• Archives of Plastic Surgery
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• v.33 no.4
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• pp.413-422
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• 2006

Purpose: This study was designed to compare the wound healing effect of silk fibroin, alginate and fibroin/ alginate blend sponge with clinically used Nu gauze in a rat skin defect model. Methods: Two full thickness excisions were made on the back of Sprague-Dawley rat. The excised wound was covered with either of the silk fibroin(SF), alginate (SA), or fibroin/alginate blend sponge(SF/SA). On the postoperative days of 3, 7, 10 and 14, the wound area was calculated by image analysis software. At the same time, a skin wound tissue was biopsied. Results: Healing time 50% ($HT_{50}$) of SF/SA sponge treated group was dramatically reduced as compared with that of control treatment. We also found that the $HT_{50}$ of SF/SA sponge was significantly decreased as compared with either those of SF or SA treatment. Furthermore, SF/SA treatment significantly increased the size of epithelialization and collagen deposition as well as the number of PCNA positive cells on epidermal basement membrane as comapred with those of control treatment. Conclusion: Our results suggest that the wound healing effect of SF/SA blend sponge is the best among other treatments including SF and SA during the whole wound healing period.

• Journal of Periodontal and Implant Science
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• v.29 no.3
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• pp.483-509
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• 1999

Biodegradable barrier membrane has been demonstrated to have guided bone regeneration capacity on the animal study. The purpose of this study is to evaluate the effects of cultured calvarial cell inoculated on the biodegradable barrier membrane for the regeneration of the artificial bone defect. In this experiment 35 Sprague-Dawley male rats(mean BW 150gm) were used. 30 rats were divided into 3 groups. In group I, defects were covered periosteum without membrane. In group II, defects were repaired using biodegradable barrier membrane. In group III, the defects were repaired using biodegradable barrier membrane seeded with cultured calvarial cell. Every surgical procedure were performed under the general anesthesia by using with intravenous injection of Pentobarbital sodium(30mg/Kg). After anesthesia, 5 rats were sacrificed by decapitation to obtain the calvaria for bone cell culture. Calvarial cells were cultured with Dulbecco's Modified Essential Medium contained with 10% Fetal Bovine Serum under the conventional conditions. The number of cell inoculated on the membrane were $1{\times}10^6$ Cells/ml. The membrane were inserted on the artificial bone defect after 3 days of culture. A single 3-mm diameter full-thickness artificial calvarial defect was made in each animal by using with bone trephine drill. After the every surgical intervention of animal, all of the animals were sacrificed at 1, 2, 3 weeks after surgery by using of perfusion technique. For obtaining histological section, tissues were fixed in 2.5% Glutaraldehyde (0.1M cacodylate buffer, pH 7.2) and Karnovsky's fixative solution, and decalcified with 0.1M disodium ethylene diaminetetraacetate for 3 weeks. Tissue embeding was performed in paraffin and cut parallel to the surface of calvaria. Section in 7${\mu}m$ thickness of tissue was done and stained with Hematoxylin-Eosin. All the specimens were observed under the light microscopy. The following results were obtained. 1 . During the whole period of experiment, fibrous connective tissue was revealed at 1week after surgery which meant rapid soft tissue recovery. The healing rate of defected area into new bone formation of the test group was observed more rapid tendency than other two groups. 2 . The sequence of healing rate of bone defected area was as follows ； test group, positive control, negative control group. 3 . During the experiment, an osteoclastic cell around preexisted bone was not found. New bone formation was originated from the periphery of the remaing bone wall, and gradually extended into central portion of the bone defect. 4 . The biodegradable barrier membrane was observed favorable biocompatibility during this experimental period without any other noticeable foreign body reaction. And mineralization in the newly formed osteoid tissue revealed relatively more rapid than other group since early stage of the healing process. Conclusively, the cultured bone cell inoculated onto the biodegradable barrier membrane may have an important role of regeneration of artificial bone defects of alveolar bone. This study thus demonstrates a tissue-engineering the approach to the repair of bone defects, which may have clinical applications in clinical fields of the dentistry including periodontics.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.545-545
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• 2008

Poly-Si is an essential material for floating gate in NAND Flash memory. To fabricate this material within region of floating gate, chemical mechanical polishing (CMP) is commonly used process for manufacturing NAND flash memory. We use colloidal silica abrasive with alkaline agent, polymeric additive and organic surfactant to obtain high Poly-Si to SiO2 film selectivity and reduce surface defect in Poly-Si CMP. We already studied about the effects of alkaline agent and polymeric additive. But the effect of organic surfactant in Poly-Si CMP is not clearly defined. So we will examine the function of organic surfactant in Poly-Si CMP with concentration separation test. We expect that surface roughness will be improved with the addition of organic surfactant as the case of wafering CMP. Poly-Si wafer are deposited by low pressure chemical vapor deposition (LPCVD) and oxide film are prepared by the method of plasma-enhanced tetra ethyl ortho silicate (PETEOS). The polishing test will be performed by a Strasbaugh 6EC polisher with an IC1000/Suba IV stacked pad and the pad will be conditioned by ex situ diamond disk. And the thickness difference of wafer between before and after polishing test will be measured by Ellipsometer and Nanospec. The roughness of Poly-Si film will be analyzed by atomic force microscope.

• Composites Research
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• v.34 no.6
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• pp.337-344
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• 2021

In this study, the progressive failure behavior of the composite fan blade dovetail element under tensile loading is numerically investigated through finite element(FE) simulation. The accuracy of prediction by FE simulation is verified through tensile testing. The dovetail element is one of the joints for coupling the fan blade with the disk in a turbofan engine. The dovetail element is usually made of a metal material such as titanium, but the application of composite material is being studied for weight reduction reasons. However, manufacturing defects such as drop-off ply and resin pocket inevitably occur in realizing complex shapes of the fan blade made by composite materials. To investigate the effect of these manufacturing defects on the composite fan blade dovetail element, we performed numerical simulation with FE model to compare the prediction of the FE model and the tensile test results. At this time, the cohesive zone model is used to simulate the delamination behavior. Finally, we found that FE simulation results agree with test results when considering thermal residual stress and through-thickness compression enhancement effect.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.372-379
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• 2009

Purpose: The purpose of this study was to compare the effect on antibacterial activities and wound healing effect of silver containing dressings with which of Betadine against Staphylococcus aureus and Pseudomonas aeruginosa. Methods: One full thickness skin defects in rats(n=72) were developed on the back and were given rise to infection with S. aureus(n=36) and P. aeruginosa(n=36). The 72 mice were divided into 6 groups : Acticoat$^{(R)}$, Aquacel$^{(R)}$-Ag, Medifoam silver$^{(R)}$, Polymen silver$^{(R)}$, Ilvadon$^{(R)}$ and Betadine(control group) dressing groups. Five silver containing dressings and Betadine were assesed on infected wound. Measurement of wound size change, bacterial colonies count and histologic findings was applied. Antibacterial activity was analyzed with bacterial restricted zone in Mueller Hinton agar. Results: On S. aureus, wound size was more decreased in all treated groups as compared with betadine, however Ilvadon$^{(R)}$ was less decreased on P. aeruginosa. In histologic findings, experimental group showed more effective findings than others on S. aureus, however on P. aeruginosa, which was showed similar. Acticoat$^{(R)}$ was best effective in wound healing against S. aureus and P. aeruginosa. The bacterial colonies count was increased in all treated groups except Acticoat$^{(R)}$ as compared with the control group on S. aureus, which was decreased in Acticoat$^{(R)}$ and Ilvadon$^{(R)}$ group on P. aeruginosa. There were not statistical differences. The restricted zone was shown in Mueller - Hinton agar of all groups except Medifoam silver$^{(R)}$ group on S. aureus, which was shown of all groups on P. aeruginosa. There were statistical differences. Conclusion: This study suggests that silver containing dressings may have not better potential than Betadine in assisting management of wounds at risk of infection on S. aureus and P. aeruginosa. However, which have better antibacterial activity on S. aureus and P. aeruginosa.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.264-264
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• 2010

Single-walled carbon nanotubes (SWCNTs) were grown on a Si wafer by using thermal chemical vapor deposition (t-CVD). We investigated the effect of the catalyst deposition rate on the types of CNTs grown on the substrate. In general, smaller islands of catalyst occur by agglomeration of a catalyst layer upon annealing as the catalyst layer becomes thinner, which results in the growth of CNTs with smaller diameters. For the same thickness of catalyst, a slower deposition rate will cause a more uniformly thin catalyst layer, which will be agglomerated during annealing, producing smaller catalyst islands. Thus, we can expect that the smaller-diameter CNTs will grow on the catalyst deposited with a lower rate even for the same thickness of catalyst. The 0.5-nm-thick Fe served as a catalyst, underneath which Al was coated as a catalyst support as well as a diffusion barrier on the Si substrate. The catalyst layers were. coated by using thermal evaporation. The deposition rates of the Al and Fe layers varied to be 90, 180 sec/nm and 70, 140 sec/nm, respectively. We prepared the four different combinations of the deposition rates of the AI and Fe layers. CNTs were synthesized for 10 min by flowing 60 sccm of Ar and 60 sccm of $H_2$ as a carrier gas and 20 sccm of $C_2H_2$ as a feedstock at 95 torr and $810^{\circ}C$. The substrates were subject to annealing for 20 sec for every case to form small catalyst islands prior to CNT growth. As-grown CNTs were characterized by using field emission scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, UV-Vis NIR spectroscopy, and atomic force microscopy. The fast deposition of both the Al and Fe layers gave rise to the growth of thin multiwalled CNTs with the height of ${\sim}680\;{\mu}m$ for 10 min while the slow deposition caused the growth of ${\sim}800\;{\mu}m$ high SWCNTs. Several radial breathing mode (RBM) peaks in the Raman spectra were observed at the Raman shifts of $113.3{\sim}281.3\;cm^{-1}$, implying the presence of SWCNTs (or double-walled CNTs) with the tube diameters 2.07~0.83 nm. The Raman spectra of the as-grown SWCNTs showed very low G/D peak intensity ratios, indicating their low defect concentrations.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.4
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• pp.246-252
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• 2000

Stellite 12 alloy-powder was overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of characteristic of microstructure and hardness of deposit with current(90~150 A) and preheat temperature(R.T.~$400^{\circ}C$) was investigated. Important conclusion obtained are as follows; All welding conditions used produced a sound deposit layer with no defect in single pass welding. The maximum deposit had 4.0~4.8 mm in thickness and its bead width was increased with increase of current and preheat temperature. The deposit showed hypoeutectic microstruture, which was consisting of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. The amount of eutectic carbides was decreased and its dendritic secondary arm spacing was increased with increase of current. Hardness of the deposit was decreased with increase of current. Preheat temperature up to $400^{\circ}C$, however, showed little influence on the hardness and microstructure. The hardness was also influenced by diluted Fe content near the interface in addition to microstructure and dendritic secondary arm spacing. Hot hardness at $500^{\circ}C$ showed higher than 300 HV.

• Restorative Dentistry and Endodontics
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• v.18 no.2
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• pp.277-290
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• 1993

Dental caries is considered to be caused by demineralization by organic acid produced by microorganism. But the formation of subsurface lesion in initial caries make it diffcult to explain by simple demineralization. This study is carried out on the basis of thermodynamic concept proposed by Margolis and Moreno. The purpose of this study is to evaluate the effects of acid concentration and pH of lactate buffer system on the artificial caries lesion progress. 160 teeth without any crack, defect or opaque enamel were used and coated with nail varnish except the window ($2{\times}3$ mm). Under the constant degree of saturation(D.S.). The teeth were divided into 8 groups according to acid concentration(10mM, 25mM, 50mM, 100mM) and pH(4.3, 5.0, 6.0). Each group was immersed in buffer solution for 3, 6, 9, 18 days under controlled temperature($25^{\circ}C$). After cutting through the window and grinding, the specimens, 100-150 um in thickness, were imbibed in water or air and examined using polarilizing microscope. The depth of the surface and subsurface surface lesion were measured. 1. In the constant pH and D. S. value, the subsurface lesion progresses more rapidly as the concentration of lactic acid increases. (0.01, 0.025, 0.05, 0.1) 2. In the constant acid concentration and DS value, the subsurface lesion progresses more slowly as the pH increases. (4.3, 5.0, 5.5, 6.0) 3. The width of surface lesion seems to be constant independant of pH and acid concentration.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.55-55
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• 2018

Recently, amorphous oxides such as InGaZnO (IGZO) and InZnO (IZO) as a channel layer of an oxide TFT have been attracted by advantages such as high mobility, good uniformity, and high transparency. In order to apply such an amorphous oxide TFTs to a display, the stability in various environments must be ensured. In the InGaZnO which has been studied in the past, Ga elements act as a suppressor of oxygen vacancy and result in a decreased mobility at the same time. Previous studies have been showed that the InZnO, which does not contain Ga, can achieve high mobility, but has relatively poor stability under various instability environments. In this study, the TFTs using $IZO/Al_2O_3$ double layer structure were studied. The introduction of an $Al_2O_3$ interlayer between source/drain and channel causes superior electrical characteristics and electrical stability as well as reduced contact resistance with optimally perfect ohmic contact. For the IZO and $Al_2O_3$ bilayer structures, the IZO 30nm IZO channels were prepared at $Ar:O_2=30:1$ by sputtering and the $Al_2O_3$ interlayer were depostied with various thickness by ALD at $150^{\circ}C$. The optimal sample exhibits considerably good TFT performance with $V_{th}$ of -3.3V and field effect mobility of $19.25cm^2/Vs$, and reduced $V_{th}$ shift under positive bias stress stability, compared to conventional IZO TFT. The enhanced TFT performances are closely related to the nice ohmic contact properties coming from the defect passivation of the IZO surface inducing charge traps, and we will provide the detail mechanism and model via electrical analysis and transmission line method.

• Design & Manufacturing
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• v.18 no.3
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• pp.71-80
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• 2024

Sink marks are a common defect that occurs due to differences in shrinkage in areas with significant thickness variations in injection-molded parts. In this paper, we investigated the reduction of sink marks and the improvement of gas venting in injection molding processes using External Gas Injection (EGI). A mold was designed with considerations for EGI core pins, O-ring grooves to prevent gas leakage, and ejector-pin sealing. The sink marks were then examined through a series of experiments. When the delay time for injecting compressed air was set to 2.2 seconds, the depth of the sink marks was minimized. However, when the delay time was either too short or too long, the depth of the sink marks increased. There was almost no difference in the depth of the sink marks at discharge pressures of 30 and 50 bar of compressed air, but the sink marks were significantly reduced at a discharge pressure of 70 bar. Under the conditions of a 2.2-second delay time and a supply pressure of 70 bar, the smallest depth, 0.594 ㎛, was observed when the supply time was between 6 and 7 seconds. This represents a reduction of approximately 94% compared to the sink mark depth of 10.078 ㎛ observed with conventional injection molding. To verify the gas venting effect of compressed air injection, an experiment was conducted using non-dried PC. The silver streaks that appeared on the exterior of the molded part were completely eliminated when the air supply pressure was set to 20 bar. This indicates that by injecting compressed air into the mold cavity before injecting the resin, the appearance quality of the injection-molded part can be improved without the need to dry the resin in advance.