• Convergence Security Journal
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• v.8 no.2
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• pp.15-25
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• 2008

In today's broadcasting and communication systems, many applications are converged information in a complicated manner by interworking with various networks such as satellite networks. Specifically, as broadcasting and communication systems have become more advanced in terms of technology and capacity, the increase in information assets has created new types of threats and vulnerabilities that we're not previously apparent. This paper has proposed the following methodologies for analyzing the risks and estimating the economical that could arise in broadcasting and communication convergence systems. First, the assets are prioritized by grading them according to confidentiality(copyrights), integrity, and availability. Based on such an analysis, this paper presents a model that can be used for verifying the risk variables caused by changing threats and vulnerabilities. Second, this paper presents a method for quantitatively estimating the economical caused by countermeasure costs for each time period.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.8-15
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• 2002

For the large scale computation of turbulent flows around an arbitrarily shaped body, a parallel LES (large eddy simulation) code has been recently developed in which domain decomposition method is adopted. METIS and MPI (message Passing interface) libraries are used for domain partitioning and data communication between processors, respectively. For unsteady computation of the incompressible Wavier-Stokes equation, 4-step splitting finite element algorithm [1] is adopted and Smagorinsky or dynamic LES model can be chosen fur the modeling of small eddies in turbulent flows. For the validation and performance-estimation of the parallel code, a three-dimensional laminar flow generated by natural convection inside a cube has been solved. Then, we have solved the turbulent flow around MIRA (Motor Industry Research Association) model at $Re = 2.6\times10^6$, which is based on the model height and inlet free stream velocity, using 32 processors on IBM SMP cluster and compared with the existing experiment.

• Structural Engineering and Mechanics
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• v.41 no.1
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• pp.25-41
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• 2012

Kriging surrogate model provides explicit functions to represent the relationships between the inputs and outputs of a linear or nonlinear system, which is a desirable advantage for response estimation and parameter identification in structural design and model updating problem. However, little research has been carried out in applying Kriging model to crack identification. In this work, a scheme for crack identification based on a Kriging surrogate model is proposed. A modified rectangular grid (MRG) is introduced to move some sample points lying on the boundary into the internal design region, which will provide more useful information for the construction of Kriging model. The initial Kriging model is then constructed by samples of varying crack parameters (locations and sizes) and their corresponding modal frequencies. For identifying crack parameters, a robust stochastic particle swarm optimization (SPSO) algorithm is used to find the global optimal solution beyond the constructed Kriging model. To improve the accuracy of surrogate model, the finite element (FE) analysis soft ANSYS is employed to deal with the re-meshing problem during surrogate model updating. Specially, a simple method for crack number identification is proposed by finding the maximum probability factor. Finally, numerical simulations and experimental research are performed to assess the effectiveness and noise immunity of this proposed scheme.

• Structural Engineering and Mechanics
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• v.42 no.6
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• pp.849-866
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• 2012

Single span historic bridges often contain non-prismatic members identified with a varying depth along their span lengths. Commonly, the symmetric parabolic height variations having the constant haunch length ratio of 0.5 have been selected to lower the stresses at the high bending moment points and to maintain the deflections within the acceptable limits. Due to their non-prismatic geometrical configuration, their assessment, particularly the computation of fixed-end horizontal forces (FEFs) and fixed-end moments (FEMs) becomes a complex problem. Therefore, this study aimed to investigate the behavior of non-prismatic beams with symmetrical parabolic haunches (NBSPH) having the constant haunch length ratio of 0.5 using finite element analyses (FEA). FEFs and FEMs due to vertical loadings as well as the stiffness coefficients and the carry-over factors were computed through a comprehensive parametric study using FEA. It was demonstrated that the conventional methods using frame elements can lead to significant errors, and the deviations can reach to unacceptable levels for these types of structures. Despite the robustness of FEA, the generation of FEFs and FEMs using the nodal outputs of the detailed finite element mesh still remains an intricate task. Therefore, this study advances to propose effective formulas and dimensionless estimation coefficients to predict the FEFs, FEMs, stiffness coefficients and carry-over factors with reasonable accuracy for the analysis and re-evaluation of the NBSPH. Using the proposed approach, the fixed-end reactions due to vertical loads, and also the stiffness coefficients and the carry-over factors of the NBSPH can be determined without necessitating the detailed FEA.

• ETRI Journal
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• v.36 no.4
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• pp.662-672
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• 2014

Human action recognition is used in areas such as surveillance, entertainment, and healthcare. This paper proposes a system to recognize both single and continuous human actions from monocular video sequences, based on 3D human modeling and cyclic hidden Markov models (CHMMs). First, for each frame in a monocular video sequence, the 3D coordinates of joints belonging to a human object, through actions of multiple cycles, are extracted using 3D human modeling techniques. The 3D coordinates are then converted into a set of geometrical relational features (GRFs) for dimensionality reduction and discrimination increase. For further dimensionality reduction, k-means clustering is applied to the GRFs to generate clustered feature vectors. These vectors are used to train CHMMs separately for different types of actions, based on the Baum-Welch re-estimation algorithm. For recognition of continuous actions that are concatenated from several distinct types of actions, a designed graphical model is used to systematically concatenate different separately trained CHMMs. The experimental results show the effective performance of our proposed system in both single and continuous action recognition problems.

• Computers and Concrete
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• v.21 no.6
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• pp.697-703
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• 2018

Compressive strength is one of the most important engineering properties of concrete, and testing of the compressive strength of concrete specimens is often costly and time consuming. In order to provide the time for concrete form removal, re-shoring to slab, project scheduling and quality control, it is necessary to predict the concrete strength based upon the early strength data. However, concrete compressive strength is affected by many factors, such as quality of raw materials, water cement ratio, ratio of fine aggregate to coarse aggregate, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete. The concrete compressive strength is a quite nonlinear function that changes depend on the materials used in the concrete and the time. This paper presents an adaptive neuro-fuzzy inference system (ANFIS) for the prediction of concrete compressive strength. The training of fuzzy system was performed by a hybrid method of gradient descent method and least squares algorithm, and the subtractive clustering algorithm (SCA) was utilized for optimizing the number of fuzzy rules. Experimental data on concrete compressive strength in the literature were used to validate and evaluate the performance of the proposed ANFIS model. Further, predictions from three models (the back propagation neural network model, the statistics model, and the ANFIS model) were compared with the experimental data. The results show that the proposed ANFIS model is a feasible, efficient, and accurate tool for predicting the concrete compressive strength.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.41.1-41.1
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• 2018

We constrain cosmological parameters by combining three different power spectra measured from galaxy clustering, galaxy-galaxy lensing, and cosmic shear using the Deep Lens Survey (DLS). Two lens bins (centered at z~0.27 and 0.54) and two source bins (centered at z~0.64, and 1.1) containing more than one million galaxies are selected to measure the power spectra. We re-calibrate the initial photo-z estimation of the lens bins by matching with SHELS and PRIMUS and confirm its fidelity by measuring a cross-correlation between the bins. We also check the reliability of the lensing signals through the null tests, lens-source flipping and cross shear measurement. Residual systematic errors from photometric redshift and shear calibration uncertainties are marginalized over in the nested sampling during our parameter constraint process. For the flat LCDM model, we determine S_8=sigma_8(Omega_m/0.3)^0.5=0.832+-0.028, which is in great agreement with the Planck data. We also verify that the two independent constraints from the cosmic shear and the galaxy clustering+galaxy-galaxy lensing measurements are consistent with each other. To address baryonic feedback effects on small scales, we marginalize over a baryonic feedback parameter, which we are able to constrain with the DLS data alone and more tightly when combined with Planck data. The constrained value hints at the possibility that the AGN feedback in the current OWLS simulations might not be strong enough.

• Ocean Systems Engineering
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• v.12 no.2
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• pp.143-157
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• 2022

In this study, the nominal wake field of a semi-displacement type high-speed vessel was computed at full scale by using CFD (Computational Fluid Dynamics) and GEOSIM-based approaches. A scale effect investigation on nominal wake field of benchmark Athena vessel was performed with two models which have different model lengths. The members of the model family have the same Fr number but different Re numbers. The spatial components of nominal wake field have been analyzed by considering the axial, radial and tangential velocities for models at different scales. A linear feature has been found for radial and tangential components while a nonlinear change has been obtained for axial velocity. Taylor wake fraction formulation was also computed by using the axial wake velocities and an extrapolation technique was carried out to get the nonlinear fit of nominal wake fraction. This provides not only to observe the change of nominal wake fraction versus scale ratios but also to estimate accurately the wake fraction at full-scale. Extrapolated full-scale nominal wake fractions by GEOSIM-based approach were compared with the full-scale CFD result, and a very good agreement was achieved. It can be noted that the GEOSIM-based extrapolation method can be applied for estimation of the nominal wake fraction of semi-displacement type high-speed vessels.

• Earthquakes and Structures
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• v.24 no.2
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• pp.97-109
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• 2023

This experimental study investigates the effectiveness of applying carbon fiber reinforced polymer (CFRP) jackets for the retrofit of short reinforced concrete (RC) columns with inadequate transverse reinforcement and stirrup spacing to longitudinal rebar diameter equal to 12. RC columns scaled at 1/3, with round and square section, were subjected to axial compression up to failure. A damage scale is introduced for the assessment of the damage severity, which focusses on the extent of buckling of the longitudinal rebars. The damaged specimens were subsequently repaired with unidirectional CFRP jackets without any treatment of the buckled reinforcing bars and were finally re-tested to failure. Test results indicate that CFRP jackets may be effectively applied to rehabilitate RC columns (a) with inadequate transverse reinforcement constructed according to older practices so as to meet modern code requirements, and (b) with moderately buckled bars without the need of previously repairing the reinforcement bars, an application technique which may considerably facilitate the retrofit of earthquake damaged RC columns. Factors for the estimation of the reduced mechanical properties of the repaired specimens compared to the respective values for intact CFRP-jacketed specimens, in relation to the level of damage prior to retrofit, are proposed both for the compressive strength and the average modulus of elasticity. It was determined that the compressive strength of the retrofitted CFRP-jacketed columns is reduced by 90% to 65%, while the average modulus of elasticity is lower by 60% to 25% in respect to similar undamaged columns jacketed with the same layers of CFRP.

• Korea Trade Review
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• v.47 no.2
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• pp.31-46
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• 2022

The purpose of this study is to measure the degree of discrepancies in the bilateral trade data between South Korea and its five major trade partners and to identify the key factors causing the discrepancies. By analyzing statistics based on the CIF/FOB ratio estimation and taking into consideration the trade flow via Hong Kong, the study finds that the discrepancies in South Korea's trade data with the US, Vietnam, and Japan are insignificant. In case of Hong Kong, however, the value of South Korea's import from Hong Kong is extensively inconsistent with Hong Kong's export to South Korea(i.e. the mirror data) while the value of South Korea's export to Hong Kong generally corresponds to its mirror data. Such discrepancies are caused by differences in recording re-exports, which are often found in the trade flow via entrepôt economics including Hong Kong. Meanwhile, discrepancies in reported bilateral trade flows between South Korea and People's Republic of China(PRC) remain relatively marginal. The discrepancy of statistics between South Korea as the exporter and PRC as the importer is mainly caused by the trade flow via Hong Kong. On the other hand, the discrepancy of statistics between South Korea as the importer and PRC as the exporter is assumably due to the differences in attribution of trade partners.