Magnetic Properties of Nanocrystalline Fe_(60)Cr_(40) Powders Prepared by Mechanical Alloying in Vacuum and Air

1　Introduction　Sincethediscoveryofgiantmagnetoresistance(GMR),magneticmaterialswithrandommixtureofferromagneticandantiferromagneticpropertieshaverecentlyrecievedalotofattention[1].ThemagneticpropertiesofFeandCrarequitedifferentfromeachother.Feisferromagneticbelow1043K,whileCrisantiferromagneticatroomtemperature.GMRexistesnotonlyinsandwichandmultilayerfilms,butalsoinothernanostructuralmaterials,suchasgranularfilmsandnanostructurebulkmaterialspreparedbymechanicalalloying(MA).MAhasbeendev…     

Acquiring an attacking forehand drive: the effects of static and dynamic environmental conditions

Two groups of 10 novice subjects each were trained to perform attacking forehand drives in table tennis and land the balls as fast and as accurately as possible onto a target on the opposite side of the net under two different training conditions. Under the static training condition, the balls were to be struck from a constant position, and under the dynamic training condition, balls approached the subjects in a normal way. Both groups were tested under dynamic conditions prior to and after four days of training, during which they received 1,600 practice trials. Both groups of subjects were shown to increase the number of balls that landed on the target, and learning was also evident from an increased consistency of the direction of travel of the bat at the moment of ball/bat contact. However, no increase in consistency was found for the location of the bat at the moment of ball/bat contact and for the movement times. Thus, learning can occur in the absence of externally generated time-to-contact information, but this is not due to the establishment of a consistent movement form. Learning appears to progress from control at the moment of ball/bat contact backward, toward the moment of initiation.     

A Bibliography for Philosophy and Constructivism in Science Education

The research literature on educational constructivism is voluminous (see the Carmichael (1990) Pfundt & Duit (1994) and Driver et al. (1994b) bibliographies cited below). The research - in both the Piagetian and Alternative Conception traditions - covers children's learning, cognitive development, curriculum development, classroom practices, teacher education, and much else. There is a further enormous literature on constructivism in philosophy of science (see Leplin (1984) and Churchland & Hooker (1985)), and on constructivism in the sociology of science (see Brown (1984), McMullin (1988, 1992). In turn these latter literatures overlap with the ocean of writing on post-modernist theory of knowledge and cognition (see Gross & Levitt (1994)). The following references relate mostly to educational constructivism, and then, with some exceptions, to articles that address epistemological and philosophical matters in science education. Even so it is not an exhaustive list, but hopefully it will be useful for teachers and researchers in the field. The author welcomes additions or omissions being brought to his attention.