• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2913-2917
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• 2007

Turbocharger has been widely used in many passenger cars in application with diesel engines because of high power and fuel efficiency. However, flow-induced noise (whoosh or hissing noise) which is generated within the compressor during its operation at marginal surge line can deteriorate noise characteristics. Hissing noise excitation was associated with the generation of turbulence within the turbocharger compressor and radiated through the transmission path in turbocharger system. In this study, a sharp-edged reactive-type muffler was devised and installed in the transmission path to reduce the hissing noise. Acoustic and fluid dynamic characteristics for the muffler were investigated which is related to the unsteadiness of turbulence and pressure in turbocharger system. A transfer matrix method was used to analyze the transmission loss of the muffler. Simple expansion muffler with extended tube of the reactive type is proposed for the reduction of high frequency component noise. Turbulence computation was carried out by a standard ${\kappa}-{\varepsilon}$ model. An optimal design condition of the muffler was obtained by extensive acoustic and fluid dynamic analysis on the engine dynamometer with anechoic chamber. A significant reduction of the hissing noise was achieved at the optimal design of the muffler as compared with the conventional turbocharger system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.4
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• pp.310-318
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• 2004

For many industrial problems originating from aerodynamic noise, noise prediction techniques, reliable and easy to apply, would be of great value to engineers and manufacturers. General algorithm is presented for the prediction of internal flow-induced noise from quick opening throttle valve in an automotive engine. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curle's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve show good agreement with actual measurements. The results show that the dipole noise is dominant in this phenomena and the origin of noise sources is attributed to the anti-vortex lines formed in the down-stream from a throttle valve. This illustrative computation shows that the current method permits generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.26-32
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• 2006

This paper targets a direct and quantitative prediction of characteristics of unstable waves in a combustion chamber, which employs the governing equations derived in terms of amplification factors of flow variables. A freshly formulated nonlinear acoustic equation is obtained and the analysis of unsteady waves in a rocket engine is attempted. In the present formalism, perturbation method decomposes the variables into time-averaged part that can be obtained easily and accurately and time-varying part which is assumed to be harmonic. Excluding the use of conventional spatially sinusoidal eigenfunctions, a direct numerical solution of wave equation replaces the initial spatial distribution of standing waves and forms the nonlinear space-averaged terms. Amplification factor is also calculated independently by the time rate of changes of fluctuating variables, and is no longer an explicit function for compulsory representation. Employing only the numerical computation, major assumptions inevitably inherent, and in erroneous manner, in up to date analytical methods could be avoided. With two definitions of amplification factor, 1-D stable wave and 3-D unstable wave are examined, and clearly demonstrated the potentiality of a suggested theoretical-numerical method of combustion instability.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06b
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• pp.111-115
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• 1998

The Internet today is teemed with not only text data but also other media such as sound, still and moving images in a variety of formats. Unlike text, however, that can be retrieved easily with the help of numerous search engines, there has been few way to access data of other media unless the exact location or the URL is known. Multimedia data in the WWW are contained in or linked via anchors in the hyper-documents. They can most reliably be retrieved by analyzing the binary data content, which is far from being practical yet by the current state of the art. Instead we present another technique of searching based on textual descriptions which are found at or around the multimedia objects. The textual description used in this research includes file name (URL), anchor text and its context, alternative descriptions found in ALT HTML tage. These are actually the clues assumedly relevant to the contents. Although not without a possibility of missing or misinterpreting images and sounds, the description-based search is highly practical in terms of computation. The prototype search engine will soon be deployed to the public service through the prestige search engine, InfoDetective, in Korea.

• The Journal of the Acoustical Society of Korea
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• v.22 no.4E
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• pp.183-196
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• 2003

General algorithm is developed for the prediction of internal flow-induced noise. This algorithm is based on the integral formula derived by using the General Green Function, Lighthill's acoustic analogy and Curl's extension of Lighthill's. Novel approach of this algorithm is that the integral formula is so arranged as to predict frequency-domain acoustic signal at any location in a duct by using unsteady flow data in space and time, which can be provided by the Computational Fluid Dynamics Techniques. This semi-analytic model is applied to the prediction of internal aerodynamic noise from a throttle valve in an automotive engine. The predicted noise levels from the throttle valve are compared with actual measurements. This illustrative computation shows that the current method penn its generalized predictions of flow noise generated by bluff bodies and turbulence in flow ducts.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.329-334
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• 2014

This paper proposes the hardware architecture of high performance multi-mode 2D forward transform for HEVC which has same number of cycles for processing any type of four TUs and yield high throughput. In order to make the original image which has high pixel and high resolution into highly compressed image effectively, the transform technique of HEVC supports 4 kinds of pixel units, TUs and it finds the optimal mode after performs each transform computation. As the proposed transform engine uses the common computation operator which is produced by analyzing the relationship among transform matrix coefficients, it can process every 4 kinds of TU mode matrix operation with 35cycles equally. The proposed transform block was designed by Verilog HDL and synthesized by using TSMC 0.18um CMOS processing technology. From the results of logic synthesis, the maximum operating frequency was 400MHz and total gate count was 214k gates which has the throughput of 10-Gpels/cycle with the $4k(3840{\times}2160)@30fps$ image.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.421-427
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• 2005

This work analyzes the behaviors of aerated lubricant in the gap between con-rod bearing and journal. It is assumed that the film formation with aerated lubricant is influenced by the two major factors. One is the density characteristics of the lubricant due to the volume change of lubricant for the formation of bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble in the lubricant. These two major factors surprisingly increase the load capacity in some ranges of bubble sizes and densities. Modified Reynolds' equation is developed for the computation of fluid film pressure with the effects of aeration ratio in the lubricant. From the calculated load capacity by solving modified Reynolds' equation, journal locus is computed with Mobility method after comparing it with the applied load at each time step. The differences of journal orbits between aerated and pure lubricants are shown in the computed results.

• Journal of information and communication convergence engineering
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• v.9 no.3
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• pp.266-270
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• 2011

The advancement of technology enables smart phones or handheld devices to render complex 3D graphics. However, the processing power and memory of smart phones remain very limited to render high polygon and details 3D models especially on games which requires animation, physic engine, or augmented reality. In this paper, several techniques will be introduced to speed up the computation and reducing the number of vertices of the 3D meshes without losing much detail.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.63-69
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• 2001

The transient flow fields in direct injection engines were analyzed by using the STAR-CD CFD code during the intake/compression processes. The analyses were focused on the computation grid generation by using the IC3M code which is a pre-developed and especially well adapted for the analyses of internal combustion engines. The results showed that the used grid generation technique was well suited for the flow analyses on any internal combustion engines.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.112-117
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• 2007

With the Euro-4 regulation coming into effect, the domestic car industry is forced to look for newer options to reduce NOX in the exhaust. EGR(Exhaust Gas Recirculation) Cooler is an effective method for the reduction of NOX form a diesel engine. High efficiency, low pressure loss and compactness are desirable features of an EGR Cooler. The cooling performance of EGR depends on the shape of tubes and the location of the entrance and exit. This paper reports the computational work conducted to estimate the performance of EGR cooler with three different cross section tubes and a triangular spiral tube. Three dimensional computation results show that the triangular tube is more effective than circular and rectangular tube. The most effective geometry is a triangular spiral tube with offset inlet and outlet locations.