支持复杂语义的数据流滑动窗口连接建模和查询优化

数据流连接操作的执行方式直接影响到查询执行的效率和结果的正确性.在STREAM项目流化方法的基础上,对复杂应用下的数据流滑动窗口连接的准确语义进行了分析和建模,以时间窗口连接的增量维护为例提出了两种改进的基本维护策略,给出了针对元组窗和分组窗的维护方法,讨论了根据参数和环境的不同进行适应性的维护.实验证明了在不同的窗口、流速和选择度下,适应性地选择不同的优化算法会达到最优的处理性能.     

Strong quantum-confined Stark effect in germanium quantum-well structures on silicon

Silicon is the dominant semiconductor for electronics, but there is now a growing need to integrate such components with optoelectronics for telecommunications and computer interconnections. Silicon-based optical modulators have recently been successfully demonstrated; but because the light modulation mechanisms in silicon are relatively weak, long (for example, several millimetres) devices or sophisticated high-quality-factor resonators have been necessary. Thin quantum-well structures made from III-V semiconductors such as GaAs, InP and their alloys exhibit the much stronger quantum-confined Stark effect (QCSE) mechanism, which allows modulator structures with only micrometres of optical path length. Such III-V materials are unfortunately difficult to integrate with silicon electronic devices. Germanium is routinely integrated with silicon in electronics, but previous silicon-germanium structures have also not shown strong modulation effects. Here we report the discovery of the QCSE, at room temperature, in thin germanium quantum-well structures grown on silicon. The QCSE here has strengths comparable to that in III-V materials. Its clarity and strength are particularly surprising because germanium is an indirect gap semiconductor; such semiconductors often display much weaker optical effects than direct gap materials (such as the III-V materials typically used for optoelectronics). This discovery is very promising for small, high-speed, low-power optical output devices fully compatible with silicon electronics manufacture.     

Detection and analysis system for hybridization images of lab-in-a-tube microarray

A lab-in-a-tube microarray system is developed for sample inspection and signal detection by fabricating a fiat transparent window cap of the Eppendorf tube. The oligonucleotide microarray is immobilized on the inner surface of the cap. A small vessel is placed in an Eppendorf tube for storing hybridization solutions. With the microarray system, the full biochemical processes, including gene fragment amplification, fluorescence labeling, hybridization, and fluorescence detection, have been performed in the sealed tube without opening the cap. The images are obtained from a fluorescence microscope and captured by a CCD, and the data are transported to a computer through the universal serial bus （USB）. After noise reduction, signal intensity is determined from hybridization image and the presence of gene fragments is identified. The final data output includes sample information, process steps, and hybridization results. A lab-ina-tube microarray system for detecting ten respiratory viruses at a single detection is designed. High detection throughput and accuracy have been demonstrated with the system.     

Os isotopic composition of the earth’s primitive upper mantle

The osmium isotopic ratio of¹⁸⁷Os/¹⁸⁸Os ranging from 0.126 to 0.127 for the primitive upper mantle (PUM) is obtained according to the correlation between¹⁸⁷Os/¹⁸⁸Os and Al₂O₃ of mantle-derived xenoliths and orogenic peridotites, which consists with Allegre and Luck’s ALM value and similar to Yin’s nuggets uniform reservoir (NUR) value. It shows that the Os isotope ratio is lower than enstatite or ondinary chondrites, similar to carbonaceous chondrites (CV3).     

醋酸甲酯催化精馏水解塔的模拟

以平衡级模型用块状三对角矩阵技术,对强极性的醋酸甲酯催化精馏水解过程进行模拟,在改变空速、水酯比、回流比等操作条件以及塔板数下,用模拟的酯水解率、塔内温度、水解液的酸水比与实验值进行了比较,结果令人满意     

杭州湾北岸漕泾-柘林近岸海域浮游生物的调查

1996年11月和1997年3月,对漕泾－柘林的近岸海域的浮游生物进行了调查,1996年11月浮游植物平均密度为3．39×104个／L,密集于高潮带,主要有舟形藻、圆筛藻、直链藻等5种藻类,舟形藻为优势种;1997年3月平均密度为1．65×104个／L,密集于潮下带,主要有囊裸藻、针杆藻、小球藻等7种,囊裸藻为优势种．1996年11月,浮游动物的平均个体数为2．84×102个地,原生动物为优势种类;1997年3月,平均个体数为1．83×102个／L,以多毛类疣足幼虫为主;两次调查时浮游动物都密集于低潮带．     

中国健康中老年男性血沉参考值与地理因素的关系

为制定中国健康中老年男性血沉参考值（温氏法）的统一标准提供科学依据,本文收集了中国各地测定的健康中老年男性血沉参考值（温氏法）,并对其与地理因素的关系进行了研究,发现海拔高度是影响健康中老年男性血沉参考值（温氏法）最主要的因素,随着海拔高度的逐渐增大,健康中老年男性血沉参考值（温氏法）在逐渐的减小,相关性很显著．用逐步回归分析的方法推导出了一个回归方程,如果知道了中国某地的地理因素,变可以用这个回归方程估算这个地区的健康中老年男性血沉参考值（温氏法）,依据健康中老年男性血沉参考值（温氏法）与地理因素的依赖关系把中国分为青藏区,西南区,西北区,东南区,华北区,东北区等六个区．     

一阶非线性时滞系统的渐近性和振动性

讨论了一阶非线性具有变号系数的滞系统解的渐近性和振恸 性,得到了几个充分条件和必要条件。     

The reconstruction and interpretations of lake status at 6 ka and 18 ka B.P.in inland mainland Asia

By means of survey of literature through compilations of sedimentological, biogeological and geomorphologic data, the inland lake level changes in arid or semi-arid mainland Asia at 6 and 18 ka B. P. have been reconstructed. The results showed that the lakes from western and northwestern Asia were characterized by very high water levels at 18 ka B. P., but low or intermediate water stands at 6 ka B. P. The high lake level in this region was associated with the southward displacement of westerlies, therefore, the extent of the high lake stand indicated the southern flank of westerlies during the glaciation. Conversely, the lakes from the eastern and southern Asia registered comparative low levels at 18 ka B. P. and significantly high one at 6 ka B. P. The lowering of lake level at 18 ka B. P. was caused by the weakened summer monsoon and the high lake level at 6 ka B. P. by the enhanced summer monsoon induced by the enlarged thermal contrast between land and ocean. The extent of high lake levels indicated the northern boundary of monsoon expansion. Between the above two regions, there is a climatic transitional zone in the Central Asia where the lake behavior was close to that in southeastern Asia at 6 ka B. P. but became similar to that in northwestern Asia at 18 ka B. P. Thus this zone became a transitional sector from the monsoon to the westerlies.     

Double-stream-pouring technique for production of gradient materials by continuous casting

A novel method for producing gradient materials by continuous casting is introduced. By using many-stream-pouring technique, samples with gradient distribution of alloy composition along the cross section have been prepared. The main difference of this method from the conventional continuous casting is the pouring system equipped with two sets of tundishes for liquid metals of different alloy compositions. Special consideration is given to the promotion and control of the crass-sectional mass transport. The steady heat transfer and mass flow ensure a partial mixing of two metals and yield a continously varying composition distribution. By adjusting the processing parameters, composition profile with different shapes can be achieved. First experiments have been carried out in Al-Si system and Al-Cu system for three series of Al/AlSi, AlSi/Al and AlCu/Al. It is shown that the alloy composition, the microntructure and the mechanical property change smoothly from the centre to the surface of the samples. This simple and practical method is potential for mass prodution of “structural gradient materials” and may offer a new way for alloy design.