• Smart Structures and Systems
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• v.4 no.3
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• pp.319-342
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• 2008

Identification of the nonlinear hysteretic behavior of a reinforced concrete (RC) bridge pier subjected to earthquake loads is carried out based on acceleration measurements of the earthquake motion and bridge responses. The modified Takeda model is used to describe the hysteretic behavior of the RC pier with a small number of parameters, in which the nonlinear behavior is described in logical forms rather than analytical expressions. Hence, the modified extended Kalman filter is employed to construct the state transition matrix using a finite difference scheme. The sequential modified extended Kalman filter algorithm is proposed to identify the unknown parameters and the state vector separately in two steps, so that the size of the problem for each identification procedure may be reduced and possible numerical problems may be avoided. Mode superposition with a modal sorting technique is also proposed to reduce the size of the identification problem for the nonlinear dynamic system with multi-degrees of freedom. Example analysis is carried out for a continuous bridge with a RC pier subjected to earthquake loads in the longitudinal and transverse directions.

• Current Research on Agriculture and Life Sciences
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• v.31 no.2
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• pp.75-82
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• 2013

Haploids are plants with a gametophytic number of chromosomes in their sporophytes. Androgenesis occurs from asymmetric division of pollen grains into generative cells and vegetative cells, followed by re-entry of the vegetative cell during S-phase, which causes microspores progress into G2/M transition in culture. One of the most interesting features of haploids is the possibility to produce doubled haploid (DH) individuals. Doubled haploidy is extremely useful to plant breeders because it enables shortened breeding periods and efficiency in selection of useful recessive agronomic traits. Doubled-haploid technology is not only applicable to breeding, but also to transformation programs of desired genes. In addition to practical breeding programs, DH lines provide useful materials of fundamental genetics including exploitation of QTLs and genes conferred with various agronomic traits by establishing DH populations. This paper provides historical overviews on androgenesis and describes several mechanisms associated with pollen embryogenesis, including mode of actions in pollen embryogenesis, mechanisms of chromosome doubling and factors affecting androgenesis. We also discuss recent progress in application of haploids to breeding, genes associated with in vitro response and drawbacks to anther culture for application of doubled haploids in crop breeding.

• Wind and Structures
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• v.12 no.1
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• pp.63-76
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• 2009

The vortex-induced vibration of an ${\sqcap}$-shaped bridge deck sectional model is studied in this paper via the wind tunnel experiment. The vibratory behavior of the model shows that there is a transition of the predominant vibration mode from the vertical to the rotational degree of freedom as the wind speed increases gradually or vice versa as the wind speed decreases gradually. The vertical vibration is, however, much weaker in the latter case than in the former. This is a phenomenon which is difficult to model by existing parametric models for vortex-induced vibrations. In order to characterize the aeroelastic property of the ${\sqcap}$-shaped sectional model, a time domain force identification scheme is proposed to identify the time history of the aeroelastic forces. After the application of the proposed method, the resultant fluid forces are re-sampled in dimensionless time domain so that reduced frequency response function (RFRF) can be obtained to explore the properties of the vortex-induced wind forces in reduced frequency domain. The RFRF model is proven effective to characterize the correlation between the wind forces and bridge deck motions, thus can explain the aeroelastic behavior of the ${\sqcap}$-shaped sectional model.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.79-84
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• 1996

Small punch test was performed on CF8 duplex stainless steel aged at 370 and 400$^{\circ}C$ up to 5,000 h to evaluate the degree of the thermal aging embrittlement. At room temperature, the SP load-displacement curve was in a similar shape to those of ferritic steels and had a good reproducibility in spite of two-phase structure. The aging heat treatment resulted in a slight increase of the yield strength. As test temperature was lowered, the SP load showed a sudden drop followed by serrations before the SP specimen was fractured, resulting from the cracking of ferrite phase. The extent of thermal embrittlement was assessed in terms of the SP energy. Aging treatment at higher temperature led to a larger shift in the transition temperature and the corresponding change in the fracture mode. The main cause of the degradation was the embrittlement of ferrite phase. Additionally the phase boundary separation profoundly contributed to the degradation of the specimen aged at 400$^{\circ}C$.

• Nuclear Engineering and Technology
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• v.52 no.7
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• pp.1417-1428
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• 2020

The design of a nuclear reactor core requires basic thermal-hydraulic information concerning the heat transfer regime at which onset of nucleate boiling (ONB) will occur, the pressure drop and flow rate through the reactor core, the temperature and power distributions in the reactor core, the departure from nucleate boiling (DNB), the condition for onset of flow instability (OFI), in addition to, the critical velocity beyond which the fuel elements will collapse. These values depend on coolant velocity, fuel element geometry, inlet temperature, flow direction and water column above the top of the reactor core. Enough safety margins to ONB, DNB and OFI must-emphasized. A heat transfer package is used for calculating convection heat transfer coefficient in single phase turbulent, transition and laminar regimes. The main objective of this paper is to study the possibility of power upgrading of WWR-S research reactor from 2 to 10 MW_th. This study presents a one-dimensional mathematical model (axial direction) for steady-state thermal-hydraulic design and analysis of the upgraded WWR-S reactor in which two types of plate fuel elements are employed. FOR-CONV computer program is developed for the needs of the power upgrading of WWR-S reactor up to 10 MW_th.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.864-867
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• 2006

In order to satisfy with the clear visibility without any difficulties such as blurring and tailing, the high refreshing rate technology and fast response time of LC itself were applied to TFT-LCDs. In proportion to the decrease of holding time of 1 frame, the fast transition of LC behavior was necessary to both maintain the luminance and minimize the tailing appearance. The introduction of a new LC mixture for faster response times was realized by the good combination of newly introduced dielectrically neutral LC material so called 'Super Low Viscosity' (SLV) and highly polar $CF_2O-linkage$ LC material. This resulted in about a 20% reduction in the ${\gamma}_1$ of the new LC mixture compared to the references. In accordance with a new LC mixture with low ${\gamma}_1$, fast response time of 5ms has been made for S-IPS LCD TV application. Consequently, by applying the high frame frequency of 120Hz driving alongside the 5ms response time characteristics, the MPRT value was reduced by half.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.54-54
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• 2010

This article reports a spontaneous method for controlling the growth mode from vertically arrayed ultra-slim MgZnO nanowires to nanowalls through the Zn random motion of seeds formed by surface phase separation by Mg injection near an evaporation temperature of Zn. The random motion of single crystal MgZnO seeds with relative Zn rich phase played a vital role in the growth of the MgZnO nanowalls. The seeds were networked with increasing Zn flux compared with Mg flux and closing to the evaporation temperature of Zn on phase separation layers. We achieved fabrication of MgZnO nanowalls on various non- and conducting substrates by this advanced growth method. The MgZnO nanowalls hydrogen sensor showed an improved sensing performance compared to the MgZnO nanowires grown under the similar conditions. Based on the microstructural characterizations, the growth procedure and models for the evolution of the structure transition from MgZnO nanowires to nanowalls on the Si substrates are proposed for phased growth times.

• Publications of The Korean Astronomical Society
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• v.25 no.1
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• pp.23-28
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• 2010

We present results of a test-study of the large-scale survey using the multi-beam receiver system recently installed on the 14 m telescope at Taeduk Radio Astronomy Observatory (TRAO). We have tested several modes of mapping, and found suitable (time-saving) mapping parameters of 'ON-SOURCE' = 8, 'OFF-SOURCE' = 1 when using 'RPT' = 3 as a position-switching mode. We observed 504 spectra towards the NGC 7538, a star forming molecular cloud in the transition of J = 1 - 0 of $^{12}CO$. From the Outer Galaxy Survey database (Heyer et al., 1998) we obtained 504 spectra for the same region. We compared integrated intensities, line profiles of two databases, and found that they are consistent to each other. From the intensity ratio of these two databases we also found that the value of forward spillover scattering of the TRAO telescope system is 0.58.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.294-298
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• 2003

The complex, unsteady, self-sustained pressure oscillations induced by supersonic flow past a rectangular cavity is investigated using numerical simulations. The present numerical study is performed using a parallel, multiblock solver for the two-dimensional, compressible Navier­Stokes equations. Open cavities with length-to-depth (L / D) ratio in the range 0.5 - 3.3 are considered. This paper sheds light on the cavity physics, cavity oscillatory mechanism, and the organisation of vortical structures inside the cavity. The vortex shedding phenomenon, the shear layer impingement event at the aft wall and the movement of the acoustic/compression wave within the cavity are well predicted. The vortical structures· and the source of the acoustic disturbances are found to be located near the aft wall of the cavity. With the increase in the cavity length, strong recompression of the flow near the aft wall leading to a sudden jump in the cavity form drag is observed. The estimated cavity tones are in good agreement with the available semi­empirical relation. Multiple peaks are noticed in deep and long cavities. For the present free­stream Mach number 1.71, it is observed that around L/D=2.0, the cavity oscillatory mechanism changes from the transverse to longitudinal oscillatory mode. The effects of this transition on various fluid dynamics and acoustic properties are also discussed.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.570-577
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• 2001

Three-dimensional time-dependent flow past a circular cylinder is numerically investigated using direct numerical simulation for Reynolds number 280 and 300. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme and the pressure and viscosity terms are applied by the 4th order central difference. And in spanwise, Navier-Stokes equation is distributed using of Spectral Method. At Reynolds number 259 the two-dimensional wake becomes linearly unstable to a second branch of modes with wavelength about 1.0 diameters at onset (B-mode). Present results of three-dimensional effects of in wake of a circular cylinder is represented with spanwise and streamwise vorticity contours as Reynolds numbers.