Miracle-dz/UniFAR-FTUs huggingface dataset:
Transformation of Transverse Acoustic Velocity of the Burner Approach Flow Into Flame Dynamics

Modern, large gas turbines for power generation have multiple burners, which are distributed around the circumference of the engine and which generate flames in combustors of either annular or can-annular geometry. In both cases considering only the axial modes has proven to be insufficient for the assessment of the thermoacoustic stability. An adequate analysis requires consideration of the circumferential acoustic coupling, generated by the acoustic field in the upstream and downstream annuli and the open passages between the cans, respectively. As in annular combustors the particularly critical eigenmodes with low frequencies are predominantly of circumferential nature, the stability of annular combustors is often governed by the onset of circumferential acoustic oscillations. In this study one single radial swirl burner is exposed to a transverse velocity fluctuation comparable to a circumferential oscillation in the plenum annulus. The transverse velocity fluctuation is transformed into a rotational flow oscillation through a convective process depending on excitation frequency and mass flow rate. The characteristics of this process are determined and the resulting dynamic flow structure in the burner nozzle is analyzed. Phase plots show that the rotational flow oscillation is transported into the flame causing a rotational flame pulsation. The influence of transverse velocity fluctuation on the global dynamic flame behavior is determined through FTF measurements. It is concluded from the increased FTF amplitude observed for transverse velocity excitation that the modification of the acoustic field at the burner exit due to circumferential acoustic modes has to be taken into account for a reliable prediction of the stability limits of annular gas turbines.Copyright © 2012 by ASME
Effect of Altitude on the Essential Oil Constituents of Artemisia roxburghiana Besser var. purpurascens (Jacq.) Hook

Abstract Mature vegetative plants of Artemisia roxburghiana Besser var. purpurascens (Jacq.) Hook were collected from Mussoorie (2205 m), Bhatwari (1218 m) and Bhaldana (850 m) from Garhwal Himalayas and their essential oils were isolated and subjected to GC and GC/MS analysis. The oil yield was lowest (0.2%) in the plants collected from the relatively higher altitude of Mussoorie; it was rich in borneol (21.2%) followed by linalyl acetate (7.4%) and α- humulene (6.7%). The oils from plants collected from the lower altitudes of Bhatwari and Bhaldana yielded higher percentage of oils (0.8–0.85%) which were dominated by β-caryophyllene (16.3%, 18.4%) followed by α-thujone (12.0%) in the former and eugenol (16.2%) in the later.
Time dependent optical emission spectroscopy of sub-microsecond pulsed plasmas in air with water cathode

This paper reports an experimental study of sub-microsecond pulsed discharges between a metal pin electrode and a tap water cathode in atmospheric pressure air. The dynamics of excited molecular and atomic species produced in the discharge is investigated by time resolved optical emission spectroscopy. The initial diffuse plasma constricts around 300 ns after the start of the voltage pulse. This constriction is correlated with an increase in gas temperature from 1000 to 5000 K and a strong increase in emission from O (777 nm), Hα and NH(A–X). The formation of OH(A–X) is discussed in the framework of OH (and thus H2O2 production) in plasmas in and in contact with liquids. It is argued that electron dissociative recombination of the water ion plays an important role in the production of OH(A) and that the relative intensity of the OH(A) emission may not provide a good estimate of the OH concentration without correction for electronic quenching of OH(A).
Reaction mechanisms for atomic layer deposition of aluminum oxide on semiconductor substrates

In this work, we have studied the TMA/H2O (TMA = Al(CH3)3) atomic layer deposition (ALD) of Al2O3 on hydroxyl (OH) and thiol (SH) terminated semiconductor substrates. Total reflection x-ray fluorescence reveals a complex growth-per-cycle evolution during the early ALD reaction cycles. OH and SH terminated surfaces demonstrate growth inhibition from the second reaction cycle on. Theoretical calculations, based on density functional theory, are performed on cluster models to investigate the first TMA/H2O reaction cycle. Based on the theoretical results, we discuss possible mechanisms for the growth inhibition from the second reaction cycle on. In addition, our calculations show that AlCH3 groups are hydrolyzed by a H2O molecule adsorbed on a neighboring Al atom, independent of the type of backbonds (Si-O, Ge-O, or Ge-S) of AlCH3. The coordination of Al remains four-fold after the first TMA/H2O reaction cycle.
Groundwater vulnerability assessment using a composite model combining DRASTIC with extensive agricultural land use in Israel's Sharon region

Abstract Vulnerability assessment to define areas critical for the maintenance of groundwater quality has been shown throughout the world to be an effective tool for establishing monitoring networks required for surveillance of potential pollution sites. One objective of this study has been to integrate the impact of extensive land use over long periods of time upon aquifer media as an additional parameter to the DRASTIC model to assess the potential level of groundwater vulnerability to pollution. An additional objective involved adaptation of this composite model to a specific region of a coastal aquifer, at a scale commensurate with effective hydrological management needs. The methodology employs empirical means to integrate aquifer media and extensive agriculture land use data covering the study area. The final assessment thus incorporates both the natural state of the vadose zone and aquifer media as well as the potential danger posed by the long-term effect upon the media of existing extensive land usage to the region's groundwater. The assessment utilizes Geographic Information System (GIS) technology. The study's unique contribution involves estimation of a composite index for each cell, enabling comparison with a potential index of vulnerability to groundwater pollution which includes land use impact and the empirical situation of groundwater quality in the field. The results exhibit certain correspondence for Israel's coastal Sharon region between the DRASTIC Index, The Composite DRASTIC—Agricultural Land use Index, and high nitrate levels. Such results delineate areas of high pollution risk, and increase the feasibility of applying such models world-wide.
High-Resolution Adiabatic Calorimetry Measurements in the Vicinity of the Liquid Crystal Phase Transitions

Abstract High-resolution adiabatic calorimetry has been used for the study of the liquid_crystal phase transitions in mixtures of 4-n-hexyloxyphenyl-4″-n-octyloxybenzoate ( ), 4-n-hexyloxy-phenyl-n-decyloxybenzoate ( ) and 4-n-hexyloxyphenyl-4″-n-dodexyl-oxybenzoate ( ) with emphasis on the vicinity of the NAC (nematic-smectic A-smectic C) multicritical point and the tricritical point along the NA (nematic-smectic A) line. Our results demonstrate the fluctuation nature of both these multi-critical points.
Stereoelectronic Effects in the Si−C Bond: A Study of the Molecular Structure and Conformation of Tetraphenylsilane by Gas-Phase Electron Diffraction and Theoretical Calculations

The molecular structure and conformation of tetraphenylsilane have been investigated by gas-phase electron diffraction and ab initio/DFT and molecular mechanics calculations. The structure of the free molecule is consistent with an S4 symmetry conformation; the calculations indicate that the twist angle τ between the plane of the phenyl group and the plane defined by the Si−C bond and the S4 axis is about 40°. Analysis of the low-frequency modes indicates that the four phenyl groups undergo large-amplitude torsional and bending vibrations about the respective Si−C bonds. The electron diffraction intensities from a previous study [Csakvari, E. ; Shishkov, I. F. ; Rozsondai, B. ; Hargittai, I. J. Mol. Struct. 1990, 239, 291] have been reanalyzed, using constraints from the calculations. A dynamical model accounting for the large-amplitude bending motion of the phenyl groups was used in the refinement. The new analysis yields accurate values for the twist angle of the phenyl group, τ = 40 ± 2°, and the Si−Ph bo.
Thermophysical Properties of Stone Fruit

The thermophysical properties of the stone fruits plum, peach, and nectarine were modeled from experimental data as functions of moisture content. Samples were dried to preset moistures in a laboratory cabinet dryer, and the thermal conductivity, specific heat, apparent density, bulk density, and porosity of the fruit were determined. The thermal conductivity and specific heat were found to be linear functions of moisture content, whereas apparent bulk density and porosity followed second-order polynomials. Temperature dependence was not found to be significant.
Optical birefringence imaging of the phase transition of K2Mn2(SO4)3

The present paper reports on the observation of the optical birefringence as a function of temperature of the langbeinite-type crystal K 2 Mn 2 (SO 4 ) 3 by using an imaging version of the so-called rotating-polarizer method. This method provides separate moving images of the orientation of the optical indicatrix and the magnitude of the optical anisotropy, showing the domain-wall behaviour during temperature changes. Some new results on the domain behaviour of the phase transition of K 2 Mn 2 (SO 4 ) 3 have been obtained. It is concluded that the sample single crystal consists of local regions, indicating the coexistence of two phases in this langbeinite-type crystal.
NMR study of fumarprotocetraric acid, a complex lichen depsidone derivative from Cladonia furcata

A lichen depsidone derivative, fumarprotocetraric acid, was obtained as the major constituent of Cladonia furcata (Huds.) Schrad. collected in Iceland. In the 1H NMR spectrum (in DMSO‐d6) of this compound, the trans double bond proton signals of the fumaryl unit appeared as overlapping singlets. To confirm the presence of a trans double bond in the molecule, fumarprotocetraric acid was treated with triethylamine. The 1H NMR spectrum of the resultant triethylamine salt displayed a pair of clear doublets with coupling constants of 15.7 Hz, which are characteristic of a trans double bond. Unambiguous 1H and 13C NMR spectral data for both fumarprotocetraric acid and its triethylamine salt were assigned for the first time based on the interpretation of their 2D NMR (HMQC, HMBC and NOESY) spectra. Copyright © 2003 John Wiley & Sons, Ltd.
The 1H and 13C NMR spectra of alternating isobutene/maleic anhydride copolymer and the corresponding acid and sodium salt — a stereochemical analysis

The 1H and 13C NMR spectra of an alternating isobutene/maleic anhydride copolymer and the corresponding acid and sodium salt forms were reexamined by 1D and 2D NMR methods. This copolymer contains only threo-succinyl units. The tacticity is characterized by a 53/47 ratio of threo-diisotactic and threo-disyndiotactic triads. The preference of the diisotactic triad was concluded from NMR data. A model was proposed to explain the stereoselectivity of the copolymerization reaction. This model also leads to the conclusion that the diisotactic triad should be preferred for steric reasons. 13C-T1 values and nuclear Overhauser effect (NOE) values for these three copolymers were determined and discussed in terms of segmental motion.
Doping, strain, defects and magneto-optical properties of Zn1−xMnxO nanocrystals

This paper presents the co-relation between doping induced defects, structural, magnetic and optical properties of chemically grown Mn doped ZnO nanocrystals. The solubility limit of Mn in ZnO is found to be ∼10%. X-ray diffraction (XRD), Raman spectroscopy and high resolution transmission electron microscope (HRTEM) are employed to study the doping induced defects. These studies confirm that undoped and Mn doped (up to 10%) nanoparticles have lesser defects as compared to 15–20% Mn doped nanocrystals. Noticeable increases in strain with a significant decrease in lattice parameters and bond length were observed for nanocrystals doped with 10% or higher Mn concentrations. In contrast to previous observations of room temperature ferromagnetism in undoped ZnO nanoparticles, we observe diamagnetic behavior of the sample due to lesser oxygen vacancies in these samples. Doped samples show room temperature ferromagnetism and as Mn concentration increases, saturation magnetization decreases due to enhanced anti-ferromagnetic interaction between Mn–Mn ions. Luminescence studies show a significantly visible change in the emission (bright blue → bright green) characteristics with increasing dopant concentration. Currently, LEDs giving UV emission have been combined with broadband visible green phosphors to make white-light LEDs. Thus observed magnetic and optical properties could be utilized in different opto-electronic, dilute magnetic semiconductors (DMS)/spintronics and bio-imaging applications, underlying the findings and importance of current investigations.
XPS characterization of wood chemical composition after heat‐treatment

XPS was used to characterize the chemical changes occurring after drying or applying a heat‐treatment to beech wood samples. Our results indicate that the surface of this air‐exposed material could be strongly affected either by the ambient atmosphere during storage or by the complex atmosphere in the oven during drying or heat‐treatment. However, the O/C ratio measured after removal of a thin slice of a few millimetres of an untreated sample is in reasonable agreement with that calculated from the well‐established chemical composition of beech. Through this methodology (equivalent to scraping for hard materials) it is expected to get a realistic characterization of the wood. The reliability and repeatability of the XPS measurements have been checked and the method applied to the study of the chemical changes of the beech samples subjected to heat‐treatment. Heating at 240 °C induces a significant decrease of the O/C ratio from 0.55 before to 0.44 after the treatment. Heat‐treatment induces also a decrease of the C2 carbon contribution (carbon atom bound to a single non‐carbonyl oxygen) associated with an increase of the C1 carbon contribution (carbon atoms bound only to carbon or hydrogen atoms), in agreement with chemical modifications reported previously in the literature. Thanks to the small analysed area of the equipment used in this study, different spots were analysed to demonstrate the presence or absence of a gradient of chemical composition due to thermal degradation or migration of extractives from within the wood structure to its surface. At the scale of our observations, the different wood samples investigated (dried or heat treated) appear to be homogeneous. Copyright © 2006 John Wiley & Sons, Ltd.
Microthermal sensors for determining fluid composition and flow rate in fluidic systems

To analyze fluid mixtures a simple and low cost measurement method is realized using a microthermal sensor that introduces a short heat pulse into the fluid under test whilst the resulting temperature increase reflects thermal parameters of the fluid. For methanol in water this principle showed an almost linear dependence of the temperature increase on the methanol content for the volume concentration range 0–20 %. The sensitivity was determined to S = 0.19 K/(% (V/V)) for a heat pulse of 0.5 s duration and a heater power of 30 mW. The accuracy achieved in stopped-flow single pulse measurements is ~0.5 % (V/V). By integrating additional temperature sensors in front and behind the microheater the flow rate of the liquid can also be determined using thermal anemometry. The low cost sensor construction and simple signal analysis make this principle promising for use in low cost mobile applications like DMFC power supplies for laptops.
Determination of Toxic Substances Based on Enzyme Inhibition. Part II. Electrochemical Biosensors for the Determination of Pesticides Using Flow Systems

Enzyme inhibition coupled to flow injection systems set-ups are a powerful tool for the monitoring of environmental toxics. The present review examines the latest contributions to this field where electrochemical detection is used. The advantages and limitations of the FIA technique in the context of enzyme inhibition analytical procedures are discussed. The present review is organized in accordance to the enzyme (cholinesterases, tyrosinases, or alkaline phosphatase) used in the measurement.
Analysis of Total Respiratory Deposition of Inhaled Ultrafine Particles in Adult Subjects at Various Breathing Patterns

Ultrafine particles are ubiquitous in the ambient air, and their unique physicochemical characteristics may pose a potential health hazard. Accurate lung dose information is essential to assess a potential health risk from exposure to these particles. In the present study, we measured total respiratory tract deposition fraction (TDF) of inert ultrafine aerosols (NMD = 0.04, 0.06, 0.08, and 0.10 μm and σg 1.3) in a group of young healthy adults (11 males and 11 females). A fast-response ultrafine condensation particle counter was used for continuous monitoring of inhaling aerosols breath by breath. Six different breathing patterns were used: three different tidal volumes (Vt = 500, 750, and 1000 ml) and two different flow rates for each Vt. The mean respiratory time (Tm) ranged from 2 to 4 s. The measured data showed that TDF increased with a decrease in particle size, thereby an increase in diffusion coefficient (D), and with an increase in Tm and Vt. For a given particle size both Tm and Vt were almost equally influential to TDF. TDF was generally comparable for men and women at the same breathing pattern. A slight increase in TDF was noticed for women only for smaller size particles (e.g., 0.04 μm). From the parametric analysis a composite parameter, (DTm)0.5Vk t, was identified by which all TDF data could be consolidated into a single curve (k = 0.49, (σ2 = 0.97). The results show that TDF of ultrafine particles can be reliably estimated by a unique empirical formula, and this may provide a convenient means of assessing respiratory dose of ultrafine particles.
Synthesis of microporous organic polymers with high CO2-over-N2 selectivity and CO2 adsorption

A series of microporous organic polymers (MOPs) were synthesized by Schiff base condensation of 1,3,5-tris(4-aminophenyl)benzene and a number of dialdehyde monomers. The polymers were structurally characterized by in situ infrared and ex situ solid state 13C{1H} nuclear magnetic resonance (NMR) spectroscopy. Synthesis conditions were optimized to enhance CO2 uptake by the MOPs. Synthesis at low temperatures results in the MOPs being linked by imine groups. Heating of the MOPs reduces the number of imine groups and after heating to >300 °C nitrile groups were found to be present in the MOPs. The MOPs have specific surface areas up to 614 m2 g−1 and narrow pore size distributions of ∼4 to 8 A. The selectivity of CO2-over-N2 at 273 K and 1 bar was 56–77, which requires either an influence of chemisorption on CO2 or a molecular sieving (or kinetic selection) of CO2-over-N2. The materials had also heats of adsorption typical for physisorption of CO2.
Motion of gas bubbles in non-Newtonian liquids

The available theoretical knowledge of the motion of gas bubbles in Newtonian liquids is reviewed, and the possibility of extension to non-Newtonian liquids, both purely viscous and viscoelastic, is studied. Experimental data on the rising velocities of gas bubbles in a variety of non-Newtonian liquids are presented and interpreted on the basis of theoretical knowledge. Peculiarities that have been observed in highly elastic liquids are discussed, and a tentative interpretation is offered.
Depth of Fenton-Like Oxidation in Remediation of Surface Soil

A series of soil columns was used to investigate the depth of Fenton-like reactions provided by the surface application of catalyzed hydrogen peroxide. Initial experiments examined the effect of four stabilizers (monobasic potassium phosphate, dibasic potassium phosphate, sodium tripolyphosphate, and silicic acid) on H{sub 2}O{sub 2} decomposition and the depth to which H{sub 2}O{sub 2} could be detected. The H{sub 2}O{sub 2} dynamics along the depth of the column showed that the addition of the most effective stabilizers, monobasic potassium phosphate, increased the depth of the detectable H{sub 2}O{sub 2} in the soil by three times the depth in soil columns without stabilization. The oxidation of sorbed hexadecane, a highly hydrophobic compound (log K{sub ow} = 9.07), by Fenton-like reactions focused on the process variables of H{sub 2}O{sub 2} concentration, number of H{sub 2}O{sub 2} applications, and pH. A single application of 15 M H{sub 2}O{sub 2} with pH governed by the buffering of KH{sub 2}PO{sub 4} provided maximum hexadecane oxidation. Minimal desorption (<10%) in the soil columns was found in control experiments using deionized water in place of H{sub 2}O{sub 2}, suggesting that hexadecane oxidation occurred in the sorbed phase. More detailed investigation of the process variables was conductedmore » using central composite rotatable designs. The results showed that a KH{sub 2}PO{sub 4} concentration greater than 30 mM provided increased hexadecane oxidation while maintaining minimal H{sub 2}O{sub 2} decomposition relative to unstabilized H{sub 2}O{sub 2}. For higher KH{sub 2}PO{sub 4} concentrations (60--75 mM), the central composite results documented greater than 90% hexadecane oxidation in the top 2 cm of the soil column and 20--40% oxidation in the 10--15 cm depths. « less
High pressure synthesis and investigation of single crystals of metastable boron phases

In the present work we have confirmed the existence of the tetragonal boron phase T-50 that was disputed for more than a half of a century. This phase was reproducibly synthesized at high pressures and high temperatures (HPHT) in the form of single crystals and its structure was refined based on single-crystal synchrotron X-ray diffraction data. We also present here a previously unknown rhombohedral boron phase synthesized in a limited HPHT field. Its structure was solved based on in house single-crystal X-ray diffraction data and found to be similar to that of boron carbide. After hitherto known stable α-B, β-B, and γ-B polymorphs, T-50 and the newly obtained rhombohedral boron phases were designated in the present work as δ-B and ϵ-B, correspondingly. From the experimental evidences, both the phases are considered as metastable.