首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
Air temperature and relative humidity have been the main parameters of meteorology study.In the past data could be obtained from in-situ observations,but the observations are local and sparse,especially over ocean.Now we can get them from satellites,yet it is hard to estimate them from satellites directly so far.This paper presents a new method to retrieve monthly averaged sea air temperature(SAT) and relative humidity(RH) near sea surface from satellite data with artificial neural networks(ANN).Compared with the observations in Pacific and Atlantic,the root mean square(RMS) and the correlation between the estimated SAT and the observations are about 0.911 and0.99,respectively.The RMS and the correlation of RH are about 3.73%and 0.65,respectively.Compared with the multiple regression mediod,the ANN methodology is more powerful in building nonlinear relations in this research.Thus the global monthly average SAT and RH are retrieved from the fixed ANN network from July 1987 to May 2004.In general the annual average SAT shows the increasing trend in recent 18 years.The abnormality of SAT is decomposed with the empirical orthogonal function(EOF).The leading three EOFs could explain 84%of the total variation.EOF1(76.1%) presents the seasonal change of the SAT abnormality.EOF2(4.6%) is mainly related with ENSO.EOF3(3.3%) shows some new interesting phenomena appearing in the three main currents in Pacific,Atlantic and Indian Ocean.  相似文献   

3.
为保证船舶在北极航道特殊环境下正常航行,对船舶金属材料进行冰黏附测试就显得极为重要.对黄铜、6061铝合金和Q235这三种船舶常用金属进行实验,测量不同温度和不同湿度下这三种金属的表面冰黏附强度,并分析其与表面温度以及表面湿度之间的关系.结果表明,冰黏附强度变化规律与类液层理论相符;黄铜、6061铝合金和Q235的切向...  相似文献   

4.
Abrupt changes in flagellar rotation observed by laser dark-field microscopy   总被引:14,自引:0,他引:14  
S Kudo  Y Magariyama  S Aizawa 《Nature》1990,346(6285):677-680
Bacteria such as Escherichia coli and Salmonella typhimurium swim by rotating their flagella, each of which consists of an external helical filament and a rotary motor embedded in the cell surface. The function of the flagellar motor has been examined mainly by tethering the flagellar filament to a glass slide and observing the resultant rotation of the cell body. But under these conditions the motor operates at a very low speed (about 10 r.p.s.) owing to the unnaturally high load conditions inherent in this technique. Lowe et al. analysed the frequency of light scattered from swimming cells to estimate the average rotation speed of flagellar bundles of E. coli as about 270 r.p.s. To analyse motor function in more detail, however, measurement of high-speed rotation of a single flagellum (at low load) with a temporal resolution better than 1 ms is needed. We have now developed a new method--laser dark-field microscopy--which fulfils these requirements. We find that although the average rotation speed of S. typhimurium flagella is rather stable, there are occasional abrupt slowdowns, pauses and reversals (accomplished within 1 ms). These changes were frequently observed in mutants defective in one of the motor components (called the switch complex), suggesting that this component is important not only in switching rotational direction but also in torque generation or regulation.  相似文献   

5.
山东地区不同区域闪电与湿度的相关分析   总被引:1,自引:0,他引:1  
利用山东地区2006年6月至2007年toY]的闪电资料和的湿度资料,分析了该地区闪电和湿度的季节变化特征以及二者的相关关系.结果表明:正、负闪电频次有一致的双峰谷季节变化特征,主峰值在夏季8月份,分别占全年闪电频次的35.58%和59.93%,次峰值在春末5月份,谷值在冬季,但负闪电在春末5月份的次峰值并不明显;湿度季节变化特征呈单峰值特征,峰值除鲁西北在夏季7月份,其他三地区均在夏季8月份,谷值都在春季4月份,但在秋冬季的下降变化中出现了波动现象;闪电频次、闪电平均强度与湿度的季节变化有较好的一致性,存在正响应,但都出现了春季异常.  相似文献   

6.
用人工降雨的方法,通过单雨滴溅蚀实验,分析在不同雨径、坡度、含水率、结皮厚度下对土壤溅蚀的影响。结果表明,降雨强度是影响溅蚀量的显著因子,溅蚀量与雨径、坡度、含水率呈正相关,与结皮厚度呈负相关。  相似文献   

7.
物理学习困难的归因分析和实践研究   总被引:2,自引:1,他引:1  
本文根据学习困难和归因理论研究成果,进行物理学习困难的归因研究,包括归因训练和归因结果的测量.归因测量结果表明,我们采取的教育干预促进了学生对学习困难的积极归因,它的研究方法和思路也可以应用到其他学科学习困难的研究中去,这也为基础教育和教学提供了帮助.  相似文献   

8.
试验通过控制水温,观察膨胀岩在水中崩解、软化的快慢,以及固体颗粒物粒径的大小,得出了温度对膨胀岩吸水崩解软化作用的影响规律。通过对各组温湿度状态下的膨胀岩进行直剪实验,获得了温湿度对膨胀岩抗剪强度的影响规律。结果表明:随着温度的升高,膨胀岩内部矿物颗粒吸水速率变快、吸水量增大、分子运动加速、膨胀作用增强,崩解速率也逐渐加快,吸水软化所需时间更短;温度的升高,加大了膨胀岩内部水分的蒸发,导致岩体失水收缩,内部结构变得紧密,水的润滑作用也减弱,膨胀岩的黏聚力和摩擦角均增大;随着含水率的增加,膨胀岩吸水发生体积膨胀,分子间吸引力减小,内部矿物颗粒胶结变得松散,水的润滑作用加强,黏聚力和摩擦角均降低。  相似文献   

9.
The small martian satellites Phobos and Deimos orbit in synchronous rotation with inclinations of only 0.01 degrees and 0.92 degrees , respectively, relative to the planet's equatorial plane. Thus, an observer at near-equatorial latitudes on Mars could occasionally observe solar eclipses by these satellites (see ref. 1, for example). Because the apparent angular diameter of the satellites is much smaller than that of the Sun, however, such events are more appropriately referred to as transits. Transit data can be used for correcting and refining the orbital ephemerides of the moons. For example, Phobos is known to exhibit a secular acceleration that is caused by tidal dissipation within Mars. Long-term, accurate measurements are needed to refine the magnitude and origin of this dissipation within the martian interior as well as to refine the predicted orbital evolution of both satellites. Here we present observations of six transits of Phobos and Deimos across the solar disk from cameras on Mars aboard the Mars Exploration Rovers Spirit and Opportunity. These are the first direct imaging observations of satellites transiting the Sun from the surface of another planet.  相似文献   

10.
基于桥梁结构的影响面,针对公路活荷载的系列性和流动性,用C语言编写了影响面活荷载加载效应计算程序。此程序的计算模型是:①由影响面形成三角网;②根据荷载等级由规范确定车列,在影响面上的每个确定位置求车列的加载效应,并求出每个加载子域的最大值;③由各子域最大值求一列车或两列车或三列车……的最大加载效应值。算例表明,本程序方便灵活、精确快捷。  相似文献   

11.
“归因训练”在普通高校羽毛球选项课中的运用   总被引:1,自引:0,他引:1  
刘青 《南昌高专学报》2008,23(4):158-160
本文主要采用教学实验法和问卷调查法对随机抽取的宿迁学院06级羽毛球选修教学班120名受试对象进行为期4个月的归因训练的教学干预。通过教学实验表明,“归因训练”对羽毛球选项课的作用明显优于传统教学方法,有利于促进学生羽毛球成绩的提高。  相似文献   

12.
The global dibtributiorls of the rale of precipitation change at seasonal, interannual and interdeadel scales are computed from the observed global data sets. The analysis has revealed that the monscnn regions in hie and West Africa, and to lesser extent Australia, have the highest rate of precipitation change at all time scales in the world. Thew changes are manifested as seasonal jump, high interannual and interdecadal variability and abrupt changes between climate regimes.  相似文献   

13.
为了拓宽便携式高频地波雷达(OSMAR-S)的应用场合,提高其海态监测的能力,通过船载雷达系统走航的方式获取大范围的海洋回波信息.利用实测数据中形态多样的一阶海洋回波谱图,分析了海流、风向和雷达探测张角对回波谱的影响,讨论了径向流速和风向信息提取的可行性.研究结果表明:在船沿岸走航的情况下,海流引起回波谱频点的偏移,风向规律地改变谱图的形态,岸基单站雷达的风向模糊问题得以解决;在船四面环海航行的情况下,单个回波频点存在双到达角和风向模糊的问题.  相似文献   

14.
Thompson DW  Kennedy JJ  Wallace JM  Jones PD 《Nature》2008,453(7195):646-649
Data sets used to monitor the Earth's climate indicate that the surface of the Earth warmed from approximately 1910 to 1940, cooled slightly from approximately 1940 to 1970, and then warmed markedly from approximately 1970 onward. The weak cooling apparent in the middle part of the century has been interpreted in the context of a variety of physical factors, such as atmosphere-ocean interactions and anthropogenic emissions of sulphate aerosols. Here we call attention to a previously overlooked discontinuity in the record at 1945, which is a prominent feature of the cooling trend in the mid-twentieth century. The discontinuity is evident in published versions of the global-mean temperature time series, but stands out more clearly after the data are filtered for the effects of internal climate variability. We argue that the abrupt temperature drop of approximately 0.3 degrees C in 1945 is the apparent result of uncorrected instrumental biases in the sea surface temperature record. Corrections for the discontinuity are expected to alter the character of mid-twentieth century temperature variability but not estimates of the century-long trend in global-mean temperatures.  相似文献   

15.
菲降解菌的降解特性及菲对其细胞表面形态的影响   总被引:1,自引:0,他引:1  
从长期受PAHs污染的土壤中分离得到一株菲降解菌B4—氧化节杆菌(Arthrobacter oxydans).对其菲耐受能力及降解性能进行了考察,结果表明,该菌在有氧环境中能够耐受2 000 mg/L的菲,并对菲具有显著降解作用.当无机盐培养液中菲初始质量浓度为50 mg/L,B4投菌量为20 g/L(湿重,含水率:94.55%),菌龄为48 h,pH为7.0~8.0时,5 d内菲降解率为60%左右.通过原子力显微镜对菲降解前后菌体表面形态进行观察,结果显示,菲对该菌株存在一定毒性,随着作用时间的增加,细胞形态明显发生改变,其表面超微结构也趋于复杂.  相似文献   

16.
Wang  Fang  Ge  QuanSheng 《科学通报(英文版)》2012,57(14):1708-1715
Since the 1980s,China has undergone rapid urbanization.Meanwhile,the climate has been warming substantially.In this paper,the urbanization effect on observed temperatures from 1980 to 2009 in China is estimated,based on analysis of urban land use from satellite observation.Urban land-use expansion(U) during 1980-2005 is applied as an urbanization index.According to these U values,stations are divided into three categories:(C1) intense urbanization around the stations;(C2) moderate urbanization around the stations;and(C3) minimal urbanization around the stations.Most C1 stations are in municipalities or provincial capitals,while C2 stations tend to be in prefecture-level cities.C3 stations are mostly in counties.The urban heat island(UHI) effect can be estimated if the urban effect on C3 is negligible.The warming of C1 or C2 relative to that of C3 represents their urbanization effects,assuming that the same larger-scale natural warming has affected each category.For C1,the local urbanization effect is 0.258°C/10 a over 1980-2009,accounting for 41% of the total warming;the trend at C2 is 0.099°C/10 a,or 21%.For all China,the urbanization effect is 0.09°C/10a,accounting for 20% of the total national warming.Winter urban warming is greater than in summer.The assumption of negligible urbanization effect on C3 is debatable,and so the true urbanization effect may equal or slightly exceed estimates.Further,the U index may have some uncertainties,for it is only one of the urbanization indices.However,it provides a new and direct estimation of environmental change,in contrast to indirect indices.  相似文献   

17.
河西走廊历史时期气候干湿状况变迁考略   总被引:13,自引:0,他引:13  
检索整理了河西走廊史载以来的气候旱涝资料,采用湿润指数公式进行处理分析;探讨了该地区历史上气候干湿状况变迁的概貌  相似文献   

18.
《科学通报(英文版)》2012,57(11):1351-1351

Trend

The influence of estrogen on female mood changes  相似文献   

19.
Effect of relative humidity on the surface adhesion force of several inorganic crystals of mica, CaF2 and KCl was studied by atomic force microscopy (AFM). The results showed that the magnitude of surface adhesion force is mainly dependent on the surface free energy of the adsorbed liquid film, but almost independent of the thickness of the film. Furthermore, the deliquescence on the crystal surface was investigated, which demonstrated the capability of the force spectrum method to monitor changes in ionic concentrations of adsorbed liquid film in real-time.  相似文献   

20.
Long-term measurements from a pair of High-Frequency radar systems deployed near the coast of southern Fujian Province showed that surface currents in the southwestern Taiwan Strait were composed mainly of the monsoon-driven, seasonal fluctuation of longshore current and a persistent northeastward background flow with speeds around 10 cm/s. Measurements from bottom-moored ADCPs further indicated that below the surface Ekman layer longshore currents also directed to the north all year round.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号