• Corrosion Science and Technology
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• 제19권4호
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• pp.174-188
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• 2020

Atmospheric corrosion is a natural surface degradation process of metal due to changes in environmental parameters in the surrounding atmosphere. It is very sensitive to environmental parameters such as temperature, relative humidity, sulphur dioxide, and chloride, making it a major global economic challenge. Existing forecasting empirical corrosion models including the ISO standard are based on statistical analysis of experimental studies without considering the behavior of atmospheric parameters. The present study proposes a reliable global empirical model for estimating short and long-term atmospheric corrosion rates based on environmental parameters and corrosion mechanisms obtained from a parametric study. Repercussion of atmospheric corrosion rate due to individual and combined influences of environmental parameters specifies their importance in the estimation. New global empirical coefficients obtained for environmental parameters are statistically established (R² =0.998) with 95% confidence limit. They are validated using experimental datasets of existing studies observed at 88 different continental locations. The current proposed model can predict atmospheric corrosion by means of corrosion formation mechanisms influenced by combined effects of environmental parameters, further abating applicability limitations of location and time.

• 한국도로학회논문집
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• 제16권1호
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• pp.57-62
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• 2014

PURPOSES : Capacity is a main factor of determining the number of lane in highway design or the level of service in road on operation. Previous studies showed that breakdown may occur before capacity is reached, and then it was concluded that capacity is a stochastic value rather than a deterministic one. In general, estimating capacity is based on average over maximum traffic volume observed for capacity state. This method includes the empirical distribution method(EDM) and would underestimate capacity. This study estimated existing empirical methods of estimating stochastic highway capacity. Among the studied methods are the product limit method(PLM) and the selected method(SM). METHODS : Speed and volume data were collected at three freeway bottleneck sites in Cheonan-Nonsan and West Sea Freeway. The data were grouped into a free-flow state or capacity state with speeds observed in the bottlenecks and the upstream. The data were applied to the empirical methods. RESULTS : The results show that the PLM and SM estimated capacity higher than EDM. The reason is that while the EDM is based on capacity observations only, the PLM and SM are based on free-flow high volumes and capacity observations. CONCLUSIONS : The PLM and SM using both free-flow and capacity observations would be improved to enhance the reliability of the capacity estimation.

• 공업화학
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• 제29권6호
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• pp.789-798
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• 2018

고분자전해질 연료전지(PEMFC)의 성능을 예측할 수 있는 empirical equation의 역할이 중요하게 대두되고 있다. 본 연구에서는 polarization curve에서 activation loss, ohmic loss, mass transfer loss 영역을 분리하였고, 현재까지 개발된 model 중 Kim의 model과 Hao의 model을 선정하여 각 영역의 fitting을 시행하였다. 온도, 압력, 산소 농도 및 막 두께를 운전변수로 설정하여 조건 변화에 대한 각 loss의 변화를 비교하였다. 기존 model은 전반적으로 좋은 fitting 정확도를 보였지만, 분리된 loss 영역에서는 부정확한 fitting 결과를 보이기도 하였다. 연료전지 성능 예측의 정확도를 개선하기 위하여 converge coefficient를 도입한 새로운 model을 제안하였다. 본 연구에서 제안한 model을 연료전지 성능 예측에 적용한 경우에 신뢰도 평가에서 개선된 결과를 얻을 수 있었다.

• 수산해양기술연구
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• 제57권3호
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• pp.246-255
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• 2021

Most fishing vessels are less than 100 m in length (LBP), which is not mandatory for the IMO standards for ship maneuverability. Therefore, research on estimating the maneuverability of fishing vessel hull shapes are somewhat lacking compared to that of merchant ship hull shapes, and at the design stage, the numerical simulation method developed for merchant ships are applied without modification to estimate the maneuverability. Since this can cause estimation errors, the authors have derived a modified empirical formula that can improve the accuracy of estimating the maneuverability of fishing vessels in a previous study. In this study, using the modified empirical formula, the IMO maneuverability evaluation items, the turning motion test and Z-test simulations were performed on the fisheries training vessel BAEK-KYUNG and compared with the sea trial test result to verify the validity of the modified empirical formula. In conclusion, the modified empirical formula was able to estimate quantitatively and qualitatively similar to the result of the sea trial test. Such a study on estimating the maneuverability of fishing vessels will be a good indicator for fishing vessel operators and will help them analyze marine accidents.

• Computers and Concrete
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• 제26권6호
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• pp.533-546
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• 2020

The prediction of spall response of reinforced concrete members like columns and slabs have been attempted by earlier researchers with analytical solutions, as well as with empirical models developed from data generated from physical or numerical experiments, with different degrees of success. In this article, compared to the empirical models, more versatile and accurate models are developed based on model-free approach of artificial neural network (ANN). Synthetic data extracted from the results of numerical experiments from literature have been utilized for the purpose of training and testing of the ANN models. For two concrete members, namely, slabs and columns, different sets of ANN models were developed, each of which proved to have definite advantages over the corresponding empirical model reported in literature. In case of slabs, for all three categories of spall, the ANN model results were superior to the empirical models as evaluated by the various performance metrics, such as correlation, root mean square error, mean absolute error, maximum overestimation and maximum underestimation. The ANN models for each category of column spall could handle three variables together: namely, depth, spacing of longitudinal and transverse reinforcement, as contrasted to the empirical models that handled one variable at a time, and at the same time yielded comparable performance. The application of the ANN models for spall prediction of concrete slabs and columns developed in this study has been discussed along with their limitations.

• The Journal of Asian Finance, Economics and Business
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• 제8권8호
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• pp.487-496
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• 2021

This study examines the environmental performance of firms in Vietnam and its determinants. The contribution of the paper is on both theoretical and empirical aspects. On the theoretical matter, the research proposes a new index measuring environmental management at the firm level, namely the Environmental Management Index with a clear illustration for the case of Vietnam. On the empirical matter, the study points out and estimates determinants of the corporate environmental performance of Vietnamese firms measured by the newly proposed index. Due to data availability and the impossibility of getting more updated data, the empirical analysis covers only the period from 2004-2009. However, findings are still meaningful because, on the one hand, it provides some evidence for Vietnamese policymakers; on the other hand, with the robust methodology proposed, when more recent data are available, researchers can easily replicate the estimation for more insights. Empirical results show that factors having positive impacts on the environmental performance of Vietnamese firms are profit, capital stock, and interestingly public pressure proxied by the population of the province where the firm is located. Firm ownership does also matter in explaining the corporate environmental performance of Vietnam.

• 아태비즈니스연구
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• 제10권3호
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• pp.17-35
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• 2019

This paper analyzes the reality of Myanmar workers' consciousness and reports the results of exploratory empirical studies that examined the influence of workers' consciousness on organizational commitment. To accomplish the purpose of the study, we performed conceptual and empirical research and mainly focused on empirical research through questionnaires on 262 workers in the manufacturing industry in Myanmar. Results of this empirical study are summarized as follow. First, the consciousness of the labor union of Myanmar labors such as 'Necessity of Union', 'Necessity of Strong Union', 'Militant Ideology' and 'Democracy' was high. The wage fair consciousness, which is a core consciousness related to the working conditions, is high, and class consciousness and collectivism, which are corporate and social consciousness, are also high but the 'growth ideology' and 'competitiveness ideology' are low. Second, the younger generation, less than high school graduates, and Yangon's workers have highly consciousness increasing the instability of industrial relations. Third, consciousness factors which have significant influence on organizational commitment were labor-management cooperation consciousness (+), democracy (-), competitiveness ideology (+), class consciousness (-) and authoritarianism (+). Lastly, implications and limitations of this empirical study, and suggestions for future research are suggested.

• 한국방재안전학회논문집
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• 제15권1호
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• pp.35-46
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• 2022

본 연구에서는 토석류 피해 발생지역에 대해 토사유출량 산정에 많이 사용되고 있는 RUSLE와 NILIM 그리고 Marchi의 경험식을 통해 토사유출량을 산정하였으며, 토사유출량 산정 방법의 국내 적용성을 검토하기 위해 정밀측량 및 현장조사를 통해 측정된 토사유출량을 비교하였다. RUSLE 방법은 실측 토사유출량에 비해 평균 2.13배 과다 산정되었으며, Marchi의 경험식은 평균 2.83배, NILIM 경험식의 경우 평균 1.26배로 세 가지 경험식 중 가장 낮은 오차가 발생하였다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4159-4169
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• 2022

Hydrogen mitigation using Passive Autocatalytic Recombiners (PARs) has been widely accepted methodology inside reactor containment of accident struck Nuclear Power Plants. They reduce hydrogen concentration inside reactor containment by recombining it with oxygen from containment air on catalyst surfaces at ambient temperatures. Exothermic heat of reaction drives the product steam upwards, establishing natural convection around PAR, thus invoking homogenisation inside containment. CFD models resolving individual catalyst plate channels of PAR provide good insight about temperature and hydrogen recombination. But very thin catalyst plates compared to large dimensions of the enclosures involved result in intensive calculations. Hence, empirical correlations specific to PARs being modelled are often used in integral containment studies. In this work, an experimentally validated CFD model of PAR has been employed for developing an empirical correlation for Indian PAR. For this purpose, detailed parametric study involving different gas mixture variables at PAR inlet has been performed. For each case, respective values of gas mixture variables at recombiner outlet have been tabulated. The obtained data matrix has then been processed using regression analysis to obtain a set of correlations between inlet and outlet variables. The empirical correlation thus developed, can be easily plugged into commercially available CFD software.

• The Journal of Asian Finance, Economics and Business
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• 제9권1호
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• pp.167-176
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• 2022

By analyzing the impact of oil prices on economic growth, this study has shown a new insight into the link between oil price inflation and economic growth. The primary goal of this study is to determine if oil prices are pro-growth or anti-growth. To provide empirical proof, the series data for both the core and control variables from 1972 to 2020 was used to justify the association on empirical grounds. To account for the presence of a unit root, the Augmented Dickey-Fuller Test was used, and after making the series compatible for co-integration, the Autoregressive distributed lag model was used to determine the empirical estimate. Additionally, the empirical models were used to diagnose heteroscedasticity and autocorrelation. The reference point model reveals that in developing nations like Pakistan, economic growth is anti-growth with an increase in prices, and it responds negatively to economic growth in the long and short run. As a result, oil price inflation in Pakistan fails to have a significant beneficial impact on economic growth in both the long and short run, but it does raise the general price level in the economy.