Effects of soil profile and characteristic of exciting force on propagation of ground vibrations

Railway Engineering Science - Ground-borne vibrations caused by vibration sources such as road traffic and construction exhibit complicated properties during propagation from the vibration source...     

Ultrasonic attenuation monitoring of fatigue damage in low carbon steels with electromagnetic acoustic resonance (EMAR)

We studied microstructure evolution during tension-compression fatigue in low carbon steels, containing C: 0.15 mass%. In situ monitoring of axial-shear-wave attenuation and velocity was achieved with electromagnetic acoustic resonance (EMAR), which is a combination of the resonant spectroscopy technique and a noncontacting electromagnetic acoustic transducer (EMAT). Transduction occurs with the magnetostriction effect and is the key to establish a continuous monitoring of microstructural changes in the surface region of the metals with high sensitivity. We found for the first time that the attenuation is highly sensitive to the accumulated fatigue damage, showing a minimum around 20% of the whole life. This phenomenon is interpreted in terms of drastic change of dislocation mobility and rearrangement, which is supported by TEM observation for dislocation structure. This technique has the potential to assess the damage advance and to predict the fatigue life of metals.     

Effects of MgO addition on the microwave dielectric properties of high thermal-conductive silicon nitride ceramics sintered with ytterbia as sintering additives

1 mol% of MgO was added together with 7 mol% of Yb₂O₃ as sintering additives to silicon nitride powder to fabricate advanced silicon nitride ceramics with both high thermal conductivity and low dielectric loss at 2 GHz. The mixed powder was CIPed at a pressure of 120 MPa and was gas-pressure sintered at 1900 °C to >98% of theoretical density. The sintered Si₃N₄ sample exhibited a high thermal conductivity of ～100 W m^?1 K^?1 and a loss tangent (tan δ) of ～4 × 10^?4, concurrently. The tan δ was further reduced by half after the heat treatment at 1300 °C for 24 h. The improvement in tan δ due to the annealing was explained from the point of crystallization of the intergranular glassy phase.     

Nanomodification of Glass Using fs Laser

We review the interaction of glass with intense ultrashort laser pulses revealing new phenomena and recent demonstrations of rewritable 5D optical memory and polarization imaging filter mediated by the self-organization of nanostructure. Particularly, we experimentally verify linearly polarized intense ultrashort pulses can control the direction of local optical anisotropy in homogeneous medium based on the interference between photon and electron plasma. These so-called “nanogratings” composed of the photoinduced oxygen defects emerge in the course of multiple laser pulses and are oriented perpendicularly to the laser polarization direction. The nanograting structures, which exhibit form birefringence, have evolved from residual birefringence along with lowering threshold for defect formation into self-assembly of oxygen defects.     

Crack profiles under a Vickers indent in silicon nitride ceramics with various microstructures

The effect of microstructure on crack morphology under a Vickers indentation was studied using 20 various silicon nitride ceramics including bearing-grade silicon nitrides. The indentation load was decreased from 98 N to 9.8 N and a transition of the crack types from half-penny crack to radial one was observed with both decoration method and serial sectioning technique. All of the indented samples possessed the half-penny cracks at the load of 98 N. The transition of crack profiles in the samples with coarse microstructure occurred when the load decreased from 49 N to 19.6 N, whereas the transition load for the sample with fine microstructure was ～9.8 N. Half-penny cracks were formed regardless of the microstructures when the ratio of the half of crack length to the half of diagonal size of an indentation, c/a, was above ～2. The dependence of the transition load on both Vickers hardness and fracture resistances was analyzed using Pajares's equation.     

Precise Synthesis of Novel Ferrocene-Based Star-Branched Polymers by Using Specially Designed 1,1-Diphenylethylene Derivatives in Conjunction with Living Anionic Polymerization

The precise synthesis of novel ferrocene-based regular and asymmetric star-branched polymers by a methodology using specially designed 1,1-diphenylethylene derivatives in conjunction with living anionic polymerization of ferrocenylmethyl methacrylate (FMMA) is described. The methodology involves three reaction steps, i.e., (1) introduction of 3-(tert-butyldimethylsilyloxymethyl)phenyl (SMOP) group(s) at the polymer chain end or in-chain, (2) conversion of the SMOP group(s) to α-phenyl acrylate function(s), and (3) a linking reaction of the α-phenyl acrylate function(s) with the living anionic polymer of FMMA or methyl methacrylate. By developing this methodology, a variety of 3-arm \textAA^￠₂ {\text{AA}^{\prime}_{2}} , A₂B, AB₂, ABC and 4-arm A₄, A₃B, A₂B₂, A₂BC, and ABC₂ star-branched polymers with well-defined structures have been successfully synthesized. The A, B, and C segments are poly(FMMA), polystyrene, and poly(methyl methacrylate), respectively.     

X-ray diffraction studies on stress transfer of kenaf reinforced poly(l-lactic acid) composite

Mechanical reinforcement of environmentally friendly composite, composed of kenaf fibers as reinforcement and poly-l-lactic acid (PLLA) resin as matrix, was investigated. The stress on the incorporated fibers in the composite under transverse load was monitored in situ and non-destructively using X-ray diffraction. The outer applied stress was found to be well transferred to the incorporated kenaf fibers through the PLLA matrix, which suggests a strong interaction between the fiber and the matrix. In addition, it was also revealed that a silane-coupling treatment to the kenaf fiber was effective for the improvement of interfacial adhesion.     

Water absorption of water-based anticorrosive coatings and its effect on mechanical property and adhesive performance

We focused on the water absorption of newly developed water-based anticorrosive coatings, which contain low volatile organic compounds. We investigated (1) the water absorption behavior of the coatings, (2) the effect of water absorption on the mechanical property of the coatings, and (3) the relationship between the water-absorbing properties and adhesive performance under accelerated aging conditions. It was found that the water absorption of the coatings indicated Fickian diffusion, and the saturated water content M _∞ and diffusion coefficient D of the coatings were quantitatively determined. The storage modulus E′ of the coatings decreased due to water absorption. However, in the coating that exhibited higher crosslink density, the effect of water absorption on the decrease in E′ was relatively small in spite of its higher M _∞ . The lower M _∞ and higher D coating resulted in better adhesive performance than the higher M _∞ and lower D coating. Thus, M _∞ value affected adhesive performance under accelerated aging conditions much more than D value.     

Preparation of Macroporous Titania Films by a Sol-Gel Dip-Coating Method from the System Containing Poly(ethylene glycol)

Macroporous titania (TiO₂) films have been prepared via a sol-gel dip-coating method from a titanium tetraisopropoxide solution that contains poly(ethylene glycol) (PEG). The macroporous morphology-i.e., the size, distribution, and shape of the macropores-is controlled by varying the content and molecular weight of PEG, the withdrawal speed, and the temperature of the dipping solution. The morphology of the TiO₂ film is determined by competitive contributions of the following factors: (i) decrease in fluidity, because of the evaporation of solvent; (ii) network formation by polycondensation reactions; and (iii) domain formation during phase separation into gel phases and solvent phases.     

Diffusion of platinum, vanadium and manganese in Ni3Al phase under high pressure

Diffusion of platinum, vanadium, and manganese in the Ni₃Al phase is investigated under high pressure. Platinum atoms occupy cubic face centred sites (α) in the L1₂ ordering structure. Vanadium atoms occupy cubic corner sites (β). Manganese atoms occupy both sites. Activation volumes ΔV for diffusion of these diffusing atoms to the molar volume of the Ni₃Al phase V₀ are as follows: