• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.169-172
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• 2005

A flywheel system is an electromechanical energy storage device that stores energy by rotating a rotor. The rotating part, supported by magnetic bearings, consists of the metallic shaft, composite rims of fiber-reinforced materials, and a hub that connects the rotor to the shaft. The delamination in the fiber wound composite rotor often lowered the performance of the flywheel energy storage system. In this work, an advanced hybrid composite rotor with a split hub was designed to both overcome the delamination problem in composite rim and prevent separation between composite rim and metallic shaft within all range of rotational speed. It was analyzed using a three-dimensional finite clement method. In order to demonstrate the predominant perfom1ance of the hybrid composite rotor with a split hub, a high spin test was performed up to 40,000 rpm. Four radial strains and another four circumferential strains were measured using a wireless telemetry system. These measured strains were in excellent agreement with the FE analysis. Most importantly, the radial strains were reduced using the hybrid composite rotor with a split hub, and all of them were compressive. As a conclusion, a compressive pressure on the inner surface of the proposed flywheel rotor was achieved, and it can lower the radial stresses within the composite rotor, enhancing the performance of the flywheel rotor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.117-122
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• 2012

A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

• Composites Research
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• v.18 no.1
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• pp.45-54
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• 2005

The delamination in the filament-wound composite flywheel rotor often lowers the performance of the flywheel energy storage system. A conventional ring type hub usually causes tensile stresses on the inner surface of the composite rotor, resulting in lowering the maximum rotational speed of the rotor. In this work, the stress and strain distributions within a hybrid composite rotor were derived from the two-dimensional governing equation with the specified boundary conditions, and an optimum pressure at the inner surface of the rotor was proposed to minimize the strength ratio and maximize the storage energy. A split type hub was introduced to apply the calculated optimum pressure at the inner surface, and a spin test was performed up to 40,000 rpm to demonstrate the performance of the split type hub with radial and circumferential strains measured using a wireless telemetry system. From the analysis and the test, it was found that the split type hub successfully generates a compressive pressure on the inner surface of the rotor, which can enhance the performance of the composite rotor by lowering the strength ratio within the rotor.

• Acta Via Serica
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• v.7 no.1
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• pp.29-52
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• 2022

This study investigates why Khwārazmshāh's rulers abandoned Khwārazm, their capital before the Mongols invaded this city. From a local dynasty in Khwārazm under the Saljuqs, the Khwārazmshāh dynasty (ca.469-628/1077-1231) rapidly expanded in the region. After conquering the Saljuqs (ca.429-590/1037-1194), they extended their territory from Hamedān in western Iran to Samarqand in Transoxiana and beyond that to Otrār to become one of the world's great medieval empires. During this critical time, Khwārazm remained their central hub of power. However, the split in the power of the Khwārazmshāh dynasty under Sultan Muhammad (ca.596-617/1200-1220) contributed to their failure to recognize the strategic role of Khwārazm in retaining and reconstructing their power. In essence, the Khwārazmshāh state was divided before the Mongol Invasion.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.25-31
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• 2013

A blisk with rotor shroud is usually adopted in LRE turbine to maximize its performance. However it experiences the severe thermal load and resulting damage during engine stating and stop. Shroud splitting is devised to relieve the thermal stress on the turbine rotor. Structural analysis confirmed the reduction of plastic strain at the blade hub and tip. However, split gap at the rotor shroud entails additional tip leakage and results performance degradation. In order to assess the effect of shroud split on the turbine performance, tests have been performed for various settings of shroud split. For the maximum number of shroud splitting, measured efficiency reduction ratio was 2.65% to the value of original shape rotor.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.860-880
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• 2024

Breast cancer is a major health concern affecting women and men globally. Early detection and accurate classification of breast cancer are vital for effective treatment and survival of patients. This study addresses the challenge of accurately classifying breast tumors using machine learning classifiers such as MLP, AdaBoostM1, logit Boost, Bayes Net, and the J48 decision tree. The research uses a dataset available publicly on GitHub to assess the classifiers' performance and differentiate between the occurrence and non-occurrence of breast cancer. The study compares the 10-fold and 5-fold cross-validation effectiveness, showing that 10-fold cross-validation provides superior results. Also, it examines the impact of varying split percentages, with a 66% split yielding the best performance. This shows the importance of selecting appropriate validation techniques for machine learning-based breast tumor classification. The results also indicate that the J48 decision tree method is the most accurate classifier, providing valuable insights for developing predictive models for cancer diagnosis and advancing computational medical research.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.129-134
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• 2002

This study is focused on the layout design with sizing for the main propulsion shafting with controllable pitch propeller system. For appropriate design and successful manufacturing of controllable pitch Propeller system, it is based on specifications to be required from the customer as well as the stresses calculation and analysis of main propulsion system for hollow shafting. And it must be performed according to the U.S military specifications MIL-STD-2189(SH) with drawing of NAVSHIPS 803-2145807, and also the stress analysis by applying safety factor. The results are as follows : 1. For the main propulsion system with controllable pitch propeller, it is designed the following items propeller diameter, hub diameter, dimensions of oil distribution or actuating unit based on shaft mounting type, diameters of propeller and intermediate shaft, dimension of split muff coupling, coupling flange thickness and of coupling bolt diameter. 2. As the results, we can get complete our own design ability for the main propulsion shafting with controllable pitch propeller system with critical data which are necessary to establish shafting arrangement from the ship building companies.