Showing papers by "Harbin Institute of Technology published in 1999"
Stony Brook University1, University of California, Davis2, Lawrence Berkeley National Laboratory3, Columbia University4, Ohio State University5, Brookhaven National Laboratory6, Purdue University7, Harbin Institute of Technology8, Kent State University9, Carnegie Mellon University10, Saint Mary's College of California11, University of Auckland12, École des mines de Nantes13
TL;DR: In this article, the proton elliptic flow excitation function for the Au + Au system spanning the beam energy range 2 -8 AGeV was measured and compared with calculations from a relativistic Boltzmann-equation.
Abstract: We have measured the proton elliptic flow excitation function for the Au + Au system spanning the beam energy range 2 -- 8 AGeV. The excitation function shows a transition from negative to positive elliptic flow at a beam energy, $E_{tr} \sim$ 4 AGeV. Detailed comparisons with calculations from a relativistic Boltzmann-equation are presented. The comparisons suggest a softening of the nuclear equation of state (EOS) from a stiff form (K \sim 380 MeV) at low beam energies (E_{Beam} \le 2 AGeV) to a softer form (K \sim 210 MeV) at higher energies (E_{Beam} \ge $ 4 AGeV) where the calculated baryon density $ \rho \sim 4 \rho_0$.
175 citations
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
10 May 1999
TL;DR: In this paper, wall-climbing robots of two different absorption schemes were introduced: one with single suction cup and the other with permanent magnetic crawlers for cleaning both the ceramic tile and glass surfaces of high-rise buildings.
Abstract: In this paper we introduce wall-climbing robots of two different absorption schemes: one with single suction cup and the other with permanent magnetic crawlers. The former adopts an omnidirectional vehicle and can perform remote-control inspection of nuclear storage tanks. Moreover, it is further developed for cleaning both the ceramic tile and glass surfaces of high-rise buildings. The latter consists of two types of robots: one is for maintenance automation of storage tanks in petrochemical enterprises, which can perform operations of sand-blasting, spray-painting and inspection; and the other is for monitoring the boiler wall water tubing.
117 citations
TL;DR: In this paper, the design and the characteristics of a new piezodriven precision micropositioning stage utilizing flexure hinges are discussed, and a series of formulae for the static and dynamic behaviour of the stage are derived.
Abstract: A precision micropositioning system with a high displacement resolution and wide motion range has been required for industrialized applications for a long time. This paper discusses the design and the characteristics of a new piezodriven precision micropositioning stage utilizing flexure hinges. Two-grade amplifying and a monolithic symmetrical mechanism are adopted in the design. An analytical model is presented and a series of formulae for the static and dynamic behaviour of the stage are derived. Based on the theoretical analysis, the optimum design schema is put forward. The experimental demonstration to study the performance of the stage is described, and the method for reducing nonlinearity errors is proposed. The experimental results are in close agreement with those predicted by the theoretical analysis.
115 citations
TL;DR: A tool breakage monitoring system based on DWT of an acoustic emission and an electric feed current signal using an effective algorithm is discussed and the experiment results show overall 98.5% reliability and the good real-time monitoring capability of the proposed methodology for detecting tool breakages during drilling.
Abstract: Detection of tool breakage is of vital importance in automated manufacturing. Various methods have been attempted, and it is considered that the use of discrete wavelet transform (DWT), which is much more efficient and just as accurate wavelet analysis, may provide a realistic solution to the detection of tool breakage in operation. The DWT uses an analyzing wavelet function which is localized in both time and frequency to detect a small change in the input signals. In addition, it requires less computation than Fast Fourier Transformation (FFT). This paper discusses a tool breakage monitoring system based on DWT of an acoustic emission (AE) and an electric feed current signal using an effective algorithm. The experiment results show overall 98.5% reliability and the good real-time monitoring capability of the proposed methodology for detecting tool breakage during drilling.
104 citations
TL;DR: In this article, the wear mechanisms and their transitions of 52100 and 1080 steels with various microstructures in dry sliding were systematically studied by wear testing and SEM observations of worn surfaces and wear particles.
94 citations
TL;DR: In this paper, the behavior of carbon deposition on Ni/Al 2 O 3 catalysts promoted by CeO 2, MgO and CeO2-MgO in CO 2 reforming methane to synthesis gas was investigated using TG, CO 2 -TPD, TPSR, TPR and other techniques.
Abstract: The behavior of carbon deposition on the Ni/Al 2 O 3 catalysts promoted by CeO 2 , MgO and CeO 2 –MgO in CO 2 reforming methane to synthesis gas was investigated using TG, CO 2 -TPD, TPSR, TPR and other techniques. The results indicate that the resistance to carbon deposition of catalysts promoted by CeO 2 and MgO is improved. It is found that the promoter MgO is the most effective one in the suppression of CH 4 dehydrogenation. The CeO 2 promoted catalysts can lower the temperature of the reforming reaction of CH 4 with CO 2 and improve the resistance to carbon deposition. The enlarged experiment result shows that the activity promoted by CeO 2 and MgO keeps well over 900 h. This indicates that the catalyst has not only high activity and selectivity, but also high stability and good resistance to carbon deposition.
90 citations
TL;DR: In this article, the wear behavior of steels 52100 and 1080 with different microstructures in dry sliding were systematically studied and the results showed that in the region of mild wear there was no obvious difference in wear volume for the various micro-structures.
88 citations
TL;DR: A new method of tool wear detection with cutting conditions and detected signals is presented, which includes the model of wavelet fuzzy neural network with acoustic emission and the models of fuzzy classification with motor current.
Abstract: In the paper, a new method of tool wear detection with cutting conditions and detected signals is presented, which includes the model of wavelet fuzzy neural network with acoustic emission (AE) and the model of fuzzy classification with motor current. The results of tool wear estimated by cutting conditions and detected signals (spindle motor current, feed motor current and AE) are fused by fuzzy inference. Experimental results show that the method of tool wear detection is reliable and practical.
84 citations
TL;DR: In this article, tensile tests at various temperatures are employed to investigate the mechanical behavior of Ti-Ni-Hf alloy with different matrix structures, from full martensite to full parent phase structure, with the corresponding deformation mechanism discussed.
80 citations
TL;DR: In this article, field equations of the non-local elasticity were solved to determine the state of stress in a Griffith crack subject to the anti-plane shear, and a set of dual-integral equations was solved using Schmidts method.
TL;DR: In this article, a tool breakage detection of small diameter drills by monitoring the AC servo motor current is presented, where the continuous wavelet transform was used to decompose the spindle AC servos motor current signal, and the discrete wavelet transformer was used for decomposing the feed AC servoS motor signal in time-frequency domain.
Abstract: This paper presents on-line tool breakage detection of small diameter drills by monitoring the AC servo motor current. The continuous wavelet transform was used to decompose the spindle AC servo motor current signal and the discrete wavelet transform was used to decompose the feed AC servo motor current signal in time–frequency domain. The tool breakage features were extracted from the decomposed signals. Experimental results show that the proposed monitoring system possessed an excellent on-line capability; in addition, it had a low sensitivity to change of the cutting conditions and high success rate for the detection of the breakage of small diameter drills.
TL;DR: In this article, the typical microstructures and the phases present in the coatings were investigated using scanning and transmission electron microscopies, and it was found that WC particulates partially dissolved on the surface of the particulates in the melt pool during the laser cladding.
Abstract: 30 vol.% WCp reinforced Ni–Cr–B–Si–C composite coatings were deposited on AISI1045 steel by laser cladding. The typical microstructures and the phases present in the coatings were investigated using scanning and transmission electron microscopies. It was found that WC particulates partially dissolved on the surface of the particulates in the melt pool during the laser cladding. Upon cooling, the bar-like α-W 2 C, blocky β-W 2 C and quadrilateral η 1 M 6 -C carbides were formed from the laser-generated melt pool, and the final eutectic reaction resulted in the formation of γ-Ni+Ni 3 B lamellar eutectic. The rapidly solidified microstructure of the laser melt is composed of γ-Ni+Ni 3 B lamellar eutectic in which bar-like α-W 2 C, blocky β-W 2 C and quadrilateral η 1 -M 6 C carbides are distributed. The coating thus consists not only of thermodynamically stable, but also of metastable phases. The presence of the latter can be attributed to the nonequilibrium solidification arisen from the high cooling rates involved during the processing.
TL;DR: In this paper, the authors developed a method for demulsification of emulsified water-in-oil droplets using wetting coalescence materials, which achieved an efficiency of 97% when the conditions are optimized.
TL;DR: In this paper, an electroless nickel plating (EN) bath was recovered by electrodialysis and the process was characterized in terms of limiting current density, membrane fouling, removal of main components, and current efficiency.
TL;DR: In this article, the deformation mechanism of conventional spinning is studied through experiment and analysis, and three types of roller trace have been applied: straight line, concave curve and convex curve.
TL;DR: This paper deals with a learning problem appearing in the process of simplifying fuzzy rules, proves that the solution optimization is NP-hard and gives its heuristic algorithm, regarded as a new, fuzzy learning algorithm.
TL;DR: In this paper, the wear micromechanisms of various microstructures in 52100 and 1080 steels were studied, using scanning electron microscopy, transmission electron microscope, X-ray diffraction and microhardness indentation.
TL;DR: In this paper, the problem of determining the stress field in an elastic strip of finite width when the uniform tension is applied to the faces of two collinear symmetrical cracks situated within it is considered.
TL;DR: In this article, a continuous-wave CO 2 laser was used to clad a TiC particle-reinforced Ni-Cr-B-Si-C composite coating on an AISI 1045 steel substrate.
Abstract: A continuous-wave CO 2 laser was used to clad a TiC particle-reinforced Ni–Cr–B–Si–C composite coating on to an AISI 1045 steel substrate. The microstructure of the clad was investigated by means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that partial dissolution of the TiC occurred on melting, and epitaxial growth of the remaining particles takes place by the precipitation of TiC upon cooling. This epitaxial TiC layer has an additional alloying effect by using elements such as chromium and silicon from the matrix. The pushing of TiC particles (TiC p ) by the solidification front causes them to be unequally spaced. Besides the TiC p , the microstructure of the coating is a mixture of feather-like colonies and a small amount of (γ-Ni+M 23 C 6 ) eutectic. The feather-like colonies consist of CrB laths distributed in a γ-Ni solid solution and grow radially from the TiC particles because of the large difference between the thermal properties of TiC and the Ni–Cr–B–Si–C matrix alloy.
TL;DR: In this article, the authors derived the radiative transfer coefficient (RTC) under specular reflection in an absorbing, emitting and isotropic scattering parallel slab, considering both multi-reflection and multi-scattering in the derivation.
TL;DR: In this paper, the cold-drawing and rotary-forging precision forming technology of pin parts used in locomotives and rail carriages is introduced, and the determination of the drawing loads and the rotary forging loads, and deformation mechanism and product quality are discussed.
TL;DR: With the development of tire mechanics and computer technology, tire deformation, rolling resistance, and temperature distribution under rolling conditions may be predicted accurately as mentioned in this paper, but this is not the case for all vehicles.
Abstract: With the development of tire mechanics and computer technology, tire deformation, rolling resistance, and temperature distribution under rolling conditions may be predicted accurately thro...
TL;DR: In this paper, the effects of heat treatment on the microstructure, microhardness and resistance to erosion of laser surface-clad Ni alloy on a 0.2% C martensitic stainless steel were investigated by means of scanning electron microscopy, X-ray diffraction, energy dispersive Xray analysis, micro-hardness testing and erosion testing.
Abstract: The effects of heat treatment on the microstructure, microhardness and resistance to erosion of laser surface-clad Ni alloy on a 0.2% C martensitic stainless steel were investigated by means of scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, microhardness testing and erosion testing. The hardness of the stainless steel increased from 230 HV to 500–700 HV on applying a laser surface-clad Ni-base alloy, and heat treatment enabled the microhardness of the clad layer to be further increased to 850–1120 HV. Under the conditions of a water solution with a quartz sand slurry containing H 2 SO 4 and NaCl, 7 m s −1 nominal test speed, and 45° test angle, the erosion properties of the stainless steel were improved by the laser-clad Ni-base alloy. After applying heat treatment to the clad layer, a further improvement in erosion resistance was achieved. The erosion rates of the surface alloy layer with and without heat treatment were reduced by factors of about 9 and 2 as against that of the stainless steel substrate, respectively. It is suggested that the marked improvement in erosion is closely related to the cladding layer being strengthened owing to the increase of coating hardness, formation of a more ductile structure, and precipitation of M 23 B 6 borides produced by heat treatment.
TL;DR: In this article, the scattering of harmonic shear waves by two collinear symmetric cracks is studied using the non-local theory, and the Fourier transform is applied and a mixed boundary value problem is formulated.
Abstract: In this paper, the scattering of harmonic shear waves by two collinear symmetric cracks is studied using the non-local theory. The Fourier transform is applied and a mixed boundary value problem is formulated. Then, a set of triple integral equations is solved using a new method, namely Schmidt's method. This method is simple and convenient for solving this problem. Contrary to the classical elasticity solution, it is found that no stress singularity is present at the crack tip. The non-local dynamic elastic solutions yield a finite hoop stress at the crack tip, thus allowing for a fracture criterion based on the maximum dynamic stress hypothesis. The finite hoop stress at the crack tip depends on the crack length.
TL;DR: In this paper, the authors have calculated the stresses and bursting pressure of filament wound solid-rocket motor cases which are a kind of composite pressure vessel, and a stiffness-degradation model was introduced to the failure analysis.
TL;DR: In this article, the authors used the discrete ordinates method to develop a solution to an inverse radiation problem of temperature field in rectangular furnaces, assuming that, with the exception of the inhomogeneous temperature field, all aspects of the radiation transport problem are known.
TL;DR: In this paper, a theoretical steady-state rate-equation analysis is presented for investigating the critical conditions for the conversion from reverse saturable absorption (RSA) to saturated absorption (SSA).
TL;DR: The embedding j (Wu and Zhang) is used, from noncompact fuzzy number space E into the concrete Frechet space C (0,1) × C ( 0,1] , to discuss some properties of the E -valued functions such as measurability, integrability, etc.
TL;DR: In this article, an alias-free exponential time-frequency distribution is introduced, which combines features of distributions of the Cohen class and the generalized Wigner distribution, and is shown to be well suited to the analysis of signals with transient components.
Abstract: Bilinear time-frequency distributions, which provide simultaneous high resolution in both time and frequency domains, offer advantages for the analysis of vibration signals where the harmonic components and sidebands may be closely spaced. However, the Choi-Williams exponential distribution is found to be unsuitable, and aliasing produced by distributions of the Cohen class also causes problems. An alias-free exponential time-frequency distribution is introduced, which combines features of distributions of the Cohen class and the generalized Wigner distribution. The new distribution is shown to be well suited to the analysis of signals with transient components.