scholarly journals MICA sounding rocket observations of conductivity‐gradient‐generated auroral ionospheric responses: Small‐scale structure with large‐scale drivers

2015 ◽  
Vol 120 (11) ◽  
pp. 9661-9682 ◽  
Author(s):  
K. A. Lynch ◽  
D. L. Hampton ◽  
M. Zettergren ◽  
T. A. Bekkeng ◽  
M. Conde ◽  
...  
Keyword(s):  
Large Scale ◽  
Scale Structure ◽  
Sounding Rocket ◽  
Small Scale ◽  
Small Scale Structure ◽  
Conductivity Gradient

scholarly journals Heterogeneity, Permeability Patterns, and Permeability Upscaling: Physical Characterization of a Block of Massillon Sandstone Exhibiting Nested Scales of Heterogeneity

2000 ◽  
Vol 3 (04) ◽  
pp. 283-291 ◽  
Author(s):  
V.C. Tidwell ◽  
J.L. Wilson
Keyword(s):  
Predictive Models ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure ◽  
Permeability Upscaling ◽  
Block Face ◽  
The Cross ◽  
Permeability Data

Summary Over 75,000 permeability measurements were collected from a meter-scale block of Massillon sandstone, characterized by conspicuous crossbedding that forms two distinct nested scales of heterogeneity. With the aid of a gas minipermeameter, spatially exhaustive fields of permeability data were acquired at each of five different sample supports (i.e., sample volumes) from each block face. These data provide a unique opportunity to physically investigate the relationship between the multiscale cross-stratified attributes of the sandstone and the corresponding statistical characteristics of the permeability. These data also provide quantitative physical information concerning the permeability upscaling of a complex heterogeneous medium. Here, a portion of the data taken from a single block face cut normal to stratification is analyzed. The results indicate a strong relationship between the calculated summary statistics and the cross-stratified structural features visibly evident in the sandstone sample. Specifically, the permeability fields and semivariograms are characterized by two nested scales of heterogeneity, including a large-scale structure defined by the cross-stratified sets (delineated by distinct bounding surfaces) and a small-scale structure defined by the low-angle cross-stratification within each set. The permeability data also provide clear evidence of upscaling. That is, each calculated summary statistic exhibits distinct and consistent trends with increasing sample support. Among these trends are an increasing mean, decreasing variance, and an increasing semivariogram range. The results also clearly indicate that the different scales of heterogeneity upscale differently, with the small-scale structure being preferentially filtered from the data while the large-scale structure is preserved. Finally, the statistical and upscaling characteristics of individual cross-stratified sets were found to be very similar because of their shared depositional environment; however, some differences were noted that are likely the result of minor variations in the sediment load and/or flow conditions between depositional events. Introduction Geologic materials are inherently heterogeneous because of the depositional and diagenetic processes responsible for their formation. These heterogeneities often impose considerable influence on the performance of hydrocarbon bearing reservoirs. Unfortunately, quantitative characterization and integration of reservoir heterogeneity into predictive models are complicated by two challenging problems. First, the quantity of porous media observed and/or sampled is generally a minute faction of the reservoir under investigation. This gives rise to the need for models to predict material characteristics at unsampled locations. The second problem stems from technological constraints that often limit the measurement of material properties to sample supports (i.e., sample volumes) much smaller than can be accommodated in current predictive models. This disparity in support requires measured data be averaged or upscaled to yield effective properties at the desired scale of analysis. The concept of using "soft" geologic information to supplement often sparse "hard" physical data has received considerable attention.1,2 Successful application of this approach requires that some relationship be established between the difficult to measure material property (e.g., permeability) and that of a more easily observable feature of the geologic material. For example, Davis et al.3 correlated architectural-element mapping with the geostatistical characteristics of a fluvial/interfluvial formation in central New Mexico; Jordan and Pryor4 related permeability controls and reservoir productivity to six hierarchical levels of sand heterogeneity in a fluvial meander belt system; while Istok et al.5 found a strong correlation between hydraulic property measurements and visual trends in the degree of welding of ash flow tuffs at Yucca Mountain, Nevada. Phillips and Wilson6 mapped regions where the permeability exceeds some specified cutoff value and related their dimensions to the correlation length scale by means of threshold-crossing theory. Also, Journel and Alabert7 proposed a spatial connectivity model based on an indicator formalism and conditioned on geologic maps of observable, spatially connected, high-permeability features. The description and quantification of heterogeneity is necessarily related to the issue of scale. It is often assumed that geologic heterogeneity is structured according to a discrete and disparate hierarchy of scales. For example, the hierarchical models proposed by Dagan8 and by Haldorsen9 conveniently classify heterogeneities according to the pore, laboratory, formation, and regional scales. This assumed disparity in scales allows parameter variations occurring at scales smaller than the modeled flow/transport process to be spatially averaged to form effective media properties,10–14 while large-scale variations are treated as a simple deterministic trend.2,15 However, natural media are not always characterized by a large disparity in scales as assumed above;16 but rather, an infinite number of scales may coexist,17–20 leading to a fractal geometry or continuous hierarchy of scales.21

Study on Simple Vibration Attenuation System for Light Weight Structure

2007 ◽  
Author(s):  
Osamu Furuya ◽  
Hiroshi Kurabayashi
Keyword(s):  
Large Scale ◽  
Base Isolation ◽  
Scale Structure ◽  
Small Scale ◽  
Response Analysis ◽  
Light Weight ◽  
Seismic Safety ◽  
Small Scale Structure ◽  
Vibration Attenuation ◽  
Weight Structure

Various vibration attenuation methods such as a base isolation and vibration control are suggested as seismic safety technique for large scale architectural and civil structure, and these methods have been practical used now. In recent years, these vibration reduction technology begins to be applied to a small scale structure. In case that the technology is applied to a small scale structure, specifications and a cost of the device must be examined well. In this study, a vibration attenuation system for light weight structure with low cost and simple mechanizm. This paper describes the effectiveness of the proposed vibration attenuation system which was evaluated from preliminary seismic response analysis.

scholarly journals The small-scale structure of the Magellanic stream as a foundation for galaxy evolution

2010 ◽  
pp. 1-10 ◽  
Author(s):  
S. Stanimirovic ◽  
J.S.III Gallagher ◽  
L. Nigra
Keyword(s):  
Galaxy Evolution ◽  
Large Scale ◽  
Critical Role ◽  
Neutral Hydrogen ◽  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure ◽  
Northern Portion ◽  
Cool Gas ◽  
Magellanic Stream

The Magellanic Stream (MS) is the nearest example of a gaseous trail formed by interacting galaxies. While the substantial gas masses in these kinds of circumgalactic structures are postulated to represent important sources of fuel for future star formation, the mechanisms whereby this material might be accreted back into galaxies remain unclear. Recent neutral hydrogen (HI) observations have demonstrated that the northern portion of the MS, which probably has been interacting with the Milky Way's hot gaseous halo for close to 1000 Myr, has a larger spatial extent than previously recognized, while also containing significant amounts of small-scale structure. After a brief consideration of the large-scale kinematics of the MS as traced by the recently-discovered extension of the MS, we explore the aging process of the MS gas through the operation of various hydrodynamic instabilities and interstellar turbulence. This in turn leads to consideration of processes whereby MS material survives as cool gas, and yet also evidently fails to form stars. Parallels between the MS and extragalactic tidal features are brie'y discussed with an emphasis on steps toward establishing what the MS reveals about the critical role of local processes in determining the evolution of these kinds of systems.

scholarly journals A Search for Very Compact Structure in 17 OH Masers

1988 ◽  
Vol 129 ◽  
pp. 255-256
Author(s):  
A. J. Kemball ◽  
P. J. Diamond ◽  
F. Mantovani
Keyword(s):  
Galactic Disk ◽  
Hii Regions ◽  
Scale Structure ◽  
Small Scale ◽  
Compact Structure ◽  
Small Scale Structure ◽  
Interstellar Scattering

The apparent spot sizes of OH masers appear to be significantly broadened when seen through the inner galaxy or large extents of the galactic disk (Burke 1968). Bowers et al (1980) found evidence of small-scale structure (≲ 50 mas) in OH sources at distances of less than 5 kpc but this was characteristically absent in very distant sources (≳ 8kpc) at galactic longitudes 1 ≲ 40°. This result is typically explained in terms of interstellar scattering (ISS) by intervening diffuse HII regions.

Analysis of the small-scale structure of turbulence on smooth and rough walls

2003 ◽  
Vol 15 (1) ◽  
pp. 35-46 ◽  
Author(s):  
D. Poggi ◽  
A. Porporato ◽  
L. Ridolfi
Keyword(s):  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure ◽  
Rough Walls

Small-scale structure of the Taylor–Green vortex

1983 ◽  
Vol 130 (-1) ◽  
pp. 411 ◽  
Author(s):  
Marc E. Brachet ◽  
Daniel I. Meiron ◽  
Steven A. Orszag ◽  
B. G. Nickel ◽  
Rudolf H. Morf ◽  
...  
Keyword(s):  
Scale Structure ◽  
Small Scale ◽  
Small Scale Structure
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