• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.279-284
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• 2016

Single-shot echo planar imaging(SS-EPI) is well established as high sensitivity for ischemic stroke. However, it is prone to susceptibility artifact in brain stem that diminish the image quality. single-shot turbo spin echo(SS-TSE) is a new DWI technique that can reduce susceptibility artifact. Thus, this research was conducted so as to reduce geometric distortion in brain stem by using single-shot turbo spin echo technique. Thirty patients without brain disease underwent diffusion MR on a 3T scanner with SS-EPI and SS-TSE. Obtained images with both sequences were analyzed for geometric distortion and error percentage as well. Image quality in terms of geometric distortion of SS-TSE were found to be significantly better than those for SS-EPI. And error percentage was considerably reduced for 2.4% of b0 image(from 11.1% to 8.7%), 1.2% of b1000 image(from 11.4% to 10.1%), respectively. In summary, diffusion MR using SS-TSE significantly reduce geometric distortion compared to SS-EPI in brain stem and may provide improved diagnostic performance.

• Clean Technology
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• v.27 no.1
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• pp.47-54
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• 2021

The adsorption of Acid Fuchsin (AF) on granular activated carbon (GAC) was investigated for isothermal adsorption and kinetics and thermodynamic parameters by experimenting with the initial concentration, contact time, temperature, and pH of the dye as adsorption parameters. In the pH effect experiment, the adsorption of AF on activated carbon showed a bathtub type with increased adsorption at pH 3 and 11. The adsorption equilibrium data of AF fit well with the Freundlich isotherm model, and the calculated separation factor (1/n) value was found in which activated carbon can effectively remove AF. The pseudo-second-order kinetic model fits well within 7.88% of the error percent in the adsorption process. According to Weber and Morris's model plot, it was divided into two straight lines. The intraparticle diffusion rate was slow because the stage 2 (intraparticle diffusion) slope was smaller than that of stage 1 (boundary layer diffusion). Therefore, it was confirmed that the intraparticle diffusion was a rate-controlling step. The activation energy of AF (13.00 kJ mol-1) corresponded to the physical adsorption process (5 - 40 kJ mol-1). The free energy change of the AF adsorption by activated carbon showed negative values at 298-318 K. As the spontaneity increased with increasing temperature. The adsorption of AF was an endothermic reaction (ΔH = 22.65 kJ mol-1).

• Information Systems Review
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• v.19 no.1
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• pp.75-100
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• 2017

Today, firms are constantly transforming and innovating to survive under the rapidly changing business environment. The introduction of cloud computing services has become popular throughout society as a whole and is expected to result in many changes and developments not only in firms and but also in the public sector subject to innovation. The purpose of this study is to investigate the effect of the characteristics of cloud computing services on the perceived expected performance according to innovativeness based on innovation diffusion theory. The results of the analysis of the data collected from this research are as follows. The convenience and understanding of individuals' work as well as the benefits of cloud computing services to them depend on the innovative trend of cloud computing services. Further, the expectations for personal benefit and those for organizational benefit of cloud computing services are different from each other. Leading firms in the global market have been actively engaged in the utilization of cloud computing services in the public sector as well as in private firms. In consideration of the importance of cloud computing services, using cloud computing services as the target of innovation diffusion research is important. The results of the study are expected to contribute to developing future research models for the diffusion of new technologies, such as big data, digital convergence, and Internet of Things.

• Journal of Yeungnam Medical Science
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• v.24 no.2
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• pp.119-128
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• 2007

Purpose : The purpose of this study was a phantom study to measure the diffusion properties of water molecules by steady-state free precession diffusion-weighted imaging (SSFP- DWI) with a low b-value and to determine if this sequence might be useful for application to the evaluation of bone marrow pathology. Materials and methods : 1. The phantom study: A phantom study using two diffusion weighted sequences for the evaluation of the diffusion coefficient was performed. Three water-containing cylinders at different temperatures were designed: phantom A was $3^{\circ}C$, B was $23^{\circ}C$ and C was $63^{\circ}C$. Both SSFP and echo planar imaging (EPI) sequences (b-value: $1000s/mm^2$) were performed for comparison of the diffusion properties. The Signal to noise ratios (SNR) and apparent diffusion coefficient (ADC) values of the three phantoms using each diffusion-weighted sequence were assessed. 2. The Clinical study: SSFP-DWI was performed in 28 patients [sacral insufficiency fractures (10), osteoporotic lumbar compression fractures (10), malignant compression fractures (8)]. To measure the ADC maps, a diffusion-weighted single shot stimulated echo-acquisition mode sequence ($650s/mm^2$) was obtained using the same 1.5-T MR imager Results : For the phantom study, the signal intensity on the SSFP as well as the classic EPI-based DWI was decreased as the temperature increased in phantom A to C. The ADC values of the phantoms on EPI-DWI were $0.13{\times}10^{-3}mm^2/s$ in phantom A, $0.22{\times}10^{-3}mm^2/s$ in B and $0.37{\times}10^{-3}mm^2/s$. in C. The SSFP can be regarded as a DWI sequence in view of the series of signal decreases. Conclusion : Bone marrow pathologies with different diffusion coefficients were evaluated by SSFP-DWI. All benign fractures were hypointense compared to the adjacent normal bone marrow where as the malignant fractures were hyperintense compared to the adjacent normal bone marrow.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.922-929
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• 1997

As the size of semiconductor devices shrinks in the horizontal as well as vertical dimension it is difficult to estimate the transport-velocity of electron because they drift in non-equilibrium with a few scattering. In this paper HYbrid Monte Carlo simulator which employs the drift-diffusion model for hole-transport and Monte Carlo model for electron-transport in order to reduce the simulation time and increase the accuracy as well has been developed and applied to analyze the electron-transport in InAlAs/InGaAs HBT which is attractive for an ultra high speed active device in high speed optical fiber transmission systems in terms of the velocity and energy distribution as well as cutoff frequency.

• Journal of the Korean institute of surface engineering
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• v.27 no.4
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• pp.223-233
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• 1994

It is well known that compositionally modulated Cu-Ni alloy can be produced by an electrochemical method in Ni sulfate solution containing trace amount of Cu. a mathematical model is presented to describe the current distribution and weight percent of Cu in Ni layer on the rotating disk electrode. The model includes convective-diffusion equation, the Laplace's equation and various overpotentials, and is solved numerically. The thickness of Cu layer is almost uniform whereas the thickness of Ni layer as well as the Ni/Cu weight ratio are increased approaching to the edge of the disk. These results agree well with the experimental values. The ohmic potential drop is suggested as a major cause of a nonuniformity in Ni layer. The optimum plating condition for the fabrication of susperlattice is proposed based on the results of this study.

• 한국연소학회:학술대회논문집
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• 2003.05a
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• pp.65-73
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• 2003

An experimental study on flame lift-off characteristics of propane jet flame highly diluted with nitrogen has been conducted introducing acoustic forcing with a tube resonant frequency. A flame stability curve is attained according to forcing strength and nozzle exit velocity for $N_2$ diluted flames. Flame lift-off behavior with forcing strength and nozzle exit velocity is globally categorized into three; a well premixed behavior caused by a collapsible mixing for large forcing strength, a coexistent behavior of well-premixed and edge flames interacting with well-organized inner fuel vortices for moderate forcing strengths, and edge flame behavior for small forcing strengths. Special focus is concentrated on the coexistent behavior of the flame base in lifted flame since this may give a hint to a possibility which the flame base behaves like a well-mixed premixed flame in highly turbulent lifted flames. It is also shown that the acoustic forcing to self-pulsating laminar lifted flame affects flame lift-off behavior considerably which is closely related to downstream flow velocity, mixture strength, effective fuel Lewis number, and flame stretch.

• Journal of the Korean Vacuum Society
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• v.22 no.1
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• pp.7-12
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• 2013

We fabricated ZnO-ZnMgO single quantum well (SQW) samples having different well-widths by using the atomic layer deposition technique. The QW samples exhibit different optical transition behaviors with different QW widths. We confirm that when the well-width of 1.5 nm does not have a confined quantum energy level due to the Mg diffusion into the well caused by after-thermal treatment whereas the QWs wider than 1.5 nm show optical transitions between the confined energy levels.

• Proceedings of the Korean Magnestics Society Conference
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• 2006.06a
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• pp.32-33
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• 2006

• Proceedings of the IEEK Conference
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• 2000.11d
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• pp.231-234
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• 2000

This paper has been studied a method that effectively displaying color image to monochromatic display such as PDA and movable-phone. Generally, the Floyd-Steinberg dithering algorithm has been used in this area and its' effectiveness were well known. But it shows some ugly patterns in white area and also shows some directionality in vertical and horizontal directions. To reduce those directionality, I suggest the error diffusion direction to be rotated randomly according to the bit value of the current position. This can also mitigate some ugly pattern in white area