情人节

Valentine's Day has come and gone for this year, and I only got one small present. That may sound like I'm complaining, but I'm not, for it was the most wonderful gift I have ever received on that special day.     

The educational technology mix: Production functions from “Sesame Street”

This is a re-analysis of data collected in an evaluation of Sesame Street. The data were obtained from 695 kindergarten-aged children randomly selected from five areas of the United States. The purpose of the study was to examine the effects of Sesame Street in a multi-variate framework, and to develop production functions showing the contributions which could be derived from the production function paradigm, most especially what might be gained by examining the possible results of mixing television viewing with teacher effort.The major findings are that the more a child watches Sesame Street, the more he learns; the higher a child's social class the more he learns from watching the program; and that Sesame Street does not affect disadvantaged children more than advantaged children, and hence has limited utility as a means of reducing differences in school performance between the rich and poor. Limitations in the data prevented calculation of production functions estimating trade-offs between teacher input and television viewing, but the limited data available suggest that mixes are better than either teacher alone or television alone.This research was partially supported by Grant #Y-NGL-008-054 from the National Aeronautics and Space Administration. The authors would also like to acknowledge the support of their colleagues in Washington University's Center for Development Technology.     

号码锁的秘密

几十年来,许多人都像《科学美国人》的读者Billy Ellis那样,曾经对日常生活中的一些小事感到纳闷.     

The limited benefits of rereading educational texts

Though rereading is a study method commonly used by students, theoretical disagreement exists regarding whether rereading a text significantly enhances the representation and retention of the text’s contents. In four experiments, we evaluated the effectiveness of rereading relative to a single reading in a context paralleling that faced by students in the classroom. Participants read educational texts (textbook chapters or a Scientific American article) under intentional learning instructions. Learning and memory were tested with educationally relevant summative assessments (multiple choice, short-answer questions, and text summaries). With only several exceptions, rereading did not significantly increase performance on the assessments. We also found that reading comprehension ability did not alter this pattern. It appears that when using ecologically valid materials such as a textbook chapter, immediate rereading may have little or no benefit for improving performance on educationally relevant summative assessments.     

The production of hydrocarbons from coal

There are two main routes for converting coal to refined hydrocarbons. The first is to add hydrogen directly to coal under high pressure and temperature and then refine the resultant crude products. The reliability of this process still needs to be demonstrated, and to date no commercial operations exist. The second is first to completely gasify the coal and then catalytically to convert the carbon monoxide and hydrogen to hydrocarbons. This Fischer-Tropsch process is commercially proven, having been operated by Sasol in South Africa for over twenty years: it is versatile in that different hydrocarbon cuts can be maximized by adapting operating procedures.