• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.221-228
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• 1998

In this study, the $\beta$-Polyvinylidene fluoride(PVDF) thin films were fabricated by physical vapor deposition method. Also, the properties of dielectric relaxation were studied to understand carrier's behavior of PVDF thin films, to be regarded as the excellent piezo and pyroelectricity. In the process of vapor deposition, the $\beta$-PVDF thin films have been fabricated under the condition of the substrate temperature at 3$0^{\circ}C$, the applied electric field at 142.8kV/cm and the pressure at 2.0${\times}10^{-5}$torr. The dielectric properties of PVDF have been studied in the frequency range 10Hz to 1MHz at temperature from 30 to $100^{\circ}C$. The relative dielectric constant of $\alpha$ and $\beta$-PVDF were 6.8 and 9.8, respectively, under a frequency of 1kHz. Such a phenomenon was caused by the decrease in intermolecular forces originated by the phase-transition from the TGTG' molecular conformation to the TT planar zig-zag conformation. And the relative dielectric constant is increased as a measuring temperature increases, because of the reduction of relaxation time caused by the decrease of intermolecular force.

• Journal of Advanced Marine Engineering and Technology
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• v.7 no.2
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• pp.15-21
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• 1983

Preparing for treatment and management of the emulsified fuel oil which will be generalized henceforth, this paper is an attempt to examine the viscosity-temperature characteristics of emulsified heavy fuel oil which is mixed with water and emulsifier in various mixture ratio by mechanical mixer. The experimental results are summarized as follows: 1. The viscosity-temperature characteristics of the emulsified C & B grade heavy fuel oil mixed with water of same or less weight, is changed according to log.log(v+0.6)=b-3.8log T. 2. The emulsifier has to be added to the emulsified A grade heavy fuel oil mixed with water of same or less weight, because it is instable. Especially if the emulsifier is sodium stearate, it is added more than 0.3% of the weight of oil and water. 3. In the emulsified A grade heavy fuel oil mixed with water and emulsifier, the higher the ratio of water addition becomes, the higher the viscosity is and the more the viscosity-temperature slope decreases. But the higher the ratio of emulsifier addition is, the more the viscosity-temperature slope increases. In this case, the linearity of viscosity-temperature characteristic curve is poorer than that of B and C grade heavy fuel oil. 4. In the emulsified A grade heavy fuel oil mixed with emulsifier of 0.3% or less, the emulsion type is O/W type when water addition ratio is 40%, but it is W/O type when it is 10%, 20%, 30% and 50%.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.2
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• pp.279-286
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• 2010

Livestock production in Vietnam is, as in most Asian countries, increasing rapidly and changing into specialized highly intensified operations. The volume of animal excreta generated exceeds the capacity of the operation land base and cannot be utilized efficiently. As a consequence, there is a loss of plant nutrients from livestock farms that causes environmental pollution. This study carried out a feed and excretion experiment measuring fecal characteristic, daily fecal production, daily nitrogen and phosphorous excretion from grower-finisher pigs fed prevalent rations in Vietnam. Furthermore, equations for assessing the excretion were tested, which can be used in farm models for optimal recycling of manure while focusing on reducing pollution. The results indicated that fecal production and nutrient excretion were affected by the different rations tested. This study showed that five selected equations for predicting excretion from grower-finisher pigs in Danish conditions can also be used with precision in Vietnamese pig farming systems. The equations have been proven valid and can, therefore, be used as a much needed tool for assessing fecal production and nitrogen in excreta on pig farms. The study also showed that about 12% of nitrogen excreted was emitted during housing. Waste water contains more than half of the nitrogen excreted, mainly in ammonium form which has a high potential for gaseous emission.

• KIEE International Transactions on Power Engineering
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• v.4A no.3
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• pp.129-133
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• 2004

This paper deals with the design and implementation of a TCSC (Thyristor Controlled Series Capacitor) simulator, which is a module for an analog type power system simulator. Principally, it presents configuration of controller hardware/software and its experimental results. An analog type power system simulator consists of numerous power system components, such as various types of generator models, scale-downed transmission line modules, transformer models, switches and FACTS (Flexible AC Transmission System) devices. It has been utilized for the verification of the control algorithm and the study of system characteristics analysis. This TCSC simulator is designed for 50% line compensation rate and considered for damping resister characteristic analysis. Its power rate is three phase 380V 20kVA. For hardware extendibility, its controller is designed with VMEBUS and its main CPU is TMS320C32 DSP (Digital Signal Processor). For real time control and communications, its controller is applied to the RTOS (Real Time Operation System) for multi-tasking. This RTOS is uC/OS-II. The experimental results of capacitive mode and inductive mode operations verify the fundamental operations of the TCSC.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.463-467
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• 2000

In this paper, the new LIGBT structures with trap injection are proposed to improve switching characteristics of the conventional SOI LIGBT. The Simulations are performed in order to investigate the effects of the positiion, whidth and concentration of trap injection region with a reduced minority carrier lifetime using 2D device simulator MEDICI. Their electrical characteristics are analyzed and the optimum design parameters are extracted. As a result of simulation, the turn off time for the model A with the trap injection is $0.78\mus$. These results indicate the improvement of about 2 times compared with the conventional SOI LIGBT because trap injection prevents minority carriers which is stored in the n-drift region during turn off switching. The latching current is $1.5\times10^{-4}A/\mum$ and forward blocking voltage is 168V which are superior to those of conventional structure. It is shown that the trap injection is very effective to reduce the turn off time with a little increasing of on-state voltage drop if its design and process parameters are optimized.

• Transactions on Electrical and Electronic Materials
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• v.3 no.4
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• pp.16-20
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• 2002

The high bias voltage associated with the thick layer (typically 500-1000 ㎛) of selenium required to have an acceptable x-ray absorption in radiography and fluoroscopy applications may have some practical inconvenience. A hybrid x-ray detector with zinc sulfide-amorphous selenium structure has been developed to improve the x-ray sensitivity of a a-Se based flat-panel digital imaging detector. Photoluminescence(PL) characteristic of a ZnS:Ag phosphor layer showed a light emission peak centered at about 450 nm, which matches the sensitivity spectrum of selenium. The dark current of the hybrid detector showed similar characteristics with that of a a-Se detector. The x-ray sensitivity of hybrid and a-Se x-ray detector was 345 pC/㎠/mR and 295 pC/㎠/mR at an applied voltage of 10 V/㎛, respectively. The purpose of this study was to evaluate the pertinence of a solution using a thin selenium layer, as a photosensitive converter, with a thick coating of silver doped zinc sulfide phosphor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.41-46
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• 2009

The low dielectric SiOCH films were deposited on p-type Si(100) substrates through the dissociation of BTMSM $(((CH_3)_3Si)_2CH_2)$ precursors with oxygen gas by using PECVD method. BTMSM precursor was introduced with the flow rates from 42 to 60 sccm by 2 sccm step into reaction chamber but with the constant flow rate of 60 sccm $O_2$. SiOCH thin films were annealed at $450^{\circ}C$ for 30 minutes. The electrical property of SiOCH thin films was studied by MIS, Al/SiOCH/p-Si(100), structure. Annealed samples showed large reduction of the maximum capacitance yielding low dielectric constant owing to reductions of surface charge density. After exposure at room temperature and atmospheric pressure, dielectric constant of SiOCH films was totally increased. However, annealed SiOCH thin films were more stable than as-deposited SiOCH thin films for natural oxidation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.187-187
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• 2007

This paper presents the electrical properties of SiGe HBTs designed with bottom collector and single metal layer structure for RF power amplifier. Base layer was formed with graded-SiGe/Si structures and the collector place to the bottom of the device. Bottom collector and single metal layer structures could significantly simplify the fabrication process. We studied about the influence of SiGe base thickness, number of emitter fingers and temperature dependence (< $200^{\circ}C$) on electrical properties. The feasible application in 1~2GHz frequency from measured data $BV_{CEO}$ ~10V, $f_r$~14 GHz, ${\beta\simeq}110$, NF~1 dB using packaged SiGe HBTs. We will discuss the temperature dependent current flow through the e-b, b-c junctions to understand stability and performance of the device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.344-348
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• 2004

The CdSe thin films wee grown on the Si(100) wafers by a hot wall epitaxy method(HWE). The source and substrate temperature are $600^{\circ}C\;and\;430^{\circ}C$ respectively. The crystalline structure of epilayers was investigated by double crystal X-ray diffraction(DCXD). Hall effect on the sample was measured by van der Pauw method and studied on the carrier density and mobility dependence on temperature. From Hall data, the mobility was increased in the timperature range 30K to 150K by impurity scatering and decreased in the temperature range 150K to 293K by the lattice scattering. In order to explore the applicability as a photoconductive cell, we measured the sensitivity($\gamma$), the ratio of photocurrent to darkcurrent(pc/dc), maximum allowable power dissipation(MAPD), spectral response and response time. The results indicated that the photoconductive characteristic were the best for the samples annealed in Cu vapor compare with in Cd, Se, air and vacuum vapour. Then we obtained the sensitivity of 0.99, the value of pc/dc of $1.39{\times}10^7$, the MAPD of 335mV, and the rise and decay time of 10ms and 9.5ms, respectively

• Journal of Hydrogen and New Energy
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• v.29 no.6
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• pp.668-679
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• 2018

Experimental and numerical data were compared through a counterflow burner for the characteristic of basic flame about SNG- C11. In order to use the numerical mechanism accurately, the validation was carried out at strain rate ($a_g=30$, $120s^{-1}$) and the UCSD model showed satisfactory results. The effective Lewis number of the extinction boundary, and the behavior of extinction for the symmetric flames of the SNG-C11, could be explained through the trend of $Le_V$, and the flame of the extinction condition was inspected by the major species, key radicals and the chemical reaction paths. The interactions phenomenon in the merged flames has chemical reaction path for producing $HO_2$ were generated at stagnation point. It can be expected the one of major factors in interaction phenomenon.