• Current Optics and Photonics
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• 제1권4호
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• pp.402-411
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• 2017

Combined LIBS-Raman spectroscopy has been widely studied, due to its complementary capabilities as an elemental analyzer that can acquire signals of atoms, ions, and molecules. In this study, the classification of polymorphs was performed by laser-induced breakdown spectroscopy (LIBS) to overcome the limitation in molecular analysis; the results were verified by Raman spectroscopy. LIBS signals of the $CaCO_3$ polymorphs calcite and aragonite, and $CaSO_4{\cdot}2H_2O$ (gypsum) and $CaSO_4$ (anhydrite), were acquired using a Nd:YAG laser (532 nm, 6 ns). While the molecular study was performed using Raman spectroscopy, LIBS could also provide sufficient key data for classifying samples containing different molecular densities and structures, using the peculiar signal ratio of $5s{\rightarrow}4p$ for the orbital transition of two polymorphs that contain Ca. The basic principle was analyzed by electronic motion in plasma and electronic transition in atoms or ions. The key factors for the classification of polymorphs were the different electron quantities in the unit-cell volume of each sample, and the selection rule in electric-dipole transitions. The present work has extended the capabilities of LIBS in molecular analysis, as well as in atomic and ionic analysis.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.5-6
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• 2006

Molecular motion at the surface of monodisperse polystyrene (PS) films with various chain end groups was studied by scanning probe microscopy. Surface glass transition temperature ($T_{g^s}$) of the PS films was much lower than the corresponding bulk value. And, the magnitude of $T_{g^s}$ was strongly dependent on chain end chemistry. This result can be explained in terms of the chain end concentration at the surface. Time-temperature superposition principle was applied to rheological analysis at the surface. The apparent activation energy of the surface ${\alpha}_{a}$-relaxation process was approximately a half of that for the bulk sample. This result clearly indicates that the cooperativity for the surface segmental motion was reduced in comparison with that in the bulk region.

• Applied Science and Convergence Technology
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• 제26권1호
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• pp.6-10
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• 2017

We investigated the stability of ionic configurations of the tip of the cantilever in non-contact AFM.; For this, we used a computational model that couples the ionic motion of the MgO surface and the oscillating cantilever. The motion of ions was connected to the oscillating cantilever using a coupling method that had been recently developed. The adhesive process on the ionic MgO surface leads to energy dissipation of the cantilever. It is shown that limited types of ionic configurations of the tip are stable during the adhesive process. Based on the present computational model, we discuss the adhesive mechanism leading to energy dissipation.

• 대한화학회지
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• 제29권3호
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• pp.205-212
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• 1985

2,2'-bipyridyl crown ether에 관한 allosteric 효과를 분자진동연구방법을 사용하여 연구하였는데, 방법으로는 mass-weighted-cartesian 좌표방법을 사용하였다. Crown ether의 pore opening 운동에 관여하는 모드로는 235, 234, 188 그리고 178cm$^{-1}$에 해당되는 파수가 얻어졌고, biphenyl축을 통한 회전운동이 crown ether에 영향을 미치는 rotational vibration 운동은 168, 104 그리고 67cm$^{-1}$에서 파수가 얻어졌다. 특히 178cm$^{-1}$의 모드는 allosteric효과를 가장 많이 포함한 것으로 생각되어 진다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.265-270
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• 2001

Hip joint simulator which Is an essential device for evaluating the wear of biomaterials (ultrahigh molecular weight polyethylene, Co-Cr alloy, alumina, etc.) used in total hip joint replacement was developed. This hip joint simulator mimics the joint motion and joint loading of human gait by adapting the 4 degree of freedom in kinematic motion (flexing/extension, adduction/abduction, Internal rotation/external rotation) and axial loading, Four stations are operated by 8 servo-motors and harmony drives. Joint leading was imposed by displacement control from a ball screw, LM guide, and spring system. Each kinematic link system operates separately or coupled modes. A heater and a thermocouple were installed for keeping the body temperature in each station.

• Bulletin of the Korean Chemical Society
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• 제20권9호
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• pp.1010-1016
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• 1999

We synthesized the photoresponsive side chain polymers containing aminonitro azobenzene for studying the effect of temperature on photoinduced birefringence. Four different copolymers were prepared using methacrylate, α-methylstyrene, and itaconate monomer. Photoisomerization was observed under the exposure of UV light using UV-VIS absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532 nm. The change of the birefringence was observed with increasing the sample temperature under a continuous irradiation of excitation light. We could estimate the activation energy of molecular motion in thermal and photochemical mode. Besides the effect of glass transition temperature on the activation energy, we focused our interests on the effect of geometrical hindrance of polar azobenzene molecules and cooperative motion of environmental mesogenic molecules in the vicinity of polar azobenzene molecules.

• 천문학회보
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• 제44권1호
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• pp.47.2-47.2
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• 2019

We present a kinematic study of the two young OB associations Cygnus OB2 and Carina OB1 using the recently released Gaia astrometric data. The unimodal distributions of parallaxes of stars indicate that these associations are real stellar systems, rather than line-of-sight coincidences. The associations are found to comprise dense star clusters and a sparse halo which have different proper motions. Clusters have small spatial sizes with small dispersions in proper motion, while the haloes extending to tens of parsecs have a large dispersion in proper motion. We speculate that this aspect is related to that found in molecular clouds, the so-called "line width-size" relation. In this talk, the formation process of these associations is discussed, based on our findings.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.1102-1107
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• 2005

The analysis of the thermal boundary resistance is very important in the both cases of microscale and macroscale systems because it plays a role of thermal barrier against a heat flow. Especially, since fairly large heat energy is generated in microscale or nanoscale systems with electronic chips, the thermal boundary resistance is a key factor to guarantee the performance of those devices. In this study, the transfer of the oscillator's motion information with 2 degrees of freedom is investigated for clarifying the mechanism of a thermal boundary resistance. We found that the transfer of the oscillator's motion information is defined as a cross-correlation coefficient and the magnitude of it determines the temperature jump over a solid interface. That is, the temperature jump over an interface increases as the magnitude of a cross-correlation coefficient decreases and vice versa.

• 한국지구과학회지
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• 제39권6호
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• pp.519-532
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• 2018

우리는 오리온 분자운 복합체의 북부 필라멘트(이하 NF)에 대하여 $^{12}CO$ (J=1-0) 분자선의 자료를 이용하여 은하 평면이 분자의 운동과 운동학에 미치는 영향을 연구하였다. 6 m 서울대학교 전파망원경(Seoul Radio Astronomy Observatory, SRAO)을 이용하여 2arcmin 공간분해능으로 은하면으로부터 먼 순서로 NF1, NF2, NF3 세 곳을 총 270시간 동안 관측된 자료를 사용하였다. 은하면과 OMC NF는 $^{12}CO$ (J=2-1) 경우 3% 밀도에서, 티끌의 경우 9% 밝기 수준에서 자기장을 따라 서로 연결되어 있었다. $^{12}CO$ (J=1-0), $^{12}CO$ (J=2-1), 성간 티끌 관측결과를 비교해본 결과, 세 경우 모두 NF3에서는 고루 분포했지만, NF1과 NF2에서는 비교적 밀도가 높은 특정 영역에서만 함께 나타났다. NF는 단일 구조를 보였으며, NF1에서는 부분 수축 운동을, NF2에서는 하단에서 회전 운동이 나타났고, NF3에서는 유일하게 명확히 자기장에 연관된 나선형 회전이 보였다. 위치-속도 분석 결과, $^{12}CO$ (J=1-0)를 비롯한 물질들은 NF2와 NF3을 따라 은하면을 향하여 흐를 가능성이 있음을 확인할 수 있었다. 은하면을 향하여 물질이 흐르는 명백한 원인을 이번 연구결과에서 볼 수 없었지만 추후의 더 정교한 관측결과가 NF1과 NF2 상단부의 회전 운동을 확인 할 수 있겠다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.990-994
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• 2004

This paper presents a method to predict the transient characteristic of the air lubricated slider head in a hard disk drive by using optimization technique. The time dependent modified Reynolds equation based on the molecular slip flow approximation equations was used to describe the fluid flow within the air bearing and the implicit finite difference scheme is applied to calculate the pressure distribution under the slider head. The exhaustive search combined with the Broyden-Fletcher-Goldfarb-Shanno method were employed to obtain optimum design variables which are taper angle, rail width and taper length in order to keep the forces and moments acting on the slider head in dynamic equilibrium. The results show that the optimal head slider of the magnetic head has good stability characteristic that can reach the steady state within 0.5 microsecond.