• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.577-583
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• 2017

Objective : Laminoplasty is an effective surgical method for treating cervical degenerative disease. However, postoperative complications such as kyphosis, restriction of neck motion, and instability are often reported. Despite sufficient preoperative lordosis, this procedure often aggravates the lordotic curve of the cervical spine and straightens cervical alignment. Hence, it is important to examine preoperative risk factors associated with postoperative kyphotic alignment changes. Our study aimed to investigate preoperative radiologic parameters associated with kyphotic deformity post laminoplasty. Methods : We retrospectively reviewed the medical records of 49 patients who underwent open door laminoplasty for cervical spondylotic myelopathy (CSM) or ossification of the posterior longitudinal ligament (OPLL) at Pusan National University Yangsan Hospital between January 2011 and December 2015. Inclusion criteria were as follows : 1) preoperative diagnosis of OPLL or CSM, 2) no previous history of cervical spinal surgery, cervical trauma, tumor, or infection, 3) minimum of one-year follow-up post laminoplasty with proper radiologic examinations performed in outpatient clinics, and 4) cases showing C7 and T1 vertebral body in the preoperative cervical sagittal plane. The radiologic parameters examined included C2-C7 Cobb angles, T1 slope, C2-C7 sagittal vertical axis (SVA), range of motion (ROM) from C2-C7, segmental instability, and T2 signal change observed on magnetic resonance imaging (MRI). Clinical factors examined included preoperative modified Japanese Orthopedic Association scores, disease classification, duration of symptoms, and the range of operation levels. Results : Mean preoperative sagittal alignment was $13.01^{\circ}$ lordotic; $6.94^{\circ}$ lordotic postoperatively. Percentage of postoperative kyphosis was 80%. Patients were subdivided into two groups according to postoperative Cobb angle change; a control group (n=22) and kyphotic group (n=27). The kyphotic group consisted of patients with more than $5^{\circ}$ kyphotic angle change postoperatively. There were no differences in age, sex, C2-C7 Cobb angle, T1 slope, C2-C7 SVA, ROM from C2-C7, segmental instability, or T2 signal change. Multiple regression analysis revealed T1 slope had a strong relationship with postoperative cervical kyphosis. Likewise, correlation analysis revealed there was a statistical significance between T1 slope and postoperative Cobb angle change (p=0.035), and that there was a statistically significant relationship between T1 slope and C2-C7 SVA (p=0.001). Patients with higher preoperative T1 slope demonstrated loss of lordotic curvature postoperatively. Conclusion : Laminoplasty has a high probability of aggravating sagittal balance of the cervical spine. T1 slope is a good predictor of postoperative kyphotic changes of the cervical spine. Similarly, T1 slope is strongly correlated with C2-C7 SVA.

• Transactions of Materials Processing
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• v.28 no.6
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• pp.335-346
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• 2019

Thick plate forming is presented to manufacture a large and curved member of steam turbine diaphragm. Due to three-dimensional asymmetry of target geometry, it is hard to consistently keep the blank position in die cavity between forming punch and die. In order to relieve the position instability of the blank during the thick plate forming, a blank support structure is proposed to be composed of guide pins and linear bearing, and blank guide arm enlarged from both longitudinal ends of the thick blank. In this study, parametric investigations with regard to the geometric position and width of the blank guide arm are carried out. As main geometric parameters, 2 positions such as maximum curvature region and minimum one on a curved cross-section profile of the target shape are selected, and 14 widths of the blank guide arm are considered. Using 28 variable combinations, three-dimensional numerical simulations are performed to predict the appropriate range of the process parameters. The compatibility and validity of the blank support structure with the blank guide arm for the thick plate forming is verified through the thick plate forming experiments.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.277-280
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• 2009

Mechanism of combustion frequencies occurring during combustion is experimentally investigated in model combustor with V-gutter flameholder. this combustor has a long duct shape with a cross section area of $40{\times}40\;mm$. The v-gutter type flameholder with 14mm width is mounted at the bottom of combustor. Kerosene and methane were used as fuel, and these fuel were injected transversely into air crossflow. It is found that combustion frequencies were considered as 1L longitudinal mode caused by combustor geometry and vortex shedding mode of flameholder. And fuel phase effect and nozzle effect were also observed in the low frequency range.

• Archives of Reconstructive Microsurgery
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• v.9 no.1
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• pp.75-79
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• 2000

The foot plays a vital role in standing and gait. This function results from harmonious interaction of bones, joints, and soft tissue. An imbalance or a defect in such structures can lead to impaired function of the foot. The mid foot, composed of cunieforms, navicular and cuboid bone, plays a vital role in maintaining longitudinal and transverse arches and injury or defects to this region can cause instability of the foot. This paper reports a case of complex foot injury; soft tissue defect of dorsum of foot, and medial and intermediate cuneiform bone defect, reconstructed in a single stage using vascularized osteocutaneous fibular free flap. Segmented to fit the defects of medial and intermediate cuneiform bones and a skin paddle providing adequate coverage, restored the stability to the arches and function of the midfoot. The fibula osteocutaneous free flap has appealing characteristics for reconstruction of the foot and the complex mid foot injuries can be considered to the long list of indications.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1564-1570
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• 2007

There are normally two types of the energy absorbers used in the crashworthiness of trains. The first is a structure type, which mainly used in not only the primary structures of the train but also the crash energy absorbers at the accident. The second is a module type, which just absorbs the crash energy independent of the primary structures and attached to the structures of the train. The expansion and inversion tube are widely used as the module type crash energy absorbers, especially in the train. The tubes should not be buckled under the load acting on the end of the tube in longitudinal direction during absorbing the crash energy. The buckling stability of the tubes is affected by the boundary conditions, thickness and length of tube. In this study, the effects of the length and thickness of the tubes on the buckling load are studied by using the ABAQUS, a commercial finite element analysis program, and then presents the guideline to design the tube. The analysis processes to compute the buckling load consist of a linear buckling analysis and a nonlinear post-buckling analysis. The buckling modes are evaluated by the linear buckling analysis, as using these modes, the buckling loads are computed by the nonlinear post-buckling analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.119-128
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• 2001

Recently safety systems for the commercial vehicle have been rapidly developed. However, we still have many problems in the vehicle stability and the braking performance. Especially, a commercial vehicle may meet a dangerous braking condition when the vehicle is lightly loaded or empty and the road is wet or slippery. To design the air brake system for commercial vehicles, since the air brake system has many design variables, there must have been intensive researches on a method how to prevent dynamic instability and how to maximize the vehicle deceleration. In this study, mathematical models about an 8$\times$4 vehicle and an air brake system including an ABS controller have been constructed for computer simulation. Also, simple examples are applied to show the usefulness of the computer program. Designers can use this simulation program for understanding the braking characteristics of 8$\times$4 commercial vehicles such as trajectory, braking distance, longitudinal deceleration, lateral deceleration, and yaw rate on various road conditions.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.1
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• pp.162-168
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• 2008

A design objective for variable stability flight control system is to develop a controller of in-flight simulation capability that forces the aircraft being flown to follow the dynamics of other aircraft. This paper presents a model-following variable stability control system (VSS) for in-flight simulation which consists of feedforward and feedback control laws, the aircraft dynamic model to be simulated, and switching and fader logics to reduce the transient effect between two aircraft dynamics. The separate design techniques for feedforward and feedback control law proposals are based on model matching and augmented linear quadratic (LQ) techniques. The system allows pilots to select and engage VSS mode, and when deselected, the aircraft reverts to the baseline flight control system. Both the baseline flight control laws and VSS control laws are computed continuously during flight. Initialization of the state values are necessary to prevent instability, since VSS control laws have integrators and filters in longitudinal, and lateral/directional axes. This paper demonstrates and validates the effectiveness and quality of VSS with F-16 models embedded in T-50 in-flight simulation aircraft.

• Ocean Systems Engineering
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• v.1 no.1
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• pp.31-57
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• 2011

Impact pressure due to sloshing is of great concern for the ship owners, designers and builders of the LNG carriers regarding the safety of LNG containment system and hull structure. Sloshing of LNG in partially filled tank has been an active area of research with numerous experimental and numerical investigations over the past decade. In order to accurately predict the sloshing impact load, a new numerical method was developed for accurate resolution of violent sloshing flow inside a three-dimensional LNG tank including wave breaking, jet formation, gas entrapping and liquid-gas interaction. The sloshing flow inside a membrane-type LNG tank is simulated numerically using the Finite-Analytic Navier-Stokes (FANS) method. The governing equations for two-phase air and water flows are formulated in curvilinear coordinate system and discretized using the finite-analytic method on a non-staggered grid. Simulations were performed for LNG tank in transverse and longitudinal motions including horizontal, vertical, and rotational motions. The predicted impact pressures were compared with the corresponding experimental data. The validation results clearly illustrate the capability of the present two-phase FANS method for accurate prediction of impact pressure in sloshing LNG tank including violent free surface motion, three-dimensional instability and air trapping effects.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.555-558
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• 2010

This paper presents a design of solid rocket motor with high length to diameter applied composite propellant. Solid rocket motor with high L/D ratio can be generated erosive burning and combustion instability on longitudinal mode. Especially, Erosive burning can effectively prolong the initial pressure spike in some star grain motors. That is, the study shows design of grain, internal ballistics and structural analysis in order to perform system requirements.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.469-471
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• 2010

Supercavitating vehicles which cruise under water undergo high longitudinal force caused by thrust and drag. These combination may cause structural buckling. Static and dynamic buckling analysis method by using FEM can be used to predict this structural failure behavior. In this paper, some principles which include method for solution eigenvalue problem for buckling analysis are introduced. And before buckling analysis, we predicted some mode shape and natural frequency of cylindrical shell by using DIAMOND/IPSAP eigen-solver.