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Effect of pH on Dimethylamine Borane Reduced Electroless Nickel Deposits on AISI/SAE 1045 Steel Surface
No full textAbstract: Electroless Ni B coatings using DMAB-reduced plating baths at different pH conditions were formed on AISI/SAE 1045 carbon steel. Substrates were grit-blasted with alumina, generating a rough surface suitable for anchorage and nucleation of the coating. The surface of the substrates were examined at selected times of electroless treatment using scanning electron microscopy. The structure of the coating was studied by means of X-ray diffraction. A low-cost boron determination procedure was implemented in order to determine the amount of boron incorporated into the electroless coatings. Coatings nucleate faster at acid and neutral pH conditions; however, at the end of the plating process all coatings were adherent, with the typical morphology of Ni B electroless coatings. Substrates slightly corroded inside the plating bath at acid pH condition. The amount of boron into the coatings was approximately 2.15, 2.14 and 1.10% (wt%) for the acid, neutral and alkaline pH plating baths, respectively. Graphic Abstract: [Figure not available: see fulltext.]. © 2019, The Korean Institute of Metals and Materials
CO2 activation on small Cu-Ni and Cu-Pd bimetallic clusters
No full textThe use of CO2 to produce methanol is a reaction of growing interest, where bimetallic Cu-M catalysts become relevant as an alternative to the known Cu/Zn/Al2O3 catalyst. However, there is a lack in the understanding of bimetallic systems at atomic label and its capability towards CO2 activation, a key step in CO2 valorization. In this work, Cu-Pd and Cu-Ni small clusters are studied using DFT. Among the evaluated bimetallic systems, the binding of CO2 on Cu3Pd has the highest thermodynamics stability (28.82 kcal/mol) and the lowest energy barrier (40.91 kcal/mol). The activation energy for the dissociation of CO2 (CO2? CO+ O) follows the trend: Cu4 < Cu3Pd < Pd4 < CuPd3 < Cu2Pd2. Therefore, the ideal composition in terms of adsorption energy and activation barrier is the Cu3Pd bimetallic system. The interaction O-M is weak while C-M is responsible of the binding, a charge migration from cluster to CO2 was seen, and the band around 1150 cm?1 in the IR was only found in activated CO2. The results of this work indicate that the Cu3Pd cluster has catalytic potential towards CO2 activation and dissociation, opening the doors to explore further the Cu3Pd system both theoretically and experimentally. © 2019 Elsevier B.V
A Note About Measures, Jacobians and Moore–Penrose Inverse
No full textSome general problems of Jacobian computations in non-full rank matrices are revised in this work. We prove that the Jacobian of the Moore Penrose inverse derived via matrix differential calculus is incorrect. In addition, the Jacobian in the full rank case is derived under the simple and old theory of the exterior product. © 2020, Iranian Mathematical Society
la Cuarta Revolución Industrial [Era de la cuarta revolución industrial]
No full text[No abstract available
Automated velocity estimation by deep learning based seismic-to-velocity mapping
No full textWe propose a novel method for velocity estimation that leverages the newest advances in Deep Learning (DL) technology. This method is fully automatic and maps seismic shot-domain data to corresponding depth-domain velocity fields via two neural networks. Our new method is conceptually different from conventional methods such as seismic tomography or Full Waveform Inversion (FWI) that minimize a fixed objective function. Here, a system of neural networks automatically and continuously learns an objective function while training the seismic-to-velocity mapping. The newly introduced method avoids many of the drawbacks of conventional velocity estimation techniques, such as dependence on initial models or cycle-skipping. It uses the full seismic wavefield and avoids picking of first-arrival traveltimes. The system needs to be trained with hundreds or thousands of examples of seismic data paired with their corresponding velocity models relevant for the current project. Training the system is the main computationally demanding step and produces a mapping function that contains the seismic know-how for the presumed geologic setting. The computational cost of the subsequent estimation of velocity from new seismic data is negligent. Our first tests on complex two-dimensional synthetic data produce impressive results, underlining the potential of DL for velocity analysis. © 81st EAGE Conference and Exhibition 2019. All rights reserved
Fractional Diffusion Modulates Distribution of Action Potential Duration in Fibrotic Atrial Strands
No full textBackground: Fibroblast proliferation, as a component of the fibrotic process, plays a role in structural remodeling, but also can alter the electrophysiology of the cardiomyocytes. Aim: To study the action potential duration dispersion (dAPD) in fibrotic atrial strands, where fibroblasts exerts both, structural and electrical influence on the propagation, using a fractional diffusion model. Methods: The Courtemanche model of human atrial cell is implemented under chronic atrial fibrillation (AF) remodeling conditions. The atrial strands are designed as 1D domains, having a fibrotic portion localized in the middle. Fibrosis is modeled taking into account an electrical component, implemented by coupling a number of fibroblasts to a single cardiomyocyte, and a structural component, implemented through a q-order fractional derivative. Results: The variations of q define two dAPD dispersion regimes. For q < 1.4, the fibrosis density and the number of fibroblast per cardiomyocyte do not alter the dAPD. For q ? 1.4, the dAPD depends on the fibrosis spatial characteristics. Conclusion: This study shows that the structural component of fibrosis, modeled using fractional diffusion, modulates the spatial dAPD in a domain including electrical coupling of cardiomyocytes and fibroblasts, under chronic AF conditions. © 2018 Creative Commons Attribution
Logistics education for business management students: A learning-doing and service-learning approach
No full textThis article develops a teaching methodology in logistics for students of business administration programs to solve real problems in companies and integrate the knowledge acquired in logistics management courses. The methodology integrates project management tools with the support of MSExcel and promotes the elaboration of managerial reports according to the requirements of working environments. The methodology generates high satisfaction in the students, to the extent that it allows them to know in depth the logistic system of a company, identifies opportunities for improvement and proposes solutions based on technical and economic aspects. Likewise, the methodology allows the students to have contact with the directives of a real company and supports the improvement of logistics processes based on qualitative and quantitative information. © Primrose Hall Publishing Group
Operations management strategies for the textile-clothing sector in Colombia
No full textThe textile and clothing industry in Colombia is facing several challenges that have motivated the redesign and optimization of production and logistics processes to remain competitive in global markets. The purpose of this paper is to introduce operations management strategies to create value and address the intense competition in both the national and international markets for the textile-clothing sector in Colombia. Strategies focused on inventory management, over inventory and overproduction, and reducing high production costs are proposed. It is concluded that operations management allows addressing current problems for the textile-clothing sector through integrating, optimizing and coordinating business processes for the long, medium and short term. © 2019 International Business Information Management Association (IBIMA)
Security in SDN: A comprehensive survey
No full textSoftware Defined Networking (SDN) is a revolutionary paradigm that is maturing along with other network technologies in the next-gen trend. The separation of control and data planes in SDN enables the emergence of novel network features like centralized flow management and network programmability that encourage the introduction of new and enhanced network functions in order to improve prominent network deployment aspects such as flexibility, scalability, network-wide visibility and cost-effectiveness. Although SDN exhibits a rapid evolution that is shaping this technology as a key enabler for future implementations in heterogeneous network scenarios, namely, datacenters, ISPs, corporate, academic and home; the technology is far from being considered secure and dependable to this day which inhibits its agile adoption. In recent years, the scientific community has been attracted to explore the field of SDN security to close the gap to SDN adoption. A twofold research context has been identified: on the one hand, leveraging SDN features to enhance security; while on the other hand one can find the pursue of a secure SDN system architecture. This article includes a description of security threats that menace SDN and a list of attacks that take advantage of vulnerabilities and misconfigurations in SDN constitutive elements. Accordingly, a discussion emphasizing the duality SDN-for-security and SDN-security is also presented. A comprehensive review of state-of-the art is accompanied by a categorization of the current research literature in a taxonomy that highlights the main characteristics and contributions of each proposal. Finally, the identified urgent needs and less explored topics are used to outline the opportunities and future challenges in the field of SDN security. © 2020 Elsevier Lt
Incidence of the RS(255,223) encoder in the performance of a Zigbee point-to-point system in an indoor environment [Incidencia del codificador RS(255,223) en el desempeño de un sistema punto a punto Zigbee en un ambiente indoor]
No full textThis paper presents the incidence of the RS error correction technique on the performance of a point-to-point link based on Zigbee technology, the measurements show that the RS scheme (255,223) allows the Zigbee system to achieve better performance in cases of interference. The evaluation of the RS technique uses the Euclidiano and Berlekamp Masey algorithms, in both processes requiring operations based on finite fields. © 2019 AISTI