• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.9
• /
• pp.45-50
• /
• 2016

This paper reports a Ringer's solution detector and transceiver design for the efficient management of patients. The ringer's solution detection and transceiver consisted of the main control part, ringer's solution detection part, display and warning light part, wireless transceiver, and power supply part. The light receiving part of the ringer's solution detection part employed TSL260R-LF photodiode; light permeating part, Water-Clear type LED; and wireless transceiver part, the RF wireless data transceiver module, NR-FPCX. As a result of this Ringer's solution detector and transceiver design that can manage the patient efficiently, it was found that when the ringer's solution was detected by the double photodiode, the operating frequency was 11.95kHz; when it was not detected, the number was 9.6kHz. In the ringer's solution receiver, when the ringer's solution was detected, the number was 0. The corresponding unique RF code was displayed when not detected. The power used in the ringer's solution detection part was converted to the Sleep mode to operate under battery save mode. The ringer's solution transceiver can exchange wireless communication approximately within a 700m radius.

• Ecology and Resilient Infrastructure
• /
• v.8 no.4
• /
• pp.194-203
• /
• 2021

With the recent increase in maintenance works on water and sewer pipes as well as district heating supply pipes, pavement cutting work using pavement cutter is on the rise. The pavement cutting operation generates considerable dust (cutting sludge) as well as noise; therefore, it is necessary to apply eco-friendly technologies that have low noise and dust recovery capability. Thus far, various equipment for recovering dust have been developed; however, there is a limitation in that the environmental friendliness is not quantified. Therefore, in this study, we developed a low-noise, dust-recovery type pavement cutter that can fundamentally remove the causes of environmental hazards such as noise and dust and evaluated the eco-friendliness of the pavement cutting process performed by this cutter. To this end, an integrated water cooling-sludge recovery system composed of a vacuum device and a sludge suction unit was developed, and the developed system was applied to a pavement cutter. Subsequently, the developed equipment was applied to the test bed, and data related to its eco-friendliness were collected and evaluated. The results showed that the cutting sludge recovery rate of the developed equipment was greater than 83%, the noise level was approximately 82 - 83 dB, and the sound power level was 115 dB. The results of this study will be used as basic data to develop improved pavement cutters in the future with improved cutting sludge recovery performance and lower noise.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2004.04a
• /
• pp.472-472
• /
• 2004

Numerous studies on urban groundwater have been carried out in many other countries. Urban groundwater shows a unique hydrologic system because of complex urban characteristics such as road pavement, sewers and public water supply systems. These urban facilities may change the characteristics of groundwater recharge but contaminate its quality as well. There have been several researches on urban groundwater in Seoul. Seoul has been industrialized very rapidly so that the city has large population. The recent population in Seoul amounts to more than ten millions, corresponding to a very high density of about 17, 000 people/km$^2$. Therefore, many factors affect the groundwater quality and quantity in Seoul. Nowadays, groundwater in Seoul is being extracted for construction, industrial use, and drinking and so on. There are 15, 714 wells in Seoul and its annual usage is 41, 425, 977m$^3$(in 2001). Therefore, systematic studies are needed to properly manage and use the groundwater in Seoul. The purposes of this study in progress are to identify geochemical characteristics of groundwater in Seoul and to determine the extent of groundwater contamination and its relationship with urban characteristics. For this study, groundwater was sampled from more than 400 preexisting wells that were randomly selected throughout the Seoul area. For all samples, major cations together with Si, Al, Fe, Pb, Hg For 200 samples among them, TCE, PCE, BTEX were also analyzed by GC. Our study shows that groundwater types of Seoul are distributed broadly from Ca-HCO$_3$ type to Ca-Cl＋NO$_3$ type. The latter type indicates anthropogenic contamination. Among cations, Ca is generally high in most samples. In some samples, Na and K are dominant. The dominant anions change widely from HCO$_3$ to Cl＋NO$_3$. The anion composition is considered to effectively indicate the contribution of distinct anthropogenic sources. In addition, major ions are positively proportional to total dissolved solid (TDS) except K and NO$_3$. Thus, we consider that TDS may be used as an effective indicator of the extent of pollution. However, the increase of TDS may result from increased water-rock interaction. To determine the extent of groundwater contamination, it is needed to figure out the baseline water quality in Seoul. Furthermore, detailed geochemical studies are required to find out pollution sources and their corresponding hydrochemical parameters.

• Journal of Korea Water Resources Association
• /
• v.46 no.2
• /
• pp.123-137
• /
• 2013

This study investigated impacts of the two different types of El Ni$\tilde{n}$o on summer rainfall (June-September) in the Han River and its sub-basins. The patterns of rainfall anomalies show a remarkable difference between conventional El Ni$\tilde{n}$o and El Ni$\tilde{n}$o Modoki years. During conventional El Ni$\tilde{n}$o years, it was found that the Han River basins show decreases in the seasonal rainfall totals with high variations (CV=0.4). In contrast, during El Ni$\tilde{n}$o Modoki years, distinct positive anomalies appear in the Han River basin with a relatively small variation (CV=0.23). In addition, 11 out of 30 sub-basins show significant above-normal rainfall in southern part of the Han River Basin. For El Ni$\tilde{n}$o Modoki years, the number of heavy rainy days exceeding 30 mm/day and 50 mm/day were 9.9-day and 5.4-day, respectively. Consequently, this diagnostic study confirmed that El Ni$\tilde{n}$o Modoki has significant impacts on the variability of summer rainfall over the Han River Basin. We expect the results presented here provide useful information for the stability of the regional water supply system, especially for basins like the Han River Basin showing relatively high variability in seasonal rainfall.

• Korean Journal of Organic Agriculture
• /
• v.7 no.2
• /
• pp.115-124
• /
• 1999

This study was conducted to investigate the effects of fertigation level such as 50%, 75% and 100% N of standard amount of chemical fertilizer,m and fertigation interval such as every irrigation, intervals of 1 and 2 weeks of piggery waste water(PWW) on the growth, yield of red pepper plant and the chemical properties of soil used. In early stage, growth of red pepper plant fertigated with PWW and that of red pepper plant applicated standard chemical fertilezer was the same, while it were increased as increasing application amounts of PWW, and later growth and total yield of red pepper plant were much more at 75% N fertigation of PWW. Inorganic content such as nitrogen, phosphate and potassium and chlorophyll content of red pepper leaves were increased as increasing fergigation amount of PWW. 50% fertigation level showed the lowest rate of fruit setting of red peper plant. For soil chemical properties, pH was slightly decreased, but available $P_2O_5$, and exchangeable K content were increased as increasing fertigation amount of PWW. Because there was not statistically significant difference in the growth, the yield of red pepper and chemical properties of soil used according to various fertigation intervals, and no need to artificially supply PWW, therefore fertigation by simple automatic system with tensiometer was thought to be better.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.1
• /
• pp.21-27
• /
• 2019

R-404A, which is used widely in small-scale ice makers, is scheduled to be phased out because of its high global warming potential. In this study, drop-in tests were conducted using R-448A and R-449A, which replace R-404A, to modify the outdoor air and supply water temperatures. The results showed that the daily ice production rate of R-404A was 5.3% higher than that of R-448A and 4.2% higher than that of R-449A. This was attributed to the larger vapor density of R-404A, which resulted in a larger mass flow rate in the system. Between R-448A and R-449A, R-448A yielded a larger amount of ice at low air and water temperatures, whereas R-449A yielded a larger amount of ice at high air and water temperatures. The daily power consumption of R-404A was approximately 10% larger than those of R-448A and R-449A. The resulting COPs of R-448A and R-449A was similar, only 3.0% larger than that of R-404A. The literature survey showed that the condensation or evaporation data of R-448A or R-449A are very limited, and research on this issue is recommended.

• Journal of Korea Water Resources Association
• /
• v.57 no.5
• /
• pp.311-320
• /
• 2024

Climate change has been intensifying drought frequency and severity. Such prolonged droughts reduce reservoir levels, thereby exacerbating drought impacts. While previous studies have focused on optimizing reservoir operations using historical data to mitigate these impacts, their scope is limited to analyzing past events, highlighting the need for predictive methods for future droughts. This research introduces a novel approach for predicting minimum inflow at the Seomjingang dam which has experienced significant droughts. This study utilized the Stochastic Analysis Modeling and Simulation (SAMS) 2007 to generate inflow sequences for the same period of observed inflow. Then we simulate reservoir operations to assess firm yield and predict minimum inflow through synthetic inflow analysis. Minimum inflow is defined as the inflow where firm yield is less than 95% of the synthetic inflow in many sequences during periods matching observed inflow. The results for each case indicated the firm yield for the minimum inflow is on average 9.44 m³/s, approximately 1.07 m³/s lower than the observed inflow's firm yield of 10.51 m³/s. The minimum inflow estimation can inform reservoir operation standards, facilitate multi-reservoir system reviews, and assess supplementary capabilities. Estimating minimum inflow emerges as an effective strategy for enhancing water supply reliability and mitigating shortages.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.5
• /
• pp.54-59
• /
• 2020

Coarse aggregate is produced in various ways depending on the location and production method. Currently, the construction industry is in need of a stable supply of coarse aggregate and a way to secure standard quality. The purpose of this study is to examine whether the use of coarse aggregate in 3D printing can help solve this problem. ABS filament was selected for use in 3D printing. CATIA was used for the design of the coarse aggregate, and CUBICON Single Plus was used for the production. Six specimens were produced and cured in water for 28 days. Three of them were made with AE agent, and three were made without it. A compressive strength test confirmed that when the AE agent was used, the compressive strength was greater than the lightweight concrete design criterion specified in the concrete standard specification. This suggests that coarse aggregate produced by a 3D printer may be used for lightweight concrete. A mass production system using this method could help to solve the problems facing the construction industry, such as stable supply and demand for coarse aggregate and securing standard quality.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.34 no.8
• /
• pp.767-774
• /
• 2010

In a passive-type PEMFC stack, axial fans operate to supply both oxidant and coolant to cathode side of the stack. It is possible to make a simple system because the passive-type PEMFC stack does not require additional cooling equipment. However, the performance of a cooling system in which water is used as a coolant is better than that of the air-cooling system. To ensure system reliability, it is essential to make cooling system effective by adopting an optimal stack design. In this study, a numerical investigation has been carried out to identify an optimum cooling strategy. Various channel configurations were applied to the test section. The passive-type PEMFC was tested by varying airflow rate distribution at the cathode side and external heat transfer coefficient of the stack. The best cooling performance was achieved when a channel with thick ribs was used, and the overheating at the center of the stack was reduced when a case in which airflow was concentrated at the middle of the stack was used.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.32 no.2
• /
• pp.144-148
• /
• 1999

This study was conducted to test actual oxygen consumption rates of Nile tilapia (Oreochromis niloticus) at a commercial scale high density culture tank in the recirculating culture system, with a special emphasis on the oxygen consumption rate of this species with different daily feeding frequencies. Nile tilapia, an average of 400 g and a total wright of 390 kg, were stocked in a circular concrete tank of 2.9 m in diameter and 0.8 m in depth, in a recirculating culture system. The fish were fed commercial diet 1, 2, 5, and 9 times per day between 09:00 h and 19:00 h. feed was evenly supplied where the fish were fed more than once a day. Dissolved oxygen of influent and effluent water was monitored every 50 seconds by a computer with electrodes for 24 hours. The standard metabolic rate of tilapia was $39.31{\pm}4.4mg\;O_2/kg$ fish/hr in the present study. The maximum oxygen consumption was reached between 30 to 50 minutes after feeding. The maximum oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were 161.2, 123.4, 111.1 and 111.1 mg $O_2/kg$ fish/hr, respectively. While the mean oxygen consumption levels of 1, 2, 5, and 9 feeding times per day were $79.9{\pm}21.5,\;81.3{\pm}14.8,\;84.2{\pm}9,9$ and $98,9{\pm}11.0mg\;O_2/kg$ fish/hr, respectively. These results show that oxygen consumption rates are not much different between the feeding frequencies. These results could be used to design to provide desirable oxygen supply system in the recirculating high-density tilapia culture system.