• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.1
• /
• pp.25-37
• /
• 1993

This paper describes the use of the J-integral, a one parameter of the non-linear fracture mechanics(NLFM), as a means to measure toughness of steel fiber reinforced concrete. This parameter can be conveniently evaluated from experimentally determined load-deflection curves from flexural tests when a maximum-load failure criterion is employed. And, for high strength concrete which was reinforced steel fiber, with two different fiber length in the form of notched beams, were tested under 3-point bending, and $J_{IC}$, as well as the linear elastic fracture mechanics(LEFM) parameters $K_{IC}$ and $G_{IC}$ were evaluated. The results suggest that $J_{IC}$ is a promising fracture criterion for all of these. while $K_{IC}$(or $G_{IC}$) almost certainly are not. Also it was found that a fiber addition of less than 0.5% did not improve the fracture toughness of the high strength concrete. However, at more than 1.0% in fiber contents, $J_{IC}$ showed significant increases. reflecting the changed character of the concrete; $K_{IC}$ and $G_{IC}$ did not.

• Tunnel and Underground Space
• /
• v.30 no.3
• /
• pp.256-269
• /
• 2020

The objective of this study is to evaluate the stress thresholds in crack development and the corrected fracture toughness of KURT granite under dry and saturated conditions. The stress thresholds were identified by calculation of inelastic volumetric strain from an uniaxial compression test. The corrected fracture toughness was estimated by using the Level II method (Chevron Bend specimen), suggested by ISRM (1988), in which non-linear behaviors of rock was taken into account. Average crack initiation stress(σ_ci) and crack damage stress(σ_cd) under a dry condition were 91.1 MPa and 128.7 MPa. While, average crack initiation stress(σ_ci) and crack damage stress(σ_cd) under a saturated condition were 58.2 MPa and 68.2 MPa. The crack initiation stress and crack damage stress of saturated ones decreased 36% and 47% respectively compared to those of dry specimens. A decrease in crack damage stress is relatively larger than that of crack initiation stress under a saturated condition. This indicates that the unstable crack growth can be more easily generated because of the saturation effect of water compared to the dry condition. The average corrected fracture toughness of KURT granite was 0.811 MPa·m^0.5. While, the fracture toughness of saturated KURT granite(K_CB) was 0.620 MPa·m^0.5. The corrected fracture toughness of rock in saturated condition decreases by 23.5% compared to that in dry condition. It is found that the resistance to crack propagation decreases under the saturated geological condition.

• Proceedings of the Korean Magnestics Society Conference
• /
• 1991.05a
• /
• pp.35-36
• /
• 1991

• Applied Chemistry for Engineering
• /
• v.10 no.5
• /
• pp.789-795
• /
• 1999

In this study, carbon fiber reinforced cement composites(CFRCs) reinforced with short noncircular type carbon fibers were fabricated and properties(drying shrinkage, resistance to freezing and thawing, and fracture toughness) were compared with those of the CFRCs reinforced with circular type carbon fibers. It was found that these properties greatly depended on the shape and length of carbon fibers. The drying shrinkage of CFRCs reinforced with C-type carbon fiber was superior to other CFRCs. This effect was increased with a high aspect ratio of fiber. The resistance to freezing and thawing was increased with the fiber length and fiber volume percent, but there was on remarkable effect to fiber shape. Fracture toughness and resistance to crack propagation of CFRCs reinforced with C-CFs were improved compared with other CFRCs. It was believed that the more absorption of fracture energy into the larger interface caused an increase in fracture toughness and resistance to crack propagation.

• 대한공업교육학회지
• /
• v.42 no.2
• /
• pp.47-66
• /
• 2017

As the necessity of humanistic education has recently been socially emphasized, aptitude and character test has been conducted in the stage of training instructors to focus on making them equipped with proper ability of humanistic education. Especially, considering characteristics of students in specialized high schools with stronger negative concept of ego along with higher proportion of students looking for job in early ages compared to regular high schools, instructors in specialized high schools need to pay more attention on humanistic education of students compared to those in regular high schools. Therefore, this study has developed social emotion learning (SEL) of preliminary teachers in specialized high schools and analyzed the influence of developed programs on characters in teaching positions of preliminary instructors in specialized high schools. In this study, ADDIE model has been used developing SEL programs, and developed programs were comprised of total six sessions. Social emotion learning has been performed on 27 preliminary teachers in experiment group, and regular academic education courses were given on 30 preliminary teachers in control group. At this time, as for class contents, 'self-recognition' has been dealt with in the first and second sessions followed by 'self-management' in the second and third sessions, 'adjustment in relationship' in the fourth session, 'responsible decision making' in the fifth session, and 'personal relationship' in the sixth session. Classes have been conducted for 90 minutes in average. Since intentional sampling method has been used in this study, difference of pre-scores between groups might influence on the difference on post-scores. Therefore, ANCOVA that adjusted the pre-scores to be consistent has been utilized. As a result, there was a significant difference on the post-scores in characters in teaching positions between experiment group and control group.

• Korean Journal of Materials Research
• /
• v.2 no.6
• /
• pp.452-460
• /
• 1992

Effects of the microalloyed elements, temperatures and cooling rates on the strength and toughness of the medium carbon microalloyed hot forging steels obtained by air cooling(A.C.) method and the low carbon microalloyed forging steels by direct quenching(D.Q.) method were investigated. Combined additions of V+Nb produced the optimum combination of strength and toughness with ferrite-pearlite structure of the medium carbon steel by the A.C. method. 831MPa in UTS and 52.1J in toughness were obtained for 0.40c+0.12V+0.07Nb. It was martensite structure for the low carbon steel by the D.Q. method. The highest UTS and toughness obtained by Mo additions were 855MPa and 108j by 0.12C+0.10V+0.03Nb+1.13Mo respectively. Especially, the toughness of the low carbon steel was twice better than that of the medium carbon steel. 110$0^{\circ}C$was more appropriate than 120$0^{\circ}C$ for the reheating and forging temperature and 1.$2^{\circ}C$ /s was the best cooling rate from the viewpoint of the strength and toughness. Multiple regression analysis was used to quantify the influence of the microalloyed elements, temperatures and cooling rates on the strength, toughness, austenite grain size, and the pearlite interlamellar spacing.

• Journal of Scientific & Technological Knowledge Infrastructure
• /
• s.3
• /
• pp.134-136
• /
• 2000

최근 문화, 예술, 과학 등 많은 분야에 걸쳐 컴퓨터 그래픽의 중요성이 부각되고 있다. 특히 컴퓨터 그래픽의 한 분야인 3D 그래픽은 영화, 광고, 게임, 교육 CAD/CAM, 과학적 가시화 등 많은 분야에서 널리 쓰이면서 그 중요성이 더욱 커졌다. 그러나 이와 관련된 국내 기술력은 외국의 기술력에 비해 많이 뒤쳐진 상태다. 국내의 컴퓨터 그래픽관련 기술력을 세계적인 수준으로 끌어올리기 위해 연구에 매진하고 있는 서강대학교 컴퓨터그래픽스연구실의 임인성 교수님을 만나보았다.

• Tunnel and Underground Space
• /
• v.19 no.2
• /
• pp.86-94
• /
• 2009

A three dimensional rock joint element was developed considering fracture mechanics and subcritical crack growth to simulate non-linear behavior and the progressive failure of rock joints. Using this 3-D joint element, joint shear tests of rock discontinuities were simulated by a numerical method. The asperities on the joint surface began to fail at stress levels lower than the rock fracture toughness and continued progressively due to subcritical crack growth. As a result of progressive failing in each and every asperity, the joint showed non-linear stress-time behavior including stress hardening/softening and the reaching of a residual stress.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
• /
• v.9 no.5
• /
• pp.281-290
• /
• 2019

The study aims to analyze teachers' perception of the "personality" area, which can be subjective in the in-depth interview process of selecting gifted children and is easily shunned due to its weak immediate effect. To this end, First, when asked about their difficulties as gifted teachers, many of them answered "professionalism and workload" and cited personality as the most important area to address in-depth interviews in selecting gifted students. It also recognized that personality interviews are necessary for the most basic virtues of education and social contribution, and cited cooperation, consideration, and concession as the sub-components to be dealt with in the personality interview. It was necessary to check whether each student's capabilities were evaluated in a variety of ways in an in-depth interview of the teacher's observing and recommending system. And it needed to be supplemented by in-depth observations such as the development of a valid question, camp or debate in the evaluation of the personality area. In order to reflect the needs of the education field, it will be necessary to supplement the personality interview in the gifted children's selection. And there is also a need to continue to study how to guide the personality education of already selected gifted children.

• The Journal of Internal Korean Medicine
• /
• v.36 no.1
• /
• pp.69-75
• /
• 2015

Objectives : To investigate the clinical features of drug-induced liver injury (DILI) and traditional Korean medicine (TKM) -based management. Methods : A female patient diagnosed with DILI caused by Western drugs had been treated with Oriental therapies, then the subjective clinical outcome and biochemical parameters were monitored. Results : A 73-year-old female had taken Western drugs (nonsteroidal anti-inflammatory and skeletal muscle relaxants) for about 3 months, and complained of severe abdominal discomfort and tiredness. Her RUCAM score was 9, which met the criteria for DILI (AST 90 IU/L, ALT 100 IU/L, ALP 191 IU/L, and GGT 614 IU/L). She was treated with herbal drugs, moxibustion, and acupuncture, and her symptoms completely resolved, with normalized hepatic enzymes within two weeks. Conclusions : This case report provides a clinical characteristic for a typical DILI caused by Western medicine, and shows an example of a TKM-based application.