• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.2
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• pp.127-139
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• 2023

In this study, minoxidil, which is well known as a pharmaceutical raw material, and diaminopyrimidine oxide (DAO), which is a cosmetic raw material, were used as active ingredients to evaluate the physical properties of niosomes and compare the skin penetrations of artificial skin. To prepare niosomes of the size of nanoparticles, a high pressure homogenization method was used, and physical properties were evaluated with a zetasizer. The particle size of the noisome including the active ingredient was measured to be 99 to 123 nm according to HLB, and the zeta potential was measured in the range of -60 to -81 mV. Through DSC (differential scanning colorimetry), it was confirmed that minoxidil, a crystalline component, was uniformly dissolved in an amorphous state in niosomes. In order to confirm and compare skin penetration, it was measured by the in vitro Franz diffusion cell method, and the niosome formulation showed 3.4 times higher penetration for minoxidil and 11.1 times higher penetration for DAO than the control gel formulation. In addition, when comparing the skin penetration of minoxidil niosome and DAO niosome, a similar trend was shown, and the penetration amount of DAO was relatively high. The shapes of the niosome formulations with different HLB values were observed using Cryo-TEM, and it was confirmed that vesicles were formed in all of them and that they were intermediate between SUV (small unilamella vesicle) and LUV (large unilamella vesicle). Through this study, minoxidil, an effective drug for hair loss, and DAO, a cosmetic raw material, can be effectively delivered to the skin by encapsulating them in a noisome formulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2C
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• pp.109-117
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• 2010

Gas hydrate dissociation can generate large amounts of gas and water in gas hydrate bearing sediments, which may eventually escape from a soil skeleton and form voids within the sediments. The loss of fine particles between coarse particles or collapse of cementation due to water flow during heavy or continuous rainfall may form large voids within soil structure. In this study, the effect of void formation resulting from gas hydrate dissociation or loss of some particles within soil structure on the strength of soil is examined. Glass beads with uniform gradation were used to simulate a gas hydrate bearing or washable soil structure. Glass beads were mixed with 2% cement ratio and 7% water content and then compacted into a cylindrical sample with five equal layers. Empty capsules for medicine are used to mimic large voids, which are bigger than soil particle, and embedded into the middle of five equal layers. The number, direction, and length of capsules embedded into each layer vary. After two days curing, a series of unconfined compression tests is performed on the capsule-embedded cemented glass beads. Unconfined compressive strength of cemented glass beads with capsules depends on the volume, direction and length of capsules. The volume and cross section formed by voids are most important factors in strength. An unconfined compressive strength of a specimen with large voids decreases up to 35% of a specimen without void. The results of this study can be used to predict the strength degradation of gas hydrate bearing sediments in the long term after dissociation and loss of fine particles within soil structure.

• Journal of the Korea Society of Computer and Information
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• v.28 no.7
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• pp.113-120
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• 2023

The purpose of this study was the accuracy of cardiac compression, fatigue, and physiological changes of the rescuer for different mask type in cardiopulmonary resuscitation(CPR). Data collection was from 9 to 12 May 2022, the participants were a total of 24 paramedic students with a BLS provider at D University. The students participated in an experiment in which 12 students each wore a surgical mask (Dental mask) and a fine particle 94% blocking mask (KF94 mask) and performed CPR for 2 minutes over a total of 7 times. As a result of the study, in the analysis of the quality of the rescuer's chest compression according to the type of mask, there was a significant difference in the compression speed (F=24.91, p<.001) and bad compression hand position (F=14.54, p=.024) in the group wearing the KF94, Fatigue showed significant differences in both the Dental mask group (F=51.16, p<.001) and the KF94 mask group (F=63.49, p<.001). Among the physiological changes, heart rate showed a significant difference between the Dental mask group (F=34.79, p<.001) and the KF94 mask group (F=35.55, p<.001), and the respiratory rate showed a significant difference between the Dental mask group (F=25.02, p=.001) and the KF94 mask group(F=23.02, p=.002). Therefore, in order to improve the quality of efficient chest compression and reduce the fatigue and physiological changes of rescuers, it will be necessary for rescuers to wear suitable personal protective equipment.

• Progress in Medical Physics
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• v.33 no.4
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• pp.129-135
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• 2022

Purpose: A full-energy-peak (FEP) efficiency correction is required through a Monte Carlo simulation for accurate radioactivity measurement, considering the geometrical characteristics of the detector and the sample. However, a relative deviation (RD) occurs between the measurement and calculation efficiencies when modeling using the data provided by the manufacturers due to the randomly generated dead layer. This study aims to optimize the structure of the detector by determining the dead layer thickness based on Monte Carlo simulation. Methods: The high-purity germanium (HPGe) detector used in this study was a coaxial p-type GC2518 model, and a certified reference material (CRM) was used to measure the FEP efficiency. Using the MC N-Particle Transport Code (MCNP) code, the FEP efficiency was calculated by increasing the thickness of the outer and inner dead layer in proportion to the thickness of the electrode. Results: As the thickness of the outer and inner dead layer increased by 0.1 mm and 0.1 ㎛, the efficiency difference decreased by 2.43% on average up to 1.0 mm and 1.0 ㎛ and increased by 1.86% thereafter. Therefore, the structure of the detector was optimized by determining 1.0 mm and 1.0 ㎛ as thickness of the dead layer. Conclusions: The effect of the dead layer on the FEP efficiency was evaluated, and an excellent agreement between the measured and calculated efficiencies was confirmed with RDs of less than 4%. It suggests that the optimized HPGe detector can be used to measure the accurate radioactivity using in dismantling and disposing medical linear accelerators.

• Steel and Composite Structures
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• v.46 no.1
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• pp.53-73
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• 2023

Man-made structure materials like concrete usually contain inclusions. These inclusions affect the mechanical properties of concrete. In this investigation, the influence of inclusion length and inclination angle on three-dimensional failure mechanism of concrete under uniaxial compression were performed using experimental test and numerical simulation. Approach of acoustic emission were jointly used to analyze the damage and fracture process. Besides, by combining the stress-strain behavior, quantitative determination of the thresholds of crack stress were done. concrete specimens with dimensions of 120 mm × 150 mm × 100 mm were provided. One and two holes filled by gypsum are incorporated in concrete samples. To build the inclusion, firstly cylinder steel tube was pre-inserting into the concrete and removing them after the initial hardening of the specimen. Secondly, the gypsum was poured into the holes. Tensile strengths of concrete and gypsum were 2.45 MPa and 1.5 MPa, respectively. The angle bertween inclusions and axial loadind ary from 0 to 90 with increases of 30. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Diameter of the hole was 20 mm. Entirely 20 various models were examined under uniaxial test. Simultaneous with experimental tests, numerical simulation (Particle flow code in two dimension) were carried out on the numerical models containing the inclusions. The numerical model were calibrated firstly by experimental outputs and then failure behavior of models containing inclusions have been investigated. The angle bertween inclusions and axial loadind vary from 0 to 90 with increases of 15. The length of inclusion vary from 25 mm to 100 mm with increases of 25 mm. Entirely 32 various models were examined under uniaxial test. Loading rate was 0.05 mm/sec. The results indicated that when inclusion has occupied 100% of sample thickness, two tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusion has occupied 75% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. When inclusions have occupied 50% and 25% of sample thickness, four tensile cracks originated from boundaries of sample and spread parallel to the loading direction until being integrated together. Also the inclusion was failed by one tensile crack. The compressive strength of samples decease with the decreases of the inclusions length, and inclusion angle had some effects on that. Failure of concrete is mostly due to the tensile crack. The behavior of crack, was affected by the inclusion length and inclusion number.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.71-77
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• 2023

With the continuous industrial development, not only natural resource depletion, waste generation, but also various weather conditions are becoming more frequent. Efforts are continuing to recycle industrial by-products to overcome the climate crisis and save resources. Slag is a representative by-product generated in the steel industry, and it is characterized by improving rutting resistance and moisture sensitivity by increasing strength and reducing deformation when used as a material for asphalt concrete. On the other hand, slag has expansion properties so it is used as a relatively low-value-added material such as embankment and refilling materials. In order to expand the application of slag, an experiment was conducted to evaluate the crack resistance of slag asphalt concrete pavement. As a result of the indirect tensile strength test, it was found that the asphalt mixture using slag aggregate showed a value 1.13 times higher than that of the general HMA with the same particle size, and the toughness was 1.17 units, improving crack resistance. In addition, it was found that the failure number of the 4-point beam fatigue experiment and the slag asphalt mixture was 20,409, which was more than doubled compared to the general HMA. Furthermore, Overlay Test showed a tensile load residual rate of 4 times or more, improving crack resistance to repeated fatigue. Accordingly, the use of slag aggregate will likely have various advantages in improving the performance of asphalt concrete pavement.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.587-592
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• 2023

Cobalt oxide (Co₃O₄·CoO) ultra fine particles were synthesized by liquid phase precursor method. cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) was as a starting material. A plant-derived crystalline cellulose was used as impregnating materials. A impregnated precursor was calcined at a temperature of 350 to 900℃ to obtain cobalt oxide particles having a particle size of 1 to 10㎛. The crystallization process and morphology according to the calcination temperature were examined, and the properties of the synthesized powder were evaluated using SEM and XRD. It was confirmed that a crystal phase of Co₃O₄ began to form around 350℃ and crystal growth occurred up to 900℃. At a temperature above 500℃, the Co₃O₄ crystal was changed to another crystal phase CoO.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.315-321
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• 2008

Recently, in the light of environments and utilization, countermeasures to preserve beaches in coastal area are required without depending on such as jetties and breakwaters. The necessity of integrated sand management including not only coastal sediment but also sediment discharge from hinterland rivers is increased so as to establish long-term counterplan for sediment transport. In this regard, the following subjects are examined in this study; efficient ways for discharged sand to be transported from a river to the neighboring coast, the river terrace occurrence and its growth at the river delta, measures to improve storage efficiency of the discharged sand and measures to prevent the sand resources from being discharged into the deep sea during flooding. In recent, A jetty of 260 m length was constructed at Namdae River mouth in the year of 2005 as a countermeasure against the occurrence of sand-bar at river mouth and its close. In this study, a series of numerical experiments were carried out to investigate the characteristics of sediment transport and morphological change due to the construction of jetty at the entrance of Namdae River mouth. Firstly, The sand discharge from Namdae River is quantified by one-dimensional numerical analysis assuming the mixed sand of three different particle diameters. Then, in order to understand the transport behavior of the sand discharge from river and river mouth phenomena the numerical experiments were then conducted to examine the flow behaviors of river efflux and wind generated circulations in coastal area. And, after establishing the numerical model system, which predicts the sea bed changes obtained from the flux model combining with the wave propagation, wave-induced currents and sediment transport models, the sediment transport in the vicinity of Namdae River mouth is analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5A
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• pp.861-872
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• 2006

The element free Galerkin method is extended by the local partition of unity method to model the cohesive cracks in two dimensional continuum. The shape function of a particle whose domain of influence is completely cut by a crack is enriched by the step enrichment function. If the domain of influence contains a crack tip inside, it is enriched by a branch enrichment function which does not have the LEFM stress singularity. The discrete equations are obtained directly from the standard Galerkin method since the enrichment is only for the displacement field, which satisfies the local partition of unity. Because only particles whose domains of influence are influenced by a crack are enriched, the system matrix is still sparse so that the increase of the computational cost is minimized. The condition for crack growth in dynamic problems is obtained from the material instability; when the acoustic tensor loses the positive definiteness, a cohesive crack is inserted to the point so as to change the continuum to a discontiuum. The crack speed is naturally obtained from the criterion. It is found that this method is more accurate and converges faster than the classical meshless methods which are based on the visibility concept. In this paper, several well-known static and dynamic problems were solved to verify the method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3C
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• pp.201-207
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• 2006

Soil tests are generally conducted using a membrane to measure a pore water pressure. However, it has also been recognized that the membrane penetrates into the specimen by the change of the confining pressure, and it results in the erroneous measurement in the pore water pressure and the volumetric strain. This study examined the effectiveness of the correction equation of the membrane penetration on the basis of the experimental data acquired during the isotropic unloading and the cyclic shear process using the hollow cylindrical shear test equipment. The results showed that the membrane penetration by the correction equation could be overestimated when the mean effective stress was lower than 20kPa in this study. The limitations originated from the sudden increase near the zero effective stress, and in order to prevent the overestimation in low effective stress condition, the use of the constant a was proposed in this study. Furthermore, the correction equation for the membrane penetration had to be applied carefully when the initial relative density was high and the density changes were occurred by the relocation of the soil particle by the liquefaction.