• 대한기계학회논문집A
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• 제20권8호
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• pp.2468-2479
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• 1996

An upper bound solution is obtained to perform the process analysis of hot strip rolling process. The material flows within the roll bite at various geometries and frictional conditions are obtained from finite element analysis and the typical flow pattern which is necessary to determine the kinematically admissible velocity field is assumed. From the kinematically admissible velocity field, the upper bound energy is calculated and the rolling load, angle of neutral point and forward slip ratio at various operational conditions are obtained from upper bound energy. The process analysis of above mentioned parameters at various operational conditions have provided valuable information which is hard to obtain during rolling operation and the predicted ranges of quantitive values from these analyses lie whthin the bound of actual operational data.

• Earthquakes and Structures
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• 제17권5호
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• pp.435-445
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• 2019

The collapses of curved bridges are mainly caused by the damaged columns, subjected to the combined loadings of axial load, shear force, flexural moment and torsional moment, under earthquakes. However, these combined loadings have not been fully investigated. This paper firstly investigated the mechanical characteristics of the bending-torsion coupling effects, based on the seismic response spectrum analysis of 24 curved bridge models. And then 9 reinforced concrete (RC) and circular column specimens were tested, by changing the bending-tortion ratio (M/T), axial compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratio, respectively. The results show that the bending-torsion coupling effects of piers are more significant, along with the decrease of girder curvature and the increase of pier height. The M/T ratio ranges from 6 to 15 for common cases, and influences the crack distribution, plastic zone and hysteretic curve of piers. And these seismic characteristics are also influenced by the compression ratio, longitudinal reinforcement ratio and spiral reinforcement ratios of piers.

• 공업화학
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• 제32권3호
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• pp.348-356
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• 2021

The lignocellulose-based dried watermelon rind (WR) was modified with sulfuric acid, namely SWR for enhancement of methylene blue (MB) adsorption from the aqueous solution. According to FT-IR analysis, after the modification of WR with sulfuric acid, the functional groups of R-SO₃H, COOH and -OH groups was formated or enhanced on the surface of the WR. Moreover, the point of zero charge (pHpzc) was changed from 6.3 to 4.1 after modification, which widened the range for adsorbing of cationic dye MB. The adsorption process of MB onto the SWR was suitable for pseudo-2nd-order and Langmuir model and the maximum adsorption capacity of Langmuir was found to be 334.45 mg/g at pH 7. In adition, the adsorption process occurs through the electrostatic interaction, hydrogen bridge formation, electron donor-acceptor relationship, and 𝜋-𝜋 electron dispersing force between functional groups on the carbon surface with MB molecules. Depending on functional groups available on the SWR surface, the MB adsorption mechanism can occur in combination with various interactions.

• Geomechanics and Engineering
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• 제34권2호
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• pp.187-195
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• 2023

Intensive rainfall during the summer season in Korea has triggered numerous devastating landslides outside of downtown in mountainous areas. The 2D slope stability analysis that is generally used for cut slopes and embankments is inadequate to model slope failure in mountainous areas. This paper presents a new 3D slope stability formulation using the global sliding vector in the limit equilibrium method, and it uses an ellipsoidal slip surface for static and quasi-static analyses. The slip surface's flexibility of the ellipsoid shape gives a lower FS than the spherical failure shape in the Fellenius, Bishop, and Janbu's simplified methods. The increasing sub-columns of each column tend to increase the FS and converge to a steady value. The symmetrical geometric conditions of the convex turning corners do not indicate symmetrical failure of the surface in 3D analysis. Pseudo-static analysis shows that the horizontal seismic force decreases the FS and increases the mass volume at the critical failure state. The stability index takes the FS and corresponding sliding mass into consideration to assess the potential risk of slope failure in complex mountainous terrain. It is a valuable parameter for selecting a vulnerable area and evaluating the overall risk of slope failure.

• 대한토목학회논문집
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• 제8권1호
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• pp.87-95
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• 1988

극지(極地) 해역(海域)의 경우(境遇) 극심(極甚)한 환경(環境) 조건(條件)으로 인(因)하여 육중(肉重)한 중력식(重力式) 해양구조물(海洋構造物)이 제안(提案)되고 있는데 이와 같이 구조물(構造物)의 특성(特性)길이가 입사파(入射波)의 파장(波長)에 비(比)하여 무시(無視)할 수 없을 정도(程度)이면 선형(線形) 회절(廻折) 이론(理論)을 적용(適用)하여 구조물(構造物)에 작용(作用)하는 전(全) 파력(波力)을 계산(計算)하여 왔다. 그러나 구조해석(構造解析)과의 연계(連繫)를 고려(考慮)하면 수심별(水深別) 파력(波力)의 분포(分布)와 파랑압력(波浪壓力)의 분포(分布)가 요구(要求)되어지므로 기개발(旣開發)된 연직(鉛直) 축대칭(軸對稱) 물체(物體)에 작용(作用)하는 전파력계산(全波力計算) 프로그램을 일부(一部) 수정(修正)하였다. 압력(壓力)의 경우(境遇) 고정(固定) 원통(圓筒)에 대한 MacCamy-Fuchs의 해석적(解析的) 해(解)와 비교(比較)해본 결과(結果) Green함수(凾數)의 Fourier Mode, l값은 해석해(解析解)를 계산(計算)할 경우(境遇)는 6을 사용(使用)하고 수식해(數植解)를 계산(計算)할 경우(境遇)에는 5로 하여 계산(計算)하면 충분(充分)한 정확도(正確度)를 얻을 수 있었다. 이렇게 구한 파랑하중(波浪荷重) 자료(資料)들은 구조물(構造物)의 응사(凝似) 정적해석(靜的解析), 동적해석(動的解析) 및 피로해석시(疲勞解析時)에 사용(使用)되어 질 것이다.

• 한국재료학회지
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• 제21권12호
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• pp.697-702
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• 2011

Two-dimensional (2D) nano patterns including a two-dimensional Bravais lattice were fabricated by laser interference lithography using a two step exposure process. After the first exposure, the substrate itself was rotated by a certain angle, $90^{\circ}$ for a square or rectangular lattice, $75^{\circ}$ for an oblique lattice, and $60^{\circ}$ for a hexagonal lattice, and the $90^{\circ}$ and laser incident angle changed for rectangular and the $45^{\circ}$ and laser incident angle changed for a centered rectangular; we then carried out a second exposure process to form 2D bravais lattices. The band structure of five different 2D nano patterns was simulated by a beam propagation program. The presence of the band-gap effect was shown in an oblique and hexagonal structure. The oblique latticed ZnO nano-photonic crystal array had a pseudo-bandgap at a frequency of 0.337-0.375, 0.575-0.596 and 0.858-0.870. The hexagonal latticed ZnO nano-crystallite array had a pseudo-bandgap at a frequency of 0.335-0.384 and 0.585-0.645. The ZnO nano structure with an oblique and hexagonal structure was grown through the patterned opening window area by a hydrothermal method. The morphology of 2D nano patterns and ZnO nano structures were investigated by atomic force microscopy and scanning electron microscopy. The diameter of the opening window was approximately 250 nm. The height and width of ZnO nano-photonic crystals were 380 nm and 250 nm, respectively.

• 한국지반신소재학회논문집
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• 제21권3호
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• pp.41-48
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• 2022

수처리 지중구조물의 내진설계에서 내진설계 시보다 일반설계의 경우에 부재력 값이 더 크다고 알려져 있다. 그러나 이는 수처리 지중구조물의 종류 즉, 정수지 구조물, 침전지 구조물, 공동구 구조물에 따라서 다르다. 또한 최근 국내에서 발생한 지진의 규모를 보면 대형지진이 빈번하므로 설계지진력의 크기가 커질 때 수처리 지중구조물의 내진거동의 규명 및 대처방안이 필요하다. 본 연구에서는 수처리 지중구조물의 종류별로 하중계수 즉, 설계지진가속도를 일정 비율로 증가시키면서 지중구조물의 지진응답을 분석하고 변화를 나타내는 식을 제안하여 향후 설계기준 개정시에 참조하도록 하였다. 해석은 등가 정적해석법과 응답 변위해석법을 적용하고, 지하수 유무, 토피고에 따라서 다양하게 분석하였다. 본 연구에서 제안된 식은 향후 수처리 지중구조물의 설계기준 개정시에 유용할 것으로 판단된다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2719-2723
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• 2012

A kinetic study is reported for nucleophilic substitution reactions of benzyl 4-pyridyl carbonate 6 with a series of alicyclic secondary amines in MeCN. The plot of pseudo-first-order rate constant ($k_{obsd}$) vs. [amine] curves upward, which is typical for reactions reported previously to proceed through a stepwise mechanism with two intermediates (i.e., a zwitterionic tetrahedral intermediate $T^{\pm}$ and its deprotonated form $T^-$). Dissection of $k_{obsd}$ into the second- and third-order rate constants (i.e., $Kk_2$ and $Kk_3$, respectively) reveals that $Kk_3$ is significantly larger than $Kk_2$, indicating that the reactions proceed mainly through the deprotonation pathway (i.e., the $k_3$ process) in a high [amine] region. This contrasts to the recent report that the corresponding aminolysis of benzyl 2-pyridyl carbonate 5 proceeds through a forced concerted mechanism. An intramolecular H-bonding interaction was suggested to force the reactions of 5 to proceed through a concerted mechanism, since it could accelerate the rate of leaving-group expulsion (i.e., an increase in $k_2$). However, such H-bonding interaction, which could increase $k_2$, is structurally impossible for the reactions of 6. Thus, presence or absence of an intramolecular H-bonding interaction has been suggested to be responsible for the contrasting reaction mechanisms (i.e., a forced concerted mechanism for the reaction of 5 vs. a stepwise mechanism with $T^{\pm}$ and $T^-$ as intermediates for that of 6).

• 동력기계공학회지
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• 제16권2호
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• pp.66-74
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• 2012

In this paper, the authors propose a new approach to control a barge type surface vessel. It is based on the Dynamic Positioning System(DPS) design. The main role of barge ship is to carry and supply the materials to the floating units and other places. To carry out this job, it should be positioned in the specified area. However sometimes the thrust systems are installed on it, and in general the rope control by mooring winch system is used. It may be difficult to compare the control performances of two types. If we consider this problem in point of usefulness, we can easily find out that the winch control system is more useful and applicable to the real field than the thrust control system except a special use. Therefore, in this paper we consider a DPS design problem which can be extended to the many application fields. The goal of this paper is twofold. First, the sliding mode controller (SMC) for positioning the our vessel is proposed. Especially, in this paper, a robust stability condition is given based on descriptor system representation. In the result, the sliding mode control law guarantees to keep the vessel in the defined area in the presence of environmental disturbances. And second, the thrust allocation problem is solved by using redistributed pseudo-inverse (RPI) algorithm to determine the thrust force and direction of each individual actuator. The proposed approach has been simulated with a supply vessel model and found work well.

• Archives of Pharmacal Research
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• 제14권2호
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• pp.181-187
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• 1991

The muscarinic antagonist 1-[benzilic 4, 4'-$[^3H]$ QUINUCLIDINYL BENZILATE $([^3H]$ QNB) bound to a single class of muscarinic receptors with high affinity in rabbit ileal membranes. The $K_D\;and\;B_{ max}$ values for $([^3H]$ QNB calculated from analysis of saturation isotherms were 52.5 pM AND 154 fmol/mg, respectively. Chlopheniramine (CHP), histamine $H_1$ blocker, increased $K_D$ vlue for $([^3H]$QNB without affecting the binding site concentrations and Hill coefficient. The $K_i$ value of CHP for inhibition of $([^3H]$QNB binding in ileal membranes was 1.44\mu{M}$ and the pseudo-Hill coefficient for CHP was close to unit. In the functional assay carbachol, muscarinic agonist, increased the contractile force of ileum with $ED_{50}$ value of $0.11\mu{M}$. CHP caused the rightward shift of the dose-response curve to carbachol. The $pA_2$ value of CHP determined from Schild analysis of carbacholinduced contraction was 5.77 and the slope was unity indicating competitive antagonism with carbachol. The dissociation constant $(K_i)$ of CHP obtained in competitive experiments with $([^3H]$ QNB was similar to the $K_A$ value (1.69 \mu{M)}$ of CHP as inhibitor of carbachol induced contraction in rabbit ileum. This result suggest that the binding of $H_i$ blocker. CHP, vs $([^3H]$QNB to muscarinic receptors in ileal membranes represents an interaction with a receptor of physiological relevance.