• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.117-121
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• 2008

The effect of tip clearance on the performance of a supersonic impulse turbine was investigated experimentally. Test was performed using high pressure air in wide ranges of pressure ratio and rotational speeds. Test revealed that efficiency gradient of the subject turbine at a reference test point was a very low value of 0.05. Turbine efficiency was varied non-linearly with respect to tip clearance. It has been found that efficiency gradient is proportional to the cube of rotational speed at a fixed turbine pressure ratio. It also has been found that efficiency gradient shows its minimum at a reference test pressure ratio irrespective of rotational speeds.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.36 no.1
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• pp.1-7
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• 2013

This study is aimed to investigate the association between anaerobic-aerobic exercise intensity and hand steadiness. Hand steadiness is the decisive contributor to affecting the job performance just as in the rifle shooting and archery in sports and the microscope-related jobs requiring hand steadiness in industries. In anaerobic exercise condition hand steadiness is measured through hand steadiness tester having 9 different diameter holes after each subject exerts 25%, 50%, 75%, and 100% of maximum back strength. In aerobic exercise occasion it is evaluated at each time heart rate reaches 115%, 130%, and 145% of reference heart rate measured in no task condition after they do jumping jack. The results indicate that an increased intensity in both types of exercise reduces hand steadiness, but hand steadiness at 25% of maximum back strength and 115% of reference heart rate is rather greater than at no exercise. Just as the relation between cognitive stress and job performance has upside-down U form, so does the association of physical loading to hand steadiness, which means that a little exercise tends to improve hand steadiness in comparison with no exercise.

• 대한공업교육학회지
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• v.37 no.2
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• pp.127-146
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• 2012

The purpose of this study is to exploring the procedure of developing hands-on activity and provide the generalized development procedure adjusted for the technology subject. The research method for this study is mainly based on document and experience. exploration of hands-on activity and development procedure of hands-on activity given by preceded researchers and the common factor was derived from them. For the result of the study. first. the concept of experience and hands-on activity was examined and the procedure of developing hands-on activity in technology education was reviewed. Second. suggested 3 steps for the procedure of developing hands-on activity in technology education ; preparation. development. improvement and the detailed steps. Third. presented contents included for hands-on activity task materials. For the teachers. those are ; hands-on activity subject. readings before the class. object for the course class. main activity in class courses. material. tools and facility. design brief. reference data. score sheet. detailed class process. For the students. those are; subject for class. matters to be attended to. portfolio and etc.

• Journal of the Korean Chemical Society
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• v.65 no.5
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• pp.347-357
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• 2021

The purpose of this study is to compare and analyze the science curriculum of Korea and Estonia with a focus on the chemistry domain, and draw implications for reference when revising the next curriculum. To this end, the overall curriculum design centered on science subjects and the core concepts of chemistry covered in subjects corresponding to the common curriculum of the two countries were compared. As a result of the analysis, first, Estonia specifically suggested how the core competencies suggested in the general lecture were specifically connected to science subject. In addition, there was a characteristic that the inquiry function, attitude, and value were specifically presented in the curriculum document. Second, as a result of analyzing the core concepts of chemistry, most of the concepts dealt with in Korea were also dealt with in Estonia. However, Estonia has a tendency to deal more qualitatively with broader concepts. The concepts covered in the chemistry subject exceeded the level of the common curriculum in Korea, but this subject also had the characteristic of attempting a qualitative approach.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.3
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• pp.448-458
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• 2020

Indoor positioning based on trilateration using common chord estimates location of a mobile subject by using intersection points between each circles which the radius is same as distance between the mobile subject and each radio-frequency transmitter. However, if the intersection points are not found due to error of the distance measurement, it causes failure of estimating the mobile subject's location. To prevent this case, numbers which is proportionate to radius of each circles, are temporarily added to each distances in order to lengthen radius of the circles. Although the estimated location includes error due to the radius extension, it is corrected again by the added value and distance from reference point. With introduction of the advanced correction algorithm, potential issues of existing trilateration such as failure of estimating location and distance measurement error will be minimized.

• Journal of the Korea Society of Computer and Information
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• v.27 no.3
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• pp.217-223
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• 2022

In this paper, the needs and environment of the 'AI Convergence Education Method' were analyzed for elementary and secondary teachers, and based on this, teaching efficacy of informatics education was verified. For the research, elementary and secondary teachers who take the subject were selected, and based on the results of analyzing the general characteristics, pre-knowledge level, and needs of the subject, curriculum for 15 weeks was developed. As a result of verifying the teaching efficacy effectiveness of the developed 'AI Convergence Education Method' subject for 15 weeks, the effectiveness of the information education teaching efficacy was verified. Among the factors, there were statistically significant differences in information teaching values and information teaching strategies. In the future, it is necessary to conduct follow-up research to secure teachers' professionalism, such as linking with schools and convergence with other subjects. Various teaching and learning materials and teaching and learning methods such as educational contents and materials, reference literature, and artificial intelligence education platforms need to be prepared.

• Physical Therapy Korea
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• v.8 no.1
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• pp.76-88
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• 2001

Back extension exercises have been used for rehabilitation of the injured low back, prevention of injury, and fitness training programs. However, excessive loading on low back can exacerbate existing structural weakness. The purpose of this study was to compare muscle activity of low back muscles during back extension exercises. Twenty healthy male subject s were evaluated. Electromyographic (EMG) activities of low back muscles at L1 and L5 level were recorded during seven different back extension exercises and two reference tasks by surface EMG and saved for data analysis. Reference tasks of lifting 20% and 40% of their body weight were included for comparison. The result were as follows: 1) Single-arm extension and single-leg extension exercises on quadruped position appeared to constitute a low-risk exercise for initial extensor strengthening. 2) When arm extension was combined with contralateral leg extension on quadruped position, EMG activities of low back muscles were increased. 3) EMG activity of low back muscles was highest during the trunk extension exercises on prone position. 4) EMG activities of low back muscles during arm and leg extension exercises on quadruped position were less than those of reference task of lifting 40% of their body weight. These result s have important implications for progressive back extensor muscle strengthening exercises in patients with back pain.

• The korean journal of orthodontics
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• v.43 no.2
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• pp.54-61
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• 2013

Objective: The purpose of this study was to evaluate the effectiveness of the use of Reference Ear Plug (REP) during cone-beam computed tomography (CBCT) scan for the generation of lateral cephalograms from CBCT scan data. Methods: Two CBCT scans were obtained from 33 adults. One CBCT scan was acquired using conventional methods, and the other scan was acquired with the use of REP. Virtual lateral cephalograms created from each CBCT image were traced and compared with tracings of the real cephalograms obtained from the same subject. Results: CBCT scan with REP resulted in a smaller discrepancy between real and virtual cephalograms. In comparing the real and virtual cephalograms, no measurements significantly differed from real cephalogram values in case of CBCT scan with REP, whereas many measurements significantly differed in the case of CBCT scan without REP. Conclusion: Measurements from CBCT-generated cephalograms are more similar to those from real cephalograms when REP are used during CBCT scan. Thus, the use of REP is suggested during CBCT scan to generate accurate virtual cephalograms from CBCT scan data.

• Journal of Global Scholars of Marketing Science
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• v.10
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• pp.91-110
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• 2002

The purpose of this research is as follows; First, the reference price ads are to investigate how the price cues and prior knowledge of service products have an effect on consumers' perception by the type of information. Second, this study suggests some marketing strategy guides to service marketing managers for price promotion strategy. To achieve these research goals, the hypothesis was established through reviewing the previous studies and the data collected from the experimental design. The experiment of this study was a 2$\times$2$\times$2 among the subject factorial design in which the factors were present in price cue presentation (presentation/non- presentation), the level of prior knowledge(high/low), and the type of information(positive/negative). The major findings of this research can be summarized as follows; First, there are some significant statistical differences in the consumers' perception value by level of price cues(hypothesis 1). Second, there are some significant statistical differences in the consumers' price-quality perception by level of price cues(hypothesis 2). Third, there are some significant statistical differences in the price-quality perception by the level of prior knowledge and the type of information(hypothesis 3).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.416-422
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• 2016

This paper presents preliminary performance analysis of a satellite formation flying testbed, which is under development by Astrodynamics and Control Laboratory, Department of Astronomy, Yonsei University. A model reference adaptive controller (MRAC) with a first-order reference model is chosen to enhance the response of reaction wheel system which is subject to uncertainties caused by unmodelled dynamics and measurement noise. In addition, an on-line parameter estimation (OPE) technique based on the least square is combined to eliminate the effect of angular measurement noise by estimating the moment of inertia. Both numerical simulations and hardware experiments with MRAC support the effectiveness and applicability of the adaptive control scheme, which maintains the tracking error below $0.25^{\circ}$ for the entire time span. However, the high frequency control input generated in hardware experiment strongly suggests design modifications to reduce the effect of deadzone.