The Correct Response Negativity (CRN) is an event-related potential component that is affected by the act of deception. However, there have been inconsistent findings on the effect of deception on the CRN. Suchotzki, et al. (2015) suggested that the design of the paradigm used to elicit the deceptive response is what controls the size of the CRN. Specifically, motivation to deceive changes the size of deception relative to telling the truth. This study attempted to follow up on suggestions made by Suchotzki et al. (2015) to investigate if extraneous motivation to lie does indeed invert the ratio of CRN in lie compared to truth responses in a deception experiment by manipulating the motivation to lie. This study used a modification of the image-based guilty knowledge test (GKT) paradigm used in Langleben et al. (2002). The first hypothesis of this experiments was that a larger CRN during deception relative to truth-telling will be observed when participants are not motivated to lie, while a larger CRN during truth-telling relative to deception will be observed when participants are motivated to lie. The hypothesis was not supported. The second hypothesis of this experiment was that the P300 component would be larger when participants were motivated to lie, as compared to when they were instructed to lie. Results indicated that P300 was significantly higher in the lie conditions than in the truth conditions; however, there was no difference in amplitude as a function of whether they were in the informed or motivated lie condition.

<p>Thin films of metals and compounds have a very wide range of applications today. Many of the deposition methods used for the production of such films utilize plasma to support the growth the film, e.g. by the supply of energy and the enhancement of reactivity. This thesis focuses on the physical vapor deposition (PVD) of thin films by high density plasma sources based on hollow cathodes and aims to increase the understanding of the deposition process and its influence on the film properties.</p><p>Titanium nitride films reactively deposited by the low-pressure hybrid plasma (HYP LP) source exhibited excellent properties and was deposited at considerable higher rates than films deposited by conventional methods.</p><p>An original finding in this work is the influence of substrate material on the deposition process and consequently on the properties of the deposited film. In the deposition of TiN films by the HYP LP source it was found that the substrate temperature was higher for Si substrates than for steel substrates due to a more efficient absorption of microwave power in Si than in steel. Further, it was found that ferromagnetic substrates influence the film growth in magnetized plasma systems. An effect of the ferromagnetic substrates is the enhancement of ion bombardment that increases the growth temperature and affects the texture and morphology of the growing films. It was also found that a DC bias can change the TiN film properties considerably and compensate the effect of ferromagnetic substrates.</p><p>High rate depositions of chromium and chromium nitride films by the RF hollow cathode plasma jet (RHCPJ) source were studied. The performance of the reactive diffuse arc process and the CrN film properties indicates that the process can be transferred from small cylindrical cathodes to linear magnetized hollow cathodes which allow deposition on considerable larger areas and this is important for industrial applications.</p>

Thin films of metals and compounds have a very wide range of applications today. Many of the deposition methods used for the production of such films utilize plasma to support the growth the film, e.g. by the supply of energy and the enhancement of reactivity. This thesis focuses on the physical vapor deposition (PVD) of thin films by high density plasma sources based on hollow cathodes and aims to increase the understanding of the deposition process and its influence on the film properties. Titanium nitride films reactively deposited by the low-pressure hybrid plasma (HYP LP) source exhibited excellent properties and was deposited at considerable higher rates than films deposited by conventional methods. An original finding in this work is the influence of substrate material on the deposition process and consequently on the properties of the deposited film. In the deposition of TiN films by the HYP LP source it was found that the substrate temperature was higher for Si substrates than for steel substrates due to a more efficient absorption of microwave power in Si than in steel. Further, it was found that ferromagnetic substrates influence the film growth in magnetized plasma systems. An effect of the ferromagnetic substrates is the enhancement of ion bombardment that increases the growth temperature and affects the texture and morphology of the growing films. It was also found that a DC bias can change the TiN film properties considerably and compensate the effect of ferromagnetic substrates. High rate depositions of chromium and chromium nitride films by the RF hollow cathode plasma jet (RHCPJ) source were studied. The performance of the reactive diffuse arc process and the CrN film properties indicates that the process can be transferred from small cylindrical cathodes to linear magnetized hollow cathodes which allow deposition on considerable larger areas and this is important for industrial applications.

Élaborer et optimiser des nouveaux matériaux restent toujours parmi les enjeux liés à l'amélioration de la performance de la durabilité des matériaux.Le domaine des traitements de surface et plus particulièrement les nanotechnologies utilisées pour produire des revêtements en couches minces plus précisément les dépôts physiques en phase vapeur (PVD), permet de synthétiser des nouveaux matériaux qui peuvent résister dans des conditions sévères de diverses applications.L'industrie des outils de coupe et plus précisément le bois dans notre cas, nécessitent de plus en plus la synthèse des nouveaux matériaux et nanomatériaux pour améliorer la tenue en service des outils de coupe.L'objectif de ce présent travail est de développer et caractériser des revêtements dont le matériau de base est le chrome et/ou le silicium en vue de les optimiser. L'élaboration a été réalisée par différentes méthodes à savoir la pulvérisation cathodique magnétron radio fréquence ou encore en mode courant direct. En outre, la RGPP (reactive gas pulsing process) a été exploité pour la première fois dans ce travail dont le but est de surmonter les difficultés rencontrées avec la pulvérisation réactive.Les différentes caractéristiques mécaniques et tribologiques des couches ont été étudiées et corrélées avec les caractéristiques physicochimiques et microstructurales.Il s'avère que la pulvérisation cathodique en mode courant direct prouve son importance par l'obtention des couches de meilleure qualité que celles obtenues en mode radio fréquence. Pour des contenus d'azote similaires on obtient des propriétés mécaniques et tribologiques plus importantes. On note que les propriétés mécaniques réalisent un gain de 60 % par rapport à celles obtenues en mode RF. En outre l'ajustement des paramètres de la méthode RGPP (le rapport cyclique et la période des pulses) influe considérablement les caractéristiques des couches obtenues et on montre une amélioration de la performance des couches. A l'issue de l'injection pulsée du gaz réactif, on montre que l'alternance entre l'ouverture et la coupure de la vanne du gaz réactif est indispensable pour la déposition dans un milieu réactif afin d'éliminer les composés métalliques sur les cibles obtenus lors de dépôt.Enfin, l'ajout de silicium au CrN mène à obtenir des solutions solides ou une structure nanocomposite selon la teneur de silicium dans la couche ce qui implique une amélioration des caractéristiques mécaniques et par la suite celles tribologiques.L'apport de ce travail de thèse est de présenter une étude globale sur la performance des couches CrN et CrSiN en corrélant ses caractéristiques mécaniques et tribologiques avec les paramètres physiques de dépôt et en adoptant plusieurs méthodes d'élaboration.

Radiofrequency spectrum is a finite resource that consists of the frequencies in the range 3 kHz to 300 GHz. It is used for wireless communication and supports several applications and services. Whether it is at the personal, community or society level, and whether it is for applications in consumer electronics, building management, smart utility networks, intelligent driving systems, the Internet of Things, industrial automation and so on, the demand for wireless communication is increasing continuously. Together with this increase in demand, there is an increase in the quality of service requirements in terms of throughput, and the reliability and availability of wireless services. Industrial wireless sensor networks, for example, operate in environments that are usually harsh and time varying. The frequency spectrum that is utilised by industrial wireless protocols such as WirelessHART and ISA 100.11a, is also used by many other wireless technologies, and with wireless applications growing rapidly, it is possible that multiple heterogeneous wireless systems will need to operate in overlapping spatiotemporal regions in the future. Increased radiofrequency interference affects connectivity and reduces communication link quality. This affects reliability and latency negatively, both of which are core quality service requirements. Getting multiple heterogeneous radio systems to co-exist harmoniously in shared spectrum is challenging. Traditionally, this has been achieved by granting network operators exclusive rights that allow them to access parts of the spectrum assigned to them and hence the problems of co-existence and limited spectrum could be ignored. Design time multi-access techniques have also been used. At present, however, it has become necessary to use spectrum more efficiently, to facilitate the further growth of wireless communication. This can be achieved in a number of ways. Firstly, the policy that governs the regulation of radiofrequency spectrum must be updated to accommodate flexible, dynamic spectrum access. Secondly, new techniques for multiple-access and spectrum sharing should be devised. A revolutionary new communication paradigm is required, and one such paradigm has recently emerged in the form of Cognitive Radio technology. Traditional methods to sharing spectrum assume that radios in a wireless network work together in an unchanging environment. Cognitive radios, on the other hand, can sense, learn and adapt. In cognitive radio networks, the interactions between users are taken into account, in order for adjustments to be made to suit the prevailing radio environment. In this thesis, the problem of spectrum scarcity and coexistence is addressed using cognitive radio techniques, to ensure more efficient use of radio-frequency spectrum. An introduction to cognitive radio networks is given, covering cognitive radio fundamentals, spectrum sensing, dynamic spectrum management, game theoretic approaches to spectrum sharing and security in cognitive radio networks. A focus is placed on wireless industrial networks as a challenging test case for cognitive radio. A study on spectrum management policy is conducted, together with an investigation into the current state of radio-frequency spectrum utilisation, to uncover real and artificial cases of spectrum scarcity. A novel cognitive radio protocol is developed together with an open source test bed for it. Finally, a game theoretic dynamic spectrum access algorithm is developed that can provide scalable, fast convergence spectrum sharing in cognitive radio networks. This work is a humble contribution to the advancement of wireless communication. / Thesis (PhD)--University of Pretoria, 2016. / Centre for Telecommunication Engineering for the Information Society / Electrical, Electronic and Computer Engineering / PhD / Unrestricted

Cognitive radio networks (CRN) have been tipped as one of the most promising paradigms for next generation wireless communication, due primarily to its huge promise of mitigating the spectrum scarcity challenge. To help achieve this promise, CRN develop mechanisms that permit spectrum spaces to be allocated to, and used by more than one user, either simultaneously or opportunistically, under certain preconditions. However, because of various limitations associated with CRN, spectrum and other resources available for use in CRN are usually very scarce. Developing appropriate models that can efficiently utilise the scarce resources in a manner that is fair, among its numerous and diverse users, is required in order to achieve the utmost for CRN. 'Resource allocation (RA) in CRN' describes how such models can be developed and analysed. In developing appropriate RA models for CRN, factors that can limit the realisation of optimal solutions have to be identified and addressed; otherwise, the promised improvement in spectrum/resource utilisation would be seriously undermined. In this thesis, by a careful examination of relevant literature, the most critical limitations to RA optimisation in CRN are identified and studied, and appropriate solution models that address such limitations are investigated and proffered. One such problem, identified as a potential limitation to achieving optimality in its RA solutions, is the problem of heterogeneity in CRN. Although it is indeed the more realistic consideration, introducing heterogeneity into RA in CRN exacerbates the complex nature of RA problems. In the study, three broad classifications of heterogeneity, applicable to CRN, are identified; heterogeneous networks, channels and users. RA models that incorporate these heterogeneous considerations are then developed and analysed. By studying their structures, the complex RA problems are smartly reformulated as integer linear programming problems and solved using classical optimisation. This smart move makes it possible to achieve optimality in the RA solutions for heterogeneous CRN. Another serious limitation to achieving optimality in RA for CRN is the strictness in the level of permissible interference to the primary users (PUs) due to the activities of the secondary users (SUs). To mitigate this problem, the concept of cooperative diversity is investigated and employed. In the cooperative model, the SUs, by assisting each other in relaying their data, reduce their level of interference to PUs significantly, thus achieving greater results in the RA solutions. Furthermore, an iterative-based heuristic is developed that solves the RA optimisation problem timeously and efficiently, thereby minimising network complexity. Although results obtained from the heuristic are only suboptimal, the gains in terms of reduction in computations and time make the idea worthwhile, especially when considering large networks. The final problem identified and addressed is the limiting effect of long waiting time (delay) on the RA and overall productivity of CRN. To address this problem, queueing theory is investigated and employed. The queueing model developed and analysed helps to improve both the blocking probability as well as the system throughput, thus achieving significant improvement in the RA solutions for CRN. Since RA is an essential pivot on which the CRN's productivity revolves, this thesis, by providing viable solutions to the most debilitating problems in RA for CRN, stands out as an indispensable contribution to helping CRN realise its much-proclaimed promises. / Thesis (PhD)--University of Pretoria, 2017. / Electrical, Electronic and Computer Engineering / PhD / Unrestricted

No description available.

Super duplex stainless steels are applied in highly corrosive environments. To withstand such conditions, they designed with increased content of alloying elements and a duplex microstructure consisting of austenitic and ferritic phases. The result of this combination is the desired improvement in corrosion resistance, but also, the enhancement of mechanical properties. Machining super duplex stainless steels involves strain hardening of the workpiece, intense adhesive wear and elevated temperatures within the cutting zone leading to rapid tool wear and poor machined surface integrity. This research pertains to the application of commercially available PVD coatings to minimize the detrimental effects when turning super duplex stainless steel S32750. The selected coatings for this study were Alcronos (AlCrN), Alnova (AlCrN + AlCrSiN), Formera (CrN + CrAlTiN), Croma Plus (Cr + CrN + OX), Fortiphy (CrN) and Certiphy (TiAlN). The wear behavior and mechanisms in two distinct machining experiments were evaluated, and all tools failed by chipping preceded by intense adhesive wear and BUE formation. The use of AlCrN coatings improved tool life significantly. Data on the cutting force, chip formation, and workpiece surface integrity indicate less workpiece strain hardening effects, improved friction conditions at the tool/chip interface, as well as thinner chips being formed when machining with Alcronos coated carbide inserts. The micro-mechanical properties of the selected coatings were assessed and Alcronos combined high hardness and elastic modulus with a high plasticity index value that allows this coating to better manage the friction in the cutting zone and better dissipate the energy generated during cutting. / Thesis / Master of Applied Science (MASc) / Super duplex stainless steels are designed to be applied in highly corrosive environments. Like any other stainless steels, processing the super duplex grade can be challenging, especially when it comes to machining. The major causes of poor machined surface quality and rapid tool wear are high temperature, the workpiece enhanced mechanical properties, surface hardening and the tendency to stick to the cutting tool causing adhesive wear. This research explores the application of coated cutting tools to improve the machinability of the super duplex stainless steel UNS S32750. Different commercially available coatings were tested and two, Alcronos and Alnova, improved tool life significantly. These two coatings were capable of improving the friction conditions within the cutting zone which, in turn, helps with the formation of the chips and leads to a better machined surface integrity and an approximately 5 to 6 times longer tool life.

A Cognitive Radio Network (CRN) is a technology that allows unlicensed users to utilise licensed spectrum by detecting an idle band through sensing. How- ever, most research studies on CRNs have been carried out without considering the impact of sensing on the performance and security of CRNs. Sensing is essential for secondary users (SUs) to get hold of free band without interfering with the signal generated by primary users (PUs). However, excessive sensing time for the detection of free spectrum for SUs as well as extended periods of CRNs in an insecure state have adverse effects on network performance. Moreover, a CRN is very vulnerable to attacks as a result of its wireless nature and other unique characteristics such as spectrum sensing and sharing. These attacks may attempt to eavesdrop or modify the contents of packets being transmitted and they could also deny legitimate users the opportunity to use the band, leading to underutilization of the spectrum space. In this context, it is often challenging to differentiate between networks under Denial of Service (DoS) attacks from those networks experiencing congestion. This thesis employs a novel Stochastic Activity Network (SAN) model as an effective analytic tool to represent and study sensing vs performance vs security trade-offs in CRNs. Specifically, an investigation is carried out focusing on sensing vs security vs performance trade-offs, leading to the optimization of the spectrum band’s usage. Moreover, consideration is given either when a CRN experiencing congestion and or it is under attack. Consequently, the data delivery ratio (PDR) is employed to determine if the network is under DoS attack or experiencing congestion. In this context, packet loss probability, queue length and throughput of the transmitter are often used to measure the PDR with reference to interarrival times of PUs. Furthermore, this thesis takes into consideration the impact of scalability on the performance of the CRN. Due to the unpredictable nature of PUsactivities on the spectrum, it is imperative for SUs to swiftly utilize the band as soon as it becomes available. Unfortunately, the CRN models proposed in literature are static and unable to respond effectively to changes in service demands. To this end, a numerical simulation experiment is carried out to determine the impact of scalability towards the enhancement of nodal CRN sensing, security and performance. Atthe instant the band becomes idle and there are requests by SUs waiting for encryption and transmission, additional resources are dynamically released in order to largely utilize the spectrum space before the reappearance of PUs. These additional resources make the same service provision, such as encryption and intrusion detection, as the initial resources. To this end,SAN model is proposed in order to investigate the impact of scalability on the performance of CRN. Typical numerical simulation experiments are carried out, based on the application of the Mobius Petri Net Package to determine the performance of scalable CRNs (SCRNs) in comparison with unscalable CRNs (UCRNs) and associated interpretations are made.

No description available.