An experimental comparison of a genetic algorithm and a hill-climber for term selection

Purpose – The term selection problem for selecting query terms in information filtering and routing has been investigated using hill-climbers of various kinds, largely through the Okapi experiments in the TREC series of conferences. Although these are simple deterministic approaches which examine the effect of changing the weight of one term at a time, they have been shown to improve the retrieval effectiveness of filtering queries in these TREC experiments. Hill-climbers are, however, likely to get trapped in local optima, and the use of more sophisticated local search techniques for this problem that attempt to break out of these optima are worth investigating. To this end, we apply a genetic algorithm (GA) to the same problem. Design/Methodology/Approach – We use a standard TREC test collection from the TREC-8 filtering track, recording mean average precision and recall measures to allow comparison between the hillclimber and GA algorithms. We also vary elements of the GA, such as probability of a word being included, probability of mutation and population size in order to measure the effect of these variables. Different strategies such as Elitist and Non-Elitist methods are used, as well as Roulette Wheel and Rank selection GA algorithms. Findings – The results of tests suggest that both techniques are, on average, better than the baseline, but the implemented GA does not match the overall performance of a hill-climber. The Rank selection algorithm does better on average than the Roulette Wheel algorithm. There is no evidence in this study that varying word inclusion probability, mutation probability or Elitist method make much difference to the overall results. Small population sizes do not appear to be as effective as larger population sizes. Research limitations/implications – The evidence provided here would suggest that being stuck in a local optima for the term selection optimization problem does not appear to be detrimental to the overall success of the hill-climber. The evidence from term rank order would appear to provide extra useful evidence which hill-climbers can use efficiently and effectively to narrow the search space. Originality/Value – The paper represents the first attempt to compare hill-climbers with GAs on a problem of this type

A study of school-choice students in the Southgate Community School District

The purpose of this study was to describe and explain the experiences of school-choice students at Southgate Anderson High School (SAHS). Qualitative methods were utilized to complete this interpretive study. The conceptual framework combined socialization theory with organizational theory. The researcher worked as a participant observer who conducted interviews, recorded observation data, and studied archival documents. Conceptually-driven sequential sampling was used to identify participants for initial interviews. Data collected through the initial round were analyzed and led to the use of purposive sampling for the remaining interviews. Interview transcripts, archival data, and observation logs were analyzed until a point of data saturation was reached. Southgate Community School District (SCSD) is located approximately 5 miles south of Detroit in Southeast Michigan’s Wayne County. The community that SCSD serves was incorporated in 1958 and grew rapidly during the exodus of Caucasian residents from Detroit in the 1950s, 1960s, and 1970s. The State of Michigan began a statewide interdistrict public schools-of-choice program in 1996. As of the 2004–2005 school year, 687 school-choice students were enrolled in SCSD from nearby school districts. The history of Southeast Michigan and of Michigan school funding shaped the experiences of school-choice students. The experience of schoolchoice students at SAHS was a cultural experience, and the adaptive socialization response chosen by the students fell along the lines of racial and socio-cultural congruence. The relationship between school-choice students and the culture of vi SAHS shaped the experiences of school-choice students. Schools-of-choice, Proposal A, and the culture of the community combined to create conflict between organizational rationalities. This conflict framed the experiences of school-choice students at SAHS. Michigan’s school funding system and schools-of-choice policy was intended to create a market-driven system that would result in increased effectiveness of schools. Schools-of-choice, in this case, was a competition between communities and not a competition between schools. Perceptions related to socio-cultural characteristics of communities shaped the experiences of school-choice students

An immune-inspired swarm aggregation algorithm for self-healing swarm robotic systems

© 2016 Elsevier Ireland Ltd Swarm robotics is concerned with the decentralised coordination of multiple robots having only limited communication and interaction abilities. Although fault tolerance and robustness to individual robot failures have often been used to justify the use of swarm robotic systems, recent studies have shown that swarm robotic systems are susceptible to certain types of failure. In this paper we propose an approach to self-healing swarm robotic systems and take inspiration from the process of granuloma formation, a process of containment and repair found in the immune system. We use a case study of a swarm performing team work where previous works have demonstrated that partially failed robots have the most detrimental effect on overall swarm behaviour. We have developed an immune inspired approach that permits the recovery from certain failure modes during operation of the swarm, overcoming issues that effect swarm behaviour associated with partially failed robots

Underuse of coronary revascularization procedures in patients considered appropriate candidates for revascularization.

Background: Ratings by an expert panel of the appropriateness of treatments may offer better guidance for clinical practice than the variable decisions of individual clinicians, yet there have been no prospective studies of clinical outcomes. We compared the clinical outcomes of patients treated medically after angiography with those of patients who underwent revascularization, within groups defined by ratings of the degree of appropriateness of revascularization in varying clinical circumstances.Methods: This was a prospective study of consecutive patients undergoing coronary angiography at three London hospitals. Before patients were recruited, a nine-member expert panel rated the appropriateness of percutaneous transluminal coronary angioplasty (PTCA) and coronary-artery bypass grafting (CABG) on a nine-point scale (with 1 denoting highly inappropriate and 9 denoting highly appropriate) for specific clinical indications. These ratings were then applied to a population of patients with coronary artery disease. However, the patients were treated without regard to the ratings. A total of 2552 patients were followed for a median of 30 months after angiography.Results: Of 908 patients with indications for which PTCA was rated appropriate (score, 7 to 9), 34 percent were treated medically; these patients were more likely to have angina at follow-up than those who underwent PTCA (odds ratio, 1.97; 95 percent confidence interval, 1.29 to 3.00). Of 1353 patients with indications for which CABG was considered appropriate, 26 percent were treated medically; they were more likely than those who underwent CABG to die or have a nonfatal myocardial infarction - the composite primary outcome (hazard ratio, 4.08; 95 percent confidence interval, 2.82 to 5.93) - and to have angina (odds ratio, 3.03; 95 percent confidence interval, 2.08 to 4.42). Furthermore, there was a graded relation between rating and outcome over the entire scale of appropriateness (P for linear trend = 0.002).Conclusions: On the basis of the ratings of the expert panel, we identified substantial underuse of coronary revascularization among patients who were considered appropriate candidates for these procedures. Underuse was associated with adverse clinical outcomes. (N Engl J Med 2001;344:645-54.) Copyright (C) 2001 Massachusetts Medical Society

Meta-stable memory in an artificial immune network

Abstract. This paper describes an artificial immune system algorithm which implements a fairly close analogue of the memory mechanism proposed by Jerne(1) (usually known as the Immune Network Theory). The algorithm demonstrates the ability of these types of network to produce meta-stable structures representing populated regions of the antigen space. The networks produced retain their structure indefinitely and capture inherent structure within the sets of antigens used to train them. Results from running the algorithm on a variety of data sets are presented and shown to be stable over long time periods and wide ranges of parameters. The potential of the algorithm as a tool for multivariate data analysis is also explored.

An artificial immune system for self-healing in swarm robotic systems

Swarm robotics is concerned with the decentralised coordination of multiple robots having only limited communication and interaction abilities. Although fault tolerance and robustness to individual robot failures have often been used to justify the use of swarm robotic systems, recent studies have shown that swarm robotic systems are susceptible to certain types of failure. In this paper we propose an approach to self-healing swarm robotic systems and take inspiration from the process of granuloma formation, a process of containment and repair found in the immune system. We use a case study of a swarm performing team work where previous works have demonstrated that partially failed robots have the most detrimental effect on overall swarm behaviour. In response this, we have developed an immune inspired approach that permits the recovery from certain failure modes during operation of the swarm, overcoming issues that effect swarm behaviour associated with partially failed robots

An artificial immune system for self-healing in swarm robotic systems

Swarm robotics is concerned with the decentralised coordination of multiple robots having only limited communication and interaction abilities. Although fault tolerance and robustness to individual robot failures have often been used to justify the use of swarm robotic systems, recent studies have shown that swarm robotic systems are susceptible to certain types of failure. In this paper we propose an approach to self-healing swarm robotic systems and take inspiration from the process of granuloma formation, a process of containment and repair found in the immune system. We use a case study of a swarm performing team work where previous works have demonstrated that partially failed robots have the most detrimental effect on overall swarm behaviour. In response this, we have developed an immune inspired approach that permits the recovery from certain failure modes during operation of the swarm, overcoming issues that effect swarm behaviour associated with partially failed robots

A stakeholder approach to sustainable development in UK aviation

Aviation has become an integral component of a modern transportation system. The economic and social benefits of flight are numerous and extensive. Increasing concern about the negative environmental and social costs of aviation has begun to question projected growth of the industry. Sustainable development has become an accepted principle of development in both government policy and business. Aviation development involves the complex interaction of a wide network of stakeholders, and the resultant perceived socio-economic and environmental impacts. This complex interaction forms the basis of this thesis. The development of UK aviation is concerned with not just the development of new infrastructure and technology, but also the utilisation of existing infrastructure and technology. Future development could be by any number of alternative scenarios. However, which future scenario is superior to others? And, how should this comparison be assessed? Sustainable development evolved as a multi-disciplinary concept and this thesis draws from a wide variety of disciplines to explore the phenomenon. The stakeholder research tradition is utilised to develop a participatory stakeholder-based methodology to identify and measure the relevant impacts of sustainable development. This new ‘stakeholder-sustainable development framework’ can analyse and evaluate the current system and inform the selection and integration of assessment techniques, and the rationale behind their selection. This methodology is applied to UK aviation to identify perceived impacts and explore epistemological interpretations of sustainable development. Through semi-structured interviews, participants are invited to share the perceived impacts and their understanding of sustainable development in relation to aviation. Methods of assessment, for the identified impact of noise, are reviewed and one applied. The research proposes a network of stakeholder actors key to the future development of aviation in the UK, and whose needs should be considered. The make-up of stakeholder representation at the airport level is relatively consistent at different airport scales

Construction of Minitransposons for Constitutive and Inducible Expression of Pertussis Toxin in Bvg-Negative Bordetella-Bronchiseptica

Appropriately detoxified pertussis toxin (PT) of Bordetella pertussis is considered to be an essential component of new-generation whooping cough vaccines, but the development of a procedure to obtain high levels of purified toxin has been and continues to be a major difficulty. To produce a system enabling the biological separation of PT from other virulence determinants of B. pertussis and the attainment of high yields of the toxin, minitransposons containing the PT operon were constructed and stably integrated into the chromosome of Bordetella virulence regulatory gene (bvg)-negative Bordetella bronchiseptica ATCC 10580. Since the minitransposons introduced into Bordetella spp. lack the cognate transposase function, they are unable to undergo further transposition events or mediate gene deletions and rearrangements that lead to strain instability. The TnPtacPT minitransposon contains the PT operon under the control of the tac promoter and directs IPTG (isopropyl-beta-D-thiogalactopyranoside)-inducible expression of PT in B. bronchiseptica ATCC 10580. The level of IPTG-induced PT expression was, however, lower than that found for the wild-type B. pertussis Tohama I strain. The TnfusPT minitransposon contains a promoterless PT operon which is only expressed after insertion of the transposon downstream of an appropriately oriented indigenous promoter. After "promoter probing" of B. bronchiseptica with the transposon, clones were screened for PT production by immunoblotting with specific monoclonal antibodies. One clone, designated B. bronchiseptica 10580:: TnfusPT1, expresses significantly higher levels of PT than does B. pertussis Tohama I. The recombinant toxin produced was biologically active in the Chinese hamster ovary cell-clustering assay. High-level expression of PT from a B. bronchiseptica host promoter should provide better yields of the toxin from bacteria not producing other bvg-regulated pathogenesis factors that may play a role in the undesired side effects of current pertussis vaccine preparations