• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.65-71
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• 2019

Conventional methods of measuring ground resistance and ground resistance field measurement are used to measure voltage drop according to the resistance value of the site by applying current by installing a constant interval of measurement electrode. If the stratified structure of the site site is unique, errors in boundary conditions will occur in the event of back acid and the analysis of the critical ground resistance in the ground design will show much difference from simulation. This study utilizes the Arduino module and smart ground measurement technology in the convergent information and communication environment to develop a reliable smart land resistance measuring device even if the top layer of land is unique, to analyze the land resistance and accumulate data to predict the change in the age of the land. Considering the topographical characteristics of the site, we propose a ground resistance measuring device and its method of measuring ground resistance so that the auxiliary electrode can be installed by correctly positioning the angle and distance in measuring ground resistance. Not only is ground resistance value obtained through electrodes installed to allow accurate ground resistance values to be selected, but it can also be used as a useful material for installing electrical facilities in similar areas. Moreover, by utilizing reliable data and analyzing the large sections of the site, a precise analysis of the site, which is important in ground design as well as construction cost, is expected to be used much in ground facility design such as potential rise.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.06a
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• pp.3-17
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• 2004

Space-borne Earth observation technique is one of the most cost effective and rapidly advancing Earth science research tools today and the potential field and micro-wave radar applications have been leading the discipline. The traditional optical imaging systems including the well known Landsat, NOAA - AVHRR, SPOT, and IKONOS have steadily improved spatial imaging resolution but increasing cloud covers have the major deterrent. The new Earth observation satellites ENVISAT (launched on March 1 2002, specifically for Earth environment observation), ALOS (planned for launching in 2004 - 2005 period and ALOS stands for Advanced Land Observation Satellite), and RADARSAT-II (planned for launching in 2005) all have synthetic aperture radar (SAR) onboard, which all have partial or fully polarimetric imaging capabilities. These new types of polarimetric imaging radars with repeat orbit interferometric capabilities are opening up completely new possibilities in Earth system science research, in addition to the radar altimeter and scatterometer. The main advantage of a SAR system is the all weather imaging capability without Sun light and the newly developed interferometric capabilities, utilizing the phase information in SAR data further extends the observation capabilities of directional surface covers and neotectonic surface displacements. In addition, if one can utilize the newly available multiple frequency polarimetric information, the new generation of space-borne SAR systems is the future research tool for Earth observation and global environmental change monitoring. The potential field strength decreases as a function of the inverse square of the distance between the source and the observation point and geophysicists have traditionally been reluctant to make the potential field observation from any space-borne platforms. However, there have recently been a number of potential field missions such as ASTRID-2, Orsted, CHAMP, GRACE, GOCE. Of course these satellite sensors are most effective for low spatial resolution applications. For similar objects, AMPERE and NPOESS are being planned by the United States and France. The Earth science disciplines which utilize space-borne platforms most are the astronomy and atmospheric science. However in this talk we will focus our discussion on the solid Earth and physical oceanographic applications. The geodynamic applications actively being investigated from various space-borne platforms geological mapping, earthquake and volcano .elated tectonic deformation, generation of p.ecise digital elevation model (DEM), development of multi-temporal differential cross-track SAR interferometry, sea surface wind measurement, tidal flat geomorphology, sea surface wave dynamics, internal waves and high latitude cryogenics including sea ice problems.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.1
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• pp.56-67
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• 1999

It is desired to use a domestically manufactured ocean data buoy for the long-term operational ocean monitoring. The ocean data buoy manufacturing technology was introduced through the research cooperation with the Qingkong University of Taiwan. The introduced ocean data buoy system was further expanded and improved for more efficient application for the marine environmental monitoring in Korea. The size of the ocean data buoy is 2.5 m in diameter, which is smaller compared to the NOAA's 3.0 m discus buoy to allow easy land transportation and ocean deployment as well. From the dynamic response test of the buoy carried out numerically, it was shown that the measurement of waves with period greater than 4 seconds is acceptable. The measurement and control system of the data buoy were improved to increase the number of measuring parameters, to reduce power consumption and to enhance better data analysis and management. Each component of the improved data buoy system was described in detail in this paper. Water quality sensors of water temperature, salinity, DO, pH and turbidity were added to the system in addition to the marine meteorological sensors of wind speed and direction, air temperature, humidity, air pressure and wave. Inmarsat satellite communication system is used for the real-time data telemetry from the buoy deployed offshore. A field performance test of the improved and domestically manufactured buoy was carried out for a month at the open sea off Pohang together with DatawelI's Wave-rider buoy to compare the wave data. The results of the test were satisfactory.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.319-325
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• 2021

A fine dust measurement using drones is becoming an increasingly common technology, and air pollutants can be identified through dust monitoring in partial industrial areas. A station for measuring fine dust provides information at large construction site offices. On the other hand, it was difficult to check the fine dust in the pollutant source accurately. Therefore, the drone took measurements directly after been placed at the site. While measuring fine dust, monitoring noise occurred due to the influence of the drone's down-wind during landing, but the measurements were similar to the numerical value of the grounded pollution source on the height of 30 m. The field applicability to the study area has limitations in periodic updates using satellite images because the terrain was constantly changing due to considerable flattening fieldwork. Therefore, this study implemented a system that can reflect real-time field information through GIS mapping using drones.

• The Journal of the Acoustical Society of Korea
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• v.9 no.2
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• pp.42-52
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• 1990

A method of measuring impulse response of acoustic system, two kinds of cross-correlation methods (the direct correlation method and the M-sequence modulation correlation method) were applied. According to the direct correlation method, by using stationary random noise source and by calculating the cross-correlation function between the sourece and the output signal, equivalent impulse response can be obtained not being influenced by the back ground noises. By applying this method, the measurement of echo-time patterns in rooms and oblique incident sound absorption characteristics of sound absorbing materials was carried out. In the case of the M-sequence modulation correlation method which was contrived by Aoshima, an intermittent random nosie modulated by M-sequence signal is used as the source signal, and the cross-correlation function between the M-sequence signal and the squared output signal is calculated. According to this method, equivalent energy impulse response (squared impulse response) of te propagation system can be obtained without being influenced by the back ground noises and the air fluctuation caused by wind. As the applcaition of this measuring method to the architectural acoustics, the meaurements of echo-time patterns, reverberation decays and sound pressure lev디 distributions in rooms and sound insulation efficiencies in buildings were carried out. From these experimental studies, it has been found that this M-sequence modulation correlation method is markedly useful especially for the field masurement of sound insulation under high back ground noise condition.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1726-1733
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• 2015

In order to study the effect of the high-altitude and dusty weather in northwest of China on the corona characteristics of transmission lines, a corona caged based experimental system with sandy and dusty flow condition is numerically investigated and designed. This system overcomes the difficulties caused by harsh environment and offers easy usage for off-site tests. The design parameters are mainly determined by the characteristics of strong sandstorm in northwest region and test requirements. By the comparison of numerical simulation of the particle diffusion in four programs with rectangular or circular air-duct, a practical technology, which introduces swirl to control the particle diffusion length, is obtained. Accordingly, the structure of round air-duct with swirl elbow in inlet and outlet of high level segment is selected as final program. Systems of control and measurement are designed at the same time. Field tuning results show that the test system could ensure the range of sandy and dusty coverage. The wind speed, sandy and dusty concentration could be controlled and meet the requirements of accuracy. The experimental system has many features, such as simple structure, easy to be assembled, disassembled, transported and operated, small space occupied.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.48-57
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• 2009

A two-dimensional (2D), laterally-averaged hydrodynamic and water quality model, CE-QUAL-W2 was applied to evaluate the performance on simulating the effect of flushing from Daecheong Reservoir on the downstream water quality variations during the flushing events held on November, 2003 and March, 2008. The hydraulic and water quality simulation results were compared with field measurement data, as well as a one-dimensional (1D), unsteady model (KORIV1) that revealed limited capability in the previous study due to missing the resuspension process of river bottom sediments. The results showed that although the 2D model made satisfactory performance in reproducing the temporal variations of dissolved matters including phosphate, ammonia and nitrate, it revealed poor performance in simulating the increase of biological oxygen demand and suspended sediment (SS) concentrations during the passage of the flushing flow. The reason of the error was that the resuspension process of the 2D model is only the function of shear stress induced by wind. In reality, however, as shown by significant correlation between bottom shear stress ($\tau$) and observed SS concentration, the resuspension process can be significantly influenced by current velocity in the riverine system, especially during flushing event. The results indicate that the resuspension of river bottom materials should be incorporated into the water quality modeling processes if $\tau$ is greater than a critical shear stress (${\tau}_c$) for better simulation of flushing effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.2
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• pp.99-108
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• 2020

In the field of aircraft icing prediction, surface roughness has been considered as critical factor because it enhances convective heat transfer and changes local collection efficiency. For this significance, experimental studies have been conducted to acquire the quantitative data of the formation process. Meanwhile, these experiments was conducted under low-speed condition due to the measurement difficulties. However, it has not been investigated that how the flow characteristic of low-speed will effects to the surface roughness. Therefore, the present study conducted experiment under low-speed icing condition, and analyzed the relation between surface roughness characteristics and icing condition. As an analysis method, the dominant parameters used in the previous high-speed experiments are employed, and roughness characteristics are compared. The size of roughness element was consistent with the previous known tendency, but not the smooth zone width.

• Journal of Korean Society of Forest Science
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• v.98 no.2
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• pp.156-162
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• 2009

Nebkhas are widely distributed in farming-pastoral zones, typical grassland and desert margins. In the southeast of the Inner Mongolia Plateau, it is mainly distributed at the leeward of cultivated land and alluvial fan, severe deterioration rangeland and around residential points. Through the field measurement and statistical analysis of Caragana microphylla Lam. Nebkhas morphological parameters (length, width and height of Nebkhas are included), the results show that there were close correlations between the Nebkhas morphological parameters. The ranges of height and width of Nebkhas changed dramatically and have reached up to 11.44 m and 7.97 m respectively, however, the change range of height was relatively smaller and just 1.09 m. The morphological parameters change of the same type Nebkhas in the same region was large ranging from 0.56 m in height, 3.56 m in width to 6.96 m in length, while the morphological characteristics of the same type Nebkhas in different regions were much similar. A correlation between length and width was significantly positive, but the correlations between height and length, and between height and width were much more complicated. It can be concluded that the Nebkhas in Zhengxiangbai Banner and Taipusi Banner were at the initially growing stage, while the Nebkhas in Huade County belonged to a transitional stage from the growing phase to the stabilizing phase. The changing regularity of distance between Nebkhas in along-wind direction was not consistent.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.9
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• pp.1-8
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• 2005

This paper explored the effects of separation control through the use of pulsating jet blowing on a two dimensional elliptical airfoil. To develop an active control technique of flow separation, a flow control actuator utilizing continuous/pulsed jet of pressurized air was designed and installed in a wind tunnel testing model of elliptic wing. PIV measurement and flow visualization of the wing near field were conducted to access the feasibility and effectiveness of the pulsed jet blowing on controlling the stall of the elliptical wing in subsonic flow. PIV experimental results show that separation control can provide significant reduction in turbulent flow wake and separation bubbles by jet blowing. The pulsating jet blowing is more effective on the separation control than continuous one. Increased jet frequency suppressed the turbulent separated flow wake effectively at even higher AOAs.