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   Science & Technology Review
2009, Vol.27, No. 0902
28 January 2009

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Explore in the Wisdom of Science Communication

Science & Technology Review. 2009, 27 (0902): 19-20. ;  doi:
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Abstract ( 802 )
Dissemination and popularization are essential for science to have its impact on society. Otherwise, science and technology would be meaningless to human activities. Exploration and popularization are eternal topics of human scientific activities. It is the duty of a scientist to enrich human knowledge, to enhance human capability, to solve practical problems, to share the insight of science with public, to disseminate science and to make good advices.
Spescial Issues

Experimental Investigation on Nonlinear Vibrations of Simply Supported Rectangular Thin Plate Subjected to Transverse Excitation

Science & Technology Review. 2009, 27 (0902): 21-24. ;  doi:
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Abstract ( 848 )
Nonlinear vibrations of a simply supported rectangular plate subjected to transverse exitation are experimentally investigated in this paper. The plate is placed in a special test frame in which four thick blocks with V-grooves hold the test plate to enforce required boundary conditions. The two groups of plate edges are movable during the test. A shaker fixed above the plate is used to provide the desired excitation. The resonance frequencies are obtained by hammering method and the vibration experiments are carried out in the resonance frequency zones. Nonlinear analyses are made by changing the exciting frequency and amplitude. The waveforms, phase portraits and amplitude spectrums are obtained to show that this system can exhibit complicated nonlinear dynamic characteristics, including periodic doubling bifurcations and chaotic motions under certain excitation frequency and amplitude conditions.

Analysis of the steady-state response of nonlinear axially moving viscoelastic beams with time-dependent velocity

Science & Technology Review. 2009, 27 (0902): 25-28. ;  doi:
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Abstract ( 812 )
Axially accelerating beams can be used to simulate many engineering devices. As a parametric vibration is excited by the variation of the beam tension or the beam axial speed, a large transverse motion of axially moving beams may occur under certain conditions. In this paper, the steady-state response of nonlinear axially moving beams with time-dependent velocity is analyzed. The material time derivative is used in the viscoelastic constitutive relation. Asymptotic analysis is proposed to investigate the governing equation of an axially accelerating viscoelastic beam. Beams are constrained by elastic joints at both ends in all time. The supporting conditions may be formulated as simple supports with torsion springs. The axial speed is characterized as a simple harmonic variation about a constant mean speed. If the axial speed variation frequency approaches the sum of any two natural frequencies, the summation parametric resonance may occur. The stability-state equation and amplitude equation are obtained for the combined parametric resonance via the asymptotic analysis. Numerical examples show the effects of the viscoelasticity, the amplitude of fluctuation and the nonlinearity of the beam on stability-state response.

Research on the Detection Approach for Locating Rub-Impacts in Rotor Systems Using a Nonlinear Output Frequency Response Functions

Science & Technology Review. 2009, 27 (0902): 29-32. ;  doi:
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Abstract ( 741 )
A novel method for locating rub-impacts along a rotor shaft is proposed based on the concept of Nonlinear Output Frequency Response Functions(NOFRFs). As one of the most common damaging malfunctions of rotating machineries, the rub-impacts in a rotor system are often modeled as a nonlinear problem and the identification of their locations is important in industrial applications. The NOFRFs were developed based on the Volterra series theory of nonlinear systems and found to be effective in detecting nonlinear components in a multi-DOF vibrating system. The simulations of shaft node transverse vibrations are carried out with finite element method for different rub-impact positions along the shaft. And then the NOFRFs are calculated and their values are used to indicate the possible range where there exist rub-impacts.

Dynamical Analysis of a Two DOF Vehicle Suspension System Using Revised Bingham Model

Science & Technology Review. 2009, 27 (0902): 33-37. ;  doi:
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Abstract ( 1522 )
A revised Bingham model for MRF damping is used to describe the nonlinear damping force of vehicle suspension. The nonlinear stiffness of tire is in a form of squared relations. An analytical solution for the two DOF vehicle system's dynamical response is obtained by averaging method, which is verified by the numerical solution. In addition, the effect of system parameters on the dynamical tire force is also studied. It is found that with the increase of C1, Fy and V0 in the revised Bingham model, the tire force decreases and the effect of C1 and Fy on the tire force is greater than that of V0 ; the effect of square nonlinearity of the tire stiffness on the tire force is small. The results of this study may be relevant to the vehicle vibration control and the avoidance of road damage.

Synchronization of Time Delay and Star Coupling H-R Neural Networks

Science & Technology Review. 2009, 27 (0902): 38-42. ;  doi:
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Abstract ( 810 )
Chaotic synchronization of Hindmarsh-Rose (H-R) neural networks linked by the time delay coupling function according to the matrix of star coupling coefficients is investigated. With the coupling strength and the time delay taken as the separated controlling parameters, the ideal synchronization of a star connected H-R neural network is discussed, and the range of the coupling strength and the time delay under synchronization are obtained. It is also shown that some unique synchronization phenomenon is associated with H-R star linked networks.

A Neumann Problem for Quasilinear Elliptic Equation with Logarithmic Nonlinearity in a Ball

Science & Technology Review. 2009, 27 (0902): 43-46. ;  doi:
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Abstract ( 1625 )
The nonlinear quasilinear elliptic problem -div(|?塄u|p-2?塄u)=logu+h(x)uq in a ball BR?奂Rn with Neumann boundary conditions on ?坠BR are studied. For each 0<ε<1, a family of approximate problems -div(|?塄u|p-2?塄u)=log■+h(x)uq is considered. Then, it is natural to look for a family of solutions of this problem and then to pass the limit as ε→0 to obtain a solution to the first problem. Because we cannot use Poincaré inequality to solve the second problem directly by variational methods, for each 0<r<R, ArR:=BR\Br is defined. Consider the third family of the problem, a solution to the second problem is obtained when r→0+. By means of a double perturbation argument, a positive radial solution u∈C1(BR\{0})∩C(BR) is obtained.

An Approximate Analytical Solution to the Family of Time Fractional Klein-Gordon Equations

Science & Technology Review. 2009, 27 (0902): 47-52. ;  doi:
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Abstract ( 869 )
In this paper, the Adomian decomposition method is used to obtain an approximate analytical solution to the time fractional Klein-Gordon equation, where the fractional derivatives are in Caputo sense. Some examples are given to show the efficiency of the method, the approximate solution and exact solution of the error are given by four tables, and it is shown that the Adomian decomposition method in solving the time fractional Klein-Gordon equation can be very high precision.

Non-linear Dynamics and Control of Flutter of Airfoil

Science & Technology Review. 2009, 27 (0902): 53-61. ;  doi:
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Abstract ( 919 )
This paper presents our studies on the flutter of airfoil by using modern nonlinear dynamics and control methods, including mainly the following three parts. (1) Studies on Hopf bifurcation flutter of airfoil in a supersonic flow field using the normal form direct method. An analysis of the obtained coefficients of the normal form indicates that the Hopf bifurcation can change from super-critical type to sub-critical type, consequently, the flutter instability changes from "benign" type to "catastrophic" type, as the flight Mach number increases. (2) The wash-out filter technique is used to control the flutter of a two dimensional airfoil with cubic non-linearity in an incompressible flow. For the introduced wash-out filter controller, the linear control gain of the controller is determined according to the Hopf bifurcation condition and the non-linear one is determined based on a relationship between the bifurcation type and the parameters of the normal form obtained by the normal form direct method. As a result the sub-critical Hopf bifurcation can be transformed to the super-critical one. (3) Influence of initial conditions on flutter of airfoil with bilinear structural nonlinearity is investigated by the improved cell mapping technique. Different types of motions, including damped stable motion, limit cycle oscillation, complicated periodic motion, chaotic motion and divergent flutter are determined as a function of initial conditions.

Applications of Iterative Methods to Studies on Stability and Hopf Bifurcation of Time-Delay Systems

Science & Technology Review. 2009, 27 (0902): 62-65. ;  doi:
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Abstract ( 797 )
This paper presents a brief review on the recent advances in applications of iterative methods to studies on stability and Hopf bifurcation of time-delay systems. In stability analysis, the Newton-Raphson iterative method is used to calculate the rightmost characteristic root(s), with the help of the Lambert W function. In Hopf bifurcation analysis, the iterative method is applied for finding an approximate solution of the bifurcated periodic solution. In both cases, the iterative methods are very effective.
Articles

Design and Applications of 20 MHz Ultrasonic Focused Transducer

Science & Technology Review. 2009, 27 (0902): 66-69. ;  doi:
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Abstract ( 710 )
High sensitivity transducers are essential in improving the image resolution of industrial ultrasonic microscopes. The equivalent circuits of the ultrasonic focused transducer are analysed by Mason's equivalent circuit, the pulse focused sound fields are simulated with Matlab in the direction of the focused transducer axis,and the results are compared with the sound fields of circle flat transducer. The transducing piezoid is developed with special technologies, and with the mixture of epoxide and tungsten powder for backing, the ultrasonic transducers enjoy good qualities of narrow pulse, higher sensitivity, higher resolution, among others. In applications, the returning wave of broadband narrow pulse focused transducer (with center frequency of 20 MHz) is merely of one waveform and the image resolution for flaws in testing multi-layer composite materials reaches up to 0.4 mm.

Dynamic Modeling of Robot for Repairing Hydraulic Turbines

Science & Technology Review. 2009, 27 (0902): 70-72. ;  doi:
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Abstract ( 803 )
JZ-3 Robot is used for welding and grinding for repairing hydraulic turbines damaged by cavitation and wear in hydro power plants. For the special working conditions, JZ-3 Robot should meet some requirements, such as small volume, light weight, easy movement from one stream channel to another. The structure of JZ-3 Robot is carefully analyzed with its six degrees of freedom, including the track, moving car, arm of three degrees of freedom, wrist of two degrees of freedom. A dynamic model of JZ-3 robot is built, based on Lagrange Equation. The terms of inertia gravity and Jacobian matrix are analyzed and calculated, which can provide a basis for the self-adapted control of the forces of the robot and also for motion planning and motion simulation.

Numerical Simulation of Natural Ventilation in Atrium of Residential Building

Science & Technology Review. 2009, 27 (0902): 73-77. ;  doi:
Full text: HTML (0 KB)  PDF  (567 KB)  ( 509 )
Abstract ( 1606 )
In order to study the effects of the natural ventilation on the inside environment of the atrium and inhabitants in residential buildings, thermal and wind environments in the atrium are simulated by numerical methods, with RNG ?资-ε turbulent model under the summer climates, to obtain the extraventricular airflow entering the atrium from south and to analyze the results combined with theory of natural ventilation. The study indicates the preferable thermal environment and satisfactory wind field in the atrium when the windows of the atrium are fully open, which improves the comfort of the residential environment as well as saves building energy.

GUI for De-Noising in Wavelet (Packet) Method and Its Application to DSS Data Processing

Science & Technology Review. 2009, 27 (0902): 78-82. ;  doi:
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Abstract ( 798 )
In a deep seismic sounding data processing, filtering methods based on the Fourier transform and second-order correlation denoising in the wavelet domain are still used. In view of the fact that the local time-frequency information can not be obtained with the Fourier transform in processing non-steady state seismic signals, which can be obtained with the wavelet (packet) transform, and also of the fact that the higher-order correlation denoising is better than a second-order correlation denoising, graphical user interface software is developed based on the wavelet and wavelet packet denoising as well as higher-order correlation denoising method, which can be used to eliminate the additive Gaussian white noise. The software can quickly and easily display seismic record sections, can do adaptive threshold denoising in the wavelet domain, can do the second-order and higher-order correlation denoising in the wavelet and wavelet packet domains, and can do also the filtering based on the Fourier transform. Examples of the deep seismic sounding data show that the methods and software are effective.

Temporal and Spatial Variations of the Nonlinear Principal Mode of Summer Sea Level Pressure Anomalies over Eurasia

Science & Technology Review. 2009, 27 (0902): 83-87. ;  doi:
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Abstract ( 804 )
Eurasian summer sea level pressure anomalies during 1948-2007 were investigated by applying a Nonlinear Principal Component Analysis (NLPCA) method. The results show that the Eurasian summer sea level pressure anomalies show a distinct nonlinear nature, and the NLPCA can be used to describe more general characteristics of the low-dimension structure of the sea level pressure. The spatial distribution is obviously asymmetrical when the first principal nonlinear component (NLPC1) takes positive or negative values for the anomalies. This nonlinear spatial mode accounts for 47.5% of variance, which is 12.8% higher than that of the first linear principal component(PC1), as very strongly nonlinear. Moreover, the time coefficient of NLPC1 has an uneven oscillation on the time scale of 2~4 years, with the intensity of nonlinear oscillation getting stronger significantly after 1967. These changes are closely linked to the atmosphere internal nonlinear interaction in East Asia, reflecting the spatial and temporal asymmetrical evolutions of the nonlinear low frequency wave for the summer sea level pressure.

Biological Basis of Northwest Dry and Cold Syndrome

Science & Technology Review. 2009, 27 (0902): 88-93. ;  doi:
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Abstract ( 878 )
In order to study the effects on biological bodies of a dry and cold environment, several male ICR mice were put under a dry and cold condition to simulate Xinjiang's unique dry and cold environment, to establish a mice model of northwest dry and cold syndrome for the first time in China based on the theory of traditional Chinese medicine. After 21 days, the animals organs were taken out in order to observe histological changes by optical microscopy, and to observe ultra-structural changes by electron microscopy, and a comparison is made between two groups. Monoamine neurotransmitters were determined with reversed phase ion pair (RP-IP)-HPLC and results are compared between normal control group and dry and cold group. The morphological changes are mainly in the blood vessel's mild expansion, and cell's ultra structural changes are mainly in edema. After the stressing of 21 days of dry and cold environment, the quantity of norepinephrine (NE) and dopamine(DA) in serum was significantly lower than that in the normal control group (P<0.01), while the quantity of 5-HT was higher(P<0.05). But in brain, they are all in a lower quantity than the normal control group. Dry and cold environment can lead to the appearance of a kind of symptom (Qi) related to dry and cold, so it may be concluded that dry and cold environment is one of the most imporment causes of northwest dry and cold syndrome; and the disorder of the northwest dry and cold syndrome is related not to just one organ but the body as a whole, with systemic, systematic changes.
Reviews

Regulation of microRNA on Proliferation and Differentiation of Tumour Cells

Science & Technology Review. 2009, 27 (0902): 94-98. ;  doi:
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Abstract ( 932 )
The microRNA (miRNA) is one of RNAs, with about 22 nucleotides, short and noncoding, that mainly regulates the gene expression at the postranscriptional level. According to the degree of base pairing to its complementary sites within its 3'-untranslated region (3'UTR), it degrades or negatively regulates the translation of the target miRNA. Mutation, deletion or over-expression of miRNA can cause physiological anomaly or disease and correlate with various human cancers. miRNAs involve tumor cell proliferation, differentiation and apoptosis processes in a role of oncogenes or tumor supressors. It is expected that microRNA might be applied in the diagnosis and treatment of malignant tumors as a powerful tool.

Capilary Stiction Action in the MEMS/NEMS

Science & Technology Review. 2009, 27 (0902): 99-101. ;  doi:
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Abstract ( 802 )
Capillary action exists on all scales, but is particularly important on the micro-nano scale. With the rapid development and in-depth study of the MEMS/NEMS technology, the MEMS/NEMS devices have found wide applications. In the processing and applications of the MEMS/NEMS devices, due to the capillary force, stiction failures may occur in different degrees, which affects their reliability and commercialization. In view of the importance of capillary stiction with respect to the performance of MEMS/NEMS device, this paper analyzes the effects of stiction failures on the MEMS/NEMS device performance, the capillary stiction mechanisms on micro/nano scales, as well as the capillary stiction control technology.

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