• Transactions of Materials Processing
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• v.27 no.6
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• pp.331-338
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• 2018

Electrohydraulic forming (EHF) process is a high speed forming process that utilizes the electric energy discharge in fluid-filled chamber to deform a sheet material. This process is completed in a very short time of less than 1ms. Therefore, finite element analysis is essential to observe the deformation mechanism of the material in detail. In addition, to perform the numerical simulation of EHF, the material properties obtained from the high-speed status, not quasi static conditions, should be applied. In this study, to obtain the parameters in the constitutive equation of Al 6061-T6 at high strain rate condition, a surrogate model using an artificial neural network (ANN) technique was employed. Using the results of the numerical simulation with free-bulging die in LS-DYNA, the surrogate model was constructed by ANN technique. By comparing the z-displacement with respect to the x-axis position in the experiment with the z-displacement in the ANN model, the parameters for the smallest error are obtained. Finally, the acquired parameters were validated by comparing the results of the finite element analysis, the ANN model and the experiment.

• Journal of the Mineralogical Society of Korea
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• v.18 no.4 s.46
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• pp.249-257
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• 2005

Garnet is one of the major minerals down to the top of lower mantle approximately 660 km with spinel and pyroxenes. Garnet transforms into perovskite and corundum in the lower mantle, however its sequence is still in controversy. We measured the compressibility of a natural almandine at high-pressure up to 62 CPa using Mao-Bell type diamond anvil cell (DAC) at room temperature. Chemical formula of the specimen is ($Fe_{2.52}Ca_{0.21}Mg_{0.18}Mn_{0.12})Al_{2.23}Si_{2.97}O_{12}$. Results of this compression study are as follows: a : $10.175\;{\AA}$, V : $1251.16\;{\AA}^{3}$, $D_{x}$ : $5.265\;g/cm^{3}$ at 62 GPa; bulk modulus is 156 GPa using Birch-Murnaghan equation of state (EoS) with a fixed $K_{0}\;'$ of 4. This study would be the first time attempt accomplished with the high pressure DAC using synchrotron radiation at the Pohang Light Source (PLS) in Korea.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.3 s.309
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• pp.25-33
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• 2006

This paper proposed device-independent color matching algorithm based on the 3D RGB lookup table (LUT) between mobile camera and mobile LCD (Liquid Crystal Display) to improve the color-fidelity. Proposed algorithm is composed of thee steps, which is device characterization, gamut mapping, 3D RGB-LUT design. First, the characterization of mobile LCD is executed using the sigmoidal function, different from conventional method such as GOG (Gain Offset Gamma) and S-curve modeling, based on the observation of electro-optical transfer function of mobile LCD. Next, mobile camera characterization is conducted by fitting the digital value of GretagColor chart captured under the daylight environment (D65) and tristimulus values (CIELAB) using the polynomial regression. However, the CIELAB values estimated by polynomial regression exceed the maximum boundary of the CIELAB color space. Therefore, these values are corrected by linear compression of the lightness and chroma. Finally, gamut mapping is used to overcome the gamut difference between mobile camera and moible LCD. To implement the real-time processing, 3D RGB-LUT is designed based on the 3D RGB-LUT and its performance is evaluated and compared with conventional method.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.1-7
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• 2017

The purpose of this paper is to examine how multi-cultural acceptability affects the perception of necessity of unification through structural equation model. The multi-cultural acceptability, familiarity with North Korean defectors, and awareness of unification were selected as the latent variables and the full / partial mediator models were built for structural equations. The observed variables for each latent variable were data that were collected through the National Survey on the Integration of North and South Korea conducted by the Korea Institute for National Unification in 2015. As a result, the acceptance of multiculturalism had a significant effect on the intimacy of the defectors, which had a positive effect on the recognition of the need for unification. The intimacy of the defectors was more influential as a parameter for full mediation than for partial mediation. Although the consciousness of unification gets weakened by postwar generations, that the phenomenon that changes into a multicultural society plays a part in recognizing the necessity of unification. In addition, the increase of North Korean defectors may ultimately become a factor in recognizing the need for unification. This study demonstrated that increasing the acceptance of multiculturalism can increase the need for unification, which means that more research fields can be derived.

• Journal of Digital Convergence
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• v.12 no.4
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• pp.379-397
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• 2014

The purpose of this study was to develop the Job Functional Assessment Scale. This study was involved took third steps. First, 93 preliminary items were developed based on theoretical literature and International Classification of Functioning, Disability and Health (ICF) Model. To verify the content validity, 3 rehabilitation experts rated those items. Second, the scale consisting of 73 items was administered to sample of 880 people with disabilities. Finally, items of the scale were reduced to 58 items. Factor analysis showed evidence of construct validity of the scale. Internal consistency (Cronbach's ${\alpha}$) of total score showed .94 and Cronbach's ${\alpha}$ of 7 subfactor demonstrated .74~.90. Thus, Job Functional Assessment Scale demonstrated satisfactory convergent validity and discriminant validity. In addition, the practical use of the scale was discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1167-1173
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• 2013

This study aimed to calculate the CFFs (critical flow functions) of a sonic nozzle bank with a 12-nozzle package within 1 s. Toward this end, the Helmholtz free energy of natural gas was formulated by using the AGA8-dc equation of state in a form without integral terms, and thereafter, thermodynamic properties such as the enthalpy, entropy, speed of sound, and heat capacity, which are used in CFF calculation, were derived in analytical form. As a result, the calculation time of CFFs was improved from 6.7 s in a previous study to 0.6 s per 12-nozzle package and kept almost constant regardless of the number of components in natural gas. Furthermore, it was confirmed that the calculated CFF values were in agreement with the results of a CFF international comparison test carried out under ISO management in 1998-1999.

• Journal of Korea Water Resources Association
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• v.38 no.9 s.158
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• pp.699-711
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• 2005

In this study, the U.S. Geological Survey's DR3M-II(Distributed Routing Rainfall-Runoff Model) was applied for small urban drainage. DR3M-II is a watershed model for routing storm runoff through a branched system of pipes and natural channels using rainfall input. The model was calibrated and verified using short term rainfall-runoff data collected from Sanbon basin. Also, the parameters were optimized using Rosenbrock technic. An estimated simulation error for peak discharge was about 7.4 percent and the result was quite acceptable. Results of the sensitivity analysis indicate that the percent of effective impervious area and ${\alpha}$ defining surface slope and roughness were the most sensitive variables affecting runoff volumes and peak discharge for low and high intensity storm respectively. In most cases, soil moisture accounting and infiltration parameters are the variables that give more effects to runoff volumes than peak discharge. Parameter ${\alpha}$ showed the opposite result.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.12 s.138
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• pp.1583-1595
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• 2004

Simon and Sullivan(l993) estimated that clothing and textile related brand equity had the highest magnitude comparing any other industry category. It reflects that fashion brands reinforce the symbolic, social values and emotional characteristics being different from generic brands. Recently, Kim and Lim(2002) developed a fashion brand equity scale to measure a brand's psychometric properties. However, they suggested that additional psychometric tests were needed to compare the relative magnitude of each brand's equity. The purpose of this study was to recognize the psychometric constructs of fashion brand equity and validate Kim and Lim's fashion brand equity scale using the measurement invariance test of cross-group comparison. First, we identified the constructs of fashion brand equity using confirmatory factor analysis through structural equation modeling. Second, we compared the relative magnitude of two brands' equity using the measurement invariance test of multi-group simultaneous factor analysis. Data were collected at six major universities in Seoul, Korea. There were 696 usable surveys for data analysis. The results showed that fashion brand equity was comprised of 16 items representing six dimensions: customer-brand resonance, customer feeling, customer judgment, brand imagery, brand performance and brand awareness. Also, we could support the measurement invariance of two brands' equities by configural and metric invariance tests. There were significant differences in five constructs' mean values. The greatest difference was in customer feeling; the smallest, in customer judgment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.359-368
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• 2016

In the 21st century, the Korean university education system is focused on innovation and change, including cooperation between industry and universities. It should be a goal to foster an industry-university ecosystem through interactions between universities and industry. Therefore, it is important to measure their relationships and to find advisable ways to measure the final results of industry-university cooperation. This paper sets out the achievements in cooperation and the satisfaction from such enterprises and measures mutual relationships influencing satisfaction from industry-university cooperation as to adherence and cooperation. Therefore, this research focuses on regression equation analysis in order to analyze the influence from satisfaction with industry-university cooperation based on factors in the relations between industry and universities. Also, as we examined the multicollinearity problem, before analyzing multiple regression, the multicollinearity problem appeared to be relatively irrelevant. In particular, the satisfaction variable, which can also be set as a subordinate variable, was in this research constructed as a high-dimensional subordinate variable composed of five individual variables. We then analyzed how the adherence construct factor and degree of cooperation construct factor influences the respective and subordinate satisfaction variables. As a result, the degree of realization of local customized programs was shown by the most significant variables. The biggest factor influencing satisfaction with industry-university cooperation proves the degree of realization for appropriate programs under local conditions, such as education, research, and technique guidance.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.124-129
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• 1990

This paper describes a new method to eliminate some selected harmonics (5,7,11) in PWM waveforms using Walsh and related orthogonal functions. Previous analyses of PWM waveforms are based on the nonlinear equations requiring iterative solution methods which are not practical in real-time systems. In addition, synthesis of low harmonics waveform at high power system is not easy to implement with power electronic hardware. The goal of this paper is to achieve the harmonics elimination in a PWM waveform by replacing the nonlinear equations in Fourier analysis with linear algebraic equations resulting from the use of orthogonal Walsh equation. This paper also describes how to synthesize low ordered harmonic waveforms with practical power electronic hardware. Walsh and Radmacher functions are easily manipulated by Harmuth's array generator, and those algorithms are accurate, computationally efficient and faster than algorithm based on Fourier analysis. In addition, this method is simulated to synthesize periodic PWM waveforms. From the experi-mental results, it is shown that single-phase PWM waveform are identified with the proposed method. And these methods are also extended to three-phase PWM waveforms in this paper.