• Journal of Korean Society of Environmental Engineers
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• v.38 no.6
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• pp.291-298
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• 2016

Electrochemical water treatment process as a useful treatment method for the removal of non-degradable matter has been consistently studied for several decades. Key process of electrochemical water treatment are oxidation reaction from an anode and reduction from a cathode. In this study, the effect of pre-treatment methods in the insoluble electrode manufacturing process for the water treatment has been evaluated for the life time of electrode The results of this study showed that pre-treatment methods of a base metal such as surface roughness, clean method and interlayer formation influenced to life time of electrode when the same condition (catalyst electrode layer coating method and material system) was applied for pre-treatment methods. This study was conducted by using $IrO_2/Ti$ electrode In the test of sand-blasting process, an electrode manufactured by using sanding media of different sizes resulted in the most effective electrode life time when the size of alumina was used for $212{\sim}180{\mu}m$ praticle size (#80). The most effective method was considered using arc plasma in the additional roughness control and cleaning process, sputtering method to form Ta type interlayer formation process.

• Journal of Bio-Environment Control
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• v.10 no.2
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• pp.75-79
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• 2001

Stem firmness and flowering response of cut lily as influenced by medium composition (Control; Upland soil, Pt; Peatmoss, Pe; Perilite, Ve; Vermiculite, Rrh; Rotted rice-hull, RPt: Russian Peatmoss) were studied. For 'Casa Blanca', plant height and length of flower stalk increased when bulbs were planted in Pt:Rrh:Ve (1:1:1, v.v$^{-1}$ ), and dried leaves of lower part plants decreased in RPt:Pe:Rrh (1:1:1, v.v$^{-1}$ ). In case of 'Marco Polo', plant height and length of lower stalk increased in Pt:Rrh (1:1, v.v$^{-1}$ ) as compared to other treatment, number of leaves and dried leaves increased when bulbs were planted in RPt:Pe:Rrh (1:1:1, v.v$^{-1}$ ) as compared to the control. Flowering of 'Casa Blanca' increased in RPt:Pe:Rrh (1:1:1, v.v$^{-1}$ ) as compared to the control and that o 'Marco Polo' increased when bulbs planted in Pt:Rrh(1:1, v.v$^{-1}$ ). Flower-bud blasting of both cultivars increased with Pt as compared. Stem firmness of 'Casa Blanca' increased in Pt:Pe:Ve (1:1:1, v.v$^{-1}$ ), and especially stem firmness of upper part plant of 'Marco Polo' increased in Pt:Rrh (1:1, v.v$^{-1}$ ) as compared to the control. Generally, stem firmness of 'Casa Blanca' was not influenced by the culture medium.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.4
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• pp.291-299
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• 2005

Objectives : It is well known that cigarette smoking is harzardous to the osseointegration of dental implant, due to the impaired wound healing accompanied by reduced alveolar bone density. The aim of this study is to evaluate the influence of cigarette smoke on the implant osseointegration by the time factor consideration. Materials and methods : Twenty-four male Spraque-Dawley rats (8 weeks, weighting 200 to 250g) were used in this study. In the experimental group, 13 rats were exposed to cigarette smoke, 8 minutes per day during 6 weeks, and 12 rats in the control group were not exposed at any time. RBM (Resorbed blasting media) surfaced implant (diameter 3.3mm, length 5.0mm, AVANA Co., Korea) was placed in the right femur of each rat. Each implant with surrounding bone was prepared with microtome (cutting band 0.2mm$^{(R)}$, EXAKT Co., Germany) after 1 day, 2, 4, 8 and 12 weeks and stained with toluidine blue (1%). Another clinical investigation of each implant was also done at each evaluation time. Results : Clinical investigation around implant fixture showed that there were no significant differences between the control and experimental group. Microscopic observation around implant fixture showed that there were significant differences between the control and experimental group at the initial stage after implant fixture installation. Experimental group showed a decreased bone to implant contact within 4 weeks compared to control group, but showed similar characteristics after 4 weeks. Conclusion : Smoking inhalation effect on the dental implant showed the impaired wound healing by vasoconstriction and decreased intramedullary blood flow at initial stage of osseointegration. This experimental results can be clinically useful to the implant surgery of smoking patients.

• Journal of Periodontal and Implant Science
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• v.37 no.3
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• pp.585-597
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• 2007

The present study was performed to evaluate the effect of Tetracycline-HCI and Saline on the change of implant surface microstructure and surface roughness according to application time. Implants with resorbable blasting media surface were utilized. Before test all 13 implants were measured surface roughness. Among them, 6 implants were rubbed with 50mg/ml Tetracycline-HCl solution and other 6 implants with saline for $\frac{1}{2}$min., 1min., $1\frac{1}{2}$min., 2min., $2\frac{1}{2}$min and 3min. Then, specimens were processed for scanning electron microscopic observation and surface roughness after test. The results of this study were as follows. 1. Control group showed a few irregular, rough, uneven surface with crater-like depression. 2. The test group with Tetracycline-HCl conditioning showed an altered surface when Tetracycline-HCl was applied for 30secs, and showed a various surface alteration as application times go on. 3. The test group with Saline conditioning showed no significant surface differences and surface roughness. 4. The significant increase of Ra value was showed when Tetracycline-HCl was applied for 30secs. In conclusion, the 50mg/ml Tetracycline-HCl must not be applied for the RBM surface implant for surface treatment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.1
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• pp.1-15
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• 2008

Recently, because of the various factors by uncertainty of underground, the risks in tunnelling have been occurred increasingly. Therefore, it is very important to estimate and control the risks considering geotechnical conditions for tunnel stability and environmental problems by tunnel construction. In this study, the risk analysis for tunnel stability was carried out by classifying the risk factors such as ground support capacity, ground settlement, the inflow of groundwater into the tunnel and the damage by the earthquake. Also, the risk assessment for the environmental problems was performed by calculating the vibration and noise by blasting and the drawdown of the groundwater level caused by tunnel construction. Each risk factor was evaluated quantitatively based on the probabilistic and statistic technique, then it was analyzed the distribution characteristic along overall tunnel site. Finally, it was evaluated that how much each risk factor influences on the construction cost with a period for tunnel construction, so it is possible to perform reasonable tunnel design which was capable of minimizing the risks in the tunnel construction.

• Tunnel and Underground Space
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• v.24 no.1
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• pp.97-109
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• 2014

In order to identify the characteristics of the propagation depending on delay time (20, 25 ms) and priming location (top priming, middle priming, bottom priming), test blasts were carried out a total of 4 times using different spacing, burden, drilling length, charge per delay and was derived the formula to predict blast vibration. This study investigated the characteristics of vibration by analysis of the nomogram and prediction of Peak Particle Velocity (PPV) from delay time and priming location by the formula to predict ground vibration. And it analyzed the trends of vibration increase by standards charge 0.5, 1.6, 5, 15 kg. Standards charge is "Blasting design and construction guidelines to road construction" by the Ministry of Land, Infrastructure and Transport. Depending on the charge in favor of vibration control method is proposed. Thus, when the design was to be used as a variable.

• Geotechnical Engineering
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• v.13 no.4
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• pp.121-134
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• 1997

Vibrations induced by traffic loading and construction activities are extremely important due to their potential to cause damage to adjacent structures and toy complaints to the neighbors. Vibration induced damage to the built environment may be caused by the direct transmission of vibrations as well as by the, vibration induced differential settlement. In order to effectively control the vibration related problems, the accurate in-situ vibration monitoring is essential. In this paper, a calibration technique of a geophone which is widely used in practice was described. Once the frequency characteristics of individual geophones were calibrated, the 3fomponent geophone was developed for the in-depth vibration measurement, and the dot ailed calibration and application techniques of the 3fomponent geophone were described. Vibrations caused by blasting, train loading, and pile driving were measured and the applicability of the 3fomponent geophone was assessed.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.5
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• pp.665-674
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• 2007

Purpose: The purpose of this study was to investigate the effect of sire and shape of retention element on the bond strength of indirect composite resin and metal. Material and method: The metal disk specimens, each 6mm in diameter, were cast from CrCo alloy. They were divided into 8 groups by applied retention element. retention bead group $B2\;({\phi}\;0.2mm),\;B4\;({\phi}\;0.4mm),\;B6\;({\phi}\;0.6mm),\;B8\;({\phi}\;0.8mm)$, retention crystal group C2 (0.2mm), C5 (0.5mm), C8 (0.8mm) and sandblasting group SB ($110{\mu}m\;Al_2O_3$ blasting) as control. Eighty-eight metal specimens were veneered with $TESCERA^{(R)}$ Indirect resin system. One specimen of each group was sectioned and the resin-metal bonding pattern at the interface was observed under measuring microscope. Other specimens were then tested for tensile bond strength on an Instron universal testing machine at a crosshead speed of 2mm/min. Results: 1. Compared to sandblasting, beads or crystals increased the resin-metal bond strength (P<.05). 2. 0.2mm retention crystals were most effective in improving the resin-metal bond strength (P>.05). 3. 0.2mm beads showed the highest bond strength among retention bead groups, but there was no statistically significant difference (P>.05). 4. Retention crystals tend to be higher in bond strength than retention beads due to wider surface area. 5. The larger retention element, the larger the undercut for the mechanical retention, but the gap at resin-metal interface was also increased. Conclusion: Within the limitations of this study, 0.2mm retention crystals were most effective in improving the resin-metal bond strength.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.345-352
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• 2022

The existing NATM (New Austrian Tunneling Method) has induced civil compliants due to blasting vibration and noise. Machanized excavation methods such as TBM (Tunnel Boring Machine) are being adopted in the planning and construction of tunneling projects. Shield TBM method is composed of repetition processes of TBM excavation and segment installation, the machine has to be stopped during the later process. Consecutive excavation technology using helical segment is under developing to minimize the stoppage time. The modification of thrust jacks and module are planned to ensure the advance force acting on the inclined surface of helical segment. Also, the integrated system design of hydraulic circuit will be remodeled. This means that the system deactivate the jacks on the installing segment while the others automatically act the thrusting forces on the existing segments. This report briefly introduces the mechanical research part of the current consecutive excavation technological development project of TBM.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.3
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• pp.167-174
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• 2013

Purpose: This study was conducted to evaluate the roughness and surface alternations of three differently blasted titanium discs treated by $Nd:YVO_4$ Laser irradiation in different conditions. Materials and methods: Thirty commercially pure titanium discs were prepared and divided into three groups. Each group was consisted of 10 samples and blasted by $ZrO_2$ (zirconium dioxide), $Al_2O_3$ (aluminum oxide), and RBM (resorbable blasted media). All the samples were degreased by ultrasonic cleaner afterward. Nine different conditions were established by changing scanning speed (100, 300, 500 mm/s) and repetition rate (5, 15, 35 kHz) of $Nd:YVO_4$ Laser (Laser Pro D-20, Laserval $Korea^{(R)}$, Seoul, South Korea). After laser irradiation, a scanning electron microscope, X-ray diffraction analysis, energy dispersive X-ray spectroscopic analysis, and surface roughness analysis were used to assess the roughness and surface alternations of the samples. Results: According to a scanning electron microscope (SEM), titanium discs treated with laser irradiation showed characteristic patterns in contrast to the control which showed irregular patterns. According to the X-ray diffraction analysis, only $Al_2O_3$ group showed its own peak. The oxidation tendency and surface roughness of titanium were similar to the control in the energy dispersive X-ray spectroscopic analysis. The surface roughness was inversely proportional to the scanning speed, whereas proportional to the repetition rate of $Nd:YVO_4$. Conclusion: The surface microstructures and roughness of the test discs were modified by the radiation of $Nd:YVO_4$ laser. Therefore, laser irradiation could be considered one of the methods to modify implant surfaces for the enhancement of osseointegration.