• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.277-280
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• 2009

This paper deals with the performance evaluation of Barlat's and BBC yield criteria by the directional variation prediction of the yield stresses and the R-values. for the evaluation of yield criteria, three kinds of Aluminum alloys and two kinds of steels were selected and their material properties are from Stoughton and Yoon's work. The experimental data required for the parameter evaluation included the uniaxial yield stresses and R-values (width-to-thickness strain ratio in uniaxial tension) measured in rolling direction, diaganol direction and the transverse direction, the equibiaxial yield stress and the R-value of equibiaxial tension. The optimization method, the Downhill Simplex method, was selected for the coefficient identification of Barlat91, Barlat97 and Barlat2000 yield criteria. Yield surface shapes, yield stress and R-value directionalities of Barlat's and BBC yield criteria were investigated and compared with the experimental data. Barlat2000 and BBC yield criteria were extremely qualified for the shape of the yield surface and the directionality of the yield stresses and the R-values.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.1
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• pp.8-13
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• 2015

The objective of this paper is to provide design data of fin-tube heat exchanger which have a large diameter oval tube for dryer application. In this study, the heat transfer and pressure drop performance characteristics of the fin-tube heat exchanger were compared with Dittus-Boelter and a new correlation equation using Wilson plot method. The simulation results based on section by section method were compared with experimental results. These results showed that a new correlation equation using Wilson plot method provided better prediction, about 3 to 12%, than the Dittus-Boelter equation, from the experiment comparison. Also, the pressure drop of simulation results showed much more deviation with the experimental results.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.229-240
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• 2002

This paper is an experimental and numerical work of Investigating the bearing capacity of shallow foundation of rubble mound under eccentric loads. Parametric centrifuge model tests at the 50g level environments with the model footings in the form of strip footing were performed by changing the loading location of model footing, relative density and materials for ground foundation. For the model ground, crushed rock sampled from a rocky mountain was prepared with a grain size distribution of having an identical coefficient of uniformity to the field condition. Model ground was also prepared with relative densities of 50 % and 80 %. For loading condition, model tests with and without eccentric load were carned out to investigate the effect of eccentric loads and a numerical analysis with the commertially available software of FLAC was performed. For numerical estimation with FLAC, the hyperbolic model of a nonlinear elastic constitutive relationship was used to simulate the stress-stram constitutive relationship of model ground and a series of triaxial compression test were carried out to find the parameters for this model Test results were analyzed and compared with Meyerhof method (1963), effective area method based on the limit equilibrium method, and a numerical analysis with FLAC.

• Geomechanics and Engineering
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• v.16 no.4
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• pp.415-421
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• 2018

A location determining method is proposed for critical sliding surface in the stability analysis of the filling materials in karst caves. First, a preliminary location of the sliding surface is determined based on simulation results which includes displacement contour and plastic zone. The sliding surface will locate on the bottom contact interface when the friction angle is relative small. However, a weakened contact interface always becomes the critical sliding surface no matter what the friction angle is. Then when the friction angle becomes larger, the critical sliding surface inside fillings can be determined by a parabola, the coefficient of which increases linearly with the friction angle under the same cohesion. Finally, the critical sliding surface approximately remains unchanged with friction angle. The influence of cohesion is similar to that of friction angle. Although affected by shape, size or position of the karst cave, the critical sliding surface mainly depends on both friction angle and cohesion. Thus, this method is always useful in determining the critical sliding surface.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.5
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• pp.535-541
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• 2010

In this paper, we have derived a continuum-based adjoint design sensitivity of general performance functionals with respect to Young' modulus and heat conduction coefficient for steady-state nonlinear thermoelastic problems. An adjoint equation for temperature and displacement fields is defined for the efficient computation of the coupled field design sensitivity. Through numerical examples, we investigated the mesh dependency of the topology optimization method in the thermoelastic problems. Also, comparing the dominant loading cases of thermal and mechanical ones, the loading dependency of topology design optimization in coupled multi-physics problems is investigated.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.17-22
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• 2011

This study conducted wide-tank experiments and numerical calculations for a vessel in various positions such as upright and inclined by 2 and 4 degrees, with the goal of investigating the motion amplitude response of a small damaged fishing boat subject to a beam sea. Numerical calculations were conducted based on the three-dimensional source distribution method. The good agreement of the numerical calculation and experimental results confirmed that the present calculation method can be efficiently used for the initial design of a small fishing boat. In addition, while the chine-line type has been frequently adopted to improve a ship's resistance performance in the design of a small fishing boat, it is considered that the possibility of a deterioration in rolling performance should be thoroughly considered.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.283-289
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• 2013

Wave profiles coming with oblique angle to trapezoidal submerged breakwater on the porous seabed are computed numerically by using a boundary element method. The analysis method is based on the wave pressure function with the continuity in the analytical region including fluid and structure. When compared with the existing results on the oblique incident wave, the results of this study show good agreement. The fluctuation of wave profiles is increased in the rear of the submerged breakwater due to the increase of the transmission coefficient, as the incident angle increases. In addition, in the case of the wave profiles passing over the submerged breakwater on porous seabed, it is able to verify that the attenuation of wave height occurs more significantly due to the wave energy dissipation than that of passing over the submerged breakwater on the impermeable seabed. The results indicate that wave profile own high dependability regarding the change of oblique incident waves and porous seabed. Therefore, the results of this study are estimated to be applied as an accurate numerical analysis referring to oblique incident waves and porous seabed in real sea environment.

• Journal of Pharmaceutical Investigation
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• v.21 no.3
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• pp.171-177
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• 1991

A reverse-phase, ion-pair high performance liquid chromatographic (HPLC) method for the simultaneous quantative determination of pyridostigmine and its hydrolytic product, 3-hydroxy-N-methylpyridinium (HMP), is descrihed, The assay of pyridostigmine and HMP was linear in the range of amount from 24 to 60 mg/tablet and from 2.4 to 12.0 mg/tablet, respectively, with coefficient of variation (C.V.) of 0.05-0.12% (n=7) and 0.25-0.52% (n=5), respectively, and applicable conveniently even in the case of the mixture of pyridostigmine and HMP. Meanwhile, the conventional UV method gave inaccurate results for the aged pyridostigmine tablets. In the extraction of pyridostigmine from tablets prior to be assayed by HPLC, methanol was found to be more effective than ethanol or distilled water. Multiple extraction (four times) with methanol resulted in the full recovery of pyridostigmine, whereas ethanol gave 95% recovery even after four times extraction. Based on these results. the present method would be very useful for the accurate determination of pyridostigmine in the aged pyridostigmine tablets.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 2001.10a
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• pp.140-140
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• 2001

A sensitive analytical method based on gas chromatograpy-mass spectrometry with a selected ion monitoring (GC/MS-SIM) with the purge-and-trap concentration and with headspace method (in limited applications) was developed for determining of epichlorohydrin in canned beverages coated with epoxy resin. The calibration curve in the range of $0.5\sim50ng$ had correlation coefficient greater than 0.998 and a detection limit of $0.l\mug/L$ was obtained using a sample volume of 20ml. The predominant ions of epichlorohydrin produced in MSD using electron ionization(EI) were m/z 57 ([M-CI]+) and 62/64 $([M-CH_2O]+)$. In survey of epichlorohydrin in thirty commercial canned beverage samples, none of them was detected.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1832-1842
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• 2014

A novel probabilistic small signal stability analysis (PSSSA) method considering load correlation is proposed in this paper. The superiority Latin hypercube sampling (LHS) technique combined with Monte Carlo simulation (MCS) is utilized to investigate the probabilistic small signal stability of power system in presence of load correlation. LHS helps to reduce the sampling size, meanwhile guarantees the accuracy and robustness of the solutions. The correlation coefficient matrix is adopted to represent the correlations between loads. Simulation results of the two-area, four-machine system prove that the proposed method is an efficient and robust sampling method. Simulation results of the 16-machine, 68-bus test system indicate that load correlation has a significant impact on the probabilistic analysis result of the critical oscillation mode under a certain degree of load uncertainty.