Mind change optimal learning of Bayes net structure

This paper analyzes the problem of learning the structure of a Bayes net (BN) in the theoretical framework of Gold’s learning paradigm. Bayes nets are one of the most prominent formalisms for knowledge representation and probabilistic and causal reasoning. We follow constraint-based approaches to learning Bayes net structure, where learning is based on observed conditional dependencies between variables of interest (e.g., “X is dependent on Y given any assignment to variable Z”). Applying learning criteria in this model leads to the following results. (1) The mind change complexity of identifying a Bayes net graph over variables V from dependency data is |V| 2 , the maximum number of edges. (2) There is a unique fastest mind-change optimal Bayes net learner; convergence speed is evaluated using Gold’s dominance notion of “uniformly faster convergence”. This learner conjectures a graph if it is the unique Bayes net pattern that satisfies the observed dependencies with a minimum number of edges, and outputs “no guess” otherwise. Therefore we are using standard learning criteria to define a natural and novel Bayes net learning algorithm. We investigate the complexity of computing the output of the fastest mind-change optimal learner, and show that this problem is NP-hard (assuming P = RP). To our knowledge this is the first NP-hardness result concerning the existence of a uniquely optimal Bayes net structure.

Learning from the experts: exploring playground experience and activities using a write and draw technique

Background: Qualitative research into the effect of school recess on children’s physical activity is currently limited. This study used a write and draw technique to explore children’s perceptions of physical activity opportunities during recess.

Methods: 299 children age 7–11 years from 3 primary schools were enlisted. Children were grouped into Years 3 & 4 and Years 5 & 6 and completed a write and draw task focusing on likes and dislikes. Pen profiles were used to analyze the data.

Results: Results indicated ‘likes’ focused on play, positive social interaction, and games across both age groups but showed an increasing dominance of games with an appreciation for being outdoors with age. ‘Dislikes’ focused on dysfunctional interactions linked with bullying, membership, equipment, and conflict for playground space. Football was a dominant feature across both age groups and ‘likes/dislikes’ that caused conflict and dominated the physically active games undertaken.

Conclusion: Recess was important for the development of conflict management and social skills and contributed to physical activity engagement. The findings contradict suggestions that time spent in recess should be reduced because of behavioral issues.

Investor heterogeneity and the cross-sectional stock returns in China

We examine the relationship between divergence of opinion and the cross-sectional stock returns in Chinese A share market where short-selling of stocks is prohibited by law. Using a proxy for divergence of opinion among the entire investor base, we document a positive relationship between divergent beliefs and future stock returns. This is in sharp contrast to Miller's (1977) prediction of a negative relationship between the two. The result is likely to be driven by the dominance of individual investors and their speculative trading behaviors in China. Miller's prediction is confirmed when divergence of opinion is measured using data on mutual fund holdings. Our results are robust to a number of common return predictors. We also find a significantly negative relationship between the fraction of tradable shares in listed Chinese companies and future stock returns. Increase in the fraction of tradable shares tends to reduce the predictability of stock returns using divergence of opinion.

High activity and Levy searches : jellyfish can search the water column like fish

Over-fishing may lead to a decrease in fish abundance and a proliferation of jellyfish. Active movements and prey search might be thought to provide a competitive advantage for fish, but here we use data-loggers to show that the frequently occurring coastal jellyfish (Rhizostoma octopus) does not simply passively drift to encounter prey. Jellyfish (327 days of data from 25 jellyfish with depth collected every 1 min) showed very dynamic vertical movements, with their integrated vertical movement averaging 619.2 m d−1, more than 60 times the water depth where they were tagged. The majority of movement patterns were best approximated by exponential models describing normal random walks. However, jellyfish also showed switching behaviour from exponential patterns to patterns best fitted by a truncated Lévy distribution with exponents (mean μ = 1.96, range 1.2–2.9) close to the theoretical optimum for searching for sparse prey (μopt ≈ 2.0). Complex movements in these ‘simple’ animals may help jellyfish to compete effectively with fish for plankton prey, which may enhance their ability to increase in dominance in perturbed ocean systems.

Establishing Competitive Domination Cycles for Peer-to-peer Game Combat

Games require balance to be fair and enjoyable. In two player combat settings balance can be achieved by ensuring that both units are equally capable. The possibility of alliances changes the nature of balance when additional players are introduced. One approach to achieving balance is to use a domination loop between agents in a rock, scissors, paper style approach. This paper investigates whether such loops exist within the existing rules of game combat. Search processes within the attribute space of the game units are used to identify loops within an existing game architecture. A dominance metric is used to identify cycles where the victory is achieved by a clear threshold. Cycles with up to 5 players are demonstrated, although larger cycles require more effort to find. Use of models of game play and attribute space search are recommended as a mechanism for balancing games of this format.

Artificial ornaments manipulate intrinsic male quality in wild-caught zebra finches (Taeniopygia guttata)

The addition of red and green color bands is a commonly used method for manipulating male attractiveness in the zebra finch (Taeniopygia guttata), providing insight into the study of maternal investment and sexual selection. The addition of artificial ornaments has been assumed to manipulate a females’ perception of the male, rather than affecting intrinsic qualities of the male himself. Here, however, we reveal that the artificial band color worn by a male changes his body mass, condition, and courtship display rate. Males wearing red color bands in aviaries prior to mate-choice trials had a significantly higher song rate during trials than those wearing green color bands, alongside a significant increase in mass change and condition. Male song rate was found to significantly correlate with female preference alongside a female preference for red-banded males. However, male song rate in turn increased when female response was positive, suggesting a social feedback between the interacting birds. Our data suggest the presence of socially mediated feedback mechanisms whereby the artificial increase in attractiveness or dominance of a male directly affects other aspects of his attractiveness. Therefore, housing birds in social groups while manipulating attractiveness can directly influence other male qualities and should be accounted for by future studies.

‘Wasting talent’? Gender and the problematics of academic disenchantment and disengagement with leadership

Confronted with the processes of massification, commercialisation, internationalisation and reduced funding, universities also face an ageing academic workforce, with implications of a shrinking pool from which to recruit managerial and research leaders. A feminist analysis suggests that the policy problematic has been wrongly conceptualised as disengagement with leadership due to the characteristics of the academic workforce. Instead, it is argued that the corporatisation of the academy has produced academic disenchantment due to managerial dominance, commercialisation and privatisation and disengagement with the dominant values, practices and images of university leadership. Furthermore, the intensification of academic labour and the lack of diversity in leadership discourage many women from aspiring to or achieving leadership.

Meta-analysis and research synthesis in education

This bibliography begins with this introduction followed by a general overview of meta-analysis and research synthesis methods in education. The third section cites references to illustrate how the concept of statistical integration of research findings dates back to early 20th century. Citations in the fourth section highlight early calls from educational researchers to recognize the process of synthesizing research as a scholarly endeavor in its own right. As evident from the citations in the fifth section, it was in the 1980s when monographs exclusively devoted to research synthesis methods started to be published. Since then, a number of books have been published on research synthesis methods. The sixth section cites some of the most comprehensive books on research synthesis methods and includes contributions from key players of meta-analysis current at the time. The citations in the seventh section illustrate how meta-analysis has become very popular over time. Several large organizations have been set up and software developed to support systematic reviews of research. These are cited in the eighth section. Citations in the ninth section illustrate critiques of systematic reviews. As qualitative research is becoming popular in education, sophisticated discussions of issues associated with synthesizing qualitative research have also been published, some of which are cited in the tenth section. The eleventh section presents a methodologically inclusive account of current developments in research synthesis methods. The final section cites examples of journals exclusively devoted to publishing research reviews and exemplary research synthesis with different methodologies. Individual methods of research synthesis are discussed chronologically as they became popular in educational research. Accordingly, this bibliography starts with a discussion of statistical methods of integrating research that parallels the dominance of quantitative research in education until the 1970s. As the popularity and diversity of qualitative research methods have been increasing in educational research, more methodologically inclusive discussions of research synthesis methods are becoming popular as described in the later sections of this bibliography.

Blokey' newsroom culture

This paper seeks to address the gap in Australian media studies and feminist media scholarship relating to the way newsroom culture is embodied. How does the numerical dominance of men in journalism, particularly in decision-making roles, affect newsroom culture? How do male and female journalists understand this inequality? The paper first briefly attends to research into occupational culture and feminist theories of the body to address the central question ‘How is newsroom culture embodied?’ It then engages with this question more thoroughly via an analysis of my own interviews with 17 Australian male and female print news media journalists. It finds that, even though women have entered the industry in unprecedented numbers, a ‘blokey’ or hegemonic masculinity continues to shape news newsroom culture.

The politics of recognition and social justice : transforming subjectivities and new forms of resistance

Via a wide range of case studies, this book examines new forms of resistance to social injustices in contemporary Western societies. Resistance requires agency, and agency is grounded in notions of the subject and subjectivity. How do people make sense of their subjectivity as they are constructed and reconstructed within relations of power? What kinds of subjectivities are needed to struggle against forms of dominance and claim recognition? The participants in the case studies are challenging forms of dominance and subordination grounded in class, race, culture, nationality, sexuality, religion, age, disability and other forms of social division. It is a premise of this book that new and/or reconstructed forms of subjectivity are required to challenge social relations of subordination and domination. Thus, the transformation of subjectivity as well as the restructuring of oppressive power relations is necessary to achieve social justice. By examining the construction of subjectivity of particular groups through an intersectional lens, the book aims to contribute to theoretical accounts of how subjects are constituted and how they can develop a critical distance from their positioning.

Influence of orientation on twin nucleation and growth at low strains in a magnesium alloy

The resolved shear stress is believed to play an important role in twin formation. The present study tests this idea for an extruded magnesium alloy by examining "tension" twinning in different grain orientations. Electron backscatter diffraction analysis is employed for alloy AZ31 tested in compression along the extrusion axis to strains between 0.008 and 0.015. For heavily twinned grains, it is seen that twinning occurs on 2.3 twin systems per grain on average. The active systems are also most commonly those with, or very near to, the highest Schmid factor. The most active system in multiply twinned grains accounts on average for ∼0.6 of the twinning events. In addition, it is found that the twin habit plane falls within 6° of the K1 plane. Orientations with the highest Schmid factors (0.45-0.5) for twinning display twin aspect ratios greater by ∼40% and twin number densities greater by ∼10 times than orientations with maximum Schmid factors for twinning of 0.15-0.2. Thus the Schmid factor for twinning is seen to affect nucleation more than thickening in the present material. Viscoplastic crystal plasticity simulations are employed to obtain approximations for the resolved shear stress. Both the twin aspect ratio and number density correlate quite well with this term. The effect of the former can be assumed to be linear and that of the latter follows a power law with exponent ∼13. Increased aspect ratios and number densities are seen at low Schmid factors and this may relate to stress fluctuations, caused most probably in the present material by the stress fields at the tips of blocked twins. Overall, it is evident that the dominance of twinning on high Schmid factor systems is preserved at the low strains examined in the present work, despite the stress fluctuations known to be present. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A two-stage dynamic group decision making method for processing ordinal information

In group decision making (GDM) problems, ordinal data provide a convenient way of articulating preferences from decision makers (DMs). A number of GDM models have been proposed to aggregate such kind of preferences in the literature. However, most of the GDM models that handle ordinal preferences suffer from two drawbacks: (1) it is difficult for the GDM models to manage conflicting opinions, especially with a large number of DMs; and (2) the relationships between the preferences provided by the DMs are neglected, and all DMs are assumed to be of equal importance, therefore causing the aggregated collective preference not an ideal representative of the group's decision. In order to overcome these problems, a two-stage dynamic group decision making method for aggregating ordinal preferences is proposed in this paper. The method consists of two main processes: (i) a data cleansing process, which aims to reduce the influence of conflicting opinions pertaining to the collective decision prior to the aggregation process; as such an effective solution for undertaking large-scale GDM problems is formulated; and (ii) a support degree oriented consensus-reaching process, where the collective preference is aggregated by using the Power Average (PA) operator; as such, the relationships of the arguments being aggregated are taken into consideration (i.e., allowing the values being aggregated to support each other). A new support function for the PA operator to deal with ordinal information is defined based on the dominance-based rough set approach. The proposed GDM model is compared with the models presented by Herrera-Viedma et al. An application related to controlling the degradation of the hydrographic basin of a river in Brazil is evaluated. The results demonstrate the usefulness of the proposed method in handling GDM problems with ordinal information.

Board structure and firm performance : evidence from an emerging economy

We investigate the relationship between corporate board structure and firm performance of Bangladeshi companies. Using a sample of 654 firm- year observations for the period 2005-2009, the results show some support for aspects of agency theory as a greater proportion of independent directors on boards is related to better firm performance. Supporting resource dependence theory our result also suggest that larger boards provide valuable business experience, expertise, skill and social and professional networks which might add substantial business resources to the firms and thus positively impact on performance. We also find that female and foreign directors in Bangladesh provide more monitoring which leads to better firm performance. Our study contributes to extant research on board structure–performance relationship by providing evidence from an emerging economy context which is characterised by ownership concentration, family dominance and poor regulatory oversight.

Leaders benefit followers in the collective movement of a social sawfly

The challenges of maintaining cohesion while making collective decisions in social or aggregating insects can result in the emergence of a leader or leaders. Larval aggregations of the steel-blue sawfly Perga affinis forage nocturnally, and some larvae lead the aggregation on foraging trips more often than expected by chance. We investigated the relationship between these leader and follower roles by comparing the weight and growth of individual larvae with different roles. Our observations reveal no significant difference between the growth of leaders and followers, suggesting that the role of leadership may not provide direct foraging benefits. However, by experimentally manipulating the social structure of larval aggregations, we found that individuals within aggregations that comprise a mixture of leaders and followers enjoy higher growth rates than those in aggregations comprising a single behavioural type. These data demonstrate, for the first time, individual benefits to maintaining a balance of leader and follower roles within larval aggregations, and highlight the importance of considering the perspectives of both leaders and followers when investigating the evolutionary significance of this behavioural variation within animal groups.