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A low-cost functionalization method was used to treat diatomite, and an efficient adsorbent for ammonia nitrogen was prepared by optimizing the functionalization conditions. The functionalized diatomite (DTCA-Na) was characterized by SEM, EDS, BET, XRD, FT-IR and TG. The results demonstrate that DTCA-Na has excellent adsorption performance after being modified with H2SO4 (60.00 wt.%), NaCl (5.00 wt.%) and calcination at 400 °C for 2 h. While studying the effect of adsorption factors on the removal of ammonia nitrogen, the kinetic and thermodynamic behaviors in the adsorption process were discussed. The removal efficiency of the simulated wastewater with the initial ammonia nitrogen concentration of 10.00 mg/L by the DTCA-Na was more than 80% when the contact time was 60 min, pH was 6-10, the dosage of adsorbent was 1.00 g, the temperature was 25 °C. The adsorption process of ammonia nitrogen was conformed to the pseudo-first-order and Langmuir isothermal model. The removal efficiency of ammonia nitrogen was still above 80% after 5 times adsorption-desorption experiments. The DTCA-Na has a brighter prospect of application in the field of ammonia nitrogen wastewater treatment due to its excellent adsorption performance and low-cost advantage.

An effective scheme of frequency doubling up-conversion is proposed and demonstrated, which achieves the generation of high-frequency microwave signal and the compensation of chromatic dispersion-induced power fading (CDIPF). The system structure is based on a cascading of a Sagnac loop and a Mach-Zehnder modulator (MZM), where a phase modulator is used in the Sagnac loop. In the loop, only the clockwise propagating light wave is modulated by a small local oscillator signal, leaving the counterclockwise propagating light wave unmodulated because of the velocity mismatch. The output signal is divided into two parts, one traveling into an MZM and the other entering an optical phase shifter. The intermediate frequency signal is supplied to the MZM, which is biased at its minimum point and then the carrier-suppressed double sideband is achieved. With the adjustment of the optical phase shift, the CDIPF can be compensated at any frequency. In the simulation, by comparing the frequency responses of the proposed link with and without dispersion compensation, we successfully demonstrate the performance of power fading compensation for 60-and 80-km link. Consequently, the spurious-free dynamic range is effectively improved by 13.54 dB at 22.6 GHz for 60-km link.

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