• 융합정보논문지
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• 제9권12호
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• pp.147-156
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• 2019

동심 이중관에서 기본유체 물과 나노입자 산화알미늄의 혼합인 나노유체를 적용한 대향유동을 유한체적법의 수치적 방법으로 열전달 특성을 규명하였다. 고온유체는 내부 원형관으로 흐르며 열을 외부 환형관으로 흐르는 저온유체로 전달한다. 고온유체와 저온유체의 체적유량 및 나노입자의 체적농도를 변수로 두어 열전달 및 유동 특성을 조사했다. 결과는 나노입자의 체적농도와 체적유량의 증가함에 따라 열전달 성능이 증가함을 보였다. 외부와 내부 관 모두에서 나노유체인 경우가 기본유체보다 나노입자의 체적농도가 8%일 때 나노유체가 열전달 성능이 최대 17% 증가하는 것을 확인했다. 또한 기본유체에 비해 환형관의 대류열전달 계수는 최대 31% 증가함을 보였으며 열교환기의 유용도는 약 20%가 상승함을 확인하였다. 하지만 나노입자의 체적농도가 8%일때 마찰인자가 최대 136% 커지는 것을 확인하였다.

• Composites Research
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• 제20권5호
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• pp.20-25
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• 2007

열주기법은 다공성 소재의 열확산도를 측정하는데 유용한 방법이다. 본 논문의 주 목적은 진공환경에서 다공성 소재의 열확산도 측정 시스템을 개발하고 검증하는데 있다. 이 방법을 검증하기 위하여 알루미나 시편과 폴리스티렌 폼의 열확산도를 측정하였다. 이 시편들의 열확산도는 참고값과 일치하였다. 탄소/에폭시 소재와 다공성 단열소재의 열확산도를 대기상온과 대기진공 환경에서 측정하였다. 탄소/에폭시 소재와 다공성 단열소재의 진공환경에서 열확산도는 대기환경에 비하여 각각 66.4%와 64.9% 감소하였다. 이 차이는 소재내의 기공에 있는 공기의 영향으로 추정된다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제32권6호
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• pp.514-523
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• 2006

The purpose of the present study was to evaluate the effects of several implant surface treatments to the bone formation, by placing Machined implants, 75${\mu}m$ Calcium phosphate-blasted implants and $Al_2O_3$-blasted and acid-etched implants in rabbit tibia through histomorphometric study. Two animals of each group were sacrificed at 2, 4, 8 weeks. The specimens containing the implants were dehydrated and embedded into hard methylmethacrylate plastic. Thereafter, the sections were ground to 50${\mu}m$. The specimens were stained with Villanueva bone stain for a light microscopic study. The results were as follows; 1. When the surface roughness of three different implants was measured by Surfcorder, the Ra of the Machined group, the RBM group and the SLA group was 0.16${\mu}m$, 0.44${\mu}m$, and 1.08${\mu}m$. 2. When examining the surfaces of the implants in the scanning microscope, Machined implant has the smooth surface with a few scratches, RBM implant has the rough surface with curled ridges and valleys, and SLA implant has the rough surface structures such as sharp protruding parts and micropits measuring 1-2${\mu}m$ in diameter. 3. After 2 weeks of implantation, the percentage of bone-to-implant contact of the Machined group, the RBM group and the SLA group was 26.86%, 35.40% and 45.99%. However, its differences between each group decreased during the healing periods. 4. After 2 weeks of implantation, the percentage of bone area inside the threads of the Machined group, the RBM group and the SLA group were 21.55%, 30.43% and 41.18%. However, its difference of bone area between machined group and surface treatment groups was maintained but the difference within the surface treatment groups decreased during the healing periods. In summary, the amount of bone formation in RBM and SLA group was greater than Machined group in early healing stage. These results suggest that RBM and SLA implants can reduce the healing period for osseointegration and may be suitable for early function.

• 구강회복응용과학지
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• 제30권2호
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• pp.131-137
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• 2014

목적: 이 연구는 다양한 거칠기를 가진 알루미늄 옥사이드 연마석으로 치주기구 날 세우기를 시행시 연마석의 거칠기에 따른 치주기구 날 세우기의 효율성 및 마모도를 비교 평가하였다. 연구 재료 및 방법: 30개의 No. 9 - 10 그레이시 큐렛이 사용되었고, 모든 큐렛은 치석제거술 및 치근활택술을 시행함으로써 날을 무디게 만들고 3가지 그룹(240, 600, 800 grit)으로 임의로 나누었다. 치주기구의 예민도는 연마석을 최대 20회 기구에 적용한 후 평가되었고, 마모도는 최대 80회 후 기구 날의 끝 1 mm와 2 mm에서 기구 날의 폭으로 평가되었다. 결과: 치주기구 예민도는 5회와 10회 상하 운동시 240 grit에서 유의하게 높게 나타났으며(P < 0.001), 15회, 20회에서는 유의한 차이는 없었다(P > 0.05). 마모도는 240 grit의 경우 600 grit과 800 grit에 비해 약간 높게 나타났지만 통계적 유의성은 없었다. 결론: 알루미늄 옥사이드 연마석의 입자가 클수록 치주기구 날 세우기의 효율성은 증가하였다. 하지만 기구의 마모에 유의해야 한다.

• Bulletin of the Korean Chemical Society
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• 제28권2호
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• pp.251-256
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• 2007

The crystal structure of fully dehydrated partially Cs+-exchanged zeolite X, [Cs52Na40Si100Al92O384], a = 24.9765(10) A, has been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21 °C. The crystal was prepared by flow method for 5 days using exchange solution in which mole ratio of CsOH and CsNO3 was 1 : 1 with total concentration of 0.05 M. The crystal was then dehydrated at 400 °C and 2 × 10-6 Torr for 2 days. The structure was refined to the final error indices, R1 = 0.051 and wR2 (based on F2) = 0.094 with 247 reflections for which Fo > 4σ (Fo). In this structure, about fifty-two Cs+ ions per unit cell are located at six different crystallographic sites with special selectivity; about one Cs+ ion is located at site I, at the centers of double oxygen-rings (D6Rs), two Cs+ ions are located at site I', and six Cs+ ions are found at site II'. This is contrary to common view that Cs+ ions cannot pass sodalite cavities nor D6Rs because six-ring entrances are too small. Ring-opening by the formation of ?OH groups and ring-flexing make Cs+ ions at sites I, I', and II' enter six-oxygen rings. The defects of zeolite frameworks also give enough mobility to Cs+ ions to enter sodalite cavities and D6Rs. Another six Cs+ ions are found at site II, thirty-six are located at site III, and one is located at site III' in the supercage, respectively. Forty Na+ ions per unit cell are located at two different crystallographic sites; about fourteen are located at site I, the centers of D6Rs and twenty-six are also located at site II in the supercage. Cs+ ions and Na+ ions at site II are recessed ca. 0.34(1) A and 1.91(1) A into the supercage, respectively. In this work, the highest exchange level of Cs+ ions per unit cell was achieved in zeolite X by conventional aqueous solution methods and it was also shown that Cs+ ion could pass through the sixoxygen rings.

• 대한치과보철학회지
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• 제39권2호
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• pp.157-170
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• 2001

The bond strength is the most important factor in establishing long-term success of resin-retained fixed prostheses. So, various surface treatment methods have been introduced to improve the bond strength of metal surface and bonding resin till now This study was performed to compare the effect of silicoating with that of metal primer and analyze the correlation between treatment time of sandblasting and the bond strength, so that meant to find more effective surface treatment method that could enhance the bond strength of resin-retained fixed prostheses. The surfaces of all specimens made of $Verabond^{(R)}$ alloys were air abraded with $250{\mu}m\;Al_2O_3$ according to treatment time of sandblasting and they were subdivided to be treated with only sandblasting(S group), silicoating following sandblasting(SS group) and metal primer application after sandblasting(SM group). Then pairs of metal specimens (${\phi}10mm{\times}h\;2mm,\;{\phi}6{\times}h\;2mm$) were bonded with Super bond $C&B^{(R)}$. The specimens were stored in $38^{\circ}C$ water for 48 hours and shear bond strength was measured using the universal testing machine. The results were as follows, 1. In the comparison of shear bond strength according to treatment time of sandblasting, bond strength was increased in the order of 0', 15', 30', 45', 60' group. 0' group had significantly lower value than any other, while 0', 15' group were significantly different with 30', 45', 60' group(p<0.05). 2. In the comparison of shear bond strength according surface treatment methods, bond strength was increased in the order of S group. SS group and SM group. S group was significantly different with SS group and SM group(p<0.05). 3. Observing the mode of bond failure. 0', 15' group showed only adhesive failure, and 30', 45', 60' group did mostly adhesive & cohesive failure in S group. In SS group and SM group, all other groups except 0', 15' group showed mostly cohesive failure. From the above results, it is considered that sandblasting should be treated for more than 30 seconds, and metal primer be more effective and available clinically than silicoater system which is complicate, technique-sensitive and time-consuming method, when nonprecious metal surface is planning be treated with in order enhance the bond strength of resin-retained fixed prostheses.

• 대한약침학회지
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• 제18권2호
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• pp.7-18
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• 2015

Objectives: Lawsone (1,4 naphthoquinone) is a non redox cycling compound that can be catalyzed by DT diaphorase (DTD) into 1,2,4-trihydroxynaphthalene (THN), which can generate reactive oxygen species by auto oxidation. The purpose of this study was to evaluate the toxicity of the phytomarker 1,4 naphthoquinone and its metabolite THN by using the molecular docking program AutoDock 4. Methods: The 3D structure of ligands such as hydrogen peroxide ($H_2O_2$), nitric oxide synthase (NOS), catalase (CAT), glutathione (GSH), glutathione reductase (GR), glucose 6-phosphate dehydrogenase (G6PDH) and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) were drawn using hyperchem drawing tools and minimizing the energy of all pdb files with the help of hyperchem by $MM^+$ followed by a semi-empirical (PM3) method. The docking process was studied with ligand molecules to identify suitable dockings at protein binding sites through annealing and genetic simulation algorithms. The program auto dock tools (ADT) was released as an extension suite to the python molecular viewer used to prepare proteins and ligands. Grids centered on active sites were obtained with spacings of $54{\times}55{\times}56$, and a grid spacing of 0.503 was calculated. Comparisons of Global and Local Search Methods in Drug Docking were adopted to determine parameters; a maximum number of 250,000 energy evaluations, a maximum number of generations of 27,000, and mutation and crossover rates of 0.02 and 0.8 were used. The number of docking runs was set to 10. Results: Lawsone and THN can be considered to efficiently bind with NOS, CAT, GSH, GR, G6PDH and NADPH, which has been confirmed through hydrogen bond affinity with the respective amino acids. Conclusion: Naphthoquinone derivatives of lawsone, which can be metabolized into THN by a catalyst DTD, were examined. Lawsone and THN were found to be identically potent molecules for their affinities for selected proteins.

• Applied Microscopy
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• 제18권2호
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• pp.102-118
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• 1988

This study was carried out to examine in vitro first whether the storage proteins, which the fat bodies of last larvae from Hyphantria cunea secrete into haemolymph, can be uptaked by the fat body cells of prepupa and then how the uptaked storage proteins can be accumulated in the fat body cells, if uptaken. The fat bodies which had been isolated from last instar larvae were cultured in 1 ml of Grace's insect medium containing $50{\mu}l$ of $^{3}H$-leucine (5.0 mCi/mol, Dupont) at $28{\pm}2^{\circ}C$ for 6 hrs. After the homogenates of the cultured fat bodies were centrifuged at 10,000 rpm for 10 minutes, the proteins included in the supernatant were separated by polyacrylamide gel electrophoreses (non-SDS, 6%). The next treatment of the electrophoresed gel was followed by rinsing. A storage protein band of several bands in the rinsed gel was sliced off. With elution of sliced storage protein bands in Tris-glycine buffer, the purification of radioactive storage proteins from fat bodies was finished. After the purified radioactive storage proteins were added in Grace's insect midis containing fat bodies of the prepupae, they were cultured for the randomly following minutes given as 3, 5, 7, 10, 15, 20 and 30 and for the randomly following hours given as 1, 2, 3 and 4 respectively. The double fixations of the cultured fat bodies in aldehyde and $OsO_4$, were followed by preparation of ultrathin sections from Epon-Araldite blocks through dehydration and embedding. The electron microscope autoradiographic treatment of all prepared sections were performed by the dipping method (Kim et al., 1987). The finally prepared specimens were examined with electron microscope. The fat body cells of the prepupa could be found to uptake the storage preteins of the last instar larvae, which were included in the culture medium, mostly by formation of coated vesicles. The in vitro uptake of the storage proteins actively occurred by 30 minutes after the addition of purified storage proteins in the culture medium. After culture for 7 minutes with the storage proteins, the uptaked radioactive storage proteins labelled a number of lysosomal granules. After culture for 20 minutes with the storage proteins, the radioactive storage proteins were finally incorporated and accumulated in lipid droplets and protein granules. The frequency in the fat body cell of radiolabelled lipid droplets occurs approximately 60%, while the frequency, in which the radiolabelled protein granules occurs in a fat body cell, is approximately 40%.

• 한국토양비료학회지
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• 제16권1호
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• pp.20-27
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• 1983

제주도(濟州道) 화산회토양유기물(火山灰土壌有機物)의 화학성(化学性), 유기물(有機物) 성상(性狀) 및 부식산(腐植酸)의 광학적(光学的) 특성(特性)을 알고져 수종(数種)의 화산회토양(火山灰土壌)을 공시(供試)하여 실내시험(室內試験)한 결과(結果)를 요약(要約)하면 다음과 같다. 가. 토양(土壌)의 화학적(化学的) 성질(性質) 1) 화산회토양(火山灰土壌)은 비화산회토양(非火山灰土壌)에 비(比)하여 유기물(有機物)(4~27%), 유효규산(有効珪酸)(291~884ppm), 활성(活性) 알루미늄(150~478ppm) 및 활성철함량(活性鉄含量)(0.77~0.86%)이 많고 반대(反対)로 유효인산(有効燐酸)(4~15ppm) 함량(含量)이 현저(顕著)히 낮았다. 2) 가리(加里), 석화(石火), 고토등(苦土等)은 밭의 경우 화산회토양(火山灰土壌)에서 높은 편이나 삼림지(森林地) 및 유휴지토양(遊休地土壌)은 낮은 경향(傾向)을 보였다. 3) 화산회토양(火山灰土壌)은 규반비(珪礬比) 및 규산(珪酸)/유기물비(有機物比)가 낮은 반면(反面) K/Ca+Mg, Al/Fe(활성(活性)) 및 C/P비(比)가 현저(顕著)히 높았다. 나. 유기물(有機物) 및 질소분별정량(窒素分別定量) 1) 화산회토양(火山灰土壌)은 유기물(有機物)의 총탄소중(総炭素中) Humin-C의 비율(比率), 유기물중(有機物中) Humin산(酸) 그리고 Humin중(中) C/N율(率)이 비화산회토양(非火山灰土壌)보다 현저(顕著)히 높았다. 2) 화산회토양(火山灰土壌)은 비화산회토양(非火山灰土壌)에 비(比)하여 총질소(総窒素), 산(酸) 및 알카리가용성(可溶性) 질소함량(窒素含量)이 현저(顕著)히 높은 반면(反面) 총질소중(総窒素中) 무기태질소(無機態窒素)로 방출(放出)될 수 있는 무기화율(無機化率)은 높지 않았다. 다. 토양부식(土壌腐植)의 형태(形態) 1) 화산회토양(火山灰土壌)은 비화산회토양(非火山灰土壌)에 비(比)하여 광흡(光吸) 수능(收能)이 높고(K600, RF치(値), ${\delta}logK$) 부식화도(腐植化度)가 진전(進展)될수록 색농도(色濃度)가 짙은 것으로 나타났다. 2) 화산회토양(火山灰土壌)은 산화제(酸化劑)에 대(対)한 저항성(抵抗性)이 높고 산(酸) 및 알카리 가수분해성(加水分解性)이 강(强)하여 부식화도(腐植化度)가 높아 부식(腐植)의 자연분해(自然分解)가 극(極)히 어려운 것으로 나타났다. 라. Humin의 관능기조사(官能基調査) 화산회토양(火山灰土壌)의 유출부식산(油出腐植酸)의 관능기(官能基)는 phenolic-OH기(基), Alcoholic-OH기(基) 및 Carboxyl기(基)가 많고 비화산회토양(非火山灰土壌)은 Methoxyl기(基) 및 Carbonyl기(基)가 많았다. 마. 부식산(腐植酸)의 흡광도(吸光度) 1) 공시토양(供試土壌)의 가시광역(可視光域)은 200~500nm부근의 단파장영역(短波長領域)이었으며 주로 350, 420, 450 및 480nm 에서 4개(個)의 흡광곡선(吸光曲線)을 나타내었다. 2) 화산회토양(火山灰土壌)인 흑악통(黑岳統)은 362nm부근에서 단일(單一)의 높은 흡광도(吸光度)를 보였으며 비화산회토양(非火山灰土壌)인 영악통(永楽統)은 360nm와 390nm에서 2개(個)의 단순(單純)한 높은 흡광대(吸光帶)를 나타내었다. 마. 분해촉진제(分解促進剤) 처리효과(處理効果) 화산회토양(火山灰土壌)에 대(対)한 분해촉진효과(分解促進効果)는 이도통(統)은 역분해성(易分解性) 유기물(有機物) 첨가(添加)에 따른 "Priming Effect"가 증가(增加)되었으며 남원(南元)과 흑악통(黑岳統)은 Na-Pyrophosphate의 첨가효과(添加効果)가 있었다.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.638-646
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• 2023

Recently, active research has been conducted to enhance the power characteristics and thermal stability of lithium-ion batteries (LiBs) by modifying separators using a ceramic coating method. However, since the thermal properties and surface features of the separator vary depending on the characteristics of the ceramic powders applied to the separator, it is crucial to manufacture ceramic powders optimized for the separator's performance. In this study, we evaluated the characteristics of three types of α-alumina (A-1, A-2, and A-3) produced with varying dispersant contents and milling times, in addition to commercial α-alumina (AES-11). Subsequently, the optimized powders (A-3) were coated onto the separator using an aqueous binder for comparison with the characteristics of an AES-11 coated separator and an uncoated PE separator. The A-3 coated separator improved electrolyte wettability with a low contact angle (44.69°) and increased puncture strength (538 gf). Furthermore, it exhibited excellent thermal stability, with a shrinkage value of 5.64% when exposed to 140℃ for 1 hour, compared to the AES11 coated separator (6.09%) and the bare PE separator (69.64%).