• Nuclear Engineering and Technology
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• v.42 no.1
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• pp.55-64
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• 2010

The KIER's Korean historical earthquake catalog was revised for MMI${\geq}$VI events recorded from the years 27 A.D. to 1904. the magnitude of each event was directly determined from the criteria suggested by Seo. The criteria incorporated the damage phenomena of the Japanese historical earthquake catalog, recent seismological studies, and the results of tests performed on ancient structures in Korea. Thus, the uncertainty of the magnitudes of the Korean historical earthquakes can be reduced. Also, the Gutenberg-Richter parameter values were estimated based on the revised catalog of this study. It was determined that the magnitudes of a maximum inland and minimum offshore event were approximately 6.3 and 6.5, respectively. The Gutenberg-Richter parameter pairs of the historical earthquake catalog were estimated to be a=5.32${\pm}$0.21, b=0.95${\pm}$0.19, which were somewhat lower than those obtained from recent complete instrumental earthquakes. No apparent change in the Gutenberg-Richter parameter is observed for the $16^{th}-17^{th}$ centuries of the seismically active period.

• Structural Engineering and Mechanics
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• v.69 no.2
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• pp.205-219
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• 2019

This paper analyzes nonlinear free vibration of the circular nano-tubes made of functionally graded materials in the framework of nonlocal strain gradient theory in conjunction with a refined higher order shear deformation beam model. The effective material properties of the tube related to the change of temperature are assumed to vary along the radius of tube based on the power law. The refined beam model is introduced which not only contains transverse shear deformation but also satisfies the stress boundary conditions where shear stress cancels each other out on the inner and outer surfaces. Moreover, it can degenerate the Euler beam model, the Timoshenko beam model and the Reddy beam model. By incorporating this model with Hamilton's principle, the nonlinear vibration equations are established. The equations, including a material length scale parameter as well as a nonlocal parameter, can describe the size-dependent in linear and nonlinear vibration of FGM nanotubes. Analytical solution is obtained by using a two-steps perturbation method. Several comparisons are performed to validate the present analysis. Eventually, the effects of various physical parameters on nonlinear and linear natural frequencies of FGM nanotubes are analyzed, such as inner radius, temperature, nonlocal parameter, strain gradient parameter, scale parameter ratio, slenderness ratio, volume indexes, different beam models.

• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.97-103
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• 2019

An automated signal-acquisition method for the NASA's space geodesy satellite laser ranging (SGSLR) system is described as a selection of two system parameters with specified probabilities. These parameters are the correlation parameter: the minimum received pulse number for a signal-acquisition and the frame time: the minimum time for the correlation parameter. The probabilities specified are the signal-detection and false-acquisition probabilities to distinguish signals from background noise. The steps of parameter selection are finding the minimum set of values by fitting a curve and performing a graph-domain approximation. However, this selection method is inefficient, not only because of repetition of the entire process if any performance values change, such as the signal and noise count rate, but also because this method is dependent upon system specifications and environmental conditions. Moreover, computation is complicated and graph-domain approximation can introduce inaccuracy. In this study, a new method is proposed to select the parameters via a conditional equation derived from characteristics of the signal-detection and false-acquisition probabilities. The results show that this method yields better efficiency and robustness against changing performance values with simplicity and accuracy and can be easily applied to other satellite laser ranging (SLR) systems.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.5
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• pp.853-859
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• 2022

In this study, we analyzed the instantaneous trajectory generation capability and target arrival rate of a mobile robot by changing the parameter of the TEB (Timed Elastic Band) Local Planner among local planners that affect the instantaneous obstacle avoidance ability of the mobile robot using ROS (Robot Operating System) simulation and real experience. As a result, we can expect a decrease in the target arrival time of the mobile robot through a decrease in the parameter values of the TEB Local Planner's min_obstacle_dist, inflation_dist, and penalty_epsilon. However, if this parameter is reduced too much, the risk of obstacle collision of the moving robot is increases, so it is important to combine the appropriate values to construct the parameter.

• 전자공학회논문지 IE
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• v.48 no.4
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• pp.13-18
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• 2011

In this paper, we have examined electrical characteristics of LDO regulator according to the process variation using a 1 ${\mu}m$ 20 V high voltage CMOS process. The electrical analysis of LDO regulator have been performed with three kind of SPICE parameter sets (Typ : typical, FF : fast, SS : slow) by process variation which cause change of SPICE parameter such as threshold voltage and effective channel length of MOS devices. From simulation results, we confirmed that in case of SS type SPICE parameter set, the LDO regulator has 3.6 mV/V line regulation, 0.4 mV/mA load regulation and 0.86 ${\mu}s$ output voltage settling time. And in case of Typ type SPICE parameter set, the LDO regulatorhas 4.2 mV/V line regulation, 0.44 mV/mA load regulation and 0.62 ${\mu}s$ output voltage settling time. Finally, in the FF type SPICE parameter set, the LDO regulator has 7.0 mV/V line regulation, 0.56 mV/mA load regulation and 0.27 ${\mu}s$ output voltage settling time.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.4
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• pp.52-57
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• 2003

A PID parameter tuning method was presented by the fuzzy singleton inference, based on step response-shaping of plant and experience knowledge of expert. The parameter-tuning has tow levels. The higher level determines modified coefficients for the controller based on operator's tuning know-how for characteristics of plant which can not be modeled. The lower level determines specified coefficients based on characteristics of response by Ziegler-Nickel's bounded sensitivity method. The last level parameters tuning of a PID controller is adjusted which the modified and specified coefficients makes adjustment rule, and is adjusted the proper value to each parameters by fuzzy singleton inference. Moreover, proposed the tuning method can reflex exporter knowledge and operator's tuning know-how and fuzzy singleton inference is rapidly operated.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.7
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• pp.102-111
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• 1997

In this paper, a patern recognition method of surface mount device(SMD) IC using wavelet transform and neural network is proposed. We chose the feature parameter according to the characteristics of coefficient matrix which is obtained from four level discrete wavelet transform (DWT). These feature parameters are normalized and then used for the input vector of neural network which is capable of adapting the surroundings such as variation of illumination, arrangement of objects and translation. Experimental results show that when the same form of feature pattern, as is used for learning, is put into neural network and gained 100% rate ofrecognition irrespective of SMD IC kinds, location and variation of illumination. In the case of unused feature pattern for learning, the recognition rate is 85.9% under the similar surroundings, where as an average recognition rate is 96.87% for the case of reregulated value of illumination. Proosed method is relatively simple compared with the traditional space domain method in extracting the feature parameter and is also well suited for recognizing the pattern's class, position and existence. It can also shorten the processing tiem better than method extracting feature parameter with the use of discrete cosine transform(DCT) and adapt the surroundings such as variation of illumination, the arrangement and the translation of SMD IC.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.69-72
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• 2002

The high temperature deformation behavior of SiCp/2124Al composite and 2124Al alloy was investigated by hot compression test in a temperature ranged $400~475^{\circ}C$ over a strain rate ranged $10^{-3}~1s^{-1}$. The billets of 2124Al alloy and SiCp/2124Al composite were fabricated by vacuum hot pressing process. The stress-strain curve during high temperature deformation exhibited a peak stress, and then the flow stress decreased gradually into a steady state stress with increasing the strain. It was found that the flow-softening behavior was attributed to the dynamic recovery, local dynamic recrystallization and dynamic precipitation during the deformation. The precipitation phases were identified as S' and S by TEM diffraction pattern. Base on the TEM inspection, the relationship between the Z-H parameter and subgrain size was found based on the experiment data. The dependence of flow stress on temperature and strain rate could be formulated well by a hyperbolic-sinusoidal relationship using the Zener-Hollomon parameter.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.1
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• pp.44-54
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• 2015

Breakwaters are the coastal structures constructed either perpendicular (shore connected) or parallel (detached) to the coast. The main function of breakwater is to create a tranquil medium on its leeside by reflecting the waves and also dissipating the wave energy arriving from seaside, resulting in ease of manoeuvrability to boats or ships to their berthing places. Different types of breakwaters are being used at present, such as rubble mound breakwater, vertical wall type breakwater and composite breakwater. The objective of this paper is to investigate reflection coefficients (Kr) and dissipation (loss) coefficients (Kl) for physical models of Quarter circle caisson breakwater of three different radii of 0.550 m, 0.575 m and 0.600 m with S/D ratio of 2.5 (S=spacing between perforations, D=diameter of perforations). The models were tested in the monochromatic wave flume of the department, for different incident wave heights (Hi), Wave periods (T) and water depths (d). It was observed that reflection coefficient increased with increase in the wave steepness (Hi/gT2) and decreased with increase in depth parameter (d/gT2) and hs/d (Height of structure including rubble base/depth of water). The loss coefficient decreased with increase in the wave steepness and increased with increase in depth parameter and hs/d.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.79-86
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• 2007

The Magnus effect measurement apparatus was designed and built for spinning wind tunnel model which would simulate the rotation of projectiles. Prior to the high speed test, the ground functional test and the low speed test were carried out in the Agency for Defense Development's Low Speed Wind Tunnel(ADD-LSWT) at spin rates from about 6,000 to 10,000 rpm. Magnus force and moment were measured on the spinning projectile model at velocity of 100 m/s. It was shown that the Magnus force and moment were linear function of spin parameter. The test results were compared with Magnus test run on the same configuration in the Arnold Engineering Development Center's Propulsion Tunnel 4T(AEDC-4T).