• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.55-68
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• 1995

Approximately 30 to 70 % of the mechanical losses in a reciprocating engine are contributed by the friction at the piston ring-cylinder interface. The friction characteristics of the piston ring during engine operation is known to as mixed lubrication experimentally. The mixed lubrication models based on the Average Reynolds Equation have been used by this time in order to study the tribological performance of the ring. However, the Average Reynolds Equation contains the expected value term(${\bar{h}}_r$) of local film thickness as well as nominal film thickness(h), so that the work of numerically solving ${\bar{h}}_r$ must be included to obtain the pressure in the oil film. The process of solving ${\bar{h}}_T$ causes a greater multiplying in the numerical solution. In this paper the mixed lubrication analysis using the Simplified Average Reynolds Equation in the piston ring is presented. This equation has only h as oil film thickness term. Therefore the tedious numerical procedure required to obtain ${\bar{h}}_T$ is not needed, and also, computation time can be reduced.

• Korean Journal of Crystallography
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• v.1 no.1
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• pp.14-18
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• 1990

Econazole nitrate, 1-{2-[(4-chlorophenyl)methoxy]-2-(2,4-dichlorophenyl) ethy1}-1H-imidazole mono-nitrate.C18 H16 CI13 N3 O4 Mw=444.7 Monoclinic P/2₁c,a=17.337(4)A, b=15.191(5), c=7.601(3)A, β=91.72(2)', V=2000.9A3, Z=4, Dc=1.49g/cm3, Dm=1.45g/cm3(mo-ka)= 0.7107A, μ=4.31cm-1, F(000)=912.0, T=298'K, final R=0.061 for 1330 unique observed reflection. Each of the three ring system for the stars with B,A and C ring in order whilst A and C ring of econazole lie close to the same plane which is nearly 60˚with B ring. The hydrogen binding nitrogen of C ring and oxygen of nitrate contributes to stailization of econazole nitrate. Intr and intermolecular distances and angles are within the values recorded for simiar compounds.

• Bulletin of the Korean Chemical Society
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• v.22 no.6
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• pp.575-580
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• 2001

Intramolecular ring-ring interactions in the model compounds, $8-methoxypsoralen-CH_2O(CH_2)n-adenine(MOPCH_2OCnAd$, n=2, 3, 5, and 6) in which 5' position of 8-methoxypsoralne (8-MOP) is linked by different polymethylene bridges to N9 of adenine, have been investigated by hypochromism measurements. Efficient ring-ring stacking interactions have been observed in $MOPCH_2CO2Ad$ (7) from the percent hypochromism(%H) and fluorescence spectra of the models and a reference molecule. The 8-methoxyposralen-adenine systems have shown stronger ring-ring stacking interaction than the psoralen-adenine system.

• Korean Journal of Mathematics
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• v.30 no.3
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• pp.425-431
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• 2022

Let ℤ and ℚ be the ring of integers and the field of rational numbers, respectively. Let h(ℤ, ℚ) be the ring of composite Hurwitz polynomials. In this paper, we study the factorization of composite Hurwitz polynomials in h(ℤ, ℚ). We show that every nonzero nonunit element of h(ℤ, ℚ) is a finite *-product of quasi-primary elements and irreducible elements of h(ℤ, ℚ). By using a relation between usual polynomials in ℚ[x] and composite Hurwitz polynomials in h(ℤ, ℚ), we also give a necessary and sufficient condition for composite Hurwitz polynomials of degree ≤ 3 in h(ℤ, ℚ) to be irreducible.

• Bulletin of the Korean Chemical Society
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• v.27 no.10
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• pp.1641-1647
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• 2006

Vibrational relaxation and competitive C-$H_{methyl}$ and C-$H_{ring}$ bond dissociations in vibrationally excited methylpyrazine in the collision with HF have been studied by use of classical trajectory procedures. The energy lost by the vibrationally excited methylpyrazine upon collision is not large and it increases slowly with increasing total vibrational energy content between 20,000 and 45,000 $cm^{-1}$. Above the energy content of 45,000 $cm^{-1}$, however, energy loss decreases. The temperature dependence of energy loss is negligible between 200 and 400 K, but above 45,000 $cm^{-1}$ the energy loss increases as the temperature is raised. Energy transfer to or from the excited methyl C-H bond occurs in strong collisions with HF, that is, relatively large amount of translational energy is transferred in a single step. On the other hand, energy transfer to the ring C-H bond occurs in a series of small steps. When the total energy content ET of methylpyrazine is sufficiently high, either or both C-H bonds can dissociate. The C-$H_{methyl}$ dissociation probability is higher than the C-$H_{ring}$ dissociation probability. The dissociation of the ring C-H bond is not the result of the direct intermolecular energy flow from the direct collision between the ring C-H and HF but the result of the intramolecular flow of energy from the methyl group to the ring C-H stretch.

• Korean Journal of Mathematics
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• v.27 no.2
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• pp.465-474
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• 2019

Let ${\mathbb{Z}}$ be the ring of integers and ${\mathbb{Z}}[X]$ (resp., $h({\mathbb{Z}})$) be the ring of polynomials (resp., Hurwitz polynomials) over ${\mathbb{Z}}$. In this paper, we study the irreducibility of Hurwitz polynomials in $h({\mathbb{Z}})$. We give a sufficient condition for Hurwitz polynomials in $h({\mathbb{Z}})$ to be irreducible, and we then show that $h({\mathbb{Z}})$ is not isomorphic to ${\mathbb{Z}}[X]$. By using a relation between usual polynomials in ${\mathbb{Z}}[X]$ and Hurwitz polynomials in $h({\mathbb{Z}})$, we give a necessary and sufficient condition for Hurwitz polynomials over ${\mathbb{Z}}$ to be irreducible under additional conditions on the coefficients of Hurwitz polynomials.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.559-563
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• 1996

Total 215 magnet power supplies are under operation in Pohang Light Source(PLS). Current, voltage and peak power handling capabilities of DC power supply are in the range of 21 to 643V, 45 to 850A and 0.94 to 531KW, respectively. The DC power supplies can be categoriezed as uni-polar and bipolar power. Typical required stability and ripple of uni-polar power supplies are ${\pm}0.005%$ and ${\pm}0.05%$, respectively. The bipolar power supplies should be maintained within ${\pm}0.05%$ stability and ${\pm}0.5%$ ripple. Precise measurement results show that all power supplies meet or exceed the required specifications. The long term operation reliability to be sufficient for a stable operation of the Pohang Light Source.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.4
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• pp.78-87
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• 1995

Specular reflection appears with metals, plastics, glasses and many other solid objects which are required to be inspected, assembled, moved, or processed automatically. Recongnizing such shiny objects with specular reflections is a hard problem for computer vision, since specular reflections appear, disappear, or change their shapes abruptly, due to tiny movements of the view. Traditionally, such specular reflections are discarded as annoying noise for recongnition purposes. In this paper a technique is represented for obtaining shapes of specular objects. The ring illumin- ation system employes a ring source which is positioned on the axis of the camera. The concept of the proposed method is that if specular objects are illuminated by the ring they show their own dis- tinctive specularity features in surface from which we can infer the shape of the object. A series of experiments are performed to evaluate the performance of this system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.183-184
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• 2011

• Bulletin of the Korean Mathematical Society
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• v.48 no.5
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• pp.917-922
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• 2011

Let R be a prime ring, H a generalized derivation of R, L a noncentral Lie ideal of R, and 0 ${\neq}$ a ${\in}$ R. Suppose that $au^sH(u)u^t$ = 0 for all u ${\in}$ L, where s; t ${\geq}$ 0 are fixed integers. Then H = 0 unless satisfies $S_4$, the standard identity in four variables.