이온빔 스퍼터링법에 의해 증착된 Ni-Zn 페라이트 박막의 특성연구

학위논문(석사)--서울대학교 대학원 :무기재료공학과,1996.Maste

수직축 조류발전 터빈의 성능에 미치는 설계인자들의 영향 연구

The west and south coastal region of Korea has very strong tidal current speeds and therefore accommodates many suitable sites for the application of Tidal Current Power. This paper deals with effect that design parameter of tidal current vertical axis turbine to performance. For the analysis on VATT(Vertical-Axis Tidal current Turbine), the numerical approach was made by using the commercial CFD software FLUENT 6.3. First at all, they ascertained that characteristic of turbine parameters such as span, turbine diameter, number of blade, shape of blade, tip speed ratio, solidity and current speed. Second, this paper provided that effect of turbine diameter and current speed on the efficiency of VATT. And than, study on the effect of Reynolds number in turbine efficiency quite big especially at low Reynolds number below. Third, the paper deal with any blockages such as duct or flow fence around the turbine. turbine performance has benefit by a blockage effect. Fourth, present paper has proposed optimal solidity for VATT.C o n t e n t s Contents ⅰ Abstract ⅲ Nomenclatures ⅳ List of Tables ⅴ List of Figures ⅵ 제 1 장 서 언 1.1 연구배경 1 1.2 연구 방향 7 1.3 수직축 조류발전 터빈의 특성 8 제 2 장 조류발전 수직축 터빈의 설계변수 정의 2.1 날개수 (Z) 10 2.2 날개 형상 11 2.3 터빈 직경 12 2.4 터빈 블레이드의 길이 (span) 13 2.5 터빈 축 직경 14 2.6 터빈 회전 속도와 조류 속도 15 2.7 끝단속도비(tip speed ratio, λ) 17 제 3 장 조류발전 수직축 터빈의 성능에 미치는 설계인자 3.1. 계산 검증 18 3.1.1 검증 대상 19 3.1.2 검증 결과 20 3.2. 직경, 유속의 영향 검토 21 3.2.1 개요 21 3.2.2 계산조건 22 3.2.3 유속 변화 영향 24 3.2.4 유속 변화 영향 25 3.2.5 결과 검토 26 3.3. 제한 수로의 영향 검토 27 3.3.1 개요 27 3.3.2 계산조건 28 3.3.3 결과 검토 29 3.3.4 정리 32 3.4. 날개 수, 코드 길이 변화의 영향 33 3.4.1 개요 33 3.4.2 계산 조건 34 3.4.3 날개 수 변화 영향 36 3.4.4 코드 변화 영향 37 3.4.5 결과 검토 38 제 4 장 결 론 39 참고문헌 4

Characterization of antihypertensive angiotensin I-converting enzyme inhibitor from Saccharomyces cerevisiae

This study describes the purification and characterization of a novel antihypertensive angiotensin I-converting enzyme (ACE) inhibitory peptide from Saccharomyces cerevisiae. Maximal production of the ACE inhibitor from Saccharomyces cerevisiae was obtained from 24 h of cultivation at 30°C and its ACE inhibitory activity was increased by about 1.5 times after treatment of the cell-free extract with pepsin. After the purification of ACE inhibitory peptides with ultrafiltration, Sephadex G-25 column chromatography, and reverse-phase HPLC, an active fraction with an IC50 of 0.07 mg and 3.5% yield was obtained. The purified peptide was a novel decapeptide, showing very low similarity to other ACE inhibitory peptide sequences, and its amino acid sequence was Tyr-Asp-Gly-Gly-Val-Phe-Arg-Val-Tyr-Thr. The purified inhibitor competitively inhibited ACE and also showed a clear antihypertensive effect in spontaneously hypertensive rats (SHR) at a dosage of 1 mg/kg body weightope

Quenching Activities of Keto-carotenoids on the Oxygenation by Singlet Oxygen.

The singlet oxygen quenching activites of various carotenoids obtained from natural products were studied. The 102 quenching rate constants (Kq) of β-carotene, capsanthin, capsanthin monoester, capsanthin diester and fucoxanthin were determined and compared quantitatively. The relationship between the structures of carotenoids and its 102 quenching activities were discussed in the light of the substituent effects on the structure. In methanolic solution, the Kqs of capsanthin, capsanthin monoester and fucoxanthin ￦ere shown to be 2.29×10¹⁰, 2.23×10¹⁰ and 0.96×10¹⁰ M⁻¹ sec⁻¹ respectively, while the Kq of βcarotene was determined as 2.36 × 10¹⁰ M⁻¹ sec⁻¹, And the Kq/Kd values of capsanthin monoester, diester and lycopene in benzene-methanol (3 : 5) solution were 1.33×10⁵, 1.26×10⁵ and 2.06×10⁵, respectively. Under the experimental condition, there was no pronounced differences in 102 quenching activity between capsanthin and capsanthin esters. The 102 quenching activity of fucoxanthin was shown to be two-fifth of the β-carotene's These results indicated that the activity of quenching decreased as the introduction of hydroxy or carbonyl group. Carotenoid-fatty acid esters showed lower quenching activity than corresponding free carotenoids, and diester was less active than monoester. These results implied that the existance of long fatty acid chain in carotenoid ester molecules might reduce the quenching actitvity by the reduction of the effective cross-secion of the reaction

Increasing potential risks of contamination from repetitive use of endoscope

BACKGROUND: Medical devices inserted into the human body can be divided into single-use devices and reusable medical devices (RMDs) depending on the method of use. RMDs are applied to >1 patient, and users reprocess them prior to repeat use. Therefore, reprocessing of RMDs has become more difficult, and issues related to infection risk have become more prevalent. METHODS: Research was performed to compare differences in surface alterations between not-aged (NA) samples and accelerated-aging (AA) samples. NA and AA samples were exposed to potential contaminants and treated with the same cleaning conditions. Then the residual contaminants were analyzed, and adhesion characteristics were investigated. RESULTS: Significant differences between the 2 sample groups were observed in the pattern of physical surface alterations. Similar to the endoscope for clinical use, a deep crack was found in the surface of the AA sample. According to the binding affinity test, highly likely potential contaminants were found more frequently on AA samples. CONCLUSION: The results suggest the necessity of limiting the duration of time that RMDs may be used, considering the potential risk of infection from repetitive use of RMDs, and also raised the possibility of applying this simulation model of AA. This methodology can be applied to various RMDs, including endoscopes.ope

The effective control of a bleeding injury using a medical adhesive containing batroxobin

Many types of hemostatic agents have been studied for the effective control of bleeding. In this study, a powdery medical adhesive composed of aldehyded dextran and ε-poly (L-lysine) was used with the recombinant batroxobin. Batroxobin is a venomous component from the snake Bothrops atrox moojeni and catalyzes fibrinogen conversion to form soluble fibrin clots. This research aims to examine the performance of the batroxobin-containing adhesive for hemostasis, and evaluate its potential as a novel hemostatic adhesive. The fibrinogen conversion ability of batroxobin was evaluated by a fibrinogen clotting assay and a whole blood clotting assay. Both experiments demonstrated the effectiveness of the batroxobin-containing adhesive for blood clot formation. Animal experiments were also conducted. After a pricking wound was made in an ICR (imprinting control region) mouse liver, the adhesive and various concentrations of batroxobin were applied. The total amount of blood loss was reduced with increasing concentrations of batroxobin. For excessive bleeding conditions, the femoral artery wound model of SD (Sprague-Dawley) rats was adopted. With higher concentrations of batroxobin, hemostasis was more rapidly achieved. Histological analysis of the liver model also supports the hemostatic effects through fibrin clot formation. In conclusion, batroxobin and medical adhesive effectively facilitate blood coagulation, and could be developed for clinical use.ope

Biological Advantages of Porous Hydroxyapatite Scaffold Made by Solid Freeform Fabrication for Bone Tissue Regeneration

Presently, commercially available porous bone substitutes are manufactured by the sacrificial template method, direct foaming method, and polymer replication method (PRM). However, current manufacturing methods provide only the simplest form of the bone scaffold and cannot easily control pore size. Recent developments in medical imaging technology, computer-aided design, and solid freeform fabrication (SFF), have made it possible to accurately produce porous synthetic bone scaffolds to fit the defected bone shape. Porous scaffolds were fabricated by SFF and PRM for a comparison of physical and mechanical properties of scaffold. The suggested three-dimensional model has interconnected cubic pores of 500 μm and its calculated porosity is 25%. Whereas hydroxyapatite scaffolds fabricated by SFF had connective macropores, those by PRM formed a closed pore external surface with internally interconnected pores. SFF was supposed to be a proper method for fabricating an interconnected macroporous network. Biocompatibility was confirmed by testing the cytotoxicity, hemolysis, irritation, sensitization, and implantation. In summary, the aim was to verify the safety and efficacy of the scaffolds by biomechanical and biological tests with the hope that this research could promote the feasibility of using the scaffolds as a bone substitute.ope