• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.1
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• pp.12-16
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• 2015

$(Na,K)NbO_3$-based piezoelectric ceramics were synthesized by a solid phase sintering method with various milling solvents. The solvents were varied with acetone, ethanol, and pure water to investigate the effect on the microstructure and electrical properties. NKN ceramics showed the maximum values of the relative density (94%), the mechanical quality factor (Qm: 78) and the electro-mechanical coupling factor ($k_p$: 0.25) at the ethanol solvent. It might mean that a solid phase sintering of the NKN piezoelectrics with a suitable solvent could improve the relative density and the piezoelectric properties.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.273-276
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• 2002

Many artificial steel reefs are being built in Japan, however, in Korea, only few steel reefs were manufactured by POSCO, recently. In order to develop their novel types suitable for marine environments near the Korean Peninsula, it is very important to carry out model tests in the initial design stage. In the Ocean Engineering Wide Tank($L{\times}B{\times}D=30{\times}20{\times}2.5m$) and the Circulating Water Channel of the University of Ulsan, Korea, fluid drag forces acting on models of steel reefs with different sizes are measured in waves and currents. Also numerical predictions based on the Wavier-Stokes equation are made and compared with experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.35-41
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• 2019

Contrail is a kind of cloud that is formed during the flight by vapor condensation of engine exhaust in a cold atmospheric condition. Owing to the negative effects of contrails on the environment and in military applications, several studies for contrail mitigation had been performed in developed countries. The goal of this research is to design a lab-scale contrail generator, and to validate the contrail mitigation technology suggested by previous studies. The contrail generator was made using superheated vapor and a low temperature wind tunnel. Using this generator, the ineffectiveness of ethanol and surfactant suggested in the previous paper on contrail mitigation was found experimentally.

• Journal of Korean Society of Water and Wastewater
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• v.12 no.3
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• pp.118-124
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• 1998

To use chlorine residual as an surrogate parameter of the water quality change during the transportation in the water distribution system(WDS), the correct prediction model of chlorine residual must be established in advance. This paper shows the procedure and the result of applying the water quality model to the field WDS. To begin with, hydraulic model was calibrated and verified using fluoride as an tracer. And chlorine residual was predicted through simulation of water quality model. This predicted value was compared with the observed value. With adjusting the bulk decay coefficient(kb) and the wall decay coefficient(kw) according to the pipewall environment, the predicted chlorine residual can represent the observed value relatively well.

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.313-315
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• 2006

Proper water management is important to achieve high performance and durability of Polymer electrolyte fuel cell (PEFC). Among various stack components, gas diffusion layer (GDL) is considered as a core part to determine the gas and water transportation in a cell. To optimize the water management, the changes of properties as well as basic properties of GDLs were investigated before and after clamping of colls. Thickness, electric conductivity, porosity, hydroppobicity etc. were characterized by the same criteria. The amount of residual water after cell operation also was compared by direct measuring of weight. Based on the amount of residual water the endurance on the freeze condition was evaluated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.980-985
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• 2008

The environment of IT is, currently, on its developing process to the period of web 2.0 and mashup which not only enable computer and internet to be utilized like the water or the air, but also be a new motivating force for its advance. One of the biggest changes of the industry that lies ahead is consolidated transportation. However, no party outstands as the leading party for nationwide improvement of logistics, nor does the right analysis and design for it. Therefore, successful nationwide logistics model is yet to exist. This study provides individual parties, which consider consolidated transportation model as their implementation and design of the framework, with instructions for logistics information system so that they could be competitive in the market. It also helps companies collect user requirements for logistics information system consolidated transportation, and utilize it for its development. Finally, the study provides a implementation and design of pilot system for consolidated transportation model.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.385-394
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• 2007

The objective of this study was to estimate social cost on rehabilitation of existing water pipes by investigating the willingness-to-pay (WTP) of residents at INJE County to avoid the loss and inconvenience of transportation and business resulting from the sudden failure and leaks of old water pipes. Contingent valuation method was used through conducting survey to 180 residents in Inche County, with questions of double-bounded dichotomous choice. The resulting WTP of residents at Inche was 7,682 won/month/household. The annual social cost could be estimated as 960 million won, which might be caused by the failure of the old water pipes at INJE County.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.728-733
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• 2002

The measurement of river discharge is among the most fundamental observations and is necessary for understanding many water-related issues, such as flooding hazards, sediment transportation, and nutrient movement. Traditionally river discharge is estimated by measuring the water stage and converting the measurement to discharge using a stage-discharge rating curve. The possibility of monitoring river discharge from satellites has been largely ignored, because it is difficult to measure water surface information from space with sufficient precision. In this paper, an efficient approach to discharge estimation using mainly satellite data is developed and described. The proposed method, which focuses on the measurement of water-surface width coupled with river width-stage and stage-discharge relationships, is applied to the Yangtze River with good results.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.1
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• pp.23-33
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• 2020

With growing expectations for economic cooperation between the two Koreas, there is much interest in participating in the construction of infrastructure in North Korea. In particular, water and sewage infrastructure is the four major social infrastructures in addition to housing, transportation, electricity and telecommunications. North Korea is known to have severe water pollution and ecosystem destruction in major rivers, water pollution and soil pollution in mining areas are serious, and water and sewage infrastructures in cities other than Pyongyang are known to be weak. Preemptive investment in water supply and drainage in North Korea is the foundation for securing the quality of life of the North Korean and is the foundation of public health and industry. It is a leading investment to reduce the cost of unification and is a new growth engine for the water reloded industry. In this study, we proposed a plan to exchange and cooperate in water environment for building water infrastructure of North Korea by examining the data related to water quality, water resources, water disaster, related legal system and human resources exchange situations in North Korea.

• The Korean Journal of Food And Nutrition
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• v.29 no.1
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• pp.1-11
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• 2016

To enhance the physiological activities of roasted coffee (RC), 30 kinds of green coffee beans (GCB) with different cultivating areas and varieties were fermented with Monascus ruber mycelium (MR) by solid-state culture. After the dried MR-fermented GCB was subjected medium roasting, each RC was extracted with hot-water. Among the hot-water extracts, the highest yield was the hot-water extract of RC from MR-fermented Indonesia Mandheling GCB (15.5%). However, the hot-water extract of RC from MR-fermented Ethiopia Sidamo GCB showed significantly higher polyphenolic contents (3.08 mg GAE/100 mg) and ABTS free radical scavenging activity (25.41 mg AEAC/100 mg). Meanwhile, the hot-water extract of RC from MR-fermented Vietnam Robusta GCB showed not only the effective inhibition of $TNF-{\alpha}$ level (73.7% inhibition of LPS-stimulated control) from LPS-stimulated RAW 264.7 cells but also significant inhibition of lipogenesis (63.5% inhibition of lipid differentiation control) in 3T3-L1 pre-adipose cells. In conclusion, these results suggest that roasted coffees from Ethiopia Sidamo and Vietnam Robusta green coffee beans fermented with Monascus ruber mycelium using solid-state culture could have industrial applications as functional coffee beverages.