Equivalent Energy Research Articles

A Grand Challenge Update: Geothermal Energy

_ This is the first of a series of six articles on SPE’s Grand Challenges in Energy, formulated as the output of a 2023 workshop held by the SPE Research and Development Technical Section in Austin, Texas. Described in a JPT article last year, each of the challenges will be discussed separately in this series: geothermal energy; improving recovery from tight/shale resources; net-zero operations; carbon capture, storage, and utilization; digital transformation; and education and advocacy. _ SPE identified five technical “Grand Challenges” in 2023 which, if successfully developed, could advance the interests of the SPE community in a net-zero world and help ensure our longevity and contributions to a prosperous future (Halsey et al. 2023). Access to the subsurface is a key skillset of the SPE community, including geology and geophysics, well construction and completion, reservoir engineering, production operations, and facilities. The challenges that geothermal faces to become a leading player in the net-zero world are well within the areas of expertise of the SPE community, ranging from rapid technology implementation and learning-by-doing to assure competitiveness, to establishing suitable funding mechanisms to secure access to capital. The increasing presence of geothermal-related sessions in SPE workshops and conferences shows the interest to explore novel methods to harness geothermal energy for power supply, thermal-use applications, and energy storage, illustrated by the threefold increase in OnePetro references since 2020 (Fig. 1). The Role of the Oil and Gas Industry Geothermal energy offers a path forward using business models that are well-suited to the oil and gas industry, which can apply its current technology and expertise to produce clean, reliable power and thermal energy at scale. Geothermal is also the only baseload renewable energy source that produces heat, presenting an avenue to mitigate the largest contribution humanity makes to carbon emissions: heating and cooling which account for 40% of all carbon emissions globally (Lund and Toth 2021). Table 1 presents some of the current applications. In 2023, the Energy Institute of The University of Texas at Austin released a comprehensive report, “The Future of Geothermal in Texas,” led by Project InnerSpace (Beard and Jones 2023). The report presented a challenge to leverage the technical capabilities and resources in the state. It estimated that “should the industry drill 15,000 geothermal wells each year for four years, it would provide the energy equivalent of all oil and gas used for electricity and heat production in the State today, including industrial heat.” This initiative is part of a broader movement in Texas, the spiritual home of the US fossil fuel industry, where a new geothermal energy ecosystem is emerging with veterans of the oil and gas business playing pivotal roles. Geothermal energy cannot only help to reduce the state’s emissions but also through its baseload and energy storage capabilities, it can support a power grid that has struggled to cope with severe weather events as demand has grown. Texas serves as a prime example of a location deeply tied to fossil fuels, where numerous oil and gas developers are announcing plans for geothermal expansion. This trend is not confined to Texas alone; similar developments are underway in other US states, Europe, the Middle East, and the Far East.

Cyclic behavior of carbon steel and austenitic stainless steel hollow laminated viscoelastomer-filled steel tube damper under unidirectional and bidirectional loadings

The hollow laminated viscoelastomer-filled steel tube damper (HLVSTD) is a metallic damper with stable working performance and excellent energy dissipation capability. It can exhibit equal mechanical performance in any single horizontal direction based on the geometric features of the circular shape. However, the impact of carbon steel tube material, stainless steel tube material and bidirectional loading on the mechanical behavior of HLVSTD remains unclear. The objective of this study is to analyze the mechanical performance of HLVSTD under bidirectional loading conditions using carbon steel tubes and austenitic stainless steel tubes, which are commonly utilized in China. Experimental tests were conducted using both unidirectional loading and bidirectional loading to comprehensively assess the performance. The results indicate that, under unidirectional and bidirectional loading, HLVSTDs made from both carbon steel and austenitic stainless steel tubes exhibit stable hysteresis curves. In comparison to the carbon steel tube HLVSTD, the counterpart with an austenitic stainless steel tube demonstrates higher equivalent stiffness, ultimate force, energy dissipation and low-cycle fatigue performance. Moreover, HLVSTDs under bidirectional loading exhibit a similar trend in mechanical performance compared to those under unidirectional loading. Regardless of whether the tube material is carbon steel or austenitic stainless steel, the cumulative displacement and cumulative energy under bidirectional loading were found to be twice as much as those observed under unidirectional loading, which demonstrates the excellent mechanical performance of HLVSTD under bidirectional loading.

Mechanical property of bolted-assembled reinforced concrete column-steel composite joints

Herein, a new type of bolted-assembled reinforced-concrete column-steel (RCS) beam composite joint is proposed by analysing the force and force transmission process of RCS beam composite joints. The practicality and uniqueness of the structure apply to beam–column joints in large shopping malls, mid- to high-rise office buildings, factories, garages and other building structures. By the finite-element software modelling, a numerical simulation is established and used to analyse the variation of stress and equivalent plastic deformation, hysteresis curve, skeleton curve, stiffness degradation and energy dissipation coefficient under monotonic displacement–load and cyclic displacement–load. Results elaborate that the RCS composite connection has good ductility under monotonic displacement–load. Besides, under the cyclic displacement–load capacity, the hysteresis curve is full, the stiffness degradation is not obvious and the ductility and energy dissipation are good. This study is expected to promote the engineering application and guide follow-up research of the new nodes.

Optimizing Nutrient and Energy Efficiency in a Direct-Seeded Rice Production System: A Northwestern Punjab Case Study

This study was carried out in Amritsar, Punjab, to find out how efficiently nutrients were used and how much energy was employed in direct-seeded rice (DSR) production. In this study, four levels of nitrogen (0, 40, 50, and 60 kg N ha−1) and three levels of phosphorus (0, 37.5, and 45 kg P2O5 ha−1) were tested. In a rice production system, the energy indices of various inputs and outputs were evaluated through the application of energy equivalency. The nutrient-use efficiencies in rice were assessed using different efficiency indices. The maximum grain yields of 38.9 q ha−1 and 36.9 q ha −1 were recorded at 50 kg N ha−1 and 45 kg P2O5 ha−1, respectively. On the other hand, application of nitrogen at 60 kg N ha−1 and phosphorus at 45 kg P2O5 ha−1 resulted in maximum straw yield of 57.1 q ha−1 and 51.1 q ha−1, respectively. In comparison with the control, application of 60 and 50 kg N ha−1 resulted in 161.9% and 151.0% higher grain yield, respectively. On the other hand, with applications of 45 kg P2O5 ha−1 and 37.5 kg P2O5 ha−1, an increase in the grain yield of 17.3 and 28.6%, respectively, over the control was recorded. Moving further towards nutrient-use efficiencies (NUEs), the highest values of partial factor productivity of nitrogen (PFPN), agronomic efficiency of nitrogen (AEN), partial nutrient balance of nitrogen (PNBN), and recovery efficiency of nitrogen (REN) were 89.1, 50.4, 1.78 and 0.72, respectively, which were obtained at 40 kg N ha−1, after which the values started decreasing steadily. In the case of phosphorus, the partial factor productivity (PFPP) of 88.6 was the maximum at 37.5 kg P2O5 ha−1, but partial nutrient balance (PNBP) of 0.36 and recovery efficiency (REP) of 0.08 were highest at 45 kg P2O5 ha−1. The main results revealed that the farmer field had an excessive amount of non-renewable energy inputs. The experimental field depicted greater energy-usage efficiency (EUE) of 4.5, energy productivity (EP) of 0.14, and energy profitability (EP1) of 3.5. These results were primarily ascribed to a significant drop in energy inputs under direct-seeded rice (DSR). In the case of non-renewable energy inputs, fertilizer made the maximum contribution to energy input (47.9%) in the farmer’s field. We conclude that nutrient-use efficiencies and energy-use efficiency were highest at 50 kg N and 45 kg P2O5 ha−1. This recommendation is beneficial for farmers because lower inputs and higher outputs are the main objective of every farmer.

Equivalent plate model of shape memory polymer composite based variable height corrugated structure

In this work, an equivalent plate model for a shape memory polymer composite based corrugation structure with varying height, for morphing application, is developed. A thermodynamically consistent constitutive relation based on temperature dependent phase transformation concept for shape memory polymer matrix is used in the composite model. The homogenization model is based on the equivalence of strain energy of a representative unit volume. Following validation, as an application, commonly used airfoil profile NACA 63210 was considered to demonstrate the model utility. Parametric studies have been undertaken to investigate the influence of corrugation parameters like thickness and number of corrugations.

Inverse dynamic design for motion control of soft machines driven by dielectric elastomer actuators

Dielectric elastomers (DEs) are a sort of electroactive polymers with large and fast responses, light masses and high energy densities. Hence, they are regarded as one of the most potential materials for artificial muscles and soft robots. Previous researches on DEs focused mainly on experimental prototypes and property optimization in a component level, while the system-level design and control of dynamic motions of DE actuators are still open problems. In this study, the computational method of inverse dynamic design (IDD) for input voltages of DE actuators is proposed by taking the electromechanical coupling mechanics and the effects of rigid-body motions into account. The proposed inverse dynamic design with nonlinear finite elements enables one to realize the high-precision modeling of soft actuators and to derive the dynamic voltages for desired trajectories in a system level. To describe the overall motions and deformations of DE actuators, the gradient constraints of the dynamic configurations of the actuators are introduced upon the assumption of time-varying uniform curvatures for the desired deformation. And then, based on the principle of energy equivalence, the dynamic voltages for the target deformations in motions are computed inversely from the Lagrange multipliers of the desired trajectories. In addition, the forward simulations by removing the constraints and applying the voltages are further conducted to validate and predict the final configurations. Finally, five numerical case studies and demonstrative experiments are presented to validate the effectiveness of the proposed method. This study endeavors to establish a universal inverse dynamic design method for the motion control of soft DE actuators, allowing for the application of theoretical methodology to engineering problems.

Anaerobic biodegradation of brown grease and its potential as a source of renewable energy

The purpose of the study was twofold. The first was to study the anaerobic digestibility and the biochemical methane potential (BMP) of brown grease (BG)–fats and oils collected from restaurants and similar food production facilities. The second objective was to investigate the effects of adding dry, food waste derived hydrochar to enhance the digestion process, specifically as a possible in situ agent to improve biogas quality. The BMP tests involved various BG loadings between 3 and 30 g BG/L. The results indicate that BG is highly digestible under anaerobic conditions with 354 mL CH4/g COD equivalent of BG at 1 atm and 35°C testing conditions, which translates into 28 million gasoline gallon equivalent (GGE) potential energy that could be recovered by anaerobically digesting or co-digesting BG. The particular hydrochar investigated in this study did not show any potential to increase biogas CH4 content.

Extracorporeal Shockwave Therapy (ESWT), a Novel Method for Transferring Oral Implant Primary Failures to Final Clinical Success: A Test Case Report Followed up over More than 6 Years.

To evaluate the feasibility of reversing a primary failure through therapeutic mechanical stimulation induced by transcutaneous application of acoustic waves (ESWT) in the peri-implant tissues. Materials and Μethods: This clinical report evaluates the outcome of a new protocol proposed to treat a primary failure (loosened oral implant); application of three cycles of ESWT, once session per week for 3 consecutive weeks, with an equivalent positive energy of 0,18 mJ/mm² (therapeutic dose: 2000 impulses/ 8Hz/ 4.0 bar). Standardized intraoral radiographs, Cone Beam Computed Tomography (CBCT), Implant Stability Quotient (ISQ) and clinical evaluations were performed. It was possible to verify a progressive increase in the ISQ value after the ESWT protocol; 17 (initial), 46 (after two months) and 68 (after four months), which led to successful implant prosthetic rehabilitation (35 N/cm measured). Our evaluation at 6 years of follow-up confirms that the new bone-implant interface is preserved and ESWT as a safe non-invasive treatment. In the context of the new dynamic model of osseointegration, the Foreign Body Equilibrium (FBE), this represents the first report of a host-Implant equilibrium re-established after an early failure process. However, it is necessary to perform studies to determine both the medical device and the most effective therapeutic range for clinical applications of this technology in oral implantology.

Modeling for Hysteresis Contact Behavior of Bolted Joint Interfaces with Memory Effect Penalty Constitution

A novel penalty contact constitution was developed to replicate the hysteresis memory effect observed in contact interfaces. On this basis, a refined finite element analysis (FEA) was performed to study the stick–slip friction contact behavior of bolted joint interfaces. The analysis was validated by comparing it with the experimental hysteresis loops in the literature. The simulated hysteresis loops were subsequently used to identify four parameters of the Iwan model. Additionally, the effects of bolt clamping, friction coefficient, and excitation amplitude were individually examined. It was found that the deterioration in bolt clamping performance resulted in a decrease in both the equivalent joint stiffness and energy dissipation. Similarly, the reduction in the friction coefficient yielded a comparable impact. Furthermore, the identified model parameters of critical stick–slip force and displacement exhibited a quasi-linear relationship to the bolt preload and friction coefficient.

Post-exercise energy expenditure of half squat and bench press at different load percentages and controlled cadence

The aim of this study was to analyze the effect of movement velocity and intensity on EPOC fast component in bench press and half squat exercises performed to concentric failure. Twelve healthy recreational bodybuilders performed 10 days of experimental procedures: the 1st and 2nd days were to load determination (1RM test and re-test), the 3rd to 10th days performing the bench press and half squat exercises with 60 and 80% 1RM performed in slow (1s/1s) and high (2s/2s) movement velocity cadence 52 beats. Oxygen consumptionas continuously measured in the first 20-min post-exercise using Cosmed K4 b2 portable device. A multivariate analysis compared the EPOC averaged in each minute post-exercise according to the different exercises, intensities and movement velocities. Was observed that EPOC declines fast from the 1st to 2nd minute and attains almost 100% of the decline near resting VO2 values at the 3rd minute of recovery both exercises. Greatest EPOC accumulated, during the eight minutes, was to exercise that involved the largest muscle group (half squat) with high intensity (80% 1RM) and greater movement velocity (1s/1s). In the full 20-min interval, the half squat had an energy equivalent of almost 80% more compared with the bench press. The higher velocities enhance energy expenditure to a greater extent than a more fatiguing slower exercise.

EVALUATING THE INTEGRATION OF ADVANCED IT SOLUTIONS FOR EMISSION REDUCTION IN THE OIL AND GAS SECTOR

The oil and gas sector is a significant contributor to greenhouse gas emissions, making the integration of advanced IT solutions imperative for emission reduction. This study evaluates the effectiveness of integrating advanced IT solutions in mitigating emissions within the oil and gas industry. The research employs a mixed-methods approach, combining qualitative analysis through literature review and quantitative analysis via case studies and data analysis. The literature review identifies various advanced IT solutions currently available, such as Internet of Things (IoT), Artificial Intelligence (AI), and Big Data analytics, and their potential applications for emission reduction in the oil and gas sector. Case studies are conducted to examine real-world implementations of these solutions by leading companies in the industry. These case studies provide insights into the challenges, benefits, and best practices associated with integrating advanced IT solutions for emission reduction. Furthermore, quantitative data analysis is conducted to assess the environmental impact of these IT solutions based on emission reduction metrics, such as carbon dioxide equivalent (CO2e) emissions and energy efficiency improvements. The findings indicate that the integration of advanced IT solutions holds significant promise for emission reduction in the oil and gas sector. IoT-enabled sensors enable real-time monitoring and optimization of operations, reducing emissions from production processes. AI algorithms enhance predictive maintenance, optimizing equipment performance and minimizing emissions from fugitive sources. Big Data analytics facilitate comprehensive emissions tracking and reporting, enabling proactive emissions management strategies. Overall, this research contributes to a deeper understanding of the potential of advanced IT solutions in reducing emissions in the oil and gas sector and provides valuable insights for industry practitioners, policymakers, and researchers alike.
 Keywords: IT, Emission, Reduction, Oil and Gas, Review.

Mechanics of inner core debonding of composite sandwich beam with CFRP hexagonal honeycomb

The inner core debonding of composite sandwich beams with carbon fiber reinforced polymer (CFRP) hexagonal honeycomb core is investigated theoretically and experimentally. Based on the principle of minimum potential energy, a theoretical model is established to reveal the core debonding mechanism with Timoshenko’s beam theory and Extended High-Order Sandwich Panel Theory (EHSAPT) for composite face sheets and CFRP hexagonal honeycomb core, respectively. The theoretical approach of core debonding simulation is based on the framework of the cohesive zone model (CZM). By constructing the constitutive relation of the core interface as the discontinuous stress and displacement boundary conditions, the vertical core debonding can be simulated overcoming the singularity of equilibrium equations. The crack propagation process is decomposed into three stages with the consideration of the double crack propagation mechanism. In experiments, the regular and reinforced hexagonal honeycomb sandwich beams are designed and fabricated, and the quantification of the defect degree of the core bonding interface is achieved by equivalent energy release rate obtained from the homogenized hexagonal honeycomb. The double cantilever beam (DCB) experiments are performed to determine the equivalent energy release rate and reveal the core debonding mechanism of CFRP hexagonal honeycomb sandwich beams. Comparing the load–displacement curves and debonding deformation patterns indicates that the established theoretical model can effectively predict the core debonding mechanical response. Finally, parametric analysis is carried out to discuss the impact of structural dimension parameters, defect location and defect degree on the debonding modes of CFRP hexagonal honeycomb sandwich beams.

New Physics – The Negation of Einstein’s Theories of Relativity

From ontological considerations alone, a new revolutionary quantum dynamical-materialist dialectical (Quantum Dialectics or QD) perspective of space-time-matter-motion achieves a new quantitative mass-energy-velocity relation for any ponderable fundamental particles. This new relation, based on the quantum uncertainty principle, gives the mass m of any free fundamental particle at its origin, in terms of the inverse cube of its velocity v. This quantitative relation is different and is a negation of the one derived from mechanical-metaphysical (Classical Mechanics or CM) approach since Isaac Newton and its relativistic post-quantum formulation of Albert Einstein. This new mass-energy-velocity relation is in conformity with known knowledge and is appropriately substantiated by the recent reports that “high-energy photons of gamma radiation from a distant galaxy arrived at Earth four minutes after lower-energy photons, although they were apparently emitted at the same time”; and another saying that “the time delays of gamma-ray photons are inversely proportional to their energy”. These findings would contradict Einstein's theory of relativity, which says that all photons (particles of light) must move at the same speed c. QD considers matter-antimatter particle pairs in their elementary virtual forms and kinetic motion as an eternal quantum dynamical process of existence and non-existence (Being-Nothing) arising from abstract space and abstract time in a contradiction to each other. The virtual particles can transition to real particles through quantum tunnelling or when equivalent energy becomes available. Any existence in this view is a contradiction; vulnerable to change, motion, evolution, development etc. The aggregation of the elementary particles and their motions mediated by chance and necessity, give rise to the phenomenology of this infinite, eternal and ever-changing universe. The CM approach on the contrary is based on epistemology and considers that matter (ordinary + light) and motion have an esoteric origin from the mystery of the single act of creation by God; of a finite universe in the finite past; where the premise of conservation laws and “ex nihilo nihil fit” prevail. In its relativistic version, this approach makes a fundamental difference between ponderable matter and light and in fact question the existence of particulate matter. Two axiomatic assumptions, one by Newton of one-sided universal gravitational attraction and the other by Einstein that the velocity of light c is an absolute and universal constant has brought in unphysical objects and phenomena into scientific discourse leading to century-long confusion and scholastic debates among the physicists; with no end in sight!

Adaptive Equivalent Factor-Based Energy Management Strategy for Plug-In Hybrid Electric Buses Considering Passenger Load Variations

Energy management strategies (EMSs) are one of the key technologies for the development of plug-in hybrid electric buses (PHEBs). This paper addresses the issue of optimal energy distribution for PHEBs under significant variations in passenger load at different bus stations, which cannot be solved by a single equivalent factor equivalent fuel consumption minimization energy management strategy (ECMS). An adaptive equivalent factor equivalent fuel consumption minimization energy management strategy (A-ECMS) considering passenger load is proposed. First, the powertrain system of the PHEB is modeled, and the accuracy of the model is verified in a simulation environment. Then, the reference SOC descent trajectory of the battery is obtained using a dynamic programming (DP) algorithm, the recursive least squares (RLS) method is employed to identify the passenger load, and the influence of different loads on the state of charge (SOC) trajectory under a single equivalent factor is analyzed. Finally, a genetic algorithm (GA) is used to establish the correspondence between passenger load, bus station, and equivalent factor, enabling the actual SOC to follow the reference SOC descent trajectory, thereby achieving optimal energy distribution. Simulation results demonstrate that the A-ECMS reduces fuel consumption of the PHEB per 100 km by 2.59% and 10.10% compared to the ECMS and rule-based EMS, respectively, validating the effectiveness of the proposed strategy.

A non-metal single atom nanozyme for cutting off the energy and reducing power of tumors.

Enzymes are considered safe and effective therapeutic tools for various diseases. With the increasing integration of biomedicine and nanotechnology, artificial nanozymes offer advanced controllability and functionality in medical design. However, several notable gaps, such as catalytic diversity, specificity and biosafety, still exist between nanozymes and their native counterparts. Here we report a non-metal single-selenium (Se)-atom nanozyme (SeSAE), which exhibits potent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mimetic activity. This novel single atom nanozyme provides a safe alternative to conventional metal-based catalysts and effectively cuts off the cellular energy and reduction equivalents through its distinctive catalytic function in tumors. In this study, we have demonstrated the substantial efficacy of SeSAE as an antitumor nanomedicine across diverse mouse models without discernible systemic adverse effects. The mechanism of the NADPH oxidase-like activity of the non-metal SeSAE was rationalized by density functional theory calculations. Furthermore, comprehensive elucidation of the biological functions, cell death pathways, and metabolic remodeling effects of the nanozyme was conducted, aiming to provide valuable insights into the development of single atom nanozymes with clinical translation potential.

A non‐metal single atom nanozyme for cutting off the energy and reducing power of tumors

AbstractEnzymes are considered safe and effective therapeutic tools for various diseases. With the increasing integration of biomedicine and nanotechnology, artificial nanozymes offer advanced controllability and functionality in medical design. However, several notable gaps, such as catalytic diversity, specificity and biosafety, still exist between nanozymes and their native counterparts. Here we report a non‐metal single‐selenium (Se)‐atom nanozyme (SeSAE), which exhibits potent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase‐mimetic activity. This novel single atom nanozyme provides a safe alternative to conventional metal‐based catalysts and effectively cuts off the cellular energy and reduction equivalents through its distinctive catalytic function in tumors. In this study, we have demonstrated the substantial efficacy of SeSAE as an antitumor nanomedicine across diverse mouse models without discernible systemic adverse effects. The mechanism of the NADPH oxidase‐like activity of the non‐metal SeSAE was rationalized by density functional theory calculations. Furthermore, comprehensive elucidation of the biological functions, cell death pathways, and metabolic remodeling effects of the nanozyme was conducted, aiming to provide valuable insights into the development of single atom nanozymes with clinical translation potential.

The contemporaneous phase of GRB afterglows – application to GRB 221009A

ABSTRACT The TeV observations of GRB 221009A provided us with a unique opportunity to analyse the contemporaneous phase in which both prompt and afterglow emissions are seen simultaneously. To describe this initial phase of gamma-ray burst afterglows, we suggest a model for a blast wave with an intermittent energy supply. We treat the blast wave as a two-element structure. The central engine supplies energy to the inner part (shocked ejecta material) via the reverse shock. As the shocked ejecta material expands, its internal energy is transferred to the shocked external matter. We take into account the inertia of the shocked external material so that the pressure difference across this region determines the derivative of the blast wave’s Lorentz factor. Applied to GRB 221009A, the model yields a very good fit to the observations of the entire TeV light curve except for three regions where there are excesses in the data with respect to the model. Those are well correlated with the three largest episodes of the prompt activity and thus, we interpret them as the reverse shock emission. Our best-fitting solution for GRB 221009A is an extremely narrow jet with an opening angle θj ≈ 0.07° (500/Γ0) propagating into a wind-like external medium. This extremely narrow angle is consistent with the huge isotropic equivalent energy of this burst, and its inverse jet break explains the very rapid rise of the afterglow. Such inverse jet break occurs in an accelerating blast wave when the relativistic beaming becomes narrower than the jet’s opening angle. Interestingly, photon–photon annihilation does not play a decisive role in the best-fitting model.

Equivalent Minimum Hydrogen Consumption of Fuzzy Control-Based Fuel Cells: Exploration of Energy Management Strategies for Ships

Aiming to solve the problems of insufficient dynamic responses, the large loss of energy storage life of a single power cell, and the large fluctuation in DC (direct current) bus voltage in fuel cell vessels, this study takes a certain type of fuel cell ferry as the research object and proposes an improved equivalent minimum hydrogen consumption energy management strategy, based on fuzzy logic control. First, a hybrid power system including a fuel cell, a lithium–iron–phosphate battery, and a supercapacitor is proposed, with the simulation of the power system of the modified mother ship. Second, a power system simulation model and a double-closed-loop PI (proportion integration) control model are established in MATLAB/Simulink to design the equivalent hydrogen consumption model and fuzzy logic control strategy. The simulation results show that, under the premise of meeting the load requirements, the control strategy designed in this paper improves the Li-ion battery’s power, the Li-ion battery’s SOC (state of charge), the bus voltage stability, and the equivalent hydrogen consumption significantly, compared with those before optimization, which improves the stability and economy of the power system and has certain practical engineering value.

Study on fracture characteristics and mechanisms of red sandstone under high-voltage pulse discharge

To investigate the influences of geometrical size and discharge voltage of the pulse discharge equipment on the fracture characteristics and mechanisms of sandstone under high-voltage pulses, a series of experiments was conducted using a high-voltage pulse discharge device on sandstone circular disc specimens of sandstone with a thickness of 10 mm. These experiments covered a range of disc diameters ranging from 50 mm to 142 mm and discharge voltages from 15 kV to 40 kV. Through these experiments, the fracture characteristics of sandstone at both macroscopic and microscopic levels were investigated. In the experiments, a quantitative analysis of surface fracture was undertaken based on fracture density and fractal damage. Additionally, using the principle of energy equivalence, numerical simulation methods were used to study the damage evolution process in sandstone. The research results indicate that the formation and distribution of fractures in the sandstone specimens are significantly affected by geometrical size and discharge voltage. By analyzing the interaction between stress waves and fracture propagation, combined with indoor experimental results, the fracture mechanism was revealed. The high temperature and shock wave generated by the plasma channel leads to the crushing zone near the electrode, while the circumferential tensile component of the stress wave can result in radial fractures, and the reflected tensile wave leads to circumferential and radial fractures near the boundary.

Transient thermal stress analysis of a thin rotating FGM blade based on the exact shear correction factor: a comparison of ROM and LRVE homogenization models

This work is an attempt to develop a simple and accurate finite element formulation based on first-order shear deformation theory (FSDT) for the transient thermal stress analysis of a pre-twisted and tapered thin rotating functionally graded material (FGM) blade, induced due to the thermal shock. The neutral surface of the FGM blade is taken as the reference plane and the exact shear correction factor is obtained from the equivalent energy principle. The temperature-dependent material property at a point in the thickness direction is estimated according to the rule of mixture (ROM) and the Local representative volume elements (LRVE) homogenization model. A finite element formulation using FSDT in conjunction with the eight-noded isoparametric element, taking five degrees of freedom is developed. The top layer of the thin FGM blade is subjected to a thermal shock and the bottom layer is kept at the ambient temperature. The governing equation for the present formulation is obtained using Hamilton’s principle. The accuracy of the present finite element formulation is established by comparing the results with the benchmark results. The parametric studies are conducted to investigate the effect of the angle of twist, variable chord and span, rotational speed, and accurate shear correction factor on the transient thermal stresses due to the thermal shock. Notably, there can be significant differences in the transient thermal stresses calculated by the two homogenization models viz., ROM and LRVE. Also, it is important to consider the exact shear correction factor in the formulation.