• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.301-306
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• 2009

This paper describes the design and fabrication of 16$\times$16 microbolometer infrared focal plane arrays based on iMEMS technology. Amorphous silicon was used for infrared-sensitive material, and it showed the resistance of 18 Mohm and the temperature coefficient of resistivity of -2.4 %. The fabricated sensors exhibited responsivity of 78 kV/W and thermal time constant of 8.0 msec at a bias voltage of 0.5 V. The array performances had satisfactory uniformity less than 5 % within one-sigma. Also, 1/f noise of pixel was measured and the noise factor of $6\times10^{-11}$ was extracted. Finally, we obtained detectivity of $1.27\times10^9cmHz^{0.5}/W$ and noise equivalent temperature difference of 200 mK at a frame rate of 30 Hz.

• Journal of the Korean Magnetics Society
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• v.26 no.6
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• pp.201-205
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• 2016

In this report, we measured the impedance spectrum in TMR device, and the relaxation behavior of the real and imaginary impedance spectrum was analyzed by using the equilibrant circuit of tunneling capacitance ($C_T$) and tunneling resistance ($R_T$). The relaxation frequency was increased with AC voltage in both the parallel and antiparallel alignment of two magnetic layers. The $R_T$ with AC voltage showed the typical bias voltage dependence. However, the $C_T$ showed large value than the expected geometrical capacitance. The huge increase of $C_T$ was affecting as a limiting factor for the high speed operation of TMR devices. Thus, the supercapacitance of $C_T$ should be considered to design the high speed TMR devices.

• Korean Journal of Materials Research
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• v.20 no.11
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• pp.570-574
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• 2010

A diamond-like carbon (DLC) film deposited on a WC disk was investigated to improve disk wear resistance for injection molding of zirconia optical ferrule. The deposition of DLC films was performed using the filtered vacuum arc ion plating (FV-AIP) system with a graphite target. The coating processing was controlled with different deposition times and the other conditions for coating, such as input power, working pressure, substrate temperature, gas flow, and bias voltage, were fixed. The coating layers of DLC were characterized using FE-SEM, AFM, and Raman spectrometry; the mechanical properties were investigated with a scratch tester and a nano-indenter. The friction coefficient of the DLC coated on the WC was obtained using a pin-on-disk, according to the ASTM G163-99. The thickness of DLC films coated for 20 min. and 60 min. was about 750 nm and 300 nm, respectively. The surface roughness of DLC films coated for 60 min. was 5.9 nm. The Raman spectrum revealed that the G peak of DLC film was composed of $sp^3$ amorphous carbon bonds. The critical load (Lc) of DLC film obtained with the scratch tester was 14.6 N. The hardness and elastic modulus of DLC measured with the nano-indenter were 36.9 GPa and 585.5 GPa, respectively. The friction coefficient of DLC coated on WC decreased from 0.2 to 0.01. The wear property of DLC coated on WC was enhanced by a factor of 20.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.422-448
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• 1996

Low-temperature epitaxial growth of Si and SiGe layers of Si is one of the important processes for the fabrication of the high-speed Si-based heterostructure devices such as heterojunction bipolar transistors. Low-temperature growth ensures the abrupt compositional and doping concentration profiles for future novel devices. Especially in SiGe epitaxy, low-temperature growth is a prerequisite for two-dimensional growth mode for the growth of thin, uniform layers. UHV-ECRCVD is a new growth technique for Si and SiGe epilayers and it is possible to grow epilayers at even lower temperatures than conventional CVD's. SiH and GeH and dopant gases are dissociated by an ECR plasma in an ultrahigh vacuum growth chamber. In situ hydrogen plasma cleaning of the Si native oxide before the epitaxial growth is successfully developed in UHV-ECRCVD. Structural quality of the epilayers are examined by reflection high energy electron diffraction, transmission electron microscopy, Nomarski microscope and atomic force microscope. Device-quality Si and SiGe epilayers are successfully grown at temperatures lower than 600℃ after proper optimization of process parameters such as temperature, total pressure, partial pressures of input gases, plasma power, and substrate dc bias. Dopant incorporation and activation for B in Si and SiGe are studied by secondary ion mass spectrometry and spreading resistance profilometry. Silicon p-n homojunction diodes are fabricated from in situ doped Si layers. I-V characteristics of the diodes shows that the ideality factor is 1.2, implying that the low-temperature silicon epilayers grown by UHV-ECRCVD is truly of device-quality.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.267-277
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• 2009

Partial safety factors of the load, resistance, and reliability function are evaluated according to the target probability of failure on sliding mode of monolithical vertical caisson of composite breakwaters. After reliability function is formulated for sliding failure mode of caisson of composite breakwaters regarding bias of wave force, uncertainties of random variables related to loads, strengths are analyzed. Reliability analysis for the various conditions of water depth, geometric, and wave conditions is performed using Level II AFDA model for the sliding failure. Furthermore, the reliability model is also applied to the real caisson of composite breakwaters of Daesan, Dong- hae, and Pohang harbor. By comparing the required width of caisson of composite breakwater according to target probability of failure with the other results, the partial safety factors evaluated in this study are calibrated straightforwardly. Even though showing a little difference on the 1% of target probability, it may be found that the present results agree well with the other results in every other target probability of failure.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.445-453
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• 2000

In this paper, the method of designing an active inductor for MMIC is proposed. The proposed tunable active inductor is composed of a cascade FET with feedback capacitors and resistors. Because of a very low series resistance in the proposed inductor, a very high Q factor can be obtained. Also it has an excellent characteristics suitable for high frequency band. The inductance value can be changed by controlling feedback capacitors, resistors and a bias voltage respectively. When the feedback resistor and parallel resistor within circuits are varied, the inductance value is changed from 0.2 nH to 1.7 nH in the range 1 to 15 GHz. Also we designed bandpass filter using the proposed active inductor and it shows the insertion loss of 0.4 dB and return loss, 20 dB.

• Computers and Concrete
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• v.15 no.2
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• pp.259-277
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• 2015

The lack of experimental studies on the mechanical behavior of reinforced concrete (RC) haunched beams leads to difficulties in statistical and reliability analyses. This study performs stochastic and reliability analyses of the ultimate shear capacity of RC haunched beams based on nonlinear finite element analysis. The main aim of this study is to investigate the influence of uncertainty in material properties and geometry parameters on the mechanical performance and shear capacity of RC haunched beams. Firstly, 65 experimentally tested RC haunched beams and prismatic beams are analyzed via deterministic nonlinear finite element method by a special program (ATENA) to verify the efficiency of utilized numerical models, the shear capacity and the crack pattern. The accuracy of nonlinear finite element analyses is verified by comparing the results of nonlinear finite element and experiments and both results are found to be in a good agreement. Afterwards, stochastic analyses are performed for each beam where the RC material properties and geometry parameters are assigned to take probabilistic values using an advanced simulating procedure. As a result of stochastic analysis, statistical parameters are determined. The statistical parameters are obtained for resistance bias factor and the coefficient of variation which were found to be equal to 1.053 and 0.137 respectively. Finally, reliability analyses are accomplished using the limit state functions of ACI-318 and ASCE-7 depending on the calculated statistical parameters. The results show that the RC haunched beams have higher sensitivity and riskiness than the RC prismatic beams.