Robust nonparametric spectral estimation includes generating an accurate estimate of the Power Spectral Density (PSD) for a given set of data while trying to minimize the bias due to data outliers. Robust nonparametric spectral estimation is applied in the domain of electrical communications and digital signal processing when a PSD estimate of the electromagnetic spectrum is desired (often for the goal of signal detection), and when the spectrum is also contaminated by Impulsive Noise (IN). Power Line Communication (PLC) is an example of a communication environment where IN is a concern because power lines were not designed with the intent to transmit communication signals. There are many different noise models used to statistically model different types of IN, but one popular model that has been used for PLC and various other applications is called the Middleton Class A model, and this model is extensively used in this thesis. The performances of two different nonparametric spectral estimation methods are analyzed in IN: the Welch method and the multitaper method. These estimators work well under the common assumption that the receiver noise is characterized by Additive White Gaussian Noise (AWGN). However, the performance degrades for both of these estimators when they are used for signal detection in IN environments. In this thesis basic robust estimation theory is used to modify the Welch and multitaper methods in order to increase their robustness, and it is shown that the signal detection capabilities in IN is improved when using the modified robust estimators. / Master of Science / One application of blind spectral estimation is blind signal detection. Unlike a car radio, where the radio is specifically designed to receive AM and PM radio waves, sometimes it is useful for a radio to be able to detect the presence of transmitted signals whose characteristics are not known ahead of time. Cognitive radio is one application where this capability is useful. Often signal detection is inhibited by Additive White Gaussian Noise (AWGN). This is analogous to trying to hear a friend speak (signal detection) in a room full of people talking (background AWGN). However, some noise environments are more impulsive in nature. Using the previous analogy, the background noise could be loud banging caused by machinery; the noise will not be as constant as the chatter of the crowd, but it will be much louder. When power lines are used as a medium for electromagnetic communication (instead of just sending power), it is called Power Line Communication (PLC), and PLC is a good example of a system where the noise environment is impulsive. In this thesis, methods used for blind spectral estimation are modified to work reliably (or robustly) for impulsive noise environments.

This thesis examines the complex relationship between impulsive buying behavior,perceptions of brand "coolness," and their impact on Generation Z consumers. Datacollected from 11 semi-structured interviews reveals that witnessing impulsive purchasesonline can have both positive and negative effects on a brand's perceived coolness. Key factors in this dynamic include the allure of community and a desire for socialvalidation. Using the Stimulus-Organism-Response (SOR) framework, impulsivepurchase posts (User-Generated content) act as stimuli, triggering emotional responsesthat influence brand perception. Consumers are more likely to make impulsive purchasesfrom brands they consider cool as a means of aligning themselves with a desirable imageor group. However, excessive exposure to impulsive buying posts can undermine abrand's exclusivity and diminish its cool factor. The study finds that coolness is inherently subjective, with individual interviewees' valuesand experiences shaping their responses. Brands that prioritize community, authenticity,and a carefully cultivated sense of exclusivity are best positioned to navigate the complexrelationship between impulsive purchase behavior and overall brand perception.

No / Noise amplitude distribution measurements relevant to%satellite-mobile radio systems are reported. The rationale for the%measurements is outlined and the choice of measurement parameters%justified. The measurement equipment and measurement methodology are%described in detail. Results characterizing the elevation angle%distribution of impulsive noise are presented for rural, suburban and%urban environments and also for an arterial road (U.K. motorway)%carrying high density, fast moving traffic. Measurements of the levels%of impulsive noise to be expected in each environment for high- and%low-elevation satellite scenarios using appropriate antenna%configurations are also presented

A hybrid system is a dynamical system that exhibits both continuous and discrete dynamic behavior. Hybrid systems arise in a wide variety of important applications in diverse areas, ranging from biology to computer science to air traffic dynamics. The interaction of continuous- and discrete-time dynamics in a hybrid system often leads to very rich dynamical behavior and phenomena that are not encountered in purely continuous- or discrete-time systems. Investigating the dynamical behavior of hybrid systems is of great theoretical and practical importance. The objectives of this thesis are to develop the qualitative theory of nonlinear hybrid systems with impulses, time-delay, switching modes, and stochastic disturbances, to develop algorithms and perform analysis for hybrid systems with an emphasis on stability and control, and to apply the theory and methods to real-world application problems. Switched nonlinear systems are formulated as a family of nonlinear differential equations, called subsystems, together with a switching signal that selects the continuous dynamics among the subsystems. Uniform stability is studied emphasizing the situation where both stable and unstable subsystems are present. Uniformity of stability refers to both the initial time and a family of switching signals. Stabilization of nonlinear systems via state-dependent switching signal is investigated. Based on assumptions on a convex linear combination of the nonlinear vector fields, a generalized minimal rule is proposed to generate stabilizing switching signals that are well-defined and do not exhibit chattering or Zeno behavior. Impulsive switched systems are hybrid systems exhibiting both impulse and switching effects, and are mathematically formulated as a switched nonlinear system coupled with a sequence of nonlinear difference equations that act on the switched system at discrete times. Impulsive switching signals integrate both impulsive and switching laws that specify when and how impulses and switching occur. Invariance principles can be used to investigate asymptotic stability in the absence of a strict Lyapunov function. An invariance principle is established for impulsive switched systems under weak dwell-time signals. Applications of this invariance principle provide several asymptotic stability criteria. Input-to-state stability notions are formulated in terms of two different measures, which not only unify various stability notions under the stability theory in two measures, but also bridge this theory with the existent input/output theories for nonlinear systems. Input-to-state stability results are obtained for impulsive switched systems under generalized dwell-time signals. Hybrid time-delay systems are hybrid systems with dependence on the past states of the systems. Switched delay systems and impulsive switched systems are special classes of hybrid time-delay systems. Both invariance property and input-to-state stability are extended to cover hybrid time-delay systems. Stochastic hybrid systems are hybrid systems subject to random disturbances, and are formulated using stochastic differential equations. Focused on stochastic hybrid systems with time-delay, a fundamental theory regarding existence and uniqueness of solutions is established. Stabilization schemes for stochastic delay systems using state-dependent switching and stabilizing impulses are proposed, both emphasizing the situation where all the subsystems are unstable. Concerning general stochastic hybrid systems with time-delay, the Razumikhin technique and multiple Lyapunov functions are combined to obtain several Razumikhin-type theorems on both moment and almost sure stability of stochastic hybrid systems with time-delay. Consensus problems in networked multi-agent systems and global convergence of artificial neural networks are related to qualitative studies of hybrid systems in the sense that dynamic switching, impulsive effects, communication time-delays, and random disturbances are ubiquitous in networked systems. Consensus protocols are proposed for reaching consensus among networked agents despite switching network topologies, communication time-delays, and measurement noises. Focused on neural networks with discontinuous neuron activation functions and mixed time-delays, sufficient conditions for existence and uniqueness of equilibrium and global convergence and stability are derived using both linear matrix inequalities and M-matrix type conditions. Numerical examples and simulations are presented throughout this thesis to illustrate the theoretical results.

A hybrid system is a dynamical system that exhibits both continuous and discrete dynamic behavior. Hybrid systems arise in a wide variety of important applications in diverse areas, ranging from biology to computer science to air traffic dynamics. The interaction of continuous- and discrete-time dynamics in a hybrid system often leads to very rich dynamical behavior and phenomena that are not encountered in purely continuous- or discrete-time systems. Investigating the dynamical behavior of hybrid systems is of great theoretical and practical importance. The objectives of this thesis are to develop the qualitative theory of nonlinear hybrid systems with impulses, time-delay, switching modes, and stochastic disturbances, to develop algorithms and perform analysis for hybrid systems with an emphasis on stability and control, and to apply the theory and methods to real-world application problems. Switched nonlinear systems are formulated as a family of nonlinear differential equations, called subsystems, together with a switching signal that selects the continuous dynamics among the subsystems. Uniform stability is studied emphasizing the situation where both stable and unstable subsystems are present. Uniformity of stability refers to both the initial time and a family of switching signals. Stabilization of nonlinear systems via state-dependent switching signal is investigated. Based on assumptions on a convex linear combination of the nonlinear vector fields, a generalized minimal rule is proposed to generate stabilizing switching signals that are well-defined and do not exhibit chattering or Zeno behavior. Impulsive switched systems are hybrid systems exhibiting both impulse and switching effects, and are mathematically formulated as a switched nonlinear system coupled with a sequence of nonlinear difference equations that act on the switched system at discrete times. Impulsive switching signals integrate both impulsive and switching laws that specify when and how impulses and switching occur. Invariance principles can be used to investigate asymptotic stability in the absence of a strict Lyapunov function. An invariance principle is established for impulsive switched systems under weak dwell-time signals. Applications of this invariance principle provide several asymptotic stability criteria. Input-to-state stability notions are formulated in terms of two different measures, which not only unify various stability notions under the stability theory in two measures, but also bridge this theory with the existent input/output theories for nonlinear systems. Input-to-state stability results are obtained for impulsive switched systems under generalized dwell-time signals. Hybrid time-delay systems are hybrid systems with dependence on the past states of the systems. Switched delay systems and impulsive switched systems are special classes of hybrid time-delay systems. Both invariance property and input-to-state stability are extended to cover hybrid time-delay systems. Stochastic hybrid systems are hybrid systems subject to random disturbances, and are formulated using stochastic differential equations. Focused on stochastic hybrid systems with time-delay, a fundamental theory regarding existence and uniqueness of solutions is established. Stabilization schemes for stochastic delay systems using state-dependent switching and stabilizing impulses are proposed, both emphasizing the situation where all the subsystems are unstable. Concerning general stochastic hybrid systems with time-delay, the Razumikhin technique and multiple Lyapunov functions are combined to obtain several Razumikhin-type theorems on both moment and almost sure stability of stochastic hybrid systems with time-delay. Consensus problems in networked multi-agent systems and global convergence of artificial neural networks are related to qualitative studies of hybrid systems in the sense that dynamic switching, impulsive effects, communication time-delays, and random disturbances are ubiquitous in networked systems. Consensus protocols are proposed for reaching consensus among networked agents despite switching network topologies, communication time-delays, and measurement noises. Focused on neural networks with discontinuous neuron activation functions and mixed time-delays, sufficient conditions for existence and uniqueness of equilibrium and global convergence and stability are derived using both linear matrix inequalities and M-matrix type conditions. Numerical examples and simulations are presented throughout this thesis to illustrate the theoretical results.

The thesis "Purchasing tendency of consumers buying fair-trade products" examines aspects that influence consumer behaviour when buying fair-trade products. The thesis is based on a combination of two research methods - secondary data analysis and semi-structured interview. Secondary research uses data from a survey focused on the purchase, preferences and attitudes of fair-trade that was carried out by the Institute of evaluations and social analysis (INESAN). The quantitative part consist of two texts. The first part concentrates on finding aspects that can play a role in consumers' preference in purchasing fair-trade products. The second part concentrates on the purchase itself. It focuses on the extent to which consumers' purchase of fair- trade products is planned or impulsive. The qualitative part is based on quantitative analysis and focuses on established facts in detail. The thesis concludes that buying fair-trade products is influenced by social aspects, quality, price, availability and awareness of fair-trade products and the level of planning depends on the situation.

E-handeln växer i rask takt på grund av digitaliseringen och har på så sätt påverkat företagen till att vara mer online idag. Det har även gjort att den digitala sensoriska marknadsföringen behöver utvecklas för att kunna påverka konsumenters beteenden även online. Marknaden behöver anpassa sig för att kunna påverka konsumenterna till att genomföra impulsiva köp på andra sätt än vad som tidigare gjorts i fysiska butiker.  Syftet med denna studie var att undersöka hur kundernas sinnen påverkas av digital sensorisk marknadsföring, som sedan leder till ett impulsivt köp, vid onlineshopping inom mode. Med tanke på syftet men också för att kunna bidra med vidare forskning kring ämnet formulerades forskningsfrågan frågan: * Hur påverkar digital sensorisk marknadsföring konsumentens impulsiva köpbeteende inom mode online?  I denna studie valdes en kvalitativ metod med en induktiv ansats att användas. Elva respondenter intervjuades med semistrukturerade frågor. Studien valde att studera konsumenter i Sverige, där också ett urval från populationen gjordes. Det eftersom att hela populationen inte kunde undersöka, där urvalsgruppen bestod av kvinnor i åldrarna 20-35.  Genom empiri och teori blir det i denna studie tydligt att konsumenter faktiskt blir påverkade av digital sensorisk marknadsföring till att genomföra impulsiva köp. Främst framkom det att synen var den största faktorn till att konsumenter handlar mer impulsivt online. Detta genom, exempelvis, rea, struktur på hemsidan, influencers och sociala medier, etcetera. Det framgick även att många av intervjuernas deltagare inte var så insatta i ämnet om varken digital sensorisk marknadsföring eller impulsiva köp, och därmed inte var fullt medvetna kring hur de genom sinnena blir påverkade i sin konsumtion online. / E-commerce is growing rapidly due to digitalization, and this has influenced companies to be more online today. It has also necessitated the development of digital sensory marketing to influence consumer behavior online. The market needs to adapt to influence consumers to make impulsive purchases in ways different from those previously used in physical stores. The purpose of this study was to examine how customers’ senses are affected by digital sensory marketing, which then leads to impulsive purchases in online fashion shopping. Considering the purpose and to contribute to further research on the topic, the research question was formulated as follows:  *How does digital sensory marketing affect consumer’s impulsive buying behavior in online fashion? In this study a qualitative method with an inductive approach was chosen. Eleven respondents were interviewed using semi-structured questions. The study focused on consumers in Sweden, with a sample selected from the population. Since the entire population could not be studied, the sample group consisted of women aged 20-35. Through empirical data and theory, it becomes clear in this study that consumers are indeed influenced by digital sensory marketing to make impulsive purchases. It primarily emerged that vision was the most significant factor leading consumers to shop more impulsively online. This occurs through, for example, sales, website layout, influencers and social media, etcetera. It also emerged that many of the interview participants were not very knowledgeable about the topic or either digital sensory marketing or impulsive purchases, and thus were not fully aware of how their senses influence their online consumption.

Aero-engine assemblies are complex structures typically involving two or three nested rotors mounted within a flexible casing via squeeze-film damper (SFD) bearings. The deployment of SFDs into such structures is highly cost-effective but requires careful calculation since they can be highly nonlinear in their performance, particularly if they are unsupported (i.e. without a retainer spring). The direct study of whole-engine models with nonlinear bearings has been severely limited by the fact that current nonlinear computational techniques are not well-suited for complex large-order systems. The main contributions of this thesis are: • A procedure for unbalance response computation, suitable for generic whole-engine models with nonlinear bearings, which significantly extends the capability of current finite element packages. This comprises two novel nonlinear computational techniques: an implicit time domain integator referred to as the Impulsive Receptance Method (IRM) that enables rapid computation in the time domain; a whole-engine Receptance Harmonic Balance Method (RHBM) for rapid calculation of the periodic response in the frequency domain. Both methods use modal data calculated from a one-off analysis of the linear part of the engine at zero speed.• First-ever analyses on real twin-spool and three-spool engines. These studies illustrate the practical use of these solvers, provide an insight into the nonlinear dynamics of whole-engines and correlate with a limited amount of industrial experimental data. Both IRM and RHBM are directly formulated in terms of the relative response at the terminals of the nonlinear bearings. This makes them practically immune to the number of modes that need to be included, which runs into several hundreds for a typical engine. The two solvers are extensively tested on two/three-shaft engine models (with 5-6 SFDs) provided by a leading engine manufacturer using an SFD model that is used in industry. The tests show the IRM to be many times faster than an established robust conventional implicit integrator while achieving a similar level of accuracy. It is also shown to be more reliable than another popular implicit algorithm. The RHBM enables, for the first time, the frequency domain computation of the nonlinear response of whole-engine models. Its use is illustrated for both Single-Frequency Unbalance (SFU) excitation (unbalance confined to only one shaft) and Multi-Frequency Unbalance (MFU) excitation (unbalance located on two or more shafts, rotating at different speeds). Excellent correlation is demonstrated between RHBM and IRM.The parametric studies compare and contrast the frequency spectra for SFU and MFU cases. They also reveal the varying degree of lift at the unsupported SFDs. The sensitivity of the response to end-sealing and bearing housing alignment is also illustrated. It is demonstrated that the use of suitably preloaded vertically oriented “bump-springs” at the SFDs of heavy rotors produces a significant improvement in journal lift. It is also shown that the consideration of a slight amount of distributed damping in the structure significantly affects the predicted casing vibration levels, bringing them closer to measured levels, while having little effect on the SFD orbits.

Background: Internet and smartphones enable people to purchase online independent of time and place, and this have resulted in that impulsive purchases on the internet have increased. Different generations have been described to be more or less susceptible to impulse buying. Generation Y, the first generation that grew up with technology, have generally been described as impulsive, while Generation X, who were introduced to technology later in life, have been described as more rational. Further, consumers’ impulsive buying behavior has shown to be crucial and common, especially within the fashion industry. Purpose: The purpose was to investigate how Gen Y purchase apparel impulsively online compared to the older Gen X. Also, which one of them that make most apparel purchases online, and which one of them who do most web browsing of apparel. Further, the authors wanted to investigate how four different factors affect the generations’ impulsive buying behavior in the case of apparel online. These were based on an adjustment of the Revised CIFE-model. Method:  This research was conducted through a quantitative method, and seven hypotheses were formulated based on the theory. An online survey was constructed and shared through social media, and the final sample consisted of 709 respondents from both Gen X and Gen Y. These responses were analyzed through SPSS, and the hypotheses were tested by combining questions. Conclusion: The results showed that Gen Y are browsing more apparel online than Gen X, and also that they more often purchase apparel impulsively online. However, Gen X buy more apparel online in general. The findings further showed that Gen Y are more affected than Gen X by external trigger cues, normative evaluation, and internal factors when it comes to impulsive e-purchases of apparel. There was no difference between the generations’ impulse buying tendency. Findings from the open-ended questions showed that Gen X often are affected by advertising, while Gen Y are more affected by influencers. Sales and special offers influenced both generations.

O presente trabalho apresenta a teoria de sistemas dinâmicos dissipativos impulsivos. Apresentamos resultados suficientes e necessários para obtermos dissipatividade para sistemas impulsivos autônomos e não autônomos utilizando funções de Lyapunov. No que segue, desenvolvemos a teoria de estabilidade para a seção nula de um sistema dinâmico não autônomo com impulsos. Utilizando os resultados da teoria abstrata para sistemas não autônomos com impulsos, apresentamos o estudo da estabilidade de um modelo presa-predador com controle e impulsos. / The present work presents the theory of impulsive dissipative dynamical systems. We present necessary and sufficient conditions to obtain dissipativity for autonomous and non-autonomous impulsive dynamical systems via Lyapunov functions. In the sequel, we develop the theory of stability for the null section of non-autonomous dynamical systems with impulses. Using the results from the abstract theory we present the study of stability for a controlled prey-predator model under impulse conditions.