Showing papers by "Dalian University of Technology published in 1998"
TL;DR: Based on the homogeneous balance method, a simple and efficient method for obtaining exact solutions of nonlinear partial differential equations is proposed in this paper, where some equations are investigated by this means and new solitary wave solutions or singular traveling wave solutions are found.
543 citations
TL;DR: In this paper, a non-probabilistic, interval modeling of uncertain-but-non-random parameters for structures is developed for antioptimization analysis, consisting in determining the least favorable responses.
367 citations
TL;DR: In this article, it was shown that various well-known generalizations of Stirling numbers of the first and second kinds can be unified by starting with transformations between generalized factorials involving three arbitrary parameters.
156 citations
TL;DR: In this paper, the effect of reaction conditions on catalytic activity and selectivity of Raney nickel catalysts was examined and it was found that all Raney Nickel catalysts modified with salts of heteropolyacids (HPA) have higher catalytic performance and selectivities than unmodified RaneyNickel catalysts; 12-molybdophosphates gave the best results among the modifiers.
Abstract: In this paper, liquid phase selective hydrogenation of furfural on Raney nickel which has been modified by impregnation of salts (including alkali metals, alkaline earth metals, and transition metals) of heteropolyacids (HPAs) having Keggin type structure was studied. Effects of reaction conditions on catalytic activity and selectivity were examined. It has been found that all Raney nickel catalysts modified with salts of HPAs show higher catalytic activity and selectivity than unmodified Raney nickel catalysts; 12-molybdophosphates give the best results among the modifiers. As far as the effect of competitive cations on catalytic properties is concerned, transition metals are better than both alkali metals and alkaline earth metals. Among the transition metal salts, Cu salt is superb in performance. A Raney nickel catalyst on which 7.1% Cu3/2PMo12O40 has been deposited, under reaction conditions of temperature 353 K, hydrogen pressure 2.0 MPa, amount of catalyst 0.5 g, volume of reactant 10 ml and reaction time 1 h, gave a conversion of furfural and selectivity for furfuryl alcohol of as high as 98.1% and 98.5%, respectively. In this work, the salt of HPA only plays the role of a modifying agent rather than acting as a catalyst. This can be inferred from the experimental evidence that salts of HPAs deposited on active carbon showed no catalytic activity in selective hydrogenation of furfural under similar conditions.
131 citations
TL;DR: Using an improved homogeneous balance method, several kinds of exact solutions which include Wang's results were obtained for a system of coupled KdV equations in this paper, where Wang's exact solution was used to solve the problem.
122 citations
TL;DR: In this paper, the authors describe a CMOS compatible integrated gas sensor, which was designed so that the front-end fabrication is fully compatible with the standard CMOS process and the non-CMOS compatible fabrication steps were carried out as post-processing steps.
Abstract: This paper describes a CMOS compatible integrated gas sensor. The device was designed so that the front-end fabrication is fully compatible with the standard CMOS process. The non-CMOS compatible fabrication steps were carried out as post-processing steps. This included the silicon anisotropic etch to create the thermally isolated micro-hotplate (MHP) and the deposition of gas-sensitive thin films using maskless r.f. SnO 2 sputtering. The sensors exhibited high sensitivities to gases, such as ethanol and hydrogen.
81 citations
TL;DR: In this paper, the precipitate phase of the approximate composition of (Ti0.6Hf0.4)Ni is identified to be face-centered orthorhombic lattice with lattice parameters A=1.287nm, B=0.874nm and C=2.622nm.
79 citations
TL;DR: In this paper, three series of poly(aryl ether sulfone)s (PAESs) containing the phthalazinone moiety in the polymer backbone were synthesized by solution polycondensation of bis(4-chlorophenyl) sulfone with three commercial bisphenols and 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one.
Abstract: Three series of poly(aryl ether sulfone)s (PAESs) containing the phthalazinone moiety in the polymer backbone were synthesized by solution polycondensation of bis(4-chlorophenyl) sulfone with three commercial bisphenols and 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one. Bisphenol-A, hydroquinone, and bis(4-hydroxyphenyl) sulfone, or bisphenol-S, were selected as the commercial bisphenols for copolymerization. The synthesized polymers exhibited very high glass transition temperatures and excellent thermooxidative properties. They also showed superior mechanical properties and fair rheological properties. The introduction of relatively flexible moieties, such as benzene rings, onto the poly(phthalazinone ether sulfone) (PPES) chain led to a decrease in glass transition temperature with respect to the phthalazinone homopolymer. However, the processability of PPES was improved dramatically by the addition of these commercial bisphenols. The properties of synthesized PAESs can be tailored by changing the molar ratios of bisphenols to phthalazinone monomer. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:137–143, 1998
71 citations
TL;DR: Pt/HZSM-5 showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 400°C and its catalytic performance was higher than that of commercial CoMo/Al2O3 catalyst.
65 citations
TL;DR: An improved genetic algorithm (IGA) is proposed to provide a systematic approach and tools for synthesis design and retrofits of distillation systems, which inherits main ideas in evolutionary computing.
61 citations
TL;DR: In this paper, a new line of aqueous/organic two-phase catalysis termed the thermoregulated phase-transfer catalysis (TRPTC) has been described.
TL;DR: In this article, the in-plane magnetic anisotropy of Co thin films on GaAs(001) was studied using reflection high-energy electron diffraction, a high-resolution transmission electron microscope, and the magneto-optical Kerr effect.
Abstract: Epitaxial growth of Co on GaAs(001) and its in-plane magnetic anisotropy are studied using reflection high-energy electron diffraction, a high-resolution transmission electron microscope, and the magneto-optical Kerr effect. In the initial and final stages of growth, Co exists in single-crystalline body-centered-cubic (bcc) and hexagonal-closed-packed (hcp) phases, respectively, while in the middle stage the coexistence of the bcc and hcp structures is observed. For the bcc Co thin films on GaAs(001), a fourfold in-plane magnetic anisotropy with easy axes along the [100] directions is realized and discussed. [S0163-1829(98)04915-7].
TL;DR: In this article, the carbon migration between a ferritic steel and an austenitic steel was studied in submerged arc-welded 5Cr-0.5Mo/21Cr-12Ni dissimilar metal welds after aging at 500°C for various times and after long-term service in technical practice.
Abstract: The carbon migration between a ferritic steel and an austenitic steel was studied in submerged arc-welded 5Cr-0.5Mo/21Cr-12Ni dissimilar metal welds (DMWs) after aging at 500°C for various times and after long-term service in technical practice. The distribution of carbon, chromium, nickel, and iron in the areas around the weld interface was determined by electron probe microanalysis, and the microstructural aspect in the carbon-depleted/enriched zone was characterized by optical microscopy and transmission electron microscopy (TEM). Furthermore, the precipitation sequences and composition characteristics of the carbides were identified by diffraction pattern microanalysis and energy-dispersive X-ray (EDX) microanalysis. It was found (1) that there exists a coherent relationship between intracrystalline M23C6 and the austenitic matrix; (2) that the composition of M23C6 in the carbon-enriched zone is independent of the duration of aging and service; (3) that the maximum carbon concentration is determined by the carbide type, the composition characteristic of precipitated carbides, and the concentration of carbide-forming Cr adjacent to the weld interface in the carbon-enriched zone; and (4) that the carbon migration in the 5Cr-0.5Mo/21Cr-12Ni DMWs can be described by a diffusion model.
TL;DR: Histochemical analysis showed that the CCA were structurally organized to facilitate nutrient transport and kinetics for CCA growth and salidroside synthesis were similar to that of shake-flask cultures though the biomass was relatively small.
TL;DR: In this article, a combined PQP (Parametric Quadratic Programming) and iteration method is constructed in order to avoid the unknown slip direction of the tangential force and exhausting computing time when the double nonlinear problems are considered.
TL;DR: In this paper, a complete finite element approach and a pseudo-excitation method were used for buffeting analysis of long span bridges, featuring mainly by a complete element approach, and the accuracy of the new algorithm was examined by comparison with the Scanlan's method through an example bridge deck.
TL;DR: In this paper, the independent-continuous topological variable is proposed to establish its corresponding smooth model of structural topological optimization, which can overcome difficulties that are encountered in conventional models and algorithms for the optimization of the structural topology.
Abstract: A concept of the independent-continuous topological variable is proposed to establish its corresponding smooth model of structural topological optimization. The method can overcome difficulties that are encountered in conventional models and algorithms for the optimization of the structural topology. Its application to truss topological optimization with stress and displacement constraints is satisfactory, with convergence faster than that of sectional optimizations.
TL;DR: In this article, the authors investigated the effect of temperature on extract formation rate, extract yields and product components at different pressures and end temperatures on a semi-continuous apparatus for extracting Dayan lignite in sub-and supercritical states.
TL;DR: The activity of tyrosol glucosyltransferase (TGase) of Rhodiola sachalinensis cells was found to be the highest at the exponential growth phase while the intracellular tyrosols accumulated in large amounts at the stationary growth phase.
TL;DR: It is proved that the new strategy can guarantee the convergence of refined approximate eigenvectors if the corresponding Ritz values do and the resulting refined iterative algorithm is much more efficient than the iterative block Arnoldi algorithm.
TL;DR: Strategies of elicitation and precursor feeding were applied to improve salidroside production in cell suspension cultures of Rhodiola sachalinensis, and of the seven elicitors examined, that extracted from Aspergillus niger was the most effective.
Abstract: Strategies of elicitation and precursor feeding were applied to improve salidroside production in cell suspension cultures of Rhodiola sachalinensis. Of the seven elicitors examined, that extracted from Aspergillus niger was the most effective, increasing the salidroside content by five-fold when added on the day of inoculation 40 mg carbohydrate is medium. Three possible precursors for salidroside synthesis, L-phenylalanine, L-tyrosol and L-tyrosine were added to the cultures. A high content of salidroside (1.440%) was attained with an initial L-tyrosol concentration of 0.5 mM in the medium. Combined application of the two strategies resulted in a significantly high salidroside content of 1.734%, corresponding to a salidroside yield of 200 mg/l.
TL;DR: In this paper, a novel nonionic water-soluble octylpolyglycol-phenylene-phosphite (OPGPP) was synthesized and two-phase hydroformylation of styrene catalyzed by an OPGPP/Rh catalyst was investigated fully.
TL;DR: The Al3Cu4 composition, with an e/a ratio of 1.86 being close to ternary Al-Cu-TM (Transition Metal) quasicrystals, has been chosen for the search of AI-Cu approximants.
Abstract: The Al3Cu4 composition, with an e/a ratio of 1.86 being close to ternary Al-Cu-TM (Transition Metal) quasicrystals, has been chosen for the search of AI-Cu approximants. Phase structures and compositions were studied using TEM, ii-ray diffraction and EPMA techniques. Two new phases were found: face-centered orthorhombic oF-Al43.2Cu56.8 (a = 0.816(6), b = 1.414(9), c = 0.999(5) nm) and body-centered orthorhombic oI-Al41.3Cu58.7 (oI, a = 0.408(3), b = 0.707(4), c = 0.999(5) nm). Their e/a ratios are the same as that of the Al-Cu-Fe icosahedral quasicrystal. Their space groups are probably oF-Fmm2 and oI-Imm2. Both are B2 vacancy-containing superstructures; unit cell compositions can be expressed approximately as oF-Al(36)Cu(48)square(12) and oI-Al(8)Cu(12)square(4) (square: vacancies). They both exist in twinning variants of the types 120 degrees/[001] and 180 degrees/[310]. Such twinning modes indicate that these orthorhombic phases are the decomposition products of a high-temperature parent phase epsilon 2-Al2Cu3, the atomic structure of which contains pentagonal atomic arrangements. Therefore the of, oI, and epsilon 2 phases are all B2-based approximants corresponding to the Al-Cu-TM quasicrystals.
TL;DR: Liquid-cultivated compact callus aggregates of Rhodiola sachalinensis showed some level of cellular/tissue differentiation, which was perhaps responsible for the increased salidroside production, and a higher ratio of cytokinin/auxin was found to be beneficial both for CCA growth and salid roside accumulation.
Abstract: Liquid-cultivated compact callus aggregates (CCA) of Rhodiola sachalinensis were initiated from the explant of stems. Microscopic analysis showed that CCA displayed some level of cellular/tissue differentiation, which was perhaps responsible for the increased salidroside production. A higher ratio of cytokinin/auxin was found to be beneficial both for CCA growth and salidroside accumulation. Sucrose (> 100 g l-1) had a positive effect on salidroside synthesis, which was not due to an osmotic effect of the medium. The medium containing 40 g l-1 sucrose, 1.5 μM naphthaleneacetic acid and 15 μM 6-benzylaminopurine yielded ca. 120 mg l-1 salidroside after 24 days of culture.
TL;DR: Based on the nature of the carbon-halogen bond to be broken and the halogen atoms to be replaced in photohydrolysis reactions, the method of factor analysis and cluster analysis was used to group 45 substituted aromatic halides into three clusters.
TL;DR: A multi-frontal parallel algorithm is developed to solve fully coupled heat, water and gas flow in deformable porous media using the modified e⁄ective stress concept together with the capillary pressure relationship and takes phase change and latent heat transfer into account.
Abstract: In this paper, a multi-frontal parallel algorithm is developed to solve fully coupled heat, water and gas flow in deformable porous media. The mathematical model makes use of the modified e⁄ective stress concept together with the capillary pressure relationship and takes phase change and latent heat transfer into account. The chosen macroscopic field variables are displacement, capillary pressure, gas pressure and temperature. The parallel program is developed on a cluster of workstations. The PVM (Parallel Virtual Machine) system is used to handle communications among networked workstations. The multi-frontal method has advantages such as numbering of the finite element mesh in an arbitrary manner, simple programming organization, smaller core requirements and shorter computation times. An implementation of this parallel method on workstations is discussed. The speedup and eƒciency of this method is demonstrated and compared with a general domain decomposition method based on band matrix methods by numerical examples. ( 1998 John Wiley & Sons, Ltd.
TL;DR: A deep analysis exposes that the approximate eigenvectors or Ritz vectors obtained by general orthogonal projection methods including generalized block methods may fail to converge theoretically for a general unsymmetric matrix A even if corresponding approximate Eigenvalues or Ritzer values do.
Abstract: Generalized block Lanczos methods for large unsymmetric eigenproblems are presented, which contain the block Arnoldi method, and the block Arnoldi algorithms are developed The convergence of this class of methods is analyzed when the matrix A is diagonalizable Upper bounds for the distances between normalized eigenvectors and a block Krylov subspace are derived, and a priori theoretical error bounds for Ritz elements are established Compared with generalized Lanczos methods, which contain Arnoldi's method, the convergence analysis shows that the block versions have two advantages: First, they may be efficient for computing clustered eigenvalues; second, they are able to solve multiple eigenproblems However, a deep analysis exposes that the approximate eigenvectors or Ritz vectors obtained by general orthogonal projection methods including generalized block methods may fail to converge theoretically for a general unsymmetric matrix A even if corresponding approximate eigenvalues or Ritz values do, since the convergence of Ritz vectors needs more sufficient conditions, which may be impossible to satisfy theoretically, than that of Ritz values does The issues of how to restart and to solve multiple eigenproblems are addressed, and some numerical examples are reported to confirm the theoretical analysis
TL;DR: In this article, high energy ball milling was applied to the Pb-Al immiscible binary system by using the method of high energy balls milling to obtain nanocrystalline microstructure.
Abstract: In the present work, mechanical alloying has been applied to the Pb-Al immiscible binary system by using the method of high energy ball milling. The microstructural features of the milled powder, such as grain size, lattice constant and morphology of phases have been studied by X-ray diffraction, analytical transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Besides, energy dispersive spectroscopy was used to analysis chemical composition of phases presented after milling. Differential Scanning Calorimetry measurement was also made on the milled Pb-Al powder. The results show that homogenous blending of Pb and Al can be easily achieved by high energy ball milling in spite of their mutual immiscibility and large difference in density. The obtained alloy exhibits nanocrystalline microstructure. Further more, the experiment result implies the formation of supersaturated solid solution in immiscible Pb-Al system by high energy ball milling.