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No description available.

Most of the drinking water supply in rural Bangladesh comes from groundwater collected using shallow tubewells. The tubewells, usually shallow because of the increased cost involved in deeper tubewells, have been installed by local drillers. A Sediment Color Tool was developed, with input from local drillers, that associated the arsenic concentration with specific sediment colors, in order to help the drillers install safe tubewells. This tool was digitized into the phone application, ASMITAS, to reduce subjectivity in sediment color determination due to human error or surrounding conditions, when used with a color sensor. The purpose of this study was to carry out a preliminary assessment of the application performance and usability, and the results provided by the application for color identification. 35 sediments were used and assigned into 4 different data sets to allow for comparison. Two data sets were assigned a Munsell color manually, while two were assigned the Munsell Soil Color (or Red-Green-Blue color) through use of the digital app. The sensor, the Nix Color Sensor Pro 2, was validated through a literature review and is considered accurate in identifying the color of the soil sediments. The data sets were compared based on the Delta E 2000 formula to determine the color difference between the data sets. The most relevant result of this method was between the Red-Green-Blue that the Nix Sensor originally provided to the application versus the closest matching Munsell code that the application could provide. It showed that the library from which the Munsell color was drawn was not yet expansive enough to accurately identify all sediments that may be scanned. Cyan-Magenta-Yellow-Black color comparisons were made to ascertain which aspects of the color are the most difficult to identify. It was found that both the sensor and the human eye had difficulties in identifying differences in the yellow percentage of several of the samples. The results showed that there may be greater need for distinction of which yellow percentages of Cyan-Magenta-Yellow-Black belong to which color sediment. Overall, the application appears to have a small number of less prominent features and functions to improve on prior to the publication of the application. At this stage of development, the main goal lies in the improvement and building of the Munsell color code reference library and the library of arsenic concentrations associated with each sediment color within the application, in order to improve the accuracy of the results. / Största delen av dricksvattenförsörjningen i lantlig Bangladesh kommer från grundvatten som samlas in med rörbrunnar. Rörbrunnarna, som vanligtvis är grunda som en följd av kostnaderna, har installerats av lokala borrare. Under 2007 antogs det att färgen på sedimentet i vilket rörbrunnarna placeras ger en indikation på arsenikens koncentration. Därför utvecklades Sediment Color Tool med input från de lokala borrarna. Verktyget vidareutvecklades till en digital app, ASMITAS, för att minska subjektiviteten i markfärgbestämning på grund av mänskliga fel eller omgivande förhållanden. Syftet med denna studie var att utvärdera applikationens prestanda i detta stadie av dess utveckling och färgidentifiering som genomförts av applikationen. 35 sediment användes i första bedömningen och klassificerades fyra gånger i fyra olika datamängder för att möjliggöra jämförelse. Två datamängder tilldelades en Munsell Soil Color manuellt, medan två tilldelades sin färg genom användning av den digitala appen. Sensorn som användes, Nix Color Sensor Pro 2, validerades genom en litteraturöversikt och anses vara korrekt när det gäller att identifiera färgen på sediment. De fyra datamängderna jämfördes visuellt med användning av färgbrickor. De jämfördes baserat på DE2000-formeln för att bestämma färgskillnaden mellan datamängden. Det mest avslöjande resultatet med denna metod var mellan dem två digitalt förvärvade datamängderna. Resultatet föreslår att referensbiblioteket i ASMITAS, från vilket matchen togs, ännu inte var tillräckligt stort för att identifiera alla sedimentprover noggrant för att ej vara märkbar för det mänskliga ögat. Cyan-Magenta-Gul-Svart jämförelser gjordes för att se vilka aspekter av färgen som är svårast att identifiera. Resultaten visade att både sensorn och det mänskliga ögat hade svårigheter att identifiera skillnader i den gula procentandelen av flera av proverna och sedimentfärgerna. Resultaten visade att det kan finnas ett större behov av åtskillnad av vilka gula procentsatser som tillhör vilken färg av sediment (och motsvarande arsenikkoncentration). Det finns ytterligare aspekter och funktioner av appen som är mindre centrala för dess prestanda som bör förbättras innan applikationen publiceras. I detta utvecklingsstadium ligger emellertid huvudmålet i förbättring och uppbyggnad av Munsell- färgkodreferensbiblioteket och biblioteket med arsenik-koncentrationer som är kopplad till varje sedimentfärg i applikationen. Detta för att öka resultatets noggrannhet.

Concrete filled steel tubular columns have been extensively used in modern construction owing to that they utilise the most favourable properties of both constituent materials. It has been recognized that concrete filled tubular columns provide excellent structural properties such as high load bearing capacity, ductility, large energy-absorption capacity and good structural fire behaviour. This paper presents the structural fire behaviour of a series of concrete filled steel tubular stub columns with four typical column sectional shapes in standard fire. The selected concrete filled steel tube stub columns are divided into three groups by equal section strength at ambient temperature, equal steel cross sectional areas and equal concrete core cross sectional areas. The temperature distribution, critical temperature and fire exposing time etc. of selected composite columns are extracted by numerical simulations using commercial FE package ABAQUS. Based on the analysis and comparison of typical parameters, the effect of column sectional shapes on member temperature distribution and structural fire behaviour are discussed. It shows concrete steel tubular column with circular section possesses the best structural fire behaviour, followed by columns with elliptical, square and rectangular sections. Based on this research study, a simplified equation for the design of concrete filled columns at elevated temperature is proposed.

This thesis investigates the impedance of acoustic liners, to attenuate noise originating from jet engines and enable compliance with international standards and regulations regarding noise from airplane jet engines. Experimental tests of two supplied liners were conducted in an impedance tube; one liner with known and predictable properties, and one liner with unknown properties. The tests included tonal excitations in the formats of stepped sine and random noise with frequencies within set boundaries. After post-processing of the captured data, the desired impedance could be analysed in terms of excitated frequencies and sound pressure levels. The conclusions from this project are that both of the liners deviated from their expected behavior, which was that liner 1 should have been unaffected by the alternated sound pressure levels, and liner 3 should have shown bigger affection due to the changed sound pressure level. Since the results were different than expected, there might have been minor sources of error during the measurements. It could be investigated if there is leakage from the mounting of the liners, or if the 3D printing resolution is sufficient. Because of limitations in time, there is more left in this project to investigate. Therefore, conducting similar studies where more frequencies, sound pressure levels, and multi-tonal measurements can be included, is suggested as future work.

[ES] Hyperloop es considerado el quinto medio de transporte, después del coche, barco, tren y avión. Consiste en una capsula de levitación magnética que viaja dentro de un tubo en el que la presión de aire ha sido reducida. Entonces, la fricción con el suelo y resistencia aerodinámica son minimizadas, alcanzando ultra altas velocidades a nivel de tierra. Actualmente hay en desarrollo varios trenes maglev y conceptos hyperloop. La mayoría proponen levitar usando Suspensión Electromagnética (EMS). Zeleros, la compañía donde esta Tesis ha sido realizada, tiene una propuesta similar. Zeleros usa un EMS Híbrido (HEMS), combinando imanes y electroimanes para reducir los requerimientos de energía. Respecto a la propulsión, la propuesta es única ya que hace uso de un compresor de la industria aeroespacial. Simulaciones CFD prueban que usar un compresor reduce considerablemente la resistencia aerodinámica en el ambiente cerrado, ya que el efecto pistón es mitigado. Para el mismo tamaño de tubo y presión, un hyperloop con compresor requiere hasta 70 % menos potencia. En otros términos, si la misma potencia es instalada en el vehículo, el diámetro de la infraestructura puede ser 2.8 veces más pequeño. Esta Tesis desarrolla un simulador 0D para evaluar el rendimiento de la solución hyperloop propuesta. Resolver su aerodinámica requiere solucionar un fujo interno y externo de Fanno. El último combina efectos de Couette y Poisuille en un dominio anular. Así, se desarrolla un modelo simplificado para flujos de Fanno, acelerando así el modelado básico. Esta aproximación matemática incluye información de la velocidad de la pared y de la forma del dominio, evitando integrar un sistema de EDOs. La solución tiene una desviación en la ratio de presiones de 5 % respecto a CFD, y del 10 % en la longitud crítica. El simulador modela toda la termodinámica del vehículo, incluyendo el compresor, conductos, turbina, tobera y flujo externo. Este modelado es similar al del ciclo de Bryton, sin cámara de combustión. Además, se incluye un modelo para predecir la masa y longitud de la cápsula y sus componentes. Así, las pérdidas de fricción y requerimientos de potencia y energía son obtenidos. Estos resultados presentan una desviación máxima del 20 % respecto a CFD. Además, un proceso de optimización para encontrar la solución más eficiente se ha desarrollado con el código, para vehículos de 50 y 150 pasajeros. Se ha encontrado que es más beneficioso absorber menos gasto másico con el compresor, ya que la energía requerida para comprimir el flujo interno es más alta que las pérdidas en el canal externo. Comparando el consumo de energía específico de esta solución con otros medios de transporte, el hyperloop se encuentra cercano al rendimiento de los maglev. Éste es, también, entre tres y cinco veces más eficiente que los aviones. Además, es más competitivo que el avión en términos de velocidad media en una ruta hasta los 800 km. Por último, se desarrolla un modelo similar para un sistema de escala media. Este prototipo, cuya velocidad objetivo es de 500 km/h, es diseñado por Zeleros previo al sistema de escala real. Su simulador incluye además los efectos transitorios y la termodinámica del tubo, asumiendo una velocidad del sonido infinita. Gracias a este código, se puede obtener el rendimiento en una misión. Inicialmente, el prototipo incrementa la presión del tubo aguas arriba, y la reduce aguas abajo debido al efecto pistón, generando una velocidad inducida. Al final de la misión, el flujo puede ser transferido otra vez, y las presiones se equilibran otra vez. Este modelo también predice el par y potencia del motor eléctrico, además de los parámetros de la batería (voltaje, corriente y profundidad de descarga). / [CA] Hyperloop és considerat el cinquè mitjà de transport, després del cotxe, vaixell, tren i avió. Consisteix en una càpsula de levitació magnètica que viatja dins d'un tub on la pressió d'aire es reduïda. Aleshores, la fricció amb el sòl i resistència aerodinàmica són minimitzades, aconseguint ultra altes velocitats a nivell de terra. Actualment hi ha en desenvolupament diversos trens maglev i conceptes hyperloop. La majoria proposen levitar usant Suspensió Electromagnètica (EMS). Zeleros, la companyia on aquesta Tesi ha sigut realitzada, té una proposta similar. En particular, el concepte de Zeleros utilitza un EMS Híbrid (HEMS), combinant imants i electroimants per reduir els requeriments d'energia. Pel que fa a la propulsió, la proposta és única, ja que fa ús d'un compressor de la indústria aeroespacial. Simulacions CFD proven que utilitzar un compressor redueix considerablement la resistència aerodinàmica en un ambient tancat, ja que l'efecte pistó és mitigat. Per a la mateixa grandària de tub i pressió, un hyperloop amb compressor requereix fins a 70 % menys potència. En altres termes, si la mateixa potència és instal·lada al vehicle, el diàmetre de la infraestructura pot ser 2.8 vegades més menut. Aquesta Tesi desenvolupa un simulador 0D per avaluar el rendiment de la solució hyperloop proposada. Resoldre l'aerodinàmica del hyperloop requereix solucionar un flux intern i extern de Fanno. L'últim combina efectes de Couette i Poiseuille en un domini anular. Així, es desenvolupa un model simplificat per a fluxos de Fanno, accelerant així el modelatge bàsic. Aquesta aproximació matemàtica inclou informació de la velocitat de la paret i de la forma del domini, evitant integrar un sistema de EDOs. La solució té una desviació a la ràtio de pressions de 5 % respecte a CFD, i del 10 % a la longitud crítica. El simulador modela tota la termodinàmica del vehicle, incloent-hi el compressor, conductes, turbina, tovera i flux extern. Aquest modelat es similar al del cicle de Bryton, sense càmera de combustió. A més, s'inclou un model per predir la massa i la longitud de la càpsula i els seus components. Així, les pèrdues de fricció i requeriments de potència i energia són obtinguts. Aquests resultats presenten una desviació màxima del 20 % comparat amb CFD. A més, un procés d'optimització per trobar la solució més eficient ha estat desenvolupat amb el codi, per a vehicles de 50 i 150 passatgers. S'ha trobat que és més beneficiós absorbir menys massa amb el compressor, ja que l'energia requerida per comprimir el flux intern és més alta que les pèrdues al canal extern. Comparant el consum d'energia específic d'aquesta solució amb altres mitjans de transport, el hyperloop és proper al rendiment dels maglev. Aquest també és entre tres i cinc vegades més eficient que els avions. A més, és més competitiu en termes de velocitat mitjana en una ruta fins a 800 km. Finalment, es desenvolupa un model semblant per a un sistema d'escala mitjana. Aquest prototip, la velocitat objectiu del qual és de 500 km/h, és dissenyat per Zeleros previ al sistema d'escala real. El seu simulador inclou a més els efectes transitoris i la termodinàmica del tub, assumint una velocitat del so infinita. Gràcies a aquest codi, es pot obtenir el rendiment en una missió. Inicialment, el prototip incrementa la pressió del tub aigües amunt, i la redueix aigües avall degut a l'efecte pistó, generant una velocitat induïda. Al final de la missió, el flux pot ser transferit una altra vegada, i les pressions s'equilibren una altra vegada. Aquest model també prediu el parell i potència del motor elèctric, a més dels paràmetres de la bateria (voltatge, corrent i profunditat de descàrrega). / [EN] Hyperloop is considered the fifth means of transportation, after the car, boat, train and plane. It consists of a magnetically levitating capsule that travels within a tube in which the air pressure has been reduced. Thus, the ground friction and aerodynamic drag are minimised, reaching ultra high-speeds at ground level. Several maglev trains and hyperloop concepts being developed currently. Most of them propose levitating using Electromagnetic Suspension (EMS). Zeleros, the company where this Thesis was done, has a similar approach. It employs a Hybrid EMS (HEMS)In particular, the Zeleros approach employs a Hybrid EMS (HEMS), combining permanent and electromagnets to reduce energy requirements. As for the propulsion, the approach is unique as it uses a compressor from the aeronautical industry. CFD simulations prove that using a compressor considerably reduces the aerodynamic drag in the closed environment, as the piston effect gets mitigated. For the same tube size and pressure, a hyperloop with compressor requires up to 70 % less power. In other terms, if the same power is installed on the vehicle, the infrastructure diameter can be 2.8 times smaller. This Thesis develops a 0D simulator to evaluate the performance of the proposed hyperloop solution. Solving the aerodynamics of the hyperloop requires solving internal and external Fanno flows. For the latter, the flow combines Couette and Poiseuille effects in an annular domain. Thus, a simplified model for Fanno flows is developed to accelerate the basic modelling. This mathematical approach includes the information of the wall speed and the shape of the domain, avoiding integrating an ODE system. The solution has a deviation in the pressure ratio of 5 % and 10 % in the critical length regarding CFD. The simulator models all the vehicle thermodynamics, including the compressor, duct, turbine, nozzle, and external flow. This modelling is similar to a Bryton cycle, without a combustion chamber. Also, a model to predict the mass and length of the capsule and its components is included. Thus, the friction losses and the energy and power requirements can be extracted. These outputs are compared with CFD results, with a maximum deviation of 20 %. Moreover, an optimisation process is conducted with the code to find the most efficient solution for 50- and 150-passenger vehicles. It is found that shallowing less mass flow with the compressor is better, as the energy required to compress the internal flow is higher than the losses on the external channel. Comparing the specific energy consumption of this solution with other means of transportation, the hyperloop is close to the maglev performance. It is also between three and five times more efficient than aeroplanes. Furthermore, the hyperloop is more competitive than the plane in terms of average speed on a route, up to 800 km. The last part of this work develops a similar model for a middle-scale system. This prototype, which aims to reach 500 km/h, is being designed by Zeleros before the real-scale one. Its simulator also includes the transient effects and the tube thermodynamics, assuming an infinite sound speed. Thanks to this code, the performance in a mission is obtained. The prototype initially increases the upstream tube pressure and reduces the downstream one due to the piston effect, generating an induced speed. At the end of the mission, the flow can be transferred again, and the pressures equilibrate again. This model also predicts the electric motor torque and power and the battery parameters (voltage, current, and deep of discharge). / Este trabajo ha recibido una subvención parcial del Ministerio de Ciencia, Innovación y Universidades bajo la ayuda “Doctorandos Industriales” número DI-17-09616. / Lluesma Rodríguez, F. (2022). Design and Optimisation of a Virtual Prototype of a Ground Transportation System at Very High-Speeds in Conditions Close to Vacuum [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191409

Concrete filled steel tubes are regarded as ideal frame members in seismic resisting systems, as they combine large axial and flexural capacity with ductility. The combination of the two materials increases the strength of the confined concrete and avoids premature local buckling of the steel tube. These benefits are more prominent for circular than for rectangular concrete filled steel tubes. However, most common connection configurations for circular concrete filled tubes are not economic in the US market due to (a) the desire of designers to use only fully restrained connections and its associated (b) high cost of fabrication and field welding. Research indicates that well designed partially restrained connections can supply equal or even better cyclic behavior. Partially restrained connections also possess potential capability to develop self-centering system, which has many merits in seismic design. The goal of this research is to develop a new connection configuration between circular concrete filled steel columns and conventional W steel beams. The new connection configuration is intended to provide another option for rapid assembling on site with low erection costs. The proposed connection is based on an extended stiffened end plate that utilizes through rods. The rods are a combination of conventional steel and shape memory alloy that provide both energy dissipation and self-centering capacity. The new connection configuration should be workable for large beam sizes and can be easily expanded to a biaxial bending moment connection. / Ph. D.

Recent terrorist attacks and accidental explosions have prompted increased interest in the blast resistant design of high-risk facilities, including government offices, private sector buildings, transportation terminals, sporting venues, and military facilities. Current blast resistant design standards prioritize the protection of the primary structural system, such as walls, columns, and beams, to prevent a disproportionate collapse of the entire structure. Secondary structural systems and non-structural components, such as blast resistant doors, are typically outside the focus of standard building design. Components such as blast resistant doors are designed and manufactured by private sector entities, and their details are confidential and considered proprietary business information. For this reason, scientific research on blast resistant doors is sparse and most test results are unavailable for public consumption. Nevertheless, the performance of blast doors is crucial to the survival of building occupants as they are relied upon to contain blast pressures and remain operable after a blast event to allow ingress/egress. These important roles highlight the critical need for further research and development to enhance the level of protection provided by components that are often not considered in any detail by protective design practice. This thesis presents a combined experimental and analytical research program intended to support the development of blast resistant hollow metal doors. A total of 18 static beam-assembly tests were conducted, which consisted of the flexural four-point bending of door segments, to inform on the performance characteristics of full-sized blast resistant doors. Six tests were conducted to evaluate the effectiveness of three skin-core construction methodologies, which consisted of one epoxy and two weld attachment specifications, between door skins and their internal reinforcing structures. The remaining 12 tests were performed to evaluate the in-situ performance of hinge hardware typically installed on blast resistant door assemblies. The results of the skin-core construction tests demonstrated that closely spaced weld patterns would provide the best blast performance. The results of the hinge hardware tests demonstrated that hinges which provided a continuous load-path directly into the primary ii structural core elements of the door frame and door were ideal; furthermore, robust hinges with fully-welded or continuous knuckles were best suited for limiting undesirable deformations. A semi-empirical analytical methodology was developed to predict the global deformation response of full-sized hollow metal doors subjected to blast loading in the seated direction. The goal was to provide practicing engineers who are competent but non-expert users of high fidelity simulations with the flexibility to conduct in-house evaluation of the blast resistance of hollow metal doors without having to conduct live explosive or simulated blast tests. A finite element analysis was first performed to compute the door resistance function. Hollow metal door construction was idealized using a bulk material sandwiched between sheet metal skins and internally stiffened by stringers. The properties of the bulk material were calibrated such that the deformability of the idealized core reasonably approximated the global load-deformation behavior which occurs due to loss of composite action when welds fail. The resistance curves were then used in a singledegree-of-freedom dynamic analysis to predict the displacement response of the door subjected to blast loading. The proposed methodology was first validated against the static beam-assembly flexural tests. It was then extended to the case of a full-sized door subjected to shock tube blast testing using results published in the literature. The proposed methodology was found to reasonably approximate the out-of-plane load-deformation response of beam-assemblies and full-size doors, provided the bulk material properties of the idealized core are calibrated against experimental data. Finally, the new Virginia Tech Shock Tube Testing Facility was introduced. A description of the facility, including an overview of the shock tube's location, construction, main components, instrumentation, and key operating principles, were discussed. Operating guidelines and procedures were outlined to ensure safe, controlled, and repeated blast testing operations. A detailed calibration plan was proposed, and future work pertaining to the development of blast resistant hollow metal doors was presented. / Master of Science / Recent terrorist attacks and accidental explosions have motivated an increase in the demand for blast protection of critical infrastructure. Secondary components, such as doors, play a pivotal role in the protection of occupants as they ensure blast pressures are contained and ingress/egress is possible after a blast event. Experiments have been conducted to characterize the performance of several door construction methodologies (i.e., epoxy, reduced weld requirements) and the in-situ performance of hinge hardware through quasi-static testing of beams whose construction closely mimics that of a full-size door. Results of door construction testing indicated that, whenever possible, blast resistant doors should be constructed with full weld attachment (maximum specification with weld spaced every 3”) as these doors were found to provide the greatest resistance. Due to inconsistent and sudden failure mode, epoxy skin-core construction is not recommended for use in blast resistant doors at this time. Hinge testing determined that hinge mounting plates (which hinge hardware leaves are attached to) should be integrally connected to the frame and door internal reinforcing elements to provide adequate strength and that hinges with fully welded knuckles should be used for blast applications to limit deformation and facilitate post-blast operability. An ABAQUS finite element analysis methodology utilizing a “skins and stringers” approach to generate a beam-assembly model resulted in an adequate prediction of load deflection results recorded during beam-assembly testing after calibration of the model. An extension of this modeling approach was used to model full-size doors and adequately captured their dynamic performance when subjected to blast loading. Finally, preparation of the Virginia Tech Shock Tube Testing Facility, which is currently in progress, is summarized with regards to its calibration and the first round of testing which will focus on providing more data for comparison with the analysis methodology developed in this research.

The use of lateral divert thrusters on hypersonic vehicles would allow for fine-tuned attitude control at high Mach numbers. However, the jet interaction effects of lateral thrusters on the hypersonic flow field have not been investigated thoroughly. Computational Fluid Dynamics (CFD) can provide preliminary modeling of the jet interaction, but several variables such as vehicle geometry, velocity, and altitude, result in computationally expensive modeling or loss in accuracy of the results. Therefore, the goal of chemical kinetics testing and chemical model verification is to enhance the fidelity of the jet interaction effects, specifically the plume reaction with air and the plume interaction with vehicle instrumentation.

No / Small-angle neutron scattering measurements on a series of monodisperse linear entangled polystyrene melts in nonlinear flow through an abrupt 4:1 contraction have been made. Clear signatures of melt deformation and subsequent relaxation can be observed in the scattering patterns, which were taken along the centerline. These data are compared with the predictions of a recently derived molecular theory. Two levels of molecular theory are used: a detailed equation describing the evolution of molecular structure over all length scales relevant to the scattering data and a simplified version of the model, which is suitable for finite element computations. The velocity field for the complex melt flow is computed using the simplified model and scattering predictions are made by feeding these flow histories into the detailed model. The modeling quantitatively captures the full scattering intensity patterns over a broad range of data with independent variation of position within the contraction geometry, bulk flow rate and melt molecular weight. The study provides a strong, quantitative validation of current theoretical ideas concerning the microscopic dynamics of entangled polymers which builds upon existing comparisons with nonlinear mechanical stress data. Furthermore, we are able to confirm the appreciable length scale dependence of relaxation in polymer melts and highlight some wider implications of this phenomenon.