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Thermodynamic analysis of the immobilisation of arsenic during the pressure oxidation and curing processes

MINERALS ENGINEERING 2022年第0期185卷

作者： Liu, Yanhua Ng, Wei Sung Chen, Miao RMIT Univ Sch Sci Melbourne Vic 3001 Australia CSIRO Mineral Resources Clayton Vic 3169 Australia

In recent decades, there has been increasing interest in the application of hydrothermal treatment as a pathway for the immobilisation of arsenic waste from the treatment of complex ores. These techniques can involve temperatures up to 250 ?, where thermodynamic data is often limited due to the challenges involved in the in situ measurement of arsenic-bearing phases at elevated temperatures. A potential approach is the use of thermodynamic modelling to predict and understand the behavior of the aqueous arsenic complexes and arsenate minerals at high temperatures. Herein, the polyhedral method has been used to estimate the standard Gibbs free energy of formation (& UDelta;Gof) of 52 arsenate minerals and enthalpy of formation (& UDelta;Hof) of 26 arsenate minerals from 25 ? to 300 ?. The predicted values for the arsenate minerals showed good agreement with experimental results from literature, with average relative errors and absolute deviations of 0.32% and 6.77 kJ/mol for delta Gof and 0.17% and 4.69 kJ/mol for delta Hfo. Subsequently, the polyhedral method and Helgeson-Kirkham-Flowers model were combined to estimate the solubility product constant (Ksp) of the arsenate minerals at 1.013 bar and 25, 50, 100 ?, and at saturation pressure and 150, 200, 250 and 300 ?. Based on the estimated values, the phase diagram for the Fe-As-S-H2O system demonstrated that scorodite is one of the most thermodynamically stable ferric arsenates at acidic conditions and temperatures below 130 ?, while ferric arsenate subhydrate (FAsH) and basic ferric arsenate sulfate (BFAS) were thermodynamically favoured at higher temperature. Under similar conditions, the model also predicts the preferential formation of BFAS over FAsH with increasing concentrations of SO42? and higher temperatures.

关键词： Arsenate minerals Thermodynamic properties polyhedral method Phase diagram Pressure oxidation

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Study on the modeling method of sunflower seed particles based on the discrete element method

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COMPUTERS AND ELECTRONICS IN AGRICULTURE 2022年 198卷

作者： Wang, Shuai Yu, Zhihong Zhang, Wenjie Aorigele Inner Mongolia Agr Univ Coll Mech & Elect Engn Hohhot 010018 Peoples R China

A modeling and simulation method was developed to comprehensively describe and build discrete element model for non-spherical particles based on the discrete element method (DEM). To popularize the application of sunflower seeds in computer digital simulation technology, the motion patterns and dynamic response characteristics of sunflower seeds in key processes such as sowing and harvesting are explored with the help of discrete element analysis methods to optimize the dimensional parameters and structural performance of related mechanical components. This paper takes edible sunflower seeds 1013 as the research object, and proposes a discrete element analysis model building method for individual sunflower seeds and groups of sunflower seeds particles by testing and analyzing the triaxial dimensions and three-dimensional volumes of sunflower seeds and the shape simplification of the seeds. 6 sunflower seed multi-sphere models (25 sub-spheres, 28 sub-spheres, 31 sub-spheres, 34 sub-spheres, 37 sub-spheres, 40 sub-spheres) with different accuracy and 2 sunflower seed polyhedral models (cuboid and triangle pyramid) with different shapes were established using the multi-sphere and polyhedron filling methods. The physical tests and angle of repose simulation tests were applied to measure and calibrate the intrinsic parameters and contact parameters of sunflower seeds. The physical test results of the bulk density and angle of repose are compared with the simulation test results to verify the feasibility of the discrete element modeling method for sunflower seeds proposed in this paper. The results show that the simulation results of bulk density and angle of repose are closer to the experimental results when the multi-sphere model is 31 sub-spheres and the polyhedral model is cuboid, considering fewer spheres and faster simulation rates. And the accuracy and applicability of the discrete element model and parameters of sunflower seeds are further verified through the sim

关键词： Discrete element method Sunflower seed Particle modeling Multi-sphere method polyhedral method Parameter calibration

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Solar-photon sail hovering orbits about single and binary asteroids

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ADVANCES IN SPACE RESEARCH 2019年第11期63卷 3691-3705页

作者： D'Ambrosio, Andrea Circi, Christian Zeng, Xiangyuan Sapienza Univ Rome Dept Astronaut Elect & Energy Engn Via Salaria 851 I-00138 Rome Italy Beijing Inst Technol Sch Automat Zhongguancun South Str 5 Beijing 100081 Peoples R China

Solar-photon sails can be useful for missions towards and about asteroids. Indeed, for the interplanetary transfer phase, missions to asteroids often require a large variation in inclination and solar-photon sails perform very well for such high energy missions. In the same way, solar-photon sails are also expected to perform well in the phase about the asteroid. This paper studies single and binary asteroids' hovering regions by using a sailcraft. In order to consider a sailcraft with its own mass and shape, the mutual polyhedral method (usually used to study asteroid dynamics) is used;therefore, the sailcraft is designed by means of tetrahedra. The procedure to obtain the hovering regions about a single asteroid is presented and an accurate analysis of the control variables is carried out. Moreover, control torques required to maintain hovering orbits are obtained by considering the gravitational torques acting on the sailcraft due to the asteroid. In the end, the theory for hovering orbits is extended to binary-asteroid systems and applied to the binary system 1999 KW4. (C) 2019 COSPAR. Published by Elsevier Ltd. All rights reserved.

关键词： Binary-asteroid systems polyhedral method Hovering orbits Solar sail

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Simple, Accurate, Analytical Time Modeling and Optimal Tile Size Selection for GPGPU Stencils 17

Simple, Accurate, Analytical Time Modeling and Optimal Tile ...

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22nd ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming (PPoPP)

作者： Prajapati, Nirmal Ranasinghe, Waruna Rajopadhye, Sanjay Andonov, Rumen Djidjev, Hristo Grosser, Tobias Colorado State Univ Ft Collins CO 80523 USA IRISA Rennes France LANL Los Alamos NM USA ETH Dept Comp Sci Zurich Switzerland

ISBN: (纸本)9781450344937

Stencil computations are an important class of compute and data intensive programs that occur widely in scientific and engineering applications. A number of tools use sophisticated tiling, parallelization, and memory mapping strategies, and generate code that relies on vendor-supplied compilers. This code has a number of parameters, such as tile sizes, that are then tuned via empirical exploration. We develop a model that guides such a choice. Our model is a simple set of analytical functions that predict the execution time of the generated code. It is deliberately optimistic, since we are targeting modeling and parameter selections yielding highly tuned codes. We experimentally validate the model on a number of 2D and 3D stencil codes, and show that the root mean square error in the execution time is less than 10% for the subset of the codes that achieve performance within 20% of the best. Furthermore, based on using our model, we are able to predict tile sizes that achieve a further improvement of 9% on average.

关键词： gpgpu performance prediction stencils polyhedral method analytical models hybrid hexagonal classic tiling

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Computing All Space Curve Solutions of Polynomial Systems by polyhedral methods 1

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18th International Workshop on Computer Algebra in Scientific Computing (CASC)

作者： Bliss, Nathan Verschelde, Jan Univ Illinois Dept Math Stat & Comp Sci 851 S Morgan StM-C 249 Chicago IL 60607 USA

ISBN: (数字)9783319456416

ISBN: (纸本)9783319456409;9783319456416

A polyhedral method to solve a system of polynomial equations exploits its sparse structure via the Newton polytopes of the polynomials. We propose a hybrid symbolic-numeric method to compute a Puiseux series expansion for every space curve that is a solution of a polynomial system. The focus of this paper concerns the difficult case when the leading powers of the Puiseux series of the space curve are contained in the relative interior of a higher dimensional cone of the tropical prevariety. We show that this difficult case does not occur for polynomials with generic coefficients. To resolve this case, we propose to apply polyhedral end games to recover tropisms hidden in the tropical prevariety.

关键词： Newton polytope polyhedral end game polyhedral method Polynomial system Puiseux series Space curve Tropical basis Tropical prevariety Tropism

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On Monomial Reduction and Polynomial Expressions with Respect to Binomial Ideals

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COMMUNICATIONS IN ALGEBRA 2015年第10期43卷 4054-4069页

作者： Sabeti, Rostam Olivet Coll Math & Comp Sci Dept Olivet MI 49076 USA

Let I subset of K[x(1),..., x(n)] be an ideal and G be the reduced Grobner basis of I with respect to lexicographic monomial order. We introduce the index of an expression of fK[x(1),..., x(n)] with respect to G. A minimal expression is characterized as the one with zero G-index. In case where I is a binomial prime ideal, a new division algorithm with minimal and unique expression is presented. The application of our new method on benchmark polynomial systems cyclic-9 and cyclic-12 shows its superiority in comparison with the existing division algorithm.

关键词： Computational algebraic geometry Components of solutions Division algorithm polyhedral method Primary: 14Q15 Secondary 65H10 68W30 13P05

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Energy Modeling and Optimization for Tiled Nested-Loop Codes 29

Energy Modeling and Optimization for Tiled Nested-Loop Codes

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29th IEEE International Parallel and Distributed Processing Symposium (IPDPS)

作者： Prajapati, N. Ranasinghe, W. Tandrapati, V. Andonov, Rumen Djidjev, Hristo Rajopadhye, Sanjay Colorado State Univ CS Dept Ft Collins CO 80523 USA IRISA INRIA Rennes France Los Alamos Natl Lab Los Alamos NM USA

ISBN: (纸本)9781467376846

We develop a methodology for modeling the energy efficiency of tiled nested-loop codes running on a graphics processing unit (GPU) and use it for energy efficiency optimization. We assume that a highly optimized and parametrized version of a tiled nested-loop code-either written by an expert programmer or automatically produced by a polyhedral compilation tool-is given to us as an input. We then model the energy consumption as an analytical function of a set of parameters characterizing the software and the GPU hardware. Most previous attempts at GPU energy modeling were based on low-level machine models that were then used to model whole programs through simulations, or were analytical models that required low level details. In contrast, our approach develops analytical models based on (i) machine and architecture parameters, (ii) program size parameters as found in the polyhedral model and (iii) tiling parameters, such as those that are chosen by auto-or manual tuners. Our model therefore allows efficient optimization of the energy efficiency with respect to a set of parameters of interest. We illustrate the framework on three nested-loop codes: Smith-Waterman, and one-dimensional and two-dimensional Jacobi stencils, and analyze the accuracy of the resulting models. We also show that the models can be used for optimal tile-size selection for energy efficiency. With optimal choice of model parameters the RMS error is less than 4%. Two factors allow us to attain this high accuracy. The first is domain-specificity: we focus only on tile-able nested-loop codes. The second is that we decouple the energy model from a model of the execution time, a known hard problem.

关键词： energy efficiency GPU Jacobi stencil nested-loops polyhedral method Smith-Waterman stencil computations

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Branch-and-cut for complementarity-constrained optimization

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MATHEMATICAL PROGRAMMING COMPUTATION 2014年第4期6卷 365-403页

作者： de Farias, I. R., Jr. Kozyreff, E. Zhao, M. Texas Tech Lubbock TX 79409 USA SAS Cary NC USA

We report and analyze the results of our computational testing of branch-and-cut for the complementarity-constrained optimization problem (CCOP). Besides the MIP cuts commonly present in commercial optimization software, we used inequalities that explore complementarity constraints. To do so, we generalized two families of cuts proposed earlier by de Farias, Johnson, and Nemhauser that had never been tested computationally. Our test problems consisted of linear, binary, and general integer programs with complementarity constraints. Our results on the use of complementarity cuts within a major commercial optimization solver show that they are of critical importance to tackling difficult CCOP instances, typically reducing the computational time required to solve them tremendously.

关键词： Complementarity Multiple-choice Special ordered set Mixed-integer programming Knapsack set polyhedral method Branch-and-cut

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polyhedral methods for Space Curves Exploiting Symmetry Applied to the Cyclic n-roots Problem

Polyhedral Methods for Space Curves Exploiting Symmetry Appl...

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15th International Workshop on Computer Algebra in Scientific Computing (CASC)

作者： Adrovic, Danko Verschelde, Jan Univ Illinois Dept Math Stat & Comp Sci Chicago IL 60607 USA

ISBN: (纸本)9783319022970;9783319022963

We present a polyhedral algorithm to manipulate positive dimensional solution sets. Using facet normals to Newton polytopes as pretropisms, we focus on the first two terms of a Puiseux series expansion. The leading powers of the series are computed via the tropical prevariety. This polyhedral algorithm is well suited for exploitation of symmetry, when it arises in systems of polynomials. Initial form systems with pretropisms in the same group orbit are solved only once, allowing for a systematic filtration of redundant data. Computations with cddlib, Gfan, PHCpack, and Sage are illustrated on cyclic n-roots polynomial systems.

关键词： Algebraic set Backelin's Lemma cyclic n-roots initial form Newton polytope polyhedral method polynomial system Puiseux series symmetry tropism tropical prevariety

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The piecewise linear optimization polytope: new inequalities and intersection with semi-continuous constraints

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MATHEMATICAL PROGRAMMING 2013年第1-2期141卷 217-255页

作者： Zhao, Ming de Farias, Ismael Regis, Jr. SAS Cary NC USA Texas Tech Univ Dept Ind Engn Lubbock TX 79409 USA

We give new facets and valid inequalities for the separable piecewise linear optimization (SPLO) knapsack polytope. We also extend the inequalities to the case in which some of the variables are semi-continuous. Finally, we give computational results that demonstrate their efficiency in solving difficult instances of SPLO and SPLO with semi-continuous constraints.

关键词： Piecewise linear optimization Mixed-integer programming Knapsack problem Special ordered set Semi-continuous variables polyhedral method Branch-and-cut

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