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 31 毫秒
1.
东、南洞庭湖的径流、泥沙特征及冲淤规律   总被引:4,自引:2,他引:2  
通过实地调查并对1957年以来水文、泥沙观测资料做系统分析和计算,探讨东、南洞庭湖出、入湖水量、沙量的年际和年内变化特征,以及长江下荆江段裁弯对湖区径流和泥沙的影响。提出了湖区泥沙汛淤枯冲的变化规律及水位升降与湖区泥沙冲淤的关系;论证了丰、平、枯年湖区淤积严重,面积日益缩小对径流的调节作用正在减弱。  相似文献   

2.
石油与天然气的成因问题关系到我国乃至世界各国能源结构的配置及其能源在社会与经济发展中的地位和导向.自从17世纪展开对石油的有机与无机成因的争论以来,至今已有约300~400年的历史.尽管有机成因论占据了统治地位,但是无机成因论亦不断地在兴起!通过对这二者的理解和研究,从理论上讲他们都具有一定的物质基础和论据.基于对国内、外一些特异油田的生储环境,原油中所富含的微量金属元素的聚集与散失,某些油田中并未找到卟啉分子这样的生物标志物,碳、氢、氧化学合成实验等方面取得了一定的成效,故全盘否定无机生油的论点和论据确尚感为时过早或欠妥!显然,在以有机物成油为主体的前提下,无机物亦可生成部分石油,并通过运移、渗透到各油田的储集层中应是完全可能的.基于这样的分析、研究和探索,现提出石油的双机(a有机+b无机)混合成因的新理念.诚希能在今后的石油工业发展中,从理论、技术、实验和实践中强化对双机混合成因新理念的深化研究与探索,以达深切理解和扩展石油生、储空间环境等是不无裨益的!  相似文献   

3.
本文提出我国北方含水量高的低洼地段公路工程中路基填方铺设方法,重点研究了材料配合比不确定、工程地质条件复杂、充填施工质量不易控制等问题,进行二灰土击实与压缩性能的试验研究,得出了石灰、粉煤灰和土3种充填材料的配合比,并针对工程特点,提出了确保施工质量的措施。室内试验及现场施工均取得了较满意的结果,该研究为公路路基填方提供了可借鉴的经验。  相似文献   

4.
滕吉文 《地球物理学报》2010,53(8):1749-1766
进入21世纪以来,全球范围内强烈地震频频发生,势已进入到一个新的地震活动时期.我国大陆内部、周边和台湾岛内一系列强烈地震(MS≥6.5)的发生,特别是2008年5月12日汶川MS8.0大地震的突发与其震前的异常平静表明:地表与上地壳均未见有明显的或确切能构成短、临强烈地震预测的浅表层活动过程,大地震由深部壳、幔物质运动,即深层动力过程所致.基于对强烈地震孕育、发生和发展的初步研究提出:(1)面对强烈地震的预测必须强化震源深部介质和构造环境的研究与探索,以达对未来地震发生地点的预测.(2)在地震强烈活动地区长期坚守介质破裂效应及其派生物理响应的井中观测,即"抚模"震源区介质与结构的动态"脉搏",以达对地震发生时间的逐步逼近或预测.(3)深入剖析强烈地震活动区、带、点的深、浅层空间结构与动力过程,历史地震在地震活动地域的纵向和横向的分布特征及可靠前兆信息的同步性经验和统计效应与发展态势,以对未来强烈地震发生强度的估计.这三个方面均必须以地壳深部信息的采集和研究为前提,是地震学和地震预测深化研究与探索的必经之途!  相似文献   

5.
The patterns of temporal variations of precipitation (P), streamflow (SF) and baseflow (BF) as well as their nitrate-nitrogen (nitrate) concentrations (C) and loads (L) from a long-term record (28 years) in the Raccoon River, Iowa, were analyzed using variogram and spectral analyses. The daily P is random but scaling may exist in the daily SF and BF with a possible break point in the scaling at about 18 days and 45 days, respectively. The nitrate concentrations and loads are shown to have a half-year cycle while daily P, SF, and BF have a one-year cycle. Furthermore, there may be a low-frequency cycle of 6–8 years in C. The power spectra of C and L in both SF and BF exhibit fractal 1/f scaling with two characteristic frequencies of half-year and one-year, and are fitted well with the spectrum of the gamma distribution. The nitrate input to SF and BF at the Raccoon watershed seems likely to be a white noise process superimposed on another process with a half-year and one-year cycle.  相似文献   

6.
套损检测新技术   总被引:2,自引:0,他引:2       下载免费PDF全文
介绍了套损检测的紧迫性和油田开发中的重要意义,从声波、井径、光学、电磁等方面论说了当前世界上如斯伦贝谢、哈利伯顿、阿特拉斯、松旦克斯及俄罗斯地球物理等公司研制的具有特色套损检测先进仪器,详细介绍了各种仪器原理、特点和技术指标,各种检测仪国内油田基本上有应用,而且引进了部分仪器.  相似文献   

7.
搜救犬目前在地震应急救援中发挥着突出作用。本文旨通过提出搜救犬注意力概念,并对犬的注意力进行分类。通过对搜救犬有意注意和无意注意的实践性阐述,提出搜救犬的注意力在工作中的重要性,并提出切实可行的训练和实践方法。  相似文献   

8.
A study of the chemical trends displayed by lunar armalcolites has been made in conjunction with single-crystal X-ray structure refinements of lunar and synthetic armalcolite in order to assess the possible importance of Ti3+ in lunar armalcolite and to characterize the effects of cation substitutions on the structure. The apparent cation deficiencies found in lunar armalcolites analyzed with the electron microprobe most likely reflect the presence of Ti3+, although the existence of vacancies cannot be ruled out. Structure refinements of an Apollo 17 armalcolite are consistent with either interpretation. These results support experimental evidence suggesting the presence of Ti3+ in armalcolite and indicate that virtually all lunar armalcolites probably contain ~4–11 mol.% Ti23+Ti4+O5 component in solid solution. The cation distribution in lunar armalcolite is essentially completely ordered. However, synthetic crystals quenched from near 1200°C have been found to retain significant cation disorder.  相似文献   

9.
Drought, a normal recurrent event in arid and semiarid lands such as Iran, is typically of a temporary nature usually leaving little permanent aftermath. In the current study, the rainfall and drought severity time series were analyzed at 10 stations in the eastern half of Iran for the period 1966–2005. The drought severity was computed using the Standardized Precipitation Index (SPI) for a 12‐month timescale. The trend analyses of the data were also performed using the Kendall and Spearman tests. The results of this study showed that the rainfall and drought severity data had high variations to average values in the study period, and these variations increased with increasing aridity towards the south of the study area. The negative serial correlations found in the seasonal and annual rainfall time series were mostly insignificant. The trend tests detected a significant decreasing trend in the spring rainfall series of Birjand station at the rate of 8.56 mm per season per decade and a significant increasing trend in the summer rainfall series of Torbateheydarieh station at the rate of 0.14 mm per season per decade, whereas the rest of the trends were insignificant. Furthermore, the 12‐month values of the standardized precipitation index decreased at all the stations except Zabol during the past four decades. During the study period, all of the stations experienced at least one extreme drought which mainly occurred in the winter season. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

10.
Characteristics of phenanthrene and pyrene's sorption and desorption on two local soils in solutions of simulated groundwater,simulated lung fluid,and simulated saliva were studied with batch equilibrium experiments to understand the fate of PAHs in the karst region of southwestern China and to assess the environmental exposure and the health risk of PAHs.The results showed that the sorption and desorption isotherms of phenanthrene and pyrene on two target soils in the three solution systems could be adequately described by the Freundlich model,while the fitted isotherm parameters for the simulated groundwater solution distinguished notably from those for the simulated body fluid solutions.For the sorption experiments,in the simulated groundwater,the n values were 0.722 and 0.672 for phenanthrene and were 0.724 and0.663 for pyrene,respectively,on the yellow soil and the limestone soil;The log KF values were 3.118 and 3.323 for phenanthrene and were 3.648 and 3.846 for pyrene,respectively,on the yellow soil and the limestone soil.In the simulated body fluids,the n values for phenanthrene and pyrene ranged from 0.622 to 0.836 and from 0.590 to0.865,respectively,and the log KF values of phenanthrene and pyrene ranged from 2.845 to 3.327 and from 3.344 to3.779,respectively.For the desorption experiments,in the simulated groundwater,the n values were 0.662 and 0.744 for phenanthrene and were 0.702 and 0.647 for pyrene,respectively,on the yellow soil and the limestone soil.The log K_F values were 3.666 and 3.686 for phenanthrene and were 4.128 and 4.225 for pyrene,respectively,on the yellow soil and the limestone soil.In the simulated body fluids,the n values for phenanthrene and pyrene ranged from 0.612 to 0.668 and from 0.631 to 0.819,respectively,and the log KF values of phenanthrene and pyrene ranged from 3.134 to 3.407 and from 3.533 to 3.839,respectively.The limestone soil had relatively higher log KF values but lower K_(OC) values compared to those of the yellow soil,indicated that the nature of sorbent soils played the dominant role in sorption and desorption behaviors of PAHs.The experimental results showed a remarkable differences in sorption and desorption behaviors of PAHs in simulated body fluids and groundwater.The nonlinearities of measured isotherms and the measured sorption capacities of soils in simulated body fluids were significantly lower than corresponding those in the simulated groundwater,and HI values for simulated body fluids systems were significantly smaller than corresponding those for the simulated groundwater systems.The results underscore cautions in assessing environmental exposure and health risks of PAHs based on their sorption-desorption data in simulated groundwater as this is traditionally done.  相似文献   

11.
福建沿海、台湾海峡GPS观测分析及地球动力学特征研究   总被引:1,自引:1,他引:1  
利用 3期GPS联测结果所获得的福建沿海地壳水平运动信息 ,采用ITRF94全球框架为基础的GPS测站地壳运动模型及其处理软件 ,对所获得的观测数据进行处理和精度分析。得到福建省高精度的GPS测站大地坐标、边长及其位移矢量 ,其精度达到 1 7×10 - 8。计算了福建地壳运动速率、主应变率 ,东西与南北向线应变率、面应变率、剪应变率、大地转动率和最大剪应变率等值线并给出了它们的分布图象。根据多年形变和现今GPS观测资料 ,分析福建地壳垂直运动与水平运动 ,显示区域应力场优势分布特征。最后 ,对福建沿海及台湾海峡地壳动力学特征作了初步的探讨  相似文献   

12.
Reliable projections of extremes at finer spatial scales are important in assessing the potential impacts of climate change on societal and natural systems, particularly for elevated and cold regions in the Tibetan Plateau. This paper presents future projections of extremes of daily precipitation and temperature, under different future scenarios in the headwater catchment of Yellow River basin over the 21st century, using the statistical downscaling model (SDSM). The results indicate that: (1) although the mean temperature was simulated perfectly, followed by monthly pan evaporation, the skill scores in simulating extreme indices of precipitation are inadequate; (2) The inter-annual variabilities for most extreme indices were underestimated, although the model could reproduce the extreme temperatures well. In fact, the simulation of extreme indices for precipitation and evaporation were not satisfactory in many cases. (3) In future period from 2011 to 2100, increases in the temperature and evaporation indices are projected under a range of climate scenarios, although decreasing mean and maximum precipitation are found in summer during 2020s. The findings of this work will contribute toward a better understanding of future climate changes for this unique region.  相似文献   

13.
Sophocleous M 《Ground water》2007,45(4):393-401
Conflicts between ecosystems and human needs for fresh water are increasing. The purpose of this paper is to raise awareness in the hydrogeologic community of environmental flows (EFs) and to address the major challenges involved in their protection. Ground water is a key component of EFs, and therefore hydrogeologists are called upon to get involved in the ongoing debates about maintaining healthy riverine ecosystems. Promising opportunities for achieving EFs in both underallocated and overallocated basins as well as new methods for protecting fresh water ecosystems developed in different countries are outlined. EF protection measures include private water trusts, "upside-down instream flow water rights," the "public trust" doctrine, and water markets, among other measures. A number of knowledge gaps are identified, to which hydrogeologists could contribute, such as our rudimentary knowledge about ground water-dependent ecosystems, aspects of stream-aquifer interactions, and the impacts of land-use changes. The values that society places on the different uses of water ultimately determine where the water is allocated. EF requirements can be legitimately recognized and addressed by basing the environmental needs of hydrologic systems on robust science, focusing on increasing the productivity of water use, engaging society in understanding the benefits and costs of decisions that affect ecosystems, and taking advantage of various opportunities for achieving EF goals.  相似文献   

14.
我国地震科技进步的回顾与展望(一)   总被引:9,自引:2,他引:9  
陈章立 《中国地震》2001,17(3):231-245
本文对近半个世纪以来我国地震科技发展所经历的艰辛历程和所取得的长足进步作了简要回顾。阐明了如下3点:(1)全社会对减轻地震灾害及减轻地震对社会经济生活影响的强烈要求是推动我国地震科技发展的强劲动力;(2)为人民生命财产安全、经济可持续发展和社会稳定提供更好的保障是推动我国地震科技发展的根本目的;(3)坚持地震监测等技术系统建设与地震科学研究的辩证统一,并处理好任务性、科学性、可行性之间的关系是推动我国地震科技进步性质遵循的重要原则。地震预报预防工作所取得的某些成功和所遭受的许多挫折不断加深了人们对地震的发生条件和孕育发生过程复杂性的认识,促进了地震监测等技术系统的改造与现代化建设和地震科学研究的深入。尤其是20世纪最后5年,地震监测等技术系统的改造和现代化建设使地震预报预防研究与实践的技术支撑得到较明显的改善,既突出重点,又广泛探索的地震科学研究,使人们对我国大陆地震的发生条件和孕育发生过程,以及震害特征与机理研究等取得一些新的重要认识。所取得的长足进步不仅使防震减灾工作实效得以明显提高,而且为加速新世纪,首先是“十五”期间我国地震科技的进步进一步奠定了基础。在回顾历史的基础上,阐明了当前和今后一段时期我国地震科技发展的总体要求和应重点加强的10个方面的工作,即地震观测台网的数字化改造与建设;地震前兆观测台网的改造与建设;强地震动观测台网的建设;地震实验室的建设;地震信息和应急指挥与紧急救援技术系统的建设;地震短临预报的研究;地震中长期预报的研究;地震动衰减和震害机理与震害控制的研究;城市地震活动断层探测与震害预测的研究;地震科学和地球科学有关领域的基础研究。期望通过这些努力使我国地震科技全面达到国际先进水平,地震预报预防的理论、技术、方法显著改进,防震减灾工作实效显著提高。  相似文献   

15.
用SNMR和TEM方法探测地下水的研究与实践   总被引:1,自引:0,他引:1  
地面核磁共振找水方法是在近二十多年里发展起来的直接找水的物探新方法,该方法具有找水原理新颖、解释结果量化的特点,已取得了很好的应用成果。瞬变电磁法是近年来国内外发展得较快、地质效果较好的一种电法勘探分支方法。理论和实践表明,这两种找水方法的合理配合,优势互补,得到好的地质效果。本文通过对SNMR和TEM找水方法的原理和特点对比,论述了两者优势互补的可行性,并通过实例说明了综合利用两种方法的效果。  相似文献   

16.
A close correlation in spatial distribution of local seismic activity and energy release patterns before and after the 1979 Petatlan, Mexico earthquake suggests heterogeneity within the fault plane of this major low-angle thrust event associated with subduction along the Middle America Trench. A simple two-asperity model is proposed to account for the complexity. Foreshocks and aftershocks of the neighboring 1981 Playa Azul earthquake showed a similar pattern. As both events occurred at the junction of the Orozco Fracture Zone and the Middle America Trench, we speculate that the observed complex fault plane is caused by subduction of the rugged ocean floor of the Orozco Fracture Zone. Short-term precursory seismicity prior to the Petatlan earthquake can be explained by using the asperity model and migration of a slip front from the south-east to the north-west across the main shock source region.  相似文献   

17.
目的:探讨睑板腺癌(SC)与基底细胞癌(BCC)的CT及MRI表现,提高对二者的鉴别诊断能力。方法:回顾性分析经手术证实的14例SC和7例BCC患者的临床资料和影像表现。结果:在14例SC患者中6例行CT平扫检查,7例行MRI平扫检查,1例行CT与MRI检查;在7例BCC患者中1例行CT平扫检查,5例行MRI平扫检查,1例行CT与MRI检查。SC病例中92.9% 为女性(13/14),50% 发生于上睑(7/14),病灶形态多数呈环条状和结节状(12/14),半数病灶边界不清晰(7/14),病灶内常出现“弧形征”(5/14)和气体征(4/7),1例侵犯邻近眼眶组织;BCC病例男女患者比例相近,病灶全部位于下睑(7/7),近半数病灶形态呈结节状(3/7),边界多数较清晰(6/7),1例病灶内见钙化灶,未见病灶侵犯邻近组织。结论:SC与BCC在流行病学、发病部位、影像学特征等方面均有一定的差异,掌握二者鉴别要点可提高术前定性诊断准确性。   相似文献   

18.
Baseline characterization of concentrations and isotopic values of dissolved natural gases is needed to identify contamination caused by the leakage of fugitive gases from oil and gas activities. Methods to collect and analyze baseline concentration‐depth profiles of dissolved CH4 and C2H6 and δ13C‐CH4 in shales and Quaternary clayey tills were assessed at two sites in the Williston Basin, Canada. Core and cuttings samples were stored in Isojars® in a low O2 headspace prior to analysis. Measurements and multiphase diffusion modeling show that the gas concentrations in core samples yield well‐defined and reproducible depth profiles after 31‐d equilibration. No measurable oxidative loss or production during core sample storage was observed. Concentrations from cuttings and mud gas logging (including IsoTubes®) were much lower than from cores, but correlated well. Simulations suggest the lower concentrations from cuttings can be attributed to drilling time, and therefore their use to define gas concentration profiles may have inherent limitations. Calculations based on mud gas logging show the method can provide estimates of core concentrations if operational parameters for the mud gas capture cylinder are quantified. The δ13C‐CH4 measured from mud gas, IsoTubes®, cuttings, and core samples are consistent, exhibiting slight variations that should not alter the implications of the results in identifying the sources of the gases. This study shows core and mud gas techniques and, to a lesser extent, cuttings, can generate high‐resolution depth profiles of dissolved hydrocarbon gas concentrations and their isotopes.  相似文献   

19.
为研究崇明岛河网浮游植物和无机、有机氮的时空分布特征及其相互关系,于2014年1、4、7和10月在崇明岛河网内选取界河、堡镇港、八滧港3条河道9个采样点采集浮游植物和表层水样,并选取崇西水闸作为对照点进行研究.结果表明:河网内浮游植物以绿藻和硅藻为主,其中水闸和堡镇港夏季裸藻生物量所占比例超过50%.八滧港总溶解性氮(TDN)的主要组分是溶解性无机氮,而水闸、界河和堡镇港溶解性有机氮(DON)在TDN中的比例在夏、秋季低于冬、春季,农田土壤释放可能是DON的重要来源.水温、溶解氧和化学需氧量是影响铵态氮浓度变化的重要环境因素.此外,通过冗余分析发现,铵态氮影响绿藻和裸藻分布,尿素影响甲藻分布.  相似文献   

20.
在数据资料基础上,从学科分布、网络传播、载文信息、期刊质量等方面,对《CT理论与应用研究》期刊近年来的发展与现状进行了比较全面的统计和分析,在数量上反映了期刊取得的进步以及存在的问题。得出纵向自身比较进步明显,横向同类比较与同类期刊有差距,特别是在载文量方面差距明显。可为期刊今后的发展提供了参考依据,对期刊的长远规划也...  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