• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.5
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• pp.60-67
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• 2007

In this paper, a simulation method of the internal winding fault is proposed to calculate winding current and electromagnetic force in a distribution power transformer by suing FEM program. The model of the transformer is a single phase, 60[Hz], 1[MVA], 22.9[kV]/220[V], cable-type winding. The short-circuit current and electromagnetic force are calculated by FEM(Finite Element Method) program(Flux2D) and the results we verified with theoretical formula and PSPICE program. The simulation results are fairly good agreement with the other verified methods within 5[%] error rate. The turn-to-turn short-circuit current is 500 times of the rated current and the electromagnetic force is about $20{\sim}200times$. The method presented in this study may serve as one of the useful tools in the electromagnetic force analysis of the transformer winding behavior under the short circuit condition for design of the structure.

• The Korean Journal of Pain
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• v.13 no.1
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• pp.74-78
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• 2000

Background: Epidural Adhesiolysis is an interventional pain management technique for patients with low back pain. In addition to local anesthetics and corticosteroid, hypertonic saline (NaCl) are used for the technique. Present study was aimed to compare analgesic and adverse effects of two different concentration of hypertonic saline in Epidural Adhesiolysis. Methods: Fifty-three subjects with low back pain with radiculopathy were assigned to one of two epidural adhesiolysis treatment groups: 8% (Group I, n=26) or 10% (Group II, n=27) hypertonic saline. 17 G epidural needle was inserted at sacral hiatus and catheter was advanced untill its tip was located at lesion site under fluoroscopic guidance. Subjects in all treatment groups received epidural corticosteroid and local anesthetic. And then, hypertonic saline injection via catheter were carried out daily for 3 days. Evaluation included assessment of pain relief (Numerical Rating Scale; NRS) at post-epidural adhesiolysis 1, 2, 3 days, 1 week, and 1, 3 months. We also looked for complications of epidural adhesiolysis at different concentration of hypertonic saline. Results: Statistical analysis demonstrated that NRS was not significantly different between two groups during 3 months after epidural adhesiolysis. There were no major differences of complications between two groups and disappeard after a few months without residual sequelae. Conclusions: We conclude that epidural adhesiolysis using 8% hypertonic saline is effective for relief of low back pain with proven lumbosacral fibrosis without any residual sequelae compared with 10%.

• The Journal of the Acoustical Society of Korea
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• v.21 no.1
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• pp.73-81
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• 2002

The transmission of vibration energy through beam-plate junctions in vibration intensity analysis called power new analysis (PFA) has been studied. PFA is an analytic tool for the prediction of frequency averaged vibration response of built-up structures at medium to high frequency ranges. The power transmission and reflection coefficients between the semi-infinite beam and plate are estimated using the wave transmission approach. For the application of the power coefficients to practical complex structures, the numerical methods, such as finite element method are needed to be adapted to the power flow governing equation. To solve the discontinuity of energy density at the joint, joint matrix is developed using energy flow coupling relationships at the beam-plate joint. Using the joint matrix developed in this paper, an idealized ship stem part is modeled with finite element program, and vibration energy density and intensity are calculated.

• Journal of Institute of Control, Robotics and Systems
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• v.12 no.3
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• pp.208-220
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• 2006

Energy of wheeled mobile robot is usually supplied by batteries. In order to extend operation time of mobile robots, it is necessary to minimize the energy consumption. The energy is dissipated mostly in the motors, which strongly depends on the velocity profile. This paper investigates various 3-step (acceleration - cruise - deceleration) speed control methods to minimize a new energy object function which considers the practical energy consumption dissipated in motors related to motor control input, velocity profile, and motor dynamics. We performed an analysis on the energy consumption various velocity profile patterns generated by standard control input such as step input, ramp input, parabolic input, and exponential input. Based on these standard control inputs, we analyzed the six 3-step velocity profile patterns: E-C-E, P-C-P, R-C-R, S-C-S, R-C-S, and S-C-R (S means a step control input, R means a ramp control input, P means a parabolic control input, and E means an exponential control input, C means a constant cruise velocity), and suggested an efficient iterative search algorithm with binary search which can find the numerical solution quickly. We performed various computer simulations to show the performance of the energy-optimal 3-step speed control in comparison with a conventional 3-step speed control with a reasonable constant acceleration as a benchmark. Simulation results show that the E-C-E is the most energy efficient 3-step velocity profile pattern, which enables wheeled mobile robot to extend working time up to 50%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7C
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• pp.715-723
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• 2009

In this paper, we propose a new detection method called dual-cell combining (DCC) detection for the acquisition in time of spread spectrum codes in the presence of residual frequency offset (RFO). When the RFO exists, the correlation peak used for detection during the acquisition process is split into two neighboring peaks with smaller amplitudes, resulting in considerable degradation in the overall acquisition performance of conventional methods. In the DCC detection method, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the RFO can be alleviated. Numerical results show that the DCC detection method can offer better mean-time-to-synchrouization performance than the conventional method based on the cell-by-cell detection.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.145-153
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• 1996

The fracture process zone in concrete is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important roles. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominani: mechanism governing the fracture process of concrete. Fracture mechanics does work for concrete provided that the fracture process zone is being considered, so that the development of model for the fracture process zone is most important to describe fracture phenomena in concrete. In this paper the bridging zone, which is a part of extended rnacrocrack with stresses transmitted by aggregates in concrete, is modelled by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the analysis of progressive cracking in concrete based on the discrete crack approach: one with crack element, the other without crack element. The advantage of the technique with crack element is that it dees not need to update the mesh topology to follow the progressive cracking. Numerical results by the techniques are demonstrated.

• Journal of Korean Neurosurgical Society
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• v.58 no.3
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• pp.225-230
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• 2015

Objective : The clinical outcomes according to the radiological results after cervical total disc replacement (TDR) are not well established. Here, the authors reviewed the clinical results according to the asymmetry in radiographs. Methods : This retrospective analysis included patients after TDR ($Mobi-C^{(R)}$ disc) with at least 12 months follow up, and the clinical and radiological data were obtained preoperatively and postoperatively for 12 months. Clinical outcome measures numerical rating scale (NRS) score for neck pain, visual analog scale (VAS) for arm pain, and the Oswestry disability index (ODI) value. The asymmetries of TDRs were evaluated on the anterior-posterior (AP) and the lateral radiographs, and the radiographic adjacent segment degenerations were evaluated for 12 months. Results : A total of 24 patients (one level cervical TDR; 10 male and 14 female; aged $41.50{\pm}8.35years$) were included in this study. The clinical results including NRS for neck pain, VAS for arm pain, and ODIs were similar between the normal and asymmetrized TDRs in AP and lateral radiographs. The radiographic adjacent segment degenerations were significantly increased in deviated TDRs (AP >10 mm asymmetry and lateral>10 mm asymmetry). Conclusion : Asymmetrical location of TDR is not related to the clinical outcomes, but related to the risk of radiographic adjacent disc segment degeneration.

• Journal of Korean Neurosurgical Society
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• v.50 no.6
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• pp.497-502
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• 2011

Objective : This study was conducted to compare the effect of etomidate with that of thiopental on brain protection during temporary vessel occlusion, which was measured by burst suppression rate (BSR) with the Bispectral Index (BIS) monitor. Methods : Temporary parent artery occlusion was performed in forty one patients during cerebral aneurysm surgery. They were randomly assigned to one of two groups. General anesthesia was induced and maintained with 1.5-2.5 vol% sevoflurane and 50% $N_2O$. The pharmacological burst suppression (BS) was induced by a bolus injection of thiopental (5 mg/kg, group T) or etomidate (0.3 mg/kg, group E) according to randomization prior to surgery. After administration of drugs, the hemodynamic variables, the onset time of BS, the numerical values of BIS and BSR were recorded at every minutes. Results : There were no significant differences of the demographics, the BIS numbers and the hemodynamic variables prior to injection of drugs. The durations of burst suppression in group E ($11.1{\pm}6.8$ min) were not statistically different from that of group T ($11.1{\pm}5.6$ min) and nearly same pattern of burst suppression were shown in both groups. More phenylephrine was required to maintain normal blood pressure in the group T. Conclusion : Thiopental and etomidate have same duration and a similar magnitude of burst suppression with conventional doses during temporary arterial occlusion. These findings suggest that additional administration of either drug is needed to ensure the BS when the temporary occlusion time exceed more than 11 minutes. Etomidate can be a safer substitute for thiopental in aneurysm surgery.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.15 no.1
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• pp.87-94
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• 2011

Objectives: The purpose of our study was to verify whether the Seven Emotions evaluated by Guibi-Tang questionnaire (GTQ) were predictive of self-awareness level of one's quality of life (QOL). Methods: Eighty volunteers participated in this study and completed the GTQ. In addition, the volunteers were asked to answer one's self-awareness of the QOL using numerical scale. Factor analysis was conducted for extraction of GTQ factors. Structural Equation Model (SEM) was conducted to verify path structure. Results: The estimates of the four factors on the level of one's QOL demonstrated that Chest Factor (=-0.330) showed the highest level of correlation followed by the seven emotions (=-0.213); Deficient fire (=0.141); and Qi Deficiency (=-0.023). Model fit is $X^2$=34.740 (df=36), GFI=0.931, AGFI=0.873, NFI=0.867, RFI=0.797, IFI=0.975, TLI=1.006, CFI=1.009, RMSEA=0.000. Therefore, considering these values, SEM could be accepted as a workable model. Conclusions: Our study results suggest that According to SEM, The Seven Emotions evaluated by GTQ are predictable for self-awareness of one's QOL.

• Journal of KIISE:Information Networking
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• v.34 no.1
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• pp.41-47
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• 2007

The Hierarchical Mobile IPv6 (HMIPv6) has been proposed to accommodate frequent mobility of the Mobile Node and to reduce the signaling load. A Mobility Anchor Point is a router located in a network visited by the Mobile Node. The Mobile Node uses the Mobile Anchor Point as a local Home Agent. The absence of any protections between Mobile Node and Mobile Anchor Point may lead to malicious Mobile Nodes impersonating other legitimate ones or impersonating a Mobile Anchor Point. In this paper, we propose a mechanism of the secure Mobile Anther Point discovery in HMIPv6. The performance analysis and the numerical results presented in this paper show that our proposal has superior performance to other methods.