This research examines the impact of external shocks on Nigeria’s output performance for the period 1981 – 2015. It aims to bring to the fore the importance of considering external shocks during policy design and implementation. The multivariate VAR and VECM frameworks were used to evaluate the impact of the shock variables on Nigeria’s output performance and to achieve the stated objectives. Findings show that the external shock and domestic policy variables have short-run effects on Nigeria’s output performance. Also, all the measures of external shocks and domestic policies display some viable information in explaining the variabilities in Nigeria’s output performance over the horizon. The comparison between the results of the VECM and the unrestricted VAR shows that the unrestricted VAR model outperformed the VECM. The overall result of the study confirms the view about the vulnerability of the Nigerian economy to external shocks. These shocks explain more than half of the variance in real output performance and have varying effects on output performance in Nigeria. The dynamic response of output performance to each of the defined shock variables show that output performance responds rapidly to the shock variables, while its response to the domestic economic variables is seemingly moderate. Finally, the variance decomposition show that international crude oil price and terms of trade have the largest share in accounting for the variability in output performance, followed closely by the shares of capital inflows and monetary policy.

Lightning current with high amplitude disseminates through the body of aircraft and causes physical damages including the delamination and puncture of materials. Also , such high-amplitude and high-frequency current could interfere with electronic devices through electromagnetic coupling with the conductive interfaces of an airplane. Hence, robust protection against lighting strike is essential in the aerospace industry. Carbon Fiber Reinforced Polymer (CFRP) Matrix Composites have become significant alternatives to conventional metal-base materials. Despite the superior physical and structural properties of CFRP composites, these materials are vulnerable to lightning strikes due to the low electrical conductivity compared to the metal counterpart. Many researchers have been working on the lightning strike damage mitigation of CFRP composites by increasing the electrical conductivity of materials. Conventional methods are adding conductive layers such as metal foil and copper mesh to the composite structures. These layers are added to the composite structure during the manufacturing process and are placed at the top layer for the effective bypassing of lightning current to the ground. While adding the conductive layers reduces the lightning strike damage significantly, the industry is more interested in using conductive nanofillers to prevent the corrosion of metal layers in contact with carbon fibers and to avoid the higher weight of conductive layers than nanofillers. The lightning damage mitigation methods are studied by applying lightning strike current to the CFRP composites using an impulse current generator. Conventional lightning strike damage tolerance of CFRP composites are prone to misinterpretation. The risk of misinterpretation originates from the lack of standards clearly defining testbed design requirements including electrode size and ground electrode edge configuration. In this dissertation, the effects of testbed configuration including discharge and ground electrode on lightning strike damage evaluation studies are demonstrated. Finite element analysis is applied to perform the simulations through the COMSOL Multiphysics to validate the experimental test results. Furthermore, after improving the testbed design, carbon black was added to the CFRP composites as a cost-effective additive for lightning strike damage mitigation performance. Correlations between lightning strike damage intensity and the added carbon black fillers as well as with other additive nanofillers are reported.

No description available.

The objective of this thesis is to investigate the flow conditions that lead to coarse grain entrainment at near incipient motion conditions. Herein, a new conceptual approach is proposed, which in addition to the magnitude of hydrodynamic force or flow power, takes into account the duration of the flow event. Two criteria for inception of grain entrainment, namely the critical impulse and critical energy concepts, are proposed and compared. These frameworks adopt a force or energy perspective, considering the momentum or energy transfer from each flow event to the particle respectively, to describe the phenomenon. A series of conducted mobile particle experiments, are analyzed to examine the validity of the proposed approaches. First a set of bench-top experiments incorporates an electromagnet which applies pulses of known magnitude and duration to a steel spherical particle in a controlled fashion, so as to identify the critical level for entrainment. The utility of the above criteria is also demonstrated for the case of entrainment by the action of turbulent flow, via analysis of a series of flume experiments, where both the history of hydrodynamic forces exerted on the particle as well as its response are recorded simultaneously. Statistical modeling of the distribution of impulses, as well as conditional excess impulses, is performed using distributions from Extreme Value Theory to effectively model the episodic nature of the occurrence of these events. For the examined uniform and low mobility flow conditions, a power law relationship is proposed for describing the magnitude and frequency of occurrence of the impulse events. The Weibull and exponential distributions provide a good fit for the time between particle entrainments. In addition to these statistical tools, a number of Adaptive Neuro-Fuzzy Inference Systems employing different input representations are used to learn the nonlinear dynamics of the system and perform statistical prediction. The performance of these models is assessed in terms of their broad validity, efficiency and forecast accuracy. Even though the impulse and energy criteria are deeply interrelated, the latter is shown to be advantageous with regard to its performance, applicability and extension ability. The effect of single or multiple highly energetic events carried by certain coherent flow structures (mainly strong sweep events) with regard to the particle response is also investigated. / Ph. D.

As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group performed identical pre-intervention fall testing as the control group, and was then required to receive four 1-hour training sessions in the course of two weeks, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. Falls were induced in both forward and backward directions using a tether-release protocol. Differences between control and training groups at pre-training, and group differences in the change in dependent measures with training, were examined using Mann-Whitney U tests. The results showed that, following stage-combat fall training, the training group exhibited 32% and 35% reduction in median impact forces for forward and backward falls respectively, while the control group exhibited 5% and 2% reductions (p = 0.002 and <0.001). In addition, the training group showed shorter backward fall duration as well as longer impact time, larger impulse, and longer or larger center-of-pressure based measures for both directions of falling than the control group. However, training was not associated with reduced impact force during the naturalistic falls of the training group. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries. While these falls were induced from standing, whether these results would transfer to an unanticipated fall while walking due to a slip/trip remain to be explored. / Master of Science / As falls and fall-related injuries are a major cause of injuries, the purpose of this study was to investigate whether, and to what extent, the stage combat fall technique training could reduce the impact forces of falls from standing. Twenty-six healthy young adults (14 males and 12 females) participated in our study, and were randomly assigned to either a training group or non-training (control) group. Both groups completed a pre-intervention and a post-intervention fall testing session, separated by two weeks, in which they performed naturalistic falls. The training group was required to receive four 1-hour training sessions in the two-week intervention period, led by a certified stage combat fall technique training instructor. The training group then completed a post-intervention fall testing session where they performed naturalistic falls and also falls using the fall technique they learned. The results showed that, following stage-combat fall training, the training group exhibited nearly a 1/3rd reduction in impact forces for both forward and backward falls, while the control group only exhibited 5% and 2% reductions respectively. Our analysis also showed that the training group achieved this reduction in impact force by increasing the impact time and spreading out their bodies more, to distribute the impact over a larger area. To our knowledge, this was the first study to investigate the stage combat fall technique training and demonstrate its effectiveness as an intervention to reduce impact forces of falls, thereby exploring the potential to reduce the number of fall-related injuries.

Despite the fact ultra-wideband (UWB) technology has been around for over 30 years, there is a newfound excitement about its potential for communications. With the advantageous qualities of multipath immunity and low power spectral density, researchers are examining fundamental questions about UWB communication systems. In this work, we examine UWB communication systems paying particular attention to transmitter and receiver design. This thesis is specifically focused on a software radio transceiver design for impulse-based UWB with the ability to transmit a raw data rate of 100 Mbps yet encompasses the adaptability of a reconfigurable digital receiver. A 500 ps wide Gaussian pulse is generated at the transmitter utilizing the fast-switching characteristics of a step recovery diode. Pulse modulation is accomplished via several stages of RF switches, filters, and amplifiers on a fully designed printed circuit board specifically manufactured for this project. Critical hardware components at the receiver consist of a bank of ADCs performing parallel sampling and an FPGA employed for data processing. Using a software radio design, various modulation schemes and digital receiver topologies are accommodated along with a vast number of algorithms for acquisition, synchronization, and data demodulation methods. Verification for the design is accomplished through transmitter hardware testing and receiver design simulation. The latter includes bit error rate testing for a variety of modulation schemes and wireless channels using a pilot-based matched filter estimation technique. Ultimately, the transceiver design demonstrates the advantages and challenges of UWB technology while boasting high data rate communication capability and providing the flexibility of a research testbed. / Master of Science

Christmas is a delightful time of the year for many, evoking a range of emotions as people are influenced by various sensory experiences. In recent years, there has been a significant increase in digitalisation, leading to more online shopping. Therefore, the aim of this research is to investigate how the digitalisation of sensory Christmas marketing influences the impulse buying behaviour of Millennials. Additionally, this study aims to examine how Millennials' purchasing behaviour is impacted by these evolving aspects of sensory marketing. This research will aid companies seeking to market Christmas products online using sensory strategies. Furthermore, a qualitative method was utilised to obtain responses for the primary data collection. By employing semi-structured interviews, responses from 15 different participants from the Millennial generation, born between 1981-1996, could be gathered. These participants are also heavy social media users and have a high enthusiasm for Christmas. Once the primary data was collected, the data was analysed alongside existing literature. In conclusion, the findings of this study indicates that Christmas is difficult to experience in the same way in the online space as a physical space. The study has identified that Millennials can experience sensory cues online using their memories and their imagination, and then this might lead to a Christmas feeling. Different factors contribute to whether Millennials are impacted by digital Christmas, and whether this leads to impulse buying behaviour, such as family situation, online or physical preference, limited edition, attention, and emotional responses. The research has yielded various opportunities and challenges in this area, as well as what can be utilised for further research.

With the rapid growth of mobile commerce (m-commerce), understanding consumer behaviour in online shopping contexts has become increasingly vital for marketers and retailers. This study examines the influence of product recommendations on consumers' impulse buying behaviour and post-purchase emotions within m-commerce. Employing a quantitative survey method, the study investigates the experiences and perceptions of Swedish online shoppers.  The findings reveal significant insights into how product recommendations impact impulse buying behaviour. Specifically, product recommendations are primarily driven by hedonic motives. However, the relationship between impulse buying and post-purchase emotions is complex, with varied emotional responses observed. While some consumers experience heightened satisfaction, others grapple with feelings of dissatisfaction or regret. The interplay between hedonic and utilitarian motivations, alongside cognitive processes like cognitive dissonance, further complicates the picture. Contrary to expectations, neither hedonic nor utilitarian motives significantly correlate with post-purchase emotions, highlighting the influence of economic considerations and cognitive processes. The study underscores the multifaceted nature of consumer emotions and behaviours in online shopping contexts, emphasising the importance of considering internal and external factors. This study contributes theoretical and practical insights into consumer behaviour in online shopping while paving the way for future research endeavours in understanding the complexities of impulse buying and post-purchase emotions in m-commerce.

Floors have traditionally been designed only for strength and deflection serviceability. As technological advances have been made in medical, scientific and micro-electronics manufacturing, many types of equipment have become sensitive to vibration of the supporting floor. Thus, vibration serviceability has become a routinely evaluated limit state for floors supporting sensitive equipment. Equipment vibration tolerance limits are sometimes expressed as waveform peak acceleration, and are more often expressed as narrowband spectral acceleration, or one-third octave spectral velocity. Current floor vibration prediction methods, such as those found in the American Institute of Steel Construction Design Guide 11, Floor Vibrations Due to Human Activity, the British Steel Construction Institute P354, Design of Floors for Vibration: a New Approach and the British Concrete Centre CCIP-016 A Design Guide for Footfall Induced Vibration of Structures, have limitations. It has been observed that non-structural components such as light-weight partitions could significantly change floor dynamic properties. Current prediction methods do not provide a fundamental frequency manual prediction method nor finite element modeling guidance for floors with non-structural components. Current prediction methods only predict waveform peak acceleration and do not provide predictions for frequency domain response including narrowband spectral acceleration or one-third octave spectral velocity. Also, current methods are not calibrated to provide a specific level of conservatism. This research project provides (1) a fundamental frequency manual prediction method for floors with lightweight partitions; (2) an improved finite element modeling procedure for floors with light-weight partitions; (3) a procedure to predict the vibration response in narrow-band spectrum and one-third octave band spectrum which can be directly compared with vibration tolerance limits; and (4) a simplified experimental procedure to estimate the floor natural frequencies. An experimental program including four steel-framed building floors and a concrete was completed. Modal tests were performed on two of the steel-framed buildings and the concrete building using an electrodynamic shaker. Experimental modal analysis techniques were used to estimate the modal properties: natural frequencies, mode shapes, and damping ratios. Responses to walking excitation were measured several times in each tested bay for individuals walking at different walking speeds. During each test, the walker crossed the middle of the bay using a metronome to help maintain the intended cadence. The proposed method was used to predict the modal properties and responses to walking. The measurements are used to assess the precision of the proposed methods and to calibrate the prediction methods to provide a specific probability that the actual response will exceed the predicted response. Comparison of measurements and predictions shows the proposed methods are sufficiently accurate for design usage.

Thesis (MComm)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Lifestyles offer a comprehensive view of behaviour and the motives that underlie many of the purchases made by consumers. Impulsive buying behaviour is a complex phenomenon, and it has not yet been actively researched within a South African context. The aim of this study was to investigate the lifestyle of an impulsive student buyer, and to compile a lifestyle profile of such a buyer. A total of 499 respondents from the particular tertiary institution participated in the study. The sample population reflected young consumers in the age group 17 to 33 years. The students were mostly undergraduates studying in a full-time capacity. This study was exploratory and descriptive in nature. An electronic web-based survey was used as the method of data gathering. The survey was programmed and posted for a period of three weeks on the student portal of the tertiary institution where the survey was conducted. The validation of participation in the electronic survey was done in accordance with the requirements of the sample selection criteria. The questionnaire was tested during a pilot study. Factor analysis and Cronbach’s coefficient alpha was used to assess the validity of the questionnaire and to determine its internal consistency. Mean scores and standard deviations were computed to divide the data into three groups. To determine the current lifestyle dimensions of the students, the Activities, Interests and Opinion statements (AIOstatements) were factor analyzed. The factor matrix was rotated by means of an oblique rotation of axes, making use of the Direct Oblimin rotation technique. This resulted in a solution of five activity and interest factors, and two opinion factors. Mean scores and standard deviations were computed for all the valid life style characteristics. The frequency of impulsive shopping was measured through frequency distribution. Pearson’s product moment correlation coefficient analysis was performed between the differentiating variables, namely lifestyle and impulsive shopping behaviour to establish the relationship between these variables. Multivariate analysis of variance (MANOVA) and univariate (one way) analysis of variance (ANOVA) were used to determine differences between the groups. The five activity and interest factors that were identified, included clothes shopping/clothing specific lifestyle, social interaction, media usage, fashion oriented clothes shopping/fasion oriented clothing lifestyle, and cultural activities and interests. The two opinion factors identified, were positive vision for the future and importance of training/education. However, the opinion factors did not differ in terms of statistic significance between the groups, and was therefore not used in the consequent typology of the groups. Three groups of student consumers were identified based on the respondents’ perceptions of their activities and interests, and impulsive shopping behaviour. The students were categorized into the following three groups: Group 1: Non-impulsive shoppers – Non-impulsive Conservatives/ Traditionalists Group 2: Low impulsive shoppers – Moderates Group 3: High impulsive shoppers – Impulsive Trendsetters The three groups differed in terms of their activities and interests, and impulsive shopping behaviour. The following activities and interests characteristics were considered important: clothes shopping/clothing specific lifestyle, social interaction and media usage. The activities and interests factors that are responsible for differences between the groups could provide retailers with valuable means to identify market segments, and to satisfy their specific needs. Young South African consumers should not be considered as a homogeneous group of consumers. The South African market is a highly competitive environment providing a wide variety of shops and products to consumers which can be targeted at a specific segment to exert an impact on shopping and specifically impulsive shopping. Therefore the retailer and marketer ought not to underestimate this type of shopping behaviour. Implications for retailers and marketers are stated and recommendations for future research are suggested in order to encourage further investigation in a scientific manner in the field of impulsive shopping behaviour, and lifestyle. / AFRIKAANSE OPSOMMING: Lewenstyl bied ‘n uitgebreide en omvattende beeld van verbruikers se gedrag en die motiewe onderliggend aan die aankope van verbruikers. Impulsiewe aankoopgedrag is ‘n komplekse fenomeen en ‘n studierigting waarin beperkte navorsing in Suid- Afrika gedoen is. Hierdie studie poog om ondersoek in te stel na die lewenstyl van ‘n impulsiewe studente-aankoper en om dan gevolglik ‘n lewenstyltipering van hierdie student te doen. ‘n Totaal van 499 respondente het aan hierdie studie deelgeneem. Die steekproef is uit jong verbruikers in die ouderdomsgroep 17 tot 33 jaar geneem. Die studente was meerendeels voorgraads voltyds ingeskrewe studente. Hierdie studie was verkennend en beskrywend van aard. Data is deur middel van ‘n elektroniese webgebaseerde-opname versamel. Die vraelys is tydens ‘n loodsstudie getoets. Die vraelys is geprogrammeer en vir ‘n tydperk van drie weke op die portaal van die studente aan die betrokke tersiêre instansie geplaas. Die vraelys het uit vier afdelings bestaan. Die kontrole van die deelnemers aan die elektroniese opname is in ooreenstemming met die steekproefseleksiekriteria opgestel. Faktorontleding en Cronbach se koëffisiënt alfa is gebruik om die geldigheid en interne konsekwentheid van die vraelys te ondersoek. Deur gebruik te maak van gemiddelde tellings en standaardafwykings is die data in drie groepe verdeel. Om die bestaande lewenstyldimensies van die studente te bepaal, is die Aktiwiteite, Belangstellings en Opinie-stellings (AIO-stellings) aan faktorontleding onderwerp. Die faktormatriks is volgens die skuinsas-rotasietegniek met behulp van die Direct Oblimin-metode geroteer. Vyf aktiwiteite-en-belangstellingsfaktore en twee opiniefaktore is uit die data verkry. Gemiddelde tellings en standaardafwykings is vir al die geldige lewenstyleienskappe bereken. Die frekwensie van impulsiewe aankoopgedrag is deur middel van frekwensieverspreiding gemeet. Pearson se produk-moment korrelasiekoëffisiënt-ontleding is op die data toegepas om die korrelasies tussen die onderskeie veranderlikes, naamlik lewenstyl en impulsiewe aankoopgedrag, te bepaal. Meervoudige ontleding van variansie (MANOVA) en enkelvoudige ontleding van variansie (ANOVA) is gebruik om verskille tussen die groepe te bepaal. Die belangrikste aktiwiteite-en-belangstellingsfaktore wat geïdentifiseer is, sluit klereaankope/klere-spesifieke lewenstyl, sosiale interaksie, mediaverbruik, modieuse klereaankope/modieuse klere-lewenstyl en kuns en kulturele aktiwiteite en belangstellings in. Die belangrikste opiniefaktore sluit positiewe toekomsvisie en belangrikheid van opleiding in. Die opiniefaktore het egter nie statisties beduidend tussen die groepe onderskei nie en is gevolglik nie in die tipering van die groepe gebruik nie. Drie groepe studenteverbruikers is geïdentifiseer, gebaseer op die respondente se persepsie van hul lewenstyl en impulsiewe aankoopgedrag. Die drie groepe is soos volg gekategoriseer: Groep 1: Nie-impulsiewe kopers – Nie-impulsiewe Konserwatiewes/ Tradisioneles Groep 2: Lae impulsiewe kopers – Gematigdes Groep 3: Hoë impulsiewe kopers – Impulsiewe Tendensaanwysers Die drie groepe het volgens hul impulsiewe aankoopgedrag en aktiwiteite en belangstellings verskil. Die volgende aktiwiteite en belangstellingseienskappe is oor die algemeen die hoogste aangeslaan: klereaankope/klere-spesifieke lewenstyl, sosiale interaksie en mediaverbruik. Die aktiwiteite en belangstellings wat beduidend tussen die groepe onderskei, kan moontlik aan kleinhandelaars waardevolle inligting bied om marksegmente te identifiseer en om aan die behoeftes van die onderskeie verbruikersgroepe te voldoen. Jong Suid-Afrikaanse verbruikers behoort nie as ‘n homogene groep verbruikers beskou te word nie. Die Suid-Afrikaanse mark is hoogs kompeterend met ‘n wye reeks winkels en produkte wat op ‘n spesifieke segment gerig kan word om sodoende ‘n impak op aankope en spesifiek impulsiewe aankope uit te oefen. Die kleinhandelaar en bemarker behoort derhalwe nie hierdie tipe aankoopgedrag gering te skat nie. Implikasies vir die kleinhandelsektor en bemarker is gestel en aanbevelings vir verdere navorsing word gemaak ten einde toekomstige navorsing op ‘n wetenskaplik gefundeerde wyse op die gebied van impulsiewe aankoopgedrag en lewenstyl aan te moedig.