Syfte: Att undersöka läshastigheten på datorskärm och om den kan förbättras med hjälp av färgade overlays, samt om det finns någon skillnad i läshastighet på utskrivet papper och datorskärm. Metod: Deltagarna (n=30) fick läsa ett Wilkins rate of reading test översatt till svenska, där antalet ord som hann läsas upp högt under en minut jämfördes då de läste på papper utan overlay och på datorskärm med och utan overlay. Studien gjordes på studenter mellan 18-31 år. Resultat: Den här studien visar att det inte finns någon signifikant skillnad i läshastighet mellan läsning på utskrivet papper och datorskärm (p=0,508). Deltagarna läste 1,6 ± 13,3 ord mer/min på datorskärm än på papper. En signifikant skillnad kan däremot ses mellan läsning på datorskärm med och utan färgat overlay (p=0,008). Läshastigheten ökade med 4,7 ± 9,1 ord/min med färgat overlay. Slutsats: Läshastigheten på papper och datorskärm är ungefär densamma. Man kan öka läshastigheten på datorskärm genom att placera ett färgat overlay över texten. / Purpose: To investigate reading speed on a computer screen and if it can be improved by using coloured overlays, and also if there is any difference in reading speed on printed paper and computer screen. Methods: The participants (n=30) read a Wilkins rate of reading test translated into Swedish, where the number of words read out loud in one minute was compared when reading on a paper without overlay and on a computer screen with and without an overlay. This study was performed on students aged 18-31 years. Results: This study shows that there is no significant difference in reading speed between reading on a printed paper and on a computer screen (p=0.508). The participants read 1.6 ± 13.3 words/min more on the computer screen than on the paper. A significant difference however was found in reading on a computer screen with and without coloured overlay (p=0.008). The reading speed increased with 4.7 ± 9.1 words/min with a coloured overlay. Conclusions: The reading speed on paper is similar to the reading speed on computer screen. The reading speed on the computer screen can be increased by placing a coloured overlay in front of the text.

Syfte: Syftet var att undersöka om det fanns någon skillnad i läshastighet med hjälp utav ett färgat filter (overlay) framför en text. Det undersöktes också om det var någon skillnad i ändringen av läshastighet mellan två olika åldersgrupper, en där deltagarna var över 18 år och en grupp där deltagarna var under 18 år gamla. Metod: Studien bestod av ett antal kliniska tester, klarade deltagarna normalvärdena för dessa tester fick de läsa ett lästest i en minut där antalet ord istället räknades och antecknades. Ett overlay valdes sedan och deltagaren läste då ett andra test i en minut där det också räknades ord och antecknades för att se om det fanns någon skillnad mellan läsningarna. Färgen och vilken sida på overlayet som valdes antecknades. Resultat: En signifikant skillnad mellan att läsa med och utan overlay fanns (p < 0,001). I de båda åldersgrupperna skedde en ökning av läshastighastigheten med hjälp utav ett overlay. Ökningen i den yngre åldersgruppen var 7,3 % med hjälp av overlay och i gruppen där deltagarna var över 18 år var förbättringen 6,1 %. I de båda grupperna fanns det också ett fåtal deltagare som läste saktare med overlay. Slutsats: Överlag visar detta att overlays kan hjälpa till att öka läshastigheten både hos barn och vuxna. Valet av färg på overlays skiljde sig åt mellan grupperna. / The aim of this study was to investigate if there was any difference in the reading speed with a coloured overlay when it was used on top of the text of a newly developed swedish reading test. The study also investigated if there were any differences in the change of reading speed between two different age groups. The study consisted of a number of clinical tests, the tests were visual aquity assessment for near and distance, colour vision and stereopsis. If the participants managed the normal values for these tests they were allowed to read a swedish reading test out loud three times for one minute each. The first time was for learning the structure of the reading test, the second time was read without overlay and the third time was read with an overlay. In the last two times the number of words were counted and noted. There was a significant difference in the reading speed with and without overlay (p < 0.001). In both the age groups there was an increase in reading speed when the overlay was used. The increase was 7.3 % with overlay in the younger age group and in the group where the participants were over 18 years old, the increase was 6.1 %. In both of the groups there was a small number of people whose reading speed was reduced when using an overlay. Overall this study shows that overlays can increase the reading speed in both children and adults. The chosen colour on the overlay differed between the two groups.

Yes / Around 3-6% of children in the United Kingdom have substantial difficulties learning to read, a condition often referred to as dyslexia. They are at high risk of educational underachievement. In a 1996 editorial in The BMJ, Margaret Snowling argued that dyslexia is a verbal (not a visual) disorder.1 An accumulation of evidence supports this position and shows that reading difficulties are best dealt with by interventions that target underlying weaknesses in phonological language skills and letter knowledge.2 The 2009 Rose report, which provides guidance for professionals in schools on identifying and teaching young people with dyslexia and reading difficulties, stresses the importance of early, phonological interventions.3 Despite this evidence, dyslexia is often associated with subjective experiences of visual distortions that lead to discomfort during reading (sometimes termed visual stress). It has been argued that these symptoms can be alleviated by using coloured overlays and lenses.4 Symptoms of visual stress are not unique to dyslexia, and proponents do not claim that the use of colour directly addresses the underlying cause of the reading difficulty. However, they argue that the reduction in visual distortion brought about by a change in colour can improve reading accuracy and fluency.4

Yes / We thank Professors Evans and Allen for their interest in our article.1 2 The charity websites we reviewed refer to colour as though it offers a scientific, evidence based treatment; none referred to feedback from the membership. For example, one charity website makes the claim that “Research in the UK and in Australia shows that people who need coloured filters, who are said to have visual stress, need to have exactly the right colour.” This is incorrect. The research overwhelmingly shows little advantage, or at best conflicting results.3 4 5

As the role of the Internet has been steadily gaining in importance, overlays are increasingly being used to provide new services and to deploy older ones. Some of the services for which overlays have been proposed include multicast, quality of service (QoS), search, and resilient networks. The use of overlays, in turn, has led to more interest in improving their performance. The performance of an overlay network depends significantly on how the network is structured, i.e., the placement of the nodes in the underlying network topology, the links between the overlay nodes and the access links of these nodes. This thesis focuses on algorithms for improving the performance of

Sensor networks comprise of a collection of resource-constrained, low cost, sometimes fragile wireless motes which have the capability to gather information about their surroundings through the use of sensors, and can be conceived as a distributed computing platform for applications ranging from event detection to environmental monitoring. A Sensor Network Query Processor (SNQP) is a means of collecting data from sensor networks where the requirements are defined using a declarative query language with a set of Quality of Service (QoS) expectations. As sensor networks are often deployed in hostile environments, there is a high possibility that the motes could break or that the communication links between the motes become unreliable. SNQP Query Execution Plans (QEPs) are often optimised for a specific network deployment and are designed to be as energy efficient as possible whilst ensuring the QEPs meet the QoS expectations, yet little has been done for handling the situation where the deployment itself has changed since the optimisation in such a way as to make the original QEP no longer efficient, or unable to operate. In this respect, the previous work on SNQPs has not aimed at being resilient to failures in the assumptions used at compilation/optimisation time which result in a QEP terminating earlier than expected. This dissertation presents a collection of approaches that embed resilience into a SNQP generated QEPs in such a way that a QEP operates for longer whilst still meeting the QoS expectations demanded of it, thereby resulting in a more reliable platform that can be applicable to a broader range of applications. The research contributions reported here include (a) a strategy designed to adapt to predictable node failures due to energy depletion; (b) a collection of strategies designed to adapt to unpredictable node failures; (c) a strategy designed to handle unreliable communication channels; and (d) an empirical evaluation to show the benefits of a resilient SNQP in relation to a representative non-resilient SNQP.

Highway bridge decks are often overlaid to extend service life by reducing the rate of chloride ion ingress and the rate of corrosion of reinforcing steel in the sound chloride-contaminated concrete that is left in-place. Bridge deck overlays in Virginia are usually either latex-modified concrete or microsilica concrete, and both types of overlay are considered equivalent in terms of performance. However, the latex-modified concrete overlays are more expensive to construct than the microsilica concrete overlays. Thus, it is important to determine if these overlays do perform equivalently to ensure that short-term savings do not lead to higher long-term costs. Shrinkage is one of the overlay performance parameters. Shrinkage is a three-dimensional deformation of concrete that results in an overall reduction in volume. Total shrinkage may be measured under either restrained or unrestrained conditions. This research examines the shrinkage performances of Virginia Department of Transportation-approved latex-modified and microsilica concrete overlay mixtures and was conducted on both field-sampled and laboratory-fabricated restrained and unrestrained specimens. Based on crack and delamination surveys of sampled bridge decks and laboratory test results, a shrinkage performance-based specification for the Virginia Department of Transportation was developed. There was no significant difference between the unrestrained shrinkage values of latex-modified and microsilica concrete overlay mixtures for the specified time periods. Restrained microsilica concrete specimens generally cracked earlier and more frequently than restrained latex-modified concrete specimens. However, the bridge deck crack and delamination surveys show that construction conditions and quality and traffic type and frequency may have a greater effect on cracking than the overlay material. / Master of Science

Yes / Purpose: There are many anecdotal claims that coloured lenses and overlays improve reading performance and there is a substantial literature on the topic of whether reading performance is enhanced through the use of colour. Here we present the results of a systematic review of this literature and examine the quality of the evidence concerning the assertion that reading can benefit from use of coloured overlays or lenses. Methods: We systematically reviewed the literature concerning the effect of coloured lenses or overlays on reading performance by searching the PsychInfo, Medline and Embase databases. Our searches revealed 51 published items (containing 54 data sets). Different systems are in use for issuing coloured overlays or lenses and we reviewed the evidence under four separate system headings (Intuitive, Irlen, Harris/Chromagen and Other). We classified each published item using the Cochrane Risk of Bias tool. Results: Although the different colour systems have been subjected to different amounts of scientific scrutiny, the results do not differ according to the system type, or whether the sample under investigation have been classified as having visual stress (or a similarly defined condition), reading difficulty, or both. The majority of studies are subject to ‘high’ or ‘uncertain’ risk of bias in one or more key aspects of study design or outcome. Studies at lower risk from bias offered less support for the benefit of colour on reading ability. Whilst many studies report improvements with colour, the effect size is generally small and/or similar to the improvement found with a placebo condition. We discuss the strengths and shortcomings of the published literature and, whilst acknowledging the difficulties associated with conducting trials of this type, offer some suggestions about how future trials might be conducted. Conclusions: Consistent with previous reviews and advice from several professional bodies, we conclude that the use of coloured lenses or overlays to ameliorate reading difficulties cannot be endorsed and that any benefits reported by individuals in clinical settings are likely to be the result of placebo, practice or Hawthorne effects.

The threat of surveillance by governmental and industrial parties is more eminent than ever. As communication moves into the digital domain, the advances in automatic assessment and interpretation of enormous amounts of data enable tracking of millions of people, recording and monitoring their private life with an unprecedented accurateness. The knowledge of such an all-encompassing loss of privacy affects the behavior of individuals, inducing various degrees of (self-)censorship and anxiety. Furthermore, the monopoly of a few large-scale organizations on digital communication enables global censorship and manipulation of public opinion. Thus, the current situation undermines the freedom of speech to a detrimental degree and threatens the foundations of modern society. Anonymous and censorship-resistant communication systems are hence of utmost importance to circumvent constant surveillance. However, existing systems are highly vulnerable to infiltration and sabotage. In particular, Sybil attacks, i.e., powerful parties inserting a large number of fake identities into the system, enable malicious parties to observe and possibly manipulate a large fraction of the communication within the system. Friend-to-friend (F2F) overlays, which restrict direct communication to parties sharing a real-world trust relationship, are a promising countermeasure to Sybil attacks, since the requirement of establishing real-world trust increases the cost of infiltration drastically. Yet, existing F2F overlays suffer from a low performance, are vulnerable to denial-of-service attacks, or fail to provide anonymity. Our first contribution in this thesis is concerned with an in-depth analysis of the concepts underlying the design of state-of-the-art F2F overlays. In the course of this analysis, we first extend the existing evaluation methods considerably, hence providing tools for both our and future research in the area of F2F overlays and distributed systems in general. Based on the novel methodology, we prove that existing approaches are inherently unable to offer acceptable delays without either requiring exhaustive maintenance costs or enabling denial-of-service attacks and de-anonymization. Consequentially, our second contribution lies in the design and evaluation of a novel concept for F2F overlays based on insights of the prior in-depth analysis. Our previous analysis has revealed that greedy embeddings allow highly efficient communication in arbitrary connectivity-restricted overlays by addressing participants through coordinates and adapting these coordinates to the overlay structure. However, greedy embeddings in their original form reveal the identity of the communicating parties and fail to provide the necessary resilience in the presence of dynamic and possibly malicious users. Therefore, we present a privacy-preserving communication protocol for greedy embeddings based on anonymous return addresses rather than identifying node coordinates. Furthermore, we enhance the communication’s robustness and attack-resistance by using multiple parallel embeddings and alternative algorithms for message delivery. We show that our approach achieves a low communication complexity. By replacing the coordinates with anonymous addresses, we furthermore provably achieve anonymity in the form of plausible deniability against an internal local adversary. Complementary, our simulation study on real-world data indicates that our approach is highly efficient and effectively mitigates the impact of failures as well as powerful denial-of-service attacks. Our fundamental results open new possibilities for anonymous and censorship-resistant applications. / Die Bedrohung der Überwachung durch staatliche oder kommerzielle Stellen ist ein drängendes Problem der modernen Gesellschaft. Heutzutage findet Kommunikation vermehrt über digitale Kanäle statt. Die so verfügbaren Daten über das Kommunikationsverhalten eines Großteils der Bevölkerung in Kombination mit den Möglichkeiten im Bereich der automatisierten Verarbeitung solcher Daten erlauben das großflächige Tracking von Millionen an Personen, deren Privatleben mit noch nie da gewesener Genauigkeit aufgezeichnet und beobachtet werden kann. Das Wissen über diese allumfassende Überwachung verändert das individuelle Verhalten und führt so zu (Selbst-)zensur sowie Ängsten. Des weiteren ermöglicht die Monopolstellung einiger weniger Internetkonzernen globale Zensur und Manipulation der öffentlichen Meinung. Deshalb stellt die momentane Situation eine drastische Einschränkung der Meinungsfreiheit dar und bedroht die Grundfesten der modernen Gesellschaft. Systeme zur anonymen und zensurresistenten Kommunikation sind daher von ungemeiner Wichtigkeit. Jedoch sind die momentanen System anfällig gegen Sabotage. Insbesondere ermöglichen es Sybil-Angriffe, bei denen ein Angreifer eine große Anzahl an gefälschten Teilnehmern in ein System einschleust und so einen großen Teil der Kommunikation kontrolliert, Kommunikation innerhalb eines solchen Systems zu beobachten und zu manipulieren. F2F Overlays dagegen erlauben nur direkte Kommunikation zwischen Teilnehmern, die eine Vertrauensbeziehung in der realen Welt teilen. Dadurch erschweren F2F Overlays das Eindringen von Angreifern in das System entscheidend und verringern so den Einfluss von Sybil-Angriffen. Allerdings leiden die existierenden F2F Overlays an geringer Leistungsfähigkeit, Anfälligkeit gegen Denial-of-Service Angriffe oder fehlender Anonymität. Der erste Beitrag dieser Arbeit liegt daher in der fokussierten Analyse der Konzepte, die in den momentanen F2F Overlays zum Einsatz kommen. Im Zuge dieser Arbeit erweitern wir zunächst die existierenden Evaluationsmethoden entscheidend und erarbeiten so Methoden, die Grundlagen für unsere sowie zukünftige Forschung in diesem Bereich bilden. Basierend auf diesen neuen Evaluationsmethoden zeigen wir, dass die existierenden Ansätze grundlegend nicht fähig sind, akzeptable Antwortzeiten bereitzustellen ohne im Zuge dessen enorme Instandhaltungskosten oder Anfälligkeiten gegen Angriffe in Kauf zu nehmen. Folglich besteht unser zweiter Beitrag in der Entwicklung und Evaluierung eines neuen Konzeptes für F2F Overlays, basierenden auf den Erkenntnissen der vorangehenden Analyse. Insbesondere ergab sich in der vorangehenden Evaluation, dass Greedy Embeddings hoch-effiziente Kommunikation erlauben indem sie Teilnehmer durch Koordinaten adressieren und diese an die Struktur des Overlays anpassen. Jedoch sind Greedy Embeddings in ihrer ursprünglichen Form nicht auf anonyme Kommunikation mit einer dynamischen Teilnehmermengen und potentiellen Angreifern ausgelegt. Daher präsentieren wir ein Privätssphäre-schützenden Kommunikationsprotokoll für F2F Overlays, in dem die identifizierenden Koordinaten durch anonyme Adressen ersetzt werden. Des weiteren erhöhen wir die Resistenz der Kommunikation durch den Einsatz mehrerer Embeddings und alternativer Algorithmen zum Finden von Routen. Wir beweisen, dass unser Ansatz eine geringe Kommunikationskomplexität im Bezug auf die eigentliche Kommunikation sowie die Instandhaltung des Embeddings aufweist. Ferner zeigt unsere Simulationstudie, dass der Ansatz effiziente Kommunikation mit kurzen Antwortszeiten und geringer Instandhaltungskosten erreicht sowie den Einfluss von Ausfälle und Angriffe erfolgreich abschwächt. Unsere grundlegenden Ergebnisse eröffnen neue Möglichkeiten in der Entwicklung anonymer und zensurresistenter Anwendungen.

The threat of surveillance by governmental and industrial parties is more eminent than ever. As communication moves into the digital domain, the advances in automatic assessment and interpretation of enormous amounts of data enable tracking of millions of people, recording and monitoring their private life with an unprecedented accurateness. The knowledge of such an all-encompassing loss of privacy affects the behavior of individuals, inducing various degrees of (self-)censorship and anxiety. Furthermore, the monopoly of a few large-scale organizations on digital communication enables global censorship and manipulation of public opinion. Thus, the current situation undermines the freedom of speech to a detrimental degree and threatens the foundations of modern society. Anonymous and censorship-resistant communication systems are hence of utmost importance to circumvent constant surveillance. However, existing systems are highly vulnerable to infiltration and sabotage. In particular, Sybil attacks, i.e., powerful parties inserting a large number of fake identities into the system, enable malicious parties to observe and possibly manipulate a large fraction of the communication within the system. Friend-to-friend (F2F) overlays, which restrict direct communication to parties sharing a real-world trust relationship, are a promising countermeasure to Sybil attacks, since the requirement of establishing real-world trust increases the cost of infiltration drastically. Yet, existing F2F overlays suffer from a low performance, are vulnerable to denial-of-service attacks, or fail to provide anonymity. Our first contribution in this thesis is concerned with an in-depth analysis of the concepts underlying the design of state-of-the-art F2F overlays. In the course of this analysis, we first extend the existing evaluation methods considerably, hence providing tools for both our and future research in the area of F2F overlays and distributed systems in general. Based on the novel methodology, we prove that existing approaches are inherently unable to offer acceptable delays without either requiring exhaustive maintenance costs or enabling denial-of-service attacks and de-anonymization. Consequentially, our second contribution lies in the design and evaluation of a novel concept for F2F overlays based on insights of the prior in-depth analysis. Our previous analysis has revealed that greedy embeddings allow highly efficient communication in arbitrary connectivity-restricted overlays by addressing participants through coordinates and adapting these coordinates to the overlay structure. However, greedy embeddings in their original form reveal the identity of the communicating parties and fail to provide the necessary resilience in the presence of dynamic and possibly malicious users. Therefore, we present a privacy-preserving communication protocol for greedy embeddings based on anonymous return addresses rather than identifying node coordinates. Furthermore, we enhance the communication’s robustness and attack-resistance by using multiple parallel embeddings and alternative algorithms for message delivery. We show that our approach achieves a low communication complexity. By replacing the coordinates with anonymous addresses, we furthermore provably achieve anonymity in the form of plausible deniability against an internal local adversary. Complementary, our simulation study on real-world data indicates that our approach is highly efficient and effectively mitigates the impact of failures as well as powerful denial-of-service attacks. Our fundamental results open new possibilities for anonymous and censorship-resistant applications. / Die Bedrohung der Überwachung durch staatliche oder kommerzielle Stellen ist ein drängendes Problem der modernen Gesellschaft. Heutzutage findet Kommunikation vermehrt über digitale Kanäle statt. Die so verfügbaren Daten über das Kommunikationsverhalten eines Großteils der Bevölkerung in Kombination mit den Möglichkeiten im Bereich der automatisierten Verarbeitung solcher Daten erlauben das großflächige Tracking von Millionen an Personen, deren Privatleben mit noch nie da gewesener Genauigkeit aufgezeichnet und beobachtet werden kann. Das Wissen über diese allumfassende Überwachung verändert das individuelle Verhalten und führt so zu (Selbst-)zensur sowie Ängsten. Des weiteren ermöglicht die Monopolstellung einiger weniger Internetkonzernen globale Zensur und Manipulation der öffentlichen Meinung. Deshalb stellt die momentane Situation eine drastische Einschränkung der Meinungsfreiheit dar und bedroht die Grundfesten der modernen Gesellschaft. Systeme zur anonymen und zensurresistenten Kommunikation sind daher von ungemeiner Wichtigkeit. Jedoch sind die momentanen System anfällig gegen Sabotage. Insbesondere ermöglichen es Sybil-Angriffe, bei denen ein Angreifer eine große Anzahl an gefälschten Teilnehmern in ein System einschleust und so einen großen Teil der Kommunikation kontrolliert, Kommunikation innerhalb eines solchen Systems zu beobachten und zu manipulieren. F2F Overlays dagegen erlauben nur direkte Kommunikation zwischen Teilnehmern, die eine Vertrauensbeziehung in der realen Welt teilen. Dadurch erschweren F2F Overlays das Eindringen von Angreifern in das System entscheidend und verringern so den Einfluss von Sybil-Angriffen. Allerdings leiden die existierenden F2F Overlays an geringer Leistungsfähigkeit, Anfälligkeit gegen Denial-of-Service Angriffe oder fehlender Anonymität. Der erste Beitrag dieser Arbeit liegt daher in der fokussierten Analyse der Konzepte, die in den momentanen F2F Overlays zum Einsatz kommen. Im Zuge dieser Arbeit erweitern wir zunächst die existierenden Evaluationsmethoden entscheidend und erarbeiten so Methoden, die Grundlagen für unsere sowie zukünftige Forschung in diesem Bereich bilden. Basierend auf diesen neuen Evaluationsmethoden zeigen wir, dass die existierenden Ansätze grundlegend nicht fähig sind, akzeptable Antwortzeiten bereitzustellen ohne im Zuge dessen enorme Instandhaltungskosten oder Anfälligkeiten gegen Angriffe in Kauf zu nehmen. Folglich besteht unser zweiter Beitrag in der Entwicklung und Evaluierung eines neuen Konzeptes für F2F Overlays, basierenden auf den Erkenntnissen der vorangehenden Analyse. Insbesondere ergab sich in der vorangehenden Evaluation, dass Greedy Embeddings hoch-effiziente Kommunikation erlauben indem sie Teilnehmer durch Koordinaten adressieren und diese an die Struktur des Overlays anpassen. Jedoch sind Greedy Embeddings in ihrer ursprünglichen Form nicht auf anonyme Kommunikation mit einer dynamischen Teilnehmermengen und potentiellen Angreifern ausgelegt. Daher präsentieren wir ein Privätssphäre-schützenden Kommunikationsprotokoll für F2F Overlays, in dem die identifizierenden Koordinaten durch anonyme Adressen ersetzt werden. Des weiteren erhöhen wir die Resistenz der Kommunikation durch den Einsatz mehrerer Embeddings und alternativer Algorithmen zum Finden von Routen. Wir beweisen, dass unser Ansatz eine geringe Kommunikationskomplexität im Bezug auf die eigentliche Kommunikation sowie die Instandhaltung des Embeddings aufweist. Ferner zeigt unsere Simulationstudie, dass der Ansatz effiziente Kommunikation mit kurzen Antwortszeiten und geringer Instandhaltungskosten erreicht sowie den Einfluss von Ausfälle und Angriffe erfolgreich abschwächt. Unsere grundlegenden Ergebnisse eröffnen neue Möglichkeiten in der Entwicklung anonymer und zensurresistenter Anwendungen.