Temperature and CO2 concentration measurements in the exhaust stream of a liquid-fueled combustor using dual-pump coherent anti-Stokes Raman scattering (CARS) spectroscopy

Single-shot, dual-pump coherent anti-Stokes Raman scattering (CARS) measurements of N₂ and CO₂ were performed in the exhaust stream of a swirl-stabilized JP-8-fueled combustor under sooting conditions. The combustor is designed to study particulate formation and particle-size distributions for different flame conditions and therefore is operated at near-stoichiometric overall fuel-air ratios. Various jet fuels and additive concentrations were studied. These conditions pose a significant challenge for temperature measurements using standard N₂ CARS due to strong flame emission and absorption of the CARS signal by the C₂ Swan band. With the dual-pump CARS technique employed in this study, the N₂ CARS signal is generated at a wavelength (496 nm) that is not absorbed by C₂, and concentration measurements of CO₂ can be performed. The standard deviations of the single-shot temperature measurements were approximately 3-4% of the mean values for equivalence ratios ranging from 0.4 to 1.1, whereas those of the single-shot CO₂ concentration measurements were between 9 and 20% of the mean values. Previous single-shot temperature and CO₂ concentration measurements using dual-pump CARS in this liquid-fueled combustor were limited to an equivalence ratio of 0.45, with standard deviations in temperature of about 5-6% of the mean value of 1143 K (Lucht et al., AIAA J. 41 (4) (2003) 679-686). The current study demonstrates a significant improvement in the applicability of single-shot CARS temperature and CO₂ concentration measurements to practical, swirl-stabilized combustors under sooting conditions.     

Narrow-linewidth megahertz-repetition-rate optical parametric oscillator for high-speed flow and combustion diagnostics

We demonstrate the ability to generate ultra-high-frequency sequences of broadly wavelength-tunable, high-intensity laser pulses using a custom-built optical parametric oscillator pumped by the third-harmonic output of a "burst-mode" Nd:YAG laser. Burst sequences consisting of 6-10 pulses separated in time by 6-10 mus are obtained, with average total conversion efficiency from the 355 nm pump to the near-IR signal and idler wavelengths of approximately 33%. Typical individual pulse output energy for the signal and idler beams is in the range of 4-6 mJ, limited by the available pump energy. Line narrowing is demonstrated by means of injection seeding the idler wave using a low-power external-cavity diode laser at 827 nm. It is shown that seeding reduces the time-averaged linewidth of both the signal and idler outputs to approximately 300 MHz, which is near the 220 MHz Fourier transform limit. Line narrowing is achieved without recourse to active cavity stabilization.     

Spatial correlation coefficient images for ultrasonic detection

In ultrasonics, image formation and detection are generally based on signal amplitude. In this paper, we introduce correlation coefficient images as a signal-amplitude independent approach for image formation. The correlation coefficients are calculated between A-scans digitized at adjacent measurement positions. In these images, defects are revealed as regions of high or low correlation relative to the background correlations associated with noise. Correlation coefficient and C-scan images are shown to demonstrate flat-bottom-hole detection in a stainless steel annular ring and crack detection in an aluminum aircraft structure.     

Thulium Oxide Nanopowders Obtained by Precipitation

The aim of this work was to investigate the influence of precipitation parameters on the morphology of obtained thulium oxide powders. Tm₂O₃ precursor powders were synthesized by precipitation method using 0.1–0.25M water solutions of thulium nitrate and 1.5M ammonium hydrogen carbonate water solution as a precipitation agent. The processes were conducted at different temperatures (25–50°C). The result showed that the morphology of the obtained thulium oxide (Tm₂O₃) powders depends both on the molar concentration of thulium nitrate and the temperature of precipitation. Small, round, loosely agglomerated Tm₂O₃ nanoparticles were obtained after air calcination of precursor precipitated at room temperature with the use of 0.1M thulium nitrate solution.     

Classifying Facial Actions

The Facial Action Coding System (FACS) [23] is an objective method for quantifying facial movement in terms of component actions. This system is widely used in behavioral investigations of emotion, cognitive processes, and social interaction. The coding is presently performed by highly trained human experts. This paper explores and compares techniques for automatically recognizing facial actions in sequences of images. These techniques include analysis of facial motion through estimation of optical flow; holistic spatial analysis, such as principal component analysis, independent component analysis, local feature analysis, and linear discriminant analysis; and methods based on the outputs of local filters, such as Gabor wavelet representations and local principal components. Performance of these systems is compared to naive and expert human subjects. Best performances were obtained using the Gabor wavelet representation and the independent component representation, both of which achieved 96 percent accuracy for classifying 12 facial actions of the upper and lower face. The results provide converging evidence for the importance of using local filters, high spatial frequencies, and statistical independence for classifying facial actions.     

Antioxidant Potential of Pea Beans (Phaseolus vulgaris L.)

ABSTRACT: Four bean varieties ( Phaseolus vulgaris L.) (white kidney, red pinto, Swedish brown, and black kidney) and their hull fractions were extracted with 80% acetone and evaluated for their phenolic contents and antiradical activities. Total phenolic content of bean hulls and whole seed extracts ranged from 6.7 to 270 and 4.9 to 93.6 mg/g extract as catechin equivalents, respectively. Trolox equivalent antioxidant capacity (TEAC) assay revealed that the antioxidant capacity of red, brown, and black whole seed extracts was in the same order of magnitude with little variation. TEAC values of red and brown whole seed extracts were superior to that of black whole seed extract. On the basis of the total phenolic content and TEAC values, it can be deduced that colored beans possess superior antioxidative activity compared with white beans. The hydrogen peroxide scavenging capacity of different bean extracts ranged from 58% to 67% at 50 ppm and 65% to 76% at 100 ppm. The corresponding superoxide radical scavenging capacity was 24% to 29% at 50 ppm and 53% to 60% at 100 ppm. The 2,2–diphenyl-1–picrylhydrazyl (DPPH) radical scavenging capacity of black bean whole seed extracts was 22% at 50 ppm, whereas the other extracts showed 100% scavenging of this radical at both 50 and 100 ppm levels. The hydroxyl radical scavenging capacities of the bean extracts at 50 and 100 ppm were 12% to 29% and 32% to 49%, respectively. All extracts used prevented human low-density lipoprotein (LDL) cholesterol oxidation by 61.4% to 99.9% at 2 to 50 ppm level as catechin equivalents.