Reliability is of the utmost importance for safety of electronic systems built for the automotive, industrial, and medical sectors. In these systems, the embedded memory is especially sensitive due to the large number of minimum-sized devices in the cell arrays. Memory failures which occur after the manufacture-time burnin testing phase are particularly difficult to address since redundancy allocation is no longer available and fault detection schemes currently used in industry generally focus on the cell array while leaving the peripheral logic vulnerable to faults. Even in the cell array, conventional error control coding (ECC) has been limited in its ability to detect and correct failures greater than a few bits, due to the high latency or area overhead of correction [43]. Consequently, improvements to conventional memory resilience techniques are of great importance to continued reliable operation and to counter the raw bit error rate of the memory arrays in future technologies at economically feasible design points [11, 36, 37, 53, 56, 70]. In this thesis we examine the landscape of design techniques for reliability, and introduce two novel contributions for improving reliability with low overhead. To address failures occurring in the cell array, we have implemented an erasurebased ECC scheme (EB-ECC) that can extend conventional ECC already used in memory to correct and detect multiple erroneous bits with low overhead. An important component of this scheme is the method for detecting erasures at runtime; we propose a novel ternary-output sense amplifier design which can reduce the risk of undetected read latency failures in small-swing bitline designs. While most study has focused on the static random access memory (SRAM) cell array, for high-reliability products, it is important to examine the effects of failures on the peripheral logic as well. We have designed a wordline assertion comparator (WLAC) which has lower area overhead in large cache designs than competing techniques in the literature to detect address decoder failure.

Aim: This study looks at the effect of orthokeratology on a number of biometric parameters and refractive error in an adult population. Method: Forty three myopic subjects were recruited to a twelve month study into the effects of orthokeratology on ocular biometry and refractive error. Two different back surface lens designs were applied right eye) pentacurve and left eye) aspheric. The aspheric design was chosen to more closely mimic the cornea's natural shape. Anterior and posterior apical radii and p-values; corneal thickness and anterior chamber depth were measured using the Orbscan IIz; together with ocular biometry by IOL Master and a standard clinical refraction. All measurements were repeated at one night, one week, one, three, six and twelve months. Refractive changes were analysed against biometric changes. Results: Twenty seven participants completed one month of lens wear. Twelve subjects completed twelve months of lens wear. Subjects with myopia ≤ -4.00DS were successfully treated with orthokeratology. Both anterior and posterior apical radii and p values were altered by orthokeratology. Corneal thickness changes were in agreement with previously published studies. Axial length and anterior chamber depth were unaffected by the treatment. Conclusion: Orthokeratology should be available as an alternative to laser refractive surgery. It is best restricted to myopes of up to -4.00DS with low levels of with the rule corneal astigmatism. The use of an aspheric back design contact lens did not produce a significant benefit over that of a pentacurve.

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Statistics and Actuarial Science / Master / Master of Philosophy

published_or_final_version / Statistics / Doctoral / Doctor of Philosophy

In the context of the SERVIR-Africa project, the SERVIR Arizona Team is developing streamflow forecast systems on African basins using Satellite Precipitation Products (SPP) to drive the models. These products have errors that need to be addressed before using them to drive hydrologic models. An analysis of the errors of the Satellite Precipitation Products TMPA-3B42RT, CMORPH, and PERSIANN over Africa is presented, followed by bias correction and error reduction methods to improve the remote sensed estimates. The GPCP 1-degree-day reanalysis product was used as the rainfall truth dataset. The Bias Correction Spatial Downscaling (BCSD) method developed by Wood et al., was used successfully to reduce the errors of SPP. The original and bias corrected estimates from the three SPP are used to calibrate and simulate three catchments of the Senegal River basin using HYMOD, finding that the use of bias corrected estimates produces a significant improvement in streamflow simulation.

The aim of this research is to investigate the long-run co-integrating relationships in the Asian markets. Our research focuses on 4 areas; pair trading, out-of-sample forecasting, testing the unbiased forward exchange rate hypothesis and testing the expectation hypothesis of the term structure of interest rates. The introduction is provided in chapter one. In chapter two, we develop a pairs trading strategy using individual stocks listed in the Stock Exchange of Thailand. Engle and Granger approach is used to identify the potential pairs that are cointegrated. The results show that pairs trading strategy is profitable in this market. Chapter three examines the forecasting performance of the error correction model on daily share price series from the Stock Exchange of Thailand. The disequilibrium term is classified into “correct” and “mix” sign based on Alexander (2008)’s criterion; the results indicate that the error correction component can help to improve the predictability in the long run. Chapter four tests the unbiased forward rate hypothesis of 11 Asian exchange rates using linear conventional regression, ECM and logistic smooth transition regression with the forward premium as the transition variable. Out-of-sample forecasting results also suggest that inferior forecasting performance could be obtained as a result of using linear models. In chapter five, we investigate the expectation hypothesis of the term structure of interest rate for four Asian countries. We employ linear models and nonlinear approaches that allow to capture asymmetric and symmetric adjustments. The result also indicates that the term structure can be better modeled by means of LSTR models. The forecasting exercise also confirms these findings.

Produsente van landboukommoditeite, veral in ontwikkelende lande, word blootgestel aan prysrisiko's. Markte vir landboukommoditeite in Suid-Afrika, soos in die res van die wêreld, is die afgelope aantal jare gekenmerk deur prosesse van deregulering. Die bemarkingsrade wat aanvanklik verantwoordelik was vir die bemarking van landbouprodukte, het ontbind en produsente van landbouprodukte moes nuwe metodes vind om hulle produkte te bemark. Een van die metodes wat gebruik word, is termynkontrakte. Witmielies en geelmielies is die twee landboukommoditeite wat in die grootste hoeveelhede geproduseer word in Suid-Afrika. Witmielies en geelmielies word as twee afsonderlike kommoditeite verhandel op die termynbeurs. Witmielies word hoofsaaklik aangewend vir menslike verbruik en geelmielies vir dierevoer. Hierdie studie fokus hoofsaaklik op witmielies. Die prys van mielies word beïnvloed deur veranderinge in die vraag daarna en aanbod daarvan. Faktore wat die vraag en aanbod van mielies beïnvloed is, onder andere, oesskattings, reënval, die wisselkoers en die pryse van mielies op die buitelandse mark, veral die markte in die VSA. In Suid-Afrika vorm die invoerpariteit en uitvoerpariteit 'n band waarbinne die prys van mielies varieer. Die doel van hierdie studie is om 'n regressievergelyking te konstrueer ten einde prys van die witmielietermynkontrakte te verklaar. Die regressie-analise word deur middel van 'n foutherstellende model met outoregressiewe foutterme behartig. Die regressie-analise slaag daarin om die prys van witmielietermynkontrakte te verklaar. / Thesis (M.Com. (Economics))--North-West University, Potchefstroom Campus, 2004.

There is growing evidence that young adult readers frequently fail to create exhaustive textbased representations as they read. Although there has been a significant amount of research devoted to age-related effects on text processing, there has been little research concerning this so-called shallow processing by older readers. This dissertation uses eye tracking to explore age-related effects in shallow processing across different levels of text representations. Experiment 1 investigated shallow processing by older readers at the textbase level by inserting semantic anomalies into passages read by participants. Older readers frequently failed to report the anomalies, but no more frequently than did younger readers. The eye-fixation behaviour revealed that older readers detected some of the anomalies sooner than did younger readers, but had to allocate disproportionately more processing resources to looking back to the anomalies to achieve comparable levels of detection success as their younger counterparts. Experiment 2 examined age-related effects of shallow processing at the surface form by inserting syntactic anomalies into passages read by older and younger adults. Older readers were less likely to detect syntactic anomalies when first encountering them relative to younger readers and engaged in increased regressive fixations to the anomalies. However, older readers with high iii reading comprehension skill were able to use their familiarity with text content to increase their likelihood of syntactic anomaly detection. Experiment 3 investigated the role of aging on shallow processing of the temporal dimension of the situation model. No age-related differences reporting the anomalies were found. The eye-fixation behaviour revealed that older readers with high working memory capacity detected some anomalies sooner than did younger readers; however, they had to allocate increased processing resources looking back to the anomalies to achieve comparable levels of detection as younger readers. Together, the results demonstrate that older readers are susceptible to shallow processing, but no more so than younger readers when they can rely on their linguistic skill or their existing knowledge to help reduce processing demands. However, older readers appear to require additional processing time to achieve comparable levels of anomaly detection as younger readers.

Tidigare forskning är inte enig om aktivt förvaltade fonder presterar bättre eller sämre än index. Då hänsyn inte tas till olika nivåer av aktivitet tycks de flesta studier visa att aktiv förvaltning är en förlustaffär för fondsparare. Vi introducerar ett nytt mått på aktivitet, aktivitetsgrad, som utgår från de åtgärder förvaltaren vidtar. Aktivitetsgraden definieras av mängden och storleken på förändringar i portföljsammansättningen som sker under ett kvartal. Vi undersöker aktivitetsgraden hos 22 svenska småbolagsfonder mellan 2008 och 2013 och finner att de flesta fonder har en låg aktivitetsgrad. Vi finner att aktivitetsgraden verkar negativt på prestation samt att aktivitetsgrad är bättre på att förutsäga prestation än Tracking Error.