Documents published in Scipedia

• PROPOSAL TO STRENGTHEN EDUCATIONAL BUILDING ANCIENT II-MOP TYPE. VENEZUELA

  J. Yépez, M. Dikdan, L. Andrade, R. Rojas

  Example of a collection (2017).

  
  

  Abstract

  This article presents the study of structural reinforcement for a building of educational use, known as "Old Type II". The school was built before the creation of the Venezuelan SeismoresistantCovenin 1756. The results of the structural analysis showed insufficient responsiveness to service requests, high vulnerability to seismic action and deficiencies in the quantity and distribution of reinforcing steel. For this reason, the reinforcement of the superstructure was proposed by the construction of panel walls, verifying their action on the existing piloting system. For the modeling, the values of resistance of the concrete obtained in the destructive tests made by the materials laboratory of the School of Civil Engineering of the Universidad Centroccidental Lisandro Alvarado and the soil parameters from the geotechnical study were used.

  Abstract
  This article presents the study of structural reinforcement for a building of educational use, known as "Old Type II". The school was built before the creation of the Venezuelan [...]

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• IMPLEMENTATION OF VIRTUAL CONSTRUCTION TO IMPROVE THE PLANNING OF WORKS. USE OF 4D MODEL IN URBANISM LOCATED IN VALENCIA, VENEZUELA

  Z. Giménez, R. Gutiérrez, G. Hernández

  Example of a collection (2017).

  
  

  Abstract

  The construction industry is considered as one of the industries with lower yields, frequent delays and reprogramming. Due to this and to avoid losses of time, costs and inconveniences in the execution, the virtual construction is used, that allows to analyze previously the constructive sequences and the possible interferences between the different activities through a real time scenary according to the programmed schedule . This article shows the implementation of BIM technology in a modular housing development in Venezuela. Four 4D simulations were carried out, two initially due to the original planning and its timely improvement, and two subsequent corresponding to reprogramming due to actual delays in execution due to lack of concrete supply. The main results were: problems of programming logic, interferences between activities, unreal sequences, among others in the first models. As for the models of the reprogramming gave resulting times very similar to reality; This means that the models work both in ideal situations and in situations of uncertainty. Building information modeling solutions introduce a new way of working, based on the creation and use of coherent and coordinated information, wich allows for faster decision making, better documentation and the possibility of predicting the drawbacks Even before the work began.

  Abstract
  The construction industry is considered as one of the industries with lower yields, frequent delays and reprogramming. Due to this and to avoid losses of time, costs and inconveniences [...]

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• MODELO DE FUERZAS INTERATÓMICAS PARA EL GRAFENO A PARTIR DEL POTENCIAL AIREBO

  M. Ariza, C. Ventura, M. Ortiz

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  Dado que las propiedades eléctricas y térmicas del grafeno están influenciadas por la presencia de defectos topológicos en el material y que éstos condicionan así las futuras aplicaciones del grafeno como material base de componentes nanoelectrónicos, es necesario disponer de un modelo de comportamiento del grafeno que permita incluir dichos defectos. En este trabajo se ha obtenido un modelo de fuerzas interatómicas a partir del potencial AIREBO (Adaptive Intermolecular Reactive Empirical Bond-Order), desarrollado por Stuart et al. [1], que incluye interacciones atómicas hasta vecinos de orden cuarto. Se presentan, tanto expresiones explícitas de las derivadas del potencial, como los valores de las constantes de fuerza. Hemos verificado que el modelo de fuerzas cumple con las simetrías del cristal y las curvas de dispersión de fonones del correspondiente modelo dinámico presentan un buen acuerdo con las obtenidas por otros autores. Además, hemos verificado que las interacciones con vecinos terceros y cuartos no modifican, ni la estructura del campo de desplazamientos alrededor de los núcleos de dislcocación, ni sus correspondientes energías de formación que se predicen a partir de la teoría discreta de dislocaciones de Ariza y Ortiz [2]. Summary In view of the influence that topological defects have on the thermal and electrical properties of graphene, and given the pivotal role that such properties play in potential applications of graphene as a building block for nano-electronic components, models of graphene behavior that allow for the consideration of such defects are of the essence. In the present work, we have obtained an atomic force-constant model from the AIREBO potential (Adaptive Intermolecular Reactive Empirical Bond-Order), of Stuart et al. [1], that accounts for interatomic interactions up to fourth neighbors. We present explicit expressions of the potential derivatives as well as the force-constant values. We have verified that the force-constant model is invariant under the crystal symmetries and that the phonondispersion curves of the corresponding dynamic model are in good agreement with those obtained by other authors. In addition, we have verified that the thirdand fourth-neighbor interactions affect neither the displacement field in the vicinity of dislocation cores nor the corresponding formation energies predicted by the theory of discrete dislocations of Ariza and Ortiz [2].

  Abstract
  Dado que las propiedades eléctricas y térmicas del grafeno están influenciadas por la presencia de defectos topológicos en el material y que éstos condicionan así las [...]

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• PUMI: UN CÓDIGO EXPLÍCITO NO ESTRUCTURADO PARA RESOLVER LAS ECUACIONES DE EULER

  R. Flores, E. Ortega, E. Oñate

  Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (2017). Vol. 33, (1)

  
  

  Abstract

  El código PUMI se ha desarrollado en CIMNE para resolver rápidamente problemas de flujo compresible alrededor de geometrías complejas. En la actualidad se llevan a cabo de manera rutinaria cálculos con mallas que contienen decenas de millones de elementos. PUMI fue diseñado específicamente para tratar problemas de esta escala usando hardware modesto; por tanto la eficiencia del código ha sido uno de los objetivos fundamentales durante su diseño. Se buscó una utilización mínima de memoria, excelente comportamiento en entornos de ejecución secuencial y escalado satisfactorio hasta un número moderado de procesos (para su uso eficiente en estaciones de trabajo multiprocesador). Para facilitar en lo posible las tareas de generación de mallas se eligió una formulación no estucturada basada en elementos finitos. El presente artículo describe los fundamentos teóricos del algoritmo así como detalles de implementación que mejoran la robustez y eficiencia del código. Summary The PUMI flow solver has been developed at CIMNE in order to address the need for fast solutions of the flow field around complex geometries. Nowadays calculations involving a number of cells on the order of tens of millions are performed routinely. PUMI was created to deal with this kind of large-scale problem using modest hardware, therefore special emphasis was placed on the computational efficiency of the code. Design guidelines where minimum memory requirement, very fast single-threaded performance as well as satisfactory parallel scaling up to a moderate number of threads (as found on current entry-level SMP workstations). In order to simplify the mesh generation activities an unstructured finite element formulation was selected. This paper describes the theoretical basis of the algorithm as well as details of the implementation that increase the robustness and efficiency of the code.

  Abstract
  El código PUMI se ha desarrollado en CIMNE para resolver rápidamente problemas de flujo compresible alrededor de geometrías complejas. En la actualidad se llevan a cabo [...]

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• Left atrial geometry and pump function in ischemic cardiomyopathy

  M. Abdelzaher, W. Atteia

  Collection of IJC Heart & Vasculature (2017).

  
  

  Abstract

  Many of the factors that are known to alter left atrial (LA) contractility are present in patients with ischemic cardiomyopathy (ICM). Nevertheless, preservation of LA contractile function in this group of patients was reported in previous studies. The aim of this study was to assess the changes in LA size, geometry and contractile function in ICM. 60 subjects (age: 49 ± 12 years, 53% males) in sinus rhythm undergoing coronary angiography (CA), were enrolled in this study, 15 subjects as a control group, 30 patients with reduced ejection fraction (EF) and significant coronary artery disease, as the ICM group, and 15 with reduced EF and normal CA, as the dilated cardiomyopathy (DCM) group. LA dimensions, volume, active emptying fraction (ACTEF) and eccentricity index (LAEi) as well as late diastolic velocities of the mitral annulus (a′) and LA free wall (A3) were measured. Compared with the control group, ICM patients had larger LA volume and reduced ACTEF, a′ and A3, with no significant difference between patients with ICM and DCM in any of these parameters. LA eccentricity was, non-significantly, higher in both cardiomyopathy groups than in the control group. Patients with ICM have increased LA volume and reduced LA contractile function in comparison with normal controls. LA enlargement, LA contractile dysfunction and LA geometric changes in ICM are similar to that occurring in DCM. LA size, contractile function and eccentricity may not be reliable in differentiating ischemic from idiopathic dilated cardiomyopathy.

  Abstract
  Many of the factors that are known to alter left atrial (LA) contractility are present in patients with ischemic cardiomyopathy (ICM). Nevertheless, preservation of LA contractile [...]

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• Altered global gene expression profiles in human gastrointestinal epithelial Caco2 cells exposed to nanosilver

  S. Sahu

  Example of a collection (2017).

  
  

  Abstract

  Extensive consumer exposure to food- and cosmetics-related consumer products containing nanosilver is of public safety concern. Therefore, there is a need for suitable in vitro models and sensitive predictive rapid screening methods to assess their toxicity. Toxicogenomic profile showing subtle changes in gene expressions following nanosilver exposure is a sensitive toxicological endpoint for this purpose. We evaluated the Caco2 cells and global gene expression profiles as tools for predictive rapid toxicity screening of nanosilver. We evaluated and compared the gene expression profiles of Caco-2 cells exposed to 20 nm and 50 nm nanosilver at a concentration 2.5 μg/ml. The global gene expression analysis of Caco2 cells exposed to 20 nm nanosilver showed that a total of 93 genes were altered at 4 h exposure, out of which 90 genes were up-regulated and 3 genes were down-regulated. The 24 h exposure of 20 nm silver altered 15 genes in Caco2 cells, out of which 14 were up-regulated and one was down-regulated. The most pronounced changes in gene expression were detected at 4 h. The greater size (50 nm) nanosilver at 4 h exposure altered more genes by more different pathways than the smaller (20 nm) one. Metallothioneins and heat shock proteins were highly up-regulated as a result of exposure to both the nanosilvers. The cellular pathways affected by the nanosilver exposure is likely to lead to increased toxicity. The results of our study presented here suggest that the toxicogenomic characterization of Caco2 cells is a valuable in vitro tool for assessing toxicity of nanomaterials such as nanosilver.

  Abstract
  Extensive consumer exposure to food- and cosmetics-related consumer products containing nanosilver is of public safety concern. Therefore, there is a need for suitable in [...]

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• Chemically reacting micropolar fluid flow and heat transfer between expanding or contracting walls with ion slip, Soret and Dufour effects

  O. Ojjela, N. Kumar

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The aim of the present study is to investigate the Hall and ion slip currents on an incompressible free convective flow, heat and mass transfer of a micropolar fluid in a porous medium between expanding or contracting walls with chemical reaction, Soret and Dufour effects. Assume that the walls are moving with a time dependent rate of the distance and the fluid is injecting or sucking with an absolute velocity. The walls are maintained at constant but different temperatures and concentrations. The governing partial differential equations are reduced into nonlinear ordinary differential equations by similarity transformations and then the resultant equations are solved numerically by quasilinearization technique. The results are analyzed for velocity components, microrotation, temperature and concentration with respect to different fluid and geometric parameters and presented in the form of graphs. It is noticed that with the increase in chemical reaction, Hall and ion slip parameters the temperature of the fluid is enhanced whereas the concentration is decreased. Also for the Newtonian fluid, the numerical values of axial velocity are compared with the existing literature and are found to be in good agreement.

  Abstract
  The aim of the present study is to investigate the Hall and ion slip currents on an incompressible free convective flow, heat and mass transfer of a micropolar fluid in a [...]

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• MHD flow over a permeable stretching/shrinking sheet of a nanofluid with suction/injection

  S. Naramgari, C. Sulochana

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  In this study we analyzed the influence of thermal radiation and chemical reaction on two dimensional steady magnetohydrodynamic flow of a nanofluid past a permeable stretching/shrinking sheet in the presence of suction/injection. We considered nanofluid volume fraction on the boundary is submissive controlled, which makes the present study entirely different from earlier studies and physically more realistic. The equations governing the flow are solved numerically. Effects of non-dimensional governing parameters on velocity, temperature and concentration profiles are discussed and presented through graphs. Also, coefficient of skin friction and local Nusselt number is investigated for stretching/shrinking and suction/injection cases separately and presented through tables. Comparisons with existed results are presented. Present results have an excellent agreement with the existed studies under some special assumptions. Results indicate that the enhancement in Brownian motion and thermophoresis parameters depreciates the nanoparticle concentration and increases the mass transfer rate. Dual solutions exist only for certain range of stretching/shrinking and suction/injection parameters.

  Abstract
  In this study we analyzed the influence of thermal radiation and chemical reaction on two dimensional steady magnetohydrodynamic flow of a nanofluid past a permeable stretching/shrinking [...]

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• CFD investigations of data centers’ thermal performance for different configurations of CRACs units and aisles separation

  S. Nada, M. Said, M. Rady

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The thermal performance of data centers is numerically studied for different configurations of computer room air conditioning (CRAC) units and physical separations of cold and hot aisles. Temperature distribution, air flow characteristics and thermal management of data centers racks array are predicted and evaluated for the different arrangements. Measureable performance indices: supply/return heat index (SHI/RHI), return temperature index (RTI) and return cooling index (RCI) are used to measure the thermal management effectiveness of data center racks. The results showed that: (i) hot air recirculation, cold air bypass and the measurable performance indices of the racks strongly depend on the racks location in the racks array, (ii) the CRACs units layout affects the thermal managements of the racks array especially the sides and middle racks in the array, and (iii) using cold aisle containments enhances the thermal performance of the data center.

  Abstract
  The thermal performance of data centers is numerically studied for different configurations of computer room air conditioning (CRAC) units and physical separations of cold [...]

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• Subdivision depth for triangular surfaces

  G. Mustafa, M. Hashmi, F. Khan

  Collection of Alexandria Engineering Journal (2017).

  
  

  Abstract

  The aim of this attempt was to present an efficient algorithm for the evaluation of error bound of triangular subdivision surfaces. The error estimation technique is based on first order difference and this process is independent of parametrization. This technique can be easily generalized to higher arity triangular surfaces. The estimated error bound is expressed in-terms of initial control point sequence and constants. Here, we efficiently estimate error bound between triangular surface and its control polygon after k-fold subdivision and further extended to evaluate subdivision depth of the scheme.

  Abstract
  The aim of this attempt was to present an efficient algorithm for the evaluation of error bound of triangular subdivision surfaces. The error estimation technique is based [...]

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