• Journal of Korea Technology Innovation Society
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• v.1 no.1
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• pp.69-82
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• 1998

As a new medium for knowledge diffusion, E-Journal is expected to be a general type of scholarly communication. However, the techno - economic problems have hindered the advancement of the E-Journal. For the technical aspects, there are problems such as the standardization of document format, automatization of the document preparation, forward and backward link between documents. Also there are necessities for the support of the information infrastructure of digital library and information superhighway. For the economic domain, reengineering of total publishing cycle is considered and the new paradigm of peer review is analyzed. We pointed out that the main difficulties in the diffusion of E-Journal are on the promotion of service and technological advance, not the price and marketing strategy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.4
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• pp.1373-1391
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• 2022

We investigate mobile multiple-input multiple-output (MIMO) molecular communication via diffusion (MCvD) system which is consisted of two source nodes, two destination nodes and one relay node in the mobile three-dimensional channel. First, the combinations of decode-and-forward (DF) relaying protocol and network coding (NC) scheme are implemented at relay node. The adaptive thresholds at relay node and destination nodes can be obtained by maximum a posteriori (MAP) probability detection method. Then the mathematical expressions of the average bit error probability (BEP) of this mobile MIMO MCvD system based on DF and NC scheme are derived. Furthermore, in order to minimize the average BEP, we establish the optimization problem with optimization variables which include the ratio of the number of emitted molecules at two source nodes and the initial position of relay node. We put forward an iterative scheme based on block coordinate descent algorithm which can be used to solve the optimization problem and get optimal values of the optimization variables simultaneously. Finally, the numerical results reveal that the proposed iterative method has good convergence behavior. The average BEP performance of this system can be improved by performing the joint optimizations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.557-562
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• 2006

In order to predict the dispersion of suspended sediment arising from dredging operation in port and navigation channel, a hybrid model for dispersive transport of turbidity plume was developed using Lee's(1998) hybrid method. Using hybrid modeling scheme advection-diffusion equation was solved by the forward particle-tracking method for advection process and by the fixed Eulerian grid method for diffusion process. To examine numerical model simulation in accuracy, the simulated results for 1-D, 2-D, and 3-D cases were compared with the analytical solutions including Kuo, et al's (1985) 3-D mathematical model. The model results were in a good agreement with the analytical solutions and mathematical model for the dispersion of turbidity plume.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.37-40
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• 2001

This paper presents the modeling methodology of Zinc diffusion process applied for high-speed avalanche photodiode fabrication using neural networks. Three process factors (sealing pressure, amount of Zn$_3$P$_2$ source per volume, and doping concentration of diffused layer) are examined by means of D-optimal design experiment. Then, diffusion rate and doping concentration of Zinc in diffused layer are characterized by a static response model generated by training fred-forward error back-propagation neural networks. It is observed that the process models developed here exhibit good agreement with experimental results.

• Journal of the Korean Statistical Society
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• v.24 no.1
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• pp.141-147
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• 1995

A diffusion model for a system subject to random shocks is introduced. It is assumed that the state of system is modeled by a Brownian motion with negative drift and an absorbing barrier at the origin. It is also assumed that the shocks coming to the system according to a Poisson process decrease the state of the system by a random amount. It is further assumed that a repairman arrives according to another Poisson process and repairs or replaces the system i the system, when he arrives, is in state zero. A forward differential equation is obtained for the distribution function of X(t), the state of the systme at time t, some boundary conditions are discussed, and several interesting characteristics are derived, such as the first passage time to state zero, F(0,t), the probability of the system being in state zero at time t, and F(0), the limit of F(0,t) as t tends to infinity.

• Membrane and Water Treatment
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• v.8 no.5
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• pp.449-462
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• 2017

Direct treatment of municipal wastewater by forward osmosis (FO) process was evaluated in terms of water flux decline, reverse salt diffusion, pollutants rejection and concentration efficiency by using synthetic seawater as the draw solution. It was found that when operating in PRO mode (active layer facing the draw solution), although the FO membrane exhibited higher osmotic water flux, more severe flux decline and reverse salt diffusion was also observed due to the more severe fouling of pollutants in the membrane support layer and accompanied fouling enhanced concentration polarization. In addition, although the water flux decline was shown to be lower for the FO mode (active layer facing the feed solution), irreversible membrane fouling was identified in both PRO and FO modes as the water flux cannot be restored to the initial value by physical flushing, highlighting the necessity of chemical cleaning in long-term operation. During the 7 cycles of filtration conducted in the experiments, the FO membrane exhibited considerably high rejection for TOC, COD, TP and $NH_4{^+}-N$ present in the wastewater. By optimizing the volume ratio of seawater draw solution/wastewater feed solution, a concentration factor of 3.1 and 3.7 was obtained for the FO and PRO modes, respectively. The results demonstrated the validity of the FO process for direct treatment of municipal wastewater by using seawater as the draw solution, while facilitating the subsequent utilization of concentrated wastewater for bioenergy production, which may have special implications for the coastline areas.

• Membrane Journal
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• v.20 no.3
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• pp.235-240
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• 2010

The aim of this paper is to evaluate and compare the performances of forward osmosis (FO) membranes using different materials. The FO membranes were synthesized using interfacial polymerization method on hydrophobic polysulfone (PSf) and relatively hydrophilic polyethersulfone (PES) supports. The FO performance such as flux and back diffusion was measured. The resulting fluxes of PSf and PES FO membranes were $4.3\;L/m^2hr$ and $17.8\;L/m^2hr$, respectively. The flux of the PES FO membrane was higher than that of the PSf FO membrane. The results indicated that hydrophillictity of the support membrane is important for increasing flux in FO process. Moreover, with decreasing the support layer thickness, flux increased considerably.

• International Journal of Contents
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• v.11 no.4
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• pp.56-69
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• 2015

This paper proposes an efficient image encryption scheme based on quintuple encryption using two chaotic maps. The encryption process is realized with quintuple encryption by calling the encrypt(E) and decrypt(D) functions five times with five different keys in the form EDEEE. The decryption process is accomplished in the reverse direction by invoking the encrypt and decrypt functions in the form DDDED. The keys for the quintuple encryption/decryption processes are generated by using a Tent map. The chaotic values for the encrypt/decrypt operations are generated by using a Gumowski-Mira map. The encrypt function E is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage scrambles all the rows and columns to chaotically generated positions. This stage reduces the correlation radically among the neighboring pixels. The pixel value rotation stage circularly rotates all the pixels either left or right, and the amount of rotation is based on chaotic values. The last stage performs the diffusion four times by scanning the image in four different directions: Horizontally, Vertically, Principal diagonally and Secondary diagonally. Each of the four diffusion steps performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. This stage ensures the resistance against the differential attacks. The security and performance of the proposed method is investigated thoroughly by using key space, statistical, differential, entropy and performance analysis. The experimental results confirm that the proposed scheme is computationally fast with security intact.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.4
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• pp.417-425
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• 2016

Desalination is a key technology to overcome water shortage problem in a near future. High energy consumption is an Achilles' heel in desalination technology. Osmotically driven membrane processes like forward osmosis(FO) was introduced to address this energy issue. Characterizing membrane properties such as water permeability(A), salt permeability(B), and the resistance to salt diffusion within the support layer($K_{ICP}$) are very important to predict the performance of scaled-up FO processes. Currently, most of researches reported that the water permeability of FO membrane was measured by reverse osmosis(RO) type test. Permeating direction of RO and FO are different and RO test needs hydraulic pressure so that several problems can be occurred(i.e. membrane deformation, compaction and effect of concentration polarization). This study focuses on measuring water permeability of FO membrane by FO type test results in various experimental conditions. A statistical approach was developed to evaluate the three FO membrane properties(A, B, and $K_{ICP}$) and it predicted test result by the internal and external concentration polarization model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.44-48
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• 1999

In order to the investigate for the DC(forward-reverse) breakdown properties of gate oxide in MOSFET, we are manufactured the specimen as following. The resistivity is 1.2($\Omega$ $.$ cm), 1.5($\Omega$ $.$ cm) and 1.8($\Omega$ $.$ cm) when thickness is 600(${\AA}$), and the diffusion time is both 110[min] and 150[min] when thickness is 600[${\AA}$]. In DC dielectric strength due to the each resistivity, it is confirmed that almost of the leakage current and breakdown current is flowed through n+ source when positive bias is applied, but is flowed through P region when negative bias is applied. It is thought that the dielectric strength due to the diffusion time is the contribution as increasing of p region.