• Journal of Korean Association for Spatial Structures
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• v.14 no.3
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• pp.47-56
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• 2014

This paper investigates the characteristics of unstable behaviour and critical buckling load by joint rigidity of framed large spatial structures which are sensitive to initial conditions. To distinguish the stable from the unstable, a singular point on equilibrium path and a critical buckling level are computed by the eigenvalues and determinants of the tangential stiffness matrix. For the case study, a two-free node example and a folded plate typed long span example with 325 nodes are adopted, and these adopted examples' nonlinear analysis and unstable characteristics are analyzed. The numerical results in the case of the two-free node example indicate that as the influence of snap-through is bigger; that of bifurcation buckling is lower than that of the joint rigidity as the influence of snap-through is lower. Besides, when the rigidity decreases, the critical buckling load ratio increases. These results are similar to those of the folded-typed long span example. When the buckling load ratio is 0.6 or less, the rigidity greatly increases.

• The KSFM Journal of Fluid Machinery
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• v.14 no.4
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• pp.38-44
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• 2011

This paper deals with the detail rotordynamic analysis for BB5 eight stages pump as development of API 610 BB5 type pump. Dry-run analytical model, not considering operating fluid, and wet-run analytical model, considering operating fluid are established. In addition, plain circular and pressure dam bearings are chosen and it was discussed that each bearing has an effect on dynamic characteristics of pump rotor system. A rotordynamic analysis includes the critical speed map, Campbell diagram, stability, and unbalance response. As results, it was predicted that rated speed of the pump rotor passes through 1st critical speed in dry-run condition regardless of bearings, however, it was verified that, in wet-run condition, the rotor system doesn't have critical speeds even if more than twice rated speed. Hence the resonance problem caused by the critical speeds does not happen since actual operating is in wet-run condition including operating fluid. As a result of unbalance response analysis, the pump rotor has stable vibration response at rated speed, regardless of operating fluid and the proposed bearing types.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.877-884
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• 2019

As technology advances, equipment installed in Nuclear facilities are changing from analog system to digital system. Nuclear facilities have been exposed to cyber threats as the proportion of computers and digital systems increases. As a result, interest in cyber security has increased and there has been a need to protect the system from cyber attacks. KINAC presented 101 cyber security controls for critical digital asset. However, this is a general measure that does not take into account the characteristics of digital assets. Applying all cyber security controls to critical digital assets is a heavy task and can be lower efficient. In this paper, we propose an effective cyber security controls by identifying the characteristics of critical digital assets and presenting proper security measures.

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.61-75
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• 2003

Comprehensive review on the determination of critical state parameters in sandy soils from standard triaxial testing was performed to facilitate the application of critical state soil mechanics to the shear behavior of sandy soils. First, semantic differences in literature were clarified, inferring that critical state should be considered as the ultimate state at large deformation. Second, the characteristics of critical state parameters were discussed, and also the uniqueness of critical state line and the sensitivity of quasi-steady state condition were verified in relation to initial state, fabric, loading condition, and drainage condition. Third, as an example, the critical state soil mechanics was applied to evaluate the post-liquefaction shear strength, i.e. the reliable ultimate shear strength in liquified soils, in terms of critical state parameters.

• The Journal of Korean Academic Society of Nursing Education
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• v.23 no.2
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• pp.214-223
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• 2017

Purpose: This study was conducted to investigate the factors influencing the competence in intensive and critical care nursing of senior nursing students. Methods: A descriptive survey was used to examine the factors that influence competence in intensive and critical care nursing. The data were collected using self-administered questionnaires; 237 senior nursing students were asked about general characteristics, critical thinking, communication competence, self-esteem, self-resilience, and self-leadership. Results: Multiple regression analysis indicated that self-leadership, self-esteem, and confidence in intensive care unit practice predicted the competence in intensive and critical care nursing (37.8% of explanatory power). Critical thinking, communication competence, and self-resilience were not shown to be significant predictors of, but were positively correlated with, the competence in intensive and critical care nursing. Conclusion: Based on the results, it is suggested that self-leadership, self-esteem, and confidence in intensive care unit practice should be considered in nursing education in order to improve nursing students' level of competence in intensive and critical care nursing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.11
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• pp.771-778
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• 2015

In this work, vibration characteristics of high speed rotary bell cup for paint atomizer are numerically investigated. New type of bell cup model is proposed and additional corresponding models with design parameter variations for length and diameter are constructed. Dynamic characteristics, such as natural frequencies and corresponding mode shapes, are studied for each model as a first step. To investigate operation stability, critical speed of rotary bell cup is numerically analyzed based on Campbell diagram and separation margin between operating speed and critical speed is identified. Unbalance vibration responses are also investigated with respect to design parameter variation, operating speed and balancing quality grade of G. Then the proper design guideline for stable operation of high speed rotary bell cup for paint atomizer is suggested.

• Transactions of the Society of Information Storage Systems
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• v.5 no.2
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• pp.82-88
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• 2009

Understanding the adhesion behavior and characteristics of toner film is required to achieve image and text printing with high quality resolution. Toner can be considered as a thin film coating on a media such as paper or polymer film. Quantitative measurement of adhesion characteristics of the thin film is important to assess the reliability of the system. In this work the main objective was to investigate the adhesion characteristic between the toner and the media by ramp loading scratch test method. The scratch test may be used to obtain quantitative information about the adhesion of the film to the substrate. In the scratch test a diamond tip was used to scratch the surface of the toner film under an increasing normal load until the toner detached or fractured. The critical load (LC) was obtained from the experimental results. Also, the relationship between the critical load and the adhesive strength of the interface between the substrate and the toner was obtained by measuring the normal and tangential forces during the scratch test. Finally, theoretical analysis of the toner scratch characteristics was performed based on Benjamin and Weaver theory, Plowing model, and Laugier model.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.892-897
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• 2002

The research was requested by Meridian Rail Corporation in United States. The Swing Motion Bogie can application by Korea style if synthesize study result of bogie strength evaluation, bogie dynamic characteristics analysis, actual test(maximum speed, derailment coefficient, lateral force, vertical force, vibration acceleration, steady state lateral acceleration) etc..

• Journal of KSNVE
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• v.10 no.1
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• pp.74-81
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• 2000

The vibrational model of a helical gear pair is developed with considering the elastic deformation of the active teeth and the body to be a rigid. The main source of vibration in geared system which has been known to be the gear transmission error is mathematically formulated and used for the analysis of vibrational characteristics of geared system. As an example, a simple geared system containing a helical gearing is considered. The critical speeds are found by the campbell diagram and compared with the experimental results.

• Journal of Korean Institute of Industrial Engineers
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• v.29 no.2
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• pp.179-189
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• 2003

Gate poly-silicon critical dimension is a prime characteristic of a metal-oxide-semiconductor field effect transistor. It is important to achieve the uniformity of gate poly-silicon critical dimension in order that a semiconductor device has acceptable electrical test characteristics as well as a semiconductor wafer fabrication process has a competitive net-die-per-wafer yield. However, on gate poly-silicon critical dimension, the complexity associated with a semiconductor wafer fabrication process entails hierarchical variance components according to run-to-run, wafer-to-wafer and even die-to-die production unit changes. Specifically, estimates of the hierarchical variance components are required not only for disclosing dominant sources of the variation but also for testing the wafer-level uniformity. In this paper, two experimental designs, a two-stage nested design and a randomized complete block design are considered in order to estimate the hierarchical variance components. Since gate poly-silicon critical dimensions are collected from fixed die positions within wafers, a factor representing die positions can be regarded as fixed in linear statistical models for the designs. In this context, the two-stage nested design also checks the wafer-level uniformity taking all sampled runs into account. In more detail, using variance estimates derived from randomized complete block designs, Duncan's multiple range test examines the wafer-level uniformity for each run. Consequently, a framework presented in this study could provide guidelines to practitioners on estimating the hierarchical variance components and testing the wafer-level uniformity in parallel for any characteristics concerned in semiconductor wafer fabrication processes. Statistical analysis is illustrated for an experimental dataset from a real pilot semiconductor wafer fabrication process.