• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.2
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• pp.273-280
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• 2017

As massive integration technology of transistors has been developing, multi-core circuit is fabricated on a silicon chip and a clock frequency is getting faster to meet the system requirement. But increasing the clock frequency can induce some problems to violate the operation of system such as clock synchronization, so it is very import to avoid metastability events to design digital chips. In this paper, metastability windows are measured by bisection method in H-spice depending on temperature, supply voltage, and the size of transmission gate with D-FF designed with 180nm CMOS process. The simulation results show that the metastability window(: MW) is slightly increasing to temperature and supply voltage, but is quadratic to the area of a transmission gate, and the best area ration of P and Ntransitor in transmission gate is P/N=4/2 to get the least MW.

• Computational Structural Engineering
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• v.10 no.4
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• pp.315-325
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• 1997

This paper describes the application of discretized continuum-type optimality criteria (DCOC) and the development of optimum design program for the multispan partially prestressed concrete beams. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non-prestressing steel and formwork is minimized. The design constraints include limits on the maximum deflection, flexural and shear strengths, in addition to ductility requirements, and upper and lower bounds on design variables as stipulated by the design Code. Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables-effective depth, eccentricity of prestressing steel and non-prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. The self-weight of the structure is included in the equilibrium equation of the real system, as is the secondary effect resulting from the prestressing force. An iterative procedure and computer program for updating the design variables are developed. Two numerical examples of multispan PPC beams with rectangular cross-section are solved to show the applicability and efficiency of the DCOC-based technique.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.6 no.3
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• pp.205-215
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• 1994

A 3-dimensional numerical model of wind-induced flows has been established. and comparative evaluation of determination methods of vertical eddy viscosity has been performed. The model uses turbulence models to calculate vertical eddy viscosity. The examined methods arp 0-equation model of functional form, 1-equation model of turbulence kinetic energy, and two 2-equation models ($textsc{k}$-$\varepsilon$ and $textsc{k}$-ι models). The evaluation includes the verification tests against experimental data for wind-driven current On a closed one-dimensional channel and a recirculating one-dimensional channel. Comparative study of turbulence models has shown that the proper distribution of turbulence scale is parabolic and the eddy viscosity is depending strongly on mixing depth due to wind.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.2
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• pp.281-291
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• 2002

This paper describes the minimum cost design of prestressed reinforced concrete (PRC) hem with rectangular section. The cost of construction as objective function which includes the costs of concrete, prestressing steel, non prestressing steel, and formwork is minimized. The design constraints include limits on the minimum deflection, flexural and shear strengths, in addition to ductility requirements, and upper-Lower bounds on design variables as stipulated by the specification. The optimization is carried out using the methods based on discretized continuum-type optimality criteria(DCOC). Based on Kuhn-Tucker necessary conditions, the optimality criteria are explicitly derived in terms of the design variables - effective depth, eccentricity of prestressing steel and non prestressing steel ratio. The prestressing profile is prescribed by parabolic functions. In this paper the effective depth is considered to be freely-varying and one uniform for the entire multispan beam respectively. Also the maximum eccentricity of prestressing force is considered in every span. In order to show the applicability and efficiency of the derived algorithm, several numerical examples of PRC continuous beams are solved.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.10
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• pp.147-153
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• 2014

In this paper, we present a non-dyadic lens distortion correction model and image restoration method based on local self-similarity to remove jagging and blurring artifacts in the peripheral region of the geometrically corrected image. The proposed method can be applied in various application areas including vehicle real-view cameras, visual surveillance systems, and medical imaging systems.

• Journal of the Korean Wood Science and Technology
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• v.15 no.2
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• pp.26-52
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• 1987

Among the diffuse-porous woods which arc dominant in Korea and used as construction materials due to their wood quality, ten species of six genus involving seven species of three genus in Betulaceae were studied on the radial variation of structural demenb. The species studied were Betula platyphylla var. japonica, B. ermanii, B. davurica, B. scstata, B. schmidtii, Carpinus laxifora, Alnus japonica, Prunus sargentii. Acer mono and Diospyros kaki. Wood fiber, vessel elements and ray increased rapidly in size from pith to a certain annual ring. After then the radial variation in size of the main structural elements seemed to be divided into three types; levelled off curve pattern indicating constant size(type I), continuously increasing curve pattern showing ever increase in size (type II) and parabolic curve pattern showing the gradual decrease after the maximum (type III), but the variation types by structural dements were different even in the same species. Based on the results from this study, it appears to be reasonable to consider the stabilized age of wood fiber, vessel elements and ray rather than considering wood fiber length in distinguishing mature woods from juvenile woods.

• Journal of Ecology and Environment
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• v.29 no.3
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• pp.237-245
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• 2006

Changes of the biomass, net primary productivity and P/B ratio during abandoned field succession after shifting cultivation were investigated in Pyoungchang, Gangwon-Do, Korea. Aboveground standing biomass of herb species showed the maximum value (3.8 ton/ha) in the 5 year old-field, and decreased thereafter. Litter dry weight was depicted as a parabola form showing the gradual increment during the first 50 years and slight decrease thereafter. Basal area tended to increase logarithmically during abandoned field succession. Tree density showed the gradual increment during the first 15 years and decreased thereafter by the self-thinning process. In the later successional stage (80 years old-field), the shoot density distribution of the tree species by DBH class showed the reverse J shaped curve and Quercus mongolica dominated. Total standing biomass increased slowly in the earlier successional stages and later successional stages, and increased rapidly during the mid-successional stages ($10{\sim}50$ years old-field). Total standing biomass in the 5, 10, 20, 50 and 80 years old-fields were estimated 5, 14, 75, 251 and 373 ton/ha, respectively. Annual net primary productivity were depicted as a parabola form showing the gradual increment during the first 35 years and declined thereafter. The increment rates of the annual net primary productivity in the earlier successional stages showed the higher value than mid-successional stages. The annual net primary productivities in the 5, 10, 20, 35, 50 and 80 years old-field were estimated 8.6, 9.3, 12.9, 15.1, 13.7 and 3.6 ton/ha/yr, respectively. The estimated P/B ratio tended to decrease exponentially during abandoned field succession. The estimated P/B ratio in the 5, 10, 20, 50 and 80 years old-field were 0.60, 0.39, 0.19, 0.06 and 0.01, respectively. These results were fairly in accordance with the bioenergetics model during the forest succession projected by Odum(1969).

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.505-512
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• 2012

In this paper, an efficient yet accurate method for the thermal stress analysis using a first order shear deformation theory(FSDT) is presented. The main objective herein is to systematically modify transverse shear strain energy through the mixed variational theorem(MVT). In the mixed formulation, independent transverse shear stresses are taken from the efficient higher-order zigzag plate theory, and the in-plane displacements are assumed to be those of the FSDT. Moreover, a smooth parabolic distribution through the thickness is assumed in the transverse normal displacement field in order to consider a transverse normal deformation. The resulting strain energy expression is referred to as an enhanced first order shear deformation theory, which is obtained via the mixed variational theorem with transverse normal deformation effect(EFSDTM_TN). The EFSDTM_TN has the same computational advantage as the FSDT_TN(FSDT with transverse normal deformation effect) does, which allows us to improve the through-the-thickness distributions of displacements and stresses via the recovery procedure. The thermal stresses obtained by the present theory are compared with those of the FSDT_TN and three-dimensional elasticity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.43-54
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• 1992

For shallow arches with large dynamic loading, linear analysis is no longer considered as practical and accurate. In this study, a method is presented for the dynamic analysis of shallow arches in which geometric nonlinearity must be considered. A program is developed for the analysis of the nonlinear dynamic behavior and for evaluation of critical buckling loads of shallow arches. Geometric nonlinearity is modeled using Lagrangian description of the motion. The finite element analysis procedure is used to solve the dynamic equation of motion and Newmark method is adopted in the approximation of time integration. A shallow arch subject to radial step loads is analyzed. The results are compared with those from other researches to verify the developed program. The behavior of arches is analyzed using the non-dimensional time, load, and shape parameters. It is shown that geometric nonlinearity should be considered in the analysis of shallow arches and probability of buckling failure is getting higher as arches are getting shallower. It is confirmed that arches with the same shape parameter have the same deflection ratio at the same time parameter when arches are loaded with the same parametric load. In addition, it is proved that buckling of arches with the same shape parameter occurs at the same load parameter. Circular arches, which are under a single or uniform normal load, are analyzed for comparison. A parabolic arch with radial step load is also analyzed. It is verified that the developed program is applicable for those problems.

• Food Science and Preservation
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• v.22 no.6
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• pp.859-866
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• 2015

The purpose of this study was to develop a supplemental healthy food that can help prevent high blood pressure-related diseases caused due to the excessive consumption of sodium in salt. This was achieved by using ion-displacement techniques to produce mineral salt with lower sodium content by using fermented brown rice by-products rich in minerals. Mineral salt containing 2019.2 mg/100 g of potassium, 678.5 mg/100 g of magnesium, 48.7 mg/100 g of calcium, and 19.5 mg/100 g of sodium was obtained by fermenting brown rice by-products to create a culture medium for the mineral salt. Mineral salt containing 1769.7 mg/100 g of potassium, 573.6 mg/100 g of magnesium, 35.3 mg/100 g of calcium, and 19.5 mg/100 g of sodium was obtained by filtering and refining the by-product extract of fermented brown rice. The results showed that when the stream velocity of the instrument used for electrolysis was 200 mL/min and the current and the concentration of the reactive liquid in the purified water chamber were higher, the effect of electrolysis was greater. Ion hot water extraction of the fermented brown rice by-products improved by up to 95% and was collected as purified water within 90 min of the reaction time. Chloride ions with pH 7.4 were produced by mixing sodium hydroxide in a purified saline water chamber with electro-analyzed water. The salt produced in this study contained low sodium, 5.7~30%, as compared to 40% sodium content of the normal salt.