확장 칼만 필터를 활용한 Z-R 관계식의 매개변수 실시간 결정

김정호,유철상 한국수자원학회 2014 한국수자원학회논문집 Vol.47 No.2

본 연구에서는 Z-R 관계식의 매개변수를 안정적인 값으로 실시간 예측하고자 확장 칼만 필터기법을 적용하였다. 이를 위해 Z-R 관계식의 비선형을 고려하여 확장 칼만 필터로 매개변수 결정모형을 구축하였다. 상태-공간 모형은 Adamowski and Muir(1989)의 연구를 기반으로 구축하였다. 상태-공간 모형의 상태변수는 Z-R 관계식의 두 매개변수로 설정하였다. 결과적으로 칼만이득과 상태변수가 발산하지 않는 안정적인 모형을 구축하였다. 주목할 점으로는 기존 방법으로 추정된 과대 혹은 과소한 매개변수가 필터링 되어 일부 제거되었다는 것이다. 부적절한 매개변수의 적용은 물리적으로 비현실적인 강우강도 추정 결과를 불러일으키는 원인이기 때문에 이러한 결과는 정량적 강수량 추정측면에서 효과가 크다고 할 수 있다. 또한 확장 칼만 필터로 예측한 매개변수로 레이더 강우를 추정한 결과, 편의보정계수가 1.0에 근사하게 나타나 편의보정과정 없이도 지상 강우강도와의 평균적인 차이는 근소한 것으로 나타났다. 또한 기존 방법으로 레이더 강우를 추정한 결과보다 전반적으로 정확도 높은 강우 추정이 가능한 것으로 나타났다. The study adopted extended Kalman filter technique in an effort to predict Z-R relationship parameter as a stable value in real-time. Toward this end, a parameter estimation model was established based on extended Kalman filter in consideration of non-linearity of Z-R relationship. A state-space model was established based on a study that was conducted by Adamowski and Muir(1989). Two parameters of Z-R relationship were set as state variables of the state-space model. As a result, a stable model where a divergence of Kalman gain and state variables are not generated was established. It is noteworthy that overestimated or underestimated parameters based on a conventional method were filtered and removed. As application of inappropriate parameters might cause physically unrealistic rain rate estimation, it can be more effective in terms of quantitative precipitation estimation. As a result of estimation on radar rainfall based on parameters predicted with the extended Kalman filter, the mean field bias correction factor turned out to be around 1.0 indicating that there was a minor difference from the gauge rain rate without the mean field bias correction. In addition, it turned out that it was possible to conduct more accurate estimation on radar rainfall compared to the conventional method.

Measurement and Analysis of Gate Finger Number Dependence of Input Resistance for Sub-micron MOSFETs

Jahyun Ahn(안자현),Seonghearn Lee(이성현) 대한전자공학회 2014 전자공학회논문지 Vol.51 No.12

Detection Analysis of Burn-in Socket Defects using a Daisy-chain Coplanar Waveguide

Donghee Yu,Moonjung Kim 대한전자공학회 2021 IEIE Transactions on Smart Processing & Computing Vol.10 No.3

In this paper, we report the results of a study on the detection and location of defects in a burn-in socket and a printed circuit board. A defect detection method was developed using a daisy-chain coplanar waveguide and S-parameter and Z-parameter analysis methods. The results were verified using 3D electromagnetic field simulation. The burn-in socket is composed of a number of contact pins, so a method for inspecting all the pins at once is required for efficient defect detection. A printed circuit board with a coplanar waveguide was designed and placed above and below the burn-in socket to form a daisy-chain path passing through all the pins. Open and short defects were placed at 6 points along the daisy-chain path. S-parameters for daisy-chain paths with and without defects were calculated, and the results were compared to analyze whether defects occurred in a path. Both types of defects cause impedance discontinuity in the daisy-chain path and result in changes in the S-parameter. The movement of the defect location in the daisy-chain path causes changes in the capacitance and inductance, which eventually change the Z-parameter. It was verified that defects and their locations in the daisy-chain path can be detected by analyzing the S-parameter and Z-parameter.

미래형 원자로 구조 재료용 Gr. 91 강의 장시간 크리프 강도의 신뢰성 예측

김우곤 ( Woo Gon Kim ),박재영 ( Jae Young Park ),윤송남 ( Song Nan Yin ),김대환 ( Dae Whan Kim ),박지연 ( Ji Yeon Park ),김선진 ( Seon Jin Kim ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.4

This paper focuses on reliability prediction of long-term creep strength for Modified 9Cr-1Mo steel (Gr. 91) which is considered as one of the structural materials of next generation reactor systems. A “Z-parameter” method was introduced to describe the magnitude of standard deviation of creep rupture data to the master curve which can be plotted by log stress vs. The larson-Miller parameter (LMP). Statistical analysis showed that the scattering of the Z-parameter for the Gr. 91 steel well followed normal distribution. Using this normal distribution of the Z-parameter, the various reliability curves for creep strength design, such as stress-time temperature parameter reliability curves (σ-TTP-R curves), stress-rupture time-reliability curves (σ-tr-R curves), and allowable stress-temperature- reliability curves ([σ]-T-R curves) were reasonably drawn, and their results are discussed.

크리프 수명 예측의 신뢰성 평가 방법

김우곤(Woo-Gon Kim),노영진(Roh -Young Jin),김선화(Seon-Hwa Kim),김선진(Seon-Jin Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

This paper presents methodology of reliability assessment in long-term creep life prediction. A number of creep rupture data were used for Gr. 91 steel collected through literature surveys, and the long-term creep life was predicted by Larson- Miller parameter. A “Z parameter” method was used to describe the magnitude of the deviation of the creep rupture data to a master curve. A “Service Condition-creep Rupture property Interference (SCRI) model” based on the Z parameter was used to simultaneously consider the scattering of the creep rupture data of materials and the fluctuations of service conditions in reliability assessment. A number of random variables for Zs describing service conditions and Zcr describing the dispersion of the creep rupture data were generated using a Monte-Carlo simulation technique. As examples for application, the creep rupture life under a certain service conditions of Gr. 91 steel was reasonably demonstrated from the viewpoints of reliability.

레이더 수평반사도-강우강도 관계의 유효 영역 탐색

강민석(Kang, Minseok),유철상(Yoo, Chulsang) 한국방재학회 2020 한국방재학회논문집 Vol.20 No.2

본 연구에서는 수평반사도를 이용한 강우추정 관계식을 유효성 측면에서 재평가하였다. 이를 위해, 강우추정 관계식의 유도과정을 다시 살펴보고, 관측자료를 가지고 강우입자분포의 매개변수를 추정할 수 있도록 식의 형태를 변환하였다. 이 식을 이용하여 관악산 레이더, 비슬산 레이더에서 관측된 반사도-강우강도의 쌍 자료에 대한 강우입자분포 매개변수를 추정하였다. 마지막으로 추정된 매개변수 대푯값을 다시 강우추정 관계식 유도에 사용하였다. 이렇게 결정된 강우추정 관계식이 관측된 수평반사도-강우 강도 자료를 얼마나 잘 대표하는지를 평가하였으며, 그 결과, 레이더 반사도가 작아지면 작아질수록 강우추정 관계식의 이론적 배경과 관측자료의 괴리가 커지는 것으로 나타났다. 또한 강우입자분포를 지수분포로 가정한 형태의 강우추정 관계식이 모든 반사도 구간에서 유의하지 않을 수 있다는 것을 확인하였다. This study evaluated the applicability of the reflectivity-rainfall (Z-R) relationship using horizontal reflectivity. We reviewed the derivation procedure of the Z-R relationship and transformed the equation to estimate the parameters of drop size distribution from the observational data. The parameters of drop size distribution were estimated for the paired data of horizontal reflectivity and rainfall rate observed at the Gwanaksan and Biseulsan radar stations by applying this equation. Subsequently, the representative values of these estimated parameters were used to derive the Z-R relationship. Finally, we evaluated the performance of the Z-R relationship for representing the observed horizontal reflectivity-rainfall intensity data. It was observed that the difference between the theoretical estimation and the observed data increases as the radar reflectivity decreases. Moreover, the results confirmed that the Z-R relationship based on the assumption of exponentially distributed drop size distribution may not be applicable for all reflectivity ranges.

Type 316L 스테인리스강의 고온 기계적 거동

김우곤,이형연 한국압력기기공학회 2020 한국압력기기공학회 논문집 Vol.16 No.1

High-temperature mechanical behaviors of Type 316L stainless steel (SS), which is considered as one of the major structural materials of Generation-IV nuclear reactors, were investigated through the tension and creep tests at elevated temperatures. The tension tests were performed under the strain rate of 6.67×10-4 (1/s) from room temperature to 650oC, and the creep tests were conducted under different applied stresses at 550oC, 600oC, 650oC, and 700oC. The tensile behavior was investigated, and the modeling equations for tensile strengths and elongation were proposed as a function of temperature. The creep behavior was analyzed in terms of various creep equations: Norton’s power law, modified Monkman-Grant relation, damage tolerance factor(λ), and Z-parameter, and the creep constants were proposed. In addition, the tested tensile and creep strengths were compared with those of RCC-MRx. Results showed that creep exponent value decreased from n=13.55 to n=7.58 with increasing temperature, λ = 6.3, and Z-parameter obeyed well a power-law form of Z=5.79E52(σ/E)9.12. RCC-MRx showed lower creep strength and marginally different in creep strain rate, compared to the tested results. Same creep deformation was operative for dislocation movement regardless of the temperatures.

초고온 가스로용 Alloy 617의 크리프 수명예측 신뢰성 평가

김우곤 ( Woo Gon Kim ),박재영 ( Jae Young Park ),김선진 ( Seon Jin Kim ),홍성덕 ( Sung Deok Hong ),김용완 ( Yong Wan Kim ) 대한금속재료학회(구 대한금속학회) 2012 대한금속·재료학회지 Vol.50 No.10

This paper evaluates the reliability of creep rupture life under service conditions of Alloy 617, which is considered as one of the candidate materials for use in a very high temperature reactor (VHTR) system. A Z-parameter, which represents the deviation of creep rupture data from the master curve, was used for the reliability analysis of the creep rupture data of Alloy 617. A Service-condition Creep Rupture Interference (SCRI) model, which can consider both the scattering of the creep rupture data and the fluctuations of temperature and stress under any service conditions, was also used for evaluating the reliability of creep rupture life. The statistical analysis showed that the scattering of creep rupture data based on Z-parameter was supported by normal distribution. The values of reliability decreased rapidly with increasing amplitudes of temperature and stress fluctuations. The results established that the reliability decreased with an increasing service time.

Analysis of Z-Source Inverters in Wireless Power Transfer Systems and Solutions for Accidental Shoot-Through State

Tianfeng Wang,Xin Liu,Nan Jin,Dianguang Ma,Xijun Yang,Houjun Tang,Muhammad Ali,Khurram Hashmi 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

Wireless power transfer (WPT) technology has been the focus of a lot of research due to its safety and convenience. The Z-source inverter (ZSI) was introduced into WPT systems to realize improved system performance. The ZSI regulates the dc-rail voltage in WPT systems without front-end converters and makes the inverter bridge immune to shoot-through states. However, when the WPT system is combined with a ZSI, the system parameters must be configured to prevent the ZSI from entering an “accidental shoot-through” (AST) state. This state can increase the THD and decrease system power and efficiency. This paper presents a mathematical analysis for the characteristics of a WPT system and a ZSI while addressing the causes of the AST state. To deal with this issue, the impact of the system parameters on the output are analyzed under two control algorithms and the primary compensation capacitance range is derived in detail. To validate the analysis, both simulations and experiments are carried out and the obtained results are presented.

Analysis of Z-Source Inverters in Wireless Power Transfer Systems and Solutions for Accidental Shoot-Through State

Wang, Tianfeng,Liu, Xin,Jin, Nan,Ma, Dianguang,Yang, Xijun,Tang, Houjun,Ali, Muhammad,Hashmi, Khurram The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.3

Wireless power transfer (WPT) technology has been the focus of a lot of research due to its safety and convenience. The Z-source inverter (ZSI) was introduced into WPT systems to realize improved system performance. The ZSI regulates the dc-rail voltage in WPT systems without front-end converters and makes the inverter bridge immune to shoot-through states. However, when the WPT system is combined with a ZSI, the system parameters must be configured to prevent the ZSI from entering an "accidental shoot-through" (AST) state. This state can increase the THD and decrease system power and efficiency. This paper presents a mathematical analysis for the characteristics of a WPT system and a ZSI while addressing the causes of the AST state. To deal with this issue, the impact of the system parameters on the output are analyzed under two control algorithms and the primary compensation capacitance range is derived in detail. To validate the analysis, both simulations and experiments are carried out and the obtained results are presented.