In wireless communication, multipath fading distorts the phase and the amplitude of received signals and increases error rate, which degrades causes communication quality. Multiple-input-multiple-output (MIMO) techniques can be adopted to achieve diversity gain and reduce error rate. However, MIMO is hard to be implemented in mobile devices due to size limitation. With this regard, cooperative communications are proposed to allow users to cooperate each other¡¦s and then achieve diversity without equipping multiple antennas. On the other hand, if source and relays adopt fixed-rate transmission under time-varying wireless channels, it requires timely feedback about channel-information for transmitters to adjust the rate of channel encoder. To reduce overhead required for aforementioned scheme, we adopt rateless fountain codes in cooperative networks. In recent year, most related studies focus on information-theoretical aspect, but it lacks discussion of practical coding. In our work, we use fountain codes in dual-hop cooperative communication and analyse transmission rate in terms of transmitting time. Fountain code was first proposed as Luby transform codes(LTC) for erasure channels. We combine low-density parity-check code( LDPC code) and LTC in cooperative communication networks, and analyze required transmission time under different cooperative protocols.

Constructing and maintaining a formation is critical in applications of cooperative control of multi-agent systems. In this research we address the formation control problem of generating a formation for a group of nonholonomic mobile agents. The formation control scheme proposed in this work is based on a fusion of leader-follower and virtual reference approaches. This scheme gives a formation constraint representation that is independent of the number of agents in the formation and the resulting control algorithm is scalable. One of the important desired features in controller design is that the formation errors defined by formation constraints should be stabilized globally and exponentially by the controller. The proposed controller is based on feedback linearization, and formation errors are shown to be globally exponentially stable in the sense of Lyapunov. Since formation errors are stabilized globally, the proposed controller is applicable to both formation keeping and formation construction problems. As a possible application, the proposed algorithm is implemented in a cooperative ground moving target surveillance scenario. The proposed algorithm enables the determination of the minimal number of agents required for surveillance of a moving target. The number of agents returned by this scheme is not optimal and hence is a conservative solution. However, this is justified by the computational savings the scheme offers.

Homeschooling is a growing trend in America. Studies on homeschooling in the past three decades have focused on the reasons why parents choose to homeschool, the academic and social quality of homeschooling, and the perceptions of public and private school officials towards homeschooling, as well as homeschooling parents' perceptions of public and private schools. The literature on homeschool cooperatives is scarce. A homeschool cooperative (co-op) is a group of homeschooling parents who have gathered to collectively teach their children. Co-ops might teach core subjects, electives, athletics, or just serve as an opportunity for homeschooling families to gather for fellowship and social time. This dissertation is a study of a homeschool co-op in San Antonio, Texas. The researcher for this study attempted to answer two questions: 1) What is a history of the co-op, and 2) What are the daily operations of the co-op? This researcher observed the selected co-op in action, reviewed documents supplied by co-op members, and interviewed four members of the co-op who have varying degrees of participation in the co-op. Through triangulation of interviews, observations, and documents, this researcher has described a history of the selected co-op, including its founding and daily operations. The co-op, formed in 2005, is a large, Catholic-affiliated co-op that meets weekly for twelve weeks each semester. The teachers, all paid, are either parents of co-op students or individuals hired from outside the co-op. Students in the co-op have twenty to twenty-five courses from which to choose each semester. The participants in the study are satisfied with their experiences in the Quality Homeschool Co-op. The participants state that the co-op is providing quality academic classes that supplement the curricula used at home. The participants are also pleased with the positive socialization that their children receive while attending the co-op. This study adds to the literature on homeschooling cooperatives. Although further research on this study is possible based on different research questions, this researcher has presented a history of Quality Homeschool Co-op and has documented the co-op's daily operations.

The purpose of this study is to describe and examine the attitudes of coffee cooperative members towards the ownership of the SPREAD cooperatives in relation to cooperative sustainability. In addition this study identifies barriers faced by member farmers and subsequently provides recommendations on ways in which SPREAD can help its member farmers achieve a more sustainable livelihood. Previous analysis of the SPREAD project and its member cooperatives has suggested that coffee cooperative members do not feel ownership of the cooperative and have not benefited from the cooperatives, leaving the sustainability of the cooperatives to question. The research questions used for this study focused on issues of sustainability, ownership and organizational impact and barriers. All of the cooperatives studied over the course of this project receive funds from the USAID funded project SPREAD. The population of interest comprised members from three of the fourteen cooperatives receiving aid from the SPREAD project. A sample of 52 individuals participated in the study, with the data being collected from mid-July to mid-August, 2009. Quantitative data were collected using a close-ended category-scale questionnaire. The close-ended category-scale questionnaires were analyzed based on the frequency and percentage of responses. Major findings of this study included that coffee cooperative members felt that in the absence of SPREAD, the coffee cooperatives would be unable to function. In regards to ownership, members felt as if they owned the cooperatives. The disparity between these two constructs shows that once SPREAD no longer supports the cooperatives, then sustainability is to question and further they are more susceptible to collapse.

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The primary goal of the research described in this thesis concern the synthesis, characterization and study of 1,8-bis(diarylmethylium)naphthalenediyl dications. Such dications have been prepared from the corresponding diols and have been fully characterized. Single crystals X-ray diffraction studies indicate that the two cationic centers of these derivatives are separated by 3.0 - 3.1 ??. The enforced proximity of the cationic centers intensifies the electron deficiency of these derivatives which behave as strong organic oxidants. As indicated by cyclic voltammetry, these dications undergo a two-electron reduction to afford the corresponding acenaphthenes. The newly formed C-C bond which links the former methylium are remarkably long (1.628-1.706 ??.) and can, in some instances, be oxidatively cleaved in the presence of acids. These dications can also be reduced chemically by reducing reagent, such as hydride, chloride, bromide and iodide. Remarkably, the reaction of 1,8-bis(diphenylmethylium)naphthalenediyl dication with fluoride anion results in the formation of a mono fluorinated cation which features an unsymmetrical C-F?C bridge between the former methylium centers. As indicated by 1H NMR spectroscopy, the structure of this cation is fluxional with the fluorine atom oscillating between the former methylium centers. Finally, this thesis also deals with the synthesis and study of 4,6-bis(dimesitylboryl)dibenzofuran and isoelectronic dications.

This thesis presents a control algorithm to be used by a team of ECAVs (Electronic Combat Air Vehicle) to deceive a network of radars through the generation of a phantom track. Each ECAV has the electronic capability of intercepting and introducing an appropriate time delay to a transmitted pulse of a radar before transmitting it back to the radar, thereby deceiving the radar into seeing a phantom target at a range beyond that of the ECAV. A radar network correlates targets and target tracks to detect range delay based deception. A team of cooperating ECAVs, however, precisely plans their trajectories in a way all the radars in the radar network are deceived into seeing the same phantom. Since each radar in the network confirms the target track of the other, the phantom track is considered valid. An important feature of the algorithm achieving this is that it translates kinematic constraints on the ECAV dynamic system into constraints on the phantom point. The phantom track between two specified way points then evolves without violating any of the system constraints. The evolving phantom track in turn generates the actual controls on the ECAVs so that ECAVs have flyable trajectories. The algorithms give feasible but suboptimal solutions. The main objectives are algorithm development for phantom track generation through a team of cooperating ECAVs, development of the algorithms to be finite dimensional searches and determining necessary conditions for feasible solutions in the immediate horizon of the searches of the algorithm. Feasibility of the algorithm in deceiving a radar network through phantom track generation is demonstrated through simulation results.

Semiconductors absorb photos with energy greater than their band gap energy may induce electron-hole pairs. In semiconductor physics, increasing charge carrier improves the electric conductivity of semiconductor. The following methodology was taken to investigate the electric conductivity and the electron hole pairs affected performance of a dye sensitized solar cell. I applied 3 specific monochromatic light (365nm, 405nm and 437nm, respectively.) mixed with xenon light and normal xenon light separately illuminating on dye sensitized solar cells. At the assumption of the normalized photon to current conversion efficiency of solar cell illuminated by 437nm monochromatic light is 100%, the normalized photon to current conversion efficiency of the solar cell illuminated by 365nm monochromatic light was only 28%, however, that illuminated by 365nm monochromatic light mixed xenon light raised to 58%. The more intense mixed light produced more excited electrons than only 365nm monochromatic light. The holes generated by 365nm monochromatic light is easier to be captured by the electrons in the more intense mixed xenon light irradiation results in higher photon to current conversion efficiency. The output of photocurrent of the dye sensitized solar cell irradiated by 365nm ultraviolet light mixed xenon light was enhanced most significantly by 6.53% compared with that by normal xenon light irradiation.

The purpose of this research was to investigate, with the strategy of cooperative learning and traditional narrative teaching, the learning achievement, scientific attitude, and the diversity of different class environment for the seventh graders¡¦ learning in biological reproduction of natural science. In addition, the progress of learning and teaching were studied followed up. In the quasi-experimental design, 27 subjects of the experimental group were taught by Student¡¦s Team Achievement Division (STAD) of cooperative learning, and 27 subjects of control group were by traditional narrative teaching. They were all seventh grade students in Kaohsiung County. The instruments consist of ¡§Biological Reproduction Learning Achievement Test,¡¨ ¡§Science Attitudes Scale,¡¨ ¡§What Is Happening in This Class? Questionnaire,¡¨and ¡§Cooperation Learning Questionnaire.¡¨ The data were analyzed by applying descriptive statistics and ANCOVA. The results of the research were summarized as follows: STAD cooperative learning teaching method stimulated students to show more positive scientific attitudes and experienced more class environment encouragement. Moreover, it promoted the seventh graders¡¦ learning achievement in study the unit of reproduction and exhibited retentive effect. During the different stages of group discussion, students were in a hopeless tangle in the beginning, followed by a more cooperative manner gradually, and finally they were leading group learning. The processes of the sharing of the groups were embarrassing in the beginning and then they were gradually open-handed at the end .Objectively, students think they could complete the learning of biology with cooperative learning and subjectively, they also enjoyed this kind of learning atmosphere and hope the teacher could use the teaching strategy of cooperative teaching more often. On the other hand, the teacher was able to follow up the students¡¦ thought and progress to guide them in more details during the group discussion and group sharing. Also the teacher should listen and respect the students¡¦ opinion and will even though the teacher worried about the methodology didn¡¦t suit for the students in the beginning.

"This paper was originally a thesis submitted to the College of Graduate Studies and Research in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Extension at the University of Saskatchewan, Saskatoon". / Publisher's website: http://www.usaskstudies.coop/. Includes bibliographical references. Issued also in print format.