• Journal of dental hygiene science
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• v.22 no.1
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• pp.20-29
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• 2022

Background: The purpose of this study is to investigate the effect of liquefied digestive medicines on the composite resin surface. Methods: Three types of liquefied digestive medicines (Gashwalmyeongsu, Wicheongsu, and Saengrokcheon) were selected as experimental groups, Samdasoo and Chamisul as negative controls, and Trevi as positive controls were selected to measure pH and titratable acidity. The samples filled with resin at acrylic were made total 300, 50 per group. To evaluate the erosion risk of the composite resin, the specimens were immersed in a liquefied medicine for 1, 3, 5, 15, and 30 minutes, and then the surface microhardness was measured using the Vickers Hardness Number, and the surface change was observed with scanning electron microscope (SEM). Results: The average pH of the three liquefied medicine was 3.75±0.30, the Saengrokcheon was the lowest at 3.45±0.01, and the Trevi was 4.66 and Samdasoo and Chamisul were 7.40 and 8.58, respectively. The amount of NaOH reaching pH 5.5 and 7.0 was the lowest in the order of Trevi, Gashwalmyeongsu, Wicheongsu, and Saengrokcheon. The largest surface hardness reduction value was shown in Gashwalmyeongsu (-11.85±3.73), followed by Saengrokcheon (-9.79±3.11) and Wicheongsu (-8.28±2.83), and Samdasoo (-0.84±1.56) and Chamisul (-6.24±0.42) had relatively low surface hardness reduction values. However, Trevi (-16.67±5.41), a positive control group containing carbonic acid, showed a higher decrease in surface hardness than the experimental group. As a result of observation with SEM, experimental group and positive control group, showed rough surfaces and irregular cracks, and negative control groups showed smooth patterns similar to before immersion. Conclusion: The liquefied digestive medicine with low pH could weaken the composite resin surface, and the carbonic acid component could more effect on the physical properties of the composite resin than pH.

• Geomechanics and Engineering
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• v.38 no.3
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• pp.215-229
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• 2024

Because of the various patterns of deep-water inrush and complicated mechanisms, accurately predicting mine water inflows is always a difficult problem for coal mine geologists. In study presented in this paper, the water inrush channels were divided into four basic water diversion structures: aquifer, rock fracture zone, fracture zone and goaf. The fluid flow characteristics in each water-conducting structure were investigated by laboratory tests, and multistructure and multisystem coupling flow analysis models of different water-conducting structures were established to describe the entire water inrush process. Based on the research of the water inrush flow paths, the analysis model of different water inrush space structures was established and applied to the prediction of mine water inrush inflow. The results prove that the conduction sequence of different water-conducting structures and the changing rule of permeability caused by stress changes before and after the peak have important influences on the characteristics of mine water-gushing. Influenced by the differences in geological structure and combined with rock mass RQD and fault conductivity characteristics and other mine exploration data, the prediction of mine water inflow can be realized accurately. Taking the water transmitting path in the multistructure as the research object of water inrush, breaking through the limitation of traditional stratigraphic structure division, the prediction of water inflow and the estimation of potentially flooded area was realized, and water bursting intensity was predicted. It is of great significance in making reasonable emergency plans.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.2
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• pp.95-102
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• 2005

There are many tube and pipeline in nuclear power plant under high temperature and high pressure. Erosion and corrosion defects were expected on these tube and pipe-line by environmental and mechanical factors. These erosion and corrosion defects ran be evaluated by ultrasonic technique. In these study, Scanning Laser Source(SLS) technique was applied to detect defect and construct image. This technique also makes detection possible on rough and curved surfaces such as tube and pipe-line by scanning. Conventional ultrasonic scanning technique requires immersion of specimen or water jet for transferring ultrasonic wave between transducer and specimen. However, this SLS technique does not need contacting and couplant to generate surface wave and to get flaw images. Therefore, this SLS technique has several advantages, for complicated production inspection, non-contact, remote from specimen, and high resolution. In this study, SLS images were obtained with various conditions of generation laser ultrasound and receiving in order to enhance detectability of flaws on the tube. Stress corrosion cracks were produced on tube and images of stress corrosion cracks were constructed by using SLS technique.

• Archives of Pharmacal Research
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• v.21 no.6
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• pp.645-650
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• 1998

The dual drug-loaded alginate beads simultaneously containing drug in inner and outer layers were prepared by dropping plain (single-layered) alginate beads into $CaCl_2$ solution. The release characteristics were evaluated in simulated gastric fluid for 2 h followed by intestinal fluids thereafter for 12 h. The surface morphology and cross section of dual drug-loaded alginate beads was also investigated using scanning electron microscope (SEM). The poorlv water-soluble ibuprofen was chosen as a model drug. The surface of single-layered and dual drug-loaded alginate beads showed very crude and roughness, showing aggregated particles, surface cracks and rough crystals. The thickness of dual drug-loaded alginate beads surrounded by outer layer was ranged from about 57 to 329mcm. The distinct chasm between inner and outer layers was also observed. In case of single-layered alginate bead, the drug was not released in gastric fluid but was largely released in intestinal fluid. However, the release rate decreased as the reinforcing $Eudragit^{\circledR}$ polymer contents increased. When the plasticizers were added into polymer, the release rate largely decreased. The release rate of dual drug-loaded alginate beads was stable in gastric fluid for 2 h but largely increased when switched in intestinal fluid. The drug linearly released for 4 h followed by another linear release thereafter, showing a distinct biphasic release characteristics. There was a difference in the release profiles between single-layered and dual drug-loaded alginate beads due to their structural shape. However, this biphasic release profiles were modified by varying formulation compositions of inner and outer layer of alginate beads. The release rate of dual drug-loaded alginate beads slightly decreased when the outer layer was reinforced with $Eudragit^{\circledR}$ RS1OO polymers. In case of dual drug-loaded alginate beads with polymer-reinforced outer layer only, the initial amount of druc released was low but the initial release rate (slope) was higher due to more swellable inner cores when compared to polymer-reinforced inner cores. The current dual drug-loaded alginate beads may be used to deliver the drugs in a time dependent manner.