HRMC_1.1: Hybrid Reverse Monte Carlo method with silicon and carbon potentials

The Hybrid Reverse Monte Carlo (HRMC) code models the atomic structure of materials via the use of a combination of constraints including experimental diffraction data and an empirical energy potential. This energy constraint is in the form of either the Environment Dependent Interatomic Potential (EDIP) for carbon and silicon and the original and modified Stillinger–Weber potentials applicable to silicon. In this version, an update is made to correct an error in the EDIP carbon energy calculation routine.

New version program summary

Program title: HRMC version 1.1Catalogue identifier: AEAO_v1_1Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAO_v1_1.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 36 991No. of bytes in distributed program, including test data, etc.: 907 800Distribution format: tar.gzProgramming language: FORTRAN 77Computer: Any computer capable of running executables produced by the g77 Fortran compiler.Operating system: Unix, WindowsRAM: Depends on the type of empirical potential use, number of atoms and which constraints are employed.Classification: 7.7Catalogue identifier of previous version: AEAO_v1_0Journal reference of previous version: Comput. Phys. Comm. 178 (2008) 777Does the new version supersede the previous version?: YesNature of problem: Atomic modelling using empirical potentials and experimental data.Solution method: Monte CarloReasons for new version: An error in a term associated with the calculation of energies using the EDIP carbon potential which results in incorrect energies.Summary of revisions: Fix to correct brackets in the two body part of the EDIP carbon potential routine.Additional comments: The code is not standard FORTRAN 77 but includes some additional features and therefore generates errors when compiled using the Nag95 compiler. It does compile successfully with the GNU g77 compiler (http://www.gnu.org/software/fortran/fortran.html).Running time: Depends on the type of empirical potential use, number of atoms and which constraints are employed. The test included in the distribution took 37 minutes on a DEC Alpha PC.     

HRMC: Hybrid Reverse Monte Carlo method with silicon and carbon potentials

Fortran 77 code is presented for a hybrid method of the Metropolis Monte Carlo (MMC) and Reverse Monte Carlo (RMC) for the simulation of amorphous silicon and carbon structures. In additional to the usual constraints of the pair correlation functions and average coordination, the code also incorporates an optional energy constraint. This energy constraint is in the form of either the Environment Dependent Interatomic Potential (applicable to silicon and carbon) and the original and modified Stillinger-Weber potentials (applicable to silicon). The code also allows porous systems to be modeled via a constraint on porosity and internal surface area using a novel restriction on the available simulation volume.

Program summary

Program title: HRMC version 1.0Catalogue identifier: AEAO_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAO_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 200 894No. of bytes in distributed program, including test data, etc.: 907 557Distribution format: tar.gzProgramming language: FORTRAN 77Computer: Any computer capable of running executables produced by the g77 Fortran compilerOperating system: Unix, WindowsRAM: Depends on the type of empirical potential use, number of atoms and which constraints are employedClassification: 7.7Nature of problem: Atomic modeling using empirical potentials and experimental dataSolution method: Monte CarloAdditional comments: The code is not standard FORTRAN 77 but includes some additional features and therefore generates errors when compiled using the Nag95 compiler. It does compile successfully with the GNU g77 compiler (http://www.gnu.org/software/fortran/fortran.html).Running time: Depends on the type of empirical potential use, number of atoms and which constraints are employed. The test included in the distribution took 37 minutes on a DEC Alpha PC.     

A Monte Carlo evaluation of the moving method, k-means and two self-organising neural networks

In recent years there has been increasing interest in the comparative clustering abilities of k-means, moving methods and self-organising neural networks. However, most comparative studies have either been restricted to specific problem areas or have been conducted with other limitations that do not provide a more general evaluation of the relative abilities of these methods under a wide variety of conditions. This report provides a systematic empirical evaluation of the clustering abilities of k-means, moving methods and two commonly used self-organising neural network architectures. Monte Carlo simulation examining the effects of cluster shape, dimensionality, noise, dispersion and number of clusters in the data is used to evaluate the above methods. Results indicate that, on average, k-means, moving methods and winner take all self-organising networks perform equally well in terms of clustering ability. However, as the moving method consistently converges faster than k-means, under circumstances where convergence speed is an important factor it may well represent a more appropriate benchmark for future comparisons between pattern partitioning methods.     

Nonlinear stochastic receding horizon control: stability,robustness and Monte Carlo methods for control approximation

This work considers the stability of nonlinear stochastic receding horizon control when the optimal controller is only computed approximately. A number of general classes of controller approximation error are analysed including deterministic and probabilistic errors and even controller sample and hold errors. In each case, it is shown that the controller approximation errors do not accumulate (even over an infinite time frame) and the process converges exponentially fast to a small neighbourhood of the origin. In addition to this analysis, an approximation method for receding horizon optimal control is proposed based on Monte Carlo simulation. This method is derived via the Feynman–Kac formula which gives a stochastic interpretation for the solution of a Hamilton–Jacobi–Bellman equation associated with the true optimal controller. It is shown, and it is a prime motivation for this study, that this particular controller approximation method practically stabilises the underlying nonlinear process.     

Laser beam welded structures for a regional aircraft: weight,cost and carbon footprint savings

Laser beam welded structures offer great opportunities for the lightweight design of fuselage structures in order to reduce structural weight for increased fuel efficiency. Our main objective is to validate and demonstrate that laser beam welding (LBW) technology provides the best opportunities in terms of weight reduction, production time and energy consumption for manufacturing aircraft components. To this end, a comparison in terms of energy, process time, cost and carbon footprint is assessed against the ‘conventional’ manufacturing process of riveting, to prove that LBW is actually an environmental friendly process. Manufacturing of a four-stringer stiffened flat subscale component was the case of the present work that was called in the Clean Sky Eco-Design Airframe (EDA) project as the B1 demonstrator (742 mm × 384 mm). The LBW process has been broken down into several sub-processes and activities according to the Activity Based Costing (ABC) methodology and the weight reduction, production time and energy consumption results were compared against the respective of the riveting process. It was proved that for the specific subscale LBW component, it consumes half the energy and can be processed in less than half the time needed (in serial processing of the component) with riveting. Manufacturing of the component with the LBW process (door to door approach) is more environmentally friendly, since it produces 53% less CO_2e emissions than the respective riveted process. This is a clear advantage to this manufacturing process in order to assure a sustainable life cycle of the final product.     

On the complex formation of CdCl2 with 1-furoylthioureas: Preconcentration and voltammetric behavior of Cd(II) at carbon paste electrodes modified with 3-monosubstituted and 3,3-disubstituted derivatives

Two series of 1-furoylthioureas were used as modifiers of carbon paste electrodes (CPE). The preconcentration of Cd(II) at CPE modified with these 3-monosubstituted and 3,3-disubstituted 1-furoylthioureas and its subsequent voltammetric determination was studied with Cd(II) test solution. The preconcentration of cadmium at the surface of the modified CPE varied with the steric and electronic nature of the present CS neighboring groups. This is in accord with the changes observed in the Raman spectra of the ligands after complexation with CdCl₂, and with the chemical yields of the complexes obtained.     

Effect of the reaction time, reagent concentration and sample thickness on the thermal derivatisation of p porous silicon with α-undecene and ω-carboxy alkenes: A FTIR investigation

This paper presents a detailed study, based on Fourier transform infrared (FTIR) analysis, on the derivatisation of p⁺-type porous silicon (PS) via thermal activated hydrosilylation of α-undecene. The α-undecene was used as a model for alkene precursor to calculate the efficiency of the hydrosilylation reaction, determined by comparing the integrated intensity of the SiH_x peaks (2200–2000 cm⁻¹) of the as-prepared and modified sample, by varying three parameters: the reaction time, the reagent concentration and the sample thickness. This study aims to optimize the PS derivatisation as a function of the thickness, in order to consider the thermal activation as a useful process for modifying PS slab waveguide for sensing application. Moreover two methods using ω-carboxy alkenes (where the carboxylic moiety was an ester or an acid) to obtain a PS surface –COOH-terminated, to be exploited for bioconjugation protocols, were tested and the reactions efficiency compared with the alkene model, i.e. α-undecene. FTIR spectroscopy and contact angle measurements were used to characterize the modified PS samples.