Energy Method Research Articles

Theoretical and Numerical Investigation of the Effective Mechanical Properties of an Arc Star-Shaped Auxetic Honeycomb

Background: Auxetic honeycombs have attracted a lot of attention due to their excellent properties, including lightweight, and outstanding impact resistance and energy absorption. Methods: This study focuses on a new type of arc star-shaped honeycomb (ASSH) by replacing the tip angles of the classical star-shaped honeycomb (SSH) with curved edges. The theoretical expressions of the effective Poisson’s ratio and Young’s modulus are deduced by using the Timoshenko beam theory and energy method. Furthermore, the numerical model is also established through the Finite Element Method (FEM); then, both the analytical and computational approaches are adopted to conduct parametric analysis. Results: It was found that the effective mechanical properties obtained by theoretical analysis and the FEM are consistent with each other, and ASSH bears tunable effective Poisson’s ratio and Young’s modulus under varying geometric configurations. Conclusion: The present work may provide some guidance for the design and analysis of future auxetic honeycombs.

Sensitivity and sustainability analysis of combined cycle plant with integrated LNG pressure energy recovery

Although combined cycle power plants (CCPPs) and liquefied natural gas (LNG) have arisen as solutions to the intermittent nature of renewable energy sources, they still need creative methods for performance enhancement and sustainability of the energy systems. Moreover, the energy efficiency of CCPPs is negatively impacted by environmental conditions, higher specific fuel consumption and a large quantity of waste heat released into the ambient. On the other hand, using seawater as a heating medium in LNG regasification circuits has a detrimental effect on the marine ecosystem. In this context, the LNG pressure energy recovery system through a direct expansion cycle (DEC) integrated with CCPP is proposed to improve sustainability, enhance exergetic performance and to reduce the heat recovery steam generator (HRSG) exhaust loss. To improve the cycle performance, low grade heat harnessed from CCPP is used as the heat source in the DEC rather than seawater. The system performance is analyzed by the energy and exergy method through a mathematical model. Moreover, the sensitivity analysis of the combined system is accomplished to examine the influence of LNG flow rate and ambient temperature on various performance indicators of the total system. It is observed that the integration of DEC boosts the HRSG performance by reducing the stack exergy loss and the efficiency is sensitive to LNG flow rate. The total integrated system energy efficiency ηtot, enhanced to 1.55% compared to the base case. Whereas, for ambient temperature in range of 15 – 45 °C, the system minimum and maximum exergetic efficiency ηex,tot is found to be 54.52 % and 55.94 %. Furthermore, the comparison of exergetic sustainability indicators is calculated and presented for three different simulation cases. The results demonstrate that increase in ηex,tot, affects the environment impact factor, ref and the sustainability index, θsi and improved 2.09 % compared to base case combined cycle.

Effect of Intake Acoustic Reflection on Blade Vibration Characteristics

Recent studies in turbomachinery have shown that the phase of acoustic wave reflection within an intake can have either positive or negative effects on the aeroelastic stability of fan rotor blades. However, the typical flow structures, such as the shock wave, within rotor blade passages with acoustic wave reflection remain unclear. The aim of this research was to address this gap by investigating how these flow structures impact blade aeroelastic stabilities with acoustic wave reflections. The focus of this study was the NASA Rotor 67 blade with an extended intake. Moreover, a bump is incorporated on the shroud at different distances from the fan to reflect acoustic waves of varying phases. Utilizing the energy method, variations in the aerodynamic work density on blade surfaces were calculated under different phases of reflected acoustic waves. Analysis indicates that the spatial position of the shock wave undergoes periodic changes synchronized with the phase of acoustic reflection, marking the first instance of such an observation. This synchronization is identified as the primary factor causing variations in the aeroelastic stability of blades due to acoustic wave reflection, contributing to a deeper understanding of the mechanism behind acoustic flutter. The acoustic–vortex coupling at the blade tip leads to unpredictable variations in unsteady pressures on the blade suction surface, although its effect on blade aeroelastic stabilities is relatively limited compared to that of the shock wave.

Sustainable Optimization of Mold Heating: A Dual Approach with SWARA and MARCOS Methods

There are many methods and raw materials in the manufacturing of fiber reinforced plastics (FRP) with hot press, such as Sheet Molding Compound (SMC), Bulk Molding Compound (BMC), and Prepreg fabrics. In most applications, it is commonly used to put the new dough into the mold without cooling the mold, press it again and cure it. Putting the mold into the dough without cooling causes the surface of the poured product to cure faster than the inner region, thus causing a structurally discontinuous structure in the product. Therefore, in more professional manufacturings, the mold is lowered to approximately 120 oC and the dough is put into the mold at this stage. However, this increases energy consumption and carbon emissions for the heating and cooling phases. In this study, the energy efficiency in the manufacturing of fiber reinforced plastics (FRP) produced by the hot press method was investigated. At the end of this study, by using alternative energy methods in manufacturing processes, results such as investment cost, depreciation expenses, reduction in invoices, and carbon emissions were achieved. In order to find the best alternative among these results, the criteria weights were determined with SWARA, and the founded alternatives ranked by the MARCOS method. As a result of this ranking, the best alternative was determined as a 40 kWh battery and a 25 kW solar panel option among the solar panel power and battery capacity alternatives.

A comprehensive quantitative DFT procedure to evaluate rate-capability and electron conduction of intercalation electrode materials: Assessment of novel Li[Mi]1/3[Mj]1/3[Mk]1/3O2 electrodes as case studies

This paper uses comprehensive approach to propose quantitative evaluations of the electrode materials’ electronic rate-capability calculated by density functional theory (GGA/GGA + U). Here, a novel approach is introduced to evaluate electrical rate-capability by calculating electronic conductivity (σ) for the case studies. Application of the evaluated materials as electrodes of Li-ion battery is taken into account. Also, thermal conductivity and Seebeck coefficient for the materials are calculated. Here, three novel alternatives for LiNi1/3Co1/3Mn1/3O2 (NCM111), in which introduced by substitution of transition metals, are LiNi1/3Mn1/3Fe1/3O2(NMF), LiMn1/3Fe1/3Co1/3O2(MFC), and LiFe1/3Co1/3Ni1/3O2(FCN). The evaluated materials are compared with each other and other relevant electrodes, based on structural, electrochemical, and electrical properties. The voltage reaction of the cathode materials is calculated by two approaches, namely internal and Fermi energy methods. According to the obtained results, MFC and NMF have superior properties on NCM. It is concluded that the NMF can be the best alternative for NCM conditionally.

A rapid prediction model for the radiation efficiency of baffled constrained layer damping plate

It’s well-known that constrained layer damping (CLD) can effectively reduce the vibration and radiation noise from the (plate-like or shell-like) thin-walled structures under various of dynamic excitations. As one of the key properties deciding the CLD’s performance, the CLD’s acoustic radiation characteristics has always been a focus of researchers. In this study, an analytical model based on equivalent principle is proposed to predict the acoustic radiation efficiency of the CLD plate. In this model, a laminated CLD plate is equivalent to a single-layer plate and the equivalent stiffness and loss factor are obtained using the strain energy method. The vibration velocity of the plate is calculated using mode-superposition method and the sound pressure on the plate surface is calculated using Rayleigh integral formula. Variable mesh sizes and frequency steps are employed to improve the calculation efficiency. The difference between the base and CLD plates in sound radiation characteristics is investigated using this model. The results indicate that CLD involving a damping layer with a low Young’s modulus can mitigate more vibration at low frequencies. A higher Young’s modulus of the damping layer results in a higher radiation efficiency of the CLD plate between the fundamental and critical frequencies. By increasing the loss factor, the spatially averaged mean square velocity would decrease, more modes would contribute to the response, and the CLD plate can consequently achieve a higher radiation efficiency below the critical frequency. Moreover, the simplified formulae for the average radiation efficiency of the CLD plate is developed to achieve the rapid calculation. Its accuracy is then validated by comparing the results to the more comprehensive model.

Existence of solutions for anisotropic parabolic Ni-Serrin type equations originated from a capillary phenomena with nonstandard growth nonlinearity

We consider an initial boundary value problem for a class of anisotropic parabolic Ni-Serrin type equations with nonstandard nonlinearity in a bounded smooth domain with homogeneous Dirichlet boundary condition. Because the nonlinear perturbation leads to difficulties (it does not have a definite sign) in obtaining a priori estimates in the energy method, we had to modify the Tartar method significantly. Under suitable assumptions, we obtain the global existence, decay and extinction of solutions.

Dynamic stability of the euler nanobeam subjected to inertial moving nanoparticles based on the nonlocal strain gradient theory

This research studied the dynamic stability of the Euler-Bernoulli nanobeam considering the nonlocal strain gradient theory (NSGT) and surface effects. The nanobeam rests on the Pasternak foundation and a sequence of inertial nanoparticles passes above the nanobeam continuously at a fixed velocity. Surface effects have been utilized using the Gurtin-Murdoch theory. Final governing equations have been gathered implementing the energy method and Hamilton's principle alongside NSGT. Dynamic instability regions (DIRs) are drawn in the plane of mass-velocity coordinates of nanoparticles based on the incremental harmonic balance method (IHBM). A parametric study shows the effects of NSGT parameters and Pasternak foundation constants on the nanobeam's DIRs. In addition, the results exhibit the importance of 2T-period DIRs in comparison to T-period ones. According to the results, the Winkler spring constant is more effective than the Pasternak shear constant on the DIR movement of nanobeam. So, a 4 times increase of Winkler and Pasternak constants results in 102 % and 10 % of DIR movement towards higher velocity regions, respectively. Furthermore, the effect of increasing nonlocal and material length scale parameters on the DIR movement are in the same order regarding the magnitude but opposite considering the motion direction. Unlike nonlocal parameter, an increase in material length scale parameter shifts the DIR to the more stable region.

Modeling compliant bistable mechanisms: An energy method based on the high-order smooth curvature model

This paper applies an energy method based on the high-order smooth curvature model to address the challenges of kinetostatically modeling the complicated nonlinear post-buckling behavior of inclined compliant beams. The proposed energy method is grounded in the principle of minimum strain energy, implying that the total strain energy is minimized at the equilibrium configuration. In this work, the high-order smooth curvature model is adopted to accurately model the bending strain energy of large deformation beams. Subsequently, the Lagrange multiplier method is employed to ascertain the minimum of strain energy while concurrently determining the corresponding tip loads. Additionally, the deformation shape and maximum stress are determined via the smooth curvature model. The proposed method is introduced for the first time in modeling compliant bistable mechanisms, and it is proven that the method can be used for modeling compliant beams with inclined angles ranging from 0 to 90 degrees. Following the modeling, finite element analysis and experimental tests are conducted to verify the accuracy of the proposed energy method. A comprehensive comparative analysis between proposed method and existing methods is conducted. The comparison results prove that the model is more computationally efficient without compromising modeling accuracy The proposed modeling method can not only be used for modeling compliant bistable mechanisms but also has extendable applications in modeling initially-curved compliant beams, contact-aid design problems, and distributed load problems.The present work not only advances the practical application of the proposed energy method but also lays the foundation for future research in modeling compliant mechanisms.

Economics of physics-based solar forecasting in power system day-ahead scheduling

A high-quality solar power forecasting system that strictly adheres to grid regulations is valuable for system operators to formulate strategies for power system scheduling. Some grid operators, therefore, enact penalty schemes for the forecasts submitted by photovoltaic (PV) plant owners, as a means to fortify truthful and high-quality forecast submissions. From the perspectives of both plant owners and grid operators, this study inquires into the quality-to-value mapping of solar forecasts in the context of power system day-ahead scheduling. A physics-based solar power forecasting method is presented, which consists of two steps. Firstly, ensemble numerical weather prediction (NWP) is summarized into point forecasts. Then irradiance is converted to power via a physical model chain. The results reveal that the two-step physics-based forecasting method has an advantage over a winning method in Global Energy Forecasting Competition 2014 in terms of several accuracy measures. Subsequently, the economics of solar forecasting is quantified through performing day-ahead scheduling on a modified IEEE 30-bus system with PV and battery storage. It is demonstrated that, by respecting the statistical theory on consistency and elicitability when extracting point forecasts from NWP ensembles, both power system operators and PV plant owners can benefit profoundly in terms of cost savings. The former sees fewer needs for reserves, while the latter is less penalized. The data and Python code used to produce the results are also provided to enhance the reproducibility of this work.

Multireference Correlated Oscillator Strengths from Adiabatic Connection Approaches Based on Extended Random Phase Approximation.

We show that accurate oscillator strengths can be obtained from adiabatic connection (AC) approaches based on the extended random phase approximation (ERPA) combined with multireference (complete active space, CAS) wave functions. The oscillator strengths calculated using the perturbation-corrected ERPA transition density matrices, proposed in this work, and the excitation energies calculated with recently introduced AC correlation energy methods, AC0 and AC0D, compete with accuracy in the perturbational CASPT2 approach and require less computational effort. AC0 and AC0D methods scale more favorably with the number of active orbitals than multiconfigurational perturbation approaches like CASPT2 and NEVPT2 thanks to their dependence on reduced density matrices up to the order of 2. Importantly, the newly developed approach for computing correlated transition dipole moments does not entail any additional costs, as all intermediate quantities become available when AC0 energies are being computed. We also test the performance of the recently proposed AC method corrected for the negative-transition contributions to the correlation energy, AC0D, for triplet excitation energies. Similarly, as for the singlet excitations, the correction improves the performance of the AC0 method, particularly for the low-lying excited states.

Experimental and feasibility study of bio-waste valorization through pyrolysis for energy and materials production in the concept of circular economy

The pyrolysis and co-pyrolysis characteristics of large abundant bio-wastes, namely date pits (DP), peanut shells (PS), coffee grounds (CG), and tea waste (TW) were investigated in detail. The TG/DTG and pyrolysis procedures were used to examine the thermal pyrolysis behavior of these agro-wastes and their blends (50%CG/50%DP, 50%CG/50%PS, 50%DP/50%PS, 50%TW/50% DP,50%TW/50%PS and 50%CG/50% TW by weight). The characterization of these feedstock has shown their suitability for energy and material valorization. Experiments were carried out in a batch pyrolysis at a medium heating rate of 10 °C/min. The goal was to identify the best combination aiming to produce either char or hydrogen-rich gas, which can contribute to the development of the circular bio-economy. It was demonstrated that pyrolysis favored the liquid product, fluctuating from 34.31% (TW) to 50.92% (DP), while the co-pyrolysis greatly increased the gaseous product, which ranged between 42.02% (TW-DP) and 55.17% (PS-TW). The blending of CG and PS resulted in heightened reactivity, leading to an enhanced generation of H2 (34.44%). The optimal mixture was found to be CG-TW, showcasing superior performance in terms of gas quality (38.39% H2) and yield (53.74%). This outcome underscores the potential of CG and TW as a synergistic blend for efficient hydrogen-rich gas production. The FTIR findings revealed that the recovered biochars have the potential to serve as solid fuels, biofertilizers, or carbon materials. Additionally, they could be used as eco-friendly precursors for chemical and related industries. By analyzing various waste mixtures and their respective pyrolysis properties, this research aims to contribute to the development of sustainable waste management practices as well as efficient energy and material production methods.

Optimal operation of multi-microgrid systems considering multi-level energy-certificate-carbon coupling trading

Under the background of sustainable development, the microgrid (MG) has become an important method for energy saving, emission reduction and meeting multiple energy demand. With the continuous promotion of China's carbon emission right market and green certificate market, to further promote the low-carbon development of MG, a multi-level trading optimization strategy is proposed for multi-microgrids (MMG) that considers the coupling of energy-certificate-carbon market. First, a MMG trading framework including a two-level certification-carbon and a three-level electric-thermal coupled trading is proposed. Second, based on the game theory pricing strategy and the elastic price mechanism of the supply-demand ratio, the MMG operation optimization strategy model is constructed considering multi-level energy-certification-carbon coupled trading. Finally, based on the principle of fair benefit allocation, the Shapley value method is utilized to redistribute the comprehensive income among the alliance members. The simulation results show that compared with the MMG baseline scenario, the overall economic efficiency of the proposed trading model is improved by 3.94 % and the carbon emissions are reduced by 11.71 %. In this way, it can effectively release the potential of MMG resource sharing and mutual benefit, so as to optimise the trade-off strategy for joint participation in the energy-certificate-carbon market.

A deterministic energy method for predicting the response of coupled finite structures

The forced response of finite, thin rectangular plates coupled by a line joint can be predicted using well-established analytical methods. However, such methods become difficult to implement for thick panels coupled by complex joints. In these cases, the finite element (FE) method and conventional statistical energy analysis (SEA) are viable alternatives. However, the FE method can be time-consuming at mid/high frequencies while SEA involves various approximations and assumptions. This paper develops a deterministic energy method for predicting the forced response of coupled complex panels based on a hybrid finite element/wave finite element (WFE) method, modelling the panels as coupled wave-bearing subsystems. The method involves meshing only a small segment of the panel and the joint using finite elements, and is able to model complex structures such as laminated panels and joints with low computational cost. Excitations of the structure by a time-harmonic point force and the rain-on-the-roof excitations are both considered. The wave subsystem energy and power flow formulations corresponding to these excitations are derived to be the sum of wave components. The energy/power formulations are then used for establishing an SEA-like model for predicting the coupling data between the subsystems. Numerical examples of two thin, rectangular plates coupled by an “L” shaped joint and coupled practical cross-laminated-timber (CLT) panels connected by L-shaped joints with/without an elastic layer are presented to illustrate this method. Wave subsystem energy and power transmission between subsystems are calculated for the coupled structures. The normalised energy responses of the coupled CLT panels are also calculated and compared with measurements. Good agreement between the predictions and the measurements is achieved.

Design of an Intelligent Energy Management System for Electric Vehicle Charging Station

In today’s world there are more outcomes in environmental change due to the overutilization of petroleum products in this manner prompting a genuine effect on the climate. So there is a need for a substitute answer for lessen the consumption of such non – sustainable assets. One such exertion made in the field of Freeways is the advancement of "Solar Freeways" which can be an elective arrangement. Sun oriented streets consolidate various arrangements in one – it can assist us with improving the creation of power utilizing sun based boards, to give a computerized stage to our future country's ventures like Smart Cities, and to work with the arising electric vehicles that supplant the petroleum driven vehicles and substantially more. Motivated by the fact that there are numerous amount of clean and sustainable energy we receive from roadways, the following study puts forward some of the event and application of an innovative charging method for the renewable energy driven electric cars, buses by using the roadway and also implementation of revolutionary nanotechnology along with the latest best in the house power electronics and power system analysis tools. A small scale prototype model was made by our team to attest the working of smart inductive charging process. Our project team was successful to improve the working of the model by improving the use of the preinstalled solar panels and also implement its use on the very concept we are trying to improve. On the vehicle, there will be the use of coils which are experimentally made for the flow of charges that are needed to provide charge to a moving electric vehicle (EV). The detailed strategy is presented in this report. Key Words: Environmental change, Overutilization of petroleum products, Solar Freeways, Renewable energy, Electric vehicles (EVs), Smart Cities, Nanotechnology

A new methodology of non-destructive testing in a set of two parallel immersed plates using time reversal process and leaky Lamb waves

Ultrasound has been identified as a suitable method for inspecting complex structures (such as nuclear reactors), as it can propagate through both liquids and steel elements to be inspected. Leaky Lamb waves have been extensively researched to detect damages in plate-shaped structures, which are waves that reemit bulk waves towards the surrounding fluid. An imaging method based on the time reversal of Lamb waves has been applied in preliminary work to detect the edge of a single immersed plate and a machined notch. In this study, the frequency-domain topological energy method is applied to a set of two parallel immersed plates to succeed in accurately localizing defects represented by the edges of the plates. Firstly, the behaviour of leaky Lamb waves is briefly addressed. A 2D-STFT (two-dimensional Short Time Fourier Transform) is then used to separate the different Lamb modes, which is a powerful tool for tracking the modes involved in the propagation over time. The Fast Topological Imaging Method (FTIM), which allows for faster computations with less data storage, is applied to the case of Lamb waves in a set of parallel plates. Lamb modes can be identified then selected to improve the analysis of the obtained images. An original methodology is proposed based on spots (maxima) analysis for interpreting the results of this topological energy and identifying the edges of the two plates. This process could be applied, in the same manner, to other scattering defects in ultrasound non-destructive testing of plates.

Investigating mechanical properties and bending behavior of an auxetic plate with 4-star unit cell

This study derives the constitutive relationships between stress resultants and strain measures for 4-star auxetic structures using force-moment analysis of a representative unit cell and the Castigliano strain energy method. To validate the accuracy of the constitutive model, bending analysis is performed for a 4-star auxetic rectangular plate under Levy boundary conditions. The analytical and numerical results show excellent agreement, confirming the validity of the constitutive relations extracted from the generic 4-star unit cell. This work establishes a theoretical framework for designing 4-star auxetic metamaterials and demonstrates their potential for diverse engineering applications.

Application of an alchemical free energy method for the prediction of thermostable DuraPETase variants

Non-equilibrium (NEQ) alchemical free energy calculations are an emerging tool for accurately predicting changes in protein folding free energy resulting from amino acid mutations. In this study, this method in combination with the Rosetta ddg monomer tool was applied to predict more thermostable variants of the polyethylene terephthalate (PET) degrading enzyme DuraPETase. The Rosetta ddg monomer tool efficiently enriched promising mutations prior to more accurate prediction by NEQ alchemical free energy calculations. The relative change in folding free energy of 96 single amino acid mutations was calculated by NEQ alchemical free energy calculation. Experimental validation of ten of the highest scoring variants identified two mutations (DuraPETaseS61M and DuraPETaseS223Y) that increased the melting temperature (Tm) of the enzyme by up to 1 °C. The calculated relative change in folding free energy showed an excellent correlation with experimentally determined Tm resulting in a Pearson’s correlation coefficient of r = − 0.84. Limitations in the prediction of strongly stabilizing mutations were, however, encountered and are discussed. Despite these challenges, this study demonstrates the practical applicability of NEQ alchemical free energy calculations in prospective enzyme engineering projects.Key points• Rosetta ddg monomer enriches stabilizing mutations in a library of DuraPETase variants• NEQ free energy calculations accurately predict changes in Tmof DuraPETase• The DuraPETase variants S223Y, S42M, and S61M have increased TmGraphical

A second-order fitted scheme combined with time two-grid technique for two-dimensional nonlinear time fractional telegraph equations involving initial singularity

In this paper, we derive the improved regularity for two-dimensional nonlinear time fractional telegraph equations by virtue of the technic of decomposition at first. Then, the famous L2-1σ formula is adopted to approximate the Caputo derivative and the central finite difference method is used for spatial discretization. The convergence accuracy of the proposed method is second order in both temporal and spatial direction. Meanwhile, for the sake of reducing the time of solving the high dimensional nonlinear problems, an efficient time two-grid algorithm is proposed. Furthermore, stability analysis of the proposed scheme is studied by the energy method. At last, numerical experiments are presented to verify the validity of the theoretical statements.

The Dissipative Bresse-Timoshenko System without a Second Spectrum is Well-Posedness and Exponential Stability

Aims: This paper investigates the dissipative Bresse-Timoshenko system without second spectrum. Study Design: Cross-sectional study.Place and Duration of Study: This paper was completed at the School of Mathematics and Statistics at Southwest University during from May 2023 to February 2024.Methodology: Using the theory of C0-semigroup.Results: The results show that the suitability of the system solution is established and the exponential stability is established.Conclusion: The C0-semigroup theory are applied to study the well-posedness and exponential stability, which is different from others, where the multiplying method and energy method were used to study the exponential stability. This result substantially improves earlier results in the literature.