• 한국전기전자재료학회논문지
• /
• 제34권6호
• /
• pp.487-494
• /
• 2021

Piezoelectric generators use direct piezoelectric effects that convert mechanical energy into electrical energy. Many studies were attempted to fabricate piezoelectric generators using piezoelectrics such as ZnO, PZT, PVDF. However, these various inorganic/organic piezoelectric materials are not suitable for bio-implantable devices due to problems such as brittleness, toxicity, bio-incompatibility, bio-degradation. Thus, in this paper, piezoelectric generators were prepared using a silk fibroin film which is bio-compatible by dip-coating method. The silk fibroin films are a mixed state of silk I and silk II having stable β-sheet type structures and shows the d₃₃ value of 8~10 pC/N. There was a difference in output voltages according to the thickness. The silk fibroin generators, coated 10 times and 20 times, revealed the power density of 16.07 μW/cm² and 35.31 μW/cm² using pushing tester, respectively. The silk fibroin generators are sensitive to various pressure levels, which may arise from body motions such as finger tapping, foot pressing, wrist shaking, etc. The silk fibroin piezoelectric generators with bio-compatibility shows the applicability as a low-power implantable piezoelectric generator, healthcare monitoring service, and biotherapy devices.

• Elastomers and Composites
• /
• 제54권3호
• /
• pp.225-231
• /
• 2019

Bio-based polyester polyol was synthesized via esterification between azelaic acid and isosorbide. After esterification, bio-based polyurethanes were synthesized using polyester polyol, 1,3-propanediol as the chain extender, and 4,4'-diphenylmethane diisocyanate, in mixing ratios of 1:1:1.5, 1:1:1.8, 1:1:2, and 1:1:2.3. The bio TPU (Thermoplastic Polyurethane) samples were characterized by using FT-IR (Fourier Transform Infrared Spectroscopy), TGA (Thermal Gravimetric Analysis), DSC (Differential Scanning Calorimetry), and GPC (Gel Permeation Chromatography). The mechanical properties (tensile stress and hardness) were obtained by using UTM, a Shore A tester, and a Taber abrasion tester. The viscoelastic properties were tested by an Rubber Processing Analyzer in dynamic strain sweep and dynamic frequency test modes. The chemical resistance was tested with methanol by using the swelling test method. Based on these results, the bio TPU synthesized with the ratio of 1:1:2.3, referred to as TPU 4, showed the highest thermal decomposition temperature, the largest molecular weight, and most compact matrix structure due to the highest ratio of the hard segment in the molecular structure. It also presented the highest tensile strength, the largest elongation, and the best viscoelastic properties among the different bio TPUs synthesized herein.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.509-512
• /
• 2006

We have many environmental problems by the polluted materials as a results of mechanical development these days. So people want to use building products made from natural things and take a good effect for people from those bio products. We can instance electron wave shelding, far infrared ray and anion emission, and anti-bacterial property as the latest trend of the bio building material. So we had a experiment to investigate how much bio materials affect concrete when we use in the concrete with cement substitution. We tested slump, 7days compressive strength, and air contents for physical properties of bio concrete. The result is that bio concretes with four bio ingredients have proper values comparing with target values for slump and air content but lower compressive strength than plain concrete.

• 전기화학회지
• /
• 제11권3호
• /
• pp.165-169
• /
• 2008

CODH(Carbon Monoxide Dehydrogenase)에 의한 이산화탄소 환원에 있어서 작업전극을 유리탄소전극을 사용한 경우와 금전극을 사용한 경우를 비교하여 그 영향을 관찰하였다. 금전극을 사용한 경우에는 수소발생과 섞이기 때문에 전기분해의 전위를 잘 선택해야 효율적인 이산화탄소의 환원 반응을 관찰할 수 있는데 반하여, 유리탄소전극은 금전극보다 수소 환원에 대한 과전압이 크기 때문에 -650 mV vs. NHE 까지도 중성수용액에서 수소발생 없이, 효율적인 이산화탄소의 환원을 관찰할 수 있었다. CODH를 이용한 이산화탄소의 환원에는 가해주는 전기분해 전위가 큰 영향을 미침을 알 수 있었는데, $-570{\sim}600\;mV$ vs. NHE 근처가 가장 효율적임을 알 수 있었고 이보다 더 음의 전위를 걸어주었을 때는 효소활성의 감소 및 수소발생이 복합적으로 영향을 미쳐 일산화탄소 생성의 전류효율이 급격히 감소함을 알 수 있었다.

• 한국미생물학회:학술대회논문집
• /
• 한국미생물학회 2005년도 International Meeting of the Microbiological Society of Korea
• /
• pp.205.1-205
• /
• 2005

• The Plant Pathology Journal
• /
• 제17권6호
• /
• pp.376.2-376
• /
• 2001

• Journal of the Korean Wood Science and Technology
• /
• 제32권3호
• /
• pp.71-78
• /
• 2004

The purpose of this study was to investigate the water absorption and thickness swelling of biocomposites at room temperature. These properties of bio-composites mainly depend on the ability of the agro-flour to absorb water through hydrogen bonding between water and the hydroxyl groups of the holocellulose and lignin in the cell wall. As the content of agro-flour increased, the water absorption and thickness swelling of the bio-composites increased. The effects of agro-flour content and rice husk flour (RHF) particle size on the water absorption and thickness swelling of the bio-composites were evaluated. In general, wood-based materials showed significantly higher water absorption and thickness swelling than the bio-composites. This might be attributed to the ability of the polybutylene succinate (PBS) hydrophobic polymer to prohibit the water absorption and thickness swelling of the bio-composites, Therefore, the use of agro-flour filled PBS bio-composites, which exhibit improved dimensional stability in comparison with wood-based materials, is recommended.

• 한국고분자학회지:고분자과학과기술
• /
• 제26권4호
• /
• pp.313-322
• /
• 2015

• Journal of Microbiology and Biotechnology
• /
• 제13권6호
• /
• pp.969-975
• /
• 2003

Two conserved amino acid residues in the extra sugar-binding space near the catalytic site of Thermus maltogenic amylase (ThMA) were analyzed for their role in the hydrolysis and transglycosylation activity of the enzyme. Site-directed mutagenesis was carried out by replacing N33l with a lysine (N331K), E332 with a histidine (E332H), or by replacing both residues at the same time (N331K/E332H). The measured $K_m$ values indicated that affinities toward all substrates tested, including starch, pullulan, ${\beta}-cyclomaltodextrin$, and acarbose, were lower in all the mutants compared to that of wild-type ThMA, leading to reduced hydrolysis activity. In addition, the lower ratio of transglycosylation to hydrolysis in the mutants compared to that in the wild-type ThMA indicated that these mutants preferred hydrolysis to the transglycosylation reaction. These results demonstrated that the conserved dipeptide at 331 and 332 of ThMA is directly involved in the formation and accumulation of transfer products by accommodating acceptor sugar molecules.

• Journal of the Korean Wood Science and Technology
• /
• 제43권1호
• /
• pp.86-95
• /
• 2015

본 연구는 기존에 제조되었던 교호집성재의 휨강도의 단점을 보완하고 새로운 특성을 가진 교호 집성재 즉, 합판을 코어로 이용한 집성재가 가진 기계적강도의 효과를 알아보기 위해 수행되었다. 집성재와 합판의 구성 방법, 적층 방향에 따라 그 값을 비교하였으며, 그에 따른 휨강도와 탄성계수를 측정하여 분석한 결과, 중심부를 집성판과 합판을 혼합하여 구성한 합판 코어 집성재의 휨강도(MOR) 값이 59.6% 강도가 향상되어 교호집성재구조 대조군보다는 우수하고, 집성재구조 대조군과는 유사한 강도를 나타냈다. 휨탄성계수(MOE)는 합판 코어 집성재의 구조 및 적층 방향성에 상관없이 모두 집성재구조 대조군과 유사한 MOE 값을 나타냈다. 치수 안정성 실험에서는 합판을 코어에 사용한 합판코어 집성재가 합판 사용으로 인하여, 수축 팽창률 모두 집성재와 교호집성재구조 대조군에 비해서 더 안정적인 것으로 나타났다.