This thesis studies the impact of mobility and wireless channel characteristics, i. e. , variability and high bit-error-rate, on the performance of integrated voice and data wireless systems from network, transport protocol and application perspectives. <br /><br /> From the network perspective, we study the impact of user mobility on radio resource allocation. The goal is to design resource allocation mechanisms that provide seamless mobility for voice calls while being fair to data calls. In particular, we develop a distributed admission control for a general integrated voice and data wireless system. We model the number of active calls in a cell of the network as a Gaussian process with time-dependent mean and variance. The Gaussian model is updated periodically using the information obtained from neighboring cells about their load conditions. We show that the proposed scheme guarantees a prespecified dropping probability for voice calls while being fair to data calls. Furthermore, the scheme is stable, insensitive to user mobility process and robust to load variations. <br /><br /> From the transport protocol perspective, we study the impact of wireless channel variations and rate scheduling on the performance of elastic data traffic carried by TCP. We explore cross-layer optimization of the rate adaptation feature of cellular networks to optimize TCP throughput. We propose a TCP-aware scheduler that switches between two rates as a function of TCP sending rate. We develop a fluid model of the steady-state TCP behavior for such a system and derive analytical expressions for TCP throughput that explicitly account for rate variability as well as the dependency between the scheduler and TCP. The model is used to choose RF layer parameters that, in conjunction with the TCP-aware scheduler, improve long-term TCP throughput in wireless networks. A distinctive feature of our model is its ability to capture variability of round-trip-time, channel rate and packet error probability inherent to wireless communications. <br /><br /> From the application perspective, we study the performance of wireless messaging systems. Two popular wireless applications, the short messaging service and multimedia messaging service are considered. We develop a mathematical model to evaluate the performance of these systems taking into consideration the fact that each message tolerates only a limited amount of waiting time in the system. Using the model, closed-form expressions for critical performance parameters such as message loss, message delay and expiry probability are derived. Furthermore, a simple algorithm is presented to find the optimal temporary storage size that minimizes message delay for a given set of system parameters.

<p>Background: Obesity is the number one health risk facing Americans. The obesity epidemic in America is attributed to physical inactivity, unhealthy food choices, and excessive food intake. Structured weight loss programs have been successful in initiating behavior change and weight loss; however, weight is almost always regained over time. The rate of weight gain is highest immediately after cessation of a structured weight loss program. Thus, effective interventions are needed that can successfully be used following a structured weight loss program to sustain weight loss and prevent weight relapse. Due to low cost, ubiquity, and ease of use, healthcare communicated through mobile technology, or "mHealth", may be able to serve as an effective medium to reach a large number of people to facilitate weight loss behaviors. Short message service (SMS), also known as text messaging, is easy to use, ubiquitous, affordable, and can target people directly where they are regardless of geographic location, socioeconomic status, or demographic factors. A review of the literature demonstrated limited information regarding message content, timing and frequency of message delivery and only 3 of 14 SMS-related interventions reviewed demonstrated a statistically significant effect on weight loss, diet or exercise. Additionally, information on how to integrate and leverage SMS as a health promotion tool for weight loss was also limited in the literature.</p><p>The Behavior Change Process model was used as a guide to understand how to develop an intervention to help people sustain recent weight loss. Furthermore, research suggests interventions that target and frame messages about how people reach goals in their life through either a prevention or promotion focus may be beneficial at motivating people to self-regulate and sustain recent behavioral changes. The goal of this study was to design an intervention that would help people stay in the continued response phase of the Behavior Change Process and help prevent weight relapse. Using the Behavior Change Process and regulatory focus theory, an intervention was developed that leveraged short message service (SMS) to deliver messages to people who have recently lost weight in attempt to help them sustain weight loss and prevent relapse.</p><p>Methods: First, a pilot study was conducted to inform the development of a SMS software application, the development of message content and the frequency and timing of message delivery. Second, an exploratory 3-arm mixed methods randomized controlled trial was conducted to test the feasibility, acceptability, perception of the usefulness, and efficacy of a weight loss sustaining mHealth SMS intervention among people with obesity. Participants (N=120) were randomized to a promotion message group, a prevention message group, or an attention-control general health message group. Participants completed baseline assessments, and reported their weight at 1 and 3 months post-baseline to assess efficacy of the intervention on sustaining weight loss. In addition, participants partook in a phone interview follow completion of the intervention to assess acceptability and usefulness. </p><p>Results: Participants found the message content and intervention acceptable and a majority perceived value in receiving messages via SMS that promote weight loss sustaining behaviors. Interview data implied that the intervention served as a reminder and daily cue to action. Participants were favorable towards receiving a daily reminder, which they noted helped them to stay focused, and in some cases to keep them motivated to continue losing weight. And a majority, 42 (91%) who participated in a telephone interview said that they preferred to get messages on their cell phone due to accessibility and convenience. A minimum of one message per day delivered at approximately 8:00 A.M. was deemed the optimal delivery time and frequency. This was particularly true for weight loss, which many participants reported as a daily struggle that begins every morning. With regards to sustaining weight loss, there was a statistical trend in sustained weight loss at months 1 and 3 in the promotion and prevention framed message groups compared to the control group in both the intent-to-treat and evaluable case analyses. Clinically, there was a significant decrease in mean weight of approximately 5 pounds at month 3 in the promotion and prevention groups compared to the control. Additionally, effect sizes indicated a large effect of the intervention on sustaining weight loss in the promotion and prevention groups relative to the control group.</p><p>Conclusion: Overall results showed that at the continued response phase of the behavioral change process, it was feasible to design an application to deliver promotion and prevention framed weight loss sustaining messages. In particular, prevention framed messages may have been more useful in helping participants sustain weight loss. Though there was less than 80% power to detect a statistically significant difference, the observed effect sizes in this study were significant and demonstrated a large effect of the promotion and prevention interventions on sustaining weight loss relative to control. Furthermore, there was a clinically significant increase in mean weight loss and in the number of people who sustained weight loss in the promotion and prevention intervention groups compared to control.</p><p>These findings may serve as a reference for future interventions designed to help people thwart relapse and transition from a state of sustaining recent weight loss behaviors to a state of maintenance. Technological tools such as this SMS intervention that are constructed and guided by evidence-based content and theoretical constructs show promise in helping people sustain healthy behaviors that can lead to improved health outcomes.</p> / Dissertation

Nowadays, the internet is an unseperatable part of human life and instant messaging software becomes an important role of communication channel. There are 40 million global IM registration popularity who use IM and billions of messages are sent everyday. In Taiwan, there are 6.5 million registration popularity and IM is the third important internet appilication, besides WWW and e-mail. As IM has become more and more important, there was few academic researchs published. We investigated consumer IM adoption behavior by focus group interview and structural equation model analysis. After holding a focus group interview, some antecedent of adopting IM was found out. Then we integrated technology acceptance model with media richness, computer self-efficacy and subjective norm as the antecedents of perceived usefulness(PU) and perceived ease of use(PEU) and analysised this structural equation model with LISREL. We found that subjective norm is an antecedent of PU, media richness and computer self-efficacy are PEU¡¦s antecedents. Finally, we made some suggestion for practice and other researchers base on the result.

Instant Messaging ¡]IM¡^ has becomes an important tool of communication. Currently, eighty percent of the Internet users use IM to communicate each other. This study uses the dimensions of performance expectancy and effort expectancy of the Unified Theory of Acceptance and Use of Technology and the interpersonal communication need to investigate factors that influence IM acceptance. There are 211 completed questionnaires were returned and analyzed. It¡¦s found that performance expectancy, effort expectancy, and interpersonal communication show significantly positive and significant impacts on IM users¡¦ intention. The intention significantly and positively affects their IM usage. According to the results, it¡¦s suggestted that IM software should make the IM more user-friendly and the software interface is not too complicated, so that users might feel that IM software is easy to use.

Since 1993 The US government took the lead to propose the ¡§National Information Infrastructure, (NII)¡¨ plan, many countries started to establish the electronic government to provide the populace with innovation services.. The services of electronic government have to evolve from ¡§Do Government Better¡¨ into ¡§Do Better Government¡¨. Now the network has evolved into a new generation that emphasizes on users co-constructing the cyber contents - Web 2.0. Could Web 2.0 be applied to the web services of the electronic government? How should the electronic government provide the innovation services by using Web 2.0? What are the Web 2.0 services provided by the local government in Taiwan? The above questions are the key points of this research. This research was based on the web service type of government and the mature application of Web 2.0 to establish 4 categories (Blog, Instant Messaging, Podcast and RSS) and 17 indicators to construct questionnaire, and review local government web services in Taiwan. This research used the census method to observe 25 local government website by the researcher during 2008/4/7~2008/4/9. Also the all 25 local government website administrators in Taiwan completed the questionnaire separately during 2008/4/21~2008/5/13. According to the research results, that Web 2.0 services on Taiwan local government were: (1) the primary service provided by local government is automatic information service, (2) the online multimedia playing service is getting mature gradually, (3) the web call is the main online intercommunication service, (4) the concepts of blog service has not established yet, (5)there are many problems to surmount for advancing Web 2.0 Services, such as the definitions of Web 2.0 Services, the doubts of information security etc.. Overall, Web 2.0 for local government online services is still at beginning stage in Taiwan. Besides this research provides the following suggestions about Web 2.0 innovations for government services online: (1) to establish the better understanding of Web 2.0 Services, (2) to develop guidelines of Web 2.0 services and evaluation criteria, (3) to provide financial motivation and technical support.

Obesity has been described as a global health crisis due to the rapid increases seen worldwide (Whitlock et al., 2005; Harris et al., 2009; Yetter, 2009). The consequences of obesity are far-reaching and include the physiological and psychological implications for obese individuals, as well as the financial impact it has on both the individual and national health care. Children, especially those of minority ethnic background and lower socioeconomic status, are at increased risk for developing obesity (Yetter, 2009; Veldhuis et al., 2009). Intervention programs targeting underlying causes of childhood obesity have been developed, but little consistent success has been achieved (Summerbell et al., 2005; Sherry, 2005). One factor that could be influencing the lack of success is the stigmatization that can be felt by children taking part in intervention programs. Furthermore, many programs have targeted behavior change without determining underlying attitudes about behaviors. It is critical that effective obesity intervention programs be developed for children at high risk of developing obesity. This study used indirect messaging to address health issues related to overweight and obesity in children. An education program about animal health was presented to two groups of eight and nine year old children. The program included a combination of classroom instruction and practical application both in the classroom and at the Palm Beach Zoo with real animals. The children's attitude, knowledge, and practice of healthy behavior was measured before and after exposure to the program to evaluate its effect. It was hypothesized that learning about what being healthy entails for animals will have positive implications for the children's own health. It was found that children who participated in this study were already knowledgeable about healthy behaviors and also had overall positive attitudes towards health. However, they did not have high levels of health behavior practices. Participation in the program did not significantly improve the knowledge, attitudes, or practice of health behavior in the children. Zoos should consider designing program that specifically target increasing the practice of health behaviors in children.

Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme (Fakultaet fuer Informatik) der TU Chemnitz. Workshop-Thema: Infrastruktur der ¨Digitalen Universitaet¨ Zur unmittelbaren Kommunikation zweier oder mehrerer Kommunikationspartner werden heute sogenannte Instant Messaging Systeme eingesetzt. Der Vortrag zeigt zwei moegliche Ansaetze fuer ein Protokoll, das diese Art von Kommunikation bewerkstelligen kann. Zum einen handelt es sich um das Protokoll einer freien Implementierung eines IM Systems, Jabber. Zum anderen ist dies das Protokoll eines im Rahmen einer Diplomarbeit an der Fakultaet fuer Informatik entstandenen IM Systems, Locom.

Gemeinsamer Workshop von Universitaetsrechenzentrum und Professur Rechnernetze und verteilte Systeme der Fakultaet fuer Informatik der TU Chemnitz. Jabber ist eine XML basierte Instant Messaging und Präsenz-Management Lösung. Dieser Vortrag beinhaltet einen Überblick über die grundlegenden Konzepte von Instant Messaging, die Betrachtung von Jabber, als IM-Alternative, die Dienste, die auf dem Jabber-Protokoll aufbauen und das Phänomen X-Internet, als Webdienstplattform.

Workshop "Netz- und Service-Infrastrukturen" In dem Vortrag wird der Instant-Messaging-Dienst Jabber eingeführt. Neben dem Vergleich mit anderen Diensten dieser Art werden im Besonderen das Adressierungsschema, der Ablauf einer Kommunikation und das Zusammenspiel mit anderen Diensten erläutert.

Instant Messaging besitzt zweifelsohne eine sehr gro&szlig;e Zukunft. Es ist vergleichbar mit dem Short Message Service (SMS), der einen sehr gro&szlig;en Stellenwert im Mobilfunk hat. Neben der f&uuml;r SMS charakteristischen schnellen &Uuml;bermittlung von Textnachrichten bietet Instant Messaging weitere Vorteile: es ist f&uuml;r den Sender auf den ersten Blick ersichtlich, ob der Gespr&auml;chspartner f&uuml;r eine Kommunikation zur Verf&uuml;gung steht. Neben Textnachrichten k&ouml;nnen aber auch Informationen wie Bilder, Videos oder andere Formate &uuml;bermittelt werden. <br> <br> Auch f&uuml;r Organisationen ist ein Einsatz von Instant Messaging sehr interessant. Besonders in diesem Zusammenhang spielt die Sicherheit eine sehr wichtige Rolle. Daher besch&auml;ftigt sich diese Diplomarbeit vorrangig mit Instant Messaging-Systemen hinsichtlich der Prinzipien der Systemsicherheit wie Integrit&auml;t, Vertraulichkeit und Verf&uuml;gbarkeit. <br> <br> Ein weiterer Aspekt ist das Fehlen eines standardisierten Instant Messaging-Protokolls. Viele Anbieter von Instant Messaging-Systemen halten ihr System f&uuml;r das Beste und versuchen, soviele Kunden wie m&ouml;glich an sich zu binden. Daher befasst sich diese Diplomarbeit ebenfalls mit den verbreitetsten Instant Messaging-Systemen, um deren Vor- und Nachteile herauszukristallisieren. Im Weiteren wird die Funktionsweise der Protokolle erkl&auml;rt. <br> <br> Gerade im privaten Bereich spielen Konferenzsysteme (&quot;Chat&quot;) eine wichtige Rolle. Neben den Instant Messaging-Systemen wird auch diese M&ouml;glichkeit der Kommunikation beleuchtet. <br> <br> Diese Diplomarbeit wird vom Bundesamt f&uuml;r Sicherheit in der Informationstechnik (BSI), Referat &quot;IT-Sicherheitsmanagement und IT-Grundschutz&quot; betreut.