B-52“同温层堡垒”型战略轰炸机(上)

从50多年前波音公司研制的YB-52首次升空开始,B-52“同温层堡垒”（Stratofortress）型战略轰炸机一直是展示美国军事力量以及美国政府在必要情况下于任何时间和地点使用武力的军事意志的重要标志。目前,美军仍然没有显示出替换这种轰炸机的迹象,作为波音公司研发杰作之一的B-52仍将是美军在21世纪的一种关键性武器装备。     

Constructing normalcy: a qualitative study of parenting children with Asperger's Disorder

Children with Asperger's Disorder present unique challenges due to their impairments in social functioning. In order to better understand the experiences of parents of children with Asperger's Disorder, interviews were conducted with 20 parents. The interviews were taped, transcribed, and coded using the systematic methods of Grounded Theory. The central phenomenon of “constructing normalcy” emerged from the data as a salient construct for participants. Parents interviewed described a process of meaning‐making with respect to standards of “normalcy” and an effort to create adaptive environments for their children.     

Sandcastle competitions

This commentary discusses reasons that lead scholars to feel entitled to make judgements in areas where they have little or no expertise. Three current reports about the future of online learning are considered, issued by the Global Learning Council, Massachusetts Institute of Technology, and the Gates Foundation. Two of these publications contain contradictions and confusion that may simply be due to lack of awareness of distance education (DE) and online learning research. The third report gives good evidence but has been criticized for being too academic. The conflicting standards and criteria evident in such writings may be due to institutional pressures to promote policies and principles despite lack of supportive evidence, and to weaknesses in the DE literature itself. As major institutional policies about online learning are likely to be based on the recommendations of such reports, it is important for DE specialists to challenge them where appropriate.     

Evaluating item response theory linking and model fit for data from PISA 2000–2012

ABSTRACT

Based on concerns about the item response theory (IRT) linking approach used in the Programme for International Student Assessment (PISA) until 2012 as well as the desire to include new, more complex, interactive items with the introduction of computer-based assessments, alternative IRT linking methods were implemented in the 2015 PISA round. The new linking method represents a concurrent calibration using all available data, enabling us to find item parameters that maximize fit across all groups and allowing us to investigate measurement invariance across groups. Apart from the Rasch model that historically has been used in PISA operational analyses, we compared our method against more general IRT models that can incorporate item-by-country interactions. The results suggest that our proposed method holds promise not only to provide a strong linkage across countries and cycles but also to serve as a tool for investigating measurement invariance.     

Technology Knowledge and Use: A Survey of Science Educators

The purpose of this study was to determine the current state of technology use and know-how among members of the Association for the Education of Teachers in Science. A web-based survey site and an e-mail merge invited members to participate in the study. The survey examined the differences between current and desired levels of knowledge about using technology as an instructional tool, to support research, to enhance productivity in classroom applications, and to enhance data collection and analysis. Large mean differences about using technology as an instructional tool were found, including: (1) teaching students at a distance, (2) database applications, and (3) desktop publishing. Small mean differences were found for telecommunications and word processing.     

Differences in Career Aspirations,Influences, and Motives as a Function of Class Standing: An Empirical Evaluation of Undergraduate Criminal Justice Majors

The purpose of this study was to determine whether career aspirations, influences, and motives differ by class standing (freshman, sophomore, junior, and senior). A cross-sectional analysis of surveys completed by 204 criminal justice majors revealed a negative correlation between class standing and student interest in a law enforcement career (i.e. freshman and sophomores showed greater interest in a law enforcement career than juniors and seniors). Further analysis indicated that television and movies had a greater impact on the career aspirations of underclassmen, whereas teachers and professors had a greater impact on the career aspirations of upperclassmen. Motivational factors did not differ by class standing, however: students, regardless of class standing, reported that helping others and the interesting nature of the subject matter were their two strongest motives for seeking a criminal justice career and wearing a uniform and power were the two weakest motives for seeking a criminal justice career.     

The development of flexibility in equation solving

This paper explores the development of students’ knowledge of mathematical procedures. Students’ tendency to develop rote knowledge of procedures has been widely commented on. An alternative, more flexible endpoint for the development of procedural knowledge is explored here, where students choose to deviate from established solving patterns on particular problems for greater efficiency. Students with no prior knowledge of formal linear equation solving techniques were taught the basic transformations of this domain. After instruction, students engaged in problem-solving sessions in two conditions. Treatment students completed the “alternative ordering task,” where they were asked to re-solve a previously completed problem but using a different ordering of transformations. Those completing alternative ordering tasks demonstrated greater flexibility.     

The design and development of the dragoon intelligent tutoring system for model construction: lessons learned

This paper describes Dragoon, a simple intelligent tutoring system which teaches the construction of models of dynamic systems. Modelling is one of seven practices dictated in two new sets of educational standards in the U.S.A., and Dragoon is one of the first systems for teaching model construction for dynamic systems. Dragoon can be classified as a step-based tutoring system that uses example-tracing, an explicit pedagogical policy and an open learner model. Dragoon can also be used for computer-supported collaborative learning, and provides tools for classroom orchestration. This paper describes the features, user interfaces, and architecture of Dragoon; compares and contrasts Dragoon with other intelligent tutoring systems; and presents a brief overview of formative and summative evaluations of Dragoon in both high school and college classes. Of four summative evaluations, three found that students who used Dragoon learned more about the target system than students who did equivalent work without Dragoon.     

Use of Computer Modeling of Site-Directed Mutagenesis of a Selected Enzyme: A Class Activity for an Introductory Biochemistry Course

For an introductory undergraduate biochemistry class, we developed an interactive, out of classroom, team project that would allow students to gain a better understanding of protein structure and function. This project involved the use of the molecular visualization program RasMol and computer simulated site-directed mutagenesis of selected amino acids of the enzyme, Uroporphyrinogen decarboxylase. Survey data from students after completion of the project indicated that they had developed a more complete understanding of protein three-dimensional structure leading to functionality.