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Search Results: 1 - 10 of 549290 matches for " J.-S. "
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Solar wind modulation of the Martian ionosphere observed by Mars Global Surveyor
J.-S. Wang,E. Nielsen
Annales Geophysicae (ANGEO) , 2004,
Abstract: Electron density profiles in the Martian ionosphere observed by the radio occultation experiment on board Mars Global Surveyor have been analyzed to determine if the densities are influenced by the solar wind. Evidence is presented that the altitude of the maximum ionospheric electron density shows a positive correlation to the energetic proton flux in the solar wind. The solar wind modulation of the Martian ionosphere can be attributed to heating of the neutral atmosphere by the solar wind energetic proton precipitation. The modulation is observed to be most prominent at high solar zenith angles. It is argued that this is consistent with the proposed modulation mechanism.
Asymptotic Radiation Field of Asymmetric Planar Dielectric Waveguide
J.-S. Lee D. P. Nyquist
PIER , 2003, DOI: 10.2528/PIER03020801
Abstract: This paper describes the steepest-descent evaluation of the radiation field for both TE and TM modes of an asymmetric planar open waveguide. The cover, film and substrate field will be formulated in the spectral domain. The steepest-descent path in the complex axial transform plane ( -plane) is identified as a direct method and that in the complex -plane ( = +j ·: complex polar coordinate) is also identified as an indirect method in order to validate the steepestdescent path in the complex axial transform plane ( -plane). The branch cut integration will be rigorously analyzed through complexphasor diagrams. An alternative integration path will be also identified since it is an effective method to validate the steepest-descent and branch cut integrations. Then, the steepest-descent evaluation of cover and substrate fields and numerical results for TE modes will be presented and numerical implementation for TM modes will be accommodated in the future research.
The Proper Current Spectra of an Open Integrated Microstrip Waveguide
J.-S. Lee D. P. Nyquist
PIER , 2004, DOI: 10.2528/PIER03051201
Abstract: Continuous current spectrum of an integrated open waveguide structure is identified as the branch cut contribution to singularity expansion of those currents in the complex axial transform plane. Those singularities in that plane include poles associated with the guiding structure and branch points contributed by layered background environments. The manner in which singularities in background environments manifest themselves as branch points in the complex axial transform plane is reviewed. Based on spectral integral equation formulation, approximate and analytical expression for spatial microstrip current is obtained. That approximation is based on Maxwellian distribution for the transverse current profile. This result is the representation of currents in terms of proper propagation mode spectrum. During the integration around branch cuts, singularities in the transverse transform plane migrate in a complicated manner. The trajectories of this migration are identified and suitably accommodated during the real axis integration in that plane. This overall procedure leads to a decomposition of the total currents into bound modes and continuous spectrum contributions. This representation is validated by real axis integration in the axial transform plane. The quasi TEM characteristic impedance of bound mode is calculated and validated by comparison with well-known empirical formula.
Multifractal earth topography
J.-S. Gagnon, S. Lovejoy,D. Schertzer
Nonlinear Processes in Geophysics (NPG) , 2006,
Abstract: This paper shows how modern ideas of scaling can be used to model topography with various morphologies and also to accurately characterize topography over wide ranges of scales. Our argument is divided in two parts. We first survey the main topographic models and show that they are based on convolutions of basic structures (singularities) with noises. Focusing on models with large numbers of degrees of freedom (fractional Brownian motion (fBm), fractional Levy motion (fLm), multifractal fractionally integrated flux (FIF) model), we show that they are distinguished by the type of underlying noise. In addition, realistic models require anisotropic singularities; we show how to generalize the basic isotropic (self-similar) models to anisotropic ones. Using numerical simulations, we display the subtle interplay between statistics, singularity structure and resulting topographic morphology. We show how the existence of anisotropic singularities with highly variable statistics can lead to unwarranted conclusions about scale breaking. We then analyze topographic transects from four Digital Elevation Models (DEMs) which collectively span scales from planetary down to 50 cm (4 orders of magnitude larger than in previous studies) and contain more than 2×108 pixels (a hundred times more data than in previous studies). We use power spectra and multiscaling analysis tools to study the global properties of topography. We show that the isotropic scaling for moments of order ≤2 holds to within ±45% down to scales ≈40 m. We also show that the multifractal FIF is easily compatible with the data, while the monofractal fBm and fLm are not. We estimate the universal parameters (α, C1) characterizing the underlying FIF noise to be (1.79, 0.12), where α is the degree of multifractality (0≤α≤2, 0 means monofractal) and C1 is the degree of sparseness of the surface (0≤C1, 0 means space filling). In the same way, we investigate the variation of multifractal parameters between continents, oceans and continental margins. Our analyses show that no significant variation is found for (α, C1) and that the third parameter H, which is a degree of smoothing (higher H means smoother), is variable: our estimates are H=0.46, 0.66, 0.77 for bathymetry, continents and continental margins. An application we developped here is to use (α, C1) values to correct standard spectra of DEMs for multifractal resolution effects. Full Article (PDF, 3467 KB) Citation: Gagnon, J.-S., Lovejoy, S., and Schertzer, D.: Multifractal earth topography, Nonlin. Processes Geophys., 13, 541-570, doi:10.5194/npg-13-541-2006, 2006. Bibtex EndNote Reference Manager XML
The Kuroshio exchange with the South and East China Seas
T. Matsuno,J.-S. Lee,S. Yanao
Ocean Science (OS) & Discussions (OSD) , 2009,
Abstract: The Kuroshio flows along the edges of the marginal East Asian seas such as the South China Sea (SCS) and East China Sea (ECS). Exchanges of materials and energy between the Kuroshio and the marginal seas partly control the environments of the marginal seas. In particular, saline water from the Kuroshio maintains certain salinity in the shelf water in the ECS. Nutrients from the subsurface of the Kuroshio may influence primary production on the shelf. We summarize how the Kuroshio comes into contact with the shelf water or marginal seas, describing phenomena related to the exchange between the Kuroshio and the ECS along with the SCS, using reports in the literature along with original data. The Kuroshio tends to intrude into the SCS through the Luzon Strait in various manners such as direct intrusion, associated with eddies and as a loop current. The Kuroshio intrusion into the shelf region of the ECS has distinct seasonal variation and the Taiwan Warm Current plays a significant role in the determination of water properties in the outer shelf associated with the Kuroshio intrusion. We then examine physical processes related to the interaction between the Kuroshio and shelf water. Interaction between the Kuroshio and the bottom topography is an important process in the control of the exchange around the shelf break. Vertical mixing and frontal eddies are also important factors that control the water exchange and formation of water masses in the outer shelf. Wind stress plays a significant role in the exchange with a rather event-like manner. To determine the source of the water masses, chemical tracers could be powerful tools and it is suggested that a significant part of the shelf water consists of Kuroshio intermediate water.
Influence of the Kuroshio on the water properties in the shelf
T. Matsuno,J.-S. Lee,S. Yanao
Ocean Science Discussions (OSD) , 2009,
Abstract: The Kuroshio flows along the edges of the marginal East Asian seas such as the South China Sea (SCS) and East China Sea (ECS). Exchanges of materials and energy between the Kuroshio and the marginal seas partly control the environments of the marginal seas. In particular, saline water from the Kuroshio maintains certain salinity in the shelf water in the ECS. Nutrients from the subsurface of the Kuroshio may influence primary production on the shelf. We summarize how the Kuroshio comes into contact with the shelf water or marginal seas, describing phenomena related to the exchange between the Kuroshio and the ECS along with the SCS, using reports in the literature along with original data. The Kuroshio tends to intrude into the SCS as a loop current around the Luzon Strait. The Kuroshio intrusion into the shelf region of the ECS has distinct seasonal variation and the Taiwan Warm Current plays a significant role in the determination of water properties in the outer shelf associated with the Kuroshio intrusion. We then examine physical processes related to the interaction between the Kuroshio and shelf water. Interaction between the Kuroshio and the bottom topography is an important process in the control of the exchange around the shelf break. Vertical mixing and frontal eddies are also important factors that control the water exchange and formation of water masses in the outer shelf. Wind stress plays a significant role in the exchange with a rather event-like manner. To determine the source of the water masses, chemical tracers could be powerful tools and it is suggested that a significant part of the shelf water consists of Kuroshio intermediate water.
On Sequences of Numbers and Polynomials Defined by Linear Recurrence Relations of Order 2
Tian-Xiao He,Peter J.-S. Shiue
International Journal of Mathematics and Mathematical Sciences , 2009, DOI: 10.1155/2009/709386
Abstract: Here we present a new method to construct the explicit formula of a sequence of numbers and polynomials generated by a linear recurrence relation of order 2. The applications of the method to the Fibonacci and Lucas numbers, Chebyshev polynomials, the generalized Gegenbauer-Humbert polynomials are also discussed. The derived idea provides a general method to construct identities of number or polynomial sequences defined by linear recurrence relations. The applications using the method to solve some algebraic and ordinary differential equations are presented.
The energetics response to a warmer climate: relative contributions from the transient and stationary eddies
D. Hernández-Deckers,J.-S. von Storch
Earth System Dynamics (ESD) & Discussions (ESDD) , 2011, DOI: 10.5194/esd-2-105-2011
Abstract: We use the Lorenz Energy Cycle (LEC) to evaluate changes in global energetic activity due to CO2-doubling in the coupled atmosphere-ocean ECHAM5/MPI-OM model. Globally, the energetic activity – measured as the total conversion rate of available potential energy into kinetic energy – decreases by about 4 %. This weakening results from a dual response that consists of a strengthening of the LEC in the upper-troposphere and a weakening in the lower and middle troposphere. This is fully consistent with results from a coarser resolution version of the same coupled model. We further use our experiments to investigate the individual contributions of the transient and stationary eddy components to the main energetics response. The transient eddy terms have a larger contribution to the total energetic activity than the stationary ones. We find that this is also true in terms of their 2 × CO2-response. Changes in the transient eddy components determine the main energetics response, whereas the stationary eddy components have very small contributions. Hence, the dual response – strengthening in the upper troposphere and weakening below – concerns mainly the transient eddy terms. We can relate qualitatively this response to the two main features of the 2 × CO2 warming pattern: (a) the tropical upper-tropospheric warming increases the pole-to-equator temperature gradient – strengthening the energetic activity above – and enhances static stability – weakening the energetic activity below; and (b) the high-latitude surface warming decreases the pole-to-equator temperature gradient in the lower troposphere – weakening the energetic activity below. Despite the small contribution from the stationary eddies to the main energetics response, changes in stationary eddy available potential energy (Pse) reflect some features of the warming pattern: stronger land-sea contrasts at the subtropics and weaker land-sea contrasts at the high northern latitudes affect Pse regionally, but do not affect the global energetics response.
Generalized analytical solution for advection-dispersion equation in finite spatial domain with arbitrary time-dependent inlet boundary condition
J.-S. Chen,C.-W. Liu
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2011,
Abstract: This study presents a generalized analytical solution for one-dimensional solute transport in finite spatial domain subject to arbitrary time-dependent inlet boundary condition. The governing equation includes terms accounting for advection, hydrodynamic dispersion, linear equilibrium sorption, and first order decay processes. The generalized analytical solution is derived by using the Laplace transform with respect to time and the generalized integral transform technique with respect to the spatial coordinate. Some special cases are presented and compared to illustrate the robustness of the derived generalized analytical solution. Result shows an excellent agreement between the analytical and numerical solutions. The analytical solutions of the special cases derived in this study have practical applications. Moreover, the derived generalized solution which consists an integral representation is evaluated by the numerical integration to extend its usage. The developed generalized solution offers a convenient tool for further development of analytical solution of specified time-dependent inlet boundary conditions or numerical evaluation of the concentration field for arbitrary time-dependent inlet boundary problem.
Terrain surfaces and 3-D landcover classification from small footprint full-waveform lidar data: application to badlands
F. Bretar,A. Chauve,J.-S. Bailly,C. Mallet
Hydrology and Earth System Sciences Discussions , 2009,
Abstract: This article presents the use of new remote sensing data acquired from airborne full-waveform lidar systems. They are active sensors which record altimeter profiles. This paper introduces a set of methodologies for processing these data. These techniques are then applied to a particular landscape, the badlands, but the methodologies are designed to be applied to any other landscape. Indeed, the knowledge of an accurate topography and a landcover classification is a prior knowledge for any hydrological and erosion model. Badlands tend to be the most significant areas of erosion in the world with the highest erosion rate values. Monitoring and predicting erosion within badland mountainous catchments is highly strategic due to the arising downstream consequences and the need for natural hazard mitigation engineering. Additionaly, beyond the altimeter information, full-waveform lidar data are processed to extract intensity and width of echoes. They are related to the target reflectance and geometry. Wa will investigate the relevancy of using lidar-derived Digital Terrain Models (DTMs) and to investigate the potentiality of the intensity and width information for 3-D landcover classification. Considering the novelty and the complexity of such data, they are presented in details as well as guidelines to process them. DTMs are then validated with field measurements. The morphological validation of DTMs is then performed via the computation of hydrological indexes and photo-interpretation. Finally, a 3-D landcover classification is performed using a Support Vector Machine classifier. The introduction of an ortho-rectified optical image in the classification process as well as full-waveform lidar data for hydrological purposes is then discussed.
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