• Computational Structural Engineering
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• v.8 no.4
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• pp.189-198
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• 1995

The conventional finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements of commonly used displacement and pressure interpolations. The criterion for the stability in the pressure solution is the so-called Babugka-Brezzi stability condition, and the above elements do not satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element interfaces is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. This pressure residual is implemented in Q1P0 element derived from the conventional incompressible elasticity. The pressure solutions can be stable with the pressure residual though they exhibit sensitivity to the stabilization parameters. Parametric study for the solution stabilization is also discussed.

• Journal of the Society of Naval Architects of Korea
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• v.51 no.3
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• pp.212-219
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• 2014

As subsea production has been revived up, the demand of subsea equipment has also been increased. Among the equipment, subsea tree plays a major role in safety. The tubing hanger is one of the most important components in subsea tree. In this study structural reliability analysis on dual bore tubing hanger of subsea tree is performed. The target reliability which is introduced in ISO regulation is used for judging whether tubing hanger is safe or not. The considered loads are working pressure, working temperature and suspended tubing weight. Thermal-stress analysis on tubing hanger is performed and kriging model is created based on the results of FEM analysis. According to von Mises criterion, limit state equation can be estimated. Reliability analysis is performed by using level 2 method and the result is verified by that of Monte Carlo Simulation. For finding most probable failure point, enhanced HL-RF method is adopted. Because the reliability of model doesn't reach target reliability, an improvement measure should be considered. Thus, it is suggested to change the material of tubing hanger main body to AISI 4140.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.325-331
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• 2009

In this paper, a simulation approach for the optimum design of cogeneration system is described. For the purpose of the systematic analysis, a simulation tool is developed with which the prediction of the energy load, calculation of operation data according to prime mover or capacity of it, and estimation of economic gains can be carried out. As for the criterion of the optimum design, the economic gains by adopting cogeneration system is taken. Based on the capital, operation, and maintenance costs etc, LCC analysis is to be carried out for the scenarios respectively. In this study, the simulation for the apartment complex is performed and the analysis of the results are described in detail. The effects of the operation parameters such as capital cost, fuel cost, and unit cost for the purchase or sale of heat and electricity on overall economy are also be considered by sensitivity study.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.172-184
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• 2012

An infection risk model for Phytophthora blight on chili pepper was developed to estimate the first date of disease occurrence in the field. The model consisted of three parts including estimation of zoosporangium formation, soil water content, and amount of active inoculum in soil. Daily weather data on air temperature, relative humidity and rainfall, and the soil texture data of local areas were used to estimate infection risk level that was quantified as the accumulated amount of active inoculum during the prior three days. Based on the analysis on 190 sets of weather and disease data, it was found that the threshold infection risk of 224 could be an appropriate criterion for determining the primary infection date. The 95% confidence interval for the difference between the estimated date of primary infection and the observed date of first disease occurrence was $8{\pm}3$ days. In the model validation tests, the observed dates of first disease occurrence were within the 95% confidence intervals of the estimated dates in the five out of six cases. The sensitivity analyses suggested that the model was more responsive to temperature and soil texture than relative humidity, rainfall, and transplanting date. The infection risk model could be implemented in practice to control Phytophthora blight in chili pepper fields.

• Journal of Welding and Joining
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• v.31 no.5
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• pp.59-63
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• 2013

A bendable electronic module has been developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In flexible embedded electronic module, a thin silicon chip was embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. To confirm reliability and durability of prototype bendable module, the following tests were conducted: Moisture sensitivity level, thermal shock test, high temperature & high humidity storage test, and pressure cooker tester. Those experiments to induce failure of the module due to temperature variations and moisture are the experiment to verify the reliability. Failure criterion was 20% increase in bump resistance from the initial value. The mechanism of the increase of the bump resistance was analyzed by using non-destructive X-ray analysis and scanning acoustic microscopy. During the pressure cooker test (PCT), delamination occurred at the various interfaces of the bendable embedded modules. To investigate the failure mechanism, moisture diffusion analysis was conducted to the pressure cooker's test. The hygroscopic characteristics of the encapsulating polymeric materials were experimentally determined. Analysis results have shown moisture saturation process of flexible module under high temperature/high humidity and high atmosphere conditions. Based on these results, stress factor and failure mechanism/mode of bendable embedded electronic module were obtained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.225-233
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• 2004

In this study, the seismic safety of containment building is assessed using response surface method. The structural analyses considering random variables such as load, resistance and analysis by ABAQUS are performed to obtain the structural response. The structural response is represented by polynomial of random variables, and the reliability analysis is performed by Level II method. Drucker-Prager failure criterion is applied as limit state function to take bi-axial stress states into account in the concrete. The lifetime probability of failure is evaluated by considering the lifetime of containment building, the annual occurrence rate of earthquake and the conditional probability of failure. Also the sensitivity analysis on the selection of sampling points is performed to obtain the steady results from response surface method.

• The Research Journal of the Costume Culture
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• v.10 no.5
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• pp.493-503
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• 2002

This study examined consumer characteristics and consumers' clothing purchase behavior for each of the four fashion brand types. The ultimate purpose of this study is to suggest the most effective marketing strategy for competitive advantage in fashion brand strategy. The subjects selected for the final analysis are 412 women of age 20 thru 34 in Seoul and areas. The data were analyzed using frequency, percentage, factor analysis, chi-square test, ANOVA, duncan test. The results of our study indicate that it is possible to meaningfully describe and contrast four brand types based on consumer's characteristics and purchase behavior. 1. The clothing brand is classified into four types : Designer brand 10.9%, National brand 27.2%, Middle-price brand 36.2%, Low-price brand 25.7%. 2. There are significant diferences according to four brand types in the demographic traits such as age education and income the average monthly spending on clothing. 3. There are an important discrimination according to tow brand types in their clothing purchase behavior such as information usage, clothing choice criterion and brand choice motivation. 4. Based on the result of this analysis and the review of literature, the brand strategy is suggested that characteristic and products development is efficient way to each brand consumers' purchase need. Therefore each brand which pursue an added value must frame marketing strategy on the basis of the target consumers' sensitivity characteristic according to the fashion consciousness.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.22-28
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• 2008

It proposes the novel design conditions to maximize the power coupling of active directional couplers with mismatched access guides. To verify the validity and accuracy of the conditions proposed, a new coupling efficiency is defined and it depends on the reflection coefficients occurred at the discontinuous input/output interfaces. The numerical results reveal that the phase-matched condition and the minimum-gap condition for those couplers are no longer suitable to optimize the design parameters and a new criterion is needed.

• International Journal of Reliability and Applications
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• v.13 no.1
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• pp.19-35
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• 2012

This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.

• Steel and Composite Structures
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• v.18 no.3
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• pp.547-563
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• 2015

Deflection in a beam of a composite frame is a serviceability design criterion. This paper presents a methodology for rapid prediction of long-term mid-span deflections of beams in composite frames subjected to service load. Neural networks have been developed to predict the inelastic mid-span deflections in beams of frames (typically for 20 years, considering cracking, and time effects, i.e., creep and shrinkage in concrete) from the elastic moments and elastic mid-span deflections (neglecting cracking, and time effects). These models can be used for frames with any number of bays and stories. The training, validating, and testing data sets for the neural networks are generated using a hybrid analytical-numerical procedure of analysis. Multilayered feed-forward networks have been developed using sigmoid function as an activation function and the back propagation-learning algorithm for training. The proposed neural networks are validated for an example frame of different number of spans and stories and the errors are shown to be small. Sensitivity studies are carried out using the developed neural networks. These studies show the influence of variations of input parameters on the output parameter. The neural networks can be used in every day design as they enable rapid prediction of inelastic mid-span deflections with reasonable accuracy for practical purposes and require computational effort which is a fraction of that required for the available methods.