• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.23-31
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• 2023

The escalating settlements observed in concrete slab tracks pose a significant challenge in Korea, raising concerns about their adverse impact on the safe operation of high-speed railways and the substantial costs involved in restoration. A primary contributor to these settlements is identified as the utilization of rock materials sourced from tunnel construction, incorporated into the lower subgrade without the requisite soil mixing to achieve an appropriate particle size distribution. This study employs numerical analysis to evaluate the efficacy of partial reinforcement in reducing settlements in rock-filled lower subgrades. Column-shaped reinforcement areas strategically positioned at regular intervals in the lower subgrade induce soil arching in the upper subgrade, leading to a concentration of soil loads on the reinforced areas and consequent settlement reduction. The analysis employs finite element methods to investigate the influence of the size, stiffness, and spacing of the reinforced areas on settlement reduction in the lower subgrade. The numerical results guide the formulation of an optimal design approach, proposing a method to determine the minimum spacing required for reinforcements to effectively limit settlements within acceptable bounds. This research contributes valuable insights into addressing the challenges associated with settlement in concrete slab tracks, offering a basis for informed decision-making in railway infrastructure management.

• Resources Recycling
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• v.32 no.6
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• pp.79-89
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• 2023

One of the foremost environmental challenges, alongside the contemporary focus on achieving carbon neutrality, pertains to the pervasive issue of plastic waste. Thermochemical recycling technology, operating under high-temperature conditions to covert organic matter and recycle it into raw materials and energy, represents a transformative approach surpassing the conventional bounds of material recycling predominantly applied in plastic waste management. The thermochemical recycling paradigm is emerging as a pivotal technology within the circular economy, capable of transforming waste plastics into raw materials for producing original plastics. Its significance extends beyond national borders, garnering global attention due to its versatility as a chemical or energy recycling method, contingent upon the subsequent processes and final products. This study aims to scrutinize three quintessential thermochemical recycling technologies: combustion, gasification, and pyrolysis. Furthermore, the study discusses the recent major technology trends of these technologies.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.504-509
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• 2022

In this paper, we deal with the stability condition of linear time-varying interval discrete systems with time-varying delays and unstructured uncertainty. For the time-varying interval discrete system which has interval matrix as its system matrices, time-varying delay time within some interval value and unstructured uncertainty which can include non-linearity and be expressed by only its magnitude, the stability condition is proposed. Compared with the previous result derived by using a upper bound solution of the Lyapunov equation, the new result is derived by the form of simple inequality based on Lyapunov stability condition and has the advantage of being more effective in checking stability. Furthermore, the proposed condition is very comprehensive, powerful and inclusive the previously published conditions of various linear discrete systems, and can be expressed by the terms of magnitudes of the time-varying delay time and uncertainty, and bounds of interval matrices. The superiority of the new condition is shown in the derivation, and the usefulness and advantage of the proposed condition are examined through numerical example.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.3
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• pp.179-186
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• 2024

In this paper, a modification coefficient for equivalent single degree of freedom (SDOF), considering the plasticity range of the member subjected to shock wave type of blast load, was developed. The modification coefficient for the equivalent SDOF was determined through comparison with the analysis of a multi-degree of freedom (MDOF) system. The parameters influencing the equivalent SDOF system analysis were chosen as the boundary conditions of the member and the ratio of the duration of blast load to the natural period of the member. The modification coefficient was calculated based on the elastic load-mass transformation factor. The modification coefficient curve was derived using an elliptical equation to ensure it exists between the upper and lower parameter bounds. Using the modification coefficient on examples with varying cross sections and boundary conditions reduced the SDOF analysis error rate from 15% to 3%. This study shows that using the modification coefficient significantly improves the accuracy of SDOF analysis. The modification coefficient proposed in this study can be used for blast analysis.

• Journal of the Chungcheong Mathematical Society
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• v.37 no.1
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• pp.27-40
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• 2024

In this paper, we consider the higher-order HartreeFock equations. The higher-order linear Schrödinger equation was introduced in [5] as the formal finite Taylor expansion of the pseudorelativistic linear Schrödinger equation. In [13], the authors established global-in-time Strichartz estimates for the linear higher-order equations which hold uniformly in the speed of light c ≥ 1 and as their applications they proved the convergence of higher-order Hartree-Fock equations to the corresponding pseudo-relativistic equation on arbitrary time interval as c goes to infinity when the Taylor expansion order is odd. To achieve this, they not only showed the existence of solutions in L² space but also proved that the solutions stay bounded uniformly in c. We address the remaining question on the convergence of higherorder Hartree-Fock equations when the Taylor expansion order is even. The distinguished feature from the odd case is that the group velocity of phase function would be vanishing when the size of frequency is comparable to c. Owing to this property, the kinetic energy of solutions is not coercive and only weaker Strichartz estimates compared to the odd case were obtained in [13]. Thus, we only manage to establish the existence of local solutions in H^s space for s > $\frac{1}{3}$ on a finite time interval [-T, T], however, the time interval does not depend on c and the solutions are bounded uniformly in c. In addition, we provide the convergence result of higher-order Hartree-Fock equations to the pseudo-relativistic equation with the same convergence rate as the odd case, which holds on [-T, T].

• Structural Engineering and Mechanics
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• v.89 no.3
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• pp.253-263
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• 2024

Slope stability is generally paid more attention to in slope protection works, especially for slope containing weak layers. Two indexes of safety factor and failure model are selected to perform slope stability. Moreover, the finite element limit analysis method comprehensively combines the advantage of the limit analysis method and the finite element method obtaining the upper and lower bounds of the safety factor and the failure mode under the slope stability limit state. In this study, taking a waste dump containing a weak layer as an engineering background, the finite element limit analysis method is adopted to explore the potential failure mode. Meanwhile, the sensitivity analysis of slope stability is performed on geometrical and geotechnical parameters of the waste dump. The results show that the failure mode of the waste dump slope is two wedges if the weak layer is located on the ground surface (Model A), while the slope can be observed as three wedges failure if the weak layer is below the ground surface (Model B). In addition, both failure modes are highly sensitive to the friction angle of the weak layer and the shear strength of waste disposal, and moderately sensitive to the heap height, the dip angle and cohesion of the weak layer, while the toe cutting has limited effect on the slope stability. Moreover, the sensitivity to the excavation of the ground depends on the location of the weak layer and failure mode.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.292-301
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• 2012

The rise in sea surface temperature (SST) as a global warming enhance overall typhoon activity. We assumed that there exist thermodynamic limits to intensity that apply in the absence of significant interaction between storms and their environment. The limit calculations depend on SST and atmospheric profiles of temperature and moisture. This approach do appear to provide resonable upper bounds on the intensities of observed storms and may even be useful for predicting the change in intensity over a long period time. The maximum storm intensities was estimated through the global warming scenarios from IPCC-AR4 report over the North-East Asia. The result shows stronger intensities according to scenarios for increase of carbon dioxide levels. And storm surge simulations was performed with the typhoons which were combined route of the typhoon Maemi (2003) and intensity as climate change scenarios. The maximum increase of storm surge heights was shown about 29~110 cm (36~65%) regionally. Especially at Masan, the result of simulated maximum surge height exceed the 200 years return period surge.

• Proceedings of the KSPS conference
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• 1997.07a
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• pp.11-25
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• 1997

This presentation will focus on building basic English Prosodic Skills which are very useful and helpful for Japanese learners of English. The focus first will be on recognizing the seven basic nuclear tones, analysing intonation structures, distinguishing intonation patterns and then on the way of improving speaking ability using sufficient verbal contents of intonation (mini-dialogue). My presentation deals mainly with some difficulties which Japanese learners of English have in the field of RP intonation, It is chiefly concerned with identifying, describing and analysing tone-group sequences. It sometimes happens that Japanese learners of English can pronounce isolated bounds correctly and read phonetic symbols sufficiently, bet have difficult problems in carrying out accurate prosodic features. The use of wrong intonation is sometimes the cause of misunderstanding of speaker's attitude, connotation and shades of meaning, etc.. However accurately students can pronounce the nuclear tone or tone-group of English, they have to learn how to connect tone-groups properly for suitable sequences in respect to meaning or implication. We are faced with the complicated theory of RF intonation on the one hand and difficult realization of it on the other. Japanese learners of English have special difficulties in employing "rising tune" and "falling + rising tune". If students are taught pitch movements by indicating dots graphically between two horizontal lines, they can easily understand the whole shape of pitch movements. In this presentation, I illuminate several tone-group sequences which are very useful for Japanese learning English intonation. Among them, four similar Pitch Patterns, such as, (1) (equation omitted)- type, (2) (equation omitted) - type, (3) (equation omitted) - type and (4) (Rising Head) (equation omitted)- type are clarified and other important tone-group sequences aye also highlighted from the point of view of teaching English as a foreign language. The intonation theory, tone marks and technical terms are, in all essentials, those of Intonation of Colloquial English by O'Connor, J. D. and Arnold, G. F., Longman, 2nd ed., 1982. The changes of tone are shown graphically between two horizontal lines representing the ordinary high and low zones of the utterance. A.C.Gimson (1981:314) : The intonation of English has been studied in greater detail and for longer than that of any other language. No definitive analysis, classifying the features of RP intonation, has yet appeared (though that presented by O'Connor and Arnold (1973) provides the most comprehensive and useful account from the foreign learner's point of view).

• Journal of Gifted/Talented Education
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• v.15 no.2
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• pp.101-125
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• 2005

We applied functional magnetic resonance imaging (fMRI) techniques to examine whether general intelligence (g) could be assessed using a neurobiological signal of the brain. Participants were students in a national science academy and several local high schools. They were administered diverse intelligence (RAPM and WAIS) and creativity tests (TTCT-figural and TTCT-verbal). Forty of them were scanned using fMRI while performing complex and simple g tasks. In brain regions of greater blood flow in complex compared with simple g tasks, the gifted group with an exceptional g level was not significantly different from the average group with an ordinary g level: both of them activated the lateral prefrontal, anterior cingulate, posterior parietal cortices. However, the activation levels of the gifted group were greater than those of the average group, particularly in the posterior parietal cortex. Correlation analysis showed that the activity of the posterior parietal cortex has the highest correlation ($(r=0.73{\sim}0.74)$) with individual g levels and other regions also have moderate correlation ($(r=0.53{\sim}0.66)$). On the other hand, two-sample t test showed a striking contrast in intelligence tests scores between the gifted and the average group, whereas it did not show in creativity tests scores. These results suggest that it is within the bounds of possibility that a neurobiological signal of the brain is used in the assessment of the gifted and also suggest that creativity has to be given a great deal of weight on the assessment of the gifted.

• Journal of Korea Water Resources Association
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• v.42 no.6
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• pp.457-464
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• 2009

This paper proposes methodologies for analyzing the accuracy of the proportional hazards model in predicting consecutive break times of water mains and estimating the time interval for economical water main replacement. By using the survival functions that are based on the proportional hazards models a criterion for the prediction of the consecutive pipe breaks is determined so that the prediction errors are minimized. The criterion to predict pipe break times are determined as the survival probability of 0.70 and only the models for the third through the seventh break are analyzed to be reliable for predicting break times for the case study pipes. Subsequently, the criterion and the estimated lower and upper bound survival functions of consecutive breaks are used in predicting the lower and upper bounds of the 95% confidence interval of future break times of an example water main. Two General Pipe Break Prediction Models(GPBMs) are estimated for an example pipe using the two series of recorded and predicted lower and upper bound break times. The threshold break rate is coupled with the two GPBMs and solved for time to obtain the economical replacement time interval.