Showing papers by "Shanghai University published in 1998"
TL;DR: In this article, a variational iteration method is used to give approximate solutions of the problem of seepage flow in porous media with fractional derivatives, and the results show that the proposed iteration method, requiring no linearization or small perturbation is very effective and convenient.
1,265 citations
TL;DR: In this article, a new iteration method is proposed to solve nonlinear problems with convolution product nonlinearities and the results reveal that the approximations obtained by the proposed method are uniformly valid for both small and large parameters in non-linear problems.
490 citations
TL;DR: In this article, a homotopy perturbation method with an imbedding parameter is proposed, which can take full advantage of the traditional perturbations methods and the hom-otopy technique.
161 citations
TL;DR: In this article, an approximate analytical solution is obtained via the variational iteration method for the Blasius' equation, with boundary conditions, and the comparison with Howarth's numerical solution reveals that the proposed method is of high accuracy.
125 citations
TL;DR: In this article, a Gegenbauer approximation algorithm is proposed to solve the problem of multiple-dimensional problems in unbounded domains using variable transformation, where differential equations on the whole line are changed to certain equations on a finite interval.
72 citations
TL;DR: In this article, a Newton-like iteration method is proposed to solve an approximate solution of an algebraic equation and the iteration formula obtained by homotopy perturbation method contains the well-known Newton iteration formula in logic.
72 citations
TL;DR: In this article, the frequency-varying method (FVM) is proposed to measure the complex permittivity and permeability of materials simultaneously with an open-ended coaxial probe, which achieves the independent reflections via changing frequency.
Abstract: To measure the complex permittivity and permeability of materials simultaneously with an open-ended coaxial probe, one needs at least two independent reflections. Based on the fact that frequency is an independent variable for the probe's reflection coefficient, a new concept, namely the frequency-varying method (FVM), which achieves the independent reflections via changing frequency, has been proposed. Since the electromagnetic (EM) properties of materials themselves are functions of frequency, the FVM introduces interpolation techniques into the process of extracting EM parameters from multiple reflection coefficients. The successful experimental results on radar-absorbing coatings show the feasibility and good prospects of the FVM for characterizing EM properties of materials in situ. Compared with the thickness-varying method (TVM), which makes two measurements with two samples of different thicknesses, the FVM needs only one frequency-swept reflection measurement, thus simplifying and speeding up the measurement process, and improving accuracy and repeatability. Furthermore, the FVM has the ready capability to be extended to multiple-parameter measurements, and we may also find potential applications in other fields.
53 citations
TL;DR: Rubrene was injected into the hole transport layer of an organic thin film electroluminescent (OTFEL) device with a double-layered structure as discussed by the authors, which has a profound influence on the EL characteristics - it changed the region of light emission, increased the luminescence efficiency by more than 50% and improved the device stability tenfold.
Abstract: Rubrene was doped into the hole transport layer of an organic thin film electroluminescent (OTFEL) device with a double-layered structure. It was found that the dopant has a profound influence on the EL characteristics - it changed the region of light emission, increased the luminescence efficiency by more than 50% and improved the device stability tenfold. The reasons for these effects are discussed based on injection theory and the energy level diagram of the device.
48 citations
TL;DR: In this article, an improved technique of using rectangular waveguide aperture for simultaneous measurement of the electromagnetic parameters /spl epsiv/sub /spl gamma/ and /spl mu/sub/spl gamma// of materials is developed, where multilayer and single-layer medium sheet samples can be tested.
Abstract: An improved technique of using rectangular waveguide aperture for simultaneous measurement of the electromagnetic parameters /spl epsiv//sub /spl gamma// and /spl mu//sub /spl gamma// of materials is developed in this paper. Both multilayer and single-layer medium sheet samples can be tested. Samples are sandwiched between a flange of an open-ended waveguide and a shorting plate. The parameters are obtained by using an optimization technique by fitting the theoretical values of the reflection coefficients /spl Gamma/(/spl epsiv//sub /spl gamma//,/spl mu//sub /spl gamma//) to the measured values with /spl epsiv//sub /spl gamma//,/spl mu//sub /spl gamma// as the argument. The related details, test theories, waveguide design, sample preparation, and error analysis are also discussed in this paper. The experimental results are validated by the measurements performed using the reflection-transmission method using an automatic network analyzer and the published data from manufactures. By virtue of its open-ended waveguide configuration, this technique is well suited for sheet or coating materials, and it might be applied for industrial on-the-worksite testing or biomedical analysis.
46 citations
TL;DR: In this paper, a new optical technique which allows the roughness of moving surfaces to be determined was developed, which is called the dark/bright ratio (DBR) method, which utilizes the combined effects of speckle and scattering phenomena.
43 citations
TL;DR: In this paper, the effect of absorbed dose, AAcrylic acid concentration, reaction temperature, reaction time, storage time, as well as the impact of ferrous ion and sulfuric acid on the degree of grafting were determined.
TL;DR: In this article, the structural evolution and the crystallite size changes of the powders during mechanical alloying were monitored by X-ray diffraction and the effects of small VC additions on the grain size, density and hardness of sintered samples were also investigated.
Journal Article•
TL;DR: Evidence is given that the hairy roots may be a new source of A. membranaceus and regaining the immunity function of rats with low immunity after feeding the aqueous extract of the hairy Roots produced by large-scale culture showed that its capacity was similar to the dry roots.
TL;DR: The physical basis of meridians and acupoints is in a complex system mainly of connective tissue and interwoven with the blood capillaries, nerves, lymph vessels, etc as mentioned in this paper.
Abstract: The physical basis of meridians and acupoints (acupuncture points) is in a complex system mainly of connective tissue and interwoven with the blood capillaries, nerves, lymph vessels, etc. Elements of Ca, P, K, Fe, Zn, Mn, etc are found concentrated in the deep connective tissue structures in locations corresponding to acupoints. On this physical basis, the specific waveband of high efficiency for transmission of infrared rays exists in the collagenous fibre in a liquid crystal state. The development direction and new idea of researching on acupuncture and meridians are discussed.
TL;DR: In this article, the nonlinear mathematical model of viscoelastic thin plates, by the Karman's hypotheses of a large deflection plate and the Boltzmann's law of anisotropic viscocelastic materials, is established by means of the Laplace transformation and its inverse as well as so-called structural functions introduced in this paper.
TL;DR: In this paper, the effective elastic moduli E ∗ and μ ∗ of concrete were obtained from the analytical solution of a two-dimensional microstructural model, and the relationships between E ∆, μ ∆ and the elastic modulus of each constituent of concrete are studied.
25 Nov 1998
TL;DR: In this article, the authors designed a new type of micro robot for inspection of small pipes with an edgy current detector and a CCD-camera, which can climb in pipe of 20 mm diameter with a speed of about 6-8 mm/s in horizontal or in vertical under voltage 12-20 volt, 30-70 Hz.
Abstract: Millimeter size machines based on modern precision machining have various potential applications. Especially in case of a small pipe, it necessary to develop a new type of micro robot to carry an edgy current detector or CCD-camera for inspection of internal defects. Hence we attempted to design a new type of micro robot for small pipes. The dimensions of the prototype are /spl Phi/15/spl times/30 mm and the weight is 25 g. According to an experiment, it was shown this robot can climb in pipe of 20 mm diameter with a speed of about 6-8 mm/s in horizontal or in vertical under an applied voltage 12-20 volt, 30-70 Hz. This paper describes the structure and the principle of the motion of the robot.
TL;DR: In this paper, the ionic composition distribution profiles in the interdiffusion region were examined by electron probe microbeam analysis (EPMA), based on a diffusion model of the overlapped diffusion solution from thin slab, which was in agreement with the EPMA result.
Abstract: The interfacial diffusion reaction between lead zirconate titanate (PZT) and lead nickel niobate (PbNi1/3Nb2/3O3:PNN) phases in the PZT/PNN functionally gradient piezoelectric ceramics were investigated as a function of the diffusion temperature and time, respectively. The ionic composition distribution profiles in the interdiffusion region were examined by electron probe microbeam analysis (EPMA). Based on a diffusion model of the overlapped diffusion solution from thin slab, the numerical simulation for the ionic composition distribution was carried out by computer, which was in agreement with the EPMA result. The diffusion coefficients for the Ni2+, Nb5+, Ti4+ and Zr4+ ions were determined, which were 33.8, 22.6, 10.8 and 9.9×10-12 m2 s-1, respectively. The apparent activation energies for these ions were 94.4, 171.7, 257.5 and 325.8 kJ mol-1, respectively. The differences in the ionic diffusion coefficients and apparent activation energies were discussed from the viewpoint of the crystal chemistry. © 1998 Chapman & Hall
TL;DR: In this paper, the ion-coordination reaction was introduced to prepare nanometer-sized Mn-doped ZnS clusters stuck to a chitosan medium, and the X-ray diffraction showed that the clusters have a cubic structure like bulk crystals and the cluster sizes were estimated from the diffraction linewidth to be 2-4nm based on Scherre's equation.
TL;DR: In this paper, the mechanism of the formation of intermetallics in the reactive sintering of iron and aluminum mixing powders has been studied by investigating iron-aluminum diffusion couples.
Abstract: The mechanism of iron and aluminum intermetallics formation in the reactive sintering of iron and aluminum mixing powders has been studied by investigating iron-aluminum diffusion couples. The couples were treated at 600°C, 700°C, 800°C, 900°C and 1000°C respectively. It was found that an Al-rich intermetallics FeAl3 has formed in iron adjacent to the interface of iron and aluminum by aluminum diffusion into iron at 600°C (below the eutectic temperature), and that in the case above 700°C (above the eutectic temperature) there was a liquid, an intermetallics Fe2Al5 has formed in both side of the interface. The diffusion of iron and aluminum atoms is companied with the Fe-Al reaction during the treatment under the both conditions. The diffusion coefficients of iron and aluminum and the activation energy were determined. The mechanism of the intermetallics formation in the couples is also discussed.
TL;DR: In this paper, the tensile properties of Ni{sub 3}Al doped with Zr and B in O{sub 2} and air and the apparent hydrogen diffusivity in these alloys were investigated.
09 Aug 1998
TL;DR: In this article, serial corner feeding of a square patch with two ports is proposed to realize dual polarization for the four-element dual-polarized array, a novel coplanar feedline network is presented.
Abstract: In this paper, serial corner feeding of a square patch with two ports is proposed to realize dual polarization. For the four-element dual-polarized array, a novel coplanar feedline network is presented. An efficient method of analysis is developed and a practical array is manufactured. The measured isolation is less than -40 dB at 6.07 GHz. The proposed array occupies a smaller area than other dual-polarized arrays commonly used and is easier to further combine to form a larger coplanar array.
TL;DR: Based on the static equilibrium of electrochemical reaction kinetics, a relationship has been established between the equilibrium potential during discharge (Ee) and hydrogen concentration (CH) in a hydride alloy.
TL;DR: In this article, a modified form of open-plus-closed-loop control for chaotic oscillations described by a non-autonomous second-order ordinary differential equation is presented.
TL;DR: In this article, the analytical expressions of the effective elastic modulus E ∗ for concrete or other composite materials under a uniform stress field, a uniform strain field and a uniform field at infinity are obtained based on elastic theory.
Abstract: In this paper, the analytical expressions of the effective elastic moduli E ∗ for concrete or other composite materials under a uniform stress field, a uniform strain field and a uniform field at infinity are obtained based on elastic theory. The new expressions provide a better estimate of E ∗ than the existing engineering formulas, and the differences between them are compared numerically. It is found that the effective elastic modulus E ∗ depends not only on the geometrical and physical parameters of microstructure, but also on stress state. The value of E ∗ is found to vary within a narrow region.
TL;DR: In this paper, the authors investigated the hydrogen diffusivity in a Fe{sub 3}Al-based alloy with different grain shapes or sizes, showing that the effect of morphology of the microstructure on the sensitivity to environmental embrittlement may be related to the different hydrogen diffusion.
TL;DR: Some new upper bound formulas are obtained forR(G1,G2andR(m,n), and some new upper bounds for Ramsey numbers are derived here.
Abstract: The Ramsey numberR(G1,G2) is the smallest integerpsuch that for any graphGonpvertices eitherGcontainsG1orGcontainsG2, whereGdenotes the complement ofG. LetR(m,n)=R(Km,Kn). Some new upper bound formulas are obtained forR(G1,G2andR(m,n), and we derive some new upper bounds for Ramsey numbers here.
TL;DR: In this article, a semi-inverse method of establishing generalized variational principles for one-dimensional unsteady compressible flow in an imagine plane τ − Ψ (defined by τ=t, Ψ- path-function) has been deduced.
TL;DR: In this paper, the geometry change of a single asperity due to lubricated wear was studied by an experimental simulation with a ball-on-disc set up, which led to the formation of a tilted section at the tip of the ball, which was proved to be due to the presence of oil during the process.
Abstract: The geometry change of a single asperity due to lubricated wear was studied by an experimental simulation with a ball‐on‐disc set up. The wear leads to the formation of a tilted section at the tip of the ball, which is proved to be due to the presence of oil during the process. The effect of the geometry change of rough surface contacts due to wear was examined by a micro‐EHL analysis. A non‐Newtonian visco‐plastic fluid model which includes the effect of a limiting shear strength was used.