• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1674-1676
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• 1999

Oxide of the form $Mn_3O_4-CuO-Co_3O_4$-NiO-ZnO present properties that make them useful as power NTC thermistor for current limited. Power NTC thermistor electric properties of $Mn_3O_4-CuO-Co_3O_4$-NiO-ZnO system has been measured as a function of temperature and composition and current - voltage, time constant, activation energy, heat dissipation coefficient have also been determined.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.265-267
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• 2001

In this paper, some optical parameters which have effects on the measuring precision and sensitivity of optical current sensor are analyzed. Each parameter occurs changes of specific characteristics of optical sensor system. The influences of performance and characteristics variation of optical current sensor are described in accordance with the changes of optical output power, optical bias point which is called phase difference, and a specific constant related to sensor material and wavelength of light source.

• 한국세라믹학회지
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• 제49권4호
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• pp.385-396
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• 2012

Thermal shock test methods and thermal shock parameters for ceramics were reviewed from the following viewpoints: (1) The test methods should be based on the precise estimation of both temperature and thermal stress distributions in a specimen taking into account the temperature-dependent thermo-mechanical properties; (2) The thermal shock parameters must be defined as a physical property of the materials and described as a function of temperature at the fracture point of the specimen; (3) The relation between the strength and fracture toughness of brittle ceramics under a thermal shock load must be the same as the relation under a mechanical load. In addition, appropriate thermal shock parameters should be defined by the thermal shock strength and thermal shock fracture toughness based on stress and energy criteria, respectively. A constant heat flux method is introduced as a testing technique suitable for estimating these thermal shock parameters directly from the electric power charged.

• 한국안전학회지
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• 제28권2호
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• pp.6-13
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• 2013

This study focuses on finding ECO driving patterns which consider driving safety of the ATO system train and reliability and which optimize efficiency of the driving energy consumption. Research results derived by performing simulation of those 5 models show that the emergency braking which affects safety of passenger and the machinery is minimized, and safe driving speed is maintained by the prohibition of drastic acceleration/deceleration, coasting and constant-speed driving. Therefore if this result is applied to the urban railway train by amending or making ATO program to save energy usage that improve environmental quality, its effects as ECO driving pattern is huge.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.476-481
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• 2001

In a vacuum circuit breaker mechanism, a spring-actuated linkage system is used to satisfy the desired opening and closing characteristics of electric contacts. Because the opening dynamics of electric contacts is determined by such a linkage system, the stiffness, free length and attachment points of a spring become the important design parameters. In this paper, based on the energy conservation that the total system energy is constant throughout the operating range of a mechanism, a systematic design procedure of determining the spring design parameters is presented. The proposed procedure is applied to the design of an opening spring for satisfying the specified opening characteristics.

• 한국정밀공학회지
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• 제19권11호
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• pp.37-45
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• 2002

This paper presents the field-dependent Bingham characteristics and damping force control of an electro-rheological (ER) fluid under squeeze mode operation. The squeeze force of the ER fluid due to the imposed electric field is analyzed and an appropriate size of the disk-type electrode is devised. On the basis of the theoretical model of the ER fluid under squeeze mode operation, the yield stress and response speed of the ER fluid are distilled from the time responses of squeeze force to the step electric potentials. Measured squeeze forces under various excitation conditions are compared with the predicted ones from Bingham model and time constant obtained at the transient response test. In addition, the controllability of the field-dependent damping force of the ER fluid under squeeze mode is experimentally demonstrated by implementing simple PID controller.

• 제어로봇시스템학회논문지
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• 제6권12호
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• pp.1053-1060
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• 2000

In this paper, a discrete-time variable structure control method using recursively defined switching function and a decoupled variable structure disturbance compensator is used to achieve high performance circular motion control of a CNC machining center. The discrete-time variable structure control with the decoupled disturbance compensator method developed in this paper uses a recursive switching function defined as the sum of the current tracking error vector and the previous value of the switching function multiplied by a positive constant less than one. This recursive switching function provides much improved performance compared to the method that uses a switching function defined only as a linear combination of the current tracking error. Enhancements in tracking performance are demonstrated in the circular motion control using a CNC milling machine.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.227-232
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• 1991

Silicone resin which is made from silicone(Si) is well known by its heat-resistant property. Its good heat-resistant enables silicons resin being used in high temperature (up to $200^{\circ}C$) heavy-dury environment for electric insulation. This paper has dealed with the electrical properties of silicone resin such as dielectric constant and tan ${\delta}$ with heat treatment temperature $(200^{\circ}C{\sim}450^{\circ}C)$. To investigate the electrical insulation of silicone resin, dielectric strength by A.C and anti-tracking properties under both AC and D.C have been performed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1664_1665
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• 2009

Many years ago, most of thermal power plants built in this country were of subcritical pressure, of medium or small size, of constant pressure operations and of drum type steam generators with circulation type boilers. But, nowadays almost all of them were of high efficiency, of supercritical pressure, of big capacity, of sliding pressure operations, and of once through type steam generator. It has such advantage as the reduction of startup duration, but it control system and operation method are very complicated. It has a big difference in operation method of turbine and boiler. The feedforward control needs to be introduced to prevent such problems as thermal shock during the transit from normal operation into bypass operation. This paper introduces the turbine control and turbine bypass control during startup of thermal power plants.

• Tribology and Lubricants
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• 제16권2호
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• pp.75-83
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• 2000

The present paper proposes a new type of an electro-rheological squeeze film damper (ER SFD) of which the damping capacity can be controlled by the application of electric field. The new ER .SFD- is sealed with slotted rings having electrodes at the inside of the constant gap. The ER SFD can provent the problem of electric short which might be occurred in a previous ER SFD. Reynolds lubrication equation for a Newtonian fluid and the end leakage equation for ER fluids are numerically solved to get the pressure distributions and the damping coefficients of the ER SFD. The results show that the damping coefficients greatly increase with increasing the yield shear stress of ER fluid. In addition, the unbalance response analysis of a flexible rotor supported on the new ER SFD implies that the rotor system can be operated with the minimum of rotor amplitude and force transmissibility by controlling the yield shear stress of ER fluids properly.