• Tunnel and Underground Space
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• v.26 no.1
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• pp.46-58
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• 2016

In this study, a LIDAR laser scanner was used to scan a rock slope around Mt. Gwanak and to produce point cloud from which directional information of rock joint surfaces shall be extracted. It was analyzed using two different algorithms, i.e. Ball Pivoting and Wrap algorithm, and four sampling intervals, i.e. raw, 2, 5, and 10 cm. The results of Fuzzy K-mean clustering were analyzed on the stereonet. As a result, the Ball Pivoting and Wrap algorithms were considered suitable for extraction of rock surface orientation. In the case of 5 cm sampling interval, both triangulation algorithms extracted the most number of the patch and patched area.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1464-1470
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• 2009

RBDO approach based on a sampling method with the Kriging metamodel and Constraint Boundary Sampling (CBS), which is sequential sampling method to generate metamodels is proposed. The major advantage of the proposed RBDO approach is that it does not require Most Probable failure Point (MPP) which is essential for First-Order Reliability Method (FORM)-based RBDO approach. The Monte Carlo Sampling (MCS), most well-known method of the sampling methods for the reliability analysis is used to assess the reliability of constraints. In addition, a Cumulative Distribution Function (CDF) of the constraints is approximated using Moving Least Square (MLS) method from empirical distribution function. It is possible to acquire a probability of failure and its analytic sensitivities by using an approximate function of the CDF for the constraints. Moreover, a concept of inactive design is adapted to improve a numerical efficiency of the proposed approach. Computational accuracy and efficiency of the proposed RBDO approach are demonstrated by numerical and engineering problems.

• The Korean Journal of Applied Statistics
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• v.27 no.3
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• pp.501-512
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• 2014

Modified cut-off sampling is widely used for highly skewed data. A serious drawback of modified cut-off sampling is the difficulty of adjustment of non-response in take-all stratum. Therefore, solutions of the problems of non-response in take-all stratum have been studied in various ways such as substitute of samples, imputation or re-weight method. In this paper, a new cut-off point based on minimizing MSE being used in exponential and power functions is suggested and it can be reduced the number of take-all stratum. We also investigate another cut-off point determination method with underlying distributions such as truncated log-normal and truncated gamma distributions. Finally we suggest the optimal cut-off point which has a minimum of take-all stratum size among suggested methods. Simulation studies are performed and Labor Survey data and simulated data are used for the case study.

• Journal of the Korean Solar Energy Society
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• v.33 no.5
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• pp.51-59
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• 2013

It is usual to evaluate the performance of the cool roof by measuring in-site rooftop temperature using thermal infra-red camera. The principal advantage of rooftop thermal infrared image acquired in oblique vantage point of super high-rise building as a remote sensor is to provide, in a cost-effective manner, area-wide information required for a scattered rooftop target with different colors, utilizing wide view angle and multi-temporal data coverage. This research idea was formulated by incorporating the concept of traditional remote sensing into rooftop temperature monitoring. Correlations between infrared image of super high-rise building and in-situ data were investigated to compare rooftop surface temperature for a total of four different rooftop locations. The results of the correlations analyses indicate that the rooftop surface temperature by the infrared images of super high-rise building alone could be explained yielding $R^2$ values of 0.951. The visible permanent record of the oblique thermal infra-red image was quite useful in better understanding the nature and extent of rooftop color that occurs in sampling points. This thermal infrared image acquired in oblique vantage point of super high-rise made it possible to identify area wide patterns of rooftop temperature change subject to many different colors, which cannot be acquired by traditional in-site field sampling. The infrared image of super high-rise building breaks down the usual concept of field sampling established as a conventional cool roof performance evaluation technique.

• Journal of Integrative Natural Science
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• v.5 no.4
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• pp.241-245
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• 2012

Categorical data collected based on complex sample design is not proper for the standard Pearson multinomial-based chi-squared test because the observations are not independent and identically distributed. This study investigates effects of bias of point estimator of population proportion and its variance estimator to the standard Pearson chi-squared test statistics when the sample is collected based on complex sampling scheme. This study examines the effect under two population homogeneity test. The standard Pearson test statistic can be partitioned into two parts; the first part is the weighted sum of ${\chi}^2_1$ with eigenvalues of design matrix as their weights, and the additional second part which is added due to the biases of the point estimator and its variance estimator. Our empirical analysis shows that even though the bias of point estimator is small, Pearson test statistic is very much inflated due to underestimate the variance of point estimator. In the connection of design-based variance estimator and its design matrix, the bigger the average of eigenvalues of design matrix is, the larger relative size of which the first component part to Pearson test statistic is taking.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.10C
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• pp.1378-1386
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• 2004

In this paper, we propose an OFDM scheme to increase the BER performance. The proposed OFDM scheme makes the baseband OFDM signal by using the oversampled OFDM signal values which are obtained by inserting N(=2$\^$k/) zeros and carrying out 2N point IFFT. In the demodulation part, the sampling operation for A/D conversion is carried out with the 2 times high sampling speed. 2 N point FFT is carried out for the data demodulation. In this paper, we show, with the mathematical method and the computer simulation, that the SNR of the proposed OFDM scheme is 3 dB higher than that of the conventional OFDM in the same AWGN channel conditions given.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.4
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• pp.483-490
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• 2021

In Indonesia, coffee shops, commonly called warung or kedai shops, have begun to appear amid society from remote villages to urban centers. Therefore, the purpose of this study is to examine the effect of cafe atmosphere (i.e., exterior, interior, interior point-of-purchase displays and store layout) on the purchase decision of Generation Z. This study is conducted because of cafe competition is currently overgrowing. This study model consisted of five variables: exterior, interior, interior point-of-purchase displays, store layout, and purchase decision. Sampling in this study used non-probability, with a purposive sampling technique. According to predetermined criteria, the data collection technique employed a questionnaire distributed online to consumers had visited a cafe at least once in the last three months. This study's sample was 137 cafe visitors in Yogyakarta, representing one of the big cities in Indonesia. Therefore, the data was analyzed by using multiple regression. The results of the study indicated that the exterior and interior had a positive and significant effect on purchasing decision. Likewise, interior point-of-purchase displays and store layout positively and significantly affected purchase decision. In addition, this study's findings generally concluded that the cafe atmosphere had a positive and significant effect on purchase decision.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.114-122
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• 2011

We propose an automatic localization technique based on Uniform Arc Length Sampling (UALS) of 360 degree range sensor data. The proposed method samples 3D points from dense a point-cloud which is acquired by the sensor, registers the sampled points to a digital surface model(DSM) in real-time, and determines the location of an Unmanned Ground Vehicle(UGV). To reduce the sampling and registration time of a sequence of dense range data, 3D range points are sampled uniformly in terms of ground sample distance. Using the proposed method, we can reduce the number of 3D points while maintaining their uniformity over range data. We compare the registration speed and accuracy of the proposed method with a conventional sample method. Through several experiments by changing the number of sampling points, we analyze the speed and accuracy of the proposed method.

• Journal of Biosystems Engineering
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• v.17 no.2
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• pp.156-170
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• 1992

The force-deformation relationship gives the basic physical properties of the fruits such as the bioyield point, the rupture point, and the deformations at the bioyield point and the rupture point. These informations are very important to study the stress-strain relationships of the fruits. This study was conducted to analyze those physical properties according to the sampling position of the fruits, and to determine the bioyield point, the rupture point, and the deformations at the bioyield point and the rupture point of the fruits for two different storage conditions(low temperature and normal temperature) and the storage period, and to investigate the effect of loading rate on those physical properties, the hysteresis on the loading-unloading condition and the degree of elasticity of the fruits. The results of the study were as follows : 1. The physical properties(BS, US, BD, and RD) of the test specimen selected from the different sampling positions were quite different. The values of the physical properties were shown smallest ones at the cheek of the fruits, and the statistical test results of the physical properties between the cheek from the other two positions of the fruits showed that there were significant difference at the 1 % level between them. 2. The effect of loading rate on the physical properties of the fruits was relatively large, all the considered physical propertis of the fruits increased with the loading rate, but the hysteresis loss decreased with it. 3. The physical properties of the fruits according to the storage conditions and period showed different, and the bioyield deformation and the rupture deformation of the fruits increased with the storage period, but the bioyield strength and the ultimate strength of the fruits decreased with it. The effect of the storage conditions on the those physical properties showed that the normal temperature storage condition was a little higher than the low temperature storage condition. 4. As a whole, it was shown that the bioyield strength and the ultimate strength of the pear decreased a little faster than those of the apple, and the bioyield deformation and rupture deformation of the pear increased a little faster than those of apple at the two storage conditions.

• Proceedings of the KIEE Conference
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• 2008.04c
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• pp.65-67
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• 2008

An adaptive response surface method with Latin Hypercube sampling strategy is employed to optimize a magnet pole shape of large scale BLDC motor to minimize the cogging torque. The proposed algorithm consists of the multi-objective Pareto optimization and ($1+{\lambda}$) evolution strategy to find the global optimal points with relatively fewer sampling data. In the adaptive RSM, an adaptive sampling point insertion method is developed utilizing the design sensitivities computed by using finite element method to set a reasonable response surface with a relatively small number of sampling points. The developed algorithm is applied to the shape optimization of PM poles for 6MW BLDC motor.