• Journal of Radiation Protection and Research
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• 제43권1호
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• pp.29-38
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• 2018

Background: Radon contributing about 42% of annual average dose, mainly comes from soil. In this paper, standard measurement procedures for soil radon exhalation rate are suggested and their measurement uncertainties are analyzed. Materials and Methods: We used accumulation method for estimating surface exhalation rate. The closed-loop measurement system was made up with a RAD7 detector and a surface chamber. Radon activity concentrations in the system were observed as a function of time, with data collection of 5 and 15-minute and the measurement time of 4 hours. Linear and exponential fittings were used to obtain radon exhalation rates from observed data. Standard deviations of measurement uncertainties for two approaches were estimated using usual propagation rules. Results and Discussion: The exhalation rates (E) from linear approach, with 30 minutes measurement time were $44.8-48.6mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.14-2.32atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with relative measurement uncertainty of about 10%. The contributions of fitting parameter A, volume (V) and surface (S) to the estimated measurement uncertainty of E were 59.8%, 30.1% and 10.1%, in average respectively. In exponential fitting, at 3-hour measurement we had E ranged of $51.6-69.2mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.46-3.30atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with about 15% relative uncertainty. Fitting with 4-hour measurement resulted E about $51.3-68.2mBq{\cdot}m^{-2} {\cdot}s^{-1}$ or $2.45-3.25atom{\cdot}cm^{-2}{\cdot}s^{-1}$ with 10% relative uncertainty. The uncertainty contributions in exponential approach were 75.1%, 13.4%, 8.7%, and 2.9% for total decay constant k, fitting parameter B, V, and S, respectively. Conclusion: In obtaining exhalation rates, the linear approach is easy to apply, but by saturation feature of radon concentrations, the slope tends to decrease away from the expected slope for extended measurement time. For linear approach, measurement time of 1-hour or less was suggested. For exponential approach, the obtained exhalation rates showed similar values for any measurement time, but measurement time of 3-hour or more was suggested for about 10% relative uncertainty.

• 한국산림과학회지
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• 제100권2호
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• pp.149-153
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• 2011

본 연구는 리기다소나무림의 줄기밀도와 바이오매스 확장계수에 대한 불확실성을 평가하고자 하였다. 총 57본의 표본목을 벌채하였으며, 리기다소나무 20년생 이하의 유령임분과 21년생 이상의 성숙임분을 구분하여 t-검정을 실시한 결과, 줄기밀도는 영급별 차이가 나타나지 않는 반면(p=0.8070), 바이오매스 확장계수는 영급별 차이가 나타났다(p=0.0001). IPCC(Intergovernmental Panel on Climate Change)에서 제시한 불확실성 평가 방법을 이용하여 줄기밀도에 대한 불확실성을 평가한 결과, 20년생 이하에서 30.92%, 21년생 이상에서 25.12%으로 나타났으며, 바이오매스 확장계수에 대한 불확실성은 20년생 이하에서 60.32%, 21년생 이상에서 22.42%으로 나타났다. 줄기밀도의 불확실성은 영급별로 약 5.8%의 차이를 나타낸 반면, 바이오매스 확장계수의 불확실성은 20년생 이하가 21년생 이상 보다 약 37.9%로 매우 높은 것으로 나타났다. 즉, 성숙임분은 불확실성이 상대적으로 작게 나타났으며, 반면에 유령임분은 높게 나타났다. 따라서 줄기밀도와 바이오매스 확장계수를 사용할 경우, 20년생 이하의 영급과 21년생 이상의 영급을 구분하여 줄기밀도와 바이오매스 확장계수를 적용하여야 할 것으로 사료된다.

• 대한원격탐사학회지
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• 제39권3호
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• pp.355-361
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• 2023

지구 표면에 대한 정보는 기상 및 대기 역학의 이해나 인간을 포함한 동물에 큰 영향을 미치는 극한 열현상에 대응함에 있어서 핵심적인 지구 물리량이다. 지구 영역에 대한 온도를 추정하기 위하여 위성에 탑재된 열적외 센서가 널리 활용되어 왔는데, 정밀한 활용을 위해서는 온도 추정 과정의 불확도에 대한 이해가 선행되어야 한다. 하지만 온도추정 불확도에 영향을 미치는 많은 요소 중에서 한반도 주변의 환경 하에서의 온도추정 알고리즘의 불확도 산정에 대한 연구는 미미하였다. 본 연구에서는 한반도 주변의 대기 및 해양 조건하에서 범용성이 높은 single-channel 알고리즘의 불확도를 추정하는 연구를 수행하였다. 알고리즘의 입력자료로 필요한 재분석자료(reanalysis)의 영향성을 평가하기 위하여 두 가지의 재분석자료, 즉 fifth generation of European Centre for Medium-Range Weather Forecasts reanalysis of the global climate and weather (ERA5)와 Modern-Era Retrospective analysis for Research and Applications-2 (MERRA-2)를 사용하였고, 복사전달모델은 MODerate resolution atmospheric TRANsmission (MODTRAN)을 사용하였다. MODTRAN 모의와 온도 추정 정확도 검증에 사용되는 현장 관측 수온은 한반도 인근 해역에 위치한 해양 기상 부이(buoy)로부터 획득했다. 실험 결과, 알고리즘 불확도는 대기 수증기량에 따라서 선형에 가깝게 증가하는 것을 확인하였고, 가장 건조한 조건에서는 약 0.35K 그리고 평균적으로 0.45K 가량의 불확도가 발생함을 확인하였다. 이러한 결과는 재분석자료의 종류에 상관없이 유사하게 도출되어 알고리즘이 가지는 순수한 불확도라고 추정할 수 있었다.

• 한국수자원학회논문집
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• 제56권1호
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• pp.35-43
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• 2023

미래 유량분석은 기후변화 시나리오와 수문모형의 매개변수에 영향을 받고 이에 따른 불확실성이 존재한다. 본 연구에서는 Shared Socioeconomic Pathway (SSP) 시나리오와 수문모형 매개변수에 따른 미래 유량 분석의 불확실성을 분석하고자 하였다. SSP 시나리오 중, 대표적으로 사용되는 SSP2-4.5와 SSP5-8.5시나리오를 사용하였으며, 수문모형으로는 Soil and Water Assessment Tool (SWAT) 모형을 사용하였다. SWAT 모형의 매개변수는 SWAT-CUP을 이용해 관측된 유량 데이터에 따라 총 11개의 기간에 대해 매개변수 최적화를 각각 수행하였다. 그 후 분포의 차이를 계산 할 수 있는 Jensen-Shannon Divergence (JS-D)를 이용해 과거 유량 대비 미래 추정된 유량의 불확실성 분석을 수행하였다. 분석결과 미래 유량의 불확실성은 SSP5-8.5에서 SSP2-4.5보다 더 크게 분석되었으며, 가까운 미래(2021-2060년) 보다 먼 미래(2061-2100년)에서 더 크게 분석되었다. 강우-유출 분석은 수문모형 매개변수에 따라 88.5%-108.5%까지 차이가 발생하였으며, 이에 따라 미래 유량을 추정하는데 불확실성이 발생하였다. 본 연구에서의 수문 모형의 매개변수에 따른 미래 유량 추정의 불확실성은 평년 대비 유량이 적은 연도의 관측 유량 데이터를 이용한 매개변수를 이용할 시 불확실성이 크게 분석되었다. 또한 평년 대비 유량 변화가 큰 기간의 매개 변수일수록 미래 유량 추정의 불확실성이 크게 분석되었다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 1999년도 춘계공동학술대회:정보화시대의 지식경영
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• pp.426-426
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• 1999

;There are many sources of uncertainty in a typical production and inventory system. There is uncertainty as to how many items customers will demand during the next day, week, month, or year. There is uncertainty about delivery times of the product. Uncertainty exacts a toll from management in a variety of ways. A spurt in a demand or a delay in production may lead to stockouts, with the potential for lost revenue and customer dissatisfaction. Firms typically hold inventory to provide protection against uncertainty. A cushion of inventory on hand allows management to face unexpected demands or delays in delivery with a reduced chance of incurring a stockout. The proposed strategies are used for the design of a probabilistic inventory system. In the traditional approach to the design of an inventory system, the goal is to find the best setting of various inventory control policy parameters such as the re-order level, review period, order quantity, etc. which would minimize the total inventory cost. The goals of the analysis need to be defined, so that robustness becomes an important design criterion. Moreover, one has to conceptualize and identify appropriate noise variables. There are two main goals for the inventory policy design. One is to minimize the average inventory cost and the stockouts. The other is to the variability for the average inventory cost and the stockouts The total average inventory cost is the sum of three components: the ordering cost, the holding cost, and the shortage costs. The shortage costs include the cost of the lost sales, cost of loss of goodwill, cost of customer dissatisfaction, etc. The noise factors for this design problem are identified to be: the mean demand rate and the mean lead time. Both the demand and the lead time are assumed to be normal random variables. Thus robustness for this inventory system is interpreted as insensitivity of the average inventory cost and the stockout to uncontrollable fluctuations in the mean demand rate and mean lead time. To make this inventory system for robustness, the concept of utility theory will be used. Utility theory is an analytical method for making a decision concerning an action to take, given a set of multiple criteria upon which the decision is to be based. Utility theory is appropriate for design having different scale such as demand rate and lead time since utility theory represents different scale across decision making attributes with zero to one ranks, higher preference modeled with a higher rank. Using utility theory, three design strategies, such as distance strategy, response strategy, and priority-based strategy. for the robust inventory system will be developed.loped.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권5호
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• pp.1131-1145
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• 2013

Energy detection is a widely used method for spectrum sensing in cognitive radios due to its simplicity and accuracy. However, it is severely affected by the noise uncertainty. To solve this problem, a blind multiband spectrum sensing scheme which is robust to noise uncertainty is proposed in this paper. The proposed scheme performs spectrum sensing over the total frequency channels simultaneously rather than a single channel each time. To improve the detection performance, the proposal jointly utilizes the likelihood function combined with Gerschgorin radii of unitary transformed covariance matrix. Unlike the conventional sensing methods, our scheme does not need any prior knowledge of noise power or PU signals, and thus is suitable for blind spectrum sensing. In addition, no subjective decision threshold setting is required in our scheme, making it robust to noise uncertainty. Finally, numerical results based on the probability of detection and false alarm versus SNR or the number of samples are presented to validate the performance of the proposed scheme.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1438-1441
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• 2005

To establish of standard technique of nano-length measurement in 2D plane, new AFM system has been designed. In this system, measurement uncertainty is dominantly affected by the Abbe error of XY scanning stage. No linear stage is perfectly straight; in other words, every scanning stage is subject to tilting, pitch and yaw motion. In this paper, an AFM system with minimum offset of XY sensing is designed. And XY scanning stage is designed to minimize rotation angle because Abbe errors occur through the multiply of offset and rotation angle. To minimize the rotation angle optimal design has performed by maximizing the stiffness ratio of motion direction to the parasitic motion direction of each stage. This paper describes the design scheme of full AFM system, especially about XY stage. Full range of fabricated XY scanner is $100um\times{100um}$. And tilting, pitch and yaw motion are measured by autocollimator to evaluate the performance of XY stage. Using this AFM system, 3um pitch specimen was measured. As a result, the uncertainty of total system has been evaluated.

• 한국전자파학회논문지
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• 제17권4호
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• pp.387-392
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• 2006

K-대역에서 동작하는 3.5 mm 동축형 감쇠량 표준기를 개발하고 그 측정 불확도를 평가하였다. 전력비 전달방식의 4개의 모듈로 구성된 이 표준기는 18 GHz부터 26.5 GHz까지의 광대역에서 동작하며 각 모듈은 약 20 dB의 감쇠량을 가진다. 측정 가능한 최대 감쇠량은 80 dB이고 이때의 확장 불확도는 약 95% 신뢰수준에서 0.01 dB이다.

• Journal of Communications and Networks
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• 제18권2호
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• pp.173-181
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• 2016

In this paper, we address a new robust optimization problem in a multiuser multiple-input single-output broadcasting system with simultaneous wireless information and power transmission, where a multi-antenna base station (BS) sends energy and information simultaneously to multiple users equipped with a single antenna. Assuming that perfect channel-state information (CSI) for all channels is not available at the BS, the uncertainty of the CSI is modeled by an Euclidean ball-shaped uncertainty set. To optimally design transmit beamforming weights and receive power splitting, an average total transmit power minimization problem is investigated subject to the individual harvested power constraint and the received signal-to-interference-plus-noise ratio constraint at each user. Due to the channel uncertainty, the original problem becomes a homogeneous quadratically constrained quadratic problem, which is NP-hard. The original design problem is reformulated to a relaxed semidefinite program, and then two different approaches based on convex programming are proposed, which can be solved efficiently by the interior point algorithm. Numerical results are provided to validate the robustness of the proposed algorithms.

• 한국항공운항학회지
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• 제14권3호
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• pp.1-6
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• 2006

The altitude engine test is a sort of engine performance tests carried out to measure the performance of a engine at the simulated altitude and flight speed environments prior to that at the flight test. During the performance test of a engine, various values such as pressures and temperatures at different positions, air flow rate, fuel flow rate, and the load by thrust are measured. These measured values are used to derive the representative performance values such as the net thrust and the specific fuel consumption through a momentum equation. Hence each of the measured values has certain effects on the total uncertainty of the performance values. In this paper, the combined standard uncertainties of the performance variables at the engine test were estimated by the uncertainty analysis of the measurement values and the repeatability and reproducibility of the altitude test measurement were assessed by the analysis of variation on the repeated test data with different operator groups.