• 터널과지하공간
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• 제31권5호
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• pp.360-373
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• 2021

지반공학 분석에는 재료정수의 샘플링 및 실험기술에 이르기까지 많은 불확실성의 원인이 존재한다. 암반사면의 평면파괴에 대한 기존의 결정론적 안정성 분석은 안전율은 계산하지만, 파괴확률이나 신뢰지수를 고려하지 않는다. 기존의 사면안정해석에서는 지반의 불확실성을 전체적 안전율로 평가하여 현실적인 암반사면의 안정성을 자세히 평가하기가 힘들다. 본 논문에서는 암석사면의 평면파괴에 적용되는 MCS, FOSM, PEM, Taylor Series와 같은 기존의 확률론적 분석기법을 자세히 검토한다. 몬테카를로 방법(MCS)은 가장 정확한 확률론적 안전율을 계산한다. 그러나 이 방법은 시간이 많이 걸리는 문제가 발생되므로 간이 확률론적 방법은 MCS에 대한 대안이 될 수 있다. 이 연구에서는 간이 확률론적 방법을 사용하여 암반사면의 평면파괴에 대한 확률분석을 제시하였다.

• Journal of Ecology and Environment
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• 제41권2호
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• pp.34-44
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• 2017

Background: Monitoring terrestrial vegetation cover condition is important to evaluate its current condition and to identify potential vulnerabilities. Due to simplicity and low cost, point intercept method has been widely used in evaluating grassland surface and quantifying cover conditions. Field-based digital photography method is gaining popularity for the purpose of cover estimate, as it can reduce field time and enable additional analysis in the future. However, the caveats and uncertainty among field-based vegetation cover estimation methods is not well known, especially across a wide range of cover conditions. We compared cover estimates from point intercept and digital photography methods with varying sampling intensities (25, 49, and 100 points within an image), across 61 transects in typical steppe, forest steppe, and desert steppe in central Mongolia. We classified three photosynthetic groups of cover important to grassland ecosystem functioning: photosynthetic vegetation, non-photosynthetic vegetation, and bare soil. We also acquired normalized difference vegetation index from satellite image comparison with the field-based cover. Results: Photosynthetic vegetation estimates by point intercept method were correlated with normalized difference vegetation index, with improvement when non-photosynthetic vegetation was combined. For digital photography method, photosynthetic and non-photosynthetic vegetation estimates showed no correlation with normalized difference vegetation index, but combining of both showed moderate and significant correlation, which slightly increased with greater sampling intensity. Conclusions: Results imply that varying greenness is playing an important role in classification accuracy confusion. We suggest adopting measures to reduce observer bias and better distinguishing greenness levels in combination with multispectral indices to improve estimates on dry matter.

• Nuclear Engineering and Technology
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• 제19권2호
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• pp.85-98
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• 1987

중대사고시 LMFBR의 에어로졸(aerosol) 동특성을 살피기 위해 전산코드인 MCAD (Multicomponent Aerosol Dynamics)가 개발되었다. 사고경과에 따른 두 방사능원의 상대적인 충돌확률을 적용하여 에어로졸계를 모사할 수 있다. Brownian 확산과 중력작용에 의한 결합 및 제거과정을 고려했으며, 입자형태를 묘사하기 위해 밀도보정과 형태요소(shape factor)를 동시에 고려하였다. ORNL의 NSPP-300 계열 실험자료와 기존의 코드를MCAD의 입증에 이용하였다. 그 결과 MCAD의 계산치와 실험치 및 기존의 코드 계산값이 일치함을 보여준다. 여러 입력자료의 불화실한 값들을 정의하고, 그들값의 한계로 설정하기 위하여 불확실성 및 민감도해석을 수행하였다. 14개의 입력자료를 선택하여 실험계획법과 Latin hypercube sampling에 의한 입력자료를 조합하여 그 회귀 (regression) 정도를 반응표면 계획법(Response surface method)에 의해 구하였다. 각 변수들의 중요성 및 시간경과에 따른 그들의 상대적인 등위를 결정하기 위하여 단계식 회귀방법 (Stepwise regression method)을 고려했다. LHS에 의한 회귀모형에 Monte Carlo Method를 적용하여 계산값 및 변수들에의 신뢰도를 향상시켰다.

• 환경영향평가
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• 제20권6호
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• pp.879-890
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• 2011

The GOSAT (Greenhouse gases Observing SATellite) data provide new opportunities the most regionally complete and up-to-date assessment of $CO_2$. However, in practice, GOSAT records often suffer from missing data values mainly due to unfavorable meteorological condition in specific time periods of data acquisition. The aim of this research was to identify optimal spatial interpolation techniques to ensure the continuity of $CO_2$ from samples taken in the North East Asia. The accuracy among ordinary kriging (OK), universal kriging (UK) and simple kriging (SK) was compared based on the combined consideration of $R^2$ values, Root Mean Square Error (RMSE), Mean Error (ME) for variogram models. Cross validation for 1312 random sampling points indicate that the (UK) kriging is the best geostatistical method for spatial predictions of $CO_2$ in the East Asia region. The results from this study can be useful for selecting optimal kriging algorithm to produce $CO_2$ map of various landscapes. Also, data users may benefit from a statistical approach that would allow them to better understand the uncertainty and limitations of the GOSAT sample data.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1615-1625
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• 2013

Modelling and simulating the wind power intermittent behaviour are the basis of the planning and scheduling studies concerning wind power integration. The wind power outputs are evidently correlated in space and time and bring challenges in characterizing their behaviour. This paper provides a methodology to model and simulate the clustered wind power considering its spatio-temporal correlations using the theory of copula. The sampling approach captures the complex spatio-temporal connections among the wind farms by employing a conditional density function calculated using multidimensional copula function. The empirical study of real wind power measurement shows how the wind power outputs are correlated and how these correlations affect the overall uncertainty of clustered wind power output. The case study validates the simulation technique by comparing the simulated results with the real measurements.

• 경영과정보연구
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• 제6권
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• pp.267-290
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• 2001

Today's firms are experiencing severe competition and lots of change under uncertainty of the future. In order to survive in rapidly changing environment, companies have steadily adopted information technology(IT) environment. The advancement of information technology allows people to access information and knowledge resources without the limitation of time and location through internet. Many organizations have developed their own information systems not only for internal efficiency but also for effectiveness of external customer services. This study is intended to provide a theoretical framework of information and knowledge and their relationship, that the infusion of powerful information networks into business environments is beginning to have a profound a significant difference of the nature between information satisfaction and accounting information system(AIS) in the business activity. This paper is to maximize the efficiency of university libraries human resources management by determining the followings the relationship between the level of information technology implement and the job satisfaction of the librarian, the main factors that affect job satisfaction. Questionnaire was sent to 120 companies from 20 corporations chosen by random sampling and the methods of ANOVA, T-test, and correlation analysis were used. The results of the analysis are as follows; 1) There is a unsignificant difference in the level of information satisfaction by accounting information system and the motivation factor according to the level of implementation of IT. 2) There is a relatively high in a significant difference in information satisfaction by the level of net income. 3) There is high a significant difference is shown in the accounting years while implementing the IT and information satisfaction.

• 대한환경공학회지
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• 제38권1호
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• pp.42-46
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• 2016

환경에 존재하는 인공방사성핵종 중 방사성요오드($^{131}I$)는 주로 갑상선질환의 치료에 사용되며 환자의 배출과정을 통해 체외로 방출된다. 붕괴가 채 끝나지 않은 $^{131}I$는 환경으로 방출되어 공공수역에서 검출될 수 있다. 본 연구는 공공수역에서 검출된 $^{131}I$ 방사능 결과의 정확도 및 신뢰도에 영향을 미치는 불확도 중 계측 과정에서 발생하는 불확도에 대하여 금강수계의 실제 사례를 조사하였다. 시료는 금강권역 삽교천 수계의 하천수 및 그 상류의 하수처리장 방류수를 대상으로 하였으며, 시료량에 따른 불확도를 확인하기 위하여 각 지점의 시료를 1, 10, 20 L로 채수하였다. 채취한 시료는 시료량에 따라 전 처리를 거친 후 1 L 마리넬리 비커에 충전하여 HPGe (High Purity Germanium) 감마선 검출기를 이용하여 10,000초 단위로 계측 분석하여 계측시간 및 방사능에 따른 측정불확도를 비교하였다. 각 지점의 방사능 농도는 0.03~1.8 Bq/L로, 채취시점에 따라 차이가 있는 것으로 나타났다. $^{131}I$의 방사능 농도가 0.3 Bq/L 수준인 경우 시료량이 1 L이면 약 80,000초 계측 시까지 핵종의 존재여부를 판단하지 못하는 경우가 발생하였으나, 같은 조건에서 시료량을 증가시켜 계측한 경우 10,000초 이상의 계측시간부터 불확도 10% 범위에 포함되는 것으로 나타났다. $^{131}I$의 짧은 반감기를 고려하여 즉시 계측이 가능한 1 L 생시료 계측 방법을 사용할 수 있으나, 불확도 수준과 전처리 및 계측에 소요되는 시간을 비교하였을 때, 10 L 시료의 계측을 통해 높은 신뢰도의 측정 결과를 얻을 수 있는 합리적인 방법이라고 판단되었다.

• 환경영향평가
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• 제22권1호
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• pp.89-97
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• 2013

RADCONS Ver. 1.0 (RADiological CONSequence Assessment Program) was developed for radiological risk assessment in this study. A Gaussian plume model was used to analyze the fate and transport of radionuclides released into the air in case of accidents. Both single meterological data and time series meterological data can be used in RADCONS. To assess the radiological risk of the early phase after an accident, ED (Effective Dose) estimated by both deterministic and probabilistic approaches are presented. These EDs by deterministic and probabilistic will be helpful to efficient decision making for decision makers. External doses from deposited materials by time are presented for quantifying the effects of mid and late phases of an accident. A radiological risk assessment was conducted using RADCONS for an accident scenario of 1 Ci of Cs-137. The maximum of ED for radii of 1,000 meters from the accident point was 8.51E-4 mSv. After Monte-Carlo simulation, considering the uncertainty of the breathing rate and dispersion parameters, the average ED was 8.49E-4, and the 95 percentile was 1.10E-3. A data base of the dose coefficients and a sampling module of the meteorological data will be modified to improve the user's convenience in the next version.

• 디지털콘텐츠학회 논문지
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• 제11권4호
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• pp.597-606
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• 2010

본 논문에서는 증강현실 환경에서 보다 강건한 카메라 정보 추정을 위한 입자필터 기반의 카메라 추적 기법에 대해서 설명한다. 실시간 카메라 추적을 위해서는 일반적으로 칼만 필터, 또는 확장 칼만 필터 등이 많이 이용되지만, 카메라의 급격한 흔들림 및 장면의 가려짐 등과 같은 불안정한 조건에서는 정상적인 카메라 추적이 매우 힘들다는 단점이 있다. 본 논문에서 제안하는 입자필터링 기법은 시스템 상태에 대한 측정 표본입자의 가중치를 별도의 가중치 계산과정을 이용하지 않고 가우스 분포를 기반으로 계산하였으며, 카메라 입자를 수렴시키기 위한 별도의 처리과정을 거치지 않고 시스템의 실제 불확실도에 근사화되도록 재표본화된 표본입자 집합을 이용하여 카메라 상태의 추정을 수행하였다. 또한 제안된 방법은 보다 많은 수의 표본 입자를 이용하는 환경에서도 실시간 처리가 가능한 장점이 있다. 실험을 통하여 다양한 환경 하에서 제안된 방법의 효율성과 정확성을 확인하였다.

• 전기학회논문지
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• 제66권2호
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• pp.328-338
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• 2017

In this paper, a zero torque control scheme adopting current sharing function (CSF) used in integrated Switched Reluctance Motor (SRM) drive with DC battery charger is proposed. The proposed control scheme is able to achieve the keeping position (KP), zero torque (ZT) and power factor correction (PFC) at the same time with a simple novel current sharing function algorithm. The proposed CSF makes the proper reference for each phase windings of SRM to satisfy the total charging current of the battery with zero torque output to hold still position with power factor correction, and the copper loss minimization during of battery charging is also achieved during this process. Based on these, CSFs can be used without any recalculation of the optimal current at every sampling time. In this proposed integrated battery charger system, the cost effective, volume and weight reduction and power enlargement is realized by function multiplexing of the motor winding and asymmetric SR converter. By using the phase winding as large inductors for charging process, and taking the asymmetric SR converter as an interleaved converter with boost mode operation, the EV can be charged effectively and successfully with minimum integral system. In this integral system, there is a position sliding mode controller used to overcome any uncertainty such as mutual inductance or DC offset current sensor. Power factor correction and voltage adaption are obtained with three-phase buck type converter (or current source rectifier) that is cascaded with conventional SRM, one for wide input and output voltage range. The practicability is validated by the simulation and experimental results by using a laboratory 3-hp SRM setup based on TI TMS320F28335 platform.