Showing papers by "Nanjing University of Science and Technology published in 2006"

Driver Fatigue Detection: A Survey

Abstract: Driver fatigue is an important factor in a large number of accidents. There has been much work done in driver fatigue detection. This paper presents a comprehensive survey of research on driver fatigue detection and provides structural categories for the methods which have been proposed. The methods of fatigue detection mainly focused on measures of the driver's state, driver performance and the combination of the driver's state and performance. The measures of driver's state included PERCLOS, mouth shape and head position; the measures of driver performance included lane tracking and tracking of distance between vehicles. These approaches are presented and discussed in detail. Some typical driver monitoring systems are also introduced in this paper. Finally, summary and conclusions are presented.

A new LMI condition for delay-dependent asymptotic stability of delayed Hopfield neural networks

Abstract: In this paper, a new delay-dependent asymptotic stability condition for delayed Hopfield neural networks is given in terms of a linear matrix inequality, which is less conservative than existing ones in the literature. This condition guarantees the existence of a unique equilibrium point and its global asymptotic stability of a given delayed Hopfield neural network. Examples are provided to show the reduced conservatism of the proposed condition.

Security Analysis of A Chaos-based Image Encryption Algorithm

Abstract: The security of Fridrich Image Encryption Algorithm against brute-force attack, statistical attack, known-plaintext attack and select-plaintext attack is analyzed by investigating the properties of the involved chaotic maps and diffusion functions. Based on the given analyses, some means are proposed to strengthen the overall performance of the focused cryptosystem.

PAPR reduction of an OFDM signal by use of PTS with low computational complexity

Abstract: One of the major drawbacks of orthogonal frequency division multiplexing (OFDM) is the high peak-to-average power ratio (PAPR) of the transmitted OFDM signal. Partial transmit sequence (PTS) technique can improve the PAPR statistics of an OFDM signal. However optimum PTS (OPTS) technique requires an exhaustive search over all combinations of allowed phase factors, the search complexity increases exponentially with the number of sub-blocks. By combining sub-optimal PTS with a preset threshold, a novel reduced complexity PTS (RC-PTS) technique is presented to decrease the computational complexity. Numerical results show that the proposed approach can achieve better performance with lower computational complexity when compared to that of other PTS approaches.

A compact single layer monopulse microstrip antenna array

Abstract: A compact single layer monopulse microstrip patch antenna array for the application of monopulse radar has been designed, manufactured and tested. The array, the monopulse comparator and the feed network are placed on the same layer, resulting in a very compact structure. The limitation of this structure is discussed. The effects of spurious radiation and blockage caused by the comparator on the sidelobe level are estimated. A space mapping (SM) technique is applied to design microstrip subarray. The bandwidth (VSWR<2) of the antenna is 5.6%, the operating frequency is between 13.85-15.1 GHz and the designed central frequency is 14.25 GHz. Our measurements show that, both for the E plane and for the H plane, the sidelobe levels of the sum pattern are less than -17 dB, and the null depths of the difference pattern are less than -30 dB. The maximum gain at the operating frequencies is 24.5 dBi.

Computational Studies on Polynitrohexaazaadmantanes as Potential High Energy Density Materials

Abstract: Polynitrohexaazaadamantanes (PNHAAs) have been the subject of much recent research because of their potential as high energy density materials (HEDMs). The B3LYP/6-31G* method was employed to evaluate the heats of formation (HOFs) for PNHAAs by designing isodesmic reactions. The HOFs are found to be correlative with the number (n) and the space orientations of nitro groups. Detonation velocities (D) and detonation pressures (P) were estimated for PNHAAs by using the well-known Kamlet−Jacobs equations, based on the theoretical densities (ρ) and HOFs. It is found that D and P increase as n ranges from 1 to 6, and PNHAAs with 4−6 nitro groups meet the criteria of an HEDM. When n is over 6, ρ of PNHAAs slightly increases; however, the chemical energy of detonation (Q) decreases so greatly that both D and P decrease. The calculations on bond dissociation energies suggest that the N−N bond be the trigger bond during the pyrolysis initiation process of each PNHAA, and with increasing n, N−N bond dissociation ene...

Theoretical studies on the structures, thermodynamic properties, detonation properties, and pyrolysis mechanisms of spiro nitramines.

Abstract: Density function theory (DFT) has been employed to study the geometric and electronic structures of a series of spiro nitramines at the B3LYP/6-31G level. The calculated results agree reasonably with available experimental data. Thermodynamic properties derived from the infrared spectra on the basis of statistical thermodynamic principles are linearly correlated with the number of nitramine groups as well as the temperature. Detonation performances were evaluated by the Kamlet-Jacobs equations based on the calculated densities and heats of formation. It is found that some compounds with the predicted densities of ca. 1.9 g/cm3, detonation velocities over 9 km/s, and detonation pressures of about 39 GPa (some even over 40 GPa) may be novel potential candidates of high energy density materials (HEDMs). Thermal stability and the pyrolysis mechanism of the title compounds were investigated by calculating the bond dissociation energies (BDE) at the B3LYP/6-31G level and the activation energies (E(a)) with the selected PM3 semiempirical molecular orbital (MO) based on the unrestricted Hartree-Fock model. The relationships between BDE, E(a), and the electronic structures of the spiro nitramines were discussed in detail. Thermal stabilities and decomposition mechanisms of the title compounds derived from the B3LYP/6-31G BDE and the UHF-PM3 E(a) are basically consistent. Considering the thermal stability, TNSHe (tetranitrotetraazaspirohexane), TNSH (tetranitrotetraazaspiroheptane), and TNSO (tetranitrotetraazaspirooctane) are recommended as the preferred candidates of HEDMs. These results may provide basic information for the molecular design of HEDMs.

Molecular Dynamics Simulations for Pure ε-CL-20 and ε-CL-20-Based PBXs

Abstract: Molecular dynamics has been employed to simulate the well-known high energy density compound e-CL-20 (hexanitrohexaazaisowurtzitane) crystal and 12 e-CL-20-based PBXs (polymer bonded explosives) with four kinds of typical fluorine polymers, i.e., polyvinylidenedifluoride, polychlorotrifluoroethylene, fluorine rubber (F2311), and fluorine resin (F2314) individually. The elastic coefficients, isotropic mechanical properties (tensile moduli, bulk moduli, shear moduli, and poission's ratios), and bonding energy are first reported for e-CL-20 crystal and e-CL-20-based polymer bonded explosives (PBXs). The mechanical properties of e-CL-20 can be effectively improved by blending with a small amount of fluorine polymers, and the whole effect of the adding fluorine polymers to improve mechanical properties of PBXs along the three crystalline surfaces of e-CL-20 is found to be (100) ≈ (001) > (010). The interaction between each of the crystalline surfaces and each of the fluorine polymers is different, and the orde...

Brønsted Acidic Ionic Liquids and Their Use as Dual Solvent−Catalysts for Fischer Esterifications

Abstract: Some novel Bronsted acidic ionic liquids (TSILs) that bear an alkane sulfonic acid group in an acyclic trialkanylammonium cation were synthesized and their uses as dual solvent−catalysts for Fischer esterification reactions of acetic acid, metacetonic acid, and benzoic acid with ethanol, butanol, and benzyl alcohol were investigated. The reactions were completed smoothly at room temperature to 110 °C for 1.5−3.0 h with good yields of 88−95%. The results indicate that catalytic activity depends on anion acidity and the solubility of the starting material in TSILs. The increasing of the anion's acidity improves the catalytic activity of the TSILs. Furthermore, the produced esters could be separated by decantation after the reaction and the TSILs could be reused without noticeably decreasing the catalytic activity.

Wideband Circularly-Polarized Patch Antenna

Abstract: A novel wideband circularly-polarized patch antenna is presented First, a new broadband 90deg hybrid feed network is proposed to have a bandwidth of 75% for the 10-dB return loss, good two output ports amplitude balance and a consistent 90deg (plusmn3deg) phase difference between two output ports Then, a circular patch antenna fed by four sequential-rotation proximity-coupled L-probes orientated to have phase of 0deg, 90deg, 180deg and 270deg is presented The four L-probes are connected to the respective ports of a feed network comprising a pair of the proposed broadband 90deg hybrid It is found that the antenna can deliver a measured impedance bandwidth of 794% from 104 to 241 GHz for SWR 3 dBi The simulated impedance bandwidth is 94% from 09 to 25 GHz for SWR 3 dBi Good agreement is observed between simulation and measurement

New Exponential Estimates for Time-Delay Systems

Abstract: This note considers the problem of exponential stability for time-delay systems. In terms of linear matrix inequalities, a new sufficient condition for exponential stability is obtained. Based on this, an improved upper bound of the decay rate can be easily calculated. When time-varying norm-bounded parameter uncertainties appear, a new sufficient condition for robust exponential stability of uncertain time-delay systems is also provided. The reduced conservatism of the proposed conditions is illustrated via two numerical examples

Effect of Fe2O3 in Fe2O3/AP Composite Particles on Thermal Decomposition of AP and on Burning Rate of the Composite Propellant

Abstract: A technique of composite processing of Fe2O3 and ammonium perchlorate (AP) was employed in making the propellant. The effects of composite processing of Fe2O3 on catalytic activity, on the thermal decomposition of AP, and on the burning rate of the composite propellant were investigated in this paper. Fe2O3/AP composite particles were prepared by a novel solvent-nonsolvent method. The results show that AP is successfully coated on the surface of Fe2O3. Composite processing of Fe2O3 and AP can improve the catalytic activity of Fe2O3. Fe2O3 exhibits better catalytic effect with increasing Fe2O3 content. The larger interface between Fe2O3 and AP and lower density of composite propellant (with the added Fe2O3/AP composite particles) are responsible for the enhancement of the catalytic activity of Fe2O3.

Surface modification of neural probes with conducting polymer poly(hydroxymethylated-3,4- ethylenedioxythiophene) and its biocompatibility.

Abstract: A novel conducting polymer, poly(hydroxymethylated-3,4-ethylenedioxy-thiophene) (PEDOT-MeOH), was electrochemically deposited onto the electrodes of micromachined neural probes. Uniformly distributed film was obtained from aqueous solution when doped with polystyrenesulfonate. The surface morphology was rough and had good cellular adhesion. Impedance spectroscopy showed that the magnitude of coated electrode was lower than that of the bare gold over a range of frequencies from 100 to 105 Hz. Since the biocompatibility of the interface between the neural probes and brain tissue plays an important role when the probes are implanted in the central nervous system for long-term application, biomolecules were incorporated into the coating. Nonapeptide CDPGYIGSR was codeposited as the counterion in the conducting films. The surface morphology of the coating was fuzzy, providing many bioactive sites for interaction with neural cells. The magnitude of impedance was as low as 53 kω at the biologically relevant frequency of 1 kHz. An in vitro experiment demonstrated that the neuroblastoma cells grew preferentially on the PEDOT-MeOH/CDPGYIGSR-coated electrode sites and spread beyond the electrode area.