• Journal of Korean Neurosurgical Society
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• v.59 no.5
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• pp.471-477
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• 2016

Objectives : The correction of clinical and radiologic abnormalities in patients with symptomatic ossification of the posterior longitudinal ligament (OPLL) is the current mainstay of treatment. This study aimed to identify radiographic predictors of severity of myelopathy in patients with symptomatic OPLL. Methods : Fifty patients with symptomatic cervical OPLL were enrolled. Based on Japanese Orthopedic Association (JOA) scores, patients were divided into either the mild myelopathy (n=31) or severe myelopathy (n=19) group. All subjects underwent preoperative plain cervical roentgenogram, computed tomography (CT), and MR imaging (MRI). Radiological parameters (C2-7 sagittal vertical axis, SVA; C2-7 Cobb angle; C2-7 range of motion, ROM; OPLL occupying ratio; and compression angle) were compared. Compression angle of OPLL was defined as the angle between the cranial and caudal surfaces of OPLL at the maximum level of cord compression Results : The occupying ratio of the spinal canal, C2-7 Cobb angle, C2-7 SVA, types of OPLL, and C2-7 ROM of the cervical spine were not statistically different between the two groups. However, the OPLL compression angle was significantly greater (p=0.003) in the severe myelopathy group than in the mild myelopathy group and was inversely correlated with JOA score (r=-0.533, p<0.01). Furthermore, multivariate regression analysis demonstrated that the compression angle (B=-0.069, p<0.001) was significantly associated with JOA scores (R=0.647, p<0.005). Conclusion : Higher compression angles of OPLL have deleterious effects on the spinal cord and decrease preoperative JOA scores.

• Journal of the Korean Society for Railway
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• v.3 no.3
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• pp.109-116
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• 2000

An air spring which is a part of the railroad vehicle suspension system is used to reduce and absorb the vibration and the noise. Main components of the air spring are a cord reinforced rubber bellows, a upper plate, a lower plate and a stopper rubber spring. The characteristics of the air spring which are the load capacity, the vertical and the horizontal stiffness are determined by the configuration of the rubber bellows, the angle of cord, and the mechanical properties of cord. Computer simulations using a commercial finite element analysis codes are executed to predict and evaluate the load capacity and the stiffness. The appropriate shape and cord angle of the air spring are selected to meet the required specifications of the air spring. Several samples of the air spring are manufactured and experimentally evaluated. It is shown that the results by computer simulation arc in close agreement with the test results.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.11 no.1
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• pp.20-27
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• 2000

To determine what is the change of pre and postoperative voice and image analysis parameters and correlations between them, videostroboscopy was analyzed in each 18 patients with unilateral vocal cord paralyses or vocal polyps before and after the surgery from November, 1996 to April, 1999. The correlation between acoustic and aerodynamic parameters was investigated. The software-Videolink and $\pi$-View(Mediface Co, Seoul, Korea)-was used in a quantitative analysis. In unilateral vocal cord paralysis, the glottic angle is well correlated with maximum phonation time, jitter and shimmer preoperatively. The postoperative glottic angle is also correlated with preoperative maximum phonation time. In patients with the vocal polyp, the chink is postoperatively decreased, but the size of the chink and the polyp is not correlated with pre and postoperative voice analysis parameters. These findings reveal that glottic an and vocal fold angle are good indicators of e postoperative glottic configuration in unilateral vocal cord paralysis. Vocal fold ratio is also a useful indicator that represents the length of vocal folds. We consider that the computerized analysis through videostroboscopy is one of objective diagnostic methods in many voice disorders if we can measure a distance between the telelaryngoscope and vocal folds.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1183-1194
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• 2006

The aim of this study was to identify the characteristics of the flexion withdrawal reflex modulated by the hip angle and hip movement in spinal cord injury (SCI). The influence of the hip position and passive movement were tested in 6 subjects with chronic SCI. Each subject placed in a supine position and lower leg was fixed with the knee at 5 -45 degree flexion and the ankle at 25-40 degree plantar flexion. A train of 10 stimulus pulses were applied at 200 Hz to the skin of the medial arch to trigger flexion reflexes. From results of the regression analysis, static properties of normalized muscle activation of flexor muscles have the linear relationship with respect to hip angle (P< 0.05). In order to verify the neural contribution of flexion reflex, we compared the static and dynamic gains of estimated muscle activations with measured EMG of ankle flexor muscle. Form this study, we postulate that the torque and muscle response of flexion withdrawal reflex have linear relationship with hip angle and angular velocity.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.626-633
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• 2000

An air spring which is a part of the railroad vehicle suspension system is used to reduce and absorb the vibration and the noise. Main components of the air spying are a cord reinforced rubber bellows, a upper plate, a lower plate and a stopper rubber spring. The characteristics of the air spring which are the load capacity, the vertical and the horizontal stiffness are depended on the configuration of rubber bellows, the angle of cord and the mechanical properties of cord. The computer simulation using commercial finite element analysis codes are executed to predict and evaluate the load capacity and the stiffness. The appropriate shape and cord angle of the air suing are selected to adjust the required performance of the air spring. Several samples of the air spring are manufectured and experimented. It is shown that the results by computer simulation are in close agreement with the test results.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.3
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• pp.357-362
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• 2011

Air springs are prevalently used as suspension in train. However, air springs are seldom used in automobiles where they improve stability and comfort by enhancing the impact-relief, breaking, and cornering performance. Thus, this study proposed a new method to analyze air springs and obtained some reliable design parameter which can be utilized in vehicle suspension system in contrast to conventional method. Among air spring types of suspension, this study focused on sleeve type of air spring as an analysis model since it has potential for ameliorating the quality of automobiles, specifically in its stability and comfort improvement by decreasing the shock through rubber sleeve. As a methodology, this study used MARC, as a nonlinear finite element analysis program, in order to find out maximum stress and maximum strain depending on reinforcement cord's angle variation in sleeves. The properties were found through uniaxial tension and pure shear test, and they were developed using Ogden Foam which is an input program of MARC. As a result, the internal maximum stresses and deformation according to the changes of cord angle are obtained. Also, the results showed that the Young's modulus becomes smaller, then maximum stresses decrease. It is believed that these studies can be contributed in automobile suspension system.

• The tire
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• s.111
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• pp.20-29
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• 1984

유한요소법에 의하여 축대칭 정적하중을 받는 승용차용 래디알 타이어의 변형을 해석하였다. 요소는 8절점 parabolic-isoparametric 요소를 사용하였으며 타이어를 구성하는 cord-rubber복합체를 선형직교성을 갖는다고 가정하고, 그 복합체의 물성치를 간단한 식으로 표시하여 적용하였다. 공기압으로 인해 변형된 모양 및 cord에 작용하는 장력을 계산해 냈으며 이 변형된 모양을 plaster cast를 이용하여 측정한 실험치와 비교하였다. 또 타이어를 구성하는 구조가 달라지면 공기압으로 인하여 변형형태가 어떻게 변화하는가를 계산해 보았다. 이 결과로 belt의 cord수가 감소하거나 belt cord angle이 증가하면 타이어 외경이 증가함을 알 수 있다.

• Textile Coloration and Finishing
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• v.22 no.4
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• pp.300-305
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• 2010

Poly(ethylene terephthalate)(PET) tire cord has relatively lower adhesion properties caused by limited reacting sites. In order to improve the adhesion force between PET tire cord and rubber, an additional process to activate surface of PET has been employed. Atmospheric plasma was used to substitute the chemical finishing process of PET tire cord as a green dipping process. Contact angle was measured to confirm surface change of PET after plasma treatment. The treated PET tire cords with/without resorcinol-formaldehyde-latex(RFL) and unvulcanized rubber were vulcanized in a testing mold at $160^{\circ}C$. After atmospheric plasma treatment of PET tire cord, adhesion force was somewhat increased under some conditions.

• 연구논문집
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• s.26
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• pp.15-24
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• 1996

In this study, we performed the static analysis of a cord-reinforced rubber airspring and generated the three-dimensional half-symmetry model which use the finite-strain shell elements to model the airbag. the three-dimensional hydrostatic fluid elements to model the air-filled cavity, and the rebar elements to model the multi-ply nylon reinforcement of airbag. In addition, a three-dimensional rigid surface is used to define the contact between the airspring and metal bead. The air inside the airspring cavity has been modeled as a compressible fluid satisfying the ideal gas law. The conclusions of this study are as follows. 1) In the pressurization step of analysis, we could predict the change of vertical reaction force, cavity volume and pressure within the airspring. 2) In the second step of analyzing vertical static stiffness, the increase of the vertical load increases the vertical stiffness. 3) In case of changing the angle of nylon cord, the increase the angle of nylon cord increases the vertical stiffness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.245-248
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• 2008

This paper deals with the parameter study of roller leveling process of steel cord using finite element analysis. A simplified model of roller leveling process is constructed for the efficient numerical simulation considering the computing time. Using the constructed simulation scheme, the parameter study of main process parameters, such as back-tension and intermesh, is carried out in order to evaluate elastic recovery angle and roller force quantitatively. The effect of the initial shape of steel cord is also evaluated during the parameter study. And the mechanism of roller leveling process is verified by investigating the residual stress distribution.