Hierarchical task decompositions play an essential role in the design of complex simulation and decision systems, such as the ones that arise in video games. Game designers find it very natural to adopt a divide-and-conquer philosophy of specifying hierarchical policies, where decision modules can be constructed somewhat independently. The process of choosing the parameters of these modules manually is typically lengthy and tedious. The hierarchical reinforcement learning (HRL) field has produced elegant ways of decomposing policies and value functions using semi-Markov decision processes. However, there is still a lack of demonstrations in larger nonlinear systems with discrete and continuous variables. To narrow this gap between industrial practices and academic ideas, we address the problem of designing efficient algorithms to facilitate the deployment of HRL ideas in more realistic settings. In particular, we propose Bayesian active learning methods to learn the relevant aspects of either policies or value functions by focusing on the most relevant parts of the parameter and state spaces respectively. To demonstrate the scalability of our solution, we have applied it to The Open Racing Car Simulator (TORCS), a 3D game engine that implements complex vehicle dynamics. The environment is a large topological map roughly based on downtown Vancouver, British Columbia. Higher level abstract tasks are also learned in this process using a model-based extension of the MAXQ algorithm. Our solution demonstrates how HRL can be scaled to large applications with complex, discrete and continuous non-linear dynamics. / Science, Faculty of / Computer Science, Department of / Graduate

This thesis explains a method based on the homogenisation of zeta potential charges on carbon supports for the production of hierarchical structured zeolitic composites. The modification of carbons’ surface chemistry allowed zeolite particles to be fixed to the support by electrostatic interactions. In order to achieve this, the size reduction of zeolite particles was carried out by two different methods: a) ball milling and b) a synthetic route to produce zeolite colloidal dispersions. Also, the seeding method, based on hydrothermal growth was compared. The prepared materials in this work were designed to be used in the sorption of cations, and to allow vitrification and thereby reduce the final adsorbent volume. Results showed that a large pollutant amount can be trapped using a lower volume of material reducing costs and final waste disposal. The zeolites used in this work were selected based on their low density framework and low Si/Al ratio. Synthetic zeolites A, Y and clinoptilolite were successfully produced. Natural clinoptilolite was also utilised in this work. Also, zeolite A was produced at nanometre scale following the clear solutions method. All materials were successfully incorporated onto supports to produce multimodal porosity materials. The hierarchical modification of natural clinoptilolite, following a straightforward and nonexpensive methodology, is one the most significant contributions of this work. Carbons are used as supports due to their high surface area, they can be obtained from low-cost sources such as agroindustrial wastes and carbons allow volume reduction if materials are vitrified at high temperatures. In this work, carbons were produced from corn cob and husk, sugar cane bagasse, cherry stones, date stones and hazelnut shells. The prepared composite materials were tested in the removal of toxic ions from water solutions: cobalt, copper and caesium ions were effectively removed from aqueous media. Adsorption experiments showed that the distribution of supported zeolite particles improved their uptake efficiency and capacity. The kinetic studies revealed an enhanced rate constant for carbon-zeolites composites in comparison with pure zeolites. Diffusivity results suggested that mass transfer characteristics are modified by using hierarchical porous materials; results showed that particle size or support nature can modify diffusion resistances, reducing intraparticle diffusion and accelerating the overall kinetic processes. Adsorption equilibrium data was correlated using Langmuir and Freundlich models.

The current study evaluated the performance of traditional versus modern MDTs in the estimation of fixed-effects and variance components for data missing at the second level of an hierarchical linear model (HLM) model across 24 different study conditions. Variables manipulated in the analysis included, (a) number of Level-2 variables with missing data, (b) percentage of missing data, and (c) Level-2 sample size. Listwise deletion outperformed all other methods across all study conditions in the estimation of both fixed-effects and variance components. The model-based procedures evaluated, EM and MI, outperformed the other traditional MDTs, mean and group mean substitution, in the estimation of the variance components, outperforming mean substitution in the estimation of the fixed-effects as well. Group mean substitution performed well in the estimation of the fixed-effects, but poorly in the estimation of the variance components. Data in the current study were modeled as missing completely at random (MCAR). Further research is suggested to compare the performance of model-based versus traditional MDTs, specifically listwise deletion, when data are missing at random (MAR), a condition that is more likely to occur in practical research settings.

Introduction: Student leadership is currently a critical topic at South African universities. Leadership skills are essential to the development of humanity and universities play a vital role in the development of students to become future leaders. The development and practice of leadership at university level can benefit student development and can contribute to the good of society, which is crucial at this date and time. However, very limited research has been done on what motivates students to develop their own leadership skills. Research purpose: The objective of this study was to explore the factors that motivate students participation in leadership development at a selected South African Higher Education Institution. In essence, the study aims to explore possible factors that contribute to students participation in leadership development and to make recommendations for future leadership development initiatives at university level. Motivation for the study: As far as could be determined, this was the first study on the motivational factors that influence students interest in leadership development at university level, in particular in South Africa. This study can assist universities in exposing more students to leadership development. Essentially, it can enable universities to grow their own pipeline of leaders that can be engaged in the universities own leadership structures and will contribute to the good of society. Research methodology: An exploratory quantitative research design with supplementary qualitative questions was used. Convenience sampling was used and data were gathered from students of a selected South African Higher Education Institution (N = 78). Participants completed the Leadership Attitudes and Beliefs Scale (LABS), the Academic Motivation Scale (AMS) as well as biographical questions. Main findings: The results of the study indicated that the LABS and AMS are valid and reliable instruments for use in higher educational institutions. The results of the empirical findings of this study were unexpected. No significance in terms of hierarchical and systematic thinking was found in the descriptive statistics. A strong correlation was found between EM identified and EM external regulation. The results indicated that gender differed significantly on the subscale Intrinsic motivation toward accomplishment as well as Extrinsic motivation identified and Extrinsic motivation external regulation. The study found that previous leadership exposure might serve as motivation for students to further develop their leadership competence. Significance of the study: No similar research could be found in South Africa or in the international context. The findings of this study do not only provide valuable insights into the theory of student leadership, but also provide insight into the practical implementation of student leadership development at universities. The study creates awareness of the critical importance of investment by universities in student leadership development. Limitations and future research: This study emphasised the need for and relevance of future research on this topic. The convenience and homogeneous nature of the sample as well as the sample size complicated the effort to make definite conclusions about motivational factors. It is therefore recommended that a larger sample size be used in future research to ensure a representative distribution of a heterogeneous student population. Conclusion: The development of student leadership is a critical issue for universities and society as a whole. In light of the results of this study and the current situation that universities in South Africa are faced with in so far as student leadership is concerned, further research should be conducted into this topic. / Mini Dissertation (MCom)--University of Pretoria, 2016. / tm2016 / Human Resource Management / MCom / Unrestricted

A popular model for spatial association is the conditional autoregressive (CAR) model, and generalizations exist in the literature that utilize intrinsic CAR (ICAR) models within spatial hierarchical models. One generalization is the class of Bayesian hierarchical normal ICAR models, abbreviated HNICAR. The Bayesian HNICAR model can be used to smooth areal or lattice data, estimate the directional strength of spatio-temporal associations, and make posterior predictions at each point in space or time. Furthermore, the Bayesian HNICAR model allows for sample-based posterior inference about model parameters and predictions. R package CARrampsOcl enables fast, independent sampling-based inference for a Bayesian HNICAR model when data are complete and the spatial precision matrix is expressible as a Kronecker sum of lower order matrices. This thesis presents an independent sampling algorithm to accommodate incomplete data and arbitrary precision structures, a parallelized implementation of the algorithm that can be executed on a wide range of hardware, including NVIDIA and AMD graphical processing units (GPUs) and multicore Intel CPUs, analysis of the effects of missingness on the posterior distribution of model parameters and predictive densities, and a survey of model comparison methods for CAR models. The merits of the model and algorithm are demonstrated through both simulation and analysis of an environmental data set.

Clustering is an important analytical technique that has proven to affect human life positively through its application in cancer research, market segmentation, city planning etc. In this time of growing technological systems, mixed data has seen another face of longitudinal, directional and functional attributes which is worth paying attention to and analyzing. Previous research works on clustering relied largely on the inverse weight technique and B-spline in smoothing data and assessing the performance of various clustering algorithms. In 1971, Gower proposed a method of clustering for mixed variable types which has been extended to include functional and directional variables by Hendrickson (2014). In this study, we will do a comparative analysis of the performance of the hierarchical clustering mechanism using a simulated Functional data with mixed structure. We will adopt the Fourier basis smoothing procedure and use the Rand index (Rand 1971) and adjusted Rand index for the comparison of the various clustering algorithms.

This paper deals with IPTV (Internet Protocol Television) transmission of feedback and is showing options and ways of construction, problems and optimalization of signalization protocol. In the beginning are described IPTV and technology terms that this technology uses. Here can be found information about classical TV (Television) transmitting and comparing with IPTV technology, the advantages and disadvantaged of IPTV and answers why this solution has future. Next parts are about history of IPTV and real use over ADSL (Asymmetric Digital Subscriber Line) in present. Here are explained all the necessary units like Head-End, feedback target, root feedback target, ADSL, DSLAM (Digital Subscriber Line Access Multiplexer) and methods of data stream transmission. Also here are described the techniques of video stream compression (MPEG-2 and MPEG-4) and all options of data transmission as broadcast, unicast and multicast. Important part is about transmission speed and needs. The realization also contains applications, written in the C++ language, for transmitting and receiving packets by UDP (User Datagram Protocol) protocol. The task of these applications is to load the main server, where the measurement of packet loss and CPU (Central Processing Unit) load takes place. The result is a table of measured values for specified packet sizes and for specified time intervals between them. The meaning of this measuring is to find the maximal number of computer nodes, which the feedback target is able to proceed. Last part is about realization of 2 applications in JAVA language, which get the information about end-nodes. Both algorithms are using 2 threads to increase speed of getting the information. The client has few random generators within one thread, which will be later replaced by special algorithms for getting real values.

abstract: In order for a robot to solve complex tasks in real world, it needs to compute discrete, high-level strategies that can be translated into continuous movement trajectories. These problems become increasingly difficult with increasing numbers of objects and domain constraints, as well as with the increasing degrees of freedom of robotic manipulator arms. The first part of this thesis develops and investigates new methods for addressing these problems through hierarchical task and motion planning for manipulation with a focus on autonomous construction of free-standing structures using precision-cut planks. These planks can be arranged in various orientations to design complex structures; reliably and autonomously building such structures from scratch is computationally intractable due to the long planning horizon and the infinite branching factor of possible grasps and placements that the robot could make. An abstract representation is developed for this class of problems and show how pose generators can be used to autonomously compute feasible robot motion plans for constructing a given structure. The approach was evaluated through simulation and on a real ABB YuMi robot. Results show that hierarchical algorithms for planning can effectively overcome the computational barriers to solving such problems. The second part of this thesis proposes a deep learning-based algorithm to identify critical regions for motion planning. Further investigation is done whether these learned critical regions can be translated to learn high-level landmark actions for automated planning. / Dissertation/Thesis / Masters Thesis Computer Science 2019

abstract: Understanding intratumor heterogeneity and their driver genes is critical to designing personalized treatments and improving clinical outcomes of cancers. Such investigations require accurate delineation of the subclonal composition of a tumor, which to date can only be reliably inferred from deep-sequencing data (>300x depth). The resulting algorithm from the work presented here, incorporates an adaptive error model into statistical decomposition of mixed populations, which corrects the mean-variance dependency of sequencing data at the subclonal level and enables accurate subclonal discovery in tumors sequenced at standard depths (30-50x). Tested on extensive computer simulations and real-world data, this new method, named model-based adaptive grouping of subclones (MAGOS), consistently outperforms existing methods on minimum sequencing depth, decomposition accuracy and computation efficiency. MAGOS supports subclone analysis using single nucleotide variants and copy number variants from one or more samples of an individual tumor. GUST algorithm, on the other hand is a novel method in detecting the cancer type specific driver genes. Combination of MAGOS and GUST results can provide insights into cancer progression. Applications of MAGOS and GUST to whole-exome sequencing data of 33 different cancer types’ samples discovered a significant association between subclonal diversity and their drivers and patient overall survival. / Dissertation/Thesis / Doctoral Dissertation Biomedical Informatics 2019

This study investigates the potential benefits and challenges of using layer 3 Internet Protocol version 6 (IPv6) configuration commands. Although any other type of layers 3 devices could have been used in this study, only Cisco routers and multilayer switches are considered. The study is conducted using a simulator called Graphical Network Simulator-3 (GNS3). Even though real Cisco Internetwork Operating System (IOS) software is reliably used in this simulator, an avoidable limitation of this method involves not using this software on real routers and multilayer switches. However, it has been found that contrary to Cisco documentation, using the outgoing local interface as next hop address causes IPv6 static routing not to work; it only works when the neighbouring global unicast address is used as the next hop address. Other findings show that when static addresses are configured with Routing Information Protocol Next Generation (RIPng), Enhanced Interior Gateway Routing Protocol version 6 (EIGRPv6) or Open Shortest Path First version 3 (OSPFv3), RIPng has the best round-trip time (RTT), while OSPFv3 gives the best traceroute results. Likewise, 64-bit Extended Unique Identifier (EUI-64) addresses produce better RTT and traceroute results with RIPng than with EIGRPv6 and OSPFv3. Nonetheless, one challenge for RIPng involves failure to start the RIPng process by misconfiguring the ipv6 router rip name and ipv6 rip name enable commands. The benefit of EIGRPv6 is that its RTT is faster than that of OSPFv3 and even if the router identifiers (router-ids) are configured the same on all the routers, the EIGRPv6 process still works well. However, configuring different autonomous system numbers and failing to configure the "no shutdown" or router-id commands results in routing challenges. On the other hand, configuring the same router-id on different layer 3 devices causes OSPFv3 not to work. In spite of this challenge, when OSPFv3 is used with Hot Standby Router Protocol version 2 (HSRPv2), it generates faster RTT than EIGRPv6 and RIPng. However, the success rate of OSPFv3 for failover time of the active router to the standby router is 4% lower than EIGRPv6. In comparison to Internet Protocol version 4 (IPv4), configuring of static and EUI-64 address commands is a very challenging task, because of the hexadecimal nature of IPv6 addresses. Despite this challenge, one benefit of these commands is the ability to use slash notation such as /64 for the prefix length. When used on dual stack commands, static addresses give better native router processing performance with no encapsulation overheads. However, configuring these addresses on dual stack commands in large networks is a challenge. With regard to manual IPv6 tunnelling, configuring the tunnel interface addresses in the same network and failure to configure the tunnel mode ipv6ip command, prevents this technique from working. Although IPv6 static Network Address Translation-Protocol Translation (NAT-PT) commands are easy to configure and to troubleshoot, the NAT-PT router raises the challenge of being a single point of failure in the network. On the whole, given these benefits and challenges, implementing IPv6 in industrial networks should not be scary. The results of this study are useful guidelines on how to efficiently design and configure IPv6 networks in a smooth way. / Dissertation (MEng)--University of Pretoria, 2016. / Electrical, Electronic and Computer Engineering / MEng / Unrestricted