• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.36-43
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• 2015

Since the crack generation and its propagation caused by welding defects is one of the main hull damage patterns, the simulation of crack propagation process has an important significance for ship safety. Based on interface element method, a finite element model to simulate crack propagation is studied in the paper. A Lennard-Jones type potential function is employed to define potential energy of the interface element. Tensile tests of steel flat plates with initial central crack are carried out. Surface energy density and spring critical stress that are suitable for the simulation of crack propagation are determined by comparing numerical calculation and tests results. Based on a large number of simulation results, the curve of simulation correction parameter plotted against the crack length is calculated.

• Journal of the Korean Mathematical Society
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• v.54 no.2
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• pp.663-673
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• 2017

We consider the multi-harmonic model for the bubble evolution in the Rayleigh-Taylor instability in two and three dimensions. We extend the multi-harmonic model in two dimensions to a high-order and present a new class of steady-state solutions of the bubble motion. The growth rate of the bubble is expressed by a continuous family of two free parameters. The critical point in the family of solutions is identified as a saddle point and is chosen as the physically significant solution. We also present the multi-harmonic model in the cylindrical geometry and find the steady-state solution of the axisymmetric bubble. Validity and limitation of the model are also discussed.

• Environmental Engineering Research
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• v.22 no.3
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• pp.231-236
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• 2017

Solid waste disposal and management is a critical problem in Nigeria. Annually, a huge quantity of municipal solid waste is generated in Aba. Municipal solid waste disposal in Aba poses severe challenge to environmental safety, public health and welfare of citizens. The situation is made worse by the indiscriminate dumping of refuse at roadsides, streets, waterways and empty lands. The impact of this waste management practice in Aba is environmental deterioration. Efforts to improve waste management in Aba have not recorded significant success. This paper therefore aims to highlight the challenges facing the waste management sector in Aba and proffer solutions on how to improve the sector.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.116-117
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• 2006

Increasing the solvent molecular size leads to shrinkage of the polymer chains and increase of the critical overlap concentrations. In addition, the dependency of $R_{g}$ on polymer concentration under normal solvent conditions and solvent molecular size is in good agreement with scaling laws. When the solvent molecular size approaches the ideal end-to-end distance of the polymer chain, an extra aggregation of polymer chains occurs, and the solvent becomes the so-called medium-sized solvent. When the size of solvent molecules is smaller than the medium size, the polymer chains are swollen or partially swollen. However, when the size of solvent molecules is larger than the medium size, the polymer coils shrink and segregate, enwrapped by the large solvent molecules.

• Journal of the Korean Ceramic Society
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• v.27 no.3
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• pp.423-429
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• 1990

YBa2Cu3Ox ceramics superconductors fabricated using solid state reaction usually contain second phases, such as BaCuO2 and CuO. These second phases are located long the grain boundaries and enhance the abnormal growth of YBa2Cu3Ox grains and, consequently, generate the microcracks. These second phaases were reduced by adding Y2BaCuO5 into solid state reacted YBa2Cu3Ox ceramics. Y2BaCuO5 reacts with grain boundary second phases and reduces the grian size of the ceramics. It was observed the critical current density was improved by adding Y2BaCuO5 into solid state reacted YBa2Cu3Ox ceramic superconductor.

• 한국초전도학회:학술대회논문집
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• v.10
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• pp.41-44
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• 2000

The mixed-state Hall angle has been measured in Hg-based superconducting thin films as functions of magnetic fields (H) up to 18 T. The temperature dependence of the Hall angle shows a peak (T$^{\ast}$) at low temperature, which is consistent with a crossover point from the thermally activated flux flow (TAFF) to a critical region (CR). At low fields below 10 T, T$^{\ast}$ shifts to low temperature with increasing fields. Interestingly, however, we found that T$^{\ast}$ is independent of fields above 10 T, suggesting unusual vortex state. A physical implication of H - T$^{\ast}$ line will be discussed.

• Progress in Superconductivity
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• v.2 no.1
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• pp.39-42
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• 2000

The mixed-state Hall angle has been measured in Hg-based superconducting thin films as functions of magnetic fields (H) up to 18 T. The temperature dependence of the Hall angle shows a peak (T*) at low temperature, which is consistent with a crossover point from the thermally activated flux flow (TAFF) to a critical region (CR). At low fields below 10 T, T* shifts to low temperature with increasing fields. Interestingly, however, we found that T* is independent of fields above 10 T, suggesting unusual vortex state. A physical implication of H-T* line will be discussed.

• Progress in Superconductivity and Cryogenics
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• v.2 no.2
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• pp.15-19
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• 2000

The stability of variable cross-sectional area HTS current lead is considered. The cross-sectional area is varied to have a constant safety factor which is defined as the ratio of operating current and critical current of superconductor. As the constant area HTS lead, the variable cross-sectional area HTS lead also has three steady states above the bifurcation point and only one steady state below the bifurcation point. The temperature profiles and current sharing ratios for each steady state are calculated. The heat dissipation into cryogenic system for super-conducting, intermediate, and upper states are compared. For Bi-2333 sheathed with silver-gold alloy 2m length of current lead, and the maximum temperature of upper state seems to be burn-out free below 5m length.

• Journal of ILASS-Korea
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• v.2 no.3
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• pp.32-43
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• 1997

A comparison of predicted molar volume, vapor - liquid equilibrium, enthalpy of vaporization, droplet size history. and vaporization rates with several forms of equation of state has been made. The equation of state (EOS) investigated in this study includes the EOS given by Redlich - Kwong, the Soave - Redlich - Kwong, and the Peng - Robinson. Numerical results indicate that the Peng - Robinson EOS yields more accurate predictions of vapor - liquid equilibrium under a broader range of temperature and pressure conditions, especially at high pressures and near the critical point.

• Journal of Construction Engineering and Project Management
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• v.7 no.3
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• pp.15-25
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• 2017

The existence of material price volatility in construction projects puts forward substantial risks for all parties involved. Depending on the parties involved in the project, type of contracts, and state of the market various risk management strategies are practiced by contracting parties to manage project risks related to price volatility. Unfortunately, in many cases companies fail to select an adequate approach to better manage volatilities of material prices due to the lack of a decision support system to aid in the selection of an appropriate strategy based on the project characteristics. The aim of this study is to identify critical project factors and align them to documented strategies to manage price volatility based on an extensive literature review and industry interviews. This study found Integrated Project Delivery (IPD) as the ideal strategy with respect to project duration; quantitative risk management methods with respect to the cost; and Price Adjustment Clauses (PAC) with respect to the risk allocation, as the top price volatility management strategies.