• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.373-384
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• 1989

The motions of a spinning rotor and a fluid enclosed in its cavity are known to have mutual interactions, which change the frequencies of forced vibrations and cause instabilities. These phenomena are of technical importance for fluid-cooled turbines as well as spin-stabilized satellites or rockets containing liquid fuels. In this paper the characteristics of unstable whirling of a rotor containing a partitioned cavity filled with two kinds of liquids are investigated experimentally. It studies the influence of rotational speed and filling ratio of two kinds of liquids on unstable whiring. As a result, it is found that the whirl velocity is approximately equal to, or slightly lower for large masses of trapped fluid than rotor critical speed. In case of a spinning rotor partially filled with two kinds of liquids the boundary surface plays a similar role to the free surface, and cases unstable forward whirl.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.855-860
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• 2022

Today, the metaverse is understood as a concept in which the boundaries between the real and the virtual are blurring and the economic, social, and cultural activities of the real and virtual worlds are interconnected. In this study, we intend to examine the current status of the metaverse platform at home and abroad. Through this, if we can confirm the current location of the metaverse platform in Korea, we will try to identify the field of metaverse application suitable for the domestic situation. In addition, we will try to find ethical problems among the problems of the metaverse that developed rapidly. This will serve as a basis for finding solutions when using the Metaverse platform in the future.

• Korean Journal of Labor Studies
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• v.17 no.1
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• pp.297-323
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• 2011

Part-time jobs in Sweden are highly feminized yet are in fair conditions in terms of job security, earnings, and collective representation. Three points are considered to be important to understand why part-time work in Sweden carries such positive characteristics. First, the part-time work in Sweden is widely spread not as a result of employers' need for labor flexibilization but as means to enhance the work-life balance, a value pursued within a broader social policy package to change the breadwinner model. Second, discrimination against part-time workers is restrained in Sweden because the boundary between part-time and full-time is not conspicuous. Most of part-time jobs are occupied by regular workers who exert the right to part-time work, hence may go back to the full-time status any time. Third, the regulation on overtime work of part-time workers as well as full-time workers is strong. It is largely agreed among researchers that part-time work contributed greatly to an increase of female employment rate in Sweden. Since the 1970s, the increased availability of part-time jobs induced married women who used to be economically inactive to the labor market and maintained them to be economically active throughout the child rearing period. From the gender perspective, one may still raise issues regarding part-time work in Sweden such as persistent feminization and strong occupational sex segregation. However, the observed trend shows that the part-time work in Sweden has functioned more as a stepping stone to the full-time work for women than as a women's trap.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.1-7
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• 2011

In this paper, based on an isogeometric approach, we have developed a shape design optimization method for plane elasticity problems subjected to design-dependent loads. The conventional shape optimization using the finite element method has some difficulties in the parameterization of geometry. In an isogeometric analysis, however, the geometric properties are already embedded in the B-spline basis functions and control points so that it has potential capability to overcome the aforementioned difficulties. The solution space for the response analysis can be represented in terms of the same NURBS basis functions to represent the geometry, which yields a precise analysis model that exactly represents the normal and curvature depending on the applied loads. A continuum-based isogeometric adjoint sensitivity is extensively derived for the plane elasticity problems under the design-dependent loads. Through some numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.403-421
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• 2021

Most of the urban tunnels in Korea, which are represented by the 1st to 3rd subways, use the drainage tunnel by NATM. Recently, when a construction project that actively utilizes large-scale urban space is promoted, negative effects that do not conform to the existing empirical rules of urban tunnels may occur. In particular, there is a high possibility that groundwater fluctuations and hydrodynamic behavior will occur owing to the practice of tunnel technology in Korea, which has mainly applied the drainage tunnel. In order to solve the problem of the drainage tunnel, attempts are being made to control groundwater fluctuations. For this, the establishment of tunnel groundwater management standard concept and the analysis of the tunnel hydraulic behavior were performed. To prevent the problem of groundwater fluctuations caused by the construction of large-scale tunnels in urban areas, it was suggested that the conceptual transformation of the empirical technical practice, which is applied only in the underground safety impact assessment stage, to the direction of controlling the inflow in the tunnel, is required. And the relationship between the groundwater level and the inflow of the tunnel required for setting the allowable inflow when planning the tunnel was derived. The introduction of a tunnel groundwater management concept is expected to help solve problems such as groundwater fluctuations, ground settlement, depletion of groundwater resources, and decline of maintenance performance in various urban deep tunnel construction projects to be promoted in the future.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.239-247
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• 2020

This study is about design and verification of stress reduction of bearings for wind turbines. In a slewing bearing having a typical four-contact structure, the contact point moves to the end of the raceway due to a large moment load, resulting in a stress concentration. A bearing was designed to reduce such contact point movement. The deformation behavior of typical ball bearings and newly designed bearings was calculated through finite element analysis under ultimate load by replacing the ball with a spring element. The contact stress between the ball and the raceway was calculated by finite element analysis by inputting the deformation behavior analysis result as a boundary condition. The effectiveness of the bearing stress analysis method using spring elements was verified through comparison of the contact stress according to the bearing structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2492-2500
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• 2009

This study was carried to examine overall psychopathological patterns of the Vietnam Civil War Veterans(Agent Orange patients)and Korean Civil War veterans(wounded soldier) using Rorschach tests. Test protocols of were compared with those of twenty Vietnam Civil War Veterans group and twenty-one Korean Civil War veterans. Rorschach protocols were administrated, scored, analysed according to the Exner's comprehensive system. Specifically, each Rorschach variable was divided into 3 clusters(e.g., core section, response determinants, and several special indices. The results of t-tests between the Vietnam Civil War Veterans group and the Korean Civil War veterans showed that Vietnam Civil War Veterans group were characterized as 1)cognitive rigidity, 2) ineffective problem solving, 3)emotional represion, 4)hypervigilance, 5)anxiety and 6) depressive tendency. These patterns suggest that still Vietnam Civil War Veterans experience the past trauma and lasting psychological seguela. Other implications and limitations of this study were discussed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.2
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• pp.161-172
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• 1997

In this paper, electromagnetic scattering by a perfectly conducting strip grating on dielectric multilayers is analyzed for the normalized reflected and transmitted power by applying the Fourier-Galeakin moment method. The induced current density is expanded in a series of multiplication of chebyshev polynomials of the first kind and functions with appropriate edge boundary condition, the continuous condition of electromagnetic field is applied in the boundary planes. The confirm the validity of the proposed method, the nor- malized reflected and transmitted power obtained by varying the relative permittivity and thickness of each dielectric layers are evaluated and compared with those of the existing numerical method and a paper, and then the numerical results in this paper are in good agreement with those of the existing numerical method and the paper. The sharp variation position in the geometrically normalized reflected and transmitted power can be moved by the incident angle, grating period, and the relative permittivity and thickness of the dielectric multilayers, these sharp variation points which are called the Wood's anomaly of the Geome- trically normalized reflected power are observed as a main factor when the reflected powers of the higher order mode are transitted between propagating and evanescent modes, and the local minimum positions are slightly moved to the left hand direction in which grating period is getting small according to the increase of the relative permittivity of dielectric layers.

• Journal of Korea Multimedia Society
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• v.8 no.3
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• pp.336-344
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• 2005

In this paper, we extracted the contour of lung parenchyma on EBT images with the improved active contour model. The objects boundary in conventional active contour model can be extracted by controlling internal energy and external energy as energy minimizing form. However, there are a number of problems such as initialization and the poor convergence about concave part. Expecially, contour can not enter the concave region by discouraging characteristic about stretching and bending in internal energy. We controlled internal energy by moving local perpendicular bisector point of each control point in the contour and implemented the object boundary by minimizing energy with external energy The convergence of concave part could be efficiently implemented toward lung parenchyma region by this internal energy and both lung images for initial contour could also be detected by multi-detection method. We were sure this method could be applied detection of lung parenchyma region in medical image.

• Journal of Intelligence and Information Systems
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• v.9 no.1
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• pp.71-89
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• 2003

Although many studies demonstrate that one technique outperforms the others for a given data set, there is often no way to tell a priori which of these techniques will be most effective in the classification problems. Alternatively, it has been suggested that a better approach to classification problem might be to integrate several different forecasting techniques. This study proposes the linearly combining methodology of different classification techniques. The methodology is developed to find the optimal combining weight and compute the weighted-average of different techniques' outputs. The proposed methodology is represented as the form of mixed integer programming. The objective function of proposed combining methodology is to minimize total misclassification cost which is the weighted-sum of two types of misclassification. To simplify the problem solving process, cutoff value is fixed and threshold function is removed. The form of mixed integer programming is solved with the branch and bound methods. The result showed that proposed methodology classified more accurately than any of techniques individually did. It is confirmed that Proposed methodology Predicts significantly better than individual techniques and the other combining methods.