• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.169-169
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• 2023

Most distributed water is not used effectively due to water loss occurring in pipe networks. These water losses are caused by leakage, typically due to high water pressure to ensure adequate water supply. High water pressure can cause the pipe to burst or develop leaks over time, particularly in an aging network. In order to reduce the amount of leakage and ensure proper water distribution, it is important to apply pressure management. Pressure management aims to maintain a steady and uniform pressure level throughout the network, which can be achieved through various operational schemes. The schemes include: (1) installing a variable speed pump (VSP), (2) introducing district metered area (DMA), and (3) operating pressure-reducing valves (PRV). Applying these approaches requires consideration of various hydraulic, economic, and environmental aspects. Due to the different functions of these approaches and related components, an all-together optimization of these schemes is a complicated task. In order to reduce the optimization complexity, this study recommends a sequential optimization method. With three network operation schemes considered (i.e., VSP, DMA, and PRV), the method explores all the possible combinations of pressure management paths. Through sequential optimization, the best pressure management path can be determined using a multiple-criteria decision analysis (MCDA) to weigh in factors of cost savings, investment, pressure uniformity, and CO₂ emissions. Additionally, the contribution of each scheme to pressure management was also described in the application results.

• International Journal of Stem Cells
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• v.15 no.3
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• pp.283-290
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• 2022

Background and Objectives: Difficulties often encountered in separating and purifying active muscle satellite cells (MSCs) from skeletal muscle tissues have limited the supply of cells for muscle therapy and artificial meat production. Here, we report an effective isolation protocol to economically and conveniently retrieve active MSCs from skeletal muscle tissues in mice. Methods and Results: We optimized an enzyme-based tissue digestion protocol for isolating skeletal muscle-derived primary cell population having a large number of active MSCs and described a method of differential plating (DP) for improving purity of active MSCs from skeletal muscle-derived primary cell population. Then, the age of the mouse appropriate to the isolation of a large number of active MSCs was elucidated. The best isolation yield of active MSCs from mouse skeletal muscle tissues was induced by the application of DP method to the primary cell population harvested from skeletal muscle tissues of 2-week-old mice digested in 0.2% (w/v) collagenase type II for 30 min at 37℃ and then in 0.1% (w/v) pronase for 5 min at 37℃. Conclusions: The protocol we developed not only facilitates the isolation of MSCs but also maximizes the retrieval of active MSCs. Our expectation is that this protocol will contribute to the development of original technologies essential for muscle therapy and artificial meat industrialization in the future.

• Journal of Environmental Health Sciences
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• v.47 no.5
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• pp.410-424
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• 2021

Background: Subway stations have the characteristics of being located underground and are a representative public-use facility used by an unspecified number of people. As concerns about indoor air quality (IAQ) increase, various management measures are being implemented. However, there are few systematic studies and cases of long-term continuous measurement of underground station air quality. Objectives: The purpose of this study is to analyze changes and factors influencing IAQ in subway stations through real-time continuous long-term measurement using IoT-based IAQ sensing equipment, and to evaluate the IAQ improvement effect of a bio-filter system. Methods: The IAQ of a subway station in Seoul was measured using IoT-based sensing equipment. A bio-filter system was installed after collecting the background concentrations for about five months. Based on the data collected over about 21 months, changes in indoor air quality and influencing factors were analyzed and the reduction effect of the bio-filter system was evaluated. Results: As a result of the analysis, PM₁₀, PM_2.5, and CO₂ increased during rush hour according to the change in the number of passengers, and PM₁₀ and PM_2.5 concentrations were high when a PM warning/watch was issued. There was an effect of improving IAQ with the installation of the bio-filter system. The reduction rate of a new-bio-filter system with improved efficiency was higher than that of the existing bio-filter system. Factors affecting PM_2.5 in the subway station were the outdoor PM_2.5, platform PM_2.5, and the number of passengers. Conclusions: The IAQ in a subway station is affected by passengers, ventilation through the air supply and exhaust, and the spread of particulate matter generated by train operation. Based on these results, it is expected that IAQ can be efficiently improved if a bio-filter system with improved efficiency is developed in consideration of the factors affecting IAQ and proper placement.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.357-358
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• 2005

Compact power amplifier modules (PAM) for WCDMA/KPCS and GSM/WCDMA dual-band applications based on multilayer low temperature co-fired ceramic (LTCC) substrates are presented in this paper. The proposed modules are composed of an InGaP/GaAs HBT PAs on top of the LTCC substrates and passive components such as RF chokes and capacitors which are embedded in the substrates. The overall size of the modules is less than 6mm $\times$ 6mm $\times$ 0.8mm. The measured result shows that the PAM delivers a power of 28 dBm with a power added efficiency (PAE) of more than 30 % at KPCS band. The adjacent-channel power ratio (ACPR) at 1.25-MHz and 2.25-MHz offset is -44dBc/30kHz and -60dBc/30kHz, respectively, at 28-dBm output power. Also, the PAM for WCDMA band exhibits an output power of 27 dBm and 32-dB gain at 1.95 GHz with a 3.4-V supply. The adjacent-channel leakage ratio (ACLR) at 5-MHz and 10-MHz offset is -37.5dBc/3.84MHz and -48dBc/3.84MHz, respectively. The measured result of the GSM PAM shows an output power of 33.4 dBm and a power gain of 30.4 dB at 900MHz with a 3.5V supply. The corresponding power added efficiency (PAE) is more than 52.6 %.

• Journal of the Korean Society for Environmental Technology
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• v.19 no.6
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• pp.576-585
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• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.

• Plant Journal
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• v.13 no.2
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• pp.46-51
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• 2017

In this study, the boiler efficiency and the change of boiler combustion state with the burner operation of the uppermost layer of 870MW opposite fired coal boiler were measured. Test results showed that the boiler efficiency was high in the order of the uppermost layer simultaneous operation of the front and rear burners, the front burner, and the rear burner operation. When the front and rear burners were operated simultaneously, the heat absorption rate of water walls in the boiler furnace was uniform at four side, and the temperature deviation of the left and right steam on the convection front surface decreased. As the heat absorption rate of the boiler improved, the loss of boiler exhaust gas decreased and the coal supply amount decreased by 8 tons/hour compared to the operation of the rear burner. This will contribute not only to the reduction of fuel cost but also to the reduction of greenhouse gas emissions.

• Korean Journal of Poultry Science
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• v.15 no.3
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• pp.219-227
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• 1988

This experiment was carried out to evaluate biological availability of Ca and P in 4 different sources of tricalcium phosphate in young chicks. One hundred and twenty five-day-old male Single Comb White Leghorn chicks (10 treatments$\times$3replication$\times$4chicks) were used in trial 1 and 2, respectively, for 12 days of feeding period. Trial I was to evaluate the availability of phosphorus in the supplements, Standard purified diets were prepared to supply 0.07, 0.14 and 0.21％P using a mixture (1 : 1) of NaH$_2$PO$_4$ and KH$_2$PO$_4$ as the reference Phosphorus sources. Bone breaking strength of the tibia determeined by an Instron instrument appeared inadequate to be used as a criterion due to very high variations of the measurement within a treatment. Thus, tibia bone ash content was utilized as a criterion to evaluate th biological avilability of phosphorus in the supplements. The levels of the biological availability of the four different sources of dicalcium phoshate were 77.1, 91.0, 96.4 and 95.5％, respectively, and those of the three tricalcium phosphate sources were 94.1, 95.0 and 99.5％ , respectively. Trial 2 was to determeine the levels of Ca biologically available in the supplements. Standard purified diets were made to supply 0.2, 0.3 and 0.4％ Ca using CaCo$_3$ as the reference calcium source. When bone ash content was utilized as a criterion for the availability, the levels of calcium biologically available to the chicks were 78.3, 234.1, 87.6 and 244.5％, respectively, for the 4 different sources of dicalcium phosphate and 99.5, 84.0 and 101.5％ , respectively, for the 3 different sources of tricalcium phosphate. The observation that two calcium sources appeared to be utilized with an unusual efficiency can hardly be explained at this moment. When they were revaluated on the basis of body weight gain, the availabilities of the four sources of dicalcium phosphate were 89.2, 58.2, 104.1 and 103.1％ and of the three tricalcium phosphate were 112.6, 106.0 and 96.3％ , respectively.

• Journal of agriculture & life science
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• v.44 no.5
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• pp.129-135
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• 2010

This experiment was carried out to commercialize an irrigation control system by finding out problems and solving them in application of a nutrient supply system through this experiment. Its efficiency had been tested through hydroponic cultivation of tomato and cucumber using this system in the farmer's plastic house (1-2W, 20a : Yanggyo-ri, Oseong-myeon Gyeonggi-do) from November. 2006, too. In the first cultivation, tomato seeds (cultivar Coco, Takii Seed Co. Japan) were sowed on November 8, 2006, and transplanted on January 8, 2007. and then, in the second, cucumber (Chuichong, Nongwoo Seed Co.) were cultivated in the same plastic house (sowing date : June 27, transplanting date : July 13). In the third, another cucumber cultivar (Jo-woon, Dongbu-hannong Seed Co.) were cultivated (sowing date : September 5, transplanting date : September 23). All of seedlings were transplanted on perlite bag ($W340{\times}L1,200{\times}H150mm$, 40L). By using this system, 971 boxes (5 kg/box) of tomato were produced and sold, and then total income was 5,466 thousand won per 10a. On the second cultivation, total amount of cucumber production was 489 boxes (50 ea/box), and total income was 7,380 thousand won. On the third cultivation, total amount of production was 67 boxes (100 ea/box), and total income was 1,854 thousand won. On the other hand, this system saved irrigated water by 50% ($4,000{\rightarrow}2,000L/10a/day$) in tomato cultivation, and by 44%($4,500{\rightarrow}2,500L/10a/day$) in cucumber cultivation. It also saved cost of nutrients by 50% in tomato ($1,648{\rightarrow}824thousand\;won/10a$), and 44% in cucumber ($1,648{\rightarrow}725thousand\;won/10a$). Furthermore this irrigation system maintained moisture content in perlite bag stable during cultivation period. Therefore, this system was successfully applied on farmer's greenhouse without a problem and can be commercialized for farmers.

• The Journal of Engineering Geology
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• v.28 no.4
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• pp.541-552
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• 2018

The implementation of drought measures in the upstream areas of river basins is seldom considered with respect to water supply. However, the demand for such measures is increasing rapidly owing to the occurrence of severe droughts, and interventions on streams and the water supply are needed. Physical interventions are an option to prevent streams from becoming dry and to maintain stream water flow, but dam construction is challenging because of environmental and ecological considerations. Here, a feasibility study was conducted to assess the potential effects of sand dams, which are widely used in arid regions in Africa. The SWAT-K model, which is a hydrologic model used for Korean watersheds, is used to estimate the flow rate of water in an ungauged watershed. The changes in water storage of the sand-dammed reservoir and in downstream flow rates are estimated for two types of sand dam (natural and dredged). The results show that sand dams are capable of increasing the downstream flow rate during normal conditions and of mitigating water supply problems caused by the withdrawal of water during drought periods.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.4 no.2
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• pp.249-255
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• 2001

Methylmalonic acidemia is a rare congenital autosomal recessive metabolic disease. It is caused by blocking in the pathways of isoleucine, valine, threonine, methionine, cholesterol and odd-chain fatty acids to succinyl CoA, resulting in the increase of L-methylmalonyl CoA and methylmalonic acid. In most cases, there are symptoms such as recurrent vomitings, lethargy and laboratory abnormalities including metabolic acidosis and hyperammonemia from the neonatal period. We had a 6-month-old infant with methylmalonyl acidemia who presented with recurrent vomiting episodes since 3 months of age, failure to thrive and developmental delay. The laboratory findings showed hyperammoninemia and ketotic metabolic acidosis. Plasma amino acid analysis showed nonspecific finding. Urine organic acid ananysis by gas chromatography and mass spectrometry detected large amount of methylmalonic acid excreted in the urine. We restrained the supply of protein in the amount of 1~1.5 g/kg of body weight a day using leucine, isoleucine and valine-r-estrained milk and administered vitamine $B_{12}$, in the amount of 1mg per day. During the follow-up in the outpatient clinic, He could control his head and showed increased muscle strength.