Statistical prediction of waterflooding performance by K-means clustering and empirical modeling

Statistical prediction is often required in reservoir simulation to quantify production uncertainty or assess potential risks.Most existing uncertainty quantification procedures aim to decompose the input random field to independent random variables,and may suffer from the curse of dimensionality if the correlation scale is small compared to the domain size.In this work,we develop and test a new approach,K-means clustering assisted empirical modeling,for efficiently estimating waterflooding performance for multiple geological realizations.This method performs single-phase flow simulations in a large number of realizations,and uses K-means clustering to select only a few representatives,on which the two-phase flow simulations are implemented.The empirical models are then adopted to describe the relation between the single-phase solutions and the two-phase solutions using these representatives.Finally,the two-phase solutions in all realizations can be predicted using the empirical models readily.The method is applied to both 2D and 3D synthetic models and is shown to perform well in the P10,P50 and P90 of production rates,as well as the probability distributions as illustrated by cumulative density functions.It is able to capture the ensemble statistics of the Monte Carlo simulation results with a large number of realizations,and the computational cost is significantly reduced.

Empirical-Statistical Methodology and Methods for Modeling and Forecasting of Climate Variability of Different Temporal Scales

Main problem of modern climatology is to assess the present as well as future climate change, For this aim two approaches are used: physic-mathematic modeling on the basis of GCMs and palaeoclimatic analogues. The third approach is based on the empirical-statistical methodology and is developed in this paper. This approach allows to decide two main problems: to give a real assessment of climate changes by observed data for climate monitoring and extrapolation of obtained climate tendencies to the nearest future (10-15 years) and give the empirical basis for further development of physic-mathematical models. The basic theory and methodology of empirical-statistic approach have been developed as well as a common model for description of space-time climate variations taking into account the processes of different time scales. The way of decreasing of the present and future uncertainty is suggested as the extraction of long-term climate changes components in the particular time series and spatial generalization of the same climate tendencies in the obtained homogeneous regions. Algorithm and methods for realization of empirical-statistic methodology have been developed along with methods for generalization of intraannual fluctuations, methods for extraction of homogeneous components of different time scales (interannual, decadal, century), methodology and methods for spatial generalization and modeling, methods for extrapolation on the basis of two main kinds of time models: stochastic and deterministic-stochastic. Some applications of developed methodology and methods are given for the longest time series of temperature and precipitation over the world and for spatial generalization over the European area.

Empirical Models for the Evaluation of Global Solar Radiation for the Site of Abeche in the Province of Ouaddaï, in Chad

The global sustainability plan for future development relies on solar radiation which is the main source of renewable energy. Thus, this work studies the performance of six models to estimate global solar radiation on a horizontal surface for the Abeche site in Chad. The data used in this work were collected at the General Directorate of National Meteorology of Chad. The reliability and accuracy of different models for estimating global solar radiation were validated by statistical indicators to identify the most accurate model. The results show that among all the models, the Sabbagh model has the best performance in estimating the global solar radiation. The average is 6.354 kWh/m2 with an average of -3.704%. This model is validated against NASA data which is widely used.

Science of empirical design in mining ground control

Many problems in rock engineering are limited by our imperfect knowledge of the material properties and failure mechanics of rock masses. Mining problems are somewhat unique, however, in that plenty of real world experience is generally available and can be turned into valuable experimental data.Every pillar that is developed, or stope that is mined, represents a full-scale test of a rock mechanics design. By harvesting these data, and then using the appropriate statistical techniques to interpret them,mining engineers have developed powerful design techniques that are widely used around the world.Successful empirical methods are readily accepted because they are simple, transparent, practical, and firmly tethered to reality. The author has been intimately associated with empirical design for his entire career, but his previous publications have described the application of individual techniques to specific problems. The focus of this paper is the process used to develop a successful empirical method. A sixstage process is described: identification of the problem, and of the end users of the final product; development of a conceptual rock mechanics model, and identification of the key parameters in that model;identification of measures for each of the key parameters, and the development of new measures(such as rating scales) where necessary; data sources and data collection; statistical analysis; and packaging of the final product. Each of these stages has its own potential rewards and pitfalls, which will be illustrated by incidents from the author's own experience. The ultimate goal of this paper is to provide a new and deeper appreciation for empirical techniques, as well as some guidelines and opportunities for future developers.

基于三种方法的径流变化贡献率对比分析--以彭冲涧小流域为例

小流域径流变化是气候变化和人类活动共同作用的结果,定量评价两者对径流变化的贡献率已成为当前的研究热点。以彭冲涧小流域为研究对象,对比分析水文模型模拟法、经验统计分析法、累积量斜率变化率比较法的径流变化贡献率计算结果,并归纳分析3种方法的优缺点。结果表明:在春、夏季及年尺度上,水文模型模拟法计算的降水变化对径流减少的贡献率分别为61.00%,81.60%,70.00%,大于另外2种方法;而累积量斜率变化率比较法考虑了蒸散发的贡献率,其降水变化和植被恢复的贡献率在春、夏季及年尺度上分别为50.88%,42.60%,31.26%和16.23%,16.69%,26.10%,均为最小。

彭冲涧小流域降水与植被恢复对径流的影响--经验统计分析法与水文模型模拟法比较

降水变化与植被恢复对小流域径流变化的贡献率分析是当前研究的热点。运用Mann-Kendall检验法对江西省九江市都昌县彭冲涧小流域1983—2014年的降水、径流序列进行突变分析,采用经验统计法与水文模型模拟法计算降水变化与植被恢复对径流影响的贡献率。结果显示:2003年为降水与径流的一致突变点;因此,以1983—2003年为基准期,2004—2014年变化期的年降水量、年径流深分别减少8.7%和29.2%,年平均减少幅度分别为12.7和22.1 mm。相对于基准期,春季、夏季及年尺度上变化期的平均径流深分别减少100.2、105.8和243.0 mm。经验统计分析法的研究结果表明,降水变化和植被恢复对径流减少的贡献率分别为58.9%、41.1%,71.6%、28.4%和57.1%、42.9%;而水文模型模拟法的研究结果分别为61.0%、39.0%,81.6%、18.4%和70.0%、30.0%。可知,尺度不同,研究结果存在较大差异,且降水变化的贡献率均大于植被恢复。同时,2种方法的研究结果总体上较接近,说明均比较可信,能为从更深层次上认识植被对径流的影响程度提供科学依据。

Estimation of leaf area index from high resolution ZY-3 satellite imagery in a catchment dominated by Larix principis-rupprechtii,northern China

Leaf area index(LAI) is a key factor that determines a forest ecosystem's net primary production and energy exchange between the atmosphere and land surfaces.LAI can be measured in many ways, but there has been little research to compare LAI estimated by different methods. In this study, we compared the LAI results from two different approaches, i.e., the dimidiate pixel model(DPM) and an empirical statistic model(ESM) using ZY-3 high-accuracy satellite images validated by field data. We explored the relationship of LAI of Larix principis-rupprechtii Mayr plantations with topographic conditions. The results show that DPM improves the simulation of LAI(r = 0.86,RMSE = 0.57) compared with ESM(r = 0.62, RMSE =0.79). We further concluded that elevation and slope significantly affect the distribution of LAI. The maximum peak of LAI appeared at an aspect of east and southeast at an elevation of 1700–2000 m. Our results suggest that ZY-3 can satisfy the needs of quantitative monitoring of leaf area indices in small-scale catchment areas. DPM provides a simple and accurate method to obtain forest vegetation parameters in the case of non-ground measurement points.

Performance of a data-driven technique applied to changes in wave height and its effect on beach response

In this study the medium-term response of beach profiles was investigated at two sites： a gently sloping sandy beach and a steeper mixed sand and gravel beach. The former is the Duck site in North Carolina, on the east coast of the USA, which is exposed to Atlantic Ocean swells and storm waves, and the latter is the Milford-on-Sea site at Christchurch Bay, on the south coast of England, which is partially sheltered from Atlantic swells but has a directionally bimodal wave exposure. The data sets comprise detailed bathymetric surveys of beach profiles covering a period of more than 25 years for the Duck site and over 18 years for the Milford-on-Sea site. The structure of the data sets and the data-driven methods are described. Canonical correlation analysis （CCA） was used to find linkages between the wave characteristics and beach profiles. The sensitivity of the linkages was investigated by deploying a wave height threshold to filter out the smaller waves incrementally. The results of the analysis indicate that, for the gently sloping sandy beach, waves of all heights are important to the morphological response. For the mixed sand and gravel beach, filtering the smaller waves improves the statistical fit and it suggests that low-height waves do not play a primary role in the medium-term morohological resoonse, which is primarily driven by the intermittent larger storm waves.

Improved empirical DC I-V model for 4H-SiC MESFETs

A novel empirical large signal direct current （DC）Ⅰ-Ⅴ model is presented considering the high saturation voltage, high pinch-off voltage, and wide operational range of drain voltage for 4H-SiC MESFETs. A comparison of the presented model with Statz, Materka, Curtice-Cubic, and recently reported 4H-SiC MESFET large signal Ⅰ-Ⅴ models is made through the Levenberg-Marquardt method for fitting in nonlinear regression. The results show that the new model has the advantages of high accuracy, easily making initial value and robustness over other models. The more accurate results are obtained by the improved channel modulation and saturation voltage coefficient when the device is operated in the sub-threshold and near pinch-off region. In addition the new model can be implemented to CAD tools directly, using for design of 4H-SiC MESFET based RF＆MW circuit, particularly MMIC （microwave monolithic integrate circuit）.

Blockwise Empirical Likelihood Method for Spatial Dependent Data

Existing blockwise empirical likelihood(BEL)method blocks the observations or their analogues,which is proven useful under some dependent data settings.In this paper,we introduce a new BEL(NBEL)method by blocking the scoring functions under high dimensional cases.We study the construction of confidence regions for the parameters in spatial autoregressive models with spatial autoregressive disturbances(SARAR models)with high dimension of parameters by using the NBEL method.It is shown that the NBEL ratio statistics are asymptoticallyχ^(2)-type distributed,which are used to obtain the NBEL based confidence regions for the parameters in SARAR models.A simulation study is conducted to compare the performances of the NBEL and the usual EL methods.

ESTAR-GARCH模型的单位根检验

ESTAR-GARCH模型的单位根检验所选取的统计量通常需要估计方差,因此本文提出了经验似然比统计量,避免了方差计算带来的误差,并推导出了该统计量的极限分布.通过模拟其临界值,对比研究了经验似然比统计量和基于QML法的KSS型检验统计量t(δ)的检验功效.Monte Carlo模拟证实,本文提出的经验似然比统计量比检验统计量t(δ)具有更好的检验水平和更高的检验功效.因此本文提出的统计量通过避免方差的计算而提高了检验的准确性.最后,通过上证指数的实证分析,进一步说明了该统计量具有良好的检验功效.

A semiparametric Wald statistic for testing logistic regression models based on case-control data

We propose a semiparametric Wald statistic to test the validity of logistic regression models based on case-control data. The test statistic is constructed using a semiparametric ROC curve estimator and a nonparametric ROC curve estimator. The statistic has an asymptotic chi-squared distribution and is an alternative to the Kolmogorov-Smirnov-type statistic proposed by Qin and Zhang in 1997, the chi-squared-type statistic proposed by Zhang in 1999 and the information matrix test statistic proposed by Zhang in 2001. The statistic is easy to compute in the sense that it requires none of the following methods: using a bootstrap method to find its critical values, partitioning the sample data or inverting a high-dimensional matrix. We present some results on simulation and on analysis of two real examples. Moreover, we discuss how to extend our statistic to a family of statistics and how to construct its Kolmogorov-Smirnov counterpart.

A Medium/Long-Range Forecast of Pacific Subtropical High Based on Dynamic Statistic Model Reconstruction

Based on the 500-hPa geopotential height field series of T106 numerical forecast products, by empirical orthogonal function （EOF） time-space separation, and on the hypotheses of EOF space-models being stable, the EOF time coefficient series were taken as dynamical statistic model variables. The dynamic system reconstruction idea and genetic algorithm were introduced to make the dynamical model parameters optimized, and a nonlinear dynamic statistic model of EOF separating time coefficient series was established. By the model time integral and EOF time-space reconstruction, a medium/long-range forecast of subtropical high was carried out. The results show that the dynamical model forecast and T106 numerical forecast were approximately similar in the short-range forecast （≤5 days）, but in the medium/long-range forecast （≥5 days）, the forecast results of dynamical model was superior to that of T106 numerical products. A new method and idea were presented for diagnosing and forecasting complicated weathers such as subtropical high, and showed a better application outlook.

The Systematics Study of (n, p) Reaction Cross-Sections at 14.7 MeV Neutron Energy

Based on the statistical model and taking into account the Q-value dependence and odd-even effects, we proposed a new empirical formula to reproduce the cross sections of the (n, p) reactions at 14.7 MeV neutron energy and at the target mass number 14 ≤ A ≤ 198 for even A and 29 ≤ A ≤ 205 for odd A. All calculated results from the proposed empirical formula were compared to the experimental data as well as the available semi-empirical formula obtained by other authors. A high level of agreement has been found between the collected experimental data and the most of semiempirical formulae obtained by others.

Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin

In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.

基于光学卫星遥感的海岸带水体盐度反演方法研究

海岸带区域地表水体的盐度信息可以反映海水侵袭、海岸线退化以及土地盐碱化等生态状况,对滨海区域的海洋和陆地生态系统的研究、保护和资源开发有重要意义,但其监测主要依赖于现场测验,技术手段较为单一。卫星遥感方法具有高效、大范围的优势,本文采用高空间分辨率的光学遥感卫星开展海岸带地表水体盐度的反演方法研究,在分析单波段反射率、波段比值及常用的光谱指数与水体盐度相关性基础上,确定了水体盐度的敏感波段,构建了经验模型、半经验模型和随机森林模型,并对盐度反演的精度和结果进行比较与分析。结果表明,随机森林模型反演结果的检验精度较高,决定系数R^(2)为0.81,RMSE为193.01μS/cm,且精度稳定;半经验辐射传输模型检验的决定系数R^(2)为0.53,RMSE为303.82μS/cm;经验统计模型检验的决定系数R^(2)为0.16,RMSE为407.46μS/cm。该研究为掌握海岸带地表水质空间特征、分析水质时间变化、评价水资源可利用性提供了重要的技术途径,对海岸带生态环境的调查监测、修复治理具有重要意义。

武汉地区电离层电子浓度总含量的统计经验模式研究

由武汉电离层观象台一个太阳黑子周期（１９８０—１９９０年）的实测电离层电子浓度总含量（ＴＥＣ）资料，统计分析得出了武汉地区的一个 ＴＥＣ经验模式．模式很好地再现了武汉地区的ＴＥＣ观测值．其预测误差在太阳活动高年稍大，低年较小；在春秋两季稍大，冬夏两季较小；在当地时间白天和傍晚稍大，夜间和早晨较小．此外，与国际参考电离层模式ＩＲＩ的计算结果比较，本模式预测的ＴＥＣ值更接近于实际观测结果．同时，本文也初步探讨了ＴＥＣ的半年变化特征和冬季异常现象．

我国最低工资统计测算模型研究

最低工资统计测算模型研究,历来是各国政府极为重视的问题之一。它涉及到运用统计调查方法、经济计量模型和计算机辅助测算等方法对最低工资测算、劳动者生存质量以及对制度法规等问题进行定性定量分析的跨学科研究的问题,由于该课题在我国研究的时间较短,特别是统计学者介入研究不够,导致各级劳动和社会保障部门虽然亟需解决最低工资统计测算模型问题,但囿于统计技术问题,其发展极为缓慢。这也是本课题组亟力推动研究之动力。

基于经典计量模型的统计数据质量评估方法

本文以经济理论为基础,从整个经济系统出发,利用研究对象的相关影响因素构造计量模型,在既定模型下,运用异常值的检验方法及统计诊断原理进行数据质量的定量评估。通过选择合适的模型对考察对象的变化规律进行模拟,找出异常数据(离群值),判断异常数据是否显著异常,对异常数据进行多方查证和原因分析来进一步判断数据的质量,并对我国的统计数据质量进行了实证分析。

近45年来降水变化和人类活动对潮河流域年径流量的影响

近45a来，随着流域降水量减少，以及修建水利工程、引水、实施水土保持等人类活动的增加，潮河流域年径流量呈明显减少趋势。利用降水-径流经验统计模型，定量评估了潮河流域降水变化与人类活动对流域年径流量的影响程度。结果表明：1981—1990、1991—2000、2001～2005、1981—2005年，受人类活动影响所产生的年均减水量分别为1．32、0．67、1．46、1．09×10^8m^3，占相应时段总减水量的95．1％，98．9％，60．7％和83．2％；受降水变化影响所产生的年均减水量分别为0．07、0．01、0．95、0．22×10^8m^3，占相应时段总减水量的4．9％，1．1％，39．3％和16．8％。人类活动因素的贡献率远大于降水因素。