Deep Denitrification of Domestic Sewage by Sulfur-based Mixotrophic Denitrification Filter

As a result of relevant policies and regulations, most wastewater treatment plants are faced with upgrading to further improve the level of effluent targets. To this end, this paper conducts an experimental study on deep denitrification in the sulfur Oyster shells mixotrophic nitrification filter process using sulfur as filler. During the experiments, when the water temperature in the mixotrophic pool was 15 °C, the nitrogen load of the inflow was 7.3 × 10−3kg/m3·d and HRT equaled to 3.5 h, the average TN concentration in the effluent is 3.42 mg/L, and the TN removal rate reaches 54.49%, which can stably meet the core control area standard in the "Discharge Standard of Water Pollutants in Daqing River Basin" (DB13/2795-2018) and are the best operating parameters during the experimental period. The test results show that oyster shells can provide a large amount of alkalinity, alleviating the pH drop in the water column and effectively mitigating the acidification of the water column. Based on experimental calculations, without considering the loss of packing material, the operating cost of the sulphur-mixed denitrification filter process is reduced by $ 0.191 per tonne of water compared with the existing deep treatment unit in the WWTP. The above results show that the sulphur mixer denitrification filter has the ability to degrade the secondary effluent TN in depth, which provides some experimental basis for the sulphur mixer denitrification filter to be used as a deep treatment unit

First-principles study of vibrational and dielectric properties of {\beta}-Si3N4

First-principles calculations have been conducted to study the structural, vibrational and dielectric properties of {\beta}-Si3N4. Calculations of the zone-center optical-mode frequencies (including LO-TO splittings), Born effective charge tensors for each atom, dielectric constants, using density functional perturbation theory, are reported. The fully relaxed structural parameters are found to be in good agreement with experimental data. All optic modes are identified and agreement of theory with experiment is excellent. The static dielectric tensor is decomposed into contributions arising from individual infrared-active phonon modes. It is found that high-frequency modes mainly contribute to the lattice dielectric constant.Comment: 15pages, 1 figure, 5 table

Coherent model for cross-polarization coupling from a single point-like perturbation in optical fibers

The transfer matrix is proposed to describe the coherent cross-polarization coupling (CPC) induced by a single point-like perturbation (PLP) in optical fibers. This matrix remains independent of the fiber length, making it suitable for characterizing the PLP that have a zero-dimensional impact on fiber length. Consequently, the fiber can be fully characterized by a matrix combining the transfer matrix of CPC and the Jones matrix of the fiber birefringence. The polarization performance of fibers exhibiting both CPC and birefringence is analyzed using the developed combined model