• Wind and Structures
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• v.30 no.3
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• pp.261-273
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• 2020

This paper deals with the design, wind tunnel testing, and performance analysis of small wind turbines targeting low-power applications. Three different small-size blade designs in terms of size, shape, and twisting angle are considered and tested. We conduct wind tunnel tests while measuring the angular speed of the rotating blades, the generated voltage, and the current under varying resistive loading and air flow conditions. An electromechanical model is also used to predict the measured voltage and power and verify their consistency and repeatability. The measurements are found in qualitative agreement with those reported in previously-published experimental works. We present a novel methodology to estimate the mechanical torque applied to the wind turbine without the deployment of a torque measuring device. This method can be used to determine the power coefficient at a given air speed, which constitutes an important performance indicator of wind turbines. The wind tunnel tests revealed the capability of the developed wind turbines to deliver more than 1225 mW when subject to an air flow with a speed of 7 m/s. The power coefficient is found ranging between 26% and 32%. This demonstrates the aerodynamic capability of the designed blades to extract power from the wind.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.658-665
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• 2002

This paper presents a new winding method in electronic descaling (ED) technology. Conventional ED technology Produces an oscillating electric field via Faraday's law to provide the necessary molecular agitation to dissolve mineral ions. However, the proposed method produces an additional agitation force for mineral ions, called Lorentz's force. Experiments were performed using various Renolds numbers. A series of tests was conducted to measure the pressure drop across the test section and the overall heat transfer coefficient as a function of time. In order to accelerate the rate of fouling, artificial hard water, 1000ppm CaCO$_3$, was used throughout the tests. The results show that the new winding method accelerates the collision of the mineral ions, thereby improving the system efficiency. The present study can develope more effective fouling-removing equipment with change of estabishment method of coil.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.7
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• pp.621-627
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• 2013

Field tests of hybrid desiccant cooling systems were conducted from July to August 2011. Data were monitored and transferred in real time over the Internet. The monitored variableswere analyzed to determine the performance characteristics under outdoor conditions. A series of system simulations has been conducted for outdoor conditions of the field tests. The results agree well with the experimental data in general. The system performance has been shown to deteriorate for wetter conditions, as predicted by the simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.10
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• pp.866-872
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• 2008

Torsional oscillations of the mechanical drivetrain in electric vehicles are generated under rapid driving conditions. These lead to an uncomfortable jerking of the vehicle and to an increased stress of the mechanical components. To analyze this phenomenon, a drivetrain model is constructed with lumped parameters. The model parameters are identified by geometrical design data and experimental tests. The proposed model is validated by simulation and experimental tests in the time and the frequency domains. As a result, the torsional oscillations are observed at 7Hz of a low damped natural frequency. Also, the analysis of the effect of the parameter variations on the oscillations shows that the oscillation characteristic is mainly dependent on the rotor inertia, and the stiffness of the mounting of the drive aggregate and the driveshaft. The results will be utilized on the basis of the design of an electric drivetrain and an active control of drivetrain oscillations.

• Tunnel and Underground Space
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• v.18 no.5
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• pp.317-327
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• 2008

About 70% of domestic land is mountainous and the construction of many geotechnical structures is inevitable for building transportation networks across region. Many geotechnical surveys, including rock physical and mechanical tests, are performed during construction. Thus study is a basic research for establishing database of physical and mechanical properties in domestic rocks, and analyzing the rock mechanical relationships between 2,000 rock properties obtained from laboratory tests in KOLAS. For the construction of useful database, systematic management, based on the standard information as well as reliable data accumulation, is required.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.145-151
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• 2008

Material degradation such as high temperature oxidation of metallic material is a severe problem in energy generation systems or manufacturing industries. The metallic materials are oxidized to form oxide films in high temperature environments. The oxide films act as diffusion barriers of oxygen and metal ions and thereafter decrease oxidation rates of metals. The metal oxidation is, however, accelerated by mechanical fracture and spalling of the oxide films caused by thermal stresses by repetition of temperature change, vibration and by the impact of solid particles. It is therefore very important to investigate mechanical properties and adhesion of oxide films in high temperature environments, as well as the properties in a room temperature environment. The oxidation tests were conducted for Ni and Ni-Co alloy under high temperature corrosive environments. The hardness distributions against the indentation depth from the top surface were examined at room temperature. Dynamic indentation tests were performed on Ni oxide films formed on Ni surfaces at room and high temperature to observe fractures or cracks generated around impact craters. As a result, it was found that the mechanical property as hardness of the oxide films were different between Ni and Ni-Co alloy, and between room and high temperatures, and that the adhesion of Ni oxide films was relatively stronger than that of Co oxide films.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.1-7
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• 2018

The Continuous Ship Unloader (CSU) is an equipment that unloads freight from the ship docked in the port to the land. And the design target life time is designed to be 30 to 50 years, and it is classified as a semi-permanent large facility. However, cracks may occur due to structural defects, abnormal loads, and corrosion, and fatigue failure may occur before the design life is reached. In this study, we predicted the remaining life time of the main component of the CSU considering crack. And also proposed inspection cycle for maintenance of CSU based on the results of the remaining life time prediction. For this purpose, the structure, operational stresses of the CSU were analyzed and main members were selected. And tensile tests and fatigue crack propagation tests were performed with SM490YA and SM570TMC, which are used as main materials for CSU.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.5
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• pp.153-160
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• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.3
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• pp.107-112
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• 2021

Pressure, which is a dynamic characteristic of a floodgate, is predicted using an FSI analysis method. A fluid analysis model and a hydrology analysis model were used as analysis models. As a result of the analysis, we found that a warped model has smaller acceleration than a square model. Additionally, this numerical analysis technique was applied to the actual hydrology, and the analysis results were compared with the results of the vibration tests. As a result, we confirmed that there is a small difference between the results of the vibration tests and the results of the FSI analysis. Through this analysis, the applicability and reliability of the FSI analysis method were verified. We concluded that the pressure of a floodgate can be measured through an FSI analysis method.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.425-430
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• 2005

This Study presents to be Agitator maintenance for Water and Wastewater treatment Plant. This procedures offers methods of Design Creteria and performance tests on mixing equipment. These tests may be conducted to determine process performance, mechanical reliability. or suitability of equipment for the intended use. The reasons for conducting performance tests can be varied, but the methods presented should be generally applicable to most situations.