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평직구조 CFRP 적층판 복합재의 강도 및 균열진전특성에 대한 AE 평가
윤유성,권오헌 한국안전학회 2004 한국안전학회지 Vol.19 No.1
The mechanical strength and crack propagation of plain woven carbon fiber fabric laminate composites are examined by acoustic emission(AE). AE signals are measured during the tensile test and fracture tests. Thus, the relationship between AE signal and load-displacement curves and crack extension length are shown. Also the fracture mechanisms in terms of AE characteristics are discussed in viewpoint of crack propagation behavior.
윤유성,권오헌,고성석 한국산업안전학회 2002 한국안전학회지 Vol.17 No.2
Recently the car and elevator accidents as well as the fire, explosion and collapse increased. The passenger elevator accident from 1993 year to 2001 has about 56.7% of total accidents and the human victims of 180according to the Korea Elevator Safety Institute. Accident cause and prevention were investigated for the elevator having the fall, impact and narrowness accident types. The prevention and protection methods of the elevator accident from analysis results were suggested by comparing and analogizing the accident statistics about the accident investigation of the passenger elevator according to the elevator accidents.
Comparative Analysis of Tuberculous Lymphadenitis and Kikuchi Disease of the Neck
윤유성,한종규,신형철,김영통,배상병,조성식 대한영상의학회 2014 대한영상의학회지 Vol.71 No.1
Purpose: To compare the clinical and CT manifestations of Kikuchi disease (KD) and tuberculous lymphadenitis (TL). Materials and Methods: 111 patients with TL (55 men, 56 women, mean age 38.6 years, range 13--80 years) and 73 patients with KD (24 men, 49 women, mean age 26.8 years, range 8--61 years) were included in the study. Two observers independently compared sex, age, peripheral white blood cells, erythrocyte sedimentation rate (ESR), nodal distribution, nodal bilaterality, perinodal fat infiltration, muscle abscess, nodal conglomeration, necrotic and non-necrotic lymph nodes in the patients with TL and KD. Results: KD patients showed a female predominance (67.1%). Patients with TL were older. Leukocytopenia and increased ESR were more frequent in patients with KD. KD more commonly affected lymph nodes in level II, III, and V, while TL more commonly involved lymph nodes in the upper paratracheal area. Perinodal fat infiltration was more frequent in KD. Muscle abscess was seen in patients with TL only (14%). Necrotic lymph nodes were more frequent in TL. A thin type was more frequent in TL. Conclusion: KD showed female predominance, leukocytopenia, increased ESR, involvement of levels II, III, and V and frequent perinodal fat infiltration. TL patients were older than KD patients, were commonly affected in the upper paratracheal area, abscesses were shown only in this group and thin type necrotic lymph nodes were more frequent.
측면 홈을 가지는 STS316 CT시험편의 정적 성장균열에 대한 프랙탈 기하학의 응용
윤유성,권오헌 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4
The application of fractal concept provides an useful method in the study for the quantitative analysis of irregular variations like fracture surfaces and crack profiles. Fractal curves have characteristics that represents a self-similarity based on the fractal dimension. The fractal dimensions were obtained by the box counting method. In this report, we obtained the nearly stable fractal dimensions of fracture crack profiles for STS316 with CT specimens as the crack advances and the relationships between crack length and fractal dimension. Moreover fractal fracture parameter that corresponds to J-R curve is shown by the relationships between fractal dimension and crack extension. From the results, we concluded that the crack extension of high toughness material also shows the fractal characteristics, which can be used in order to evaluate the crack life precisely.
[0/90 0 ]s CFRP 복합재의 드릴작업손상과정 모니터링에 대한 AE의 적용
윤유성,권오헌,Yun, Yu-Seong,Gwon, O-Heon 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.6
In recent years, CFRP composite materials have been increasingly used in various fields of engineering because of a high specific strength and stiffness properties. Drilling is one of the most impo rtant cutting processes that are generally carried out on CFRP materials owing to the need for the structural integration. However, delamination are often occurred as one of the drilling damages. Therefore, there are needs studying for the relationships between CFRP drilling and delamination in order to avoid low strength of the structures and inaccuracies of the integration. In this study, AE signals and thrust forces were used for the evaluations of the delamination from a drilling process in [0/900]s CFRP materials. And the drilling damage processes were observed and measured by a real time monitoring technique with a video camera. From the results, we found that the relationships between the delamination from drilling and AE characteristics and drill thrust forces for [0/900]s CFRP composites. Also, we proposed the monitoring method for a visual analysis of drilling damages.
윤유성,윤영철 대한초음파의학회 2020 ULTRASONOGRAPHY Vol.39 No.3
Purpose: The objectives of this study were to demonstrate the benefits of ultrasonography-guided intra-articular steroid injection in the hip (UISIH) for the treatment of partial tear or degeneration of the round ligament of the femur and to determine the prognostic factors for this treatment. Methods: We retrospectively analyzed the records of 40 patients who were diagnosed with a partial tear or degeneration of the round ligament of the femur and who underwent UISIH between August 2014 and November 2018. The inclusion criteria were a lack of history of UISIH or other interventional procedure and the presence of follow-up records after the hip injection. The short-term clinical outcome was evaluated at the first follow-up appointment after UISIH. Possible prognostic factors for UISIH such as age, sex, injection side, and average follow-up time were analyzed using the chi-square test, the Fisher exact test, and the t test. Results: UISIH was found to have been effective in 35 of the 40 patients (87.5%) at the first follow-up visit. The average follow-up time was 43 days. No significant differences were observed in the clinical outcome of UISIH with respect to age, sex, injection side, or follow-up time. Conclusion: In this study, we demonstrated that UISIH was a safe and effective treatment in patients with a partial tear or degeneration of the round ligament of the femur over the course of short-term follow-up. Age, sex, injection side, and follow-up time were not identified as prognostic factors for this treatment.