Mechanical Properties of Gangue Cement Stabilized Road Foundation Mixture

In this study, coal gangue was used to replace the four single-graded natural gravels of 0~5 mm, 5~10 mm, 10~20 mm, and 20~26.5 mm to design the mix ratio and to study the influence in particle size changes of coal gangue on the mechanical properties of the mixture. The research results show that: The maximum dry density of the mixture with coal gangue is lower than the density of the natural crushed stone water-stable mixture, and the optimal moisture content is higher than that of natural crushed stone water-stable mixture; coal gangue aggregate is mixed with cement stabilized in the crushed stone mixture, and the 7d and 28d unconfined compressive strength, splitting strength, and compression rebound modulus values of the mixture are all reduced, which has a degrading effect on the mechanical properties of the mixture; however, both can attain high speed, which is the basic strength requirements for expressways, including first-class highways.

The de Finetti structure behind some norm-symmetric multivariate densities with exponential decay

We derive a sufficient condition on the symmetric norm ||·|| such that the probability distribution associated with the density function f (x) ∝exp(−λ ||x||) is conditionally independent and identically distributed in the sense of de Finetti’s seminal theorem. The criterion is mild enough to comprise the ℓp-norms as special cases, in which f is shown to correspond to a polynomially tilted stable mixture of products of transformed Gamma densities. In another special case of interest f equals the density of a time-homogeneous load sharing model, popular in reliability theory, whose motivation is a priori unrelated to the concept of conditional independence. The de Finetti structure reveals a surprising link between time-homogeneous load sharing models and the concept of Lévy subordinators.

Are cover crop mixtures better at suppressing weeds than cover crop monocultures?

Cover crops are increasingly being used for weed management, and planting them as diverse mixtures has become an increasingly popular strategy for their implementation. While ecological theory suggests that cover crop mixtures should be more weed suppressive than cover crop monocultures, few experiments have explicitly tested this for more than a single temporal niche. We assessed the effects of cover crop mixtures (5- or 6-species and 14-species mixtures) and monocultures on weed abundance (weed biomass) and weed suppression at the time of cover crop termination. Separate experiments were conducted in Madbury, NH, from 2014 to 2017 for each of three temporal cover-cropping niches: summer (spring planting–summer termination), fall (summer planting–fall termination), and spring (fall planting–subsequent spring termination). Regardless of temporal niche, mixtures were never more weed suppressive than the most weed-suppressive cover crop grown as a monoculture, and the more diverse mixture (14 species) never outperformed the less diverse mixture. Mean weed-suppression levels of the best-performing monocultures in each temporal niche ranged from 97% to 98% for buckwheat (Fagopyrum esculentum Moench) in the summer niche and forage radish (Raphanus sativus L. var. niger J. Kern.) in the fall niche, and 83% to 100% for triticale (×Triticosecale Wittm. ex A. Camus [Secale × Triticum]) in the winter–spring niche. In comparison, weed-suppression levels for the mixtures ranged from 66% to 97%, 70% to 90%, and 67% to 99% in the summer, fall, and spring niches, respectively. Stability of weed suppression, measured as the coefficient of variation, was two to six times greater in the best-performing monoculture compared with the most stable mixture, depending on the temporal niche. Results of this study suggest that when weed suppression is the sole objective, farmers are more likely to achieve better results planting the most weed-suppressive cover crop as a monoculture than a mixture.

Preparation and Characterization of Chitosan - Double Walled Carbon Nanotubes Hydrogels

In the present article, the authors have prepared nanocomposites based on chitosan (CS) and double walled carbon nanotubes (functionalized with carboxyl groups (DWCNT-COOH) and un treated DWCNT) by casting the stable mixture in a mold. Different concentrations of DWCNT were used in the preparation of nanocomposite hydrogels. These differently concentrated DWCNT hydrogels were chemically characterized using Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Thermal analysis and calorimetry (TGA). The dispersion of the carbon nanotubes were observed in the chitosan matrix by SEM. The addition of DWCNT in the composite hydrogel significantly reduced the water uptake ability. However, the water uptake ability of the CS/DWCNT-COOH nanocomposite has been better than the CS/ DWCNT. Also, dispersion of functionalized DWCNT in the chitosan matrix, was increased the thermal stability of hydrogels.

Nucleation and Growth of Solid Oxide and Hydroxide Phases

In this chapter, we consider what happens when solids begin to form from solution. To grow solids from solution, solution conditions are changed from a condition in which all species are completely soluble to a condition in which they are insoluble. In the context of hydrolysis diagrams, the solution composition moves in pH and total dissolved metal concentration from a regime below a solubility or saturation limit (given by the bold solid line in Figs. 5.2 and 5.3) to a regime above this limit where the solution is supersaturated. Supersaturated solutions are inherently unstable and have the potential to generate hydroxide or oxide solids. Sometimes these solutions can be maintained in a metastable state in which precipitation does not occur immediately. However, Mother Nature eventually reduces the energy of the solution by forming a stable mixture of solids plus solution species. As solids form, soluble complexes are removed from solution until concentrations drop back to the solubility limit. The precipitation of a solid from an aqueous solution is a surprisingly complex process, involving nucleation and growth phenomena that occur at nanometer-length scales. Nucleation involves reactions between oligomers to form new clusters or particles that are sufficiently large that they do not redissolve spontaneously via the reversible reactions denoted in hydrolysis diagrams. Homogeneous and heterogeneous nucleation processes represent events that occur within the bulk solution or at the interface of another phase, respectively. Growth involves the addition of monomers to clusters in solution or oligomers to existing particles or surfaces. The combination of nucleation and growth phenomena can lead to oxides exhibiting a bewildering range of sizes, shapes, and crystal structures. How do metal complexes decide whether to form a new particle or add to an existing particle? What determines the size, shape, and crystal structure of evolving particles? Do the particles aggregate with one another in an organized fashion? Because nucleation typically involves extremely rapid (<1 millisecond) events involving objects that are extremely small (on the order of a nanometer), it is difficult to probe such phenomena at a molecular level.

Bayesian Stable Mixture Model of State Densities of Generalized Chua's Circuit

In this paper, the probability density functions (PDFs) of the states of Generalized Chua's Circuit (GCC) have been modeled by Finite Mixture α-Stable (FMαS) distributions which is a Bayesian mixture model of α-stable distributions and it provides semiparametric characterization for the distributions of multiscroll chaotic attractors. Fully Bayesian approach has been applied to estimate the mixture parameters of multimodal distributions corresponding to the multiscroll chaotic attractors.