Uniaxial-deformation behavior of ice Ih as described by the TIP4P/Ice and mW water models

Using molecular dynamics simulations, we assess the uniaxial deformation response of ice Ih as described by two popular water models, namely, the all-atom TIP4P/Ice potential and the coarse-grained mW model. In particular, we investigate the response to both tensile and compressive uniaxial deformations along the [0001] and [01̄10] crystallographic directions for a series of different temperatures. We classify the respective failure mechanisms and assess their sensitivity to strain rate and cell size. While the TIP4P/Ice model fails by either brittle cleavage under tension at low temperatures or large-scale amorphization/melting, the mW potential behaves in a much more ductile manner, displaying numerous cases in which stress relief involves the nucleation and subsequent activity of lattice dislocations. Indeed, the fact that mW behaves in such a malleable manner even at strain rates that are substantially higher than those applied in typical experiments indicates that the mW description of ice Ih is excessively ductile. One possible contribution to this enhanced malleability is the absence of explicit protons in the mW model, disregarding the fundamental asymmetry of the hydrogen bond that plays an important role in the nucleation and motion of lattice dislocations in ice Ih.Fil: Santos Flórez, Pedro Antonio. Universidade Estadual de Campinas; BrasilFil: Ruestes, Carlos Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: de Koning, Maurice. Universidade Estadual de Campinas; Brasi

Nonequilibrium Processes in Repulsive Binary Mixtures

We consider rapid cooling processes in classical, 3-dimensional, purely repulsive binary mixtures in which an initial infinite-temperature (ideal-gas) configuration is instantly quenched to zero temperature. It is found that such systems display two kinds of ordering processes, the type of which can be controlled by tuning the interactions between unlike particles. While strong inter-species repulsion leads to chemical ordering in terms of an unmixing process, weak repulsion gives rise to spontaneous crystallization, maintaining chemical homogeneity. This result indicates the existence of a transition in the topography of the underlying potential-energy landscape as the intra-species interaction strength is varied. Furthermore, the dual-type behavior appears to be universal for repulsive pair-interaction potential-energy functions in general, with the propensity for the crystallization process being related to their behavior in the neighborhood of zero separation

GESTÃO DO PROCESSO DE CAPTAÇÃO DE LEITE: UM ESTUDO DE CASO NA COOPERATIVA AGRÃCOLA ALTO RIO GRANDE LTDA (CAARG)

The aim of this work was to assess the milking process in an agricultural cooperative in Lavras, Minas Gerais state. The study was done between August and November/2004, employing a qualitative research methodology that involved the researchers and the cooperative’s employees. Process management promotes the organization and management of information in the company, favoring cost administration and control. The study presented some lines with average costs above R$ 1.51/Km, and others below. This fact could impair the efficiency of the process. To ensure quality, legal parameters were defined, through laboratory analysis, to classify the milk. The observance of the strong and weak points are the best way to maximize the organization’s efficiency. However, these weak points deserve special attention from the CAARG’s decision makers in order to guarantee the cooperative’s performance. The main strategies implemented were financing and allowance of the outgoing tanks, combined with payment according to the volume and quality of the milk. Nevertheless, vertical integration should be adopted through supply contracts or quota definition, which is extremely important in guaranteeing not only the supply, but mainly the quality of the raw-material.competitive Strategy, Agricultural Cooperative, Vertical Integration, and costs of milk transportation, Agribusiness, Agricultural Finance, Industrial Organization,

Water versus Wireless Coverage in Rural Mali: Links and Paradoxes

Water and wireless coverage were evaluated in a rural commune of southern Mali. All improved water sources in the area were checked for operability, accessibility, and water quality, while wireless coverage was tested by means of smartphones, phone calls, and instant messaging applications. Theoretical water coverage exceeded 82% of the total village surface area, thus beating the national and sub-Saharan African averages, but dropped to just 39% when considering only serviceable and contamination-free sources. In contrast, wireless coverage exceeded 90%. These outcomes highlight a triple paradox: (1) water from theoretically safe (i.e., improved) water sources is often unsafe to drink; (2) wireless access is better than water access even though water is essential for human survival and telecommunications are not; and (3) excellent Internet coverage does not help a large number of people, who lack the skills, devices, or need to access it. While telecommunications seem to be making inroads towards universal access faster than the water sector, a survey of water committees uncovered a hidden nexus between both resources, revealing that increased wireless access is actually contributing to underpin water coverage in a variety of ways

Atomistic Simulation of Nanoindentation of Ice Ih

Using molecular dynamics simulations, we study the nanoindentation response of the ice Ih basal surface using two popular water models, namely, the all-atom TIP4P/Ice potential and the coarse-grained mW model. In particular, we consider two markedly different temperatures at which a quasi-liquid layer (QLL) is or is not present. We discuss loading curves, hardness estimates, deformation mechanisms, and residual imprints, considering the effect of the QLL, indenter size, and penetration rate. At very low temperatures, in the absence of a QLL, both potentials produce similar loading curves and deformation mechanisms. Close to the melting temperature, however, important differences were found, including deviations in the QLL thickness and fraction as well as the presence of a competition between pressure-induced melting and recrystallization events. Nevertheless, both potentials exhibit similar deformation mechanisms and steady-state hardness estimates that are consistent with experimental data. In addition to contributing to the discussion regarding the interpretation of experimental AFM loading curves, the present results provide valuable information concerning the simulation of contact problems involving ice and the behavior of these two popular water models under such circumstances.Fil: Santos Flórez, Pedro Antonio. Universidade Estadual de Campinas; BrasilFil: Ruestes, Carlos Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Interdisciplinario de Ciencias Básicas. - Universidad Nacional de Cuyo. Instituto Interdisciplinario de Ciencias Básicas; ArgentinaFil: De Koning, Maurice. Universidade Estadual de Campinas; Brasi

La actuación docente de los formadores de formación profesional y ocupacional

En el presente artículo se analiza la actuación docente de los formadores en los ámbitos de formación profesional y ocupacional presentando los resultados obtenidos sobre el perfil del formador de formación profesional y ocupacional. La síntesis del conjunto de información registrada por procedimientos cuantitativos y cualitativos destaca la interacci6n entre la teoria y la práctica y la participación de los alumnos. En el primer aspecto se manifiestan matices diferenciales en el seno de ambos tipos de formación para el empleo. El segundo de los aspectos señalados apunta coincidencias en los dos ámbitos analizados y se evidencia la pertinencia de partir de las necesidades de los alumnos.En aquest article s'analitza la actuació docent dels formadors en els àmbits de formació professional i ocupacional presentant els resultats obtinguts sobre el perfil del formador de formació professional i ocupacional. La síntesi del conjunt d'informació registrada per procediments quantitatius i qualitatius destaca la interacció entre la teoria i la pràctica i la participació dels alumnes. En el primer aspecte es manifesten matisos diferencials en el si dels dos tipus de formació¡ per a l'ocupació. El segon dels aspectes assenyalats apunta coincidències en els dos àmbits analitzats i es fa palesa la pertinència de partir de les necessitats dels alumnes.The teaching performance of the trainers in occupational and vocational training area is analysed in this study. It shows the obtained results about the vocational occupational trainer professional profile. The synthesis of the whole information that has been reported through quantitative and qualitative process, emphasises the interaction between theory and practice and theparticipation of students. At the first sight the different shades are dernostrated in both types of ernployrnent training. The second one sets down sorne coincidences in the analysed areas and it proves that starting forrn students needs is pertinent

Simulações atomísticas : propriedades mecânicas do gelo e processos fora do equilíbrio em misturas binárias repulsivas

Orientador: Maurice de KoningTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb WataghinResumo: A partir do uso de técnicas de simulações atomísticas, que podem ser consideradas como un método de "microscopia computacional in situ", estudamos as propriedade mecânicas do gelo Ih observando em detalhe os mecanismos de deformação a escalas atómicas. Como segunda parte desta Tese, também investigamos através de simulações atomísticas, os processos fora do equilíbrio em misturas binárias repulsivas. Usando simulações de dinâmica molecular, avaliamos a deformação uniaxial e a resposta à nanoindentação do gelo Ih, descrito por dois modelos populares de água, o potencial TIP4P/Ice e o modelo de água monoatômica (mW). Em particular, investigamos a resposta às deformações uniaxiais de tração e compressão ao longo de direções cristalográficas e temperaturas diferentes. Enquanto o modelo TIP4P/Ice falha por clivagem frágil sob tensão a baixas temperaturas ou por amorfização/fusão em larga escala, o potencial mW comporta-se de forma muito mais dúctil, apresentando inúmeros casos em que o alívio de tensão envolve a nucleação e subsequente atividade de discordâncias na estrutura cristalina. Estudamos também o processo de nanoindentação sob o plano basal, considerando duas temperaturas diferentes nas quais, respectivamente, uma camada quase-líquida (QLL) está ou não presente. A temperaturas muito baixas, na ausência de uma QLL, ambos os potenciais produzem curvas de carga e mecanismos de deformação similares. Perto da temperatura de fusão, porém, foram encontradas diferenças importantes, incluindo desvios na espessura e fração da QLL, bem como a presença de uma competição entre eventos de fusão e recristalização induzidos por pressão. No entanto, ambos os potenciais apresentam mecanismos de deformação semelhantes e estimativas de dureza que são consistentes com os dados experimentais. Na segunda parte, consideramos os processos fora do equilíbrio de misturas binárias clássicas descritas por um conjunto de diferentes potenciais de interação de pares puramente repulsivos, nos quais uma configuração de temperatura infinita (gás ideal) é rapidamente resfriada até a temperatura zero. Encontra-se que tais sistemas apresentam dois tipos de processos de ordenamento, cujo tipo pode ser controlado através do ajuste das interações entre partículas, sendo que, uma forte repulsão inter-espécies leva ao ordenamento químico em termos de uma separação de fase, e uma fraca repulsão dá origem à cristalização espontânea, mantendo a homogeneidade química. Além disso, o comportamento do tipo dual parece ser universal para funções repulsivas de energia potencial em geral, com a propensão para o processo de cristalização sendo relacionada ao seu comportamento na vizinhança de separação zeroAbstract: Using atomistic simulation techniques, which can be considered as a method of "computational microscopy in situ", we study the mechanical properties of ice Ih by observing in detail the deformation mechanisms at atomic scales. As a second part of this Thesis, we also investigate through atomistic simulations, the nonequilibrium processes in repulsive binary mixtures. Using molecular dynamics simulations, we assess the uniaxial deformation and nanoindentation response of ice Ih as described by two popular water models, namely, the all-atom TIP4P/Ice potential and the coarse-grained mW model. In particular, we investigate the response to both tensile and compressive uniaxial deformations along different crystallographic directions and temperatures. While the TIP4P/Ice model fails by either brittle cleavage under tension at low temperatures or large-scale amorphization/melting, the mW potential behaves in a much more ductile manner, displaying numerous cases in which stress relief involves the nucleation and subsequent activity of lattice dislocations. We study also the nanoindentation process on the basal plane, considering two different temperatures at which, respectively, a quasi-liquid layer (QLL) is or is not present. At very low temperatures, in the absence of a QLL, both potentials produce similar loading curves and deformation mechanisms. Close to the melting temperature, however, important differences were found, including deviations in the QLL thickness and fraction, as well as the presence of a competition between pressure-induced melting and recrystallization events. Nevertheless, both potentials exhibit similar deformation mechanisms and hardness estimates that are consistent with experimental data. Secondly, we consider nonequilibrium processes for classical binary mixtures described by a set of different purely repulsive pair interaction potentials in which an infinite-temperature (ideal-gas) configuration is rapidly quenched to zero temperature. It is found that such systems display two kinds of ordering processes, the type of which can be controlled by tuning the interactions between unlike particles. While strong inter-species repulsion leads to chemical ordering in terms of an unmixing process, weak repulsion gives rise to spontaneous crystallization, maintaining chemical homogeneity. Furthermore, the dual-type behavior appears to be universal for repulsive pair-interaction potential- energy functions in general, with the propensity for the crystallization process being related to their behavior in the neighborhood of zero separationDoutoradoFísicaDoutor em Ciências1583238/2016CAPE

Estudo da influência de um sistema HHO no desempenho de um motor de combustão interna

Com a exagerada dependência dos combustíveis fósseis que são finitos, necessitamos de alternativas energéticas que possam ser utilizados. Mas enquanto essas alternativas não chegam (o tempo de maturação é bastante longo) pode ser feita uma outra abordagem no sentido da redução do consumo nos sistemas de propulsão já existentes (como exemplo os motores a gasolina) fazendo com que seja necessário menos combustível ou pelo aumento da sua eficiência. Pela, dir-se-ia excessiva, dependência que fomos criando no uso dos combustíveis fósseis, estes são por excelência os que mais poderão afetar o futuro do planeta, por um lado pela dependência, mas por outro pela poluição imensa que o seu uso provoca. Há vários anos que existem diversos projetos de aplicação de outros tipos de energia como por exemplo a solar, a eólica, a mare motriz, o gás natural (fóssil) e o hidrogénio. Alguns deles têm já um período de gestação muito longo e estão, por isso, em utilização com resultados expressivos. Outros ainda não foram postos em prática apesar dos avanços que já existem. Todos sabemos que estas novas fontes de energia, consideradas renováveis, levarão muito tempo para substituir as já existentes, sobretudo pelo elevado custo de substituição de todos os sistemas e equipamentos instalados. Enquanto este processo avança, é importante gastar menos e melhor a energia das fontes não renováveis. O aumento da eficiência dos motores de combustão interna é fulcral nesta fase e é perseguido pelos construtores de motores. O hidrogénio contido na molécula de água é o que vai ser alvo deste estudo. O uso do hidrogénio (contido na água) como combustível tem vindo a ganhar interesse desde há algumas décadas e existem ensaios um pouco por todo o mundo (a internet permite-nos conhecê-los com facilidade) mas, por não ter encontrado estudo científico que os valide, apresenta-se este trabalho. O facto de o hidrogénio ter uma capacidade calorifica muito grande, cerca de 4 vezes superior ao da gasolina, faz com que se deseje o seu uso. Por outro lado, o perigo de explosão está sempre patente. Mas este perigo reside no armazenamento do hidrogénio e não no seu uso. O objeto deste trabalho é testar um sistema (aparelho) que produz uma pequena quantidade de hidrogénio ou melhor que separa o hidrogénio do oxigénio, fazendo que esses dois gases sejam introduzidos na admissão do motor de combustão interna, montado num banco de ensaio, e analisar os ganhos que são apregoados pelo fabricante desse mesmo aparelho. O aparelho é ligado ao sistema elétrico do automóvel e o resultado da eletrolise (que serão moléculas de hidrogénio e oxigénio) vai ser misturada no ar de admissão. Pretende-se validar se a inclusão destes gases diretamente na admissão vão fazer com que o motor consuma menos gasolina. O motor está ligado a um banco de potência para que se possa variar as condições de carga e desta forma obter o máximo de resultados com variações de rotação e de carga de acelerador. Foram feitos testes exaustivos com diferentes combinações tendo sempre o cuidado de afastar o fator humano dos resultados. A conclusão a que se chega é que o sistema HHO não promove uma melhora o desempenho dos motores no que respeita à redução dos consumos de combustível fóssil.With the exaggerated dependence on fossil fuels that are finite, we need alternative energy sources that could be used. But while these alternatives do not reach (the maturation time is quite long) we can make another approaches towards reducing consumption in propulsion systems which already exist (for example petrol engines) changing it to need less fuel or by increasing their efficiency. We were creating an excessive dependence in the use of fossil fuels, these are par excellence the ones that can most affect the future of the planet, on one hand by the dependency that it creates, and by other hand for the massive pollution that its use causes. For many years there are several implementation projects of other types of energy such as solar, wind, driving mare, natural gas (fossil) and hydrogen. Some of them already have a long gestation period and are therefore used with impressive results. Others have not yet been implemented despite advances that already exist. We all know that these new sources of energy, renewable, will take a long time considered to replace existing ones, especially the high replacement cost of all systems and equipment installed. As this process moves forward, it is important to spend less and better non-renewable sources of energy. Increased efficiency of internal combustion engines is key at this stage and is pursued by the engine builders. The hydrogen contained in the water molecule is what will be the target of this study. The use of hydrogen (contained in the water) as fuel has gained interest from a few decades and there are tests all over the world (the internet allows us to meet them easily) but none is a scientific work that can be trustable. That was the main reason to do this study Hydrogen has a very big power, about 4 times higher than petrol, and this is why many people wish to use it. On the other hand, the danger of explosion is always present. However this danger lies in hydrogen storage and not on its use. The object of this work is to test a system (apparatus) that produces a small amount of hydrogen or even better, that separates the hydrogen from the oxygen, and putting these two gases introduced into the admission of the internal combustion engine, mounted on a test bench, and analyze the gains that are told by the manufacturer of this specific device. The apparatus is connected to the electric system of the car and the result of electrolyzes (which will be hydrogen and oxygen molecules) will be mixed in the intake air. The aim is to validate whether the inclusion of these gases directly on admission will cause less petrol consumption. The engine is connected to a test bench that allows varying the load conditions and thus obtaining maximum results with variations in rotation and accelerator load. Extensive tests were made with different combinations always taking care to keep off the human factor of the results. In conclusion, we can say that the HHO system does not improves engine performance in regard to the reduction of fossil fuel consumption

Environmental Education in Initial Training: Effects of a Physical Activities and Sports in the Natural Environment Program for Sustainable Development

This research has been carried out within the R+D+i project ‘University Service-Learning in Physical Activity and Sport. Opportunity for social inclusion’, reference PID2019-105916RB-I00. In addition, funding has also been obtained from the Spanish Sports Council, through the RIADIS Research Network with reference code 03/UPB/20.Training for sustainable development is an educational challenge of prime importance. Physical activity and sports in natural environments provide training committed to sustainability and environmental education. The objective of this study was to assess the effects of an undergraduate training program in Physical Activities and Sports in Natural Environments concerned with sustainable development. A total of 113 students from the Autonomous University of Madrid (Spain) who are studying a Bachelor’s Degree in Physical Activity and Sports Sciences and a Master’s Degree in Teacher Training for Secondary Education and High School (specializing in Physical Education) were involved. Specifically, we aimed to assess the impact of this training program on three dimensions related to Environmental Education (knowledge, behaviors, and attitudes). Its effect was also examined bearing in mind students’ sex, age and educational profile (sportive and educational). Mixed-methods were used: for the quantitative approach, data were collected with the Environmental Attitude in Physical Activities in Natural Environments validated scale; for the qualitative approach individual reflective diaries completed by students that attended the program were analyzed. The results show positive effects on the students regarding the three dimensions of Environmental Education, for both the sportive and educational training profiles. The quantitative results do not present significant differences concerning the gender variable, although the qualitative information shows that female students perceived a greater environmental sensitivity during their practices. Regarding the age variable, significant differences are found in the youngest students with an educational profile. To conclude, the study ratifies that the program carried out generated improvements in terms of knowledge, behaviors and attitudes toward the environment and sustainable development. Future research should use larger samples and consider other variables related to education for sustainability.PID2019-105916RB-I00Spanish Sports Council 03/UPB/2