• Journal of the Korea Concrete Institute
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• v.26 no.2
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• pp.181-188
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• 2014

In this study, an interactive analysis considering column-pile interaction is performed on the basis of an equivalent base spring model for supplementing virtual fixed point design of bent pile structures. Through this analytical method, the application of the minimum steel reinforcement ratio of the pile (0.4%) is analyzed by taking into account the major influencing parameters. Furthermore, the limit depth for steel reinforcement ratio is proposed through the relationships between column and pile conditions. To obtain the detailed information, it is found that an interactive analysis is intermediate in theoretical accuracy between the virtual fixed point model analysis and full-modeling analysis. Base on this study, it is also found that the maximum bending moment is located within cracking moment of the pile when material nonlinearity is considered. Therefore, the minimum steel reinforcement ratio is appropriately applicable for the optimal design of bent pile structures. Finally, the limit depth for steel reinforcement ratio ($L_{As=x%}$) is proposed by considering the field measured results. It is shown that the normalized limit depth ratio for steel reinforcement ratio ($L_{As=x%}/L_P$) decreases linearly as the length-diameter ratio of pile ($L_P/D_P$) increases, and then converges at a constant value.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.506-515
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• 2004

The objective of this study was to compare the rate of in vitro demineralization of bovine permanent (BP), human deciduous (HD) and human permanent (HP) enamel. Twenty aye flattened and polished enamel samples for each group (BP, HD, HP) were immersed in a demineralizing solution (0.1 mol/L lactic acid, 0.2% Carbopol 907, and 50% saturated hydroxyapatite) for 1, 2, 4 or 8 days. All 25 samples from each group were subjected to Quantitative light induced fluorescence analysis (QLF) and 5 samples from each group were randomly selected for Transverse Microradiography analysis (TMR). Integrated mineral loss (IML) and lesion depth (LD) were determined by TMR. The fluorescence radiance (FR) of sound enamel $(FR_S)$, demineralized enamel $(FR_D)$ were determined by QLF and FR ratio $(FR_D/FR_S)$ was calculated. Bovine enamel samples showed significant correlation between FR ratio and lesion depth(p<0.05) and deciduous enamel samples does not showed significant correlation between FR ratio and lesion depth(p>0.05). Permanent enamel samples showed significant correlation between FR ratio and lesion depth(p<0.05) The constant of demineralization time between FR ratio from regression analysis were as follows: bovine enamel was -4.643(p<0.05) deciduous enamel was -5.421(p<0.05) and permanent enamel was -4.435(p<0.05).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.720-723
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• 2004

Lever mechanisms are usually employed to enlarge output displacement in precision stages. In this study, theoretical analysis of a lever is presented including bending effect and relation between dimension parameters and an objective function. The objective function is chosen as multiplication of magnification ratio and forcedisplacement transmission. Through theoretical analysis, this study presents optimal values for the parameters and the analysis is verified by finite element method.

• Korea Journal of Hospital Management
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• v.17 no.1
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• pp.79-112
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• 2012

The purpose of this study is to examine the differences of profitability based on the analysis of business and medical service performances of four hospitals in Incheon area with similar size. and to compare hospitals with the best and the worst performances and analyze the factors behind the differences. The differences could be caused by differences in medical service statistics, number of staff, and financial results, etc. The data was acquired through the homepage of the National Tax Service(financial statements for the fiscal year 2009) and the Medical Record Association of Incheon(medical service statistics for the years 2008 and 2009) along with questionnaire survey to the hospitals(personnel data for the year 2009). The results of the study are as follows. Medical profits to medical revenues ratio for the hospitals(referred as Hospital A, B, C, and D) shows, in order, C(8.2%), A(8.0%), B(7.8%), and D(7.4%). However, net income to medical revenues ratio shows otherwise: C(8.5%), D(5.8%), A(3.0%), and B(0.6%). Hospital B shows a high medical profit to revenue ratio but the lowest net income to revenue ratio due to large interest expenses. The leverage ratio of Hospital B is the highest (419.6%), resulting in a very low interest coverage ratio(1.1). On the other hand, Hospital C shows favorable results in both profit ratios, with 8.2% and 8.5% each. Hospital C has the lowest leverage ratio(53.0%) and the highest interest coverage ratio(34.9). Therefore, the results show Hospital C has the best performance while Hospital B the worst. The two hospitals(B and C) show similar results in certain areas and big differences in other areas. The area that has the biggest influence on financial results turns out leverage ratio. Hospital B shows 'very good' to 'good' results in terms of medical service statistics in general. However, the leverage ratio is too high and the liquidity ratio too low, resulting in a very low profit ratio. The results of this study have some limitations in terms of generalization as only four hospitals in Incheon area were selected for the study, resulting in a deficiency in the representativeness of the sample. Further studies with bigger sample size and deeper analysis are expected in this area.

• Structural Engineering and Mechanics
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• v.17 no.6
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• pp.819-828
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• 2004

A new process for estimating the natural frequency and the corresponding damping ratio in large structures is discussed. In a practical situation, it is very difficult to analyze large structures precisely because they are too complex to model using the finite element method and too heavy to excite using the exciting force method; in particular, the measured signals are seriously influenced by ambient noise. In order to identify the structural impulse response associated with the information of natural frequency and the corresponding damping ratio in large structures, the analysis process, a so-called "multiresolution blind system identification algorithm" which combines Mallat algorithm and the bicepstrum method. High time-frequency concentration is attained and the phase information is kept. The experimental result has demonstrated that the new analysis process exploiting the natural frequency and the corresponding damping ratio of structural response are useful tools in structural analysis application.

• Journal of Power System Engineering
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• v.17 no.3
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• pp.57-64
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• 2013

This study focus on the analysis of the energy performance in accordance with apartment houses arrangement type by using Ecotect Analysis. Korea, energy-poor country, the rate of dependence on imports amount to 94%, have to reduce energy consumption part of building except in industry and transport which affect the economic. Apartment houses are built in various forms in order to reduce energy, are modelled in each window area ratio, shape, orientation, climate through simulation. Through this study, we can analyze energy performance by form, window area ratio, orientation, climate change and know the optimal elements by the form. In particular, although there have been studied research on the window area ratio and research related to the arrangement form, determined that the information on the regional climate characteristics and the direction of placement is less than existing research. To supplement those problem, adding to seven direction(West, S-60-W, S-30-W, South, S-30-E, S-60-E, East) and climatic element(southern region) is characteristic of this study. The form of apartment houses was modelled for apartment houses built in the 10 years since. And each modeling were analyzed by Ecotect Analysis.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.12
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• pp.909-917
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• 2020

The research aims to analyze the firm-specific and macroeconomic factors that affect insurance company's financial performance. The research explores the variables that influence the financial performance of the United Arab Emirates (UAE)' insurance companies. The analysis for determining financial performance considers the following variables: the firm's age, retention ratio, capital adequacy, underwriting risk/loss ratio, financial-leverage, reinsurance dependency, and macro-economic factors such as GDP per capita, inflation rate considered as independent factors. The return-on-asset (ROA) is the key measuring indicator; it is regarded as the dependent variable for financial performance measures. The research focuses on secondary information obtained from insurance companies' financial statements. The researcher targeted 18 insurance companies listed on the UAE stock exchanges for study purposes. The research examines the overall factors that influence the financial performance of an insurance company. For analysis of data, software package of social sciences (SPSS version 20) is used. The studies used correlation and multiple linear regression analysis to determine financial performance and their effects. The analysis suggests that there are important and constructive relationships between the size, capital adequacy, and reinsurance dependency, while loss ratio, retention ratio, and financial leverage indicate a major negative relationship. And there's no link between GDP per capita and inflation.

• International Journal of Highway Engineering
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• v.15 no.6
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• pp.69-78
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• 2013

PURPOSES : In this study blast furnace slag, an industrial byproduct, was used with an activating chemicals, $Ca(OH)_2$ and $Na_2SiO_3$ for carbon capture and sequestration as well as strength development. METHODS : This paper presents the optimized mixing design of Carbon-Capturing and Sequestering Activated Blast-Furnace Slag Mortar. Design of experiments in order to the optimized mixing design was applied and commercial program (MINITAB) was used. Statistical analysis was used to Box-Behnken (B-B) method in response surface analysis. RESULTS : The influencing factors of experimental are water ratio, Chemical admixture ratio and Curing temperature. In the results of response surface analysis, to obtain goal performance, the optimized mixing design for Carbon-Capturing and Sequestering Activated Blast-Furnace Slag Mortar were water ratio 40%, Chemical admixture ratio 58.78% and Curing temperature of $60^{\circ}C$. CONCLUSIONS : Compared with previous studies of this experiment is to some extent the optimal combination is expected to be reliable.

• Steel and Composite Structures
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• v.30 no.2
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• pp.185-199
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• 2019

Modular construction is an emerging technology to accommodate the increasing restrictions in terms of construction period, energy efficiency and environmental impacts, since each structural module is prefabricated offsite beforehand and assembled onsite using industrialized techniques. However, some innate structural drawbacks of this innovative method are also distinct, such as connection tying inaccessibility, column instability and system robustness. This study aims to explore the theoretical and numerical stability analysis of a tenon-connected square hollow section (SHS) steel column to address the tying and stability issue in modular construction. Due to the excellent performance of composite structures in fire resistance and buckling prevention, concrete-filled steel tube (CFST) columns are also taken into account in the analysis to evaluate the feasibility of adopting composite sections in modular buildings. Characteristic equations with three variables, i.e., the length ratio, the bending stiffness ratio and the rotational stiffness ratio, are generated from the fourth-order governing differential equations. The rotational stiffness ratio is recognized as the most significant factor, with interval analysis conducted for its mechanical significance and domain. Numerical analysis using ABAQUS is conducted for validation of characteristic equations. Recommendations and instructions in predicting the buckling performance of both SHS and CFST columns are then proposed.

• Earthquakes and Structures
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• v.22 no.6
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• pp.571-584
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• 2022

The residual displacement ratio (RDRs) response spectra have been generally used as an important means to evaluate the post-earthquake repairability, and the ratios of residual to maximum inelastic displacement are considered to be more appropriate for development of the spectra. This methodology, however, assumes that the expected residual displacement can be computed as the product of the RDRs and maximum inelastic displacement, without considering the correlation between these two variables, which inevitably introduces potential systematic error. For providing an adequately accurate estimate of residual displacement, while accounting for the collapse resistance performance prior to the repairability evaluation, a probability-based procedure to estimate the residual displacement demands using the nonlinear static analysis (NSA) is developed for single-degree-of-freedom (SDOF) systems. To this end, the energy-based equivalent damping ratio used for NSA is revised to obtain the maximum displacement coincident with the nonlinear time history analysis (NTHA) results in the mean sense. Then, the possible systematic error resulted from RDRs spectra methodology is examined based on the NTHA results of SDOF systems. Finally, the statistical relation between the residual displacement and the NSA-based maximum displacement is established. The results indicate that the energy-based equivalent damping ratio will underestimate the damping for short period ranges, and overestimate the damping for longer period ranges. The RDRs spectra methodology generally leads to the results being non-conservative, depending on post-yield stiffness. The proposed approach emphasizes that the repairability evaluation should be based on the premise of no collapse, which matches with the current performance-based seismic assessment procedure.