• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.351-359
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• 2004

Velocity-type repisratory air flow transducer measures dynamic pressure converted from air velocity based on the we1l-known Bernoulli's principle. It requires multiple velocity sampling holes on the flow plane. Measurement error theoretica1ly estimated by computer simulation was demonstrated to significantly reduce by unequally locating the velocity sampling holes. The flow plane was divided into multiple equi-area rings and the sampling holes were located on the circles also equally dividing each ring's area, which decreased measurement error down to 1/5 of the simple equi-radius ring division method. Also, less than 1 ％ relative error was estimated with 4 or more sampling holes. The present technique was less sensitive by <1/2 to the velocity profile change compared to the euqi-radius sampling. Therefore, the present unequal distance velocity sampling technique should be of great use to design the structure of the velocity-type respiratory air flow transducer.

• Journal of Broadcast Engineering
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• v.2 no.1
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• pp.16-23
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• 1997

Among the main technologies to implement 3D TV succeeding HDTV, multi-viewpoint image display technique is rising as an important issue, which can display the viewpoint-dependent images corresponding to viewer's position. This paper presents a novel method that solves too much computational overload that is main drawback of previous methods. Using down sampling technique, multiresolution EPIs are made from multi-viewpoint image set and trace lines are detected in the lowest resolution EPI. The parameters of detected trace lines are transferred to higher resolution EPIs and revised by utilizing the information of the previous resolution EPI. This procedure is iterated until orignal resolution EPI. Using the proposed method, we have achieved the reduction of computational time and the robustness to noise in comparison to previous method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.879-885
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• 2004

This paper describes an adaptive signal processing of digital receiver with digital down convertor(DDC). DDC is composed of numerically controlled oscillator(NCO) and digital low pass filler and the received signal is processed by numerical algorithm. The simulation results of digital receiver using the passband sampling technique are presented and we confirmed that the received low IF signal is converted to zero IF by numerically processed DDC. Direction of arrival(DOA) estimation technique using multiple signal classification(MUSIC) algorithm with high resolution is also discussed. We knew that an accurate resolution of DOA depends on the input sampling numbers and antenna element numbers.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.2
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• pp.65-72
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• 2006

In digital signal processing, the polyphase decomposition of signal has been often used in the implementation of multirate system. Especially, in the design of digital filter and so forth the method in very useful to improve the performance of various algorithms because it provides the multi-channel for paralled processing. Generally, the polyphase-decomposed signals tend to expand the frequency band by including more high frequencies than original signal from decimation for down sampling. This property brings about the significant limitation in the structure or the performance of digital polyphase signal processing system. In this paper we theoretically propose a perfect band compression and reconstruction method for polyphase component signals, then experimentally show its effectiveness through Matlab simulation.

• Journal of Information Processing Systems
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• v.19 no.5
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• pp.688-701
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• 2023

The conventional methods of network intrusion detection system (NIDS) cannot measure the trend of intrusiondetection targets effectively, which lead to low detection accuracy. In this study, a NIDS method which based on a deep neural network in a big-data environment is proposed. Firstly, the entire framework of the NIDS model is constructed in two stages. Feature reduction and anomaly probability output are used at the core of the two stages. Subsequently, a convolutional neural network, which encompasses a down sampling layer and a characteristic extractor consist of a convolution layer, the correlation of inputs is realized by introducing bidirectional long short-term memory. Finally, after the convolution layer, a pooling layer is added to sample the required features according to different sampling rules, which promotes the overall performance of the NIDS model. The proposed NIDS method and three other methods are compared, and it is broken down under the conditions of the two databases through simulation experiments. The results demonstrate that the proposed model is superior to the other three methods of NIDS in two databases, in terms of precision, accuracy, F1- score, and recall, which are 91.64%, 93.35%, 92.25%, and 91.87%, respectively. The proposed algorithm is significant for improving the accuracy of NIDS.

• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.195-208
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• 2023

This study aimed to use three-dimensional point cloud data (PCD) obtained from Terrestrial Laser Scanning (TLS) and Mobile Laser Scanning (MLS) to evaluate a deep learning-based species classification model for two tree species: Pinus koraiensis and Larix kaempferi. Sixteen models were constructed based on the three conditions: LiDAR platform (TLS and MLS), down-sampling intensity (1024, 2048, 4096, 8192), and deep learning model (PointNet, PointNet++). According to the classification accuracy evaluation, the highest kappa coefficients were 93.7% for TLS and 96.9% for MLS when applied to PCD data from the PointNet++ model, with down-sampling intensities of 8192 and 2048, respectively. Furthermore, PointNet++ was consistently more accurate than PointNet in all scenarios sharing the same platform and down-sampling intensity. Misclassification occurred among individuals of different species with structurally similar characteristics, among individual trees that exhibited eccentric growth due to their location on slopes or around trails, and among some individual trees in which the crown was vertically divided during tree segmentation.

• Journal of Environmental Impact Assessment
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• v.24 no.6
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• pp.607-618
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• 2015

Five years have passed since the first set of environmental samples was taken in 2011 to represent various ecosystems which would help future generations lead back to the past environment. Those samples have been preserved cryogenically in the National Environmental Specimen Bank(NESB) at the National Institute of Environmental Research. Even though there is a strict regulation (SOP, standard operating procedure) that rules over the whole sampling procedure to ensure each sample to represent the sampling area, it has not been put to the test for the validation. The question needs to be answered to clear any doubts on the representativeness and the quality of the samples. In order to address the question and ensure the sampling practice set in the SOP, many steps to the measurement of the sample, that is, from sampling in the field and the chemical analysis in the lab are broken down to evaluate the uncertainty at each level. Of the 8 species currently taken for the cryogenic preservation in the NESB, pine tree samples from two different sites were selected for this study. Duplicate samples were taken from each site according to the sampling protocol followed by the duplicate analyses which were carried out for each discrete sample. The uncertainties were evaluated by Robust ANOVA; two levels of uncertainty, one is the uncertainty from the sampling practice, and the other from the analytical process, were then compiled to give the measurement uncertainty on a measured concentration of the measurand. As a result, it was confirmed that it is the sampling practice not the analytical process that accounts for the most of the measurement uncertainty. Based on the top-down approach for the measurement uncertainty, the efficient way to ensure the representativeness of the sample was to increase the quantity of each discrete sample for the making of a composite sample, than to increase the number of the discrete samples across the site. Furthermore, the cost-effective approach to enhance the confidence level on the measurement can be expected from the efforts to lower the sampling uncertainty, not the analytical uncertainty. To test the representativeness of a composite sample of a sampling area, the variance within the site should be less than the difference from duplicate sampling. For that, a criterion, ${i.e.s^2}_{geochem}$(across the site variance) <${s^2}_{samp}$(variance at the sampling location) was proposed. In light of the criterion, the two representative samples for the two study areas passed the requirement. In contrast, whenever the variance of among the sampling locations (i.e. across the site) is larger than the sampling variance, more sampling increments need to be added within the sampling area until the requirement for the representativeness is achieved.

• 대한방사선방어학회:학술대회논문집
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• 2009.04a
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• pp.254-255
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• 2009

국내 경수로 원전의 경우, 원전의 효율적, 경제적 운영차원에서 장주기 운전으로 패턴을 바뀌면서 핵연료봉 표면상에 크러드(crud)의 침적량은 점점 증가하는 경향을 나타내고 있다. 이러한 경향은 원자로의 출력 제어와 직결되면서 이에 대한 문제 해결을 위한 대표성이 있는 시료의 채취와 재현성이 있는 부식 생성물의 측정이 요구되어져 왔다. 원자로 계통 내에서 부식생성물의 농도변화에 대한 평가, 특히 입자농도가 증가되어지면 축방향 출력편차(Axial Offset Anomaly, AOA)가 발생될 수 있는 위험에 노출되거나, 핵연료 교체를 위해 발전소 정지시(shut down) 부식생성물의 방출이 급격히 증가되는 것으로 나타났다. 특히 입자성을 띤 물질은 존재의 특성상 이들 물질에 대한 대표시료의 채취가 어려울 뿐 아니라 grab 채취로 인해, 분석결과에 대한 재현성이 낮으며 계통 선량율의 제어와 작업자 피폭관리에 많은 어려움이 뒤따르고 있어 선진 원전 운영국에서는 앞 다투어 대표시료를 채취 할 수 있는 capillary sampling 법이나 integrated sampling법을 적용해 오고 있다. 본 논문에서는 국내 경수로 원전에서 일반적으로 사용하고 있는 grab sampling 법에 대한 문제점 파악과 해외 원전에서 사용 중인 capillary sampling 법의 국내 적용 가능성에 대해 살펴보았다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.162-170
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• 2015

In the bandpass sampling (BPS), the sampling frequency is lower than the frequency of the signal to be sampled. In this method, the baseband spectrum can be directly obtained by the sampling operation. This makes the frequency down converter unnecessary as well as the receiver's circuit simpler. In the second-order BPS system, two sampling devices are used. When aliasing occurs due to the sampling operation, the aliased component can be cancelled by combining the two sampled signals. In this paper, it is presented a design method of the second-order BPS system when multiple interferences are simultaneously aliased to the signal component. The optimum phase of the interpolant filter is searched for maximizing the signal-to-interference ratio, and a practical formula for the suboptimal phase is derived in terms of the power spectrum profile of the BPS input. A computer simulation has been performed for the proposed second-order BPS system, and it has been shown that the signal-to-interference ratio can be increased by considering multiple aliasing.

• Journal of Environmental Impact Assessment
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• v.12 no.2
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• pp.73-86
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• 2003

In this study, we performed 8 times of water quality sampling and continuous measurement of flow to identify wastewater flow characteristics for wastewater treatment basins of Namyangju city. The field survey has been conducted 6 times in dry weather period and 2 times in wet weather period. Each survey conducted 24-hr water quality sampling in the interval of 2-hr. From the analysis of flow data and water quality data, the following conclusions can be drawn. For Namyangju-1 station, which represents residential and commercial mixed area, flow rises early in the morning before office-going hour and moves up and down within narrow range, and lasted after office-leaving hour, resulting from continuous commercial activity. In case of Namyangju-5 station representing community and Namyangju- 6 station representing residential area, the flow immediately falls down after rising early in the morning and later rises again at the office-leaving hour, and arrives at peak flows around late evening. In the analysis of wastewater characteristics for weekdays and weekends, without landuse types the flow rate of weekends is higher than that of weekdays because it reflects population, being not contributed to generate wastewater during the working hours of weekdays, stay home and produce wastewater for weekends period.