• 한국태양에너지학회 논문집
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• 제29권5호
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• pp.73-80
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• 2009

A tidal current turbine is designed and analyzed numerically by using blade element momentum theory. The rated power has a limitation because the diameter of the tidal current turbine cannot exceed the depth of sea water. This study investigates a horizontal axis tidal-current turbine with a rated power of 500 kW. NACA-6 series laminar foil shape is used for basic airfoil along the blade span. The distributions of chord length and twist angle along the blade span are obtained from the hydrodynamic optimization procedure. Prandtl's tip loss correction and angle of attack correction considering the three-dimensional effect are applied for this study. The power coefficient curve shows maximum peak at the rated tip speed ratio of 6.0, and the maximum torque coefficient is developed at the tip speed ratio of 4. The drag coefficient reaches about 0.85 at the design tip speed ratio.

• International Journal of Contents
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• 제6권3호
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• pp.83-88
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• 2010

Aerobic exercise affects cerebral circulation, action of neurotransmitters, glucose, oxygen, and energetic substances and influence on the central nervous system for cognition. This study suggests that both the intensity of exercise and the level of cognitive task need to be considered. Computerized neurobehavioral testing is a more effective method, compared to conventional methods, of neuropsychological testing when measuring cognition objectively, in cases that we found. The intensity of 80% max HR had effect on more complex tasks such as 3 Digit Addition and Digit Span Backward, and the intensity of 65% max HR had an effect on more simple tasks such as Color Word Vigilance and Digit Span Forward. We can assume that different intensity of aerobic exercise might involve specific areas of the brain as they could have different sensitivities, so further studies measuring regional cerebral blood flow or electroencephalogram are needed to confirm the results.

• Journal of Pharmaceutical Investigation
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• 제12권2호
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• pp.45-53
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• 1982

The effects of mixture of tween 20 and span 20 or span 80 on griseofulvin absorption in rabbit were studied. The plasma concentration of griseofulvin in blood samples was determined by high pressure liquid chromatographic procedure. Griseofulvin suspension with 0.05% surfactant increased mostly drug absorption and produced about two times higher plasma level of griseofulvin than that of the suspension with 1% and 0.1% surfactant. Surfactants with H.L.B. value 4.3 resulted $2.74{\mu}g/ml$ of maximum plasma levels of griseofulvin at 18 hours after its oral administration and surfactants with H.L.B. value 16.7 resulted $0.56{\mu}g/ml$ of peak plasma levels of griseofulvin at 1 hour after its oral administration.

• Structural Engineering and Mechanics
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• 제45권6호
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• pp.723-740
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• 2013

This paper presents a parametric study of reinforced concrete bridge tall piers with hollow, rectangular sections. Such piers are typically used in railway construction of prestressed concrete viaducts. Twenty one different piers have been studied with seven column heights of 40, 50, 60, 70, 80, 90 and 100 m and three types of 10-span continuous viaducts, whose main span lengths are 40, 50 and 60 m. The piers studied are intermediate columns placed in the middle of the viaducts. The total number of optimization design variables varies from 139 for piers with column height of 40 m to 307 for piers with column height of 100 m. Further, the results presented are of much value for the preliminary design of the piers of prestressed concrete viaducts of high speed railway lines.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.159-164
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• 2000

In this study, the deformation analysis of 80mm optical disk holder considering the creep characteristics of plastic materials has been conducted and experimentally verified. It is very important to remedy the unrecoverable creep deformation and relaxation of holding force of an optical disk holder for the reliability of DVDR-P, DVD-ROM. A disk holder inserted in a cartridge case has been kept in the chamber with $60^{\circ}C$ temperature and 90% humidity for 24 hours. After storage test, the arm span and holding force of a disk holder have been measured after 24 hours at room temperature and normal humidity. The predicted results are in good agreement with experimentally measured one.

• 한국도로학회논문집
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• 제15권4호
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• pp.127-133
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• 2013

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

• 대한청각학회지
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• 제25권4호
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• pp.178-188
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• 2021

Background and Objectives: The influence of musical aptitude on cognitive test performance in musicians is a long-debated research question. Evidence points to the low performance of nonmusicians in visual and auditory cognitive tasks (working memory and attention) compared with musicians. This cannot be generalized to all nonmusicians, as a sub-group in this population can have innate musical abilities even without any formal musical training. The present study aimed to study the effect of musical aptitude on the working memory and selective attention. Subjects and Methods: Three groups of 20 individuals each (a total of 60 participants), including trained-musicians, nonmusicians with good musical aptitude, and nonmusicians with low musical aptitude, participated in the present study. Cognitive-based visual (Flanker's selective attention test) and auditory (working memory tests: backward digit span and operation span) tests were administered. Results: MANOVA (followed by ANOVA) revealed a benefit of musicianship and musical aptitude on backward digit span and Flanker's reaction time (p<0.05). Discriminant function analyses showed that the groups could be effectively (accuracy, 80%) segregated based on the backward digit span and Flanker's selective attention test. Trained musicians and nonmusicians with good musical aptitude were distinguished as one cluster and nonmusicians with low musical aptitude formed another cluster, hinting the role of musical aptitude in working memory and selective attention. Conclusions: Nonmusicians with good musical aptitude can have enhanced working memory and selective attention skills like musicians. Hence, caution is required when these individuals are included as controls in cognitive-based visual and auditory experiments.

• Journal of Audiology & Otology
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• 제25권4호
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• pp.178-188
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• 2021

Background and Objectives: The influence of musical aptitude on cognitive test performance in musicians is a long-debated research question. Evidence points to the low performance of nonmusicians in visual and auditory cognitive tasks (working memory and attention) compared with musicians. This cannot be generalized to all nonmusicians, as a sub-group in this population can have innate musical abilities even without any formal musical training. The present study aimed to study the effect of musical aptitude on the working memory and selective attention. Subjects and Methods: Three groups of 20 individuals each (a total of 60 participants), including trained-musicians, nonmusicians with good musical aptitude, and nonmusicians with low musical aptitude, participated in the present study. Cognitive-based visual (Flanker's selective attention test) and auditory (working memory tests: backward digit span and operation span) tests were administered. Results: MANOVA (followed by ANOVA) revealed a benefit of musicianship and musical aptitude on backward digit span and Flanker's reaction time (p<0.05). Discriminant function analyses showed that the groups could be effectively (accuracy, 80%) segregated based on the backward digit span and Flanker's selective attention test. Trained musicians and nonmusicians with good musical aptitude were distinguished as one cluster and nonmusicians with low musical aptitude formed another cluster, hinting the role of musical aptitude in working memory and selective attention. Conclusions: Nonmusicians with good musical aptitude can have enhanced working memory and selective attention skills like musicians. Hence, caution is required when these individuals are included as controls in cognitive-based visual and auditory experiments.

• 한국안전학회지
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• 제32권4호
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• pp.66-72
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• 2017

Recently, the use of high-strength concrete is increasing due to the trend of constructing high-rise and long span structures. The benefit of using the high-strength concrete is that it increases the durability and strength while it reduces the cross-sectional area of the bridge deck slabs. Moreover, it offers more safety as these bridge deck slabs applying high-strength requires strict structural performance verification. In this study, the fatigue performance of the bridge deck slabs applying 80 MPa high-strength concrete was verified through various experiments. The experimental results showed that the specimens satisfy the conditions of flexural strength, punching shear strength, deflection and cracking. In conclusion, the bridge deck slabs designed by 80 MPa high-strength concrete are enough safe despite of its low thickness.

• 대한인간공학회지
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• 제32권6호
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• pp.503-509
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• 2013

Objective: The purpose of this study is to analyze the individual finger force between dominant hand and non-dominant hand and to investigate an effect of the individual finger on the total grip strength depending on dominant hand and non-dominant hand. Background: Many studies on the ratio of the grip force between dominant hand and non-dominant hand has been researched. While a 10% rule which is a ratio of the grip force between dominant hand and non-dominant hand has been applied in most studies, studies on the rate of the individual finger force between dominant hand and non-dominant hand have been insufficiently researched. Method: The experiment was preceded with 17 subjects (male, mean 25.8 ages). The individual finger force and total grip strength were measured using pliers being able to change the grip span from 45 to 80mm. Results: The difference of total grip strength between dominant hand and non-dominant hand is following 10% rule. However, the difference of individual finger force between dominant hand and non-dominant hand are not same as the difference of total grip strength. Especially in the case of grip span with 50mm, the differences between total grip strength, index finger, middle finger, ring finger, and little finger were $9.87{\pm}14.80%$, $8.95{\pm}37.17%$, $13.71{\pm}28.27%$, $6.77{\pm}24.35%$, $39.29{\pm}42.46%$, respectively, with p=0.018 of statistical significance. Additionally, the results of regression analysis in 50 and 60mm of grip span showed that the difference in ring finger affected the most to the total grip strength; and the effects followed in order of index finger, middle finger, and little finger. Conclusion: Our study suggests that an effect of individual finger and grip span of pliers have to be considered when explaining the difference of the total grip strength between dominant hand and non-dominant hand. Application: This result is expected to be used for designing ergonomic hand tool.