• Journal of Aerospace System Engineering
• /
• v.14 no.1
• /
• pp.28-35
• /
• 2020

This paper presents the design improvements made for the crack which is in the mounting structure of the mechanical structure of rotary wing aircraft. The doubler added to the mounting structure of rotary wing aircraft was designed and manufactured based on the load at the development stage, and a crack was found in the surface of doubler at a certain point during the operation of the aircraft. To identify the cause of the crack, the initial deformation of the structure, which may occur as a result of fastening condition, was considered and the dynamic analysis of the natural frequency of the structure comparing to the blade passing frequency of the aircraft were additionally reviewed. As a result of this study, a shim was added to remove the physical gap of the fastening area, and a doubler with thickened reinforcement was installed. The increase of structural strength is shown by reviewing the results of dynamic analysis for the structural verification of the improved design, and the fatigue evaluation complied to the requirement of the aircraft lifetime.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.7
• /
• pp.580-586
• /
• 2016

The ultra-long stroke engine was developed to generate greater power at lower speeds than previous designs to enhance the propulsion efficiency. The torsional exciting force, on the other hand, was increased significantly. Therefore, it is possible to control the torsional vibration of its shaft system equipped with the fuel efficient ultra-long stroke engine by adopting a damper although the torsional vibration could be controlled adequately by applying tuning and turning wheels on the engine previously. In this paper, the dynamic characteristics of a viscous-spring damper used to control the torsional vibration of the corresponding shaft system are reviewed and then examined to determine what vibration characteristics might be used to optimize the viscous-spring damper. In some cases, operators of eco-ships have recently experienced the problem of delayed RPM acceleration. It has been suggested that the proper measures for controlling the torsional vibration in the shaft system should involve adjusting the design parameters of its damper determined by the optimum damper design theory to avoid the fatigue damage of shafts.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.45 no.6
• /
• pp.498-507
• /
• 2017

Electronic equipments comprised of high density components with various packaging types have been recently applied to a satellite. Therefore, to guarantee high reliability of electrical equipment, a design approach, which can reduce the development period and cost through an early diagnosis in potential risks of failure, should be established. In the previous research, the reliability assesment of the electronic equipments have based on Steinberg's fatigue failure theory. However, this theory was not enough for further investigation of life prediction and reliability of the electronic equipments comprised of various sizes and packaging types due to its theoretical limitations and analysis results sensitivity with regard to different modeling technic. In that case, if detailed finite element model is established, aforementioned problems can be readily solved. However, this approach might arise disadvantage of spending much time. In this paper, to establish strategy for high reliability design of electronic equipment, we performed mechanical reliability evaluation of CCB (Camera Controller Box) at qualification level based on the approach using Sherlock unlike design techniques applied to existing business.

• International Journal of Highway Engineering
• /
• v.7 no.2 s.24
• /
• pp.33-43
• /
• 2005

This paper describes a new approach to minimize the amount of shrinkage cracking in cement treated base(CTB). CTB is a stiffness base having lots of merits such as higher rutting resistance, minimizing fatigue cracking, and the ability to distribute upper loads. However, It is not applied to asphalt pavement system in Korea because of possible cracks caused by dry shrinkage. The goal of this study is the development of cement treated base with lower shrinkage for preventing reflection cracks and rutting. After identifying factors affecting dry shrinkage and analyzing mechanism of each admixture, the laboratory and field tests were designed and performed. Through the preliminary tests, the mix design containing 25 percent o( fly ash and 7 percent of cement was suggested. This mix design was satisfied with strength for Korea specification standard. According to the results considering strength, shrinkage, and economical efficiency, two mix designs were selected; 1) containing 25 percent of fly ash and 2) containing 25 percent of fly ash with 10 percent of expensive additive. For field test based on the result of laboratory test, the optimized alternative in cement treated base with lower shrinkage was the mix design containing 25 percent of fly ash with 10 percent of expansive additive.

• International Journal of Highway Engineering
• /
• v.8 no.3 s.29
• /
• pp.49-61
• /
• 2006

This study suggests long-life asphalt pavement method which can save maintenance cost by increasing the design and performance period of pavements. The high modulus asphalt binder developed and then various physical tests are performed. Laboratory performance tests and accelerated pavement test are conducted for the high modulus and conventional mixtures. The test results show that dynamic modulus values of high modulus mixtures are higher than those of the conventional mixtures, The high modulus mixtures yield better fatigue, rutting and moisture damage performance than conventional mixtures. Structural analysis is performed and a database is built up for long life asphalt pavement design. Pavement response model is developed through a multiple regression analysis program, SPSS using the database. A design software for the long life pavements is developed based on the pavement response model and laboratory and field performance tests results. In addition, optimum pavement sections and materials are suggested. The suggested AC thickness of long life asphalt pavement is 29cm. A Life cycle cost analysis(LCCA) is conducted to check the economical efficiency of the long life pavement section. The LCCA result shows that initial construction costs of long life and conventional pavements are almost equal, but long life pavement is more profitable in terms of the LCCA.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.45 no.1
• /
• pp.94-104
• /
• 2017

With the recent increasing interest in preventive medicine, observation has been made regarding the positive relationship between a routinized place that includes activity and health improvement. This study evaluates the effective value of a designed landscape for seeing a healing environment and sees the difference of the effective value of classified physical settings regarding Evidence Based Design. Therefore, the study evaluates the perceived restorativeness scale of Cheonggyceheon's 1.5km section and five type settings in the same section regarding how much it works as a healthy urban park. The research methodology used to study sub-settings' and the research site's restoration effects was observation and questionnaires. A PRS (Perceived Restorativeness Scale) questionnaire survey was the research tool employed. The study drew two major results. Firstly, PRS 6.12 is the score of the whole research site, so the study identifies that Cheonggycheon has a mental fatigue restoration function. Secondly, the sub-setting named 'Near Sidewall' was the most attention restorative, according to the ANOVA results. In conclusion, this study suggests significant information support regarding the reasons for creating green areas in urban settings by identifying a particular designed healing sit.

• Journal of Convergence for Information Technology
• /
• v.10 no.7
• /
• pp.185-193
• /
• 2020

This purpose of this study was to investigate the effects of 16-week long-term walking exercise on the feeling, mood state, and life stress of college students. Participations in this study were 50 college students, and 24 Walking Group and 26 Control Group were random sampled to experiment the psychological effect of exercise walking. The experimental design was designed by factorial design by 2×3 repeated measurements. Data collection was conducted for 0week, 8week, 16week of feeling, mood state and life stress of college students. As a result, WG showed a positive increase in feeling status compared to CG. Negative mood state such as tension, anger, depression, fatigue, and confusion have been greatly reduced, vigor has increased, and stress on college student life such as friends, study, economy, future, and values has decreased statistically. The results of this study can be used as a way of coping with the stress of college students to improve their study motivation and quality of life.

• The Journal of the Korea Contents Association
• /
• v.21 no.12
• /
• pp.175-181
• /
• 2021

The purpose of this study is to improve and develop the quality of non-face-to-face classes according to the types of presence by analyzing the effects of teaching presence and learning presence on the learning satisfaction of the non-face-to-face classes that have been suddenly conducted due to COVID-19. For this purpose, a survey on online classes of H University in Gwangju Metropolitan City was conducted to analyze learning satisfaction, teaching presence (learning design, direct promotion), and learning presence (cognitive presence, social presence). The results of the analysis showed that the learning contents of cognitive presence, which is a sub-factor of learning presence, were understood (=.589, p<.001), the direct promotion (=.420, p<.001), and the learning design (=.397, p<.01), which are the sub-factors of teaching presence, were influential in order.This means that the suddenly changed teaching method should have an attitude to improve the intimacy between the instructor and the fellow learners with positive emotional exchange or interaction. The instructor should try to overcome the limitations of time and space through blended learning that is both online and offline for high quality learning design, but the learning medium and learning method considering the physical fatigue of the learner should be developed.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.10 no.6 s.52
• /
• pp.1-8
• /
• 2006

This paper describes the procedures developing the algorithm for analyzing signals acquired from the Bridge Weigh-in-Motion (BWIM) system installed in Seohae Bridge as a part of the bridge monitoring system. Through the analysis procedure, information about heavy traffics such as weight, speed, and number of axles are attempted to be extracted from time domain strain data of the BWIM system. One of numerous pattern recognition techniques, artificial neural network (ANN) is employed since it can effectively include dynamic effects, bridge-vehicle interaction, etc. A number of vehicle running experiments with sufficient load cases are executed to acquire training and/or test set of ANN. Extracted traffic information can be utilized for developing quantitative database of loading effect. Also, it can contribute to estimate fatigue lift or current health condition, and design truck can be revised based on the database reflecting recent trend of traffic.

• Journal of Acupuncture Research
• /
• v.30 no.2
• /
• pp.43-53
• /
• 2013

Objectives : The purpose of this study is to review of Clinical trials related to the treatment of chemotherapy induced-toxicity by acupuncture therapy. Methods : We searched PubMed by using word of "chemotherapy induced, acupuncture" (Limits : Full text available, 10 years, Clinical trials, Humans, English). We analyzed 15 research paper and examined published journals, years, countries, topic, study design, their results, interventions, participants and instruments of assessment. Results : Eleven journals with fifteen papers were searched. These papers were published in USA, Germany, etc. On the topic of these clinical trials, seven of them were about nausea(vomiting), two about peripheral neuropathy, two about hot flash, two about arthralgia and one about neutropenia, one about fatigue. Six of these studies were single blinded, randomized controlled trial. Twelve studies reported significant effect. The median for number of final participants was 35.5 persons. Assessment for outcomes were versatile questionnaire, nerve conduction studies, WBC, ANC, G-CSF examination, etc. Conclusions : Their median for impact factor was 3.650 and average modified Jadad score of six RCTs was 4.33. In order to provide appropriate evidence regarding the effectiveness of acupuncture in treatment for chemotherapy-induced toxicity, more rigorous and well-designed studies are necessary.