Papers by Author: Jian Ping Cheng

Abstract: Spectral drift of any origin consisting of detectors and nuclear electronics affects the long-term stability in a gamma-ray spectrometer, which is essential to maintaining the high quality of gamma energy spectra. The feedback regulation according to the quantity of spectral drift can restore the system’s stability. A new algorithm for spectral drift calculation is given in this paper. A digital logic unit is developed in a FPGA chip based on the algorithm, and a MCU coordinating with it can fast calculate the spectral drift within only less than 110 instruction periods.

Abstract: Gold nanostructures were synthesized at room temperature under irradiation of a fluorescent lamp in mixture of gold seeds smaller than 10 nm, HAuCl4, and poly(vinylpyrrolidone) (PVP). N,N'-dimethylformamide (DMF), water or ethylene glycol (EG) was used as solvent respectively. The products were characterized by transmission electron microscopy, X-ray diffraction and absorption spectra, and the results indicated that under light irradiation at ambient, the reducibility of the three solvents for HAuCl4 ranked as: EG> water> DMF, all far weaker than that of PVP; PVP also prevented the nanostructures from precipitating; gold seeds seemed to impose an autocatalytic effect to facilitate the reduction of HAuCl4; light irradiation was essential for high-yield production of gold particles; the above factors influenced the morphology and size of the gold structures, and led to formation of particles within nano or micron scale in shape of spheroid, rod or plate.