Showing papers by "Northeastern University (China) published in 1994"
01 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the lattice parameters of the Ni3P nanophases with grain sizes ranging from 80 to 6.0 nm were measured by X-ray diffraction.
Abstract: Nanocrystalline Ni-P alloy samples consisting of the compound Ni3P and Ni solution with different grain sizes were synthesized by crystallization of the amorphous alloy. The lattice parameters of the Ni3P nanophases with grain sizes ranging from 80 to 6.0 nm were measured by X-ray diffraction. It was found that for the nanometer-sized Ni3P phase, the lattice parameter a is always larger and c is smaller than the equilibrium values a0 and a0, of the perfect crystal lattice respectively. With a reduction in the grain size, the value of a increases and c decreases, resulting in more significant lattice distortion. The origin of such lattice distortion was analyzed according to the thermodynamic state of the nanometer-sized crystallites.
38 citations
TL;DR: In this article, isopiestic measurements have been made for the quaternary system (mannitol + sorbitol + sucrose) and its ternary sub-system (mannitol + sorbitol) at T = 298.15 K. The results were in excellent agreement with the partial ideal-mixture model.
35 citations
TL;DR: In this paper, a vortex finder attachment was designed for a new hydrocyclone with a central cone and a vortex-finder attachment, and the experimental results showed that the sharpness of separation for the new cyclone was higher than that for the conventional one.
Abstract: Recent experimental research into the motion of solid particles in a hydrocyclone has shown that some particles in the inner helical flow move towards the hydrocyclone wall in the cylindrical section. Enlightened by this result, a new hydrocyclone has been developed with a central cone. In addition, because some coarse particles discharge directly with the overflow as a result of the short-circuit flow, the new hydrocyclone has also been designed with a vortex finder attachment. Separation experiments were carried out with the new hydrocyclone, comparing it with the conventional one. The experimental results showed that the sharpness of separation for the new hydrocyclone, with a central cone and vortex finder attachment, was higher than that for the conventional hydrocyclone. The optimum geometric parameters and position of the central cone were also determined experimentally.
32 citations
TL;DR: Isopiestic measurements have been made for the quaternary system {NaCl (m B ) + NH 4 Cl (m c ) + BaCl 2 (m D )}(aq) at the temperature T = 298.15 K as discussed by the authors.
32 citations
TL;DR: In this paper, the same authors used X-ray diffraction and vibrating sample magnetometer to obtain the magnetic properties of the gamma-Fe powder at room temperature and showed clear crystal habit of polyhedra.
31 citations
TL;DR: Gong, B (reprint author), ACAD SINICA, INST MET RES,STATE KEY LAB FATIGUE & FRACTURE MAT,SHENYANG 110015,PEOPLES R CHINA as mentioned in this paper.
Abstract: NE UNIV TECHNOL,DEPT PHYS,SHENYANG 110006,PEOPLES R CHINA;GONG, B (reprint author), ACAD SINICA,INST MET RES,STATE KEY LAB FATIGUE & FRACTURE MAT,SHENYANG 110015,PEOPLES R CHINA
27 citations
TL;DR: In this paper, two thermal models for periphery grinding with slotted wheel and vertical spindle face grinding with segmented wheel are established respectively in order to choose the slotting or segmental parameters more reasonably and predict grinding temperature.
25 citations
TL;DR: In this article, B is incorporated into the TiO[sub 2]-Al system to constitute the TiB[Sub 2]-B-Al system, and the properties of the composite can be improved through addition of B.
Abstract: In the present investigation, B is incorporated into the TiO[sub 2]-Al system to constitute the TiO[sub 2]-B-Al system. According to the investigation on the Ti-B-Al system, it is expected that the Ti displaced from the reaction between TiO[sub 2] and Al reacts with B to form TiB[sub 2] instead of Al to form Al[sub 3]Ti. TiB[sub 2] is a more effective reinforcement than Al[sub 2]O[sub 3], so the properties of the composite can be improved through addition of B. Such an investigation has not been reported to date.
24 citations
TL;DR: In this article, the Ni(P) solution nanophase was determined according to the Vegard's law, which was found to be 10 ∼ 15 times the equilibrium solubility.
23 citations
TL;DR: In this article, the steady state laminar film condensation process of pure saturated vapour at atmospheric pressure on an isothermal vertical flat plate is established and its equations provide a complete account of the physical process for consideration of variable thermophysical properties, except for surface tension at the liquid-vapour interface.
Abstract: The extended theory of the steady state laminar film condensation process of pure saturated vapour at atmospheric pressure on an isothermal vertical flat plate is established. Its equations provide a complete account of the physical process for consideration of various physical factors including variable thermophysical properties, except for surface tension at the liquid-vapour film interface.
22 citations
15 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effects of 1% Cu and 3% Nb on the nucleation and growth characteristics of amorphous Fe77.5Si13.5B9 alloys were investigated using differential scanning calorimetry and X-ray diffraction.
Abstract: Isothermal crystallization processes in amorphous Fe77.5Si13.5B9 alloy with the addition of 1% Cu and/or 3% Nb were investigated using differential scanning calorimetry and X-ray diffraction. A symmetric exothermal peak resulting from precipitation of crystalline α-Fe and FeB compounds in Fe74.5Si13.5B9Nb3, and an asymmetric peak originating from the formation of α-Fe(Si) solid solution in both Fe76.5Si13.5B9Cu1 and Fe73.5Si13.5B9Cu1Nb3 have been observed. From the measured curves of the crystallized volume fraction x(t) vs. the annealing time t, we have plotted the relationships of the local Avrami exponent n(x) and the local activation energy Ec(x), respectively, varying with x(t), and have calculated the values of the activation energy Eg for the growth of nuclei in the amorphous Fe74.5Si13.5B9Nb3, Fe73.5Si13.5B9Cu1Nb3 and Fe76.5Si13.5B9Cu1 alloys. Changes in the average grain size of the α-Fe(Si) crystallite during the isothermal crystallization process have also been examined. Based on these results, the effects of Cu and Nb on the nucleation and growth characteristics in amorphous FeSiB(Cu)(Nb) alloys have been further confirmed, i.e. Cu accelerates the nucleation process of the α-Fe phase and Nb suppresses growth of the α-Fe phase.
14 Dec 1994
TL;DR: In this article, a class of large-scale systems composed of several similar subsystems interconnected with an external system in a symmetrical fashion is discussed, and a method of solving the set of fixed modes of such a system with respect to decentralized (or partly decentralized) control is presented in terms of the modified subsystems.
Abstract: This paper discusses a class of large-scale systems composed of several similar subsystems interconnected with an external system in a symmetrical fashion. A method of solving the set of fixed modes of such a system with respect to decentralized (or partly decentralized) control is presented in terms of the modified subsystems. The completeness of these systems is studied, a simple condition for such a system to be complete is derived. >
TL;DR: In this paper, the problem of eigenstructure assignment of singular systems is investigated and a new method of EIG assignment by proportional plus derivative state feedback in singular systems was proposed.
TL;DR: A new formula for computing conditional belief functions is introduced and the impossibility of finding a sensible form of conditioning of belief functions that has all the properties desired is discussed.
TL;DR: In this article, the Gibbs free energy change of formation of Sn 3 O 4 was given by Δ G o Sn 3 o 4 = -1.163,960 + 417.36 T (J/mol).
01 Jan 1994-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, an improved high-temperature isopiestic technique has been applied to the ternary slag PbO-SiO2-B2O3 and its binary subsystems at 1273 K.
Abstract: An improved high-temperature isopiestic technique has been applied to the ternary slag PbO-SiO2-B2O3 and its binary subsystems PbO-SiO2 and PbO-B2O3 at 1273 K. The isopiestic measurements agree well with the literature data for the two binaries. Each entire isoactivity curve of PbO in the ternary slag was determined by only one experiment. The activities of SiO2 and B2O3 were then calculated analytically. The measured and calculated results for the ternary slag approximately fit a partial ideal solution model proposed previously.
01 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: The thermal stability of dispersive particles in melt-spun ribbons was studied by differential thermal analysis, X-ray diffraction, energy-dispersive Xray analysis and transmission electron microscopy.
Abstract: The thermal stability of the dispersive particles in melt-spun ribbons was studied by differential thermal analysis, X-ray diffraction, energy-dispersive X-ray analysis and transmission electron microscopy. The experimental results show that nearly spherical b.c.c. α-Al 13 (Fe, V) 3 Si dispersoids exist at room temperature. No noticeable growth of the dispersoids is observed up to 510 °C for 100 h. Polygonal h.c.p. θ-Al 2 (Fe, V, Si) dispersoids appear when the temperature rises to 650 °C. At 650 °C for 25 h band-shaped (Al, Si) 13 Fe 14 dispersoids are formed in the specimen and spherical, polygonal and band-shaped dispersoids are coexistent. The reason for the fineness and very slow growth rate of the dispersoids and the role of V atoms in the phase transformation are discussed.
TL;DR: In this paper, a model for pool film boiling of both subcooled and saturated liquids along an isothermal vertical plate, taking into consideration all matching conditions including variable thermophysical properties, is established.
TL;DR: It is shown that under some conditions the preconditioned S OR method gives improvement in the rate of convergence compared with the unpreconditioned SOR method for 0 1.
Abstract: In this paper we investigate how the convergence rate of the successive overrelaxation (SOR) method is affected if the linear system Ax = b is preconditioned by performing certain elementary row operations on A. It is shown that under some conditions the preconditioned SOR method gives improvement in the rate of convergence compared with the unpreconditioned SOR method for 0 1.
TL;DR: A new model reference robust adaptive controller which does not require a priori knowledge of the norm desired controller parameter vector is presented, which is shown to be zero when reference input is persistently exciting.
TL;DR: SiC whisker reinforced Al-8.5Fe-1.7Si alloy composite was fabricated by a P/M technique as discussed by the authors, and the composite and matrix alloy exhibit medium room-temperature strength due to the significant coarsening of the dispersoids at the elevated fabrication temperature.
TL;DR: In this paper, the interphase boundaries between alpha and delta are mostly semi-coherent and the distances between the misfit dislocations are consistent approximately with a geometrical analysis estimation.
Abstract: Atomic images of delta-hydride and interphase boundaries between alpha-Ti and delta-hydride in Ti-H alloys containing 0.47 and 1.52 wt% H respectively, have been investigated by means of high resolution transmission electron microscopy (HRTEM). (0111BAR)alpha twins as well as (111)delta twins were generated due to a large volume expansion during hydride formation. The ledge structure can be observed at the (O111BAR)alpha twin interface with height n*d(0111BAR) (n = 2, 4, 6...). The interphase boundaries between alpha and delta are mostly semi-coherent and the distances between the misfit dislocations are consistent approximately with a geometrical analysis estimation. Two basic orientation relationships (O.R.) between matrix alpha and delta phases were defined and further two O.R.s were also derived from their twin structures.
TL;DR: In this paper, an Al-23Si alloy was inoculated with coinoculants containing phosphorus, rare earths, and sulfur, and the results showed that rare earth and sulfur can refine primary crystal silicon and modify eutectic silicon in hypereutective Al-Si alloys.
Abstract: This paper describes an Al-23Si alloy that was inoculated with coinoculants containing phosphorus, rare earths, and sulfur. The results show that coinoculants containing phosphorus and sulfur, phosphorus and rare earths, and rare earths and sulfur can refine primary crystal silicon and modify eutectic silicon in hypereutectic Al-Si alloys. Further, it seems that the refinement effect of the rare earths and sulfur coinoculant is better than that of the other tested coinoculants.
TL;DR: In this article, a direct adaptive generalized predictive control scheme is proposed for multi-input multi-output (MIMO) systems and global convergence analysis of the scheme is carried out under some reasonable assumptions by using a normalization technique and a parameter estimation with a dead zone.
Abstract: A direct adaptive generalized predictive control scheme is proposed for multi-input multi-output systems. Global convergence analysis of the scheme is carried out under some reasonable assumptions by using a normalization technique and a parameter estimation with a dead zone. A simulation example is presented to demonstrate the effectiveness of the proposed direct adaptive algorithm.
TL;DR: In this article, the evolution of dislocation patterning in creep was simulated on a computer, and the creep curves of the strain rate versus time were obtained, while the dependence of internal stress distribution as well as structural parameters at a steady state on an applied stress was obtained.
Abstract: In past decades, creep deformation was one of most interesting subjects. By theoretical and experimental studies, many investigators found that a typical creep curve was composed of four stages, i.e. instantaneous strain or incubation period, transient or primary creep, steady state or secondary creep, and tertiary creep usually connected with fracture. In respect to theoretical research, many different deformation mechanisms and theoretical models were proposed in terms of experimental results. These models were successfully used for explaining the behavior of creep under low applied stress and high temperature. However, there exist some unsolved problems, such as the variation of subgrain size, stress power, etc., which were attributed to a lack of understanding the behavior of dislocation populations. In recent years, some investigators studied the variation of dislocation patterning using a non-linear method. In this paper, the new model of dislocation evolution is derived on the basis of dissipative structure and synergetics. The evolution of dislocation patterning in creep was simulated on a computer, and the creep curves of the strain rate versus time were obtained. Meanwhile, the dependence of internal stress distribution as well as structural parameters at a steady state on an applied stress was obtained.
15 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the structures of Fe73.5Cu1Nb3Si13.5B9 alloys were investigated by X-ray diffraction and positron annihilation spectroscopy.
Abstract: The structures of Fe73.5Cu1Nb3Si13.5B9 alloys annealed in the temperature range 400-600-degrees-C for 30 min are investigated by X-ray diffraction and positron annihilation spectroscopy. The grain size and the lattice parameter of the alpha-Fe(Si) phase in the alloys annealed at different temperatures are determined. The variations of the Si content in die nanocrystalline alpha-Fe(Si) phase with the annealing temperatures are obtained for the alloys. With T(a) increasing, the positron lifetime tau1 and the intensity ratio I1/I2 decrease, which indicates that the residual amorphous phase is changed in both composition and structure. The relationship between the structural characteristics and the magnetic properties for the alloys is discussed.
TL;DR: In this article, the critical temperature and parallel susceptibility of layered Heisenberg systems were studied using the double-time temperature spin Green function theory, and it was shown that for weak interlayer coupling strengths δ = J⊥⧸J, the critical temperatures can be expressed in asymptotic form, k B T C ={ [8π JS(S + 1)] 3 }⧁ ln (32⧂δ), which is in very good agreement with the numerical value for δ ⩽ 0.02
15 May 1994-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructural change of amorphous alloy Fe79Si7B14 during electropulsing was investigated by Mossbauer spectroscopy, and the saturation magnetization and electrical resistance were also measured.
Abstract: The microstructural change of amorphous alloy Fe79Si7B14 during electropulsing was investigated by Mossbauer spectroscopy. The saturation magnetization and electrical resistance were also measured. The experimental results show that d.c. pulses of high current density can induce microstructural relaxation of the amorphous alloy. The longer the pulsing time and the higher the frequency, the greater the relaxation effect.
TL;DR: A direct adaptive generalized predictive control algorithm is suggested and stability of the closed-loop system is proved under some assumptions and the effectiveness of the algorithm is demonstrated.
Abstract: In this paper a direct version of adaptive generalized predictive control is considered. A direct adaptive generalized predictive control algorithm is suggested and stability of the closed-loop system is proved under some assumptions. A simulation example demonstrates the effectiveness of the algorithm.