• KSBB Journal
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• 제9권5호
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• pp.525-531
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• 1994

본 연구에서는 tyrosinase 효소반응시에 발생하는 반응 비활성화를 막아 조엽 얀정성을 향상시키는 것을 목적으로 연구를 수행하였다. Quinone에 의해 친핵성 공격을 받는 lysine기를 bifunctional rea gent인 glutaraldehyde로 변형시켜 줌으로써 효소 의 비활성화를 줄일 수 있었다. 또한, 고정화된 효소 를 충진층 반응기에 충진시켜 비활생화를 열으키는 생산물을 연속적으로 제거함으로써 효소의 얀정성을 크게 향상시켰다. 고정화 방법으로는 glass bead를 이용한 담체 가교법을 이용하였으며, 이때 glutaral­d dehyde와 효소의 lysine이 반응하게 되어 qumone 에 의한 친핵성 공격을 받지 않게 되어 안정성이 더욱 향상되 었다. 반응매 질로 borate buffer를 이용하 게되면 catechol과 borate의 복합체 형성으로 catechol에서 qumone으로의 전환이 줄어들게 되어 효소 비활성화가 감소하였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.295-296
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• 2006

• 한국세라믹학회지
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• 제43권9호
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• pp.544-551
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• 2006

The sealing technique between a glass tube and a copper heat pipe in an evacuated tube solar collector is studied. In this study two different sealing techniques, such as flame method and furnace firing, are examined. After the sealing of a copper to a glass, the oxidation state of the copper and its bonding morphology were examined by SEM and XRD. Its oxidation was retarded by coating of borate solution on the copper, and $Cu_2O(cuprite)$ turned into CuO(tenorite) with increase in a firing temperature and firing time. Porous structure was found in the oxide layer when CuO formed. The best sealing morphology was observed when the thickness of the oxidation layer was less than $20{\mu}m$. The sealing technique performed in a furnace was promising and the satisfactory result was obtained when the sample was fired at $950^{\circ}C$ for 5 min under $N_2$ atmosphere. Annealing procedure is recommended to remove the stress left at the bonding zone.

• Nuclear Engineering and Technology
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• 제53권1호
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• pp.282-293
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• 2021

This paper examines gamma-ray shielding properties of SBC-Bx glass system with the chemical composition of 40SiO₂-10B₂O₃-xBaO-(45-x)CaO- yZnO- zMgO (where x = 0, 10, 20, 30, and 35 mol% and y = z = 6 mol%). Mass attenuation coefficient (µ/ρ) which is an essential parameter to study gamma-ray shielding properties was obtained in the photon energy range of 0.015-15 MeV using PHITS Monte Carlo code for the proposed glasses. The obtained results were compared with those calculated by WinXCOM program. Both the values of PHITS code and WinXCOM program were observed in very good agreement. The (µ/ρ values were then used to derive mean free path (MFP), electron density (N_eff), effective atomic number (Z_eff), and half value layer (HVL) for all the glasses involved. Additionally, G-P method was employed to estimate exposure buildup factor (EBF) for each glass in the energy range of 0.015-15 MeV up to penetration depths of 40 mfp. The results reveal that gamma-ray shielding effectiveness of the SBC-Bx glasses evolves with increasing BaO content in the glass sample. Such that SBC-B35 glass has superior shielding capacity against gamma-rays among the studied glasses. Gamma-ray shielding properties of SBC-B35 glass were compared with different conventional shielding materials, commercial glasses, and newly developed HMO glasse. Therefore, the investigated glasses have potential uses in gamma shielding applications.

• Nuclear Engineering and Technology
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• 제52권6호
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• pp.1297-1303
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• 2020

In this study, nuclear radiation shielding and rigidity parameters of Y (0.1-x)B0.6Bi1.8O3La2x glassy system were investigated in order to determine it's suitability for use as nuclear radiation shielding materials. Therefore, a group of bismuth borate glass samples with La₂O₃ additive were synthesized using the technique of melt quenching. According to the results, the increase of the La₂O₃ additive increases the density of the glass samples and the mass attenuation coefficient (μ_m) values, whereas the half-value layer (HVL) and mean free path (MFP) values decrease. The effective atomic number (Z_eff) is also enhanced with an increment of both mass removal cross section for neutron (Σ_R) and absorption neutron scattering cross section (σ_abs). In addition to the other parameters, rigidity parameter values were theoretically examined. The increase of La₂O₃ causes some other important magnitudes to increase. These are the average crosslink density, the number of bonds per unit volume, as well as the stretching force constant values of these glass samples. These results are in concordance with the increase of elastic moduli in terms of the Makishima-Mackenzie model. This model showed an increase in the rigidity of the glass samples as a function of La₂O₃.

• Nuclear Engineering and Technology
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• 제53권3호
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• pp.949-959
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• 2021

The current study aims to explore the shielding properties of multi-component borate-based glass series. Seven glass-samples with composition of (80-y)H₃BO₃-10ZnO-10Na₂O-yBaO where (y = 0, 5, 10, 15, 20, 25 and 30 mol.%) were synthesized by melt-quench method. Various shielding features for photons, neutrons, and protons were determined for all prepared samples. XCOM, Phy-X program, and SRIM code were performed to determine and explain several shielding properties such as equivalent atomic number, exposure build-up factor, specific gamma-ray constants, effective removal cross-section (Σ_R), neutron scattering and absorption, Mass Stopping Power (MSP) and projected range. The energy ranges for photons and protons were 0.015-15 MeV and 0.01-10 MeV, respectively. The mass attenuation coefficient (μ/ρ) was also determined experimentally by utilizing two radioactive sources (¹⁶⁶Ho and ¹³⁷Cs). Consistent results were obtained between experimental and XCOM values in determining μ/ρ of the new glasses. The addition of BaO to the glass matrix led to enhance the μ/ρ and specific gamma-ray constants of glasses. Whereas the remarkable reductions in Σ_R, MSP, and projected range values were reported with increasing BaO concentrations. The acquired results nominate the use of these glasses in different radiation shielding purposes.

• 한국안광학회지
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• 제5권1호
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• pp.49-53
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• 2000

Sodium borate silicate 유리는 $10Na_2O-39B_2O_3-50SiO_2-CoO$ mol%와 $20Na_2O-14B_2O_3-65SiO_2-CoO$ mol%의 조성비로 혼합한 후 전기로에서 $1210^{\circ}C$ 온도로 2시간 동안 용융하여 공기 중에서 급냉 시켜 제작하였다. 급냉한 유리의 유전적 거동을 조사하기 위하여 온도와 주파수 함수로 유전상수와 비저항을 측정하였다. 유전율 스펙트럼에서 유리전이온도는 $Na_2O$ 20 mol%시료가 낮아졌으며 $Na_2O$ 함량이 증가함에 따라 유전상수는 크게 나타났다. 유리의 비저항 주파수 의존성은 non-Debye형 완화를 보였다.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2006년도 춘계학술대회
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• pp.198-201
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• 2006

To produce fine structure with uniform surface of barrier ribs in PDP, acid etching process has been used in manufacture process. It is necessary to understand the mechanism of etching, particularly on the interface of ceramic fillers and matrix glass. We investigated the effect of ceramic fillers (ZnO, $Al_{2}O_3$) on the microstructure of borate glass system to find an etching mechanism of barrier ribs. The harrier ribs was etched with a several steps, dissolving a small amount of residual glass, taking out alumina fillers, and removing a cluster type of ZnO fillers and glass matrix.

• 반도체디스플레이기술학회지
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• 제5권3호
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• pp.33-36
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• 2006

To produce a fine structure with uniform surface of barrier ribs in PDP, acid etching process has been used in manufacture process. It is necessary to understand the mechanism of etching, particularly on the interface of ceramic fillers and matrix glass. We investigated the effect of ceramic fillers (ZnO, $Al_2O_3$) on the microstructure of borate glass system to find an etching mechanism of barrier ribs. The barrier ribs was etched with several steps, dissolving a small amount of residual glass, taking out alumina fillers, and removing a cluster type of ZnO fillers and glass matrix.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2711-2717
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• 2024

The current work aims to fabricate metal oxide-doped (PbO, Fe₂O₃, MgO, and Al₂O₃, each of which boasts a purity of 99%) zinc barium borate glasses through the melt quenching technique at the 1000 ℃ melting temperature. The results showed that adding 5 mol.% of metal oxides PbO, Fe₂O₃, Al₂O₃, and MgO increases the density of the zinc barium borate glasses. Additionally, the fabricated glasses' mechanical properties were determined based on the Makishima-Mackenzie model, which proved that the highest mechanical properties were achieved for glasses doped with Al₂O₃ compounds. The mechanical moduli for the glasses doped with Al₂O₃ reach 80.95 GPa (Young), 59.90 GPa (bulk), 31.75 GPa (shear), and 102.23 GPa (longitudinal). Additionally, the Al₂O₃-doped glasses' microhardness reaches 4.77 GPa. Moreover, estimation of the fabricated glasses' gamma-ray shielding capacity utilized Monte Carlo simulation. The highest linear attenuation coefficients are 29.132, 19.906, 19.243, and 18.923 cm^-1 obtained at 0.033 MeV for glasses dopped by PbO, Fe₂O₃, MgO, and Al₂O₃, respectively. Therefore, glasses doped with 5 mol.% of PbO have high gamma-ray shielding capacities followed by glasses doped by Fe₂O₃.