• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.820-823
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• 2002

The asymptotic problem of a semi-infinite conducting crack parallel to the poling direction in ferroelectric ceramics subjected to electric fields is analyzed. The main mechanism for the conducting crack growth behavior is thought to be ferroelectric domain switching leading to the development of a process zone around the crack. The shape and size of the switching zone is shown to depend strongly on the relative magnitude on the ratio of the coercive electric field to the yield electric field. It is shown that the crack growth can be either enhanced or retarded depending on the ratio of the coercive electric field to yield electric field.

• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.243-248
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• 2004

Disk galaxies abound with intermediate-scale structures such as OB star complexes, giant clouds, and dust spurs in a close geometrical association with spiral arms. Various mechanisms have been proposed as candidates for their origin, but a comprehensive theory should encompass fundamental physical agents such as self-gravity, magnetic fields, galactic differential rotation, and spiral arms, all of which are known to exist in disk galaxies. Recent numerical simulations incorporating all these physical processes show that magneto-Jeans instability (MJI), in which magnetic tension resists the stabilizing Coriolis force of galaxy rotation, is much more powerful than swing-amplification or the Parker instability in forming self-gravitating intermediate-scale structures. The MJI occurring in shearing and expanding flows off spiral arms rapidly forms structures elongated along the direction perpendicular to the arms, remarkably similar to dust spurs seen in HST images of spiral galaxies. In highly nonlinear stages, these spurs fragment to form bound clumps, possibly evolving into bright arm and interarm H II regions, suggesting that all these intermediate-scale structures in spiral galaxies probably share a common dynamical origin.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.10 no.1
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• pp.93-115
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• 1999

This Study is the summary of studies in analysis of‘Lecture Evaluation’made at H university where such evaluation for every course established has been carried out since 1990. This contains the contents of questionnaire drawn up through OMR scanner which has 7 fields with 10 items respectively. to investigate the general direction of the results, results of evaluation by lectures, different results of evaluation by fields, and the like. I applied such techniques of statistical analysis as T-test, analysis of variance table(Anova-table), and Regression analysis to examine the most important factor of successful lecturing.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1895-1905
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• 2009

Recently it is required to present a new goal and direction regarding a railroad industrial informatization in order to respond to external change of environment along sharp development technical information communication (ICT), establish a strategic plan for o establish a strategic plan for harmonious developments of private and public sector through harmonious developments of private and public sector and efficient investments on an railroad industrial informatization. Forwarding plans for informatization industrial the existing railroad have been proceeded mainly around informatization of related organization regarding railroads. Study to have read to this established informatization architecture industrial a railroad for establishing deliberate systematic forwarding regarding informatization industrial a railroad of the center functional service a railroad taking charge of. we selected a system sub-of 25 by each fields for this after classifying it to, eight fields such as construction, train driving control, environment, maintenance, logistics, a train, assets management, passenger service.

• East Asian mathematical journal
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• v.36 no.2
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• pp.115-129
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• 2020

In order to overcome the heterogeneity of mathematics education in South Korea and North Korea in preparation for the future integration of North and South Korea, research on North Korean mathematics education needs to be studied qualitatively in various aspects and fields. In order to do this, it is necessary first to elaborate and analyze the results of the research on North Korean mathematics education reported so far, to find important implications and find out the research fields that have been neglected in the meantime. Therefore, this study analyzed the trends of previous studies for establishing the direction of future studies on mathematics education in North and South Korea. As a result, it can be seen that the study on North Korean mathematics education in Korea is limited to curriculum analysis, textbook comparison, and comparison of mathematical terms between North and South.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.48-53
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• 2004

This paper suggested the method determing the stress intensity factor (SIF) for functionally gradient materials (FGMs) by photo elastic experimental method. The SIF for the center crack in a finite rectangulat plate with a linear variation of shear modulus with constant density and Poisson's ratio along the direction of the crack under mode I static loading is obtained. The exponential and linear variation of stress fields are used for obtaining the SIF. The greater crack length, the increaser the difference of the SIF between right and left side crack tip.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.5
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• pp.90-97
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• 2002

The interaction between airflow and liquid phase LfG (Liquefied Petroleum Gas) sprays was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside intake port of LPG engines with liquid injection system. The spray developments in flowing fields with the mean velocities of 5.4, 21.5 and 42.4m/s were identified by spray visualization techniques such as Mie scattering and shadowgraph. The microscopic visualization using a telescopic lens system was performed to investigate the shape and size of liquid droplets in the spray. PDA measurement was used to get 1-dimensional velocity and diameter of liquid droplets. The fast co-flows make the spray field be compact and be lead upward to the injection direction. SMD of the spray was smaller at the fast flowing field. Spray width got bigger and SMD of the spray was smaller with higher injection pressure.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.5
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• pp.234-241
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• 2005

The performance of passive conductor loop (hereinafter 'loop') method which is used to mitigate the magnetic field around overhead power transmission line is dependent on its configuration and installed location, which are affected by installation conditions of the loops such as objective areas and levels of magnetic field mitigation. Thus, because the design problem of loops is difficult and cumbersome by variety of their configuration and complexity of magnetic coupling mechanism, it is need to be formulated as a computer-based optimum problem to determine the most effective and reasonable loop model satisfying the installation conditions. In this paper, the optimum locations of the multi-wired multiple loops including series reactance compensations are searched by using the genetic algorithm (GA) to mitigate effectively the magnetic fields of relatively near points or far points from transmission line at Am height, and the magnetic fields mitigation characteristics of each loop are analyzed in the view of magnitude, direction and phase of cancellation fields by polarized vector concept to identify their adequacy and rationality for the installation objectives.

• Journal of the Korean Society of Safety
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• v.21 no.4 s.76
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• pp.119-126
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• 2006

Though safety signs are important since they transmit hazard information even after diverse accident prevention treatments, their functional effectiveness were never tested in Korea so that even those provided by Occupational Safety & Health Act(OSHAct) could not accomplish their objectives, "effective accident prevention", This research was carried out to understand confronted problems and improvement direction for safety signs provided by OSHAct. For them, current safety signs were analyzed with a semiotic view on one hand, and a questionnaire survey was conducted with safety-related people in industrial fields on the other hand. To summarize problems in semiotic aspects, geometric simplicity of pictograms in safety signs seemed to be so emphasized that they might fail to induce realistic action, and their esthetic sensation seemed to be lower than those of developed countries. And according to present questionnaire survey, it was pointed out that; 1) legal systems related with safety signs were not classified appropriately, 2) safety signs were recognized as difficult to understand and inapplicable to industrial fields, and eventually 3) safety signs were not effectively utilized for industrial accident prevention. Therefore, discussions for improving confronted problems and relation to international standards were added at the end.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.77.1-77.1
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• 2014

Galactic spiral arms are abundant with interesting gaseous substructures. It has been suggested that arm substructures arise from the wiggle instability (WI) of spiral shocks. While the nature of the WI remained elusive, our recent work without considering magnetic fields shows that the WI is physically originated from the accumulation of potential vorticity (PV) generated by deformed shock fronts. To elucidate the characteristics of the WI in more realistic galactic situations, we extend our previous linear stability analysis of spiral shocks by including magnetic fields. We find that magnetic fields reduce the amount of density compression at shocks, making the shock fronts to move toward the upstream direction. Magnetic tension forces from bent field lines stabilize the WI by prevent the generation of PV. When the spiral-arm forcing is F=5% of the centrifugal force of galaxy rotation, the maximum growth rate of the WI is found to be about 1.0, 0.4, and 0.2 times the orbital angular frequency for the plasma parameter ${\beta}=100$, 10, and 5, respectively. Shocks with ${\beta}=1$ are stable to the WI for F=5%, while becoming still unstable when F=10%.