• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.233-238
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• 2005

S${\"{a}}$rndal (1996) and Knottnerus (2003) had a critical look at the well known variance estimator of Sen (1953) and Yates and Grundy (1953) in probability proportional to size sampling. In this paper, we point out that although their approaches can avoid the difficulties in variance estimation with respect to the joint probabilities, there exist the disadvantages in practice. Also, we describe a sampling procedure available in statistical software that are useful for the variance estimation.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2011년도 추계학술대회
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• pp.205-211
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• 2011

The papaer reviews four theoretical acceptance sampling plans as OC(Operating Characteristics) curve based inspection, rectifying inspection, switching inspection, and continuous inspection. In addition, the study presents practical limitations of theoretical acceptance sampling by attribute and by variable. Finally, following research also recommends the sampling inspection based on production technology. However, the inspection method requires quality expertise with various experience and implicit knowledge of the field.

• 한국지반공학회논문집
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• 제16권1호
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• pp.145-155
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• 2000

불연속면의 방향성은 암반의 과도변형이나 안정성에 영향을 미치는 특성 때문에 암반사면의 안정성 평가에 있어서 매우 중요한 역할을 한다. 불연속면의 방향측정에는 시추공(borehole)을 이용한 측정법이나 노두에서의 scanline을 이용하는 측정법과 같은 선형 측정법이 보편적으로 이용되나 이러한 측정 기법을 이용하여 획득한 자료들은 측선의 방향에 따라 쉽게 왜곡된다. 이러한 왜곡을 수정하기 위한 가중치 (weighting factor)가 적용되어도 특정 방향의 측선을 따라 자료를 획득할 경우 그 왜곡은 쉽게 보정되어지지 않는다. 즉, 불연속면의 방향자료 수집을 위해 이용된 선형 측선이 불연속면의 방향과 평행할 경우 대부분의 측선과 평행한 불연속면들은 조사 결과에 포함되지 않으며 이러한 현상은 불연속면들의 방향성 파악에 심각한 오류를 발생시킬 수 있다. 본 연구에서는 수직 측선 (borehole)에 의해 수집되어진 방향자료들과 수평 측선 (scanline)에 의해 수집되어진 방향자료들을 비교하였다. 서로 다른 두 방법에 의해 수집되어진 방향자료들은 큰 차이를 보이며, 이로 인해 불연속면들의 대표적인 방향성 결정에 장애가 되어진다. 불연속면의 경사각 분포와 수평과 수직 측선에 의해 수집되어진 자료들의 비교를 위해 등면적 극 평사투영망(polar stereo net)을 이용하였다.

• 한국산업보건학회지
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• 제24권2호
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• pp.201-207
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• 2014

Objectives: Flow rate stability is very important for obtaining reliable measurements. However there is no easily used method for checking whether the flow rate set at the initial stage is sustained during sampling. The purpose of this study was to develop a method to evaluate the flow rate performance of gas sampling pumps with adsorbents commonly used to sample gases. Materials and methods: We tested the back pressure of gas sampling pumps commonly used in Korea with adsorbents such as charcoal and silica tubes and attempted to discover the combination conditions of adsorbents in accordance with back pressure required by ISO standard 13137. Results: We found the combination of sampling adsorbents to be applicable to the pressure drop required by the ISO standard for evaluating flow rate stability under increasing pressure drop and long term (eight-hour) performance. Conclusions: This evaluation method of using a sampling media matrix for checking flow rate stability as proposed by this study could be a highly useful tool for determining the reliability of the performance pumps before sampling.

• 한국음향학회지
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• 제11권4호
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• pp.36-44
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• 1992

리던던시(redundancy)가 존재하는 신호의 데이타 압축을 위한 한 방법으로 비균일 표본화 방법이 연구되어져 왔다. 그런데 많은 리던던시가 존재한다고 알려진 음성신호에 기존의 비균일 표본화 방법을 그대로 적용하며, 데이타량이 PCM과 같은 균일 표본화에 의한 것에 필적하게 되거나 오히려 많아지게 된다. 이 문제를 해결하기 위하여 본 논문에서는 음성의 인지측면에서 리던던트한 샘플을 제거하는, 극대점과 극소점에서 비균일 표본화하는 방법을 제안한다. 그리고 본 논문에서는 제안된 방법의 성능을 분석하고자, 실험적인 방법으로 압축비관계를 살펴보며, 아울러 묶음구간 처리에 의하여 압축비를 크게 향상 시킬 수 있음을 보인다. 실험결과로써는 8kHz 8-bit PCM신호에 대하여 1.54배, 묶음처리를 한 경우에는 2.88배의 압축비를 얻었다.

• 산업경영시스템학회지
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• 제45권4호
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• pp.233-239
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• 2022

The injection molding process is a process in which thermoplastic resin is heated and made into a fluid state, injected under pressure into the cavity of a mold, and then cooled in the mold to produce a product identical to the shape of the cavity of the mold. It is a process that enables mass production and complex shapes, and various factors such as resin temperature, mold temperature, injection speed, and pressure affect product quality. In the data collected at the manufacturing site, there is a lot of data related to good products, but there is little data related to defective products, resulting in serious data imbalance. In order to efficiently solve this data imbalance, undersampling, oversampling, and composite sampling are usally applied. In this study, oversampling techniques such as random oversampling (ROS), minority class oversampling (SMOTE), ADASYN(Adaptive Synthetic Sampling), etc., which amplify data of the minority class by the majority class, and complex sampling using both undersampling and oversampling, are applied. For composite sampling, SMOTE+ENN and SMOTE+Tomek were used. Artificial neural network techniques is used to predict product quality. Especially, MLP and RNN are applied as artificial neural network techniques, and optimization of various parameters for MLP and RNN is required. In this study, we proposed an SA technique that optimizes the choice of the sampling method, the ratio of minority classes for sampling method, the batch size and the number of hidden layer units for parameters of MLP and RNN. The existing sampling methods and the proposed SA method were compared using accuracy, precision, recall, and F1 Score to prove the superiority of the proposed method.

• Journal of Electrical Engineering and Technology
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• 제12권5호
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• pp.1743-1753
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• 2017

Since there are multiple random variables in the probabilistic load flow (PLF) calculation of distribution system containing distributed generation (DG) and electric vehicle charging load (EVCL), a Monte Carlo method based on composite sampling method is put forward according to the existing simple random sampling Monte Carlo simulation method (SRS-MCSM) to perform probabilistic assessment analysis of voltage quality of distribution system containing DG and EVCL. This method considers not only the randomness of wind speed and light intensity as well as the uncertainty of basic load and EVCL, but also other stochastic disturbances, such as the failure rate of the transmission line. According to the different characteristics of random factors, different sampling methods are applied. Simulation results on IEEE9 bus system and IEEE34 bus system demonstrates the validity, accuracy, rapidity and practicability of the proposed method. In contrast to the SRS-MCSM, the proposed method is of higher computational efficiency and better simulation accuracy. The variation of nodal voltages for distribution system before and after connecting DG and EVCL is compared and analyzed, especially the voltage fluctuation of the grid-connected point of DG and EVCL.

• 방송공학회논문지
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• 제9권4호
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• pp.384-390
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• 2004

본 논문에서는 44.1KHz에서 48KHz로 표본화 주파수를 변환하는 알고리듬들의 성능을 비교한다. 비교 한 기법은 다위상 구조로 구현된 기본적인 기법, sinc 함수를 이용한 기법, 다위상 구조의 다단계 구현 기법, 그리고 B-spline을 이용한 기법 등이다. 먼저, 공정한 비교를 위해 이 4가지 기법을 이용한 표본화율 변환기들을 고품질 조건하에 재설계하고, 이들의 H/W 복잡도를 메모리 요구량과 계산량 측면에서 비교하였다. 그 결과, 메모리 요구량 측면에서는 B-spline을 이용한 기법이 가장 우수하였지만, 계산량 측면에서는 기본적인 기법과 sinc 함수를 이용한 기법이 가장 우수함을 확인할 수 있었다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.872-878
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• 2013

In industrial control systems, flow measurement is a very important issue. It is frequently needed to calculate how much total fluid or gas flows through a cross-section. Flow volume measurement tools use simple sampling or rectangle methods. Actually, flow volume measurement process is an integration process. For this reason, measurement systems using instantaneous sampling technique cause considerably high errors. In order to make more accurate flow measurement, numerical integration methods should be used. Literally, for numerical integration method, Rectangular, Trapezoidal, Simpson, Romberg and Gaussian Quadrature methods are suggested. Among these methods, trapezoidal rule method is quite easy to calculate and is notably more accurate and contains no restrictive conditions. Therefore, it is especially convenient for the portable flow volume measurement systems. In this study, the volume measurement of air which is flowing through a cross-section is achieved by using PLC ladder diagram. The measurements are done using two different approaches. Trapezoidal rule method is proposed to measure the flow sensor signal to minimize measurement errors due to the classical sampling method as a different approach. It is concluded that the trapezoidal rule method is more effective than the classical sampling.

• 한국어류학회지
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• 제20권3호
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• pp.228-232
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• 2008

To investigate a proper sampling method for anchovy eggs and larvae in coastal waters of the South Sea, replicated samplings were made by different towing methods with different sampling gears and compared in terms of abundance and length composition. There was no significant difference in abundance in samples from vertical and oblique tows with a ring net. The abundance by replicated vertical tows with a ring net was not significantly different, but significant difference in abundance among sampling stations were found. The ring net sampled anchovy eggs in significantly greater numbers than collected by a NORPAC net, but both gears were not effective in obtaining quantitative samples of anchovy larvae larger than 3 mm. Therefore, samples by vertical tows with a ring net during the day at various stations is more efficient at estimating the density of anchovy eggs in an area compared to replicated sampling at a single station.