• Korean Journal of Veterinary Research
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• v.41 no.3
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• pp.395-400
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• 2001

The present study analyze the morphological aspects of the cerebrum of mice with prenatal exposure to high and low dose (0.5, 1, 2 Gy) of $\gamma$-radiation on gestation day 12 or 16. The animal were allowed to give birth and the offspring were sacrificed at postnatal days 28 for gross and microscopic examination of cerebrum. Their body weight, brain weight, brain length, brain width, cortical thickness and area of cingulum bundle were examined. The histological and planimetric analysis were performed observing coronal sections. The gross malfomation (microcephaly) and abnormality of cortical architecture were prominent after exposure to 2 Gy on day 12 of gestation. significant dose-related reductions in body weight, brain weight, brain size were found in all irradiated groups. A significant change was found in thickness of the cerebral cortex and area of the cingulum bundle in the groups exposed to 0.5 Gy or more. There was no difference a lamina patter of six layers in cerebral cortex between the control and irradiated groups, but cell packing density increased significantly in the group exposed to 1 Gy or more. These results suggested that dose as low as 0.5 Gy could cause a morphologically reduce change in developing mouse cerebrum and exposure on day 12 of gestation to $\gamma$-irradiation is a particularly sensitive phase in causing malformation and abnormality of central nerve system.

• Journal of Wetlands Research
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• v.15 no.2
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• pp.233-250
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• 2013

Gradually or radically change how the characteristics of the climate characteristic using change point analysis for the precipitation indicators were investigated. Significantly the amount, extreme and frequency were separated by precipitation indicators, each indicator RIA(Rainfall Index for Amount), RIE(Rainfall Index for Extremes) and RIF(Rainfall Index for Frequency) was defined. Bayesian Change Point was applied to investigate changing over time of precipitation indicators calculated. As the result of analysis, precipitation indicators in South Korea was found to recently increase all indicators except for the annual precipitation days and 200-yr precipitation. RIA revealed that there was a very clear point of significance for the change in Ulleungdo, Relatively significant results for RIE were identified in Gumi, Jecheon and Seogwipo. Also, since the 1990s, an increase in the number of variation points, and the horizontal width of the fluctuation point was being relatively wider. Based on these results, rethink the precipitation on the assumption of stationarity was judged necessary.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2007.10a
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• pp.63-79
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• 2007

Several remedial works were attempted to stabilize the collapsed area of the inlet slopes of diversion tunnel, but prevention of any further movement was being only carried out at beginning stage by filling the area with aggregates and rock debris, after several cracks had been initiated and developed around the area. The extra specialty developed folding zone is consisted with highly weathered Greywacke and Black shale. The suggested solution is to improve the properties of the rock mass of failed area by choosing the optimum level of reinforcement through the increment of slope rock support design so as to control the movement of slopes during the re-excavation. The Bakun hydroelectric project includes the construction of a hydroelectric power plant with an installed capacity of 2,520MW and a power transmission system connecting to the existing transmission networks in Sarawak and Western Malaysia. The power station will consist of a 210m height Concrete Faced Rockfill Dam. During the construction of the dam and the power facilities the Balui River has to be diverted of the tunnels is 12m and the tunnel width is 16m at the portal area. This paper describes the stability analysis and design methods for the open cut rock slopes in the inlet area of the diversion tunnels. The geotechnical parameters employed in stability calculations were given as a function of four defined Rock Mass Type (RMT) which were based on RMR system from Bieniawski. The stability calculations procedure of the rock slopes are divided into two stages. In the first stage, it is calculated for the stability of each "global" slope without any rock support and shotcrete system. In the second stage, it is calculated for each "local" slope stability with berms and supported with rock bolts and shotcrete. The monitoring instrumentation was performed continuously and some of the design modification was carried out in order to increase the safety of failed area based on the unforeseen geological risks during the open cut excavation.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1027-1036
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• 2018

In this paper a new generalized space vector pulse width modulation scheme is proposed based on the principle of reverse mapping to drive the switches of multilevel inverters. This projected scheme is developed based on the middle vector of the subhexagon which holds the tip of the reference vector, which plays a major role in mapping the reference vector. A new approach is offered to produce middle vector of the subhexagon which holds tip of the reference vector in the multilevel space vector plane. By using middle vector of the subhexagon, reference vector is linked towards the inner two level sub-hexagon. Then switching vectors, switching sequence and dwell times corresponding to a particular sector of a two-level inverter are determined. After that, by using the two level stage findings, the switching vectors related to exact position of the reference vector are directly generated based on principle of the reverse mapping approach and do not need to be found at n level stage. In the reverse mapping principle, the middle vector of subhexagon is added to the formerly found two level switching vectors. The proposed generalized algorithm is efficient and it can be applied to an inverter of any level. In this paper, the proposed scheme is explained for a five-level inverter and the performance is analyzed for five level and three level inverters through MATLAB. The simulation results are validated by implementing the propose scheme on a V/f controlled three-level inverter fed induction motor using dSPACE control desk.

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.2
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• pp.21-26
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• 2014

This paper introduces general concepts of jointless bridges and field construction case of semi-integral bridge with psc girder integrating end-diaphragm. The expansion joints need to satisfy thermal and safety conditions of bridges. General bridges with joints have some problems, which are frequently replacement cycle time from mechanical damage or unstable movement, maintenance cost and more. To solve these problems, Integral Abutment Bridges(IAB) have been applied overseas in the 1930s. In Korea, first IAB was constructed in the early 2000s and precast IAB systems was invented and applied lately. Kyungshin overpass bridge in Incheon is the Semi-IAB constructed, the span length is 2@35=70m and the width is 13.9m. The original plan was to use general joint bridge but design field changed with expectations for advanced economic estimation and maintenance. This changed method of B.I.B bridge construction provided not only workability, construction cost but also safety improvement at the same time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.11
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• pp.907-913
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• 2017

The performance of a spark jet driven by pulsed-arc plasma was investigated experimentally for various energy input. A high-speed jet (about 330 m/s) was obtained by rapid gas heating produced by 37 mJ of deposited energy per pulse. The peak velocity and penetration distance of the jet were proportional to the deposited power and the deposited energy per pulse, respectively. A smaller orifice diameter produces a higher velocity jet at lower energy levels. For the same deposited energy, higher-current pulses produce a higher jet velocity than higher-pulse-width pulses. A total deposited energy of about 10 mJ per pulse with a pulse duration of about $10{\mu}s$ was found to be the optimum for energy- efficient operation.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1540-1551
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• 2015

The detection of position and speed in BLDC motors without using position sensors has meant many efforts for the last decades. The aim of this paper is to develop a sensorless technique for detecting the position and speed of BLDC motors, and to overcome the drawbacks of position sensor-based methods by improving the performance of traditional approaches oriented to motor phase voltage sensing. The position and speed information is obtained by computing the derivative of the terminal phase voltages regarding to a virtual neutral point. For starting-up the motor and implementing the algorithms of the detection technique, a FPGA board with a real-time processor is used. Also, a versatile hardware has been developed for driving BLDC motors through pulse width modulation (PWM) signals. Delta and wye winding motors have been considered for evaluating the performance of the designed hardware and software, and tests with and without load are performed. Experimental results for validating the detection technique were attained in the range 5-1500 rpm and 5-150 rpm under no-load and full-load conditions, respectively. Specifically, speed and position square errors lower than 3 rpm and between 10º-30º were obtained without load. In addition, the speed and position errors after full-load tests were around 1 rpm and between 10º-15º, respectively. These results provide the evidence that the developed technique allows to detect the position and speed of BLDC motors with low accuracy errors at starting-up and over a wide speed range, and reduce the influence of noise in position sensing, which suggest that it can be satisfactorily used as a reliable alternative to position sensors in precision applications.

• Journal of Microbiology and Biotechnology
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• v.30 no.6
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• pp.848-855
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• 2020

Land subsidence induced by underground coal mining leads to severe ecological and environmental problems. Arbuscular mycorrhizal fungi (AMF) have the potential to improve plant growth and soil properties. We aimed to assess the effects of AMF on the growth and soil properties of sea buckthorn under field conditions at different reclamation times. Inoculation with AMF significantly promoted the survival rate of sea buckthorn over a 50-month period, while also increasing plant height after 14, 26, and 50 months. Crown width after 14 months and ground diameter after 50 months of inoculation treatment were significantly higher than in the uninoculated treatment. AMF inoculation significantly improved plant mycorrhizal colonization rate and promoted an increase in mycelial density in the rhizosphere soil. The pH and electrical conductivity of rhizosphere soil also increased after inoculation. Moreover, after 26 and 50 months the soil organic matter in the inoculation treatment was significantly higher than in the control. The number of inoculated soil rhizosphere microorganisms, as well as acid phosphatase activity, also increased. AMF inoculation may play an active role in promoting plant growth and improving soil quality in the long term and is conducive to the rapid ecological restoration of damaged mining areas.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.5
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• pp.87-97
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• 2005

The field scale experiment was performed to examine the effect of physical design parameters on the constructed wetland performance and recommend the feasible design of constructed wetland in Korean polder areas. Four sets (each set of 0.85 ha) of wetland (0.8 ha) and pond (0.08 ha) systems were used. Two different wetland systems, a wetland-pond system and a pond-wetland system, were studied to examine the effect of wetland and pond configuration. And two different length-to-width ratios were used, 2: 1 and 0.8: 1, to examine the effect of aspect ratio. A pond-wetland system was more preferable than a wetland-pond system, and also requires a smaller area than a wetland-pond system or a wetland system to reduce T-P. There was no difference in effluent concentration between the 2:1 system and the 0.8:1 system. Although the linear velocity of the 2:1 aspect was higher than the 0.8:1 aspect, resuspension was not a factor in this study due to a very low linear velocity. From this study and other literature review, it was found that design method of paddy rice field could be applied and expanded to the design of constructed wetland in Korea. Further investigation for the detailed design parameters of constructed wetland needs be continued for design method of paddy rice to be applied in full scale.

• Korean Journal of Environmental Agriculture
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• v.17 no.4
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• pp.335-340
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• 1998

This study was conducted to determine the morphological responses of barley seedlings to NaCl stress and to investigate histological changes of cells with transmission electron microscope(TEM) after NaCl stress. Plant height and root length of 10-day old barley seedlings with NaCl stress were reduced and inhibition level was found to be more severe in the plant height than in the root length. The leaf length, leaf width and leaf area were shorter as well with NaCl stress than without NaCl stress. However, there was no difference in the number of roots between NaCl treatments. The weight of dry matter decreased at higher NaCl concentrations, especially at 100mM NaCl. The water content of shoots tend to decrease at higher NaCl concentrations, but there was no difference in the water content of roots, The reduced sugar content was greatly increase than starch. Cellulose content was higher in NaCl stressed-plant than control, and tended to decreased at higher NaCl concentrations. Lignin content also decreased NaCl stressed-plant but there was no tendency at NaCl stress concentrations. Electric conductivity of cell sap with seedlings was high with NaCl stressed-plant. Amount of cell sap gradually increased with time in the roots than in the shoots, The grana of chloroplasts was changed by 150mM NaCl concentration. The christe of mitochondria in root meristematic sells ruined in structure and cell wall of leaf and root was also ruined by NaCl stress.