scholarly journals On the maximum bias functions of MM-estimates and constrained M-estimates of regression

2007 ◽  
Vol 35 (1) ◽  
pp. 13-40 ◽  
Author(s):  
José R. Berrendero ◽  
Beatriz V. M. Mendes ◽  
David E. Tyler
Keyword(s):  
Maximum Bias ◽  
M Estimates

scholarly journals Correlation of Metabolic Profiles of Plasma and Cerebrospinal Fluid of High-Grade Glioma Patients

Metabolites ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 133
Author(s):  
Artem D. Rogachev ◽  
Nikolay A. Alemasov ◽  
Vladimir A. Ivanisenko ◽  
Nikita V. Ivanisenko ◽  
Evgeniy V. Gaisler ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Molecular Mechanisms ◽  
High Grade Glioma ◽  
Diagnostic Procedures ◽  
Metabolic Profiles ◽  
High Grade ◽  
Wide Range ◽  
Targeted Screening ◽  
M Estimates ◽  
Metabolite Content

This work compares the metabolic profiles of plasma and the cerebrospinal fluid (CSF) of the patients with high-grade (III and IV) gliomas and the conditionally healthy controls using the wide-range targeted screening of low molecular metabolites by HPLC-MS/MS. The obtained data were analyzed using robust linear regression with Huber’s M-estimates, and a number of metabolites with correlated content in plasma and CSF was identified. The statistical analysis shows a significant correlation of metabolite content in plasma and CSF samples for the majority of metabolites. Several metabolites were shown to have high correlation in the control samples, but not in the glioma patients. This can be due to the specific metabolic processes in the glioma patients or to the damaged integrity of blood-brain barrier. The results of our study may be useful for the understanding of molecular mechanisms underlying the development of gliomas, as well as for the search of potential biomarkers for the minimally invasive diagnostic procedures of gliomas.

scholarly journals Asymptotic Distributions of M-Estimates for Parameters of Multivariate Time Series with Strong Mixing Property

2021 ◽  
Vol 5 (1) ◽  
pp. 19
Author(s):  
Alexander Kushnir ◽  
Alexander Varypaev
Keyword(s):  
Time Series ◽  
Asymptotic Normality ◽  
Multivariate Time Series ◽  
Asymptotic Properties ◽  
Asymptotic Distributions ◽  
Stationary Time Series ◽  
Strong Mixing ◽  
Statistical Estimates ◽  
Distribution Parameters ◽  
M Estimates

The publication is devoted to studying asymptotic properties of statistical estimates of the distribution parameters u∈Rq of a multidimensional random stationary time series zt∈Rm, t∈ℤ satisfying the strong mixing conditions. We consider estimates u^nδ(z¯n), z¯n=(z1T,…,znT)T∈Rmn that provide in asymptotic n→∞ the maximum values for some objective functions Qn(z¯n;u), which have properties similar to the well-known property of local asymptotic normality. These estimates are constructed by solving the equations δn(z¯n;u)=0, where δn(z¯n;u) are arbitrary functions for which δn(z¯n;u)−gradhQn(z¯n;u+n−1/2h)→0(n→∞) in Pn,u(z¯n)-probability uniformly on u∈U, were U is compact in Rq. In many cases, the estimates u^nδ(z¯n) have the same asymptotic properties as well-known M-estimates defined by equations u^nQ(z¯n)=arg maxu∈UQn(z¯n;u) but often can be much simpler computationally. We consider an algorithmic method for constructing estimates u^nδ(z¯n), which is similar to the accumulation method first proposed by R. Fischer and rigorously developed by L. Le Cam. The main theoretical result of the article is the proof of the theorem, in which conditions of the asymptotic normality of estimates u^nδ(z¯n) are formulated, and the expression is proposed for their matrix of asymptotic mean-square deviations limn→∞nEn,u{(u^δ(z¯n)−u)(u^δ(z¯n)−u)T}.

Predictability of strong motions from the Northridge, California, earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S100-S114 ◽  
Author(s):  
John G. Anderson ◽  
Guang Yu
Keyword(s):  
Vertical Component ◽  
Source Model ◽  
Statistical Characteristics ◽  
Peak Acceleration ◽  
Blind Test ◽  
Peak Displacement ◽  
Velocity Models ◽  
Maximum Bias ◽  
Standard Deviations ◽  
A Site

Abstract The composite source model for generating synthetic strong ground motions is tested for its ability to predict the statistical characteristics of Northridge accelerograms recorded in or adjacent to the San Fernando valley. The general problem is prediction of strong motions at a site of engineering interest with sufficient realism to be useful for engineering applications. The strongest test of any proposed method is a blind prediction. For this study, a completely blind test was not possible. Our objective was to use only a preliminary description of fault geometry and magnitude and previously published velocity models and, without iteration to improve the quality of fit, to evaluate the differences between predicted and observed accelerograms. The parameters that we predict are peak acceleration, peak velocity, peak displacement, Fourier spectra at seven frequencies, and pseudorelative velocity response (5% damping) at seven periods. Our results are given for 14 stations. For the horizontal components, these parameters are all predicted with a maximum bias of under 50% and an average bias of observations exceeding predictions by 6%. For peak acceleration and some response spectral periods, the bias for this model is smaller than at least some regressions, when applied to this specific earthquake. On the vertical component, the maximum bias is a factor of 2, and the average gives predictions exceeding observations by 25%. Standard deviations of the common logarithm of the ratio of observed-to-predicted parameters are typically about 0.3, which is perhaps 50% greater than the standard deviations typical of regressions but comparable to standard deviations of observations from this earthquake compared to regressions. In the future, it is likely that, in some cases, traditional regressions will be replaced with synthetic calculations of some type, such as the method used here. Based on the results of this study, the amount of progress that has been made in obtaining that goal is very encouraging.

scholarly journals Reaeration and oxygen dissipation into a circular hydraulic channel: experimental and dimensionless approach

RBRH ◽  
2018 ◽  
Vol 23 (0) ◽  
Author(s):  
Felipe Keiji Feital Harano ◽  
Murilo de Souza Ferreira ◽  
Marcos Vinícius Mateus ◽  
Deusmaque Carneiro Ferreira ◽  
Julio Cesar de Souza Inácio Gonçalves
Keyword(s):  
Interfacial Phenomena ◽  
Linear Regression Method ◽  
Hydraulic Parameters ◽  
Empirical Equations ◽  
Hydraulic Conditions ◽  
Do Concentration ◽  
Hydraulic Channel ◽  
M Estimates ◽  
Semi Empirical ◽  
Key Parameter

ABSTRACT Dissolved oxygen (DO) is a key parameter in water quality. The DO concentration in a water body can be changed by interfacial phenomena such as reaeration and oxygen dissipation, which can be represented by the coefficients K2 and KD, respectively. Few studies have jointly correlated K2 and KD with physical and hydraulic parameters of the channel. The present work investigated the behavior of these coefficients over a range of hydraulic conditions, and developed semi-empirical equations capable of relating both coefficients. Reaeration and DO dissipation tests were conducted in a circular hydraulic channel with flow velocity ranging from 0.20 to 0.79 m.s-1 and depth ranging from 0.09 to 0.15 m. Estimates of K2 and KD were performed using the non-linear regression method. Semi-empirical equations were obtained based on classical dimensional analysis and multiple regression analysis. The comparison between measured and estimated coefficients yielded R2 for reaeration and dissipation of 0.940 and 0.844, respectively. KD was higher than K2 for all turbulence levels applied at the hydraulic channel. An estimate obtained by the relation between the semi-empirical equations indicates that the transfer of oxygen in the water-air direction (dissipation) is approximately twice as fast as the transfer in the air-water direction (reaeration).

scholarly journals Redescending $M$-Estimates of Multivariate Location and Scatter

1991 ◽  
Vol 19 (4) ◽  
pp. 2102-2119 ◽  
Author(s):  
John T. Kent ◽  
David E. Tyler
Keyword(s):  
Multivariate Location ◽  
M Estimates

Accuracy of Satellite Land Surface Reflectance Determination

1991 ◽  
Vol 30 (7) ◽  
pp. 960-972 ◽  
Author(s):  
O. Arino ◽  
G. Dedieu ◽  
P. Y. Deschamps
Keyword(s):  
Land Surface ◽  
Surface Albedo ◽  
Maximum Error ◽  
Surface Reflectance ◽  
Relative Uncertainty ◽  
Calibration Uncertainty ◽  
Maximum Bias ◽  
Calibration Accuracy ◽  
The Difference

Abstract An accuracy budget of the surface reflectance determination from Meteosat geostationary satellite data is performed. Error analysis allows identification of three main problems: calibration uncertainty of the Meteosat instrument, atmospheric corrections, and surface effects (spectral and directional). Calibration accuracy is 10%, leading to a 10% relative uncertainty on reflectance. Spectral effects of the surface lead to a maximum bias of 0.01 for a vegetated surface as sensed by Meteosat, while directional effects can lead to a bias of 0.035 between two measurements taken at two different sun zenith and azimuth angles at the same view angle over savannas. The maximum error due to the atmosphere is estimated to be of the order of 0.03 in reflectance for a surface reflectance of 0.40 and 0.01 for, a surface reflectance of 0.10. Validation with in situ measurement is within the expected error over savanna. But the difference is still high over the southwest France site of HAPEX-MOBILHY, certainly due to the joint spectral and directional errors. Comparisons with surface albedo maps from literature show the same spatial and spatial evolutions with a better spatial and temporal determination in our results.

A Comparison of Liquid Scintillation and Geiger–Müller Estimates of Primary Productivity in an in situ Experiment

1973 ◽  
Vol 30 (5) ◽  
pp. 708-711 ◽  
Author(s):  
F. J. Ward ◽  
Masami Nakanishi
Keyword(s):  
Light Intensity ◽  
Surface Area ◽  
Primary Productivity ◽  
Liquid Scintillation ◽  
Lake Biwa ◽  
In Situ Experiment ◽  
M Estimate ◽  
M Estimates ◽  
Loss Rates

For an in situ experiment conducted in Shiozu Bay, Lake Biwa, Japan, primary productivity estimates from liquid scintillation radioactivity counts of wet algae were generally higher than those from Geiger–Müller radioactivity counts of desiccated algae. Values at 0 m were similar, the G–M estimate at 0.5 m was 10% higher, but from 3 to 13 m the liquid scintillation values ranged from 11 to 33% higher than G–M estimates. The 20-m estimates were low and similar. Differences were caused primarily by 14C losses during desiccation prior to G–M counting. Increasing loss rates between 0.5 and 3.0 m may have been caused by decreasing light intensity. On the basis of surface area, the estimate from liquid scintillation data was 27% greater than that obtained from G–M data.

On solvability of an equation arising in the theory of m-estimates

1990 ◽  
Vol 19 (1) ◽  
pp. 363-380 ◽  
Author(s):  
Z. D. Bai ◽  
Y. H. Wu ◽  
X. R. Chen ◽  
B. Q. Miao
Keyword(s):  
M Estimates
Sign in / Sign up

Export Citation Format

Share Document