• Communications for Statistical Applications and Methods
• /
• v.10 no.2
• /
• pp.553-566
• /
• 2003

In many cases, the measurement error variances may be functions of the unknown true values or related covariates. This paper considers design-based estimators of the parameters of these variance functions based on the within-unit sample variances. This paper devotes to: (1) define an error scale factor $\delta$; (2) develop estimators of the parameters of the linear measurement error variance function of the true values under large-sample and small-error conditions; (3) use propensity methods to adjust survey weights to account for possible selection effects at the replicate level. The proposed methods are applied to medical examination data from the U.S. Third National Health and Nutrition Examination Survey (NHANES III).

• Journal of the Korea Computer Industry Society
• /
• v.5 no.4
• /
• pp.471-480
• /
• 2004

A estimating capability of software effort, duration and cost is based on accurate size estimate of the software to be developed. A simplified function point (FP) approach to software size estimation is described, which first skip the computation step for value adjustment factor, thus directly obtaining final adjusted FP from unadjusted FP. The research seeks suitable models based on statistical regression models in the context of case study based on 783 software projects. The approach also are built for subsets of projects using new development, enhancement and re-development types.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2011.07a
• /
• pp.567-569
• /
• 2011

최근 비디오를 즐기는 방법에 있어서 다양한 형식 및 기기가 사용되고 있으며, 이러한 실질적 요구를 충족시키기 위한 방법으로 빠른 비디오 변환 기술이 필요하다. 비디오 변환 기술 중 해상도 축소를 위한 새로운 움직임 벡터 재예측 방법을 제안한다. 줄어든 영상 내 블록의 움직임 벡터를 결정하기 위해 원본 영상 내 대응 되는 위치의 2개 이상의 움직임 벡터들을 K-means clustering 방법 기반으로 다중 후보 움직임 벡터를 결정하고, 결정된 움직임 벡터 중에서 차이의 절대값 합이 최소가 되는 움직임 벡터를 줄어든 영상 내 블록을 위한 움직임 벡터로 결정한다,. 실험 결과 비디오 변환 없이 압축을 수행한 연산시간에 비해 9% 정도의 연산시간이 필요하였으며, 압축 효율은 BR-RATE가 약 17정도 증가하여 기존의 방식의 증가량에 비해 60%로 줄어든 결과를 보여주었다.

• The Journal of Korea Robotics Society
• /
• v.2 no.1
• /
• pp.29-39
• /
• 2007

We present an implementation of particle filter algorithm for global localization and kidnap recovery of mobile robot. Firstly, we propose an algorithm for efficient particle initialization using sonar line features. And then, the average likelihood and entropy of normalized weights are used as a quality measure of pose estimation. Finally, we propose an active kidnap recovery by adding new particle set. New and independent particle set can be initialized by monitoring two quality measures. Added particle set can re-estimate the pose of kidnapped robot. Experimental results demonstrate the capability of our global localization and kidnap recovery algorithm.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.330-333
• /
• 2006

In this paper experimental tests were performed to evaluate velocities of the acoustic waves through prestressed concrete beam and source locations using AE technique. Seven AE sensors are mounted on the surface of 5m length test beam with equal spacing and using Schmidt Hammer AE events are made 18 locations. The velocities of AE signals are evaluated using the time differences of arrival times and the distances between the AE source loactions and the AE sensor locations. In addition, using the Least Square Method, the AE source locations are re-evaluated reversely using both of the arrival times and the velocities of AE signals. Test results show the average velocity of the AE signals is about 4,000m/sec and the velocity decreased with the increase of the trevalling times due to the effect of attenuation. Based on the estimation of the source locations, it is observed that the accuracy of source location is increased when the velocity of each AE sensor used rather than the average velocity.

• Computers and Concrete
• /
• v.5 no.1
• /
• pp.37-60
• /
• 2008

Structural health monitoring of existing infrastructure is currently an important field of research, where elaborate experimental programs and advanced analytical methods are used in identifying the current state of health of critical and important structures. The paper outlines two methods of system identification of beam-like reinforced concrete structures representing bridges, through static measurements, in a distributed damage scenario. The first one is similar to the stiffness method, re-cast and the second one to flexibility method. A least square error (LSE) based solution method is used for the estimation of flexural rigidities and damages of simply supported, cantilever and propped cantilever beam from the measured deformation values. The performance of both methods in the presence of measurement errors is demonstrated. An experiment on an un-symmetrically damaged simply supported reinforced concrete beam is used to validate the developed method. A method for damage prognosis is demonstrated using a generalized, indeterminate, propped cantilever beam.

• Journal of the Korea Society of Computer and Information
• /
• v.21 no.7
• /
• pp.85-92
• /
• 2016

The law of large numbers, central limit theorem, and connection among binomial distribution, normal distribution, and statistical estimation require dynamics of continuous visualization for students' better understanding of the concepts. During this visualization process, the differences and similarities between statistical probability and mathematical probability that students should observe need to be provided with the intermediate steps in the converging process. We propose a visualization method that can integrate intermediate processes and results through Excel. In this process, students' experiences with dynamic visualization help them to perceive that the results are continuously changed and extracted from multiple situations. Considering modeling as a key process, we developed a classroom exercise using Excel to estimate the population mean and standard deviation by using a sample mean computed from a collection of data out of the population through sampling.

• Journal of the Ergonomics Society of Korea
• /
• v.11 no.1
• /
• pp.31-38
• /
• 1992

The population of aged people in industries has been increased remarkably due to the decline of birth rates and the increase of average life span. Also, the current automation trends makes aged people to work easy in industries since automation technologies help them to avoid physically hard tasks. Therefore the evaluation of aged workers' adaptability would be an important research topic. In the study, the mean and standard deviation of the reaction time are calculated to see the differences with four lamps's types and ages. It is found that the mean reaction time and the standard deviation are increased with the the increase of age. The quantitative approach provides an important information to be used not only for the adaptability estimation of aged workers but also for the working capability qualification for re-employment.

• Proceedings of the KSR Conference
• /
• 2007.11a
• /
• pp.1871-1876
• /
• 2007

To establish the national railway safety system, the railway total safety technology development project has been promoted by Ministry of Construction and Transportation (MOCT) since August 2004. The project has producted successful results in many areas of railway safety, however, it is required that the research field should be re-examined to meet the aim of the project. To do that, the precedence of the investment of research resources should be reviewed and determined. The risk of serious railway accidents such as train collision, derailment and level crossing accidents are estimated. From the estimation result and the statistics on the railway accidents over fast few years, the risk factors of railway accidents can be calculated.

• Proceedings of the IEEK Conference
• /
• 2003.07e
• /
• pp.2040-2043
• /
• 2003

General-purpose MPEG-2 video transcoders must be able to achieve any conversion between 18 ATSC (Advanced television system committee) video formats for DTV (digital television), e.g., scan format, size format, and frame rate format conversion. Especially, scan format conversion is hard to implement because frame rate and size format conversion often happen together. This paper proposes a fast motion estimation(ME) algorithm for MPEG-2 video transcoding supporting scan format conversion. Firstly, we extract and compose a set of candidate motion vectors (MV's) from the input bit-stream to comply with the re-encoding format. Secondly, the best MV is chosen among several candidate MV's by using a weighted median selector. Simulation results show that the proposed ME algorithm reduces significantly transcoding complexity with a minor PSNR degradation.