• 한국의학물리학회지:의학물리
• /
• 제25권3호
• /
• pp.157-166
• /
• 2014

뉴론에서 ATP는 분비 과립내에 신경전달물질과 함께 다량 저장되어 있다가 신경전달물질과 함께 분비되는 것으로 알려져 있으므로 신경전달물질의 자극-분비(stimulus-secretion) coupling 과정에 있어 중요한 조절작용을 할 것으로 기대된다. 그러므로 본 연구에서는 뉴론과 그 발생학적 기원이 동일한 부신수질 세포(adrenal chromaffin cell)를 대상으로 하여 세포막 칼슘통로를 통한 세포막 전류에 미치는 ATP의 영향을 측정함으로써 신경전달물질이 자극-분비 coupling 과정에 작용하는 ATP의 조절 작용을 알아보고자 하였다. 부신수질 세포의 칼슘통로를 통한 세포막 전류는 패치클램프 테크닉으로 기록하였다. 10 mM $Ba^{2+}$을 포함한 세포 외 용액에서, $Ba^{2+}$ current는 0.1 mM ATP를 세포외부에 처치했을 때, 평균 $36{\pm}6%$ (n=6) 감소되어 나타났고 ATP를 씻어준 후 전류는 다시 회복되는 가역적 반응을 보였다. ATP의 전류 억제 기전을 알아보고자 칼슘통로에서 관찰되는 현상 중의 하나인 소통(facilitation)현상을 기록하였다. +80 mV의 큰 prepulse를 준 후 바로 테스트 펄스를 주며 측정한 전류는 큰 prepulse에 의해 억제효과가 풀리는(disinhibition) 현상을 나타내었다. ATP 처치 후 큰 자극을 주어 $37{\pm}5%$ (n=11)의 $Ba^{2+}$ 전류 증가가 있었고 이는 ATP가 없는 상태에서 순수하게 큰 자극에 의해 소통되는 $25{\pm}3%$ (n=12)과 유의한 차이를 보였다(p<0.05). ATP의 억제 기전이 G-protein을 매개로 한 것인지를 알아보고자 가수분해 되지 않는 GTP 유도체인 $GTP{\gamma}S$를 세포 내에 준 후 $Ba^{2+}$ 전류를 기록하였다. $GTP{\gamma}S$에 의해 55%의 전류 크기의 감소가 있었고 이 환경에서 큰 prepulse를 인가하였을 때 $34{\pm}4%$ (n=19)의 소통현상을 보였다. 이는 $GTP{\gamma}S$가 없는 환경에서의 $25{\pm}3%$ (n=12)의 소통현상을 보인 것과 유의한 차이를 보였다(p<0.05). $Ba^{2+}$ current trace의 활성화 과정(activation)을 curve-fitting한 결과, control은 single exponential curve로 fitting된 반면, ATP 또는 $GTP{\gamma}S$를 처치한 경우, 그리고 ATP와 $GTP{\gamma}S$ 모두 처치한 경우에서는 double-exponential curve로 가장 잘 fitting이 되었다. 즉, ATP나 $GTP{\gamma}S$를 처치했을 때 모두 전류가 더 느리게 활성화되는 모양을 나타내었고, 이상의 결과로 미루어 ATP와 $GTP{\gamma}S$는 같은 방식으로 칼슘통로를 억제하고, 이러한 억제효과는 세포막에 아주 큰 전압을 걸어주면 칼슘 통로에 결합했던 G-protein이 막전압 의존적으로 떨어짐으로써 소실(disinhibition)된다고 해석된다. 본 연구에서 확인한 ATP의 칼슘통로 억제효과는 자체 크로마핀 세포 또는 주변 세포에서 아드레날린이 적게 분비되게 하는 autocrine 또는 paracrine inhibition 과정의 중요한 기전으로 작용할 것이다.

• 한국해양공학회지
• /
• 제3권2호
• /
• pp.108-117
• /
• 1989

This paper deals with a fatigue life prediction of a surface crack based on the experimentally obtained relationship between surface crack length ratio $a/a_{f}$ and cycle ratio $N/N_{f}$ using micro computer. Firstly $a/a_{f}$-$N/N_{f}$ curves obtained from experimental tests, were assumed as three curves UC(the upper limit curve), LC(the lower limit curve) and MC(the middle curve), and these were utilized to predict the fatigue life. Comparing the calculated values which represent the characteristics of crack growth behaviors from the three assumed curves with the experimental ones, it has been found that in the stable crack growth region, they coincide reasonably well each other. And the differences between the fatigue lives obtained from the assumed curves and the experimental fatigue life did not exceed 20%. Using the characteristics of $a/a_{f}$-$N/N_{f}$ curves, it is possible to predict the da/dN-Kmax curves and the S-$N_{f}$ curves.

• Nuclear Engineering and Technology
• /
• 제38권3호
• /
• pp.277-284
• /
• 2006

In order to ensure the structural integrity of nuclear welded structures during design life, the fatigue life has to be evaluated by fatigue analysis procedures presented in technical codes such as ASME B&PV Code Section III. However, existing fatigue analysis procedures do not explicitly consider the presence of welded joints. A new fatigue analysis procedure based on a structural stress/fracture mechanics approach has been recently developed in order to reduce conservatism by erasing uncertainty in the analysis procedure. A recent review of fatigue crack growth data under various mean loading conditions using the structural stress/fracture mechanics approach, does not consider the mean loading effect, revealed some significant discrepancies in fatigue crack growth curves according to the mean loading conditions. In this paper, we propose the use of the stress intensity factor range ${\Delta}K$ characterized with loading ratio R effects in terms of the structural stress. We demonstrate the effectiveness in characterizing fatigue crack growth and S-N behavior using the well-known data. It was identified that the S-N data under high mean loading could be consolidated in a master S-N curve for welded joints.

• 대한조선학회논문집
• /
• 제56권2호
• /
• pp.161-167
• /
• 2019

In general, fatigue analysis is performed by using deterministic model to estimate the optimal parameters. However, the deterministic model is difficult to clearly describe the physical phenomena of fatigue failure that contains many uncertainty factors. With regard to this, efforts have been made in this research to compare with the deterministic model and the stochastic models. Firstly, One deterministic S-N curve was derived from ordinary least squares technique and two P-S-N curves were estimated through Bayesian-linear regression model and Markov-Chain Monte Carlo simulation. Secondly, the distribution of Long-term fatigue damage and fatigue life were predicted by using the parameters obtained from the three methodologies and the long-term stress distribution.

• 한국안전학회지
• /
• 제22권4호
• /
• pp.37-42
• /
• 2007

Flash points for the flammable binary systems, n-propanol+acetic acid and n-propanol+n-propionic acid, were measured by Cleveland open cup tester. The Raoult's law, the van Laar equation and the UNIQUAC equation were used for predicting flash points and were compared with experimentally-derived data. The calculated values based on the van Laar and UNIQUAC equations were found to be better than those based on the Raoult's law. And the predictive curve of the flash point prediction model based on the UNIQUAC equation described the experimentally-derived data more effectively than was the case when the prediction model was based upon the the van Laar equation.

• International Journal of Computer Science & Network Security
• /
• 제21권3호
• /
• pp.60-70
• /
• 2021

In this paper we study the problem of implementation of security issues of blue tooth, especially secure simple pairing, with the help of an efficient four user authenticated key (4UAK) for an elliptic curve cryptography (ECC). This paper also deals with the design, implement and performance evaluation of secure simple pairing (SSP) using an elliptic curve cryptography, such as Diffie Hellman protocol when four users are involved. Here, we also compute the best, worst and average case step counts (time complexities). This work puts forth an efficient way of providing security in blue tooth. The time complexity of O(n⁴) is achieved using Rabin Miller Primality methodology. The method also reduces the calculation price and light communication loads.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2007년도 추계학술대회 논문집
• /
• pp.30-34
• /
• 2007

Structural integrity of railway vehicles should last for a long period against various and continuous fatigue loadings, and the carbody structures of railway vehicle are manufactured by applying multiform welding types for each material. Since the most of cracks are occurred and proceeded at the vicinity of welding area during the lifetime of carbody structure, the fatigue strength evaluation for welding area of carbody structure should have been carried out. Rotem Company has evaluated lifetime and fatigue strength of carbody structure according to the fatigue analysis based on the international standard and/or inner-official regulation. This study introduces the fatigue analysis method that we have evaluated and calculated the damages for the welding areas of carbody structure under various fatigue loading conditions using cumulative fatigue damage rule(Miner's rule) to verify whether the cumulative damage does exceed unity. This study contains the fatigue test of specimens to derive stress-life relations(S-N curve), sub-modeling analysis and the calculation of cumulative damages under fatigue loading. The fatigue analysis verifies the welding area shall be capable of withstanding under fatigue loading, identifies how critical area shall be selected and presents the principles to be used for design verification.

• 대한수학회보
• /
• 제55권4호
• /
• pp.1103-1107
• /
• 2018

Let M be a complete spacelike hypersurface in the (n + 1)-dimensional Minkowski space ${\mathbb{L}}^{n+1}$. Suppose that every unit speed curve X(s) on M satisfies ${\langle}X^{\prime\prime}(s),X^{\prime\prime}s){\rangle}{\geq}-1/r^2$ and there exists a point $p{\in}M$ such that for every unit speed geodesic X(s) of M through the point p, ${\langle}X^{\prime\prime}(s),X^{\prime\prime}s){\rangle}=-1/r^2$ holds. Then, we show that up to isometries of ${\mathbb{L}}^{n+1}$, M is the hyperbolic space $H^n(r)$.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2004년도 추계학술대회 논문집
• /
• pp.222-227
• /
• 2004

Under cyclic loading, the fatigue failures of welded joints occur at weld toes which induce stress concentration by weld shape. So we need to obtain the peak stress and the S-N curve to assess the fatigue strength of welded joints. However the measurement of peak stress is of high uncertainty and low reproducibility, so we use nominal stress instead in fatigue tests of welded joints. In this study, fatigue tests to obtain S-N curves and FE analyses to obtain stress concentration factors were conducted for the two types of cruciform fillet welded joints, that is, load-carrying and non load-carrying types. Then we changed the obtained S-N curves to that based on peak stress using the hot-spot stress concept. From the analyses of the S-N curves obtained, we have concluded that there is a need to develop a new method to evaluate the fatigue life.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2007년도 춘계학술대회A
• /
• pp.997-1002
• /
• 2007

A guideway vehicle is used in automobile, semiconductor and LCD manufacturing industries to transport products efficiently. Since the operating speed of the guideway vehicle should be increased for maximum productivity, the weight of the vehicle has to be reduced. This may cause parts in the system to fail before the life of the system. Therefore estimation of the fatigue life of the parts becomes an important problem. In this study, the fatigue life of the driving wheel in the guideway vehicle is estimated using a S-N curve. To obtain the fatigue life of a part, the S-N curve, load time history applied on a driving wheel and material property are required. The S-N curve of the driving wheel is obtained using the fatigue experiment on wheels. Load time history of the wheel is obtained from multibody dynamics analysis. To obtain the material properties of the driving wheel, which is composed of aluminum with urethane coating, a compression hardware testing has been done with the static analysis of the FE model. The fatigue life prediction using computational analysis model guarantees the safety of the vehicle at the design stage of the product.