Dynamic behavior of a hydraulic crane operating a freely suspended payload     

Bozhidar Grigorov  Rosen Mitrev 《浙江大学学报(A卷英文版)》2017,18(4):268-281

We describe an investigation of the dynamic behavior of a hydraulically driven crane with a freely suspended payload during luffing and slewing motions. To simplify the task, the two movements are considered separately. Taking into account only one motion at a time, the crane is regarded as a three-link kinematic chain with revolute joints. The forward dynamics problem is solved for a crane with three rotational degrees of freedom, two of which describe the load swinging. In both the cases studied, the links are driven by a torque applied via a hydraulic drive, i.e., a linear actuator for the luffing case and a rack and pinion mechanism for the slewing motion. To compose the set of differential equations for the forward dynamics problem, a method based on a general Newton-Euler algorithm is used. From these simulations the time histories of various parameters, namely the swinging angles, hydraulic pressures, and joint forces, are determined. The results obtained via simulations are confirmed experimentally and a good agreement between the two outputs is observed. The results also show that a hydraulic drive system using fast opening flow direction control valves increases the load swing and imposes extensive inertial forces and problems of fatigue and reliability.  相似文献   

The Case for Women Mentoring Women     

Betty Ann Block  Tara Tietjen-Smith 《Quest (Human Kinetics)》2016,68(3):306-315

ABSTRACT

The authors argue that there will be a critical mass of women in leadership positions in kinesiology and across higher education for substantial gender-based mentoring to take place in the 21st century. First, the current state of women in higher education leadership, trends in mentoring, and the reasons it is important for women who have aspirations to advance in their careers are examined. The authors argue that it is important to have access to gender-based guidance and support that are critical to successful leadership into the future. The authors advocate for a focused, purposeful type of mentoring supported by relational-cultural theory and narrative practice. Men will continue to be important mentors for women, but the authors argue that, at the same time, women also need to have access to the perspectives of other women who have forged the way into higher education administration.  相似文献   

Recipes for fun     

Ann Cole  Carolyn Haas  Elizabeth Heller  Betty Weinberger 《Early Childhood Education Journal》1974,2(2):35-41

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Are all phonemic awareness tests created equally? A comparison of the Yopp‐Singer and the task of auditory analysis skills (TASS)     

Jerry Wilde  Betty Goerss  Jennifer Wesler 《Journal of Research in Reading》2003,26(3):295-303

This study examined two screening instruments designed to measure phonemic awareness (Test of Auditory Analysis Skills‐TAAS and Yopp‐Singer Test of Phoneme Segmentation). Participants included 25 second‐semester kindergarten children who were administered both instruments. The dependent measure (the STAR Reading Test) was administered in February of their First‐Grade year. The investigation was designed to determine if these instruments are both evaluating the same skills and identify which was more effective in predicting success in reading near the end of First Grade. The children's scores from the Yopp‐Singer and the TAAS were correlated (r=0.56, p<0.01) and so were the scores between the TAAS and STAR (r=0.51, p<0.01). Comparison of scores between the Yopp and the STAR produced non‐significant results (r=0.31). Although the TAAS produced a higher correlation with reading achievement than the Yopp‐Singer, the difference between these two measures failed to reach significance (t=1.16). Implications of these findings, along with possible explanations of the results, are discussed.  相似文献   

Remembering Activities Performed Versus Imagined: A Comparison of Children with Mental Retardation and Children with Normal Intelligence     

Kenneth G. Jens  Betty N. Gordon  Anthony J. Shaddock 《International Journal of Disability, Development & Education》1990,37(3):201-213

CHILDREN with mental retardation and children with normal intelligence were asked to perform a series of tasks or to only imagine performing them. They were then asked to remember which tasks had been performed and which had been imagined at an immediate interview and after an eight week delay. There were no overall differences between the two groups in the number of correct responses. However, all children gave more correct responses to specific probes than to open‐ended probes and remembered activities performed better than those imagined. Performance was more accurate for both groups at the immediate interview than at the delayed interview. Responses to questions about activities neither performed nor imagined were good for both groups of children to the initial questions but decreased significantly in response to a follow‐up probe. Accuracy of responses to these misleading questions decreased over the eight week delay.  相似文献   

Videoconferencing     

Barbara J. Ehrhard  Betty L. Schroeder 《TechTrends》1997,42(3):32-34

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The structured flexibility of Orton-Gillingham     

Betty B. Sheffield 《Annals of dyslexia》1991,41(1):41-54

This paper discusses a philosophic basis for Orton-Gillingham teaching and attempts to demonstrate how certain of the features of such multisensory teaching act to remediate language problems exhibited by many dyslexic students. The common basis of the array of programs coming from both Orton and Gillingham is addressed. Some individual strengths and minor differences between Orton and Gillingham variations are examined. The author is grateful to Margaret Rawson who coined the phrase “Structured Flexibility” in her article, “The Structure of English: The language to be learned,” in theBulletin of the Orton Society 20:103.  相似文献   

Television Violence and Its Effects on Young Children     

Betty Jo Simmons  Kelly Stalsworth  Heather Wentzel 《Early Childhood Education Journal》1999,26(3):149-153

This article examines research on television violence and links violence to specific programs commonly watched by young children. Although there are some who try to disprove any connection between television and aggresive behavior, there is evidence to suggest that such linkages do exist.  相似文献   

Elixir     

Norma Rosen 《Academic Questions》1998,12(1):63-78

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Designing for Differences: Cultural Issues in the Design of WWW-Based Course-Support Sites   总被引：1，自引：0，他引：1  

Betty Collis 《British journal of educational technology : journal of the Council for Educational Technology》1999,30(3):201-215

Culture is a critical influence on the acceptance, use of, and impact of learning resources. WWW-based course-support sites are becoming an increasingly familiar type of learning resource in higher education. How might different aspects of culture be predicted to affect the institution's, instructor's, and student's reactions to WWW-based course-support sites? How can such sites be designed to adapt to different expectations and learner preferences, especially those related to culture? This article analyses various of these cultural aspects, and argues that WWW-based course-support sites should be designed to be adaptable to different types of cultural differences through the application of a set of ten design guidelines. An example illustrating the design guidelines, the TeleTOP Method from the University of Twente, is described and evaluated relative to the design guidelines. Important considerations related to feasibility as well as to conceptual and strategic choices are included in the scope of the guidelines; the instructor's cultural ecology requires particular attention. But WWW sites and guidelines in themselves are not enough for cultural flexibility; sensitivity and appropriate responsiveness remain human activities.  相似文献