998 resultados para Micro-Tom
Resumo:
The importance of oil palm sector for Indonesia is inevitable as the country currently serves as the world’s largest producer of crude palm oil. This paper focuses on the situation of workers on Indonesian oil palm plantations. It attempts to investigate whether the remarkable development of the sector is followed by employment opportunities and income generation for workers. This question is posed within the theoretical framework on the link between trade liberalisation and labour rights, particularly in a labour-intensive and low-skilled sector. Based on extensive field research in Riau, this paper confirms that despite the rapid development of the oil palm plantation sector in Indonesia, the situations of workers in the sector remain deplorable, particularly their employment status and income. This also attests that trade liberalisation in the sector adversely affects labour rights. The poor working conditions also have ramifications for food security at the micro level.
Resumo:
This thesis presents a new actuator system consisting of a micro-actuator and a macro-actuator coupled in parallel via a compliant transmission. The system is called the Parallel Coupled Micro-Macro Actuator, or PaCMMA. In this system, the micro-actuator is capable of high bandwidth force control due to its low mass and direct-drive connection to the output shaft. The compliant transmission of the macro-actuator reduces the impedance (stiffness) at the output shaft and increases the dynamic range of force. Performance improvement over single actuator systems was expected in force control, impedance control, force distortion and reduction of transient impact forces. A set of quantitative measures is proposed and the actuator system is evaluated against them: Force Control Bandwidth, Position Bandwidth, Dynamic Range, Impact Force, Impedance ("Backdriveability'"), Force Distortion and Force Performance Space. Several theoretical performance limits are derived from the saturation limits of the system. A control law is proposed and control system performance is compared to the theoretical limits. A prototype testbed was built using permanenent magnet motors and an experimental comparison was performed between this actuator concept and two single actuator systems. The following performance was observed: Force bandwidth of 56Hz, Torque Dynamic Range of 800:1, Peak Torque of 1040mNm, Minimum Torque of 1.3mNm. Peak Impact Force was reduced by an order of magnitude. Distortion at small amplitudes was reduced substantially. Backdriven impedance was reduced by 2-3 orders of magnitude. This actuator system shows promise for manipulator design as well as psychophysical tests of human performance.
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This paper presents the research and development of a 3-legged micro Parallel Kinematic Manipulator (PKM) for positioning in micro-machining and assembly operations. The structural characteristics associated with parallel manipulators are evaluated and the PKMs with translational and rotational movements are identified. Based on these identifications, a hybrid 3-UPU (Universal Joint-Prismatic Joint-Universal Joint) parallel manipulator is designed and fabricated. The principles of the operation and modeling of this micro PKM is largely similar to a normal size Stewart Platform (SP). A modular design methodology is introduced for the construction of this micro PKM. Calibration results of this hybrid 3-UPU PKM are discussed in this paper.
Resumo:
Holes with different sizes from microscale to nanoscale were directly fabricated by focused ion beam (FIB) milling in this paper. Maximum aspect ratio of the fabricated holes can be 5:1 for the hole with large size with pure FIB milling, 10:1 for gas assistant etching, and 1:1 for the hole with size below 100 nm. A phenomenon of volume swell at the boundary of the hole was observed. The reason maybe due to the dose dependence of the effective sputter yield in low intensity Gaussian beam tail regions and redeposition. Different materials were used to investigate variation of the aspect ratio. The results show that for some special material, such as Ni-Be, the corresponding aspect ratio can reach 13.8:1 with Cl₂ assistant etching, but only 0.09:1 for Si(100) with single scan of the FIB.
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A novel process based on the principle of layered photolithography has been proposed and tested for making real three-dimensional micro-structures. An experimental setup was designed and built for doing experiments on this micro-fabrication process. An ultraviolet (UV) excimer laser at the wavelength of 248 nm was used as the light source and a single piece of photo-mask carrying a series of two dimensional (2D) patterns sliced from a three dimensional (3D) micro-part was employed for the photolithography process. The experiments were conducted on the solidification of liquid photopolymer from single layer to multiple layers. The single-layer photolithography experiments showed that certain photopolymers could be applied for the 3D micro-fabrication, and solid layers with sharp shapes could be formed from the liquid polymer identified. By using a unique alignment technique, multiple layers of photolithography was successfully realized for a micro-gear with features at 60 microns. Electroforming was also conducted for converting the photopolymer master to a metal cavity of the micro-gear, which proved that the process is feasible for micro-molding.
Resumo:
A promising technique for the large-scale manufacture of micro-fluidic devices and photonic devices is hot embossing of polymers such as PMMA. Micro-embossing is a deformation process where the workpiece material is heated to permit easier material flow and then forced over a planar patterned tool. While there has been considerable, attention paid to process feasibility very little effort has been put into production issues such as process capability and eventual process control. In this paper, we present initial studies aimed at identifying the origins and magnitude of variability for embossing features at the micron scale in PMMA. Test parts with features ranging from 3.5- 630 µm wide and 0.9 µm deep were formed. Measurements at this scale proved very difficult, and only atomic force microscopy was able to provide resolution sufficient to identify process variations. It was found that standard deviations of widths at the 3-4 µm scale were on the order of 0.5 µm leading to a coefficient of variation as high as 13%. Clearly, the transition from test to manufacturing for this process will require understanding the causes of this variation and devising control methods to minimize its magnitude over all types of parts.
The Inertio-Elastic Planar Entry Flow of Low-Viscosity Elastic Fluids in Micro-fabricated Geometries
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The non-Newtonian flow of dilute aqueous polyethylene oxide (PEO) solutions through microfabricated planar abrupt contraction-expansions is investigated. The contraction geometries are fabricated from a high-resolution chrome mask and cross-linked PDMS gels using the tools of soft-lithography. The small length scales and high deformation rates in the contraction throat lead to significant extensional flow effects even with dilute polymer solutions having time constants on the order of milliseconds. The dimensionless extra pressure drop across the contraction increases by more than 200% and is accompanied by significant upstream vortex growth. Streak photography and videomicroscopy using epifluorescent particles shows that the flow ultimately becomes unstable and three-dimensional. The moderate Reynolds numbers (0.03 ⤠Re ⤠44) associated with these high Deborah number (0 ⤠De ⤠600) microfluidic flows results in the exploration of new regions of the Re-De parameter space in which the effects of both elasticity and inertia can be observed. Understanding such interactions will be increasingly important in microfluidic applications involving complex fluids and can best be interpreted in terms of the elasticity number, El = De/Re, which is independent of the flow kinematics and depends only on the fluid rheology and the characteristic size of the device.
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El encuentro 'Let's Learn To Decide Together' realizado en la ciudad de Tur??n en noviembre de 2008 ha congregado setenta centros escolares de diez y ocho pa??ses. De este seminario han surgido diferentes iniciativas, entre ellas est?? aquella en la que participar?? el Colegio Santo Tom??s de Avil??s junto a otros seis colegios de B??lgica, Finlandia, Italia, Reino Unido y Rep??blica Checa. El proyecto conjunto se sustentar?? en los recursos audiovisuales y girar?? entorno al medio ambiente y las energ??as renovables.
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This is a recording of a talk given on 12 March 2010 by Tom Chapman of Headstream, a marketing company who specialise in the use of digital social media to promote products and brands.
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Según estudios realizados por la Federación Colombiana de Fútbol de Salón, en Colombia existen al menos 1.2 millones de jugadores de este deporte, de los cuales una cuarta parte (300.000, aproximadamente) se encuentra en Bogotá. Tan sólo en la capital del país se juegan en un fin de semana más de 2.000 partidos oficiales y su liga es una de las más competitivas a nivel nacional. A continuación presento tres crónicas que retratarán de cerca la popularidad del microfútbol en la ciudad de Bogotá. Son más de 50 años de un deporte que llegó al país gracias al doctor Jaime Arroyave Rendón pero que en cuarenta minutos se reinventa en los pies de los ‘micreros’ bogotanos.
Resumo:
This is a collection of 12 micro-lectures, to be used by students in advance of practical sessions. Durations range for 3 min to 10 min. Topics include: ****** 1. Introduction ****** 2. Data classes ****** 3. Matrices ****** 4. Getting help ****** 5. Index notation ****** 6. 1- and 2-dimensional data ****** 7. 3-dimensional data ****** 8. Booleans (True/False) ****** 9. Designing a programme (Algorithms) ****** 10. Flow control: If-then statements ****** 11. Flow control: For-do loops ****** 12. Making nicer figures ******
Resumo:
Telmex es una organización que inicia su operación como empresa estatal mexicana con bajos niveles de eficiencia, posterior a su privatización tomó un nuevo rumbo en sus procesos internos, llevándola a generar modelos de negocio diferenciados y enfocados a la prestación de servicios de telecomunicación a la vanguardia. A partir de la búsqueda de nuevos horizontes la compañía logra tener presencia en la mayoría de los países del continente americano operando bajo la marca de “Telmex Internacional”, y a su vez, con sus respectivas subsidiarias en cada uno de los diferentes países, con el objetivo de satisfacer las necesidades locales con mayor efectividad. Con el apoyo de los diferentes acercamientos teóricos se busca identificar los patrones que le permitieron a Telmex llegar a posicionarse como una compañía líder en el sector de las telecomunicaciones en Latinoamérica y específicamente en Colombia, manteniéndose en un mercado competitivo mediante la oferta de servicios de empaquetamiento ajustados a las necesidades de los clientes.
Resumo:
Por medio de la realización de un análisis comparativo de las mejores prácticas y la situación actual del sector ecoturismo en Costa Rica y Colombia y teniendo como referente las diversas teorías de internacionalización, se generaron numerosas estrategias de internacionalización para poder posicionar al turismo de naturaleza en Colombia como un sector de talla mundial. A partir del análisis general del sector ecoturismo a nivel mundial y profundizando después en Costa Rica y Colombia, se identificó el comportamiento del sector en Costa Rica para posicionarse como un país líder en ecoturismo, para así concluir con las estrategias de internacionalización comúnmente usadas en ese país y llevarlas al contexto colombiano. El indiscutible éxito del sector ecoturismo de Costa Rica en el mundo, es el motivo por el cual se tomó como patrón y base para dicho análisis comparativo. Sus prácticas y estrategias pueden ser utilizadas por el sector colombiano para realizar su proceso de internacionalización y de ésta manera mejorar su productividad, proyectarse internacionalmente y generar empleo para así contribuir con el desarrollo económico del país y la calidad de vida de sus habitantes.
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Esta investigación toma como marco general la Política de Reintegración Social y económica de personas y grupos alzados en armas en Colombia, en donde tras el estudio de las trayectorias en el conflicto de un grupo de 9 excombatientes, se aborda la relación existente entre los beneficios otorgados por dicha política y aquello que facilitó y motivó el ingreso, la permanencia y desmovilización de los grupos armados. Se presenta una caracterización e interpretación conceptual de las denominadas trayectorias en el conflicto, son establecidas relaciones y diferencias entre las organizaciones ilegales FARC y las AUC, se revisan las percepciones que frente a los beneficios del programa de reintegración tienen excombatientes y profesionales de la entidad que lidera dicho proceso y a partir de ello, es argumentada la incidencia que sobre el éxito de esta política tienen las características individuales y particulares, tanto de los excombatientes como de las organizaciones armadas ilegales.
Resumo:
Lo que este trabajo trata de exponer y hacernos más simple es la posición de un país en el mundo, por medio del estudio de sus producciones culturales que revelan la forma en que los símbolos y el lenguaje, son elementos que sirven para darnos un lugar en el mundo, ayudarnos a tomar una posición frente a lo que somos y a lo que los otros son. También pretende mostrar que los Estados no son ajenos a la manipulación de las creencias humanas, pues ellos provienen de su sistematización en rituales y hábitos. Este trabajo nos va a proporcionar herramientas para analizar las Relaciones Internacionales, en cuanto a sus aspectos intersubjetivos, que no carecen de importancia en la toma de decisiones ni en las acciones estatales. Las culturas siempre están en el fondo, como fundamento del mundo material u objetivo. No debemos marginar el estudio de lo subjetivo en esta disciplina, pues la visión de mundo caótico y anárquico es el resultado de las cosmovisiones, de las creencias de los actores; las ideas sí importan como dice Wendt, pues ellas son el motor de muchas posiciones asumidas en el escenario internacional.