Calculation of nonlinear optical coefficients of orthorhombic Re-2(MoO4)(3) crystals

From the chemical bond viewpoint, the second-order nonlinear optical (NLO) tensor coefficients of some Re-2(MoO4)(3) (ReMO)-type tare earth molybdates, with Re = Pr, Nd, Sm, Eu, Gd, Tb and Dy, have been calculated by using the chemical bond theory of complex crystals and the modified bond charge model. All kinds of constituent chemical bonds are considered in the calculation. The major part of the NLO properties of these ReMO crystals is found from the ReO7 groups. The NLO coefficients of these ReMO crystals decrease with Re from Pr to Dy. (C) 1998 Elsevier Science Ltd. All rights reserved.

原子力显微镜及其在电化学和电分析化学中的应用

本文评述了原子力显微镜原理和技术及其在现场电化学和电分析化学领域中的应用,并展望了扫描隧道显微镜和原子力显微镜在电化学和电分析化学中的发展方向.

可可西里地区藏羚的社群特征

藏羚(Pantholops hodgsoni)的集群类型有雌性群、雄性群、母仔群、雌雄混群和独羚5种形式。2002年7月～2003年12月，在可可西里地区沿青藏公路设立试验区，直接观察到936群次，计13795只次藏羚。藏羚的集群类型受到生育周期的影响，季节间差异显著。春季以雌性群(60．49％)和雄性群(30．86％)为主；夏季和秋季主要为雌性群(41．65％，49．66％)和母仔群(49．36％，33．67％)；雌雄混群(58．14％)主要出现在冬季。雄性群在1年中很少见，尤其是夏秋两季，冬季较为常见，多由亚成体雄性组成。独羚是一种特殊的集群类型，占11．32％。常见的集群大小为2～20只，占71．90％，其次是21～200只的群，占16．35％；>200只的集群极少，仅占0．43％，且仅出现于夏季产羔往返迁徙途中。藏羚的集群大小受竞争、捕食风险以及迁徙繁殖的共同影响。藏羚的集群极不稳定，交配期雌雄混合群受雄性亚成体的干扰经常改变，而在迁徙季节大群和小群之间的转换也很频繁。大型集群为雌性群或母仔群，其最适集群大小为2～20只。

Modeling trophic positions of the alpine meadow ecosystem combining stable carbon and nitrogen isotope ratios

Stable carbon and nitrogen isotope ratios of single tissues or whole bodies were analyzed to establish trophic positions of main consumers living at the alpine meadow ecosystem in the Tibetan Plateau. The results demonstrated that delta C-13 and delta N-15 values of vertebrates showed great variations and ranged from -26.83 to -22.51 parts per thousand and from 2.33 to 8.44 parts per thousand, respectively. Plateau pika, root vole, plateau hare, infants of rodents and hatchlings of passerine bird species had the lowest delta C-13 and delta N-15 values. delta C-13 and delta N-15 values of omnivorous and insectivorous birds and amphibians showed intermediate. Carnivorous species, steppe polecat and Upland buzzard, and omnivorous Robin accentor and White wagtail possessed extremely higher VC and delta N-15 values. Omnivorous birds captured in earlier year had significantly less negative delta C-13 and greater delta N-15 values than those captured later. Based on steady angular enrichment between trophic levels, an "alpha and vector model" combing delta C-13 and delta N-15 values was introduced to reveal trophic positions, the results indicated that Tibetan sheep, Tibetan yak, plateau pika, root vole, plateau hare, infants of small rodents showed the lowest trophic positions (TP 1.81-2.38). While omnivorous and insectivorous birds, their hatchlings and amphibians showed intermediate trophic positions (TP 2.06-2.89), carnivorous species steppe polecat and Upland buzzard, migrant birds possessed extremely higher trophic positions (TP 2.89-3.05). The isotopic investigation of organisms and the introduced "alpha and vector model" successfully demonstrated the same trophic positions and diet prediction of consumers as nitrogen enrichment model at the alpine meadow ecosystem. Besides of this information, the "alpha and vector model" can also be incorporated into multiple isotope signatures to infer trophic relationships. This angular enrichment model has the potential to address basic ecological questions, such as trophic structure, trophic dynamics, and energy flow in other terrestrial ecosystems of properly handled. (C) 2005 Elsevier B.V. All rights reserved.

机器人化三腿磨削机床的研制

以钢坯修磨为实用目的研制的一台机器人化三腿机床，具有刚度大、负载能力强、机构简单、工作空间大、无运动耦合及奇异位形等优点，首次解决了钢坯局部修磨自动化问题，配以其它加工执行器还可实现多种工艺要求。建立了该机床的运动学逆、正解方程，对其工作空间和受力分析进行了介绍，并介绍了局部修磨自动化控制系统