The Distributed Coordination Function (DCF) is the oldest and most widely-used IEEE 802.11 contention-based channel access control protocol. DCF adds a significant amount of overhead in the form of preambles, frame headers, randomised binary exponential back-off and inter-frame spaces. Having accurate and verified performance models for DCF is thus integral to understanding the performance of IEEE 802.11 as a whole. In this document DCF performance is measured subject to two different workload models using an IEEE 802.11g test bed. Bianchi proposed the first accurate analytic model for measuring the performance of DCF. The model calculates normalised aggregate throughput as a function of the number of stations contending for channel access. The model also makes a number of assumptions about the system, including saturation conditions (all stations have a fixed-length packet to send at all times), full-connectivity between stations, constant collision probability and perfect channel conditions. Many authors have extended Bianchi's machine model to correct certain inconsistencies with the standard, while very few have considered alternative workload models. Owing to the complexities associated with prototyping, most models are verified against simulations and not experimentally using a test bed. In addition to a saturation model we considered a more realistic workload model representing wireless Internet traffic. Producing a stochastic model for such a workload was a challenging task, as usage patterns change significantly between users and over time. We implemented and compared two Markov Arrival Processes (MAPs) for packet arrivals at each client - a Discrete-time Batch Markovian Arrival Process (D-BMAP) and a modified Hierarchical Markov Modulated Poisson Process (H-MMPP). Both models had parameters drawn from the same wireless trace data. It was found that, while the latter model exhibits better Long Range Dependency at the network level, the former represented traces more accurately at the client-level, which made it more appropriate for the test bed experiments. A nine station IEEE 802.11 test bed was constructed to measure the real world performance of the DCF protocol experimentally. The stations used IEEE 802.11g cards based on the Atheros AR5212 chipset and ran a custom Linux distribution. The test bed was moved to a remote location where there was no measured risk of interference from neighbouring radio transmitters in the same band. The DCF machine model was fixed and normalised aggregate throughput was measured for one through to eight contending stations, subject to (i) saturation with fixed packet length equal to 1000 bytes, and (ii) the D-BMAP workload model for wireless Internet traffic. Control messages were forwarded on a separate wired backbone network so that they did not interfere with the experiments. Analytic solver software was written to calculate numerical solutions for thee popular analytic models for DCF and compared the solutions to the saturation test bed experiments. Although the normalised aggregate throughput trends were the same, it was found that as the number of contending stations increases, so the measured aggregate DCF performance diverged from all three analytic model's predictions; for every station added to the network normalised aggregate throughput was measured lower than analytically predicted. We conclude that some property of the test bed was not captured by the simulation software used to verify the analytic models. The D-BMAP experiments yielded a significantly lower normalised aggregate throughput than the saturation experiments, which is a clear result of channel underutilisation. Although this is a simple result, it highlights the importance of the traffic model on network performance. Normalised aggregate throughput appeared to scale more linearly when compared to the RTS/CTS access mechanism, but no firm conclusion could be drawn at 95% confidence. We conclude further that, although normalised aggregate throughput is appropriate for describing overall channel utilisation in the steady state, jitter, response time and error rate are more important performance metrics in the case of bursty traffic.

The rapid adoption of the internet has occurred despite the lack of a ubiquitous identity meta-system. The status quo is a patchwork of proprietary security systems. A number of security issues have arisen as a result which threaten to lead to a loss of trust in the internet, and may limit the scope of applications built on it; effectively constraining the potential of the internet as a platform for business and services. Current initiatives by a broad consortium of industry leaders promise a vastly improved landscape with a set of interoperable protocols and systems, built on open specifications, and guided by a set of core identity principles, enabling a more secure online experience. Simultaneously there have arisen a large number of location aware web application and services which detect and use a user’s location to enhance their application experience. These advances, although useful, present new security and privacy issues. This paper investigates the operation of one of the new identity technologies, information cards, and proposes extensions to the existing supported schemas to incorporate recent advances in geo-location technology. The proposal is supported by reference to existing o pen source implementations.

The Arizona Child Acoustic Database consists of longitudinal audio recordings from a group of children over a critical period of growth and development (ages 2-7 years). The goal of this database is to 1) document acoustic changes in speech production that may be related to physical growth 2) inform development of a model of speech production for child talkers. This work was funded by NSF BSC-1145011 awarded to Kate Bunton, Ph.D. and Brad Story, Ph.D, Principal Investigators. This database contains longitudinal audio recordings of 55 American English speaking children between the ages of 2-7 at 3-month intervals. Since children began the study at different ages, some children have fewer recording sessions than others. The database can also be used to provide cross-sectional data for children of a specific age. Please refer to the subject data table for information on specific sessions available here http://arizona.openrepository.com/arizona/handle/10150/316065. All children were recorded using the same protocol; therefore, task numbers are consistent across children and sessions. A calibration tone is included as Record 1 for all sessions. The speech protocol focused on production of English monopthong and diphthong vowels in isolation, sVd, hVd, and monosyllabic real words. In addition, the protocol includes several nonsense vowel-to-vowel transitions. Speakers were prompted either verbally by investigators or by graphical prompts. Details of the protocol with reference to task numbers can be found in the protocol spreadsheet available here http://arizona.openrepository.com/arizona/handle/10150/316065. Details on data recording: All samples were recorded digitally using an AKG SE 300B microphone with a mouth to mic distance of approximately 10 inches. Signals were recorded digitally using a Marantz PMD671, 16 bit PCM (uncompressed) at 44.1KHz. Recordings are made available in .wav format. Individual zip files contain all recordings from a single session.

No description available.

The purpose of the study was to analyze the impact on 4-H policy council members, extension professionals and 4-H adult leaders regarding the incorporation of a 4-H urban program into the traditional 4-H program. The study was designed to provide data for Cooperative Extension Service personnel concerning the impact of changes in attitudes toward policy and administration of a-H programs, as well as develop ways and means for the integration of an urban 4-H program into the traditional. 4-H program. The documentation produced by the study offered new base line information and will enhance efforts by Extension Administrators in determining resources, training and programmatic needs of an urban 4-H program.The following assumptions were made relative to the study:1. Millions of boys and girls throughout the United States have been helped through 4-H.2. Leadership skills and abilities, as well as interpersonal communication skills, have been developed by 4-H members.3. The Indiana 4-H program is a proven creditable program.4. A vast number of urban boys and girls have been omitted from the 4-H program in Indiana.5. Two distinct and definable 4-H program styles currently exist in Indiana--one rural and one urban. 6. Variations created by long histories of traditions woven into the ongoing 4-H program cannot feasibly be controlled in the research setting and will be assumed to be equivalent for each sample population. The following research questions were attendant to the study:1. How have the attitudes of 4-H policy council members, extension professionals and 4-H adult leaders in the three selected Indiana counties been affected?2. How will/should the Indiana Cooperative Extension Service policy be affected?3. How will/should the Indiana Cooperative Extension Service Administration be affected?The potential population for the study was defined as all 4-H policy council members, 4-H adult leaders and extension professionals (Youth Department, County Extension Coordinator, and Area Administrator) in three selected Indiana counties (Lake, Marion and Vigo). The population also included the State Director, the Associate Directors, and the entire 4-H State Staff. The study population was a stratified random policy council members and 4-H adult leaders resultingFrom sample. One-third of the potential population, 414 individuals, were asked to complete and return questionnaires.A review of related research and literature was conducted and revealed limited research efforts have been devoted to the impact on attitudes of extension professionals, 4-H the incorporation of an urban 4-H program into the traditional 4-H program. The first section of Chapter II included selected information on attitude change, cognitive models of attitude change and problems for research related to changing attitudes. The second section was devoted to studies relative to organizational change in the Cooperative Extension Service; incorporation infers growth and growth will cause change. The third section dealt with management and leadership behavior of extension professionals.Data for the study were obtained from six sources:(1) federal and state Extension Management Information System; (2) yearly 4-H summaries; (3) 1970 U.S. Census Records; (4) State 4-H Department records; (5) County 4-H Department records; and (6) a survey instrument administered to 4-H policy council members, 4-H adult leaders and extension professionals. The questionnaires consisted of thirty statements divided equally into three areas--policy, personnel and program relative to the Indiana 4-H program. Validation of the survey instrument was implemented and completed through appropriate field testing in a county in Indiana not selected for the study.The data were analyzed using a frequency of distribution for each group of the study population--4-H policy council members, 4-H adult leaders, and extension professionals in each of the three selected counties, as well as the three councils, leader groups and extension professionals. A frequency distribution was also developed for the total population sample of the study. Data obtained from the questionnaires were summarized and presented in narrative form. Tables were developed to report raw data.The respondents were in general agreement with six statements, and predominantly in disagreement with one statement. The statements in the survey instrument were divided into three sections: policy 1-10, personnel 11-20 and program 21-30. Eighty-five percent of the respondents agreed with the policy statements, 80 percent of the respondents agreed with the personnel statements and 84 percent of the respondents agreed with the program statements.

The Arizona Child Acoustic Database consists of longitudinal audio recordings from a group of children over a critical period of growth and development (ages 2-7 years). The goal of this database is to 1) document acoustic changes in speech production that may be related to physical growth 2) inform development of a model of speech production for child talkers. This work was funded by NSF BSC-1145011 awarded to Kate Bunton, Ph.D. and Brad Story, Ph.D, Principal Investigators. This database contains longitudinal audio recordings of 55 American English speaking children between the ages of 2-7 at 3-month intervals. Since children began the study at different ages, some children have fewer recording sessions than others. The database can also be used to provide cross-sectional data for children of a specific age. Please refer to the subject data table for information on specific sessions available here http://arizona.openrepository.com/arizona/handle/10150/316065. All children were recorded using the same protocol; therefore, task numbers are consistent across children and sessions. A calibration tone is included as Record 1 for all sessions. The speech protocol focused on production of English monopthong and diphthong vowels in isolation, sVd, hVd, and monosyllabic real words. In addition, the protocol includes several nonsense vowel-to-vowel transitions. Speakers were prompted either verbally by investigators or by graphical prompts. Details of the protocol with reference to task numbers can be found in the protocol spreadsheet available here http://arizona.openrepository.com/arizona/handle/10150/316065. Details on data recording: All samples were recorded digitally using an AKG SE 300B microphone with a mouth to mic distance of approximately 10 inches. Signals were recorded digitally using a Marantz PMD671, 16 bit PCM (uncompressed) at 44.1KHz. Recordings are made available in .wav format. Individual zip files contain all recordings from a single session.

Thesis (M.S.)--Virginia Polytechnic Institute, 1965. / Vita. Abstract. Includes bibliographical references (leaves 127-131). Also available via the Internet.

Thesis (M.M.)--University of Rochester, 1953. / Bibliography: leaf 130. Digitized version available online via the Sibley Music Library, Eastman School of Music http://hdl.handle.net/1802/2455

Diss. (sammanfattning) Stockholm : Karol. inst., 1999. / Härtill 4 uppsatser.

Zugl.: Darmstadt, Techn. Universiẗat, Diss., 2007.