynamic instabilities, linked to local topographic effects and debris, constitute major real-world hazards. A comparison between a number of flow conditions deemed unsafe for individuals, along with guidelines, suggests that many recommendations are over-optimistic and unsafe in real floodwaters and natural disasters. A series of more conservative guidelines is proposed, particularity relevant to flood events.

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