[en] In this study, tungsten inert gas (TIG) welded AZ31 magnesium alloy joint was subjected to two-pass rapid cooling friction stir processing (RC-FSP). The main results show that, two-pass RC-FSP causes the significant dissolution of the coarse eutectic β-Mg_1_7Al_1_2 phase into the magnesium matrix and the remarkable grain refinement in the stir zone. The low-hardness region which frequently located at heat-affected zone was eliminated. The stir zone showed ultrafine grains of 3.1 μm, and exhibited a good combination of ultrahigh tensile strength of 284 MPa and large elongation of 7.1%. This work provides an effective strategy to enhance the strength of TIG welded magnesium alloy joint without ductility loss.

No abstract available

[en] Vertebral compression fractures (VCFs) are common complications of osteoporosis. The expansion of VCFs with a Sky Bone Expander is a new procedure which improves kyphotic deformities and decreases pain associated with VCFs. The purpose of this study was to investigate the preliminary results for the treatment of painful osteoporotic VCFs with a Sky Bone Expander. Twenty-six patients with pain-causing VCFs were treated with a Sky Bone Expander. This operation involved the percutaneous insertion of the Sky Bone Expander into a fractured vertebral body transpedicularly. Following the expansion, the Sky Bone Expander was contracted and removed, resulting in a cavity to be filled with bone cement. All fractures were analyzed for improvement in sagittal alignment. Clinical complications, pain relief and ambulation status were evaluated 1 day, 1 week, 1 month, and 3 months after the operation. Twenty-four hours after the operation, all the patients treated experienced some degree of pain relief. In addition, no postoperative neurologic complications were noted. The average operative time was 42.4 ± 15.5 min per vertebra. Moreover, an average cement volume of 3.5 mL (range, 2.5 ± 5.0 mL) was injected per vertebra. The average anterior height was 18.4 ± 5.1 mm preoperatively and 20.5 ± 5.3 mm postoperatively (p < 0.01). Furthermore, the average midline height was 15.5 ± 5.2 mm preoperatively and 18.9 ± 4.0 mm postoperatively (p < 0.01). The Cobb angle improved from 18.5 ± 8.2 degrees preoperatively to 9.2 ± 4.0 degrees postoperatively (p < 0.01). The Visual Anabog Scale scores decreased from 7.7 ± 1.8 points preoperatively to 3.1 ± 2.0, 2.9 ± 1.7, 2.6 ± 1.5 and 2.9 ± 11.3 after 1 day, 1 week, 1 month and 3 months after the operation, respectively. Cement extrusion was observed in four patients without any neurologic symptoms. As a result of this study, we can postulate that the expansion of compressed vetrebra with a Sky Bone Expander is a safe and minimally invasive procedure resulting in the restoration of vertebral body height and the relief of pain associated with VCFs

[en] In this work, 2 mm thick Cu-30Zn brass plates were successfully joined by using large-load and low-speed friction stir welding. Heat-affected zone was eliminated due to the significantly improved thermal cycle. The stir zone exhibited ultra-fine grains, with high fraction of twin boundaries and low dislocation density. Also, several nano-scale twin boundaries were introduced into the stir zone. Grain structure refinement in the weld was attributed to the combination of discontinuous, continuous, geometric and shear-band-assisted dynamic recrystallization mechanisms. Consequently, the stir zone showed excellent strength-ductility synergy compared to that of the severe plastic deformed and the conventional friction stir welded Cu-30Zn brass. A feasible one-step strategy was developed herein, to increase the strength of the friction stir welded Cu-30Zn brass joint, while avoiding ductility loss. Moreover, this study offers a new insight and choice for joining metals or alloys with higher melting points, such as steel and titanium alloys.

[en] Room-temperature photoluminescence and optical transmittance spectroscopy of Co-doped (1 × 10¹⁴, 5 × 10¹⁶, and 1 × 10¹⁷ cm⁻²) and Cu-doped (5 × 10¹⁶ cm⁻²) ZnO wafers irradiated by D—D neutrons (fluence of 2.9 × 10¹⁰ cm⁻²) have been investigated. After irradiation, the Co or Cu metal and oxide clusters in doped ZnO wafers are dissolved, and the würtzite structure of ZnO substrate for each sample remains unchanged and keeps in high c-axis preferential orientation. The degree of irradiation-induced crystal disorder reflected from the absorption band tail parameter (E₀) is far greater for doped ZnO than the undoped one. Under the same doping concentration, the Cu-doped ZnO wafer has much higher irradiation-induced disorder than the Co-doped one. Photoluminescence measurements indicate that the introduction rate of both the zinc vacancy and the zinc interstitial is much higher for the doped ZnO wafer with a high doping level than the undoped one. In addition, both crystal lattice distortion and defect complexes are suggested to be formed in doped ZnO wafers. Consequently, the Co- or Cu-doped ZnO wafer (especially with a high doping level) exhibits very low radiation hardness compared with the undoped one, and the Cu-doped ZnO wafer is much less radiation-hard than the Co-doped one

[en] We studied the multielectron ionization and Coulomb explosion of O₂ irradiated by 110 fs, 810 nm laser pulses at an intensity of 10¹⁵ W cm^-2. Strong anisotropic angular distributions with the same widths were observed for the atomic ions Oⁿ⁺ (n = 1-3). Using two linearly polarized laser pulses with crossed polarization, we found that the atomic ions generated in the second laser pulse were strongly depleted by the first laser pulse for various delay times. The results demonstrate that dynamic alignment dominates for O₂ under the experimental conditions. Moreover, the same angular distributions for all the atomic ions Oⁿ⁺ (n = 1-3) further demonstrate that dynamic alignment mainly occurs at the rising edge of the laser pulse with laser intensity below the ionization threshold and the neutral O₂ aligns along the laser polarization vector prior to ionization

[en] A coarse homogeneous grain structure with a strong basal texture intensity is usually formed in AZ91D Mg alloy, which is produced by friction stir processing, and its strength and ductility are often unsatisfactory. In this work, the microstructure and mechanical properties of die-cast AZ91D were modified using low-temperature friction stir processing. A fine-grained structure was obtained in the stir zone, and abundant {10–12} twins, dislocations, and β-Mg₁₇Al₁₂ precipitates formed in the grains. The grain refinement mechanism was determined to be a mixture of continuous dynamic recrystallization, twinning-induced dynamic recrystallization, and particle-stimulated nucleation recrystallization. The appearance of a heterogeneous microstructure was attributed to the low heat input. The new grains originated from the {10–12} twins and randomized {0002} basal texture, and various strengthening mechanisms contributed to the increased yield strength. The {10–12} twin boundaries provided more locations for dislocation nucleation and slip, which increased the strain hardening capacity and ductility; therefore, a satisfactory combination of strength and ductility with a strength of 294 MPa and a total elongation of 18% was obtained in the stir zone. This study provides an efficient one-step strategy to produce heterogeneous grain structures that can balance the strength and ductility of AZ91D without using a cooling medium.

[en] In order to verify whether the U(VI) in groundwater under anoxic conditions can be bioreduced, microcosms were prepared with the uranium contaminated groundwater and sediment, amended with ethanol, lactate and glucose, and incubated under anoxic conditions. After 121 days of incubation, uranium L₃-edge X-ray absorption fine structure spectra analysis indicated that more than 40 % of the U(VI) was reduced to U(IV) in the amended microcosms, and the initial U(VI) which was bound to C- and P-containing ligands was no longer bound to C-containing ligands after 121 days of incubation. The results show that the U(VI) in groundwater under anoxic conditions can be bioreduced. (author)

[en] This paper describes full-field, three-dimensional, non-contact measurements of displacement and strain under high temperature condition based on digital image correlation (DIC). To conduct DIC measurements at high temperatures, two important factors need to be considered: (1) the ability of the coating to resist heat and withstand deformation without cracking or peeling off; (2) the radiation from the specimen's surface at high temperature. This paper proposes a solution to both of the most important issues in high temperature DIC measurement. First, different coating materials were investigated, and a procedure to generate a necessary speckle pattern required by DIC to resist heat and withstand deformation at high temperature has been developed. Second, a monochromatic illumination system in combination with a filter set has been studied to eliminate the radiation effect. A DIC system which enables a high temperature displacement and strain measurement up to 1100 °C is presented and demonstrated by experimental measurements. (paper)

[en] We experimentally and theoretically investigate the evolution of the rotational wave packet of N₂O at room temperature created by two strong femtosecond laser pulses. The rotational-state populations of the molecule are also calculated after the excitation of the two laser pulses. The results demonstrate that the rotational-state populations and the revival structures can be controlled for the wave packet by precisely adjusting the time delay between the two laser pulses.