• The Journal of Korean Academy of Prosthodontics
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• v.57 no.2
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• pp.127-133
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• 2019

Purpose: The purpose of present study was to investigate fracture strength and mode of failure of endodontically treated teeth restored with metal cast post-core system, prefabricated fiber post system, and newly introduced polyetherketoneketone (PEKK) post-core system. Materials and methods: A total of 21 mandibular premolar were randomly grouped into 3 groups of 7 each according to the post material. Group A was for metal cast post core; Group B for prefabricated glass fiber post and resin core; and Group C for milled PEKK post cores. All specimens were restored with metal crown. The fracture strength of each specimen was measured by applying a static load of 135-degree to the tooth at 2 mm/min crosshead speed using a universal testing machine. After the fracture strength measurement, the mode of failure was observed. The results were analyzed using Kruscal-Wallis test and post hoc Mann-Whitney U test at confidence interval ${\alpha}=.05$. Results: Fracture resistance of PEKK post core was lower than those of cast metal post and fiber reinforced post with composite resin core. In the aspect of fracture mode most of the root fracture occurred in the metal post core, whereas the post detachment occurred mainly in the fiber reinforced post. In the case of PEKK post core, teeth and post were fractured together. Conclusion: It is necessary to select appropriate materials of post for extensively damaged teeth restoration and clinical application of the PEKK post seems to require more research on improvement of strength.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.524-537
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• 2017

Post-Environmental impact investigation(Post-EII) plays an important role in investigating and reducing the environmental impacts of construction operations in South Korea. To date, it has been estimated that the results for Post-EII showed the low reliability; however, understanding those reliability has rarely been studied. We investigated the effect on water qualities by construction operations of the quarry mine, training center, and golf club in South Korea. In addition, the results of water quality analysis in this study were compared and analyzed with those in Post-EII. Treated wastewater in a quarry mine showed high concentrations of biochemical oxygen demand(BOD), suspended solid(SS), total nitrogen(T-N), and total phosphorus(T-P). Compared with the water quality results between this study and Post-EII, the concentrations of BOD, SS, T-N, and T-P in the treated wastewater were higher than the interquartile range(IQR) as well as the range of the results from minimum to maximum in Post-EII(p<0.05). The concentrations of BOD, SS, T-N, and T-P in treated wastewater were high under constructions in a training center. The concentrations of BOD and SS exceeded the consultation standard for the treated wastewater. These concentrations showed the significant difference with the IQR and the range from minimum to maximum of the water quality results in Post-EII(p<0.05). Therefore, the management and monitoring for water quality should be conducted in the treated wastewater by of construction operations. In addition, the alternative to enhance the reliability for the water quality results should be sought in Post-EII.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.452-455
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• 2009

A cost-effective route to synthesize $\beta$-SiAlONs from Si mixtures by reaction bonding followed by post-sintering was investigated. Three different z values, 0.45, 0.92 and 1.87, in $Si_{6-z}Al_zO_zN_{8-z}$ without excess liquid phase were selected to elucidate the mechanism of SiAlON formation and densification. For RBSN (reaction-bonded silicon nitride) specimens prior to post-sintering, nitridation rates of more than 90% were achieved by multistep heating to $1400^{\circ}C$ in flowing 5%$H_2$/95%$N_2$; residual Si was not detected by XRD analysis. An increase in density was acquired with increasing z values in post-sintered specimens, and this tendency was explained by the presence of higher amounts of transient liquid phase at larger z values. Measured z values from the synthesized $\beta$-SiAlONs were similar to the values calculated for the starting compositions. Slight deviations in z values between measurements and calculations were rationalized by a reasonable application of the characteristics of the nitriding and post-sintering processes.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.27 no.2
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• pp.75-81
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• 2018

The aim of this study was to evaluate the biomechanical behavior and long-term safety of high performance polymer PEKK as an intraradicular dental post-core material through comparative finite element analysis (FEA) with other conventional post-core materials. A 3D FEA model of a maxillary central incisor was constructed. A cyclic loading force of 50 N was applied at an angle of $45^{\circ}$ to the longitudinal axis of the tooth at the palatal surface of the crown. For comparison with traditionally used post-core materials, three materials (gold, fiberglass, and PEKK) were simulated to determine their post-core properties. PEKK, with a lower elastic modulus than root dentin, showed comparably high failure resistance and a more favorable stress distribution than conventional post-core material. However, the PEKK post-core system showed a higher probability of debonding and crown failure under long-term cyclic loading than the metal or fiberglass post-core systems.

• Journal of Korean Clinical Nursing Research
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• v.29 no.1
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• pp.85-94
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• 2023

Purpose: The purpose of this study was to investigate the influencing factors of post-traumatic growth in patients with gastrointestinal cancer. Methods: A cross-sectional study was conducted, enrolling 120 patients with gastrointestinal cancer. Their general characteristics, disease-related characteristics, perceived illness intrusiveness, levels of optimism, social support, and post-traumatic growth were assessed through self-administered questionnaires. The collected data were analyzed using descriptive statistics, independent t-test, oneway ANOVA, Pearson's correlation, and multiple regression analysis. Results: The mean score of post-traumatic growth was 52.74 points(total score of 92 points). Among the subscales of post-traumatic growth, levels of the preciousness of life were the highest, and relating with others was the lowest. The post-traumatic growth was found to be significantly correlated with optimism (r=.48, p<.001), social support (r=.47, p<.001), and depression (r=-.37 p<.001). Factors associated with post-traumatic growth were optimism (β=.36, p<.001), social support (β=.31, p<.001), and depression (β=-.27, p<.001). Conclusion: Given that prevalence of gastrointestinal cancer is increasing in Korea, identifying general, psychological, and social factors affecting post-traumatic growth among this population will be helpful in clinical practice. Integrated strategies to increase optimism and social support and lower depression should be considered to improve the post-traumatic growth of patients with gastrointestinal cancer.

• IMMUNE NETWORK
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• v.9 no.4
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• pp.115-121
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• 2009

Natural killer (NK) cells play key roles in innate and adaptive immune defenses. NK cell responses are mediated by two major mechanisms: the direct cytolysis of target cells, and immune regulation by production of various cytokines. Many previous reports show that the complex NK cell activation process requires de novo gene expression regulated at both transcriptional and post-transcriptional levels. Specialized un-translated regions (UTR) of mRNAs are the main mechanisms of post-transcriptional regulation. Analysis of posttranscriptional regulation is needed to clearly understand NK cell biology and, furthermore, harness the power of NK cells for therapeutic aims. This review summarizes the current understanding of mRNA metabolism during NK cell activation, focusing primarily on post-transcriptional regulation.

• Solar Energy
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• v.10 no.1
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• pp.80-91
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• 1990

The purpose of this study is to provide materials necessary for planning and designing of passive solar post offices by comparing and analyzing the satisfaction degree on old passive solar post office environment characteristics according to the post office pattern. In conclusion, passive solar systems are effective and economical when they are applied to post offices for heating systems.

• Journal of the Korean Institute of Landscape Architecture International Edition
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• no.1
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• pp.183-191
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• 2001

The purpose of this study is to provide guidelines for planning, designing and managing neighborhood parks. Results form POE(Post-Occupancy-Evaluation) and RPOE(Re-Post-Occupancy-Evaluation) are analyzed for this study. Bundang Central Park in Bundang Newtown was selected for this study. This study compared the previous POE completed in 1996 with a RPOE conducted in 2001 to find out how the user, proximate environmental context, and the park administration changed in time and apply feedback for purposes of immediate problem solving. The results of this study showed that RPOE has to be initiated and utilized periodically as a device and the guideline for neighborhood park design, conservation, administration and operation.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.290-295
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• 2016

Socket-outlets and plugs are essential devices that supply electric power into user appliances. During plug-out operation of an engaged plug from the socket-outlet, the consistent arc between the plug and the socket-outlet could develop into heavy fires in DC systems but only a small spark in AC systems. This paper proposes a pre-/post-electrode method to prevent plugs and socket-outlets from melting by sustaining arc energy. To implement the proposed pre-/post-electrodes, an experimental plug is manufactured with two electrodes, in which a post resistance Rs is connected in between. This paper investigates the function of the post resistance Rs, in which the best value of the post resistance Rs is obtained through simulation and experiment.

• Korean Management Science Review
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• v.33 no.3
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• pp.1-18
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• 2016

Recently, ordinary mail is decreasing continuously by the development of ICT (Information and Communications Technology) including E-mail, messenger service, and etc. On the contrary, parcel post is increasing by the increase of online shopping, home shopping, and etc. Aside from these changes, the demand for various mail acceptance and delivery means is increasing with the increase of single households and dual-income couples. To overcome these environmental changes, Korea Post installs unmanned post offices which are composed of various unmanned mail acceptance and delivery postal systems. In this paper, we propose the methodological approach for the site selection of unmanned post office among the existing post offices and the installation standard of unmanned postal system considering the operation cost by the mail volume.