• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.180-193
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• 2021

The complex resistivity method is an exploration technique that can obtain various characteristic information of underground media by measuring resistivity and phase in the frequency domain, and its utilization has recently increased. In this paper, a three-dimensional inversion algorithm for the CR data was developed to increase the utilization of this method. The Poisson equation, which can be applied when the electromagnetic coupling effect is ignored, was applied to the modeling, and the inversion algorithm was developed by modifying the existing algorithm by adopting comlex variables. In order to increase the stability of the inversion, a technique was introduced to automatically adjust the Lagrangian multiplier according to the ratio of the error vector and the model update vector. Furthermore, to compensate for the loss of data due to noisy phase data, a two-step inversion method that conducts inversion iterations using only resistivity data in the beginning and both of resistivity and phase data in the second half was developed. As a result of the experiment for the synthetic data, stable inversion results were obtained, and the validity to real data was also confirmed by applying the developed 3D inversion algorithm to the analysis of field data acquired near a hydrothermal mine.

• Journal of the Society of Disaster Information
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• v.11 no.4
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• pp.520-526
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• 2015

Reinforcing bar splices are inevitable in reinforced concrete structure. In these days, there are three main types of splices used in reinforced concrete construction site - lapped splice, mechanical splice and welded splice. Low cost, practicality in construction site, less time consuming and high performance make gas pressure welding become a favorable splice method. However, reinforcing bar splice experiences thermal loading history during the welding procedure. This may lead to the presence of residual stress in the vicinity of the splice which affects the fatigue life of the reinforcing bar. Therefore, residual stress analysis and tensile test of the gas pressure welded splice are carried out in order to verify the load bearing capacity of the gas pressure welded splice. The reinforcing bar used in this work is SD400, which is manufactured in accordance with KS D 3504. The results show that the residual stresses in welded splice is relatively small, thus not affecting the performance of the reinforcing bar. Moreover, the strength of the gas pressure welded splice is high enough for the development of yielding in the bar. As such, the reinforcing bar with gas pressure welded splice has enough capacity to behave as continuous bar.

• Spatial Information Research
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• v.21 no.6
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• pp.43-55
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• 2013

Recently, the research to visualize and to reproduce evacuation situations such as terrorism, the disaster and fire indoor space has been come into the spotlight and designing a model for interior space and reliable analysis through safety evaluation of the life is required. Therefore, this paper aims to develop simulation model which is able to suggest evacuation route guidance and safety analysis by considering the major risk factor of fire in actual building. First of all, we designed 3D-based fire and evacuation model at a subway station building in Incheon and performed fire risk analysis through thermal parameters on the basis of interior materials supplied by Incheon Transit Corporation. In order to evaluate safety of a life, ASET (Available Safe Egress Time), which is the time for occupants to endure without damage, and RSET (Required Safe Egress Time) are calculated through evacuation simulation by Fire Dynamics Simulator. Finally, we can come to the conclusion that a more realistic safety assessment is carried out through indoor space model based on 3-dimension building information and simulation analysis applied by safety guideline for measurement of fire and evacuation risk.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.95-102
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• 2001

Nano-scale gate length MOSFET devices require extremely shallow source/drain eftension region with junction depth of 20∼30nm. In this work, 20nm $n^{+}$-p junctions that are realized by using this $As_{2}^{+}$ low energy ($\leq$10keV) implantation show the lower sheet resistance of the $1.0k\Omega$/$\square$ after rapid thermal annealing process. The $As_{2}^{+}$ implantation and RTA process make it possible to fabricate the nano-scale NMOSFET of gate length of 70nm. $As_{2}^{+}$ 5 keV NMOSFET shows a small threshold voltage roll-off of 60mV and a DIBL effect of 87.2mV at 100nm gate length devices. The electrical characteristics of the fabricated devices with the heavily doped and abrupt $n^{+}$-p junctions ($N_{D}$〉$10^{20}$$cm^{-3}$, $X_{j}$$\leq$20nm) suggest the feasibility of the nano-scale NMOSFET device fabrication using the $As_{2}^{+}$ low energy ion implantation.

• Journal of the Korean Vacuum Society
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• v.17 no.1
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• pp.51-57
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• 2008

we have demonstrated structural evolution and optical properties of Si-nanowires (NWs) synthesized on Si (111) substrates with nanoscale Au-Si islands by rapid thermal chemical vapor deposition (RTCVD). The Au-Si nano-islands (10-50nm in diameter) were employed as a liquid-droplet catalysis to grow Si-NWs via vapor-liquid-solid mechanism. The Si-NWs were grown by a mixture gas of SiH4 and H2 at a pressure of 1.0 Torr and temperatures of $500{\sim}600^{\circ}C$. Scanning electron microscopy measurements showed that the Si-NWs are uniformly sized and vertically well-aligned along <111> direction on Si (111) surfaces. The resulting NWs are ${\sim}60nm$ in average diameter and ${\sim}5um$ in average length. High resolution transmission microscopy measurements indicated that the NWs are single crystals covered with amorphous SiOx layers of ${\sim}3nm$ thickness. In addition, the optical properties of the NWs were investigated by micro-Raman spectroscopy. The downshift and asymmetric broadening of the Si main optical phonon peak were observed in Raman spectra of Si-NWs, which indicates a minute stress effects on Raman spectra due to a slight lattice distortion led by lattice expansion of Si-NW structures.

• Journal of the Korean Vacuum Society
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• v.16 no.4
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• pp.279-285
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• 2007

We have demonstrated structural evolution and optical properties of the Si-NWs on Si (111) substrates with synthesized nanoscale Au-Si islands by rapid thermal chemical vapor deposition(RTCVD). Au nano-islands (10-50nm in diameter) were employed as a liquid-droplet catalysis to grow Si-NWs via vapor-liquid-solid mechanism. Si-NWs were grown by a mixture gas of $SiH_4\;and\;H_2$ at pressures of $0.1{\sim}1.0$Torr and temperatures of $450{\sim}650^{\circ}C$. SEM measurements showed the formation of Si-NWs well-aligned vertically for Si (111) surfaces. The resulting NWs are 30-100nm in diameter and $0.4{\sim}12um$ in length depending on growth conditions. HR-TEM measurements indicated that Si-NWs are single crystals convered with about 3nm thick layers of amorphous oxide. In addition, optical properties of NWs were investigated by micro-Raman spectroscopy. The downshift and asymmetric broadening of the Si optical phonon peak with a shoulder at $480cm^{-1}$ were observed in Raman spectra of Si-NWs.

• Journal of the Korean Geotechnical Society
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• v.31 no.5
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• pp.23-33
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• 2015

In the present study, a ground heat exchanger was installed for each heat source in the system at the site to evaluate ground heat conductivity, constructability, and economic feasibility; the factors considered in the study included ground heat, groundwater, fillers (such as bentonite and pea pebbles) and the shape of the heat exchange pipe (e.g., U and D-U). The aim was to determine the ground heat exchanger appropriate for the geothermal system in the 3rd-phase construction of Incheon International Airport. A comparative cost analysis of the initial costs based on the above information showed that although the initial costs of the regular vertical closed loop-II and modified vertical closed loop were lower than those of the regular vertical closed loop-I, they could not be expected to deliver high economic efficiency from the viewpoint of constructability (filler injection, heat exchange pipe insertion). The initial costs proved to be higher in the case of Geohil.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.4
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• pp.63-69
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• 1999

The electrical properties of rf-magnetron sputtered $Ba_{0.5}Sr_{0.3}TiO_3$ (BST) capacitors were investigated by varying annealing temperature and atmosphere of the rapid thermal annealing (RTA). The electrical properties of Pt/BST/Pt capacitors were found to strongly depend on the RTA condition. It seems that the dependence of the electrical properties of the Pt/BST/Pt capacitors on the RTA condition is related to the oxygen vacancies in BST thin films. In order to clarify the relation between the oxygen vacancies and the electrical properties of Pt/BST/Pt capacitors, we have examined the two different annealing methods. One annealing method was performed in $O_2$ gas and the other was done in $O_2$-plasma at the same condition of 450$^{\circ}C$, 20 mtorr. It was found that the leakage current densities of $O_2$-plasma annealed capacitor were much lower than those of $O_2$ annealed capacitor. The dielectric constants of $O_2$ annealed capacitor decreased about 14% comparing with those of as-deposited. In contrast, there was no decrease in the dielectric constant of $O_2$-plasma annealed. These results indicate that $O_2$-plasma annealing is very effective in compensation the oxygen vacancies in BST thin films. It can be also concluded that the oxygen vacancies greatly affect the electrical properties of Pt/BST/Pt capacitors.

• Korean journal of applied entomology
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• v.51 no.4
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• pp.421-429
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• 2012

The developmental time period of Aphis gossypii was studied in laboratory (six constant temperatures from 15 to $30^{\circ}C$ with 50~60% RH, and a photoperiod of 14L:10D) and in a cucumber plastic house. The mortality of A. gossypii in the laboratory was high in the 2nd (20.0%) and 3rd stage(13.3%) at low temperature but high in the 3rd (26.7%) and 4th stage (33.3%) at high temperatures. Mortality in the plastic house was high in the 1st and 2nd stage but there was no mortality in the 4th stage at low temperature. The total developmental period was longest at $15^{\circ}C$ (12.2 days) in the laboratory and shortest at $28.5^{\circ}C$ (4.09 days) in the plastic house. The lower threshold temperature at the total nymphal stage was $6.8^{\circ}C$ in laboratory. The thermal constant required to reach the total nymphal stage was 111.1DD. The relationship between the developmental rate and temperature fit the nonlinear model of Logan-6 which has the lowest value for the Akaike information criterion(AIC) and Bayesian information criterion(BIC). The distribution of completion of each development stage was well described by the 3-parameter Weibull function ($r^2=0.89{\sim}0.96$). This model accurately described the predicted and observed outcomes. Thus it is considered that the model can be used for predicting the optimal spray time for Aphis gossypii.

• Journal of Internet Computing and Services
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• v.16 no.1
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• pp.57-65
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• 2015

As information technology fusion is accelerated, the researches to improve the quality and productivity of crops inside a plant factory actively progress. Advanced growth environment management technology that can provide thermal environment and air flow suited to the growth of crops and considering the characteristics inside a facility is necessary to maximize productivity inside a plant factory. Currently running plant factories are designed to rely on experience or personal judgment; hence, design and operation technology specific to plant factories are not established, inherently producing problems such as uneven crop production due to the deviation of temperature and air flow and additional increases in energy consumption after prolonged cultivation. The optimization process has to be set up in advance for the arrangement of air flow devices and operation technology using computational fluid dynamics (CFD) during the design stage of a facility for plant factories to resolve the problems. In this study, the optimum arrangement and air flow of air circulation fans were investigated to save energy while minimizing temperature deviation at each point inside a plant factory using CFD. The condition for simulation was categorized into a total of 12 types according to installation location, quantity, and air flow changes in air circulation fans. Also, the variables of boundary conditions for simulation were set in the same level. The analysis results for each case showed that an average temperature of 296.33K matching with a set temperature and average air flow velocity of 0.51m/s suiting plant growth were well-maintained under Case 4 condition wherein two sets of air circulation fans were installed at the upper part of plant cultivation beds. Further, control of air circulation fan set under Case D yielded the most excellent results from Case D-3 conditions wherein air velocity at the outlet was adjusted to 2.9m/s.