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41.
大气环流对中国稻飞虱危害的影响及其预测 总被引:1,自引:0,他引:1
稻飞虱是中国和许多亚洲国家水稻生产上最重要的害虫。文中通过对上一年1月至当年8月74项大气环流特征量构建所有不同时段的组合,全面分析了大气环流特征量与中国稻飞虱发生面积率的相关关系。筛选出了影响中国稻飞虱发生面积率的关键环流特征因子52项,其对中国稻飞虱发生影响的重要次序为副热带高压类→极涡类→槽类→其他类;影响的时段主要为当年7—8月,其次为上年6月至当年6月。其中,副热带高压类、极涡类关键环流因子分别有35项和12项,占全部关键环流特征因子的67%和23%,在很大程度上决定着中国稻飞虱发生的面积。确定的直接影响中国稻飞虱发生的关键环流特征因子有11项,其中6项较好地表征了中国稻飞虱发生面积率轻、偏轻、偏重、重4个级别的气候特征。用直接影响中国气候的关键环流特征因子建立了当年3—9月的中国稻飞虱发生面积率月预测模式,每月初可以制作预报。该模式历史拟合效果较好,对2003年中国稻飞虱发生面积率的外延预报准确率分别达85.6%、90.5%、90.5%、90.4%、90.9%、93.2%、96.3%。同时,本研究还利用1—11月稻区月降水量、平均气温、日照时数所构建的所有不同时段的组合,分析了关键环流特征因子与稻区生态气象条件、中国稻飞虱发生面积率之间的关系。结果表明:三者之间相关密切,这种关系表现为大气环流通过影响稻区日照、气温和降水的变化导致稻飞虱发生条件的灾变,进而影响稻飞虱发生面积率。 相似文献
42.
本文主要介绍了基于ADO.Net的数据管理系统的开发研究。它从数据库的构建,系统的具体开发引入到其中几项关键技术的研究,如多数据格式的处理,参数化查询等等。最后对基于ADO.Net的Web型分布式数据库开发作了展望。 相似文献
43.
44.
对兴隆60cm望远镜主焦CCD系统的测光性能进行了测试和研究.测定了CCD快门时间函数,讨论了快门延迟效应对短时间曝光观测的可能影响.通过观测大批Landolt标准星,较准确地定出了BVRI宽带测光的星等系统转换关系,结果表明本系统与标准BVRI系统很接近.对CCD系统的天文测光精度作了仔细的检验和分析,并对PSF拟合测光和孔径测光两种方法进行了比较 相似文献
45.
发光细菌在渔业水域污染物急性毒性快速检测中的应用 总被引:1,自引:0,他引:1
以明亮发光杆菌为指示生物,对渔业水域中污染物的急性毒性进行了检测,同时研究了PH值、温度对试验结果的影响。研究表明,发光细菌毒性试验是一种快速、简便的毒性测试方法,在温度20~30℃,pH6.0~9.0条件下所进行的测试,其结果与鱼类毒性试验可以互相替代。 相似文献
46.
Jing Wu Jian Yin Yonghong Hao Yan Liu Yonghui Fan Xueli Huo Youcun Liu Tian‐Chyi J. Yeh 《水文研究》2015,29(13):2855-2866
The traditional hydrological time series methods tend to focus on the mean of whichever variable is analysed but neglect its time‐varying variance (i.e. assuming the variance remains constant). The variances of hydrological time series vary with time under anthropogenic influence. There is evidence that extensive well drilling and groundwater pumping can intercept groundwater run‐off and consequently induce spring discharge volatility or variance varying with time (i.e. heteroskedasticity). To investigate the time‐varying variance or heteroskedasticity of spring discharge, this paper presents a seasonal autoregressive integrated moving average with general autoregressive conditional heteroskedasticity (SARIMA‐GARCH) model, whose the SARIMA model is used to estimate the mean of hydrological time series, and the GARCH model estimates its time‐varying variance. The SARIMA‐GARCH model was then applied to the Xin'an Springs Basin, China, where extensive groundwater development has occurred since 1978 (e.g. the average annual groundwater pumping rates were less than 0.20 m3/s in the 1970s, reached 1.20 m3/s at the end of the 1980s, surpassed 2.0 m3/s in the 1990s and exceeded 3.0 m3/s by 2007). To identify whether human activities or natural stressors caused the heteroskedasticity of Xin'an Springs discharge, we segmented the spring discharge sequence into two periods: a predevelopment stage (i.e. 1956–1977) and a developed stage (i.e. 1978–2012), and set up the SARIMA‐GARCH model for the two stages, respectively. By comparing the models, we detected the role of human activities in spring discharge volatility. The results showed that human activities caused the heteroskedasticity of the Xin'an Spring discharge. The predicted Xin'an Springs discharge by the SARIMA‐GARCH model showed that the mean monthly spring discharge is predicted to continue to decline to 0.93 m3/s in 2013, 0.67 m3/s in 2014 and 0.73 m3/s in 2015. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
47.
Z. F. Gao Q. H. Peng N. Wang C. K. Chou W. S. Huo 《Astrophysics and Space Science》2011,336(2):427-439
As soon as the energies of electrons near the Fermi surface exceed Q, the threshold energy of inverse β-decay, electron capture (EC) dominates inside a neutron star. The high-energy neutrons released by EC will destroy anisotropic
3
P
2 neutron Cooper pairs in the degenerate superfluid. By colliding with the neutrons produced in the process n+(n↑n↓)→n+n+n, the kinetic energies of the neutrons released by EC will be transformed into thermal energy. A portion of this thermal energy
will be transported from the star interior to the star surface by conduction, then converted to a thermal spectrum of soft
X-rays and γ-rays. By introducing two important parameters: the Landau level-superfluid modified factor and the overal soft X/γ-ray efficiency coefficient, we compute the theoretical luminosity L
X
of a magnetar under our model and plot a diagram of L
X
as a function of magnetic field strength B. Numerical calculations based on our model agree well with the observed properties of magnetar candidates. 相似文献
48.
49.
Using NCEP/NCAR reanalysis data and the sand-storm frequency data fi'om 37 weather stations in the Tarim Basin for the period 1961-2009, the relationship between the frequency of spring sandstorms in the Tafim Basin and the associated atmospheric circu- lation pattems is analyzed in this study. We found significantly negative correlations between sandstorm frequency and the 500-hPa geopotential height over the Paris Basin and midwestem Mongolia, while there were positive correlations over the Ural River region. The rising of the 500-hPa geopotential height in midwestem Mongolia and its falling over the Ural region corre- spond to a weakening of the large-scale wave patterns in the Eurasian region, which directly causes the frequency of the sand-dust storms in the Tarim Basin to decline. Also, the abrupt decline in the spring sandstorm frequency in the Tarim Basin observed in the last half-century is associated with profound changes in the atmospheric circulation in these key regions. At the interannual scale, the strengthened cyclonic atmospheric circulation patterns in the western part of Mongolia and the anticyclonic patterns over the East European plains at 500-hPa geopotential height, are responsible for frequent sandstorm occurrences in the Tarim Basin. 相似文献
50.
Zhongming Huo Zhaoping Wang Jian Liang Yuehuan Zhang Jianping Shen Tuo Yao Jiaqi Su Ruihai Yu 《中国海洋大学学报(英文版)》2014,13(4):666-670
This study examined the effects of salinity on embryonic development, survival, and growth of the Hong Kong oyster Crassostrea hongkongensis. The embryos, larvae, and juveniles of C. hongkongensis were held in artificial seawater at three different salinities (low, 15; medium, 23; and high, 30) to determine the optimum hatchery and nursery conditions for mass production of the seeds. Results showed that the percentage production of straight-hinged larvae from fertilized eggs was significantly lower at the high salinity than at the low- and medium-salinities (P < 0.05). The survival rates of larvae and juveniles differed significantly among the three salinity trials, with the highest survival rate observed at the low salinity (P < 0.05). The shell height of larvae was significantly larger at the low salinity than at the high and medium salinities from days 9 to 15 (P < 0.05), whereas that of juveniles was significantly larger at the low salinity than at the high and medium salinities on day 70 (P < 0.05). These results indicate that the larvae and juveniles of C. hongkongensis are tolerant to a wide range of salinities (15 to 30), but show better growth and survival at relatively low salinities. Thus, it is recommended to use relatively low salinities in hatchery and nursery systems for improved yields of C. hongkongensis. 相似文献