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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.
1

Metal Recovery via Automated Sortation

Yu, Hao 17 April 2014 (has links)
Each year, millions of tons of non-ferrous scrap metal are discarded in the US. This metal is wasted due to a lack of proper recovery methods. Recent developments in spectroscopic technology have made it possible to identify the waste composition of scrap metal in real-time. This has opened the door for high-speed automated metal sortation and recovery, especially for the recovery of high value precious metals, such as titanium, nickel, cobalt, molybdenum and tantalum. Automated sortation systems typically consist of three main phases: (i) Feeding of material, (ii) Composition identification, and (iii) Physical separation. Due to their low volume and industry fragmentation, high-strength precious metal chips usually come in the form of chips smaller than 10 mm. Therefore it is extremely difficult to feed metal chips individually into the sorting system. At CR3, a new feeding mechanism was invented and developed in order to provide single layer feeding of small metal chips. A laboratory-scale prototype was built and proven to be feasible, scalable and reliable. A model was developed to predict the output of feeding variables based on initial input parameters. An operation window of the process was also defined for various metal chip resources. These will be presented, reviewed and discussed in the following paper.
2

Simulation-based optimization of geometry and motion of a vertical tubular bag machine

Frank, Matthias, Holzweißig, Johann 11 March 2016 (has links) (PDF)
For food industry processes packaging machines with high throughput are required and one way to improve the overall machine efficiency is to increase its working speed. However, testing of prototypes is time and cost expensive. Therefore, simulation is used to evaluate the process and adapt it. Optimization can help to find better machine designs by using simulations to evaluate one solution. This work uses the Discrete Element Method to model a vertical tubular bag machine for packaging basmati rice. The Covariance Matrix Adaption Evolution Strategy optimizes the simulation model and results in a significant machine speedup. This work is a guidance to adapt this method for similar problems.
3

Simulation-based optimization of geometry and motion of a vertical tubular bag machine

Frank, Matthias, Holzweißig, Johann January 2016 (has links)
For food industry processes packaging machines with high throughput are required and one way to improve the overall machine efficiency is to increase its working speed. However, testing of prototypes is time and cost expensive. Therefore, simulation is used to evaluate the process and adapt it. Optimization can help to find better machine designs by using simulations to evaluate one solution. This work uses the Discrete Element Method to model a vertical tubular bag machine for packaging basmati rice. The Covariance Matrix Adaption Evolution Strategy optimizes the simulation model and results in a significant machine speedup. This work is a guidance to adapt this method for similar problems.
4

Analytical and numerical modelling of undulatory locomotion for limbless organisms in granular/viscous media

Rodella, Andrea 26 August 2020 (has links)
Undulatory locomotion is a common and powerful strategy used in nature at different biological scales by a broad range of living organisms, from flagellated bacteria to prehistoric snakes, which have overcome the complexity of living in ”flowable” media. By taking inspiration from this evolution-induced strategy, we aim at modelling the locomotion in a granular and viscous environment with the objective to provide more insights for designing robots for soil-like media exploration. Moreover, in contrast to common types of movement, the granular locomotion is still not well understood and is an open and challenging field. We approached this phenomenon with several tools: (i.) numerically, via coupling the Finite Element Method (FEM) with the Discrete Element Method (DEM) using ABAQUS; (ii.) analytically, by employing the Lagrangian formalism to derive the equations of motion of a discrete and continuous system subject to non-conservative forces, and (iii.) experimentally, by creating an ad-hoc set up in order to observe the migration of microfibres used for the treatment of spinal cord injuries. The computational attempts to model the motion in a granular medium involved the simulation of the dynamics of an elastic beam (FEM) surrounded by rigid spherical particles (DEM). A propulsion mechanism was introduced by sinusoidally forcing the beam’s tip normally to the longitudinal axis, while the performance of the locomotion was evaluated by means of a parametric study. Depending on the parameters of the external excitation, after a transient phase, the slender body reached a steady-state with a constant translational velocity. In order to gain physical insights, we studied a simplified version of the previous continuous beam by introducing a discrete multi-bar system. The dynamics of the latter was analytically derived, by taking into account the forces exchanged between the locomotor and the environment, according to the Resistive Force Theory. By numerically solving the equations of motion and evaluating the input energy and dissipations, we were able to define the efficiency and thus provide an effective tool to optimise the locomotion. It is worth mentioning that the two approaches, despite the different physical hypothesis, show a qualitatively and quantitatively good accordance. The numerical and analytical models previously analysed have shown promising results for the interpretation of "ad-hoc" experiments that demonstrate the migration of a microfibre embedded in a spinal cord-like matrix. This migration needs to be avoided, once the regenerative microfibre is implanted in the lesioned spinal cord, for the sake of the patients health.
5

Estudos fluidodinâmicos e de secagem de fertilizantes em diferentes tipos de secadores rotatórios

Silvério, Beatriz Cristina 20 December 2012 (has links)
Universidade Federal de Goiás - Goiânia / Drying is an important process that a lot of products were submitted. However, this process is usually very energy-intense and has a large commercial impact on the cost of the final product. The conventional direct rotary dryer consists of equipment widely used in industrial area due to advantages such as, a high processing capacity of a wide variety of materials. This dryer is commonly used to dry and process granular materials, and has application across a wide range of industries like the fertilizer industry. In the Triangulo Mineiro region and Alto Paranaiba, where is also located the city of Uberlândia - MG, the fertilizer industry exemplifies the use this equipment for removing moisture from the final product. The drum of the rotary cascade dryer is equipped with lifting flights. Many potential benefits can be obtained through a greater understanding of the rotary drying process. One such benefit could be energy savings, whose magnitude can be determined by estimating the energy cost of drying in the particleboard industry. In order to improve drying efficacy, another version of the rotary dryer, known as the ―rotoaerated‖ dryer, was evaluated by Lisboa (2007) and Arruda (2008). the roto-aerated version provides better mass and energy transfer between the hot air and the solids than the conventional countercurrent rotary dryer. The main characteristic of the rotoaerated dryer is its aerated system, which consists of a central pipe (encased in the drum), from which a series of mini-pipes carry hot air directly to the particle bed flowing at the bottom of the drum (without flights). The present work analyzes the drying of granulated fertilizers in a rotoaerated dryer. This work has tested several positions and different diameters of mini pipes. Due to finding the optimum drying performance presented by rotoaerado dryer, the present work aims to study the drying of SSPG fertilizer granules in rotoaerated dryers with different configurations that have not studied, varying the diameter, the provision and quantity of mini pipes. The performance of rotary dryers configurations, were compared based on experimental results. The results of this study have values of loading, residence time, drying rate, and the difference between rotoaerated dryer and concurrent and countercurrent rotary dryers, working under the same operating conditions. It was also found that while the configurations evaluated in previous studies showed results of the drying rate four times higher compared to conventional version, in this work it was possible to find configurations with superior results reaching a drying rate up to 18 times higher compared the conventional version. This study also study different parameters in a Discret Element Method (DEM) simulation method with a linear model. / A secagem é uma importante operação à qual se submetem diversos produtos industrializados. Porém, este processo é concebido como uma operação unitária que demanda uma intensa quantidade de energia, o que implica em um grande impacto comercial no custo do produto final. Secadores do tipo rotativos são comumente usados na secagem e processamento de materiais granulados por suportar grande volume de material, possui vasta aplicação no âmbito do beneficiamento de sementes, produção de alimentos e fertilizantes. Além de amenizar os custos com armazenamento e transporte, evitando desintegração dos grânulos do produto, o empedramento e reduzir a formação de incrustações no interior dos equipamentos, a secagem possibilita o atendimento às imposições do mercado consumidor e às leis de regulamentação para a comercialização do produto. O equipamento convencional usado para a operação de secagem constitui-se de um casco cilíndrico com uma pequena inclinação em relação à horizontal, que gira em torno do seu eixo longitudinal, equipado com suspensores, e recebe o nome de secador rotativo. O secador rotativo convencional de contato direto consiste em um equipamento amplamente difundido na área industrial por apresentar vantagens como, por exemplo, alta capacidade de processamento de uma grande variedade de materiais. Com o objetivo de aumentar a eficiência da secagem, outra configuração do secador rotativo foi desenvolvida na FEQUI/UFU, conhecida como secador rotoaerado, avaliada primeiramente por Lisboa et al. (2007) e depois por Arruda (2008). O secador rotoaerado é constituído por um tubo central que possui uma série de minitubos conectados a ele, responsáveis por conduzir o ar quente diretamente para o leito de partículas localizadas no fundo do tambor em rotação. Em trabalhos anteriores constatou-se que o secador rotoaerado apresentou maior eficiência quando comparado com o equipamento convencional, usando suspensores. Devido à constatação da ótima eficiência de secagem apresentada pelo secador rotoaerado, o presente trabalho teve como objetivo, estudar a secagem de fertilizantes super fosfato simples granulado em secadores rotoaerados com diferentes configurações ainda não estudadas variando os diâmetros, a disposição e a quantidade dos minitubos conectados ao tubo central. Com os resultados experimentais deste trabalho observou-se que a distribuição e o diâmetro dos minitubos avaliados tiveram influência nos resultados de tempo médio de residência, água removida e taxa de secagem. Verificou-se também que, enquanto as configurações avaliadas em trabalhos anteriores apresentaram resultados de taxa de secagem até quatro vezes maior em comparação à versão convencional, neste trabalho foi possível encontrar configurações com resultados superiores chegando a uma taxa de secagem até 18 vezes maior em comparação à versão convencional. Além dos estudos experimentais, também foi possível realizar a simulação através da Fluidodinâmica Computacional (CFD) do escoamento do ar no tubo central do secador rotoaerado, a fim de se obter a predição das velocidades de saída no ar em cada minitubo e verificou-se a influência da velocidade de saída do ar no escoamento das partículas. Além disso, foi feito um estudo utilizando o Método dos Elementos Discretos (DEM) para simulação do escoamento de partículas de fertilizante em tambores rotativos avaliando-se diferentes parâmetros e as interações entre eles para a simulação em fase discreta. / Doutor em Engenharia Química
6

Zařízení pro zásyp odpichového otvoru obloukové pece / Device for filling tap hole of arc furnace

Juda, Lukáš January 2015 (has links)
Diploma thesis describes design and function verification of device for filling tap hole of electric arc furnace with tap hole diameter from 190 mm to 250 mm. The theses includes drive design calculation of chute swinging movement and bearing calculations. Another part of the thesis deals with verification of device functions which it is completed with process description of creating DEM simulation in program YADE. The thesis also includes basic experiments for determination angle of internal friction, angle of repose, coefficient of restitution and angle of material friction on a steel surface. Drawing documentation of selected assemblies is part of the thesis.

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