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Cálculo analítico de la potencia nominal en transmisión por correa dentada
González Rey,Gonzalo; García Domínguez,Maria Eugenia;
Ingenier?-a Mec??nica , 2010,
Abstract: in the current context of the international standards, there is not enough information to face the analytical calculation of the power rating of synchronous belt drives. it's practical habitual to use power rating diagrams or tables offered by belt manufacturers with limitation to implement computational procedures, and for calculating ratings which are out of the range of speed or number of teeth of pulleys conditions shown in the power rating diagrams or tables. for such a reason, this article presents some useful results and detailed formulae based in iso standard 5295 for power ratings, together with appropriate correction terms and analytical factors used in the calculation of power rating of synchronous belt drives. formulae and analytical factors for the study and design of synchronous belt transmissions are presented. moreover, some results of optimal values of belt velocity for maximum power capacity are offered. results presented in this paper were the bases for an informative proposal annexed to the cuban standard nc-iso 5295:2010 referred to the analytical calculation of power ratings in synchronous belt drives.
An analytical calculation of the power rating of v-belt Estimación analítica de la potencia mecánica nominal transmisible por correa trapecial
Gonzalo González Rey,Maria Eugenia García Domínguez
Revista Cubana de Ingeniería , 2010, DOI: 10.1234/rci.v1i1.9
Abstract: In the current context of the International Standards, there is not enough information to face the analytical calculation of the power rating of V-belts. It's practical habitual to use power rating diagrams or tables offered by belt manufacturers with limitation to implement computational procedures, and for calculating ratings which are out of the range of speed or diameter conditions shown in the power rating diagrams or tables. For such a reason, this article presents some useful results and detailed formulae based in ISO Standard 5292 for power ratings, together with appropriate correction terms and analytical factors used in the calculation of power rating of V-belts. Formulae and analytical factors are generally acceptable for the study and design of V-belt transmissions with two pulleys. Moreover, some results of optimal values of belt velocity for maximum power capacity are presented. Results presented in this paper were the bases for an informative proposal annexed to the Cuban Standard NC-ISO 5292:2009 referred to the analytical calculation of power ratings in belt transmissions. En el contexto de las actuales normas internacionales, no se dispone de información suficiente para enfrentar el cálculo analítico de la potencia transmisible por una correa trapecial y en estos casos es práctica habitual recurrir a limitados procedimientos gráficos o tabulados que son ofertados por fabricantes de correas en catálogos técnicos o libros de texto. Esta situación restringe el desarrollo de un cálculo computacional o la estimación de la potencia nominal de las correas para casos no contemplados en los datos declarados en la literatura especializada. Por tal motivo, y con el interés de difundir el cálculo analítico de la potencia nominal en transmisiones por correas trapeciales, se proporcionan en este trabajo fórmulas de potencias nominales generalmente aceptables y también términos y factores de corrección apropiados para el estudio y dise o de transmisiones por correas trapeciales con dos poleas. Además, se muestran algunos resultados asociados al problema de la determinación de la velocidad óptima de la correa para máxima capacidad de potencia. Estos resultados fueron base de una propuesta incorporada a la norma cubana NC-ISO 5292:2009 referida al cálculo de las potencias nominales de correas trapeciales clásicas y estrechas.
Rational Design of Spur Gears Directed to Increase Efficiency and Decrease Loss by Friction Dise o racional de engranajes cilíndricos orientado a aumentar eficiencia y disminuir pérdidas por fricción
Gonzalo González Rey,Alejandra García Toll,Maria Eugenia García Domínguez
Revista Cubana de Ingeniería , 2010, DOI: 10.1234/rci.v1i3.32
Abstract: External parallel-axis cylindrical gears are considered as very efficient means for transmitting mechanical power, but for requirements of maximum efficiency in the current machines and equipments a precision in the procedures of calculation of power losses is necessary. In this sense, the Technical Report ISO / TR 14179-1:2001 offers formulas with empirical and theoretical bases to evaluate the gear efficiency considering gear mesh losses, windage and churning losses, and losses by bearings and seals. In particular, this article presents some results derived from a study of ISO/TR 14179-1:2001 and mathematical models described the interrelation of gear geometry, working parameters and efficiency. The results offer solution to the problem of increasing gear efficiency through a convenient relationship between the load, speed and rational gear geometry. Finally, through multiple regression a new formulation was estimated for the calculation of gear efficiency as a function of the load density, module, speed, gear ration and number of pinion teeth. Los engranes de ruedas cilíndricas y ejes paralelos con contacto exterior constituyen transmisiones mecánicas muy eficientes, pero los requerimientos de máxima eficiencia en las actuales máquinas y equipos hacen necesaria una precisión en los procedimientos de cálculo de pérdidas de potencia. En este sentido, el Reporte Técnico ISO/TR 14179-1:2001 ofrece fórmulas con bases empíricas y teóricas para evaluar la eficiencia de engranajes considerando pérdidas por rozamiento en el contacto diente-diente, por batimiento del aceite y por rozamiento en cojinetes y sellos. En este artículo, se presentan algunos de los resultados derivados de un estudio de ISO/TR 14179-1:2001 y del coeficiente de fricción en engranajes. El estudio fue realizado sobre la base de modelos matemáticos que permitieron interrelacionar la geometría del engranaje y los parámetros de explotación con la eficiencia del engranaje. Los resultados aportan soluciones al problema de aumentar la eficiencia de los engranajes mediante una relación conveniente entre la carga y la velocidad, y una geometría racional del dentado de las ruedas. Finalmente, mediante un análisis de regresión múltiple se establece una nueva formulación de la eficiencia del engranaje en función de la densidad de carga en el engranaje, el módulo, la velocidad de trabajo, la razón de transmisión y la cantidad de dientes en el pi ón.
Integral Model of Sand-Cleaning Machine Structure Modelo integral de la estructura móvil de una máquina limpia-playa
María Eugenia García Domínguez
Revista Cubana de Ingeniería , 2010, DOI: 10.1234/rci.v1i3.31
Abstract: A proposes of model of sand-cleaning machine structure for the analysis of loaded structure is presented in this paper. The analysis of the structure is developed in the principal components such as the pull bar, chassis and supports. Using this rational model of the structure of the sand-cleaning machine, it can be carried out an analysis of the tensions and displacements in the two more critical situations of operation: Sieved and discharge. By finite elements method was developed a physical-mathematical model for the sand-cleaning machine and were analyzed the tensions and displacements in the structure. According to the characteristics of the Cuban beaches and results derivate of this study, the machine analyzed and exposed in this paper fulfills all the technical, economic and ecological requirements for good operation. Se propone el modelo de la estructura móvil de una máquina limpia-playa, con un análisis integral de la estructura y sus componentes fundamentales como la barra de tiro, bastidor y el soporte del puente. Utilizando este modelo racional de la estructura de la máquina limpia-playa, se realiza un análisis de las tensiones y desplazamientos que ocurren en los dos estados más críticos de operación de la máquina: cribado y descarga. Para el análisis de las tensiones y los desplazamientos en la máquina limpiadora de playa fue elaborado el modelo físico-matemático de la estructura por el método de los elementos finitos y siguiendo las reglas establecidas. Con el estudio realizado y considerando las características que ofrecen las playas cubanas, se pretende que la máquina analizada en este trabajo cumpla con los requerimientos técnicos, económicos y ecológicos para su óptima puesta en marcha.
The ICT as a Teaching Aid in the Formation of Professional Competence Within Engineering Students Las TIC como medios de ense anza en la formación de competencias profesionales de estudiantes de ingeniería
Gonzalo González Rey,Alejandra García Toll,María Eugenia García Domínguez
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i3.53
Abstract: In present days, the application of information and communication technologies (ICTs) in teaching processes has made great changes in engineering teaching. In this article, the possibilities that the application of ICTs offers in the educational process as a teaching aid are exposed. In the career of Mechanical Engineering during the courses of Machine Elements Design some ICTs application as a teaching medium are used in a systematic and consistent manner. After which, the impact of its application is evaluated with regard to the formation of professional competence within mechanical engineering students. En la actualidad, la aplicación de las tecnologías de la información y las comunicaciones en el proceso de ense anza producen grandes cambios en las ense anzas de las ingenierías. En este trabajo se muestran algunas de las posibilidades de las Tecnologías de la Información y las Comunicaciones (TIC) en el proceso docente-educativo como medios de ense anza y en la formación de las competencias profesionales de estudiantes de la carrera de Ingeniería Mecánica. Los ejemplos de aplicación de las TIC como medios de ense anza y la valoración de su impacto en la formación de las competencias profesionales son analizados después de un trabajo sistémico y sostenido en los cursos de Elementos de Máquinas de la disciplina de Mecánica Aplicada de la carrera de Ingeniería Mecánica.
Mechanical Properties of Composite Mortars Using Flurogypsum and PVC Particles  [PDF]
Luisa Maria Flores-Vélez, Hector Valle, Gabriel García, Roberto Torres, Martha Lomelí, Octavio Domínguez
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.54026
Abstract:

The present work describes the viability of a mortar binder based on two industrial by-products: poly(vinyl chloride) (PVC) particles from scrap and anhydrite (CaSO4) from fluorgypsum. Mortar composites were made incorporating different amounts of PVC particles and cured at constant room temperature during various periods of time. From X-ray diffraction, it was possible to follow the hydration process and to estimate the effect of the PVC particles on anhydrite transformation to gypsum (CaSO4·2H2O). Compressive strength from uniaxial testing was measured from stress-strain curves carried out at room temperature. According to these results, the hydration rates of the composites depend on the concentration of PVC particles and there is an enhancement in their compressive strength as particle content increases, reaching values of 36 MPa after 28 days.

The Activity of Standardization and the Development of Professional Competence in Engineering Students Actividad de normalización y desarrollo de competencias profesionales en estudiantes de ingeniería
Gonzalo González Rey,Alejandra García Toll,María Eugenia García Domínguez,Pablo Frechilla Fernández
Revista Cubana de Ingeniería , 2011, DOI: 10.1234/rci.v2i1.35
Abstract: The following article shows that work done on the standardization results in the cultivation of professional competence among engineering students. In particular, professional competence can be considered as: good communication and interpersonal skills, computer literacy, ability to work in team and to dominate well those principles and practices that define a good professional. Also, the Standardization Cuban Committee of Machine Elements (CTN-108) shows that it helps to instil professional competence in those students of the career mechanical engineering. Se muestran resultados en la formación de competencias profesionales de estudiantes de carreras de ingeniería derivados del trabajo en la normalización. En particular, son consideradas competencias profesionales como: buena comunicación y colaboración, utilización de la computación y las tecnologías de información y comunicación, visión interdisciplinaria y dominio de los fundamentos y conocimientos teórico-prácticos de la profesión. Adicionalmente, se exponen evidencias del aporte de las actividades del Comité de Normalización Cubano de Elementos de Máquinas (CTN-108) en la formación de competencias profesionales básicas de estudiantes de las carreras de Ingeniería Mecánica.
The Thermal Decomposition of Ammonium Perchlorate-Aluminum Propellants in Presence of Metallic Zinc Particles  [PDF]
Mónica Rodríguez-Pesina, Jorge García-Domínguez, Felipe García-Hernández, Luisa Maria Flores-Vélez, Octavio Domínguez
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.86030
Abstract: The thermal decomposition of ammonium perchlorate (AP) with Al and Zn metallic particles was studied at different heating rates in dry air atmosphere and the combustion behavior of AP/Al/Zn propellant was evaluated. The exothermic reaction kinetics was studied by differential thermal analysis (DTA) in non-isothermal conditions and compare with the thermal decomposition of pure AP and AP/aluminum particles analyzed in the same experimental conditions. The Arrhenius parameters were estimated according to the Ozawa and Kissinger methods. The calculated activation energies for the low and high temperature exothermic reactions were 91 and 229 kJ/mol for pure AP, 90 and 112 kJ/mol for 80 wt% AP/20 wt% Al particles. When zinc was incorporated, activation energy of 56 kJ/mol was determined for the only exothermic peak observed for 90 wt% AP/10 wt% Zn and 44 kJ/mol for 78.4 wt% AP/19.6 wt% Al/2 wt% Zn propellant composition.
El proyecto de curso en la formación de competencias profesionales en estudiantes de ingeniería mecánica
González-Rey,Gonzalo; García-Toll,Alejandra; Wellesley-Bourke-Funcasta,Jorge; García-Domínguez,María Eugenia;
Ingenier?-a Mec??nica , 2011,
Abstract: the professional specific competences constitute a range of competences associated fundamentally with the action and apprehension of the reality. these competences are very influence by the professional formation and experience in the profession. for that reason, in the case of professional specific competences is very important and necessary an organized formation professional characterized by the accumulation of learning and abilities in specific tasks linked with the profession. in the present paper, two experiences in projects of courses developed by engineering students in the learning process are showed; moreover some results in the formation and development of professional specific competences associated with mentioned projects are illustrated. these experiences allow affirming that the professional specific competences can be developed during the professional formation with the introduction in the learning process of certain activities practical-professionals. in this sense, the practical activity in the academic with reproduction of frequent problems in relation with the profession is a very appropriate environment to develop the formation of professional specific competences demand in the current context of action for the graduate of careers of mechanical engineering.
Influencia de la suplementación en la dieta con levaduras y minerales sobre la producción de ovocitos de ovejas púberes estimuladas ováricamente
González Parra,Eugenia I; Navarrete Sierra,Luis F; Cruz Tamayo,Alvar A; Domínguez Rebolledo,Alvaro; Sanginés García,José R; Ramón Ugalde,Julio P;
Revista Científica , 2007,
Abstract: the superovulatory response of pre-pubertal or pubertal ewes fed with protein suplement that contained yeast or organic minerals was evaluated in order to obtain ?in vivo? maturated oocytes. eighteen females (7 months of age) were allocated to one of the following treatment and fed as follow: treatment a (ta): 1 kg food with 15% pc+yea sacc? (yeast saccharomyces cerevisiae stump 1026), dose: 5 gr/animal/day and hay ad libitum. treatment b (tb): 1 kg food with 15% pc+bioplex plus? (cultivation of live yeasts and organic minerals), dose: 4 gr/animal/day and hay ad libitum. treatment c (tt: control): 1 kg food with 15% pc and hay ad libitum. the estrous cycle was synchronized through the insertion of vaginal sponges with 40 mg of fluorogestone acetate (fga) during 12 days. at day 10th of the sponges insertion 225 mg of prostaglandin f2á was administered per ewe. to induce supra-ovulation 100 mg-nih fshp and 500 ui ecg in a single dose were applied 36 h before the withdrawal of the sponges, and 24 h from the last application 100 μg of gnrh was also injected. the ovulation rate was measured by endoscopy and ovulated oocytes collected by flushing. the total of ovulation (to) was greater in the ta and tb (16.6±6.84 and 15.5±4.18) treatment, than on the control tt (9.16±3.81) (p<0.05). the oocyte recovery (tr) after flashing was significantly higher in the ta (93.9%) treatment compared to tb (56.9%) and tt (61.8%). finally, the proportion (p<0.05) of grade i oocytes in the diet supplementation in ta was in higher than the quality of oocytes in the tb and tt treatment. in conclusion, the addition of with yeasts, to supra-ovulated pre-pubertal ewes promotes ovulation rate and oocytes quality
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