• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.288-290
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• 2022

As part of the SOC digitization for smart water management and flood prevention, the government reported that automatic and remote control system for drainage facilities (180 billion won) to 57% of national rivers and established a real-time monitoring system (30 billion won). In addition, they were also planning to establish a smart dam safety management system (15 billion won) based on big data at 11 regions. Therefore, research is needed for smart water management and flood prevention system that can accurately calculate the flow rate through real-time flow rate measurement of rivers. In particular, the most important thing to improve the system implementation and accuracy is to ensure the accuracy of real-time flow rate measurements. To this end, radar sensors for measuring the flow rate of electromagnetic waves in the United States and Europe have been introduced and applied to the system in Korea, but demand for improvement of the system continues due to high price range and performance. Consequently, we would like to propose an improved flow rate measurement and flood forecast system by developing a radar sensor for measuring the electromagnetic surface current meter for real-time flow rate measurement.

• Resources Recycling
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• v.31 no.6
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• pp.81-91
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• 2022

The use of lithium-ion batteries increases significantly with the rapid spread of electronic devices and electric vehicle and thereby an increase in the amount of waste batteries is expected in the near future. Therefore, studies are continuously being conducted to recover various resources of cathode active material (Ni, Co, Mn, Li) from waste battery. In order to recover the cathode active material, black mass is generally recovered from waste battery. The general process of recovering black mass is a waste battery collection - discharge - dismantling - crushing - classification process. This study focus on the crushing/classification process among the processes. Specifically, the particle size distribution of various samples at each crushing/classification step were evaluated, and the particle shape of each particle fraction was analyzed with a microscope and SEM (Scanning Electron Microscopy)-EDS(Energy Dispersive Spectrometer). As a result, among the black mass particle, fine particle less than 74 ㎛ was the mixture of cathode and anode active material which are properly liberated from the current metals. However, coarse particle larger than 100 ㎛ was present in a form in which the current metal and active material were combined. In addition, this study developed a PBM(Population Balance Model) system that can simulate two-species mixture sample with two different crushing properties. Using developed model, the breakage parameters of two species was derived and predictive performance of breakage distribution was verified.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.7 no.6
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• pp.709-718
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• 2017

The installation of the elevator ARD(Automatic Rescue Device) system has been forced into law in these days in order to safely rescue passengers during power failure. The configuration of the ARD system consists of energy storage device, power converter and control systems. The EDLC(Electric Double Layer Capacitor) are used as energy storage device for rapid charge/discharge purposes. The power conditioning system (PCS) consists of bi-directional converter, 3-phase converter and control system. The dead-beat control system is adopted for most systems however it requires complex mathematical calculations, the high performance microprocessors are mandatory and thus it can be a cause of high manufacturing cost. In this paper the new control method for average current mode control is presented for simple structure. The control algorithm is applied to the single phase system and then expands to three phase system to meet the sysem requirements. The mathematical modeling using average modeling method is presented and analysed by PSIM computer simulation to verifie the validity of the proposed control methods.

• Korean Journal of Ecology and Environment
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• v.34 no.1 s.93
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• pp.9-19
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• 2001

contrasting monsoon between 1993 and 1994 produced an interannual difference in hydrology. Theoretical water residence time (TWRT) in monsoon 1993 averaged 27 d, which was>3 months shorter compared to the TWRT in monsoon 1994. A dominant physical process influencing thermal stratification, water movement, and mixing regime was an interflow current in 1993. During summer 1993, river water plunged to mid-lake (location 27 km) and passed through the 10${\sim}$20m stratum of the reservoir, resulting in an isolation of epilimnetic lake water from advected river water. The interflow disrupted thermal stratification and produced a meta-hypolimnetic warming of >4$^{\circ}C$ downlake, thereby increased a mixing depth (>13 m). In contrast, during monsoon 1994 density currents were not observed and strong thermal stratification occurred in the entire reservoir, resulting in > 2 fold greater thermal resistance (8.2${\times}10^{5}$ erg)compared to 1993 (4.0${\times}10^{5}$ erg). This reservoir was identified as a typical warm monomictic reservoir which showed one mixis during early winter. The timing of overturn, however, differed between the two years as a result of distinct contrast in TWRT and thermal regime; overturn in 1993 occured about one month earlier relative to that in 1994. Hypolimnetic warming was predictable in this system; the variation in discharge accounted (Y = 4.35-0.06X+0.10X$^{2}$, p<0.0001)for 98% of the interannual variation in hypolimnetic temperature. Overall data suggest that thermal stability, the timing of fall overturn, and water residence time in this system are primarily regulated by the intensity of monsoon.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.4
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• pp.286-294
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• 2014

The purpose of this study is to investigate the effects of applying density current generator (hereafter referred to as DCG to large lakes on the operating conditions of DCG, de-stratification, water quality improvement and inhibition of algae occurrence. As a result of a survey conducted to derive the optimum operating parameters of DCG in a condition to minimize eco-toxicity, the following conclusions were obtained. During the survey period, a marked stratification appeared in September to October 2011 and May 2012. At this time, the average depth of water to form thermocline was found to be $5{\pm}2$ m, so the location of discharge port for the operation of DCG was determined to be about 5 m below from the surface. To minimize the adverse effects of benthos and obtain the effect of water mixture at the time of water circulation, the mixing ratio of surface water and deep water was designed to be 3:1 by means of ecotoxicological assessment on the DCG operating characteristics. To select the appropriate operating hours for DCG, DCG was operated by 12 hr, 24 hr, 36 hr and 48 hr. As its result, the formation of thermocline did not occur during the operation of 36 hr. Also, It was effected that start reoperating from 3rd day after stop 2days under the condition of operated during 36 hr with calculated power consumption. Under the above conditions, the results of DO and water temperature analysis during the operation of DCG showed that the stratification, which was distinct previously, appeared to be weak, and relatively lower levels than those before operation were found as a result of water quality analysis on COD and chlorophyll-a, which leads to the conclusion that the water body is maintained at a stable condition due to the circulation of water by the occurrence of density current resulting from the operation of DCG.

• Journal of Preventive Medicine and Public Health
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• v.24 no.4 s.36
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• pp.531-548
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• 1991

To assess the adequacy of medical manpower and medical fee for the newborn nursery care, the author visited 20 out of 24 hospitals with the pediatric training program in Youngnam area between July 29 and August 14, 1991. Total number of newborn, both normal and sick, admission and discharge in 1-30 June 1991 was obtained from the logbook of nursery. Head nurse and staff pediatrician of the nursery were interviewed to get the current staffing for the nursery and their subjective opinion on the adequacy of nursery manpower and the difficulties in recruiting manpower. Average medical fee charged for the maternity and normal newborn nursery care was obtained from the division of self-audit of medical insurance claim of each hospital. Average minimum requirement of nursing care time for one normal newborn per day was 179.5 (${\pm}58.6$) minutes; 202.3(${\pm}50.7$) minutes for the university hospitals and 164.2(${\pm}60.5$) minutes for the general hospitals. The ratio of minimum requirement of nursing care time and available nursing time was 1.42 on the average. Taking the additional requirement of nursing care for the sick newborns into consideration, the ratio was 2.06. The numbers of R. N. and A. N. in the nurserys of study hospitals were 31%, and 17%, respectively, of the nursing manpower for the nursery recommended by the American Academy of Pediatrics. These findings indicate that the nursing manpower in newborn nursery is in severe shortage. Ninety percent of the head nurses and 85% of the staff pediatrician stated that the newborn nursery is short of R.N. and 75% of them said that the nurse's aide is also short. Major reason for not recruiting R.N. was the financial constraint of hospital. For the recruitment of nurse's aide, short supply was the second most important reason next to the financial constraint. However, limit of quarter in T.O. was the mar reason for the national university hospitals. Average total medical fee for the maternity and newborn nursery cares of a normal vaginal delivery who stayed two nights and three days at hospital was 219,430won. Out of the total medical fee, 20,323won(9.3%) was for the newborn nursery care. In case of C-section delivery who stayed six nights and seven days, total medical fee was 732,578won and out of the total fee 76,937won (12.0%) was for the newborn care. Cost for a newborn care per day by cost accounting was 16,141won for the tertiary care hospitals and 14,576won for the all other hopitals. The ratio of cost and the fee schedule of the medical insurance for a newborn care per day was 5.0 for the tertiary care hospitals and 4.9 for the all other hospitals. Considering the current wage level of the medical personnel, capital investment for the hospital facilities and equipments, and the cost for hospital maintenance, it is hard to expect adequate quality care in the newborn nursery under the current medical insurance fee schedule.

• Tuberculosis and Respiratory Diseases
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• v.49 no.5
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• pp.624-632
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• 2000

Background : Home ventilation can decrease hospital-acquired infection, increase physical activity, improve nutritional status, enhance quality of life, and reduce medical costs. The number of patient using home ventilators has been increasing, particularly in Europe and United States. Although the number of patients with home ventilation has been increasing in Korea, the current status of these patients is not well known. This study was undertaken to obtain basic information upon these patients in addition to evaluating any problems related to patients' home care in our country. Methods : A register of 92 patients with home ventilators in Seoul and Kyunggi Province were obtained from commercial ventilator supply companies. The patients were contacted by phone and 29 of them accepted our visit. Information concerning education about home care before discharge, equipment cost, and problems related to home care were documented. The mode and preset variables of the home ventilator were checked; tidal volume (TV), peak airway pressure, and oxygen saturation were measured. Results : There were 26 males (90%) and their mean age was 48.0 (${\pm}20.1$) years. The underlying diseases were : 21 neuromuscular disorders, 2 spinal cord injuries, 6 chronic lung diseases. Among the caregivers, spouses (n=14) predominated. Education for home care before discharge was performed primarily by intensive care unit nurses and the education for ventilator management by commercial companies. Twenty-five of the 29 patients had tracheostomies. Volume targeted type (VTT ; n=20, 69%) was more frequently used than the pressure targeted type (PTT). Twenty-three of the 29 patients purchased a ventilator privately, which cost 7,450,000 (${\pm}$3,290,000) won for a PTT, and 14,280.000 (${\pm}$3,130,000) won for a VTT. Total cost for the equipment was 11,430,000 (${\pm}$634,000) won. The average cost required for home care per month was 1,120,000 (${\pm}$1,360, 000) won. Conclusion : The commonest underlying disease of the patients was neuromuscular disease. The VTT ventilator was primarily used with tracheostomy. Patients and their families considered the financial difficulties associated with purchasing and maintaining equipment for home care an urgent problem. Some patients were aided by a visiting nurse, however most patients were neglected and left without professional medical supervision.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.687-697
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• 2019

By monitoring sediment grain size and level variation of tidal flat surface for 6 years (2005-2011), and also by mooring TISDOS (tidal-flat sediment dynamics observation system) on the low intertidal flat in 2008, we investigated the sedimentary environment of tidal flat in the dammed Yeongsan River Estuary. The tidal flat of the Yeongsan River Estuary lost 82 % of its area because of coastal development projects, and a narrow tidal flat below mean sea level now remains. Most of the tidal flat sediments are composed of silt up to 70-94 %, and show the characteristics of clay deficiency and silt dominance. This is closely related with the coastal development, which led to the destruction of high tidal flats where most mud settled, and the modification of tidal current patterns. Moreover, the estuarine tidal-flat sediments reveal seasonal variation. They are coarse with abundant silt during windy autumn to spring, fine with abundant clay during the less-windy and high-discharge summer. This phenomenon indicates that the behavior of sediment particles on the low intertidal flats of the Yeongsan River Estuary is influenced by wind waves for silt and fresh water discharge and the tidal process for clay. Monitoring results of the altitude of tidal flat surface showed that the study area had eroded at an average rate of -2.6 cm/y during the period of 2005-2011, and also that an unusual deposition with a rate of 4 cm/y occurred in 2010. The erosion can be explained by an increased tidal amplitude and a strengthened ebb-dominant tidal asymmetry after the construction of an estuary dike and the Yeongam Kumho Seawall. The deposition in 2010 seems to have been closely related to the mass production of suspended materials from dredging of the estuary.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.4
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• pp.357-368
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• 2003

Time-series CTDT (Conductivity/Temperature/Depth/Transmissivity) were obtained at one point near tidewater glacier of Marian Cove (King George Islands, Antarctica) to present water column properties and SPM (suspended particulate matter) dispersal pattern in relation with tide, current, meteorological data, and SPM concentration. Four layers were divided from the water column characteristics measured in the interval of an hour for about 2 days: 1) cold, fresh, and turbid surface mixed layer between 0-20 m in water depth, 2) warm, saline, and relatively clean Maxwell Bay inflow between 20-40 m in water depth, 3) turbid/cold tongue of subglacial discharges compared with the ambient waters between 40-70 m in water depth, and 4) cold, saline, and clean bottom water beneath 70 m in water depth. Surface plume, turbid freshwater at coastal/cliff area in late summer (early February), had the characteristic temperature and SPM concentration according to morphology, glacial condition, and composition of sediments. The restrict dispersion only over the input source of meltwater discharges was due to calm wether condition. Due to strong wind-induced surface turbulence, fresh and turbid surface plume, englacial upwelling cold water, glacier-contact meltwater, and Maxwell Bay inflow was mixing at ice-proximal zone and the consequent mixed layer deepened at the surface. Large amount of precipitation, the major controlling factor for increasing short-term glacial discharges, was accompanied by the apparent development of subglacial discharge that resulted in the rapid drop of salinity below the mid depth. Although amount of subglacial discharge and englacial upwelling may be large, however, their low SPM concentration would have small influence on bottom deposition of terrigenous sediments.

• Journal of the Korean Society for Marine Environment & Energy
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• v.12 no.4
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• pp.227-234
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• 2009

Using a finite volume ocean circulation model based on an unstructured grid (FVCOM), we studied the structure of a fresh water bulge that influences on the Region Of Freshwater Influence. Fresh water discharged a river forms a coastal boundary current to the righthand side and a cyclonically circulation freshwater bulge that grows with time. In the middle of the bulge, vertical motions bring fresh water to the bottom. When tidal motions are included, the bulge disappears while the boundary currents becomes wider. Through a simple comparison of areas occupied low salinity water we quantified vertical and horizontal mixing due to the tide and showed that the tidal motion enhances the vertical mixing. During the first few tidal cycles right after the onset of the river discharge, due to tidal excursion the horizontal mixing becomes stronger. The vertical mixing by the tide mixes the fresh water After a certain time the water around the river mouth is well mixed and the horizontal excursion of the fresh water near the river mouth does not have much effect on the horizontal mixing. When there is no tidal motion horizontal mixing is mainly by the inertial instability at the surface and the horizontal mixing becomes stronger over time.