Fast Energy Research Articles

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.

Layer stacked polyimide with great built-in electronic field for fast lithium-ion storage based on strong p-p stacking effect

Polyimide has been regarded as a potential organic cathode for lithium-ion batteries (LIBs) due to its excellent solvent resistance, thermodynamic stability and flexibly programmable polymer structure. However, the poor conductivity, easy entanglement and agglomeration of PI chains lead to slow ion diffusion, poor electron transfer, and insufficient reaction, which make it difficult to effectively exert its theoretical capacity at high current density. Herein, a layer stacked polyimide cathode (NT-U) based on π-π stacking effect was successfully obtained. NT-U possesses a large molecular dipole moment that induced by the strong electronegative groups in PI and further enhanced by the π-π stacking structure, which contributes to the formation of a robust built-in electric field (BIEF). The strong BIEF in this highly crystalline PI plays a critical role in accelerating the charge transport dynamics and improving electrochemical performances of LIBs, as verified by in-situ XRD, ex-situ FTIR, ex-situ XPS, and ex-suit SEM, DFT calculations. These findings provide new insights into the construction of PIs cathode based on the mechanism of dipole and BIEF for fast and efficient energy storage.

Design and performance evaluation of a compact thermal and fast neutron spectrometer

Measurement of the space neutron radiation environment has put forward new requirements for the miniaturization and lightweight design of neutron spectrometers. In this paper, a compact broad-spectrum neutron spectrometer was designed, in which the fast neutron detector was based on the EJ-254 scintillator-coupled with SiPMs array, and the thermal and epithermal neutron detectors were based on the NaI(Tl + Li) (NaIL) scintillator coupled with SiPMs array encapsulated in Al and Cd shells, respectively. The overall weight of the neutron spectrometer was only 2.4 kg, and its dimensions were 154 mm × 123 mm × 115 mm. The fast neutron energy spectrum was obtained based on the capture-gated method and the Maximum Likelihood Expectation Maximization (MLEM) unfolding algorithm; the counts of thermal and epithermal neutrons were obtained based on the optimized frequency-domain Pulse Shape Discrimination (PSD) method and cadmium difference method. The proposed neutron spectrometer with all applied methods was tested as a whole system with a252Cf and a241Am–Be source. The spectrum result was compared to an ISO standard source. The accuracy of fast part of 0.5–10 MeV was 5.9% in definition of Relative Root Mean Squared Error (RRMSE). The thermal and epithermal neutron counts were far higher than standard spectrum, and we proved it being effected by laboratory introduced neutron scattering through a simulation, thus the thermal and epithermal flux measurements was believed to be decent. The Figure of Merit (FoM) of the NaIL's PSD neutron gamma discrimination were 2.57 and 2.90 respectively.

Hybrid Biomass Fast Pyrolysis Process and Solar Thermochemical Energy Storage System, Investigation and Process Development

Hybrid Biomass Fast Pyrolysis Process and Solar Thermochemical Energy Storage System, Investigation and Process Development

Tuning methods for multigap drift tube linacs.

Multigap cavities are used extensively in linear accelerators to achieve velocities up to a few percent of the speed of light, driving nuclear physics research around the world. Unlike for single-gap structures, there is no closed-form expression to calculate the output beam parameters from the cavity voltage and phase. To overcome this, we propose to use a method based on the integration of the first and second moments of the beam distribution through the axially symmetric time-dependent fields of the cavity. A beam-based calibration between the model's electric field scaling and the machine's rf amplitudes is presented, yielding a fast online energy change method, returning cavity amplitude and phase necessary for a desired output beam energy and energy spread. The method is validated with 23Na6+ beam energy measurements.

Anisotropic temperatures in multi-layered 2D materials

For multi-layered 2D materials, although its c-axis has a much lower thermal conductivity than the a-axis, its phonon mean free path has been confirmed to be very long, e.g., in the order of 100s nm at room temperature for multi-layered graphene. An anisotropic specific heat concept has been proposed in the past to explain this very long mean free path. This work carries out detailed atomistic modeling to quantify the anisotropic specific heat concept and reports the discovery of anisotropic temperatures in multi-layered 2D materials under ultrafast surface heating. Extremely fast c-phonon energy transport is discovered, and the non-Fourier effect is observed for both a-phonons and c-phonons. The energy coupling factor between these two modes of phonons is determined to be in the order of 1016 W K−1 m−3, with the specific number depending on the structure location. The anisotropic temperature concept is also quantitatively confirmed based on the lattice Boltzmann method simulation. The anisotropic temperature concept does not violate the physics that temperature is a scalar; rather, it is developed to distinguish the temperatures of phonons that travel in different directions. This concept is universally applicable to other 2D materials to describe the heat conduction in the in-plane and out-of-plane directions that feature different interatomic bonds.

Calculation And Uncertainty Analysis of Core Parameters of ALMANAR Reactor Using New Nuclear Data Libraries

Abstract A small modular lead-cooled fast spectrum core concept called ALMANAR designed to produce 45 MWth power for 22 years operating without refuelling was proposed in a previous study. The neutronics investigation showed its excellent inherent safety features. It could be considered as a candidate for future electricity source for the near future. It is noteworthy that the target accuracy for eigenvalue calculation for keff regardless of spectrum is set to 300 pcm. However, findings in this analysis revealed that the keff uncertainty was larger for the recently released nuclear data libraries (about 800 pcm), mostly from 235U capture cross section (624 pcm) in the case of ENDF/B-VIII.0 and 238U inelastic scattering cross section (437 pcm) in the case of JENDL-5. Selected kinetic parameters of the ALMANAR core and their uncertainty were also evaluated and analysed. No major impact on the total ßeff, leffeff and λeff simulation results was found. In order to improve the reliability of criticality calculations of the lead-cooled small fast reactor, the accuracy of capture and fission cross section of 235,238U, the capture cross section of 10B and the elastic scattering cross section of 208Pb at the fast energy range of ENDF/B-VIII.0 should be improved. Furthermore, the inelastic scattering and capture cross section of 238U, fission and capture cross section of 235U and the capture cross section of 10B of JENDL-5 should also be improved.

Preliminary study on the application of fluorescence intensity ratio method in fast neutron energy measurement

Preliminary study on the application of fluorescence intensity ratio method in fast neutron energy measurement

Rainforest transformation reallocates energy from green to brown food webs

Terrestrial animal biodiversity is increasingly being lost because of land-use change1,2. However, functional and energetic consequences aboveground and belowground and across trophic levels in megadiverse tropical ecosystems remain largely unknown. To fill this gap, we assessed changes in energy fluxes across ‘green’ aboveground (canopy arthropods and birds) and ‘brown’ belowground (soil arthropods and earthworms) animal food webs in tropical rainforests and plantations in Sumatra, Indonesia. Our results showed that most of the energy in rainforests is channelled to the belowground animal food web. Oil palm and rubber plantations had similar or, in the case of rubber agroforest, higher total animal energy fluxes compared to rainforest but the key energetic nodes were distinctly different: in rainforest more than 90% of the total animal energy flux was channelled by arthropods in soil and canopy, whereas in plantations more than 50% of the energy was allocated to annelids (earthworms). Land-use change led to a consistent decline in multitrophic energy flux aboveground, whereas belowground food webs responded with reduced energy flux to higher trophic levels, down to −90%, and with shifts from slow (fungal) to fast (bacterial) energy channels and from faeces production towards consumption of soil organic matter. This coincides with previously reported soil carbon stock depletion3. Here we show that well-documented animal biodiversity declines with tropical land-use change4–6 are associated with vast energetic and functional restructuring in food webs across aboveground and belowground ecosystem compartments.

The Non-Thermal Radio Emissions of the Solar Transition Region and the Proposal of an Observational Regime

The transition region is a very thin but most peculiar layer in the solar atmosphere located between the solar chromosphere and the corona. It is a key region for understanding coronal heating, solar eruption triggers, and the origin of solar winds. Here, almost all physical parameters (density, temperature, and magnetic fields) have the maximum gradient. Therefore, this region should be highly dynamic, including fast energy releasing and transporting, plasma heating, and particle accelerating. The physical processes can be categorized into two classes: thermal and non-thermal processes. Thermal processes can be observed at ultraviolet (UV) and extreme ultraviolet (EUV) wavelengths via multi-wavelength images. Non-thermal processes accelerate non-thermal electrons and produce radio emissions via the gyrosynchrotron mechanism resulting from the interaction between the non-thermal electrons and magnetic fields. The frequency range spans from several GHz to beyond 100 GHz, in great number of bursts with narrowband, millisecond lifetime, rapid frequency drifting rates, and being referred to as transition region small-scale microwave bursts (TR-SMBs). This work proposes a new type of Solar Ultra-wide Broadband Millimeter-wave Spectrometer (SUBMS) that can be used to observe TR-SMBs. From SUBMS observations, we can derive rich dynamic information about the transition region, such as information about non-thermal energy release and propagation, the flows of plasma and energetic particles, the magnetic fields and their variations, the generation and transportation of various waves, and the formation and evolution of the source regions of solar eruptions. Such an instrument can actually detect the non-thermal signals in the transition region during no flare as well as the eruptive high-energy processes during solar flares.

An improved equalization circuit with bidirectional CUK converter for series-connected battery strings

This paper proposed an improved equalization circuit based on a bidirectional CUK converter. Compared with traditional bus equalization circuits based on CUK converter, it owns a simpler structure with fewer inductors, resulting in a smaller volume and higher energy density of the proposed equalization circuit. The operation principle and steady-state characteristic of the equalizer are analysed. The equalizer is applied to the energy balance of the series-connected battery strings, and the balance principle is designed. The proposed equalization system achieves a fast energy balance of the battery pack. Simulation results verify the effectiveness of the designed equalization circuit and balance strategy.

Fast-charging graphite anode for lithium-ion batteries: Fundamentals, strategies, and outlooks

The basic requirements for lithium-ion batteries in the field of electric vehicles are fast charging and high energy density. This will enhance the competitiveness of electric vehicles in the market while reducing greenhouse gas emissions and effectively preventing environmental pollution. However, the current lithium-ion batteries using graphite anodes cannot achieve the goal of fast charging without compromising electrochemical performance and safety issue. This article analyzes the mechanism of graphite materials for fast-charging lithium-ion batteries from the aspects of battery structure, charge transfer, and mass transport, aiming to fundamentally understand the failure mechanisms of batteries during fast charging. In addition, we review and discuss recent advances in strategies for optimizing fast-charging performance and summarize current improvement methods in graphite electrodes, electrolytes, battery structures, and charging algorithms. Moreover, the challenges and promising concepts for developing future fast-charging graphite anode are emphasized. This review is of great significance for better designing and optimizing graphite materials for high-safety and fast-charging lithium-ion batteries.

Self-templated formation of hierarchically porous TiO2 hollow microspheres with fast lithium-uptake performance

Hollow TiO2 microspheres composed of low-dimensional anisotropic building blocks (such as nanowires or nanosheets) possess a hierarchical porosity and thus favor mass/Li+ transfer. However, developing an easy-control method to synthesize this type of TiO2 is still a challenge. Herein, an aerosol-assisted self-assembly method is developed to construct the nanowire-assembled TiO2 hollow microspheres (NW-TOHMS). The nanowire-intertangle configuration results in forming large surface area (∼207 m2 g−1) and hierarchical porosity with a broad pore-size distribution from 2 to 100 nm. Moreover, finite element analysis suggests that nanowire-constructed open meso-/macro-pores benefit the Li+-transport/storage kinetics. As a consequence, the NW-TOHMS electrode exhibits a high specific capacity of 117 mA h g−1 at 5 A g−1 after 1000 cycles. Excitingly, the activated carbon/NW-TOHMS Li-ion capacitors demonstrate an energy density as high as 37 Wh kg−1 at the maximum power density of 6.1 kW kg−1. This work offers a new pathway for the synthesis of mesoporous TiO2 hollow superstructures used to fast energy storage and conversion.

A data-driven framework for fast building energy demand estimation across future climate conditions

Abstract The rapid and precise forecasting of building energy requirements plays a crucial role in decision-making processes for architects during the early design phase. This study introduces a data-driven framework capable of projecting energy demands in the context of evolving climate conditions. We evaluated four widely-used machine learning algorithms. Our results indicated that a hybrid approach, integrating Catboost and Bayesian optimization, excelled in both accuracy and efficiency for predicting building energy demand under climate change conditions. The framework proposed herein has potential applications in fostering sustainability in early-stage architectural design.

Effects of co‐fermentation of high‐yield ester Zygosaccharomyces rouxii and Saccharomyces cerevisiae on the quality of rice wine

AbstractBackgroundAt present, rice wine has the characteristics of fast fermentation, energy saving, and simple production due to the addition of commercial Saccharomyces cerevisiae. However, this kind of fermented rice wine has the disadvantages of single flavor and weak taste. To address this concern, the combination of Saccharomyces cerevisiae and non‐Saccharomyces yeast has been identified as an effective approach to enhance the quality of fermented rice wine. This research aims to further enhance the ethyl ester and higher alcohol components of rice wine by utilizing the co‐fermentation method of high‐yield ester Zygosaccharomyces rouxii and Saccharomyces cerevisiae, thereby increasing the aroma complexity of rice wine.ResultsAccording to the fermentation performance and gas chromatography–mass spectrometry (GC–MS) analysis, it was found that S. cerevisiae GJM and Z. rouxii SC01 have a strong metabolic ability for glucose and sucrose. Furthermore, the crucial alcohols such as isobutanol, isoamyl alcohol, and phenylethyl alcohol increased by 85%, 29%, and 138%, respectively, when compared to single S. cerevisiae GJM. Additionally, the ethyl acetate and phenylethylene acetate were increased by 1.35 and 1.45 times, respectively, when compared to single S. cerevisiae GJM. These findings were comparable with the results of sensory evaluation and electronic nose analysis, where the fruit flavor score and the content of mellow substances were found to be higher.ConclusionThese findings suggest that the co‐fermentation of S. cerevisiae and high‐yield ester Z. rouxii has the potential to enhance the quality and diversity of aroma in liquid rice wine.

Phase smoothing for diffractive deep neural networks

Optical neural networks have shown promising advantages over its electronic counterpart due to fast computational speed, high throughput, and low energy consumption. For the deep neural networks mimicked by the cascaded phase masks, the conventional training algorithm results in abruptly varying phase profiles. In this work, we show that even two kinds of diffraction formulas give completely different results for the identical rough phase masks, which denotes that the training process harvests the inaccuracy of the used diffraction modeling, which prevents the results from being replicated when the diffraction is formularized by other numerical methods or implemented in the real world. The modeling inaccuracy of each phase mask accumulates to prevent the successful optical implementation. In this work, we propose a two-step training framework to enforce smooth phase masks, and thus reduce the mismatch between numerical modeling and practical deployment.

Feasibility study of multiple-energy Bragg peak proton FLASH on a superconducting gantry with large momentum acceptance.

While the Bragg peak proton beam (BP) is capable of superior target conformity and organs-at-risk sparing than the transmission proton beam (TB), its efficacy in FLASH-RT is hindered by both a slow energy switching process and the beam current. A universal range shifter (URS) can pull back the high-energy proton beam while preserving the beam current. Meanwhile, a superconducting gantry with large momentum acceptance (LMA-SC gantry) enables fast energy switching. This study explores the feasibility of multiple-energy BP FLASH-RT on the LMA-SC gantry. A simultaneous dose and spot map optimization algorithm was developed for BP FLASH-RT treatment planning to improve the dose delivery efficiency. The URS was designed to be 0-27cm thick, with 1cm per step. BP plans using the URS were optimized using single-field optimization (SFO) and multiple-field optimization (MFO) for ten prostate cancer patients and ten lung cancer patients. The plan delivery parameters, dose, and dose rate metrics of BP plans were compared to those of TB plans using the parameters of the LMA-SC gantry. Compared to TB plans, BP plans significantly reduced MUs by 42.7% (P<0.001) with SFO and 33.3% (P<0.001) with MFO for prostate cases. For lung cases, the reduction in MUs was 56.8% (P<0.001) with SFO and 36.4% (P<0.001) with MFO. BP plans also outperformed TB plans by reducing mean normal tissue doses. BP-SFO plans achieved a reduction of 56.7% (P<0.001) for prostate cases and 57.7% (P<0.001) for lung cases, while BP-MFO plans achieved a reduction of 54.2% (P<0.001) for the prostate case and 40.0% (P<0.001) for lung cases. For both TB and BP plans, normal tissues in prostate and lung cases received 100.0% FLASH dose rate coverage(>40Gy/s). By utilizing the URS and the LMA-SC gantry, it is possible to perform multiple-energy BP FLASH-RT, resulting in better normal tissue sparing, as compared to TB plans.

TRU utilization and MA transmutation in thorium-based fluorinated molten salt fast reactor

In this paper, a thorium-based fluorinated molten salt fast neutron reactor is taken as the research object, and the utilization of thorium resources, reuse of transuranic waste (TRU), and transmutation of minor actinide (MA) in fast reactor are the research purpose. The fast reactor adopts a multi-layer core structure, in which the fuel is divided into an inner fission fuel zone and an outer breeding fuel layer, respectively loaded with fluorinated molten salts LiF+ThF4+XF4 (where X is 233U, TRU, or 233U+MA) and LiF+ThF4. In addition to serving as nuclear fuel, these two molten salts also act as coolants in the primary circuits.Through the cross sections of nuclear reactions, transmutation chain of actinide nuclides, and the particle population density formula of actinide nuclides in nuclear reaction equilibrium, the possible nuclear reactions of actinide nuclides in thorium-based fast reactors are analyzed. The calculated results show that the thorium-based fast reactor has the following characteristics: fast neutron energy spectrum, negative temperature reactivity coefficient, effective utilization of thorium resources, the ability to breed fissle fuel such as 233U, production of high-purity radioisotope 238Pu material, and the ability to incinerate Pu and MAs in the TRU spent fuel.In the 233U fuel scheme, the 233U fuel is breeded, breeding ratio of fissile fuels is 1.21, the reaction products contain very little Np, and almost no Pu, Am, and Cm long-lived radionuclides. In the TRU fuel scheme, the annual capacity to incinerate MAs and Pu is 1072.6 kg, while producing a large amount of 233U and 233Pa fuel (together 1162.5 kg/year).In the 233U+2.0 wt% TRU-MAs fuel scheme, 127.35 kg of MA waste can be incinerated annually, and their transmutation rate is 15.95%, which is equivalent to the annual production of MA nuclear waste from 4.9 conventional 1000 MWe light water reactors. Here, TRU-MAs is the mixtured MA fuels after separation of Pu from the TRU fuel. At the same time, radioactive fuel 238Pu, which can be used for space nuclear power, is produced with an annual yield of 87.89 kg and an isotopic abundance of 87.57%. If the added TRU-MAs fuel is replaced with 2.0 wt% 237Np fluorinated salt, the annual yield and isotope abundance of 238Pu are further increased to 130.24 kg and 95.4%.

Fast and Generic Energy Flow Analysis of the Integrated Electric Power and Heating Networks

Energy flow analysis is a fundamental tool to determine the network states of the integrated energy systems (IES). For the widely deployed IES with coupled power grids (PG) and heating networks (HN), we still lack a generic tool that can be easily employed to calculate the quasi-dynamic energy flows of it. In this paper, we have developed a generic code package (named as MATHN) for energy flow analysis of the quality-regulated HN. After that, a generic solution framework that leverages MATPOWER and MATHN to realize decomposed energy flow calculation of PG and HN is proposed. Behind the MATHN tool, a model reformulation technique is proposed to eliminate the massive indirect variables of the basic HN model discretized by finite difference, which finally derives a compact matrix formulation (similar to the network equation of power grid: I=YU) for generic description of any HN and also slashes the original model scale by around 20 times. Moreover, the solution strategy behind the MATHN tool further converts this matrix formulation into a standard system of non-homogeneous linear equations, with which some existing well-recognized algorithms can be directly applied for efficient and accurate solution. Case studies on three different scales of test systems demonstrate the generality, efficiency and accuracy of our methods. All the codes and input data are packaged into the MATHN tool and are made open-source for non-commercial use.

Optimization of switching charge and recoverable energy density mediated by structural transformation in Sr-substituted BaNiO3 perovskites.

Because of their distinctive characteristics, ferroelectric perovskites are considered among the most potent and auspicious candidates for energy storage and pulsed power devices. But their energy storage properties and switching capabilities need to be further enhanced which can be done by substitutions of appropriate cations. Hence, a series of lead-free Ba1-xSrxNiO3 (x = 0.00, 0.33, 0.67, and 1.00) ceramics was fabricated using a sol-gel auto combustion technique. Rietveld's refinement of X-ray diffraction plots verified the complete development of the required hexagonal perovskite structure. Scanning electron microscopy images revealed a gradual increase in average grain sizes and agglomeration with the increase in Sr-content. Moreover, the existence of all the constituent elements exactly in proportion to their stoichiometric ratios was verified by energy dispersive X-ray spectroscopy. The characteristic parameters of ferroelectric materials such as ferroelectric response, electrical conductivity, and switching charge density were also determined. The P-E loops indicated that with the increase in Sr-content, the coercive field, remanent polarization, and maximum polarization all decreased gradually, but the recoverable energy density (Wrec) increased as the loops became slimmer. The maximum value of Wrec was found in the Ba0.33Sr0.67NiO3 sample. Moreover, SrNiO3 exhibited minimum energy loss with the highest efficiency of ∼47.21%. The existence of a current barrier in all the samples was proved from the low leakage current values (∼10-7 A). In addition, the pure SrNiO3 showed a low electrical conductivity and minimum value of switching charge density. All these findings make SrNiO3 a promising candidate for fast switching and energy storage applications.