• 한국IT서비스학회지
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• 제14권4호
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• pp.137-157
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• 2015

The development of Social Network Service (SNS) has brought many positive changes to the ways people communicate, interact and share information. However, using the SNS does not always leads to in a positive results, particularly when it is addictively used. In fact, the addictive use of SNS results in many negative effects in our society. Recently, SNS users feel negative emotions such as expecially stress and fatigue while using SNS. Thus, the purpose of this study is to empirically examine antecedents of user fatigue on SNS, which can be explained by the degree of Individual, environment and SNS characteristics. This study also examines consequences of user fatigue on SNS. Lastly, we examine the moderating effects of Habit among SNS fatigue, barrier of living and task performance decline. The data for empirical analysis were collected 401 responses on SNS users in Korea. The results of this study are as follows; First, reputation perception, loneliness, unwanted relation, privacy concern, information overload, social presence and interaction are significantly related to SNS fatigue. Second, SNS fatigue, barrier of living and Task performance decline are significantly related to discontinuous usage intention. Third, the moderating effect of Habit of SNS using is found in the relationship among SNS fatigue, barrier of living and task performance decline. Based on the results of this study, Theoretical and practical suggestions were discussed.

• 대한전기학회논문지:시스템및제어부문D
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• 제50권5호
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• pp.247-254
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• 2001

Silent period(SP) is transient stops of muscle activity that are induced by mechanical or electrical stimulus and the duration of silent period is a important parameter that have been associated with symptoms of masticatory dysfunction. Muscle fatigue is induced by sustained muscular contractions. It is associated with the external manifestations as the inability to maintain a desired force output, muscular tremor, and localized pain. Muscle fatigue is a parameter that have been measured or monitored the deterioration of a performance of muscles. On the study of relationship between SP and masticatory muscle fatigue, Nagasawa suggested that SP increases up to 3 min. from the beginning of clenching when the subjects performed sustained contractions at 50% maximum clenching level. In this paper, in order to evaluate a relationship between SP and muscle fatigue, 10 SPs per 1 minute are measured at 10%, 20%, 50% maximum clenching level. We used the median frequency in order to quantify the degree of muscle fatigue. However, the results shows that the duration of silent period was not significantly affected by differing levels of muscle fatigue. Therefore, we suggest that the SP is not increased or decreased as the results of muscle fatigue, also the origin of the SP generation mechanism is discussed.

• 비파괴검사학회지
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• 제19권6호
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• pp.439-447
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• 1999

복합재료-금속 접착접합부가 사용 중 반복하중을 받을 때 발생하는 피로손상을 실시간에 평가할 수 있는 기법으로 음향초음파(acousto-ultrasonics; AU)법을 채택하였으며, 피로시험 중의 단일겹치기(single-lap) 및 이중겹치기 (double-lap) 평판형 시험편에서 취득한 신호로부터 계산된 음향초음파변수(acousto-ultrasonic parameters: AUP)와 피로손상도 사이의 상관관계를 나타내는 곡선을 얻을 수 있었다. 곡선은 피로손상에 의한 고분자기지 복합재료의 강성율 저하($E/E_o$)를 나타내는 곡선과 매우 유사하며, 이를 바탕으로 피로손상도의 실시간 예측이 가능하다. 다만 단일겹치기 시험편의 경우에는 Amplitude와 AUP2를, 이중겹치기 시험편의 경우에는 Amplitude와 AUP1을 기준 변수로 채택할 때 보다 일관성 있는 결과를 얻고 있는 점으로부터 실제 구조물에 적용함에 있어서는 각각의 형상에 따른 최적변수를 선택하여 활용해야 할 것으로 사료된다.

• 대한한의학회지
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• 제34권1호
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• pp.29-34
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• 2013

Objectives: This report aimed to demonstrate effect of human placental extract (HPE) pharmacopuncture in students suffering fatigue due to hard work and mental stress. Methods: Thirty-four college students, preparing for the final-term exam, received pharmacopuncture of HPE into Kwanwon (CV4) subcutaneously twice a week for 7 weeks. After every pharmacopuncture of HPE, degree of fatigue was surveyed by questionnaire including physical condition, physical endurance, concentration and memory. Results: Pharmacopuncture of HPE into CV4 gently improved physical condition, physical endurance, concentration and memory. Improvement of physical condition was especially positively correlated with the increasing number of pharmacopuncture of HPE into CV4 as confirmed by calculation of Pearson coefficient. Conclusions: Pharmacopuncture of HPE into CV4 alleviated fatigue in the students from hard work and mental stress.

• 항공우주의학회지
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• 제31권2호
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• pp.31-32
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• 2021

In Vol. 31, No. 2, our journal prepared a review article, two original papers, and three case reports. First, autonomous systems are increasingly being introduced in aircraft systems. Therefore, it is crucial that flight crews are trained to adapt and handle these autonomous systems better. Consequently, we discussed crew resource management for handling autonomous systems. The fatigue of aviation workers is one of the biggest threats to aviation safety. Therefore, we analyzed the degree of fatigue in commercial aircraft pilots and evaluated the relationship between fatigue and their workload and the effect of fatigue on sleep. Since obesity has a significant impact on the health of aviation workers, we also comparatively analyzed the prevalence of obesity in Korea and Japan based on the data from the National Health and Nutrition Examination Survey. We defined cases that are difficult for aviation medical examiners to evaluate. This issue included cases of peripheral dizziness and tinnitus, cases of atopic dermatitis treated with biological agents, and cases of malignant tumors.

• 대한치과보철학회지
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• 제30권4호
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• pp.508-525
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• 1992

The purpose of this study was to evaluate the effect of some resistance form designs on the bond strength of resin-retained prosthesis. Six sub-groups are designed in natural teeth group and resin teeth group . The framework designs in natural teeth group: 1) no groove preparation 2) groove at the center of distal surface 3) groove at the distobuccal line angle 4) 45 degree lateral load with no groove 5) 45 degree lateral load with center groove 6) splint two teeth with no groove. The framework designs in resin teeth group: 1) no groove preparation 2) groove at the center of distal surface 3) groove at the distobuccal line angle 4) metal covered the 1/2 of distal surface 5) metal covered the 1/2 of mesial surface 6) metal extended over the 114 of buccal surface. Specimens were treated electrolytic etching by Oxy-Etch and cemented with Panavia EX. Failure load was measured by Instron. Another 30 specimens were carried out fatigue tests by MTS 810 fatigue testing machine for 5000 cycles at different load level. The following results were obtained from this study. 1. The failure load was significantly increased by resistance forms. 2. The failure load was not increased by increase of total surface area bonded with teeth. The distal surface area played an important role in failure load. 3. In 45 degree lateral load group, the failure load was decreased significantly than that of in vertical load group. 4. Bond failure modes between static test and fatigue test exhibited no differences.

• 대한기계학회논문집
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• 제8권1호
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• pp.34-40
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• 1984

In this study, martensite-ferrite dual phase steel composed of martensite in hard phase and ferrite in soft phase is made as model material, and the difference of fatigue crack propagation behavior resulted from the structural size is investigated by fracture mechanics and microstructural method. The main results obtained are as follows; 1)Fatigue crack propagation rate is influenced by ferrite grain size. In other words, in the low .DELTA. K region fatigue crack propagation rate is decreased with decreasing of grain size but the difference of propagation rate resulted from the structural size is decreased as .DELTA.K is increased. 2)The above result is explained by the degree of crack arrest effect of second phase for fatigue crack propagation depending on the ratio of reversed plastic zone size to ferrite grain size.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.199-204
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• 2001

Big accidents of flyings, vessel, subways, gas equipments, buildings and bridge happens frenquently. Therefore many people are suffering harm of property. The destruction cause of macaine components is almost accused by fatigue. This study is test for STS304 specimen using pure and cantilever bending state. Rounded specimen and notched specimen including fracture surface investigation was comparatively experimented, fatigue life according to degree of surface finishing was examined. Fatigue fracture probability of notched canilever specimens were predicted by P-S-N curve, median rank and Weibull distribution. And at the relation with the rotational speed and stress, the fatigue life of the test specimen was higher at high speed than low speed.

• 한국안전학회지
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• 제25권6호
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• pp.28-33
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• 2010

Stainless steel is useful material for various industrial facilities such as the nuclear and steam power plant and the heavy chemical industry due to its good corrosion resistance and mechanical properties. However, it has also a large problem that is sensitized in the welding process and its corrosion resistance and mechanical properties decreases by sensitization. Thus, corrosion and corrosion fatigue characteristics of artificially sensitized austenitic STS304 were investigated through the EPR test and corrosion fatigue test. Obtained results are as follows: 1) According to the sensitizing period increase, Cr deficiency layer is linearly expanded. 2) Degree of sensitization(Ia/Ir) proportionally increased with sensitizing period. However, after 4hrs, it showed constant value. 3) Cr-carbide($Cr_{23}C_6$) in the grain boundary increased as sensitizing period increases until six hours. 4) corrosion fatigue strength of sensitized STS304 were remarkably reduced compare to non-sensitized ones.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1328-1336
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• 2004

According to our fatigue tests carried out at 20 Hz, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short life range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.