• 한국해양공학회지
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• 제26권2호
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• pp.33-38
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• 2012

The effects of the diffusible hydrogen content and hardness on the cold cracking in high strength weld metal were investigated. The diffusible hydrogen contents were influenced by welding parameters such as the voltage and contact tip-to-work distance (CTWD). The diffusible hydrogen content increased with an increase in voltage. However, it was decreased with an increase in CTWD. CTWD also influenced the weld metal hardness,especially when the wire used had a higher strength than the base metal. This showed that weld metal hardness had a more powerful effect on weld metal cold cracking than the diffusible hydrogen content in this experiment.

• Tribology and Lubricants
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• 제17권4호
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• pp.276-282
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• 2001

Nano adhesion between SPM (scanning probe microscope) tips and 075 (octadecyltrichlorosilane) SAM (self-assembled monolayer) was experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM(atomic force microscope) and LFM(lateral force microscope) modes in various conditions of relative humidity. OTS SAM was formed on Si-wafer (100) surfaces, and Si$_3$N$_4$ tips of different radius of curvature were used. When the surface was hydrophobic, the adhesion and friction forces were found lower than those of bare Si-wafer. Results also showed that micro-adhesion force increased as the relative humidity and the tip radius of curvature increased. The main parameter for affecting the micro-adhesion was found absorbed humidity on the contact surface. These results were discussed with the JKR model and a capillary force caused by absorbed water.

• Journal of Welding and Joining
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• 제24권3호
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• pp.34-41
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• 2006

The CD (Capacitor Discharge) stud welding utilizes the arc heat and pressure to attach the stud to the workpiece, which consists of the arc. ignition, arcing and pressure welding stages. In order to predict the dynamic behavior of the CD stud welding process, mechanical and electrical models are employed in this work. While the mechanical model estimates the duration of each stage, the electrical model predicts the voltage and current waveforms using the RLC circuit. Effects of process parameters such as the electric components and spring force are analyzed through simulation. It is found that the contact resistance and gap between the stud and base metal influence the tip fusing and arcing duration. The calculated results showed reasonably good agreements with the experiment results.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.67.3-68
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• 2003

The purpose of this study is to improve repeatability of a non-invasive blood glucose measurement. The portable NIR system that was newly integrated by our lab includes a tungsten halogen lamp, a specialized reflectance fiber optic probe and a photo diode array type InGaAs detector, which was developed by a microchip technology based on the lithography. Reflectance NIR spectra of finger tip were recorded by using a fiber optic probe. The probe was fixed in the system and subjects put their finger on the probe head. (omitted)

• International Journal of Korean Welding Society
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• 제1권1호
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• pp.71-77
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• 2001

The characteristics of the fume generation in a flux cored arc welding were investigated using the fume collection chamber developed. The Korean Standard concerning the method for the evaluation of the fume generation rate(FGR) was updated by the evaluation method obtained through this study. It was found that the effect of humidity in the test environment should be considered and the automatic welding method had to be employed for the purpose of the exact evaluation of the fume generation rate. The results showed that the fume generation rate was influenced by the welding parameters. The important factors were the welding current arc voltage, travel speed, and contact tip to work distance(CTWD) that affected the heat input as well as the torch angle and the shielding gas flow rate that influenced the shielding effect. The fume generation rate increased as the heat input increased and the shielding effect decreased. It was also observed that the effect of the welding current is much grater than the other welding parameters.

• 한국산업융합학회 논문집
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• 제27권4_2호
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• pp.973-980
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• 2024

Dependence of dynamic fracture path on loading velocity was observed from experimental results based on the three point bending fracture in cast iron. In this study, 3D and 2D numerical simulations are used to evaluate singular stress fields near crack tip and fracture mechanics parameters. Moving finite element technique, 2D and 3D Delauney automatic mesh generation and contact-noncontact evaluation is introduced into the numerical method. Dynamic fracture thoughness is decreased with increase of impact loading velocity. Fracture mode-ratio corresponds to initial kink angle of fracture path. The numerical result shows that the maximum hoop stress criterion cannot be applied to dynamic fracture of cast iron.

• 구강회복응용과학지
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• 제24권4호
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• pp.317-324
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• 2008

이 논문의 목적은 전부주조관에서 교합점의 위치와 교합력의 방향이 합착용 시멘트층 내의 응력에 미치는 영향에 대해서 알아보는 것이다. 하악 제 1대구치상에서 서로 다른 9 개의 교합점과 3가지 교합력 방향을 가진 27가지 조합의 유한요소 모델을 상정하였다. 금관의 소재는 제 3형 금합금이고, 변연의 형태는 chamfer이다. 합착용 시멘트로는 전 층에서 균일하게 $70{\mu}m$의 두께를 가지는 글라스 아이오노머 시멘트가 사용되었다. 금관에는 100N의 하중을 적용하였다. 협측과 설측 변연의 근접도에 따라서 시멘트층 내 응력은 다른 양상을 나타내었다. 협측은 변연으로부터 약 0.5 mm, 설측은 변연으로부터 약 1 mm 내측에서 최대 응력 값을 가졌다. 하중 방향이 치축에 대해 경사가 클수록, 하중점이 교두첨에 근접해 있을수록 더 큰 응력이 발생하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.32-32
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• 2009

Silicon carbide (SiC) is a wide-bandgap semiconductor that has materials properties necessary for the high-power, high-frequency, high-temperature, and radiation-hard condition applications, where silicon devices cannot perform. SiC is also the only compound semiconductor material. on which a silicon oxide layer can be thermally grown, and therefore may fabrication processes used in Si-based technology can be adapted to SiC. So far, atomic force microscopy (AFM) has been extensively used to study the surface charges, dielectric constants and electrical potential distribution as well as topography in silicon-based device structures, whereas it has rarely been applied to SiC-based structures. In this work, we investigated that the local oxide growth on SiC under various conditions and demonstrated that an increased (up to ~100 nN) tip loading force (LF) on highly-doped SiC can lead a direct oxide growth (up to few tens of nm) on 4H-SiC. In addition, the surface potential and topography distributions of nano-scale patterned structures on SiC were measured at a nanometer-scale resolution using a scanning kelvin probe force microscopy (SKPM) with a non-contact mode AFM. The measured results were calibrated using a Pt-coated tip. It is assumed that the atomically resolved surface potential difference does not originate from the intrinsic work function of the materials but reflects the local electron density on the surface. It was found that the work function of the nano-scale patterned on SiC was higher than that of original SiC surface. The results confirm the concept of the work function and the barrier heights of oxide structures/SiC structures.

• Journal of Korean Neurosurgical Society
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• 제29권11호
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• pp.1538-1541
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• 2000

Apenetrating head injury by an arrow is extremely rare being only two cases reported in the literature. We report a case of 12-year-old boy who presented with an arrow lodged at the posterior fossa through nasal nostril. He was slightly drowsy, but neurologically intact except a sixth nerve palsy in the left eye. Brain CT showed no intracerebral hemorrhage. The arrow was entered through the right nostril and the tip was stucked in the left cere-bello-pontine angle through the sphenoid sinus. We removed the arrow without craniotomy since the tip was verified smooth and no cerebral arteries were in contact with the arrow. The patient recovered well without any significant complications. The sixth nerve palsy resolved completely after six months. The verification of the shape of the offending material, a retrograde removal of the arrow in the direction of its line of trajectory, and an identification of adjacent cerebral arteries seem to be important in the management of this type of injury.

• 한국전기전자재료학회논문지
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• 제22권8호
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• pp.632-636
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• 2009

The local oxidation using an atomic force microscopy (AFM) is useful for Si-based fabrication of nanoscale structures and devices. SiC is a wide band-gap material that has advantages such as high-power, high-temperature and high-frequency in applications, and among several SiC polytypes, 4H-SiC is the most attractive polytype due to the high electron mobility. However, the AFM local oxidation of 4H-SiC for fabrication is still difficult, mainly due to the physical hardness and chemical inactivity of SiC. In this paper, we investigated the local oxidation of 4H-SiC surface using an AFM. We fabricated oxide patterns using a contact mode AFM with a Pt/Ir-coated Si tip (N-type, 0.01-0.025 ${\Omega}cm$) at room temperature, and the relative humidity ranged from 40 to 50 %. The height of the fabricated oxide pattern (1-3 nm) on SiC is similar to that of typically obtained on Si ($10^{15}^{\sim}10^{17}$ $cm^{-3}$). We perform the 2-D simulation to further analyze the electric field between the tip and the surface. We demonstrated that a specific electric field (4 ${\times}$ $10^7\;V/m$) and a doping concentration ($^{\sim}10^{17}$ $cm^{-3}$) is sufficient to switch on/off the growth of the local oxide on SiC.