Showing papers by "Shanghai University published in 2001"

Micro-machined gas sensor array based on metal film micro-heater

Abstract: An integrated gas sensor array is promising to overcome the poor selectivity and drift encountered by individual gas sensor. Micro-machined gas sensor array was fabricated using the post-process micro-machining technology of silicon integrated circuit (IC). The size of a 2×4 array is 2 mm ×4 mm, and the active area of each cell is 50 μm ×50 μm. The electric properties, thermal characteristics, and the response to standard gases of the sensor array were investigated. The micro-heater can be driven to 400°C with about 9 mW applied power, and thermal response time constant of a micro-heater is about 10 ms. The techniques of oxygen radical assisted EB evaporation was utilized to prepare SnO2 sensitive films that show high sensitivity and good selectivity to C2H5OH.

Iteration Perturbation Method for Strongly Nonlinear Oscillations

Abstract: In this paper, the author proposes a new perturbation technique coupling with iteration method, yielding a powerful mathematical tool for an analytical solution of nonlinear equations. The obtained results are valid not only for weakly nonlinear problems but also for strongly nonlinear ones. Furthermore, the approximate solutions are valid for the whole solution domain, and even the first-step iteration leads to high accuracy Some examples are given to illustrate its effectiveness.

Design and 3D electromagnetic field analysis of non-slotted and slotted TORUS type axial flux surface mounted permanent magnet disc machines

Abstract: Nonslotted and slotted external rotor internal stator TORUS type surface mounted permanent magnet (PM) machines (TORUS-NS and TORUS-S) have simple structures, relatively high efficiencies and low cost These machines can be used for the applications that require high power and torque density, high efficiency and low noise with the use of neodymium-iron-boron (NdFeB) magnets providing relatively small overall size and weight In this paper, sizing equations of the TORUS machines are derived using generalized sizing equations The optimum machine design is illustrated by choosing the magnet pole-arc ratio and the skew angle of the rotor magnets Using the optimum design data, field analysis of TORUS-NS and TORUS-S machines are investigated Pulsating torque analyses including the cogging torque and the ripple torque are carried out using a 3D finite element analysis (FEA) software Utilizing the techniques such as modifying the winding structure and skewing the rotor magnets, minimization of cogging torque and ripple torque for the TORUS-NS and TORUS-S machines are obtained and verified using 3D FEA Finally a comparison of the TORUS topologies in terms of torque quality is illustrated in the paper

Electromagnetic vibration and noise assessment for surface mounted PM machines

Abstract: Analysis of electromagnetic vibration and acoustic noise assessment and methods to minimize resultant sound power level for low noise motor design is presented in this paper. The linear model of the exciting force wave is derived to evaluate the exciting force and to optimize the design of stator winding, rotor PM shape and rotor PM skew angle for minimization of sound power level for low noise motor design. Mode number and frequency of the exciting force wave, natural vibration frequency, maximum vibration velocity and maximum vibration displacement of main vibration source are introduced to evaluate machine vibration. Resultant sound power levels for the cylindrical sound wave and the plane sound wave models are introduced to analyze the acoustic noise assessment of both axial and radial flux PM machines respectively. Finally, electromagnetic vibration and acoustic noise assessment of both radial and axial flux surface mounted motor structures are completed and illustrated in the paper.

High temperature Raman spectra of sodium disilicate crystal, glass and its liquid

Abstract: Raman spectra of Na2Si2O5 in solid and liquid states from room temperature to 1773 K were measured to observe phase transition and analyze the temperature-dependent variations of the structure units, five kinds of SiO4 tetrahedrons, which are defined as Q 4 , Q 3 , Q 2 , Q 1 and Q0 species corresponding to the number of bridging oxygen binding to each Si A pulsed copper vapor laser was used as laser source coupled with time resolved detection system to eliminate the dense thermal emission background while temperature was >1273 K Temperature-dependent Raman spectra can clearly indicate melting point of a crystal around 1143 K Gaussian deconvolutions of complex stretching vibrational bands of crystal and amorphous states (glass and liquid) were described Raman sensitivity factors were introduced to calculate the mole fractions of the different SiO4 tetrahedrons There is a decrease of Q3 species and an increase of Q4 and Q2 species with increasing temperature And after melting, the ratio of the components remain unchanged Q3 species decomposes again after about 1573 K More Qn species would form with increasing temperature Although the Qn distribution of the glass is similar to that of the liquid of melting temperature, T m ∼1143 K , the liquid structure has a greater disorder than that of the glass

Some studies of the chromatographic properties of gels ("artificial antibodies/receptors") for selective adsorption of proteins

Abstract: Although conventional imprinting involving the use of charged functional monomers has been used by many authors for selective adsorption of small molecules, it has not been very successful with high-molecular-weight substances, for example proteins (“...macromolecules, such as proteins are difficult to apply as templates...”; H. S. Andersson, Doctoral Thesis, Trycki Hogskolan Kalmar, 1999, p. 8.). Four years ago we therefore introduced an alternative method based on the polymerization ofnon-charged monomers (acrylamide andN,N′-methylenebisacrylamide) in the presence of the protein of interest. The selectivity of the gels for proteins was high (for instance, myoglobin from horse was adsorbed by a column designed to be selective for this protein, whereas, myoglobin from whale was not adsorbed) and they can therefore be regarded as ‘artificial antibodies’ (or ‘artificial receptors’). This paper deals with improvements of the chromatographic properties of these gels. For example, by modifying the polymerization conditions the protein (hemoglobin) capacity, as well as the flow rate were increased fouifold. This was achieved by entrapment of the selective soft polyacrylamide gel in the pores of a rigid inert gel by letting the monomers and the protein diffuse into the pores of agarose beads (SepharoseTM) before starting the polymerization. The gel formed was cut into pieces. The agarose beads were freed from the surrounding polyacrylamide gel by stirring. This technique is universal and is recommended also for molecular imprinting studies of small molecules. Another universal method has been introduced for rapid screening of potential monomers and gels for the preparation of selective adsorbents. This very simple method is based on the assumption that the absorption maximum of a protein changes when the protein interacts with the free monomers or the adsorbent synthesized from the monomers (and does not change when the protein does not interact). Preliminary docking experiments indicate that selective adsorption of the protein by the polyacrylamide matrix is based primarily on hydrogen-bonding and dipole-dipole interactions. The strengths of these interactions can be varied by choosing different gel matrices (for removal of a given protein the interactions should be very strong, whereas they should be weaker for chromatographic analysis).

TORUS concept machines: pre-prototyping design assessment for two major topologies

Abstract: Two different external-rotor-internal-stator TORUS type axial flux PM machines can be derived based on the direction of the flux In the first type of the TORUS machine, magnet driven flux enters the stator and travels circumferentially along the stator core while, in the second type, the flux enters the stator and travels axially along the machine axis of rotation The major differences between the two topologies are the direction of the magnet driven flux, the winding arrangement and the thickness of the stator yoke In this paper, the sizing equations are derived for both types of TORUS machines Based on the sizing analysis, optimum design is achieved for minimum ripple torque and maximum torque density Furthermore, finite element analysis (FEA) of both TORUS structures are investigated to get an insight in 3D field distribution, flux directions and paths in different parts of the machines for different load conditions Minimization of the cogging and ripple torque components of the TORUS concept machines are displayed using 3D FEA for the insight in pulsating torques, ripple torques and cogging torques Finally the comparison of the TORUS topologies are made in terms of flux densities, cogging and ripple torques and the results are illustrated in the paper

Optimum design and 3D finite element analysis of nonslotted and slotted internal rotor type axial flux PM disc machines

Abstract: Axial flux internal rotor external stator surface mounted permanent magnet (AFIR) disc machines have simple structures, relatively high efficiencies and low cost. These machines can be used for the applications that require high power and torque density, high efficiency and low noise with the use of neodymium iron boron magnets. In this paper, sizing equations of the AFIR machines are derived using generalized sizing equations. Optimum machine design is illustrated by choosing the diameter ratio and the airgap flux density. Using the optimum design data, field analysis of the slotless and slotted AFIR machines are investigated. Pulsating torque analyses are carried out using a 3D finite element analysis (FEA) software. Minimization of cogging torque and ripple torque for both topologies is obtained using FEA utilizing the techniques such as modifying winding structure and skewing the rotor magnets. Finally the comparison of the two topologies in terms of torque quality is illustrated in the paper.

Irradiation of crosslinked, poly(vinyl alcohol) blended hydrogel for wound dressing

Abstract: In order to obtain a more ideal hydrogel wound dressing, crosslinked hydrogel films blended with polyvinyl alcohol (PVA), polyvinyl pyrrolidone, kappa-carrageenan (KC), and powder silk were prepared by electron beam, and their physiochemical properties were investigated as a combination of function factors. The experimental results showed that the gel fraction of the hydrogel films depended mainly on irradiation dose and the monomer concentration of the polymers, the properties of hydrogel could be greatly extended or improved by blending homopolymers. The rate of gel formation of the hydrogel was raised, and the water evaporation from hydrogel could be retarded after mixing with KC, while the tensile strength of hydrogel films were obviously increased after mixing with silk. Toxicity and healing effect of PVA/PVP/KC/silk blended hydrogel films as wound dressings were evaluated. The irradiated blended hydrogel showed satisfactory properties for wound dressing, the hydrogel did not induceany acute general toxic effects, and it is effective for fast healing of wound.

Hamilton Principle and Generalized Variational Principles of Linear Thermopiezoelectricity

Abstract: Via the semi-inverse method, a family of various variational principles is established for thermopiezoelectricity, including a Hamilton principle and a minimum complementary energy principle.

Estimation of the phase diagram for the ZrO2–Y2O3–CeO2 system

Abstract: Comprehensive descriptions of the thermodynamic properties and experimental information in three oxide systems ZrO 2 –Y 2 O 3 , ZrO 2 –CeO 2 and Y 2 O 3 –CeO 2 are given and thermodynamic models for the calculation of these systems are discussed. The phase diagrams of the quasi-ternary ZrO 2 –Y 2 O 3 –CeO 2 system in the zirconia-rich corner are estimated at different temperatures with a substitutional model and Muggianu's extrapolation. The equilibrium phase diagram calculation is extended to low temperatures, as well as the Gibbs free energy of the tetragonal, monoclinic and cubic phases of zirconia doped with yttria and ceria.

A convexification method for a class of global optimization problems with applications to reliability optimization

Abstract: A convexification method is proposed for solving a class of global optimization problems with certain monotone properties. It is shown that this class of problems can be transformed into equivalent concave minimization problems using the proposed convexification schemes. An outer approximation method can then be used to find the global solution of the transformed problem. Applications to mixed-integer nonlinear programming problems arising in reliability optimization of complex systems are discussed and satisfactory numerical results are presented.

Torque quality assessment and sizing optimization for surface mounted permanent magnet machines

Abstract: Torque quality assessment and optimization methods are presented in this paper General purpose sizing equations are obtained and sizing optimization of the slotless TORUS machine is shown for maximum power density or efficiency points For pulsating torque analysis, general instantaneous electromagnetic torque equation and torque ripple factor (TRF) analysis are carried out Besides, stator winding distribution factor and rotor PM skew factor, excitation field form factor to indicate the excitation field harmonics, open slot factor to indicate the slot effect based on the calculation of airgap permeance are introduced for nonslotted and slotted axial flux surface mounted PM machines Based on the above analysis, optimum design can be achieved for minimum ripple torque On the other hand, cogging torque can be canceled using nonslotted structure A slotless TORUS machine is used as a sample application for the torque ripple minimization in the paper Furthermore, 2D and 3D finite element analysis (FEA) of both nonslotted and slotted surface mounted PM TORUS type (axial flux external rotor internal stator) structure, AFIR type (axial flux internal rotor external stator) structure and RFSM (radial flux internal rotor external stator) type structures are investigated for an insight into pulsating torques, ripple torques and cogging torques The results obtained from both TRF analysis and 2D/3D FEA are illustrated in the paper

Effects of salviainolic acid A (SA-A) on liver injury: SA-A action on hepatic peroxidation.

Abstract: Background/Aims: This study aimed to investigate the actions of salviainolic acid A (SA-A), an antiperoxidative component of Salvia miltiorrhiza (Sm), on rat liver injury and fibrosis Methods: Acute and chronic rat liver injury models were established using carbon tetrachloride (CCl 4 ) After 48 h (acute) or during 6 weeks of CCl 4 injection, rats were further divided and treated with biphenyl dimethyl-dicarboxylate (BDD) or colchicine, as a control antifibrotic treatment, with Sm, a herbal compound, or SA-A, a water-soluble extract of Sm Liver function was investigated by assessing alanine transaminase (ALT) and aspartate transaminase (AST) activities, histological analysis, hydroxyproline (Hyp) and malondiadehyde (MDA) content In vitro, isolated cultured hepatocytes were injured with CCl 4 gas for 24 h, followed by treatment with either vitamin E or various concentrations of SA-A The extent of hepatocyte injury was monitored by analyzing various lipid peroxidative parameters such as superoxide dismutase (SOD), glutathione (GSH), catalase (CAT), lactase dehydrogenase (LDH), and glutathione peroxidase (GSH-PX) levels in hepatocyte supernatants Results: SA-A significantly decreased abnormal serum ALT activity both in acutely and chronically injured rat livers, decreased abnormal serum AST activity, Hyp and MDA content and attenuated hepatic collagen deposition After CCl 4 incubation and injury, the activities of AST, ALT CAT, GSH-PX and LDH and MDA content in hepatocyte supernatants increased significantly, but GSH levels decreased significantly SA-A markedly improved these pathological changes in a dose-dependent manner 10 -4 mol/l SA-A had stronger inhibitory action than vitamin E Conclusions: Our studies suggest that SA-A has antiperoxidative effects on injured hepatocytes in liver injury and fibrosis induced by CCl 4

A general algorithm for accurate computation of field variables and its derivatives near the boundary in BEM

Abstract: A general algorithm was proposed in the paper for the accurate computation of the field variables and its derivatives at domain points near the boundary in attempt to solve the so-called boundary layer effect in the boundary element method. The algorithm is based on the parameter, including modified Gauss–Tschebyscheff quadrature formula with the aid of the approximate distance function introduced, where the parameter is defined as the ratio of the minimum distance of the domain point to the boundary and the length of the boundary element. The algorithm is not only numerically stable because the singular part of the integrand serves as the weight function in the modified Gauss–Tschebyscheff quadrature formula but also independent of the kind of boundary elements. The method can be extended to the three-dimensional case with little modifications. Numerical examples of the potential problem and the elastic problem of plane strain were given by using the cubic and the quadratic boundary elements, respectively, showing the feasibility and the effectiveness of the proposed algorithm.

The effect of calcination on the microwave dielectric properties of Ba(Mg1/3Ta2/3)O3

Abstract: In this study, the role of calcination, its effect upon microstructural development and the correlation with dielectric losses at microwave frequencies were investigated. Ceramics with the composition Ba(Mg1/3Ta2/3)O3 (BMT) were prepared by a conventional mixed-oxide route using controlled calcination. Commercial processing often uses sintering and calcination conditions to modify the dielectric properties of ceramics. However, the mechanism by which the calcination conditions influence the dielectric losses is not clear. The BMT powders were calcinated at 1000–1300 °C for 4–10 h in air or flowing oxygen. Resonator samples were then sintered at 1600–1650 °C for 3 h. Scanning electron microscopy and X-ray diffraction were used to examine the phase composition and the microstructure of the sintered bodies. The microwave dielectric properties were measured at 10 GHz. We found a significant influence of the calcination conditions on the quality factor (Qf) -value. The influences of the phase composition on dielectric losses appear to dominate those of the microstructure. A significant effect was also found for specimens calcinated in different atmospheres. By controlling the calcination and sintering a pure BMT ceramic with a dielectric constant of 24.5, a Qf -value of 120,000 GHz and an τf of 6 ppm/°C was obtained.

Dynamical stability of viscoelastic column with fractional derivative constitutive relation

Abstract: The dynamic stability of simple supported viscoelastic column, subjected to a periodic axial force, is investigated. The viscoelastic material was assumed to obey the fractional derivative constitutive relation. The governing equation of motion was derived as a weakly singular Volterra integro-partial-differential equation, and it was simplified into a weakly singular Volterra integro-ordinary-differential equation by the Galerkin method. In terms of the averaging method, the dynamical stability was analyzed. A new numerical method is proposed to avoid storing all history data. Numerical examples are presented and the numerical results agree with the analytical ones.

Convexification, Concavification and Monotonization in Global Optimization

Abstract: We show in this paper that via certain convexification, concavification and monotonization schemes a nonconvex optimization problem over a simplex can be always converted into an equivalent better-structured nonconvex optimization problem, e.g., a concave optimization problem or a D.C. programming problem, thus facilitating the search of a global optimum by using the existing methods in concave minimization and D.C. programming. We first prove that a monotone optimization problem (with a monotone objective function and monotone constraints) can be transformed into a concave minimization problem over a convex set or a D.C. programming problem via pth power transformation. We then prove that a class of nonconvex minimization problems can be always reduced to a monotone optimization problem, thus a concave minimization problem or a D.C. programming problem.