• Geotechnical Engineering
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• v.7 no.4
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• pp.25-34
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• 1991

In this study, relationships between CBR values tested by Korean Standards (KS CBR) and the elastic moduli from CU compression tests are developed for the subgrade soils. Triaxial compression and KS CBR tests are carried out on five types of samples from 15 points in Korean ezpressways. Triaxial compression tests are performed under 3 types of coifining pressures to generalize the CBR -elastic modulus relationship as functions of confining pressured and mean principal stresses. From the regression analyses of experimental results, equations for relationships between the KS CBR and elastic moduli of roadbed Boils are proposed. An equation for the relation- ship between the KS CBR and the maximum dry density of roadbed soil is also proposed.

• Journal of Korea Water Resources Association
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• v.40 no.5
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• pp.373-382
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• 2007

The exact resolution of channel initiation points is not so easy because of the dynamic behaviors of water movement on the hillslope. To this end, Kim, Joocheol and Kim, Jaehan(2007) have represented the channel network in real world basins for slope-area regimes using DEM. This study is its sequential content and then proposes the reliabilities of the hypothetical channel networks identified from DEM, which are assessed based on the geometric characteristics of drainage density and source-basin. The resulting drainage structures on the natural basin can be found to be depicted remarkably depending on the hypothetical channel network applied by slop-area threshold criterion. In addition, it is shown that there is a wonderful geometric similarity between the shapes of source- basin in a geomorphologically homogeneous region. Area threshold criterion could have restricted the shape of source-basin, so that it might bring about the incorrect drainage structures. But the hypothetical channel networks identified from DEM deserves special emphasis on expressing the space-filling structures nonetheless.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.3
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• pp.149-154
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• 2014

The cross-correntropy concept can be expressed with inner products of two different probability density functions constructed by Gaussian-kernel density estimation methods. Blind algorithms based on the maximization of the cross-correntropy (MCC) and a symbol set of randomly generated N samples yield superior learning performance, but have a huge computational complexity in the update process at the aim of weight adjustment based on the MCC. In this paper, a method of reducing the computational complexity of the MCC algorithm that calculates recursively the gradient of the cross-correntropy is proposed. The proposed method has only O(N) operations per iteration while the conventional MCC algorithms that calculate its gradients by a block processing method has $O(N^2)$. In the simulation results, the proposed method shows the same learning performance while reducing its heavy calculation burden significantly.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.1C
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• pp.7-16
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• 2012

In this paper, using the principle of Static Measurement Methods suggested by Huang (1998), a new experimental device has been made and used in order to calculate the unsaturated permeability of Nak-dong river sand with silt which is an important basic property in the unsaturated soil. This device was designed to measure changes of the unsaturated permeability according to the increase of matric suction. The value of the unsaturated permeability obtained in testing and that obtained using the empirical permeability functional formula were compared and analyzed. As a result, the value of the unsaturated permeability tends to be decreased according to the increase of relative density, silt content and matric suction. This tendency shows it is very closely related to the change of moisture content and void ratio. The empirical permeability functional formula presented by Frelund & Xing (1995) was regarded as the most appropriate model to represent the unsaturated permeability of Nak-dong River silty sand.

• Journal of IKEEE
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• v.15 no.3
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• pp.198-204
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• 2011

In this letter, another analytical approach for the opportunistic amplify-and-forward (OAF) relay systems is proposed over Rayleigh fading channels. Based on set-operation at the selected relay node, its selection probability as the best relay is derived and then, the probability density function (PDF) of the received instantaneous signal-to-noise ratio (SNR) is expressed as a more tractable form in which the number of summations and the length of each summation are specified. Then, the average error rate, outage probability, and average channel capacity are obtained as approximated closed-forms. Simulation results are finally presented to validate that the proposed analytical expressions can be a unified frame work covering all Rayleigh fading channel conditions. Furthermore, it is confirmed that OAF schemes can outperform the other non-selective schemes on the average error rate, outage probability, and average channel capacity.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.61-66
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• 2001

Defocused Fourier plane holograms are stored in disk-type holographic memories where thin recording media are used, the areal storage density per hologram and the intensity uniformity of the signal beam at the recording plane are studied. As the pixel pitch of the spatial light modulator that represents binary data increases, the storage density per hologram increases if exact Fourier holograms are stored. When defocused Fourier plane holograms are stored, however, we show that there exists an optimal pixel pitch that maximizes the area storage density per hologram in general, to increase the areal storage density per hologram, f/# of the Fourier transform lens that focuses the data image should be as small as possible. In this case, not only the intensity distribution at the recording plane but also the recording area becomes very sensitive to the degree of defocusing. Therefore, even if the exact Fourier plane holograms are stored, the defocusing effect owing to the medium thickness should be taken into account to achieve the maximal areal storage density per hologram.logram.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.169-177
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• 2009

In this paper, the rotated hexagonal lattice model (RHLM) was proposed, which is applied to pedestrian flow, and developed the simulation model for the pedestrian counterflow. RHLM is an upgrade version of the square lattice model(SLM) and hexagonal lattice model(HLM). The simulation was performed at the hexagonal lattice $20{\times}20$ and evaluated by different speed, density and flow conditions. Simulation results are compared with SLM and show that RHLM can replicate the characteristics of pedestrian traffic more effectively and reliably than any other existing models from several perspectives. First, RHLM can explain the shortest-path movement of pedestrians and more realistic avoidance motion. If they cannot move straight direction, they can move shorter distance from previous position to destination. Second, RHLM reflects the characteristics that the pedestrian can move with higher capacity and the speed of pedestrian flow is hard to zero.

• Journal of the Korea Society for Simulation
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• v.15 no.4
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• pp.29-39
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• 2006

Sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. A number of routing protocols to transmit the data between the base station and sensor nodes have been proposed. Intanagonwiwat et al. proposed the directed diffusion in which the base station sends interest messages and waits for data from the nodes in the specific regions. Since the directed diffusion propagates every interest message to whole nodes in the network, it causes energy dissipation of nodes. In this paper, we propose a novel data propagation method, which limits the data transmission area according to a threshold value for reducing the energy consumption in the network. A fuzzy logic is exploited to determine the threshold value by considering the energy and density of all the deployed nodes. The simulation models are designed and implemented based on DEVS formalism which is theoretically well grounded means of expressing discrete event simulation models.

• Journal of the Korean Chemical Society
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• v.42 no.4
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• pp.398-410
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• 1998

For non-linear solution of the Boltzmann equation, the cumulant moment method has been studied. To apply the method to the normal shock wave problem, we restricted ourselves to the monatomic Maxwell molecular gases. The method is based on the iterative approach developed by Maxwell-Ikenberry-Truesdell (MIT). The original MIT approach employs the equilibrium distribution function for the initial values in beginning the iteration. In the present work, we use the Mott-Smith bimodal distribution function to calculate the initial values and follow the MIT iteration procedure. Calculations have been carried out up to the second iteration for the profiles of density, temperature, stress, heat flux, and shock thickness of strong shocks, including the weak shock thickness of Mach range less than 1.4. The first iteration gives a simple analytic expression for the shock profile, and the weak shock thickness limiting law which is in exact accord with the Navier-Stokes theory. The second iteration shows that the calculated strong shock profiles are consistent with the Monte Carlo values quantitatively.

• Journal of Intelligence and Information Systems
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• v.8 no.2
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• pp.177-187
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• 2002

Spatial data mining is a process to discover interesting relationships and characteristics those exist implicitly in a spatial database. Many spatial clustering algorithms have been developed. But, there are few approaches that focus simultaneously on clustering spatial data and assigning weight to non-spatial attributes of objects. In this paper, we propose a new spatial clustering algorithm, called DBSCAN-W, which is an extension of the existing density-based clustering algorithm DBSCAN. DBSCAN algorithm considers only the location of objects for clustering objects, whereas DBSCAN-W considers not only the location of each object but also its non-spatial attributes relevant to a given application. In DBSCAN-W, each datum has a region represented as a circle of various radius, where the radius means the degree of the importance of the object in the application. We showed that DBSCAN-W is effective in generating clusters reflecting the users requirements through experiments.