scholarly journals The Fast Simulation of Scattering Characteristics from a Simplified Time Varying Sea Surface

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Yiwen Wei ◽  
Lixin Guo ◽  
Xiao Meng
Keyword(s):  
Realistic Model ◽  
Short Wave ◽  
Capillary Waves ◽  
Long Waves ◽  
Sea Surface ◽  
Surface Model ◽  
Time Varying ◽  
Resonant Condition ◽  
Scattering Coefficients ◽  
Doppler Shifts

This paper aims at applying a simplified sea surface model into the physical optics (PO) method to accelerate the scattering calculation from 1D time varying sea surface. To reduce the number of the segments and make further improvement on the efficiency of PO method, a simplified sea surface is proposed. In this simplified sea surface, the geometry of long waves is locally approximated by tilted facets that are much longer than the electromagnetic wavelength. The capillary waves are considered to be sinusoidal line superimposing on the long waves. The wavenumber of the sinusoidal waves is supposed to satisfy the resonant condition of Bragg waves which is dominant in all the scattered short wave components. Since the capillary wave is periodical within one facet, an analytical integration of the PO term can be performed. The backscattering coefficient obtained from a simplified sea surface model agrees well with that obtained from a realistic sea surface. The Doppler shifts and width also agree well with the realistic model since the capillary waves are taken into consideration. The good agreements indicate that the simplified model is reasonable and valid in predicting both the scattering coefficients and the Doppler spectra.

scholarly journals Study of the Electromagnetic Waves Propagation over the Improved Fractal Sea Surface Based on Parabolic Equation Method

2016 ◽  
Vol 2016 ◽  
pp. 1-7
Author(s):  
Wenwan Ding ◽  
Kun Wang ◽  
Yunliang Long
Keyword(s):  
Parabolic Equation ◽  
Electromagnetic Waves ◽  
Capillary Waves ◽  
Sea Surface ◽  
Surface Model ◽  
Waves Propagation ◽  
The One ◽  
Rough Sea Surface ◽  
Rough Sea ◽  
Spectrum Inversion

An improved fractal sea surface model, which can describe the capillary waves very well, is introduced to simulate the one-dimension rough sea surface. In this model, the propagation of electromagnetic waves (EWs) is computed by the parabolic equation (PE) method using the finite-difference (FD) algorithm. The numerical simulation results of the introduced model are compared with those of the Miller-Brown model and the Elfouhaily spectrum inversion model. It has been shown that the effects of the fine structure of the sea surface on the EWs propagation in the introduced model are more apparent than those in the other two models.

scholarly journals Doppler spectrum of microwave SAR signals from two-dimensional time-varying sea surface

2016 ◽  
Vol 30 (10) ◽  
pp. 1265-1276 ◽  
Author(s):  
Yunhua Wang ◽  
Yanmin Zhang ◽  
Huimin Li ◽  
Ge Chen
Keyword(s):  
Sea Surface ◽  
Doppler Spectrum ◽  
Time Varying ◽  
Two Dimensional

Surface waves on shear currents: solution of the boundary-value problem

1993 ◽  
Vol 252 ◽  
pp. 565-584 ◽  
Author(s):  
Victor I. Shrira
Keyword(s):  
Boundary Value Problem ◽  
Growth Rates ◽  
Wave Motion ◽  
Boundary Value ◽  
A Priori ◽  
Approximate Solutions ◽  
Short Wave ◽  
Capillary Waves ◽  
Potential Motion ◽  
Approximate Expressions

We consider a classic boundary-value problem for deep-water gravity-capillary waves in a shear flow, composed of the Rayleigh equation and the standard linearized kinematic and dynamic inviscid boundary conditions at the free surface. We derived the exact solution for this problem in terms of an infinite series in powers of a certain parameter e, which characterizes the smallness of the deviation of the wave motion from the potential motion. For the existence and absolute convergence of the solution it is sufficient that e be less than unity.The truncated sums of the series provide approximate solutions with a priori prescribed accuracy. In particular, for the short-wave instability, which can be interpreted as the Miles critical-layer-type instability, the explicit approximate expressions for the growth rates are derived. The growth rates in a certain (very narrow) range of scales can exceed the Miles increments caused by the wind.The effect of thin boundary layers on the dispersion relation was also investigated using an asymptotic procedure based on the smallness of the product of the layer thickness and wavenumber. The criterion specifying when and with what accuracy the boundary-layer influence can be neglected has been derived.

Short-wave infrared continuous-variable quantum key distribution over satellite-to-submarine channels

2022 ◽  
Author(s):  
Qingquan Peng ◽  
Qin Liao ◽  
Hai Zhong ◽  
Junkai Hu ◽  
Ying Guo
Keyword(s):  
Quantum Key Distribution ◽  
Key Distribution ◽  
Short Wave ◽  
Continuous Variable ◽  
Sea Surface ◽  
Quantum Communications ◽  
Submarine Channels ◽  
Alternative Scheme ◽  
Transmission Distance ◽  
Short Wave Infrared

Abstract The trans-media transmission of quantum pulse is one of means of free-space transmission which can be applied in continuous-variable quantum key distribution (CVQKD) system. In traditional implementations for atmospheric channels, the 1500-to-1600-nm pulse is regarded as an ideal quantum pulse carrier. Whereas, the underwater transmission of this pulses tends to suffer from severe attenuation, which inevitably deteriorates the security of the whole CVQKD system. In this paper, we propose an alternative scheme for implementations of CVQKD over satellite-to-submarine channels. We estimate the parameters of the trans-media channels, involving atmosphere, sea surface and seawater and find that the short-wave infrared performs well in the above channels. The 450 nm pulse is used for generations of quantum signal carriers to accomplish quantum communications through atmosphere, sea surface and seawater channels. Numerical simulations show that the proposed scheme can achieve the transmission distance of 600 km. In addition, we demonstrate that non-Gaussian operations can further lengthen its maximal transmission distance, which contributes to the establishment of practical global quantum networks.

scholarly journals Improving the Positioning Accuracy of Satellite-Borne GNSS-R Specular Reflection Point on Sea Surface Based on the Ocean Tidal Correction Positioning Method

2019 ◽  
Vol 11 (13) ◽  
pp. 1626 ◽  
Author(s):  
Fan Wu ◽  
Wei Zheng ◽  
Zhaowei Li ◽  
Zongqiang Liu
Keyword(s):  
Specular Reflection ◽  
Tidal Height ◽  
Sea Surface ◽  
Time Varying ◽  
Reference Surface ◽  
Positioning Error ◽  
Reflection Point ◽  
Positioning Accuracy ◽  
Static State ◽  
Elevation Difference

The positioning error of the specular reflection point is the main error source of Global Navigation Satellite System Reflectometry (GNSS-R) satellite sea surface altimetry. The existing specular reflection point geometric positioning methods do not consider the static-state elevation difference of tens of meters and the decimeter-level time-varying elevation difference between the reflection reference surface and the instantaneous sea surface. The resulting positioning error restricts the GNSS-R satellite sea surface altimetry from reaching cm-level high accuracy on the reference datum. Under the premise of the basic static-state elevation positioning error correction, reducing the time-varying elevation positioning error is the key to improving positioning accuracy. In this study, based on the principle of elevation correction of GNSS-R reflection reference surface, the main parameter that determines the real-time variation of sea surface height, ocean tide, is used to correct the specular reflection point from geoid to ocean tidal surface. The positioning error caused by the time-varying elevation error of the reflection reference surface is reduced, the positioning accuracy is improved, and the improvement is quantified. According to the research results, the ocean tidal correction positioning (OTCP) method improves the positioning accuracy by 0.31 m. The positioning accuracy improvement has a good correlation with the corresponding tidal height modulo, and the improvement is 1.07 times of the tidal height modulo. In the offshore, the tidal height gradient modulo is greater than the deep sea, the gradient of the tidal positioning correction has a good response to the tidal height gradient modulo, while the sensitivity of this response decreases in the deep sea.

scholarly journals HETEROGENEOUS EXPECTATIONS AND ASSET PRICE DYNAMICS

2020 ◽  
pp. 1-31 ◽  
Author(s):  
Noemi Schmitt
Keyword(s):  
Financial Markets ◽  
Asset Price ◽  
Realistic Model ◽  
Fixed Number ◽  
Time Varying ◽  
Pricing Model ◽  
Rational Agents ◽  
Asset Pricing Model ◽  
Method Of Simulated Moments ◽  
Agents Heterogeneity

Within the seminal asset-pricing model by Brock and Hommes (Journal of Economic Dynamics Control 22, 1235–1274, 1998), heterogeneous boundedly rational agents choose between a fixed number of expectation rules to forecast asset prices. However, agents’ heterogeneity is limited in the sense that they typically switch between a representative technical and a representative fundamental expectation rule. Here, we generalize their framework by considering that all agents follow their own time-varying technical and fundamental expectation rules. Estimating our model using the method of simulated moments reveals that it is able to explain the statistical properties of the daily and monthly behavior of the S&P500 quite well. Moreover, our analysis reveals that heterogeneity is not only a realistic model property but clearly helps to explain the intricate dynamics of financial markets.

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