• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.805-808
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• 2008

Due to the fact that bare FBG sensors are very fragile, bare FBG sensor is not properly applied in practical infrastructures as it is not suitable to the rudeness of construction. Therefore packaged FBG sensors are developed for construction application. Since FBG senses strain and temperature simultaneously, temperature compensation for FBG strain sensors is indispensable. In this paper, temperature compensation techniques for steel sleeve packaged FBG sensors are brought forward. And its application on monitoring concrete beam was carried to test the feasibility of the temperature compensation technique. Temperature compensation technique used in this paper is feasible to be extended to structure health monitoring in civil engineering especially in large infrastructures etc.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.124-130
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• 2016

NDIR $CO_2$ gas sensor was built with ASIC implemented thermopile sensor which included temperature sensor and unique elliptical waveguide structures in this paper. The temperature dependency of dual infrared sensor module ($CO_2$ and reference IR sensors) has been characterized and its output voltage characteristics according to the temperature and gas concentration were proposed for the first time. NDIR $CO_2$ gas and reference IR sensors showed linear output voltages according to the variation of ambient temperatures from 243 K to 333 K and their slopes were 14.2 mV/K and 8.8 mV/K, respectively. The output voltages of temperature sensor also presented a linear dependency according to the ambient temperature and could be described with V(T)=-3.191+0.0148T(V). The output voltage ratio between $CO_2$ and reference IR sensors revealed irrelevant to the changes of ambient temperatures and gave a constant value around 1.6255 with standard deviation 0.008 at 0 ppm. The output voltage of $CO_2$ gas sensor at zero ppm $CO_2$ gas consisted of two components; one is caused by the HPB (half pass-band) of IR filter and the other is attributed to the part of $CO_2$ absorption wavelength. The characteristics of output voltages of $CO_2$ gas sensor could be accurately modeled with three parameters which are dependent upon the ambient temperatures and represented small average error less than 1.5% with 5% standard deviation.

• Journal of Sensor Science and Technology
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• v.25 no.5
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• pp.377-381
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• 2016

NDIR $CO_2$ gas sensor was prototyped with ASIC implemented thermopile sensor which included temperature sensor and White-Cell structure in this paper. The temperature dependency of dual infrared sensors ($CO_2$ and reference IR sensors) has been characterized and their output voltage ratios according to the temperature and gas concentration were presented in this paper for achieving temperature compensation algorithm. The initial output voltages of NDIR $CO_2$ gas and reference IR sensors showed $3^{rd}$ order polynomial and linear output voltages according to the variation of ambient temperatures from 253 K to 333 K, respectively. The output voltages of temperature sensor presented a linear dependency according to the ambient temperature and could be described with V(T) = -3.0069+0.0145T(V). The characteristics of output voltage ratios could be modeled with five parameters which are dependent upon the ambient temperatures and gas concentration. The estimated $CO_2$ concentrations showed relatively high error below 300 ppm (maximum 572 % at 7 ppm $CO_2$ concentration), however, as the concentration increased from 500 ppm to 2,000 ppm, the overall estimated errors of $CO_2$ concentrations were less than ${\pm}10%$ in this research.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.220-226
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• 2020

Graphene has been widely considered a promising candidate for high-quality chemical sensors, owing to its outstanding characteristics, such as sensitive gas adsorption at room temperature, high conductivity, high flexibility, and high transparency. However, the main drawback of a graphene-based gas sensor is the necessity for external heaters due to its slow response, incomplete recovery, and low selectivity at room temperature. Conventional heating devices have limitations such as large volume, thermal safety issues, and high power consumption. Moreover, metal-based heating systems cannot be applied to transparent and flexible devices. Thus, to solve this problem, a method of supplying the thermal energy necessary for gas sensing via the self-heating of graphene by utilizing its high carrier mobility has been studied. Herein, we provide a brief review of recent studies on self-activated graphene-based gas sensors. This review also describes various strategies for the self-activation of graphene sensors and the enhancement of their sensing properties.

• Journal of Sensor Science and Technology
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• v.11 no.4
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• pp.218-223
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• 2002

NASICON sensors that the NASICON electrolytes with various CaO amounts were sintered at low temperature($900^{\circ}C$), were fabricated to improve $CO_2$ sensitivity and stability in sensing behaviors. The manufactured device was shown good sensing characteristics and stability of output electromotive force at $250^{\circ}C$, comparatively low operating temperature.

• Journal of Sensor Science and Technology
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• v.29 no.6
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• pp.382-387
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• 2020

Hydrogen (H₂) is considered as a new clean energy resource for replacing petroleum because it produces only H₂O after the combustion process. However, owing to its explosive nature, it is extremely important to detect H₂ gas in the ambient atmosphere. This has triggered the development of H₂ gas sensors. 2-dimensional (2D) graphene has emerged as one of the most promising candidates for chemical sensors in various industries. In particular, graphene exhibits outstanding potential in chemoresistive gas sensors for the detection of diverse harmful gases and the control of indoor air quality. Graphene-based chemoresistive gas sensors have attracted tremendous attention owing to their promising properties such as room temperature operation, effective gas adsorption, and high flexibility and transparency. Pristine graphene exhibits good sensitivity to NO₂ gas at room temperature and relatively low sensitivity to H₂ gas. Thus, research to control the selectivity of graphene gas sensors and improve the sensitivity to H₂ gas has been performed. Noble metal decoration and metal oxide decoration on the surface of graphene are the most favored approaches for effectively controlling the selectivity of graphene gas sensors. Herein, we introduce several strategies that enhance the sensitivity of graphene gas sensors to H₂ gas.

• Journal of Biosystems Engineering
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• v.40 no.4
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• pp.368-372
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• 2015

Purpose: The purpose of this study is to verify the feasibility of using an infrared sensor to measure the body temperature of a sow. We first conducted experiments on three pigs by using three infrared sensors and one indoor temperature sensor. Methods: The three infrared sensors were installed inside our model house and were used to take temperature measurements per second of the backs of the pigs. While feeding, the temperatures of the backs of the pigs were measured at distances of 10 cm, 20 cm, and 30 cm from the infrared sensors. Results: We concluded that the relation between the temperature of the pigs' backs and the indoor temperature was y =0.549x + 18.459 at a measuring distance of 30 cm. The relation was y = 0.645x + 15.461 for a distance of 20 cm and y = 0.760x + 11.913 for a distance of 10 cm. We found high correlation between the indoor temperature and the temperature of the pigs' backs. Conclusions: It is possible to use an infrared thermometer to monitor the temperature of pigs' backs. This system seems to be feasible and effective in monitoring pig temperature. The use of an infrared thermometer will also make daily monitoring easy. In later experiments, the possibility of developing a system that can determine if an error can be corrected by using infrared sensor is explored by considering humidity variables.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1431-1433
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• 1995

This paper describes the characteristics of Si Hall sensors fabricated on a SOI(Si-on-insulator} structure, in which the SOI structure was forrmed by SDB(Si-wafer direct bonding) technology. The Hall voltage and the sensitivity of implemented Si Hall devices show good linearity with respect to the applied magnetic flux density and supplied current. The product sensitivity of the SDB SOI Hall device is average $600V/A{\cdot}T$. In the temperature range of 25 to $300^{\circ}C$, the shifts of TCO(Temperature Coefficient of the Offset Voltage) and TCS(Temperature Coefficient of the product Sensitivity) are less than ${\pm}6.7{\times}10^{-3}/^{\circ}C$ and ${\pm}8.2{\times}10^{-4}/^{\circ}C$, respectively. From these results, Si Hall sensors using the SOI structure presented here are very suitable for high-temperature operation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1416-1419
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• 2005

Design and manufacturing of plastic injection mold with cavity pressure/temperature sensors were performed in the present study for tensile test specimen. Standards of mold-base and tensile test specimen were used to design an injection molding system. Cavity pressure and temperature sensors were placed on the side of fixed platen of injection mold machine to prevent them from external impact damage. Injection molding experiments with variations of injection speed and melt temperature were performed and polycarbonate tensile specimens were prepared for the tensile test. It was shown that injection molding processing parameters can have effect on the mechanical properties of the plastic injection molded part.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.11
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• pp.84-90
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• 2007

In this study, design and manufacturing of plastic injection mold with cavity pressure/temperature sensors were performed fur tensile test specimen. International standard system for plastic tensile specimen was applied to design an injection molding system. Cavity pressure and temperature sensors were placed on the side of fixed platen of the injection mold to prevent them from external impact damage. Injection molding experiments with variations of injection speed and melt temperature were performed and then tensile test of the manufactured polycarbonate specimens was also performed. It was shown that injection molding processing parameters can have effect on the mechanical properties of the plastic injection molded part.