Recent algorithms for video coding achieve a high-quality transmission at moderate bit rates. On the other hand, those coders are very sensitive to transmission errors. Many research projects focus on methods to conceal such errors in the decoded video sequence. Motion compensated prediction is commonly used in video coding to achieve a high compression ratio. This thesis proposes an algorithm which uses the motion compensated prediction of a given video coder to predict a sequence of several complete frames, based on the last correctly decoded images, during a transmission interruption. The proposed algorithm is evaluated on a video coder which uses a dense motion field for motion compensation. A drawback of predicting lost fields is the perceived discontinuity when the decoder switches back from the prediction to a normal mode of operation. Various approaches to reduce this discontinuity are investigated.

Video coding standards such as H.264 AVC (Advanced Video Coding) rely on predictive coding to achieve high compression efficiency. Predictive coding consists of predicting each frame using preceding frames. However, predictive coding incurs a cost when transmitting over unreliable networks: frames are no longer independent and the loss of data in one frame may affect future frames. In this thesis, we study the effectiveness of Flexible Macroblock Ordering (FMO) in mitigating the effect of errors on the decoded video and propose solutions to improve the error concealment on H.264 decoders. After introducing the subject matter, we present the H.264 profiles and briefly determine their intended applications. Then we describe FMO and justify its usefulness for transmission over lossy networks. More precisely, we study the cost in terms of overheads and the improvements it offers in visual quality for damaged video frames. The unavailability of FMO in most H.264 profiles leads us to design a lossless FMO removal scheme, which allows the playback of FMO-encoded video on non FMO-compliant decoders. Then, we describe the process of removing the FMO structure but also underline some limitations that prevent the application of the scheme. Finally, we assess the induced overheads and propose a model to predict these overheads when FMO Type 1 is employed. Eventually, we develop a new error concealment method to enhance video quality without relying on channel feedback. This method is shown to be superior to existing methods, including those from the JM reference software and can be applied to compensate for the limitations of the scheme proposed FMO-removal scheme. After introducing our new method, we evaluate its performance and compare it to some classical algorithms.

Most cases of lung cancer have a commonly-understood behavioral etiology. Thus, individuals with lung cancer are often blamed for their illness by others and may therefore seek to avoid this blame by concealing their diagnosis from others. This study sought to determine the prevalence of diagnosis concealment, examine potential predictors of concealment, and test parts of a cognitive-affective-behavioral model of the effects of concealing a concealable stigma among individuals receiving treatment for lung cancer. With regard to predictors of concealment, it was hypothesized that concealment would be positively associated with male gender, introversion, and trait social anxiety and would be negatively associated with social support and the use of seeking guidance and support as a coping strategy. Hypothesized correlates of concealment included poorer self-esteem as well as greater anxiety, cancer-specific distress, and social avoidance. A sample of 117 participants receiving chemotherapy or radiation for stage I-IV non-small cell lung cancer and limited to extensive stage small cell lung cancer was recruited during routine outpatient visits. A medical chart review was conducted to assess clinical factors and participants completed a standard demographic questionnaire as well as measures of coping strategies, introversion, trait social anxiety, social avoidance, social support, anxiety, depression, cancer-specific distress, self-esteem, perceived stigma, public self-consciousness, and private self-consciousness. Results indicated that 31% of participants concealed their diagnosis from others since their diagnosis and 26% concealed their diagnosis in the month preceding their participation in the study. Hypotheses regarding predictors and correlates of concealment were not supported. However, exploratory analyses identified use of alcohol, recency of a recurrence of lung cancer, use of positive reappraisal as a coping strategy, and social support as predictors of concealment as well as internalized shame as a correlate of concealment. These findings serve to extend existing literature on concealing a concealable stigma and support parts of an existing model on the effects of concealment. Future research should aim to test the impacts of concealment in the context of certain social situations to examine longitudinal relationships between predictors and consequences of concealment.

The aim of this study was to examine sex workers openness in regards to sex sale when communicating with other people and authorities. The essential questions that laid the foundation of this research were different factors that influence an individual on their choice of openness and concealment of their experiences, and also how they cope with the consequences of this. The results of this study are based on qualitative interviews conducted with five sex workers. The theoretical framework used to analyze the study’s findings is Erving Goffman’s theory of Stigma and Dramaturgical metaphor. The results indicate that sex workers experience difficulties with being open with other entities, including relationships and authorities. The underlying factors behind this appear to be among other things, based on current laws and social stigma in the society. Sex workers experiences of openness to people in their environment have been both positive and negative. Nevertheless, they have mostly been met with prejudices and dislikes. This signifies that many sex workers feel compelled to withhold and conceal their experiences to others. Our findings also show that sex workers use different strategies when coping with concealment of sex sale, which can have an emotional distress for some individuals.

A covert communications network (CCN) is a connected, overlay peer-to-peer network used to support communications within a group in which the survival of the group depends on the confidentiality and anonymity of communications, on concealment of participation in the network to both other members of the group and external eavesdroppers, and finally on resilience against disconnection. In this dissertation, we describe the challenges and requirements for such a system. We consider the topologies of resilient covert communications networks that: (1) minimize the impact on the network in the event of a subverted node; and (2) maximize the connectivity of the survivor network with the removal of the subverted node and its closed neighborhood. We analyze the properties of resilient covert networks, propose measurements for determining the suitability of a topology for use in a covert communication network, and determine the properties of an optimal covert network topology. We analyze multiple topologies and identify two constructions that are capable of generating optimal topologies. We then extend these constructions to produce near-optimal topologies that can “grow” as new nodes join the network. We also address protocols for membership management and routing. Finally, we describe the architecture of a prototype system for instantiating a CCN.

Video transmission over noisy wireless channels leads to errors on video, which degrades the visual quality notably and makes error concealment an indispensable job. In the literature, there are several error concealment techniques based on estimating the lost parts of the video from the available data. Utilization of data hiding for this problem, which seems to be an alternative of predicting the lost data, provides a reserve information about the video to the receiver while unchanging the transmitted bit-stream syntax / hence, improves the reconstruction video quality without significant extra channel utilization. A complete error resilient video transmission codec is proposed, utilizing imperceptible embedded information for combined detecting, resynchronization and reconstruction of the errors and lost data. The data, which is imperceptibly embedded into the video itself at the encoder, is extracted from the video at the decoder side to be utilized in error concealment. A spatial domain error recovery technique, which hides edge orientation information of a block, and a resynchronization technique, which embeds bit length of a block into other blocks are combined, as well as some parity information about the hidden data, to conceal channel errors on intra-coded frames of a video sequence. The errors on inter-coded frames are basically recovered by hiding motion vector information along with a checksum into the next frames. The simulation results show that the proposed approach performs superior to conventional approaches for concealing the errors in binary symmetric channels, especially for higher bit rates and error rates.

A gap in the literature exists regarding the chemical effects of household acids at different concentrations on restored and non-restored dentition. The present study examines the effects of household corrosive products on human dentition. A total of 105 adult teeth consisting of restorations composed of silver amalgam, porcelain-fused-to-metal crowns, and teeth lacking restorative material were used. The household products utilized were hydrochloric acid (Clorox® Bleach Cleaner and The Works® Toilet Bowl Cleaner) and sulfuric acid (Drano® Drain Opener and Watchdog® Battery Acid), along with one control base (Biz® Detergent). Teeth were radiographed before and after exposure to the products and were removed from the solutions after 1, 2, 4, 8, 24, 72, 120 and 264 hours. Documentation included weight, mesiodistal and buccolingual crown measurements, ordinal scoring of alterations, and photography. The results indicate 86% of the teeth could be positively identified by radiographs after exposure. Hydrochloric acid had the most destructive effects to teeth without restorations and those with silver amalgam restorations but had a minimal effect on the porcelain-fused-to-metal samples. Sulfuric acid minimally altered the restored teeth and deteriorated some parts of the enamel and dentin of the non-restored samples. Exposure to the detergent resulted in no change. A logistic regression analysis was conducted to determine if there was statistical relevance in acid type, acid concentration, and the type of restoration of the tooth. Results indicate that acid type, acid concentration and the type of restoration are all statistically relevant for positively identifying an individual through radiographs. The results of this study demonstrate that various household corrosive substances can affect the morphology of teeth, and in some cases, destroy teeth, which could mask the identification of an individual. However, the porcelain-fused-to-metal crowns were minimally affected by corrosive agents and can therefore be used for positive identifications.

La thèse reconstitue un débat entre Hegel et Heidegger à partir de la question sur la constitution du sens. La thèse propose une notion méthodologique de la négativité, qui soutient qu’une détermination conceptuelle est caractérisée par le paradoxe d’être simultanément révélatrice et dissimulant. Le constituant d'un phénomène se dissimule en faveur de l’immédiateté du phénomène constitué. Le rapport de tension entre sens et concept, et donc la confrontation entre Hegel et Heidegger, découle de cette conception de la négativité. Car si elle suppose que le constituant du sens est latent, il faut clarifier comment cette dimension de latence peut être révélée et articulée. Et si la détermination conceptuelle dissimule ce qu'elle révèle, se pose la question si la pensée peut conscientiser et surmonter cette tension inhérente. La dimension latente du sens est-elle une dimension non-conceptuelle ou, à l'inverse, le non-conceptuel est-il incapable d’avoir une portée dans le domaine sémantique? / My thesis maps out a debate between Hegel and Heidegger starting from the question concerning the constitution of meaning. It proposes a methodological notion of negativity, according to which a conceptual determination is characterized by the paradox of being simultaneously revealing and concealing. In other words, the constituent of a phenomenon is concealed in the immediacy of the constituted phenomenon. The tension between meaning and concept, reflected in the dispute between Hegel and Heidegger, arises from this conception of negativity. If the constituent of meaning is latent, it is necessary to clarify how this dimension of latency can be revealed and articulated. And if every conceptual determination conceals what it reveals, the question arises whether thought can become aware of this inherent tension and overcome it. Is the latent dimension of meaning non-conceptual, or is the non-conceptual irrelevant in the semantic domain?

Deux écrivains : Gide et Mahfouz, deux visages, l’un occidental, français, l’autre oriental, égyptien d’origine, deux univers de littérature de réputation mondiale reliés dans notre étude par un seul thème : le silence. Diverses sont les similitudes qui se présentent à travers ce thème chez les deux écrivains et dans leurs œuvres. Mais nombreuses sont aussi les divergences. Quel que soit le cas, le thème du silence gidien et mahfouzien peut refléter l’autre visage de la parole, l’art qui consiste à faire taire la parole pour laisser parler le silence.Si le silence est semblable, en apparence, chez Gide et Mahfouz, il est différent quand il s’agit de descendre en détails dans le for intérieur de l’être humain aux prises avec ses évolutions dans des environnements socio-familiaux. La divergence, bien que liée à la situation familiale et sociale, provient aussi de l’éducation des romanciers qui expriment des attitudes personnelles à l’égard d’une incompréhension ou d’une injustice qu’ils ressentent, fruits de leurs propres conditions.Dans le cours de la vie, il y a des plaisirs et des tendres engagements. Certains personnages gidiens utilisent le silence comme un jeu pour marquer leur intelligence et leur pondération face à la course vers les désirs sensuels. Le silence auquel ils ont recours n’est pas l’aveu de leur erreur, mais il reflète une protestation intérieure capable de conduire à une situation de révolte à l’encontre de diverses situations familiales ou sociales.Quant à Mahfouz, qui est avant tout un écrivain réaliste, le silence se présente comme une réalité qui s’impose à la plupart de ses personnages, surtout féminins, une réalité volontairement acceptée et amèrement admise. Dans La Trilogie, les personnages obéissent non seulement par connivence aux règles imposées, mais ils s’arrangent aussi entre eux, dans la plupart des cas, pour que le silence réponde aux conditions familiales et sociales afin de régner obligatoirement. / Two writers: Gide and Mahfouz, two faces, one western and French, the other Eastern and Egyptian of origin, two universes of literature of world reputation connected in our study by a single theme: silence. There are various similarities in the two writers and in their works. But there are also many divergences. Whatever the case, the theme of Gidian silence and Mahfouzain can reflect the other face of speech, the art of silencing speech to make the silence speak.If the silence is similar, in appearance, with Gide and Mahfouz, is different when it is a question to going down into details in the inner-self of the human being struggling with his evolutions in socio-familial environments. The divergence, although related to the family and social situation, also comes from the education of novelists, who express personal attitudes towards a misunderstanding or an injustice they feel, fruits of their own conditions.In the course of life, there are pleasures and tender engagements. Some Gidean’s characters use silence as a game to mark their intelligence and their weight in face of the race towards sensual desires. The silence they use is not the admission of their error, but it reflects an inner protest capable of leading to a situation of revolt against various family or social situations.As for Mahfouz, who is above all a realistic writer of Eastern tradition, silence presents itself as a reality which imposes itself on most of his characters, especially feminine, a reality that is deliberately accepted and bitterly admitted. In the Trilogy, the characters not only obey the imposed rules, but they also arrange themselves, in most cases, so that silence responds to family and social conditions in order to rule.

Port-knocking is a security mechanism used in computer systems to hide available network services. Its operation relies on a drop policy firewall setting in order to make impossible for port-scanning attacks to occur. This project researches the impact of implementing such a software solution. Furthermore, it looks into the behavior of three chosen implementations and make conclusions on the benefits and disadvantages that they bring. In addition, the surrounding implications related to both user and administrator are explored. This thesis includes tests on the resource consumption of the implementations as well as records of the added delay of using the mechanism when initiating a SSH session. There has not been such research performed in this field and the results of it could be beneficial to those who are involved in computer science and network security in particular. Finally, the product of this study state that port-knocking is overlooked and has great benefits in preventing zero-day exploits and hacker tools relying on exposed network services.