• Journal of Ocean Engineering and Technology
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• v.17 no.4
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• pp.31-36
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• 2003

In case of this thick rolling-steel for a multistory building, a large oil-drilling structure, a large vessel, a bridge and so on, Lamella Tearing around the welded joint zone is the most serious problems. In order to prevent Lamella Tearing, not only is choice of material important, but also the comprehensive investigation for the structural design and the construction. The Lamella Tearing that is a staircase-shape occurs due to the contraction stress to the thickness direction of the plate and has the character that the cracks progress along the elongated inclusion by rolling. In general, because cracks occur at the heat affected zone and around HAZ, it is necessary to establish the safety and the confidence of the welded structure to restrain the welding defect such as Lamella Tearing. The mechanical approaches are the easier and more economical than the approaches of the material and the construction method. In addition, the appropriate welding profile and the optimum welding condition contribute toward the improvement of the productivity and influence on the standardization of the manufacturing technology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.411-416
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• 2006

A new reading technology for the ultra-high density data storage device utilizing AFM technology was proposed and its experimental results were discussed in this paper. For the experiments, an about $2{\mu}m$ thick conductive polymer layer was spin-coated on the heavily doped n-type Si wafer and an about $0.1{\mu}m$ thick PMMA layer was also been spin-coated on it. After then, the $5{\times}5$ memory way was fabricated by making indents on the surface of the wafer with the heated AFM tip, and the data reading was performed by scanning the surface with the tip biased at 10 V and the measuring the current flowing out at the end of the tip. The experimental results clearly showed that the new data reading technology worked superbly. The current measured was about 0.92 pA at the cell with the indent, and it was not only below 0.31 pA at the cell without the indent, but also at the cell where the indent was erased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.4
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• pp.367-370
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• 2004

We fabricated SiGe BiCMOS devices, which are important for ultra high speed RF IC chips, by employing $0.35\mu{m}$ CMOS process. To meet with the requirement of low noise level with linear base leakage current at low VBE region, we try to minimize polysilicon/ silicon interface traps by optimizing capping silicon thickness and EDR(emitter drive-in RTA) temperature. We employed $200\AA$and $300\AA$-thick capping silicon, and varied the EDR process condition at temperature of $900-1000^\circ{C}$, and time of 0-30 sec at a given capping silicon thickness. We investigated current gain behavior at each process condition. We suggest that optimum EDR process condition would be $975^\circ{C}$-30 sec with $300\AA$-thick capping silicon for proposed $0.35\mu{m}$-SiGe HBT devices.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3060-3063
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• 1999

We made a multi-layer conveyor sterilizing system using UV rays to prolong a storage period of dried marine products. The system is composed of 5 layer conveyor belt of 3 m long each, thus 15 m long in total. It is designed to radiate UV rays for 10 minutes the dried marine products, and can process 300 kg/hour. Eight UV lamps of 30 cm long and 15 W of power with 254 nm wave length are installed in parallel, 15 cm high above in each belt, and 40 lamps in total. The whole system is covered by 1 mm thick metal plates to block the UV rays except a front side which is covered with 5 mm thick plastic plates coated with UV protection film to survey inside of the system. A sterile ratio is about 99.97% with 10 minutes sterilization using this system.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.237.2-237.2
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• 2016

A pure hafnium-carbide (HfC) coating layer was deposited onto carbon/carbon (C.C) composites using a vacuum plasma spray system. By adopting a SiC buffer layer, we successfully integrated C.C composites with a $100-{\mu}m-thick$ protective coating layer of HfC. Compared to the conventional chemical vapor deposition process, the HfC coating process by VPS showed increased growth rate, thickness, and hardness. The growth behavior and morphology of HfC coatings were investigated by FE-SEM, EDX, and XRD. From these results, it was shown that the addition of a SiC intermediate layer provided optimal surface conditions during the VPS procedure to enhance adhesion between C.C and HfC (without delamination). The thermal ablation test results shows that the HfC coating layer perfectly protected inner C.C layer from thermal ablation and oxidation. Consequently, we expect that this ultra-high temperature ceramic coating method, and the subsequent microstructure that it creates, can be widely applied to improve the thermal shock and oxidation resistance of materials under ultra-high temperature environments.

• Korean Journal of Materials Research
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• v.16 no.9
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• pp.592-597
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• 2006

A deoxidized low-phosphorous (DLP) copper was processed by accumulative roll-bonding (ARB) for ultra grain refinement and high strengthening. Two copper sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked to each other, and roll-bonded by about 50% reduction rolling without lubrication at ambient temperature. The bonded sheet is then cut to the two pieces of same dimensions and the same procedure was repeated to the sheets up to eight cycles (${\varepsilon}{\sim}6.3$). TEM observation revealed that ultrafine grains were developed after the 4th cycle, and their size decreased at higher cycles. Tensile strength of the copper increased with the equivalent strain, and it reached 547 MPa which was 3 times higher than that of the initial material. It is concluded that the ARB process is an effective method for high strengthening of the DLP copper.

• Journal of Mechanical Science and Technology
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• v.18 no.10
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• pp.1772-1781
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• 2004

The mechanical as well as tribological characteristics of coating films as thin as a few nm become more crucial as applications in micro-systems grow. Especially, the amorphous carbon film has a potential to be used as a protective layer for micro-systems. In this work, quantitative evaluation of nano-indentation, scratching, and wear tests were performed on the 7nm thick amorphous carbon film using an Atomic Force Microscope (AFM). It was shown that AFM-based nano-indentation using a diamond coated tip can be feasibly utilized for mechanical characterization of ultra-thin films. Also, it was found that the critical load where the failure of the carbon film occurred was about 18${\mu}$N by the ramp load scratch test. Finally, the wear experimental results showed that the quantitative wear rate of the carbon film ranged 10$\^$-9/～10$\^$-8/ ㎣ /N cycle. These experimental methods can be effectively utilized for a better understanding the mechanical and tribological characteristics at the nano-scale.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.756-759
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• 2007

We have fabricated pentacene OTFT on ultra-thin flexible polyimide film with a rigid glass support. Polyimide film of the thickness of $10{\mu}m$ has formed on glass by spin coating from the solution. After the entire OTFT process, the OTFT exhibited a fieldeffect mobility of $0.4\;cm^2/Vs$, an $I_{on}/I_{off}$ ratio of $10^7$ and a subthreshold swing of 0.7 V/dec. The OTFT on polyimide film has been detached from the glass support and laminated on a plastic support of $130\;{\mu}m-thick$ PET film. After the detach process, in spite of the degrading of its field-effect mobility, the OTFT showed high $I_{on}/I_{off}$ as high $as{\sim}10^6$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.421-421
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• 2008

Generally, the polymer thick-film resistors for embedded organic or hybrid substrate are patterned by screen printing so that the accuracy of resistor pattern is not good and the tolerance of resistance is too high(${\pm}$20~30%). To reform these demerits, a method using Fodel$^{(R)}$ technology, which is the patterning method using a photosensitive resin to be developable by aqueous alkali-solution as a base polymer for thick-film pastes, was recently incorporated for the patterning of thermosetting thick-film resistor paste. Alkali-solution developable photosensitive resin system has a merit that the precise patterns can be obtained by UV exposure and aqueous development, so the essential point is to get the composition similar to PSR(photo solder resist) used for PCB process. In present research, we made the photopatternable resistor pastes using 8 kinds of epoxy acrylates and a conductive carbonblack (CDX-7055 Ultra), evaluated their developing performance, and then measured the resistance after final curing. To become developable by alkali-solution, epoxy acrylate oligomers with carboxyl group were prepared. Test coupons were fabricated by patterning copper foil on FR-4 CCL board, plating Ni/Au on the patterned copper electrode, applying the resistor paste on the board, exposing the applied paste to UV through Cr mask with resistor patterns, developing the exposed paste with aqueous alkali-solution (1wt% $Na_2CO_3$), drying the patterned paste at $80^{\circ}C$ oven, and then curing it at $200^{\circ}C$ during 1 hour. As a result, some test compositions couldn't be developed according to the kind of oligomer and, in the developed compositions, the measured resistance showed different results depending on the paste compositions though they had the same amount of carbonblack.

• Advances in pediatric surgery
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• v.7 no.1
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• pp.59-63
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• 2001

The authors, over the last 6 months, have treated 2 patients with perforated typhlitis complicating acute lymphocytic leukemia (ALL) with good outcome. The first patient was a 13-year-old male who developed intermittent high fever, abdominal pain, abdominal distention and diarrhea during the course of maintenance chemotherapy. The peripheral leukocyte ranged from 230-470/$mm^3$. Serial ultra sonograms and CT scans demonstrated irregular thickening of the cecal and ascending colonic walls and subsequent ragged perforation of the posterior wall of the cecum. He survived after treatment by right hemicolectomy and aggressive supportive measures. The patient case was a 3 year-old female who developed intermittent high fever, right lower abdominal pain, a mass, and watery diarrhea during the course of maintenance chemotherapy. Serial ultra sonograms and CT scans demonstrated irregular thickening of the cecal wall (6-15mm in thickness) and subsequent small perforation of the posterior wall of the cecum with thick-walled localized abscess. She has recovered completely after aggressive medical management. We learned two lessons from our experience treating these patients:1) early diagnosis provided by a high index of suspicion and the use of ultra sonogram or CT scan is essential. And 2) although perforation is one of the surgical indications for the treatment of typhlitis, it is possible to manage the perforation nonoperatively in selected cases with localized abscess.