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To study the adsorption performance of coal bodies after alkaline solution erosion and the microscopic mechanism of alkali erosion on coal bodies, isothermal adsorption experiments at different pH values and with different numbers of soaking days were conducted on high-order coal bodies from the Chengzhuang mine. The results showed that the adsorption capacity of the coal bodies after alkali leaching was improved compared to that of the original coal, all of which was in accordance with the Langmuir equation. The unit adsorption capacity of coal samples increased gradually with an increase in the number of soaking days and solution pH, reaching the maximum at pH 13 and eight soaking days. The adsorption constant aof the coal sample was positively correlated with the pH, and the number of soaking days was a power exponential function; the adsorption constant bincreased gradually with an increase in the pH of the solution and increased first and then decreased with an increase in the number of soaking days. The change in the adsorption of coal samples occurs because the alkaline solution reacts with the minerals in the coal as well as the mineral ions, and the resulting complex gels and precipitates block the pore channels of the coal body, which in turn inhibits the adsorption of gases. The presence of Na, Mg, Al, Si, Ca, Fe, and other elemental compounds detected in the generated sediments verified the mechanism of alkaline solution erosion. The changes in the microscopic pore structure of the coal body were quantified by low-temperature liquid nitrogen adsorption experiments. The small and medium pore volumes of the coal samples reached the maximum values at pH 13 and with eight soaking days, which is in agreement with the conclusion of optimal alkali modification.

This paper presents a study on the characteristics of graphite-like crystallites (GCs) in coals with different maximum vitrinite reflectance (Ro,max) which can be used to describe the rank of coal. Laser Raman spectroscopy (LRS), X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) were used in testing 17 coal samples with different ranks. Results show that the GCs in coal undertook through three consecutive processes including aromatisation, condensation and polymerisation. Five coalification upgrading yield to six stages that are corresponding to six different ranges of Ro,max. With the increasing coal rank, the GCs grow larger with improving quality and eventually evolve into graphite crystals. HRTEM observation also reveals that GCs in coal have undergone a graphitization process with increases in percentage, size, and order. [Received: April 13, 2017; Accepted: November 28, 2017]

•Three deflector shape structures are proposed to enhance the cooling efficiency of the glass.•The combination of numerical simulation and experimentation was used to analyze the glass's heat transfer properties.•The rectangular deflector increased the heat transfer rate by 0.37%, 1.54% and 0.87% compared to the other three shapes.•The proposed design provides a suitable solution for the energy savings and efficiency of tempering equipment.

In general, the linewidth of the Ramsey central fringe (RCF) is equal to 1/(2T), where T is the Ramsey free-evolution time. We demonstrate that the RCF linewidth of a pulsed optically pumped (POP) atomic clock with orthogonal polarization detection based on the magneto-optical rotation effect can be narrowed down to 1/(4T). The Allan deviation of the POP atomic clock decreases from 2.4×10^−13τ^−1/2 to 1.4×10^−13τ^−1/2. This corresponds to an improvement in the frequency stability by about 60%. We also estimate the main noise sources that limit the short-term frequency stability of the POP atomic clock.

By employing a thermally active magnetic material, we theoretically design a kind of electromagnetic metamaterial with intrinsic magnetic response, termed magnetic metamaterial (MM). The retrieved effective electric permittivity ε_eff and magnetic permeability μ_eff exhibit a nearly continuous transition from double negative to double zero, and then to double positive by controlling the temperature, indicating a flexible tunability of the effective refractive index. The beam splitting, collimation, focusing, and total reflection are achieved at different typical temperatures. Most importantly, with the MM implemented under a gradient temperature, a gradient negative-zero-positive index metamaterial (NZPIM) can possibly be realized, thus providing a new platform to study wave features in NZPIM.

Optically pumped magnetometers (OPMs) have developed rapidly in the bio-magnetic measurement field, which requires lasers with stable frequency and intensity for high sensitivity. Herein we stabilize a vertical-cavity surface-emitting laser (VCSEL) without any additional setup except for the parts of an OPM. The linewidth of the absorption spectrum as a frequency reference is broadened to 40 GHz owing to pressure broadening. To enhance performance, the VCSEL injection current and temperature are tuned simultaneously using a closed-loop control system. The experiments reveal that the VCSEL frequency stability achieves 2×10^−7 at an average time of 1 s, and the intensity noise is 1×10^−6 V/Hz ^1/2 at 1–100 Hz. This approach is useful for suppressing OPM noise without additional sensor probe parts.