• Journal of Sensor Science and Technology
• /
• v.3 no.3
• /
• pp.36-44
• /
• 1994

A fiber-optic temperature sensor utilizing InP as a sensing medium was implemented and tested to determine the dependance of the optical characteristics of InP on physical parameters for the use as design parameters in this type of sensors. The optical absorption coefficient of InP has been determined through the experimental measurement of the fundamental optical absorption characteristics at various temperature points. The transmission characteristics of light source at three temperature points($249^{\circ}K$, $298^{\circ}K$, $369^{\circ}K$) are computed from the optical absorption coefficient for a fixed length of InP. A series of measurement concluded that optical absorption edge moves to longer wavelength region at a speed of 0.42 nm / $^{\circ}K$ as the specimen gets hotter, and that increasing the thickness of the InP sensing layer shifts power density curve to lower temperature region.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.63 no.2
• /
• pp.75-84
• /
• 2021

As the weather changes become frequent, weather disasters are increasing, causing more damage to plastic greenhouses. Among the damage caused by various disasters, damage by snow to the greenhouse takes a relatively long time, so if an alarm system is properly prepared, the damage can be reduced. Existing greenhouse design standards and snow warning systems are based on snow depth. However, even in the same depth, the load on the greenhouse varies depending on meteorological characteristics and snow density. Therefore, this study aims to secure the structural safety of greenhouses by developing sensors that can directly measure snow loads, and analysing the warning criteria for load using a stochastic model. Markov chain was applied to estimate the failure probability of various types of greenhouses in various regions, which let users actively cope with heavy snowfall by selecting an appropriate time to respond. Although it was hard to predict the precise snow depth or amounts, it could successfully assess the risk of structures by directly detecting the snow load using the developed sensor.

• Tunnel and Underground Space
• /
• v.34 no.4
• /
• pp.267-282
• /
• 2024

This study aims to develop a wireless communication system for long-term monitoring of high-level radioactive waste disposal facilities. Conventional wired sensors can lead to a deterioration in buffer quality and management difficulties due to the use of cables for power supply and data transmission. This study proposes the adoption of a wireless communication system and compares the received signal strengths within bentonite using modules such as WiFi, ZigBee, and LoRa. Increases in dry density of bentonite and distance between transceivers led to reduced received signal strength. Additionally, using the low-frequency band exhibited less signal attenuation. Based on these findings, a conceptual design for a wireless network-based THM integrated sensor system was proposed. Results of this study can be used as foundational data for long-term monitoring of disposal facility.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.48 no.2
• /
• pp.106-116
• /
• 2011

USN(Ubiquitous Sensor Network) environment permits us to access whatever information we want, whenever we want. The technologies to provide a basement to these environments premise an accurate location establishment. Especially, ITS(Intelligent Transportation Systems) is easily constructed by applying USN technology. Localization can be categorized as either Range-based or Range-free. Range-based is known to be not suitable for the localization based on sensor network, because of the irregularity of radio propagation and the additional device requirement. The other side, Range-free is much appropriated for the resource constrained sensor network because it can actively locate by means of the communication radio. But, generally the location accuracy of Range-free is low. Especially, it is very low in a low-density environment. So, these two methods have both merits and demerits. Therefore, it requires a new method to be able to improve tracking accuracy by combining the two methods. This paper proposes the tracking scheme based on range-hybrid, which can markedly enhance tracking accuracy by effectively using the information of surrounding nodes and the RSSI(Received Signal Strength Indication) that does not require additional hardware. Additionally, we present a method, which can improve the accuracy of vehicle tracking by adopting the prediction mechanism. Simulation results show that our method outperforms other methods in the transportation simulation environment.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.2
• /
• pp.397-407
• /
• 2015

In this paper, we designed 1 chip IC for 3-axis gyroscope and 3-axis accelerometer used for various IoT/M2M mobile devices such as smartphone, wearable device and etc. We especially focused on analysis of gyroscope noise and proposed new architecture for removing various noise generated by gyroscope MEMS and IC. Gyroscope, accelerometer and geo-magnetic sensors are usually used to detect user motion or to estimate moving distance, direction and relative position. It is very important element to designing a low noise IC because very small amount of noise may be accumulated and affect the estimated position or direction. We made a mathematical model of a gyroscope sensor, analyzed the frequency characteristics of MEMS and circuit, designed a low noise, compact and low power 1 chip 6-axis inertial sensor IC including 3-axis gyroscope and 3-axis accelerometer. As a result, designed IC has 0.01dps/${\sqrt{Hz}}$ of gyroscope sensor noise density.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.17 no.3
• /
• pp.329-338
• /
• 2019

Suction of unsaturated bentonite buffers is a very important input parameter for hydro-mechanical performance assessment and design of an engineered barrier system. This study analyzed suction measurement techniques and constitutive models of unsaturated porous media reported in the literature, and suggested suction measurement techniques and constitutive models suitable for bentonite buffer in an HLW repository. The literature review showed the suction of bentonite buffer to be much higher than that of soil, as measured by total suction including matric suction and osmotic suction. The measurement methods (RH-Cell, RH-Cell/Sensor) using a relative humidity sensor were suitable for suction measurement of the bentonite buffer; the RH-Cell /Sensor method was more preferred in consideration of the temperature change due to radioactive decay heat and measurement time. Various water retention models of bentonite buffers have been proposed through experiments, but the van Genuchten model is mainly used as a constitutive model of hydro-mechanical performance assessment of unsaturated buffers. The water characteristic curve of bentonite buffers showed different tendencies according to bentonite type, dry density, temperature, salinity, sample state and hysteresis. Selection of water retention models and determination of model input parameters should consider the effects of these controlling factors so as to improve overall reliability.

• Journal of Sensor Science and Technology
• /
• v.30 no.3
• /
• pp.154-164
• /
• 2021

In this study, the IoT sensor technology required for improving the survival rate and high-density productivity of individual shrimp in smart shrimp farming (which involves the usage of recirculating aquaculture systems and biofloc technology) was analyzed. The principles and performances of domestic and overseas water quality monitoring IoT sensors were compared. Furthermore, the drawbacks of existing aquaculture monitoring technologies and the countermeasures for future aquaculture monitoring technologies were examined. In particular, for farming white-legged shrimp, an IoT sensor was employed to collect measurement indicators for managing the water quality environment in real-time, and the IoT sensor-based real-time monitoring technology was then analyzed for implementing the optimal farming environment. The results obtained from this study can potentially contribute to the realization of an autonomous farming platform that can improve the survival rate and productivity of shrimp, achieve feed reduction, improve the water quality environment, and save energy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.05a
• /
• pp.27-30
• /
• 2022

The plasma process, which has many advantages in terms of efficiency and environment compared to conventional process methods, is widely used in semiconductor manufacturing. Plasma Sheath is a dark region observed between the plasma bulk and the chamber wall surrounding it or the electrode. The Plasma Sheath Monitoring Sensor (PSMS) measures the difference in voltage between the plasma and the electrode and the RF power applied to the electrode in real time. The PSMS data, therefore, are expected to have a high correlation with the state of plasma in the plasma chamber. In this study, a model for predicting the state of nitrogen ions in the plasma chamber is training by a deep learning machine learning techniques using PSMS data. For the data used in the study, PSMS data measured in an experiment with different power and pressure settings were used as training data, and the ratio, flux, and density of nitrogen ions measured in plasma bulk and Si substrate were used as labels. The results of this study are expected to be the basis of artificial intelligence technology for the optimization of plasma processes and real-time precise control in the future.

• Journal of Sensor Science and Technology
• /
• v.31 no.3
• /
• pp.180-186
• /
• 2022

Photosynthetically active radiation flux density (PPFD) and daily light integral (DLI) values related to plant photosynthesis were obtained using the sunlight time and insolation data points in the agricultural weather sensor data for Jinan-gun, Jeollabuk-do, Korea from 2016 to 2020. The objective was to optimize the photo-environmental conditions for cultivating ginseng. The range of average monthly sunshine duration was 395.5-664.1 min, with the longest duration observed in June. The range of average annual accumulated daily insolation was 11.98-17.65 MJ·m^-2. The range of average daily external DLI calculated from the insolation and solar time data was 22.3-36.1 mol·m^-2·d^-1, and the annual cumulative DLI was 8,156-13,175 mol·m^-2·d^-1. Both the insolation and DLI values were the highest in 2016 and lowest in 2020. Based on the PPFD required for ginseng growth (111-185 µmol·m^-2·s^-1), the monthly average daily DLI and monthly cumulative DLI were 3.51-5.87 and 82-228 mol·m^-2·d^-1, respectively. The range of five-year average value for the external monthly cumulative DLI was 298-1,459 mol·m^-2·d^-1, and the monthly cumulative DLI values when a black double shading film and blue-white shading film were applied were 101-496 and 36-175 mol·m^-2·d^-1, respectively. A comparative analysis of DLI values indicated that shading was required to ginseng growth throughout the year under natural light. When the black double shading film was used, shading was required from March to October. When the blue-white shading film was applied from April to August, (i.e., the period with active ginseng growth) the appropriate DLI for ginseng growth could be continuously maintained. Regional weather differences due to climate change are gradually increasing, and even in one region, monthly and cumulative DLI values are different every year. Therefore, in order to implement a precise agricultural environment for ginseng cultivation, precise analysis and continuous research using agricultural weather sensor big data is required.

• International Journal of Highway Engineering
• /
• v.18 no.6
• /
• pp.87-96
• /
• 2016

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between different sizes of variable speed limit signs and the legibility distance under various fog density conditions. By using this study, appropriate sizes of signs can be selected depending on the density of fog. METHODS : An actual tunnel was selected as the area for this test, as other places cannot maintain the fog condition because of rapid air current. A total 121 subjects were recruited for this test, which took place over the course of four days. The test on the first day was conducted under normal weather conditions for comparison. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS : The test results show the relationship between the different sizes of signs and the legibility distance corresponding to the visibility distance due to both non-fog and fog generated conditions. According to the technical test results, appreciable amount of reduction in legibility distance due to fog was resulted in all sizes of signs. Moreover, the legibility distance is reduced proportionately with the decrease in the visibility distance due to fog. CONCLUSIONS : The results of this study can be used to select appropriate sizes of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.