• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.51-59
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• 2002

The aim of the present study was to investigate the distribution of periodontally hopeless teeth in patients who had not been treated. Five hundred nineteen teeth of 163 patients who had visited at the Department of Periodontology, Chonbuk National University Hospital during the period from January 1999 to July 2001 were selected as a periodontally hopeless tooth. Selection criteria were as follows: 1) probing pocket depth more than 8mm, 2) tooth mobility of degree III, 3) radiographic bone loss more than 75%. The contralateral tooth to a hopeless tooth (experimental tooth) was designated as a control tooth. Between the experimental and control tooth, differences in probing pocket depth, tooth mobility and amount of radiographic bone loss were examined as well as correlation. The results showed that hopeless teeth were most frequently found in the maxillary first molar position and least frequently in the maxillary canine position. Differences between experimental and control teeth were 2mm in probing depth, 1 degree in tooth mobility, and 20% in amount of bone loss (p<0.01). The periodontal conditions between the experimental and control teeth showed correlation in general, however, statistical significances were found in posterior teeth positions. Within limitations of this study, it can be concluded that local factors may play a role in deterioration of periodontal disease along with symmetrical character of periodontal disease.

• Research in Community and Public Health Nursing
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• v.32 no.3
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• pp.312-324
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• 2021

Purpose: Tuberculosis is an infectious condition with a high disease burden, and the stigma in patients with tuberculosis causes negative health outcomes. The purpose of this study was to define and clarify the concept of self-stigma among patients with tuberculosis. Methods: The analysis was conducted using Walker and Avant's conceptual approach. Twenty-seven studies met the selection criteria. Results: Self-stigma in patients with tuberculosis can be defined by the following attributes: 1) self-esteem decrement; 2) fear; 3) negative emotions to oneself; 4) social withdrawal; and 5) discrimination. The antecedents identified were 1) inappropriate knowledge of tuberculosis, 2) spread of improper health information through media and social communications, 3) stereotypes and prejudices, 4) visibility due to symptoms appearing, 5) recognizing the risk of infection, and 6) low financial status. The consequences were 1) concealing the disease, 2) treatment delay, 3) poor treatment adherence, 4) poor quality of life, and 5) deterioration in or lack of social activities. Conclusion: The definition and attributes of self-stigma identified by this study can be applied to enhance the understanding of stigma in tuberculosis patients and to improve communications between healthcare providers and researchers. It can also be used to develop theories and measurements related to stigma in patients with tuberculosis.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.15-21
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• 2018

Ships may collide with reefs or other objects during operation, when arriving or departing ports. The hull plate may be damaged due to the contact with other ships. The total number of domestic powered fishing vessels has decreased, but that of FRP fishing vessels has increased by 0.7% and the ratio of FRP fishing vessels to the total fishing vessels increased to 96%. Recently, fishing vessels has been used as fishing boats for income of non-fishermen as well as fishermen. Therefore, safety management for repair and maintenance is necessary. The penetration of moisture and moisture in the composite material such as FRP may deteriorate the mechanical properties and the salt (NaCl) component of the damaged portion may cause a relatively high deterioration in material strength. The gel coat painting is the final stage of repairs ans maintenance of FRP fishing vessels. The thickness criteria in the domestic and foreign gel coat is 0.3~0.762 mm. The joint specimens, which was immersed in seawater for 120 days, were compared with those without seawater immersion. As a result, the tensile strength was 83 ~ 121.8% and the flexural strength was 83 ~ 113% compared with the specimens without seawater immersion. According to the previous study the tensile strength decreased by more than 29% and the flexural strength decreased by more than 50% when the composite material was immersed in seawater for 1,083 hours without coating. As a result, it was found that the gel coat with 0.5 mm thickness is very effective in preventing the strength decrease of the composite material.

• Korean Chemical Engineering Research
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• v.59 no.3
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• pp.333-338
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• 2021

The durability of the PEMFC stack for large commercial vehicles should be more than 5 times that for passenger vehicles. If the Chemical Accelerated Stress Test (AST) of PEMFC(Proton Exchange Membrane Fuel Cells) membrane for passenger cars is applied as it is for large commercial vehicles, there is a problem that the AST time becomes more than 2,500 hours. In order to shorten the AST time of DOE (Department of Energy), the chemical durability of the polymer membrane was evaluated using oxygen instead of air as a cathode gas. In this study, Nafion XL was used as a polymer membrane to evaluate accelerated durability under OCV, 90?, RH 30%, H₂/(air or oxygen) conditions. Among the DOE membrane durability target criteria, the decrease rate of short resistance was the fastest. By using oxygen instead of air, the degradation rate of the polymer membrane was accelerated while being less affected by electrode deterioration, reducing the polymer membrane durability evaluation time to less than half.

• Journal of Environmental Health Sciences
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• v.14 no.2
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• pp.1-12
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• 1988

Airborne dust and asbestos fiber concentrations were determined in subway stations located in Seoul area. Two stations, such as Eulchiro 4-Ka Station of Line #2, constructed during a period of 1980-1984 and Hyehwa Station of Line #4, opened in 1985, were selected. The results of the study are as follows. 1. Daily time-weighted average (TWA) concentrations of airborne dusts from 07:00 to 20:00 hours in Line #2 and Line #4 were 0.43$\pm$0.08 mg/m$^3$ and 0.37$\pm$0.12 mg/m$^3$, respectively. Thus, the dust levels in Line #2 were significantly higher than the levels in Line #4 (p < 0.05). 2. Dust levels in the morning (07:00-11:00 hours), noon (11:00-16:00 hours) and in the evening (16:00-20:00 hours) in Line #2 were 0.47$\pm$0.17 mg/m$^3$, 0.37$\pm$0.08 mg/m$^3$, and 0.46$\pm$0.07 mg/m$^3$ respectively. Thus, dust levels in the morning and evening (i.e., during rush hours) were significantly higher than levels in the noon (p < 0.02). However, there was no such difference in dust levels by time in Line #4. 3. Airborne total dust concentrations were well below the occupational health standard of 10 mg/m$^3$, however, the levels were exceeding the ambient air standard recommended by the Korean Environment Administration. 4. All of airborne asbestos fiber concentrations were equal to or below 0.005 fibers/cc. The levels are within both occupational health standards and U.S. EPA criteria. 5. A consideration should be given to the improvements of cleaning methods (such as use of vacuum cleaning instead of brushing) and the existing ventilation (such as more air change and filtration of supply air) for a reduction of dust levels. 6. It is recommended that routine monitoring of airborne dusts and asbestos fibers be conducted because more dusts and asbestos fibers can be produced in the air due to the deterioration of facilities by age and water damage in future.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.5
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• pp.73-84
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• 2020

In this study, we compared and analyzed the static and dynamic analysis method for agricultural reservoirs. In addition, we assumed the aging of reservoir as the deterioration of the internal friction angle and cohesion. The internal friction angle and cohesion were applied by dividing into 4 case for each reservoir. As a result of comparing the stability of the reservoir embankment, it was found that the dynamic stability analysis method showed a greater risk than the static stability analysis method when dynamic loads such as earthquakes were applied. Therefore, when detailed review such as liquefaction is required, it is considered that the dynamic stability analysis method should be applied first. If a study on the change in material properties due to the aging of the reservoir is conducted, the stability analysis of the reservoir due to the aging of the reservoir can be performed more accurately. In addition, if a study comparing the results of dynamic stability analysis and static stability analysis for earthquakes with various characteristics for more reservoirs is conducted, detailed criteria for the case where dynamic stability analysis should be considered can be presented.

• Journal of Information Processing Systems
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• v.13 no.3
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• pp.599-617
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• 2017

Due to the rapid growth and expansion of the Internet, the digital multimedia such as image, audio and video are available for everyone. Anyone can make unauthorized copying for any digital product. Accordingly, the owner of these products cannot protect his ownership. Unfortunately, this situation will restrict any improvement which can be done on the digital media production in the future. Some procedures have been proposed to protect these products such as cryptography and watermarking techniques. Watermarking means embedding a message such as text, the image is called watermark, yet, in a host such as a text, an image, an audio, or a video, it is called a cover. Watermarking can provide and ensure security, data authentication and copyright protection for the digital media. In this paper, a new watermarking method of still image is proposed for the purpose of copyright protection. The procedure of embedding watermark is done in a transform domain. The discrete cosine transform (DCT) is exploited in the proposed method, where the watermark is embedded in the selected coefficients according to several criteria. With this procedure, the deterioration on the image is minimized to achieve high invisibility. Unlike the traditional techniques, in this paper, a new method is suggested for selecting the best blocks of DCT coefficients. After selecting the best DCT coefficients blocks, the best coefficients in the selected blocks are selected as a host in which the watermark bit is embedded. The coefficients selection is done depending on a weighting function method, where this function exploits the values and locations of the selected coefficients for choosing them. The experimental results proved that the proposed method has produced good imperceptibility and robustness for different types of attacks.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.313-322
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• 2007

The PCS system, which consists of precast concrete column and steel beam, is a kind of composite structural systems. In this paper, experimental study has been conducted to analyze seismic performance of bolted beam-to-column connections for the PCS system. Based on experimental results from the seismic testing of eight interior PCS specimens, it shows that behavior of PCS system is satisfactory to seismic performance criteria of ACI such as strength deterioration, stiffness degradation and energy dissipation capacity except initial stiffness. All of the specimens maintain their strength at large levels of story drift without significant loss of stiffness and show high ductility level for inelastic behavior. The energy dissipation capacity is two times greater than requirement of ACI criterion. But the initial stiffness of all specimens does not satisfy ACI criterion, and this phenomenon is similar to the other composite structural systems such as RCS, CFT system.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.569-575
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• 2015

The current Total Pollution Load Control (TPLC) sets the Target Water Quality (TWQ) by utilizing the delivery ratio, unit loads, and water quality modeling, it also allocates the watershed's permitted discharge load. Currently, common target pollutants of every unit watershed in TPLC are BOD and T-P. This study has reviewed the 1th and 2th of TWQ setting process for the Nakdong River 3th TWQ setting in Total Pollution Load Control (TPLC). As a result of review, 1th and 2th were divided into one management basin (mulgeum) for setting management goals. However, 3th was divided into six management basins (mulgeum, gnagjeong, geumho river, nam river, miryang river, end of nakdong river). The principle of management goal setting were to achieve the objective criteria of Medium Areas for the linkage of the water environment management policy. And Anti-Degredation (principle of preventing deterioration) were applied to the 3th TWQ. Also, additional indicators were considered in accordance with the reduction scenarios for the final management goals.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.101-104
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• 2008

The cost of repairing the deterioration of concrete structures due to corrosion of the reinforcement steel has been the prominent figure in the maintenacne of the reinforced-concrete infrastructures. As an alternative material to steel reinforcement, the use of Fiber Reinforced Polymer (FRP) bar in concrete is being actively studied for the high resistance of chemical environment and high strength to weight ratio properties of FRP. However, there remain various aspects of FRP properties that still need to be studied before the standard design criteria can be established. One of the imminent issues is the bond between FRP and concrete. In this study, the bond-behavior of FRP bars in concrete is investigated via the pullout test with three varying parameters: surface condition of FRP bars, concrete compression strength, and cyclic loading patterns. As a result of experiment, the bond strength of GFRP increased with the concrete compression strength increasing and decreased with applying cyclic load.