• Ocean Science Journal
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• v.42 no.3
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• pp.135-152
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• 2007

The ecological aspect of meiofaunal communities in Can Gio mangrove forest, Ho Chi Minh city, Vietnam has not been investigated before. The composition, distribution, density and biodiversity of meiofaunal communities were studied along an intertidal transect at the Khe Nhan mudflat. Each time, three replicate samples were collected in four stations along a transect following the water line from low tide level up to the mangrove forest edge. In total, 18 meiofaunal taxa were found with the dominant taxa belonging to Nematoda, Copepoda, Sarcomastigophora and Polychaeta. The densities of meiofauna ranged from $1156inds/10cm^2$ to $2082inds/10cm^2$. The increase in densities from the mangrove forest edge towards the low water line was significant Along the mudflat transect, the biodiversity (expressed by different indices) was relatively high at different taxonomic levels but did not vary significantly along the mudflat except for taxa richness. Eighty nematode genera belonging to 24 families with Comesomatidae having the highest abundance 33.8 % were found. Theristus and Neochromadora decreased in densities from the lower water line towards the mangrove forest edge, while Paracomesoma and Hopperia are typical and more abundant at the middle of the mudflat. Halalaimus increased from high on the mudflat to the low water line.

• Applied Chemistry for Engineering
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• v.8 no.4
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• pp.653-659
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• 1997

Due to the rising cost of energy, new separation processes based on extraction are becoming more attractive than before. Thus, the need for calculating and predicting liquid-liquid equilibria(LLE) compositions has very much increased. The purpose of this study is to determine the binodal curves, tie line, plait point, distribution and selectivity for the ternary systems of 2-propanol-water with methyl ethyl ketone, methyl isobutyl ketone, ethylacetate, toluene and o-xylene as solvents at $25^{\circ}C$. And those tie line data were used to examine thermodynamic consistency. The experimental tie line data were correlated with NRTL and UNIQUAC models.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3122-3127
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• 2007

Water resource can be examined using biological sensors. Algae has been one of the biological sensors used to evaluate and monitor the water pollution. The monitoring system, however, could determine whether the examined water was safe or not. It needs additional expensive chemical test to figure out the cause of the water pollution. In this study, an endeavor is given to identify the toxicant in the water using the shape of the chlorophyll fluorescence induction curve(FIC) from algae using monitoring system. Fundamental curves are obtained from the experiments with specified amount of toxicant. Baysian method is utilized to determine the unknown toxicant in the water by comparing it with the fundamental curves. The results shows that the proposed method works fairly well.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.2
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• pp.214-220
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• 2005

Errors may occur due to analysis methods and water quality during the application of the on-line particle counter In water treatment process. Errors caused by analysis methods include particle destruction by shear force due to inflow speed and tube friction, as well as interruption by screening, bubbles and contaminants. Since errors happen frequently because of these factors, it is necessary to examine and evaluate such errors during the application of a particle counter. Errors can be large due to screening and bubbles. Measurement values are effective for water analysis after filtration process. However, because of screening, only measurement values for particles above $7{\mu}m$ are valid for water with a turbidity between 3-10NTU. As particle numbers around $10{\mu}m$ increase a lot after ozone treatment, sufficient pretreatment process is necessary. Physical conditions should keep stable for inflow to decrease errors caused by shear force.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.98-113
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• 2016

A reactor vessel level monitoring system measures the water level in a reactor during normal operation and abnormal conditions. A drop in the water level can expose nuclear fuel, which may lead to fuel meltdown and radiation spread in accident conditions. A level monitoring system mainly consists of a sensing line and pressure transmitter. Over a period of time boron sediments or other impurities can clog the line which may degrade the accuracy of the monitoring system. The aim of this study is to determine blockage in a sensing line using the energy of the composite signal. An equivalent Pi circuit model is used to simulate blockages in the sensing line and the system's response is examined under different blockage levels. Composite signals obtained from the model and plant's unblocked and blocked channels are decomposed into six levels of details and approximations using a wavelet filter bank. The percentage of energy is calculated at each level for approximations. It is observed that the percentage of energy reduces as the blockage level in the sensing line increases. The results of the model and operational data are well correlated. Thus, in our opinion variation in the energy levels of approximations can be used as an index to determine the presence and degree of blockage in a sensing line.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.152-158
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• 2003

Titration method is one of the widely used methods for the concentration measurement of absorbent ammonia/water. However, this method is inconvenient because the solution should be extracted for the measurement. Moreover, significant error can be introduced by the evaporation of ammonia during the sampling and measuring procedure. In this study a reliable in-line concentration measurement method was proposed. To prove the validity of the concept, a measuring apparatus was designed, built, and tested with water. It is found that the location of flow inlet and exit is important in the measurement accuracy. The flow inlet and exit located in the middle of the test cell showed the best result. By the error analysis, it is expected that the ammonia concentration can be measured within the error of $\pm$0.18% assuming the error of 0.1 K in temperature measurement and 0.1 g in weight measurement.

• Journal of Korean Society of Water and Wastewater
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• v.22 no.3
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• pp.281-288
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• 2008

Cake resistance is influenced by floc size deposited on membrane surface. Enlarging floc size can reduce cake resistance. The small particles are enlarged by coagulation and flocculation process in conventional mixing tank at membrane filtration system. Fully-grown flocs for reducing the cake resistance, however, are ruptured while passing through a pump. In light of this fact, this study aims to experimentally look at the reaggregation phenomenon of mixing system. In addition, reaggregation phenomenon of mixing system is compared with first-aggregation of in-line injection system in which coagulant is injected just before a pump. These results suggest that first-aggregation of in-line injection system is better than reaggregation of mixing system for G-value above $3100sec^{-1}$. Since G-value in pipe of actual membrane filtration system are usually larger than $3100sec^{-1}$. The performance of in-line injection system is expected to be better than the conventional mixing tank system.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.110-118
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• 2021

In a liquid rocket engine system, the flow of oxidizer into the combustion chamber is controlled by the main oxidizer shut-off valve. When the valve is closed, the oxidizer flows via the recirculation line, not into the combustion chamber. In this situation, the measured pressure could be much higher than a design value because of the water hammer phenomenon. In this paper, the experiments on the water hammer in the recirculation line with different initial conditions were conducted in order to study the pressure wave produced in each case. According to the experimental results, characteristics of the pressure wave in the recirculation line depend on the initial condition. To be specific, the pressure surge is maximized in case that the shock is condensation-oriented in the end of the recirculation line.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.20-25
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• 2007

KTX is being operated on Kyung-Pu High Speed Railroad Line and Ho-Nam Railroad Line from April 2004. Reduction units is occurring water infiltration at heavy snow and oil leakage because of labyrinth structure. This paper describes design method and evaluation technology to improve structure to prevent water infiltration and oil leakage for reduction units of KTX. This reduction units need high power and high speed to run and they have to make optimal lubricant without change current interface.

• Korean Chemical Engineering Research
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• v.56 no.3
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• pp.388-403
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• 2018

We investigated design requirements of vent lines for Sodium-Water Reaction Pressure Relief System of Prototype Generation-IV Sodium-Cooled Fast Reactor. We developed design requirements of areas of the rupture disks of the steam generator, a diameter of the gas vent line of the sodium dump tank, a diameter of the gas vent line of the water dump tank, a diameter of the water dump line of the steam generator. With the design requirements, we calculated the time to vent fluid inside the steam generator and analyzed the transient pressure behavior, also evaluated the close pressure value of the isolation valve of the water dump line. Our results are expected to be used as basis information to design Sodium-Water Reaction Pressure Relief System of Prototype Generation IV Sodium-Cooled Fast Reactor.