• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.104-109
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• 2018

Generally, the durability of the parking lock gear is evaluated through an endurance test for the entire transmission but no test standard exists for the durability test of one part of a parking lock gear. Therefore, in this study, the durability test standards of the parking lock gear were determined autonomously, and the durability performance test was conducted. A static fracture test was carried out to determine the yield strength of the parking lock gear, and a durability test condition was set to 60 % of the yield strength. The durability test of 1,000,000 times was conducted under the given conditions using a dedicated test jig manufactured for the test. Because the jig fractured during the static fracture test, finite element analysis for the jig was carried out and the jig was re-designed. The modified jig was manufactured and the durability test was carried out based on the test standard of autonomously. The basic data on the performance and endurance limit of the parking lock gear were obtained using these tests and analyses, and the basic data will be used as fundamental materials for the design and the development of the parking lock gear.

• Journal of Sensor Science and Technology
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• v.23 no.1
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• pp.24-28
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• 2014

A lock-in amplifier was proposed for capacitive sensor applications. This amplifier was based on a general-purpose microcontroller and had only a charge amplifier as analog circuits. All the other functions of lock-in amplifier except for the charge amplifier were implemented with firmware and the internal resources of the microcontroller. A rectangular signal, generated by the microcontroller, was used in a sensor-driving signal instead of a conventional sinusoidal signal. This makes it possible that the phase comparison circuit in the lockin amplifier is made with analog-to-digital converter, a timer and an interrupt controller. Using the oversampling method and the rectangular driving signal, we can make it easy to implement the peak detection function with software and sample the peak-to-peak signal at charge amplifier output. A charge amplifier was proposed to cancel out the base capacitance existing in capacitive sensors structurally. The experimental results show that the lock-in amplifier operating in the supply voltage of 3.0 V cancels out the base capacitance and has good linearity.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.689-693
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• 2009

We investigate the comparison of fault current characteristics between the separates three-phase flux-lock type superconducting fault current limiter(SFCL) and integrated three-phase flux-lock type superconducting fault current limiter(SFCL). The single-phase flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil on an iron core and superconducting elements are connected to secondary coil in series. Superconducting elements are used by the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. But the integrated three-phase flux-lock type SFCL consists of three-phase flux-reactors wound on an iron core. Flux-reactor consists of the same turn's ratio between coil 1 and coil 2 for each single phase. To compare the current limiting characteristics of the separated three-phase flux-lock type SFCL and integrated three-phase flux-lock type SFCL, the short circuit experiments are carried out fault condition such as the single line-to-ground fault. The experimental result shows that fault current limiting characteristic of the separated three-phase flux-lock type SFCL was better than integrated three-phase flux-lock type SFCL. And the integrated three-phase flux-lock type SFCL has an effect on sound phase.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.2
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• pp.141-146
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• 2011

When the current of the superconducting element exceeds its critical current by the fault occurrence, the quench of the high-$T_C$ superconducting fault current limiter (HTSC) comprising the flux-lock type superconducting fault current limiter (SFCL) occurs. Simultaneously, the magnetic flux in the iron core induces the voltage in each coil, which contributes to limit the fault current. In this paper, the fault current limiting characteristics of the flux-lock type SFCL as well as the load voltage sag suppressing characteristics according to the flux-lock type SFCL's winding direction were investigated. To confirm the fault current limiting and the voltage sag suppressing characteristics of the this SFCL, the short-circuit tests for the simulated power system with the flux-lock type SFCL were carried out. The flux-lock type SFCL designed with the additive polarity winding was shown to perform more effective fault current limiting and load voltage sag suppressing operations through the fast quench occurrence right after the fault occurs and the fast recovery operation after the fault removes than the flux-lock type SFCL designed with the subtractive polarity winding.

• The Safety technology
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• no.49
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• pp.24-27
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• 2002

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.1
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• pp.23-33
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• 2002

A hysteresis control is widely used to control output current of inverter. A hysteresis bandwidth is affected by system parameters such as source voltage, device on/off time, load inductance and resistance. The frequency limiter is used to protect switching devices overload. In the conventional hysteresis controller, a lock-out circuit with D-latch and timer is used to device protection circuit. But switching delay time and harmonic components are appeared in output current. In this paper the performance of lock-out circuit is tested, and new circuit for switching device fault protection is proposed ad it's performance is simulated.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.21-29
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• 2005

The Purpose of this study was to seek determinant factors through analysis of 65 snatch skill kinematic factors of Athletics participated in 2001 Asian weightlifting competetion. The conclusion were as follows ; 1. In order to enhance snatch skill, when barbell move on knee position, One should be flex knee joint to 105-110 degree, and In pull motion, One should be move powerful extension of knee and hip joint. 2. In last pull motion, One try to make more lock out motion than extra extention motion of hip joint 3. In order to enhance snatch skill, It is inportant that elevate barbell highly by last pull motion through powerful knee extention, poweful hip flextion and One should be make lock out motion fast in the same time. 4. In order to enhance snatch skill, anterior-posterior movement width of shoulder joint should be small. 5. In order to enhance snatch skill, Hip joint should be move vertically on start and lock out phase, but In pull phase, extension motion of hip joint shoulde be performed more largely and powerfully.

• 한국가시화정보학회:학술대회논문집
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• 2004.11a
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• pp.18-21
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• 2004

Lock-on characteristics of the flow around a circular cylinder performing a rotationally oscillation with a relatively high forcing frequency have been investigated experimentally using flow visualization and hot-wire measurements. Dominant parameters are Reynolds number (Re), amplitude of oscillation $(\theta_A)$, and frequency ratio $F_R=f_f\;/\;f_n$, where $f_f$ is the forcing frequency and if is the natural frequency of vortex shedding. Experiments were carried out under the conditions of $Re=4.14\times10^3,\;\pi/15\leq\theta_A\leq\pi/3$, and $F_R=1.0$. The effects of this active control technique on the lock-on flow regime of the cylinder wake were evaluated through wake velocity measurements and spectral analysis of hot-wire signals. The rotary oscillation modified the flow structure of near wake significantly. The lock-on phenomenon was found to occur in the range of frequency encompassing the natural vortex shedding frequency. In addition, when the amplitude of oscillation is less than a certain value, the lock-on phenomenon was occurred only at $F_R=1.0$. The lock-on range expanded and vortex formation length decreased as the amplitude of oscillation increases. The rotary oscillation generated small-scale vortex structure just near the cylinder surface.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.9-18
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• 2016

The slender structures such as high rise building or marine riser are highly susceptible to dynamic force exerted by fluid-structure interactions among which vortex-induced vibration(VIV) is the main cause of dynamic unstability of the structural system. If VIV occurs in natural frequency regime of the structure, fatigue failure likely happens by so-called lock-in phenomenon. This study presents the numerical analysis of dynamic behavior of both structure and fluid in the lock-in regimes and investigates the subjacent phenomena to hold the resonance frequency in spite of the change of flow condition. Unsteady and laminar flow was considered for a two-dimensional circular cylinder which was assumed to move freely in 1 degree of freedom in the direction orthogonal to the uniform inflow. Fluid-structure interaction was implemented by solving both unsteady flow and dynamic motion of the structure sequentially in each time step where the fluid domain was remeshed considering the movement of the body. The results show reasonable agreements with previous studies and reveal characteristic features of the lock-in phenomena. Not only the lift force but also drag force are drastically increasing during the lock-in regime, the vertical displacement of the cylinder reaches up to 20% of the diameter of the cylinder. The correlation analysis between lift and vertical displacement clearly show the dramatic change of the phase difference from in-phase to out-of-phase when the cylinder experiences lock-in. From the results, it can be postulated that the change of phase difference and flow condition is responsible for the resonating behavior of the structure during lock-in.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.9-15
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• 2006

Experiments are conducted to compare fuel economy of FTP-75 mode on two different lock-up conditions; (A) Lock-up on at engine speed of 1,200(rpm) and above for 3rd & 4th gear, (B) Lock-up on at engine speed of 1400rpm and above for 4th gear only. As a result, case A had better fuel economy about 2.75(%) than case B for FTP-75 mode. Simulation(CRUISE, AVL) study is also carried out in order to estimate the effect of Lock-up control strategy for vehicle fuel economy. The fuel economy simulation result agrees with the measured fuel economy within error of 2(%). The improved Lock-up control strategy is proposed by simulation.