PBDDs/Fs and PCDDs/Fs in the raw and clean flue gas during steady state and transient operation of a municipal waste combustor

Concentrations of polybrominated dibenzo-p-dioxins, and -dibenzofurans (PBDDs/Fs) and polychlorinated dibenzo-p-dioxins, and -dibenzofurans (PCDDs/Fs), were determined in the pre- and post-air pollution control system (APCS) flue gas of a municipal waste combustor (MWC). Operational transients of the combustor were found to considerably increase levels of PBDDs/Fs and PCDDs/Fs compared to steady state operation, both for the raw and clean flue gas; ΣPBDDs/Fs increased from 72.7 to 700 pg dscm(-1) in the raw, pre-APCS gas and from 1.45 to 9.53 pg dscm(-1) in the post-APCS flue gas; ΣPCDDs/Fs increased from 240 to 960 ng dscm(-1) in the pre-APCS flue gas, and from 1.52 to 16.0 ng dscm(-1) in the post-APCS flue gas. The homologue profile of PBDDs/Fs and PCDDs/Fs in the raw flue gas (steady state and transients) was dominated by hexa- and octa-isomers, while the clean flue gas homologue profile was enriched with tetra- and penta-isomers. The efficiency of the APCS for PBDD/F and PCDD/F removal was estimated as 98.5% and 98.7%, respectively. The cumulative TEQ(PCDD/F+PBDD/F) from the stack was dominated by PCDD/F: the TEQ of PBDD/F contributed less than 0.1% to total cumulative toxic equivalency of MWC stack emissions.     

Chemiluminescence of isotactic polypropylene induced by photo‐oxidative degradation and natural weathering

The analysis of the chemiluminescence (CL) kinetic parameters (induction time, oxidation rate, and activation energy) after the UV irradiation and outdoor exposure of isotactic polypropylene (i‐PP) films have been studied. The initial CL emission intensity increased with increasing photodegradation time of i‐PP films. On photodegradation, the activation energies were found to decrease linearly with time of UV‐irradiation and outdoor exposure. The slopes of these linear dependences were used to indicate the degree of photodegradation of the polymer and also for the characterization of the stabilizing effect of the additive. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4623–4629, 2006     

A 3.1–4.8-GHz direct-conversion mixer in 0.35-μm CMOS for mode-1 MB-OFDM UWB systems

This paper presents a CMOS direct-conversion mixer for TFI-OFDM receiver of UWB group #1 bands, providing a 110 Mbits/s rate and optimized for 0.35-μm technology. The proposed mixer uses the current-bleeding technique in both the driver and switching stages with wideband impedance matching, consisting of a bandpass filter embedding the RF stage. The 1/f noise of the switching pairs dominates the noise performance for down-converted frequencies below 1 MHz. Above 1 MHz, the insertion of an inductor at the tail of switching pairs reduces uniformly the noise figure by 2.2 dB. Over 3.1–4.8 GHz, the circuit drawing 6 mA from 3-V supply, shows a conversion gain of 14.0 ± 1.0 dB, IIP3 of 0 ± 2 dBm, double-sideband noise figure of 4.5–4.8 dB, and port-to-port isolation above 61.0 dB. The mixer output bandwidth is 460 MHz. The RF power and LO amplitude marginally affect these performances within, respectively, the FCC-power limits and 2.5–3.4 V range.     

A High-Performance Doubly-Balanced Mixer in 0.35-μm CMOS for Mode-1 MB-OFDM UWB Receivers

A new design of CMOS doubly-balanced down-conversion mixer intended for Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) receiver of UWB group#1 bands and optimized for 0.35-μm technology is presented. The proposed mixer uses the current-bleeding technique in both the driver and switching stages with wideband impedance matching, consisting of a bandpass filter embedding the RF stage. The mixer performances are optimized for the AMS 0.35 μm CMOS process parameters. Over 3.1–4.8 GHz, the circuit drawing 6 mA from 3-V supply, shows a conversion gain of 14.0±1.0 dB, IIP3 of 0±2 dBm, doubly-sideband noise figure of 4.5–4.8 dB, and port-to-port isolation above 61.0 dB.

Aqueous hydrazine borane N2H4BH3 and nickel-based catalyst: An effective couple for the release of hydrogen in near-ambient conditions

Nickel-based bimetallic catalysts were screened using the sodium borohydride NaBH₄ hydrolysis and the aqueous hydrazine borane N₂H₄BH₃ dehydrogenation. A total of 22 bimetallic catalysts were synthesized according to an easy process while focusing on metals like Fe, Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt and Au. In the end, the bimetallic candidate Ni_87.5Pt_12.5 showed to be the most active and the most selective for the dehydrogenation of N₂H₄BH₃. At 70?°C, it is able to decompose N₂H₄BH₃ into 5.8 equivalents of H₂+N₂ in less than 12?min such as: N₂H₄BH₃?+?3H₂O?→?0.95 N₂?+?0.1 NH₃?+?B(OH)₃?+?4.85H₂. Durability and stability tests were also performed. In our conditions, Ni_87.5Pt_12.5 was found to suffer from small loss of performance because of an electronic evolution of the catalytic surface leading to modified sorption properties of the catalytic sites. Our main results are reported and discussed herein.     

Near-infrared photoluminescence of V-doped GaN

The visible and infrared luminescence of vanadium-doped GaN (GaN:V) grown by metalorganic vapour phase epitaxy technique (MOVPE) on SiN-treated sapphire substrate were examined. Growth process was in-situ monitored by laser reflectometry. At room temperature and in the visible spectral range, photoluminescence (PL) shows a strong blue emission band. At 10 K, the near-infrared PL spectra exhibit several emissions dominated by a zero-phonon line (ZPL) at 0.821 eV with a full-width at half-maximum (FWHM) of 8.8 meV. Other peaks emerge in the low- and high-energy side of ZPL, which can be assigned to the fine structure of the charge state or the satellite lines. By increasing the temperature, the peaks’ intensities decrease and disappear above 150 K. The red-shift and the FWHM of the 0.821 eV line increase versus temperature, indicating a high contribution of the photonic Raman processes. This emission was assigned to be a vanadium intracenter emission.     

Reducing and manipulating complex trace data

In performance analysis of computer systems, trace-driven simulation techniques have the important advantage of credibility and accuracy. Unfortunately, traces are usually difficult to obtain, and little work has been done to provide efficient tools to help in the process of reducing and manipulating them. This paper presents TRAMP, a tool for the data reduction and data analysis phases of trace-driven simulation studies. TRAMP has three main advantages: it accepts a variety of common trace formats; it provides a programmable user interface in which many actions can be directly specified; and it is easy to extend. TRAMP is particularly helpful for reducing and analysing complex trace data, such as traces of file system or database activity. This paper presents the design principles and implementation techniques of TRAMP and provides a few concrete examples of the use of this tool.     

A Constructive Globally Convergent Adaptive Speed Observer For Port‐Hamiltonian Mechanical Systems with Non‐Holonomic Constraints

This paper presents an adaptive speed observer for general port‐Hamiltonian mechanical systems with non‐holonomic constraints in the presence of unknown friction forces and constant disturbances. Unlike the observers recently reported in the literature, which have been designed either under the assumptions of no friction and the absence of disturbances or for a specific class of mechanical systems with the requirement of an explicit solution of certain Partial Differential Equations (PDEs) that cannot be derived a priori, this observer proposes a design that obviates the solution of PDEs and ensures global convergence for general mechanical systems with k‐non‐holonomic constraints. The observer is totally constructive and given by explicit expressions. The simulation results testify to the effectiveness and the robust features of the developed observer.     

Kinetic Study of Hindered Amine Light Stabilizer Photografting in Poly(propylene) Films under Natural Weathering and Accelerated UV Conditions: Effect of Additive Concentration

Full Paper: The objective of this work is aimed at determining the kinetics of HALS photografting in PP films as a function of the additive concentration under both natural weathering and accelerated UV conditions. The stabilizer studied had a single structure that combined HALS and a UV absorbing unit detectable at 308 nm in the UV spectrum of PP, capable of inducing a photoreaction with the polymer matrix. The kinetics of HALS photografting on PP films at various additive concentrations was determined by direct spectroscopic measurements on film samples through the absorption band of the stabilizer positioned at 308 nm in the UV spectra, which was attributed to the highly conjugated methylenic double bond. The content of free HALS was determined as a function of exposure time by UV spectroscopy for all the additive concentration ratios used. It is shown that the kinetics of HALS photografting increase with a decrease in the additive concentration ratio. The whole grafting process under conditions of natural weathering occurred in the PP film after almost 350 h of exposure, while approximately 20 h were necessary under accelerated UV conditions. Moreover, these kinetics are well described by a third order polynomial model, validated by a maximum value of the coefficient of correlation close to unity. This was also confirmed by a comparison of the time values measured at 50% of the total grafting calculated from the model with those observed experimentally. This finding was consistent with the data obtained on the free HALS content determined by UV spectroscopy.

The percentage of HALS photografting in PP films as a function of time under natural weathering, determined by UV spectroscopy.     

Robust inversion for material parameters identification from correlated outlying observations

In this paper, a novel robust inversion method for correlated observations (RIMCO) is proposed to determine the material parameters from correlated observations under the effect of outliers and leverage points. This method is based on a full equivalent weight matrix established from the original measurement weight matrix and an adapted full weight matrix with hard rejection to outliers. This equivalent weight matrix plays key role to refine the stochastic model, while keeping the original correlation of measurements unchanged on the one hand, and ensuring simultaneously high robustness and statistical efficiency of the proposed method, on the other hand. The performance of the proposed method is demonstrated by considering a rockfill dam as an example, where the material parameters are identified from geotechnical and geodetic measurements after achievement of the construction, and during the first filling up of reservoir. Results of comparison of RIMCO with least squares and M Huber methods concerning their robustness and efficiency are presented for various configuration options.