Limit analysis of flow through conical converging dies

A variety of mathematical models may be used to analyse plastic deformation during a metal-forming process. One of these methods—limit analysis—places the estimate of required power between an upper bound and a lower bound. The upper and lower bound analyses are designed so that the actual power or forming stress requirement is less than that predicted by the upper bound and greater than that predicted by the lower bound. Finding a lower upper bound and a higher lower bound reduces the uncertainty of the actual power requirement. Upper and lower bounds will permit the determination of such quantities as required forces, limitations on the process, optimal die design, flow patterns, and prediction and prevention of defects.Fundamental to the development of both upper bound and lower bound solutions is the division of the body into zones. For each of the zones there is written either a velocity field (upper bound) or a stress field (lower bound). A better choice of zones and fields brings the calculated values closer to actual values.In the present work, both upper and lower bound solutions are presented for axisymmetric flow through conical converging dies. For the upper bound triangular velocity fields have been solved and compared to previously published work on spherical velocity fields. It is found that each type provides a lower solution over a part of the range of process variables. A previously published lower bound solution for axisymmetric flow is refined.     

The Best of the Recent Literature Focusing on the User

This will be my first time authoring this column, and I'm delighted to have the opportunity it presents to explore the intersection of library technology and public services. As the recent title of the 2008 Internet Librarian conference indicates, Beyond Library 2.0: User-Focused Tools and Technologies, the tide of what for several years has felt like library technology evangelism is turning. A focus on more effective tech-based development in libraries is underway, one that privileges the actual impact of services on patrons over our need to keep up with the proverbial Joneses. This is a natural correction—libraries experienced a sort of “tech bubble” as early adopters enthusiastically explored the promise of new Web-based communication methods and user-created tools. After several years of trial and error, many early adopters now find themselves adjusting expectations, considering overall scalability, and evaluating outcomes of their early experiments. Much can be learned from these experiences, and a wealth of evidence, conjecture, and rules of thumb can now assist librarians in any stage of technology development prevent duplication of effort (and error). With this in mind, I will attempt to make this column as practically oriented as possible. I will draw from the knowledge of those who have confronted the types of issues and pitfalls inherent to library innovation, and I will explore proven approaches that can help librarians in the public services develop more effective and user-centered technologies. At times I will invite guest authors to describe best practices developed at their own institutions and/or explore topics that carry broad implications for public service practitioners.     

Proportionnalité et Pourcentage Chez des Apprentis Vendeurs. Réflexion sur la Relation Mathématiques / Réalité dans une Formation 'en Alternance'

This article presents the results of a research study conducted with apprentices in order to examine the double hypothesis that vocational training incorporating work placement gives the opportunity to construct authentic situations out of the everyday practices of students and that these situations allow students to improve their understanding of mathematical problems. After analysis of workplace situations had shown that the only mathematical concept used by apprentices was that of proportionality applied to percentage calculations, we first analysed the way in which students at several levels handled this idea of percentage. We then devised an experimental framework in order to help the apprentices to transfer their knowledge. RéSUMé: Cet article présente les résultats d'une recherche menée avec des apprentis vendeurs afin de vérifier la double hypothèse qu'un enseignement professionnel en alternance donne l'opportunité de construire des situations authentiques, à partir des pratiques quotidiennes des élèves et que ces situations permettent aux élèves d'améliorer leur compréhension des problèmes mathématiques. L'analyse des situations de travail ayant montré que le seul concept mathématique dont les apprentis ont l'usage est le concept de proportionnalité appliqué aux calculs de pourcentage, nous avons d'abord analysé le comportement d'élèves de plusieurs niveaux face à cette notion de pourcentage. Nous avons ensuite mis en place un dispositif expérimental afin d'aider les apprentis à transférer leurs connaissances. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improving the Cultural Competency of Social Work Students With a Social Privilege Activity

This article describes the development and utilization of an instructional activity created by the authors for the purposes of preparing social work students for culturally competent practice with members of historically oppressed populations. Experiential activities in the classroom provide an alternative approach to traditional pedagogical methods by positioning the learner at the center of an educational process that is grounded in reality. The activity is designed to highlight the social privileges of individuals and the inherent risks that are taken when deciding to challenge or confront oppressive structures, attitudes, and behaviors.     

Improving Museum Docents' Communication Skills

This article presents the results of a study evaluating a program to help museum docents improve accessibility for visitors with communication challenges (such as hearing, language and/or speech disorders). This was done by adapting docent presentations. The docents' speech patterns were evaluated before and after a training program, and showed significant improvements in the rate, duration, and use of pauses in their speech. There also was significant improvement in ensuring that view of their faces remained unobstructed—important for people with communication disorders—in order to facilitate the consistent visibility of their facial expressions and visual cues. The training was found to be effective in adjusting the docents' presentations so that the museum experience would be improved for visitors with communication challenges.     

Upper extremity kinematic trends of fly-casting: establishing the effects of line length

Fly-fishing is a popular form of recreation. Recent evidence has associated overhand fly-casting movements with upper extremity pain. However, little research exists on the motions and coordination common to fly-casting. The aim of this study was to establish upper extremity kinematic trends of fly-casting while casting greater line lengths. It was hypothesized that kinematic casting parameters would increase and time between peak angular velocities would decrease with greater line length. Eighteen males participated in the study. Three-dimensional motion capture was conducted to calculate shoulder, elbow, and wrist kinematics during casting conditions of 6.1, 12.2, 18.3, and 24.4 m of line. Multiple analyses of variance were used to assess the condition effect of line length on the kinematic variables (P = 0.05). Overall, total range of movement increased with increasing length of line cast. Peak angular velocity exhibited a proximal-to-distal trend: peak shoulder internal rotation followed by elbow extension, then wrist ulnar deviation. Time between peak shoulder and elbow angular velocities increased significantly as line length increased. Our findings indicate that specific changes in total range of movement accommodate the demands of casting greater lengths of line. Also, joint velocity coordination patterns of fly-casting appear to follow a proximal-to-distal pattern. These findings represent an initial foundation for connections between kinematics and upper extremity pain reported by fly-fisherman.     

Practical precooling: effect on cycling time trial performance in warm conditions

The purpose of this study was to compare the effects of two practical precooling techniques (skin cooling vs. skin + core cooling) on cycling time trial performance in warm conditions. Six trained cyclists completed one maximal graded exercise test (VO2(peak) 71.4 +/- 3.2 ml x kg(-1) x min(-1)) and four approximately 40 min laboratory cycling time trials in a heat chamber (34.3 degrees C +/- 1.1 degrees C; 41.2% +/- 3.0% rh) using a fixed-power/variable-power format. Cyclists prepared for the time trial using three techniques administered in a randomised order prior to the warm-up: (1) no cooling (control), (2) cooling jacket for 40 min (jacket) or (3) 30-min water immersion followed by a cooling jacket application for 40 min (combined). Rectal temperature prior to the time trial was 37.8 degrees C +/- 0.1 degrees C in control, similar in jacket (37.8 degrees C +/- 0.3 degrees C) and lower in combined (37.1 degrees C +/- 0.2 degrees C, P < 0.01). Compared with the control trial, time trial performance was not different for jacket precooling (-16 +/- 36 s, -0.7%; P = 0.35) but was faster for combined precooling (-42 +/- 25 s, - .8%; P = 0.009). In conclusion, a practical combined precooling strategy that involves immersion in cool water followed by the use of a cooling jacket can produce decrease in rectal temperature that persist throughout a warm-up and improve laboratory cycling time trial performance in warm conditions.