• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.12
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• pp.881-887
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• 2015

The stiffness and natural frequencies for blades, flexbeam, and torque tube of bearingless rotor system are measured to determine the material input properties such as mass distributions and stiffness distribution for the rotor dynamics and load analysis. The flap stiffness, lag stiffness, and torsional stiffness are calculated by measuring section strain or twist angle, gages position, and applied loads through bending and twist tests. The modal tests are undertaken to find out the natural frequencies for flap, lag, torsion modes in non-rotating conditions. The stiffness values and mass properties are tuned and updated to match prediction frequencies to the measured frequencies. The rotorcraft comprehensive code(CAMRAD II) is used to analyze the natural frequencies of the specimens. The analysis results with the updated material properties agree well with the measured frequencies. The updated properties will be used to analyze the rotor stability, dynamic characteristics and loads for the rotor rotation test in a whirl tower.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.39-47
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• 2005

Fiber reinforced soils have recently implemented to fills and base layers of highways and railroads, and deformation behaviors of reinforced soils in turn should be investigated. The paper evaluated deformation characteristics of fiber reinforced sands and their effectiveness of reinforcement using resonant column tests. The specimens were prepared by varying gradation and mixing polypropylene staple fibers of 0.3% fiber content. Maximum shear moduli of reinforced sands were increased by up to 30% with increasing uniformity coefficient. Shear moduli of well-graded reinforced sands were larger than those of poorly-graded ones regardless of confining pressure in the whole range of shearing strain and reinforcement was, in turn, more effective with higher uniformity coefficient.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.67-89
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• 2007

This study addresses manufacturers' ability to influence their supply chain network in order to adapt to their competitive environment. From the perspective of a manufacture, the supply chain comprises a network of suppliers and customers, and is theoretically viewed as a complex adaptive system. This study considers the following questions: (1) How can adaptability of supply chain network be operationally defined? (2) How does adaptability of supply chain network lead to combinative capabilities? (3) What is the influence of adaptability of supply chain network on business performance? Drawing on literature streams in supply chain management, operations strategy, organizational change and learning, and complexity theory, this study develops and tests the constructs and operational measures of adaptability of supply chain network and model the nomological set of relationships among constructs that form the basis of our theory. This study then develops and tests a model describing the outcomes of adaptability of supply chain network and its influence on combinative capability and business performance. Empirical results of this study show that adaptability supply chain network directly and positively affects combinative capability. Further, this study finds that adaptability of supply chain network does not impact business performance directly, but rather is mediated through combinative capability, which provides the requisite variety for firms to survive and thrive in dynamic environments.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1708-1711
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• 2007

This paper presents high cycle fatigue properties of an Al-3%Ti thin film, used in a RF (radio-frequency) MEMS switch for a mobile phone and also describes new test method for obtaining static and dynamic characteristics of thin film and reliability evaluation method on MEMS device with thin film developed by authors. Durability should be ensured for such devices under cycling load. Therefore, with the proposed specimen and test procedure, tensile and fatigue tests were performed to obtain mechanical and fatigue properties. The specimen was made with dimensions of $1000{\mu}m$ long, $1.0{\mu}m$ thickness, and 3 kinds of width, 50, 100 and $150{\mu}m$. High cycle fatigue tests for each width were also performed, from which the fatigue strength coefficient and the fatigue strength exponent were found to be 193MPa and .0.02319 for $50{\mu}m$, 181MPa and -0.02001 for $100{\mu}m$, and 164MPa and -0.01322 for $150{\mu}m$, respectively. We found that the narrower specimen is, the longer fatigue life of Al-3%Ti is and the wider specimen is, the more susceptible to stress level fatigue life of Al-3%Ti was.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.232-237
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• 2007

The deformation of polymers under high loading-rate conditions will be a governing factor to be considered in their impact-resistant applications such as protective shields and transparent armor. In this paper, the deformation and fracture behaviors of polymeric materials such as PE, PC and PEEK have been investigated by Taylor Impact tests. Taylor cylinder impact tests and high speed photography are introduced to examine the deformation behavior under dynamic loading condition. 20 mm air gun was used to perform the impact experiments. Cylindrical projectiles have been impacted onto a hardened steel anvil at a velocity ranging from 100 to $350\;ms^{-1}.$ Along the barrel line, a photo-sensor which measures the speed of the projectile, four digital cameras which has shutter speed of 1/917,000sec and a rigid anvil were set up. After impact experiments, the shapes of projectiles and images taken using high speed cameras were analysed. Depending on materials adopted, they showed a variety in deformation and fracture behaviors.

• Journal of KSNVE
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• v.8 no.2
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• pp.331-335
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• 1998

A design modification was made on the 9-th stage wheel dovetail of a high-intermediate pressure (HIP) turbine rotor for a fossil power plant that necessitates the use of new long-shank buckets for the row. A bucket vibration test is necessary to verify that the new 9-th stage buckets have adequate frequency margin from a nozzle passing frequency when running at speed. A finite element analysis (FEA) has been performed using a commercial S/W to approximately estimate bucket natural frequencies, and thus to help the vibration test. A row of the new buckets has assembled on the HIP rotor for the vibration tests using dynamic balancing facilities. The tests have been done during deceleration run with air excitation. The test results are compared with the calculation using our empirical formula, and show that the modified design meets the frequency-margin requirements.

• Environmental and Resource Economics Review
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• v.18 no.1
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• pp.105-138
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• 2009

This study investigates the spatial distribution of the degree of water pollutants in Han River using data obtained by the water pollution observation stations. This study estimates a non -parametric kernel density function for each water pollutants, and tests a significant difference between two estimated distribution functions. Next, Generalized Entropy inequality indices are evaluated and this research tests difference of inequality indices between two years using bootstrapping method. Lastly in a dynamic of view, it is analyzed that there are significant changes in the ranking of water pollution level. Estimation results show that the degree of inequality in spatial distribution of water pollution tends to be stable or decreasing for last 15 years in a great part of water pollutants, and ranking of water pollution level hardly changes in Han River.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.5
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• pp.524-536
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• 2015

The paper aims to design and verify tearing tube type energy absorption device applied in tram to ensure safety in case of collision accident. Energy capacity of tearing tube is determinated based on EN15227 and Standard Collision Scenarios Criterion in Detail in Republic of Korea. Tearing tube is designed based on theoretical model suggested by X.Huang et al. and assumption by T.Y. Reddy et al. Real scale collision tests are conducted to analyze the energy absorption characteristics and deformation mode. Bending of curl tips is absorbed collision energy when curl tips and tube body are contacted to each other from the tests and we suggest and include the formula on bending of curl tips in theoretical model.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.771-780
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• 2017

In this study, free vibration and damping behaviors of multilayered symmetric sandwich beams and single layered beams made of Functionally Graded Materials were investigated, experimentally and numerically. The beams were composed of Aluminum and Silicon Carbide powders and they were produced by powder metallurgy. Three beam models were used in the experiments. The first model was isotropic, homogeneous beams produced by using different mixing ratios. In the second model, the pure metal layers were taken in the middle of the beam and the weight fraction of the ceramic powder of each layer was increased towards to the surfaces of the beam in the thickness direction. In the third model, the pure metal layers were taken in the surfaces of the beam and the weight fraction of the ceramic powder of each layer was increased towards to middle of the beam. Then the vibration tests were performed. Consequently, the effects of stacking sequence and mixing ratio on the natural frequencies and damping responses of functionally graded beams were discussed from the results obtained. Furthermore, the results obtained from the tests were supported with a finite-element-based commercial program, and it was found to be in harmony.

• The Journal of Asian Finance, Economics and Business
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• v.5 no.2
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• pp.15-24
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• 2018

The study examines the magnitude of economic spillover and the impact of foreign direct investment (FDI) inflows on the efficiency of the bank industry in China. This study employs unit root tests, cointegration tests and cointegrating regression analysis, including fully modified ordinary least squares (FMOLS), canonical cointegrating regression (CCR) and dynamic OLS (DOLS) to test the proposed hypotheses. The sample is restricted to the period of time in which monthly data is available and comparable among variables for the period from January 2002 to October 2013 (142 observations). All of the time series data was collected and retrieved from the People's Bank of China, China Monthly Statistics from the National Bureau of Statistics of China, and International Financial Statistics database from International Monetary Fund. The results of the Johansen cointegration test suggest that there is a long-run equilibrium relationship between FDI inflows, foreign exchange rate and banks performance in China. The results of cointegrating regression analysis using FMOLS, CCR and DOLS suggest that M2 supply and FDI inflows are significant at the 0.01 level. The results confirm that FDI inflows in the banking sector are positively related to the increase of banks productivity and performance and short-term loans in China. However, the results suggest that Chinese Yuan currency exchange rate to U.S. dollar is not significant in the banking and financial industry of China.