• Advances in Computational Design
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• v.2 no.2
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• pp.121-131
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• 2017

Collapse was one of the typical common geological hazards during the construction of tunnels. The risk assessment of collapse was an effective way to ensure the safety of tunnels. We established a prediction model of collapse based on Bayesian Network. 76 large or medium collapses in China were analyzed. The variable set and range of the model were determined according to the statistics. A collapse prediction software was developed and its veracity was also evaluated. At last the software was used to predict tunnel collapses. It effectively evaded the disaster. Establishing the platform can be subsequent perfect. The platform can also be applied to the risk assessment of other tunnel engineering.

• International conference on construction engineering and project management
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• 2015.10a
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• pp.213-216
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• 2015

Despite the significant increase of Korean contractors in the international construction market, many SMCCs (Small & Medium Construction Companies) have suffered in the global financial crisis, and some of them have been kicked out of the international market after experiencing huge losses on projects. SMCCs face obstacles in the international market, such as an insufficient ability to gather information and inappropriate management of associated risks, which lead to difficulties in establishing effective business strategies. In other words, making immature decisions without an effective business strategy may cause not only the failure of one project but also the bankruptcy of the SMCC. To overcome this, the research presented herein aims to propose a decision support system for SMCCs, which would screen projects and make a go/no-go decision at the early stages of international projects. The proposed system comprises a double axis: (1) a profit prediction model, which evaluates 10 project properties using an objective methodology based on a historical project performance database and roughly suggests expected profit rate, and (2) a feasibility assessment model, which evaluates 17 project environment factors in a subjective and quantitative methodology based on experience and supervision. Finally, a web-based system is established to enhance the practical usability, which is expected to be a good reference for inexperienced SMCCs to make proper decisions and establish effective business strategies.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.17-23
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• 2012

In this study, the numerical simulation and basin model test have been performed to evaluate sea worthiness and resistance performance for a small pre-planning three type of leisure boats which are U, V, Y shapes of hull forms. As a well known commercial CFD code, Maxsurf, was applied for modeling hull forms used as the solver of motion analysis. Also the model resistance test was carried out to estimate the effective power of boat in the basin tank. Numerical simulation and model test results show that Y-shaped hull is better than the other types in terms of heave and pitch motion, having a key effect on a boat sea worthiness. But V-type hull is more efficiency than others cases in resistance performance.

• International Journal of Quality Innovation
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• v.4 no.1
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• pp.213-219
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• 2003

This paper proposes an efficient and effective BOM management scheme for small and medium manufacturing (SME) companies that produce automobile parts. Automobile part's manufacturers produce very various products due to various automobile characteristics such as types, colors, and options of cars. These products are classified into product groups with common parts and like this product groups with commonality are regarded as product family. This paper proposes a BOM data model for product family structures and implements the practical EXCEL-based BOM management system for real small and medium manufacturing (SU) companies that produces automobile parts.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.6
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• pp.3-12
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• 2008

It is important to estimate accurate effective rainfall to analyse flood flow and long-term runoff for the rational planning, design, and management of water resource. The initial abstraction is also important to estimate effective rainfall. The Soil Conservation Service (SCS) has developed a procedure and it has been most commonly applied to estimate effective rainfall. But the SCS method still has weak points, because of unnatural assumptions such as antecedent moisture conditions and initial abstraction. The coefficient of initial abstraction(K) is depending on the soil moisture condition and antecedent rainfall. The maximum storage capacity of Umax which is calibrated by stream flow data in the proposed watershed was derived from the DAWAST(DAily WAtershed STreamflow) model. The values of K obtained from 69 storm events at the five watersheds are ranging from 0.133 to 0.365 and its mean value is 0.207. Effective rainfall could be estimated more reasonably by introducing new concept of initial abstraction. The equation of $K=0.076Sa^{0.255}$ was recommended instead of 0.2 and it could be applicable to the small-medium rural watersheds.

• Nuclear Engineering and Technology
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• v.29 no.4
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• pp.320-326
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• 1997

The nuclide transport in the one-dimensional porous medium is considered as a first step in developing a decay chain transport in multidimensional inhomogeneous media. A method of solving conventional advection-dispersion equation with decay chain of arbitrary length by using the method of characteristics (MOC) is introduced. In specific cases where the advection are dominant rather than dispersion, the method is known to be useful : one of the most distinctive advantages in applying the model is that the MU minimizes the numerical dispersion, which is distinguished in such common numerical schemes as finite element method and finite difference method. The suggested model is considered to be effective through several illustrations for the case that decay chain of arbitrary length is involved during transport which is difficult to solve by standard numerical solutions if the medium becomes more complicated.

• Coupled systems mechanics
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• v.8 no.4
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• pp.299-313
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• 2019

The paper represents computer modeling of the deformed state of physically nonlinear transversally isotropic bodies with hole. In order to describe the anisotropy of the mechanical properties of transversally-isotropic materials a structurally phenomenological model has been used. This model allows representing the initial material in the form of the coupled isotropic materials: the basic material (binder) considered from the positions of continuum mechanics and the fiber material oriented along the anisotropy direction of the original material. It is assumed that the fibers perceive only the axial tensile-compression forces and are deformed together with the base material. To solve the problems of the theory of plasticity, simplified theories of small elastoplastic deformation have been used for a transversely-isotropic body, developed by B.E. Pobedrya. A simplified theory allows applying the theory of small elastoplastic deformations to solve specific applied problems, since in this case the fibrous medium is replaced by an equivalent transversely isotropic medium with effective mechanical parameters. The essence of simplification is that with simple stretching of composite in direction of the transversal isotropy axis and in direction perpendicular to it, plastic deformations do not arise. As a result, the intensity of stresses and deformations both along the principal axis of the transversal isotropy and along the perpendicular plane of isotropy is determined separately. The representation of the fibrous composite in the form of a homogeneous anisotropic material with effective mechanical parameters allows for a sufficiently accurate calculation of stresses and strains. The calculation is carried out under different loading conditions, keeping in mind that both sizes characterizing the fibrous material fiber thickness and the gap between the fibers-are several orders smaller than the radius of the hole. Based on the simplified theory and the finite element method, a computer model of nonlinear deformation of fibrous composites is constructed. For carrying out computational experiments, a specialized software package was developed. The effect of hole configuration on the distribution of deformation and stress fields in the vicinity of concentrators was investigated.

• ETRI Journal
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• v.31 no.2
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• pp.225-227
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• 2009

A new planar metamaterial (MTM) with simultaneous negative values of permittivity (${\varepsilon}$) and permeability (${\mu}$) is proposed. Our MTM is composed of two identical copper patterns etched on both sides of dielectric laminate, which is very thin and easy to fabricate. Unlike conventional MTMs, the proposed structure shows a negative refractive index (NRI) behavior with respect to a normally incident wave. To explain the underlying principle of the NRI characteristics, an equivalent resonant circuit model based on surface current density distribution is investigated. An eigenmode analysis and a three-dimensional wave simulation for the stacked MTM prism are also performed to verify the existence of negative refraction. The experimental results from the transmission and reflection measurement ensure the validity of our design approach and show good agreement with the theoretically predicted effective medium parameters.

• Journal of Soil and Groundwater Environment
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• v.16 no.5
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• pp.9-17
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• 2011

Positive effect of multiple-PGPR (Plan Growth Promoting Rhizobacteria), isolated from heavy metal contaminated soil, on the germination of Barnyard grass (Echinochloa crus-galli var. frumentacea) was quantitatively estimated in 5 heavy metal (Cd, As, Ni, Cu, and Pb) contaminated liquid medium. The $EC_{50}$ value for respective heavy metal was estimated by TSK (Trimmed Speraman-Karber) model based on germination rate. The results showed overall increase in $EC_{50}$ with PGPR inoculation. The $EC_{50}$ value increased 1.4% from 96.0 mg/L (control) to 97.4 mg/L (PGPR-treated) in As contaminated medium. In Ni contaminated medium, the $EC_{50}$ value increased 31.9% from 148.0 mg/L (control) to 195.2 mg/L (PGPR-treated), while the $EC_{50}$ showed 4.8% increase from 63.4 mg/L (control) to 66.5 mg/L (PGPR-treated) in Cu medium. Overall seedling growth was stronger in the PGPR treated seeds than that in the control, but positive effect on seedling growth was not conspicuous. At effective concentration of 100 mg/L, the average seedling length of the PGPR treatment in As, Cd, Cu, and Ni medium, respectively, was 1.13, 0.14, 0.40, and 0.06 cm longer than that in the control. However, the increase of seedling growth was statistically insignificant (p < 0.05). These results suggest that inoculation of the isolated-PGPR exerts positive effects on seed germination by reducing heavy metal toxicity and can be an effective tool for application of phytoremediation on heavy metal contaminated soils.

• Journal of the Korean Geotechnical Society
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• v.29 no.1
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• pp.93-107
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• 2013

Thermal conduction of the particulate composites or granular materials can be widely used in porous materials and geotechnical engineering. And it has continued to develop "effective thermal conductivity" of medium by modeling energy relationship among particles in medium. This study focuses on the development of the effective thermal conductivity at the unsaturated conditions of soils using the modified network model approach assisted by synthetic 3D random packed systems (DEM method, Discrete Element Method) at the particle scale. To verify the network model, three kinds of glass beads and the Jumunjin sand are used to obtain experimental values at various unsaturated conditions. The PPE (Pressure Plate Extractor) test is then performed to obtain SWCC (Soil-Water Characteristic Curve) of soil samples. In the modified network model, SWCC is used to adjust the equivalent radius of thermal cylinder at contact area between particles. And cutoff range parameter to define the effective zone is also adjusted according to the SWCC at given conditions. From a series of laboratory tests and the proposed network model, the modified network model which adopts a SWCC shows a good agreement in modeling thermal conductivity of granular soils at given conditions. And an empirical correlation between the fraction of the mean radius (${\chi}$) and thermal conductivity at given saturated condition is provided, which can be used to expect thermal conductivity of the granular soils, to estimate thermal conductivity of granular soils.