Resumen: En esta investigación se propone una metodología basada en ciencia de datos para estimar la factibilidad técnica de implementación de sistemas de potencia híbridos solares-eólicos, a partir del cálculo del factor de planta o factor de capacidad (CF). Los datos son obtenidos a partir de la estación meteorológica NOVALYNX 110-WS-18, entre el año 2018 y 2020, para determinar el potencial energético disponible en la sede Candelaria del campus de la Universidad de la Salle (Colombia). Mediante el uso del software Matlab, se aplica el algoritmo de agrupamiento de datos k-medias en los siguientes descriptores: tiempo, radiación solar, velocidad del viento y temperatura. Los resultados muestran que el sistema fotovoltaico y el sistema eólico tienen un CF correspondiente a 36.69 % y 2.15 % respectivamente. Se concluye que es factible técnicamente la implementación de un sistema fotovoltaico en la Universidad de La Salle; sin embrago, un sistema eólico no cumple con el CF mínimo.

Abstract: This research study proposes a methodology based on data science to estimate the technical feasibility of implementing hybrid solar-wind power systems by calculating the plant factor, also known as capacity factor (CF). Data is gathered from the NOVALYNX 110-WS-18 weather station, between the years 2018 and 2020, to determine the energetic potential available for the Candelaria campus at the La Salle University (Colombia). A k-means data clustering algorithm, developed in Matlab, is applied over the following descriptors: time, solar radiation, wind speed, and temperature. The results show that the photovoltaic and wind power systems have a CF of 36.69% and 2.15%, respectively. It is concluded that it is technically feasible to implement a photovoltaic system at the La Salle University, but not a wind power system as it does not meet the minimum CF required.

ABSTRACT In this work, a mathematical model of efficiencies for hybrid Fuel Cell (FC) systems is presented, considering the series (SH), parallel (PH), and serial-parallel (SPH) topologies. In these systems, were implemented modular non-inverting Buck-Boost converters. Their efficiency functions depend on their operating points, particularly their output currents and operation modes (Buck, Boost, and Buck-Boost). In addition, the DC Bus efficiency has been modeled and used in each system, corresponding to a function of the load duty cycle with a frequency of 100 Hz. This DCBus'speakpower and nominal voltage correspond to 1.5 kW and 48 V, respectively. These hybrid systems were implemented in SIMULINK/MATLAB®, considering the capacitors' initial voltage or pre-charge conditions to reduce the computation time. The analytical and experimental results are validated using the Nash-Sutcliffe Coefficient of Efficiency (NSE).

RESUMEN En este trabajo se presenta un modelo matemático de eficiencias para sistemas híbridos Fuel Cell (FC), considerando las topologías serie (SH), paralelo (PH) y serie-paralelo (SPH). En estos sistemas, se implementaron convertidores Buck-Boost modulares no inversores. Sus funciones de eficiencia dependen de sus puntos de operación, particularmente de sus corrientes de salida y modos de operación (Buck, Boost y Buck-Boost). Además, la eficiencia del Bus de DC se ha modelado y utilizado en cada sistema, el cual corresponde una función del ciclo de trabajo de carga con una frecuencia de 100 Hz. La potencia pico y la tensión nominal de este bus de CC corresponden a 1,5 kW y 48 V, respectivamente. Estos sistemas híbridos fueron implementados en SIMULINK / MATLAB®, considerando condiciones iniciales de tensión o de precarga en los capacitores para reducir el tiempo de cómputo. Los resultados analíticos y experimentales se validan mediante el coeficiente de eficiencia de Nash-Sutcliffe (NSE).

Three new triterpenes, 3,4-seco-3,11β-epoxyfriedel-4(23)-en-3β-ol (1), friedelan-3α,11β diol (2), 7β,26-epoxyfriedelan-3a,7a-diol (3), a mixture of two new triterpenes 3α-hydroxyfriedelan-29-yl palmitate (4) and 3α-hydroxyfriedelan-29-yl stearate (5) and eleven known compounds were obtained from the hexane extract of Maytenus quadrangulata leaves. The structures and the relative stereochemistry of the new triterpenes were established through 1D/2D nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS), and Fourier transform infrared (FTIR) spectral data. The hexane extract and isolated compounds were submitted to the cytotoxicity assays against leukemia (THP-1 and K562), ovarian (TOV-21G) and breast cancer (MDA-MB-231) cell lines. Compounds 1, 2 and 11β-hydroxyfriedelan-3-one (15) displayed high cytotoxicity and selectivity against leukemic cells when compared to positive control cytarabine (for THP-1) and imatinib (for K562). Furthermore, compound 2 showed similar cytotoxicity and an enhanced selectivity towards ovarian and breast cells in comparison to positive control etoposide.

Abstract Immunodeficiency virus and feline leukemia virus represent major problems for domestic felines due to the multiplicity of symptoms they manifest. The objective of the present study was to establish, retrospectively, the prevalence in the presentation of FeLV and FIV in patients from six small animal clinics in Bogota and Chia, related to factors such as age, race, and gender. A cross-sectional and retrospective study was carried out, collecting data from 1.014 clinical records of feline patients who were admitted to six clinics in the city of Bogota and Chia, to determine the prevalence of FIV and FeLV and their association with factors such as age, gender, and race, between 2015 and 2019 through the OR test. The detection of the viruses was carried out through a rapid test based on immunochromatography. The highest prevalence for each disease per year was 12,3% for FIV in 2012 and 18% for FeLV in 2019. Males presented higher seroprevalences for both diseases during most of the years evaluated. Factors such as race (Creole: FIV: 1,85; FeLV: 2,01), gender (male: FIV: 1.53 OR, FeLV: 1,64), and age (> 7 years: FIV: 3.82; FeLV: 3.21) were positively related to the presentation of both diseases in the feline population evaluated.

Resumen Los virus de inmunodeficiencia y leucemia felina representan un problema de gran envergadura para los felinos domésticos debido a la multiplicidad de sintomatologías que manifiestan. El objetivo del presente estudio fue establecer, retrospectivamente, la prevalencia en la presentación de ViLeF y VIF en pacientes de seis clínicas de pequeños animales en Bogotá y Chía, en relación con factores como su edad, raza y género. Se realizó un estudio transversal y retrospectivo, mediante la recopilación de datos de 1.014 historias clínicas de pacientes felinos que ingresaron a seis clínicas de la ciudad de Bogotá y Chía, para determinar la prevalencia de VIF y ViLeF y la asociación de estas con factores como edad, género y raza, entre 2015 y 2019, a través de la prueba OR. La detección de los virus se realizó mediante una prueba rápida basada en inmunocromatografía. La mayor prevalencia para cada enfermedad por año fue: 12,3% para VIF en 2012 y 18% para ViLeF en 2019. Los machos presentaron mayores seroprevalencias para ambas enfermedades durante la mayoría los años evaluados. Factores como raza (criolla: VIF: 1,85; ViLeF: 2,01), género (macho: VIF: 1,53 OR; ViLeF: 1,64) y edad (> 7 años: VIF: 3,82; ViLeF: 3,21) se relacionaron positivamente con la presentación de ambas enfermedades en la población felina evaluada.

ABSTRACT A mathematical model was developed to describe the dynamics of the primary infection of dengue virus in infants who were born to a mother immune to some serotype of the dengue virus. The model is given by a system of nonlinear ordinary differential equations with time-dependent variables for the number of dengue virus antibodies of the infant transferred from their immune, uninfected, and infected monocytes and dengue virus. The mathematical analysis was carried out where the conditions for the existence of the disease-free equilibrium and the endemic equilibrium were established. The numerical simulations were performed considering different scenarios for a basic reproductive number, R 0, illustrating the global convergence of the numerical results for the equilibrium points. The results are in agreement with our derived global stability analysis. It can be concluded that dengue hemorrhagic fever in infants could occur in the peaks observed for the infected monocytes and dengue virus.

RESUMO A capacidade de sistemas de irrigação é tipicamente definida assumindo probabilidades de não-excedência de valores de evapotranspiração. O uso de valores médios mensais de ET0 pode conduzir a subdimensionamento da capacidade, enquanto valores máximos diários podem resultar em superdimensionamento. Este estudo teve os seguintes objetivos: (1) analisar uma série de 30 anos contendo dados diários de ET0 em Piracicaba, SP, Brasil, avaliando a aptidão da distribuição de Gumbel para a estimativa de valores máximos de ET0 organizados em períodos de até 30 dias; (2) determinar valores máximos prováveis e selecionar valores de ET0 considerando o intervalo entre irrigações e o risco de falha em termos de capacidade do sistema de irrigação. Dados diários, de 1990 a 2019, foram utilizados para calcular a ET0 pelo modelo de Penman-Monteith. A distribuição de Gumbel se ajustou aos dados e foi adequada para caracterizar a distribuição de frequência de valores máximos de ET0. A ET0 provável para o projeto de sistemas de irrigação foi estimada com base na vida útil do sistema, intervalo entre irrigações e período de retorno de valores máximos de ET0. Quanto maior for a vida útil do sistema de irrigação, maior deve ser o período de retorno adotado para reduzir o risco de falha. O uso da média dos valores máximos de ET0 conduz a subdimensionamento e alto risco de falha em termos de capacidade do sistema de irrigação.

ABSTRACT Irrigation system capacity is typically defined by analyzing probabilities of non-exceedance of evapotranspiration. The use of mean monthly values of ET0 may lead to underestimation of the required capacity, whereas use of maximum daily values may result in overestimation of required capacity. This study had the following objectives: (1) to analyze a 30-year series of daily ET0 data from Piracicaba, SP, Brazil, to evaluate the suitability of the Gumbel distribution for estimating the maximum values of ET0 organized in periods of up to 30 days; (2) to determine probable maximum values and to select ET0 values considering the irrigation interval and the risk of failure in terms of irrigation system capacity. Daily data from 1990 to 2019 were used to calculate ET0 using the Penman-Monteith model. The Gumbel distribution fitted to the data and was suitable for characterizing the frequency distribution of the maximum ET0. The probable ET0 for designing irrigation systems can then be estimated based on the expected lifespan, irrigation interval, and return period of ET0 maximum values. The higher the anticipated irrigation system lifespan, the higher the return period needed to attain a low risk of failure. Using the average of maximum ET0 values alone leads to underestimation of system capacity and a high risk of failure in terms of irrigation system capacity.

RESUMO Objetivou-se neste estudo avaliar três metodologias para a estimativa da vazão de água em placas de orifício, quantificando erros nas determinações de vazão a fim de sugerir a faixa de medição apropriada para cada condição avaliada. Foram avaliados dois modelos de placa de orifício (diâmetros nominais 100 e 150 mm) com restrição de 50% em relação ao diâmetro nominal. Nas equações teóricas, o coeficiente de descarga foi obtido pela equação de Reader-Harris/Gallagher (Método 1) e aproximado a partir de dados experimentais pelo coeficiente angular de uma reta com intercepto igual a zero (Método 2). A faixa de medição recomendada para manter os erros inferiores a 5% para a placa de 100 e 150 mm foi de 30 a 65 m3 h-1 e de 70 a 130 m3 h-1 utilizando a equação teórica e de 20 a 65 m3 h-1 e de 40 a 130 m3 h-1 utilizando a equação empírica, respectivamente. A equação de Reader-Harris/Gallagher (Método 1) estimou adequadamente o coeficiente de descarga dos modelos de placas de orifício, entretanto o uso de equações empíricas (Método 3) proporcionou menores erros de medição e maior rangeabilidade dos medidores de vazão avaliados.

ABSTRACT This study aimed to evaluate three methodologies for orifice-plate water-flow estimation by quantifying errors in the flow determinations to propose an appropriate measurement range for each evaluated condition. Two orifice-plate models (nominal diameters of 100 and 150 mm) with 50% restriction in the flow section were evaluated. In the theoretical equations, the discharge coefficient was obtained using the Reader-Harris/Gallagher equation (Method 1) and approximated from experimental data using the angular coefficient of a zero-intercept straight line (Method 2). The recommended measurement ranges for errors that were lower than 5% for the 100 and 150 mm plates were 30 to 65 m3 h-1 and 70 to 130 m3 h-1 using the theoretical equation and 20 to 65 m3 h-1 and 40 to 130 m3 h-1 using the empirical equation, respectively. The Reader-Harris/Gallagher equation (Method 1) adequately estimated the discharge coefficient of the orifice plates; however, the use of empirical equations (Method 3) demonstrated smaller measurement errors and greater rangeability of the evaluated flow meters.

RESUMO Objetivou-se neste estudo quantificar o efeito de variações da temperatura da água na vazão de fitas gotejadoras colapsáveis, de parede fina, com emissores integrados não regulados. Os ensaios foram conduzidos em laboratório utilizando estrutura de ensaios automatizada. Foram realizados ensaios para determinação das curvas vazão-pressão sob temperaturas de ensaio na faixa de 20 a 50 ºC, para nove modelos de emissores com três espessuras de parede (6, 8 e 9 MIL). Curvas vazão-pressão apresentaram distintos parâmetros K e x para cada temperatura. Para os emissores planos de fluxo turbulento (x < 0,5), a vazão diminuiu com o incremento da temperatura. Para os emissores contínuos de fluxo turbulento, respostas diferentes foram obtidas, sendo que no emissor D (x > 0,5) a vazão aumentou com o incremento da temperatura, enquanto no emissor C (x < 0,5), a vazão diminuiu e as maiores variações de vazão ocorreram a partir de 60 kPa. Para o emissor moldado, a vazão aumentou em função da temperatura, porém, a maior variação ocorreu nas menores pressões. Para nenhum dos emissores houve diferença significativa na variação de vazão entre as espessuras de parede.

ABSTRACT The objective of this study was to quantify the effect of water temperature variations on the discharge of collapsible thin-walled drip tapes with integrated non-pressure-compensating emitters. The tests were conducted in the laboratory using an automated test bench. Tests were performed to determine the discharge-pressure curves by varying the water temperature from 20 to 50 °C. Nine emitter models of three wall thicknesses (6, 8, and 9 MIL) were evaluated. The coefficients K and x of the discharge-pressure curves varied according to the water temperature. In flat emitters of turbulent flow (x < 0.5), the discharge decreased as the temperature increased. In the welded emitters of turbulent flow, several responses were observed. Regarding emitter D (x > 0.5), the discharge increased as the temperature was increased, while for emitter C (x < 0.5), the discharge decreased; the highest discharge variations occurred at pressures higher than 60 kPa. For embossed emitters, the discharge increased as a function of temperature, however, the greatest variation occurred at the lowest pressures. None of the emitters showed significant difference in the discharge variation due to wall thicknesses.

ABSTRACT Objective: Obesity is characterized by a state of chronic, low-intensity systemic inflammation frequently associated with insulin resistance and dyslipidemia. Materials and methods: Given that chronic inflammation has been implicated in the pathogenesis of mood disorders, we investigated if chronic obesity that was initiated early in life – lasting through adulthood – could be more harmful to memory impairment and mood fluctuations such as depression. Results: Here we show that pre-pubertal male rats (30 days old) treated with a high-fat diet (40%) for 8-months gained ~50% more weight when compared to controls, exhibited depression and anxiety-like behaviors but no memory impairment. The prefrontal cortex of the obese rats exhibited an increase in the expression of genes related to inflammatory response, such as NFKb, MMP9, CCl2, PPARb, and PPARg. There were no alterations in genes known to be related to depression. Conclusion: Long-lasting obesity with onset in prepuberal age led to depression and neuroinflammation but not to memory impairment.

RESUMO O objetivo deste estudo foi avaliar o teor residual da aplicação de doses fosforo (P) via fertilizante organomineral (FO) em dois solos cultivados com repolho e alface em sucessão. Em blocos casualizados, utilizou-se cinco doses de FO como fonte de P. No Oxisol aplicaram-se: 0; 50; 100; 200 e 300% da dose de P recomendada para o repolho com utilização de FO, mais um tratamento com 100% da dose via fertilizante mineral. No Entisol aplicaram-se: 0; 50; 100; 200 e 300% da dose de P com FO para a cultura do repolho, além de um tratamento adicional (100% mineral), com quatro repetições. Avaliaram-se a produção de massa fresca (MF) e seca (MS), estado nutricional do repolho e da alface e o efeito residual de nutrientes no solo. O teor residual do P no solo aumentou (p ≤ 0,05) quanto maior foi à dose de FO utilizada no Oxisol nos dois ciclos avaliados, enquanto que no Entisol isto só ocorreu no primeiro ciclo. Usando 50% da dose de FO no repolho em ambos os solos proporciona produção de MF e MS no mínimo 11% superior, comparado à adubação mineral.

ABSTRACT The objective of this study was to evaluate the residual concentration from the application of levels of phosphorus contained in an organomineral fertilizer (OMF) in two soils cultivated with cabbage and lettuce in succession. In randomized blocks, five doses of OMF were used as a source of P in Oxisol (0, 50, 100, 200, and 300% of the P dose was recommended for cabbage crop using OMF), plus an additional treatment (100% mineral). The doses applied to the Entisol were as follows: 0, 50, 100, 200, and 300% of the recommended P dose with OMF for cabbage crop, plus an additional treatment (100% mineral), with four repetitions. The production of fresh matter (FM) and dry matter (DM), the nutritional status of the cabbage and lettuce, and the residual effect of nutrients in the soil were also evaluated. The P concentration in the soil increased (p ≤ 0.05) with higher doses of OMF in the Oxisol in the two cycles evaluated. However, this occurred only in the first cycle in the Entisol. Using the 50% dose of OMF in the cabbage in both soils provided FM and DM production values that were at least 11% higher than those attained with mineral fertilizer.

RESUMO Jean-Martin Charcot, o neurologista mais célebre do século XIX, teve uma influência profunda na carreira de Sigmund Freud. Freud visitou o Departamento de Neurologia do Hospital Salpêtrière, em Paris, chefiado pelo professor Charcot, durante o inverno de 1885-1886. Durante este período, ele foi várias vezes à casa de Charcot para participar dos famosos saraus de terça-feira, sob a orientação de GiUes de la Tourette. Nessas ocasiões, Freud ficava sempre muito orgulhoso pelo convite, curioso por encontrar a elite intelectual Parisiense, mas também muito apreensivo, e fazia uso frequente de cocaína. Devido à ansiedade e à necessidade de aparentar-se produtivo diante de Charcot, é possível que Freud tenha usado cocaína outras vezes.

ABSTRACT Jean-Martin Charcot, the most celebrated neurologist of the 19th century, had a profound influence on Sigmund Freud's career. Freud spent the winter of 1885-1886 working in Charcot's neurology department in Paris. During this period, he went to Charcot's house on several occasions to participate in the very famous Tuesday soirées under the guidance of Gilles de la Tourette. Freud was always very proud to be invited and curious to meet the Parisian intellectual elite. On these occasions, however, he was very apprehensive and made frequent use of cocaine. Due to anxiety and the need to appear creative in front of Charcot, it is possible that Freud used cocaine at other times.

Resumo: Objetivos: Verificar o efeito da preparação psicológica no alívio da ansiedade pré-operatória de crianças e avaliar se há correlação com a ansiedade dos pais. Método: Após a aprovação do Comitê de Ética e Pesquisa da Faculdade de Medicina e obtenção do consentimento pelos responsáveis dos pacientes, foram selecionadas prospectivamente 118 crianças, de ambos os sexos, entre dois e oito anos, classificação de estado físico ASA I, atendidas no ambulatório de avaliação pré-anestésica do Hospital Universitário e submetidas a cirurgias ambulatoriais. Foram randomizados dois grupos controlados de 59 crianças: grupo de preparação básica e grupo de preparação psicológica. No dia da cirurgia, todas as crianças foram avaliadas em relação ao seu grau de ansiedade através da Escala de Ansiedade Pré-operatória de Yale Modificada e seus pais, avaliados quanto ao seu nível de ansiedade pela Escala Visual Analógica. O avaliador era cego sobre qual grupo do estudo a criança e seu familiar pertenciam. Resultados: Na análise dos resultados, foram excluídas nove crianças e familiares de cada grupo. As crianças do grupo preparado tiveram reduções significativas no grau de ansiedade em relação ao grupo controle, (p = 0,04). Não houve correlação entre os graus de ansiedade das crianças e seus pais (p = 0,78). Conclusão: A preparação psicológica foi eficaz na redução do grau de ansiedade das crianças no momento da cirurgia. Não houve, entretanto, relação entre os graus de ansiedade dos pais e seus filhos.

Abstract Objective: To verify the effect of psychological preparation on the relief of preoperative anxiety in children and to correlate parents' and children's levels of anxiety. Method: After the approval of the institutional Research Ethics Committee and written consent of the children's parents or guardians, 118 children of both genders were prospectively selected, aged between 2 and 8 years, physical condition classification ASA I, who were treated in the pre-anesthetic evaluation ambulatory of the University Hospital and who underwent ambulatory surgeries at the same hospital. Two controlled groups of 59 children were randomized: control group basic preparation and psychological preparation group. On the day of surgery, all selected children were evaluated regarding their level of anxiety using the modified Yale Preoperative Anxiety Scale and their parents were evaluated regarding their level of anxiety through the Visual Analog Scale. The evaluator was blinded to which study group the child and family member belonged to. Results: Nine children and their family members were excluded per group when the results were analyzed. Children from the prepared group showed significant reductions in their level of anxiety in relation to the control group (p = 0.04). There was no correlation between the level of anxiety of children and their parents' levels (p = 0.78). Conclusion: The psychological preparation was effective in reducing the level of anxiety of children. However, there was no relation between the level of anxiety of children and their parents' level.

RESUMO Injetores Venturi são comumente empregados para fins de fertirrigação na agricultura, extraindo fertilizante de um tanque para a linha de irrigação. O conhecimento da quantidade de líquido a ser injetado por este dispositivo é útil para assegurar operação e manejo adequados da fertirrigação. Os objetivos desta pesquisa foram: (1) conduzir testes funcionais de injetores Venturi seguindo as normas estabelecidas pela ISO 15873; e (2) modelar a vazão de injeção utilizando Análise Dimensional pelo teorema de Buckingham Pi. Quatro modelos de injetores Venturi foram submetidos a testes operacionais usando água limpa como fluido motriz e como fluido succionado. Um modelo geral para predição da vazão de injeção foi proposto e validado, sendo este dependente das propriedades do fluido, das condições hidráulicas operacionais e das características geométricas do injetor. Outro modelo para estimar a vazão motriz, em função da pressão de entrada e da pressão diferencial foi ajustado e validado para cada tamanho de Venturi. Finalmente, um exemplo de aplicação foi apresentado. O tamanho do injetor Venturi foi selecionado para atender aos requisitos da aplicação e as condições de operação foram estimadas utilizando os modelos propostos.

ABSTRACT Venturi injectors are commonly employed for fertigation purposes in agriculture, in which they draw fertilizer from a tank into the irrigation pipeline. The knowledge of the amount of liquid injected by this device is used to ensure an adequate fertigation operation and management. The objectives of this research were (1) to carry out functional tests of Venturi injectors following requirements stated by ISO 15873; and (2) to model the injection rate using dimensional analysis by the Buckingham Pi theorem. Four models of Venturi injectors were submitted to functional tests using clean water as motive and injected fluid. A general model for predicting injection flow rate was proposed and validated. In this model, the injection flow rate depends on the fluid properties, operating hydraulic conditions and geometrical characteristics of the Venturi injector. Another model for estimating motive flow rate as a function of inlet pressure and differential pressure was adjusted and validated for each size of Venturi injector. Finally, an example of an application was presented. The Venturi injector size was selected to fulfill the requirements of the application and the operating conditions were estimated using the proposed models.

RESUMO Informações sobre perda de carga localizada em conexões utilizadas em sistemas de microirrigação são difíceis de serem encontradas na literatura. O objetivo desta pesquisa foi determinar experimentalmente as perdas de carga localizada em conexões comumente empregadas nesses sistemas e propor modelos matemáticos utilizando o teorema de Buckingham. A metodologia dos ensaios foi baseada em recomendações de normas técnicas internacionais. Os ensaios foram realizados sob pressão de entrada controlada em 150 kPa, com cinco a dez unidades testadas para cada modelo de conexão. As curvas relacionando vazão e perda de carga localizada foram plotadas com base em 15 condições de vazão, obtidas sob incremento e decréscimo de vazão. Para cada condição, foram coletados 30 pontos, resultando num conjunto de 900 registros de dados a cada ensaio. Em cada modelo de conexão avaliado, foram obtidas as seguintes informações: curvas de perda de carga localizada em função da vazão e do coeficiente de perda de carga localizada (KL). Os valores de KL variaram de 2,72 a 24,16, o qual tornar-se constante para um número de Reynolds acima de 10000. Verificou-se também a sensibilidade do coeficiente KL relacionado com a proporção das seções internas nas conexões. Os expoentes de vazão apresentaram valores próximos ao que é aplicado pela equação de Darcy-Weisbach (m = 2). Os modelos matemáticos desenvolvidos para as conexões apresentaram desempenho satisfatório.

ABSTRACT Information about local head loss caused by connections employed in micro-irrigation systems is hard to be found in literature. The objective of this research was to experimentally determine the local head losses in connections commonly used in micro-irrigation and propose mathematical models using the theorem of Buckingham. The methodology of tests was based on international standards. The tests were carried out under controlled inlet pressure, at 150 kPa, and five to ten units of each connection model were tested. The curves relating flow and head losses were drawn based on 15 flow conditions, obtained under increase and decrease of flow rate. For each condition, 30 points were collected resulting in a sample size of 900 points in each test. For each connection model evaluated, the following information was obtained: curves of local head loss as a function of flow rate and of local head loss coefficient (KL). The obtained values of KL ranged from 2.72 to 24.16, which become constant for Reynolds number higher than 10,000. The sensitivity of the coefficient related to a ratio of the internal sections in the connections was also verified. The flow exponents presented values close to the one applied by the Darcy-Weisbach equation (m = 2). The models developed for the connections presented a satisfactory performance.