Colloquiam: Documents published in 2022

Simulating the Influence of Particle Geometry and Arrangement on the Collapse of a Submerged Granular Step

Scipedia content — Tue, 15 Feb 2022 12:25:04 +0100

Insights into the behaviour of fluid-saturated granular media, by using a simulation that combines the Discrete Element Method for the granular particles and the Finite Element Method for the fluid.

Effect of cohesive forces on fluctuations in granular flows: linking experiments and simulations

Scipedia content — Tue, 15 Feb 2022 12:24:39 +0100

Granular flow is a complex process depending on a large set of parameters such as grain morphology, surface friction, flow geometry, stress field and cohesion (e.g. attractive interaction between grains). The latter arises from the presence of humidity, electrostatic charges and Van der Waals forces within the grains that lead, among other effects, to the appearance of surface flow fluctuations also called avalanches. Those surface fluctuations produce an intermittent granular flow and determine the processability of a powder in many application. In order to link the flow fluctuations and the cohesion between grains, we reproduced numerically with a DEM model the flow of cohesive granular materials in a 2D rotating drum. A simplified cohesive interaction between circular grains has been implemented and the granular flow has been analyzed through the flowing angle and the interface fluctuations. The numerical results are compared with experimental results obtained with GranuDrum instrument and a set of silicon carbide grains with different grain sizes and therefore different cohesiveness. The motivation behind this study is to determine to what extent a simplified model can reproduce a complex flow. The similarities between numerical and experimental results and also the discrepancies are discussed. This comparison gives a fundamental background to the cohesive index parameter measured with GranuDrum instrument from the interface fluctuations. Finally, we show that comparing the flow inside a rotating drum obtained numerically and experimentally is a practical way to calibrate a set of parameters before the simulation of a complex process.

A HYBRID TIME-FREQUENCY METHODOLOGICAL PROPOSAL TO SIMULATE GROUND RESPONSE UNDER HARMONIC ACCELERATIONS IN A MATERIAL-POINT FRAMEWORK

Scipedia content — Tue, 15 Feb 2022 12:24:22 +0100

The response of geomaterials to seismic excitations, which are usually described with time history data, can be estimated by solving governing equations in the frequency domain and transferring quantities back to the time domain. However, one limitation of frequency analysis is the simplification of soil response by assuming constant stiffness during the action of seismic input. Therefore, when the frequency approach is used in ground response problems, linear-equivalent models of soil behaviour that allow the description of non-linear stiffness are implemented. In order to simulate large fields of displacements induced by seismic actions, this paper introduces a methodological proposal based upon a hybrid Finite Element (FE) time-frequency approach, coupled with the Material Point Method (MPM). In the FE solution, the soil stiffness changes after certain number of cycles and the equation of motion is solved in the frequency domain while the soil stiffness remains constant. Mapping of kinematic quantities between nodes of the finite element mesh and material points is performed via a Newton-Raphson numerical scheme. Each change of the stiffness matrix is marked by a convective material-point phase and the recalculation of material point locations. By following this approach, large deformations of geomaterials under constant amplitude harmonic accelerations can be simulated using a linear equivalent approach for the non-linear response. A model test case subjected to harmonic shaking is explained.

Numerics of Discrete Element Simulations in Milli-g Environments: Challenges and Solutions

Scipedia content — Tue, 15 Feb 2022 12:24:06 +0100

This work gives an overview of numerical issues arising when performing DEM soil simulations in milli-g environments. The cause for those issues as well as their effect on simulation results and numerical stability are discussed. Lastly, strategies and solutions to avoid numerical issues with floating-point arithmetics in milli-g environments are proposed, implemented and their effectiveness is reviewed.

Modelling of the dust release from bulk solids in the event of particle impact through enhanced dust detachment functions

Scipedia content — Tue, 15 Feb 2022 12:23:43 +0100

In terms of environmental, health and explosion protection, it is important to assess the extent of diffuse dust emissions. In addition to standardized dustiness tests and measurements under field conditions on real dust emissions, numerical methods such as the Discrete Element Method (DEM) coupled to Computational Fluid Dynamics (CFD) are promising approaches for the prediction of the latter. Thereby the DEM calculates the bulk solid particle motion and the CFD provides information about the flow parameters of the fluid phases in terms of location and time. Due to computing time restrictions when simulating larger processes, each dust particle is usually not modelled in detail, but rather described using so-called dust detachment functions. In this study, detachment functions are adapted and developed based on a benchmarking with dust-resolved DEM simulations. Therefore, the adhesive contacts of fine dust particles attached to coarse bulk solid particles are modelled with an adhesive contact model (JKR approach). Depending on the bulk particle velocity, impact angle, material properties and bulk particle rotation in the case of single particle-wall and single particle-particle contacts, a good match between dust-resolved DEM and DEM with integrated detachment functions can be provided. For the further derivation and verification of the method, it is planned to compare numerical results also to experimental investigations. Therefore, the fine dust particle amount is reproducibly applied to coarse bulk solid particles by a well-defined calcium carbonate powder. The adhesion of the powder phase is then analysed before and after an impact.

Direct Observation and Simulation for of Ladle Pouring and Plunger Advancing behaviours in Die Casting Process

Scipedia content — Tue, 15 Feb 2022 12:23:22 +0100

The ladle pouring and plunger advancing processes are parts of the die casting which has advantages of high speed, good quality and mass production. The molten metal is quickly poured into the sleeve by tilting the ladle, and immediately injected into the die cavity with high speed and high pressure by advancing the plunger. Since the entrapment of air and the generation of solidified layer in the ladle pouring may cause the defects of cast products, it is necessary to simulate the ladle pouring behavior. In the present study, the pouring experiment into the sleeve using die casting aluminum alloy JIS-ADC12 are carried out to observe the flow behavior by tilting the ladle. Further the molten aluminum alloy is injected to the cavity from the sleeve by advancing the injection plunger. Dynamics of the molten aluminum alloy is influenced by the oxide film [1][2]. The flow behaviors in ladle pouring and plunger advancing of molten aluminum alloy are simulated using "COLMINA CAE", which is the casting analysis software by particle method SPH [3]. The experiments and simulation are executed varying with the shot time lag, which is the interval from finish of ladle pouring to start the plunger advancing, and plunger speeds. Wave behavior obtained by simulation is almost agreed with the actual phenomena. Flow and heat transfer simulation using SPH method with a function of the oxide film is effective method that ladle pouring and plunger advancing of molten aluminum alloy with free surface flow can be simulated accurately.

Improving the prediction ability of simplified discrete element models on complex loading paths

Scipedia content — Tue, 15 Feb 2022 12:22:52 +0100

Discrete element method has been proved to be an effective method in predicting quantitatively the constitutive response of soils, even in the case of complex loadings (with rotation of principal stress directions, or loading/unloading cycles) where conventional elastoplastic constitutive relations may fail to simulate realistic responses [10]. For granular soils with a narrow grading, a direct representation of soil grains by polyhedral particles or with the level set method is possible [5], whereas for finer soils, or soils with a wider grading, alternative solutions should be considered. Spherical particles with enriched contact laws (e.g. by introducing rolling resistance at the contact) or rather simplified clumps of spheres can be used. This study aims to compare such different approaches. This comparison is done in terms of the prediction abilities at the macroscopic scale of the constitutive responses of soils, in particular for complex loading paths. Two kinds of discrete models are considered: (i) spherical particles with a rolling resistance, (ii) simple clumps made of 2 to 6 spheres. The models are calibrated from two drained triaxial compressions on dense and loose Hostun sand samples. They are then assessed, according to the macroscopic response, on loading paths strongly different from the calibration loading paths (isochoric compressions, circular stress paths in the deviatoric strain plane, constant deviatoric stress path, . . . ). The objective is to produce an optimized discrete element model in terms of prediction ability with respect to the computational cost, able to represent natural soils with possibly a wide particle size distribution, in order to tackle boundary value problems (as geotechnical structures) subjected to complex loadings.

Triaxial compression and direct shear tests in the parametrization of soil modeled via the Discrete Element Method

Scipedia content — Tue, 15 Feb 2022 12:22:31 +0100

Investigation in the parametrization of soil modeled with DEM based on measurements in triaxial compression and direct shear tests.

MPM developments in soil-water-structure interaction implemented in Anura3D

Scipedia content — Tue, 15 Feb 2022 12:22:12 +0100

Many geotechnical problems involve large deformations, non-linear material behaviour, soil-structure interactions, and multiphase (solid, liquid, gas) interactions, which poses significant challenges for numerical simulations. The material point method (MPM) showed to be well suited to study slope instabilities, such as landslides, earth embankment and levee failures, underground excavations, explosions, soil-penetration problems, such as pile installation, Cone Penetration Testing, Free Fall Penetrometer testing, etc. Moreover, erosion and sedimentation problems require considering phase transitions (from solid-like to fluid-like), and This contribution will show the latest numerical developments of MPM with respect to the above-mentioned aspects as implemented in the open-source software Anura3D. Particular attention is given to some geotechnical applications, such as the simulation of slope collapse due to earthquake or water pressure changes, erosion problems, porous sea defences, installation problems, and many more.

Coupled CFD-MPM simulation of soil-fluid interaction in geotechnics

Scipedia content — Tue, 15 Feb 2022 12:21:47 +0100

Material Point Method (MPM) can be used to simulate large deformations in geotechnics such as debris flows or landslides [1]. However, simulating the submarine debris flows using MPM is quite challenging as it involves complex interactions between debris flow (soil) and seawater (fluid) such as turbulence or hydroplaning mechanisms. This paper presents a coupled Computational Fluid Dynamics and MPM (CFD-MPM) approach [2] to simulate the behavior of soil-fluid interaction for applications in geotechnical engineering. MPM is employed to model the porous media system, while the CFD is used to simulate the fluid flow by solving the Navier–Stokes equations. The soil-fluid interaction is considered by drag forces and buoyancy forces in the multi-phase governing equations. We implemented the formulations in the Uintah computational framework. Numerical simulations are performed and compared with the experiment to highlight the capability of the coupled CFD-MPM model. REFERENCES [1] Q. A. Tran and W. Sołowski, “Generalized Interpolation Material Point Method modelling of large deformation problems including strain-rate effects – Application to penetration and progressive failure problems,” Computers and Geotechnics, vol. 106, pp. 249-265, 2019. [2] J. E. Guilkey, T. Harman and B. Banerjee, “An Eulerian-Lagrangian approach for simulating explosions of energetic devices,” Computers & Structures, vol. 85, no. 11-14, pp. 660-674, 2007.

Toward CFD-DEM simulations of the blast furnace raceway

Scipedia content — Tue, 15 Feb 2022 12:21:27 +0100

Gas injections at the bottom of the blast furnace create void regions in the coke matrix called the raceways which play a role in the gas distribution in the furnace and is directly linked to the iron production. In this region, complex physical phenomena occur, including particle-fluid with combustion, and, to our knowledge, there is no consensus on its shape and dynamics as well as its creation and stability. A better understanding of the raceway region could lead to a more efficient and stable blast furnace process. An unresolved CFD-DEM approach is used to study the gas-solid flows where coke particles are modelled as a discrete phase and the gas as continuous solving the RANS modelling of the turbulence. In order to clarify the main phenomena occurring in the raceway dynamics, we develop a CFD-DEM model of a 1/5 scale 2d slot pilot of the blast furnace for which alternative raceway collapses are monitored. First, DEM simulations are realized without the fluid contribution and shows that the pilot geometry influences the mechanical load applied on the raceway with a saturation of the granular stress inside the pilot. Also, dry raceway collapse shows a modification of this stress in a short characteristic time. Then, CFD-DEM model of the pilot permits to investigate the gas and granular flows when the raceway is imposed as in the experiment. The dynamics of the collapse with the coupling is solved and displays a complex particle-gas 3d flow. Further implementation in the model will allow coke particle combustion.

Simulation of centrifugal pumps based on MPS solver

Scipedia content — Tue, 15 Feb 2022 12:21:04 +0100

In this article, a three dimensional full-scale centrifugal pump is, for the first time, simulated using the moving particle semi-implicit method(MPS). The genetic smooth wall boundary(GSW) is used and extended to three dimension to deal with the complicated wall shape and thin blades in turbo-machines. The non-surface detection technique(NSD) based on conceptual particles is combined with this wall model to avoid the loss of particle number density near wall boundaries. A local wall particle refinement method is developed. Fine particles and coarse particles are applied to curved surface and flat surface respectively so as to reduce the computational cost while maintain the high discretization precision. The fully developed velocity inflow and pressure outflow boundary conditions are proposed. Three typical cases including hydrostatic cases with complicated geometry, flows over a two-dimensional backward-facing step, and flows in a three-dimensional tube are tested to verify the proposed models. This paper constructs a framework for the simulation of incompressible fluid machines, in which 3D complex revolving bodies can be integrally discretized and interactions between the stator and rotor can be integrally solved within a single coordinate. This paper provides a particle-based solver for incompressible fluid machinery and has the potential to study its inner flow with multiphase or phase change.

Modelling and experimental analysis of the cooling liquid flow in ejector deep drilling processes

Scipedia content — Tue, 15 Feb 2022 12:20:44 +0100

Presentation of the Ejector Deep Drilling process, its importance, intrinsic characteristics as well as it's problematic aspects. The goal of the work is to achieve a deeper understanding of the behaviour of the cutting fluid in all the tricky areas, such as the cutting zone, the inflow area and the supply zone. This is achieved with the combined use of a simulation tool based on the Smoothed Particle Hydrodynamics method (SPH) and an experimental investigations.The better knowledge of the behaviour of the lubricant obtained will be crucial to define new design strategies and to improve the drilling efficiency.

A scalable Lagrangian particle tracking method

Scipedia content — Tue, 15 Feb 2022 12:19:23 +0100

Particle tracking within an underlying flow field is routinely used to analyse both industrial processes and natural phenomena. In a computer code running on a
distributed-memory architecture, the different behaviour of fluid-particle systems must be taken into account to properly balance element-particle subdivision among processes.
In unsteady simulations, the parallel efficiency is even more critical because it changes over time. Another challenging aspect of a scalable implementation is the initial particle
location due to the arbitrary shapes of each subdomain. In this work, an innovative parallel ray tracing particle location algorithm and a two-constrained domain subdivision
are presented. The former takes advantage of a global identifier for each particle, resulting in a significant reduction of the overall communication among processes. The latter is
designed to mitigate the load unbalance in the particles evolution while maintaining an equal element distribution. A preliminary particle simulation is performed to tag the cells
and compute a weight proportional to the probability to be crossed. The algorithm is implemented using MPI distribute memory environment. A cloud droplet impact test
case starting from an unsteady flow around a 3D cylinder has been simulated to evaluate the code performances. The tagging technique results in a computational time reduction
of up to 78% and a speed up factor improvement of 44% with respect to the common flow based domain subdivision. The overall scalability is equal to 1.55 doubling the number of
cores.

Flexible Bodies for Investigation of Chip Jamming and Drill Breakage in Deep-Hole Drilling

Scipedia content — Tue, 15 Feb 2022 12:18:34 +0100

The risk of chip jamming and thereby caused breakage of the drill is a major concern for deep-hole drilling mostly by long-shaped chips. While a twist drill acts as an Archimedean screw, which supports besides the transport of the cutting fluid also the transport of the chips, the single-lip drill (SLD) has only a single straight flute for the chip evacuation. Therefore, the cutting-fluid flow and the chip shape have a major influence on the process reliability. In previous works, the transient process of chip evacuation for deep-hole drilling was modeled by a coupled SPH-DEM simulation. The cutting fluid was modeled by SPH, whereas the chips, the drill, and the borehole were modeled by DEM. However, the chips were assumed to be rigid, which showed to be a good starting point for the modeling of the cutting-fluid flow and the chip evacuation. In reality, the chips have a rather low stiffness due to their small thickness and are thereby highly flexible. For a first investigation of the chip jamming a virtual barrier is added, which is permeable for the fluid but blocks the chips from their further evacuation. Further, the deformation of the chips and the drill have to be included in the modeling for a better understanding of the process of chip jamming itself and the occurring forces. The aim of this contribution is to present some progress for modeling flexible bodies in the process of deep-hole drilling and their usage for the investigation of chip jamming and drill breakage.

A 3D-1D model for the simulation of plant-scale chemical reactors

Scipedia content — Tue, 15 Feb 2022 12:16:08 +0100

A 3D-1D model has been developed to simulate the methane dehydroaromatization (MDA) process in plant-scale catalytic reactors. The 3D part of the model consists of CFD-DEM coupled simulations of some relevant volume elements (RVEs), while the 1D part is a low-order model bridging the solution between the RVEs. The CFD-DEM model, implemented in the CFDEM®coupling software, uses an immerse boundary method to resolve: 1) the flow around the catalytic structures, 2) the heat exchange between solid and fluid, 3) the MDA reaction at the fluid-catalyst interface. The CFD-DEM solution is scaled-up by the 1D model to allow the simulation of industrial-scale processes at acceptable computational cost. The effect of design parameters (e.g., catalyst geometry) and operating conditions (e.g., reactor operating temperature) on the methane conversion rate and pressure drop can be investigated using the proposed model and the main results will be presented.

PFEM analysis of installation effects on axial performance of jacked piles in chalk

Scipedia content — Tue, 15 Feb 2022 12:15:53 +0100

Chalk is present in a large area of the East and South coast of the UK where renewables are now being installed. In most cases they are founded on displacement piles, whose design uses empirical methods or partial (wished-in-place) simulations. Installation effects such as grain crushing and pore pressure generation are conservatively estimated (if considered at all), as the change of chalk properties around the pile due to pile installation cannot be easily quantified. In this work it is shown how advanced numerical modelling can be used to guide the design of the foundations in these complex soils.

Micromechanical framework for a 3D solid cohesion model –implementation, validation and perspectives

Scipedia content — Tue, 15 Feb 2022 12:15:21 +0100

Natural soil deposits such as carbonate sands in the marine environment may show an effective cohesion due to intergranular solid bridges formed by calcareous precipitation. Such cementation effect endows the granular material with the ability to resist some degree of tensile stress in addition to the compressive and shearing resistance proper of uncemented frictional sands. tensile resistance of such materials may be quantified based on measures of debonding force at the micro-scale and using appropriate homogenization techniques. However, it is still a challenge to assess the influence of solid intergranular cohesion on the mechanical behaviour of soils in many practical engineering problems. Recent advances both in computational hardware and parallelization strategies make it nowadays possible to address such problems from a micromechanical perspective. Here we introduce a simple model for solid cohesion and its implementation within a 3D discrete element framework. The model involves a classical viscoelastic bond rheology and specific debonding modes for tensile, shearing, bending and torsional solicitations. We finally present a calibration of the model to match experimental data from an artificial granular soil made out of cemented glass beads and a validation of the approach with a macro-mechanical application.

Micellisation and aggregation of self-propelled hard circulangles.

Scipedia content — Tue, 15 Feb 2022 12:14:34 +0100

Self-organization in active materials, inspired by biological systems, shows many features, not found in passive materials. In order to explore the influence of shape asymmetry, a new 2D shape, named a circulangle, is introduced. Kinetic Monte Carlo simulations of two-dimensional hard Brownian circulangles are presented. Self-propulsion is introduced by additional MC moves along particles' axes. The system undergoes transition from homogeneously distributed particles to micellar structures arranged in clusters/networks. Circulangles appear to be the first known self-propelled particles, which form micelles without attractive forces. The newly discovered phenomenon may have wide implications in design of (meta)materials for energy conversion and storage, sensorics, micromechanics, targeted drug delivery, swarm intelligence, etc.

Various Mathematical Approaches to Mechanical Simulations in Wound Healing Processes

Scipedia content — Tue, 15 Feb 2022 11:07:12 +0100

Skin contraction during wound healing is mainly caused by fibroblasts (skin cells) and myofibroblasts (differentiated fibroblasts) that exert pulling forces on the surrounding extracellular matrix (ECM). Modelling is done in multiple scales: agent–based modelling on the microscale and continuum–based modelling on the macroscale. The momentum equilibrium equation is used to simulate this phenomenon in both models, with different expression of the cellular forces. In this manuscript, we managed to rigorously establish the link between the two modelling approaches for both closed–form solutions and finite–element approximations in one dimension.

The Impact of Al₂O₃ and Multi-Wall Carbon Nanotubes on the Morphology of Roller-Compacted Concrete

Yousef Zandi — Sat, 12 Feb 2022 18:53:04 +0100

Roller-compacted concrete (RCC) is a dry, zero-slump concrete prepared from the same ingredients as conventional cement but with a lower cement percentage. It is frequently compacted in the same way as dirt is. RCC is utilized chiefly to build massive structures such as dams and vast horizontal surfaces like highway foundations. Because of the low cement concentration, it slows the rise of temperature in mass concrete and decreases thermal strains. However, this paper analyzes the possibility of a chemical link forming between functionalized Multi-Wall Carbon Nanotubes and Nano-alpha Alumina in Roller-Compacted Concrete (RCC) structure using spectroscopic analysis. Various characterization methods, including X-ray diffraction patterns, Fourier-transform infrared (FT-IR) spectrometry, and scanning electron microscopy (SEM), were employed to analyze the nanocomposite's interaction. Based on X-ray diffraction pattern results, Multi-Wall Carbon Nanotubes (MWCNT) peaks show that the powder is amorphous, but it becomes crystalline when combined at high temperatures. The X-Ray diffraction (XRD) profile of the carbon nanotube-doped alumina sample reflects the leading share of Al₂O₃, with angles and diffraction plates of Al₂O₃ being the same as α- Al₂O₃ orthorhombic crystalline phase owing to the low carbon concentration. Besides, scanning electron microscope analysis revealed that α-Al2O3 powder samples without MWCNT and containing MWCNT have a shell state that the doped sample tends to be spherical.

The Impact of Al2O3 and Multi-Wall Carbon Nanotubes on the Morphology of Roller-Compacted Concrete

Yousef Zandi — Sat, 12 Feb 2022 15:48:26 +0100

LA RESTAURACIÓN DE LA TAPIA EN L A PENÍNSUL A IBÉRICA

José Manuel Torres-Carbonell — Tue, 08 Feb 2022 22:01:02 +0100

El libro «La restauración de la arquitectura de tapia en la Península Ibérica. Criterios, técnicas, resultados y perspectivas» constituye el resultado principal del proyecto de investigación homónimo concedido por el Ministerio de Ciencia e Innovación a un equipo compuesto por investigadores de diversas universidades españolas y extranjeras. El libro pretende ofrecer un panorama de la restauración de la arquitectura de tapia en la Península Ibérica a través de los caracteres constructivos de la tapia en este territorio, la restauración de esta arquitectura ordenada por áreas geográficas y un amplio abanico de ejemplos de edificios restaurados que permitan esclarecer los criterios y las técnicas empleados en la restauración de la arquitectura monumental de tapia en los últimos treinta años

Prony's method and matrix pencil method performance on determining the complex natural resonance frequencies of a linear system

Raul Barroso — Tue, 08 Feb 2022 04:12:12 +0100

Characterization of a physical system is an important issue to approach some applied physics and engineering problems. The complex natural resonance frequencies of the system which are included in its impulsive response are characteristic of such system and are part of its description. Few works written in English language show a comparisson among discrete methods that extract natural complex frequencies from a system impulsive response. Much less common is to find works written in Spanish language about this important research topic. Given this situation, important discrete numeric methods to estimate the complex natural resonance frecuencies of a system through its impulsive response are described, tested and compared in different simulation scenarios in this document. According to the obtained results, the matrix pencil method with a SVD filter is the less sensitive method to the noise, while the Prony method and its different versions are the fastest ones. Scenarios that could be more suitable for each method are discussed.

Research on dynamic characteristics of three-shafts ring-plate magnet gear

Dongning Liu — Mon, 07 Feb 2022 12:47:44 +0100

Stable transmission characteristics of reduction gear play an important role in the dynamic performance and structural reliability of reduction gear. To solve the problem of mechanical gear damage of three-ring reducer and improve the working environment of the rotating bearing of the inner ring in magnetic gear with small tooth difference, due to the bearing pressure is larger, a new structure of Three-Shafts Ring-Plate Magnet Gear (TRMG) is proposed by combining the transmission mode of cycloidal permanent magnet gear and ring-plate mechanical gear. Based on its motion mechanism and dynamic model, the balance equations of force and torque of TRMG components are established, and the forces act on the input shaft and support shafts are solved by combining electromagnetic FEM and mathematical analysis. The dynamic characteristics of TRMG are optimized by changing the dynamic input mode of TRMG. Finally, the feasibility of the proposed new transmission mode is verified by multi-body dynamics analysis.

Digging por restoration. The take of an archaeologist

José Manuel Torres-Carbonell — Sat, 05 Feb 2022 18:12:02 +0100

La Arqueología es la disciplina que estudia los restos materiales de pasado. Es una disciplina histórica tanto por el tipo de preguntas que plantea como por los medios que utiliza para responderlas. Es una ciencia en la medida en que aplica el método científico: se recurre a la observación, la inducción, la comparación, se generan hipótesis y se contrastan. Lo que da a la Arqueología contemporánea su carácter científico es el uso de un sistema de registro que identifica y describe no sólo los hallazgos, muebles o inmuebles, sino también los depósitos estratificados en los que se encuentran esos hallazgos. Esto permite datar unos y otros. Es lo que se conoce como “método arqueológico”, y de ahí la expresión “excavar con metodología arqueológica”.

Aquí nos interesan las actuaciones arqueológicas en las que las estructuras construidas, su devenir en el tiempo, constituyen el grueso de la evidencia a estudiar, con vistas a su restauración y puesta en valor. Se discutirá en qué consiste una excavación arqueológica, por qué forma parte esencial de cualquier intervención de restauración, y qué herramientas conceptuales puede aportar al proceso de conocimiento del objeto sobre el que se interviene.

Excavar para restaurar. Cómo piensa un arqueólogo.

José Manuel Torres-Carbonell — Sat, 05 Feb 2022 18:07:02 +0100

Study of dynamic simulators with ADAMS and Matlab/Simulink for control systems

Cesar Guzmán — Tue, 25 Jan 2022 21:41:04 +0100

ADAMS-MATLAB co-simulation is widely used in complex system development to control models of closed-loop mechanisms. An advantage of ADAMS is to facilitate the configuration of parameters such as friction. However, its mathematical friction model is unknown. There are alternatives such as Simscape Multibody that facilitate the configuration of any friction model. This paper presents a case study of dynamic simulation using the mathematical model of a mechanism in order to compare it with ADAMS and Simscape Multibody. The state-space model uses the parameters b and fc – viscous and Coulomb friction coefficients. However, ADAMS uses only one dynamic friction parameter µ. Since both friction parameters do not appear in ADAMS, a parametric identification procedure was used to determine the equivalency between the friction coefficients b and fc compared to µ. To identify the friction model of ADAMS, open-loop and closed-loop simulations were proposed. To compare the simulation results numerically, the L2 norm was used. The reference was the model solved with the ODE45 function.

Automotive Software Market To Generate $78,894.2 Million Revenue by 2030

Puneet Shah — Fri, 21 Jan 2022 11:19:36 +0100

Factors such as the burgeoning demand for connected cars, surging adoption of innovative technologies for advanced user interface, and rising research and development (R&D) activities in autonomous driving technology are expected to drive the automotive software market at a healthy CAGR, of 12.4%, during the forecast period (2020–2030). Additionally, the increasing demand for advanced automobiles will also catalyze the market growth in the forthcoming years. Owing to these factors, the market revenue will surge from $28,214.6 million in 2019 to $78,894.2 million by 2030.

The surging deployment of innovative technologies for advanced user interface is one of the major growth drivers for the market, worldwide. Various automobile manufacturers are increasingly integrating software into their offerings, as it has become essential to design automotive technologies that are more personal and human. For example, the Model S by Tesla Inc. is equipped with a few manual controls on or near the steering wheel and many automatic controls for secondary functions such as media player, rear-view mirror, cell phone, and climate control.

At present, the automotive software market is fragmented in nature, due to the presence of numerous players, such as SAP SE, Green Hills Software LLC, NVIDIA Corp., Ignite Ltd., Alphabet Inc., Continental AG, NORDSYS GmbH, NXP Semiconductors N.V., Connexion Telematics Ltd., Airbiquity Inc., Renesas Electronics Corp., CloudMade, Robert Bosch GmbH, Intellias Ltd., Harman International Industries Inc., and BlackBerry Ltd. In recent years, these companies have taken strategic measures, such as partnerships, to consolidate their position in the market.

According to P&S Intelligence, Asia-Pacific (APAC) accounted for the largest share in the automotive software market in 2019, due to the increase in purchasing power of customers, growth in economy, and presence of the largest automobile market, in the region. Moreover, the booming demand for advanced automobile features, owing to the economic development, will also drive the demand for automotive software in APAC. Additionally, the surging sales of electric vehicles in China, primarily on account of the growing environmental concerns, will also augment the regional market growth.

Thus, the increasing adoption of advanced technologies in vehicles and the surging need for OTA software updates will support the market growth in the forecast years.

Codification Model of Sports Tourism in Isfahan Based on Market Segmentation Approach

JOURNAL OF HUMAN SPORT & EXERCISE — Thu, 20 Jan 2022 19:49:02 +0100

This research is a survey study in terms of type and applied in terms of objective. Field method also was used to collect the data in this research. The research population included 100000 sports tourists and top managers of Isfahan Sport and Youth General Directorate, Isfahan Sport and Youth Department, Isfahan Cultural Heritage and Tourism Organization, Isfahan Sport Board Heads, Physical Education Department Professors, and Marketing and Tourism of Isfahan Azad and State Universities (n=81). Delphi technique was used to develop the questionnaire. In descriptive statistics section of this research, frequency, percentage, mean and standard deviation were used based on the questionnaire. In the inferential section, the exploratory factor analysis (EFA) and confirmatory factor analysis (CFA) methods were used to determine the importance and identification of the important factors in sports tourism based on sustainable development with a market segmentation approach from the viewpoint of the research subjects. The advanced method of factor analysis was used in multivariate analyses. Its main function is determining the weight or importance of factors. Moreover, multivariate analysis of variance (MANOVA) was used to evaluate the interactive effects of demographic characteristics. PLS method was also used to establish the relationship between dependent and independent variables. The model fit was also assessed. In order to provide a basis to compare the views of experts with those of sports tourists, questionnaires of these two groups were encoded separately and the collected data were presented using spss21 software.

Encapsulation Component and Its Incidence into Scientific Software Performance

Miguel Botto Tobar — Thu, 20 Jan 2022 14:55:02 +0100

Performance is considered an important feature rather than the application of programming techniques for better software design in most scientific software developers. Therefore, the problem arises if the software is developed without considering a specific paradigm or some programming technique when performing maintenance; tasks related to this activity are complicated, since almost no one would understand the source code. The goal of this research is to verify the performance of the software with or without an encapsulation component. An ex-post-facto experimental methodology has been implemented, carrying out a descriptive analysis of the data and then concluding by verifying the hypothesis by means of a robust test. This work was carried out by running algorithms written in the programming language Java by using three data groups in different conditions to analyze their behavior. Results show is that the application of the encapsulation component of the object-oriented paradigm does affect the execution of the scientific software performance.

Sorting Algorithms and Their Execution Times an Empirical Evaluation

Miguel Botto Tobar — Thu, 20 Jan 2022 14:52:02 +0100

One of the main topics in computer science is how to perform data classification without requiring plenty of resources and time. The sorting algorithms Quicksort, Mergesort, Timsort, Heapsort, Bubblesort, Insertion Sort, Selection Sort, Tree Sort, Shell Sort, Radix Sort, Counting Sort, are the most recognized and used. The existence of different sorting algorithm options led us to ask: What is the algorithm that us better execution times? Under this context, it was necessary to understand the various sorting algorithms in C and Python programming language to evaluate them and determine which one has the shortest execution time. We implement algorithms that help create four types of integer arrays (random, almost ordered, inverted, and few unique). We implement eleven classification algorithms to record each execution time, using different elements and iterations to verify the accuracy. We carry out the research using the integrated development environments Dev-C++ 5.11 and Sublime Text 3. The products allow us to identify different situations in which each algorithm shows better execution times.

Is stack overflow in portuguese attractive for brazilian users?

Miguel Botto Tobar — Thu, 20 Jan 2022 14:47:02 +0100

Stack Overflow (SO) is the reference for asking and answering programming-related questions. In early 2014 Stack Overflow em Português (SO-PT) was announced with the goal to reach developers that are not sufficiently proficient in the English language to fully participate in SO. Almost four years later we study how the simultaneous availability of SO and SO-PT impacted Brazilian software developers. A priori, the impact could have been either empowering or impeding. To address this question, we combine interviews, analysis of trace data from SO and SO-PT and a survey of 229 Brazilian software developers. Our results indicate that the developers recognize availability of the information, response speed and accessibility as strong points of SO, and lower barrier to entry and presence of Brazilian-specific information as strong points of SO-PT. In large, SO remains more popular than SO-PT, and SO-PT is not perceived as a viable alternative to SO. of barriers to SO participation Ford et al. [12] identified through interviews and survey such barriers as “Nothing Left to Answer' and “Fear of Negative Feedback'. Importance of English as a foreign language when training future software developers has been stressed by Bakanova [5]. She argued that English has influenced modern programming languages far beyond the choice of specific words as

Boletín de la Sociedad Mexicana de Computación Científica y sus Aplicaciones (2021)

Gerardo Tinoco-Guerrero — Wed, 05 Jan 2022 04:00:03 +0100

Progressive Collapse of Structures: A Robustness Interpretation of Intact Vs. Damaged Frames

Alessandro Calvi — Thu, 30 Dec 2021 13:08:12 +0100

This paper deals with the critical issue of structural collapses and introduce a novel interpretation of the concept of Structural Robustness applied to Intact and Damaged Frames in order to quantify the critical load multiplier in each case, by a simple set of mathematical equations.

Optimization of titanium cranial implant designs using generalized reduced gradient method, analysis of finite elements, and artificial neural networks

Carolina Hernández Navarro — Fri, 24 Dec 2021 07:47:04 +0100

When cranial bone needs to be removed or lost, subsequent reconstruction of the defect is necessary to protect the underlying brain, correct aesthetic deformities, or both. Cranioplasty surgical procedures are performed to correct the skull defects requiring reconstruction of form and function. Personalized cranial implants can repair severe injuries to the skull can be done through This study presents the optimization of cranial titanium implants. A total of sixty different models were subjected to a simulation by Finite Element Analysis (FEA) applying the mechanical properties of a grade 5 titanium alloy (Ti6Al4V) implant material. The material was subjected to intracranial pressure (ICP) conditions, with a typical range (10 mm Hg) and twelve fixation points in the boundary conditions. An artificial neural network (ANN) was created to connect the designs, obtaining maximum displacements. Optimal designs were obtained using a generalized reduced gradient that minimizes the amount of material, maintaining as a restriction a maximum displacement of 0.1 mm for the 5th to 95th percentiles, which represent the group of individuals under study.

Prediction of distant recurrence in breast cancer using a deep neural network

Saiful Izzuan Hussain — Thu, 23 Dec 2021 09:06:03 +0100

Breast cancer is the most common cancer diagnosed in women, and it is ranked as the second highest cancer with high mortality rate. Breast-cancer recurrence is the cancerous tumor that returned after treatment. Cancer treatments such as radiotherapy are performed mainly to kill cancer cells; however, some cells may have survived and multiply themselves at the same area as the original cancer (local recurrence) or to any other part (distant recurrence). Distant recurrence occurs when cancer cells spread to other parts of the body, most commonly to bone, breast, liver, and lungs. This study employed an Artificial Neural Network of the deep learning approach to predict distant recurrence of breast cancer. Factors that contribute to the risk of recurrence are age, type of surgery performed, tumor size, breast subtype, estrogen receptor, progesterone receptor, undergoing chemotherapy or not, and lymph node involvement. The actual value of distant recurrence is also considered to be a variable. Principal Component Analysis using five and three principal components was conducted. The outcome indicates that the model has accuracy of up to 0.80 using three principal components.

Fractal dimension measured over areas and perimeters using “Box Counting” technique applied over a Mandelbrot figure.

Cesar Acosta — Tue, 14 Dec 2021 18:40:11 +0100

Measuring fractal dimension in general is made over edges of a figure, however this kind of calculations could be made over a 1D, 2D or even a 3D images. With the FracLac plugin of ImageJ application, it has been possible to measure both dimensions, over the area and over the edge of a Mandelbrot fractal, using the Box Counting technique.

State estimation of electrical power systems based on optimal deployment of PMU considering contingencies

Diego Carrión — Wed, 01 Dec 2021 17:55:18 +0100

The present research proposes to design and apply a state estimator algorithm in electrical power systems, applying the Weighted Least Squares methodology, through a process called non-linear hybrid estimator, the same one that uses measurements from PMUs and conventional measurements. in addition, to find the optimal PMU locations respecting the observability and redundancy restrictions for the Electric Power Systems, through mixed integer linear programming, considering the N-1 contingencies in the SEP. The proposed state estimator is adjusted to the measurements obtained, in the presence of contingencies in the SEP. The simulations obtained as a result of the implementation of the hybrid state estimator show that the proposal improves the precision of the estimator and the speed of convergence, considering the minimum error of system measurements and the number of PMUs placed in the Power System, after a contingency occurs, which may be the departure of a PMU or the loss of one of the transmission lines of the SEP.

Environmental and economic impact of SF6 leakage on ENEL-CODENSA substations

Benjamin Mailhé — Tue, 30 Nov 2021 03:33:04 +0100

This paper analyzes data provided by ENEL-CODENSA with information about substation assets, including sulphur hexafluoride (SF_6) containing equipment and its top-up operations over the last ten years. The information has been used to estimate the total SF_6 mass in the current fleet and to determine historical emissions. The environmental and economic impacts are evaluated using the obtained results on simple models. Recommendations are made in order to mitigate the estimated impacts.

Integration of game theory and response surface method for robust parameter design

Sangmun Shin — Fri, 19 Nov 2021 10:18:05 +0100

The basic principle of robust parameter design (RPD) is to determine the optimal values of a set of controllable parameters that minimize the quality performance fluctuations caused by noise factors. The dual response surface method is one of the most widely applied approaches in RPD that tries to simultaneously minimize the deviation of the process mean from target and the process variance. However, there are situations when a compromise between the process mean and process variance is necessary, then the trade-off between them becomes an intractable problem. In order to solve the problem, we introduce a method that attempts to integrate the bargaining game theory concept into RPD to determine the optimal solutions. To verify the efficiency of our proposed method, the lexicographic weighted Tchebycheff method is applied to identify if the calculated solution is on the associated Pareto frontier. Two numerical examples show that our model works well in convex frontier cases. Lastly, several sensitivity analyses are conducted to examine the effect of the disagreement point value on the final solution.

Kinematic restriction method for tensegrity structures

Andrés González-Fallas — Fri, 12 Nov 2021 18:50:51 +0100

The use of tensegrity structures in robotics has been studied in recent years thanks to their properties of light weight, efficient distribution of forces and the possibility of applying control methods for the active shape reconfiguration, with crawling and rolling as examples. The structural composition of tensegrities, particularly the use of tensile elements, results in the presence of infinitesimal mechanisms. These affine motions have been considered for the development of control strategies that follow the manifold of stable positions described by these mechanisms. However, in robotic applications, the presence of rigid body motions can cause undesired effects, such as tensegrity structures flipping over. The form finding methods available in literature consider only the statics of tensegrities and most dynamic models work assume free-standing structures, while few consider fixed structures but do not deepen into the process of removing the rigid body motions. In this paper, the formulation of the equilibrium equations of tensegrity structures is reviewed, to describe the presence of the affine motions in the vector spaces of the equilibrium matrix. A simplified method for removing rigid body motions from the equilibrium equations is detailed, and the effect on the set of affine motions is explained. To verify the validity of this process, two numerical examples are given, including a single unit and a two stage tensegrity structures.

Experimental characterization and two-dimensional hydraulic-hydrologic modelling of the infiltration process through permeable pavements

Marcos Sanz-Ramos — Wed, 10 Nov 2021 18:49:05 +0100

Permeable pavements are a common solution for wearing course layers in roads and urban areas. They are composed by highly porous materials with permeability several orders of magnitude above of the natural terrain. This work presents, on one hand, the experimental characterisation of the hydraulic behaviour of a permeable asphalt concrete wearing course layer and, on the other hand, the development and validation of a two-dimensional coupled hydraulic-hydrological distributed numerical model to reproduce the effect of the infiltration in the rainfall-runoff transformation and in the overland flow propagation processes. Experiments show linear and potential trends for permeability-hydraulic head relations when considering constant and variable hydraulic heads, respectively, reaching permeability up to 0.04 m/s for 1 m of hydraulic head. Experiments are reproduced numerically by incorporating new infiltration formulas, which consider the infiltration rate as a function of the hydraulic head, and a specific numerical scheme for properly dealing the mass conservation when negative values of the water depth may occur numerically due to high infiltration rates. This two-dimensional coupled hydraulic-hydrological distributed numerical model is a validated tool for simulating the effect of permeable pavements not only in the rainfall-runoff process, but also for the overland flow propagation.

Consolidation of soil induced by pile installation considering disturbance effect

Li, Ping — Thu, 04 Nov 2021 02:53:17 +0100

In practice, the consolidation of soil around the pile has a great influence on the time-dependent bearing capacity of pile. However, most of the consolidation theory of soil around the pile neglects the disturbance effect of pile-driving on surrounding soil and regards the soil as homogeneous, which overestimates the consolidation efficiency of the soil, and obtains a higher pile bearing capacity. In view of this, a consolidation model of soil around a pipe pile considering soil disturbance effect is presented in this paper. Fourier transform and separation of variables are used to obtain the analytical solution, and then the solution is verified by degradation analysis and Finite Difference Method (FDM). Firstly, the radial and vertical distribution of excess pore pressure generated after pile-driving is analyzed. In the radial direction, the excess pore pressure decreases rapidly from the radius of pipe pile to the radius of the disturbed zone, then slowly decays to 0 from the radius of disturbed zone to the influencing radius of pipe pile. In the vertical direction, the excess pore pressure along the vertical direction grows linearly. Subsequently, the variation of the average excess pore pressure at the pile-soil interface with the permeability coefficient and radius of disturbance zone are analyzed. The permeability coefficient of disturbance zone has a remarkable negative effect on the excess pore pressure during the whole consolidation period. Increasing the radius of the disturbance zone will hinder the dissipation of the excess pore pressure in the intermediate and later stages. Finally, the validity of the proposed analytical solution is illustrated by comparing with the laboratory results.

A TSP-based nested clustering approach to solve multi-depot heterogeneous fleet routing problem

Morteza Mollajafari — Sat, 16 Oct 2021 16:47:04 +0200

The distribution of goods and urban services has made the issue of vehicle routing of particular importance to researchers. Advanced Routing Vehicle (RVRP) Rich Vehicle Routing Problem As a hybrid optimization problem, it is widely used in many transportation and logistics planning. The approach of this paper is to present a heuristic method for solving the problem called Nested Clustering for Traveling Salesman Problem (NC-TSP), in this method to optimize the search space, we break the problem in consecutive space. In the first step, using the nearest neighbor (Knn) algorithm with the center of each depot, and then using the fuzzy C-means clustering method within each cluster obtained from the Knn method, to find the optimal set of nodes. Then we solve the problem using the extension of MILP linear functions to the heterogeneous nature of the transport fleet and the warehouses that supply the goods, using the optimization algorithm (GA). The proposed approach, despite its great complexity, solves the problem to a large extent and shows promising cost-effective results in the existing criteria.

A method for the robustness evaluation of cable-stayed bridges with steel truss girders under different reinforcement cases

Xiaobo Zheng — Sat, 16 Oct 2021 03:35:26 +0200

Structural robustness, an index for structural geometrical agreement, is used to assess the alternative load paths of structures subjected to loads. Therefore, robustness can be extended to evaluate the robustness of bridges with local failure in individual members. In this work, a method that includes the use of a radar chart is proposed to assess the robustness of cable-stayed bridges by considering the mechanical performance of bridges with local failure in the cables and chords. Four plans regarding the truss girder and cables are designed to reinforce a damaged bridge. The results indicate that these two alternative path plans disperse the stress in the members in the truss girder, and the reduction of alternative path plan 2 (AP2) is greater than that of alternative path plan 1 (AP1). Similarly, the two plans regarding the cables are found to decrease the vertical displacement of the truss girder under gravity, and the reduction of the first plan is slightly greater than that of the second plan. Consequently, the two alternative load path plans improve the indexes of the truss girder, leading to an increase in the value of ''I_Rob'' to 0.74. Moreover, regarding the truss girder, the two alternative cable plans are used to increase the indexes, and the values are all found to be larger than the corresponding values of the intact cable-stayed bridge. The proposed method including the use of a radar chart, which is associated with several indexes, can be used to assess the structural robustness of intact and damaged bridges, thereby allowing for the development of reinforcement plans.

Development of a video game for teaching in an electrical machine laboratory

Sergio Rivera — Thu, 07 Oct 2021 04:14:02 +0200

Nowadays, the world has focused on digital media. There have been voices for and against virtual education. Gamification has been described as a strategy to transmit knowledge through the design and use of games. This article describes the first phase of the development of a game aimed at the transmission of knowledge related to engineers dedicated to the commercialization, diagnosis, and repair of induction motors; these are electrical machines widely used in industry. In this way, this paper shows the Electric Motor Store Simulator (hereinafter STME for its acronym in Spanish) is a free software project that aims to develop a game for users to have a closer idea about small businesses. It was developed as a minimum viable product under free software licensing, which allows anyone with the necessary knowledge to expand the functionality by adding or improving modules.

Design parameters of dental implants: A review

Milad Heidari — Fri, 24 Sep 2021 22:29:05 +0200

An ideal dental implant is a design that maximizes the anchorage strength of implants in human jawbones and minimizes peak stress values in bone-implant interfaces under given standard loads. The stress concentration at the bone-implant contact is controlled by implant design, which determines the bone biological response. Implant design has improved as a result of marketing demands. The modification of shape, size, material, and surface topography of primary designs has been the focus of dental implant design in response to marketing needs. Since the integration of bone-implant has been highlighted in dentistry investigations, improving implant design depends on the prediction of mechanical reactions and remodeling response of bony tissues around implants. There are four types of implants design including Screws, cylinders, Conical cylinders, and Blades type implants. The major difference between these designs is in implant primary stability. With the development of computational technologies, researchers can predict long term oral bone remodeling around implants by use of the finite element method. This review considers the design parameters of dental implants in which affect stress, strain in bone-implant interfaces, and bone remodeling around the implant.

Structural analysis of a railway bridge using the FEM-DEM technique

Francisco Zarate — Wed, 22 Sep 2021 11:18:09 +0200

The objectives of this work are focused on giving an answer to the problems presented in the operation of a railway bridge, using the FEM-DEM numerical technique considering static and dynamic loads. The purpose is to find out the existing breakage mechanisms in the bridge.

From a social aspect, there is concern about the possible collapse of the bridge, with the corresponding economic loss and eventually human losses; therefore, the interest and social involvement of the study has repercussions not only on the repair mechanisms that can be adopted but also on the possible revision of the calculation and design aspects in this type of works.

The FEM-DEM technique developed by Zárate et al. [1,2] has been validated in various laboratory tests [3-5]. Due to the characteristics of the problem, the technique used is an ideal tool to study the structural behaviour of the bridge from a static and dynamic point of view. Considering the reinforcing steel in the bridge is fundamental to carry out the structural analysis, which is why the implementation of this type of reinforcement in the FEM-DEM formulation is described.

The paper is organized as follows. First, the problems found in the civil works under study are described. Subsequently, a small sketch of the FEM-DEM technique is made, and the inclusion of reinforcing steel is formulated. After that, the different results of the static and dynamic studies carried out are presented.

Numerical solution of diffusion equation using a method of lines and generalized finite differences

Gerardo Tinoco-Guerrero — Sat, 18 Sep 2021 20:59:17 +0200

One of the greatest challenges in the area of applied mathematics continues to be the design of numerical methods capable of approximating the solution of partial differential equations quickly and accurately. One of the most important equations, due to the hydraulic and transport applications it has, and the large number of difficulties that it usually presents when solving it numerically is the Diffusion Equation.

In the present work, a Method of Lines applied to the numerical solution of the said equation in irregular regions is presented using a scheme of Generalized Finite Differences. The second-order finite difference method uses a central node and 8 neighbor points in order to address the spatial approximation. A series of tests and numerical results are presented, which show the accuracy of the proposed method.

Effects of fly ash, slag pozzolans, and polycarboxylate on mechanical properties of concretes and economical evaluation

Yousef Zandi — Fri, 10 Sep 2021 07:22:04 +0200

In this research, steel furnace slag, fly ash and new synthesized polycarboxylate was used to replace cement in concrete composition. Concrete was made in three grades of 400, 450 and 500 using steel furnace slag, fly ash and polymer with different percentages of dry weight. Also, the amount of water to cement was selected as one of the effective parameters in concrete strength and production costs. The results showed that slag percent had a positive effect on improving samples strength. Also, increasing the percentage of polycarboxylate and decreasing the amount of water per cement ratio increased the strength of concretes. Finally, by examining the effect of several parameters on the strength of concrete, an economic evaluation was performed to manage the cost of increasing the strength of concrete. The results also indicated that with increasing percentage of resistance, the amount of costs increased in all three grades ; 400, 450 and 500.

Numerical simulation of erosion wear and leakage flow field of gas-solid two-phase flow in a T-shaped pipeline

Hongwei Yan — Thu, 05 Aug 2021 08:36:15 +0200

In the process of natural gas transportation in pipeline, because the natural gas contains mud and sand, the pipeline will undergo erosion wear under the impact of gas-solid two-phase flow. Erosion wear seriously reduces the performance of the inner wall of the pipeline, which is not conducive to the stability of the conveying process and the safe operation of the equipment. Among them, the erosion wear of special pipe fittings such as tee pipe and bend pipe are especially serious. In this paper, the erosion of natural gas T-shaped tee pipeline is simulated by FLUENT software, and the erosion wear and fluid-solid coupling analysis are completed. The erosion characteristics of gas-solid two-phase flow under different fluid velocities, different mass flow rates and different particle diameters are studied, and the maximum erosion rates and corresponding variation trends under different influencing factors are obtained. The flow field characteristics of T-shaped pipeline were analyzed based on the small hole leakage model. The characteristics of the leakage flow field were studied from the three aspects of the pressure inside the pipe, the area of the leakage orifice and the shape of the leakage orifice. The experimental platform was built, and the simulation and experimental results were compared and analyzed to verify the correctness of the established model and CFD simulation.

Analysis and influence of rainfall infiltration of ancient city wall based on in-situ monitoring: A case study of The XingChun gate Lishui Prefecture

Jun Shao — Sat, 31 Jul 2021 06:38:02 +0200

Rainfall infiltration is an important factor affecting the stability of the ancient city wall.To state the wall line spring door where, for example, soil temperature and humidity sensor, the earth pressure meter and rain gauge carried out such as rainfall, volume moisture content and soil pressure monitoring, analyzed the inner core wall soil volume moisture content and soil pressure response law of rainfall different rainfall conditions is studied through numerical simulation method the stability of the ancient city wall.The results show that :(1) rainfall has a significant effect on the volume moisture content and earth pressure of the inner core soil;(2) The response to rainfall is different at different depths of the city wall, and the response to rainfall in the middle part of the city wall has a certain hysteresis.(3) Compared with the low-intensity and long-duration rainfall, the high-intensity and short-duration rainfall has a greater impact on the stability of the city wall.The research results have certain guiding significance for the protection and monitoring of the ancient city wall.

Estilos de aprendizaje y rendimiento académico en Matemática Superior

Marvin Coto — Fri, 21 May 2021 21:11:03 +0200

Los estilos de aprendizaje han sido estudiados ampliamente en diversas partes del mundo para reconocer las diferencias que se presentan entre estudiantes para adquirir el conocimiento. Estos estilos pueden medirse con instrumentos establecidos, y sus resultados permiten caracterizar poblaciones de estudiantes, y dirigir las estrategias de enseñanza afines a estos estilos. En el presente artículo se muestra la influencia que ha tenido la presencia de diferentes estilos de aprendizaje en una población de estudiantes de educación superior, en la carrera de Ingeniería Eléctrica de la Universidad de Costa Rica. Los estilos han sido medidos utilizando el test de Felder-Silverman, en grupos del curso Matemática Superior durante tres ciclos semestrales, y muestran correlación en el rendimiento de estudiantes y diversas preferencias en los estilos.

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Efficiency assessment of the complex process of variable cutting parameters

Diamond20210 — Fri, 30 Apr 2021 11:27:23 +0200

Saving energy and low carbon strategy has becoming the future trend of manufacturing industry. Cutting process in mechanical manufacturing has the characteristics of heavy energy consumption and complex process. The estimation and evaluation of energy consumption and energy efficiency of cutting process are hot topics in research groups and industry. The energy consumption of cutting process is determined by the load, which is related to the cutting parameters under fixed cutting systems, while the cutting parameter might change with the cutting process and material. Based on the relationship between energy consumption and cutting characteristics and the quality requirements, the cutting specific energy u(t) = P(t)/M(t), which is varies with time is proposed to evaluate the energy consumption of various cutting parameters under complex machining processes. The influence of cutting parameters on cutting energy consumption is studied by experiments and a calculation method is proposed to calculate cutting energy consumption. Finally, a case study of complex curve machining in mold manufacturing is illustrated to prove the effectiveness of the proposed evaluation method.

Investigation and numerical analysis of steel beams strengthened with CFRP

heydar dashti naserabadi — Sun, 18 Apr 2021 23:34:03 +0200

One of the most common methods of strengthening concrete structures is the use of composite fibers such as FRP. These fibers have found a special place in structural retrofitting methods due to a number of specific ability including lightness and ease of performance. Reinforced concrete structures have long been considered by design engineers for the possibility of retrofitting high strength composite steel structures. In this study, twenty-two steel beam models were modeled by ANSYS software. Variable parameters studied in the modeled steel beams can be referred to the number, orientation and thickness of composite layers.

A complexity task of optimization in logistic distribution: A new approach to the green multi-objective vehicle routing problem

Júlio César Ferreira — Sat, 17 Apr 2021 03:11:03 +0200

Logistic distribution involves many costs for organizations. Therefore, opportunities for optimization in this respect are always welcome. The purpose of this work is to present a methodology to provide a solution to a complexity task of optimization in Multi-objective Optimization for Green Vehicle Routing Problem (MOOGVRP) applied to a transport passenger’s problem. For that, it was considered two objective functions (environmental issues and also balancing work between the routes) ensuring savings and satisfaction for the users. The methodology, was divided into three stages: Stage 1, “data treatment”, where the asymmetry of the routes to be formed and other particular features were addressed; Stage 2, “metaheuristic approaches” (hybrid or non-hybrid), used comparatively, more specifically: NSGA-II (Non-dominated Sorting Genetic Algorithm II), MOPSO (Multi-Objective Particle Swarm Optimization), which were compared with the new approaches proposed by the authors, CWNSGA-II (Clarke and Wright’s Savings with the Non-dominated Sorting Genetic Algorithm II) and CWTSNSGA-II (Clarke and Wright’s Savings, Tabu Search and Non-dominated Sorting Genetic Algorithm II); and, finally, Stage 3, “analysis of the results”, with a comparison of the algorithms. Using the same parameters as the current solution, an optimization of 5.2% was achieved for Objective Function 1 (OF1; minimization of CO2 emissions) and 11.4% with regard to Objective Function 2 (OF2; minimization of the difference in demand), with the proposed CWNSGA-II algorithm showing superiority over the others for the approached problem. Furthermore, a complementary scenario was tested, meeting the constraints required by the company concerning time limitation. For the instances from the literature, the CWNSGA-II and CWTSNSGA-II algorithms achieved superior results.

Multi-index cutting parameters optimization for surface quality and cutting energy consumption of boring

2021Diamond — Mon, 22 Feb 2021 04:25:25 +0100

Saving energy is one of the ways to achieve sustainable development. As an important equipment for manufacturing, machine tool has the characteristics of high energy consumption and high emission. In order to cope with reducing energy consumption and carbon emissions without reducing processing quality, the search for optimal cutting parameters requires balancing the contradiction between machining quality and cutting energy consumption, so that cutting parameters can both reduce energy consumption and ensure the quality of processing. It plays an important role in achieving energy saving and emission reduction. In this paper, the processing quality (residual stress, surface roughness) and cutting energy consumption are selected as the optimized multiple indicators, and the selected optimization indicators are analyzed. Weighted grey correlation analysis is used to obtain the multi-index gray correlation degree value, and the multi-index weight coefficient is determined. Based on weighted grey correlation analysis and multi-index orthogonal optimization method, the cutting parameters of the boring process are optimized, and the optimal parameter combination is that cutting depth of 0.05 mm, cutting speed of 120 m/min, and feed rate of 80 mm/min.

Design of fast and zero voltage switching of interleaved flyback converter with H6 type inverter for photovoltaic applications

Arulmozhiyal R — Sat, 05 Dec 2020 17:37:04 +0100

In this paper, a design of interleaved flyback converter with H6 inverter topology is proposed. Flyback converter is one among the DC-DC converter with high frequency which is used or low power applications. Because of high frequency operation switching losses and stresses are more. To reduce stresses and losses across the switch of interleaved flyback converter is proposed. In the grid tied inverter system leakage current is one of the disadvantages and to avoid this H6 type inverter is used.With this advantage of H6 inverter andflyback converter this paper is mainly focused on stresses across switches and eliminating leakage current, harmonic reduction. Further the fast switching is proposed within converter in order to deliver maximum power transfer delivered to load through grid. To validate the overall performance the proposed converter modeled in MATLAN-SIMULINK and prototype developed using DSP DSP TMS320F28377S and connected to grid connected load.

Employing fuzzy logic for debris management after earthquakes. Case study: Khorramabad city

Mahmoud Rahimi — Mon, 28 Sep 2020 08:54:02 +0200

Debris treatment after earthquakes is very important matter especially after large-scale disasters. Efficient debris treatment is leading to faster reconstruction. Particularly, this article examines fuzziness in debris treatment planning. The problem reduces to a standard transport problem by fundamental formulation. A fuzzy debris transport problem for supply and demand formulated fuzzy constraints. A problem-solving algorithm by referring numerical example demonstrates an irrelevant approach. Realistic debris transport planning can be defined by using the recommended method.