基于GPIB接口的计数器数据采集与控制软件   总被引：2，自引：1，他引：1  

杨旭海  胡永辉  李志刚 《时间频率学报》2002,25(1):43-46

在Windows平台上 ,使用VC 6 .0开发了一套基于GPIB接口的计数器数据采集与控制软件 ,其特点是采用了多线程机制 ,可实现对计数器的控制 ,以及数据的采集与实时显示。  相似文献   

子午环度盘对径改正测试的研究     

杜慕群  李志刚 《时间频率学报》1997,20(6):101-106

  相似文献   

DCMT光电扫描主测微器的设计与研究     

李志刚  李焕信  方福胜  朱紫  许林生 《时间频率学报》1993,(1)

DCMT主测微器不同于其它类型的子午环测微器,它具有自校准测定仪器参数的功能。该测微器采用了活动光栅的方案,其优点是能观测近极星和各类准直像;活动光栅另一个显著优点是不同赤纬星几乎可用相同的观测时间.对“V”形光栅的工作原理和误差进行了详细讨论,并给出了一组严格的公式。其系统误差来源有:光栅形状改正、光栅驱动方向相对于光栅的倾斜、光栅驱动方向相对于赤径方向的倾斜、星径曲率改正。  相似文献   

用层次分析法决策地下水库回灌方案的排序问题     

李云峰  王文科  李志刚  王希宁 《地球科学与环境学报》1992,(2)

本文引用了一种新的系统分析方法(层次分析法)对地下水库人工回灌的复杂系统进行了择优排序研究,取得了满意的结果。实践证明,层次分析法对于地下水库人工回灌方案的择优是一种简捷实用的决策方法。  相似文献   

Determinants and characteristics of female migration: a case study of Salem City in Tamil Nadu,India     

Nangia S  Samuel MJ 《Population geography : a journal of the Association of Population Geographers of India》1983,5(1-2):34-43

A random sample of 521 male and 481 female migrants surveyed in Salem city in Tamil Nadu, India, during 1980-1981 was analyzed on the basis of a classification related to reasons (association, marriage, distress, and voluntary) for migration. Women were found to outnumber males in associational migration, both in rural to urban and urban to urban streams. They also formed almost all the marriage migrants. They were more numerous in distress migration as well. There were, however, comparatively few women among voluntary migrants. The incidence of illiteracy among migrant women was generally high, except for voluntary migrants who had completed high school. The share of working women was not negligible, but in most cases present work status was achieved after migrating.  相似文献   

Comparison of polycyclic aromatic hydrocarbon distributions and sedimentary organic matter characteristics in contaminated, coastal sediments from Pensacola Bay, Florida     

Simpson MJ  Chefetz B  Deshmukh AP  Hatcher PG 《Marine environmental research》2005,59(2):139-163

In this study, we examined the distribution of polycyclic aromatic hydrocarbons (PAHs) in a contaminated coastal area and the characteristics of the natural organic matter in tandem. We present a detailed study of PAH concentration, distribution, and organic matter characteristics of three core samples from Pensacola Bay, Florida. Solid-state 13C Nuclear Magnetic Resonance (NMR), pyrolysis gas chromatography coupled with mass spectrometry (GC-MS), and tetramethyl ammonium hydroxide (TMAH) thermochemolysis GC-MS were applied to obtain structural details about the sedimentary organic matter. Elemental compositions (carbon and nitrogen) and estimates of black carbon contents are also reported. These coastal sediments were found to contain more PAHs in the upper 15 cm layers than in the bottom 15-25 cm samples. The samples that contained the most PAHs also contained the least amount of aromatic carbon and contained a significant amount of paraffinic carbon. Lignin-derived pyrolysis and TMAH thermochemolysis products were abundant and generally higher in all of the samples in comparison to those reported for modern coastal sediments, indicating a large flux of terrestrial carbon. The black carbon contents were found to range from 4.3% to 6.8%, which are significantly lower than other reports of black carbon in sediments, which represent as much as 65% of the total organic carbon content. The low black carbon content suggests that this type of refractory carbon may not be as responsible for regulating PAH distribution as indicated by other researchers.  相似文献   

Cloning of a chub metallothionein cDNA and development of competitive RT-PCR of chub metallothionein mRNA as a potential biomarker of heavy metal exposure   总被引：3，自引：0，他引：3  

Hayes RA  Regondi S  Winter MJ  Butler PJ  Agradi E  Taylor EW  Kevin Chipman J 《Marine environmental research》2004,58(2-5):665-669

Metallothionein has been assayed in a range of aquatic animal tissues as an indicator of metal exposure. We sequenced chub (Leuciscus cephalus) metallothionein cDNA which showed over 90% homology to common carp, goldfish and stone loach and 77% homology to rainbow trout sequences for metallothionein. We then used the extended primer method to develop an accurate quantitative competitive RT-PCR assay for metallothionein mRNA. RT-PCR was used to measure metallothionein mRNA in feral chub from a range of field sites, with different levels of heavy metal pollution, in the West Midlands, UK. Measurements were complemented by analysis of liver and gill metallothionein protein by capillary electrophoresis. There was no significant difference in the metallothionein protein levels between fish of different rivers and there was no evidence of elevation of mRNA at the sites of highest metal exposure. The level of metal exposure (e.g. zinc, nickel and cadmium each ranging between 15 and 28 microg/l ) at the pH (7.5-8.5) of these rivers appears insufficient to elevate hepatic or gill metallothionein in chub. A lack of elevation of hepatic metallothionein mRNA in chub exposed to zinc, copper and manganese for 24 h and 10 days in the laboratory also suggests a non-responsiveness of this species.  相似文献   

Species, tissue and gender-related organochlorine bioaccumulation in white-sided dolphins, pilot whales and their common prey in the northwest Atlantic   总被引：5，自引：0，他引：5  

Weisbrod AV  Shea D  Moore MJ  Stegeman JJ 《Marine environmental research》2001,51(1):29-50

Organochlorine concentrations were measured in white-sided dolphins, pilot whales, and their prey from the Gulf of Maine and used to identify species, tissue, and gender differences, and trophic transfer trends, in bioaccumulation. Polychlorinated biphenyl concentrations ([PCB]) in dolphin blubber (13 +/- 7.1 micrograms/g fresh wt.) were twice those in pilot whales, but pesticide concentrations (20 +/- 13 micrograms/g fresh) were similar between species. 4,4'-DDE, trans-non-achlor, Cl6(153) and Cl6(138) concentrations were highest. Skin tissues had more recalcitrant organochlorines than the internal organs. Male dolphins bioaccumulated higher concentrations of nonmetabolizable PCBs and hexachlorocyclohexane (HCH) isomers, whereas pilot whales had no gender-related differences in bioaccumulation. Pilot whales, mackerel, and herring had proportionately higher concentrations of DDTs, whereas [PCB] were higher in dolphins and squid. Although these odontocetes feed at the same trophic level and store a similar suite of contaminants, dolphins bioaccumulated higher and potentially hazardous 4,4'-DDE and PCB concentrations from food in their more geographically restricted range.  相似文献   

安徽淮河中游平原第四纪下限     

金权  王平  王松根  李志刚  张桂祥 《海洋地质与第四纪地质》1986,(2)

安徽淮河中游平原第四系研究,最早是由杨钟健、周明镇先生进行的.他们根据江苏泗洪下草湾、戚咀和泊岗村附近地层中的哺乳动物化石和瓣鳃类化石研究,将更新统自下而上划为下草湾组、泊岗组、戚咀组.六十年代初,张可迁同志根据淮北1:20万综合水文地质普查资料,对区内第四系提出了不同的划分意见,将下更新统称为下草湾组,上更新统称为下蜀组,且认为中更新统可能缺失.七十年代,安徽省地质矿产局区域地质调查队,根据安徽省地质矿产局第一水文地质工程地质队在近卅年来于淮北平原施工的大量第四纪钻孔资料,将更新统自下而上建立了蒙城组、潘集组、茆塘组.显而易见,本区第四纪下限的专门性工作很不深入,基本是以岩性为分层依据;  相似文献   

基于GIS的天水市区南北两山生态敏感性分析   总被引：2，自引：0，他引：2  

王伟伟  李志刚  张彦彦 《地理空间信息》2008,6(4):90-92

基于地理信息系统（GIS）的空间分析技术对生态敏感性进行了分析研究,按得分与赋权重的方法,研究出四个级别的敏感性分布,为天水市的规划提供了可靠的科学判断和决策依据,  相似文献