• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.372-375
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• 1988

The III-V ternary alloy semiconductor $In_{l-x}Ga_{x}As$ were grown by the temperature Gradient of $0.60{\leq}x{\leq}0.98$. The electrical properties were investigated by the Hall effect measurement with the Van der Pauw method in the temperature range of $90{\sim}300K$. $In_{l-x}Ga_{x}As$ were revealed n-type and the carrier concentration at 300K were in the range of $9.69{\times}10^{16}cm^{-3}{\sim}7.49{\times}10^{17}cm^{-3}$. The resistivity was increased and the carrier mobility was decreased with increasing the composition ratio. The optical energy gap determined by optical transmission were $20{\sim}30meV$ lower than theoretical valves on the basis of absorption in the conduction band tail and it was decreased with increasing the temperature by the Varshni rule. In the photoluminescence of undoped $In_{l-x}Ga_{x}As$ at 20K, the main emission was revealed by the radiative recombination of shallow donor(Si) to acceptor(Zn) and the peak energy was increased with increasing the composition, X. The diffusion depth of Zn increases proportionally with the square root of diffusion time, and the activation energy for the Zn diffusion into $In_{0.10}Ga_{0.90}As$ was 2.174eV and temperatures dependence of diffusion coefficient was D = 87.29 exp(-2.174/$K_{B}T$). The Zn diffusion p-n $In_{x}Ga_{x}As$ diode revealed the good rectfying characteristics and the diode factor $\beta{\approx}2$. The electroluminescence spectrum for the Zn-diffusion p-n $In_{0.10}Ga_{0.90}As$ diode was due to radiative recombation between the selectron trap level(${\sim}140meV$) and Zn acceptor level(${\sim}30meV$). The peak energy and FWHM of electroluminescence spectrum at 77K were 1.262eV and 81.0meV, respectively.

• Journal of the Korean Geophysical Society
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• v.6 no.3
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• pp.139-153
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• 2003

Subsurface information is one of the most important factors in the archaeological excavation. To obtain the information on the underground, geophysical prospecting is becoming a popular method. This study is on the small rocky islands located 200m away from the shoreline of Gampo, Gyeongju city, Korea. According to the historical records and field surveys, it was revealed as the tomb of King Munmu of Shilla Dynasty. However, the questions and debates, such as whether it is really the tomb of King Moonmu or not, and whether it is a buried place or not, are still remains, in addition to the incompletion of precise surveying and scientific studies. The scope of this study contains the researches on the above problems and debates using the geophysical and geological methods and techniques. The rocky islands around the submerged Tomb of King Moonmu is composed of granite, and sag exists inside of the islands. Sea water enters through the east groove by wave and is drained to the west slot by hydraulic gradient, since west slot is 15cm lower than the east. Sag inside of the islands is believed to be extended and widened from pre-existed sinkage by applying tools like chisel in the joints and cracks. It is concluded that the submerged megalith inside of sag was from the rock block which was developed by joints. Geophysical surveys reveal that there is no artificial structure or stone/china/steel chest, under the m egalith and rocky island. Researches show that the tomb of King Moonmu was constructed in the small rocky island artificially. However, the evidences show that planners and constructors of the tomb made every possible effort to preserve the natural environment and condition. It is strongly believed that the megalith was sort of alter to sprinkle bone-ash rather than buried place.

• Journal of the Korean Ceramic Society
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• v.42 no.7 s.278
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• pp.475-482
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• 2005

Zn$_{l-x}$Co$_{x}$O (x = 0.05 - 0.20) films were grown on Coming 7059 glass by sol-gel process. A homogeneous and stable Zn$_{l-x}$Co$_{x}$O sol was prepared by dissolving zinc acetate dihydrate (Zn(CH$_{3}$COO)$_{2}$$\cdot$2H$_{2}$O), cobalt acetate tetrahydrate ((CH$_{3}$)$_{2}$$\cdot$CHOH) and aluminium chloride hexahydrate (AlCl$_{3}$ $\cdot$ 6H$_{2}$O) as solute in solution of isopropanol ((CH$_{3}$)$_{2}$$\cdot$CHOH) and monoethanolamine (MEA:H$_{2}$NCH$_{2}$CH$_{2}$OH). The films grown by spin coating method were postheated in air at 650°C for 1 h and annealed in the condition of vacuum (5 $\times$ 10$^{-6}$ Torr) at 300$^{\circ}C$ for 30 min and investigated the nature of c-axis preferred orientation and physical properties with different Co concentrations. Znl_xCOxO thin films with different Co concentrations were well oriented along the c-axis, but especially a highly c-axis oriented Zn$_{l-x}$Co$_{x}$O thin film was grown at 10 at$\%$ Co concentration. The transmittance spectra showed that Zn$_{l-x}$Co$_{x}$O thin films occur typical d-d transitions and sp-d exchange interaction became activated with increasing Co concentration. The electrical resistivity of the films at 10 at$\%$ Co had the lowest value due to the highest c-axis orientation. X-ray photoelectron spectroscopy and alternating gradient magnetometer analyses indicated that no Co metal cluster was formed, and the ferromagnetic properties appeared, respectively. The characteristics of the electrical resistivity and room temperature ferromagnetism of Zn$_{l-x}$Co$_{x}$O thin films suggested the possibility for the application to dilute magnetic semiconductors.

• Proceedings of the KSMRM Conference
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• 2001.11a
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• pp.137-137
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• 2001

Purpose： The purpose of this study was to identify cerebral cortices related with sexual arousal fro visual sexual stimulation in healthy males using BOLD-based functional MR imaging Method： Sixteen male volunteers with sexually potent(mean age：24) were examined for thi study. Functional MRI was performed on a 1.5T MR scanner(GE Signa Horizon) with birdcage-type head coil. In this study, blood oxygenation level dependent(BOLD) technique was utilized to create fMR image reflecting local brain activities. The BOLD-based fMRI d were obtained from 7 oblique planes using gradient-echo EPI with $90^{\circ}$flip angle, 50ms TE 6000ms TR, $26cm{\times}26$ cm FOV, $128{\times}128$ matrix, and 10mm slice thickness. The sexual stimulation paradigm consisted of two alternating periods of rest and activati and it began with a 1 minute rest, followed by a 2 minute stimulation by a documentary a erotic video film. Brain activation maps were generated by cross-correlation of imag acquired during rest and activation periods. The index of activation was used to compare t number of pixels activated by each task in each volunteer, where the significance of th differences was evaluated by using Students t-test.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.2
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• pp.257-263
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• 1999

It is well known that discard of seminal plasma from the semen and separation of motile sperm should be preceded before insemination for IUI or IVF. Till now, more than ten kinds of semen treatment methods have been developed. Of those, swim-up and Percoll methods have been used widely in ART laboratories as a routine semen treatment methods because of its advantages. However, there are reports that Percoll can make a genetic trouble because of its chemical structure and therefore the necessity has been arisen to substitute Percoll for other equivalent materials. This study was performed to evaluate the effects of three different sperm preparation methods (swim-up, Percoll and Sil-Select) on sperm motility, sperm recovery rate and fertilization rate. Also, the feasibility of using Sil-Select instead of Percoll in ART was evaluated. Each semen samples were divided into three fractions and motile sperm were recovered by swim-up, Percoll and Sil-Select gradient centrifugation methods. Normal and sub-normal criteria of fifteen semen samples and seventeen IVF cycles were included in these study. As results, no significant difference was found in sperm recovery rate in normal semen treated by a Swim-up, Percoll and Sil-Select method ($13.2{\times}10^6,\;17.5{\times}10^6\;and\;17.7{\times}10^6$ respectively). The initial sperm motility was 61.9% and this increased to 87.1%, 92.6% and 89.5% through Swim-up, Percoll and Sil-Select treatment, respectively. Higher motility was observed in Percoll and Sil-Select treated groups (81.5%, 79.2%, respectively) than swim-up group (66.8%) after incubation for 24hrs. In sub-normal group, sperm recovery rates were higher in Sil-Select group $(2.9{\times}10^6)$ than Percoll gradients group $(1.8{\times}10^6)$. In IVF cycles, the outcomes of fertilization using sperm treated by swim-up and Sil-Select group were similar (82.2%, 79.7% respectively). In conclusion, our results indicate that Sil-Select can be used as a substitute material for sperm preparation instead of Percoll.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.535-542
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• 2014

A simple and efficient preconcentration method was developed using three-phase liquid phase microextraction prior to HPLC-UV for simultaneous extraction and determination of tetracycline antibiotics (tetracycline, oxytetracycline, and chlortetracycline). The tetracycline antibiotics were separated simultaneously on a column ($C_8$, $3.0{\times}150mm$, $3{\mu}m$) with high selectivity and sensitivity using gradient elution. Under optimized conditions (extraction solvent, heptanal; pH of donor, 9.0; pH of acceptor, 1.0; stirring speed, 700 rpm; NaCl salt, 0%; and extraction time, 60 min), enrichment factors (EF) were between 5.6 and 22.3. The limit of detection (LOD) and limit of quantitation (LOQ) in the spiked urine matrix were in the concentration range of $0.08{\sim}0.8{\mu}g/mL$ and $0.4{\sim}1.6{\mu}g/mL$, respectively. The calibration curves were linear within the range of $0.1{\sim}32{\mu}g/mL$ with the square of the correlation coefficient being more than 0.995. The precision (as a relative standard deviation, RSD) and accuracy (as a relative recovery) within working range were 1.3~9.1% and 84~118%, respectively.

• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.575-579
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• 2014

Development of liposomes has been actively studied for effective delivery of drug at tumor site. However, despite their preferential accumulation at tumor site, the therapeutic efficacy of such liposomal drug has been limited because of low drug release. Therefore, we developed a temperature-sensitive liposome (TSL), which can be made to maximize release of drug by external stimulation such as ultrasound. Doxorubicin (DOX) as a model drug was encapsulated into TSL by a pH gradient method. The particle size of the TSL was $142.0{\pm}6.24nm$. Surface charge was $-10.55{\pm}1.12mV$. Release of drug from TSLs was up to 80% within 15 min at over $42^{\circ}C$ measured by fluorescence intensity. Cytotoxicity of released DOX from TSLs with ultrasound was highly increased compared to TSLs without ultrasound. Taken together, we demonstrate that temperature sensitive drug release from TSLs with ultrasound, which may be useful for cancer therapy to increase drug concentration at tumor site by external stimulation.

• Korean Journal of Agricultural Science
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• v.23 no.1
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• pp.138-149
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• 1996

This study was aimed at predicting to running speed related to alignment factors of forest road, and recommending the improvement method of forest road construction using the running speed of vehicles. For these purposes, this study proceeds to select forest roads after reviewing the planning papers and maps, to measure the road alignment factors such as longitudinal gradient, width of roadway, radius of curve, length of curve, superelevation, and conditions of road surface on the subject forest road. It was found that the average running speed of logging truck showed lower value than that of the expected speed of 'Forest Road Construction Regulations and Rules', and the average running speed of loaded truck showed 70-85% of the speed of empty truck. According to the road conditions, speed index (reductive ratio of running speed) was also calculated with respect to radius of curve, longitudinal dradient. The results of the study on the running speed of vehicle subject to the alignment of forest roads make it possible for one to judge the quality of the existed and to be constructed forest roads, to select the structure of forest road to improve the running speed of vehicle on forest road.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.483-490
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• 2016

In plant industry, sulfur storage tank is made of steel and annular plate is connected with concrete foundation of ring wall type by anchor bolt. Due to keep sulfur at high temperature in tank by coil, sulfur storage tank is expanded larger than another tank stores fluid at room temperature. Generally, structural design of tank foundation is performed analysis with loading of temperature gradient between inner and outer surface, this method can't consider the phenomenon that load is intensively transferred to concrete foundation at anchor bolt. This means that temperature load is underestimated and causes crack of concrete near anchor bolt. In this study, evaluation formula considering temperature load transfer mechanism through anchor bolt is proposed and load acting on concrete foundation is rationally decided. For this purpose, it is analyzed variation of thermal load per various anchor bolt number using finite element model including tank annular plate and anchor bolt. Solution is proposed as specified term combining result of analysis and theoretical solution for evaluating load transferred by anchor bolt. For confirmation of validation of proposed formula, it is applied in design of sulfur storage tank at plant site, it shows that the formula can be practically applied.

• 한국지구물리탐사학회:학술대회논문집
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• 2004.08a
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• pp.157-179
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• 2004

The application of magnetic method for archaeoprospection has been carried out through two archaeological areas in Egypt, Abydos and Abu Sir, In order to find out tile ancient Egyptian archaeological features. The magnetic work at the selected archaeological site of Abydos area was carried out by gradiometer survey, while magnetic work at the selected archaeological site of Abu Sir area was carried out by gradiometer survey and magnetic susceptibility measurements. A gradiometer survey with raster of 0.5 m/0.5 m has been carried out on a surface area of $9600 m^2$ at Abydos area to relocate the buried Solar Boats. The magnetic data were processed using Geoplot software to treat the field noises and enhance the quality of the obtained images. The final magnetic images indicate the existence of 12 Solar Boats as well as tombs, remains of ancient rooms and walls. All of them are expected to belong to the Middle Kingdom, particularly from the 18th to 20th Dynasties. Two magnetic tools have been applied over a selected site of $25600 m^2$ at Abu Sir area in order to detect the hidden archaeological features nearby the Sun Temple. The acquisition of the magnetic data was initiated by the measurements of the topsoil magnetic susceptibility of 272 samples collected from the whole studied area, and then followed by the gradiometer survey to measure tile vertical gradient of the geomagnetic field over an area of $14400 m^2$. The magnetic susceptibility results show the presence of high concentration at the middle part of the study area with a little extension to the south western side, with maximum value of about $36{\times}10^5$ SI. They may indicate the proximity of ritual monuments. Also, they offered the site of interest for carrying out a gradiometer survey. The gradiometer results show tile existence of numerous distributed archaeological features made of mud-bricks with different shapes and sizes. They may indicate tombs, burial rooms, dissected walls; all of them are expected to belong to the 5th Dynasty of pharaohs, who used to build their buildings by mud bricks. The depth of the expected buried archaeological features has been estimated from tihe gradiometer. It is around 1.2m for deep features and 0.42 m for shallow features.