Energy Method Research Articles

Investigation of amyl acetate sorption impact on high‐density polyethylene bottle properties

AbstractThermoplastics based on polyolefins, including polypropylene, high‐density polyethylene and low‐density polyethylene, are extensively utilized across various packaging sectors. The selection of these materials for specific applications is influenced by multiple factors, such as the polymer's absorption characteristics and the impact on its mechanical properties when in contact with the packaged product. This study presents an experimental methodology designed to simulate the effects of absorption on the macroscopic and microscopic properties of high‐density polyethylene bottles in contact with amyl acetate. Macroscopic degradation was evaluated by modeling mechanical damage using unified theory and the energy method. Analytical techniques such as gravimetric analysis, scanning electron microscopy and Fourier transform infrared spectrometry were employed. The findings of this research provide valuable insights for suppliers and industries to experimentally determine the usability and safety intervals of plastic packaging through comprehensive macroscopic and microscopic analyses within relatively short timescales. © 2024 Society of Chemical Industry.

Exploring the Dynamic Interplay of Deleterious Variants on the RAF1-RAP1A Binding in Cancer: Conformational Analysis, Binding Free Energy, and Essential Dynamics.

The RAF1-RAP1A interaction activates the MAPK/ERK pathway which is very crucial in the carcinogenesis process. This protein complex influences tumor formation, proliferation, and metastasis. Understanding aberrant interactions driven by clinical mutations is vital for targeted therapies. Hence, the current study focuses on the screening of clinically reported substitutions in the RAF1 and RAP1A genes using predictive algorithms integrated with all-atoms simulation, essential dynamics, and binding free energy methods. Survival analysis results revealed a strong association between RAF1 and RAP1A expression levels and diminished survival rates in cancer patients across different cancer types. Integrated machine learning algorithms showed that among the 134 mutations reported for these 2 proteins, only 13 and 35 were classified as deleterious mutations in RAF1 and RAP1P, respectively. Moreover, one mutation in RAF1 reported elevated levels of binding between RAF1 and RAP1P while in RAP1A, 7 mutations were reported to increase the binding affinity. The high-binding mutations, P34Q and V60F, were subjected to protein-protein coupling which confirmed the increase in the binding affinity. Wild-type and mutant RAF1-RAP1P bound complexes were subjected to molecular simulation investigation, revealing enhanced structural stability, increased compactness, and stabilized residue fluctuations of the mutant systems in contrast to the wild-type. In addition, hydrogen bonding analysis revealed a variation in the binding paradigm which further underscores the impact of these substitutions on the coupling of RAF1 and RAP1A. Principal component analysis (PCA) and free energy landscape (FEL) evaluation further determined dynamical variations in the wild-type and mutant complexes. Finally, the Gibbs free energy for each complex was estimated and found to be -71.94 ± 0.38 kcal/mol for the wild-type, -95.57 ± 0.37 kcal/mol for the V60F, and -85.76 ± 0.72 kcal/mol for P34Q complex. These findings confirm the effect of these variants on increasing the binding affinity of RAF1 to RAP1P. These mutations can therefore be targeted for cancer therapy to modulate the activity of the MAPK/ERK signaling pathway.

PRODUÇÃO DE BIODIESEL E CARVÃO ATIVADO A PARTIR DA BORRA DE CAFÉ

The research seeks a new sustainable use for the compounds that would be discarded incorrectly. Due to the chemical characteristics of coffee grounds making possible a transformation of the grounds into biodiesel, the research focused on effective and sustainable ways to accomplish this, with the highest possible utilization of the compounds. For this, the extraction of coffee oil present in the grounds was carried out by means of a reflux distillation, with the use of a Soxhlet extractor. Subsequently, a transesterification reaction of this oil obtained from the coffee was performed with the intention of converting it into biodiesel. In addition, from the remainder of the coffee grounds left from the biodiesel extraction, activated carbon was obtained through carbonization, followed by activation. The results proved satisfactory and open perspective to propose solutions to various environmental and social problems, among them the development of a renewable energy method, so that fossil energies are replaced by more effective and sustainable methods, through compounds that would be incorrectly discarded. Besides using the activated carbon to solve other problems, such as water purification in environments that do not have basic sanitation.

Failure criterion and damage evolution of high-strength geopolymer concrete under compression-shear composite loading after high temperatures

Geopolymer concrete (GPC) holds significant potential for building fire safety design due to its green, low-carbon, and high-temperature resistant properties. In practical applications, concrete structures often face multiaxial composite loads. Therefore, investigating the composite stress performance of high-strength geopolymer concrete (HGPC) after exposure to high temperatures is crucial for assessing structural damage and enhancing fire prevention measures. This paper examines the compressive shear performance of HGPC at various temperatures T (20°C, 200°C, 400°C, 600°C) and stress ratios k (0.15, 0.3, 0.45, 0.6). The study analyzes failure patterns, shear load-displacement curves, shear strengths and their components, and peak shear deformation. Failure criteria are proposed to describe the damage patterns of HGPC under compressive shear loading after high temperatures. Additionally, the damage evolution process is evaluated using the energy method. The results show that HGPC damage surfaces penetrate the coarse aggregate at room temperature under compression-shear composite loading but shift to the aggregate-mortar interface at 600°C. Shear stiffness, peak shear strength, and residual strength increase with higher stress ratios but decrease with rising temperatures. Temperature affects peak shear strength by over 95 %, significantly more than the stress ratio. The shear strength decreases more slowly than compressive strength up to 400°C but more rapidly beyond 400°C. The cohesive strength of HGPC decreases with increasing stress ratio under different temperatures, while contact friction strength exceeds 50 % of peak shear strength. Shear dilation strength generally increases, then decreases, peaking at k = 0.45. The failure criterion based on the modified twin shear unified strength theory aligns best with experimental results. Furthermore, an increased stress ratio retarded the development of damage evolution, which was first accelerated and then slowed with rising temperature.

Effect of Fines Content on Cyclic Strength Development of Sand–Clay Mixtures under Cyclic Loading: A Process Evaluation Using Energy Methods

Effect of Fines Content on Cyclic Strength Development of Sand–Clay Mixtures under Cyclic Loading: A Process Evaluation Using Energy Methods

Research progress on topology and energy management of fuel cell hybrid power ships

Abstract With the increasing awareness of environmental protection, the maritime industry is moving towards green and low-carbon development. Fuel cells, due to their pollution-free and high-efficiency characteristics, are one of the key technologies driving the green transformation of traditional ships. However, fuel cells have relatively soft output characteristics and often require other energy storage components to provide supplementary power. This paper reviews the types, advantages, and disadvantages of the topologies of fuel cell hybrid power ships, analyses the current development status of energy management goals and methods, and finally provides an outlook on the development of fuel cell hybrid power ships.

Short-Circuit Impedance Analysis of HTS Traction Transformer With Flux Diverters Using Magnetic Energy Method

Short-Circuit Impedance Analysis of HTS Traction Transformer With Flux Diverters Using Magnetic Energy Method

The inverse problem of identifying complex hyperbolic equation source terms in electromagnetic propagation

Abstract This article investigates the inverse problem of determining the source term of the hyperbolic equation for electromagnetic propagation using terminal data. This study is an important method for identifying propagation sources in electromagnetics. Unlike wave equations, the complexity of the underlying equations can make theoretical analysis quite difficult. Firstly, the uniqueness of the inverse problem was proved using the energy method. Then, based on the optimal control framework, the inverse problem was transformed into an optimal control problem, and the existence of the optimal solution and its necessary conditions were established. Secondly, the global uniqueness and stability of the optimal solution have been proven, which is a completely new conclusion. This has laid a solid theoretical foundation for numerical algorithms. Finally, it is proposed to apply the Landweber iteration method and conjugate gradient method to this problem, and some numerical examples are provided to demonstrate the effectiveness and convergence speed of these two algorithms.

Fatigue Life Prediction of 2024-T3 Al Alloy by Integrating Particle Swarm Optimization—Extreme Gradient Boosting and Physical Model

The multi-parameter characteristics of the physical model pose a challenge to the fatigue life prediction of 2024-T3 aluminum (Al) alloy. In response to this issue, a parameter-solving method that integrates particle swarm optimization (PSO) with extreme gradient boosting (XGBoost) is proposed in this study. The fatigue performance and failure mechanism of the 2024-T3 Al alloy are analyzed. Furthermore, the fatigue life prediction physical model of the 2024-T3 Al alloy is established by using the energy method of fracture mechanics. The physical model incorporates critical physical parameters. Meanwhile, the PSO algorithm optimizes the hyperparameters of the XGBoost model based on fatigue data of the 2024-T3 Al alloy. Eventually, the optimized XGBoost model is used to solve the parameters of the physical model. Furthermore, the analytical equation of the fatigue life prediction model is obtained. This paper provides a new method for solving the parameters of the fatigue life prediction model, which reduces the error and cost of obtaining the model parameters in the experiment and shortens the time required.

Robust optimization bidding strategy for user-side resource-side participation in the market distribution of electrical energy and peaking ancillary services considering risk expectations and opportunity constraints

Compared to traditional resources, user-side resources are of various types and have more significant uncertainty about their regulatory capacity, leading to difficulties in coordinating decisions about their simultaneous participation in the electric energy and peaking ancillary services markets. This paper proposes a joint bidding decision-making method for the day-ahead electricity energy and peak shaving auxiliary service market based on distributed robust opportunity constraints, which addresses the problem of difficulty in using an accurate probability density distribution to represent the uncertainty process of user-side resources. Firstly, a data-driven method for characterizing the uncertainty of load regulation capacity is investigated, and fuzzy sets are constructed without assuming specific probability distributions of random variables. Then, to minimize the risk expectation of the joint bidding cost on the customer side, a bidding strategy that considers the uncertainty is proposed. Finally, an example simulation verifies the reasonableness and effectiveness of the proposed joint bidding method, and the results show that the constructed model overcomes the problem of over-conservatism of the robust model, and the computational adaptability is better than that of the stochastic model, which achieves a better balance between robustness and economy.

Learning from different perspectives for regret reduction in reinforcement learning: A free energy approach

Reinforcement learning (RL) is the core method for interactive learning in living and artificial creatures. Nevertheless, in contrast to humans and animals, artificial RL agents are very slow in learning and suffer from the curse of dimensionality. This is partially due to using RL in isolation; i.e. lack of social learning and social diversity. We introduce a free energy-based social RL for learning novel tasks. Society is formed by the learning agent and some diverse virtual ones. That diversity is in their perception while all agents use the same interaction samples for learning and share the same action set. Individual difference in perception is mostly the cause of perceptual aliasing however, it can result in virtual agents’ faster learning in early trials. Our free energy method provides a knowledge integration method for the main agent to benefit from that diversity to reduce its regret. It rests upon Thompson sampling policy and behavioral policy of main and virtual agents. Therefore, it is applicable to a variety of tasks, discrete or continuous state space, model-free, and model-based tasks as well as to different reinforcement learning methods. Through a set of experiments, we show that this general framework highly improves learning speed and is clearly superior to previous existing methods. We also provide convergence proof.

Comparative assessment of physics-based in silico methods to calculate relative solubilities.

Relative solubilities, i.e. whether a given molecule is more soluble in one solvent compared to others, is a critical parameter for pharmaceutical and agricultural formulation development and chemical synthesis, material science, and environmental chemistry. In silico predictions of this crucial variable can help reducing experiments, waste of solvents and synthesis optimization. In this study, we evaluate the performance of different physics-based methods for predicting relative solubilities. Our assessment involves quantum mechanics-based COSMO-RS and molecular dynamics-based free energy methods using OPLS4, the open-source OpenFF Sage, and GAFF force fields, spanning over 200 solvent-solute combinations. Our investigation highlights the important role of compound multimerization, an effect which must be accounted for to obtain accurate relative solubility predictions. The performance landscape of these methods is varied, with significant differences in precision depending on both the method used and the solute considered, thereby offering an improved understanding of the predictive power of physics-based methods in chemical research.

Are Triboelectric Nanogenerators More Efficient Than Piezoelectric Transducers in Generating Energy from Precipitation?

This review examines two primary methods for harvesting energy from precipitation: triboelectric nanogenerators (TENGs) and piezoelectric transducers, which are leading technologies in converting mechanical energy from rain into electrical energy. The comparison between TENGs and piezoelectric transducers focuses on their operational mechanisms, material characteristics, and environmental factors such as water pH and temperature. The review highlights that TENGs offer greater design flexibility, efficiency in low-intensity rain, and cost-effectiveness, while piezoelectric transducers excel in high-frequency environments. The development of hybrid systems combining both technologies presents a more efficient and sustainable solution for rain energy harvesting.

Exponential Stability of a Kirchhoff Plate Equation with Structural Damping and Internal Time Delay

In this manuscript, we investigate the exponential stability of a Kirchhoff plate equation with free boundary conditions in a bounded domain of R2. First, we consider the case where the model is subjected only to structural damping and, using the energy method, we prove the exponential decay of the energy associated with this model. Second, we consider the case where structural damping with a linear internal time delay term is applied, and we use the same technique to derive the exponential stability of the new model. Finally, we examine the scenario where the model is governed by structural damping with an added fractional time delay term and, by constructing an appropriate Lyapunov function, we show that the energy associated with the system is exponentially stable. This work improves upon prior results concerning the Kirchhoff plate equation with frictional damping, where exponential stability could not be achieved.

Optimal decay of the Boltzmann equation

The Boltzmann equation is a typical example of partially dissipative equations, where the linearized collision operator is positive definite with respect to the microscopic part and the dissipation of the hydrodynamic part is discovered from the coupling structure between the transport operator and the linearized collision operator. Guo and Wang (Comm. Partial Differential Equations, 37, 2012) developed a general energy method for proving the optimal time decay rates of the solution to such type of equations in the whole space; however, the decay rate of the highest order spatial derivatives of the solution is not optimal. In this paper, by incorporating the high‐low frequency decomposition in the energy estimates, both linearly and nonlinearly, we prove the optimal decay rates of any high order spatial derivatives of the low frequency part of the solution to the Boltzmann equation and the almost exponential decay rate of the high frequency part, which imply in particular the optimal decay rate of the highest order spatial derivatives of the solution. Moreover, the velocity‐weighted assumption of the initial data required in Guo and Wang (Comm. Partial Differential Equations, 37, 2012) is removed by capturing the time‐weighted dissipation estimates via the time‐weighted energy method. The method can be applied to the compressible Navier–Stokes equations and many partially dissipative equations in kinetic theory and fluid dynamics.

Stability of planar diffusion wave for three‐dimensional bipolar Euler–Poisson system with time‐dependent over‐damping

This paper is concerned with the asymptotic behavior of the solution to the Cauchy problem for the three‐dimensional bipolar Euler–Poisson system with time‐dependent over‐damping. We prove that the Cauchy problem admits a unique global‐in‐time smooth solution that tends to the planar diffusion wave as time goes to infinity provided that the initial perturbation is sufficiently small. Moreover, we also obtain the convergence rate of the solution toward the planar diffusion wave. The proof is completed by the time‐weighted energy method.

High‐Gain Boost Converter Based Energy Harvesting Method for the Ultra‐Low Voltage Difference of HVDC Transmission Line

ABSTRACTOnline monitoring sensors are crucial for ensuring the long‐term stable operation of high‐voltage direct current (HVDC) transmission systems. However, ensuring a sustainable and reliable energy supply for these sensors in the HVDC transmission line is extremely challenging. Energy harvesting is an efficient solution to meet the energy supply needs of self‐powered online monitoring sensors. This work proposes a novel method for harvesting energy from the ultra‐low voltage difference of HVDC transmission line using a high‐gain boost converter. Firstly, the structure of the energy harvesting system is proposed. Then, the mechanism by which the gain of the boost converter is easily affected by parasitic parameters of the circuit and device under ultra‐low input voltage is analyzed. A method for automatically stabilizing the output voltage of the boost converter using a post‐stage energy management circuit is proposed. This method avoids the use of closed‐loop control circuits, which would otherwise increase losses. Finally, the boost converter with high gain is designed to elevate the ultra‐low voltage difference to a higher voltage, providing sufficient power for the online monitoring sensors. The effectiveness of the proposed method has been verified through simulations and experiments, demonstrating that the energy harvesting system can extract energy from a voltage difference as low as 35 mV. Additionally, the system can produce a stable output power of up to 128 mW when the voltage difference is 100 mV.

On type I blowup of some nonlinear heat equations with a potential

In this paper, we are concerned with the following initial-boundary value problem{ut=Δu+Q(|x|)|u|p−1u,x∈BR,t>0u(x,t)=0,x∈∂BR,t>0u(x,0)=u0(x),x∈BR, where p≥ps:=N+2N−2, u0∈L∞(BR), and Q(r)∈C1([0,R]), 0<C_≤Q(r)≤C‾<∞,Q′(r)≤0. We extend the asymptotic behavior results, which is well-known when Q is constant according to Matano-Merle (cf. [25]), for the blow-up solutions. More precisely, we show that when ps≤p<p⁎, the blowup of radial solution to this problem is always of Type I. This result partially generalizes the conclusions in [25] for Q≡1. This extension is nontrivial due to the appearance of Q. The quasi-monotonicity formula established by the third author and Cheng in [8] allows us to use an energy method to get a priori estimates on the rescaled solutions. The contraction mapping principle shows the existence of singular stationary solutions to an associated elliptic equation with a potential. In the end, the properties of zero number for solutions lead to the nonexistence of type II singularity for the problem.

ON WELL-POSED BOUNDARY CONDITIONS AND ENERGY STABLE FINITE-VOLUME METHOD FOR THE LINEAR SHALLOW WATER WAVE EQUATION

Abstract We derive and analyse well-posed boundary conditions for the linear shallow water wave equation. The analysis is based on the energy method and it identifies the number, location and form of the boundary conditions so that the initial boundary value problem is well-posed. A finite-volume method is developed based on the summation-by-parts framework with the boundary conditions implemented weakly using penalties. Stability is proven by deriving a discrete energy estimate analogous to the continuous estimate. The continuous and discrete analysis covers all flow regimes. Numerical experiments are presented verifying the analysis.

A temperature rise calculation model of wind turbine gearbox gear considering crack fault and tooth number difference

AbstractThe crack fault of gear is usually accompanied by temperature rise. Therefore, to master the temperature characteristics of the cracked gear of the wind turbine gearbox, a temperature rise calculation model of wind turbine gearbox gear considering crack fault and tooth number difference is proposed. Firstly, the time‐varying meshing stiffness model of the cracked gear considering the tooth number difference is established based on the potential energy method. Secondly, the calculation method of the meshing surface normal load of the cracked gear is deduced. Thirdly, the temperature rise calculation model of the meshing surface of the cracked gear is constructed based on Blok flash temperature theory. Finally, the data of the high‐speed gear of a wind turbine gearbox in northern China is selected for simulation verification. By comparing with the finite element method, the effectiveness of the proposed method is verified. The simulation results reveal the gear temperature characteristics of the wind turbine gearbox with different crack ratios. The research can provide some theoretical support for the accurate fault diagnosis and maintenance of wind turbine gearbox, and can also be applied to the fault diagnosis of gear cracks in other mechanical structures with a large transmission ratio.