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 171 毫秒
1.
我们的 VAX—11/780程计算机序库包括四大部分:1.通用程序库、2.STYR 库、3.稀疏矩阵计算软件包、4.数值线性代表软件包。各部分的内容为:1.通用程序库:多项式及特殊函数的计算,数值程分、数值微分、富氏分析、快速富氏变换、插值逼近,线性拟合、矩阵、向量运算、线性方程组、非线性方程求解、微分方程、积分方程、统计分析及概率,运筹学及管理科学等,单精度型,双精度型,及复型齐全,输出直方图及等值线,内部信息传送,数据处理,调试辅助程序,量子力学及粒子物理学,随机数及实用子程序;寻找直方图通道等。  相似文献   

2.
目的:探讨膝胫股关节软骨损伤与膝关节股骨角、胫骨角、股骨胫骨角及关节间隙角的相关性。方法:回顾性分析2017年1月至2017年6月于承德医学院附属医院南院区进行膝关节MRI检查的患者587例,通过纳入标准及排除标准随机选取病例组及对照组各100例。分别测量两组人群的股骨角、胫骨角、股骨胫骨角及关节间隙角,并利用SPSS19.0对相关角度数据进行统计分析,统计方法包括秩和检验、Spearman相关性检验及ROC曲线。结果:病例组股骨角、胫骨角、股骨胫骨角及关节间隙角分别为83.22(81.85~84.40)°、95.60(94.10~96.87)°、179.00(177.50~180.25)°及1.92(1.43~2.43)°,对照组股骨角、胫骨角、股骨胫骨角及关节间隙角分别为82.50(81.70~83.60)°、94.25(93.20~95.52)°、177.20(175.90~178.17)°及0.58(0.50~0.95)°。两组胫骨角、股骨胫骨角及关节间隙角差异有统计学意义(P<0.05),股骨角差异无统计学意义(P>0.05);软骨损伤程度与关节间隙角呈显著正相关(rs=0.852,P<0.001),与胫骨角及股骨胫骨角无显著相关性。胫骨角的最佳临界值、敏感性及特异性分别为95.15°、56%、72%;股骨胫骨角的最佳临界值、敏感性及特异性分别为179.05°、49%、92%;关节间隙角的最佳临界值、敏感性及特异性分别为1.255°、84%、96%。结论:胫骨角、股骨胫骨角及关节间隙角的增大会影响膝胫股关节软骨,导致其损伤;且随关节间隙角的增大,膝胫股关节软骨损伤程度加重。   相似文献   

3.
一、《地球物理学报》是中国地球物理学会主办的有关地球物理科学的综合性学术刊物。读者对象主要是从事地震及地球内部物理学和化学、地磁及空间物理、重力及大地测量学、大地构造物理学、地球动力学、勘探地球物理、海洋及大气物理,以及与地球物理有关的其他学科的国内外科学技术工作者和大专院校师生.在国内外公开发行。 二、主要内容  相似文献   

4.
通过对建新镇供水工程区的资料收集,开展野外地质调查、测绘、钻探及室内外试验等专项研究,从供水厂房区地层岩性、场地类别、砂土液化、软土震陷及厂房区稳定性等方面分析及评价区内工程地质条件,提出区内岩土物理力学指标及建议值,推荐出基础类型及持力层;同时调查供水管线地质状况,得出工程地质结论及建议,对工程设计和施工有一定的使用价值,同时为后续开展村村通供水工程勘察和设计提供参考。  相似文献   

5.
目的:探讨甲状旁腺腺瘤(PA)的4D-DECT影像特征及物质成分信息,评价其定位及定性诊断价值.资料和方法:回顾性分析经手术及病理证实的53例PA患者的临床资料及4D-DECT影像资料,逐一观察并记录CT征象,分别对病变与邻近组织的CT衰减值(HU)、碘浓度、Rho、Z值及DEI进行测定及比较分析.结果:53例患者中,...  相似文献   

6.
本文据白城ZK6井水位的记震能力及特征、结合省内及国内一些地震观测井孔的水文地质和井孔结构特征,经综合对比分析研究从为一眼观测井的记震能力(记震次数、记震的百分比、水震波的振幅及持续时间)的强弱,主要决定于含水层岩性的坚硬程度、渗透系数及单位涌水量、水位的埋深.其次还与含水层的厚度、并孔直径大小及井孔的封闭条件好坏有关.  相似文献   

7.
全国地震数据库系统的设计和实现   总被引:2,自引:0,他引:2  
本文概要地介绍了建立全国地震数据库系统的目的、系统的运行环境及系统的构成、功能和技术特点等。此系统是由地震目录数据库及地震活动性处理子系统、全国综合前兆数据库及其应用子系统、地理底图和地质构造数据库及计算机制图子系统、全国台站信息库及其管理子系统等组成,它具有数据规模大、数据联机共享、冗余度小、检查速度快、处理功能丰富、安全性能好及使用简便等特点。  相似文献   

8.
邓韫 《华南地震》2003,23(1):51-56
根据1900~2000年中国大陆、台湾及全球地层记录及前人的研究,论证了地层周期存在的可能性及形成机制。作者认为,是太阳活动、月球运动轨道及各行星运动轨道的周期性变化,通过磁力及万有引力改变地球内部物质的分布,从而引起地球自转速度的周期性变化,最终致使地展出现周期性的活跃期及平静期。  相似文献   

9.
为了进一步明确湖泊及流域科学学科发展方向 ,研讨“十五”及 2 0 1 0年湖泊及流域科学优先资助领域及重点研究方向 ,国家自然科学基金委员会地球科学部联合中国科学院南京地理与湖泊研究所于 2 0 0 2年 3月 2 6 - 2 8日在南京召开了“湖泊及流域科学学科发展与优先领域学术研讨会” .来自中国科学院、水利部、南京大学、东南大学、河海大学、华东师范大学、浙江大学等 1 5个单位的专家、学者 6 5人参加了会议 .国家自然科学基金委员会地球科学部柴育成副主任、宋长青处长出席会议并发表讲话 ,中国科学院南京地理与湖泊研究所秦伯强常务副所…  相似文献   

10.
COVID-19虽以肺部表现为主,但该病除累及呼吸系统外,还可累及多个系统,其中尤以对骨肌系统影响的研究较为缺乏。本研究纳入33例有入院、出院及1年后随访胸部CT资料的COVID-19患者,分析其骨及体质成分特征,共纳入无症状感染者、轻型、普通型、重型患者各2、8、19和4人,无危重型患者。平均住院时长为(29.5±9.6)d,平均随访时间为(423.0±53.6)d。入院、出院及1年后胸椎骨密度未见明显变化;胸12~腰1椎间隙层面腹部皮下脂肪、腹腔内脂肪及腹部总脂肪面积亦未见明显变化。无症状感染者及轻型组患者入院及1年随访胸1~胸12平均BMD高于普通型及重型组;普通型及重型组患者入院及1年后随访腹腔内脂肪面积及腹部总脂肪面积大于无症状感染者及轻型组。本研究首次探索COVID-19对骨肌系统的影响,提示感染COVID-19一年后,并未导致患者胸椎骨密度和腹部脂肪发生明显变化。  相似文献   

11.
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   

12.
Detailed knowledge of the flood period of Arctic rivers remains one of the few factors impeding rigorous prediction of the effect of climate change on carbon and related element fluxes from the land to the Arctic Ocean. In order to test the temporal and spatial variability of element concentration in the Ob River (western Siberia) water during flood period and to quantify the contribution of spring flood period to the annual element export, we sampled the main channel year round in 2014–2017 for dissolved C, major, and trace element concentrations. We revealed high stability (approximately ≤10% relative variation) of dissolved C, major, and trace element concentrations in the Ob River during spring flood period over a 1‐km section of the river channel and over 3 days continuous monitoring (3‐hr frequency). We identified two groups of elements with contrasting relationship to discharge: (a) DIC and soluble elements (Cl, SO4, Li, B, Na, Mg, Ca, P, V, Cr, Mn, As, Rb, Sr, Mo, Ba, W, and U) negatively correlated (p < 0.05) with discharge and exhibited minimal concentrations during spring flood and autumn high flow and (b) DOC and particle‐reactive elements (Al, Fe, Ti, Y, Zr, Nb, Cs, REEs, Hf, Tl, Pb, and Th), some nutrients (K), and metalloids (Ge, Sb, and Te), positively correlated (p < 0.05) with discharge and showed the highest concentrations during spring flood. We attribute the decreased concentration of soluble elements with discharge to dilution by groundwater feeding and increased concentration of DOC and particle‐reactive metals with discharge to leaching from surface soil, plant litter, and suspended particles. Overall, the present study provides first‐order assessment of fluxes of major and trace elements in the middle course of the Ob River, reveals their high temporal and spatial stability, and characterizes the mechanism of river water chemical composition acquisition.  相似文献   

13.
Water temperature, dissolved oxygen, and concentrations of salts in surface water bodies can be affected by the natural environment and local human activities such as surface and ground water withdrawals, land use and energy extraction, and variability and long‐term trends in atmospheric conditions including temperature and precipitation. Here, we quantify the relationship between 121 indicators of mean and extreme temperature and precipitation and 24 water quality parameters in 57 Texas reservoirs using observational data records covering the period 1960 to 2010. Over time scales ranging from 1 week to 2 years, we find that water temperature, dissolved oxygen, pH, specific conductance, chloride, sulfate, and phosphorus all show consistent correlations with atmospheric predictors, including high and low temperature extremes, dry days, heavy precipitation events, and mean temperature and precipitation. Based on these relationships combined with regional climate projections, we expect climate change to increase water temperatures, decrease dissolved oxygen levels, decrease pH, increase specific conductance, and increase levels of sulfate and chloride in Texas reservoirs. Over decadal time scales, this may affect aquatic ecosystems in the reservoirs, including altering the risk of conditions conducive to algae occurrence, as well as affecting the quality of water available for human consumption and recreation. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

14.
Rotifera density, biomass, and secondary production on two marginal lakes of Paranapanema River were compared after the recovery of hydrologic connectivity with the river (São Paulo State, Brazil). Daily samplings were performed in limnetic zone of both lakes during the rainy season immediately after lateral inflow of water and, in the dry period, six months after hydrologic connectivity recovery. In order to identify the factors that affect rotifer population dynamics, lake water level, volume, depth, temperature, transparency, dissolved oxygen, pH, alkalinity, conductivity, suspended solids, nutrients, and chlorophyll-a were determined. Variations of water physical and chemical factors that affect rotifer population were related to the lake-river degree of connection and to water level rising after drought. The water lateral inflow from the river resulted in an increase in lake water volume, depth, and transparency and a decrease in water pH, alkalinity, and suspended solids. The lake with the wider river connection, more frequent biota exchange, and larger amount of particulate and dissolved materials was richer and more diverse, while rotifer density, biomass, and productivity were lower in both periods studied. Density, biomass, and secondary production were higher in the lake with the smaller river connection and the higher physical and chemical stability. Our results show that the connectivity affects the limnological stability, associated to seasonality. Stable conditions, caused by low connectivity in dry periods, were related with high density, biomass and secondary production. Conversely, instability conditions in rainy periods were associated to elevated richness and diversity values, caused by exchange biota due to higher connectivity.  相似文献   

15.
The Marcell Experimental Forest (MEF) in northern Minnesota, USA, with hydrological research and monitoring of peatland catchments in a low-topographic relief landscape, contrasts with the mountainous terrain that typifies most research catchments. Six research catchments were instrumented and hydrological and meteorological monitoring was initiated during 1960. Paired-catchment studies, which started during 1969, have been used to assess land management and environmental change effects on forests, water availability, and biogeochemistry. Over the decades, the research and collaborations have proliferated to include new monitoring and ecosystem experiments. We provide an overview of available datasets and access information for hydrological and meteorological data. Data on streamflow, water table elevation, precipitation, snow, ground frost, air temperature, soil moisture, upland runoff, and water chemistry are discoverable with associated metadata and are archived through several Web-based, community repositories. The research programme is ongoing and we anticipate updates on an annual or more frequent basis. Additionally, we aim to release other physical, chemical, and isotopic measurements associated with long-term catchment monitoring and studies at the MEF.  相似文献   

16.
Biogeomorphology has been expanding as a discipline, due to increased recognition of the role that biology can play in geomorphic processes, as well as due to our increasing capacity to measure and quantify feedback between biological and geomorphological systems. Here, we provide an overview of the growth and status of biogeomorphology. This overview also provides the context for introducing this special issue on biogeomorphology, and specifically examines the thematic domains of biogeomorphological research, methods used, open questions and conundrums, problems encountered, future research directions, and practical applications in management and policy (e.g. nature-based solutions). We find that whilst biogeomorphological studies have a long history, there remain many new and surprising biogeomorphic processes and feedbacks that are only now being identified and quantified. Based on the current state of knowledge, we suggest that linking ecological and geomorphic processes across different spatio-temporal scales emerges as the main research challenge in biogeomorphology, as well as the translation of biogeomorphic knowledge into management approaches to environmental systems. We recommend that future biogeomorphic studies should help to contextualize environmental feedbacks by including the spatio-temporal scales relevant to the organism(s) under investigation, using knowledge of their ecology and size (or metabolic rate). Furthermore, in order to sufficiently understand the ‘engineering’ capacity of organisms, we recommend studying at least the time period bounded by two disturbance events, and recommend to also investigate the geomorphic work done during disturbance events, in order to put estimates of engineering capacity of biota into a wider perspective. Finally, the future seems bright, as increasingly inter-disciplinary and longer-term monitoring are coming to fruition, and we can expect important advances in process understanding across scales and better-informed modelling efforts. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

17.
1 INTRODUCTION Soil erosion is serious in Western China. With the implementation of a development strategy for western China, soil and water conservation and ecological restoration in western China earn more attention because economic development requires parallel efforts on ecological restoration. To protect the ecology of the upper reaches of the Yangtze River, integrated management of sediment and ecological restoration are being conducted in Sichuan Province. The Yufeng Watershed…  相似文献   

18.
Catchments in the Luquillo Experimental Forest (LEF) of Puerto Rico are warm, wet and tropical with steep elevational relief creating gradients in temperature and rainfall. Long-term objectives of research at the site are to understand how changing climate and disturbance regimes alter hydrological and biogeochemical processes in the montane tropics and to provide information critical for managing and conserving tropical forest ecosystems globally. Measurements of hydrology and meteorology span decades, and currently include temperature, humidity, precipitation, cloud base level, throughfall, groundwater table elevation and stream discharge. The chemistry of rain, throughfall, and streams is measured weekly and lysimeters and wells are sampled monthly to quarterly. Multiple data sets document the effects of major hurricanes including Hugo (1989), Georges (1998) and Maria (2017) on vegetation, biota and catchment biogeochemistry and provide some of the longest available records of biogeochemical fluxes in tropical forests. Here we present an overview of the findings and the data sets that have been generated from the LEF, highlighting their importance for understanding montane tropical watersheds in the context of disturbance and global environmental change.  相似文献   

19.
Total and subcellular hepatic Zn, Cu, Se, Mn, V, Hg, Cd, and Ag were determined in a mother-fetus pair of Dall's porpoises (Phocoenoides dalli). Except for higher fetal Cu concentration, all maternal elements were higher. Elements existed mostly in the cytosol of both animals except in the case of maternal Ag in the microsome and fetal Cu and Ag in the nuclei and mitochondria. In the maternal cytosol, Zn, Mn, Hg, and Ag were present in the high-molecular-weight substances (HMW); Se and V were present in the low-molecular-weight substances (LMW); Cu and Cd were mostly sequestered by metallothionein (MT). In the fetal cytosol, Zn, Se, Mn, Hg, Cd, and Ag were present in the HMW and V in the LMW, while Cu and Ag were mostly associated with MT. MT isoforms were characterized using the HPLC/ICP-MS. Two and four obvious peaks appeared in the maternal and fetal MT fractions, respectively. The highest elemental ion intensities were at a retention time of 7.8 min for the mother, and for the fetus the peak elemental ion intensities occurred at a retention time of 4.3 min, suggesting that different MT isoforms may be involved in elemental accumulation in maternal and fetal hepatocytosols.  相似文献   

20.
湖冰光谱特征是湖冰遥感反演的物理基础,是研究湖冰光学特性和空间分布的理论依据。本文以查干湖为例,使用ASD Field Spec 4便携式地物光谱仪采集冰封期不同类型湖冰、积雪和水体光谱,利用Savitzky-Golay滤波法和包络线去除法分析白冰、灰冰、黑冰、雪冰、积雪和水体的反射光谱特征,探索气泡对湖冰反射光谱特征的影响。积雪和雪冰、白冰和灰冰、黑冰和水体的反射特征随着波长的变化特征基本一致,冰的反射率介于积雪和水体之间,其中白冰的反射率高于灰冰和黑冰,在包络线去除结果中,黑冰和水体在440 nm吸收谷处的吸收面积为5.184和10.878、吸收深度为0.052和0.106,雪、雪冰、白冰、灰冰在800和1030 nm吸收谷处的吸收面积和吸收深度的变化表现为雪<雪冰<灰冰<白冰。气泡是影响湖冰光谱特征的重要因素,气泡使白冰反射率减小和黑冰反射率增大,并且气泡使得白冰在800/1030nm和黑冰在440 nm处的吸收面积和吸收深度减小,其中气泡大小和疏密程度的不同会导致湖冰反射率的影响程度存在差异。同时,本文选取时间同步的Landsat 8 OLI遥感影像,在完成辐...  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