• 설비공학논문집
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• 제23권7호
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• pp.513-519
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• 2011

The object of this study is to investigate the performance characteristics of refrigerators using a single-circuit multi cycle and a bypass two-circuit multi cycle. Each refrigeration cycle was tested by varying secondary fluid mass flow rate and temperature. Based on the experimental data, the optimum refrigerant charge was 48 g and the COP at the optimum secondary fluid mass flow rate was 1.53 for the single-circuit multi cycle. For freezer(F)-only mode, both the single-circuit multi cycle and the bypass two-circuit multi cycle were operated at overcharge conditions, resulting in an increase of the secondary fluid mass flow rate. The maximum COPs of the single-circuit multi cycle and the bypass two-circuit multi cycle were 1.22 and 1.35, respectively. The COP increased by 10.7% with the application of the bypass two-circuit multi cycle.

• 대한전자공학회논문지
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• 제10권1호
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• pp.9-17
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• 1973

본논문온 전류안정부저항특성을 나타내는 회로를 구성하는데 있어서, 입력전류가 변하는 어느 구간에서 입력전류의 변화에 따라서, SAMUEL SEELY가 제시한 Beam저항을 도입하여, Beam저항이 감소하는 원리를 적용하였다. 이러한 원리에 따르는 회로의 모델을 트랜지스터 회로로써 구체화하였다. 구체화된 트런지스터회로는 PNP 트런지스터와 NPN트랜지스터와 저항으로 이루어졌다. 이 회로의 전압-전류특성이 안정되도록 하기 위하여 회로를 수정하여 회로의 동작을 추정하여 해석하였다. 추정된 동작과 부저항치를 실험을 통하여 모두 뒷밭침 하였다. 여기서 얻어진 회로은 쟈이레이터의 구성과 SCR동작의 모의화등에 유용하게 이용될 것이며, 전류안정중저항회로의 구성에 관한 평이화를 기하였다.

• 전자공학회논문지T
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• 제35T권1호
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• pp.48-58
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• 1998

본 논문은 센서에서 수반되는 기생용량과 온도 드리프트 및 누설전류의 영향을 경감하기 위한 C-V변환회로 및 C-V변환회로에 관한 실험결과를 제시하고, 또한 논문에서 제안한 센싱 주파수를 기준주파수로 나누어줌으로써 상기 영향들을 줄일 수 있는 새로운 인터페이스 회로를 제시한다 이 회로는 용량비의 출력신호를 디지털 방식으로 16진수로 계수 함으로써 신호의 전송이나 컴퓨터 처리가 쉬울 뿐 아니라 비트수의 증가에 따라 분해 능을 향상시킬 수 있는 이점도 있다. 시작한 인터페이스 회로의 C-V 및 C-F 변환회로에서 전원전압 4.0V, 피이드백 커패시턴스10pF, 압력 0∼10 KPa범위에서 감도는 각각 28 ㎷/㎪·V, -6.6 ㎐/㎩로서 양호하였고, 온도 드리프트 특성은 0.051 %F.S./℃ 및 0.078 %F.S./℃로서 크게 개선되었다.

• 전기전자학회논문지
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• 제3권2호
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• pp.236-242
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• 1999

BiCMOS 공정으로 제조된 바이폴라 트랜지스터의 베이스 분산저항 ${\gamma}_{bb}$에서 발생되는 1/f 잡음을 실험 적으로 분석하였다. 공통컬렉터 잡음등가회로의 해석으로부터 $g_m^{-1}-{\gamma}_{bb}-R_B$값이 매우 작을 때는 출력측에서의 1/f 잡음은 순수하게 ${\gamma}_{bb}$에서 발생되는 잡음임을 실험을 통해서 확인할 수 있었다. $S^{1/f}_{Irbb}=K_fI_b{^{A_1}}/f$에서 $A_f=2,\;K_f{\simeq}5{\times}10^{-9}$를 얻었다. 그리고 Hooge상수 ${\alpha}$ 값은 ${\sim}10^{-3}$ 범위로 추출되었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.277-278
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• 2005

Admittance Spectroscopic analysis was applied to study the effect of LiF buffer layer and to model the equivalent circuit for poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV)-based polymer light emitting diodes (PLEDs) with the LiF cathode buffer layer. The single layer device with ITO/MEH-PPV/Al structure can be modeled as a simple parallel combination of resistor and capacitor. Insertion of a LiF layer at the Al/MEH-PPV interface shifts the highest occupied molecular orbital level and the vacuum level of the MEH-PPV layer as a result the barrier height for electron injection at the Al/MEH-PPV interface is reduced. The admittance spectroscopy measurement of the devices with the LiF cathode buffer layer shows reduction in contact resistance ($R_c$), parallel resistance ($R_p$) and increment in parallel capacitance ($C_p$).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.805-807
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• 2002

In this paper, a method for an accurate and fast transient analysis, which employs a single slot model for the rotor, is presented. The equivalent circuit parameters are extracted from a combined method of F. E. M and equivalent circuit on 1 slot rotor boundary condition. Two kinds of circuit parameters for each slip are applied to equivalent circuit controlled by variable-voltage variable- frequency. One is the constant parameters at rated speed, and the other is the parameters varying in accordance with slip-frequency. The computer characteristics of the suggested method for four-pole 1.5KW induction motor are compared with those of Equivalent circuit for the transient analysis.

• Journal of Advanced Marine Engineering and Technology
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• 제9권1호
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• pp.61-73
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• 1985

The induction motor is widely used in the power equipments of the ship and the various industrial drive applications because it is robust and relatively simple and cheap to manufacture, but it has a disadvantage that the speed of induction motor is not controlled in wide range such as d.c motor. In this paper, the characteristics relating to the Kramer system that the speed of three phase wound type induction motor is controlled by changing the exciting e.m.f. of the secondary circuit is described. In order to analyze the characteristics, a new simplified and approximated T-type equivalent circuit from the Kramer circuit with three phase graetz connection and d.c machine is proposed. The stator current, motor torque and mechanical output power are computed by the current, torque and power equations derived by its equivalent circuit. Through the experiments, the $I_f-N$, torque-slip and current-slip characteristic curves of the tested motor are obtained and the various needed constants are determined. The numerical values obtained from the above method are compared with experimental values under the same conditions. As a result of the above investigation, it is found that the induction motor speed by the Kramer system is controlled by 28 per cent under the rated speed by changing the field current of d.c motor and the values computed by the current and torque equations derived by the simplified and approximated T-type equivalent circuit generally come to approach the experimental values.

• 한국전자파학회논문지
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• 제8권1호
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• pp.94-99
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• 1997

발진기의 위상잡음에 영향윤 주는 요인은 여러 가지가 있다. 그러나 발진기의 위상잡음은 주로 캐리어(carrier)와 l/f의 특성을 잦는 DC 근처 저주파 잡음과의 혼합으로 발생되므로, 저주파 플리커 잡음에 의해 지배된다. 본 논문에서는 능동 바이어스 회로로 구현된 저주파 궤환회로를 이용하여 플리커 잡음의 영향을 최소화함으로써 발진기의 위상잡음을 줄이는 기법을 제안하고, DBS 수신기에 사용 가능한 DRO를 제작하였다. 제작된 DRO의 위상잡음을 측정한 갤과 10 kHz 옵셋 주파수에서 약 -92 dBc/Hz로 제안된 방볍이 상당히 효과적임을 확인 하였다

• 오토저널
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• 제4권3호
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• pp.48-55
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• 1982

In the present the strain gauge type torque transducers consist of solid shaft as sensor, slip ring, brush and bridge circuit as detecting circuit. So in the case of measuring the low-capacity torque, the error caused by technical mistake in mounting stain gauge on the small sensor and especially by contact resistance between slip ring and brush takes place more than the large sensor. Therefore in this study constant voltage in order to have no effect of contact resistance is supplied to the hollow shaft and Schrobron Bridge Circuit. Through the experiment good results were obtained as follows; linearity, hysterisis and zero drift as static characteristics is within 1% F.S respectively. Also when loading, zero drift is about 2% F.S.

• Journal of Electrical Engineering and information Science
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• 제2권5호
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• pp.129-133
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• 1997

A circuit model for a field emission triode has been proposed. The model parameters have been extracted from he fabricated silicon tip array and verified by comparing with the results simulated by circuit simulator(SPICE). The cut-off frequency can be calculated from the parametric capacitance and the transconductance values extracted from measurements. For the field emission triode, the capacitance of 3.45fF/tip and the transconductance of 0.94nS/tip have been measured under the emission current of 4.1nA/tip. From these values, the cut-off frequency is predicted to be 43 kHz but th measured one came out to be 6 kHz. because o the parasitic capacitance components.