Nonlinear evolution characteristics and seepage mechanical model of fluids in broken rock mass based on the bifurcation theory.

With the deep extension of coal mining in China, fault water inrush has become one of the major disasters threatening the safety production of coal mine. Based on the control equations of steady state and non-Darcy seepage in fractured rock mass, the multi-parameter nonlinear dynamic seepage equations of fractured rock mass are established in this paper. Based on the nonlinear dynamics theory, the function of the state variable in the system is derived, and the influence of the gradual change of non-Darcy flow factors on the structural stability of seepage system is studied.

Microstructure Study of High-Rank Coal in an Alkaline Solution at the Chengzhuang Mine.

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.

Study on the Critical Value of Residual Gas Content Based on the Difference of Adsorption Structure between Soft and Hard Coal.

In view of the difference of the adsorption structure between soft and hard coal, there is a big difference in the critical value of the inspection index for the regional outburst risk caused by the gas content. For the coal seams with soft and hard coal stratification, the model of gas content in the equilibrium state was established first, and the microscopic parameters of different rank coals were determined by the low-temperature liquid nitrogen adsorption test and mercury intrusion test. Then, the adsorption capacity of coal samples was determined by the adsorption test.

Loaded Microwave Cavity for Compact Vapor-Cell Clocks.

Vapor-cell devices based on microwave interrogation provide a stable frequency reference with a compact and robust setup. Further miniaturization must focus on optimizing the physics package, containing the microwave cavity and atomic reservoir. In this article, we present a compact cavity-cell assembly based on a dielectric-loaded cylindrical resonator.

Pulsed optically pumped atomic clock with a medium- to long-term frequency stability of 10.

Herein, we report a significant improvement in the medium- to long-term frequency stability of our pulsed optically pumped (POP) vapor-cell rubidium clock. Such an achievement is established with the better control of our system and the environment. An integrated optical module, including a distributed Bragg reflector laser and an acousto-optic modulator, is developed to improve the stability of the laser.

Intensity Detection Noise in Pulsed Vapor-Cell Frequency Standards.

Laser intensity noise is currently recognized as one of the main factors limiting the short-term stability of vapor-cell clocks. In this article, we propose a signal theory approach to estimate the contribution of the laser intensity fluctuations to the short-term stability of vapor-cell clocks working in a pulsed regime. Specifically, given the laser intensity noise spectrum, an analytical expression is derived to evaluate its impact on the clock Allan deviation (ADEV).

Note: Pulsed optically pumped atomic clock based on a paraffin-coated cell.

We report on the implementation of a pulsed optically pumped atomic clock based on a paraffin-coated cell. The relaxation times are measured, with the longitudinal relaxation time, T = 9.7 ± 0.

Frequency stability of a pulsed optically pumped atomic clock with narrow Ramsey linewidth.

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.

Pulsed optically pumped atomic clock with zero-dead-time.

By alternatively operating two pulsed optically pumped (POP) atomic clocks, the dead time in a single clock can be eliminated, and the local oscillator can be discriminated continuously. A POP atomic clock with a zero-dead-time (ZDT) method is then insensitive to the microwave phase noise. From τ = 0.

Continuously tuning effective refractive index based on thermally controllable magnetic metamaterials.

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.

Color-encoded microcarriers based on nano-silicon dioxide film for multiplexed immunoassays.

Multiplexed analysis allows researchers to obtain high-density information with minimal assay time, sample volume and cost. Currently, microcarrier or particle-based approaches for multiplexed analysis involve complicated or expensive encoding and decoding processes. In this paper, a novel optical encoding technique based on nano-silicon dioxide film is presented.