Effects of OH concentration and temperature on NO emission characteristics of turbulent non-premixed CH4/NH3/air flames in a two-stage gas turbine like combustor at high pressure

This study examined the effects of OH concentration and temperature on the NO emission characteristics of turbulent, non-premixed methane (CH₄)/ammonia (NH₃)/air swirl flames in two-stage combustors at high pressure. Emission data were obtained using large-eddy simulations with a finite-rate chemistry method from model flames based on the energy fraction of NH₃ (E_NH3) in CH₄/NH₃ mixtures. Although NO emissions at the combustor exit were found to be significantly higher than those generated by CH₄/air and NH₃/air flames under both lean and stoichiometric primary zone conditions, these emissions could be lowered to approximately 300 ppm by employing far-rich equivalence ratios (?) of 1.3 to 1.4 in the primary zone. This effect was possibly due to the lower OH concentrations under far-rich conditions. An analysis of local flame characteristics using a newly developed mixture fraction equation for CH₄/NH₃/air flames indicated that the local temperature and NO and OH concentration distributions with local ? were qualitatively similar to those in NH₃/air flames. That is, the maximum local NO and OH concentrations appeared at local ? of 0.9, although the maximum temperature was observed at local ? of 1.0. Both the temperature and OH concentration were found to gradually decrease with the partial replacement of CH₄ with NH₃. Consequently, NO emissions from CH₄/NH₃ flames were maximized at E_NH3 in the range of 20% to 30%, after which the emissions decreased. Above 2100 K, the NO emissions from CH₄/NH₃ flames increased exponentially with temperature, which was not observed in NH₃/air flames because of the lower flame temperatures in the latter. But, the maximum NO concentration in CH₄/NH₃ flames was occurred at a temperature slightly below the maximum temperature, just as in NH₃/air flames. The apparent exponential increase in NO emissions from CH₄/NH₃ flames is attributed to a similar trend in the OH concentration at high temperatures.     

Coarse Metal Powder-Assisted pulsed CO2 Laser-induced Breakdown Spectroscopy for the Direct Determination of Heavy Metals in Soil

A novel method of laser-induced plasma spectroscopy utilizing a pulsed transversely excited atmospheric CO₂ laser has been developed for the high-sensitivity determination of heavy metals in soil. A coarse metal powder was used to trap the soil and to assist with plasma generation. When the CO₂ laser (10.6?µm, 1.5?J, 200?ns) was irradiated on the metal and soil powder, a high-temperature and long-lifetime luminous plasma was induced. Fine particles of soil were dissociated and were excited in the plasma region. The method was used for the rapid determination of Cr, Pb, and Hg in loam. The limits of detection for Cr, Pb, and Hg were approximately 0.8, 15, and 0.7?mg/kg, respectively.     

Ionic liquid salt bridge based on tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide for stable liquid junction potentials in highly diluted aqueous electrolyte solutions

A moderately hydrophobic ionic liquid, tributyl(2-methoxyethyl)phosphonium bis(pentafluoroethanesulfonyl)amide ([TBMOEP⁺][C₂C₂N⁻]), shows a very stable liquid junction potential upon contact with an aqueous solution whose ionic strength is as low as 1 μmol dm⁻³. The stability with the maximum excursion of the potential within ±0.5 mV for 30 min is very promising for accurate determination of pH and other single ion activities potentiometrically.     

Fast image enlargement using predefined codebook and eigenspace backprojection for lost pixel

In this paper, a new image enlargement method applying the backprojection for lost pixel (BPLP) to the predefined codebook-based method is proposed. BPLP is a method for image restoration. In BPLP, the eigenspace reflecting the characteristics of an input image is generated from the remained pixels and is used to restore the missing pixels. In the proposed method, the eigenspace is replaced by one generated from the predefined codebook (PDC). PDC represents edge-blurring properties in a small image patch and consists of pairs of low- and high-frequency image patches on various edge patterns. By replacing the PDC-based estimation of lost high-frequency components with BPLP, a fast image enlargement method retaining its performance can be developed. Through some experiments, the effectiveness of the proposed method was demonstrated. Especially, it was confirmed that the processing time of the proposed method was shortened to about 1/50 that of the PDC-based method.     

Public policy structuring incorporating reciprocal expectation analysis

This paper proposes a method of structuring public policy by incorporating reciprocal expectation analysis. The proposed method is characterized by three components: identification of the problem structure perceived by stakeholders using cognitive maps, policy structuring analysis with a value–driver matrix and a reciprocal expectation matrix, and feasibility analysis of agreements among the stakeholders. The three types of relationship among stakeholders are derived from the feasibility analysis, which are “Dosho-imu”, “Isho-imu”, and “Domu”. Three tests of feasibility to reach the agreement are then proposed: “information-sharing test”, “bargaining test”, and “reframing test”. A case study is presented, applying the method to strategic transportation planning in the Kanto region of Japan. Finally, the potential functions of the proposed method in practice are discussed.     

Czochralski-growth of germanium crystals containing high concentrations of oxygen impurities

Oxygen-containing germanium (Ge) single crystals with low density of grown-in dislocations were grown by the Czochralski (CZ) technique from a Ge melt, both with and without a covering by boron oxide (B₂O₃) liquid. Interstitially dissolved oxygen concentrations in the crystals were determined by the absorption peak at 855 cm⁻¹ in the infrared absorption spectra at room temperature. It was found that oxygen concentration in a Ge crystal grown from melt partially or fully covered with B₂O₃ liquid was about 10¹⁶ cm⁻³ and was almost the same as that in a Ge crystal grown without B₂O₃. Oxygen concentration in a Ge crystal was enhanced to be greater than 10¹⁷ cm⁻³ by growing a crystal from a melt fully covered with B₂O₃; with the addition of germanium oxide powder, the maximum oxygen concentration achieved was 5.5×10¹⁷ cm⁻³. The effective segregation coefficients of oxygen in the present Ge crystal growth were roughly estimated to be between 1.0 and 1.4.     

Investigation of void formation beneath thin AlN layers by decomposition of sapphire substrates for self-separation of thick AlN layers grown by HVPE

Void formation at the interface between thick AlN layers and (0 0 0 1) sapphire substrates was investigated to form a predefined separation point of the thick AlN layers for the preparation of freestanding AlN substrates by hydride vapor phase epitaxy (HVPE). By heating 50–200 nm thick intermediate AlN layers above 1400 °C in a gas flow containing H₂ and NH₃, voids were formed beneath the AlN layers by the decomposition reaction of sapphire with hydrogen diffusing to the interface. The volume of the sapphire decomposed at the interface increased as the temperature and time of the heat treatment was increased and as the thickness of the AlN layer decreased. Thick AlN layers subsequently grown at 1450 °C after the formation of voids beneath the intermediate AlN layer with a thickness of 100 nm or above self-separated from the sapphire substrates during post-growth cooling with the aid of voids. The 79 μm thick freestanding AlN substrate obtained using a 200 nm thick intermediate AlN layer had a flat surface with no pits, high optical transparency at wavelengths above 208.1 nm, and a dislocation density of 1.5×10⁸ cm⁻².     

Conformationally controlled (entropy effects), stereoselective vibrational quenching of singlet oxygen in the oxidative cleavage of oxazolidinone-functionalized enecarbamates through solvent and temperature variations

On photooxygenation (methylene blue as sensitizer) of E/Z enecarbamates, equipped with the oxazolidinone chiral auxiliary, the oxidative cleavage of the alkenyl functionality releases the enantiomerically enriched methyldesoxybenzoin (MDB) product. The extent (% ee) as well as the sense (R vs S) of the stereoselectivity in the MDB formation depends on the choice of the alkene configuration; the efficacy of stereocontrol may be tuned by appropriate solvent and temperature conditions. Highlighted is the finding that the formation of the preferred MDB enantiomer (R or S) depends for the E isomer on the chosen solvent and temperature, but not for the corresponding Z isomer. The activation parameters for the various solvents disclose that differential entropy effects (ΔΔS^‡) dominate the conformationally more flexible E diastereomers. As mechanistic rationale for this unprecedented conformationally imposed stereochemical behavior, we propose the competitive action of stereoselective vibrational quenching of the attacking singlet oxygen by the enecarbamate versus sterically controlled stereoselective oxidative cleavage of its double bond.     

Finite difference simulation of nonlinear waves generated by ships of arbitrary three-dimensional configuration

A modified marker-and-cell method is developed in order to simulate nonlinear wave making in the near-field of ships of arbitrary three-dimensional (3D) configuration advancing steadily in deep water. The 3D Navier-Stokes equations are solved by a finite difference scheme under proper boundary conditions. Efforts are particularly focused on the treatment of the boundary conditions on the body surface and free surface which have complicated 3D configurations. An orthogonal cell system with more than 70,000 cells is used for the computation of the waves and flow field of ships. The agreement of computational results with experiment is good, and it promises effectiveness for engineering purposes.