一种改进的变结构混沌序列性能分析

自提出了基于广义混沌映射切换的混沌同步保密通信方法以来,这种通过混沌映射切换来改变混沌系统结构,以此产生伪随机序列的方法被频繁引用.但这种方法产生的序列的综合性能却一直未能得到有力的证明,而且尚存在不能充分保证序列周期足够长的致命弱点.本文对这种变结构混沌序列产生方法作了动力学分析,并通过数值仿真对该方法产生的序列做了统计性能分析和抗预测性能研究.为了解决周期问题,本文在变结构混沌序列基础上引入了m序列扰动.结果表明:这种改进的变结构混沌序列具有典型的混沌特性,而且产生序列的周期,相空间分布,线性复杂度,相关性以及抗预测性等方面的性能明显优于基于单一混沌系统的序列.

Modeling hot strip rolling process under framework of generalized additive model

This research develops a new mathematical modeling method by combining industrial big data and process mechanism analysis under the framework of generalized additive models(GAM)to generate a practical model with generalization and precision.Specifically,the proposed modeling method includes the following steps.Firstly,the influence factors are screened using mechanism knowledge and data-mining methods.Secondly,the unary GAM without interactions including cleaning the data,building the sub-models,and verifying the sub-models.Subsequently,the interactions between the various factors are explored,and the binary GAM with interactions is constructed.The relationships among the sub-models are analyzed,and the integrated model is built.Finally,based on the proposed modeling method,two prediction models of mechanical property and deformation resistance for hot-rolled strips are established.Industrial actual data verification demonstrates that the new models have good prediction precision,and the mean absolute percentage errors of tensile strength,yield strength and deformation resistance are 2.54%,3.34%and 6.53%,respectively.And experimental results suggest that the proposed method offers a new approach to industrial process modeling.

Prediction of HLA-A 2.1-restricted CTL epitopes from IGFBP7 antigen of lung carcinoma

Objective： With the development of peptide-based cancer specific immunotherapy, the prediction of CTL epitopes from insulin-like growth factor-binding protein 7 （IGFBP7） is very important for some research about tumor metastasis. Because HLA-A2.1-expressing individuals cover 〉50% in the population of China, we aimed at identifying IGFBPT-encoded peptide presented by HLA-A2.1. Methods： In our study, a HLA-A2.1 restricted CTL epitope was identified by using the following two-step procedure： （a） computer-based epitope prediction from the amino acid sequence of IGFBP7 antigen; （b） Validation with epitope molecular modeling. Results： We obtained four epitopes with high immunogenicity scores by all of the three algorithms, i.e., BIMAS, SYFPEITH1 and IMTECH. Each of the four candidates satisfied the criteria of the HLA-A2.1- restricted CTL epitopes in molecular modeling analysis. Conclusion： The combination of BIMAS, SYFPEITHI and IMTECH method can improve the prediction efficiency and accuracy. Due to this research herein, this four epitopes have potential value for further studied, also have potential application in peptide-mediated immunotherapy. These epitopes may be useful in the design of therapeutic peptide vaccine for lung carcinoma and as immunotherapeutic strategies against lung carcinoma after identified by immunology experiment.

Prediction of antigenic determinants of trichosanthin by molecular modeling

The antigenic determinants of trichosanthin were predicted by molecular modeling. First, the threedimensional structure model of the antigen-binding fragment of anti-trichosanthin immunoglobulin E was built on the basis of its amino-acid sequence and the known three-dimensional structure of an antibody with similar sequence. Secondly, the preferable antigen-antibody interactions were obtained based on the known three-dimensional structure of trichosanthin and of the hypervariable regions of anti-trichosanthin immunoglobulin E. Two regions in the molecular surface of trichosanthin were found to form extensive interactions with the hypervariable regions of the antibody and have been predicted to be the possible antigenic determinants: one is composed of two polypeptide segments, Ile201-Glu210 and Ile225-Asp229, which are close to each other in the three-dimensional structure; and the other is the segment Lys173-Thr178. The former region seems to be the more reasonable antigenic determinant than the latter one.

Predictive current control system of PMSM based on LADRC

For a permanent magnet synchronous motor(PMSM)model predictive current control(MPCC)system,when the speed loop adopts proportional-integral(PI)control,speed regulation is easily affected by motor parameters,resulting in the inability to balance the system robustness and dynamic performance.A PMSM optimal control strategy combining linear active disturbance rejection control(LADRC)and two-vector MPCC(TV-MPCC)is proposed.Firstly,a mathematical model of a PMSM is presented,and the PMSM TV-MPCC model is developed in the synchronous rotation coordinate system.Secondly,a first-order LADRC controller composed of a linear extended state observer and linear state error feedback is designed to reduce the complexity of parameter tuning while linearly simplifying the traditional active disturbance rejection control(ADRC)structure.Finally,the conventional PI speed regulator in the motor speed control system is replaced by the designed LADRC controller.The simulation results show that the speed control system using LADRC can effectively deal with the changes in motor parameters and has better robustness and dynamic performance than PI control and similar methods.The system has a fast motor speed response,small overshoot,strong anti-interference,and no steady-state error,and the total harmonic distortion is reduced.

Predicting size effect on diffusion-limited current density of oxygen reduction by copper wire

The size effect of copper wire radius (0.04–0.82 mm) on the diffusion-limited current density of an oxygen reduction reaction in stagnant simulated seawater (naturally aerated 0.5 mol/L NaCl) is investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) and compared with the results obtained in 0.5 mol/L H2SO4. In the oxygen diffusion-limited range, size effect is found to occur independent of electrolytes, which is attributed to non-linear diffusion. Additionally, to satisfy application in a marine setting, an empirical equation correlating oxygen diffusion-limited current density to copper wire radius is proposed by fitting experimental data.

QSAR prediction of antagonistic activity of PCBs towards human PXR by using heuristic method and best subset modeling

Polychlorinated biphenyls(PCBs) can antagonize human pregnane X receptor(hPXR) activation.Such chemicals could pose a serious threat to the reproductive and developmental ability of humans.The quantitative structure activity relationship(QSAR) provides a promising method for the estimation of PCBs' antagonistic activity.In this investigation,a QSAR model was developed by using heuristic method and best subset modeling(r2 = 0.873,q2LOO=0.742).The built model was validated externally by splitting the original data set into training and prediction sets.The results of the model derived are as follows:r2 = 0.907,q2LOO=0.709,r2pred=0.676,suggesting developed QSAR model had good robustness and predictive ability.The applicability domain(AD) of the model was assessed by Williams plot.The antagonistic activity(?logKi) of 108 PCBs,which are unavailable by experiment at present,was predicted within the applicability domain of the model.The critical structural features related to the activity of PCBs were identified.

Experiments on and predictions about properties of sand bonded by microbe cement

Microbe cement as a new bonding material is presented. Sandstone （0.05 m diameter, 0.5 m height） and sandpile （0.125 m^3） are joined by microbe cement to make a whole body. Evolutions in the related properties of treated sand samples are examined through compressive strength and calcite content. Results indicate that the structure of the cemented body is nonuniform, that the calcite content decreases with distance from the injection port, and that the compressive strength also decreases with dis- tance from the injection port. In addition, evolutions in the measured calcite content and compressive strength are summarized by a numerical model that considers microbe concentration distribution. The numerical results of the calcite content at different positions for 0.5 m height sandstone are similar to the test results, and the experimental results for calcite content and compres- sive strength of 0.125 m^3 cubic sandpile are similar to the numerical results. Prediction results indicate that the simulations should become a significant supplementary tool when microbe cement is applied in actual engineering projects.