• Resources Recycling
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• v.27 no.3
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• pp.3-7
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• 2018

Development of extractive metallurgical processes for metal sulfides has become of importance owing to the depletion of oxide ores with rich metal contents. Most of the leaching reactions of metal sulfides is electrochemical reaction and can be classified as $H_2S$, S, and ${SO_4}^{2-}$ evolution type. The acidity of leaching solution and the presence and concentration of an oxidizing agent affect the formation of reaction intermediates containing sulfur. Frost diagram of sulfuroxoanion indicates that the oxoanions with higher oxidation number are more thermodynamically stable in the presence of oxidizing agents.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.443-444
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• 2011

This paper discusses a model order reduction for large order rotor dynamics systems results from the finite element discretization. Typical rotor systems consist of a rotor, built-on parts, and a support system, and require prudent consideration in their dynamic analysis models because they include unsymmetric stiffness, localized nonproportional damping and frequency dependent gyroscopic effects. When the finite element model has a very large number of degrees of freedom because of complex geometry, repeated dynamic analyses to investigate the critical speeds, stability, and unbalanced response are computationally very expensive to finish within a practical design cycle. In this paper, the Krylov-based model order reduction via moment matching significantly speeds up the dynamic analyses necessary to check eigenvalues and critical speeds of a Nelson-Vaugh rotor system. With this approach the dynamic simulation is efficiently repeated via a reduced system by changing a running rotational speed because it can be preserved as a parameter in the process of model reduction. The Campbell diagram by the reduced system shows very good agreement with that of the original system. A 3-D finite element model of the Nelson-Vaugh rotor system is taken as a numerical example to demonstrate the advantages of this model reduction for rotor dynamic simulation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.646-655
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• 1990

A practically useful system for elastic-plastic fracture mechanics analysis has been developed. The developed system is comprised of the deformation plasticity failure assessment diagram(DPFAD) approach and the J-integral/Tearing modulus(J/T) approach. The system contains analysis routines for five types of fracture specimens : compact tension, center cracked tension, single edge craked plate in uniform tension, single edge cracked plate in three point bending and double edge cracked plate in tension. A double interpolation scheme was adopted to interpolate J values from the EPRI developed EPFM handbook and the Newton-Raphson method was used to obtain proper loadings for displacement control conditions. A graphic output system was utilized to present numerical results. Several case studies were performed to evaluate the accuracy and the usefulness of the code. It was found that the J/T approach and the DPFAD approach yielded similar results. However, the DPFAD approach is more convenient for qick assessment of integrity of cracked structures while the J/T approach is more useful in evaluating the full history of the fracture process.

• The Korean Journal of Physiology
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• v.6 no.1
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• pp.1-9
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• 1972

In order to observe a possible effect of CO intoxication on the activities of surfactant, the rabbit war exposed either to 0.1, 0.2 and 0.4% CO gas for two to six hours or 0. 1% CO gas for two hours daily for 1, 3 and 5 days, and the lung extract was prepared. The tension-area diagram of the lung extract was recorded automatically using the modified Langmuir-wilhelmy balance with a synchronized recording system, and the results were compared with control (i. e. : non-CO gas exposed normal rabbits). The results obtained are summarized as follows: 1. The maximal and minimal surface tensions, width of the tension-area diagram at the surface area of 40% in lung extract, and stability index of the normal rabbit lung extracts were $31.6{\pm}3.11\;dynes/cm,\;8.2{\pm}0.56\;dynes/cm,\;21.4{\pm}4.40dynes/cm\;and\;1.12{\pm}0.22$, respectively. 2. The activities of surfactant in the CO gas exposed group did not show any significant change from the control. 3. The above results suggest that CO gas produced no noticeable effect on the surfactant system of the lung.

• The Journal of Engineering Geology
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• v.11 no.2
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• pp.175-190
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• 2001

This study investigates the existing theoretical backgrounds in order to examine the behavior of lateral flow according to the plasticity of soils when unsymmetrical surcharge is worked on polluted soft soils by comparing and analyzing the results measured through model tests. Model tests are canied out as follows soil tank, bearing frame and bearing plate are made. By increasing unsymmetrical surcharge to the ground soils with the consistent water content and with gradually increased polluted materials at intervals, the amounts of settlement, lateral displacement and upheaval were respectively observed. In conclusion, the value of critical surcharge was expressed as q$_{cr}$=2.78$_{cu}$ which was similar to those Tschebotarioff(q$_{cr}$=3.0$_{cu}$) and Meyerhof(q$_{cr}$=(B/2H+$\pi$/2)$_{cu}$) had been proposed. The value of ultimate capacity was expressed as q$_{ult}$=4.84$_{cu}$ which was similar to that of Prandtl. The lateral flow pressure is adeQuately calculated by the eQuation(P$_{max}$=K$_o$ r H) and the maximum value of lateral flow pressure is found near O.3H of layer thickness(H) and is higher to ground surface than the ones in composition pattern, Poulos distribution pattern and softclay soils (CL, CH) which is not polluted. The stability control method used in this research followed the management diagram of Tominaga.Hashimoto, Shibata.Sekiguchi, Matsuo.Kawamura who use the amounts of plasticity displacement by lateral flow. As a result, the ultimate capacity values in the diagram {S$_v$-(Y$_m$/S$_v$)} of Matsuo.Kawamura and in the diagram {(q/Y$_m$)-q} of Shibata. Sekiguchi were smaller than in the ones of load-settlement curve (q-S$_v$).

• The Korean Journal of Physiology
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• v.2 no.2
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• pp.63-73
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• 1968

It is well known that mammalian alveolar membrane is covered with a very thin layer of surfactant film which characteristically reduces surface tension of alveolar membrane, and maintains alveolar stability. Since Clements in 1957 demonstrated that the surfactant is extractable by mincing the lung tissue in saline, various studies on the subject have been succeeded by many workers. However, the effect of radiation on the surfactant is not well clarified. Present study was attempted to observe the effect of x-irradiation on the activity of surfactant in rabbits. X-ray in dose of 300 r, 600 r or 900 r was irradiated to the chest of rabbits. The lung was removed from normal or irradiated rabbits sacrificed by arterial blood shedding, and lung-saline extract, adding 3 grams of lung tissue to 50 mili-liters of saline, was prepared by means of Vertis homogenizer. Tension-area diagram of lung extract was recorded automatically by a modified Langmuir-Wilhelmy balance with a synchronized recording system designed in this department. The surface tension of lung extract was measured at 1st, 2 nd, 3 rd, 7 th and 15 th post-radiation day in 300 r irradiated group, at 3 rd, 7 th and 15 th post-radiation day in 600 r irradiated group, 3 rd and 7 th post-radiation day in 900 r irradiated group respectively. For the histo-pathological study, lung tissue preparations were made in all irradiatiated groups on the day of experiment and in normal group. The results obtained are summarized as follows: 1. The minimal surface tension, maximal surface tension and stability index of normal rabbits lung extracts were 7.68 dynes/cm, 38.84 dynes/cm, and 1.39 respectively. 2. The activity of surfactant was depressed prominently by x-irradiation. However, increase in the dose of x-irradiation did not show any significant change in the degree of surfactant activity suppression. The most marked depression in surfactant was observed at the third post-radiation day in all irradiated groups. 3. Activity of surfactant depressed by x-irradiation showed a tendency of recovering to normal on 15 th post-radiation day. 4. The tendency of change in activity of surfactant following x-irradiation was somewhat correlative with histo-pathological changes. But the degree of depression of surfactant by x-irradiation did not correspond to the degree of histo-pathological changes, and recovery of lung tissue from radiation damage, tissue edema and congestion, seemed to be followed by restoration of surfactant activity. 5. The width of the tension-area diagram was measured at the surface area of 40% in lung extract of normal and x-irradiated rabbits. And it was found that the changes of the width corresponded well with that of minimum surface tension and of stability index in all normal and x-irradiated groups.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.555-562
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• 2019

This study was undertaken to develop a stable self-microemulsifying drug delivery system (SMEDDS) for trans-cinnamaldehyde, a known antibacterial and antifungal agent. A simultaneous analytical method was established for quantification of trans-cinnamaldehyde and its degradant, cinnamic acid. Various surfactants were applied to assess their effect on the aqueous solubility of trans-cinnamaldehyde, and pseudo-ternary phase diagrams were plotted. Of the various formulations tested, the liquid SMEDDS composed of trans-cinnamaldehyde (oil), Cremophor EL (surfactant) and Transcutol P (cosurfactant) at a volume ratio of 10/70/20, produced the smallest emulsion droplet size (around 23 nm). The stability test determined the superior stability of the trans-cinnamaldehyde SMEDDS with constant trans-cinnamaldehyde content and z-average diameter of emulsion, under accelerated and heat stressed condition. Thus, we believe that this novel trans-cinnamaldehyde SMEDDS formulation has the potential to be applied for the development of trans-cinnamaldehyde medicines in the pharmaceutical industry.

• Advances in materials Research
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• v.13 no.1
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• pp.63-86
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• 2024

Asphalt concrete (AC), is a mixture of bitumen and aggregates, which is very sensitive in the design of flexible pavement. In this study, the Marshall stability of the glass and carbon fiber bituminous concrete was predicted by using Artificial Neural Network (ANN), Support Vector Machine (SVM), Random Forest (RF), and M5P Tree machine learning algorithms. To predict the Marshall stability, nine inputs parameters i.e., Bitumen, Glass and Carbon fibers mixed in 100:0, 75:25, 50:50, 25:75, 0:100 percentage (designated as 100GF:0CF, 75GF:25CF, 50GF:50 CF, 25GF:75CF, 0GF:100CF), Bitumen grade (VG), Fiber length (FL), and Fiber diameter (FD) were utilized from the experimental and literary data. Seven statistical indices i.e., coefficient of correlation (CC), mean absolute error (MAE), root mean squared error (RMSE), relative absolute error (RAE), root relative squared error (RRSE), Scattering index (SI), and BIAS were applied to assess the effectiveness of the developed models. According to the performance evaluation results, Artificial neural network (ANN) was outperforming among other models with CC values as 0.9147 and 0.8648, MAE values as 1.3757 and 1.978, RMSE values as 1.843 and 2.6951, RAE values as 39.88 and 49.31, RRSE values as 40.62 and 50.50, SI values as 0.1379 and 0.2027 and BIAS value as -0.1 290 and -0.2357 in training and testing stage respectively. The Taylor diagram (testing stage) also confirmed that the ANN-based model outperforms the other models. Results of sensitivity analysis showed that the fiber length is the most influential in all nine input parameters whereas the fiber combination of 25GF:75CF was the most effective among all the fiber mixes in Marshall stability.

• Korean Journal of Materials Research
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• v.14 no.8
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• pp.547-551
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• 2004

The sulfidation behaviour of Fe-XAl-0.3Y(X=5, 10, 14, 25 $wt.\%$) alloys was investigated at 1123 K in $H_2/H_{2}S$ gas atmosphere for $1\sim24$ hrs using SEM/EDX, XRD and EPMA. The weight changes of Fe-XAl-0.3Y alloys followed the parabolic rate law, Sulfidation rates of iron aluminide alloys with high Al content were one-twentieth lower than that of 5Al alloys. This is due to the formation of protective $Al_{2}O_3$ oxides on the surface of 10Al, 14Al and 25Al alloys. By calculating partial pressure of impurity oxygen contained $H_2/H_{2}S$ gas, the $Al_{2}O_3$ oxides formation could be explained using Fe-Al-S-O thermodynamic stability diagram. The sulfidation product scales of the 5Al alloy showed that thick iron sulfide scale(FeS) containing porosities formed during early stages of sulfidation. With continued sulfidation, aluminum sulfide was formed at the alloy/scale interface.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.12
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• pp.1112-1119
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• 2011

The goal of this study is the stability evaluation of a vacuum pump through modal test and rotor dynamics. Roots type vacuum pump, which is a dry vacuum pump, is necessary for the manufacturing process of the semiconductor and the display. Eigenvalue was solved by the finite-element method(FEM) using 2D and 3D models, then the modal test result was compared with the FEM result. According to the comparison, the analysis result using the 2D was more accurate than the 3D model. Therefore, rotor dynamics was performed by the 2D model. Campbell diagram and root-locus maps, which were calculated by complex-eigenvalue analysis, were used to evaluate the stability of the rotors of the vacuum pump. And displacement solved by unbalance response analysis was compared with the minimum clearance between two rotors of the vacuum pump. Thus, the vacuum pump is assumed operated under steady state through the evaluation of the rotor dynamics.