Rising time restoration for nuclear pulse using a mathematic model.

The rising time of a nuclear pulse is slowed before being digitized because of the effect of distributed capacitance and resistance. This results in the waveform distortion of a shaped pulse. In this study, the effect of distributed capacitance and resistance is equivalent to the result of RC network. The mathematical model of the network is established to restore the rising time of the input nuclear pulse. Experimental results show that the leading edge of the nuclear pulse becomes steep after rising time restoration, and the shape of the shaped pulse is also improved. The energy spectrum obtained with rising time restoration is compared with that without rising time restoration. The comparison result indicates that using rising time restoration can extend the measurement range of pulse amplitude without affecting the energy resolution of the system.

[Manganese Oxidation Characteristics and Oxidation Mechanism of a Manganese-Oxidizing Bacterium Arthrobacter sp. HW-16].

Manganese is a common inorganic pollutant, which is difficult to remove from the environment. In this research, a high efficient manganese-oxidizing bacterium Arthrobacter sp. HW-16 was isolated from the manganese-rich soil using selective media. Besides, high-throughput sequencing revealed that there were significant differences of the microbial community compositions when bacteria were acclimated in different conditions, and Arthrobacte was the dominant genus in Mn(Ⅱ) containing media. In this paper, the microbiological properties of strain HW-16 and Mn(Ⅱ) oxidation mechanism were investigated. The results indicated that the maximal Mn(Ⅱ) tolerance mass concentration of strain HW-16 was 5000 mg·L-1,and it exhibited a decent Mn(Ⅱ) oxidation efficiency with the highest value of 66.28% at a Mn(Ⅱ) concentration of 3000 mg·L-1. Single factor experiments demonstrated that environmental factors could affect the growth and Mn(Ⅱ) oxidation efficiency of strain HW-16. At 30℃ or pH 7.0, at 1% or 3% salinity, and at 200 r·min-1, strain HW-16 got the highest biomass. While the highest Mn(Ⅱ) oxidation efficiency occurred at high temperature (≥40℃), high pH (≥7), high shaking speed and low salinity. Strain HW-16 could oxidize Mn(Ⅱ) by producing Mn(Ⅱ) oxidizing active factor and turn Mn(Ⅱ) into precipitation by synthesizing alkaline metabolites.

[Study on the High Speed and Precision Gaussian Function Fitting Algorithm for Nuclear Single Spectral Peak].

In nuclear spectrum, Gaussian function least square fitting is a commonly used method. Usually the method has high precision, but it is very much sensitive to noise, which causes that the residual vector is larger near the peak in the Gaussian function. To solve the problem, Gaussian function least square fitting was deduced particularly, and the causes are analyzed. As a result, Gaussian function weighted least square fitting is proposed, i.e., a weight factor, which had an opposite tendency to the data weight reduction tendency after taking logarithm, or it had the same tendency to the origin data. This was introduced based on Gaussian function least square fitting to reduce noise sensitivity. In the process of solving Gaussian parameter, to improve the real-time performance, the solution process of inverse matrix was transferred to the solution process of simple equations because the computation of inverse matrix was time consuming. Gaussian function parameter, amplitude, center value and variance, were given with the fast calculation formulas. By applying these two methods to the practical fitting of 55Fe characteristic X-ray single spectrum peak, respectively, the results show that Gaussian function weighted least square fitting is more satisfactory. It indicates the proposed method can decrease the noise sensitivity and reduce the residual vector near the peak; in addition, the fitting precision is also improved. What's more, the real-time performance is improved by applying fast calculation formulas, which makes it possible to apply the proposed method to portable equipment efficiently.