• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2282-2291
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• 2024

In this work we study the effects of different factors of dislocation loop on its obstacle strength when interacting with an edge dislocation. At first, the interaction model for dislocation and dislocation loop is established and the full and partial absorption mechanism is obtained. Then, the effect of temperature, size and burgers vector of dislocation loop are investigated. The relation between the obstacle strength and irradiation dose has been established, which bridges the irradiation source and microscale properties. Except that, the obstacle strength of C, Cr, Ni, Mn, Mo and P decorated dislocation loop is studied. Results show that the obstacle strength for dislocation loop decorated by alloy element decreases in the sequence of Cr, Ni, Mn, C, P and Mo, which could be used to help parameterize and validate crystal plasticity finite element model and therein integrated constitutive laws to enable accounting for irradiation-induced chemical segregation effects.

• PNF and Movement
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• 제21권1호
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• pp.119-128
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• 2023

Purpose: Obstacle crossing training is being used to improve the walking ability of stroke patients, but studies on which method is more effective when performing obstacle crossing training with an unaffected limb lead (OCT-ULL) and an affected limb lead (OCT-ALL) are not well known. As such, this study aims to compare the intervention effects of obstacle crossing training using unaffected limb leads (OCT-ULL) and obstacle crossing training using affected limb leads (OCT-ALL). Methods: In total, 25 patients with chronic stroke were studied and assigned randomly to the obstacle crossing training with unaffected limb leads (OCT-ULL) group or the obstacle crossing training with affected limb leads (OCT-ALL) group. A lower extremity strength test, balance and gait test, and fall efficacy test were conducted as preliminary tests, and all patients participated in the intervention for 30 minutes a day, five days a week for four weeks, and the same preliminary tests were conducted post-intervention. Results: Compared with the OCT-ALL group, the OCT-ULL group showed a significant improvement in the strength of the affected hip abductor muscle and in balance and gait, as well as in fall efficacy (p<.05). Conclusion: This study suggested that applying the OCT-ULL training method in the obstacle crossing training of stroke patients is more effective for improving balance and gait functions than OCT-ALL.

• 한국운동역학회지
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• 제17권4호
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• pp.141-148
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• 2007

Falls associated with tripping over an obstacle can be dangerous, yet little is known about the strategies used for stepping over obstacles in older Parkinson disease. The purpose of this study was to investigate the lower extremity muscle activity on the obstacle gait according to obstacle height in older Parkinson diseases. The obstacle gait of 7 older Parkinson disease was examined during a 5.0 m approach to, and while stepping over, obstacles of 0, 25, 52, and 152mm. Seven pairs of surface electrodes(Noraxon MyoResearch, USA) were attached to the right-hand side of the body to monitor the adductor longus(AL), gluteus medius(GME), gluteus maximus(GMA), biceps femoris(BF), rectus femoris(RF), gastrocnemius(GA), tibialis anterior(TA). Electromyography data were filtered using a 10Hz to 350 Hz Butterworth band-pass digital filter and normalized to the maximum value in the analyzed phases. A one-way ANOVA for repeated measures was employed for selected electromyography variables to analyze the differences of the height of four obstacles. The results showed significant differences between 0.0mm and 25, 52, and 152mm obstacle height in TA and GA activities during the second phase(swing phase). But the more increase obstacle height, the more not increase the muscle activities. This means that the Parkinson disease stepping over obstacle inefficiency. To prevent and reduce the frequency of falls, elderly Parkinson disease maintained and improved their balance, muscular strength, neuromuscular control and mobility.

• Journal of Advanced Marine Engineering and Technology
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• 제20권5호
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• pp.45-57
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• 1996

Flow characteristics and contamination behavior in a three-dimensional room with the desk-type obstacle have been investigated numerically by the k-${\varepsilon}$ two equation turbulence model. The room model has one supply opening on the ceiling and two exhaust openings on the side walls. Thirty six sets of calculation have been performed for twelve contamination sources of $1{\times}10^{-4}kg_c/(m^3{\cdot}s)$ strength at different inlet velocities(0.1, 1, 10m/s). This study can conclude that the source points of contaminant are located near the obstacle edge of Z-axis, at which the maximum contaminant diffusion fields are occured.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.83-84
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Therefore, in this research, the proper use of VMA was suggested to prevent segregation.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.56-57
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• 2020

The purpose of this study is to achieve a sufficient fluidity without segregation for normal compressive strength grade concrete mixture. The major obstacle of achieving fluidity of normal compressive strength grade concrete mixture is segregation. Hence, in this research, VMA was used to prevent segregation.

• 전기전자학회논문지
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• 제24권4호
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• pp.1064-1068
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• 2020

논문에서는 65 kHz 장파대역을 사용하는 단축형 지선식 안테나의 전파 장애물에 의한 근거리 전파전파 특성을 분석하였다. 구축되는 65 kHz 장파대역 단축형 지선식 안테나를 모델링하고, 전파 장애물인 산 높이와 안테나 근접도에 따른 모델링을 통하여 전파 장애물이 안테나 전파 특성에 미치는 영향을 분석하였다. 일반적인 송신 안테나 사이트에 인접한 산 높이와 안테나와의 이격거리를 적용할 경우, 약 1.7 dB 이내의 전계 강도 변화가 발생되었다. 그러나 전파 장애물과 안테나와의 일정한 이격거리 이상에서는 전파 장애물에 의한 영향이 무시될 정도의 전파전파 특성을 나타내었다. 본 논문의 결과는 65 kHz 동작 주파수를 갖는 송신국 안테나 사이트 설계 및 구축 운영에 활용될 수 있다.

• 해양환경안전학회지
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• 제14권4호
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• pp.333-338
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• 2008

해안 지역은 해수의 운동에너지의 대부분은 해안에서 소산되며 이 과정에서 해안의 토사 등이 유실된다. 수면에 돌출된 방파제에 비해 수중구조물은 해수의 유통을 가능하게 하고 해안선을 따라 해수순환을 가능케 한다. 이 연구에서는 해안 침식을 방지 기능을 갖는 수중구조물을 하부틈새를 갖는 수중장애물로 형상화 하고 후방의 흐름특성을 규명하였다. 실험은 Re =$1.2{\times}10^4$ 조건에서 2프레임 입자영상유속계를 이용하여 속도장을 계측하여 고찰하였다. 측정된 시간평균 속도분포를 분석한 결과 유선의 곡률 효과가 현저히 나타났으며 전단층 주위 유체의 유입 등의 영향으로 박리 전단층 내에서 커다란 와구조가 연속적으로 발생하였다. 또한 하부틈새의 크기가 증가할수록 재순환 영역의 중심이 후류로 이동하고 재순환영역의 강도도 약해지는 결과를 보였다.

• 한국운동역학회지
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• 제19권3호
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• pp.539-547
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• 2009

본 연구의 목적은 낙상 예방을 위한 12주간의 수중 운동 수행 후 장애물 보행의 특성을 운동학 및 운동역학적으로 분석하는 것이다. 여성 노인 8명이 참여하였으며, 대상자들은 수중 운동 전 후에 네 높이의 장애물(0, 2.5, 5.1, & 15.2cm)을 자기선호 속도로 넘었다. 수중 운동 수행 후 고관절의 최대각, 최소각, ROM(Range Of Motion)이 유의하게 증가하였으며, Swing 과 Stance 국면에서 소요시간은 줄어들었다. 수중 운동 후 모든 높이에서 보폭은 유의하게 증가하였고, 보간은 줄어들었다. 수중 운동 후 장애물을 넘는 순간 장애물과 오른발 사이의 수직 최단거리는 증가하였고(15.2cm 장애물 제외), 장애물을 넘는 속도는 증가하였다. 수중 운동 수행 후 제동력, 추진력, 제동 운동량, 추진 운동량은 통계적으로 유의하게 변화하였다. 12주간의 수중 운동은 여성 노인의 근력과 평형성을 향상시켰으며 이는 낙상과 관련된 장애물 보행의 운동학 및 운동역학적 변인의 변화를 가져와 여성 노인들이 장애물을 안전하고 신속하게 넘을 수 있었다. 따라서 노인에게 보행 능력 향상과 낙상 예방 운동으로 수중 운동이 추천된다.

• 한국세라믹학회지
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• 제45권10호
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• pp.600-604
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• 2008

Although titanium-ceramic systems have gained substantial interests in dental prosthetic field, bonding problem between porcelain and titanium has not been solved. Main obstacle in titanium-porcelain bonding is excessive oxidation of titanium during porcelain firing. The effects of several coating materials on the bonding strength of titanium-porcelain system were investigated in this study. RF sputtering and electroplating of platinum significantly increased the bonding strength of porcelain-titanium specimen. However, coatings of Ni-Au, Ir, and ceramics(zirconia and hydroxyapatite) did not showed a significant effect on bonding strength. Platinum might be a promising material for the protective layer of excessive oxidation of titanium during porcelain firing, resulting in increase in the bonding strength.