Teses / dissertações sobre o tema "Message losses"

Cette thèse se penche sur les systèmes distribués tolérants les pannes, et s'intéresse plus particulièrement au problème de la diffusion fiable dans des environnements asynchrones sujets à des défaillances hybrides. Elle introduit un nouveau modèle de calcul combinant des défaillances byzantines de processus avec un adversaire de messages. Elle définit ensuite l'abstraction de Diffusion Fiable Byzantine Tolérante aux Adversaires de Messages (MBRB) et prouve sa condition de résilience optimale. Elle propose enfin trois algorithmes clés pour réaliser cette abstraction : un algorithme MBRB simple basé sur les signatures, une nouvelle primitive appelée k2l-cast pour des implémentations MBRB sans cryptographie, et un algorithme MBRB basé sur les codes correcteurs d'erreurs optimisant la complexité de communication. Ces contributions font progresser la compréhension des systèmes distribués tolérants les pannes, et participent aux fondations nécessaires à la conception d'algorithmes répartis résilients et efficaces, avec des applications dans les infrastructures critiques, les systèmes financiers et les technologies blockchain
This thesis explores fault-tolerant distributed systems. It focuses more specifically on implementing reliable broadcast in asynchronous environments prone to hybrid failures. We introduce a novel computing model combining Byzantine process failures with a message adversary. We then define the Message-Adversary-tolerant Byzantine Reliable Broadcast (MBRB) abstraction and prove its optimal resilience condition. We present three key algorithms implementing this abstraction: a simple signature-based MBRB algorithm, a new primitive called k2l-cast for cryptography-free MBRB implementations, and an erasure-coding-based MBRB algorithm optimizing communication complexity. These contributions advance the understanding of fault-tolerant distributed systems and provide a foundation for designing resilient and efficient distributed algorithms, with applications in critical infrastructures, financial systems, and blockchain technologies

In this thesis we investigated whether using compression when sending inter-process communication (IPC) messages can be beneficial or not. A literature study on lossless compression resulted in a compilation of algorithms and techniques. Using this compilation, the algorithms LZO, LZFX, LZW, LZMA, bzip2 and LZ4 were selected to be integrated into LINX as an extra layer to support lossless message compression. The testing involved sending messages with real telecom data between two nodes on a dedicated network, with different network configurations and message sizes. To calculate the effective throughput for each algorithm, the round-trip time was measured. We concluded that the fastest algorithms, i.e. LZ4, LZO and LZFX, were most efficient in our tests.
I detta examensarbete har vi undersökt huruvida komprimering av meddelanden för interprocesskommunikation (IPC) kan vara fördelaktigt. En litteraturstudie om förlustfri komprimering resulterade i en sammanställning av algoritmer och tekniker. Från den här sammanställningen utsågs algoritmerna LZO, LZFX, LZW, LZMA, bzip2 och LZ4 för integrering i LINX som ett extra lager för att stödja komprimering av meddelanden. Algoritmerna testades genom att skicka meddelanden innehållande riktig telekom-data mellan två noder på ett dedikerat nätverk. Detta gjordes med olika nätverksinställningar samt storlekar på meddelandena. Den effektiva nätverksgenomströmningen räknades ut för varje algoritm genom att mäta omloppstiden. Resultatet visade att de snabbaste algoritmerna, alltså LZ4, LZO och LZFX, var effektivast i våra tester.

Vehicular ad-hoc networks (VANETs) are used for vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications. The IEEE 802.11p/WAVE (Wireless Access in Vehicular Environment) and with WAVE Short Messaging Protocol (WSMP) has been proposed as the standard protocol for designing applications for VANETs. This communication protocol must be thoroughly tested before reliable and efficient applications can be built using its protocols. In this paper, we perform on-road experiments in a variety of scenarios to evaluate the performance of the standard. We use commercial VANET devices with 802.11p/WAVE compliant chipsets for both BSM (basic safety messages) as well as video streaming applications using WSMP as a communication protocol. We show that while the standard performs well for BSM application in lightly loaded conditions, the performance becomes inferior when traffic and other performance metric increases. Furthermore, we also show that the standard is not suitable for video streaming due to the bursty nature of traffic and the bandwidth throttling, which is a major shortcoming for V2X applications.

Short message service (SMS) message compression allows either more content to be fitted into a single message or fewer individual messages to be sent as part of a concatenated (or long) message. While essentially only dealing with plain text, many of the more popular compression methods do not bring about a massive reduction in size for short messages. The Global System for Mobile communications (GSM) specification suggests that untrained Huffman encoding is the only required compression scheme for SMS messaging, yet support for SMS compression is still not widely available on current handsets. This research shows that Huffman encoding might actually increase the size of very short messages and only modestly reduce the size of longer messages. While Huffman encoding yields better results for larger text sizes, handset users do not usually write very large messages consisting of thousands of characters. Instead, an alternative compression method called lossy dictionary-based (LD-based) compression is proposed here. In terms of this method, the coder uses a dictionary tuned to the most frequently used English words and economically encodes white space. The encoding is lossy in that the original case is not preserved; instead, the resulting output is all lower case, a loss that might be acceptable to most users. The LD-based method has been shown to outperform Huffman encoding for the text sizes typically used when writing SMS messages, reducing the size of even very short messages and even, for instance, cutting a long message down from five to two parts. Keywords: SMS, text compression, lossy compression, dictionary compression

Weight loss programs for women are on the rise, including both face to face and online programs. However, current research is limited on the process measures and content which produce adherence and the largest outcomes. With obesity on the rise in the United States, it is important to understand out health coaches can strengthen their programs to better support the obese population in their weight loss journey. The purpose of this pilot study was to develop and test the acceptability of text message nudges among women participating in an online weight loss program; determine how dose may be associated with weight loss outcomes; and to test how goal setting text messaging nudges improve percent body weight loss among women participating in an online weight loss program. It was found that the implementation of text message nudges did not provide enough to continue to improve and extend the program to be more successful. However, qualitative data was recorded and found to provide helpful insight into what content was preferred by the participants.

As the leading cause of death in the United States, coronary heart disease (CHD) is a growing public health problem, despite the fact that many risk factors for the disease are preventable, especially if addressed early in life. The purpose of the current study was to examine the effects of loss-framed versus gain-framed versus information-only health messages on both intention to attend and actual attendance at an appointment to get screened for CHD risk factors (i.e., hypertension, diabetes, and dyslipidemia). It was hypothesized that a population of young adults would be more likely to view screening for CHD risk factors as a low-risk, health-affirming behavior as opposed to a risky, illness-detecting behavior and would thus be more strongly influenced by gain-framed messages than loss-framed messages. Additional goals included the exploration of the extensively researched individual health beliefs of perceived threat (as defined by the health belief model) and health locus of control as they relate to message frames. One hundred forty-three undergraduate students were randomly assigned to either the loss-framed, gain-framed, or information-only control conditions. Framing manipulation checks revealed that participants failed to discern differences in the tone and emphasis of the experimental pamphlets. As a result, no tests of framing effects could be conducted. Sixteen (11.2%) of the 143 participants who participated in Part 1 of the experiment participated in Part 2 (i.e., attended a risk factor screening appointment). Multiple regression analysis revealed risk index, age, and powerful others health locus of control as significant predictors of screening intention. Gender was the only demographic or health related variable that was significantly related to screening outcome, such that women were more likely to get screened than men. Limitations and recommendations are discussed.

Over the course of last decade, the demand for VoIP (Voice over Internet Protocol) applications has increased significantly among enterprises and individuals due to its low cost. This increasing demand resulted in a significant increase in users who require reliable VoIP communication systems. QoS (Quality of Service) is a major issue in VoIP implementation and is a method to impel the development of real-time multimedia services like VoIP and videoconferencing. However, there are certain challenges in achieving QoS for VoIP application, which need special attentions; like latency and packet loss. The VoIP servers which are functioning on single core software/hardware model have high latency and packet loss issues due to their limited processing bandwidth. A multicore software/hardware model is the solution to cope up with the increasing demands of VoIP and yet an active research area in telecommunication. Using a multicore software/hardware model for VoIP has several challenges, one of the challenges is to design and implement QoS Benchmarking module for VoIP client and server on multicore. In this thesis the focus is on latency and packet loss of SIP messages on OpenSIPS server. This is done by performing stress testing for QoS benchmarking, where delay and call drop rate is calculated for SIP (Session Initiation Protocol) signaling messages on parallel VoIP client server model. The model is built in C for multicore and is used as a simulation tool. SIP is widely deployed protocol for call establishment, maintenance and termination in VoIP.

Les protocoles de communication asynchrones sont naturellement modélisés par des automates communicants via des canaux FIFO non bornés. Dans cette thèse nous nous intéressons aux variantes des Lossy Channel Systems pour lesquelles les pertes de messages dans les canaux sont probabilistes. Plus précisément, on considère des sémantiques sous forme de chaînes de Markov et de processus de décision markoviens. Un théorème général de convergence de points fixes dans les systèmes de transition bien structurés, permet de prouver pour les PLCS et NPLCS de nombreux résultats de décidabilité pour la vérification de propriétés du temps linéaire. Nous donnons également les limites des modèles par l'intermédiaire de résultats d'indécidabilité. Un prototype a fait l'objet de l'implémentation des algorithmes développés dans la thèse. Malgré la grande complexité des problèmes cet outil a permis de prouver des propriétés de vivacité sur des protocoles tels que le Bit Alterné et le protocole de Pachl.

Loss is a prominent theme in the works of American playwright Tennessee Williams (1911-1983). The four plays discussed in this study (The Glass Menagerie, A Streetcar Named Desire, Suddenly Last Summer and Cat on a Hot Tin Roof) illuminate aspects of an ethics of loss which advocates the acceptance of the integrity of the lost object leading to a dynamic of mourning rather than to a melancholic incorporation of a 'part object' as a result of an inability to acknowledge the loss and one's guilt resulting from one's contribution to the loss of the loved object. Thus, each of the four plays discussed presents conflicting narratives, when one is aiming to become the dominant through silencing other potential narratives as an avoidant manner of rejecting one’s feelings of guilt for the loss one has experienced. Amanda, Stanley, Mrs. Venable and Brick all struggle against validating narratives of loss differing from their own. At the same time, the unacknowledged losses of those marginalised by society (in these plays- homosexuals and 'mental patients') are given voice in those plays (often by the main character or one of the main characters). Theories by Sigmund Freud, Melanie Klein, Nicholas Abraham and Maria Torok addressing loss and incorporation as a result of a failure of mourning provide the psychoanalytic background to the literary analysis of the plays.

Thesis (MNutr)--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: Obesity has become one of the major conditions contributing towards chronic lifestyle diseases. The management of obesity, in order to prevent chronic lifestyle disease, requires a combination of treatment modalities. There is therefore a constant need to search for innovative behavioural and awareness programmes regarding the treatment of obesity, and to develop innovative strategies to improve compliance and ultimately to change lifestyles. The notion of utilizing short message services (SMS), during a weight reduction progamme to provide regular reminders and information to achieve the aforementioned goals, was therefore used as an intervention in the study. Furthermore a questionnaire validating the effectiveness of the short message service was devised and completed by the recipients of the intervention. The purpose of the questionnaire was to statistically quantify the effectiveness of the SMS as an intervention. Each question had four graded answers, with a score allocated to each - 1 being the least effective and 4 being the most. These values were converted to percentages and according to these percentages a rating of effectiveness was ascertained. Ultimately the study set out to determine whether the intervention had a statistically significant effect on weight reduction, compliance in attending appointments and on the attrition rate. This was a double blinded randomized, controlled study in which 75 participants were recruited at a general medical practice in Gauteng. The sample comprised of three groups. Group 1 (N = 25) had no intervention; Group 2 (N = 25) received a SMS weekly and Group 3 (N = 25) received a SMS three times per week. The weight reduction programme, which included dietary modifications and lifestyle advice was standardized and remained the same for each group. The programme extended over a 12 week period and the questionnaire was completed at the end of the programme. Upon analysis of the results there was a decrease in the mean BMI and waist circumference for all the three groups, with no statistically significant difference (p-value > 0.05) between them. The percentages of the participants completing the programme in each group were – Group 1: 44%, Group 2: 60% and Group 3: 68%. The effectiveness of the intervention was manifested by the compliance of attendance at each visit and the reduced attrition rate in the intervention groups, although this was not found to be statistically significant. The analysis of the scores allocated to the responses of the questionnaire, equated to an outcome of above 75% and was assessed as being very successful in both the intervention groups. In conclusion the use of short message servicing in this weight reduction programme improved the compliance and reduced the attrition rate although not statistically and was perceived by the participants as a successful intervention.
AFRIKAANSE OPSOMMING: Vetsug (obesiteit) het een van die primêre kondisies geword wat bydrae tot chroniese leefstyl siektes. Die hantering van obesiteit vereis 'n kombinasie van behandelingsmodaliteite, ten einde hierdie siektes te voorkom, Daar is dus 'n konstante soeke na innoverende gedrags- en bewustheidsprogramme rakende die behandeling van obesiteit, asook 'n behoefte om innoverende strategieë te ontwikkel om inskiklikheid te verbeter en uiteindelik leefstyle te verander. Die idee om kortboodskapdienste (SMS) gedurende 'n gewigsverliesprogramme te gebruik om gereelde aanmanings en inligting te kommunikeer ten einde die genoemde doelwitte te bereik, is aangewend as intervensie in hierdie studie. 'n Vraelys is ontwikkel wat die effektiwiteit van die kortboodskapdiens valideer, en is voltooi deur die ontvangers van die intervensie. Die doel van die vraelys was om die effektiwiteit van die SMS as 'n intervensie te kwantifiseer. Elke vraag het vier gegradeerde antwoorde gehad, met 'n telling wat aan elk toegeken is – 1 wat aandui minste effektief en 4 wat aandui die meeste. Hierdie waardes was omgeskakel tot persentasies en na aanleiding van die persentasies is 'n waarde van effektiwiteit bepaal. Uiteindelik was die doel van die studie dus om vas te stel of die intervensie ʼn statisties beduidende effek op gewigsverlies, die nakom van afsprake en uitvalskoerse het. Hierdie was 'n dubbelblind, ewekansige gekontroleerde studie waarin 75 deelnemers gewerf was by 'n algemene mediese praktyk in Gauteng. Die steekproef het bestaan uit 3 groepe. Groep 1 (N = 25) het geen intervensie gehad nie; Groep 2 (N = 25) het 'n weeklikse SMS ontvang en Groep 3 (N = 25) het 'n SMS ontvang drie keer per week. Die gewigsverliesprogramme, wat dieetaanpassings en leefstyl advies ingesluit het, was gestandardiseer en het dieselfde gebly vir elke groep. Die programme het gestrek oor 'n 12 weke periode en die vraelys was voltooi aan die einde van die programme. Analise van die resultate het 'n afname getoon in die gemiddelde LMI (Liggaamsmassa indeks) en middelomtrek vir al drie groepe, met geen statisties beduidende verskil (p-waarde > 0.05) tussen groepe nie. Die persentasies van die deelnemers wat die programme voltooi het in elke groep was Groep 1: 44%, Groep 2: 60% en Groep 3: 68%. Die effektiwiteit van die intervensie was gemanifesteer deur die inskiklikheid van bywoning tydens elke besoek en die verlaagde uitvalkoers in die intervensie groepe, alhoewel dit nie statisties beduidend was nie. 'n Analise van die tellings geallokeer aan die response tot die vraeslys, dui 'n uitkoms aan van bo 75% en was beskou as baie suksesvol in albei die intervensie groepe. Die gebruik van kortboodskapdienste (SMS) in hierdie gewigsverliesprogramme het inskiklikheid verbeter en uitvalskoerse verlaag, alhoewel nie statisties beduidend nie, en was deur die deelnemers beskou as 'n suksesvolle intervensie.

Thesis (M.A.)--Georgia State University, 2007.
Title from file title page. Cynthia Hoffner, committee chair; Yuki Fujioka, Holley Wilkin, committee members. Electronic text ( 81 p.) : digital, PDF file. Description based on contents viewed Nov. 8, 2007. Includes bibliographical references (p. 57-65).

The current research investigates how and why consumers' construal levels and the appeals framed either by gains or losses jointly influence persuasion. The findings across four experiments indicate that matching high-level construals with gain frames and low-level construals with loss frames leads to a) higher intentions to engage in cholesterol lowering behavior (experiment 1), b) more favorable brand attitudes (experiment 2), c) greater willingness to donate to an environmental organization (experiment 3), and d) higher buying intentions for a brand (experiment 4). It seems that these outcomes occur because matches between construal level and message frames encourage people to pay attention to the information they evaluate (experiments 1 ˜4), and this enhanced attention induces greater perceptions of processing fluency, which in turn leads to positive attitudes (experiments 2˜4). Further, this research demonstrates that an adequate amount of cognitive resources is required for this matching effect to occur (experiment 4). The current research contributes to the construal level, message framing, and matching literatures by unveiling the specific mechanism underlying the matching relationship between construal level and gain versus loss frames on persuasion and by identifying a boundary condition for it. This research also has managerial implications for marketing managers and policymakers in that it suggests a strategic way to use construal level and message frames to enhance marketing communication and advertising effectiveness.

The current PhD thesis aimed to cross-culturally investigate the effectiveness of gain- and loss-framed physical activity messages among the university students in Turkey and the UK. This study sought to test the impact of the physical activity messages focusing on stress-related effects on physical activity intentions, attitudes and behaviours of the target group. The messages were developed based on the findings of a series of preliminary studies targeting to determine the characteristics and needs of the target groups, and identify the barriers to engage in physical activity. Two quasi-experimental studies were conducted with 309 university students from the two countries (200 participants from Turkey and 109 participants from the UK) to test the effects of framed messages on intentions and attitudes towards physical activity, and physical activity behaviour change in two weeks after message exposure. Results showed that immediate effects of both gain- and loss-framed messages on physical activity intentions and attitudes were significant in Turkey and the UK. However, these effects could not be maintained in the two weeks following the message exposure. Moreover, the loss-framed message led to a message reactance in the UK, and physical activity intensity of the participants in the loss-framed group were significantly decreased compared to their baseline physical activity levels. The present study was the first message framing study comparing Turkey and the UK in terms of the impact of gain- and loss-framed framed physical activity messages. Therefore, this study contributes to the literature through providing evidence on the effects of message framing interventions which are developed and implemented in different cultures. Recommendations for future message framing research include measuring physical activity behaviour through objective methods, and examining the impact of the tailored messages through using different dissemination methods in larger samples.

This research examined cover blurbs on popular men’s and women’s magazines and the messages they communicate to their readers about women. The content analysis looked at the covers of Esquire, Gentlemen’s Quarterly, Vogue, and Good Housekeeping from 1999 through 2003 to see what these magazines were cultivating and framing through their cover text during the time surrounding the new millennium. The women’s magazines examined promoted gendered messages, messages encouraging an idealistic or unattainable ideal of women, to their readers more so than the men’s magazines researched. There also appeared to be an increase of gendered messages in the men’s and women’s magazine sample as a whole from 1999 through 2003. In order to counteract these findings and for progress to be made during the current millennium, individuals working within the communication field must realize the power of the written word and make efforts to discourage the presentation of gendered messages.

碩士
國立中正大學
資訊工程研究所
104
Data hiding techniques have been widely used to protect secret data by hiding the secret data into a multimedia file. These techniques are categories based on working domain, such as spatial domain, compressed domain and transform domain. In this thesis, proposed three reversible data hiding scheme, the first and second schemes are hiding secret information on the compressed domain, the third scheme is hiding secret information on the spatial domain. The first scheme presents an improved data hiding method, which employs LZW compression codes to embed secret information since it requires a very low computational cost. The second scheme presents an effective reversible data hiding (RDH) method in Absolute mean block truncation coding (AMBTC) compression code, which uses new joint neighborhood coding (JNC) to embed secret information. The third scheme presents an efficient RDH scheme that uses the AMBTC code and the difference between the original pixels and AMBTC decompression pixels to encrypt the original image and vacate more hiding spaces to embed secret information.