Cutting process dynamics by nonlinear time series and wavelet analysis

We have modeled the dynamics of a cutting process by a two-degree-of-freedom mass-spring system with dry friction. Using nonlinear time series and wavelet analysis, we have investigated the vibrational instabilities of the system for different values of the cutting force. By constructing the phase portraits and calculating the Lyapunov exponents we have delineated the conditions for which a periodic or chaotic motion can occur. The results are verified by means of a time-scale representation of the wavelet power spectrum.     

Structure formation during isothermal crystallization of oriented isotactic polystyrene

Isothermal crystallization from the glassy state of oriented isotactic polystyrene (iPS) was studied using in situ Fourier transform infrared (FTIR) spectroscopy and in situ wide‐angle X‐ray diffraction (WAXD) studies. The oriented amorphous films of iPS were prepared by rolling the amorphous iPS film to a draw ratio of 3 or 4. In situ FTIR was used to investigate the ordering process of polymer chains prior to crystallization by measuring the change in the dichroic ratio with time, while in situ WAXD studies were used to investigate the development of the crystalline structure. The studies showed that the orientation process and the conformation change preceded crystallization. This observation suggests that polystyrene chains undergo an ordering process during the induction period of crystallization. The degree of orientation markedly increases with time in the induction period, suggesting that heat treatment of oriented amorphous materials under constraint provides a useful method for processing highly oriented materials. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2912–2921, 2000     

Spectrophotometric study of molecular complex formation between o-chloranil and a series of methylated pyridines

o-Chloranil has been shown to form 1:1 molecular complexes with pyridine and 2-, 3- and 4-picolines in CCl4 medium. Isosbestic points have been found but charge-transfer bands could not be detected. The formation constants of the complexes exhibit a very good linear free energy relationship from which the Hammett p parameter for the complexation reaction is found to be -3.67.     

A stopping rule for symbolic dynamic filtering

One of the key issues in symbolic dynamic filtering (SDF) is how to obtain a lower bound on the length of symbol blocks for computing the state probability vectors of probabilistic finite-state automata (PFSA). Having specified an absolute error bound at a confidence level, this short work formulates a stopping rule by making use of Markov chain Monte Carlo (MCMC) computations.     

Studies on the molecular interaction of safranin-T with surfactants

The spectrophotometric studies of safranin-T (Saf-T) dye in an aqueous solution containing three different types of surfactants such as CTAB (cationic), SLS (anionic) and Triton X-100 (TX-100), Tween-20, 40, 60 and 80 (nonionic) show that Saf-T forms a 1:1 molecular complex with TX-100, Tweens and SLS. Such a type of interaction is absent in Saf-T and CTAB. The thermodynamic and spectrophotometric properties of these complexes suggest that Saf-T forms a strong charge transfer (CT) complex with TX-100 and Tweens, whereas the interaction of Saf-T with SLS is coulombic in nature. Photogalvanic and photoconductometric studies also support the above interactions. In addition to this, the electron-donating ability among the nonionic surfactants i.e. TX-100 and Tweens towards dye, role of surface in CT interaction, the site of CT interaction and the intensity and stability of CT interaction between Saf-T and nonionic surfactants have been pointed out.     

Wavelet Space Partitioning for Symbolic Time Series Analysis

A crucial step in symbolic time series analysis （STSA） of observed data is symbol sequence generation that relies on partitioning the phase-space of the underlying dynamical system. We present a novel partitioning method, called wavelet-space （WS） partitioning, as an alternative to symbolic false nearest neighbour （SFNN） partitioning. While the WS and SFNN partitioning methods have been demonstrated to yield comparable performance for anomaly detection on laboratory apparatuses, computation of WS partitioning is several orders of magnitude faster than that of the SFNN partitioning.     

Interactions of Fe atom with single wall armchair SiC nanotubes: an ab initio study

A systematic study of Fe atom encapsulation and adsorption in armchair SiC nanotubes (SiCNT) with diameters in the range of 5.313 to 10.582 Å has been performed using hybrid density functional theory and a finite cluster approximation. A detailed comparison of the binding energies, equilibrium positions, Mulliken charges, and spin magnetic moments of Fe atoms has been performed for three types of nanotubes. The electronic states, HOMO–LUMO gaps, and changes in gaps with respect to the bare nanotube gaps have been investigated as well. Our results show that the properties of SiCNT can be modified by Fe atom encapsulation and adsorption. Binding energies of the encapsulated and adsorbed systems indicate that these structures are stable and show site dependence. For both cases a significant band gap decrease is observed for type 1 nanotubes enabling band gap tailoring. This decrease is not observed for the other two types with a larger diameter. All structures are found to have magnetic ground states with high magnetic moments indicating the possibility of them being used in spintronics applications.