• Applied Microscopy
• /
• v.48 no.3
• /
• pp.73-80
• /
• 2018

Ductile cast iron is widely used for many automotive components due to its high wear resistance and fatigue resistance in addition to the low cost of fabrication. The improvement of wear resistance and fatigue properties is key to the life time extension and performance increase of the automobile parts. Surface nanocrystallization is a very efficient way of improving the performance of materials including the wear- and fatigue-resistance. Shot peening treatment, as one of the popular and economic surface modification methods, has been widely applied to various materials. In this study, ductile cast iron specimens were ultrasonic shot peening (USP) treated for 5 to 30 min using different ball size. The microstructures were then microscopically analyzed for determination of the microstructural evolution. After the USP treatment, the hardness of pearlite and ferrite increased, in which ball size is more effective than treatment time. With USP treatment, the graphite nodule count near the surface was decreased with grain refinement. The lager balls resulted in an increased deformation, whereas the smaller balls induced more homogenously refined grains in the deformation layer. In addition, formation of nanoparticles was formed in the surface layer upon USP.

• Journal of Korean Physical Therapy Science
• /
• v.15 no.4
• /
• pp.19-26
• /
• 2008

Background: This study examines the changes in muscular strength and muscle fatigue substances when taping treatment is applied in squat exercise and treadmill exercise, in which quadriceps femoris muscles are used frequently so as to clarify the effects of taping as an aid of exercise ability improvement. Methods: 20 healthy male adults in their 20's participated in the study, in which tapes were put on their quadriceps femoris muscles, and various variables as the indicator of muscular strength and muscle fatigue substances were measured by means of the measuring tool before and after exercises. Results: the following conclusion was drawn up: 1. In exercise using muscular strength of the right knee extension, the reduction of muscular strength after exercise of the taping group showed significant statistical difference from that of the non-taping group. 2. In exercise using muscular strength of the lower limbs, the reduction of blood Glaucos after exercise of the taping group showed significant statistical difference from that of the non-taping group. 3. In exercise using muscular strength of the lower limbs, the value of lactic acid after exercise of the taping group showed significant statistical difference from that of the non-taping group. Conclusion: Therefore, the results of this study demonstrate that the application of taping treatment in sports activity or daily life where quadriceps femoris muscles are used a lot can have positive effects on the improvement of muscular strength and relief of muscle fatigue.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.9
• /
• pp.26-31
• /
• 2003

Aging aircraft accumulates widespread fatigue damage commonly referred to as multiple site damage(MSO). For ductile material such as 2024-T3 aluminum, MSO may lower the service life below that which is predicted by conventional fracture mechanics. The present paper is concerned with the fatigue life extension by pre-indentation technique for thin 2024-T3 aluminum plate to decelerate the crack propagation rate in the panels with MSO. The panel with fastener holes can be simply modelled by Hole/Slot type Middle-Tension specimen. Results of fatigue testing show significantly improving failure cycles from 10 to 40 times. This retardation effect is decreased by increasing the loading level in the constant amplitude loading. In the sense of retardation mechanism, the crack propagation rate is gradually attenuated by entering the indentation mark and maintains at the lowest value for a long period after the edge of crack passes the center of indentation area.

• Journal of Korean Academy of Nursing
• /
• v.36 no.2
• /
• pp.310-320
• /
• 2006

Purpose: The purpose of this study was to investigate the effects of a rehabilitation program on physical health, physiological indicators and quality of life in breast cancer mastectomy patients. Methods: The subjects included thirty-one patients with breast cancer(17 in the experimental group and 14 in the control group). The subjects in the experimental group participated in a rehabilitation program for 10 weeks, which was composed of an exercise program, teaching, counseling and support for 2 sessions per week. Results: There was a significant increase in flexion, internal rotation and external rotation but no significant increase in extension in the experimental group compared to the control group. The total cholesterol, triglyceride, HDL, LDL, and CD56 in the experimental group compared to the control group was not significantly decreased after the rehabilitation program. Compared to the control group, quality of life in the experimental group was significantly improved and fatigue in that group was significantly decreased after the rehabilitation program. Conclusion: The 10-week rehabilitation program showed a large affirmative effect on physical health, physiological indicators and quality of life in breast cancer mastectomy patients.

• Journal of Welding and Joining
• /
• v.30 no.6
• /
• pp.74-79
• /
• 2012

It depends on the joint configuration, dimensions and constraints of the joint whether the residual stress at the root of single-sided butt weld is tensile or not. Therefore, recommendation is generally made that high R ratio should be used in the fatigue test of welded joint in order to prevent excessively long life caused by compressive residual stress. In this research, the residual stress profile in butt weld joint was obtained through compliance method, using successive extension of a slot and measurement of the variation of strain during the slot extension. The residual stress profile was firstly assumed to be the linear summation of Legendre polynomials up to 9th order excluding 0th and 1st order. Strain variation on the surface was measured while the slot was being extended by cutting to find out the 8 unknown coefficients of each polynomial term. The cut was made by the electric discharge machine. It was concluded that the residual stress near the surface is positive valued, however, it turned into the negative value as soon as it passed through 2 or 3 mm of the depth.

• Journal of Life Science
• /
• v.20 no.6
• /
• pp.870-876
• /
• 2010

The purpose of this study was to examine the effect of kinesio taping on muscle strength and changes of muscle fatigue and damage. 10 male subjects participated in 1-RM and isometric cybex muscle strength tests with and without taping application. Muscle strength (bench press, leg press) and extension (knee, shoulder) strength were significantly increased after taping, but there was no significant difference in flexion (knee, shoulder) strength. The concentration of fatigue factors (ammonia, phosphorous), muscle damage index substances (CK, LDH), IGF-I and creatinine were reduced after taping, but there were no significant differences.

• Journal of the Korea Concrete Institute
• /
• v.24 no.6
• /
• pp.677-684
• /
• 2012

In recent years, extension of life span of buildings is becoming an important issue in our society. To improve the life span of buildings, rhamen structure construction and long-spanned structures are advantageous. And in order to achieve this goal, structural elements of buildings must be light and slender. As an alternative method, general porous slabs are used frequently domestically and internationally. But the study on the porous slabs using T-deck plate and assembly of light weight precast construction is insufficient at present. In this study, flexural and fatigue tests were performed on six specimens to verify structural performance and serviceability. The main parameters of the specimens were light weight and T-deck plate construction possibility as well as slab thickness. The test results indicated that the strength of porous slabs using T-deck plate and assembly of light weight were much better than general RC slabs and porous slabs without T-deck plate. And stiffness was much better than that of other tested slabs.

• Fire Science and Engineering
• /
• v.29 no.3
• /
• pp.59-64
• /
• 2015

This study analyzed results of the causes of failure in 1,022 fire trucks currently being used in South Korea (aerial ladder, aerial platform, pumper, and chemical fire trucks). The results show that 46% of aerial ladder trucks have defective in the elevator brake systems, 29% of aerial platform trucks have contamination in the hydraulic oil, 37% of pumpers have defective in the pneumatic cylinders of the air supply system, and 39% of chemical fire trucks have defective in the powder fire extinguishing systems. The principal reasons for malfunctions are deterioration of the apparatuses, and accumulated fatigue from repetitive use of certain components, such as pneumatic cylinders in the air supply system and wire rope jamming in rollers in the ladder apparatus. These manufacturing defects should be improved upon in the manufacturing process. As a result, the fire trucks, which are used for 5 years or more, need precise inspections in accordance with the Regulation on Fire Apparatus Maintenance. Fire apparatuses have a service life of 10 to 12 years or more. They need to be replaced or require life extension, and they should be kept in top shape with the best maintenance for public safety.

• Journal of Korean Academy of Nursing
• /
• v.28 no.4
• /
• pp.958-969
• /
• 1998

In this study, we attempted to investigate the needs and problems of the terminal cancer patients and their family caregivers to provide them with nursing information to improve their quality of life and prepare for a peaceful death. Data was collected from August 1, 1995 to July 31, 1996 at the internal medicine unit of S hospital in Seoul area with the two groups of participants who were family members of terminal cancer patients seventy four of them were in-patients and 34 were out-patients who were discharged from the same hospital for home care. The research tool used in this study has been developed by selecting the questionnaires from various references, modifying them for our purpose and refining them based on the results of preliminary study. While general background information about the patients was obtained by reviewing their medical records, all other information was collected by interviewing the primary family caregivers of the patients using the questionnaire. The data collected were analyzed with the SPSS PC/sup +/ program. The results of this study are summarized as follows ; 1) Most frequently complained symptoms of the terminal cancer patients were in the order of pain(87%), weakness(86.1%), anorexia(83.3%) and fatigue (80.6%). 2) Main therapies for the terminal cancer patients were pain control (58.3%), hyperalimentation(47.2%) and antibiotics(21.3%). 3) Special medical devices that terminal cancer patients used most were oxygen device (11.1%), and feeding tube(5.6%). Other devices were used by less than 5% of the patients. 4) The mobility of 70.4% of the patients was worse than ECOG 3 level, they had to stay in bed more than 50% of a day. 5) Patients wanted their medical staffs to help relieve pain(45.4%), various physical symptoms(29.6%), and problems associated with their emotion(11.1%). 6) 16.7% of the family caregivers hoped for full recovery of the patients, refusing to admit the status of the patients. Also, 37% wished for the extension of the patient's life at least for 6 months. 7) Only 38.9% of the family members was preparing for the patient's funeral. 8) 45.4% of family caregivers prefer hospital as the place for the patient's death, 39.8% their own home, and 14.8% undetermined. 9) Caregivers of the patients were mostly close family members, i.e., spouse(62%), and sons and daughters or daughter-in-laws(21.3%). 10) 43.5% of the family caregivers were aware of hospice care. 46.8% of them learned about the hospice care from the mass media, 27.7% from health professionals, and the rest from books and other sources. 11) Caregivers were asked about the most difficult problems they encounter in home care, 41 of them pointed out the lack of health professionals they can contact, counsel and get help from in case of emergency, 17 identified the difficulty of finding appropriate transportation to hospital, and 13 stated the difficulty of admission in hospital as needed. 12) 93.6% of family caregivers demanded 24-hour hot line, 80% the visiting nurses and doctors, and 69.4% the volunteer's help. The above results indicate that terminal patients and their family caregivers demand help from qualified health professionals whenever necessary. Hospice care system led by well-trained medical and nursing staffs is one of the viable answers for such demands.

• Progress in Medical Physics
• /
• v.20 no.2
• /
• pp.80-87
• /
• 2009

Phase transformation, superelastic characteristics and variation of surface residual stress were studied for Nitinol shape memory alloy through application of UNSM technology, and life extension methods of stent were also studied by using elastic resilience and corrosion resistance. Nitinol wire of ${\phi}1.778$ mm showed similar surface roughness before and after UNSM treatment, but drawing traces and micro defects were all removed by UNSM treatment. It also changed the surface residual stress from tensile to compressive values, and XRD result showed less intensive austenite peak and clear martensite and additional R-phase peaks after UNSM treatment. Fatigue resistance could be greatly improved through removal of surface defects and rearrangement of surface residual stress from tensile to compressive state, and development of surface modification system to improve not only bio-compatability but also resistance to corrosion and wear will make it possible to develop vascular stent which can be used for circulating system diseases which run first cause of death of recent Koreans.