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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Quantitative microscopy of coating uniformity

Dahlström, Christina January 2012 (has links)
Print quality demands for coated papers are steadily growing, and achieving coating uniformity is crucial for high image sharpness, colour fidelity, and print uniformity. Coating uniformity may be divided into two scales: coating thickness uniformity and coating microstructure uniformity, the latter of which includes pigment, pore and binder distributions within the coating layer. This thesis concerns the investigation of both types of coating uniformity by using an approach of quantitative microscopy.First, coating thickness uniformity was analysed by using scanning electron microscope (SEM) images of paper cross sections, and the relationships between local coating thickness variations and the variations of underlying base sheet structures were determined. Special attention was given to the effect of length scales on the coating thickness vs. base sheet structure relationships.The experimental results showed that coating thickness had a strong correlation with surface height (profile) of base sheet at a small length scale. However, at a large length scale, it was mass density of base sheet (formation) that had the strongest correlation with coating thickness. This result explains well the discrepancies found in the literature for the relationship between coating thickness variation and base sheet structure variations. The total variance of coating thickness, however, was dominated by the surface height variation in the small scale, which explained around 50% of the variation. Autocorrelation analyses were further performed for the same data set. The autocorrelation functions showed a close resemblance of the one for a random shot process with a correlation length in the order of fibre width. All these results suggest that coating thickness variations are the result of random deposition of particles with the correlation length determined by the base sheet surface textures, such as fibre width.In order to obtain fundamental understandings of the random deposition processes on a rough surface, such as in paper, a generic particle deposition model was developed, and systematic analyses were performed for the effects of particle size, coat weight (average number of particles), levelling, and system size on coating thickness variation. The results showed that coating thickness variation3grows with coat weight, but beyond a certain coat weight, it reaches a plateau value. A scaling analysis yielded a universal relationship between coating thickness variation and the above mentioned variables. The correlation length of coating thickness was found to be determined by average coat weight and the state of underlying surfaces. For a rough surface at relatively low coat weight, the correlation length was typically in the range of fibre width, as was also observed experimentally.Non-uniformities within the coating layer, such as porosity variations and binder distributions, are investigated by using a newly developed method: field emission scanning electron microscopy (FESEM) in combination with argon ion beam milling technique. The combination of these two techniques produced extremely high quality images with very few artefacts, which are particularly suited for quantitative analyses of coating structures. A new evaluation method was also developed by using marker-controlled watershed segmentation (MCWS) of the secondary electron images (SEI).The high resolution imaging revealed that binder enrichment, a long disputed subject in the area, is present in a thin layer of a 500 nm thickness both at the coating surface and at the base sheet/coating interface. It was also found that the binders almost exclusively fill up the small pores, whereas the larger pores are mainly empty or depleted of binder.
42

A study of thermal comfort and cost effectiveness of stratum ventilation

Fong, Alan Ming-Lun January 2015 (has links)
This studyh focuses on thermal comfort and cost effectiveness of stratum ventilation in subtropical Hong Kong Special Adminstation Region (HKSAR). The need for studying thermal comfort with various air distribution strategies becomes a significant issue recently due to climate change, increasing energy prices and the governmental energy efficiency policy. Stratum ventilation, with air supplied at breathing level, can probably provide satisfactory thermal comfort at a relatively elevated indoor temperature in which less energy use is consumed. It seems that only limited studies on the evaluation of neutral temperature, which is a condition of neither slightly warm nor slightly cool, are supported by actual human comfort surveys. Moreover, study on the related thermal comfort and cost effectiveness as other paradigms in comparison with the mixing and displacement air distribution design is rare. New environmental chamber of laboratory-based air-conditioning systems has been developed for investigating the actual benefit of cost effectiveness and balance of thermal comfort satisfaction with the stratum air distribution strategy under subtropical climates. American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 7-point questionnaires have been collected from human comfort tests so as to estimate the neutral temperature of stratum ventilation in comparison with mixing and displacement ventilation at pre-set conditions. The neutral temperatures of HKSAR people under the mode of mixing, displacement, stratum, modified-stratum-1, modified-stratum-2, and modified-stratum-3 are found to be 24.6℃, 25.1℃, 25.6℃, 26.0℃, 27.1℃ and 27.3℃ at 10 air change per hour (ACH) respectively, which become 24.8℃, 25.3℃, 26.6℃, 27.4℃, and 27.9℃ at 15 ACH respectively. Life cycle assessment results in 10 service year indicate that 7.73% and 7.32% of cost reduction, and 14.52% and 11.91% of greenhouse gas emission reduction in stratum ventilation by comparing with mixing and displacement ventilation. As a result, stratum ventilation should be the best option on both of cost reduction, and less carbon emission in small-to-medium size air-conditioned space for new building and retrofitting existing works.
43

CFD in the design of gas quenching furnace

Macchion, Olivier January 2005 (has links)
<p>This thesis focuses on the numerical and theoretical studies of gas quenching in industrial furnaces. Gas quenching is the rapid cooling of metal pieces, aiming at forcing a phase transformation of the metal structure to improve its mechanical properties. The numerical methodology has been evaluated with respect to the desired accuracy and different aspects of the flow with importance for achieving an optimized process have been investigated. Initially, attention was paid to the flow and heat transfer fields both in an empty furnace and in a furnace loaded with different charges with the objective to study the influence of the charge configuration on the flow and heat transfer uniformity. This study led to the identification of several possible improvements, which are currently being implemented by the industrial partners of this project. As earlier studies had shown the importance of flow uniformity on the quality of the heat treatment, the subsequent work focused substantially on the flow uniformity upstream of the quenching zone resulting in design recommendations for the particular type of furnace under consideration. The dependence of the performance of the coolant medium on its composition was investigated theoretically and an analysis of most important parameters was carried out. Improved knowledge of the effect of gas mixture composition on heat transfer was added to the body of knowledge already available.</p>
44

The effect of ingredient properties, liquid system and mix time on uniformity of mix and testing of uniformity of mix

Saensukjaroenphon, Marut January 1900 (has links)
Master of Science / Department of Grain Science and Industry / Charles R Stark / The uniformity of a feed mixture is determined from the coefficient of variation (CV) of ten samples in a single batch of feed. The feed industry standard is a %CV of less than 10 using a single source tracer such as salt, trace minerals or iron filings. The uniformity of mix can be affected by many factors including ingredient properties, equipment design, mix time, sampling method, sample preparation and overall precision of method. The objectives of this thesis were to verify the chloride ion test by the Quantab® chloride titrator method and to determine the effect of extended mixing time, salt particle size, sample preparation, wet mix time, spray condition, application time of the liquid addition, percent liquid addition and mixer type on the uniformity of mix. The first experiment evaluated the effect of water temperature, technician, extraction time, dissolution time on the chloride ion test by the Quantab® chloride titrator method. The salt concentration was significantly affected by water temperature and dissolution time. The results of Experiment 1 demonstrated the 60ºC water temperature and the 30 s extraction time by stirring followed by immediately placing the strip into the solution after extraction should be used for the Quantab® chloride titrator method. The second experiment evaluated the effect of extended mix time, particle size of salt and sample preparation on the %CV. The extended mix time did not result in segregation (P > 0.30). However, particle size of the salt and sample preparation significantly affected the uniformity of mix. The results of Experiment 2 indicated that the extended mix time of up to 60 minutes did not increase the %CV of the feed; the particle size of the salt used in the uniformity of mix test can significantly change the results of the test; and grinding the sample prior to analysis improved the precision of the Quantab® chloride titrator method when coarse salt is used in the manufacturing process. The third experiment evaluated the effect of wet mix time and the timing of the liquid addition using different spray conditions on the %CV. The wet mix time significantly changed the %CV of the mixture (P = 0.0057). The use of a spray nozzle had no effect on the %CV of the feed mixture when a 1.14% of a 23% saline solution was sprayed on to the feed (P = 0.7435). The results of Experiment 3 indicated the wet mix time had a greater influence on the uniformity of mix than the type of nozzle used to apply the liquid; and the shorter liquid application time allowed more time for the mechanical shear of the ribbons and paddles to break up the agglomerated wet particles and distribute them throughout the feed mixture when the total time of the liquid addition plus wet mix time was fixed. The fourth experiment evaluated the effect of different percent liquid addition, application time and mixer type with different wet mix times on the uniformity of mix. The %CV of feed mixed using a fixed wet mix time setting did not change when the percent liquid addition was increased, while the %CV of the feed mixed using a fixed total liquid mix time setting increased when increasing the percent liquid addition. The %CV of feed mixed with a ribbon mixer did not change when the liquid application time was decreased while the %CV of the feed mixed with a paddle mixer increased when decreasing the liquid application time. Differences were observed in the %CV based on the parameters of liquid cycle time, mixer type and mixer size. The results of Experiment 4 indicated the liquid addition time and the percent of liquid addition affected the uniformity of mix. The uniformity of liquid application should be tested with the highest percent liquid addition. Furthermore, application and wet mix times should be determined for each mixer type and size to establish the optimal batch cycle.
45

Manipulation of processing technologies to enhance growth performance and (or) reduce production costs in pigs

Paulk, Chad Bennett January 1900 (has links)
Master of Science / Department of Animal Sciences and Industry / Joe D. Hancock / Nine experiments were completed to evaluate the effects of feed manufacturing practices on milling characteristics of diets and growth performance and stomach morphology in pigs. In Exp. 1 and 2, reducing the particle size of sorghum from 800 to 400 μm improved (P < 0.04) efficiency of gain in finishing pigs by 5% but had negative effects on cost of milling and stomach morphology. In Exp. 3 and 4, finishing pigs fed diets with 10 mg/kg of ractopamine HCl, had improved (P < 0.05) ADG, G:F, HCW, dressing percentage, and percentage carcass lean. However, increasing mix time of the diet from 0 to 360 s did not affect (P > 0.06) the response of finishing pigs to ractopamine HCl. In Exp. 5 and 6, adding ground and cracked corn to a pelleted supplement for nursery pigs decreased (P < 0.01) growth performance compared to feeding a complete pellet. In Exp. 7, increasing the percentage of cracked corn in a diet for finishing pigs decreased development of stomach lesions but also had a generally negative effect on efficiency of gain. In Exp. 8, adding cracked corn to a pelleted supplement (as done for the nursery pigs) decreased milling costs and improved health of stomach tissue. But, G:F was decreased by 6% (P < 0.05) which will make this technology unattractive to swine producers. In our final experiment (Exp. 9), pigs fed pellets tended to have the greatest growth performance, pigs fed mash the worst, and pigs fed pellets for only part of the grow-finish phase fell in between. In conclusion, grinding sorghum-based diets for finishing pigs improved efficiency of growth but extensive mixing to maximize diet uniformity had no effect on growth performance or carcass measurements. Use of cracked corn in diets does decrease diet costs and improve stomach health in finishing pigs but feeding of complete pellets for the entire finishing period supports maximum rate and (or) efficiency of gain.
46

Optimizacija linijskih sistema javnog prevoza putnika / Optimization of public transportation system

Pitka Pavle 29 September 2016 (has links)
<p>Analizom procesa kretanja vozila duž linije identifikovani su parametri koji utiču na širenje poremećaja intervala sleđenja. Na osnovu utvrđenih relacija između parametara, formiran je deterministički model. Modelom je predstavljeno širenje i slaganje više prostih poremećaja intervala sleđenja po stajalištima duž linije i po polascima u redu vožnje na jednoj liniji javnog gradskog prevoza putnika. U radu je izvršena matematička analiza složenog uticaja različitih parametara na širenje poremećaja intervala sleđenja vozila. Rezultati analize su pokazali da je u fazi projektovanja sistema u velikoj meri moguće uticati na sekundarne poremećaje intervala sleđenja i preventivno delovati na povećanje stepena ravnomernosti intervala sleđenja na liniji. U skladu sa zaključcima analize modela razvijen je postupak optimizacije kojim se sa aspekta vremena boravka putnika u sistemu i dostignute ravnomernosti intervala sleđenja, vrednuje podela dijametralne linije na dve radijalne.</p> / <p>An analysis of the process of vehicle movement along the line was used to identify the parameters which influence irregular headway propagation. The established relations between the parameters were used to form a deterministic model. The model describes the propagation and concurrence of numerous primary headway irregularities by the stops along the line and by the scheduled departure times at one urban public transport system line. The paper presents a mathematical analysis of the complex effect of various parameters on the irregular headway propagation. The results of the analysis have shown that the secondary headway irregularites could be largely affected during the transport system design phase, thus preventing the increase in the degree of headway uniformity along the line. In accordance with the conclusions of the model analysis, an optimisation method has been developed, which is used to evaluate the division of the diametrical line into two radial lines from the aspect of on-line travel time and the achieved headway uniformity.</p>
47

Microaspersor com microtubos: um novo conceito hidráulico na irrigação localizada / Micro-sprinkler with microtube emitters: a new trickle irrigation hydraulic concern

Almeida, Ceres Duarte Guedes Cabral de 19 November 2008 (has links)
O microtubo é um emissor simples, de baixo custo, com a grande vantagem de melhor adaptação em condições de topografias onduladas e montanhosas, onde a pressão na linha lateral varia consideravelmente. Este estudo constitui a elaboração de um modelo para dimensionamento hidráulico de microaspersores, cujo emissor é um microtubo de tamanho variável. O fundamento teórico do estudo baseia-se na premissa da compensação da perda de carga na linha lateral e das diferenças topográficas do terreno, através da variação do comprimento do microtubo. Os objetivos específicos deste trabalho foram: determinar as características hidráulicas do microtubo; desenvolver um modelo para dimensionamento do sistema de irrigação proposto e sugerir um defletor para o microaspersor; avaliar a uniformidade de vazão ao longo de linhas laterais experimentais em declive e desenvolver uma planilha eletrônica, para dimensionamento de microtubos. Dois microtubos de diferentes diâmetros foram utilizados neste estudo. Entre as características hidráulicas determinadas, estão o diâmetro interno real, relação vazão-pressão e pressão-comprimento. A determinação do diâmetro interno médio dos microtubos foi realizada em laboratório através da medida de fluxo sob regime laminar e pelo projetor ótico de perfil. Uma equação resultante da combinação das equações de energia desenvolvida por Bernoulli e Darcy-Weisbach além da equação de Hagen-Poiseuille para cálculo do fator de atrito (f), foi deduzida para cálculo do diâmetro. Uma bancada de ensaios foi montada para realização dos ensaios. Os experimentos foram realizados numa faixa de número de Reynolds entre 8000 e 17000, portanto regime de escoamento turbulento. A equação de Darcy-Weisbach foi utilizada para cálculo da perda de carga total e a equação de Blasius foi utilizada para cálculo do fator de atrito (f). Duas laterais foram dimensionadas e instaladas em diferentes declividades (0,5 e 2,3 %). Medidas de dispersão foram utilizadas para avaliar e classificar o sistema de irrigação. Dois modelos de defletores foram desenvolvidos em laboratório, e avaliados em termos de distribuição espacial da água e facilidade construtiva. A análise dos resultados experimentais foi realizada em bases empíricas e teóricas. A avaliação hidrodinâmica do diâmetro dos microtubos aproximou-se muito da determinação através do projetor ótico de perfil, o que indica ser uma alternativa viável para o dimensionamento. A estimativa da pressão de operação do microaspersor baseada nas equações propostas foi bem próxima à pressão observada. O modelo empírico estimou o comprimento do microtubo em função da pressão com bastante precisão, consequentemente a uniformidade de vazão ao longo da lateral foi classificada como excelente em ambas as situações de declive, com coeficientes superiores a 95 %. Uma análise de sensibilidade para estimar as implicações no desempenho hidráulico do sistema, dos erros ou das mudanças nas variáveis envolvidas no dimensionamento, mostrou que o desempenho do emissor é extremamente sensível ao diâmetro do microtubo. Baseado nos resultados obtidos com os ensaios de distribuição pode-se afirmar que é necessário um maior aprofundamento no projeto do defletor do microaspersor. Em geral, a metodologia proposta oferece a possibilidade de ajustar quaisquer variações na carga de pressão ou na topografia do terreno e assim, obter vazão constante ao longo da linha lateral. / The microtube is a simple and cheap emitter which has advantage of be suitable for undulating and hilly conditions, where pressure in the lateral line varies considerably. This study aims to develop an empirical approach to the design of a novel micro-sprinkler that uses microtube as the emitters whose length is variable. The theoretic concern is the irrigation system should be designed to compensate variations along lateral line as a function of the friction loss and elevation. General objectives were: hydraulic characterization of the microtube; empiric equations to design; to develop a kind of deflector; to evaluate application uniformity for micro-sprinkler and to do a worksheet to design this system. The relationship between discharge, pressure, and length for microtube emitters of two different diameters were done. The diameter was measured based on flow measurements under laminar flow condition and by accurate optical equipment. Combination of the energy (Bernoulli) and Darcy-Weisbach equations and Hagen-Poiseuille equation (friction factor laminar flow) gives the diameter. A test table to do tests was built. The range of Reynolds numbers during the experiment was 8,000 to 17,000, then turbulent flow. The friction head losses were calculated using the Darcy-Weisbach equation and the friction factor by Blasius equation. Two experimental lines were designed and laid on different slopes (0.5 % and 2.3 %). To evaluate the uniformity of application of water, dispersion measures are used. Two deflectors were created and tested in the laboratory by spatial distribution analysis and easily to manufacture. The data was analyzed by theoretical and empirical approaches. The diameter values of the microtubes were very close to those by optical equipment, then it is a good alternative method to determinate the diameter of the microtube. The pressure observed values were very close to estimated. The empirical approach determined the length required for the microtube emitters with high accuracy, consequently the flow rate uniformity along lateral line was excellent for both laterals, their uniformity coefficients were above 95%. A sensitivity analysis to estimate the implications of errors or changes in key variables on the hydraulic performance of this system showed that the emitter performance is particularly sensitive to the emitter diameter. The deflector tests results showed low spatial uniformity, so we can say that it is necessary more studies at this part of this micro-sprinkler. Finally, the methodology proposed allow adjust any head pressure or elevation variations to high uniformity along of lateral line.
48

Metodologia para dimensionamento do intervalo de pressões de operação de linhas laterais de microirrigação com emissores do tipo microtubo / Methodology for designing intervals of pressures to operate laterals of microirrigation with microtube emitters

Katsurayama, Geancarlo Takanori 26 January 2015 (has links)
Os projetos de irrigação são convencionalmente dimensionados para operar com potência constante, garantindo-se, assim, um desempenho aceitável a campo. Contudo, existem sistemas de bombeamento que não atendem a esse requisito diretamente, como nos casos da energia fotovoltaica e da eólica. Nesses casos, inclui-se algum componente no sistema para regulação da pressão, como reservatórios, emissores regulados e/ou válvulas reguladoras. Apesar de solucionar o problema, pode haver encarecimento do projeto. Em alternativa aos emissores regulados, podem ser utilizados emissores do tipo microtubo. Estes, além de mais baratos, permitem variar seu comprimento a fim de se compensar a diferença de pressão ao longo da linha lateral. Assim, teoricamente, tem-se 100% de uniformidade na vazão dos emissores. Ainda, pode-se variar a pressão na entrada da linha lateral, dentro de certo limite, sem comprometer a uniformidade mínima de aplicação de água dos emissores. Isso permitiria o acoplamento direto do sistema de irrigação com o sistema de bombeamento, em sistemas com potência variável, sem a necessidade de algum mecanismo de interface entre os dois. Portanto, o objetivo deste trabalho foi desenvolver uma metodologia e um aplicativo para o dimensionamento de linhas laterais de sistemas de microirrigação com emissores do tipo microtubo, em que fosse obtido o intervalo de pressão recomendado para operação da mesma. O aplicativo foi desenvolvido em linguagem de programação PHP, para disponibilização aos interessados. O dimensionamento da linha lateral ocorreu em duas etapas: a primeira para se obter os comprimentos dos emissores; e a segunda para se obter os limites de pressão para temperaturas de 10 a 35 °C, respeitando uma variação de vazão de 7%. Após o desenvolvimento do aplicativo, foi instalada uma linha lateral com 250 emissores, com vazão de 1 L h-1 por emissor, e espaçamento de 10 cm. A avaliação do conjunto foi realizada coletando-se a vazão de 51 emissores para três pressões: a máxima (84,43 kPa), a mínima (16,32 kPa) e a ótima (39,00 kPa), sendo esta a que fornecia a menor variação de vazão. As uniformidades de distribuição do menor quartil obtidas para a pressão mínima, ótima e máxima, respectivamente, foram de 95,25, 97,80 e 97,83%; e os coeficientes de uniformidade estatísticos 96,79, 98,37 e 98,37%. Ambos os índices, portanto, podem ser classificados como excelentes. Dessa forma, pode-se concluir que aplicativo desenvolvido foi capaz de fornecer tanto os comprimentos dos microtubos, quanto os intervalos de pressão para operação da linha lateral, para a variação de vazão admitida. / Irrigation projects are conventionally designed to operate at constant power, and thus guarantee an acceptable field performance. However, there are pumping systems that do not directly satisfy such requirement, as photovoltaic, and wind energy. For these cases, some components are add to the system to regulate pressure, such as tanks with constant level, regulated emitters, or regulating valves. Despite of the solution of the problem, the project can be enhanced. As an alternative to regulated emitters, microtubes may be used, which are less expensive and allow varying its length in order to compensate the pressure difference along the lateral line. Hence, theoretically, it provides 100% of emitting uniform flow. Furthermore, the inlet pressure of the line can be varied, within certain limits, without compromising the minimal application uniformity. This would permit direct coupling of the irrigation system to the pumping system, for those with variable power, without needing some mechanisms to interface the two systems. Therefore, the purpose of this study was to develop a methodology and a software for the design laterals with microtube emitters of microirrigation systems, from where the intervals of pressure to operate the system can be obtained. The software was developed in the PHP programming language in order to share it with the users. Laterals were designed in two steps: first to obtain the lengths of the emitters, and second to obtain the pressure limits at temperatures from 10 to 35 ° C, regarding to flow variation of 7%. After developing the software, a lateral line with 250 emitters with flow rate of 1 L h-1, and 10-cm spaced. Evaluations of the arrangement were carried out collecting flow of 51 emitters at three pressures: the maximum (84.43 kPa), minimum (16.32 kPa), and the optimal (39.00 kPa), which provided the lower flow variation. The uniformity of distribution of the lower quartile obtained for the lowest, optimal, and greatest pressure were, respectively, 95.25, 97.80 and 97.83%; and the statistical uniformity coefficients were 96.79, 98.37 and 98.37%. Both indices of uniformity may be then rated as excellent. Therefore, it can be concluded that the software was capable of providing both length of microtubes, and intervals of pressure to operate the lateral line, within the admitted flow variation.
49

Les métropoles au prisme du modèle territorial français / No English title available

Regourd, Cécile 02 July 2018 (has links)
La création des métropoles ne relève pas simplement d'une réforme supplémentaire de l'organisation territoriale française. Elle en exprime un changement de paradigme, découlant d'un nouveau contexte lié à la globalisation économique et se traduisant par la mise en concurrence des territoires. Cette création est indissociable d'un processus de plus grande amplitude de recomposition des territoires selon une problématique distincte de celle des lois antérieures dites de décentralisation. Cette recomposition territoriale ne surgit pas ex nihilo. Les prémisses en sont notamment décelables dans le changement de nature de l'intercommunalité, ayant substitué l'intégration à la coopération. Ce processus produit une déconstruction des cadres juridiques du modèle territorial hérité de plus de deux cent ans d'histoire. C'est ainsi, en particulier, que par-delà l'éclatement de l'uniformité, la distinction même entre collectivités territoriales et établissements publics perd son intelligibilité et ses critères constitutifs, ou que le principe de libre administration tend à être privé de sa propre substance. La reconfiguration du droit des collectivités territoriales requiert ainsi de nouvelles typologies conformes aux mutations des régimes juridiques. / No English summary available.
50

Estudo da uniformidade de emissão de água utilizando diferentes espaçamentos entre gotejadores na linha lateral /

Andrade, Luiz Antonio de, 1956- January 2009 (has links)
Orientador: João Carlos Cury Saad / Banca: Raimundo Leite Cruz / Banca: Rubens Duarte Coelho / Banca: Tarlei Arriel Botrel / Banca: Everaldo Chartuni Mantovani / Resumo: A irrigação por gotejamento no Brasil está crescendo no cultivo de hortaliças e frutas de ciclo anual. O adequado dimensionamento do projeto de irrigação por gotejamento visando altos Coeficientes de Uniformidade de Emissão de água é coerente com a pressão da sociedade pelo uso racional dos recursos naturais, especialmente a água. A utilização de linhas laterais mais longas promove redução de custos na instalação do projeto, entretanto pode reduzir a uniformidade de emissão de água, sendo que a otimização deste fator é importante objetivo de todo projeto criteriosamente executado. Propôs-se um modelo de mangueira gotejadora com dois segmentos, sendo o ultimo com um espaçamento padrão, e o segmento inicial com um espaçamento especial entre os emissores, com o objetivo de obter linhas mais longas sem prejudicar o Coeficiente de Uniformidade de Emissão de água. Mangueira gotejadora dimensionada teoricamente conforme o modelo proposto, com lateral de 150,6 m sendo 59,7 m iniciais com espaçamento entre emissores de 0,35 m associada com 90,9 m finais com distancia entre gotejadores de 0,30 m apresentou variação de vazão de 8,05 % e CUECVf de 97,62% e foi 36% mais longa que a mangueira gotejadora com único espaçamento de 0,30 m, com variação de vazão de 10 %, e CUECVf de 94,71.Ganhos semelhantes foram obtidos com os espaçamentos padrões de 0,40 e 0,50 m. Concluiu-se que modelo proposto tem possibilidade de ser aplicado na pratica da irrigação por gotejamento em cultivo adensado, por apresentar melhor CUE, lateral mais longa e menor variação de vazão. / Abstract: The use of drip irrigation in horticultural and annual cycle fruits in Brazil is growing. The correct sizing of a drip irrigation project, using High Emission Uniformity Coefficients, is in accordance with society's pressure for a rational use of natural resources. Sizing longer lateral irrigation lines promotes a cost reduction in the installation costs of a project. A model for a drip irrigation lateral composed of two segments is proposed; the last having a standard spacing, the initial segment having a special spacing between emitters, higher than the standard, with the objective of obtaining longer laterals, without decreasing the Emission Uniformity Coefficient of water, EUC.A theoretically dimensioned drip hose, in accordance with the proposed model, with a total length of 150.6 m, having the initial 59.7 m an emitter spacing of 0.3508 m, while the final 90.9 m an emitter spacing of 0.30 m, presented a flow variation of 8.05% and an EUC of 97.62%. It is 36% longer than a drip irrigation hose with a 0.30 m emitter spacing, with a 10% flow variation and a EUC of 94.71%. A substitution of the standard lateral model for the proposed lateral model still needs a field trial validation in order to justify its use, considering that the commercial production of this model is viable. / Doutor

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