• 대한토목학회논문집
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• 제2권2호
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• pp.11-18
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• 1982

가열혼합식(加熱混合式) 칼라포장용(鋪裝用)바인더는 스트레이트아스팔트와 물리적(物理的)인 제성질(諸性質)은 유사(類似)하면서 색깔이 흑갈색(黑褐色)이 아닐 것이 요구된다. 위의 제성질(諸性質)을 갖는 담황색(淡黃色)의 합성수지조성물(合成樹脂組成物)을 개발하여 이를 골재(骨材)와 믹싱한 혼합물(混合物)과 스트레이트아스팔트혼합물(混合物)과 각종시험(各種試驗)으로 비교한 결과 칼라포장용(鋪裝用)바인더로 사용가능성(使用可能性)을 확인(確認)했다. 색깔을 내기위한 안료(顔料) 역시 국산재료(國産材料)의 사용가능성(使用可能性)을 시험(試驗)을 거쳐 확인(確認)했다. 아스팔트 믹싱플랜트로 시험혼합(試驗混合)과 현장포설(現場鋪設)을 거쳐 실용화단계(實用化段階)에 이르게 되었다. 칼라포장용(鋪裝用) 혼합물(混合物)의 혼합(混合) 및 포설(鋪設)은 일반적(一般的)인 아스팔트콘크리트혼합물(混合物)과 같은 방식(方式)으로 하되 안료(顔料)만큼 미네랄필러분에서 차감(差減)하여 대체(代替)한다. 안료(顔料)의 배합량(配合量)은 사용(使用)하는 타재료(他材料)에 의해 시험혼합(試驗混合)에서 결정한다.

• 대한소아치과학회지
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• 제41권4호
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• pp.335-343
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• 2014

재생적 근관치료는 치수 괴사를 보이는 미성숙 영구치 치료에 있어서 괴사된 치수를 치유하고 계속되는 치근의 발달을 유도할 수 있다. 그러나 여기에는 몇 가지 단점과 불리한 결과들이 있다. 이 중 재생적 근관치료에 가장 큰 임상적 부작용은 minocycline과 MTA에 의한 변색이다. 본 증례에서는 재생적 근관치료 후에 나타나는 치관 변색을 방지하기 위해 minocycline을 clindamycin으로 대체한 triple antibiotics와 칼슘 지르코늄 알루민산염 시멘트인 Retro MTA를 사용하였다. 치수 괴사된 미성숙 영구치에서 근관 와동 형성 및 근관 세척 후 수정된 triple antibiotics를 적용하고, 혈병 또는 콜라겐 스펀지를 스캐폴드(scaffold)로 하여 Retro MTA로 근관을 폐쇄하였다. 정기적인 검진 결과 미성숙 영구치의 치근 성장 및 정상적인 치아 주위 조직들이 관찰되었으며, 치관 변색 없이 모두 양호한 치유 결과를 얻었다.

• Advances in concrete construction
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• 제2권4호
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• pp.249-259
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• 2014

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.

• Steel and Composite Structures
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• 제22권4호
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• pp.797-820
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• 2016

This paper simulates the hysteretic behavior of steel reinforced recycled concrete (SRRC) columns under cyclic loads using OpenSees software. The effective fiber model and displacement-based beam-column element in OpenSees is applied to each SRRC columns. The Concrete01 material model for recycled aggregate concrete (RAC) and Steel02 material model is proposed to perform the numerical simulation of columns. The constitutive models of RAC, profile steel and rebars in columns were assigned to each fiber element. Based on the modelling method, the analytical models of SRRC columns are established. It shows that the calculated hysteresis loops of most SRRC columns agree well with the test curves. In addition, the parameter studies (i.e., strength grade of RAC, stirrups strength, steel strength and steel ratio) on seismic performance of SRRC columns were also investigated in detail by OpenSees. The calculation results of parameter analysis show that SRRC columns suffered from flexural failure has good seismic performance through the reasonable design. The ductility and bearing capacity of columns increases as the increasing magnitude of steel strength, steel ratio and stirrups strength. Although the bearing capacity of columns increases as the strength grade of RAC increases, the ductility and energy dissipation capacity decreases gradually. Based on the test and numerical results, the flexural failure mechanism of SRRC columns were analysed in detail. The computing theories of the normal section of bearing capacity for the eccentrically loaded columns were adopted to calculate the nominal bending strength of SRRC columns subjected to vertical axial force under lateral cyclic loads. The calculation formulas of horizontal bearing capacity for SRRC columns were proposed based on their nominal bending strength.

• 한국구조물진단유지관리공학회 논문집
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• 제19권3호
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• pp.22-29
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• 2015

본 연구에서는 압축강도 24MPa 이상 열전도율이 기존 콘크리트보다 2배 감소된 구조용 단열성능 향상 콘크리트를 개발하고 현장적용하기 위한 실험을 진행하였다. 슬럼프 및 공기량 시험결과 Plain과 규조토 미분말을 사용한 배합은 경과시간에 따라 슬럼프와 공기량 저하가 나타났으며, 마이크로기포제를 사용한 배합은 슬럼프와 공기량 저하가 나타나지 않았다. 또한 단열성능 향상 재료를 사용한 배합의 단위용적질량은 Plain 대비 감소하였다. 압축강도는 단열성능 향상 콘크리트가 Plain보다 감소한 결과를 나타내었으나 목표강도 24MPa를 만족하였으며, 열전도율은 Plain보다 감소하는 경향을 보였다. 단열성능 향상 콘크리트의 동결융해 저항성은 Plain과 유사하였고, 중성화 저항성은 규조토 미분말을 사용한 배합이 재령 4주에 Plain과 유사했으며, 마이크로기포제를 사용한 배합은 Plain보다 중성화 저항성이 저하되었고, 길이변화율은 Plain보다 전체적으로 증가되었다.

• Restorative Dentistry and Endodontics
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• 제39권3호
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• pp.201-209
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• 2014

Objectives: This study evaluated the solubility, dimensional alteration, pH, electrical conductivity, and radiopacity of root perforation sealer materials. Materials and Methods: For the pH test, the samples were immersed in distilled water for different periods of time. Then, the samples were retained in plastic recipients, and the electrical conductivity of the solution was measured. The solubility, dimensional alteration, and radiopacity properties were evaluated according to Specification No. 57 of the American National Standards Institute/American Dental Association (ANSI/ADA). Statistical analyses were carried out using analysis of variance (ANOVA) and Tukey's test at a significance level of 5%. When the sample distribution was not normal, a nonparametric ANOVA was performed with a Kruskal-Wallis test (${\alpha}$ = 0.05). Results: The results showed that white structural Portland cement (PC) had the highest solubility, while mineral trioxide aggregate (MTA)-based cements, ProRoot MTA (Dentsply-Tulsa Dental) and MTA BIO ($\hat{A}$ngelus Ind. Prod.), had the lowest values. MTA BIO showed the lowest dimensional alteration values and white PC presented the highest values. No differences among the tested materials were observed in the the pH and electrical conductivity analyses. Only the MTA-based cements met the ANSI/ADA recommendations regarding radiopacity, overcoming the three steps of the aluminum step wedge. Conclusions: On the basis of these results, we concluded that the values of solubility and dimensional alteration of the materials were in accordance with the ANSI/ADA specifications. PCs did not fulfill the ANSI/ADA requirements regarding radiopacity. No differences were observed among the materials with respect to the pH and electrical conductivity analyses.

• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.173-179
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• 2003

실제 현장에서 사용하고 있는 고강도 콘크리트 배합의 단위시멘트량은 대부분의 경우 소요의 슬럼프를 확보하는데 필요한 양으로 결정된다. 이 방법은 보통 강도 콘크리트의 배합설계 개념을 적용한 것이기 때문에 필요 이상의 단위시멘트량을 사용하게 된다. 따라서 상대적으로 많은 양의 시멘트를 사용하게 되어 콘크리트의 내구성을 저하시키게 된다. 이에 본 연구에서는 고강도 콘크리트의 내구성과 시공성 및 강도를 동시에 고려한 적정 단위시멘트량을 분석하였으며, 적정 단위시멘트량을 사용함에 따른 혼화제 첨가량 및 적정잔골재율에 대해 검토하였다. 실험 결과, 본 연구의 실험조건에서 단위시멘트량을 $370kg/m^3$으로부터 $550kg/m^3$까지 사용하더라도 압축강도의 차이는 거의 없는 것으로 나타났다. 따라서 콘크리트의 배합시 소요의 설계강도뿐만 아니라 내구성과 시공성을 동시에 만족하는 최소의 단위시멘트량을 결정하여 적용하여야 할 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제45권5호
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• pp.573-580
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• 2013

The combined effects of reactivity coefficients, along with other core nuclear characteristics, determine reactor core behavior in normal operation and accident conditions. The Power Coefficient of Reactivity (PCR) is an aggregate indicator representing the change in reactor core reactivity per unit change in reactor power. It is an integral quantity which captures the contributions of the fuel temperature, coolant void, and coolant temperature reactivity feedbacks. All nuclear reactor designs provide a balance between their inherent nuclear characteristics and the engineered reactivity control features, to ensure that changes in reactivity under all operating conditions are maintained within a safe range. The $CANDU^{(R)}$ reactor design takes advantage of its inherent nuclear characteristics, namely a small magnitude of reactivity coefficients, minimal excess reactivity, and very long prompt neutron lifetime, to mitigate the demand on the engineered systems for controlling reactivity and responding to accidents. In particular, CANDU reactors have always taken advantage of the small value of the PCR associated with their design characteristics, such that the overall design and safety characteristics of the reactor are not sensitive to the value of the PCR. For other reactor design concepts a PCR which is both large and negative is an important aspect in the design of their engineered systems for controlling reactivity. It will be demonstrated that during Loss of Regulation Control (LORC) and Large Break Loss of Coolant Accident (LBLOCA) events, the impact of variations in power coefficient, including a hypothesized larger than estimated PCR, has no safety-significance for CANDU reactor design. Since the CANDU 6 PCR is small, variations in the range of values for PCR on the performance or safety of the reactor are not significant.

• 대한소아치과학회지
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• 제40권2호
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• pp.120-126
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• 2013

심한 우식을 보이는 미성숙 영구치 치료에 있어서 치수생활력을 보존하는 것은 중요하다. 치수절단술을 시행 시 생체적합성이 있는 재료를 이용하여 치료함으로써 남아있는 생활력이 있는 치수를 보호하며 미성숙 영구치의 치근 성장을 도모할 수 있다. 혈소판 농축 섬유소는 환자의 혈액을 직접 채취하여 적용하기 때문에 생체적합성이 뛰어나며 다양한 성장인자를 함유하고 있어 치수생활력을 유지하고 미성숙 영구치의 치근 발육을 촉진시킬 수 있다. 본 증례에서는 심한 치아 우식증을 보이는 미성숙 영구치에서 치수절단술 시행 후 남아 있는 치수 상부에 혈소판 농축 섬유소를 적용하였다. 정기적인 검진 결과 미성숙 영구치의 치근 성장 및 정상적인 치아 주위 조직들이 관찰되었다. 향후 장기간의 임상적 관찰이 필요할 것이며 더 많은 임상 증례를 바탕으로 한 연구가 필요할 것이다.

• Biomolecules & Therapeutics
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• 제19권4호
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• pp.472-476
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• 2011

Hypercholesterolemia indirectly increases the risk of arterial and venous thrombosis by enhancing the ability of platelets to aggregate. Yacon (Smallanthus sonchifolius) is composed of fructooligosaccharides, proteins, minerals and phenolic compounds, and has potential benefits for the management of diabetes. This study investigated whether the consumption of yacon in the diet inhibits platelet aggregation under hypercholesterolemic conditions. Male New Zealand white rabbits were fed one of five dietary interventions: a normal control diet, 0.5% cholesterol diet, 0.5% cholesterol diet+a low dose of yacon (0.5 g/kg body weight given orally each day), 0.5% cholesterol diet+a high dose of yacon (2.5 g/kg body weight given orally each day), or a 0.5% cholesterol diet+lovastatin (2 mg/kg body weight given orally each day). After 8 weeks, blood was collected to measure the amount of collagen- and thrombin-induced platelets present. Yacon inhibited the platelet aggregation induced by low doses of agonists (0.5 ${\mu}g/mL$ collagen and 0.02 units/ml thrombin) in a concentration-dependent manner. In addition, yacon concentration-dependently inhibited collagen-induced arachidonic acid liberation. Moreover, n-hexane, chloroform and ethyl acetate fractions showed a marked and selective inhibition of the platelet aggregation induced by collagen, again in a dose-dependent manner. These fractions, especially that of chloroform, significantly suppressed platelet aggregation. The results of this study demonstrate that when yacon is added to a cholesterol-enriched diet, cholesterol-induced platelet aggregation returns to control levels. This may also be beneficial in preventing atherosclerosis and reducing risk factors for coronary artery disease and stroke.