• 전자공학회논문지B
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• 제32B권1호
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• pp.110-119
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• 1995

The lateral resolution in an ultrasound imaging system is one of the most important factors for quality of the image and is determined by the beam focusing. For the better lateral resolution SDF(Sampled Delay Focusing) capable of digital focusing was proposed. The second-order sampling, one of band-width sampling methods, is suggested as being the best suitable for SDF because it allows total digital processing and is simple and economical. By proving that it introduces too much error, this article shows the second-order sampling is not appropriate for sampling of the wide-band signal generally used in ultrasound imaging systems. Also, this article suggests new sampling methods that maintain the advantages and reduce the unavoidable errors of the second-order sampling method. From computer simulation it is expected that the proposed methods reduce the errors of the second-order sampling method and can be used in real applications.

• 전기학회논문지
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• 제57권2호
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• pp.294-302
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• 2008

In this paper, we present a new image up-sampling method which registers low resolution images to the high resolution grid when Bayesian super-resolution image processing is performed. The proposed up-sampling method interpolates high-resolution pixels using high-frequency data lying in all the low resolution images, instead of up-sampling each low resolution image separately. The interpolation is based on B-spline non-uniform re-sampling, adjusted for the super-resolution image processing. The experimental results demonstrate the effects when different up-sampling methods generally used such as zero-padding or bilinear interpolation are applied to the super-resolution image reconstruction. Then, we show that the proposed hybird up-sampling method generates high-resolution images more accurately than conventional methods with quantitative and qualitative assess measures.

• Communications for Statistical Applications and Methods
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• 제14권3호
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• pp.667-677
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• 2007

In this paper, we propose a method for estimating the mean of a population which has a linear trend, when both n, the sample size, and k, the reciprocal of the sampling fraction, are odd numbers. The proposed method, not having the drawbacks of centered systematic sampling, centered modified sampling and centered balanced sampling, consists of selecting a sample by balanced systematic sampling and estimating the population mean by using interpolation. We compare the efficiency of the proposed method and existing methods under the criterion of the expected mean square error based on the infinite superpopulation model.

• ETRI Journal
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• 제23권3호
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• pp.129-137
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• 2001

A random sampling or systematic sampling method is commonly used to assess the accuracy of classification results. In remote sensing, with these sampling methods, much time and tedious work are required to acquire sufficient ground truth data. So, a more effective sampling method that can represent the characteristics of the population is required. In this study, fractal analysis is adopted as an index for reference sampling. The fractal dimensions of the whole study area and the sub-regions are calculated to select sub-regions that have the most similar dimensionality to that of the whole area. Then the whole area's classification accuracy is compared with those of sub-regions, and it is verified that the accuracies of selected sub-regions are similar to that of whole area. A new kind of reference sampling method using the above procedure is proposed. The results show that it is possible to reduce sampling area and sample size, while keeping the same level of accuracy as the existing methods.

• Journal of Genetic Medicine
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• 제11권2호
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• pp.43-48
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• 2014

Chorionic villus sampling has gained importance as a tool for early cytogenetic diagnosis with a shift toward first trimester screening. First trimester screening using nuchal translucency and biomarkers is effective for screening. Chorionic villus sampling generally is performed at 10-12 weeks by either the transcervical or transabdominal approach. There are two methods of analysis; the direct method and the culture method. While the direct method may prevent maternal cell contamination, the culture method may be more representative of the true fetal karyotype. There is a concern for mosaicism which occurs in approximately 1% of cases, and mosaic results require genetic counseling and follow-up amniocentesis or fetal blood sampling. In terms of complications, procedure-related pregnancy loss rates may be the same as those for amniocentesis when undertaken in experienced centers. When the procedure is performed after 9 weeks gestation, the risk of limb reduction is not greater than the risk in the general population. At present, chorionic villus sampling is the gold standard method for early fetal karyotyping; however, we anticipate that improvements in noninvasive prenatal testing methods, such as cell free fetal DNA testing, will reduce the need for invasive procedures in the near future.

• 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.

• 한국통신학회논문지
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• 제31권12C호
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• pp.1249-1256
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• 2006

본 논문은 대역통과 샘플링(bandpass sampling)이론을 사용하여 N개 RF 신호를 하나의 통신기기에서 직접 하향변환(down-conversion)할 때 요구되는 유효 샘플링 주파수 영역(valid sampling frequency range) 및 최소 샘플링 주파수를 찾는 방법을 제안하였다. 이 방식은 기존의 방식보다 효율적이며 복잡성이 낮은 방식을 새롭게 고안하여 N개의 신호에 대하여 수식을 유도하고 일반화 하였으며 컴퓨터 모의실험(simulation)을 통해 이 수식들을 증명하였다. 그리고 제안한 알고리즘은 샘플링 주파수를 결정할 때 인접 IF 신호간의 보호대역(guard-band)이 고려되어 실제적인 하드웨어 설계 측면에 도움이 되도록 하였다. 또한 기존의 방식과의 비교를 통해 그 복잡성(complexity) 및 정확성에서도 우수한 성능을 보여주었다.

• 대한기계학회논문집A
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• 제30권6호
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• pp.691-697
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• 2006

Metamodel, model of model, has been widely used to improve an efficiency of optimization process in engineering fields. However, global metamodels of constraints in a constrained optimization problem are required good accuracy around neighborhood of optimum point. To satisfy this requirement, more sampling points must be located around the boundary and inside of feasible region. Therefore, a new sampling strategy that is capable of identifying feasible domain should be applied to select sampling points for metamodels of constraints. In this research, we suggeste sequential feasible domain sampling that can locate sampling points likely within feasible domain by using penalty function method. To validate the excellence of feasible domain sampling, we compare the optimum results from the proposed method with those form conventional global space-filling sampling for a variety of optimization problems. The advantages of the feasible domain sampling are discussed further.

• 한국시뮬레이션학회논문지
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• 제9권2호
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• pp.75-87
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• 2000

In this paper, nonstationary multiple sampling plans are discussed which are difficult to solve by analytical method when there exists dependency between the sample data. The initial solution is found by the sequential sampling plan using the sequential probability ration test. The number of acceptance and rejection in each step of the multiple sampling plan are found by grouping the sequential sampling plan's solution initially. The optimal multiple sampling plans are found by simulation. Four search methods are developed U and the optimum sampling plans satisfying the Type I and Type ll error probabilities. The performance of the sampling plans is measured and their algorithms are also shown. To consider the nonstationary property of the dependent sampling plan, simulation method is used for finding the lot rejection and acceptance probability function. As a numerical example Markov chain model is inspected. Effects of the dependency factor and search methods are compared to analyze the sampling results by changing their parameters.

• 한국조사연구학회지:조사연구
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• 제6권2호
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• pp.1-32
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• 2005

출구조사에서 투표소 추출방법은 출구조사의 정확성을 결정하는 중요한 요소이다. 본 연구에서는 대표구 추출법을 대신할 수 있는 정렬계통추출법을 제안하고 그 활용 가능성 및 효율성을 분석한다. 아울러 제시된 정렬계통추출법을 사용하는 경우 추정량의 표본추출오차(sampling error)가 어느 정도 되며, 원하는 목표 오차를 만족하기 위한 표본크기를 결정하는 문제를 고려한다. 2004년 17대 총선 개표자료를 토대로 경험적인 분석을 통해 제시된 정렬계통추출법이 기존의 대표구 추출법에 비해 평균예측오차 관점에서 효율적이라는 사실을 규명하고, 기존의 출구조사에서 표본크기 및 추정오차를 해석하는 과정에서 발생하는 오류를 집락효과를 이용해 설명했다. 아울러 제안한 정렬추출법에서 얻어지는 추정량의 분산을 구하고, 설계효과 개념을 이용해 표본크기 결정문제를 다루었다.