• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1217-1220
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• 1987

We have developed a Ultra Sound Pulsed Doppler System with two-dimensional M-mode image and Spectrum analyzer. The image of the M-mode is composed of time and depth axes. The Spectrum analyzer shows the spectrum of Doppler signal which represents the velocity component of time dependent blood-flow behavior. The spectrogram using Spectrum analyzer is composed of frequency and amplitude axes. The outputs of the system are audio signals, velocity curves, velocity profiles, M-mode images and spectrogram.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.5
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• pp.213-219
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• 2014

The source parameters of four earthquakes with magnitude larger than 4.0 nearby the offshore Sinan are analyzed. The waveform inversion method is used for analyzing the source parameters of two events (20 August 2012 and 21 April 2013) with C&B and AK135-c crustal velocity structure models. The source parameters of the other two events (26 July 1994 and 23 March 2003) are obtained from references. Focal mechanisms of the events are strike slip faulting or strike slip faulting with a thrust component. The directions of P-axes of the events are ENE-WSW or NE-SW which are similar to previous studies on P-axes in and around the Korean peninsula. With regard to the events nearby the offshore Sinan, the regional stress, rather than being local stress, is seen to be the result of the combination of tectonic forces from the compression of plates colliding to the Eurasian Plate.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.36.3-36.3
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• 2008

KARI (Korea Aerospace Research Institute) is going to launch a Communication, Ocean and Meteorological Satellite (COMS) at summer of 2009. It will be first thing to be developed for a geostationary satellite through domestic technology. Of course, KARI has performed this development program with EADS Astrium in France since 2005. COMS has the non-symmetric configuration that the solar array is only attached on the south panel. Due to the configuration, momentum of satellite will be rapidly accumulated induced by solar pressure and then 3 wheels of large momentum are located on roll-yaw plane for attitude control. Therefore, to prevent the saturation of wheel momentum, wheel off-loading will be performed two times per day during 10 minutes for each one. At the moment, translation movement on 3-axes direction appears because of using thrusters. In this paper, strategy of the wheel off-loading and triaxiality which is the translation effect on 3-axes are introduced. Consequently, the result of optimized triaxiality considering the wheel off-loading strategy is summarized.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.229-232
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• 2000

This research aims at developing a low-cost PC-NC system based on one-CPU and investigating the feasibility of its application to a simple-function lathe. Its hardware consists a two axes motion control board including a 24bit counter, 8253 timer, a 12bit DA converter, DIO board for PLC operation and a PC with Intel Pentium 466MHz. The fundamental real-time MC functions such as G-code interpretation, interpolation, position and velocity control of axes are performed. User programming interface with functions of icon manipulation, tool-path simulation and NC-code generation was implemented. In order to achieve real-time control and safety, axis control, NC interpretation, interpolation and user communication are completely executed during every interrupt interval of I msec.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.190-199
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• 1993

In this study a three-axes mobile robot which has two independently controlled driving wheels and a function of simultaneously steering the driving wheels has been developed. Two-motion modes of the mobile robot, the first is a differential velocity motion of two driving wheels and the second is a equal driving and steering motion, have been analyzed and the kinematic and dymanic analyses about the each motion mode have been carried out. As a result of dynamic analysis, the torque used on a motor control and acceleration have been derived explicitly. Hence, a computation time is saved effectively and a real time control of the mobile robot considering the dynamics has become possible. Through a simulation the results considering the dynamics have been compared with that no regarding the dynamics and the possibility of real-time control has been proved.

• Korean Journal of Applied Biomechanics
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• v.21 no.4
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• pp.449-458
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• 2011

There are many functional methods for estimating the mean axis of rotation of a joint. However, it is still a controversial issue which method is superior. The purpose of this study was to compare functional methods for estimated axes of rotation from synthetic data. The comparison was made in terms of suitabilities on describing humans in sports. For a more practical situation, the axis error as well as measurement and marker movement error were applied to generated data. Simulations having 1000 times of 80 rotational displacements were performed. The functional methods used in the study were two transformation methods, two fitting methods, and one more transformation method called M. The M method is a combination of S$\ddot{o}$derk & Wedin(1993) and Mardia & Jupp(2000). Another factor of the study was angular velocity with levels of .01, .025, .05, .5 and 1 rad/s. The method M resulted in unbiased, stable, and consistent axis of rotation vectors in all levels of angular velocity except .01 rad/s. Therefore, the method M had the highest validity and reliability of all the methods. The fitting methods were very sensitive in small angular velocities and stable only in the velocities of more than .5 rad/s. The most suitable method for analyzing human motion by using marker photogrammetry is M.

• The Journal of Engineering Geology
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• v.13 no.2
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• pp.257-266
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• 2003

Jurassic granites of three sites, Pocheon, Geochang and Habcheon, were tested to investigate the effect of microcracks on Physical and mechanical properties of the granites. Fifteen oriented core specimens were used for the physical property test. The test result shows that porosity is almost proportioned to water content. P-wave velocity is the highest in the direction of axis ‘H’, intersection of two major microcrack sets and the lowest in the axis ‘R’, normal to the rift plane. Compressional strength tests were carried out for each core specimen taken parallel with axes ‘R’, ‘G’ and ‘H’, measuring strains. The results revealed a strong correlation between microcrack orientation and other mechanical properties such as rock strength.

• The Journal of the Acoustical Society of Korea
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• v.16 no.6
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• pp.61-67
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• 1997

Piezoelectric gyroscopes are the devices to measure angular rotational velocity of a system with respect to an inertial frame of reference means of the Coriolis principle. Most of current piezoelectric gyroscopes detect rotational velocity about a single axis of rotation. This paper describes development of a new dual axial gyroscope made out of the piezoelectric ceramic, PZT, which can overcome the limitation of the current single axial type. The validity of the new structure is checked through finite element analysis. Based on the design, an experimental sample of the sensor is fabricated and its performance is discussed in comparison with the theoretical expectation. The resutls show that the present gyroscope is capable of measuring the rotational velocity over two orthogonal axes simultaneously with good enough sensitivity and distinction between the two axial components of the rotation.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.2
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• pp.116-124
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• 2008

Current paper investigates the dynamic behavior and stability of an infrared search and track subjected to external disturbance having gimbal structure with three rotating axes keeping constant angular velocity in the azimuth direction. Euler-Lagrange equation is applied to derive the coupled nonlinear dynamic equation of motion of infrared search and track and the characteristics of dynamic coupling are investigated. Two equilibrium points with small variations from the nonlinear coupling system are derived and the specific condition from which a coupled equation can be three independent equations is derived. Finally, to examine the stability of system, Lyapunov direct method was used and system stability and stability boundaries are investigated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1866-1870
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• 2005

Typical small desktop robots have limied application due to their intrinsic feaures like friction, backlash, etc. However, a newly developed small gantry desktop robot needs smaller footprint and shows better performance in position accuracy, velocity, and acceleration. In order to achieve such results, synchronization control of two axes, position compensation methods in plane are suggested.