• The Journal of Korean Academy of Prosthodontics
• /
• v.29 no.3
• /
• pp.141-170
• /
• 1991

This study was to analyze the displacement and the magnitude and mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment teeth and the mandibular supporting bone when various abutment designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. The models of overdenture and mandibe with the canine and the second premolar remaining, were fabricated. In the first design, a 1 mm space was prepared between the denture and the dome abutment with the height of 2 mm(OS). In the second design, a contact between the denture and the occlusal third of the dome abutment with the hight of 2 mm was prepared(OC). In the third design, a 0.5 mm space was prepared between the denture and 8 degree tapered cylindrical abutments with the height of 7 mm(TS). In the fourth design, a contact between the denture and the occlusal two thirds of the conical abutments with the height of 7 mm was prepared(TC). In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 Kgs on the first molar region (P1) and 7 Kgs on the central incisor region (P2) in a vertical direction. The force of 10 Kgs was then applied distributively from the first premolar to the second molar of each motel in a vertical direction (P3). The results were as follows: 1. The vertical load on the central incisor region(P2) produced the higher displacement and stress concentration than that on the posterior region(P1, P3). 2. The case of space between abutment and denture base produced higher displacement than that of contact, and the case of long abutment produced higher displacement than that of short abutment because of low rigidity of denture base. 3. The magnitude of the torque and vertical force to the abutment teeth and the stress distribution to the denture base was higher in the telescope coping than in the overdenture coping. 4. The vertical load on the central incisor region(P2) produced higher equivalent stress in the mandible than that on the posterior region(P1, P3). 5. The case of space between abutment and denture base produced better stress distribution to the farther abutment from the loading point than that of contact. 6. In case of sound abutment teeth, the type of telescope coping can be used, hilt in case of weak abutment, the type of overdenture coping is considered to be favorable generally.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.4
• /
• pp.423-428
• /
• 2016

The last stage blades of a low pressure (LP) turbine get frequently fractured because of stress corrosion cracking. This is because they operate in a severe corrosive environment that is caused by the impurities dissolved in condensed steam and high stress due to high speed rotation. To improve the reliability of the blades under severe conditions, 12% Cr martensitic stainless steel, having excellent corrosion resistance and higher strength, is widely used as the blade material. This paper shows the result of root cause analysis on a blade which got fractured suddenly during normal operation. Testing of mechanical properties and microstructure examination were performed on the fractured blade and on a blade in sound condition. The results of testing of mechanical properties of the fractured blade showed that the hardness were higher but impact energy were lower, and were not meeting the criteria as per the material certificate specification. This result showed that the fractured blade became embrittled. The branch-type crack was found to have propagated through the grain boundary and components of chloride and sulfur were detected on the fractured surface. Based on these results, the root cause of fracture was confirmed to be stress corrosion cracking.

• Science of Emotion and Sensibility
• /
• v.22 no.3
• /
• pp.47-54
• /
• 2019

We examined previous studies of the correlation analysis of heart rate variability as a method to reduce the stress caused by outside noise during driving, and we investigated whether there are electrocardiographic changes when drivers play music, which provides a stable sound source amid the noise. Because the number of cars increases every year, drivers and passengers show an increase in stress caused by outside noise. The stress from outside noise while a person is driving can cause several disorders, such as anxiety, immunosuppression, depression, and heart disease. Subjects in this study operated a vehicle simulator to reduce the stress from outside noise and were given different auditory stimuli, and we studied the drivers' responses to the stimuli. Repeated-measures analysis of variance revealed a significant differences between subjects exposed to different auditory stimuli (ρ < 0.05). Through post hoc analyses, we examined these differences. We found significant differences between factor 1 (stability) and factor 2 (simulation driving), between factor 1 (stability) and factor 3 (driving + police siren), and between factor 1 (stability) and factor 4 (driving + police siren + music). In addition, the factor that produced the highest level of sympathetic nervous system activity was factor 4 (driving + police siren + music), followed by factor 3 (driving + police siren), factor 2 (driving), and factor 1 (stability). In conclusion, even when a police siren was heard during driving, there were no significant differences on electrocardiograms (ECGs). In addition, even when the siren was heard over the music, there was no difference on the ECGs (ρ < 0.01). In future studies, investigators should determine which types of music help stabilize the heart rate during driving.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.4
• /
• pp.156-163
• /
• 2020

This study was conducted to provide basic data for realistic applicable changes of sirens by identifying the stress due to the currently used sirens and the need for improving siren. The data was collected from an online survey of 267 subjects who voluntarily agreed to join this study from August 2019 to September, 2019. A structured questionnaire was used as a research tool. The results were analyzed by means and standard deviations, percentages and frequency analysis, and independent t-tests using SPSS. For the current workplace emergency siren type, it is believed that the number of hybrid formats was 143, the most negative opinion of the siren is high at 132, so periodic replacement is needed. For contextual stresses, the highest was 4.35 ± 0.94, when the siren was heard during bedtime. In the stress during sleep, which was based on the daily mean number of movements,, a statistically significant difference was shown between groups of 9 or more movements and below 9 movements (p <0.05). The type of siren paramedics wanted was 'soft music' and 'sound of nature'. More than half of 168 people (62.9%) wanted to replace the current siren, and 163 (91.6%) wanted that periodically within 24 months. Therefore, it is necessary to improve the siren.

• Ecology and Resilient Infrastructure
• /
• v.7 no.2
• /
• pp.97-113
• /
• 2020

Soil is the foundation of human life and the basis for food security. Considering this it is prioritized in the UN's Sustainable Development Goals (SDG). Therefore, research on soil resilience in the agricultural environment is crucial for sound and sustainable soil management, especially in highly uncertain and unpredictable conditions. Soil resilience is defined in different ways by several researchers; however, its definition typically includes the concepts of recovery and resistance to stress. The physical, chemical, and biological characteristics of soils that are used to assess the soil resilience, i.e., the response of soil to various types of stress are summarized in this study. In addition, various statistical processing techniques and quantification methods are summarized considering the wide spatial and temporal scope of soil resilience research. Several soil resilience studies typically conduct the following five steps: (1) soil and site selection (2) stress (independent variable) setting (3) soil characteristics and indicator (dependent variable) setting (4) performing various spatiotemporal scale experiments (5) statistical analysis. The previous and present studies present a general introduction of soil resilience, based on which, further practical research considering domestic agricultural environment should be conducted. The extensive range of soil resilience measurements will require collaboration between researchers in various fields.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.11B no.4
• /
• pp.175-179
• /
• 2001

The switched reluctance drive exhibits higher levels of vibration and acoustic noise than that of most competing drives. The main source of vibration in the switched reluctance drive is generated by rapid change of radial force when phase current is extinguished by commutation action. A new excitation strategy for a Switched Reluctance Motor with Auxiliary Winding (SRMAW) is described and tested. This scheme has auxiliary winding with one diode which is sound to all th poles in one winding. In this scheme, auxiliary winding is used to reduce magnetic stress during commutations. The abrupt change of a phase excitation produces mechanical stresses and it results in vibration and noise. The acoustic noise is reduced remarkably through 2-stage commutation. The operational principle and a characteristic comparison to that of the conventional SRM show that this scheme has some advantages including noise reduction as well as high efficiency drive.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.19 no.9
• /
• pp.15-23
• /
• 2020

Spline is a machine component using transmits rotating energy with grooves on internal of boss and external periphery of shaft. Internal spline is generally produced by machining process. However, to reduce manufacturing cost and save time, plastic deformation process such as backward extrusion is gradually adapted for spline production. In plastic deformation process, forming load, stress on tools and flow flaws should be taken into account to have sound products. For this purpose, kinematically admissible velocity fields for Upper Bound Method in backward extrusion of internal spline has been suggested, then forming load and relative pressure have been calculated. Internal spline forming experiments have been con-ucted under hydraulic press and the calculated forming load well predicts the load of experiment.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.47 no.6
• /
• pp.124-130
• /
• 2010

Current traffic guidance system offers the information of traffic light using a speaker to everybody including the blinds without object certification. Therefore, the current system gives stress by noisy sound to normal person. It is difficult for the blind to hear informations such as location, current traffic sign light status, and weather information, because of the vehicle noise and surroundings noise. If the blind or sight disabled person who has the RFID tag or has a white stick with RFID tag approaches to street crossing, RFID reader recognizes the tag and it serves necessary information through speaker or bluetooth. And also it is possible for the blind to use less expensive one with RFID tag than the white stick with RFID Reader.

• Journal of Advanced Marine Engineering and Technology
• /
• v.32 no.2
• /
• pp.315-322
• /
• 2008

Titanium and its alloys have excellent corrosion resistance, high strength to weight ratios and creep properties in high temperature, which make them using many various fields of application. Especially, pure titanium, which has outstanding resistance for the stress corrosion cracking, crevice corrosion, pitting and microbiologically influenced corrosion, brings out to the best material for the heat exchanger, ballast tank, desalination facilities, and so on. Responding to these needs, welding processes for titanium are also being used GTAW, GMAW, PAW, EBW, LBW, resistance welding and diffusion bonding, etc. However, titanium is very active and highly susceptible to embrittlement by oxygen, nitrogen, hydrogen and carbon at high temperature, so it needs to shield the weld metal from the air and these gases during welding by non-active gas. In this study, it was possible to get sound beads without humping and spatter with a decrease of peak power according to increase of pulse width, change of welding speed and overlap rate for heat input control, and shield conditions at pulsed laser welding of titanium plates for Lap welding.

• Research in Community and Public Health Nursing
• /
• v.28 no.1
• /
• pp.78-87
• /
• 2017

Purpose: The purpose of this study is to identify factors influencing the quality of life of the elderly living alone and living with their families with regard to their health statuses and health behavior experiences. Methods: We used source data from the 2014 Community Health Survey. The subjects of this study included some elderly people aged 65 and over, and analyzed the data of 13,373 elders living alone and 13,322 elders living with family. Results: Factors influencing the quality of life of the elderly living alone and living with their families include gender, age, education, household income, current occupation, subjective stress level, depression, number of diagnosed diseases, walking exercise, the experience of health screening, and the experience of not having necessary medical services (p<.001). Region was a significant variable influencing the quality of life of the elderly living with their families (p<.001). Conclusion: In order to improve the quality of life of the elderly, it is necessary to provide sound conditions for working, emotional support, walking exercise and promotion of health screening, and to supplement the environment and institution for them to receive necessary medical services.