• 제목/요약/키워드: Threshold condition

검색결과 490건 처리시간 0.022초

순서기반 비정상행위 탐지 센서의 임계치 결정 방법 (The Decision Method of A Threshold in Sequence-based Anomaly Detection Sensor)

  • 김용민;김민수;김홍근;노봉남
    • 정보처리학회논문지C
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    • 제8C권5호
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    • pp.507-516
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    • 2001
  • 본 논문은 SOM과 HMM을 이용하여 시스템 호출 수준에서 순서기반의 비정상행위 탐지 센서를 구현하였다. 그리고, 시스템 호출에서 중요한 정보가 무엇이고 임계값은 어떻게 설정해야하는 지를 분석하였다. 본 논문에서 사용한 SOM의 새로운 필터링 규칙과 축약 규칙은 HMM의 입력 크기를 줄일 수 있었다. 이러한 축약은 HMM기반 비정상행위 탐지의 실시간 처리능력을 보장해 준다. 또한, 비정상행위 수라는 개념을 도입하여 HMM의 탐지결과에 대한 민감성을 둔화시켜서, 사용자가 탐지결과를 쉽게 이해하고 false-positive를 줄이는 효과가 있었다. 그리고, 능동적으로 threshold 값을 조정하여 시스템 상황에 따라 탐지센서가 적응할 수 있도록 하였다.

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SIMULATION OF HIGH BURNUP STRUCTURE IN UO2 USING POTTS MODEL

  • Oh, Jae-Yong;Koo, Yang-Hyun;Lee, Byung-Ho
    • Nuclear Engineering and Technology
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    • 제41권8호
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    • pp.1109-1114
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    • 2009
  • The evolution of a high burnup structure (HBS) in a light water reactor (LWR) $UO_2$ fuel was simulated using the Potts model. A simulation system for the Potts model was defined as a two-dimensional triangular lattice, for which the stored energy was calculated from both the irradiation damage of the $UO_2$ matrix and the formation of a grain boundary in the newly recrystallized small HBS grains. In the simulation, the evolution probability of the HBS is calculated by the system energy difference between before and after the Monte Carlo simulation step. The simulated local threshold burnup for the HBS formation was 62 MWd/kgU, consistent with the observed threshold burnup range of 60-80 MWd/kgU. The simulation revealed that the HBS was heterogeneously nucleated on the intergranular bubbles in the proximity of the threshold burnup and then additionally on the intragranular bubbles for a burnup above 86 MWd/kgU. In addition, the simulation carried out under a condition of no bubbles indicated that the bubbles played an important role in lowering the threshold burnup for the HBS formation, thereby enabling the HBS to be observed in the burnup range of conventional high burnup fuels.

설마천 연구지역에서의 토양수분량을 활용한 유출 발생 특성분석 (An analysis of runoff characteristic by using soil moisture in Sulma basin)

  • 김기영;이용준;정성원;이연길
    • 한국수자원학회논문집
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    • 제52권9호
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    • pp.615-626
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    • 2019
  • 토양수분과 유출은 매우 밀접한 관계를 가지고 있으며, 특히 토양 내의 여러 요소들에 의해 토양의 수분보유능력과 배수의 특성이 결정된다. 본 연구에서는 2016년, 2017년 설마천 유역에서 총 40개의 사상을 분리하였다. 선정한 사상별로 constant-K 방법을 적용하여 직접유출과 기저유출을 분리하고 유출계수를 산정하였다. 산정된 유출계수는 선행토양함수와 지수함수 형태의 증가를 보였다. 또한 유출계수가 급증하기 시작하는 토양수분의 임계값을 선정하였으며, 이 값은 유출과 지하수면과의 큰 상관관계를 나타내었다. 선행토양함수뿐만 아니라 초기 토양수분, 토양 저류량, 강우량 등 여러 인자들도 유출 결과에 영향을 미치는 것으로 분석되었다. 또한 선행토양수분의 임계값에 따라 강우사상을 건조, 습윤 상태로 분리하여 시작 반응과 첨두 반응을 분석해 보았으며, 습윤 상태에서의 반응이 건조 상태에서 보다 빠르게 발생하였다. 건조 상태에 속하는 대부분의 사상에서는 토양수분이 정점에 도달한 후 지하수면과 유출량 순으로 정점에 도달하는 첨두 반응이 일어났으나 습윤 상태에서는 반대로 지하수면과 유출량이 토양수분보다 먼저 정점에 도달하였다. 본 연구의 결과는 유출에 기여하는 인자들 사이의 상호작용을 확인하고 토양의 다양한 조건과 유출 사이의 관계를 규명하는 데에 크게 기여할 것으로 판단된다.

장시간 스트레스 조건에서 submicron MOSFET의 열전자 트래핑에 의한 노화현상에 대한 연구 (A study on the degradation by the hot carrier trapping of the submicron MOSFET with long stress condition)

  • 홍순석
    • E2M - 전기 전자와 첨단 소재
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    • 제8권3호
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    • pp.357-361
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    • 1995
  • An experiment on characteristics of nMOSFET's in the long stress condition with the maximum of the substrate current has been carried out in order to study on the degradation due to the hot-carrier effect. Based on the measured result of the threshold voltage, the damage is mostly due to the hole injection into the oxide. After long stress, it was shown that the drain current increased at low gate voltages and hence decreased at high gate voltages.

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Orofacial Thermal Quantitative Sensory Testing (QST): A Study of Healthy Korean Women and Sex Difference

  • Ahn, Sung-Woo;Kim, Ki-Suk
    • Journal of Oral Medicine and Pain
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    • 제40권3호
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    • pp.96-101
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    • 2015
  • Purpose: Thermal sensory test as an essential part of quantitative sensory testing (QST) has been recognized as a useful tool in the evaluation of the trigeminal nerve function. Normative data in the orofacial region have been reported but the data on differences in the test site, sex and ethnicity are still insufficient. Thus, this study aimed to investigate the normal range of orofacial thermal QST data in the healthy Korean women, and assess sex difference of thermal perception in the orofacial regions. Methods: Thermal QST was conducted on 20 healthy women participants (mean age, 26.4 years; range, 21 to 34 years). The thermal thresholds (cold detection threshold, CDT; warm detection threshold, WDT; cold pain threshold, CPT; and heat pain threshold, HPT) were measured bilaterally at the 5 trigeminal sites (the forehead, cheek, mentum, lower lip and tongue tip). The normative thermal thresholds of women in the orofacial region were evaluated using one-way ANOVA and compared with the previously reported data from age- and site-matched 30 healthy men (mean age, 26.1 years; range, 23 to 32 years) using two-way ANOVA. One experienced operator performed the tests of both sexes and all tests were done in the same condition except the time variability. Results: Women showed significant site differences for the CDT (p<0.001), WDT (p<0.001), and HPT (p=0.047) in the orofacial region. The CDT (p<0.001) and the CPT (p=0.007) presented significant sex difference unlike the WDT and the HPT. Conclusions: The thermal sensory evaluation in the orofacial region should be considered in the context of site and sex and the normative data in this study could be useful for assessment of the sensory abnormalities in the clinical setting.

대용변수를 이용한 상태기반 보전정책의 설계 (Design of a Condition-based Maintenance Policy Using a Surrogate Variable)

  • 권혁무;홍성훈;이민구
    • 품질경영학회지
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    • 제49권3호
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    • pp.299-312
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    • 2021
  • Purpose: We provide a condition-based maintenance policy where a surrogate variable is used for monitoring system performance. We constructed a risk function by taking into account the risk and losses accompanied with erroneous decisions. Methods: Assuming a unique degradation process for the performance variable and its specific relationship with the surrogate variable, the maintenance policy is determined. A risk function is developed on the basis of producer's and consumer's risks accompanied with each decision. With a strategic safety factor considered, the optimal threshold value for the surrogate variable is determined based on the risk function. Results: The condition-based maintenance is analyzed from the point of risk. With an assumed safety consideration, the optimal threshold value of the surrogate variable is provided for taking a maintenance action. The optimal solution cannot be obtained in a closed form. An illustrative numerical example and solution is provided with a source code of R program. Conclusion: The study can be applied to situation where a sensor signal is issued if the system performance begins to degrade gradually and reaches eventually its functional failure. The study can be extended to the case where two or more performance variables are connected to a same surrogate variable. Also estimation of the distribution parameters and risk coefficients should be further studied.

기상해일사례분석을 통한 기상해일발생 임계조건 도출 (A Study on the Meteorological Threshold of the Meteo-Tsunami Occurrence in the Yellow Sea, Korea)

  • 최요환;김현수;우승범;김명석;김유근
    • 한국환경과학회지
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    • 제27권1호
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    • pp.11-25
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    • 2018
  • Both the propagation velocity and the direction of atmospheric waves are important factors for analyzing and forecasting meteo-tsunami. In this study, a total of 14 events of meteo-tsunami over 11 years (2006-2016) are selected through analyzing sea-level data observed from tidal stations along the west coast of the Korean peninsula. The propagation velocity and direction are calculated by tracing the atmospheric disturbance of each meteo-tsunami event predicted by the WRF model. Then, the Froude number is calculated using the propagation velocity of atmospheric waves and oceanic long waves from bathymetry data. To derive the critical condition for the occurrence of meteo-tsunami, supervised learning using a logistic regression algorithm is conducted. It is concluded that the threshold distance of meteo-tsunami occurrence, from a propagation direction, can be calculated by the amplitude of air-pressure tendency and the resonance factor, which are found using the Froude number. According to the critical condition, the distance increases logarithmically with the ratio of the amplitude of air-pressure tendency and the square of the resonance factor, and meteo-tsunami do not occur when the ratio is less than 5.11 hPa/10 min.

노인의 삶의 질 관련요인 분석 (The Effects of Related Factors on Quality of Life for the Elderly)

  • 강이주
    • 가정과삶의질연구
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    • 제26권5호
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    • pp.129-142
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    • 2008
  • This study examines how economic and psychological characteristics affect the quality of life (QoL) of elderly individuals age 60 and older, who live in the Seoul-metropolitan area. Relationships among socio-demographic status, economic conditions, psychological characteristics, family life, health status, and QoL are examined by t-test and ANOVA(Duncan's test as post hoc multiple comparisons), and the multiple regression analysis is used to estimate QoL determinants in the elderly. The major findings of the study are as follows. First, younger age, higher education levels, better health status, harmonious family relations, higher levels of household income, lower levels of loneliness, and higher self-esteems are related to higher QoL levels. Second, the impacts of factors on QoL are differentiated according to tercile groups that divide monthly allowance of respondents into three categories: below normal (threshold amount below 21MW), near normal (threshold amount between 21MW and 35MW), and above normal (threshold amount above 35MW). For each tercile group, poor health status or higher loneliness have negative effects on QoL, while harmonious family relationship has a positive effect. For the below-normal group, years of education or self-esteem have positive effects, while age or retirement status have negative effects when controlling for other factors. For the near-normal group, being married, or perceived financial insecurity create lower QoL levels, while higher self-esteem increases QoL levels. For the above-normal group, being widowed, employed, or retired have positive effects on QoL, when controlling for other variables. Third, even among elderly with high allowances, the effects of health status and family relationship are significant determinants that explain QoL levels. This result suggests that, for te elderly, poor health status and poor family relationships severely decrease QoL in later life, regardless of economic condition.

능동 제어 유체 윤활 베어링으로 지지된 축-베어링 시스템의 동특성에 관한 연구 (A Study on Dynamic Characteristics of a Rotor-Bearing System Supported by Actively Controlled Fluid Film Journal Bearing)

  • 노병후;김경웅
    • 한국정밀공학회지
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    • 제18권8호
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    • pp.116-121
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    • 2001
  • The paper presents the dynamic characteristics of a rotor-bearing system supported by an actively controlled hydrodynamic journal bearing. The proportional. derivative and integral controls are adopted for the control algorithm to control the hydrodynamic journal bearing with an axial groove. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than conventional analysis, which uses the Reynolds condition. The speed at onset of instability of a rotor-bearing system is increased by both proportional and derivative control of the bearing. The proportional control increases the stability threshold without affecting the whirl ratio. However, for the derivative control of the bearing, increase of stability threshold speed is accompanied by a parallel reduction of the whirl ratio. The integral control has no effect on stability characteristics of hydrodynamic journal bearing. The PD-control is more effective than proportional or derivative control. Results 7how the active control of bearing can be adopted for the stability improvement of a rotor-bearing system.

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