• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.33-36
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• 2005

In this research, for the smart health monitoring of the hydrogen storage high pressure composite vessel, the feasibility study of an embedded fiber Bragg grating(FBG) sensor is carried out. To verify strain measurement in various temperature environment which is needed for the hydrogen pressure vessel, tensile test of a composite specimen with both an embedded FBG sensor and a strain gauge is made in low temperature. Before we try a real-size hydrogen storage pressure vessel, a small & cheap composite pressure vessel having the same structure is fabricated with embedded FBG sensors and tested. In the case of an aluminum liner inside the vessel, survivability of FBG sensors at the interface is lower than the other areas.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1088-1092
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• 2017

In this study, a comparison of dynamic pressure data measured in hot-firing tests of liquid rocket engine gas generators with different types of dynamic pressure sensors is presented. The dynamic pressure sensors of different types and manufacturers have exhibited different dynamic pressure due to the influence of thermal shock. However, for the characteristic frequencies and RMS(root mean square) values which are important factors for the analysis of combustion instability, the differences between sensors have been found to be negligible.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.93-99
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• 2019

A pressure sensor is a device that converts an applied physical pressure into an electrical signal. Such sensors have a range of applications depending on the pressure level, from low to high pressure. Sensors that use physical pressure, when compared to those operating under air pressure, are not widely applied as they are inefficient. To solve this problem, graphene oxide, which exhibits good mechanical and electrical characteristics, was used to increase the efficiency of these pressure sensors. Graphene oxide has properties that control the movement of charges within the dielectric. Exploiting these properties, we evaluated the change in electrical characteristics when pressure was applied according to the ratio and thickness of the oxidation graph added to the pressure sensor.

• Composites Research
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• v.18 no.4
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• pp.1-7
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• 2005

In-situ structural health monitoring of filament wound pressure tanks were conducted during water-pressurizing test using embedded fiber Bragg grating (FBG) sensors. We need to monitor inner strains during working in order to verify the health condition of pressure tanks more accurately because finite element analyses on filament wound pressure tanks usually show large differences between inner and outer strains. Fiber optic sensors, especially FBG sensors can be easily embedded into the composite structures contrary to conventional electric strain gages (ESGs). In addition, many FBG sensors can be multiplexed in single optical fiber using wavelength division multiplexing (WDM) techniques. We fabricated a standard testing and evaluation bottle (STEB) with embedded FBG sensors and performed a water-pressurizing test. In order to increase the survivability of embedded FBG sensors, we suggested a revised fabrication process for embedding FBG sensors into a filament wound pressure tank, which includes a new protecting technique of sensor heads, the grating parts. From the experimental results, it was demonstrated that FBG sensors can be successfully adapted to filament wound pressure tanks for their structural health monitoring by embedding.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1810-1814
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• 2017

This paper develops an approach to the algorithm of Gait pattern Analysis and step measurement with Multi-Pressure Sensors. The process of gait consists of 8 steps including stance and swing phase. As 3 parts of foot is supporting most of human weight, multiple pressure sensors are attached on the parts of foot: forefoot, big toe, heel. As 3 parts of foot is supporting most of human weight, multiple pressure sensors are attached on the parts of foot: forefoot, big toe, heel. normal gait proceed from heel, forefoot and big toe over time. While normal gait proceeds, values of heel, forefoot and big toe can be changed over time. So Each values of pressure sensors over time could discriminate whether it is normal or abnormal gait. Measuring Device consists of non-inverting amplifiers and low pass filter. Through timetable of values, normal gait pattern can be analyzed, because of supported weight of foot. Also, the peak value of pressure can judge whether it is walking or running. While people are running, insole of shoes is floating in the air on moment. Using this algorithm, gait analysis and step count can be measured.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.35-40
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• 2016

Pulse diagnosis is one of the representative diagnostic methods in Oriental medicine. In this study, a pulse pressure sensor array coated with silicone, which includes 6 piezo-resistive sensors and 1 thermistor, is fabricated for pulse measurement. It is necessary to coat the pulse sensor array with silicone to avoid the fracture or damage of pressure sensors when the sensor is in contact with the skin and a constant pressure is applied. However, the silicone coating on the pulse sensor array can cause signal interference among the sensors in the pulse sensor array. The interference number (IN), a calculation for expressing the degree of interference among channels, is changed according to the silicone thickness on the pulse sensor array. The IN is increased by a thick silicone coating, but the fabrication error, an important index for the mass production of the sensor array, is reduced by the thickness of the silicone coating. We propose that the thickness of the silicone on the pulse sensor array is an important consideration for the performance of the fabricated sensor and manufacturing repeatability.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.10a
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• pp.70-74
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• 2004

Pressure and temperature in the cavity of injection molding have been investigated. Special injection mold was designed to install pressure and temperature sensors. The sensors were supplied by KISTLER and the pressure and temperature were measured for various operational conditions, such as injection pressure, holding pressure, cooling time, mold temperature, and injection temperature. As injection pressure increased cavity pressure and temperature increase. There were no big differences in temperatures according to the holding pressures. As mold temperature increased pressure and temperature in the cavity increase. The flowability of resin increases as mold temperature increases subsequently the pressure in the cavity increases since the pressure loss is less in the low viscous medium than high ciscous medium. The cavity temperature highly depends upon mold temperature.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.141-145
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• 2003

The FBG sensors are inserted on the liners of the filament wound pressure tanks. The strains near the welding region of the liners are monitored in the hydro-pressurizing tests. The hydro-pressurizing tests consist of the proof tests at 4500 or 3300 psi and repeated test at the operating pressure, 3000 psi. The FBG sensors work well under $3000\mu\varepsilon$, but the strains calculated from the reflected signals are instable at the high strain level. The transverse compression on the sensor head results in the split of the reflected peaks, and the calculating algorism from the split peaks is not robust under the various signal condition. The FBG sensors fracture near $7500\mu\varepsilon$ level and lose their function permanently.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.5
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• pp.405-410
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• 2006

We fabricated gas sensors using carbon nanotubes (CNTs) as electron emitters for the purpose of detecting inert gases. By using the silicon-glass anodic bonding and glass patterning technologies with the typical Si process, we improved the compactness of the sensors and the reliability in process. The proposed sensor, based on, an electrical discharge theory known as Paschen's law in principle, works by figuring the variation of the discharge current depending on gas concentration. In the experiment, the initial breakdown characteristics were measured for air and Ar as a function of gas pressure. As the result, even though it should be realized that there are many other factors which have an effect on the breakdown of a gap, the sensors led to similar result as predicted by Paschen's law, and they showed a possibility as gas sensors which enable to detect the gas density ranged to the vacuum pressure from 1 to $10^{-3}$ Torr.

• Journal of Sensor Science and Technology
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• v.26 no.2
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• pp.141-147
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• 2017

A pressure sensor in pulse measurement system is a core component for precisely measuring the pulse waveform of radial artery. A pulse sensor signal that measures the pulse wave in contact with the skin is affected by the temperature difference between the ambient temperature and skin surface. In this study, we found experimentally that the signal changes of the pressure sensors and a temperature sensor were caused by the temperature of the wrist surface while the pressure sensor was contacted on the skin surface for measuring pulse wave. To observe the signal change of the pulse sensor caused by temperature increase on sensor surface, Peltier device that can be kept at a set temperature was used. As the temperature of Peltier device was kept at $35^{\circ}C$ (the maximum wrist temperature), the device was put on the pulse sensor surface. The temperature and pressure signals were obtained simultaneously from a temperature sensor and six pressure sensors embedded in the pulse sensor. As a result of signal analysis, the sensor pressure was decreased during temperature increase of pulse sensor surface. In addition, the signal difference ratio of pressure and temperature sensors with respect to thickness of cover layer in pulse sensor was increased exponentially. Therefore, the signal of pressure sensor was modified by the compensation equation derived by the temperature sensor signal. We suggested that the thickness of cover layer in pulse sensor should be designed considering the skin surface temperature.