• Progress in Medical Physics
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• v.18 no.3
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• pp.161-166
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• 2007

A model theory of passive-targeted drug delivery in sphere-shaped solid tumors is introduced on the basis of Fick's law of diffusion, with appropriate boundary and initial conditions. For a uniform initial concentration inside the tumor, the concentration is obtained as a function of time and radial position. The concentration is shown to approach the equilibrium distribution as the time elapses, as is expected by the Gedanken Experiment. The time-evolution rate is found to be determined by the diffusion coefficient of the drug in the tissue, the size of the tumor, the volume of the drug-injected region, and the concentration gradient at the boundary.

• Asia pacific journal of information systems
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• v.13 no.4
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• pp.257-277
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• 2003

Recently, organizations intend to adopt new information technology for acquiring relative advantages in competitive business environment. Especially, many companies have paid attention to web-based electronic commerce. But research in this area has largely been performed to the operational and technical aspects of web site. Also the World Wide Web(web) has become one of the most widely used information technologies, but research indicates that there are many firm that are still considering whether to establish a web presence. This study examines factors influencing adoption of corporate web site over time. To examine why companies adopt web site, this study regards web site as an innovation and finds out these reason through Innovation Diffusion Theory. Independent variables of this research are composed of innovation characteristics, organizational characteristics and environmental characteristics. By the result of logistic regression analysis, we find that there are significant differences between early adopters and late adopters of web site for three adoption factors : top management support, organization size, environmental uncertainty. These findings confirm the theoretical frame for adoption of corporate web site. Also this study will provide good guidelines to the companies and the vendors in shaping the strategies of IT adoption and IT diffusion respectively.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.37.1-37.1
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• 2017

Since the seminal work of Perrin, physicists have understood in the context of kinetic theory how ink slowly diffuses in a glass of water. The fluctuations of the stochastic forces acting on water molecules drive the diffusion of the ink in the fluid. This is the archetype of a process described by the so-called fluctuation-dissipation theorem, which universally relates the rate of diffusion to the power spectrum of the fluctuating forces. For stars in galaxies, a similar process occurs but with two significant differences, due to the long-range nature of the gravitational interaction: (i) for the diffusion to be effective, stars need to resonate, i.e. present commensurable frequencies, otherwise they only follow the orbit imposed by their mean field; (ii) the amplitudes of the induced fluctuating forces are significantly boosted by collective effects, i.e. by the fact that, because of self-gravity, each star generates a wake in its neighbours. In the expanding universe, an overdense perturbation passing a critical threshold will collapse onto itself and, through violent relaxation and mergers, rapidly converge towards a stationary, phase-mixed and highly symmetric state, with a partially frozen orbital structure. The object is then locked in a quasi-stationary state imposed by its mean gravitational field. Of particular interests are strongly responsive colder systems which, given time and kicks, find the opportunity to significantly reshuffle their orbital structure towards more likely configurations. This presentation aims to explain this long-term reshuffling called gravity-driven secular evolution on cosmic timescales, described by extended kinetic theory. I will illustrate this with radial migration, disc thickening and the stellar cluster in the galactic centre.

• Journal of the Semiconductor & Display Technology
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• v.13 no.2
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• pp.37-44
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• 2014

In this study, the performance of dye-sensitized solar cells with different thickness of the photelectrode film was simulated by using the electron-diffusion differential model. Through this simulation, the relationships between the thickness of the photoelectrode film and the performances (open-circuit voltage, short-circuit current density, and overall photoelectric-conversion efficiency) of cells were understood and the performances with different thickness of the photoelectrede film were also examined. For considering the refractive index in the liquid electrolyte and exploring the scattering effect of titanium dioxide particles with different sizes using the Mie light-scattering theory, the highest scattering effect of each particles was found out and the optimal size of the titanium dioxide particle was determined for light scattering in the photoelectrode film of dye-sensitized solar cell. Through experiment, the mixed titanium dioxide cell was better than the single titanium dioxide cell and generated a higher overall conversion efficiency because the optimal titanium dioxide particles in the phoelectrode film as light scattering.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.43.2-43.2
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• 2009

Electron microbursts are the intense electron precipitation which durations are less than one second. We measured the energy spectra of the microbursts from 170 keV to 340 keV with solid state detectors aboard the low-altitude (680km), polar-orbiting Korean STSAT-1 (Science and Technology SATellite). The data showed that the loss cone at these energies is empty except when microbursts abruptly appear and fill the loss cone in less than 50 msec. This fast loss cone filling requires pitch angle diffusion coefficients larger than ~ 10-2rad2/sec, while ~10-5 rad2/sec was proposed by a wave particle interaction theory. We recalculated the diffusion coefficient, and reviewed of electron microburst generation mechanism with test particle simulations. This simulation successfully explained how chorus waves make pitch angle diffusion within such short period. From considering the resonance condition between wave and electrons, we also showed ~ 100 keV electrons could be easily aligned to the magnetic field, while ~ 1MeV electrons filled loss cone partially. This consideration explained why precipitating microbursts have lower e-folding energy than that of quasi-trapped electrons, and supports the theory that relativistic electron microbursts that have been observed by satellite in-situ measurement have same origin with ~100 keV electron microbursts that have been usually observed by balloon experiments.

• Journal of the Korean Chemical Society
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• v.43 no.4
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• pp.469-474
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• 1999

In this study, the simulation program using the randomwalk model is developed. Generally, students in the chemistry class have some difficulties to understand the motion of atomic particles or molecules. And then, they have many mis-conceptions about the motion of molecules. This program expressed by the computer simulations using the randomwalk theory may help students to understand visually the process of molecular motion. This program can be used easily, because it is based on Web by application of JAVA languages. The program consists of two parts. One is 'Diffusion' program, expressing the process of molecular diffusion as a computer simulation. Another is 'Randomwalk' program, expressing the trajectory of molecular motion to help the students to follow the random motion virtually.

• Structural Engineering and Mechanics
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• v.28 no.1
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• pp.19-38
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• 2008

A general solution to the field equations of homogeneous isotropic generalized thermoelastic diffusion with two relaxation times (Green and Lindsay theory) has been obtained using the Fourier transform. Assuming the disturbances to be harmonically time.dependent, the transformed solution is obtained in the frequency domain. The application of a time harmonic concentrated and distributed loads have been considered to show the utility of the solution obtained. The transformed components of displacement, stress, temperature distribution and chemical potential distribution are inverted numerically, using a numerical inversion technique. Effect of diffusion on the resulting expressions have been depicted graphically for Green and Lindsay (G-L) and coupled (C-T) theories of thermoelasticity.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.11a
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• pp.144-147
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• 2003

It is important to understand the process of technology diffusion among end users for effectively implementing adoption and coping with frequent changes in the environment. Previous studies indicate that information and communication technology (ICT) adoption is affected by innovation influence such as usefulness, ease of use and self-efficacy. Most of these studies, however, bypassed imitation influence such as subjective norms, word-of-mouth, and advertising, specifically, interactive innovation having critical mass in technology acceptance research. Thus, this study investigates imitation influence in individual adoption of mobile communication technology, more specifically, mobile phones, using Mahaian's diffusion model in individual ICT adoption.

• 연구논문집
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• s.34
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• pp.21-28
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• 2004

In this study, we report an investigation for the charging and collection of aerosol nanoparticles in an electrostatic precipitator (ESP) according to particle charging and diffusion effects. The competition between charging probability and diffusion effect determines the collection efficiency of nanoparticles in the ESP. In conclusion, collection efficiency continuously decreased with the reduction in the particle size. This indicates that poor partial charging effect of nanoparticles is more dominant than their diffusion effect in the ESP for the nanoparticles in the particle size range of 4-20 nm. Theoretical calculations using a unipolar diffusion charing theory were in good agreement with the experimental data for the nanoparticles less than 20 nm in diameter.

• Journal of the Korean Society of Food Culture
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• v.27 no.5
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• pp.496-504
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• 2012

The objective of this study was to investigate the phasic characteristics of the adjustment process to Korean food with an analysis of Japanese independent tourist culture social resistance factors. To collect data for empirical study, a survey was distributed to 284 Japanese tourists through Korean travel agencies. Logistic regression analysis was carried out in order to determine media and cultural beliefs affecting the diffusion process of Korean food. The results showed that cultural beliefs had no significant effects on the diffusion process of most Korean food. However, people who valued similarities between the two countries-South Korea and Japan-demonstrated a significant effect on performance and identification group. Therefore, cultural beliefs did not influence the diffusion of Korean food, although there are surely cultural beliefs and subjective factors affecting their reform decisions.