DCDA is a new method for evaluating the in-situ stress of rocks based on the elliptical deformation of boring cores with stress relief. If the condition of in-situ stress is anisotropic, the core must expand elastically in an asymmetric shape. The cross sectional shape of the expanded core can be measured precisely, and the differential stress SHmax－Shmin and azimuths of SHmax and Shmin can be determined from the measured shape data. In order to confirm the reliability of DCDA, laboratory verifications were conducted focusing on a manner how the core expands with stress relief caused by drilling.We used 300 mm cube mortar specimens in which strain gages were embedded.The specimen was set into a steel frame where it was subject to an uniaxial compressive stress using a pair of flat jacks. While holding the applied stress, a core sample was drilled out from the specimen and the strain in the core was recorded. Following results are obtained; 1) The relief strain caused in the core has the same magnitude with the strain in the specimen caused by applying a uniaxial compressive stress, while those strains are opposite in sign. 2) The experimentally-observed core expansion with drilling was consistent with that predicted by a linear elastic FEM. 3) Some core bits may scrape partially the surface of the expanded core, then DCDA will underestimate the applied stress. A specially-designed core bit must be necessary for DCDA to avoid scraping the expanded core.
Batch desorption experiments and bench-scale electrokinetic experiments were performed to elucidate the electrokinetic remediation mechanisms of cationic metals from artificially contaminated kaolinite. The electrokinetic experiments demonstrated that the remediation efficiency was increased in the order of Pb<Cd<Mg, which is consistent with the order of water solubility under the experimental pH condition investigated in this study (pH ≈ 6.9). A series of electrokinetic experiments also showed that applying a pulse voltage clearly affected the remediation efficiencies, but the manner in which it did and the extent of the effect depended on the cation type and pulse duration. The electrokinetic experiments in which a pulse voltage (3 hours ON, 3 hours OFF) was applied demonstrated that applying the pulse voltage reduced electricity consumption for recovering Cd in the cathode well; this trend was not observed for Mg. These electrokinetic experimental results, with the support of metal desorption data obtained from batch experiments, indicate that the remediation rate-limiting step for Cd was the desorption of Cd into the interstitial water rather than the migration of the dissolved Cd toward the cathode. It was also demonstrated that applying a pulse voltage (2 seconds ON, 2 seconds OFF) was found to negatively affect the remediation performance with respect to the electricity consumption when compared to the case in which a pulse voltage (3 hours ON, 3 hours OFF) was applied.
Deterioration of the performance of rare earth fluorescent lamps and phosphors after use, and these relationships were studied. In recent years, the demand of the recovery of valuable rare earth from used fluorescent lamps is increasing. However, recycling of rare earths is not progressing much because of the difficulty due to their chemical characteristics. On the other hand, recently, the reuse business of the materials recovered from used fluorescent lamps has begun in some places. Fluorescent lamps which are partially constructed from recycled materials are being slightly manufactured. Decrease in emission intensity of the phosphors was lower than that of fluorescent lamps. There are other factors such as consumption of mercury and emitter to reduce light quantity of the lamps. On the other hand, the main factor that decrease the emission intensity of the phosphors was concluded to contamination by adhesion of the emission materials made of lamp components, such as glass, mercury and emitter in this study. Although, chemical change, oxidation of the activator, and deterioration of the crystalline, those mean internal degradation of phosphor materials, were not significant. It is suggested that it becomes valid way to reuse the phosphors exhibiting a relatively high brightness, those are recovered from the fluorescent tubes cut off the portion surrounding the emitter, because the fouling by emitting substances is intense about that portion.
In this paper, the results of experimental and analytical studies of the performance of an electrostatic free-fall separator for plastic mixtures for recycling are presented. The principle behind the separation technique is based on the difference in the Coulomb force acting on the plastic particles after triboelectric charging. The separator has two thin sheets and makes it possible to suppress the rebounding of highly charged particles with the electrodes. Separation tests were performed on a sample containing 50% polystyrene (PS) and 50% Acrylonitrile Butadiene Styrene (ABS) plastics. Plastic particles obtained from crushed plastic plates were used. The amount of charge accumulated on the plastics was measured with a Faraday cage system. Recovery rate in each collection tray was calculated, taking into account the charge distribution. The tray that collected PS or ABS in the largest quantities in the calculated results is the same as that in the experimental results. It was found that the separation efficiency depends on the tribocharging time, the rotation speed of the tribocharger, setting angle of the shock absorbing sheets and the distance between the electrodes. The experimental results confirm that it is possible to obtain a high purity and recovery rate for the initial compositions considered in this study.
The effect of gelatin on the deposition behavior and the crystal texture of Zn from the electrowinning solution containing an extremely low concentration of antimony was investigated. In a solution containing 10 μg/L of antimony only, the both polarization curves for Zn deposition and hydrogen evolution were depolarized by 10 to 20 mV. The current efficiency for Zn deposition was slightly higher in solution containing 10 μg/L of antimony and 1 mg/L of gelatin than that in solution without antimony and gelatin.Although the large holes resulting from the foam mark of hydrogen evolution were observed in Zn deposited from a solution containing 10 μg/L of antimony, the gelatin extinguished the large holes. The crystallite size of Zn was decreased with increasing antimony concentration in solutions with and without gelatin. In a solution containing 10 μg/L of antimony and 1 mg/L of gelatin, the deposited Zn showed an unoriented dispersed type of crystals, which was more uniform and finer than that in the solutions containing gelatin and antimony alone. In a solution containing 10 μg/L of antimony and 10 mg/L of gelatin, the deposited Zn was composed of mixture of fine fibrous and granular crystals. Although Zn platelet crystals grew largely perpendicular to substrate in a solution containing 10 mg/L of gelatin only, the coexistent antimony suppressed the coarsening and the preferred orientation of <1120> and <1010> of Zn crystals. Even in a solution containing extremely low concentration of antimony as 10 μg/L, the crystal texture of Zn deposited from the solution in the coexistence of gelatin was obviously different from those in the solutions containing gelatin and antimony alone, showing the synergistic effect of gelatin and antimony on the crystal texture of Zn.