• 대한기계학회논문집B
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• 제24권7호
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• pp.967-975
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• 2000

Transient characteristics of a boiler and turbine system for a steam power plant are simulated. One-dimensional unsteady models are introduced for each component. An interaction between boiler and turbine and a control of the water level in the drum are taken into account. Transient responses of the system to the variations of main system variables such as fuel and air flow rate, cooling water injection rate at the attemperator, gas recirculation rate at the furnace and opening of the turbine control valve are examined. Effect of fluid inertia and tube wall thermal inertia on predicted dynamic behavior is investigated.

• International Journal of Air-Conditioning and Refrigeration
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• 제8권1호
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• pp.29-39
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• 2000

A series of tests were performed to verify the transient characteristics of heat pump in heating and cooling mode when operating speed was varied over the 30 to 102Hz. One of the major issues that has not been addressed so far is transient characteristics during speed modulation. The model for cycle simulation has been developed to predict the cycle performance under conditions of decreasing drive frequency and the results of the theoretical study were compared with the results of the experimental study. The simulated results were in good agreement with the experimental result within 10%. The transient cycle migration of the liquid state refrigerant causes significant dynamic change in system. Thus, the migration of refrigerant was the most important factor whenever do experimental results analysis or develop simulation model.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 센서 박막재료 반도체 세라믹
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• pp.208-212
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• 2003

Silicon transient voltage suppressors (TVSs) are clamping devices that limit voltage spikes by low impedance avalanche breakdown of a rugged silicon PN junction. They are used to protect sensitive components from electrical overstress such as that caused by induces lightning, inductive load switching and electrostatic discharge. In this paper, we present static and dynamic characteristics of TVS diode using thermal analysis simulation software. And also, it is presented that the thermal dissipation characteristics of TVS diode in the transient state.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.133-134
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• 2005

When Power MOSFET is operated, it causes lots of heat, which influences negatively on the characteristics of the devices and shorten the lifespan of them. Therefore, a heat sink should be mounted on to emit the heat. In this experiment, we've found the changes of the characteristics of Thermal Transient of MOSFET when a heat sink is applied. In addition, we've found other changes when heat sink compound is applied as well.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1947-1949
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• 1999

Carrier lifetime in silicon power devices caused switching delay and excessive power loss at high frequency switching. We studied transient turn-on/turn-off transient characteristics of electron irradiated and proton irradiated silicon pn junction diodes. Both the electron and proton irradiation of power devices have already become a widely used practice to reduce minority carrier lifetime locally[1]. The sample is n+p junction diode, made by ion implantation on a $20\Omega.cm$ p-type wafer. We investigated turn-on/turn-off transient & breakdown voltage characteristics by digital oscilloscope. Our data show that proton irradiated samples show better performance than electron irradiated samples.

• Water Engineering Research
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• 제4권2호
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• pp.69-85
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• 2003

Previously developed empirical equations used to calculate the parameters of the transient storage model are analyzed in depth in order to evaluate their behavior in representing solute transport in the natural streams with storage zone. A comparative analysis of the existing theoretical and experimental equations used to predict parameters of the transient storage (TS) model is reported. New simplified equations for predicting 4 key parameters of the TS model using hydraulic data sets that are easily obtained in the natural streams are also developed. The weighted one-step Huber method, which is one of the nonlinear multi-regression methods, is applied to derive new parameters equation. These equations are proven to be superior in explaining mixing characteristics of natural streams with the transient storage zone more precisely than the other existing equations.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1802-1812
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• 2001

The theoretical method is developed to investigate the effects of ring stiffeners on free vibration characteristics and transient response for the ring stiffened composite cylindrical shells subjected to the impulse pressure Loading. In the theoretical procedure, the Love's thin shell theory combined with the discrete stiffener theory to consider the ring stiffening effect is adopted to formulate the theoretical model. The concentric or eccentric ring stiffeners are laminated with composite and have the uniform rectangular cross section. The modal analysis technique is used to develop the analytical solutions of the transient problem. The analysis is based on an expansion of the loads, displacements in the double Fourier series that satisfy the boundary conditions. The effect of stiffener's eccentricity, number, size, and position on transient response of the shells is examined. The results are verified by comparison with FEM results.

• 한국전산유체공학회지
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• 제10권2호
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• pp.69-81
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• 2005

A fluid transient analysis for the propellant flow in a monopropellant propulsion system is conducted by using the method of characteristics(MOC). It reviews algebraic simultaneous equations method and Cramer's rule method utilized to drive the compatible and characteristic equations to understand MOC extensively. The identification of fluid transient phenomena of propulsion system of Koreasat 1 is carried out through parametric studies. The valve response time is one of the dominant parameters governing the fluid transient phenomena. The results show that the shorter closing time induces the greater pressure response amplitude. And it shows that the installation of in-line orifice is effectively to limit the fluid transients in rapid valve response time and at high pressure. But it seems that the effect of orifice weakens at slow valve response time and at low pressures.

• 한국초전도ㆍ저온공학회논문지
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• 제4권2호
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• pp.68-72
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• 2002

This work investigates the transient cooling characteristics of an Infrared (IR) detector cryochamber, which has a critical effect on the cooling load. The current thermal modeling considers the conduction heat transfer through a cold well. the gaseous conduction due to outgassing. and the radiation heat transfer. The transient cooling Performance. i.e. the penetration depth and cooling load, is determined using a finite difference method. It is found that the penetration depth increases as the bore conductivity increases. Gaseous conduction and radiation hardly affect the penetration depth. The transient cooling load increases as the bore conductivity increases. The effects of gaseous conduction and radiation on transient heat transfer are weak at initial stages of cooling. However, their effects become significant as the cooling Process Proceeds.

• Transactions on Electrical and Electronic Materials
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• 제4권6호
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• pp.32-37
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• 2003

In this paper, the trap characteristics of thin silicon oxides is investigated in the ULSI implementation with nano structure transistors. The stress and transient currents associated with the on and off time of applied voltage were used to measure the distribution of high voltage stress induced traps in thin silicon oxide films. The stress and transient currents were due to the charging and discharging of traps generated by high stress voltage in the silicon oxides. The transient current was caused by the tunnel charging and discharging of the stress generated traps nearby two interfaces. The stress induced leakage current will affect data retention in electrically erasable programmable read only memories. The oxide current for the thickness dependence of stress current, transient current, and stress induced leakage currents has been measured in oxides with thicknesses between 113.4nm and 814nm, which have the gate area 10$\^$-3/ $\textrm{cm}^2$. The stress induced leakage currents will affect data retention, and the stress current and transient current is used to estimate to fundamental limitations on oxide thicknesses.