• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.218-222
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• 2007

In this study, Acoustic emission(AE) sensors were fabricated using lead-free piezoelectric ceramics for prohibiting environmental pollution. Structure of AE sensors were designed as Langvin type air backing form. Here, the piezoelectic element was used as PZT(EC-65)(AE1) and NKN(AE2), respectively. The measured resonant frequency, the maximum sensitivity frequency and sensitivity of AE sensors were as follows ; 143 kHz, 29.4 kHz and 69.3 dB in AE1 and 179 kHz, 29.4 kHz and 66.3dB in AE2, respectively.

• Agricultural and Biosystems Engineering
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• v.4 no.1
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• pp.28-33
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• 2003

Achievements in the real-time soil spectro-photometer are: an improved soil penetrator to ensure a uniform soil surface under high speed conditions, real-time collecting of underground soil reflectance, getting underground soil color images, use of a RTK-GPS, and all units are arranged for compactness. With the soil spectrophotometer, field experiments were conducted in a 0.5 ha paddy field. With the original reflectance, averaging and multiple scatter correction, Kubelka-Munk (KM) transformation as soil absorption, its 1st and 2nd derivatives were calculated. When the spectra was highly correlated with the soil parameters, stepwise regression analysis was conducted. Results include the best prediction models for moisture, soil organic matter (SOM), nitrate nitrogen (NO$_3$-N), pH and electric conductivity (EC), and soil maps obtained by block kriging analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.439-446
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• 2017

Portable low-cost Kinect sensor was used to analyze standing balance ability of the elderly. Eighty subjects who can walk alone and have a normal cognitive level participated in this experiment. Based on Berg Balance scale (BBS) test with 52 points, subjects were divided into Healthy older (HO: 46 persons, BBS: $53.80{\pm}1.19$) and Impaired older (IO: 34 persons, BBS: $49.06{\pm}2.03$) group. Each subject performed 30 seconds four different standing balance tests (EO: Eyes Open, EC: Eyes Close, EOf: Eyes Open on foam, ECf: Eyes Close on foam). Five variables (Mean distance, Range of distance, Root mean square, Mean velocity, 95% ellipse area) were calculated from the hip joint center movement of Kinect sensor. Results showed that there were significant differences between groups for four different standing tests. Calculated variables from kinect sensor showed significant correlation with BBS score. Especially, mediolateral mean distance, mediolateral root mean square, mediolateral range of distance and 95% ellipse area showed discriminative ability for all tests. Mean values of variables of IO were higher than those of HO, which means the decreased balance ability in IO compared with HO. Therefore, it was possible to estimate simple balance assessment of the elderly using portable low-cost Kinect sensor.

• Journal of Biosystems Engineering
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• v.39 no.1
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• pp.39-46
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• 2014

Purpose: Monitoring and control of environmental condition is highly important for optimum control of the conditions, especially in greenhouses and plant factories, and the condition is not uniform within the facility. Objectives of the study were to investigate variability in soil water content and to provide information useful for better irrigation control. Methods: Experiments were conducted in a strawberry-growing greenhouse (greenhouse 1) and a cherry tomato-growing greenhouse (greenhouse 2) in winter. Soil water content, electrical conductivity (EC), and temperature were measured over the entire area, at different distances from an irrigation pump, and on ridge and furrow areas. Results: When measured over the entire greenhouse area, soil water content decreased and temperature and electrical conductivity increased over time from morning to afternoon after irrigation. Water content decreased by distance from the irrigation pump up to 70 m and increased after that, and temperature showed an inverse pattern. Soil water contents on the ridge were lower than those on the furrow, and the differences were 10.2~18.4%, indicating considerable variability. The lowest EC were observed on the furrow and highest values were observed on the ridge. Soil water contents were less and temperature levels were greater at the window side than in the center locations. Conclusions: Selection of number and location of soil water content sensor would be the first step for better water content monitoring and irrigation control. Results of the study would provide basic data useful for optimum sensor location and control for underground greenhouse environment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.387-391
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• 2004

[ $(Bi_{1/2}Na_{1/2})TiO_3$ ](BNT) is considered to be an excellent candidate for the key material of lead-free piezoelectric ceramic due to properties of strong ferroelectricity with a relatively large remanent polarization $Pr=38{\mu}C/cm^2$, and a large coercive field, Ec=73KV/cm. In this study, electrical properties of pressure sensor using a $0.96Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3+0.04SrTiO_3+0.2wt%La_2O_3$ ceramics are investigated. Resonant frequency of pressure sensor was decreased with increasing pressure. However, its anti-resonant frequency was increased with increasing pressure.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.667-669
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• 2003

A bio-optical model was developed specific for turbid and shallow waters. Special studies were carried out to estimate absorption and scattering properties as well as backscattering probability of suspended matter. The inversion of bio-optical model allows for direct retrieval of turbidity and chlorophyll- a from the visible-near infrared (VNIR) range sensor. Time-series satellite imagery from ASTER AM-1 sensor, were used to monitor the Laguna de Bay water quality condition. Spatial distribution of temperature for the lake was extracted from the thermal infrared (TIR) sensor. Corresponding field surveys were conducted to parameterize the bio -optical model. In-situ measurements include suspended particle and chlorophyll-a concentrations profiles from nephelometric devices and processing of water samples. Hyperspectral measurements were used to validate results of the bio -optical model and satellite- based estimation. This study provides a theoretical basis and a practical illustration of applying space- based measurements on an operational basis.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.17 no.1
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• pp.76-81
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• 2024

Recently, agricultural methods are changing from experience-based agriculture to data-based agriculture. Changes in agricultural production due to the 4th Industrial Revolution are largely occurring in three areas: smart sensing and monitoring, smart analysis and planning, and smart control. In order to realize open-field smart agriculture, information on the physical and chemical properties of soil is essential. Conventional physicochemical measurements are conducted in a laboratory after collecting samples, which consumes a lot of cost, labor, and time, so they are quickly measured in the field. Measurement technology that can do this is urgently needed. In addition, a soil analysis system that can be carried and moved by the measurer and used in Korea's rice fields, fields, and facility houses is needed. To solve this problem, our goal is to develop and commercialize software that can collect soil samples and analyze the information. In this study, basic soil composition measurement was conducted using soil composition measurement sensors consisting of hardness measurement and electrode sensors. Through future research, we plan to develop a system that applies soil sampling using a CCD camera, ultrasonic sensor, and sampler. Therefore, we implemented a sensor and soil analysis UI that can measure and analyze the soil condition in real time, such as hardness measurement display using a load cell and moisture, PH, and EC measurement display using conductivity.

• Korean Journal of Remote Sensing
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• v.36 no.6_3
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• pp.1669-1679
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• 2020

This study examines the washing effect of precipitation on particulate matter (PM) and the rainwater quality (pH, electrical conductivity (EC), water-soluble ions concentration). Of six rain events in total, rainwater samples were continuously collected every 50 mL from the beginning of the precipitation using rainwater collecting devices at Pukyong National University, Busan, South Korea, from March 2020 to July 2020. The collected rainwater samples were analyzed for pH, EC, and water-soluble ions (cations: Na+, Mg2+, K+, Ca2+, NH4+, and anions: Cl-, NO3-, SO42-). The concentrations of particulate matter were continuously measured during precipitation events with a custom-built PM sensor node. For initial rainwater samples, the average pH and EC were approximately 4.3 and 81.9 μS/cm, and the major ionic components consisted of NO3- (5.4 mg/L), Ca2+ (4.2 mg/L), Cl- (4.1 mg/L). In all rainfall events, rainwater pH gradually increased with rainfall duration, whereas EC gradually decreased due to the washing effect. When the rainfall intensities were relatively weak (<5 mm/h), PM10 reduction efficiencies were less than 40%. When the rainfall intensities were enhanced to more than 7.5 mm/h, the reduction efficiencies reached more than 60%. For heavy rainfall events, the acidity and EC, as well as ions concentrations of initial rainwater samples, were higher than those in later samples. This appears to be related to the washing effect of precipitation on PM10 in the atmosphere.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.1
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• pp.43-54
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• 2008

Management and control of ammonia at the sources and ambient largely depend on sampling and measurement techniques. Good sampling and measurement techniques provide high quality data. The main purpose of the study is compare the analytical characteristics of the Indolphenol method which is one of the standard method in Korea with automatic analyzers for continued measuring gaseous ammonia. For comparison with other analytical methods, the verification test was designed to evaluate performance parameters; linearity, absorption efficiency, reproducibility and repeatability test, accuracy, and response time test. $R^2$ of calibration curve using IPM and CLM was very high (value is 1.000), but for EcSM $R^2$ value was estimated to be lower than IPM and CLM (as 0.991). The RSD of the CLM ranged from 0.1 to 2.3% over the nine concentration levels measured, %Ds was 0.1 to 10.7%, and average RA over all the measurements was 3.3%. The RSD of IPM and EcSM was ranged from 1.0 to 8.1, 3.9 to 14.0 respectively, and average RA were 8.71, 4.9% respectively. Rise in response times of EcSM was estimated to be 1 minute. It is found to be more sensitive than response time (which ranged from 2 to 9 minute) of CLM. For ammonia concentration measured using the IPM and the CLM from the same ammonia source, linear regression of IPM versus CLM show a slope of 0.805, an intercept of 637 ppb, and $R^2$ of 0.868.

• Journal of Practical Agriculture & Fisheries Research
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• v.17 no.1
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• pp.57-71
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• 2015

This study was conducted to develop the fertigation system with a peristaltic hose pump and brushless DC motor. The fertigation system was consisted of sensor, main controller, motor control unit, peristaltic pump, water supply pump, control panel, and filter. The peristaltic pump discharges liquid by squeezing the tube with rollers. Rollers attached to the external circumference of the rotor compresses the flexible tube. The fluid is contained within a flexible tube fitted inside a circular pump casing. The developed fertigation system has no mixing tank but instead injects directly a concentrated nutrient solution into a water supply pipe. The revolution speed of the peristaltic pump is controlled by PWM (Pulse width modulation) method. When the revolution speed of the peristaltic pump was 300rpm, the flow rate of the 3.2, 4.8, 6.3mm diameter tube was 202, 530, 857mL/min, respectively. As increasing revolution speed, the flow rate of the peristaltic pump linearly increased. As the inner diameter of a tube larger, a slope of graph is more steep. Flow rate of three roller was more than that of four roller. Flow rate of a norprene tube with good restoring force was more than that of a pharmed tube. As EC sensor probe was installed in direct piping in comparison with bypass piping showed good performance. After starting the system, it took 16~17 seconds to stabilize EC. The maximum value of EC was 1.44~1.7dS/m at a setting value of 1.4dS/m. The developed fertigation system showed ±0.06dS/m deviation from the setting value of EC. In field test, Cucumber plants generally showed good growth. From these findings, this fertigation system can be appropriately suitable for fertigation culture for crops.