Showing papers by "Southeast University published in 1999"
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01 Nov 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a functionally-graded biomaterial (FGM) in a hydroxyapatite (HA)-Ti system was developed by an optimized powder metallurgical process and investigated by microstructural analysis and mechanical tests.
Abstract: A functionally-graded biomaterial (FGM) in a hydroxyapatite (HA)–Ti system was developed by an optimized powder metallurgical process and investigated by microstructural analysis and mechanical tests. The constituents in sintered HA–Ti FGM distribute gradually with the variation in chemical composition, eliminating the macroscopic interfaces, such as that in HA–Ti direct joint. Partial decomposition of HA phase was found in interlayers of the FGM due to the co-existence of Ti during sintering. Mechanical properties in HA–Ti FGM also exhibit gradient distributions. Vickers hardness and Young’s modulus are strongly affected by the porosity. However, bending strength and fracture toughness increase remarkably with the rise of Ti content, especially in the Ti-rich region. Maximum strength and toughness (971.96 Mpa and 29.691 MPam 1/2 respectively) were reached in the pure Ti layer, which are far higher than those of human bone. In addition, the strengthening and toughening mechanism was discussed. In summary, HA–Ti FGM is a promising biomaterial for use as a hard-tissue replacement implant, considering its mechanical behaviors.
157 citations
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TL;DR: In this paper, the impact and fatigue performance of high-strength concrete (HSC), silica fume high strength concrete (SIFUHSC) and steel fiber SFRHSC under the action of repeated dynamic loading were investigated.
150 citations
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TL;DR: In this article, the authors present the damage of concrete and its dependence on different strength grades of concrete under the simultaneous action of load and freeze-thaw cycles, and analyzes the inhibiting effect of air entrainment and steel fibers on damage.
149 citations
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TL;DR: The scheme of routing based on a genetic algorithm (GA) is proposed after the analysis of related works and the QoS routing algorithms for unicast and multicast based on improved GA are described.
125 citations
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TL;DR: In this article, an approximate analysis for the propagation of Bessel, Bessel-Gauss, and Gaussian beams with a finite aperture is derived, based on the fact that the circ function can be expanded into an approximate sum of complex Gaussian functions, so that these three beams are typically expressed as a combination of a set of infinite-aperture Bessel Gauss beams.
Abstract: An approximate analysis is derived for the propagation of Bessel, Bessel–Gauss, and Gaussian beams with a finite aperture. This treatment is based on the fact that the circ function can be expanded into an approximate sum of complex Gaussian functions, so that these three beams are typically expressed as a combination of a set of infinite-aperture Bessel–Gauss beams. Correspondingly, the evaluation of the diffracted field distribution of the beams is reduced to the summation of Bessel–Gauss functions. From analytical results, the present approach provides a good description of the diffracted beams in the region far (greater than a factor of the Fresnel distance) from the aperture. A possible extension of this method to other apertured beams is also discussed.
115 citations
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TL;DR: In this paper, the authors presented results of ten high-strength reinforced concrete beams and steel fiber-reinforced high strength concrete beams, with steel fiber content of 1% by volume.
Abstract: This paper presents research results of ten high-strength reinforced concrete beams and steel fiber-reinforced high strength concrete beams, with steel fiber content of 1% by volume. The enlarged ends of mild carbon steel fibers with three different dimensions were selected. This research shows that the flexural rigidity before yield stage and the displacement at 80% ultimate load in the descending curve are improved, and crack number and length at comparable loads is reduced after the addition of steel fibers. The descending part of the load-displacement curve of the concrete beams without steel fibers is much steeper than that with steel fibers, which shows that the addition of steel fibers makes the high strength concrete beams more ductile.
104 citations
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TL;DR: In this paper, a cold standby repairable system consisting of two identical components and one repairman is studied, and an optimal replacement policy is proposed to maximize the long-run expected reward per unit time.
82 citations
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TL;DR: In this article, the W-4f core level of WO3 film at different levels of coloration has been investigated using XPS, showing that the W4f peaks become broader after coloration.
67 citations
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26 Feb 1999-Microsystem Technologies-micro-and Nanosystems-information Storage and Processing Systems
TL;DR: In this paper, an electrothermally and laterally driven microactuator is analyzed based on the asymmetrical thermal expansion of the microstructure with different lengths of two beams.
Abstract: An electro-thermally and laterally driven microactuator is analytically examined which is based on the asymmetrical thermal expansion of the microstructure with different lengths of two beams. Deflection of the microactuator is modeled by the structural analysis. Analytical results are compared with the finite element model (FEM) results, and show a reasonable agreement. The magnitude of the deflection depends strongly on the geometry of the microactuator. The analytical model allows one to optimize efficiently the laterally driven thermal actuators.
65 citations
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TL;DR: A stochastic inverse technique based on a genetic algorithm to invert particle-size distribution from angular light-scattering data is developed and can be successfully applied to inverse problems with high stability in the presence of random noise and low susceptibility to the shape of distributions.
Abstract: A stochastic inverse technique based on a genetic algorithm (GA) to invert particle-size distribution from angular light-scattering data is developed. This inverse technique is independent of any given a priori information of particle-size distribution. Numerical tests show that this technique can be successfully applied to inverse problems with high stability in the presence of random noise and low susceptibility to the shape of distributions. It has also been shown that the GA-based inverse technique is more efficient in use of computing time than the inverse Monte Carlo method recently developed by Ligon et al. [Appl. Opt.35, 4297 (1996)].
58 citations
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TL;DR: The dielectric properties of human red cells are strongly affected by the applied electric field, especially the frequency, and patterns formed by DEP force are identical with the distribution of the electric field.
Abstract: The dielectric properties of human red cells are strongly affected by the applied electric field, especially the frequency. Under the high frequency, the cells are acted on by positive dielectrophoresis (DEP) force and move to the tip region of the interdigitated electrode where the electric field is strongest. The cells are acted on by negative DEP force and aggregated in the "bay" zone between the neighboring electrode castellation tips and the surface of the electrodes. The patterns formed by DEP force are identical with the distribution of the electric field.
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TL;DR: In this article, the authors measured supercooled liquid region (ΔTx), tensile fracture strength (σf), and Vickers hardness (Hv) of Fe-B-Zr-Nb amorphous alloys.
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TL;DR: In this paper, microwave freeze drying characteristics of unsaturated raw beef were studied experimentally for various levels of electric field strength, vacuum pressure, sample thickness and initial saturation, and the results showed that drying time is proportional to initial saturation and inversely proportional to the electric fields strength and sample thickness.
Abstract: Microwave freeze drying characteristics of unsaturated raw beef were studied experimentally for various levels of electric field strength, vacuum pressure, sample thickness and initial saturation. The results show that drying time is proportional to initial saturation and inversely proportional to the electric field strength and sample thickness. The effect of vacuum pressure on drying time is negligible. Some advantages of microwave freeze-drying over conventional freeze drying with radiant heating are pointed out
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TL;DR: Compared with existing methods, the proposed approach is superior in that it explains the curve, instead of simple labeling, and it performs based on human perception.
Abstract: The problem of corner detection on planar curves is examined based on human perception of local graphic features. First, a set of fuzzy patterns of contour points are established. Then, corner detection is characterized as a fuzzy classification problem that contains three stages: evaluation, classification, and location. Compared with existing methods, the proposed approach is superior in that it explains the curve, instead of simple labeling, and it performs based on human perception. Experimental results on shapes of various complexities are presented. The performance with respect to noise is also addressed.
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TL;DR: In this paper, the wear behavior of in situ aluminum-based composites fabricated from TiO2-Al-B and Al2O3/Al composites was studied by using a pin-on-disk test at room temperature.
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01 Jun 1999TL;DR: A convenient and efficient method for the site-directed incorporation of aldehydes generated on the oligosaccharide moieties at the C-terminal of immunoglobulin (IgG) using NaIO4 oxidation reaction is explored.
Abstract: A convenient and efficient method for the site-directed incorporation of aldehydes generated on the oligosaccharide moieties at the C-terminal of immunoglobulin (IgG) using NaIO4oxidation reaction is explored as a means of ensuring controlled assembly of IgG antibodies onto aminopropyltriethoxylsilane (APTES) derivatized silicon wafer surfaces. The orientation and antigen binding capacity (AgBC) of site-directly assembled IgG antibodies on derivatized surfaces were investigated using atomic force microscopy (AFM) and enzyme immunoassay (EIA), respectively. A major difference in preferential orientation is observed when the incubation of derivatized surfaces with oxidized IgG molecules is compared in two different kinds of buffer solutions. We obtained the stable and homogeneous IgG layer without loss of the AgBC on the APTES derivatized surface using the controlled incubation condition.
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TL;DR: In order to reduce the computation time of entropy function, a fast recurring algorithm for 2-D entropic thresholding method is presented and the experimental results show that the processing time to obtain the threshold vector from 2- D histogram is reduced from 30 to 0.15 s.
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TL;DR: In this article, the authors attempt to fabricate hybrid composites composed of Al-4 wt pct Cu matrix, boron nitride (BN), and SiC particulates.
Abstract: During the last decade, aluminum alloys discontinuously reinforced with ceramic particulates have received increasing attention for various high-performance applications in automotive, aerospace, and transportation industries due to their high strength-to-weight ratio and superior wear resistance. Particulate-reinforced MMCs can be produced by ingot metallurgy (IM) and powder metallurgy (PM) processing routes. The advantages of PM over IM processing in the fabrication of MMCs include near-net-shape fabrication, lower processing temperatures, and improved microstructural homogeneity. In this study, the authors attempt to fabricate hybrid composites composed of Al-4 wt pct Cu matrix, boron nitride (BN), and SiC particulates. The BN particulates are selected because of their low density (2.3 g/cm{sup 3}) and self-lubricant property. It is expected that BN additions can further substantially improve the wear performance of SiC/Al-4 pct Cu composites.
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TL;DR: In this paper, the blow-up properties of solutions to semilinear heat equation with nonlinear boundary conditions were investigated and the necessary and sufficient conditions for the solution to have a finite time blowup and exact blowup rates were established.
Abstract: This paper deals with the blow-up properties of solutions to semilinear heat equation \(u_t-u_{xx}=u^p \text{ in }(0,1)\times(0,T)\) with the nonlinear boundary conditions \(u_x(0,t)=0,u_x(1,t)=u^q\text{ on }[0,T)\). The necessary and sufficient conditions for the solution to have a finite time blow-up and the exact blow-up rates are established. It is also proved that the blow-up will occur only at the boundary x = 1.
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TL;DR: The procedure of getting the marginal evaluation for each objective and aggregating them synthetically into a global evaluation is presented in this paper and various objectives are synthetically considered by the fuzzy systematic technique instead of the frequently employed weighted-average method.
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TL;DR: In this article, a rate equation model for the Bi-EDFA was developed to calculate the signal gain, pump absorption and output noise spectrum, and the effects of numbers of signals, pumps of arbitrary direction, amplified spontaneous emission (ASE) and inherent loss were taken into account.
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TL;DR: In this article, the existence and nonexistence of global positive solutions of quasilinear reaction diffusion systems with nonlinear boundary conditions were investigated. Necessary and sufficient conditions on the global existence of all positive solutions were obtained.
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TL;DR: In this article, a mesostructured Titanium Dioxide (Ti-TMS) was firstly synthesized with different length chain alkylphosphate and alkylamine surfactants as templates, which can be successfully removed by reflux in the EtOH/H2O/KOH solution instead of calcination.
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TL;DR: The method proposed in this paper attacks such problems from the dual side, alternatively arranging computations of the simplex method using the QR factorization and a new crash heuristic, having a clear geometrical meaning towards an optimal basis, is developed to provide “good” input.
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TL;DR: A Geographic Information System (GIS) based map overlay method is developed to analyze comprehensively the environmental vulnerability around road and its impact on the environment, which is adapted for the comprehensive assessment of road environmental impact and the optimal selection of road alignments.
Abstract: By integrating the merits of the map overlay method and the matrix method, a Geographic Information System (GIS) based map overlay method is developed to analyze comprehensively the environmental vulnerability around road and its impact on the environment, which is adapted for the comprehensive assessment of road environmental impact and the optimal selection of road alignments. The assessment process of the GIS based map overlay method and a detailed case study are presented, which include deciding the system structure and weights of assessment factors, making environmental vulnerability grade maps, calculating the respective coefficients of road impact extent for each factor, and evaluating the alternative alignments comprehensively to obtain the best one.
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15 Jun 1999-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a reaction-processed Al-Cu/α-Al2O3 (p) composites were fabricated via the chemical reactions between copper oxide (CuO) and aluminium.
Abstract: Reaction-processed Al-Cu/α-Al2O3 (p) composites, in which α-Al2O3 particles are distributed homogeneously, were fabricated via the chemical reactions between copper oxide (CuO) and aluminium. From the examination of the wear properties of the composites, it is proposed that the wear resistance of the composites is better than that of the corresponding matrix alloy, since α-Al2O3 particles play the main role in taking the external load and there is good interfacial cohesion between α-Al2O3 particles and the alloy matrix.
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TL;DR: The proposed generalized fast computational algorithm for the n-dimensional discrete cosine transform of length N=2/sup m/ (m/spl ges/2) is proved and its efficiency is evaluated theoretically.
Abstract: In this paper, a generalized fast computational algorithm for the n-dimensional discrete cosine transform (DCT) of length N=2/sup m/ (m/spl ges/2) is presented. The developed algorithm is proved and its efficiency is evaluated theoretically. The theoretical results show that compared with the conventional method of computing the one-dimensional along n directions, the number of multiplications needed by our algorithm is only 1/n of that required by the conventional method; for the total number of additions, the latter is a bit more when N/spl les/8 and much fewer when N/spl ges/16 than the former. To validate the proposed algorithm, we take the case when n=3 as an example and apply it to motion-picture coding. The results show that our method is superior to MPEG-2 in speed and coding performance. The algorithm is clearly described and it is easy to make a computer program for implementation.
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TL;DR: In this paper, the analytical soliton solutions to some physical models were found by using special truncated expansions, and they were shown to be the same as the analytical solution to the soliton problem.
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TL;DR: In this article, a new concept of agile concurrent engineering (ACE) characterized by the agile teams is presented, which is more applicable to the product development in firms, especially in medium-sized or small companies.
Abstract: On the basis of analyzing the drawbacks of the existing concurrent engineering (CE), a new concept of agile concurrent engineering (ACE) characterized by the agile teams is presented. The organization method of the agile teams is discussed. The implementation and quantitative process modeling problems of ACE are dealt with. Contrasted with the existent CE, ACE puts the problems of resource sharing into special consideration. Its realization requires as little reform of the current organizational structures of enterprises as possible. ACE is more applicable to the product development in firms, especially in medium‐sized or small companies.