• Proceedings of the Korean Association for Survey Research Conference
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• 2001.11a
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• pp.77-85
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• 2001

In this paper we study the calibration estimator and its variance estimator for the population total using a bootstrap method according to the levels of an auxiliary information having strong correlation with an interested variable in nonresponse situation. At this point, we find tire calibration estimator in case of auxiliary information for population and sample, and then we drive the bootstrap variance estimator of it. By simulation study we compare the efficiencies with the Taylor and Jackknife variance estimators.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.1
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• pp.57-63
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• 2003

A comparative study was performed for a suspension bridge to grasp the possible differences in seismic responses evaluated by several analytical methods. The items mainly investigated are the linear vs. nonlinear response, the response spectrum method vs. the linear dynamic analysis method, and the damping ratio and it's implementation into analysis procedures. According to the numerical example, it is found that the seismic responses are considerably affected by the damping-related parameters even though slight differences are shown depending on the response quantities and the exciting directions. On the other hand, it is also confirmed that the seismic responses are less affected by the analysis method-related parameters such as the response spectrum method vs. the linear dynamic analysis method, and the linear and nonlinear analysis method. The response spectrum method is expected to give conservative results for the examined bridge, provided that the design response spectrum in the Korean Highway Design Specification is modified according to the proper damping ratio.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.306-314
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• 2004

Some receiver(and most transmit) beamforming algorithms with an array antenna at a cellular CDMA base stations require accurate internal and external calibrations. The external calibration, which usually needs to be done only once, determines the array manifolds, i.e. the complex response of each antenna as a function of DOA(Directions of Arrival). The internal calibrations are necessary because characteristics of RF/IF circuity of each receiver chain vary differently in response to temperature or humidity changes. We propose an iterative subspace-based calibration algorithm for an asynchronous CDMA-based antenna away in the presence of unknown gain and phase error is presented. We verify the subspace-based calibration algorithms by performing the experiment using measured data. Also, we propose an efficient algorithm using the simulated annealing technique. This algorithm overcomes the problem of the initial guessing in the subspace-based approach.

• The Korean Journal of Applied Statistics
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• v.35 no.4
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• pp.485-499
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• 2022

Controlling the total survey error including sampling error and non-sampling error is very important in sampling design. Non-sampling error caused by non-response accounts for a large proportion of the total survey error. Many studies have been conducted to handle non-response properly. Recently, a lot of non-response imputation methods using machine learning technique and traditional statistical methods have been studied and practically used. Most imputation methods assume MCAR(missing completely at random) or MAR(missing at random) and few studies have been conducted focusing on MNAR (missing not at random) or NN(non-ignorable non-response) which cause bias and reduce the accuracy of imputation. In this study, we propose a non-response imputation method that can be applied to non-ignorable non-response. That is, we propose an imputation method to improve the accuracy of estimation by removing the bias caused by NN. In addition, the superiority of the proposed method is confirmed through small simulation studies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.147-151
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• 2007

Load testing is an effective means in calculating the rating value of bridge. In Korea, load carrying capacity of bridge is modified by response modification factor that is determined from comparisons of measured values and analysis results. This paper presents the development of a method for determining the response modification factor, using traffic load. The proposed method is based on the results of computer simulations of traffic action effects. A comparison between the proposed method and the present method shows good agreement in estimating the modified load carrying capacity of bridges.

• The Journal of the Convergence on Culture Technology
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• v.8 no.5
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• pp.469-475
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• 2022

As the recent structure construction is constructed as a large-scale and deep underground excavation in close proximity to the building, the installation of retaining wall and supporters (Struts) has become complicated, and the number of supporters to avoid interference of the structural slab has increased. This construction process becomes a factor that causes an increase in construction joints of a structure, leakage and an increase in wall cracks. In addition, this reduced the durability and workability of the structure and led to an increase in the construction period. This study planned to dismantle the two struts simultaneously as a plan to reduce the construction joints, and corrected the earth pressure by assuming the reaction force value by the initial earth pressure and the measured data as the response ratio. After recalculating the corrected earth pressure through the iterative trial method, it was verified by numerical analysis that simultaneous disassembly of the two struts was possible. As a result of numerical analysis applying the final corrected earth pressure, the measured value for the design reaction force was found to be up to 197%. It was analyzed that this was due to the effect of grouting on the ground and some underestimation of the ground characteristics during design. Based on the result of calculating the corrected earth pressure in consideration of the response ratio performed in this study, it was proved analytically that the improvement of the brace dismantling process is possible. In addition, it was considered that the overall construction period could be shortened by reducing cracks due to leakage and improving workability by reducing construction joints. However, to apply the proposed method of this study, it is judged that sufficient estimations are necessary as there are differences in ground conditions, temporary facilities, and reinforcement methods for each site.

• The Korean Journal of Applied Statistics
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• v.37 no.3
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• pp.283-295
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• 2024

Many studies have been conducted to properly handle nonresponse. Recently, many nonresponse imputation methods have been developed and practically used. Most imputation methods assume MCAR (missing completely at random) or MAR (missing at random). On the contrary, there are relatively few studies on imputation under the assumption of MNAR (missing not at random) or NN (nonignorable nonresponse) that are affected by the study variable. The MNAR causes Bias and reduces the accuracy of imputation whenever response probability is not properly estimated. Lee and Shin (2022) proposed a nonresponse imputation method that can be applied to nonignorable nonresponse assuming homoscedasticity in super-population model. In this paper we propose an generalized version of the imputation method proposed by Lee and Shin (2022) to improve the accuracy of estimation by removing the Bias caused by MNAR under heteroscedasticity. In addition, the superiority of the proposed method is confirmed through simulation studies.

• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1185-1199
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• 2016

Two phase sampling (double sampling) is often used when there is inadequate population information for proper stratification. Many recent papers have been devoted to the estimation method to improve the precision of the estimator using first phase information. In this study we suggested outlier weight adjustment methods to improve estimation precision based on the weight of the generalized ratio-cum-product estimator. Small simulation studies are conducted to compare the suggested methods and the usual method. Real data analysis is also performed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.71-79
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• 1992

In general, the accelerogram of earthquake ground motion or the accelerogram obtained from dynamic tests contain various errors. In these errors of the accelerograms, there are instrumental errors(magnitude and phase distortion) due to the response characteristics of accelerometer and the digitizing error concentrated in low and high frequency components and random errors. Then, these errors may be detrimental to the results of data processing and dynamic analysis. An efficient method which can correct the errors of the accelerogram is proposed in this study. The correction of errors can be accomplished through four steps as followes ; 1) using an interpolation method a data form appropriate to the error correction is prepared, 2) low and high frequency errors of the accelerogram are removed by band-pass filter between prescribed frequency limits, 3) instrumental errors are corrected using dynamic equilibrium equation of the accelerometer, 4) velocity and displacement are obtained by integrating corrected accelerogram. Presently, infinite impulse response(IIR) filter and finite impulse response (FIR) filter are generally used as band-pass filter. In the proposed error correction procedure, the deficiencies of FIR filter and IIR filter are reduced and, using the properties of the differentiation and the integration of Fourier transform, the accuracy of instrument correction and integration is improved.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.4
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• pp.342-348
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• 2013

In this paper, the evaluation method for the responsivity and noise characteristics of an infrared thermal imaging camera was presented. Signal transfer function and noise equivalent temperature difference of the infrared thermal imaging camera were obtained by using a differential mode blackbody that is able to control the temperature difference ${\Delta}$T between an infrared target and its background. And we verified the suitability of our evaluation method through comparison between the found noise equivalent temperature difference and the specification of the camera. In addition, the difference of 0.01 K of the two noise equivalent temperature differences calculated from with and without nonuniformity correction suggests that the nonuniformity correction is essential process for the evaluation of the infrared thermal imaging camera.