Nonlinear Earthquake Response Characteristics of a Central Clay Core Rockfill Dam

The effect of the 2008 Iwate-Miyagi Nairiku earthquake (M_J 7.2), Japan on the Aratozawa dam, which is a 74.4 m high rockfill dam with a central clay core located in the area, was studied with a main focus on the change in the vibration period, shear wave velocity, shear modulus, and pore-water pressure. In a vertical section of the central part of the dam, three sets of 3-component accelerometers and 15 pore water pressure meters were installed. During the main shock, the acceleration exceeded 10 m/s² at the gallery, inducing large shear strains in excess of 10^-3 and a sudden build-up of the excess pore water pressure in the core. Due to the large strains, the shear wave velocity and shear modulus showed a significant decrease from their initial values and the vibration period was elongated. The decreased shear wave velocity gradually recovered toward the end of the main shock, and continued to recover with the passage of time. The full recovery of the wave velocity was found to take at least one year, while the dissipation of the excess pore water pressure proceeded more quickly than the recovery of the wave velocity.     

Fretting fatigue behaviour of Ni-free high-nitrogen stainless steel in a simulated body fluid

Abstract

Fretting fatigue behaviour of Ni-free high-nitrogen steel (HNS) with a yield strength of about 800 MPa, which was prepared by nitrogen gas pressurized electroslag remelting, was studied in air and in phosphate-buffered saline (PBS(-)). For comparison, fretting fatigue behaviour of cold-rolled SUS316L steel (SUS316L(CR)) with similar yield strength was examined. The plain fatigue limit of HNS was slightly lower than that of SUS316L(CR) although the former had a higher tensile strength than the latter. The fretting fatigue limit of HNS was higher than that of SUS316L(CR) both in air and in PBS(-). A decrease in fatigue limit of HNS by fretting was significantly smaller than that of SUS316L(CR) in both environments, indicating that HNS has better fretting fatigue resistance than SUS316L(CR). The decrease in fatigue limit by fretting is discussed taking into account the effect of friction stress due to fretting and the additional influences of wear, tribocorrosion and plastic deformation in the fretted area.     

Sensory‐motor control mechanism for reaching movements of a redundant musculo‐skeletal arm

This paper studies the human arm's sensory‐motor control mechanism in reaching movements. First, we formulate both the kinematics and dynamics of a two‐link planar arm model with six redundant muscles. The nonlinear muscle dynamics is modeled based on several biological understandings. We then show the stability of the overall system and perform some numerical simulations. By considering the internal forces induced by the redundant muscles, we show that the damping factors in each joint can be regulated, and as the result, it can realize humanlike quasistraight line reaching movements. In addition, we also propose the gravity compensation method at the muscle input level and present the result of numerical simulation to verify the usefulness of this method. © 2005 Wiley Periodicals, Inc.     

Self-assembly of a silica-surfactant nanocomposite in a porous alumina membrane

A mesoporous membrane composed of nanochannels with a uniform diameter has a potential use for precise size-exclusive separation of molecules. Here, we report a novel method to form a hybrid membrane composed of silica-surfactant nanocomposite and a porous alumina membrane, by which size-selective transport of molecules across the membrane becomes possible. The nanocomposite formed inside each columnar alumina pore was an assembly of surfactant-templated silica-nanochannels with a channel diameter of 3.4 nm; the channel direction being predominantly oriented along the wall of the columnar alumina pore. Molecules could be transported across the membrane including the silica-surfactant nanocomposite with a capability of nanometre-order size-exclusive separation. Our proposed membrane system has a potential use not only for separation science, but also catalysis and chip technologies.     

Simple and comprehensive two-dimensional reversed-phase HPLC using monolithic silica columns

Simple and comprehensive two-dimensional (2D)-HPLC was studied in a reversed-phase mode using monolithic silica columns for second-dimension (2nd-D) separation. Every fraction from the first column, 15 cm long (4.6-mm i.d.), packed with fluoroalkylsilyl-bonded (FR) silica particles, was subjected to the separation in the 2nd-D using one or two octadecylsilylated (C(18)) monolithic silica columns (4.6-mm i.d., 3 cm). Monolithic silica columns in the 2nd-D were eluted at a flow rate of up to 10 mL/min with separation time of 30 s that meets the fractionation every 15-30 s at the first dimension (1st-D) operated at a flow rate of 0.4-0.8 mL/min. Three cases were studied. (1) In the simplest scheme of 2D-HPLC, effluent of the 1st-D was directly loaded into an injector loop of 2nd-D HPLC for 28 s, and 2 s was allowed for injection. (2) Two six-port valves each having a sample loop were used to hold the effluent of the 1st-D alternately for 30 s for one 2nd-D column to effect comprehensive 2D-HPLC without the loss of 1st-D effluent. (3) Two monolithic silica columns were used for 2nd-D by using a switching valve and two sets of 2nd-D chromatographs separating each fraction of the 1st-D effluent with the two 2nd-D columns alternately. In this case, two columns of the same stationary phase (C(18)) or different phases, C(18) and (pentabromobenzyloxy)propylsilyl-bonded (PBB), could be employed at the 2nd-D, although the latter needed two complementary runs. The systems produced peak capacity of approximately 1000 in approximately 60 min in cases 1 and 2 and in approximately 30 min in case 3. The three stationary phases, FR, C(18), and PBB, showed widely different selectivity from each other, making 2D separations possible. The simple and comprehensive 2D-HPLC utilizes the stability and high efficiency at high linear velocities of monolithic silica columns.     

The influence of a fibre structure on optical loss in a graded-index fibre

For designing a fibre structure, the influence of structural parameters on optical loss is investigated experimentally for a graded-index fibre. The fibre with large cladding/outer-layer index difference and small cladding thickness is found to have large excess loss near excitation points, such as a launching point and a splicing point.     

Studies on synthetic-polymer plates with high surface energy. II. Diethylene glycol bis(allyl carbonate)–unsaturated carboxylic acid system

Polymer plates with high surface energy were prepared by the procedure described in the previous paper, using diethylene glycol bis(allyl carbonate) as a substrate polymer and acrylic acid or methacrylic acid as a hydrophilic monomer. By the alkali treatment (immersing in an aqueous 0.1N NaOH solution for 2 h), the resulting polymer plates had good water wettability (contact angle for water = 10°) and sufficient mar resistance (the scratching hardness = 45–50 g) in a dry state, and their clarities were higher than those for DAP systems previously reported. The surface densities of carboxyl groups on the polymer plate estimated by use of the McBain's equation were 0.18–0.46 molecule/Ų.     

Polymerization of ethylene and propylene initiated by milled alumina powder

Generation of free radicals (mechano-radicals) by the milling of alumina powder at 77 K was demonstrated by ESR. After milling of alumina in the presence of ethylene (simultaneous milling) at 77 K, polyethylene-propagating radicals instead of the alumina mechano-radicals were detected by ESR. Also the contact of ethylene with the milled alumina converted alumina mechano-radicals into polyethylene propagating radicals at a temperature above the melting point of ethylene. The products extracted by hot toluene from the simultaneous milling were identified by IR to be polyethylene, and their molecular weights were roughly 10,000. The residues after the extraction were bonded with the alumina. Polypropylene was also produced by a similar method of milling of alumina in the presence of propylene. The obtained polyproylene was atactic, and its molecular weight was about 400.