Factores internos y externos que influyen en el desempeño de las exportaciones de quinua al mercado de China, año 2020

La presente investigación tuvo como objetivo general evidenciar los factores internos y externos que influyen en el desempeño de las exportaciones de quinua a China, año 2020. Para ello, se aplicó un diseño de investigación mixta de tipo secuencial exploratorio, el cual incluyó dos fases secuenciales: cualitativa y cuantitativa. Para el estudio cualitativo se diseñó una entrevista semi-estructurada que abarcó ítems referidos a los factores internos y externos que condicionan el desempeño exportador, la cual se aplicó a una muestra de nueve gerentes de empresas exportadoras de quinua a China, año 2020, siendo procesada en AtlasTi 7.0. Por su parte, el estudio cuantitativo se derivó de una muestra de nueve empresas exportadoras de quinua a China (grupo de estudio) y nueve empresas exportadoras de quinua al resto del mundo (grupo control), cuyo desempeño se comparó mediante el análisis de varianza factorial al 5% de significancia en el software SPSS 25. Los hallazgos cualitativos y cuantitativos coincidieron en la identificación de factores internos: experiencia en la gestión de exportaciones y relaciones locales con los proveedores (p≤0,05). Por otra parte, los factores externos: conocimiento de la cultura local y apoyo gubernamental, solo resultaron relevantes desde una perspectiva cualitativa requiriendo estudios cuantitativos complementarios. Así, se obtuvo que no existe diferencia significativa en entre el desempeño exportador de los grupos evaluados (p>0,05), es decir el valor de las exportaciones a China todavía no superan al total de resto del continente asiático.The general objective of this research was to highlight the internal and external factors that influence the performance of quinoa exports to China in 2020. To this end, a mixed research design of sequential exploratory type was applied, which included two sequential phases: qualitative and quantitative. For the qualitative study, a semi-structured interview was designed that included items related to internal and external factors that condition export performance. This interview was applied to a sample of nine managers of quinoa exporting companies to China in 2020, and was processed in AtlasTi 7.0. On the other hand, the quantitative study was derived from a sample of nine companies exporting quinoa to China (study group) and nine companies exporting quinoa to the rest of the world (control group), whose performance was compared through the analysis of factor variance at 5% significance in the SPSS 25 software. The qualitative and quantitative findings coincided in the identification of internal factors: experience in export management and local relations with suppliers. On the other hand, the external factors: knowledge of local culture and government support, were only relevant from a qualitative perspective requiring complementary quantitative studies. Thus, it was obtained that there is no significant difference between the export performance of the groups evaluated (p>0.05), that is, the value of exports to China still does not exceed the total of the rest of the Asian continent.Tesi

Identification of a possible superconducting transition above room temperature in natural graphite crystals

Measuring with high precision the electrical resistance of highly ordered natural graphite samples from a Brazil mine, we have identified a transition at $\sim$350~K with $\sim$40~K transition width. The step-like change in temperature of the resistance, its magnetic irreversibility and time dependence after a field change, consistent with trapped flux and flux creep, and the partial magnetic flux expulsion obtained by magnetization measurements, suggest the existence of granular superconductivity below 350~K. The zero-field virgin state can only be reached again after zero field cooling the sample from above the transition. Paradoxically, the extraordinarily high transition temperature we found for this and several other graphite samples is the reason why this transition remained undetected so far. The existence of well ordered rhombohedral graphite phase in all measured samples has been proved by x-rays diffraction measurements, suggesting its interfaces with the Bernal phase as a possible origin for the high-temperature superconductivity, as theoretical studies predicted. The localization of granular superconductivity at these two dimensional interfaces prevents the observation of a zero resistance state or of a full Meissner state.Comment: 14 pages with 21 figure

Estudo da produção e evolução de pinholes em filmes finos de a-Ge0.9Si0.1:H e a-Ge0.9Si0.1

Orientador: David ComediDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica "Gleb Wataghin"Resumo: Neste trabalho, apresentamos resultados experimentais de um estudo de pinholes em filmes finos de a-Ge0.9Si0.1: H e a-Ge0.9Si0.1. As amostras foram depositadas pela técnica de Ion Beam Sputtering Deposition, usando kriptônio e argônio como gás de sputtering. Os pinholes foram observados por microscopia óptica em amostras crescidas sobre vidro usando diferentes pressões parciais de hidrogênio, em 6 e 12 regiões de 1mm2 escolhidos aleatoriamente perto do centro das amostras. A concentração de hidrogênio nas amostras foi determinada por medidas de transmitância no infravermelho. Foi observado um aumento imediato do numero médio de pinholes em função do tempo de armazenamento das amostras a temperatura ambiente, atingindo-se uma saturação após 20 dias aproximadamente. O número médio de pinholes a qualquer tempo depois da deposição é maior conforme a concentração de hidrogênio na amostra aumenta. Foi também medido o stress nos filmes em função do tempo o qual manteve-se constante dentro da margem de erro. Para explicar estes resultados, propor-se um modelo teórico, baseado em observações prévias reportadas na literatura, o qual considera as bolhas como precursores dos pinholes nos filmes. Para determinar os parâmetros do modelo fez-se um estudo da altura das bolhas usando um profilômetro e do diâmetro das mesmas por microscopia óptica. O ajuste do modelo teórico aos dados experimentais é bom, e os parâmetros obtidos a partir do mesmo não estão em contradição com os dados disponíveis na literaturaAbstract: In this work, experimental results of a study of pinholes in a-Ge0.9Si0.1: H and a-Ge0.9Si0.1thin films are presented. These films were prepared using the ion beam sputtering deposition technique, with krypton and argon as working gases and using different hydrogen partial pressures. The pinholes were observed by optical microscopy in films deposited on corning glass substrates, in 6 and 12 regions of 1 mm2 random selected near to sample¿s center. The concentrations of hydrogen in the samples were determined by infrared transmission spectroscopy. We have observed immediate increase of the average number of pinholes with sample storage time at room temperature, attaining saturation after 20 days approximately. The average number of pinholes at any time after the deposition is higher as the sample hydrogen concentration increases. We have also measured the stress in the films as a function of time, which was constant within the experimental error. In light of the results, we have suggested a theoretical model based on prior observations reported in the literature, which consider the bubbles as the precursors of pinholes in the films. To determine the parameters of the model, we performed a study of the bubbles height using a perfilometer and of their diameter by optical microscopy. The agreement of the model with the experimental dataset is good, and the parameters obtained are not in contradiction with the data available in the literatureMestradoFísicaMestre em Físic

Study of the thermomechanical and structural properties in amorphous carbon and carbon nitride

Orientador: Francisco das Chagas MarquesTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Nesta tese estudamos a influência da incorporação de nitrogênio nas propriedades termomecânicas e estruturais em matrizes de carbono amorfo hidrogenado (a-C:H) e não hidrogenado (a-C). Duas técnicas de deposição foram utilizadas para o crescimento dos filmes. Os filmes hidrogenados foram preparados utilizando um sistema de glow discharge e as não hidrogenadas foram preparadas por IBAD. Um estudo preliminar foi feito em função do bias e a pressão do metano CH4, com o objetivo de escolher duas condições para a incorporação de nitrogênio. Deste primeiro estudo foi observado um aumento do coeficiente de dilatação térnica dos filmes de a-C:H com o aumento das ligações sp2. A partir desta série, uma segunda série de amostras com matriz tipo diamond-like e graphite-like de a-C:H foram estudadas, nas quais observamos que independente da matriz, a incorporação de nitrogênio produz um aumento no coeficiente de dilatação térnica (CTE) de até 9x10-6 C-1 para cerca de 6% de nitrogênio, próximo do valor do CTE do grafite (8x10-6C-1). A influência do nitrogênio no carbono amorfo aumenta a geração das hibridizações sp e sp2, o qual facilita a fornação de clusters grafíticos dentro dos filmes de a-C:H:Nx. O empilhamento dos clusters e a influência destes no CTE dos filmes são amplamente discutidos, para o qual técnicas espectroscópicas como Raman, infravermelho e perda de energia dos elétrons (EELS) são estudadas nesta tese. Por outro lado, para ter uma visão mais clara da influência do N, amostras com matrizes não hidrogenadas de a-C foram preparadas pela técnica de IBAD. Com nesta técnica temos filmes de a-C:Nx com altas concentrações de nitrogênio (até ~30%). Foi observado que mesmo com altas concentrações de N, o CTE dos filmes de a-C:Nx não consegue atingir valores acima de 5xl0-6 C-1. Este fato, faz pensar que o hidrogênio cumpre um papel muito importante no ernpilhamento dos clusters grafíticos. A partir das medidas feitas pela técnica de TIB (o qual foi desenvolvido em nosso laboratório e utilizado para medir o stress, CTE e módulo biaxial dos filmes) e a Nanoindentação obtivemos separadamente o módulo de Young (E) e a razão de Poisson (v), nas três séries de amostras estudadas. Os resultados são discutidos como uma função dos tipos de hibridizações dos filmes de a-C:H, a-C:H:Nx e a-C:NxAbstract: In this work, we studied thenno mechanical and structural properties of hydrogenated amorphous carbon (a-C: H), hydrogenated carbon nitride (a-C:H:Nx) and carbon nitride (a-C:Nx) thin films. Two techniques were used to prepare the samples: glow discharge for depositing hydrogenated amorphous carbon (a-C:H) and carbon nitride (a-C:H:Nx) and ion beam assisting deposition (IBAD) for unhydrogenated amorphous carbon nitride (a-C:Nx) films. The curvature of the film/substrate composites was measured using the thermally induced bending (TIB) technique in order to determine the stress of the films. By varying the temperature and using films deposited in several different substrates one was able to obtain the coefficient of thermal expansion (CTE) and the biaxial modulus (E/(l-v)) of the films. Complementarily to this technique, we perfonned nanohardness measurements, which also allows to obtaining the elastic constant (E/(1-v2)) as well. Using both techniques, TIB and nanohardness, we determined, for the first time, separately the Young's modulus (E) and the Poisson's ratio (v) of a-C:H, a-C:H:Nx and a-C:Nx. These thermomechanical properties were investigated as a function of sp2-bond, or graphite's cluster, concentrations, using the following techniques: EELS, infrared spectroscopy, visible and ultraviolet Raman spectroscopy. The influence of the incorporation of nitrogen in the hydrogenated and unhydrogenated matrixes is discussed. We observed that the CTE of a-C:H depends strongly on the concentration of Sp2 sites approaching the value for graphite as the concentration tends to 100 %. The nitrogen incorporation increases the cluster formation in matrixes, inducing a substantial increase of the CTE of the fi1ms. On the other hand, in the matrix free of hydrogen it was observed that the CTE is not strongly influenced by the nitrogen concentration. These observations indicate that hydrogen plays an important role on the value of the CTE in amorphous carbon nitrogen filmsDoutoradoFísica da Matéria CondensadaDoutor em Ciência

Low-cost 3D-printing system for the deposition of reduced graphene oxide (rGO) thin films by dip-coating with application for electrode fabrication

A low-cost 3D-printing system is reported for the deposition of thin films by a dip-coating technique. The structure was constructed using 3D-printed pieces of polylactic acid (PLA) joined by simple snap-fit. This structure assembly and design simplifies the construction and replicability of dip-coating equipment. The components used are affordable and accessible, reducing the cost of implementation. An Arduino controls the system through a C++ program that varies the pulling and dipping speed from 0.5 to 20 mm/s. The pulling and dipping process uses a servomotor motion transformed into linear by a rack and pinion mechanism. The performance of the presented system was validated by comparison of thin-film reduced graphene oxide (rGO) deposition onto gold. The rGO thin films obtained were homogeneous and smooth, capable of being used as electrodes in biosensors.</p

Process optimization proposal to reduce validation time and improve organizational efficiency.

Este trabajo se centra en la mejora de la gestión de asistencias docentes en una institución educativa, abordando los desafíos de validación de clases y la optimización de procesos. Se presentan tres alternativas estratégicas: asignar un Equipo de Validación Adicional, actualizar el Sistema de Tecnología de la Información y implementar un Sistema de Notificación de Fallas. Cada alternativa se analiza en términos de ventajas, desventajas y alineación con los objetivos organizativos. La primera alternativa propone asignar personal adicional en momentos críticos para garantizar la validación de asistencias. La segunda alternativa se centra en modernizar el sistema de TI, utilizando automatización y algoritmos de procesamiento de datos en tiempo real. La tercera alternativa se basa en una plataforma de notificación de fallas que permite a los docentes informar problemas de manera eficiente. Cada alternativa busca mejorar la eficiencia operativa, garantizar la integridad de los registros académicos y promover la satisfacción de los docentes. Se destaca la importancia de un análisis comparativo para tomar decisiones informadas.This document focuses on improving teacher attendance management in an educational institution by addressing the challenges of class validation and process optimization. Three strategic alternatives are presented: adding an additional validation team, upgrading the information technology system, and implementing an error reporting system. Each alternative is analyzed in terms of advantages, disadvantages, and alignment with organizational goals. The first alternative proposes adding additional staff at critical times to ensure attendance validation. The second alternative focuses on modernizing the IT system using automation and real-time data processing algorithms. The third alternative is based on a fault reporting platform that allows teachers to efficiently report problems. Each alternative aims to improve operational efficiency, ensure the integrity of academic records, and promote teacher satisfaction. The importance of comparative analysis in making informed decisions is emphasized.Trabajo de Suficiencia Profesiona

Hints of granular superconductivity in natural graphite verified by trapped flux transport measurements

This study describes electrical transport measurements as a function of magnetic field and temperature that provide hints of the existence of superconductivity with a critical temperature of $T_c \sim 350$ K in a natural graphite sample. The measurements were done in a restricted temperature 300 K $\leqslant T \leqslant 450$ K and magnetic field $B \leqslant 400$ mT range. Electrical resistance measurements at remanence (zero field), after the application of a magnetic field, indicate the existence of trapped flux, which remains nearly unchanged within ${\sim}30$ min but it vanishes at a temperature of ${\sim}330$ K. The apparent transition is accompanied by a clear enhancement of the magnetoresistance at $T \lt T_c$ . Raman measurements on the bulk sample reveal the existence of the rhombohedral stacking order, which interfaces with the usual Bernal phase were predicted to lead to high temperature superconductivity due to the formation of robust flat bands in the electron dispersion relation

Partial pseudospin polarization, latticetronics and Fano resonances in quantum dots based in graphene ribbons: a conductance spectroscopy

In this work we study, as a function of the height V and width Lb of the potential barriers, the transport of Dirac quasi-particles through quantum dots in graphene ribbons. We observed, as we increase V, a partial polarization (PP) of the pseudospin due to the participation of the hyperbolic bands. This generates polarizations in the sub-lattices A or B outside the dot regions for single, coupled, and open dots. Thus for energies around the Dirac point, the conductance G at both sides of the dot shows a latticetronics of conductances GA and GB as a function of V and Lb. This fact can be used as a PP spectroscopy which associates hole-type waves with the latticetronics. A periodic enhancement of PP is obtained with the increase of V in dots formed by barriers that completely occupy the nanoribbon width. For this case, a direct correspondence between G(V) and PP(V) exists. On the other hand, for the open dots, the PP(V) and the G(V) show a complex behavior that exhibit higher intensities when compared to the previous case. In the Dirac limit we have no backscattering signs, however when we move slightly away from this limit the first signs of confinement appear in the PP(V) (it freezes in a given sub-lattice). In the last case the backscattering fingerprints are obtained directly from the conductance (splittings). The open quantum dots are very sensible to their opening wd and this generates Fano line-shapes of difficult interpretation around the Dirac point. The PP spectroscopy used here allows us to understand the influence of wd in the relativistic analogues and to associate electron-type waves with the observed Fano line-shapes