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  • Articles  (53)
  • Springer  (36)
  • American Geophysical Union  (9)
  • Wiley  (8)
  • American Chemical Society
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (30)
  • Geosciences  (24)
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  • Articles  (53)
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  • 1
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    Cirrus cloud simulations using WRF with improved radiation parameterization and increased vertical resolution (2011)
    Wiley
    Details
    Publication Date: 2011-03-30
    Description: The capability of Weather Research and Forecasting (WRF) model in the simulation of cirrus clouds has been examined, with a focus on the effects of radiative processes and vertical model resolution. We incorporate in WRF a new radiation module, referred to as the Fu-Liou-Gu scheme, which is an improvement and refinement based on the Fu-Liou scheme, particularly in reference to parameterization of the single-scattering properties of ice crystal size and shape. We conducted a number of real-time WRF simulations for cirrus cases that were observed in the coastal and western United States on 29–30 March 2007, and we compared these with available observations from Moderate Resolution Imaging Spectroradiometer (MODIS) and GOES visible and IR images over the same areas. Simulation results show that WRF is capable of generating reasonable cirrus cloud fields and their movement and dissipation processes, especially those associated with the large-scale frontal system. Radiative processes are important in cirrus cloud simulations by affecting the vertical thermal structure and hence convection. The newly implemented radiation module, the Fu-Liou-Gu scheme, has been demonstrated to work well in WRF and can be effectively used for studies related to cirrus cloud formation and evolution and aerosol-cloud-radiation interactions. With the newly implemented radiation scheme, the simulations of cloud cover and cloud and ice water path (CWP and IWP) have been improved for cirrus clouds, with a more consistent comparison with the corresponding MODIS observations in terms of CWP and IWP means and CWP frequency distribution, especially for optically thin cirrus with an improvement of about 20% in simulated mean IWP. The model-simulated ice crystal sizes have also been shown to be comparable to those determined from MODIS cloud products. Finally, we have demonstrated that model vertical resolution plays a significant role in cirrus cloud simulation in terms of altering vertical velocity field and the associated regional circulation.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    System Identification and Data‐Driven Forecasting of AE Index and Prediction Uncertainty Analysis Using a New Cloud‐NARX Model (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Severe geomagnetic storms caused by the solar wind disturbances have harmful influences on the operation of modern equipment and systems. The modeling and forecasting of AE index are extremely useful to understand the geomagnetic substorms. This study presents a novel cloud‐nonlinear autoregressive with exogenous input (NARX) model to predict AE index 1 hr ahead. The cloud‐NARX model provides AE index forecasting results, with a correlation coefficient of 0.87 on the data of whole year 2015. The benchmarks on the data of the two interested periods of 17–21 March 2015 and 22–26 June 2015 are presented. The presented model uses uncertainty “cloud” model and cloud transformation to quantify the uncertainty throughout the structure detection, parameter estimation, and model prediction. The new predicted band can be generated to forecast AE index with confidence interval. The proposed method provides a new way to evaluate the model based on uncertainty analysis, revealing the reliability of model, and visualize the bias of model prediction.
    Print ISSN: 2169-9380
    Electronic ISSN: 2169-9402
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    System Identification and Data‐Driven Forecasting of AE Index and Prediction Uncertainty Analysis Using a New Cloud‐NARX Model (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract Severe geomagnetic storms caused by the solar wind disturbances have harmful influences on the operation of modern equipment and systems. The modeling and forecasting of AE index are extremely useful to understand the geomagnetic substorms. This study presents a novel cloud‐nonlinear autoregressive with exogenous input (NARX) model to predict AE index 1 hr ahead. The cloud‐NARX model provides AE index forecasting results, with a correlation coefficient of 0.87 on the data of whole year 2015. The benchmarks on the data of the two interested periods of 17–21 March 2015 and 22–26 June 2015 are presented. The presented model uses uncertainty “cloud” model and cloud transformation to quantify the uncertainty throughout the structure detection, parameter estimation, and model prediction. The new predicted band can be generated to forecast AE index with confidence interval. The proposed method provides a new way to evaluate the model based on uncertainty analysis, revealing the reliability of model, and visualize the bias of model prediction.
    Print ISSN: 1539-4964
    Electronic ISSN: 1542-7390
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Stochastic parameterization for light absorption by internally mixed BC/dust in snow grains for application to climate models (2014)
    Wiley
    Details
    Publication Date: 2014-06-03
    Description: A stochastic approach has been developed to model the positions of BC/dust internally mixed with two snow-grain types: hexagonal plate/column (convex) and Koch snowflake (concave). Subsequently, light absorption and scattering analysis can be followed by means of an improved geometric-optics approach coupled with Monte Carlo photon tracing to determine BC/dust single-scattering properties. For a given shape (plate, Koch snowflake, spheroid, or sphere), the action of internal mixing absorbs substantially more light than external mixing. The snow-grain shape effect on absorption is relatively small, but its effect on asymmetry factor is substantial. Due to a greater probability of intercepting photons, multiple inclusions of BC/dust exhibit a larger absorption than an equal-volume single inclusion. The spectral absorption (0.2 – 5  μ m) for snow grains internally mixed with BC/dust is confined to wavelengths shorter than about 1.4  μ m, beyond which ice absorption predominates. Based on the single-scattering properties determined from stochastic and light absorption parameterizations and using the adding/doubling method for spectral radiative transfer, we find that internal mixing reduces snow albedo substantially more than external mixing and that the snow-grain shape plays a critical role in snow albedo calculations through its forward scattering strength. Also, multiple inclusion of BC/dust significantly reduces snow albedo as compared to an equal-volume single sphere. For application to land/snow models, we propose a two-layer spectral snow parameterization involving contaminated fresh snow on top of old snow for investigating and understanding the climatic impact of multiple BC/dust internal mixing associated with snow grain metamorphism, particularly over mountain/snow topography.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Effect of Urbanization on Ozone and Resultant Health Effects in the Pearl River Delta Region of China (2019)
    Wiley
    Details
    Publication Date: 2019
    Description: Abstract The United Nations has reported that 55% of the global population resides in urban areas, and 68% of the population is expected to be urban dwellers by 2050. Urbanization has critical implications for global land cover. Relevant literature has provided evidence attributing climatic effects to urban expansion; however, few studies have investigated the effect on public health and pollutant sensitivity to emissions. This study aimed to characterize the effect of urbanization‐induced changes in regional climate on ozone (O3), to evaluate ozone sensitivity to nitrogen oxide (NOx) and volatile organic compound (VOC) emissions, and to estimate premature mortalities due to O3 exposure. We employed atmospheric models with the higher‐order decoupled direct method (HDDM) to simulate effects of urbanization on O3 and to determine O3 sensitivity to NOx and VOC emissions. China‐specific concentration response functions were utilized to estimate cardiovascular and respiratory mortalities due to ozone exposure. Urbanization increased O3, which translated to a 39.6% increase in O3‐induced premature mortality (1,100 deaths). Moreover, O3 has become less/more sensitive to unit changes in NOx and VOC emissions in various cities. Urban greening may reduce urban temperature, but it may increase O3 in some cities due to the additional VOC emissions of greening. These findings highlight the strong interactions between land‐use policies, urban climate adaptation strategies, and air quality policies, suggesting the need of cobeneficial strategies and policies. We proposed a “precision environmental management” concept that emphasizes the importance of considering the specific atmospheric condition and composition of a city when formulating its environmental policies.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
    Electronic Resource
    Electronic Resource
    Meshless local Petrov–Galerkin (MLPG) method in combination with finite element and boundary element approaches (2000)
    Springer
    Computational mechanics 26 (2000), S. 536-546 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The meshless local Petrov–Galerkin (MLPG) method is an effective truly meshless method for solving partial differential equations using moving least squares (MLS) interpolants. It is, however, computationally expensive for some problems. A coupled MLPG/finite element (FE) method and a coupled MLPG/boundary element (BE) method are proposed in this paper to improve the solution efficiency. A procedure is developed for the coupled MLPG/FE method and the coupled MLPG/BE method so that the continuity and compatibility are preserved on the interface of the two domains where the MLPG and FE or BE methods are applied. The validity and efficiency of the MLPG/FE and MLPG/BE methods are demonstrated through a number of examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660000203
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  • 7
    Electronic Resource
    Electronic Resource
    Coupling of element free Galerkin and hybrid boundary element methods using modified variational formulation (2000)
    Springer
    Computational mechanics 26 (2000), S. 166-173 
    Details
    ISSN: 1432-0924
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  A novel method is proposed by coupling the element free Galerkin (EFG) and the hybrid boundary element (HBE) methods to achieve solution efficiency and accuracy for stress analysis in solids. A modified variational formulation is derived for the present coupled EFG/HBE method so that the continuity and compatibility can be preserved on the interface between the domains of EFG and HBE. The coupled EFG/HBE method has been coded in FORTRAN. The validity and efficiency of the proposed method are demonstrated through a number of example problems. It is found that the present method can take advantages of both EFG and HBE methods. The present method is very easy to implement, and very flexible for obtaining displacements and stresses of desired accuracy in solids, as the efforts for meshing the problem domain have been significantly reduced due to the use of boundary element method (BEM).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004660000164
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  • 8
    Electronic Resource
    Electronic Resource
    Structural shape optimization integrated with CAD environment (1990)
    Springer
    Structural and multidisciplinary optimization 2 (1990), S. 23-28 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The research work presented here is based on the concept of the integration of optimization techniques and numerical analysis with the finite element method (FEM) and computer-aided design (CAD). A microcomputer aided optimum design system, MCADS, has been developed for general structures. Certain techniques to be discussed in the paper, e.g. the semi-analytical method for design sensitivity analysis, optimization analysis modelling for shape design, application oriented user interfaces and the coupling of automated optimization and user intervention have rendered MCADS pratical and versatile in applications for engineering structures. The above techniques and an application are presented in this paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01743517
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  • 9
    Electronic Resource
    Electronic Resource
    Structural modelling and sensitivity analysis of shape optimization (1993)
    Springer
    Structural and multidisciplinary optimization 6 (1993), S. 29-37 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract It is presented in this paper that the structural modelling of shape optimization is composed of, in general cases, four distinct processes on geometry, design, analysis and perturbation models. The relationships between these models are discussed. An integrated modelling approach based on geometric shape parameterization and automatic mesh generation is proposed. In cooperation with this modelling approach, the semi-analytic sensitivity analysis has been effectively employed. These techniques join shape optimization with FEM and CAD packages and apply it versatilely to optimum designs of general structures. The implementation and applications of the integrated modelling approach and semi-analytic sensitivity analysis to shape optimization of structures with coupling of stress and temperature fields are illustrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01743172
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  • 10
    Electronic Resource
    Electronic Resource
    Carbon nitride films prepared by ion implantation (1996)
    Springer
    Journal of materials science 15 (1996), S. 1355-1357 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240806
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