Taxonomy of Q

Geophysics ◽  
2015 ◽  
Vol 80 (1) ◽  
pp. T41-T49 ◽  
Author(s):  
Igor Morozov ◽  
Amin Baharvand Ahmadi
Keyword(s):  
Spatial Resolution ◽  
Theoretical Models ◽  
Structural Formula ◽  
Quality Factors ◽  
Resolution Limit ◽  
Localized Structures ◽  
Geometric Spreading ◽  
Viscoelastic Theory ◽  
Group 3 ◽  
Inversion Techniques

The seismic quality factors [Formula: see text] used in many applications of exploration seismology are not automatically equivalent. We identified three groups of usage of the concept of a [Formula: see text]: (1) a measure of internal mechanical friction within rocks, as implied in petrophysical interpretations, (2) several types of apparent [Formula: see text] arising from attenuation measurements, and (3) axiomatic [Formula: see text] defined in the viscoelastic theory. These groups differ by their roles in the interpretation, sensitivity to model assumptions, frequency dependences, and particularly by the temporal and spatial resolution. Among all types of [Formula: see text], those that are most robust and useful for characterizing the material are also strongly limited in resolution and accuracy. For example, from spectral coherency studies, it is known that to measure a [Formula: see text] of approximately 100 with modest accuracy of 30%, measurement time intervals of about 500 ms are required. Although several inversion techniques offer models of [Formula: see text] at much higher resolution, such detailed [Formula: see text] models are usually dominated by the effects of localized structures, such as “colored” transmission across boundaries, reflectivity, or scattering. Such types of [Formula: see text] can be called “structural,” and they differ from the [Formula: see text]-factor of the medium. Detailed [Formula: see text] images are also sensitive to theoretical models such as background geometric spreading and assumptions about the frequency dependence of the [Formula: see text]. Direct association of such [Formula: see text] with material properties may be inaccurate and unreliable. Measurement of geometric spreading and averaging of the structural [Formula: see text] produce estimates of “geometric” and scattering attenuation; however, these estimates are also strongly limited in accuracy and resolution. The viscoelastic [Formula: see text] (group 3 above) heavily relies on a specific mathematical model. Despite producing detailed images, the spatial resolution of viscoelastic [Formula: see text] is inherently limited by the nature of its relation to the frequency-dependent velocity. This resolution limit is difficult to assess quantitatively.

The Spatial Resolution Limit for an Individual Domain Wall in Magnetic Nanowires

Nano Letters ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 5869-5874 ◽  
Author(s):  
Sumit Dutta ◽  
Saima A. Siddiqui ◽  
Jean Anne Currivan-Incorvia ◽  
Caroline A. Ross ◽  
Marc A. Baldo
Keyword(s):  
Domain Wall ◽  
Spatial Resolution ◽  
Magnetic Nanowires ◽  
Resolution Limit ◽  
Individual Domain

Remote-sensing concept using polariscopy for orientation determination below the spatial resolution limit

2021 ◽  
Author(s):  
Soon Hock Ng ◽  
Vijayakumar Anand ◽  
Alan Duffy ◽  
Alexander Babanin ◽  
Meguya Ryu ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Spatial Resolution ◽  
Resolution Limit ◽  
Orientation Determination

scholarly journals The second solar spectrum and the hidden magnetism

2008 ◽  
Vol 4 (S259) ◽  
pp. 211-222
Author(s):  
Jan O. Stenflo
Keyword(s):  
Magnetic Flux ◽  
Spatial Resolution ◽  
Zeeman Effect ◽  
Solar Spectrum ◽  
Coherent Scattering ◽  
Small Scale ◽  
Solar Photosphere ◽  
Resolution Limit ◽  
New Paradigm ◽  
Hanle Effect

AbstractApplications of the Hanle effect have revealed the existence of vast amounts of “hidden“ magnetic flux in the solar photosphere, which remains invisible to the Zeeman effect due to cancellations inside each spatial resolution element of the opposite-polarity contributions from this small-scale, tangled field. The Hanle effect is a coherency phenomenon that represents the magnetic modification of the linearly polarized spectrum of the Sun that is formed by coherent scattering processes. This so-called “Second Solar Spectrum” is as richly structured as the ordinary intensity spectrum, but the spectral structures look completely different and have different physical origins. One of the new diagnostic uses of this novel spectrum is to explore the magnetic field in previously inaccessible parameter domains. The earlier view that most of the magnetic flux in the photosphere is in the form of intermittent kG flux tubes with tiny filling factors has thereby been shattered. The whole photospheric volume instead appears to be seething with intermediately strong fields, of order 100G, of significance for the overall energy balance of the solar atmosphere. According to the new paradigm the field behaves like a fractal with a high degree of self-similarity between the different scales. The magnetic structuring is expected to continue down to the 10m scale, 4 orders of magnitude below the current spatial resolution limit.

scholarly journals HOLIMO II: a digital holographic instrument for ground-based in-situ observations of microphysical properties of mixed-phase clouds

2013 ◽  
Vol 6 (3) ◽  
pp. 4183-4221 ◽  
Author(s):  
J. Henneberger ◽  
J. P. Fugal ◽  
O. Stetzer ◽  
U. Lohmann
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Mixed Phase ◽  
Size Spectrum ◽  
Research Station ◽  
Resolution Limit ◽  
Microphysical Properties ◽  
Cloud Particles ◽  
Mixed Phase Clouds

Abstract. Measurements of the microphysical properties of mixed-phase clouds with high spatial resolution are important to understand the processes inside these clouds. This work describes the design and characterization of the newly developed ground-based field instrument HOLIMO II (HOLographic Imager for Microscopic Objects II). HOLIMO II uses digital in-line holography to in-situ image cloud particles in a well defined sample volume. By an automated algorithm, two-dimensional images of single cloud particles between 6 and 250 μm in diameter are obtained and the size spectrum, the concentration and water content of clouds are calculated. By testing the sizing algorithm with monosized beads a systematic overestimation near the resolution limit was found, which has been used to correct the measurements. Field measurements from the high altitude research station Jungfraujoch, Switzerland, are presented. The measured number size distributions are in good agreement with parallel measurements by a fog monitor (FM-100, DMT, Boulder USA). The field data shows that HOLIMO II is capable of measuring the number size distribution with a high spatial resolution and determines ice crystal shape, thus providing a method of quantifying variations in microphysical properties. A case study over a period of 8 h has been analyzed, exploring the transition from a liquid to a mixed-phase cloud, which is the longest observation of a cloud with a holographic device. During the measurement period, the cloud does not completely glaciate, contradicting earlier assumptions of the dominance of the Wegener–Bergeron–Findeisen (WBF) process.

scholarly journals Empirical Modelling of Public Lighting Emission Functions

2021 ◽  
Vol 13 (19) ◽  
pp. 3827
Author(s):  
Brian R. Espey
Keyword(s):  
Theoretical Models ◽  
Zenith Distance ◽  
Potential Health ◽  
Empirical Modelling ◽  
Analytical Functions ◽  
Cost Of Energy ◽  
Digital Elevation ◽  
Complex Models ◽  
Closing The Loop ◽  
Inversion Techniques

Study of light at night has increased in recent decades due to the recognition of its impact on the environment, potential health concerns, as well as both the financial and carbon cost of energy waste. The advent of more extensive and improved ground-based measurements together with quantifiable satellite data has revolutionised the field, and provided data to test improved theoretical models. However, “closing the loop” and finding a detailed connection between these measurements requires knowledge of the “city emission function”, the angular distribution of upwelling radiation with zenith distance. Simplified analytical functions have been superseded by more complex models involving statistical approximation of emission sources and obstructions and inversion techniques now permit the estimation of emission functions from the observed sky brightness measurements. In this paper, we present an efficient GIS-based method to model public lighting using real-world photometric data and high-resolution digital elevation maps of obstructions such as buildings and trees at a 1 m scale. We discuss the results of this work for a sample of Irish towns as well as a city area. We also compare our results to previous emission functions as well as to observed asymmetries in emission detected by satellites such as SUOMI VIIRS.

STEM/X-ray microanalysis across α/γ interfaces in Fe-Ni meteorites

1978 ◽  
Vol 36 (1) ◽  
pp. 416-417
Author(s):  
D. B. Williams ◽  
J. I. Goldstein
Keyword(s):  
Electron Beam ◽  
Spatial Resolution ◽  
Ion Beam ◽  
Finite Thickness ◽  
Theoretical Models ◽  
X Ray ◽  
Internal Precipitation ◽  
Precipitation Reactions ◽  
Two Phases ◽  
Characteristic Microstructure

Fe-Ni meteorites have cooled at rates ∼1-10°C/106 years giving rise to a characteristic microstructure of Widmanstatten bcc α plates that have nucleated and grown from the parent fcc γ phase. This transformation results in rejection of Ni into the remaining γ, which also exhibits a variety of internal precipitation reactions. The Ni concentration at the α/γ interface should be close to the equilibrium value between the two phases and this has been determined in several meteorites, using a Philips EM300 TEM/STEM equipped with X-ray microanalytical facilities. The sharp α/γ interface also permits a practical determination to be made of the spatial resolution of the technique. This has been performed and the result compared with the predictions of two theoretical models describing the spatial resolution in terms of the spreading of the electron beam within specimens of finite thickness.Specimens of the meteorites were sectioned such that the α/γ interface was normal to the surface, then 3mm discs were spark machined, ground to ∼100 μm thick, then ion beam thinned to electron transparency

Near-Field Scanning Optical Microscopy

1987 ◽  
Vol 45 ◽  
pp. 184-187
Author(s):  
E. Betzig ◽  
M. Isaacson ◽  
A. Lewis ◽  
K. Lin
Keyword(s):  
Spatial Resolution ◽  
Structural Damage ◽  
Near Field ◽  
Far Field ◽  
Resolution Limit ◽  
Field Methods ◽  
General Applicability ◽  
Minimal Sample ◽  
Near Field Imaging ◽  
Field Imaging

The spatial resolution of most of the imaging or microcharacterization methods presently in use are fundamentally limited by the wavelength of the exciting or the emitted radiation being used. In general, the smaller the wavelength of the exciting probe, the greater the structural damage to the sample under study. Thus, the requirements of minimal sample alteration and high spatial resolution seem to be at odds with one another.However, the reason for this wavelength resolution limit is due to the far field methods for producing or detecting the radiation of interest. If one does not use far field optics, but rather the method of near field imaging, the spatial resolution attainable can be much smaller than the wavelength of the radiation used. This method of near field imaging has a general applicability for all wave probes.

12 Solar radiation & structure

1997 ◽  
Vol 23 (1) ◽  
pp. 149-163
Keyword(s):  
High Resolution ◽  
Recent Work ◽  
Spatial Resolution ◽  
Mean Free Path ◽  
Solar Photosphere ◽  
Image Correction ◽  
Resolution Limit ◽  
Earth’S Atmosphere ◽  
Earth's Atmosphere ◽  
Solar Telescopes

Spatial structures in the solar photosphere are likely to be seen down to scales of the order of the photon mean free path, which is about 70 km in the lower photosphere. This scale corresponds to an angle of O.”1 at disk center. Structures associated with magnetic fields may be expected on even smaller scales. Existing solar telescopes typically have diameters of slightly less than one meter. Hence, even in the visible part of the spectrum, the scales of solar structures extend out to the diffraction limit of current solar telescopes. Therefore, the achievable spatial resolution is limited by turbulence in the Earth’s atmosphere (seeing). This has led to the development of various techniques to overcome this resolution limit and achieve diffraction-limited resolution. This report covers selected highlights and recent work done in the context of high-resolution techniques published in the period from July 1, 1993 to June 30, 1996. Due to the lack of space the report remains necessarily incomplete, and I apologize to all the authors of important contributions that are not cited here. This review does not cover space and balloon-borne instruments that try to achieve high spatial resolution by observing from above the Earth’s atmosphere. Recent work on ground-based high-resolution techniques has been collected in the proceedings of the 13thSacramento Peak Summer Workshop on Real Time and Post Facto Solar Image Correction (Radick 1993).

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