Showing papers by "Harbin Institute of Technology published in 2000"
TL;DR: In this article, the authors present a review of the extensive research in the field of ceramic rolling element bearings that has been carried out over the past decade or so and show that hot isostatically pressed silicon nitride (HIPed Si 3N4), has emerged as an extremely promising material for fabricating high performance all-ceramic or hybrid steel/ceramic rolling contact bearings.
192 citations
TL;DR: A new image encryption algorithm based on a generalized fractional Fourier transform, to which it is referred as a multifractional Fouriers transform, is proposed.
Abstract: We propose a new image encryption algorithm based on a generalized fractional Fourier transform, to which we refer as a multifractional Fourier transform. We encrypt the input image simply by performing the multifractional Fourier transform with two keys. Numerical simulation results are given to verify the algorithm, and an optical implementation setup is also suggested.
182 citations
TL;DR: In this article, the impact crushing behavior and energy absorption efficiency of glass/epoxy composite externally wrapped circular metal tubes have been studied and the predicted instantaneous velocity and displacement formulae are presented and compared with experimental results.
179 citations
TL;DR: In this article, the microstructure and compressive mechanical properties of the in-situ titanium matrix composites are examined using four reactive systems, namely Ti-B, Ti-TiB{sub 2}, Ti-Bi{sub 4}C and Ti-BN, and the objective of this work is to assess which system can produce in-Situ titanium composites with a higher mechanical strength.
170 citations
TL;DR: This paper points out the inherent defect of the likes of Fuzzy ID3, presents two optimization principles of fuzzy decision trees, proves that the algorithm complexity of constructing a kind of minimum fuzzy decision tree is NP-hard, and gives a new algorithm which is applied to three practical problems.
158 citations
TL;DR: In this article, two typical high-temperature dielectric materials, fused silica and BN, have been used to form a composite with an attempt to overcome their own drawbacks.
Abstract: Two typical high-temperature dielectric materials, fused silica and BN, have been used to form a composite with an attempt to overcome their own drawbacks. In the resultant BN–SiO 2 composites, BN platelike grains were preferentially orientated by hot pressing and homogeneously distributed in the fused silica matrix. An evident co-operative enhancement has been achieved by the combination of the constituents. The sinterability and the thermal shock resistance of the BN materials were increased and the ablation surface temperature was decreased by the involvement of the fused silica. On the other hand, the strength, fracture toughness, and flame ablation resistance of the fused silica were increased due to the addition of BN. Furthermore, an amorphous Si–B–O–N structure was identified in the surface layer of the ablated composites, to which attention should be further paid in the development of new elevated temperature dielectric materials.
148 citations
TL;DR: The existence and uniqueness theorem is obtained for the Cauchy problem x 0 =f(t;x) ;x ( t 0)=x0, when f satises the generalized Lipschitz condition.
125 citations
Journal Article•
TL;DR: In this article, the necessarity and sufficiency condition of weakly sequential semicontinuity for variational integrals are obtained in the setting of Orlicz\|Sobolev space.
Abstract: In this paper, variational problems with nonpolynomial growth are studied by means of Orlicz space theory. The necessarity and sufficiency condition of weakly sequential semicontinuity for variational integrals are obtained in the setting of Orlicz\|Sobolev space, which generalizes the corresponding results for variational problems with polynomial growth.
123 citations
TL;DR: A method of embedding a gray-level digital watermark into an image by the stack filter threshold decomposition technique, which is decompounded into a series of binary digital images for implementing multiple watermarking.
Abstract: Digital watermarking has been presented in the literature as a technique to protect the copyright of multimedia data. But most of these literature concentrates on algorithms of embedding one-dimensional watermarks or two-dimensional binary digital watermarks. In this paper, a method of embedding a gray-level digital watermark into an image is proposed. By the stack filter threshold decomposition technique, a gray-level digital watermark is decompounded into a series of binary digital images for implementing multiple watermarking. The experimental results show that the proposed techniques are tolerant to reasonable image processing operations and the lossy compression techniques such as Joint Photographic Experts Group (JPEG).
116 citations
01 Aug 2000
TL;DR: Experimental results show that the proposed system can reliably detect tool conditions in drilling operations in real time and is viable for industrial applications.
Abstract: Wavelet transforms and fuzzy techniques are used to monitor tool breakage and wear conditions in real time according to the measured spindle and feed motor currents, respectively. First, continuous and discrete wavelet transforms are used to decompose the spindle and feed ac servo motor current signals to extract signal features so as to detect the breakage of drills successfully. Next, the models of the relationships between the current signals and the cutting parameters are established under different tool wear states. Subsequently, fuzzy classification methods are used to detect tool wear states based on the above models. Finally, the two methods above are integrated to establish an intelligent tool condition monitoring system for drilling operations. The monitoring system can detect tool breakage and tool wear conditions using very simple current sensors. Experimental results show that the proposed system can reliably detect tool conditions in drilling operations in real time and is viable for industrial applications.
115 citations
01 Jan 2000
TL;DR: The basic idea is to use (fuzzy) conjunctions and implications which are adjoint in the definition of dilations and erosions, respectively, which gives rise to a large class of morphological operators for grey-scale images.
Abstract: There exist several methods to extend binary morphology to grey-scale images. One of these methods is based on fuzzy logic and fuzzy set theory. Another approach starts from the complete lattice framework for morphology and the theory of adjunctions. In this paper, both approaches are combined. The basic idea is to use (fuzzy) conjunctions and implications which are adjoint in the definition of dilations and erosions, respectively. This gives rise to a large class of morphological operators for grey-scale images. It turns out that this class includes the often used grey-scale Minkowski addition and subtraction.
TL;DR: A digital image watermarking technique based on vector quantisation (VQ) is presented that uses codeword indices to carry the watermark information and simulation results prove the effectiveness of this technique.
Abstract: A digital image watermarking technique based on vector quantisation (VQ) is presented. This technique uses codeword indices to carry the watermark information. The technique is secret and efficient, and the watermarked image is robust to VQ compression with the same codebook. The simulation results prove the effectiveness of this technique.
TL;DR: The feed cutting force estimated with the aid of an inexpensive current sensor installed on the AC servomotor of a computerized numerical control tuning center is used to monitor tool wear condition.
Abstract: Tool wear condition monitoring has the potential to play a critical role in ensuring the dimensional accuracy of the workpiece and prevention of damage to cutting equipment. It could also help in automating cutting processes. In this paper, the feed cutting force estimated with the aid of an inexpensive current sensor installed on the AC servomotor of a computerized numerical control tuning center is used to monitor tool wear condition. To achieve this, the feed drive system is modeled, using neuro-fuzzy techniques, to provide the framework for estimating the feed cutting force based on the feed motor current measured. Functional dependence of the feed cutting force on tool wear and cutting parameters are then expressed in the form of a difference equation relating variation in the feed cutting force to tool wear rate. The computerized system automatically compares successive feed cutting force estimates and determines the onset of accelerated tool wear in order to issue a request for tool replacement. Experimental results show that the tool wear condition monitoring is effective and industrially applicable.
TL;DR: In this paper, a steady state model of a coal-fired circulating fluidized-bed boiler, based on hydrodynamics, heat transfer and combustion, is presented, which predicts the flue gas temperature, the chemical gas species (O 2, H 2 O, CO, CO 2 and SO 2 ) and char concentration distributions in both the axial and radial locations along the furnace including the bottom and upper portion.
TL;DR: A system designed for helping the deaf to communicate with others is presented and an algorithm based on geometrical analysis for the purpose of extracting invariant feature to signer position is presented.
Abstract: In this paper, a system designed for helping the deaf to communicate with others is presented. Some useful new ideas are proposed in design and implementation. An algorithm based on geometrical analysis for the purpose of extracting invariant feature to signer position is presented. An ANN–DP combined approach is employed for segmenting subwords automatically from the data stream of sign signals. To tackle the epenthesis movement problem, a DP-based method has been used to obtain the context-dependent models. Some techniques for system implementation are also given, including fast matching, frame prediction and search algorithms. The implemented system is able to recognize continuous large vocabulary Chinese Sign Language. Experiments show that proposed techniques in this paper are efficient on either recognition speed or recognition performance.
TL;DR: In this paper, the shape memory properties of a Ti 36 Ni 49 Hf 15 high temperature shape memory alloy (SMA) by bending tests were studied and the shape recovery ratio is constant at 92% when the deformation temperature is below 457 K, then rapidly decreases to zero above 590 K for the specimen deformed to 4.5%.
TL;DR: In this article, a new precipitate phase of the composition of (Ti0.4Hf0.6)Ni of a spindle-like shape with a habit plane of (100) P//(001)M and a long axis of [001]P//[1#10]M was observed.
TL;DR: In this article, the Fourier and Laplace transforms were used to analyze the dynamic and steady response of non-homogeneous composite materials with arbitrary varying material properties through thickness direction and the crack number.
TL;DR: In this paper, a new approach based on fuzzy comprehensive evaluation (FCE) and a genetic algorithm (GA) is presented to obtain a rational tolerance allocation for the parts, and an actual example is used to verify the feasibility of the above method; the computed result shows that the method can produce tolerance allocations economically and accurately.
Abstract: It is very important to know how to allocate tolerances economically for parts in a CAD/CAM system because this directly affects the machining costs.of the parts, A new approach based on fuzzy comprehensive evaluation (FCE) and a genetic algorithm (GA) is presented to obtain a rational tolerance allocation for the parts. First, the current methods for tolerance allocation are reviewed in detail. Then, FCE is used to evaluate the machinability of a part; a new optimal model, which can fully exploit DFA (design for assembly) and DFM (design for manufacturing), is established by combining the functional sensitivity factors and machinability factors of parts. A genetic algorithm (GA) is developed and used to optimise the above model. Finally, an actual example is used to verify the feasibility of the above method; the computed result shows that the method can produce tolerance allocations economically and accurately.
TL;DR: In this article, the optical properties of the two clusters were investigated first with an 8 ns pulsed laser at 532 nm and the results showed that they exhibit strong third-order NLO absorption effects (α2 1.5, 1.6, and 1.8 J cm−2 for 2 respectively).
Abstract: Reactions combining stoichiometric amounts of (Et4N)2MS4 (M = Mo or W) and CuCN (1∶4) in pyridine afforded interesting three-dimensional cluster polymers with open frameworks {[Et4N]2[MS4Cu4(CN)4]}n (M = Mo 1 or W 2). Crystal structure determination shows that the anionic MS4Cu4 units bridged by cyanide produce three-dimensional channels running down the crystallographic a axis. An alternative way to view this framework is in terms of the diamond structure, where C has alternately been replaced by a MS4Cu4 aggregate and C–C by two parallel cyanide bridging ligands. In these intersecting channels the shortest distances between Cu atoms along the b and c axes are 15.22 and 8.11 A respectively. Non-linear optical properties of the two clusters were investigated first with an 8 ns pulsed laser at 532 nm. These two clusters exhibit large optical limiting performance with limiting threshold values of 0.28 for 1, 0.15 J cm−2 for 2 respectively. Both compounds show strong third-order NLO absorption effects (α2 1.5 × 10−91, 1.6 × 10−9 m W−12) and self-focusing performance (n2 1.84 × 10−161, 1.22 × 10−16 m2 W−12) in 3.64 × 10−51 and 2.93 × 10−5 mol dm−32 DMF solution separately. The corresponding effective NLO susceptibilities χ(3) are 4.58 × 10−91 and 5.12 × 10−9 esu 2 while the corresponding hyperpolarizabilities (γ(1) = 1.15 × 10−29 and γ(2) = 1.26 × 10−29 esu) are also reported.
TL;DR: A vector-quantisation (VQ)-based watermarking method is presented which utilises the codebook expansion technique and is efficient, provides enhanced security and the watermarked image is robust against the effects of VQ compression.
Abstract: A vector-quantisation (VQ)-based watermarking method is presented which utilises the codebook expansion technique. This method is efficient, provides enhanced security and the watermarked image is robust against the effects of VQ compression. Moreover, the watermark extraction can be performed without the original image. Experimental results are presented which demonstrate the effectiveness of this algorithm.
31 Mar 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the combustion synthesis reaction was combined with quasi-isostatic pressing (QIP) technique to fabricate full density TiC-xNi composites in a single processing operation.
Abstract: The combustion synthesis reaction was combined with quasi-isostatic pressing (QIP) technique to fabricate full density TiC–xNi composites in a single processing operation. Combustion wave velocity and temperature of Ti–C–Ni were measured and the microstructure of the product was characterized by X-ray diffraction and scanning electron microscopy. With increasing Ni content in TiC–xNi, both the combustion wave velocity and temperature decrease. The Ni additive, mainly as a diluent and the binder of TiC grains in a matrix, formed a quasi-continuous phase enveloping spheroidal TiC particles and brought about a grain size decrease from 9 to 1 μm. TiC-20 wt% Ni cermet produced by the combustion synthesis/quasi-isostatic pressing process under 160 MPa for 20 s show near full density, high hardness and transverse rupture strength (1024.2 MPa).
TL;DR: Several necessary and sufficient conditions of ( H ) integrability for fuzzy-number-valued functions are given by means of abstract Henstock–Pettis integral theory.
TL;DR: In this paper, a hybrid learning method was used to map the relationship between the features of cutting vibration and the tool wear condition, and the experimental results showed that it can be used effectively to monitor the tool wearing in drilling.
Abstract: In automated manufacturing systems such as flexible manufacturing systems (FMSs), one of the most important issues is the detection of tool wear during the cutting process. This paper presents a hybrid learning method to map the relationship between the features of cutting vibration and the tool wear condition. The experimental results show that it can be used effectively to monitor the tool wear in drilling. First, a neural network model with fuzzy logic (FNN), responding to learning algorithms, is presented. It has many advantageous features, compared to a backpropagation neural network, such as less computation. Secondly, the experimental results show that the frequency distribution of vibration changes as the tool wears, so the r.m.s. of the different frequency bands measured indicates the tool wear condition. Finally, FNN is used to describe the relationship between the characteristics of vibration and the tool wear condition. The experimental results demonstrate the feasibility of using vibration signals to monitor the drill wear condition.
TL;DR: In this paper, a novel method of citric acid production from beet molasses was developed, in which an anion-exchange resin packed-column was connected to a fermenter for separation of Citric acid from fermentation broth.
29 Feb 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructure and linear superelasticity of cold-drawn TiNi alloy have been investigated using CTEM, HREM and in-situ transition electron microscopy observations and tensile tests.
Abstract: The microstructure and linear superelasticity of cold-drawn TiNi alloy have been investigated using CTEM, HREM and in-situ transition electron microscopy observations and tensile tests. The microstructural evolution procedure of the martensite variants with increasing degree of area reduction was found to be that the quantities of ( 11 1 ) Type I, (001) compound, (011) Type I and (111) Type I twinning plates increase gradually with decreasing the amount of the 〈011〉 Type II twinning bands. The corresponding dominant deformation mechanism changed from the coalescence of martensite variants to the reorientation of substructural bands inside martensite variants utilizing the most favorably oriented twin systems. The intrinsic reason for the linear superelasticity of the moderately cold-drawn TiNi alloy was confirmed to be associated with the appearance and disappearance of (001) microtwinning inside the 〈011〉 Type II substructural bands.
Posted Content•
TL;DR: This paper presents a comparison of modeling approaches for use with EMS modeling tools and proposes an approach that overcomes significant problems inherent in other approaches and leverages the productivity enhancement afforded by direct group access and still results in production of complete, integrated, high quality models.
Abstract: This paper presents results of an ongoing research effort to support effective user involvement during modeling and analysis meetings. Productivity and user participation of traditional group meetings have been limited by chauffeured facilitation and single-user tools. These tools have been designed to be used by analysts rather than for direct use by non-analyst users. Recently, electronic meeting systems (EMS) modeling tools that allow users to work in parallel to contribute directly during meetings have been developed. Such tools allow more domain experts to participate directly and productively during model development meetings than is possible using the traditional approach. Although previous research has demonstrated that EMS modeling tools may be used to develop some model content, little research had been done on collaborative facilitation methods that support these tools. This paper presents a comparison of modeling approaches for use with EMS modeling tools and proposes an approach that overcomes significant problems inherent in other approaches. It leverages the productivity enhancement afforded by direct group access and still results in production of complete, integrated, high quality models. This approach allows models to be developed two to four times faster than with traditional modeling support and yet avoids model ambiguities and inconsistencies.
TL;DR: In this article, a novel in situ reaction process-in-melt reaction method was developed, where spherical in shape and having an average diameter of about 0.93 µm, the distribution of TiB2 particles in the matrix was uniform.
Abstract: A novel in situ reaction process-in-melt reaction method was developed. TiB2 particles form in situ through the reaction of TiO2, H3BO3, and Na3AlF6 in an aluminum alloy melt. The results showed that the in situ TiB2 particles formed were spherical in shape and had an average diameter of about 0.93 µm. Moreover, the distribution of TiB2 particles in the matrix was uniform. The interface between the TiB2 particles and the matrix showed good cohesion. The tensile strength and the yield strength of the composite increase with increasing TiB2 content. When TiB2 particle content in the matrix was 10 vol pct, the tensile strength, yield strength, and elongation of Al-4.5Cu/TiB2 composite were 417 MPa, 317 MPa, and 3.3 pct, respectively.
15 Feb 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: A modified squeeze casting process, two-step squeeze casting, was proposed for fabrication of metal matrix composites (MMCs), and SiCw/ZK51A magnesium matrix composite was fabricated by this new technique as discussed by the authors.
Abstract: A modified squeeze casting process, two-step squeeze casting, was proposed for fabrication of metal matrix composites (MMCs), and SiCw/ZK51A magnesium matrix composite was fabricated by this new technique. The mechanical properties of the composite were investigated by means of tension test, and the microstructure and fracture surface were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. It was revealed that the two-step squeeze casting is an effective route for fabrication of magnesium matrix composites. The SiCw/ZK51A composite fabricated by this new technique possesses very high modulus and mechanical strength as compared with the unreinforced matrix alloy, with the increment in modulus and 0.2% offset yield strength of the composite being linearly proportional to the whisker volume fraction. The optimal casting temperature for the fabrication of the SiCw/ZK51A composite was found to be about 760°C. Furthermore, no evidence of any interfacial reaction was found in the SiCw/ZK51A composite, attesting that SiC whiskers are very stable reinforcements for magnesium matrix composites.
TL;DR: In this paper, balance laws and constitutive relations for a binary granular mixture with unequal granular temperature were derived and the complete pair distribution function for two colliding spheres was assumed as the product of the Maxwellian velocity distribution for each species.
Abstract: We derive balance laws and constitutive relations for a binary granular mixture with unequal granular temperature. The complete pair distribution function for two colliding spheres was assumed as the product of Maxwellian velocity distribution for each species. The constitutive relations together with the transport equations form a model for binary granular mixture with unequal granular temperature.