Long-term deformational simulation of PC bridges based on the thermo-hygro model of micro-pores in cementitious composites

Creep deflections that greatly exceed the predicted values by the linear creep law are being found in measurements on actual PC bridge viaducts. In this study, structural creep deformations were reproduced by using the multi-scale coupled thermo-hygro and mechanical modeling which enables to deal with an interaction of chemo-physical events of differing dimensions ranging from the kinematics of moisture in micro-pores to the macroscopic structural mechanics, and the effect of various factors was analytically investigated. The numerical analysis approximately reproduced the excessive deflection measured on an actual bridge viaduct. It was confirmed that the creep bending of the viaduct having the hollow cross-section varies significantly due to the ambient temperature, humidity and the structural specific surface area. The macroscopic structural responses in association with the thermodynamic state of moisture in the micro-pores are also discussed.     

Physical evaluation of pure zein films by atomic force microscopy and thermal mechanical analysis

Biodegradable edible films can be made from corn protein, α-zein. Pure zein films are cast from an organic solution of α-zein. This report outlines the surface conditions of such pure zein films. First, the transition temperature, T _t′ of the pure zein film was measured with a thermomechanical analyzer. T _t was between 167.0 and 172.7°C. The thermal elongation of the films depended on the drying conditions used during film preparation. Second, the surface microstructure of pure zein films, produced under several different drying conditions, was observed by atomic force microscopy. The surface had a morphology that showed depressions either with acutely (90–120°) or obtusely (121–180°) angled features depending upon the drying conditions. On the other hand, the surface microstructure after thermal elongation analysis appeared to have a pattern of projections that was repeated every 25 nm. Third, we measured the contact angle of the pure zein films. We found a correlation between surface microstructure and contact angle. Pure zein films with projections smaller than 200 nm in base diameter on the surface had a high contact angle (>70°).     

Polymer electrolyte membranes having sulfoalkyl grafts into ETFE film prepared by radiation‐induced copolymerization of methyl acrylate and methyl methacrylate

Polymer electrolyte membranes (PEMs) containing alkylsulfonic acid grafts can be prepared by radiation‐induced graft copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) into a poly(ethylene‐co‐tetrafluoroethylene) film followed by sulfonation of the MA units in the copolymer grafts using an equimolar complex of chlorosulfonic acid and 1,4‐dioxane (ClSO₃H‐Complex). PEMs with MA/MMA copolymer grafts that are 33%–79% MA units were prepared by preirradiation with a dose of 20 kGy and grafting in bulk comonomers at 60°C. The grafted films are treated with ClSO3H‐Complex to obtain PEMs with ion exchange capacity of 0.36‐0.81 mmol/g (sulfonation degrees of 20%–40%) and proton conductivity of 0.04‐0.065 S/cm. These values can be controlled by changing the MA content the sulfonation occurring at an α‐carbonyl carbon. The PEMs with higher MMA content showed higher durability in water (80°C) and under oxidative conditions (3% H₂O₂) at 60°C. This is because the PMMA grafts in the PEMs have no proton at an α‐carbonyl carbon, which is considered to be a trigger of the degradation of grafting polymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of fluorinated polymer electrolyte membranes by radiation grafting and atom transfer radical polymerization techniques

A novel polymer electrolyte membrane was synthesized by radiation-induced grafting and consequent atom transfer radical polymerization (ATRP). First, bromine-containing perfluorinated grafts were prepared by radiation grafting of 2-bromotetrafluoroethyl trifluorovinyl ether (BrTFF) into a poly(ethylene-co-tetrafluoroethylene) (ETFE) film. Then, the bromine atoms in the ETFE-g-PBrTFF grafted films were acted as initiators, and the films were treated with Cu(I)-based catalytic system of a CuBr and 2,2′-bipyridyl (bpy) for the ATRP. By adjusting the molar ratio of initiator/CuBr/bpy and the reaction temperature, branched poly(styrene) with a grafting yield of above 100% on the poly(BrTFF) main chains was constructed in ETFE-g-PBrTFF films. Thermal analysis revealed that the perfluorinated poly(BrTFF) main chains were miscible to ETFE, whereas the hydrocarbon poly(styrene) branches were phase-separated from the ETFE-g-PBrTFF film. Sulfonic groups could be further introduced into the poly(styrene) grafts of ETFE-g-PBrTFF-g-PS films with homogeneous distribution in a perpendicular direction to the membrane surface. The resulting membrane with a styrene grafting yield of 15% exhibited higher proton conductivity than commercial Nafion 117 membrane. Likewise, it had better chemical stability than ETFE-g-PSSA membrane prepared by conventional radiation-induced grafting.     

Physical Factors Determining Thermal Conductivities of Isotropic Conductive Adhesives

The thermal conductivities of a typical isotropic conductive adhesive (ICA) composed of an epoxy-based binder containing flake-shaped and spherical Ag particles have been studied. The ICA specimens exhibit anisotropy in their thermal conductivities between the vertical and in-plane directions. In addition, their thermal conductivities apparently depend on their thermal history during the curing and subsequent annealing processes, even if they are fully cured during the preliminary curing stage. The thermal conductivities tend to increase with decreasing electrical resistivities. The experimental values for the thermal conductivities of the ICA specimens were apparently higher than␣those predicted using Bruggemann’s equation. Analysis using the Wiedemann–Franz (W–F) law indicates that their thermal conductivities increase with increasing contribution from electrical conduction. In order to discuss the thermal conductivities of ICA specimens that exhibit relatively low electrical resistivities (below 10⁻³ Ω cm), the contribution of the conducting electrons must be included.     

Effect of carbon nanomaterials on the germination and growth of rice plants

For the successful diverse applications of different nanomaterials in life sciences, it is necessary to understand the ultimate fate, distribution and potential environmental impacts of manufactured nanomaterials. Phytotoxicity studies using higher plants is an important criterion for understanding the toxicity of engineered nanomaterials. We studied the effects of engineered carbon nanomaterials of various dimensionalities (carbon nanotubes, C60, graphene) on the germination of rice seeds. A pronounced increase in the rate of germination was observed for rice seeds in the presence of some of these carbon nanostructures, in particular the nanotubes. Increased water content was observed in the carbon nanomaterial treated seeds during germination compared to controls. The germinated seeds were then grown in a basal growth medium supplemented with carbon nanomaterials for studying their impact on further seedling growth. Treated seedlings appeared to be healthier with well-developed root and shoot systems compared to control seedlings. Our results indicate the possible use for carbon nanomaterials as enhancers in the growth of rice seedlings.     

Bauschinger effect and multiaxial yield behavior of stress-reversed mild steel

Thin-walled cylindrical specimens subjected to torsional prestraining are stress-reversed along the Bauschinger curve. The Bauschinger effect (BE), yield behavior, and flow behavior of the stress-reversed mild steel were examined by using combined loadings of axial load, internal pressure, and torsion. The results indicate that the stress-reversed steel has the same yield stress at 0.2 pct offset strain in reloading tests of forward and reverse torsion, when the reverse strain is =0.77 pct. Furthermore, it is possible to cause the yield stresses in forward and reverse torsion to coincide in any offset strain. The yield locus of the stress-reversed steel is symmetric with respect to the tensile stress axis in a tension-torsion stress field. However, it has been found to be an anisotropy in the stress-reversed steel, and the magnitude of anisotropy is related to the offset strain. For example, there is a stronger anisotropy at 0.2 pct offset strain than at 2 pct offset strain, even though the BE is eliminated for the former. It is shown that the reduction in the BE by stress reversal is concerned with the relief of the long-range back-stress generated by prestraining. Besides, the roles of aging in the stress-aging process lie in the contributions to age hardening and development of directional back-stress.     

Control System Design Automation for Mechanical Systems

In this paper, a user-friendly and comprehensive control system design package called Control System Design Automation (CSDA) is described. The system consists of five main blocks: a requirement interpretation block, a modeling block, an analysis/design block, a database management and knowledge base block, and a verification block. The requirement interpretation block transforms the specifications in terms of the application to those in terms of control. The analysis/design block selects an optimal control structure and determines the controller parameters. In addition to the conventional design methods, CSDA also contains the more recent design methods such as the LMI design approach and the Kessler/Manabe method. The LMI approach can obtain a controller which satisfies multiple specification items at the same time. The configuration of the system as well as the analysis/design block are described in detail in this paper.     

Artificial life based on the programmed self-decomposition model, SIVA

To examine the effect and significance of the phenomenon of death, we have developed an artificial life simulator, SIVA-III (simulator for individuals of virtual automata III), based on a “programmed self-decomposition model”. The architecture of this simulator consists of a “finite heterogeneous habitation environment” and “artificial life with programmed individual death and concurrent self-decomposition”. We conducted experiments under various settings to comparare and contrast mortal life and immortal life. The results clearly demonstrated the validity of a self-decomposing, programmed individual death, and the limitations inherent in immortal life, suggesting a striking superiority of mortal life over immortal life. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Self-intersections of offsets of quadratic surfaces: Part I, explicit surfaces

Although offset surfaces are widely used in various engineering applications, their degenerating mechanism is not well known in a quantitative manner. Offset surfaces are functionally more complex than their progenitor surfaces and may degenerate even if the progenitor surfaces are regular. Self-intersections of the offsets of regular surfaces may be induced by concave regions of surface where the positive offset distance exceeds the maximum absolute value of the negative minimum principal curvature or the absolute value of the negative offset distance exceeds the maximum value of the positive maximum principal curvature. It is well known that any regular surface can be locally approximated in the neighborhood of a pointp by the explicit quadratic surface of the form r(x,y)=[x,y1/2(x²+y²)]^T to the second order where – and – are the principal curvatures at pointp. Therefore investigations of the selfintersecting mechanisms of the offsets of explicit quadratic surfaces due to differential geometry properties lead to an understanding of the self-intersecting mechanisms of offsets of regular parametric surfaces. In this paper, we develop the equations of the self-intersection curves of an offset of an explicit quadratic surface. We also develop an algorithm to detect and trace a small loop of a self-intersection curve of an offset of a regular parametric surface based on our analysis of offsets of explicit quadratic surfaces. Examples illustrate our method.