Showing papers by "Tsinghua University published in 2001"
TL;DR: In this paper, weekly PM2.5 samples were simultaneously collected at a residential (Tsinghua University) and a downtown (Chegongzhuang) site in Beijing from July 1999 through September 2000.
1,024 citations
TL;DR: This paper presents a novel single-patch wide-band microstrip antenna: the E-shaped patch antenna, where two parallel slots are incorporated into the patch of a micro Strip antenna to expand it bandwidth.
Abstract: This paper presents a novel single-patch wide-band microstrip antenna: the E-shaped patch antenna. Two parallel slots are incorporated into the patch of a microstrip antenna to expand it bandwidth. The wide-band mechanism is explored by investigating the behavior of the currents on the patch. The slot length, width, and position are optimized to achieve a wide bandwidth. The validity of the design concept is demonstrated by two examples with 21.2% and 32.3% bandwidths. Finally, a 30.3% E-shaped patch antenna, resonating at wireless communication frequencies of 1.9 and 2.4 GHz, is designed, fabricated and measured. The radiation pattern and directivity are also presented.
989 citations
TL;DR: Support Vector Machine has been introduced to predict the subcellular localization of proteins from their amino acid compositions and can be a complementary method to other existing methods based on sorting signals.
Abstract: Motivation: Subcellular localization is a key functional characteristic of proteins. A fully automatic and reliable prediction system for protein subcellular localization is needed, especially for the analysis of large-scale genome sequences. Results: In this paper, Support Vector Machine has been introduced to predict the subcellular localization of proteins from their amino acid compositions. The total prediction accuracies reach 91.4% for three subcellular locations in prokaryotic organisms and 79.4% for four locations in eukaryotic organisms. Predictions by our approach are robust to errors in the protein N-terminal sequences. This new approach provides superior prediction performance compared with existing algorithms based on amino acid composition and can be a complementary method to other existing methods based on sorting signals. Availability: A web server implementing the prediction method is available at http://www.bioinfo.tsinghua.edu.cn/ SubLoc/.
871 citations
TL;DR: The first use of the SVM approach to predict protein secondary structure is described here, with good performance of segment overlap accuracy and a useful "reliability index" for the predictions was developed.
574 citations
TL;DR: It is demonstrated that the use of the parametric channel model can effectively reduce the signal subspace dimension of the channel correlation matrix for the sparse multipath fading channels and, consequently, improve the channel estimation performance.
Abstract: We present an improved channel estimation algorithm for orthogonal frequency-division multiplexing mobile communication systems using pilot subcarriers. This algorithm is based on a parametric channel model where the channel frequency response is estimated using an L-path channel model. In the algorithm, we employ the ESPRIT (estimation of signal parameters by rotational invariance techniques) method to do the initial multipath time delays acquisition and propose an interpath interference cancellation delay locked loop to track the channel multipath time delays. With the multipath time delays information, a minimum mean square error estimator is derived to estimate the channel frequency response. It is demonstrated that the use of the parametric channel model can effectively reduce the signal subspace dimension of the channel correlation matrix for the sparse multipath fading channels and, consequently, improve the channel estimation performance.
487 citations
TL;DR: The authors find that it can be regarded as the generalized frequency band energy (FBE) and is hence useful, which results in the FBE-MFCC, and propose a better analysis, namely the auto-regressive analysis, on the frame energy, which outperform its 1st and/or 2nd order differential derivatives.
Abstract: The performance of the Mel-Frequency Cepstrum Coefficients (MFCC) may be affected by (1) the number of filters, (2) the shape of filters, (3) the way in which filters are spaced, and (4) the way in which the power spectrum is warped. In this paper, several comparison experiments are done to find a best implementation. The traditional MFCC calculation excludes the 0th coefficient for the reason that it is regarded as somewhat unreliable. According to the analysis and experiments, the authors find that it can be regarded as the generalized frequency band energy (FBE) and is hence useful, which results in the FBE-MFCC. The authors also propose a better analysis, namely the auto-regressive analysis, on the frame energy, which outperform its 1st and/or 2nd order differential derivatives. Experiments with the “863” Speech Database show that, compared with the traditional MFCC with its corresponding auto-regressive analysis coefficients, the FBE-MFCC and the frame energy with their corresponding auto-regressive analysis coefficients form the best combination, reducing the Chinese syllable error rate (CSER) by about 10%, while the FBE-MFCC with the corresponding auto-regressive analysis coefficients reduces CSER by 2.5%. Comparison experiments are also done with a quite casual Chinese speech database, named Chinese Annotated Spontaneous Speech (CASS) corpus. The FBE-MFCC can reduce the error rate by about 2.9% on an average.
455 citations
TL;DR: A new candidate for fluoride adsorption from water, amorphous Al2O3 supported on carbon nanotubes (Al 2O3/CNTs) is reported in this article.
401 citations
08 Dec 2001
TL;DR: A two-step statistical modeling approach that integrates both a global parametric model and a local nonparametric model is developed, which can generate photorealistic face images.
Abstract: In this paper, we study face hallucination, or synthesizing a high-resolution face image from low-resolution input, with the help of a large collection of high-resolution face images. We develop a two-step statistical modeling approach that integrates both a global parametric model and a local nonparametric model. First, we derive a global linear model to learn the relationship between the high-resolution face images and their smoothed and down-sampled lower resolution ones. Second, the residual between an original high-resolution image and the reconstructed high-resolution image by a learned linear model is modeled by a patch-based nonparametric Markov network, to capture the high-frequency content of faces. By integrating both global and local models, we can generate photorealistic face images. Our approach is demonstrated by extensive experiments with high-quality hallucinated faces.
379 citations
TL;DR: In this article, a qualitative relationship between peak intensities of the X-ray diffraction patterns and the degrees of nanotube alignments was established, which provides a simple way to characterize the alignment degree of as-grown large-area CNTs.
302 citations
TL;DR: Large scale production of poly(3-Hydroxybutyrate-co-3-hydroxyhexanoate) by Aeromonas hydrophila 4AK4 was examined in a 20,000 l fermentor, and the copolymer produced was found to be a random copolymers.
Abstract: Large scale production of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] by Aeromonas hydrophila 4AK4 was examined in a 20,000 l fermentor. Cells were first grown using glucose as a carbon source, and polyhydroxyalkanoate (PHA) biosynthesis was triggered by the addition of lauric acid under conditions of limited nitrogen or phosphorus. When cells first grown in a medium containing 50 g glucose l(-1) were further cultivated after the addition of 50 g lauric acid l(-1) under phosphorus limitation, a final cell concentration, PHA concentration and PHA content of 50 g l(-1), 25 g l(-1), and 50 wt%, respectively, were obtained in 46 h, equivalent to PHA productivity of 0.54 g l(-1)t h(-1). The copolymer produced was found to be a random copolymer, and the 3HHx fraction was 11 mol%.
284 citations
TL;DR: A parallel and easily implemented hybrid optimization framework is presented, which reasonably combines genetic algorithm with simulated annealing, and applies it to job-shop scheduling problems.
07 Oct 2001
TL;DR: A novel method of relevance feedback is presented based on support vector machine learning in the content-based image retrieval system that shows the generalization ability of SVM under the condition of limited training samples.
Abstract: A novel method of relevance feedback is presented based on support vector machine learning in the content-based image retrieval system. A SVM classifier can be learned from training data of relevance images and irrelevance images marked by users. Using the classifier, the system can retrieve more images relevant to the query in the database efficiently. Experiments were carried out on a large-size database of 9918 images. It shows that the interactive learning and retrieval process can find correct images increasingly. It also shows the generalization ability of SVM under the condition of limited training samples.
TL;DR: In this paper, the authors reviewed the stationary and non-stationary characteristics of attached, turbulent cavitating flows around solid objects, including incipient cavitation with traveling bubbles, sheet cavitation, cloud cavitation and supercavitation.
TL;DR: In this paper, the authors established some variant fountain theorems without (P.S.)-type assumption for Dirichlet boundary value problems under no Ambrosetti-Rabinowitz's superquadraticity condition.
Abstract: In this paper we establish some variant fountain theorems without (P.S.)-type assumption. The abstract results will be used to study the symmetric nonlinear Schrodinger equations and Dirichlet boundary value problems. Under no Ambrosetti–Rabinowitz's superquadraticity condition, we obtain infinitely many large energy and small negative energy solutions respectively.
TL;DR: A novel method for multimodality medical image fusion is proposed using wavelet transform and fusion rule is proposed and used for calculating the wavelet transformation modulus maxima of input images at different bandwidths and levels.
Abstract: Medical image fusion has been used to derive useful information from multimodality medical image data. In this research, we propose a novel method for multimodality medical image fusion. Using wavelet transform, we achieved a fusion scheme. A fusion rule is proposed and used for calculating the wavelet transformation modulus maxima of input images at different bandwidths and levels. To evaluate the fusion result, a metric based on mutual information (MI) is presented for measuring fusion effect. The performances of other two methods of image fusion based on wavelet transform are briefly described for comparison. The experiment results demonstrate the effectiveness of the fusion scheme.
TL;DR: In this article, the effective self-consistent scheme (ESCS) based on the three-phase model was proposed for estimating the effective properties of matrix-inclusion composites.
Abstract: For estimating the effective properties (elasticity, conductivity, piezoelectricity, etc.) of composites of the matrix-inclusion type, we develop a new micromechanical model, the effective self-consistent scheme (ESCS), based on the three-phase model. As a simplified and explicit version of the ESCS estimate, the interaction direct derivative (IDD) estimate is further proposed. The IDD estimate has an explicit and almost the simplest structure in comparison with other existing micromechanical estimates, with clear physical significance for all the involved components. It is universally applicable for various multiphase composites of the matrix-inclusion type, for any material symmetries of matrix, inclusions and effective medium, and distribution, shapes, orientations, and concentration of inclusions. Applications to effective elastic properties of composites with spherical inclusions and materials damaged due to voids of various shapes and microcracks (up to any high microcrack density) are presented, in comparison with a number of refined or accurate numerical simulation results. The IDD estimate seems to provide the best predictions in most of our examined cases. A further exploration of the proposed two estimates is given by Du and Zheng (Acta Mech. (2001), in press).
TL;DR: In this article, the influence of the dimensions of the micro-channels on the heat transfer performance was analyzed numerically, based on these computations, deep micro-channel were used for the experimental studies reported here.
TL;DR: The fuzzy random simulation, neural network, and genetic algorithm are integrated to produce a more powerful and effective hybrid intelligent algorithm for solving fuzzy random programming models and illustrate its effectiveness by some numerical examples.
Abstract: By fuzzy random programming, we mean the optimization theory dealing with fuzzy random decision problems. This paper presents a new concept of chance of fuzzy random events, and constructs a general framework of fuzzy random chance-constrained programming. We also design a spectrum of fuzzy random simulations for computing uncertain functions arising in the area of fuzzy random programming. To speed up the process of handling uncertain functions, we train a neural network to approximate uncertain functions based on the training data generated by fuzzy random simulation. Finally, we integrate the fuzzy random simulation, neural network, and genetic algorithm to produce a more powerful and effective hybrid intelligent algorithm for solving fuzzy random programming models and illustrate its effectiveness by some numerical examples.
TL;DR: In this article, a finite point method, least square collocation meshless method, is proposed, where the equilibrium conditions are satisfied not only at the collocation points but also at the auxiliary points in a least square sense.
Abstract: A finite point method, least-squares collocation meshless method, is proposed. Except for the collocation points which are used to construct the trial functions, a number of auxiliary points are also adopted. Unlike the direct collocation method, the equilibrium conditions are satisfied not only at the collocation points but also at the auxiliary points in a least-squares sense. The moving least-squares interpolant is used to construct the trial functions. The computational effort required for the present method is in the same order as that required for the direct collocation, while the present method improves the accuracy of solution significantly. The proposed method does not require any mesh so that it is a truly meshless method. Three numerical examples are studied in detail, which show that the proposed method possesses high accuracy with low computational effort. Copyright © 2001 John Wiley & Sons, Ltd.
TL;DR: In this article, coupled magnetic-mechanical-electric effects involving linearly and nonlinearly coupling interactions in ferroic composites are investigated using a Green's function technique.
Abstract: Coupled magnetic-mechanical-electric effects involving linearly and nonlinearly coupling interactions in ferroic composites are investigated using a Green's function technique. We use the theory to suggest a possible giant magnetoelectric effect in a ferroelectric poly(vinylidene fluoride-trifluorethylene) copolymer filled by giant magnetostrictive rare-earth--iron alloy particles, which is markedly larger than that in the best known magnetoelectric materials. The flexible composite is expected to exhibit large magnetostriction. Our results show how to design such flexible polymer-matrix magnetoelectric composites with better performance and may stimulate further interest in the areas of coupled multifield effects and magnetoelectric materials for practical applications.
TL;DR: This work first proves asymptotic compactness and then establishes the existence of global attractors and the upper semicontinuity of the global attractor is also obtained when the lattice differential equations are approached by finite-dimensional systems.
Abstract: We study the asymptotic behavior of solutions for lattice dynamical systems. We first prove asymptotic compactness and then establish the existence of global attractors. The upper semicontinuity of the global attractor is also obtained when the lattice differential equations are approached by finite-dimensional systems.
TL;DR: In this paper, a novel preparation method for MgO nanocrystals was reported, which makes use of a conventional hydrogel of Mg(OH) 2 derived from inorganic magnesium chloride.
TL;DR: Two kinds of autotrophic microalgae, Spirulina platensis and Chlorella protothecoides, were pyrolyzed at the heating rates of 15, 40, 60 and 80 degrees C/min up to 800 degrees C in a thermogravimetric analyzer to investigate theirpyrolytic characteristics.
TL;DR: In this paper, the emission spectra of the Sr 4 Al 14 O 25 −Eu,Dy photoluminescent material with high brightness and long afterglow was prepared by sintering at high-temperature and weak reducing atmosphere.
TL;DR: Characterized by an oxygen consumption rate, sludge specific activities both for organic decomposition and nitrification of ammonia nitrogen varied with SRT, but volumetric oxygen consumption rates of the membrane bioreactor, representing the whole ability of the process for decomposing pollutants, were enhanced as SRT increased.
01 Apr 2001
TL;DR: A Function-based Object Model (FOM) is presented that attempts to understand authors’ intention by identifying Object function instead of semantic understanding and a system for web content adaptation over Wireless Application Protocol (WAP) is developed.
Abstract: Content understanding is a crucial issue for website adaptation. In this paper we present a Function-based Object Model (FOM) that attempts to understand authors’ intention by identifying Object function instead of semantic understanding. Every Object in a website serves for certain functions (Basic and Specific Function) which reflect authors’ intention towards the purpose of an Object. Based on this consideration we have proposed the FOM model for website understanding. FOM includes two complementary parts: Basic FOM based on the basic functional properties of Object and Specific FOM based on the category of Object. An automatic approach to detect the functional properties and category of Object is presented for FOM generation. Two level adaptation rules (general rules and specific rules) based on FOM are combined for practical adaptation. A system for web content adaptation over Wireless Application Protocol (WAP) is developed as an application example of the proposed model. Experiments have shown satisfactory results and extensibility.
TL;DR: Low-complexity windowed discrete Fourier transform (DFT)-based minimum mean square error (MMSE) channel estimators are proposed and analyzed for both the interpolation and noninterpolation cases for orthogonal frequency-division multiplexing (OFDM) mobile communications systems.
Abstract: Low-complexity windowed discrete Fourier transform (DFT)-based minimum mean square error (MMSE) channel estimators are proposed and analyzed for both the interpolation and noninterpolation cases for orthogonal frequency-division multiplexing (OFDM) mobile communications systems. In the proposed method, the frequency domain data windowing is used to reduce the aliasing errors for the interpolation case and get better noise filtering performance for the noninterpolation case. The time domain MMSE weighting is also used to suppress the channel noise for both cases. Moreover, the optimal generalized Hanning window shape is searched to minimize the channel estimation mean square error (MSE). Analysis and simulation results show that the proposed method performance is close to the optimal MMSE estimator and is much better than the direct DFT-based estimator for both cases. Compared with the optimal MMSE estimator, however, the computation load of the proposed method can be significantly reduced because the IDFT/DFT transforms can be implemented with the fast algorithms IFFT/FFT.
TL;DR: In this paper, a unified numerical approach for point contact problems is presented, which is capable of simulating the entire transition from the full film EHD, mixed, down to boundary lubrication, using measured 3-D roughness.
Abstract: A complete computer program package has been developed in the present work based on a recently developed unified numerical approach for point contact problems. This approach is capable of simulating the entire transition from the full film EHD, mixed, down to boundary lubrication, using measured 3-D roughness. The numerical solution can cover a full range of λ ratio, from infinity down to zero. Based on the calculated film thickness (or gap) and pressure distribution in the contact, subsurface stresses can readily be predicted. Also, friction and flask temperatures can be computed by using a non-Newtonian fluid model in the hydrodynamic regions and a measured (or assumed) coefficient of friction for boundary lubrication in the contact regions. Sample cases show that this computer program package is robust with no convergence problems encountered even under severe operating conditions. It appears to be a useful engineering tool for industrial applications.
TL;DR: In this paper, a free-radical melt grafting of the multi-monomer system of maleic anhydride (MAH)/styrene (St) onto polypropylene (PP) was studied using a single-screw extruder.