Seasonal Changes in Mayfly Communities and Abundance in Relation to Water Physicochemistry in Two Rivers at Different Elevations in Northern Peninsular Malaysia     

Suhaila Abdul Hamid  Mohd Ravi Che Salmah  Hamady Dieng  Abu Hassan Ahmad  Tomomitsu Satho  Fumio Miake 《湿地科学》2011,9(3):240-250

A field study was performed at rivers in Gunung Jerai forest reserve(Kedah,Malaysia) to assess seasonal changes in mayfly community structure and abundance in relation to altitude and water physicochemistry.Rivers at lower(Batu Hampar River) and higher(Teroi River) elevations were visited through dry and wet seasons in September 2007 to August 2008.Monthly visits were made to 20 sites on each river,and water and aquatic insects were sampled using D-pond aquatic nets.Water was warmer,more acid,and more turbid in Teroi River during wet season.Ammonia was the only nutrient exhibiting significant seasonal variations(greater during wet season).Chemical oxygen demand content was higher in Teroi River where biochemical oxygen demand content was low during wet season.Species richness was higher in Batu Hampar River,but displayed seasonal variations only in Teroi River.Among the eight families encountered,Baetidae was the commonest.Baetid abundance was usually high during wet season,and those belonging to the dominant genus(Baetis) were more abundant in Teroi River.Heptageniidae was the second commonest family;its predominant genus,Thalerospyrus was more abundant in Teroi River during dry season.Caenidae,Leptophlebiidae and Oligoneuriidae were only found in Batu Hampar River where their abundances peaked during dry season,i.e.,Habrophlebiodes sp.and Isonychia sp.Ephemerellidae and Teloganodidae occurred only in Teroi River,with the first found only during dry season.Mayflies were recorded under very distinct physicochemical conditions,illustrating their potential usefulness for assessing water quality.Caenids,leptophlebids,oligoneurids ephemerellids and teloganodids seem to be particularly sensitive to temperature,acidity,turbidity,chemical oxygen demand and biochemical oxygen demand,parameters that varied with river altitude.  相似文献   

Stream-coordinate structure of oceanic jets based on merged altimeter data     

孙澈  张林林  闫晓梅 《中国海洋湖沼学报》2011,29(1):1-9

The jet structure of the Southern Ocean front south of Australia is studied in stream-coordinate with a new altimeter product—Absolute Dynamic Topography (ADT) from AVISO. The accuracy of the ADT data is validated with the mooring data from a two-year subantarctic-front experiment. It is demonstrated that the ADT is consistent with in-situ measurements and captures the meso-scale activity of the Antarctic Circumpolar Current (ACC). Stream-coordinate analysis of ADT surface geostrophic flows finds that ACC jets exhibit large spatio-temporal variability and do not correspond to particular streamfunction values. In the circumpolar scope ACC jets display a transient fragmented pattern controlled by topographic features. The poleward shift of jet in streamfunction space, as revealed by a streamwise correlation method, indicates the presence of meridional fluxes of zonal momentum. Such cross-stream eddy fluxes concentrate the broad ACC baroclinic flow into narrow jets. Combined with a recent discovery of gravest empirical mode (GEM) in the thermohaline fields, the study clarifies the interrelationship among front, jet and streamfunction in the Southern Ocean.  相似文献   

PC机在控制金刚石合成工艺方面的应用          下载免费PDF全文

车朝红  赵义文 《探矿工程》1996,(5):54-55

通过开发压机ＰＣ机的内在功能，编制合理的控制程序，改进了设备的工况，提高了金刚石合成工艺的控制精度。  相似文献   

Seismic self‐centering steel beam‐to‐column moment connections using bolted friction devices     

Keh‐Chyuan Tsai  Chung‐Che Chou  Chi‐Lon Lin  Pei‐Ching Chen  Sheng‐Jhih Jhang 《地震工程与结构动力学》2008,37(4):627-645

This paper first presents the force–deformation relationship of a post‐tensioned (PT) steel beam‐to‐column connection constructed with bolted web friction devices (FDs). This paper then describes the test program conducted in the National Center for Research on Earthquake Engineering, Taiwan, on four bolted FDs and four full‐scale PT beam‐to‐column moment connection subassemblies using the FDs. Tests confirm that (1) the hysteretic behavior of four bolted FDs is very stable, (2) the friction coefficient between the steel plate and the brass shim is about 0.34, (3) the proposed force–deformation relationships reasonably predict the experimental responses of the PT connections under cyclically increasing deformations up to a beam peak rotation of 0.05 rad, and (4) the decompression moments do not degrade as beam cyclic deformations increase. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

冕宁冶勒地区石炭纪花岗岩的确定及其意义     

朱学波  陈玉禄 《四川地质学报》2000,(1)

位于扬子地块西缘中段的冶勒花岗岩体 ,为钾质过铝质地壳重熔型S型花岗岩。在岩体中获 350± 19Ma的年龄值 ,表明其侵位时代为早石炭世 ,为攀西古裂谷孕育时期的裂前台背斜隆起阶段的产物。这一成果填补了该区早石炭世岩浆活动的空白。  相似文献   

利用数字遥感图像研究长白山天池火山近代喷发规模   总被引：2，自引：1，他引：1       下载免费PDF全文

单新建  陈国光  叶洪 《地震地质》2000,22(2):187-194

利用LandsatTM、ERS - 1SAR遥感图像资料 ,结合地质考察、测年资料 ,采用多源数据融合技术 ,运用GIS、正交小波变换、人工神经元网络 ,对图像进行了分类 ,研究了长白山天池火山近代喷发规模及喷发物分布特点 ,为火山灾害评价提供了重要依据  相似文献   

用流动形变观测判定强震危险地点的研究   总被引：1，自引：1，他引：0  

车兆宏  刘善华  刘天海  刘向军 《大地测量与地球动力学》1996,(1)

分析了形变异常形成的机理，认为形变异常的空间与时间分布特征可以用断层活动闭锁区的形成及发展来解释，活动断层的闭锁区为强震发生地点。提出了半年至几年时间尺度判定强震危险地点的原则和判定危险区与危险地点的具体方法。  相似文献   

流动形变及重磁综合监测断层的研究     

车兆宏  巩曰沐 《大地测量与地球动力学》1995,(4)

分析了目前利用流动形变、重力、地磁复测资料进行地震预测所存在的困难，探讨了综合利用三种手段追踪应力场及地下介质动态的途径，提出了断层综合监测布点的原则，并介绍了依此原则所建的京西试验场的基本情况。  相似文献   

Aerosol Hygroscopicity during the Haze Red-Alert Period in December 2016 at a Rural Site of the North China Plain     

Xuefei?Qi  Junying?SunEmail author  Lu?Zhang  Xiaojing?Shen  Xiaoye?Zhang  Yangmei?Zhang  Yaqiang?Wang  Haochi?Che  Zhouxiang?Zhang  Junting?Zhong  Kaiyan?Tan  Huarong?Zhao  Sanxue?Ren 《Acta Meteorologica Sinica》2018,32(1):38-48

A humidification system was deployed to measure aerosol hygroscopicity at a rural site of the North China Plain during the haze red-alert period 17–22 December 2016. The aerosol scattering coefficients under dry [relative humidity (RH) < 30%] and wet (RH in the range of 40%–85%) conditions were simultaneously measured at wavelengths of 450, 550, and 700 nm. It is found that the aerosol scattering coefficient and backscattering coefficient increased by only 29% and 10%, respectively when RH went up from 40% to 80%, while the hemispheric backscatter fraction went down by 14%, implying that the aerosol hygroscopicity represented by the aerosol scattering enhancement factor f(RH) is relatively low and RH exerted little effects on the aerosol light scattering in this case. The scattering enhancement factors do not show significant differences at the three wavelengths, only with an approximate 2% variation, suggesting that the aerosol hygroscopicity is independent of the wavelength. Aerosol hygroscopicity is highly dependent on the aerosol chemical composition. When there is a large mass fraction of inorganics and a small mass fraction of organic matter, f(RH) reaches a high value. The fraction of NO₃^– was strongly correlated with the aerosol scattering coefficient at RH = 80%, which suggests that NO₃^– played an important role in aerosol hygroscopic growth during the heavy pollution period.  相似文献   

Weekday AOD smaller than weekend AOD in eastern China on the basis of the MODIS AOD product     

Song  Jingjing  Xia  Xiangao  Zhang  Xiaoling  Che  Huizheng  Li  Xiaojing 《Theoretical and Applied Climatology》2018,131(3-4):1019-1041

Theoretical and Applied Climatology - A weekly cycle of surface particulate matter (PM) characterized by smaller values during weekends and larger values during weekdays was reported in eastern...  相似文献