• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.345-351
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• 1995

We have studied experimentally the propagation characteristics of fundamental dark spatial solitons on finite-width backgrounds and conpared with the result of numerical simulations. It was verified experimentally that the width of dark solitons decreased but that of background increased as the beam intensity increased. The refractive index change obtained from soliton constant, which is for infinite-width background, was smaller than that from Z-scan method. Numerical simulations of fundamental dark solitons on a finite-width backgrounds showed that the peak intensity of background, the width of dark soliton and the soliton constant varied with the propagation length. If the change of soliton constant on finite-width backgrounds was considered, the refractive index change was in good agreement with that from Z-scan method. ethod.

• Korean Management Science Review
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• v.21 no.2
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• pp.191-213
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• 2004

This study addresses the evaluation criteria of multimedia authoring tools(MATs), the way which decision-maker can exclude outlier matrix from group using the concept of the compatibility index, and how AHP can be applied to the selection of MATs in a group decision-making environment. The AHP technique allows an evaluator to quantify the relative importance of elements at each hierarchy and to calculate the composite relative weights for each product(i.e. MATs). This decision process allows setting to priority of the MATs based on the AHP. The results indicated that technical ability of MATs was the most significant factor in affecting their decision, trailed by managerial efficiency and vendor support. To the experts, multimedia data support was the less important than development interface. Also, the results indicated that product A(0.510) was their first choice, trailed by product C(0.286) and B(0.204). Assessing the composite relative weights revealed that expert group's members were consistent with the rankings of decision variables(evaluation criteria variables) statistically in selecting their MATs. Therefore, we believed that expert group's members have achieved sufficient agreement to permit the use of geometric mean to average the group's preference without obscuring the differences of individual opinions.

• Structural Engineering and Mechanics
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• v.36 no.4
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• pp.463-479
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• 2010

Based on damage accumulation of multi-grid composite walls, a method of dynamic reliability estimations is proposed. The multi-grid composite wall is composed of edge frame beam, edge frame columns, grid beams, grid columns and filling blocks. The equations including stiffness, shear forces at filling blocks cracking and multi-grid composite walls yielding, ultimate displacement, and damage index are obtained through tests of 13 multi-grid composite wall specimens. Employing these equations in reliability calculations, procedures of dynamic reliability estimations based on damage accumulation of multi-grid composite walls subjected to random earthquake excitations are proposed. Finally the proposed method is applied to the typical composite wall specimen subjected to random earthquake excitations which can be specified by a finite number of input random variables. The dynamic reliability estimates, when filling blocks crack under earthquakes corresponding to 63% exceedance in 50 years and when the composite wall reach limit state under earthquakes corresponding to 2-3% exceedance in 50 years, are obtained using the proposed method by taking damage indexes as thresholds. The results from the proposed method which show good agreement with those from Monte-Carlo simulations demonstrate the proposed method is effective.

• Advances in Computational Design
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• v.3 no.2
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• pp.165-190
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• 2018

In this article, the static behavior of non-prismatic sandwich beams composed of functionally graded (FG) materials is investigated for the first time. Two types of beams in which the variation of elastic modulus follows a power-law form are studied. The principle of minimum total potential energy is applied along with the Ritz method to derive and solve the governing equations. Considering conventional boundary conditions, Chebyshev polynomials of the first kind are used as auxiliary shape functions. The formulation is developed within the framework of well-known Timoshenko and Reddy beam theories (TBT, RBT). Since the beams are simultaneously tapered and functionally graded, bending and shear stress pushover curves are presented to get a profound insight into the variation of stresses along the beam. The proposed formulations and solution scheme are verified through benchmark problems. In this context, excellent agreement is observed. Numerical results are included considering beams with various cross sectional types to inspect the effects of taper ratio and gradient index on deflections and stresses. It is observed that the boundary conditions, taper ratio, gradient index value and core to the thickness ratio significantly influence the stress and deflection responses.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.1
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• pp.1-7
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• 2021

PURPOSE: The purpose of this study is to conduct inter-rater and intra-rater reliability tests in patients with low back pain (LBP) using the prone instability test (PIT) and side-lying instability test (SIT). We have analyzed the Korean version Oswestry disability index (K-ODI) correlations and radiograph finding (RF) for validity. METHODS: Individuals (n = 51) (mean age of 40.27 ± 13.28) with LBP for at least over a week were recruited, together with two participating physical therapist examiners. The measurement consisted of PIT, PST, K-ODI, and RF. Sensitivity (Sn), specificity (Sp), positive predictive value, negative predictive value, prevalence index, agreement %, Cohen's kappa, and prevalence-adjusted bias-adjusted kappa (PABAK) were calculated. The PIT and SIT were compared with RF for validity analysis, while PIT, SIT, K-ODI, and RF were calculated for the correlation analysis. RESULTS: The intra-rater reliability test measured for the PIT (kappa = .79, PABAK = .88) and SIT (kappa = .73, PABAK = .84), and inter-rater reliability test measured for the SIT (kappa = .80, PABAK = .88) showed good agreements. The PIT (Sn = .65, Sp = .63) and SIT validities (Sn = .68, Sp = .70) were compared with RF, showing a significant correlation in PIT and RF (r = .69), SIT and RF (r = .73), and PIT and K-ODI (r = .53). CONCLUSION: The SIT is a more comfortable position test than the PIT in patients. Both PIT and SIT have acceptable reliability and validity.

• Journal of radiological science and technology
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• v.46 no.3
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• pp.231-238
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• 2023

This study aimed to compare the results of delivery quality assurance (DQA) using MapCHECK and OCTAVIUS for radiation therapy. Thirty patients who passed the DQA results were retrospectively included in this study. The point dose difference (DD) and gamma passing rate (GPR) were analyzed to evaluate the agreement between the measured and planned data for all cases, Plan complexity was evaluated to analyze dosimetric accuracy by quantifying the degree of modulation according to each plan. We analyzed the monitor units (MUs) and total MUs for each plan to evaluate the correlation between the MUs and plan complexity. We used a paired t-test to compare the DD and GPRs that were obtained using the two devices. The DDs and GPRs were within the tolerance range for all cases. The average GPRs difference between the two devices was statistically significant for the brain, and head and neck for gamma criteria of 3%/3 mm and 2%/2 mm. There was no significant correlation between the modulation index and total MUs for any of the cases. These DQA devices can be used interchangeably for routine patient-specific QA in radiation therapy.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.3
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• pp.158-164
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• 1998

We introduce a statistical scheme to classify seabed from acoustic profiling data acquired using Chirp sonar system. The classification is based on grouping of signal traces by similarity index, which is computed using the K-L (Karhunen-Lo$\grave{e}$ve) transform of the Chirp profiling data. The similarity index represents the degree of coherence of bottom-reflected signals in consecutive traces, hence indicating the acoustic roughness of the seabed. The results of this study show that similarity index is a function of homogeneity, grain size of sediments and bottom hardness. The similarity index ranges from 0 to 1 for various types of seabed material. It increases in accordance with the homogeneity and softness of bottom sediments, whereas it is inversely proportional to the grain size of sediments. As a real data example, we classified the seabed off Cheju Island, Korea based on the similarity index and compared the result with side-scan sonar data and sediment samples. The comparison shows that the classification of seabed by the similarity index is in good agreement with the real sedimentary facies and can delineate acoustic response of the seabed in more detail. Therefore, this study presents an effective method for geoacoustic modeling to classify the seafloor directly from acoustic data.

• Journal of Korea Port Economic Association
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• v.36 no.4
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• pp.93-106
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• 2020

Trade is an important economic activity. In particular, since the establishment of the World Trade Organization (WTO), the scope of trade has been expanding due to events such as the entry of China into the WTO in 2001, the establishment of a multilateral trading system, mitigation and integration of trade barriers, and the establishment of the free trade agreement (FTA). Despite the expansion of the trade market, however, extreme events such as the 2008 global financial crisis, the 2016 Brexit, and the 2018 US-China trade war have had a direct negative impact on the trade market. Therefore, the present this study analyzed the dependence structure between the international shipping freight rate index, a variable representing trade activities, and the trade uncertainty between the US and China. The following is a summary of the analysis results. First, the US-Chinese trade policy uncertainty and international shipping freight rate index presented a Frank copula and rotated Clayton copula 270° distribution, respectively, showing the same distribution structure for each country. Second, the Kendall's tau correlation revealed a negative dependence between the international shipping freight rate index and US-Chinese trade policy uncertainty. The degree of dependence was greater in the combination of uncertainty in China's trade policy and international shipping freight rates. In other words, the dependence of global demand and trade policy uncertainty confirmed that China was stronger than the US. Finally, the tail dependence results revealed that the US-Chinese trade policy uncertainty and international shipping freight rates were independent of each other. This means that extreme events related to the trade policy uncertainty or international shipping rate index were not affected by each other.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.9
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• pp.610-619
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• 2011

This paper investigates the simplified comfort index and control logic for VRF (Variable Refrigerant Flow) system by using 3 environmental factors such as temperature, humidity and air flow. Indoor test under thermal load was conducted to explore relationship of each environment factors that is related to simplified comfort index. Simplified comfort function that has 3 environmental variables was proposed based on survey results. Each factor is measured and comfort preference was surveyed by more than 30 subjects in the indoor comfort test. Moreover, control logic for VRF system was developed and then simulated by using thermal load calculation method and verified with test. The proposed comfort function was in good agreement with survey results, and also verification test trend of comfort change and maintenance are quite similar with survey. Furthermore, through the additional test data analysis some differences of comfort according to position of people staying in the test room were additionally investigated by air flow. People being under an exit of air in the indoor air-conditioner feel more comfortable condition and speed of response to comfort change is relatively fast.

• Economic and Environmental Geology
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• v.41 no.5
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• pp.475-484
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• 2008

In this study, we analyzed national mining investment security and country risk, and suggested a new index for exploration and development investment for mining projects in abroad by an analysis of relationship between these grades and mineral resource development investment. For this, potential risks for mining in mineral-rich countries are assessed, and the risk of the exploration and development investment for mining projects is relatively evaluated by OECD country risk. It is noted that countries of the lower ranks in OECD are consistently good agreement with the high grade in Behre Dolbear Group Inc. for favorable mineral exploitation, whereas the higher ranks have shown diverse and high risks for the mining investigation and development. Consequently, it is necessary that assessment of the relationship between mineral resource index and country risk for mining projects to be investigated and developed in future should be applied before business decision of mineral investigation projects in abroad.