• 한국기계가공학회지
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• 제20권6호
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• pp.51-58
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• 2021

The notion of leisure has changed with industrial development and improvement in life quality. Bicycling is a healthy sport; it is an exercise performed while enjoying nature. There have been many changes in the materials that are used to manufacture the bicycle frame. Iron and aluminum have been mainly used in bicycle frames. However, carbon-based materials are lighter and stronger than metal frames. The bicycles made of carbon composite changes frame rigidity depending on the direction of the carbon sheet sacking angle. We study the direction of composite material and how they affect the stiffness of frames based on the stacking angle.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.353-360
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• 2017

This study presents the Big Bang and Big Crunch (BB-BC) optimization algorithm for detection of structure damage in large severity. Local damage is represented by a perturbation in the elemental stiffness parameter of the structural finite element model. A nonlinear objective function is established by minimizing the discrepancies between the measured and calculated acceleration responses (AR) of the structure. The BB-BC algorithm is utilized to solve the objective function, which can localize the damage position and obtain the severity of the damage efficiently. Numerical simulations have been conducted to identify both single and multiple structural damages for beam, plate and European Space Agency Structures. The present approach gives accurate identification results with artificial measurement noise.

• 한국운동역학회지
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• 제33권3호
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• pp.101-109
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• 2023

Objective: The aim of this study is to verify the differences in muscle characteristics of elite level swimmers before and after a 2-hour practice session. Method: The study was conducted on 15 elite swimmers. Preliminary measurements for each muscle (Anterior Deltoid, Triceps Brachii, Biceps Brachii, Flexor Carpi Ulnaris) were taken using the MyotonPRO device before training. After approximately 2 hours of training, the same muscle areas were measured again. The collected data was analyzed through descriptive statistics and two-way 2×2 RG·RM ANOVA, and all statistical significance levels were set at α=.05. Results: After analyzing the characteristics of the Flexor Carpi Ulnaris (FCU) before and after training in both proficiency level swimmers (excellent, non-excellent), it was found that the interaction effect of group X repetition in muscle tension (F), muscle stiffness (S), and body recovery time (R) was statistically significant. Secondly, in the analysis of the Biceps Brachii (BB), the main effect of repetition in muscle tension (F), muscle stiffness (S), and body recovery time (R) was statistically significant. Furthermore, the interaction effect of group X repetition in muscle stiffness (S) and body recovery time (R) was statistically significant. Conclusion: The efficient use of FCU and BB suggests that it is an important factor distinguishing the performance of excellent and non-excellent swimmers in swimming. Therefore, if we develop and apply measures to efficiently utilize FCU and BB during training, it can help improve the performance of the athletes.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.735-745
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• 2018

The Big Bang-Big Crunch (BB-BC) algorithm is an effective global optimization technique of swarm intelligence with drawbacks of being easily trapped in local optimal results and of converging slowly. To overcome these shortages, an improved BB-BC algorithm (IBB-BC) is proposed in this paper with taking some measures, such as altering the reduced form of exploding radius and generating multiple mass centers. The accuracy and efficiency of IBB-BC is examined by different types of benchmark test functions. The IBB-BC is utilized for damage detection of a simply supported beam and the European Space Agency structure with an objective function established by structural frequency and modal data. Two damage scenarios are considered: damage only existed in stiffness and damage existed in both stiffness and mass. IBB-BC is also validated by an existing experimental study. Results demonstrated that IBB-BC is not trapped into local optimal results and is able to detect structural damages precisely even under measurement noise.