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The construction industry is facing a reality where the dependency on fossil fuels needs to cease and be replaced by options that are more climate friendly. One such option is the electrification that has not made a breakthrough in the construction industry yet and therefore needs to be examined. In this thesis an investigation is made by two different systems of wheel loaders and trucks. One system that conducts machines run by electricity and another one where the system is powered by diesel. The investigation is based on goal formulation which serves as the basis for answering these questions. The machines were examined in such as to obtain results that illustrate which system of machines that are profitable with regards to time, energy consumption, carbon dioxide emissions and total costs. This thesis has also as an intent to identify any advantages and disadvantages of each transport method. This is done in order to lend structure to any further research conducted in the future. To be able to compare and examine the properties of the machines, these machines were applied to a tunneling project. The project that was received was the metro station Hagalunds industriområde. The planned expansion of the subway will lead to a new metro line between Arenastaden and Odenplan, where Hagalunds industriområde will become an intermediate station. In order to truly optimize our efforts and carry out the calculations, the focus was placed on a partial stretch of 1 000 meters with respect to the main tunnel and working tunnel. The result obtained shows that the electric wheel loader leads to less time, carbon dioxide emissions and better energy efficiency than the diesel-powered wheel loader. On the other hand, the disadvantage is that the purchase cost of the electric wheel loader leads to greater total costs. These investments may be necessary to break the dependence on fossil fuels. When comparing the trucks, the result showed that the electric truck is a better alternative from an environmental perspective and total costs. While the diesel-powered truck saves on both time and energy. The reason why the total cost of the diesel-powered truck differs greatly from the electricpowered truck is the rental costs. If the diesel-powered truck was instead purchased, the total cost difference could be reduced. / Bygg- och anläggningssektorn står inför en verklighet där beroendet av fossila bränslen behöver brytas och ersättas med miljövänligare alternativ. Ett sådant alternativ är elektrifieringen som inte riktigt har slagit igenom för anläggningssektorn och därför behöver undersökas. I detta examensarbete undersöks två olika system av hjullastare och lastbilar. Ett system där maskinerna drivs med el och ett annat system med maskiner som drivs på diesel. Undersökningen hade målformuleringen som utgångspunkt för att besvara frågeställningarna. Maskinerna granskades för att erhålla ett resultat som visar vilket system av maskiner som är lönsammare att använda med avseende på tidsåtgång, energiförbrukning, koldioxidutsläpp samt totala kostnader. Examensarbetet har även som syfte att redogöra eventuella för-och nackdelar för respektive transportmetod. Detta för att ge ytterligare underlag till vidare forskning. För att kunna jämföra och undersöka maskinernas egenskaper applicerades dessa maskiner på ett tunneldrivningsprojekt. Projektet som erhölls var tunnelbanestationen Hagalunds industriområde. Den planerade utbyggnaden av tunnelbanan kommer att leda till en ny tunnelbanelinje mellan Arenastaden och Odenplan, där Hagalunds industriområde kommer bli en mellanliggande station. För att avgränsa arbetet och genomföra beräkningarna lades fokus på en delsträcka om 1 000 meter med avseende på huvudtunnel och arbetstunnel. Resultatet som erhölls visar att den eldrivna hjullastaren leder till mindre tidsåtgång, koldioxidutsläpp och bättre energieffektivitet än den dieseldrivna hjullastaren. Däremot är nackdelen att inköpskostnaden för den eldrivna hjullastaren leder till större totala kostnader. Dessa investeringar kan vara nödvändiga att vidta för att beroendet av fossila bränslen ska brytas. Vid jämförelse av lastbilarna visade resultatet att den eldrivna lastbilen är ett bättre alternativ ur miljöperspektiv och totala kostnader. Medan den dieseldrivna lastbilen sparar på både tid och energi. Anledningen till att totala kostnaden för dieseldrivna lastbilen skiljer sig mycket från den eldrivna lastbilen är hyreskostnaderna. Om den dieseldrivna lastbilen istället köptes in, kunde den totala kostnadsskillnaden reduceras.

This is predominantly a qualitative study on the manufacturing of micronozzles with an additive manufacturing (AM) technique, namely the laser-powered powder bed fusion (PBF-LB).  Manufacturing of micronozzles with standard microelectromechanical system technology often results in 2.5-D or close to 3-D structures and does not yield a fully rotationally symmetric nozzle. For this reason, AM can be a better solution. However, the structures obtained with PBF-LB exhibit very rough surfaces which will impair the performance of the micronozzle. To improve the surface finish electropolishing was performed on the interior walls.  Given the shape and the scale of the components, uniformity of the polishing is a challenge, calling for an inventive electrode configuration and electrolyte feed solution. The approach was to integrate an electrode on the inside of the converging part of the nozzle, to serve as a cathode for the electropolishing, already in the process, and to make the nozzle itself the vital part of the fluidic system.  With this, titanium micronozzles were manufactured with throat diameters varying between 300 and 800 μm. With the resolution of the used AM technique, it was possible to integrate the internal electrode in the micronozzles with a designed throat diameter down to 600 μm. Below this, the anode, and cathode, sometimes made contact short-circuiting the cell. Profilometry showed a decrease of the average surface roughness (𝑅𝑅𝑎𝑎) with 15-60 % for the electropolished micronozzles. The Schlieren imaging showed an exhaust that followed the throat’s axial direction and also demonstrated pressure disks and, hence, a supersonic jet exhaust. This study has shown that AM is a viable choice for manufacturing of rotationally symmetric micronozzles, and that electropolishing could be used to decrease the surface roughness on their inside uniformly with the integration of a cathode.

Walkers provided stability to the elderly but cannot assist a person from sitting to standing. The objective of this project is to present the design and analysis of a lift assist walker. This report discusses the design and analysis of a collapsible lift assist walker capable of lifting a patient up to 250 lbs. from seated to standing in under 10 seconds. The designed walker utilized a two stage scissor mechanism with a gas spring assisted embedded linear actuator.

<p> This work focuses on solving the general optimal control problems with smart-learning-enabled and theory-supported optimal control (SET-OC) approaches. The proposed SET-OC includes two main directions. Firstly, according to the basic idea of the direct method, the smart-learning-enabled iterative optimization algorithm (SEIOA) is proposed for solving discrete optimal control problems. Via discretization and reformulation, the optimal control problem is converted into a general quadratically constrained quadratic programming (QCQP) problem. Then, the SEIOA is applied to solving QCQPs. To be specific, first, a structure-exploiting decomposition scheme is introduced to reduce the complexity of the original problem. Next, an iterative search, combined with an intersection-cutting plane, is developed to achieve global convergence. Furthermore, considering the implicit relationship between the algorithmic parameters and the convergence rate of the iterative search, deep learning is applied to design the algorithmic parameters from an appropriate amount of training data to improve convergence property. To demonstrate the effectiveness and improved computational performance of the proposed SEIOA, the developed algorithms have been implemented in extensive real-world application problems, including unmanned aerial vehicle path planning problems and general QCQP problems. According to the theoretical analysis of global convergence and the simulation results, the efficiency, robustness, and improved convergence rate of the optimization framework compared to the state-of-the-art optimization methods for solving general QCQP problems are analyzed and verified. Secondly, the onboard learning-based optimal control method (L-OCM) is proposed to solve the optimal control problems. Supported by the optimal control theory, the necessary conditions of optimality for optimal control of the optimal control problem can be derived, which leads to two two-point-boundary-value-problems (TPBVPs). Then, critical parameters are identified to approximate the complete solutions of the TPBVPs. To find the implicit relationship between the initial states and these critical parameters, deep neural networks are constructed to learn the values of these critical parameters in real-time with training data obtained from the offline solutions.  To demonstrate the effectiveness and improved computational performance of the proposed L-OCM approaches, the developed algorithms have been implemented in extensive real-world application problems, including two-dimensional human-Mars entry, powered-descent, landing guidance problems, and fuel-optimal powered descent guidance (PDG) problems. In addition, considering there is no thorough analysis of the properties of the optimal control profile for PDG when considering the state constraints, a rigid theoretical analysis of the fuel-optimal PDG problem with state constraints is further provided. According to the theoretical analysis and simulation results, the optimality, robustness, and real-time performance of the proposed L-OCM are analyzed and verified, which indicates the potential for onboard implementation. </p>

The flow field of a twin jet impinging on ground plane with and without free-stream and at low jet-height-to-diameter ratios was investigated using the Particle Image Velocimetry (PIV) technique. Detailed, time-averaged flow field data are obtained via the high-resolution and the high-sampling rate instantaneous velocity field that is made available via the PIV technique. A model of twin jet issuing from 0.245m circular plate, with 0.019m jet exit diameter, and with jet span to diameter ratio of 3.0 is placed in a water tunnel with the jets in tandem arrangement with respect to the free-stream. The recently upgraded PIV system, in the ESM department fluid mechanics laboratory at VA-Tech, allowed us to capture instantaneous velocity field images of about 0.076m x 0.076m, at 512(H)x512(V) frame resolution. Sampling rates of 1000 and 1200 fps were employed. Understanding the flow field at lower heights is of crucial significance to the VSTOL aircraft application. Huge jet thrust is required to initiate the take-off operation due to the high lift loss encountered while the airframe is in proximity to the ground. Therefore, jet-height-to-diameter ratios of 2 and 4 were employed in this study. Jet-to-free-stream velocity ratios of 0.12, 0.18 and 0.22 were employed in addition to the no-free-stream case. In the current study, only time-averaged flow field properties were considered. These properties were extracted from the available instantaneous velocity field data. In order to provide some details in the time-averaged velocity field, the data were obtained along several planes of interrogation underneath the test model in the vicinity of the twin jet impinging flow. Images were captured in a single plane normal to the free-stream and five planes parallel to the free-stream. A vortex-like flow appears between the main jet and the fountain upwash. This flow is found to experience spiral motion. The direction of such flow spirals is found to be dependent on the jet exit height above the ground, and on the jet-to-free stream, velocity ratios. The flow spirals out towards the vortex flow periphery and upon increasing the free-stream it reverses its direction to be inward spiraling towards the core of the vortex. The flow reversal at certain height of the jet above the ground depends on the free-stream velocity. In our discussion, more emphasis is given to the case of jet-height-to-diameter ratio of two. We also found that the largest turbulent kinetic energy production rate is found to be at the fountain upwash formation zone. / Master of Science

Andelen av produkter med integrerad artificiell intelligens och tjänster som bygger på AI har ökat de senaste åren. Implementering och användning av tekniken är en snabbt växande marknad där tillväxten sker inom privata bolag och offentlig sektor. AI-verktyg lockar verksamheter för att kunna effektivisera processer, förbättra produkter och tjänster med hjälp av chatbotar som integreras i applikationer och webbplatser. En chatbot är en programvara som använder olika tekniker och modeller för att förstå och svara på frågor, simulera mänsklig konversation och hantera olika uppgifter. Trots alla fördelar som AI-drivna chatbotar medför, har vissa utmaningar framkommit. Användare har blivit mer tveksamma till de synliga och osynliga tillämpningarna av AI och hur de påverkar ens interaktioner och beslutsfattande. Det är viktigt för utvecklare och designers av AI-drivna chatbotar att ta hänsyn till användarnas upplevelser och reflektera över användarvänligheten under hela processen. Därför syftar denna studie till att undersöka användandet av gränssnitt i applikationer som är baserade på AI-drivna chatbotar för att identifiera faktorer som optimerar upplevelser ur ett människocentrerat perspektiv. Studiens fokus ligger på chatbotar som används i mobilapplikationer och webbplatser, och som integrerar med användare genom text i ett digitalt gränssnitt. Genom kvalitativa forskningsmetoder, intervjuer och observation, med teoretisk bakgrund från litteraturen, samlades information in om användares erfarenheter och preferenser. Undersökningen genomfördes med totalt sju deltagare, där fem slutanvändare utvärderade två gränssnitt i applikationer som bygger på AI-drivna chatbotar och två apputvecklare delade med sig av sina erfarenheter. Det resulterade i att datainsamlingen identifierade tolv kvalitativa faktorer inom fyra problemområden: kommunikation, mänsklig kontroll, transparens i systemfunktioner och visuell presentation, som har en påverkan på användarupplevelsen. Utifrån undersökningen har rekommendationer formulerats som beskriver vad som bör beaktas vid design av AI-baserade applikationer. Detta arbete bidrar till framtida arbete med utveckling av användbara applikationer baserade på artificiell intelligens. / Implementing artificial intelligence in products and services has increased significantly in recent years. AI tools, such as chatbots integrated into applications and websites, have become popular among companies to simplify work-related tasks and improve user satisfaction. “Chatbot” is software that uses different techniques and models to understand and answer users' questions, simulate human conversation and handle various tasks. However, users have become more doubtful about AI using implicit and explicit in products and services and how it affects interaction and decision-making. It is important that developers and designers of AI-powered chatbots consider user experiences and reflect on the usability and user experience of the chatbots. Therefore, this work aims to investigate the use of interfaces in applications based on AI-powered chatbots to identify factors that optimise the user experience. To reach this purpose, the researcher of this bachelor thesis collected information about users' experiences and preferences through qualitative research methods, interviews and observation. The research involved seven participants, two developers sharing their expertise, and five users evaluating two chatbots where users interacted with chatbots through text in a digital interface. As a result, the collected data identified twelve qualitative factors within four problem areas: communication, human control, transparency in system functions and visual presentation, which impact the user experience. This study suggests recommendations considering these factors that can increase user satisfaction and contribute to future work in developing applications based on artificial intelligence.

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