• Journal of Power System Engineering
• /
• v.13 no.4
• /
• pp.5-10
• /
• 2009

Urea-SCR system, the selective catalytic reduction using urea as reducing agent, is a powerful technique to reduce nitrogen oxides(NOx) emitted from diesel engines. However, a tank of urea(32.5 wt%)-water solution can be frozen in low ambient temperature levels of below $-11^{\circ}C$. The purpose of this study is to understand freezing and melting phenomena of the urea-water solution, and its can be applied to get the urea-water solution from frozen it within 5 minutes after cold start. Factors considered were the type of heater and the urea tank shape. From the results, it was found that melting volume of cartridge heater B during 5 minutes of heating period was 83ml when supplying electric power of 150W. Horizontal heater B, which was put in the narrow bottom space of the tank T1, had fast melting characteristics.

• Journal of the Korean Society of Safety
• /
• v.16 no.2
• /
• pp.13-21
• /
• 2001

The effect of water spray for the fire sprinkler depends on droples distribution over maximum possible floor area. The present study are carried out for the characteristics of water spray and droplets experimentally and numerically km two fire sprinkler heads which are CHM head and CHl heal CHl head is self-production and CHl head is widely used up to date. As the result of using CHM head, water spray and droplets are distributed over large area because CHM head has smooth surface and non-flamed shape. When the pressure of fire sprinkler head is low, SMD(sauter mean diameter) is large and when the pressure of fire sprinkler head is high, SMD is small.

• Journal of Korean Society of Water and Wastewater
• /
• v.26 no.5
• /
• pp.659-668
• /
• 2012

In Korea, almost every water treatment plant suffers from seasonal problem of algae and turbidity which result from eutrophication and heavy rainfall. To relieve this problem, experimental investigation was performed to study the applicability of a floating-media and sand filter to preliminary water treatment in terms of algae and turbidity removal. Experimental results using pure-cultured algae influent showed that the shape of algae species as well as filtration velocity affects the removal efficiency. From the experiments using natural river water, it was concluded that algae removal is more sensitive to floating-media depth but turbidity more sensitive to sand depth. As the filtration velocity increased, the removal of turbidity decreased but that of algae was not affected. The floating-media and sand filter removed more than 30 % of TP, TN, turbidity, Chl-a and CODcr, and less than 20 % of DOC and $UV_{254}$.

• Animal Systematics, Evolution and Diversity
• /
• v.32 no.3
• /
• pp.197-206
• /
• 2016

Two cold-water coral taxa, Octocorallia in the class Anthozoa and Stylasteridae in the class Hydrozoa, were identified. Deep-water samples were collected in fishing nets at depths ranging between 20 and 200 m along the coasts of the East Sea in Korea from 1976 to 1993. The two species found in this study represent new records for Korea: Paragorgia arborea (Linnaeus, 1758) in the class Anthozoa, and Stylaster profundiporus Broch, 1936 in the class Hydrozoa. Two families, Paragorgiidae and Stylasteridae, are also newly recorded in Korea. Furthermore, the species name of another cold-water gorgonian species, Primnoa pacifica (Kinoshita, 1907) in the family Primnoidae, is amended in this report. The two newly recorded cold-water coral species from Korea are described in detail based on their morphological characteristics. Paragorgia arborea is characterized by its growth form, medulla and cortex, zooid dimorphism, canal system, and spicule composition. Stylaster profundiporus is distinguished by its external skeletal characteristics, such as the coordination of dactylopores and gastropores, presence or absence of gastrostyles and dactylostyles, cyclosystem orientation, ampullar position, gastropore tube shape, and coenosteal texture.

• Tunnel and Underground Space
• /
• v.4 no.2
• /
• pp.92-101
• /
• 1994

Water jet has been employed in extraacton of minerals for many years but the applications of low pressure jent s ar emodfined to some fields. With increasing strength of equipment it is possible to consider the use of high speed water jets for cutting hard rock. The high speed water jet technology is applied to various engineering fiels such as precessing rocks, quarrying rocks, mechanical fracturing as wel as rock excavation under the sea. For slot cutting in rocks with high speed water jets it is necessary to establish the empirical formula for estiamation of the cutting depth. The cutting depth is influenced by cutting parameters such as driving pressure, traverse speed, standoff distance, and shape and diameter of nozzel. Tests were carried out with a variety of cutting parameters on three types of granite. Nozzle pressures ranged from 1,200 to 2,800 bar, traverse speeds from 0.45 to 10.38 cm/min, standoff distances from 4.5 to 13.5 mm, and three types of nozzle diameter were used.

• The KSFM Journal of Fluid Machinery
• /
• v.13 no.1
• /
• pp.23-28
• /
• 2010

A draft tube which has impeller to elevate bottom water and spread it over surface of lake water, induces convective circulation of lake water, a Long-Distance Circulation (LDC). Circulation of lake water make stratified water mixed and enhance DO (Dissolved Oxygen) of bottom water. Circulation rate of water is determined by draft rate of the tube, which is dependent on design parameters of the draft tube system, i. e. dimension of impeller and diffuser, inclined angle of impeller, impeller shape, and rotational speed. In this study, change in draft rate and power consumption of circulation equipment was investigated numerically with changing impeller dimension, angle and rotational speed. It was found that flowrate of draft water was increased as the dimensions of draft tube and impeller, and rotational speed and inclined angle of impeller increased. The power consumption was also elevated with increasing parameter values, and final selection of parameter values was made to satisfy target flowrates and power consumption.

• Water for future
• /
• v.13 no.2
• /
• pp.49-54
• /
• 1980

Meandering has been attributed to the earth's rotation, to the excessive slope and energy of a river, to changes in stage, etc. The purpose of this study is a geometrical approach of meander shape and to derive the relationship among meander characteristics. In the analysis of sime field examples, in spite of variety of meander shapes, the sine-generated curve was fit actual quite well and better than alternatives against the channel distance. An attempt is made to find considerable relation among meander characteristics. But width and meanderbelt did not show any defined trend considerable scatter of points was observed.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.6
• /
• pp.1250-1259
• /
• 2001

This study was experimentally performed to investigate sea water freezing behavior along parallel cooled plate with bubbly flow The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled-plate temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layer.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.81-84
• /
• 2006

To investigate the characteristics of water droplet on the gas diffusion layer from both upper-view and side-view of flow channel, a rig test apparatus was designed and fabricated with L-shape acryl plate in a $1mm{\times}1mm$ micro-channel. This experimental device is used to simulate the single droplet growth and its transport process under fuel cell operating condition. As a first step, we investigated the growth and transport of single water droplet with working temperature and air flow velocity. The contact angle and its hysteresis of water droplet at departing moment are measured and analyzed. It is expected that this study can provide the basic understanding of liquid water droplet behavior in gas flow channel and GDL interface during the PEM fuel cell operation.

• Wind and Structures
• /
• v.4 no.5
• /
• pp.383-398
• /
• 2001

The paper describes the results of the monitoring of an elevated steel water-tank with unusual shape, 85 m high and 40 m wide. The research was carried out analysing both the static and dynamic behaviour under wind actions. The instruments used (some of which were employed for the first time for this project) are described and the data processing procedures are discussed. Comparison between the experimental results and those obtained through a numerical model gives interesting information both on the structural behaviour and on the characterisation of wind actions.