• 한국잠사곤충학회지
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• 제41권1호
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• pp.54-60
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• 1999

염산 또는 수산화나트륨 수용액의 농도, 온도, 시간 등 처리조건에 따른 작잠견사의 가수분해율을 측정하였으며 산처리 작잠분말과 알칼리처리 작잠분말의 형태 및 구조특성을 주사전자현미경, 적외선 분광분석, X-선 회절분석 등의 방법으로 분석한 결과 다음과 같은 결과를 얻었다. 1. 작잠견사에 대한 염산 및 수산화나트륨의 처리농도와 온도가 높을수록 또한 처리시간이 길어질수록 작잠견사의 가수분해율은 증가하는 경향을 나타내었으나 고온, 고농도의 조건하에서 수산화나트륨을 작잠견사에 처리하는 경우 작잠견사의 가수분해율이 오히려 떨어지는 경향을 보였다. 2. 산 및 알칼리 처리에 의하여 제조된 작잠분말의 형태는 용해도가 30 wt% 부근에서는 섬유상의 형태를 유지하였으며 산처리 분말의 경우 용해도가 증가함에 따라 섬유축 방향으로 조각난 미세한 입자형태를 나타내었으나 알칼리처리 분말의 경우에는 부정형의 입자형태를 나타내었다. 3. 적외선 분광분석 결과 작잠분말은 처리조건과 무관하게 ${\beta}$-sheet 구조의 특성을 반영하는 1635, 1532, 1226, 960, 700 cm$^{-1}$ 흡수대와 ${\alpha}$-helix 구조의 특성을 반영하는 616 cm$^{-1}$ 흡수대가 뚜렷하게 나타나 작잠분말의 주요 conformation은 ${\beta}$-sheet 구조와 ${\alpha}$-helix 구조임을 확인하였다. 4. X-선 회절분석 결과 가수분해율이 낮을 경우 (35 wt%)에는 ${\beta}$-sheet 구조와 ${\alpha}$-helix 구조에 기인하는 회절 피크가 뚜렷하게 나타났으나 가수분해율이 80 wt% 이상으로 증가하면 2${\theta}$=17.1$^{\circ}$ 및 20.0$^{\circ}$의 회절피크만 강하게 나타났다.

• 한국결정성장학회지
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• 제29권6호
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• pp.329-337
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• 2019

스플린터(splinter) 및 판상(plate shape) 형상을 가지는 티탄산칼륨염(K₂O·nTiO₂, PT)을 합성하고 브레이크 마찰재의 보강재로 이용하여 마찰 특성을 평가하였다. 스플린터형 티탄산칼륨염을 합성하기 위하여 먼저 판상 형상을 가지는 사티탄산칼륨염(K₂O·4TiO₂, PT4)을 합성하고 칼륨 이온(K⁺)을 일부 산침출(acid leaching)하여 육티탄산칼륨염(K₂O·6TiO₂, PT6)으로 변환시킨 후, 800℃에서 열처리하여 스플린터 형상의 입자를 얻었다. 판상형 티탄산칼륨염을 합성하기 위해서 염화칼륨을 융제로 사용하고 마그네슘(Mg)을 일부 첨가하여 판상의 형상을 가지는 마그네슘티탄산칼륨염(K_0.8Mg_0.4Ti_1.6O₄, PMT)을 합성하였다. 얻어진 육티탄산칼륨염 및 마그네슘티탄산칼륨염 입자를 보강재로 이용하여 브레이크 패드 마찰재를 제작하고 1/ 5-스케일 다이나모미터(scale dynamometer)를 이용하여 마찰 마모 특성을 평가하였다. 평가 결과, 두 종류의 보강재가 유사한 마찰계수 및 Fade & recovery 특성을 보였으며 판상형 마그네슘티탄산칼륨염의 경우, 스플린터형 육티탄산칼륨염보다 우수한 내마모성을 보이는 것을 알 수 있었다.

• 대한전자공학회논문지SD
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• 제42권6호
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• pp.23-30
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• 2005

본 논문에서는 다양한 에미터 금속 재료를 이용하여 산화된 다공질 폴리실리콘(Oxidized Porous Poly-Silicon) 전계방출 소자를 제조하였으며 에미터 금속의 열처리 효과가 산화된 다공질 폴리실리콘 전계방출소자의 특성에 미치는 영향을 조사하였다. 다양한 에미터 금속 중 구동전극을 가진 Pt/Ti 에미터 전극을 $300^{\circ}C$-1hr 열처리한 경우 전자방출 효율은 $V_{ps}$=12 V에서 최대 $2.98\%$의 효율을 나타내었으며, $350^{\circ}C$-1hr 열처리한 경우 $V_{ps}$=16V에서 $3.37\%$의 가장 높은 효율을 나타내었다. 이는 열처리 공정을 통해 OPPS 전계방출 소자 표면에 다수의 결정립 경계와 무수히 많은 미세한 다공질 간의 흡착성의 개선으로 인한 면 저항 감소에 의한 것을 알 수 있다. OPPS 전계 방출 소자를 디스플레이소자로 적용하기 위해 형광체 발광 특성을 조사해 본 결과, $900^{\circ}C$-50min 산화 후 Pt/Ti(5nm/2nm) 에미터 전극을 사용하여 제조된 OPPS 전계 방출 소자의 경우 15 V에서 3600 cd/$m^2$, 20 V에서 6260 cd/$m^2$의 상대적으로 높은 휘도를 나타내었다. 열처리는 Ti층과 OPPS 간의 흡착성을 개선시키고 에미터 전극에 고른 전계를 가하는 중요한 역할을 한다.

• 전자공학회논문지
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• 제53권10호
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• pp.123-130
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• 2016

고주파 유도가열장치는 LC 공진회로에 고주파 전원을 인가하여 금속을 가열 할 수 있다. 공진회로는 워크 코일과 전도 냉각 커패시터로 구성되며, 커패시터의 특성에 따라 열처리 설비의 성능을 좌우한다. 그러나 전도 냉각 커패시터는 국내 원천기술의 연구개발 부족으로 해외 수입 의존도가 높다. LC 공진 시 커패시터 내부의 발열을 최소화하고, 무효 전력손실을 줄이며, 내 전압특성이 우수한 커패시터가 요구된다. 국산화를 위하여, 선진 제조사의 완성품 커패시터의 주파수 응답 특성 분석에 대한 선행 연구가 필요하다. 주어진 로그-로그 특성 곡선의 임의 점에서 값을 읽기 위한 보간법을 연구하여 매틀랩 코딩으로 커패시터의 분석 도구로 적용하였다. 커패시터를 간단 화 된 RC 직렬 등가 회로로 가정하고, 등가 직렬 저항 ESL 값을 구하여 주파수 응답 특성 곡선을 재현하는 시뮬레이션을 시도하였다. 실제 무효전력의 피크 치에 대한 특성과 시뮬레이션 특성을 비교할 때 재현율이 83% 이상 결과 값으로 나타나는 것을 확인할 수 있었고, 이 알고리즘은 간단화 된 모델의 커패시터 특성곡선을 분석하여 예측 할 때 적용이 가능하다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권12호
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• pp.4885-4890
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• 2015

Background: Helicobacter pylori plays an important role in gastric cancer and typical eradication regimens are no longer effective in many countries, including Thailand. The aim of our study was to compare the effect of Lactobacillus delbrueckii and Streptococcus thermophillus on tailored triple therapy for Helicobacter pylori eradication. Materials and Methods: This prospective single-center study was conducted in Thailand. Helicobacter pylori associated gastritis patients were randomized to 2 groups: group 1 (n=100) was tailored triple therapy with placebo (esomeprazole 20 mg bid, clarithromycin 500 mg bid or metronidazole 400 mg tid if clarithromycin resistance and amoxicillin 1000 mg bid), and group 2 was tailored triple therapy plus pretreatment with probiotic containing yogurt. Successful eradication was defined as both negative histology and negative rapid urease test at four weeks after treatment. Results: A total of 200 infected patients were enrolled. PP analysis involved 194 patients: 96 in the tailored triple therapy with placebo group (group 1) and 98 the in tailored triple therapy plus pretreatment with probiotic containing yogurt group (group 2). Successful eradication was observed in 170 (87.6%) patients; by PP analysis, the eradication rate was significantly higher in group 2 (P = 0.04, 95%CI; 0.02-0.13) than in group 1. ITT analysis also showed that the value was significantly higher in the tailored triple threapy plus pretreatment with probiotic containing yogurt group (group 2) (89/100; 89%) than in the tailored triple therapy with placebo group (group 1) (P= 0.01, 95%CI; 0.04-0.15). In terms of adverse events, there was no significant difference between the two groups. Conclusions: Pretreatment with probiotic containing yogurt can improve Helicobacter pylori eradication rates with tailored triple therapy. Adding probiotics does not reduce adverse effects of the medication.

• Nutrition Research and Practice
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• 제6권3호
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• pp.226-231
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• 2012

The purpose of the study was to assess the effects of a 12 weeks aged garlic extract (AGE) regimen with regular exercise on cardiovascular disease (CVD) risk in postmenopausal women. A total of 30 postmenopausal women ($54.4{\pm}5.4$ years) were randomly divided into the following four groups: Placebo (Placebo; n = 6), AGE intake (AGEI; n = 8), exercise and placebo (Ex + Placebo; n = 8), exercise and AGE (Ex + AGE; n = 8) groups. The AGE group consume 80 mg per day, and exercise groups performed moderate exercise (aerobic and resistance) three times per week. After 12 weeks of treatment, body composition, lipid profile, and CVD risk factors were analyzed. Body weight was significantly decreased in AGEI, Ex + Placebo, and Ex + AGE groups compared to baseline. Body fat % was significantly decreased in the AGEI and Ex + Placebo groups. Body mass index (BMI) was significantly decreased in the AGEI, Ex + Placebo, and Ex + AGE groups. Fat-free mass was significantly decreased in the AGEI group. Total cholesterol (TC) was significantly lower in the Ex + Placebo compared to the Placebo group. AGE supplementation or exercise effectively reduced low-density lipoprotein (LDL-C). Triglyceride (TG) was significantly increased in the AGEI group. Malondialdehyde (MDA) levels were significantly decreased in the AGEI, Ex + Placebo, and Ex + AGE compared to the placebo group. AGE supplementation reduced homocysteine levels regardless of whether the women also exercised. The present results suggest that AGE supplementation reduces cardiovascular risk factors independently of exercise in postmenopausal women.

• 미생물학회지
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• 제17권4호
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• pp.165-178
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• 1979

Phages of Lactobaciilus casei (PLC) isolated from plant drainage were classified and characterized. The results are as follows : 1. On the basis of host range pattern, phages could be divided into 2 groups (PLC-B and PLC-C). PLC-B group phages could be further divided into 5 sub-groups $(B_1, \;B_2, \;B_3, \;B_4, \;and\;B_5)$. Although PLC-C group phages had the same host range, they could be also divided into 2 sub-groups $(C_1\;and\;C_2)$ by morphlogical type. 2. It was $B_3$ group phages that represented a major proportion (44.4%) of phages tested. However, $B_1$ group phages were shown to have the widest host range. 3. Electron micrographs revealed that the phages fell into three different morphological types. $(B_1, \;B_2, \;and\;B_3)$ group phages hd a hexagonal head (52nm in diameter) and a sheathless noncontractile (245 nm in length). $B_4\;and\;C_2$ group phages had a hexagonal head (56 nm) and a short flexible tail (169nm) having no sheath. $B_5\;and\;C_1$ group phages were shown to have a hexagonal head (81 nm) and a contractile tail (140 nm) having a sheath, a base plate and tail fibers. 4. The inactivation of the phages by antisera indicated that serological relationships correlated completely with morphological types. 5. $B_1, \;C_1\;and\;C_2$ group phages produced a large (1, 2 mm in diameter) plaque with a clear ring. The morphology of plaques of $B_3\;and\;B_5$ group phages was the same as those produced by the above, but the average plaque sizes for $B_3\;and\;B_5$ were 0.8 mm abd 0.5 mm, respectively. $B_2\;and\;B_4$ group phages produced a small (0.5 mm) turbid plaque with an irregular edge. 6. The latent period and the average burst size of $B_1\;and\;B_3$ group phages were 90 min and 100, respectively. These phages reuqired calcium ions for their miltiplication. 7. $B_3$ group phages could not be absrobed to R-variant $KC_1$. 8. The order of resistance of phages to heat was $B_2\;>\;B_1, B_4\;and\;B_5\;>\;B_3\;and\;C_2, \;B_5$ group phages were more stable than $B_3$ in various pH values. $C_2$ group phages were more sensitive to UV irradiation than $B_1\;and\;B_3$ group phages. 9. Strains YIT9018 and IAM 1043 were induced by mitomycin C treatment. Phage particles detected in the lysates had a hexagonal head (38 and 49 nm, respectively), but no tail. Any sensitive indicator strain could not be isolated in spite of repaeated trials.

• Restorative Dentistry and Endodontics
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• 제20권1호
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• pp.193-213
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• 1995

The purpose of this study is to investigate a possible contribution of nonspecific esterases, which occur in the oral cavity, to the degradation of ester bonds in polymethacrylates. One of the problems connected with the use of composite resins for restorations is their inadequate resistance to wear. It has been shown that methacrylate hydrolysis can be catalyzed by enzymes and that a carboxylic hydrolase (porcine liver esterase) catalyzed the hydrolysis of several mono - and dimethacrylates. The softening effect on a BISGMA/TEGDMA polymer induced by hydrolase will accelerate the in vivo wear of the polymer. Porcine liver esterase (EC 3.1.1.1) 3.2 mol/L $(NH_4)_2$ $SO_4$ was obtained from Sigma Chemical Company. The esterase activity of one unit is defined as the amount of enzyme capable of hydrolyzing $l{\mu}mol$ ethyl butyrate per min at pH 8.0 AT $25^{\circ}C$. Phosphate buffer, 10mmol/L, pH 7.0, was made by adjustment of a solution of $Na_2HPO_4$ with $H_3PO_4$. Composite resins used in this study are Silux Plus, Z-100, Durafil VS, and Prisma APH. Cylindrical specimens, 14mm in diameter and 3mm thick, of Silux Plus, Z-100, Durafil VS, Prisma APH were polymerized under the celluloid strip. 60 specimens were divided into 2 groups. One group was emersed only in buffer solution, the other group was emersed in buffer and enzyme solution. Silux Plus and Z-100 were divided into 2 subgroups, one subgroup was cured only Visilux 2. And the other subgroup was cured Visilux 2 and Triaid II. Thereafter, specimens were polished to its best achievable surface according to manufacture's directions. The Vickers hardness of the specimens was measured after 1, 2, 4, 7, 9, 15, 50 days. The solutions were changed after each measurement. Composite resin surfaces were evaluated for the surface roughness with profilometer (${\alpha}$-step 200, Tencor instruments, USA) after 1 and 50 days. And then surfaces of specimens were pictured with stereosopy after 1 and 50 days. The results were as follows. 1. The surface hardness of Silux plus, durafil VS, and Prisma APH were decreased with time. But, the surface hardness of Z-100 was not decreased. 2. The surface hardness of all composite resins was decreased by esterase. 3. Composite resins, which were light-cured by Visilux 2 and concomitantly baked by oven, showed more hardened surface than light-cured by Visilux 2 only. 4. Significant surface changes were occured in Silux plus after esterase treatment.

• 한국표면공학회지
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• 제41권6호
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• pp.292-300
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• 2008

Dental implant system is composed of abutment, abutment screw and implant fixture connected with screw. The problems of loosening/tightening and stability of abutment screw depend on surface characteristics, like a surface roughness, coating materials and friction resistance and so on. For this reason, surface treatment of abutment screw has been remained research problem in prosthodontics. The purpose of this study was to investigate the stability of TiN and WC coated dental abutment screw, abutment screw was used, respectively, for experiment. For improving the surface characteristics, TiN and WC film coating was carried out on the abutment screw using EB-PVD and sputtering, respectively. In order to observe the coating surface of abutment screw, surfaces of specimens were characterized, using field emission scanning electron microscope(FE-SEM) and energy dispersive x-ray spectroscopy(EDS). The stability of TiN and WC coated abutment screw was evaluated by potentiodynamic, and cyclic potentiodynamic polarization method in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion potential of TiN coated specimen was higher than those of WC coated and non-coated abutment screw. Whereas, corrosion current density of TiN coated screws was lower than those of WC coated and non-coated abutment screw. The stability of screw decreased as following order; TiN coating, WC coating and non-coated screw. The pitting potentials of TiN and WC coated specimens were higher than that of non-coated abutment screw, but repassivation potential of WC coated specimen was lower than those of TiN coated and non-coated abutment screws due to breakdown of coated film. The degree of local ion dissolution on the surface increased in the order of TiN coated, non-coated and WC coated screws.

• 한국응용과학기술학회지
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• 제31권4호
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• pp.694-702
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• 2014

마이크론 크기를 가지는 ITO(indium tin oxide) 입자들은 인듐과 틴의 수용성 전구체들과 유기 첨가제를 분무 열분해하여 얻었다. 유기 첨가제로서는 에틸렌글리콜과 시트르산을 이용하였다. 분무 열분해 시 에틸렌글리콜과 시트르산과 같은 유기첨가제를 첨가하지 않고 얻어진 ITO 입자들은 구형이며 속이 꽉찬 형태를 가지는데 비해 유기 첨가제를 첨가하여 분무 열분해를 하면 얻어지는 ITO 입자들은 유기 첨가제의 양이 증가 할수록 껍질이 얇고 다공성이 증대된 중공 입자가 얻어진다. 유기첨가제를 첨가하지 않고 분무 열분해를 통해 얻어지는 마이크론 크기를 가지는 ITO는 $700^{\circ}C$에서 두 시간 동안의 후소성과 24 시간동안의 습식 볼밀링에 의해 나노 크기의 ITO로 전환되지 않으나, 유기첨가제를 첨가하고 분무 열분해를 통해 얻어지는 마이크론 크기를 가지는 ITO는 $700^{\circ}C$에서 두 시간 동안의 후소성과 24 시간 동안의 습식 볼밀링에 의해 나노 크기의 ITO로 쉽게 전환되었다. 응집된 나노 크기의 ITO의 일차 입자의 크기를 Debye-Scherrer 식에 의해 계산하였고 ITO 입자를 압축하여 만든 펠렛의 표면저항을 측정하였다.