• Fire Science and Engineering
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• v.24 no.4
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• pp.12-17
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• 2010

The purpose of this study is to determine how effectively waste tire recycled material mixed with flame retardant work in combating fire. As discovered in the previous study, waste tire mixed with cement mortar has more insulation capacity. However, this mortar is weak against fire. Therefore flame retardant, with a specific proportional mix, will be added to increase its fire prevention capacity. Tests will be made in accordance with ISO 5657 procedures for measuring fire ignition time, flame and shape variation of test pieces at the Building Material Test Institute. The test piece will be set up with horizontal levels having a constant radiation heat of $1{\sim}5W/cm^2$. Temperature transfers and increases from the surface into the interior. Combustible gases result due to pyrolysis, and regular contact is maintained between the fire source and the center of the test piece for assessment purposes. Ignition has not been occurred without adding retardant meaning that there is almost no possibility of ignition of waste tire particle. This fact can be considered as fire load to appreciate a volume of combustion materials. Flame is not occurred due to heat-absorbing effect by adding non-organic series retardant into waste tire particle. Conclusions have been summarized as follows; 1) Combustion of building material can be decreased by adding retardant to waste tire-mixing mortar. But compressive strength and insulation capacity of the material should be measured later. 2) Firing prevention and ignition are main points of building fire. Reasonable fire engineering assessment of interior material should be made for establishing effective disaster prevention system.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.23-32
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• 2017

The joints between precast PSC slabs of the intermediate road slab in double deck tunnel are inevitably generated in the road traffic vehicle traveling direction. Therefore, it is important to make the behavior of parts on the joint in one piece. The imtermediate road slab system of double deck tunnel in great depth proposed in this study will be constructed with precast PSC slab in order to minimize the construction period. And the joint connection between the precast slab has been developed in two methods: the 'Transverse tendon reinforcement method' and 'High strength bolts connection method'. Also, the experiments were performed for the full scale model in order to evaluate the performance of the intermediate road deck slab with two type joints systems, the structural stability was verified through the F.E.M analsysis. The results of static loading test and F.E.M analysis investigated a very stable behavior of intermediate road deck slab in double deck tunnel applying the joint methods developed in this study, in the cracks and deflections to satisfy the design standards of Highway Roads Bridges (2011), it was determined that there is no problem even servicebility.

• Elastomers and Composites
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• v.39 no.1
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• pp.12-22
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• 2004

The plasma surface modification of natural rubber vulcanizate was carried out using chlorodifluoromethane in a radio-frequency (13.56 MHz) electrodeless bell type plasma reactor. The modification was qualitatively assessed by Fourier transform infrared spectroscopy. The frictional force of the plasma-treated surface was found to decrease with the time of plasma treatment. An increase in the surface polarity, as evidenced by the decrease in contact angle of a sessile drop of water and ethylene glycol on the natural rubber vulcanizate surface, was noted with the plasma modification. In the case of similar plasma treatment of glass surface, only a reduction in the polarity was observed. The use of geometric and harmonic mean methods was found to be useful to evaluate the London dispersive and specific components of surface free energy. Irrespective of the method used for evaluation, an increasing trend in the surface free energy was noted with increasing plasma treatment time. However, the harmonic mean method yielded comparatively higher values of surface free energy than the geometric mean method. The plasma surface modification was found to vary the frictional coefficient by influencing the interfacial, hysteresis and viscous components of friction in opposing dual manners.

• Polymer(Korea)
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• v.38 no.6
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• pp.815-819
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• 2014

Scaffolds of tissue engineering should be biocompatible and biodegradable for cell attachment, proliferation and differentiation. In the various scaffold fabrication, 3D printing technique can make the three dimensional scaffold with interconnected pores for cell ingrowth. Polycaprolactone (PCL) is biodegradable polyester with a low melting temperature and has been approved by the Food and Drug Administration (FDA). In this study, PCL scaffold was fabricated by 3D bioprinting system and surface modification of PCL scaffold was controlled by NaOH treatment. Morphological change and wetability of NaOH-treated scaffold were observed by SEM and contact angle measurement system. The remnant of PCL treated with NaOH was measured by ATR-FTIR. In vitro study of scaffolds was evaluated with WST-1 and ALP activity assay. NaOH treatment of PCL scaffolds increased surface roughness, hydrophilicity, cell proliferation and osteogenic differentiation. These results indicate that NaOH-treated PCL scaffold made by 3D bioprinting has tissue engineered potential for the development of biocompatible material.

• Journal of Gastric Cancer
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• v.10 no.3
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• pp.141-148
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• 2010

We have always attempted to create a standard treatment protocol for patients with gastric cancer. However, many debates still exist regarding gastric cancer treatment. For the past 2 years, at the Annual Congress of the Korean Gastric Cancer Association, we have presented a grand symposium on the "Debates on the strategy for treating gastric cancer". In 2008, four major topics were discussed and voted on after discussion. The four major topics were proximal location treatment for early gastric cancer, management choices for pyloric obstruction with advanced gastric cancer, management of liver metastasis, and reconstruction methods after a distal gastrectomy. The opinions of the audience for six minor topics were expressed by an electronic voting system. In 2009, the four main topics were treatment for submucosal tumor sized around 2 cm, laparoscopic gastrectomy in T2N1 gastric cancer, choices for managing gastric lymphoma, and application of a pylorus preserving procedure for early gastric cancer at the antrum. The opinions of the audience for these six minor topics were expressed by an electronic voting system, as was conducted in 2008. It was good opportunity to identify a point of contact about the debates on managing gastric cancer. The results of these debates and studies will identify the best methods to treat patients with gastric cancer.

• Journal of The Korean Dental Society of Anesthesiology
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• v.9 no.2
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• pp.108-115
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• 2009

Trauma to any nerve may lead to persistent paresthesia. Trauma to the nerve sheath can be produced by the needle. The patient frequently reports the sensation of an electric shock throughout the distribution of the nerve involved. It is difficult for the type of needle used in dental practice to actually sever a nerve trunk or even its fibers. Trauma to the nerve produced by contact with the needle is all that is needed to produce paresthesia. Hemorrhage into or around the neural sheath is another cause. Bleeding increases pressure on the nerve, leading to paresthesia. Injection of local anesthetic solutions contaminated by alcohol or sterilizing solution near a nerve produces irritation; the resulting edema increases pressure in the region of the nerve, leading to paresthesia. Persistent paresthesia can lead to injury to adjacent tissues. Biting or thermal or chemical insult can occur without a patient's awareness, until the process has progressed to a serious degree. Most paresthesias resolve in approximately 8 weeks without treatment. In most situations paresthesia is only minimal, with the patient retaining most sensory function to the affected area. In these cases there is only a very slight possibility of self injury. But, the patient complaints the discomfort symptoms of paresthesia, such as causalgia, neuralgiaform pain and anesthesia dolorosa. Most paresthesias involve the lingual nerve, with the inferior alveolar nerve a close second. This is the report of a case, that had the persistent paresthesia care on left lingual & buccal shelf regions after the lingual and long buccal nerve block anesthesia.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1141-1147
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• 2006

In order to applicate a newly method for powdered activated carbon(PAC) selection based on economic efficiency, PAC adsorption tests were performed for removal of MIB and dissolved organic carbon(DOC) in drinking water supplies. The removal rate of MIB increased when the PAC dose increased. The Coal-based PACs were superior for adsorption of MIB compared to wood-based PACs. PAC adsorption of DOC and $UV_{254}$ were a little different for different PACs and types of raw water, but both were lower than adsorption of MIB. Among the tested PACs, the one called P-1000 was most effective for removal of MIB, DOC and $UV_{254}$. Most of the organics in the tested samples were proven by excitation emission matrix(EEM) results to be fulvic-like materials. Especially, fulvic-like materials, humic-like materials, and soluble microbial byproduct(SMP)-like materials decreased after contact with PAC. P-1000 which had the lowest MIB cost index(MCI) was selected as the optimum PAC for the target water. PAC efficiency and treatability, particle size and distribution, and the cost associated with PAC dosing for MIB removal according to DOC concentration should all be considered before making the final selection of the best PAC for the target water.

• Journal of the Korean Institute of Landscape Architecture
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• v.21 no.4
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• pp.55-68
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• 1994

It has been generally agreed that the city form especially in the preindustrial age resembled their own world view, either in the western or the eastern cultural sphere. So, we aimed to redefine the characteristics of oriental world views compared with the western one, in order to find the relative nature of the Korean townscapes. It is said that the both world views(of western and oriental) are composed of the contrastive binary concepts in common, but there seems to have been nearly contrary differences in these two world views. Wheareas the former was based on the passively segregational and oppositional dualism, the latter, on the dynamically harmonious and complementary dualism, called generally as 'Yin(陰) and Yang(陽)'. Thus, the oriental world view can be thought as the 'philosophy of the relationship', which aim to unify the dualism ultimately with the help of this relationship. So, we can assume a certain third and intermediate concept between these dual concepts of the world view, which can unify these two into the one holistic whole. And the focuses of the most traditional oriental philosophies were concentrated on this, so called, 'the third concept', namely Taoistic 'Tochu(道樞)', Buddhistic 'Kong(空)' or Confucian 'Chung(中)'. And this triple concept, including the third one, of the oriental world view revealed a more concrete form of the cosmological relationship, as the triple structure; 'Heaven(天), Earth(地), and Man(人)', in which the 'Man' is thought as the middle or the center of the world. In this manner, we could found this oriental 'triple world view' was revealed in the real topology of most places in the Korean traditional city and the whole townscape itself. So, in the scale of houses and the roads around them, we can construe the 'Maru(a central board-floored room)' and the 'Madang(a inner court)' as the 'third and intermediate space(中)' between the interior space(陰) and exterior space(陽) in the former, and between the private house(陰) and the public residential road(陽) in the former case, and between the dual parts(陰,陽) of the city representing the contrary social classes and the contrastive visual landscapes. So, we insist that this 'triple world view' represented in the townscape can be one of the most important characteristics of Korean traditional townscape. And this third intermediate spaces, which generate the active social contact and the harmonious relationship among the people, can be the most important cues, as the central places, in the interpretation of the Korean townscapes even in contemporary circumstance, which inherits its spatial and social frame more or less from the preceding one.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.490-497
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• 2016

This study compared and analyzed the pollution levels of radiation shielding aprons and ways to sterilize them using 30 lead aprons. After collecting samples from the center of the lead apron, where contact is most frequent, experiments were conducted employing Coagula and Latex methods. Using the culture medium where bacteria grew, measurements of the pathogen count and identification were performed. The greatest number of pathogens were $7.16{\pm}10$, which were detected on the lead apron from general X-ray room #2, but there was no significant difference according to the facilities (p > 0.05). Compared to how many pathogens remained between using the disinfectant ethanol and tissue, the pathogens decreased by $0.01{\pm}0.4$ (p < 0.05) after using disinfectant ethanol and by $0.87{\pm}1.7$(p < 0.05) after using disinfectant tissue. The Pearson correlation test revealed a significant correlation (-0.296, p < 0.05) between them. According to this research, there were pathogens on the lead aprons and the number of pathogens was determined by statistical analysis. It is expected that the rate of radiology technologists, patients, and medical equipment infected by pathogens will be reduced by the proper use of sterilization with a disinfectant ethanol.

• Restorative Dentistry and Endodontics
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• v.42 no.3
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• pp.206-215
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• 2017

Objectives: To determine the combined effect of fatigue cyclic loading and thermocycling (CLTC) on the shear bond strength (SBS) of a resin cement to zirconia surfaces that were previously air-abraded with aluminum oxide ($Al_2O_3$) particles at different pressures. Materials and Methods: Seventy-two cuboid zirconia specimens were prepared and randomly assigned to 3 groups according to the air-abrasion pressures (1, 2, and 2.8 bar), and each group was further divided into 2 groups depending on aging parameters (n = 12). Panavia F 2.0 was placed on pre-conditioned zirconia surfaces, and SBS testing was performed either after 24 hours or 10,000 fatigue cycles (cyclic loading) and 5,000 thermocycles. Non-contact profilometry was used to measure surface roughness. Failure modes were evaluated under optical and scanning electron microscopy. The data were analyzed using 2-way analysis of variance and ${\chi}^2$ tests (${\alpha}=0.05$). Results: The 2.8 bar group showed significantly higher surface roughness compared to the 1 bar group (p < 0.05). The interaction between pressure and time/cycling was not significant on SBS, and pressure did not have a significant effect either. SBS was significantly higher (p = 0.006) for 24 hours storage compared to CLTC. The 2 bar-CLTC group presented significantly higher percentage of pre-test failure during fatigue compared to the other groups. Mixed-failure mode was more frequent than adhesive failure. Conclusions: CLTC significantly decreased the SBS values regardless of the air-abrasion pressure used.