• Journal of Korean Society of Water and Wastewater
• /
• v.23 no.6
• /
• pp.779-788
• /
• 2009

This study is the result of a field survey of four sewer networks selected from in domestic sanitary sewers. The main purpose of this study is to understand the characteristics of sediment in domestic sanitary sewers and to verify sewer design criteria using minimum Shear Stess for preventing sedimnet. This investigation was carried out at a total of 22 points in the four areas. The characteristics of the sanitary solids that were sampled for suspended solids and bedload matter showed a specific gravity of 1.09, a median particle size of 1.26mm, and 88.9% organic contents. On the other hand, deposited sediment was found at 6 points out of the 22 monitoring points. The analysis results of disposed sediment showed a specific gravity of 2.16, a median particle size of 1.31mm, and 15% organic contents. In flow velocity, the majority of deposited sites have under 0.6m/s. However, one-site which was in large-diameter collector sewers, has recorded over 0.6m/s. The analysis results of tractive force showed that the ability of tractive force has to be $1.5{\sim}2.0N/m^2$ to prevent sediment in domestic Sanitary sewers. In conclusion, to prevent sediment it is necessary to apply a design velocity criteria higher than 0.6m/s in the large diameter collector sewer.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.11
• /
• pp.907-913
• /
• 2017

The performance of a spark jet driven by pulsed-arc plasma was investigated experimentally for various energy input. A high-speed jet (about 330 m/s) was obtained by rapid gas heating produced by 37 mJ of deposited energy per pulse. The peak velocity and penetration distance of the jet were proportional to the deposited power and the deposited energy per pulse, respectively. A smaller orifice diameter produces a higher velocity jet at lower energy levels. For the same deposited energy, higher-current pulses produce a higher jet velocity than higher-pulse-width pulses. A total deposited energy of about 10 mJ per pulse with a pulse duration of about $10{\mu}s$ was found to be the optimum for energy- efficient operation.

• Transactions of the Korean hydrogen and new energy society
• /
• v.28 no.3
• /
• pp.300-307
• /
• 2017

This study is to investigate particle size and velocity profile of gasoline port injector using Phase Doppler Particle Analyzer (PDPA). In this experiment, a GV 250 Delphi port injector used for motorcycles was used for liquid injection. The injector consists of four holes and has a static flow rate of 2.13 g/s. The fuel used in the injection was N-heptane, which is similar to gasoline, as an alternative fuel. The test fuel was injected at an atmospheric temperature of $20^{\circ}C$ and an open atmosphere of 1 atm. The injection time was 10 ms and the injection pressure was 3.5 bar in PDPA experiment. The experimental target position was fiexd at 30, 50 and 75 mm from the nozzle tip and data were collected for a total of 10,000 samples. The experimental results show that the length diameter (D10), the Sauter mean diameter ($D_{32}$), and the mean droplet velocity (MDV) are $45-54{\mu}m$, $99-115{\mu}m$ and 15-21 m/s, respectively.

• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.1
• /
• pp.125-133
• /
• 2006

It is important to understand flow characteristics and performances of sails for both sailors and designers who want to have efficient thrust of yacht In this Paper the viscous flows around sail-like rigid wings, which are similar to main and jib sails of a 30 feet sloop, are calculated using a CFD tool. Lift, drag and thrust forces are estimated for various conditions of gap distance between the two sails and the center of effort of the sail system is obtained. Wind tunnel experiments are also carried out to measure aerodynamic forces acting on the sails system and to validate the computation. It is found that the combination of two sails produces the lift force larger than the sum of that produced separately by each sail and the gap distance between the two sails is an important factor to determine total lift and thrust.

• Journal of Chest Surgery
• /
• v.22 no.4
• /
• pp.589-593
• /
• 1989

The frequency spectrum of the metallic closing sound and its loudness were measured by non invasive techniques in 66 patients. They had examined a total of 7 Carbomedics valve, 10 Duromedics valve, 11 St. Jude heart valve in mitral position and 8 Carbomedics, 10 Duromedics, 20 St. Jude heart valve prostheses functioning normally in aortic position. Statistical comparison of the loudness from sound produced by the three valves in each position, the following; The Carbomedics valve has the lowest average loudness, followed by the St. Jude medical valve, and finally the Edward Duromedics valve. And we analysis the changing factor of the loudness of valve sound, only the velocity of the flow through the valve influenced to the valve sound.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.163.2-163.2
• /
• 2011

Due to global warming, the need to secure an alternative resource has become more important nationally. Due to the high tidal range of up to 9.7m on the west coast of Korea, numerous tidal current projects are being planned and constructed. To extract a significant quantity of power, a tidal current farm with a multi-arrangement is necessary in the ocean. The rotor, which initially converts the energy, is a very important component because it affects the efficiency of the entire system, and its performance is determined by various design variables. The power generation is strongly dependent on the size of the rotor and the incoming flow velocity. However, the interactions between devices also contribute significantly to the total power capacity. Therefore, rotor performance considering the interaction problems needs to be investigated for generating maximum power in a specific field. This paper documents the characteristics of wake induced by horizontal axis tidal current power turbine.

• Proceedings of the Membrane Society of Korea Conference
• /
• 2004.11a
• /
• pp.199-203
• /
• 2004

Fibrous arsenic (As) adsorbent was synthesized by loading zirconium (Zr) on fibrous phosphoric adsorbent that was directly synthesized by radiation-induced graft polymerization of 2-hydroxyethyl methacrylate phosphoric acid on polyethylene-coated polypropylene nonwoven fabric. Zirconium reacted with phosphoric acid grafted in the polyethylene layer. Zirconium density of the resulting adsorbent was 4.1 mmol/g. The breakthrough curve of As(V) adsorption was independent of the flow rate up to $1300\;h^{-1}$ in space velocity. The total capacity of As(V) was 2.0 mmol/g-adsorbent at pH of 2. The adsorbed Zr(IV) could be evaluated by 0.4 M sodium hydroxide solution because negligible Zr(IV) could be found in the eluted solution.

• Journal of Ocean Engineering and Technology
• /
• v.13 no.3B
• /
• pp.116-126
• /
• 1999

The purpose of this study is to analyze the economic aspect of sea transportation system between Inchon and Youngjong island in which Inchon international airport is being constructed. Total demand of sea transportation arising from in the airport and Yongyu Muwi leisure complex was estimated. To select optimum transportation route, environmental conditions in and around Inchon harbour and Youngjong island including the change of water depth by tide current, fog, rain, wind adn typhoon, ets., were investigated. The preliminary consideration on ships (size, velocity, transport capacity, price), routes, operational modes, terminals and berthing facilities were carried out. The transportation cost per passenger by sea transportation system was estimated to compare with that of land transportation system. It was found that sea transportation system proposed is competitive to the transportation system.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.28 no.2
• /
• pp.63-68
• /
• 2018

Natural convection of a two dimensional laminar steady-state incompressible fluid flow in a rectangular enclosure has been investigated numerically for low aspect ratios with the physical vapor transport crystal growth. Results show that for aspect ratio (Ar = L/H) range of $0.1{\leq}Ar{\leq}1.5$, with the increase in Grashof number by one order of magnitude, the total mass flux is much augmented, and is exponentially decayed with the aspect ratio. Velocity and temperature profiles are presented at the mid-width of the rectangular enclosure. It is found that the effect of Grashof number on mass transfer is less significant when the enclosure is shallow (Ar = 0.1) and the influence of aspect ratio is stranger when the enclosure is tall and the Grashof number is high. Therefore, the convective phenomena are greatly affected by the variation of aspect ratios.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.4
• /
• pp.977-985
• /
• 1994

New computer-aided calibration methods for the hot-wire and split film probes are presented. The proposed modified king's law takes into account instantaneous flow angle as well as the variation of calibration coefficients due to the total velocity magnitude change. It is found that the look-up table method has many advantages with respect to the accuracy on data and reducing run time for calibration over other conventional methods. In order to investigate the local sensitivity of the static calibration, a dynamic calibration procedure is also carried out.