• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.11
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• pp.83-89
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• 1997

An optimize delectroabsorption modulator structure is designed for high speed optical communication systems considering the extinction efficiency, operating bandwidth, polarization loss, and wavelength chirping. the operating wavelength region is $1.55\mu\textrm{m}$ and the deep ridge structure is adapted for th eminimum polarization loss. Simulations show that the absorption layer thickness larger than $0.25\mu\textrm{m}$, and the modulator length shorter than $200\mu\textrm{m}$ are required for the bandwidth over 10GHz. To obtain the modulatiron efficiency over 10dB/V, a wavelength detuning needs to be determined less than 40meV.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.136-147
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• 2005

A theoretical design evaluation based on a hydrodynamic transport simulation of strained Si-SiGe on insulator (SSOI) type nMOSFETs is reported. Although, the net performance improvement is quite limited by the short channel effects, simulation results clearly show that the strained Si-SiGe type nMOSFETs are well-suited for gate lengths down to 20 nm. Simulation results show that the improvement in the transconductance with decreasing gate length is limited by the long-range Coulomb scattering. An influence of lateral and vertical diffusion of shallow dopants in the source/drain extension regions on the device performance (i.e., threshold voltage shift, subthreshold slope, current drivability and transconductance) is quantitatively assessed. An optimum layer thickness ($t_{si}$ of 5 and $t_{sg}$ of 10 nm) with shallow Junction depth (5-10 nm) and controlled lateral diffusion with steep doping gradient is needed to realize the sub-50 nm gate strained Si-SiGe type nMOSFETs.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.4
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• pp.7-13
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• 1978

This paper is concerned with the realization of sequential machines using shift-register modules as their memory elements. Other methods were to select shift-registers under the specific conditions and didn't consider the complexity of combinational circuits driving them. By using an integer valued function, all shift-registers with minimum length could be selected and an optimum assignment with lowest complexity could be obtained by comparing the number of input lines of combinational logic circuits driving them.

• ETRI Journal
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• v.31 no.1
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• pp.68-70
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• 2009

In this letter, a parametric analysis of the Fresnel-field antenna measurement method is performed for a square aperture. As a result, the optimum number of Fresnel fields for one far-field point is guided as $M_{opt}=N_{opt}=D^2/{\lambda}R+5$, where D is the antenna diameter, ${\lambda}$ is the wavelength, and R is the distance between the source antenna and the antenna under test. For the aperture size 5 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 20, the tolerable distances for gain errors of 0.5 dB and 0.2 dB can be guided as $R_{0.5\;dB}$ ${\approx}$ $1.2Lx/{\lambda}$ and $R_{0.2\;dB}$ ${\approx}$ $2.0L_x/{\lambda}$, where $L_x$ is the lateral length of the square aperture. The tolerable distances for 20 ${\leq}$ $L_x/{\lambda}$ ${\leq}$ 200 are also proposed. This measurement guideline can be fully utilized when performing the Fresnel-field antenna measurement method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.28-33
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• 2001

Screw conveyors are used extensively in industrial for conveying and elevating materials. Despite their apparent simplicity, the mechanics of the conveying action is very complex. so many engineers depend on experiential data. Capacities of screw are pumping, steady flow of polymer melts, steady volumetric throughput etc. they are affected by geometry of screw, heat flux, pressure on inside barrel, rotating velocity, friction coefficient at screw surface etc. by computation volumetric efficiency increases as rotating velocity increases and decreases as friction coefficient increases. also it decreases with short pitch length. and double flight screw is more effective than single flight screw. The temperature of polymer melts by heating pad and injection pressure play a very important role in the injection molding machine. so in this paper we analyze thermal distortion and stress of screw includes pressure and temperature distributions by finite element analysis to understand what design factors influence on volumetric throughput efficiency of the screw and thermo-mechanical characteristics of screw.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.415-423
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• 2001

In is well recognized that the ultrasonic method is one of the most common and reliable nondestructive testing(NDT) methods for the quantitative estimation of defects in welded structures. However, NDT techniques applying for adhesively bonded joints have not been clearly established yet. In this paper, the detection of interface crack by the ultrasonic method was applied for the measurement of interface crack length in the adhesively bonded joints of double-cantilever beam(DCB). The optimum condition of transmission coefficients and experimental accuracy by the ultrasonic method in the adhesively bonded joints have been investigated. The experimental values are in good agreement with the computed results by boundary element method(BEM) and Riplings equation.

• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1938-1948
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• 2003

This paper represents that an enhanced genetic algorithm (EGA) is applied to optimal design of a squeeze film damper (SFD) to minimize the maximum transmitted load between the bearing and foundation in the operational speed range. A general genetic algorithm (GA) is well known as a useful global optimization technique for complex and nonlinear optimization problems. The EGA consists of the GA to optimize multi-modal functions and the simplex method to search intensively the candidate solutions by the GA for optimal solutions. The performance of the EGA with a benchmark function is compared to them by the IGA (Immune-Genetic Algorithm) and SQP (Sequential Quadratic Programming). The radius, length and radial clearance of the SFD are defined as the design parameters. The objective function is the minimization of a maximum transmitted load of a flexible rotor system with the nonlinear SFDs in the operating speed range. The effectiveness of the EGA for the optimal design of the SFD is discussed from a numerical example.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.299-304
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• 2003

The design of an occupant protection equipment has been considered as the important process in developing a new car since the crash performance plays an important role on the market. The cost is increased when an unexpected real test is carried out in the proto-design stage. Thus, the exact prediction of a crash performance can reduce the number of full-car test. In this research, the robust design of an airbag system considering the frontal crash is suggested to predict the more reliable responses. On the contrary, most existing researches do not consider the uncertainties. The uncertainties treated in this research are the tolerances of the vent hole, the time to fire and the length of a strap in airbag and the tolerance of the load limiter load in seat belt. The Taguchi method is utilized to determine the robust optimum of each parameter

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.177-184
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• 2003

The purposes of this study are to develop the real coding genetic algorithm and to obtain the shape optimization of a cable domes by using this scheme. Generally, the structural performance of the cable dome is influenced very sensitively by prestress, geometry and length of the mast because of flexible structures. So, it is very important to decide the optimum shape to get maximum stiffness of cable domes. We use the two models to verify the usefulness of this algorithm for shape optimization and analyze the roof system of Seoul olympic gymnastic arena as one analytical model of practical structures

• Plant Resources
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• v.5 no.3
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• pp.192-195
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• 2002

Special objective of this study is to investigate morphological characteristics of seeds and effects of environmental factors such as light and temperature on their germination and seedling growth of Angelica acutilobu in Umbelliferae plants, using them as oriental medicine materials. Seed shape of Angelica acutilobu is ovate. Color of seed coats varied from yellow to dark brown. Seed size was 5.5 mm in length, 4.0mm in width. One thousand-seed weight of Angelica acutilobus was 3,210mg. Optimum temperatures for seed germination and seedling growth ranged from 20 to $25^{\circ}C$.