• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.73.1-73.1
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• 2010

For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.53-57
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• 1992

We report the crystal growth and the electro-optic characteristics of $CdS_{1-x}Se_{x}$ thin films. $CdS_{1-x}Se_{x}$ thin films wire deposited on the alumina plate by electron beam evaporation technique in pressure of $1.5{\times}10^{-7}$ torr, voltage of 4kV, current of 2.5mA and substrate temperature of $300^{\circ}C$. The deposited $CdS_{1-x}Se_{x}$ thin films were proved to be a polycrystal with hexagonal structure through X-ray diffraction patterns. $CdS_{1-x}Se_{x}$ photoconductive films showed high photoconductivity after annealing at $550^{\circ}C$ for 30 minutes. And the films have been investigated the Hall effect, photocurrent spectra, sensitivity, maximum allowable power dissipation and response time.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.271-275
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• 2010

Forming tool design is carried out for a manufacturing a outer shell structure of the nozzle extension of regenerative cooling thrust chamber. The method which manufactures outer shell structure of nozzle extension is a metal forming process using thin plate. Because the configuration of outer shell structure is changed after forming process by springback effect, the outer shell structure can't be exactly formed with the same forming tool as configuration of the nozzle extension. Therefore forming tool design considering springback effect is necessary for manufacturing the outer shell structure of the nozzle extension. In this study, new designed forming tool configuration was generated to decrease the errors between nozzle contour and formed structure. The analysis results show that the errors between nozzle contour and formed structure is significantly decreased using the new designed forming tool.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.6
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• pp.471-477
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• 2000

The position control accuracy of a robot arm is significantly deteriorated when a long arm robot is operated at a high speed. In this case, the robot arm must be modeled as a flexible structure, not a rigid one, and its control system should be designed with its elastic modes taken into account. In this paper, the tip position control scheme of a one-link flexible manipulator using 2-DOF controller with sliding mode is presented. The robot consists of a flexible arm manufactured with a thin aluminium plate, an AC servo motor with a harmonic drive for speed reduction, an optical encoder and a CCD camera as a vision sensor for on-line measuring the tip deflection of the flexible m. Simulation and experimental results of the flexible manipulator with a proposed controller are provided to show the effectiveness of the controller.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1347_1348
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• 2009

We fabricated FEDs based on ZnO nanowires. ZnO nanowires were synthesized on Au thin films by hydrothermal method on hot plate. After 2 hours, we obtained nanowires of chin form. The high-purity nanowires showed sharp tips geometry with a wurtzite structure. The field emission properties of the ZnO nanowires were investigated in high vacuum chamber. The turn-on field for the ZnO nanowires was found to be about 4.1 V/${\mu}m$ at a current density of $0.1{\mu}A/cm^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.664-667
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• 2001

A flat-type L$_1$-B$_{8}$ Mode Ultrasonic motor(USM) uses longitudinal-bending multi-mode vibrator which is constructed with the metal-piezoceramic composite thin plate vibrator. Especially, the characteristics of vibrating displacement of the vibrator are important for the fabrication of USM. So, in this study, we tried to analyze them by the FEM(finite element method) simulation program. ANSYS 5.6 we used is a finite element software enabling the analysis of 2 or 3 dimensional structure of piezoelectric materials. Using this made us analyzing the resonance frequency and calculating displacement of vibrator and then the position of the projection.n.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.229-232
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• 1996

The position control accuracy of the robot arm is decreased significantly when a long arm robot is operated at high speed. In this case, the robot arm must be modeled as a flexible structure, not a rigid one, and its control system will be necessarily designed with its elastic modes taken into account. In this paper, the vibration control of a one-link flexible robot arm is presented. The robot system consists of a flexible arm manufactured with thin aluminium plate, AC servomotor with a harmonic drive for speed reduction, optical encoder and accelerometer. The system is modeled with limited number of elastic modes, and its parameters are determined from the results of the experiments. The implemented control schemes are LQ control and sliding mode control. The experiments and digital simulations are carried out to test the validity of the system modeling, controller design, and active control implementation.

• YAKHAK HOEJI
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• v.22 no.1
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• pp.22-26
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• 1978

The purposes of this investigation were to study the characteristic properties of bismuthoxynitrate formed by hydrolysis of bismuthnitrate according to various reaction conditions and to propose the property difference between synthesized pearl pigment and bismuthsubnitrate as pharmaceuticals by means of X-ray diffraction, IR, DTA and TGA. The pearl pigment could be obtained by reaction of bismuth nitrate-diluted nitric acid solution with cold water (5.deg.) agitation at lower pH. The pearl pigment was BiO. NO$_{3}$. 2H$_{2}$O. in composition and crystalline form was thin plate of monoclinic system and its combination with water was assumed to be hydrated hydrous form between Bi-H$_{2}$O bond. On the other hand, bismuthsubnitrate was 5BiO.4NO$_{3}$.6H$_{2}$O in composition and crystalline form was pillar of rhombic system and the bond between Bi and H$_{2}$O molecules was assumed to be hydrous form. The different properties between two compounds in structure are presumed to be caused by the hydrolysing conditions of bismuthnitrate respectively.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.220-227
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• 1999

The position control accuracy of a robot arm is significantly deteriorated when a long slender arm robot is operated at a high speed. In this case, the robot arm needs to be modeled as a flexible structure, not a rigid one, and its control system needs to be designed with its elastic modes taken into account. In this paper, the vibration control scheme of a one-link flexible manipulator using adaptive input shaper in conjunction with PID controller is presented. The robot consists of a flexible arm manufactured with a thin aluminium plate, an AC servo motor with a harmonic drive for speed reduction, an optical encoder and an accelerometer. On-line identification of the vibration mode is done using the pruned decimation-in-time FFT algorithm to estimate the parameter of the input shaper. Experimental results of the flexible manipulator with a PID controller and input shaper are provided to show the effectiveness of the advocated controllers.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.71-81
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• 2001

This paper analyzes the effectiveness of minimizing vibration and sound transmission on/through a thin rectangular plate by both feedback control and hybrid control which combines adaptive feedforward control with a feedback loop. An experimental system identification technique using the matrix-fractional curve-fitting of the frequency response data is introduced for complex shaped structures. This identification technique reduces the model order o the MIMO(Multi-Input Multi-Output) system which simplifies the practical implementation. The adaptive feedforward control uses a Multiple filtered-x LMS(Least Mean Square) algorithm and the feedback control uses a multivariable digital LQG(Linear Quadratic Gaussian) algorithm. Experimental results show that an effective reduction of sound transmission is achieved by the hybrid control scheme when both vibration and noise measurement signals are incorporated in the controller.