245 resultados para Vibratory conveyor
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Contact Spatially Resolved Spectroscopy (SRS) measurements by means of a fiber-optics probe were employed for nondestructive assessment and monitoring of Braeburn apples during shelflife storage. SRS measurements and estimation of optical properties were calibrated and validated by means of liquid optical phantoms with known optical properties and a metamodeling method. The acquired optical properties (absorption and reduced scattering coefficients) for the apples during shelf-life storage were found to provide useful information for nondestructive evaluation of apple quality attributes (firmness and SSC) and for monitoring the changes in their microstructure and chemical composition. On-line SRS measurement was achieved by mounting the SRS probe over a conveyor system
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An approximate procedure for studying harmonic soil-structure interaction problems is presented. The presence of Rayleigh waves is considered and the resulting governing equations of the dynamic soil-structure system are solved in the time domain. With this method the transient and steady states of a vibratory motion and also the nonlinear behaviour of the soil can be studied. As an example, the dynamic earth pressure against a rigid retaining wall is investigated. The loads are assumed to be harmonic Rayleigh waves with both static and dynamic surface surcharges. The dependence of the results on the excitation frequency is shown.
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El objeto de la tesis doctoral se centra en la obtención de una banda transportadora de minería exenta de halógenos o al menos con el menor contenido posible, es por ello que se ha realizado un estudio de diferentes matrices poliméricas sin halógenos y se han evaluado diferentes sistemas ignifugantes. Se ha partido de mezclas con base polimérica de caucho natural y de estireno butadieno ya que son cauchos sin halógenos y con los que se pueden obtener mezclas de buenas propiedades mecánicas. Los resultados obtenidos durante el desarrollo de la tesis han sido muy satisfactorios, ya que se fabricaron bandas a gran escala para poder realizar los ensayos descritos en la normativa UNE EN 14973. La clasificación adquirida, categoría B1, alcanza dos de los objetivos marcados al inicio de los trabajos de investigación, y por tanto puede dar lugar a: - La fabricación a nivel industrial - La comercialización de una banda retardante de llama para minería y obra subterránea, formulada con un nuevo aditivo que reduce notablemente el contenido en cloro. - Disminución de la contaminación derivada de los humos tóxicos producidos cuando una banda transportadora arde accidentalmente. Los aditivos retardantes de llama sin halógenos, son muy efectivos en dosis elevadas, para la obtención de mezclas con propiedades ignífugas, pero las propiedades mecánicas de las mezclas se debilitan. Se ha buscado un compromiso entre las propiedades ignífugas y mecánicas, por lo que resulta adecuado obtener aditivos que posean un tamaño de partícula tal que actúen como cargas semi-reforzantes para poder utilizarlos en mayor proporción y así poder conseguir las propiedades ignífugas deseadas sin alterar de forma significativa las demás propiedades de la mezcla. ABSTRACT The purpose of this thesis is to obtain a mining conveyor belt with minimal halogen content, with the final objective of being halogen-free. Several polymer matrices without halogen and as well as fireproof systems have been analyzed to achieve this goal. The polymer mixtures studied are based on natural rubber and styrene butadiene, due to the fact that are rubbers without halogens and which their mixtures have good mechanical properties. The outcome of the thesis research is satisfactory, since the results are manufactured conveyor belts that comply with the tests described in the UNE EN 14973. The obtained B1 classification achieves two objectives set at the beginning of the research, and therefore can lead to: - Manufacturing at industrial level - Marketing of a flame retardant conveyor belt for mining and underground works formulated with a new additive that significantly reduces the chlorine content - Reduce pollution produced of the toxic fumes generated when a conveyor accidentally burns Additive flame retardant halogen-free are very effective in high doses to obtain blends with flame retardant properties, but the mechanical properties of the blends are below standards. A compromise between the fire retardant and mechanical properties has been successfully obtained, making possible to obtain additives that show a particle size that act as semi-reinforcing load in order to use a greater extent and thus be able to achieve the pursued fire retardant properties without altering significant other properties of mixture.
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John Summerson, en El Lenguaje Clásico de la Arquitectura, defiende que los órdenes clásicos que empleaban los arquitectos romanos para decorar sus edificios, no tienen una función estructural pero hacen expresivos a los edificios. Les hacen hablar. Arthur Schopenhauer afirma que “el destino de la Bella Arquitectura es poner de manifiesto la lucha entre el peso y la rigidez de los elementos estructurales”. Y Auguste Perret define la Arquitectura como “el arte de hacer cantar al punto de apoyo”. El objetivo de esta Tesis Doctoral es profundizar en la capacidad de expresión de la estructura. A través del estudio de las estructuras históricas, que se realiza en la primera parte de la Tesis, podemos concluir que existen tres categorías, tres maneras de expresión de la Estructura. Estructuras Vistas, que hablan, Estructuras Ocultas, que se esconden y Estructuras Ilusorias, que fingen. El Partenón y la Sainte Chapelle de París se estudian en el apartado de Estructuras Vistas. El Panteón, el Palacio de Carlos V, la Catedral de San Pablo en Londres, y otras arquitecturas renacentistas y romanas, en el apartado de Estructuras Ocultas. Y como Estructuras Ilusorias, la Alhambra (Dos Hermanas, Comares, el Patio de los Leones), Santa Sofía, y otras arquitecturas del barroco italiano. En la segunda parte de la Tesis se analiza la obra completa de Mies van der Rohe desde el punto de vista de esas tres categorías. Lo visto, lo oculto y lo ilusorio en las estructuras de Mies. Se estudia la evolución en la estructura de la casa, desde las primeras casas con Estructura Oculta de muro de ladrillo, hasta las últimas casas con Estructura Vista y columnas adelantadas, pasando por una etapa intermedia de casas con estructura mixta de muro de ladrillo en la que el acero comienza a hacer su aparición. Se analizan también seis soluciones estructurales en los Bloques y en las Torres: Estructura Vista reverberante, expresiva o inexpresiva vs Estructura Oculta con vestido horizontal, vestido reticular o vestido vertical. Y por último, se estudian las tres soluciones de Estructura Ilusoria que emplea Mies en sus Pabellones. La metodología de trabajo que se ha empleado se divide en cuatro apartados: El análisis bibliográfico; el análisis in situ de los edificios, que nos permite comprobar, por ejemplo, los efectos lumínicos de la columna acanalada del Partenón, o el efecto reverberante de las columnas de la Weissenhofsiedlung; el análisis crítico de planos y detalles constructivos, que nos lleva a concluir que la disposición de pantallas del Pabellón de Barcelona anula la lectura de la crujía estructural, y que la columna del restaurante Cantor se dispone con su alma perpendicular a la cercha, y no paralela, como cabría suponer si se quisiera aprovechar toda la capacidad portante del perfil en H; y por último, el análisis numérico y estructural, que nos lleva a confirmar el sobredimensionado de la Estructura del Patio de los Leones de la Alhambra o el sobredimensionado de la Estructura de la Casa Farnsworth. Lo que se confirma con esta Tesis Doctoral es que la Estructura es algo más, mucho más, que sólo transmisión de las cargas. ABSTRACT John Summerson, in The Classic Language of Architecture, argues that the classic orders used by Roman architects in the decoration of their buildings did not have a structural function, but made buildings expressive. They make them speak. Arthur Schopenhauer affirms that “the goal of Great Architecture is to highlight the struggle between the gravity and rigidity of structural elements”. And Auguste Perret defines Architecture as “the art of making the points of support sing”. The objective of this Doctoral Thesis is to examine the expressive capacity of structure. Following a study of historic structures in the first part of the thesis, we conclude that three categories exist, three ways of expressing Structure. Visible Structures that speak, Concealed Structures that are hidden and Illusory Structures that pretend. The Parthenon and the Sainte Chapelle in Paris are studied in the section on Visible Structures. The Pantheon, the Palace of Charles V, Saint Paul’s Cathedral in London, and other Renaissance and Roman architectures are dealt with in the Concealed Structures section. And, as examples of Illusory Structures, we focus on the Alhambra (The Hall of the Two Sisters, the Comares and the Court of the Lions), Saint Sophia, and other Italian Baroque architectures. In the second part of the Thesis the complete work of Mies van der Rohe is analysed from the perspective of these three categories. The visible, the concealed and the illusory, in the structures of Mies. We study how the structure of the house evolves, from the first houses with the Hidden Structure of the brick wall, to the later houses with Visible Structures and columns, via an intermediate phase of mixed-structure houses with brick walls, where steel first began to make its appearance. We also analyse six structural solutions in the Blocks and Towers: reverberant, expressive or inexpressive Visible Structure vs Concealed Structure with horizontal cladding, reticular cladding or vertical cladding. And finally, we look at the three Illusory Structure solutions that Mies employs in his Pavilions. The methodology employed is divided into four sections: a bibliographic analysis; an analysis in situ of the buildings, which allows us to test, for example, the lighting effects of the fluted column in the Parthenon, or the reverberant effect of the Weissenhofsiedlung columns; a critical analysis of plans and constructive details, which leads us to conclude that the arrangement of panels in the Barcelona Pavilion cancels out the structural centreline, and that the column in the Cantor restaurant is placed with its web perpendicular to the truss, and not parallel to it, as one might expect if one wanted to avail of all the load-bearing capacity of the H beam; and lastly, a numeric and structural analysis, which confirms the oversizing of the Court of the Lions structure in the Alhambra or the oversized structure of Farnsworth House. All of which confirms in this Doctoral Thesis that structure is something more, much more, than a mere conveyor of loads.
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Our current understanding of the sound-generating mechanism in the songbird vocal organ, the syrinx, is based on indirect evidence and theoretical treatments. The classical avian model of sound production postulates that the medial tympaniform membranes (MTM) are the principal sound generators. We tested the role of the MTM in sound generation and studied the songbird syrinx more directly by filming it endoscopically. After we surgically incapacitated the MTM as a vibratory source, zebra finches and cardinals were not only able to vocalize, but sang nearly normal song. This result shows clearly that the MTM are not the principal sound source. The endoscopic images of the intact songbird syrinx during spontaneous and brain stimulation-induced vocalizations illustrate the dynamics of syringeal reconfiguration before phonation and suggest a different model for sound production. Phonation is initiated by rostrad movement and stretching of the syrinx. At the same time, the syrinx is closed through movement of two soft tissue masses, the medial and lateral labia, into the bronchial lumen. Sound production always is accompanied by vibratory motions of both labia, indicating that these vibrations may be the sound source. However, because of the low temporal resolution of the imaging system, the frequency and phase of labial vibrations could not be assessed in relation to that of the generated sound. Nevertheless, in contrast to the previous model, these observations show that both labia contribute to aperture control and strongly suggest that they play an important role as principal sound generators.
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Enhanced Atlantic overturning during the Pliocene was first proposed almost 10 yrs ago. Evidence for this Pliocene super conveyor scenario has been collected using a number of proxies (e.g., benthic d13C, Nd isotopic composition of manganese crusts). The present study contributes to the existing evidences by using carbonate dissolution and current vigour history of early Pliocene sediments from the Ceará Rise (ODP Sites 927 and 929). In order to reveal carbonate dissolution history, a number of commonly used and newly established proxies were applied, i.e., sand and carbonate contents, foraminifer fragmentation index, Bulloides Dissolution Index and carbonate silt grain-size distributions. Terrigenous silt grain-size distributions were used to unravel variations in relative current strength and sediment input to the two sites. Overall good carbonate preservation at the shallow Site 927 (3314 m water depth) shows that this level was bathed in North Atlantic Deep Water throughout the early Pliocene. The contrastingly poor carbonate preservation record of the deeper Site 929 (4358 m water depth, at present exposed to Antarctic Bottom Water) is frequently interrupted by phases of good carbonate preservation. These results indicate that the depth of the calcite lysocline was mainly tied to present level (ab. 4200 m water depth), and sometimes even dropped to water depths greater than 4360 m due to even more enhanced circulation. Surprisingly the expansion of NADW is not clearly reflected by an increase in current speed as shown by continuously fine terrigenous grain size.
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As shown by the work of Dansgaard and his colleagues, climate oscillations of one or so millennia duration punctuate much of glacial section of the Greenland ice cores. These oscillations are characterized by 5°C air temperature changes, severalfold dust content changes and 50 ppm CO2 changes. Both the temperature and CO2 change are best explained by changes in the mode of operation of the ocean. In this paper we provide evidence which suggests that oscillations in surface water conditions of similar duration are present in the record from a deep sea core at 50°N. Based on this finding, we suggest that the Greenland climate changes are driven by oscillations in the salinity of the Atlantic Ocean which modulate the strength of the Atlantic's conveyor circulation.
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The Arctic Ocean System is a key player regarding the climatic changes of Earth. Its highly sensitive ice Cover, the exchange of surface and deep water masses with the global ocean and the coupling with the atmosphere interact directly with global climatic changes. The output of cold, polar water and sea ice influences the production of deep water in the North Atlantic and controls the global ocean circulation ("the conveyor belt"). The Arctic Ocean is surrounded by the large Northern Hemisphere ice sheets which not only affect the sedimentation in the Arctic Ocean but also are supposed to induce the Course of glacials and interglacials. Terrigenous sediment delivered from the ice sheets by icebergs and meltwater as well as through sea ice are major components of Arctic Ocean sediments. Hence, the terrigenous content of Arctic Ocean sediments is an outstanding archive to investigate changes in the paleoenvironment. Glazigenic sediments of the Canadian Arctic Archipelago and surface samples of the Arctic Ocean and the Siberian shelf regions were investigated by means of x-ray diffraction of the bulk fraction. The source regions of distinct mineral compositions were to be deciphered. Regarding the complex circumpolar geology stable christalline shield rocks, active and ancient fold belts including magmatic and metamorphic rocks, sedimentary rocks and wide periglacial lowlands with permafrost provide a complete range of possible mineral combinations. Non- glaciated shelf regions mix the local input from a possible point source of a particular mineral combination with the whole shelf material and function as a sampler of the entire region draining to the shelf. To take this into account, a literature research was performed. Descriptions of outcropping lithologies and Arctic Ocean sediments were scanned for their mineral association. The analyses of glazigenic and shelf sediments yielded a close relationship between their mineral composition and the adjacent source region. The most striking difference between the circumpolar source regions is the extensive outcrop of carbonate rocks in the vicinity of the Canadian Arctic Archipelago and in N Greenland while siliciclastic sediments dominate the Siberian shelves. In the Siberian shelf region the eastern Kara Sea and the western Laptev Sea form a destinct region defined by high smectite, (clino-) pyroxene and plagioclase input. The source of this signal are the extensive outcrops of the Siberian trap basalt in the Putorana Plateau which is drained by the tributaries of the Yenissei and Khatanga. The eastern Laptev Sea and the East Siberian Sea can also be treated as one source region containing a feldspar, quartz, illite, mica, and chlorite asscciation combined with the trace minerals hornblende and epidote. Franz Josef Land provides a mineral composition rich in quartz and kaolinite. The diverse rock suite of the Svalbard archipelago distributes specific mineral compositions of highly metamorphic christalline rocks, dolomite-rich carbonate rocks and sedimentary rocks with a higher diagenetic potential manifested in stable newly built diagenetic minerals and high organic maturity. To reconstruct the last 30,000 years as an example of the transition between glacial and interglacial conditions a profile of sediment cores, recovered during the RV Polarstern" expedition ARK-VIIIl3 (ARCTIC '91), and additional sediment cores around Svalbard were investigated. Besides the mineralogy of different grain size fractions several additional sedimentological and organo-geochemical Parameterswere used. A detailed stratigraphic framework was achieved. By exploiting this data set changes in the mineral composition of the Eurasian Basin sediments can be related to climatic changes. Certain mineral compositions can even be associated with particular transport processes, e.g. the smectitel pyroxene association with sea ice transport from the eastern Kara Sea and the western Laptev Sea. Hence, it is possible to decipher the complex interplay between the influx of warm Atlantic waters into the Southwest of the Eurasian Basin, the waxing and waning of the Svalbard1Barents- Sea- and Kara-Sea-Ice-Sheets, the flooding of the Siberian shelf regions and the surface and deep water circulation. Until now the Arctic Ocean was assumed to be a rather stable System during the last 30,000 years which only switched from a completely ice covered situation during the glacial to seasonally Open waters during the interglacial. But this work using mineral assemblages of sediment cores in the vicinity of Svalbard revealed fast changes in the inflow of warm Atlantic water with the Westspitsbergen Current (< 1000 years), short periods of advances and retreats of the marine based Eurasian ice sheets (1000-3000 years), and short melting phases (400 years?). Deglaciation of the marine-based Eurasian and the land-based north American and Greenland ice sheets are not simultaneous. This thesis postulates that the Kara Sea Ice Sheet released an early meltwater signal prior to 15,000 14C years leading the Barents Sea Ice Sheet while the western land-based ice sheets are following later than 13,500 14C years. The northern Eurasian Basin records the shift between iceberg and sea-ice material derived from the Canadian Arctic Archipelago and N-Greenland and material transported by sea-ice and surface currents from the Siberian shelf region. The phasing of the deglaciation becomes very obvious using the dolomite and quartd phyllosilicate record. It is also supposed that the flooding of the Laptev Sea during the Holocene is manifested in a stepwise increase of sediment input at the Lomonosov Ridge between the Eurasian and Amerasian Basin. Depending on the strength of meltwater pulses from the adjacent ice sheets the Transpolar Drift can probably be relocated. These movements are traceable by the distribution of indicator minerals. Based on the outcome of this work the feasibility of bulk mineral determination can be qualified as excellent tool for paleoenvironmental reconstructions in the Arctic Ocean. The easy preparation and objective determination of bulk mineralogy provided by the QUAX software bears the potential to use this analyses as basic measuring method preceding more time consuming and highly specialised mineralogical investigations (e.g. clay mineralogy, heavy mineral determination).
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Thesis (Master's)--University of Washington, 2016-06
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Mussorgsky's Sunless cycle is aesthetically and stylistically an anomalous member of his oeuvre. Its notably effaced, pared-down, and withdrawn qualities present challenges to critical interpretation. Its uniqueness, however, renders it a crucial work for furnishing the fullest possible picture of Mussorgsky as a creative artist. The author of its texts, Golenishchev-Kutuzov (whose relationship with Mussorgsky at the time of its writing possibly extended beyond the platonic) has been identified by recent scholarship as an essential eye-witness for those to whom Stasov's populist characterization of the composer does not ring entirely true. Golenishchev-Kutuzov believed that in Sunless Mussorgsky first revealed his authentic artistic self. According to Golenishchev-Kutuvoz, Mussorgsky regarded his signal achievement in Sunless to have been the eradication of all elements other than feeling. In other words, he had thrown off the stylistic shackles imposed by the aesthetics of realism and relied entirely on intuitive harmonic invention as the sole conveyor of a purely subjective, affective meaning in the cycle. This hypothesis forms the point of departure for an investigation of select numbers of the cycle. Analysis reveals that the affective aspect is riot the only significant element operative. Alongside remnants of the realist style, there is evidence, of varying degrees of subtlety, for a knowing use of symmetrical pitch organization. Mussorgsky not only adapted the usual referential attachments of symmetrically based chromaticism-typically found in Russian operas of the second half of the nineteenth century-he also, through extremely simple but effective means, synthesized the intuitive harmonic and rational symmetrical elements of the cycle's pitch organization so that the latter emerges seamlessly out of the former. This remarkable synthesis ensures the cycle's uniformity of tone while also allowing for a reading that extends beyond the generally affective to the symbolically more specific. This symbolic level of reading offers several interpretative possibilities, one of which may refer even to the relationship of the poet and the composer. Irrespective of such potentials for interpretation, the most significant achievement in the cycle remains the synthesis of the intuitive/affective and rational/symbolic elements of its organization. Songs 1, 2, 3, and 6 of the cycle are considered in detail.
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Purpose – To investigate the role of simulation in the introduction of technology in a continuous operations process. Design/methodology/approach – A case-based research method was chosen with the aim to provide an exemplar of practice and test the proposition that the use of simulation can improve the implementation and running of conveyor systems in continuous process facilities. Findings – The research determines the optimum rate of re-introduction of inventory to a conveyor system generated during a breakdown event. Research limitations/implications – More case studies are required demonstrating the operational and strategic benefits that can be gained by using simulation to assess technology in organisations. Practical implications – A practical outcome of the study was the implementation of a policy for the manual re-introduction of inventory on a conveyor line after a breakdown event had occurred. Originality/value – The paper presents a novel example of the use of simulation to estimate the re-introduction rate of inventory after a breakdown event on a conveyor line. The paper highlights how by addressing this operational issue, ahead of implementation, the likelihood of the success of the strategic decision to acquire the technology can be improved.
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The aim of this work was to design and build an equipment which can detect ferrous and non-ferrous objects in conveyed commodities, discriminate between them and locate the object along the belt and on the width of the belt. The magnetic induction mechanism was used as a means of achieving the objectives of this research. In order to choose the appropriate geometry and size of the induction field source, the field distributions of different source geometries and sizes were studied in detail. From these investigations it was found the square loop geometry is the most appropriate as a field generating source for the purpose of this project. The phenomena of field distribution in the conductors was also investigated. An equipment was designed and built at the preliminary stages of thework based on a flux-gate magnetometer with the ability to detect only ferrous objects.The instrument was designed such that it could be used to detect ferrous objects in the coal conveyors of power stations. The advantages of employing this detector in the power industry over the present ferrous metal electromagnetic separators were also considered. The objectives of this project culminated in the design and construction of a ferrous and non-ferrous detector with the ability to discriminate between ferrous and non-ferrous metals and to locate the objects on the conveying system. An experimental study was carried out to test the performance of the equipment in the detection of ferrous and non-ferrous objects of a given size carried on the conveyor belt. The ability of the equipment to discriminate between the types of metals and to locate the object on the belt was also evaluated experimentally. The benefits which can be gained from the industrial implementations of the equipment were considered. Further topics which may be investigated as an extension of this work are given.
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The high capital cost of robots prohibit their economic application. One method of making their application more economic is to increase their operating speed. This can be done in a number of ways e.g. redesign of robot geometry, improving actuators and improving control system design. In this thesis the control system design is considered. It is identified in the literature review that two aspects in relation to robot control system design have not been addressed in any great detail by previous researchers. These are: how significant are the coupling terms in the dynamic equations of the robot and what is the effect of the coupling terms on the performance of a number of typical independent axis control schemes?. The work in this thesis addresses these two questions in detail. A program was designed to automatically calculate the path and trajectory and to calculate the significance of the coupling terms in an example application of a robot manipulator tracking a part on a moving conveyor. The inertial and velocity coupling terms have been shown to be of significance when the manipulator was considered to be directly driven. A simulation of the robot manipulator following the planned trajectory has been established in order to assess the performance of the independent axis control strategies. The inertial coupling was shown to reinforce the control torque at the corner points of the trajectory, where there was an abrupt demand in acceleration in each axis but of opposite sign. This reduced the tracking error however, this effect was not controllable. A second effect was due to the velocity coupling terms. At high trajectory speeds it was shown, by means of a root locus analysis, that the velocity coupling terms caused the system to become unstable.