Defect Analysis and Detection of Cutting Regions in CFRP Machining Using AWJM

The use of composite materials with a polymeric matrix, concretely carbon fiber reinforced polymer, is undergoing further development owing to the maturity reached by the forming processes and their excellent relationship in terms of specific properties. This means that they can be implemented more easily in di erent industrial sectors at a lower cost. However, when the components manufactured demand high dimensional and geometric requirements, they must be subjected to machining processes that cause damage to the material. As a result, alternative methods to conventional machining are increasingly being proposed. In this article, the abrasive waterjet machining process is proposed because of its advantages in terms of high production rates, absence of thermal damage and respect for the environment. In this way, it was possible to select parameters (stand-o distance, traverse feed rate, and abrasive mass flow rate) that minimize the characteristic defects of the process such as taper angle or the identification of di erent surface quality regions in order to eliminate striations caused by jet deviation. For this purpose, taper angle and roughness evaluations were carried out in three di erent zones: initial or jet inlet, intermediate, and final or jet outlet. In this way, it was possible to characterize di erent cutting regions with scanning electronic microscopy (SEM) and to distinguish the statistical significance of the parameters and their e ects on the cut through an analysis of variance (ANOVA). This analysis has made it possible to distinguish the optimal parameters for the process

A cultura da entronização e da eternização da elite política

Para além de outras contingências, as consequências práticas da entrada em vigor da lei da limitação dos mandatos1 revelaram uma tendência da elite política para o cultivo de estratégias de residência permanente nos lugares de representação. As atitudes sequentes dos políticos, colhidos pela legislação, em procurar, imediatamente, outros cargos com visibilidade e poder na administração pública ou em passar dos órgãos executivos para os órgãos deliberativos, denunciam, genericamente, uma cultura política estabelecida e uma predisposição propensa ao torneamento de regulamentos, verificando- -se, desse modo, uma fórmula similar de funcionamento das diversas organizações partidárias e um espírito pariforme na interpretação do fenómeno político pelos seus agentes.info:eu-repo/semantics/publishedVersio

Vector-borne disease risk indexes in spatially structured populations

There are economic and physical limitations when applying prevention and control strategies for urban vector borne diseases. Consequently, there are increasing concerns and interest in designing efficient strategies and regulations that health agencies can follow in order to reduce the imminent impact of viruses like Dengue, Zika and Chikungunya. That includes fumigation, abatization, reducing the hatcheries, picking up trash, information campaigns. A basic question that arise when designing control strategies is about which and where these ones should focus. In other words, one would like to know whether preventing the contagion or decrease vector population, and in which area of the city, is more efficient. In this work, we propose risk indexes based on the idea of secondary cases from patch to patch. Thus, they take into account human mobility and indicate which patch has more chance to be a corridor for the spread of the disease and which is more vulnerable. They can also indicate the neighborhood where hatchery control will reduce more the number of potential cases. In order to illustrate the usefulness of these indexes, we run a set of numerical simulations in a mathematical model that takes into account the urban mobility and the differences in population density among the areas of a city. If i is a particular neighborhood, the transmission risk index TR_i measures the potential secondary cases caused by a host in that neighborhood. The vector transmission risk index VTR_i measures the potential secondary cases caused by a vector. Finally, the vulnerability risk index VR_i measures the potential secondary cases in the neighborhood. Transmission indexes can be used to give geographical priority to some neighborhoods when applying prevention and control measures. On the other hand, the vulnerability index can be useful to implement monitoring campaigns or public health investment.Comment: 16 pages, 5 figure

Rugosidad a larga distancia en una aleación de aluminio dendrítica

Se estudia la rugosidad a larga distancia de la superficie de fractura de una aleación dendrítica de aluminio, el análisis se efectúa en un amplio intervalo de escalas de longitud. Se realizó el análisis de autoafinidad a muestras fracturadas en ensayos de impacto de Charpy. El uso conjunto de microscopía de fuerza atómica (MFA), microscopía electrónica de barrido (MEB) y perfilometría permitió cubrir una espectro de longitudes de escala desde un nanómetro hasta cerca de un centímetro. Se obtuvo el exponente de rugosidad, así como la longitud de correlación, utilizando el método de ventana de ancho variable. Se obtuvo un valor de z @ 0.8 para el exponente de rugosidad, correspondiendo el valor re- portado como “universal”. Se encontró que el valor de la longitud de correlación corresponde a las longitudes características de las mayores heterogeneidades presentes en la microestructura compleja del material. Estos resultados proveen información que ayuda a mejorar nuestra comprensión del papel de los parámetros microestructurales en los mecanismos de propagación de grietas

Surface Quality and Free Energy Evaluation of s275 Steel by Shot Blasting, Abrasive Water Jet Texturing and Laser Surface Texturing

Surface modification by different technologies prior to joining operations or improving tribological properties is a point of great interest. Improving surface activation by increasing the roughness of the metal is a relationship that is becoming more defined. In turn, an increase in surface wettability by evaluating contact angles indicates surface activation by obtaining a high surface free energy. Technologies such as shot blasting and laser surface texturing (LST) have generated several scientific studies where they have identified the influence of parameters on the formation of rough surfaces with defined patterns. However, the application of abrasive water jet texturing (AWJT) has been little studied as an alternative. This article compares these technologies in the texturing of a carbon steel s275 in order to identify the relationship between surface quality and surface activation. It has been determined that AWJT produces the highest Rt values close to 64 mu m with a cross feed of 0.45 mm and a traverse speed of 5000 mm/min. Furthermore, LST obtains the best values of free surface energy by combining a power of 20 W with a frequency of 20 kHz and a sweeping speed of 10 mm/s. Finally, contour diagrams have been obtained which relate these variables to the texturing parameter

On the Machinability of an Al-63%SiC Metal Matrix Composite

This paper presents a preliminary study of aluminium matrix composite materials during machining, with a special focus on their behavior under conventional processes. This work will expand the knowledge of these materials, which is considered to be strategic for some industrial sectors, such as the aeronautics, electronics, and automotive sectors. Finding a machining model will allow us to define the necessary parameters when applying the materials to industry. As a previous step of the material and its machining, an experimental state-of-the-art review has been carried out, revealing a lack of studies about the composition and material properties, processes, tools, and recommended parameters. The results obtained and reflected in this paper are as follows; SiC is present in metallic matrix composite (MMC) materials in a very wide variety of sizes. A metallographic study of the material confirms the high percentage of reinforcement and very high microhardness values registered. During the machining process, tools present a very high level of wear in a very short amount of time, where chips are generated and arcs are segmented, revealing the high microhardness of the material, which is given by its high concentration of SiC. The chip shape is the same among other materials with a similar microhardness, such as Ti or its alloys. The forces registered in the machining process are quite di erent from conventional alloys and are more similar to the values of harder alloys, which is also the case for chip generation. The results coincide, in part, with previous studies and also give new insight into the behavior of this material, which does not conform to the assumptions for standard metallic materials, where the hypothesis of Sha er is not directly applicable. On the other hand, here, cutting forces do not behave in accordance with the traditional model. This paper will contribute to improve the knowledge of the Al-63%SiC MMC itself and the machining behavior

Synovial giant cell tumor of the knee

Tumor gigantocelular sinovial é uma neoplasia benigna, raramente sendo relatada na forma de metástase maligna. A localização mais comum de ocorrer um tumor gigantocelular sinovial é na mão e as mais infrequentes são tornozelo e joelho. No presente estudo os autores têm como objetivo descrever um caso raro de tumor gigantocelular sinovial localizado no joelho e o tratamento escolhido. A artroscopia demonstrou, nesse caso, ser o método ideal para o tratamento da lesão, uma vez que permitiu abordagem pouco agressiva e, ao mesmo tempo, boa visualização de todos os compartimentos da articulação do joelho e a completa ressecção do tumor.Synovial giant cell tumor is a benign neoplasm, rarely reported in the form of malignant metastasis. Synovial giant cell tumor most frequently occurs on the hand, and, most uncommon, on the ankle and knee. In the present study, the authors describe a rare case of synovial giant cell tumor on the knee as well as the treatment approach. Arthroscopy has been shown, in this case, to be the optimal method for treating this kind of lesion, once it allowed a less aggressive approach, while providing good visualization of all compartments of knee joint and full tumor resection

Comparison of two diets with modified human milk regarding growth and bone mineralization of very low birth weight infants

OBJETIVO: Comparar a eficácia e tolerabilidade de duas dietas à base de leite humano (LH) acrescido de fórmula láctea (PreNan®) ou complemento nutricional especial (FM 85®) na promoção do crescimento pôndero-estatural, mineralização óssea e tempo de hospitalização de recém-nascidos de muito baixo peso (RNMBP). MÉTODO: Foram constituídos, por sorteio, dois grupos de crianças acompanhadas a partir do 15º dia de vida, até atingir o peso de alta (2000±20g): Grupo A, 14 RNMBP receberam LH+FM 85® (5g/100mL LH); Grupo B, 11 RNMBP receberam LH+PreNan® 19% em volumes iguais. Foram avaliados: peso, comprimento, perímetro cefálico e prega cutânea tricipital média esquerda, calculando-se os incrementos de peso e o tempo para atingir 2000g. Foram dosados: cálcio, fósforo, magnésio e creatinina séricos e urinários e fosfatase alcalina sérica, calculando-se as taxas de reabsorção tubular de fósforo (%TPR). A mineralização óssea foi avaliada por meio de técnicas radiológicas padronizadas. RESULTADOS: 11 RNMBP de cada grupo completaram o estudo. Ambas as dietas foram bem toleradas e os índices antropométricos e dosagens séricas iniciais não apresentaram diferenças entre os grupos. Os incrementos de peso do Grupo B foram superiores aos do Grupo A e a fosfatase alcalina sérica do Grupo A foi maior que do Grupo B no final da observação. Não houve diferenças entre os grupos quanto à %TPR; mineralização óssea e tempo de hospitalização. CONCLUSÕES: Ambas as dietas foram bem toleradas. O leite humano enriquecido com PreNan® 19% volume a volume (v/v) se mostrou mais eficiente em relação ao ganho de peso e ao metabolismo ósseo em comparação ao leite humano acrescido de FM 85®.OBJECTIVE: To compare the efficacy and tolerability of two diets based on human milk (HM) added with PreNan® or FM 85® on physical growth, bone mineralization and duration of hospitalization. METHODS: Two groups of very low birth weight (VLBW) infants were studied: Group A, 14 infants fed with HM+FM 85® (5g/100mL HM) and Group B, 11 infants fed with HM+PreNan® 19% volume to volume (v/v), from the 15th day of life up to 2000g of weight. The parameters measured were: weight, length, head circumference; mean left triciptal skinfold thickness; calcium, phosphorus, magnesium and creatinine (serum and urine) and alkaline phosphatase (serum) at the beginning and at the end of the observation. The tubular phosphorus reabsorption rate (%TPR) was calculated and bone mineralization was assessed by X-ray. RESULTS: 11 infants of each group completed the study. There were no differences between the two groups at the beginning of the study. Weight gain per day (g/d) or per kg per day (g/kg/d) was significantly higher in Group B, and duration of hospitalization was shorter. Serum calcium, phosphorus and magnesium levels did not differ between groups, but alkaline phosphatase levels were higher in Group A at the end of the study. Groups were similar regarding bone mineralization and %TPR. CONCLUSIONS: Both diets were well tolerated. In terms of weight gain and bone metabolism, supplementation of HM with PreNan® 19% v/v was slightly but significantly better than with FM 85®

Comparativo de variedades y densidad poblacional en el rendimiento del cultivo de arveja (Pisum sativum L.), bajo las condiciones edafoclimáticas de Pampa del Arco, Distrito de Huamanga – Región Ayacucho

El trabajo de tesis “Comparativo de variedades y densidad poblacional en el rendimiento del cultivo de arveja (Pisum sativum L.), bajo las condiciones edafoclimáticas de Pampa del Arco, Distrito de Huamanga – Región Ayacucho” se llevó a cabo en Pampa del Arco el 12 de Agosto de 2017 al 20 de enero del 2018, con los objetivos: Evaluar el comparativo de variedades y densidad poblacional en el rendimiento del cultivo de arveja, determinar la altura de planta, número de vainas por planta y evaluar la interacción de variedades y densidad poblacional y determinar costos de producción. Las variedades fueron: Usui (V1), Criollo (V2 testigo), Remate (V3), Alderman (V4) y Blanco criollo (V5), las densidades de siembra, 0,20 metros (D1), 0,30 metros (D2) y 0,40 metros (D4) y se utilizó el diseño experimental de bloques completamente al azar (DBCA), con arreglo en factorial (V x D) con cinco niveles factor V y factor D con tres niveles y tres bloques y 15 tratamientos con 45 unidades experimentales. El análisis estadístico empleado fue el análisis de varianza (ANVA) a una probabilidad f de 0,05 y 0,01, se realizó la prueba de significación de Tukey al 95 % de confiabilidad, en rendimiento se obtuvo interacción donde la combinación (V3D2) obtiene 8,92 kg/10,80 m2; resultando la variedad Alderman (V3) el mejor con 8,54 kg/10,80 m2 y en la densidad la (D2) con 7,42 kg/10,80 m2 y por un sol invertido ganan 1,62 soles.Tesi