• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.779-789
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• 2015

Because cable-supported bridges have long spans and large members, their movements and geometrical changes by temperatures tend to be bigger than those of small or medium-sized bridges. Therefore, it is important for maintenance engineers to monitor and assess the effect of temperature on the cable-supported bridges. To evaluate how much the superstructure expands or contracts when subjected to changes in temperature is the first step for the maintenance. Thermal movements of a cable-stayed bridge in service are evaluated by using long-term temperatures and displacements data. Displacements data are obtained from extensometers and newly installed GNSS (Global Navigation Satellite System) receivers on the bridge. Based on the statistical data such as air temperatures, each sensor's temperatures, average temperatures and effective temperatures, correlation analysis between temperatures and displacements has been performed. Average temperatures or effective temperatures are most suitable for the evaluation of thermal movements. From linear regression analysis between effective temperatures and displacements, the variation rate's of displacement to temperature have been calculated. From additional regression analysis between expansion length's and variation rate's of displacement to temperature, the thermal expansion coefficient and neutral point have been estimated. Comparing these parameters with theoretical and analytical results, a practical procedure for evaluating the real thermal behaviors of the cable-supported bridges is proposed.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.4
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• pp.245-251
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• 2019

Sonar bearing accuracy is the correspondence between the target orientation predicted by sonar and actual target orientation, and is obtained from measurements. However, when measuring sonar bearing accuracy, many errors are included in the results because they are made at sea, where complex and diverse environmental factors are applied. In particular, parallax error caused by the difference between the position of the GPS receiver and the sonar sensor, and the time delay error generated between the speed of underwater sound waves and the speed of electromagnetic waves in the air have a great influence on the accuracy. Correcting these parallax errors and time delay errors without an automated tool is a laborious task. Therefore, in this study, we propose a sonar bearing accuracy measurement equipment with parallax error and time delay error correction. The tests were carried out through simulation data and real data. As a result of the test it was confirmed that the parallax error and time delay error were systematically corrected so that 51.7% for simulation data and more than 18.5% for real data. The proposed method is expected to improve the efficiency and accuracy of sonar system detection performance verification in the future.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1092-1098
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• 2007

Since one decade, the detection of HFPD (High frequency Partial Discharge) has been proposed as one of the effective method for the diagnosis of the power component under service in power grids. As a tool for HFPD detection, Metal Foil sensor based on the embedded technology has been commercialized for mainly power cable due to its advantages. Recently, for the on-site noise discrimination, several PA (Pulse analysis) methods have been reported and the related software, such as Neural Network and Fuzzy, have been proposed to separate the PD (Partial Discharge) signals from the noises since their wave shapes are completely different from each other. On the other hand, the relevant fundamental investigation has not yet clearly made while it is reported that the effectiveness of the current methods based on PA is dependant on the types of sensors. Moreover, regarding the identification of the vital defects introducible into the Power Cable, the direct identification of the nature of defects from the PD signals through Metal Foil coupler has not yet been realized. As a trial for solving above shortcomings, different types of software have been proposed and employed without any convincing probability of identification. In this regards, our novel algorithm 'PA Map' based on the pulse analysis is suggested to identify directly the defects inside the power cable from the HFPD signals which is output of the HFCT and metal foil sensors. This method enables to discriminate the noise and then to make the data analysis related to the PD signals. For the purpose, the HFPD detection and PA (Pulse Analysis) system have been developed and then the effect of noise discrimination has been investigated by use of the artificial defects using real scale mockup. Throughout these works, our system is proved to be capable of separating the small void discharges among the very large noises such as big air corona and ground floating discharges at the on-site as well as of identifying the concerned defects.

• Journal of the Korean Ceramic Society
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• v.16 no.4
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• pp.213-224
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• 1979

The present work was undertaken: (1) to determine if CaO-partially stabilized $ZrO_2$ prepared by Hot Petroleum Drying Method would show better ionic conductor as an oxygen sensor in molten metals than that prepared by Oxide Wet Mixing Method and than CaO-fully stabilized $ZrO_2$, and (2) to understand the nature of conduction mechanism of CaO-partially stabilized $ZrO_2$ by a comparison of measured electrical conductivity data with theory on defect structure of pure monoclinic $ZrO_2$ and fully stabilized cubic $ZrO_2$. The DC electrical conductivity was measured by 3-probe technique and the AC electrical conductivity by 2-probe technique as a function of temperature in the range 973-1373 K and oxygen partial pressure in the range 10-1-10-25Mpa. The results of the experiments were as follows: 1. CaO-partially stabilized $ZrO_2$ prepared by Hot petroleum Drying Method showed at T=1094-1285 K and $Po_2$=10-7-10-25 MPa a nearly ionic conduction with 4 times higher conductivity than that prepared by Oxide Wet Mixing Method. 2. High-oxygen pressure conductivity tends toward a Po_2^{+1/5}-Po_2^{+1/6}$dependence. An analysis of possible defect structures suggests that CaO-partially stabilized $ZrO_2$ has an anti-Frenkel defect in which singly or doubly ionized oxygen interstitials and defect electrons predominate at T=1094-1285 K and $Po_2$=10-1-10-7MPa. 3. The activation energy for pure electron hole-conduction and ionic conduction of CaO-partially stabilized $ZrO_2$ was found to be 130 KJ/mol at T=973-1373 K, $Po_2$=2, 127 10-2 MPa(air) and 153KJ/mol at T=1094-1285 K respectively.

• Journal of Korea Multimedia Society
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• v.20 no.3
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• pp.474-481
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• 2017

In Korea, foot-and-mouth disease has not been reported for several decades, but it began to develop again in 2000. For 2010~2011, when the worst occurred, 3.5 million animals were disposed of resulting in a loss of 2.8 trillion won. In order to prevent the harmful effects of foot-and-mouth disease, vaccination and housing management are being implemented. Despite these measures, foot-and-mouth disease is infected with air through the respiratory tract and accompanies fever after latency. Therefore, it is recognized that measuring and managing the body temperature of livestock at the early stage is the first step of managing this disease. In this paper, we propose a temperature monitoring system that can measure the body temperature by incorporating temperature sensor mounted in ear-tag of cattle and collect body temperature data of each individual cattle through BLE into the control server. The proposed body temperature monitoring system has various advantages such as easy installation without the help of livestock specialists and not damaging the organs of the livestock. So, it is possible to manage the abnormal symptom of cattle in real time and it is believed that the proposed monitoring system will revolutionize the prevention of foot-and-mouth disease.

• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.2
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• pp.53-65
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• 2016

Static wireless multi-hop networks, such as wireless mesh networks and wireless sensor networks have proliferated in recent years because of they are easy to deploy and have low installation cost. Two key measures are used to evaluate the performance of a multicast tree algorithm or protocol : end-to-end delay and the number of transmissions. End-to-end delay is the most important measure in terms of QoS because it affects the total throughput in wireless networks. Delay is similar to the hop count or path length from the source to each destination and is directly related to packet success ratio. In wireless networks, each node uses the air medium to transmit data, and thus, bandwidth consumption is related to the number of transmission nodes. A network has many transmitting nodes, which will cause many collisions and queues because of congestion. In this paper, we optimize two metrics through a guaranteed delay scheme. We provide an integer linear programming formulation to minimize the number of transmissions with a guaranteed hop count and preprocessing to solve the aforementioned problem. We extend this scheme not only with the guaranteed minimum hop count, but also with one or more guaranteed delay bounds to compromise two key metrics. We also provide an explanation of the proposed heuristic algorithm and show its performance and results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.599-603
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• 2003

This paper present an error compensation system and On-Machine Measurement(OMM) system for improving the machining accuracy of ultra-precision lathe. The Fast-Tool-Servo(FTS) driven by a piezoelectric actuator is applied for error compensation system. The controller is implemented on the 32bit DSP for feedback control of piezoelectric actuator. The control system is designed to compensates three kinds of machining errors such as the straightness error of X-axis slide, the thermal growth error of the spindle. and the squareness between spindle and X-axis slide. OMM is preposed to measure the finished profile of workpiece on the machine-tool using capacitive sensor with highly accurate ruby tip probe guided by air bearing. The data acquisition system is linked to the CNC controller to get the position of each axis in real-time. Through the experiments, it is founded that the thermal growth of spindle and tile squareness error between spindle and X-axis slide influenced to machining error more than straightness error of X-axis slide in small travel length. These errors were simulated as a sinusoidal signal which has very low frequency and the FTS could compensate the signal less than 30 m. The implemented OMM system has been tested by measuring flat surface of 50 mm diameter and shows measurement error less than 400 mm

• The Journal of Engineering Geology
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• v.21 no.1
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• pp.45-55
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• 2011

We examined the interactions between surface and groundwater through (1) flowmeter logging, (2) measurements of seasonal and vertical changes in temperature within a well, and (3) geochemical analyses of water samples from nine groundwater-monitoring wells. At two wells adjacent to a stream, subsurface water was found to flow from the stream to a surrounding alluvial fan, and the seasonal change in groundwater temperature is similar to those of surface water and air. Geochemical analyses at two wells indicated hydro-geochemical features affected by streamwater inflow, showing seasonal variations. Accordingly, these two wells are located in an area with active interaction between surface water and groundwater. The Thermochron I-button used in the present study is useful for this type of study of groundwater?surface water interaction because of its low cost and small size.

• Journal of Biosystems Engineering
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• v.36 no.1
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• pp.33-39
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• 2011

An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applied to investigate the potential of reflectance sensing in estimating soil properties for Korean paddy fields. Soil cores up to a 65-cm depth were collected from 42 paddy fields representing 14 distinct soil series that account for 74% of the total Korean paddy field area. These were analyzed in the laboratory for several important physical and chemical properties. Using air-dried, sieved soil samples, reflectance data were obtained from 350 to 2500 nm on a 3 nm sampling interval with a laboratory spectrometer. Calibrations were developed using partial least squares (PLS) regression, and wavelength bands important for estimating the measured soil properties were identified. PLS regression provided good estimations of Mg ($R^2$ = 0.80), Ca ($R^2$ = 0.77), and total C ($R^2$ = 0.92); fair estimations of pH, EC, $P_2O_5$, K, Na, sand, silt, and clay ($R^2$ = 0.59 to 0.72); and poor estimation of total N. Many wavelengths selected for estimation of the soil properties were identical or similar for multiple soil properties. More important wavelengths were selected in the visible-short NIR range (350-1000 nm) and the long NIR range (1800-2500 nm) than in the intermediate NIR range (1000-1800 nm). These results will be useful for design and application of in-situ close range sensors for paddy field soil properties.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.2
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• pp.208-214
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• 2012

The spectral radiance received by a remote sensor is consisted of the self-emitted component directly from the target surface, the reflected component of the solar irradiance at the target surface, and the scattered component by the atmosphere without ever reaching the object surface. In general, the self-emitted component is the most important part in the infrared signatures from the target. We measured the solar irradiation, sky irradiation, air temperature, wind velocity, wind direction, relative humidity, and atmospheric pressure together with the surface temperatures of rectangular parallelepiped targets. The measured diurnal surface temperature variations on the three different rectangular parallelepiped targets constructed by the steel, aluminum and bakelite are obtained at the same time intervals. The measured surface temperature results show that the top surface temperature of bakelite recorded up tp $7.6^{\circ}C$ higher than that of aluminium and $6.1^{\circ}C$ higher than that of steel at 11 AM on the sunny condition. A complete set of measured data including the surface temperature of rectangular parallelepiped targets together with the detailed weather information can be a valuable reference for future study.