Low Energy Yield Research Articles

Pyrolysis of sesame residue: Evolution of the volatiles and structures of biochar versus temperature

Sesame residue is a solid waste produced in the process of production of sesame oil, which can be used as feedstock for the production of biofuels and carbon materials via thermochemical process. This study explores the pyrolysis behavior of sesame residue at different pyrolysis temperatures and heating rates, aiming to explore the effects of temperature and heating rates on the distribution and properties of sesame residue products. Sesame residue contains more aliphatic alkanes and N-containing organics than biomass, and thus cracking reactions dominated distribution of products, at especially increased pyrolysis temperature with high heating rates. Majority of the nitrogen-containing organics were cracked into condensable organics at 350 °C and into gases above this temperature. The abundant long-chain aliphatics also made the bio-oil different from that from biomass pyrolysis. The organic components in sesame residual were generally not thermally stable, a significant portion of which was converted into volatile organics or gases, producing the biochar with low carbon yield, low heating value and the low energy yield. Additionally, the change of functionalities of the biochar versus temperature was investigated, providing reference information for tailoring structure of biochar for further use as functional carbon materials. • Pyrolysis of sesame residue at different temperature and heating rates was studied. • Nitrogen-containing organics was not stable and mostly cracked above 350 °C. • Cracking of alkanes in sesame residual produced abundant aliphatics in bio-oil. • Dominant cracking leads to biochar of low carbon yields and heating value. • Evolution of functionality of biochar with pyrolysis temperature was characterized.

Global assessment of historical, current and forecast ocean energy infrastructure: Implications for marine space planning, sustainable design and end-of-engineered-life management

Thousands of structures are currently installed in our oceans to help meet our global energy needs. This number is set to increase with the transition to renewable energy, due to lower energy yield per structure, growing energy demand and greater and more diverse use of ocean space (e.g. for food, industrial or scientific activity). A clear and comprehensive picture of the spatial and temporal distribution of ocean energy assets is crucial to inform marine spatial planning, sustainable design of ocean infrastructure and end-of-engineered-life management, to prevent an exponentially increasing asset base becoming an economic and environmental burden.Here we define the spatial and temporal dimensions of the challenge that lies before us through creation of a comprehensive global dataset of past, current and forecast ocean energy infrastructure and offshore energy resources, both hydrocarbon and wind, for the period 1960–2040. The data is collected together for the first time and made available in the public domain through an interactive online map. The resulting oceanscape provides insight into the type, quantity, density and geographic centres of the accumulating asset base, which in turn enables informed consideration of how marine space alongside design and end-of-engineered-life of ocean infrastructure can be managed responsibly and sustainably.

Plasma-assisted catalysis for ammonia synthesis in a dielectric barrier discharge reactor: key surface reaction steps and potential causes of low energy yield

Ammonia synthesis experiments were carried out in a coaxial dielectric barrier discharge (DBD) reactor packed with several different supports and metal catalysts. There was a marked increase in the reaction rate, over that obtained in an empty DBD plasma reactor, upon introduction of a packed bed of γ-Al2O3, Ru/γ-Al2O3, or SiO2 particles. The difference in the reaction rates over γ-Al2O3 and Ru/γ-Al2O3 was minimal. Complementary zero-dimensional plasma kinetic model analysis was also performed using inputs from experimental data. This kinetic analysis allowed for gas phase reactions, Eley–Rideal (E–R) reactions, and direct adsorption of radical species on the γ-Al2O3 surface. On the metal surface, dissociative adsorption of N2 and H2, and Langmuir–Hinshelwood reactions were also included. This analysis revealed that, under the conditions of our experiments, ammonia synthesis proceeds principally by the formation of reactive radicals in the gas phase, which then adsorb and participate in E–R reactions on both the metal and support material surfaces. This finding illustrates a challenge for substantially increasing the energy yield for plasma-assisted ammonia synthesis in typical DBD reactors containing packed catalyst beads.

Lithium-Sulfur Batteries with Robust Cycle Life For Space Applications

While lithium-ion (Li-ion) batteries offer tremendous performance advantages over their battery predecessors (e.g., nickel-cadmium, lead-acid), they are approaching an asymptotic limit in specific energy (~250 Wh/kg at cell level) and do not adequately address next generation space platform requirements (e.g., by NASA [1]). As a result, there has been intense research and development (R&D) on higher specific energy batteries that have been coined beyond Li-ion. Rechargeable lithium-sulfur (Li-S) battery is a particularly attractive beyond Li-ion battery chemistry because it offers a high theoretical specific energy of 2500 Wh/kg (at materials level) [2] and a demonstrated practical specific energy >300 Wh/kg (at cell level) [3], making it a promising battery chemistry for future space applications that demand higher specific energy in batteries.Currently, no commercial Li-S battery exists due to several significant technical challenges that have thus far prevented the realization of the Li-S chemistry’s tremendous performance potential. These technical challenges include: (i) Low practical energy yield and significant capacity loss with cycling, due to lithium polysulfide formation/dissolution/migration during discharge [4]. (ii) High self-discharge rates and low Coulombic efficiency, due to redox shuttle reactions of the dissolved polysulfides. (iii) Safety concerns, mainly due to Li dendrite growth from the unprotected Li anodes [5].We will present our efforts in the development of a high energy density, long cycle life, long shelf life and enhanced reliability/safety Li-S battery technology, using a holistic and comprehensive approach to overcome technical challenges that hinder commercialization of Li-S batteries. In particular, we will demonstrate impact of various battery testing parameters, such as depth-of-discharge, charge/discharge current C-rate, on Li-S cell cycle performance and shelf life.Our investigation results showed that, using material engineered (active and inactive) cell components, the resultant Li-S cells demonstrated excellent cycle life performance, while achieving high specific capacities and energies when cycled under optimized battery testing schemes. The advanced Li-S battery technology has shown a great promise to achieve unprecedented specific energy/energy density and long-term cycle/shelf life stability for future space applications. References 2020 NASA Technology Taxonomy, https://www.nasa.gov/offices/oct/taxonomy/index.htmlZhang, Sheng S., Power Sources, 231, 153-162, 2013.Weibing Xing, # A02-0364, 238th Electrochemical Society Meeting (PRiME), Honolulu, HI, October 4-9, 2020.Besenhard JO. Handbook of Battery Materials. Wiley: New York; 1998.James R. Akridge, Battery Power Products & Technology, October 2001. Acknowledgement We would like to acknowledge financial support from NASA Glenn Research Center for this R&D work.

Crop diversification practice faces a tradeoff between increasing productivity and reducing carbon footprints

Increasing crop biodiversity often increases agro-ecosystem services, however, the effects of crop biodiversity on crop yield and environmental benefits are still unclear. Thus, we conducted a 4-yr field experiment in northeastern China including continuous maize (CM), continuous soybean (CS), maize and soybean rotation (M-S), and maize and soybean intercropping (M/S) to evaluate the crop productivity, economic returns, carbon footprint (CF) and carbon sustainability index (CSI) among the cropping system regimes. Compared with CM treatment, M-S and M/S achieved lower energy yield (EY) and maize equivalent economic yield (MEEY), but higher economic returns. The mean annual net revenue of M-S treatment was 7.2% higher, and the mean annual benefit: cost ratio of M-S and M/S treatments were 12.0% and 8.8% higher than those of CM treatment. Based on the life cycle assessment (LCA), lower CFs were observed in the M-S and M/S systems. The CF per unit of area (CFA) of M-S and M/S treatments was 21.4% and 51.3% lower than that of the CM treatment, respectively. The CF per kg of energy yield (CFEY) of M/S treatment was 35.4% lower, compared with that of the CM treatment. The CF per kg of maize equivalent economic yield (CFMEEY) under M/S treatment was 44.0% lower, than that of the CM treatment. Moreover, CF per unit of economic output (CFE) of M/S treatment was 45.0% lower than that of the CM treatment. The highest CSI was observed in M-S treatment, and it was 61.4% higher than that of CM treatment. Our findings indicate that diversified crop practice (e.g. maize-soybean intercropping and rotation systems) could achieve lesser carbon footprint and higher profitability, however, might compromise grain or energy yield.

Defects Impact on PV System GHG Mitigation Potential and Climate Change

Solar photovoltaic (PV) systems are widely used to mitigate greenhouse gases (GHG), due to their green renewable nature. However, environmental factors such as bird drops, shade, pollution, etc., accommodation on PV panels surface reduce photons transmission to PV cells, which results in lower energy yield and GHG mitigation potential of PV system. In this study, the PV system’s energy and GHG mitigation potential loss is investigated under environmental stresses. Defects/hotspots caused by the environment on PV panel surface have unknown occurrence frequency, time duration, and intensity and are highly variable from location to location. Therefore, different concentrations of defects are induced in a healthy 12 kWp PV system. Healthy PV system has the potential to avoid the burning of 3427.65 L of gasoline by 16,157.9 kWh green energy production per annum. However, in 1% and 20% defective systems, green energy potential reduces to 15,974.3 and 12,485.6 kWh per annum, respectively. It is equivalent to lesser evasion burning of 3388.70, and 2648.64 L of gasoline, respectively. A timely solution to defective panels can prevent losses in the PV system to ensure optimal performance.

Pyrolysis of soybean residue: Understanding characteristics of the products

Soybean residue (SR) is a main solid waste produced during the extraction of soybean oil with bulk volume. In addition to the use as vegetable protein feed, SR could also be used as feedstock for producing biofuels and carbon materials via pyrolysis. In this study, the pyrolysis behaviors of SR at varied temperatures and heating rates were investigated. The results show that the pyrolysis of the organic components in SR could reach completion even at 500 °C, due to the lower thermal stability of the organic component than that in the typical biomass. This also leads to the bio-oil with little heavy organics and also low carbon content of the resulting biochar, as the organic components decomposed to a significant extent while the charring reactions were insignificant. This leads to the biochar with low heating value and low energy yield when compared with that in the pyrolysis of typical biomass. In addition, the high content of proteins, amino acids and other nitrogen-containing nutrients make the SR derived bio-oil nitrogen-rich and a significant portion of nitrogen could also be retained in the biochar. These specialties have to be considered during their applications as either biofuels or functional carbon materials.

Structure of the far-red light utilizing photosystem I of Acaryochloris marina

Acaryochloris marina is one of the cyanobacterial species that can use far-red light to drive photochemical reactions for oxygenic photosynthesis. Here, we report the structure of A. marina photosystem I (PSI) reaction center, determined by cryo-electron microscopy at 2.58 Å resolution. The structure reveals an arrangement of electron carriers and light-harvesting pigments distinct from other type I reaction centers. The paired chlorophyll, or special pair (also referred to as P740 in this case), is a dimer of chlorophyll d and its epimer chlorophyll d′. The primary electron acceptor is pheophytin a, a metal-less chlorin. We show the architecture of this PSI reaction center is composed of 11 subunits and we identify key components that help explain how the low energy yield from far-red light is efficiently utilized for driving oxygenic photosynthesis.

Nuclear de-excitations in low-energy charged-current νe scattering on Ar40

Background: Large argon-based neutrino detectors, such as those planned for the Deep Underground Neutrino Experiment, have the potential to provide unique sensitivity to low-energy (few to tens of MeV) electron neutrinos produced by core-collapse supernovae. Despite their importance for neutrino energy reconstruction, nuclear de-excitations following charged-current $\nu_e$ absorption on $^{40}$Ar have never been studied in detail at supernova energies. Purpose: I develop a model of nuclear de-excitations that occur following the $^{40}\mathrm{Ar}(\nu_e,e^{-})^{40}\mathrm{K}^*$ reaction. This model is applied to the calculation of exclusive cross sections. Methods: A simple expression for the inclusive differential cross section is derived under the allowed approximation. Nuclear de-excitations are described using a combination of measured $\gamma$-ray decay schemes and the Hauser-Feshbach statistical model. All calculations are carried out using a novel Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields). Results: Various total and differential cross sections are presented. Two de-excitation modes, one involving only $\gamma$-rays and the other including single neutron emission, are found to be dominant at few tens-of-MeV energies. Conclusions: Nuclear de-excitations have a strong impact on the achievable energy resolution for supernova $\nu_e$ detection in liquid argon. Tagging events involving neutron emission, though difficult, could substantially improve energy reconstruction. Given a suitable calculation of the inclusive cross section, the MARLEY nuclear de-excitation model may readily be applied to other scattering processes.

Enhanced Photocatalytic Activity of CuWO4 Doped TiO2 Photocatalyst Towards Carbamazepine Removal under UV Irradiation

Abatement of contaminants of emerging concerns (CECs) in water sources has been widely studied employing TiO2 based heterogeneous photocatalysis. However, low quantum energy yield among other limitations of titania has led to its modification with other semiconductor materials for improved photocatalytic activity. In this work, a 0.05 wt.% CuWO4 over TiO2 was prepared as a powder composite. Each component part synthesized via the sol-gel method for TiO2, and CuWO4 by co-precipitation assisted hydrothermal method from precursor salts, underwent gentle mechanical agitation. Homogenization of the nanopowder precursors was performed by zirconia ball milling for 2 h. The final material was obtained after annealing at 500 °C for 3.5 h. Structural and morphological characterization of the synthesized material has been achieved employing X-ray diffraction (XRD), Fourier transform infra-red (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) N2 adsorption–desorption analysis, Scanning electron microscopy-coupled Energy dispersive X-ray spectroscopy (SEM-EDS), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy (UV-vis DRS) for optical characterization. The 0.05 wt.% CuWO4-TiO2 catalyst was investigated for its photocatalytic activity over carbamazepine (CBZ), achieving a degradation of almost 100% after 2 h irradiation. A comparison with pure TiO2 prepared under those same conditions was made. The effect of pH, chemical scavengers, H2O2 as well as contaminant ion effects (anions, cations), and humic acid (HA) was investigated, and their related influences on the photocatalyst efficiency towards CBZ degradation highlighted accordingly.

Ranking with hamiltonian dynamics

In data science, a ranking or linear ordering problem is to place items into a linear order based on comparison data. In this article, we consider a Hamiltonian system, in which particles, representing the items to be ordered, exert forces on each other as determined by the comparison data. An ordering of the items can be derived from the relative positions of the particles in any state of the system. The Hamiltonian is designed so that states with low potential energy yield orderings that agree strongly with the comparison data. Although the dynamics are related to the Toda lattice, no usable ranking information seems to be available from that variation of the Hamiltonian. Instead, a Toda-like Hamiltonian plus a confinement potential yields better results. Several algorithms based on Hamiltonian trajectories, minimization of a ranking potential, and a Hamiltonian Markov chain are compared to the widely used RankBoost algorithm. They all perform relatively well on synthetic test data and on problems from a library of test cases, but none is clearly the best in all circumstances. The trajectory-based methods and Markov chain show interesting dynamics. Furthermore, since these methods attach particle positions to the items as well as an ordering, the distances between the particles indicate how rankable the items are.

Study on Comprehensive Adjustment Countermeasures of Weak Alkali ASP Flooding in Low Water Cut Period

The problems occurred in the production process of weak alkali ASP flooding industrial demonstration area in Class II oil layer of Block A are systematically analyzed, such as the injection pressure of some injection wells rising too fast, the low energy and low yield of some production wells after ASP flooding, and the water cut rising too fast. Aiming at the problem of time, the research work of comprehensive adjustment was carried out, and the effective ways to improve the test effect were summarized Improve the injection-production relationship of well groups and reduce the plane and interlayer differences; Better development results have been achieved by improving the effectiveness of oil wells.

Cartographing dynamic stall with machine learning

Abstract. Once stall has set in, lift collapses, drag increases and then both of these forces will fluctuate strongly. The result is higher fatigue loads and lower energy yield. In dynamic stall, separation first develops from the trailing edge up the leading edge. Eventually the shear layer rolls up, and then a coherent vortex forms and then sheds downstream with its low-pressure core causing a lift overshoot and moment drop. When 50+ experimental cycles of lift or pressure values are averaged, this process appears clear and coherent in flow visualizations. Unfortunately, stall is not one clean process but a broad collection of processes. This means that the analysis of separated flows should be able to detect outliers and analyze cycle-to-cycle variations. Modern data science and machine learning can be used to treat separated flows. In this study, a clustering method based on dynamic time warping is used to find different shedding behaviors. This method captures the fact that secondary and tertiary vorticity vary strongly, and in static stall with surging flow the flow can occasionally reattach. A convolutional neural network was used to extract dynamic stall vorticity convection speeds and phases from pressure data. Finally, bootstrapping was used to provide best practices regarding the number of experimental repetitions required to ensure experimental convergence.

Long-term enrichment of anaerobic propionate-oxidizing consortia: Syntrophic culture development and growth optimization

Propionate is a quantitatively important methanogenic intermediate in anaerobic digesters and only limited number of microbes can utilize it under syntrophic association with methanogens. The syntrophic propionate oxidizing bacterias are known to be slow growers due to the low energy yield. Thus, propionate get accumulated frequently in anaerobic digesters and it negatively affect digester performance. In this study, propionate degrading consortia from four different seeding sources were enriched in sequential bath mode in two phases; first adaption phase with 1 g/L of propionate concentration and later, high-strength phase with 3 g/L. From 16s rRNA gene based metagenomics analysis of the former phase, four syntrophic microbial groups, Syntrophaceae, Syntrophomonadaceae, Methanobacterium and Methanosaeta were found to be dominant with complete degradation of propionate. The substrate accelerated microbial shifts were observed at high-strength phase with significant decrease of Syntrophaceae up to 26.9 %. Using Response Surface Methodology, pH 6.8–6.9 and temperature 34.5–34.9 °C were found to be optimum growth conditions for the propionate degradation culture. Observed results could be useful to improve degradation efficiencies and obtained enriched culture can be used to recover propionate-accumulated digesters by bio-augmentation.

Comparison on solid biofuel production from wet and dry carbonization processes of food wastes

In this research, three categories of food waste (dried cabbage, chicken, and rice) were separately subjected to hydrothermal carbonization (HTC) under 180 °C, 200 °C, and 220 °C and pyrolytic carbonization (PC) under 200 °C, 250 °C, 300 °C, 350 °C, and 400 °C for solid biofuel production, respectively. Carbonization pathways, solid yield, high heating value (HHV), the transformation of nitrogen and ash, and char reactivity were detailly compared. After both pre-treatments, the ratio of fixed carbon (FC) to volatile matter (VM) of solid increased with the increase of the temperature, except for HTC of chicken. HTC of chicken led to more VM in solid product with very low solid yield and significantly lower N content. HTC-chars showed higher VM even at the same temperature as PC despite more severe carbonization (higher C content). Even though the N content can be reduced by both HTC and PC, HTC showed superiority than PC in regards to reducing the N content, indicating the potential to mitigate the N-related emission. Even though the HHV of HTC char was higher than that of PC char at the same pretreatment temperature, the product yield of the former one was much lower, resulting in lower energy yield in HTC char. The alkaline index (AI) can be used as the main factor for comparisons of gasification reactivity between (1) HTC and PC-chars and (2) Among HTC-chars from different temperatures. PC-chars presented higher reactivity than HTC-chars for all types of feedstock when considering at the same pre-treatment temperature at 200 °C. In conclusion, the key parameters including VM, the solid yield, HHV, the N content reduction, and char reactivity can be adopted to well evaluate the solid biofuel qualities production from different processes of HTC and PC, respectively.

Biosurfactant Production in Sub-Oxic Conditions Detected in Hydrocarbon-Degrading Isolates from Marine and Estuarine Sediments.

Hydrocarbon bioremediation in anoxic sediment layers is still challenging not only because it involves metabolic pathways with lower energy yields but also because the production of biosurfactants that contribute to the dispersion of the pollutant is limited by oxygen availability. This work aims at screening populations of culturable hydrocarbonoclastic and biosurfactant (BSF) producing bacteria from deep sub-seafloor sediments (mud volcanos from Gulf of Cadiz) and estuarine sub-surface sediments (Ria de Aveiro) for strains with potential to operate in sub-oxic conditions. Isolates were retrieved from anaerobic selective cultures in which crude oil was provided as sole carbon source and different supplements were provided as electron acceptors. Twelve representative isolates were obtained from selective cultures with deep-sea and estuary sediments, six from each. These were identified by sequencing of 16S rRNA gene fragments belonging to Pseudomonas, Bacillus, Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium genera. BSF production by the isolates was tested by atomized oil assay, surface tension measurement and determination of the emulsification index. All isolates were able to produce BSFs under aerobic and anaerobic conditions, except for isolate DS27 which only produced BSF under aerobic conditions. These isolates presented potential to be applied in bioremediation or microbial enhanced oil recovery strategies under conditions of oxygen limitation. For the first time, members of Ochrobactrum, Brevundimonas, Psychrobacter, Staphylococcus, Marinobacter and Curtobacterium genera are described as anaerobic producers of BSFs.

Evaluating biogeochemical indicators of methanogenic conditions and thermodynamic constraints in peat

Burial of organic matter in deep peat deposits has already been experimentally demostrated to slow down or even inhibit anaerobic decomposition due to lack of diffusive transport and end-product accumulation. However, so far little is known about potential biogeochemical or thermodynamic indicators for the observed inhibition of further decomposition. For example, theoretical energy yields for methanogenesis, hydrogen partial pressures, stable isotope fractionation factors between CO2 and CH4, and electrochemical properties of dissolved organic matter have been proposed as thermodyamic indicators for such inhibition. To test the applicability and explanatory power of these indicators to identify conditions inhibiting organic matter decomposition, we incubated homogenized ombrotrophic peat for 300 days at 20 °C under diffusive flux conditions as control, and compared the observed effects to a treatment with vertical advective transport by water circulation and to a treatment in which both the unsaturated and water-saturated zone of the peat profile were kept anoxic. Results of energy yields of acetoclastic and hydrogenotrophic methanogenesis were compared to hydrogen partial pressures, to 13C isotope fractionation factors and to redox properties of dissolved organic matter as obtained from mediated electrochemical oxidation and reduction. While CO2 and CH4 production slowed substantially in the deep peat profile, a concomitant decrease of Gibs free energy yields available to hydrogenotrophic and acetoclastic methanogensis and hydrogen and acetate concentrations over time supported a thermodynamic constraint on methanogenesis. Although, energy yields for the hydrogenotrophic pathway were close to or below the theoretical energy minimum levels already after 15 days. Transiently elevated H2 concentrations, not related to actual methanogenesis rates were observed for about 150–225 days. Thereafter, hydrogen concentrations diminished to levels below thresholds to thermodynamically support ongoing methanogenesis. Thus even on incubation timescales of 150–225 days, steady-state hydrogen concentrations as would be expected from thermodynamic considerations did not adjust on the bulk scale of observation. Gibbs free energy estimates for methanogenesis based on hydrogen partial pressures were consequently biased and did not reach the minimum required threshold despite ovious net CH4 production. Ratios between electron accepting (EAC) and donating (EDC) capacity of dissolved organic matter, however, turned out to provide suitable indicators of predominant redox conditions along gradients, stabilizing at low values upon onset of methanogenesis. Thus, our study demonstrated that the thermodynamically driven slow down of decomposition in deep peat deposits, preventing the peat to decompose further, cannot be easily identified based on a single indicator. However, constant and high concentrations of decomposition end-products, indicating zero net turnover and low energy yields, and constantly low EAC/EDC ratios, indicating no further availability of terminal electron acceptors, seem to be characteristic of the onset of conditions inhibiting further significant decomposition of peat.

A comprehensive study of sawdust torrefaction in a dual-compartment slot-rectangular spouted bed reactor

A dual-compartment slot-rectangular spouted bed (DSRSB) reactor was designed and built to torrefy sawdust. The effects on torrefaction performance of temperature from 240 to 300 °C, sawdust feedrate from 600 to 1400 g/h and oxygen concentration from 0 to 9 vol% were explored. The temperature difference between the adjacent compartments was limited. Pressure drop across the reactor was affected by biomass feedrate, and was higher for the downstream compartment than for the upstream one. The weight loss of the sawdust was 9.3–38.2 wt%, while the energy yield was 65.7–99.6%. Oxidative torrefaction resulted in greater weight loss and lower energy yield than non-oxidative torrefaction. The product properties were significantly affected by the reactor temperature and oxygen concentration. Solids, liquid and gaseous products were characterized. The results showed that the DSRSB is a promising reactor for biomass torrefaction.

Cartographing dynamic stall with machine learning

Airfoil stall is bad for wind turbines. Once stall has set in, lift collapses, drag increases and then both of these forces will fluctuate strongly. The result is higher fatigue loads and lower energy yield. In dynamic stall, separation first develops from the trailing edge up the leading edge, eventually the shear layer rolls up and then a coherent vortex forms and then sheds downstream with it's low pressure core causing a lift spike and moment dump. When 50+ experimental cycles of lift or pressure values are averaged, this process appears clear and coherent in flow visualizations. Unfortunately, stall is not one clean process, but a broad collection of processes. This means that the analysis of separated flows should be able to detect outliers and analyze cycle to cycle variations. Modern data science/machine learning can be used to treat separated flows. In this study, a clustering method based on dynamic time warping is used to find different shedding behaviors. This method captures that secondary and tertiary vorticity vary strongly and in static stall with surging flow; the flow can occasionally reattach. A convolutional neural network was used to extract dynamic stall vorticity convection speeds and phases from pressure data. Finally, bootstrapping was used to provide best practices regarding the number of experimental repetitions required to ensure experimental convergence.

Anaerobic Microbial Degradation of Polycyclic Aromatic Hydrocarbons: A Comprehensive Review.

Polycyclic aromatic hydrocarbons (PAHs) are a class of hazardous organic contaminants that are widely distributed in nature, and many of them are potentially toxic to humans and other living organisms. Biodegradation is the major route of detoxification and removal of PAHs from the environment. Aerobic biodegradation of PAHs has been the subject of extensive research; however, reports on anaerobic biodegradation of PAHs are so far limited. Microbial degradation of PAHs under anaerobic conditions is difficult because of the slow growth rate of anaerobes and low energy yield in the metabolic processes. Despite the limitations, some anaerobic bacteria degrade PAHs under nitrate-reducing, sulfate-reducing, iron-reducing, and methanogenic conditions. Anaerobic biodegradation, though relatively slow, is a significant process of natural attenuation of PAHs from the impacted anoxic environments such as sediments, subsurface soils, and aquifers. This review is intended to provide comprehensive details on microbial degradation of PAHs under various reducing conditions, to describe the degradation mechanisms, and to identify the areas that should receive due attention in further investigations.