• 열처리공학회지
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• 제4권2호
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• pp.1-8
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• 1991

The spheroidization of cold rolled lamellar pearlite in annealing at the temperatures between 600 and $700^{\circ}C$ has been studied by quantitative micrography. It was foud that the spheroidization proceeded as two stageh. The first stage was the stage of relieving the stored energy by cold work, the second was the stage of reducing the interface energy between ferrite and cementite. The spheroidization rate combining the spheroidization rate of each stages is described by the following equation : $$d(1/S)/dt=k_3{\cdot}D/_{(1/s)}\{{\sigma}V/_{(1/s)}+k_4{\cdot}{\exp}(-bt)\}$$ Where, S is the total area of the interface between ferrite and cementite per unit volume, D is the diffusion coefficient, ${\sigma}$ is the boundary energy, V is the volume fraction of the cementite, and $k_3$, $k_4$, b are constants.

• 열처리공학회지
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• 제8권1호
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• pp.3-11
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• 1995

A theoretical model which combines gaseous transport and solid state diffusion was used to study aluminide coating process by pack cementation. The aluminide coatings were applied in the high activity pack containing $NH_4Cl$ activator with Ni substrate under argon atmosphere. On the basis of the process conditions, the suggested model allows the surface composition, the growth rate of coating layers and the aluminium concentration profiles in coatings to be calculated. In the case of $NH_4Cl$ activator, careful consideration was required in the analysis, because activator contains nitrogen and hydrogen as well as halogen element to activate the pack. A good agreement is obtained between the theoretical predictions and the experimental results.

• 한국의류학회지
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• 제48권2호
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• pp.300-311
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• 2024

Amid global environmental concerns, initiatives to adopt sustainable industrial processes have garnered significant attention in diverse sectors. Efforts have centered on utilizing natural resources as dyeing and functionalizing agents in the textile industry. However, the limited color fastness and functional endurance of natural compounds remains a substantial challenge. This research investigated whether ultrasound could enhance the finishing effect of natural compounds on cotton fabrics. Chestnut shell extract was prepared and applied to cotton fabrics using a pad-dry-cure technique, with concurrent application of ultrasonic power. Once integrated into the fabrics, the chestnut shell extract exhibited prolonged health benefits for users. The findings demonstrated that ultrasound treatment during the finishing process facilitated the diffusion of natural compounds from the chestnut shell extract into the fabric structure, resulting in a substantial enhancement of the finishing effect, notably augmenting the antibacterial properties of the treated cotton fabrics.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.336-340
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• 1999

Glasses in the system $CaO-TiO_2-SiO_2-Al_2O_3-ZrO_2-B_2O_3$ were investigated to find the glass seal compositions suitable for use in the planar solid oxide fuel cell (SOFC). Glass-ceramics prepared from the glasses by one-stage heat treatment at $1,000^{\circ}C$ showed various thermal expansion coefficients (i,e., $8.6\times10^{-6^{\circ}}C^{-1}$ to $42.7\times10^{-6^{\circ}}C^{-1}$ in the range 25-$1,000^{\circ}C$) due to the viscoelastic response of glass phase. The average values of contact angles between the zirconia substrate and the glass particles heated at 1,000-$1,200^{\circ}C$ were in the range of $131^{\circ}\pm4^{\circ}$~$137^{\circ}\pm9^{\circ}$, indicating that the glass-ceramic was in partial non-wetting condition with the zirconia substrate. With increasing heat treatment time of glass samples from 0.5 to 24 h at $1,100^{\circ}C$, the DC electrical conductivity of the resultant glass-ceramics decreased from at $800^{\circ}C$. Isothermal hold of the glass sample at $1100^{\circ}C$ for 48h resulted in diffusion of Ca, Si, and Al ions from glass phase into the zirconia substrate through the glass/zirconia bonding interface. Glass phase and diffusion of the moving ion such as $Ca^{2+}$ in glass phase is responsible for the electrical conduction in the glass-ceramics.

• Biomolecules & Therapeutics
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• 제24권2호
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• pp.199-205
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• 2016

This study aimed to investigate the in vivo relevance of P-glycoprotein (P-gp) in the pharmacokinetics and adverse effect of phenformin. To investigate the involvement of P-gp in the transport of phenformin, a bi-directional transport of phenformin was carried out in LLC-PK1 cells overexpressing P-gp, LLC-PK1-Pgp. Basal to apical transport of phenformin was 3.9-fold greater than apical to basal transport and became saturated with increasing phenformin concentration ($2-75{\mu}M$) in LLC-PK1-Pgp, suggesting the involvement of P-gp in phenformin transport. Intrinsic clearance mediated by P-gp was $1.9{\mu}L/min$ while passive diffusion clearance was $0.31{\mu}L/min$. Thus, P-gp contributed more to phenformin transport than passive diffusion. To investigate the contribution of P-gp on the pharmacokinetics and adverse effect of phenformin, the effects of verapamil, a P-gp inhibitor, on the pharmacokinetics of phenformin were also examined in rats. The plasma concentrations of phenformin were increased following oral administration of phenformin and intravenous verapamil infusion compared with those administerd phenformin alone. Pharmacokinetic parameters such as $C_{max}$ and AUC of phenformin increased and CL/F and Vss/F decreased as a consequence of verapamil treatment. These results suggested that P-gp blockade by verapamil may decrease the phenformin disposition and increase plasma phenformin concentrations. P-gp inhibition by verapamil treatment also increased plasma lactate concentration, which is a crucial adverse event of phenformin. In conclusion, P-gp may play an important role in phenformin transport process and, therefore, contribute to the modulation of pharmacokinetics of phenformin and onset of plasma lactate level.

• 공업화학
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• 제10권4호
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• pp.502-508
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• 1999

서로 다른 기공크기를 가진 $Al_2O_3$막을 기질로 사용하여 단량체인 $CHF_3$로 플라즈마 중합시키고, 플라즈마 중합된 막을 Ar 플라즈마로 처리하여 표면을 개질시켜 $O_2/N_2$에 대한 투과도와 선택도를 비교하여 그 특성을 검토하고 기질의 기공크기가 투과메카니즘에 미치는 영향을 살펴보았다. 중합된 고분자 막을 cathode에 근접한 위치에서 Ar 플라즈마의 처리 시간과 rf-power 출력에 따라 표면 처리하였을 때 질소에 대한 산소의 선택도는 크게 향상된, 반면 투과도는 저하됨을 확인하였다. 또한 동일한 증착조건에서 서로 다른 기공크기를 갖는 기질에 플라즈마 중합시켰을 때, 증착된 비 다공성막인 고분자막에서는 동일하게 용해-확산 모델이 적용되나, 비 다공성층을 통과한 분자들은 Knudsen 확산모델에 의해 기질의 크기와 투과도와의 상관관계를 나타냈으며, 이로부터 투과메카니즘은 중합된 고분자막의 기능기와 기질의 기공크기에 지배적인 영향을 받음을 알 수 있었다.

• 한국재료학회지
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• 제9권11호
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• pp.1102-1107
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• 1999

FeAl 기지 복합재료는 hot-pressing에 의해서 성공적으로 제조할 수 있다. 이러한 FeAl 합금의 기계적 특성에 대한 연구는 많이 진행되었으나 플라즈마 질화에 의한 표면 경화특성에 관한 연구는 아직 미흡한 실정이다. 본 연구에서는 hot-pressing으로 제조된 소결 복합재료의 미세구조와 플라즈마 질화처리시 표면경화의 관계를 분석하였다. FeAl을 기지로 하는 합금은 플라즈마 질화처리에 의해서 표면경도가 상승하는 경향을 보였고, 이러한 경향은 질화처리 시간이 증가할수록 더욱 뚜렷하였다($\textrm{H}_{\textrm{v}}$ 100gf, 확산층 : 1100~1450kg/$\textrm{mm}^2$, matrix : 330~360kg/$\textrm{mm}^2$). FeAl 합금으로 플라즈마 질화처리에 의해서 매우 우수한 표면경화특성을 얻을 수 있었다. 확산층은 플라즈마 질화처리시간이 증가할수록 두꺼워졌으며, SiC(sub)p의 함유량이 증가함에 따라 확산층은 감소하였다.

• 한국산림과학회지
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• 제96권4호
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• pp.470-476
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• 2007

튜립나무, 산수유, 은행나무, 느티나무, 단풍나무 등, 총 다섯 수종을 대상으로 phytotron에서 저농도 오존을 처리한 후 이에 따른 식물의 반응을 고찰하였다. 엽록소함량, 잎 기공저항, 잎 증산량, 항산화효소인 APX(Ascorbate peroxidase)를 통해 분석하였고, 이에 따른 결과는 수종마다 각기 다르게 나타났다. 본 실험기간동안 가시피해현상이 나타난 수종은 튜립나무와 산수유 뿐이었지만 가시피해현상이 없는 수종도 포함, 전 수종이 저농도 오존에 의해 엽록소함량, 기공저항, 기공전도도, 항산화효소 활성에서 낮은 생리적 활성을 보임을 확인할 수 있었다.

• Journal of Mycology and Infection
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• 제23권4호
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• pp.91-98
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• 2018

Background: Malassezia, a lipophilic yeast, is a causative agent for dandruff and seborrheic dermatitis. Many biological agents have been studied for anti-Malassezia effect but further studies are needed for their clinical application. Objective: The study was conducted to evaluate the inhibitory effect of different natural essential oils and a fruit extract on Malassezia species in an in vitro study and a clinical trial. Methods: The antifungal effects of natural essential oils and a fruit extract on Malassezia species (M. furfur and M. sympodialis) were evaluated by measuring the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) and using the disc diffusion method. Natural essential oils of citron seed, lavender, and rosemary and citrus junos fruit extract were used for the in vitro study. The clinical trial was conducted with a shampoo containing four ingredients. A total of 22 subjects used the shampoo every day for 4 weeks and were evaluated using clinical photography, trichoscopy, and sebumeter at baseline, 2 weeks, and 4 weeks after treatment. Results: Antifungal activity of agents was relatively lower in lavender and rosemary essential oils at MIC and MFC. Disc diffusion method revealed same results. In the clinical trial, the amount of sebum decreased statistically significantly and erythema, dandruff, and lesion extent also improved. Conclusion: The natural essential oils and fruit extract are effective for suppressing Malassezia activity, therefore these might be used as an alternative for treatment of dandruff and seborrheic dermatitis.

• 한국결정성장학회지
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• 제29권2호
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• pp.50-53
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• 2019

박막 태양전지에 주로 적용되는 다결정 규소층을 AIC(Aluminum Induced Crystallization) 공정을 이용하여 제조하였다. 결정립의 확대를 위하여 selective diffusion barrier 사용하였다. 이 diffusion barrier는 $Al_2O_3$ 막을 사용하였다. 공정시간의 단축을 위하여 열처리는 RTA(Rapid Thermal Annealing) 공정으로 진행하였다. 비정질 실리콘의 결정화는 XRD 측정을 통해 분석했다. 그 결과 $500^{\circ}C$에서 결정화되었으며, 결정 크기는 $15.9{\mu}m$로 계산되었다.