• Restorative Dentistry and Endodontics
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• 제45권1호
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• pp.5.1-5.8
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• 2020

Objectives: The obturation quality of MTA, Biodentine, Total Fill BC root canal sealer (RCS), and warm gutta-percha (WGP) in teeth with simulated internal root resorption (IRR) was evaluated by using micro-computed tomography. Materials and Methods: Standardized IRR cavities were created using 40 extracted maxillary central incisor teeth and randomly assigned into 4 groups (n = 10). IRR cavities were filled with MTA, Biodentine, Total Fill BC RCS (bulk-fill form) and WGP + Total Fill BC RCS. Percentage of voids between resorptive cavity walls and obturation material (external void), and inside the filling materials (internal voids) were measured. Results: Total Fill BC sealer in the bulk-fill form presented significantly highest values of external and internal void percentages (p < 0.05). Biodentine showed a significantly lowest external void percentage (p < 0.05). WGP + Total Fill BC RCS presented significantly lower values of internal void percentages than all groups (p < 0.05), except Biodentine (p > 0.05). Conclusion: None of the filling materials were created void-free obturation in resorption cavities. Biodentine may favor its application in teeth with IRR over Angelus MTA and bulkfill form of Total Fill BC.

• Nuclear Engineering and Technology
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• 제45권3호
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• pp.295-310
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• 2013

Industry- or regulatory-sponsored research activities on the resolution of Generic Safety Issue (GSI)-191 were reviewed, especially on the chemical effects. Potential chemical effects on the head loss across the debris-loaded sump strainer under a post-accident condition were experimentally evidenced by small-scale bench tests, integrated chemical effects test (ICET), and vertical loop head loss tests. Three main chemical precipitates were identified by WCAP-16530-NP: calcium phosphate, aluminum oxyhydroxide, and sodium aluminum silicate. The former two precipitates were also identified as major chemical precipitates by the ICETs. The assumption that all released calcium would form precipitates is reasonable. CalSil insulation needs to be minimized especially in a plant using trisodium phosphate buffer. The assumption that all released aluminum would form precipitates appears highly conservative because ICETs and other studies suggest substantial solubility of aluminum at high temperature and inhibition of aluminum corrosion by silicate or phosphate. The industry-proposed chemical surrogates are quite effective in increasing the head loss across the debris-loaded bed and more effective than the prototypical aluminum hydroxide precipitates generated by in-situ aluminum corrosion. There appears to be some unresolved potential issues related to GSI-191 chemical effects as identified in NUREG/CR-6988. The United States Nuclear Regulatory Commission, however, concluded that the implications of these issues are either not generically significant or are appropriately addressed, although several issues associated with downstream in-vessel effects remain.

• 한국분말재료학회지
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• 제29권6호
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• pp.499-504
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• 2022

The objective of this study is to assess the impact of spray drying conditions on medium-chain triglyceride (MCT) loading, solubility, and release of an MCT-loaded solid self-emulsifying system in a water-insoluble oily substance. MCT-loaded solid self-emulsifying systems are prepared by spray drying with SDS and calcium silicate. The effects of inlet temperature (60, 80, or 100℃) and feed solution composition (0, 10, 50, 90, or 100% ethanol) on physicochemical properties of MCT-loaded solid self-emulsifying systems are studied. The inlet temperature significantly affects the water solubility of MCT. Moreover, the feed solution composition significantly affects water solubility, release rate, and MCT loading. The MCT-loaded solid self-emulsifying system obtained at 60℃ using 90% ethanol feed solution shows the best physicochemical properties among the synthesized products and exhibits better water solubility (4.43 ± 0.44 vs. 0 ㎍/mL) and release (94.4 ± 1.6 vs. 32.8 ± 7.4%, 60 min) than a commercial product. Furthermore, the MCT-loaded solid self-emulsifying system shows an excellent emulsion droplet size (approximately 230 nm).

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4062-4071
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• 2022

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

• 한국토양비료학회지
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• 제48권5호
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• pp.492-498
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• 2015

The long-term changes in the soil properties are closely related to the policy direction and the national program for the soil management. In this study, chemical properties of paddy soils in Jeonnam province were investigated at four-year interval since 1999 and the factors affecting change of chemical properties were analyzed in relation to the soil management policies. Chemical fertilizers supplied to Jeonnam province reduced by 57% in 2013 as compared with 1999, and the ratio of Jeonnam province to the national fertilizer supply gradually decreased to 14.1% in 2013 from 17.6% in 1999 due to national policies to reduce use of chemical fertilizers in the 2000s. In the chemical analysis of paddy soils in Jeonnam province, pH value tended to increase gradually within the optimal range. Available phosphate and exchangeable potassium content were always higher than the optimal range and showed no significant difference since 1999. Organic matter, exchangeable calcium and available silicate content were found to be lower than average content in the whole country as well optimal range for rice cultivation in 1999, but were higher than average content in the whole country and optimal range in 2011 because of faster rate of increase in Jeonnam province than the other region since the mid-2000s. The cause of increase in organic matter, exchangeable calcium and available silicate contents is considered to be the increased use of green manure crops and by-products fertilizer as an alternatives for conventional application of chemical fertilizers and soil amendment such as silicate fertilizer for agronomic control of the disease and insect pest in rice cultivation of environmentally-friendly agriculture.

• 한국건설순환자원학회논문집
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• 제6권4호
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• pp.103-111
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• 2012

압축강도 50 MPa이상의 압출성형 시멘트 패널은 고온고압 증기양생으로 생산된다. 고온고압 증기양생에서 요구 강도를 얻기 위해서는 시멘트에 포함되어 있는 CaO와의 반응에 필요한 적정량의 $SiO_2$를 공급하는 것이 관건이다. $SiO_2$의 공급원으로 가장 널리 사용되는 원료는 규석분인데, 이는 환경파괴를 전제로 하기 때문에 친환경적인 제품 생산을 위하여 본 연구에서는 규석분을 대신하여 폐석분을 활용한 시멘트 2차 제품을 생산하고 이에 대한 압출성과 물리적인 특성비교를 실시하였다. 이를 위하여 화성 석산에서 채취한 폐석분을 건조 파쇄한 후 이를 규석분 사용량의 최대 50%까지 치환하여 압출성 및 물리적 특성 실험을 수행하였다. 실험결과 평균 입경은 폐석분과 규석분의 크기가 유사하였으나 물리적 특성은 규석분을 폐석분으로 단순 치환하였을 경우, 대부분 낮게 발현되었다. 따라서 폐석분을 활용할 경우 수화활성을 위한 첨가제 등의 활용이 필요할 것으로 판단된다.

• 한국환경농학회지
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• 제5권1호
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• pp.61-66
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• 1986

소석회(消石灰)와 유기물(有機物)의 병용(竝用) 및 규산(硅酸)칼슘의 시용(施用)이 카드뮴으로 오염(汚染)된 토양(土壤)에서 배추의 생육(生育) 및 Cd 함량(含量)에 주는 영향(影響)을 밝히기 위(爲)하여 카드뮴이 처리(處理)된 토양(土壤) 150g 씩을 담은 소형(小型) 화분(花盆)에 시험(試驗)한 결과(結果)는 다음과 같다. 1. 소석회(消石灰) 단용(單用)은 1, 2작(作)에서 배추의 생육(生育)을 심(甚)히 억제(抑制)시켰으며 제(第) 3작(作)에 가서는 오히려 다른 처리구(處理區)보다 생육(生育)을 왕성(旺盛)하게 하였다. 2. 소석회(消石灰)+유기물구(有機物區)는 초기(初期)부터 배추생육(生育)이 량호(良好)하였고, 배추의 Cd 함량(含量)도 소석회단용구(消石灰單用區) 이하(以下)로 낮추었으며 그 효과(效果)는 3작(作)까지 계속(繼續)되었다. 3. 규산(硅酸)칼슘은 토양(土壤)의 pH에는 큰 영향(影響)을 못주면서도 배추를 정상적(正常的)으로 생육(生育)케 하고 소석회(消石灰)만은 못하였으나 배추의 생육(生育)을 억제(抑制)하지 않는 범위(範圍)인 건조(乾燥) 배추 100g 당(當) 0.21me까지 Cd함량(含量)을 감소(減少)시켰다. 4. 대조구(對照區)와 유기물(有機物)만을 단용(單用)했을 때는 토양(土壤)의 pH가 심(甚)히 낮아지고 배추의 Cd함량(含量)도 높았으며 2작(作)부터는 배추가 거의 다 고사(枯死)되었다. 5. 배추의 Cd함량(含量)은 Ca흡수량(吸收量)과는 부상관(負相關), Mg, K, 함량(含量)과는 정상관(正相關)을 보였는데 Mg 함량(含量)과 더 밀접(密接)한 상관(相關)을 갖고 특(特)히 재배(栽培)가 거듭될수록 동관계(同關係)는 더 현저(顯著)하였다.

• 대한소아치과학회지
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• 제45권4호
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• pp.455-463
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• 2018

이 연구의 목적은 근관 내 약제가 규산칼슘 재료의 압출 강도(Push-out bond strength)에 미치는 영향을 평가하는 것이다. 단일 근관을 가진 40개의 인간 하악 소구치들은 대조군과 수산화칼슘, 이중 항생제, 삼중 항생제를 사용한 군 중 하나로 나뉘어졌다. 근관 세척을 통해 약제를 제거 후, 1 mm 두께로 시편들을 제작하였다. 그 후 ProRoot MTA$^{(R)}$와 Biodentine$^{(R)}$을 근관 내에 적용하였고, 압출 강도 실험과 파절 양상 관찰을 수행하였다. 삼중 항생제와 이중 항생제 군은 대조군과 비교하여 두 종류의 규산칼슘 기반 재료의 상아질 결합력에서 유의한 영향을 미치지 않았고, 수산화칼슘을 사용한 군은 유의한 결합력의 증가를 나타내었다. 대조군과 각각의 실험군 내에서 치근 상아질에 대한 Biodentine$^{(R)}$의 탈락 저항은 ProRoot MTA$^{(R)}$보다 크게 나타났다. 파절 양상에 따라 응집 파절, 혼합 파절, 접착 파절의 순서로 압출 강도의 유의한 감소가 나타났고, 대조군과 비교하여 수산화칼슘을 사용한 군에서는 응집 파절이, 항생제를 사용한 군에서는 접착 파절이 우세하였다.

• 대한소아치과학회지
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• 제50권2호
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• pp.217-228
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• 2023

이 연구의 목적은 4가지 규산 칼슘계 시멘트를 대상으로 물리적 특성을 비교하고 평가하는 것이다. 2종의 분말-용액 혼합형 재료인 RetroMTA^® [RTMX], Endocem^® MTA Zr [EZMX] 그리고 2종의 기혼합형 재료인 Well-Root^TMPT [WRPR], Endocem MTA^® premixed [ECPR]를 사용하여 경화시간, 용해도 및 압축강도를 비교하였다. 가장 짧은 경화 시간은 EZMX (123.33 ± 5.77초)에서 관찰되었으며, RTMX (146.67 ± 5.77초), ECPR (260.00 ± 17.32초) 및 WRPR (460.00 ± 17.32초) 순으로 증가하였다. 가장 높은 용해도는 WRPR (9.01 ± 0.55%)에서 관찰되었으며, RTMX (2.17 ± 0.07%), EZMX(0.55 ± 0.03%) 및 ECPR (0.17 ± 0.03%) 순으로 감소하였다. 또한 압축강도는 ECPR(76.67 ± 25.67 Mpa)에서 가장 높게 나타났고, WRPR (38.39 ± 7.25 Mpa), RTMX(35.07 ± 5.34 Mpa), EZMX (4.07 ± 0.60 Mpa) 순으로 감소하였다. 결론적으로 기혼합형 규산 칼슘계 시멘트들은 분말-용액 혼합형에 비해 긴 경화 시간을 나타내었다. 용해도 실험 결과 가장 낮은 용해도를 보인 ECPR과 가장 높은 용해도를 보인 WRPR에서 통계적 차이가 관찰되었다(p < 0.0083). 압축강도 실험결과 가장 낮은 압축 강도를 보인 EZMX와 가장 높은 압축 강도를 보인 ECPR에서 통계적 차이가 관찰되었다(p < 0.0083). ECPR은 분말-용액 혼합형에 비해 긴 경화 시간을 나타내지만, 미리 혼합되어 있어 혼합 시간이 필요하지 않고 용해도와 압축 강도가 개선되었으므로 임상 사용 시 선택될 수 있는 유망한 재료이다.

• 한국세라믹학회지
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• 제16권3호
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• pp.164-168
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• 1979

In the previous paper, it was reported that formation of desirable calcium alunimate(CA) in clinker was considerably affected by sulfur-contaminated alumina which was prone to form a disadvantageous mineral, $C_4A_3S$. In this study, however, sulphate-free alumina cement was made from sulfur-free alumina refined from alunite and corresponding materials. The major minerals in the clinker were identified by X-ray diffraction patterns as calcium aluminate (CA), calcium dialuminate $(CA_2)$ and dicalcium alumino silicate $(C_2AS)$. The formation of CA was more effective with decreasing contents of silica to 2 per cent or less and sulfur in the refined alumina. Physical properties of prepared alumina cement such as setting time, stability and compressive strength were measured. The values were similar to those of commercial alumina cements.