• Journal of the Korean Society for Precision Engineering
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• v.16 no.4 s.97
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• pp.64-70
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• 1999

A new multi-beam optical system is presented on the grounds of tri-positioning systems in this paper. The system has been developed to improve the data transfer rate for the optical disk system. The actuating system is composed of a tracking and focusing actuating system basically and a newly developed beam rotating actuator. The beam rotating actuator is employed in a multi-beam optical system to trace more than one track simultaneously. The multi-beam optics is established through the optical simulation and several experimental trials. The differential phase tracking method is used in the tracking error signal detection based on the only one beam spot. We also analyze the characteristics of multi-beam optical system. The experimental result shows that the multi-beam positioning system has performance adequate to the multi-beam optical disk system.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.501-508
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• 2001

Free vibration analysis of multi-delaminated composite beam-columns subjected to axial compression load is performed in the present study. In order to investigate the effects of multi-delaminations on the natural frequency and elastic buckling load of multi-delaminated beam-columns, the general kinematic continuity conditions are derived from the assumption of constant slope and curvature at the multi-delamination tip. Characteristic equation of multi-delaminated beam-column is obtained by dividing the global multi-delaminated beam-columns into segments and by imposing recurrence relation from the continuity conditions on each sub-beam-column. The natural frequency and elastic buckling load of multi-delaminated beam-columns according to the incremental load of axial compression, which is limited to the maximum elastic buckling load of sound laminated beam-column, are obtained. It is found that the sizes, locations and numbers of multi-delaminations have significant effect on natural frequency and elastic buckling load, especially the latter ones.

• Laser Solutions
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• v.18 no.4
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• pp.12-16
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• 2015

The research on multi electron beam systems is being carried out by various methods. We are studying multi electron beam system using miniaturized electron beam columns. The column consists of electrostatic lenses, electrostatic deflector and tip emitter. Our operating system controls 4 column array, captures images of each column and maintains the instrument. We present the usefulness of our operating system for multi columns by capturing images of each column.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.199-207
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• 2003

The Timoshenko beam model has been known as the most accurate model for representing beam structures. However, the Timoshenko beam model may give rise to a significant error when it is applied to multi-stepped beam structures. This paper is intended to demonstrate the modeling error of Timoshenko beam based finite element model for multi-stepped beam structures and to suggest a new modeling method to improve the accuracy. A tentative bending spring is introduced into the stepped section to represent the softening effect due to the presence of step. This paper also proposes a finite element modeling method in the light with the tentative bending spring model for the step softening effect. The proposed method rigorously adapts computation results from a commercial finite element code. The validity of the proposed method is demonstrated through a series of simulation and experiment.

• Journal of the Korea Society of Computer and Information
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• v.16 no.8
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• pp.129-135
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• 2011

In this paper, we propose a multi target's elevation angle estimation method using multi beam forming technique. This method make a stacked beam to digital processing a received signal in array element. There can be desired receiving beam to application weight value at antenna element in beam forming. Currently, we are to make multi stacked beam using fast fourier transform in stead of phase shifter to be a computer performance much improvement. Also, we improve multi beam directivity using beam steering error correction technique in order to beam steering to desired direction in receiver. Through simulation, we show that the proposed elevation estimation method based on fast fourier transform and beam steering error correction technique, improves th performance of target estimation compared to previous method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2058-2066
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• 1999

The present paper proposes a new dynamic analysis method for multi-span Timoshenko beam structures supported by joints with damping subject to moving loads. An exact dynamic element matrix method is adopted to model Timoshenko beam structures. A generalized modal analysis method is applied to derive response formulae for beam structures subject to moving loads. The proposed method offers an exact and closed form solution. Two numerical examples are provided for validating and illustrating the proposed method. In the first numerical example, a single span beam with multiple moving loads is considered. A dynamic analysis on a multi-span beam under a moving load is considered as the second example, in which the flexibility and damping of supporting joints are taken into account. The numerical study proves that the proposed method is useful for the vibration analysis of multi-span beam-hype structures by moving loads.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.788-791
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• 2002

The Timoshenko beam model has been acknowledged as the most accurate model for representing beam structures. However, the Timoshenko beam model may give rise to significant error when it is applied to multi-stepped beam structures. This paper is intended to demonstrate and improve the modeling error of Timoshenko beam theory for multi-stepped team structures. A tentative bending spring is introduced to represent the stiffness change around a step in beams. This paper proposes a finite element modeling method in the light with the bending spring. The proposed method is rigorously compared with commercial finite element codes. The validity of the proposed method is also demonstrated through an experiment..

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.3
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• pp.523-534
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• 2002

Free vibration and buckling analysis of multi-delaminated composite beam-columns subjected to axial compressive load is performed in the present study In order to investigate the effects of multi-delaminations on the natural frequency and the elastic buckling load of multi-delaminated beam-columns, the general kinematic continuity conditions are derived from the assumption of constant slope and curvature at the multi-dclamination tip. The characteristic equation of multi-delaminated beam-column is obtained by dividing the global multi-delauunated beam-columns into segments and by imposing recurrence relation from the continuity conditions on each sub-beam-column. The natural frequency and the elastic buck)ing load of multi-delaminated beam-columns according to the incremental load of axial compression, which is limited to the maximum elastic buckling load of sound laminated beam-column, are obtained. It is found that the sizes, locations and numbers of multi-delaminations have significant effect on natural frequency and elastic buckling load, especially the latter ones.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.663-663
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• 2002

The National Oceanographic Research Institute of KOREA started to survey for the basic data necessary to territorial sea and EEZ identification and marine development with Multi-Beam Echo Sounder(L3 SeaBeam 2112) since 1996. The Multi-Beam surveys has provided a very new and precise way of describing the morphology and nature of the underwater seabed. Multi-Beam Echo Sounder systems employ sound waves propagating at angles which vary from vertical to nearly horizontal. The locations on the bottom where echoes are generated cover a swath whose port to starboard width may be equal to many times the water depth. Newer Multi-beam bathymetric sonars provide both a beam by beam depth and backscatter amplitude of the bottom. But The backscattered amplitude didn't use for identification of bottom properties because backscatter amplitude effects by the many environmental variables of underwater and seabed. We investigates the utilization of geo-referenced backscatter amplitude and analysis of relationship between The Backscattered Amplitude and Sidescan Sonar imagery from Sea Beam 2112. For the backscattered amplitude imagery mainly represents the properties of sediment, we computed the beam geometry, time-varied amplifier gain, and mainly incidence angle to the topography using bathymetric model at each ping. In this paper, those issues are illustrated, and the angular independent imagery based on swath topographic model is described.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.25-32
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• 2002

Free vibration analysis of radialiy multi-delaminated beams with through-the-width multi-delamination is performed in the present study. The multiple delaminations are considered to be in a radial manner through the thickness from the top surface of the beam. The natural frequencies of the radially multi-delaminated beams are calculated from a new algorithm that is based on the single compound delaminated beam model. That is, beams with radial multi-delaminations are regarded as the sum of a single compound delamlnated beam that is the single sub-delaminated beam from the top surface of global beam. Each result of frequency equation for the single delaminated beam with unknown boundary conditions obtained through continuity conditions Is updated to the next one, With these sequential operations, the final frequency equation of radially multi-delaminated beams is obtained for both ends boundary conditions of global beam. The numerical results carried out for the beams are compared with those of some references to give the reliance on the proposed algorithm and to investigate the effects of the shape, number, size of multi-delaminations on the natural frequency. Compared with the other previously presented model, the proposed algorithm is more flexible in modeling and formulating as the total array size of frequency equation is always four by four. Therefore, the proposed algorithm will reduce the effort of user in formulating the physical model to the numerical model.