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The authors designed those experiments to test the sensitivity of graphene when it is exposed to NO₂ gas, to find a way to decrease the recovery time of graphene and to find the difference effect between monolayer and bilayer graphene in the experiments.

The authors transferred graphene from film on Cu foil to NO₂ sensor sample and measured the resistances of on monolayer and bilayer graphene when they were exposed to NO₂ gas under different concentration; then, the authors obtained the results.

The results show that monolayer graphene exhibits a linear response when the NO₂ concentration is below 20 ppm. But the monolayer graphene will not be so sensitive to NO₂ gas when the concentration continues to reduce. The desorption time of monolayer graphene is longer when compared with bilayer graphene. It shows faster recovery time and higher response of bilayer graphene under low NO₂ concentration. And the limit detectable NO₂ concentration of bilayer graphene is 50 ppb. Desorption time of bilayer graphene is shortened to below 20 s under UV light.

The authors found a reliable way to decrease the recovery time of graphene when it is exposed NO₂ gas and got the concrete data.

The paper aims to explore multilingual thesauri automation construction based on the freely available digital library resources. The key methods and study results are presented in the paper. It also proposes a way that terms are automatically extracted from multilingual parallel corpus.

The study adopted the technology of natural language processing to analyze the linguistics characteristics of terms, and combined this with statistical analyses to extract the terms from technological documents. The methods consist of automatically extracting and filtering terms, judging and building relationship among terms, building the multilingual parallel corpus, and extracting term pairs between Chinese and foreign languages through calculating their associated probability. The experiments run on the Java test platform.

The study obtains the following conclusions: finding the similarities and differences between the Chinese thesaurus standard and international thesaurus standard. The methods for automatically extracting terms and building relationships among them are presented. Eventually the multilingual terms' translation sets are generated based on real corpora. The results of the study show that the proposed methods can obtain better performance. The effect of automatic terms' translation alignment method is better than that of traditional IBM model method.

The study results can provide references for further study and application of multilingual thesauri automation construction using Chinese as a pivot.

The paper proposes new ideas on thesaurus automation construction in the digital age. The presented method based on linguistics and statistics is a new attempt. According to the experimental results, this exploration and study is innovative and valuable. In addition, these ideas and methods give a good start for improving information services of the PRC's National Science and Technology Digital Library.