This paper surveys a number of recent advances in the error analysis in the frequency domain for a digital simulation model. It is emphasized to discuss the errors in characteristic roots and transfer funcnon of the d...This paper surveys a number of recent advances in the error analysis in the frequency domain for a digital simulation model. It is emphasized to discuss the errors in characteristic roots and transfer funcnon of the digital simulation model, the frequency domain errors of the data transfers between thesimulation submodels, and some compensation methods for the errors. Some of the questions to be answered are also presented.展开更多
Contrast Analysis (CA), Interlanguage(IL),cognitive approach are considered as three aspects closely related to Error Analysis (EA).Originated from CA, EA takes IL as its linguistic basis and cognitive approach as its...Contrast Analysis (CA), Interlanguage(IL),cognitive approach are considered as three aspects closely related to Error Analysis (EA).Originated from CA, EA takes IL as its linguistic basis and cognitive approach as its psychological support.Comparing with CA, EA pays more attention to the learner himself rather than the linguistic forms, and error is therefore shifted from what should be avoided to the crucial approach to the exploration of the learner’s cognitive process.展开更多
It is natural for language learner to make errors in the process of second language acquisition.But different linguists hold different views on the nature of errors and the methods of dealing with learner' s error...It is natural for language learner to make errors in the process of second language acquisition.But different linguists hold different views on the nature of errors and the methods of dealing with learner' s errors.Three main Western theories on errors are Contrastive Analysis,Error Analysis and the Interlanguage Theory.This paper first examines three most influential error theories,and then probes into their enlightenment on second language teaching.展开更多
Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network mode...Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network model and measured data,a 3-D fracture network dynamic modeling method based on error analysis was proposed.Firstly,errors of four fracture volume density estimation methods(proposed by ODA,KULATILAKE,MAULDON,and SONG)and that of four fracture size estimation methods(proposed by EINSTEIN,SONG and TONON)were respectively compared,and the optimal methods were determined.Additionally,error index representing the deviation between fracture network model and measured data was established with integrated use of fractal dimension and relative absolute error(RAE).On this basis,the downhill simplex method was used to build the dynamic modeling method,which takes the minimum of error index as objective function and dynamically adjusts the fracture density and size parameters to correct the error index.Finally,the 3-D fracture network model could be obtained which meets the requirements.The proposed method was applied for 3-D fractures simulation in Miao Wei hydropower project in China for feasibility verification and the error index reduced from 2.618 to 0.337.展开更多
Writing as a productive skill is challenging for the learners as it requires rich linguistic and cognitive abilities to match words with ideas well. A learner of any language as Second Language (SL), for example Engli...Writing as a productive skill is challenging for the learners as it requires rich linguistic and cognitive abilities to match words with ideas well. A learner of any language as Second Language (SL), for example English, Arabic, Chinese, or German, enters an early, natural, and inevitable stage of making various errors in writing compositions. The errors could be due to dissimilar linguistic systems of the two languages (L1 and L2) or the lack of understanding the SL linguistic rules. This study focuses on investigating the frequent and common inter-lingual errors (the negative influence) committed by Arabic-speaking learners of English as Second Language (ESL). The study is based on Error Analysis (EA) of the essays of a group of English major undergraduate students from the University of Bisha, Al-Namas, Saudi Arabia. Contrastive Analysis Hypothesis (CAH)is included to predict most of the errors in the collected samples. The findings of the study show that common errors in the data are interlingual (54.03%). The errors within the Grammatical Category include the misuse of tenses, dropping the subjects, dropping verb to be-copular and word order misplacement. The majority of errors in the study are due to the interference of L1 linguistic system including the different orthographic, phonological,morpho-syntactic components. For instance, the participants’ dropping subjects in English can be attributed to the fact that Arabic as L1 and as Null Subject Language (NSL), unlike English, allows subject drop. The results also find that within the Lexical Category,preposition and article errors are the most frequent errors and that spelling errors are the most dominant errors within the Mechanics Category. The study gives some pedagogical implications and suggestions to avoid and minimize the interlingual errors of such type. For instance, teachers need to focus more on enlightening their students about the contrastive language systems from the early stage of learning ESL.展开更多
With the increasing importance of English writing,how to improve students’writing ability is a big challenge.Contrastive analysis and error analysis are two popular approaches to error correction in English writing.T...With the increasing importance of English writing,how to improve students’writing ability is a big challenge.Contrastive analysis and error analysis are two popular approaches to error correction in English writing.This paper is going to compare the differences between contrastive analysis and error analysis,in English writing for Chinese EFL learners,from perspectives,such as,English writing purpose,English writing errors and attitude towards English writing.After that,some better suggestions will be given at the end of the paper.展开更多
A Chebyshev fitting way for a propeller atlas across four quadrants is discussed. As an example, Chebyshev polynomial fitting results and its error analysis are given. Because it’s difficult generally to get a propel...A Chebyshev fitting way for a propeller atlas across four quadrants is discussed. As an example, Chebyshev polynomial fitting results and its error analysis are given. Because it’s difficult generally to get a propeller atlas across four quadrants, a way is used to construct an alternative with higher accuracy based on the properties. As an application example, an alternative for the propeller property of a Deep Submergence Vehicle across four quadrants is given practically and a simulation model of the four quadrants propeller for dynamic condition is set up. The model lays a foundation for DSV full operating-condition movement simulation. A lot of simulation work shows that the results are very close to the practical data and, therefore, are effective.展开更多
This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measur...This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measurement system based on stereo deflectometry typically consists of a fringe-displaying screen,a main camera,and a reference camera.The arrangement of the components of a stereo deflectometry system is important for achieving high-accuracy measurements.In this paper,four geometric parameters of a stereo deflectometry system are analyzed and evaluated:the distance between the main camera and the measured object surface,the angle between the main camera ray and the surface normal,the distance between the fringe-displaying screen and the object,and the angle between the main camera and the reference camera.The influence of the geometric parameters on the measurement accuracy is evaluated.Experiments are performed using simulated and experimental data.The experimental results confirm the impact of these parameters on the measurement accuracy.A measurement system based on the proposed analysis has been set up to measure a stock concave mirror.Through a comparison of the given surface parameters of the concave mirror,a global measurement accuracy of 154.2 nm was achieved.展开更多
Based on the Error Analysis theory and Contrastive Analysis theory,this thesis aims to investigate the phenomenon of negative transfer of mother tongue at the levels of substance,lexis and syntax by taking advantage o...Based on the Error Analysis theory and Contrastive Analysis theory,this thesis aims to investigate the phenomenon of negative transfer of mother tongue at the levels of substance,lexis and syntax by taking advantage of quantitative analysis method,and an attempt is made to analyze and classify writing errors in L2 writings by English majors.Anyhow,it is hoped that current research can achieve the purpose of avoiding the negative transfer of mother tongue and to improve English majors’writing capability accordingly.展开更多
Transfer occurs as long as second language learning goes on. In the C —E translation of instructions of goods,transfer occurs as well. It is necessary to give a through study into those negative transfers in the inst...Transfer occurs as long as second language learning goes on. In the C —E translation of instructions of goods,transfer occurs as well. It is necessary to give a through study into those negative transfers in the instructions to improve the quality of translation. This paper takes the English instructions of electronic appliance in the New Century Supermarket in N anchang University as the subjects. Through a qualitative and a quantitative study of the subjects, the author concludes that negative transfer can be found here and there in the English instructions-negative transfer at lexical level, syntactical level and discourse level, negative transfer at syntactical level having the highest frequency. This paper also explores the reason why the phenomena occurs.展开更多
The role of the native language in second language acquisition has long been a hotly debated issue in the area of SLA.Variousstudies on the subject are reviewed and controversial views are examined in the paper,referr...The role of the native language in second language acquisition has long been a hotly debated issue in the area of SLA.Variousstudies on the subject are reviewed and controversial views are examined in the paper,referring to Behaviorism,Contrastive Analysis Hy-pothesis,Error Analysis Hypothesis,Creative Construction Hypothesis,Common Underlying Proficiency Hypothesis,and MarkednessTheory,etc.,so as to provide a more comprehensive and deeper analysis of the role L1 plays in L2 acquisition.展开更多
Error analysis methods in frequency domain are developed in this paper for determining the characteristic root and transfer function errors when the linear multipass algorithms are used to solve linear differential eq...Error analysis methods in frequency domain are developed in this paper for determining the characteristic root and transfer function errors when the linear multipass algorithms are used to solve linear differential equations. The relation between the local truncation error in time domain and the error in frequency domain is established, which is the basis for developing the error estimation methods. The error estimation methods for the digital simulation model constructed by using the Runge-Kutta algorithms and the linear multistep predictor-corrector algorithms are also given.展开更多
In this paper, the composition of the hardware-in-the-loop simulation system of missile guidance system and the characteristic and function of every equipment in this simulation system are discussed. Then the principl...In this paper, the composition of the hardware-in-the-loop simulation system of missile guidance system and the characteristic and function of every equipment in this simulation system are discussed. Then the principle of this system is discussed in terms of theory, and the resemblance of prototype system with simulation system is analyzed. Also, many key problems such as equipment interface, equipment installation, modelling and software design are dealt with. At the end, the error source of simulation system is analyzed, and a strong base is built for the study of simulation system precision.展开更多
Adopted for some small-size short range surface-to-air missiles and antitank guided missiles is a single-channel control method of making missile rotating around its longitudinal axis. In hardware-in-the-loop simulati...Adopted for some small-size short range surface-to-air missiles and antitank guided missiles is a single-channel control method of making missile rotating around its longitudinal axis. In hardware-in-the-loop simulations of the guidance and control system for these kinds of spinning missiles, improper use of special simulation equipment and test method will cause significant errors, even lead to failure of the simulation. In this article, the author gives an analysis of the causes of significant errors and failure of the simulation, and puts forward a solution, which is improved workable in making the hardward-in-the-loop simulation successful.展开更多
A servo control system is prone to low speed and unsteadiness during very-low-frequency follow-up. A design method of feedforward control based on intelligent controller is put foward. Simulation and test results show...A servo control system is prone to low speed and unsteadiness during very-low-frequency follow-up. A design method of feedforward control based on intelligent controller is put foward. Simulation and test results show that the method has excellent control characteristics and strong robustness, which meets the servo control needs with very-low frequency.展开更多
The concept of cointegration describes an equilibrium relationship among a set of time-varying variables, and the cointegrated relationship can be represented through an error-correction model (ECM). The error-correct...The concept of cointegration describes an equilibrium relationship among a set of time-varying variables, and the cointegrated relationship can be represented through an error-correction model (ECM). The error-correction variable, which represents the short-run discrepancy from the equilibrium state in a cointegrated system, plays an important role in the ECM. It is natural to ask how the error-correction mechanism works, or equivalently, how the short-run discrepancy affects the development of the cointegrated system? This paper examines the effect or local influence on the error-correction variable in an error-correction model. Following the argument of the second-order approach to local influence suggested by reference [5], we develop a diagnostic statistic to examine the local influence on the estimation of the parameter associated with the error-correction variable in an ECM. An empirical example is presented to illustrate the application of the proposed diagnostic. We find that the short-run discre pancy may have strong influence on the estimation of the parameter associated with the error-correction model. It is the error-correction variable that the short-run discrepancies can be incorporated through the error-correction mechanism.展开更多
This paper introduces some theories concerning language transfer, such as behaviorist views and cognitive views, and the relationship between language transfer and contrastive and error analysis, interlanguage, fossil...This paper introduces some theories concerning language transfer, such as behaviorist views and cognitive views, and the relationship between language transfer and contrastive and error analysis, interlanguage, fossilization, universial grammar. It is believed that incorporating the concept of language transfer in English teaching may facilitate students’ learning of the language.展开更多
We revisit a comparison of two discriminant analysis procedures, namely the linear combination classifier of Chung and Han (2000) and the maximum likelihood estimation substitution classifier for the problem of classi...We revisit a comparison of two discriminant analysis procedures, namely the linear combination classifier of Chung and Han (2000) and the maximum likelihood estimation substitution classifier for the problem of classifying unlabeled multivariate normal observations with equal covariance matrices into one of two classes. Both classes have matching block monotone missing training data. Here, we demonstrate that for intra-class covariance structures with at least small correlation among the variables with missing data and the variables without block missing data, the maximum likelihood estimation substitution classifier outperforms the Chung and Han (2000) classifier regardless of the percent of missing observations. Specifically, we examine the differences in the estimated expected error rates for these classifiers using a Monte Carlo simulation, and we compare the two classifiers using two real data sets with monotone missing data via parametric bootstrap simulations. Our results contradict the conclusions of Chung and Han (2000) that their linear combination classifier is superior to the MLE classifier for block monotone missing multivariate normal data.展开更多
The use of nonsystematic flood data for statistical purposes depends on reliability of assessment both flood magnitudes and their return period. The earliest known extreme flood year is usually the beginning of the hi...The use of nonsystematic flood data for statistical purposes depends on reliability of assessment both flood magnitudes and their return period. The earliest known extreme flood year is usually the beginning of the historical record. Even though the magnitudes of historic floods are properly assessed, a problem of their retun periods remains unsolved. Only largest flood (XM) is known during whole historical period and its occurrence carves the mark of the beginning of the historical period and defines its length (L). So, it is a common practice of using the earliest known flood year as the beginning of the record. It means that the L value selected is an empirical estimate of the lower bound on the effective historical length M. The estimation of the return period of XM based on its occurrence, i.e. , gives the severe upward bias. Problem is to estimate the time period (M) representative of the largest observed flood XM. From the discrete uniform distribution with support of the probability of the L position of XM one gets ?which has been taken as the return period of XM and as the effective historical record length. The efficiency of using the largest historical flood (XM) for large quantile estimation (i.e. one with return period T = 100 years) has been assessed using maximum likelihood (ML) method with various length of systematic record (N) and various estimates of historical period length ?com- paring accuracy with the case when only systematic records alone (N) are used. The i-th simula- tion procedure incorporates systematic record and one largest historic flood (XMi) in the period M which appeared in the Li year backward from the end of historical period. The simulation result for selected distributions, values of their parameters, different N and M values are presented in terms of bias (B) and root mean square error (RMSE) of the quantile of interest and widely discussed.展开更多
文摘This paper surveys a number of recent advances in the error analysis in the frequency domain for a digital simulation model. It is emphasized to discuss the errors in characteristic roots and transfer funcnon of the digital simulation model, the frequency domain errors of the data transfers between thesimulation submodels, and some compensation methods for the errors. Some of the questions to be answered are also presented.
文摘Contrast Analysis (CA), Interlanguage(IL),cognitive approach are considered as three aspects closely related to Error Analysis (EA).Originated from CA, EA takes IL as its linguistic basis and cognitive approach as its psychological support.Comparing with CA, EA pays more attention to the learner himself rather than the linguistic forms, and error is therefore shifted from what should be avoided to the crucial approach to the exploration of the learner’s cognitive process.
文摘It is natural for language learner to make errors in the process of second language acquisition.But different linguists hold different views on the nature of errors and the methods of dealing with learner' s errors.Three main Western theories on errors are Contrastive Analysis,Error Analysis and the Interlanguage Theory.This paper first examines three most influential error theories,and then probes into their enlightenment on second language teaching.
基金Project(51321065)supported by the Innovative Research Groups of the National Natural Science Foundation of ChinaProject(2013CB035904)supported by the National Basic Research Program of China(973 Program)Project(51439005)supported by the National Natural Science Foundation of China
文摘Accurate 3-D fracture network model for rock mass in dam foundation is of vital importance for stability,grouting and seepage analysis of dam foundation.With the aim of reducing deviation between fracture network model and measured data,a 3-D fracture network dynamic modeling method based on error analysis was proposed.Firstly,errors of four fracture volume density estimation methods(proposed by ODA,KULATILAKE,MAULDON,and SONG)and that of four fracture size estimation methods(proposed by EINSTEIN,SONG and TONON)were respectively compared,and the optimal methods were determined.Additionally,error index representing the deviation between fracture network model and measured data was established with integrated use of fractal dimension and relative absolute error(RAE).On this basis,the downhill simplex method was used to build the dynamic modeling method,which takes the minimum of error index as objective function and dynamically adjusts the fracture density and size parameters to correct the error index.Finally,the 3-D fracture network model could be obtained which meets the requirements.The proposed method was applied for 3-D fractures simulation in Miao Wei hydropower project in China for feasibility verification and the error index reduced from 2.618 to 0.337.
文摘Writing as a productive skill is challenging for the learners as it requires rich linguistic and cognitive abilities to match words with ideas well. A learner of any language as Second Language (SL), for example English, Arabic, Chinese, or German, enters an early, natural, and inevitable stage of making various errors in writing compositions. The errors could be due to dissimilar linguistic systems of the two languages (L1 and L2) or the lack of understanding the SL linguistic rules. This study focuses on investigating the frequent and common inter-lingual errors (the negative influence) committed by Arabic-speaking learners of English as Second Language (ESL). The study is based on Error Analysis (EA) of the essays of a group of English major undergraduate students from the University of Bisha, Al-Namas, Saudi Arabia. Contrastive Analysis Hypothesis (CAH)is included to predict most of the errors in the collected samples. The findings of the study show that common errors in the data are interlingual (54.03%). The errors within the Grammatical Category include the misuse of tenses, dropping the subjects, dropping verb to be-copular and word order misplacement. The majority of errors in the study are due to the interference of L1 linguistic system including the different orthographic, phonological,morpho-syntactic components. For instance, the participants’ dropping subjects in English can be attributed to the fact that Arabic as L1 and as Null Subject Language (NSL), unlike English, allows subject drop. The results also find that within the Lexical Category,preposition and article errors are the most frequent errors and that spelling errors are the most dominant errors within the Mechanics Category. The study gives some pedagogical implications and suggestions to avoid and minimize the interlingual errors of such type. For instance, teachers need to focus more on enlightening their students about the contrastive language systems from the early stage of learning ESL.
文摘With the increasing importance of English writing,how to improve students’writing ability is a big challenge.Contrastive analysis and error analysis are two popular approaches to error correction in English writing.This paper is going to compare the differences between contrastive analysis and error analysis,in English writing for Chinese EFL learners,from perspectives,such as,English writing purpose,English writing errors and attitude towards English writing.After that,some better suggestions will be given at the end of the paper.
文摘A Chebyshev fitting way for a propeller atlas across four quadrants is discussed. As an example, Chebyshev polynomial fitting results and its error analysis are given. Because it’s difficult generally to get a propeller atlas across four quadrants, a way is used to construct an alternative with higher accuracy based on the properties. As an application example, an alternative for the propeller property of a Deep Submergence Vehicle across four quadrants is given practically and a simulation model of the four quadrants propeller for dynamic condition is set up. The model lays a foundation for DSV full operating-condition movement simulation. A lot of simulation work shows that the results are very close to the practical data and, therefore, are effective.
文摘This paper presents a novel geometric parameters analysis to improve the measurement accuracy of stereo deflectometry.Stereo deflectometry can be used to obtain form information for freeform specular surfaces.A measurement system based on stereo deflectometry typically consists of a fringe-displaying screen,a main camera,and a reference camera.The arrangement of the components of a stereo deflectometry system is important for achieving high-accuracy measurements.In this paper,four geometric parameters of a stereo deflectometry system are analyzed and evaluated:the distance between the main camera and the measured object surface,the angle between the main camera ray and the surface normal,the distance between the fringe-displaying screen and the object,and the angle between the main camera and the reference camera.The influence of the geometric parameters on the measurement accuracy is evaluated.Experiments are performed using simulated and experimental data.The experimental results confirm the impact of these parameters on the measurement accuracy.A measurement system based on the proposed analysis has been set up to measure a stock concave mirror.Through a comparison of the given surface parameters of the concave mirror,a global measurement accuracy of 154.2 nm was achieved.
文摘Based on the Error Analysis theory and Contrastive Analysis theory,this thesis aims to investigate the phenomenon of negative transfer of mother tongue at the levels of substance,lexis and syntax by taking advantage of quantitative analysis method,and an attempt is made to analyze and classify writing errors in L2 writings by English majors.Anyhow,it is hoped that current research can achieve the purpose of avoiding the negative transfer of mother tongue and to improve English majors’writing capability accordingly.
文摘Transfer occurs as long as second language learning goes on. In the C —E translation of instructions of goods,transfer occurs as well. It is necessary to give a through study into those negative transfers in the instructions to improve the quality of translation. This paper takes the English instructions of electronic appliance in the New Century Supermarket in N anchang University as the subjects. Through a qualitative and a quantitative study of the subjects, the author concludes that negative transfer can be found here and there in the English instructions-negative transfer at lexical level, syntactical level and discourse level, negative transfer at syntactical level having the highest frequency. This paper also explores the reason why the phenomena occurs.
文摘The role of the native language in second language acquisition has long been a hotly debated issue in the area of SLA.Variousstudies on the subject are reviewed and controversial views are examined in the paper,referring to Behaviorism,Contrastive Analysis Hy-pothesis,Error Analysis Hypothesis,Creative Construction Hypothesis,Common Underlying Proficiency Hypothesis,and MarkednessTheory,etc.,so as to provide a more comprehensive and deeper analysis of the role L1 plays in L2 acquisition.
基金This project was supported by the National Natural Science Foundation of China (No. 19871080).
文摘Error analysis methods in frequency domain are developed in this paper for determining the characteristic root and transfer function errors when the linear multipass algorithms are used to solve linear differential equations. The relation between the local truncation error in time domain and the error in frequency domain is established, which is the basis for developing the error estimation methods. The error estimation methods for the digital simulation model constructed by using the Runge-Kutta algorithms and the linear multistep predictor-corrector algorithms are also given.
文摘In this paper, the composition of the hardware-in-the-loop simulation system of missile guidance system and the characteristic and function of every equipment in this simulation system are discussed. Then the principle of this system is discussed in terms of theory, and the resemblance of prototype system with simulation system is analyzed. Also, many key problems such as equipment interface, equipment installation, modelling and software design are dealt with. At the end, the error source of simulation system is analyzed, and a strong base is built for the study of simulation system precision.
文摘Adopted for some small-size short range surface-to-air missiles and antitank guided missiles is a single-channel control method of making missile rotating around its longitudinal axis. In hardware-in-the-loop simulations of the guidance and control system for these kinds of spinning missiles, improper use of special simulation equipment and test method will cause significant errors, even lead to failure of the simulation. In this article, the author gives an analysis of the causes of significant errors and failure of the simulation, and puts forward a solution, which is improved workable in making the hardward-in-the-loop simulation successful.
基金This project was supported by the Foundation of Ministry of Machine-Building Industry.
文摘A servo control system is prone to low speed and unsteadiness during very-low-frequency follow-up. A design method of feedforward control based on intelligent controller is put foward. Simulation and test results show that the method has excellent control characteristics and strong robustness, which meets the servo control needs with very-low frequency.
基金This project was supported by the National Natural Science Foundation (No. 79800012 and No. 79400014).
文摘The concept of cointegration describes an equilibrium relationship among a set of time-varying variables, and the cointegrated relationship can be represented through an error-correction model (ECM). The error-correction variable, which represents the short-run discrepancy from the equilibrium state in a cointegrated system, plays an important role in the ECM. It is natural to ask how the error-correction mechanism works, or equivalently, how the short-run discrepancy affects the development of the cointegrated system? This paper examines the effect or local influence on the error-correction variable in an error-correction model. Following the argument of the second-order approach to local influence suggested by reference [5], we develop a diagnostic statistic to examine the local influence on the estimation of the parameter associated with the error-correction variable in an ECM. An empirical example is presented to illustrate the application of the proposed diagnostic. We find that the short-run discre pancy may have strong influence on the estimation of the parameter associated with the error-correction model. It is the error-correction variable that the short-run discrepancies can be incorporated through the error-correction mechanism.
文摘This paper introduces some theories concerning language transfer, such as behaviorist views and cognitive views, and the relationship between language transfer and contrastive and error analysis, interlanguage, fossilization, universial grammar. It is believed that incorporating the concept of language transfer in English teaching may facilitate students’ learning of the language.
文摘We revisit a comparison of two discriminant analysis procedures, namely the linear combination classifier of Chung and Han (2000) and the maximum likelihood estimation substitution classifier for the problem of classifying unlabeled multivariate normal observations with equal covariance matrices into one of two classes. Both classes have matching block monotone missing training data. Here, we demonstrate that for intra-class covariance structures with at least small correlation among the variables with missing data and the variables without block missing data, the maximum likelihood estimation substitution classifier outperforms the Chung and Han (2000) classifier regardless of the percent of missing observations. Specifically, we examine the differences in the estimated expected error rates for these classifiers using a Monte Carlo simulation, and we compare the two classifiers using two real data sets with monotone missing data via parametric bootstrap simulations. Our results contradict the conclusions of Chung and Han (2000) that their linear combination classifier is superior to the MLE classifier for block monotone missing multivariate normal data.
基金This research project was partly financed by the grant of the Polish National Science Centre titled“Modern statistical models for analysis of flood frequency and features of flood waves”,decision nr DEC-2012/05/B/ST10/00482.
文摘The use of nonsystematic flood data for statistical purposes depends on reliability of assessment both flood magnitudes and their return period. The earliest known extreme flood year is usually the beginning of the historical record. Even though the magnitudes of historic floods are properly assessed, a problem of their retun periods remains unsolved. Only largest flood (XM) is known during whole historical period and its occurrence carves the mark of the beginning of the historical period and defines its length (L). So, it is a common practice of using the earliest known flood year as the beginning of the record. It means that the L value selected is an empirical estimate of the lower bound on the effective historical length M. The estimation of the return period of XM based on its occurrence, i.e. , gives the severe upward bias. Problem is to estimate the time period (M) representative of the largest observed flood XM. From the discrete uniform distribution with support of the probability of the L position of XM one gets ?which has been taken as the return period of XM and as the effective historical record length. The efficiency of using the largest historical flood (XM) for large quantile estimation (i.e. one with return period T = 100 years) has been assessed using maximum likelihood (ML) method with various length of systematic record (N) and various estimates of historical period length ?com- paring accuracy with the case when only systematic records alone (N) are used. The i-th simula- tion procedure incorporates systematic record and one largest historic flood (XMi) in the period M which appeared in the Li year backward from the end of historical period. The simulation result for selected distributions, values of their parameters, different N and M values are presented in terms of bias (B) and root mean square error (RMSE) of the quantile of interest and widely discussed.