Thesis (PhD) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT:Heavy metals are persistent environmental contaminants whose sources of inputs into the environment are both natural and anthropogenic. The levels of heavy metals (cadmium, copper, nickel, lead and zinc) in the False Bay intertidal zone were measured in the water, sediments and invertebrate species between August 2000 and August 2001. The results of the water and sediment analyses revealed that most pollution was associated with the northern shore of the bay between Strand and Muizenberg, where the most populated and industrial catchments occur. Significant spatial variations occurred, indicating the presence of localised contamination, while seasonal variations may be related to changes in precipitation and runoff at different times of the year. The concentrations of cadmium, nickel and lead were occasionally higher than the levels recommended by the South African Water Quality Standards. The possible sources of pollution at the different sites are also discussed. The concentrations of the five metals in the different invertebrate species (Oxystele tigrina, 0. sinensis, Choromytilus meridionalis, Patella oculus, Patiriella exigua and Tetraclita serrata) also revealed significant seasonal and spatial variations, with both the soft tissues and shells accumulating heavy metals. The barnacle T serrata from Rooiels had the highest cadmium concentration (70.67 J.lg/g dry weight), which may be related to historic pollution inputs from the military activities which took place at a weapons testing site at this site between 1987 and 1994, although no evidence was found to confirm this. The periwinkle 0. tigrina from Strand had the highest copper concentration (70.25 J.lg/g) while the limpet P. oculus from the same site had the highest nickel concentration (35.75 J.lg/g). The shells of the mussel C. meridionalis from Muizenberg had the highest concentration of lead (25.75 J.lg/g). Since cadmium occurs as a constituent of phosphate fertilisers used widely in the False Bay catchments, the effects of cadmium exposure on the different species were investigated during 14-day laboratory exposures to 200 and 400 J.lg/LCdCh. The results revealed a general pattern of tissue metal increase in the exposed organisms, followed by slight reductions after decontamination in clean seawater. The viscera and kidneys of C. meridionalis accumulated most of the dissolved cadmium. The shells of the mussels also accumulated cadmium, indicating the possible use of shells as a detoxification matrix. / AFRIKAANSE OPSOMMING:Swaarmetale is persisterende omgewingskontaminante waarvan die insetbronne beide natuurlik of van menslike oorsprong kan wees. Die kontaminasievlakke van swaarmetale (kadmium, koper, nikkel, lood en sink) in die Valsbaai tussengetysone is in die water, sedimente en invertebraatspesies bepaal vanaf Augustus 2000 tot Augustus 2001. Voorlopige resultate van die water- en sedimentontledings het getoon dat die meeste besoedeling by die noordelikke oewer van die baai voorgekom het tussen Strand and Muizenberg, waar die mees digbewoonde en ge-industrialiseerde opvangsgebiede is. Betekenisvolle ruimtelike en seisoenale variasie het in die konsentrasies van swaarmetale voorgekom, met die ruimtelike variasie wat moontlik gelokaliseerde kontaminasie aandui terwyl die seisoenale variasies weer verband mag hou met veranderings in die neerslag en afloop gedurende verskillende tye van die jaar. Die konsentrasie van kadmium, nikkel en lood was somtyds hoer as die vlakke wat deur die Suid-Afrikaanse Waterkwaliteitsstandaarde voorgestel word. Die moontlike bronne van besoedeling in die verskillende areas is ook in bespreking genoem. Die konsentrasies van die vyf swaametale in die verskillende invertebraatspesies (Oxystele tigrina, 0. sinensis, Choromytilus meridionalis, Patella oculus, Patiriella exigua and Tetraclita serrata) het ook seisoenale en ruimtelike variasies vertoon, die swaarmetale het in die sagte weefsel en skulpe van die invertebrate geakkumuleer. Die hoogste gemiddelde konsentrasie van kadmium (70.67 ).lg/g droe massa) is in die heel-liggaam monsters van die eendemossel T serrata gemeet wat by Rooiels versamel is. Die vlakke mag verband hou met die oprigting en aktiwiteite van die wapentoetsingsaanleg in die opvanggebied van die Rooiels lokaliteit tussen 1987 en 1994, maar geen bewyse daarvan is gevind nie. Die tolletjie, 0. tigrina wat in die 10kaliteit by Strand versamel is het die hoogste gemiddelde konsentrasie koper gehad 70.25 pig droe massa), terwyl die klipmossel P. oculus by dieselfde versamelpunt die hoogste konsentrasie nikkel (35.75 ).lg/gdroe massa) gehad het. Eksperimentele studies is ook uitgevoer op vier invertebraat spesies wat vir 14 dae in akwaria blootgestel is aan see-water met 200 en 400 p,g/L CdCh, en daama gedekontamineer is in skoon seewater. / The NRF and the University of Stellenbosch, for funding this study.

The construction of state highway projects is bid out each year at approximately three billion dollars. Claims from contractors for additional compensation are common. This paper investigates the policies and procedures for handling claims and explores the False Claims Act case law and its implications for the Department of Transportation's contract administration.

abstract: The flexibility in power system networks is not fully modeled in existing real-time contingency analysis (RTCA) and real-time security-constrained economic dispatch (RT SCED) applications. Thus, corrective transmission switching (CTS) is proposed in this dissertation to enable RTCA and RT SCED to take advantage of the flexibility in the transmission system in a practical way. RTCA is first conducted to identify critical contingencies that may cause violations. Then, for each critical contingency, CTS is performed to determine the beneficial switching actions that can reduce post-contingency violations. To reduce computational burden, fast heuristic algorithms are proposed to generate candidate switching lists. Numerical simulations performed on three large-scale realistic power systems (TVA, ERCOT, and PJM) demonstrate that CTS can significantly reduce post-contingency violations. Parallel computing can further reduce the solution time. RT SCED is to eliminate the actual overloads and potential post-contingency overloads identified by RTCA. Procedure-A, which is consistent with existing industry practices, is proposed to connect RTCA and RT SCED. As CTS can reduce post-contingency violations, higher branch limits, referred to as pseudo limits, may be available for some contingency-case network constraints. Thus, Procedure-B is proposed to take advantage of the reliability benefits provided by CTS. With the proposed Procedure-B, CTS can be modeled in RT SCED implicitly through the proposed pseudo limits for contingency-case network constraints, which requires no change to existing RT SCED tools. Numerical simulations demonstrate that the proposed Procedure-A can effectively eliminate the flow violations reported by RTCA and that the proposed Procedure-B can reduce most of the congestion cost with consideration of CTS. The system status may be inaccurately estimated due to false data injection (FDI) cyber-attacks, which may mislead operators to adjust the system improperly and cause network violations. Thus, a two-stage FDI detection (FDID) approach, along with several metrics and an alert system, is proposed in this dissertation to detect FDI attacks. The first stage is to determine whether the system is under attack and the second stage would identify the target branch. Numerical simulations demonstrate the effectiveness of the proposed two-stage FDID approach. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Made available in DSpace on 2016-03-15T19:30:42Z (GMT). No. of bitstreams: 1 Marcelo de Jesus.pdf: 753815 bytes, checksum: 4b3631ad6c0a3a4e6928e2b70685850d (MD5) Previous issue date: 2011-02-01 / This study investigates, for the period between 2002 and 2009, what is the impact of luck on the performance of stocks mutual funds managers with active management in Brazil to surpass its benchmark. To that purpose, we used a new method, the False Discovery Rate approach - FDR to empirically test those impact. To measure precisely luck and unluck, ig, the frequency of false positives (Type I errors) in the tails of the cross-section of the tdistribution associated with the alphas of funds in the sample, this new approach was applied to measure the skills of grouped shape managers of stock funds with active management in Brazil. The FDR approach offers a simple and objective method to estimate the proportion of skilled funds (with a positive alpha), alpha-zero funds, and unskilled funds (with a negative alpha) across the population. Applying the FDR technique, it was found as a result of research that the majority of funds were alpha-zero, then no truly skilled funds, and only a small proportion of truly skilled funds. / Esta pesquisa investiga, para o período entre 2002 e 2009, qual o impacto da sorte na performance dos gestores de fundos de investimentos em ações com gestão ativa no Brasil que superam o seu benchmark. Para tanto, foi usado um novo método, a abordagem False Discovery Rate - FDR para testar empiricamente esse impacto. Para mensurar precisamente sorte e azar, ou seja, a freqüência de falsos positivos (erros do tipo I) nas caudas do crosssection da distribuição t associadas aos alfas dos fundos da amostra, foi aplicada essa nova abordagem para mensurar de forma agrupada a habilidade dos gestores de fundos de ações com gestão ativa no Brasil. A abordagem FDR oferece um método simples e objetivo para estimar a proporção de fundos habilidosos (com um alfa positivo), fundos de alfa-zero, e fundos não habilidosos (com um alfa negativo) em toda a população. Aplicando-se a técnica FDR, encontrou-se como resultado da pesquisa que a maioria dos fundos foram alfa-zero, seguida pelos fundos verdadeiramente não habilidosos, e apenas uma pequena proporção de fundos verdadeiramente habilidosos.

Cette thèse est composée de deux parties: une première partie traite le problème de changement de régime et une deuxième partie concerne le processusautorégressif à seuil dont les innovations ne sont pas indépendantes. Toutefois, ces deux domaines de la statistique et des probabilités se rejoignent dans la littérature et donc dans mon projet de recherche. Dans la première partie, nous étudions le problème de changements derégime. Il existe plusieurs méthodes pour la détection de ruptures mais les principales méthodes sont : la méthode de moindres carrés pénalisés (PLS)et la méthode de derivée filtrée (FD) introduit par Basseville et Nikirov. D’autres méthodes existent telles que la méthode Bayésienne de changementde points. Nous avons validé la nouvelle méthode de dérivée filtrée et taux de fausses découvertes (FDqV) sur des données réelles (des données du vent sur des éoliennes et des données du battement du coeur). Bien naturellement, nous avons donné une extension de la méthode FDqV sur le cas des variables aléatoires faiblement dépendantes.Dans la deuxième partie, nous étudions le modèle autorégressif à seuil (en anglais Threshold Autoregessive Model (TAR)). Le TAR est étudié dans la littérature par plusieurs auteurs tels que Tong(1983), Petrucelli(1984, 1986), Chan(1993). Les applications du modèle TAR sont nombreuses par exemple en économie, en biologie, l'environnement, etc. Jusqu'à présent, le modèle TAR étudié concerne le cas où les innovations sont indépendantes. Dans ce projet, nous avons étudié le cas où les innovations sont non corrélées. Nous avons établi les comportements asymptotiques des estimateurs du modèle. Ces résultats concernent la convergence presque sûre, la convergence en loi et la convergence uniforme des paramètres. / This thesis has two parts: the first part deals the change points problem and the second concerns the weak threshold autoregressive model (TAR); the errors are not correlated.In the first part, we treat the change point analysis. In the litterature, it exists two popular methods: The Penalized Least Square (PLS) and the Filtered Derivative introduced by Basseville end Nikirov.We give a new method of filtered derivative and false discovery rate (FDqV) on real data (the wind turbines and heartbeats series). Also, we studied an extension of FDqV method on weakly dependent random variables.In the second part, we spotlight the weak threshold autoregressive (TAR) model. The TAR model is studied by many authors such that Tong(1983), Petrucelli(1984, 1986). there exist many applications, for example in economics, biological and many others. The weak TAR model treated is the case where the innovations are not correlated.

Security deficiencies that occur in web applications can have major consequences. PHP is a language that is often used for web applications and it places high demands on how the language is used to ensure it is safe. There are several features in PHP that should be handled with care to avoid security flaws. Static code analysis can help find vulnerabilities in code, but there are some drawbacks that can occur with static code analysis tools. One disadvantage is false positives which means that the tool reports vulnerabilities that do not exist. There are also false negatives which means the tool cannot find the vulnerability at all which can lead to a false sense of security for the user of the tool. With the help of completed test cases, three tools have been investigated in a case study to find out if the tools differ in their ability to avoid false positives and false negatives. The study also examines whether the tools' rules consider the PHP language's vulnerable functions. To answer the research question, a document collection was conducted to obtain information about the tools and various vulnerabilities. The purpose of this study is to compare the ability of static code analysis tools to find PHP code vulnerabilities. The tools that were investigated were SonarQube, Visual Code Grepper (VCG) and Exakat. The study's analysis shows that VCG found the most vulnerabilities but failed to avoid false positive vulnerabilities. Exakat had zero false positives but could not avoid false negatives to the same extent as VCG. SonarQube avoided all false positives but did not find any of the vulnerabilities tested in the test cases. According to the rules of the tools, VCG had more consideration for the risky functions found in PHP. The study's results show that the tools' ability to avoid false positives and false negatives differed and their adaptation to the PHP language's vulnerable functions. / Säkerhetsbrister som förekommer i webbapplikationer kan leda till stora konsekvenser. PHP är ett språk som ofta används för webbapplikationer och det ställer höga krav på hur språket används för att det ska vara säkert. Det finns flera funktioner i PHP som bör hanteras varsamt för att inte säkerhetsbrister ska uppstå. Statisk kodanalys kan hjälpa till med att hitta sårbarheter i kod men det finns vissa nackdelar som kan uppkomma med statiska kodanalysverktyg. En nackdel är falska positiva vilket betyder att verktyget rapporterar in sårbarheter som inte finns. Det finns också falska negativa som betyder att verktyget inte hittar sårbarheten alls vilket kan leda till en falsk trygghetskänsla för användaren av verktyget. Med hjälp av färdiga testfall så har tre verktyg utretts i en fallstudie för att ta reda på om verktygen skiljer sig i sin förmåga till att undvika falska positiva och falska negativa. Studien undersöker också om verktygens regler tar PHP-språkets sårbara funktioner i beaktning. För att kunna besvara forskningsfrågan har en dokumentsinsamling genomförts för att få information om verktygen och olika sårbarheter. Studiens syfte är att jämföra statiska kodanalysverktygs förmåga att hitta sårbarheter i PHP-kod. De verktyg som utreddes var SonarQube, Visual Code Grepper (VCG) och Exakat. Studiens analys visar att VCG hittade mest sårbarheter men lyckades inte undvika falska positiva sårbarheter. Exakat hade noll falska positiva men kunde inte undvika falska negativa i lika stor utsträckning som VCG. SonarQube undvek alla falska positiva men hittade inte någon av de sårbarheter som testades i testfallen. Enligt verktygens regler visade sig VCG ta mest hänsyn till de riskfyllda funktioner som finns i PHP. Studiens resultat visar att verktygens förmåga att undvika falska positiva och falska negativa och deras anpassning för PHP språkets sårbara funktioner skiljde sig åt.

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International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / An Improved AMI (Alternate Mark Inverse) Code used in telemetry system is proposed, its implementation and properties analysis are reported, including error performance analysis, power spectrum analysis, the relationship between acqusition probability of the first frame marker and error threshold and length of frame marker, etc. This type of code has the approximately identical power spectrum performance as the AMI Code. In addition, there have no long continuous zeroes in the data stream, which will cause phase-locked loop to fail. Using the Improved AMI Code, the equal probability of 0 and 1 is changed, which will increase acqusition probability of the first frame marker. Detailed description about how to create the Improved AMI Code is also discussed in this paper.

This study analyzes and maps barriers preventing Sri Lankan female workers in Export Processing Zones (EPZs) from participating in awareness raising activities by NGOs. These barriers can furthermore be discussed as preventing them from an enhanced empowerment. The gathered data is mostly based on interviews conducted during a three-week long fieldtrip in Sri Lanka. By using both a literature analysis on the field of research together with group interviews with both female EPZ workers as well as with personnel from a women’s organization in Sri Lanka the study identifies five barriers hindering the women’s participation; time and distance; lack of motivation or interest; limited knowledge of the organization; someone opposing the choice; and fear of loosing the employment. The study derives the root-causes of the barriers to the current social norms and roles, which are internalized in the young women’s mind from their background as well as through the reproduction of them in their new environment, but also to EPZs as discouraging an improvement of the women’s situation.