• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.2
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• pp.29-37
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• 1996

High speed engines with high power are increasingly on demands and almost engines employ crankshafts Such problems as bending and torsional vibrations become the point at issue in crankshaft analysis and design. In this study to overcome the diffiiculty with the large amount of computation in finite element vibration analysis of a crankshaft, a reduction method based on influence coefficient and lumped parameter is presented. which reduces the computation amount effectively and can be used in vibrational analysis and design of any types of crankshafts Crank journal and pinparts are meodelled as elements with 6degrees of freedom per node. Crank web part is modelled using equivalent mass and stiffness matices . based up on lumped parameter and influence coefficient respectively to reduce total degrees of freedom considerablely. To confirm the scheme of the study the results are compared with the known data and they are coincident. Also a simple crankshaft is designed and manufactured for experiments. The calculated results using reduction method and the experimental results agree well The scheme of this study can be utilized in evaluation results agree well. The calculated result are compared with the known data and they are coincident. Also a simple crankshaft is designed and manufactured for experiments. The calculated results using reduction method and the experimental results agree well. The scheme of this study can be utilized in evaluation and development of high speed engine.

• Journal of Environmental Health Sciences
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• v.16 no.2
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• pp.55-61
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• 1990

Laboratory methods commonly used today are biochemical oxygen demand, chemical oxygen demand, and total organic carbon. Establishment of constant relationships among the various measures of organic content depends primarily on the nature of the wastewater and its source. Of all the measures, the most difficult to correlate to the others is the BODs test, because of the problems associated with biological tests. The results were summarized as follwos, 1. For typical municipal wastes, however, the SBOD$_{5}$/SCOD$_{cr}$ ratio varies from 0.14 to 0.34(mean 0.21), SBOD$_{5}$/STOC ratio varies from 0.35 to 1.19(mean 0.69) 2. Correlation analysis between the SBOD$_{5}$ and SCOD$_{cr}$ gave good correlation coefficient r = 0.903 and the equation Y = 3.756X + 16,221 was obtained. 3. The correlation between the SBOD$_{5}$ and STOC was well presented with equation : Y = 1,070X + 7,637, and also correlation coefficient r = 0.821 4. The correlation between the SCOD$_{cr}$ and STOC was well presented with equation : Y = 0.256X +5.513 and also correlation coefficient r = 0.816. 5. Because of the rapidity with which the TOC test can be conducted, it is anticipated that more use will be made of these tests in the future.

• Journal of Environmental Science International
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• v.18 no.11
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• pp.1299-1307
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• 2009

In order to measure in-situ suspended particle size, volume concentration of suspended particulate matter and current speed, mooring observation was performed at the Gwangyang Bay by using of an optical instrument, 'LISST-100' and an acoustic instrument, 'ADV'(St. S1). And the sediment flux was obtained based on the concentration of suspended particulate matter and current speeds measured at three lines of Gwangyang Bay during ebb and flood tide of August 2006. To investigate the spatial variation of suspended particulate matter, profiling observations were measured difference echo intensity and beam attenuation coefficient by using of ADCP and Transmissometer (Line A, B, C). The suspended sediment flux rate at the mouth of Gwangyang Bay was observed to be higher during asymmetrical than symmetrical of current speeds. The flux of suspended particulate matter concentration and current speeds were transported to southeastern direction of surface layer and northwestern direction of bottom layer at the western area at line A of Gwangyang Bay. Small suspended particles have been found to increase attenuation and transmission more efficiently than similar large particles using acoustic intensity (ADV/ADCP) or optical transmit coefficient (LISST-100/Transmissometer). The application and problems as using optical or acoustic instruments will be detected for use in time varying calibrations to account for non-negligible changes in complex environments in situ particle dynamics are poorly understood.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.2
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• pp.170-177
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• 1998

The purpose of superconducting magnetic bearing flywheel energy storage system(SMB-FESS) is to store unused nighttime electricity as kinetic energy and convert it to electricity during daytime. The SMB-FESS is proposed as an efficient energy storage system because there is no mechanical problems, such as friction and wear The flywheel over SMB is rotated at a high speed, 50,000rpm. The major source of energy loss in the SMB-FESS is vibration of flywheel. Therefore, the vibration characteristics of SMB-FESS should be identified. In this study, the axial/radial stiffness and damping coefficient of SMB are measured by a vibration test. Natural frequencies and natural modes of flywheel and magnet are analyzed by a finite element method. The modal analysis of system is performed using the modal parameters of each component and the measured stiffness/damping coefficient. So, natural at frequencies and mode shapes of the joined system can be obtained. According to critical speed analysis, the system has two rigid conical modes in the low speed range. Nevertheless, the system has not been affected by the critical speed in the main operating range.

• Journal of Power System Engineering
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• v.5 no.4
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• pp.82-89
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• 2001

To design a structural or a mechanical system with the best performance, the main procedure of a typical design usually consists of repeated modifications of design parameters and the investigation of the system response for each set of these parameters. But this procedure requires much time, effort and experience. Sensitivity analysis can provide systematic information for improving performance of a system. The author has studied on the development of the structural analysis algorithm and suggested recently the transfer stiffness coefficient method(TSCM). This method is very suitable algorithm to a personal computer because the concept of the TSCM is based on the transfer of the nodal stiffness coefficients which are related to force and displacement vectors at each node. In this paper, a new sensitivity analysis algorithm using the concept of the TSCM is formulated for the computation of state variable sensitivity in static problems. The trust of the proposed algorithm is confirmed through the comparison with the computation results using existent sensitivity analysis algorithm and reanalysis for computation models.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.430-437
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• 2000

Fertilizer impaction mechanism was simulated using a commercial program RecurDyn$^{(R)}$ a dynamic program that could handle contact problems. Even if there had been numerous papers on modeling of fertilizer applicator, the performance predictions were not satisfactory due to simplification in modeling. The most significant simplification was assumption of fertilizer particles as a solid particle. The assumption would eliminate rotation of fertilizer particles during the impaction mechanism. However, impaction of rotating body would be different from that of a solid particle. This paper introduced how the impaction was modeled using RecurDyn$^{(R)}$. In order to simulate, restitution coefficient and contact time was measured. A stiffness coefficient and a damping coefficient of a fertilizer was theoretically estimated using the measured data. Validity of the simulation result was not proved yet, but judged to be promising.ged to be promising.ing.

• Journal of Digital Convergence
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• v.11 no.9
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• pp.147-151
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• 2013

On retrieving high frequency keywords in information retrieval system, mismatchings to user's request are problems because of the various meanings of keywords in the existing ontology configuration. In this paper, it is to construct personnel selection ontology and rules in personnel management which are composed of various concepts and knowledges based on semantic web technology and suggest selection procedures to support these rules and knowledge retrieval system to verify suitability of selection results. This system utilizes a method of extraction of speech features by using non-parametric correlation coefficient. This proposed method has been validated by showing that the result average SNR of the experiment evaluation of the proposed techniques was shown to be decreased by .752dB.

• Journal of the Korean institute of surface engineering
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• v.49 no.1
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• pp.104-109
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• 2016

Graphite's thermal stability facilitates its widespread use as crucibles and molds in high temperatures processes. However, carbon atoms can be rather easily detached from pores and outer surfaces of the graphite due to the weak molecular force of the c axis of graphites. Detached carbon atoms are known to become a source of dust during fabrication processes, eventually lowering the effective yield of products. As an effort to reduce these problems of dust scattering, we have fabricated SiC composites by employing Si vapor infiltration method into the pores of graphites. In order to understand the diffusion process of the Si vapor infiltration, Si and C atomic percentages of fabricated SiC composites are carefully measured and the diffusion law is used to estimate the diffusion coefficient of Si vapor. A quadratic equation is obtained from the experimental results using the least square method. Diffusion coefficient of Si vapor is estimated using this quadratic equation. The result shows that the diffusion length obtained through the Si vapor infiltration method is about 10.7 times longer than that obtained using liquid Si and clearly demonstrates the usefulness of the present method.

• Tribology and Lubricants
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• v.30 no.6
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• pp.356-363
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• 2014

Marine diesel engines operate in environments in which damage easily occurs from corrosion. Recently, damage to cylinder liners has increased from corrosion wear caused by increased engine power. This damage can cause serious problems in the economy. Thus, many researchers have treated and studied damaged cylinder liners. However, a method is necessary for real-time monitoring of damage to cylinder liners during operation of the engine, before serious damage can occur. This study carries out reciprocating friction and wear tests on a cast iron specimen under various corrosion atmospheres and verifies the variations of friction coefficient and friction surface. Additionally, the friction coefficient and friction status are predicted by using a neural network that learns the vibration and frequency spectrum data from an acceleration sensor. According to our conclusions, amplitude is distributed highly at high frequencies, and values of standard deviation and kurtosis are high when damage to the friction surface is serious. The accuracy rate of the friction coefficient predicted by the neural network is over 80% of the real measured value without NaCl, and application of the neural network is very effective for diagnosing the friction condition and damage to the cylinder liner.

• Journal of Information Processing Systems
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• v.17 no.5
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• pp.1004-1019
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• 2021

To solve the problems of the low image contrast, fuzzy edge details and edge details missing in noisy image fusion, this study proposes a noisy infrared and visible light image fusion algorithm based on non-subsample contourlet transform (NSCT) and an improved bilateral filter, which uses NSCT to decompose an image into a low-frequency component and high-frequency component. High-frequency noise and edge information are mainly distributed in the high-frequency component, and the improved bilateral filtering method is used to process the high-frequency component of two images, filtering the noise of the images and calculating the image detail of the infrared image's high-frequency component. It can extract the edge details of the infrared image and visible image as much as possible by superimposing the high-frequency component of infrared image and visible image. At the same time, edge information is enhanced and the visual effect is clearer. For the fusion rule of low-frequency coefficient, the local area standard variance coefficient method is adopted. At last, we decompose the high- and low-frequency coefficient to obtain the fusion image according to the inverse transformation of NSCT. The fusion results show that the edge, contour, texture and other details are maintained and enhanced while the noise is filtered, and the fusion image with a clear edge is obtained. The algorithm could better filter noise and obtain clear fused images in noisy infrared and visible light image fusion.