Adapting the Knuth–Morris–Pratt algorithm for pattern matching in Huffman encoded texts

In the present work we perform compressed pattern matching in binary Huffman encoded texts [Huffman, D. (1952). A method for the construction of minimum redundancy codes, Proc. of the IRE, 40, 1098–1101]. A modified Knuth–Morris–Pratt algorithm is used in order to overcome the problem of false matches, i.e., an occurrence of the encoded pattern in the encoded text that does not correspond to an occurrence of the pattern itself in the original text. We propose a bitwise KMP algorithm that can move one extra bit in the case of a mismatch since the alphabet is binary. To avoid processing any bit of the encoded text more than once, a preprocessed table is used to determine how far to back up when a mismatch is detected, and is defined so that we are always able to align the start of the encoded pattern with the start of a codeword in the encoded text. We combine our KMP algorithm with two practical Huffman decoding schemes which handle more than a single bit per machine operation; skeleton trees defined by Klein [Klein, S. T. (2000). Skeleton trees for efficient decoding of huffman encoded texts. Information Retrieval, 3, 7–23], and numerical comparisons between special canonical values and portions of a sliding window presented in Moffat and Turpin [Moffat, A., & Turpin, A. (1997). On the implementation of minimum redundancy prefix codes. IEEE Transactions on Communications, 45, 1200–1207]. Experiments show rapid search times of our algorithms compared to the “decompress then search” method, therefore, files can be kept in their compressed form, saving memory space. When compression gain is important, these algorithms are better than cgrep [Ferragina, P., Tommasi, A., & Manzini, G. (2004). C Library to search over compressed texts, http://roquefort.di.unipi.it/~ferrax/CompressedSearch], which is only slightly faster than ours.     

Integrating inquiry science and language development for English language learners

The traditional approach to the education of language minority students separates English language development from content instruction because it is assumed that English language proficiency is a prerequisite for subject matter learning. The authors of this article take the alternate view that the integration of inquiry science and language acquisition enhances learning in both domains. The report describes a conceptual framework for science–language integration and the development of a five‐level rubric to assess teachers' understanding of curricular integration. The science–language integration rubric describes the growth of teacher expertise as a continuum from a view of science and language as discreet unrelated domains to the recognition of the superordinate processes that create a synergistic relationship between inquiry science and language development. Examples from teacher interviews are used to illustrate teacher thinking at each level. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 664–687, 2002     

在家工作的现实

在家工作既可以避免上下班的劳累,又可以较自由地安排自己的时间。但在家工作仍存在一些难题,比如:怎样避免受到他人的干扰?怎样防止自由散漫、浪费时间?本文将向有机会在家工作的人介绍一些合理安排生活的方法。     

STEM education: A deficit framework for the twenty first century? A sociocultural socioscientific response

The ubiquitous of STEM education initiatives in recent years has created a bandwagon that has moved at nearly light speed. The impulse of the science education community and policy-makers is to grab hold for dear life or be marginalized from subsequent discussions about the necessity and consequences of using STEM initiatives to prepare and inform our next generation of citizens. This commentary questions the prudence of STEM-related science education goals, as typically represented and discussed in the literature, and likens the current practice to a deficit framework. A sociocultural perspective framed through socioscientific considerations is offered as an alternative conceptualization as well as surplus model to hegemonic STEM practices.     

Discipline in the context of development: a case of the social sciences in Malawi,Southern Africa

Changes in research production precipitated by the globalization have generally been theorized as applying across nations and disciplinary projects. This article examines the relation of discipline to research production from the situational vantage point of the developing world, specifically the Southern African country of Malawi, and from the empirical perspective of the social sciences. Evidence derives from eight months of ethnographic fieldwork conducted in Malawi in 2003 and 2004, drawing specifically from over 100 formal interviews and from analysis of historical and contemporary documents. The article finds that against depictions of academic disciplines as inflexible, arbitrary, and in need of restructuring, the case of the social sciences in Malawi demonstrates the value of distinctly disciplined expertise in problem-oriented research. This efficacy is, however, precariously dependent on the capacity of local disciplinary communities to regenerate and reproduce their expertise and compete effectively in the increasingly competitive knowledge market.

Reducing students’ ‘absent presenteeism’ and mobile misbehaviour in class: an empirical study of teacher perspectives and practices

ABSTRACT

Advances in information technology and communication through new social media platforms have enormous benefits in many contexts, including education. At the same time, self-distractive use of technology – or ‘absent presenteeism’ – can have negative effects in the classroom. The main research question of this study is the relationship between organisational leadership, enforcement of discipline and self-distractive use of technology in the secondary school setting. The finding indicated that the permissive style of discipline appeared to be the most effective at reducing self-distractive mobile phone use. However, a more authoritative style of discipline, short teacher tenure and the principal’s transformational leadership style contributed to high self-distractive mobile phone use. The authors rely on empirical data collected in Israeli public high schools from two independent sources: 144 teachers and 591 students, which yielded 4440 teacher-student events. Implications of the findings are discussed in the context of the school setting characterised by rapid changes in technology.     

ENHANCING STUDENTS’ COMMUNICATION SKILLS IN THE SCIENCE CLASSROOM THROUGH SOCIOSCIENTIFIC ISSUES

Communication skills are one of the most important competencies for 21st century global citizens. Our guiding presupposition was that socioscientific issues (SSIs) could be used as an effective pedagogical tool for promoting students’ communication skills by increasing peer interactions, stimulating students’ reasoning, and in constructing shared social knowledge. We implemented a SSI program on gene modification (GM) technology to 132 9th graders in South Korea and investigated to what extent this SSI instruction contributed to enhancing students’ communication skills. Data sources included pre- and post-scores on the Communication Skills Questionnaire (CSQ), semi-structured interviews with the students and instructor, and classroom observations. The results demonstrated that SSI instruction could bring about a moderately large impact on students’ ability to understand the key ideas of others and to value others’ perspectives, as well as a marginal positive effect on developing active assertions. However, SSI instruction appeared to have a lesser impact on students’ ability to develop shared understanding. Overall, this research indicates the potential that even a limited SSI classroom could have in terms of promoting students’ communication skills in the context of their regular science class.     

The discursive negotiation of international student identities

Research about identity has undergone a discursive turn in recent years, with a shift from conceptualising identity as an essentialistic, pre-existing construct that drives social interaction, to a more fluid and hybrid construct that is constituted through discourse. As a result, a number of recent studies investigating the construction of international student identities have supposedly adhered to this latter, postmodernist-inspired notion of identity in their analyses. However, upon closer examination, these studies appear to be premised on the assumption that what international students say can be equated with their identities, without critical attention being paid to the way in which identities emerge as a conjoint construct through interaction. In this paper, it is argued that identities are invariably jointly constructed by participants through discourse, even in interviews and focus groups where the researcher is ostensibly taking a neutral stance, and thus more attention needs to be paid to the ways in which identities are discursively negotiated through interaction.     

Identifying mediating factors of moral reasoning in science education

The purpose of this research was to examine how science content knowledge, moral reasoning ability, attitudes, and past experiences mediate the formation of moral judgments on environmental dilemmas. The study was conducted in two phases using environmental science majors and nonscience majors of college age. Phase One determined if environmental science majors exhibited higher levels of moral reasoning on nontechnical environmental social issues than on general social issues and examined the extent to which possible mediating factors accounted for differences in moral reasoning. Phase Two was qualitative in nature, the purpose of which was to observe and identify trends in conversations between subjects as to how certain mediating factors are revealed as people form moral judgments. The framework on which this study was constructed incorporates a progressive educational position; a position that views science education as being interdisciplinary, and a social means to a social end.