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Changsha, China

Zhang L.,Shenzhen University | Zhang L.,Changsha University | Liu K.,Shenzhen University | Zhong H.,Shenzhen University | And 4 more authors.
Optics Express | Year: 2015

We study both analytically and numerically the propagation dynamics of an initially chirped Airy pulse in an optical fiber. It is found that the linear propagation of an initially chirped Airy pulse depends considerably on whether the second-order dispersion parameter β2 and chirp C have the same or opposite signs. For β2C < 0, the chirped Airy pulse first undergoes an initial compression phase, then reaches a breakup area as depending on the values of C, and then experiences a lossy inversion transformation such that it continues to propagate with an opposite acceleration. The chirped Airy pulse is always dispersed during propagation in the case ofβ2C > 0. The impact of truncation coefficient and Kerr nonlinearity on the chirped Airy pulse propagation is also disclosed separately. © 2015 Optical Society of America.

Zhang P.-K.,Hunan First Normal College
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2010

Through establishing and solving differential equation of motion of the loudspeaker's cone driven by low-frequency tone burst signals, the cone's motion was analyzed with MAPLE software, analytic expression of the cone's velocity-time relation and a way of describing its velocity-time curve were given. Factors affecting the speaker's transient characteristics were studied, and theoretical results were tested by experiment. In addition, a possible way was proposed to measure the speaker's quality factor Q. The results show that the characteristics of the front and back edges of the speakers are interrelated; both the speaker's mechanical quality factor (Q m) and its electrical quality factor (Q e) have equivalent influence on the characteristics of the front and back edges of the speaker. Total quality factor (Q t) really affects the speaker's transient characteristics. As to tone burst signals in a certain range of frequency, the smaller the Q t of the speaker, the better its characteristics of the front and back edges. But too small Q t leads to degradation of sound pressure frequency characteristics. When designing speakers, the transient response and sound pressure frequency characteristics should be comprehensively taken into consideration to determine the appropriate Q t.

Huang G.,Shanghai University | Huang G.,Shaoyang University | Huang G.,Hunan First Normal College | Hu J.,University of Houston-Victoria
Current Bioinformatics | Year: 2013

Mainly based on pKa (NH3 +) values of amino acid, a novel graphical method without degeneracy for protein sequences has been proposed firstly, which assists in viewing, aligning and comparing multiple sequences visually. Then, a new algorithm to extract a 40-dimensional numerical vector from graphical curves has been presented to characterize protein sequences. The similar relationship among sequences is computed by Euclidean distance on corresponding numerical vectors. Finally, our method is applied for similarity analysis of protein sequences on two data sets. The results are in agreement with the acknowledged view proved by a great deal of evidence from anatomy and hence demonstrate the validity of this approach. © 2013 Bentham Science Publishers.

Zhang L.,Shenzhen University | Zhang L.,Changsha University | Zhang J.,Hunan First Normal College | Chen Y.,Changsha University | And 2 more authors.
Journal of the Optical Society of America B: Optical Physics | Year: 2014

The dynamic propagation of the finite-energy Airy pulse (FEAP) is studied numerically in the presence of higherorder effects, including Raman scattering, self-steepening (SS), and third-order dispersion (TOD). It is shown that the Raman-induced frequency shift (RIFS) of a FEAP can be tailored by varying the truncation coefficient of the FEAP. In particular, the combined effects of Raman scattering and SS (or TOD) on the nonlinear propagation of a FEAP are identified. It is found that both TOD and SS effects tend to slow down the RIFS during the nonlinear propagation of a FEAP. In addition, the simultaneous contributions of Raman, TOD, and SS effects to the nonlinear propagation of FEAP are further discussed. Compared to the conventional symmetric pulses, such as Sech pulses, the FEAP can generate a broadening spectrum that is extended toward the blue side, in addition to the conventional red-shifted components. These results demonstrate that the FEAP can be used for supercontinuum generation and broadband sources. © 2014 Optical Society of America.

Huang G.,Shaoyang University | Zhou H.,Shaoyang University | Li Y.,Hunan First Normal College | Xu L.,Shaoyang University
Journal of Theoretical Biology | Year: 2011

In order to compare different genome sequences, an alignment-free method has proposed. First, we presented a new graphical representation of DNA sequences without degeneracy, which is conducive to intuitive comparison of sequences. Then, a new numerical characterization based on the representation was introduced to quantitatively depict the intrinsic nature of genome sequences, and considered as a 10-dimensional vector in the mathematical space. Alignment-free comparison of sequences was performed by computing the distances between vectors of the corresponding numerical characterizations, which define the evolutionary relationship. Two data sets of DNA sequences were constructed to assess the performance on sequence comparison. The results illustrate well validity of the method. The new numerical characterization provides a powerful tool for genome comparison. © 2011 Elsevier Ltd.

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