Showing papers by "Wuhan University of Technology published in 2001"

Some fractal characters of porous media

Abstract: In this paper, a unified model for describing the fractal characters of porous media is deduced. The theoretical predictions from the proposed unified model are compared with those from the previous models and from the box-counting method. The results from the proposed model are found to be in good agreement with both the previous models and box-counting method. The results also indicate that the proposed unified model is applicable to both the exactly and statistically self-similar fractal media. A statistical property of porous media is also described based on the basic fractal theory and technique. A criterion, for determining whether a porous medium can be characterized by fractal theory and technique or not, is proposed based on the fractal statistical property.

Effects of partial substitution of Ni by Pd on the thermoelectric properties of ZrNiSn-based half-Heusler compounds

Abstract: We report on the effects of partial substitution of nickel by palladium on the thermoelectric properties of ZrNiSn-based half-Heusler compounds. It is shown that the substitution of palladium for nickel results in a significant, beneficial reduction of the thermal conductivity. The Seebeck coefficient also decreases, but only by a small amount. In the Hf0.5Zr0.5Ni0.8Pd0.2Sn0.99Sb0.01 compound, a power factor of 22.1 μW K−2 cm−1 and a thermal conductivity as low as 4.5 W/m K are measured at room temperature. The dimensionless figure of merit ZT increases with increasing temperature and reaches a maximum value of 0.7 at about 800 K.

The grain size and surface hydroxyl content of super-hydrophilic TiO2/SiO2 composite nanometer thin films

Abstract: The grain size and surface hydroxyl content of super-hydrophilic TiO2/SiO2 composite nanometer thin films JIAGUO YU∗ State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, People’s Republic of China; Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, People’s Republic of China E-mail: yujiaguo@public.wh.hb.cn

Synthesis and adsorption properties of magnetic resin microbeads with amine and mercaptan as chelating groups

Abstract: Three magnetic chelating resins containing amino and mercapto groups were prepared by the suspended condensation polymerization of 2-chloroethoxymethyl thiirane with diamines. The magnetic resins were microbeads whose diameter was in the range of 10 to 45 μm. The structure of the resins was characterized by XPS, IR, and elemental analysis. Their adsorption properties for Hg(II), Au(III), Pd(II), Pt(IV), Ag(I), Cu(II), Zn(II), and Pb(II) were investigated. The experimental results show the magnetic resins have high affinity for Hg(II) and noble metal ions. In the competitive adsorption, the resins predominantly adsorbed Hg(II) or Pd(II) in the coexistence of Cu(II), Zn(II), and Mg(II). Desorption of Pd(II) loaded on the resins was studied by using 2M hydrochloric acid solution containing 1% thiourea as desorbent. A high desorption ratio (up to 96.5%) was observed, and repeated adsorption/desorption operations showed the probability of repeated use of the magnetic resins. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1587–1592, 2001

Second-harmonic generation in Ge(20)As(25)S(55) glass irradiated by an electron beam.

Abstract: Second-harmonic generation was observed in Ge20As25S55 chalcogenide glass irradiated by an electron beam. The second-harmonic intensity increased with increasing electron-beam current and accelerating voltage. The second-harmonic generation in Ge20As25S55 glass was caused by the space-charge electrostatic field that was generated by irradiation of an electron beam. Second-order nonlinearity χ2 as great as 0.8 pm/V was obtained. The results of measurements of thermally stimulated depolarization current indicated that the glass was poled in the thin layers of its surface (several micrometers) and that the nonlinearity was stable.

Synthesis of Mg2Si1−xGex thermoelectric compound by solid phase reaction

Abstract: By two-stage solid phase reaction, a series of Mg 2 Si 1− x Ge x continuous solid solutions were successfully synthesized at low temperature (823 K) for the first time. The product was single-phased without any oxide or carbide and the particle size was substantially reduced than that of the raw powders. X-ray diffraction (XRD) techniques were used to explore the products’ phases and differential thermal analysis (DTA) to the changing tendency of heat quantity during the solid phase reaction. The influence of Ge substitution to Mg 2 Si 1− x Ge x was illustrated by the changes of lattice parameter and the existence of the complete solid solubility between Mg 2 Si and Mg 2 Ge was established, too.

High-temperature thermoelectric properties of n-type BayNixCo4-xSb12

Abstract: Effects of Ba filling fraction and Ni content on the thermoelectric properties of n-type BayNixCo4−xSb12 (x = 0−0.1, y = 0−0.4) were investigated at temperature range of 300 to 900 K. Thermal conductivity decreased with increasing Ba filling fraction and temperature. When y was fixed at 0.3, thermal conductivity decreased with increasing Ni content and reached a minimum value at about x = 0.05. Lattice thermal conductivity decreased with increasing Ni content, monotonously (y ≤ 0.1). Electron concentration and electrical conductivity increased with increasing Ba filling fraction and Ni content. Seebeck coefficient increased with increasing temperature and decreased with increasing Ba filling fraction and Ni content. The maximum ZT value of 1.25 was obtained at about 900 K for n-type Ba0.3Ni0.05Co3.95Sb12.

Synthesis and thermoelectric properties of filled skutterudite compounds CeyFexCo4-xSb12 by solid state reaction

Abstract: Filled skutterudite compounds, CeyFexCo4−xSb12(x= 0–1.0, y= 0–0.15), were synthesized by solid state reaction using Co, Fe, Sb and CeCl3· nH2O powders as source materials. The lattice constants of CeyFexCo4−xSb12increased with increasing substitution of Fe at Co sites and with increasing Ce filling fraction in the Sb-icosahedron voids. All specimens showed p-type conduction. Carrier concentration (p) and electrical conductivity (σ) increased with increasing substitution of Fe at Co sites and decreased with increasing Ce filling fraction. The Seebeck coefficient (α) decreased with increasing Fe content and increased with increasing Ce filling fraction. Thermal conductivity (κ) decreased with increasing substitution of Fe at Co sites and with increasing Ce filling fraction. A maximum ZTvalue of 0.8 was obtained for Ce0.12Fe0.71Co3.29Sb12at 750 K.

Degradation of yttria stabilized zirconia at 370 K under a low applied stress

Abstract: The tetragonal-to-monoclinic phase transformation in ZrO 2 –3mol.%Y 2 O 3 containing 0–5% A1 2 O 3 during aging in hot water (370 K) under 100 MPa stress is investigated. It is found that while a small tensile stress accelerates the degradation, a compressive stress has little affect on the degradation. The degradation of PSZ under tensile stress is considered to be caused by the reaction between Y 2 O 3 and H 2 O. Small amount of A1 2 O 3 addition does not change the degradation mechanism of PSZ, but it prevents further continuation of degradation when the transformed volume reaches a certain value.

Dynamic traveling salesman problem based on evolutionary computation

Abstract: In the optimization process of some ordering problems, we compare them to the traveling salesman problem (TSP) and put forward the conception of a virtual map. Based on this conception, the problems are all put into the framework of the dynamic traveling salesman problem (DTSP). The paper makes a lot of comparisons between TSP and DTSP about their characteristics, and finds out the commonality and differences between them. At the same time, we consider that the presentation of DTSP conception is attributed to the rise of modern optimization methods founded on probability, and evolutionary computation is one of the best algorithms to solve DTSP nowadays.

Semi‐active control of seismic response of tall buildings with podium structure using ER/MR dampers

Abstract: A tall building with a large podium structure under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the podium structure. This paper thus explores the possibility of using electrorheological (ER) dampers or magnetorheological (MR) dampers to connect the podium structure to the tower structure to prevent this whipping effect and to reduce the seismic response of both structures. A set of governing equations of motion for the tower–damper–podium system is first derived, in which the stiffness of the member connecting the ER/MR damper to the structures is taken into consideration. Based on the principle of instantaneous sub-optimal active control, a semi-active sub-optimal displacement control algorithm is then proposed. To demonstrate the effectiveness of semi-active control of the system under consideration, a 20-storey tower structure with a 5-storey podium structure subjected to earthquake excitation is finally selected as a numerical example. The results from the numerical example imply that, as a kind of intelligent control device, ER/MR dampers can significantly mitigate the seismic whipping effect on the tower structure and reduce the seismic responses of both the tower structure and the podium structure. Copyright © 2001 John Wiley & Sons, Ltd.

An object-oriented intelligent CAD system for ceramic kiln

Abstract: This paper describes an integrated intelligent computer-aided design (CAD) system for the ceramic kiln, with an object-oriented database as its core, utilizing object-oriented approach. In addition to the structure and methods of the object-oriented database, the knowledge-based system and the drafting system are discussed. The idea of an integrated intelligent CAD environment is introduced, which can greatly improve design efficiency and quality.

The controllability of linear systems over F(z)

Abstract: The controllability of the linear systems over the field F(z) of rational functions with real coefficients in q independently variable parameters is studied. Some conditions are derived.