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546,196 artículos

Año: 2022
ISSN: 1886-516X, 1886-516X
León Mendoza, Juan Celestino; Valcárcel Pineda, Paolo
https://www.upo.es/emch/portada
This study aims to identify the business owners’ sociodemographic characteristics that influence the achievement of business success in Peru. Using data from the 2018 National Household Survey on Living Conditions and Poverty, econometric estimates were made with the Ordinary Least Squares method. Considering the success of a business as the magnitude of the profit obtained, the econometric results indicate that its achievement is conditioned by gender, age, years of education achieved, state of health, marital status, number of children, belonging to a social network, ethnic self-perception, business persistence and intensity of internet use. Likewise, the achievement of business success is also influenced by factors considered as control variables in this study, such as the size of the company, the use of accounting systems and the regional and zonal location.
Año: 2022
ISSN: 1886-516X, 1886-516X
Escobar Elexpuru, Gonzalo; Valdés de la Fuente, Iván
https://www.upo.es/emch/portada
The main aim of this research is to measure the variation of market power exercised by a vertically integrated firm in the market of transactions carried out through payment cards, because of changes given by the entry of competitive firms in the market of purchasing shops, which increase the level of downstream competition in the industry. To achieve this, it is used as a model based on an oligopolistic structure where there is a leading firm and a fringe of competitive firms that compete each other, based on Stackelberg competition. The econometric model estimates indirectly the residual elasticity demand for the period January 2013-May 2020. As a result, the market power is directly related to the market share of the leading firm, equivalent to 1.14% to 114.35%, being the last predominant value in the trading account.
Año: 2022
ISSN: 2215-3373, 1409-2433
Angulo Sibaja, Andrés A.; Alvarado Marín, Rodrigo; Vargas Obando, Mauricio
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
In this paper, two exact solutions of the Einstein’s equations are obtained for an anisotropic and homogeneous symmetry of Petrov Type D, the difference between both solutions lies in how relevant is the expansion that is presented initially, either on an axis or on a perpendicular plane. Both solutions represent a mixture of two fluids with minimum interaction: dark energy (P = −µ) and radiation (P = µ/3). The singularities and the influence that these fluids have on this metric are studied; the Hubble parameters, the deceleration parameter and the role that these fluids represent on them are determined and analyzed. Additionally, their temperature and the role that both play on this magnitude are determined.
Año: 2022
ISSN: 2215-3373, 1409-2433
Centeno-Mora, Oscar; Gónzalez-Évora, Felipe
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
Coding and analyzing open-ended questions from opinion survey is often time consuming. Text mining offers an alternative for this type of problem. Data comes from the 2019 National Survey of Perception on Transparency open-ended questions. Text mining is applied from a descriptive and predictive approach: the latter has a predominant interest in performing the automatic coding of responses or categories using supervised machine learning. Support vector machine algorithms, naïve Bayes classifier, random forests, XGBoost, and closest neighbors are used. The results of the descriptive analysis improve the descriptions, visualizations and relationships in the analysis of the open-ended questions. The predictive analysis reports that the algorithms with the highest selection occurrence for the open-ended questions were the naive Bayes classifier and the random forests, showing accuracies between 48% and 76%. Similar results were obtained compared with the pre-established categories. Satisfactory results are seen in the comprehensive analysis of the 12 survey questions.
Año: 2022
ISSN: 2215-3373, 1409-2433
Pantí-Trejo, Henry G.; Guerrero-Lara, Ernesto A.; López-Flores, Jesús E.
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
Maximum likelihood estimators are calculated for the parameters that define the compound Poisson process in the classical risk process with exponential claims. It is proved consistency and asymptotic normality for estimators obtained. Finally, with the help of invariance property of the maximum likelihood estimators, asymptotic normality and delta method, point and interval estimation of the ruin probability is performed.
Año: 2022
ISSN: 2215-3373, 1409-2433
Román, Krishna; Cumbicus, Andy; Infante, Saba; Fonseca-Delgado, Rigoberto
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
Deep neural network models (DGPs) can be represented hierarchically by a sequential composition of layers. When the prior distribution over the weights and biases are independently identically distributed, there is an equivalence with Gaussian processes (GP) in the limit of an infinite net[1]work width. DGPs are non-parametric statistical models used to character[1]ize patterns of complex non-linear systems due to their flexibility, greater generalization capacity, and a natural way of making inferences about the parameters and states of the system. This article proposes a hierarchi[1]cal Bayesian structure to model the weights and biases of a deep neural network. We deduce a general formula to calculate the integrals of Gaussian processes with non-linear transfer densities and obtain a kernel to estimate the covariance functions. In the methodology, we conduct an empirical study analyzing an electroencephalogram (EEG) database for diagnosing Alzheimer’s disease. Additionally, the DGPs models are esti[1]mated and compared with the NN models for 5, 10, 50, 100, 500, and 1000 neurons in the hidden layer, considering two transfer functions: Recti[1]fied Linear Unit (ReLU) and hyperbolic Tangent (Tanh). The results show good performance in the classification of the signals. Finally, we use the mean square error as a goodness of fit measure to validate the proposed models, obtaining low estimation errors.
Año: 2022
ISSN: 2215-3373, 1409-2433
Delgado-Moya, Erick; Pietrus, Alain
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
In this paper, taking advantage of the use of fractional order derivatives in the Caputo sense, we present a study of optimal control of tuberculosis (TB) treatment efficacy in the presence of HIV/AIDS and diabetes. The mathematical model to which control is applied is found in [17] and studies the relationship between TB, HIV/AIDS and diabetes with respect to treatment efficacy and differentiates into multidrug-resistant TB (MDRTB), and extensively drug-resistant TB (XDR-TB). The definition of controls focuses on avoiding reinfection/reactivation, MDR-TB and XDR-TB in the different subpopulations (TB only, TB-HIV/AIDS and TB-Diabetes). The model which is divided into subpopulations allows us to differentiate transmission and resistance behaviors and to evaluate the different costs in the application of controls. We performed computational simulations with literature data to study our control problem in a specific scenario. We explored the behavior of the basic reproduction number by varying the effective contact rate and the parameters associated with the resistance for different values of _ (fractional order). We studied different control strategies based on the activation of the controls and found that the most effective is when we activate all the controls. With this strategy, we reduce the number of resistant cases, mainly in XDR-TB in diabetics which has a strong impact on the dynamics of TB resistance and transmission. In addition, this strategy avoids future growth in the number of resistant cases.
Año: 2022
ISSN: 2215-3373, 1409-2433
Zhang, Robin
Universidad de Costa Rica, Centro de Investigación en Matemática Pura y Aplicada (CIMPA)
This exposition examines the theory of orthogonal groups and their subgroups over fields of positive characteristic, which has recently been used as an important tool in the study of automorphic forms and Langlands functionality. We present the classification of orthogonal groups over a finite field using the theory of bilinear forms and quadratic forms in positive characteristic. Using the determinant and spinor norm when the characteristic of F is odd and using the Dickson invariant when the characteristic of F is even, we also look at special subgroups of the orthogonal group.
Año: 2022
ISSN: 1886-516X, 1886-516X
Escalante Yaulilahua, Danton Arturo; Jeri Huanaco, Yon Clever; Apolinario Torres, Rossel Melser; Roque Durand, Ronaldo Roberto; Venegas Rodríguez, Pedro Bernabé
https://www.upo.es/emch/portada
The export of minerals contributes in great proportion to the Peruvian economy, allowing the development of different sectors. The main objective of this research is to identify the behavior of the five main Peruvian export mining products and compare the results with the main exporting countries in order to determine their level of competitiveness. For this, a modification to the CEPAL competitiveness matrix made by Ramón and Lacayo in 2007 was used, complemented with the RCA, ICTB and PCE indicators; the data were obtained for the period from 2010 to 2019 from ITC-Trade Map. As a result, a high degree of specialization and competitiveness was evidenced in all evaluated Peruvian mining products. Copper, the category with the highest level of comparative advantage and the second with the highest growth rate, is the main export product contributing more than 25% of export earnings. Gold, the second category with the highest competitiveness rate, has reduced this level in the period. Zinc and Refined Copper has high levels of specialization, however, its competitiveness is on the decline. Finally, the Iron category is the one that showed the least competitiveness, but with a higher growth rate than the others.
Año: 2022
ISSN: 1886-516X, 1886-516X
Ortigosa Hernández, Mauricio
https://www.upo.es/emch/portada
In Mexico the National Institute of Statistic and Geography (INEGI) publishes a monthly indicator of business confidence (ICE) for various economic sectors using the Monthly Survey of Business Opinion (EMOE). In the present work reference is made only to the construction segment as it is one of the most sensitive sectors for the growth of the economy in Mexico. The official information issued by the INEGI about the ICE for this sector, is the result of the simple arithmetic mean of five qualitative indicators already projected and weighted. When applying the arithmetic mean at the end of the process to obtain an indicator of such importance, gives rise to the classic debate of applying this descriptive statistic in mean qualitative variables in Likert type questions. To overcome this problem, it is proposed to take the labels used in the answer options of the questions used in the EMOE questionnaire, to linguistic variables, where through the methodology of fuzzy inference systems, a Fuzzy Business Confidence Indicator (ICED) is obtained as a result. To validate the proposed system, the new fuzzy confidence indicators were calculated from January 2012 to February 2021 and compared to the official figures issued by the INEGI, obtaining similar results with the advantage that the indicators derived by the system, turned out to be higher or lower in general. What allows this path is to be more sensitive to changes in opinion among entrepreneurs, avoiding centralizing opinions by using the simple arithmetic mean.

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