Research on the readout noise suppression method for digital correlated double sampling

As the areas of CCD detectors and CCD mosaics have become larger and larger,the number of readout channels in astronomical cameras has increased accordingly to keep the image readout time within an acceptable range.For the large area cameras or the mosaic cameras,the analog Correlated Double Sampling(aCDS)circuit used in traditional astronomical cameras for suppressing readout noise is difficult to integrate into the camera controllers within the constraints of the space and energy consumption.Recently,digital CDS(dCDS)technology has been developed to solve this problem,which also offers novel analysis and noise suppression methods.In this study,a mathematical model is presented to conveniently analyze the frequency characteristic of a dCDS circuit,which is then simulated by a numerical method for investigating the noise suppression capability with different sampling weights.Importantly,using this model,the extreme point with lowest readout noise can be predicted for a certain dCDS model;and for a specific CCD readout frequency,readout noise can be suppressed by selecting the proper dCDS model.A testing system is then constructed for validating the efficiency of the proposed method.

The Effect of PM2.5 on Economic Situation of Beijing and Solutions

China＇s environmental problems have become increasingly serious, which have caused great attention of the relevant departments of the state. Through the survey, we found that in most of the cities in our country, the inhalable particulate matter PM10 is one of the main pollutants, especially in the capital of China -- Beijing, which is the arch-criminal cause of the air pollution. According to the quality control report released in Beijing City Environmental Protection Bureau, as can be learned, in recent years, Beijing＇s air quality goes from bad to worse, and in the overall atmospheric pollutants, the PM10 is up to above nine tenths. There are more reports saying that the air pollution levels in Beijing have been not suitable for the human habitation. With the increasing of the air pollution, the term PM2.5 is also more and more familiar to us. The air more intensified the pollution is, the greater the ratio of PM2.5 in PM10 is. In that case, it not only seriously affects the people＇s health, but also brings the huge economic losses. This paper is aimed to analyze the influence of PM2.5 on the economic situation of Beijing, and puts forward the concrete solutions.

A unified model for ductile-to-brittle transition in body-centered cubic metals

Ductile-to-brittle transition(DBT)is a well-known phenomenon in body-centered-cubic(BCC)metals,in-termetallics and semiconductor materials.A quantitative prediction of the DBT temperature,however,has so far remained intractable.Here,we propose a unified model based on the efficacy of dislocation multi-plication as the controlling factor for DBT,with the dislocation source efficiency governed by the relative mobility of screw versus edge dislocations.The model successfully predicts the DBT temperature of iron,molybdenum and tungsten,and also covers the influence of grain size,initial dislocation density,and the multiplicity of dislocation sources.A comparison with experiments indicates that the model captures the key DBT features,providing new insight into the toughness of BCC metals.

Dy_(2-x)Y_xTi_2O_7: phonon vibration and magnetization with dilution

In this paper, the dilution effects of non-magnetic Y ions on spin-ice compound Dy_2Ti_2O_7 by infrared and Raman spectra and magnetization measurements were investigated. An anomalous phonon softening with temperature decreasing is found in both the parent and diluted compounds, and Y doping can relax the softening of phonons except that of the IR mode near 233 cm^-1, indicating a strong phonon–phonon coupling in the spin-ice material.The magnetization measurements reveal that the nonmagnetic impurities do not severely influence the spin-ice rules in the ground state when the level of dilution is not very high. However, a large amount of dilution enhance the disorder and break the spin-ice state because the collective spin-flip clusters are no longer available.