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阻滞势分析器经过半个世纪的发展,在国际上已经成为就位探测电离层离子密度、离子温度和离子速度的重要手段.本文介绍了阻滞势分析器的工作原理,建立了多种仿真模型,从微观上比较几种模型对粒子的作用特性.栅网和等离子体鞘层是影响阻滞势分析器误差的主要因素,本文重点研究了这两个因素对离子透过率的影响,分析发现鞘层电场会进一步影响栅网的电场畸变,从而加剧栅网对离子的"聚焦"作用.最后,我们通过仿真生成伏安特性曲线,利用理想模型公式进行最小二乘拟合并获得离子参数,对两种模型在不同温度输入时离子密度、离子温度和离子法向速度的探测误差做出了分析. 相似文献
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藏南普莫雍错流域水体离子组成与空间分布及其环境意义 总被引：18，自引：3，他引：15
对藏南普莫雍错湖水及其周围人湖河流水体进行了离子化学成分分析,对部分湖泊和河流水样作氧同位紊分析.结果显示,不同入湖河流离子组成与湖水本身离子组成有较大差异.湖水的主要离子组合是Mg2 -Ca2 -HCO3-SO42-,而主要补给河流加曲为Ca2 -Mg2 -HCO3-.加曲人湖河口2m水深以内水化学性质差异大,湖泊其他地区差异小.加曲对河口三角洲之上湖水影响显著.其他河流对河口处湖水影响较小.Gibbs图显示湖水离子的组成主要与流域内的岩石风化有关.离子比例和三角图分析说明控制入湖河水离子主要过程是碳酸盐、黄铁矿和硅酸盐风化.湖泊与河流水体离子的组成差异较大,原因可能是蒸发浓缩导致的CaCO3的沉淀.其结果有助于正确理解湖泊沉积碳酸盐的环境指示意义. 相似文献
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采用积分安培-离子色谱法同时测定地下水中的溴离子和碘离子,该方法的相关性好（ r＞0．999）,精密度高（RSD％＜4．0）,样品加标回收率为90～110％,溴离子检出限为5．6μg/L ,碘离子检出限为2．1μg/L。本法简便、快速、准确且选择性好,可用于分析地下水中的溴离子和碘离子。 相似文献
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本文利用DMSP F13和F15卫星观测数据,对2001—2005年58个磁暴(-472 nT≤Min.Dst≤-71 nT)期间高纬顶部电离层离子整体上行特征进行了统计研究.观测表明,磁暴期间,顶部电离层离子上行主要发生在极尖区和夜间极光椭圆区.在北半球,磁正午前,高速的离子上行(≥500 m·s-1)多集中在65° MLat以上;午后,高速离子上行区向低纬度扩展,上行速度要略高于午前;在南半球,磁午夜前,DMSP卫星在考察区域内几乎所有的纬度上都观测到了高速上行的离子;午夜后,各纬度上观测到上行离子的速度明显降低.离子上行期间,DMSP卫星在极区顶部电离层高度上也频繁地观测到电子/离子增温,且电子增温发生的频率要远高于离子增温.O+密度变化分析显示,DMSP卫星磁暴期间观测到的上行离子更多地源于顶部电离层高度.这些结果表明电子增温在驱动暴时电离层离子整体上行过程中起着重要作用. 相似文献
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本文对比分析了太阳活动高、低年期间高纬日侧顶部电离层离子上行随地磁活动水平的变化特征.按地磁活动水平，将DMSP卫星在太阳活动高年（2000-2002年，F13和F15）及太阳活动低年（2007-2009年，F13；2007-2010年，F15）期间的SSIES离子漂移速度观测数据分为三组：地磁平静期（Kp<3），中等地磁扰动期（3 ≤ Kp < 5）和强地磁活动期（Kp ≥ 5），分别统计分析了高纬日侧顶部电离层离子上行特征的时空分布.对比分析发现：（1）太阳活动低年期间，高纬日侧电离层离子上行发生率以及上行速度峰值均是太阳活动高年的2倍多，而离子上行通量峰值只有高年的1/6-1/4；（2）在相同太阳活动条件下，地磁活动水平对日侧电离层离子上行发生率峰值的影响并不明显，但对离子上行发生率的空间分布有着显著的控制作用：电离层离子上行高发区随地磁活动向低纬度扩展，并在强地磁活动期间呈现饱和的趋势；（3）日侧顶部电离层等离子体似乎存在两个效率相当的上行区域，一个位于极尖/极隙区纬度附近，离子可沿开放磁力线上行进入磁尾；另一个位于晨侧亚极光区附近，离子沿闭合磁力线上行，有可能进入日侧等离子体层边界层. 相似文献
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西藏湖泊水体中主要离子分布特征及其对区域气候变化的响应 总被引：3，自引：0，他引：3
于2009 2010年对西藏34个湖泊表层水体进行采样和水质参数测量,测试不同湖泊水体主要离子浓度,分析其分布特征和对区域气候变化的响应.研究表明,不同湖泊水体的主要离子浓度及其水质参数存在差异,西藏大部分湖泊离子浓度高于全国甚至全球湖泊平均水平.湖泊的水化学类型主要为氯化物型,少部分是硫酸盐型.西藏湖泊受强烈蒸发作用的影响,水化学类型从东南到西北依次为碳酸盐型-硫酸钠型-硫酸钾型-氯化物型.对比1990s前的研究发现,大部分湖泊水体的主要离子浓度较上世纪有所降低,且部分湖泊水化学类型也发生了变化,该变化反映了过去几十年来西藏湖泊水化学对区域气候变化的响应. 相似文献
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《地震地磁观测与研究》2016,(5)
CIC-200型离子色谱仪观测高浓度离子水样时,对水样稀释500—1 000倍,但观测误差大。考虑仪器观测的精密度,兼顾各离子正常图谱形态,福州地震台对高浓度离子水样进行不同倍数稀释实验,即进行高浓度标准溶液和标准添加的准确度和精密度实验,结果均满足国标要求,说明CIC-200离子色谱仪观测高浓度离子水样是可行的。 相似文献
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本文介绍了有关磁层中电离层离子起主要作用区域（地顶内区）的观测资料和磁层中电离层离子随地磁活动和太阳活动变化的观测资料,根据这些资料简单分析了上行离子的密度和通量密度及地顶的变化。 相似文献
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Recharge estimation for transient ground water modeling 总被引：11，自引：0，他引：11
Reliable ground water models require both an accurate physical representation of the system and appropriate boundary conditions. While physical attributes are generally considered static, boundary conditions, such as ground water recharge rates, can be highly variable in both space and time. A practical methodology incorporating the hydrologic model HELP3 in conjunction with a geographic information system was developed to generate a physically based and highly detailed recharge boundary condition for ground water modeling. The approach uses daily precipitation and temperature records in addition to land use/land cover and soils data. The importance of the method in transient ground water modeling is demonstrated by applying it to a MODFLOW modeling study in New Jersey. In addition to improved model calibration, the results from the study clearly indicate the importance of using a physically based and highly detailed recharge boundary condition in ground water quality modeling, where the detailed knowledge of the evolution of the ground water flowpaths is imperative. The simulated water table is within 0.5 m of the observed values using the method, while the water levels can differ by as much as 2 m using uniform recharge conditions. The results also show that the combination of temperature and precipitation plays an important role in the amount and timing of recharge in cooler climates. A sensitivity analysis further reveals that increasing the leaf area index, the evaporative zone depth, or the curve number in the model will result in decreased recharge rates over time, with the curve number having the greatest impact. 相似文献
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Herbert Ssegane Devendra M. Amatya Augustine Muwamba George M. Chescheir Tim Appelboom E.W. Tollner Jami E. Nettles Mohamed A. Youssef François Birgand R.W. Skaggs 《水文研究》2017,31(20):3458-3471
Historically, paired watershed studies have been used to quantify the hydrological effects of land use and management practices by concurrently monitoring 2 similar watersheds during calibration (pretreatment) and post‐treatment periods. This study characterizes seasonal water table and flow response to rainfall during the calibration period and tests a change detection technique of moving sums of recursive residuals (MOSUM) to select calibration periods for each control–treatment watershed pair when the regression coefficients for daily water table elevation were most stable to minimize regression model uncertainty. The control and treatment watersheds were 1 watershed of 3–4‐year‐old intensely managed loblolly pine (Pinus taeda L.) with natural understory, 1 watershed of 3–4‐year‐old loblolly pine intercropped with switchgrass (Panicum virgatum), 1 watershed of 14–15‐year‐old thinned loblolly pine with natural understory (control), and 1 watershed of switchgrass only. The study period spanned from 2009 to 2012. Silvicultural operational practices during this period acted as external factors, potentially shifting hydrologic calibration relationships between control and treatment watersheds. MOSUM results indicated significant changes in regression parameters due to silvicultural operations and were used to identify stable relationships for water table elevation. None of the calibration relationships developed using this method were significantly different from the classical calibration relationship based on published historical data. We attribute that to the similarity of historical and 2010–2012 leaf area index on control and treatment watersheds as moderated by the emergent vegetation. Although the MOSUM approach does not eliminate the need for true calibration data or replace the classic paired watershed approach, our results show that it may be an effective alternative approach when true data are unavailable, as it minimizes the impacts of external disturbances other than the treatment of interest. 相似文献
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时空特征分析对全面掌握水质变异规律具有重要意义,但现有的水质时空特征分析方法仍存在水质变异次序不分、水质变幅极值不清、水质评价特征值不明等不足。为更加清晰地探析水质时空特征信息,以秦淮河为研究对象,参考工程水文学经验频率法,建立“水文频率-水质”拟合曲线用于探索流域内高/低活动区不同时间段和丰/枯水期不同河段水质变异特征,并与传统的箱线图法进行对比。结果表明:与箱线图相比,“水文频率-水质”拟合曲线可量化关键水质评判点与特征值信息,使水质时空变异过程更为清晰。在时间上“水文频率-水质”拟合曲线的最佳形式为线性曲线,水质浓度一般不会发生突变;在空间上“水文频率-水质”拟合曲线的最佳形式为指数曲线,水质浓度有较大可能发生突增。各时间段高活动区氮磷浓度大于低活动区,各水体断面丰水期氮磷浓度低于枯水期。该方法分析过程简单方便,结果直观有序,能将水质信息以统计规律自动反映出来,在水质采样点、采样时间和采样频率典型时可作为优选方法用于河流水质时空特征研究。 相似文献
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水位校测对提高流体观测网的运行质量与监测效能具有重要意义,是规范井水位观测技术的关键环节。基于电极法的水位校测装置广泛应用于地震流体观测台站,其校测精度受到装置本身、使用者熟练程度等因素影响。为提高水位校测装置的测量精度,设计一种地震流体井下水位校测装置,采用多电极探针的校测探头,并设计读数模块,将各电极接触水面的电信号通过无线模块传输,触发蜂鸣器报警和指示灯显示。该设计方案的可行性在实验中得到验证。 相似文献
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Daniel T. Myers Darren L. Ficklin Scott M. Robeson Ram P. Neupane Alejandra Botero-Acosta Pedro M. Avellaneda 《水文研究》2021,35(2):e14045
The selection of calibration and validation time periods in hydrologic modelling is often done arbitrarily. Nonstationarity can lead to an optimal parameter set for one period which may not accurately simulate another. However, there is still much to be learned about the responses of hydrologic models to nonstationary conditions. We investigated how the selection of calibration and validation periods can influence water balance simulations. We calibrated Soil and Water Assessment Tool hydrologic models with observed streamflow for three United States watersheds (St. Joseph River of Indiana/Michigan, Escambia River of Florida/Alabama, and Cottonwood Creek of California), using time period splits for calibration/validation. We found that the choice of calibration period (with different patterns of observed streamflow, precipitation, and air temperature) influenced the parameter sets, leading to dissimilar simulations of water balance components. In the Cottonwood Creek watershed, simulations of 50-year mean January streamflow varied by 32%, because of lower winter precipitation and air temperature in earlier calibration periods on calibrated parameters, which impaired the ability for models calibrated to earlier periods to simulate later periods. Peaks of actual evapotranspiration for this watershed also shifted from April to May due to different parameter values depending on the calibration period's winter air temperatures. In the St. Joseph and Escambia River watersheds, adjustments of the runoff curve number parameter could vary by 10.7% and 20.8%, respectively, while 50-year mean monthly surface runoff simulations could vary by 23%–37% and 169%–209%, depending on the observed streamflow and precipitation of the chosen calibration period. It is imperative that calibration and validation time periods are chosen selectively instead of arbitrarily, for instance using change point detection methods, and that the calibration periods are appropriate for the goals of the study, considering possible broad effects of nonstationary time series on water balance simulations. It is also crucial that the hydrologic modelling community improves existing calibration and validation practices to better include nonstationary processes. 相似文献
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包头地震台形变干扰分析 总被引：2，自引：2，他引：0
整理包头地震台伸缩仪、水管倾斜仪和水平摆倾斜仪观测资料,依据干扰类型分析发现,风扰、雷电降雨、温度与气压、标定与地震,仪器故障与停电是影响3台仪器观测的主要因素,干扰特征主要表现为缺记断记、数据突跳、尖脉冲、高频干扰、台阶、毛刺,大幅度变化、曲线加粗和趋势性变化等。不同类型观测仪器对干扰的响应不同,识别并剔除干扰,有利于地震观测数据应用,对地震异常判定具有参考价值。 相似文献
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J. F. Devlin 《Ground Water Monitoring & Remediation》1996,16(3):179-185
The uncertainty associated with a volatile organic concentration measurement is a function of variability and bias introduced at the various levels of sample handling: collection, storage, and analysis. During the past decade, sampling materials and the development and/or improvement of sampling protocols have been the subject of considerable research activity. As a result, in cases of samples properly handled, the analytical variability can be the dominant source of uncertainty in a given concentration value. Here analytical variability refers to any error that might arise during analysis, including the detector response error and any sample handling errors common to both standards and samples. This can be a particular concern for field analyses by gas chromatography (GC), Well-established statistical methods are available to estimate analytical uncertainty from linear calibration curves, but these methods are poorly suited for the analysis of volatile organics because organic samples frequently require instrument calibration (usually GC) over several orders of magnitude in concentration. If a single linear calibration curve is used to determine sample concentrations and uncertainties, then unrealistically large uncertainties may be assigned to low concentration samples. However, the methods can be adopted for extended concentration range calibration curves by breaking the overall calibration line down into smaller sub-calibration lines that span smaller ranges. These can then be examined and used selectively to determine concentrations with more appropriate uncertainties attached. The method of multiple callbration line analysis described here is suitable for programming with any high level computer language. It can be used to calculate meaningful analytical uncertainty values for any substance analyzed over a wide range in concentrations (i.e., an order of magnitude or more). 相似文献
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