中国科学院力学研究所2001年度科研状况与主要进展

<正>2001年是跨入新世纪的第一年,也是“十五”的第一年．在此年度,力学所的科研工作在诸多层面上都取得了重要的突破和进展．

Positron-annihilation study of compensation defects in InP

Positron-annihilation lifetime and positron-annihilation Doppler-broadening (PADB) spectroscopies have been employed to investigate the formation of vacancy-type compensation defects in n-type undoped liquid encapsulated Czochrolski grown InP, which undergoes conduction-type conversions under high temperature annealing. N-type InP becomes p-type semiconducting by short time annealing at 700 degreesC, and then turns into n-type again after further annealing but with a much higher resistivity. Long time annealing at 950 degreesC makes the material semi-insulating. Positron lifetime measurements show that the positron average lifetime tau(av) increases from 245 ps to a higher value of 247 ps for the first n-type to p-type conversion and decreases to 240 ps for the ensuing p-type to n-type conversion. The value of tau(av) increases slightly to 242 ps upon further annealing and attains a value of 250 ps under 90 h annealing at 950 degreesC. These results together with those of PADB measurements are explained by the model proposed in our previous study. The correlation between the characteristics of positron annihilation and the conversions of conduction type indicates that the formation of vacancy-type defects and the progressive variation of their concentrations during annealing are related to the electrical properties of the bulk InP material. (C) 2002 American Institute of Physics.

国家自然科学基金半导体学科2001年项目概况分析

简介并分析最近几年半导体学科基金项目申请和资助的发展趋势以及2001年半导体学科基金申请与资助概况，并附2001年半导体学科批准资助的面上及重点项目，供有关科技工作者参考。

Tree-ringbased drought reconstruction (a.d. 1855-2001) for the Qilian mountains；northwestern China

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Sporopollen analysis of Core B10 in the southern Yellow Sea and the reflected characteristics of climate changes

Eight sporopollen zones have been divided based on the results of high-resolution sporopollen analysis of Core B10 in the southern Yellow Sea. Based on the results along with C-14 datings and the subbottom profiling data, climatic and environmental changes since the last stage of late Pleistocene are discussed. The main conclusions are drawn as follows: (1) the vegetation evolved in the process of coniferous forest-grassland containing broad-leaved treesconiferous and broad-leaved mixed forest --> coniferous and broad-leaved mixed forest-grassland prevailed by coniferous trees --> coniferous and broad-leaved mixed forest-grassland containing evergreen broad-leaved trees- coniferous and broad-leaved mixed forest-grassland prevailed by broad-leaved trees-deciduous broad-leaved forest-meadow containing evergreen broad-leaved trees- coniferous and broadleaved mixed forest-grassland prevailed by broad-leaved trees- coniferous and broad-leaved mixed forest containing evergreen broad-leaved trees; (2) eight stages of climate changes are identified as the cold and dry stage, the temperate and wet stage, the cold and dry stage, the warm and dry stage, the temperate and wet stage, the hot and dry stage, the temperate and dry stage, then the warm and dry stage in turn; (3) the sedimentary environment developed from land, to littoral zone, to land again, then to shore-neritic zone; and (4) the Yellow Sea Warm Current formed during early-Holocene rather than Atlantic stage.

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers (ADPs) deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M-2 current is the most dominant primary tidal constituent, while MS4 and M-4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.