Showing papers by "Wuhan University of Technology published in 1996"
TL;DR: In this article, the equations of static equilibrium, the governing differential equation of shear and flexural vibrations of straight bars with variable cross-section are written in the form of unified self-conjugate differential equations of the second-order.
91 citations
TL;DR: In this paper, the authors address the phenomena of mechanical creep and deformation in rock formations, coupled with the hydraulic effects of fluid flow through the correspondence principle, based on Biot's poroelasticity.
Abstract: This paper addresses the phenomena of mechanical creep and deformation in rock formations, coupled with the hydraulic effects of fluid flow. The theory is based on Biot's poroelasticity, generalized to encompass viscoelastic effects through the correspondence principle. Based on the resultant poroviscoelastic theory, stress and deformation analyses are performed. The interactions between the fluid pore pressure diffusion and the elastic/viscoelastic rock matrix deformation are illustrated via two important examples. First, the problem of a borehole subject to a non-hydrostatic stress state, but deforming under plane strain condition, is examined. Second, a cylinder under generalized plane strain conditions is solved. Three rocks, Berea Sandstone, Danian Chalk, and a deep water Gulf of Mexico Shale, covering a wide range of permeabilities, are considered. The significance of poro-and viscoelastic time-dependent effects is discussed.
80 citations
TL;DR: In this paper, a data stream of actual demands for a typical product is used and forecasts are made over different time periods for production planning, warehouse allocations, and transshipments.
Abstract: Alternative distribution strategies for delivering to a retailer's regional depots are compared. These include supplying all the manufacturer's warehouses from the factory and allowing every possible lateral transshipment with partial stock rebalancing over different time periods. The principal alternative is to have a hierarchical system. Effects of making emergency transfers to deliberately delayed delivery vehicles are evaluated. A data stream of actual demands for a typical product is used and forecasts are made over different time periods for production planning, warehouse allocations and transshipments. The conclusions are examined for various production frequencies and levels of stock cover.
36 citations
TL;DR: In this paper, a 9 mol% Y 2 O 3 -stabilized ZrO 2 ball of an oxygen sensor that has been used in a carburization furnace for four months is studied, and no apparent phase change is detected by X-ray diffraction analysis.
Abstract: A zirconia (ZrO 2 ) darkening phenomenon in oxygen sensors has been discovered and a 9 mol% Y 2 O 3 -stabilized ZrO 2 ball of an oxygen sensor that has been used in a carburization furnace for four months is studied in the present work. No apparent phase change is detected by X-ray diffraction analysis. However, an oxygen deficiency is recorded in a thermogravimetric experiment. No valence-state changes of Zr, Y and O are discovered by X-ray photoelectron spectroscopy. The ionic transport number of the ZrO 2 ball is measured with an oxygen-pumping approach; electron conduction is observed at high temperatures. The ZrO 2 darkening is thus considered to be mainly due to the formation of F-centres resulting from the electrochemical reaction occurring at the cathode and the ZrO 2 surface and body in contact with the carburization atmosphere. After use for four to five months, it is proposed that the darkened ZrO 2 be reoxidized to prolong the lifetime of the oxygen sensor.
35 citations
TL;DR: In this paper, the authors have imaged vortices in superconducting thin films with a low-temperature magnetic force microscope that utilizes microfabricated piezoresistive cantilevers with built-in tips.
Abstract: We have imaged vortices in superconducting thin films with a low‐temperature magnetic force microscope that utilizes microfabricated piezoresistive cantilevers with built‐in tips. The films of YBa2Cu3O7−x and Bi2Sr2Ca1Cu2O8+x, are made by laser ablation and molecular beam epitaxy, respectively. The vortices usually appear as round features in the noncontact image with a diameter of about 1 μm or slightly less. In some cases the position of the vortices is correlated to defects observed in the topographic image of the same area. The vortices move sometimes, especially after taking a topographic (contact mode) scan.
31 citations
01 Jan 1996
29 citations
TL;DR: In this paper, an idea of increasing the grain-boundary conductivity by the segregations of solutes with positive effective charge is proposed, and the feasibility of this idea has been proved by some experimental and theoretical results.
Abstract: According to a space-charge theory analysis, the space-charge potential of YSZ is negative, which corresponds to a V 0 .. depletion in the space-charge layer. An extremely low grain-boundary conductivity of the high-purity YSZ is thus explained. Under the condition that the bulk property is ensured by the optimal dopant additions, an idea of increasing the grain-boundary conductivity by the segregations of solutes with positive effective charge is put forward. The most likely driving force for the segregations is the elastic strain energy. And the feasibility of this idea has been proved by some experimental and theoretical results.
28 citations
TL;DR: In this paper, the influence of gypsum and anhydrite on the strength and hydration of ordinary Portland cement (OPC) has been investigated under an initial steam-curing condition (65 °C × 4 h).
23 citations
TL;DR: In this article, a class of reaction diffusion functional differential equations is investigated and the global existence and uniqueness of solutions and the stability of the trivial solution are obtained, and some applications are also discussed.
15 citations
TL;DR: In this paper, it was shown that there exist 4-{ν, κ, α, β, ε, λ, δ, ν, γ, θ, Γ, , Ά, Θ, Ξ, Κ, Ω, Π, Φ, ξ, Ρ, Δ, Β, Ε, Α, Ζ, ΐ, Ι, Λ, Μ, , ά, ΰ, Ϋ, β,
13 citations
TL;DR: Inverse gas chromatography (IGC) was used in the analysis of surface free energy of the sample as discussed by the authors, and it was concluded that the London dispersive component increases continuously with grinding, while the polar component firstly increases with grinding and then decreases and finally disappears, when grinding proceeds.
TL;DR: In this paper, the 3CaO · 3Al2O3 · SrSO4 single crystals are prepared and defined with PbCl2 as a flux, by means of structure analyzing the overall crystal parameters are obtained.
TL;DR: In this paper, the convergence rates of the empirical Bayes estimators of parameters in the multi-parameter exponential families were obtained, which can approximate to 0(n=1) arbitrarily.
Abstract: This paper obtains the convergence rates of the empirical Bayes estimators of parameters in the multi-parameter exponential families. The rates can approximate to 0(n=1) arbitrarily. The paper presents the multivariate orthogonal polynomials which are continuous on the total space Rp.
TL;DR: In this paper, a hot isostatic pressing (HIP) based Ni composite was used to test its flexural strength at elevated temperature by means of three-point bending.
TL;DR: In this article, the formation kinetics of BaTiO{sub 3} from the solid-state BaCOµsub 3 and TiOµµ powder in a microwave field was investigated.
Abstract: The formation kinetics of BaTiO{sub 3} from the solid-state BaCO{sub 3} and TiO{sub 2} powder in a microwave field was investigated. The quantitative XRD analysis and the model considered the volume change between reactant and product were used in this experiment. Results show that the formation rate of BaTiO{sub 3} in a microwave field is much faster than upon conventional heating. The activation energy of the solid state reaction for BaTiO{sub 3} was measured as 58 kJ/mol. This indicates the enhancement of diffusion by the microwave heating process.
TL;DR: In this article, the authors performed local density calculations of energy eigenvalue, bond order and the density of states of MgO(100)/Ag(100) interface using discrete variation Xα method for different cluster models.
TL;DR: In this article, the authors derived the transmission coefficient and the resonance condition by taking into account the mass difference between well and barrier layers in a multiple-barrier structure with arbitrary potential profile.
TL;DR: In this paper, a relation between multiple-scattering theory and micromechanical models of effective elastic material properties of heterogeneous materials has been established within a unified theoretical framework, and exemplified on three important approximations, the average t-matrix (or Mori-Tanaka), symmetric self-consistency (coherent potential), and asymmetric self Consistency approximimations.
TL;DR: In this paper, the pyroelectric properties of diphasic polar glass-ceramic (Sr{sub 2}TiSi, sub 2}O{sub 8} and SrTiO{ sub 3}) were investigated in the temperature range from 10 to 300 K.
Abstract: The pyroelectric properties of the diphasic polar glass-ceramic (Sr{sub 2}TiSi{sub 2}O{sub 8} and SrTiO{sub 3}) are investigated in the temperature range from 10 to 300 K. The pyroelectric coefficient of the diphasic polar glass-ceramic is {minus}1.8 {times} 10{sup {minus}7} C/(m{sup 2}{center_dot}K) at room temperature. It is interesting that the absolute value of p{sub 3} decreases quickly below 100 K and eventually becomes positive below 40 K, corresponding to the structural phase transition of the crystalline SrTiO{sub 3} in the glass-ceramic. XRD, DTA, and SEM were used to investigate the coupling patterns of Sr{sub 2}TiSi{sub 2}O{sub 8} and SrTiO{sub 3} crystallites in the glass-ceramic and to explain the special coupling effects.
TL;DR: The structure and magnetostriction of preferentially oriented polycrystalline R(Fe0.95Al0.05), alloys (R = Dy0.65Tb0.25 Pr-0.1, 1.85) prepared by Czochralski technique, have been investigated using optical and SEM metallography, X-ray diffraction, transmission electron microscopy and standard strain gauge techniques as mentioned in this paper.
TL;DR: In this article, a small area X-ray photoelectron spectroscopy technique is employed to study the chemical bonding of metal-ceramic interfaces and the results show that there is a chemical reaction at the interface.
TL;DR: In this paper, the chemical bonding of non-stoichiometric compounds of (Nb y Ti 1 − y )C x, in which the amount of Nb element added is increased from zero to 40% (weight percent), synthesized with self-propagating high temperature synthesis, are studied with SCF-X α-DV, a quantum chemistry calculating method.
TL;DR: In this paper, the authors reported the preparation of nanostructured composites of titanium nitride-nickel (TiN-Ni) by synthesis and condensation of nanosize powders in d.c. arc plasma and in situ powder compacting at high pressure in high vacuum.
Abstract: The nanostructured materials, named polycrystals, with a small crystalline size at length scale below 100 nm, possess a special structure in the interfaces between the crystallites. This gives rise to novel material properties and may promise future technological applications. The first studies on nanostructured materials, produced by evaporating and compacting small crystallites, were initiated by Professor Gleiter and his co-workers [1]. Further investigations have been performed by many researchers in recent years [2, 3]. However, nanostructured metal-non-metal composites have not been studied in detail. This letter reports the preparation of nanostructured composites of titanium nitride-nickel (TiN-Ni) by synthesis and condensation of TiN-Ni nanosize powders in d.c. arc plasma and in situ powder compacting at high pressure in high vacuum. The grain growth of nanostructured TiN-Ni composites and their density at different temperatures were also studie& High purity alloy of titanium and nickel was evaporated and nitrided by d.c. plasma in nitrogen atmosphere of 60 kPa. The reactants of TiN-Ni were carried rapidly to a cold finger of liquid nitrogen by plasma gas and were scraped, in situ, into a high pressure compacting device. There, the powders were compacted at a pressure of 3 GPa in high vacuum (1.333 x 10-4pa). Meanwhile the compacted TiN-Ni specimens were sintered for 1 h sequentially at 500 °C, at intervals of 200 °C, up to 1500 °C in nitrogen atmosphere. The particle size of the TiN-Ni composites was analysed by transmission electron microscopy (TEM). The purity of the powders was examined by chemical methods and an HZG4-PC X-ray diffractometer using CoK« radiation. Scanning electron microscopy (SEM) was performed to study the microstructure of nanostructured TiN-Ni specimens at different temperatures. The purity and particle size of TiN-Ni powders can be controlled by adjusting the temperature distribution of plasma in the reactor, the partial pressure of nitrogen and the cooling temperature of the cold finger. Fig. 1 shows the XRD pattern of nanosized TiN--Ni powders. A T E M micrograph of nanosized powders is shown in Fig. 2. The results indicate that the average particle size was about 20 nm and the purity was more than 98% (wt%), with Ni content of about 20% (wt %).
TL;DR: In this paper, the preferential direction of grain growth and magnetostriction of Dy0.6Tb0.3Pr 0.95Mn0.05) alloys (1.80 less than or equal to x less than and equal to 1.95) prepared by the Czochralski method were investigated.
22 Mar 1996
TL;DR: The Graph Transformation Expert System, is an expert system which has been developed by WUT for applying techniques of artificial intelligence to the architectural design of data and signal processing systems.
Abstract: The design of many industrial and engineering systems can often be accomplished using flow graphs of various types. Examples include manufacturing processes and data processing applications, Graph Transformation Expert System, is an expert system which has been developed by WUT for applying techniques of artificial intelligence to the architectural design of data and signal processing systems. Software and hardware architectures may be defined for such systems using data flow graphs, in which nodes represent data processing steps and directed areas represent the `flow' of data between the processing steps. Starting with a user- defined generic processing graphic, this expert will transform the graph by applying transformation rules in order to specialize the processing graph to satisfy specified design goals and/or hardware constraints. Although the particular application for which this expert is designed is that of data and signal processing systems, it can provide an expert system framework for other problems specified graphically; for example, manufacturing systems, information systems, and product distribution systems.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
TL;DR: In this paper, a ridge rectangular waveguide is designed, and its cutoff frequency, impedance and electric field intensity are given by formulas or curves, and a few ceramic samples are sintered in it by microwave energy.
Abstract: In this paper, a ridge rectangular waveguide is designed, and its cutoff frequency, impedance and electric field intensity are given by formulas or curves. A few ceramic samples are sintered in it by microwave energy. It is concluded that the device can be as a satisfactory microwave sintering cavity.