Types Of Stacks Research Articles

Machine learning algorithms improve MODIS GPP estimates in United States croplands

Introduction: Machine learning methods combined with satellite imagery have the potential to improve estimates of carbon uptake of terrestrial ecosystems, including croplands. Studying carbon uptake patterns across the U.S. using research networks, like the Long-Term Agroecosystem Research (LTAR) network, can allow for the study of broader trends in crop productivity and sustainability.Methods: In this study, gross primary productivity (GPP) estimates from the Moderate Resolution Imaging Spectroradiometer (MODIS) for three LTAR cropland sites were integrated for use in a machine learning modeling effort. They are Kellogg Biological Station (KBS, 2 towers and 20 site-years), Upper Mississippi River Basin (UMRB - Rosemount, 1 tower and 12 site-years), and Platte River High Plains Aquifer (PRHPA, 3 towers and 52 site-years). All sites were planted to maize (Zea mays L.) and soybean (Glycine max L.). The MODIS GPP product was initially compared to in-situ measurements from Eddy Covariance (EC) instruments at each site and then to all sites combined. Next, machine learning algorithms were used to create refined GPP estimates using air temperature, precipitation, crop type (maize or soybean), agroecosystem, and the MODIS GPP product as inputs. The AutoML program in the h2o package tested a variety of individual and combined algorithms, including Gradient Boosting Machines (GBM), eXtreme Gradient Boosting Models (XGBoost), and Stacked Ensemble.Results and discussion: The coefficient of determination (r2) of the raw comparison (MODIS GPP to EC GPP) was 0.38, prior to machine learning model incorporation. The optimal model for simulating GPP across all sites was a Stacked Ensemble type with a validated r2 value of 0.87, RMSE of 2.62 units, and MAE of 1.59. The machine learning methodology was able to successfully simulate GPP across three agroecosystems and two crops.

Computational Investigation of MAX as Intercalation Host for Rechargeable Aluminum‐Ion Battery

AbstractLayered carbides and their analogs with MAX phase (general formula AMn+1Xn) have emerged as promising candidates for energy storage and conversion applications. One frontier for energy storage is using MAX as an Al‐ion intercalation electrode. Given that many MAXs have Al as the A sites, the structure can potentially serve as a stable host for Al intercalation. Here in this work, 425 ternary MAX Al‐ion battery electrodes are computationally enumerated. Specifically, first principal phase diagram calculations are performed on the combinatorial space of 17 types of typical transition metals, five types of anions (C, N, B, Si, and P), three types of stoichiometries (n = 1, 2, and 3) and two types of layered stackings (α and β). Among all the ternary MAX materials, 44 candidates show reasonable synthetic accessibility, and six with extraordinary performance are predicted to be promising Al‐ion battery electrodes. With the phase stability, and electrochemical performance (average voltage, theoretical capacity, energy density, and Al diffusion barrier), the work provides a comprehensive computational assessment of the great opportunities behind MAX‐based Al‐ion batteries.

Tuning the Solid State Luminescence of Benzofuran-Cyanostilbenes by Functionalization with Electron Donors or Acceptors.

Three series of linear extended benzofuran derivatives associating cyanovinyl unit and electron withdrawing systems such as paracyanophenyl (series 1) and pentafluorophenyl (series 2) units or the electron donor 3,4-dimethoxyphenyl (series 3) moiety have been prepared. The donor character of the benzofuran part is adjusted either without modifying the conjugation by adding electron-donating methoxy groups to positions 5 and 6 of the benzofuran (compounds BF2 and BF3) or by increasing the extension of the conjugation with the naphthofuran unit (BF4), and by the insertion of a furan ring between the benzofuran and the cyanovinylene bond (BF5). While most of the compounds show very low emission in solution, microcrystalline powders of almost all compounds show middle at strong emissions under excitation at 350-400 nm with emission colors ranging from blue - green to red. It is shown that this variation of the emission colors is essentially due to the type of stacking of the molecules in the solids for series 1 and 2. For series 3, it is above all the extension of the conjugation of the compounds which leads to the red shift.

Ellipsometric studies of CH3NH3PbI3 perovskite thin film on different underlayers and its effect on photovoltaic device performance

Measurement of optical constants of semiconducting thin films is an ongoing strive for optoelectronics and related applications. The optical constants (refractive index (n) and extinction coefficient (k)) plays a vital role in optimizing the thicknesses of different layers for improved performance in optoelectronic devices such as solar cells, photodetectors, light-emitting diodes, etc. In the present work, we measured the optical constants of methylammonium lead iodide (CH3NH3PbI3 or MAPbI3) deposited on five different underlying layers/substrates and estimated the error in simulated current density estimation for a device with the architecture of Glass/ITO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au. The optical modeling and performance analysis of this device has been done using transfer matrix method while spectroscopic ellipsometry has been used to measure the optical constants of MAPbI3 film on five different types of underlayer stacks. A maximum error of around 10.6% has been observed when the optical constants are taken from MAPbI3 films deposited on the different underlying stacks. Additionally, experimental aspects of these films such as surface morphology, structural, and optical properties have also been studied to better understand and correlate the observed differences.

Cost analysis of hydrogen production by high-temperature solid oxide electrolysis

We estimate construction and operation costs of gigawatt-scale solid oxide electrolysis (SOE) facilities for producing high purity hydrogen gas from water. Manufacturing and assembly costs for two types of SOE cell stacks are estimated using a detailed design for manufacture and assembly (DFMA®) analysis. Modular balance of plant (BOP) process equipment is designed and sized with Aspen®, and cost estimated using equipment vendor quotes. Factory and on-site assembly and installation costs for SOEC stack and BOP equipment integration into modular SOE process units are calculated using a simplified DFMA® method. Total stack costs on a stack input power (SIP) basis reduce to <$100/kWe DCSIP for >500 MWe DCSIP/year production rates with electrode cermet, interconnects, and high-temperature heat treatments dominating the total cost. Integration of stacks with larger BOP equipment operating at higher pressures offers ∼36% cost reduction in total facility capital cost due to an economies of physical scale effect since BOP equipment comprises >50% of facility costs. Optimized H2 prices decrease from ∼$4/kgH2 to ∼$2/kgH2 for 1 GWe DCSIP facilities using $0.025/kWh electricity price. All costs are reported in 2021 US dollars.

Dynamic Analysis of Elastically Supported Functionally Graded Sandwich Beams Resting on Elastic Foundations Under Moving Loads

Vibration behaviors of elastically supported functionally graded (FG) sandwich beams resting on elastic foundations under moving loads are investigated. The transformed-section method is first applied to establish the bending vibration equations of FG sandwich beams, then the Chebyshev collocation method is used to study free and forced vibrations. Two types of sandwich beams with FG faces-isotropic core and isotropic faces-FG core are considered. The material properties of FG materials are assumed to vary across the beam thickness according to a simple power function. Regarding the free vibration analysis, bending vibration frequencies are calculated numerically by forming a matrix eigenvalue equation. As for the forced vibration analysis, the backward differentiation formula method is employed to solve the time-dependent ordinary differential equations to obtain the dynamic deformations of the beam. To ensure the accuracy of the proposed model, some calculated results are compared with those in the published literature. Parametric studies are then performed to demonstrate the effects of material gradient indexes, stack types, layer thickness ratios, slenderness ratios, excitation frequency and speed of moving loads, and foundation and support stiffness parameters on the dynamic characteristics of FG sandwich beams.

Interpenetration Phenomena via Anion Template Effects in Fe(II) and Co(II) Coordination Networks with a Bis-(1,2,4-triazole) Ligand.

Seven new coordination networks, [Fe(tbbt)3](BF4)2 (1), [Co(tbbt)3](BF4)2 (2), [Fe(tbbt)3](ClO4)2 (3), [Co(tbbt)3](ClO4)2 (4), [Fe(NCS)2(tbbt)2] (5), [Co(NCS)2(tbbt)2] (6), and [Fe(H2O)2(tbbt)2]Br2·2H2O (7), were synthesized with the linker 1,1'-(trans-2-butene-1,4-diyl)bis-1,2,4-triazole (tbbt) and structurally investigated. The structure of complexes 1-4 is composed of three interpenetrating, symmetry-related 3D networks. Each individual 3D network forms a primitive, nearly cubic lattice (pcu) with BF4- or ClO4- anions present in the interstitial spaces. The structure of compounds 5 and 6 is composed of two-dimensional sql layers, which are parallel to each other in the AB stacking type. These layers are interpenetrated by one-dimensional chains, both having the same formula unit, [M(NCS)2(tbbt)2] (M = Fe, Co). The structure of compound 7 consists of parallel, two-dimensional sql layers in the ABCD stacking type. The interpenetration in 1-6 is not controlled by π-π-interactions between the triazole rings or C=C bonds, as could have been expected, but by (triazole)C-H⋯F4B, C-H⋯O4Cl, and C-H⋯SCN anion hydrogen bonds, which suggests a template effect of the respective non-coordinated or coordinated anion for the interpenetration. In 7, the (triazole)C-H⋯Br anion interactions are supplemented by O-H⋯O and O-H⋯Br hydrogen bonds involving the aqua ligand and crystal water molecules. It is evident that the coordinated and non-coordinated anions play an essential role in the formation of the networks and guide the interpenetration. All iron(II) coordination networks are colorless, off-white to yellow-orange, and have the metal ions in the high-spin state down to 77 K. Compound 5 stays in the high spin state even at temperatures down to 10 K.

Four Slip-Stacked Arrangements, Three Types of Photophysics: Crystal Structure and Solid-State Fluorescence of 3,6-Diaryl Substituted Furo[3,4-c]furanone Polymorphs and Regioisomers.

Six symmetrical 3,6-diaryl (aryl=phenyl, 2-, 3- and 4-tolyl, 2,4- and 3,5-xylyl) substituted furo[3,4-c]furanones (DFF) were synthesized. The computational analysis, based on density functional theory, found eight possible centrosymmetrical slipped π-stack arrangements, formed according to electron repulsion minimization principle, as for previously reported for π-isoelectronic diketopyrrolopyrroles (DPP). One of these slipped stack arrangements was found to form infinite columns in the crystals of a new polymorph of parent phenyl derivative (with centre-to-centre distance CC=6.975 Å), other three types of stacks were found for 3-tolyl (CC=6.153 Å), 4-tolyl (CC=3.849 Å) and 2,4-xylyl (CC=4.856 Å) derivatives by single crystal X-ray diffractometry. All six derivatives show intense solution fluorescence in blue/green region, with a maximum driven entirely by a number and position of methyl substituents on phenyl rings. On the other hand, the solid-state fluorescence from yellow over orange to red is observed only for four derivatives and its presence/absence, spectral position and vibronic structure is driven exclusively by the slips in π-stacks (with interplanar distance always less than 3.5 Å) of almost planar DFF molecules, resulting in J-type emission, H-type excimer-like emission and H-type quenching.

New Lyotropic Complex Fluid Structured in Sheets of Ellipsoidal Micelles Solubilizing Fragrance Oils.

New lyotropic, fragranced, viscoelastic fluid with a complex structure is obtained from fragranced microemulsions by the addition of a fatty acid. Nonhomogeneous mixing of an appropriate nonionic surfactant, a fatty acid, and a fragrance oil led to the formation of anisotropically shaped and highly oriented micelles in aqueous solution. The nano- and microstructures, and consequently the viscosity, are controlled by the balance of fatty acids used as a cosurfactant and fragrance molecules, which partly behave as a cosurfactant and partly segregate in the micelles of the hydrophilic nonionic surfactant. The transition from isotropic microemulsion to a more structured viscoelastic solution is characterized by X-ray scattering and rheological methods. Considering our X-ray scattering results, we propose a structure composed of planar sheets of ellipsoidal micelles arranged in a lamellar type of stacking. The complex structured, low viscous, transparent fluid is capable of solubilizing a fragrance inside the ellipsoidal micelles, as well as retaining microparticles containing fragrance, without the addition of a polymeric thickener or another gelator. These features allow the creation of a 2-in-1 fragrance-solubilizing liquid product compatible with all types of home and body care consumer products.

Topological invariant of multilayer Haldane models with irregular stackings

We study multilayer Haldane models with irregular type of stacking. Considering the nearest interlayer hopping, we prove that the value of the topological invariant is equal to the number of layers times the value of the topological invariant of monolayer Haldane model for irregular stacking(except AA), and interlayer hoppings do not induce direct gap closing or phase transitions. However, if the next-to-nearest hopping is taken into account, phase transitions can occur.

Structural and electronic properties of collapsed armchair single-walled [formula omitted]-graphyne nanotubes

The properties of radially collapsed armchair single-walled α-graphyne nanotubes (α-SWGNTs) are investigated using density functional theory with van der Waals (vdW) corrections. Here, our main goal is to study the structural properties of stable collapsed SWGNT forms and how the corresponding electronic structure are modified in comparison to the circular counterparts. The presence of carbon atoms with sp and sp2 hybridization makes the SWGNTs to present an intriguing geometry for their cross section in the collapsed form and, as a result, the electronic structure of these system is sensitivity to the stacking mode between layers. We find a threshold diameter (26 Å) for which the collapsed structure is more stable than the circular phase, indicating that the natural form of large SWGNTs is radially collapsed. Furthermore, we identified that the collapsed structure is semiconductor when the diameter of the circular phase is greater than 19 Å, with band gap values adjusted by the type of stacking between layers. We believe these results can open up possibilities of using such structures in the setups of nanoelectronic device, and provide a basis for future experimental and theoretical research about collapsed graphyne nanotubes.

Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization (2)

Three types of SOFC stacks have been operated in a NEDO’s project from FY2020 to FY2024 in order to clarify the technical issues for high efficiency and toughness of SOFC stacks and establish the methods for advanced degradation diagnosis of SOFC stacks. Long-term durability tests of two types of SOFC stacks as flatten-tubular type and planar type have been conducted toward 20,000 h under the high fuel utilization at 80 and 85 %, respectively close to the operational limits of the stacks. In addition, the degradation factors of SOFCs were analyzed by using the electrode polarization model developed by CRIEPI. As a result, cathode overvoltage and IR loss were the major degradation factors in the durability tests over 10,000 h.

Interface Design Development for High Durability of SOFC Interconnectors Using Electrodeposition Coating

Solid Oxide fuel cell (SOFC) mounted in ENE-FARM type S has been commercialized since 2012. For further market expansion of ENE-FARM type, higher efficiency, higher durability, and lower cost of SOFC stacks are required. A key technology to advance its performance is a coating on SOFC metallic interconnector for the long-term durability of SOFC stacks. We achieved significant reduction in resistance and improved durability by improving the highly mass producible electrodeposition coating method. In this research, the coating technology of the SOFC interconnector has been developed. Long-term durability was confirmed through high-temperature acceleration evaluation, and the electrodeposition coating on the SOFC interconnector was installed in the ENE-FARM type S.

Stretchable Clay Nanocomposite Barrier Film for Flexible Packaging

The goal of reconciling all packaging requirements, e.g., mechanical resistance, transparency, flexibility, and gas barrier properties, is immensely challenging for packaging materials. Particularly, the combination of flexibility and good gas barrier properties poses a serious problem, especially when barrier requirements can only be met by lamination with a metal foil, metalization, or vapor-deposited ceramic layers, as all of these tend to be nonstretchable. In this work, we produced a stretchable nanocomposite barrier composed of one-dimensional (1D) crystalline (Bragg stack) barrier films composed of alternating layers of poly(ethylene glycol) (PEG) and synthetic sodium fluorohectorite (Hec) nanosheets. By sandwiching the Bragg stack type film between two plasticized poly(vinyl alcohol) (PVOH) layers, a waterborne laminate was obtained that outperforms commercial polymer materials in terms of water vapor permeability (WVP = 2.8 g mm m-2 day-1 bar-1 at 23 °C and 85% relative humidity), which is remarkable for an entirely water-soluble film. Moreover, no deterioration of barrier performance up to 10% elongation was observed, rendering the transparent self-standing laminate promising for thermoformed blister packaging, shrink wrap, or vacuum packaging. Besides the low WVP, the scalable and green processing method makes this technology auspicious for real-world applications.

Selection of the configuration of the cross-section of a multi-flue stacks with four inner flues of different diameters

Despite the widespread use of single-flue stacks, due to the possibility of increasing the rise of flue gases into the atmosphere due to the close location of individual flues in a common shell and ensuring the high reliability of this shell by isolating it from flue gases, multi-flue stacks are increasingly being used. To minimize their cost, it is necessary to determine such an arrangement of flues, in which the diameter of the stack shell will be minimal.THE PURPOSE. Consider the main types of multi-flue stacks used in world practice. Obtain an analytical solution for determining the minimum possible diameter of the reinforced concrete shell of a four-flue stack with flues of different diameter.METHODS. Graphical and analytical methods using computer modeling, as well as the use of computer-aided design systems.RESULTS. An analytical solution is obtained to determine the minimum possible diameter of the reinforced concrete shell of a four-flue stack with stems of different diameters at given distances between the flues and between the flues and the containment shell as a solution to a system of algebraic and trigonometric equations. The distances between the flues and between the flues and the containment can be set to any. In this paper, a new methodology and calculation program for four-flue stacks has been developed. It is shown that the shell diameter depends on the arrangement of flues of different diameters. In the absence of space restrictions for flues, flues with the largest diameters should be placed opposite each other. The obtained method for determining the shell diameter due to more accurate design and when all specified conditions are met, allows to reduce the cost of the shell by 4–9 % compared to the current method for determining the shell diameter.

Soil Physical Properties as Influence by Poultry and Cow Dung from Different Housing and Stacking Types Following Telfairia occidentalis (Hook F.) Production

Soil physical properties play significant function in the yield of crop produce. Sustaining food supply of the teeming population depends on the degree of preserving soil physicalproperties, therefore enhancing soil productivity. Experiments were conducted to establish the influence of poultry and cow dung from different housing and stacking types on physical properties of soil following Telfairia occidentalis production in 2017 and 2018. Amendments were applied in both years after which data were analyzed using Analysis of Variance. The experiment reveals that amendments statistically increased soil porosity, moisture content, hydraulic conductivity and therefore reduced bulk density above control in both years. It is concluded that for improved soil physical properties in the study area, bagged poultry manure in palm fronds house (PPB) at 5.4 tha-1 is recommended to farmers.

Modulating the electronic properties and thermal conductivity of trilayer BX (X=N,P) by bias voltage and magnetic field

Two-dimensional materials with controllable electronic properties have a significant effect on improving the performance of nanoelectronic devices. In this study, the electronic and thermal conductivity of the trilayer BP (3L-BP) and BN (3L-BN) in the presence of the bias voltage and magnetic field are investigated by tight binding model and Kubo-Greenwood formula. The different stacking types for all structures are selected. All selected configurations exhibit semiconductor properties and their electronic properties can be affected under the influence of an external electric field. Their band gap decrease to zero in critical field strength and the magnetic field shows a higher decreasing rate, compared to the bias voltage. The external fields increase the thermal conductivity of all cases and 3L-BP has higher thermal intensity than that 3L-BN. The results show that by applying stronger bias voltage or magnetic field, the thermal conductivity of 3L-BN structures can be enhanced in order to 3L-BP, independent of its wide band gap.

An exceptionally strong, ductile and impurity-tolerant austenitic stainless steel prepared by laser additive manufacturing

The effective strategy for structural steel with excellent tolerance of impurities is to increase solidification rate to prevent the formation of segregation and intermetallic during fabrication.Carbon (C) and oxygen (O) as impurities in austenitic stainless steel are often controlled at extremely low levels to ease their detrimental effects on toughness and corrosion resistance. Hence, high-quality austenitic stainless steels are poor in impurity tolerance and moderate in strength. Here, we use laser additive manufacturing successfully engineering C, N and O with high contents as interstitial atoms coordinated with Cr in the form of short-range ordered assembly in steel, and develop an impurity-tolerant supersaturated austenitic stainless steel with an ultrahigh strength of 961±40 MPa, a good ductility (37.5 ± 3%), an enhanced corrosion resistance (0.0745 Ecorr/V) and acceptable thermal stability up to 500 °C. First-principles calculations indicate that a coordinated hexahedron C4Cr4, as a stable unit in the austenite, can be assembled via three basic types of stacking. With the presence of N and O, N1C6Cr8, O1C6Cr7 and O1C6Cr8 are also stable coordination assembly units. Such short-range ordered assembly of interstitial atoms can produce significant super-saturated interstitial solid solution strengthening, which is responsible for the enhancement of tensile strength while maintaining ductility. The novel approach in engineering impurities by laser additive manufacturing may open up a new avenue in developing advanced high-impurity-tolerance steels for potential industrial applications at a low cost.

Anomalous quantum oscillations in AA and AB bilayer graphene

We study the quantum oscillations in AA and AB graphene bilayers with broken intralayer P-symmetry in the presence of a gate voltage. We consider both doped (weakly) and undoped cases. The presence of a gate voltage leads to the appearance of an inverted band region in the spectrum of the bilayer, which results in additional peaks in the density of states oscillations. We demonstrate the existence of oscillations in the dielectric phase when the chemical potential is pinned within band gap. These effects are analyzed for different types of layer stacking in a bilayer. It is shown that the graphene bilayer is better suited for the experimental study of anomalous oscillations compared to narrow-gap topological insulator. It is worth mentioning that our results can be applied to other graphene-like bilayer materials, such as transition metal dichacolgenides bilayers.

Band engineering of valleytronics WSe2–MoS2 heterostructures via stacking form, magnetic moment and thickness

Spin-valley polarization and bandgap regulation are critical in the developing of quantum devices. Here, by employing the density functional theory, we investigate the effects of stacking form, thickness and magnetic moment in the electronic structures of WSe2–MoS2 heterostructures. Calculations show that spin-valley polarization maintains in all situations. Increasing thickness of 2H-MoS2 not only tunes the bandgap but also changes the degeneracy of the conduction band minimums (CBM) at K/K 1 points. Gradual increase of micro magnetic moment tunes the bandgap and raises the valence band maximums (VBM) at Γ point. In addition, the regulation of band gap by the thickness of 2H-MoS2 and introduced magnetic moment depends on the stacking type. Results suggest that WSe2–MoS2 heterostructure supports an ideal platform for valleytronics applications. Our methods also give new ways of optical absorption regulation in spin-valley devices.