• Structural Engineering and Mechanics
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• v.70 no.4
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• pp.479-497
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• 2019

In the current code design, the use of a uniform internal pressure coefficient of cooling towers as internal suction cannot reflect the 3D characteristics of flow field inside the tower body with different ventilation rate of shutters. Moreover, extreme weather such as heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind. In this study, the world's tallest cooling tower under construction, which stands 210m, is taken as the research object. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed iteratively using continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind speed and rainfall intensity on the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower body is analyzed. The combination of wind velocity and rainfall intensity that is most unfavorable to the cooling tower in terms of distribution of internal pressure coefficient is identified. On this basis, the wind/rain loads, distribution of aerodynamic force and working mechanism of internal pressures of the cooling tower under the most unfavorable working condition are compared between the four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the amount of raindrops captured by the internal surface of the tower decreases as the wind velocity increases, and increases along with the rainfall intensity and ventilation rate of the shutters. The maximum value of rain-induced pressure coefficient is 0.013. The research findings lay the basis for determining the precise values of internal surface loads of cooling tower under extreme weather conditions.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.85-91
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• 2021

Aggregate waste separator with rotating separating net was designed for applying classification process of construction waste. In order to evaluate the performance of the aggregate waste separator, according to the type of waste, standardized waste samples are prepared using acrylic. The appropriate operating point was evaluated by the classification efficiency and misclassification rate of recycled aggregate according to the control frequency of the blower operating and inlet position of the separating net. The classification efficiency at the operating point of the aggregate waste separator was evaluated through flow analysis assuming recycled aggregate and waste sample as particles. As a result of the performance test, when the distance. between the conveyor belt and the inlet was 0.2m, the classification efficiency was 95%, but the misclassification rate of recycled aggregate was 2% or more, which satisfies the classification efficiency and the misclassification rate of less than 2%. The operating point was shown at a control frequency of 58Hz at a suction distance of 0.254m. As a resu lt of flow analysis, there was no misclassification of recycled aggregate. In order to redu ce constru ction waste in the existing recycled aggregate production process, adsorption system using a rotating separating net that can be operated as an installation type was built.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.2
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• pp.65-72
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• 2015

Performance tests of a turbopump for the developing 7-tonf liquid rocket engine were conducted. The performance of turbopump components and their power matching were measured and examined firstly under the LN2 and water environment. In the real propellant(LOX and kerosene) environment tests, design and off-design performances of turbopump were fully verified. During the off-design tests, turbopump running time was set the same as engine operating time and pump inlet pressure were set lower than nominal operating value in order to investigate pump suction capability. It have been verified that subject turbopump satisfies required performance - flow rate, head, suction performance and operational time - in the operating regime of developing liquid rocket engine.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.248-254
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• 2015

There has been no previous study on technology development of large capacity drainage pump for rescue sinking ship in the country. The agricultural drainage pump was widely used for rescue sinking ship but this pump has several problems such as efficiency, low displacement and malfunction in winter. Therefore, this paper proposes to solve the problems for swiftly rescue sinking ship and develops the drainage pump system that has $20m^3/min$ mass flow rate specification at suction head 8 m. The centrifugal pump type the most commonly used in the field of naval architecture and ocean engineering was selected and designed based on the requirement specification. The blade design of impeller was derived from the Stepanoff coefficient and requirement specification and used computational fluid dynamics to review the target mass flow rate according to the impeller RPM at design operating conditions. We also performed structure analysis of the impeller to find structurally vulnerable points for the pump in service and completed the theoretical design of drainage pump system.

• Journal of Biosystems Engineering
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• v.33 no.6
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• pp.384-389
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• 2008

Three prototype chestnut harvesters were constructed and evaluated their chestnut collection ability and field efficiency. Air-lock paddle system successfully picked up all loose material, and pick up efficiency was about 56 kg/h. Power required to operate this system was evaluated to be 8.7 kW with an air flow rate of $32.6\;m^3/min$. A radial blade type blower with 0.41 m impeller diameter was considered to be a minimum size for this system. For the auger system, air was sucked into the cylinder as the hinged flat cover began to be opened by the material pushed by the auger, and the empty burrs flew back to the container through the space between auger flights and collected in the bottom of the container. It was considered to add a device to prevent air from flowing back or to use the back flowing air for separation of burrs and nuts inside the container. The venturi system could not pick up chestnuts, as they only carried part way up to the suction hose. Consideration was given to an idea that the venturi could be used as a cleaning and separation mechanism for containers filled with both empty burrs and good nuts. A minimum vacuum of 129 mm wg was required to pick up chestnuts, and the corresponding inlet air velocity was 19.3 m/s. 104 mm of vacuum, which was about 81 % of that required for nuts, was enough to pick up burrs with nuts inside. Also, empty burrs with higher moisture content recorded the same pressure as for the burrs with nuts.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.566-575
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• 2011

Since LPG (Liquefied petroleum gas) fuel supply system has an advantage of low emission characteristics, many studies have been conducted. In spite of the advantage of LPG supply system, a higher vapor pressure and lower viscosity than diesel or gasoline fuel may cause unstable running of fuel pump by the deterioration in lubrication performance and chemical reaction with rubber parts than that of diesel and gasoline fuel. Therefore its physical properties can cause the deterioration of durability. In this research, we developed an external type LPG pump which has the advantage of the price competitiveness and the convenient maintenance for LPLi system. The experiments were carried out in order to assess characteristics of the external type fuel pump at different fuel composition and temperature. As a result, there aren't any differences between internal and external type pump performance. It is observed that the same level of efficiency was maintained for both pumps as flow rate was increased with higher fuel temperature and more contents of propane in the fuel. And the pressure difference in LPLi system is maintained at constant with the various fuel compositions and temperatures due to their own characteristics of fuel supply system.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.644-649
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• 2000

A new cyclone system for the vacuum cleaner to collect dusts has been studied experimentally and numerically to meet the constant suction power, hygienic exhaust and a reduction of maintenance cost. The cyclone system of the vacuum cleaner consists of twin cyclones for improving dust collection efficiency. The first. cyclone catches large dust particles and the second one having two separated flows to decrease pressure drop collects small dust particles. The optimal design factors such as dust collection efficiency, pressure drop, and cut-size are investigated from the experimental results by the Taguchi method. Cyclone cleaner systems designed in this study has a good Performance taking into account the dust collection efficiency of 93% and the cut-size of $1.6{\mu}m$ in mass median diameter at the flow rate of 1 CMM. The cyclone vacuum cleaner showed the potential to be an effective method to collect dusts generated in the household.

• Archives of Plastic Surgery
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• v.35 no.4
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• pp.393-399
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• 2008

Purpose: Chronic infected wounds sustained over 4 weeks with exposed tendon or bone are difficult challenges to plastic surgeons. Vacuum assisted closure (VAC) device has been well used for the management of chronic wounds diminishing wound edema, reducing bacterial colonization, promoting formation of granulation tissue and local blood flow by negative pressure to wounds. But Commercial ready-made VAC device might have some difficulties to use because of its high expenses and heavy weight. So we modified traditional VAC device with silver dressing materials as topical therapeutic agents for control of superimposed bacterial wound infection such as MRSA, MRSE and peudomonas. Methods: We designed the modified VAC device using wall suction, 400 cc Hemovac and combined slow release silver dressing materials. We compared 5 consecutive patients' data treated by commercial ready-made VAC device(Group A) with 11 consecutive patients' data treated by modified VAC device combined with silver dressing materials(group B) from September 2004 to June 2007. Granulation tissue growth, wound discharge, wound culture and wound dressing expenses were compared between the two groups. Results: In comparison of results, no statistical differences were identified in reducing rate of wound size between group A and B. Wound discharge was significantly decreased in both groups. Modified VAC device with silver dressing materials showed advantages of convenience, cost effectiveness and bacterial reversion. Conclusion: In combination of modified VAC device and silver dressing materials, our results demonstrated the usefulness of managing chronic open wounds superimposed bacterial infection, cost effectiveness compared with traditional VAC device and improvement of patient mobility.

• Journal of Korean Society on Water Environment
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• v.22 no.3
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• pp.534-539
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• 2006

The supply of oxygen for aeration is the largest energy consumer at activated sludge wastewater treatment plants. Replacement of less efficient aeration systems with fine pore aeration devices can save up to 50 percent of aeration energy costs. The purpose of this study was the diagnosis and evaluation of a domestic wastewater aeration system by the off-gas method which had been studied by US EPA and ASCE. For this study, an off-gas analyzer and its hood were made to collect off-gas. Also, a vacuum pump was connected to the analyzer to make suction of off-gas. Experiments were conducted at a domestic activated sludge wastewater treatment plant which had a single spiral roll aeration system installed with P.E tube diffuser. Data on OTE(f), SOTE(pw), OUR, and air flow rate were obtained from these experiments. In case of replacing an aeration system, it is recommended that it should be replaced with perforated membrane disc or ceramic disc fine bubble diffusers installed in a full floor coverage or grid pattern.

• Archives of Plastic Surgery
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• v.37 no.3
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• pp.227-232
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• 2010

Purpose: Continuous irrigation method is an important step in managing wound infection. V.A.C. devices have been used in intractable wounds for reducing discharge, improving local blood flow, and promoting healthy granulation tissue. We expect synergistic effects of reduced infection and more satisfactory, accelerated wound healing when using both methods simultaneously. This study evaluated continuous irrigation combined with V.A.C. appliance for treatment of infected chronic wounds. Methods: We reviewed data from 17 patients with infected intractable chronic wounds. V.A.C. device (Group A) was used in 9 patients, and V.A.C. with antibiotics irrigation (Group B) was used in 8 patients. We placed Mepitel$^{(R)}$ on the surface of wound and placed an irrigation and aspiration tube on each side. A sponge was placed on the Mepitel$^{(R)}$ and covered with film dressing. The wound was irrigated continuously with mixed antibiotics solution at the speed of 200 cc/hr and aspirated through the wall suction at the pressure of -125 mmHg. V.A.C. applied time, wound culture and wound size were compared between the two groups. Results: No complication were seen in two groups. Compared with Group A, in the Group B, V.A.C. applied time was shortened from 32.7 days to 25.6 days and showed efficacy in the reduction rate of wound size. No statistical differences were shown in bacterial reversion. Conclusion: V.A.C. appliance with continuous irrigation is an effective new method of managing infected chronic wounds and useful to reduce treatment duration and decrease wound size. Moreover it could be applied more widely to infected wound.