• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2007.11a
• /
• pp.469-473
• /
• 2007

For the quantitative analysis of inclusion using OES data, separating of noise and inclusion is needed. In previous methods assuming that noises come from a normal distribution, intensity levels beyond a specific threshold are determined as inclusions. However, it is not possible to classify inclusions in low intensity region using this method, even though every inclusion is an element of some chemical compound. In this paper, we assume that distribution of OES data is a Gaussian mixture and estimate the parameters of the mixture model using EM algorithm. Then, we calculate mixing ratio of noise and inclusion using these parameters to separate noise and inclusion.

• Journal of Power System Engineering
• /
• v.17 no.6
• /
• pp.142-148
• /
• 2013

High-power ultrasonic promotes a chemical reaction by its own energy, thus it has been used for sonochemistry applications. For example, it has been mostly used for mixing, reaction catalyst, dispersion and disintegration. High-power ultrasonic transducer is made with structure based on a Bolt-clamped Langevin type Transducer (BLT), But it has difficulty in the development because degradation of piezoelectric ceramic by the heat generation of BLT. In this study, for a development of the transducer of 25 kHz and 1000 W used in sonochemistry and industrial cleaning, BLT with a hole in its center and tubular type waveguide of the transducer were designed based on finite element method (FEM). The transducer was fabricated based on the design parameter, and the impedance characteristics are measured experimentally and compared with the numerical results.

• Journal of Ocean Engineering and Technology
• /
• v.12 no.3 s.29
• /
• pp.68-74
• /
• 1998

An increase of concrete construction in marine environments as well as an increasing use of marine aggregate at the mixing stage of concrete has provoked an important problem. A high concentration of chloride ion in the vicinity of steel bars in concrete is the principal cause of premature reinforcement corrosion in concrete structures. In this study, the behavior of chloride ions introduced into concrete from concrete surface by marine evironment was analysed. A mathematical model including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete and the chemical reactions of chloride ions with solid phase was presented. Finite element method was employed to carry out numerical analysis. The results of this study may be used to predict the onset of reinforcement corrosion and to identify the maximum limit of chloride ions contained in concrete admixtures.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.122-128
• /
• 2003

Rock bolts are widely used as a supplementary roof support system in hard-rock mining since a long time. Since the performance of fully grouted passive bolts depends on bond strength, in the present investigation extensive laboratory pull-out as well as push-out tests were conducted varying the bolt diameter, length and cement-water mixing ratios of grout. The load-displacement curves were developed and were verified with the numerical results obtained from finite element analysis using ALGOR software. Numerical models were validated for push-out tests and a detailed analysis was carried out to know the displacement, stress, strain distribution along the bolt.

• Applied Microscopy
• /
• v.45 no.2
• /
• pp.52-57
• /
• 2015

Bulk metallic glass (BMG) shows higth strength, high elastic limit, corrosion resistance and good wear resistance and soft magnetic properties and has been considering as a candidate for new structural materials. But they show limited macroscopic plasticity and lack of tensile ductility due to highly localized shear deformation, which should be solved for real structural application. In this paper researches on the enhancement of plasticity of BMG were reviewed briefly. Introducing heterogeneous structure in glass is effective to induce more shear transformation zones (STZs) active for multiple shear band initiation and also to block the propagating shear band. Several methods such as BMG alloy design for high Poisson's ratio, addition of alloying element having positive heat of mixing, pre-straining BMG and variety of BMG composites have been developed for homogenous distribution of locally weak region, where local strain can be initiated. Therefore enhancement of plasticity of BMG is normally accompanied with some penalty of strength loss.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1997.10a
• /
• pp.269-274
• /
• 1997

Recently, premature reinforcement corrosion in concrete structures exposed to chloride containing environments has an important problem. This is due to an increasing use of marine aggregate of chloride containing admixture a the mixing stage and due to an increase of concrete construction in marine environments. In this study, the behavior of chloride ions introduced into concrete from concrete surface by a marine environment was modeled. The physicochemcial processes including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reaction of chloride ion with solid phase were analyzed by using the finite element method. The results of this study may be used to predict the onset of reinforcement corrosion, and identify the maximum limit of chloride ions contained in admixtures.

• Proceedings of the KSME Conference
• /
• 2001.06a
• /
• pp.860-864
• /
• 2001

Today's industrialized plants are required to reduce SOx emitted from stacks at factories, utility power stations, etc. For this purpose, flue gas desulfurization (FGD) system is installed and gas-gas heater (GGH) is used to play a vital role to reheat the wet treated gas from FGD. The sector plates are located at cold and hot sides of gas gas heater. They serve as sealing to prevent mixing treated and untreated gases. Therefore, the deformation of the sector plate due to its dead weight and gas pressure should be considered as major factor for the sector plate design.

• Proceedings of the KSME Conference
• /
• 2000.04b
• /
• pp.574-579
• /
• 2000

In this study. an off-design performance prediction program for centrifugal pumps is developed. To estimate the losses in an impeller flow passage, two-zone model and two-element in series(TEIS) model are used. At impeller exit. the mixing process occurs with an increase in entropy. In two-zone model. there are both primary zone and secondary zone for an isentropic core flow and an average of all non-isentropic streamtubes respectively. The level of the core flow diffusion in an impeller was calculated by using TEIS model. While internal losses in an impeller an automatically estimated by using the above models, some empirical correlations far estimating external losses. far example, disk friction loss, recirculation loss and leakage loss are used. In order to analyze the vaneless diffuser flow. the momentum equations for the radial and tangential directions are used and solved together with continuity and energy equations.

• The KSFM Journal of Fluid Machinery
• /
• v.8 no.6 s.33
• /
• pp.33-39
• /
• 2005

A thermal vapor compressor in which the subsonic/supersonic flow appears simultaneously, has been accurately designed through the CFD analysis for the various shape parameters such as the primary nozzle shape, converging duct shape, mixing tube diameter, and so on. The performance of the developed thermal vapor compressor has been experimentally verified to be installed in a Multi Effect Desalination(MED) plant as an important element. In this paper, the effects of each parameter are discussed on the basis of CFD results and the experimental results for various boundary conditions(motive pressure, suction pressure, and discharge pressure) are presented in compared with CFD results. The two results show a good agreement with each other within 2 % accuracy with regard to the entrainment ratio.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.14 no.7
• /
• pp.599-606
• /
• 2002

uniform temperature. The surfaces of the block are taken at a constant higher temperature. The channel walls are assumed to be adiabatic. Results on the time-dependent temperature field are obtained and averaged over a cycle of pulsation. The effect of the important governing parameters, such as the Strouhal number on the flow and the heat transfer is investigated in detail. The results indicate that the recirculating flow behind the block are substantially affected by the pulsation frequency. These, in turn, have a strong influence on the thermal transport from the heated element to the pulsating flow. The frequency at which the enhancement is maximum is determined.