• Geomechanics and Engineering
• /
• 제15권5호
• /
• pp.1113-1124
• /
• 2018

Geological dynamic hazards during deep coal mining are caused by the failure of a composite system consisting of the rock and coal layers, whereas the joint in coal affects the stability of the composite system. In this paper, the compression test simulations for the rock-coal combined body with single joint in coal were conducted using $PFC^{2D}$ software and especially the effects of joint length and joint angle on strength and failure characteristics in a rock-coal combined body were analyzed. The joint length and joint angle exhibit a deterioration effect on the strength and affect the failure modes. The deterioration effect of joint length of L on the strength can be neglected with a tiny variation at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ between the loading direction and joint direction. While, the deterioration effect of L on strength are relatively large at ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$. And the peak stress and peak strain decrease with the increase of L. Additionally, the deterioration effect of ${\alpha}$ on the strength becomes larger with the increase of L. With the increase of ${\alpha}$, the peak stress and peak strain first decrease and then increase, presenting "V-shaped" curves. And the peak stress and peak strain at ${\alpha}$ of $45^{\circ}$ are the smallest. Moreover, the failure mainly occurs within the coal and no apparent failure is observed for rock. At ${\alpha}$ between $30^{\circ}$ and $60^{\circ}$, the secondary shear cracks generated in or close to the joint tips, cause the structural instability failure of the combined body. Therefore, their failure models present as a shear failure along partial joint plane direction and partially cutting across the coal body or a shear failure along the joint plane direction. However, at ${\alpha}$ of $60^{\circ}$ and L of 10 mm, the "V-shaped" shear cracks cutting across the coal body cause its final failure. While crack nucleations at ${\alpha}$ of $0^{\circ}$ or $90^{\circ}$ are randomly distributed in the coal, the failure mode shows a V-shaped shear failure cutting across the coal body.

• 전기학회논문지
• /
• 제62권7호
• /
• pp.1009-1013
• /
• 2013

In this study, we developed a fiber-optic goniometer for the continuous measurement of knee joint angle which provides important medical information on Alzheimer's disease. The fiber-optic goniometer is composed of a light-emitting diode (LED), a plastic optical fiber (POF), and a voltage output photodiode (PD). As a sensing part of the fiber-optic goniometer, a unclad fiber with regular intervals of 1 mm was fabricated to improve efficiency of bending loss according to the angle variation of knee joint. The emitting light with a center wavelength of 470 nm from a LED is guided by a POF to the PD, the transmitted light is then attenuated by the bending loss inside the bent POF. The intensity variation of the light transmitted from the POF gives rise to a change in output voltage in the fiber-optic goniometer. Therefore, we measured the real-time output voltage of the proposed fiber-optic goniometer using the unclad fiber according to the knee joint angle. Through the repeated experiments, the fiber-optic goniometer shows that it has a reversibility and a wide measurable angle range.

• Physical Therapy Rehabilitation Science
• /
• 제10권4호
• /
• pp.450-456
• /
• 2021

Objective: Studies confirming the lumber spine kinematics of direct or indirect segmental mobility under the application of joint mobilization, which induces passive force on the spine, are insufficient.Therefore, this study aims to obtain the underlying clinical data by identifying direct or indirect segmental mobility produced by Maitland's PA mobilization technique. Design: Randomized controlled trial design. Methods: Thirty subjects with no back pain participated in this study. X-ray testing equipment (SIG-40-525, Ecoray Inc., Korea) was used to verify the segmented movement of their lumbar. Joint mobilization was performed by physiotherapists with more than 10 years of experience in prescription therapy, and radiography was performed once without PA joint mobilization and once without the mobilization for comparing the lumbar vertebrae before and after the mobilization. The radiographs taken were analyzed using the picture archiving and communication system (PACS) program to measure the spinal displacement, intervertebral height, intervertebral angle, and lumbar lordosis angle. Results: Significant differences were observed in the lumbar displacement, intervertebral angle, and lumbar lordosis angle in all lumbar vertebrae before and after the mobilization. The intervertebral height indicated significant differences in all ventral vertebrae and only in L3-L4 and L4-L5 in dorsal vertebrae. Conclusions: This study suggests that the segmental mobility produced through indirect approaches plays an important role in inducing therapeutic effects in patients with back pain.

• Archives of Reconstructive Microsurgery
• /
• 제12권2호
• /
• pp.93-98
• /
• 2003

Purpose : The purpose of this study is to investigate an occurrence of valgus deformity of ankle joint after vascularized fibular graft in children. Materials and Methods : Four children under 15 years who were surgically treated with vascularized fibular graft were studied. The age of the patients was from 4 years to 13 years, the follow-up period was from 24 months to 108 months. The causes of vascularized fibular graft were open fracture (1 case), congenital psuedarthrosis (2 cases), hypoplastic ulna (1 case). The tibiofibular synostosis was done in 3 cases and not in 1 case. We measured the tibiotalar angle and bimalleolar angle at immediately postoperative and final radiography, and checked ankle motion, pain, and instability of ankle joint. Results : The A-P mortise angle was not different between initial and final radiography in all cases. The intermalleolar angle increased in all cases at the final radiography. There were no pain, instability and limitation of ankle motion. Conclusion: We consider the tibiofibular synostosis can prevent from ankle valgus deformity after vascularized fibular graft in children.

• Advances in biomechanics and applications
• /
• 제1권1호
• /
• pp.57-66
• /
• 2014

The purpose of the study was to investigate the kinematics between the double collar-tie and double underhook Thai Boxing clinching positions. Ten amateur mixed martial arts athletes executed six knee strikes for both clinching positions with their dominant limb directed towards a target. A standard two-dimensional video motion analysis was conducted, and the results showed a statistical significant difference at the hip joint angle and the angular acceleration of the knee and ankle. Within both clinching positions, there was a statistically significant correlation between the hip and knee joint angles, hip and knee angular velocities, and hip angular acceleration. Between both clinching positions, there was a statistically significant correlation at the knee joint angle, knee angular velocity, and hip angular acceleration. This study demonstrates the importance of the hip and knee joint movements in both clinching positions, which implies the applications of strength training and flexibility at these joints for sports performance and injury prevention. It is suggested that future studies analyzing the non-dominant leg are warranted to fully understand the Thai Boxing clinch.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.65-68
• /
• 2004

In the seismical capacity evaluation for RC structure wall-slab joint is very important factor. Because lateral load is resistance element and gravity load resistance element are acted mutually in the wall-slab joint. In this paper, to improve the seismic capacity of the wall-slab joint in the existing wall type apartments experiment which improve and retrofit a seismic capacity by unequal angle bracing and carbon sheet attachment are carried out. These methods are also economic and simple in mitigating seismic hazard, improve earthquake-resistance performance, and reduce risk level of building occupants. From the experimental results, the change of strength, degration of stiffness, and energy dissipation are evaluated. It can be concluded that these methods are effective in improving the seismic performance.

• 한국운동역학회지
• /
• 제13권3호
• /
• pp.163-180
• /
• 2003

This paper aims at collecting the guantitative data of kenematic variables by analysing the gait patterns of the normal adult men and the handicapped. The gait motions were taped with 4 video cameras, the cinematographic analyses were performed by the DLT technique of three dimensional image treatment. The following results were obtained in the analysis of the variables: 1. The ratio of stance time and swing time did not show any significant difference in the groups of the normal men and the handicapped when both foot of the former and the right feet of the latter were compared. The stride peeriod time of these two groups were 1.12 and 1.11 second, respectively. 2. In the handicapped group, the step width was wider, the step length and stride length were shorter, and especially, the step length of the right foot was shorter, 3. The small vertical displacement of left toes of the handicapped group showed that the heal contact and the left midstance are almost simultaneous. 4. The two groups have almost the same horizontal displacement of the center of gravity and the same vertical rate of extension. In view of the velocity of the center of gravity the normal adults showed the constant speed of movement. However, the handicapped adults were reduced from the right midstance to the right toe-off. 5. The handicapped showed prominently low angle on the left toe-off in the ankle joint angle, they also had the tendency to walk in the patterns of extended knee in the knee joint angle. Both the handicapped and the normal had the hyperextension on the toe-off in the hip joint angle. In the back and front angle of body, both showed the slightly back-sided walking positions. 6. Both groups had the abduction of both feet in foot placement angle, but the handicapped did not show serious abduction of left midstance.

• International journal of advanced smart convergence
• /
• 제12권3호
• /
• pp.61-67
• /
• 2023

Gait analysis plays a key role in the research field of exploring and understanding human movement. By quantitatively analyzing the complexity of human movement and the various factors that influence it, it is possible to identify individual gait characteristics and abnormalities. This is especially true for people with walking difficulties or special circumstances, such as amputee, for example. This is because it can help us understand their gait characteristics and provide individualized rehabilitation plans. In this paper, we compare and analyze the differences in ankle joint motion and angles between normal and amputee. In particular, a filtering process was applied to the ankle joint angle data to obtain high accuracy results. The results of this study can contribute to a more accurate understanding and improvement of the gait patterns of normal and amputee.

• 한국정보통신학회논문지
• /
• 제22권10호
• /
• pp.1355-1360
• /
• 2018

헬스케어 산업은 빅데이타, ICT(Information and Communications Technologies), IT 기기 등의 결합으로 서비스 범위가 확대되고 관리가 생애주기 전반에 걸쳐 이뤄질 것으로 예상된다. 본 논문은 헬스케어의 한 분야로 엄지손가락에 대한 손허리손가락관절굽힘과 손가락뼈사이관절굽힘에 대하여 알아보도록 한다. 손허리손가락관절굽힘은 엄지 손허리손가락 관절을 구부리는 것을 말하고 손가락뼈사이관절굽힘은 엄지손가락뼈사이 관절을 구부리는 것을 말한다. 관절을 구부릴 때 일정한 정해진 각도에 미달하거나 통증을 느끼면 이상이 발생한 것이다. 또한 엄지손가락관절의 이상에 대한 예방법과 치료법도 제시하였다. 50대 50명을 대상으로 엄지손가락 관절에서 손허리손가락관절굽힘과 손가락뼈사이관절굽힘에 대한 실험을 수행하였다. 본 시스템은 몸의 일부에 한정되어 있지만, 이를 부분적으로 확대해 나간다면 빅데이타 헬스케어시스템 구축의 기반이 될 것이다.

• 한국지반공학회논문집
• /
• 제25권10호
• /
• pp.17-30
• /
• 2009

지하에 공동을 건설하는 터널 공사의 경우 초기 응력의 집중 및 발파와 같은 시공단계에서의 과도한 에너지의 적용으로 인하여 주변 암반에 손상을 발생시킨다. 이러한 손상의 발생은 터널에 작용하는 하중 및 터널 주변 암반의 흐름조건에 상당한 영향을 끼친다. 이러한 이유로 터널 주변에 발생하는 손상구간에 대하여 다양한 연구가 수행되었다. 본 연구에서는 유사암석으로 제작된 공동이 존재하는 절리모델의 이축압축실험을 통하여 공동주변의 손상발생을 연구하였다. 절리면은 수평면과 $30^{\circ}$, $45^{\circ}$, $60^{\circ}$의 조건으로 형성되었으며, 초조강시멘트 재료를 이용하여 유사절리모델을 제작하였다. 이축압축 실험결과 공동주변에서는 절리면에 수직한 방향으로 인장균열의 발생이 관측되었으며, 균열의 진행으로 인하여 암반블록이 형성되었으며, 진행하는 인장균열이 다른 절리면에 도달하여 암반블록이 완전히 형성된 경우 탈락하는 과정을 보였다. 이러한 인장균열의 진전은 절리면의 각도에 따라 상이한데 절리면의 각도가 클수록 안정적이며 진행성의 균열 진전 양상이 관측되었다. 이러한 인장균열의 발달은 절리면으로 구성된 암편을 보로 가정 할 경우 공동의 곡률로 인한 기하학적 형상의 불규칙성으로 인하여 모멘트가 작용하는 것으로 판단된다. 이상의 실험결과를 입자요소해석 방법을 기반으로 하는 PFC 2D를 이용하여 모사하였다. 해석결과 실험에서 관측한 바와 같이 절리면 각도가 작을수록 손상대의 폭은 넓어지며 인장균열의 진행에 의한 암반블록의 형성이 관측되었다. 또한 상호작용이 발생하는 균열을 조사한 결과 수치해석에서도 절리면의 각도가 작은 조건에서 진행성의 파괴가 나타났다.