• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.1
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• pp.41-46
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• 2011

Reliable information on the surface solar radiation is indispensable for rebuilding food production system in the famine plagued North Korea. However, transfer of the related modeling technology of South Korea is not possible simply because raw data such as solar radiation or sunshine duration are not available. The objective of this study is restoring solar radiation data at 27 synoptic stations in North Korea by using satellite remote sensing data. We derived relationships between MODIS radiation estimates and the observed solar radiation at 18 locations in South Korea. The relationships were used to adjust the MODIS based radiation data and to restore solar radiation data at those pixels corresponding to the 27 North Korean synoptic stations. Inverse distance weighted averaging of the restored solar radiation data resulted in gridded surfaces of monthly solar radiation for 4 decadal periods (1983-1990, 1991-2000 and 2001-2010), respectively. For a direct application of these products, we produced solar irradiance estimates for each sub-grid cell with a 30 m spacing based on a sun-slope geometry. These products are expected to assist planning of the North Korean agriculture and, if combined with the already prepared South Korean data, can be used for climate change impact assessment across the whole Peninsula.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.101-107
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• 2001

A highly selective, sensitive and reliable ozone sensing $In_2O_3$ thin film was fabricated by a sol-gel method. The fabricated film is operated at a relatively lower temperature than ever developed thin films and saved operating power. $In_2O_3$ films deposited by sol-gel technique has been recently attracted because it is an economical and energy saving method and precisely controlled microstructure. Indium alkoxide precursor was synthesized from the reaction between indium hydroxide and butanol. PVA binder was used to improve adhesion of the films. The $In_2O_3$ thin films were obtained by spin coating from 1 to 5 times followed by drying at $100^{\circ}C$ and calcining at $600^{\circ}C$ for 1h. The film thickness was controlled by the number of coating time. The morphology and the thickness of the $In_2O_3$ films were examined by a SEM and XRD. The $In_2O_3$ thin films show a high sensitive to ozone gas at operating temperature of $250^{\circ}C$. The $In_2O_3$ sensor has very good selectivity to $CH_4$, CO, $C_4H_{10}$ and ethanol.

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.1-8
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• 2000

One of today's very critical and sensitive accurate accelerometer which can be used higher temperature than $200^{\circ}C$ and corrosive environment, is particularly demanded for automotive engine. Because silicon is a material of large temperature dependent coefficient, and the piezoresistors are isolated with p-n junctions, and its leakage current increase with temperature, the performance of the silicon accelerometer degrades especially after $150^{\circ}C$. In this paper, The temperature characteristic of a accelerometer using silicon on insulator (SOI) structure is studied theoretically, and compared with experimental results. The temperature coefficients of sensitivity and offset voltage (TCS and TCO) are related to some factors such as thermal residual stress, and are expressed numerically. Thermal stress analysis of the accelerometer has also been carried out with the finite-element method(FEM) simulation program ANSYS. TCS of this accelerometer can be reduced to control the impurity concentration of piezoresistors, and TCO is related to factors such as process variation and thermal residual stress on the piezoresistors. In real packaging, The avarage thermal residual stress in the center support structure was estimated at around $3.7{\times}10^4Nm^{-2}^{\circ}C^{-1}$ at sensing resistor. The simulated ${\gamma}_{pT}$ of the center support structure was smaller than one-tenth as compared with that of the surrounding support structure.

• Journal of Sensor Science and Technology
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• v.7 no.3
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• pp.188-196
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• 1998

The sensing and electrical characteristics of $WO_{3}$-based n-type semiconductor gas sensors are investigated. In normal air condition, $TiO_{2}$(4 wt. %)-doped $WO_{3}$-based sensor fabricated without any binder shows the grain boundary ( GB ) potential barrier height of 0.26 V. Sensors fabricated with alumina, PVA and silica sol binders show 0.17, 0.22 and 0.26 V of GB potential barrier height, respectively. In the ambience of 120 ppm $NO_{x}$ concentration, the GB potential barrier height of the sensor fablicated without binder is increased to 0.59 V. The sensors were fabricated with alumina, PVA, silica sol binders show 0.43, 0.66 and 0.52 V of potential barrier, respectively. Thus the variation of the potential barrier at GB is largest in the sensor fabricated with the PVA binder. This is found to be the main reason why the sensor fabricated with the PVA binder shows the best sensitivity. It is also found that the decrease of sensitivity at a temperature higher than the optimum operation temperature is due to the temperature dependence of the sensor resistance in normal air condition rather than the desorption of the adsorbed $NO_{x}$ gas particles. In the ambience of 250 ppm CO concentration, the GB potential barrier heights of the sensors fabricated without binder and with PVA binder are about 0.2 V showing negligible change compared to the case of normal air ambience. This fact indicates that these sensors are good candidates for the selective detection of $NO_{x}$ gas in the mixture of CO and $NO_{x}$ gases.

• Journal of Sensor Science and Technology
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• v.5 no.1
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• pp.30-36
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• 1996

ZnO thin-film sensors were fabricated by RF magnetron sputtering method. The composition of the device material was 4 wt. % $Al_{2}O_{3}$, 1 wt. % $TiO_{2}$ and 0.2 wt. % $V_{2}O_{5}$ on the basis of ZnO material for developing the high sensitive TMA gas sensor which have an appropriate resistivity and the stability for practical use. They were also grown on the $SiO_{2}/Si$ substrates heated at $250^{\circ}C$ under a pure oxygen pressure of about 10 mTorr with a power of about 80 watts for 10 minutes. So as to enhance the stability of the resistivity, the thin films were annealed from $400^{\circ}C$ to $800^{\circ}C$. The sensors made with the thin film which were annealed at $700^{\circ}C$ for 60 minutes in pure oxygen gas exhibited a good sensing properties for TMA gas. The thin film grown at this condition showed the maximum sensitivity of 550 in TMA gas concentration of 160 ppm, and exhibited a good stability and excellent linearity.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.1
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• pp.113-121
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• 2015

Remote sensing technology using a multi-spectral satellite imagery can be utilized for the analysis of urban heat island effect in large area. However, weather condition of Korea mostly has a lot of clouds and it makes periodical observation using time-series of satellite images difficult. For this reason, we proposed the analysis of urban heat island effect using time-series of Landsat TM images and ATC model. To analyze vegetation condition and urbanization, NDVI and NDBI were calculated from Landsat images. In addition, land surface temperature was calculated from thermal infrared images to estimate the parameters of ATC model. Furthermore, the parameters of ATC model were compared based on the land cover map created by Korean Ministry of Environment to analyze urban heat island effect relating to the pattern of land use and land cover. As a result of a correlation analysis between calculated spectral indices and parameters of ATC model, MAST had high correlation with NDVI and NDBI (-0.76 and 0.69, respectively) and YAST also had correlation with NDVI and NDBI (-0.53 and 0.42, respectively). By comparing the parameters of ATC model based on land cover map, urban area had higher MAST and YAST than agricultural land and grassland. In particular, residential areas, industrial areas, commercial areas and transportation facilities showed higher MAST than cultural facilities and public facilities. Moreover, residential areas, industrial areas and commercial areas had higher YAST than the other urban areas.

• Journal of Sensor Science and Technology
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• v.11 no.2
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• pp.67-76
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• 2002

We have presented a 2-dimensional fluxgate sensor with ferrite core, excitation, and pick-up coil. This fluxgate sensor system consists of a sensing element, driving circuits for excitation coil and signal processing for detecting second harmonic frequency component which is proportional to the DC magnetic to be measured. The sensor core is excited by a square waveform of voltage through the excitation coil of 80 turns. The second harmonic output of pick-up coil(x and y axis: 100 turns) is measured by FFT spectrum analyzer. This result is compared with output of PSD(phase sensitive detector) unit for detecting the second harmonic component. The measured maximum sensitivity is about 1580 V/T at driving frequency of 1.5 kHz and excitation current of 2 App. The nonlinearity of this system is measured about 2.3%(PSD) and about 1%(second harmonics of the pick-up). The angle error of the system is ${\pm}2$ %/FS.

• Applied Microscopy
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• v.40 no.2
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• pp.117-123
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• 2010

This study has examined experimentally the Beer's law which is a precondition for quantitative electron tomography. We used carbon support film and latex spheres, which have similar absorption coefficients with biological samples, as the test samples to take a tilt-series of images for electron tomography. First, the 3D information of carbon film and latex spheres was obtained by electron tomography. Then, the regression analysis on the relationship between the intensities of the incident and the transmitted beams in a tilt series was carried out to examine the Beer's law. The regression results with RMS error of 0.976 show the linear intensity variations of the transmitted beam as the tilt angles were increased. In addition, the relative absorption coefficients of carbon support film and latex spheres calculated experimentally through the Beer's law were 1.71 (5) and 2.67 (6)/${\mu}m$, respectively. The absorption coefficients remained constant within a full tilt range. Therefore, it is expected that quantitative electron tomography could be performed for biological samples by applying Beer's law provided the exact intensity of incident beam can be obtained under the thoroughly controlled experimental conditions.

• Applied Microscopy
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• v.38 no.4
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• pp.285-291
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• 2008

We have evaluated the effects of experimental factors on transmitted electron beam intensities for quantitative analysis in electron tomography. For the correct application of Beer's law in electron tomography, the transmitted beam intensity should reflect the net effect of mass properties on beam path. So, the any other effects of the objective aperture and the specimen holder on beam path should be removed. The cut-off effects of objective aperture were examined using Quanti-foil holey carbon film and a transmission electron microscope operated at 120 kV. The transmitted beam intensities with $30{\mu}m$ objective aperture dropped about 16.7% compared to electron beam intensities without the objective aperture. Also, the additional losses of about 14.2% at high tilt angles were occurred by cut-off effects of the objective apertures. For the precise quantitative analysis in electron tomography, the effect of the objective aperture on transmitted electron beam intensities should be considered. It is desirable that 2-D tilt series images are obtained without the objective aperture for correct application of Bee's law.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.207-212
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• 2008

Bathymetry, side scan sonar, and magnetic survey data for the summit area of Dokdo obtained by Korea Ocean Research & Development Institute in 1999, 2004, and 2007 were analyzed to investigate the geophysical characteristics of the summit. Bathymetry and topographic data for the summit of Dokdo show uneven seabed and irregular undulations from costal line to -90 m in water depth, indicating the effects of partial erosions and taluses. The stepped slope in the bathymetry is supposed to be a coastal terrace suggesting repetition of transgressions and regressions in the Quaternary. The bathymetry and the side scan sonar data show a small crater, assumed to be formed by post volcanisms, at depth of $-100\;{\sim}\;-120\;m$ in the northeastern and the northwestern parts of the survey area. Except some areas with shallow sand sedimentary deposits, there are rocky seafloor and lack of sediments in the side scan sonar images of the survey area, dominantly. The analytic signal of the magnetic anomaly coincides with other geophysical results regarding to the location of the residual crater. The geophysical constraints of the summit of Dokdo propose that the islets and the rocky seabed elongated northeastward and northwestward from the islets might be the southern crater of the Dokdo volcano.