• 한국신뢰성학회지:신뢰성응용연구
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• 제18권2호
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• pp.122-129
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• 2018

Purpose: This article develops an optimal reliability acceptance sampling plan for the case where the degradation quantity of the performance characteristic follows Weibull distribution. Method: For developing reliability acceptance sampling plans, the sample size and the acceptance constant are determined based on the accelerated characteristic of the test condition and the product. Results: The sample size and the acceptance constant are provided such that the constraints of the producer and the consumer risks are satisfied. Conclusion: Reliability acceptance sampling plans based on the accelerated degradation test method can be used for the quality control within a resonable amount of cost and time. In this article. an optimal reliability sampling plans are newly developed for this purpose.

• 한국융합학회논문지
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• 제11권11호
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• pp.89-94
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• 2020

자기공명영상 고주파를 차단할 수 있는 금속물질 중 자장에 영향을 받지 않으며 가격이 저렴하고 주위에서 쉽게 구할 수 있는 알루미늄 호일을 이용하여 차폐체를 제작하였다. Phantom 실험 결과 over-sampling 기법을 적용한 경우 적용 전보다 aliasing artifact가 약 94% 감소하였고, 알루미늄 차폐체를 적용한 경우도 적용 전 보다 약 92% 감소하였다. 그리고 scan time도 over-sampling 기법의 경우 적용 전보다 약 3배이상 증가한 반면, 알루미늄 차폐체의 경우는 적용 전과 변화가 없는 것으로 나타났다. 따라서 알루미늄 호일을 이용한 차폐체도 기존의 흡수재 및 차폐체들과 마찬가지로 scan time의 증가 없이 aliasing artifact를 효율적으로 제거할 수 있는 것을 확인하였다.

• 한국환경보건학회지
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• 제38권4호
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• pp.360-368
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• 2012

Objective: This study was carried out to use pine needles as a passive air sampler (PAS) of atmospheric Polychlorinated Biphenyls (PCBs). Methods: PCB concentrations in ambient air ($C_a$, ng/$m^3$) and deposited on pine needles ($C_p$, ng/g dry) were analyzed simultaneously from June 1 to December 31. Air samples were taken using a low volume PUF active air sampler and the overall average air volume was about 900-1,000 $m^3$. Pine needles were collected at the end of August and December near the air sampler. Results: $C_a$ were higher at higher air temperature and lower chlorinated PCB congeners, but $C_p$ showed irregular distribution. The average PCB sampling rates from air to pine needles were 0.116 (0.002-0.389) $m^3$/day - g dry. Conclusions: A poor correlation was shown between $C_a$ and $C_p$. However, a good correlation was shown between the logarithm of octanol-air partitioning coefficient ($logK_{oa}$) and log ($C_p/C_a$), and the interrelation was better with longer sampling time (June to December) than shorter sampling time (June to August). The average PCB sampling rates from air to pine needles were the lowest with respect to PUF disk, XAD-2 resin and semipermeable membrane devices (SPMDs) PAS. The average ratio ($C_{a-calc}/C_{a-meas}$) of calculated ($C_{a-calc}$) and measured ($C_{a-meas}$) PCB concentration was 0.69 with a shorter sampling time and 1.24 with a longer, so $C_{a-calc}$ was close to $C_{a-meas}$. It was found that pine needles can be used as PAS of atmospheric PCBs, and are especially suitable for long-time PAS.

• Journal of Preventive Medicine and Public Health
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• 제43권4호
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• pp.301-308
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• 2010

Objectives: In most DEHP exposure assessment studies, single spot urine sample was used. It could not compare the exposure level among studies. Therefore, we are going to represent the necessity of selection of proper sampling time of spot urine for assessing the environmental DEHP exposure, and the association urinary DEHP metabolites with steroid hormones. Methods: We collected urine and plasma from 25 men. The urine sampling times were at the end of the shift (post-shift) and the next morning before the beginning of the shift (pre-shift). Three metabolites of DEHP {mono(2-ethylhexyl) phthalate [MEHP], mono-(2-ethyl-5-hydroxyhexyl)phthalate [MEHHP], and mono(2-ethyl-5-oxohexyl)phthalate [MEOHP]} in urine were analyzed by HPLC/MS/MS. Plasma luteinzing hormone, follicle stimulating hormone, testosterone, and $17{\beta}$- estradiol were measured at pre-shift using a ELISA kit. A log-transformed creatinine-adjusted urinary MEHP, MEHHP, and MEOHP concentration were compared between the post- and pre-shift. The Pearson’s correlation was calculated to assess the relationships between log-transformed urinary MEHP concentrations in pre-shift urine and hormone levels. Results: The three urinary metabolite concentrations at post-shift were significantly higher than the concentrations in the pre-shift (p<0.0001). The plasma hormones were not significantly correlated with log-transformed creatinine - adjusted DEHP metabolites. Conclusions: To assess the environmental DEHP exposure, it is necessary to select the urine sampling time according to the study object. There were no correlation between the concentration of urinary DEHP metabolites and serum hormone levels.

• 대한기계학회논문집A
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• 제24권10호
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• pp.2597-2602
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• 2000

The most effective means of evaluating remaining life is through the creep testing of samples removed from the component. But sampling of large specimen from in-service component is actually impossible. So, sampling device and small-specimen creep tester have been applied. Sampling device has been devised to extract mechanically small samples by hemispherical, diamond -coated cutter from the surface of turbine rotor bores and thick-walled pipes without subsequent weld repairs requiring post weld heat treatment. A method of manufacturing small creep specimen, 2min gage diameter and 10min gage length, using electron beam welding to attach grip section, has been proven. Small-specimen creep tester has been designed to control atmosphere to prevent stress increment by oxidation during experiment. To determine whether the small specimens successfully reproduce the behavior of large specimens, creep rupture tests for small and large specimens have been performed at identical conditions. Creep rupture times based on small specimens have closely agreed within 5% error compared with that of large specimen. The errors in rupture time have decreased at longer test period. This comparison validates the procedure for fabricating and testing on small specimen. This technique offers potential as an efficient method for remaining life assessment by direct sampling from in -service high temperature components.

• 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.

• Smart Structures and Systems
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• 제17권4호
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• pp.647-667
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• 2016

In this paper, dynamic displacement is estimated with high accuracy by blending high-sampling rate acceleration data with low-sampling rate displacement measurement using a two-stage Kalman estimator. In Stage 1, the two-stage Kalman estimator first approximates dynamic displacement. Then, the estimator in Stage 2 estimates a bias with high accuracy and refines the displacement estimate from Stage 1. In the previous Kalman filter based displacement techniques, the estimation accuracy can deteriorate due to (1) the discontinuities produced when the estimate is adjusted by displacement measurement and (2) slow convergence at the beginning of estimation. To resolve these drawbacks, the previous techniques adopt smoothing techniques, which involve additional future measurements in the estimation. However, the smoothing techniques require more computational time and resources and hamper real-time estimation. The proposed technique addresses the drawbacks of the previous techniques without smoothing. The performance of the proposed technique is verified under various dynamic loading, sampling rate and noise level conditions via a series of numerical simulations and experiments. Its performance is also compared with those of the existing Kalman filter based techniques.

• 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.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.680-687
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• 2018

시추공 레이다는 지하자원 및 지질탐사 목적으로 사용되는 레이다로서 수 ns의 펄스폭을 갖는 전자파를 송신하고 탐사 대상으로부터 반사되어 입력되는 수십에서 수백MHz의 반사파를 수신하기 위하여 고속 샘플러가 반드시 필요하다. 수십MHz의 샘플링 클럭 주파수로도 수GHz급의 샘플링 성능을 낼 수 있는 ETS(Equivalent-Time Sampling)는 시추공 레이다용 수신기의 샘플러로 사용이 적합하다. ETS 샘플러 설계에 있어 가장 중요한 요소인 샘플링 클럭 지연을 제어하는 방법으로 본 연구에서는 하나의 클럭 소스에 대해 각 $90^{\circ}$씩 위상 차이를 가지는 4개의 클럭을 이용한 방법을 제시하였다. 제안하는 방법은 기존의 지연 발생기를 이용하는 방법보다 설정한 구간 내에서 데이터를 획득하는 시간이 1/23로 단축 가능하다. 구현된 샘플러를 기존 시추공 레이다의 수신기에 적용하면 단축된 샘플링 시간으로 인해 추가로 64회 누적이 가능해져 지하 터널 탐사를 위한 수신신호 품질 개선 효과를 얻을 수 있다. 또한, 목표 샘플링 범위를 만족하기 위해서 여러 개의 샘플링 클럭 지연제어 로직을 사용하는 기존 방식에 비하여 하나의 지연제어 로직을 사용함으로써 그간 반드시 필요하였던 보정 과정의 생략이 가능하다. 그 결과 시스템의 구조를 단순화할 수 있었으며 균일한 샘플러의 구현이 가능하였다.

• Asian-Australasian Journal of Animal Sciences
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• 제14권12호
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• pp.1683-1689
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• 2001

The levels of urea nitrogen both in blood (BUN) and milk (MUN), and milk protein (MP) reflect protein and energy intake in dairy herd feeding. Blood and milk constituents may be changes rhythmically and influence by different sampling time within a day and after feeding. Trials were conducted using five dietary treatments in both lactating and dry cows to study the effects of sampling time on concentrations of BUN, MUN and whole blood ammonia nitrogen (BAN) in practical dairy cow feeding in Taiwan. The conventional feed ingredients and forages including corn silage, alfalfa hay, timothy or pangola hay and corn grain were used as major source of the diet to follow practical dairy cow feeding. Five different diets were varying in amounts (low=L; standard=S; high=H) of crude protein (P) and energy (E) according to the NRC (1989). The energy to protein ratios in kcal/kg for the PSES, PLES, PHES, PSEH and PSEL were 10.82, 12.54, 9.41, 12.53 and 9.13 in lactating cows, and 11.38, 13.33, 9.78, 13.28 and 9.74 in dry cows, respectively. Results showed that after feeding at 9:30, BUN reached peak at 13:30 and was significantly higher than those to that sampled at 14:30 to 18:30 (p<0.05) in dry cows. Therefore the best blood sampling time for urea nitrogen assay in dry cows is 4 hours after morning feeding. In lactating cows, BUN of 13:30 was significantly higher than those of 8:30 to 11:30 (p<0.05), but there were no significant difference between the BUN values of other sampling time. Hence the suitable blood sampling time for BUN value in lactating cows was located on 3 to 8 hours after morning feeding, but the best time was 4 hours after morning feeding. MUN content is significantly higher in the afternoon collected bulk milk than the fore-strip morning milk (p<0.05), therefore the best sampling time for MUN is from afternoon collected bulk milk. Diurnal BAN changed without traceable rhythmic pattern and was negatively correlated to the BUN (r = -0.78). It is suggested that BAN may not be a good indicator for monitoring dairy cow feeding.