• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.3
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• pp.183-195
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• 2007

MEMS technology is proven to be an enabling technology to realize many components for optical networking applications. Due to its widespread applications, VOA has been one of the most attractive MEMS based key devices in optical communication market. Micromachined shutters and refractive mirrors on top of silicon substrate or on the device layer of SOI (Silicon-on-insulator) substrate are the approaches trapped tremendous research activities, because such approaches enable easier alignment and assembly works. These groups of devices are known as the planar VOAs, or two-dimensional (2-D) VOAs. In this review article, we conduct the comprehensively literature survey with respect to MEMS based planar VOA devices. Apparently MEMS VOA technology is still evolving into a mature technology. MEMS VOA technology is not only the cornerstone to support the future optical communication technology, but the best example for understanding the evolution of optical MEMS technology.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.701-705
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• 1998

The objective of this study is to develop the practical program which can check the constructible possibility of prestressed concrete box girder bridges for design. Checking constructible possibility is defined as checking the interference of each elements in a PSC box girder bridge and computing the distances of each elements. To check the constructible possibility of a PSC box girder bride, bridge must be modelled using solid in three dimension. By using a 3 dimensional solid modeling system, engineers can get the photo realistic 3D viewing images of the bridge and produce FEM analytic model of it. Users can manipulate their drawings easier and take off quantity of the whole structure and its elements as well as check the constructible possibility of their PSC box girder bridges.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.903-905
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• 2000

For an accurate analysis of three dimensional linear magnetostatic problems, a new boundary integral equation formulation is presented. This formulation adopts difference magnetic field concept and uses single layer magnetic surface charge as unknown. The proposed method is capable of eliminating numerical cancellation errors inside ferromagnetic materials. In additions, computing time and storage memory are reduced by 75% in comparison with the reduced and total scalar potential formulation. Two examples are given to show its efficiency and accuracy.

• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.99-102
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• 2006

The electrical characteristics of CMOS inverter with LDMOSFET are studied for high power and digital circuit application by using two dimensional MEDICI simulator. The simulation is done in terms of voltage transfer characteristic and on-off switching properties of CMOS inverter with variation of channel length and channel doping levels. The channel which surrounds a junction-type source in LDMOSFET is considered to be an important parameter to decide a circuit operation of CMOS inverter. The digital logic levels of input voltage show to increase with increase of n-channel length and doping levels while the logic output levels show to the almost constant.

• 한국전산유체공학회:학술대회논문집
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• 2003.08a
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• pp.152-157
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• 2003

As computer capacity has been progressed continuously, the studies of the flow characteristics have been performing by the numerical methods actively. Recent numerical simulation has a tendency to require the higher-order accuracy in time, as well as in space. This tendency is more true in LES and acoustic noise simulation. In this study, 3-dimensional unsteady Incompressible Navier-Stokes equation was solved by numerical method using the fractional step method with the fourth order compact pade scheme to achieve high accuracy To validate the present code and algorithm, 3D flow-field around a cylinder was simulated. The drag coefficient and lift coefficient were computed and, then, compared with experiment. The present code will be tailored to LES simulation for more accurate turbulent flow analysis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.61-66
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• 2010

Pay off reel is the device to release in the form of coil. Every time the device becomes a hassle to exchange, each diameter of two forms has been applied to the coil reel. There is the change of reel diameter of the sleeve portion to be the part of segment geometry. This unit is conducting on 3-dimensional modeling design. The basic strength and deformation of the device could be checked in advance by the basis of 3-d modeling data to perform simulations. The production of each part can be completed and assembled. Conducted for the final product which is tested and measured, all items are satisfied within the limits of targets. Due to the development of this device, the efficiency on operations can be increased and the production time becomes shortened.

• Proceedings of the KSMRM Conference
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• 2002.11a
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• pp.135-135
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• 2002

Purpose： To assess diagnostic accuracy of dynamic contrast enhanced MR mammography in differentiating between benign and malignant lesions. Materials and methods： Ninety-three patients with suspicious mammographic, sonographic or palpable findings underwent pre- or postoperative contrast-enhanced MR imaging of breast using three dimensional fast low-angle shot (3D FLASH) sequence (16/4 msec［repetition time / echo time］, 20 flip angle, 3mm slice thickness with no slice gap, 256 by 256 in-plane matrix) covering whole breasts. T1 weighted images were obtained before and after bolus administration of gadopentetate dimeglumine (0.15 mmol/kg). Subtraction images and time-signal intensity curves of region of interest were obtained sequentially and correlated with pathologic diagnoses of lesions.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.549-555
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• 2009

Based on three-dimensional(3-D) finite element limit analyses, this paper provides limit and TES (Twice-Plastic Load) loads for mitred pipe bends under bending and pressure. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly-plastic materials using the small and large geometry change option. A wide range of parameters related to the mitred bend geometry is considered. Based on the finite element results, closed-form approximations of plastic limit and TES plastic load solutions for mitred pipe bends under bending are proposed.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.29-38
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• 2010

This paper presents a procedure for the design optimization of a centrifugal compressor. The centrifugal compressor consists of a centrifugal impeller, vaneless diffuser and volute. And, optimization techniques based on the radial basis neural network method are used to optimize the impeller of a centrifugal compressor. The Latin-hypercube sampling of design-of-experiments is used to generate the thirty design points within design spaces. Three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model are discretized by using finite volume approximations and solved on hexahedral grids to evaluate the objective function of the total-to-total pressure ratio. Four variables defining the impeller hub and shroud contours are selected as design variables in this optimization. The results of optimization show that the total-to-total pressure ratio of the optimized shape at the design flow coefficient is enhanced by 2.46% and the total-to-total pressure ratios at the off-design points are also improved significantly by the design optimization.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.163-167
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• 2003

A novel method for 3-dimensional dynamic analysis of marine slender structure gas been developed by using Euler parameters. The Euler parameter rotation, which is being widely used in aerospace vehicle dynamics and multi-body dynamics, has been applied to elastic structure analysis. Large deformation of flexible slender structures is described by means of Euler parameters. Euler parameter method is implemented effectively in incremental-iterative algorithm for 3D dynamic analysis. The normalization constraint of Euler parameters is efficiently satisfied by means of a sequential updating method.