• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.315.2-315.2
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• 2014

Pt-functionalized ZnS nanowires were synthesized on Au-deposited c-plane sapphire substrates by thermal evaporation of ZnS powders followed by wet Pt coating and annealing. The $NO_2$ gas sensing properties of multiple-networked Pt-functionalized ZnS nanowire sensors were examined. Scanning electron microscopy showed the nanowires with diameters of 20-80 nm. Transmission electron microscopy and X-ray diffraction showed that the nanowires were wurtzite-structured ZnS single crystals. The Pt-functionalized ZnS nanowire sensors showed enhanced sensing performance to $NO_2$ gas at $150^{\circ}C$ compared to pristine ZnS nanowire sensors. Pristine and Pt-functionalized ZnS nanowire sensors showed responses of 140-211% and 207-488%, respectively, to 1-5 ppm $NO_2$, which are better than or comparable to those of many oxide semiconductor sensors. In addition, the underlying mechanism of the enhancement of the sensing properties of ZnS nanowires by Pt functionalization is discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.277.2-277.2
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• 2014

For next-generation electronic applications, human-machine interface devices have recently been demonstrated such as the wearable computer as well as the electronic skin (e-skin). For integration of those systems, it is essential to develop many kinds of components including displays, energy generators and sensors. In particular, flexible sensing devices to detect some stimuli like strain, pressure, light, temperature, gase and humidity have been investigated for last few decades. Among many condidates, a pressure sensing device based on organic field-effect transistors (OFETs) is one of interesting structure in flexible touch displays, bio-monitoring and e-skin because of their flexibility. In this study, we have investigated a flexible e-skin based on highly sensitive, pressure-responsive OFETs using microstructured ferroelectric gate dielectrics, which simulates both rapidly adapting (RA) and slowly adatping (SA) mechanoreceptors in human skin. In SA-type static pressure, furthermore, we also demonstrate that the FET array can detect thermal stimuli for thermoreception through decoupling of the input signals from simultaneously applied pressure. The microstructured highly crystalline poly(vinylidene fluoride-trifluoroethylene) possessing piezoelectric-pyroelectric properties in OFETs allowed monitoring RA- and SA-mode responses in dyanamic and static pressurizing conditions, which enables to apply the e-skin to bio-monitoring of human and robotics.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1397-1399
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• 2002

Effects of bottom electrode materials (Al, Cu, Ti, and Mo), included in film bulk acoustic resonators (FBARs), on the orientation of piezoelectric AlN thin films and the frequency response characteristic of resonators were investigated. The texture coefficient (TC) for (002) orientation, crystallite size, full width half maximum (FWHM), and surface roughness of deposited AlN films were measured for the various bottom electrodes. The return tosses estimated from the frequency responses of fabricated resonators were also compared. Experimental results showed that the difference of lattice constant and thermal expansion coefficient between the bottom electrode and the AlN film were the most important factors for achieving a high performance resonator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.798-805
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• 2010

Whole composite structure small class (150kg) satellite, STSAT-3, was initially developed in Korea. The structure does have aluminum frames that support the structure, and it is composed of only composite sandwich panels. A number of electronic boxes and mechanical apparatus will be shielded within the compartments built up by the composite panels. This study focused on the random vibration responses of the satellite. For this objective, vibration tests and analyses have been successfully performed with respect to STM (structure and thermal model) of the satellite. Additionally, through the experiment and theoretical analyses, the both results' accuracy was verified by comparison each other.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.203-206
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• 2006

The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_2$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.223-226
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• 2006

The micro-gas sensor based on carbon nanotubes (CNTs) was fabricated and its gas sensing characteristics on nitrogen dioxide ($NO_2$) have been investigated. The sensor consists of a heater, an insulating layer, a pair of contact electrodes, and CNT-sensing film on a micromachined diaphragm. The heater plays a role in the temperature change to modify sensor operation. Gas sensor responses of CNT-film to $NO_2$ at room temperature are reported. The sensor exhibits a reversible response with a time constant of a few minutes at thermal treatment temperature of $130^{\circ}C$.

• Steel and Composite Structures
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• v.19 no.3
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• pp.661-678
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• 2015

Buckling Restrained Braces (BRB) have been widely used in the construction industry as they utilize the most desirable properties of both constituent materials, i.e., steel and concrete. They present excellent structural qualities such as high load bearing capacity, ductility, energy-absorption capability and good structural fire behaviour. The effects of size and type of filler material in the existed gap at the steel core-concrete interface as well as the element's cross sectional shape, on BRB's fire resistance capacity was investigated in this paper. A nonlinear sequentially-coupled thermal-stress three-dimensional model was presented and validated by experimental results. Variation of the samples was described by three groups containing, the steel cores with the same cross section areas and equal yield strength but different materials (metal and concrete) and sizes for the gap. Responses in terms of temperature distribution, critical temperature, heating elapsed time and contraction level of BRB element were examined. The study showed that the superior fire performance of BRB was obtained by altering the filler material in the gap from metal to concrete as well as by increasing the size of the gap. Also, cylindrical BRB performed better under fire conditions compared to the rectangular cross section.

• Korean Journal of Human Ecology
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• v.12 no.2
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• pp.253-263
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• 2003

The purposes of this study were to find out an evaluation scale that could predict wear comfort and to investigate the effect of the skin-contacting fiber type on the subjective sensation and microclimate. Sensorial evaluation was basically followed by the Human Perception Analysis (HPA) interviewing 144 consumers. Sixteen female subjects were participated in the sleeve wear test with and without wearing vapor permeable water repellent outerwear. Experimental sleeves were constructed using the same double knit by turning inside out to control other material effects except the skin-contacting fiber type, hence each different side of double knit, cotton side and the cotton/polypropylene blend side, was next to skin in each trial of the experiment. As results, it was noted that the term representing a combined feeling of thermal and wetness sensation, and muggy appeared to be a powerful language to measure perceptual responses of human subject among five dimensions of evaluation. although the ordinary users did not use the term very often. As for the comfort properties of double knits, it seemed that subjects slightly more preferred polypropylene/cotton blend to cotton as the skin-contacting fiber type when they wore outerwear and their skin were covered with sweat, although the result was rot statistically significant and need to be confirmed under higher work load.

• The Korean Journal of Community Living Science
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• v.20 no.4
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• pp.515-522
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• 2009

This study was to develope the functional work clothing for livestock farmers. Major demanding performances for livestock work clothing are anti-soil and anti-bacterial properties. On surveys, functional fabrics that have anti-soil, anti-bacterial and waterrepellent performances were developed and the work clothing that have adaptability to body movements were manufactured. The designs of livestock working clothes were two piece and one piece with rubber bade in waist. The thermal responses of subjects wearing the winter working clothes for stock farming worker were measured in the climate chamber($17^{\circ}C$, 40% R.H.). The main results were summarized as follows: Total body weight loss was smaller and the mean skin temperature was higher in developed clothes than the market product. Clothing micro-climate of developed clothes was lower than the market clothes. Subjective sensation did not have significant differences. From the results of various evaluation, developed garments for livestock workers showed better efficiency than the market product.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.399-404
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• 2010

Test results including the variation of propellant-inlet pressure, pulsed thrust, and environment vacuum with the accompanying thermal responses are presented for the pulse-mode operation of a set of monopropellant hydrazine thrusters producing $0.95lb_f$ of nominal steady-state thrust at an inlet pressure of 350 psia. The test data are reduced into the impulse bit, specific impulse, and force centroid that are the factors typically characterizing pulse-mode performance of small rocket engines. With a scrutiny to the performance parameters, their comparison to the reference criteria of 1 lbf standard monopropellant rocket engine are successfully made.