• Tunnel and Underground Space
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• v.13 no.2
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• pp.77-86
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• 2003

The finite element method and statistics of the convergence measurement are useful method of the stability analysis of the tunnel adjacent to the pier. It is the purpose of the this case study to certificate of validity of the application of those methods. The safety of the pilot tunnel method and LW pre-grouting has been evaluated from the FEM analysis. The three-dimensional finite element method is carried out for the decision of the level of stress redistribution at the two-dimensional numerical analysis. An analysis of the convergence is carried out by the estimation of preceding convergence at tunnel excavation. F-examination is applied for this estimation. As results of that analysis, The F-value is from 10.81 to 158.74 and the coefficient of determination is from 0.82 to 0.99. An analysis of convergence is carried out by using regression analysis. Consequently, it is shown that the convergence can be modeled as following function C(t)=a[1-exp(-bt)].

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.299-311
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• 2003

This paper presents a finite element procedure to estimate the ultimate strength of space frames considering spread of plasticity. The improved displacement field is introduced based on the inclusion of second-order terms of finite rotations. All the non-linear terms due to bending moment, torsional moment, and axial force are precisely considered. The concept of plastic hinges is introduced and the incremental load/displacement method is applied for elasto-plastic analyses. The initial yield surface is defined based on the residual stress, and the full plastification surface is considered under the combined action of axial forces, bending and torsional moments. The elasto-plastic stiffness matrices are derived using the flow rule and the normality condition of the limit function. Finite element solutions for the ultimate strength of space frames are compared with available solutions and experimental results.

• Journal of Korean Society of Steel Construction
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• v.13 no.6
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• pp.673-681
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• 2001

The objective of this study is the development of size, shape and topology discrete optimum design algorithm which is based on the genetic algorithm. The algorithm can perform both shape and topology optimum designs of trusses. The developed algorithm was implemented in a computer program. For the optimum design, the objective function is the weight of trusses and the constraints are stress and displacement. The basic search method for the optimum design is the genetic algorithm. The algorithm is known to be very efficient for the discrete optimization. The genetic algorithm consists of genetic process and evolutionary process. The genetic process selects the next design points based on the survivability of the design points selected form the genetic process. The evolutionary process evaluates the survivability of the design points. The evolutionary process evaluates the survivability of the design points selected form the genetic process. The efficiency and validity of the developed size, shape and topology discrete optimum design algorithm was verified by applying the algorithm to optimum design examples.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1605-1614
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• 1992

The effects of % overload (% O.L), baseline stress intensity factor range (.DELTA. $K_{b}$) and dimension-less crack depth (a/W) are examined for the retardation behaviors after a single overload and high-low block loads in 7075-T73 aluminum alloy. And wheeler model, which is one of the fatigue life prediction models, is modified to predict retardation life using these test results. The retardation cycles( $N_{d}$) increased with a decrease in a/W and an increase in % O.L. and (.DELTA. $K_{b}$) These effects are more severe after high-low block loads than single overload. In the case of single overload, the main mechanisms of the retardation are the crack closure and the relaxation of K due to crack branching. But in the case of high-low block loads, that of the main mechanism is the crack closure caused by the accumulated compressive residual stree at the crack tip, which is related with the contact of fracture surfaces. Test results were multiple regression analyzed and got regressed shaping correction factors, (n)$_{REG}$, as function of %O.L., a/W and (.DELTA. $K_{b}$) Wheeler model is modified by using these (n)$_{REG}$. The number of delay cycles calculated by modified Wheeler model were in good agreement with the test results of this study.y.udy.y.y.y.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.9
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• pp.1788-1795
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• 1992

Numerical simulations have been performed to investigate various spectral estimators used in LDV signal processing. In order to simulate a particle arrival time statistics known as the doubly stochastic poisson process, an autoregressive vector model was adopted to construct a primary velocity field. The conditional Poisson process with a random rate parameter was generated through the rescaling time process using the mean value function. The direct transform based on random sampling sequences and the standard periodogram using periodically resampled data by the sample and hold interpolation were applied to obtain power spectral density functions. For low turbulent intensity flows, the direct transform with a constant Poisson intensity is in good agreement with the theoretical spectrum. The periodogram using the sample and hold sequences is better than the direct transform in the view of the stability and the weighting of the velocity bias for high data density flows. The high Reynolds stress and high fluctuation of the transverse velocity component affects the velocity bias which increases the distortion of spectral components in the direct transform.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.9 no.2
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• pp.81-91
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• 1991

This thesis aims to improve the analysis accuracy of remotely sensed digital imagery, and the improvement is achieved by considering the weight factors(a priori probabilities) of Bayesian MLC in the classification stage. To be concrete, Bayesian decision theory is studied from remote sensing field of view, and the equations in the n-dimensional form are derived from normal probability density functions. The amount of the misclassified pixels is extracted from probability function data using the thres-holding, and this is a basis of evaluating the classification accuracy. The results indicate that 5.21% of accuracy improvement was carried out. The data used in this study is LANDSAT TM(1985.10.21 ; 116-34), and the study area is within the administrative boundary of Seoul.

• Food Science of Animal Resources
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• v.29 no.2
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• pp.278-282
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• 2009

Previous studies indicate that BF-7 enhances learning and memory in normal and elderly individuals. Here, we evaluated whether milk containing BF-7 (BF-7 milk) could improve the brain function, with thirty normal university students $(21{\pm}1.2 years)$. Two versions of the Paced Auditory Serial Addition Test were used under double-blinded conditions to measure the efficacy of BF-7 milk on learning and memory, especially working memory and attention, and on mathematical ability. As a result, BF-7 milk improved the accuracy of the task more than 3-fold. Furthermore, BF-7 milk protected cultured neuronal cells from 3-hydroxykynurenine, a normal endogenous brain stress agent. These results indicate that BF-7 milk enhances memory, attention and mathematical ability in normal persons.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.174-183
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• 2006

The resistance spot-welded region in most current finite element crash models is characterized as a rigid beam at the location of the welded spot. The region is modeled to fail with a failure criterion which is a function of the axial and shear load at the rigid beam. The role of this rigid beam is simply to transfer the load across the welded components. The calculation of the load acting on the rigid beam is important to evaluate the failure of the spot-weld. In this paper, numerical simulation is carried out to evaluate the calculation of the load at the rigid beam. The load calculated from the precise finite element model of the spot-welded region considering the residual stress due to the thermal history during the spot welding procedure is regarded as the reference value and the value of the load is compared with the one obtained from the spot-welded model using the rigid beam with respect to the element size, the element shape and the number of imposed constraints. Analysis results demonstrate that the load acting on the spot-welded element is correctly calculated by the change of the element shape around the welded region and the location of welded constrains. The results provide a guideline for an accurate finite element modeling of the spot-welded region in the crash analysis of vehicles.

• Journal of the Korean Magnetics Society
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• v.15 no.1
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• pp.25-29
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• 2005

Magnetic properties of YIG films grown by solid phase epitaxy (SPE) was measured as a function of temperature with focus on magneto-crystalline and perpendicular magnetic anisotropy. Perpendicular magnetic anisotropy was not induced in the SPE YIG films annealed at low temperature by relaxing residual stress through formation of dislocation. On the contrary the films annealed at high temperature showed perpendicular magnetic anisotropy which shows very low density of dislocation. Perpendicular magnetic anisotropy field decreased linearly up to a high temperature of $230^{\circ}C$ above which magneto-crystalline anisotropy disappeared. Coercivity also decreased linearly with temperature up 세 $230^{\circ}C$. Magneto-crystalline anisotropy of perpendicular anisotropy induced epitaxial (111) YIG films can be measured using $H_k=4K_1/3M_s$. Temperature behavior of initial susceptibility can be successfully explained by Hopkinson effects. Curie temperature of YIG films grown on GGG substrate with high paramagnetic susceptibility can be easily measured using the results.

• Journal of Korean Society of Rural Planning
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• v.3 no.2
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• pp.36-49
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• 1997

The drastic change of mountain community, which have led existing villages to a size reduction or an extinction, makes this study concentrate on finding out the new community unit as a spatial zone of dayily life and agricultural production. The communality which has played a key role in a aura settlement consistency has been focused on the socio-economic aspect till now, neglecting the spatia] nature. The settlement-communality( SC) putting a stress on the spatial aspect can be, therefore, shapec as being multi-dimensional, composed of both a horizontally areal coverage on the surface of the residential place and a vertically hierarchial relationship between settlements, by analyzing thro( elements of communality that are the economic, socio -cultural and spatial activities. The research site is located administratively in Milan-Myoun, Pyoungchang-Gun, Gangwon-Do that ha: the characteristics as a typical mountain community. The results of field survey of which the method i: to draw the activity zone from an interview with every village's head and some residents with th( prepared questionaire can be summarized as followings. Firstly, the SC in almost all villages tended to be weakened or extincted, none the less, the spatia zone of that overally enlarged and got out of natural village unit(hamlet). However the areal coverall on which the SC has an influence reaches up to the alliant domain of a few villages generally congruen with the lowest level administrative district, Secondly, the economic and social activity pattern in village life has a tendency to be directly linked with a upper central place, so that has induced the function of a central village in the middle-low settlement hierarchy to be largely shrinked. Not only the conventional residents'access to goods service but also the recent service-delivers'access to residents has gradually formed the vertical communality with direct linkage between the upper and the bottom level settlements Lastly, the enfeeblement of the SC in the lowest settlement level tends to be supplemented by enlarging the horizontal zone of the SC or especially by strengthening the vertical direct linkage system. The very this point makes the mountain community open to the external world and also makes the spatial unit of community be multi-dimensional just like a cubic.