• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1390-1393
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• 2003

Work factor approach is conveniently used in metal fracture mechanics to determine fracture toughness from a single fracture test. In this work, we investigated the applicability of the work factor approach in order to determine fracture toughness of thick graphite/epoxy composites in the hydrostatic pressure environment from a single fracture test. The effect of hydrostatic pressure on the elastic work factor was studied, The stacking sequence used was multi-directional, [0$^{\circ}$/${\pm}$45$^{\circ}$/90$^{\circ}$]. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 300 MPa. The results showed that the elastic work factor was not affected by the hydrostatic pressure, The elastic work factor decreased in a linear fashion with crack length.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.5
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• pp.370-376
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• 2004

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it ispossible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way (uni-directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two-stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.969-972
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• 2003

The overall aim of this paper is to determine coupling loss factor of welding point between shell and cylinder using loss factor and structural loss factor. For this purpose, two kinds of loss factor were adopted. One is loss factor of each sub structure, another is structural loss factor based on the complex welded or assembled structure. Using these two parameters, it is possible to derive the coupling loss factor which represent characteristic condition of SEA theory. Coupling loss factor of conjunction in complex structure was expressed as power balance equation. The derived equation for a coupling loss factor has been simplified on the assumption of one way(nl- directional) power flow between multi-sub structures. Using these conditions, it is possible to find the equation of coupling loss factor expressed as above two loss factors. To check the effectiveness of above equation, this paper used two stage application. The first approach was application between simple cylinder and shell. The next was adopted rotary compressor. Rotary compressor has three main conjunctions between shell and internal vibration part. This equation was applied to find out the optimum welding Point with respect to reduce the noise propagation. It shows the effective tool to evaluate the coupling loss factor in complex structure

• Atmosphere
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• v.25 no.2
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• pp.249-260
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• 2015

The changes in thermodynamic and dynamic aspects on near (2025~2049) and long-term (2075~2099) future climate changes between the historical run (1979~2005) and the Representative Concentration Pathway (RCP) 4.5 run with 20 coupled models which employed in the phase five of Coupled Model Inter-comparison Project (CMIP5) over East Asia (EA) and the Korean Peninsula are investigated as an extended study for Moon et al. (2014) study noted that the 20 models' multi-model ensemble (MME) and best five models' multi-model ensemble (B5MME) have a different increasing trend of precipitation during the boreal winter and summer, in spite of a similar increasing trend of surface air temperature, especially over the Korean Peninsula. Comparing the MME and B5MME, the dynamic factor (the convergence of mean moisture by anomalous wind) and the thermodynamic factor (the convergence of anomalous moisture by mean wind) in terms of moisture flux convergence are analyzed. As a result, the dynamic factor causes the lower increasing trend of precipitation in B5MME than the MME during the boreal winter and summer over EA. However, over the Korean Peninsula, the dynamic factor causes the lower increasing trend of precipitation in B5MME than the MME during the boreal winter, whereas the thermodynamic factor causes the higher increasing trend of precipitation in B5MME than the MME during the boreal summer. Therefore, it can be noted that the difference between MME and B5MME on the change in precipitation is affected by dynamic (thermodynamic) factor during the boreal winter (summer) over the Korean Peninsula.

• International Journal of Computer Science & Network Security
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• v.23 no.6
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• pp.27-34
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• 2023

This paper proposed an Inter-Carrier-Interference (ICI) Canceling Orthogonal Frequency Division Multiplexing (OFDM) receiver for 5G mobile system to support 500 km/h linear motor high speed terrestrial transportation service. A receiver in such high-speed train sees the transmission channel which is composed of multiple Doppler-shifted propagation paths. Then, a loss of sub-carrier orthogonality due to Doppler-spread channels causes ICI. The ICI Canceler is realized by the following three steps. First, using the Demodulation Reference Symbol (DMRS) pilot signals, it analyzes three parameters such as attenuation, relative delay, and Doppler-shift of each multi-path component. Secondly, based on the sets of three parameters, Channel Transfer Function (CTF) of sender sub-carrier number 𝒏 to receiver sub-carrier number 𝒍 is generated. In case of 𝒏≠𝒍, the CTF corresponds to ICI factor. Thirdly, since ICI factor is obtained, by applying ICI reverse operation by Multi-Tap Equalizer, ICI canceling can be realized. ICI canceling performance has been simulated assuming severe channel condition such as 500 km/h, 2 path reverse Doppler Shift for QPSK, 16QAM, 64QAM and 256QAM modulations. In particular, for modulation schemes below 16QAM, we confirmed that the difference between BER in a 2 path reverse Doppler shift environment and stationary environment at a moving speed of 500 km/h was very small when the number of taps in the multi-tap equalizer was set to 31 taps or more. We also confirmed that the BER performance in high-speed mobile communications for multi-level modulation schemes above 64QAM is dramatically improved by the use of a multi-tap equalizer.

• Korean Journal of Organic Agriculture
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• v.26 no.1
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• pp.151-161
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• 2018

This study was designed to investigate the effects of multi-enzyme on diarrhea and immune responses of weaned pigs. A total 36 weaned pigs ($5.92{\pm}0.48kg\;BW$; 28 d old) were randomly allotted to 2 dietary treatments (3 pigs/pen, 6 replicates/treatment) in a randomized complete block design. The dietary treatments were a typical diet based on corn and soybean meal (CON) and CON with 0.1% multienzyme (Multi; mixture of ${\beta}-mannanase$, xylanase, ${\alpha}-amylase$, protease, ${\beta}-glucanase$, and pectinase). Pigs were fed their respective diets for 6 wk. Frequency of diarrhea, levels of packed cell volume (PCV), white blood cells (WBC), immunoglobulins, cortisol, tumor necrosis $factor-{\alpha}$ ($TNF-{\alpha}$), transforming growth $factor-{\beta}$ ($TGF-{\beta}$), and C-reactive protein (CRP) were measured. Multi group tended to decrease (p<0.1) diarrhea frequency than CON group during 2 wk after weaning. Lower values of PCV on d 3 (p<0.05) and d 7 (p<0.1) were found in Multi group compared with CON group. There were no significant differences on WBC number and immunoglobulin (Ig) M and A between Multi and CON groups. However, Multi group tended to increase (p<0.1) Ig G on d 7 than CON group. Moreover, Multi group showed modulated immune responses, indicated by decreased levels of cortisol (p<0.05) on d 7 and 14, $TNF-{\alpha}$ on d 3 (p<0.05) and d 7 (p<0.10), $TGF-{\beta}$ on d 2 (p<0.05) and d 7 (p<0.10), and CRP (p<0.10) on d 3 and 7 after weaning compared with CON group. Consequently, inclusion of multi-enzyme in diets for weaned pigs improved gut health and modulated immune responses of weaned pigs.

• Journal of Korean Society for Quality Management
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• v.31 no.1
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• pp.21-41
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• 2003

The purpose of this research is to identify if psychological temptation, site quality and sense of community influence user's flow and addiction and if causalities among flow, addiction, customer satisfaction and customer loyalty are different between Korean and Japanese online games. To perform our research, we use MCSF(Multi-group Confirmatory Factor Analysis) and MSEM(Multi-group Structural Equation Model). The empirical results of SEM(Structural Equation Model) including high-order factor analysis indicate that all of paths in our model are the same for both countries. Therefore, site quality and sense of community have impacts on the flow, while on the other hand, psychological temptation has impacts on the addiction. Customer satisfaction and loyalty are positively related not with the addiction but with the flow. In addition, customer loyalty is significantly influenced by the flow and the customer satisfaction. In Conclusion, the empirical results of MSEM(Multi-group Structural Equation Model) indicate sense of community to flow, flow to loyalty and customer satisfaction to loyalty are different between Korea and Japan. This indicates that companies to penetrate into Japa online game industry should have a concern with Japanese Social and Cultural features and to develop strategies which correspond with Japanese culture.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.337-342
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• 2007

A multi-objective optimization technique was implemented to obtain optimal topologies of the inner reinforcement for a vehicle's hood simultaneously considering the static stiffness of bending and torsion and natural frequency. In addition, a smoothing scheme was used to suppress the checkerboard patterns in the ESO method. Two models with different curvature were chosen in order to investigate the effect of curvature on the static stiffness and natural frequency of the inner reinforcement. A scale factor was employed to properly reflect the effect of each objective function. From several combinations of weighting factors, a Pareto-optimal topology solution was obtained. As the weighting factor for the elastic strain efficiency went from 1 to 0, the optimal topologies transmitted from the optimal topology of a static stiffness problem to that of a natural frequency problem. It was also found that the higher curvature model had a larger static stiffness and natural frequency than the lower curvature model. From the results, it is concluded that the ESO method with a smoothing scheme was effectively applied to topology optimization of the inner reinforcement of a vehicle's hood.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.501-505
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• 2008

In this paper, we present a multi-turn circular loop antenna for portable terrestrial DMB. In order to satisfy the two contradictory requirements of small antenna size and high receiving capability, the proposed antenna's diameter and turns are fixed to be 4 mm and 80 turns, respectively and its quality factor $\mathcal{Q}$ is set 1 in order to have high transfer function. The fabricated antenna length is 30 mm as small and its measured gain is -15 dBd. The antenna receiving power is verified by measurement very comparable with the receiving power of a commercial terrestrial DMB monopole antenna of length 190 mm.

• The Korean Journal of Physiology and Pharmacology
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• v.20 no.1
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• pp.53-62
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• 2016

Mesenchymal stem cells (MSCs) in the bone marrow and other somatic tissues reside in an environment with relative low oxygen tension. Cobalt chloride ($CoCl_2$) can mimic hypoxic conditions through transcriptional changes of some genes including hypoxia-inducible factor-$1{\alpha}$ (HIF-$1{\alpha}$) and vascular endothelial growth factor (VEGF). This study evaluated the potential role of $CoCl_2$ preconditioning on multi-lineage differentiation of C3H/10T1/2, a murine MSC line to understand its possible molecular mechanisms in vitro. $CoCl_2$ treatment of MSCs markedly increased HIF-$1{\alpha}$ and VEGF mRNA, and protein expression of HIF-$1{\alpha}$. Temporary preconditioning of MSCs with $CoCl_2$ induced up-regulation of osteogenic markers including alkaline phosphatase, osteocalcin, and type I collagen during osteogenic differentiation, followed by enhanced mineralization. $CoCl_2$ also increased chondrogenic markers including aggrecan, sox9, and type II collagen, and promoted chondrocyte differentiation. $CoCl_2$ suppressed the expression of adipogenic markers including $PPAR{\gamma}$, aP2, and $C/EBP{\alpha}$, and inhibited adipogenesis. Temporary preconditioning with $CoCl_2$ could affect the multi-lineage differentiation of MSCs.