谁才是英雄?

多年前,在怀俄明州,我从一辆燃烧的汽车中救出一家人.上周,我接到了一位女士的电话,她哭着告诉我,我的一个故事挽救了她的准备自杀的儿子.……     

Understanding Magnetic and Electrostatic Actuators Using Bond Graphs and a Mechanical Model

Magnetic actuators in relays, solenoids, and valve positioners and electrostatic loudspeakers and microphones store electrical and mechanical energy and are inherently nonlinear. They are harder to understand than transformer or gyrator transducers such as hydraulic pistons or voice coil drives which transduce power instantaneously and are essentially linear. Bond graph models show that magnetic and electrostatic transducers are mathematically analogous although electrically dual. An all-mechanical equivalent model shows the nonlinear behavior clearly and aids in the intuitive understanding of the problems associated with the use of such actuators.     

Factors underlying distance learner satisfaction with televised college‐level courses

Abstract

Two investigations were conducted to identify the major dimensions of distance learner satisfaction with live‐broadcast, interactive (one‐way video, two‐way audio) televised college‐level courses. In the first study, factor analyses were used to explore the responses of 201 currently enrolled students to the Telecourse Evaluation Questionnaire. The analyses identified seven distinct dimensions of course satisfaction. A comparable study was conducted one year later using a different sample of 177 distance learners who were also enrolled in the televised courses. A factor analysis of these data validated the original results in that, as predicted, seven comparable dimensions were identified. Overall results are discussed in terms of the practical benefits the research offers to both program personnel and evaluation researchers.