• Journal of computational fluids engineering
• /
• v.21 no.1
• /
• pp.43-49
• /
• 2016

Thermal cracking is commonly modeled as plug flow reaction, neglecting the lateral gradients present. In this paper, 2-dimensional computational fluid dynamics including turbulence model and molecular reaction scheme are carried out. This simulation is solved by means of coupled implicit scheme for stable convergence of solution. The reactor is modeled as an isothermal tube, whose length is 1.2 m and radius is 0.01 m, respectively. At first, The radial profile of velocity and temperature at each point are predicted in its condition. Then the bulk temperature and conversion curve along the axial direction are compared with other published data to identify the reason why discussed variations of properties are important to product yield. Finally, defining a new non-dimensional number, Effect of interaction with turbulence, heat transfer and chemical reaction are discussed for design of thermal cracking furnace.

• Proceedings of the KSME Conference
• /
• 2001.11a
• /
• pp.266-271
• /
• 2001

Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steels were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• Coupled systems mechanics
• /
• v.3 no.3
• /
• pp.247-265
• /
• 2014

This article discusses the dynamic response of Bernoulli-Euler straight beam with angular elastic supports subjected to moving load with variable velocity. A new engineering approach for determination of the dynamic effect from the moving load on the stressed and strained state of the beam has been developed. A dynamic coefficient, a ratio of the dynamic to the static deflection of the beam, has been defined on the base of an infinite geometrical absolutely summable series. Generalization of the R. Willis' equation has been carried out: generalized boundary conditions have been introduced; the generalized elastic curve's equation on the base of infinite trigonometric series method has been obtained; the forces of inertia from normal and Coriolis accelerations and reduced beam mass have been taken into account. The influence of the boundary conditions and kinematic characteristics of the moving load on the dynamic coefficient has been investigated. As a result, the dynamic stressed and strained state has been obtained as a multiplication of the static one with the dynamic coefficient. The developed approach has been compared with a finite element one for a concrete engineering case and thus its authenticity has been proved.

• Nuclear Engineering and Technology
• /
• v.49 no.2
• /
• pp.373-379
• /
• 2017

Seismic probabilistic safety assessments are used to help understand the impact potential seismic events can have on the operation of a nuclear power plant. An important component to seismic probabilistic safety assessment is the seismic hazard curve which shows the frequency of seismic events. However, these hazard curves are estimated assuming a normal distribution of the seismic events. This may not be a strong assumption given the number of recorded events at each source-to-site distance. The use of a normal distribution makes the calculations significantly easier but may underestimate or overestimate the more rare events, which is of concern to nuclear power plants. This paper shows a preliminary exploration into the effect of using a distribution that perhaps more represents the distribution of events, such as the t-distribution to describe data. The integration of a probability distribution with potentially larger tails basically pushes the hazard curves outward, suggesting a different range of frequencies for use in seismic probabilistic safety assessments. Therefore the use of a more realistic distribution results in an increase in the frequency calculations suggesting rare events are less rare than thought in terms of seismic probabilistic safety assessment. However, the opposite was observed with the ground motion prediction equation considered.

• Journal of Power System Engineering
• /
• v.8 no.4
• /
• pp.11-16
• /
• 2004

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests were conducted on 2124-T851 aluminum alloy specimens. Three test spectra were generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results were compared with the data obtained from the flight-simulation loading. The experimental results show that the ranges equal to or smaller than 5% of the maximum load do not contribute to crack growth behavior because these are below the initial stress intensity factor range. Omitting these from the flight-simulation loading, test time can be reduced by 54%. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decreased, and crack growth curve deviated from the crack growth data under the flight-simulation loading because loading cycles above fatigue fracture toughness were omitted.

• Nuclear Engineering and Technology
• /
• v.33 no.6
• /
• pp.626-637
• /
• 2001

A series of study on energy dependence in chemiluminescence dosimetry with sugar and sorbite produced in two different countries was carried out administering a dose of 5 Gy to the samples at six different mean photon energies of 30, 50, 80, 130, 662 and 1250 keV. The results revealed distinct energy dependence of chemiluminescence(CL) output of sugar and sorbite. Although the energy dependence, in general, could be fitted by a polynomial of (os E, with I being radiation energy, up to cubic term, we reached a conclusion that the adoption of a fitting function, $y_{R}$$^{=a}$.(1-e $^{-b.logE}$)$^{c}$ +d, deduced from theoretical energy response curve calculated as the ratio of the mass energy absorption of the samples of interest to the soft tissue is more reasonable and rational. Herecoefficients $y_{R}$ is CL intensity, and a, b, c and d are constants to be determined in the fitting process. Energy dependence of relative sensitivities of one sample to the other, discrepancy in sensitivities of the samples from the two countries, and prominent grain size effect in Sorbitol were also shown.shown.

• Nuclear Engineering and Technology
• /
• v.53 no.7
• /
• pp.2396-2406
• /
• 2021

The Pacific Earthquake Engineering Research (PEER) Center has been developing a performance-based earthquake engineering (PBEE) methodology, which is based on explicit determination of performance, e.g., monetary losses, in a probabilistic manner where uncertainties in earthquake ground motion, structural response, damage estimation, and losses are explicitly considered. To carry out the PEER PBEE procedure for a component of the nuclear power plant (NPP) such as the cable tray system, hazard curve and spectra were defined for two hazard levels of the ground motions, namely, operation basis earthquake, and safe shutdown earthquake. Accordingly, two sets of spectral compatible ground motions were selected for dynamic analysis of the cable tray system. In general, the PBEE analysis of the cable tray in NPP was introduced where the resulting floor motions from the time history analysis (THA) of the NPP structure should be used as the input motion to the cable tray. However, for simplicity, a finite element model of the cable tray was developed for THA under the effect of the selected ground motions. Based on the structural analysis results, fragility curves were generated in terms of specific engineering demand parameters. Loss analysis was performed considering monetary losses corresponding to the predefined damage states. Then, overall losses were evaluated for different damage groups using the PEER PBEE methodology.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.5
• /
• pp.43-52
• /
• 2021

This study is the first to scrutinize how real effective exchange rate, together with the vehicle currency exchange rate, asymmetrically influences the total trade balance between ASEAN (Association of Southeast Asian Nations) and the EU (European Union). This research employs quarterly data between 2000Q1 and 2018Q1, which is derived from several sources. We introduce a method for constructing the double-aggregated real effective exchange rate between ASEAN and the EU that captures the roles of all their currencies. Moreover, we propose the formula to compute vehicle currency exchange rate to assess the importance of vehicle currency in ASEAN-EU trade. Additionally, as asymmetrical impacts of exchange rate on trade balance are well documented by current studies, we employ Nonlinear Autoregressive Distributed Lag (NARDL) model of Shin et al. (2014) to analyze the impacts of currency depreciation as well as appreciation in detail. The findings confirm the prominence of USD as vehicle currency in ASEAN-EU trade. Both depreciation and appreciation of ASEAN's currencies against USD can foster ASEAN's trade balance in the long run. Short-run asymmetrical impacts as well as J-curve effect are found in the vehicle currency models only. The results are robust for the cases of EU-28 and EU-27.

• Nuclear Engineering and Technology
• /
• v.54 no.4
• /
• pp.1312-1320
• /
• 2022

The earlier studies have analyzed theoretical links between nuclear energy and carbon dioxide (CO₂) emissions concerning territorial (or production-based) emissions. Here using the latest available dataset, this study explores the impacts of nuclear energy on production-based and consumption-based CO₂ emission in the era of globalization for the Organization for Economic Co-operation and Development (OECD) countries. The Driscoll-Kraay regression method reveals that nuclear energy is beneficial for the reduction of production-based CO₂ emissions. However, it is revealed that nuclear energy does not reduce consumption-based CO₂ emissions that are traded internationally and hence not comprised in conventional production-based emissions (territory) inventories. Globalization tends to reduce both production-based and demand-based carbon emissions. Finally, Environmental Kuznets Curve (EKC) is validated for both kinds of CO₂ emissions. The findings may deliver practical policy implications related to nuclear energy and CO₂ emissions for selected countries.

• Journal of Korean Port Research
• /
• v.6 no.1
• /
• pp.69-91
• /
• 1992

A new type of horizontal submerged break water or fixed structure to control waves near coastal area is introduced to focus wave energy before or behind it. Intentionally, the water depth near the structure is changed gradually to get a refraction and diffraction effect. The concentration of wave energy due to the structure was analyzed for the selected design of structure. The shape of the submerged structure in consideration is a circular combined with elliptical curve not to cause reflection of waves at the extreme edge of the structure but cause wave scattering. The direction of the structure against the incident wave is changed easily in the model Applying a regular wave train the following were examined. 1) whether a crescent plain submerged structure designed by the wave refraction theory can concentrate wave energy at a focal zone behind and before it without wave breaking phenomenon. 2) Location of maximum wave amplification factor in terms of the incident wave direction, wave period, etc. In any event the study would contribute to control waves near coastal area and to protect a beach from erosion without interruption of ocean view it is an useful study for the concentration of wave energy efficiently with the increase of wave height.