聚丁二烯能量弛豫过程的分维时间模型

根据聚丁二烯的在其玻璃化转变Ｔ８≈１７８Ｋ附近的比热，研究其在弛豫过程中释放能量△Ｑ随其物理老化时间Ｔｗ的关系，发现△Ｑ（ｔｗ）满足Ｋｏｈｌｒａｕｓｃｈ—Ｗｉｌｌｉａｍｓ—Ｗａｔｔａ关系：其中Ｑ０＝２．３１Ｊ·ｇ－１；τ＝９３ｍｉｎ；β＝０．６０．同时结合聚丁二烯的微观结构用分维时间模型解释了实验结果．

凝聚态物质驰豫：分维时间模型

本文提出凝聚态物质驰豫的一个简单的分维时间模型，理论研究表明，凝聚态物质内的反常驰豫是由于绝热近似遭破坏的结果，且需要引入三个不同时间标度描述间断驰豫过程替代连续驰豫过程．本文提出模型不仅能很自然给出持续指数型驰豫ｅｘｐ［－（ｔ／τ）β］，而且能解释实验中观测到β的标度行为．

北西地震带地震活动空间的模糊时间分维

选用北西地震带１９７０年至１９９０年２１年地震资料，对所发生地震的模糊时间分维结构进行了分析和研究。分别以二个月为一个单位和一年为一个单位计算了模糊时间维数Ｄｏ并绘出以二个月Ｄｏ随ｔ变化和２１年每年Ｄｏ随ｔ变化曲线。为了更好突出中强震选取了覆盖北西地震带６个面积相等小区，分别进行了模糊时间分维计算，求出每年６个Ｄｏ来，再（１／６）ΣＤｏ，计算出每年的平均Ｄｏ来并绘出每一小区二个月Ｄｏ随ｔ变化和２１年每年Ｄｏ随ｔ变化曲线。经计算可得以下结果。（１）多数较强地震之前Ｄｏ明显降低。（２）六小区模糊时间分维Ｄｏ随ｔ变化特征可识别地震带不同区域活动性。（３）可划分未来发生较强震所在地区。

云南地区强震前时空强分维特征

本文以标度变换法、相关函数法、最小二乘法分别计算时间分维D_t、空间分维D_s、强度分维D_m(b值),系统清理了云南地区1976年以来6级以上强震前时空强分维的变化特征,表明强震前的降维现象是普遍存在的,但各次强震前的异常三要素又表现出复杂的多样性。结果还表明,强震前小震活动在时间分布上的明显不均匀性主要表现在强震孕育地区,而在空间分布上的明显不均匀性却主要表现在强震孕育的外围地区。

分形理论视野下的园林设计

分形理论认识到在极度复杂的现象背后存在着意想不到的简单规则。规则形态的城市、建筑与不规则形态的园林属于不同类型的分形。中国古典园林空间形态表现出广义的、非严格数学意义上的分形特征,具有多层次的嵌套自相似性,属于非线性变换下的分形,可由多次迭代映射生成。分形理论丰富了园林创作思想和手法,使园林设计更加贴近自然和人性,且不会陷于平庸、千篇一律的泥潭。

TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions

Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C （VC） and the triplet excited states of 9,10-phenanthrenequinone （PAQ） in ethylene glycol-water （EG-H2O） homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ （3PAQ＊） abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3pAQ＊ abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3pAQ＊ by VC is close to the diffusion-controlled value of 1.41 × 108 L/（mol.s）. In hexadecyltrimethylammonium bromide （CTAB）/EG-H2O and aerosol OT （AOT）/EG- H2O reversed micelle solutions, 3pAQ＊ and VC react around the water-oil interface of the reversed micelle. Exit of 3pAQ＊ from the lipid phase slows down the quenching reaction. For Triton X-100 （TX-100）/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3pAQ＊ by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As＇- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3pAQ＊ from VC.

分形学对建筑与城市设计领域的启示

分形美学是一种新的美学观点,将其引入建筑领域具有拓展意义。文章对已有建筑设计中分形美学的形式,从城市规划、建筑单体设计中分形学的应用及设计中的时间维度分形三个方面,进行分析和论述。希望为建筑创作,评估建筑作品时提供一种新视角。

煤电极化性质的分形特征

无序材料中荷电载流子介电响应是分形时间过程和分形结构上的导电性引起的 ,而中低变质煤属于一种结构无序材料。作者据此利用时间分形几何理论对煤的电极化性质进行了进一步的探讨。结果表明 ,煤在恒电场中的电极化性质具有分形特征 ,极化参数b与分形时间维数的关系为 :Dt=kb ,且常数k可能与煤的变质程度有关。

NUMERICAL SIMULATIONS OF EVOLUTIONS FROM WALL PULSE TO TURBULENT COHE RENT STRUCTURES

The high order compact d if ference method is developed for solving the perturbation equations based on Navi er Stokes equations, and is used in studying complex evolution processes from w all negative pulse to the turbulent coherent structure in the channel flow. Th is method contains three dimensional coupling difference scheme with high accur acy and high resolution, and the high order time splitting methods. Compared with the general spectral method, the method can be used to research turbule nt coherent structure under more general boundary conditions and in flow domains . In this paper, the generation and evolution of the turbulent coherent structur es ind uced by wall pulse in the channel flow are simulated, and the basic characterist ics and rules of the turbulent coherent structure are shown. Computational r esults indicate that a wall negative pulse is more convenient than the resonant three wave model.

Competition of Spatial and Temporal Instabilities under Time Delay near Codimension-Two Turing-Hopf Bifurcations

Competition of spatial and temporal instabilities under time delay near the codimension-two Turing-Hopfbifurcations is studied in a reaction-diffusion equation.The time delay changes remarkably the oscillation frequency,theintrinsic wave vector,and the intensities of both Turing and Hopf modes.The application of appropriate time delaycan control the competition between the Turing and Hopf modes.Analysis shows that individual or both feedbacks canrealize the control of the transformation between the Turing and Hopf patterns.Two-dimensional numerical simulationsvalidate the analytical results.

Remaining Useful Life Prediction of Aeroengine Based on Principal Component Analysis and One-Dimensional Convolutional Neural Network

In order to directly construct the mapping between multiple state parameters and remaining useful life(RUL),and reduce the interference of random error on prediction accuracy,a RUL prediction model of aeroengine based on principal component analysis(PCA)and one-dimensional convolution neural network(1D-CNN)is proposed in this paper.Firstly,multiple state parameters corresponding to massive cycles of aeroengine are collected and brought into PCA for dimensionality reduction,and principal components are extracted for further time series prediction.Secondly,the 1D-CNN model is constructed to directly study the mapping between principal components and RUL.Multiple convolution and pooling operations are applied for deep feature extraction,and the end-to-end RUL prediction of aeroengine can be realized.Experimental results show that the most effective principal component from the multiple state parameters can be obtained by PCA,and the long time series of multiple state parameters can be directly mapped to RUL by 1D-CNN,so as to improve the efficiency and accuracy of RUL prediction.Compared with other traditional models,the proposed method also has lower prediction error and better robustness.

Reliability modeling of hydraulic system of drum shearer machine

The hydraulic system plays an important role in supplying power and its transition to other working parts of a coal shearer machine. In this paper, the reliability of the hydraulic system of a drum shearer was analyzed. A case study was done in the Tabas Coal Mine in Iran for failure data collection. The results of the statistical analysis show that the time between failures （TBF） data of this system followed the 3-parameters Weibull distribution. There is about a 54% chance that the hydraulic system of the drum shearer will not fail for the first 50 h of operation. The developed model shows that the reliability of the hydraulic system reduces to a zero value after approximately 1 650 hours of operation. The failure rate of this system decreases when time increases. Therefore, corrective maintenance （run-to-t^ailure） was selected as the best maintenance strategy for it.

Anticoagulation early after mechanical heart valve replacement

Objective： To explore the changes of coagulation activity and the characters of anticoagulation early after mechanical heart valve replacement. Methods： All patients only took warfarin orally for anticoagulation. The predicted international normalized ratio （INR） was 1.5 to 2.0. Several coagulation markers were monitored early after valve replacement. Complications associated with anticoagulation were recorded and analyzed. The patients were divided into three groups based on the number and position of mechanical valve prothesis, including group M （mitral valve replacement）, group A （aortic valve replacement） and group D （mitral and aortic valve replacement）.Comparison was made between the three groups. Results： Three events of mild cerebral embolism and five events of mild bleeding occurred during the early postoperative period. One patient suffered from mild cerebral embolism on the 4th day after operation, accompanied by large volume of pericardial drainage. Two patients with bleeding had lower INRs than predicted range. However, INR in one patient with mild cerebral embolism was in the predicted range. There was no significant difference in thrombo time （TT）, activated partial thromboplastin time （APTT） and 1NR on the 3rd day after operation compared to those before operation; meanwhile, plasma fibrinogen （FIB） concentration was higher than that before operation （P〈0.05）. 1NR had no significant changes on the 2nd day after the beginning of anticoagulation compared to that before operation; however, 1NR was significantly elevated on the 4th day （P〈0.05）. Warfarin doses and INRs were similar among the three groups, but FIB concentrations in plasma were higher in groups M and D than in group A （P〈0.01）. Conclusion： Hypercoagulabale state exists early after mechanical heart valve replacement. When anticoagulation begins is determined by the change of coagulation markers, not by the volume of chest or pericardial drainage. INR can not accurately reflect the coagulation state sometimes, especially during the first 3 days after anticoagulation. The number and position of mechanical valve prothesis could affect coagulation state. Therefore, anticoagulation therapy should be regulated accordingly.

ESTIMATING MULTI-COUNTRY PROSPERITY INDEX: A TWO-DIMENSIONAL SINGULAR SPECTRUM ANALYSIS APPROACH

With the development of the global economy, interaction among different economic entities from one region is intensifying, which makes it significant to consider such interaction when constructing composite index for each country from one region. Recent advances in signal extraction and time series analysis have made such consideration feasible and practical. Singular spectrum analysis （SSA） is a well-developed technique for time series analysis and proven to be a powerful tool for signal extraction. The present study aims to introduce the usage of the SSA technique for multi-country business cycle analysis. The multivariate SSA （MSSA） is employed to construct a model-based composite index and the two dimensional SSA （2D-SSA） is employed to establish the multi-country composite index. Empirical results performed on Chinese economy demonstrate the accuracy and stability of MSSA-based composite index, and the 2D-SSA based composite indices for Asian countries confirm the efficiency of the technique in capturing the interaction among different countries.

Stability and superconvergence analysis of the FDTD scheme for the 2D Maxwell equations in a lossy medium

This paper is concerned with the stability and superconvergence analysis of the famous finite-difference time-domain (FDTD) scheme for the 2D Maxwell equations in a lossy medium with a perfectly electric conducting (PEC) boundary condition, employing the energy method. To this end, we first establish some new energy identities for the 2D Maxwell equations in a lossy medium with a PEC boundary condition. Then by making use of these energy identities, it is proved that the FDTD scheme and its time difference scheme are stable in the discrete L2 and H1 norms when the CFL condition is satisfied. It is shown further that the solution to both the FDTD scheme and its time difference scheme is second-order convergent in both space and time in the discrete L2 and H1 norms under a slightly stricter condition than the CFL condition. This means that the solution to the FDTD scheme is superconvergent. Numerical results are also provided to confirm the theoretical analysis.

Dynamical analysis of the avian-human influenza epidemic model using multistage analytical method

In this paper, analytical result of avian-human influenza epidemic model has been inves- tigated by applying homotopy analysis method （HAM） and by expanding it to hybrid numeric-analytic method which is known as multistage HAM （MSHAM）. HAM is an algorithm which gives us the approximate solution of the problem in an arrangement of time interims and by modifying it to multistage one. Some advantages such as flexibility of picking the auxiliary linear operator and the auxiliary parameter are emerged, that leads us to achieve some excellent results in this work. Furthermore, in this analyti- cal work, obtained results are compared and reported with numerical ones which were obtained previously from methods such as the Runge-Kutta （RK4） method.

Sub-picosecond chirped pulse propagation in concave-dispersion-flattened fibers

We propose the sub-picosecond chirped soliton pulse propagation in copcave-dispersion-flattened fibers （CDFF）. The effects of pulse characteristics and the fiber dispersion parameters on propagation characteristics of the chirped soliton pulse are numerically investigated in the CDFF by the split-step Fourier method （SSFM）. The unchirped soliton pulse can stably propagate with unchanged pulse width in the CDFE The temporal full width at half maximum （FWHM） of the chirped soliton performs a damped oscillation with the increase of propagation distance. The period and amplitude of the oscillation increase with the increase of the chirp parameter ｜C｜. The effect of high-order dispersion （β3-β6） on soliton propagation characteristics can be neglected. The soliton pulse slightly broadens with the increase of propagation distance and still maintains soliton characteristics when the fiber loss （ATT） is further considered. The variation of root-meansquare （RMS） spectral width with propagation distance is opposite to that of the temporal width. The output spectrum of soliton has a single peak for the unchirped case, while has multi-peak for chirped case. The temporal width of the soliton obviously increases with the increase of the initial width, decreases with the increase of dispersion peakD0 of the fiber, and slightly increases with the decrease of dispersion coefficients k1 and k2 of the fiber.

Effect of Pore Distribution on Melting Behavior of Paraffin in Fractal Metal Foam

An unsteady model of melting heat transfer in metal foam filled with paraffin is developed and numerically analyzed. In the model, the pore distribution of metal foam is described by Sierpinski fractal. By this fractal description,six types of metal foams with the identical porosity, different pore distributions are reconstructed. The effect of pores distribution on the heat transfer performance of the paraffin/copper foam composite is emphatically investigated. The solid-liquid distribution, the evolution of the melting front, the dynamic temperature response and the total melting time in these six fractal structures are all examined and analyzed. The results indicate that, the pores distribution has a significant impact on the melting heat transfer of the paraffin in the metal foam. When the first-level fractal pore is located near the heat source boundary, the thermal hysteresis effect of the paraffin on the solid matrix heat transfer is more significant. If the cross-sectional length of the pores along the normal direction of heat transfer is larger, the heat transfer barrier of the solid matrix is greater. It is favorable for the paraffin heat transfer when the pores specific surface area is larger.

Oscillation control for n-dimensional congestion control model via time-varying delay

Time delay or round trip time (RTT) is an important parameter in the model of Internet congestion control. On the one hand, the delay may induce oscillation via the Hopf bifurcation. In the present paper, a congestion control model of n dimensions is considered to study the delay-induced oscillation. By linear analysis of the n-dimensional system, the critical delay for the Hopf bifurcation is obtained. To describe the relation between the delay and oscillation analytically, the method of multiple scales (MMS) is employed to obtain the bifurcating periodic solution. On the other hand, it can be understood that the oscillation will increase the risk of congestion for the network system. To avoid the congestion derived from the oscillation, a new control scheme is proposed by perturbing the delay periodically. Particularly, according to our study, it is possible to control the oscillation by perturbing only one of the n delays. This provides a practical scheme for the oscillation control in the real network system. By MMS, the strengths of the perturbations are predicted analytically such that the oscillation disappears. To give an example, an eight-dimensional model is studied in detail. The analytical results are in good agreement with the numerical simulations.