• Journal of Welding and Joining
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• v.10 no.4
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• pp.240-249
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• 1992

The objective of this study is to investigate the characteristics of welded joints on the Zircaloy-4 resistance upset welding for HWR(Heavy Water reactor)fuel rods. To estimate the characteristics of welded joints, the various tests were performed on the test coupons systematically with a wide range of each welding parameters in terms of a tensile test, burst test, knoop hardness test and metallography. Major results obtained in this study are as follows: 1. The tube and machined with 120.deg. projection was the reliable weld joint design for the nuclear fuel rod end cap welding. 2. As the weld current and the amount of upset increased linearly with increasing welding main heat input, it could make an estimate of their variation in accordance with the phase shift control. 3. It was found that an increase in squeeze force has an effect on the upset contour of welded joint because the amount of upset were increased by the change of squeeze force.

• Journal of IKEEE
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• v.22 no.2
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• pp.484-487
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• 2018

5 MeV proton-irradiation with total dose of $10^{15}/cm^2$ was performed on AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) with various gate metals including Ni, TaN, W, and TiN to investigate the degradation characteristics. The positive shift of pinch-off voltage and the reduction of on-current were observed from irradiated HEMTs regardless of a type of gate materials. Hall and transmission line measurements revealed the reduction of carrier mobility and sheet charge concentration due to displacement damage by proton irradiation. The shift of pinch-off voltage was dependent on Schottky barrier heights of gate metals. Gate leakage and capacitance-voltage characteristics did not show any significant degradation demonstrating the superior radiation hardness of Schottky gate contacts on GaN.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.305-310
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• 2001

Hydraulic power shifting systems of hydraulic travel motor may be far safer than mechanical power transmission systems. Thus, hydraulic power shifting systems are widely used for speed control on the hydraulic equipments. In the case of liquid shifting lines, the rapid change of area, such as valve closing, can result in a large pressure transient. It is necessary to assure proper control method in order to obtain the smallest shift shock. This study conducts the shock characteristics of hydraulic power shifting system of the hydraulic travel motor. Experimental results show that shock pressure depends on the operating pressure, flow rate and pipe line area. The shock characteristics can be applied for reducing shocks.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.409-412
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• 1996

In this paper, the response characteristics of organic gases were investigated by using quartz crystal microbalance(Q.C.M) with different polymeric sensitive materials. The new linear parameter was discussed in order to develope gas sensing system using neural network and pattern recognition. We analyzed the response characteristics by the area of resonant frequency shift of quartz crystal, which mean affinities of organic gases for polymeric sensitive firm. The experimental results shows that the parameter made by the area of frequency shift which was linear with injection amount of organic gases has possibility to be used for pattern recognition and neural network. And they have different normalized pattern.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.1
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• pp.109-117
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• 2000

A full bridge type double resonant high frequency resonant inverter to give VVVF function in the inverter used as power source of induction heating at high frequency is presented in this paper. This proposed inverter can reduce distribution of the switching current because of using the current of serial resonant circuit to the input current of the parallel one and this paper also realize the output control of independence irrespective of the switching frequency using Phase-shift. The analysis of the proposed circuit is generally described by using the normalized parameters. Also, the principle of basic operating and the its characteristics are estimated by the parameters, such as switching frequency, the variation of phase angle ($\phi$) of Phase-shift.

• Safety and Health at Work
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• v.10 no.4
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• pp.512-517
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• 2019

Background: Rest breaks at work are reported to reduce fatigue and job stress. Apartment janitors in Korea who perform night shift work and work long hours can be exposed to various health problems (HPs). However, few studies have evaluated relationships between their rest breaks and HPs. This study was conducted to examine the relationships between long working hours, shift work, and insufficient rest breaks and HPs among Korean apartment janitors. Methods: Data on 1,212 selected male apartment janitors were obtained from the 3rd and 4th Korean Working Conditions Surveys. Demographic and occupational characteristics were collected using self-reported questionnaires. Rest breaks at work were classified as "sufficient" or "insufficient." Long working hours were considered as working more than 60 hours per week. Zero-inflated negative binomial (ZINB) regression was performed to investigate the effects of shift work and long working hours on HPs and the effects of rest breaks on relationships between HPs and long working hours and shift work. Results: Among those with insufficient rest breaks at work, significant associations were found between long working hours and the risk of HPs [odds ratio (OR) = 1.489; 95% confidence interval (CI) = 1.038-2.136] and work-related HPs (WRHPs) [OR 1.621; 95% CI = 1.156-2.272], and between shift work and HPs [OR = 1.603; 95% CI = 1.084-2.372]. These relationships became nonsignificant when sufficient rest breaks were provided. Conclusion: It is important to provide breaks at work to reduce HPs because of long working hours and shift work among aged workers such as apartment janitors.

• Archives of design research
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• v.15 no.3
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• pp.241-248
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• 2002

Researches of Hangul automation have been focused mainly on the set of character system. But, practical problem of using the Korean standard keyboard system of two sets is increment of errors and fatigue due to frequent use of shift keys. The author formulate a hypothesis as follows to solve the problem. 'Changing location and design of shift keys can reduce errors in typing Korean by avoiding interferences with other keys when pressing shift keys.' This study verify the hypothesis by the analysis of experiments using improved keyboard prototypes which have changed layout and design of shift keys. On the result, change of shift key location causes confusion to experienced user. But, while keeping its location, removing other keys at the bottom row and magnifying size of shift keys decrease errors in typing by avoiding interferences. And, the efficiency of typing in Korean is increased, too, because there is not any influence on typing speed. This study focuses on layout and design of shift keys only, but further study for entire layout of keyboard including alternative location of other function keys is needed to improve general usability.

• PNF and Movement
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• v.17 no.1
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• pp.93-101
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• 2019

Purpose: This study aimed to investigate lower extremity muscle activation to the variable weight shift on the affected side of patients with hemiplegia. Methods: Eighteen patients with chronic hemiplegia volunteered to participate in this study. All participants performed three types of weight shift (sideways, forward, and backward) in limits of stability on the affected side. Muscle activation in a paralyzed leg was measured with electromyography on the gluteus medius, tensor fasciae latae, rectus femoris, and biceps femoris; furthermore, the attached area was recommended by SENIAM projects. Each weight shift was performed three times, and then the mean value of the three measurements was analyzed. The data were analyzed by measuring the symmetrically standing position with the reference voluntary contraction (RVC) and was standardized with the percentage of RVC method. Results: No significant difference in lower extremity muscle activation occurred according to the three types of variable weight shift. However, significant differences in lower extremity muscle activation did occur with each weight shift position. In addition, activation increased at the rectus femoris and decreased at the gluteus medius and tensor fasciae latae. Conclusion: Hip abductor muscle strength training and variable weight shifts on the affected side must increase to improve patients'balance and limits of stability.

• Clinical and Experimental Emergency Medicine
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• v.5 no.4
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• pp.240-248
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• 2018

Objective Determine differences between faculty, residents, and nurses regarding night shift preparation, performance, recovery, and perception of emotional and physical health effects. Methods Survey study performed at an urban university medical center emergency department with an accredited residency program in emergency medicine. Results Forty-seven faculty, 37 residents, and 90 nurses completed the survey. There was no difference in use of physical sleep aids between groups, except nurses utilized blackout curtains more (69%) than residents (60%) and faculty (45%). Bedroom temperature preference was similar. The routine use of pharmacologic sleep aids differed: nurses and residents (both 38%) compared to faculty (13%). Residents routinely used melatonin more (79%) than did faculty (33%) and nurses (38%). Faculty preferred not to eat (45%), whereas residents (24%) preferred a full meal. The majority (>72%) in all groups drank coffee before their night shift and reported feeling tired despite their routine, with 4:00 a.m. as median nadir. Faculty reported a higher rate (41%) of falling asleep while driving compared to residents (14%) and nurses (32%), but the accident rate (3% to 6%) did not differ significantly. All had similar opinions regarding night shift-associated health effects. However, faculty reported lower level of satisfaction working night shifts, whereas nurses agreed less than the other groups regarding increased risk of drug and alcohol dependence. Conclusion Faculty, residents, and nurses shared many characteristics. Faculty tended to not use pharmacologic sleep aids, not eat before their shift, fall asleep at a higher rate while driving home, and enjoy night shift work less.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.20-24
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• 1994

The read/write characteristics of CoCr/NiFe double layered media are strongly affected by the magnetic properties of NiFe magnetic soft layer as well as those of CoCr recording layer. Modification of the permalloy layer by NiFe/Ge multilayer scheme resulted in the higher recording sensitivity and the higher reproduced voltage of CoCr/NiFe medium and this is attributed to the higher permeability of the back layer and high perpendicular anisotropy of the CoCr recording layer. Although higher permeability of back layer results in higher recording sensitivity, the increment of the reproduced voltage was not remarkable, which can be confirmed in the FEM numerical analysis. On the contrary, peak shift characteristics of the CoCr/NiFe medium with the NiFe multi back layer was deteriorated compared to that of the CoCr/NiFe medium with NiFe single back layer. Insertion of ferromagnetic thin CoZrNb intermediate layer between CoCr and NiFe layer was effective to ensure large reproduced voltage and low peak shift. These recoridng characteristics were also discussed in connection with microstructural characteristics.