• Membrane Journal
• /
• v.25 no.5
• /
• pp.406-414
• /
• 2015

In this study, partially fluorinated cation exchange membranes were prepared by direct sulfonation of Poly(VDF-co-hexafluoropropylene) copolymers (PVDF-co-HFP) followed by a casting method for application in the Membrane capacitive deionization (MCDI). The structure of sulfonated PVDF-co-HFP (SPVDF) was confirmed by Fourier-transform infrared (FT-IR) and $^1H$ Nuclear magnetic resonance ($^1H$ NMR) analysis. For quantitative analysis of the chemical composition, the X-ray Photoelectron Spectroscopy (XPS) was used. The membrane properties such as water uptake, ion exchange capacity and electrical resistance were measured. It was suggested that the optimum direct sulfonation condition of PVDF-co-HFP ion exchange membranes was $60^{\circ}C$ and 7 hours for temperature and duration of sulfonation, respectively. The water uptake of the SPVDF ion exchange membrane was 21.5%. The ion exchange capacity and electrical resistance were 0.89 meq/g and $3.70{\Omega}{\cdot}cm^2$, respectively. It was investigated that if it is feasible to apply these membranes in MCDI at various cell potentials (0.9~1.5 V) and initial flow rates (10~40 mL/min). In the MCDI process, the maximum salt removal rate was 62.5% in repeated absorption-desorption cycles.

• Neonatal Medicine
• /
• v.16 no.2
• /
• pp.154-162
• /
• 2009

Purpose: Death is an important problem for physicians and parents in neonatal intensive care unit. This study was intended to evaluate the mortality rate, causes of death, and the change of mortality rate by year for infants admitted to the neonatal intensive care unit. Methods: We retrospectively surveyed the medical records of the infants who were admitted to the neonatal intensive care unit at Asan Medical Center and who died before discharge between 1998 and 2007. Gestational age, birth weight, gender, time to death and the underlying diseases related to the causes of infant deaths and obtained from the medical records and analyzed according to year. Results: A total of 6,289 infants were admitted and 264 infants died during the study period. The overall mortality rate was 4.2%. For very low and extremely low birth weight infants, the mortality rate was 10.6% and 21.4%, respectively. There was no significant change in the mortality rate during the study period. Prematurity related complications and congenital anomalies were the conditions most frequently associated with death in the neonatal intensive care unit. of the infant deaths 37.1% occurred within the first week of life. Conclusion: Even though a remarkable improvement in neonatal intensive care has been achieved in recent years, the overall mortality rate has not changed. To reduce the mortality rate, it is important to control sepsis and prevent premature births. The first postnatal week is a critical period for deaths in the neonatal intensive care unit.

• Journal of Energy Engineering
• /
• v.29 no.2
• /
• pp.68-78
• /
• 2020

According to the new climate change agreement, technology development to reduce greenhouse gases is actively conducted worldwide, and research on energy efficiency improvement in the field of power generation and transmission and distribution is underway [1,2]. Economic analysis of the operation method of storing and supplying surplus electricity using energy storage devices, and using energy storage devices as a frequency adjustment reserve power in regional cogeneration plants has been reported as the most profitable operation method [3-7]. Therefore, this study conducted an economic analysis for the installation of energy storage devices in the combined heat and power plant in the Czech Republic. The most important factor in evaluating the economics of battery energy storage devices is the lifespan, and the warranty life is generally 10 to 15 years, based on charging and discharging once a day. For the simulation, the ratio of battery and PCS was designed as 1: 1 and 1: 2. In general, the primary frequency control is designed as 1: 4, but considering the characteristics of the cogeneration plant, it is set at a ratio of up to 1: 2, and the capacity is simulated at 1MW to 10MW and 2MWh to 20MWh according to each ratio. Therefore, life was evaluated based on the number of cycles per year. In the case of installing a battery energy storage system in a combined heat and power plant in the Czech Republic, the payback period of 3MW / 3MWh is more favorable than 5MW / 5MWh, considering the local infrastructure and power market. It is estimated to be about 3 years or 5 years from the simple payback period considering the estimated purchase price without subsidies. If you lower the purchase price by 50%, the purchase cost is an important part of the cost for the entire lifetime, so the payback period is about half as short. It can be, but it is impossible to secure profitability through the economy at the scale of 3MWh and 5MWh. If the price of the electricity market falls by 50%, the payback period will be three years longer in P1 mode and two years longer in P2 and P3 modes.