• 영어어문교육
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• 제13권1호
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• pp.111-131
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• 2007

This study explores teacher's corrective feedback types in an error treatment sequence in Korean EFL classroom setting. Corrective feedback moves are coded as explicit correction, recast, or initiations to self-repair. The frequency and distribution of each corrective feedback type are examined. But the special focus was given on feedback types eliciting learner's self-repair (clarification request, metalinguistic feedback, elicitation, and repetition of error) because initiations to self-repair are believed to facilitate language learning more than other strategies. The results of the study are as follows. First, there was an overwhelming tendency for teacher to use recasts whereas initiations to self-repair were not used as much as recast (52.4% vs. 29.5%). Second, the teacher tended to select feedback types in accordance with error types: namely, recasts after phonological, lexical, and translation errors and initiations to self-repair after grammatical errors though the differences were not significant. Finally, teacher's belief and students' expectation on corrective feedback were compared with actual corrective feedback representations respectively and some mismatches were found. Though both teacher and the students acknowledged the importance and necessity of self-repair, self-repair were not put into practice as such. Therefore, this study suggests more initiations to self-repair be used for effective language learning.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2657-2675
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• 2013

A novel neighbor selection-based fingerprinting algorithm using matrix correlation (MC) for Wi-Fi localization is presented in this paper. Compared with classic fingerprinting algorithms that usually employ a single received signal strength (RSS) sample, the presented algorithm uses multiple on-line RSS samples in the form of a matrix and measures correlations between the on-line RSS matrix and RSS matrices in the radio-map. The algorithm makes efficient use of on-line RSS information and considers RSS variations of reference points (RPs) for localization, so it offers more accurate localization results than classic neighbor selection-based algorithms. Based on the MC algorithm, an error estimation method using artificial neural network is also presented to fuse available information that includes RSS samples and localization results computed by the MC algorithm and model the nonlinear relationship between the available information and localization errors. In the on-line phase, localization errors are estimated and then used to correct the localization results to reduce negative influences caused by a static radio-map and RP distribution. Experimental results demonstrate that the MC algorithm outperforms the other neighbor selection-based algorithms and the error estimation method can reduce the mean of localization errors by nearly half.

• 대한토목학회논문집
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• 제9권2호
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• pp.91-98
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• 1989

지상사진측량에서 단모델의 해석은 구조물이 커지면 적용하기가 어려워지므로 정밀한 좌표해석에서는 불럭조정기법을 사용하여야 한다. 기준점의 배치는 불럭조정결과의 오차특성에 커다란 영향을 주게 된다. 따라서 기준점 배치에 따른 오차분포특성을 조사하기 위해 블럭조정 기법을 이용한 단위모델법을 이용하였다. 연구결과에서 지상사진측량에 있어서 브리징 간격과 오차에 관한 2차다항식의 오차관계식을 개발하였다. 또한 블럭조정기법과 단모델기법의 비교에서 평균제곱근 오차가 0.44mm와 1.06mm로 나타냈다.

• The Journal of Asian Finance, Economics and Business
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• 제6권4호
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• pp.83-90
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• 2019

The purpose of this study is to test the effect of business strategy on valuation error. Business strategy includes managerial decision making and managerial tendency. In previous research, there is a negative relationship between business strategy and accounting quality. In this study, we try to confirm whether strategy tendencies affected valuation errors. In order to confirm empirically between business strategy and overvaluation, we use 8,117 firms that between 2006 and 2017 and listed in KSE and KOSDAQ. We calculated business strategy which is introduced by Bentley, Omer, and Sharp (2013). We also used the overvaluation method introduced in Rhodes-Kropf, Robinson, and Viswanathan (2005). The results show that the more the leading business strategy is, the greater the value error becomes. In the case of dividing into leading and defensive companies, the lead firms showed a significant positive correlation with the valuation errors, while the defensive firms showed the negative relationship with overvaluation. This study examined the business strategy and the overvaluation. we confirmed whether the management strategy deepens the evaluation error caused by the firm characteristics. The results are meaningful that we extended the study on the quality of financial reporting of leading strategic firms.

• Communications for Statistical Applications and Methods
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• 제17권1호
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• pp.127-140
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• 2010

본 논문에서는 중간분석에서 사용되는 집단축차 검정법으로 이산형 반응변수인 경우, 오류 분배율 함수를 적용한 집단축차 검정법을 제안한다. 특히 제 1종 오류와 제 2종 오류를 모두 적용한 집단축차 검정법을 제안하며, 기존의 오류 분배율 함수를 포함하는 새로운 오류 분배율 함수를 제안한다. 반응변수가 이산형인 경우 정확한 크기 ${\alpha}$ 검정을 할 수 없으므로 각 검정단계에 사용될 오류율을 분배하는 대신 각 검정단계까지 사용되어야 할 누적 오류율을 이용한다. 오류 분배율 함수를 적용한 집단축차 검정은 기존의 집단축차 검정 보다 빠른 연산과 유연한 검정이 가능하다는 장점을 지니고 있으며, 본 논문에서 제시된 오류 분배율 함수를 이용해 특성을 비교한다.

• 한국환경과학회지
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• 제27권7호
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• pp.499-507
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• 2018

Agricultural meteorological information is an important resource that affects farmers' income, food security, and agricultural conditions. Thus, such data are used in various fields that are responsible for planning, enforcing, and evaluating agricultural policies. The meteorological information obtained from automatic weather observation systems operated by rural development agencies contains missing values owing to temporary mechanical or communication deficiencies. It is known that missing values lead to reduction in the reliability and validity of the model. In this study, the hierarchical Bayesian spatio-temporal model suggests replacements for missing values because the meteorological information includes spatio-temporal correlation. The prior distribution is very important in the Bayesian approach. However, we found a problem where the spatial decay parameter was not converged through the trace plot. A suitable spatial decay parameter, estimated on the bias of root-mean-square error (RMSE), which was determined to be the difference between the predicted and observed values. The latitude, longitude, and altitude were considered as covariates. The estimated spatial decay parameters were 0.041 and 0.039, for the spatio-temporal model with latitude and longitude and for latitude, longitude, and altitude, respectively. The posterior distributions were stable after the spatial decay parameter was fixed. root mean square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and bias were calculated for model validation. Finally, the missing values were generated using the independent Gaussian process model.

• Communications for Statistical Applications and Methods
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• 제28권6호
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• pp.595-610
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• 2021

Recently a few articles have derived robust first-order rotatable and D-optimal designs for the lifetime response having distributions gamma, lognormal, Weibull, exponential assuming errors that are correlated with different correlation structures such as autocorrelated, intra-class, inter-class, tri-diagonal, compound symmetry. Practically, a first-order model is an adequate approximation to the true surface in a small region of the explanatory variables. A second-order model is always appropriate for an unknown region, or if there is any curvature in the system. The current article aims to extend the ideas of these articles for second-order models. Invariant (free of the above four distributions) robust (free of correlation parameter values) second-order rotatable designs have been derived for the intra-class and inter-class correlated error structures. Second-order rotatability conditions have been derived herein assuming the response follows non-normal distribution (any one of the above four distributions) and errors have a general correlated error structure. These conditions are further simplified under intra-class and inter-class correlated error structures, and second-order rotatable designs are developed under these two structures for the response having anyone of the above four distributions. It is derived herein that robust second-order rotatable designs depend on the respective error variance covariance structure but they are independent of the correlation parameter values, as well as the considered four response lifetime distributions.

• 로봇학회논문지
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• 제17권1호
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• pp.25-31
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• 2022

Moving among multiple floors is one of the most challenging tasks for indoor autonomous robots. Most of the previous researches for indoor mapping and localization have focused on singular floor environment. In this paper, we present an algorithm that creates a multi-floor map using 3D point cloud. We implement localization within the multi-floor map using a LiDAR and an IMU. Our algorithm builds a multi-floor map by constructing a single-floor map using a LOAM-based algorithm, and stacking them through global registration that aligns the common sections in the map of each floor. The localization in the multi-floor map was performed by adding the height information to the NDT (Normal Distribution Transform)-based registration method. The mean error of the multi-floor map showed 0.29 m and 0.43 m errors in the x, and y-axis, respectively. In addition, the mean error of yaw was 1.00°, and the error rate of height was 0.063. The real-world test for localization was performed on the third floor. It showed the mean square error of 0.116 m, and the average differential time of 0.01 sec. This study will be able to help indoor autonomous robots to operate on multiple floors.

• 무역학회지
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• 제47권3호
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• pp.211-232
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• 2022

Due to the impact of the public health event COVID-19 epidemic, the Chinese futures market showed "Black Swan". This has brought the unpredictable into the economic environment with many commodities falling by the daily limit, while gold performed well and closed in the sunshine(Yan-Li and Rui Qian-Wang, 2020). Volatility is integral part of financial market. As an emerging market and a special precious metal, it is important to forecast return of gold futures price. This study selected data of the SHFE gold futures returns and conducted an empirical analysis based on the generalised autoregressive conditional heteroskedasticity (GARCH)-type model. Comparing the statistics of AIC, SC and H-QC, ARMA (12,9) model was selected as the best model. But serial correlation in the squared returns suggests conditional heteroskedasticity. Next part we established the autoregressive moving average ARMA-GARCH-type model to analysis whether Volatility Clustering and the leverage effect exist in the Chinese gold futures market. we consider three different distributions of innovation to explain fat-tailed features of financial returns. Additionally, the error degree and prediction results of different models were evaluated in terms of mean squared error (MSE), mean absolute error (MAE), Theil inequality coefficient(TIC) and root mean-squared error (RMSE). The results show that the ARMA(12,9)-TGARCH(2,2) model under Student's t-distribution outperforms other models when predicting the Chinese gold futures return series.

• 한국전자파학회논문지
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• 제8권3호
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• pp.221-231
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• 1997

본 논문은 다중 m-분포 페이딩 환경에서 하이브리드 DS /SFH-CDMA MFSK의 성능을 분석하였다. MPI와 MUI를 고려하였고, 스펙트럼 효과는 단순 채널 부호화 시스템과 마찬가지로 부호화하지 않았을 때 평가하였다. 컨벌루션 부호화와 다중 CCl Canceller를 함께 사용하였을 때 BER을 개선시켰다. 비동기 하이브리드 시스템 BER은 가우시안 간섭의 근사치를 이용하여 얻었다. 결과적으로, 페이딩의 심도가 깊으면 깊을수록 오율 성능이 더욱 저하됨을 알 수 있었다. DS부분의 변조는 MPl에 방해하는 것이고. FH부분의 겸파는 MUI를 크게 한다. 채널 코딩의 형태들을 고려함으로써 검파전 코딩은 충분한비트에러 수행을하는데 필요함을 보여 준다. 본 결과는 DS /SFH-CDMA MFSK 통신 시스템은 AWGN과 MUI에 있는 PN코드 길이의 비율에 의하여 증가한다. m-분포의 페이딩 환경은 페이딩 지수에 의하여 용량성이 증가한다. CCl Canceller와 컨벌루션 부호화 기법을 각각 채용할 때 용량성은 증가되고 오율 성능은 향상된다. Canceller기법을 사용하지 않은 경우 PN코드의 길이 N=31일 때 $8\times10^{-2}$의 오율을 얻을 수 있었으나 Can celler기법을 사용한 경우 $4\times10^{-2}$의 오율에 도달할 수 있었다. 또한 부호화 기법을 이용하지 않았올 때에는 오율 이 10-2에도 미치지 못했지만 컨별루션 부호화의 부호율 $\gamma$=1/2인 경우 약 $10^{-5}$에 도달하는 것을 알 수 있다.