• Proceedings of the Korean Association for Survey Research Conference
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• 2006.12a
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• pp.11-40
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• 2006

시간의 흐름에 따라 사회 구성원들에 대한 행태 연구나 사회의 변화가 개인의 행동양식에 미치는 영향 등에 대한 조사에서는 어느 한 시점에서의 구성원들에 대한 횡단면 조사와는 다르게 다년간 지속적으로 조사개체를 추적조사 해야 하는 종단면 조사 또는 패널조사를 수행해야 한다. 패널조사는 횡단면 조사와는 달리 최초 표본이 시간이 지남에 따라 조사 대상 표본으로부터 탈락함으로서 발생하는 표본의 마모와 그에 따른 대표성 상실의 문제이다. 그러므로 이러한 표본의 대표성 상실 문제를 적절히 해결하기 위해 적용 가능한 방법이 가중치 조정 방법이다 횡단면 조사에서는 (1)추출가중치의 조정, (2)무응답 가중치 조정, (3)사후층화 가중치 조정과 같이 3단계의 가중치 조정과정을 수행하지만, 패널 조사의 경우 이와 더불어 원 표본의 대표성을 유지하기 위해 종단면 가중치(longitudinal weight)를 함께 고려해야 한다. 이러한 관점에서 본 연구에서는 다양한 패널형태에 따른 가중치 조정 방법에 대해 고찰하고, 향후 수행될 한국복지패널(Korea Welfare Panel Study: KWPS)의 가중치 산정에 관한 이론적 근거를 마련함과 동시에 현재 국내에서 수행되고 있는 패널조사의 가중치 조정방법과 비교하고자 한다.

• Survey Research
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• v.12 no.3
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• pp.173-186
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• 2011

We introduced the methodologies used to construct the longitudinal weights and cross-sectional weight that are required for the analysis of Korea Youth Panel Survey. To analyze the longitudinal dynamic change of the population, we derived the longitudinal weight through nonresponse adjustment based on logistic regression and post-stratification. Cross-sectional weights that are necessary to produce an asymptotically unbiased estimator of the population parameter were constructed through simple nonresponse adjustment based on overall response rate and post-stratification.

• Survey Research
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• v.12 no.2
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• pp.89-112
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• 2011

This study shows the results of constructing panel data using Farm Household survey and presents some examples of empirical application. This study shows that ex post constructed panel data using repeated cross-sectional survey can be used in various dynamic analyses. This paper also shows that the well known difficult problem of longitudinal weights can be easily solved by using the existing cross-sectional weights in original cross-section data. Based on these results, we propose that the National Statistical Office not only try to construct panel data, but also construct panel data by using existing repeated cross-section data. The benefits of this approach seems to be very big in establishment survey.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.261-268
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• 2013

In this paper, we propose the algorithm that improves the linearity of the walking assistant robot on lateral slopes. The walking assistant robot goes out of the course due to the rotational moment which is caused by the weight of the robot and the slope. To compensate this, we give the weight to each driving axle after comparing the real rotational angular velocity with the target rotational angular velocity which is entered by an user. The results of applying the algorithm to the real walking assistant robot show that the yaw axis deviation of the robot without the algorithm diverges, but the yaw axis deviation of the robot with the algorithm lies within 20cm, which can be recognized as stable. In addition, the changing rate of the course deviation is stabilized and shows no more course deviation, after moving 300cm.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1296-1301
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• 2005

하천자연도 평가는 하천이용과 보전, 복원계획에 대한 적합성의 근거를 파악하고 이에 가치를 부여하기 위해 주로 평가가 이루어진다. 최근 많은 하천들이 자연형 공법을 적용하여 정비되고 있지만 하천 정비에 따른 실효성 검토가 제대로 이루어지지 않고 있다. 자연형 하천으로 정비된 하천의 실효성을 검토하는 하나의 방법으로 지속적인 모니터링을 통해 하천생태계의 구조와 기능을 파악하고 수집된 자료를 분석하여 공사전과 공사후 하천자연도를 평가할 필요가 있다. 본 연구에서는 GIS를 이용하여 공사전과 공사후의 하천자연도 평가를 수행하였다. 평가항목은 종단면, 횡단면, 하상구조, 하천주변, 하천수질, 식생, 어류, 조류 등 8개 부문 29개 항목을 반영하였고 공사전과 후의 자연도 평가를 비교하기 위해 공사전 모니터링을 통해 얻은 자료를 바탕으로 부문별 평가항목 7개 부문에 17항목을 평가하였다. 평가의 척도는 정량적 지수로서 $1\~5$의 점수로 하였고 하천자연도의 표현은 5등급 체계로 구분하고 가중치는 부문별로 동일하게 하였다. 본 연구의 결과는 공사전 평가지수 3.3으로 하천자연도 III등급이었으나 공사후에는 평가지수 2.7로 II등급을 나타내었다.

• The Korean Journal of Applied Statistics
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• v.22 no.6
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• pp.1315-1329
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• 2009

The panel survey is need to have a more concern about a response due to a secession and non-response of a sample. And generally a population is not fixed and continuously changed. Thus, the rotation sample design can be used by the method replacing the panel research. This paper is the study of comparison to equal weight method, Duncan weight, Design weight method, weight share method in rotation sample design. More specifically, this paper compared variance estimators about the existing each method for the efficiency comparison, and to compare the precision using the relative efficiency gain by the Coefficient Variance(CV) after getting the design weight from the actual data.

• The KIPS Transactions:PartB
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• v.10B no.3
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• pp.339-346
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• 2003

In this paper, we propose a new method in which interpolation images are created by using a small number of axiai T2-weighted images instead of using many sectional images for 3D visualization of brain MR images. For image Interpolation, an important part of this process, we first segment a region of interest (ROI) that we wish to apply 3D reconstruction and extract the boundaries of segmented ROIs and MBR information. After the image size of interpolation layer is determined according to the changing rate of MBR size between top slice and bottom slice of segmented ROI, we find the corresponding pixels in segmented ROI images. Then we calculate a pixel's intensity of interpolation image by assigning to each pixel intensity weights detected by cube interpolation method. Finally, 3D reconstruction is accomplished by exploiting feature points and 3D voxels in the created interpolation images.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.321-326
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• 2012

Used as an ingredient in the hospital for orthopedic prosthetic stainless and titanium metal the same size as on the MRI diagnostic value of imaging were compared. Center of images, background high band portion of the video signal is converted into a weighted intensity values Normal images and compared. The area of normal slice and also the distortion of images and cross-sectional imaging of a range of quantitative and sagittal planes were compared. As a result, the periphery high band signal intensity values of Stainless video phantom 2, pig bone 1.8, Titanium imaging of phantom 1.7 has higher value than Normal video pig bone 1.3 times the signal strength rivers. MRI distortion of the shape and the distortions of the range, if the cross-sectional area compared to Normal Slice Stainless case of phantom 65.8 %, pig bone 61.5 %, Titanium distortion phantom 23.1 %, pig bone 38.5 % of the range of community found. In this experiment, as a result, MRI was found to be Titanium more diagnostic value than the specimen with respect to the signal intensity weighted value and low distortion range, Stainless.

• The Korean Journal of Nuclear Medicine
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• v.32 no.5
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• pp.414-424
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• 1998

Purpose: Cross-modality coregistration of positron emission tomography (PET) and magnetic resonance imaging (MR) could enhance the clinical information. In this study we propose a refined technique to improve the robustness of registration, and to implement more realistic visualization of the coregistered images. Materials and Methods: Using the sinogram of PET emission scan, we extracted the robust head boundary and used boundary-enhanced PET to coregister PET with MR. The pixels having 10% of maximum pixel value were considered as the boundary of sinogram. Boundary pixel values were exchanged with maximum value of sinogram. One hundred eighty boundary points were extracted at intervals of about 2 degree using simple threshold method from each slice of MR images. Best affined transformation between the two point sets was performed using least square fitting which should minimize the sum of Euclidean distance between the point sets. We reduced calculation time using pre-defined distance map. Finally we developed an automatic coregistration program using this boundary detection and surface matching technique. We designed a new weighted normalization technique to display the coregistered PET and MR images simultaneously. Results: Using our newly developed method, robust extraction of head boundary was possible and spatial registration was successfully performed. Mean displacement error was less than 2.0 mm. In visualization of coregistered images using weighted normalization method, structures shown in MR image could be realistically represented. Conclusion: Our refined technique could practically enhance the performance of automated three dimensional coregistration.