• 한국대기환경학회지
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• 제15권2호
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• pp.121-138
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• 1999

This study was carried out to evaluate the performance of a sampling and analytical methodology for the measurement of selected volatile organic compounds (VOCs) in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/FID and GC/MSD analysis. Target analytes were aromatic VOCs, including BTEX, 1,3,5-and 1,2,4,-trimethylbenzenes(TMBs), and naphthalene. The methodology was investigatedwith a wide range of performance criteria such as repeatability, linearity, lower detection limits, collection efficiency, thermal conditioning, breakthrough volume and calibration methods using internal and external standards. standards. Stability of samples collected on adsorbent tubes during storage was also investigated. In addition, the sampling and analytical method developed during this study was applied to real samples duplicately collected in various indoor and outdoor environments. Precisions for the duplicate samples and distributed volume samples appeared to be well comparable with the performance criteria recommended by USEPA TO-17. The audit accuracy was estimated by inter-lab comparison of both duplicate samples and standard materials between the two independent labs. The overall precision and accuracy of the method were estimated to be within 30% for major aromatic VOCs such as BTEX. This study demonstrated that the adsorbent sampling and thermal desorption method can be reliably applied for the measurement of BTEX in ppb levels frequently occurred in common indoor and ambient environments.

• 전자공학회논문지B
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• 제30B권5호
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• pp.62-72
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• 1993

The phased array antenna has the ability to perform adaptive sampling by directing the radar beam without inertia in any direction. The adaptive sampling capability of the phased array antenna allows each sampling time interval to be varied for each target, depending on the acceleration of each target at any time. In this paper we design a three dimensional adaptive target tracking algorithm for the phased array radar system with a given set of measurement parameters. The tracking algorithm avoids taking unnecessarily frequent samples, while keeping the angular prediction error within a fraction of antenna beamwidth so that the probability of detection will not be degraded during a track updata illuminations. In our algorithm, the target model and the sampling rate are selected depending on the target range and the target maneuver status which is determined by a maneuver level detector. A detailed simulation is conducted to test the validity of our tracking algorithm for target trajectories under various conditions of maneuver.

• International Journal of Automotive Technology
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• 제8권2호
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• pp.149-154
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• 2007

The engine behavior in a transient condition is important to not only emission regulations but also fuel economy. A fast response gas analyzer can be a useful tool to investigate exhaust gas in a transient operation. It should be designed to analyze gas concentration with a short time constant by a fast sampling module and an appropriate measuring method for each emission element. In this study, a new fast sampling module is introduced and flow analysis is performed by numerical simulation. The analysis has shown the proper operating condition and the sensitivity of the module for practical application. Calculated flow to the sampling module has $0.5{\sim}4%$ error, while backflow toward the expansion tube is expected when pressure in CP (Constant Pressure) chamber is over 0.6 bar. For a stable supply of flow to the optical cell, sample gas pressure should be in the range, $0.35{\sim}1.90$ bar, when the pressure in the CP camber and the optical cell are 0.2 bar and 0.158 bar, respectively.

• 한국수산과학회지
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• 제42권5호
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• pp.442-448
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• 2009

Bacteriological examination of a 12,700 ha area within Jaranman Saryangdo area, located in Jaran bay and Saryangdo island, was conducted with 35 fixed (designated areas and adjacent areas) seawater sampling stations between January 2006 and December 2008. According to results, the geometric mean range and the estimated 90th percentile range of fecal coliform counts in sea water samples collected in the designated area were <1.8-2.4 and <1.8-8.6 MPN/100mL, respectively. The estimated 90th percentile range of fecal coliform counts in sea water samples collected from 6 sampling stations in the adjacent areas were 6.1-34.6 MPN/100mL. Based on these results, bacteriological water quality of the designated areas in the Jaranman. Saryangdo area meet the NSSP (National Shellfish Sanitation Program) guidelines for approved area. The bacteriological sea water quality in Jaranman.Saryangdo area has been shown to be favorable at all investigated sampling stations except for July and August which coincided with heavy rainfall. In fact, the bacteriological water quality was not affected if rainfall was less than 30 mm rainfall. However, the degree of bacteriological contamination increased rapidly and the water quality exceeded approved NSSP guidelines set for rainfall above 60 mm.

• 한국항공우주학회지
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• 제50권11호
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• pp.809-817
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• 2022

무인 로봇과 UAV의 발달로 경로 계획 알고리즘의 필요성이 높아지고 있으며 다양한 환경에서 잘 작동하는 RRT^* 알고리즘이 여러 분야에서 유용하게 활용되고 있다. RRT^* 알고리즘에 다양한 변형을 통해 더 좋은 경로를 생성하기 위한 많은 연구가 진행되고 있으며, 이러한 노력 덕분에 알고리즘의 성능 향상은 거듭되는 중이다. 본 논문은 이러한 연구의 연장선에서 샘플링 범위의 제한을 이용하여 효율적인 경로를 생성하는 방법을 제안한다. 장애물이 있는 환경에서 경로가 장애물에 근접할수록 최적의 경로에 가까워진다는 발상에 근거하여 더 짧은 경로를 얻기 위해 장애물 근처에 노드를 생성한다. 또한 경로가 장애물을 휘감는 경우 변경된 재연결 방법을 통해 빠르게 직선화된 경로를 얻는다. 기존의 알고리즘과 제안하는 방법을 비교 분석하여 성능을 검증하고, 무인항공기의 운동학 모델을 도입하여 생성된 경로를 추적할 수 있음을 확인한다.

• 한국산업융합학회 논문집
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• 제23권5호
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• pp.747-756
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• 2020

In recent years, measurement in a smart-phone environment is attracting attention in various fields due to its easy set-up process, various functions, convenience and expandability. Even in the field of safety evaluation and maintenance of large-scale infra-structures, the appropriate application of these effective and convenient measurement techniques can be of great help. In this paper, an experimental study was conducted to investigate the effectiveness, problems and complementary methods of applying smart-phone accelerometers to the measurement in infra-structure such as bridges. In model bridge subjected to impact and moving loads, the measured accelerations using a smart-phone and a professional accelerometer were directly compared in time domain. And the statistical and frequency characteristics of the measured signal and transfer function were also examined in frequency domain. The results show that the accuracy of measurement using smart-phone sensor is primarily affected by its incomplete sampling performance. In conclusion, smart-phone sensors cannot be considered suitable for precise assessment, where measurements must be accurate over a wide frequency range, but we can say that the technique is still useful and fairly accurate for some purpose over a limited frequency range, such as the low pass frequency range, which is a major concern for civil structures.

• 센서학회지
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• 제19권4호
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• pp.285-290
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• 2010

In this paper, a dynamic range(DR) extension technique based on a 3-transistor active pixel sensor(APS) and dual image sampling is proposed. The feature of the proposed APS is that the APS uses two or more photodiodes with different sensitivities, such as a high-sensitivity photodiode and a low-sensitivity photodiode. Compared with previously proposed wide DR(WDR) APS, the proposed approach has several advantages, such as no-external equipments or signal processing, no-additional time-requirement for additional charge accumulation, simple operation and adjustable DR extension by controlling parasitic capacitance and sensitivity of two photodiodes. Approximately 16 dB of DR extension was evaluated from the simulation for the situation of 10 times of sensitivity difference and the same size of parasitic capacitance between those two photodiodes.

• Korean Journal of Hydrosciences
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• 제4권
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• pp.51-63
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• 1993

This study is to verify the applicability of statistical models in predicting flood frequency at the stage gaging stations of which the flow is under natural condition in the Han River basin. The results of the study show that the statistical flood frequency models were proven to be fairly reasonable to apply in practice, and also were compared with sampling variance to calibrate the statistical efficiency of the estimators of the T year floods Q(T) by two different flood frequency models. As a result, it was showed that for return periods greater than about T = 10 years the annual exceedance series estimators of Q(T) has smaller sampling variance than the annual maximum series estimators. It was showed that for the range of return periods the partial duration series estimators of !(T) has smaller sampling variance than the annual maximum series estimate only if the POT model contains at least 2N(N : record length) items or more in order to estimate Q(T) more efficiently than the ANNMAX model.

• The Journal of the Acoustical Society of Korea
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• 제16권2E호
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• pp.47-54
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• 1997

This paper presents two results on intersymbol interferences in baseband digital communication over an additive white Gaussian noise channel-the interferences due to mismatched square-root raised-cosine filters, in which the filters have different roll-off factors, and / or due to sampling-time jitter. The result for the mismatched filters is that even the jitter-free sampling causes intersymbol interference and it is negligibly small for a wide range of signal-to-noise ratio up to 10dB, for the roll-off factor ranging from 0.2 to 0.5, the mismatch loss being within 0.1dB from the optimum at around 10-6 .For jitter interference an approximation formula for the bit error probability is derived in case of the matched filters, which shows how the roll-off factors and the amount of jitter affect the system performance. The formula is reasonably accurate.

• 한국경영과학회지
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• 제22권4호
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• pp.1-16
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• 1997

The cell loss probability recommended in the B-ISDN is in the range $10^{-8}~10^{-12}$. When a simulation technique is used to analyze the performance of the ATM node, an enormous amount of computer processing time is required. In this study, we derive an importance sampling simulation technique that can be used to evaluate the performance of the ATM node very quickly, that is, the probability that the queue size at the ATM node reaches some large value N. The simulation results show that the backlog probability obtianed by the importance saimpling simulation is very close to that obtained by the ordinary simulation and the computer time can be reduced drastically by the importance sampling simulation.