• Journal of Welding and Joining
• /
• v.28 no.2
• /
• pp.47-53
• /
• 2010

According to the research report for the recent a few years, the dissimilar welding of Cu and STS 304 alloy have been presented that a weldability is very poor. This article present a study on Lap joint by Electron beam welding dissimilar materials. The weld metals was constituted between pure copper and STS 304 steel. The experiment was performed with 125mA welding current, 520mA focusing current. The Vacuum condition of chamber is 5${\times}$10-5torr and welding speed is 300mm/min. Showing the bead shape of weld metal, the thickness of the stainless 304 using as the protect materials is 3mm and the thickness of a copper is 15mm. The analysis about the microstructure were carried out in which it was observed with SEM. The results showed that complex heterogeneous fusion zone microstructure characterized both by rapid cooling and mixing of the molten metal, however the liquation crack was formated in the fusion line.

• Journal of Korean Foot and Ankle Society
• /
• v.8 no.2
• /
• pp.171-175
• /
• 2004

Purpose: We evaluated the clinical and radiological results of arthroscopic ankle fusion using 2 medial screws which had advantages of less morbidity, early weight-bearing and high union rate. Material and Methods: From April, 2002 to March, 2004, 8 patients who had ankle osteoarthritis were treated by ankle fusion using 2 medial screws under arthroscopy; five patients with post-traumatic osteoarthritis, two with post-infectious arthritis and one with paralytic foot. There were 5 male and 3 female. Average age was 67 years old ranging from 57 to 71 years. We evaluated them clinically preoperative and postoperative using AOFAS score, VAS pain scale and patient's satisfaction. In regard to radiological fusion, we checked them by simple AP, lateral and mortise view. Follow up period was average 11 months (range, $6{\sim}24$ months). Results: All ankles were successfully fused with 2 medial screws under arthroscopy. The mean time of fusion was 10.5 weeks (range, $8{\sim}14$ weeks). Patient's satisfaction checked at 6 months after operation had favorable results (excellent and good 75%). One case had pain on medial malleolar area because of screw's protrusion. Conclusion: Arthroscopic ankle fusion using 2 medial screws was good modality of ankle fusion with less morbidity and early weight-bearing in some cases of ankle arthritis.

• Journal of Korean Neurosurgical Society
• /
• v.59 no.4
• /
• pp.363-367
• /
• 2016

Objective : To compare the fusion rate of a hydroxyapatite demineralized bone matrix (DBM) with post-laminectomy acquired autograft in lumbar interbody fusion surgery and to evaluate the correlation between fusion rate and clinical outcome. Methods : From January 2013 to April 2014, 98 patients underwent lumbar interbody fusion surgery with hydroxyapatite DBM (HA-DBM group) in our institute. Of those patients, 65 received complete CT scans for 12 months postoperatively in order to evaluate fusion status. For comparison with autograft, we selected another 65 patients who underwent lumbar interbody fusion surgery with post-laminectomy acquired autograft (Autograft group) during the same period. Both fusion material groups were matched in terms of age, sex, body mass index (BMI), and bone mineral density (BMD). To evaluate the clinical outcomes, we analyzed the results of visual analogue scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey (SF-36). Results : We reviewed the CT scans of 149 fusion levels in 130 patients (HA-DBM group, 75 levels/65 patients; Autograft group, 74 levels/65 patients). Age, sex, BMI, and BMD were not significantly different between the groups (p=0.528, p=0.848, p=0.527, and p=0.610, respectively). The HA-DBM group showed 39 of 75 fused levels (52%), and the Autograft group showed 46 of 74 fused levels (62.2%). This difference was not statistically significant (p=0.21). In the HA-DBM group, older age and low BMD were significantly associated with non-fusion (61.24 vs. 66.68, p=0.027; -1.63 vs. -2.29, p=0.015, respectively). VAS and ODI showed significant improvement after surgery when fusion was successfully achieved in both groups (p=0.004, p=0.002, HA-DBM group; p=0.012, p=0.03, Autograft group). Conclusion : The fusion rates of the hydroxyapatite DBM and Autograft groups were not significantly different. In addition, clinical outcomes were similar between the groups. However, older age and low BMD are risk factors that might induce non-union after surgery with hydroxyapatite DBM.

• Polymer(Korea)
• /
• v.35 no.5
• /
• pp.378-384
• /
• 2011

Silk fibroin is a biocompatible and slowly biodegradable natural polymer. This natural polymer has excellent mechanical properties, non-toxicity, and non-immunogenic properties and has been demonstrated to support tissue regeneration. Also, gelatin is a natural material derived from collagen by hydrolysis and has an almost identical composition as that of collagen. Silk fibroin/gelatin scaffolds have been fabricated by using the freeze-drying method. To establish the scaffold manufacturing condition for silk fibroin and gelatin, we made scaffolds with various compositions of gelatin, glutaldehyde and silk fibroin. The silk fibroin/gelatin scaffolds were characterized using SEM, DSC, and water absorption ability tests. The cellular proliferation was evaluated by WST assay. These results suggested that a scaffold containing 8% of gelatin, 1% of glutaldehyde and 0.3 g of silk fibroin provided suitable characterstics for cell adhesion and proliferation. In conclusion, the silk fibroin/gelatin scaffold may serve as a potential cell delivery vehicle and a structural basis for tissue engineering.

• Nuclear Engineering and Technology
• /
• v.40 no.6
• /
• pp.451-458
• /
• 2008

After more than 10 years construction, KSTAR (Korea Superconducting Tokamak Advanced Research) had finally completed its assembly in June 2007, and then achieved the goal of first-plasma in July 2008 through the four month's commissioning. KSTAR was constructed with fully superconducting magnets with material of $Nb_3Sn$ and NbTi, and their operation temperatures are maintained below 4.5K by the help of Helium Refrigerator System. During the first-plasma operation, plasmas of maximum current of 133kA and maximum pulse width of 865ms were obtained. The KSTAR Integrated Control System (KICS) has successfully fulfilled its missions of surveillance, device operation, machine protection interlock, and data acquisition and management. These and more were all KSTAR commissioning requirements. For reliable and safe operation of KSTAR, 17 local control systems were developed. Those systems must be integrated into the logically single control system, and operate regardless of their platforms and location installed. In order to meet these requirements, KICS was developed as a network-based distributed system and adopted a new framework, named as EPICS (Experimental Physics and Industrial Control System). Also, KICS has some features in KSTAR operation. It performs not only 24 hour continuous plant operation, but the shot-based real-time feedback control by exchanging the initiatives of operation between a central controller and a plasma control system in accordance with the operation sequence. For the diagnosis and analysis of plasma, 11 types of diagnostic system were implemented in KSTAR, and the acquired data from them were archived using MDSpius (Model Driven System), which is widely used in data management of fusion control systems. This paper will cover the design and implementation of the KSTAR integrated control system and the data management and visualization systems. Commissioning results will be introduced in brief.

• Journal of Korea Foundry Society
• /
• v.14 no.6
• /
• pp.541-547
• /
• 1994

The effects of weld repair on the durability in Al-10%Si-0.3%Mg castings were evaluated. The strength and fracture toughness in fusion zone were higher than those in the base metal by rapid cooling of fusion zone after welding. There were no significant differences between fatigue properties in castings and weld repaired specimen as the results of low cycle fatigue and rotating bending fatigue test. Therefore it was concluded that weld repairing did not have any significant effect on the mechanical properties of castings.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.10
• /
• pp.736-740
• /
• 2013

In this study, the influence of electrochemical properties by mixing Tetrabutylammonium hydroxide (TBAOH) and ammonium hydroxide (NH4OH) electrode on the dssc. The titanias were prepared using a sol-gel method by mixing Tetrabutylammonium hydroxide and Ammonium hydroxide. The $TiO_2$ nanopowder prepared by sol-gel methode, and to improve the distributed properties of $TiO_2$ nanopowder, the TBAOH and NH4OH was added. The I-V values of cells show that the Tetrabutylammonium has 6.51% efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.171-171
• /
• 2010

Electro-optic characteristics of liquid crystal display using fringe field switching(FFS) device depend on many parameters such as cell retardation, electrode structure, rubbing angle, cell gap and dielectric anisotropy. In this paper, the light efficiency of FFS mode will be analyzed to confirm the electro-optic characteristics according to positive dielectric anisotropy such as transmittance, operating voltage and response time.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.120-120
• /
• 2010

To detect the PD events, we have studied a fusion sensor, the UHF sensor and the single-walled carbon nanotube(SWNT) gas sensor. We are accustomed to the UHF sensor which have employed to detect the partial discharges in apparatus GIS-like. But the SWNT gas sense is a newly way proposed to detect the partial discharges. In this study, we monitored not only the changes of the electrical conductance of the SWNT sensors in responding to the PD events but also the signal of the UHF sensor at the same time with IEC 60270 standard method for reference on the partial discharge events.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.173-173
• /
• 2010

We proposed viewing angle switchable liquid crystal display(LCD) associated with fringe-field switching (FFS) mode with high aperture ratio characteristic. In the device, single pixel is separated into two regions, named as main pixel for displaying images and sub pixel for viewing angle control. In sub pixel region, add the common electrode on the top substrate and the initial alignment of liquid crystal is Hybrid Alignment Nematic (HAN) state. In conclusion, we suggested that the device has high aperture ratio characteristic because the LC directors are rotated in which viewing angle control region are generated fringe electric field.