[en] The effect of neutron irradiation damage on the low-temperature yield stress of single-crystal niobium subjected to compression is assessed in order to determine whether the yield stress varies in a manner similar to that of vanadium as a function of oxygen concentration. Another objective is to determine how and whether the rate-controlling mechanism of slip changes as a function of oxygen concentration and neutron damage, and whether a correlation exists between the neutron damage observed by TEM and the changes in yield stress due to neutron irradiation. It is shown that the neutron irradiation damage has a very little effect on the magnitude of the effective stress of irradiated samples irrespective of oxygen concentration. The finding that the density of defects increases with increasing oxygen content for a given neutron flux supports the concept that the oxygen atoms or oxygen atom clusters act as nucleation sites for observable defects. The changes in effective-stress differences between irradiated and nonirradiated samples are due to the effect of oxygen on the effective stress of nonirradiated samples and a scavenging mechanism

[en] Inelastic neutron scattering experiments on a single crystal of the metastable fcc phase of lanthanum metal reveal a pronounced temperature dependent anomaly in the tranverse [111] branch of the phonon dispersion curves. A first principles band structure calculation yields a Fermi surface with a nesting feature along the [111] direction and a peak in the bare susceptibility at the same wave vector as the observed experimental anomaly. The calculation differs from previous studies by excluding the 4f states. 7 references

[en] A novel concept to detect pin-diversion from spent fuel assembly is proposed and described. The instrument will use multiple tiny neutron and gamma detectors in a form of cluster (detector cluster) and high precision driving system to collect radiation signatures inside pressurized water reactor (PWR) assembly. In order to validate our concept, a Monte Carlo study was done using a Monte Carlo code MCNP5. MONTEBURNS, a computational tool that links MCNP and ORIGEN, was used to produce accurate PWR spent fuel isotopic compositions. Monte Carlo simulations, using realistic fuel geometry and actual fuel material information, were performed to study radiation field inside a PWR spent fuel assembly. The preliminary Monte Carlo simulation study shows that indeed 2 dimensional neutron data, when obtained in the presence of missing pins, have data profiles distinctly different from the profiles obtained without missing pins

[en] In this paper, in order to instruct the next optimization work, a two-dimension Computational Fluid Dynamics (CFD) model is developed to simulate temperature distribution and velocity distribution of oscillating fluid in the DPTC by individual phase-shifting. It is found that the axial temperature distribution of regenerator is generally uniform and the temperatures near the center at the same cross setion of two pulse tubes are obviously higher than their near wall temperatures. The wall temperature difference about 0-7 K exists between the two pulse tubes. The velocity distribution near the center of the regenerator is uniform and there is obvious injection stream coming at the center of the pulse tubes from the hot end. The formation reason of temperature distribution and velocity distribution is explained. (paper)

[en] The reproductive characteristics of Capparis spinosa (Capparaceae) were examined at the Turpan Eremophytes Botanical Garden in Xinjiang, China. The flowering period was approximately five months long (from May to mid-October of 2011), during which time, two main and overlap flowering peaks emerged. Several significant differences between the two peaks were found: the number of flowers and duration of the flowering period for male flowers were identical in both peaks, but differed for perfect flowers(contain stamens and pistil); the filaments of both long and short stamens in male and perfect flowers in the first peak were longer than those in the second, whereas anther length showed the opposite trend; the frequency of fruit set and size in the first peak was respectively higher and larger than the second; and the seeds produced in the first peak were smaller and lighter than the second. These results provide that the continuously blooming C. spinosa and the variation in the proportion of male and perfect flowers have played a positive role in ensuring a continuous supply of pollen and controlling the investment of fruit. (author)

[en] This study was carried out to assess the ability to eliminate meaningful quantities of americium in a primarily thermal neutron flux by 'spiking' modern BWR fuel with this minor actinide (MA). The studies carried out so far include the simulation of modern 10 x 10 BWR lattices employing the Westinghouse lattice physics code PHOENIX-4 alongside validation studies using MCNP5 models of the same lattices that were spatially depleted via the MONTEBURNS code coupling to ORIGEN. When considering the total inventory of minor actinides in Am-spiked pins, excluding isotopes of uranium and plutonium, the results indicate that a reduction of approximately 50% or more in the total mass inventory of these minor actinides is viable within the selected pins. Therefore, these preliminary results have encouraged the extension of this work to the development of improved lattice designs to help optimize the transmutation rates as well as absolute MA inventory reductions. The ultimate goal being to design batches of these advanced BWR bundles alongside multi-cycle core reload strategies. (authors)

[en] An optimization procedure for composite second-stage intertank truss assembly used for connecting the fuel (Liquid Hydrogen, LH₂) tank and the oxidizer (Liquid Oxygen, LO₂) tank is proposed. The typical working conditions of X-shaped truss are 30 tons tensile load and 5.55 tons compressive load in sequence. Parametric geometrical model and finite element model are created in Catia R21 and Abaqus 6.14, respectively. An optimization procedure integrating geometrical model and finite element model has been constructed in Isight 2018, the algorithm of which is multi-islands genetic algorithm. The result shows that the weight of the optimal structure decreased by 26.50% comparing with the initial design. (paper)

[en] A major problem with the undergraduate mechanical course is the limited exposure of students to software packages coupled with the long learning curve on the existing software packages. This work proposes the use of appropriate software packages for the entire mechanical engineering curriculum to ensure students get sufficient exposure real life design problems. A variety of software packages are highlighted as being suitable for undergraduate work in mechanical engineering, e.g. simultaneous non-linear equations; uncertainty analysis; 3-D modeling software with the FEA; analysis tools for the solution of problems in thermodynamics, fluid mechanics, mechanical system design, and solid mechanics.

[en] Non-diffraction guiding modes covering the full broad band of a photonic crystal with elliptical rods for TM mode are reported in this paper. All such modes can be used to effectively guide electromagnetic waves since they have near-zero group velocity components along the ΓX' direction. In the fourth dispersion surface of the photonic crystal, the two wide flat regions spanning the first Brillouin zone possess unique properties: one dimension corresponds to a broad band, while the other corresponds to full incident angles of 0-90⁰. These properties have many potential applications; as an example, here a broadband all-angle supercollimation with a bandwidth of 169 nm around 1550 nm is demonstrated. For the inverted structure of elliptical holes in a dielectric, similar results can be achieved over 140 nm around 1550 nm for TE mode.

[en] In order to simulate contact fatigue crack propagation, the ANSYS APDL and Franc3D were used. The rolling contact model was established by the ANSYS APDL, then the distribution of the contact stress field under various loads was analyzed. The contact stress value demonstrated an error within ± 6%, compared to the obtained results from the Hertz theory. The contact stress field was imported into the Franc3D with a preset radical crack, the crack tip stress intensity factor distribution was calculated and the growth path of the three-dimensional contact fatigue cracks was analyzed. The comparisons with the experimental results demonstrated that the fatigue crack profile path from the peeling position of the subcutaneous layer was consistent with the simulated path, which was in a circular arc form. The main reason for this result was the fatigue crack change from the opening type I to the sliding type II. The a-N curves of the crack growth life under various load conditions were predicted based on the Franc3D, whereas the results displayed that the crack growth life decreased as the compressive stress increased. (paper)