A dynamic general equilibrium analysis on fostering a hydrogen economy in Korea

Hydrogen is anticipated to become one of the major alternative energy technologies for a sustainable energy system. This study analyzes the dynamic economic impacts of building a hydrogen economy in Korea employing a dynamic Computable General Equilibrium (CGE) model. As a frontier technology, hydrogen is featured as having a slow diffusion rate due to option value, positive externality, resistance of old technology, and complementary vintages. Without government intervention, hydrogen-derived energy will supply up to 6.5% of final energy demand by 2040. Simulation outcomes show that as price subsidy rates increase by 10%, 20%, and 30%, hydrogen demand will increase by 9.2%, 15.2%, and 37.7%, respectively, of final energy demand by 2040. The output of the transportation sector will increase significantly, while demands for oil and electricity will decline. Demands for coal and LNG will experience little change. Household consumption will decline because of the increase of income taxes. Overall GDP will increase because of the increase in exports and investments. CO₂ emission will decline for medium and high subsidy rate cases, but increase for low subsidy cases. Ultimately, subsidy policy on hydrogen will not be an effective measure for mitigating CO₂ emission in Korea when considering dynamic general equilibrium effects.     

Investigation of microwave dielectric properties in the BaO–Nb2O5–P2O5 system

BaNb₂P₂O₁₁ and Ba₃Nb₂P₄O₁₈ compounds with corner-sharing NbO₆ octahedra and PO₄ tetrahedra were prepared by a conventional solid-state reaction method. The crystal structure and microstructure were investigated by X-ray powder diffraction and field emission scanning electron microscope, respectively. The microwave dielectric properties were measured using a network analyzer. Both ceramics were sintered at a relatively low temperature of 1150 °C and had a relative density of ～96%. Compared to Ba₃Nb₂P₄O₁₈, BaNb₂P₂O₁₁ had a higher permittivity of 31.7. However, the quality factor of BaNb₂P₂O₁₁, was smaller than Ba₃Nb₂P₄O₁₈. Furthermore, the effect of the crystal structure on the microwave dielectric properties was investigated.     

Piezoelectric properties of textured Bi3.25La0.75Ti2.97V0.03O12 ceramics fabricated by reactive templated grain growth method

We have fabricated Bi_3.25La_0.75Ti_2.97V_0.03O₁₂ (BLTV) ceramics by reactive templated grain growth method using a Bi₄Ti₃O₁₂ template and investigated the electromechanical coupling coefficient (k) and temperature coefficient of a resonant frequency as a function of temperature. The highly preferentially [00l] oriented BLTV ceramics were obtained and the grain-orientation factor (Lotgering factor) was 83%. The electromechanical coupling coefficient of the longitudinal vibration mode (k ₃₃) and the temperature coefficient of resonant frequency of textured BLTV ceramics were enhanced compared to those of nontextured BLTV ceramics.     

The effect of Bi4Ti3O12 particles addition in lead-free Bi0.5(Na0.75K0.25)0.5TiO3 ceramics

We studied the effect of Bi₄Ti₃O₁₂ (BiT) platelet addition in Bi_0.5(Na_0.75K_0.25)_0.5TiO₃ (BNKT) ceramics by preparing two kinds of BNKT ceramics. One type of BNKT ceramic was fabricated by a conventional solid state reaction method (normal sample), while the other by addition of 15 wt% BiT platelets to BNKT powders (BiT-added sample). In the case of BiT-added BNKT ceramics, plate like grains were formed by the reaction of BiT platelets with Na₂CO₃, K₂CO₃, and TiO₂ during the sintering process. The grain size of BiT-added BNKT ceramics was 10 times larger than that of normal BNKT ceramic. The piezoelectric strain and d₃₃ values of BiT-added BNKT ceramics were 0.135% and 225 pm/V, respectively. These values were 35% higher than those of normal BNKT ceramics. The piezoelectric properties of BiT-added BNKT ceramics were enhanced by the higher domain activity due to a decrease in domain density at larger grain sizes.     

Managing demand uncertainty through fuzzy inference in supply chain planning

In this paper, we investigate methods for managing the irregular and uncertain demands involved in supply chain planning. We first build a supply chain planning model based on fuzzy linear programming, which defines demand as a fuzzy parameter. Next, we propose a fuzzy inference approach for converting fuzzy demand into crisp demand. In the proposed fuzzy inference-based approach, judgments of upcoming demand from both internal and external experts are used as input variables to reflect the expected demand irregularity. By adopting fuzzy inference, we can compensate for the limitations of the existing demand treatment approaches, which usually demonstrate poor forecasting performance in cases of irregular demand and thus reduce the accuracy of supply chain planning. To verify the feasibility of the proposed approach, we present an illustrative example of a Korean electronics company.     

The effects of Si on the mechanical twinning and strain hardening of Fe–18Mn–0.6C twinning-induced plasticity steel

The stacking-fault energy (SFE), dislocation slip, mechanical twinning, strain hardening, and yield and tensile strengths were systemically investigated in Fe–18Mn–0.6C–1.5Si twinning-induced plasticity (TWIP) steel. The results were also compared with those for Fe–18Mn–0.6C and Fe–18Mn–0.6C–1.5Al TWIP steels. The SFE decreased by 4 mJ m^?2 per 1 wt.% Si. The addition of Si increased both the yield strength, due mainly to solid solution hardening, and the tensile strength, owing to the high strain hardening that occurred while maintaining a large elongation of over 60%. To examine this high strain hardening, especially at low strains, the volume fractions of the primary and secondary mechanical twins were quantitatively evaluated by combining the merits of electron backscattered diffractometry and transmission electron microscopy. The volume fractions of both the primary and secondary twins were the highest in the Fe–18Mn–0.6C–1.5Si TWIP steel, which had the lowest SFE of the three TWIP steels. In particular, the volume fraction of the secondary mechanical twins increased rapidly with the addition of Si. The contributions of dislocation storage, mechanical twinning and dynamic strain aging (DSA) to the strain hardening were also quantitatively evaluated in the three TWIP steels. The Si-added TWIP steel had the highest strain hardening, due mainly to the active primary and secondary twinning, and experienced negligible DSA. In contrast, the Al-added TWIP steel exhibited the lowest strain hardening due to the reductions in both the mechanical twinning and DSA.     

Head Loss Coefficient Evaluation Based on CFD Analysis for PWR Downcomer and Lower Plenum

Nuclear vendors and utilities perform numerous simulations and analyses in order to ensure the safe operation of nuclear power plants (NPPs). In general, the simulations are carried out using vendor-specific design codes and best-estimate system analysis codes, most of which were developed based on one-dimensional lumped parameter models. During the past decade, however, computers, parallel computation methods, and three-dimensional computational fluid dynamics (CFD) codes have been dramatically enhanced. The use of advanced commercial CFD codes is considered beneficial in the safety analysis and design of NPPs. The present work analyzes the flow distribution in the downcomer and lower plenum of Korean standard nuclear power plants using STAR-CD. The lower plenum geometry of a pressurized water reactor (PWR) is very complicated, as there are many reactor internals, which hinders CFD analysis for real reactor geometry up to now. The present work takes advantage of 3D CAD model so that real geometry of a PWR is used. The results give a clear figure about flow fields in the downcomer and lower plenum of a PWR, which is one of major safety concerns. The calculated pressure drop across the downcomer and lower plenum appears to be in good agreement with the data in engineering calculation. An algorithm that can evaluate the head loss coefficient, which is necessary for thermal-hydraulic system code running, was suggested based on these CFD analysis results.