Análisis del fenómeno gravitacional a través de las formas diferenciales

Se compara el formalismo vectorial clásico de la gravitación newtoniana con el tratamiento de las formas diferenciales, de tal manera que se puedan visualizar geométricamente los dos métodos y analizar las ventajas de éstos. Se describirán las ecuaciones fundamentales que rigen los fenómenos gravitacionales mostrando una alternativa para conceptualizar y abordar los problemas que se tratan en dicha teoría

Espinores y física de partículas

Presento el concepto de espinores, desde el punto de vista de la solución de la ecuación de Dirac para el electrón. Muestro al espinor desde una perspectiva geométrica para poder analizar sus características básicas, enfatizando en la invariancia de Lorentz, mostrando una alternativa para conceptualizar fenómenos físicos que requieran estar conectados con la teoría de la relatividad especial

Porous Titanium for Biomedical Applications: Evaluation of the Conventional Powder Metallurgy Frontier and Space-Holder Technique

Titanium and its alloys are reference materials in biomedical applications because of their desirable properties. However, one of the most important concerns in long-term prostheses is bone resorption as a result of the stress-shielding phenomena. Development of porous titanium for implants with a low Young’s modulus has accomplished increasing scientific and technological attention. The aim of this study is to evaluate the viability, industrial implementation and potential technology transfer of different powder-metallurgy techniques to obtain porous titanium with stiffness values similar to that exhibited by cortical bone. Porous samples of commercial pure titanium grade-4 were obtained by following both conventional powder metallurgy (PM) and space-holder technique. The conventional PM frontier (Loose-Sintering) was evaluated. Additionally, the technical feasibility of two different space holders (NH4HCO3 and NaCl) was investigated. The microstructural and mechanical properties were assessed. Furthermore, the mechanical properties of titanium porous structures with porosities of 40% were studied by Finite Element Method (FEM) and compared with the experimental results. Some important findings are: (i) the optimal parameters for processing routes used to obtain low Young’s modulus values, retaining suitable mechanical strength; (ii) better mechanical response was obtained by using NH4HCO3 as space holder; and (iii) Ti matrix hardening when the interconnected porosity was 36–45% of total porosity. Finally, the advantages and limitations of the PM techniques employed, towards an industrial implementation, were discussed.Ministry of Economy and Competitiveness of Spain Grant MAT2015-71284-PJunta de Andalucía Grant P12-TEP-1401Comisión Nacional de Investigación, Científica y Tecnológica (CONICYT) of the Chilean government project FONDECYT 1116086

Titanium scaffolds with multi-scale porosity obtained by controlled chemical and electrochemical treatments of porous solids from PM space holder technique

Junta de Andalucía (Spain) / FEDER (EU), through the project Ref. P12-TEP-140

Influence of the Compaction Pressure and Sintering Temperature on the Mechanical Properties of Porous Titanium for Biomedical Applications

In the present work, the use of porous titanium is proposed as a solution to the difference in stiffness between the implant and bone tissue, avoiding the bone resorption. Conventional powder metallurgical technique is an industrially established route for fabrication of this type of material. The results are discussed in terms of the influence of compaction pressure and sintering temperature on the porosity (volumetric fraction, size, and morphology) and the quality of the sintering necks. A very good agreement between the predicted values obtained using a simple 2D finite element model, the experimental uniaxial compression behavior, and the analytical model proposed by Nielsen, has been found for both the Young’s modulus and the yield strength. The porous samples obtained by the loose sintering technique and using temperatures between 1000 °C −1100 °C (about 40% of total porosity) are recommended for achieving a suitable biomechanical behavior for cortical bone partial replacement.Ministry of Economy and Competitiveness of the State General Administration of Spain grant MAT2015-71284-

Hard Metal Production by ERS: Processing Parameter Roles in Final Properties

Cemented carbide is a hard composite material, used widely in a variety of industries. The value of the global tungsten carbide market is expected to grow by 4.4% (compound annual growth rate) from 2017 to 2022. One of the main markets is in metal cutting and wear parts, where small pieces (or inserts), a few grams in weight, are used. Field-assisted sintering technique (FAST) technologies allow for the production of small blanks in a single step from powder, which are near final dimensions. Production cycles are very short. In this paper, one of the FAST processes, the ERS technology, is applied to obtain WC10Co parts. A review of the process variable effects on the final properties of the parts is accomplished. Final properties of a range of conventionally produced inserts are obtained, using 100 MPa compacting pressure, 80 MA/m2 of current density, and processing times of around 800 ms.This research was funded by EU, grant number FoF.NMP.2013-10 608729 (7th Framework Programme) EFFIPRO

Implementation of an effective time-saving two-stage methodology for microstructural characterization of cemented carbides

Linear intercept on scanning electron microscopy micrographs is the most commonly used measurement method to determine carbide grain size and contiguity in WC–Co cemented carbides (hardmetals). However, it involves manual time-consuming measurements and is critically dependent on the quality of the micrographs as well as on the identification and definition of grain boundaries. In this study a two-stage methodology for microstructural characterization of hardmetals is presented. First, a digital semi-automatic image analysis procedure for grain size determination of the carbide phase is presented. It involves an experimental assessment of grain size on processed images corresponding to a series of WC–Co and WC–Ni cemented carbide grades with different microstructural characteristics. Obtained results are then compared to the values obtained by means of the linear intercept technique. A good correlation between the mean grain sizes determined following both measurement techniques was attained. Based on experimental findings, a series of empirical relations were found to correlate grain size distributions obtained following both methods. Second, an empirical relation for estimating carbide contiguity in WC–Co cemented carbides is proposed. This relation considers simultaneously the influence of the binder content and the experimentally determined mean grain size on contiguity. The proposed equation for contiguity estimation is based on extensive data collection from open literature. An excellent agreement was attained between contiguity values estimated from such equation and those obtained using the linear intercept technique. This validates the two-stage procedure as an effective time-saving methodology for microstructural characterization of WC–Co cemented carbides.Peer ReviewedPostprint (author's final draft

Análisis de la incidencia de la ley del IGV justo en empresas, de los regímenes general y mype tributario : principios de igualdad y justicia; liquidez y rentabilidad, 2016-2017

En la presente investigación, lo que se pretende demostrar, es la desigualdad e injusticia tributaria, que hay, en la aplicación de las normas y leyes tributarias, aplicado a todos los contribuyentes; justificando que la presente tesis, servirá para presumir la existencia de dicha desigualdad y justicia tributaria, evaluando la Aplicación de la Ley N° 30524 IGV Justo y su Incidencia en los Principios de Igualdad y Justicia Tributaria, en las empresas del Régimen General y Mype Tributario, así como su impacto en la liquidez y rentabilidad; aplicando el método teórico y las técnicas de observación (fichaje documental, análisis documental), y encuesta (entrevista); llegando a la conclusión que hay desigualdad e injusticia tributaria entre las grandes y pequeñas empresas; señalando también que la presente investigación aporta en conocimiento y de la veracidad de la injusticia y desigualdad tributaria que hay en nuestro país

Estudio financiero aplicativo web para propiedad horizontal

Trabajo de investigaciónEsta investigación se realizó para construir el estudio financiero de un aplicativo web para propiedad horizontal, para eso fue necesario realizar una investigación detallada para conocer los elementos teóricos de la propiedad horizontal, personas que intervienen en el ejercicio de la gestión, leyes que la regulan, procesos y herramientas informáticas que se utilizan en el medio. Una vez realizada la investigación de los elementos teóricos se procedió a ejecutar el estudio de mercado en el que se aplicaron métodos de investigación cualitativa para lo que se realizaron entrevistas a los administradores de propiedad horizontal y cuantitativa donde se aplicó una encuesta a propietarios y residentes de conjuntos residenciales, con el fin de indagar la percepción de las partes involucradas en esta actividad, profundizar en las principales necesidades insatisfechas, falencias y oportunidades de mejora que se presentan en este sector. Finalmente se trabajó en la construcción del estudio técnico para revisar los requerimientos de recursos financieros, infraestructura y personal, se describe el aplicativo de acuerdo a las necesidades y oportunidades de mejora identificadas en la etapa de diagnóstico y se procede a determinar la viabilidad financiera realizando la proyección de ventas de acuerdo a las unidades y precios para determinar los ingresos y se fijan los gastos mensuales, se proyecta el flujo de caja, se calcula la TIR, TIO, VAN y por último se construyen los estados financieros proyectados a cinco años con lo que se evidencio que el proyecto es factible.INTRODUCCIÓN 1. CAPITULO No. 1. ELEMENTOS TEORICOS 2. CAPITULO No. 2. DIAGNOSTICO 3. CAPITULO No. 3. PROPUESTA APLICATIVO WEB PARA PROPIEDAD HORIZONTAL 4. CONCLUSIONES RECOMENDACIONES BIBLIOGRAFÍAEspecializaciónEspecialista en Formulación y Evaluación Social y Económica de Proyecto