• Structural Engineering and Mechanics
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• v.6 no.7
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• pp.773-784
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• 1998

To assess the collapse risk of transmission line structures subject to natural hazards, it is important to identify what hazard may cause the structural collapse. In Australia and many other countries, a large proportion of failures of transmission line structures are caused by severe thunderstorms. Because the wind loads generated by thunderstorms are not only random but time-variant as well, a time-dependent structural reliability approach for the risk assessment of transmission line structures is essential. However, a lack of appropriate stochastic models for thunderstorm winds usually makes this kind of analysis impossible. The intention of the paper is to propose a stochastic model that could realistically and accurately simulate wind loading due to severe thunderstorms. With the proposed thunderstorm model, the collapse risk of transmission line structures under severe thunderstorms is assessed numerically based on the computed failure probability of the structure.

• International Journal of Reliability and Applications
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• v.17 no.1
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• pp.21-49
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• 2016

Many mechanical, electrical and electronic products have more than one performance characteristics (PCs). For example the performance degradation of rubidium discharge lamps can be characterized by the rubidium consumption or the decreasing intensity the lamp. The product may degrade due to all the PCs which may be independent or dependent. This paper deals with the design of optimal bivariate step-stress partially accelerated degradation test (PADT) with degradation paths modelled by gamma process. The dependency between PCs has been modelled through Frank copula function. In partial step-stress loading, the unit is tested at usual stress for some time, and then the stress is accelerated. This helps in preventing over-stressing of the test specimens. Failure occurs when the performance characteristic crosses the critical value the first time. Under the constraint of total experimental cost, the optimal test duration and the optimal number of inspections at each intermediate stress level are obtained using variance optimality criterion.

• Journal of Adhesion and Interface
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• v.21 no.1
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• pp.6-13
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• 2020

The objective of the current study is to characterize the long-term stability and efficacy of a structural adhesive assembly under static load. An apparatus was designed to be used in the Instron tensile test machine that would allow for real time modeling of the failure characteristics of an assembly utilizing a moisture- cure adhesive which was bonded to concrete. A regression model was developed that followed a linear - natural log function which was used to predict the expected life of the assembly. Evaluations at different curing times confirmed the structure was more robust with longer cure durations prior to loading. Finally, the results show that under the conditions the assembly was tested, there was only a small amount of inelastic creep and the regression models demonstrated the potential for a stable structure lasting several decades.

• Structural Engineering and Mechanics
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• v.47 no.1
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• pp.27-44
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• 2013

A finite element computational procedure for the accurate analysis of quasistatic thermorheological complex structures response is developed. The geometrical nonlinearity, arising from large displacements and rotations (but small strains), is accounted for by the total Lagrangian description of motion. The Schapery's nonlinear single-integral viscoelastic constitutive model is modified for a time-stress-temperature-dependent behavior. The nonlinear thermo-viscoelastic constitutive equations are incrementalized leading to a recursive relationship and thereby the resulting finite element equations necessitate data storage from the previous time step only, and not the entire deformation history. The Newton-Raphson iterative scheme is employed to obtain a converged solution for the non-linear finite element equations. The developed numerical model is verified with the previously published works and a good agreement with them is found. The applicability of the developed model is demonstrated by analyzing two examples with different thermal/mechanical loading histories.

• Journal of Periodontal and Implant Science
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• v.33 no.3
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• pp.373-382
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• 2003

The successful use of osseointegrated implants to replace missing teeth has been demonstrated for both the completely and the partially edentulous patients. Many studies have confirmed an excellent long-term prognosis. The successful outcome of any implant procedure is surely dependent on the interrelationship of the various components that includes the following: biocompatibility of the implant material, macroscopic and microscopic nature of the implant surface, the status of the implant bed in both a health(noninfected) and a morphologic(bone quality) context, the surgical technique, the undisturbed healing phase, the subsequent prosthetic design, and long-term loading phase. Periodontally compromised patients have poor status of the implant bed and periodontal pathogen. No longitudinal data are available whether these factors affect the prognosis of implants. In this study, 102 machined $Br{{\aa}}nemark$ implants are inserted to analyze the success rate of 1-4 years and marginal bone loss in 49 chronic periodontitis patients. The following conclusions could be drawn from this study. 1. The cumulative success rate of implants at the 4-year of loading was 95.10%. 2. 5 failed implants have been removed. One implant have been removed due to infection, two implants were removed due to failure of osseointegration. and other two implants were removed due to mechanical failure caused by over-loading. 3. Mean marginal bone loss from the time of loading was 0.94mm at first year, 1.12mm at second year, 1.25mm at third year. These results suggest that implant therapy is good treatment modality in chronic periodontitis patients, and periodontal treatment including oral hygiene program is completed prior to insertion of implants.

• Journal of Biomedical Engineering Research
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• v.39 no.4
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• pp.168-174
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• 2018

Adipocytes affect obesity through the regulation of lipid metabolism. Physical loading is an important regulator of fat tissue. There are ongoing in vitro studies inducing mechanotransduction on 3T3-L1 preadipocytes with mechanical stimulus in order to treat obesity by inhibiting adipogenesis and provoking cell death. In this study, our goal was to suggest a new therapy for obesity by investigating whether fluid shear stress (FSS) changes transcription factors on 3T3-L1 related with adipogenesis and cell death. FSS loading was applied to 3T3-L1 preadipocytes at 1Pa and 1Hz. After loading, bright field images were taken and an immunofluorescence assay was conducted to observe actin stress fiber formation. Western blot analysis was conducted to identify the activation of the ERK pathway as well as the adipogenic factors, which including C/EBPs and $PPAR{\gamma}$. The expression of osteopontin, a protein related to inflammation in adipose tissue, and cell death related factors, Bax, Bcl-2, and Beclin, were also measured. Results showed that FSS stimulated the formation of actin stress fibers in 3T3-L1 and also that the activation of C/EBPs decreased significantly when compared with the control group. $PPAR{\gamma}$ activation in the 2 hour FSS group was lower than the 1 hour FSS group, which implied that the results were time dependent. Additionally, there were no differences in the expression of cell death factors after FSS loading. In summary, similar to other fibroblasts, the formation of actin stress fibers induced by mechanotransduction may affect the differentiation of 3T3-L1, leading to inhibition of adipogenesis and inflammation.

• Structural Engineering and Mechanics
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• v.86 no.2
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• pp.167-180
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• 2023

This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler's and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article's findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.54-71
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• 1990

The fabrication of ceramic machine components by injection molding(CIM : Ceramic Injection Molding) is critically dependent on the shaping and binder extraction techniques. Injection molding is of keen interest to ceramic industries because CIM is suitable for making an intricate shape and manufacturing cost is lower than other process when production scale is large. The success of the molding process is dependent on the correct formulation of the organic vehicle and the achievement of optimum filler loading. Fine alumina powders and polyethylene binder systems were employed to prepare moldable blend then produce a simple specimen by compression molding. Flow characteristics of the mixture was evaluated by viscosity measurement. Optimum binder system and ceramic volume loading for injection molding were determind. A good debinding technique was utilized to improve the quality of debinded parts and save the debinding time. The simple ceramic part was successfully sintered after debinding and its microstructure examined with SEM revealed good consolidation.

• Earthquakes and Structures
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• v.10 no.4
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• pp.867-891
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• 2016

This paper addresses numerically the behavior of steel structures under Fire-after-Earthquake (FAE) loading. The study is focused on a four-storey library building and takes into account the damage that is induced in structural members due to earthquake. The basic objective is the assessment of both the fire-behavior and the fire-resistance of the structure in the case where the structure is damaged due to earthquake. The combined FAE scenarios involve two different stages: during the first stage, the structure is subjected to the ground motion record, while in the second stage the fire occurs. Different time-acceleration records are examined, each scaled to multiple levels of the Peak Ground Acceleration (PGA) in order to represent more severe earthquakes with lower probability of occurrence. In order to study in a systematic manner the behavior of the structure for the various FAE scenarios, a two-dimensional beam finite element model is developed, using the non-linear finite element analysis code MSC-MARC. The fire resistance of the structure is determined using rotational limits based on the ductility of structural members that are subjected to fire. These limits are temperature dependent and take into account the level of the structural damage at the end of the earthquake and the effect of geometric initial imperfections of structural members.

• Membrane Journal
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• v.6 no.2
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• pp.109-116
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• 1996

This work is a fundamental study for applying hybrid process coupling adsorption with microfiltration to waste-water treatment. Phenol was separated by adsorption on powdered activated carbon, adsorbed phenol with activated carbon was separated by microfiltration. As the particle size in suspension increased, filtration resistance decreased, and effect of particle concentration on resistance was less pronounced. The rate of uptake was greatly dependent on the degree of phenol loading. For a smaller amounts of activated carbon, the change of permeate concentration before break point and phenol loading with time were steeper than in the case of large amounts. Permeate concentration before break point decreased with decreasing particle size, this could be due to the increase of outer surface of particle and film mass transfer coefficient.