• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.1-6
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• 2010

Flow characteristics of differential pressure flow meters which have a shape of triangular separate bar (TSB) was investigated according to the machining conditions in pressure tapping holes. Diameter of the pressure taping holes is either 1.0 mm or 1.5 mm. Also, number of the pressure tapping holes are drilled either 9 or 17. The mass flow rate of the TSB flow meters are calibrated with a laminar flow meter by connecting them in line. The mass flow rate in the TSB flow meters are plotted with a non-dimensional parameter H which includes the gas temperature, exhaust gas pressure and differential pressure at the flow meters. An empirical correlation between the mass flow rate at the TSB flow meter and the non-dimensional parameter H was obtained. The empirical correlation showed highly linear relationship between the mass flow rate and the non-dimensional parameter H. The hole size of the pressure tapping holes has a bigger effect on the flow rate than the number of the tapping holes.

• Proceedings of the Korean Society for Quality Management Conference
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• 1998.11a
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• pp.610-621
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• 1998

In parameter design introduced by Taguchi, we analyze a signal-to-noise(SN) ratio. The SN ratio is a function of the expected loss due to the variation of quality characteristic. In this paper, an easy way for developing SN ratios is presented, which can be used to several quality characteristics simultaneously in parameter design. To develop such multivariate SN ratios, the transformation method of the expected loss and combining techniques are employed. And the analysis of real empirical data for an application of the proposed method is also presented.

• Journal of Korean Society for Quality Management
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• v.27 no.3
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• pp.67-78
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• 1999

In parameter design introduced by Taguchi, we analyze a performance measure, so called SN ratio. The SN ratio is a function of the expected loss due to the variation of quality characteristic. In this paper, an easy way for developing performance measures is presented, which can be used to control several quality characteristics simultaneously in parameter design. To develop such multivariate performance measures, the transformation method of the expected loss and combining techniques are employed. And the analysis of real empirical data for an application of the proposed method is also presented.

• Earthquakes and Structures
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• v.25 no.6
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• pp.429-442
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• 2023

To study the seismic vulnerability of the composite material structure of adobe and timber, we collected and statistically analysed empirical observation samples of 542,214,937 m² and 467,177 buildings that were significantly impacted during the 179 earthquakes that occurred in mainland China from 1976 to 2010. In multi-intensity regions, combined with numerical analysis and a probability model, a non-linear continuous regression model of the vulnerability, considering the empirical seismic damage area (number of buildings) and the ratio of seismic damage, was established. Moreover, a probability matrix model of the empirical seismic damage mean value was provided. Considering the coupling effect of the annual and seismic fortification factors, an empirical seismic vulnerability curve model was constructed in the multiple-intensity regions. A probability matrix model of the mean vulnerability index (MVI) was proposed, and was validated through the above-mentioned reconnaissance sample data. A matrix model of the MVI of the regions (19 provinces in mainland China) based on the parameter (MVI) was established.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.8
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• pp.703-710
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• 2012

At the stage of conceptual design of a helicopter, it is a general way using low fidelity analysis methods because of a large number of design calculations and trade-off studies. Determination of empirical parameters used in analysis codes for more practical design, depends on an user's design experiences, which effects on the accuracy and the fidelity of conceptual design results. Thus, more precise and logical method should be required to determine the empirical parameters used in the conceptual design of a helicopter. The present method is to be used not only in verifying the empirical parameters generated by design requirements, but also regenerate them if they contain any errors. Empirical parameters produced by present method were used to design a helicopter with a payload objective and performance constraints of an operating helicopter. As a result, weights and geometries of designed helicopter matched the target value within 5% significance level, proving that the suggested parameter generating method can be useful in the conceptual design of a helicopter.

• Geomechanics and Engineering
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• v.30 no.1
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• pp.11-26
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• 2022

One of the most important issues in tunneling, is the squeezing phenomenon. Squeezing can occur during excavation or after the construction of tunnels, which in both cases could lead to significant damages. Therefore, it is important to predict the squeezing and consider it in the early design stage of tunnel construction. Different empirical, semi-empirical and theoretical-analytical methods have been presented to determine the squeezing. Therefore, it is necessary to examine the ability of each of these methods and identify the best method among them. In this study, squeezing in a part of the Alborz service tunnel in Iran was estimated through a number of empirical, semi- empirical and theoretical-analytical methods. Among these methods, the most robust model was used to obtain a database including 300 data for training and 33 data for testing in order to develop a machine learning (ML) method. To this end, three ML models of Gaussian process regression (GPR), artificial neural network (ANN) and support vector regression (SVR) were trained and tested to propose a robust model to predict the squeezing phenomenon. A comparative analysis between the conventional and the ML methods utilized in this study showed that, the GPR model is the most robust model in the prediction of squeezing phenomenon. The sensitivity analysis of the input parameters using the mutual information test (MIT) method showed that, the most sensitive parameter on the squeezing phenomenon is the tangential strain (ε_θ^α) parameter with a sensitivity score of 2.18. Finally, the GPR model was recommended to predict the squeezing phenomenon in tunneling projects. This work's significance is that it can provide a good estimation of the squeezing phenomenon in tunneling projects, based on which geotechnical engineers can take the necessary actions to deal with it in the pre-construction designs.

• Steel and Composite Structures
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• v.33 no.2
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• pp.181-194
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• 2019

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (R) and the lowest mean square error (MSE) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.

• Water for future
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• v.20 no.2
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• pp.117-126
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• 1987

A Synthetic unit hydrograph method was suggested for the representation of a direct runoff hydrograph with empirical geomorphologic laws and geomorphologic parameters by applying geomorphologic instantaneous unit hydrograph theory and Rossois results of application of GIUH theory to the Nash Model which is a linear reservoir model. The shape parameter m and scale parameter k can be derived by the Horton's empirical geomorphologic laws $R_A,R_B,R_L$ when ordered according to Strahler's ordering Scheme, main stream length and using the maximum velocity for the dynamic characteristics of a river basin, The derived response function was tested on some observed flood datas and showed promising. For the determination of the shape parameter m, eq. (16) was showed applying and m showed a good regression with the size of basin area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.845-852
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• 2015

The runup height is an important design parameter to determine the crest elevation of coastal structures and seawalls. In this study, two dimensional wave runup tests for rubble-mound structure covered by tetrapods were conducted. Incident waves at the toe include nonbreaking, breaking and broken random wave conditions. A empirical formula to predict runup elevation of rubble-mound structure with 1:1.5 front slope was proposed on the basis of physical model test results using a surf similarity parameter. The test results from this study were compared with those from van der Meer and Stam(1992).

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.533-538
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• 2001

In general, shape optimization design of the flow system has done to obtain the effects, which are required in the engineering fields. Most of these designs are accomplished by empirical or numerical analysis. But, in empirical analysis case, it is difficult to obtain an optimal shape in the feasible design region. And, in numerical method case, it usually needs many design parameters, because of the required object-function. In this paper, we present a newly numerical analysis, the growth-strain method having only one design parameter. That optimizes a shape by distributing a design parameter such as dissipation energy to be uniformed in the flow system. Also, we apply this shape design process to the three-flow systems, and then we identify that the resulting shape approaches the known optimal shape in the numerical values. Consequently, we confirm that the proposed method is very efficient and practical in the shape optimization of the flow system.