• The Journal of Korean Academy of Prosthodontics
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• v.41 no.3
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• pp.360-368
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• 2003

Statement of Problem: The residual monomer of denture base materials causes hypersensitivity on oral mucosa and intereferes with the mechanical properties of the cured resin. The amount of residual monomer is influenced by materials, curing cycle, processing method, and etc. Purpose: The aim of this study was to investigate the residual methyl methacrylate(MMA) content of injection molded denture base polymer, and to compare this with the self-cured resin and the conventional compression molded heat-cured resin. Materials and Methods: Disc shaped test specimens (50mm in diameter and 3mm thick) were prepared in a conventional flasking technique with gypsum molding. One autopolymerized denture base resins (Vertex Sc. Dentimex. Netherlands) and two heat-cured denture base resins (Vertex RS. Dentimex. Netherlands, Ivocap. Ivoclar Vivadent, USA) were used. The three types of specimens were processed according to the manufacturer's instruction. After polymerization, all specimens were stored in the dark at room temperature for 7 days. There were 10 specimens in each of the test groups. 3-mm twist drills were used to obtain the resin samples and 650mg of the drilled sample were collected for each estimation. Gas chromatography (Agillent 6890 Plus Gas Chromatograph, Agillent Co, USA) was used to determine the residual MMA content of 10 test specimens of each three types of polymer. Results: The residual monomer content of injection molded denture base resins was $1.057{\pm}0.141%$. The residual monomer content of injection molded denture base resins was higher than that of compression molded heat cured resin ($0.867{\pm}0.169%$). However, there was no statistical significant difference between two groups (p>0.01). The level of residual monomer in self cured resin($3.675{\pm}0.791$) was higher than those of injection molded and compression molded heat cured resins (p<0.01). Conclusion: With respect to ISO specification pass / fail test (2.2% mass fraction) of residual monomer, injection molding technique($1.057{\pm}0.141%$) is a clinically useful and safe technique in terms of residual monomer.

• Journal of the Korea Convergence Society
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• v.3 no.4
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• pp.35-44
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• 2012

In this study, a simulation program is developed in order to investigate non steady-state cornering performance of 6WD/6WS special-purpose vehicles. 6WD vehicles are believed to have good performance on off-the-road maneuvering and to have fail-safe capabilities. But the cornering performances of 6WS vehicles are not well understood in the related literature. In this paper, 6WD/6WS vehicles are modeled as a 18 DOF system which includes non-linear vehicle dynamics, tire models, and kinematic effects. Then the vehicle model is constructed into a simulation program using the MATLAB/SIMULINK so that input/output and vehicle parameters can be changed easily with the modulated approach. Cornering performance of the 6WS vehicle is analyzed for brake steering and pivoting, respectively. Simulation results show that cornering performance depends on the middle-wheel steering as well as front/rear wheel steering. In addition, a new 6WS control law is proposed in order to minimize the sideslip angle. Lane change simulation results demonstrate the advantage of 6WS vehicles with the proposed control law.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.78-85
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• 2018

In this study, we analyzed risks of the fabrication process equipment and cleanroom for semiconductor/flat panel display (FPD) manufacturing facilities and studied the fundamental safety measures for the risk factors. We examined the explosion proof design models considering the specificity of equipment and environment, and planned to utilize the findings to provide technical standards and grounds for designing and manufacturing related equipment. We believe that this study will contribute to the establishment of technical standards for semiconductor/FPD industry and businesses in many different ways by providing optimized modeling of high-risk explosion site detection, developing safety standards and hazard countermeasures and voluntary activation of safety certification system for operation of fabrication process equipment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6214-6220
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• 2015

A track circuit has used stably more than 100 years for detecting train position, but solution of track circuit sort circuit incapacity due to a rust is necessary for side line in station yard, coast line and level crossing for conventional line in rural line. Domestically, Axle Counter System(ACS) has partially used for Hot Box System for high speed line and turnout for CBTC system. In contrast, most of countries has used ACS not only trunk line but also rural line and its application has increased for metro, electric car and industrial railway. In this paper, we has verified the operating status of ACS which installed with existing track circuit through log analsis to implement pilot application in mail track and turnout in station yard. And interface test with interlocking system has conducted at Obong shunting yard, as well as Cheongju station and has analyzed test result. Based on a test result, we made fail safe design, manufacturing skill and established system requirement specification for the smooth operation and maintenance.

• Journal of Korean Clinical Nursing Research
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• v.25 no.3
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• pp.221-236
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• 2019

Purpose: The purpose of this study was to systematically review and identify factors relevant to the positive psychological capital of clinical nurses. Methods: These was no limit on year of publication. Articles related to Korean clinical nurses were retrieved from computerized database using a manual search. A systematic review was conducted based on the PRISMA flow. The total correlational effect size (ESr) for each related factor was calculated from Fisher's Zr. Funnel plots, fail-safe numbers, and Egger regression tests were used to evaluate publication bias in meta-analysis studies. The correlational effect size of 25 studies was analyzed through meta-analysis using Comprehensive Meta-Analysis software 3.0 (CMA). Results: The review included 25 studies. In the systematic review, 14 demographic factors and 46 organizational factors were found to be influential. Eleven factors (6 demographic factors and 5 organizational factors) were appropriate for meta-analysis. The overall effect size was .26. The demographic total correlation effect size of related factors was .20 and the total effect size of organization was .46. Organizational commitment (ESr=.38) and job satisfaction (ESr=.54) were statistically positively related variables. Negative variables were burnout (ESr=-.61), turnover intention (ESr=-.41) and workplace bullying (ESr=-.33). The total effect size of the organizational factors was larger than the demographic total effect size. There was no publication bias except for demographic variables. Conclusion: Organizational factors and adjustable variables have a significant impact on positive psychological capital. The results of this study support the need for development of interventions focusing on organizational factors.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.4
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• pp.16-25
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• 2019

Recently, due to labor shortages in rural areas within South Korea, the demand for upland-field machinery is growing. In addition, there is a lack of development of systematic performance testing of upland-field machinery. Thus, this study examined structural safety and drawbar pull based on soil properties, as a first step for systematic performance testing on the test bed. First, the properties of soil samples from 10 spots within the experimental site were examined. Second, the strain was measured and converted into stress on 8 points of an onion harvester that are likely to fail. More specifically, the chosen parts are linked to the power, along with the drawbar pull, using a 6-component load cell equipped between the tractor and the onion harvester. The water content of the soil ranged between 5.7%-7.5%, and the strength between 250-1171 kPa. The test soil was subsequently classified into loam soil based on the size distribution ratio of the sieved soil. The onion harvester can be considered as structurally safe based on the derived safety factor and the drawbar pull of 115-1194 kgf, according to the working speed based on agricultural fieldwork.

• Structural Monitoring and Maintenance
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• v.8 no.4
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• pp.329-344
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• 2021

The use of structural control devices to minimize structural response to seismic/dynamic excitations has attracted increased attention in recent years. The use of magnetorheological (MR) dampers as a control device have captured the attention of researchers in this field due to its flexibility, adaptability, easy control, and low power requirement compared to other control devices. However, little attention has been paid to the effect of configuration and number of dampers installed in a structure on responses reduction. This study assesses the control of a five-story structure using one and two MR dampers at different stories to determine the optimal damper positions and configurations based on performance indices. This paper also addresses the fail-safe current value to be applied to the MR damper at each floor in the event of feedback or control failure. The model is mathematically simulated in SIMULINK/MATLAB environment. Linear control strategies for current at 0 A, 0.5 A, 1 A, 1.5 A, 2 A, and 2.5 A are implemented for MR dampers, and the response of the structure to these control strategies for different configurations of dampers is compared with the uncontrolled structure. Based on the performance indices, it was concluded that the dampers should be positioned starting from the ground floor, then the 2^nd floor followed by 1^st and rest of the floors sequentially. The failsafe value of current for MR dampers located in lower floors (G+1) should be kept at a higher value compared to dampers at top floors for effective passive control of multi-story structures.

• Safety and Health at Work
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• v.13 no.4
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• pp.394-400
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• 2022

Background: Impacts of exposure are generally monitored and recorded after injuries or illness occur. Yet, absence of conventional after-the-effect impacts (i.e., lagging indicators), tend to focus on physical health and injuries, and fail to inform if workers are not exposed to safety and health hazards. In contrast to lagging indicators, leading indicators are proactive, preventive, and predictive indexes that offer insights how effective safety and health. The present study is to validate an extended Voluntary Protection Programs (VPP) that consists of six leading indicators. Methods: Questionnaires were distributed to 13 organizations (response rate = 93.1%, 1,439 responses) in Taiwan. Cronbach α, multiple linear regression and canonical correlation were used to test the reliability of the extended Voluntary Protection Programs (VPP) which consists of six leading indicators (safe climate, transformational leadership, organizational justice, organizational support, hazard prevention and control, and training). Criteria-related validation strategy was applied to examine relationships of six leading indicators with six criteria (perceived health, burnout, depression, job satisfaction, job performance, and life satisfaction). Results: The results showed that the Cronbach's α of six leading indicators ranged from 0.87 to 0.92. The canonical correlation analysis indicated a positive correlation between the six leading indicators and criteria (1st canonical function: correlation = 0.647, square correlation = 0.419, p < 0.001). Conclusions: The present study validates the extended VPP framework that focuses on promoting safety and physical and mental health. Results further provides applications of the extended VPP framework to promote workers' safety and health.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.25 no.2
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• pp.214-223
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• 2023

Embolization of the middle meningeal artery (MMA) is a safe and effective adjunct in the treatment of chronic subdural hematoma. While prior authors describe the use of coils to assist embolization by preventing reflux through eloquent collaterals, we de- scribe the use of coils to further open the MMA, allowing the administration of greater amounts of embolisate for a more robust embolization. The objective of this study was to demonstrate that helical coils can safely open the MMA following the administration of polyvinyl alcohol (PVA) particles. This allows for more embolisate to be administered into the MMA for more effective treatment. A retrospective review was conducted at our institution including intraoperative images and postoperative clinical and radiographic follow up. Failure rates using MMA embolization with PVA and helical coil augmentation were compared to failure rates in the literature of MMA embolization with PVA or ethylene vinyl-alcohol copolymer alone. A total of 8 cases were reviewed in which this technique was implemented. There were no immediate complications after treatment. All patients that underwent helical coil embolization following the administration of PVA had increased amount of embolisate delivered into the MMA. All patients at follow up had resolution of the subdural hematoma on outpatient imaging. Helical coil embolization allows for more embolisate administration into the MMA and provides a technical advantage for patients that fail traditional techniques of embolization. Case series are taking place to further test this hypothesis and identify the ideal patient population that may gain maximal yield from this novel technique.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.4
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• pp.475-481
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• 2018

In this study, the safety and effectiveness of ope cutter, developed to prevent frequent accident propeller windingness at sea. First, we calculated the bolt strength of the three types of rope cutting devices used in the experiment and the torsional stresses on the shafting system theoretical equation and the finite element method. As a result, the bolts used in the rope cutter confirmed from the viewpoint of safety life design and fail safe design. Also, safety satisfactory because of the small effect on the shaft system when locking up. Experiments were carried out to cut ropes and fishing nets from the sea using the ships equipped with three types of rope cutters verified to be safe. As a result, ropes of 20 to 50 mm in thickness were generally cut. It was found that the cutting efficiency of a rope cutter attached to shafting decreased when cutting thick ropes.