ISORROPIA: A New Thermodynamic Equilibrium Model for Multiphase Multicomponent Inorganic Aerosols   总被引：16，自引：0，他引：16  

Athanasios Nenes  Spyros N. Pandis  Christodoulos Pilinis 《Aquatic Geochemistry》1998,4(1):123-152

A computationally efficient and rigorous thermodynamic model that predicts the physical state and composition of inorganic atmospheric aerosol is presented. One of the main features of the model is the implementation of mutual deliquescence of multicomponent salt particles, which lowers the deliquescence point of the aerosol phase.The model is used to examine the behavior of four types of tropospheric aerosol (marine, urban, remote continental and non-urban continental), and the results are compared with the predictions of two other models currently in use. The results of all three models were generally in good agreement. Differences were found primarily in the mutual deliquescence humidity regions, where the new model predicted the existence of water, and the other two did not. Differences in the behavior (speciation and water absorbing properties) between the aerosol types are pointed out. The new model also needed considerably less CPU time, and always shows stability and robust convergence.  相似文献   

A 3-D sea breeze model of the PBL including pollutant dispersion     

John G. Papageorgiou 《Boundary-Layer Meteorology》1988,45(1-2):9-29

A 3-D sea breeze model has been developed to study the sea breeze and the pollutant dispersion over a coastal area. Topography is also included. Similarity theory is adopted while a turbulent kinetic energy equation is used to study turbulence and to parameterize eddy diffusion. The integration is repeated in diurnal cycles and the results — meteorological and pollutant — are compared with data from the Athens area.  相似文献   

Equivalent uniform damping ratios for linear irregularly damped concrete/steel mixed structures     

A.V. Papageorgiou  C.J. Gantes 《Soil Dynamics and Earthquake Engineering》2011

Structures consisting of two parts, a lower part made of concrete and an upper part made of steel are investigated. In code-based seismic design of such structures several practical difficulties are encountered, due to inherent differences in the nature of dynamic response of each part. The specific issue addressed here is the analysis complications due to the different damping ratios of the two parts. Such structures are irregularly damped and have complex modes of vibration, so that their analysis cannot be handled with readily available commercial software. This work aims at providing a simple yet sufficiently accurate methodology for handling the damping irregularity of such structures, by proposing an overall equivalent damping ratio that can be applied to the complete structure for obtaining its dynamic response. This is achieved by first transforming MDOF irregular structures into equivalent 2-DOF oscillators, using the first mode characteristics of each part, and then using equivalent uniform damping ratios that are derived by means of a semi-empirical error minimization procedure. Thus, available commercial software can be applied for seismic analysis and design and the provisions of existing seismic codes can be adhered to.  相似文献   

An application of the scaled Runge-Kutta algorithms to some problems of celestial mechanics     

G. Papageorgiou  T. Kalvouridis  Th. Simos 《Astrophysics and Space Science》1987,137(1):129-138

New Runge-Kutta algorithms are applied for determining the solution of a system of ordinary differential equations at any point within a given integrating step. In this paper we propose the application of these new algorithms in order to determine, with the smallest possible cost, the exact point of intersection of a symmetric orbit, with the axis or plane of symmetry, which appear in various problems of celestial mechanics.  相似文献   

A comparison of numerical integration methods in the equatorial magnetic-binary problem     

T. Kalvouridis  G. Papageorgiou  Th. Simos 《Astrophysics and Space Science》1987,139(1):21-35

In this paper we compare several Runge-Kutta type methods of fourth-order when they are applied in the Equatorial Magnetic-Binary Problem (EMBP) for which the analytical solutions are not known. The results of the comparison are presented with tables and diagrams, and the most efficient method is proposed according to the used criteria which are described.Section of Mechanics.Section of Mathematics.  相似文献   

On the stability of a non-convolutional perfectly matched layer for isotropic elastic media     

Kristel C. Meza-Fajardo  Apostolos S. Papageorgiou 《Soil Dynamics and Earthquake Engineering》2010

The multi-axial perfectly matched layer (M-PML) is a material boundary condition for wave propagation problems in unbounded domains. It is obtained by extending the formulation of the split-field perfectly matched layer to a more general absorptive medium, for which damping profiles are specified along all dimensions of the problem. Under the hypothesis of small damping, it has been demonstrated that the stability of the system of partial differential equations of the M-PML can be related to the ratio of the damping profiles, and stable M-PML terminations for isotropic and orthotropic elastic media have been constructed. In the present work, we use the Routh–Horwitz determinants to demonstrate that the conclusions regarding the stability of M-PML for isotropic media for small damping are in fact valid for the more general case of damping coefficients of any (positive) value. The effectiveness of the M-PML is demonstrated by constructing stable terminations for the abovementioned media. The stability analysis is presented for 2-D in-plane (P-SV) wave propagation in elastic isotropic continua.  相似文献   

Ductility demands of tall buildings subjected to base rocking induced by Rayleigh waves     

Kristel C. Meza Fajardo  Apostolos S. Papageorgiou 《地震工程与结构动力学》2019,48(10):1174-1194

Performance-based earthquake engineering requires accurate estimation of structural response associated with different damage states because of strong ground motion. In recent work (Meza-Fajardo and Papageorgiou, 2018, EESD), we demonstrated that a significant contribution to the response of elastic soil-structure systems for high-rise buildings is attributed to base rocking associated with Rayleigh waves. The present paper presents results of a study investigating the effects of Rayleigh waves on the response of soil-structure systems with nonlinear behavior at the level of the superstructure. By introducing a rigid-elastic rotational spring at the base of the building, we take into account the stiffness reduction due to damage to the lateral load-resisting system at its root, and with it, increased displacement demands. Considering different levels of ductility and post-yield stiffness, we investigate the impact of rocking because of Rayleigh waves on maximum and residual interstory drift ratios. Our results indicate that rocking due to surface waves should be an important consideration for design and evaluation of tall buildings, as inelastic action elongates their effective natural period, and consequently, they are more prone to be damaged by resonance and excitation of extended duration because of Rayleigh waves.  相似文献   

Estimating gas saturation in a thin layer by using frequency‐dependent amplitude versus offset modelling          下载免费PDF全文

Zhaoyu Jin  Mark Chapman  Xiaoyang Wu  Giorgos Papageorgiou 《Geophysical Prospecting》2017,65(3):747-765

Various models have been proposed to link partial gas saturation to seismic attenuation and dispersion, suggesting that the reflection coefficient should be frequency‐dependent in many cases of practical importance. Previous approaches to studying this phenomenon typically have been limited to single‐interface models. Here, we propose a modelling technique that allows us to incorporate frequency‐dependent reflectivity into convolutional modelling. With this modelling framework, seismic data can be synthesised from well logs of velocity, density, porosity, and water saturation. This forward modelling could act as a basis for inversion schemes aimed at recovering gas saturation variations with depth. We present a Bayesian inversion scheme for a simple thin‐layer case and a particular rock physics model and show that, although the method is very sensitive to prior information and constraints, both gas saturation and layer thickness theoretically can be estimated in the case of interfering reflections.  相似文献   

Some new Runge-Kutta methods with interpolation properties and their application to the Magnetic-Binary Problem     

G. Papageorgiou  Th. Simos  Ch. Tsitouras 《Celestial Mechanics and Dynamical Astronomy》1988,44(1-2):167-177

Explicit Runge-Kutta methods provide a popular way to solve the initial value problem for a system of nonstiff ordinary differential equations. On the other hand, for these methods, there is no a natural way to approximate the solution at any point within a given integration step. Scaled Runge-Kutta methods have been developed recently which determine the solution of the differential system at non-mesh points of a given integration step. We propose some new such algorithms based upon well known explicit Runge-Kutta methods, and we verify their advantages by applying them to the Magnetic-Binary Problem.  相似文献   

Space very long baseline interferometry observations of polarization in the jet of 3C 380     

A. Papageorgiou  T. V. Cawthorne  A. Stirling  D. Gabuzda  A. G. Polatidis 《Monthly notices of the Royal Astronomical Society》2006,373(2):449-456

A comparison between low-frequency space very long baseline interferometry (VLBI) and high-frequency ground-based VLBI images can, in principle, be used to detect small variations in rotation measure (RM) on fine angular scales inaccessible to ground arrays alone. This paper reports an attempt to perform such a comparison using the jet in the quasar 3C 380. Observations made with the VSOP antenna HALCA together with a ground array at wavelength 1.6 GHz provide total intensity and polarization images of comparable resolution to those from the ground array alone at 5 GHz. The results provide an image showing derotated magnetic vector position angle of somewhat higher resolution than that available earlier. The results show variations in an RM around component A of the order of 10 rad m⁻² that could not have been detected with the ground array alone. It is concluded that satellite VLBI observations provide a promising means to study the distribution of matter and magnetic fields around parsec-scale jets.
The ground observations used here follow the steady outward drift of component A, which has approximately doubled its distance from the core since the first observations in 1982. They also reveal total intensity and polarization structure associated with a bright knot 0.7 arcsec from the core which is reminiscent of that expected for a conical shock wave.  相似文献