This thesis identifies some problems, the genetic algorithm (GA) is facing in the area of vehicle routing and proposes various methods to address those problems. Those problems arise from the unavailability of suitable chromosomal representation and evaluation schemes of GA for the Vehicle Routing Problem (VRP). The representation and evaluation schemes already in use have problems of high computational cost, illegal chromosomes (chromosomes not representing a legal tour) and wrong fitness assignment (fitness not truly representing chromosome genetic makeup). These problems are addressed by several proposed new schemes, namely the Self Imposed Constraints Evaluation scheme, the Contour and Reverse Contour Evaluation schemes and the Order Skipping Evaluation scheme, which are specifically tailored for various objectives, problems and situations. Apart from this, a methodology, which has previously being used in other meta-heuristics, is incorporated into GA i.e., the independent application of GA on various sub-localities of the problem. We call this GA, a Localized Genetic Algorithm (LGA). LGA is an iterative procedure between optimization and controlled de-optimization. The procedure of controlled de-optimization is also novel. It brings the solution into a new search space while controlling its cost effectively. LGA is introduced with various search techniques, i.e. intensive, extensive and selective, the use of which depends on the problem size and the availability of computational resources. Furthermore, search reduction techniques (Fitness Approximation Methods) are also introduced into the LGA, which has enabled the LGA to be applied to large scale problems. Due to the implementation of those proposals, LGA is the first GA-driven approach to be applied to very large scale CVRP problems of up to 1200 customers, i.e. datasets presented by Feiyue in 2005 and large scale VRPTW problems of up to 1000 customers, datasets presented by Gehring and Homberger in 1999. Lastly, a standard unit for computational comparison, i.e., Bellman's Evaluation Units BEUs, is also introduced to facilitate computational comparisons for future researchers. LGA has shown promising results on CVRP and VRPTW problems. It is flexible and also has the potential to be extended to not only other vehicle routing problems, but also to other ordering problems.

abstract: Micromachining has seen application growth in a variety of industries requiring a miniaturization of the machining process. Machining at the micro level generates different cutter/workpiece interactions, generating more localized temperature spikes in the part/sample, as suggested by multiple studies. Temper-etch inspection is a non-destructive test used to identify `grind burns' or localized over-heating in steel components. This research investigated the application of temper-etch inspection to micromachined steel. The tests were performed on AISI 4340 steel samples. Finding, indications of localized over-heating was the primary focus of the experiment. In addition, change in condition between the original and post-machining hardness in the machined slot bottom was investigated. The results revealed that, under the conditions of the experiment, no indications of localized over-heating were present. However, there was a change in hardness at the bottom of the machined slot compared to the rest of the sample. Further research is needed to test the applicability of temper-etch inspection to micromilled steel and to identify the source of the change in hardness. / Dissertation/Thesis / M.S.Tech Technology 2010

GONÇALVES, Fabricio Mota. Evapotranspiração e coeficientes de cultivo (KC) da cana-de-açúcar irrigada por gotejamento subsuperficial. 2010. 64 f. Dissertação (Mestrado em engenharia agrícola)- Universidade Federal do Ceará, Fortaleza-CE, 2010. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-06-21T18:44:18Z No. of bitstreams: 1 2010_dis_fmgoncalves.pdf: 3909193 bytes, checksum: b818df330f21fcd52b71e61d84782c03 (MD5) / Approved for entry into archive by José Jairo Viana de Sousa (jairo@ufc.br) on 2016-07-21T20:13:45Z (GMT) No. of bitstreams: 1 2010_dis_fmgoncalves.pdf: 3909193 bytes, checksum: b818df330f21fcd52b71e61d84782c03 (MD5) / Made available in DSpace on 2016-07-21T20:13:45Z (GMT). No. of bitstreams: 1 2010_dis_fmgoncalves.pdf: 3909193 bytes, checksum: b818df330f21fcd52b71e61d84782c03 (MD5) Previous issue date: 2010 / Sugar cane is one of the crops with the highest level of water consumption, with a high evapotranspiration demand throughout most of its cycle. Knowledge of the sugar cane water demand, the time that irrigation should be applied, and how to irrigate the crop are becoming increasingly important for the sustainable development of irrigated sugar cane cultivation, especially in areas of low water availability, as it is the case in northea stern Brazil. The experiment was carried out at the Curu Experimental Field (property of the Embrapa Tropical Agroindustry), located in the Curu-Paraipaba Irrig ation Project, city of Paraipaba-CE (3 ° 29 '20''S, 39 ° 9' 45''W and elevation 30m), in order to determine the evapotrans piration and crop coefficients (Kc) of sugarcane (Saccharum L. officinarium), subsurface drip-irrigated. It was used the SP 6949 sugar cane variety, planted in a spacing of 1.8 m between double rows and 0.4 m between rows within the double row. As to t he irrigation, we used one lateral water line for each double row, buried at a depth of 0.15 m, w ith self-compensating drip emitters, with a flow rate of 1 L h-1, spaced 0.5 m on the water line. The crop was irrigated daily and there were three fertigations per week. The irrigation de pth was periodically adjusted, keeping the soil water potential between -8 kPa to -20 kPa. The crop evapotranspiration (ETc) was determined using a wei ghing lysimeter with a surface area of 2.25 m 2. The reference evapotranspiration (ETo) was estimated by the FAO Penman-Monteith method. The durations of the phenological stages of cane sugar were estimated through analysis of soil cover, with the use of digital images. Durations of 31, 49, 237 and 118 days were observed, respectively for initial, crop development, mid-season and late season stages. The yields achieved within and outside the lysimeter were respectively 144.4 and 108.8 t ha -1 . The total ETc observed during the cycle of the sugar cane was 1074.1 m m, with maximum values of 6.6 mm d-1 during the mid-season stage. Observed Kc values for initial, mid-season and late season stages were respectively 0.23, 1 .03 and 0.50. In the crop development stage, the relationship between Kc and the (crop) soil cover was represented with good accuracy by a negative quadratic model. / A cana-de-açúcar é uma das culturas com maior consumo de água, apresentando uma alta demanda evapotranspirativa ao longo da maior parte do seu ciclo. O conhecimento das necessidades hídricas da cana-de-açúcar, do momento de aplicação da água requerida pela mesma e a forma de aplicação torna-se cada vez mais importante para o desenvolvimento sustentável da sua produção irrigada, principalmente em regiões de pouca disponibilidade hídrica, como é o caso da região Nordeste do Brasil. O experimento foi conduzido no Campo Experimental do Curu, pertencente à Embrapa Agroindústria Tropical localizado no Perímetro Irrigado Curu-Paraipaba, município de Paraipaba-CE (3° 29’ 20’’ S, 39° 9’ 45’’ W e altitude de 30 m), com o objetivo de determinar a evapotranspiração e os coeficientes de cultivo (Kc) da cana-de-açúcar (Saccharum officinarium L.), irrigada por gotejamento subsuperficial. Utilizou-se a variedade de cana SP 6949, plantada no espaçamento de 1,8 m entre fileiras duplas e 0,4 m entre linhas dentro da fileira dupla. Na irrigação utilizou-se uma linha lateral para cada fileira dupla, enterrada na profundidade de 0,15 m, com gotejadores autocompensantes, com vazão de 1 L h-1, espaçados de 0,5 m na linha. A cultura foi irrigada com freqüência diária e foram realizadas três fertirrigações por semana. A lâmina de irrigação foi ajustada periodicamente, mantendo-se o potencial de água no solo entre -8 kPa e -20 kPa. A evapotranspiração da cultura (ETc) foi determinada utilizando-se um lisímetro de pesagem com área superficial de 2,25 m2. A evapotranspiração de referência (ETo) foi estimada pelo método FAO Penman-Monteith. As durações das fases fenológicas da cana-de-açúcar foram estimadas por meio da análise da cobertura do solo pela cultura, determinada com o uso de imagens digitais. Foram observadas durações de 31, 49, 237 e 118 dias, para as fases inicial, de desenvolvimento, intermediária e final, respectivamente. A produtividade alcançada dentro e fora do lisímetro foi de 144,4 e 108,8 t ha-1, respectivamente. A ETc total observada durante o ciclo da cana-de-açúcar foi de 1.074,1 mm, com valores máximos da ordem de 6,6 mm d-1 durante a fase intermediária. Foram observados valores de Kc iguais a 0,23, 1,03 e 0,50, para as fases inicial, intermediária e final, respectivamente. Na fase de desenvolvimento vegetativo a relação entre o Kc e a cobertura do solo pela cultura foi representada com bastante exatidão por um modelo quadrático negativo.

An understanding of the ecology and behavior of white-tailed deer (Odocoileus virginianus) is necessary for proper conservation and management, especially in the face of emerging infectious diseases. The objectives of my study were to estimate juvenile survival, compare methods of quantifying contact rates (simultaneous GPS locations vs. proximity loggers [PLs]), and investigate the impact of group depopulation on contact rates of remnant adult female and juvenile deer. To achieve these goals, I captured, radiotracked, and monitored adult female and juvenile white-tailed deer in southern Illinois during 2011-2014. Survival analysis of juveniles revealed that main causes of mortality were capture related and predation, though some dead animals also showed signs of hemorrhagic disease. Comparison between simultaneous GPS locations and PLs showed evidence that deer coming within the general vicinity of each other are less likely to come in close contact if they are in neighboring social groups than deer whose home ranges overlap little, if at all. Finally, experimental removal of group members caused few if any remnant adult females to alter their contact rates or space-use, but caused remnant juveniles to have lower space-use fidelity compared to control deer and to increase their direct contact rates with other groups temporarily. Using these results, I discuss the large effects that severe weather events can have on juvenile survival, the importance of social structure on the potential transmission of disease agents among female and juvenile deer, and the difference between adult females and juvenile deer in their need for social interactions. My research provides ecologists, wildlife biologists, and managers with valuable information concerning the potential impacts of the environment, infectious diseases, and management strategies on white-tailed deer populations.

Doctor of Philosophy / Department of Civil Engineering / Dunja Peric / A low ratio between the compressive strength of concrete and its cost makes concrete one of the most widely used construction materials in civil engineering. Despite of a very good response to compressive stress, concrete exhibits a low tensile strength and limited tensile strain capacity. Adding short discrete fibers to a cementitious matrix can significantly improve its performance under tensile stress, thus ultimately exhibiting a ductile behavior. Nevertheless, in spite of their beneficial properties fiber reinforced cementitious composites remain underutilized in engineering practice. One of the main reasons for this is a lack of an adequate characterization of the tensile behavior as well as a lack of analysis methods that would allow engineers to incorporate fiber reinforced structural concrete elements into their design. Therefore, this dissertation has four key objectives: 1) to computationally model a stress-strain response of high performance fiber reinforced cementitious composites in uniaxial tension and uniaxial compression prior to macro-crack localization, 2) to develop and perform a diagnostic strain localization analysis for high performance fiber reinforced cementitious composites, the results of which can characterize effects of fibers on failure precursors, 3) to devise and perform an experimental program for characterization of ultra-high performance fiber reinforced cementitious composites, and 4) to characterize a full-fledged behavior including stress-strain and stress-crack opening displacement responses of ultra-high performance fiber reinforced cementitious composites in uniaxial tension. To quantify effects of fibers on onset of strain localization in fiber reinforced cementitious composites a combined computational/analytical models have been developed. To this end, linear-elastic multi-directional fibers were embedded into a cementitious matrix. The resulting composite was described by different types of two-invariant non-associated Drucker-Prager plasticity models. In order to investigate effects of a shape of a yield surface and hardening type linear and nonlinear yield surfaces, and linear and nonlinear hardening rules were considered. Diagnostic strain localization analyses were conducted for several plane stress uniaxial tension and uniaxial compression tests on non-reinforced cementitious composites as well as on high performance fiber-reinforced cementitious composites. It was found that presence of fibers delayed the inception of strain localization in all tests on fiber-reinforced composites. Furthermore, presence of fibers exerted a more significant effect on the strain localization direction and mode in uniaxial compression than in uniaxial tension. The main objective of experimental program was to facilitate characterization of the post-cracking tensile behavior of ultra-high performance fiber reinforced cementitious composites. To this end, five different mixes of fiber-reinforced cementitious composites were cast, whereby volumetric fiber content, fiber shape and water to binder ratio were the experimental variables. Two testing methods were adopted, a direct uniaxial tension test and four-point prism bending test. Two different post-cracking behaviors were observed in direct tension tests, softening and strain hardening accompanied with multiple cracking. On the other hand, the response from prism bending tests was less scattered. Several different inverse analyses were carried out to predict stress-strain and stress-crack opening displacement responses in uniaxial tension based on the prism bending tests. The analyses resulted in worthy correlations with the experimental data, thus suggesting that the prism bending test is a viable alternative to a much more challenging to perform direct tension test for ultra-high performance fiber reinforced composites.

Neste trabalho estudamos comportamento assintótico de problemas parabólicos semilineares do tipo ut ¡div(p(x)Nu)+l u = h(u) em um domí?nio limitado e suave W ½ Rn, com condições de Neumann na fronteira, quando o coeficiente de difusão p se torna grande em uma sub-região W0 que é interior ao domí?nio físico W. Provamos que, sob determinadas hipóteses, a família de atratores se comporta semicontinuamente inferior e superiormente quando a difusão explode em W0 / In this work we study the asymptotic behavior of semilinear parabolic problems of the form ut ¡div(p(x)Ñu)+l u = h(u) in a bounded smooth domain W ½ Rn and Neumann boundary conditions when the diffusion coefficient p becomes large in a subregion W0 which is interior to the physical domain W. We prove, under suitable assumptions, that the family of attractors behave upper and lowersemicontinuously as the diffusion blows up in W0.

Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-17T12:00:18Z No. of bitstreams: 1 arquivo total.pdf: 7270155 bytes, checksum: 94d354ad73c370abbc34bc7904858976 (MD5) / Made available in DSpace on 2016-03-17T12:00:18Z (GMT). No. of bitstreams: 1 arquivo total.pdf: 7270155 bytes, checksum: 94d354ad73c370abbc34bc7904858976 (MD5) Previous issue date: 2015-02-25 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / This dissertation deals with localized solutions in several dimensions. Initially, we review some topics in classical theory of fields by using scalar fields both in flat and curved spacetime. Here they are: kinks, lumps, vortices, monopoles, dyons, cosmology with scalar fields and branes modeled by scalar fields. After this, we present some original results. Firstly, by introducing a real or integer parameter in the models, we study a way to go from kinks to compactons in models with standard dynamics and show how the procedure works in the braneworld scenario. Finally, by using the deformation method, we present new models that support compact structures and then study their linear stability. / Esta dissertação lida com soluções localizadas em diversas dimensões. Inicialmente, fazemos uma revisão de alguns tópicos em teoria clássica de campos usando campos escalares tanto no espaço plano como no espaço curvo. São eles: kinks, lumps, vórtices, monopolos, dyons, cosmologia com campos escalares e branas modeladas por campos escalares. A seguir apresentamos alguns resultados originais. Primeiramente, introduzindo nos modelos um parâmetro que pode ser real ou inteiro, estudamos uma maneira de ir de kinks para compactons em modelos com dinâmica padrão e mostramos como o procedimento funciona no cenário de mundo brana. Por fim, usando o método da deformação, apresentamos novos modelos que suportam estruturas compactas e estudamos sua estabilidade linear.

Made available in DSpace on 2014-06-11T19:30:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-18Bitstream added on 2014-06-13T20:20:42Z : No. of bitstreams: 1 romano_mc_me_bauru.pdf: 1627459 bytes, checksum: 18d280916e43c7dadfd84a8bfbb6e9f0 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os cristais fotônicos são novos materiais em que a permissividade dielétrica e a permeabilidade magnética apresentam a periodicidade de uma rede de Bravais. No caso dos sólidos cristalinos, é a energia potencial de cada elétron que apresenta esse tipo de periodicidade. Por conta das semelhanças que existem entre as equações que descrevem os sintomas eletrônicos e fotônicos, muitos dos conceitos e métodos da teoria de estados eletrônicos vêm sendo aplicados na investigação de cristais fotônicos. Dentre esses conceitos, as funções de Wannier apresentam vantagens para o tratamento de estados eletrônicos e modos fotônicos localizados. Este trabalho aborda o caso de cristais fotônicos unidimensionais com simetria de inversão. Primeiramente são calculados e analisadas funções de Wannier bem localizadas. Em seguida são investigados os modos eletromagnéticos localizados produzidos por defeitos em cristais fotônicos, utilizando o método de matriz de transferência e o método da combinação linear das funções de Wannier. Finalmente, é feita a comparação dos resultados obtidos mediante esses métodos e são discutidas as vantagens do uso de funções de Wannier / Photonic crystal are new materials where both the dielectric permittivity and the magnetic permeability present the periodicity of a Bravais lattice. In the case of electronic states, this property is shown by the mono-eletronic potential energy. Due to the similarities between the eletronic and photonic problems, many concepts and methods of theory of electronic states are being applied to investigate photonic crystals. Among such concepts, the Wannier functions are advantageous to deal with either localized photonic modes. This work addresses the case of one-dimensional photonic crystals with inversion symmetry. First, well-localized Wannier functions are calculated and analyzed. Then, the localized modes produced by defects in photonic crystals are investigated by using either transfer matrices or linear combination Wannier functions. Finally, the results obtained by the two methods are compared and the advantages of using Wannier functions are discussed

Novas seqüências para supressão de contribuições indesejadas em Imagens e Espectroscopia por Ressonância Magnética Nuclear, tais como as provenientes da água, um solvente que sempre resulta num sinal muito intenso em sistemas biológicos, são motivos de estudo e desenvolvimento com diversas aplicações atuais. O método que estamos propondo aqui, uma versão adiabática de MEGA incorporada nas seqüências PRESS e STEAM, visa a supressão do sinal da água presente no espectro de um volume localizado em uma amostra intacta. Para o campo magnético desse estudo (2.0 Tesla) e pelas características do magneto usado nesses experimentos, o pico do solvente tem o inconveniente de apresentar uma linha espectral muito larga quando comparado com a extensão do deslocamento químico das fiações de açúcar. O resultado indesejado é a sobreposição pelas suas vertentes, das diversas outras linhas espectrais, cujo interesse é de extrema importância, como a de alguns sólidos solúveis de açúcares. O principal problema encontrado é que a separação entre os picos da água e dos açúcares próximos é da ordem de 1 ppm. A metodologia proposta consiste na aplicação de pulsos de gradiente de campo magnético intensos em conjunto com uma seqüência de pulsos de RF adiabáticos e convencionais, seletivos em freqüência e espacialmente, para suprimir o pico da água em uma região espectral muito específica, sem nenhum dano a linearidade de fase do espectro restante. Esse procedimento, aliado a uma localização espacial muito eficiente, aumenta ainda mais o poder de análise desta ferramenta, a 1H MRS. Os resultados obtidos em campo de 2.0Tesla (85 Hz/ppm) mostraram que as seqüências híbridas adiabáticas MEGA-PRESS e MEGA-STEAM são bem eficazes na supressão do pico da água, como era esperado. Além disso, sua aplicação no monitoramento do grau de maturação de frutas intactas através do seu teor de açúcar, se mostrou muito bom dadas as condições experimentais extremamente limiares apresentadas pelo espectrômetro / New sequences for suppression of undesirable contributions in Magnetic Resonance Imaging and Spectroscopy, such as water, a solvent that always represent a very strong peak in biological systems, are object of recent development for several different applications. The method proposed here, an adiabatic version of MEGA incorporated within PRESS and STEAM, aims the suppression of the water peak present on volume selected spectra of intact specimens. For the magnetic field of this study (2.0 Tesla) and for the characteristics of the magnet used in the experiments, the solvent peak has the inconvenience of having a large width as compared to the spread in chemical shift of the sugar fractions. The undesirable result is the superposition on its tail with severa1 spectral lines, whose interest is of extreme importance, such as some sugar solid solutes. The main problem encountered is that the separation between the water peak and the nearest sugar peaks is of the order of 1 ppm. The proposed methodology consists on the application of intense gradient pulses along with a sequence of adiabatic and conventional RF pulses, both frequency and spatially selective, to suppress the water peak in a very specific spectral region, without any disturbance of the phase linearity of the remaining part of the spectrum. This procedure, allied to a very efficient spatial localization, enhances the power of the very well-known tool, the 1H MRS. Results obtained at 2.0Tesla (85 Hz/ppm) show that the hybrid adiabatic sequences MEGA-PRESS and MEGA-STEAM are efficient on suppressing the water peak, as expected. Also, their application on monitoring the degree of ripeness of intact fruits through their sugar content, has shown very good results, considering the extremely limiar experimental conditions presented by the spectrometer

Para que o sistema de irrigação localizada opere com uma boa uniformidade de aplicação, é necessário que sejam adotas boas práticas de instalação e manejo, como também, que a fonte de água atenda aos requisitos de qualidade exigida e que o sistema de filtragem contribua para reduzir os riscos de obstrução. Entretanto, há condições em que o risco de obstrução pode ocorrer após o sistema de filtragem. Procedimentos inadequados de montagem e manutenção da linha podem levar a entrada de partículas sólidas que oferecem risco de obstrução. A característica da partícula associada a posição da linha pode favorecer ou reduzir os riscos de obstrução. O trabalho teve como objetivo avaliar o efeito do pulso de partículas em diferentes posições de linha. O experimento foi realizado no Instituto Nacional Ciência e Tecnologia em Engenharia de Irrigação, INCT-EI, vinculado ao Laboratório de Irrigação do Departamento de Engenharia de Biossistemas, da Escola Superior de Agricultura \"Luiz de Queiroz\"- (ESALQ/USP). Foram avaliados dois modelos de tubos gotejadores com emissores convencionais (não compensantes), integrados, de formato plano (tipo pastilha), submetidos a pulso por partículas sólidas combinando três fatores: posição da linha (para cima, para baixo e para o lado), diâmetro da partícula (0,05-0,1mm; 0,1-0,25mm; 0,25-0,5mm), concentração de partículas (5g, 10g e 20g), em sete posições de gotejadores na linha espaçados a cada 0,5 m. Foi utilizado o delineamento de blocos não casualizados, e para a comparação das médias de vazões relativas, foi adotado o teste de Tukey com significância de 5% e 10% na análise de variância. A análise fatorial revelou que o modelo de gotejador 1 apresenta maior susceptibilidade a obstrução nos quatro primeiros gotejadores, com diferença significativa para fatores isolados quanto em interação. O modelo 2 não apresentou diferença estatística para o fator concentração. Para os demais fatores e interações, foi observado que gotejadores mais distantes também podem apresentar redução de vazão quando submetidos ao pulso. Em ambos modelos, observou-se que o diâmetro da partícula é um fator que influencia a obstrução de gotejadores. Os gotejadores iniciais estão mais propensos a obstrução quando submetidos a pulsos de partículas. A posição da linha voltada para o lado contribui para redução dos riscos de obstrução. / For an irrigation system located operate with good uniformity of application, it is necessary to adopt good installation and management practices, as well as the water source meets the required quality requirements and the filtering system contributes to reduction of obstruction\'s risks. However, there are conditions where the risk of obstruction may occur after the filtering system. Inadequate line assembly and maintenance procedures can lead to the entry of solid particles that allow the clogging emitters. The particle characteristic associated with lineage may favor or reduce the risk of obstruction. The objective of this work was to evaluate the effect of the pulse of particles in different positions of the line. The experiment was carried out at the National Institute of Science and Technology in Irrigation Engineering, INCT-EI, linked to the Irrigation Laboratory of the Department of Biosystems Engineering, School of Agriculture \"Luiz de Queiroz\" - (ESALQ / USP). Two tube models of conventional drippers (non-compensating) were submitted to pulses by solid particles combining three factors: line position (up, down and to the side), particle diameter (0.05-0.1 mm, 0.1-0.25mm, 0.25- 0.5mm), particle concentration (5g, 10g and 20g) in seven positions of drippers in the line spaced every 0.5 m. The design of non-randomized blocks was used, and the Tukey test with significance of 5% and 10% as analysis of variance for comparison of means. The factorial analysis revealed that the model drip tube 1 presented greater susceptibility to obstruction in the first four drippers, with a significant difference for factors isolated and in interaction. The model 2 did not present statistical difference for the concentration factor, however, for the other factors and interactions, it was observed that more distant drippers can also present reduction of flow when submitted to the pulse. In both models, it was observed that the particle diameter is a factor that influences the drip obstruction. It has been observed that the diameter of the particle is a factor that influences the obstruction of drippers. The initial drippers are more prone to obstruction when subjected to pulses of particles. The position of the line facing the side of the contributed to reduces the risk of obstruction.