• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1050-1059
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• 2019

The self diffusion, hole volume, and flow thermodynamic parameters of polyamide fibers were calculated from rheological parameters and crystallite size in order to study of flow segments in amorphous region. The stress relaxation of polyamide filament fibers were carried out in air and various solvents at various temperatures using the tensile tester with the solvent chamber. The rheological parameters were obtained by applying the experimental stress relaxation curves to the theoretical equation of the Ree-Eyring and Maxwell non-Newtonian model. It was observed that the rheological parameters of these polyamide filament fibers are directly related to the relaxation spectra, self diffusion, viscosities, and activation energies of flow segments.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.1
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• pp.190-199
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• 1993

In order to find the effect of flame interaction on NO production, dual laminar diffusion flames issuing from two rectangular nozzles were investigated theoretically. Chemical equilibrium model and Zeldovich mechanism were used in numerical model. The effect of four major parameters on NO production were inspected. These parameters are nozzle spacing, Raynolds number, aspect ratio of nozle cross section and velocity of secondary flow. It is found that interaction of flames enhances production of n. It is also found that multiflames with large spacing, small aspect ratio and strong secondary flow product less n.

• Journal of Internet Computing and Services
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• v.7 no.1
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• pp.39-47
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• 2006

The evaluation of MDx family hash functions such as MD5 is difficult because the design background or a generalized model is unknown. In this paper, an approximated model is proposed to generalize hash functions. The diffusion of a input difference is tested by an approximated model for MD5. The results show that MD5 does not provide perfect diffusion, so MD5 is weak against some attacks. We propose a multiple chaining pattern which provides perfect diffusion in approximated model of hash function without extra calculation or memory. And We show the probability of differential characteristics of our proposal.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.9 no.3
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• pp.115-124
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• 1997

We measured the variance of eddy diffusion and associated ‘diffusion coefficients’ in coastal regions of Korea by observing the separation distances among multiple drifters deployed simultaneously at the same initial position. The variance of eddy diffusion was found to be proportional to $t^m$, where t is the time and m is a non-integer scaling exponent between 1.5 and 3.5. The observed scaling exponent of eddy diffusion cannot be reproduced by diffusion models employing constant eddy diffusivity. In this study, we applied fractal theory in simulating exponential increase of variance of eddy diffusion. We employed the fGn(fractional Gaussian noise) as a ‘modified’ random walks corresponding to the oceanic eddy diffusion. The variance of eddy diffusion, which corresponds to the fBm(fractional Brown motion) of our diffusion model, is proportional to $t^{2H}$, where H is Hurst scaling exponent. The temporal increase of the variance. with scaling exponent between 1 and 2, was successfully reproduced by our fractal diffusion model. However, our model cannot reproduce scaling exponent greater than 2. The scaling exponents greater than 2 are associated with the velocity shear of the mean flow.

• Information Systems Review
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• v.12 no.3
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• pp.89-116
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• 2010

The development and accomplishment of Open Source Software(OSS) is one of the hottest, as well as the most recent topics in the software industry. Prior studies with respects to OSS have concentrated on discovering both developers and users' rationales of participating OSS projects, analyzing specific OSS solutions or OSS movement itself. However, the empirical study on identifying determinants that influence organizational adoption of OSS and further diffusion of the technology has been a scant. Thus, the main purpose of this study is to investigate the key determinants affecting organizational adoption of OSS. The proposed research model incorporates organizational needs(Evolutional Leadership, Adaptive performance, Readiness for Change) and technological needs(Job Relevance, Cost Benefits, Software Quality) in order to explain organizational OSS adoption. Further, this study assesses the impact organizational OSS adoption has on the OSS Performance and OSS Diffusion. Results from 366 adopting organizations in various industries show three constructs in organizational needs and two constructs in technological needs with exception of Job Relevance have a significant influence on OSS Adoption; and adoption impacts its performance, and diffusion. The implications of the results suggest not only a new theoretical model for OSS research, but also the important implications for OSS diffusion.

• Journal of the Korean Electrochemical Society
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• v.2 no.2
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• pp.98-105
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• 1999

In the present study, buoyant force and its stabilizing effects in an electrostatic field were examined systematically in order to reduce the effect of natural convection with thermal stratification in a horizontal fluid-saturated porous layer. The correlation of ionic mass transport induced by double-diffusive convection in a horizontal porous layer has been derived theoretically. And the theoretical model was examined by electrochemical experiments. The theoretical correlation for mass transport which is satisfying Forchheimer's flow equation and based on the micro-turbulence model is derived as a function of soltual Darcy-Rayleigh number, thermal Darcy-Rayleigh number and Lewis number. In the experiment, the mass transport of copper ions in $CuSO_4-H_2SO_4$ solution is measured by electrochemical technique. By assembling theoretical correlation and experimental results, the mass transport correlation induced by double-diffusive convection is proposed as $$Sh=\frac{0.03054(Rs_D-LeRa_D)^{1/2}}{1-3.8788(Rs_D-LeRa_D)^{-1/10}}$$ The present correlation looks flirty reasonable with comparing experimental results, and very promising for the applications of its prototype into various systems involving heat transfer as well as mass transfer, in order to control the effects of natural convection effectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1417-1419
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• 2016

In order to improve the transmission performance of a chirp signal-based chirp spread spectrum system, the cross-correlation coefficient (CCC) should be carefully considered. In this paper, we derive the CCC for analyzing the transmission performance and propose the optimal chirp rate based on the analysis. The simulation results verify the mathematical derivations and show that the considered scheme can improve the performance by considering the CCC.

• The Journal of the Korea Contents Association
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• v.7 no.10
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• pp.202-210
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• 2007

Factor analysis, an important research method, has been conducted as a pre-analysis of empirical researches. Sometimes, the researchers expect more information than factor analysis' limitation as well. Therefore, I suggest a method to overcome this problem. This study presents a combined research method which allow to solve the limitation of the factor analysis in social science. The combined research method consist of factor analysis, AHP(analytic hierarchy process) analysis, diffusion theory and system dynamics, which is able to explain causalities.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.278-285
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• 2005

In the present work, a reaction of sulfur removal and simulation of desulfurization based on the grain model and two-phase theory were studied using natural manganese ore (NMO) as a sorbent in a continuous fluidized bed reactor. The effect of desulfurization was investigated through the grain model considered the change of pore structure as a function of desulfurization time, particle size of NMO, and diffusion velocity of $SO_2$ in the pores. Among these parameters, the diffusion of $SO_2$ in the pores of NMO was the most important factor. Moreover, the reaction of sulfur removal and desulfurization in a continuous fluidized bed reactor using NMO as a sorbent could be well predict through the grain model and two-phase theory, respectively.

• The Journal of Information Systems
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• v.23 no.1
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• pp.1-28
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• 2014

소셜 네트워크 서비스의 확산과 더불어 소셜 네트워크 게임(이하에서는 소셜게임이라 함)이 부각되고 있다. 한편, 소셜게임이 인기를 끌면서 소셜 네트워크 서비스가 더욱 확산되는 계기가 되기도 한다. 사용자들을 소셜게임에 몰입하도록 유인하는 요인이 무엇인가를 파악하면 소셜 네트워크 서비스가 더욱 발전할 수 있는 방안을 찾을 수 있다. 따라서 본 연구는 사용자들을 소셜게임에 몰입하도록 유인하는 요인이 무엇인가를 분석하는데 있다. 본 연구에서는 대표적인 소셜 네트워크 사이트라 할 수 있는 페이스북의 소셜게임 사용자들을 대상으로 설문조사를 실시하였다. 280명의 사용자들을 대상으로 한 설문을 통해, 소셜게임에의 몰입, 게임스토리, 게임그래픽, 게임사회화, 게임 통제력, 게임 사용용이성의 관계를 구조방정식모형으로 분석하였다. 특히, 게임 사회화와 게임그래픽은 몰입에 직접적으로 영향을 주기도 하며 게임 사용용이성을 통해 간접적으로도 영향을 주었다. 한편, 게임스토리는 몰입에 직접적으로만 영향을 주고, 게임 통제력을 게임사용 용이성을 통해 간접적으로 영향을 준다. 본 연구는 몰입이론과 기술수용이론을 토대로 하고 있지만, 소셜게임에서의 몰입에 대한 최초의 연구이기 때문에 후속 연구에 지침이 될 수 있다. 또한 소셜게임을 개발하는 사업자들이 무엇에 역점을 두고 게임을 개발하고 서비스해야 할 것인가에 대한 지침이 될 수 있다.