Response reconstruction is used to obtain accurate replication of vehicle structural responses of field recorded measurements in a laboratory environment, a crucial step in the process of Accelerated Destructive Testing (ADT). Response Reconstruction is cast as an inverse problem whereby the desired input is inferred using the measured outputs of a system. ADT typically involves large shock loadings resulting in a nonlinear response of the structure. A promising linear regression technique known as Spanning Basis Transformation Regression (SBTR) in con- junction with non-overlapping windows casts the low dimensional nonlinear problem as a high dimensional linear problem. However, it is determined that the original implementation of SBTR struggles to invert a broader class of sensor configurations. A new windowing method called AntiDiagonal Averaging (ADA) is developed to overcome the shortcomings of the SBTR im- plementation. ADA introduces overlaps within the predicted time signal windows and averages them. The newly proposed method is tested on a numerical quarter car model and is shown to successfully invert a broader range of sensor configurations as well as being capable of describing nonlinearities in the system. / Dissertation (MEng)--University of Pretoria, 2021. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

Master‘s Thesis deal with analysis given to diagnostic method plus her applicability to failure detection electrical machine plus apparatus in different phases their live. A further realization physical model with subtransient generátor PSG204A 4kV, for teach – in disorder on single – layer air coil plus stator winding induction motor inclusive evaluation results test.

This thesis deals with design of linear external excitation drive with oscillative motion. In the first part of the work is shown describe types of linear motors. Further is a part of analysis of concrete linear drives from patents database. In the next part of this work is straight design of linear external excitation drive with oscillative motion. The conception in-clude geometric model created with software Solidworks, calculation of forces with software Ansys and dynamic models of mechanical and electrical part of drive with software Mat-lab/Simulink. And is a mentions possibility of controls of this drive too.

This master’s thesis deals with design of a high speed steam turbine with detachable condensation module and integrated gearbox. As a source of energy is used heat waste, which is a result of the diesel engines function. Important options concerning conception of the turbo set are discussed in the master’s thesis. Subsequently, thermodynamic calculations for each module are done. Part of the thesis is also simplified calculation of the integral gearbox. Construction drawings of all modules and of the complete turbo set with electrical generator were created based on thermodynamic calculation.

Over the past years there has been a significant increase in the use of e-commerce and to which extent it is used. This has enabled a bigger market for consumption than ever before, and physical stores has now gained competition from the online based stores. Due to this market evolution, the consumers now have every opportunity to purchase goods at any time suitable. The concept of impulse-buying behaviour has thus become more relevant for research, as the markets are evolving, which raises questions if consumers are evolving parallelly. The commerce of groceries online is one market that has yet to be researched regarding impulse-buying behaviour, as it is a relatively new way of purchasing groceries. Members of Generation Y are the most frequent users of grocery shopping services online, which is why this is the demography of choice for this analysis. This study is inspired by previous research within the topic of impulse-buying behaviour, as well as the lack of research within this topic in regard to groceries. The research will aim to examine and identify how impulse purchases manifest themselves in an online environment when buying groceries. The study follows both classical impulse theory research as well as modern day consumer behaviour research, in order to gain a general understanding of impulse- buying behaviour of consumers. Existing research provides relevant information regarding the subject of impulse purchases; however, this study will contribute to the subject with a new perspective. Existing studies are focusing on either impulse purchase online or offline, impulse purchases or grocery shopping individually, which is why there is a research gap where these phenomena intersect. The study is expected to provide deeper understanding of how members of generation Y, or millennials, in Stockholm, act when shopping online, with emphasis on their perception of impulsive consumption behaviour. As well as examining online consumption, behaviour in physical stores will be examined and pitted against behaviour online in order to show differences and/or similarities between the two. Individual characteristics of generation Y will also be identified and compared to existing theories concerning their behavioural patterns. The study revealed that impulse purchases of groceries online is neither consistent, nor frequent, behaviour for consumers. Impulse purchases online were found to be most affected by income but also planning of the purchase made beforehand played a part. Delivery fees was an unexpected driver of impulse purchases in this research. A factor which indicated that this drives the consumer to purchase more impulsively to reach the delivery limit. Further, the study discovered that the proclivity of impulse purchases differs depending on whether shopping online or in a physical store. Individuals more prone to being affected by environmental stimuli and emotions also showed a higher probability of purchasing items on impulse in a physical store than online. Lastly, members of generation Y showed signs of materialistic, self-monitoring, risk-averse and socially aware characteristics, thus confirming many theories about the generation.

Hybrid rocket motors have become of great international interest during the last couple of years. A hybrid rocket motor is propelled by the use of a solid fuel and a liquid oxidizer. The fundamental principle of the hybrid propelled system is that the liquid oxidizer is injected into a combustion chamber to enable the combustion of the solid fuel. The exhaust gases are then accelerated through a nozzle to supersonic velocity to produce the desired level of thrust. To describe the overall performance of a propulsion system, it is common use the specifc impulse which expresses the performance as the total impulse per mass unit of propellant. However, in order to optimize a propulsion system, it is necessary to consider the entire system with the oxidizer tank, feed system, combustion chamber and nozzle. The issue with using the specifc impulse as a performance index is that it does not consider the total mass of the propulsion system. Therefore, this thesis will instead analyze the system specifc impulse, which expresses the performance as the total impulse per mass unit of propulsion system. By studying the entire hybrid propulsion system it is possible to determine the relations between the various parameters of the diferent components and should therefore be able to optimize the mass, volume and system specifc impulse of the system. This master’s thesis aims to illustrate how the hybrid propulsion system can be optimized depending on various fxed parameters. This analysis studies a generic hybrid propulsion systemwith Hydroxyl-terminated polybutadiene (HTPB) as a solid fuel with diferent combinations ofoxidizers. Each oxidizer- and fuel confguration shall have identical combustion chamber presssures and shall generate the same total impulse. Nevertheless, each combination will result indiferent specifc impulses since the optimal confguration for each combination will generate diffferent oxidizer and fuel masses. It is then desirable to analyze how the diferent components ofthe propulsion system are affected by the required oxidizer and fuel for each optimal confgurationand how it drives the design of the system and generates diferent system specifc impulses.

Over the years Instagram has grown successfully to an online platform whereindividuals and companies are constantly present. It has become a marketplace wherecompanies frequently can reach out to their customers with marketing. As a result, thishas created an impact on consumers' impulse buying behavior. Due to thesecircumstances, the purpose of this study was to examine whether the usage ofInstagram, time-limited discount codes, and the attitude toward influencers contributeto Swedish consumers’ impulse buying behavior. To examine this, three hypotheseswere developed from previous research on impulse buying, influencer marketing, pricepromotions, and the usage of Instagram. Primary data were collected through aquestionnaire with 306 respondents and further analyzed through the statisticalsoftware SPSS to be able to test the stated hypotheses.  The study questions to what extent time-limited discount codes on Instagram providedby influencers affect Swedish consumers’ impulse buying behavior. The results of thehypothesis testing confirm that there is a correlation between the factors, whichimplies that they have an affection for Swedish consumers. However, the test showedthat the usage of Instagram is the factor with the highest correlation with impulsebuying. Additionally, when analyzing the answers in the questionnaire it showed thatdue to various circumstances such as lifestyle and income the extent of affectiondiffers. The result is supposed to facilitate companies with their marketing to get anunderstanding of consumers’ impulsive buying behavior on Instagram for futureresearch.

Ultra Wide Band (UWB) is a new spectrum allocation which was recently approved by the Federal Communication Commission (FCC) and is under study in Europe and Asia. It has emerged as a solution to provide low complexity, low cost, low power consumption, and high-data-rate wireless connectivity devices entering the personal space. Any wireless system that has a fractional bandwidth greater than 20% and a total bandwidth larger than 500MHz enters in the UWB definition. At the emission level, UWB signals have a mask that limits its spectral power density to -41.3dBM/MHz between 3.1Ghz and 10.6GHz. There are two approaches that have been studied in order to use the 7.5Ghz allocated for UWB systems. First, OFDM techniques can be used to cover the entire spectrum; these techniques are called multi-band UWB. On the other hand, the second approach makes use of impulse radios which generate very-short-duration baseband pulses that occupy the whole spectrum. The objective of this thesis is to study, design, prototype, and test a UWB impulse radio using off-chip components. A Direct Sequence (DS) UWB transceiver architecture was selected. The transmitter uses first derivative Gaussian pulses that are modulated using a bi-phase modulation technique. The pulse rate of the system is 100MHz and the bit rates under investigation were 100Mbps, 50Mbps, 25Mbps, and 10Mbps. The transmitter and receiver were divided in functional blocks in order to execute system level simulations. The transmitter was implemented in both schematics and layout, and the UWB pulse generator block was constructed and tested in order to validate its functionality. On the other hand, the off-chip implementation of the receiver presented particular difficulties that made its construction not possible in this study. As a result, the blocks of the receiver were implemented in Matlab and the performance of the whole transceiver was estimated through numeric simulations. Finally, a case study for the multi-user capability of the system was presented.

Att konstruktioner som innehållande roterande element riskerar att utsättas för resonans är något en konstruktör alltid bör ha i åtanke. Alla konstruktioner har naturliga frekvenser även kallat egenfrekvenser, naturliga rörelsemönster, vars frekvens beror på dess massa och styvhet. Resonans uppstår då dessa naturliga frekvenser ligger nära angripande krafters frekvens. Resonansfenomenet amplifierar den dynamiska lasten och ofta uppstår väldigt höga påfrestningar på konstruktionen. Denna rapport redogör för en vibrationsanalys av en fläktkonstruktion, samt ett utvecklingsarbete för att optimera denna fläkt utifrån uppsatta krav från samarbetspartnern Quant Service Sweden AB. Fläktkonstruktionen finns hos kabeltillvärkaren NKT i Karlskrona. Arbetet har utförts tillsammans med Quant Service, ansvariga för underhållet på NKT. Fläktkonstruktionen har under flera tillfällen havererat genom att motorfästets skruvförband har gett vika efter allt för stora påfrestningar. Mycket tyder på att konstruktionen utsätts för stora vibrationer, där man tror att orsaken är resonans. Detta eftersom roterande delar enligt leverantör och egna tester ska vara balanserade inom givna gränsvärden. Samarbetspartnern Quant vill nu ha en redogörelse för om de höga vibrationerna orsakas av resonans eller inte, samt hur problemet kan lösas på bästa sätt. Arbetet innehåller två olika experiment, ett impulstest med impulshammare och ett test där fläktens motor startas och körs under två minuter. Konstruktionens respons har mätts med en accelerometer och den erhållna datan har använts för att beräkna en frekvensresponsfunktion, samt ett Power Spectra Density (PSD) i Matlab. Syftet med dessa experiment var att kartlägga konstruktionens egenfrekvenser och dynamiska laster för att se om dessa ligger nära varandra, och på så vis bekräfta att resonansfenomenet orsakat de kraftiga vibrationerna. Det experimentella resultatet visar på att konstruktionen har en dynamisk last på 48,3 Hz vilket motsvarar motorns varvtal på 2900 rpm. Denna dynamiska last ligger väldigt nära en utav konstruktionens egenfrekvenser, 45 Hz, vilket stärker hypotesen om resonans. De experimentella resultaten har validerats med hjälp av en modalanalys gjord i FEM-programmet Simulation Mechanical. Det experimentella impulstestet har också simulerats i programmet. Arbetet innehåller även utveckling av tre olika typer av förstärkning av fläktkonstruktionen. Syftet var att förstärka konstruktionen för att höja dess naturliga frekvenser och på så vis undvika resonansfenomenet. De tre konstruktionerna är rankade utifrån uppsatta krav med hjälp av en konceptbedömningsmatris enligt modellen concept scooring. Modalanalyser i FEM-programmet har gjorts för samtliga tre konstruktioner för att undersöka dess egenfrekvenser. Samtliga tre konstruktioner har inga egenfrekvenser under 100 Hz. Efter arbetet har Quant möjligheten att välja en utav de tre konstruktionerna för vidare implementering. / A designer must have in mind that constructions containing rotating elements risks being subjected to resonance. All constructions have got natural frequencies, also called eigenfrequencies, natural motions, where the frequency depends on its mass and stiffness. This report describes a work consisting a vibrational analysis of a fan construction. The fan construction is located at the cable manufacture NKT in Karlskrona. The work has been performed together with Quant Service, a company responsible for the maintenance at NKT. The fan construction struggle with recurrent breakdowns where the screw joints for the engine attachment were broken after large vibrations. The problem seems to occur due to the resonance phenomena, this because the rotating elements are balanced within limits according to the supplier of the fan wheels and own test performed by Quant themselves. The partner Quant service want to know if the large vibrations occurs due to resonance. The work contains two different experiments, one impulse test with an impulse hammer, and one experiment where the fan’s engine was running and driven for 2 minutes. The construction response was sampled with an accelerometer and the obtained data was used to calculate a frequency response function, and a power spectra density (PSD) in Matlab. The aim of these experiments were to obtain a survey of the constructions natural frequencies and dynamic force to analyse if they are close to each other, and by that confirm that resonance is the causing factor. The experimental result show that the construction has got a dynamic force acting with 48,3 Hz, which corresponds to the engine speed at 2900 rpm. This dynamic force is very close to one of the constructions natural frequencies at 45 Hz. This supports the hypothesis that the problems occur due to resonance. The experimental results have been validated with a modal analysis in the FEM program Simulation Mechanical. The experimental impulse test has been simulated in the program as well. The work also consists a development of three different types of strengthening of the fan construction. The aim is to increase the natural frequencies and by that avoid the resonance phenomena. The three constructions are ranked based on the requirements set by using a concept scooring matrix. Modal analysis for each of the three new constructions were created to confirmed the increased natural frequencies. The constructions all seems to have the first natural frequencies over 100 Hz. When the work was finished Quant had the possibility to pick one of the new constructions for further implementation.

The diploma thesis investigates the effect of oil price fluctuations on selected macroeconomic indicators for a set of four oil-producing countries. It provides a general overview of the development in oil prices as well as the oil production and presents a more thorough analysis of the oil production, consumption and trade in the selected countries. It utilizes the methods of Vector Autoregression, Granger causality and Impulse response via the econometric software Gretl in the analysis of the effects and compares the current literature with quantitative results.