Área de la Circunferencia, Elipse y Esfera Orozco Martínez, Ingrid Judith; Cisneros Díaz, Iván Augusto
Revista Científica de FAREM-Estelí: Medio ambiente, tecnología y desarrollo humano,
11/2022, Letnik:
11, Številka:
43
Journal Article
Recenzirano
Odprti dostop
Este trabajo presenta las demostraciones analíticas de la fórmula del área de la circunferencia, elipse y esfera, mediante integración en una variable e integración doble, utilizando los sistemas de ...coordenadas rectangulares, polares, esféricas, mediante el teorema del cambio de variables. Se presenta también una aplicación del teorema de Green, el cual constituye un clásico de los teoremas del Análisis Vectorial. El objetivo central es mostrar diversas variantes demostrativas mediante integración en una y dos variables y reconocer que el estudio de las diferentes técnicas y métodos de integración permiten aplicar el cálculo diferencial e integral a la resolución de problemas prácticos que se presentan en diversas situaciones demostrativas de la matemática. Cabe destacar que estas formas de demostraciones están basadas en las propiedades de la integral en una y varias variables, así también como en las aplicaciones de los sistemas de coordenadas rectangulares, polares y esféricos. La aplicación del Jacobiano al desarrollo de la integración de forma polar ofrece un camino de cambio de coordenadas que permite desarrollar diversos problemas de integración a situaciones más fáciles de integrar y por ende de obtener nuevas generalizaciones en algunas curvas cerradas, tales es el caso de la elipse y la esfera. El concepto de área y de volumen se generaliza a diversas figuras cerradas y esto permite una mayor generalidad a dichos conceptos por medio de integración. Estas demostraciones podrán construirse mediante otras estrategias de enseñanzas y aprendizaje, todas ellas basadas en el concepto de integración.
In this Perspective we summarize the most widely used definitions of free volume and illustrate the differences between them, including the important distinction between total free volume and excess ...free volume. We discuss the implications when alternative estimates for free volume are inserted into relationships that connect experimentally measured properties (e.g., the viscosity) to free volume, such as those proposed by Doolittle, Fox and Flory, Simha and Boyer, Cohen and Turnbull, and Williams, Landel, and Ferry. Turning to the results of our own locally correlated lattice (LCL) model, we demonstrate, by analyzing data for a set of over 50 polymers, that our calculations for total percent free volume not only lead to a predictive relationship with experimental glass transition temperatures but also allow us to place the different definitions of free volume within a physical picture of what the proposed contributions represent. We find that melts go glassy upon reaching a “boundary” of minimum (total) percent free volume that depends roughly linearly on temperature. We interpret this boundary as being close to the T-dependent free volume associated with solid-like segmental vibrational motions. Since the LCL model is a first-principles thermodynamic theory, we are also able to link our free volume predictions to similar patterns that we find in the predicted entropy per theoretical segment. Our results are consistent with a picture wherein the difference in entropy between the melt (liquid) state and corresponding solid state vanishes as the glass transition is approached. This leads us to a new connection with the work of Adams and Gibbs, whose model reflects a similar vanishing of the configurational entropy. We conclude by discussing why the approach to the glassy state is best viewed as being controlled via the linked contributions of free volume and temperature.
The number of biomedical applications of hydrogels is increasing rapidly on account of their unique physical, structural, and mechanical properties. The utility of hydrogels as drug delivery systems ...or tissue engineering scaffolds critically depends on the control of diffusion of solutes through the hydrogel matrix. Predicting or even modeling this diffusion is challenging due to the complex structure of hydrogels. Currently, the diffusivity of solutes in hydrogels is typically modeled by one of three main theories proceeding from distinct diffusion mechanisms: (i) hydrodynamic, (ii) free volume, and (iii) obstruction theory. Yet, a comprehensive predictive model is lacking. Thus, time and capital-intensive trial-and-error procedures are used to test the viability of hydrogel applications. In this work, we have developed a model for the diffusivity of solutes in hydrogels combining the three main theoretical frameworks, which we call the multiscale diffusion model (MSDM). We verified the MSDM by analyzing the diffusivity of dextran of different sizes in a series of poly(ethylene glycol) (PEG) hydrogels with distinct mesh sizes. We measured the subnanoscopic free volume by positron annihilation lifetime spectroscopy (PALS) to characterize the physical hierarchy of these materials. In addition, we performed a meta-analysis of literature data from previous studies on the diffusion of solutes in hydrogels. The model presented outperforms traditional models in predicting solute diffusivity in hydrogels and provides a practical approach to predicting the transport properties of solutes such as drugs through hydrogels used in many biomedical applications.
La diversidad de hitos, monolitos, instalaciones e infraestructuras en diversos estados de conservación y uso son parte de las huellas del Estado en los territorios cordilleranos. Esta presencia se ...divide entre las obras de modernización del territorio a expensas de la colonización del ambiente y del espacio simbólico, y las construcciones desplegadas por los habitantes en la expansión estatal. En este caso, nuestra atención se concentra en las primeras. La sucesión de intervenciones públicas a lo largo del siglo XX es sintomática de los modos espasmódicos en que se instala, se mantiene y se renueva la hegemonía en el mundo cordillerano. El legado de instalaciones convertidas en huellas y el entramado geométrico irregular e inconcluso que permanece, materializado en las sucesivas transformaciones de la cuenca, contribuyen a la comprensión de la eficacia operacional de formaciones estatales exiguas. Nuestra atención se concentra en los procesos modernizadores asociados al transporte ferroviario, el turismo, la generación de hidroelectricidad y los embalses de regadío, iniciativas hegemonizadas por la presencia de la central hidroeléctrica Colbún. Todas estas iniciativas han sido impulsadas y sustentadas por el Estado, y sus huellas se han metabolizado en el paisaje actual, convirtiéndose en territorio a lo largo de los últimos dos siglos.
An original design strategy for the preparation of polymers with a low dielectric constant is presented. The key to this design strategy is taking the most advantage of the secondary relaxation ...behavior of the polymer chains to obtain more free volume in the bulk, which can effectively reduce the dielectric constant of the polymer. By using this design strategy, we have successfully synthesized a novel polyimide TmBPHF with a pendant group that consists of a biphenyl unit attached to the meta-position of a phenyl ring that is part of a triaryl unit. The intrinsic k and dielectric loss values of the TmBPHF are 2.09 and 0.0012 at 10 kHz, respectively. More importantly, such outstanding low-k performance remains stable up to 300 °C. The excellent low-k performance of TmBPHF is mainly due to the secondary relaxation, especially the β relaxation, which occurs from the rotation of the pendant group. The TmBPHF film shows an ultralow moisture rate (∼0.17%), which is able to maintain the low-k property stability in different humid environments. Meanwhile, the TmBPHF film also shows excellent thermal stability and excellent mechanical properties, with a glass transition temperature (T g) of 302 °C, 5 wt % decomposition temperature (T d5%) of 549 °C, and residual of 70% at 800 °C under N2. The tensile strength and tensile modulus of the polyimide film are equal to 85.8 MPa and 2.02 GPa, respectively. In addition, the TmBPHF film is soluble in common solvents, which allows simple solution processing and efficient, low-cost, and continuous roll-to-roll processes. The design strategy is beneficial for lowering the k value and simultaneously maintaining the overall properties of polyimides, which possibly could also be extended to other novel high-performance polymer systems.
Chickpea protein has good emulsifying properties, which improve gluten-free bread volume. Tiger nut is a tuber with high lipid content of healthy fatty acid profile. Taking into account these ...characteristics, the effect of chickpea and tiger nut flours addition to gluten-free batters and breads in order to partially or totally replace emulsifier and/or shortening in gluten-free formulations has been studied. Four formulations were compared: corn starch; 7.8 g/100 g chickpea flour and corn starch; 8.6 g/100 g tiger nut flour and corn starch; 7.8 g/100 g chickpea flour + 8.6 g/100 g tiger nut flour and corn starch. The combination of three levels of shortening (5, 2.5 and 0 g/100 g) and three levels of emulsifier (2, 1 and 0 g/100 g) was evaluated in each basic formulation. Chickpea flour increased bread specific volume but tiger nut flour reduced it. When chickpea protein and emulsifier were added in the formulation, shortening increased G′and specific volume, and reduced initial crumb firmness. Bread elaborated with both chickpea and tiger nut flour maintained its baking characteristics (bake loss, specific volume, crust and crumb color and, crumb hardness) even when shortening and/or emulsifier were reduced or eliminated.
•Chickpea and tiger nut flours addition to gluten-free formulations was evaluated.•Reduction of emulsifier and shortening from gluten-free formulations was studied.•Emulsifier and shortening reduction was possible if both flours were present.
This paper presents a new method to fabricate 3D models on a robotic printing system equipped with multi-axis motion. Materials are accumulated inside the volume along curved tool-paths so that the ...need of supporting structures can be tremendously reduced - if not completely abandoned - on all models. Our strategy to tackle the challenge of tool-path planning for multi-axis 3D printing is to perform two successive decompositions, first volume-to-surfaces and then surfaces-to-curves. The volume-to-surfaces decomposition is achieved by optimizing a scalar field within the volume that represents the fabrication sequence. The field is constrained such that its iso-values represent curved layers that are supported from below, and present a convex surface affording for collision-free navigation of the printer head. After extracting all curved layers, the surfaces-to-curves decomposition covers them with tool-paths while taking into account constraints from the robotic printing system. Our method successfully generates tool-paths for 3D printing models with large overhangs and high-genus topology. We fabricated several challenging cases on our robotic platform to verify and demonstrate its capabilities.
Objetivo. Evaluar la capacidad pulmonar en función del volumen corriente (VC) y analizar su influencia en presencia de diversos factores externos, tales como actividad física (natación), alimentación ...e infección respiratoria. Métodos. El estudio fue de tipo observacional, descriptivo, transversal y prospectivo. Se realizó una encuesta online a una muestra aleatoria conformada por 50 estudiantes universitarios entre 17 y 20 años. Se midió el VC mediante el uso de un espirómetro casero y se clasificó bajo el programa IBM SPSS Statistics-24, para los respectivos análisis estadísticos. Resultados. De las encuestas, se obtuvieron los siguientes datos: El Volumen corriente VC promedio de los estudiantes que practican natación fue de (797,0 ± 2,0) ml. El VC promedio de los alumnos que siguen una alimentación saludable fue de (567,00 ± 2,0) ml y el VC promedio de aquellos con antecedentes respiratorios fue de (429,0 ± 2,0) ml. Conclusiones. Tener una dieta rica en frutas y verduras y/o realizar alguna actividad física aumenta en gran medida la capacidad pulmonar del individuo.
•New type of turbulator in appearance of nanoparticles has been analyzed.•Second law presentation has been provided by means of FVM.•Nu enhances with augment of height of turbulator.•Thermal entropy ...generation declines with augment of b.
In current modeling, turbulent heat transfer of homogeneous nanofluid due to inserting double twisted tapes has been carried out. To better describing performance of unit, generation of entropy has been examined. CuO nanomaterial has been dispersed in to H2O, to help its conductivity. The pipe was under the impact of uniform heat flux. Equations describing the flow and energy balance were solved applying finite volume method. The simulations illustrate that both augmenting pumping power and height of tape result in the reduction of thermal component and the augmentation of frictional component.
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