减振合金(二)

减振吸音的缘由 上一期提到在人们的传统观念中,金属是极易产生振动和发出响亮声音的材料,那么减振合金为什么能减振吸音呢? 大家知道,任何材料在弹性变形范围内的应力——应变过程中,一般应变总是滞后于应力。这是由于任何材料都不可能是纯弹性体所决定的。这一滞后现象及其大小表征材料内部对外界能量的衰减特性,

Correlation of Cooperatively Localized Rearrangement on the ＂Fluidized Domain＂ of Polymers to Their Nonexponentially Viscoelastic Behaviors at Double Aging Processes （I）： A Set of Reduced Universal Equations on the Stress Relaxation Modulus and Creep Comp

Based on the structure of glass （or liquid） polymers consisting of α-domain, β-co-domain, and entanglement constituent chain networks, and the nonexponentially viscoelastic behavior, a “heterophase fluctuation” model was proposed. It was found that the dynamics of cooperative rearrangement on the “fluidized domain” has a great shear rate, domain size, and temperature dependences. When the shear rate, domain size, and temperature dependences were taken account into the cooperatively localized rearrangement on the fluidized domain by the degradation of primary α-domain and the reformation of secondary β-co-domain constituent chains. A new dynamic theory of cooperatively localized rearrangement on the fluidized domain constituent chains with different size and different network chain length during physical and mechanical aging was established. The total viscoelastic free en-ergy of deformation resulting from the change in conformations of α-domain, β-co-domain, crytallite, crosslinked, and trapped entanglement constituent chains during aging processes was calculated by the combining method of kinetics and statistical mechanics. The constitu- tive equations and reduced stress relaxation modulus and creep compliances for three types of polymers were also derived. Finally, two reduced universal equations on creep compliance and stress relaxation modulus with a non-linear and two nonexponential parameters α and β were theoretically derived from the dynamic theory and a statistically extended mode coupling theory for double aging effects of polymers was developed. Results show that the two reduced universal equations have the same form as Kohlraush-Williams-Watts （K-W-W） stretched exponential function. The nonlinearity and the nonexponentiality are, respectively, originated from the memory effects of nonthermal and thermal history. The correlation of nonlinearity, α and β to the aging time, aging temperature, and the mesomorphic structure of fluidized domains was also established.

Data classification method based on network dynamics analysis and cloud model

In order to reduce amount of data storage and improve processing capacity of the system, this paper proposes a new classification method of data source by combining phase synchronization model in network clustering with cloud model. Firstly, taking data source as a complex network, after the topography of network is obtained, the cloud model of each node data is determined by fuzzy analytic hierarchy process （AHP）. Secondly, by calculating expectation, entropy and hyper entropy of the cloud model, comprehensive coupling strength is got and then it is regarded as the edge weight of topography. Finally, distribution curve is obtained by iterating the phase of each node by means of phase synchronization model. Thus classification of data source is completed. This method can not only provide convenience for storage, cleaning and compression of data, but also improve the efficiency of data analysis.

Polymorphism of Exon 3 of MHC Class Ⅱ B Gene in Chinese Alligator(Alligator sinensis)

The polymorphism of MHC class II B gene in 14 Chinese alligators was analyzed, which came from three different areas： a wild population from Xuancheng, Anhui, a captive population from Changxing, Zhejiang, and a captive population from Anhui Research Center for Reproduction of Chinese Alligators. The gene fragment was amplified using a pair of specific primers designed from the MHC gene sequence of the spectacled caiman. A total of 34 sequence haplotypes of exon 3 were detected in the sampled Chinese alligators. The numbers of haplotypes of the 3 Chinese alligator populations were 15, 10, and 9, respectively. The overall estimation of the MHC polymorphism in the Chinese alligator population was higher than those in mammals and in cypdnid fish, The rates of nonsynonymous substitutions （dN） occurred at a significantly lower frequency than that of synonymous substitutions （ds）, which were not consistent with the common rule. This result might suggest that the polymorphism of exon 3 seemed not to be maintained by the balancing selection. The neutrality test of Tajima excluded the null hypothesis that the polymorphism of exon 3 was generated by a random drift, and the fact that D = -0.401 indicated an excess of rare mutations in the Chinese alligator. The nucleotide diversity of the sequences and the phylogenetic relations were also analyzed, and the results suggested that there was no significant difference in genetic diversity among the 3 populations of Chinese alligator.

Short-term traffic flow prediction with PSR-XGBoostconsidering chaotic characteristics

To improve the level of active traffic management,a short-term traffic flow prediction model is proposed by combining phase space reconstruction(PSR)and extreme gradient boosting(XGBoost)algorithms.Firstly,the traditional data preprocessing method is improved.The new method uses hierarchical clustering to determine the traffic flow state and fills in missing and abnormal data according to different traffic flow states.Secondly,one-dimensional data are mapped into a multidimensional data matrix through PSR,and the time series complex network is used to verify the data reconstruction effect.Finally,the multidimensional data matrix is inputted into the XGBoost model to predict future traffic flow parameters.The experimental results show that the mean square error,average absolute error,and average absolute percentage error of the prediction results of the PSR-XGBoost model are 5.399%,1.632%,and 6.278%,respectively,and the required running time is 17.35 s.Compared with mathematical-statistical models and other machine learning models,the PSR-XGBoost model has clear advantages in multiple predictive indicators,proving its feasibility and superiority in short-term traffic flow prediction.

Investigation of acoustic scale effects and boundary effects for the similitude model of underwater complex shell-structure

In this paper, the acoustic scale effects and boundary effects for the similitude model of underwater complex shell-structure are investigated. The similitude conditions and relations between the similitude model and its prototype were studied in the references. This paper investigates the acoustic scale effects for the similitude model, which are influenced by loss factor, shear and rotatory inertia. At the same time, the boundary effects which are influenced by surface sound reflection are investigated in the experiment of similitude model. The results show that the acoustic scale effects may be controlled with model designing, the boundary effects can be controlled with experimental designing between the similitude model and its prototype.

Vector form Intrinsic Finite Element Method for the Two-Dimensional Analysis of Marine Risers with Large Deformations

Robust numerical models that describe the complex behaviors of risers are needed because these constitute dynamically sensitive systems. This paper presents a simple and efficient algorithm for the nonlinear static and dynamic analyses of marine risers. The proposed approach uses the vector form intrinsic finite element(VFIFE) method, which is based on vector mechanics theory and numerical calculation. In this method, the risers are described by a set of particles directly governed by Newton's second law and are connected by weightless elements that can only resist internal forces. The method does not require the integration of the stiffness matrix, nor does it need iterations to solve the governing equations. Due to these advantages, the method can easily increase or decrease the element and change the boundary conditions, thus representing an innovative concept of solving nonlinear behaviors, such as large deformation and large displacement. To prove the feasibility of the VFIFE method in the analysis of the risers, rigid and flexible risers belonging to two different categories of marine risers, which usually have differences in modeling and solving methods, are employed in the present study. In the analysis, the plane beam element is adopted in the simulation of interaction forces between the particles and the axial force, shear force, and bending moment are also considered. The results are compared with the conventional finite element method(FEM) and those reported in the related literature. The findings revealed that both the rigid and flexible risers could be modeled in a similar unified analysis model and that the VFIFE method is feasible for solving problems related to the complex behaviors of marine risers.

Mathematical model of the effects of government intervention and rehabilitation of prostitution

In the United States, prostitution is considered illegal in all but one state; Nevada allows some legal activities in exchange for substantial guidelines. In 2010, approxi- mately 43,600 females were arrested for prostitution. Numerous intervention programs were established in order to obstruct the lifestyle of a prostitute （PRP~ Project ROSE, etc.）. There are many documentations and programs that share their forethought on prostitution; however, few target prostitution directly. To determine the dynamics of prostitution, this paper constructs a four-class compartmental model that focuses on the effectiveness of government intervention and rehabilitation of prostitutes mathematically. The basic reproductive number, R0, helps to discover the threshold values for the dynamics of prostitution to become both prevalent or absent in society. This paper predominately observes government intervention to curtail a prostitution prevalent society. Various parameters and variables help to define and indicate the dynamics of pros- titution to construct viable simulations. Successful prostitution interaction prevention deemed essential in prostitution prevention; however, government intervention corresponding with successful rehabilitation competitively challenges prostitution interaction prevention in reducing basic reproductive values.

COMPLEX SYSTEM ANALYSIS OF MARKET RETURN PERCOLATION MODEL ON SIERPINSKI CARPET LATTICE FRACTAL

This paper investigates the statistical behaviors of fluctuations of price changes in a stock market.The Sierpinski carpet lattice fractal and the percolation system are applied to develop a new random stock price for the financial market.The Sierpinski carpet is an infinitely ramified fractal and the percolation theory is usually used to describe the behavior of connected clusters in a random graph.The authors investigate and analyze the statistical behaviors of returns of the price model by some analysis methods,including multifractal analysis,autocorrelation analysis,scaled return interval analysis.Moreover,the authors consider the daily returns of Shanghai Stock Exchange Composite Index,and the comparisons of return behaviors between the actual data and the simulation data are exhibited.