• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.551-554
• /
• 2005

This study uses a characteristic function to explain correlations between the objective function and design variables. Analysis of means and table of orthogonal array were carried out. The change of shape of diaphragm, thickness of diaphragm and voice coil weight based on the table of orthogonal array is made. Therefore this study carried to decide shape of diaphragm, voice coil weight and thickness of diaphragm for minimizing 1st natural frequency and maximizing 2nd natural frequency of diaphragm using design of experiments and characteristic function with constraints. we showed improved design factors that minimized 1st natural frequency and maximized 2nd natural frequency of diaphragm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.11a
• /
• pp.686-689
• /
• 2006

In a wheel loader, the tail-pipe is installed at the exhaust tube of muffler for the reduction of exhaust noise and the cooling of engine room however, the cabin noise level can be largely increased due to the tail-pipe. In this paper, to grasp and reduce the cabin noise, a series of noise and vibration tests were carried out in addition to numerical simulations. As a result, the transmission path of exhaust noise toward the cabin was exactly identified and the improved shape of tail pipe, that can reduce the cabin noise, was derived through various numerical simulations and real tests.

• Proceedings of the KIEE Conference
• /
• 1991.07a
• /
• pp.27-30
• /
• 1991

With the recent development of high performance AC superconducting wire of very small ac loss and large current carrying capacity, the possibility of superconducting air core transformer is being studied. The air core transformer has merits of no iron loss, no insulation to the core and no harmonics. But the air core transformer has large exciting current and low magnetic coupling factor. To increase the coupling factor, the transformer of toroidal shape is proposed and designed. (10KVA, 110/220V) Compared with air core transformer of solenoidal shape, the performance is improved. The exciting current occupies about 22% of the rated current.

• Proceedings of the Korea Society of Information Technology Applications Conference
• /
• 2005.11a
• /
• pp.219-224
• /
• 2005

Developable surface plays an important role in computer aided design and manufacturing systems. This paper is concerned with improving the develop ability of mesh. Since subdivision is an efficient way to design complicated surface, we intend to improve the developability of the mesh obtained from Loop subdivision. The problem is formulated as a constrained optimization problem. The optimization is performed on the coordinates of the points of the mesh, together with the constraints of minimizing shape difference and maximizing developability, a developability improved mesh is obtained.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.30 no.8 s.251
• /
• pp.715-721
• /
• 2006

In the present work, nozzle shape of a jet fan is optimized numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis. Standard $k-{\epsilon}$ model is used as a turbulence closure. Response surface method is employed as an optimization technique. The objective function is defined as maximum throw distance. Three geometric variables, i.e., length and angle of nozzle, and interval between two nozzles, are selected as design variables. As the main result of the optimization, the throw distance has been improved effectively.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.642-945
• /
• 1995

The problem of autobody corrosion has been addressed over the past decade by the increasing use of zinc and zinc alloy costed steels in automotive application. this paper describes the evaluation of formability, weldability and painted corrosion performance of galvalume steel sheet. This paper presents an overview of the program and some initial test results on the weldability, lifetime of the electrode tip shpae of the spot welding and corrosion protection. Galvalume steel sheet improved corrosion performance and spot weldability of galvalume steel has no problem for the variation of welding current. And tip lifetime was changed according to the influence of shape.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.16 no.12 s.117
• /
• pp.1238-1243
• /
• 2006

In a wheel loader, the tail-pipe is installed at the exhaust tube of muffler for the reduction of exhaust noise and the cooling of engine room, however, the cabin noise level can be largely increased due to the tail-pipe. In this paper, to grasp and reduce the cabin noise, a series of noise and vibration tests were carried out in addition to numerical simulations. As a result, the transmission path of exhaust noise toward the cabin was exactly identified and the improved shape of tail pipe, that can reduce the cabin noise, was derived through various numerical simulations and real tests.

• Journal of the Korean Society of Industry Convergence
• /
• v.3 no.1
• /
• pp.29-36
• /
• 2000

In order to reduce a aerodynamic drag of the rear, body, effects of rear lower end configuration of a vehicles were investigated by measuring the pressure distribution, visual flow phenomena by the use of digital image processing technique. The use of flow visualization in recent years has improved the general understanding of structure of complex flow and has yielded valuable information for analyzing fluid flow. As the results, it was found that the shape of rear lower part vehicles not only effected on the pressure distribution of the rear part of the vehicle but also difference of the flow phenomena.

• Earthquakes and Structures
• /
• v.15 no.3
• /
• pp.263-273
• /
• 2018

Operational modal analysis is being widely used in aerospace, mechanical and civil engineering. Common research fields include optimal design and rehabilitation under dynamic loads, structural health monitoring, modification and control of dynamic response and analytical model updating. In many practical cases, influence of noise contamination in the recorded data makes it difficult to identify the modal parameters accurately. In this paper, an improved frequency domain method called Enhanced Least Square Complex Frequency (eLSCF) is developed to extract modal parameters from noisy recorded data. The proposed method makes the use of pre-defined approximate mode shape vectors to refine the cross-power spectral density matrix and extract fundamental frequency for the mode of interest. The efficiency of the proposed method is illustrated using an example five story shear frame loaded by random excitation and different noise signals.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.10a
• /
• pp.74-77
• /
• 2000

Porthole die extrusion has a great advantage in the forming of hollow section tubes difficult to produce by conventional extrusion with a mandrel on the stem. Because of the complicated structure of die assembly, extrusion process as a forming of hollow section tubes has been investigated experimentally Therefore, analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded Welding strength is affected by many parameters, which are such as extrusion ratio, extrusion speed, die shape, porthole number, bearing length, billet temperature and mandrel shape. In this paper, the parameters, which are such as billet temperature, bearing length and tube thickness, are examined. The welding pressures are examined through 3D simulation of non steady state and compared with experimental results.