The low-temperature deposition of BaNi_(2-x)Co_xFe₁₆O₂₇ thin films with a Ba hexaferrite structure for electromagnetic shielding was studied. The BaNi_(2-x)Co_xFe₁₆O₂₇ thin films produced through the spin spray process were suitable for thin film deposition on a flexible substrate because it crystallized well at low temperature below 90℃. The change in shielding characteristics depending on the Co content of the BaNi_(2-x)Co_xFe₁₆O₂₇ thin film was investigated, and excellent shielding characteristics with S21 of -1 dB were obtained in a wide frequency range of 26~40 GHz when the Co content was 0.4 or more. The purpose of this study is to analyze changes in shielding properties caused by change in Co content in relation to phase changes in BaNi_(2-x)Co_xFe₁₆O₂₇ and obtain basic data for developing excellent flexible electromagnetic wave shielding materials.

An algorithm was developed to detect and block serial arc currents using HPF. The AC series arc problem is that the load current is greater than the fault current and no leakage current occurs. As a solution, an arc detection method utilizing differences in high- frequency amplitudes was developed. HPT was applied to the load current and FFT was applied to eliminate low frequencies. An algorithm has been developed to detect arc waveforms when they exceed a certain value compared to the average of normal waveforms. Using one cycle of data, arc detection is faster and arc accidents are prevented.

In this study, an induction heating system using resonance is developed to remove remaining moisture and contaminations which could be generated during fabricating secondary batteries. This system is composed of power supply and induction coil. Power supply needs an oscillator, zero crossing detection, frequency tracking function, and induction coil needs a dummy coil to obtain a uniform temperature distribution. It is very important to obtain a uniform heating temperature distribution of battery cell case in the induction heating system before pouring electrolyte into battery cell. Experimental results show a temperature distribution deviation of below 1℃ in the external position of battery cell cases. As well, the temperature of battery cell itself shows distribution of 40℃±3℃.

Magnetoelectric (ME) properties of 3-0 type particulate composites have been investigated with respect to application features for reliable magnetic sensitivity and magnetically-induced output voltage. In order to figure out the magnetoelectric characteristics in the ME composites, frequency dependent ME responses were studied from [0.948 Na0.5K0.5NbO3-0.052 LiSbO₃]-[Co_1-xZn_xFe₂O₄] (NKNLS)/Co_1-xZn_xFe₂O₄ (CZFO, x=0, 0.1, and 0.2). As a result, the maximal αME of 23.15 mV/cm·Oe was achieved from the NKNLS-CZFO (x_Zn = 0.1) composites at resonance frequency of 315 kHz and H_dc = 0 Oe. From the frequency dependent ME responses, it is clearly described that the self-biased ME composites can be used for applications as both magnetic sensors and energy harvesters, respectively.

Phase evolution, sintering behavior, microstructure, and microwave dielectric properties of (1-x) mol Ba₃V₄O₁₃ - (x) mol BaV₂O₆ system were investigated. The sintered specimens of all compositions consisted of Ba₃V₄O₁₃ and BaV₂O₆, and no secondary phase was observed. As x increased, the linear shrinkage decreased to the composition of x=0.5, and then increased again, implying that Ba₃V₄O₁₃ and BaV₂O₆ phases interfered mutually with each other during sintering. All compositions showed a dense microstructure with a large grain growth. Cracks were observed in some compositions because of the relatively high sintering temperature of 620~640℃. As x increased, the dielectric constant increased, while the quality factor was maintained from about 50,000 GHz to about 70,000 GHz up to the composition of x=0.9, and then decreased to 20,987~27,180 GHz at the composition of x=1.0. As x increased, the temperature coefficient of the resonance frequency showed a (+) value from a (-) value. The dielectric constant, the quality factor, and the temperature coefficient of resonant frequency of x=0.7 composition sintered at 640℃ for 4 hours were 10.61, 71,126 GHz, and -4.9 ppm/℃, respectively. This composition showed a good chemical compatibility with Al powder, indicating that the Ba₃V₄O₁₃-BaV₂O₆ ceramics are a candidate material for ULTCC (Ultra-Low Temperature Co-fired Ceramics) applications.

In this study, the following results were obtained by analysis of electric properties with FT-IR, DSC, XRD, and SEM, in the range of temperature 30~160℃ and frequency 0.1~200 kHz, when filling agent (0~100 phr) and silicone oil (0~12 phr) were added to raw silicone rubber. In the case of 100 phr mixed samples, the relative dielectric constant εr gradually decreased from 4.3 to 3.96 as frequency increased, and the dielectric loss tan δ decreased to 0.01 at 300 Hz, then increased to 0.022 at 30 kHz, then decreased to 200 kHz. The FT-IR analysis identified the same binding structure according to the chemical composition of added silica (SiO₂). Through DSC analysis, we could determine the change of heat quantity and the glass transition temperature of each specimen. In the XRD analysis, it was found that the images SiO₂, TiO₂, and Fe₂O₃ appeared for specimens with 0%, 50% and 100% filling agent. Finally, the SEM analysis confirmed that particles of 0.5 to 1.5 μm size with silica (SiO₂) mixing were dispersed evenly.

Porcelain insulators have been used mainly for power line fixing and electrical insulation in transmission towers. Porcelain insulators have generally a 30 years desired life, but over 50% exceed their life expectancy. Since the damage to porcelain insulators is usually accompanied by enormous loss of human resource material, their efficient maintenance has emerged as an important issue. In this regard, this study applied a frequency response function (FRF) for integrity assessment of the insulator. The characteristics of the FRF according to damage types were identified and analyzed by the change in natural frequencies, curve shape, attenuation, and Nyquist diagram stability. The results showed significant differences in the FRF according to damage types, which can be used as basic data for the effective integrity assessment of porcelain insulators.

To study the frequency response characteristics of alternating-current-driven organic light-emitting diodes (OLEDs), we fabricated blue-fluorescent OLEDs and analyzed their electroluminescent characteristics according to the alternating current voltage and frequency. The luminance-frequency characteristics of alternating-current-driven OLED was similar to that of a low-pass filter，and the luminance of high-voltage OLED decreased at higher frequency than low-voltage OLED. The luminance characteristics of the OLED according to the frequency is due to the capacitive reactance in the OLED, generated during the alternating current driving. The frequency response characteristics of the OLED according to the voltage is due to the decrease in internal resistance of the organic layer. In addition, the negative voltage component of the alternating current did not affect the frequency response of the OLED. Therefore, the electroluminescent characteristics of OLED with an alternating current power of 60 Hz are not influenced by the frequency.

The following conclusions were obtained after analyzing the data transmission characteristics using two frequencies and studying a system that selects data with a good reception frequency as a priority data. Data transmission and reception using two frequencies were measured at -41 to -51 dBm when the frequency was normal, and data transmitted at 900 MHz was selected as priority data. When priority frequency failure occurred, the frequency reception data of the next rank was automatically adopted, and when the frequency of the next rank was disturbed, the priority frequency search was performed again. The above results show that the use of two frequencies enables more stable data transmission and transmission, and further studies should be continued to expand the transmission and reception distances.

The phase evolution, microstructure, and microwave dielectric properties of Ba(Mg_0.5-2xY_2xW_0.5-xTi_x)O₃ (x＝ 0.005~0.05) ceramics sintered at 1,700℃ for 1h were investigated. All compositions exhibited a 1:1 ordered cubic perovskite structure. The field emission scanning electron microscopy image revealed a dense microstructure in all the compositions. As the value of x increased, the lattice parameter, dielectric constant, and quality factor increased. The temperature coefficient of resonant frequency changed from -19.6 ppm/℃ to -5.9 ppm/℃ with increasing x value. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of Ba(Mg_0.40Y_0.10W_0.45Ti_0.05)O₃ were 21.7, 132,685 GHz, and -5.9 ppm/℃, respectively.

CNT (carbon nanotube) resistors with low resistance and negative TCR (temperature coefficient of resistance) were fabricated with yarned CNT (carbon nanotube) fibers. The CNT fibers were prepared by yarning CNTs grown on the silicone substrate by CVD (chemical vapor deposition) method. The CNT resistors were fabricated by winding CNT fibers on the surface of ceramic rod. Both metal terminals were connected with the CNT fiber wound on the ceramic rod. We measured electrical resistance and thermal stability with the number of CNT fibers wound. The CNT resistor system shows linearly decreased resistance with the number of CNTs wound on the ceramic rod and saturated at 20 strands. The CNT resistor system has negative TCR between -1,000 ~ -2,000 ppm/℃ and stable frequency properties under 100 kHz.

Coil specimens were prepared by continuous coating on a copper wire with flexible PAI (polyamideimide) and PAI/nanosilica (5 wt%) varnish and thermally aged at 150, 200 and 250℃ for 5, 10 and 15 days, respectively. AC insulation breakdown voltage was investigated under inverter surge condition at 60 Hz and 1,000 Hz and insulation breakdown voltage decreased with increasing aging temperature and aging time at each 60 and 1,000 Hz.

A textured front surface is required in high efficiency silicon solar cells to reduce reflectance and to improve light trapping. Wet etching with alkaline solution is usually applied for mono crystalline silicon solar cells. However, alkali texturing method is not appropriate for multi-crystalline silicon wafers due to grain boundary of random crystallographic orientation. Accordingly, acid texturing method is generally used for multi-crystalline silicon wafers to reduce the surface reflectance. To reduce reflectivity of multi-crystalline silicon wafers, double texturing method with combination of acid and reactive ion etching is an attractive technical solution. In this paper, we have studied to optimize RIE condition by different RF power condition (100, 150, 200, 250, 300 W).

In this study, the properties of C-V degradation for thermal conductivity silicone rubber sample which is attached by copper-copper, copper-aluminum, aluminum-aluminum on upper-side and under-side has been measured at temperature of 80℃∼140℃. The results of this study are as follows. In case the frequency is increased, it found that the electrostatic capacity increased with increasing temperature to 80℃, 110℃, 140℃ regardless of kind of electrode. It found that the electrostatic capacity increased with becoming high temperature range of frequency regardless of kind of electrode. This result is considered to be caused by thermal absorption on the thermal conductivity silicone rubber sample. It found that the electrostatic capacity decreased with increasing temperature and frequency. This result is considered to be caused by molecular motion of C-F radical or OH radical.

In this study, the frequency properties of electrostatic capacity and dielectric loss for the samples with different types of filler has been measured in through the applied frequency range of 7 kHz -3,000 kHz at temperature of 80℃, 110℃, 140℃, 170℃. The results of this study are as follows. When the sample is degradated at the temperature of 80℃, 110℃, 140℃, 170℃ and the frequency range of 7 kHz -3,000 kHz is applied, It found that the electrostatic capacity of the sample with Polyimide film is larger than the sample with Grass fiber. It found that the dielectric loss for the sample with Polyimide film is larger than the sample with Grass fiber with increasing frequency and temperature in the 80℃, 110℃, 140℃, 170℃ range. Also, the dielectric loss decreased with increasing frequency. In case of the sample with Polyimide film, It found that the electrostatic capacity decreased with increasing temperature, and the dielectric loss gradually decreased with increasing frequency.

In this study, the temperature characteristics of electrostatic capacity and dielectric loss for thesample of Teflon film which is degradated at the 120℃∼200℃ temperature range in the oven for 10 hourshas been measured in through the applied frequency range of 0.1 kHz∼4,800 kHz at temperature of 50℃,90℃, 130℃, 170℃. Also, in the same conditions, the frequency characteristics of electrostatic capacity anddielectric loss for the sample of Teflon film has been measured in through the applied temperature rangeof 30℃∼70℃ on setting frequency of 0.1 kHz, 1 kHz, 10 kHz, 100 kHz. The results of this study are asfollows. When the frequency range of 0.1 kHz∼4,800 kHz applied to the sample of Teflon film, theelectrostatic capacity has been measured at the temperature of 50℃, 90℃, 130℃, 170℃. Through thismeasurement, it found that the electrostatic capacity decreased with increasing temperature. Regarding thisresult, may be it is because the electromagnetic coupling is degraded by thermal degradation. When thesample of Teflon film heated at 280℃ for 10 hours in oven, the dielectric loss has changed from unstablestatus to stabilizing status with increasing the degradation temperature in the 120℃, 160℃, 200℃ range. Inthis measurement, the two spectrums of dielectric loss appeared. It considers that this spectrum ofdielectric loss appeared in 300 Hz is caused by the molecular motion of the C-F or OH group. Throughthis study, It found that the electrostatic capacity decreased with increasing frequency and temperature,and there is no change in dielectric loss, although the frequency increases.

In this paper, by using a dual frequency liquid crystal material, we propose a liquid crystaldevice with a fast response characteristics. The dual frequency liquid crystal material has a positivedielectric anisotropy value at a low frequency. With a high frequency, the dielectric anisotropy becomesnegative. Therefore, the relaxation process is governed by not only the elastic deformation, but also thedielectric interaction. The measured decay time and rise time were 0.88 ms and 0.33 ms, respectively.

In this study, we fabricated a micro Pb(Zr,Ti)O3 (PZT) film piezoelectric cantilever with a Si proof mass and dual beams through MEMS process. The size of the beam and the integrated Si proof mass were about 4,320 μm × 290 μm × 12 μm and 1,380 μm × 880 μm × 450 μm each. To reduce the air damping and have the larger displacement of dual beams was used for design. After mounting micro PZT film piezoelectric cantilever on shaker, we measured the resonance frequency and a output voltage while making resonant frequency changed. The resonant frequency and the highest average power of the cantilever device were 110.2 Hz and 0.36 μW each, at 0.8 g acceleration and 23.7 kΩ load resistance,respectively.

Numerical analysis on RF (Radio Frequency) thermal plasma treatment of micro-sized Ni metal was carried out to understand the synthesis mechanism of nano-sized Ni powder by HF thermal plasma. For this puipose, the behaviors of Ni metal particles injected into HF plasma torch were investigated according to their diameters (1 100 pin). RF input power (6~12 kW) and the flow rates of carrier gases (2 and 5 slpm). From the numerical results, it is predicted firstly that the velocities of carrier gases need to be minimized because the strong injection of carrier gas can cool down the central column of RF thermal plasma significantly, which is used as a main path for RF thermal plasma treatment of micro-sized Ni metal. In addition, the residence time of the injected particles in the high temperature region of RF thermal plasma is found to be also reduced in proportion to the flow rate of the carrier gas In spite of these effects of carrier gas velocities, however, calculation results show that a Ni metal particle even with the diameter of 100 pin can be completely evaporated at relatively low power level of 10 kW during its flight of HF thermal plasma torch (< 10 ms) due to the relatively low melting point and high thermal conductivity. Based on these observations, nano-sized Ni metal powders are expected to be produced efficiently by a simple treatment of micro-sized Ni metal using HF thermal plasmas.

This paper dealt with the radiated electromagnetic wave detection of partial discharge (PD) in oil for insulation diagnostics of oil-immersed transformers. Three types of electrode system were fabricated to simulate the insulation defects that could occur in oil-immersed transformers. Frequency components of radiated electromagnetic wave in oil was measured by broadband bi-conical antennas of 300 MHz∼2 GHz and a spectrum analyzer of 9 kHz∼3 GHz. Frequency component of electromagnetic waves from PD in oil were highly distributed at 500 MHz. From the result, a narrow-band monopole antenna with the center frequency of 500 MHz was fabricated. We could detect PD signal in insulation oil without an influence of external noise by a measurement system which consists of the prototype monopole antenna, a LNA (Low Noise Amplifier), an oscilloscope and a spectrum analyzer.

Niobium oxide(Nb2O5) films were deposited on p-type Si wafers at room temperature using in-line pulsed-DC magnetron sputtering system with various frequencies. The different duty ratios were obtained by varying the frequency of pulsed DC power from 100 to 300 kHz at the fixed reverse time of 1.5 μs. From the thickness of the sputtered NbOx films, it was possible to obtain much higher deposition rate in case of pulsed-DC sputtering than RF sputtering. However, the similar leakage currents and structural characteristics were obtained from the metal-insulator-semiconductor(MIS) structure fabricated with the NbOx films and the x-ray photoelectron spectroscopy(XPS) results in spite of the different deposition rates. From the experimental results, the NbOx films sputtered by pulsed-DC sputtering are expected to be used in the fabrication process instead of RF sputtering.

This paper dealt with the measurement and analysis of electromagnetic waves radiated from a partial discharge (PD) source in insulation oil to apply condition monitoring of oil-immersed transformers. Two types of narrow-band monopole antennas with the resonant frequency of a 500 MHz and a 1 GHz were designed and fabricated. Also, a needle plane electrode system was manufactured to simulate PDs and the curvature radius of the needle is 10 pm and the diameter of the plane is 60 mm. Electromagnetic wave was measured by the PD measurement system with the monopole antennas. Detection sensitivity of the fabricated antenna was compared for the same P1) magnitude; 620 mVpeak for the 500 MHz antenna and 960 mV1,t for the 1 GHz antenna to the PD magnitude of 74 pC. Consequently, the 1 GHz monopole antenna is more effective to detect PDs in oil immersed transformers.

This study focused on the performance characteristics of solar cell using the impedance technique. We measured an impedance according to frequency from 1 Hz until 1 MHz. It could know that the impedance was decreased according to the frequency increases in solar cell. The impedance of single crystal solar cell was 0.61 Ω at 1 Hz, and kept almost settled value to 1×10(2) Hz. However, the impedance of polycrystal solar cell was 7×10(3) Ω at 1 Hz.

This paper dealt with the frequency component analysis of acoustic signals produced by corona and series-arc discharges as a diagnostic technique for closed-switchboards. Corona and series-arc discharge were simulated by a needle-plane electrode and an arc generator specified in UL1699, respectively. Acoustic signal was detected by a wideband acoustic sensor with a frequency bandwidth of 4 Hz∼100 kHz (-3 dB). We analyzed frequency spectrums of the acoustic signals detected in various discharge conditions. The results showed that acoustic signals mainly exist in ranges from 30 kHz to 60 kHz. From the experimental results, an acoustic detection system which consists of a constant current power supply (CCP), a low noise amplifier (LNA) and a band pass filter was designed and fabricated. The CCP separates the signal component from the DC source of acoustic sensor, and the LNA has a gain of 40 dB in ranges of 280 Hz∼320 kHz. The high and the low cut-off frequency are 30 kHz and 60 kHz, respectively. We could detect corona and series-arc discharges without any interference by the acoustic detection system, and the best frequency is considered in ranges of 30 kHz∼60 kHz.

In this paper, it tried to develop the core sensor for detection of micro magnetic field in electric wires. The sensor is non contact type and is consisted of ferrite core for low price. To investigate their properties for variations of current, it changed the number of winding and the length of sample core, it examined, to check the live wire situation in built-in wires, electrical characteristics due to difference between electric wires and core sensor. As the results, it verified live wire situation at the number of winding(5,000) and within length of 6[cm]. Also, it obtained magnetic field magnitude decreased inverse proportion ratio to a square about difference between electric wires and core sensor.

In this paper, we investigated the device performance on fluorine implantation, hot carrier reliability and RTS (random telegraph signal) noise characteristics of NMOSFETs. The capacitance of the fluorine implanted NMOSFET decreased due to the increase of the gate oxide thickness. RTS noise characteristics of the fluorine implated NMOSFET was improved approximately by 46% due to the decrease of trap density at Si/SiO2 interface. The improved gate oxide quality also results in the longer hot carrier life time.

Owing to the rapid growth of mobile and electronic equipment miniaturization technology, the supply of micro mobile computing machine has been fast raised. Accordingly they have performed many researches on energy harvesting technology to provide promising power supply equipment to substitute existing batteries. In this paper, in order to have low resonance frequency for piezoelectric energy harvester, we have tried to make it larger than before by adopting nickel that has much higher density than silicon. We have applied it for our energy harvesting actuator instead of the existing silicon based actuator. Through such new concept and approach, we have designed energy harvesting device and made it personally by making with micromachining process. The energy harvester structure has a cantilever type and has a dimension of 10×2.5×0.1 mm3 for length, width and thickness respectively. Its electrode type is formed by using Au/Ti of interdigitate d33 mode. The pattern size and gap size is 50 μm. Based on the measurement of the nickel-based piezoelectric energy harvester, it is found to have 778 Hz for a resonant frequency with no proof mass. In that resonance frequency we could get a maximum output power of 76 μW at 4.8 MΩ being applied with 1 g acceleration.

A cantilever-type piezoelectric generator has advantages of simple structure, ease of fabrication and large displacement by transverse vibration of a beam. It is easy to control the natural frequency, and also possible to increase the output power by changing the length, width, and thickness of the generator. In particular, the length increases, the natural frequency sharply decreases, and vice versa. Hence, the natural frequency can widely be controlled by using change in the length of elastic body. In this paper, the generator was designed and fabricated to change natural frequency using the slides of the case. In addition, the generating characteristics were confirmed through finite element analyses and vibration experiment. As a result, the maximum output characteristics could be generated due to resonance phenomenon although any frequency of external force was applied.

Recently, annual usage of energy is dramatically increasing because industrialization is going faster and more electricity is needed due to various electronic devices. This study focused on the performance characteristics of solar cell using the impedance technique. The experiment measured an impedance according to frequency`s from 2 mHz until 1 MHz. It could know that the impedance was decreased according to the frequency increases in solar cell. The imaginary part was changed from capacitance component to inductance component.

In this work, we designed and fabricated a multilayer thin film Pb(Zr,Ti)O(3) cantilever with a Si proof mass for low frequency vibration energy harvesting applications. A mathematical model of a multi-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. We fabricated a device with beam dimensions of about 4,930 μm × 450 μm × 12 μm, and an integrated Si proof mass with dimensions of about 1,410 μm × 450 μm × 450 μm. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 84.5 Hz, 88 mV, and 0.166 μWat 1.0 g and 23.7 Ω, respectively. The dimensions of the cantilever were determined for the resonance frequency of the cantilever.