Analysis of the nonlinear dynamics of inter-cycle combustion variations in an ethanol fumigation-diesel dual-fuel engine

Nonlinear Dynamics - The nonlinear dynamics of a combustion system in a modern common-rail dual-fuel engine has been studied. Using nonlinear dynamic data analysis (phase space reconstruction,...     

Electrochemical behavior of ascorbic acid at a 2,2'-[3,6-Dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone carbon paste electrode

Electrocatalytic oxidation of ascorbic acid (AA) at a carbon paste electrode, chemically modified 2,2'-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone, was thoroughly investigated. The results of cyclic voltammetry, double potential-step chronoamperometry, linear sweep voltammetry and differential pulse voltammetry (DPV) studies were used for the prediction of the mechanism of electrochemical oxidation of AA mediated with 2,2'-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone at the surface of the modified electrode. The diffusion coefficient (D = 2.45 x 10(-5) cm(2) s(-1)) and the kinetic parameters such as the electron transfer coefficient (alpha = 0.34) were also determined. The results of DPV using the 2,2'-[3,6-dioxa-1,8-octanediylbis(nitriloethylidyne)]-bis-hydroquinone-modified electrode were applied in a highly sensitive determination of AA in drug samples. A linear range of 3.0 x 10(-6) - 1.2 x 10(-4) M and the detection limit (3sigma) 3.8 x 10(-7) M were obtained for DPV determination of AA in buffered pH 7.00 solutions (0.1 M phosphate buffer).     

Generation of 150-nJ pulses from a multiple-pass cavity Kerr-lens mode-locked Ti:Al2O3 oscillator

A high-pulse-energy, prismless, Kerr-lens mode-locked, extended cavity Ti:sapphire laser is demonstrated with double-chirped mirrors and a multiple-pass cavity. The laser operates at 5.85-MHz repetition rate and generates pulse energies as high as 150 nJ with 43-fs pulse duration, corresponding to peak powers of 3.5 MW directly from the laser.     

Molecular orientation study of methylene blue at an air/fused-silica interface using evanescent-wave cavity ring-down spectroscopy

Using evanescent-wave cavity ring-down spectroscopy (EW-CRDS), we monitored the change in the absorbance of a thin film of methylene blue (MB) at an air/fused-silica interface while varying the polarization of the incident light (600 nm). We derived the average orientation angle of the planar MB molecules with respect to the surface normal and observed that the average orientation angle decreases as the surface concentration increases. At low surface concentrations, the MB molecules lie almost flat on the surface, whereas at higher surface concentrations the molecules become vertically oriented.     

Origin of InI emission in laser studies of the crossed beam reaction In+I2

When a beam of In is cross fired at a beam of I₂ and the intersection is irradiated by various cw laser sources, InI emission is observed. The origin of this emission is shown to be laser-induced fluorescence (LIF) from the ground state indium monoiodide product of the reaction In + I₂ → InI + I, rather than laser-induced chemiluminescence (LIC) through the excitation of the I₂ reagent in the reaction In + I₂³ → InI* + I. An upper bound on the cross section for the later process is estimated to be ?2.5 × 10^?16 cm². The LIF excitation spectrum reveals a strong inversion in the InI vibrational population distribution, with the fraction of the total excess energy of reaction in vibration exceeding 0.5. Preliminary results for the Tl + I₂ reaction system show the same LIF m     

A simple model for the difference between coherence time and radiative lifetime in NO2

An intramolecular mechanism is proposed to reconcile the different lifetimes obtained from direct radiative decay measurements and from Hanle effect measurements on NO₂. This mechanism predicts a dependence of the coherence lifetime on the excited state rotational quantum number which is in good agreement with the previous experiments.     

Determination of the electric dipole moment of the HSO radical in its X̃2A″(000) and Ã2A′(003) electronic states

Stark shifts were measured for the zero-field-allowed 0₀₀-1₁₀, 1₁₀-0₀₀ and zero-field-forbidden 0₀₀-1₁₁, 1₁₁-0₀₀ lines of the HSO $\text{A}\text{?}{}^2\text{A′(003)-}\text{X}\text{?}{}^2\text{A″(000)}$ transition. A single-mode dye laser is used to record the Doppler-limited fluorescence excitation spectrum as a function of applied electric field (0–11 kV/cm) for excitation polarizations parallel and perpendicular to the applied field direction. The electric dipole moment along the a axis of this near-prolate asymmetric top is determined to be μ″_a = 2.20 ± 0.08 D and μ′_a = 1.05 ± 0.08 D, in close agreement with recent ab initio calculations.     

A direct approach for the reduction of diatomic spectra to molecular constants for the construction of RKR potentials

A nonlinear fitting procedure is presented that employs all measured line positions and iteratively compares their values with those calculated from numerically diagonalized model Hamiltonians with adjustable molecular constants. Case (a) wavefunctions with definite parity are introduced as a convenient basis set, and the effects of spin-orbit, spin-spin, spin-rotation, and centrifugal distortion interactions neglected in the Born-Oppenheimer separation are included simultaneously using the Van Vleck transformation. The spectroscopic constants found by this procedure represent the minimum-variance, unbiased set and maintain, to a high degree of accuracy, the separate mechanical and magnetic meanings of the molecular constants. Arguments are presented that such spectroscopic constants with mechanical meaning allow the most accurate construction of potential energy functions using the Rydberg-Klein-Rees (RKR) procedure. Residual mechanical and magnetic ambiguities, such as engendered by Λ-type doubling, are discussed.