Search results for: Juan C. Domínguez

Authors: Francisco J. Cedano, Laura M. Pinzón, Camila I. Castro, Felipe Salcedo, Juan P. Casas, Juan C. Briceño

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Complex fractures located in articular surfaces are challenging to treat and their reduction with conventional treatments could compromise the functionality of the affected limb. An adhesive material to treat those fractures is desirable for orthopedic surgeons. This adhesive must be biocompatible and have a high adhesion to bone surface in an aqueous environment. The proposed adhesive is based on chitosan, given its adhesive and biocompatibility properties. Chitosan is mixed with calcium carbonate and hydroxyapatite, which contribute to structural support and a gel like behavior, and glutaraldehyde is used as a cross-linking agent to keep the adhesive mechanical performance in aqueous environment. This work aims to evaluate the rheological, adhesion strength and biocompatibility properties of the proposed adhesive using in vitro tests. The gelification process of the adhesive was monitored by oscillatory rheometry in an ARG-2 TA Instruments rheometer, using a parallel plate geometry of 22 mm and a gap of 1 mm. Time sweep experiments were conducted at 1 Hz frequency, 1% strain and 37°C from 0 to 2400 s. Adhesion strength is measured using a butt joint test with bovine cancellous bone fragments as substrates. The test is conducted at 5 min, 20min and 24 hours after curing the adhesive under water at 37°C. Biocompatibility is evaluated by a cytotoxicity test in a fibroblast cell culture using MTT assay and SEM. Rheological results concluded that the average gelification time of the adhesive is 820±107 s, also it reaches storage modulus magnitudes up to 106 Pa; The adhesive show solid-like behavior. Butt joint test showed 28.6 ± 9.2 kPa of tensile bond strength for the adhesive cured for 24 hours. Also there was no significant difference in adhesion strength between 20 minutes and 24 hours. MTT showed 70 ± 23 % of active cells at sixth day of culture, this percentage is estimated respect to a positive control (only cells with culture medium and bovine serum). High vacuum SEM observation permitted to localize and study the morphology of fibroblasts presented in the adhesive. All captured fibroblasts presented in SEM typical flatted structure with filopodia growth attached to adhesive surface. This project reports an adhesive based on chitosan that is biocompatible due to high active cells presented in MTT test and these results were correlated using SEM. Also, it has adhesion properties in conditions that model the clinical application, and the adhesion strength do not decrease between 5 minutes and 24 hours.

Keywords: bioadhesive, bone adhesive, calcium carbonate, chitosan, hydroxyapatite, glutaraldehyde

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Authors: Juan P. Novoa, Mario A. Rios

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This paper presents a transmission planning methodology that considers the conversion of HVAC transmission lines to HVDC as an alternative of expansion of power systems, as a consequence of restrictions for the construction of new lines. The transmission expansion planning problem formulates an optimization problem that minimizes the total cost that includes the investment cost to convert lines from HVAC to HVDC and possible required reinforcements of the power system prior to the conversion. The costs analysis assesses the impact of the conversion on the reliability because transmission lines are out of service during the conversion work. The presented methodology is applied to a test system considering a planning a horizon of 10 years.

Keywords: transmission expansion planning, HVDC, cost optimization, energy non-supplied

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Authors: Jeisson Alejandro Triana, Maria Fernanda Quiceno Vallejo, Patricia del Portillo, Juan Manuel Anzola

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Most of the known antimicrobials so far discovered are secondary metabolites. The potential for new natural products of this category increases as new microbial genomes and metagenomes are being sequenced. Despite the advances, there is no systematic way to interrogate metagenomic clones for their potential to contain clusters of genes related to these pathways. Here we analyzed 52 biosynthetic pathways from the AntiSMASH database at the protein domain level in order to identify domains of high specificity and sensitivity with respect to specific biosynthetic pathways. These domains turned out to have various degrees of divergence at the DNA level. We propose PCR assays targetting such domains in-silico and corroborated one by Sanger sequencing.

Keywords: bioinformatic, anti smash, antibiotics, secondary metabolites, natural products, protein domains

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Authors: Jean-Marie Vilaire, Ricardo Abreu-Blaya, Juan Bory-Reyes

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The classical Beltrami system of elliptic equations generalizes the Cauchy Riemann equation in the complex plane and offers the possibility to consider homogeneous system with no terms of zero order. The theory of Douglis-valued functions, called Hyper-analytic functions, is special case of the above situation. In this note, we prove an analogue of the N. Davydov theorem in the framework of the theory of hyperanalytic functions. The used methodology contemplates characteristic methods of the hypercomplex analysis as well as the singular integral operators and elliptic systems of the partial differential equations theories.

Keywords: Beltrami equation, Douglis algebra-valued function, Hypercomplex Cauchy type integral, Sokhotski-Plemelj formulae

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Authors: Yeimy L. Quintana, Juan G. Zuluaga, Sandra S. Arango

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The comet assay is a method based on electrophoresis that is used to measure DNA damage in cells and has shown important results in the identification of substances with a potential risk to the human population as innumerable physical, chemical and biological agents. With this technique is possible to obtain images like a comet, in which the tail of these refers to damaged fragments of the DNA. One of the main problems is that the image has unequal luminosity caused by the fluorescence microscope and requires different processing to condition it as well as to know how many optimal comets there are per sample and finally to perform the measurements and determine the percentage of DNA damage. In this paper, we propose the design and implementation of software using Image Processing Toolbox-MATLAB that allows the automation of image processing. The software chooses the optimum comets and measuring the necessary parameters to detect the damage.

Keywords: artificial vision, comet assay, DNA damage, image processing

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Authors: Juan Manuel Real-Espinosa

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This paper addresses the first step to evaluate language learning apps: what theoretical framework to adopt when designing the app evaluation framework. The answer is not just one since there are several options that could be proposed. However, the question to be clarified is to what extent the learning design of apps is based on a specific learning approach, or on the contrary, on a fusion of elements from several theoretical proposals and paradigms, such as m-learning, mobile assisted language learning, and a number of theories about language acquisition. The present study suggests that the reality is closer to the second assumption. This implies that the theoretical framework against which the learning design of the apps should be evaluated must also be a hybrid theoretical framework, which integrates evaluation criteria from the different theories involved in language learning through mobile applications.

Keywords: mobile-assisted language learning, action-oriented approach, apps evaluation, post-method pedagogy, second language acquisition

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Authors: Daniel Icaza, Federico Córdova, Chiristian Castro, Fernando Icaza, Juan Portoviejo

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In this article, the mathematical model is presented, and simulations were carried out using specialized software such as MATLAB before the construction of a 900-W wind turbine. The present study was conducted with the intention of taking advantage of the rotation of the blades of the wind generator after going through a process of amplification of speed by means of a system of gears to finally mechanically couple two electric generators of similar characteristics. This coupling allows generating a maximum voltage of 6 V in DC for each generator and putting in series the 12 V DC is achieved, which is later stored in batteries and used when the user requires it. Laboratory tests were made to verify the level of power generation produced based on the wind speed at the entrance of the blades.

Keywords: smart grids, wind turbine, modeling, renewable energy, robust control

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Authors: Yuban Sebastian Cuartas-Agudelo, Sandra Marcela López-Hincapié, Vivianna Alexandra Garrido-Altamar, María de los Ángeles Rodríguez-Gázquez, Camilo Ruiz-Mejía, Lina María Martínez-Sánchez, Gloria Inés Martínez-Domínguez, Luis Eduardo Contreras, Felipe Eduardo Marino-Isaza

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Introduction: Doping is a prohibited practice in competitive sports with potential adverse effects; therefore, it is crucial to describe the attitudes of athletes towards this behavior and to determine which o these increase the susceptibility to carry out this practice. Objective: To determine the attitude of high-performance athletes towards doping in a sports institute in the city of Medellin, Colombia. Methods: We performed a cross-sectional study during 2016, with a sample taken to convenience consisting of athletes over 18 years old enrolled in a sports institute of the city of Medellin (Colombia). The athletes filled by themselves the Petroczi and Aidman questionnaire: Performance Enhancement Attitude Scale (PEAS) adapted to the Spanish language by Morente-Sánchez et al. This scale has 17 items with likert answer options, with a score ranging from 1 to 6, with a higher score indicating a stronger tendency towards doping practices. Results: 112 athletes were included with an average age of 21.6 years old, a 60% of them were male and the most frequent sports were karate 17%, judo 12.5% and athletics 9.8%. The average score of the questionnaire was 35.5 points of a 102 possible points. The lowest score was obtained in the following items: Is Doping necessary 1,4 and Doping isn’t cheating, everyone does it 1,5. Conclusion: In our population, there is a low tendency towards doping practices.

Keywords: sports, doping in sports, athletic performance, attitude

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Authors: Juan Manuel Sanchez-Cartas, Gonzalo Leon

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A price competition algorithm for ABMs based on game theory principles is proposed to deal with the simulation of theoretical market models. The algorithm is applied to the classical Hotelling’s model and to a two-sided market model to show it leads to the optimal behavior predicted by theoretical models. However, when theoretical models fail to predict the equilibrium, the algorithm is capable of reaching a feasible outcome. Results highlight that the algorithm can be implemented in other simulation models to guarantee rational users and endogenous optimal behaviors. Also, it can be applied as a tool of verification given that is theoretically based.

Keywords: agent-based models, algorithmic game theory, multi-sided markets, price optimization

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Authors: Montserrat Crespi Vallbona, Marta Domínguez Pérez

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Globalization impacts on cities and especially on their centers, especially on those spaces more visible and coveted. Changes are involved in processes such as touristification, gentrification or studentification, in addition of shop trendiness. The city becomes a good of interchange rather than a communal good for its inhabitants and consequently, its value is monetized. So, these different tendencies are analyzed: on one hand, the presence of tourists, the home rental increase, the explosion of businesses related to tourism; on the other hand; the return of middle classes or gentries to the center in a socio-spatial model that has changed highlighting the centers by their culture and their opportunities as well as by the value of public space and centrality; then, the interest of students (national and international) to be part of these city centers as dynamic groups and emerging classes with a higher purchasing power and better cultural capital than in the past; and finally, the conversion of old stores into modern ones, where vintage trend and the renewal of antiquity is the essence. All these transforming processes impact the European cities and redefine their image. All these trends reinforce the impression and brand of the urban center as an attractive space for investment, keeping such nonsense meaningful. These four tendencies have been spreading correlatively impacting the centers and transforming them involving the displacement of former residents of these spaces and revitalizing the center that is financed and commercialized in parallel. The cases of Madrid and Barcelona as spaces of greater evidence in Spain of these tendencies serve to illustrate these processes and represent the spearhead. Useful recommendations are presented to urban planners to find the conciliation of communal and commercialized spaces.

Keywords: gentrification, shop trendiness, studentification, touristification

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Authors: L. Chevez, A. Apaza, J. Rodriguez, R. Puga, H. Loro, Juan Z. Davalos

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Virtual Dimension (VD) procedure is used to analyze Hyperspectral Image (HIS) treatment-data in order to estimate the abundance of mineral components of a mining sample. Hyperspectral images coming from reflectance spectra (NIR region) are pre-treated using Standard Normal Variance (SNV) and Minimum Noise Fraction (MNF) methodologies. The endmember components are identified by the Simplex Growing Algorithm (SVG) and after adjusted to the reflectance spectra of reference-databases using Simulated Annealing (SA) methodology. The obtained abundance of minerals of the sample studied is very near to the ones obtained using XRD with a total relative error of 2%.

Keywords: hyperspectral imaging, minimum noise fraction, MNF, simplex growing algorithm, SGA, standard normal variance, SNV, virtual dimension, XRD

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Authors: Encarnacion Alvarez, Noemı Hidalgo-Rebollo, Juan F. Munoz, Francisco J. Blanco-Encomienda

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Many companies use the technique named as acceptance sampling which consists on the inspection and decision making regarding products. According to the results derived from this method, the company takes the decision of acceptance or rejection of a product. The acceptance sampling can be applied to the technology management, since the acceptance sampling can be seen as a tool to improve the design planning, operation and control of technological products. The theoretical operating characteristic (OC) curves are widely used when dealing with acceptance sampling. In this paper, we carry out Monte Carlo simulation studies to compare numerically the empirical OC curves derived from the empirical results to the customary theoretical OC curves. We analyze various possible scenarios in such a way that the differences between the empirical and theoretical curves can be observed under different situations.

Keywords: single-sampling plan, lot, Monte Carlo simulation, quality control

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Authors: Guillermo Manuel Flores Figueroa, Juan Alejandro Vazquez Feijoo, Jose Navarro Antonio

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A continuous nonlinear system response may be obtained by an infinite sum of the so-called Volterra operators. Each operator is obtained from multidimensional convolution of nth-order between the nth-order Volterra kernel and the system input. These operators can also be obtained from the Associated Linear Equations (ALEs) that are linear models of subsystems which inputs and outputs are of the same nth-order. Each ALEs produces a particular nth-Volterra operator. As linear models a unitary impulse response can be obtained from them. This work shows the relationship between this unitary impulse responses and the corresponding order Volterra kernel.

Keywords: Volterra series, frequency response functions FRF, associated linear equations ALEs, unitary response function, Voterra kernel

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Authors: Sánchez Acuña, Juan Camilo, Granados Gómez, Mildred Magaly, Navarrete Rodríguez, Luisa Fernanda

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Nowadays, the main biofuels source production as bioethanol is food crops. This means a high competition between foods and energy production. For this reason, it is necessary to take into account the use of new raw materials friendly to the environment. The main objective of this paper is to evaluate the potential of the agro-industrial banana crop residues in the production of bioethanol. A factorial design of 2⁴ was used, the design has variables such as pH, time and concentration of hydrolysis, another variable is the time of fermentation that is of 7 or 15 days. In the hydrolysis phase, the pH is acidic (H₂SO₄) or basic (NaOH), the time is 30 or 15 minutes and the concentration is 0.1 or 0.5 M. It was observed that basic media, low concentrations, fermentation, and higher pretreatment times produced better performance in terms of biofuel obtained.

Keywords: bioethanol, biofuels, banana waste, hydrolysis

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Authors: Herminio Martínez-García, Juan Gámiz, Yolanda Bolea, Antoni Grau

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This article presents an interactive system for data acquisition in vehicle testing according to the test process defined in automotive directive 2004/104/EC. The project has been designed and developed by authors for the Spanish company Applus-LGAI. The developed project will result in a new process, which will involve the creation of braking cycle test defined in the aforementioned automotive directive. It will also allow the analysis of new vehicle features that was not feasible, allowing an increasing interaction with the vehicle. Potential users of this system in the short term will be vehicle manufacturers and in a medium term the system can be extended to testing other automotive components and EMC tests.

Keywords: automotive process, data acquisition system, electromagnetic compatibility (EMC) testing, European Directive 2004/104/EC

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Authors: Indra Gonzalez Ojeda, Tatiana Quinones, Manuel Rosario, Igor Lednev, Juan Lopez Garriga

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Amyloid fibrils are stable aggregates of misfolded protein associated with many neurodegenerative disorders. It has been shown that hydrogen sulfide (H2S), inhibits the fibrillation of lysozyme through the formation of trisulfide (S-S-S) bonds. However, the overall mechanism remains elusive. Here, the concentration dependence of H2S effect was investigated using Atomic force microscopy (AFM), non-resonance Raman spectroscopy, Deep-UV Raman spectroscopy and circular dichroism (CD). It was found that small spherical aggregates with trisulfide bonds and a unique secondary structure were formed instead of amyloid fibrils when adding concentrations of 25 mM and 50 mM of H2S. This could indicate that H2S might serve as a protecting agent for the protein. However, further characterization of these aggregates and their trisulfide bonds is needed to fully unravel the function H2S has on protein fibrillation.

Keywords: amyloid fibrils, hydrogen sulfide, protein folding, raman spectroscopy

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Authors: Zhang Tianping, Jia Yanhui, Li Juan, Yang Le, Yang Hao, Yang Wei, Sun Xiaojing, Shi Kai, Li Xingda, Sun Yunkui

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Lanzhou Institute of Physics (LIP) is the major supplier of electric propulsion subsystems for Chinese satellite platforms. The development statuses of these electric propulsion subsystems were summarized including the LIPS-200 ion electric propulsion subsystem (IEPS) for DFH-3B platform, the LIPS-300 IEPS for DFH-5 and DFH-4SP platform, the LIPS-200+ IEPS for DFH-4E platform and near-earth asteroid exploration spacecraft, the LIPS-100 IEPS for small satellite platform, the LHT-100 hall electric propulsion subsystem (HEPS) for flight test on XY-2 satellite, the LHT-140 HEPS for large LEO spacecraft, the LIPS-400 IEPS for deep space exploration mission and other EPS for other Chinese spacecraft.

Keywords: ion electric propulsion, hall electric propulsion, satellite platform, LIP

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Authors: Juan Peña Aguilar, Lilia Villasana, Rodrigo Valencia, Alberto Pastrana, Martin Vivanco, Juan Peña C

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Each year a growing number of companies entering Mexico in search of the domestic market share. These activities, including stores, telephone long distance and local raw materials and energy, and particularly the financial sector, have managed to significantly increase its weight in the flows of FDI in Mexico , however, you should consider whether these trends FDI are positive for the Mexican economy and these activities increase Mexican exports in the medium term , and its share in GDP , gross fixed capital formation and employment. In general stresses that these activities, by far, have been unable to significantly generate linkages with the rest of the economy, a process that has not favored with competitiveness policies and activities aimed at these neutral or horizontal. Since the nineties foreign direct investment (FDI) has shown a remarkable dynamism, both internationally and in Latin America and in Mexico. Only in Mexico the first recipient of FDI in importance in Latin America during 1990-1995 and was displaced by Brazil since FDI increased from levels below 1 % of GDP during the eighties to around 3 % of GDP during the nineties. Its impact has been significant not only from a macroeconomic perspective , it has also allowed the generation of a new industrial production structure and organization, parallel to a significant modernization of a segment of the economy. The case of Mexico also is particularly interesting and relevant because the destination of FDI until 1993 had focused on the purchase of state assets during privatization process. This paper aims to present FDI flows in Mexico and analyze the different business strategies that have been touched and encouraged by the FDI. On the one hand, looking briefly discuss regulatory issues and source and recipient of FDI sectors. Furthermore, the paper presents in more detail the impacts and changes that generated the FDI contribution of FDI in the Mexican economy , besides the macroeconomic context and later legislative changes that resulted in the current regulations is examined around FDI in Mexico, including aspects of the Free Trade Agreement (NAFTA). It is worth noting that foreign investment can not only be considered from the perspective of the receiving economic units. Instead, these flows also reflect the strategic interests of transnational corporations (TNCs) and other companies seeking access to markets and increased competitiveness of their production networks and global distribution, among other reasons. Similarly it is important to note that foreign investment in its various forms is critically dependent on historical and temporal aspects. Thus, the same functionality can vary significantly depending on the specific characteristics of both receptor units as sources of FDI, including macroeconomic, institutional, industrial organization, and social aspects, among others.

Keywords: foreign direct investment (FDI), competitiveness, neoliberal regime, globalization, gross domestic product (GDP), NAFTA, macroeconomic

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Authors: Juan Sanmartín Bastida

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When a country experiences a period of transition from authoritarianism to democracy, involving an earlier process of political liberalization and a later process of democratization, a cycle of protest usually outbreaks, as there is a reciprocal influence between that kind of political change and the frequency and scale of social protest events. That is what happened in Spain during the first years of its transition to democracy from the Francoist authoritarian regime, roughly between November 1975 and December 1978. Thus, the object of this study is to show and explain how that cycle of protest started, developed, and finished in relation to such a political change, and offer specific information about the main features of all protest cycles: the social movements that arose during that period, the number of protest events by month, the forms of collective action that were utilized, the groups of challengers that engaged in contentious politics, the reaction of the authorities to the action and claims of those groups, etc. The study of this cycle of protest, using the primary sources and analytical tools that characterize the model of research of protest cycles, will make a contribution to the field of contentious politics and its phenomenon of cycles of contention, and more broadly to the political and social history of contemporary Spain. The cycle of protest and the process of political liberalization of the authoritarian regime began around the same time, but the first concluded long before the process of democratization was completed in 1982. The ascending phase of the cycle and therefore the process of liberalization started with the death of Francisco Franco and the proclamation of Juan Carlos I as King of Spain in November 1975; the peak of the cycle was around the first months of 1977; the descending phase started after the first general election of June 1977; and the level of protest stabilized in the last months of 1978, a year that finished with a referendum in which the Spanish people approved the current democratic constitution. It was then when we can consider that the cycle of protest came to an end. The primary sources are the news of protest events and social movements in the three main Spanish newspapers at the time, other written or audiovisual documents, and in-depth interviews; and the analytical tools are the political opportunities that encourage social protest, the available repertoire of contention, the organizations and networks that brought together people with the same claims and allowed them to engage in contentious politics, and the interpretative frames that justify, dignify and motivates their collective action. These are the main four factors that explain the beginning, development and ending of the cycle of protest, and therefore the accompanying social movements and events of collective action. Among those four factors, the political opportunities -their opening, exploitation, and closure-proved to be most decisive.

Keywords: contentious politics, cycles of protest, political opportunities, social movements, Spanish transition to democracy

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Authors: Justie Su-Tzu Juan, Ming-Jheng Li, Ching-Fen Lee, Ruei-Yu Wu

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A secret image sharing scheme is a way to protect images. The main idea is dispersing the secret image into numerous shadow images. A secret image sharing scheme can withstand the impersonal attack and achieve the highly practical property of multiuse  is more practical. Therefore, this paper proposes a verifiable and detectable secret image-sharing scheme called VDGMSISS to solve the impersonal attack and to achieve some properties such as encrypting multi-secret images at one time and multi-use. Moreover, our scheme can also be used for any genera access structure.

Keywords: multi-secret image sharing scheme, verifiable, de-tectable, general access structure

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Authors: Christian Castro Samaniego, Daniel Icaza Alvarez, Juan Portoviejo Brito

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For this research work, hybrid wind-photovoltaic (SHEF) systems were considered as renewable energy sources that take advantage of wind energy and solar radiation to transform into electrical energy. In the present research work, the feasibility of a wind-photovoltaic hybrid generation system was analyzed for the La Tranca tourist viewpoint of the Chordeleg canton in Ecuador. The research process consisted of the collection of data on solar radiation, temperature, wind speed among others by means of a meteorological station. Simulations were carried out in MATLAB/Simulink based on a mathematical model. In the end, we compared the theoretical radiation-power curves and the measurements made at the site.

Keywords: hybrid system, wind turbine, modeling, simulation, validation, experimental data, panel, Ecuador

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Authors: Joselito Medina-Marin, Alexandr Karelin, Ana Tarasenko, Juan Carlos Seck-Tuoh-Mora, Norberto Hernandez-Romero, Eva Selene Hernandez-Gress

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A production line designer faces with several challenges in manufacturing system design. One of them is the assignment of buffer slots in between every machine of the production line in order to maximize the throughput of the whole line, which is known as the Buffer Allocation Problem (BAP). The BAP is a combinatorial problem that depends on the number of machines and the total number of slots to be distributed on the production line. In this paper, we are proposing a Petri Net (PN) Model to obtain the throughput in unreliable production lines, based on PN mathematical tools and the decomposition method. The results obtained by this methodology are similar to those presented in previous works, and the number of machines is not a hard restriction.

Keywords: buffer allocation problem, Petri Nets, throughput, production lines

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Authors: Mst Nazmunnahar, Juan del Val, Alena Vimmrova, Blanca Hernando, Julian González

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We report the microstructural and magnetic properties of Ni50Mn39Sn11 and Ni50Mn36Sn14 ribbon Heusler alloys. Experimental results were obtained by differential scanning calorymetry, X-ray diffraction and vibrating sample magnetometry techniques. The Ni-Mn-Sn system undergoes a martensitic structural transformation in a wide temperature range. For example, for Ni50Mn39Sn11 the start and finish temperatures of the martensitic and austenite phase transformation for ribbon alloy were Ms = 336K , Mf = 328K, As = 335K and Af = 343K whereas no structural transformation is observed for Ni50Mn36Sn14 alloys. Magnetic measurements show the typical ferromagnetic behavior with Curie temperature 207K at low applied field of 50 Oe. The complex behavior exhibited by these Heusler alloys should be ascribed to the strong coupling between magnetism and structure, being their magnetic behavior determined by the distance between Mn atoms.

Keywords: as-cast ribbon, Heusler alloys, magnetic properties, structural transformation

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Authors: Juan P. Silva, T. R. Canchala, H. J. Lubberding, E. J. Peña, H. J. Gijzen

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This study measured the fluxes of greenhouse gases (GHGs) i.e. CO₂, CH₄ and N₂O from a tropical eutrophic freshwater wetland (“Sonso Lagoon”) which receives input loading nutrient from several sources i.e. agricultural run-off, domestic sewage, and a polluted river. The flux measurements were carried out at four different points using the static chamber technique. CO₂ fluxes ranged from -8270 to 12210 mg.m^-2.d^-1 (median = 360; SD = 4.11; n = 50), CH₄ ranged between 0.2 and 5270 mg.m^-2.d^-1 (median = 60; SD = 1.27; n = 45), and N₂O ranged from -31.12 to 15.4 mg N₂O m^-2.d^-1 (median = 0.05; SD = 9.36; n = 42). Although some negative fluxes were observed in the zone dominated by floating plants i.e. Eichornia crassipes, Salvinia sp., and Pistia stratiotes L., the mean values indicated that the Sonso Lagoon was a net source of CO₂, CH₄ and N₂O. In addition, an effect of the eutrophication on GHG emissions could be observed in the positive correlation found between CO₂, CH₄ and N₂O generation and COD, PO₄^-3, NH₃-N, TN and NO₃^-N. The eutrophication impact on GHG production highlights the necessity to limit the anthropic activities on freshwater wetlands.

Keywords: eutrophication, greenhouse gas emissions, freshwater wetlands, climate change

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Authors: Laura V. Gonzalez, Juan B. Duarte, Luis A. Palacio

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Decision making can be conditioned by factors such as the environments, circumstances, behavioral biases, emotions, beliefs and preferences of the participants. The objective of this paper is to analyze the effect ‘amount of information’ and ‘number of options’, on the behavior of competitors under a bilateral negotiation context. For the above, it has been designed an experiment as a classroom game where they negotiate goods, under the condition that none of the players knows exactly the real value of the asset. The game is designed under the concept of zero-sum (non-cooperative game) and focuses on the fact that agents must anticipate the strategies of their opponent to improve their chances of winning in the negotiation. The empirical results show that, contrary to the traditional view of expected utility theory, players prefer to obtain low profits and losses, when faced with a higher expectation of losses, using sub-optimal strategies not in accordance with game theory.

Keywords: bilateral negotiation, classroom game, decision making, game theory

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Authors: Juan Li, Jiawen Qiu, Yuchuan Chu, Tianping Zhang, Wei Meng, Yanhui Jia, Xiaohui Liu

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This article developed an ion thruster optic system sputter erosion depth numerical 3D model by IFE-PIC (Immersed Finite Element-Particle-in-Cell) and Mont Carlo method, and calculated the downstream surface sputter erosion rate of accelerator grid; Compared with LIPS-200 life test data, the results of the numerical model are in reasonable agreement with the measured data. Finally, we predict the lifetime of the 20cm diameter ion thruster via the erosion data obtained with the model. The ultimate result demonstrates that under normal operating condition, the erosion rate of the grooves wears on the downstream surface of the accelerator grid is 34.6μm⁄1000h, which means the conservative lifetime until structural failure occurring on the accelerator grid is 11500 hours.

Keywords: ion thruster, accelerator gird, sputter erosion, lifetime assessment

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Authors: Yanhui Jia, Ning Guo, Juan Li, Yunkui Sun, Wei Yang, Tianping Zhang, Lin Ma, Wei Meng, Hai Geng

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The current statuses of lifetime test of LaB6 hollow cathode at the Lanzhou institute of physics (LIP), China, was described. 5A LaB6 hollow cathode was designed for LIPS-200 40mN Xenon ion thruster and it could be used for LHT-100 80 mN Hall thruster, too. Life test of the discharge and neutralizer modes of LHC-5 hollow cathode were stared in October 2011, and cumulative operation time reached 17,300 and 16,100 hours in April 2015, respectively. The life of cathode was designed more than 11,000 hours. Parameters of discharge and key structure dimensions were monitored in different stage of life test indicated that cathodes were health enough. The test will continue until the cathode cannot work or operation parameter is not in normally. The result of the endurance test of cathode demonstrated that the LaB6 hollow cathode is satisfied for the required of thruster in life and performance.

Keywords: LaB6, hollow cathode, thruster, lifetime test, electric propulsion

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Authors: Joselito Medina Marin, Norberto Hernández Romero, Juan Carlos Seck Tuoh Mora, Erick S. Martinez Gomez

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The Flow Shop Scheduling Problem (FSSP) is a typical problem that is faced by production planning managers in Flexible Manufacturing Systems (FMS). This problem consists in finding the optimal scheduling to carry out a set of jobs, which are processed in a set of machines or shared resources. Moreover, all the jobs are processed in the same machine sequence. As in all the scheduling problems, the makespan can be obtained by drawing the Gantt chart according to the operations order, among other alternatives. On this way, an FMS presenting the FSSP can be modeled by Petri nets (PNs), which are a powerful tool that has been used to model and analyze discrete event systems. Then, the makespan can be obtained by simulating the PN through the token game animation and incidence matrix. In this work, we present an adaptive PN to obtain the makespan of FSSP by applying PN analytical tools.

Keywords: flow-shop scheduling problem, makespan, Petri nets, state equation

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Authors: Juan Ignacio Arango, Andres Diaz, Giacomo Barbieri

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In soilless culture, the definition of efficient fertigation strategies is fundamental for the growth of crops. Flexible test-benches able to independently manage groups of crops are key for investigating efficient fertigation practices through experimentation. These test-benches must be able to provide nutrient solution (NS) in a precise, uniform and repeatable way in order to effectively implement and compare different fertigation strategies. This article describes a distribution module for investigating fertigation practices able to control the fertigation dose and frequency. The proposed solution is characterized in terms of precision, uniformity and repeatability since these parameters are fundamental in the implementation of effective experiments for the investigation of fertigation practices. After a calibration process, the implemented system reaches a precision of 1mL, a uniformity of 98.5% at a total cost of 735USD.

Keywords: recision horticulture, test-bench, fertigation strategy, automation, flexibility

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Authors: Gu Chun-Mei, Kung Mei-Juan

Abstract:

The aim of this research is to examine (1) how a kindergarten teacher followed the scaffolding theory to inspire children’s interest in bicycling and (2) how these children had learned the skill of bicycling. Results revealed that: first of all, the teacher (1) used questions during the teaching process to stimulate the levels of children’s abilities; (2) provided follow-up thematic clues and hints which are based on children’s abilities (e.g., would not provide instructions and demonstrations except children continued failing to solve the current problems); (3) assisted only when children needed it. Furthermore, when children continued failing the task and being frustrated, instead of providing more concrete guidance, the teacher would utilize the following strategies: (1) postulating children’s thoughts; (2) encouraging children to feel the difficulties; (3) giving children opportunities to reflect on how to solve the problems. In sum, by raising questions, allowing children to implement by themselves for the first attempt, then inducing children to correct their actions, the teacher built a scaffold with thematic teaching to develop children’s potential on bicycling.

Keywords: thematic teaching, scaffold, zone of proximal development, children

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