An examination of the use of the logratio transformation for the testing of endmember hypotheses

Given a compositional dataset in the absence of any prior information on any mixing process which may have formed it, a complete analysis of mixtures determines three distinct types of estimates in order. These are: (i) the estimate of the number of endmembers or fixed source compositions, of which all the sample compositions of the dataset must be approximate mixtures; (ii) the estimated compositions for each of these chosen number of endmembers; and (iii) the estimated contributions of each of these endmember estimates to each sample. Traditionally, the estimate for the number of endmembers has been assessed either by mapping or by inspection of the coefficients of determination between the observed and estimated variables. Mapping entails the plotting on a map of the region from which the samples were taken, either the contours of the contributions of each endmember to each sample, or some other portrayal of the distribution of endmember abundances. Because it requires the complete analysis, assessment by this method is too elaborate except for final confirmation and display. Alternatively, choosing a number of endmembers, which result in suitability high coefficients of determination for all or most variables, may account for elements which are not part of the conjectured mixing process or, worse, may result in the identification of endmembers which may never in fact have existed. Such an error is similar to overspecifying a multiple regression model. So, the obvious starting point from which to assess the validity, or otherwise choice of endmember numbers, is to examine the matrix of residuals. The differences between the logratio-transformed observed and estimated data form an array of residual logratios. A linear combination of these may be formed for each sample, which, under a random perturbation assumption, should follow a univariate normal distribution. Whether or not this scalar is normal can be readily tested. It can also be examined graphically for such desirable qualities as symmetry when the test for normality may be too severe. This procedure is employed to assess the decompositions of the U.S.G.S. Mid-Pacific data and the Nazca Plate Surface sediments.This paper was presented at the 18th Geochautauqua, Newark, Delaware, 13–14 October 1989.     

STUDY OF THE POSSIBILITIES OF USING AN AIR MASS TRANSFORMATION MODEL IN TAIYUAN

An AMT-model,consisting of a trajectory model and a one-dimensional boundary layer model,is tested fortrajectories arriving in Taiyuan to study the possibility of using it in Taiyuan.The sensitivity of the model tothe different processes was studied.Some parameters of the model were modified for the purpose of forecast-ing in specific mountainous terrain and dry climate conditions.Results of examples which we have workedout for Taiyuan circumstances for the periods of July(summer)1985 and January(winter)1986,show that the12h runs of the AMT-model are able to reproduce(on historical data)the sounding of Taiyuan.The AMT-modelcontributes fruitfully to short-range weather forecasts(12—36h ahead)during periods of severe air pollution andwhen cold waves occur.     

1966年云南东川6.5级地震的热异常时空结构分析

本文分析了１９６６年云南东川６．５级地震前后浅层地温异常的时空结构及降水异常的水平结构。分析表明，震前数月浅层地温稳定维持正异常，发震前一个月激剧增温，发震当月达最大，震后降低；震前震中区为负地温距平区，随发震时刻临近，负距平区迅速演变为正距平区，而且强度和面积都不断增大，至发震时达最大，震后不断减小；热异常是从深层传向地表的；震中区震前为旱区，震后为涝区。本文还讨论了震源处热信息传到地表的条件和可能机制，认为在水热活动异常的断裂带上，至少对于浅源地震，对流传热是一种较为可能的传热机制。     

氧化镍、二氧化钛高压相变及电导率压力效应

采用金刚石对顶砧压腔静高压技术，对氧化镍、二氧化钛在０-３２ＧＰａ压力范围内的电导率进行了测量．结果表明，电导率－压力关系曲线上的一些特征点与同一物质的高压相交点具有一致性．     

Nonequilibrium thermodynamics of pressure solution

This paper is concerned with the thermodynamic theory of solution and precipitation processes in wet crustal rocks and with the mechanism of steady pressure-solution slip in contact zones, such as grain-to-grain contacts, fracture surfaces, and permeable gouge layers, that are infiltrated by a mobile aqueous solution phase. A local dissipation jump condition at the phase boundary is fundamental to identifying the thermodynamic force driving the solution and precipitation process and is used here in setting up linear phenomenological relations to model near-equilibrium phase transformation kinetics. The local thermodynamic equilibrium of a stressed pure solid in contact with its melt or solution phase is governed by Gibbs's relation, which is rederived here, in a manner emphasizing its independence of constitutive assumptions for the solid while neglecting surface tension and diffusion in the solid. Fluid-infiltrated contact zones, such as those formed by rough surfaces, cannot generally be in thermodynamic equilibrium, especially during an ongoing process of pressure-solution slip, and the existing equilibrium formulations are incorrect in overlooking dissipative processes tending to eliminate fluctuations in superficial free energies due to stress concentrations near asperities, defects, or impurities. Steady pressure-solution slip is likely to exhibit a nonlinear dependence of slip rate on shear stress and effective normal stress, due to a dependence of the contact-zone state on the latter. Given that this dependence is negligible within some range, linear relations for pressure-solution slip can be derived for the limiting cases of diffusion-controlled and interface-reaction-controlled rates. A criterion for rate control by one of these mechanisms is set by the magnitude of the dimensionless quantityk/2C _pD, wherek is the interfacial transfer coefficient, is the mean diffusion path length,C _p is the solubility at pressurep, andD is the mass diffusivity.     

利用Radon变换进行三度体重磁异常反演

从Ｒａｄｏｎ变换角度分析解释了重磁三度体异常和二度体异常之间的等价关系，提出了利用Ｒａｄｏｎ正变换将三度体异常转化为二度体异常，对二度体异常做一维反演，然后将反演结果通过反Ｒａｄｏｎ变换实现三维场源图象重建的思想，并付诸实施，在微机上通过模型检验，证明该方法实用、可行。     

Exploratory spectral analysis of hydrological times series

Current methods of estimation of the univariate spectral density are reviewed and some improvements are made. It is suggested that spectral analysis may perhaps be best thought of as another exploratory data analysis (EDA) tool which complements, rather than competes with, the popular ARMA model building approach. A new diagnostic check for ARMA model adequacy based on the nonparametric spectral density is introduced. Additionally, two new algorithms for fast computation of the autoregressive spectral density function are presented. For improving interpretation of results, a new style of plotting the spectral density function is suggested. Exploratory spectral analyses of a number of hydrological time series are performed and some interesting periodicities are suggested for further investigation. The application of spectral analysis to determine the possible existence of long memory in natural time series is discussed with respect to long riverflow, treering and mud varve series. Moreover, a comparison of the estimated spectral densities suggests the ARMA models fitted previously to these datasets adequately describe the low frequency component. Finally, the software and data used in this paper are available by anonymous ftp from fisher.stats.uwo.ca.     

A Fourier transform method for the interpretation of self-potential anomalies due to two-dimensional inclined sheets of finite depth extent

The self-potential anomaly due to a two-dimensional inclined sheets of finite depth extent has been analysed in the frequency domain using the Fourier transform. Expression for the Fourier amplitude and phase spectra are derived. The Fourier amplitude and phase spectra are analysed so as to evaluate the parameters of the sheet. Application of this method on two anomalies (synthetic and field data) has given good results.     

Some approaches for location of centroids of quartz grain outlines to increase homology between Fourier amplitude spectra

The ability to test for similarities and differences among families of shapes by closed-form Fourier expansion is greatly enhanced by the concept of homology. Underlying this concept is the assumption that each term of a Fourier series, when compared to the same term in another series, represents the same thing. A method that ensures homology is one which minimizes the centering error, as reflected in the first harmonic term of the Fourier expansion. The problem is to chose a set of edge points derived from a much larger, but variable, number of edge points such that a valid homologous Fourier series can be calculated. Methods are reviewed and criteria given to define a proper solution. An algorithm is presented which takes advantage of the fact that minimization of the error term can be accomplished by minimizing the distance between the origin of the polar coordinate system in the calculation of the Fourier series and the shape centroid. The use of this algorithm has produced higher quality solutions for quartz grain provenance studies.     

关中地区地磁比值Rq的变化与地震关系的分析

应用小波分析空间差分法分析了泾阳台、乾陵台、周至台和郑州台的Z分量的地磁磁静日Rg值的变化规律，结果显示，各台的磁静日Rg值有较一致的年变规律。分析泾阳台与其它各台的磁静日R。差值分析和小波变换，发现1998年1月5日泾阳4．8级地震前4个月内存在较明显的异常变化。可能反映了泾阳地震的震磁效应。对远离泾阳台、乾陵台的青海昆仑山口西8．1级地震，震前也有明显异常变化。