Identification of Soft-Error at Gate Level

Due to shrinking feature size and significant reduction in noise margins, as we are moving into very deep sub-micron technology, circuits have become more susceptible to manufacturing defects, noise-related transient faults and interference from radiation. Traditionally, soft errors have been a much greater concern in memories than in logic circuits. However, due to technology scaling, logic circuits have become equally susceptible to soft errors. Moreover, enhanced usage of commercial off the shelf (COTS) electronic components for avionics has also increased the importance of analyzing soft errors in hardware circuits. Conventionally, understanding soft error glitches requires circuit level modeling, which requires information available only at late stages in the design flow. Instead of this approach some researchers have produced modeling techniques using Reduced Order Binary Decision Diagrams (ROBDD) and Algebraic Decision Diagrams (ADD), which does allow analyzing soft error at an earlier stage in design flow. In this thesis, a new methodology for modeling soft errors glitch propagation path using Multiway Decision Graphs is introduced. This modeling technique is applicable on both combinational and asynchronous circuits. The proposed glitch propagation path modeling technique jointly takes care of logical and electrical masking. Our methodology involves new ways of injecting glitches including glitch injection in feedback paths of asynchronous circuits. This work presents a complete framework to exhaustively provide all the possible sequences of signals that lead to the possibility of glitch propagation to the primary output in combinational and asynchronous circuits. In addition, a new tool is developed based on the proposed methodology called Soft Error Glitch-Propagating Path Finder (SEGP-Finder) to automate the identification of these sequences of signals. This work helps designers identify the vulnerable circuit paths at the logic abstraction level. Also, this methodology allows designers to apply radiation tolerance techniques on reduced sets of possibilities. By applying our methodology on different combinational and asynchronous circuits an improvement in terms of possible-fault injection vectors is observed. As an example, approximately 8% of all the possible input vectors and sequences is required for obtaining exhaustive glitch propagation path identification in a representative implementation of a bundled data asynchronous circuit. To the best of our knowledge, this is the first time MDG based decision diagram based soft error identification approach is proposed for combinational and asynchronous circuits

A Design for verification approach using an embedding of PSL in AsmL

In this paper, we propose to integrate an embedding of Property Specification Language (PSL) in Abstract State Machines Language (AsmL) with a top–down design for verification approach in order to enable the model checking of large systems at the early stages of the design process. We provide a complete embedding of PSL in the ASM language AsmL, which allows us to integrate PSL properties as a part of the design. For verification, we propose a technique based on the AsmL tool that translates the code containing both the design and the properties into a finite state machine (FSM) representation. We use the generated FSM to run model checking on an external tool, here SMV. Our approach takes advantage of the AsmL language capabilities to model designs at the system level as well as from the power of the AsmL tool in generating both C# code and FSMs from AsmL models. We applied our approach on the PCI-X bus standard, which AsmL model was constructed from the informal standard specifications and a subsequent UML model. Experimental results on the PCI-X bus case study showed a superiority of our approach to conventional verification

Processamento ótico e digital de sinal em sistemas de transmissão com multiplexagem por divisão espacial

The present thesis focuses on the development of optical and digital signal processing techniques for coherent optical transmission systems with spacedivision multiplexing (SDM). According to the levels of spatial crosstalk, these systems can be grouped in the ones with and the ones without spatial selectivity; drastically changing its operation principle. In systems with spatial selectivity, the mode coupling is negligible and therefore, an arbitrary spacial channel can be independently routed through the optical network and post-processed at the optical coherent receiver. In systems without spatial selectivity, mode coupling plays a key role in a way that spatial channels are jointly transmitted and post-processed at the optical coherent receiver. With this in mind, optical switching techniques for SDM transmission systems with spatial selectivity are developed, whereas digital techniques for space-demultiplexing are developed for SDM systems without spatial selectivity. With the purpose of developing switching techniques, the acoustic-optic effect is analyzed in few-mode fibers (FMF)s and in multicore fibers (MCF)s. In FMF, the signal switching between two arbitrary modes using flexural or longitudinal acoustic waves is numerically and experimentally demonstrated. While, in MCF, it is shown that a double resonant coupling, induced by flexural acoustic waves, allows for the signal switching between two arbitrary cores. Still in the context of signal switching, the signal propagation in the multimodal nonlinear regime is analyzed. The nonlinear Schrödinger equation is deduced in the presence of mode coupling, allowing the meticulous analysis of the multimodal process of four-wave mixing. Under the right conditions, it is shown that such process allows for the signal switching between distinguishable optical modes. The signal representation in higher-order Poincaré spheres is introduced and analyzed in order to develop digital signal processing techniques. In this representation, an arbitrary pair of tributary signals is represented in a Poincaré sphere, where the samples appear symmetrically distributed around a symmetry plane. Based on this property, spatial-demultiplexing and mode dependent loss compensation techniques are developed, which are independent of the modulation format, are free of training sequences and tend to be robust to frequency offsets and phase fluctuations. The aforementioned techniques are numerically validated, and its performance is assessed through the calculation of the remaining penalty in the signal-to-noise ratio of the post-processed signal. Finally, the complexity of such techniques is analytically described in terms of real multiplications per sample.A presente tese tem por objectivo o desenvolvimento de técnicas de processamento ótico e digital de sinal para sistemas coerentes de transmissão ótica com multiplexagem por diversidade espacial. De acordo com a magnitude de diafonia espacial, estes sistemas podem ser agrupados em sistemas com e sem seletividade espacial, alterando drasticamente o seu princípio de funcionamento. Em sistemas com seletividade espacial, o acoplamento modal é negligenciável e, portanto, um canal espacial arbitrário pode ser encaminhado de forma independente através da rede ótica e pós-processado no recetor ótico coerente. Em sistemas sem seletividade espacial, o acoplamento modal tem um papel fulcral pelo que os canais espaciais são transmitidos e pós-processados conjuntamente. Perante este cenário, foram desenvolvidas técnicas de comutação entre canais espaciais para sistemas com seletividade espacial, ao passo que para sistemas sem seletividade espacial, foram desenvolvidas técnicas digitais de desmultiplexagem espacial. O efeito acústico-ótico foi analisado em fibras com alguns modos (FMF) e em fibras com múltiplos núcleos (MCF) com o intuito de desenvolver técnicas de comutação de sinal no domínio ótico. Em FMF, demonstrou-se numérica e experimentalmente a comutação do sinal entre dois modos de propagação arbitrários através de ondas acústicas transversais ou longitudinais, enquanto, em MCF, a comutação entre dois núcleos arbitrários é mediada por um processo de acoplamento duplamente ressonante induzido por ondas acústicas transversais. Ainda neste contexto, analisou-se a propagação do sinal no regime multimodal não linear. Foi deduzida a equação não linear de Schrödinger na presença de acoplamento modal, posteriormente usada na análise do processo multimodal de mistura de quatro ondas. Nas condições adequadas, é demonstrado que este processo permite a comutação ótica de sinal entre dois modos de propagação distintos. A representação de sinal em esferas de Poincaré de ordem superior é introduzida e analisada com o objetivo de desenvolver técnicas de processamento digital de sinal. Nesta representação, um par arbitrário de sinais tributários é representado numa esfera de Poincaré onde as amostras surgem simetricamente distribuídas em torno de um plano de simetria. Com base nesta propriedade, foram desenvolvidas técnicas de desmultiplexagem espacial e de compensação das perdas dependentes do modo de propagação, as quais são independentes do formato de modulação, não necessitam de sequências de treino e tendem a ser robustas aos desvios de frequência e às flutuações de fase. As técnicas referidas foram validadas numericamente, e o seu desempenho é avaliado mediante a penalidade remanescente na relação sinal-ruído do sinal pós-processado. Por fim, a complexidade destas é analiticamente descrita em termos de multiplicações reais por amostra.Programa Doutoral em Engenharia Eletrotécnic

Online graduate application system

The purpose of Online Graduate Application System (OGAS) is to allow potential Computer Science and Engineering graduate students to submit and track their online applications. In addition, applicants can change and modify their references via OGAS. As part of the application requirements, the system will allow recommenders to submit and /or upload their recommendations online

Impact of Information Society Research in the Global South

Communication Studies; Information Systems Applications (incl. Internet); R & D/Technology Polic

Determination of schistosomiasis environmental contamination and microbial source tracking

Schistosomiasis and soil-transmitted helminths (STHs), cause major morbidity globally, predominantly in the world’s poorest populations, and exacerbate the cycle of poverty. Poor sanitation facilitates the transmission of the parasitic worms which cause these diseases. The transmission of the Schistosoma species, S. mansoni, can be interrupted by water, sanitation, and hygiene (WASH) interventions if they prevent the faecally deposited schistosome eggs from reaching water and infecting the parasite’s intermediate snail host. Adequate sanitation can also prevent STH ova being deposited into soils, and their ongoing transmission. The monitoring of schistosomiasis and the effect of WASH interventions has predominantly relied on epidemiological data, rather than direct examination of the parasite in the wider environment. In the last few years, environmental DNA (eDNA) techniques have been used to detect S. mansoni in water samples collected from known water contact sites in endemic areas. The sampling of the terrestrial environment has been neglected regarding environmental monitoring of schistosomiasis, despite the soil environment interfacing with sanitation practices such as open defecation and pit latrine usage. The overall aim of this thesis was to characterise the soil environment using eDNA techniques on soil samples that interface with sanitation facilities: sites of open defection and pit latrines in a community highly endemic for S. mansoni and co-endemic for STH. As the soil environment has not been previously investigated using eDNA based methods to detect S. mansoni, Chapter Two outlines the laboratory work carried out to apply existing eDNA-based techniques used on water samples, to the detection of S. mansoni in soil samples. An assay detecting the cytochrome oxidase I gene of S. mansoni was chosen and tested on soils spiked with varying numbers of S. mansoni eggs. It was tested to a lower limit of detection of a single Schistosoma egg extracted from 500 mg of soil. Although the qPCR assay could not reliably estimate the number of eggs in a sample, the assay was found to be highly sensitive. Therefore, this highly sensitive assay was then taken forward to be trialled in an absence/presence capacity on soil samples collected from a S. mansoni endemic area in Uganda in Chapter Three. Soil samples were collected from areas interfacing with sanitation (areas of open defecation and pit latrines) as well as a predicted human defecation free area (community football field). The collected soils were then tested for the detection of S. mansoni using the DNA extraction methods and qPCR-assay from Chapter Two. Although the qPCR assay performed as expected from the standard curve data generated, none of the soils collected had detectable amounts of S. mansoni DNA. Whilst this qPCR was not sensitive enough to detect S. mansoni eggs, or no eggs were present in these sanitation facilities-associated soils, that does not necessarily mean that faecal contamination of the soil environment was not occurring. Therefore, in Chapter Four, bacterial faecal markers were employed as a proxy for the presence of S. mansoni eggs, as they are transmitted into the environment through an infected individual’s faeces. To gain a broader insight into the soil environment four qPCR assays were used to detect and quantify all eukaryotic DNA (universal 18S), prokaryotic DNA (universal 16S), as well as indicators of faecal contamination using a general Bacteroides, a bacterial indicator of homeothermic (bird and mammal) faeces and a human specific Bacteroides marker. Faecal contamination was observed across all samples which could have been caused by the free roaming animals observed in this community. However, fewer samples from the predicted negative control site (the community football pitch) had human faecal markers detected, than soils from the sanitation-associated sites. As schistosomiasis is often co-endemic with STHs, including hookworm, additional studies were performed on these soil samples to assess if Chryseobacterium nematophagum (a nematode-eating bacteria) is found in areas endemic for hookworm. If found, this could indicate the potential for using these bacteria as a form of biological control for hookworm larvae in such an area. In the final experimental data chapter, Chapter Five, the soil samples collected from Uganda were therefore additionally tested for the presence of both hookworm and C. nematophagum. A single soil sample (out of 31) was positive for C. nematophagum. This soil sample was also positive for a hookworm species but as the technical replicate for this sample had CT values more than 0.5 cycles apart, they were considered too disparate from one another to be considered reliable data. Further work is therefore needed before any potential biological control intervention could be investigated further. The possible reasons for the variable results presented throughout the thesis, and recommendations for how to improve the assays, are discussed in the final chapter of the thesis, the General Discussion

Design and implementation of a network revenue management architecture for marginalised communities

Rural Internet connectivity projects aimed at bridging the digital divide have mushroomed across many developing countries. Most of the projects are deployed as community centred projects. In most of the cases the initial deployment of these projects is funded by governments, multilateral institutions and non-governmental organizations. After the initial deployment, financial sustainability remains one of the greatest challenges facing these projects. In the light of this, externally funded ICT4D interventions should just be used for “bootstrapping” purposes. The communities should be “groomed” to take care of and sustain these projects, eliminating as soon as possible a dependency on external funding. This master thesis presents the design and the implementation of a generic architecture for the management of the costs associated with running a computer network connected to the Internet, The proposed system, called the Network Revenue Management System, enables a network to generate revenue, by charging users for the utilization of network resources. The novelty of the system resides in its flexibility and adaptability, which allow the exploration of both conventional and non-conventional billing options, via the use of suitable ‘adapters’. The final goal of the exploration made possible by this system is the establishment of what is regarded as equitable charging in rural, marginalized communities - such as the community in Dwesa, South Africa

Learning from Resilience Strategies in Tanzania

Tanzania has been considered a model for development, peace, and stability despite the arrival of refugees from neighboring countries and the potential tensions related to climate change. Although it has accessed the rank of middleincome country, Tanzania still faces several challenges, particularly in the wake of the Covid-19 pandemic. The book aims at analyzing these challenges as well as the country’s successes through a multi-disciplinary approach considering economic perspectives as well as conflict prevention, dialogue integration, climate change adaptation, forests’ protection, and social perspectives – especially relating to women and girls. The current Covid situation has shaken the whole world and raised many questions on how the different regions and countries could adapt and develop resilience strategies in an uncertain and ever-changing context. Therefore, the book is not only about Tanzania but also about what we can learn from the research on Tanzania in terms of vulnerabilities and resilience strategies. This book is an outlook of International Development Challenges. This book is co-funded by the European Union in the framework of the project Pilot 4 Research and Dialogue

Tactile displays, design and evaluation

Fritschi M. Tactile displays, design and evaluation. Bielefeld: Universität Bielefeld; 2016.This thesis presents the design and development of several tactile displays, as well as their eventual integration into a framework of tactile and kinesthetic stimulation. As a basis for the design of novel devices, an extensive survey of existing actuator principles and existing realizations of tactile displays is complemented by neurobiological and psychophysical findings. The work is structured along three main goals: First, novel actuator concepts are explored whose performance can match the challenging capabilities of human tactile perception. Second, novel kinematic concepts for experimental platforms are investigated that target an almost unknown sub-modality of tactile perception: The perception of shear force. Third, a setup for integrated tactile-kinesthetic displays is realized, and a first study on the psychophysical correlation between the tactile and the kinesthetic portion of haptic information is conducted. The developed devices proved to exceed human tactile capabilities and have already been used to learn more about the human tactile sense

Point-of-care testing for HIV and TB integration of services

A thesis submitted to the Faculty of Health Sciences, university of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Doctor of Philosophy Johannesburg, 2015The United Nations Programme on HIV/AIDS (UNAIDS) have recently released challenging new Human Immunodeficiency Virus (HIV) treatment targets to be achieved globally by 2020; all of which require concentrated efforts in scaling up laboratory testing capacity for HIV diagnosis, treatment initiation and treatment monitoring. The Global Tuberculosis (TB) Strategy have also put forth a list of ambitious goals which include reducing the number of deaths due to TB by 95% and the number of new TB cases by 90%. In South Africa, which has the highest national prevalence of HIV described globally and ranks fifth in the world in terms of TB incident cases, further integration of HIV and TB services will be needed to achieve these targets. A major challenge to successful integration of these programs however, will be the ability to diagnose and monitor the progress of both infections, a process that in South Africa, is hampered by lack of access to laboratory testing. Although public pathology laboratory service providers, such as the National Health Laboratory Service (NHLS), are responding to increasing testing demands by scaling up centralised laboratory capacity, limitations such as the need for expertise, infrastructure, space, cold-chain, maintenance, logistics and cost, are challenging full implementation and scale up. Many international organisations believe that one of the ways to successfully achieve the global HIV ‘90-90-90’ and TB targets, will be through the development and scaling up of innovative, simpler and more affordable technology approaches such as Point-of-Care testing (POCT), a view shared by the South African National Department of Health (NDoH). POCT refers to testing that is performed near or at the site of the patient with the result leading to a possible or immediate change in patient management or outcome and holds promise as a strategy to extend laboratory testing capacity. Prior to large-scale POC implementation efforts can begin, defining the difficulties and potential solutions which are likely to arise, particularly in high disease burden clinical settings need to be addressed. The main objective of this study was to investigate the feasibility, performance and operational considerations of multidisciplinary POCT in South Africa, including the development of a best practice framework to guide implementation efforts. This was achieved by performing a clinical needs assessment and engaging with government, evaluating POC technologies for HIV and TB diagnosis and/or monitoring and developing a framework for how to implement POCT in the field including quality, site and training requirements. The operational requirements for healthcare workers to perform multiple POCT in the South African clinical setting, was also determined. The assays required were based on the South African National Treatment guidelines in the period of review (2011-2014). In July 2013, the South African NDoH called a meeting with various stakeholders to provide the context for POCT in South Africa and strong emphasis was placed on HIV and TB and how POCT could expand on existing laboratory infrastructure for these diseases. Outcomes from this meeting prompted a thorough literature review on the challenges likely to be faced by large-scale POC implementation efforts. One of the key issues highlighted was the lack of evaluation data on numerous HIV and TB POC technologies available and/or in the pipeline. Even though viral load (VL) testing has been available in South Africa since 2004, the global treatment guidelines (World Health Organization) now recommend a VL test for HIV antiretroviral treatment (ART) monitoring and there are talks around the possibilities of a ‘test and treat’ strategy. In light of this, two potential POC plasma-based VL technologies available at the time were evaluated in the laboratory. The Liat™ HIV-1 Plasma Quant (IQuum Inc, MA, USA; now Roche Molecular, Branchburg, MJ, USA) and the Xpert® HIV-1 VL (Cepheid, Sunnyvale, CA) assays both demonstrated good performance and were proven to be interchangeable with existing in-country high-throughput VL laboratory platforms. Both however, require centrifugation to obtain the plasma sample and thus may be more suited to a district level facility as opposed to a ‘true’ POC environment. In light of these operational challenges, two further blood-based POC VL platforms were also evaluated, the Liat™ HIV-1 Blood Quant VL assay (IQuum, Inc) and the Alere™ q HIV-1/2 assay (Alere Technologies GmbH, Jena, Germany). Both assays identified more patients as treatment failures at the 1000 copies/ml treatment failure threshold (WHO and South African treatment guideline recommended threshold) compared to plasma VL, due to their total nucleic acid extraction protocols. Thus, if either were implemented at POC, one could expect a significant upward misclassification, increasing the number of HIV-positive patients requiring follow up VL testing and programmatic costs. Application therefore, could be niched VL testing; utilising a blood-based POC VL assay in maternity wards to diagnose HIV in new-borns; plasmabased POCT for mothers to reduce risk of transmission. POCT may not be the only solution to increasing access to laboratory testing services, and thus alternative strategies for improving access were also investigated. Dried blood spots (DBS) and PrimeStore media (a sample transport media; Longhorn Vaccines and Diagnostics, San Antonio, TX, USA) were shown to be as valuable as plasma VL for detecting HIV-positive patients failing ART at the 1000 copies/ml threshold and both solve logistical issues around sample transport and maintaining sample integrity for centralized testing. For TB diagnosis, the Xpert® MTB/RIF assay (Cepheid, Sunnyvale, CA) was evaluated to determine its appropriate placement within the South African setting. Although Xpert® MTB/RIF proved superior in performance to smear microscopy, it was originally modelled as too costly for POC placement in South Africa and was implemented into smear microscopy centres nationally. Subsequently, the complexity of the analyser maintenance and power issues has reinforced the original decision. Further potential POC TB technologies are in the development pipeline, but only one other was available for evaluation, namely the EasyNAT® detection kit (Ustar Biotechnologies, Hangzou, China). Initial laboratory evaluation results look promising but the technology is still a long way from clinical evaluation due to its laborious procedure. A further challenge identified for POCT is the lack of documented implementation science to ensure quality-assured multi-disciplinary POCT in the field. To address this, three key components of a quality testing framework were developed to ensure best practice for POCT; a clinic site readiness assessment tool, a POC training module and a quality monitoring program. The clinic site assessment checklist was developed to determine site readiness for POC placement. The POC training module included standard operating procedures, quick reference and workflow charts and a practical training component which was developed specifically with the non-laboratory trained user in mind. Both these components have been adopted and modified for use by the NHLS National Priority Program (NPP). Certain POC assays already have External Quality Assessment (EQA) material, while others had to be developed. For quality management of HIV VL technologies, a standardized plasma panel was developed to ensure molecular VL platforms are ‘fit-forpurpose’ (verification, a requirement of the laboratory accreditation process). This panel, termed SAVQA, is being manufactured and supplied to aid POC assay developers in assessing their product for the South African market, and will also be further developed for use by healthcare workers at POC. Due to the hurdles encountered with the biosafety regulations for transporting TB external quality assessment (EQA) material, a quality assessment program using dried culture spots (DCS) was also developed for TB diagnostic technologies consisting of two components; a verification and an EQA program. The DCS technology has become a global product and as of 2015 is being supplied to 20 different countries. DCS were successfully shown to be suitable for use at POC by non-laboratory trained staff. The versatility of the material has been confirmed by its expansion to other molecular TB diagnostic tests, most notably the Hain Genotype MTBDrplus assay for TB drug susceptibility testing (Hain LifeScience GmbH, Nehren, Germany). This work has been acknowledged through the Research and Development team involved in the development of the DCS program, winning three awards: the NHLS Top Award for Innovation 2013, the Gauteng Accelerator Program (GAP) Biosciences Award in 2014 and a special Social Impact award for Africa Innovations held in Morocco in 2015. Incorporating the quality components developed above, a clinical evaluation of nurse operated multidisciplinary POCT was performed. Although multiple POCT could be performed as accurately as laboratory testing on venepuncture specimens, it required dedicated staff and dramatically increased POC staff duties. It was further shown that multiple POCT could be accurately performed by a nurse on a single finger slice in order to obtain adequate blood volume to perform up to four POC tests, and that finger stick VL testing was also feasible by nurses at POC. Patients were also more willing to have up to three finger sticks performed than to have a single venepuncture specimen taken. The process of using finger sticks was further ratified by demonstrating that a single finger stick can provide up to 150μl of blood, which is sufficient to perform an array of POC tests. In spite of the feasibility of nurse based POCT, limitations of current technologies using finger stick were also realised, such as the performance of the Liat™ Quant blood assay which generated increased VL misclassification at the 1000 copies/ml treatment failure threshold (70% misclassification). This would impact programmatic costs, but this technology may have value as a diagnostic tool in key populations. The work described shows that multi-disciplinary POCT within a South African setting is achievable with appropriate clinic infrastructure, dedicated staff, training and stringent quality monitoring measures in place. The HIV and TB POC technologies evaluated were found to be as accurate as laboratory-based testing however, few meet the criteria of a ‘true’ POC device and thus further research and development is required. Based on South Africa’s testing needs, a tiered hybrid model which expands on centralized laboratory capacity through incorporating POCT into very remote, hard-to-reach areas and innovations around linkage to care efforts, may help meet ’90-90-90’ targets but will require costing/modelling and future assessments of the impact and outcome of the intervention. Much of this work presented contributed towards the development of a draft National POCT policy document in support of the national strategic plan for POCT for the management of HIV and TB in South Africa