Today applications are often designed with a modular approach, dividing functionality into micro services rather than relying on a monolithic structure. This requires solutions for decoupled message exchange throughout the distributed system and can be achieved by implementing a message broker. In some cases, it is interesting to make the message broker itself a distributed system, which has been a development path for systems such as RabbitMQ, Apache Kafka, and others. This thesis seeks to understand the alternative approaches to implementing  a distributed solution for the message broker LavinMQ. To find out which algorithm would be the most suitable for this purpose, a comparative analysis of the most common alternatives was performed based on LavinMQ's requirements and a literature review of related comparisons. The results showed that Raft would be the best choice due to its simple but effective nature. To further investigate the consensus approach in LavinMQ, a Raft prototype was developed in the programming language Crystal. The prototype was then evaluated based on correctness and performance in terms of mean replication time and mean election time. The prototype successfully passed the correctness tests, showing that the prototype successfully achieves correctness according to LavinMQ standard. The mean election time results show that the prototype recovers from a leader failure in 216 ms and that the most effective range for the heartbeat timeout is 150 to 300 ms. The replication time test results show that the mean replication time is 84.45 ms and the most efficient interval for message replication is 0.13 ms. The performance results are consistent with the results of related work, however result in overall slower performance and indicate that some additional features and optimizations need to be implemented in order to consider the prototype for practical use.

This research investigated the effectiveness of in-vehicle information technologies on driver behavior in work zones. In-vehicle information devices can increase driver awareness to an oncoming change in traffic flow and provide specific guidelines for driving speed requirements, lane merging strategies, or unexpected changes in the roadway (e.g., detours and lane shifts). The overall conditional effects for vehicle speed are significant; that is, both the audio and visual groups out performed the control group within the simulated work zone. Participants in audio group did outperform the visual group, not significantly though. The overall conditional effects for total time in violation are significant; that is, both the audio and visual groups out performed the control group. The test session results for Total Time in Violation were statistically significant, F(2, 57) = 7.17, p ≤ .01. The strength of relationship between the warning messages and the Total Time in Violation with regular road signage, as assessed by η2 , was strong, the warning message factor accounting for 20% of the variance of the dependent variable.

Message passing has been the dominant parallel programming model in cluster computing, and libraries like Message Passing Interface (MPI) and Portable Virtual Machine (PVM) have proven their novelty and efficiency through numerous applications in diverse areas. However, as clusters of Symmetric Multi-Processor (SMP) and heterogeneous machines become popular, conventional message passing models must be adapted accordingly to support this new kind of clusters efficiently. In addition, Java programming language, with its features like object oriented architecture, platform independent bytecode, and native support for multithreading, makes it an alternative language for cluster computing. This research presents a new parallel programming model and a library called VCluster that implements this model on top of a Java Virtual Machine (JVM). The programming model is based on virtual migrating threads to support clusters of heterogeneous SMP machines efficiently. VCluster is implemented in 100% Java, utilizing the portability of Java to address the problems of heterogeneous machines. VCluster virtualizes computational and communication resources such as threads, computation states, and communication channels across multiple separate JVMs, which makes a mobile thread possible. Equipped with virtual migrating thread, it is feasible to balance the load of computing resources dynamically. Several large scale parallel applications have been developed using VCluster to compare the performance and usage of VCluster with other libraries. The results of the experiments show that VCluster makes it easier to develop multithreading parallel applications compared to conventional libraries like MPI. At the same time, the performance of VCluster is comparable to MPICH, a widely used MPI library, combined with popular threading libraries like POSIX Thread and OpenMP. In the next phase of our work, we implemented thread group and thread migration to demonstrate the feasibility of dynamic load balancing in VCluster. We carried out experiments to show that the load can be dynamically balanced in VCluster, resulting in a better performance. Thread group also makes it possible to implement collective communication functions between threads, which have been proved to be useful in process based libraries.

This study examines the relationship between television shows and their corresponding websites featuring interactive message boards looking at the motivations and gratifications that users cited as reasons for being connected to a program. Information found provides knowledge on why viewers are drawn to TV, and what rewards they gain from the actions they perform beyond viewing the show. Specifically, this study examines if viewing a television show and discussing it on an online message board created the gratification of a greater sense of emotional attachment with the show, and if this sense of heightened emotional connection encouraged the board user to take action or become involved in some other manner other than just viewing TV. A survey featuring Likert Scale and free response options in reference to the participants' television viewing and Internet usage habits was distributed to undergraduate students at the University of Central Florida, and also to the general population with an Internet survey. Information gained from this study will aid television producers and creators to better understand the habits of their message board audiences, and what actions could be taken to entice more viewers to view extra content in relation to the TV show, and how to get users to be more interactive with their product. By providing information about message boards' abilities to encourage emotion and action, more satisfying content can be created by the producers, and the users can gain a greater understanding of their media consumption.

The need for multiple access strategies arises whenever a number of users have to share a communication resource, since it is usually either cost prohibitive or impractical to dedicate a communication channel to a particular user. A need for such algorithms arises in many instances, particularly in applications utilizing wireless systems where all users access a common channel or medium. Such random access techniques as ALOHA and slotted ALOHA have been successfully implemented in a number of wireless applications. One of the major drawbacks of these algorithms is the necessity of a return path from the central station to each system user, which makes their use both inefficient and expensive for applications where one-way communication would suffice. For such applications, a need remained for a random access algorithm which can maximize the probability of successful message transmission in a one-way communication environment. A random access technique that addresses the above-mentioned need is developed. With this technique, each user sends an original message of predetermined length to a central receiver. The user then retransmits the message a specified number of times in a predetermined interval reserved for the retransmission process. The time interval between each successive retransmission of a given message is random. Assuming total annihilation of all colliding messages, the expression for the probability of successful transmission of a given message in terms of the major channel parameters is theoretically formulated. This technique offers a significant improvement, compared to a single transmission, in ensuring that a message is successfully received. The actual message collision dynamics in this system are experimentally studied using two different types of direct-sequence spread spectrum receivers, one employing a sliding correlator and the other using a matched filter. The spreading code in such systems offers extra protection for messages against possible interferers. The results indicate that it is often possible to properly receive a given message in the presence of co-channel interferers, thus significantly improving the overall system performance. These results are subsequently incorporated with the propagation data for several different types of microcells to arrive at a more precise theory of the link. / Ph. D.

Distributed real-time applications require support from the underlying middleware to meet the strict requirements for jitter, latency, and bandwidth. While most existing middleware standards such as MPI do not support Quality of Service (QoS), the MPI/RT standard supports QoS in addition to striving for high performance. This thesis presents HARE, the first known implementation of a subset of the MPI/RT 1.1 standard with time-driven QoS support. This thesis proves the following hypothesis: It is possible to achieve zero-sided communication (a model of communication characterized by the absence of any explicit per-message transfer calls by any of the participating sides) in a real-time environment using a QoS contract between an application and message-passing middleware. Furthermore, it is shown that the performance and predictability of a time-driven task using zero-sided communication is better than that of a best-effort task. The hypothesis is validated through compact MPI/RT application programs that achieve zero-sided communication.

With the rapid development of the Internet, increasingly universities and colleges transfer some of their teaching assignments online. Online learning plays an important role in assisting or sometimes substituting for the traditional face-toace learning. An online message board is one of several online communication tools which are used to assist online learning. We have conducted a study on the role of the online message board in teaching one of these courses, an introductory course in calculus-based physics. The study analyzed students? use of the message board and investigated whether use is correlated with performance in the class. Results suggest that students have benefited from using the online message board. Both homework related message board activities and non-learning message boardn activities were found to be correlated significantly to the grades the students earned in the course.

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