• 한국수산과학회지
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• 제54권1호
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• pp.80-89
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• 2021

In Korea, marine fish landed at ports are randomly sampled on a periodic basis (e.g., daily or weekly), and body sizes (e.g., lengths and weights) of those sampled fish are measured. The motivation for our study is whether or not such measurements reflect the size distribution, especially the length distribution of fish landed (= a population), because such length measurements are key data for a length-based assessment model. The current sampling method is to sample fish landed at ports by body size group (e.g., very small, small, medium, large, very large), using the sampling weights as the number of boxes by body size group. In this study, we showed that length composition data about fish sampled by the current method did not represent the length frequency distribution of the fish landed, and suggested that an alternative sampling method should be applied of using the sampling weights as the number of fish landed by body size group. We also introduced a method for determining an appropriate sample size.

• Geomechanics and Engineering
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• 제9권6호
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• pp.743-755
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• 2015

It is well known that the quality of sample significantly determines the accuracy of soil parameters for laboratory testing. Although sampling disturbance has been studied over the last few decades, the theoretical investigation of soil disturbance due to sampling penetration has been rarely reported. In this paper, an analytical solution for estimating the soil disturbance due to sampling penetration was presented using cavity expansion method. Analytical results in several cases reveal that the soil at different location along the sample centerline experiences distinct phases of strain during the process of sampling penetration. The magnitude of induced strain is dependent on the position of the soil element within the sampler and the sampler geometry expressed as diameter-thickness ratio D/t and length-diameter ratio L/D. Effects of sampler features on soil disturbance were also studied. It is found that the induced maximum strain decreases exponentially with increasing diameter-thickness ratio, indicating that the sampling disturbance will reduce with increasing diameter or decreasing wall thickness of sampler. It is also found that a large length-diameter ratio does not necessarily reduce the disturbance. An optimal length-diameter ratio is suggested for the further design of improved sampler in this study.

• Nuclear Engineering and Technology
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• 제47권5호
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Communications for Statistical Applications and Methods
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• 제23권2호
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• pp.119-129
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• 2016

A new sampling method is introduced based on the idea of a ranked set sampling scheme in which taken samples in each set are dependent on previous ones. Some theoretical results are presented and distribution-free confidence intervals are derived for the quantiles of any continuous population. It is shown numerically that the proposed sampling scheme may lead to 95% confidence intervals (especially for extreme quantiles) that cannot be found based on the ordinary ranked set sampling scheme presented by Chen (2000) and Balakrishnan and Li (2006). Optimality aspects of this scheme are investigated for both coverage probability and minimum expected length criteria. A real data set is also used to illustrate the proposed procedure. Conclusions are eventually stated.

• Journal of the Korean Data and Information Science Society
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• 제22권3호
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• pp.549-553
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• 2011

In this paper, we deal with the problem of deciding the length of data for estimating the parameters in geometric Brownian motion. As an approach to this problem, we consider the change point test and introduce simple test statistic based on the cumulative sum of squares test (cusum test). A real data analysis is performed for illustration.

• 한국안전학회지
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• 제11권2호
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• pp.89-95
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• 1996

To predict the service life of an organic vapor respirator cartridge, the breakthrough curve of respirator was simulated using a fixed-bed adsorption model and compared with that of sampling tube. And the effects of bed porosity, length to diameter ratio and flow rate of the sampling tube were studied. The life time of respirator cartridge was increased with the decrease of particle size and bed porosity. And the breakthrough time of sampling tube was affected by the flow rate, however not by the length to diameter ratio. The 10% breakthrough time of the sampling tube was corresponded with that of cartridge.

• 한국환경보건학회지
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• 제35권6호
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• pp.500-509
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• 2009

Passive samplers have been used for many years for the sampling of organic vapors in work environment atmospheres. Currently, all passive samplers used in domestic occupational monitoring are foreign products. This study was performed to evaluate variable parameters for the development of passive organic samplers, which include the geometry of the device and diffusive length for the sampler design. Four prototype diffusive lengths; A-1(4.5 mm), A-2(7.0 mm), A-3(9.5 mm), A-4(12.0 mm) were tested for adsorption performances to a chemical mixture (benzene, toluene, trichloroethylene, and n-hexane) according to the US-OSHA's evaluation protocol. A dynamic vapor exposure chamber developed and verified by related research was used for this study. The results of study are as follows. The results in terms of sampling rate and recommended sampling time test indicate that the most suitable model was A-3 (9.5 mm diffusive lengths on both sides) for passive sampler design in time weighted average (TWA) assessment. Sampling rates of this A-3 model were 45.8, 41.5, 41.4, and 40.3 ml/min for benzene, toluene, trichloroethylene, and n-hexane, respectively. The A-3 models were tested on reverse diffusion and conditions of low humidity air (35% RH) and low concentrations (0.2 times of TLV). These conditions had no affect on the diffusion capacity of samplers. In conclusion, the most suitable design parameters of passive sampler are: 1) Geometry and structure - 25 mm diameter and 490 $mm^2$ cross sectional area of diffusion face with cylindrical form of two-sided opposite diffusion direction; 2) Diffusive length - 9.5 mm in both faces; 3) Amount of adsorbent - 300 mg of coconut shell charcoal; 4) Wind screen - using nylon net filters (11 ${\mu}m$ pore size).

• Journal of Ecology and Environment
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• 제30권2호
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• pp.201-207
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• 2007

Researchers have used a variety of methods to measure patterns of animal movement, including the use of spatial data (mapping the position of a moving animal at specified intervals) and direct estimation of travel path length by pacing under a moving animal or group. I collected movement data from five groups of siamangs (Symphalangus syndactylus) using two different methods concurrently to estimate the effects of the method of data collection on estimates of daily path length (DPL). Estimates of DPL produced from spatial data collected at 15-minute intervals were 12% lower than estimates of DPL produced by pacing under the traveling animal. The actual magnitude of the difference was correlated with the travel distance, but there was no correlation between the proportional difference and the travel distance. While the collection of spatial data is generally preferable, as spatial data permit additional analyses of patterns of movements in two or three dimensions, the relatively small difference between the DPL's produced using different methods suggests that pacing is an acceptable substitute where the collection of spatial data is impractical. I also subsampled the spatial data at increasing time intervals to assess the effect of sampling interval on the calculation of daily path lengths. Longer sampling intervals produced significantly shorter estimates of travel paths than shorter sampling intervals. These results suggest that spatial data should be collected at short time intervals wherever possible, and that sampling intervals should not exceed 30 minutes. Researchers should be cautious when comparing data generated using different methods.

• 전자공학회논문지CI
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• 제48권6호
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• pp.114-122
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• 2011

본 논문에서는 무인 지상 차량의 (Unmanned Ground Vehicle, UGV)의 위치 추정을 위한 컴퓨터 비전 기술을 제안한다. 제안하는 방법은 연속적으로 획득되는 360도 거리 정보(range data)와 디지털 수치모델(Digital Surface Model, 이하 DSM)의 3차원 등록(3-D registration) 방법에 기반하고 있다. 많은 수의 3차원 점군(point clouds) 정보를 가지고 있는 거리 정보의 연속적 3차원 등록은 상당한 수행 시간을 필요로 한다. 실시간 위치 추정을 위해 우리는 투영 기반의 등록 방법과 Uniform Arc Length Sampling(이하 UALS) 방법을 제안한다. UALS는 거리영상에서의 GSD(ground sample distance)를 균일하게 유지하면서 동시에 3차원 샘플 포인트의 수를 줄일 수 있는 장점을 가지고 있다. 또한 투영 기반 등록 기술은 3차원 대응점의 탐색 시간을 감소시킨다. 두 개의 실제 항법 경로를 이용한 실험을 통하여 제안하는 방법의 성능을 검증하였다. 3차원 점군의 다양한 샘플링에 대하여 제안하는 기술의 속도 및 정합 성능을 기존 방법과 비교하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 B
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• pp.533-536
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• 1999

We consider digital implementation problems of continuous-time controllers. In general, digital controllers use fixed point representation of number and of finite word length(FWL). Under these conditions, this paper investigates the closed-loop stability caused by three design constraints; (i) finite precision representation of the controller parameters, (ii) realization forms such as direct form, cascade form, and parallel form, and (iii) sampling time. We calculate the coefficient stability margins of both predesigned controllers and controller to be implemented. This method can be applied to determine the word length, realization structure, and sampling time so that remains the stability.