• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.114-123
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• 2018

Wind power tower (WPT) has been used to augment the performance of vertical axis wind turbine (VAWT). However, the performance of the WPT depends on several design parameters, such as inner and outer radius, or number of guide walls. Therefore, an experimental study was conducted to investigate efficient design parameters on the WPT. A wind tunnel was utilized and its test section dimension was 2m height and 2.2m width. One story model of the WPT was manufactured with seven guide walls and a VAWT was installed within the WPT. Three different sizes of guide walls were applied to test with various design parameters. The power coefficients were measured along the azimuthal direction in a state of equal inlet velocity in order to compare its performance relatively. The experimental results showed that the gap between the inner radius of the WPT and the rotating radius of the VAWT was a major parameter to improve the performance of VAWT within the WPT.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.38-43
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• 1999

An experimental study was carried out, in order to set up the procedure for evaluation of hot fire test, to investigate the effect of mixture on combustion performance and combustion stability , and to determine the optimum design condition for designing the liquid rocket engine. $HNO_3$/Kerosene uni-element liquid rocket engine(thrust 24 $\iota{b}_f$, chamber pressure 200 psia) using impinging streams doublet injector was designed, and ground hot-fire test was carried out. To prevent or reduce the hard start during ignition period, two step ignition method was used. This was accomplished by maintaining about 25% of the designed operating pressure doting transient period, then chamber pressure was built up to the designed operating pressure. Maximum combustion efficiency was at O/F ratio 3.6, and combustion efficiency is decreased with increasing momentum ratio.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.143-148
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• 2011

In this study, the damage to the bridge structure such as the crack and water leakage was assessed due to the increase of the vehicle load and traffic on the roads. In order to make this into the database, as a part of the automation system development for the bridge maintenance, the students themselves designed and developed their own inspection robotic system based on the idea of robots currently being developed overseas. Its field testing was conducted and its applicability assessed. During the design and fabrication, its connection to the details of the unit course taken in the undergraduate level was focused. In terms of new product development, the field application was possible due to the support of the academic-industrial cooperation firms. Furthermore, through the survey of the students, the improvements in the practical skills of the students who participated in this development process was affirmed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.1008-1015
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• 2015

Thermal vacuum test should be performed prior to launch to verify satellites' functionality in extremely cold/hot temperatures and vacuum conditions. A thermal vacuum chamber used to perform the thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the gaseous nitrogen (GN2) closed loop thermal control system for thermal vacuum chambers. A final goal of this research is development of cryogenic blower. Design requirements of a blower are 150 CFM flow rate, 0.5 bara pressure difference, hot and cold temperatures. This paper describes the performance analysis of impeller by 1D, CFD commercial software, the design of the thermal protection interface between the driving part and the fluid part. The performance of the cryogenic blower is confirmed by test at the standard air condition and is verified by on the thermal vacuum chamber at the real operating condition.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.3 s.55
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• pp.33-42
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• 2007

In this study, for research on an improvement of the seismic safety of an EDG system, a small scale EDG system was manufactured. For the isolation system, the Coil Spring-Viscous Damper systems were selected. For the shaking table test, 3 kinds of seismic motions were selected which had different frequency contents. In this study, the isolation effects were different and they depended on the input seismic motion. In the case of an NRC earthquake which had low fiequency contents, the isolation effects of the horizontal direction were 20%. But for the seismic motions which had high fiequency contents, the isolation effects were $50{\sim}70%$. In the case of the vertical direction, poor isolation effects were observed. It was because the design properties and the real properties of the isolation system were a little different.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.279-289
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• 2003

Geosynthetic reinforced earth wall was introduced about 20 years ago and many structures have been constructed. Especially, segmental concrete panel facing and friction tie system are the most popular system in Korea, and this friction tie was composed of high tenacity PET filament and LDPE(Low Density Polyethylene) sheath. Due to the lack of direct-test results, design coefficients of friction tie (creep reduction factor) had been determined by quoting the previous and the foreign reference data. This is an unreasonable fact for the use of friction ties. In this study, the creep tests were performed to evaluate the creep behavior of friction tie, and the reduction factor of creep was calculated for the correct design of geosynthetic reinforced earth retaining walls. From the test results, finally it was found that the allowable creep strength of friction tie is 60% of Tult during service life, and creep reduction factor is 1.67 for each grade of friction ties.

• Journal of the Korea Society for Simulation
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• v.28 no.3
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• pp.11-23
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• 2019

An AddSIM(Adaptive distributed and parallel Simulation environment for Interoperable and reusable Models) is developed to construct a composite environment that can be used in the overall stage from military demand analysis to test and evaluation. In addition, a base system model(BSM), which is a component model of the weapon system with standardized hierarchies, has been developed. This paper describes the critical design of BSM for the guided weapon system that can be operated in AddSIM. The guided weapon system BSM is designed for reusability and interoperability, and to have the same interface for assembly, even if the subcomponents have different resolution. Then, each subcomponent is defined and implemented according to the component resolution classification scheme. Finally, Combinations of subcomponents have been used to construct the guided weapon system of various resolution and the performance is compared and analyzed through simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.65-71
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• 2016

In recent years, 3D printing has received increasing attention due to releases of low-cost 3D printers based on open-source platform. 3D printing is expected to reduce the barrier to entry in the traditional manufacturing processes by increasing flexibility and creating an advantage to manufacture customized products at low costs. In this study, a unique eyeglass frame was designed to have a snake shape, which has an asymmetric geometry unlike traditional frames. The eyeglass frame was designed in a customized manner by reflecting dimensional characteristics of a customer's face. Finite element analysis was performed to investigate the structural safety of the 3D printed frames during the assembly process. The analysis also considered the effect of anisotropic material properties as determined by tensile tests. The eyeglass frame was then printed using the customized sizes and the best building process. The eyeglass frame was successfully assembled with lenses and without structural failure during its assembly procedure.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.432-438
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• 2017

The primary objective of the current work was to develop a standardized retrofit hull form capable of saving energy based on existing vessels. The bow shape of existing vessels was investigated, giving consideration to design draft and speed. Resistance performances were assessed for existing vessels according to operating conditions. Commercial CFD codes and model test materials were used for assessment of effective power. Three retrofit hull forms with minimum resistance were selected given real operating conditions. These vessels were named after customized ready-made hull forms to enable ship owners to make easier choices. The effective power of each vessel was estimated under real operating conditions. Subjects were operated with the lowest draft, and performance for retrofit No. 3 showed an 11-16% improvement in effective power at low speed ranges of 16-18 knots compared to existing vessels. When operated with a middle draft, performance for retrofit No. 3 showed a 6-11% improvement in effective power at low speed ranges compared to existing vessels. When operated with the highest draft, performance for all vessels showed little difference in effective power.

• Journal of Korean Society of Steel Construction
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• v.24 no.2
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• pp.207-215
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• 2012

The 45-degree cone failure theory has been used in concrete anchor bolts design under shear loading, but the CCD (Concrete Capacity Design) method was adopted as a new design method since 2000. However, the method was allowed only for anchor diameters of less than 50mm because it is based on the experimental results of small size anchor bolts. Therefore, it is necessary to develop a rational concrete breakout capacity equation for medium-to-large size anchor bolts with large edge distance. In this study, shear tests on M56 cast-in-place single anchor bolt with edge distance of 350mm were performed using four test specimens. Based on the test results and findings of existing studies, a new equation for the breakout capacity of anchor bolts under shear loading with edge distance of up to 750mm was proposed.