• 전자공학회논문지S
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• 제34S권6호
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• pp.85-93
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• 1997

This paper analyzes the steady-state and dynamic characteristics of the watkings-johnson converter. the major contributions of this paper includ identification of the following characteristics unique to the watkins-johnson converter: (1) The output voltage of the converter is nearly constant at the continous conduction mode (CCM), and at discontinousou conduction mode (DCM) it decreses linerly as the output curretn increases. (2) The control-to-output transfer function is a second-order one with a left-half-plane (LHP) zero determined by the combination of the output capacitor and equivalent series resistor of the converter. This LHP zero signinificantly improves the stability of the converter. (3) The control-to-output transfer function reduces to a first-order one, as the converter moves from CCM to DCM. (4) The parastic resistance of the inductor does not cause any significant influence on poles and zeros of the transfer function.

• Nuclear Engineering and Technology
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• 제32권4호
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• pp.372-378
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• 2000

The effect of alloying elements on the creep resistance of Zr alloys was investigated using thermal creep tests that were performed as a part of advanced fuel cladding development. The creep tests were conducted at 40$0^{\circ}C$ and 150 MPa for 240 hr. A statistical model was derived from the relationship between the steady-state creep rate and the content of individual alloying elements. The creep strengthening effect decreased in the following sequence : Nb, Sn, Mn, Cr, Mo, Fe and Cu. The high creep resistance of Sn and the opposite effect of Fe on zirconium alloys seem to be associated with their lowering and enhancing, respectively, the self-diffusivity of the zirconium matrix.

• Journal of Advanced Marine Engineering and Technology
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• 제24권6호
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• pp.34-42
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• 2000

In this paper conventional technique will be described, which can be used for the measuring various parameters of induction motor. This is followed by presenting some other, alternative, techniques. The two tests are described which are suitable to obtain the electrical parameters of symmetrical 1hp three-phase squirrel-cage induction motor. These are the blocked rotor test and no load test. By the application of these, it is possible to determine the parameters which are presented in the steady-state equivalent-circuit of determining an induction motor. One conventional method of determining the inertia of an induction motors is obtained by performing retardation tests. The angular rotor speed of the motor is monitored, following its disconnection from the stator supply. Since the inertia torque J dw/dt contains the inertia coefficient J and the friction and windage torque Bw contains the coefficient B, then J and B can be determined by performing retardation tests.

• 미생물학회지
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• 제5권1호
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• pp.34-38
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• 1967

Theoretical analysis reported in this paper is on the varities of the growth rate of Chlorella ellipsoidea due to the amount of available phosphorus for the purpose of the continual mass culture. Available phosphorus in the culture media of the Chlorella was also estimated at a limiting factor as this experiment. The equation between the concentration of Chlorella n and growth period t is $\frac{dn}{dt}=Kn$, and the functional relation between the Specific growth rate K and steady state period T is the following: $K=\frac{2.303}{T}$log\frac{n}{no}$ ($n_o$=initial concentration).

• 전기의세계
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• 제26권6호
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• pp.55-58
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• 1977

This paper deals with the transient analysis of an amplidyne dc voltage regulating system under the following conditions: (1) assuming all the components of the system to be linear, (2) considering the effect of amplidyne saturation. The mathematical technique employed is state variables method. The calculated response curves are compared with the experimental results obtained on a practical system. The main results can be summerized as follows: 1) The effect of amplidyne saturation on the transient response of a dc voltage regulating system is to reduce the overshoot and setting time. 2) With the increase in level of the step reference voltage, the system response becomes apesiodic. 3) The steady output voltage is reduced appreciably compared to the linear case.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권6호
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• pp.433-439
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• 2004

The Helicopter Simulator System is non-linear and complex. Futhermore, because of absence of its accurate mathematical model, it is difficult to control accurately its attitudes such as elevation angle and azimuth one. Therefore, we proposed a Hybrid GA-PID WAVENET(Genetic Algorithm Proportional Integral Derivative Wavelet Neural Network)control technique to control efficiently these angles. The proposed Hybrid GA-PID WAVENET is made through the following process. First, the WAVENET fundamental functions are defined. And their dilation and translation values are adjusted by GA to construct the optimal WAVENET controller. Secondly, the proportional, integral, and derivative gain coefficients of PR controller are tuned optimally. Finally, WAVENET controller which has a good transient characteristic and GA-PE controller which has a good steady state characteristic is adequately combined in hybrid type. Through the computer simulations, it is proved that the Hybrid GA-PE WAVENET control technique has a more excellent dynamic response than PID control technique and GA-PID one.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.214-217
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• 1993

This paper presents a new identification method which utilizes fuzzy inference in parameter identification. The proposed system has an additional control loop where a real plant is replaced by a plant model. The control system to be designed is to satisfy the following specifications: 1) It has zero steady-state error. 2) It has adequate damping characteristics. 3) 1),2) satisfied, it has a shortest rise-time. Fuzzy rules describe the relationship between comparison results of the features and magnitude of modification in the model parameter values. This method is effective in auto-tuning because the response of the closed loop is verified. The proposed method is tested in simulation for several plants with first- order lags and dead-times. The results show that the proposed method is effective in practical use.

• Journal of Power Electronics
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• 제18권6호
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• pp.1619-1626
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• 2018

The output power of most facilities for renewable energy generation is unstable due to external environmental conditions. In distributed power systems with two or more sources, a stable output can be achieved with the complementary power supply among the different input sources. In this paper, a double-input DC-DC converter with a wide-input-voltage-range is proposed for renewable energy generation. This converter has the following advantages: the circuit is simple, and the input voltage range is wide and the fault tolerance is excellent. The operation modes and the steady-state analysis are examined. Finally, experimental results are illustrated to verify the correctness of the analysis and the feasibility of the proposed converter.

• Journal of Electrochemical Science and Technology
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• 제13권1호
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• pp.19-31
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• 2022

Lithium-ion battery development is one of the most active contemporary research areas, gaining more attention in recent times, following the increasing importance of energy storage technology. The galvanostatic intermittent titration technique (GITT) has become a crucial method among various electrochemical analyses for battery research. During one titration step in GITT, which consists of a constant current pulse followed by a relaxation period, transient and steady-state voltage changes were measured. It draws both thermodynamic and kinetic parameters. The diffusion coefficients of the lithium ion, open-circuit voltages, and overpotentials at various states of charge can be deduced by a series of titration steps. This mini-review details the theoretical and practical aspects of GITT analysis, from the measurement method to the derivation of the diffusivity equation for research cases according to the specific experimental purpose. This will shed light on a better understanding of electrochemical reactions and provide insight into the methods for improving lithium-ion battery performance.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.346-351
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• 1998

In design of a digital current controller for a 3-phase (3 ) voltage-source (VS) PWM converter, its conventional model, i.e., stationary or synchronous reference frame model, is used in obtaining its discretized version. It introduces, however, inherent errors since the following practical problems are not taken into consideration: the characteristics of the space vector-based pulse-width modulation (SVPWM) and the time delays in the process of sampling and computation. In this paper, the new hybrid reference frame model of the 3 VS PWM converter is proposed considering these problems. In addition, the direct digital current controller based on this model is designed without any prediction or extrapolation algorithm to compensate the time delay. So the control algorithm is made very simple. It represents no steady-state error in input current control and has the optimized transient responses. The validity of the proposed algorithm is proved by the computer simulation and experimental results.