bluuebunny/crossref_metadata_2025 huggingface dataset:
Acceleration Strategies Based on an Improved Bubble Packing Method
Authors: Qi Nan , Nie Yufeng , Zhang Weiwei
Published: July 2016

The bubble packing method can generate high-quality node sets in simple and complex domains. However, its efficiency remains to be improved. This study is a part of an ongoing effort to introduce several acceleration schemes to reduce the cost of simulation. Firstly, allow the viscosity coefficient c in the bubble governing equations to change according the coordinate of the bubble which are defined separately as odd and normal bubbles, and meanwhile with the saw-shape relationship with time or iterations. Then, in order to relieve the over crowded initial bubble placement, two coefficients w1 and w2 are introduced to modify the insertion criterion. The range of those two coefficients are discussed to be w1 = 1, w2 ∈ [0.5,0.8]. Finally, a self-adaptive termination condition is logically set when the stable system equilibrium is achieved. Numerical examples illustrate that the computing cost can significantly decrease by roughly 80% via adopting various combination of proper schemes (except the uniform placement example), and the average qualities of corresponding Delaunay triangulation substantially exceed 0.9. It shows that those strategies are efficient and can generate a node set with high quality.
The Stability and Convergence of Fully Discrete Galerkin-Galerkin FEMs for Porous Medium Flows
Authors: Li Buyang , Wang Jilu , Sun Weiwei
Published: July 2016

The paper is concerned with the unconditional stability and error estimates of fully discrete Galerkin-Galerkin FEMs for the equations of incompressible miscible flows in porous media. We prove that the optimal L2 error estimates hold without any time-step (convergence) conditions, while all previous works require certain time-step restrictions. Theoretical analysis is based on a splitting of the error into two parts: the error from the time discretization of the PDEs and the error from the finite element discretization of the corresponding time-discrete PDEs, which was proposed in our previous work [26, 27]. Numerical results for both two and three-dimensional flow models are presented to confirm our theoretical analysis.
On the Connection Between the Spectral Difference Method and the Discontinuous Galerkin Method
Authors: May Georg
Published: July 2016

In this short note we present a derivation of the Spectral Difference Scheme from a Discontinuous Galerkin (DG) discretization of a nonlinear conservation law. This allows interpretation of the Spectral Difference Scheme as a particular discretization under the quadrature-free nodal DG paradigm. Moreover, it enables identification of the key differences between the Spectral Difference Scheme and standard nodal DG schemes.
Hydrodynamic Interaction of Elastic Capsules in Bounded Shear Flow
Authors: Le D. V. , Tan Zhijun
Published: July 2016

This paper presents a modified Loop’s subdivision algorithm for studying the deformation of a single capsule, the hydrodynamic interaction between two capsules and the hydrodynamic diffusion of a suspension of capsules in bounded shear flow. A subdivision thin-shell model is employed to compute the forces generated on the surface of the elastic capsule during deformation. The capsule surface is approximated using the modified Loop’s subdivision scheme which guarantees bounded curvature and C1 continuity everywhere on the limit surface. The present numerical technique has been validated by studying the deformation of a spherical capsule in shear flow. Computations are also performed for a biconcave capsule over a wide range of shear rates and viscosity ratios to investigate its dynamics. In addition, the hydrodynamic interaction between two elastic capsules in bounded shear flow is studied. Depending on the wall separation distance, the trajectory-bifurcation points that separate reversing and crossing motions for both spherical and biconcave capsules can be found. Compared to the spherical capsules, the biconcave capsules exhibit additional types of interaction such as rotation and head-on collision. The head-on collision results in a large trajectory shift which contribute to the hydrodynamic diffusion of a suspension. A suspension of a large number of biconcave capsules in shear flow is also simulated to show the ability of the modified scheme in running a large-scale simulation over a long period of time.
Numerical Approximation of a Compressible Multiphase System
Authors: Abgrall Remi , Kumar Harish
Published: July 2016

The numerical simulation of non conservative system is a difficult challenge for two reasons at least. The first one is that it is not possible to derive jump relations directly from conservation principles, so that in general, if the model description is non ambiguous for smooth solutions, this is no longer the case for discontinuous solutions. From the numerical view point, this leads to the following situation: if a scheme is stable, its limit for mesh convergence will depend on its dissipative structure. This is well known since at least [1]. In this paper we are interested in the “dual” problem: given a system in non conservative form and consistent jump relations, how can we construct a numerical scheme that will, for mesh convergence, provide limit solutions that are the exact solution of the problem. In order to investigate this problem, we consider a multiphase flow model for which jump relations are known. Our scheme is an hybridation of Glimm scheme and Roe scheme.
Finite Volume Hermite WENO Schemes for Solving the Hamilton-Jacobi Equation
Authors: Zhu Jun , Qiu Jianxian
Published: July 2016

In this paper, we present a new type of Hermite weighted essentially non-oscillatory (HWENO) schemes for solving the Hamilton-Jacobi equations on the finite volume framework. The cell averages of the function and its first one (in one dimension) or two (in two dimensions) derivative values are together evolved via time approaching and used in the reconstructions. And the major advantages of the new HWENO schemes are their compactness in the spacial field, purely on the finite volume framework and only one set of small stencils is used for different type of the polynomial reconstructions. Extensive numerical tests are performed to illustrate the capability of the methodologies.
Thin Layer Models for Electromagnetism
Authors: Duruflé Marc , Péron Victor , Poignard Clair
Published: July 2016

We present a review on the accuracy of asymptotic models for the scattering problem of electromagnetic waves in domains with thin layer. These models appear as first order approximations of the electromagnetic field. They are obtained thanks to a multiscale expansion of the exact solution with respect to the thickness of the thin layer, that makes possible to replace the thin layer by approximate conditions. We present the advantages and the drawbacks of several approximations together with numerical validations and simulations. The main motivation of this work concerns the computation of electromagnetic field in biological cells. The main difficulty to compute the local electric field lies in the thinness of the membrane and in the high contrast between the electrical conductivities of the cytoplasm and of the membrane, which provides a specific behavior of the electromagnetic field at low frequencies.
On the Choice of Design Points for Least Square Polynomial Approximations with Application to Uncertainty Quantification
Authors: Gao Zhen , Zhou Tao
Published: July 2016

In this work, we concern with the numerical comparison between different kinds of design points in least square (LS) approach on polynomial spaces. Such a topic is motivated by uncertainty quantification (UQ). Three kinds of design points are considered, which are the Sparse Grid (SG) points, the Monte Carlo (MC) points and the Quasi Monte Carlo (QMC) points. We focus on three aspects during the comparison: (i) the convergence properties; (ii) the stability, i.e. the properties of the resulting condition number of the design matrix; (iii) the robustness when numerical noises are present in function values. Several classical high dimensional functions together with a random ODE model are tested. It is shown numerically that (i) neither the MC sampling nor the QMC sampling introduce the low convergence rate, namely, the approach achieves high order convergence rate for all cases provided that the underlying functions admit certain regularity and enough design points are used; (ii)The use of SG points admits better convergence properties only for very low dimensional problems (say d ≤ 2); (iii)The QMC points, being deterministic, seem to be a good choice for higher dimensional problems not only for better convergence properties but also in the stability point of view.
A Modified Gas-Kinetic Scheme for Turbulent Flow
Authors: Righi Marcello
Published: July 2016

The implementation of a turbulent gas-kinetic scheme into a finite-volume RANS solver is put forward, with two turbulent quantities, kinetic energy and dissipation, supplied by an allied turbulence model. This paper shows a number of numerical simulations of flow cases including an interaction between a shock wave and a turbulent boundary layer, where the shock-turbulent boundary layer is captured in a much more convincing way than it normally is by conventional schemes based on the Navier-Stokes equations. In the gas-kinetic scheme, the modeling of turbulence is part of the numerical scheme, which adjusts as a function of the ratio of resolved to unresolved scales of motion. In so doing, the turbulent stress tensor is not constrained into a linear relation with the strain rate. Instead it is modeled on the basis of the analogy between particles and eddies, without any assumptions on the type of turbulence or flow class. Conventional schemes lack multiscale mechanisms: the ratio of unresolved to resolved scales – very much like a degree of rarefaction – is not taken into account even if it may grow to non-negligible values in flow regions such as shocklayers. It is precisely in these flow regions, that the turbulent gas-kinetic scheme seems to provide more accurate predictions than conventional schemes.
Immersed Finite Element Method for Interface Problems with Algebraic Multigrid Solver
Authors: Feng Wenqiang , He Xiaoming , Lin Yanping , Zhang Xu
Published: July 2016

This article is to discuss the bilinear and linear immersed finite element (IFE) solutions generated from the algebraic multigrid solver for both stationary and moving interface problems. For the numerical methods based on finite difference formulation and a structured mesh independent of the interface, the stiffness matrix of the linear system is usually not symmetric positive-definite, which demands extra efforts to design efficient multigrid methods. On the other hand, the stiffness matrix arising from the IFE methods are naturally symmetric positive-definite. Hence the IFE-AMG algorithm is proposed to solve the linear systems of the bilinear and linear IFE methods for both stationary and moving interface problems. The numerical examples demonstrate the features of the proposed algorithms, including the optimal convergence in both L2and semi-H1norms of the IFE-AMG solutions, the high efficiency with proper choice of the components and parameters of AMG, the influence of the tolerance and the smoother type of AMG on the convergence of the IFE solutions for the interface problems, and the relationship between the cost and the moving interface location.
Image Charge Method for Reaction Fields in a Hybrid Ion-Channel Model
Authors: Xu Zhenli , Cai Wei , Cheng Xiaolin
Published: July 2016

A multiple-image method is proposed to approximate the reaction-field potential of a source charge inside a finite length cylinder due to the electric polarization of the surrounding membrane and bulk water. When applied to a hybrid ion-channel model, this method allows a fast and accurate treatment of the electrostatic interactions of protein with membrane and solvent. To treat the channel/membrane interface boundary conditions of the electric potential, an optimization approach is used to derive image charges by fitting the reaction-field potential expressed in terms of cylindric harmonics. Meanwhile, additional image charges are introduced to satisfy the boundary conditions at the planar membrane interfaces. In the end, we convert the electrostatic interaction problem in a complex inhomogeneous system of ion channel/membrane/water into one in a homogeneous free space embedded with discrete charges (the source charge and image charges). The accuracy of this method is then validated numerically in calculating the solvation self-energy of a point charge.
An Efficient Numerical Model for Immiscible Two-Phase Flow in Fractured Karst Reservoirs
Authors: Huang Zhao-Qin , Yao Jun , Wang Yue-Ying
Published: July 2016

Numerical simulation of two-phase flow in fractured karst reservoirs is still a challenging issue. The triple-porosity model is the major approach up to now. However, the triple-continuum assumption in this model is unacceptable for many cases. In the present work, an efficient numerical model has been developed for immiscible two-phase flow in fractured karst reservoirs based on the idea of equivalent continuum representation. First, based on the discrete fracture-vug model and homogenization theory, the effective absolute permeability tensors for each grid blocks are calculated. And then an analytical procedure to obtain a pseudo relative permeability curves for a grid block containing fractures and cavities has been successfully implemented. Next, a full-tensor simulator has been designed based on a hybrid numerical method (combining mixed finite element method and finite volume method). A simple fracture system has been used to demonstrate the validity of our method. At last, we have used the fracture and cavity statistics data from TAHE outcrops in west China, effective permeability values and other parameters from our code, and an equivalent continuum simulator to calculate the water flooding profiles for more realistic systems.
In Silico Investigation of pH-Dependence of Prolactin and Human Growth Hormone Binding to Human Prolactin Receptor
Authors: Wang Lin , Witham Shawn , Zhang Zhe , Li Lin , Hodsdon Michael , Alexov Emil
Published: July 2016

Experimental data shows that the binding of human prolactin (hPRL) to human prolactin receptor (hPRLr-ECD) is strongly pH-dependent, while the binding of the same receptor to human growth hormone (hGH) is pH-independent. Here we carryin silicoanalysis of the molecular effects causing such a difference and reveal the role of individual amino acids. It is shown that the computational modeling correctly predicts experimentally determined pKa’s of histidine residues in an unbound state in the majority of the cases and the pH-dependence of the binding free energy. Structural analysis carried in conjunction with calculated pH-dependence of the binding revealed that the main reason for pH-dependence of the binding of hPRL-hPRLr-ECD is a number of salt-bridges across the interface of the complex, while no salt-bridges are formed in the hGH-hPRlr-ECD. Specifically, most of the salt-bridges involve histidine residues and this is the reason for the pH-dependence across a physiological range of pH. The analysis not only revealed the molecular mechanism of the pH-dependence of the hPRL-hPRLr-ECD, but also provided critical insight into the underlying physic-chemical mechanism.
An Implicit Algorithm of Solving Nonlinear Filtering Problems
Authors: Bao Feng , Cao Yanzhao , Han Xiaoying
Published: July 2016

Nonlinear filter problems arise in many applications such as communications and signal processing. Commonly used numerical simulation methods include Kalman filter method, particle filter method, etc. In this paper a novel numerical algorithm is constructed based on samples of the current state obtained by solving the state equation implicitly. Numerical experiments demonstrate that our algorithm is more accurate than the Kalman filter and more stable than the particle filter.
A Runge Kutta Discontinuous Galerkin Method for Lagrangian Compressible Euler Equations in Two-Dimensions
Authors: Li Zhenzhen , Yu Xijun , Zhu Jiang , Jia Zupeng
Published: July 2016

This paper presents a new Lagrangian type scheme for solving the Euler equations of compressible gas dynamics. In this new scheme the system of equations is discretized by Runge-Kutta Discontinuous Galerkin (RKDG) method, and the mesh moves with the fluid flow. The scheme is conservative for the mass, momentum and total energy and maintains second-order accuracy. The scheme avoids solving the geometrical part and has free parameters. Results of some numerical tests are presented to demonstrate the accuracy and the non-oscillatory property of the scheme.
Examining Electrostatic Influences on Base-Flipping: A Comparison of TIP3P and GB Solvent Models
Authors: Brice Allyn R. , Dominy Brian N.
Published: July 2016

Recently, it was demonstrated that implicit solvent models were capable of generating stable B-form DNA structures. Specifically, generalized Born (GB) implicit solvent models have improved regarding the solvation of conformational sampling of DNA [1,2]. Here, we examine the performance of the GBSW and GBMV models in CHARMM for characterizing base flipping free energy profiles of undamaged and damaged DNA bases. Umbrella sampling of the base flipping process was performed for the bases cytosine, uracil and xanthine. The umbrella sampling simulations were carried-out with both explicit (TIP3P) and implicit (GB) solvent in order to establish the impact of the solvent model on base flipping. Overall, base flipping potential of mean force (PMF) profiles generated with GB solvent resulted in a greater free energy difference of flipping than profiles generated with TIP3P. One of the significant differences between implicit and explicit solvent models is the approximation of solute-solvent interactions in implicit solvent models. We calculated electrostatic interaction energies between explicit water molecules and the base targeted for flipping. These interaction energies were calculated over the base flipping reaction coordinate to illustrate the stabilizing effect of the explicit water molecules on the flipped-out state. It is known that nucleic base pair hydrogen bonds also influenced the free energy of flipping since these favorable interactions must be broken in order for a base to flip-out of the helix. The Watson-Crick base pair hydrogen bond fractions were calculated over the umbrella sampling simulation windows in order to determine the effect of base pair interactions on the base flipping free energy. It is shown that interaction energies between the flipping base and explicit water molecules are responsible for the lower base flipping free energy difference in the explicit solvent PMF profiles.
Shape Recovery of Elastic Capsules from Shear Flow Induced Deformation
Authors: Gounley John , Peng Yan
Published: July 2016

Red blood cells undergo substantial shape changes in vivo. Modeled as a viscoelastic capsule, their deformation and equilibrium behavior has been extensively studied. We consider how 2D capsules recover their shape, after having been deformed to ‘equilibrium’ behavior by shear flow. The fluid-structure interaction is modeled using the multiple-relaxation time lattice Boltzmann (LBM) and immersed boundary (IBM) methods. Characterizing the capsule’s shape recovery with the Taylor deformation parameter, we find that a single exponential decay model suffices to describe the recovery of a circular capsule. However, for biconcave capsules whose equilibrium behaviors are tank-treading and tumbling, we posit a two-part recovery, modeled with a pair of exponential decay functions. We consider how these two recovery modes depend on the capsule’s shear elasticity, membrane viscosity, and bending stiffness, along with the ratio of the viscosity of the fluid inside the capsule to the ambient fluid viscosity. We find that the initial recovery mode for a tank-treading biconcave capsule is dominated by shear elasticity and membrane viscosity. On the other hand, the latter recovery mode for both tumbling and tank-treading capsules, depends clearly on shear elasticity, bending stiffness, and the viscosity ratio.
Numerical Optimization of a Walk-on-Spheres Solver for the Linear Poisson-Boltzmann Equation
Authors: Mackoy Travis , Harris Robert C. , Johnson Jesse , Mascagni Michael , Fenley Marcia O.
Published: July 2016

Stochastic walk-on-spheres (WOS) algorithms for solving the linearized Poisson-Boltzmann equation (LPBE) provide several attractive features not available in traditional deterministic solvers: Gaussian error bars can be computed easily, the algorithm is readily parallelized and requires minimal memory and multiple solvent environments can be accounted for by reweighting trajectories. However, previously-reported computational times of these Monte Carlo methods were not competitive with existing deterministic numerical methods. The present paper demonstrates a series of numerical optimizations that collectively make the computational time of these Monte Carlo LPBE solvers competitive with deterministic methods. The optimization techniques used are to ensure that each atom’s contribution to the variance of the electrostatic solvation free energy is the same, to optimize the bias-generating parameters in the algorithm and to use an epsilon-approximate rather than exact nearest-neighbor search when determining the size of the next step in the Brownian motion when outside the molecule.
Adaptive Bayesian Inference for Discontinuous Inverse Problems, Application to Hyperbolic Conservation Laws
Authors: Birolleau Alexandre , Poëtte Gaël , Lucor Didier
Published: July 2016

Various works from the literature aimed at accelerating Bayesian inference in inverse problems. Stochastic spectral methods have been recently proposed as surrogate approximations of the forward uncertainty propagation model over the support of the prior distribution. These representations are efficient because they allow affordable simulation of a large number of samples from the posterior distribution. Unfortunately, they do not perform well when the forward model exhibits strong nonlinear behavior with respect to its input.

In this work, we first relate the fast (exponential) L2-convergence of the forward approximation to the fast (exponential) convergence (in terms of Kullback-Leibler divergence) of the approximate posterior. In particular, we prove that in case the prior distribution isuniform, the posterior is at least twice as fast as the convergence rate of the forwardmodel in those norms. The Bayesian inference strategy is developed in the framework of a stochastic spectral projectionmethod. The predicted convergence rates are then demonstrated for simple nonlinear inverse problems of varying smoothness.

We then propose an efficient numerical approach for the Bayesian solution of inverse problems presenting strongly nonlinear or discontinuous systemresponses. This comes with the improvement of the forward model that isadaptivelyapproximated by an iterative generalized Polynomial Chaos-based representation. The numerical approximations and predicted convergence rates of the former approach are compared to the new iterative numericalmethod for nonlinear time-dependent test cases of varying dimension and complexity, which are relevant regarding our hydrodynamics motivations and therefore regarding hyperbolic conservation laws and the apparition of discontinuities in finite time.
On Time-Splitting Pseudospectral Discretization for Nonlinear Klein-Gordon Equation in Nonrelativistic Limit Regime
Authors: Dong Xuanchun , Xu Zhiguo , Zhao Xiaofei
Published: July 2016

In this work, we are concerned with a time-splitting Fourier pseudospectral (TSFP) discretization for the Klein-Gordon (KG) equation, involving a dimensionless parameterɛ ∊(0,1]. In the nonrelativistic limit regime, the smallɛproduces high oscillations in exact solutions with wavelength of(ɛ2) in time. The key idea behind the TSFP is to apply a time-splitting integrator to an equivalent first-order system in time, with both the nonlinear and linear subproblems exactly integrable in time and, respectively, Fourier frequency spaces. The method is fully explicit and time reversible. Moreover, we establish rigorously the optimal error bounds of a second-order TSFP for fixedɛ=(1), thanks to an observation that the scheme coincides with a type of trigonometric integrator. As the second task, numerical studies are carried out, with special efforts made to applying the TSFP in the nonrelativistic limit regime, which are geared towards understanding its temporal resolution capacity and meshing strategy for(ɛ2)-oscillatory solutions when 0 <ɛ« 1. It suggests that the method has uniform spectral accuracy in space, and an asymptotic(ɛ−2Δt2) temporal discretization error bound (Δtrefers to time step). On the other hand, the temporal error bounds for most trigonometric integrators, such as the well-established Gautschi-type integrator in, are(ɛ−4Δt2). Thus, our method offers much better approximations than the Gautschi-type integrator in the highly oscillatory regime. These results, either rigorous or numerical, are valid for a splitting scheme applied to the classical relativistic NLS reformulation as well.
A Geometry-Preserving Finite Volume Method for Compressible Fluids on Schwarzschild Spacetime
Authors: Le Floch Philippe G. , Makhlof Hasan
Published: July 2016

We consider the relativistic Euler equations governing spherically symmetric, perfect fluid flows on the outer domain of communication of Schwarzschild space-time, and we introduce a version of the finite volume method which is formulated from the geometric formulation (and thus takes the geometry into account at the discretization level) and is well-balanced, in the sense that it preserves steady solutions to the Euler equations on the curved geometry under consideration. In order to formulate our method, we first derive a closed formula describing all steady and spherically symmetric solutions to the Euler equations posed on Schwarzschild spacetime. Second, we describe a geometry-preserving, finite volume method which is based from the family of steady solutions to the Euler system. Our scheme is second-order accurate and, as required, preserves the family of steady solutions at the discrete level. Numerical experiments are presented which demonstrate the efficiency and robustness of the proposed method even for solutions containing shock waves and nonlinear interacting wave patterns. As an application, we investigate the late-time asymptotics of perturbed steady solutions and demonstrate its convergence for late time toward another steady solution, taking the overall effect of the perturbation into account.
Using DelPhi Capabilities to Mimic Protein’s Conformational Reorganization with Amino Acid Specific Dielectric Constants
Authors: Wang Lin , Zhang Zhe , Rocchia Walter , Alexov Emil
Published: July 2016

Many molecular events are associated with small or large conformational changes occurring in the corresponding proteins. Modeling such changes is a challenge and requires significant amount of computing time. From point of view of electrostatics, these changes can be viewed as a reorganization of local charges and dipoles in response to the changes of the electrostatic field, if the cause is insertion or deletion of a charged amino acid. Here we report a large scale investigation of modeling the changes of the folding energy due to single mutations involving charged group. This allows the changes of the folding energy to be considered mostly electrostatics in origin and to be calculated with DelPhi assigning residue-specific value of the internal dielectric constant of protein. The predicted energy changes are benchmarked against experimentally measured changes of the folding energy on a set of 257 single mutations. The best fit between experimental values and predicted changes is used to find out the effective value of the internal dielectric constant for each type of amino acid. The predicted folding free energy changes with the optimal, amino acid specific, dielectric constants are within RMSD=0.86 kcal/mol from experimentally measured changes.
High-Order Symplectic Schemes for Stochastic Hamiltonian Systems
Authors: Deng Jian , Anton Cristina , Wong Yau Shu
Published: July 2016

The construction of symplectic numerical schemes for stochastic Hamiltonian systems is studied. An approach based on generating functions method is proposed to generate the stochastic symplectic integration of any desired order. In general the proposed symplectic schemes are fully implicit, and they become computationally expensive for mean square orders greater than two. However, for stochastic Hamiltonian systems preserving Hamiltonian functions, the high-order symplectic methods have simpler forms than the explicit Taylor expansion schemes. A theoretical analysis of the convergence and numerical simulations are reported for several symplectic integrators. The numerical case studies confirm that the symplectic methods are efficient computational tools for long-term simulations.
Do the dark triad and self-perceived mate value predict intention to mate poach?
Authors: Erik Ezgi , Bhogal Manpal Singh
Published: July 2016

Although much research has been conducted on the psychology of mate poaching, little research has been conducted on the factors that predict intention to mate poach, from the perspective of the poacher. Recent research has paid some attention to the role of the dark triads in mate poaching. However, very little research has been conducted investigating the relationship between self-perceived mate value and intention to mate poach. We explored the role of the dark triads (Machiavellianism, narcissism and psychopathy), self-perceived mate value, and gender on one’s intention to mate poach in 81 participants from Coventry University. We find that the only dark triad to significantly predict intention to mate poach was psychopathy, suggesting those who scored higher on psychopathic traits were more likely to mate poach. Furthermore, we find that self-perceived mate value significantly predicted intention to mate poach, suggesting those who perceive themselves as having a high mate value, are likely to engage in mate poaching, which is a novel finding.
Temperature-dependence of aerosol optical depth over the southeastern US
Authors: Mielonen Tero , Hienola Anca , Kühn Thomas , Merikanto Joonas , Lipponen Antti , Bergman Tommi , Korhonen Hannele , Kolmonen Pekka , Sogacheva Larisa , Ghent Darren , Arola Antti , de Leeuw Gerrit , Kokkola Harri
Published: July 2016

Abstract. Previous studies have indicated that summer-time aerosol optical depths (AOD) over the southeastern US are dependent on temperature but the reason for this dependence and its radiative effects have so far been unclear. To quantify these effects we utilized AOD and land surface temperature (LST) products from the Advanced Along-Track Scanning Radiometer (AATSR) with observations of tropospheric nitrogen dioxide (NO2) column densities from the Ozone Monitoring Instrument (OMI). Furthermore, simulations of the global aerosol-climate model ECHAM-HAMMOZ have been used to identify the possible processes affecting aerosol loads and their dependence on temperature over the studied region. Our results showed that the level of AOD in the southeastern US is mainly governed by anthropogenic emissions but the observed temperature dependent behaviour is most likely originating from non-anthropogenic emissions. Model simulations indicated that biogenic emissions of volatile organic compounds (BVOC) can explain the observed temperature dependence of AOD. According to the remote sensing data sets, the non-anthropogenic contribution increases AOD by approximately 0.009 ± 0.018 K−1 while the modelled BVOC emissions increase AOD by 0.022 ± 0.002 K−1. Consequently, the regional direct radiative effect (DRE) of the non-anthropogenic AOD is −0.43 ± 0.88 W/m2/K and −0.17 ± 0.35 W/m2/K for clear- and all-sky conditions, respectively. The model estimate of the regional clear-sky DRE for biogenic aerosols is also in the same range: −0.86 ± 0.06 W/m2/K. These DRE values indicate significantly larger cooling than the values reported for other forested regions. Furthermore, the model simulations showed that biogenic emissions increased the number of biogenic aerosols with radius larger than 100 nm (N100, proxy for cloud condensation nuclei) by 28 % per one degree temperature increase. For the total N100, the corresponding increase was 4 % which implies that biogenic emissions could also have a small effect on indirect radiative forcing in this region.
Evaluation of IWV from the numerical weather prediction WRF
model with PPP GNSS processing for Bulgaria
Authors: Simeonov Tzvetan , Sidorov Dmitry , Teferle Felix Norman , Milev Georgi , Guerova Guergana
Published: July 2016

Abstract. Global Navigation Satellite Systems (GNSS) meteorology is an established operational service providing hourly updated GNSS tropospheric products to the National Meteorologic Services (NMS) in Europe. In the last decade through the ground-based GNSS network densification and new processing strategies like Precise Point Positioning (PPP) it has become possible to obtain sub-hourly tropospheric products for monitoring severe weather events. In this work one year (January–December 2013) of sub-hourly GNSS tropospheric products (Zenith Total Delay) are computed using the PPP strategy for seven stations in Bulgaria. In order to take advantage of the sub-hourly GNSS data to derive Integrated Water Vapour (IWV) surface pressure and temperature with similar temporal resolution is required. As the surface observations are on 3 hourly basis the first step is to compare the surface pressure and temperature from numerical weather prediction model Weather Forecasting and Research (WRF) with observations at three synoptic stations in Bulgaria. The mean difference between the two data-sets for 1) surface pressure is less than 0.5 hPa and the correlation is over 0.989, 2) temperature the largest mean difference is 1.1 °C and the correlation coefficient is over 0.957 and 3) IWV mean difference is in range 0.1–1.1 mm. The evaluation of WRF on annual bases shows IWV underestimation between 0.5 and 1.5 mm at five stations and overestimation at Varna and Rozhen. Varna and Rozhen have also much smaller correlation 0.9 and 0.76. The study of the monthly IWV variation shows that at those locations the GNSS IWV has unexpected drop in April and March respectively. The reason for this drop is likely problems with station raw data. At the remaining 5 stations a very good agreement between GNSS and WRF is observed with high correlation during the cold part of 2013 i.e. March, October and December (0.95) and low correlation during the warm part of 2013 i.e. April to August (below 0.9). The diurnal cycle of the WRF model shows a dry bias in the range of 0.5-1.5 mm. Between 00 and 01 UTC the GNSS IWV tends to be underestimate IWV which is likely due to the processing window used. The precipitation efficiency from GNSS and WRF show very good agreement on monthly bases with a maximum in May-June and minimum in August–September. The annual precipitation efficiency in 2013 at Lovech and Burgas is about 6 %.
Distance scaling method for accurate prediction of slowly varying magnetic
fields in satellite missions
Authors: Zacharias Panagiotis P. , Chatzineofytou Elpida G. , Spantideas Sotirios T. , Capsalis Christos N.
Published: July 2016

Abstract. In the present work, the determination of the magnetic behavior of localized magnetic sources from near-field measurements is examined. The distance power law of the magnetic field fall-off is used in various cases to accurately predict the magnetic signature of an equipment under test (EUT) consisting of multiple alternating current (AC) magnetic sources. Therefore, parameters concerning the location of the observation points (magnetometers) are studied towards this scope. The results clearly show that these parameters are independent of the EUT's size and layout. Additionally, the techniques developed in the present study enable the placing of the magnetometers close to the EUT, thus achieving high signal-to-noise ratio (SNR). Finally, the proposed method is verified by real measurements, using a mobile phone as an EUT.
Model-based study of the role of rainfall and land use–land cover in the
changes in the occurrence and intensity of Niger red floods in Niamey between 1953
and 2012
Authors: Casse Claire , Gosset Marielle , Vischel Théo , Quantin Guillaume , Tanimoun Bachir Alkali
Published: July 2016

Abstract. Since 1950, the Niger River basin has gone through three main climatic periods: a wet period (1950–1960), an extended drought (1970–1980) and since 1990 a recent partial recovery of annual rainfall. Hydrological changes co-occur with these rainfall fluctuations. In most of the basin, the rainfall deficit caused an enhanced discharge deficit, but in the Sahelian region the runoff increased despite the rainfall deficit. Since 2000 the Sahelian part of the Niger has been hit by an increase of flood hazards during the so-called red flood period. In Niamey city, the highest river levels and the longest flooded period ever recorded occurred in 2003, 2010, 2012 and 2013, with heavy casualties and property damage. The reasons for these changes, and the relative role of climate versus land use–land cover (LULC) changes are still debated and are investigated in this paper. The evolution of the Niger red flood in Niamey from 1950 to 2012 is analysed based on long-term records of rainfall (three data sets based on in situ and/or satellite data) and discharge, and a hydrological model. The model is first run with the present LULC conditions in order to analyse solely the effect of rainfall variability. The impact of LULC and drainage area modification is investigated in a second step. The simulations based on the current surface conditions are able to reproduce the observed trend in the red flood occurrence and intensity since the 1980s. This has been verified with three independent rainfall data sets and implies that rainfall variability is the main driver for the red flood intensification observed over the last 30 years. The simulation results since 1953 have revealed that LULC and drainage area changes need to be invoked to explain the changes over a 60-year period.
Effects of Multiple Doppler Radar data assimilation on the numerical simulation of a Flash Flood Event during the HyMeX campaign
Authors: Maiello Ida , Gentile Sabrina , Ferretti Rossella , Baldini Luca , Roberto Nicoletta , Picciotti Errico , Alberoni Pier Paolo , Marzano Frank S.
Published: July 2016

Abstract. An analysis to evaluate the impact of assimilating multiple radar data with a three dimensional variational (3D-Var) system on a heavy precipitation event is presented. The main goal is to establish a general methodology to quantitatively assess the performance of flash-flood numerical weather prediction at mesoscale. In this respect, during the first Special Observation Period (SOP1) of HyMeX (Hydrological cycle in the Mediterranean Experiment) campaign several Intensive Observing Periods (IOPs) were launched and nine occurred in Italy. Among them IOP4 is chosen for this study because of its low predictability. This event hit central Italy on 14 September 2012 producing heavy precipitation and causing several damages. Data taken from three C-band radars running operationally during the event are assimilated to improve high resolution initial conditions. In order to evaluate the impact of the assimilation procedure at different horizontal resolution and to assess the impact of assimilating multiple radars data, several experiments using Weather Research and Forecasting (WRF) model are performed. Finally, the statistical indexes as accuracy, equitable threat score, false alarm ratio and frequency bias are used to objectively compare the experiments, using rain gauges data as benchmark.
Possible groundwater dominance in the subglacial hydrology of ice sheet interiors: example at Dome C, East Antarctica
Authors: Gooch Brad T. , Carter Sasha P. , Ghattas Omar , Young Duncan A. , Blankenship Donald D.
Published: July 2016

Abstract. We hypothesize that groundwater systems may be the main water transport mechanism over (distributed, inefficient) water sheets at large scales in the interiors of ice sheets where melt rates are very low. We compare melt rate magnitudes to potential groundwater volume fluxes and also calculate the theoretical transmissivity ranges of subglacial water sheet and groundwater flow systems. Theoretical groundwater systems are on par with or are more transmissive than water sheets for the upper half of the permeability spectrum. In addition, we develop a 2D cross-sectional subglacial flow path model that connects subglacial lakes near Dome C, East Antarctica. This model integrates subglacial water sheet flux and hypothetical groundwater flow forcing, better bridging two historically disparate modeling frameworks – subglacial hydrology and ice sheet hydrogeology. Our model results suggest that the water sheet thickness can be highly dependent on groundwater flux and that the water sheet transmissivity is within the total range of the modeled groundwater system transmissivity. We infer from these results that subglacial lake stability and basal radar reflections underneath the interior of East Antarctica may possibly be affected by groundwater flow.
Impact of Icebergs on Net Primary Productivity in the Southern
Ocean
Authors: Wu Shuang-Ye , Hou Shugui
Published: July 2016

Abstract. Productivity in the Southern Ocean (SO) is iron-limited, and supply of iron dissolved from aeolian dust is believed to be the main source from outside the marine environment. However, recent studies show that icebergs could provide comparable amount of bioavailable iron to the SO as aeolian dust. In addition, small scale areal studies suggest increased concentrations of chlorophyll, krill, and seabirds surrounding icebergs. Based on previous research, this study aims to examine whether iceberg occurrence has a significant impact on marine productivity for the entire SO (south of 40° S), using remote sensing data of monthly iceberg amount and monthly ocean net primary productivity (NPP) covering the period 2002–2014. Using global and geographically weighted multiple linear regression models, and controlling for temperature, our analyses show that iceberg presence has a small, yet statistically significant, positive impact on the SO NPP. NPP in the SO is largely influenced by temperature, which could explain 43 % of the total variance in NPP with the standardized coefficient of 0.68. However, in places with iceberg presence, temperature influence weakens, indicated by lower partial temperature R2 (0.19) and standardized coefficient (0.45). Meanwhile, iceberg probability could independently explain 2 % of the NPP variance with a standardized coefficient of 0.15. Although small, this influence is statistically significant at 0.01 level. The geographically weighted regression model reveals spatial variation of these relationships. The results suggest that as iceberg quantity increases, their positive influence on NPP also increases, as indicated by increasing iceberg partial R2 and standardized coefficient in the models.
SHAPE AND SIZE IN MEDICINE, BIOTECHNOLOGY, MATERIALS SCIENCE AND SOCIAL SCIENCES
Authors: Bongiorno Enea G , Micheletti Alessandra , Naldi Giovanni , La Torre Davide
Published: July 2016

This special issue gathers together papers presented during the workshop Shape and Size in Medicine, Biotechnology, Materials Science and Social Sciences, Milano, Italy, 16-17 February 2011, https://sites.google.com/site/shapemilan/home
O humano e o desumano: cultura visual, cultura política e as imagens feitas por George Rodger e Henri Cartier-Bresson nos campos de concentração nazistas
Authors: Zerwes Erika Cazzonatto
Published: July 2016

Este artigo busca compreender alguns aspectos da noção de humanismo na fotografia e sua proximidade com a cultura política e a cultura visual do período, a partir das experiências específicas de George Rodger e Henri Cartier-Bresson, dois fotógrafos que viveram em primeira mão e que deram testemunho do horror dos campos de concentração nazistas ao final da Segunda Guerra Mundial. George Rodger fotografou o campo de Bergen-Belsen assim que foi libertado pelas tropas britânicas. Henri Cartier-Bresson esteve com uma equipe de filmagem registrando as massas de deportados recém-libertados dos campos de concentração e extermínio nazista. Essas experiências viriam a ter impactos profundos na biografia e no trabalho de ambos. Nos dois casos, está presente uma noção de humanismo atrelada aos acontecimentos da Segunda Guerra Mundial, que se faz ver na fotografia e na representação fotográfica, de significativa consequência para a cultura visual contemporânea.
Ditadura civil-militar, cassações políticas e História em Chapecó
Authors: Siqueira Gustavo Henrique de
Published: July 2016

Resenha da obra:SILVA, Claiton Marcio da. Dos braços do povo à espada dos militares: os anos de chumbo na Fronteira Sul (1964-1970). Florianópolis: Pandion, 2014.
O que a tragédia à brasileira nos ensina sobre justiça? Orestes, um fragmento fílmico da história construída
Authors: Franco Paula
Published: July 2016

Resenha da obra:Orestes. Produção 7Estrelo Filmes, direção de Rodrigo Siqueira. Brasil, 2015. 93 min. color.A presente resenha debruça-se sobre a irreverência do documentário brasileiro Orestes  do diretor Rodrigo Siqueira. Com expectativa de gravar um filme sobre os resquícios da ditadura, Siqueira inicia a narrativa fílmica a partir da alegórica história da tragédia grega homônima e a relaciona com a história real de Ñsaindy, filha de guerrilheiros mortos durante a ditadura. O fio que rege o roteiro, todavia, não se limita à história do passado (será mesmo que é passado?) da ditadura, mas adentra a seara da discussão sobre justiça e violência como temas que atravessam o tempo na realidade brasileira. Fugindo da compossição clássica documental, trata-se de uma produção que visa refletir profundamente sobre a realidade atual e ousar novas formas e linguagens de contar uma história através do cinema.
Existe história oral na América Latina? ‐ Uma entrevista com Gerardo Necoechea Gracia
Authors: Silva Célia Santana , Pinheiro Lisandra Barbosa M. , Fagionato Yomara Feitosa Caetano de Oliveira
Published: July 2016

O Segundo Seminário Internacional História do Tempo Presente é uma iniciativa do Programa de Pós-Graduação em História da Universidade do Estado de Santa Catarina (UDESC), com o objetivo de aproximar pesquisadores nacionais e internacionais capazes de contribuir, tanto para a compreensão de fenômenos históricos transcorridos ao longo do século XX e início do século XXI, como para a reflexão sobre os desafios teóricos e metodológicos de uma “história do tempo presente”. O evento ocorreu nos dias 13, 14 e 15 de outubro de 2014, e seu formato foi pensado para garantir participações em níveis diferenciados, sem abrir mão da qualidade das discussões. Participante da mesa-redonda, Memória e Tempo Presente, Prof. Dr. Gerardo Necoechea Gracia faz algumas reflexões sobre História Oral na América Latina.