• Korean Journal of Materials Research
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• v.6 no.11
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• pp.1061-1066
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• 1996

RF magnetron reactive sputtering법으로 Fe75.5Zr8.3N16.2/SiO2(250$\AA$) 다층 박막을 FeZrN의 두께를 변화시키면서 제조하고, 제조된 박막을 진공 열처리하여 열처리 온도에 따른 포화자화, 보자력, 고주파에서의 투자율 그리고 열적 안정성을 조사하였다. Fe75.5Zr8.3N16.2/SiO2(250$\AA$) 다층박막은 FeZrN의 두께가 800$\AA$이상일 때 좋은 연자성을 나타내었다. Fe75.5Zr8.3N16.2/SiO2(250$\AA$)다층 박막을 45$0^{\circ}C$로 열처리 했을 때 포화자속밀도(1.08 T), 보자력 0.41 Oe, 1 MHz에서의 실효 투자율은 3000이상의 연자성을 나타내었다. 그 이유는 X-선 회절 분석 결과 열처리에 의해서 ZrN 미결정이 석출하여 $\alpha$-Fe 결정 성장이 억제되어 우수한 연자기적 성질이 나타난다고 판단된다. 이때 $\alpha$-Fe 입자 크기는 40-50$\AA$, ZrN의 입자 크기는 10-15$\AA$이다. 그리고 실효 투자율의 주파수 의존성에서 단층막에서는 5 MHz 이상에서 실효 투자율이 급격히 감소하는 경향을 보였으나, 다층막에서는 40MHz까지 실효 투자율이 1600이 되어 고주파에서의 연자성이 개선되었다.

• Journal of the Korean Magnetics Society
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• v.19 no.5
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• pp.165-170
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• 2009

It is well-known that a meta-stable fcc bulk Fe has an antiferromagnetic (AFM) ground state and could be synthesized by growing Fe on a proper fcc metal substrate. In this study magnetism of Fe monolayers on nonmagnetic fcc transition metal (Cu, Rh, Pd, and Ag) (001) surfaces has been investigated using the all-electron full-potential linearized augmented plane wave method. The Fe monolayers on Rh(001) and Pd(001) surfaces were calculated to be stabilized in an AFM state, whereas the Fe monlayers on Cu(001) and Ag(001) surfaces are stabilized in a ferromagnetic (FM) state. Noting that Cu and Ag have the smallest and largest lattice constants and the fcc bulk Fe with a larger lattice constant is getting stabilized in a ferromagnetic state, it is unexpectable and interesting. The calculated magnetic moments of the Fe atoms on Cu, Rh, Pd, and Ag(001) surfaces are 2.811, 2.945, 2.987, and 2.990 $_{{\mu}B}$ in FM states and 2.624, 2.879, 2.922, and 3.001 $_{{\mu}B}$ in AFM states.

• Journal of the Korean Magnetics Society
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• v.9 no.5
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• pp.223-226
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• 1999

We have investigated the magnetic properties and the electronic structures of Tc half-monolayer (0.5-ML) on Pd(001) using the full-potential linearized augmented plane wave(FLAPW) energy band method. We calculated the total energies for ferromagnetic and paramagnetic states to determine the stable magnetic state. The calculated results show that the total energy of the ferromagnetic state is lower than that of the paramagnetic one. The overlayer Tc 0.5-ML has considerably large magnetic moment $(2.09\;{\mu}_B)$, while the substrate Pd layers have been negatively polarized. The calculated density of states and total electrons inside the muffin-tin (MT) sphere are presented and discussed in relation with the magnetic properties.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.433-436
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• 2017

SIESTA를 이용하여 GaSe 단일층에서 금속 원자(Ga)를 전이금속 원자(W)로 치환하였을 때($W_{Ga}$)의 구조 deformation, 에너지 안정성, 전자구조와 자성을 확인하였다. 그 결과, 구조가 바뀌면서 평면에 수직한 방향으로 구조 변형이 나타났고, $W_{Ga}$에서 W의 NN는 Se이 되었다. Clean surface만큼 $W_{Ga}$도 안정된 구조임을 알 수 있었다. $W_{Ga}$에서 W에 의한 defect states가 up, down 6개씩 split되어 나타났으며, ${\Gamma}$ point에서 degenerated 경향을 보였다. 또한 W에 의한 magnetic moment는 $1{\mu}_B$인 것을 확인하였다. Defect states는 degenerated $d_{yz}$, $d_{zx}$ orbital character, degenerated $d_{xy}$, $dx^2-y^2$ orbital character, defect states는 $d_z{^2}$ orbital character을 띠는 것으로 나뉘었고, 이에 따라 에너지가 함께 높아졌다.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.1
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• pp.42-52
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• 2008

Purpose: Resonance Frequency Analysis(RFA) technique can be used as an effective method in measuring the implant stability and documenting the clinical results. This technique also determines how stable the implant is before performing a prosthetic practice. Having become one the guidelines of the implant therapy whose final objective is the immediate loading, the $Osstell^{TM}$ mentor is giving a lot of information to the clinicians recently. In this communication, experiments were performed to investigate how reliable the measured ISQ values by $Osstell^{TM}$ mentor are, and to see if those are also stable even after sterilization. As five objectives: 1) How stable measured ISQ values after fixation $Smartpeg^{TM}s$ for 400 times. 2) How stable measured ISQ values after 'attach-detach'$Smartpeg^{TM}'s$ for 400 times. 3) How stable measured ISQ values after clinical sterilization methods. 4) How stable measured ISQ values after repeatedly sterilization in autoclave for 10 times. 5) What is the critical temperature which is lost the magnetism of $Smartpeg^{TM}$. Materials and Methods: Clinical sterilization methods(Autoclave sterilization, Dentistar sterilization, Ultra violet sterilization, Vacuum dry unit sterilization, Boiling water sterilization, combined $H_{2}O_{2}$ and Alcohol sterilization).$Smartpeg^{TM}s$. D3 Block bone($3{\times}9{\times}2cm$). Osstem implant(${\emptyset}4.1$-10mm).$Osstell^{TM}$ mentor. Individual experiment was used 8 number of $Smartpeg^{TM}s$ and they had measured to ISQ values of before experiment and after experiment. Results: 1. The measured ISQ values did not change after fixation $Smartpeg^{TM}s$ for 400 times. 2. There was no significant changes in the measured ISQ values of 'attach-detach $Smartpeg^{TM}s'$ for 400 times. 3. The measured ISQ values did not change after the usual clinical sterilization methods. 4. The measured ISQ values did not change after sterilization in autoclave for 10 times. 5. It was impossible to exactly measure the critical temperature which is lost the magnetism of $Smartpeg^{TM}s$. But, the results was resulted to lost its magnetism in higher temperature than $150^{\circ}C$/10 minute. Conclusion: The measured ISQ values showed insignificant differences in case of no changes in the magnetism of the $Smartpeg^{TM}s$. It seems that the $Smartpeg^{TM}s$ can be used repeatedly in every measurement if the original magnetisms of the $Smartpeg^{TM}s$ can be recognized. There seems to be no significant changes in the measured ISQ values of 'attach-detach $Smartpeg^{TM}s'$ only if the screw pitches were unimpaired. The clinical sterilization methods seems acceptable because the result was resulted to lost its magnetism in higher temperature than $150^{\circ}C$/10minute.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.317-322
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• 1996

Thin films of Fe-Zr-N were fabricated by rf magnetron reactive sputtering method. The saturation magnetization and coercivity as functions of annealing temperature and partial pressure of nitrogen gas, effective permeability at high frequencies, and thermal stability were investigated. Magnetic softness was exhibited in the composition range of $Fe_{72-78}Zr_{7-10}N_{15-18}$ which was boundary between polycrystalline and amorphous structure. These films exhibited magnetic softness with saturation magentic flux density of 1.55 T and effective permeability of about 3000 at 1 MHz. These films also exhibited thermal stability by sustaining effective permeability of 2500 or above as the temperature was raised to $550^{\circ}C$. It is asswned that good magnetic softness is obtained because grain growth of $\alpha-Fe$ is prohibited due to the precipitation of ZrN nanocrystals. The grain sizes of $\alpha-Fe$ films were $40~50\AA$ and the grain sizes of ZrN nanocrystals were $10~15\AA$.

• Progress in Medical Physics
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• v.8 no.1
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• pp.69-79
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• 1997

Stability of the properties of magnetite particles in novel medicinal magnetic ointments of multipurpose application has been studied by M ssbauer spectroscopy. It has been found that the comparative analysis of the results obtained by model fitting of $^{57}$ Fe nuclei spectra with those known for the system Fe$_3$O$_4$-${\gamma}$-Fe$_2$O$_3$ allows to identify the phase composition of the particles. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (~100$\AA$), differs noticeably from the stoichiometric one. From the magnetic hyperfine field despite small particle sizes, the particles exhibit no superparamagnetism (in the temperature range from 95 to 300K). Radiative sterilization of the ointments has no effect on the magnetic component composition.

• Analytical Science and Technology
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• v.22 no.2
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• pp.159-165
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• 2009

The thermochromism of fluoran has been examined. The DCF exists as a colorless lactone in aprotic solvents. However, the DCF exists in the form of an equilibrium mixture of a colored zwitter-ion and a colorless lactone in protic solvents. When an acid is added to the solution, the DCF exists an equilibrium mixture as a colorless lactone and a colored cation even in aprotic solvents. In order to understand the interaction between the DCF and the solvent, absorption spectra of the DCF in various solvents were measured. The thermodynamic parameters of the DCF have also been investigated. From the variation of absorbance with temperature, the standard enthalpy changes ${\Delta}H^0$ of the equilibrium between the lactone and the zwitter-ion in various solvents have been determined. The standard enthalpy change ${\Delta}H^0$ is approximately -2.0 kJ/mol in protic solvents. In acidic solution, the standard enthalpy change is measured to be to zero in protic solvents within the experimental error. When the carboxylic group is protonated in acidic solution, a poor interaction between the dye and the solvent is expected.

• 전기의세계
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• v.25 no.6
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• pp.40-44
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• 1976

근대산업의 에너지원으로서 전력수요의 급격한 증대에 수반하여 전력계통의 초고전압화, 관련기기의 소형화 및 장기간에 걸친 성능의 안정성, 신뢰성이 절실히 요망 하겠금 되었다. 이로 인하여 전기절욘재료에 요구되는 제성능도 일반적으로 고도화되고 점점 가혹한 조건이 부가되고 있는 실정이라 하겠다. 근년 고분자화학의 급속한 진보와 고분자성형기술의 발달에 의하여 등장한 합성고분자재료는 그 물리, 화학적 성질 특히 전기적 성질에 많은 특징을 가지고 있으며 그 성능이 점점 높이 평가되고 있어 고분자재료의 진출이야말로 전기기기절연의 양상에 일대 변화를 줄것이라 하여도 지나친 표현이 아니겠다. 이와같이 고분자가 전기절연재료로써의 가치는 물가구조로 부터 기대되는 우수한 유전성과 전기절연성이 높이 평가되고 있는 점이라 하겠다.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.2
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• pp.169-181
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• 2008

The aim of this study was to compare the retention and stability of implant overdenture according to the shape and the number of magnetic attachment. The experimental groups were designed for the number of implants(1, 2, 4) and shape of magnetic attachments(flat, cushion, dome type) resulting in 9 subgroups. 45 attachments were tested attached to $Br{\aa}nemark$ system implants which were planted on a mandibular model. Each attachment was composed of the magnet assembly embedded in a overdenture sample and the abutment keeper screwed into the implants. Dislodging tensile forces were applied to the overdenture samples using an Instron(cross-head speed 50.80mm/min) in 3 directions simulating function: vertical, oblique, and anterior-posterior. The loading was repeated 10 times in each direction for 45 samples. The values of maximum dislodging force of each subgroup were processed statistically using SPSS V. 12.0 at the 0.05 level of significance. The results of this study were as follows: 1. Flat type magnetic overdenture was the most retentive when subjected to vertically directed forces and dome type was the lest retentive when subjected to obliquely directed forces(p<0.05). 2. In case of planting one implant, flat type had a higher vertically retentive force than anterior-posteriorly retentive force. In case of planting two implants, flat type and dome type had a higher vertically retentive force and in case of planting four implants, flat type and cushion type had a higher vertically retentive force than anterior-posteriorly retentive force(p<0.05). 3. The incremental number of dental implant, without regards to the three types of magnetic attachment shapes, showed higher retention of overdenture(p<0.05). From the results, if a patient need much more retention of implant overdenture, flat type magnetic overdenture would be a good treatment. In case of the bruxism where excessive lateral forces are already present, dome type could be expected to produce better results. In case of planting one implant, flat type is more stable than the other shape of magnet and in case of two implant, flat type and dome type are more stable and in case of four implants, flat type and cushion type are more stable. Planting more than two implants and using flat type magnetic attachment would provide better retention and stability of implant overdenture