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991.
992.
文章分析了西藏大学理学院化学实验教学中存在的主要问题,并结合学校和学生实际,探讨了化学实验教学改革的途径。 相似文献
993.
怒江水电开发,国内议论较多,争论也很激烈.怒江是三江并流的主要组成部分.对三江并流作了简要介绍,提出怒江不宜全水头进行水电开发,应以不损害自然景观及人文景观为前提,力求自然景观与人文景观和谐并存,建设更加美丽的怒江;可开发河段,既要将水资源充分利用,又要保护好怒江的自然景观和生态环境,也就是保护好三江并流这一世界自然遗产的完整性和自然性,真正做到开发怒江水电,保护自然环境,实现经济、社会、资源与环境相互协调和可持续发展,构建和谐社会. 相似文献
994.
网格模型的简化是解决复杂三维模型存储、传输和实时绘制的有效性与硬件处理能力的局限性之间矛盾的主要方法.在分析了网格模型简化的主要技术和方法的基础上,以这些方法和技术为线索,对现有模型简化主要算法进行了较为详细的介绍,并分析了各主要算法的特点;最后对模型简化技术的发展趋势进行了展望. 相似文献
995.
996.
DONG Dong ZHOU Bing Jing-Dong J. HAN 《科学通报(英文版)》2007,52(21):2938-2944
Protein-protein interaction networks serve to carry out basic molecular activity in the cell. Detecting the modular structures from the protein-protein interaction network is important for understanding the organization, function and dynamics of a biological system. In order to identify functional neighbor- hoods based on network topology, many network cluster identification algorithms have been devel- oped. However, each algorithm might dissect a network from a different aspect and may provide dif- ferent insight on the network partition. In order to objectively evaluate the performance of four com- monly used cluster detection algorithms: molecular complex detection (MCODE), NetworkBlast, shortest-distance clustering (SDC) and Girvan-Newman (G-N) algorithm, we compared the biological coherence of the network clusters found by these algorithms through a uniform evaluation framework. Each algorithm was utilized to find network clusters in two different protein-protein interaction net- works with various parameters. Comparison of the resulting network clusters indicates that clusters found by MCODE and SDC are of higher biological coherence than those by NetworkBlast and G-N algorithm. 相似文献
997.
Water isotope variations in the snow pack and summer precipitation at July 1 Glacier, Qilian Mountains in northwest China 总被引:8,自引:0,他引:8
ZHOU ShiQiao NAKAWO Masayoshi SAKAI Akiko MATSUDA Yoshihiro DUAN KeQin PU JianChen 《科学通报(英文版)》2007,52(21):2963-2972
This paper presents the stable isotope data of the snow pack and summer precipitation collected at the July 1 Glacier, Qilian Mountains in northwest China and analyses their relationships with meteorologi- cal factors. On an event scale, there is no temperature effect on the δ 18O values in the summer pre- cipitation, whereas the amount effect is shown to be clear. By tracing the moisture transport history and comparing the precipitation with its isotopic composition, it is shown that this amount effect not only reflects the change in moisture trajectory, which is related to the monsoon activities, but is also associated with the cooling degree of vapor in the cloud, the evaporation of falling raindrops and the isotopic exchange between the falling drops and the atmospheric vapor. As very little precipitation occurs in winter, the snow pack profile mainly represents the precipitation in the other three seasons. There are low precipitation δ 18O ratios in summer and high ratios in spring and autumn. The Meteoric Water Line (MLW) for the summer precipitation is δ D = 7.6 δ 18O 13.3, which is similar to that at Delingha, located in the south rim of the Qilian Mountains. The MWL for the snow pack is δ D = 10.4 δ 18O 41.4, showing a large slope and intercept. The deuterium excess (d) of the snow pack is positively correlated with δ 18O, indicating that both d and δ 18O decrease from spring to summer and increase from early autumn to early spring. This then results in the high slope and intercept of the MWL. Sea- sonal fluctuations of d in the snow pack indicate the change of moisture source and trajectory. During spring and autumn, the moisture originates from continental recycling or rapid evaporation over rela- tively warm water bodies like Black, Caspian and Aral Seas when the dry westerly air masses pass over them, hence very high d values in precipitation are formed. During summer, the monsoon is responsi- ble for the low d values. This indicates that the monsoon can reach the western part of the Qilian Mountains. 相似文献
998.
YUAN Fang ZHAO Yao ZHOU Xu 《武汉大学学报:自然科学英文版》2007,12(5):825-829
This paper proposes a new approach for classification for query interfaces of Deep Web, which extracts features from the form's text data on the query interfaces, assisted with the synonym library, and uses radial basic function neural network (RBFNN) algorithm to classify the query interfaces. The applied RBFNN is a kind of effective feed-forward artificial neural network, which has a simple networking structure but features with strength of excellent nonlinear approximation, fast convergence and global convergence. A TEL_8 query interfaces' data set from UIUC on-line database is used in our experiments, which consists of 477 query interfaces in 8 typical domains. Experimental results proved that the proposed approach can efficiently classify the query interfaces with an accuracy of 95.67%. 相似文献
999.
A tubular focused sonochemistry reactor 总被引:1,自引:0,他引:1
ZHOU GuangPing LIANG ZhaoFeng LI ZhengZhong ZHANG YiHui 《科学通报(英文版)》2007,52(14):1902-1905
This paper presents a new sonochemistry reactor, which consists of a cylindrical tube with a certain length and piezoelectric transducers at tube’s end with the longitudinal vibration. The tube can effectively transform the longitudinal vibration into the radial vibration and thereby generates ultrasound. Furthermore, ultrasound can be focused to form high-intensity ultrasonic field inside tube. The reactor boasts of simple structure and its whole vessel wall can radiate ultrasound so that the electroacoustic transfer efficiency is high. The focused ultrasonic field provides good condition for sonochemical reaction. The length of the reactor can be up to 2 meters, and liquids can pass through it continuously, so it can be widely applied in liquid processing such as sonochemistry. 相似文献
1000.
Nickel accumulation and its effects on the survival rate of Spodoptera litura Fabricius under continuous nickel stress 总被引:2,自引:0,他引:2
SUN HongXia SHU YingHua TANG WenCheng WANG Qi ZHOU Qiang ZHANG GuRen 《科学通报(英文版)》2007,52(14):1957-1963
The artificial diets mixed with various concentrations of nickel were offered to the larvae of the phytophagous insect Spodoptera litura Fabricius for 3 generations. Nickel accumulations in the 6th instar larvae, pupae and newly emerged adults of the corresponding generations of S. litura were investigated by Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and the effects of nickel accumulations on the survival rate of S. litura were also evaluated by individual rearing. The results showed that nickel accumulated in the 6th instar larvae, pupae and adults of S. litura, and the accu- mulated nickel in all the tested developmental stages within a generation increased with the increase of the nickel doses in the treated diets and showed significant dose-dependent relationship with the nickel doses in the artificial diets. The results also indicated that the nickel accumulations in the 6th instar larvae, pupae, and newly emerged adults from the 3rd generation were higher than those from the 2nd generation, which were also higher than those from the 1st generation. Nickel concentrations in pupae and adults were significantly lower than those in larvae, which indicated that the excessive nickel might be excreted during metamorphosis. Furthermore, larval survival rate, pupation rate and eclosion rate of S. litura in the tested three generations all decreased with the increase of the nickel doses in the treated diets. 相似文献