• Proceedings of the KSR Conference
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• 2005.11a
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• pp.682-687
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• 2005

High quality power supplying of power distribution system in electric railway system is the important function. Power feeding system is complicated witch is compose with distribution line, circuit break, protection facilities and so on. Among this components, role of substation is most important for elevation of reliability in electric power system. Therefore, the enhanced reliability considering the preventive inspection, repair work, replacement is necessary. In this study, a proposed the enhanced reliability method through a calculation of fault probability in power feeding system.

• 대한예방의학회:학술대회논문집
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• 1994.02a
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• pp.412-415
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• 1994

The fundamental assumption that thresholds exist for noncarcinogenic toxic effects of chemicals is reviewed; this assumption forms the basis for the no-observed-effect level/ safety-factor (NOEL/SF) approach to risk assessment for such effects. The origin and evolution of the NOEL/SF approach are traced, and its limitations are discussed. The recently proposed use of dose-response modeling to estimate a benchmark dose as a replacement for the NOEL is explained. The possibility of expanding dose-response modeling of non carcinogenic effects to include the estimation of assumed thresholds is discussed. A new method for conversion of quantitative toxic responses to a probability scale for risk assessment via dose-response modeling is outlined.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.1
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• pp.175-179
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• 2012

The objective of the study is to investigate the success rate of quit attempts and identify factors associated with success or failure of quit attempts in a quit smoking clinic. A cohort study was conducted with 495 smokers who enrolled in a quit smoking clinic from 2005 to 2008. The factors leading to quit smoking successfully were "being Malay", "having high blood pressure" "type of Nicotine Replacement Therapy" and "duration of follow up". In contrast, clerical staff had negative association to quit smoking. People who started smoking in their teenage years had a high risk of relapse. Integration of active follow up and tailor-made support programmes for quitters appear necessary in order to maintain their non-smoking status and encourage them to be permanent quitters. Integration of quit smoking clinics and primary care clinics could be another potential step for the success of quit smoking programmes.

• Smart Structures and Systems
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• v.22 no.2
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• pp.151-159
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• 2018

Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1171-1177
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• 2014

An electromagnetic shielding doorset must satisfy requirements associated with both mechanical strength/durability and electromagnetic shielding. Among the primary components of the doorset, a finger strip-a leaftype spring normally made of beryllium copper-is a core part to shield electromagnetic waves as well as to endure repetitive dry sliding friction. This study presented a reliability demonstration test method for the doorset system and, by a simple and simultaneous implementation, of the replacement interval of the finger strip. A rigorous evaluation for the qualification of maintenance or replacement interval is included in the reliability demonstration test of any series system that holds critical maintenance sub-units.

• Journal of Periodontal and Implant Science
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• v.45 no.6
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• pp.205-209
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• 2015

Purpose: Dental implants present several advantages over other tooth replacement options. However, there has been little research on masticatory function in relation to implant treatment. Therefore, the aim of the present study was to evaluate the improvement of masticatory function two weeks after implant restoration. Methods: Masticatory ability was evaluated with the subjective food intake ability (FIA) and objective mixing ability index (MAI) methods. Fifty-four subjects with first and second missing molars completed the study. The subjects were asked to complete a self-reported questionnaire about 30 different food items, and to chew wax samples 10 times both before and two weeks after implant restoration. A total of 108 waxes were analyzed with an image analysis program. Results: Dental implant restoration for lost molar teeth on one side increased the FIA score by 9.0% (P<0.0001). The MAI score also increased, by 14.3% after implant restoration (P<0.0001). Comparison between the good and poor mastication groups, which were subdivided based on the median MAI score before implant restoration, showed that the FIA score of the poor group was enhanced 1.1-fold while its MAI score was enhanced 2.0-fold two weeks after an implant surgery. Conclusions: Using the FIA and MAI assessment methods, this study showed that masticatory function was improved two weeks after implant restoration. In particular, the enhancement of masticatory function by implant restoration was greater in patients with relatively poor initial mastication than in those with good initial mastication.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.85-94
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• 2019

Purpose: The purpose of this study was to observe the degree of mask contamination in dental hygienist for general and oral bacteria and to identify areas of mask contamination after treatment. Methods: Masks were collected with every fifty dental hygienists who currently working in the department of preventive dentistry, prosthodontics, and orthodontics in Busan. The mask bacteria were collected in specific upper and side parts of the mask. Hand germs were collected using sterile cotton swabs, and then placed in a sterile conical tube. These were transferred to the laboratory. Hand germs and mask bacteria were incubated with nutrient broth (NB) and brain heart infusion broth (BHI) for 24 hrs and each cultured with NB and BHI plate at $37^{\circ}C$ for 48 hrs. Collected data were analyzed using the SPSS Window 20. Results: The number of bacteria was observed in the order of the department of preventive dentistry ($10.1{\times}10^5CFU/ml$), prosthodontics ($14.7{\times}10^5CFU/ml$), and orthodontics ($23.3{\times}10^5CFU/ml$) in the hand. In general bacteria, the difference of contamination was seen by the parts of the mask, but there was no significant difference. However, the oral bacteria were observed highly contaminated upper part of the mask in preventive dentistry. The mask contamination according to the medical departments was observed. Especially, the contamination of mask in preventive dentistry was significantly higher than other departments in oral bacteria. Conclusion: This study suggested that correct mask replacement and recognition of contamination areas can contribute to the prevention of infectious disease. and it would be necessary to increase hand hygiene performance to prevent cross-infection with masks. Also, this study may give an idea for making guidelines for mask management and supporting to establish clear criteria for the education program of personal protective equipment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.361-361
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• 2009

KEPCO High Temperature Superconducting (HTS) cable system rated with $3\Phi$, 22.9kV, 1250A was laid in 2006, and the long term test is in progress. The HTS cable system with the cooling system has been operated below cryogenic temperature. That environment exposes the system to the thermo-mechanical stress due to the significant temperature difference, and the cooling system has moving parts for the forced circulation of the coolant. Therefore the HTS cable system experiences thermal fatigue and moving part such as liquid nitrogen pump need a regular replacement every 5000 hours Building the assessment criterion, the maintenance procedure was established and regular preventive maintenance was done; improvement of the termination structure and the replacement of the bearing of liquid nitrogen pump. Following the proper process, the reliability assessment test including He leakage detection and the stability of flow rate was performed. This paper describes the process and result of the first regular maintenance of KEPCO HTS cable system

• Journal of Korean Neurosurgical Society
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• v.58 no.5
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• pp.401-411
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• 2015

More than 10 years have passed since lumbar total disc replacement (LTDR) was introduced for the first time to the world market for the surgical management of lumbar degenerative disc disease (DDD). It seems like the right time to sum up the relevant results in order to understand where LTDR stands on now, and is heading forward to. The pathogenesis of DDD has been currently settled, but diagnosis and managements are still controversial. Fusion is recognized as golden standard of surgical managements but has various kinds of shortcomings. Lately, LTDR has been expected to replace fusion surgery. A great deal of LTDR reports has come out. Among them, more than 5-year follow-up prospective randomized controlled studies including USA IDE trials were expected to elucidate whether for LTDR to have therapeutic benefit compared to fusion. The results of these studies revealed that LTDR was not inferior to fusion. Most of clinical studies dealing with LTDR revealed that there was no strong evidence for preventive effect of LTDR against symptomatic degenerative changes of adjacent segment disease. LTDR does not have shortcomings associated with fusion. However, it has a potentiality of the new complications to occur, which surgeons have never experienced in fusion surgeries. Consequently, longer follow-up should be necessary as yet to confirm the maintenance of improved surgical outcome and to observe any very late complications. LTDR still may get a chance to establish itself as a substitute of fusion both nominally and virtually if it eases the concerns listed above.

• Advances in concrete construction
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• v.4 no.2
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• pp.107-121
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• 2016

This concrete is one of the most versatile construction material widely used for almost a century now. It was considered to be very durable material and required a little or no maintenance since long time. The assumption is very true, except when it is subjected to highly aggressive environments. The deterioration of concrete structures day by day due to aggressive environment is compelling engineers to assess the loss in advance so that proper preventive measure can be taken to achieve required durability to concrete structures. The compounds present in cement concrete are attacked by many salt solutions and acids. These chemicals are encountered by almost all concrete structures. The present study has been undertaken to investigate the effect of attack of chlorides and sulphates with varying severity on compressive strength of ground granulated blast furnace slag (GGBFS) concrete after immersion in salt solution for 28 days. The results indicate that the durability of GGBFS concrete increases with the increase in percentage replacement of cement by GGBFS for 20% and then gradually decreases with increases in percentage of GGBFS with cement (as in the study for 40% and 60%). Also there is increase in strength of GGBFS concrete with increase in age. Thus the durability of concrete improves when GGBFS is added as partial replacement of cement. In this study the strength of GGBFS concrete is less affected by chemicals as compared to conventional concrete when exposed to aggressive environment.