Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part II: Stiffened panels

The present paper (Part II) is a sequel to the previous paper (Part I) [Paik JK, Seo JK. Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part I: Plate elements. Thin-Walled Struct 2008, this issue, doi:10.1016/j.tws.2008.08.005.] on the application of nonlinear finite element methods for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions. In contrast to Part I dealing with plate elements, the present paper (Part II) treats stiffened panels surrounded by strong support members such as longitudinal girders and transverse frames. In similar to Part I, some important factors of influence such as structural dimensions, initial imperfections, loading types and computational techniques in association with ultimate limit states are studied. Some useful insights in terms of nonlinear finite element method modeling are developed using ANSYS code together with the ALPS/ULSAP semi-analytical method, the latter being for the purpose of a comparison.     

Performance evaluation of a high durability asphalt binder and a high durability asphalt mixture for bridge deck pavements

This paper describes the results of laboratory and full-scale performance tests for a high durability asphalt binder (HDAB) and high durability asphalt mixture (HDAM) applicable to the wearing course in a bridge deck system. The HDAB was developed using a styrene–butadiene–styrene (SBS) modifier and hydrocarbon for improving construction workability and resistance to fatigue cracking. Various binder tests were conducted on the HDAB, and test results showed that the resistance to fatigue and low temperature cracking of the HDAB increased significantly compared to that of the PG 64-22 and PG 76-22 binders. For the mixtures, the fatigue test results showed that the HDAM has a three times longer fatigue life than the SBS-modified asphalt mixture. It was also found that the HDAM has a higher resistance against moisture-induced damage. Results from full-scale accelerated testing on the bridge deck pavement system proved that the HDAM can significantly improve pavement performance.     

Fabrication of Al matrix composite reinforced with submicrometer-sized Al<Subscript>2</Subscript>O<Subscript>3</Subscript> particles formed by combustion reaction between HEMM Al and V<Subscript>2</Subscript>O<Subscript>5</Subscript> composite particles during sintering

To fabricate an Al-V matrix composite reinforced with submicron-sized Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases, high energy mechanical milling (HEMM) and sintering were employed. By increasing the milling time, the size of mechanically milled powder was significantly reduced. In this study, the average powder size of 59 μm for Al, and 178 μm for V₂O₅ decreased with the formation of a new product, Al-Al₂O₃-Al_xV_y, with a size range from 1.3 μm to 2.6 μm formed by the in-situ combustion reaction during sintering of HEM milled Al and V₂O₅ composite powders. The in-situ reaction between Al and V₂O₅ during the HEMM and sintering transformed the Al₂O₃ and Al_xV_y (Al₃V, Al₁₀V) phases. Most of the reduced V reacted with excess the Al to form Al_xV_y (Al₃V, Al₁₀V) with very little V dissolved into Al matrix. By increasing the milling time and weight percentage of V₂O₅, the hardness of the Al-Al₂O₃-Al_xV_y composite sintered at 1173 K increased. The composite fabricated with the HEMM Al-20wt.%V₂O₅ composite powder and sintering at 1173 K for 2 h had the highest hardness.     

Assessing the effects of bacterial predation on membrane biofouling

Membrane biofouling is one of the major obstacles limiting membrane applications in water treatment. In this study, Bdellovibrio bacteriovorus HD 100, a Gram-negative predatory bacterium, was evaluated as a novel way to mitigate membrane biofouling and its subsequent performance decline. Dead-end microfiltration (MF) tests were carried out on Escherichia coli DH5α and B. bacteriovorus HD 100 co-culture feed solutions. Predation of E. coli was performed at either a low or high multiplicity of infection (MOI), which is defined as the predator to prey cell ratio. The MOIs tested were 2 and 200, and the viability of both the E. coli prey and the predator was monitored over 48 h. The higher MOI (high predator, HP) culture showed a nearly 6-log loss in E. coli number after 24 h when compared to both the control and low MOI (low predator, LP) cultures, whereas the E. coli population within both predated cultures (HP and LP) became nearly identical at 48 h and 4-log lower than that of the control. The unpredated cultures led to significant loss in water flux at 12, 24, and 48 h of culture, but the HP and LP membranes showed less loss of flux by comparison. Analysis of the total membrane resistance showed a similar trend as the flux decline pattern; however, irreversible resistance of the membrane was much higher for the 48 h LP culture compared to the unpredated and HP cultures at 48 h. This increase in irreversible resistance was attributed mainly to E. coli debris, which accumulated in the medium after the predator lysed the prey cells. These results show that pretreatment of wastewater using a suitable concentration of predatory bacteria such as B. bacteriovorus can enhance membrane performance.     

Integrity and cell-monolayer permeability of chitosan nanoparticles in simulated gastrointestinal fluids

The objective of this study was to assess the integrity and intestinal permeability of chitosan nanoparticles (CNPs) in simulated gastrointestinal fluids (SGIF). The cell-associated and transported chitosan was quantified and visualized after incubation of the CNPs with Caco-2 cell monolayer with/without SGIF treatment. In order to establish the role of proteins in the SGIF, CNPs were incubated with 4 proteins having different isoelectric points (pI). CNPs incubated with the fluids did not attach to the cell monolayer in contrast to the intact CNPs. Negatively-charged protein formed the complex with CNPs leading to particle size increase, but protected CNPs from disintegration. In contrary, positively-charged protein interacted with cross-linker causing disintegration of CNPs. CNPs incubated with the fluids did not attach to the cell monolayer in contrast to the intact CNPs. The results suggested that the surface charges of CNPs and proteins play a critical role in structural changes of CNPs in biological environment.     

Effects of consumer subsidy on household fuel switching from coal to cleaner fuels: A case study for anthracites in Korea

The Korean coal industry is in a transition under low carbon policy through the steady reduction of coal production. Since consumer subsidy for the consumption of anthracites briquette in low-income households caused a distortion in domestic coal market, the so-called coupon program will be the first target in energy reform policy in order to induce fuel switching from anthracites to alternative clean energy. This paper tries to identify various factors that influence households' fuel switching decision. Disutility from briquette consumption is also considered as an important factor. Using the 2007 census data on briquette-consuming households, it is found that the coupon program provides an adverse effect to switching fuels to clean energy while the disutility of briquettes is positively associated with the probability of fuel switching. However, the empirical finding suggests that the policy alone attempting to remove coupon program may fail to switch fuels unless the cost of boiler changes is substantially reduced through the provision of accessible networks to alternative energy sources. It indicates that reform policy for consumer subsidy must be understood in line with more comprehensive regional energy plans to resolve energy poverty issue.     

Assessment of a high-order discontinuous Galerkin method for vortex convection and wave propagation on unstructured meshes

A high-order accurate flow solver based on a discontinuous Galerkin method has been developed for the numerical simulation of vortex convection and wave propagation on unstructured meshes. To assess the performance of the present flow solver, a vortex convection problem in freestream and an acoustic benchmark problem were tested. An airfoil-vortex interaction problem was also simulated by coupling the flow solver with a dynamic mesh adaptation technique. From the mesh resolution test, the present fourth-order discontinuous Galerkin method almost perfectly preserves the vortex and also accurately resolves the acoustic waves on a mesh with an element size of half of characteristic length. It was also observed that the fourth-order method is more than ten times efficient, in terms of the number of degrees of freedom and the elapsed CPU time, compared to the second-order method.     

End-to-end framework for 4-D broadcasting based on MPEG-V standard

Advances in media technologies brought so-called 4-D movies to your neighbour. The 4-D movies represent movies (preferably in 3-D) with additional sensory effects such as motion chairs and wind effects. We present an end-to-end framework to provide sensory effects for home theaters based on MPEG-V standard. The key technologies of the 4-D broadcasting framework, required to provide sensory effect through home theaters consist of creating sensory effects synchronized with audiovisual contents, delivering the sensory effects with content to home theater devices, recognizing home devices for rendering sensory effects, and rendering contents through home theater system with connected sensory devices in a synchronized way. This paper proposes end-to-end technology required, in addition to the conventional broadcasting framework, based on international standard of MPEG-V, specifically Part 2 to describe capabilities of the home sensory devices, Part 3 to provide contents with sensory effects, and Part 5 to command the sensory devices among other parts of MPEG-V standard.