Modelamiento y simulación de un intercambiador de calor

El presente tema de intercambiador de calor está enfocado en el modelamiento matemático y la simulación en diferentes softwares, partiendo de una breve introducción de conceptos afines al intercambiador de calor, luego serán analizadas las ecuaciones que modelan al sistema dinámico de nuestro intercambiador de calor, que para mayor satisfacción serán resueltas y analizadas. Analizaremos la ecuación diferencial de primer orden que modela el comportamiento del intercambiador de calor de tubos y coraza, simularemos la ecuación no lineal y observaremos su comportamiento con respecto a dos entradas de respuesta tipo escalón, luego le aplicaremos la transformada de Laplace y con ayuda de variables de desviación lograremos linealizarla para obtener su función de transferencia y poder compararla con los software que utilizaremos. MATLAB que por un lado es un programa que se debe tener licencia para utilizarlo, así mismo el entorno de programación visual SIMULINK que funciona sobre el entorno de MATLAB, además utilizaremos el programa SCILAB que es de código abierto libre de licencia y así mismo con su entorno de programación visual XCOS que es similar a SIMULINK, finalmente simularemos en un lenguaje para el modelado orientado a objetos MODELICA, que como el programa anterior es un software libre.This issue of heat exchanger is focused on mathematical modeling and simulation in different software, starting with a brief introduction of related concepts to the heat exchanger, then the equations that model the dynamic system of our heat exchanger will be analyzed, for satisfaction will be resolved and analyzed. Analyze the first-order differential equation that models the behavior of the heat exchanger shell and tube, simulate the nonlinear equation and observe their behavior with respect to two inputs of step-like response, then we will apply the Laplace transform and using linearized deviation variables achieve for its transfer function and to compare it with the software we use. MATLAB on the one hand is a program that must be licensed to use, also the visual programming environment SIMULINK works on the MATLAB environment also use the SCILAB program is free and open source license and also with his Xcos visual programming environment that is similar to SIMULINK finally simulate a language for modeling object-oriented MODELICA, which like the previous program is free software

A Quantitative Comparison of Completely Visible Cadastral Parcels Using Satellite Images:A Step towards Automation

Estimates suggest that 70 percent of the world’s population has little or no access to formal land administration systems and hence their rights are often neither recognized nor secured by governments. A system of organized land rights information, embedded in a broader land administration system, is argued as a key pillar for underpinning any sustainable economy and equitable economic development. Cadastres are a core ingredient of any land administration system. Traditional methods for cadastral surveying and mapping are however, often lengthy and labor intensive. In response, remote sensing based techniques have great potential and are being increasingly employed for rapid creation and upgrading of cadastral maps: the Global Land Tool Network (GLTN)’s fit-for-purpose (FFP) land administration guidelines provide ample evidence in this regard. Furthermore, (semi)-automatic methods for detecting cadastral boundaries are currently under development. These methods seek to make use of very high resolution (VHR) satellite images or sensors capable of similar resolutions. Creating approaches that are both highly automated and transferable between contexts remain a challenge owing to diverse morphologies of parcel boundaries found across contexts. Anyhow, object-based image analysis methods appear highly promising as they mimic the human interpretation process to identify features from an image. A pre-step to utilizing any of these methods should be determining the quantity of the boundaries that are actually identifiable through visual interpretation. Therefore, in this paper, we assess the quantity of visible/non-visible boundaries in different contexts with the aim of determining the percentage of known cadastral parcels that are completely visible via VHR satellite images. For this purpose, we selected subsets from case locations in the contexts of Ethiopia, Ghana, Kenya, Mozambique, Rwanda, Guatemala and Nepal. To cover different landscapes, a combination of rural, peri-urban and urban areas were included. In each case, control cadastral data (i.e. vector files or existing cadastral maps) served as a reference for the assessment. Results show significant difference between visual identification for the samples from seven contexts. The percentage of completely visible cadastral parcels ranged from zero to 71 percent when compared to the reference cadastral map. These were parcels for which all boundaries were fully visible, i.e. a closed polygon. Considering the result of the study, it appears that (semi)-automated cadastral boundary extraction methods using VHR imagery will have high utility in specific contexts (e.g. smallholder and rural), whereas their use in complex urban environments may be challenging and require other methods or data. Nonetheless, an approach like this will greatly enhance the application of FFP approach in Land Administration for cadastral mapping in areas where no relaible data exists, for e.g. even if a small amount of boundaries could be automatically generated (e.g. 30 percent), potentially large cost reductions in cadastral surveying and mapping could be achieved

Geo-Biological Investigations on Azooxanthellate Cold-Water Coral Reefs on the Carbonate Mounds Along the Celtic Continental Slope

Northeast Atlantic 2004 Cruise No. 61, Leg 1 April 19 to May 4, 2004, Lisbon – Cor

New frontier in printed thermoelectrics: Formation of β-Ag2_{2}Se through thermally stimulated dissociative adsorption leads to high ZT

Printed thermoelectrics (TE) could significantly reduce the production cost of energy harvesting devices by large-scale manufacturing. However, developing a high performance printable TE material is a substantial challenge. In this work, a new one-pot synthesis and processing of high performance Ag$_{2}$Se based n-type printed TE materials is reported. Structural analyses reveal that orthorhombic β-Ag$_{2}$Se is the dominant phase in the n-type printed material compounds. For a printed material at room temperature, a breakthrough power-factor of ∼17 μW cm$^{-1}$ K$^{-2}$ with a record high figure-of-merit ZT ∼ 1.03 is achieved. A high average ZT, an important parameter for device applications, of ∼0.85–0.60 has been realized in the temperature range of 300 K to 400 K. Using this material for n-type legs in combination with commercially available PEDOT:PSS for p-type legs, a printed TE generator (print-TEG) of two thermocouples has been fabricated. An output voltage of 17.6 mV and a high maximum power output P$_{max}$ of 0.19 μW are achieved using the print-TEG at ΔT = 75 K

Global Distribution of Extended Spectrum Cephalosporin and Carbapenem Resistance and Associated Resistance Markers in Escherichia coli of Swine Origin – A Systematic Review and Meta-Analysis

Third generation cephalosporins and carbapenems are considered critically important antimicrobials in human medicine. Food animals such as swine can act as reservoirs of antimicrobial resistance (AMR) genes/bacteria resistant to these antimicrobial classes, and potential dissemination of AMR genes or resistant bacteria from pigs to humans is an ongoing public health threat. The objectives of this systematic review and meta-analysis were to: (1) estimate global proportion and animal-level prevalence of swine E. coli phenotypically resistant to third generation cephalosporins (3GCs) and carbapenems at a country level; and (2) measure abundances and global distribution of the genetic mechanisms that confer resistance to these antimicrobial classes in these E. coli isolates. Articles from four databases (CAB Abstracts, PubMed/MEDLINE, PubAg, and Web of Science) were screened to extract relevant data. Overall, proportion of E. coli resistant to 3GCs was lower in Australia, Europe, and North America compared to Asian countries. Globally, <5% of all E. coli were carbapenem-resistant. Fecal carriage rates (animal-level prevalence) were consistently manifold higher as compared to pooled proportion of resistance in E. coli isolates. blaCTX–M were the most common 3GC resistance genes globally, with the exception of North America where blaCMY were the predominant 3GC resistance genes. There was not a single dominant blaCTX–M gene subtype globally and several blaCTX–M subtypes were dominant depending on the continent. A wide variety of carbapenem-resistance genes (blaNDM–, VIM–, IMP–, OXA–48, andKPC–) were identified to be circulating in pig populations globally, albeit at very-low frequencies. However, great statistical heterogeneity and a critical lack of metadata hinders the true estimation of prevalence of phenotypic and genotypic resistance to these antimicrobials. Comparatively frequent occurrence of 3GC resistance and emergence of carbapenem resistance in certain countries underline the urgent need for improved AMR surveillance in swine production systems in these countries

The ACS Virgo Cluster Survey. XIII. SBF Distance Catalog and the Three-Dimensional Structure of the Virgo Cluster

The ACS Virgo Cluster Survey consists of HST ACS imaging for 100 early-type galaxies in the Virgo Cluster, observed in the F475W and F850LP filters. We derive distances for 84 of these galaxies using the method of surface brightness fluctuations (SBFs), present the SBF distance catalog, and use this database to examine the three-dimensional distribution of early-type galaxies in the Virgo Cluster. The SBF distance moduli have a mean (random) measurement error of 0.07 mag (0.5 Mpc), or roughly 3 times better than previous SBF measurements for Virgo Cluster galaxies. Five galaxies lie at a distance of ~23 Mpc and are members of the W' cloud. The remaining 79 galaxies have a narrow distribution around our adopted mean distance of 16.5+/-0.1 (random mean error) +/-1.1 Mpc (systematic). The rms distance scatter of this sample is 0.6+/-0.1 Mpc, with little dependence on morphological type or luminosity class (i.e., 0.7+/-0.1 and 0.5+/-0.1 Mpc for the giants and dwarfs, respectively). The back-to-front depth of the cluster measured from our sample of galaxies is 2.4+/-0.4 Mpc (i.e., +/-2sigma of the intrinsic distance distribution). The M87 (cluster A) and M49 (cluster B) subclusters are found to lie at distances of 16.7+/-0.2 and 16.4+/-0.2 Mpc, respectively. There may be a third subcluster associated with M86. A weak correlation between velocity and line-of-sight distance may be a faint echo of the cluster velocity distribution not having yet completely virialized. In three dimensions, Virgo's early-type galaxies appear to define a slightly triaxial distribution, with axis ratios of (1:0.7:0.5). The principal axis of the best-fit ellipsoid is inclined ~20-40 deg. from the line of sight, while the galaxies belonging to the W' cloud lie on an axis inclined by ~10-15 deg.Comment: 21 pages, 21 postscript figures. Also available at http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/community/ACSVCS/index.htm

Effects of δ Phase and Annealing Twins on Mechanical Properties and Impact Toughness of L-PBF Inconel 718

In this study, the effects of the δ phase and annealing twins on the hardness, tensile properties, and Charpy impact toughness of Inconel 718 fabricated using L-PBF were investigated. The as-printed components underwent two stages of heat treatment to modify their microstructure and phases. The δ phase was induced through solid-solution heat treatment at 980 °C for 1 h, while annealing twins were formed at 1100 °C for 3 h. Following precipitation hardening, specimens containing δ precipitates exhibited a higher ultimate tensile strength (13%), yield strength (27%), and hardness (12%) compared to those rich in annealing twins. The enhanced mechanical strength was attributed to the presence of δ precipitates and differences in the extent of recrystallization, leading to variations in the density of retained lattice defects, including subgrain boundaries and primary phases. Conversely, specimens with annealing twins demonstrated a significantly higher impact toughness (four times) and ductility (twice) than those with δ precipitates. Annealing twins were found to enhance plasticity by impeding dislocation movement, while δ precipitates reduced plasticity by acting as sites for void formation and crack propagation. Microstructural, compositional, phase, crystallographic, and fractographic analyses were conducted using OM, SEM, TEM, and XRD techniques to identify the factors influencing the observed differences. The results indicate that the heat treatment approach involving annealing twins can effectively enhance the ductility of Inconel 718 while maintaining the necessary mechanical strength.publishedVersio

VLTI status update: a decade of operations and beyond

We present the latest update of the European Southern Observatory's Very Large Telescope interferometer (VLTI). The operations of VLTI have greatly improved in the past years: reduction of the execution time; better offering of telescopes configurations; improvements on AMBER limiting magnitudes; study of polarization effects and control for single mode fibres; fringe tracking real time data, etc. We present some of these improvements and also quantify the operational improvements using a performance metric. We take the opportunity of the first decade of operations to reflect on the VLTI community which is analyzed quantitatively and qualitatively. Finally, we present briefly the preparatory work for the arrival of the second generation instruments GRAVITY and MATISSE.Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-1