• Childhood Kidney Diseases
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• v.19 no.2
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• pp.71-78
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• 2015

The incidence of acute kidney injury (AKI) in critically ill pediatric patients has been reported as increasing to 25 %, depending on population characteristics. The etiology of AKI has changed over the last 10-20 years from primary renal disease to the renal conditions associated with systemic illness. The AKI in pediatric population is associated with increased mortality and morbidity, and prevention is needed to reduce the consequence of AKI. It is known that the most important risk factors for AKI in critically ill pediatric patients are clinical conditions to be associated with decreased renal blood flow, direct renal injury, and illness severity. Renal hypoperfusion leads to neurohormonal activation including renin-angiotensin-aldosterone system, sympathetic nervous system, antidiuretic hormone, and prostaglandins. Prolonged renal hypoperfusion can result in acute tubular necrosis. The direct renal injury can be predisposed under the condition of renal hypoperfusion, and appropriate treatment of volume depletion is important to prevent AKI. The preventable causes of AKI include contrast-induced nephropathy, hemodynamic instability, inappropriate mediation use, and multiple nephrotoxic insults. Given the evidence of preventable factors for AKI, several actions such as the use of protocol for prevention of contrast-induced nephropathy, appropriate treatment of volume depletion, vigorous treatment of sepsis, avoidance of combinations of nephrotoxic medications, and monitoring of levels of drugs should be recommended.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.1
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• pp.24-29
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• 2000

We propose a simple method to control the crystallization depth of amorphous silicon (a-Si) deposited by PECVD or LPCVD during the excimer laser annealing (ELA). Employing the new method, we have formed poly-Si/a-Si double film and fabricated a new poly-Si TFT with vertical a-Si offsets between the poly-Si channel and the source/drain of TFT without any additional photo-lithography process. The maximum leakage current of the new poly-Si TFT decreased about 80% due to the highly resistive vertical a-Si offsets which reduce the peak electric field in drain depletion region and suppress electron-hole pair generation. In ON state, current flows spreading down through broad a-Si cross-section in the vertical a-Si offsets and the current density in the drain depletion region where large electric field is applied is reduced. The stability of poly-Si TFT has been improved noticeably by suppressing trap state generation in drain region which is caused by high current density and large electric field. For example, ON current of the new TFT decreased only 7% at a stress condition where ON current of conventional TFT decreased 89%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.195-203
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• 2005

Recently, a novel multi-bit nonvolatile memory based on double gate (DG) MOSFET is proposed to overcome the short channel effects and to increase the memory density. We need more complex voltage schemes for DG MOSFET devices. In view of peripheral circuits driving memory cells, one should consider various voltage sources used for several operations. It is one of the key issues to minimize the number of voltage sources. This criterion needs more caution in considering a DG nonvolatile memory cell that inevitably requires more number of events for voltage sources. Therefore figuring out the permissible range of operating bias should be preceded for reliable operation. We found that reliable operation largely depends on the depletion conditions of the silicon channel according to charge amount stored in the floating gates and the negative control gate voltages applied for read operation. We used Silvaco Atlas, a 2D numerical simulation tool as the device simulator.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.121-131
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• 2019

The ionospheric mid-latitude trough (IMT) is the electron density depletion phenomenon in the F region during nighttime. It has been suggested that the IMT is the result of complex plasma processes coupled to the magnetosphere. In order to statistically investigate the characteristics of the IMT, we analyze topside sounding data from Alouette and ISIS satellites in 1960s and 1970s. The IMT position is almost constant for seasons and solar activities whereas the IMT depth ratio and the IMT feature are stronger and clearer in the winter hemisphere under solar minimum condition. We also calculated transition heights at which the densities of oxygen ions and hydrogen/helium ions are equal. Transition heights are generally higher in daytime and lower in nighttime, but the opposite aspects are seen in the IMT region. Utilizing the Incoherent Scatter Radar (ISR) electron temperature measurements, we find that the electron temperature in the IMT region is enhanced at night during winter. The increase of electron temperature may cause fast transport of the ionospheric plasma to the magnetosphere via ambipolar diffusion, resulting in the IMT depletion. This mechanism of the IMT may work in addition to the simply prolonged recombination of ions proposed by the traditional stagnation model.

• Nuclear Engineering and Technology
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• v.51 no.1
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• pp.60-72
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• 2019

The air-cooled passive decay heat removal system (APDHR) was proposed to provide the ultimate heat sink for non-LOCA accidents. The APDHR is a modified one of Passive Auxiliary Feed-water system (PAFS) installed in APR+. The PAFS has a heat exchanger in the Passive Condensate Cooling Tank (PCCT) and can remove decay heat for 8 h. After that, the heat transfer rate through the PAFS drastically decreases because the heat transfer condition changes from water to air. The APDHR with a vertical heat exchanger in PCCT will be able to remove the decay heat by air if it has sufficient natural convection in PCCT. We conducted the thermal-hydraulic simulation by the MARS code to investigate the behavior of the APR + selected as a reference plant for the simulation. The simulation contains two phases based on water depletion: the early phase and the late phase. In the early phase, the volume of water in PCCT was determined to avoid the water depletion in three days after shutdown. In the late phase, when the number of the HXs is greater than 4089 per PCCT, the MARS simulation confirmed the long-term cooling by air is possible under extended Station Blackout (SBO).

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4431-4446
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• 2023

A Multiphysics coupling framework, MPCORE, has been developed to analyze safety parameters using the best estimate codes. The framework contains neutron kinetics (NK), thermal hydraulics (TH), and fuel performance (FP) codes to analyze fuel burnup, radial power distribution, and coolant temperature (T_bc). Shuffling and rotation capabilities have been verified on the Watts Bar reactor for three cycles. This study focuses on two coupling approaches for TH and FP modules. The one-way coupling approach involves coupling the FP code with the NK code, providing no data to the TH modules but getting T_bc as boundary condition from TH module. The two-way coupling approach exchanges information from FP to TH modules, so that the simplified heat conduction solver of the TH module is not used. The power profile in both approaches does not differ significantly, but there is an impact on coolant and cladding parameters. The one-way coupling approach tends to over-predict the cladding hydrogen concentration (CHC). This research highlights the difference between one-way and two-way coupling on critical boron concentration, T_bc, CHC, oxide surface temperature, and pellet centerline temperature. Overall, MPCORE framework with two-way coupling provides a more accurate and reliable analysis of safety parameters for nuclear reactors.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.3
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• pp.65-76
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• 2015

Estimating water requirements for upland crops are characterized by standing soil moisture condition during the entire crop growth period. However, scarce rainfall and intermittent dry spells often cause soil moisture depletion resulting in unsaturated condition in the fields. Changes in rainfall patterns due to climate change have significant influence on the increasing the occurrence of extreme soil moisture depletion. Therefore, it is necessary to evaluate agricultural drought for upland crop water planning and management in the context of climate change. The objective of this study is to predict the impacts of climate change on agricultural drought for upland crops and changes in the temporal trends of drought characteristics. First, the changes in crop evapotranspiration and soil moisture in the six upland crops, such as Soybeans, Maize, Potatoes, Red Peppers, Chinese Cabbage (spring and fall) were analyzed by applying the soil moisture model from commonly available crop and soil characteristics and climate data, and were analyzed for the past 30 years (1981-2010), and Representative Concentration Pathways (RCP) climate change scenarios (2011-2100). Second, the changes on the temporal trends of drought characteristics were performed using run theory, which was used to compare drought duration, severity, and magnitude to allow for quantitative evaluations under past and future climate conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.2
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• pp.126-129
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• 2006

We investigated an optimized condition of the capacitor threshold voltage implantation(capacitor $V_T$ Implant) in planar P-MOS DRAM Cell. Several samples with different condition of the capacitor $V_T$ Implant were prepared. It appeared that for the capacitor $V_T$ Implant of $BF_2\;2.0{\times}l0^{13}\;cm^{-2}$ 15 KeV, refresh time is three times larger than that of the sample, in which capacitor $V_T$ Implant is in $BF_2\;1.0{\times}l0^{13}\;cm^{-2}$ 15 KeV. Raphael simulation revealed that the lowed maximum electric field and lowed minimum depletion capacitance ($C_{MIN}$) under the capacitor resulted in well refresh characteristics.

• Proceedings of the Microbiological Society of Korea Conference
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• 2002.10a
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• pp.135-139
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• 2002

Yeast cells respond to condition of amino acid starvation by synthesizing GCN4, a typical eukaryotic transcriptional activator, which regulates the expression of many amino acids biosynthetic genes. By introducing point mutations in the DNA binding domain of GCN4, mutants with normal DNA binding activity but defective in transcriptional activity were isolated to identify unknown proteins that could suppress the mutant phenotype under an amino acid depletion condition. As a result, SSB(Stress-Seventy B) subfamily proteins were identified as suppressors of mutant GCN4. SSB proteins were known as a member of yeast hsp70 family that probably aids passage of nascent chain through ribosomes. Among them, the mechanism of suppression by SSB2 on the defective GCN4 mutant strains is under investigation. Gcn4p directly interacts with Ssb2p through the basic DNA binding domain of GCN4. It suggests the possibility that physical interaction might induce the transcriptional activation of Gcn4p.

• Journal of Korea Water Resources Association
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• v.46 no.7
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• pp.719-733
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• 2013

In this study, a watershed-based surface-water and groundwater integrated model, SWAT-MODFLOW was used to evaluate streamflow depletion induced by groundwater withdrawals and irrigation reservoirs for the Juksan-cheon watershed in South Korea. The streamflow responses to groundwater pumping and irrigation reservoirs were simulated under several different scenarios. The scenarios were (1) current pumping well withdrawals with reservoirs; (2) current pumping well withdrawals without reservoirs; (3) no pumping well withdrawals with reservoirs; (4) no pumping well withdrawals without reservoirs (natural condition). The simulated results indicated that the effects of groundwater pumping on streamflow depletion are a little more significant than those of irrigation reservoirs. Particularly, the groundwater withdrawals with irrigation reservoirs at current status (scenario 1) has induced the decrease of more than 20% in drought flow against the natural condition (scenario 4) at the outlet of the watershed. The specific drought flows through the main stream of Juksan-cheon watershed were simulated in order to assess the irrigation effects on downstream flows. It was found out that the specific drought flows are increasing as the distance from the reservoir increases due to the accumulation of the return flows to stream.