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111.
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D P Sen Gupta 《Resonance》2007,12(3):54-69
Alternating Current (AC) is used all over the world today. In India we use AC at 50 Hz (cycles per second) and in USA and
Canada at 60 Hz. During the latter part of the 19th century, even during the early part of the 20th century, Direct Current
or DC was widely used. Had we continued with DC, electricity would not have been as widely available as it is today and its
use would have been cumbersome, costly and severely restricted. We owe it mainly to the Serbian genius Nikola Tesla that electricity
has reached almost every nook and corner of most continents. 相似文献
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Lyn D. English 《Educational Studies in Mathematics》2006,63(3):303-323
This paper examines 6th grade children's local conceptual development and mathematization processes as they worked a comprehensive
mathematical modeling problem (creating a consumer guide for deciding the best snack chip) over several class periods. The
children and their teachers were participating in a 3-year longitudinal teaching experiment in which sequences of mathematical
modeling problems were implemented from the 5th grade (10 years of age) though to the 7th grade. In contrast to traditional
problem solving, mathematical modeling requires children to generate and develop their own mathematical ideas and processes,
and to form systems of relationships that are generalizable and reusable. Reported here is a detailed analysis of the iterative
cycles of development of one group of children as they worked the problem, followed by a summary of the mathematization processes
displayed by all groups. Children's critical reflections on their models are also reported. The results show how children
can independently develop constructs and processes through meaningful problem solving. Children's development included creating
systems for operationally defining constructs; selecting, categorizing, and ranking factors; quantifying quantitative and
qualitative data; and transforming quantities. 相似文献
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Tolar TD Lederberg AR Gokhale S Tomasello M 《Journal of deaf studies and deaf education》2008,13(2):225-240
Early developmental psychologists viewed iconic representation as cognitively less complex than other forms of symbolic thought. It is therefore surprising that iconic signs are not acquired more easily than arbitrary signs by young language learners. One explanation is that children younger than 3 years have difficulty interpreting iconicity. The current study assessed hearing children's ability to interpret the meaning of iconic signs. Sixty-six 2.5- to 5-year-olds who had no previous exposure to signs were required to match iconic signs to pictures of referents. Whereas few of the 2.5-year-olds recognized the meaning of the iconic signs consistently, more than half of the 3.0-year-olds and most of 3.5-year-olds performed above chance. Thus, the ability to recognize the meaning of iconic signs gradually develops during the preschool years. Implications of these findings for sign language development, receptive signed vocabulary tests, and the development of the ability to interpret iconic symbols are discussed. 相似文献
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1 Introduction Duringthe past several decades ,considerable atten-tion has been given to devising methods for solvingconstrained opti mization problemsviaunconstrainedmini mization techniques and a number of researchwork in the area of nonlinear programmi… 相似文献