• 한국산학기술학회논문지
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• 제12권7호
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• pp.2939-2944
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• 2011

용융탄산염형 연료전지 시스템의 성능 향상을 위해 핵심 부분인 스택을 수치적으로 모사할 필요성이 대두되고 있다. 스택은 다양한 재질, 즉 금속, 세라믹, 폴리머 등으로 이루어져 있고 또한 단위전지 수백 장이 적층되어 제작되기 때문에 이를 전부 세세히 모델링하여 고려하는 것은 거의 불가능하다. 이에 따라 스택 전체를 하나의 균질한 물질로 대체할 수 있는 균질 물성치 도출이 요구되고 있다. 본 논문에서는 단위전지 압축률을 도입하고 모든 압축 변형이 분리판과 매트릭스에서만 일어난다는 등의 몇 가지 기본 가정 하에서 스택의 두 가지 영역, 즉 활성 영역과 매니폴드 영역에서 각각 균질 물성치를 추정하였다. 추정된 물성치를 실제 문제에 적용하여 성공적인 결과를 얻을 수 있었다.

• 한국산학기술학회논문지
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• 제7권6호
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• pp.1302-1307
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• 2006

본 연구는 고효율의 광촉매 제조와 그것의 환경적 응용에 관한 것이다. 가시광 영역에서도 $TiO_2$와 유사한 빛 흡수와 광분해속도를 갖는 나노 광촉매를 제조하였고, 낮은 온도에서도 활성 높은 rutile상이 형성하는 $TiO_2$ 광촉매를 제조하여 $SiO_2$위에 분산시켰다 또한, 광촉매에 적용 가능한 바인더와 안정한 $TiO_2$ 광촉매 졸을 제조하였다. 이와같은 물질들은 자외선/가시광선 분광광도계, X선 회절분석기, SEM, 광촉매활성 측정과 $TiO_2$ 코팅 표면의 물성으로 평가하였다. 이 결과들은 공기정화를 위하여 POF나 금속판을 이용하는 효율적인 광촉매 시스템에 적용 할 수 있다.

• 한국가스학회지
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• 제13권5호
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• pp.33-38
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• 2009

일산화탄소, 수소와 같은 친환경 연료용 가스를 이용하여 메탄화 반응을 거쳐 합성 가스를 생성하였다. 이를 위한 촉매로 상용 알루미나에 담지된 Ni-Co 이원 금속을 증착침전법을 사용하여 제조하였으며 제조된 촉매의 촉매 활성 비교를 위하여 Ni, Co 단일 금속 촉매를 동일한 방법으로 제조하였다. 제조한 촉매를 TEM, XRD, TPR 분석을 실시하여 각각의 촉매 특성을 확인하였고 메탄화 반응을 진행하여 합성 가스 전환율을 측정하였다. 증착침전법으로 제조한 촉매의 경우, 금속 입자가 작은 크기로 분산된 것을 확인하였다. Ni, Co 두 금속이 담지된 이원 촉매는 Ni, Co가 각각 담지된 단일 금속 촉매에 비해 더욱 높은 활성을 나타내었으며 TPR 분석 결과, 이는 두 금속의 공존으로 인한 상호 작용을 통해 활성 수소를 보다 증가시켰기 때문으로 나타났다.

• Archives of Plastic Surgery
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• 제38권4호
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• pp.458-464
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• 2011

Purpose: Metacarpal fractures are common hand injury that may require operative intervention to ensure adequate reduction and stabilization. Traditionally, titanium miniplate was used for rigid fixation of bone fractures. However, the use of permanent plate lends itself to multiple complications such as infection, exposure of the hardware, tendon adhesions, tendon rupture, prolonged pain, bony atrophy and osteoporosis (stress shielding), metal sensitization, and palpation under the skin. This study evaluated the usefulness and stability of biodegradable plates and screws for treatment of metacarpal bone fractures. Methods: There was 17 patients who had surgery for metacarpal bone fracture from April 2007 to June 2010. All patients had open reduction and internal fixation. We used absorbable plates and screws (Inion CPS$^{(R)}$) for internal fixation. Postoperative results were assessed with x-ray. Stability of plates and screws, healing process and its complications were observed by clinical and radiographic assessment. Results: All patients were successfully reduced of bone fracture, and fixations with absorbable plates and screws were stable. The mean follow up period was 7.1 months. 2 patients complained postoperative pain, but they were relieved with analgesics. All patients experienced transient stiffness, but they were relieved with active assistive range of motion after removal of splint. No patients suffered complications which could be occurred by using metallic plate. Conclusion: There was no critical complications such as re-fracture or nonunion among patients. No patients suffered side effects related with metallic implants. Biodegradable implants can offer clinically stable and attractive alternative to metallic implants to stabilize metacarpal bone fractures in the hand.

• 한국정밀공학회지
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• 제23권8호
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• pp.171-177
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• 2006

This study was performed as a part of the research on the development of a maskless and electroless process for fabricating metal micro/nanostructures by using a nanoindenter and an electroless deposition technique. $2-{\mu}m$-deep indentation tests on Ni and Cu samples were performed. The elastic recovery of the Ni and Cu was 9.30% and 9.53% of the maximum penetration depth, respectively. The hardness and the elastic modulus were 1.56 GPa and 120 GPa for Ni and 1.51 GPa and 104 GPa for Cu. The effect of single-point diamond machining conditions such as the Berkovich tip orientation (0, 45, and $90^{\circ}$ ) and the normal load (0.1, 0.3, 0.5, 1, 3, and 5 mN), on both the deformation behavior and the morphology of cutting traces (such as width and depth) was investigated by constant-load scratch tests. The tip orientation had a significant influence on the coefficient of friction, which varied from 0.52-0.66 for Ni and from 0.46- 0.61 for Cu. The crisscross-pattern sample showed that the tip orientation strongly affects the surface quality of the machined are a during scratching. A selective deposition of Cu at the pit-like defect on a p-type Si(111) surface was also investigated. Preferential deposition of the Cu occurred at the surface defect sites of silicon wafers, indicating that those defect sites act as active sites for the deposition reaction. The shape of the Cu-deposited area was almost the same as that of the residual stress field.

• 공업화학
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• 제25권3호
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• pp.281-285
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• 2014

호기성 벤질 알코올 산화반응용 촉매로 팔라듐이 담지된 이산화티타늄 입자를 제조하였다. 우선 합성한 이산화티타늄입자에 10 wt% 팔라듐을 함침한 후, 다양한 온도에서 소성하여 촉매를 제조하였다. 촉매의 비표면적은 소성온도에 따라 변하였는데, $300^{\circ}C$에서 소성한 촉매의 비표면적이 가장 높게 측정되었다. 제조된 촉매의 반응 결과 $300^{\circ}C$에서 소성한 입자가 가장 우수한 반응성능을 보였다. 또한 팔라듐의 농도를 5 wt%에서 15 wt%까지 조절하여 함침한 후 $300^{\circ}C$에서 소성하여 촉매를 합성하였다. 팔라듐의 농도가 10 wt%인 $Pd/TiO_2$ 입자가 벤질알코올 산화반응에 최적의 촉매로 규명되었다. 이는 상대적으로 높은 촉매의 비표면적 및 팔라듐 분산도에 기인한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.232-232
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• 2010

Recently light emitting diodes (LEDs) have been expected as the new generation light sources because of their advantages such as small size, long lifetime and energy-saving. GaN, as a wide band gap material, is widely used as a material of LEDs and GaN nanorods are the one of the most widely investigated nanostructure which has advantages for the light extraction of LEDs and increasing the active area by making the cylindrical core-shell structure. Lately GaN nanorods are fabricated by various techniques, such as selective area growth, vapor-liquid-solid (VLS) technique. But these techniques have some disadvantages. Selective area growth technique is too complicated and expensive to grow the rods. And in the case of VLS technique, GaN nanorods are not vertically aligned well and the metal catalyst may act as the impurity. So we just tried to grow the GaN nanorods on Si substrate without catalyst to get the vertically well aligned nanorods without impurity. First we deposited the AlN buffer layer on Si substrate which shows more vertical growth mode than sapphire substrate. After the buffer growth, we flew trimethylgallium (TMGa) as the III group source and ammonia as the V group source. And during the GaN growth, we kept the ammonia flow stable and periodically changed the flow rate of TMGa to change the growth mode of the nanorods. Finally, as the optimization, we changed the various growth conditions such as the growth temperature, the working pressure, V/III ratio and the doping level. And we are still in the process to reduce the diameter of the nanorods and to extend the length of the nanorods simultaneously. In this study, we focused on the shape changing of GaN nanorods with different growth conditions. So we confirmed the shape of the nanorods by scanning electron microscope (SEM) and carried out the Photoluminescence (PL) measurement and x-ray diffraction (XRD) to examine the crystal quality difference between samples. Detailed results will be discussed.

• Biomaterials and Biomechanics in Bioengineering
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• 제2권3호
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• pp.143-157
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• 2015

Successful integration of cementless femoral stems using porous surfaces relies on effective periimplant bone healing to secure the bone-implant interface. The initial stages of the healing process involve protein adsorption, fibrin clot formation and cell osteoconduction onto the implant surface. Modelling this process in vitro, the current work considered the effect of fibrin deposition on the responses of human mesenchymal stromal cells cultured on ferritic fibre networks intended for magneto-mechanical actuation of in-growing bone tissue. The underlying hypothesis for the study was that fibrin deposition would support early stromal cell attachment and physiological functions within the optimal regions for strain transmission to the cells in the fibre networks. Highly porous fibre networks composed of 444 ferritic stainless steel were selected due to their ability to support human osteoblasts and mesenchymal stromal cells without inducing untoward inflammatory responses in vitro. Cell attachment, proliferation, metabolic activity, differentiation and penetration into the ferritic fibre networks were examined for one week. For all fibrin-containing samples, cells were observed on and between the metal fibres, supported by the deposited fibrin, while cells on fibrin-free fibre networks (control surface) attached only onto fibre surfaces and junctions. Initial cell attachment, measured by analysis of deoxyribonucleic acid, increased significantly with increasing fibrinogen concentration within the physiological range. Despite higher cell numbers on fibrin-containing samples, similar metabolic activities to control surfaces were observed, which significantly increased for all samples over the duration of the study. It is concluded that fibrin deposition can support the early attachment of viable mesenchymal stromal cells within the inter-fibre spaces of fibre networks intended for magneto-mechanical strain transduction to in-growing cells.

• 융합정보논문지
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• 제8권4호
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• pp.199-204
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• 2018

본 연구의 목적은 데뷔 50년을 맞은 조용필 음악의 특징을 분석하고 한국 대중음악사적 의의를 평가하는 것이다. 조용필이 활동한 1960년대 후반부터 현재까지의 대중음악사는 세 시기로 구분된다. 1960년대 후반부터 1980년대 초반까지는 기성세대의 트로트와 젊은이의 록이 유행했던 시기, 1980년대 중반부터 2000년대 초반까지는 소프트 록과 헤비메탈, 발라드가 혼재했던 시기, 2000대 후반부터 현재까지는 후크 송 중심의 댄스음악이 음악시장을 석권한 시기이다. 음악사의 변곡점마다 조용필은 다양한 음악 장르를 넘나들며 대한민국 대중음악의 발전에 기여하였다. 첫 번째 시기에는 트로트와 록을 접목하여 한국 고유의 정서를 담은 록음악을 발표하였고, 두 번째 시기에는 록의 전성기와 발라드의 태동기에서 두 장르 모두의 발전에 기여한다. 세 번째 시기에는 후크송을 발표해 논란을 일으키기도 하였으나 댄스 음악 장르에서도 보컬의 가창력이 중시되는 분위기를 조성하는 데 기여하였다.

• Journal of Microbiology and Biotechnology
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• 제31권4호
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• pp.570-583
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• 2021

Pyrococcus furiosus α-amylase can hydrolyze α-1,4 linkages in starch and related carbohydrates under hyperthermophilic condition (~ 100℃), showing great potential in a wide range of industrial applications, while its relatively low productivity from heterologous hosts has limited the industrial applications. Bacillus subtilis, a gram-positive bacterium, has been widely used in industrial production for its non-pathogenic and powerful secretory characteristics. This study was conducted to increase production of P. furiosus α-amylase in B. subtilis through three strategies. Initial experiments showed that co-expression of P. furiosus molecular chaperone peptidyl-prolyl cis-trans isomerase through genomic integration mode, using a CRISPR/Cas9 system, increased soluble amylase production. Therefore, considering that native P. furiosus α-amylase is produced within a hyperthermophilic environment and is highly thermostable, heat treatment of intact culture at 90℃ for 15 min was performed, thereby greatly increasing soluble amylase production. After optimization of the culture conditions (nitrogen source, carbon source, metal ion, temperature and pH), experiments in a 3-L fermenter yielded a soluble activity of 3,806.7 U/ml, which was 3.3- and 28.2-fold those of a control without heat treatment (1,155.1 U/ml) and an empty expression vector control (135.1 U/ml), respectively. This represents the highest P. furiosus α-amylase production reported to date and should promote innovation in the starch liquefaction process and related industrial productions. Meanwhile, heat treatment, which may promote folding of aggregated P. furiosus α-amylase into a soluble, active form through the transfer of kinetic energy, may be of general benefit when producing proteins from thermophilic archaea.