• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 1997.10a
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• pp.7-7
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• 1997

During sintering of very porous green bodies, as obtained by compaction of hard powders - such as tungsten carbide or ceramics - or by injection moulding, important shrinkage occurs. Due to heterogeneous green density field, gravity effects, friction on the support, thermal gradients, etc., this shrinkage is often non-uniform, which' may induce significant shape changes. As the ratio of compact dimension to powder size is very high, the mechanics of continuum is relevant to model such phenomena. Thus numerical techniques, such as the finite element method can be used to simulate the sintering process and predict the final shape of the sintered part. Such type of simulation has much been developed in the last decade firstly for hot isostatic pressing and next for die compaction. Finite element modelling has been recently applied to free sintering. The simulation of sintering should be based on constitutive equations describing the thermo-mechanical behaviour of the material under any state of stress and any temperature which may arise within the sintering body. These equations can be drawn either from experimental data or from micromechanical models. The experiments usually consist in free sintering and sinter-forging tests. Indeed applying more complex loading conditions at high temperature under controlled atmosphere is delicate. Micromechanical models describe the constitutive behaviour of aggregates of spheres from the deformation of two-sphere contact either by viscous flow or grain boundary diffusion. Such models are not able to describe complex microstructure and mechanisms as observed in real materials but they can give some basic information on the formulation of constitutive equations. Practically both experimental and theoretical approaches can be coupled to identify the constitutive equations. Such procedure has been performed for modelling the sintering of compacts obtained by die pressing of a mixture of tungsten carbide and cobalt powders. The constitutive behaviour of this material during sintering has been described by a linear viscous constitutive model, whose functions have been fitted from results of free sintering and sinter-forging experiments. This model has next been introduced in ABAQUS finite element code to simulate the sintering of heterogeneous green compacts of various geometries at constant temperature. Examples of simulations are shown and compared with experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.2
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• pp.41-50
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• 2003

In this paper, nonlinear parallel structural analyses are introduced by using the parallel multifrontal solver and damage localization for 2D and 3D crack models is presented as the application of nonlinear parallel computation. The parallel algorithms related with nonliear reduce the amount of memory used is carried out because many variables should be utilized for this highly nonlinear damage analysis. Also, Riks' continuation method is parallelized to search the solution when strain softening occurs due to damage evolution. For damage localization problem, several computational models having up to around 1-million degree of freedoms are used. The parallel performance in this nonlinear parallel algorithm is shown through these examples and the local variation of damage at crack tip is compared among the models with different degree of freedoms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.17-27
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• 2009

Two-phase RoeM and AUSMPW+ schemes are preconditioned for the simulation of all Mach number flows, which are generally of interest for many gas-liquid two-phase application problems, because of large speed of sound in liquid region and low speed of sound in mixture or gas region. Conventional characteristic based schemes lose their accuracy or robustness in low Mach number flows, because their numerical dissipation terms are scaled by speed of sound, which is too large compared with local velocity magnitude in a low Mach region. All speed versions of RoeM and AUSMPW+ reflect the eigenvalues of the preconditioned governing system, which have the same order of magnitude even in low Mach number region. From the asymptotic analysis, it is observed that the discretized system by the developed schemes is consistent with the continuum system in the incompressible limit. The numerical results show the accurate and robust behavior of the proposed shcemes for all speed two-phase flows.

• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.21-21
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• 1992

The X-ray binary pulsar Her X-1 was observed with Ginga on 1988 August 28 during the orbital phase of 0.76 to 0.85 at the main-on phase of the 35 day cycle. During the observations the X-ray intensity varied by a factor of five or more on a time scale as short as 30 sec, due mostly to the soft X-ray absorption in the pre-eclipse phase. From the studies of pulse profiles and energy spectra, we revealed that there exists in the dipphase an unpulsed component which is "3% of the intensity at the non-absorbed high-level. We suggest that scattering of the source continuum by the optically thin hot corona is responsible for the unpoised component. In the spectral analysis, we find that the high-state non-absorbed spectra can be fitted by a power-law without absorption, and the spectra observed in the different abgorption states by two components of a power-law with the same photon index. An iron-K emission line is required in to the cases of fitting. The estimated equivalent width of the iron line varies from 0.18 to 0.51 key according to the change in the absorption column density along the line of sight. We suggest that the fluorescent iron line arises in a cool and relatively small region, like the Alfvensur face, and may be partially intercepted by the optically thick gas cloud passing across the line of sight.1 Korea Astronomy Observatorya The Institute of Space and Astronautical Science in Japan3 Korea Advanced Institute of Science and Technology

• Nutrition Research and Practice
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• v.1 no.1
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• pp.46-51
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• 2007

The study objectives were to increase both the stage of readiness to eat fruit and vegetables as well as the intakes of women who participated in the Expanded Food and Nutrition Education Program (EFNEP) for families with limited incomes. The intervention was to enhance the currently used curriculum, Eating Right Is Basic III (ERIB3), with stage-specific processes based on the Trans-Theoretical Model of readiness to change. Trained EFNEP community workers taught the enhanced curriculum to 90 mothers in the experimental county and to 53 mothers in the control county. Pre- and post-intervention measures included stages of readiness to eat fruit and vegetables and to intake as assessed by 24-hour dietary recalls and staging questions. Most women recruited into EFNEP were in Action and Preparation Stages (53.5%). Fruit and vegetable intakes showed a linear trend along with the Stage of Change for fruit and vegetable. After intervention, some combination of the ERIB3 and the fruit and vegetables-enhanced ERIB3 resulted in a reported 1/2 servings/day increase in fruits and vegetables in both the control and the experimental counties, although changes were not significant. EFNEP women also moved along the Stage of Change Continuum for fruits and vegetables in both counties. The percentage of people who ate 5 or more servings of fruit and vegetables was significant, however, only in the experimental group. We encourage health professionals to apply lessons learned from this intervention and to continue to pursue theoretically based interventions to change dietary behaviors.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.129-142
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• 2016

The underground cavity known as one of the reasons of ground surface settlement is a discontinuous character. Therefore, it is limited to analyze with continuum analysis. In this research, The spherical underground cavity affecting the ground surface settlement is studied with Discrete Element Method. Ground properties, depth and diameter of the spherical underground cavity are chosen as factors of the spherical underground cavity and the effect of the each factor variations on the ground surface settlement is analyzed. Relative depth to the diameter of the spherical underground cavity is also studied. The result of the research suggests the basis of underground cavity collapse prediction and standard of support.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.159-181
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• 2012

The segment lining which consists of segments and joints are main component of shield tunnel. There are a number of methods that are being used in design which compute the sectional forces of a ring of segment lining. The traditional design methods which do not consider the effect of joints have been commonly used for design procedure without a specific verification of structural analysis. This paper presents the result of a comparative study for analytical and numerical models of the shield tunnel segment lining. For the traditional methods, the elastic equation method and the Duddeck & Erdmann method were considered. The ring-beam and the continuum analysis model were also considered as the numerical model.

• Women's Health Nursing
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• v.22 no.4
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• pp.254-263
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• 2016

Purpose: The purpose of this study was to identify effects of fatigue, depression and anxiety on quality of life in pregnant women with preterm labor. Methods: With a survey design, data were collected from 138 mothers who were admitted at a hospital in Seoul, between June 2014 and September 2015. Instruments used to collect the data for the study were: Fatigue Continuum Form, Depression anxiety stress scale (DASS-21) and maternal postpartum quality of life (MAPP-QOL). Results: The mean fatigue score was 68.30 with 50.7% of women being depressed and 79.7% of the 138 women being anxious. The mean quality of life was 18.92 with quality of life being associated with fatigue, depression and anxiety. Depression and fatigue explained 26% of the variance in quality of life. Conclusion: Depression and fatigue adversely affected women's quality of life. It is important to address appropriate management of depression and fatigue in order to improve quality of life in pregnant women with preterm labor.

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.177-180
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• 2006

We observed $2.1218{\mu}m$ $H_2$ 1-0 S(1) emission from H II region A, which is located just next to Sgr A East and one of the nearest star forming regions to the Gatactic center. Cooled Grating Spectrometer 4 (CGS4) at the 3.8 m United Kingdom Infrared Telescope (UKIRT) was used with aa echelle grating at a velocity resolution of ${\sim}$ 18km s^{-1}$ and an angular resolution of ${\sim}$ 2 arcsec. Comparing the distributions and kinematics of the observed $H_2$ emission with radio continuum and $NH_3$ emission, we find no evidence that this H II region is interacting with Sgr A East. This conclusion supports that the star formation in this region has not been stimulated by the blast wave of Sgr A East.

• The Journal of the Korea Contents Association
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• v.7 no.7
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• pp.96-103
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• 2007

Reincarnation, literally means "to be made flesh again". It is a mystical belief that the soul lives again in a new body after death. In this study, both material and spiritual elements are reincarnated in the form of the formative art in our life. This is similar to the notion of transmigration of the souls in Buddism and Taoism. Even a work of low merit can be an artifact when we give a new meaning and value through the reincarnation. Reincarnation opens another dimension in the formative art and it can be a new source of energy Andy Warhol, who is a central figure in the pop art movement, seems to have an idea of reincarnation in the base of his work. In Korea, there are many experimental arts in design and advertising which shows reincarnation. In the modem society, the activity and mind of reincarnation have been enhanced through Internet and digital medium and people consider reincarnation as a universal philosophy in the art. Especially, the reincarnation as a continuum of design has many implementations. Now the object will be freely adopted, and transformed and it will open a new age in the formative art. We should be ready to enjoy the arts.