• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.125-127
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• 2000

We report high pressure synthesis of Sr$_{0.9}$Sm$_{0.1}$CuO$_2$. Powder x-ray diffraction showed that the synthesized compounds have infinite layer structure as a major component. Slow heating at the first stage of heating processes after pressurization resulted in several larger grains. The largest grain was found to have the longest edge length of about 100 micrometer. Through magnetic property measurement in superconducting state, we found that pinning in this compound has substantial difference from that of La doped infinite layer, which has no unpaired spin at Sr site.

• 센서학회지
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• 제14권4호
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• pp.244-249
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• 2005

In this study, radiation sensor tips are fabricated for remote sensing of X or gamma ray with inorganic scintillators and plastic optical fiber. The visible range of light from the inorganic scintillator that is generated by radiation source is guided by the plastic optical fiber and is measured by optical detector and power-meter. Two kinds of sensor tips are designed and fabricated such as film type and powder type. Many kinds of inorganic scintillators are used to fabricate both sensor tips, and the different wavelength of emitting lights from them are measured to determine the optimal inorganic scintillator which has maximum light output. As a radiation source X-ray generator and Ir-192 are selected to test a performance of sensor tip. It is expected that the fiber-optic radiation sensor is widely used in nuclear industry and medical applications due to its special characteristics such as good flexibility, easy in processing, long lengths and no interference to electro magnetic field.

• 정보저장시스템학회논문집
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• 제3권2호
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• pp.66-72
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• 2007

Surface finishing using magnetorheological (MR) fluid is useful to finish small but not too small workpieces such as those in a few millimeter scale. However, due to the high surface hardness, this finishing process does not seem to be suit for applying to a hard disk slider. In this work, a preliminary study is performed on the finishing of the hard disk slider surface with a mixture of an MR fluid and diamond powder. During a wheel type MR finishing process, centrifugal force is found to be a major factor to cause a reduction in material remove rate (MRR), which is supported by a theoretical model. To facilitate this founding, the rotational speed of tool is confined to 500rpm while a rectilinear alternating motion with the mean speed, which is equivalent to the rotational speed, is additionally applied to the workpieces. As a consequence, MRR of about 2 times of the sole rotational case is obtained. This paper shows that MR finishing process can be used to polish a hard material in millimeter scale efficiently by controlling the speeds of the tool and the workpiece.

• 한국세라믹학회지
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• 제39권12호
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• pp.1119-1123
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• 2002

Nanostructured spinel NiZn ferrites were prepared by the sol-gel method from metal nitrate raw materials. Analyses by X-ray diffraction and scanning electron microscopy showed the average particle size of NiZn ferrite was under 50 nm. The single phase of NiZn ferrites was obtained by firing at 250${\circ}C$, resulting in nanoparticles exhibiting normal ferrimagnetic behavior. The nanostructured $Ni_{1-X}Zn_XFe_2O_4$ (x=0.0∼1.0) were found to have the cubic spinel structure of which the lattice constants ${\alpha}_2$ increases linearly from 8.339 to 8.427 ${\AA}$ with increasing Zn content x, following Vegard's law, approximately. The saturation magnetization $M_s$ was 48 emu/g for x=0.4 and decreased to 8.0 emu/g for higher Zn contents suggesting the typical ferrimagnetism in mixed spinel ferrites. Pure NiZn ferrite phase substituted by Cu was observed before using the additive but hematite phase was partially appeared at $Ni_{0.2}Zn_{0.2}Cu_{0.6}Fe_2O_4$. On the other hand, the hematite phase in this NiZn Cu ferrite was disappeared after using the additive of acethyl aceton with small amount. The saturation magnetization Ms of $Ni_{0.2}Zn_{0.8-y}Cu_yFe_2O_4$(y=0.2∼0.6) as measured was about 51 emu/g at 77K and 19 emu/g at room temperature, respectively.

• 대한화학회지
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• 제38권9호
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• pp.628-631
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• 1994

펄스 핵자기공명 기법을 이용하여 상자성 물질인 $CuF_2$를 조사한 결과 상온에서 $^{19}F$ 위치의 차이에 의한 확연히 구별되는 두 개의 공명선을 얻었다. 한 선은 진동수 이동이 거의 없었지만 다른 한 선은 진동수 이동이 심했다. 두 경우 모두 스핀-격자 완화시간$(T_1)$이 짧지만 진동수 이동이 심한 경우에 $T_1$ 이 더 짧았다. 이는 두 경우에 대한 주위의 전자 환경이 다르기 때문으로 해석된다.

• Bulletin of the Korean Chemical Society
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• 제30권5호
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• pp.1021-1025
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• 2009

A novel supramolecular network containing binuclear copper unit $[Cu(phen)_{2}({\mu}-ID\;A)Cu(phen){\cdot}(NO_{3})](NO_{3}){\cdot}4(H_{2}O)$ (1) was synthesized through the self-assembly of iminodiacetic acid ($H_2IDA$) and 1,10-phenanthroline (phen) in the condition of pH = 6. It has been characterized by the infrared (IR) spectroscopy, elemental analysis, single crystal X-ray diffraction, and thermogravimetric analysis (TGA). 1 shows a 2-D supramolecular structure assembled through strong and unique $\pi-\pi$ packing interactions. Density functional theory (DFT) calculations show that theoretical optimized structures can well reproduce the experimental structure. The TGA and powder X-ray diffraction (PXRD) curves indicate that the complex 1 can maintain the structural integrity even at the loss of free water molecules. The magnetic property is also reported in this paper.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.53-53
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• 2008

Piezoelectric transformers have been widely used such as DC-DC convertor, invertor, Ballast, etc. Because, the y have some merits compared with electro-magnetic transformers such as step-up ratio, high efficiency, small size and lg hit weight, etc. Piezoelectric transformer require high electromechanical coupling factor kp in order to induce a large out put power in proportional to applied electric field. And also, high mechanical quality factor Qm is required to prevent mechanical loss and heat generation. In general, PZT system ceramics should be sintered at high temperatures between 1200 and $1300^{\circ}C$ in order to obtain complete densification. Accordingly, environmental pollution due to its PbO evaporation. Hence, to reduce its sintering temperature, various kinds of material processing methods such as hot pressing, high energy mill, liquid phase sintering, and using ultra fine powder have been performed. Among these methods, liquid phase sintering is basically an effective method for aiding densification at low temperature. In this study, In order to comparis on low temperature sintering and solid state sintering piezoelectric transformers, rosen type transformers were fabricated u sing two PZT ceramics compositions and their electrical properties were investigated.

• 한국자기학회지
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• 제5권3호
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• pp.171-174
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• 1995

성자성 $CuF_{2}$의 $^{19}F$에 대한 펄스 핵자기공명을 수행하였다. 분말시료에 대하여 상온과 질소온도에서 측정된 선모양은 서로 다른 자리의 $^{19}F$에 대응하는 잘 분리된 두개의 공명선으로 구성되었다. 두 공명선의 서로 다른 주파수 이동량을 구리원자로부터 불소 원자로 부분적으로 이동된 전자에 의한 기여로 해석할 수 있었다. 두 공명선은 모두 매우 짧은 스핀-격자 완화시간($T_{1}$)을 나타내었으며 더 큰 주파수 이동을 나타내는 $^{19}F$ 공명선이 더 짧은 스핀-격자 완화시간을 보였다. 이를 두 $^{19}F$ 자리 주위의 서로 다른 전자 환경이 반영되어 나타난 것으로 해석하였다.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4122-4126
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• 2012

Cellulose-graft-poly (L-lactide) (cellulose-g-PLLA) was successfully prepared via ring-opening polymerization (ROP) by using 4-dimethylaminopyridine (DMAP) as an organic catalyst in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). The structure and morphology of the polymer was characterized by nuclear magnetic resonance (NMR) and transmission electron microscope (TEM). From wide-angle X-ray powder diffraction (WAXD) and degradation test (by acid, alkaline, PBS and enzyme solution), changes in the crystalline structure as a result of degradation was also investigated. The results indicated that materials which have low degree of crystallinity showing higher degradability, however, in acid liquor, enzyme solution, alkaline liquor and PBS system, the degradation rate of the polymer decreased by the above sequence. Moreover, with the further increase of graft degree of this material, its degradation degree decreased.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2012년도 추계학술대회
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• pp.125-127
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• 2012

With the progress of electronics and radio communication technology, human enjoys greater freedom in communication. However, EMW (Electro-Magnetic wave) environments have became complicate and more difficult to control. Thus, international organizations, such as the American National Standard Institution (ANSI), Federal Communications Commission (FCC), the Comite Internationale Special des Perturbations Radio electrique (CISPR), etc, have provided standard for controlling the EM wave environments and for the countermeasure of the electromagnetic compatibility (EMC). In this paper, the status of EMW absorber and the goal of smart EMW absorber ifor the future were described. Furthermore, design method of the smart EM wave Absorber with heat radiating function was suggested. The designed smart EM wave Absorber has the absoption ability of more than 5 dB from 2 GHz to 2.45 GHz band, one optimum aperture (hole) size of which was 6 mm, 9 mm in adjacent hole space, and 6.5 mm in thickness, respectivly. Thus, it is repected that these results can be applied to various EMC devices in electronic, communication, and controlling systems.