• Transactions of The Korea Fluid Power Systems Society
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• v.2 no.4
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.

• Journal of Applied Reliability
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• v.11 no.4
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• pp.331-342
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• 2011

The transmission of tracked vehicles performs complex functions as steering, shifting, braking, etc. and the system level life time has been a key influenced by the number of sub-parts like as gear assembly, torque converter, clutches, bearings and so on. In particular, the mechanical type steering system in tracked vehicle has impact shock torques in steering shift and those kind of shock torques can effect on the durability of many sub-parts in power train system. The field failure modes of gear assembly, steering assembly and the bearings of output shaft appear as a very complex phenomenon. In this study, the actual failure, which may occur in field, of the transmission was investigated comprehensively and that the endurance test on the resulting output shaft bearing failure analysis and life assessment was performed. Life time test method used in this study, developed for the purpose of the internal usage, and under these testing techniques the impact of the each bearing damage, which used in tracked vehicle transmission left / right outputs of different structures, was analyzed.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.1
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• pp.36-44
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• 2020

With the advent of westernized diet and a lack of exercise, young female college students are paying more attention to their bodyweight and health. Whole-body vibration has been demonstrated to be a suitable training method for improving knee extension maximal strength in young female athletes, as well as the gait performance in elderly women. This study aimed to evaluate the effects of a vertical vibration intervention on the physical fitness and postural balance in young females. Fifty-four young women were recruited; all subjects were randomly assigned to the intervention group and control group. The intervention group underwent vertical vibration with a platform for 12 weeks. The results showed that body mass index and body fat percentage had decreased (P<0.05). In addition, their muscle endurance as indicated by a sit-up test and their flexibility as indicated by a sit-and-reach test were both increased. With regard to postural balance, their 30-second sit-to-stand and timed up and go test results were improved. At the same time, their mean single-leg stance with eyes closed time increased (P<0.05). However, there were no significant differences, meanwhile, for the control group. Overall, the results showed that the whole body vibration (WBV) intervention had some beneficial effects on physical fitness and postural balance in young women.

• Journal of Family Relations
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• v.22 no.3
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• pp.73-101
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• 2017

Objectives: This study is to understand the experiences of overcoming pain of loss of family survivors in Suicide Bereavement Support Group(SBSG). Method: Experiential data was collected by in-depth interview(FGI, individual) to 10 family survivors(over 19) who having an experience participating in SBSG over 5months and analyzed using qualitative methodology. Results: We drew the result that 'SPACE model' which structuralize by 5 stages of suicide survivors' experience of SBSG of time path. SPACE model configured as follow: Stage1, Space in vacuum, the time to feel a sense of overwhelming feeling like pain, fear, alienation after loss of suicide, Stage2, Probing, when to find informations and resources to help survivors themselves, Stage3, Acclimation, having experiences empathy and healing as in SBSG, Stage4, Composure, accepting SBSG meaning as a part of their lives, loss of my family by suicide, and the beginning of bereavement, Stage5, Endurance, overcoming suffering through SBSG and try to help other survivors. Conclusions: SBSG is the opportunity for family survivors to overcome the pains from loss of suicide, shock, anger, grief, etc., and to empower them to help other suicide survivors.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.75-82
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• 2014

Recently, public works becoming bigger in Jeju are implemented various kinds of ground reinforcement method including the chemical grouting method. In this study, we have been investigated on the proper material and the injection condition for the excellent injection effect and the excellent strength of injection material and the permanent waterproof and reinforcement through the experiment. The kind of injection material has been selected through the uniaxial compression test and the endurance test of injection material as the chamber test. An experiment was performed with model ground made of scoria, the injection performance of selected material has been identified through the evaluation test of injection range using the decision test of injection amount and the calibration chamber test. As a result of test, it has been analyzed that MSG appeared to have the excellent strength, durability and injection performance all compared with the ordinary cement, this result is judged to be possible as the ancillary data of design at time of design and construction with the chemical grouting method in the future.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.1
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• pp.5-10
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• 2003

In this study, a new programming method to minimize the generation of Si-SiO$_2$interface traps of SONOS nonvolatile memory device as a function of number of porgram/erase cycles was proposed. In the proposed programming method, power supply voltage is applied to the gate. forward biased program voltage is applied to the source and the drain, while the substrate is left open, so that the program is achieved by Modified Fowler-Nordheim(MFN) tunneling of electron through the tunnel oxide over source and drain region. For the channel erase, erase voltage is applied to the gate, power supply voltage is applied to the substrate, and the source and dram are left open. Also, the asymmetric mode in which the program voltage is higher than the erase voltage, is more efficient than symmetric mode in order to minimize the degradation characteristics or SONOS devices because electrical stress applied to the Si-SiO$_2$interface is reduced due to short program time.

• Journal of Practical Engineering Education
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• v.8 no.1
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• pp.9-14
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• 2016

Depending on the college graduation project and graduation thesis regulations for the certification and graduation requirements, the quadcopter acting as a Li-Po battery that charges by solar energy are proposed a design method and improvements in theory. Quadcopter posture is balanced and confirmed by the position sensor, through a PID (Proportional Integral Differential) control. Battery switching circuit is composed of two Li-Po battery. Driving the quadcopter as one battery, and does not use other battery is charged by solar energy. A battery switching circuit is fabricated in a manner that uses two types of relays. Even if completely not charged to the battery is being driven a certain switch by the battery charging voltage from time to time, it proposes a method for increasing the endurance time and range.

• The Korean Journal of Physiology
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• v.22 no.1
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• pp.63-77
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• 1988

This study was carried out to investigate relationships between maximal running time (MRT) and glycogen supercompensation in fast twitch white fibers (white vastus, WV), fast twitch red fibers (red vastus, RV) and slow twitch red fibers (soleus muscle, SM) of endurance-trained rats. Male rats of a Sprague-Dawley strain were divided into the trained groups and untrained groups. Untrained groups were acquired to run on the treadmill 10 minutes for 3 days and remained rest and maintained with mixed diet for 4 weeks. For last 10 days of resting period, the untrained rats were divided into 3 groups i.e. mixed diet (untrained control), high and low carbohydrate (CHO) diet groups. And each group was subdivided into 2 groups, one group was tested for the MRT and the other was sacrificed to measure the blood glucose, blood lactate, glycogen contents of liver and muscles. The experimental groups were trained on treadmill by a modified method of Constable et al. (1984) maintained with mixed diet for 4 weeks. After measurement of MRT of this group, they were also divided into high and low CHO groups and fed with these diet for 2 days and MRT of each group was measured again to see the effect of high or low CHO feeding on the MRT. Each group was maintained with the same diet for next 2 days during which some of the rats were sacrificed at given time intervals for the measurements of blood glucose and lactate, liver and the muscles glycogen. The results were summarized as follows; 1) In the untrained group, there were no significant differences between subgroups in MRT, glycogen conent of SM, RV and WV. But blood glucose concentration and glycogen content of liver of low CHO group were significantly lower than those of mixed diet group. 2) The MRT and glycogen content of SM, RV and WV of trained mixed diet group were significantly increased compared to those of untrained mixed diet group, but there was no significant difference in glycogen content of liver. 3) MRT of trained mixed, high CHO and low CHO groups were $137{\pm}9.8,\;176{\pm}9.8\;and\;129{\pm}7.3\;min$ respectively with the significant difference between them. 4) There were no differences in blood lactate concentrations between the trained high and low CHO groups immediately after maximal running and during recovery period. 5) Glycogen contents in RV and SM of trained high CHO group were significantly increased, and glycogen contents in RV, WV and liver of trained low CHO group were significantly decreased compared to those of trained mixed diet group. 6) Immediately after maximal running, the blood glucose concentrations of trained high CHO and low CHO groups were $73{\pm}4.0\;and\;67{\pm}6.9mg%$ respecitively. The blood glucose of the trained high CHO group was fully recovered within one hour by feeding. But blood glucose concentration of low CHO group was slowly recovered up to $114{\pm}4.1mg%$ after two hours of feeding and maintained. Those values were still significantly lower than that of trained mixed diet group. The synthetic rates of glycogen in liver and muscles during the recovery period followed the similar time course of the blood glucose recoveries in each group. These results suggest that an increase in MRT of trained high CHO group was attributed to the glycogen supercompensation in slow twitch muscle fibers. And a decrease in MRT of trained low CHO may be due to decreased glycogen contents of liver and muscles. The results also suggest that glycogen supercompensation was more evident in slow twitch red fibers of endurance-trained rats and blood glucose is one of the limiting factors of glycogen synthesis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1521-1527
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• 2010

Since inkjet printing is being employed in production lines of electronics and display industries, the tack time for inspection of jetting failure has become very important because the throughput of the inkjet printing system can be extended to the maximum limit by adopting a shorter jetting inspection time. The most popular method for inspecting jetting failure involves the use of a linear stage, a high magnification lens, and a charge coupled devicecamera. However, this conventional approach requires approximately 60 s to complete the jetting inspection and might not be suitable for a high-speed reciprocating jetting inspection in endurance tests due to the unwanted mechanical vibration. In this study, a novel concept of an inkjet monitoring module is introduced, which has an overall inspection time of 18 s. For the shorter tack time of jetting inspection, the parameters affecting the tack time are discussed in this paper.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.51-58
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• 2008

This paper is a study of a prevention of power folding controller's thermal degradation. Power folding technology has been applied for many fields such as side rear vision mirror of vehicles, windshield wiper, antenna, power window. These controllers have been comprised with traditional DC moors, Switching electronic devices, and relays. But this methods have a limitation to overcome such problems of product reliability, endurance, noise margins. Therefore on this paper, to detect the movement of motor, sensing motor brush noise on a load sensing part has been used and controlling a precise RC timing control minimizes the thermal deterioration of motor. And using MOS FETs as a electronic switching device increases life-time and liability of control circuit. After testing such circuit and control method, repetition of operating time, cut-off time, wide operation voltage, power noise margin ware increased over eleven-fold.