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A multiple input multiple output (MIMO) power line communication (PLC) model for industrial facilities was developed that uses the physics of a bottom-up model but can be calibrated like top-down models. The PLC model considers 4-conductor cables (three-phase conductors and a ground conductor) and has several load types, including motor loads. The model is calibrated to data using mean field variational inference with a sensitivity analysis to reduce the parameter space. The results show that the inference method can accurately identify many of the model parameters, and the model is accurate even when the network is modified. [ABSTRACT FROM AUTHOR]

We demonstrate detection of nitro-containing compounds with laser photofragmentation (PF) coupled with resonance enhanced multiphoton ionization (REMPI) and ion mobility spectrometry (IMS). In PF-REMPI, a laser dissociates the parent molecules, producing fragments that can then be ionized by absorption of additional laser photons. The production of these ions strongly depends on the wavelength of laser light, with ion yields corresponding to the absorption spectrum of the fragments [nitric oxide (NO) in the present case]. Combining IMS with PF-REMPI provides further specificity, separating ions according to their mobilities through an atmospheric-pressure drift tube. In this work, we use a pulsed UV laser to examine the characteristics of atmospheric-pressure PF-REMPI, the chemistry occurring in the ionization region and drift tube, and the viability of detecting ions created by both resonance-enhanced and nonresonant ionization. Probing NO in a helium--nitrogen bath, we demonstrate that the detection of ions displays single-shot response to changes in ion generation, with an ion extraction-to-collection efficiency of ~12%. We then evaluate the sensitivity and specificity of PF-REMPI/IMS as applied to the detection of both the explosive surrogate 2, 4-dinitrotoluene and the nuisance compound nitrobenzene. [c] 2010 Optical Society of America OCIS codes: 120.0280, 300.6360, 300.6410.

The effects of collisional quenching on photofragment emission (PFE) detection of vapor-phase Hg[Cl.sub.2] in combustion flue gas constituents are investigated. Exciting Hg[Cl.sub.2] via the 1 [sup.1][[PI].sub.u] [left arrow] 1 [sup.1][[summation].sup.+.sub.g] transition, time-resolved measurements of emission from the Hg([6.sup.3][P.sub.1]) daughter in buffer-gas mixtures of [N.sub.2], [O.sub.2], and C[O.sub.2] indicate that the fragmentation pathway passes through a long-lived intermediate species, which we assign to Hg([6.sup.3][P.sub.2]). Total quenching rate coefficients of Hg([6.sup.3][P.sub.1]) by [N.sub.2], [O.sub.2], and C[O.sub.2] are consistent with values reported in the literature. In addition, total quenching rate coefficients for the intermediate Hg([6.sup.3][P.sub.2]) state are determined to be 1.72([+ or -] 0.08) x [10.sup.-10] [cm.sup.3] [molecule.sup.-1] [s.sup.-1] and 2.90([+ or -] 0.37) x [10.sup.-10] [cm.sup.3] [molecule.sup.-1] [s.sup.-1] for [N.sub.2] and [O.sub.2], respectively. An analysis of the impact of the collisionally dependent energy-transfer process that precedes the formation of Hg([6.sup.3][P.sub.1]) on the use of PFE to measure Hg[Cl.sub.2] concentration is presented. OCIS codes: 280.1120, 300.2530, 120.0280.

A real-time, noninvasive approach for detecting trace amounts of vapor-phase mercuric chloride (Hg[Cl.sub.2]) in combustion flue gas is demonstrated using a near-infrared pulsed fiber amplifier that is frequency converted to the ultraviolet. Excitation of the Hg[Cl.sub.2] ([1.sup.1][[PHI].sub.[micro]] [left arrow] [1.sup.1] [[SIGMA].sup.+.sub.g]]) transition at 213 nm generates 253.7 nm emission from the Hg ([6.sup.3][P.sub.1]) photoproduct that is proportional to the concentration of Hg[Cl.sub.2]. A measured quadratic dependence of the Hg[Cl.sub.2] photofragment emission (PFE) signal on the laser irradiance indicates that the photodissociation process involves two-photon excitation. Additionally, low concentrations of Hg[Cl.sub.2] are detected with the PFE approach in an environment characteristic of coal-fired power-plant flue gas using this compact solid-state laser source. A detection limit of 0.7 ppb is extrapolated from these results. OCIS codes: 280.1120, 300.2530, 120.0280.

The viability of pulsed laser photofragment emission (PFE) is evaluated for the in situ measurement of vapor-phase mercuric chloride (Hg[Cl.sub.2]) concentration in combustion flue gas. Dispersed emissions from both the Hg ([6.sup.3][P.sub.1]) and HgCl ([B.sup.2] [[SIGMA].sup.+] photoproducts are presented, and the dependence of the Hg[Cl.sub.2] PFE signal originating from Hg ([6.sup.3][P.sub.1]) on the collisional environment is examined for buffer-gas mixtures of [N.sub.2], [O.sub.2], and C[O.sub.2]. Integrated PFE intensity measurements as a function of buffer gas pressure support the assumption that the primary effect of the relevant flue gas constituents is to quench emission from Hg ([6.sup.3][P.sub.1]). The quenching rate constants for PFE from Hg[Cl.sub.2] were measured to be 1.37 ([+ or -] 0.16) x [10.sup.5] [Torr.sup.-1] [s.sup.-1] for [N.sub.2], 9.35 ([+ or -] 0.25) X [10.sup.6] [Torr.sup.-1] [s.sup.-1] for [O.sub.2], and 1.49 ([+ or -]) X [10.sup.6] [Torr.sup.-1] for C[O.sub.2]. These values are in good accord with literature values for the quenching of Hg ([6.sup.3][P.sub.1]). The emission cross section for Hg ([6.sup.3][P.sub.1]) generated by photodissociation of Hg[Cl.sub.2] in 760 Torr [N.sub.2] is found to be 1.0 ([+ or -] 0.2) X [10.sup.-25] [m.sup.2] by comparing the PFE signal to [N.sub.2] Raman scattering. OCIS codes: 280.1120, 300.2530, 120.0280.

A frequency-locked, injection-seeded, pulsed optical parametric generator (OPG) has been developed for short-range infrared differential absorption lidar (DIAL) applications. The periodically poled lithium niobate OPG is pumped by a passively Q-switched Nd:YAG microlaser and is seeded by a distributed feedback (DFB) diode laser. The OPG is designed for DIAL measurement of a narrow R-branch transition of methane at 3.2704 [micro]m. The output of the OPG is a two-pulse sequence with a 100-[micro]s temporal separation between the pulses, where the first pulse is absorbed by methane and the second pulse is not absorbed. The first pulse is actively locked to the methane absorption feature by use of the derivative of the transmission spectrum through a reference cell. Although the device was not optimized for output power, the 3.27-[micro]m OPG output energies of the first and second pulses are 5.5 and 5.9 [micro]J, respectively, producing 21 mW when operated at 1818 Hz. OCIS codes: 280.1910, 190.2620, 190.4970.

Degenerate four-wave mixing (DFWM) line shapes and signal intensities are measured experimentally in well-characterized hydrogen-air flames operated over a wide range of equivalence ratios. We use both low (perturbative) and high (saturating) beam intensities in the phase-conjugate geometry. Resonances in the A (super 2)(SIGMA)(super +) -X (super 2)II (0,0) band of OH are probed with multiaxial-mode laser radiation. The effects of saturation on the line-center signal intensity and the resonance linewidth are investigated. The DFWM signal intensities are used to measure OH number densities in a series of near-adiabatic flames at equivalence ratios ranging from 0.5 to 1.5. Use of saturating pump intensities minimizes the effects of beam absorption, providing more-accurate number density measurements. The saturated DFWM results are in excellent agreement with OH absorption measurements and equilibrium calculations of OH number density. The polarization dependence of the P(sub 1)(2) and R(sub 2)(1) resonances is investigated in both laser intensity regimes. There is a significant change in relative reflectivities for different polarization configurations when saturated.

Picosecond time-resolved laser-induced fluorescence (PITLIF) can potentially be used to obtain measurements of minor species concentrations in rapidly fluctuating flames. Previous studies demonstrated this potential for atomic sodium by monitoring the temporal fluorescence signal with both an equivalent-time and a real-time sampling method. In this developmental study, PITLIF is used to determine hydroxyl concentrations in laminar C[H.sub.4]-[O.sub.2]-[N.sub.2] flames by the measurement of both the integrated fluorescence signal and the fluorescence lifetime. The quenching environment can be monitored with real-time sampling, and thus the necessary quenching rate coefficient is obtained in 348 [[micro]second], which is fast enough for use in many turbulent flows. Fluorescence lifetimes of OH are also measured at different equivalence ratios in laminar flames by the use of the equivalent-time sampling technique. These results compare favorably with predicted lifetimes based on relevant quenching cross sections and calculated species concentrations. Key words: Laser-induced fluorescence, lifetime measurements, hydroxyl.

Picosecond time-resolved laser-induced fluorescence (PITLIF) has the potential to provide rapid measurements of minor-species concentrations by correction for local quenching conditions on the time scale of turbulence. Previous studies demonstrated that this technique could provide laser-induced fluorescence data and local quenching rates in flames but used equivalent-time sampling to obtain the required fluorescence decays. This precludes the use of PITLIF in turbulent systems. Fluorescence decays of sodium seeded into a laminar [H.sub.2]-[O.sub.2]-Ar diffusion flame are obtained from real-time data with an acquisition rate on the time scale of turbulence. The results obtained with this method are shown to be similar to those obtained from equivalent-time sampling. Key words: Laser-induced fluorescence, lifetime measurements.

We study the formation of dust in the expanding gas ejected as a result of a common envelope binary interaction. In our novel approach, we apply the dust formation model of Nozawa et al. to the outputs of the 3D hydrodynamic SPH simulation performed by Iaconi et al. that involves a giant of 0.88 M⊙ and 83 R⊙, with a companion of 0.6 M⊙ placed on the surface of the giant in circular orbit. After simulating the dynamic in-spiral phase, we follow the expansion of the ejecta for |$\simeq 18\, 000$|  d. During this period, the gas is able to cool down enough to reach dust formation temperatures. Our results show that dust forms efficiently in the window between ≃ 300 d (the end of the dynamic in-spiral) and ≃ 5000 d. The dust forms in two separate populations; an outer one in the material ejected during the first few orbits of the companion inside the primary's envelope and an inner one in the rest of the ejected material. We are able to fit the grain-size distribution at the end of the simulation with a double power law. The slope of the power law for smaller grains is flatter than that for larger grains, creating a knee-shaped distribution. The power-law indexes are, however, different from the classical values determined for the interstellar medium. We also estimate that the contribution to cosmic dust by common envelope events is not negligible and comparable to that of novae and supernovae. [ABSTRACT FROM AUTHOR]

The morphology of bipolar planetary nebulae (PNe) can be attributed to interactions between a fast wind from the central engine and the dense toroidal-shaped ejecta left over from common envelope (CE) evolution. Here we use the 3D hydrodynamic adaptive mesh refinement (AMR) code AstroBEAR to study the possibility that bipolar PN outflows can emerge collimated even from an uncollimated spherical wind in the aftermath of a CE event. The output of a single CE simulation via the smoothed particle hydrodynamics (SPH) code phantom serves as the initial conditions. Four cases of winds, all with high enough momenta to account for observed high momenta pre-PN outflows, are injected spherically from the region of the CE binary remnant into the ejecta. We compare cases with two different momenta and cases with no radiative cooling versus application of optically thin emission via a cooling curve to the outflow. Our simulations show that in all cases highly collimated bipolar outflows result from deflection of the spherical wind via the interaction with the CE ejecta. Significant asymmetries between the top and bottom lobes are seen in all cases. The asymmetry is strongest for the lower momentum case with radiative cooling. While real post-CE winds may be aspherical, our models show that collimation via 'inertial confinement' will be strong enough to create jet-like outflows even beginning with maximally uncollimated drivers. Our simulations reveal detailed shock structures in the shock-focused inertial confinement (SFIC) model and develop a lens-shaped inner shock that is a new feature of SFIC-driven bipolar lobes. [ABSTRACT FROM AUTHOR]

The physics of short-pulse polarization spectroscopy (PS) and the diagnostic potential for quantitative measurements of species concentration are investigated by direct numerical integration (DNI) of the time-dependent density matrix equations for a multistate system. The effects of laser power, collision rates, and Doppler broadening on the short-pulse PS signal generation process are investigated by systematically varying these parameters in the numerical calculations. It is found that the use of a short-pulse laser (laser pulse width τLC) significantly decreases the collision-rate dependence of the PS signal compared to the long-pulse laser case (τ[sub L]>τ[sub C]), even for a nonsaturating pump beam. For a saturating pump beam, the short-pulse PS signal is found to be nearly independent of collision rate. Increasing the collision rate by a factor of 100 (from 10[sup 8] to 10[sup 10] s[sup -1]), the calculated PS signal strength decreases by only a factor of 2 for a 100-ps pump laser at high intensity. This insensitivity of the PS signal to the collision rate in the medium enhances greatly the potential for quantitative application of the technique for concentration measurements in reacting flows. The underlying physics of the short-pulse PS is explored by studying the effects of collision rate, Doppler broadening, and the pump laser intensity on the temporal profile of the Zeeman state populations and the coherences between the Zeeman states. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The collisional dependence of polarization spectroscopy (PS) with a picosecond-pulse laser is investigated theoretically with a perturbative treatment and experimentally by probing hydroxyl (OH) in a flow cell with a buffer gas of argon. Using a frequency-doubled distributed-feedback dye laser (DFDL), the PS signal strength is monitored as a function of pressure using a nonsaturating pump beam and a saturating pump beam. The collisional dependence of the PS signal is found to decrease significantly with a saturating pump beam. Increasing the flow-cell pressure by a factor of 50 (from 10 torr to 500 torr), the PS signal strength produced with a nonsaturating pump beam decreases by a factor of 18 while that produced with a saturating pump decreases by only a factor of 3. A third-order perturbative (weak-field) approach is used to develop an analytical expression for the PS signal generated by single-mode, exponentially decaying laser pulses. This expression correctly predicts the experimental results acquired with the nonsaturating pump beam. The analytical solution is used to examine the effects of pulse length on the collisional dependence of the weak-field PS signal strength. Results are also presented for a numerical simulation of the time-dependent density matrix equations for the high intensity case. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Investigates the physics of the degenerate four-wave mixing process for resonant transitions between two degenerate energy levels by means of direct numerical integration of the time-dependent density matrix equations. Inclusion of the Zeeman structure of the upper and lower energy levels; Effect of saturation of the resonance line shapes.

We investigate the common envelope binary interaction, that leads to the formation of compact binaries, such as the progenitors of Type Ia supernovae or of mergers that emit detectable gravitational waves. In this work, we diverge from the classic numerical approach that models the dynamic inspiral. We focus instead on the asymptotic behaviour of the common envelope expansion after the dynamic inspiral terminates. We use the SPH code phantom to simulate one of the set-ups from Passy et al. with a 0.88 M⊙, 83 R⊙ RGB primary and a 0.6 M⊙ companion, then we follow the ejecta expansion for 50 yr. Additionally, we utilize a tabulated equation of state including the envelope recombination energy in the simulation (Reichardt et al.), achieving a full unbinding. We show that, as time passes, the envelope's radial velocities dominate over the tangential ones, hence allowing us to apply an homologous expansion kinematic model to the ejecta. The external layers of the envelope become homologous as soon as they are ejected, but it takes 5000 d (14 yr) for the bulk of the unbound gas to achieve the homologously expanding regime. We observe that the complex distribution generated by the dynamic inspiral evolves into a more ordered, shell-like shaped one in the asymptotic regime. We show that the thermodynamics of the expanding envelope are in very good agreement with those expected for an adiabatically expanding sphere under the homologous condition and give a prediction for the location and temperature of the photosphere assuming dust to be the main source of opacity. This technique ploughs the way to determining the long-term light behaviour of common envelope transients. [ABSTRACT FROM AUTHOR]

We have simulated a common envelope interaction between a 0.88 M⊙, 90 R⊙, red giant branch star, and a 0.6 M⊙, compact companion with the smoothed particle hydrodynamics code, phantom, from the beginning of the Roche lobe overflow phase to the beginning of the self-regulated inspiral, at three different resolutions. The duration of the Roche lobe overflow phase is resolution dependent and would lengthen with increased resolution beyond the ∼20 yr observed, while the inspiral phase and the post-common envelope separation are largely independent of (average) resolution. Mass transfer rates through the Lagrangian points drive the orbital evolution during the Roche lobe overflow phase, as predicted analytically. The absolute mass transfer rate is resolution dependent, but always within a factor of two of the analytical value. Similarly, the gravitational drag in the simulations is close to the analytical approximation. This verifies simulations and shows that these analytical approximations are reasonable. The L 2 and L 3 outflows observed during Roche lobe overflow remain bound, forming a circumbinary disc that is largely disrupted by the common envelope ejection. However, a longer phase of Roche lobe overflow and weaker common envelope ejection typical of a more stable Roche lobe phase may result in a surviving circumbinary disc. Finally, we examine the density distribution resulting from the interaction for simulations that include or omit the phase of Roche lobe overflow. We conclude that the degree of stability of the Roche lobe phase modulates the shape of the subsequent planetary nebula, explaining the wide range of post-common envelope planetary nebula shapes observed. [ABSTRACT FROM AUTHOR]

Investigates the polarization spectroscopy (PS) of the time-dependent density matrix equations through direct numerical integration. Inclusion of the Zeeman structure of upper and lower energy levels; Effects of strong saturation on PS signal levels and line shapes; Application of PS in flame and plasma concentration measurements.

We investigate the accuracy of temperature measurements by coherent anti-Stokes Raman spectroscopy (CARS) of [O.sub.2] and use measurements taken with [N.sub.2] CARS and a thermocouple for comparison. Scanning vibrational CARS spectra of [O.sub.2] and [N.sub.2] were recorded over a broad range of temperatures: between 294 K and 1900 K in air that wets heated in a tube furnace and at approximately 2450 K in a fuel-lean [CH.sub.4]-[O.sub.2]-[N.sub.2] flame. Temperatures were derived from least-squares fits of simulated and experimental spectra. Both the fundamental vibrational band and the first hot vibrational band were included in fitting. In the case of the tube furnace, the [N.sub.2] and the [O.sub.2] CARS temperature measurements agreed to within 3%, and results were similar with the thermocouple; in the flame the agreement was to within 1%. We conclude that, for cases in which [O.sub.2] is present in sufficient concentrations ([approximately equals]10% or greater), the accuracy of [O.sub.2] thermometry is comparable with that of [N.sub.2]. [C] 2001 Optical Society of America OCIS codes: 120.1740, 300.6230.

Polarization-spectroscopy (PS) line shapes and signal intensities are measured in well-characterized hydrogen-air flames operated over a wide range of equivalence ratios. We use both low (perturbative) and high (saturating) pump beam intensities in the counterpropagating pump-probe geometry. The effects of saturation on the line-center signal intensity and the resonance linewidth are investigated. The PS signal intensities are used to measure relative OH number densities in a series of near-adiabatic flames at equivalence ratios ([Phi]) ranging from 0.5 to 1.5. The use of saturating pump intensities minimizes the effect of pump beam absorption, providing more accurate number density measurements. When calibrated to the calculated OH concentration in the [Phi] = 0.6 flame, the saturated PS number density measurements probing the [P.sub.1](2) transition are in excellent agreement with OH absorption measurements, equilibrium calculations of OH number density, and previous saturated degenerate four-wave mixing OH number density measurements. OCIS codes: 120.1740, 300.6420.

We present hydrodynamic simulations of the common envelope binary interaction between a giant star and a compact companion carried out with the adaptive mesh refinement code ENZO and the smooth particle hydrodynamics code PHANTOM. These simulations mimic the parameters of one of the simulations by Passy et al. but assess the impact of a larger, more realistic initial orbital separation on the simulation outcome. We conclude that for both codes the post-common envelope separation is somewhat larger and the amount of unbound mass slightly greater when the initial separation is wide enough that the giant does not yet overflow or just overflows its Roche lobe. PHANTOM has been adapted to the common envelope problem here for the first time and a full comparison with ENZO is presented, including an investigation of convergence as well as energy and angular momentum conservation. We also set our simulations in the context of past simulations. This comparison reveals that it is the expansion of the giant before rapid in-spiral and not spinning up of the star that causes a larger final separation. We also suggest that the large range in unbound mass for different simulations is difficult to explain and may have something to do with simulations that are not fully converged. [ABSTRACT FROM AUTHOR]

Bayesian inference is used to calibrate a bottom-up home PLC network model with unknown loads and wires at frequencies up to 30 MHz. A network topology with over 50 parameters is calibrated using global sensitivity analysis and transitional Markov Chain Monte Carlo (TMCMC). The sensitivity-informed Bayesian inference computes Sobol indices for each network parameter and applies TMCMC to calibrate the most sensitive parameters for a given network topology. A greedy random search with TMCMC is used to refine the discrete random variables of the network. This results in a model that can accurately compute the transfer function despite noisy training data and a high dimensional parameter space. The model is able to infer some parameters of the network used to produce the training data, and accurately computes the transfer function under extrapolative scenarios. [ABSTRACT FROM AUTHOR]

The morphologies of planetary nebula have long been believed to be due to wind shaping processes in which a "fast wind" from the central star impacts a previously ejected envelope. It is assumed that asymmetries existing in the "slow wind" envelope would lead to inertial confinement, shaping the resulting interacting wind flow. We present new results demonstrating the effectiveness of Common Envelope Evolution (CEE) at producing aspherical envelopes which, when impinged upon by a spherical fast stellar wind, produce highly bipolar, jet-like outflows. We have run two simple cases using the output of a single PHANTOM SPH CEE simulation. Our work uses the Adaptive Mesh Refinement code AstroBEAR to track the interaction of the fast wind and CEE ejecta allows us to follow the morphological evolution of the outflow lobes at high resolution in 3-D. Our two models bracket low and high momentum output fast winds. We find the interaction leads to highly collimated bipolar outflows. In addition, the bipolar morphology depends on the fast wind momentum injection rate. With this dependence comes the initiation of significant symmetry breaking between the top and bottom bipolar lobes. Our simulations, though simplified, confirm the long-standing belief that CEE can plan a major role in PPN and PN shaping. These simulations are intended as an initial exploration of the post-CE/PPN flow patterns that can be expected from central source outflows and CE ejecta. [ABSTRACT FROM AUTHOR]

The calculation of laser-induced radiative transition rates for electric-dipole transitions is reviewed. The effects of laser polarization can only be understood by considering the Zeeman structure of energy levels. In particular, the case of laser coupling of degenerate levels is considered by including the Zeeman structure of the upper and lower energy levels. The interaction of the laser radiation with the atomic or molecular resonance is formulated in terms of the density matrix. The electric-dipole matrix elements are written as the product of a scalar quantity, the reduced density matrix element, and a vector quantity that is a function of the angular momentum quantum numbers J and magnetic quantum numbers M for the upper and lower Zeeman states. The calculation of absorption and stimulated emission rates, absorption coefficients, and susceptibilities for the limiting case of an isotropic medium is reviewed. Polarization effects in laser-induced fluorescence are reviewed, and the theoretical framework for the analysis of these effects is developed. The calculation of polarization spectroscopy signals and of polarization effects in resonant four-wave mixing are discussed. The effects of hyperfine structure in diatomic molecules are discussed. [Copyright &y& Elsevier]