• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.961-971
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• 2004

Methods for determination of the crack opening stress intensity factor ($K_{op}$) and for estimation of the effective stress intensity factor range ($\Delta{K}_{eff}$) are evaluated for crack growth test data of aluminum alloys. Three methods of determining $K_{op}$, visual measurement, ASTM offset compliance method, and the neural network method proposed by Kang and Song, and three methods of estimating $\Delta{K}_{eff}$, conventional, the 2/PIO and 2/PI methods proposed by Donald and Paris, are compared in a quantitative manner by using evaluation criteria. For all $K_{op}$ determination methods discussed, the 2/PI method of estimating $\Delta{K}_{eff}$ provides good results. The neural network method of determining $K_{op}$ provides good correlation of crack growth data. It is recommended to use 2/PI estimation with the neural $K_{op}$ determination method. The ASTM offset method used in conjunction with 2/PI estimation shows a possibility of successful application. It is desired to improve the ASTM method.

• Nuclear Engineering and Technology
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• v.48 no.5
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• pp.1120-1125
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• 2016

The neutron decay constant, ${\alpha}$, and effective delayed neutron fraction, ${\beta}_{eff}$, are important parameters for the control of the dynamic behavior of nuclear reactors. For the heavy water zero power reactor (HWZPR), this document describes the measurements of the neutron decay constant by noise analysis methods, including variance to mean (VTM) ratio and endogenous pulse source (EPS) methods. The measured ${\alpha}$ is successively used to determine the experimental value of the effective delayed neutron fraction as well. According to the experimental results, ${\beta}_{eff}$ of the HWZPR reactor under study is equal to 7.84e-3. This value is finally used to validate the calculation of the effective delayed neutron fraction by the Monte Carlo methods that are discussed in the document. Using the Monte Carlo N-Particle (MCNP)-4C code, a ${\beta}_{eff}$ value of 7.58e-3 was obtained for the reactor under study. Thus, the relative difference between the ${\beta}_{eff}$ values determined experimentally and by Monte Carlo methods was estimated to be < 4%.

• Journal of the Korean Chemical Society
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• v.18 no.5
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• pp.307-319
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• 1974

The accuracy of the uniform WKB solution for a two-turning point problem is examined in comparison with the corresponding numerical solution. It is found that the uniform WKB solution is extremely accurate. Various Franck-Condon factors for a model system are calculated as an example of applications of such approximate wavefunction. The accuracy of the factors thus calculated is very good. By using the uniform WKB wavefunctions, we have examined the asymptotic limit of the Frank-Condon factors and derived the condition for the frequencies of the transitions, $E'_{n'J'}-U'_{eff}(r_s)=E"_{n"J"}-U"_{eff}(r_s),$, which was obtained by Mulliken using physical arguments.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.790-802
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• 2022

Large-scale reactor simulation often requires the use of Monte Carlo calculation techniques to estimate important reactor parameters. One drawback of these Monte Carlo calculation techniques is they inevitably result in some uncertainty in calculated quantities. The present study includes parametric uncertainty quantification (UQ) and sensitivity analysis (SA) on the Advanced Test Reactor Critical (ATRC) facility housed at Idaho National Laboratory (INL) and addresses some complications due to Monte Carlo uncertainty when performing these analyses. This approach for UQ/SA includes consideration of Monte Carlo code uncertainty in computed sensitivities, consideration of uncertainty from directly measured parameters and a comparison of results obtained from brute-force Monte Carlo UQ versus UQ obtained from a surrogate model. These methodologies are applied to the uncertainty and sensitivity of k_eff for two sets of uncertain parameters involving fuel plate geometry and fuel plate composition. Results indicate that the less computationally-expensive method for uncertainty quantification involving a linear surrogate model provides accurate estimations for k_eff uncertainty and the Monte Carlo uncertainty in calculated k_eff values can have a large effect on computed linear model parameters for parameters with low influence on k_eff.

• Journal of Ocean Engineering and Technology
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• v.9 no.1
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• pp.92-100
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• 1995

The effect of different anisotropy and stress ratio on fatigue crack propagation behavior was investigated under various stress ratio(R=-0.4, -0.2, 0.2, 0.2, 0.4) using pure titanium sheet used in aerospace, chemical and food industry. The rack closure behavior under constant load amplitude fatigue crack propagation test was examined. Fatigue crack propagation rate da/dN was estimated in terms of effective stress intensity factor range, $\Delta$K$_{eff}$, regardless of various stress ratio but was influenced by anisotropy. Also, it was found that the effect of anisotropy was considerably decreased but still not negligible when he da/dN was evaluated by a conventional parameter, $\Delta$$K_{eff}$/E and when the modified da/dN.$\sqrt{\varepsilon}_f$ was evaluated by $\Delta$$K_{eff}$/E. On the other hand, da/dN could be evaluated uniquely by effective new parameter, $\Delta$K$_{eff}$/$sigma_{ys}$, regardless of anisotropy, as int he following equation da/dN=C''[\frac{{\Delta}K_{eff}}{{\sigma}_{ys}}]^{n''}. And effective stress intensity factor range ratio, U was estimated by the following equation with respect to the ratio of reversed plastic zone size, $\Delta r_{p}$ to monotonic plastic zone size, $r_p$ regardless of stress ratio and anisotropy. U=-4.45$(\Delta r_{p}/r_{p})^{2}$+4.1$(\Delta r_{p}/r_{p})$+0.245_{p})$+0.245

• Journal of Korea Trade
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• v.24 no.1
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• pp.59-81
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• 2020

Purpose - This study analyzes the scope of due diligence and risks of banks and K-Sure in trade finance covered by EFF focusing on Moneual case, one of the latest and biggest trade finance fraud cases in Korea. Also, we suggest anti-fraud measures in trade finance on the part of banks and K-Sure in order to give them a desirable way of due diligence and reasonable risk management of export insurance. Design/methodology - Based on Moneual case of trade finance fraud, this study employs the methodology of an extended literature review and analysis of court decisions. Findings - Seoul High Court of Korea failed to decide whether K-Sure was wholly obliged to pay the insurance against the banks' EFF claims, but issued a compulsory mediation order, judging that both the banks and K-Sure were responsible by 50:50. The court may have judged that both the parties had lacked their due diligence in the trade finance. It is quite difficult for trade finance providers to manually investigate whether the transaction is suspected of trade finance fraud, so digitalization of trade finance which can facilitate the prevention and detection of trade fraud needs to be realized quickly. Since there has been no international rule available for open account trade finance up till now, clearly stipulated EFF terms on the exporter's genuine export obligation might have protected K-Sure from the disaster. Originality/value - This study investigates the due diligence of the banks and K-Sure in Moneual case which few researchers have considered, to the best of our knowledge. This study also suggests several practical methods (including block chain) to prevent complicating trade finance fraud amid increasing use of an open account, and further offers reasonable risk management of EFF employing international factoring rule which is also related to problematic open account trade finance.

• Computers and Concrete
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• v.34 no.2
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• pp.247-265
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• 2024

Measuring the fracture toughness of concrete in laboratory settings is challenging due to various factors, such as complex sample preparation procedures, the requirement for precise instruments, potential sample failure, and the brittleness of the samples. Therefore, there is an urgent need to develop innovative and more effective tools to overcome these limitations. Supervised learning methods offer promising solutions. This study introduces seven machine learning algorithms for predicting concrete's effective fracture toughness (K-eff). The models were trained using 560 datasets obtained from the central straight notched Brazilian disc (CSNBD) test. The concrete samples used in the experiments contained micro silica and powdered stone, which are commonly used additives in the construction industry. The study considered six input parameters that affect concrete's K-eff, including concrete type, sample diameter, sample thickness, crack length, force, and angle of initial crack. All the algorithms demonstrated high accuracy on both the training and testing datasets, with R² values ranging from 0.9456 to 0.9999 and root mean squared error (RMSE) values ranging from 0.000004 to 0.009287. After evaluating their performance, the gated recurrent unit (GRU) algorithm showed the highest predictive accuracy. The ranking of the applied models, from highest to lowest performance in predicting the K-eff of concrete, was as follows: GRU, LSTM, RNN, SFL, ELM, LSSVM, and GEP. In conclusion, it is recommended to use supervised learning models, specifically GRU, for precise estimation of concrete's K-eff. This approach allows engineers to save significant time and costs associated with the CSNBD test. This research contributes to the field by introducing a reliable tool for accurately predicting the K-eff of concrete, enabling efficient decision-making in various engineering applications.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.825-828
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• 1992

In this paper, a Hybrid method for an effective channel length($L_{eff}$) on lightly doped drain(LDD) MOSFET's is proposed. In order to investigate the difference of the gate bias and substrate bias defendence of the $L_{eff}$ among various LDD structures, the $L_{eff}$ of the LDD's are extensively examined using simulations and measurement. one group is proposed for conventional MOSFET and the other group Is proposed for LDD MOSFET. It is shown that the $V_{bs}$-dependence of the n-region is different from $V_{gs}$-dependence of it.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.5
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• pp.13-20
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• 2012

In order to clarify the effect of overload on crack growth behaviors, fatigue tests for overload were carried out for round plain specimens of SM45C steel. In the experiment, typical semi-elliptical crack shape was found and further crack growth behaviors were tested. Using three types of single overload fatigue tests, Crack growth retardation phenomenon were examined. The growth rate of surface crack(da/dN) during retardation period was analyzed in terms of ${\Delta}K$ and ${\Delta}K_{eff}$. On the growth rate of surface crack analyzed by ${\Delta}K$, the dependence of overload stress levels appears. However, on the growth rate by ${\Delta}K_{eff}$ obtained by Willenborg analysis, there is a non-liner relationship between da/dN and ${\Delta}K_{eff}$ with narrow scatter band.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.77-86
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• 1996

We employ the SOR method to analyze CPW electrodes of Ti:$LiNbO_3$ Mach-Zehnder traveling-wave optical modulator in the tapered region of an optical modulator. In the tapered region of the modulator, we design the electrodes satisfying $Z_c=50{\Omega}$. In the modulation region, we find two find sets of design parameters. One set is for $Z_c=50{\Omega}$, $n_{eff}=2.26$ and the another is for $n_{eff}=2.2$, $Z_c=47.7{\Omega}$.