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1.
Nepheline precipitation in nuclear waste glasses during vitrification can be detrimental due to the negative effect on chemical durability often associated with its formation. Developing models to accurately predict nepheline precipitation from compositions is important for increasing waste loading since existing models can be overly conservative. In this study, an expanded dataset of 955 glasses, including 352 high-level waste glasses, was compiled from literature data. Previously developed submixture models were refitted using the new dataset, where a misclassification rate of 7.8% was achieved. In addition, nine machine learning (ML) algorithms (k-nearest neighbor, Gaussian process regression, artificial neural network, support vector machine, decision tree, etc.) were applied to evaluate their ability to predict nepheline precipitation from glass compositions. Model accuracy, precision, recall/sensitivity, and F1 scores were systemically compared between different ML algorithms and modeling protocols. Model prediction with an accuracy of ~0.9 (misclassification rate of ~10%) was observed for different algorithms under certain protocols. This study evaluated various ML models to predict nepheline precipitation in waste glasses, highlighting the importance of data preparation and modeling protocol, and their effect on model stability and reproducibility. The results provide insights into applying ML to predict glass properties and suggest areas for future research on modeling nepheline precipitation.  相似文献   
2.
To quantitatively investigate the initial crystallization of zeolite beta synthesized by direct heating, the extent of the reaction was precisely evaluated by X-ray diffraction measurements and Rietveld structural refinement, and a kinetic analysis of crystallization was performed using the Avrami-Erofe'ev equation. The activation energy for crystallization was lower than that for hydrothermal synthesis. Reaction and synthesis time curves revealed that the initial zeolite beta crystallization consisted of three stages. The first was an induction period with nucleation by the generation of building units and the formation of an initial coordinated structure. The second stage was crystal growth by a diffusion-controlled reaction, and the third stage involved slowing down of crystallization by the limitation of dehydrocondensation. These stages could be analyzed by calculation of the rate constant and Avrami exponent for each stage.  相似文献   
3.
Multicolor upconversion luminescence materials show significantly applications in materials science. In this paper, the novel Yb3+-sensitized Na3La(VO4)2 upconversion luminescence crystals are synthesized by the solid-state reaction method. Three primary colors upconversion luminescence are successfully achieved in Na3La(VO4)2:Yb3+,Tm3+, Na3La(VO4)2:Yb3+,Er3+, and Na3La(VO4)2:Yb3+,Ho3+ crystals excited by the single 980 nm LD. Multicolor upconversion luminescence can be obtained by simply adjusting the combination ratios of these three samples. Luminescence mechanisms of the Yb3+-sensitized system are discussed in detail. In the Na3La(VO4)2 host material, the Yb3+/Ho3+ codoped system exhibits unusual red upconversion luminescence based on the short decay time of Ho3+ ion 5I6 level, which provides the possibility of three primary color luminescence under 980 nm excitation.  相似文献   
4.
To develop insulating materials with a high thermally conductive anisotropy, planarly aligned mesogenic epoxy (ME) resin film was fabricated by uniaxial coating on a hydrophobic polyethylene terephthalate substrate. Grazing incidence small-angle X-ray scattering (GISAXS) and transmission SAXS measurements exhibited that the films spontaneously formed uniaxially aligned monodomain-like smectic structures by curing on the hydrophobic substrate. Then, an in- and out-of-plane thermal conductivity of 10 and 0.048 W m−1 K−1 and outstanding thermal conductivity anisotropy of 208 have been confirmed, respectively. The ME resin films with high thermal conductivity can be applied as insulating materials for multiple-layer electrical and electronic devices.  相似文献   
5.
Crude wax extracted from rice bran oil (RBO) is used to improve the oleogel properties and oxidative stability of RBO. The effect of crude rice bran wax (CrBW) on the formation characteristics and oxidative stability of oleogels is discussed. The results show that oleogels can be formed with 7.0 wt% CrBW at 20 °C. As the concentration of CrBW increases from 7.0 to 11.0 wt%, the hardness and solid fat content (SFC) of the oleogels increase significantly, and the oleogels are primarily β' crystals. Moreover, oleogel crystals formed with 5 and 7 wt% CrBW are flocculent; when the amount included is 9%, the oleogel crystals are transformed into long dendrites, and the density rises. After 90 days of storage at 20 °C, the peroxide value of oleogels formed with 9.0 wt% CrBW slowly rises from 3.21 to 6.52 mmol kg−1. Practical Applications: Oleogels prepared here by CrBW and RBO are an innovative structural lipid without trans fats. Useful information on the rich fats and nutrients in CrBW is provided, which reduces the production cost and improves the industrial production capacity.  相似文献   
6.
吕薇  姜根山  刘月超  张伟 《声学技术》2022,41(6):789-795
为了研究温度分布对于管阵列结构中的声透射特性的影响,以核电站的实际工况为背景,构建了不同的温度场以及周期性变化的非均匀温度场,利用有限元方法进行数值模拟。结果表明:(1)温度分布会改变管阵列声透射频谱的“禁带”宽度以及中心频率位置。在同一介质中,温度变化对频率较高位置的影响大于频率较低的位置。(2)在同样为10℃的温度差下,当水的平均声速为1 653 m·s-1、饱和水蒸气的平均声速为522.5 m·s-1时,介质为水时的禁带宽度及中心频率位置变化较大,即声速大的介质的频谱对于温度的变化更敏感。(3)当温度差在10℃以内,在周期性变化的非均匀温度场和与均匀温度场中管阵列声透射特性在第一中心频率23 996.1 Hz之前,两频谱差别很小,在第一禁带之后会出现明显区别。该研究成果对完善核电站应用的声学检测提供了理论基础。  相似文献   
7.
Freezing methods have evolved over the last 30 years. This review states the effect of various freezing methods on the quality of fish and seafood. Freezing temperatures, freezing, and frozen storage temperatures were also analyzed and reviewed. The changes in the ice crystal, protein, and lipid affect the fish quality and nutritional value during freezing and frozen storage. Freezing methods when combined with various additives or preprocessing approaches help improve the efficacy of freezing and frozen storage. Several experimental or emerging methods also have positive effects on the products' quality. According to the metadata reanalysis of quality markers, freshly frozen fish using different freezing methods may vary much in terms of ice diameter, but not others. High pressure freezing or immersion freezing-derived fish retains the best quality through frozen storage. More data are required on freezing methods (electrical-assisted freezing, microwave-assisted freezing, magnetic-assisted freezing, radiofrequency-assisted freezing, and the commercial's application and investment should be considered in the future. This review sheds light on finding a balanced initial shear force during freezing and the use of certain additives to control freezing-related damages. Focusing on ice diameter alone may be futile (e.g., liquid N2 freezing). Future optimization of technologies should be in a way that several processes along the farm to fork such as freezing, frozen storage, thawing, thermal processing of fish, and even refabrication of food should mutually complement each other's needs to deliver safe and high-quality fish to the consumer's plate, even after a prolonged shelf-life.  相似文献   
8.
First examples of multichain (polycatenar) compounds, based on the π-conjugated [1]benzothieno[3,2-b]benzothiophene unit are designed, synthesized, and their soft self-assembly and charge carrier mobility are investigated. These compounds, terminated by the new fan-shaped 2-brominated 3,4,5-trialkoxybenzoate moiety, form bicontinuous cubic liquid crystalline (LC) phases with helical network structure over extremely wide temperature ranges (>200 K), including ambient temperature. Compounds with short chains show an achiral cubic phase with the double network, which upon increasing the chain length, is at first replaced by a tetragonal 3D phase and then by a mirror symmetry is broken triple network cubic phase. In the networks, the capability of bypassing defects provides enhanced charge carrier mobility compared to imperfectly aligned columnar phases, and the charge transportation is non-dispersive, as only rarely observed for LC materials. At the transition to a semicrystalline helical network phase, the conductivity is further enhanced by almost one order of magnitude. In addition, a mirror symmetry broken isotropic liquid phase is formed beside the 3D phases, which upon chain elongation is removed and replaced by a hexagonal columnar LC phase.  相似文献   
9.
A systematic electronic structure density functional theory search for the zeta phase in the tantalum carbon system has been conducted, demonstrating that the zeta phase does indeed lie on the convex hull, establishing low-temperature thermodynamic stability, and is structurally stable. Even though the zeta phase is most oft reported as a ζ-Ta4C3-x structure, these new computational results reveal that the perfectly ordered zeta phase occurs at the Ta3C2 composition and belongs to the C2/m space group. Furthermore, these results suggest that the space group may be a result of an order-disorder transition and potential deviations from ideal stoichiometry at higher temperatures. The structure of this Ta3C2 compound can be described as ordered strings of carbon vacancies on a single carbon plane, which is also the preferred plane where additional carbon vacancies or interstitials form. These defects have modest formation energies, which provides further explanation for the small homogeneity range in zeta phase.  相似文献   
10.
Mullite-type RMn2O5 (R = Y, rare-earth element) ceramics are of ongoing research attentions because of their interesting crystal-chemical, physical, and thermal properties. We report a detailed structural, spectroscopic and thermal analysis of the series of mullite-type RAlGeO5 (R = Y, Sm-Lu) phases. Polycrystalline samples are prepared by solid-state synthesis methods. Each sample is characterized by X-ray powder diffraction followed by Rietveld refinements, showing that they are isotypic and crystallize in the space group Pbam. The change of the metric parameters is explained in term of the lanthanide contraction effect. A rare inversion of Al/Ge between octahedral and pyramidal sites have been observed for these mullite-type so called O10 compounds, and the inversion parameter found to be between 0.22(1) and 0.30(1) for different R-cations. The <Al/Ge–O> bond distances and their bond valence sums (BVSs) support the respective inversions. Density functional theory (DFT) calculated phonon density of states (PDOS) and electronic band structures are compared for the vibrational and electronic band gap features respectively. Analysis of UV/Vis absorption spectra using both derivation of absorption spectra fitting (DASF) and Tauc's methods demonstrates that each of the RAlGeO5 O10 compounds is high bandgap semiconductor, possessing direct transition between 4.1(1) and 5.4(1) eV. Both Raman and Fourier transform infrared spectra show clear red shift (quasi-harmonic) of the vibrational wavenumbers with respect to the ionic radii of the R-cations. Selective Raman bands at higher wavenumber region further complement the inversion of Al/Ge between two coordination sites. The higher decomposition temperature of the RAlGeO5 compounds, compared to those of RMn2O5 phases, is explained in terms of higher bond strength of Al/Ge-O than those of Mn-O. Irrespective to the inversion between Al- and Ge-sites, the decomposition temperature also depends on the type of R-cation in RAlGeO5.  相似文献   
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