Effect of Impact Load on Splice Length of Reinforcing Bars

Hyeon?Jong Hwang,Fan Yang,Li Zang,Jang?Woon Baek,Gao Ma 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

Impact loading damage of reinforced concrete (RC) members deteriorates bond strength of reinforcing bars. To understand the effect of strain rate on the bond strength of reinforcing bars in RC beams under impact load, drop hammer test was performed on twenty-four simply supported RC beams with lap spliced bars at the mid-span. The test parameters were reinforcing bar diameter, splice length, drop height, and hammer mass. The dynamic responses including the impact load history, mid-span deflection history, crack distribution, and strain history of reinforcing bar were evaluated. Although the designed bar development length was 31–69% of the requirement of current design codes under static load, the tensile strength of bar splices was greater than the dynamic yield strength when subjected to large impact energy under impact load. On the basis of the test results, existing design equations for the bar development length under static load were modified to consider the impact loading effect on the bond strength. Factors related to the strain rate effect of materials, impact damage, and impact energy loss were proposed. The prediction of the proposed method agreed well with the tensile strength of bar splices under impact load.

영구자석의 체적 변화가 자력에 미치는 영향

장항익,황현식 대한치과교정학회 1995 대한치과교정학회지 Vol.25 No.2

교정치료시 보다 효과적인 치아 이동을 위한 한 방법으로 최근 자석 사용이 고려되고 있다. 영구자석의 체적 변화가 자력에 미치는 영향을 파악하고자 한 쪽에 한 개의 자석을 고정하고 반대쪽 자석의 두께나 넓이를 일정한 비율로 증가시키면서 양측 간에 나타나는 자력을 비교 연구한 결과 다음과 같은 결과를 얻었다. 1. 두께를 증가시킨 경우에는 자력이 증가하였으나 넓이를 증가시킨 경우 자력이 오히려 감소하였다. 2. 체적 증가에 따른 자력의 증간은 대수함수 분포 양상을 나타내었다. 3. 두께 증가로 체적을 변화시킨 경우, 같은 두께라도 처음부터 크게 제작한 자석이 작은 자석을 여러 개 합한 것보다 큰 자력을 보였다. 본 연구 결과 구강내에서 자력을 증가시키기 위해서는, 마주보는 자석면은 같게 유지하면서 넓이 증가보다는 두께를 증가시키는 방법이, 그리고 처음부터 두꺼운 자석을 사용하는 것이 보다 효율적임을 알 수 있었다. Recently, magnetic forces are considered as a method for more efficient tooth movement. The purpose of this study was to evaluate the effects of the changes of the magnetic volume on the magnetic forces. The universal testing machine and the electronic balance were used for the exact measurement of the force with constant air gap. While the magnet was kept same on one side, the magnetic volume of the other side was increased gradually in four manners. In the first group, the thickness was increased by adding same size of the magnets on after another while the thickness was increased by changing with a thicker magnet gradually in the second group. In the third group, the width was increased by adding same size of the magnets while the width was increased by changing with a wider magnet gradually in the last group. The results were as follows : 1. With the increase of the thickness, the magnetic force increased, while the magnetic force decreased with the increase of the width. 2. The magnetic force according to the change of the magnetic volume showed the distribution of the logarithmic function. 3. An originally thick magnet showed larger force than the added magnets although both of them had same volume.

Cholesterol 食餌에 添加한 Pectin 및 Cellulose가 흰쥐의 血淸 脂質에 미치는 影響

張鉉淑 慶北大學校 師範大學 1987 敎育硏究誌 Vol.29 No.-

This experiment was designed to investigate the effect of dietary fibers on serum lipids of cholesterol-fed rats. Twenty-five rats of Sprague-Dowley strain weighed 100±10g were divided into 5 groups, each group receiving a different diet for 3 weeks. And five kinds of animal diets were prepared as follows; 1) Control diet: 65g corn starch contained 18g casein, 10g lard, 5g vegetable oil, vitamin and salt mixture and 1g cholesterol. 2) Ⅰ diet: 4% cellulose was added into the control diet. 3) Ⅱ diet: 8% cellulose was added into the control diet. 4) Ⅲ diet: 4% pectin was added into the control diet. 5) Ⅳ diet: 8% pectin was added into the control diet. The weight of feed was properly adjusted by reducing the content of starch. After sacrificing the animals, the contents of some chemical components in serum were analyzed. The results obtained are summarized as follows; 1) The weight of liver and heart was significantly different between the experimental groups and the control group. 2) The total lipid, total cholesterol, HDL-cholesterol, triglyceride and phosph-olipid contents of serum were not significantly different between the experimental groups and the control group. 3) The ratio of HDL-cholesterol to total cholesterol was significantly increased in pectin 4% group.

Niacin이 조골세포 분화에 미치는 영향

민현영 ․ 장원구 대구대학교 산업기술연구소 2018 産業技術硏究 Vol.29 No.2

Niacin (Vitamin B3) is a necessary nutrient for humans and animals. This study was conducted to examine the effect of niacin on osteoblast differentiation. Previous study shows that precursor of niacin suppress osteoclast formation. However, the mechanism of niacin in osteoblast differentiation is not well known. In this study we investigated the effect of niacin in osteoblasts. Niacin induced osteogenic differentiation marker genes including distal-less homeobox 5(Dlx5), runt-related transcription factor 2(Runx2), alkaline phosphatase(ALP), and osteocalcin(OC). These results suggest that niacin contributes to osteoblast differentiation by inducing the osteogenic genes.

초등학교 외부공간의 환경친화적 조성계획에 관한 연구

장대희,김현수 대한건축학회 2004 대한건축학회논문집 Vol.20 No.9

The purpose of this study is (1)to supplement City ecological problems and (2) to provide ecological school's outdoors planning factors and methods for setting up the educational space of environmental friendship First, the notion and compositive purpose of ecological schools are established, the ecological formal necessity of outdoor of schools is investigated The ecological problems of elementary schools are also understood by the on-the-spot survey The spacial planning directions and essential examples are viewed by extarcting the ecological outdoor compositive plans With the planning creteria and presentation of the essential element technology

翼端 부근의 人工的 面粗度가 揚力에 미치는 影響에 關한 硏究

李璋煥,河在賢 영남대학교 공업기술연구소 1984 연구보고 Vol.12 No.1

In this study we attempted to increase the wing lift by roughen the tip a rear of the wing surface. Two types of the wing shape (one is square and the other is swept) and two types of artificial roughness were used in the wind tunnel experiment. The cross sectional shapes of the wing models were that of NACA 0010 basic thickness form. The lift coefficients of wing models were measured and compared, and proved to gain good results. Maximum lift coefficient of the wing model which has artificial rougness was bigger than that of the smooth surface wing about 32.4%, and the stall angle was also delayed about 6.7˚. The reason of these phenomena was verified by oil-film visualization photographs of wing surface flow shapes. The separation lines of artificial roughness wing models moved back compared with the smooth surface wing, and the sizes of the stall area was also reduced. And it was verified that the adverse flow oriented direction of the arificial roughness is more profitable than random one in the case of line roughness.

청소년 지도학의 활동영역 활성화 연구

육현철,장갑석,최강진 한국체육대학교 2001 韓國體育大學校 敎養敎育論文集 Vol.- No.6

The Curriculum of National Cooking(Guidance) for the Youth Had Been established at the Myungji University in 1994 for the first time in the history of Korean college, and 8 universities Has, Recently and operate the course, These days the curriculum mostly concentrates on the subject of pedagogy and educational psychology. (ⅰ) To vitalize the juvenile's physical activity, the government concerned needs to make a political support in order each university to found the curriculum for the youth.And each university must open the course which the teenager can make physical activities free of charge. (ⅱ) The educational policy researching and developing the activity area of the youth is required.By educating them based upon the activity area, the youth can have a healthy body which results from sound spirit. (ⅲ) The youth Activity Centre is to be established and operated at each community or local district to vitalize the section for sport activity which the juvenile prefer.Physical promotion is needed to be desirable adult. (ⅳ) Today the computer system like internet and dlectronic entertainment/game give the large influence on all the juvenile.Herein we need to remind that almost young generation study by day and indulge in computer without Physical activity that lead to weak body and feeble spirit.Under those circumstances, we can find out the juvenile delinquent from to time. (ⅴ) Finally, it is greatly important and imperative to foster lots of professional experts/coaches who can understand the youth and guide them in a sound way.

유구치 I급 와동에서 와동벽 위치와 중합광원에 따른 Microtensile Bond Strength 비교 연구

이현헌,장철호,김영재,김정욱,장기택 대한소아치과학회 2007 大韓小兒齒科學會誌 Vol.34 No.1

이번 실험에서는 중합수축 응력이 가장 크게 나타나는 유구치 I급 와동에서 와동벽의 위치와 중합광원의 변화에 의해 다르게 나타나는 응력의 차이를 microtensile bond strength (MTBS)를 이용하여 알아보는 것을 목적으로 하였다. 교합면 법랑질을 제거한 하악 제 2유구치 30개를 준비하여 I급 와동을 형성하였다. 제조사의 지시에 따라 상아질 접착제를 도포 후 3가지 중합광원: 할로겐 램프, 플라즈마, 발광다이오드를 이용하여 10개씩 광중합하였다. 복합레진을 한꺼번에 충전 후 각각의 중합기로 광중합하였다. 동일 치아에서 각각 치수벽과 축벽의 MTBS 측정용 시편을 제작하고 각 군을 중합광원과 와동벽 위치에 따라 할로겐 램프-축군, 할로겐 램프-치수벽군, 플라즈마-축벽군, 플라즈마-치수벽군, 발광다이오드-축벽군, 발광다이오드-치수벽군의 6개 군으로 분류하였다. 만능시험기에서 MTBS를 측정하고 파절편과 와동의 단면을 SEM을 이용하여 관찰하였다. 동일 중합광원에서 와동벽 간 비교는 T-test, 동일 와동벽에서 중합광원 간 비교는 One-way ANOVA와 Tukey's post hoc test를 이용하였고 Weibull 분포분석을 하였다. 동일 중합광원 군간 비교에서 모두 치수벽 시편의 접착강도가 축벽 시편에 비해 유의하게 높았으며 동일 와동벽 군간 비교에서 모두 중합광원에 따른 접착강도가 유의한 차이를 보이지 않았다. 축벽 시편이 치수벽 시편보다 낮은 Weibull 변수(m)를 나타내었고 SEM 관찰 결과 축벽 시편에서 보다 더 불균일한 접착이 이루어진 것을 알 수 있었다. The purpose of present study was to determine whether different kinds of curing lights can alter microtensile bond strength(MTBS) of class I cavity pulpal and axial wall specimens in primary molar. Thirty clean mandibular 2nd primary molar's occlusal enamel were removed and class I cavity, size of 2×4×2 mm was prepared. Dentin bonding agent was applied according to manufacturer' s manual. Each group was cured with Halogen Curing Unit, Plasma Curing Unit and LED Curing Unit. Composite resin was bulk filled and photo cured with same curing unit. MTBS specimens which size is 0.7×0.7×4 mm were prepared with low speed saw. Specimens were coded by their curing lights and wall positions (Halogen - Axial wall group, Halogen - Pulpal wall group, Plasma - Axial wall group, Plasma - Pulpal wall group, LED - Axial wall group, LED - Pulpal wall group). MTBS were tested at 1 mm/min cross Head speed by Universal Testing Machine. Fractured surface and bonding surface was observed with SEM. T-test between axial and pulpal specimens in each curing lights, one-way ANOVA among different curing light specimens in each wall positions were done. Weibull distribution analysis was done. The results were as follows: Mean MTBS of pulpal wall specimens were significantly greater than that of axial wall specimens at each curing units(p<.05). There was no significant difference in the MTBS among three curing units at axial wall and pulpal wall. In Weibull distribution, pulpal wall specimens were more homogeneous than axial wall specimens.

尹善道의 漢詩와 時調의 考察

윤장현 朝鮮大學校 敎育大學院 國語敎育學會 1983 國語敎育論叢 Vol.4 No.-

CAM을 이용한 다지 분기 구조의 설계

조현묵,한일국,기장근 公州大學校工科大學生産技術硏究所 1996 論文集 Vol.5 No.-

In this thesis, Multi-way branch structure is designed to execute multiway branch instruction in the wireless LAN protocol processor. Because this structure substitute CAM(Content Addressable Memory) for target selection unit with label index information of program which branch in multiway according to system variables consist of flags & vectors. The CAM store a set of arbitrary variable conditions. Thus, this structure have feature which assign system value for multiway branch, can programming and reconfigure a set of variable conditions. The Desing of Multiway branch structure used cmn8a library which is 0.8um process of Compass tool, have about 9,500 gates and suitable for basis clock 80MHz of wireless LAN protocol processor.