Passively Q-switched Nd : GdVO4 laser with In0.25Ga0.75As being an output coupler

We report a diode-end-pumped passively Q-switched Nd:GdVO4 laser operating at 1.06 mu m with In0.25Ga0.75As being the saturable absorber as well as an output coupler. Q-switched pulses with a pulse duration of 20 ns, pulse energy 4.2 mu J and pulse repetition rate 200 kHz were produced, corresponding to peak power of 210 W. (c) 2006 Elsevier Ltd. All rights reserved.

学前儿童朴素生物学“理论”的发展——对“生长”认知的实验研究

There is a debate in cognitive development theory on whether cognitive development is general or specific. More and more researchers think that cognitive development is domain specific. People start to investigate preschoolers' native theory of human being's basic knowledge systems. Naive biology is one of the core domains. But there is argument whether there is separate native biological concepts among preschoolers. The research examined preschoolers' cognitive development of naive biological theory on two levels which is "growth" and "aliveness", and it also examined individual difference and factors that lead to the difference. Three studies were designed. Study 1 was to study preschoolers' cognition on growth, which is a basic trait of living things, and whether children can distinguish living and non-living things with the trait and understanding the causality. Study 2 was to investigate preschoolers' distinction between living things and non-living things from an integrated level. Study 3 was to investigate how children make inferences to unfamiliar things with their domain specific knowledge. The results showed the following: 1. Preschoolers gradually developed naive theory of biology on growth level, but their naive theory on integrated level has not developed. 2 Preschoolers' naive theory of biology is not "all or none", 4- and 5-year-old children showed some distinction between living and non-living things to some extent, they use non-intentional reason to explain the cause of growth and their explanation showed coherence. But growth has not been a criteria of ontological distinction of living and non-living things for 4- and 5-year-old children, most 6-year-old children can distinguish between living and non-living things, and these show the developing process of biological cognition. 3. Preschoolers' biological inference is influenced by their domain-specific knowledge, whether they can make inference to new trait of living things depends on whether they have specific knowledge. In the deductive task, children use their knowledge to make inference to unfamiliar things. 4-year-olds use concrete knowledge more often while the 6-year-old use generalized knowledge more frequency. 4. Preschoolers' knowledge grow with age, but individuals' cognitive development speed at different period. Urban and rural educational background affect cognitive performance. As time goes by, the urban-rural knowledge difference to distinguish living and nonliving things reduces. And preschoolers' are at the same developmental stage because the three age groups have similar causal explanation both in quantity and quality. 5. There is intra-individual difference on preschoolers' naive biological cognition. They show different performance on different tasks and domains, and their cognitive development is sequential, they understand growth earlier than they understand "alive", which is an integrated concept. The intra-individual differences decrease with age.