• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.35 no.6
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• pp.527-534
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• 2017

The purpose of this study is to develop unmanned equipment that can automatically move to the desired point and measure water quality at the correct depth. For this purpose, we constructed a water sampling lift and water sampling container, an unmanned vessel equipped with a VRS-GPS, an acoustic echo sounder, and a water quality sensor. Also, we developed an automatic navigation algorithm and program, an automatic water sampling program, and a water quality map generation program. As a result of the experiment in the detention pond, the unmanned vessel sailed along the planned route with an accuracy of about 93% within the error range of 3m. In addition, the water quality sensor installed in the lift was able to acquire the water quality of the target area in real time and transmit it to the server via wireless Internet, and it was possible to monitor the water quality of each site in real time. Through field experiments, the water sampling lift was able to control the desired length with an accuracy of about 94%. The stretch length accuracy experiment of the water sampling lift was impossible to measure directly in the water, so it was replaced land-based experiment. We also found some unstable problems due to the weight of the water sampling lift and the weight of the air compressor to operate the water container. Except these two problems, we accomplished purpose of this study. An automated water quality measurement method using an unmanned vessel can be used to measure the quality of water in a difficult to access area and to secure the safety of the worker.

• Journal of Biosystems Engineering
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• v.32 no.6
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• pp.448-454
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• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.2
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• pp.271-278
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• 2021

This paper is a study on the implementation of smart filter system that recognizes the external environment and automatically removes pollutants according to pollution level. Recently, the occurrence of various pollutants in indoor and outdoor space has adversely affected the human body. Especially, various fine dust generated in the atmosphere becomes worse in closed residential space or office space. Although air pollution can be temporary lowered through ventilation, it is difficult to respond to fine dust changes in real time, and such problems become serious in the space where many people reside, such as at home or industry. Therefore, it is necessary to measure the pollution level of fine dust inside the residential space in real time and to reduce the pollution of indoor ventilation through automatic ventilation with the outside. To improve these problems, this paper proposes the implementation of smart filter system for external environment recognition. The structure of smart filter system that automatically measures air quality inside and outside, removes pollutants, implements the function, and confirms the operability by manufacturing prototypes. Finally, the effectiveness of the smart filter system for solving fine dust problems was examined.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.5
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• pp.364-371
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• 2017

TPMS is a vehicle electric system that measures the air pressure of a tire, and informs the driver of current tire states. The TPMS sensor typically uses unidirectional communication for small size, light weight, and low power. The transmission period of the sensor indicates the service quality of monitoring the tire. In order to determine the optimal transmission period, frame collision probability and the life time of the sensor should be analyzed. In this paper, collision probability model using Venn diagram is designed in low power TPMS with the normal and warning mode. And the life time and a collision probability were analyzed with the ratio(n) of the normal mode to warning mode transmission period. As a result, $T_{nP}=31sec$ and $T_{wP}=2.4sec$ at 5 years, and $T_{nP}=71sec$ and $T_{wP}=2.5sec$ at 7 years.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.4
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• pp.325-329
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• 2014

This paper proposes a method to predict chatter vibration generated in milling processes and to enhance machining quality and surface finish. Chatter vibration is a common problem in the milling of thin walls and floors. It causes a poor surface finish, or even marks, to appear on the final machined surface. Therefore, an effective method is necessary to predict chatter vibration in machine tools. In this investigation, chatter vibration is measured by an accelerometer, microphone, and Acoustic Emission (AE) sensor in a machining operation. Based on the results of the experiment, a microphone can be applied for the prediction of chatter vibration in milling processes.

• Tribology and Lubricants
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• v.29 no.3
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• pp.180-185
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• 2013

The purpose of this study was to analyze the tribological characteristics of the Electronic control suspension System in a car. In the first example, the cilp used to attach the front electronic control suspension(ECS) system's control actuator was fastened very tightly. Thus, the wire was cut because of continual rotation of the shock-up shover piston rod used to adjust the height of the car. This verified the disconnection phenomenon where wire damaged makes it impossible for the ECS system to send signal to the actuator. The second example, involved a minute hole that allowed gas to leak from the ECS system. As a result, the height of the car verified the down phenomenon. In the third example, the resistance of a wire measured at $0.21{\Omega}$, when the G sensor was disconnected from the system. This verified the system shutdown and lighting of the ECS warning lamp because of body interference caused by a slight pressure on the battery cover. Therefore, quality control is always necessary to ensure safety and durability of a car.

• 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 the Korean Society of Visualization
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• v.20 no.1
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• pp.45-51
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• 2022

Airborne particulate matter(PM) has been a global environmental problem. PM whose diameter is smaller than 10 ㎛ can permeate respiratory organs and has harmful effects on human health. Therefore, PM monitoring systems are necessary for management of PM and prevention of PM-induced negative effects. Conventional PM monitoring techniques are expensive and cumbersome to handle. In the present study, two types of PM monitoring devices were designed for measuring indoor PM concentration, portably. We experimentally investigated the performance of three commercial PM concentration measurement sensors in a closed test chamber. As a result, PM2008 sensor showed the best PM concentration measurement accuracy. Linear regression method was applied to convert PM concentration value acquired from PM2008 sensor into ground truth value. A mobile application(app.) was also created for users to check the PM concentration, easily. The mobile app. also provides safety alarm when the PM₁₀ concentration exceeds 81 ㎛/m³. The developed hand-held system enables the facile monitoring of surrounding air quality.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.451-455
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• 2021

Porous copper bromide (CuBr) films are highly advantageous for detecting ammonia (NH₃). The fabrication of porous CuBr films requires complex high-temperature processes or multistep processes. Herein, we report the uncomplicated preparation of porous CuBr films by a spin-coating method and the films' excellent NH₃ sensing properties. The porous films were prepared by spin-coating 100, 150, and 200 mM CuBr solutions, and then dried in a vacuum oven for 2 h. All the films showed a high NH₃ response; in particular, the film prepared using a 100 mM CuBr solution showed an extremely high response (resistance ratio = 852) to 5 ppm NH₃. The film also showed fast response and recovery times, 272 s and 10 s respectively, even at room temperature. The outstanding NH₃ sensing characteristics were explained in relation to the porosity and thickness of the prepared films. The high-performance NH₃ sensors used in this study can be used for both indoor air quality and environmental monitoring applications.

• Journal of Advanced Navigation Technology
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• v.23 no.5
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• pp.473-480
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• 2019

The smart home is a technology that can monitor and control by connecting everything to a communication network in various fields such as home appliances, energy consumers, and security devices. The Smart home is developing not only automatic control but also learning situation and user's taste and providing the result accordingly. This paper proposes a model that can provide a comfortable indoor environment control service for the user's characteristics by detecting the user's behavior as well as the automatic remote control service. The whole system consists of ESP 8266 with sensor and Wi-Fi, Firebase as a real-time database, and a smartphone application. This model is divided into functions such as learning mode when the home appliance is operated, learning control through learning results, and automatic ventilation using indoor and outdoor sensor values. The study used moving averages for temperature and humidity in the control of home appliances such as air conditioners, humidifiers and air purifiers. This system can provide higher quality service by analyzing and predicting user's characteristics through various machine learning and deep learning.