• 대한금속재료학회지
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• 제47권8호
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• pp.494-499
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• 2009

As a novel method to produce a steel beam with 6mm thickness for buildings, a continuous roll forming process is reported. The roll shape is asymmetric and consists of 6 pairs of rollers to bend the steel plate from $0^{\circ}$ to $90^{\circ}$. Results obtained upon application of the roll forming process showed that the angle of the section plate is $90^{\circ}$. However, defects such as bowing and camber as high as 3.2 [$^{\circ}/m$] were observed. A FEM (Finite Element Method) analysis was applied to investigate the causes of the results for the region between rollers no. 5 and no. 6. The results of a FEM simulation of deformation and stress showed that there are some strong peak stresses on the upper surface and bottom surface of the material. The positions of the peak stresses did not show a correspondence between the upper and bottom surfaces. Thus, the defects in the process of roll forming with a 6 mm thick steel plate occur by the unbalanced stresses between the upper surface and bottom surface of the material in this study.

• 한국수자원학회논문집
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• 제37권7호
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• pp.527-540
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• 2004

다중 만곡부에서의 주흐름과 이차류의 흐름 특성을 분석하기 위하여 중심각 120$^{\circ}$인 두 개의 만곡부로 이루어진 사행수로에서 실험을 수행하였다. 실험수로의 횡단면은 직사각형과 곡선형 두 가지 형태로 제작하였으며, 곡선형 단면 형상 결정에는 베타함수를 이용하였다. 3차원 유속장의 측정은 micro-ADV를 이용하였다. 실험결과, 직사각형 수로에서 주흐름은 수로의 가장 짧은 경로를 따라 발생하였으며, 이는 기존 연구자들의 결과와 일치한다. 곡선형 수로에서도 주흐름이 직사각형 수로에서의 주흐름의 거동과 비슷한 양상을 보이는 것으로 밝혀졌다. 곡선형 수로에서의 실험결과가 실제 자연하천의 만곡부에서의 주흐름 거동(최심선을 따라 발생)과 상이하게 나타나는 이유는 실험수로의 바닥 조도와 사행도에 기인한 것으로 사료된다. 이차류의 정량적인 분석을 위하여 흐름함수를 도입한 결과, 만곡부에서 주 셀 뿐만 아니라 바깥제방 셀의 위치 및 형태를 확인할 수 있었다. 또한 이차류 강도를 계산한 결과, 직사각형 및 곡선형 수로에서 최대값은 두 번째 만곡부의 정점 부근에서 가장 크게 나타나며 곡선형 수로의 이차류의 강도가 직사각형 수로의 값보다 크게 나타나고 있음을 알 수 있었다. 직사각형 수로의 경우, 하폭 대 수심비가 커질수록 이차류의 강도가 증가하고 있음을 확인하였다.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3833-3838
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• 2009

본 논문은 산업용 로봇을 이용하여 운동화의 특성을 측정하는 측정장비를 소개한다. 여기서 사용된 로봇은 6관절의 퓨마타입 로봇(삼성전자의 FARA AT2 모델)을 인간의 보행 동작을 구현할 수 있도록 보완하였다. 보행 동작은 고속카메라로 분석한 후, 로봇 관절각들을 추출하여 동작구현에 사용한다. 3가지 종류의 경도 아웃솔(신발 겉창)로 만들어진 신발 시편을 준비하고, 이 로봇 시스템을 이용하여 걸음동작을 구현하여 신발에 따른 지면 충격력을 측정한다. 걸음동작에서 발생하는 발 앞축 부분을 굽히기 위해 요구되는 굽힘 모멘트의 측정과 걸음동작에서 발생하는 요동현상의 측정에 사용한다. 동일한 압축변형을 유지하도록 시스템을 설정하고, 신발을 측정한 결과 아웃솔의 경도에 따라 지면반력의 크기는 선형적으로 증가하는 추세가 관찰되었다. 또한 굽힘 모멘트와 요동현상 역시 아웃솔의 경도에 따라 선형적으로 증가하는 추세가 관찰되었다. 상기의 몇 가지 실험을 통하여, 본 로봇 시스템은 일관성 있는 실험결과를 제공하였으며, 따라서 산업용 로봇을 이용하여 신발의 유용한 특성 정보 도출이 가능하며, 추후 신발설계의 활용에 대한 가능성을 보여준다.

• 한국운동역학회지
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• 제17권1호
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• pp.145-153
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• 2007

The purpose of this study is to compare and analyze the phase-by-phase elapsed time, the COG, the body joint angle changes and the angular velocities of each phase of Handspring Salto Forward Piked performed by 4 college gymnasts through 3D movement analysis program. 1. The average elapsed time for each phase was .13sec for Phase 1, .18sec for Phase 2, .4sec for Phase 3, and .3sec for Phase 5. The elapsed time for Phase 1 to Phase 3 handspring was .35sec on average and the elapsed time for Phase 4 to Phase 5 handspring salto forward piked was .7sec on average. And so it showed that the whole elapsed time was 1.44sec. 2. The average horizontal changes of COG were 93.2 cm at E1, 138. 5 cm at E2, 215.7 cm at E3, 369.2 cm at E4, 450.7 cm at E5, and 553.1 cm at E6. The average vertical changes of COG were 83.1 cm at E1, 71.3 cm at E2, 78.9 cm at E3, 93.7 cm at E4, 150.8 cm at E5, and 97.2 cm at E6. 3. The average shoulder joint angles at each phase were 131.6 deg at E1, 153.5 deg at E2, 135.4 deg at E3, 113.4 deg at E4, 39.6 deg at E5, and 67.5 deg at E6. And the average hip joint angles at each phase were 82.2 deg at E1, 60 deg at E2, 101.9 deg at E3, 161.2 deg at E4, 97.7 deg at E5, and 167 deg at E6. 4. The average shoulder joint angular velocities at each phase were 130.9deg/s E1, 73.1 deg/s at E2, -133.9 deg/s at E3, -194.4 deg/s at E4, 29.4 deg/s at E5, and -50.1 deg/s at E6. And the average hip joint angular velocities at each phase were -154.7 deg/s E1, -96.5 deg/s at E2, 495.9 deg/s at E3, 281.5 deg/s at E4, 90.3 deg/s at E5, and 181.7 deg/s at E6. The results shows that, as for the performance of handspring salto forward piked, it is important to move in short time and horizontally from the hop step to the point to place the hands on the floor and jump, and to stretch the hip joints as much as possible after the displacement of the hands and to keep the hip joints stretched and high in the vertical position at the takeoff. And it is also important to bend the shoulder joints and the hip joints fast and spin as much as possible after the takeoff, and to decrease the speed of spinning by bending he shoulder joints and the hip joints quickly after the highest point of COG and make a stable landing.

• 콘크리트학회논문집
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• 제14권3호
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• pp.357-364
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• 2002

CLWL-DCB 시험편에 대한 변위제어 파괴실험으로 381mm의 균열성장에 대한 저항곡선이 유도되었다. 변형률 게이지를 사용하여 측정된 평균 균열성장속도는 0.70 mm/sec와 55mm/sec이었다. 초기균열에서 측정된 회전각도는 0.70 mm/sec와 55mm/sec의 균열속도에 대해 각각 최소한 171mm와 93mm의 균열성장 이전에 특이성이 존재하는 것을 보여주었다. 저항곡선의 최대 기울기는 0.70mm/sec 균열속도에 대해 25.4mm와 88.9mm 그리고 55mm/sec 균열속도에 대해 50.8 mm와 127mm의 균열성장길이 사이에서 발생되며, 미소균열 국부화에 의한 것으로 판단된다. 빠른 균열속도에서 미소균열성장 구역은 보다 길게 형성되며, 미소균열의 국부화 동안에도 큰 균열성장을 보였다. 0.70mm/sec 균열속도의 파괴저항은 152.4mm의 균열성장 이후에 평균 파괴에너지율의 약 70%인 143N/m의 비교적 일정한 값을 유지하였다. 55mm/sec 균열속도는 254mm 균열성장에서 최대 파괴저항 245N/m까지 증가한 후 파괴저항의 감소되어 불안정 균열성장이 발생될 수 있음을 보여준다. 55mm/sec 균열속도의 저항곡선은 TPB 실험과 유사하여, 시험편의 크기가 작거나 균열의 속도가 빠른 경우에 취성거동을 할 수 있는 것을 보여준다.

• 대한통합의학회지
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• 제8권4호
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• pp.223-230
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• 2020

Purpose : The purpose of this study was to examine the effects of tools (i., extracorporeal shock wave therapy, massage gun, and foam roller) on range of motion, muscle tone and pain threshold among patients with hamstring stiffness. Methods : Fourteen participants with hamstrings stiffness were recruited. Interventions were performed 6 times, and each session was for 30 seconds using the three tools. The range of motion, muscle tone, and pain threshold were measured. The order of the use of the three tools was randomly determined. The foam roller was made to move from the bottom of the hip crease to the upper part of the back of the hamstring. Additionally, velocity 5 vibration stimulation was performed on the hamstring using a massage gun. Moreover, vibration stimulation was performed on the hamstring with extracorporeal shock wave therapy 5 minutes, 5 Hz, and 1,500 strokes. The flexibility of the posterior thigh muscle was based on maintaining the knee and hip joints in a 90 ° bend in the supine position. The joint angle of the knee was measured, when the knee was actively extended, at the maximum point where the posterior thigh muscle was stretched. The elasticity of the posterior thigh muscle was measured while the subject was prone and in a relaxed state without any force. Measurements were made at the muscle abdominal area of the semitendinosus muscle of the posterior femur, and the area to be measured was marked with a pen. The measurement of the tenderness threshold of the posterior femur was measured using a tenderness meter(Commander Algometer, J-Tech, USA). The force value at the point at which the pressure sensation change to pain was measured after applying vertical pressure to the posterior femur muscle, which was the halfway point between the ischial tuberosity and the popliteal surface of the subject lying on their stomach. Results : The extracorporeal shock wave therapy increased stiffness and, muscle tone, and caused changes in the pain threshold, whereas the other two tools had no effect on these indices. Conclusion : Extracorporeal shock wave therapy has important effects on range of motion and muscle stiffness and can be used in warmup protocols.

• Journal of Korean Neurosurgical Society
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• 제65권6호
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• pp.801-815
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• 2022

Objective : To evaluate the stent apposition of a low-profile visualized intraluminal support (LVIS) device in distal internal carotid artery (ICA) aneurysms, examine its correlation with clinical and angiographic outcomes, and determine the predictive factors of ischemic adverse events (IAEs) related to stent-assisted coiling. Methods : We retrospectively analyzed a prospectively maintained database of 183 patients between January 2017 and February 2020. The carotid siphon from the cavernous ICA to the ICA terminus was divided into posterior, anterior, and superior bends. The anterior bends were categorized into angled (V) and non-angled (C, U, and S) types depending on the morphology and measured angles. Complete stent apposition (CSA) and incomplete stent apposition (ISA) were evaluated using unsubtracted angiography and flat-panel detector computed tomography. Dual antiplatelet therapy with aspirin 200 mg and clopidogrel 75 mg was administered. Clopidogrel resistance was defined as fewer responders (≥10%, <40%) and non-responders (<10%) based on the percent inhibition (%INH) of the VerifyNow system. These were counteracted by a dose escalation to 150 mg for fewer responders or substitution with cilostazol 200 mg for non-responders. IAEs included intraoperative in-stent thrombosis, transient ischemic attack, cerebral infarction, and delayed in-stent stenosis. A multivariate logistic regression analysis was used to determine the predictive factors for ISA and IAEs. Results : There were 33 ISAs (18.0%) and 27 IAEs (14.8%). The anterior bend angle was narrower in ISA (-4.16°±25.18°) than in CSA (23.52°±23.13°) (p<0.001). The V- and S-types were independently correlated with the ISA (p<0.001). However, treatment outcomes, including IAEs (15.3% vs. 12.1%), aneurysmal complete occlusion (91.3% vs. 88.6%), and recanalization (none of them), did not differ between CSA and ISA (p>0.05). The %INH of 27 IAEs (13.78%±14.78%) was significantly lower than that of 156 non-IAEs (26.82%±20.23%) (p<0.001). Non-responders to clopidogrel were the only significant predictive factor for IAEs (p=0.001). Conclusion : The angled and tortuous anatomical peculiarity of the carotid siphon caused ISA of the LVIS device; however, it did not affect clinical and angiographic outcomes, while the non-responders to clopidogrel affected the IAEs related to stent-assisted coiling.