• Journal of Soil and Groundwater Environment
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• v.20 no.3
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• pp.41-50
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• 2015

Hydrogeologic environment of the Mega City such as Seoul, suffers from rapid changes caused by urbanization, construction of underground subway or buildings, and contaminant loading by diverse anthropogenic activities. Understanding the present condition of groundwater environment and water budget is necessary to prevent natural and manmade disasters and to prepare for sustainable water resource management of urban environment. In this study, regional groundwater flow and water budget status of Seoul was analyzed using numerical simulation. Modeling result indicated that groundwater level distribution of Seoul generally followed the topography, but the significant decreases in groundwater level were observed around the subway network. Steady-state water balance analysis showed groundwater recharge by rainfall and leakage from the water supply network was about 550,495 m³/day. Surface water inflow and baseflow rate via Han River and major streams accounted for 799,689 m³/day and 1,103,906 m³/day, respectively. Groundwater usage was 60,945 m³/day, and the total groundwater leakage along the subway lines amounted to 114,746 m³/day. Modeling results revealed that the subway could decrease net groundwater baseflow by 40%. Our study result demonstrated that the subway system can have a significant influence on the groundwater environment of Seoul.

• Membrane Journal
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• v.22 no.6
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• pp.470-480
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• 2012

In this study, for a linear tubular membrane with constant diameter the mass balance considering permeate velocity of the each unit length was established. On this basis, mathematical modelling of flows in a pipe was solved using nonlinear second order differential equations as well as steady-state equation. Since this equation is nonlinear, Gauss-Seidel method or another iteration method were used to solve the differential equations. Simulation algorithm for numerical solutions was presented. Also since the permeate flow is varied as operating condition, the solution of equations at each conditions using numerical integrations such as Simpson's rules was used. In order to analyze and compare simulation results, we have performed experiments using a hollow fiber membrane with almost identical tubular membrane. Comparison of theoretical and experimental results, pressure drop, flow rate, and permeate flow in a hollow fiber membrane, were illustrated.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.124-127
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• 2000

A new triode type Ti-silicided Si FEA(field emitter array) was realized by Ti-silicidation of Ti coated Si FEA and its field emission properties were investigated. In the fabricated device, the field emission properties through the unit pixel with $200{\mu\textrm{m}}{\times}200{$\mu\textrm{m}}$ tip array in the area of $1000{\mu\textrm{m}}{\times}1000{$\mu\textrm{m}}$ were as follows : the turn-on voltage was about 70V under high vacuum condition of $10^8Torr$, and the field emission current and steady state current degradation were about 2nA/tip and 0.3%/min under the bias of $V_A=500V\;and\;V_G=150V$. The low turn-on voltage and the high current stability during long term operation of the Ti silicided Si FEA were due to the thermal and chemical stability and the low work function of silicide layer formed at the surface of Si tip.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.13 no.2
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• pp.75-83
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• 2017

In severe accident conditions of light water reactors, the loss of coolant may cause problems in integrity of zirconium fuel cladding. Under the condition of the loss of coolant, the zirconium fuel cladding can be exposed to high temperature steam and reacted with them by producing of hydrogen, which is caused by the failure in oxidation resistance of zirconium cladding materials during the loss of coolant accident scenarios. In order to avoid these problems, we develop a multi-metallic layered composite (MMLC) fuel cladding which compromises between the neutronic advantages of zirconium-based alloys and the accident-tolerance of non-zirconium-based metallic materials. Cold pilgering process is a common tube manufacturing process, which is complex material forming operation in highly non-steady state, where the materials undergo a long series of deformation resulting in both diameter and thickness reduction. During the cold pilgering process, MMLC claddings need to reduce the outside diameter and wall thickness. However, multi-layers of the tube are expected to occur different deformation processes because each layer has different mechanical properties. To improve the utilization of the pilgering process, 3-dimensional computational analyses have been made using a finite element modeling technique. We also analyze the dimensional change, strain and stress distribution at MMLC tube by considering the behavior of rolls such as stroke rate and feed rate.

• The Korean Journal of Pharmacology
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• v.32 no.2
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• pp.283-292
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• 1996

The spinal dorsal horn is the area where primary afferent fibers terminate and cutaneous sensory information is processed. A number of putative neurotransmitter substances, including excitatory and inhibitory amino acids and peptides, are present in this region. In this study, single neurons of the spinal dorsal horn were acutely isolated and the properties of whole cell current and responses to excitatory and inhibitory neurotransmitters were studied by patch clamp technique. Transverse slice ($(300{\mu}m$) of lumbar spinal cords from young rats$(7{\sim}14\;days)$ were sequentially treated with two pretenses(pronase 0.75 mg/ml and thermolysin 0.75 mg/ml), then single neurons were mechanically dissociated. These neurons showed near-intact morphology such as multipolar, ellipsoidal and bipolar, and pyramidal cells and we recorded the typical whole cell currents of $K^+$, $Ca^{2+}$ and ligand-operated channels from these neurons. Glutamate $(30{\mu}M)$ and N-methyl-D-aspartate(NMDA, $30{\mu}M)$ induced inward currents of $117{\pm}12.4$ pA(n=5) and $49{\pm}6.9$ pA(n=3), respectively. Glycine $(1{\mu}M)$ potentiated glutamate-induced currents $4{\sim}5$ times and NMDA-induced currents $8{\sim}10$ times. In addition, glycine $(30{\mu}M)$ induced Inward current ($31{\pm}6.1$ nA, n=2), which was rapidly desensitized after the peak to a new steady-state level. However, the inward currents induced by ${\gamma}-amino$ butyric acid(GABA, $1{\mu}M$) decreased continuously after the peak($226{\pm}41.6$ pA, n=3) under the similar experimental condition. The ionic currents and pharmacological responses of isolated neurons in this work were similar to those observed in vivo or in vitro spinal cord slice, indicating that acutely isolated neurons could be effectively used for further pharmacological studies.

• Journal of Periodontal and Implant Science
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• v.32 no.4
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• pp.721-731
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• 2002

Recently, soluble TNF receptor homolog osteoprotegerin(OPG) and its membrane-bound ligand osteoclast differentiation factor(ODF) were found to regulate osteoclast formation and function, and bone metabolism. It is now well established that ODF acts via RANK expressed on hematopoietic osteoclast precursor cells to facilitate their differentiation to osteoclasts, and OPG prevents the formation of osteoclasts by interfering the binding of ODF and RANK. Expression of OPG and ODF was believed to be closely related to the pathogenesis of bone resorption and destruction from osteoporosis, periodontal diseases, malignant bone tumor, and arthritis. The periodontal ligament fibroblasts (PDLF), located between the tooth and tooth socket, has been thought to play an important role in maintaining bone homeostasis of periodontal tissues. However, the exact mechanism by which bone formation and resorption are regulated by PDLF is not well understood. In this study we have prepared primary cultures of human PDLF from periodontium of malaligned tooth extracted due to orthodontic reason, and determined steady state or inflammatory signal-induced OPG and ODF expression using RT-PCR and western blot analysis. OPG and ODF mRNA and protein were expressed constitutively in the PDLF and these expression were slightly increased by osteotropic cytokine IL-1 ${\beta}$. Lipopolysaccharide-treated PDLF showed decrease in OPG mRNA and protein expression, and increase in ODF mRNA and protein expression. These results indicated that PDLF influence the osteoclastogenesis by OPG and ODF expression in the inflammatory situation as well as physiological condition, and thereby pathogenesis of periodontal alveolar bone destruction.

• Earthquakes and Structures
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• v.11 no.1
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• pp.83-107
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• 2016

In this study, the response and behavior of machine foundations resting on dry and saturated sand was investigated experimentally. A physical model was manufactured to simulate steady state harmonic load applied on a footing resting on sandy soil at different operating frequencies. Total of (84) physical models were performed. The parameters that were taken into consideration include loading frequency, size of footing and different soil conditions. The footing parameters are related to the size of the rectangular footing and depth of embedment. Two sizes of rectangular steel model footing were used. The footings were tested by changing all parameters at the surface and at 50 mm depth below model surface. Meanwhile, the investigated parameters of the soil condition include dry and saturated sand for two relative densities; 30 % and 80 %. The dynamic loading was applied at different operating frequencies. The response of the footing was elaborated by measuring the amplitude of displacement using the vibration meter. The response of the soil to dynamic loading includes measuring the stresses inside soil media by using piezoelectric sensors. It was concluded that the final settlement (St) of the foundation increases with increasing the amplitude of dynamic force, operating frequency and degree of saturation. Meanwhile, it decreases with increasing the relative density of sand, modulus of elasticity and embedding inside soils. The maximum displacement amplitude exhibits its maximum value at the resonance frequency, which is found to be about 33.34 to 41.67 Hz. In general, embedment of footing in sandy soils leads to a beneficial reduction in dynamic response (displacement and excess pore water pressure) for all soil types in different percentages accompanied by an increase in soil strength.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.E
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• pp.9-17
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• 1998

Oxides of nitrogen play important roles in atmospheric chemistry. Soil has been recognized as a major natural source of NO, and its emission depends on soil parameters such as soil nitrogen availability, soil moisture and temperature. It is necessary to understand effects of these controlling parameters on soil NO emission. In order to understand soil moisture effects on NO emission, variations of NO concentration and existence of its equilibrium concentration were observed from ammonium fertilized Japanese upland soil prepared for different soil moisture conditions. The closed chamber technique was employed for this study. The significant increases in NO with soil moisture were found. Maximum was occurred at sample ID4 (55% of water-filled pore space (WFPS)), but it decreased as soil moisture increased. No significant NO concentration was emitted from soil sample without fertilizer, but there was significant NO in fertilized soil samples. The magnitudes of NO from soil increased with time and reached at steady state within ten minutes approximately. These results suggest that nitrogen input from fertilizer takes charge in the first step of sharp increase in NO emission, and then soil moisture becomes important factor to control NO emission from the soils. NO concentrations from soil were compared to those one-day after the experiment. Results from the comparison analysis suggest that the soil NO flux might have been stimulated by soil disturbances like mixing, and this is much more effective in dry soils rather than in wet soils. It was found that much less NO came out from soils after a day; suggesting that most of NO was released from the soils within a day after fertilizer application during our experiment. The length of NO releasing time span may depend on the amounts of fertilizer applied, soil moisture condition, and other soil physical parameters.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.94-105
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• 2010

To detect faults in an inverter-fed permanent magnet synchronous motor (PMSM) drive under the circumstance having faults in a stator winding and inverter switch, an on-line basis fault detecting scheme during operation is presented. The proposed scheme is achieved by monitoring the second-order harmonic component in q-axis current and the fault is detected by comparing these components with those in normal conditions. The linear interpolation method is employed to determine the harmonic data in normal operating conditions. As soon as the fault is detected, the operating mode is changed to identify a fault type using the phase current waveform. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control algorithm is implemented using DSP TMS320F28335. Without requiring an additional hardware, the fault can be effectively detected by the proposed scheme during operation so long as the steady-state condition is satisfied.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.3
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• pp.167-178
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• 2010

To diagnose a stator winding fault caused by a short-circuited turn in a permanent magnet synchronous motor (PMSM), an on-line based fault detecting scheme during motor operation is presented. The proposed scheme is based on monitoring the second-order harmonic components in q-axis current obtained through the harmonic analysis and a winding fault is detected by comparing these components with those in normal conditions. The linear interpolation method is employed to determine harmonic data in arbitrary normal operating conditions. To verify the effectiveness of the proposed fault detecting scheme, a test motor to allow inter-turn short in the stator winding has been built. The entire control system including harmonic analysis algorithm and fault detecting algorithm is implemented using DSP TMS320F28335. The proposed scheme does not require any additional hardware and can effectively detect a fault during motor operation so long as the steady-state condition is satisfied.