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Lai X.,University of Electronic Science and Technology of China | Han Z.,University of Electronic Science and Technology of China | Peng H.,University of Electronic Science and Technology of China | Peng H.,HefeiUniversity of Technology
Journal of University of Science and Technology of China | Year: 2013

In order to attain the realizable non-diffracting pulsed wave, a new kind of pulsed Bessel ultrasonic beam was proposed. The propagation of the pulsed non-diffracting Bessel ultrasonic beam in the nonlinear medium was studied, and the pressure and distribution of the ultrasonic field was analysed. It can be concluded that the proposed construction method has the good property of non-diffraction in the non-linear medium and can hold the non-diffracting property until a certain depth of far field. Therefore, the new pulsed Bessel ultrasonic beam is important in ultrasonic medical detection.

Fu J.,Zhejiang University | Fu J.,HefeiUniversity of Technology | Yuan J.,Zhejiang University | Ren A.,Zhejiang University | And 2 more authors.
Acta Chimica Slovenica | Year: 2013

The relative stabilities of the twenty-three possible isomers for C 84O2 based on C84(D2d) were studied by using density functional theory (DFT) at B3LYP/6-31G(d) level. The most stable isomer of C84O2 was found to be 1,5,8,9-C 84O2 which contains annulene-like structures. In this isomer, two oxygen atoms are added on the same hexagon, which is called a same-ring adduct. The energy gap of C84O2 is narrower than that of C84(D2d). The chemical shifts of the bridged carbon atoms in C84O2 are changed upfield compared with those of the same carbon atoms in C84(D2d). The same-ring adduct possesses the higher aromaticity than C84(D2d). The area within the range of 0.2 nm from the cage center of C84(D 2d) or C84O2 is the most suitable area for calculating NICS values.

Wang J.-Z.,Environmental Health Science and Research Bureau | Wang J.-Z.,HefeiUniversity of Technology | Hou Y.,Southern Illinois University Carbondale | Zhang J.,Syracuse University | And 2 more authors.
Journal of Hazardous Materials | Year: 2013

A commercial brominated flame retardant 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was used as the model chemical to investigate the degradation and transformation of polybrominated diphenyl ethers (PBDEs) in gas and liquid phases, respectively, under ultraviolet (UV) irradiation. The results showed that BDE-47 can be transformed to less-brominated BDE analogs. A total of six compounds that are less-brominated BDEs and two brominated phenols were observed as transformation products in the reaction mixtures. Different degradation rates of BDE-47 in n-nonane and in isooctane in the same chamber system were observed. Degradation rate of BDE-47 in n-nonane was faster than in isooctane. Under UV irradiation, the bromine on the ortho positions of the phenyl rings was lost first to form 2,4,4'-tribromodiphenyl ether (BDE-28), which then progressively lead to 4,4'-dibromodiphenyl ether (BDE-15) or 2,4'-dibromodiphenyl ether (BDE-8). An airborne transformation pathway has been proposed according to observed transformation products. The more volatile less-brominated BDEs from transformation of BDE-47 are easily evaporated into air to be a source of secondary pollutants in the environment. © 2013.

Ni Z.,China Institute of Technology | Ni Z.,HefeiUniversity of Technology | Hu T.,China Institute of Technology | Hu T.,HefeiUniversity of Technology | And 4 more authors.
Journal of University of Science and Technology of China | Year: 2013

A new machine learning method, "fractal learning", was proposed, which aims at acquiring knowledge from high-dimension and mass data in a better way. The research object of fractal learning is the self-similarity system. The inference of fractal learning is based on the study of the self-similarity of system. Fractal dimension used to describe the degree of the self-similarity of the system is the important parameter of fractal learning. The definition of the fractal learning is given and the basic principle of the fractal learning is explained along with the key technology during the learning process of the fractal learning. Finally, the method is applied to the reduction of the case base, which has achieved a good result.

Tan X.,HefeiUniversity of Technology | Hu X.,Hefei University | Chu C.,HefeiUniversity of Technology | Chu C.,Hefei University | Shi X.,HefeiUniversity of Technology
Journal of University of Science and Technology of China | Year: 2011

Based on the theory of fuzzy random variable, fuzzy response surface method (FRSM) was proposed. FRSM combines the fuzzy cut method with stochastic response surface method, so it can consider fuzziness and randomness simultaneously, and it can be considered as an extension of stochastic response surface method. One merit of FRSM is that it can give the explicit expression of an implicit limit state function, which is very useful to demonstrate the essence of FRSM based on the theory of fuzzy random variable. It is demonstrated from an example that parameter uncertainty of fuzzy random variables can be expressed by the coefficient of variation and the coefficient of fuzziness. The coefficient of variation affects mainly the nominal value of fuzzy reliability index. The larger the value of the coefficient of variation, the smaler is the nominal value of reliability index. The coefficient of fuzziness affects mainly the fuzziness of fuzzy reliability index. The larger the coefficient of fuzziness, the wider is the range of fuzzy reliability index.

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