STATISTICAL F-TESTS FOR ABSTRACT FACTOR ANALYSIS AND TARGET TESTING

Fisher variance ratio tests are developed for determining(1)the number of statistically significantabstract factors responsible for a data matrix and(2)the significance of target vectors projected into theabstract factor space.F-tests,developed from the viewpoint of vector distributions,are applied tovarious data sets taken from the chemical literature.     

FACTOR ANALYSIS OF A SIMULATED DATA MATRIX INVOLVING AQUEOUS COMPLEX EQUILIBRIA

Abstract factor analyses were performed on databases consisting of simulated samples from aqueousequilbria.The program COMPLEX was used to generate equilibrium species in a system of three reactantmetals and five reactant bases.Reactant concentrations and pH were drawn from random-normaldistributions so that sample data vectors comprised a multivariate log-normal distribution of equilibriumconcentrations.In addition,sample groups were created containing different distributions for pH andreactant concentrations.Equilibrium species were shown to contain variance contributed by change in pH among samples aswell as change in reactant concentrations.Factor modelling revealed the qualitative relationships amongthe species and how the relationships change with pH.Factors also revealed those reactants containingvariance in the data matrix.In some cases,reactant variance obscured relationships between pH and theequilibrium species.Since factor modelling of a simulated data matrix revealed the expected chemical equilibriuminteractions,a potentially powerful tool exists for investigating the effects of outliers and error.     

Characterization and appraisal of facets influencing geochemistry of groundwater in the Kulpawn sub-basin of the White Volta Basin, Ghana

Groundwater composition in the Kulpawn basin is largely controlled by aluminosilicates dissolution and cation exchange resulting in mainly Ca-Mg-HCO₃ and NaHCO₃ water types. Principal component analysis, Piper graphical classification, and stable isotope (¹⁸O and ²H) of groundwater and surface-water samples were used to delineate geochemical processes and groundwater facies. The groundwater is mildly acid to neutral and low in conductivity. Chemical constituents except HCO₃ ⁻ and SiO₂ have low concentration. No cation shows clear majority, however, the order of relative abundance is Na⁺ > Ca²⁺ > Mg²⁺ > K⁺. HCO₃ ⁻ is the predominant anion and the order of abundance is HCO₃ ⁻ > NO₃ ⁻ > SO₄ ²⁻ > Cl⁻. SiO₂ concentration is high compared with the major cations. Dissolution of plagioclase, pyroxene and biotite and cation exchange are responsible for groundwater composition. Isotopic data suggest integrative, smooth and rapid recharge from meteoric origin. The groundwater quality is generally good for domestic usage; however, 18 and 47% of boreholes respectively have NO₃ ⁻ and F⁻ levels outside WHO recommended limits suggesting potential physiological problems in some localities. The groundwater has low sodium absorption ratio and low to moderate salinity hazard but significant magnesium hazard partially limiting its use for irrigation.     

洪湖浮游植物群落结构及其与环境因子的关系

为研究洪湖浮游植物群落结构及其与环境因子的关系,于2008年3月(枯水期)及7月(丰水期)在洪湖进行采样分析。两次采样共鉴定有浮游植物6门46属95种,细胞丰度变化范围为2.00×10~5-284×10~5 cells/L。硅藻为两个季节绝对优势门类,其次为绿藻及蓝藻;主要种属为直链藻、脆杆藻、栅藻等.丰水期与枯水期浮游植物群落结构季节差异较大;在枯水期由于硅藻对水温和光照较好的适应能力使其处于优势门类;丰水期由于其他藻类对营养盐的竞争及水体中硅含量充足使得绿藻等生长同时硅藻能继续保持优势地位。主成分分析表明在洪湖富营养化水平及水体中离子类型、水体中物质组成和污染程度是影响浮游植物生长的三类主要因素;典范对应分析结果表明浮游植物群落结构与水温、溶解氧及悬浮物浓度相关。     

THE EFFECT OF MEAN CENTERING ON PREDICTION IN MULTIVARIATE CALIBRATION

Traditionally,one form of preprocessing in multivariate calibration methods such as principal componentregression and partial least squares is mean centering the independent variables(responses)and thedependent variables(concentrations).However,upon examination of the statistical issue of errorpropagation in multivariate calibration,it was found that mean centering is not advised for some datastructures.In this paper it is shown that for response data which(i)vary linearly with concentration,(ii)have no baseline(when there is a component with a non-zero response that does not change inconcentration)and(iii)have no closure in the concentrations(for each sample the concentrations of allcomponents add to a constant,e.g.100%)it is better not to mean center the calibration data.That is,the prediction errors as evaluated by a root mean square error statistic will be smaller for a model madewith the raw data than a model made with mean-centered data.With simulated data relativeimprovements ranging from 1% to 13% were observed depending on the amount of error in thecalibration concentrations and responses.     

和硕5．0级地震前乌鲁木齐基准地震台钻孔应变异常分析

运用潮汐因子、加卸载响应比及相对应力场等分析方法,对1995年3月19日发生的新疆和硕MS5.0地震前乌鲁木齐基准地震台钻孔应变观测数据进行了分析处理。结果表明,在地震前30天应变日均值出现了典型的指数曲线异常;在地震前1个月相对应力发生快速变化,主应力方向也发生了快速偏转;全日波潮汐因子地震前1个月到地震前半个月期间,出现了大幅度的单峰或双峰异常变化;加卸载响应比值在地震前2个多月就开始出现成束的异常。可以认为和硕地震前乌鲁木齐基准地震台钻孔应变记录到了明显前兆短临异常。     

CLASSIFICATION:OLDTIMERS AND NEWCOMERS

Classification and regression techniques are among the most used tools by chemometricians.Withclassification,the two classic methods are discriminant analysis and SIMCA.In this paper we discuss theconnection between these two methods and introduce two new ones of the same family:DASCO(discriminantanalysis with shrunken covariances)and RDA(regularized discriminant analysis).We demonstrate on bothsimulated and real data sets that their performance is superior to the old favorites.This is especially truein small-sample/high-dimension settings typical in chemistry.     

我国国土主体功能区划刍议

从主体功能区划的概念、工作思路、区划方法和实施机制4方面对我国国土主体功能区划工作进行了初步探讨,从而界定了主体功能区划的概念,对比了分摊法和汇总法,提出了校核法,讨论了划分的层次和空间单元大小、定性与定量的关系、指标的选取、域值的确定等划分方法问题,对主体功能区划的实施机制进行了初步探讨。     

Geoaccumulation and distribution of heavy metals in the urban river sediment

Current study presents the application of chemometric techniques to comprehend the interrelations among sediment variables whilst identifying the possible pollution source at Langat River,Malaysia.Surface sediment samples（0-10 cm）were collected at 22 sampling stations and analyzed for total metals（~（48）Cd,~（29）Cu,~（30）Zn,~（82）Pb）,pH,redox potential（Eh）,salinity,electrical conductivity（EC）,loss on ignition（LOI）and cation exchange capacity（CEC）.The principal component analysis（PCA）scrutinized the origin of environmental pollution by various anthropogenic and natural activities：four principal components were obtained with 86.34%（5 cm）and88.34%（10 cm）.Standard,forward and backward stepwise discriminant analysis effectively discriminate 2variables（84.06%）indicating high variation of heavy metals accumulation at both depth.The cluster analysis accounted for high input of Zn and Pb at LA8,LA 10,LA 11 and LA 12 that mergers three（5 cm）and four（10cm）into clusters.This is consistent with the contamination factor（C_1）that shows high Cd（LA 1）and Pb（LA 7,LA 8,LA 10,LA 11 and LA 12）contaminations at 5cm.These indicate that Pb and Zn are the most bioavailable metals in the sediment with significant positive linear relationship at both sediment depths.Therefore,this approach is a good indication of environmental pollution status that transfers new findings on the assessment of heavy metals by interpreting large complex datasets and predicting the fate of heavy metals in the sediment.     

Is the catch quota management (CQM) mechanism attractive to fishers? A preliminary analysis of the Danish 2011 CQM trial project

There is a demand for a management mechanism that can reduce the discarding problems of EU fisheries. Catch quota management (CQM) seems to be a promising candidate for such a mechanism. Drawing on a principal–agent model, the objective of this study is to develop and test a method for investigating if the CQM mechanism is efficient in providing fishers with incentives for participating in CQM and complying with the rules. The study uses the 2011 Danish CQM trial project as its empirical basis. The results indicate that CQM fishers have a higher average gross income compared to fishers harvesting according to the conventional rules. Hence, there is an incentive for fishers to participate in the trial. However, with the possibility to cheat, CQM fishers may achieve even higher gross income. It is not obvious that the CQM mechanism׳s payoff structure (incentives) is attractive enough to ensure that the fishers comply with the rules. The empirical data illustrate that without discarding the CQM fishers achieve a lower average price for their catches. Therefore, to make the CQM mechanism sufficiently attractive to fishers, the participating fishers must be compensated.