• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.2
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• pp.204-211
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• 1983

To investigate the effects of oscillatory feed cutting on the chip breaking and surface roughness and circularity, A prototype unit developed for the experiment is used. The results obtained are as follows. (1) It is obtained the region of chip breaking as Ftmin $f_{+min}$0.03mm ( = 0.3f). (2) The surface roughness becomes worse with increasing the value of A/f, but the type of variation with respect to n/N differs from the case of A/f>1, f<1. (3) The circularity of workpiece is increasing from the fundamental mode of n/N=i to the maximum value of n/N=i+0.5, and becomes worse with increasing the value of A/f. (4) From the viewpoint of above details and tool mechanics, the condition of A/f=1.0 and n/N=i.+-. .delta. (0.3<.delta.<0.4) is recommended.

• Journal of the Korean Chemical Society
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• v.17 no.1
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• pp.1-9
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• 1973

The purpose of this paper is to investigate the mechanism of Diels-Alder reaction by assuming pseudo molecular complex (PMC) which has characters both of ionic and radical bonds. We treated this complex quantum-chemically as an intermediate between the configuration without charge transfer (radical bond character) and the configuration corresponding to the charge transfer from Diene (R) to Dienophile (S) (ionic bond character). The wave function for the complex could be expressed as: ${\psi}_{complex} = {\psi}(R,S) +{ \rho}{\psi}(R^+,S^-)$ where ${\rho}$ is the extent of charge transfer which is a constant to measure the ionic character of PMC. It has been noticed that${\rho}$is related to the difference between Fr + Fr' and Fs + Fs' in free valence (F) when R is united to S through atom r in R to atom s in S and atom r' in R to atom s' in S, That is, ${\rho}{\alpha}$ ${\Delta}F = (Fr + Fr') - (Fs + Fs')$. We have calculated ${\Delta}F$values for more than forty Diels-Alder reactions. The calculated values of ${\Delta}F$ is reversely proportional to the values of Brown's paralocalization energy (Lp) as well as Dewar's differences of delocalization energy$({\Delta}Edeloc.)$ with good linearity. This approach also presents a way of predicting the possibility and the easiness of diene synthesis between any two conjugate compounds. According to the considerations, it could be concluded that Diels-Alder reaction takes place through the united ionic-radical mechanism rather than the separated ionic or radical mechanism.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.232-238
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• 2001

Experimentally it is well known that the magnetic properties significantly deteriorate when nanocomposite bonded magnet are made from nanocomposite ribbon. A decrease in maximum energy product of F $e_3$B+N $d_2$F $e_{14}$B nanocomposite from 14 MGOe in nanocomposite ribbon to 6.5 MGOe in powder compact was fecund to be general. Thus, the present study is focused on finding out the root of exchange decoupling of N $d_4$F $e_{73.5}$ $Co_3$H $f_{0.5}$G $a_{0.5}$ $B_{18.5}$ nanocomposite powder compacts. The exchange decoupling behavior of the powder compact of F $e_3$B+N $d_2$F $e_{14}$B composition was studied by measuring DC demagnetization and isothermal remanent demagnetization curves, which are essential for plotting produced $\delta$M curve. From the $\delta$M plot the deterioration in the magnetic properties resulted from the fact that the magnetostatic interaction became dominant rather thanthe exchange interaction in powder compact. It is concluded that the demagnetization behavior governed by the dominant magnetostatic interaction reduced the remanence magnetization, which caused the reduction of maximum energy Product of the powder compact. We also found that the elimination of residual stress which is unavoidably accumulated during grinding process enhanced the magnetic properties considerably.bly.bly.

• Bulletin of the Korean Chemical Society
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• v.2 no.3
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• pp.96-104
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• 1981

(1) The flow data of f (stress) and ${\dot{s}$ (strain rate) for Fe and Ti alloys were plotted in the form of f vs. -ln ${\dot{s}$ by using the literature values. (2) The plot showed two distinct patterns A and B; Pattern A is a straight line with a negative slope, and Pattern B is a curve of concave upward. (3) According to Kim and Ree's generalized theory of plastic deformation, pattern A & B belong to Case 1 and 2, respectively; in Case 1, only one kind of flow units acts in the deformation, and in Case 2, two kinds flow units act, and stress is expressed by $f={X_1f_1}+{X_2f_2}$where $f_1\;and\;f_2$ are the stresses acting on the flow units of kind 1 and 2, respectively, and $X_1,\;X_2$ are the fractions of the surface area occupied by the two kinds of flow units; $f_j=(1/{\alpha}_j) sinh^{-1}\;{\beta}_j{{\dot{s}}\;(j=1\;or\;2)$, where $1/{\alpha}_j\;and\;{\beta}_j$ are proportional to the shear modulus and relaxation time, respectively. (4) We found that grain-boundary flow units only act in the deformation of Fe and Ti alloys whereas dislocation flow units do not show any appreciable contribution. (5) The deformations of Fe and Ti alloys belong generally to pattern A (Case 1) and B (Case 2), respectively. (6) By applying the equations, f=$(1/{\alpha}_{g1}) sinh^-1({\beta}_{g1}{\dot{s}}$) and $f=(X_{g1}/{\alpha}_{g1})sinh^{-1}({\beta}_{g1}{\dot{s}})+ (X_{g2}/{\alpha}_{g2})\;shih^{-1}({\beta}_{g2}{\dot{s}})$ to the flow data of Fe and Ti alloys, the parametric values of $x_{gj}/{\alpha}_{gj}\;and\;{\beta}_{gs}(j=1\;or\;2)$ were determined, here the subscript g signifies a grain-boundary flow unit. (7) From the values of ($({\beta}_gj)^{-1}$) at different temperatures, the activation enthalpy ${\Delta}H_{gj}^{\neq}$ of deformation due to flow unit gj was determined, ($({\beta}_gj)^{-1}$) being proportional to , the jumping frequency (the rate constant) of flow unit gj. The ${\Delta}H_{gj}\;^{\neq}$ agreed very well with ${\Delta}H_{gj}\;^{\neq}$ (self-diff) of the element j whose diffusion in the sample is a critical step for the deformation as proposed by Kim-Ree's theory (Refer to Tables 3 and 4). (8) The fact, ${\Delta}H_{gj}\;^{\neq}={\Delta}H_{j}\;^{\neq}$ (self-diff), justifies the Kim-Ree theory and their method for determining activation enthalpies for deformation. (9) A linear relation between ${\beta}^{-1}$ and carbon content [C] in hot-rolled steel was observed, i.e., In ${\beta}^{-1}$ = -50.2 [C] - 40.3. This equation explains very well the experimental facts observed with regard to the deformation of hot-rolled steel..

• Journal of the Korean Society of Radiology
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• v.6 no.1
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• pp.47-51
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• 2012

PET/CT is taken 1 hour after $^{18}F$-FDG(F-18-fluoro-2-deoxy-D-glucose) injection. However, these would be often delayed for more than 2 or 3 hours due to equipment fault or unexpected situation. In the study, SUV(standardized uptake value) were measured from got image over time according to the parts of the body. As a result, there were great and small decrease in liver(middle of the right hepatic lobe), fat(Lt pelvis), lung (Rt upper lobe), aorta(ascending aorta level) of the body in delayed image, and ${\Delta}$SUVmax was increase of 37% in bone only(L5 vertebral body) of the body. ${\Delta}$SUVmax was increase of 37.6% in lesion, and the contrast degree was greater because of uptake increase in lesion and uptake decrease in the normal body.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.608-608
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• 2013

직선운동하는 하전입자의 진행방향에 수직한 평면상에 서로 직교하는 전기장과 자기장을 걸어주면, 하전입자에는 전기장에 의한 힘 $F_E$와 자기장과 속도 v에 의한 로렌츠력 $F_B=q(v{\times}B)$가 동시에 작용하게 된다. 이때 Wien 조건 $F_B=-F_E$를 만족하는 질량 $m_A$과, 에너지 $E_A$를 가지는 하전입자 A는 휘지 않고 직선운동을 계속하나, 하전입자 A와 다른 에너지 $E_B(=E_A+{\delta}E)$나 질량 $m_B$ $(=m_A+{\delta}m)$을 가지는 하전입자는 휘게 되며, 그 휘는 정도는 ${\delta}E$나 ${\delta}m$에 비례하게 된다. 이 현상을 이용하여 다양한 종류의 에너지 또는 질량 분석기가 독일, 미국, 일본 등의 분석기기 선진국에서 개발되어 왔고, 전자현미경의 이미지 필터로도 활용되고 있으며, 통상 EXB 필터 또는 발명자의 이름을 딴 Wien 필터로 불리어지고 있다. $E{\times}B$ 필터는 일반적인 하전입자빔 렌즈와 다른 광학특성을 가진다. 예를 들면 3차 이상의 기하 수차만 가지는 일반 렌즈와는 달리 $F_B$, $F_E$ 전자기력에 의해 다양한 2차 기하 수차를 가지게 되며, 초점거리 등의 1차 광학 특성도 일반 렌즈와는 다른 경향을 보여준다. 본 발표에서는 $E{\times}B$ 필터의 전후로 각각 6극자+4극자를 조합시킨 보정기를 배치시켜 필터의 에너지 분해능의 성능을 향상시킬 수 있음을 빔 궤도 방정식을 분석적으로 계산하여 보여준다. 위 에너지 필터 구성에서 4극자는 1차 광학 특성을 조정하는 역할을 하며 6극자는 2차 수차를 줄여주는 역할을 한다. 수치해석을 통해서는 6극자+4극자를 조합시킨 보정기와 $E{\times}B$ 필터의 좀더 정확한 전극 전압 등의 제어 수치를 추출하고, 빔 궤도 방정식 분석을 통한 수차 보정 알고리즘이 유효함을 보여준다.

• Journal of Welding and Joining
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• v.28 no.3
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• pp.86-91
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• 2010

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds structures used stainless steel sheets are commonly fabricated by using the gas welding. For fatigue design of gas welded joints such as fillet and plug type joint, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. And also, the influence of the geometrical parameters of gas welded joints on stress distribution and fatigue strength must be evaluated. the ${\Delta}P-N_f$ curves were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curves were rearranged in the ${\Delta}{\sigma}-N_f$ relation with the maximum stress at the edge of fillet welded joint.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.127-131
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• 2010

Stainless steel sheets are widely used as the structural material for the railroad cars and the commercial vehicles. These kinds of structures used stainless steel sheets are commonly fabricated by using the gas welding. For fatigue design of gas welded joints such as fillet and plug type joint, it is necessary to obtain design information on stress distribution at the weldment as well as fatigue strength of gas welded joints. And also, the influence of the geometrical parameters of gas welded joints on stress distribution and fatigue strength must be evaluated. Thus, in this paper, ${\Delta}P-N_f$ curves were obtained by fatigue tests. Using these results, ${\Delta}P-N_f$ curves were rearranged in the. ${\Delta}{\sigma}-N_f$ relation with the hot spot stresses at the gas welded joints.

• Bulletin of the Korean Mathematical Society
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• v.46 no.5
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• pp.999-1011
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• 2009

In this paper, we are concerned with the following eigenvalue problems of m-point boundary value problem for p-Laplacian dynamic equation on time scales $(\varphi_p(u^{\Delta}(t)))^\nabla+{\lambda}h(t)f(u(t))=0,\;t\in(0,T)$, $u(0)=0,\varphi_p(u^{\Delta}(T))=\sum\limits_{i=1}^{m-2}a_i\varphi_p(u^{\Delta}(\xi_i))$, where $\varphi_p(u)=|u|^{p-2}$u, p > 1 and $\lambda$ > 0 is a real parameter. Under certain assumptions, some new results on existence of one or two positive solution and nonexistence are obtained for $\lambda$ evaluated in different intervals. Our work develop and improve many known results in the literature even for the continual case. In doing so the usual restriction that $f_0=lim_{u{\rightarrow}0}+f(u)/\varphi_p(u)$ and $f_\infty = lim_{u{\rightarrow}{\infty}}f(u)/\varphi_p({u})$ exist is removed. As an applications, an example is given to illustrate the main results obtained.

• Bulletin of the Korean Mathematical Society
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• v.43 no.2
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• pp.309-318
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• 2006

Let X and Y be real Banach spaces and ${\varepsilon}\;>\;0$, p > 1. Let f : $X\;{\to}\;Y$ be a bijective mapping with f(0) = 0 satisfying $$|\;{\parallel}f(x)-f(y){\parallel}-{\parallel}{x}-y{\parallel}\;|\;{\leq}{\varepsilon}{\parallel}{x}-y{\parallel}^p$$ for all $x\;{\in}\;X$ and, let $f^{-1}\;:\;Y\;{\to}\;X$ be uniformly continuous. Then there exist a constant ${\delta}\;>\;0$ and N(${\varepsilon},p$) such that lim N(${\varepsilon},p$)=0 and a unique surjective isometry I : X ${\to}$ Y satisfying ${\parallel}f(x)-I(x){\parallel}{\leq}N({\varepsilon,p}){\parallel}x{\parallel}^p$ for all $x\;{\in}\;X\;with\;{\parallel}x{\parallel}{\leq}{\delta}$.