• The KSFM Journal of Fluid Machinery
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• v.5 no.1 s.14
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• pp.13-19
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• 2002

In the present study, a numerical simulation is performed for the flow through a cooling fan. The computation was performed by using commercial code, STAR-CD. A rotating fan was simulated by rotational motions using MRF (Multiple Rotating Reference Frame) in a steady-state analysis and sliding interface (rotating meshes) in an unsteady-state analysis. The results of numerical computation were in good agreement with experimental data. In order to calculate the acoustic signal, the unsteady flow-field was firstly calculated. The acoustics of the fan is calculated by using acoustic analogy based on the unsteady flow-field. The predicted acoustic signal shows the characteristics of the uneven bladed-fan.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.10 s.181
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• pp.2529-2534
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• 2000

Torsional vibration analysis in a large two -stroke low speed diesel engine and generator system for stationary power plants is performed to verify that the vibration characteristics of shafting system meet design requirements. Our own developed S/W is employed for the analysis, whose results are evaluated comparing with measurements. Vibration analysis results of the system are presented according to the change of loading(unload, 100%load, 110% load) and operating(mis-firing, uneven firing) conditions of the stationary power plants.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.6
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• pp.494-500
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• 2004

This paper presents a machine vision system, which inspects the measurement of the ALC block on a real-time basis in the production process. The automatic measurement system was established with a CCD camera, an image grabber, and a personal computer without using assembled measurement equipment. Images obtained by this system was processed by an algorithm, specially designed for an enhanced measurement accuracy. For the realization of the proposed algorithm, a preprocessing method that can be applied to overcome uneven lighting environment, boundary decision method, unit length decision method in uneven condition with rocking objects, and a projection of region using pixel summation are developed. From our experimental results, we could find that the required measurement accuracy specification is sufficiently satisfied by using the proposed method.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.888-893
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• 2008

In This paper proposes the control algorithm for quadruped robots on irregularly sloped uneven surface. Body balance is important in stable running locomotion. Since the body balance is determined by the forces applied at the feet during touchdown phase, the ground reaction force is controlled for stable running. To control the forces at each foot, the desired force is generated. The generated desired force is compared with actual contact force, then, the difference between them modifies the foot trajectory. The desired force is generated by combination of the rate change of the angular and linear momentum at flight. Then the rate change of momentum determines each force distribution. The distribution of the force is carried out by fuzzy logic. The computer simulation is carried out with the commercial software RecurDyn$^{(R)}$. Dynamic model simulation program show that the stable running on the irregularly sloped uneven surface are accomplished by the proposed method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.690-695
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• 2006

This paper described the Performance test and sound characteristics of helicopter 'Tail-Fan' anti-torque system. In this research, Korea Aerospace Research Institute(KARI) developed 'Tail-Fan' anti-torque system for a helicopter and carried out performance and sound capturing tests of even and uneven tail fans. The performance test is carried out and the noise signals which are generated during the test are saved with microphones at the same time. The performance test's results meet the design requirements. Tone-corrected perceived noise level is reduced by replacing the even product with the uneven one.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.12
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• pp.1167-1174
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• 2004

The method to consider gravity effect on the performance of a condenser is developed, and a simple condenser having 'nU' type two circuits is analyzed. Each circuit has the same length and inlet air-side operational conditions. The only difference between two circuits is the direction of refrigerant flow, which is exactly opposite each other between the upper 'n' type circuit and the lower 'U' type circuit. It is shown that the gravity makes the distribution of refrigerant flow uneven in the two circuits at lower refrigerant flow rates; heat transfer rate also becomes uneven. Moreover, much of the refrigerant exists as liquid state in the circuit having low refrigerant flow rate, which will make the cycle balance unstable in the refrigeration cycle system like a heat pump.

• Journal of Magnetics
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• v.18 no.3
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• pp.357-360
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• 2013

A modified SQI method using magnetic leakage flux (MFL) signal for underground gas pipelines' defect detection and characterization is presented in this paper. Raw signals gathered using MFL signals include many unexpected noises and high frequency signals, uneven background signals, signals caused by real defects, etc. The MFL signals of defect free pipelines primarily consist of two kinds of signals, uneven low frequency signals and uncertain high frequency noises. Leakage flux signals caused by defects are added to the case of pipelines having defects. Even though the SQI (Self Quotient Image) is a useful tool to gradually remove the varying backgrounds as well as to characterize the defects, it uses the division and floating point operations. A modified SQI having low computational complexity without time-consuming division operations is presented in this paper. By using defects carved in real pipelines in the pipeline simulation facility (PSF) and real MFL data, the performance of the proposed method is compared with that of the original SQI.

• Wind and Structures
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• v.29 no.1
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• pp.33-41
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• 2019

The interaction of head waves with an infinite row of identical, equally spaced, rectangular breakwaters is investigated in the presence of uneven bottom topography. Using linear water wave theory and matched eigenfunction expansion method, the boundary value problem is transformed into a system of linear algebraic equations which are numerically solved to know the velocity potentials completely. Utilizing this method, reflected and transmitted wave energy are computed for different physical parameters along with the wave field in the vicinity of breakwaters. It is observed that the wave field becomes more complicated when the incoming wavelength becomes smaller than the channel width. A critical ratio of the gap width to the channel width, corresponding to the inflection point of the transmitted energy variation, is identified for which 1/3 of the total energy is transmitted. Similarly, depending on the incident wavelength, there is a critical breakwater width for which a minimum energy is transmitted. Further, the accuracy of the computed results is verified by using the derived energy relation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.38-39
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• 2021

The use of temporary container classrooms has increased in recent years due to the development of the construction industry and renovation or rehabilitation of schools. Therefore, various problems, such as errors during assembling, design and insulation issues, and noise problems, have surfaced during the construction of temporary container classrooms. This study analyzes the causes of assembly errors during the manufacturing and installation processes to improve the quality of temporary container classrooms. Assembly errors are caused by non-level planes and inaccurate cutting during the manufacturing process. In the installation process, poor leveling is a major factor that causes errors during the assembly of temporary container classrooms. These causes result in uneven horizontal or vertical planes and uneven height. To solve these problems, quality improvement measures, such as pin connection, jig, joint coupling, and surface plates are proposed in this study.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.602-606
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• 2008