Time dependence in forward scattering: Experimental results and model comparisons derived from sea surface and seabed bistatic cross sections

1998 ◽  
Vol 103 (5) ◽  
pp. 3094-3094
Author(s):  
Peter H. Dahl ◽  
Kevin L. Williams
Keyword(s):  
Time Dependence ◽  
Cross Sections ◽  
Forward Scattering ◽  
Experimental Results ◽  
Sea Surface ◽  
Model Comparisons

scholarly journals Experimental study of the $ \gamma p \rightarrow K^{0}\Sigma^{+}$, $ \gamma n \rightarrow K^{0} \Lambda$, and $ \gamma n \rightarrow K^{0} \Sigma^{0}$ reactions at the Mainz Microtron

2019 ◽  
Vol 55 (11) ◽  
Author(s):  
C. S. Akondi ◽  
K. Bantawa ◽  
D. M. Manley ◽  
S. Abt ◽  
P. Achenbach ◽  
...  
Keyword(s):  
Experimental Study ◽  
Cross Sections ◽  
Differential Cross ◽  
Legendre Polynomials ◽  
Neutral Kaon ◽  
Experimental Results ◽  
Differential Cross Sections ◽  
Theoretical Predictions ◽  
Photoproduction Reactions ◽  
Insight Into

Abstract.This work measured $ \mathrm{d}\sigma/\mathrm{d}\Omega$dσ/dΩ for neutral kaon photoproduction reactions from threshold up to a c.m. energy of 1855MeV, focussing specifically on the $ \gamma p\rightarrow K^0\Sigma^+$γp→K0Σ+, $ \gamma n\rightarrow K^0\Lambda$γn→K0Λ, and $ \gamma n\rightarrow K^0 \Sigma^0$γn→K0Σ0 reactions. Our results for $ \gamma n\rightarrow K^0 \Sigma^0$γn→K0Σ0 are the first-ever measurements for that reaction. These data will provide insight into the properties of $ N^{\ast}$N* resonances and, in particular, will lead to an improved knowledge about those states that couple only weakly to the $ \pi N$πN channel. Integrated cross sections were extracted by fitting the differential cross sections for each reaction as a series of Legendre polynomials and our results are compared with prior experimental results and theoretical predictions.

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.

Multiple ionization of argon by positron impact

1996 ◽  
Vol 74 (7-8) ◽  
pp. 373-375 ◽  
Author(s):  
R. Hippler ◽  
S. Helms ◽  
U. Brinkmann ◽  
J. Deiwiks ◽  
H. Schneider ◽  
...  
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Experimental Results ◽  
Positronium Formation ◽  
Positron Impact ◽  
Single Ionization ◽  
Multiple Ionization

Recent experimental results for the multiple ionization of argon by positron impact have been reanalysed. Absolute cross sections for the double and triple ionization of argon were obtained from measured ratios of double-to-single and triple-to-single ionization, using known cross sections for single ionization and for positronium formation. Distinct differences compared to similar results for electron impact are noted.

L X-ray fluorescence cross sections in the atomic region 59 ≤ Z ≤ 82 excited by 16.58 keV photons

1996 ◽  
Vol 74 (5-6) ◽  
pp. 230-235 ◽  
Author(s):  
D. V. Rao ◽  
R. Cesareo ◽  
G. E. Gigante
Keyword(s):  
Excitation Energy ◽  
Least Squares ◽  
Cross Sections ◽  
Experimental Results ◽  
X Ray ◽  
Experimental Cross ◽  
Average Fluorescence ◽  
Good Agreement

LL, Lα, Lβ, and Lγ X-ray fluorescence cross sections for Pr, Sm, Gd, Dy, Ho, Er, Yb, Pt Au, and Pb were measured at the excitation energy 16.58 keV. An X-ray tube and a secondary excitor system was used instead of radioisotopes for the measurements. Experimental cross sections are compared with the theoretical estimates based on relativistic Dirac–Hartree–Slater theory. Average L-shell fluorescence yields [Formula: see text] are deduced using the present experimental cross sections and the theoretical subshell photoionization cross sections. The derived average fluorescence yields are fitted by least squares to polynomials in Z of the form ΣnanZn and compared with theoretical and earlier fitted values. Good agreement is observed ' between the experimental results and the theoretical estimates based on relativistic Dirac–Hartree–Slater theory.

Assessment of the numerical and experimental performance of screw tidal turbines

2018 ◽  
Vol 232 (7) ◽  
pp. 912-925 ◽  
Author(s):  
Hamid Rahmani ◽  
Mojtaba Biglari ◽  
Mohammad Sadegh Valipour ◽  
Kamran Lari
Keyword(s):  
Output Power ◽  
Water Flow ◽  
Cross Sections ◽  
Turbine Blades ◽  
Transient State ◽  
Experimental Results ◽  
Ansys Fluent ◽  
Tidal Turbines ◽  
Collision Problem ◽  
Mesh Independence

This study was aimed at the numerical and experimental modeling of water flow during collision between water and vertical screw turbine blades with different cross sections (i.e. Darrieus, spoon, and airfoil). ANSYS Fluent was used to model water flow under tidal currents in a flume, and mesh independence was ensured after the selection of appropriate geometry. The collision problem was then solved in the transient state, and results on the momentum and power generated by different inlet velocities and different blade cross sections were analyzed. The findings showed that torque and turbine power increased with increasing inlet velocity. Subsequently, a turbine was experimentally created, with cross sections drawn in the numerical model and tested under the same conditions as that imposed on the model. Installing a multimeter on the turbine enabled the generation of turbine power in different dimensions. The resultant power increased with rising turbine dimensions. After obtaining the numerical and experimental results, the value of the output power of the turbine was validated. The validation indicated a 7% difference in output power between the numerical and experimental results, indicating acceptable accuracy.

scholarly journals Efficient Numerical Full-Polarized Facet-Based Model for EM Scattering from Rough Sea Surface within a Wide Frequency Range

2019 ◽  
Vol 11 (1) ◽  
pp. 75 ◽  
Author(s):  
Jinxing Li ◽  
Min Zhang ◽  
Ye Zhao ◽  
Wangqiang Jiang
Keyword(s):  
Cross Sections ◽  
High Efficiency ◽  
Wide Frequency Range ◽  
Sea Surface ◽  
Doppler Spectrum ◽  
Frequency Range ◽  
Em Scattering ◽  
Wind Speeds ◽  
Novel Approach ◽  
Rough Sea Surface

A full-polarized facet based scattering model (FPFSM) for investigating the electromagnetic (EM) scattering by two-dimensional electrically large sea surfaces with high efficiency at high microwave bands is proposed. For this method, the scattering field over a large sea facet in a diffuse scattering region is numerically deduced according to the Bragg scattering mechanism. In regard to near specular directions, a novel approach is proposed to calculate the scattered field from a sea surface based on the second order small slope approximation (SSA-II), which saves computer memory considerably and is able to analyze the EM scattering by electrically large sea surfaces. The feasibility of this method in evaluating the radar returns from the sea surface is proved by comparing the normalized radar cross sections (NRCS) and the Doppler spectrum with the SSA-II. Then NRCS results in monostatic and bistatic configurations under different polarization states, scattering angles and wind speeds are analyzed as well as the Doppler spectrum at Ka-band. Numerical results show that the FPFSM is a reliable and efficient method to analyze the full-polarized scattering characteristics from electrically large sea surface within a wide frequency range.

scholarly journals The Electron Impact Ionization Cross Sections of Methanol, Ethanol and 1-Propanol

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 60 ◽  
Author(s):  
Yogesh Kumar ◽  
Manoj Kumar ◽  
Sachin Kumar ◽  
Rajeev Kumar
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
Impact Ionization ◽  
Experimental Results ◽  
Oscillator Strengths ◽  
Ionization Cross ◽  
Total Ionization ◽  
Plane Wave Born Approximation ◽  
Ionization Cross Sections ◽  
Good Agreement

In the present investigation, the plane-wave Born approximation was employed to calculate the total ionization cross sections by electron impact of methanol, ethanol and 1-propanol from the threshold of ionization to 10 MeV. This method requires continuum generalized oscillator strengths (CGOSs). The two different semi-phenomenological expressions of CGOS, given by Mayol and Salvat and Weizsacker and Williams, along with approximated form of the continuum optical oscillator strength (COOS) by Khare et al. were used. Furthermore, the average of the above two CGOSs was also used. The calculated ionization cross sections were compared to the available previous theoretical results and experimental data. Out of three CGOSs, the present results with the average CGOS were found in good agreement with the available experimental results for all the considered molecules. Collision parameters CRP were also calculated from 0.1 to 100 MeV and the calculations were found to be in excellent agreement with the experimental results of Reike and Prepejchal.

The Preprocessing for Infrared Sea-Surface Target Image

2012 ◽  
Vol 433-440 ◽  
pp. 4512-4515
Author(s):  
Shu Li Lou ◽  
Jian Cun Ren ◽  
Yan Li Han ◽  
Xiao Hu Yuan ◽  
Xiao Dong Zhou
Keyword(s):  
Feature Extraction ◽  
Target Recognition ◽  
Infrared Image ◽  
Automatic Target Recognition ◽  
Experimental Results ◽  
Sea Surface ◽  
Practical Application ◽  
Target Image

The preprocessing for infrared sea-surface target image is very important to automatic target recognition and tracking. The preprocessing can reduce noise and enhance target, and it is the base of feature extraction and target recognition. The scene model of infrared sea-surface target image was established. The characteristics of infrared image are analyzed, and several methods of preprocessing nowadays were analyzed and compared. According to the different characteristic of infrared image, a preprocessing scheme is proposed. The experimental results indicate that in practical application appropriate methods should be chosen for different purpose. In order to get good preprocessing effects, these methods can be assembled into multi- process.

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