Phytate Effect on the Absorption of Total Zinc in Zinc-Depleted Rats

Kwun,In-Sook 韓國營養學會 1997 Journal of Nutrition and Health Vol.30 No.4

Effects of Phytate and Calcium on the Reabsorption of Endogenous Zinc in Zinc-Depleted Rats

Kwun,In-Sook,Oberleas,Donald 韓國營養學會 1997 Journal of Nutrition and Health Vol.30 No.4

유도초음파를 이용한 2.25Cr-1Mo재의 열화도 평가

박익근,박은수,이상용,권숙인,조윤호,윤승현 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.4

고온에서 장시간 사용으로 인하여 발생되는 경년열화 평가에는 파괴적인 방법이 신뢰성이 높지만 시험편 채취의 어려움이 있다. 그러므로 비파괴적인 방법에 의한 열화도 평가가 바람직하다. 본 연구에서는 2.25Cr-1Mo강에 대하여 장시간 등온열처리로 모의 열화시험편을 제작하여 고온설비부재에서 발생되는 탄화물의 석출 및 조대화, 불순물의 입계편석 등 금속학적 미세조직을 관찰하고, 미세조직의 변화와 유도 초음파의 전파특성과의 상관관계를 규명하고, 파괴시험치와 그 결과를 비교하여 초음파 비파괴평가에 의한 고온부재의 열화도 평가의 가능성을 실험적으로 검증하고자 한다. The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the etimation of degraded structural materials by nondestructive evaluation is strongly desired. In this paper, the use of guided wave was suggested for the evaluation of thermally damaged 2.25Cr-1Mo steel as an alternative way to compensate for limitations of fracture tests. The observation of microstructure variations of the material including carbide precipitation increase and spheroidization near gain boundary was conducted and the correlation with the guided wave features such as energy loss ratio and group velocity changes was investigated. Through this study the feasibility of ultrasonic guided wave evaluation for thermally damaged materials was explored.

분말야금 및 주조형 니켈기 초내열합금 크리프 신뢰성의 초음파 모니터링

최찬양,송진헌,오세웅,김정석,권숙인,오승탁,현창용,변재원,Choi, Chan-Yang,Song, Jin-Hun,Oh, Se-Ung,Kim, Chung-Seok,Kwun, Sook-In,Oh, Sung-Tag,Hyun, Chang-Yong,Byeon, Jai-Won 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.3

An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of ${\gamma}^{\prime}$ precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of ${\gamma}^{\prime}$ precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.

2.25Cr-1Mo 강 인공 열화재의 고주파수 초음파 감쇠특성에 관한 연구

박익근,박은수,김정석,김현묵,권숙인,변재원 한국비파괴검사학회 2001 한국비파괴검사학회지 Vol.21 No.4

재료나 설비의 고온 장시간 사용으로 인하여 발생되는 재질열화 평가에는 파괴적인 방법이 널리 사용되고 있으며, 신뢰도가 높다. 그러나, 시험편의 채취가 어렵고 많은 경비와 시간이 소요된다. 전기저항법, 레프리카법, 바크하우젠 노이즈법, 전기화학적방법, 초음파법 등과 같은 비파괴적인 열화손상 평가 방법이 주목을 받고 있다. 본 연구에서는 2.25Cr-1Mo 강을 630℃에서 장시간 등온열처리로 모의 열화시험편을 제작하고, 고온설비부재에서 발생되는 미세조직의 변화와 고주파 초음파의 전파특성(감쇠계수)과의 일대일 상관관계를 규명하여 초음파 비파괴평가에 의한 열화도 평가의 유용성 유무를 실험적으로 검증하였다. 그 결과 2.25Cr-1Mo 인공열화재의 경우 열화가 진행됨에 따라 탄화물의 석출 및 조대화가 일어나며 초음파 감쇠계수는 증가하는 경향을 나타내었으며, 그 정도는 침상의 탄화물이 거의 소멸되는 1,000 시간 이후에 초음파 감쇠계수가 급격히 증가하는 매우 좋은 상관성을 나타내었다. The destructive method is reliable and widely used for the estimation of material degradation but, it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. Ultrasonic nondestructive evaluation technique has been reported good to attain efficiency of measurement, high sensitivity of measurement, and rapidity and reliability of result interpretation. In this study, it was verified experimentally the feasibility of the evaluation of degraded 2.25Cr-1Mo steel specimens which were prepared by the isothermal aging heat treatment at 630℃ by high frequency longitudinal wave method investigating the change of attenuation coefficient by FFT analysis and wavelet transform. Because of carbide precipitation increase and spheroidization near grain boundary of microstructure to aging degradation, attenuation coefficient had a tendency to increase as degradation proceeded. It was identified possibly to evaluate degradation using the characteristics of high-frequency ultrasonics. Frequency dependence of ultrasonic attenuation coefficient to aging degradation appeared large, which made sure that attenuation coefficient is an important parameter for evaluation of aging degradation.

표면SH파에 의한 고온 구조재 열화·손상의 비파괴평가

박익근 ( Ik Keun Park ),박은수 ( Un Soo Park ),김현묵 ( Hyun Mook Kim ),안형근 ( Hyung Keun Ahn ),김정석 ( Chung Soek Kim ),권숙인 ( Sook In Kwun ),변재원 ( Jai Won Byeon ) 한국구조물진단유지관리공학회 2000 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.4 No.1

It is very important to evaluate the surface or subsurface microstructure because of th on mechanical properties of materials. Surface SH-wave which is horizontally polarized traveling along near surface and subsurface layer is an attractive technique for material difficulty in preparing specimens form in-service industrial facilities. In this stud evaluation for degraded structural materials used at high temperature by Surface SH-wave discussed. 2.25Cr-lMo steel specimens which were prepared by the isothermal aging heat tr 650° were evaluated by ultrasonic nondestructive evaluation techniques investigating th velocities, attenuation coefficient and amplitude spectra etc. In addition, it has verif the frequency-dependence of ultrasonic group velocity and attenuation coefficient using wav

초음파 에코파형의 웨이브렛 변환과 비파괴평가에의 응용

박익근,박은수,안형근,권숙인,변재원 한국비파괴검사학회 2000 한국비파괴검사학회지 Vol.20 No.6

초음파 에코파형의 시간-주파수해석법으로 Wigner 분포와 웨이브렛 변환 등과 같은 새로운 신호처리 기법이 비파괴평가 분야에 널리 응용되고 있다. 본 연구에서는 웨이브렛 변환(Wavelet transform)에 의한 음속과 감쇠계수의 주파수의존성과 초음파 결함신호의 잡음제거의 유용성 유무를 실험적으로 검증하였다. Gabor 함수를 웨이브렛의 기본 함수로 사용하였다. 초음파의 에코파형에 포함된 각 주파수성분의 속도와 감쇠계수의 주파수의존성을 추정할 수 있었으며, 초음파탐상에서 결함의 검출능 향상과 결함크기 산정의 정량화에 접근하기 위해 웨이브렛 변환에 의한 S/N 비신호처리 시뮬레이션 결과를 오스테나이트강 스텐인레스 용접부에 가공한 EDM 노치의 초음파 결함신호에 적용한 결과 임상에코를 저감하고 S/N 비를 개선하는 것이 가능하였다. Recently, advanced signal analysis which is called "time-frequency analysis" has been used widely in nondestructive evaluation appications. Wavelet transform(WT) and Wigner Distribution are the most advanced techniques for processing signals with time-varying spectra. Wavelet analysis method is an attractive technique for evaluation of material characterization nondestructively. Wavelet transform is applied to the time-frequency analysis of ultrasonic echo waveform obtained by an ultrasonic pulse-echo technique, In this study, the feasibility of noise suppression of ultrasonic flaw signal and frequency-dependent ultrasonic group velocity and attenuation coefficient using wavelet analysis of ultrasonic echo waveform have been verified experimentally. The Gabor function is adopted the analyzing wavelet. The wavelet analysis show that the variations of ultrasonic group velocity and attenuation coefficient due to the change of material characterization can be evaluated at each frequency. Furthermore, to assure the enhancement of detectability and flaw sizing performance, both computer simulated results and experimental measurements using wavelet signal processing are used to demonstrate the effectibeness of the noise suppression of ultrasonic flaw signal obtained from austenitic stainless steel weld including EDM notch.

초음파 비선형 음향 효과 및 X-선 회절법을 이용한 2.25Cr-1Mo 강의 열화 손상 평가

김덕희,박은수,박익근,변재원,권숙인 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4

It was attempted to evaluate the degree of degradation of thermally aged 2.25-1Mo steel by ultrasonic nonlinear parameter(UNP) measurement and X-ray diffraction analysis of extracted carbide. Artificial aging was performed to simulate the microstructural degradation in 2.25Cr-1Mo steel arising from long time exposure at 540℃. Microstructural analysis (number of carbides per unit area) and measurements of mechanical properties(Vickers hardness, DBTT) and degradation evaluation parameters(UNP and intensity ratio of X-ray diffraction peak of electrolytically extracted carbied) were performed. Both of UNP and intensity ratio of X-ray diffraction peak for M6C carbied to that of M23C6 carbied(IR) increased abruptly in the initial 100 hour of aging and then changed little. UNP and IR were proposed as potential parameters to evaluate the degree of aging degradation of 2.25Cr-1Mo steel.

Phytate Effect on the Absorption of Total Zinc in Zinc-Depleted Rats

Sook, Kwun-In The Korean Nutrition Society 1997 Nutritional Sciences Vol.30 No.4

It has been known that dietary phytate decreases the absorption of body zinc pool which is composed of the dietary and endogenous zinc in the body. The purpose of this study was to examine the effect of phytate on the absorption of total bodyzinc in Zn-depleted rats. Rats were Zn-depleted with either low(0.8%) or high(1.6%) Ca diet containing sodium phytate for 4 weeks. After zinc depletion, rats were assigned into phytate or non-phytate dietary groups within each low-or high-Ca dietary group. ant feces were collected for 2 weeks of the initial collection and 1 week after dietary crossover, during which the phytate and the non-phytate diet was switched over within the same Ca group. The content of Zn and Ca measured by atomic absorption spectrophotometer and phytate content was analyzed. food intake was higher in the high Ca group than in the low Ca group(p <0.0001), and was also higher in the non-phytate group than in the phytate group(p <0.0001). Food intake and phytate level affected body weight gain in rats(p <0.0001). Zinc excretion in the total feces was higher in the phytate group than in the non-phytate group at both low and high Ca level(p <0.0001), except during the crossover collection period in high Ca group. Calcium, however, didn't show any synergistic effect on phytate effect(p <0.05). This study showed that phytate decreased the absorption of total body zinc at both low and high Ca levels in Zn-depleted rats. A large portion of total body zinc originated from the endogenous zinc pool in these rats. The results of the present study showed the same effect of phytate on the endogenous zinc in Zn-depleted rats as in a previous study, confirming that phytate adversely affects zinc bioavailability, especially under marginal and poor zinc nutrition.

Phytate Effect on the Absorption of Total Zinc in Zinc-Depleted Rats

Kwun, In-Sook The Korean Nutrition Society 1997 Journal of Nutrition and Health Vol.31 No.7

It has been known that dietary phytate decreases the absorption of body zinc pool which is composed of the dietary and endogenous zinc in the body. The purpose of this study was to examine the effect of phytate on the absorption of total bodyzinc in Zn-depleted rats. Rats were Zn-depleted with either low(0.8%) or high(1.6%) Ca diet containing sodium phytate for 4 weeks. After zinc depletion, rats were assigned into phytate or non-phytate dietary groups within each low- or high-Ca dietary group. Rat feces were collected for 2 weeks of the initial collection and 1 week after dietary crossover, during which the phytate and the non-phytate diet was switched over within the same Ca group. The content of Zn and Ca measured by atomic absorption spectrophotometer and phytate content was analyzed. Food intake was higher in the high Ca group than in the low Ca group(p<0.0001), and was also higher in the non-phytate group than in the phytate group(p<0.0001). Food intake and phytate level affected body weight gain in rats(p<0.0001). Zinc excretion in the total feces was higher in the phytate group than in the non-phytate group at both low and high Ca level(p <0.0001), except during the crossover collection period in high Ca group. Calcium, however, didn't show any synergistic effect on phytate effect(p<0.05). This study showed that phytate decreased the absorption of total body zinc at both low and high Ca levels in Zn-depleted rats. A large portion of total body zinc originated from the endogenous zinc pool in these rats. The results of the present study showed the same effect of phytate on the endogenous zinc in Zn-depleted rats as in a previous study, confirming that phytate adversely affects zinc bioavailability, especially under marginal and poor zinc nutrition.