• Journal of Biomedical Engineering Research
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• v.7 no.2
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• pp.169-182
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• 1986

Pulsed ultrasonic Doppler system is a useful diagnostic instrument to measure blood-flow-velocity, velocity profile, and volume-blood-flow. This system is more powerful compare with 2-dimensional B-scan tissue image. A system has been deve- loped and ii being evaluated using TMS 32010 DSP. We use this DSP for the purpose of real-time spectrum analyzer to obtain spectrogram in singlegate pulsed Doppler system and for the serial comb filter to cancel clutter and zero crossing counter to estimate Doppler mean frequency in multigate pulsed Doppler system. The Doppler shift of the backscattered signals is sensed in a phase detector. This Doppler signal corresponds to the mean velocity over a some region in space defined by the ultrasonic beam dimensions, transmitted pulse duration, and transducer ban(iwidth. Multi- gate pulsed Doppler system enable the transcutaneous and simultaneous assessment of the velocities in a number of adjacent sample volumes as a continuous function of time. A multigate pulsed Doppler system processing the information originating from presented.

• Advances in Computational Design
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• v.1 no.1
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• pp.79-86
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• 2016

In this study, the three different meta-heuristics namely the Grey Wolf Optimizer (GWO), Stochastic Fractal Search (SFS), and Adaptive Differential Evolution with Optional External Archive (JADE) algorithms are examined. This study considers optimization of the planer frame to minimize its weight subjected to the strength and displacement constraints as per the American Institute of Steel and Construction - Load and Resistance Factor Design (AISC-LRFD). The GWO algorithm is associated with grey wolves' activities in the social hierarchy. The SFS algorithm works on the natural phenomenon of growth. JADE on the other hand is a powerful self-adaptive version of a differential evolution algorithm. A one-bay ten-story planar steel frame problem is examined in the present work to investigate the design ability of the proposed algorithms. The frame design is produced by optimizing the W-shaped cross sections of beam and column members as per AISC-LRFD standard steel sections. The results of the algorithms are compared. In addition, these results are also mapped with other state-of-art algorithms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.592-596
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• 1996

The CAD/CAM System oriented to StereoLithographic Rapid Prototyping was constructed and developed. The software architecture uses a 586PC running the windows NT operating system. An .STL file brought into the software program can be verified in divers view points and focused for a detail of concern. A variety of Entity was applied to define an array of triangular facets and sliced loops. The system provides Edit, Scale, Orient, Copy and Divide commands to modify .STL model. The NC codes are created according to various laser beam scan pattern and the software show the parts on the platform before they are constructed. This system is written in Visual C and has been proved as a powerful tool for producing solid parts directly from a CAD modelling, using actual applications.

• The Journal of the Acoustical Society of Korea
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• v.25 no.4E
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• pp.142-147
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• 2006

Blind signal separation is known as a powerful tool for enhancing noisy speech in many real world environments. In this paper, it is demonstrated that the performance of blind signal separation can be further improved by combining with a null beamformer (NBF). Cascading the blind source separation with null beamforming is equivalent to the decomposition of the received signals into the direct parts and reverberant parts. Investigation of beam patterns of the null beamformer and blind signal separation reveals that directional null of NBF reduces mainly direct parts of the unwanted signals whereas blind signal separation reduces reverberant parts. Further, it is shown that the decomposition of received signals can be exploited to solve the local stability problem. Therefore, faster and improved separation can be obtained by removing the direct parts first by null beamforming. Simulation results using real office recordings confirm the expectation.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.1005-1008
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• 2002

The authors introduce 3D display systems developed in our laboratories for recent ten years. Those are mainly realized by several technologies in holography: electro-holography. holographic stereogram, holographic optical elements (HOE) and hologram screen. We are currently focusing the development of 3D projection screen without glasses. Powerful directionality of the light beam is required for 3D projection screen unlike 2D type. We succeeded in achieving the superior diffractive efficiency of hologram screen that is based on the advanced volume holography. This technology is extensively useful to retrieve the Bragg condition of volume hologram in the three-dimensional space. Owing to this technology we could establish the principle of multi-view projection screen and have confirmed the case of 4 viewing points.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.E1
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• pp.54-62
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• 2008

Microbeam PIXE, often called micro-PIXE, is one of powerful tools for analyzing a wide range of elements for various samples. Moreover, it has important applications of interest to the atmospheric science. In the present study, a qualitative elemental imagination for various atmospheric environmental species was attempted using micro-PIXE. Especially, in combination with a novel individual droplet collection method and the micro-PIXE analytical technique, the chemical specification of various individual atmospheric samples could be carried out. Here, we briefly introduce the results of an application of micro-PIXE to the study of atmospheric environment. The detailed spatial resolution of multiple elements for various samples like individual ambient particles, individual raindrops, individual fog droplets, and individual snow crystals could be successfully achieved by scanning 2.6 MeV $H^+$ micro beam ($1{\sim}2{\mu}m$) accelerated by 3 MeV single-end accelerator.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.30-34
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• 2015

Residual stresses are inherently introduced into the engineering components during manufacturing including rolling, forging, bending and welding processes. Excessive residual stresses are known to be detrimental to the proper integrity and performance of components. Neutron diffraction has become a well-established technique for the determination of residual stresses in welds. The deep penetration capability of neutrons into most metallic materials makes neutron diffraction a powerful tool for the residual stress measurements through the thickness of the weld specimen. Furthermore, the unique volume-averaged bulk characteristic of the scattering beam and mapping capability in three dimensions is suitable for the engineering purpose. In this presentation, the neutron diffraction measurements of the residual stresses will be introduced and measurement results will highlighted in thick weld plates.

• Applied Microscopy
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• v.46 no.1
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• pp.14-19
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• 2016

Currently, focused ion beams (FIB) are widely used for specimen preparation in atom probe tomography (APT), which is a three-dimensional and atomic-scale compositional analysis tool. Specimen preparation, in which a specific region of interest is identified and a sharp needle shape created, is the first step towards successful APT analysis. The FIB technique is a powerful tool for site-specific specimen preparation because it provides a lift-out technique and a controllable manipulation function. In this paper, we demonstrate a general procedure containing the crucial points of FIB-based specimen preparation. We introduce aluminum holders with moveable pin and an axial rotation manipulator for specimen handling, which are useful for flipping and rotating the specimen to present the backside and the perpendicular direction. We also describe specimen preparation methods for nanowires and nanopowders, using a pick-up method and an embedding method by epoxy resin, respectively.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.669-682
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• 2011

A Chebyshev spectral method (CSM) for the dynamic analysis of non-uniform Timoshenko beams under various boundary conditions and concentrated masses at their ends is proposed. The matrix-based Chebyshev spectral approach was used to construct the spectral differentiation matrix of the governing differential operator and its boundary conditions. A matrix condensation approach is crucially presented to impose boundary conditions involving the homogeneous Cauchy conditions and boundary conditions containing eigenvalues. By taking advantage of the standard powerful algorithms for solving matrix eigenvalue and generalized eigenvalue problems that are embodied in the MATLAB commands, chebfun and eigs, the modal parameters of non-uniform Timoshenko beams under various boundary conditions can be obtained from the eigensolutions of the corresponding linear differential operators. Some numerical examples are presented to compare the results herein with those obtained elsewhere, and to illustrate the accuracy and effectiveness of this method.

• Journal of the Korean Society of Visualization
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• v.18 no.1
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• pp.44-49
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• 2020

Neutron radiography has been widely used in many research areas due to its different characteristics from X-rays. Neutron tomography is a powerful tool because it can clearly show the inside of an object that the eye cannot see. However, generally, commercial software is used for the reconstruction of neutron tomography. It means that maintenance costs are incurred and analysis is inefficient in some cases. In this respect, our own image processing code is required to reconstruct neutron images efficiently. In this study, an image processing code is developed for reconstruction of cross-sectional images from neutron radiography taken from the side of the object. Using the developed code, cross-sectional images of the sample are successfully reconstructed.