• Journal of Aerospace System Engineering
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• v.15 no.3
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• pp.57-64
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• 2021

In the study, to minimize the error on guided control of the KV (Kill Vehicle) and to secure the hit-to-kill performance, a position accuracy inspection for the DACS (Divert and Attitude Control System) actuation system was proposed. The accuracy performance of the DACS actuation system is one of the most important factors in the interception of ballistic missiles. In order to validate actuation control accuracy of DACS system, an inspection item was set for position accuracy, and the inspection system was designed for DACS pintle. To measure the absolute position value of the DACS pintle, an external measurement system was developed using laser displacement sensors. The inspection system was designed so that it can be compared with the actuation command in real time. The proposed position accuracy inspection system can be inspected not only in a DACS system but also in missile system level. The position accuracy inspection was performed using the designed inspection system, and analysis of the inspection result.

• IEMEK Journal of Embedded Systems and Applications
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• v.17 no.1
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• pp.9-17
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• 2022

As the COVID-19 pandemic situation worsens, the time spent indoors increases, and the exposure to indoor environmental pollution such as indoor air pollution and noise also increases, causing problems such as deterioration of human health, stress, and discord between neighbors. This paper designs and implements a system that measures and monitors indoor air quality and noise, which are representative evaluation criteria of the indoor environment. The system proposed in this paper consists of a particulate matter measurement subsystem that measures and corrects the concentration of particulate matters to monitor indoor air quality, and a noise measurement subsystem that detects changes in sound and converts it to a sound pressure level. The concentration of indoor particulate matters is measured using a laser-based light scattering method, and an error caused by temperature and humidity is compensated in this paper. For indoor noise measurement, the voltage measured through a microphone is basically measured, Fourier transform is performed to classify it by frequency, and then A-weighting is performed to correct loudness equality. Then, the RMS value is obtained, high-frequency noise is removed by performing time-weighting, and then SPL is obtained. Finally, the equivalent noise level for 1 minute and 5 minutes are calculated to show the indoor noise level. In order to classify noise into direct impact sound and air transmission noise, a piezo vibration sensors is mounted to determine the presence or absence of direct impact transmitted through the wall. For performance evaluation, the error of particulate matter measurement is analyzed through TSI's AM510 instrument. and compare the noise error with CEM's noise measurement system.

• Journal of the Korea Convergence Society
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• v.13 no.5
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• pp.1-8
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• 2022

In Korea, drones, which are at the core of the 4th industrial revolution, are used to promote Korean New Deal policies to digitalize the SOC. Overseas, the use of convergence sensors, such as thermal imaging cameras, on drones is increasing in various industrial fields. In this research, to improve pavement quality in highway bridge pavement construction, a thermal imaging camera was mounted on a drone to measure and verify the temperature of the pavement work section. Using a laser thermometer allows the partial measurement of pavement temperature. It was confirmed that the proposed method allows not only real-time temperature monitoring of the whole pavement work section but also uniformity verification by checking temperature distribution. The proposed method has the potential to control highway pavement quality and enable quick decision-making on traffic opening times by reducing the possibility of misjudging road opening times(pavement surface temperature ≦ 40℃).

• Journal of Oral Medicine and Pain
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• v.30 no.1
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• pp.69-77
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• 2005

The purposes of this study were to develop and introduce a novel intraoral appliance for bruxism composed of power switch and biofeedback device and further to examine inter- and intra-reliability of the appliance prior to clinical tests. The newly-developed appliance consisted of detection sensors, a central processing unit (CPU), a reactor and a storage unit and a displayer. Compact-sized, waterproof switches were selected as bruxism detection sensor and any sensor activation by clenching or grinding event was processed at the CPU and transmitted, by radio wave, to the reactor and storage unit and triggered auditory or vibratory signal, subsequently producing biofeedback to the patient with bruxism. The data on bruxing event in the storage unit can be displayed on the computer, making it possible analyzing frequency, duration and nature of bruxism. Cast models were obtained from ten volunteers with normal occlusion to evaluate reliability of the appliances. For inter-operator reliability on the intraoral appliances, each operator of the two fabricated the appliance for the same subject and compared the minimal contact forces provoking auditory biofeedback reaction in vertical, lateral and central directions. Intra-operator reliability was also investigated on the appliances made by a single operator at two separate times with an interval of two days. Conclusively, the newly-developed appliance is compact and safe to use in oral circumstance and easy to make. Furthermore, it had to be proven reliability excellent enough to apply in clinical settings. Thus, it is assumed that this appliance with the processor and the storage of data and auditory or vibratory biofeedback function is available and useful to analyze and control bruxism.

• Journal of Sensor Science and Technology
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• v.6 no.3
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• pp.214-220
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• 1997

A thin film optical waveguide sensor has been developed to measure and analyze quantitatively some inherent optical properties of biochemical substances. In this paper, two different kinds of thickness of thin film waveguide were prepared by RF sputtering of Corning-7059 glass(n = 1.588 at ${\lambda}=\;514nm$, Ar laser) on Pyrex glass substrates. We made a sensing membrane coated on the thin film waveguide with the poly(vinyl chloride-co-vinyl acetate-co-vinyl alcohol) (91 : 3 : 6) copolymer membrane based on $H^{+}$-selective chromoionophore and $K^{+}$-selective neutral ionophore and then proposed the thin film opptical waveguide ion sensor which can select a potassium ion. This sensor based ell the absorbance change by utilizing chromoionophore and neutral ionophore, which changes their absorption spectrum in the UV-vis region upon complexation of the corresponding ionic species, have been reported. The sensitivity dependence of the proposed sensor on interaction length, waveguide thickness, and content of a chromoionophore was investigated. This sensor has the measurement range of $10^{-6}M{\sim}1M$ for $K^{+}$ concentration and 90% response time of duration within 1 min. Also, our thin film optical waveguide sensor using the evanescent field was investigated as compared with conventional transmission sensor or optode sensor by the optical fiber. The sensitivity of thin-film waveguide $K^{+}$ sensor is higher than that of the conventional transmission sensor. The proposed sensor is expected to be useful to biochemical, medical, environmental inspection and so on.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.5
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• pp.499-507
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• 2004

We have studied tile detection techniques, which can determine the location and the weight of an intruder into infrastructure, by using fiber-optic ROTDR (Rayleigh optical time domain reflectometry) sensor and fiber-optic BOTDA (Brillouin Optical time domain analysis) sensor, which can use an optical fiber longer than that of ROTDR sensor Fiber-optic sensing plates of ROTDR sensor, which arc buried in sand, were prepared to respond the intruder effects. The signal of ROTDR was analyzed to confirm the detection performance. The constructed ROTDR could be used up to 10km at the pulse width of 30ns. The location error was less than 2 m and the weight could be detected as 4 grades, such as 20kgf, 40kgf, 60kgf and 80kgf. Also, fiber optic BOTDA sensor was developed to be able to detect intrusion effect through an optical fiber of tells of kilometers longer than ROTDR sensor. fiber-optic BOTDA sensor was constructed with 1 laser diode and 2 electro-optic modulators. The intrusion detection experiment was peformed by the strain inducing set-up installed on an optical table to simulate all intrusion effect. In the result of this experiment, the intrusion effort was well detected as the distance resolution of 3m through the fiber length of about 4.81km during 1.5 seconds.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.3
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• pp.283-290
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• 2016

Even though existing methods for orthophoto production in traditional photogrammetry are effective in large areas, they are inefficient when dealing with change detection of geometric features and image production for short time periods in small areas. In recent years, the UAV (Unmanned Aerial Vehicle), equipped with various sensors, is rapidly developing and has been implemented in various ways throughout the geospatial information field. The data and imagery of specific areas can be quickly acquired by UAVs at low costs and with frequent updates. Furthermore, the redundancy of geospatial information data can be minimized in the UAV-based orthophoto generation. In this paper, the orthophoto and DEM (Digital Elevation Model) are generated using a standard low-end UAV in small sloped areas which have a rather low accuracy compared to flat areas. The RMSE of the check points is σ_H = ±0.12 m on a horizontal plane and σ_V = ±0.09 m on a vertical plane. As a result, the maximum and mean RMSE are in accordance with the working rule agreement for the airborne laser scanning surveying of the NGII (National Geographic Information Institute) on a 1/500 scale digital map. Through this study, we verify the possibilities of the orthophoto generation in small slope areas using general-purpose low specification UAV rather than a high cost surveying UAV.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.75-80
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• 2018

The working principle of a satellite camera involves a focusing mechanism for controlling the focus of the optical system, which is essential for proper functioning. However, research on focusing mechanisms of satellite optical systems in Korea is in the beginning stage and developed technology is limited to a thermal control type. Therefore, in this paper, we propose a motor-driven focusing mechanism applicable to small satellite optical systems. The proposed mechanism is designed to generate z-axis displacement in the secondary mirror by a motor. In addition, three flexure hinges have been installed on the supporter for application of preload on the mechanism resulting in minimization of the alignment error arising due to manufacturing tolerance and assembly tolerance within the mechanism. After fabrication of the mechanism, the alignment errors (de-space, de-center, and tilt) were measured with LVDT sensors and laser displacement meters. Conclusively, the proposed focusing mechanism could achieve proper alignment degree, which can be applicable to small satellite optical system.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.59-66
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• 2007

The digital working environment and its related technology have been rapidly expanding. In the surveying field, we have changed from using optical film cameras and plotters to digital cameras, multi sensors like GPS/INS etc,. The old analog work flow is replaced by a new digital work flow. Accurate data of the land is used in various fields, efficient utilization and management of land, urban planning, disaster and environment management. It is important because it is an essential infrastructure. For this study, LiDAR surveying was used to get points clouds in the study area. It has a high vegetation penetrating advantage and we used a digital process from planning to the final products. Contour lines were made from LiDAR data and compared with national digital base maps (scale 1/1,000 and 1/5,000). As a result, the accuracy and the economical efficiency were evaluated. The accuracy of LiDAR contour data was average $0.089m{\pm}0.062\;m$ and showed high ground detail in complex areas. Compared with 1/1,000 scale contour line production when surveying an area over $100\;km^2$, approximately 48% of the cost was reduced. Therefore we prepose LiDAR surveying as an alternative to modify and update national base maps.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.174-182
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• 2014

To monitor the wind-induced responses of buildings, conventional real-time kinematic (RTK) methods based on two global positioning system (GPS) receivers (e.g., a reference and a rover) are widely applied. However, these methods can encounter problems such as difficulty in securing and maintaining a space for a reference station. With the recently developed virtual reference station (VRS)-RTK approach, the position of a structure can be measured using only a rover receiver. In this study, to evaluate the applicability of VRS-RTK methods in monitoring the lateral structural responses of frame structures, we performed free vibration tests on a one-story frame model (the first natural frequency of 1 Hz) and a three-story frame model (the first natural frequency of 0.85 Hz). To assess the reliability of the displacement and acceleration responses measured by the GPS, we performed a concurrent measurement using laser displacement sensors and an accelerometer. The accelerometer results were consistent with the GPS measurements in terms of the time history and frequency content. Furthermore, to derive an appropriate sampling rate for the continuous monitoring of buildings, the errors in the displacement responses were evaluated at different GPS sampling rates (5, 10, 20 Hz). The results indicate that as the sampling rate increased, the errors in the displacement responses decreased. In addition, in the three-story model, all modal components (first, second, and third modes) could be recorded at a sampling rate of 20 Hz.