• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.946-948
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• 2002

최근 컴퓨팅 기술의 발전으로 3차원 복합열전달(conjugate heat transfer) 문제를 계산하는 수 치해석 기술이 어느 정도 가능해 졌지만, 실제적인 전력기기 내부의 온도분포를 수치적으로 계산하는 것은 탑재된 구성요소의 다양한 크기와 형상으로 인한 매우 복잡한 경계조건을 수반하고 조밀한 격자를 요구하기 때문에 공학적이지 않다. 이를 위하여 해석적 모델을 수립하여 전력기기 열설계를 위한 수치적 해석에 적용하는 방법이 널리 사용되고 있다. 본 연구에서는 열회로망법(Thermal Network Analysis, TNA)을 이용하여 전력기기 내부의 온도분포를 예측할 수 있는 프로그램을 개발하였다. 전류가 흘러 열이 발생하고 소산되는 주회로 성분들을 각각의 노드로 분할하는 절차를 확립하였고 열접촉저항과 주울열을 적절히 선정함으로써 실제 전류가 흐르는 회로망 내 온도분포를 계산하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.611-614
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• 2005

It is well known that tire tread pattern has much influence on the tire pattern noise. The paper describes the method of pattern noise reduction by using the pitch sequence, both on the smooth asphalt roads and on the trenched concrete roads. The noise of tire is classified as either airborne or structure borne noise. Pattern noise through the airborne is considered as a major noise source at high speeds. As block impacting and air pumping by tread patterns are major noise source, tire pattern noise can be greatly influenced by optimal pitch sequence. The goal of this paper is to provide tire engineers with pitch sequence to reduce pattern noise effectively.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.900-903
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• 2003

An identification method of induction motor parameters such as rotor time constant and mutual inductance at standstill condition is discussed assuming that stator resistance and leakage has already been obtained applying two different DC voltage and single phase voltage to the induction motor, respectively. This proposed scheme is implemented by means of Model Reference Adaptive Control (MRAC) technique, which uses a rotor flux equation in voltage model as a reference model and one in current model and is demonstrated through experiment.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.634-637
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• 1997

This paper is on the research and development of new SIV(Static Inverter) using IGBT(Insulated Gate Bipolar Transistor) semiconductor for a wide range of electric railway applications. For the simplification and higher controllability, the direct PWM control method with 3level inverter topology was adopted. In the new SIV system, the cost as well as bulk and weight was appreciably reduced about 40% lower than those of conventional SIV, the electrical efficiency was increased above 95% and the audible noise level was less than 65dB. In addition, the THD(Total Harmonic Distortion) factor was below 5% and the voltage fluctuation on a transient state was below 10%.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1740-1742
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• 2004

산소 과전압이 낮은 $MnO_2$를 촉매로 사용하여 반도체 산화물계의 산소선택성 전극을 제조하고 산화물 코팅층의 미세구조와 전기화학적 특성을 분석하였다. Ti 기판에 열분해 법을 이용하여 $MnO_2$ 피막을 형성하였고, 또한 binder를 이용한 코팅 방법을 이용하여 Ti, Fb 기판에 $MnO_2$ 피막층을 형성하였다. 450$^{\circ}C$에서 1시간 열분해하여 약 1 ${\mu}m$의 $MnO_2$ 피막층을 형성 시켰으나 Ti 기판과의 접착력이 약하여 피막자체에 대한 전기화학적 특성은 관찰할 수 없었다. PVDF : $MnO_2$의 함량비가 1:1에서 1:6 까지는 DMF의 함량에 무관하게 전극 특성이 나타나지 않았지만 20:1 이상의 조성에서는 균일한 C-V 특성을 나타냈고, 산소 발생 과전압도 약 1.4V 정도로 감소되었다. 그러나 Ti 기판의 경우 열분해법을 이용하여 제조된 전극과 같이 낮은 기판과의 접착력 때문에 $MnO_2$ 피막층의 촉매효과가 현저하게 감소하였다.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.5
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• pp.667-673
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• 2009

Ninety six intact male sheep (12 months old with mean live weight of about 35 kg) were used to assess the effects of restricted feeding on intake, digestion, nitrogen balance and metabolizable energy (ME). The animals were selected from two known Iranian small and large body size breeds: 48 Sangsari (S) and 48 Afshari (A), and were divided into two equal groups: restricted (R) and a control (C). Each group had 48 sheep (24 each breed). The experiment had a duration of 15 and 75 days adaptation and treatment periods, respectively. The animals were individually placed in metabolism cages and fed a diet based on pelleted concentrate mixture consisting of alfalfa, barley grain, cottonseed meal and barley straw. The animals in group C were fed ad libitum, while animals in group R were fed at maintenance level and maintained a relatively constant live weight. During the experiment, the average daily weight gain (ADG) of S and A animals in R group was 0.34 and -0.25 g/d (0.02 and -0.02 $g/kg^{0.75}/d$), respectively. While that of S and A animals in C group was 174.4 and 194.4 g/d (10.16 and 11.48 $g/kg^{0.75}/d$), respectively. Nitrogen (N) was determined by both measured and regression methods. Animals of R group stayed at about zero N balance (0.01 and -0.00 g $N/kg^{0.75}/d$ for S and A animals, respectively). The N retention of animals of both S and A breeds in C group were similar (0.45 and 0.46 g $N/kg^{0.75}/d$, respectively). Digestible organic matter intake (DOMI) and ME requirement for maintenance (MEm) were measured by both constant weight technique and regression method by regressing N balance on DOMI and ME intake on ADG. The measured DOMI during constant weight was 24.61 and 24.27 g $DOMI/kg^{0.75}/d$ and the calculated DOMI from regression equation was 24.24 and 24.22 g $DOMI/kg^{0.75}/d$, for S and A animals, respectively. The measured MEm was 402 and 401 kJ $ME/kg^{0.75}/d$ and the calculated MEm from regression analysis was 398 and 400 kJ $ME/kg^{0.75}/d$ for S and A breeds, respectively. There were no significant differences between both measured and regression techniques. There was no significant difference between S and A breeds for DOMI, N retention, MEm, digestibility and metabolizability values. Digestibility values for OM, GE and CP and metabolizability were significantly (p<0.05) higher in restricted feeding sheep compared with that of sheep fed ad libitum.

• Analytical Science and Technology
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• v.7 no.4
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• pp.427-434
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• 1994

For the analysis of the relatively volatile lead in blood by GFAAS(graphite furnace atomic absorption spectrophotometer), one can not raise the ashing temperature beyond certain degree due to the elevation of the baseline. Previous investigations showed that background is stabilized when the ashing temperature is raised to $700^{\circ}C$ using a matrix modifier. In this study, same result was obtained at the ashing temperature of around $550^{\circ}C$ even when the matrix modifier is not used and only Triton X-100 is used as a diluent, on an instrument which is equipped with both temperature and current controller(Shimadzu, AA-6501S) and thus the temperature control is fast and accurate. Background correction methods of $D_2$ arc and SR(self reversal) were reviewed. The results show that the absorbance is higher for the $D_2$ arc method, but the background correction is higher for the SR method.

• Transactions on Electrical and Electronic Materials
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• v.15 no.4
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• pp.226-229
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• 2014

In this study, lead-free $(Ba_{0.85}Ca_{0.15})(Ti_{1-x}Zr_x)O_3$ ceramics and a bimorph-type piezoelectric actuator were fabricated using the normal oxide-mixed sintering method, and their dielectric properties, microstructure, and displacement properties were investigated. From the results of X-ray diffraction, the pattern of the specimen has a pure perovskite structure. In addition, no secondary impurity phases were found. The excellent piezoelectric coefficient of $d_{33}=454pC/N$, the electromechanical coupling factor $k_p=0.51$, the dielectric constant ${\varepsilon}_r=3,657$, the mechanical quality factor $Q_m=239$, and $T_c$(Tetragonal-Cubic) =$90^{\circ}C$ were shown at x= 0.085. ${\Delta}k_p/k_p20^{\circ}C$ and ${\Delta}f_r/f_r20^{\circ}C$ showed the maximum value of -0.255 and 0.111 at $-20^{\circ}C$ and $80^{\circ}C$, respectively. The maximum total-displacement was $60{\mu}m$ under the input voltage of 50 V. As a result, it is considered that lead-free $(Ba_{0.85}Ca_{0.15})(Ti_{1-x}Zr_x)O_3$ ceramics is a promising candidate for piezoelectric actuator application for x= 0.085.

• Bulletin of the Korean Chemical Society
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• v.15 no.11
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• pp.980-984
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• 1994

Monomeric rhodium and iridium diimine complexes $Cp^*M(HNRNH)(Cp^*$ = 1,2,3,4,5-pentamethylcyclopentadienyl : (M=lr; R=o-$C_6H_4 (1a), 4,5-(CH_3)_2-C_6H_2-1,2 (1b), 4,5-(Cl)_2-C_6H_2-1,2$ (1c), NCC=CCN-1,2 (1d): M=Rh; R=NCC=CCN-1,2 (1e)) have been synthesized from $[CP^*MCl_2]_2$ and 2 equiv. of diamine in the presence of $NEt_3$. The Crystal structure of 1a was determined by X-ray diffraction method : 1a was crystallized in the monoclinic system, space group $P2_{1/c}$, with lattice constants a=9.543 (1) ${\AA}$, b=16.286 (1) ${\AA}$, c=10.068 (1) ${\AA}$ and ${\beta}$=99.25 (1), with Z= 4. Least-squares refinement of the structure led to R factor of 0.049. The coordination sphere of rhodium and iridium can be described as a 2-legged piano-stool. All complexes are highly colored. Electrochemical studies show that 1d and 1e display quasi-reversible reduction and 1a-1c display irreversible reductions, suggesting that the acceptor orbital might be localized on the diimine ring.

• Journal of IKEEE
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• v.19 no.3
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• pp.349-356
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• 2015

Air Defense Command Control and Alert(ADC2A) system is a system that ensures simultaneity and integrity of air defense operations by combining sensors, weapons and Command and Control(C2) systems over a tactical network to protect forces, facilities and strategic points from enemy's air attack. Improving message processing speed is a very important factor for ADC2A, because it uses high frequency bit-processing of the Army standard KVMF message to communicate with internal and external systems. In this paper we proposed improved method of KVMF message processing for ADC2A system.