• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.4
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• pp.617-624
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• 2022

The small electric vehicles equipped with V2X(vehicle to everything) systems may provide more information and function to the existing navigation system of the vehicle. The key components of V2X technology include V2V (vehicle to vehicle), V2N(vehicle to network) and V2I (vehicle to infrastructure). This study is to design and implementation of VI type E-PTO which is interfaced with external equipments, the work designs the components of E-PTO such as DC/DC converter, DC/AC converter, battery bidirectional charging system etc. Also, it implements the devices and control systems for driving. The test results of VI type E-PTO components showed allowable 10% requirements of transient voltage variation rate and recovery time within 100ms for start/stop and normal operation.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.19-25
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• 2023

Although a lot of research and development has been conducted on the performance improvement of PEM (Proton Exchange Membrane) water electrolysis, the research on durability is still in early stage. This study investigated effect of temperature on the water electrolysis durability when driving temperature of the PEM water electrolysis was increased to improve performance. Voltage change, I-V, CV (Cyclic Voltammetry), LSV (Linear Sweep Voltammetry), Impedance, and FER (Fluoride Emission Rate) were measured while driving under a constant current condition in a temperature range of 50~80 ℃. As the operating temperature increased, the degradation rate increased. At 50~65 ℃, the degradation of the IrO₂ electrocatalyst mainly affected the durability of the PEM water electrolysis cell. At 80 ℃, the polymer membrane and electrode degradation proceeded similarly, and the short resistance decreased to 1.0 kΩ·cm² or less, and the performance decreased to about 1/3 of the initial stage after 144 hours of operation due to the shorting phenomenon.

• Korean Journal of Materials Research
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• v.11 no.6
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• pp.448-452
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• 2001

The ZnS:Cu,Cl thick film electroluminescent devices with the stacking type(separated with phosphors and insulator layers) and the composite type (mixed with phosphor and insulator materials) emission layers were fabricated on ITO/glass substrates by the screen printing methods. The opical and electrical properties were investigated as fundations of applied voltages and frequencies. In the stacking type, the luminance was about 58 cd/$\m^2$ at the applied voltage of 400Hz, 200V and increased to 420 cd/$\m^2$ with increasing the frequency to 30Hz. For the composite type devices, the threshold voltage was 45V and the maximum luminance was 670 cd/$\m^2$ at the driving condition of 200V, 30Hz. The value of luminance of the composite type device showed 1.5 times higher than that of stacking type device. The main emission peak was 512 nm of bluish-green color at 1Hz frequency below and shifted to 452 nm in the driving frequency over 5Hz showing the blue omission color. There were no distinct differences of the main emission peaks and color coordinate for both samples.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1240-1246
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• 2006

Generally, there are two types of main factors to affect output power quality of a auxiliary power supply an EMU(electric multiple unit). One is a voltage flicker by amplitude modulation of short time and air compressors. The other is repetitive motion of large capacity motor such as air compressors, HVAC unit etc. in main factors. This paper compared two kinds of fluorescent lamp, 32W (after remodeling interior) and 40W(before remodeling interior) and measured the light output varying input power(AC220V) for a flicker phenomenon related power supply of lamps in EMU. Also, we analyzed a flicker considering EMU operating time and density in order to grasp main factors of a load change to cause a voltage change. As a results of test, a 40W fluorescent lamp was more insensitive with 20.26% degree an eye recognition degree sides about changes of the input power and lower with 19.9% voltage side generating flicker compare with fluorescent lamp 32W. Also, we confirmed the fact which the fluorescent lamp flicker was generated by varying fluorescent lamp output voltage when the commercial EMU was in high driving density and at the busy time. Additionally, we confirmed the frequency band which an EMU passenger could feel sensitively blinking of a fluorescent lamp was visually $8Hz{\sim}15Hz$.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.197-210
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• 2008

The cathode materials for lithium ion battery have been developed in accordance with the battery performance. $LiCoO_2$ initially adapted at lithium ion battery is going to be useful even at the charging voltage of 4.3 V by surface treatment or doping which drastically improved the performance of $LiCoO_2$. On the other hand, the complicate and multiple functions of recent electronic equipments required higher operational voltage and higher capacity than ever, which is going to be driving force for developing new cathode materials. Some of them are $LiNi_{1-x}{M_xO_2}$, $Li[Ni_{x}Mn_{y}Co_{z}]O_{2}$, $Li[{Ni}_{1/2}{Mn}_{1/2}]O_{2}$. Other new type of cathode materials having high safety is also developed to apply for HEV (hybrid electrical vehicle) and power tool applications. ${LiMn}_{2}{O}_{4}$ and $LiFePO_4$ are famous for highly stable material, which are expected to give contribution to make safer battery. In near future, the various materials having both capacity and safety will be developed by new technology, such as solid solution composite.

• Smart Structures and Systems
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• v.16 no.5
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• pp.759-780
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• 2015

Based on the theory of piezoelasticity, the static performance of a piezoelectric bilayer cantilever fully covered with electrodes on the upper and lower surfaces is studied. Three models are considered, i.e., the sensor model, the driving displacement model and the blocking force model. By establishing suitable boundary conditions and proposing an appropriate Airy stress function, the exact solutions for piezoelectric bilayer cantilevers are obtained, and the effect of ambient thermal excitation is taken into account. Since the layer thicknesses and material parameters are distinguished in different layers, this paper gives unified solutions for composite piezoelectric bilayer cantilevers including piezoelectric bimorph and piezoelectric heterogeneous bimorph, etc. For some special cases, the simplifications of the present results are compared with other solutions given by other researches based on one-dimensional constitutive equations, and some amendments have been found. The present investigation shows: (1) for a PZT-4 piezoelectric bimorph, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are about 19.59%, 23.72% and 7.21%, respectively; (2) for a PZT-4-Al piezoelectric heterogeneous bimorph with constant layer thicknesses, the amendments of tip deflections induced by an end shear force, an end moment or an external voltage are 9.85%, 11.78% and 4.07%, respectively, and the amendments of the electrode charges induced by an end shear force or an end moment are both 1.04%; (3) for a PZT-4-Al piezoelectric heterogeneous bimorph with different layer thicknesses, the maximum amendment of tip deflection approaches 23.72%, and the maximum amendment of electrode charge approaches 31.09%. The present solutions can be used to optimize bilayer devices, and the Airy stress function can be used to study other piezoelectric cantilevers including multi-layered piezoelectric cantilevers under corresponding loads.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.39 no.1
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• pp.9-15
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• 2002

In this thesis, blue emission organic light emitting devices were fabricated by using vacuum deposition method. Two types of device were employed to realize blue emission. Type I had an emitting layer containing TPB-doped $Alq_3$ and type II had an emitting layer containing DPA-doped $Alq_3$. The variable dopant concentration was 0.5 ~2 wt%. The electrical and optical characteristics of these devices have been investigated. The more dopant concentration increased, the nearer the blue coordinate. Type I than type II had a lower turn on voltage and driving voltage. The emission luminescence of type II was brighter than that of type I. When we applied 15V to type II with DPA(2wt%)-doped $Alq_3$, we have achived the emission luminescence of 1282cd/$m^2$, the emission wavelength of 476nm and the blue emission CIE coordination of (0.1273, 0.0672)

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.7-13
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• 2006

Linear compressors with a free piston driven by a linear motor are widely attention in the cooling apparatus such as refrigerator due to the high efficiency The stroke of piston in the linear compressor driven by LPMSM (Linear Permanent-Magnet Synchronous Motor) can be obtained from Integrating the input voltage and current of LPMSM, but it may be diverged due to dc components in the voltage and current. The strategy to prevent the divergence of stroke using both the high-pass filter and do offset compensation was suggested. The equations for the magnitude and phase of the stroke and also dc offset including the stroke are derived as a function of the cut-off frequency of HPF. The accurate stroke of a piston can be calculated by compensating for dc offset. The performance of the newly developed stroke calculation scheme has been verified by experimentally on a linear compressor drive system, where the control was implemented by a 16-bit DSP.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.1-7
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• 2020

The manufacturing process of the resistive variable memory device, which is the based of neuromorphic device, maintained the continuity of vacuum process and applied plasma module suitable for the production of the ReRAM(resistive random access memory) and process technology for the neuromorphic computing, which ensures high integrated and high reliability. The ReRAM device of the oxide thin-film applied to the plasma module was fabricated, and research to improve the properties of the device was conducted through various experiments through changes in materials and process methods. ReRAM device based on TiO₂/TiOx of oxide thin-film using plasma module was completed. Crystallinity measured by XRD rutile, HRS:LRS current value is 2.99 × 10³ ratio or higher, driving voltage was measured using a semiconductor parameter, and it was confirmed that it can be driven at low voltage of 0.3 V or less. It was possible to fabricate a neuromorphic ReRAM device using oxygen gas in a previously developed plasma module, and TiOx thin-films were deposited to confirm performance.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1540-1551
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• 2015

The detection of position and speed in BLDC motors without using position sensors has meant many efforts for the last decades. The aim of this paper is to develop a sensorless technique for detecting the position and speed of BLDC motors, and to overcome the drawbacks of position sensor-based methods by improving the performance of traditional approaches oriented to motor phase voltage sensing. The position and speed information is obtained by computing the derivative of the terminal phase voltages regarding to a virtual neutral point. For starting-up the motor and implementing the algorithms of the detection technique, a FPGA board with a real-time processor is used. Also, a versatile hardware has been developed for driving BLDC motors through pulse width modulation (PWM) signals. Delta and wye winding motors have been considered for evaluating the performance of the designed hardware and software, and tests with and without load are performed. Experimental results for validating the detection technique were attained in the range 5-1500 rpm and 5-150 rpm under no-load and full-load conditions, respectively. Specifically, speed and position square errors lower than 3 rpm and between 10º-30º were obtained without load. In addition, the speed and position errors after full-load tests were around 1 rpm and between 10º-15º, respectively. These results provide the evidence that the developed technique allows to detect the position and speed of BLDC motors with low accuracy errors at starting-up and over a wide speed range, and reduce the influence of noise in position sensing, which suggest that it can be satisfactorily used as a reliable alternative to position sensors in precision applications.