• Smart Structures and Systems
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• 제10권2호
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• pp.181-192
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• 2012

Magnetic suspensions based on passive levitation of diamagnetic materials on permanent magnets provide attractive systems for several applications on the micro and meso scales. The magnetic properties of these kinds of suspensions dramatically reduce the global mechanical stiffness of the devices providing significant effects on their dynamic response. The goal of this paper is to investigate the static and dynamic behavior of magnetic suspensions with respect to its dependant parameters. Experimental measurements have been performed on the response of dedicated prototypes where the geometrical dimensions and magnetic field strength have been intended as variable parameters. Some benefits have been documented in the fields of energy harvesting and inertial sensing, while additional applications of magnetic suspensions are under investigation.

• 한국세라믹학회지
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• 제27권4호
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• pp.553-559
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• 1990

The nonuniform shrinkage has been investigaed in pressureless sintering of $\alpha$-SiC, where born carbide and phenolic resin as a carbon source are used as densification aids. Compacted specimens, prepared from the granulated powder, were sintered at 215$0^{\circ}C$ for 30min in Ar atmosphere. Using the fresh and unseasoned graphite crucible, the upwarped specimens were obtained, while specimens were uniformly shrunk in the seasoned crucible. This effect is mainly due to the nonuniform distributjion of boron carbide during heatig, which originates in the reaction of boron carbide with CO gas, providing from the result of SiO2 reduction with carbon during heating.

• 분석과학
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• 제16권5호
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• pp.426-429
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• 2003

Neutron induced prompt gamma-ray spectroscopy (NIPS) system equipped with a $^{252}Cf$ neutron source and a n-type coaxial HPGe detector was installed for the quantitative analysis of aqueous samples in KAERI, Korea. Since the thermal neutron flux for the $^{252}Cf$ neutron source is relatively low compared to that for the reactor, the use of a thermal neutron reflector in the NIPS system may lead to improved results. The enhancement by using various reflectors was carried out by comparing the Cl peak with or without a cadmium plate between sample and the $^{252}Cf$ source. The use of pyrolitic graphite as a reflector provided a good result.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 C
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• pp.1600-1602
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• 1997

We have studied microstructure of carbn fiber and graphite using scanning electron microscope, x-ray diffractommetry and x-ray photoelectron spectroscopy. According to the results, intercalation of lithium ion affected formation of film on carbon surface and changed structural parameter. Also, we found that film on carbon surface included lithium ion. And, the results of XPS indicated that surface of lithiated carbon materials existed P and F consisting electrolyte. Thus, We expected electrolyte cointercalated with lithium.

• 한국주조공학회지
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• 제6권2호
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• pp.93-103
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• 1986

It is very important to obtain wear resistant ductile iron by adding more economical alloying elements. In this study, 10 heat of Mg-treated ductile iron were made according to Sb content (0-0.1% Sb). Each melt was tasted to 30 ${\o}test$ bars in $CO_2$ mold under the same condition and inspected wear characteristics, mechanical properties and microstructures. The results obtained from this study are as follows; 1. It is confirmed that Sb should be a simple and useful additive for improving wear resistance in ductile iron. 2. Hardness of ferrite and pearlite is improved with increasing Sb amount in ductile iron. 3. For ductile iron, the recommended ladle addition of Sb amount is to 0.02-0.03%. 4. Sb has adverse influence on spheroidizing of graphite if the amount is over 0.04%.

• Archives of Pharmacal Research
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• 제11권1호
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• pp.74-79
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• 1988

Crystals of tolazamide, $C_{14}H_{21}N_3O_3S$, are triclinic space group $P{\bar{1}}$ with cell dimensions of a = 6.355 (2), b = 9.223 (2), c = 13.510 (3) A, ${\alpha}\;=\;101.04\;(8),\;{\beta}=92.80(5),\;{\gamma}\;=\;85.72\;(6)^{\circ}$ and Z = 2. Intensities were collected on an automated four-circle diffractometer using graphite-monochromated Cu K ${\alpha}$ radiations. The structure was solved by direct method and refined by full-matrix least-squares to an R factor of 0.058 for 1184 observed reflections. The molecules are dimerized by the $N-H{\cdots}O$ hydrogen bonds. There are only van der Waals interactions between these molecular dimers.

• 한국결정학회지
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• 제9권2호
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• pp.120-124
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• 1998

N-tert-Butyl-2-(1-acetoxy-2-fluoro-1-butyl)benzenesulfonamide의 분자 및 결정구조를 X-선회절법으로 연구하였다. 결정의 공간군은 P21/c이고, 단위포 상수는 a=8.583(2) , b=14.674(2) , c=14.703(2) , β=103.23(1)0, Z=4, V=1802.6(5) 3, Dc=1.27 Mgm-3이다. 회절반점들의 세기는 Rigaku AFC-5 Diffractometer로 얻었으며, graphite로 단색화한 Cu-KαX-선을 사용하였다. 분자구조는 직접법으로 풀었으며 최소자승법으로 정밀화하였다. 최종신뢰도 R값은 2472개의 회절반점에 대하여 0.069였다. 분자 내에 N(7)과 O(4)사이에 1개의 수소결합[2.990(4) ]을 갖으며, C(14)와 C(15)는 반대배열을 갖고 있다. 분자간 가장 인접한 거리는 3.465(5) [C(19) O(5)] (symmetry code: -x, y+1/2, -z+1/2)로 분자간 접촉은 van der Waals 힘에 의해 결합되어 있다.

• Carbon letters
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• 제5권1호
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• pp.6-11
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• 2004

In spite of unparalleled combination of essential material properties for brake linings and clutch facings, replacement for asbestos is seriously called for since it is a health hazard. Once asbestos is replaced with other material then composition and properties of brake pad changes. In certain cases hardness of the material may be high enough to affect the rotor material. In this study, hardness of the brake pad has been controlled using suitable reinforcement materials like glass, carbon and Kevlar pulp. Brake pad formulations were made using CNSL (cashew net shell liquid) modified phenolic resin as a binder, graphite or cashew dust as a friction modifier and barium sulphate, talc and wollastonite as fillers. Influence of each component on the hardness value has been studied and a proper formulation has been arrived at to obtain hardness values around 35 on Scleroscopic scale. Friction and wear properties of the respective brake pad materials have been measured on a dynamometer and their performance was evaluated.

• 한국진공학회:학술대회논문집
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• 한국진공학회 1992년도 제3회 학술발표회 논문개요집
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• pp.17-17
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• 1992

In this talk, our recent progress in experiment study on microscopic surface phonons has been reviewed. After the brief introduction concerning the concept of surface phonons, exprimental apparatus of HREELS and the principle of the measurment for surface phonon dispersions, I show the experimental data of some solide surfaces. The following points are discussed ; (1) lattice dynamical analysis of the phonon dispersions of some transi tion metal carbide (100) surfaces indicates the large changes in the force constant near the surface, which is consistent wi th a rippled structure of a topmost layer. (2) the phonon dispersions of a graphite overlayer show the modified phonon structure, which indicates that the thickness of the overlayer is one atomic layer, and in addition, the electronic structure is also modified. (3) The phonon structure of $LaB_6$ (100) surface is discussed. Lastly I telJ about new technology of extreme high vaccum less than $10^{-10}$ Pa.EX> Pa.

• Bulletin of the Korean Chemical Society
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• 제11권1호
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• pp.19-21
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• 1990

The crystal structure of Bithionol, $C_{12}H_6Cl_4O_2S$, has been determined from X-ray intensity data measured by Enraf-Nonius CAD-4 diffractometer using graphite-monochromatized $Mo-K\alpha$ radiation. The crystal data as follows; triclinic space group P{\bar{1}}$, a = 8.879(2), b = 10.782(1), c = 8.511(1)${\AA}$, ${\alpha}$ = 115.43(1), ${\beta}$ = 115.22(1), ${\gamma}\;=\;74.44^{\circ}(1)$. ${\mu}\;=\;9.51\;cm^{-1}$, F(000) = 356, Z = 2. Final R value is 0.036 for independent 2669 observed reflections. Each six-membered benzene rings are coplanar within experimesntal errors and the dihedral angle between these planes is $81.28^{\circ}$ (1). The S-(1) and S-C(7) distances are 1.787(2) and 1.791(3)${\AA}$, respectively.