• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2004년도 춘계종합학술대회
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• pp.682-684
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• 2004

Random Telegraph Signal(RTS)에 의한 1/f 잡음이 CMOS Ring Oscillator의 Phase Noise와 Jitter에 미치는 영향을 조사한다. 7단 Ring Oscillator의 각 노드에 병렬 연결된 10개의 Piece-Wise-Linear 전류원이 RTS 신호를 모델링 한다. RTS 전류원의 진폭과 Time Constant를 변화시키면서 Ring Oscillator 출력의 FFT 및 전력 스팩트럼 밀도, Jitter를 관찰한다. RTS 전류원의 진폭은 Phase Noise의 폭을 증가시키고 결과적으로 Jitter의 크기도 증가 시키는 것이 확인 되었다. 그리고 RTS Time Constant가 짧아질수록 출력 신호의 FFT peak의 폭이 커지고 Cycle to Cycle Jitter 값이 증가하였다.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.55-62
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• 1999

Cold rolled steel has much plastic strain in the material surface produced by manufacturing process. The strain causes the variation of surface residual stress, in which influences the fatigue behavior under repeated loading. As experimental results, it was confirmed that the behavior of residual stress ${\sigma}_r$, with cycle N consisted of three stages except stress amplitude near fatigue limit in SPCC steel. On the first stage compressive residual stress decreased rapidly, on the second stage gradually, and on the last stage slightly. The relation between ${\sigma}_r$, and log N appeared linear behavior except the early part of cycle ratio $N/N_f$. The average gradient of ${\sigma}_r$, with respect to log N seemed to take a constant value without initial cycle ratio. On the other hand, the $N_f$ line was regressed by the first-order polynomial equation on ${\sigma}_r-log\;N_f$ diagram. Therefore, this study showed that both the gradient of ${\sigma}_r$, with respect to log N and the $N_f$ line was useful in predicting the cycle ratio $N/N_f$.

• International Journal of Precision Engineering and Manufacturing
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• 제3권2호
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• pp.78-86
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• 2002

In general, X-ray diffraction method detects the changes of crystal lattice under material surface using the angle of diffraction 2$\theta$. This technique which deals with in the presented paper can be applied to a behavior on the slipped band or the micro crack cause to material degradation. The relation between half-value breadth and cycle numbers shows three stages, which consist of rapid decrease in the initial cycle, slight decrease in the middle cycle, and then rapid decrease in the final cycle. The ratio of half-value breadth has a constant value on B/B$\_$0/ - N diagram under the loading condition except early part of fatigue life. The ratio of half-value breadth B/B$\_$0/ - log N$\_$f/ with respect to number of cycle to failure N$\_$f/ has linear behavior on B/B$\_$0/ - log N$\_$f/ diagram. Therefore, the evaluation of fatigue life by the average gradient has much less mean error than the estimation of fatigue life by log B/B$\_$0/ - log N/N$\_$f/ relation.

• Korean Journal of Mathematics
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• 제23권4호
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• pp.607-618
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• 2015

An L(2; 1)-labeling of a graph G is a function f from the vertex set V (G) to the set of all non-negative integers such that ${\mid}f(u)-f(v){\mid}{\geq}2$ if d(u, v) = 1 and ${\mid}f(u)-f(v){\mid}{\geq}1$ if d(u, v) = 2. The ${\lambda}$-number of G, denoted ${\lambda}(G)$, is the smallest number k such that G admits an L(2, 1)-labeling with $k=\max\{f(u){\mid}u{\in}V(G)\}$. In this paper, we consider the square of a cycle and provide exact value for its ${\lambda}$-number. In addition, we also completely determine its edge span.

• Journal of Welding and Joining
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• 제2권1호
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• pp.49-57
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• 1984

The influence of weld defect, residual stress and microstructure on the Low Cycle Fatigue(L. C. F.) behaviour of AISI 304L austenitic stainless steel weldment has been studied. The specimens were welded by shielded metal are welding process, post weld heat treated(PWHT) at 900.deg.C for 1.5hrs, and tested under total strain controlled condition at room temperature. The results of the experiment showed that weld defect affected the L.C.F. behaviour of weldment deleteriously compared to the residual stress or microstructure, and it reduced the L.C.F. life about 70-80%. The PWHT exhibited beneficial effect on the L.C.F. behaviour and increased the L.C.F. life about 120%. This enhancement by PWHT was attributed to the removal of residual stress and recovery of weld metal ductility. The cyclic stress flow of as welded specimens showed intermediate cyclic softening, whereas those of heat treated specimens showed continuous cyclic hardening, and this difference was explained in terms of the residual stress removal and dislocation behaviour. Scanning electron microscopy studies of fatigue fracture surface showed that weld defects of large size and near weld surface were detrimental to the L.C.F. behaviour of weldment.

• 한국정보과학회논문지:시스템및이론
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• 제31권1_2호
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• pp.86-94
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• 2004

이 논문에서는 재귀원형군 $ G(2^m, 4), m{\geq}3$은 고장인 요소의 수가 m-2개 이하일 때, 임의의 1, 4 ${\leq}1{\leq}2^m-f_v$에 대하여 길이 1인 고장 없는 사이클을 가짐을 보인다. 여기서, f$_{v}$ 는 고장 정점의 수이다. 이를 위하여, ｜F｜$\leq$k인 임의의 고장 요소 집합 F에 대해서 G-F가 임의의 두 정점을 잇는 길이가 해밀톤 경로보다 하나 작은 경로를 가질 때, G를 k-고장 하이포해밀톤 연결된 그래프라고 정의하고, $ G(2^m, 4), m{\geq}3$은 m-3-고장 하이포해밀톤 연결된 그래프임을 보인다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.548-551
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• 2000

Spinel phase LiF $e_{y}$M $n_{2-y}$ $O_4$samples are synthesized by calcining a LiOH.$H_2O$, Mn $O_2$and F $e_2$ $O_3$mixture at 80$0^{\circ}C$ for 36h in air. Preparing LiF $e_{y}$M $n_{2-y}$ $O_4$showed spinel phase with cubic phase. The ununiform distortion of the crystallite of the spinel LiF $e_{y}$M $n_{2-y}$ $O_4$was more stable than that of the pure. The discharge capacity of the cathode for the Li/LiF $e_{0.1}$M $n_{1.9}$ $O_4$cell at the first than that of the pure. The discharge capacity of the cathode for the Li/LiF $e_{0.1}$M $n_{1.9}$ $O_4$cell at the first cycle and at the 70th cycle was about 113 and 90mAh/g, respectively. This cell capacity was retained about 82% of the first cycle after 70th cycle. Impedance profile of this cell was more stable than that pure. The resistance, the capacitance and chemical diffusion coefficients of lithium ion showed approximately 80$\Omega$, 36133.87$\mu$F ; 1.4$\times$10$^{-8}$ c $m^2$ $s^{-1}$ , respectively. , respectively.ely.

• Journal of Welding and Joining
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• 제33권6호
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• pp.42-48
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• 2015

Reduced activation ferritic/martensitic steels are recognized as the primary candidate structural materials for fusion blanket systems. Welding is an inevitable for breeding blanket for pressure tightness and radioisotope confinement. Especially, TIG welding was chosen for sealing because it has the largest gap allowance compared to the other welding methods, and its properties are controllable by feed wire and welding conditions. In this study, the low cycle fatigue test using two-type gage such as extensometer and strain gage was applied to the TIG welded joint of F82H steel, for evaluating fatigue damage accumulation behavior of the HAZs. As the result, the over-tempered HAZ have shown a higher fatigue damage accumulation compared with other materials at all the testing conditions.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.131-139
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• 1993

Low cycle fatigue characteristics of cast aluminum alloy A356 with a yield strength and ultimate strength of 229 and 283 MPa respectively was evaluated using smooth axial specimen under strain controlled condition. Reversals to failure ranged from 16 to 107. The cast aluminum alloy exhibited cyclically strain-gardening behavior. The results of low cycle fatigue tests indicated that the conventional low cycle fatigue tests indicated that the conventional low cycle fatigue life model was not a satisfactory representation of the data. This occurred because the elastic strain-life curve was not-log-log linear and this phenomena caused a nonconservative and unsafe fatigue life prediction at both extremes of long and short lives. A linear log-log total strain-life model and a bilinear log-log elastic strain-life model were proposed in order to improve the representation of data compared to the conventional low cycle fatigue life model. Both proposed fatigue life models were statistically analyzed using F tests and successfully satisfied. However, the low cycle fatigue life model generated by the bilinear log-log elastic strain-life equation yielded a discontinuous curve with nonconservatism in the region of discontinuity. Among the models examined, the linear log-log total strain-life model provided the best representation of the low cycle fatigue data. Low cycle fatigue life prediction method based on the local strain approach could conveniently incorporated both proposed fatigue life models.

• 한국가축번식학회지
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• 제17권4호
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• pp.279-285
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• 1994

The objective of the present study was to characterize the cell cycles of granulosa cell populations during follicular maturation in cattle by using flow cytometer. Granulosa cells were isolated from bovine preovulatory antral follicles of F1(>10mm), F2(5~20mm), F3(3~4mm) and F4(1~2mm) diameter and fixed and stained with fluorochromes that selectively bine to DNA. Flow cytometer equipped with a laser excitation system was used to analyze the intensity of fluorescence from stained cells. Forward angle light-scatter(FSC) and 90$^{\circ}$light-scatter(SSC) signals were adopted to measure the size and the granularity of granulosa cells. As a results of FSC/SSC analysis, granulosa cell populations(G1 phase of cell cycle) from each follicle were relatively regular in size and granularity, regardless of follicular size. However, their distribution in granularity was greater than that in size. Most of granulosa cell populations collected from each follicle were distributed in G0/G1, S and G2/M phases. As the follicles approached to ovulation the percentage of cells in the proliferative phases of cell cycle (S and G2/M) decreased significantly, but there was a concomitant increase in the percentage of granulosa cells in G1 phase. Therefore, these data indicate the proportion of main populations to cell cycle of granulosa cells may be changed from proliferative phase to G1 phase during follicular maturation in cattle.