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Showing papers by "Shanghai Jiao Tong University published in 1991"


Journal ArticleDOI
TL;DR: In this article, a theoretical analysis for the buckling and postbuckling of circular cylindrical shells under combined loading is presented using a singular perturbation technique, and the analytical results obtained are compared with some experimental data in detail, and it is shown that both agree well.
Abstract: Buckling and postbuckling behaviour of perfect and imperfect cylindrical shells of finite length subject to combined loading of external pressure and axial compression are considered. Based on the boundary layer theory which includes the edge effect in the buckling of shells, a theoretical analysis for the buckling and postbuckling of circular cylindrical shells under combined loading is presented using a singular perturbation technique. Some interaction curves for perfect and imperfect cylindrical shells are given. The analytical results obtained are compared with some experimental data in detail, and it is shown that both agree well. The effects of initial imperfection on the interactive buckling load and postbuckling behaviour of cylindrical shells have also been discussed.

78 citations


Journal ArticleDOI
TL;DR: A principle and method of optimal matching to reduce energy consumption in small-scale refrigeration systems, based on systems analysis, is described, in which the concept of transient and distributive is introduced.
Abstract: This paper describes a principle and method of optimal matching to reduce energy consumption in small-scale refrigeration systems, based on systems analysis. A knowledge of the dynamic characteristics of a refrigeration system is important for predicting the performance of the system. A simulation model of a refrigeration system consisting of a compressor, an evaporator, a condenser and a capillary tube has been established to illustrate optimal matching. For each component a mathematical model has been developed, in which the concept of transient and distributive is introduced. On the basis of dynamic simulation, a method of optimal matching to minimize power consumption is recommended. To test the reliability of the theoretical models, an experiment was carried out on a small-scale refrigeration system. The experimental data were compared with the theoretical results and it is shown that the theory is valid.

49 citations


Journal ArticleDOI
TL;DR: In this paper, it is suggested that dumbbell domains can be divided into two kinds: ID and IID, which constitute the family of hard domains in LPE garnet bubble films.

34 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure of the ordered intermetallic alloy with a nominal composition of Al66Fe9Ti24 is nearly single-phase L12 structure, with a few second phase agglomerates at some grain corners.
Abstract: The microstructure of the ordered intermetallic alloy with a nominal composition of Al66Fe9Ti24 is nearly single-phase L12 structure, with a few second phase agglomerates at some grain corners. Room temperature compression tests showed that this material exhibits a plastic strain of about 11% at fracture. Final fracture of the compression specimens occurred by a shear-off process along a surface oriented about 45 degrees to the compression axis. Fractographic analysis revealed that the fracture is transcrystalline and the fracture mode is mainly quasicleavage plus tearing. Transmission electron microscopy (TEM) was used to explore its deformation mechanisms. The dislocation density was low after homogenization, but is greatly increased during deformation. The deformation mode was found to be 〈110〉 {111} slip instead of twinning as in Al3Ti. The a〈110〉 superdislocations dissociated into two partials of a/3〈211〉-type, bounding a superlattice intrinsic stacking fault (SISF) on the {111} slip plane.

32 citations


Journal Article
TL;DR: In this article, a higher-order boundary element method (HOBEM) was proposed for calculating linear hydrodynamic loadings on large floating bodies and comparison with constant panel methods and HOBEMs that are employed in conjunction with the hybrid boundary integral equation procedure, for a variety of structural configurations.
Abstract: This paper presents the description of a higher-order boundary element method (HOBEM) for calculating linear hydrodynamic loadings on large floating bodies and comparison with constant panel methods and HOBEMs that are employed in conjunction with the hybrid boundary integral equation procedure, for a variety of structural configurations. It was concluded from the study that HOBEM has several important features: it uses many fewer boundary elements and much less computer time, with higher accuracy than conventional methods. In addition to these, the computer code for hydrodynamic loadings can easily be used for finite element structural analysis.

28 citations



Journal ArticleDOI
TL;DR: In this article, the electron self-energies due to the interaction of the electron with the LO-phonons that incorporate effects of phonon confinement in a rectangular quantum well wire have been calculated as a function of the size of the wires by the perturbative method in the framework of the effective mass approximation.

20 citations


Journal ArticleDOI
TL;DR: In this article, a non-linear adaptive fault detection filter (NAFDF) is proposed to detect on-line and isolate the faults of a class of nonlinear systems arising from accidental jumps of the process parameters.
Abstract: A novel non-linear adaptive fault detection filter (NAFDF) is proposed. It can be used to detect on-line and isolate the faults of a class of non-linear systems arising from accidental jumps of the process parameters. The extended Kalman filter and weighted sum-squared residual method are first combined to delect the faults rapidly. A non-linear filter is then proposed and used for joint state and parameter estimation of the system, resulting in a series of parameters. Based on them, Bayes' decision algorithm is modified and used to isolate and classify the faults. An alternate initialization method is also presented, which makes it possible to detect and isolate the faults repeatedly. Finally, the effectiveness of the NAFDF is demonstrated by a simulation study.

19 citations


Proceedings ArticleDOI
03 Nov 1991
TL;DR: An experimental study of climbing and walking down a slope by the JTUWM-II quadruped robot and an algorithm for the body to turn parallel with the sloping surface is developed.
Abstract: Presents an experimental study of climbing and walking down a slope by the JTUWM-II quadruped robot. A scheme by which the walking robot detects the slope and measures the gradient of the slope with tactile sensors is proposed. An algorithm for the body to turn parallel with the sloping surface is developed. In the transition area gait adjustment is made for stable walking. Also the maximum gradient of the slope for the robot and the optimum body height are given. >

16 citations



Journal ArticleDOI
TL;DR: In this article, a new model for solving the performance of gas turbine engines was proposed to obtain a more rapidly converging and more accurate solution, and a new method, the inverse algorithm, was proposed.
Abstract: This paper will discuss why the sequential algorithm resulted in error, and a new method, that is, the inverse algorithm, will be proposed. Then, a new model for solving the performance of gas turbine engines will be recommended to obtain a more rapidly converging and more accurate solution

Journal ArticleDOI
TL;DR: In this paper, the particle tracking autoradiograph (PTA) technique was combined with quantitative statistical analysis using the image processing system, to study the effect of such factors as aluminium content of base alloy, the bulk boron concentration and different heat treatments on the grain boundary segregation behaviors of Boron in Ni3Al alloys.
Abstract: The particle-tracking autoradiograph (PTA) technique has been used, combined with quantitative statistical analysis using the image processing system, to study the effect of such factors as aluminium content of base alloy, the bulk boron concentration and different heat treatments on the grain boundary segregation behaviors of boron in Ni3Al alloys. Moreover, the mechanical properties of Ni3Al alloys subjected to different heat treatments and therefore with various quantities of segregated boron have been tested. Their fracture surfaces have also been observed in SEM. The relation between the level of boron segregation and ductility has been inspected.

Journal ArticleDOI
TL;DR: In this paper, the phase diagram of the Cu-Al system has been fully utilized to derive several thermodynamic parameters of CuAl alloys on the basis of the regular solution model.
Abstract: The phase diagram of CuAl system has been fully utilized to derive several thermodynamic parameters of CuAl alloys on the basis of the regular solution model. A statistical method has also been used to deal with α → α′ and β → β′ ordering transitions accompanying the martensitic transformation in CuAl alloys. The equilibrium temperatures T 0 ∗ and T 0 , as well as Ms temperature have then been calculated theoretically in CuAl alloys with various compositions, and the Ms obtained are in good agreement with the experimental ones. The calculated results also show that the equilibrium temperature of the ordered α′ and β′ phases, T0, is higher than that of the disordered α and β phases, T 0 ∗ .

Journal ArticleDOI
TL;DR: In this article, the character tables of the association schemes obtained from the action of finite unitary groups acting on the set of nonisotropic projective points and finite group PGL(2, q) on the cosets by cyclic subgroups Zq + 1 and Zq − 1 were studied.

Journal ArticleDOI
TL;DR: In this paper, the third-order interactions imposed by a pair of atoms separated by five bonds are taken into account in computations of the mean square end-to-end distance and the mean-square radius of gyration for linear polymer chains.
Abstract: Third-order interactions imposed by a pair of atoms separated by five bonds are taken into account in computations of the mean-square end-to-end distance and the mean-square radius of gyration for linear polymer chains. The statistical weight matrices are established on the basis of the rotational isomeric state model. The conformational energy of n-hexane is calculated as a function of the CC bond rotation angles. The third-order interaction energy is obtained by comparison with that of n-pentane. The characteristic ratio of polymethylene is 6.6 in the third-order interaction approximation, which is in agreement with experimental data.

Journal ArticleDOI
TL;DR: In this Letter, a hexagonal discrete cosine transform (HDCT) for encoding the hexagonally sampled signals is presented.
Abstract: The discrete cosine transform plays an important role in rectangularly sampled image coding for its excellent performance in information compaction. Hexagonal sampling is the optimal sampling strategy for two-dimensional signals in the sense that exact reconstruction of the waveform requires a lower sampling density than with the alternative schemes. In this Letter, a hexagonal discrete cosine transform (HDCT) for encoding the hexagonally sampled signals is presented.

Journal ArticleDOI
TL;DR: In this article, a shooting-type numerical method for calculating quasi-periodic solutions in a multiexcited system by using derivatives and with an improved interpolation technique is presented.

Journal ArticleDOI
TL;DR: In this article, the degeneration of the eigenvalue equation of the discrete-time linear quadratic control problem to the continuous-time one when Δt→0 is given first.
Abstract: The degeneration of the eigenvalue equation of the discrete-time linear quadratic control problem to the continuous-time one when Δt→0 is given first. When the continuous-time n-dimensional eigenvalue equation, which has all the eigenvalues located in the left half plane, has beeh reduced from the original 2n-dimensional one, the present paper proposes that several of the eigenvalues nearest to the imaginary axis be obtained by the matrix transformation Ae=eA. All the eigenvalues of Ae are in the unit circle, with the eigenvectors unchanged and the original eigenvalues can be obtained by a logarithm operation. And several of the eigenvalues of Ae nearest to the unit circle can be calculated by the dual subspace iteration method.

Journal ArticleDOI
TL;DR: In this paper, a new formalism for equivalent refractive indices in multi-quantum-well (MQW) waveguides with arbitrarily shaped base periods, which uses the transfer matrix technique in the thin-film approximation, has been developed for TM and TE polarizations.
Abstract: A new formalism for equivalent refractive indices in multi-quantum-well (MQW) waveguides with arbitrarily shaped base periods, which uses the transfer matrix technique in the thin-film approximation, has been developed for TM and TE polarizations. It clearly illustrates the intrinsic birefringence feature and can be used to produce the dispersion relation of MQW waveguides in a way that is more straightforward than in previous methods.

Proceedings ArticleDOI
03 Nov 1991
TL;DR: The turning gait presented is being implemented in the omnidirectional quadruped walking robot JTUWM-II, which is more suitable for practical control than previous methods.
Abstract: This paper studies the realization of turning gait control, taking a quadruped walking vehicle as the subject of the research. Based on the analyses of previous works, a kind of turning gait with the center of gravity of the vehicle walking along multiple broken lines has been planned, which is more suitable for practical control than previous methods. The process of the turning gait and its feasibility are discussed in detail. The turning gait presented is being implemented in the omnidirectional quadruped walking robot JTUWM-II. >

Journal ArticleDOI
TL;DR: In this article, a two-dimensional theory of the Lau-Talbot-Moire effect by means of an Ambiguity Function is presented, and it is found that the Lau fringes are dependent upon the grating rotation angle, and the fringe pattern at the observation plane is influenced by two important factors, the coherent diffraction factor and the Lau Moire interference factor.

Journal ArticleDOI
TL;DR: A three-layer adaptive network with each neuron in the lower hidden layer representing a Gaussian basis function to estimate various probability densities and serve as a Bayes classifier is proposed.
Abstract: Based on the assumption that most probability densities in real life can be approximated by a mixture of Gaussian densities, we propose here a three-layer adaptive network with each neuron in the lower hidden layer representing a Gaussian basis function (covariance matrix equal to where I is a unit matrix) to estimate various probability densities and serve as a Bayes classifier. The width of the basis function may be the same for all neurons in this layer or it may vary from one neuron to another. This paper investigates the effectiveness of the network for both cases and presents a localized learning algorithm to adjust the network parameters. The network was trained with artificial data derived from known mixtures of memoryless Gaussian sources as well as exponential and Gamma densities. The performance of the network as a pattern density estimator was measured in terms of the relative difference between the target probability density function (p.d.f.) which generates the training and testing data and the network output representing the estimation. Samples from two mixtures corresponding to two classes were used to test the network capability as a classifier by comparing its error rate against that of a Bayes classifier. Both one- and two-dimensional cases were explored. The successfulness of the network depended on how well the target p.d.f.’s were represented by the training samples, the number of hidden neurons employed in the network and how thoroughly the network was trained. It was also found that allowing each basis function to have an independent width had a predominant effect on the network performance.

Journal ArticleDOI
TL;DR: In this article, a precursor of yttria-stabilized zirconia (YSZ) powder was prepared by the oxalate method in ethanol solution, and the crystallizability and sinterability of the precursor were studied.
Abstract: A precursor of yttria-stabilized zirconia (YSZ) powder was prepared by the oxalate method in ethanol solution. The crystallizability and sinterability of the precursor were studied. The crystallizability of the precursor depends on preparation conditions, especially acidity. The final acidity of the solution from which the precursor is produced and the temperature at which the precursor is calcined can strongly influence the crystalline phase composition of the resultant powder, and can, in turn, limit the ability of a sintering compact to reach high density. The YSZ powder which results from calcining the precursor without milling the calcined powder for a long time, may be a less-agglomerated powder with a crystallite size of about 9 nm and a specific surface area of 46.3 m2g−1. A full tetragonal zirconia polycrystal with 99% theoretical density can be obtained from the highly reactive powder by simple cold-pressing followed by pressureless sintering in air at temperatures as low as 1300 °C.

Journal ArticleDOI
TL;DR: In this paper, the softening process of the first kind of dumbbell domains with the increase of temperature was experimentally revealed as follows: IDs first convert to ordinary hard bubbles (OHBs) through a partial loss of the vertical Bloch lines (VBLs) in their walls and then these OHBs convert to soft (normal) bubbles (SBs), through a further loss of VBLs.
Abstract: The "softening" process of the first kind of dumbbell domains (IDs) with the increase of temperature was experimentally revealed as follows: IDs first convert to ordinary hard bubbles (OHBs) through a partial loss of the vertical Bloch lines (VBLs) in their walls and then these OHBs convert to soft (normal) bubbles (SBs) through a further loss of VBLs. As a result, the critical temperature for the break down of VBL chains of IDs is apparently higher than OHBs.

Journal ArticleDOI
TL;DR: In this article, the driving forces for various possible reactions within the bainitic transformation temperature range of Cu 40 at.% Zn alloy have been calculated and the results show that because of the occurrence of β→β′ ordering transition within the temperature range, driving forces ΔG β ′→ β 1 ′+ α increase inversely with decreasing temperature.
Abstract: The driving forces for various possible reactions within the bainitic transformation temperature range of Cu 40 at.% Zn alloy have been calculated. The results show that because of the occurrence of β→β′ ordering transition within the temperature range, the driving forces ΔG β ′→ α ′ and ΔG β ′→ β ′+ α increase inversely with decreasing temperature, with ΔG β ′→ α ′ > 0 and ΔG β ′→ β ′+ α T 0 of the two phases β′ and α′ is far below the experimental B s for alloys of various compositions. Therefore, the bainitic transformation in CuZn alloys can only proceed as that of diffusional reaction β ′→ β 1 ′+ α .

Proceedings ArticleDOI
01 Nov 1991
TL;DR: An algorithm named Minimum Cross-Entropy Algorithm (MCEA) for image reconstruction from incomplete projection data is presented and it is concluded that MCEA is superior to MENT for such cases where the number of projections involved are small.
Abstract: An algorithm named Minimum Cross-Entropy Algorithm (MCEA) for image reconstruction from incomplete projection data is presented here The principle of maximum entropy has been applied to image reconstruction successfully However, the application of principle of minimum cross-entropy to image reconstruction from incomplete projection data has not been found in literature When the missing data or missing angle is large, the proposed algorithm yields acceptable results Compared with the maximum entropy algorithm MENT, we conclude that (1) MCEA is superior to MENT for such cases where the number of projections involved are small; (2) Convergence performance of MCEA is better than MENT; (3) MCEA and MENT both are stable against noise; and (4) Under appropriate a priori distribution, MCEA yields satisfactory results after a couple of iterations The speed and quality of reconstruction as well as the overhead of storage for MCEA are superior to that of MENT

Journal ArticleDOI
TL;DR: An artificial neural network architecture in terms of Gaussian kernels together with an associated network training algorithm is proposed for phonetic density estimation and the recognition capability is found to be compatible with that of a Bayes classifier.

Journal Article
TL;DR: The results revealed that the appearance of the gastrointestinal mucosa in both BALB/C and KM mice resembled that in human with inflammatory bowel disease.
Abstract: Campylobacter jejuni is a major cause of human enteritis which mimics the inflammatory bowel disease (IBD). In this study, microstructural changes on the surfaces of the murine gastrointestinal tract persistently colonized by Campylobacter jejuni, strain GJ-S131, were investigated by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results revealed that the appearance of the gastrointestinal mucosa in both BALB/C and KM mice resembled that in human with inflammatory bowel disease. Under SEM, the mucosa of the jejunum and ileum, with broken or distorted villi had a "worm eaten" look; crypts were irregular in shape and size, and the mucosa showed atrophy, especially in the colon. Epithelial junctions demonstrated furrows, clefts or deep crevasses, with exudates containing a large number of leukocytes. Cytologic appearances were characterized by microvilli dysplasia and/or atrophy, patchy erosions or necrosis and pelade-like appearance due to absence of microvilli, which were similar to the findings under TEM.


Journal ArticleDOI
TL;DR: In this paper, the velocity potentials of singularities moving with an arbitrary path either in the upper fluid or in the lower fluid with or without a horizontal bottom when two fluids are present are derived.
Abstract: The derivations are carried out for the velocity potentials of singularities moving with an arbitrary path either in the upper fluid or in the lower fluid with or without a horizontal bottom when two fluids are present. In such a case, the pressure distribution is no longer equal to a constant or zero at the free interface. Taking the influence of an upper fluid upon the lower fluid into consideration, a series of fundamental solutions in closed forms are presented in this paper.