폐주불사를 혼입한 콘크리트의 내구성에 관한 연구

김태경,박정호,이정호,이주형,박제선,김연경,윤경구 강원대학교 석재복합신소재제품연구센터 1998 석재연 논문집 Vol.3 No.-

콘크리트 구조물은 자연적인 혹은 인위적인 온도의 상승, 강하로 인하여 동결-융해 작용을 받게 되어 구조물의 성능저하를 야기시킨다. 현대에 들어서면서 콘크리트의 내구특성을 파악하기 위한 연구적 요구가 증가되고 있다. 따라서 폐주물사 콘크리트를 실제 구조물에 적용하기 위해서는 내구특성에 대한 연구가 반드시 이루어져야 한다. 폐주물사를 혼입한 콘크리트의 내구특성을 파악하기 위한 동결-융해 실험은 폐주물사의 잔골재 치환율, 물-시멘트비, AE제 사용 여부를 주요 변수로 하여 실시하였다. 원형공시체를 제작하여, 동결-융해 시험기에 넣어 -18∼4℃로 급속 동결-융해를 진행시키면서 매 23싸이클마다 동탄성계수를 측정하였다. 실험결과 AE제를 첨가했을 때 물-시멘트비가 적을수록, 폐주물사의 치환율이 클수록 전반적으로 강도가 증가하는 것으로 나타났으며, 물-시멘트비가 증가함에 따라, AE제를 사용한 콘크리트가 동결-융해 저항성이 증가하는 것으로 나타났다. 특히 폐주물사 치환율이 50%일 때가 동결-융해 저항성이 가장 좋은 것으로 나타났으며 그 다음으로 25, 0% 순으로 저항성이 좋은 것으로 나타났다. 따라서 폐주물사 콘크리트가 내구성이 우수한 것으로 나타나 폐주물사를 콘크리트에 재활용 할 수 있는 것으로 나타났다. Concrete structures has been deteriorated by the freezing and thawing due to temperature gap. This study was conducted to evaluate durability of concrete which are increasingly demanded recently. Therefore the research of durability must be executed for application of waste foundry sand concrete real structures. Concrete durability properties incorporating waste foundry sand was performed with the variable of W/C ratio, Sand/Waste foundry sand ratio and Air entrainment-Non air entrainment. Cylinder specimens were made and subjected to freezing and thawing cycle at -18℃ and 4℃. Dynamic modulus of elasticity were evaluated as F/T cycle increase. The results show that strength of concrete is increased the W/C ratio decrease, the Sand/Waste foundry sand ratio increase when the concrete contains AE agent and decreasing W/C ratio and AE concrete makes improved resistance of freezing and thawing improved. Especially, resistance of freezing and thawing is improved by Fine aggregate/Waste foundry sand ratio which is 50%, 25%, 0% in a row. Therefore it is turn out the waste foundry sand could be applied to concrete from the experiment.

근관 충전재 및 치근단 역충전재의 방사선 불투과성에 관한 비교 연구

김용상,김서경,황윤찬,황인남,오원만 大韓齒科保存學會 2008 Restorative Dentistry & Endodontics Vol.33 No.2

This study was performed to assess the radiopacity of a variety of canal filling and retrograde root-end filling materials according to the specification concerning root canal obturation materials. Ten materials including Gutta-percha pellets, amalgam, Fuji II LC, Dyract^(ⓡ) AP, Super EBA^(ⓡ), IRM^(ⓡ) AH 26^(ⓡ), Sealapex™, Tubli-Seal™ and dentin were evaluated in this study In the first part, densitometric reading of an each step of aluminum step wedge on occlusal film were performed at 60 kVp (0.2, 0.3, 0.4 s), 70 kVp (0.2, 0.3, 0.33 s) to decide appropriate voltage and exposure time. In the second part, ten specimens which are 5 ㎜ in diameter and 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 ㎜ in thickness, were fabricated from each material studied. The specimens were radiographed simultaneously with an aluminum step wedge under decided condition (60 kVp, 0.2 s). The mean radiographic density values of the materials were transformed into radiopacity expressed equivalent thickness of aluminum (㎜ Al). The following results were obtained. 1. Among the various conditions including 0.2 s, 0.3 s, 0.4 s at 60 kVp and 0.2 s, 0.3 s, 0.33 s at 70 kVp, the appropriate voltage and exposure time that meet the requirement of density from 0.5 to 2.0 was 0.2 s at 60 kVp. 2. All of the materials in this study had greater radiopacity than the minimun level recommended by ISO No. 4049 standards. 3. Most of the materials had greater radiopacity than 3 ㎜ Al requirement of ANSI/ADA specification No. 57 (2000) and ISO No. 6876 (2001) standards except for Fuji II LC and Dyract. It suggests that all experimental canal filling and retrograde root-end filling materials have a Sufficient radiopacity that meet the requirement concerning root canal obturation materials except for Fuji II LC and Dyract. 본 실험에서는 다양한 방사선 노출 조건에 따른 aluminum step wedge에 대한 광학 밀도를 알아보고, 그 중 적절한 노출조건을 선택하여 수종의 근관 충전재와 치근단 역충전재의 방사선 불투과성 정도를 굉가, 비교하였다. 방사선 불투과성의 기준을 위해 11개의 step으로 구성된 aluminum step wedge를 제작하여 , 60 kVp, 70 kVp 관전압 상태에서 각각 0.2. 0.3, 0.4초와 0.2, 0.3, 0.33초의 노출시간으로 교합 필름상에서 방사선 촬영 후 적절한 노출 조건을 구하였다. 직경 5 ㎜,각각의 두께 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 ㎜인 10종 (Gutta-percha, amalgam, Super EBA^(ⓡ), MTA, IRM^(ⓡ), Fuji II LC, Dyract^(ⓡ) AP, AH 26^(ⓡ), Sealapex^(ⓡ), Tubli-Sea™의 근관 충전재와 치근단 역충전재 시편을 각 재료와 두께당 10개씩 제작한 후, 동일한 두께의 상아질 시편 , aluminum step wedge와 함께 정해진 노출조건에 따라 방사선 촬영을 하였다. 모든 필름은 자동현상기로 현상하였다. 시편의 흑화도를 densitometer (Model 07-443, Victoreen Inc, Cleveland, Ohio, USA)로 5회 반복 측정 후, 평균값을 구하여 회귀분석 후 알루미늄 두께로 환산하였다. 얻어진 정보를 분석하여 다음의 결과를 얻었다. 1. 관전압 60 kVp에서 노출시간 0.2, 0.3, 0.4초, 70 kVp에서 0.2, 0.3, 0.33초로 변화를 주어 방사선 촬영을 하였을 때, 흑화도가 0.5 - 2.5 사이여야 한다는 ISO No. 6876 규격에 가장 적합한 것은 60 kVp, 0.2초일 경우였다. 2.측정된 근관 충전재와 치근단 역충전재들의 방사선 불투과성 모두 ISO No. 4049 규격에 적합하였다. 3.광중합형 글래스 아이오노머 (Fuji II LC)와 컴포머 (Dyract)를 제외하고는 ANSI/ADA specification (2000) 또는 ISO No. 6876 (2001)규격이 제시한 최소한 3 ㎜ Al 이상의 방사선 불투과성을 지녀야 한다는 규격에 적합하였다. 이상의 결과는 본 실험에 사용된 수종의 근관 충전재와 치근단 역충전재 중 Fuji Ⅱ LC와 Dyract를 제외하고 모두 규격에 적합한 방사선 불투과성을 가지고 있음을 시사한다.

퍼지조건부 기대값에 대한 수렴정리

김윤경 東新大學校 1998 論文集 Vol.10 No.-

In this paper, we introduce the concept of conditional expectations for fuzzy random variables and prove some convergence theorems which generalize the results for the classical cases.

엔로플록사신 액제의 닭 호흡기 및 소화기 감염증에 대한 예방 및 치료효과

윤효인,박병권,조준형,정상희,박경환,장범수,김종춘,황윤환,임종환,이내경,박승춘 충남대학교 수의과대학 동물의과학연구소 2000 動物醫科學硏究誌 Vol.8 No.-

We evaluated the efficacy of the liquid form of enrofloxacin against poultry respiratory and digestive infections, the major problems in the poultry industry, from diverse diagnosis viewpoints. Results obtained through this study were as follows: 1. The liquid form of enrofloxacin showed good acceptability to poultry owing to no abhorrence to the drug by chickens, which indicated its suitability for mixing in drinking water. 2. The application of the enrofloxacin formulation improved the productivity of the chicken farm to a great extent by lowering the death toll of chicken raised in the farm. 3. The use of the drug shortened the days to the market, and increased the body weight at the time of marketing. 4. Preventive and therapeutic effects of the liquid enrofloxacin were observed higher than ampicillin, a major antibiotic used in poultry farming. From above results, the liquid form of enrofloxacin would find its use for the prevention and treatment of digestive and respiratory infections, let alone the growth promotion and feed efficiency, especially in the chicken farming practice.

근관 세척법이 Resilon/Epiphany sealer와 Gutta-percha/AH 26 sealer의 근관 상아질과의 접착에 미치는 영향

김서경,황윤찬,황인남,오원만 大韓齒科保存學會 2008 Restorative Dentistry & Endodontics Vol.33 No.2

본 연구에서는 근관 세척법이 두 가지 근관 충전재 (Gutta-percha/AH 26 sealer, Resilon/Epiphany sealer)의 근관 상아질과의 접착메 미치는 영향을 평가하였다. 총 30개의 발거된 상악 전치를 각자 5개씩 6개의 군으로 분류하여 근관 성형을 하고 마지막 세척을 다음과 같이 시행 한 후 Gl, G2, G3군은 Gutta-percha/AH 26 sealer로, Rl, R2, R3군은 Resilon/Epiphany sealer로 근관 충전하였다. Gl, Rl군 : 5.25% NaOCl세척 G2, R2군 : 5.25% NaOCl세척 후 sterile saline 세척 G3, R3군 : 5.25% NaOCl세척 후 17% EDTA, sterile saline 순으로 세척 각 군의 충전된 치아를 아크릴 레진에 매몰하고 약 1 mm 두께로 절단한 후 만능 물성 시험기상에서 push-out bond strength를 측정하였고 실험 후 파절 양상을 Image-analyzing microscope으로 관찰하여 다음과 같을 결과를 얻었다. 1. Gutta-percha/AH 26 sealer 충전군에서 Resilon/Epiphany sealer 충전군보다 push-out bond strength가 높게 나타났다 (p < 0.05). 2. Resilon/Epiphany sealer 충전군 중 17% EDTA, sterile saline순으로 세척시 5.25% NaOCl 세척에 비해 push-out bond strength가 높게 나타났다 (p<0.05). 3.파절 양상을 분석시 모든 군은 접착성과 혼합성 파절 양상을 나타내었고, Gl, G2, Rl 군은 응집성 파절 양상이 나타나지 않았으며, Resilon/Epiphany sealer 충전군은 Gutta-percha/AH 26 sealer 충전군에 비해 응집성과 혼합성 파절 망상이 더 높은 비율로 나타났다. The purpose of this study was to evaluate whether intracanal irrigation method could affect the adhesion between intracanal dentin and root canal filling materials (Gutta-percha/AH 26 sealer and Resilon/Epiphany sealer). Thirty extracted human incisor teeth were prepared. Canals were irrigated with three different irrigation methods as a final rinse and obturated with two different canal filling materials (G groups : Gutta-percha/AH 26 sealer, R groups : Resilon/Epiphany sealer) respectively. Group Gl, Rl - irrigated with 5.25% NaOCl Group G2, R2 - irrigated with 5.25% NaOCl, sterile saline Group G3, R3 - irrigated with 5.25% NaOCl, 17% EDTA, stehle saline Thirty obturated roots were horizontally sliced and push-out bond strength test was performed in the universal testing machine. After test, the failure patterns of the specimens were observed using Image-analyzing microscope. The results were as follows. 1. Gutta-percha/AH 26 sealer groups had significantly higher push-out bond strength compared with the Resilon/Epiphany sealer groups (p < 0.05). 2. Push-out bond strength was higher when using 17% EDTA followed by sterile saline than using NaOCl as a final irrigation solution in the Resilon/Epiphany sealer groups (p < 0.05). 3. In the failure pattern analysis, there was no cohesive failure in Group Gl, G2, and Rl. Gutta-percha/AH 26 sealer groups appeared to exhibit predominantly adhesive and mixed failure patterns, whereas Resilon/Epiphany sealer groups exhibited mixed failures with the cohesive failure occurred within the Resilon substrate.

접착술식에 따른 전단강도 및 Bracket위치의 비교

김상철,국윤아,박윤경 대한치과교정학회 1991 대한치과교정학회지 Vol.21 No.3

The purpose of this study was to compare the bracket placement and the shear bond strength of indirect-bonded brackets with those of direct-bonded ones. Forty eight extracted human teeth were collected and attached with brackets and tested on shear bond strength, using Instron. Fourteen patients from Wonkwang University Dental Hospital were selected for direct bonding of brackets and their teeth were measured on bracket angulation and bracket height. The obtained results were as follows: 1.The shear bond strengths of incisors were higher in direct-bonding, group, rather than indirect-bonding group. But, the shear bond strength of premolars showed no significant differences between groups. 2.The bracket angulations of indirect-bonding group were preciser than those of direct-bonding group, especially in upper first premolars, lower lateral incisors, canines, premolars. 3.In bracket height, there were no significant differences between groups.

줄눈콘크리트 포장의 줄눈 거동 측정

윤경구,김동호,홍창우,이주형 江原大學校 産業技術硏究所 2001 産業技術硏究 Vol.21 No.B

In this research, the early-age movements of joint at JPCP(Jointed Plain Concrete Pavement) were measured by field tests. The field tests were carried out for 5 days just after concrete placement, for 1 day after 52 and 72 days on Chung-Ang Expressway construction site in Dan-Yang on the 28th and 29th of May 2001. The joint movements were measured by demec gauge and clip gauge. The results of regression analysis for the data measured during early 5 days showed that the joints of No.4, No.5, No.6, No.10, No.13, and No.15 could be considered as a moving joint. From data analysis on July 20, the joints of No.2, No.9, and No.10 showed the significant correlations from the minus value of coefficient of regression. As a result of regression data on August 8, joint movements occurred at all joints. Joint freezing and closure could be judged from the regression analysis using joint opening and total temperature measured at field tests.

초속경 LMC의 시험시공을 위한 시방배합 및 현장배합 연구

윤경구,김성환,정원경,최성욱 강원대학교 부설 석재복합신소재 제품연구센터 2002 석재연 논문집 Vol.7 No.-

본 논문은 콘크리트 배합시 발생하는 과도한 기포 발생 문제점을 해결하기 위하여 최적의 소포제 종류 및 혼입률 범위를 산정하여 초속경 라텍스 개질 콘크리트 성능을 개선하는 것이다. 초속경 라텍스 개질 모르타르 실험은 4종류의 소포제 A, B, C, D와 혼입률 0, 1, 2, 3%을 주요 변수로 하여 실험을 수행하였으며, 초속경 라텍스 개질 모르타르 및 콘크리트의 특성을 분석하기 위하여 공기량 시험, 압축강도 및 휨강도 시험을 수행하였으며, 투수특성을 분석하기 위해서 염화이온 투과시험을 수행하였다. 초속경 라텍스 개질 모르타르의 공기량시험 결과 소포제 종류에 상관없이 소포제 혼입률 1%이상 첨가시 공기량은 50%이상 감소하였다. 또한, 소포제 첨가에 의한 기포발생량 감소에 의해서 압축강도의 증진을 이루었다. 초속경 라텍스 개질 콘크리트 실험은 모르타르 실험에서 우수한 특성을 나타낸 A, C 소포제로 선정하여 실험을 수행하였다. 초속경 라텍스 개질 콘크리트의 강도 특성에서는 A 소포제 혼입률 1%에서 압축강도 235 kgf/㎠, 휨강도는 조기 교통개방에 요구되는 휨강도 기준 45kgf/㎠를 초과하는 49kgf/㎠를 나타내었다. 초속경 라텍스 개질 콘크리트의 투수성을 분석하기 위한 염화이온투과시험에서 A 소포제는 각각 혼입률 1%, 2%에서 가장 우수한 투수저항성을 나타내어 재령 28일에서는 통과전하량이 100쿨롱 이하를 나타내어 불투수성을 나타내었다. The purpose of this study was to remove the excessive air foaming which was produced in mixing the RSLMC(latex-modified concrete with rapid-setting cement) by choosing the best antifoam agent type and the optimized quantity for performance improved RSLMC. A series of RSLMM(latex-modified mortar with rapid-setting cement) experiments were carried out as the basic for RSLMC with the main experimental variables such as antifiamer types (A, B, C, D), antifoamer contents (0, 1, 2, 3%), and latex contents (15%). A series of RSLMC experiments, also, were carried out with the similar main experimental variables but with the selected antifoamer types (A, C). Air content test and compressive, flexural tests were carried out to measure the improved properties of RSLMM and RSLMC. Chloride ion permeability test was carried out to estimate water permeability resistance. The results of RSLMM showed that the decrease of 50% air content was obtained by admixturing a antifoam agent by 1%. Two kinds and the optimized quantities of antifoam agent were selected for using in RSLMC. The results of RELMC were obtained at a latex content of 15% and an antifoam agent quantity of 1% with antifoamer A type. The compressive strength and flexural strength at 3 hours after RSLMC placement were 235 kgf/㎠ and 49kgf/㎠, respectively, which exceeded the flexural strength criterion of 45 kgf/㎠ in order to open the RSLMC placed to traffic. The rapid chloride permeability test was used to evaluate the permeability of RSLMC. The optimited quantity of antifoamer A and C type were 1% and 2% for the permeability test, respectively. The chloride permeability using A and C antifoamer at 28 days were below 100 coulombs, which was the permeability rating of negligible according to ASTM.

공구형상이 칩유동에 미치는 영향에 관한 연구

김경우,김우순,윤주식,채왕석,김동현 한국공작기계학회 2000 한국공작기계학회 추계학술대회논문집 Vol.2000 No.-

A new methodology is presented to evaluate material properties at high strain rates and high temperatures based on orthogonal metal cutting experiments and FEM simulations. Average strain rate and average temperature found in the deformation zone are computed and flow stress data at these conditions are modified until cutting forces calculated in simulations match those determined in experiments. Material properties obtained from this method were verified by additional metal cutting simulations. Derivation from cutting forces measured in experiments was less than 10%. The feasibility of tool design using FEM simulations is also demonstrated.

조강시멘트를 사용한 라텍스개질 콘크리트의 보수재료 개발

윤경구,김동호,최성용,최판길 강원대학교 부설 석재복합신소재 제품연구센터 2004 석재연 논문집 Vol.9 No.-

The purpose of this research was to develop an available repair material to solve the problem such as coherence, construction period and economic performance that the repair material of existing water-construction have. The latex was good at coherence and resistance of permeability and the high-early cement shorten construction period through the early strength development. Therefore, in this study, we tried to develop the High-Early Strength Latex Modified Concrete(below ; HESLMC) combining these two characteristics. First, to find the optimum mixtures according to the construction criteria, slump condition, the maximum size of coarse aggregate and the antifoam agent adjusting air-content were selected as the major variables. The unit weight of cement and percentage of fine aggregate were fixed by 400 kg and 50 %, respectively. The suitable content of latex was 15% with considering the situation of inside and outside of the country. Second, the strength tests in order to estimate the mechanical characteristics were carried out and the permeability test of chloride ion and scaling test were carried out to estimate of durability of HESLMC, respectively. In all experimental variables, the results of strength test showed that the compressive strengths and flexural strengths, at 3 days after placement, were more than 21 MPa and 4.5 MPa, respectively. Especially, the resistance of permeability was excellent when compared to that of High Early-Strength Concrete(below ; HESC). 본 연구의 목적은 기존 콘크리트 수리구조물 보수재료가 갖는 부착성, 시공기간 및 경제성의 문제를 해결하기 위한 적절한 보수재료 개발에 있다. 따라서 본 논문에서는 부착성 및 장기공용성이 우수한 라텍스의 특성과 조기강도발현을 통해 공기단축이 가능한 조강시멘트의 특성이 결합된 조강형 라텍스개질 콘크리트를 개발하고자 하였다. 첫째로 HESLMC의 시공조건에 따른 최적배합도출을 위하여 슬럼프조건, 굵은 골재 최대치수 및 소포제량을 주 변수로 설정하였다. 국내외 여건을 고려하여 단위 시멘트량과 잔골재율은 각각 400 kg, 50 %로 적정 라텍스 함량은 15 %로 하였다. 둘째로 역학적 특성 파악을 위한 강도실험과 내구성 특성을 파악하기 위한 투수저항성 실험과 표면박리저항성 실험을 실시하였다. 강도측정결과는 모든 변수에 있어 재령 3일의 압축강도가 21 MPa, 휨강도가 4.5 MPa 넘어 초기강도를 만족하는 것으로 나타났다. 특히, 투수저항성은 HESC와 비교하여 상당히 우수하게 나타났다.