987 results
Search Results
2. Capacidad de retención de hidrocarburos del endocarpio de coco en aguas aceitosas
- Author
-
Tomás Darío Marín-Velásquez and Edwin Julio Cóndor-Salvatierra
- Subjects
lcsh:TD201-500 ,lcsh:Hydraulic engineering ,Significant difference ,hidrocarburos ,Contamination ,filtración ,Pulp and paper industry ,Contaminated water ,Diesel fuel ,Filter system ,tratamiento ,lcsh:Water supply for domestic and industrial purposes ,Cocos nucifera ,lcsh:TC1-978 ,cocos nucifera ,agua contaminada ,Mathematics ,Filter material - Abstract
En la investigación en laboratorio se evaluó el uso de un material filtrante con base en endocarpio o cáscara de coco (Cocos nucifera) de forma granular para el tratamiento de aguas contaminadas con gasoil de petróleo. Se construyó un sistema de filtros con tubos PVC y se empacaron con el endocarpio, luego de que el mismo fuera triturado manualmente y tamizado a un diámetro de 2 mm. Se utilizaron cinco cantidades de material filtrante (75, 105, 135, 150 y 165 g) y tres concentraciones de gasoil en agua (5, 10 y 15 %). Las muestras de agua contaminada se dejaron fluir a través de los filtros de forma descendente por acción gravitacional y en cada filtrado se determinó la cantidad de aceites y grasas (AyG) a partir de normas internacionales. Los resultados se analizaron estadísticamente mediante ANOVA factorial y test de mínima diferencia significativa de Fisher. Los análisis estadísticos demostraron que existe influencia significativa de los dos factores (% gasoil y cantidad de material filtrante) sobre la variable respuesta en estudio (AyG) con un nivel de confianza de 95 %. Se demostró que el endocarpio de coco con el tamaño de granos utilizado es efectivo para la remoción de hidrocarburos en el agua, al lograrse porcentajes de remoción de 85.10, 84.23 y 82.10 %. Se obtuvo que a mayor cantidad del material filtrante, mayor es el grado de remoción con resultados estadísticamente significativos.
- Published
- 2021
3. Formulation of ice cream based on pulp of tamarind (Tamarindus indica L.) with hydrocoloids and enriched with vitamin C
- Author
-
Noemí Bravo Aranibar and Juan Carlos Bravo Aranibar
- Subjects
Nutrición, Dietética ,Guar ,Tamarindo ,formulation ,engineering.material ,hidrocoloide ,Tamarind ,hydrocolloid ,chemistry.chemical_compound ,ácido tartárico ,medicine ,ascorbic acid and lactic acid ,Food science ,Flavor ,Mathematics ,Guar gum ,Pulp (paper) ,General Engineering ,Ascorbic acid ,Lactic acid ,formulación ,Alimentos y bebidas ,ácido ascórbico y ácido láctico ,chemistry ,tartaric acid ,Tartaric acid ,engineering ,Xanthan gum ,medicine.drug ,Negocios, Administración - Abstract
Esta investigación se basa en la necesidad de desarrollar una nueva línea de producción de helados de fruta. Actualmente el tamarindo en el mercado nacional se puede encontrar en productos como en marcianos, cremoladas, ingrediente en la cocina, jaleas o como fruto. La propuesta del trabajo es innovadora, ya que se plantea la posibilidad de aprovechar la pulpa del fruto en helados como insumo industrial, debido a la alta concentración de ácido tartárico que se encuentra en la pulpa. Para el helado se utiliza hidrocoloides (goma guar y goma xantana) para brindarle una textura típica de los helados de fruta con leche, además de ser enriquecido con ácido ascórbico como fuente de vitamina C. Se realizó tres formulaciones de helados que en sus últimas etapas de proceso de mezclado y congelado fueron maquilados en una planta industrial de helados artesanales para tener mejores características sensoriales. Los helados fueron degustados y evaluados por medio de una encuesta para determinar el nivel de aceptación por medio de preguntas con medición de escala hedónica en relación con color, sabor, textura y apariencia general. En la percepción de los encuestados se observó la reacción de la sensación del nuevo sabor del ácido tartárico del tamarindo que, en combinación con el ácido ascórbico, ácido láctico de la leche resaltaba aún más la acidez del helado y los hidrocoloides utilizados que les proporcionaron la textura típica de un helado. Finalmente, el uso de en diferentes proporciones de las gomas guar y xantana determino que la tercera formulación con código 190 obtuvo el mayor nivel de aceptabilidad. This research is based on the need to develop a new production line for fruit ice cream. Currently, tamarind in the national market can be found in products such as marcianos, cremoladas, ingredients in the kitchen, jellies or as fruit. The proposal of the work is innovative, since it raises the possibility of taking advantage of the pulp of the fruit in ice cream as an industrial input, due to the high concentration of tartaric acid found in the pulp. For ice cream, hydrocolloids (guar gum and xanthan gum) are used to provide a typical texture of fruit ice cream with milk, in addition to being enriched with ascorbic acid as a source of vitamin C. Three ice cream formulations were made that in its last stage mixing and freezing processes were assembled at an industrial artisanal ice cream plant to have better sensory characteristics. Ice creams were tasted and evaluated by means of a survey to determine the level of acceptance by means of questions with hedonic scale measurement in relation to color, flavor, texture and general appearance. In the perception of the respondents, the reaction of the sensation of the new flavor of tartaric acid of tamarind was observed, which, in combination with ascorbic acid, lactic acid of milk further highlighted the acidity of the ice cream and the hydrocolloids used that gave them the Typical texture of an ice cream. Finally, the use of in different proportions of guar and xanthan gums determined that the third formulation with code 190 obtained the highest level of acceptability.
- Published
- 2019
4. Avaliação da qualidade de alisantes capilares contendo tioglicolato de amônio
- Author
-
Nájla Mohamad Kassab, Leonardo Prates Céspedes, James Cabral Vieira, Eveliny Letícia Moreira de Toledo, Alini Delevatti Ferreira, and Rúbia Adrieli Sversut
- Subjects
controle de qualidade ,capillary straightener ,produtos cosméticos ,Pulp and paper industry ,cosmetics products ,Alisante capilar ,chemistry.chemical_compound ,chemistry ,66 Ingeniería química y Tecnologías relacionadas/ Chemical engineering ,61 Ciencias médicas ,Medicina / Medicine and health ,General Earth and Planetary Sciences ,Thioglycolic acid ,Hair straightening ,quality control ,Ammonium thioglycolate ,General Environmental Science ,Mathematics - Abstract
Considerando a demanda do mercado por conhecimento na área de alisamento capilar, é importante realizar o controle de qualidade de cremes alisantes, a fim de garantir a segurança dos usuários e dos profissionais da área de estética. Desse modo, o objetivo deste trabalho foi avaliar a qualidade de cremes alisantes capilares que contêm em sua formulação o tioglicolato de amônio. Foram analisadas dez amostrasde cremes alisantes.Os testes realizados foram: doseamento do ácido tioglicólico ede amônia, análise das características organolépticas e determinação do pH. Quanto ao teor de ácido tioglicólico, três amostras classificadas como de uso geral apresentaram quantidade acima do permitido. No entanto, todas as amostras (de uso geral e profissional) foram aprovadas quanto ao teor de amônia. Em relação à avaliação de pH, todas as amostras apresentaram valores acima do limite permitido. O uso deprodutos com concentrações inadequadas de tioglicolato de amônio e pH acima do permitido podem gerar reações adversas ao consumidor e danos aos fios de cabelo. Sendo assim, verifica-se a importância do controle de qualidade em produtos cosméticos para proporcionar a segurança e eficácia dos mesmos. Considering the market demand for knowledge in the area of hair straightening, it is important to perform quality control procedures in smoothing creams in order to ensure the safety of its users and the aesthetic professionals. The objective of this study was to evaluate the quality of capillary straighteners that contain ammonium thioglycolate in their formula. Ten samples of hair straighteners were analyzed. Thetests performed were: dosing of thioglycolic acid and ammonia, analysis of organoleptic and pH determination. Regarding the thioglycolic acid content, three samples classified as of general use showed results above the allowed limit while all samples(both of general and professional use) were approved as far as the ammonia content goes. As for the pH evaluation, all samples had values above the established limit.The use of products with inadequate concentrations of ammonium thioglycolate and pH above the allowed limit can lead to adverse reactions to the consumer and cause damage to the hair strands. In conclusion, it is of the utmost importance to perform quality control procedures in these products in order to provide a safer experience while using them and avoid any possible adverse reactions.
- Published
- 2017
5. Optimization of castor seed oil extraction process using response surface methodology
- Author
-
Eusebio Ventura-Ramos, Mario E. Rodríguez-García, José Daniel Mosquera-Artamonov, A.A. Acosta-Osorio, Jose Fernando Vasco-Leal, Elsa Gutiérrez-Cortez, and I. Hernández-Ríos
- Subjects
0106 biological sciences ,mechanical extraction ,Yield (engineering) ,Ricinus communis L ,020209 energy ,Ingeniería ,02 engineering and technology ,01 natural sciences ,Endosperm ,Extractor ,010608 biotechnology ,0202 electrical engineering, electronic engineering, information engineering ,Operations management ,Response surface methodology ,Mathematics ,Castor Seed ,Extraction (chemistry) ,General Engineering ,food and beverages ,Diseño de experimentos ,Building and Construction ,Pulp and paper industry ,lcsh:TA1-2040 ,extracción mecánica ,Scientific method ,62 Ingeniería y operaciones afines / Engineering ,Yield limit ,lcsh:Engineering (General). Civil engineering (General) ,Experiment design - Abstract
This work focuses on the study of the oil extraction yield from castor seed using three different seed conditions: whole, minced and bare endosperm. Taguchi design was used to determine the contribution of the following parameters: seed condition, seed load in the extractor, temperature, and pressure. It was proved that it is necessary to introduce the whole seed and that the presence of the pericarp increases the extraction yield. The contribution of the control factors has an extraction yield limit. After determining which factors contributed to the process, these were left at their optimum levels aiming to reduce the control factors to only two. The complete analysis was done using a surface response methodology giving the best parameter for temperature and pressure that allows a better yielding mechanical extraction. The oil extraction yield can be kept up to 35% of the seed. Este trabajo se centra en el estudio de la extracción y la producción de aceite de semillas de ricino usando tres diferentes estados de semillas: entera, partida y sin testa. Se utilizó un diseño Taguchi para determinar la contribución de los siguientes parámetros: estado de las semillas, cantidad de semilla en el extractor, temperatura y presión. Se demostró que es necesario introducir la semilla entera para aumentar el rendimiento de la extracción. La contribución de los factores de control tiene un límite de extracción en la variable respuesta (rendimiento). Después de determinar cuáles factores contribuían altamente al proceso de extracción y cuáles no, se procedió a dejarlos en los niveles de mayor contribución con la finalidad de reducir el número de factores de control a dos. Posteriormente se utilizó la metodología de superficie de respuesta para la optimización del proceso, dando como resultado los niveles óptimos para los factores de control temperatura y presión. De acuerdo con las pruebas, el rendimiento de la extracción del aceite se puede mantener en un 35% de la semilla.
- Published
- 2016
6. A basic epistemic logic and its algebraic model
- Author
-
Hércules de Araujo Feitosa, Mariana Matulovic, and Ana Claudia de J. Golzio
- Subjects
Epistemic logic ,Knowledge and belief ,Algebraic logic ,Algebraic model ,Mathematics ,QA1-939 - Abstract
In this paper we propose an algebraic model for a modal epistemic logic. Although it is known the existence of algebraic models for modal logics, considering that there are so many different modal logics, so it is not usual to give an algebraic model for each such system. The basic epistemic logic used in the paper is bimodal and we can show that the epistemic algebra introduced in the paper is an adequate model for it.
- Published
- 2023
- Full Text
- View/download PDF
7. FIFTH REPORT ON STUDIES ON RADIOACTIVE PRECIPITATION
- Author
-
Martinez, A
- Published
- 1962
8. Automatic control with fuzzy logic of home-made beer production in maceration and cooking stages
- Author
-
Mariano Luján Corro and Víctor Vásquez Villalobos
- Subjects
cocción de malta ,automatic control ,Control automático ,lcsh:S ,home-made beer ,lógica difusa ,Soil Science ,cooking malt ,cerveza artesanal ,maceración ,Pulp and paper industry ,maceration ,lcsh:S1-972 ,Defuzzification ,Fuzzy logic ,lcsh:Agriculture ,Maceration (wine) ,Animal Science and Zoology ,fuzzy logic ,lcsh:Agriculture (General) ,Agronomy and Crop Science ,Mathematics - Abstract
The process of home-made beer production in the malt maceration and cooking stages was controlled automatically with fuzzy logic, across different performers considering the time and temperature of the process, using 2009LabVIEW. The equipment was mainly composed of three 20 L capacity stainless steel containers (water supply, maceration and cooking), an additional hops container, a data acquisition card (PIC 16F877a micro controller), three LM35 temperature sensors and 11 on/off type performers, which were governed by a total of 47 Mandani type fuzzy rules with trapezoidal membership functions, using the method of center area for the defuzzification. The performers: electrovalves (5), pumps (2), heaters (3) and a stirrer, in approximately 4 hours, were adequately controlled in their early maceration and cooking stages. The beer obtained by automatic control with fuzzy logic in the maceration and cooking stages, had the following characteristics: 0.98 g/cm3 of density, 3.9 of pH, total acidity expressed as 0.87% of lactic acid, 6.2oGL of alcoholic degree and 0.91% w/v of CO2 percentage. Se controló automáticamente con lógica difusa, el proceso de producción de cerveza artesanal en las etapas maceración y cocción de la malta; a través de diferentes actuadores y en función del tiempo y temperatura del proceso, utilizándose LabVIEW 2009. El equipo estuvo constituido principalmente de tres recipientes de acero inoxidable de 20 L de capacidad (dosificación de agua, maceración y cocción), un recipiente adicional para el lúpulo, una tarjeta de adquisición de datos (con micro controlador PIC 16F877a), tres sensores de temperatura LM35 y 11 actuadores de tipo on/off, los cuales fueron gobernados por un total de 47 reglas difusas tipo Mandani, con funciones de membresía trapezoidales, empleando para la defusificación el método del centro de área. Se controló adecuadamente en sus etapas de maceración y cocción, los actuadores: electroválvulas (5), bombas (2), calefactores (3) y un agitador; empleando un tiempo aproximado de 4 horas. La cerveza obtenida mediante el control automático con lógica difusa en las etapas de maceración y cocción, tuvo las siguientes características: densidad de 0.98 g/cm3 ; pH de 3.9; acidez total expresada como ácido láctico de 0.87%, grado alcohólico de 6.2 oGL y porcentaje de CO2 de 0.91% p/v.
- Published
- 2010
9. Extracción de aceite de café
- Author
-
Elkin Mauricio López Fontal
- Subjects
análisis sensorial ,engineering.material ,sensory analysis ,aceite de café ,volatile of the coffee ,fixed oil ,coffee pulp ,aceite fijo ,Food science ,industrialisation ,Aroma ,torta ,Mathematics ,biology ,Pulp (paper) ,General Engineering ,Significant part ,Building and Construction ,biology.organism_classification ,extrusión ,industrialización ,extrusion ,características organolépticas ,engineering ,volátiles del café ,Extraction methods ,sensory characteristics ,coffee oil - Abstract
En el presente trabajo se realiza la extracción de aceite de café mediante el método de extrusión. En dicho proceso se obtienen dos productos: el aceite de café y la torta. Para tal propósito se utilizó café tostado, el cual se caracteriza por poseer una elevada cantidad de compuestos odoríferos; es importante saber que un criterio significativo en la valoración de la calidad del café, es su aroma. Al extraer el aceite, una parte significativa del contenido aromático del café tostado, que varía según el método de extracción usado, sale con él. Es así como se obtiene un aceite fijo con una alta carga volátil, el cual presenta características organolépticas favorables. Al segundo producto que se obtiene, se le realizó análisis físico-químico en aras de mostrar sus bondades y propiedades particulares, y de acuerdo a los resultados obtenidos, es un producto que presenta un amplio potencial de utilización. The present work describes oil being extracted from toasted coffee by the extrusion method; two products are obtained from this process: coffee oil and pulp. Toasted coffee was used which has a high amount of sensorial compounds. It should be noted that a significant criterion in evaluating the quality of coffee lies in its aroma. When extracting oil from coffee, a significant part of toasted coffee’s aromatic content leaves with it, varying according to the extraction method. A fixed oil having a high volatile load is thus obtained, presenting favourable sensory characteristics. The pulp was physically and chemically analysed to show its benefit and particular properties and, according to the results so obtained, it is a product having potential usefulness.
- Published
- 2007
10. Calidad de las grasas de fritura en el sector de restauración de Andalucía
- Author
-
Gloria Márquez-Ruiz and M. C. Dobarganes
- Subjects
Quantization (signal processing) ,Organic Chemistry ,Polar compounds ,Mineralogy ,lcsh:TX341-641 ,Andalucía ,Food shops ,Used frying fat ,Pulp and paper industry ,Grasa de fritura ,Food inspection ,Oil quality ,Limit (mathematics) ,Sector de restauración ,lcsh:Nutrition. Foods and food supply ,Andalusia ,Fast food shops ,Food Science ,Mathematics ,Compuestos polares - Abstract
6 páginas. 9 tablas., [ES] En este trabajo se resumen los resultados de la evaluación de 174 muestras obtenidas por los Servicios de inspección en 143 establecimientos de preparación de alimentos de consumo inmediato. La determinación del porcentaje de compuestos polares Indicó que aproximadamente un 35% de las muestras tuvieron niveles de alteración superiores a los establecidos en la reglamentación española para desechar la grasa (25% de compuestos polares). Los niveles elevados de compuestos de polimerización y oxidación encontrados en un número significativo de muestras, demuestran la necesidad de mejorar la calidad de las grasas de fritura en este sector, [EN] In this paper, analytical results obtained from 174 frying oil samples collected from 131 fast food shops and restaurants by Food Inspection Services, are summarized. Quantization of polar compounds indicated that about 35% of the samples had alteration levels higher than the limit established in the Spanish regulation for discarding frying fats (25% polar compounds). High levels of oxidized triglycerides and polymeric compounds were found in a significant number of oils which demonstrated the need for improving frying oil quality in this sector., La Junta de Andalucía por la financiación aportada.
- Published
- 1995
11. Secado de maderas tropicales en estufas convencionales
- Author
-
David Zavala Zavala
- Subjects
Schedule ,especies tropicales ,Tropical wood ,Kiln ,Industria forestal ,Forestry ,Agrociencias ,Pulp and paper industry ,Water content ,secuelas de secado ,Mathematics ,Specific gravity - Abstract
Algunos de los problemas en el secado de la madera de especies tropicales en estufas convencionales se deben a la diversidad de sus propiedades tecnológicas, a la dificultad de contar con volúmenes adecuados de una misma especie que permitan adaptar los procesos de secado (secuelas) acordes a las características de sus maderas, y al alto costo del proceso que determina la capacidad rentable de las estufas y limita su utilización para secar volúmenes pequeños. Una alternativa para contrarrestar las limitantes señaladas, es formar grupos de especies semejantes, para integrar volúmenes acordes con las capacidades de las estufas, para aplicarles las mismas secuelas de secado. El presente trabajo se realizó con la finalidad de integrar grupos de especies de maderas tropicales que se pudiesen secar con una misma secuela para hacer más práctico su secado en estufas convencionales. Para este estudio se utilizó la madera aserrada de 33 especies tropicales, que se integraron en dos grupos con base en su densidad básica, 16 especies con densidad básica de 0.30 a 0.60 gr/cm3, y 17 de 0.60 a 0.90 gr/cm3. A cada grupo se le formuló una secuela de secado, que se evaluó en una estufa convencional, analizando los defectos de cada tabla, antes y después del secado (rajaduras, torceduras, acanalamiento, arqueamiento y encorvado). En general, las dos secuelas aplicadas a los dos grupos de especies generaron resultados favorables al no presentarse defectos significativos debidos al proceso de secado. En el grupo de especies de densidad básica menor de 0.60 gr/cm3, 10 se secaron más rápido que las otras 6, por lo que se podrían subagrupar para optimizar las estufas de secado aplicándoles otra secuela más rápida. Con la secuela utilizada para las especies con densidad básica mayor de 0.60 gr/cm3, 7 de ellas se secaron en aproximadamente la mitad del tiempo (10-14días) en relación a las otras 10, siendo posible subagruparlas también para optimizar las estufas. De no ser factible reagrupar a las especies dentro de cada categoría, se sugiere que para lograr un proceso lo más uniforme posible, coincidan los contenidos de humedad y las dimensiones de la madera en cada uno de los dos grupos de especies analizados en este trabajo.
- Published
- 2000
12. Comentari de llibres
- Author
-
C.P., M
- Subjects
00 General::00B Conference proceedings and collections of papers [Classificació AMS] ,Statistics ,Estadística ,Matemàtica ,Mathematics - Abstract
Comentari del llibre: Radhakrishna Rao, C. ESTADÍSTICA Y VERDAD: Aprovechando el Azar. Publicaciones y Promociones Universitarias. Barcelona, 1994. Comentari del llibre: Judith M. Tanur, Frederick Mosteller, William H. Kruskal, Erich L. Lehmann, Richard F. Link, Richard S. Pieters, Gerald R. Rising (editores). La estadística: Una guia de lo desconocido Alianza Editorial, SA. Madrid, 1992.
- Published
- 1994
13. Comentari de llibres
- Author
-
Cuadras, C.M. (Carlos Maria)
- Subjects
00 General::00B Conference proceedings and collections of papers [Classificació AMS] ,Statistics ,Estadística ,Matemàtica ,Mathematics - Abstract
Comentari de llibre: Rao, C. Radhakrishna. Statistics and truth. Council of Scientific and Industrial Research, New Delhi, 1989, 143 páginas, 15 tablas, 6 figuras.
- Published
- 1990
14. Two deductions systems for the Logic PM4N
- Author
-
Hércules de Araújo Feitosa, Romulo Albano de Freitas, and Marcelo Reicher Soares
- Subjects
Deduction systems ,Many-valued logics ,Tableaux ,Sequent calculus ,Mathematics ,QA1-939 - Abstract
The logic PM4N was introduced by Jean-Yves Beziau as a modal and 4-valued system. In this introductory paper, the author presented the system from a matrix logic with four values disposed in a Boolean algebra with a modal operator for the notion of necessity. From that matrix semantics, the paper shows some valid results and stresses some motivations of the matrix semantics and of the system PM4N. In this paper we develop some additional aspects of that logic and present two deductive systems for it, a simple system of tableaux and a sequent calculus.
- Published
- 2022
- Full Text
- View/download PDF
15. Generalized Graph Product and its Application on Generating Solutions of the Millennium n-Queens Problem
- Author
-
Oliver Kolossoski, Luiz Carlos Matioli, Elvis Manuel Rodriguez Torrealba, and Juliana Gomes da Silva
- Subjects
n-Queens Problem ,Graphs ,Graph Theory ,Graph Product ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
The generalized Kronecker graph product was introduced by Figueroa-Centeno et al. (2008). Later, Baca et al. (2018) used it for obtaining solutions of the n-queens problem on larger boards from solutions on smaller boards. In this paper, we generalize the graph product and the recent results by Baca et al. (2018), obtaining a larger class of solutions by knowing solutions on lower size boards in advance. We finalize the paper stating a couple of conjectures regarding conditions for obtaining composite solutions via graph product.
- Published
- 2022
- Full Text
- View/download PDF
16. The use of qualitative data analysis software: a mapping thesis in mathematics education
- Author
-
Priscila Gleden Novaes da Silva, Rosangela Ramon, Alcione Cappelin, Sandra Maria Tieppo, Fernanda Marchiori Grave, and Carbone Bruno Schmidt Krug
- Subjects
educação matemática ,pesquisa qualitativa ,caqdas ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
This paper characterizes the use of qualitative data analysis software in doctoral theses about Mathematics Education developed in Brazil, from 2010 to 2019, to support the choices of these software from paths already followed by other researchers. For this, a mapping was made to identify the theses and the aspects related to the use of these software in the field. The investigation retrieved 651 doctoral theses available in the Brazilian Digital Library of Thesis and Dissertations in which only 31 of them compose the corpus of this paper. This number evidences the little use of these software in the analyzed area. In the corpus, it was observed the predominance of the qualitative approach and the identification of nine different software, being three the most used: Atlas.ti, NVivo and CHIC, in that order. The adoption of software, as described by the authors, is linked to their potential regarding categorization, organization, visualization, data handling, time optimization and analysis facilitation and the possibility of enabling exploration of large volumes and diversity of data.
- Published
- 2021
- Full Text
- View/download PDF
17. Comercio, sobreexplotación laboral y ciclos en la periferia: una propuesta teórica y el caso ecuatoriano desde un modelo PVAR. || Trade, super-exploitation of labor power and cycles in the periphery: a theoretical proposal and the Ecuadorian case through a PVAR model
- Author
-
Cajas-Guijarro, John and Pérez-Almeida, Bryan
- Subjects
competencia real ,ventajas absolutas de costo ,sobreexplotación ,periferia capitalista ,tendencias histórico-cíclicas ,modelos pvar ,real competition ,absolute cost advantages ,super-exploitation ,capitalist periphery ,historical-cyclical trends ,pvar models ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
El presente artículo interpreta teóricamente cómo la competencia real capitalista internacional presiona a que en las sociedades periféricas los balances comerciales dependan de ventajas absolutas de costo basadas en una sobreexplotación laboral-natural, lo que crea dinámicas cíclicas en dichas sociedades. Para reforzar tal interpretación, el artículo toma como caso de estudio al capitalismo periférico ecuatoriano, sobre el que se presentan tendencias histórico-cíclicas de mediano y largo plazo, ejemplos de actividades económicas que al parecer sustentan sus superávits comerciales desde la sobreexplotación laboral-natural, y evidencia estadística de tendencias cíclicas de corto plazo a nivel sectorial, estimando un modelo PVAR sobre un panel de datos compuesto por 43 actividades económicas observadas en el período 2007-2016. Todos los resultados empíricos muestran la importancia de las ventajas absolutas de costo basadas en la sobreexplotación sobre los balances comerciales y el surgimiento de ciclos que refuerzan la condición dependiente del capitalismo ecuatoriano. || This paper theoretically interprets how international real capitalist competition pressures trade balances of the peripheral countries to depend on absolute cost advantages based on the super-exploitation of labor power and nature; dependence which creates cyclical dynamics within those countries. To reinforce such an interpretation, the paper takes as a study case the Ecuadorian peripheral capitalism, about which some historical-cyclical trends are presented as well as some examples of economic activities that seem to obtain their trade surplus through super-exploitation. Also, the paper estimates a PVAR model over a panel data of 43 economic activities observed during the period 2007-2016; from that estimation, it is found evidence of short-run cyclical dynamics among Ecuadorian economic activities. All the empirical results evidence the importance of the absolute cost advantages gained through super-exploitation of labor power and nature on the determination of trade balances and on the rise of cycles that reinforce the dependent condition of Ecuadorian capitalism.
- Published
- 2021
- Full Text
- View/download PDF
18. Myths and truths about the golden ratio: contributions of the use of historical information in the training of teachers
- Author
-
Ana Caroline Frigéri Barboza, Érica Gambarotto Jardim Bergamim, and Lucieli M. Trivizoli
- Subjects
história na educação matemática ,formação docente ,razão áurea ,mitos e verdades ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
This paper aims to identify how historical information can contribute to teacher education regarding to the Golden Ratio content. Therefore, in the theoretical framework, the relevance of the teacher's investigative stance and the contributions that the use of the History of Mathematics provides for the training of this professional are discussed, as well as about some aspects of the Golden Ratio. For this purpose, an implementation was carried out that involved the use of the History of Mathematics, in order to work on the Golden Ratio content with 4th year students of the Mathematics Degree course at a public educational institution. In this paper, the focus was directed to the study of myths and truths concerning the Golden Ratio during the planning of the implementation, as well as to the discussions of the students later. The research is qualitative in nature, based on participant observation for data collection and mixed categorization, for analysis of what had been constituted. We concluded that the use of historical information about the Golden Ratio content led to critical manifestations, so that the research teachers and students in initial training had the opportunity to deconstruct certain beliefs impregnated and disseminated in history.
- Published
- 2020
- Full Text
- View/download PDF
19. Exact and kernelization algorithms for Closet String
- Author
-
Omar Latorre Vilca
- Subjects
closest string problem ,combinatorial optimization ,exact algorithm ,fixed parameter algorithm ,kernelization ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 - Abstract
In this paper we address CLOSEST STRING problem that arises in web searching, coding theory and computational molecular biology. To solve it is to find a string that minimizes the maximum Hamming distance from a given set of strings. CLOSEST STRING is an NP-hard problem. This paper proposes two linear-time algorithms, one for the general case, a kernelization algorithm, and the other for three-strings, a linear-time algorithm called Minimization First Algorithm (MFA). A formal proof of the correctness and the computational complexity of the proposed algorithms are given.
- Published
- 2020
- Full Text
- View/download PDF
20. Analysis of the School Climate Scale in University Environments (ECEAU)
- Author
-
José Andrey Zamora-Araya, Karolayn Duarte-Abarca, Darcy Quesada-Varela, and Mónica Prado-Abarca
- Subjects
factor analysis ,higher education ,mathematics ,reliability ,school climate ,validity ,Science ,Science (General) ,Q1-390 - Abstract
[Objective] The aim of this paper is to verify the factorial structure of the School Climate Scale in University Environments (ECEAU) through structural equation models (SEM). [Methodology] A non-experimental cross-sectional study was carried out with a random sample of 381 students of the Universidad Nacional de Costa Rica (UNA), to whom the ECEAU was applied. A SEM model was proposed to confirm the factor structure of the scale and an exploratory factor analysis (EFA) was used to provide the basis for an alternative SEM model with a different structure. The reliability of scales was determined using McDonald’s omega, and the goodness of fit indexes used for the SEM models were the RMSEA, the CFI, the TLI and the GFI. The analysis was carried out using R software. [Results] The reliability of the scales in both models was adequate (w >0.70), although the metrics in the proposed model produced better results. The AFE suggested a different structure for the ECEAU, keeping some dimensions of the original structure and modifying and eliminating others. The goodness of fit indexes in both models were almost identical, with RMSEA=0.02, CFI=0.99, TLI=0.99 and GFI=0.98, which provides supporting evidence for the factorial structures proposed. [Conclusions] The original structure of the ECEAU was confirmed, while the differences in the results of the estimation and rotation methods generated another equally valid factorial structure for measuring the school climate construct in this university, and could be applied to other similar contexts.
- Published
- 2024
- Full Text
- View/download PDF
21. Episodes of interferences of War and Math in the Life and Work of Werner Fenchel
- Author
-
Tinne Hoff Kjeldsen
- Subjects
funções conjugadas convexas ,dualidade de fenchel ,história da programação matemática ,abordagem da história da matemática de múltiplas perspectivas. ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
In the present paper we study episodes of the life and work of the German-Danish mathematician Werner Fenchel from the perspective of the significance of the Second World War. On the one hand, we will see how the mathematical society, in particularly the mathematician Harald Bohr, helped Fenchel to set up an academic life in Copenhagen, Denmark. On the other hand, we will see how the organisation of scientists’ contribution to the war effort in the USA during the war, and the post war military financing of academic research in the post war period interfered with some of Fenchel’s mathematical work, especially his contribution to duality theory in nonlinear programming. As such, the study presented is this paper contributes to our understanding of how mathematics and conditions of a particular place and time interfere in the history of mathematics
- Published
- 2020
- Full Text
- View/download PDF
22. Estudio codisciplinar de la Matemática en la escuela secundaria: análisis de la gestión de una propuesta de aula para el estudio del crecimiento de plantas
- Author
-
Emanuel Berardi and Ana Rosa Corica
- Subjects
high school ,mathematics ,biology ,anthropological theory of didactic ,Education (General) ,L7-991 - Abstract
This paper presents the results of the management of a didactic device formulated by a Mathematics male and Biology female teacher from a secondary school in which they sought a codisciplinary study. Based on the Anthropological Theory of the Didactic, the results of an exploratory study that sought to characterize the management of a didactic device for the study of plant growth in secondary school are reported; In particular, we analyze the relevance of mathematical knowledge in its development. The main results indicate that the study enabled the protagonists to be the students: they formulated and answered questions, achieving autonomy and responsibility for the search for information in various media; however, mathematical knowledge did not occupy a prominent place during the study.
- Published
- 2023
- Full Text
- View/download PDF
23. Learning difficulties in Mathematics: some reflections
- Author
-
Wilson de Jesus Masola and Norma Suely Gomes Allevato
- Subjects
mathematics education ,teaching and learning ,learning difficulties ,Special aspects of education ,LC8-6691 ,Theory and practice of education ,LB5-3640 ,Mathematics ,QA1-939 - Abstract
The purpose of the present paper is to show how some current researches – published in papers and books – approach the difficulties in Mathematics learning. We intend to reflect on teaching and learning Mathematics by analysing some aspects that have been pointed out, especially about learning difficulties some students have in Mathematics area. We used the research qualitative approach with procedures of document analysis. At first, we described the meaning of the word ‘difficulty’, passing through learning difficulties and learning difficulties in Mathematics. The latest researches point the urgent need of a didactic overhaul in Mathematics teaching and maturation of all school communitiy, regardless the teaching level, concerning learning difficulties.
- Published
- 2019
- Full Text
- View/download PDF
24. Comentari de llibres
- Author
-
Corominas Subias, Albert|||0000-0002-4795-7761
- Subjects
00 General::00B Conference proceedings and collections of papers [Classificació AMS] ,Statistics ,Estadística ,Matemàtica ,Mathematics - Published
- 1988
25. Are the Sovereign CDS Premia Sound Estimators of the Stock Market Returns? Evidence from the Eurozone || ¿Son las primas CDS estimadores sólidos de los rendimientos del mercado de valores? Evidencia de la Eurozona
- Author
-
Navarrete Wic, Ana, Di Pietro, Filippo, and Martín Marín, José Luis
- Subjects
CDS premia ,stock market index return ,Granger causality test ,Eurozone ,primas CDS ,rendimiento de índices de mercado ,test de causalidad de Granger ,eurozona ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
In this paper, we explore the interconnection and existing relationships between the Sovereign Credit Default Swaps (henceforth, CDS) and the stock markets of the main European countries. Thus, the goal of this paper is to test if the CDS premia can predict the stock market returns of the most relevant economies within the Eurozone, so that, they serve as advanced indicators like mechanisms of price transmission. For this purpose, we apply the Granger Causality test to analyze ten main European stock markets from 2004 to 2016 by using daily data. Our hypothesis is proved to work for the largest economies with liquid CDS markets, whereas the transmission mechanism between CDS and stock prices is not so evident for the smallest ones. || En este documento, exploramos la interconexión y las relaciones existentes entre los Soberanos Credit Default Swaps (en adelante, CDS) y los mercados bursátiles de los principales países europeos. Por lo tanto, el objetivo de este documento es comprobar si las primas de CDS pueden predecir los rendimientos del mercado de valores de las economías más relevantes dentro de la zona euro, de modo que sirvan como indicadores avanzados como los mecanismos de transmisión de precios. Para este propósito, aplicamos la prueba de Causalidad de Granger para analizar los diez principales mercados bursátiles europeos desde 2004 a 2016 mediante el uso de datos diarios. Se ha demostrado que nuestra hipótesis funciona para las economías más grandes con mercados de CDS líquidos, mientras que el mecanismo de transmisión entre los CDS y los precios de las acciones no es tan evidente para los más pequeños.
- Published
- 2018
26. On the reachability tube of non-Newtonian first-order linear differential equations
- Author
-
Raúl Temoltzi-Ávila
- Subjects
α-generators ,non-Newtonian calculus ,non-Newtonian differential equations ,external perturbations ,reachability tube ,Mathematics ,QA1-939 - Abstract
A problem of practical interest is the determination of the reachability sets of ordinary differential equations with an external perturbation, or with a control. This problem can be extended to non-Newtonian spaces generated by continuous and injective functions α. This paper presents the problem of determining the reachability tube of a family of non-Newtonian first-order linear differential equations with an external perturbation, or with a control, that belongs to a set of functions that are α-continuous and α-bounded. The reachability tube is determined explicitly in three non-Newtonian spaces that are associated with three α-generators. The results obtained are illustrated numerically.
- Published
- 2023
- Full Text
- View/download PDF
27. Russell’s Paradox: a historical study about the paradox in Frege’s theories
- Author
-
Aline Germano Fonseca Coury and Denise Silva Vilela
- Subjects
Mathematic ,History ,Russell‟s Paradox ,Gottlob Frege ,Mathematics ,QA1-939 - Abstract
For over twenty years, Frege tried to find the foundations of arithmetic through logic, and by doing this, he attempted to establish the truth and certainty of the knowledge. However, when he believed his work wasdone, Bertrand Russell sent him a letter pointing out a paradox, known as Russell‟s paradox. It is often considered that Russell identified the paradox in Frege‟s theories. However, as shown in this paper, Russell, Frege and also George Cantor contributedsignificantly to the identification of the paradox. In 1902, Russell encouraged Frege to reconsider a portion of his work based in a paradox built from Cantor‟s theories. Previously, in 1885, Cantor had warned Frege about taking extensions of concepts in the construction of his system. With these considerations, Frege managed to identify the precise law and definitions that allowed the generation of the paradox in his system. The objective of this paper is to present a historical reconstruction of the paradox in Frege‟s publications and discuss it considering the correspondences exchanged between him and Russell. We shall take special attention to the role played by each of these mathematicians in the identification of the paradox and its developments. We also will show how Frege anticipated the solutions and new theories that would arise when dealing with logico-mathematical paradoxes, including but not limited to Russell‟s paradox.
- Published
- 2020
- Full Text
- View/download PDF
28. The Work of the Mathematician Leopoldo Nachbin (1922-1993) from FNFi
- Author
-
Clovis Pereira da Silva
- Subjects
Leopoldo Nachbin ,Mathematical Analysis ,FNFi ,Brazilian mathematical community ,Mathematics ,QA1-939 - Abstract
In this paper we discuss the professional activity of Leopoldo Nachbin (1922-1993) in the period in which he worked at National Faculty of Philosophy of the University of Brazil (FNFi/UB, in Portuguese) until his retirement by Institute of Mathematics of the Federal University of Rio de Janeiro (IM/UFRJ, in Portuguese). We identify the influence played by some mathematicians such as G. Mammana (1893-1980), L. Schwartz (1915-2002), A. Monteiro (1907-1980), A. Weil (1906-1998), J. Dieudonné (1906-1992), M. Stone (1903-1989), and A. A. Albert (1905-1972) in the professional training of L. Nachbin. We also address the serious difficulties he encountered in the Mathematics Department of FNFi when he was entered in the competition, opened in 1950, for the post of full Professor (Professor Catedrático) of Mathematics and Superior Analysis of FNFi. We emphasize in the paper, that the period from 1947 to the 1960s marks the most creative and productive phase in terms of scientific research in the academic life of L. Nachbin.
- Published
- 2020
- Full Text
- View/download PDF
29. New Isothermic surfaces in S3
- Author
-
Armando M. V. Corro and Marcelo Lopes Ferro
- Subjects
isothermic surfaces ,ribaucour transformations ,dupin surfaces ,calapso equation ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 - Abstract
In this paper, we consider a method of constructing isothermic surfaces in S3 based on Ribaucour transformations. By applying the theory to the flat torus, we obtain two family of complete isothermic surfaces in S3. One four-parameter family of complete isothermic surfaces that contains n-bubble surfaces inside and outside of the torus. We also get another four-parameter of complete isothermic surfaces which are Dupin surfaces. As aplication we obtain explicit solutions of the Calapso equation.
- Published
- 2023
- Full Text
- View/download PDF
30. ϵ-isothermic surfaces in pseudo-Euclidean 3-space
- Author
-
Armando M. V. Corro, Carlos M. C. Riveros, and Marcelo L. Ferro
- Subjects
dupin surfaces ,isothermic surfaces ,lines of curvature ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 - Abstract
In this paper, we provide a class of surfaces called ϵ-isothermic surface in the pseudo-Euclidean 3-space and we introduce the pseudo-Calapso equation. We prove that for each ϵ-isothermic surface, we can associate two solutions to the pseudo-Calapso equation. In particular, we associate solutions to the Calapso, Zoomeron and Davey-Stewartson III equations. In sequence, we classify the Dupin surfaces in pseudo-Euclidean 3-space having distinct principal curvatures and provide explicit coordinates for such surfaces. As application of the theory, we obtain explicit solutions to the pseudo-Calapso equation and from these solutions, we provide new explicit solutions of the Zoomeron and Davey-Stewartson III equations. Moreover, we also provide explicit solutions to these equations that depend on ϵ2−holomorphic functions.
- Published
- 2023
- Full Text
- View/download PDF
31. El contagio en el fracaso empresarial como consecuencia de la proximidad geográfica: un análisis con los estadísticos join-count aplicado al sector servicios || The Contagion on Business Failure by the Geographical Proximity: An Analysis with the Join-Count Tests in the Service Sector
- Author
-
Rodríguez Fuentes, Christian Camilo, Maté Sánchez-Val, María Luz, and López Hernández, Fernando A.
- Subjects
autocorrelación espacial ,fracaso empresarial ,tests join-count ,spatial autocorrelation ,business failure ,join-count test ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
El objetivo de este trabajo es contrastar el efecto de contagio en el fracaso empresarial como consecuencia de la proximidad geográfica entre empresas del mismo sector. Para ello, desarrollamos una aplicación empírica basada en el análisis de los estadísticos espaciales join-count sobre una muestra de empresas del sector servicios en el municipio de Murcia (España). Los resultados muestran un patrón de autocorrelación espacial significativo, de tal forma que la probabilidad de fracaso de una empresa no solo depende de sus características internas sino también de su proximidad a otras empresas fracasadas. Estos resultados pueden ser un interesante punto de partida para el desarrollo de análisis que incluyan los efectos de la proximidad geográfica entre empresas en la literatura de fracaso empresarial. || This paper aims to contrast the spillover effects in business failure derived from the geographic proximity among firms of the same sector. To get this purpose, we develop an empirical application based on the analysis of the join-count statistics on a sample of firms of service sector located in the municipality of Murcia (Spain). Our results show significant spatial autocorrelation pattern, therefore, the probability of failure in a firm not only depends on its internal characteristics, but also on the situation of failure of its vicinity peer companies. These results can be an interesting starting point in the development of papers which consider the interdependence effects among closer peer companies in business failure literature.
- Published
- 2017
32. Elección contable para la valoración de las inversiones inmobiliarias. Contribución de las técnicas de minería de datos para determinar patrones de decisión || Accounting Choice for Measuring Investment Properties. Data Mining Techniques Contribution to Determine Decision Patterns
- Author
-
de Vicente Lama, Marta, Molina Sánchez, Horacio, Ramírez Sobrino, Jesús N., and Torres Jiménez, Mercedes
- Subjects
elección contable ,valor razonable ,NIIF ,redes neuronales ,árboles de decisión ,accounting choice ,fair value ,IFRS ,neural networks ,decision trees ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
La normativa contable internacional ofrece con la Norma Internacional de Contabilidad 40 (NIC 40) "Inversiones inmobiliarias" un caso referente para investigar la decisión que toman las empresas cuando se les ofrece el valor razonable o el coste histórico como criterios alternativos de valoración. En este trabajo aprovechamos la oportunidad que ofrece esta norma para aportar evidencia adicional en un contexto multinacional y multisectorial sobre cuáles son los motivos que explican la elección contable. Además, en este trabajo introducimos y comparamos el uso de las redes neuronales artificiales y los árboles de decisión, con el objetivo de evaluar la capacidad predictiva de estas metodologías, frente a la tradicionalmente utilizada regresión logística para la resolución de problemas de clasificación en este área. Los resultados de la clasificación indican que tanto las redes neuronales como los árboles de decisión pueden ser una alternativa interesante a los métodos clásicos estadísticos como la regresión logística. En particular, las dos metodologías mostraron una mayor capacidad predictiva frente a la regresión logística aunque no se encontraron diferencias significativas entre ambas. || International Accounting Standard 40 (IAS 40 - Investment properties) offers an ideal setting for research on accounting choice as it represents a paradigmatic case choosing between the fair value and the historical cost as the measurement criteria. In this paper, we take the opportunity of this standard to provide additional evidence in a multinational and multi-context on the determinants that explain the accounting choice. Furthermore, in this paper, we introduce and compare the use of artificial neural networks and decision trees in order to assess the predictive capability of these methodologies, compared to other techniques commonly used to solve classification problems in this area such as the logistic regression. The classification results indicate that both neural networks and decision trees can be an interesting alternative to classical statistical methods such as the logistic regression. In particular, both methods outperformed the logistic regression in terms of predictive ability, although no significant differences were found between both.
- Published
- 2017
33. Stochastic Frontier Models with Dependent Errors based on Normal and Exponential Margins || Modelos de frontera estocástica con errores dependientes basados en márgenes normal y exponencial
- Author
-
Gómez-Déniz, Emilio and Pérez-Rodríguez, Jorge V.
- Subjects
technical and cost efficiencies ,stochastic frontier ,marginal distribution ,dependence ,Sarmanov model ,eficiencias técnica y de coste ,frontera estocástica ,distribución marginal ,dependencia ,modelo de Sarmanov ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
Following the recent work of Gómez-Déniz and Pérez-Rodríguez (2014), this paper extends the results obtained there to the normal-exponential distribution with dependence. Accordingly, the main aim of the present paper is to enhance stochastic production frontier and stochastic cost frontier modelling by proposing a bivariate distribution for dependent errors which allows us to nest the classical models. Closed-form expressions for the error term and technical efficiency are provided. An illustration using real data from the econometric literature is provided to show the applicability of the model proposed. || Continuando el reciente trabajo de Gómez-Déniz y Pérez-Rodríguez (2014), el presente artículo extiende los resultados obtenidos a la distribución normal-exponencial con dependencia. En consecuencia, el principal propósito de este artículo es mejorar el modelado de la frontera estocástica tanto de producción como de coste proponiendo para ello una distribución bivariante para errores dependientes que nos permitan encajar los modelos clásicos. Se obtienen las expresiones en forma cerrada para el término de error y la eficiencia técnica. Se ilustra la aplicabilidad del modelo propouesto usando datos reales existentes en la literatura econométrica.
- Published
- 2017
34. A Filter-SQP strategy for training Support Vector Machine models
- Author
-
Tiago Lino Bello, Luiz Carlos Matioli, Lucas Garcia Pedroso, and Daniela Miray Igarashi
- Subjects
support vector machine ,training ,optimization ,filter method ,sequential quadratic programming ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
This paper introduces a filtering strategy for addressing optimization problems arising in binary Support Vector Machine classification. The training optimization problem aims to solve the dual formulation which involves a quadratic objective function subjected to a linear and box constraints. Our approach employs a Filter algorithm with Sequential Quadratic Programming iterations that minimize the quadratic Lagrangian approximations. Notably, we utilize the exact Hessian matrix in our numerical experiments to seek the desired classification function. Moreover, we present a Filter algorithm combined with the Augmented Lagrangian method aiming to accelerate the algorithm convergence. To substantiate our method's effectiveness, we conduct numerical experiments through MATLAB, comparing outcomes with alternative methodologies detailed in existing literature. Numerical experiments shows that the Filter--SQP combined with Augmented Lagrangian method is competitive and efficient method compared with an interior-point based solver and LIBSVM software in relation of classification metrics and CPU-time.
- Published
- 2023
- Full Text
- View/download PDF
35. [Importance of stimulation of the areas involved in the mathematical processing: effects on neurodevelopment].
- Author
-
Arch-Tirado E, Lino-González AL, and Alfaro-Rodríguez A
- Subjects
- Humans, Language, Brain growth & development, Learning, Mathematics
- Abstract
This paper aims to discuss and analyze the role of mathematics in neurodevelopment, for which discusses the historical, ontogenetic and physiological bases involved. The methodology of this paper is a deductive analysis, describing the use of mathematics in ancient cultures to the specialization of brain regions. Sensory perceptions are useful for the acquisition and development of cortical functions thus sensory stimulations is essential for the maturation of specialized neurologic functions.
- Published
- 2013
36. [Prediction of mathematics achievement: effect of personal, socioeducational and contextual variables].
- Author
-
Rosário P, Lourenço A, Paiva O, Rodrigues A, Valle A, and Tuero-Herrero E
- Subjects
- Adolescent, Adolescent Behavior, Child, Child Behavior, Cognition, Female, Goals, Humans, Learning, Male, Motivation, Personal Autonomy, Self Efficacy, Social Environment, Time Management, Educational Status, Forecasting, Mathematics education, Models, Theoretical, Psychology, Adolescent, Psychology, Child
- Abstract
Based upon the self-regulated learning theoretical framework this study examined to what extent students' Math school achievement (fifth to ninth graders from compulsory education) can be explained by different cognitive-motivational, social, educational, and contextual variables. A sample of 571 students (10 to 15 year old) enrolled in the study. Findings suggest that Math achievement can be predicted by self-efficacy in Math, school success and self-regulated learning and that these same variables can be explained by other motivational (ej., achievement goals) and contextual variables (school disruption) stressing this way the main importance of self-regulated learning processes and the role context can play in the promotion of school success. The educational implications of the results to the school levels taken are also discussed in the present paper.
- Published
- 2012
37. INFINITY AND MATHEMATICAL TRUTH
- Author
-
Edo Pivčević
- Subjects
mathematics ,truth ,discreteness ,continuity ,incommensurability ,Social Sciences ,History (General) ,D1-2009 - Abstract
The paper discusses the problem of infinity with a special reference to mathematical truth. The roots of this problem, in a sense, go back to early efforts to provide a rational account of the phenomena of change, and the phenomenon of motion in particular, and, in connection with this, to the attempt to cast light on the complex relationship between continuity and discreteness. If mathematics is to serve as a tool of a rational description of the world, is it possible to construct a mathematical model of phenomenal continuity? This question was raised already by Zeno when the Pythagorean hypothesis of the essential ‘granularity’ of the world began to crumble as a result of the discovery of incommensurable magnitudes. The discovery of incommensurable magnitudes, and along with it the discovery of irrational numbers, produced well-known paradoxes and gave rise to the question to what extent, if at all, mathematics can deliver a ‘metaphysical’ description of the world. In more recent times, the idea of infinity was built into the infinitesimal calculus which became the foundation of the mathematical description of nature, but the metaphysical questions have not gone away. The issues surrounding actual and potential infinity continue to be the subject of intense debates. Whereas some recognise only potential infinities, others, like Georg Cantor, accept actually existent infinities. This is directly connected with the question of mathematical truth, which, according to the Platonist tradition exists as objectively given. The paper argues that the Cantorian transfinite set theory cannot withstand criticism, and that rather than providing a (metaphysical) description of reality mathematics merely offers possible models in terms of which the world might be better or more conveniently interpreted. The so-called ‘mathematical truth’ reduces to the question of ‘correctness’, viz. whether a given mathematical proposition does or does not follow from given premises.
- Published
- 2017
38. On the existence of a priori bounds for positive solutions of elliptic problems, I
- Author
-
Rosa Pardo
- Subjects
A priori estimates ,subcritical nonlinearity ,moving planes method ,Pohozaev identity ,critical Sobolev hyperbola ,biparameter bifurcation ,Mathematics ,QA1-939 - Abstract
This paper gives a survey over the existence of uniform L∞ a priori bounds for positive solutions of subcritical elliptic equations (P)p -\Delta_p u =f(u), in \Omega, u = 0, on \partial\Omega widening the known ranges of subcritical nonlinearities for which positive solutions are a-priori bounded. Our arguments rely on the moving planes method, a Pohozaev identity, W1,q regularity for q > N, and Morrey’s Theorem. In this part I, when p = 2, we show that there exists a-priori bounds for classical, positive solutions of (P)2 with f(u) = u2∗−1/[ln(e + u)]α, with 2∗ = 2N/(N − 2), and α > 2/(N − 2). Appealing to the Kelvin transform, we cover non-convex domains. In a forthcoming paper containing part II, we extend our results for Hamiltonian elliptic systems (see [22]), and for the p-Laplacian (see [10]). We also study the asymptotic behavior of radially symmetric solutions uα = uα(r) of (P)2 as α → 0 (see [24]).
- Published
- 2019
39. [Comparative analysis of the efficacy of a playful-narrative program to teach mathematics at pre-school level].
- Author
-
Gil Llario MD and Vicent Catalá C
- Subjects
- Audiovisual Aids, Child, Educational Measurement, Humans, Models, Educational, Play and Playthings, Program Evaluation, Child, Preschool education, Mathematics, Natural Science Disciplines education, Teaching methods
- Abstract
Comparative analysis of the efficacy of a playful-narrative program to teach mathematics at pre-school level. In this paper, the effectiveness of a programme comprising several components that are meant to consolidate mathematical concepts and abilities at the pre-school level is analyzed. The instructional methodology of this programme is compared to other methodologies. One-hundred 5-6 year-old children made up the sample that was distributed in the following conditions: (1) traditional methodology; (2) methodology with perceptual and manipulative components, and (3) methodology with language and playful components. Mathematical competence was assessed with the Mathematical Criterial Pre-school Test and the subtest of quantitative-numeric concepts of BADyG. Participants were evaluated before and after the academic course during which they followed one of these methodologies. The results show that the programme with language and playful components is more effective than the traditional methodology (p<.000) and also more effective than the perceptual and manipulative methodology (p<.000). Implications of the results for instructional practices are analyzed.
- Published
- 2009
40. La decisión de escuchar música grabada en Colombia. Un enfoque microeconométrico || The decision of listening to recorded music in Colombia. A microeconometric approach
- Author
-
Bermúdez Triviño, José A., Medina Hurtado, Lina M., and Aguado Quintero, Luis F.
- Subjects
música grabada ,participación cultural. modelos probit ,recorded music ,cultural participation ,probit models ,Colombia ,Applied mathematics. Quantitative methods ,T57-57.97 ,Mathematics ,QA1-939 ,Business ,HF5001-6182 - Abstract
El artículo tiene por objetivo determinar las variables que pueden condicionar la decisión observable de un individuo con respecto a escuchar música grabada en Colombia. Para ello, se estiman modelos probit usando microdatos de la Encuesta de Consumo Cultural 2008. Los resultados muestran que individuos con educación superior, que toman cursos y talleres culturales y se sitúan en los niveles medios y altos de estrato socio-económico presentan la mayor probabilidad de escuchar música grabada. Igualmente, se encuentra que individuos que se auto-reconocen como afro-descendientes se asocian con una menor probabilidad de escuchar música grabada. El artículo contribuye a la escasa literatura empírica sobre los determinantes de la participación cultural en países de América Latina. || This paper purpose is to determine the variables that could influence the individual observable decision of listening to recorded music in Colombia. To do so, probit models are estimated using micro-data from the Encuesta de Consumo Cultural 2008 [Cultural Consumption Survey 2008 ]. Empirical results show that individuals with higher education that take cultural courses and workshops, and belong to medium and high socio-economic strata, are those with the highest probability of listening to recorded music. Additionally, self-identied individuals as African-Colombian-descendent present the lowest likelihood. This paper contributes to the scarce empirical literature on the determinants of cultural participation in Latin America.
- Published
- 2016
41. An approach to the design of mathematical task sequences: Conceptual learning as abstraction
- Author
-
Martin A. Simon
- Subjects
Abstracción reflexiva ,Ingeniería didáctica ,Tareas matemáticas ,Teoría de aprendizaje ,Theory and practice of education ,LB5-3640 ,Mathematics ,QA1-939 - Abstract
This paper describes an emerging approach to the design of task sequences and the theory that undergirds it. The approach aims at promoting particular mathematical concepts, understood as the result of reflective abstraction. Central to this approach is the identification of available student activities from which students can abstract the intended ideas. The approach differs from approaches in which learning to solve the problem posed is the intended learning. The paper illustrates the approach through data from a teaching experiment on division of fractions.
- Published
- 2016
42. Reassembling mathematical practices: a philosophicalanthropological approach
- Author
-
Karen François and Eric Vandendriessche
- Subjects
Wittgenstein ,Language game ,Family resemblance ,Mathematical practices ,String figuremaking ,Sand drawings ,Mathematics and Culture ,Special aspects of education ,LC8-6691 ,Science ,Mathematics ,QA1-939 - Abstract
In this paper we first explore how Wittgenstein’s philosophy provides a conceptual tools to discuss the possibility of the simultaneous existence of culturally different mathematical practices. We will argue that Wittgenstein’s later work will be a fruitful framework to serve as a philosophical background to investigate ethnomathematics (Wittgenstein 1973). We will give an overview of Wittgenstein’s later work which is referred to by many researchers in the field of ethnomathematics. The central philosophical investigation concerns Wittgenstein’s shift to abandoning the essentialist concept of language and therefore denying the existence of a universal language. Languages—or ‘language games’ as Wittgenstein calls them—are immersed in a form of life, in a cultural or social formation and are embedded in the totality of communal activities. This gives rise to the idea of rationality as an invention or as a construct that emerges in specific local contexts. In the second part of the paper we introduce, analyse and compare the mathematical aspects of two activities known as string figure-making and sand drawing, to illustrate Wittgenstein’s ideas. Based on an ethnomathematical comparative analysis, we will argue that there is evidence of invariant and distinguishing features of a mathematical rationality, as expressed in both string figure-making and sand drawing practices, from one society to another. Finally, we suggest that a philosophical-anthropological approach to mathematical practices may allow us to better understand the interrelations between mathematics and cultures. Philosophical investigations may help the reflection on the possibility of culturally determined ethnomathematics, while an anthropological approach, using ethnographical methods, may afford new materials for the analysis of ethnomathematics and its links to the cultural context. This combined approach will help us to better characterize mathematical practices in both sociological and epistemological terms.
- Published
- 2016
43. [Attitudes, learning experience and performance in mathematics: gender differences].
- Author
-
Barbero García MI, Holgado Tello FP, Vila Abad E, and Chacón Moscoso S
- Subjects
- Adolescent, Data Interpretation, Statistical, Female, Humans, Male, Sex Factors, Time Factors, Attitude, Learning, Mathematics
- Abstract
In this paper, we used the data of Mathematics achievements from the sample of 13- year-old Spanish boys and girl who took part in the Second National Assessment of Educational Progress, carried out by the Educational Testing Service. With the aim of identifying variables related to high achievement, our goals are: 1) to analyse whether there are significant differences in 13-year-old Spanish boys and girls in their attitudes towards mathematics, their study strategies, and their performance; 2) to analyse the influence of their attitudes and study strategies on their performance, and to examine whether these relations are the same in boys and girls; 3) to propose a theoretical model that explains the relationship among the variables defined by means of structural equation modelling. The results show that: a) there are significant differences between boys and girls in the variables studied; b) it is not possible to reject the proposed model that relates study strategies and attitudes towards performance in mathematics; and c) the model tends to be stable both among boys and girls.
- Published
- 2007
44. Researching for a mathematics rhizocurrere for culturally responsive teaching
- Author
-
Georgios Kyriakopoulos and Charoula Stathopoulou
- Subjects
Roma ,rhizocurrere ,rhizome ,Roma students ,mathematics ,Philosophy (General) ,B1-5802 ,Science ,Social sciences (General) ,H1-99 - Abstract
This paper focuses on the reconceptualization of the mathematics curriculum with Roma students presenting a nomadic exploration of the mathematics teaching. An alternative, methodologically privileged, model is proposed which identifies the opportunity for an alternative curriculum from within rather than from a distance. The main aim of the research is to indicate how researching for a curriculum reconceptualization might be enlightened by thinking rhizomatically where common spaces of in-between are constructed by a confabulative conversation between Roma students and the researcher who takes up a nomadic position. Roma students, educational becoming and subjectivities at the level of individuals and situations involved both interact as elements of an unpredictably evolving rhizome which consists of discontinuity, rupture and constantly emerging multiplicities.
- Published
- 2023
- Full Text
- View/download PDF
45. Sea-ing into humanscapes and equal liberty. The sociocultural-ecological relations into mathematics education
- Author
-
Mônica Mesquita
- Subjects
sea-ing motion perspective ,humanscapes ,equal liberty ,human mathematics relations ,counter-colonization of mathematical knowledge ,Mathematics ,QA1-939 ,Education - Abstract
There are bottom-up movements imbued with different praxis into mathematics education, which promotes the combination of heterogeneous values – inserted in social participation, cultural diversity, and reconnection with the Pachamama. Such movements have been developed by collectives of thinkers constituted by members with the most diverse knowledge. Embedded in a counter-colonization resistance by a persistence of the horizontality into the educational process, this paper aims to dialogue around sociocultural-ecological connections experienced in processes of critical ethnography developed in community mathematics education of ascending movements in Brazil and Portugal. The aim is to promote a path in which an old necessity to share the human topological ontology constructed and reconstructed in five different ethnographic fields, in which both the humanscapes and the equal liberty, sea-ing in indissociable lines, evidenced the oppression of schooling mathematics knowledge over the sociocultural-ecological human relations. Such sea-ing motion is proposed as an alternative path to demystify, re-signify, or only complement, the how human being perceives itself in its surroundings and brings for the most diverse mathematics education processes – formal_informal_non-formal, the importance of the situationality of the apprentice as well as the relevance of the intellectual justice towards equitable societies.
- Published
- 2023
- Full Text
- View/download PDF
46. Creating an innovative primary school Mathematics teaching environment: The case of Eastern Cape Province
- Author
-
Zingiswa Mybert Monica Jojo
- Subjects
Innovation ,Mathematics ,Teaching ,Collaboration ,Technology ,Environment ,Special aspects of education ,LC8-6691 - Abstract
Today’s learner population is diverse and replete with situational, personal, emotional, and learning challenges that inevitably find their way into the mathematics classroom. This paper draws from a project intended to investigate issues of classroom practice in mathematics used, extrapolate, or improve on them for the better development of teachers and learners’ meaningful understanding of intermediate and senior phase mathematics in a district in the Eastern Cape province of South Africa during the COVID-19 lockdown period. A qualitative approach in which three teachers were interviewed has been used. Results indicated that teachers benefited from technology informed collaborations with other teachers on WhatsApp groups and used those experiences to promote learning in their own environments. Moreover, it was observed that teachers modified their instructional strategies, shared mathematics teaching practices through WhatsApp, and engagements using online tools easily accessible to their learners.
- Published
- 2023
- Full Text
- View/download PDF
47. An Introduction to Spinor Differential and Integral Calculus from q− Lorentzian Algebra
- Author
-
Julio Cesar Jaramillo Quiceno
- Subjects
q− Lorentz algebra ,q− spinor derivative and integral ,differential spinor equation ,Mathematics ,QA1-939 - Abstract
We introduce in this paper the spinor differential and integral calculus from q- lorentzian algebra, differential spinor equation and lorentzian q− spinor differential equation. Finally a few comments.
- Published
- 2023
- Full Text
- View/download PDF
48. Ramath: mathematics teaching app
- Author
-
Amadeo José Argüelles Cruz, Hiram David Cortés Díaz, and Octavio Elias Piñal Ramírez
- Subjects
augmented reality ,immersive technologies ,head mounted display ,mathematics ,gamification ,education ,Education ,Technology - Abstract
This paper presents the Ramath mobile application (app) and its second version using a head mounted display (HMD). Both use augmented reality with the support of game play mechanics in a non-game application, oriented to help 12 to 15 years old students (male and female) to learn several math subjects. We associate concepts such as «gamification» and «problem-based learning» (PBL) within the app, making the subjects much more interesting to the students and encouraging them to be fearless of math by taking advantage of the humans' psychological predisposition to engage in gaming. With the collected information from the research and the help of a predictive algorithm, we try to show how much the technology can help in education.
- Published
- 2023
- Full Text
- View/download PDF
49. Caracterización del significado de múltiplo por maestros en formación
- Author
-
Ángel López, Encarnación Castro, and María C. Cañadas
- Subjects
Conocimiento matemático ,Divisibilidad ,Maestros en formación ,Múltiplo ,Theory and practice of education ,LB5-3640 ,Mathematics ,QA1-939 - Abstract
This paper is part of a wider study focused on divisibility. Participants were prospective elementary teachers. One of the aims of the research is to characterize the meanings of multiple shown by prospective teachers. In this paper, we present the results concerning this aim. We analyse the productions of 37 prospective elementary teachers collected in a practice session, designed and developed in the context of a teaching experiment. We characterize the meanings through the following elements of the didactic analysis: conceptual structure, representation systems and phenomenology. Prospective teachers showed mostly three meanings of multiple: product, relationship and dividend in an exact division.
- Published
- 2016
50. Subjectivities in Research in Science Education presented at the National Symposium of Physics Education of the last five years
- Author
-
Sérgio Choiti Yamazaki and Josiane Fernandes Cruz
- Subjects
subjetividade no ensino ,SNEF ,pesquisas em educação científica ,Special aspects of education ,LC8-6691 ,Mathematics ,QA1-939 - Abstract
This paper presents the results of a survey conducted in a public university in the country, which aimed to identify the presence elements ordinarily related to subjective phenomena, in the works published in National Symposium of Physics Education, an event that provides meeting between teachers, researchers and students from around the country. The elements to which we have referred are found in contemporary didactic and pedagogical proposals, because it is identified that purely cognitive or even cultural rights are not sufficient to understand the phenomena that happen in the classroom, or more broadly, in education as a whole. The analysis contemplated the publications of the past 3 symposia, and the results infer a small increase of citations of these elements. However, this growth must be questioned because the quotes are made in isolation, not being taken to support the analysis of the authors. In addition, this research also shows that the presence of these elements is very small compared with the total number of papers published in the events.
- Published
- 2015
- Full Text
- View/download PDF
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.