Social learning in a multi-agent system

In a persistent multi-agent system, it should be possible for new agents to benefit from the accumulated learning of more experienced agents. Parallel reasoning can be applied to the case of newborn animals, and thus the biological literature on social learning may aid in the construction of effective multi-agent systems. Biologists have looked at both the functions of social learning and the mechanisms that enable it. Many researchers have focused on the cognitively complex mechanism of imitation; we will also consider a range of simpler mechanisms that could more easily be implemented in robotic or software agents. Research in artificial life shows that complex global phenomena can arise from simple local rules. Similarly, complex information sharing at the system level may result from quite simple individual learning rules. We demonstrate in simulation that simple mechanisms can outperform imitation in a multi-agent system, and that the effectiveness of any social learning strategy will depend on the agents' environment. Our simple mechanisms have obvious advantages in terms of robustness and design costs

Distributed Leadership in Schools: Conditions for Success

Teacher leadership has always been a necessary part of school dynamics. Through committees, union/administrative negotiations, formal and informal leadership roles, teachers play an important role in the growth and change of an educational institution. The purpose of this study is to examine teacher leadership through the perspective of distributed leadership theory; identify the conditions and components of both schools and administrators that support distributed leadership and identify essential steps to transform leadership practice to a distributed model. This is a qualitative text analysis of current theoretical papers and relevant research on the subject of distributed leadership. The information was used to identify qualities and actions of both individuals and organizations that can help create a formalized practice of distributed leadership. Results indicated that creating certain conditions in school environments and modeling and nurturing trust can support organizational change toward distributed leadership

Extremism propagation in social networks with hubs

One aspect of opinion change that has been of academic interest is the impact of people with extreme opinions (extremists) on opinion dynamics. An agent-based model has been used to study the role of small-world social network topologies on general opinion change in the presence of extremists. It has been found that opinion convergence to a single extreme occurs only when the average number of network connections for each individual is extremely high. Here, we extend the model to examine the effect of positively skewed degree distributions, in addition to small-world structures, on the types of opinion convergence that occur in the presence of extremists. We also examine what happens when extremist opinions are located on the well-connected nodes (hubs) created by the positively skewed distribution. We find that a positively skewed network topology encourages opinion convergence on a single extreme under a wider range of conditions than topologies whose degree distributions were not skewed. The importance of social position for social influence is highlighted by the result that, when positive extremists are placed on hubs, all population convergence is to the positive extreme even when there are twice as many negative extremists. Thus, our results have shown the importance of considering a positively skewed degree distribution, and in particular network hubs and social position, when examining extremist transmission

Social Learning in a Multi-Agent System

In a persistent multi-agent system, it should be possible for new agents to benefit from the accumulated learning of more experienced agents. Parallel reasoning can be applied to the case of newborn animals, and thus the biological literature on social learning may aid in the construction of effective multi-agent systems. Biologists have looked at both the functions of social learning and the mechanisms that enable it. Many researchers have focused on the cognitively complex mechanism of imitation; we will also consider a range of simpler mechanisms that could more easily be implemented in robotic or software agents. Research in artificial life shows that complex global phenomena can arise from simple local rules. Similarly, complex information sharing at the system level may result from quite simple individual learning rules. We demonstrate in simulation that simple mechanisms can outperform imitation in a multi-agent system, and that the effectiveness of any social learning strategy will depend on the agents' environment. Our simple mechanisms have obvious advantages in terms of robustness and design costs

Preliminary Design of the Naval Postgraduate School Petite Amateur Navy Satellite (PANSAT) Electric Power and Communications Subsystems

The Naval Postgraduate School\u27s (NPS) Space Systems Academic Group (SSAG) is continuing the design and development of the Petite Amateur Navy Satellite (PANSAT), a small communications satellite. The objectives of PANSAT are to provide: (i.) an educational tool for the officer students at NPS, (ii.) digital communications using spread spectrum in the amateur band, and (iii.) a low cost, space-based platform for small experiments. PANSAT is designed for an altitude of 480 km and an inclination greater than 28.5. The satellite weight is 150 Ibs and has no attitude control. The expected life of the satellite is 2 years. This paper discusses the preliminary design of the electrical power subsystem (EPS) and the communications subsystem (COMM). The BPS is a photovoltaic silicon cell system consisting of solar array, batteries, battery charge regulator (BCR) and DC to DC converters. The COMM payload uses direct sequence spread spectrum modulated BPSK with a 1 MHz bandwidth. The data rate is 1200 bps with a bit error rate of 10-5 with a 5 Watt output

A comparative study on wear and corrosion behaviour of tungsten carbide-nickel and tungsten carbide-cobalt high velocity oxy-fuel (HVOF) for carbon steel blade

Nowadays, the demand of high wear and corrosion resistance of the components in various industry is increasing from time to time. Therefore, high velocity oxy-fuel (HVOF) thermal spray was introduced to protect machine components from wear and corrosion, to restore worn components and to improve the durability of the components. HVOF is one of the process of depositing a material layer over a base metal or substrate with characteristics of high flame velocity and moderate temperature. The main purpose of this present study is to characterize the structure of the tungsten carbide 10 wt.% nickel (WC-10Ni) and tungsten carbide 12 wt.% w cobalt (WC-12Co) coating deposited by means of HVOF thermal spray onto a continuous digester (CD) blade that made up from carbon steel. The morphology and chemical composition of the coating were characterized by scanning electron microscope (SEM), electron dispersive spectrometer (EDS), and x-ray diffraction (XRD). The hardness test was carried out by using Vickers micro-hardness tester with load of 490.3 mN (0.05 HV). The wear and corrosion behavior and mechanism for both coatings was compared. Three body wear test was carried out in term of weight loss and electrochemical test was performed in acidic media (mixture of sulfuric acid, H2SO4 and ilmenite) to obtain the corrosion rate of the coating. From the result, it shows that WC-12Co coating has finer grain size that is around 2.3 μm. WC-12Co has higher wear resistance due to high volume friction, low mean free path, high hardness and lower porosity distribution compared to WC-10Ni. Besides, the formation of secondary phase, W2C also affected the hardness of both coating, where this phase is harder than WC phase. For corrosion test, WC-12Co shows good corrosion resistance with small differences of corrison rate with WC-10Ni, that is only 0.7016 mm/y. As a conclusion, WC-12Co HVOF coating shows high potential on replacement of CD blade

Species delineation using Bayesian model-based assignment tests: a case study using Chinese toad-headed agamas (genus Phrynocephalus)

<p>Abstract</p> <p>Background</p> <p>Species are fundamental units in biology, yet much debate exists surrounding how we should delineate species in nature. Species discovery now requires the use of separate, corroborating datasets to quantify independently evolving lineages and test species criteria. However, the complexity of the speciation process has ushered in a need to infuse studies with new tools capable of aiding in species delineation. We suggest that model-based assignment tests are one such tool. This method circumvents constraints with traditional population genetic analyses and provides a novel means of describing cryptic and complex diversity in natural systems. Using toad-headed agamas of the <it>Phrynocephalus vlangalii </it>complex as a case study, we apply model-based assignment tests to microsatellite DNA data to test whether <it>P. putjatia</it>, a controversial species that closely resembles <it>P. vlangalii </it>morphologically, represents a valid species. Mitochondrial DNA and geographic data are also included to corroborate the assignment test results.</p> <p>Results</p> <p>Assignment tests revealed two distinct nuclear DNA clusters with 95% (230/243) of the individuals being assigned to one of the clusters with > 90% probability. The nuclear genomes of the two clusters remained distinct in sympatry, particularly at three syntopic sites, suggesting the existence of reproductive isolation between the identified clusters. In addition, a mitochondrial ND2 gene tree revealed two deeply diverged clades, which were largely congruent with the two nuclear DNA clusters, with a few exceptions. Historical mitochondrial introgression events between the two groups might explain the disagreement between the mitochondrial and nuclear DNA data. The nuclear DNA clusters and mitochondrial clades corresponded nicely to the hypothesized distributions of <it>P. vlangalii </it>and <it>P. putjatia</it>.</p> <p>Conclusions</p> <p>These results demonstrate that assignment tests based on microsatellite DNA data can be powerful tools for distinguishing closely related species and support the validity of <it>P. putjatia</it>. Assignment tests have the potential to play a significant role in elucidating biodiversity in the era of DNA data. Nonetheless, important limitations do exist and multiple independent datasets should be used to corroborate results from assignment programs.</p