Heat transfer in vertical concentric cylinders in a high level nuclear waste repository

Modeling free convection heat transfer in a cylindrical annular enclosure is still an active area of research and an important problem to be addressed in the high level nuclear waste repository. The waste containers are vertically emplaced in the borehole 300 meters below ground. and in a horizontal grid of 30 x 8 meters apart. The borehole will be capped after the container emplacement and the container is surrounded by an enclosed vertically concentric air-gap inside the borehole. The expected initial heat generated is 4.74 kW per container and it degenerates exponentially with time. A computer simulation model is used to find the thermal performance for the air-gap and the problem is solved in two steps. The first step is to solve for the heat conduction in the rock. The second step proceeds by using the results of the first step as boundary condition to solve the more complicated convection and radiation in the air-gap. Finally a parametric study was done for three different air-gap thicknesses (5 cm, 10 cm, and 15 cm) to obtain the effect of the gap thickness on that heat transfer. Eventually the goal of this study is to obtain the temperature at the central axis of the vertical container as a function of time so that the maximum temperature of the zirconium cladding on the fuel pellets can be determined

Laves-phase evolution during aging in fine grained heat-affected zone of a tungsten-strengthened 9% Cr steel weldment

The precipitation and coarsening of Laves-phase in the fine grained heat-affected zone (FGHAZ) of a 9% Cr steel P92 welded joint during thermal aging at 923 K were investigated and compared to the base metal (BM), in order to clarify their effects on the Type IV fracture. Laves-phase precipitated mostly on the prior austenite grain boundaries of the FGHAZ. In comparison with BM, FGHAZ contained more grain boundary areas and can provide more nucleation sites for Laves-phase, resulting in an accelerated precipitation and rapidly reaching to the around 1.0% of saturated volume fraction. The coarsening of Laves-phase precipitates in FGHAZ was also much faster than that in BM, enhanced by the contribution of grain boundary diffusion resulted from its finer prior austenite grains. The FGHAZ had denser and smaller Laves-phase precipitates during the precipitation period in comparison with BM, obviously improved the creep strength by precipitation hardening. However, this effect in FGHAZ reduced sharply during coarsening owing to its coarsening rate greater than that of BM. In addition to the initial coarse polygonal subgrains with low dislocation density in FGHAZ produced by the weld thermal cycle and subsequent tempering in post-weld heat treatment (PWHT), coarse Laves-phase precipitates on grain boundaries formed in the long-term thermal aging, contributing to the formation of the creep cavities, can also play a key role in Type IV fracture of welded joint in 9% Cr steels

SNR-based adaptive acquisition method for fast Fourier ptychographic microscopy

Fourier ptychographic microscopy (FPM) is a computational imaging technique with both high resolution and large field-of-view. However, the effective numerical aperture (NA) achievable with a typical LED panel is ambiguous and usually relies on the repeated tests of different illumination NAs. The imaging quality of each raw image usually depends on the visual assessments, which is subjective and inaccurate especially for those dark field images. Moreover, the acquisition process is really time-consuming.In this paper, we propose a SNR-based adaptive acquisition method for quantitative evaluation and adaptive collection of each raw image according to the signal-to-noise ration (SNR) value, to improve the FPM's acquisition efficiency and automatically obtain the maximum achievable NA, reducing the time of collection, storage and subsequent calculation. The widely used EPRY-FPM algorithm is applied without adding any algorithm complexity and computational burden. The performance has been demonstrated in both USAF targets and biological samples with different imaging sensors respectively, which have either Poisson or Gaussian noises model. Further combined with the sparse LEDs strategy, the number of collection images can be shorten to around 25 frames while the former needs 361 images, the reduction ratio can reach over 90%. This method will make FPM more practical and automatic, and can also be used in different configurations of FPM.Comment: 11 pages, 6 figure

From Decolonial to the Postcolonial: Trauma of an Unfinished Agenda

Expression stability of the candidate reference genes under different conditions. (DOCX 13 kb

New Method for Numerically Solving the Chemical Potential Dependence of the Dressed Quark Propagator

Based on the rainbow approximation of Dyson-Schwinger equation and the assumption that the inverse dressed quark propagator at finite chemical potential is analytic in the neighborhood of $\mu=0$, a new method for obtaining the dressed quark propagator at finite chemical potential $\mu$ from the one at zero chemical potential is developed. Using this method the dressed quark propagator at finite chemical potential can be obtained directly from the one at zero chemical potential without the necessity of numerically solving the corresponding coupled integral equations by iteration methods. A comparison with previous results is given.Comment: Revtex, 14 pages, 5 figure

Sheet polymer and its complexes: Part III-Synthesis and conductive properties of polymeric tetraphenylporphyrin and its complexes

1034-103

Critical chain construction with multi-resource constraints based on portfolio technology in South-to-North Water Diversion Project

AbstractRecently, the critical chain study has become a hot issue in the project management research field. The construction of the critical chain with multi-resource constraints is a new research subject. According to the system analysis theory and project portfolio theory, this paper discusses the creation of project portfolios based on the similarity principle and gives the definition of priority in multi-resource allocation based on quantitative analysis. A model with multi-resource constraints, which can be applied to the critical chain construction of the A-bid section in the South-to-North Water Diversion Project, was proposed. Contrast analysis with the comprehensive treatment construction method and aggressive treatment construction method was carried out. This paper also makes suggestions for further research directions and subjects, which will be useful in improving the theories in relevant research fields

Clematis mae (Ranunculaceae), a new species of C. sect. Meclatis from Xinjiang, China

Clematis mae Z.Z.Yang & L.Xie, a new species of Ranunculaceae from Xinjiang, China, is described and illustrated. The new species is morphologically similar to C. orientalis and C. glauca but can be distinguished for being a less hairy plant (hairy in C. orientalis), often 2-ternate leaves (1–2-pinnate for C. orientalis and C. glauca), lanceolate to linear-lanceolate leaflets (elliptic or ovate in C. glauca), larger flowers (smaller flower in C. orientalis) and narrowly lanceolate sepals with acute to slightly attenuate apex (narrowly oblong sepals in C. orientalis and ovate to broadly lanceolate sepals in C. glauca). The new species is endemic to the southern slope of North Tianshan Mountain in Central Xinjiang. The conservation status of the species is also discussed