Herbal Extracts That Reduce Ocular Oxidative Stress May Enhance Attentive Performance in Humans

We used herbal extracts in this study to investigate the effects of blue-light-induced oxidative stress on subjects’ attentive performance, which is also associated with work performance. We employed an attention network test (ANT) to measure the subjects’ work performance indirectly and used herbal extracts to reduce ocular oxidative stress. Thirty-two subjects participated in either an experimental group (wearing glasses containing herbal extracts) or a control group (wearing glasses without herbal extracts). During the ANT experiment, we collected electroencephalography (EEG) and electrooculography (EOG) data and measured button responses. In addition, electrocardiogram (ECG) data were collected before and after the experiments. The EOG results showed that the experimental group exhibited a reduced number of eye blinks per second during the experiment and faster button responses with a smaller variation than did the control group; this group also showed relatively more sustained tension in their ECG results. In the EEG analysis, the experimental group had significantly greater cognitive processing, with larger P300 and parietal 2–6 Hz activity, an orienting effect with neural processing of frontal area, high beta activity in the occipital area, and an alpha and beta recovery process after the button response. We concluded that reducing blue-light-induced oxidative stress with herbal extracts may be associated with reducing the number of eye blinks and enhancing attentive performance

New multi-objective ranking and selection procedures for discrete stochastic simulation problems

Thesis (PhD)--Stellenbosch University, 2018.ENGLISH ABSTRACT: In stochastic simulation optimisation, several system designs are considered. These designs are ranked in order and the best is selected based on one or more performance measures. Any ranking and selection (R&S) procedure must ensure that the correct system design is chosen, and this is a challenging task in the stochastic environment. This dissertation discusses the design and development of a new multiobjective ranking and selection (MORS) procedure, called Procedure MMY, and two variants of it, called Procedures MMY1 and MMY2. Single-objective ranking and selection procedures endeavour to find the best system, i.e., the system with the minimum or maximum output, out of a limited number of feasible solutions. There are two important approaches in the single-objective R&S area: the indifference-zone (IZ) approach and the optimal computing budget allocation (OCBA) framework. While the OCBA procedure has been extended to the multi-objective domain, an MORS procedure with the IZ approach has not yet appeared in the literature. The MMY family procedures have been developed in an attempt to fill this gap, therefore they take the IZ approach. Indifference-zone procedures should guarantee that the probability of correct selection is at least a prespecified value P*, denoted by P(CS) * P*, where `correct selection' denotes the event that the system with the minimum output is selected for a single-objective minimisation problem. In the multi-objective context, Pareto optimality is employed to define `correct selection'. The concept of relaxed Pareto optimality is proposed in this research to accommodate the indifference-zone concept properly in the multi-objective domain. Thus, Procedure MMY guarantees P(CS) * P* considering the event of identifying a relaxed Pareto set as a correct selection. Procedure MMY1 tries to find the normal Pareto optimal set while Procedure MMY2 focuses on identifying Pareto optimal solutions with the IZ concept. The statistical validity of the MMY family procedures is proved through rigorous mathematical analyses in this dissertation. A Bayesian probability model was used in the P(CS) formulation in the proofs. Using a Bayesian model in the P(CS) formulation in IZ R&S procedures is a novel approach even in the single-objective context. The researcher therefore proposed a new single-objective R&S procedure, called Procedure MY, in addition to the multi-objective MMY family procedures. The MY procedure is discussed prior to the discussion of the MMY family procedures, verifying the effectiveness of the Bayesian model, thereby laying the theoretical foundation for employing it for the MMY family procedures. The performance of the proposed MMY family procedures was demonstrated using four simulation case studies. These simulation case studies provided various types of test beds to understand the behaviour of the proposed procedures. In all four cases the estimated probability of correct selection was observed to be greater than P* for all three procedures, proving the statistical validity of them empirically, too. In addition, the performance of the proposed MMY family procedures was compared to that of the MOCBA procedure, which is the only existing MORS procedure. The result showed the superiority of the MMY procedure over the MOCBA procedure in many cases.AFRIKAANSE OPSOMMING: In stogastiese simulasie-optimering word verskeie stelselontwerpe oorweeg. Hierdie ontwerpe word in rangorde rangskik en die beste gekies, gebaseer op een of meer prestasiemaatstawwe. Enige rangskik-en-kies prosedure moet verseker dat die korrekte stelselontwerp gekies word, en hierdie is 'n uitdagende taak in die stogastiese omgewing. Hierdie proefskrif bespreek die ontwerp en ontwikkeling van 'n nuwe multidoelwit rangskik-en-kies (MDRK) prosedure in stogastiese optimering. Die prosedure word MMY genoem, met twee variante genaamd MMY1 en MMY2. Enkeldoelwit rangskik-en-kies prosedures (R&K) poog om die beste stelsel, dit wil s^e, die stelsel met die minimum of maksimum afvoer, uit 'n beperkte aantal gangbare oplossings te vind. Daar is twee belangrike benaderings in die enkeldoelwit R&K area: die geen-verskilsone (GS) benadering en die optimum-rekenbegroting toedeling (ORBT) raamwerk. Hoewel die ORBT prosedure uitgebrei is na die multi-doelwitdomein, bestaan daar tans nie 'n MDRK prosedure in die GS domein nie. Die MMY familie van prosedures is geskep om hierdie gaping te vul, dus gebruik die prosedures die GS benadering tot R&K. GS prosedures behoort te waarborg dat die waarskynlikheid van korrekte keuse 'n voorafgestelde waarde P* bevredig, aangedui met P(CS) ≥ P*. Die term `korrekte keuse' dui op die gebeurtenis dat die stelsels met die minimum uitsetwaarde gekies word in 'n enkeldoelwitoptimeringprobleem, terwyl Pareto-optimaliteit in die multi-doelwitkonteks gebruik word om `korrekte keuse' te definieer. Die konsep van verslapte Pareto-optimaliteit word in hierdie navorsing voorgestel om die geen-verskilkonsep voldoende in die multidoelwitdomein te akkommodeer. Prosedure MMY waarborg P(CS) ≥ P* as 'n verslapte Pareto-versameling as korrekte keuse aanvaar word. Prosedure MMY1 poog om die streng-korrekte Paretostel te vind, terwyl Prosedure MMY2 fokus op die vind van Pareto-optimale oplossings met die GS konsep. Die statistiese geldigheid van die MMY familie van prosedures word in hierdie proefskrif bewys deur streng wiskundige analise. 'n Bayes-waarskynlikheidsmodel is gebruik in die formulering van P(CS) in die bewyse. Die gebruik van 'n Bayes-model in die formulering van P(CS) in GS R&K prosedures is uniek, selfs in die enkeldoelwit geval. Die navorser het dus 'n nuwe enkeldoelwit R&K prosedure, naamlik MY, tesame met die multidoelwit MMY familie van prosedures voorgestel. Die MY prosedure word eerste aangebied en bespreek, en daardeur word die effektiwiteit van die Bayes-model bevestig. Sodoende is die teoretiese basis vir gebruik van die Bayes-model in die MMY familie van prosedures gelê. Die prestasie van die MMY familie van prosedures word aan die hand van vier simulasiegevallestudies demonstreer. Hierdie gevallestudies verskaf verskillende tipes toetsplatforms wat bydra om die gedrag van die voorgestelde prosedures te verstaan. In al vier gevalle is die beraamde waarskynlikheid van korrekte keuse groter as P* vir al drie prosedures, wat die statistiese geldigheid daarvan empiries ondersteun. Verder is die prestasie van die voorgestelde familie van MMY prosedures met die van die ORBT prosedure vergelyk, wat die enigste multidoelwit R&K prosedure tot op hede is. Die resultate toon dat die MMY prosedures in verskeie gevalle die ORBT prosedure oorheers

Developing basic soccer skills using reinforcement learning for the RoboCup small size league

Thesis (MSc)--Stellenbosch University, 2015.ENGLISH ABSTRACT: This study has started as part of a research project at Stellenbosch University (SU) that aims at building a team of soccer-playing robots for the RoboCup Small Size League (SSL). In the RoboCup SSL the Decision- Making Module (DMM) plays an important role for it makes all decisions for the robots in the team. This research focuses on the development of some parts of the DMM for the team at SU. A literature study showed that the DMM is typically developed in a hierarchical structure where basic soccer skills form the fundamental building blocks and high-level team behaviours are implemented using these basic soccer skills. The literature study also revealed that strategies in the DMM are usually developed using a hand-coded approach in the RoboCup SSL domain, i.e., a specific and fixed strategy is coded, while in other leagues a Machine Learning (ML) approach, Reinforcement Learning (RL) in particular, is widely used. This led to the following research objective of this thesis, namely to develop basic soccer skills using RL for the RoboCup Small Size League. A second objective of this research is to develop a simulation environment to facilitate the development of the DMM. A high-level simulator was developed and validated as a result. The temporal-difference value iteration algorithm with state-value functions was used for RL, along with a Multi-Layer Perceptron (MLP) as a function approximator. Two types of important soccer skills, namely shooting skills and passing skills were developed using the RL and MLP combination. Nine experiments were conducted to develop and evaluate these skills in various playing situations. The results showed that the learning was very effective, as the learning agent executed the shooting and passing tasks satisfactorily, and further refinement is thus possible. In conclusion, RL combined with MLP was successfully applied in this research to develop two important basic soccer skills for robots in the RoboCup SSL. These form a solid foundation for the development of a complete DMM along with the simulation environment established in this research.AFRIKAANSE OPSOMMING: Hierdie studie het ontstaan as deel van 'n navorsingsprojek by Stellenbosch Universiteit wat daarop gemik was om 'n span sokkerrobotte vir die RoboCup Small Size League (SSL) te ontwikkel. Die besluitnemingsmodule (BM) speel 'n belangrike rol in die RoboCup SSL, aangesien dit besluite vir die robotte in die span maak. Hierdie navorsing fokus op ontwikkeling van enkele komponente van die BM vir die span by SU. 'n Literatuurstudie het getoon dat die BM tipies ontwikkel word volgens 'n hiërargiese struktuur waarin basiese sokkervaardighede die fundamentele boublokke vorm en hoëvlak spangedrag word dan gerealiseer deur hierdie basiese vaardighede te gebruik. Die literatuur het ook getoon dat strategieë in die BM van die RoboCup SSL domein gewoonlik ontwikkel word deur 'n hand-gekodeerde benadering, dit wil s^e, 'n baie spesifieke en vaste strategie word gekodeer, terwyl masjienleer (ML) en versterkingsleer (VL) wyd in ander ligas gebruik word. Dit het gelei tot die navorsingsdoelwit in hierdie tesis, naamlik om basiese sokkervaardighede vir robotte in die RoboCup SSL te ontwikkel. 'n Tweede doelwit was om 'n simulasie-omgewing te ontwikkel wat weer die ontwikkeling van die BM sou fasiliteer. Hierdie simulator is suksesvol ontwikkel en gevalideer. Die tydwaarde-verskil iterariewe algoritme met toestandwaarde-funksies is gebruik vir VL saam met 'n multi-laag perseptron (MLP) vir funksiebenaderings. Twee belangrike sokkervaardighede, naamlik doelskop- en aangeevaardighede is met hierdie kombinasie van VL en MLP ontwikkel. Nege eksperimente is uitgevoer om hierdie vaardighede in verskillende speelsituasies te ontwikkel en te evalueer. Volgens die resultate was die leerproses baie effektief, aangesien die leer-agent die doelskiet- en aangeetake bevredigend uitgevoer het, en verdere verfyning is dus moontlik. Die gevolgtrekking is dat VL gekombineer met MLP suksesvol toegepas is in hierdie navorsingswerk om twee belangrike, basiese sokkervaardighede vir robotte in die RoboCup SSL te ontwikkel. Dit vorm 'n sterk fondament vir die ontwikkeling van 'n volledige BM tesame met die simulasie-omgewing wat in hierdie werk daargestel is

Single- and multi-objective ranking and selection procedures in simulation : a historical review

CITATION: Yoon, M. & Bekker, J. 2017. Single- and multi-objective ranking and selection procedures in simulation : a historical review. South African Journal of Industrial Engineering, 28(2):37-45, doi:10.7166/28-2-1732.The original publication is available at http://sajie.journals.ac.zaENGLISH ABSTRACT: Ranking and selection (R&S) procedures form an important research field in computer simulation and its applications. In simulation, one usually has to select the best from a number of scenarios or alternative designs. Often, the simulated processes have a stochastic nature, which means that, to distinguish alternatives, they must exhibit significant statistical differences. R&S procedures assist the decision-maker with the selection of the best alternative with high confidence. This paper reviews past and current R&S procedures. The review traces back to the 1950s, when the first R&S procedure was proposed, and discusses the various R&S procedures proposed since then to the present day, presenting a cursory view of the research in the area. The review includes studies in both the single-objective and the multi-objective domains. It presents the research trend, discusses specific issues, and gives recommendations for future research in both domains.AFRIKAANSE OPSOMMING: Rangorde- en keuseprosedures (R&K) vorm ‘n belangrike navorsingsveld in rekenaarsimulasie en -toepassings. Simulasiestudies vereis gewoonlik dat die beste kandidaat van ‘n aantal scenarios of alternatiewe ontwerpe gekies moet word. Die gesimuleerde prosesse is gewoonlik van ‘n stogastiese aard, en hulle moet statisties-beduidend verskil ten einde onderskeid te kan tref. R&K prosedures ondersteun die besluitnemer om die beste alternatief met groot vertroue te kies. Hierdie artikel verskaf ‘n resensie van vroeë en huidige R&K prosedures. Die ondersoek strek terug tot in die 1950s toe die eerste R&K prosedures voorgestel is, en bespreek die verskeie R&K prosedures wat sedertdien ontwikkel is, terwyl ‘n oorsigtelike blik op die navorsingsveld gegee word. Die resensie sluit studies in beide enkel- en multidoelwitdomein in. Dit bespreek navorsingsneigings en spesifieke kwessies, en maak voorstelle vir verdere navorsing in beide domeins.http://sajie.journals.ac.za/pub/article/view/1732Publisher's versio

Cortical Responses and Shape Complexity of Stereoscopic Image - A Simultaneous EEG/MEG Study

Background/Aims: In exploring human factors, stereoscopic 3D images have been used to investigate the neural responses associated with excessive depth, texture complexity, and other factors. However, the cortical oscillation associated with the complexity of stereoscopic images has been studied rarely. Here, we demonstrated that the oscillatory responses to three differently shaped 3D images (circle, star, and bat) increase as the complexity of the image increases. Methods: We recorded simultaneous EEG/MEG for three different stimuli. Spatio-temporal and spatio-spectro-temporal features were investigated by non-parametric permutation test. Results: The results showed that N300 and alpha inhibition increased in the ventral area as the shape complexity of the stereoscopic image increased. Conclusion: It seems that the relative disparity in complex stereoscopic images may increase cognitive processing (N300) and cortical load (alpha inhibition) in the ventral area