• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.751-760
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• 2005

The chloride penetration model, which considers diffusion and sorption, is proposed. The FEM program developed on the basis of the diffusion and sorption model provides the estimation of chloride concentration variation according to cyclic humidity and temperature. The humidity diffusion analysis is carried out, and the chloride ion diffusion and sorption analysis are conducted on the basis of the pre-estimated humidity data in each element. Each element has different variables at different ages and locations in analysis. At early ages, the difference of relative humidity between inner and outer concretes causes the chloride ion penetration by sorption. As the humidity diffusion reduces the difference of relative humidity between inner md outer concretes with age, the effect of sorption on the chloride ion penetration decreases with age. The cyclic humidity increases the effect of sorption on the chloride ion penetration at early ages, and increases the quantity of chloride ion around steel at later ages. Therefore, the in-situ analysis of chloride ion Penetration for harbor concrete structures must be Performed considering the cyclic humidity conditionandthelongtermsorption.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.4
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• pp.3-12
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• 2011

Understanding of water sediment trends is an important part of water quality monitoring. Water quality variables change over time and space, and cannot be modeled or explained clearly by either temporal or spatial analysis alone. This research analysed the trends of temperature, pH levels and dissolved oxygen levels based on the sediment records and spatial data obtained in Lower Mekong Basin (LMB) during 1985-2005. Our aim is to evaluate spatio-temporal trends and graphical analyses using an Inverse Distance Weighting (IDW) interpolation method. The main results from this research can be summarized as follows. The maximum temperature and pH have been stable during the study period and the maximum dissolved oxygen has been increasing gradually until 2002. The minimum pH and dissolved oxygen have been changing in an unsteady trend during the period. A spatial analysis shows that the water temperature in this region has been increasing over time. The pH trend shows that it is decreasing during 1993-2005. Dissolved oxygen concentration has been increasing from 1989 onwards and stays in that track.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.95-102
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• 1985

An efficient numerical scheme for assessing the two-dimensional diffusion problem for modelling impurity profile in semiconductor is described. 4 unique combination of ADI (Al-ternating Direction Bmplicit) method and Gauss Elimination has resulted in a reduction of CPU time for most diffusion processes by a factor of 3, compared to other iteration schemes such as SOR (Successive Over-Relaxation) or Stone's iterative method without additional storage re-quirement. Various numerical schemes were compared for 2-D as well as 1-0 diffusion profile in terms of their CPU time while retaining the magnitude of relative error within 0.001%. good agree-ment between 1-D and 2-D simulation profile as well as between 1-D simulation profile and experiment has been obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7A
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• pp.554-561
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• 2009

In this paper, we propose a novel Vehicular Ad-hoc Network(VANET) which includes communication and ranging features, using Spread Spectrum(SS) multi-carrier modulation scheme. In existing methods, a spread spectrum technique was used to communicate with other vehicles and raging was possible by detecting phase difference between transmission/reception of the PN signal. However, the use of high-speed PN signals is mandatory to detect possible errors of phase difference and to increase the analysis capacity. In the proposed system, multi-carrier modulation scheme was used as solution of mentioned problem. The multi-carrier modulation scheme uses smaller PN signal and chip-rate than the single-carrier modulation, so it is possible to send multiple carrier waves using the same frequency range. This technique (multiple carrier waves) allows to have the Equal Gain Combing (EGC) diversity effect, providing better result in phase difference error detection and raging accuracy.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.273-279
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• 2014

In this paper, we propose a novel algorithm for three dimensional positioning system and implement a system over indoor wireless channel. A commercial modules are used for mobile and fixed nodes which are product of German company Nanotron Co. This module adopts chirp spread spreading scheme as modulation method to improve the ranging resolution and the module satisfies the IEEE standard 802.15.4a. The distance computation is based on received signal strength(RSS) levels and trilateration method. A testbed was set up to measure and compare the positioning estimation error of the proposed algorithm. The experiments results showed that the accuracy of location estimation was sufficiently good as much as 1m distance error in a wireless environment in an office building.

• Analytical Science and Technology
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• v.26 no.3
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• pp.174-181
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• 2013

Pyrifluquinazon is classified with a quinazoline insecticide that regulates food intake by controling the feeding behavior acting on the endocrine or nervous system of pests such as aphids and white fly. To keep safety on pyrifluquinazon residues in agricultural commodities a simple, accurate and rapid analytical method was developed and validated using high performance liquid chromatograph (HPLC-UVD). The pyrifluquinazon residues acidified with 1% formic acid in samples were extracted with acetonitrile and partitioned with hexane subsequently to dichloromethane then purified with silica solid phase extraction (SPE) cartridge. The purified samples were detected using HPLC-UVD. The method was validated using apple and pear spiked with pyrifluquinazon at 0.02, 0.05 and 0.1 mg/kg and hulled rice, pepper, soybean at 0.05 and 0.1 mg/kg. Average recoveries were 70.5~107.9% with relative standard deviation less than 10%. The result of recoveries and overall coefficient of variation of a laboratory results in Gwangju regional FDA and Daejeon regional FDA was followed with Codex guideline (CODEX CAC/GL 40). This method is appropriated at pyrifluquinazon residues determination and will be used as official method of analysis.

• Progress in Medical Physics
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• v.17 no.2
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• pp.105-113
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• 2006

This study peformed to confirm the corrected dose In different electron density materials using the superposition/FFT convolution method in radiotherapy Planning system. The experiments of the $K_2HPO_4$ diluted solution for bone substitute, Cork for lung and n-Glucose for soft tissue are very close to effective atomic number of tissue materials. The image data acquisited from the 110 KVp and 130 KVp CT scanner (Siemes, Singo emotions). The electron density was derived from the CT number (H) and adapted to planning system (Xio, CMS) for heterogeneity correction. The heterogeneity tissue phantom used for measurement dose comparison to that of delivered computer planning system. In the results, this investigations showed the CT number is highly affected in photoelectric effect in high Z materials. The electron density in a given energy spectrum showed the relation of first order as a function of H in soft tissue and bone materials, respectively. In our experiments, the ratio of electron density as a function of H was obtained the 0.001026H+1.00 in soft tissue and 0.000304H+1.07 for bone at 130 KVp spectrum and showed 0.000274H+1.10 for bone tissue in low 110 KVp. This experiments of electron density calibrations from CT number used to decide depth and length of photon transportation. The Computed superposition and FFT convolution dose showed very close to measurements within 1.0% discrepancy in homogeneous phantom for 6 and 15 MV X rays, but it showed -5.0% large discrepancy in FFT convolution for bone tissue correction of 6 MV X rays. In this experiments, the evaluated doses showed acceptable discrepancy within -1.2% of average for lung and -2.9% for bone equivalent materials with superposition method in 6 MV X rays. However the FFT convolution method showed more a large discrepancy than superposition in the low electron density medium in 6 and 15 MV X rays. As the CT number depends on energy spectrum of X rays, it should be confirm gradient of function of CT number-electron density regularly.

• Nuclear Engineering and Technology
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• v.27 no.2
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• pp.176-188
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• 1995

A particle tracking scheme was developed in order to model radionuclide transport through a tortuous flow Held in a rock fracture. The particle tacking method may be used effectively in a heterogeneous flow field such as rock fracture. The parallel plate representation of the single fracture fails to recognize the spatial heterogeneity in the fracture aperture and thus seems inadequate in describing fluid movement through a real fracture. The heterogeneous flow field une modeled by a variable aperture channel model after characterizing aperture distribution by a hydraulic test. To support the validation of radionuclide transport models, a radionuclide migration experiment was performed in a natural fracture of granite. $^3$$H_2O$ and $^{131}$ I are used as tracers. Simulated results were in agreement with experimental result and therefore support the validity of the transport model. Residence time distributions display multipeak curves caused by the fast arrival of solutes traveling along preferential fracture channels and by the much slower arrival of solutes following tortous routes through the fracture. Results from the modelling of the transport of nonsorbing tracer through the fracture show that diffusion into the interconnected pore space in the rock mass has a significant effect on retardation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.40-46
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• 1984

The extraction ratio of oil using solvent from the muscle of sardine, Sardinops melanosticta, was studied. The results were critically evaluated in the light of the theory of oil diffusion in a porous solid model. In addition the effect of temperature and moisture on the extraction rate was examined. Sardine muscle was prepared in a manner to meet the conditions required by the diffusion theory from Fick's law. The results of the model were well coincidenced to the theory derived from Fick's law. Diffusion constants at the direction to muscle fiber($D_1$) and at direction perpendicular to fiber($D_2=D_3$) when extracted at $45^{\circ}C$ were $8.16{\times}10^{-8}cm^2/sec\;and\;4.12{\times}10^{-8}cm^2/sec$, respectivly. The extraction rate was linearly propotional to absolute temperature(T) by eleventh power under the constant condition of moisture contents and muscle size. A comparison of the experiments with the highest($74.22\%$) and the lowest ($32.48\%$) moisture indicated that difference of $1\%$ in moisture contents caused to change the slope(K) of the extraction curve $0.53{\times}10^{-6}sec^{-1}$ approximately.

• Journal of Sensor Science and Technology
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• v.1 no.1
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• pp.5-12
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• 1992

We have fabricated a-Si:H multilayer for contact-type linear image sensor by means of RF glow discharge decomposition method. The ITO/i-a-Si:H/Al structure has relatively high dark current due to indium diffusion and carrier injection from both electrodes, resulting in low photocurrent to dark current. To suppress the dark current and to enhance interface electric field between ITO and i-a-Si:H film we have fabricated ITO/insulator/i-a-S:H/p-a-S:H/Al multilayer film with blocking structure. The photocurrent of ITO/$SiO_{2}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al multilayer sensor with 5V bias voltage became saturated at about 20nA under $20{\mu}W/cm^{2}$ light intensity, while the dark current was less than 0.1nA. To increase the light generation efficiency we have adopted ITO/$SiO_{x}N_{y}(300{\AA})$/i-a-Si:H/p-a-Si:H($1500{\AA}$)/Al structure, showing photocurrent of 30nA and dark current of 0.08nA with 5V bias voltage. Also the spectral photosensitivity of the multilayer was enhanced for short wavelength visible region of 560nm, compared with that of the a-Si:H monolayer of 630nm. And its photoresponse time was about 0.3msec with the film homogeneity of 5% deviation.