This investigation aimed to employ novel analyses to longitudinal jump testing data gathered from competitive weightlifters to identify how certain biomechanical and performance characteristics obtained from the countermovement jump (CMJ) relate to changes in weightlifting performance over time and if they can differentiate higher and lower performers. A linear mixed-effect model was used to assess and compare the ability of countermovement jump height and net-impulse to predict Sinclair weightlifting total. CMJ force-time waveforms were compared in cross-sectional and repeated measures analyses to distinguish the force application patterns of higher-performing weightlifters and if they change over extended periods of training. It was found that both jump height and net impulse were significant predictors of Sinclair weightlifting total; however, likely due to changes in body mass within individuals over time, net impulse was a better predictor. The primary differentiator between higher and lower-performing weightlifters within the countermovement jump was the magnitude of force produced during the propulsive phase. No changes to the athlete’s force-time waveforms were observed across three testing sessions separated each by a year. Over the three testing sessions, no significant change in jump height was found; however, net impulse increased over time. The findings of this dissertation demonstrate that countermovement jump net impulse is a beneficial metric to monitor in competitive weightlifters as it demonstrated the capacity to predict changes in weightlifting performance, differentiated levels of performers, and changes over extended periods of training.

Mobile electronic devices such as smartphones are playing an increasingly pervasive role in our daily activities. A growing body of literature is beginning to investigate how mobile technology habits might relate to individual differences in cognitive traits. The present study is an investigation into how individual differences in intertemporal preference, impulse control, and reward sensitivity, are predictive of the degree to which people engage with their smartphones, in two separate experiments. Experiment 1 utilized behavioral and self-reported measures for each of the aforementioned cognitive traits to examine their relationships with Mobile Technology Engagement (MTE) as defined in Wilmer & Chein (2016). The results replicated earlier work demonstrating that mobile technology engagement is positively correlated with a tendency to discount delayed rewards. A positive relationship was also observed between MTE and reward sensitivity. In an attempt to investigate the neural origins of the relationship observed in Experiment 1, Experiment 2 examined the association between mobile technology usage and white matter connectivity from the ventral striatum (vSTR) to the ventromedial prefrontal cortex (vmPFC) and dorsolateral prefrontal cortex (dlPFC), pathways that have been previously implicated as biological markers for individual differences in intertemporal preference. Regression analyses revealed that both pathways predicted delay discounting performance, but only vSTR-vmPFC predicted mobile technology engagement. Taken together, the results of these two experiments provide important foundational evidence for both neural and cognitive factors that predict how individuals engage with mobile technology. / Psychology

No description available.

Yes / The Daubechies, coiflet and symlet wavelets, with properties of orthogonal wavelets are suitable for multicarrier transmission over band-limited channels. It has been shown that similar wavelets can be constructed by Lagrange approximation interpolation. In this work and using established wavelet design algorithms, it is shown that ideal filters can be approximated to construct new orthogonal wavelets. These new wavelets, in terms of BER behave slightly better than the wavelets mentioned above, and much better than biorthogonal wavelets, in multipath channels with additive white Gaussian noise (AWGN). It is shown that the construction, which uses a simple simultaneous solution to obtain the wavelet filters from the ideal filters based on established wavelet design algorithms, is simple and can easily be reproduced.

Ultra-wideband (UWB) communication has been the subject of extensive research in recent years due to its unique capabilities and potential applications, particularly in short-range multiple access wireless communications. However, many important aspects of UWB-based communication systems have not yet been thoroughly investigated. The propagation of UWB signals in indoor environments is the single most important issue with significant impacts on the future direction, scope, and generally the extent of the success of UWB technology. The objective of this dissertation is to obtain a more thorough and comprehensive understanding of the potentials of UWB technology by characterizing the UWB communication channels. Channel characterization refers to extracting the channel parameters from measured data. The extracted parameters are used to quantify the effect of the channel on communication UWB systems using this channel as signal transmission medium. Data are measured in different ways using a variety of time-domain and frequency-domain techniques. The experimental setups used in channel characterization effort also include pulse generators and antennas as integral parts of the channel, since the pulse shape and antenna characteristics have significant impact on channel parameters. At a fundamental level, the propagation of UWB signals, as any electromagnetic wave, is governed, among other things, by the properties of materials in the propagation medium. One of the objectives of this research is to examine propagation through walls made of typical building materials and thereby acquire ultra-wideband characterization of these materials. The loss and the dielectric constant of each material are measured over a frequency range of 1 to 15 GHz. Ten commonly used building materials are chosen for this investigation. These include, dry wall, wallboard, structure wood, glass sheet, bricks, concrete blocks, reinforced concrete (as pillar), cloth office partition, wooden door, and styrofoam slab. The work on ultra-wideband characterization of building materials resulted in an additional interesting contribution. A new formulation for evaluating the complex dielectric constant of low-loss materials, which involves solving real equations and thus requiring only one-dimensional root searching techniques, was found. The results derived from the exact complex equation and from the new formulation are in excellent agreement. Following the characterization of building materials, an indoor UWB measurement campaign is undertaken. Typical indoor scenarios, including line-of-sight (LOS), non-line-of-sight (NLOS), room-to-room, within-the-room, and hallways, are considered. Results for indoor propagation measurements are presented for local power delay profiles (local-PDP) and small-scale averaged power delay profiles (SSA-PDP). Site-specific trends and general observations are discussed. The results for pathloss exponent and time dispersion parameters are presented. The analyses results indicate the immunity of UWB signals to multipath fading. The results also clearly show that UWB signals, unlike narrowband signals, do not suffer from small scale fading, unless the receiver is too close to walls. Multipath components are further studies by employing a deconvolution technique. The application of deconvolution results in resolving multipath components with waveforms different from those of the sounding pulse. Resolving more components can improve the design of the rake receiver. The final part of this research elaborates on the nature of multiple access interference and illustrates the application of multi-user detection to improve the performance of impulse radio systems. Measured dispersion parameters and their effects on the multiple access parameters are discussed. / Ph. D.

The movement of granular material along a streambed has been a challenging subject for researchers for more than a century. Predicting the limiting case of nearly zero bedload transport, usually referred to as threshold of motion or critical condition, is even more challenging due to the highly fluctuating nature of turbulent flow. Numerous works have advocated that the peak turbulent forces, randomly occurring in time and space with magnitudes higher than the average, initiate the bed material motion. More recent findings have shown that not only the magnitude of the peak turbulent forces acting on individual grains but their duration as well have to be considered for determining the incipient conditions. Their product, or impulse, is better suited for specifying such conditions. The goal of this study was to investigate the mechanism responsible for initiation of sediment motion under turbulent flow conditions. The impulse concept was investigated by utilizing appropriate measurement methods in the laboratory for determining the condition of incipient motion. The experimental program included measurements of particle entrainment rates of a mobile grain and turbulence induced forces acting upon a fixed grain for a range of flow conditions. In addition, near bed flow velocities were measured synchronously with both the entrainment and pressure measurements at turbulent resolving frequencies. Results of this work covered the limitations and uncertainties associated with the experimental methods employed, and the description of the inadequacies of existing incipient motion models via the impulse framework. The extreme sensitivity of bed material activity to minute adjustments in flow conditions was explained by the associated change in the frequency of impulse events. The probability density function proposed for impulse was used together with the critical impulse to estimate the particle entrainment rate for a range of flow conditions. It was shown that the impulse events with potential to dislodge the grain were occurring mostly during sweep type of flow structures. The impulse events were also typically accompanied by positive lift forces. The force patterns showed that the positive peaks in the lift consistently occurred before and after the impulse events in the drag force. The magnitude of these lift forces were significantly higher in the wake of a cylinder compared to that of uniform flow conditions. The time average lift force in the wake of a cylinder was also observed to be positive with magnitudes reaching more than 30% of the submerged weight of the particle. The cylinder caused the downstream turbulence intensity to increase slightly but the particle entrainment rate to increase significantly. This finding provided a physically based explanation for the modification of turbulent force fluctuations and resulting changes in the particle movement rates by such unsteady flow conditions. / Ph. D.

The NASA Performance Adaptive Aeroelastic Wing (PAAW) project goals include significant reductions in fuel burn, emissions, and noise via efficient aeroelastic design and improvements in propulsion systems. As modern transport airplane designs become increasingly lightweight and incorporate high aspect-ratio wings, aeroservoelastic effects gain prominence in modeling and design considerations. As a result, the influence of the flight dynamics and controls on the optimal structural and aerodynamic design needs to be captured in the design process. There is an increasing interest in more integrated aircraft multidisciplinary design optimization (MDAO) processes that can bring flight control design into the early stage of an aircraft design cycle. So, in this thesis different flight dynamics modeling methodologies are presented that can be integrated within the MDAO framework. MDAO studies are conducted to maximize the controllability and observability of a UAV type aircraft using curvilinear SpaRibs and straight spars and ribs as the internal structural layout. The impulse residues and controllability Gramians are used as surrogates for the control objectives in the MDAO to maximize the controllability and observability of the aircraft. The optimal control designs are compared with those obtained using weight minimization as the design objective. It is found that using the aforementioned control objectives, the resulting aircraft design is more controllable and can be used to expand the flight envelope by up to 50% as compared to the weight minimized design. / Doctor of Philosophy / Over the last two decades, several attempts have been made towards multidisciplinary design analysis and optimization (MDAO) of flexible wings by integrating flight control laws in the wing design so that the aircraft will have sufficient control authority across different flying conditions. However, most of the studies have been restricted to the wing design only using a predefined control architecture approach, which would be very difficult to implement at the conceptual design stage. There is a need for an approach that would be faster and more practical. Including control surface and control law designs at the conceptual design stage is becoming increasingly important, due to the complexity of both the aircraft control laws and that of the actuation and sensing, and the enhanced wing flexibility of future transport aircraft. A key question that arises is, can one design an aircraft that is more controllable and observable? So, in this thesis, a more fundamental approach, in which the internal structural layout of the aircraft is optimized to design an aircraft that is more controllable, is presented and implemented. The approach uses the fundamentals of linear systems theory for maximizing the controllability and observability of the aircraft using an MDAO framework.

The potential use of the Internet for apparel retail marketing is extremely viable (Murphy, 1998); however, most of the journal papers on apparel Internet shoppers are limited to the comparison of demographic, psychographic, and behavioral characteristics between shoppers and non-shoppers (McKinney, 2004). Little empirical research has addressed the role of impulsiveness in online apparel shopping behavior. In the past, impulse buying was considered as something bad and consumers felt guilty after impulse buying (Ainslie 1975; Levy 1976). However, most researchers now no longer view impulse buying as a negative phenomenon because studies showed that impulse buying satisfies a number of hedonic desires (Piron 1991; Rook & Fisher 1995; Thompson, Locander, & Pollio 1990). Impulse buyers exhibited greater feelings of amusement, delight, enthusiasm, and joy (Weinberg & Gottwald, 1982) and often felt uplifted or energized after a shopping experience that involves impulse buying (Rook, 1987; Gardner & Rook, 1988; 1993) because impulse buying can provide the enjoyment of novelty and surprise, and the ability of mood alteration (i.e., breaking out of negative mood state) (Gardner & Rook, 1988; Rook, 1987). Recognizing the positive feelings generated from impulse buying and considering the increasing frequency of college students'' Internet shopping (Seock, 2003), one strategy to create competitive advantages in the apparel market of college students is to understand the variables related to impulse buying and based on the understanding provide a website that generates pleasurable shopping. The purpose of this study was to examine the relationships between online apparel impulse buying behavior and apparel involvement, apparel website attributes, and product category/price. The data were collected using an online survey with a structured questionnaire. To recruit participants, 37,590 e-mails were sent to six universities located in different regions of the United States. A total of 687 college students responded to the survey including 284 online apparel buyers, 194 non-online apparel buyers, and 209 non-apparel website visitors. When the impulsiveness of online apparel purchases in general was used to divide the participants into impulse buyer and non-impulse buyer groups, the Chi-square test results showed that there were significantly more female respondents in the impulse buyer group than in the non-impulse buyer group. However, when impulsiveness of last purchase was used to divide the participants into impulse purchase and non-impulse purchase groups, the results showed no significant difference between the genders. For other results, the findings were all consistent. Respondents in the impulse buyer and purchase groups than the non-impulse buyer and purchase groups had a greater amount of total monthly income and spent more money on apparel products. The impulse buyer and purchase groups visited websites that sold clothing/accessories more frequently and purchased more apparel products online over the past six months than the non-impulse buyer and purchase groups. These results suggest that impulse buyers are an important segment of the apparel online market. Four hypotheses were put forward to test the relationships among the variables. Before the proposed hypotheses could be examined, the factor analysis was first conducted to determine the constructs of apparel involvement and website attributes. The results showed that apparel involvement consisted of three factors (i.e., sign value/perceived importance, pleasure value, risk importance/probability) and website attributes consisted of four factors (i.e., website design, product presentation, promotion, product search/policy information). The results of MANOVA showed that the impulse buyer group perceived the sign value/perceived importance and the pleasure value of apparel involvement significantly higher, and perceived the risk importance/probability of apparel involvement significantly lower than the non-impulse buyer group. Based on the results, H1 was supported. Impulsive and non-impulsive online apparel buyers differed significantly in their apparel involvement. For H2, the results indicated that the impulse purchase group evaluated the website where they bought the last apparel item significantly better in website design, product presentation, promotion, and product search/policy information than the non-impulse purchase group. Based on the results, H2 was supported. The evaluations of the attributes of websites where impulse purchases and non-impulse purchases of apparel products were made were significantly different. Test of H3 showed that some product categories purchased by the respondents in the impulse purchase group were significantly different from those bought by the non-impulse purchase group. Categories such as shirt/blouse and belt were bought more frequently by the respondents in the impulse purchase group whereas shoes were bought more frequently by those in the non-impulse purchase group. The respondents in the impulse purchase group bought more items that cost less than $25 than those in the non-impulse purchase group. Based on the results H3 was supported. The product categories purchased by the impulse purchase group and non-impulse purchase group were significantly different. The multiple regression results showed that the sign value/perceived importance of apparel involvement contributed the most in explaining impulsiveness of online apparel buying behavior, followed by product price, risk importance/probability of apparel involvement, and product presentation of website attributes. Other factors, such as the pleasure value of apparel involvement and website attributes in website design, promotion, and product search/policy information, had no significant linear relationships with the impulsiveness of online apparel buying behavior. Based on the results, H4 was partially supported. From the results of the present study, it is concluded that apparel involvement, website attributes, and product price are closely related to the impulsiveness of consumers'' online apparel buying behavior. This study is beneficial to researchers and marketers by identifying possible psychological reasons for impulse buying as well as suggesting strategies to develop an apparel website that facilitate impulse buying behavior. / Ph. D.

In Impulse Radio based Ultra Wide Band (UWB) systems, where sub-nano second pulses are used, synchronization is very challenging because of their short pulse duration and very low duty cycle. Coherent detection of ultra wide-band signals requires complex channel estimation algorithms. In impulse based UWB systems, suboptimal receivers that require no channel estimation are proposed for low data rate applications using non coherent detection of energy. This approach requires integrators that collect energy and detect the incoming stream of bits for detection and synchronization. These techniques yield reasonable performance when compared to coherent detection techniques that require complex hardware and dissipate more energy. Non-coherent detection is a promising technique for low complexity, low cost and low data rate ultra-wideband communication applications like sensor area networks. In the past, several attempts have been made to characterize the performance of the energy collection receivers for synchronization using various metrics that include time of arrival and BER measurements. A comprehensive study of the synchronization problem using Probability of False Alarm is limited. The current thesis attempts to characterize the synchronization problem using Probability of False Alarm and Probability of Detection under various channel models and also discusses the importance of the length of the integration window for energy collection receivers. The current work also focuses on the performance evaluation of synchronization for Impulse based UWB systems using energy capture method and modeling them using the Probability of False Alarm and Probability of Detection under various channel models. In these systems, the integration region of a receiver integrator significantly affects the bit error rate (BER) performance. The effect of the integration window on the performance of the algorithm is also studied. This work also discusses the trade-offs between complexity and precision in using these algorithms for synchronization of Impulse based Direct Sequence Ultra Wideband Systems (DS-UWB). Signal to Noise Ratio vs. Probability of Detection, Probability of False Alarm are plotted for different channel models. / Master of Science

Digital utveckling de senaste två decennierna har påverkat samhället och lett till en växande digital livsstil som kräver aktivitet på sociala medier och uppmärksamhet på trender. Ett marknadsföringsfenomen som blivit allt mer populärt de senaste åren är influencer-marknadsföring. Genom att företag, marknadsförare och andra aktörer ingår betalda samarbeten med influencers, kan de få sin produkt eller tjänst exponerad till en bred publik av konsumenter i form av följare till influencers. Genom trovärdigheten som influencers har bland sina följare kan de påverka konsumtionsbeteendet bland följarna vilket kan leda till impulsköp. Samtidigt som konsumenters scrollningsbeteende, och hur hedoniskt det kan beskrivas som, även identifierats som en påverkande faktor till impulsköp. En enkätundersökning genomfördes som riktade sig till respondenter som följer en influencer på Instagram, som resulterade i 555 giltiga svar som senare utgjorde grund för resultatet i studien. I resultatdelen har data från den kvantitativa undersökningen presenterats i form av en deskriptiv analys och användandet av korrelations- och regressionsanalyser. Diskussionen har därefter förts där resultatet har analyserats i relation till den teoretiska referensramen. Studien bekräftar ej tidigare forskning då korrelationskoefficienterna samt förklaringsgraden (justerade R2) var låg i samtliga tester vad gäller sambandet mellan hedoniskt scrollningsbeteende, influencers upplevda trovärdighet och konsumenters impulsköpbeteende. / The digital evolution over the past two decades has profoundly impacted society, leading to an emerging digital lifestyle that demands engagement on social media platforms and attention to trends. One marketing phenomenon that has gained substantial popularity in recent years is influencer marketing. By establishing paid collaborations with influencers, companies, marketers, and other stakeholders can expose their products or services to a wide audience of consumers through the followers of these influencers. Through the credibility that influencers have among their followers, they can influence consumption behavior among their followers, which can lead to impulse purchases. At the same time, consumers' scrolling behavior, and how hedonic it can be described as, has also been identified as an influencing factor for impulse purchases. A survey was conducted targeting respondents who follow an influencer on Instagram, which resulted in 555 valid responses that later formed the basis for the results of the study. In the results section, data from the quantitative survey has been presented in the form of a descriptive analysis and the use of correlation and regression analyses. The discussion has then been conducted where the results have been analyzed in relation to the theoretical framework. The study does not confirm previous research as the correlation coefficients and the explanatory power (adjusted R-squared) were low in all tests regarding the relationship between hedonic scrolling behavior, influencers' perceived credibility and consumers' impulse buying behavior.