• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1528-1532
• /
• 2000

The conventional optics and near field optics are compared numerically in the view points of the spot size and propagation characteristics. The decaying characteristics of near field light require the optics to access the object within several tens of nanometers. Therefore the gap control is one of the main issues in the near field optics area. In this paper the gap control is done by using the shear force of the NF(Near Field) probe and the characteristics are examined. The probe is modeled as a 2'nd order mass-spring-damper system driven by a harmonic force. The primary cause of the decrease in vibration amplitude is due to the damping force - shear force - between the surface and the probe. Using the model, damping constant and resonance frequency of the probe is calculated as a function of probe-sample distance. Detecting the amplitude and phase shift of the NF probe attached to the high Q-factor piezoelectric tuning fork, we can control the position of the NF probe about 0 to 50nm above the sample. The feedback signal to regulate the probe-sample distance can be used independently for surface topography imaging. 3-D view of the shear force image of a testing sample with the period of $1{\mu}m$ will be shown.

• 한국세라믹학회지
• /
• 제40권12호
• /
• pp.1220-1223
• /
• 2003

본 연구에서는 반도체 성질을 지닌 TiO$_2$ 분말과 촉매적 활성이 높은 물질로 예상되는 TiO$_2$-CdS계 분말을 초임계 유체법으로 제조하였다. 초임계유체법을 이용하여 제조된 미 분말들은 2-3$mu extrm{m}$ 크기의 응집체였고, 20nm크기의 아주 미세한 1차 입자들로 이루어져있었다. 또한 초임계 유체법으로 어떤 열처리 없이도 아나타제 결정질 분말을 얻을 수 가 있었다.

• 한국수소및신에너지학회논문집
• /
• 제26권4호
• /
• pp.308-317
• /
• 2015

To investigate the effect of microstructure on the formation of the desorption peak, the volumetric thermal analysis technique (VTA) was applied to the Mg-13.5 wt% Ni hydride system. The sample made by the HCS (hydriding combustion synthesis) process had two kinds of Mg microstructures. Linear heating was started with various constant heating rates. Only one peak was appeared in the case of the small initial hydrogen wt% (0.83 wt%). Yet, two peaks were appeared with increasing initial hydrogen wt% (1.85 and 3.73 wt%) when only Mg was hydrogenated. The first peak was formed through the evolution of hydrogen from $MgH_2$, made by eutectic Mg. The second peak was formed through the evolution of hydrogen from $MgH_2$, made by primary Mg. Therefore, this result shows that the microstructure also has a considerable effect on forming the desorption peak. We have also derived the hydrogen desorption equations by VTA to get apparent activation energy when the rate-controlling step for the desorption of the hydrided system is the diffusion of hydrogen through the ${\alpha}$ phase and the chemical reaction ${\beta}{\rightarrow}{\alpha}$.

• 한국수산과학회지
• /
• 제45권4호
• /
• pp.358-366
• /
• 2012

A novel neuropeptide was isolated from the skin of the conger eel Conger myriaster using hagfish Eptatretus burgeri intestine as a bioassay system. The sequence of the purified peptide was analyzed using automated amino acid sequencing and MALDI-TOF mass spectrophotometry. The molecular ion peak in the MALDI-TOF mass spectrum of the peptide was at m/z 962.89 $(M+H)^+$. The sequence of the peptide was determined to be L-P-M-L-E-T-Q-M, and was tentatively named comyrin. To investigate the complete primary structure of comyrin, comyrin-OH and comyrin-$NH_2$ were synthesized and the chemical and pharmacological properties of the synthetic peptides were compared with those of the native peptide. However, the elution time of synthetic peptides did not match that of the native peptide on the reverse-phase HPLC chromatogram. In addition, the synthetic peptides did not cause contractile activity in the intestinal smooth muscle of the hagfish. Based on these results, one possible reason for this disagreement may be the presence of a D-amino acid in comyrin.

• 대한정형도수물리치료학회지
• /
• 제14권2호
• /
• pp.34-40
• /
• 2008

Purpose: We defined osteoarthritis of the knee as knee pain and crepitus in over 40 years old. The usual clinical manifestation include pain, stiffness, crepitus and loss of function. Methods: We studied 40 cases of the degenerative arthritis of knee clinically. The body mass index(BMI, weight(kg)/height($m^2$) was used as a measure of obesity. Pain self assessment scale by Million Index in according to age, occupation, BMI. Results: Gender by pain self assessment scale was 6.5 in male and 6.6 in female(P<0.05). The prevalence rates obese was 40%. Occupation by pain self assessment scale was 7.0 in Sitting and 5.7 in Standing(P<0.05). Prevalence was increased with age by pain self assessment scale in aged 40-69 years. Conclusion: It has been known that the obesity is one of the predispsing factors of the primary degenerative arthritis of knee. A flexion weight bearing view of the knee obtained at $30^{\circ}$ to $40^{\circ}$ of the joint flexion may be more sensitive in assessing damages to hyaline cartilage because the knee flexion is an important component of the stance phase.

• 전력전자학회논문지
• /
• 제18권1호
• /
• pp.1-9
• /
• 2013

This paper proposes a ST(Switched Trans) quasi Z-source inverter using a Switched Trans Cell combing the characteristics of a Switched Inductor Cell and Trans. A DC link inductor of the conventional quasi Z-source inverter is alternated with Switched Trans Cell of the proposed ST quasi Z-source inverter. Trans Cell of the proposed method consists of one Trans and two diodes, and the proposed method has higher and more various boost function than the conventional quasi Z-source inverter by simply changing the turns ratio of primary and secondary of the Trans. The validity of the proposed ST Z-source inverter was confirmed by PSIM simulation and a DSP based experiment under the input voltage 48V and output phase voltage 30V. As a result, when compared with the traditional quasi Z-source inverter, the proposed method has the advantage of the low voltage stress under the same output voltage condition of the voltage.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
• /
• pp.159-160
• /
• 2005

The superconducting fault current limiter(SFCLs) provides the effect such as enhancement in the power system reliability due to limiting fault current in a few miliseconds. The Flux-lock type SFCL using the YBCO film among various type SFCLs consists of the primary and the secondary copper coils that are wound in parallel each other through the iron core. The operation can be controlled by adjusting the inductances and the winging directions of each the coil. We compared the current limiting performance on the additive and the subtractive polarity winding directions in case of an open-loop iron core. To analyze quench characteristics, we experimented various phase angle.

• 한국주조공학회지
• /
• 제28권5호
• /
• pp.226-230
• /
• 2008

본 논문에서는 공정조성 부근의 Al-Si 합금의 미세구조에 미치는 전자기교반(EMS)의 영향에 대하여 연구하였다. 초정 a 상의 형상에 미치는 전자기교반의 세기의 영향을 조사하기 위하여 각각 교반장치에 60, 80,및 120V의 전압을 가하여 미세조직을 관찰하였다. 60V 이하의 전압이 인가되었을 때 전자기교반의 효과가 나타나지 않은 반면에, 80V 이상의 전압으로 5초 이상 인가되었을 때 구상화된 초정 a 상을 얻을 수 있었다. 인가된 전압이 120V일 때 초정 a 상은 보다 균일한 분포를 가지며 구상화 되었다. 전자기교반의 세기와 함께 교반시간의 영향을 확인하기 위하여 교반시간을 증가시키면서 미세조직을 관찰하였다. 또한 초정 a 상의 형상에 미치는 주조변수의 영향에 대해서도 실험하였다.

• 한국분말재료학회지
• /
• 제4권1호
• /
• pp.18-25
• /
• 1997

High speed steels with commercial compositions of 10V, Rex20, Rex25, T15, and ASP30 were gas-atomized and then consolidated by hot isostatic pressing (HIPping). The microstructures of gas-atomized powder, as-HiPped billet, and heat-treated billet have been characterized using optical microscope, scanning electron microscope and X-ray diffractometer. In the gas-atomized powders, the solidification structures of 10V and Rex25 alloys show that primary MC carbides embedded within the fine equiaxed dendrites, whereas those of Rex20, T15 and ASP30 alloys exhibited eutectic MC and/or M$_2$C carbides in the interdendritic region. The trace and dendritic morphologies of gas-atomized powder have been retained in as-HiPped billets. The microstructures of as-HiPped billets have been observed to consist of ferrite, $M_6C$ and MC carbides in other alloys with the exception of 10V alloy, which consists of ferrite and MC carbides. The hardness of heat-treated billet makes a favorable comparison with that of as-HIPped billet. This seems mainly to be due to the strengthening by the precipitation of secondary carbides and the change of matrix phase from $\alpha$-ferrite to martensite.

• 한국분말재료학회지
• /
• 제24권6호
• /
• pp.444-449
• /
• 2017

Aluminum nitride (AlN) powder specimens are treated by high-energy bead milling and then sintered at various temperatures. Depending on the solvent and milling time, the oxygen content in the AlN powder varies significantly. When isopropyl alcohol is used, the oxygen content increases with the milling time. In contrast, hexane is very effective at suppressing the oxygen content increase in the AlN powder, although severe particle sedimentation after the milling process is observed in the AlN slurry. With an increase in the milling time, the primary particle size remains nearly constant, but the particle agglomeration is reduced. After spark plasma sintering at $1400^{\circ}C$, the second crystalline phase changes to compounds containing more $Al_2O_3$ when the AlN raw material with an increased milling time is used. When the sintering temperature is decreased from $1750^{\circ}C$ to $1400^{\circ}C$, the DC resistivity increases by approximately two orders of magnitude, which implies that controlling the sintering temperature is a very effective way to improve the DC resistivity of AlN ceramics.