Behavior of Liquefied Sands Under Extremely Large Strain Levels in Cyclic Torsional Shear Tests

In order to study the cyclic behavior of liquefied sands at extremely large strain levels up to double amplitude shear strain of about 100%, a series of undrained cyclic torsional shear tests while keeping the specimen height constant was performed on saturated Toyoura sand under different densities, two kinds of in-situ frozen sandy samples and their reconstituted specimens. Due correction was made for the effect of membrane force on the measured shear stress. After exceeding a certain level of overall shear strain, the specimen deformation became non-uniform, which is called as “strain localization” in the present study. The initiation of such localization was associated with the changes in the cyclic amplitude of deviator stress and the increment of shear strain. In the case of Toyoura sand, the limiting value of shear strain to initiate strain localization was found to increase with decrease in the relative density, and such a trend was consistent with the empirical correlation of soil liquefaction when the relative density is higher than 30%. In the case of in-situ frozen sandy samples, their limiting shear strain values were smaller than those of the reconstituted specimens, suggesting that their soil structures were different from each other under different degrees of natural aging effects.     

Physicochemical state of the nanotopographic surface of commercially pure titanium following anodization-hydrothermal treatment reveals significantly improved hydrophilicity and surface energy profiles

A method of coating commercially pure titanium (cpTi) implants with a highly crystalline, thin hydroxyapatite (HA) layer using discharge anodic oxidation followed by hydrothermal treatment (Spark discharged Anodic oxidation treatment ; SA-treated cpTi) has been reported for use in clinical dentistry. We hypothesized that a thin HA layer with high crystallinity and nanostructured anodic titanium oxide film on such SA-treated cpTi implant surfaces might be a crucial function of their surface-specific potential energy. To test this, we analyzed anodic oxide (AO) cpTi and SA-treated cpTi disks by SEM and AFM. Contact angles and surface free energy of each disk surface was measured using FAMAS software. High-magnification SEM and AFM revealed the nanotopographic structure of the anodic titanium oxide film on SA-treated cpTi; however, this was not observed on the AO cpTi surface. The contact angle and surface free energy measurements were also significantly different between AO cpTi and SA-treated cpTi surfaces (Tukey's, P < 0.05). These data indicated that the change of physicochemical properties of an anodic titanium oxide film with HA crystals on an SA-treated cpTi surface may play a key role in the phenomenon of osteoconduction during the process of osseointegration.     

Synthesis of polyguanamines from 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine with aromatic diamines

Solution polycondensation of 2-N,N-dibutylamino-4,6-dichloro-1,3,5-triazine (BDCT) with various aromatic diamines, including 4,4′-oxydianiline (ODA), p-phenylenediamine (pPDA), m-phenylenediamine (mPDA), o-tolidine (oTD), 4,4′-(9-fluorenylidene)dianiline (BAFL), and 2,4-diamino-6-(N,N-dibutylamino)-1,3,5-triazine (DABT), was investigated. High molecular weight (>10,000) polyguanamines (PGs) were obtained via the polymerization of BDCT with ODA, pPDA, oTD, and BAFL at 150–180 °C in N-methylpyrrolidone (NMP) for 6 h. The polymerizability with BDCT was determined on the basis of the molecular weights of the polymers and the chemical shifts of the NMR data as follows: ODA > oTD > BAFL > pPDA > mPDA ? DABT. PGs were obtained from the reaction of BDCT with ODA and mPDA in only 55–77% yield, which may be attributed to the formation of cyclic oligomers. All of the polymers showed high thermostability (5% weight-loss temperature in N₂ greater than 444 °C), and the polymers generated from reaction of BDCT with ODA, mPDA, and BAFL exhibited good solubility in tetrahydrofuran and polar aprotic solvents such as NMP.     

A study on technical feasibility of applying tubular linear induction motor to vertical movement

It is necessary for a linear induction motor (LIM) to have large thrust force in applications for the vertical movement. If it does not have sufficient thrust force, it cannot lift even itself. A ratio (thrust force/weight of motor), therefore, is the most important factor for the design of this motor. In this paper, assuming the LIM has no slot-effect and infinite length, a simple analytical model is introduced for steady-state operation. By comparison with the results of detailed numerical analysis, it is verified to be applicable for basic evaluation of the motor. The design of the motor for vertical movement is carried out and the ratio is maximized. The basic dimensions of a feasible motor are given for such application.     

Modeling the Stress-Strain Relations of Sand in Cyclic Plane Strain Loading

A modeling procedure to simulate stress-strain relations of sand subjected to cyclic loading is proposed. Results from drained plane strain compression, extension, and cyclic loading tests on Toyoura sand are analyzed. The monotonic loading behavior is simulated by the generalized hyperbolic equation to use as the skeleton curves in the simulation of cyclic behavior. To construct hysteretic stress-strain curves based on the skeleton curves, the Masing’s rule is generalized to the proportional rule consisting of the internal and external rules. The drag rule is then introduced to simulate cyclic stress-strain behavior in which the stress amplitude increases at a decreasing rate during cyclic loading with a constant strain amplitude. It is assumed that any plastic shear strain increment taking place in a certain direction drags the whole skeleton curve for loading in the opposite direction towards the direction of the concerned shear strain increment. The measured cyclic stress-strain behavior is well simulated by the proposed method.     

An airborne smoke sampling package for field measurements of fires

A unique airborne smoke sample package (ASSP) for determining the smoke yield of large fires has been developed. The uncertainty in the average smoke yield at the 95% confidence interval is about ±7% of the average of three repeat measurements. The ASSP, which weighs less than 4 kg, is light enough to be flown suspended below a tethered helium-filled balloon or attached to a small radio-controlled aircraft. Measurements are made by flying the sampling equipment into a fire's smoke plume. Additional smoke plume measurements that can be made with the ASSP include particle size distribution using a cascade impactor, smoke agglomerate structure using transmission electron microscope (TEM) grids, and polycyclic aromatic hydrocarbons (PAHs) analysis using various sorbent tubes. The application of the ASSP in measuring laboratory and large outdoors petroleum pool fires is discussed. Smoke yield values measured in field burns of Louisiana crude oil range from 0.080 to 0.137, and the primary sphere diameter of the agglomerates is as large as 0.15 µm.     

Coordination Cyclopolymerization Behavior of Diethyl Bis(2,3-butadienyl)malonate by Allylnickel Catalyst

Summary The π-allylnickel-catalyzed coordination cyclopolymerization of a bis(allene) possessing a malonate moiety, diethyl bis(2,3-butadienyl)malonate, gave a polymer which is soluble in organic solvents. The polymer was composed of an almost comparable content of the 1,2- and the 2,3-polymerized units. The polymerization was supposed to proceed through the selective formation of a six-membered ring unit in the main chain by means of the cyclopolymerization of the bis(allene). That is, the intramolecular attack of the growing allylnickel species generated from the first allene moiety upon another one was supposed to give the 1,2-polymerized unit having the six-membered ring system while the intermolecular attack of the allylnickel species derived from the second allene provides the 2,3-polymized unit selectively as is the case of the monofunctional allenes. The effect of the polymerization conditions such as the concentration of the monomer on the polymerization behavior is also described.