Rich Conditions Research Articles

Carbonate Minerals and Dissimilatory Iron-Reducing Organisms Trigger Synergistic Abiotic and Biotic Chain Reactions under Elevated CO2 Concentration.

Increasing CO2 emission has resulted in pressing climate and environmental issues. While abiotic and biotic processes mediating the fate of CO2 have been studied separately, their interactions and combined effects have been poorly understood. To explore this knowledge gap, an iron-reducing organism, Orenia metallireducens, was cultured under 18 conditions that systematically varied in headspace CO2 concentrations, ferric oxide loading, and dolomite (CaMg(CO3)2) availability. The results showed that abiotic and biotic processes interactively mediate CO2 acidification and sequestration through "chain reactions", with pH being the dominant variable. Specifically, dolomite alleviated CO2 stress on microbial activity, possibly via pH control that transforms the inhibitory CO2 to the more benign bicarbonate species. The microbial iron reduction further impacted pH via the competition between proton (H+) consumption during iron reduction and H+ generation from oxidization of the organic substrate. Under Fe(III)-rich conditions, microbial iron reduction increased pH, driving dissolved CO2 to form bicarbonate. Spectroscopic and microscopic analyses showed enhanced formation of siderite (FeCO3) under elevated CO2, supporting its incorporation into solids. The results of these CO2-microbe-mineral experiments provide insights into the synergistic abiotic and biotic processes that alleviate CO2 acidification and favor its sequestration, which can be instructive for practical applications (e.g., acidification remediation, CO2 sequestration, and modeling of carbon flux).

Experimental measurements of laminar flame speeds for highly N[formula omitted]-diluted ethanol flames under microgravity conditions

Nitrogen has been used as an alternative for CO2 in the fire suppression industry. The high nitrogen concentrations added to a reactive mixture slows down its flame propagation in case of a fire outbreak. To describe quantitatively the flame spread as a function of nitrogen dilution, it is mandatory to evaluate the mixture’s laminar flame speed. Performing experiments under earth gravity using the RWTH high-pressure, high-temperature spherical combustion chamber showed that the laminar flame speed extraction is impossible for such highly dilute conditions due to severe flame-front distortions. To overcome the influence of buoyancy, experiments were carried out under microgravity conditions in a parabolic flight campaign onboard the Airbus A310 Zero-G. The setup consists of a pressure-release-type dual chamber adequate for aircraft-related safety requirements, and a conventional shadowgraphy system to visualize the flame morphology under quasi-isobaric pressure. Only a limited number of liquid energy carriers are allowed onboard, and ethanol was chosen because of its short molecular structure and low boiling point compared to longer chain liquid alkanes such as n-heptane. Results showed a flame speed reduction induced by radiation in the order of 10% to 45% for near-stoichiometric to very rich conditions, respectively. To correct laminar flame speeds for radiation effects, an empirical correlation presented by Yu et al. (Combust. Flame 161 (2014) 2815–2824) is applied. Excellent agreement between radiation-corrected experimental data and simulations using the chemical mechanism of Cai et al. (Combust. Flame 37 (2019) 639–647) is found. This indicates that high dilution levels with nitrogen can be captured well by kinetic schemes derived for fast-burning flames. The unique experimental data obtained here, which were extremely difficult to measure and post-processed very carefully, can be used as a reference to validate/improve existing and newly developed kinetic mechanisms.

Experimental and chemical kinetic modeling study of trimethoxy methane combustion

The use of oxymethylene ethers (OMEs) as alternative fuels or fuel-additives has motivated the present study on the combustion behavior of trimethoxy methane (TMM), which is a branched version of OMEs. A detailed chemical kinetic model for TMM combustion is provided, which is based on a recent model for the structurally similar dimethoxy methane (DMM) and recent elementary reaction kinetics studies. This model is validated against TMM ignition delay times measured in a shock tube at 20 and 40 bar, under fuel lean, stoichiometric, and fuel rich conditions. Further, the TMM model is validated against laminar burning velocities, which were measured in a heat flux setup for a variation of fuel/air ratios. A good agreement between the TMM model predictions and the measured ignition delay times and laminar burning velocities is observed. At fuel rich conditions in the shock tube, however, the model underestimates the reactivity of TMM by up to 60%, which could not be compensated by physically meaningful modifications of the TMM model. The analysis of the TMM model shows that at low temperatures, TMM is primarily consumed via H-atom abstraction by ȮH radicals, followed by classical β-scission and low-temperature chemistry. At higher temperatures, a significant fraction of TMM is consumed via unimolecular decomposition, leading to a higher reactivity compared to OME2. The present model and experiments lay the foundation for future kinetic modeling of TMM and other branched OME-like compounds.

Computational study on lean and rich combustion of flame ball, counterflow flame and planar flame: Their limits and stoichiometries

To investigate (fuel-)lean/rich limits and essential stoichiometries, i.e., the borders of lean/rich combustion, one-dimensional steady computations with detailed chemistry for flame balls, counterflow flames, and stretch-free planar flames were conducted using a CH4/O2/Xe mixture that has been used in microgravity experiments. As continuous converged solutions were obtained under lean/rich conditions, it was suggested that the existence of flame ball not only under lean but also under rich condition. Flame radii and temperatures of flame balls decreased and increased toward the lean/rich limits from their maximum and minimum values, respectively. The lean limits were wider in the order of the flame ball, counterflow flame, and stretch-free planar flame. Therefore, the lean flammability limit corresponded to the lean limit of the flame ball in the mixture. Conversely, the rich limits were wider in the order of the counterflow flame, stretch-free planar flame, and flame ball. Thus, the rich flammability limit corresponded to the rich limit of the counterflow flame in the mixture. Essential stoichiometry, which represents the actual stoichiometry depending on the dominant transport in near-flame front, was not uniquely determined as conventional stoichiometry (ϕ = 1); it was located between the equivalence ratio of ϕ = 1 and ϕc, where ϕc denotes the critical equivalence ratio is evaluated using the fuel and oxidizer Lewis number of a target mixture. The results indicated that the essential stoichiometry of the stretch-free planar flame corresponded to ϕ = 1, that of the flame ball corresponded to ϕ = ϕc, and that of the stretched flame was located between ϕ = 1 and ϕc depending on the stretch rate.

An experimental and kinetic modeling study of auto-ignition and flame propagation of ethyl lactate/air mixtures, a potential octane booster

Spark ignition engines are one of the main technologies in the transport sector. The improvement and optimization of the fuels used to empower these engines are of vital importance, both for economic and environmental reasons. In particular, one of the main issues of spark ignition engines is the knock phenomenon; new formulations of fuels are being studied in order to overcome this problem. In this study, a possible innovative anti-knock, octane booster additive is considered: ethyl lactate. This molecule is almost unknown in combustion literature, as it has been used only as green solvent and food additive. The first experimental results under combustion conditions are presented, together with a kinetic mechanism. Two set-ups have been employed: a rapid compression machine, to measure ignition delay times, and an innovative spherical bomb, OPTIPRIME, to obtain laminar flame speeds. The results are encouraging for the expected application and the mechanism shows good performance. Ignition delay times at all conditions are well predicted by the mechanism and, when compared to ethanol, they are longer, implying a greater anti-knock capability. A rate of production analysis has been performed, where the unimolecular reaction leading to ethylene and lactic acid has been proved to be quite important at high temperatures and lean conditions. For laminar flame speeds, the agreement between model and experiments is good, with some discrepancies at lean conditions and high pressures. Compared to ethanol, at rich and stoichiometric conditions ethyl lactate flame speeds are slightly slower except at lean conditions, indicating that under some conditions this molecule could provide better performances than ethanol as an octane booster additive.

Chemical structure of premixed ammonia/hydrogen flames at elevated pressures

Because it is a carbon free fuel with high volumetric and gravimetric hydrogen density, ammonia is considered to be a promising hydrogen carrier molecule; its combustion chemistry, consisting of ammonia and ammonia/hydrogen blends, are of great importance in engine and gas turbine systems. This paper presents experimental data and kinetic modeling of the structure of NH3/H2/O2/Ar premixed flames at elevated pressures. Equivalence ratios were maintained at 0.8, 1.0 and 1.2, and the NH3/H2 ratio was 1:1 (molar ratio). Experiments were performed at pressures of 4 and 6 atm. Eight recently published chemical-kinetic mechanisms of ammonia combustion and oxidation were applied to numerically simulate flame structure. Experimental and numerical data showed that the main nitrogen containing compounds in the post flame zone were N2 and NO, while the concentrations of N2O and NO2 were negligible. In terms of NO emissions reduction, it was revealed that rich conditions were more effective. At the same time, pressure increases resulted in decreasing NO concentration in the post flame zone, as well as lower maximum concentration of NO and N2O. Numerical analysis showed that N2O and NO2 were formed mainly from NO. To improve the agreement between experimental and numerical data, rate kinetic parameters of these reactions should be refined.

Emergent Behavior in Oxidation Catalysis over Single-Atom Pd on a Reducible CeO2 Support via Mixed Redox Cycles

Experimental kinetics demonstrate catalytic lean CO oxidation over single Pd atoms with a CO reaction order greater than unity. A CO order greater than unity is unique to Pd single atoms supported on CeO2 nanocubes and is not observed for Pd nanoparticles on the same support nor other supported single-atom systems. A reaction mechanism including eight elementary steps, in which Pd dynamically samples three formal oxidation states, is unable to capture a reaction order in CO greater than unity. Vibrational spectroscopy of CO adsorption ranging from lean to rich conditions reveals Pd accesses an extensive array of formal oxidation states, ranging from Pd4+ to Pd0. Density functional theory calculations demonstrate Pd atoms supported on CeO2 can access four formal oxidation states during lean CO oxidation. Two catalytic redox cycles are possible, with cross-over between them leading to a reaction mechanism yielding reaction orders in CO greater than unity. A microkinetic model, utilizing Bayesian inference to adjust elementary energetics to fit the experimentally measured activation barrier and reaction orders, confirms the reaction order in CO of >1 arises from the ability of the Pd active site to access four formal oxidation states, spanning from +4 (PdO2) to −2 (Pd adjacent to a CeO2 lattice oxygen vacancy). This work demonstrates the emergent redox behavior of Pd single atoms on CeO2, which may be important to explain their high activity for low-temperature catalytic combustion of hydrocarbons.

(Invited) Enhanced Efficiency of AlInN Nanowire Ultraviolet Light-Emitting Diodes Using Photonic Crystal Structures

High efficiency ultraviolet (UV) light-emitting diodes (LEDs) are in high demand for a wide range of applications [1-3]. Due to its wide bandgap, covering from deep UV to near visible, AlGaN semiconductor has been intensively studied for high efficiency UV LEDs. However, the performance of AlGaN UV LEDs is still limited, especially in the deep UV wavelength region, due to large dislocation density and extremely inefficient p-type doping in AlGaN film. Therefore, AlGaN UV LEDs have been suffering from low internal quantum efficiency (IQE), poor light extraction efficiency (LEE), and low external quantum efficiency (EQE). Alternatively, AlInN alloy is relatively unexplored for light-emitters even though it holds great potential application in UV and visible light-emitting devices. Recent studies have reported that InAlN has a large optical gain for deep UV LEDs. In this context, we have successfully developed AlInN nanowire LEDs with strong emission in the UV wavelength regime. The AlInN nanowires achieved a high IQE of >50% and significantly strong Transverse Magnetic (TM) polarized emission at 299nm.The AlInN nanowire LED structures were spontaneously grown on n-Si (111) substrates under nitrogen rich conditions by a Veeco GEN II molecular beam epitaxy (MBE) system. The AlInN nanowire was grown on GaN nanowire template. The device active region consists of ~ 100 nm n-Al0.78In0.22N, 40 nm undoped Al0.75In0.25N well and 100 nm p-Al0.78In0.22N layers. The GaN nanowire segments were grown at ~ 800 °C, nitrogen flow rate of 0.5-1.0 sccm, and forward plasma power of ~ 400 W. However, the growth temperature of the active region was at ~ 670 ̶ 700 °C to increase the In incorporation in AlInN segments and the nitrogen flow rate was kept at 2.5 sccm. The MBE grown AlInN under nitrogen rich condition offers an effective approach to eliminate the composition inhomogeneity in the AlInN. The nanowires are vertically aligned to the Si substrate with quite uniform dimension, as illustrated in Figure 1(a). Figure 1(b) presents the structure of a single AlInN nanowire LED. The photoluminescence (PL) spectra of AlInN nanowires were measured using a 266 nm diode-pumped solid-state laser as the excitation source. The peak emissions vary from 280nm to 365nm by varying the Al/In composition in the AlInN layers. The peak emission is shifted to shorter wavelength when the substrate temperature gets increase which is attributed to the increased In adatom desorption at higher growth temperature, resulted in the reduced In composition in the AlInN segment. The AlInN/GaN nanowire exhibits relatively high IQE which is estimated of ~ 52% at room temperature [3, 4]. Illustrated in Figure 1(c), the UV nanowire LED holds strong emission spectra at ~299 nm with a negligible shift in the peak wavelength, attributing to the high crystalline quality and reduced quantum-confined Stark effect in the AlInN nanowires. The LED has a low turn-on voltage of ~5V and low reverse leakage current less, i.e., ~0.5 µA at -8.6V. Moreover, as shown in Figure 1(d), we have demonstrated that the LEE of the AlInN nanowire LEDs could reach ~ 63% using hexagonal photonic crystal nanowire structures which is significantly higher compared to that of the random nanowire arrays [5]. This study paves the way for the development of high-power ultraviolet light-emitters using AlInN nanowire arrays.

Laminar burning velocities and nitric oxide formation in premixed dimethyl ether/air flames: Experiments and kinetic modeling

Adiabatic laminar burning velocities and post-flame NO mole fractions for flat, non-stretched, premixed dimethyl ether/air flames were experimentally determined with a heat flux burner combined with laser-induced fluorescence diagnostics, over equivalence ratios ranging from 0.7 to 1.6, at atmospheric pressure and initial temperatures from 298 to 338 K. The present burning velocity measurements were then compared with selected data available in the literature obtained with different techniques. The comparison showed reasonably good agreement with recent datasets obtained at different temperatures, as well as possible outliers not suitable for the validation of kinetic models. The detailed kinetic mechanism of the authors was extended by the reactions of dimethyl ether. A comparison of experimental and computational results using two contemporary detailed chemical kinetic mechanisms, along with the one from the authors presented in this work, was also conducted and discussed. Discrepancies between experiments and model predictions and among models themselves were observed, especially under rich conditions. Further numerical analyzes were performed to identify the main causes of the observed differences. Notwithstanding, the present model showed overall good performances in reproducing both laminar burning velocities and nitric oxide mole fractions. Kinetic modeling was also performed to enhance the understanding of the intrinsic NOx emission characteristics of dimethyl ether by comparing the present measurements with those obtained for ethanol/air flames under identical conditions.

Experimental and kinetic modeling study of ethylene oxidation at elevated pressure

The oxidation of ethylene (C2H4) was performed in a jet-stirred reactor (JSR) at the equivalence ratios (Φ) of 0.5, 1.0, and 3.0, within the temperature range of 650–1000 K, at 12.0 atm. Six C1-C3 hydrocarbons and four oxygenated species were identified and quantified by using online GC and GC-MS. Among them, acrolein, propanal, and epoxypropane were newly detected compared to previous oxidation studies of C2H4. A detailed kinetic model involving 125 species and 671 reactions was developed, and its predictions were found to be in reasonable agreement with the measured data. Generally, the peak concentrations of hydrocarbons and oxygenated species tend to increase with the increase of Φ, while the inorganic substances exhibit contrary tendencies. Rate-of-production analysis indicates that C2H4 consumption is generally governed by the addition of H-atom and OH radicals, which mostly transform to C2H5 under rich conditions and to CH2CH2OH under lean condition. Sensitivity analysis reveals that the reactions H2O2(+M) <=> 2OH(+M) and CH2O + O2 <=> HCO + HO2 are the most promoting and inhibiting reactions for C2H4 consumption, respectively. By comparing the results of 1.0-59.2 atm, it can be found that the increase of pressure leads to the reduction of the initial reaction temperature. Under higher pressure, the reaction temperature interval of C2H4 shifts towards a lower temperature. The current mechanism could reproduce the literature-reported ignition delay times and laminar flame velocities under wide pressures. The results will enrich the understanding of the high-pressure oxidation of C2H4 and serve as a foundation for developing large hydrocarbon fuel models.

Hollow spheres as inert packed bed from lean to rich combustion in porous media

• Hollow spheres were used in filtration combustion processes. • Lean and rich fuel-air filtration combustion was investigated. • Numerical and experimental comparison of solid and hollow spheres. • Hydrogen and syngas were produced at high temperatures. Hollow spheres as inert packed bed is an innovative technology with high potential in filtration combustion. Their lower specific density, geometry, and the radiation inside the sphere enhance the overall heat transfer of the sphere, and therefore, increase the effective conductivity of the packed bed, while the other thermo-physical properties remain unchanged. The present work investigates numerically and experimentally the effects of the packed bed made of hollow alumina spheres filled with air, from lean to rich premixed methane-air combustion within this porous media, with focus on the production of hydrogen and carbon monoxide species on rich conditions. The experimental part considers the equivalence ratio from 0.8 to 1.3. The numerical approach contemplates a one-dimensional model based on two-temperature approximation (gas and solid) with a four-step chemical reaction mechanism for homogeneous reactions at equivalence ratios between 0.4 and 1.6, for different spheres geometries. The results of experimental and numerical investigations are in good agreement. Both indicate that the use of hollow spheres packed bed (HS), in contrast to the packed bed made of the solid spheres (SS), shows higher temperatures and flame front velocities in all the equivalence ratio ranges. At the stoichiometric equivalence ratio, the numerical investigation in the HS case results in higher temperatures of 168 K and 21 K, in the solid and gas phases, respectively, in comparison with the SS case. The combustion products for different spheres geometries and equivalence ratios present the same trend and values for both HS and SS cases. The yields of carbon monoxide and hydrogen goes up to 37% and 42%, respectively.

Effects of recess length on combustion instability in a model chamber with a gas-centered swirl coaxial injector

Combustion instability is investigated in a model chamber by changing the recess length of a gas-centered swirl coaxial injector ranging from 0 mm to 20 mm with a 4 mm interval. Effects of recess length on combustion instability are pursued by numerical simulations and experiments and compared with each other. The parameters for evaluation of instability, i.e., damping factor, decay rate, and damping coefficient, are quantified based on numerical and experimental data. The parameters show that acoustic oscillations in the combustor are suppressed relatively more as the recess length of the injector increases. Combustion stability improves more and more with the recess length and then, levels off. Improvement in stability is not appreciable when the recess length is increased further than a critical value. On the other hand, stability increases with equivalence ratio for a lean condition, reaches its maximum, and then, decreases finally for a rich condition. However, injectors with a longer recess length maintain good stability even if the equivalence ratio varies.

Soot production in high pressure inverse diffusion flames with enriched oxygen in the oxidizer stream

Catalyst degradation due to soot formation is one of the main issues in the autothermal reforming (ATR) process, which is widely regarded as the future technology for hydrogen production from natural gas. In this work, soot formation under conditions similar to ATR was systematically investigated, focusing specifically on the effects of pressure on soot formation in inverse diffusion flames (IDFs) under oxygen rich conditions. Methane was diluted with carbon dioxide; the oxygen content in the oxidizer stream varied from 55 to 70%-by-mol. Polycyclic aromatic hydrocarbon (PAH) and soot concentrations in the flames were measured by laser-induced fluorescence (LIF) and laser-induced incandescence (LII) respectively. Flame images showed that, as the pressure increased, the luminous region of the IDFs moved downward to mask the blue reaction region, and the flames became narrower. The degree of flame narrowing in the IDFs was milder than normal diffusion flames (NDFs). LIF measurements showed that increasing the pressure promoted PAH formation, which also subsequently promoted soot formation. Both PAH and soot formation increased linearly with pressure. The linear relationship was different from that of the NDFs. Flame simulations suggested that the promotion of soot formation with pressure was largely driven by PAH adsorption. Under the conditions of this study, lowering the oxygen content promotes soot formation in the IDFs. The results of this work contribute to the understanding of soot formation in IDFs at elevated pressures and the optimization of the ATR process.

A Multiphysics Co-Simulation Framework of a Gas Engine and Three-Way Catalyst toward a Complete Vehicle Design Model

In view of the increasingly stringent emission regulations, the automotive sector needs considerable support from the development of robust and reliable engine and aftertreatment models. Accurate reproduction of engine-out and tailpipe pollutants plays a crucial role in complying with these legislations. Given the difficulty in characterizing some critical phenomena, frequently caused by strong dynamics and related to experimental uncertainties, communication between several calibrated and reliable models is mandatory. This is certainly valid for powertrains that will be powered with alternative gas fuels such as natural gas, bio-methane and hydrogen in the future. This paper describes a methodology to co-simulate a 1D CNG HD 6-cyl engine model and a 1D quasi-steady Three-Way Catalyst model in a global framework for high-fidelity virtual prototyping of the vehicle system. Through the implementation of a dedicated control logic in MATLAB/Simulink, the modeling architecture allows for the reproduction of the engine performance parameters together with the evaluation of the TWC pollutants’ conversion efficiency. An extensive database of experimental tests was used to assess the model response. The latter was validated in multiple steady-state operating conditions of the engine workplan. Using a semi-predictive combustion model, the validation was carried out over a wide range of different air-to-fuel ratios and during fast rich/lean transitions to evaluate the formation and conversion phenomena of the main chemical species, both engine-out and tailpipe. Subsequently, the complete model was validated in dynamic conditions throughout a WHTC, accurately reproducing the cut-off phases and their sudden accelerations. The numerical–experimental agreement on pollutant reproduction is generally good and globally below 3%. Larger deviations occur in extremely rich conditions and in CH4 emission evaluation due to the lack of information related to the combustion process and chemical mechanisms involving the Pd surface.

Flame Structure of Ammonia/Hydrogen/Oxygen/Argon Mixtures at High Pressure

The search of alternative fuels is one of the most important issues. Hydrogen is the most attractive one since its combustion products include only water. However, due to its specific properties wide implementation of hydrogen is not possible. There is an idea to use chemical carriers of hydrogen, for example, ammonia. The addition of hydrogen, which is the product of ammonia cracking, can improve the combustion characteristics of ammonia. The work presents experimental data on the structure of NH3/H2/O2/Ar flames at 4 atm. Equivalence ratio values were 0.8, 1.0 and 1.2, NH3/H2ratio – 1/1. Flame structure was measured with molecular beam mass spectrometry with soft electron impact ionization. In the experiments, flames were stabilized on the flat burner. Temperature profiles were measured with thin S-type thermocouples. Numerical simulations were performed with PREMIX code from CHEMKIN package. The comparison of the experimental and numerical data enabled to reveal the mechanism of NH3/H2oxidation showing the best predictive capability. Experimental and numerical data showed that the nitrogen-containing species which are present in the post-flame zone are N2and NO whereas concentration of N2O and NO2is negligible. It was revealed that in terms of NO reduction slightly rich conditions are more effective. In addition, the effect of equivalence ratio on the peak concentration of NO, N2O and NO2was analyzed. Rich conditions appeared to be more effective to reduce peak concentrations of NO, N2O and NO2.

Studies of Low and Intermediate Temperature Oxidation of Propane up to 100 Atm in a Supercritical-Pressure Jet-Stirred Reactor

The low and intermediate temperature oxidation of propane has been investigated by using a novel supercritical pressure jet stirred reactor (SP-JSR) with and without 20% CO2 additions at fuel lean and rich conditions at 10 and 100 atm and 500–1000 K. The mole fractions of C3H8, O2, CO, CO2, CH2O, C2H4, CH3CHO, and C3H6 were quantified by using a micro-gas chromatograph (µ-GC). The experiment showed that different from that of 10 atm, at 100 atm only a weak negative temperature coefficient (NTC) behavior was observed because of the significant shift of the intermediate temperature HO2 chemistry to lower temperature. In addition, at 100 atm, existing models in literatures could successfully capture the onset temperatures of the low and intermediate chemistry, while under-predict the fuel oxidation quantitatively and fail to capture the NTC behavior between 650 and 780 K at both fuel lean and rich conditions. Similar discrepancy was observed in studies of n-butane and dimethyl ether (DME) oxidations in literatures, implying that there existed large uncertainties in hierarchy model development of fuels with low temperature chemistries at extremely high pressures. Reaction pathways and sensitivity analyses showed that RO2 competing reactions through (P1) RO2 = QOOH, (P2) RO2 = C3H6 + HO2, (P3) RO2 + CH2O/HO2 = RO2H + HCO / O2 dominated the low and intermediate temperature chemistries, followed by HO2 / H2O2 chemistry at 100 atm, which differed from the dominant pathway through QOOH consumption reactions at lower pressures. Especially, P3 is a new pathway of RO2 consumption at high pressures, which was not observed in importance at low pressures. Special attention should be paid to the accurate computations of n-C3H7O2 / i-C3H7O2 + CH2O and n-C3H7O2 / i-C3H7O2 + in the P3 pathway and n-C3H7O2 / i-C3H7O2 decomposition reactions in the P2 pathway at high pressures.

Methanol oxidation up to 100 atm in a supercritical pressure jet-stirred reactor

Methanol (CH3OH) has attracted considerable attention as a renewable fuel or fuel additive with low greenhouse gas emissions. Methanol oxidation was studied using a recently developed supercritical pressure jet-stirred reactor (SP-JSR) at pressures of 10 and 100 atm, at temperatures from 550 to 950 K, and at equivalence ratios of 0.1, 1.0, and 9.0 in experiments and simulations. The experimental results show that the onset temperature of CH3OH oxidation at 100 atm is around 700 K, which is more than 100 K lower than the onset at 10 atm and this trend cannot be predicted by the existing kinetics models. Furthermore, a negative temperature coefficient (NTC) behavior was clearly observed at 100 atm at fuel rich conditions for methanol for the first time. To understand the observed temperature shift in the reactivity and the NTC effect, we updated some key elementary reaction rates of relevance to high pressure CH3OH oxidation from the literature and added some new low-temperature reaction pathways such as CH2O + HO2 = HOCH2O2 (RO2), RO2 + RO2 = HOCH2O (RO) + HOCH2O (RO) + O2, and CH3OH + RO2 = CH2OH + HOCH2O2H (ROOH). Although the model with these updates improves the prediction somewhat for the experimental data at 100 atm and reproduces well high-temperature ignition delay times and laminar flame speed data in the literature, discrepancies still exist for some aspects of the 100 atm low-temperature oxidation data. In addition, it was found that the pressure-dependent HO2 chemistry shifts to lower temperature as the pressure increases such that the NTC effect at fuel-lean conditions is suppressed. Therefore, as shown in the experiments, the NTC phenomenon was only observed at the fuel-rich condition where fuel radicals are abundant and the HO2 chemistry at high pressure is weakened by the lack of oxygen resulting in comparatively little HO2 formation.

In other words in my family, “Hyeonhi must lead her stupid husband Augustin!” (Tcheonzamun 321st-336th)

French missionary Dallet (1874) wrote that the ancient Chinese people and the ancient Korean people used Tcheonzamun (The thousand character essay) as the textbook of Chinese characters. The range of present study was 16 letters of Tcheonzamun (The thousand character essay), it was (Tcheonzamun 321st-336th). The present researcher used the translating method through the meaning of Chinese character. The title of this work is ‘Hyeonhi must lead her stupid husband Augustin!’ This research was for translating Tcheonzamun (The thousand character essay), and the range was (Tcheonzamun 321st-336th). &lt;Number in Tcheonzamun Chinese characters (Pronunciation of Korean language in English alphabet)&gt; 321-324 樂(Lag) 殊(Su) 貴(Gwi) 賤(Tcheon) My husband! Do you want to make me, your wife (殊), happy (樂)? You might consider the money, from the poor condition (賤) to the rich condition (貴). Do you think that the rich can make me happy? 325-328 禮(Lye) 別(Byeol) 尊(Zon) 卑(Bi) No, it is not so. My husband! The most important thing, it is not the money but the relationship or the etiquette (禮) among the persons, between you and me (別). It is the respect, the respect (尊) for me your wife! Because you have treated me as the miserable person(卑). My husband! You thought me your wife humble! 329-332 上(Sang) 和(Hwa) 下(Ha) 睦(Mog) My husband! Do you want that I your wife can give you (上) my love (和)? If you want to get such a love from me your wife (下), you must give me your warm affection (睦)! 333-336 夫(Bu) 唱(Tchang) 婦(Bu) 隨(Su) My husband! Do you want that I your wife can sing a song (唱) to you (夫) in order to make you in ease? If you want me your wife to do so. My husband! You must follow (隨) my opinion, your wife (婦).

Design ambipolar conductivity on wide-gap semiconductors: The case of Al- and Na-doped CaS

Transparent conducting materials (TCMs) can be divided into n-type and p-type conductivities. For wide gap semiconductors, it is difficult to obtain two types conductivities in one material. Herein, based on the first-principles calculations, we predict the wide-gap semiconductor CaS is an ambipolar semiconductor. The n (p)- type conductivity can be realized via the Al (Na) substituting Ca (labeled as AlCa (NaCa)) defects under Ca (S)-rich condition. The thermodynamic simulations show as the growth temperature increases, the defect concentrations and carrier densities keep continuously rising, and the Fermi energy shifts toward band edges. After quenching the doped samples from high temperature to 300.0 K, the density of electron can reach 6.91×1017 cm−3 under Ca-rich condition, and that is 1.23×1016 cm−3 for hole under S-rich condition. High density of electron and hole, small electron and hole effective masses, together with the wide band gap indicate Al (Na)-doped CaS is a promising ambipolar transparent semiconductors. This study provides a new candidate to design and explore the ambipolar transparent conducting materials.

Co-cultures of Coccomyxa subellipsoidea and Psuedomonas denitrificans increases lipid accumulation independent of nutrient conditions

Coccomyxa subellipsoidea, a single-cell, eukaryotic green algae thriving in temperate climates, is capable of lipid accumulation in excess of 25 % (dry weight). At the front of agroeconomic challenges facing algae for the production of lipids in bioproduct development is how to effectively initiate lipid accumulation and harvesting with economically viable production costs. Co-culturing of the denitrifying bacteria Pseudomonas denitrificans with C. subellipsoidea increased total algal lipids levels, particularly neutral lipids when compared to C. subellipsoidea grown alone in BBM. Total lipid increased nearly two-fold to 16 % (dry weight); triacylglycerol (TAG) increased to 12.5 %. These findings suggest bacterial signaling induced lipid accumulation under nutrient rich condition coincident with increased biomass generation, especially in suboptimal condition using raw wastewater for co-cultures. These findings support a novel signaling mechanism originating from P. denitrificans that results in lipid accumulation in C. subellipsoidea and highlights an underexplored opportunity for an increased agroeconomic viability.