• The Journal of Korean Academy of Prosthodontics
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• v.47 no.4
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• pp.424-434
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• 2009

Statement of problem: Problems such as loosening and fractures of retained screws and fracture of implant fixture have been frequently reported in implant prosthesis. Purpose: Implant has weak mechanical properties against lateral loading compared to vertical occlusal loading, and therefore, stress analysis of implant fixture depending on its material and geometric features is needed. Material and methods: Total 28 of external hexed implants were divided into 7 of 4 groups; Group A (3i, FULL $OSSEOTITE^{(R)}$Implant), Group B (Nobelbiocare, $Br{\aa}nemark$ $System^{(R)}$Mk III Groovy RP), Group C (Neobiotec, $SinusQuick^{TM}$ EB), Group D (Osstem, US-II). The type III gold alloy prostheses were fabricated using adequate UCLA gold abutments. Fixture, abutment screw, and abutment were connected and cross-sectioned vertically. Hardness test was conducted using MXT-$\alpha$. For fatigue fracture test, with MTS 810, the specimens were loaded to the extent of 60-600 N until fracture occurred. The fracture pattern of abutment screw and fixture was observed under scanning electron microscope. A comparative study of stress distribution and fracture area of abutment screw and fixture was carried out through finite element analysis Results: 1. In Vicker's hardness test of abutment screw, the highest value was measured in group A and lowest value was measured in group D. 2. In all implant groups, implant fixture fractures occurred mainly at the 3-4th fixture thread valley where tensile stress was concentrated. When the fatigue life was compared, significant difference was found between the group A, B, C and D (P<.05). 3. The fracture patterns of group B and group D showed complex failure type, a fracture behavior including transverse and longitudinal failure patterns in both fixture and abutment screw. In Group A and C, however, the transverse failure of fixture was only observed. 4. The finite element analysis infers that a fatigue crack started at the fixture surface. Conclusion: The maximum tensile stress was found in the implant fixture at the level of cortical bone. The fatigue fracture occurred when the dead space of implant fixture coincides with jig surface where the maximum tensile stress was generated. To increase implant durability, prevention of surrounding bone resorption is important. However, if the bone resorption progresses to the level of dead space, the frequency of implant fracture would increase. Thus, proper management is needed.

• 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 Ocean Engineering and Technology
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• v.25 no.6
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• pp.66-71
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• 2011

Recently, the production of shipbuilding and offshore plant industries, with a trend toward large structures, has led to an increased use of high strength ultra-thick plates. The use of ultra-thick plates increases the welding tasks, and the welding process generates distortion and residual stress in the weldment because of the rapid heating and cooling. Welding distortion and residual stress in the welded structure resulte in many troubles such as deformation and life deterioration. In particular, the welding residual stress has an important effect on welding deformation, fatigue, buckling strength, brittleness, etc. The purpose of this study was to evaluate the residual stress at a multi-pass weldment using an experimental method for EH36 high-tension steel. In this experimental method, AIS3000 was used to measure the residual stress of a welded part, HAZ, and base metal; EPMA and XRD were used to study the material properties.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.148-156
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• 2013

Since the demand for new military vehicle to fulfill the necessary conditions such as multi-purpose, high-mobility, and survivability has raised continuously from the army, the prototype of a Korean light tactical vehicle was developed to meet these requirements using our own technology. In particular, the new tactical vehicle was equipped with a double wishbone independent suspension to improve ride and handling and maximize off-road driving performance. In this paper, a comprehensive virtual durability process to evaluate the service life of the prototype is presented. A reliability of the trimmed body model based on CATIA data was verified by comparison result between mode analysis and modal test. The dynamic model was constructed using ADAMS/Car, and then the weight distribution and lateral slope driving performance of it were compared with the results of static weight and lateral slope tests. The validity of the VTL(Virtual Test Lab) was checked with test results from the 3-inch spaced impact road. The durability performances of trimmed body and suspension components were evaluated through MSM(Modal Superposition Method) fatigue analysis. It is shown that the virtual durability process could be a helpful tool to find out the weak areas and improve their structures in developing new military vehicle.

• Women's Health Nursing
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• v.7 no.4
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• pp.631-641
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• 2001

This study is to investigate women have pre menstruation discomfort, The period of this research was almost one month (from 25, August 2001 to 25, October 2001). The PAF (Premenstrual assessment form), which was made by Park, Myonng-Wha, used for this study. The confidence rate is Crombach's $\alpha$= .9773. Correcting research papers are analyzed by SPSS 7.5 program and normal feature of the subject is divided by frequency, percentage, mean, standard deviation, t-test and ANOVA. The results of this study are as follows; 1. The average age of the subjects is 26.47 age. 220 subjects(44.6%) have gastroenteric trouble like, enteritis, stomachache, laxity. 278 subjects usually have caffeine drink in routine life. 123 subjects(24.9%) have controlled their diet. The average age of the first plowing is 13.55 ages and distribution is between 10 years and 20 years. The average of the uncomfortable point is 2.84. The way to reduce the uncomfortable feeling on the menstruation is taking relax time. 2. All subjects have experienced pre menstruation discomfort, even the degree uncomfortable feeling is different. Through eighteenth categories on the research papers, average point 2.21 were calculated and many subjects have fatigue ($2.89{\pm}1.0614$) and normal physical uncomfortable ($2.84{\pm}1.0633$) and undercurrent water symptom and unsuitability ($2.45{\pm}0.9857$). 3. According to the result of this study, that shows statistical difference; age (F=2.56. p=.037). marriage (t=2.60, p=.009) the number of children(t=2.83, p=.005), stress level(F=13.03, p=.000) job(F=3.91, p=.020). monthly income(t=2.14. p=.032) uncomfortable degree on the menstruation (F=19.121, p=.000), use of contraceptive appliance or pill(t=-2.20, p=.043), schooling (F=3.30, p=.038). Further research is need to understand pie menstruation discomforts, the variables associated with them. And nursing intervention has to considered in program to reduces of pre-menstruation discomforts.

• Journal of the East Asian Society of Dietary Life
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• v.22 no.6
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• pp.758-771
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• 2012

This research contains awareness of antioxidant and intakes of antioxidant foods for the present evaluate college students in Seoul, 375 patients were investigated. The subjects, the woman college student more than male's responded, showed a uniform distribution in the allowance, grade and the most type of residence is living apart from their family. All male and female college students recognize a lot about health, but male college students had higher than female students interested in the health, on the other hand, female college students had higher than male college students for the health efforts for the promotion of a healthy. Awareness about the oxide and active oxygen is moderate level, but knowledge about active oxygen is low level, they responded that active oxygen was caused when received stress or do strenuous exercise. General Health Functional Foods recognized that the usual intake, but intake of antioxidant was when the activity was caused by active oxygen. They recognized that the antioxidant effect is anti-aging and vitamin, wine and tea, were perceived as antioxidant foods, are popularly known. Usually, people was initially recognized through the internet in university or high school, they desire to obtain information was high but the effort to gain understanding and knowledge about antioxidant are relatively low. The result of comparing the difference of natural antioxidant foods and antioxidant healthy functional foods, recognizes of effects and absorption rate are similar, but recognizes that natural food intake is better recognition in the economics and health functional food is better recognition in the easy intake and nature foods was more preferred than functional foods because of nature friendly. Trying to intake of antioxidant foods is low, but people is expected anti-aging and fatigue recovery through the intake of antioxidant food. People think that intake is irrelevant to the season, but summer is higher than other seasons. Showed that efficacy perceptions about health supplements are higher, but efficacy perceptions about antioxidant health supplements when ingested are at a moderate level, which is lower, due to low antioxidant for understanding. Antioxidant functional health food intake will be affected the gifts or the people around them and purchase is also more influenced by surround people than themselves. So showed that most college students prefer natural antioxidant foods than antioxidant health supplements, in case of ingested antioxidant health supplements also showed that it was consumed by surround people than personal will.