Present Calculations Research Articles

Economic comparison of floating photovoltaic systems with tracking systems and active cooling in a Mediterranean water basin

Floating Photovoltaic (FPV) modules are installed on water surface to reduce land use. This original solution, potentially deployable on hydropower and aquaculture basins as well, can benefit of enhanced cooling due to the proximity to water. Thanks to this natural effect, FPV modules can work at higher operating efficiencies than ground-based (GPV) modules. However, because of the relatively young age, FPV still requires higher installation costs than GPV. This study investigates the economic competitiveness of GPV and FPV in terms of energy performance and total costs. Different PV system solutions are economically evaluated on the basis of three key figures, namely the capital costs (CAPEX), the operation and maintenance costs (OPEX) and the power generation costs (LCOE). An economic ranking is created based on the comparative analysis of these three key figures.The crucial point in the proposed economic model is that the revenues resulting from the reduced evaporations are considered as well. Every year, indeed, a significant volume of water can be preserved thanks to the shading effect of FPV modules. This water can be used for various purposes, increasing the overall revenues of the FPV system. In addition, the present LCOE calculations also take into account the performance enhancements that could be achieved through the installation of active cooling systems.In light of the expected economy of scale, a sensitivity analysis of the LCOE is carried out to account potential reductions in the capital cost of FPVs. This is done by analyzing the energy and economic performance of various FPV designs on a water basin in Southern Italy. The results demonstrate that, reducing the CAPEX of the FPV by 30 %, a nearly 20 % reduction in LCOE can be obtained compared to the reference GPV system.

Is d^*(2380) a compact hexaquark state?

The most fascinating dibaryon in the non-strange quark sector is d^*(2380), which was reported by WASA-at-COSY Collaboration and confirmed by A2@MAMI Collaboration. The reported mass and decay width are Mapprox 2.37 GeV, Gamma approx 70 MeV and the quantum numbers are IJ^P=03^+. The structure of d^*(2380) is still in controversy. In the present calculation, the powerful method in few-body system, Gaussian expansion method (GEM) is employed to explore the structure of d^*(2380) in the framework of constituent quark models without assuming the presupposed structure. The results show that the radius of d^*(2380) is around 0.8 fm, it is a very compact object. Because of the compact structure, the color singlet-singlet component has a large overlap with the color octet-octet one, two colorless, large overlapped Delta s dominate the state is possible.

Combined First-Principles and Experimental Study on the Microstructure and Mechanical Characteristics of the Multicomponent Additive-Manufactured Ti-35Nb-7Zr-5Ta Alloy.

New β-stabilized Ti-based alloys are highly promising for bone implants, thanks in part to their low elasticity. The nature of this elasticity, however, is as yet unknown. We here present combined first-principles DFT calculations and experiments on the microstructure, structural stability, mechanical characteristics, and electronic structure to elucidate this origin. Our results suggest that the studied β Ti-35Nb-7Zr-5Ta wt % (TNZT) alloy manufactured by the electron-beam powder bed fusion (E-PBF) method has homogeneous mechanical properties (H = 2.01 ± 0.22 GPa and E = 69.48 ± 0.03 GPa) along the building direction, which is dictated by the crystallographic texture and microstructure morphologies. The analysis of the structural and electronic properties, as the main factors dominating the chemical bonding mechanism, indicates that TNZT has a mixture of strong metallic and weak covalent bonding. Our calculations demonstrate that the softening in the Cauchy pressure (C' = 98.00 GPa) and elastic constant C̅44 = 23.84 GPa is the origin of the low elasticity of TNZT. Moreover, the nature of this softening phenomenon can be related to the weakness of the second and third neighbor bonds in comparison with the first neighbor bonds in the TNZT. Thus, the obtained results indicate that a carefully designed TNZT alloy can be an excellent candidate for the manufacturing of orthopedic internal fixation devices. In addition, the current findings can be used as guidance not only for predicting the mechanical properties but also the nature of elastic characteristics of the newly developed alloys with yet unknown properties.

Closed formula of test length required for adaptive testing with medium probability of solution

PurposeBased on the general formula, which depends on the length and difficulty of the test, the number of respondents and the number of ability levels, this study aims to provide a closed formula for the adaptive tests with medium difficulty (probability of solution is p = 1/2) to determine the accuracy of the parameters for each item and in the case of calibrated items, determine the required test length given number of respondents.Design/methodology/approachEmpirical results have been obtained on computerized or multistage adaptive implementation. Simulation studies and classroom/experimental results show that adaptive tests can measure test subjects’ ability to the same quality over half the test length compared to linear versions. Due to the complexity of the problem, the authors discuss a closed mathematical formula: the relationship between the length of the tests, the difficulty of solving the items, the number of respondents and the levels of ability.FindingsThe authors present a closed formula that provides a lower bound for the minimum test length in the case of adaptive tests. The authors also present example calculations using the formula, based on the assessment framework of some student assessments to show the similarity between the theoretical calculations and the empirical results.Originality/valueWith this formula, we can form a connection between theoretical and simulation results.

Effect of Graphene Reinforcement on Free Vibration and Material Properties of the FG-GPLRC Porous Cantilever Torsional Plate

This paper researches the free vibrations and corresponding material parameters of a functional gradient graphene platelets-reinforced composite (FG-GPLRC) cantilever torsional plates with both pore and graphene variations in the transverse direction. Utilizing the feature of closed-cell cellular solids, the mixture rule, and the modified Halpin–Tsai model, the material parameters of the composite are determined for different volume fractions of component materials. Then, using the classical plate theory (CLPT), the Rayleigh–Ritz technique and polynomials, the dynamic equation that can be used to obtain the free vibration mode shapes and frequencies of the rotating cantilever torsional plate is given. Comparison studies with the previous calculation results from available literature and the finite element (FE) models of cantilever plates are conducted, and the correctness of the present theoretical formulation and numerical calculation is verified. Finally, the effects of graphene platelet (GPL) distribution, porosity distribution (PD), GPL content, rotational speed, and average geometric size of GPL on free vibrations of the system are studied in depth.

Relativistic calculation of electron impact excitation of tin: cross sections of importance in plasma modeling

The present work includes the calculation of electron impact excitation cross sections for the fine structure resolved transitions in Sn I and Sn II, using the relativistic distorted wave approximation with the aid of Dirac-Fock multiconfigurational wavefunctions. For Sn I, the cross sections are calculated for the excitations from the fine structure resolved energy levels of the manifolds, , , , and including the ground state, to the fine structure resolved levels of , , , , and manifolds for a wide range of projectile electron energy from 0 to 500 eV. Further, the cross sections are also calculated for the excitations of Sn II from the fine structure resolved energy levels of the manifolds, , , , and including the ground state, to the fine structure resolved levels of , , , , and manifolds. All the cross sections for Sn I except for the excitation from the ground state to the fine-structure resolved excited states of , and manifolds and all the cross sections for Sn II are reported for the first time. In order to ensure the consistency of the present calculations, a comparison of the oscillator strengths and transition probabilities is carried out with the available calculations and measurements. The present cross sections are also compared with previous calculations and observed to be in reasonable agreement. The calculated cross sections are of great interest in the modeling and diagnostic of various plasmas such as laser induced plasma, fusion plasma, etc. Further, to ease the use of calculated cross sections, the analytic fitting of the cross sections is also provided.

DFT study on the catalytic decomposition of hydrogen peroxide by iron complexes of nitrilotriacetate.

The Fenton system in the presence of nitrilotriacetate (NTA) ligand is studied by DFT approach. The calculations show that complexation of Fe(II) with NTA significantly facilitates the H2 O2 activation. The ferric-hydroperoxo intermediate NTAFe(III)OOH predominantly decays via the disproportionation into NTAFe(II)OH2 and NTAFe(IV)O involving the formation of a μ-1,2-hydroperoxo-bridged biferric intermediate. In this mechanism, the bridged hydroperoxo is reduced by hydroperoxo ligand rather than by Fe(III). On the one hand, the NTAFe(III)OOH is sluggish to undergo hydrogen abstraction; on the other hand, it is a good nucleophile that may perform aldehyde deformylation. The present calculations suggest that both ˙OH and Fe(IV)O are generated in the NTA-assisted Fenton system. However, the polycarboxylate ligand provides a favorable environment for H2 O2 to accumulate around iron ion through hydrogen bonding. This promotes the quenching of Fe(IV)O by H2 O2 , rationalizing why the Fe(IV)O species is hardly detected in the NTA-assisted Fenton system.

K-shell X-ray production cross sections of Ti, Cr, Ni and Zn induced by chlorine ions

In this work we report on the results of the total K-shell X-ray production cross sections of Ti, Cr, Ni and Zn induced by Cl4+ and Cl5+ ions with energies ranging from 4 MeV to 10 MeV. The experimental results were compared with Atomic Orbitals Coupled-Channels (CC) calculations based on the independent electron model. The experimental X-ray production cross sections vary from about 10−2 barns for Zn up to 102 barns for Ti. The results obtained for Ti indicate that the present CC calculations underestimate the experimental cross sections up to two orders of magnitude at 10 MeV chlorine bombarding energy. However, the discrepancy between CC calculations and experimental results decreases as both bombarding energy and the atomic number of the target species increase. The dependency of the experiment-theory agreement on the asymmetry and adiabaticity parameters α and η respectively is discussed.

Microsecond Isomer at the N=20 Island of Shape Inversion Observed at FRIB.

Excited-state spectroscopy from the first experiment at the Facility for Rare Isotope Beams (FRIB) is reported. A 24(2)-μs isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV γ rays in coincidence with ^{32}Na nuclei. This is the only known microsecond isomer (1 μs≤T_{1/2}<1 ms) in the region. This nucleus is at the heart of the N=20 island of shape inversion and is at the crossroads of the spherical shell-model, deformed shell-model, and abinitio theories. It can be represented as the coupling of a proton hole and neutron particle to ^{32}Mg, ^{32}Mg+π^{-1}+ν^{+1}. This odd-odd coupling and isomer formation provides a sensitive measure of the underlying shape degrees of freedom of ^{32}Mg, where the onset of spherical-to-deformed shape inversion begins with a low-lying deformed 2^{+} state at 885keV and a low-lying shape-coexisting 0_{2}^{+} state at 1058keV. We suggest two possible explanations for the 625-keV isomer in ^{32}Na: a 6^{-} spherical shape isomer that decays by E2 or a 0^{+} deformed spin isomer that decays by M2. The present results and calculations are most consistent with the latter, indicating that the low-lying states are dominated by deformation.

Coupling heat transfer study of liquid sodium and supercritical carbon dioxide in a PCHE straight channel based on a four-equation model

The Brayton cycle using supercritical carbon dioxide (S-CO2) as the working fluid is expected to be a thermo-power conversion technology for sodium-cooled fast reactors. Printed Circuit Heat Exchanger (PCHE) is the key heat transport structure to realize the above technology. The study of conjugate heat transfer characteristics of sodium (Na) with low Prandtl number turbulent heat transfer characteristics and S-CO2 with supercritical convective heat transfer behaviors in a PCHE channel are of great significance. However, the constant turbulent Prandtl number (Prt) model obtained by the general Reynolds analogy hypothesis may affect the conjugate heat transfer assessment between Na and S-CO2. Compared with the constant Prt model, the fluid’s Prt distribution can be obtained by four-equation models, introducing the transport of turbulent kinetic energy k, dissipation rate ε of k, temperature fluctuation kθ, and dissipation rate εθ of kθ. The four-equation model is expected to obtain more effective conjugate heat transfer characteristics between Na andS-CO2, while there are no available commercial codes. Therefore, in this paper, two kinds of four-equation model, which can effectively evaluate the heat transport performance of Na with low-Prandtl number and S-CO2 away from the pseudo-critical region, respectively, are first introduced into the conjugate heat transfer solver of OpenFOAM. Then the conjugate heat transfer experiment data of Na in a pipe and the simulation data of S-CO2 in a PCHE straight channel are used to verify the validity of the numerical model in this paper. The results show that the present calculation method can effectively reproduce the numerical conjugate heat transfer process of Na and S-CO2. Finally, based on four-equation models, the coupling heat exchange performance of Na/S-CO2 are studied to obtain the effects of mass rate and temperature on the conjugate heat transfer process between Na and S-CO2 in a PCHE straight channel.

A “greenhouse gas balance” for aviation in line with the Paris Agreement

AbstractThe effects of aviation on climate pose unique policy challenges. A large fraction of the CO2 emissions (65%) is international and not (explicitly) included in the Paris Agreement. The interpretation of Article 4.1 on achieving a “balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases” is ambiguous in the context of aviation because of the substantial non‐CO2 effects associated with the sector. For the achievement of the temperature goal in Article 2, both CO2 and non‐CO2 effects are important. The non‐CO2 effects contribute 66% of the sectoral total climate effect (in terms of Effective Radiative Forcing; ERF) at present, with significant uncertainties. The largest of these non‐CO2 effects, contrail‐cirrus and the net‐effect of NOx, are not caused by direct greenhouse gas emissions, representing another ambiguity as to whether they should be included in the balance concept. We discuss the role of aviation in the context of the Paris Agreement, and present illustrative calculations of a hypothetical aviation “greenhouse gas balance.” Several questions are addressed: Which components should be included? If an aggregate of components is adopted for the “balance,” which metric should be used? How can the large differences in timescales as well as the large intrinsic underlying ERF uncertainties be handled? We demonstrate that these choices result in very different requirements for CO2‐removal from the atmosphere and different temperature outcomes over time. The article provides policymakers with an overview of issues and choices that are important regarding which approach is most appropriate for defining and achieving a greenhouse gas balance for aviation in the context of the Paris Agreement.This article is categorized under: Policy and Governance &gt; International Policy Framework Climate and Development &gt; Knowledge and Action in Development Paleoclimates and Current Trends &gt; Climate Forcing

Diffusivity and atomic mobility for Fcc Ni–Ti–V alloys: Experiment and modeling

Ni–Ti–V is one key sub-system of the Ni-based superalloys. However, there is a lack of the investigation on diffusion kinetics for Fcc Ni–Ti–V alloys. In order to remedy this situation, we combined the diffusion couple experiment and calculation by CALTPP (CALculation of ThemoPhysical Properties) software to investigate diffusion kinetics for Fcc Ni–Ti–V alloys. Totally, 12 ternary Fcc Ni–Ti–V diffusion couples were prepared and annealed at 1273, 1373 and 1473 K, for which the composition profiles were measured by EPMA (Electron Probe MicroAnalysis). Based on the measured composition profiles and available thermodynamic descriptions, the interdiffusivities and atomic mobility parameters for Fcc Ni–Ti–V system were then calculated by the numerical inverse method integrated with CALTPP software. The simulated composition profiles by CALTPP software agree well with the measured ones. Moreover, the interdiffusivities obtained by CALTPP software were confirmed to be reliable through the good consistence with those calculated by M − K (Matano-Kirkaldy) method. Thus, the present numerical calculation by CALTPP software was verified to be reasonable. Finally, based on the presently obtained mobility parameters and available thermodynamic descriptions for Fcc Ni–Ti–V alloys, the three-dimensional surfaces of the interdiffusivities, activation energies and frequency-factors against Ti and V composition were predicted. The present work provides reliable kinetic parameters for Fcc Ni–Ti–V alloys, which can be included in the diffusion database of Ni-based superalloys for material design.

A systematic investigation on the surface properties of Ti2AlC via first-principles calculations

In this study, the surface properties of Ti2AlC surface with different configurations were systematically investigated based on the analysis of surface energy and electronic structure via first-principles calculations. 18 Ti2AlC surface models of basal, prismatic or pyramidal planes were constructed and calculated. The results show that either the Ti(C)- or Al-terminated (0001) surface exhibits the lowest surface energy and highest thermodynamic stability depending on the element chemical potential. While the C-terminated (0001) surface exhibits the lowest thermodynamic stability independent of the element chemical potential. Since the atomic structures of (101¯0) and (112¯0) prismatic planes are similar to those of (101¯1)∼(101¯6) and (112¯1)∼(112¯6) pyramidal planes, respectively, they have similar surface energy and stability. The electronic structure calculations revealed that the highest thermodynamic stability of Ti(C)- or Al-terminated (0001) surface is due to their less structure relaxations. The present first-principles calculation results are well consistent with previous experimental results, and could provide theoretical guidance for the further engineering application of Ti2AlC phase.

Real options in health insurance decisions: the Portuguese ADSE system

The choice between two different health insurance providers is, more often than not, taken from a static point of view, measuring costs and benefits at a specific point in time, not considering all the relevant changes that may occur in life and in health conditions. Inspired by the new regulations set in place by the exclusive Portuguese civil servant’s insurance scheme designated by ADSE, this study proposes a novel approach based on real options for an individual that needs to choose between a private health insurance and the apparently cheaper option provided by ADSE. Starting from the net present value approach, we subsequently show that, depending on some life changing events that may occur, it would be more beneficial for the individual to either abandon the health system or enter it at a later date. By incorporating the value of these options in the net present value calculation, decisions taken are not only more flexible, but also more realistic.

A coupled model of global energy production and ERoEI applied to photovoltaic and wind, an estimation of net production

Photovoltaic (PV) and wind energy production modelling essentially follows bottom-up approaches, based on physical considerations. These models focus mostly on the calculation of Energy Return on Energy Invested (ERoEI), while some also present calculation of energy payback time or energy cannibalism, to evaluate the ability of these technologies to handle energy transition. Besides, sigmoïd or S-curve function are often used to fit the production of these industries over time, based on economical considerations, rather than physical ones. This paper aims at coupling net production and ERoEI, using energy conservation and ERoEI definition, to develop a model that could reproduce a S-curve function and allow to investigate the net energy delivered by PV and wind industries. This approach allows to explain the inconsistency which sometimes exists between bottom-up and top-down studies on PV ERoEI calculation. It also explains why the classic relationship between net and gross energy, that is a ratio equal to (ERoEI−1)/ERoEI, does not apply to low carbon energy industries before they reach a steady-state or a quasi-static evolution. As an example, net PV production is still close to zero whereas wind production began to produce a net substantial energy around 2007–2010. It finally allows to investigate how fast the energy transition can physically be to see if a risk of energy disruption exists during that transition, due to fossil fuel depletion.

Atomic and electronic structures of an Ag-containing 4A zeolite

Atomic structure of an Ag-containing 4A zeolite with the Ag/Al atomic ratio of about 10% was investigated by a pair distribution function (pdf) analysis. Valence- and conduction-band O 2p partial electronic structures of this insulating material were respectively measured by soft X-ray emission and absorption spectroscopies using an O 1s-2p resonance technique. Moreover, a density functional theory (DFT) hybridized by 25% of Hartree–Fock exchange was applied to determine the atomic structures and electronic states. Although the box size of the DFT calculation was small due to the limited computational power, the present DFT results excellently reproduce the pdf data as well as O 2p partial electron density of states (DOS). The electronic charge distributions in this zeolite with an antibacterial function obtained by the present DFT calculation revealed half-filled charges on the Ag atoms, which may act as a formation of deactivating the bacteria.

The Feasibility Analysis of “Ecological Photovoltaics” from Coal Gangue Mountains

Coal gangue is a byproduct of coal mining, and has been piled up for years in China, forming thousands of coal gangue hills, which have become an important part of abandoned mining areas. In recent years, the government has issued various policies on the ecological restoration of coal gangue hills and provided economic support. However, relying solely on policies and economic support is not a long-term solution. The key is to improve the production efficiency of coal gangue hills and promote their sustainable development. This paper conducts on-site investigations of coal gangue hills and makes proposals from the perspective of ecology and economic benefits. Firstly, it is suitable to install photovoltaics on coal gangue hills, especially those located far from residential areas, with convenient transportation and maintenance and the orientation of the coal gangue mountain. Secondly, based on the preliminary ecological restoration of coal gangue hills, a design scheme of laying photovoltaic cells on the slopes of coal gangue hills and developing ecological platforms through planting is proposed. The feasibility is explored by constructing a net present value economic calculation. The results show that the use of a slope photovoltaic laying design scheme is not only conducive to ecological development, but also can cover the daily maintenance costs of coal gangue hill ecological restoration and produce certain economic benefits. With the expansion of the scale and the improvement of location conditions, the economic benefits will also increase.

Equations of state for B2 and bcc Fe1-xSix

Composition, chemical disorder, and magnetism significantly affect the volume and bulk modulus of iron‑silicon (FeSi) alloys at ambient pressure. Here we computed the equations of state for bcc-like (ordered B2 and disordered bcc) Fe-Si alloys up to the inner-core pressure using the first-principles Korringa–Kohn–Rostoker method. Ferromagnetic (FM) and nonmagnetic (NM) states were investigated over a wide compositional range from Fe to FeSi. The present static calculations revealed that magnetism and chemical disorder increased the volume and decreased the bulk modulus also at high pressures. In order to obtain their density and bulk sound velocity under high temperatures relevant to the inner core, we calculated the Helmholtz energy by using the quasi-harmonic approximation with the assumption that the Poisson's ratio of Fe-Si alloys is equivalent to that observed in the inner core. This assumption is valid when the inner core consists of bcc-like Fe-Si. Nevertheless, the obtained density and bulk sound velocity do not match seismological observations unless a temperature gradient inside the inner core is unrealistically large, indicating that the inner core is not a bcc-like Fe-Si alloy.

Theoretical Investigation of Dissociative Electron Attachment of Acrylonitrile

Dissociative electron attachment (DEA) of acrylonitrile (C2H3CN) is investigated theoretically for two dominant anions CN- and C3N- for the electron impact energy range of 0-20 eV. The present low-energy DEA calculations are performed using the UK molecular R-matrix code using Quantemol-N. We have performed static exchange polarization (SEP) calculations by employing a cc-pVTZ basis set. Furthermore, present DEA cross-sections along with the appearance potential find good agreement with the three measurements reported many decades ago by Sugiura et al. [J. Mass Spectrom. Soc. Jpn. 1966, 14(4), 187-200], Tsuda et al. [Bull. Chem. Soc. Jpn. 1973, 46 (8), 2273-2277] and Heni and Illenberger [Int. J. Mass Spectrom. Ion Process. 1986, 73 (1-2), 127-144]. The molecule acrylonitrile and the anions are important for understanding interstellar chemistry, and it is the maiden theoretical attempt to compute a DEA cross-section for this molecule.

Evaluation of progressive collapse resistances of RC frame with contributions of beam, slab and infill wall

This study aims to present practical calculation models to predict the deformation capacity and the progressive collapse resistance of reinforced concrete (RC) frames for design purpose. It is well known that beams, floor slabs and infill walls have significant contributions to progressive collapse resistance of RC frame structures. Considering contributions from RC beams, floor slabs and infill walls, calculation models are proposed based on the summary of available experimental phenomena and data in existing studies. It is shown that the proposed calculation models give acceptable predictions to experimental and numerical data, which can be used as alternative methods for evaluations of RC frame structures in the collapse-resistance design.