• 대한토목학회논문집
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• 제5권1호
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• pp.43-53
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• 1985

강도로교(鋼道路橋)에 있어서 가장 보편적으로 사용(使用)되고 있는 강교(鋼橋)(구형(矩形)보, 판항(鈑桁), 합성항(合成桁))에 대한 신뢰성설계규준(信賴性設計規準)을 제안(提案)하고, 또 하중(荷重)-저항계수(抵抗係數) 및 공칭안전율(公稱安全率)에 대한 이론적(理論的)인 근거를 제시(提示)하는 것이 본(本) 연구(硏究)의 주요(主要) 내용(內容)이다. Cornell의 MFOSM과 Lind-Hasofer의 AFOSM을 포함하는 주요 2차(次)모멘트 신뢰성(信賴性) 이론(理論)을 비교(比較) 분석(分析)함으로써 Lind-Hasofer의 근사식(近似式)과 대수정규형(對數正規型) 근사식(近似式)을 본(本) 연구(硏究)에서 제안(提案)하는 신뢰성(信賴性) 해석(解析) 및 설계규준(設計規準)의 유도에 사용함이 적절하다는 것을 알 수 있었다. Galambo의 이론(理論)에 의해 강구조부재(鋼構造部材)의 불확실량(不確實量) 산정(算定) 알고리즘을 유도하여 저항(抵抗)의 불확실량(不確實量)을 LRFD Format 및 SGST Format로 산정(算定)했으며, 하중(荷重)의 불확실량(不確實量)은 우리의 실정(實情)을 고려한 적절한 값을 택했다. 현행(現行) 강도로교(鋼道路橋) 설계규준(設計規準)에 따라 calibration함으로써 목표신뢰성지수(目標信賴性指數) ${\beta}_0=3.5$를 우리의 현실(現實)을 반영하는 최적치(最適値)로 선택하였다. 본(本) 연구(硏究)에서 강도로교(鋼道路橋)의 LRFD 신뢰성(信賴性) 설계규준(設計規準)은 일정(一定)한 신뢰성(信賴性)을 주는 보다 합리적(合理的)인 설계(設計)가 됨을 알 수 있었다.

• 한국강구조학회 논문집
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• 제22권4호
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• pp.313-324
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• 2010

본 연구에서는 반강접 접합부 배치에 따른 구조물 거동특성을 파악하기 위하여 KBC2005 건축구조설계기준으로 비가새 5층 철골 구조물을 설계하여 모든 접합부를 완전 강접합부와 반강접 접합부로 이상화한 경우 그리고 반강접 접합부를 수직배치 및 수평배치한 경우에 대하여 비탄성 시간이력 구조해석을 실시하였다. 철골 보 및 기둥의 모멘트-곡률 관계는 화이버모델을 이용하여 확인하였으며 반강접 접합부의 모멘트-회전각 관계는 3-매개변수 파워모델 그리고 철골 보, 기둥 및 접합부의 이력거동은 3-매개변수 모델을 이용하여 나타내었다. 4개 지진파에 대한 재현주기 2400년 위험수준에 해당하는 최대지반가속도와 5% 층간변위에 대한 푸쉬오버 구조해석의 최대밑면전단력 발생 최대지반가속도에 대하여 시간이력 구조해석을 실시하여 밑면전단력, 지붕층 변위, 층간변위, 접합부 요구연성도, 기둥, 보 및 접합부의 최대휨모멘트 그리고 소성힌지 분포 등을 확인하였다. 반강접 접합부를 수직적으로 외부에 배치할수록 최대밑면전단력과 층간변위는 감소하며, 수평적으로 상부층에 배치할수록 접합부 요구연성도가 감소하였다. 푸쉬오버 구조해석과 시간이력 구조해석에서 최대층간변위 발생 위치가 다르고 크기는 푸쉬오버 구조해석에서 과대평가되었다. 밑면전단력, 층간변위 및 접합부 요구연성도를 위한 가장 바람직한 반강접 접합부 배치는 수직적으로 외부에 배치하는 것이다.

• 한국전문물리치료학회지
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• 제11권1호
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• pp.53-67
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• 2004

This simulation study investigated the characteristics of normal gait, $30^{\circ}$ crouch gait, $30^{\circ}$ crouch/equinus gait, $45^{\circ}$ crouch gait, $45^{\circ}$ crouch/equinus gait. The knee flexion angles were restricted using a specially designed orthosis. This study was carried out in a motion analysis laboratory of the National Rehabilitation Center. Fifteen healthy male subjects were recruited for the study. The purposes of this study were (1) to compare spatiotemporal parameters, kinematics, and kinetic variables in the sagittal plane among the different gait, (2) to investigate the secondary compensatory strategy, and (3) to suggest biomechanical physical therapy treatment methods. The pattern and magnitude observed in each condition were similar to those of normal gait, except the peak knee extension moment of the unrestricted ankle motion-crouch gait. However, the speed of the $45^{\circ}$ crouch gait was half that of a normal gait. The ankle joint moment in the crouch/equinus gait showed the double-bump pattern commonly observed in children with spastic cerebral palsy, and there was no significant difference in gait speed as compared with normal gait. The peak ankle plantar-flexor moment and ankle power generated during the terminal stance in the crouch/equinus conditions were reduced as compared with normal and $45^{\circ}$ crouch gaits (p<.05). The crouch/equinus gait at the ankle joint was an effective compensatory mechanism. Since ankle plantarflexion contracture can be exacerbated secondary to the ankle compensatory strategy in the crouch/equinus gait, it is necessary to increase the range of ankle dorsiflexion and the strength of plantarflexion simultaneously to decrease the abnormal biomechanical advantages of the ankle joint.

• 한국지반공학회논문집
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• 제20권6호
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• pp.127-136
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• 2004

강성옹벽에 작용하는 주동토압의 크기와 분포형태에 영향을 미치는 아칭효과는 옹벽의 안정성과 옹벽 단면의 결정에도 영향을 미치게 된다. 따라서 본 연구에서는 평행이동하는 강성옹벽의 경우에 뒷채움재에서 발생하는 아칭효과가 옹벽에 작용하는 토압과 전도모멘트, 옹벽의 안정성, 그리고 옹벽의 단면에 미치는 영향을 규명하기 위하여 아칭효과를 고려해서 토압을 산정하는 백(2003a)의 제안식과 Coulomb의 토압이론으로부터 얻어진 결과들을 서로 비교하였다. 연구결과 $\phi$와 $\delta$의 크기에 관계없이 아칭효과를 고려했을 때의 주동토압이 Coulomb 토압보다 컸으며, 옹벽에 작용하는 전도모멘트도 아칭효과를 고려했을 때가 고려하지 않았을 때보다 큰 것으로 나타났다. 그리고 토압에 의해 옹벽의 각 위치에 유발되는 전단력과 모멘트을 비교한 결과 아칭효과를 고려했을 때의 전단력과 모멘트가 아칭효과를 고려하지 않았을 때보다 컸으며, 아칭효과의 고려 유무에 따라 옹벽에 유발되는 전단력의 차이와 모멘트의 차이는 옹벽의 저면으로부터 옹벽 높이의 0.02-0.08배되는 위치에서 최대가 되었다. 따라서 Coulomb의 토압이론에 근거해서 평행이동하는 강성옹벽을 설계하면 뒷채움재에서 발생하는 아칭효과로 인해 옹벽이 활동과 전도파괴에 대하여 불안정할 수 있다. 그리고 옹벽의 단면은 옹벽에 작용하는 전단력과 모멘트를 지지하기에 충분하지 않을 수 있으며, 이러한 옹벽 단면의 부족은 옹벽의 상부보다는 하부에서 심각하게 된다.

• 대한의용생체공학회:의공학회지
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• 제27권5호
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• pp.210-217
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• 2006

Many types of interspinous distraction devices (IDDs) have been recently developed as an alternative surgical treatment to laminectomy and fusion with pedicle screws for the treatment of the lumbar spinal stenosis (LSS). They are intended to keep the lumbar spine in a slightly flexed posture to relieve pain caused by narrowing of the spinal canal and vertebral foramen. However, their biomechanical efficacies are not well known. In this study, we evaluated the kinematic behaviors and changes in intradiscal pressure (IDP) of the porcine lumbar spine implanted with IDD. For kinematics analysis, five porcine lumbar spines (L2-L6) were used and the IDD was inserted at L4-L5. Three markers (${\phi}{\le}0.8mm$) were attached on each vertebra to define a rigid body motion for stereophotogrammetric assessment of the spinal motion in 3-D. A moment of 7.5Nm in flexion-extension, lateral bending, and axial rotation were imparted with a compressive force of 700N. Then, IDD was implanted at L3-L4. IDPs were measured using pressure transducer under compression (700N) and additional extension moment (700N+7.5Nm). In kinematic behaviors, insertion of IDD resulted in statistically significant decrease 42.8% at the implanted level in extension. There were considerable changes in ROM at the adjacent levels, but statistically insignificant. In other motions, there were no significant changes in ROM as well regardless of levels. IDPs at the surgical level (L3-L4) under compression and extension moment decreased by 12.9% and 18.8% respectively after surgery (p<0.05). At the superiorly adjacent levels, IDPs increased by 19.4% and 12.9% under compression and extension, respectively (p<0.05). Corresponding changes at the inferiorly adjacent levels were 29.4% and 6.9%, but they were statistically insignificant (p>0.05). The magnitude of pressure changes due to IDD, both at the operated and adjacent levels, were far less than the previously reported values with conventional fusion techniques. Our experimental results demonstrated the IDDs can be very effective in limiting the extension motion that may cause narrowing of the spinal canal and vertebral foramens while maintaining kinematic behaviors and disc pressures at the adjacent levels.

• Bulletin of the Korean Chemical Society
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• 제33권10호
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• pp.3423-3426
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• 2012

Dielectric measurement on binary mixtures of Allyl chloride (ALC) with 2-Pentanone (2-PE) and 2-Hexanone (2-HE) has been carried out over the entire concentration range using Time Domain Reflectometry (TDR) technique at various temperatures in microwave frequency range of 10 MHz to 10 GHz. The static dielectric constant, excess static dielectric constant (${\varepsilon}^E_S$), effective Kirkwood correlation factor ($g^{eff}$) of binary mixtures over entire concentration range were determined to study the effect of increasing alkyl group of ketones on hetero molecular interaction. It was found that magnitude of excess static dielectric constant of mixtures increases with increase of alky group of ketones. The study reveals that the dipole moment of Allyl chloride in mixture have antiparallelism tendency where as 2-pentanone and 2-hexanone have parallelism tendency. Excess static dielectric constant is also fitted to Redlich-Kister equation to get information about rates of multimers formation.

• 한국지진공학회논문집
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• 제24권2호
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• pp.59-65
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• 2020

The empirical Green's function method is applied to the foreshock and the mainshock of the 2016 Gyeongju earthquake to simulate strong ground motions of the mainshock and scenario earthquake at seismic stations of seven metropolises in South Korea, respectively. To identify the applicability of the method in advance, the mainshock is simulated, assuming the foreshock as the empirical Green's function. As a result of the simulation, the overall shape, the amplitude of PGA, and the duration and response spectra of the simulated seismic waveforms are similar with those of the observed seismic waveforms. Based on this result, a scenario earthquake on the causative fault of Gyeongju earthquake with a moment magnitude 6.5 is simulated, assuming that the mainshock serves as the empirical Green's function. As a result, the amplitude of PGA and the duration of simulated seismic waveforms are significantly increased and extended, and the spectral amplitude of the low frequency band is relatively increased compared with that of the high frequency band. If the empirical Green's function method is applied to several recent well-recorded moderate earthquakes, the simulated seismic waveforms can be used as not only input data for developing ground motion prediction equations, but also input data for creating the design response spectra of major facilities in South Korea.

• 융복합기술연구소 논문집
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• 제1권2호
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• pp.6-15
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• 2011

This paper reports the design and fabrication of a micro-electro-mechanical-system(MEMS)-based electrostatic angular microactuator for a dual-stage servo. The proposed actuator employs a novel electrode pattern named "skewed electrode array(SEA)" scheme. It is shown that SEA has better linearity than a parallel plate type actuator and stronger force than a comb-drive based actuator. The moving and the fixed electrodes are arranged to make the driving force perpendicular to the rotating moment of arm. By changing the electrode overlap length, the magnitude of electrostatic force and stable displacement will be changed. In order to optimize the design, an electrostatic FE analysis was carried out and an empirical force model was established for SEA. A new assembly method which will allow the active electrodes to be located beneath the slider was developed. The active electrodes are connected by inner and outer rings lifted on the base substrate, and the inner and outer rings are connected to platform on which the slider locates. Electrostatic force between active electrodes and platform can be used for exiting out of plane modes, so this provides the possibility of the flying height control. A microactuator that can position the pico-slider over ${\pm}0.5{\mu}m$ using under 20 volts for a 2 kHz fine-tracking servo was designed and fabricated using SoG process.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.329-330
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• 2008

The 181,000 DWT Bulk Carrier has a different deck house type, which is not typical for previous bulk carriers, to meet the new international rules for bulk carriers. This new deck house has much smaller transverse breadth than the hull's transverse breath, resulting in large levels of the transverse response of the deck house. In addition, the longitudinal response of the funnel showed rather a large magnitude of vibration, which are excited by the ship's main excitations such as the main engine H-moment and the propeller surface forte when the ship operates at the NCR and the MCR speeds In the ballast condition. To solve these issues, the global forced vibration analysis has been performed for the ship and the ship structure has been modified to reduce the vibration level by increasing the girder depth and adjusting the engine room tank arrangement.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1536-1537
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• 2011

The high-voltage circuit breaker plays an important role in the electrical system because there has been a need for suitable switching devices capable of initiating and interrupting the flow of the electric fault current. It continues as the contacts recede from each other and as the newly created gap is bridged by a plasma. The arc plasma happens inside the insulation nozzle of SF6 self-blast interrupter which is newly developed as the next-generation switching principle. The ablation of PTFE nozzle is caused by this high temperature medium, the PTFE vapor from the nozzle surfaces flows toward the outlets and the pressure chamber. The vapor makes the pressure of the chamber increased by heat and mass transfer from the arcing zone. Because the rate of ablation depends on the magnitude of applied current, it decreases when the current goes to zero. The compressed gas inside the chamber flows reversely toward the arc plasma during this moment. According to this principle, the arc can be cooled down and the fault current can be interrupted successfully. In this study, we calculate arc plasmas and thermal-flow characteristics caused by fault current interruption inside a SF6 self-blast interrupter, and to investigate the effect of PTFE ablation on the whole arcing history.