• Journal of the Korean Society for Railway
• /
• v.20 no.2
• /
• pp.190-195
• /
• 2017

This paper proposes a method to detect rail broken through impedance measurement. In general, broken rails are detected in real time using the track circuit, but the proposed method not only detects the broken rails but also estimates positions of broken areas by measuring the rail impedance. To electrically insulate one side of the rail, parallel resonance is made by adding a capacitor; then, the impedance of the other rail is measured. If the measured impedance has an inductive value, there is no broken area of rail. However if the measured impedance has a capacitive value, the rail is broken. The proposed method is modeled using a transmission line; it is shown that the modeling can estimate the position of the broken rail according to the impedance value. The rail impedance is measured by the proposed method for a 60m simple rail model, and it is verified that the presence of a broken rail changes the rail impedance.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.3
• /
• pp.228-238
• /
• 2002

This paper presents a digital controller of the electronic ballast using high frequency modulation method for the metal halide lamp. The proposed controller includes the control algorithm for soft starting, no load protection, over current protection and power control. The proposed digital controller, moreover, has the high frequency modulation scheme and the tracking algorithm to avoid acoustic resonance phenomena. For the math production with the low cost using the ASICs (Application Specific Integrated Circuit), the proposed digital controller has been designed with the FPGAs(Field Programmable Gate array) only, without any microprocessor. In this paper, the detail digital control algorithms are described and the experimental results of prototype 150w metal halide electronic ballast are presented.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.39 no.6
• /
• pp.71-78
• /
• 2002

A method of soft switching in the half bridge converter using a small saturable core is presented. For the soft switching, a small dead time of both switch off is made in a pair of MOSFET switch. The saturable core is of rectangular magnetization characteristics and the core flux swings from the minus to the plus saturation during ON time of the switch. The soft switching is realized in dead time by a resonance between the saturating inductance of the core and the stray capacitance of MOSFET. As an extension of this concept, instead of the saturable core, we propose a new soft switching circuit using a linear inductance and two switches, which is especially suitable for regulating the output and also for high frequency switching. A theoretical principle of soft switching presented here was confirmed by experiments on a half bridge converter of 1.25 KW.

• International Journal of Fluid Machinery and Systems
• /
• v.4 no.1
• /
• pp.179-190
• /
• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.4
• /
• pp.1-7
• /
• 2000

In this paper, we study a cause of malfunction of switch to control drive motor in DFMS(Digital Flux Mapping System) which can measure incore neutron flux of the nuclear plant, and develope a method to solve this problem. DFMS has the type of generating contact signal by mechanical switch lever, which is operated whenever thimble detector inserted or withdrawed through thimble Guide Tube. However the characteristics of the lever tend to be changed by mechanical degrade or bad environment and the lever finally generates errotic contact signal. Therefore we installed electric coil ass'yin the outside of Guide Tube instead of mechanical switch assy's. In addition we applied resonance effect to control circuit and installed condenser in the input of power supply to protect noise and interference. After completion of this improvement, we tested this improved device repetitively under the various conditions. In conclusion, we identified the generation of the desired contact signal and the prevention of detector failure through plant surveillance test during normal plant operation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.27 no.3
• /
• pp.156-161
• /
• 2014

We have investigated the optical properties of plamonic waveguide with tapered structure based on InP material for photonic integrated circuit(PIC). The proposed plasmonic waveguide is covered with the Ag thin film to generate the plasmonic wave on metallic interface. The optical characteristics of plasmonic waveguide were calculated using the three-dimensional finite-difference time-domain method. The plasmonic waveguide was fabricated with the lengths of 2 to $10{\mu}m$ and the widths of 400 to 700 nm, respectively. The plasmonic mode and optical loss were measured. The optimum plasmonic length is $10{\mu}m$ and widths are 600 and 700 nm in the fabricated waveguide. This plasmonic waveguide can be directly integrated with other conventional optical devices and can be essential building blocks of PIC.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.4
• /
• pp.98-104
• /
• 1996

This paper propose the alteraton rule to compensate a formant trasition of several connected vowels for improving an unnatural synthesized continuous speech which is concatenated by each demisyllable without coarticulated formant transition for use in dmisyllable based synthesis by rule. To fullfill each formant transition part, the database of 42 stationary vowels which are segmented from the stable part of each vowels is appended to the one of Korean demisyllables, and the resonance circuit used in formant synthesis is employed to change the formant frequency of speech signals. To evaluate the synthesied speech by this rule, we carried out the alteration rule for connected vowels of the synthesized speech based on demisyllable, and compare spectrogram and MOS tested scores with the original and the demisyllable based synthesized speech without this rule. The result shows that this proposed rule can synthesize the more natural speech.

• Journal of the Korea Convergence Society
• /
• v.8 no.9
• /
• pp.9-16
• /
• 2017

In this paper, sub-microwave oscillator sensor is proposed to non-invasively monitor the glucose concentration level of the human biological tissue by oscillation frequency variation. Inductive slot in the ground plane of the microstrip line is combined with the biological tissue, to realize the resonator as a part of the oscillator sensor. The phantom box mimicking the human tissue is introduced for simulation of the resonator which resonance frequency correspondingly shifts up on three step glucose concentration levels(0, 400, 800 mg/dL). Oscillator sensor circuit is fabricated as a prototype. Pig tissues instead of human is used. Oscillation frequency shift of about 14 MHz per glucose level of 400 mg/dL has been successfully measured around 1,100 MHz. This proves that the proposed sensor is applicable to a blood glucose sensor.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.10 no.4
• /
• pp.356-362
• /
• 2005

In this paper, in order to develop a simple and high efficient ballast without an external ignitor, a half-bridge type ballast with a coupled inductor and a frequency controlled synchronous rectifier is proposed. The Internal LC resonance of the buck converter is used to generate a high voltage pulse for the ignition, and the coupled inductor filter is used for steady state ripple cancellation. Also, a synchronous buck converter is applied for the DC/DC converter stage. In order to improve the efficiency of the ballast, a frequency control method is proposed. This scheme reduces a circulation current and trun off loss of the MOSFET switch on the constant power operation, which results in increase of the efficiency of the ballast system about 4$\%$, compared to a fixed frequency control. It consists a 2-stage version ballast with a PFC circuit. The results are verified nth hardware experiments.

• Science of Emotion and Sensibility
• /
• v.20 no.4
• /
• pp.113-126
• /
• 2017

The purpose of the study was to find grey matter (GM) and white matter (WM) volume reduction in the brain reward system among patients with alcohol dependency. This study investigated regional GM and WM in chronic alcoholic patients, focusing primarily on the reward system, including principal components of the mesocorticolimbic reward circuit as well as cortical areas with modulating and oversight functions. Sixteen abstinent long-term chronic alcoholic men and demographically matched 16 healthy control men participated in the study. Morphometric analysis was performed on magnetic resonance brain scans using voxel-based morphometry (VBM)-diffeomorphic Anatomical Registration through Exponentiated Liealgebra (DARTEL). We derived GM and WM volumes from total brain and cortical and subcortical reward-related structures. Morphometric analyses that revealed the total volume of GM and WM was reduced and cerebrospinal fluid (CSF) was increased in the alcohol group compared to control group. The pronounced volume reduction in the reward system was observed in the GM and WM of the nucleus accumbens (NAc), GM of the amygdala, GM and WM of the hippocampus, WM of the thalamus, GM and WM of the insula, GM of the dorsolateral prefrontal cortex (DLPFC), GM of the orbitofrontal cortex (OFC), GM of the cingulate cortex (CC), GM and WM of the parahippocampal gyrus in the alcohol group. We identified volume reductions in WM as well as GM of reward system in the patients with alcohol dependency. These structural deficits in the reward system elucidate underlying impairment in the emotional and cognitive processing in alcoholism.