• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.9-16
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• 2001

In this paper, general design process for Tracked Fighting Vehicle has been suggested. Stress analysis and optimal design for ply angle of IFV's composite upper hull has been calculated using KMA CIFV and it is contained exploratory development of design process. In this point, this paper applied composite to IFV's upper hull. Finite element mesh has been made using Matlab program, and we have analyzed stress based on the given material properties and ply arrangement. For each load condition, load distribution in plane and failure index are calculated by using Tasi-Hill criterion, which is composite failure criterion and analyzing change of failure index as change of ply angle. Finally, optimal ply angles of upper hull are calculated using KMA CIFV. We can estimate the decrease of weight for IFV's upper hull.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.61-68
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• 1998

It has become important to evaluate the qualitive reliability and condition assessment of existing structural systems in order to establish a rational program for repair and maintenance. Since most of if existing structural system may suffer from defect corrosion and damage, it is necessary to account for their effects in fuzzy reliability analysis, In this paper, an attempt is made to develope a reliability analysis for damaged structural systems using failure possibility theory. Damage state is specified in terms of linguistic valiables using natural language information and numerical information, which are defined by fuzzy sets. Using a subjective condition index of failure possibility and information of the damage state is introduced into the calculation of failure probability. The subjective condition index of quantitative and qualitative analysis method is newly proposed based on the fuzzy set operations, namely logical product, drastic product, logical sum and drastic sum

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.7
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• pp.661-667
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• 2010

This paper presents a failure diagnosis and accommodation strategy which is capable of tolerating faulty actuators of a submersible vehicle. The proposed method is mainly based on a sliding mode control technique. The primary ideas include a performance index to describe the effectiveness of actuators, and a controller reconfiguration strategy using the actuator effectiveness index. The actuator effectiveness proposed in this work is defined as the relationship between the sliding surface and the controlled system behavior. The resulting actuator effectiveness is then used in reconfiguring the controller in order to counteract for the deteriorated control performance in the presence of a faulty actuator. The effectiveness of the proposed method is demonstrated by means of numerical simulations with a submersible vehicle.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.789-795
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• 2008

Slope stability is affected by various factors. For safety management of slopes, monitoring systems have been widely constructed along railway lines. The representative data from the systems are variations of ground profile such like ground water level and pore water pressure etc. and direct displacement measured by ground clinometer and tension wire sensor. Slopes are mainly effected by rainfall and rainfall causes the decrease of factor of safety(FOS). Because FOS varies linearly by the variation of ground water level and pore pressure, it has a weak point that could not define the time and proper warning sign to secure the safety of the train. In this study, alternative of FOS such as reliability index and probability of failure is applied to slope stability analysis introducing the reliability concept. FOS, reliability index, probability of failure and velocity of probability of failure of the slopes by variation of ground water level are investigated for setting up the specification of safety management of slopes. By executing case study of a slope(ILLO-IMSUNGLI), it is showed to be applied to specification of safety management.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.369-377
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• 2023

In this study, previously developed algorithm is used for Optimization of hybrid composite plates using Tsai-Wu criteria. For the stress-based Design Optimization problems, Von-Mises stress uses as design variable for isotropic materials. Maximum stress, maximum strain, Tsai Hill, and Tsai-Wu criteria are generally used to determine failure of composite materials. In this study, failure index value is used as design variable in the optimization algorithm and Tsai-Wu criteria is utilized to calculate this value. In the analyses, commonly used design domains according to different hybrid orientations are optimized and results are presented. When the optimization algorithm was applied, 50% material reduction was obtained without exceeding allowable failure index value.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.137-147
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• 2014

The present paper deals with the first ply failure analysis of the laminated composite plates under various static and dynamic loading conditions. Static analysis has been carried out under patch load and triangular load. The dynamic failure analysis has been carried out under triangular pulse load. The formulation has been carried out using the finite element method and a computer code has been developed. The first order shear deformation theory has been applied in the present formulation. The displacement time history analysis of laminated composite plate has been carried out and the results are compared with those published in literature to validate the formulation. The first ply failure load for laminated composite plates with various lamination schemes under static and dynamic loading conditions has been calculated using various failure criteria. The failure index-time history analysis has also been carried out and presented in this paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.9
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• pp.49-56
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• 2004

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joint have become a very important research area because they are often the weakest areas in composite structures. In this paper, the linear finite element analyses in which the pin of the composite joint was assumed to be the frictionless rigid body were performed and predict the strength of the mechanically fastened composite joint using the failure area index method. By the failure area index method, the strength of the mechanically fastened composite joint which has the specimen of different shape, hole size and stacking sequence could be predicted within 12.2%.

• Journal of Korea Water Resources Association
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• v.44 no.11
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• pp.903-913
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• 2011

In this paper important factors in determining improvement priorities for water pipes were categorized into the effects of a pipe failure to entire pipe network and the characteristics of individual pipe. Subsequently, mathematical models that can quantify these factors were developed using the Fuzzy techniques. The effects of a pipe failure to entire pipe network and the characteristics of individual pipe that were estimated byFuzzy techniques were coined as Fuzzy Importance Index and Fuzzy Characteristic Index, respectively. The Fuzzy Characteristic Index was further categorized into Fuzzy Deterioration Index and Fuzzy Difficulty Index. Considerations were given to applying weights to specific factors in the developed model depending on the circumstances of model applications. To provide an example of the methodology an example pipe network, Net3, of the EPANET program was used. The Fuzzy Importance Index (FII) and Fuzzy Deterioration Index (FDI) were calculated for the Net3 network by considering the hydraulic effects of a pipe failure on the entire pipe network and the pipe deterioration as one of the individual pipe characteristics. Subsequently, the improvement priorities of the pipes in the Net3 pipe network were established based on the FII and FDI.

• Journal of Korean Academy of Nursing
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• v.53 no.4
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• pp.468-479
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• 2023

Purpose: This study aimed to evaluate the use of the respiratory rate oxygenation (ROX) index, ROX-heart rate (ROX-HR) index, and saturation of percutaneous oxygen/fraction of inspired oxygen ratio (SF ratio) to predict weaning from high-flow nasal cannula (HFNC) in patients with respiratory distress in a pediatric intensive care unit. Methods: A total of 107 children admitted to the pediatric intensive care unit were enrolled in the study between January 1, 2017, and December 31, 2021. Data on clinical and personal information, ROX index, ROX-HR index, and SF ratio were collected from nursing records. The data were analyzed using an independent t-test, χ² test, Mann-Whitney U test, and area under the curve (AUC). Results: Seventy-five (70.1%) patients were successfully weaned from HFNC, while 32 (29.9%) failed. Considering specificity and sensitivity, the optimal cut off points for predicting treatment success and failure of HFNC oxygen therapy were 6.88 and 10.16 (ROX index), 5.23 and 8.61 (ROX-HR index), and 198.75 and 353.15 (SF ratio), respectively. The measurement of time showed that the most significant AUC was 1 hour before HFNC interruption. Conclusion: The ROX index, ROX-HR index, and SF ratio appear to be promising tools for the early prediction of treatment success or failure in patients initiated on HFNC for acute hypoxemic respiratory failure. Nurses caring for critically ill pediatric patients should closely observe and periodically check their breathing patterns. It is important to continuously monitor three indexes to ensure that ventilation assistance therapy is started at the right time.

• Tunnel and Underground Space
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• v.31 no.5
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• pp.360-373
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• 2021

Many sources of uncertainty exist in geotechnical analysis ranging from the material parameters to the sampling and testing techniques. The conventional deterministic stability analysis of a plane failure in rock slope produce a safety factor but not a probability of failure or reliability index. In the conventional slope stability analysis by evaluating the ground uncertainty as an overall safety factor, it is difficult to evaluate the stability of the realistic rock slope in detail. This paper reviews some established probabilistic analysis techniques, such as the MCS, FOSM, PEM, Taylor Series as applied to plane failure of rock slopes in detail. While the Monte - Carlo methods leads to the most accurate calculation of the probability of safety, this method is too time consuming. Therefore, the simplified probability methods could be alternatives to the MCS. In this study, using these simple probability methods, the failure probability estimation of a plane failure in rock slope is presented.