• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.846-855
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• 2020

A loose part monitoring system is used to detect unexpected loose parts in a reactor coolant system in a nuclear power plant. It is still necessary to develop a new methodology for the localization and mass estimation of loose parts owing to the high estimation error of conventional methods. In addition, model-based diagnostics recently emphasized the importance of a model describing the behavior of a mechanical system or component. The purpose of this study is to propose a new localization and mass-estimation method based on finite element analysis (FEA) and optimization technique. First, an FEA model to simulate the propagation behavior of the bending wave generated by a metal sphere impact is validated by performing an impact test and a corresponding FEA and optimization for a downsized steam-generator structure. Second, a novel methodology based on FEA and optimization technique was proposed to estimate the impact location and mass of a loose part at the same time. The usefulness of the methodology was then validated through a series of FEAs and some blind tests. A new feature vector, the cross-correlation function, was also proposed to predict the impact location and mass of a loose part, and its usefulness was then validated. It is expected that the proposed methodology can be utilized in model-based diagnostics for the estimation of impact parameters such as the mass, velocity, and impact location of a loose part. In addition, the FEA-based model can be used to optimize the sensor position to improve the collected data quality in the site of nuclear power plants.

• Journal of the Korean Wood Science and Technology
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• v.40 no.6
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• pp.431-444
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• 2012

Constituents of timber framed floor affect the insulation performance against impact sound significantly. Among them, installation of massive sound absorbing layer and reinforcement of stiffness of timber floor have been considered as major factors that improve the insulation performance against impact sound. Researches on evaluating the effect of floor constitutions have been carried out through the field measurements for timber framed buildings in Korea. It is concluded that the impact sound pressure level at the relatively lower frequency governs the overall insulation performance, and can be improved by the installation of sound absorbing layer and reinforcement of floor stiffness. Especially, the insulation performance against heavy impact sound was improved significantly when the massive cement mortar layer for floor heating system was installed and the stiffness was reinforced by shortening the joist span using additional beam at the mid-position of original span.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.89-99
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• 2007

The stiffness of the asphalt concrete is represented by the complex modulus $E^*$, which is very important properties in the mechanistic design of flexible pavement system. The moduli of asphalt concrete were generally determined by dynamic modulus test. However, the dynamic modulus testing method is too complex, expensive, and time consuming to be applicable on a production basis. The IR(Impact Resonance) method has been shown to be a truly simple nondestructive testing method which produces very repetitive, consistent results. The major object of this study was to estimate of the effects on IR tests for determining modulus of asphalt concrete including impact position, specimen support condition, impact steel ball size and sampling rate. The variations of IR test results with various testing conditions are within ${\pm}2.7%$.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.1072-1076
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• 2001

A biomechanical study was conducted in this study to investigate if in-line skating wrist guards can effectively reduce the impact forces so as to protect the wrist from fracture. The forearm specimens with and without wrist guards were dropped using a specially designed sled to simulate the impact on the wrist while falling. A force plate was used to measure the total impact force on the dropping weight whereas a load cell was attached to the proximal end of the specimen and used to quantify the impact transmitted through the wrist joint. From the non-destructive tests, mean peak force measured from a force plate showed no difference between the guarded and unguarded groups whereas mean impulse of the guarded group was significantly greater than that of the unguarded group (p<0.01). Comparing the peak force and impulse measured from the load cell, the peak force of the guarded group was significantly less than that of the unguarded group (p<0.001), while the impulse values were similar. When the specimens were dropped from a higher position (2.5ft ve. 1ft), all unguarded specimens had severe wrist fractures whereas fracture was found in three out of 5 guarded specimens. Comparison of mean peak forces and impulses showed as significant difference between the guarded and unguarded groups only in the mean impulse measured from the force plate. These results suggest that the wrist guard may protect the wrist by attenuating the peak force transmitted to radius and ulnar although it may not be effective when the wrist is subjected to an impact sufficiently large to cause fractures.

• Proceedings of the KOR-KST Conference
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• 1996.06a
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• pp.3-22
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• 1996

To translate the goal of redeveloping Shanghai as one of the international hubs of economy, finance and trade in 2010, the foundation is to be created, and international standing as global city is to be established preliminarily. Transformation of urban functions and approach of "High starting position and jump over" will give impetus to promote Shanghai as an international metropolitan within fairy short period of time. To transform urban functions and translate" High starting position and jump over", certain links which have great impact on Shanghai's rising-up must be handled and normal approach to develop the city must be renovated to reach the goal of establishing an international city. Four strategic approaches as following are explored in this paper : $\bullet$ To transform urban function from industry only to integrated developments. $\bullet$ To break through administrative boundary and expand urban development space. $\bullet$ To develop centralized urban infrastructure framework. $\bullet$ And to erect modern life and culture facilities towards 21st century.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.768-778
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• 1998

Human beings usually absorb a shock from terrain during walking through the damping effects of joints, muscles and skin. With this analogy, a robot-leg with a shock absorber is built to absorb the impact forces at its foot during high-speed walking on irregular terrain. To control the hip position while walking, the dynamic controller suitable for high speed walking is designed and implemented based on a dynamic model by Kane's equation. The hip position tracking performances of various controllers (PID controller, computed torque controller and feedforward torque controller) are compared through the experiments of the real robot-leg.

• Journal of KSNVE
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• v.7 no.3
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• pp.393-399
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• 1997

This study proposes a methodology with which the optimal damper positions of the feeding system in a CD-ROM drive are determined to removal the harmful tilting vibration modes. For this purpose, vibration characteristics of the feeding system are identified by a theoretical modeling as well as vibration experiments. We perform the modal testings using the impact hammer and shaker; furthermore, we establish a vibration model due to the rigid-body motion. The analysis and experiments show that the feeding system has three rigid-body vibration modes in the low-frequency region and two of them come from the tilting modes. We show that the tilting modes can be removed by determining the damper positions.

• International Commerce and Information Review
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• v.11 no.1
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• pp.379-403
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• 2009

The Purpose of this study is to research the problems of trade restriction for an environment protection. Environmental regulation relate to trade are Convention on International Trade in Endangered Species of Wild Fauna & Flora, Montreal Protocol on Substances that Deplete the Ozone Layer, Kyoto Protocol to the UN Framework Convention on Climate Change, Basel Convention on the Control of Transboundary Movements of Hazardous Wastes & Their Disposal, Cartagena Protocol on Biosafty and WTO Agreement. Regulatory action for environmental protection has economics instrument, command & control, liablity, damage compensation, voluntary agreement. In the case of our country, impact of regulatory action for environmental protection is low. Because is recognized position of developing country yet. For in the balance rules of trade and enviroment, First must satisfy WTO's basic principles and principle of quantitative restrictions prohibition, Second, operation of protection action must reasonable and objective standards Third, must satisfy GATT article 20 (b) clause and (g) protestation each essential factor To grow for environment advanced country, we should do i) using of FTA ii) international cooperation strengthening for developing country position iii) construction of environment information network

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2132-2143
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• 2015

This paper presents two distance geometry-based algorithms for wireless location in cellular network systems-distance geometry filtering (DGF) and distance geometry constraint (DGC). With time-of-arrival range measurements, the DGF algorithm estimates the mobile station position by selecting a set of measurements with relatively small NLOS (non-line-of-sight) errors, and the DGC algorithm optimizes the measurements first and then estimates the position using those optimized measurements. Simulation results show that the proposed algorithms can mitigate the impact of NLOS errors and effectively improve the accuracy of wireless location.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.192-194
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• 2006

Backlash between meshing gear teeth causes impact, tracking error and undesired vibrations. It is usually minimized by precision gear, spring-loaded anti-backlash gears and precise mechanical adjustment. Although these techniques can help to reduce the backlash gap, its cost is relatively high and performance is limited. And the classic controller is insufficient to control the dynamic system with nonlinearity. For these reason, a fuzzy controller is proposed to compensate the backlash effect at a robot system. The input variables are position error and change in error. The output variable can be defined by input voltage of motor. The performance of a fuzzy controller is verified by comparing with a PID controller. The results show that the undesired vibration is suppressed. And then diminishing the position error is observed.