A computationally efficient method for uncertainty analysis of SWAT model simulations

The physically based distributed hydrological models are ideal for hydrological simulations; however most of such models do not use the basic equations pertaining to mass, energy and momentum conservation, to represent the physics of the process. This is plausibly due to the lack of complete understanding of the hydrological process. The soil and water assessment tool (SWAT) is one such widely accepted semi-distributed, conceptual hydrological model used for water resources planning. However, the over-parameterization, difficulty in its calibration process and the uncertainty associated with predictions make its applications skeptical. This study considers assessing the predictive uncertainty associated with distributed hydrological models. The existing methods for uncertainty estimation demand high computational time and therefore make them challenging to apply on complex hydrological models. The proposed approach employs the concepts of generalized likelihood uncertainty estimation (GLUE) in an iterative procedure by starting with an assumed prior probability distribution of parameters, and by using mutual information (MI) index for sampling the behavioral parameter set. The distributions are conditioned on the observed information through successive cycles of simulations. During each cycle of simulation, MI is used in conjunction with Markov Chain Monte Carlo procedure to sample the parameter sets so as to increase the number of behavioral sets, which in turn helps reduce the number of cycles/simulations for the analysis. The method is demonstrated through a case study of SWAT model in Illinois River basin in the USA. A comparison of the proposed method with GLUE indicates that the computational requirement of uncertainty analysis is considerably reduced in the proposed approach. It is also noted that the model prediction band, derived using the proposed method, is more effective compared to that derived using the other methods considered in this study.     

Numerically based proposals for the stiffness and strength of masonry infills with openings in reinforced concrete frames

Aimed at investigating the effect of openings on the in‐plane behaviour of masonry infills in reinforced concrete frames, a parametric study is presented based on model calibration via experimental tests. Two types of openings are investigated: central window openings and different combinations of door and window openings based on the typologies of southern European countries. First, a finite element model of the structure is made using the DIANA software program. Then, after calibration with experimental results, a parametric analysis is carried out to investigate the effect of the presence and location of the different types of openings on the in‐plane behaviour of the infilled frame. Finally, different equations for predicting the initial stiffness and lateral strength of infilled frames with any types of openings were obtained. An α factor related to the geometry of the piers between openings is proposed to take into account the location of the openings in the developed equations. Subsequently, the masonry infill panel is replaced by a diagonal strut. An empirical equation is also proposed for the width of an equivalent strut to replace a masonry infill panel with openings in such a way that they possess the same initial stiffness. Copyright © 2015 John Wiley & Sons, Ltd.     

The Earth-Moon tidal force function

The concept “the tidal force function of the Earth-Moon system” is introduced and its exact determination based on the Stokes constants (harmonic coefficients) in the external gravitational potential of both bodies is outlined. The exact determination of the torque due to the Moon exerted on the Earth may be performed in terms of the Stokes constants of both bodies and the mutual position of both ellipsoids of inertia.     

On the expanding earth hypothesis

Summary The hypothesis of an expanding Earth is discussed on the basis of lunar laser ranging It is provcd that the given data do not indicate a secular increase in the principal moment of the Earth's inertia which would have to occur if the Earth were really expanding.

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Description de deux nouvelles Cyclotelles (Bacillariophyceae) de milieux alcalins et eutrophes:Cyclotella costei nov. sp. etCyclotella wuethrichiana nov. sp.

Two new species of the genus Cyclotella are presented which have been discovered during ecological and paleoecological research studies in the littoral zone of two small alkaline eutrophic lakes in France (Lake Paladru) and in Switzerland (Lake Le Loclat). These new species are namedCyclotella costei nov. sp. andCyclotella wuethrichiana nov. sp.