scholarly journals A case for limited global contraction of Mercury

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Thomas R. Watters
Keyword(s):  
Magnetic Field ◽  
Incidence Angle ◽  
Lower Degree ◽  
Tectonic Activity ◽  
Small Radius ◽  
High Incidence ◽  
Total Magnitude

AbstractMercury is a one-plate planet that has experienced significant radial contraction primarily driven by interior cooling. In some previous studies aimed at estimating the total magnitude of contraction, numerous faults are assigned to positive relief landforms, many without evidence of origin by deformation, resulting in estimates of planetary radius reduction as large as 7 km. Here we use high-incidence angle image mosaics and topography from the MESSENGER mission to map Mercury’s contractional landforms. Each landform is assigned a single, principal fault, resulting in an amount of contractional strain equivalent to a radius change of no more than 1 to 2 km. A small radius change since the end of heavy bombardment is consistent with Mercury’s long-lived magnetic field and evidence of recent tectonic activity. It is concluded that the retention of interior heat and a lower degree of contraction may be facilitated by the insulating effect of a thick megaregolith.

UNDERWATER ACOUSTIC SENSING OF SEA SURFACE WAVES

2008 ◽  
Vol 16 (01) ◽  
pp. 55-70 ◽  
Author(s):  
SUZANNE T. MCDANIEL
Keyword(s):  
Fourth Order ◽  
Cross Sections ◽  
Incidence Angle ◽  
Sea Surface ◽  
Surface Scattering ◽  
Acoustic Frequency ◽  
Acoustic Data ◽  
High Incidence ◽  
Sea Surface Waves ◽  
Scattering Cross Sections

Rough surface scattering theory is applied to the problem of estimating gravity-capillary wavenumber spectra from measurements of sea surface backscatter at high acoustic frequencies. Ensemble averaged scattering cross sections predicted by small-slope expansions are evaluated to examine the inversion of acoustic data assuming Bragg scatter. The ratio of the full fourth-order small-slope and Bragg predictions is found to exhibit a minimum value of ~ 2dB at moderate angles of incidence. At such angles, the corrections to perturbation theory depend weakly on acoustic frequency and environmental conditions. This latter finding indicates that only a modest effort is required to monitor sea surface conditions to estimate the correction. Corrections to Bragg predictions increase rapidly with increasing incidence angle and at high angles, the fourth-order contributions of the small-slope and extended small-slope expansions differ. This finding casts some doubt on the applicability of small-slope approximations to predict scattering at high-incidence angles.

scholarly journals Unsteady Pressure Measurements on a Biconvex Airfoil in a Transonic Oscillating Cascade

1986 ◽  
Vol 108 (1) ◽  
pp. 53-59 ◽  
Author(s):  
L. M. Shaw ◽  
D. R. Boldman ◽  
A. E. Buggele ◽  
D. H. Buffum
Keyword(s):  
Mach Number ◽  
Incidence Angle ◽  
Dynamic Pressure ◽  
Leading Edge ◽  
Pressure Transducers ◽  
High Incidence ◽  
Shock Motion ◽  
Plate Analysis ◽  
Phase Angles ◽  
Unsteady Pressure Measurements

Flush-mounted dynamic pressure transducers were installed on the center airfoil of a transonic oscillating cascade to measure the unsteady aerodynamic response as nine airfoils were simultaneously driven to provide 1.2 deg of pitching motion about the midchord. Initial tests were performed at an incidence angle of 0.0 deg and a Mach number of 0.65 in order to obtain results in a shock-free compressible flow field. Subsequent tests were performed at an angle of attack of 7.0 deg and a Mach number of 0.80 in order to observe the surface pressure response with an oscillating shock near the leading edge of the airfoil. Results are presented for interblade phase angles of 90 and −90 deg and at blade oscillatory frequencies of 200 and 500 Hz (semichord reduced frequencies up to about 0.5 at a Mach number of 0.80). Results from the zero-incidence cascade are compared with a classical unsteady flat-plate analysis. Flow visualization results depicting the shock motion on the airfoils in the high-incidence cascade are discussed. The airfoil pressure data are tabulated.

scholarly journals Optimization of threshold ranges for rapid flood inundation mapping by evaluating backscatter profiles of high incidence angle SAR images

2012 ◽  
Vol 3 (2) ◽  
pp. 113-122 ◽  
Author(s):  
Panchagnula Manjusree ◽  
L. Prasanna Kumar ◽  
Chandra Mohan Bhatt ◽  
Goru Srinivasa Rao ◽  
Veerubhotla Bhanumurthy
Keyword(s):  
Incidence Angle ◽  
Flood Inundation ◽  
Sar Images ◽  
High Incidence ◽  
Inundation Mapping ◽  
Flood Inundation Mapping

Terahertz radiation from a shallow incidence-angle InAs emitter in a magnetic field irradiated with femtosecond laser pulses

2001 ◽  
Vol 40 (9) ◽  
pp. 1369 ◽  
Author(s):  
Shingo Ono ◽  
Takeyo Tsukamoto ◽  
Eiji Kawahata ◽  
Takayuki Yano ◽  
Hideyuki Ohtake ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Femtosecond Laser ◽  
Terahertz Radiation ◽  
Incidence Angle ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses

Recording and reproducing properties of magnetic tape by high incidence angle nucleation method

1982 ◽  
Vol 18 (6) ◽  
pp. 1209-1211 ◽  
Author(s):  
Y. Ohta ◽  
K. Nakamura ◽  
A. Itoh ◽  
C. Hayashi
Keyword(s):  
Magnetic Tape ◽  
Incidence Angle ◽  
High Incidence

Evaluation of Compressor Blading With Blade End Slots and Full-Span Slots in a Highly Loaded Compressor Cascade

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Yumeng Tang ◽  
Yangwei Liu ◽  
Lipeng Lu
Keyword(s):  
Incidence Angle ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Main Flow ◽  
The Self ◽  
Flow Structures ◽  
Compressor Cascade ◽  
Corner Separation ◽  
High Incidence ◽  
Highly Loaded

Abstract Blade end slots were proposed to control corner separation in a highly loaded compressor cascade in our previous studies. This study focuses on the evaluation of compressor blading with blade end slots and full-span slots. First, the two-dimensional configuration performance is evaluated both for the datum and slotted profiles. The slotted configuration could effectively suppress separation, especially under positive incidence conditions when the separation is large. Thus, two three-dimensional blading with full-span slots and blade end slots (20% span height from the endwall) are compared. Results show that blading with full-span slots could effectively reduce the loss and enlarge pressure rise under relative high incidence angles, while blading with blade end slots could effectively reduce the loss and enlarge pressure rise above an incidence angle of −4 deg. Blading with slots alters the flow structures and reorganizes the flow in the blade end regions. The self-adaptive jets from the slots reenergize the low-momentum flow downstream and restrain its migration toward the mid-span, so that the corner separation is reduced and the performance is enhanced. The loss for the end slotted blade is lower than that of the full-span slotted blade under incidence angles within 4 deg. This is because the additional mixing loss of the jet and the main flow are caused by the full-span slots at the mid-span regions where the flow remains attached for the blade end slots.

Estimation of soil moisture from Sentinel data

2020 ◽  
Author(s):  
Stefan Krebs Lange-Willman ◽  
Henning Skriver ◽  
Inge Sandholt
Keyword(s):  
Soil Moisture ◽  
Incidence Angle ◽  
Speckle Noise ◽  
Detection Algorithm ◽  
Retrieval Algorithm ◽  
Innovation Fund ◽  
High Incidence ◽  
Land Cover Maps ◽  
The Impact

<p>The present project presents the technical implementation, testing and validation of a soil moisture retrieval algorithm in Python using C-band Sentinel-1 data at high incidence angle (∼42°). The retrieval algorithm is based on the alpha approximation, first developed by [Balenzano et al. 2011]. The alpha approximation utilizes the dense temporal coverage of the Sentinel-1 mission, assuming that changes in backscatter between subsequent acquisitions are only due to variations in soil moisture, such that vegetation and roughness can be neglected. The area used for testing the algorithm was chosen to be the region surrounding the Foulum test center for agricultural studies in Denmark, due to the availability of time series from 2018 of in situ soil moisture measurements to be used for validation. Masking of too densely vegetated areas have been performed using the cross-polarized component of the SAR backscatter, which have been validated using NDVI maps. </p><p>Auxiliary data, including land cover maps and parcel borders enable the computation of backscatter field means, significantly reducing the impact of speckle noise and thus decreasing uncertainty of the estimated soil moisture. Consequently, the results have field scale resolution (i.e. ∼0.1 km). The permittivity to soil moisture inversion is performed using a polynomial model by [Hallikainen et al. 1985], where a soil texture map provide the information necessary to obtain precise results. </p><p>Further work will aim toward applying a change detection algorithm in order to detect sudden temporal changes in vegetation and surface roughness, as the alpha approximation is inherently sensitive to such sudden changes.</p><p>The study has received partial funding from Innovation Fund Denmark, contract number: 7049-00004B (MOIST).</p>

Closed-Loop Flow Control of a Forebody at a High Incidence Angle

AIAA Journal ◽  
2014 ◽  
Vol 52 (7) ◽  
pp. 1430-1440 ◽  
Author(s):  
Chris Porter ◽  
Casey Fagley ◽  
John Farnsworth ◽  
Jürgen Seidel ◽  
Thomas McLaughlin
Keyword(s):  
Flow Control ◽  
Closed Loop ◽  
Incidence Angle ◽  
High Incidence

Calculation of magnitude magnetic transforms with high centricity and low dependence on the magnetization vector direction

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. I21-I30 ◽  
Author(s):  
Daniela Gerovska ◽  
Marcos J. Araúzo-Bravo
Keyword(s):  
Magnetic Field ◽  
Magnetization Vector ◽  
Field Vector ◽  
Data Sets ◽  
Volcanic Area ◽  
Square Root ◽  
Anomalous Magnetic Field ◽  
Total Magnitude ◽  
Vector Direction ◽  
Magnitude Magnetic Transforms

We present a Matlab tool that calculates five magnitude magnetic transforms (MMTs) from an input measured anomalous magnetic field. The MMTs are all based on the total magnitude anomaly (TMA), and consist of the TMA itself, the modulus of the gradient of the TMA, the Laplacian of the TMA, half of the square root of the Laplacian of the square of the TMA, and the square root of the product of the TMA plus the Laplacian of the TMA. These MMTs produce anomalies that are closer to the magnetic source’s true horizontal position and are simpler to interpret than the measured anomalous magnetic field itself. While the conventional magnetic transforms of reduction-to-the-pole (RTP), the pseudogravity field, and the analytic signal (AS) also have these properties, these MMTs have several additional advantages. They require only first-order, horizontal derivatives for their calculation. They are also more stable at low magnetic latitudes than the RTP, and have a pattern that is independent of the geomagnetic-field vector direction, in contrast to the AS. The Matlab tool is designed to deal with big data sets and is compatible with common data formats, GS ASCII grid files, and XYZ data files. A calculation of the MMTs of the total magnetic anomaly of a synthetic example at a low magnetic latitude and with a field example from the Kuju volcanic area, Japan demonstrate the effectiveness of the program.

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