• Journal of Dental Rehabilitation and Applied Science
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• v.36 no.4
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• pp.262-271
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• 2020

To restore a tooth with a fracture line extending below the marginal bone level, a surgical crown lengthening procedure accompanied by ostectomy could be considered to expose the fracture line and reestablish the biologic width. However, this procedure could lead to esthetic failure, especially in the anterior teeth. Therefore, orthodontic extrusion, which elevates the fracture line from within the alveolar socket without sacrificing the supporting bone and gingiva, is recommended. This technique allows for the proper placement of the crown on a sound tooth structure, with the reestablishment of the biologic width. Alternatively, surgical extrusion is an one-step procedure that is simpler and less time-consuming than orthodontic extrusion; placing and adjusting the orthodontic appliance does not require multiple visits. This study presents successful restoration in 2 cases with a crown-tooth root fracture of the maxillary central incisor treated using a multidisciplinary approach through orthodontic extrusion or surgical extrusion followed by successful restoration.

• Korean Journal of Construction Engineering and Management
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• v.18 no.2
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• pp.38-48
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• 2017

Finding causes of workers' unsafe behaviors is important to prevent construction accidents because 80 percent of accidents occur by workers' unsafe behaviors. In this regard, this research aims to investigate possible reasons of workers' unsafe behaviors based on workers' cognitive process model using System dynamics. This study is based on two ways of workers' cognitive process which are in relation to hazard perception and failure of hazard perception. Based on existing literature, causal loops for workers' cognitive process are developed to explain workers' habituation by staying out of accidents, safety learning by experience, failure of hazard perception, and attitude change by accidents. The interactions between the developed loops provide managerial insights to reduce workers' unsafe behaviors from a safety manager's perspective including increasing the probability of workers' hazard perception through knowledge management, maintaining workers' positive attitude toward safety, and controlling first-line supervisors to eliminate workers' unsafe behavior. The research allows us to better understand the causes and solutions of workers' unsafe behaviors in workers' cognitive perspectives.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.4
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• pp.309-322
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• 2007

This study deals with the irradiation effects on some selected components which are being used in an Advanced Spent Fuel Conditioning Process (ACP). Irradiation test components have a higher priority from the aspect of their reliability because their degradation or failure is able to critically affect the performance of an ACP equipment. Components that we chose for the irradiation tests were the AC servo motor, potentiometer, thermocouples, accelerometer and CCD camera. ACP facility has a number of AC servo motors to move the joints of a manipulator and to operate process equipment. Potentiometers are used for a measurement of several joint angles in a manipulator. Thermocouples are used for a temperature measurement in an electrolytic reduction reactor, a vol-oxidation reactor and a molten salt transfer line. An accelerometer is installed in a slitting machine to forecast an incipient failure during a slitting process. A small CCD camera is used for an in-situ vision monitoring between ACP campaigns. We made use of a gamma-irradiation facility with cobalt-60 source for an irradiation test on the above components because gamma rays from among various radioactive rays are the most significant for electric, electronic and robotic components. Irradiation tests were carried out for enough long time for total doses to be over expected threshold values. Other components except the CCD camera showed a very high radiation hardening characteristic. Characteristic changes at different total doses were investigated and threshold values to warrant at least their performance without a deterioration were evaluated as a result of the irradiation tests.

• Journal of Environmental Health Sciences
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• v.43 no.4
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• pp.247-256
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• 2017

Objectives: The deaths of Korean victims exposed to the disinfectant CMIT/MIT have remained unresolved. This is mainly due to a lack of concordance between the few available toxicity tests and the abundant epidemiological data, making it difficult to establish a cause-and-effect relationship. Therefore, this study was carried out to investigate any potential associations between CMIT/MIT exposure and death. Methods: Groups of experimental and control C57BL/6 mice were instilled (in the trachea) with chloromethylisothiazolinone/methylisothiazolinone (CMIT/MIT) using a visual instillobot. CMIT/MIT was instilled over a period of three days and eight weeks, respectively, to achieve acute and chronic exposures. A threshold dose-response model was applied for estimating the threshold level as one line of evidence for a causal association between CMIT/MIT and death. Results: An acute exposure of 1.2 mg ai/kg/day of CMIT/MIT was estimated to reflect the threshold for death. The dose-response curve with this threshold showed a very steep slope and a narrow range of CMIT/MIT exposures. The narrow range of CMIT/MIT exposures, in particular, indicated an evident boundary between survival and death, thus implicating a strong causal association. A similar threshold dose-response relationship observed following acute exposure was also seen following chronic exposure to CMIT/MIT. Airborne disinfectant exposure was visible as minimal or mild lung damage with no fibrosis, as shown by histopathological tests. However, many observations are considered to be functional respiratory tract or lung failure due to death, as observed in necropsies of the mice that died due to CMIT/MIT exposures. Conclusions: There are two strong lines of evidence for a causal association between death and CMIT/MIT exposure: 1) The threshold dose-response curve, with a very steep slope and a narrow range of CMIT/MIT exposures showing a visible boundary between survival and death; and 2) many cases of functional respiratory or lung failure.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.4
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• pp.263-273
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• 2019

South Korea's OF cable is reaching its expected design life of 30 years, and as a result, the risk of failure is increasing. Therefore, it is necessary to diagnose the long-term operating OF cables through accurate diagnosis at the right time to prevent the failure. Currently, the KEPCO periodically conducts DGA. However, the gas found in DGA is caused by oil deterioration as well as insulation paper. Therefore, the analysis of the degree of polymerization and furan compounds which is an evaluation of insulation paper considered to be the life of OF cables is required. In addition, the results of the evaluation of deterioration of insulation paper need to be checked for correlation with the results of DGA. In this study, DGA carried out through GC, the degree of polymerization was analyzed using an automatic viscometer, and HPLC was used to detect the furan compounds. In addition, the obtained results were applied to the SVM technique, which was recently introduced to determine abnormalities in OF cable. And the results which were accurate and reliable were obtained.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1178-1185
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• 2010

Recently, high speed of container freight cars is causing fatigue damage of wheel. Sudden failure accidents cause a lot of physical and human damages. Therefore, damage analysis for wheel prevents failure accident of container freight car. Wheel receives mechanical and thermal loads at the same time while rolling stocks are run. The mechanical loads applied to wheel are classified by the horizontal load from contact of wheel and rail in curve line section and by the vertical force from rolling stocks weight. Also, braking and deceleration of rolling stocks cause repeated thermal load by wheel tread braking. Specially, braking of rolling stocks is frictional braking method that brake shoe is contacted in wheel tread by high breaking pressure. Frictional heat energy occurs on the contact surface between wheel tread and brake shoe. This braking converts kinetic energy of rolling stocks into heat energy by friction. This raises temperature rapidly and generates thermal loads in wheel and brake shoe. There mechanical and thermal loads generate crack and residual stress in wheel. Wetenkamp estimated temperature distribution of brake shoe experimentally. Donzella proposed fatigue life using thermal stress and residual stress. However, the load applied to wheel in aforementioned most researches considered thermal load and mechanical vertical load. Exact horizontal load is not considered as the load applied to wheel. Therefore, above-mentioned loading methods could not be applied to estimate actual stress applied to wheel. Therefore, this study proposed safety estimation on wheel of freight car using heat-structural coupled analysis on the basis of loading condition and stress intensity factor.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.537-545
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• 2005

Traditionally Jeju island has a mild oceanic climate throughout the year and famous as worldwide resort area bemuse of its pure natural environment and dramatic coastal scenery. But unpredicted coastal erosion problem, mused by variation of environmental conditions from construction of coastal structure and renovation of the existing ports, has raised its head above the water, and is becoming serious these days just like other coastal area in Korea. The phenomena happen here along the seaside of southern part of the island show that severe changes in coastal line from erosion and even witnessed the coastal cliff failure. In advanced countries, coastal engineers and researchers have studied deeply about this kind of problem for a long time. However, as it is not sot active in Korea and lack of research data, there exists difficulties on building protection methods and thoughtless constructions might make it more complicated and fatal to the coastal environment. In this study, we investigated some case studies of other countries and intended to induce and propose some integral protection methods for coastline erosion, considering environmentally sound and water friendly way of development such as artificial reef, floating breakwater, and double cellblock breakwater. Finally, we made analysis on the proposed methods with numerical model test and evaluation on the feasibility of each method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.51-56
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• 2016

In this paper, we propose an Arduino-based plant monitoring system. The proposed system is based on the Arduino platform, using an environmental sensor and a pressure sensor for measuring temperature, humidity and illuminance in order to monitor the state of the environment and the facilities of the plant. Monitoring data are transmitted to a ZigBee coordinator connected to a server through a radio frequency transceiver. When using a pressure sensor and the environment sensor data stored on the host server, checking the pressure in the environment of the plant and equipment is intended to report any alarm status to the administrator. Using a grid line-based key distribution scheme, the authentication node dynamically generates a data key to protect the monitoring information. Applying a ZigBee wireless sensor network does not require additional wiring for the actual implementation of a plant monitoring system. Possible working-environment monitoring of an efficient plant can help analyze the cause of any failure by backtracking the working environment when a failure occurs. In addition, it is easy to expand or add a sensor function using the Arduino platform and an expansion board.

• Tuberculosis and Respiratory Diseases
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• v.65 no.2
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• pp.116-120
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• 2008

Rifampin is one of the first line drugs for treating tuberculosis, but it might be associated with serious adverse effects, including renal failure. We report here on a case of a 57-year-old patient who developed Henoch-$Sh{\ddot{o}}nlein$ purpura during antituberculosis therapy that included rifampin. The patient converted to negative on the AFB smear for tuberculosis two weeks after the initial administration of antituberculosis medication. After treatment for 60 days, this patient was diagnosed with Henoch-$Sh{\ddot{o}}nlein$ purpura by the purpura lesion on the lower legs, the leukocytoclastic vasculitis, the renal impairment and the pathological examination. After stopping rifampin, the skin lesions disappeared in about 10 days and his renal function gradually improved. This case study showed that Henoch-$Sh{\ddot{o}}nlein$ purpura can be caused by rifampin during antituberculosis therapy and we recommend that the use of rifampin should be restrained when clinical symptoms of Henoch-$Sh{\ddot{o}}nlein$ purpura are observed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.11-19
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• 2005

Traditionally Jeju island has a mild oceanic climate throughout the year and famous as worldwide resort area bacause of its pure natural environment and dramatic coastal scenery. But unpredicted coastal erosion problem, caused by variation of environmental conditions from construction of coastal structure and renovation of the existing ports, has raised its head above the water, and is becoming serious these days just like other coastal area in Korea. The phenomena happen here along the seaside of southern part of the island show that severe changes in coastal line from erosion and even witnessed the coastal cliff failure. In advanced countries, coastal engineers and researchers have studied deeply about this kind of problem for a long time. However, as it is not sot active in Korea and lack of research data, there exists difficulties on building protection methods and thoughtless constructions might make it more complicated and fatal to the coastal environment. In this study, we investigated some case studies of other countries and intended to induce and propose some integral protection methods for coastline erosion, considering environmentally sound and water friendly way of developement such as artificial reef, floating breakwater, and double cellblock breakwater. Finally, we made analysis on the proposed methods with numerical model test and evaluation on the feasibility of each method.