Showing papers by "Nanjing University of Science and Technology published in 2007"

Delay-Dependent $H_{\infty }$ Control and Filtering for Uncertain Markovian Jump Systems With Time-Varying Delays

Abstract: This paper deals with the problems of delay-dependent robust Hinfin control and filtering for Markovian jump linear systems with norm-bounded parameter uncertainties and time-varying delays. In terms of linear matrix inequalities, improved delay-dependent stochastic stability and bounded real lemma (BRL) for Markovian delay systems are obtained by introducing some slack matrix variables. The conservatism caused by either model transformation or bounding techniques is reduced. Based on the proposed BRL, sufficient conditions for the solvability of the robust Hinfin control and Hinfin filtering problems are proposed, respectively. Dynamic output feedback controllers and full-order filters, which guarantee the resulting closed-loop system and the error system, respectively, to be stochastically stable and satisfy a prescribed Hinfin performance level for all delays no larger than a given upper bound, are constructed. Numerical examples are provided to demonstrate the reduced conservatism of the proposed results in this paper.

Globally Maximizing, Locally Minimizing: Unsupervised Discriminant Projection with Applications to Face and Palm Biometrics

Abstract: This paper develops an unsupervised discriminant projection (UDP) technique for dimensionality reduction of high-dimensional data in small sample size cases. UDP can be seen as a linear approximation of a multimanifolds-based learning framework which takes into account both the local and nonlocal quantities. UDP characterizes the local scatter as well as the nonlocal scatter, seeking to find a projection that simultaneously maximizes the nonlocal scatter and minimizes the local scatter. This characteristic makes UDP more intuitive and more powerful than the most up-to-date method, locality preserving projection (LPP), which considers only the local scatter for clustering or classification tasks. The proposed method is applied to face and palm biometrics and is examined using the Yale, FERET, and AR face image databases and the PolyU palmprint database. The experimental results show that UDP consistently outperforms LPP and PCA and outperforms LDA when the training sample size per class is small. This demonstrates that UDP is a good choice for real-world biometrics applications

On Equivalence and Efficiency of Certain Stability Criteria for Time-Delay Systems

Abstract: In recent years, there have been a number of new delay-dependent stability criteria based on linear matrix inequalities published in the literature. This note aims to theoretically establish the equivalence of seven of these stability criteria. Moreover, the efficiency of these stability criteria is assessed based on the number of unknowns in the linear matrix inequalities

Robust H∞ control of descriptor discrete-time markovian jump systems

Abstract: This paper considers the stochastic stability and the robust control of descriptor discrete-time systems with Markovian jumping parameters. In terms of linear matrix inequalities, a necessary and sufficient condition is proposed, which ensures a discrete-time descriptor Markovian jump system to be regular, causal and stochastically stable. A robust admissibility condition and a robust bounded real lemma are also developed. Based on these, a sufficient condition on the existence of a state-feedback controller which guarantees the robust admissibility and the performance is also given by employing the linear matrix inequality technique. A robustly stabilizing state feedback controller can be constructed through the numerical solutions of linear matrix inequalities. Finally, an example is provided to demonstrate the effectiveness of the proposed approach.

Self-formed adaptor PCR: a simple and efficient method for chromosome walking.

Abstract: We developed a self-formed adaptor PCR (termed SEFA PCR) which can be used for chromosome walking. Most of the amplified flanking sequences were longer than 2.0 kb, and some were as long as 6.0 kb. SEFA PCR is simple and efficient and should have broad applications in the isolation of unknown sequences in complex genomes.

DFT studies on the four polymorphs of crystalline CL-20 and the influences of hydrostatic pressure on epsilon-CL-20 crystal.

Abstract: Based on density functional theory (DFT), four different methods with the generalized gradient approximation (GGA) have been employed to investigate the structural and electronic properties of the four polymorphs (alpha.H2O, beta, gamma, and epsilon phases) of CL-20, which is a well-known high energy density compound (HEDC). The relaxed crystal structures compare well with experimental data. According to the constitution of the frontier energy bands and the Mulliken population analyses, the N-NO2 bond is predicted to be the trigger bond during thermolysis. The density of states (DOS) of alpha-CL-20.H2O is somewhat different from those of the other three crystals for its inclusion of H2O molecules that contribute the frontier energy bands. The band gaps obtained from the four different methods are consistent with each other. According to the calculated values of band gaps, the sensitivity of the four polymorphs of CL-20 is predicted as epsilon < beta < gamma < alpha.H2O, which agrees well with the experimental result. The effects of hydrostatic compression on the most stable epsilon-CL-20 have also been investigated using the GGA-PBE method in the pressure range of 0-400 GPa. epsilon-CL-20 has anisotropic compressibility at low or high pressure. The band gap is found to decrease with increasing pressure, showing the corresponding sensitivity increase. Based on the changes of the band gap and DOS with pressure, 400 GPa is considered to be the critical pressure for the insulator-metal phase transition.

Effect of addition of sodium alginate on bacterial cellulose production by Acetobacter xylinum

Abstract: Bacterial cellulose (BC) production by Acetobacter xylinum NUST4.1 was carried out in the shake flask and in a stirred-tank reactor by means of adding sodium alginate (NaAlg) into the medium. When 0.04% (w/v) NaAlg was added in the shake flask, BC production reached 6.0 g/l and the terminal yield of the cellulose was 27% of the total sugar initially added, compared with 3.7 g/l and 24% in the control, respectively. The variation between replicates in all determinations was less than 5%. During the cultivation in the stirred-tank reactor, the addition of NaAlg changed the morphology of cellulose from the irregular clumps and fibrous masses entangled in the internals to discrete masses dispersing into the broth, which indicates that NaAlg hinders formation of large clumps of BC, and enhances cellulose yield. Because the structure of cellulose is changed depending on the culture condition such as additives, structural characteristics of BC produced in the NaAlg-free and NaAlg medium are compared using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD). SEM photographs show some differences in reticulated structures and ribbon width and FT-IR spectra indicate that there is the hydrogen bonding interaction between BC and NaAlg, then X-ray diffraction (XRD) analysis reveals that BC produced with NaAlg-added has a lower crystallinity and a smaller crystalline size. The results show that enhanced yields and modification of cellulose structure occur in the presence of NaAlg.

Corrosion and wear resistance of AZ91D magnesium alloy with and without microarc oxidation coating in Hank’s solution

Abstract: Immersion test, electrochemistry test and block-on-cylinder type wear test have been applied to study the corrosion and wear resistance of AZ91D Mg alloy with and without microarc oxidation (MAO) treatment in Hank’s solution. Through MAO, a ceramic coating is directly formed on the surface of AZ91D Mg alloy, by which its corrosion and wear resistances are greatly improved. The immersion test results show the mass loss of untreated AZ91D Mg is 15 times of that of MAO ones after 21 days immersion test. The electrochemical corrosion experiments show that the corrosion potential of Mg alloy is improved from −1.5786 V to −0.43019 V through MAO surface treatment, the corrosion current is reduced from 0.028703 A/cm2 to 2.0456 × 10−7 A/cm2, and the polarization resistance is improved from 1.2753 × 10−5 Ω/cm2 to 0.90886 Ω/cm2. The lubricate sliding wear test results show the mass loss of untreated AZ91D Mg is 1.5 times of that of MAO ones.

First-principles study of the four polymorphs of crystalline octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine.

Abstract: The electronic structure and vibrational properties of the four polymorphs of crystalline octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) have been studied using density functional theory within the local density approximation. The results show that the states of N in the ring make more important contributions to the valence bands than these of C and N of NO2 and so N in the ring acts as an active center. From the low frequency to high-frequency region, the molecular motions of the vibrational frequencies for the four HMX polymorphs present unique features. It is also noted that there is a relationship between the band gap and impact sensitivity for the four HMX polymorphs. From the cell bond order per unit volume, we may infer the variation order of crystal bonding for the four polymorphs and so predict their impact sensitivity order as follows: β-HMX < γ-HMX < α-HMX < δ-HMX, which is in agreement with their experimental order.

Principles of chaotic signal radar

Abstract: The noise-like chaotic signal can be generated with very simple nonlinear circuits, and has broad bandwidth and aperiodic properties. These characteristics have drawn considerable attention in the radar community. In the past, the chaotic signal or its modulated version serves as a transmitting signal, and the traditional correlation-type receiver is used for processing. In this sense, the chaotic signal acts as a radar waveform in the noise signal radar, and hence the performance advantages are not distinct. Here, we present a scheme for processing chaotic radar signals. We find a simple relation between the target parameters (range and velocity) and the system parameters of chaos-generating system. With this relation, the measurement of the target parameters is transformed into estimation of the system parameters from the radar return signals. Equipped with high resolution parameter estimation techniques, the proposed principles provide a way to develop high resolution noise signal radars.

Preparation of uniform Bi2S3 nanorods using xanthate complexes of bismuth(III)

Abstract: Orthorhombic Bi2S3 nanorods were synthesized via hydrothermal treatment from a novel kind of single-source precursors, the adducts of Bi(S2COR)3 [R = sec-butyl] with neutral ligands (pyridine [C5H5N] or 1,10-phenanthroline [C12H8N2]) The decomposition of the complex [Bi(S2COC4H9)3(C5H5N)2] (1) produces Bi2S3 nanorods with diameters in the range of 20−35 nm and lengths of hundreds of nanometers The nanodispersed Bi2S3 in dichloromethane maintains a long-term stability and shows a blue shift on the optical band edge with a band gap Eg ≈ 167 eV High-resolution transmission electron microscopy studies reveal that the Bi2S3 nanorods are oriented in a [001] growth direction

Generalization of Soft Set Theory: From Crisp to Fuzzy Case

Abstract: The traditional soft set is a mapping from parameter to the crisp subset of universe. However, the situation may be more complex in real world because the fuzzy characters of parameters. In this paper, the traditional soft set theory is expanded to be a fuzzy one, the fuzzy membership is used to describe parameter-approximate elements of fuzzy soft set. Furthermore, basic fuzzy logic operators are used to define generalized operators on fuzzy soft set and then the DeMorgan’s laws are proved. Finally, the parametrization reduction of fuzzy soft set is defined, a decision-making problem is analyzed to indicate the validity of the fuzzy soft set.

One-pot green procedure for Biginelli reaction catalyzed by novel task-specific room-temperature ionic liquids

Abstract: Cheap and reusable task-specific ionic liquids that bear an alkanesulfonic acid group in an acyclic trialkylammonium cation were found to be effective catalysts for synthesizing 3,4-dihydropyrimidine-2-(1H)-ones via the one-pot three-component Biginelli reaction. The satisfactory results were obtained with good yields, short reaction time and simplicity in the experimental procedure. The catalysts could be recycled and reused six times without noticeably decrease in the catalytic activity.

A chaotic stream cipher and the usage in video protection

Abstract: In this paper, a chaotic stream cipher is constructed and used to encrypt video data selectively. The stream cipher based on a discrete piecewise linear chaotic map satisfies the security requirement of cipher design. The video encryption scheme based on the stream cipher is secure in perception, efficient and format compliant, which is suitable for practical video protection. The video encryption scheme’s performances prove the stream cipher’s practicability.