Topological study about failure behavior and energy absorption of honeycomb structures under various strain rates

High-speed impact threats and terrorist actions on the battlefield require the development of more effective protective materials and structures,and various protective structure is designed according their energy-absorbing characteristics.In this research,the deformation behavior,microscopic failure modes and energy absorption characteristics of re-entrant hexagonal structure,regular hexagonal structure and regular quadrilateral structure are studied under different strain rates impact.The re-entrant hexagonal structure forms a“X”-shaped deformation zone,the regular quadrilateral and regular hexagonal structure form an“I”-shaped deformation zone.The microscopic appearance of the section is a mixed fracture form.The effects of the topological shape,cell angle,and cell height on the impact behavior of the structure were evaluated.When the cell height is fixed and the cell angle is changed,the energy absorption of the structure increase and then decrease as the relative density increase.The mechanical properties of the structure are optimal when the relative density is about 18.6%and the cell angle is22.5°.When the cell angle is fixed and the cell height is changed,as the relative density increases,the energy absorption of the structure gradually increases.The regular quadrilateral structure and the reentrant hexagonal structure experienced clear strain rate effects under dynamic impact conditions;the regular hexagonal structure did not exhibit obvious strain rate effects.The results presented herein provide a basis for further rational design and selection of shock-resistant protective structures that perform well in high-speed impact environments.

Hybrid Network Model Based on Data Enhancement for Short-term Power Prediction of New PV Plants

This study proposes a hybrid network model based on data enhancement to address the problem of low accuracy in photovoltaic(PV)power prediction that arises due to insuffi cient data samples for new PV plants.First,a time-series gener ative adversarial network(TimeGAN)is used to learn the distri bution law of the original PV data samples and the temporal correlations between their features,and these are then used to generate new samples to enhance the training set.Subsequently,a hybrid network model that fuses bi-directional long-short term memory(BiLSTM)network with attention mechanism(AM)in the framework of deep&cross network(DCN)is con structed to effectively extract deep information from the origi nal features while enhancing the impact of important informa tion on the prediction results.Finally,the hyperparameters in the hybrid network model are optimized using the whale optimi zation algorithm(WOA),which prevents the network model from falling into a local optimum and gives the best prediction results.The simulation results show that after data enhance ment by TimeGAN,the hybrid prediction model proposed in this paper can effectively improve the accuracy of short-term PV power prediction and has wide applicability.

Effects of coal-fired power plants on soil microbial diversity and community structures

Long-term deposition of atmospheric pollutants emitted from coal combustion and their effects on the eco-environment have been extensively studied around coal-fired power plants.However,the effects of coal-fired power plants on soil microbial communities have received little attention through atmospheric pollutant deposition and coal-stacking.Here,we collected the samples of power plant soils(PS),coal-stacking soils(CSS)and agricultural soils(AS)around three coal-fired power plants and background control soils(BG)in Huainan,a typical mineral resource-based city in East China,and investigated the microbial diversity and community structures through a high-throughput sequencing technique.Coal-stacking significantly increased(p<0.05)the contents of total carbon,total nitrogen,total sulfur and Mo in the soils,whereas the deposition of atmospheric pollutants enhanced the levels of V,Cu,Zn and Pb.Proteobacteria,Actinobacteria,Thaumarchaeota,Thermoplasmata,Ascomycota and Basidiomycota were the dominant taxa in all soils.The bacterial community showed significant differences(p<0.05)among PS,CSS,AS and BG,whereas archaeal and fungal communities showed significant differences(p<0.01)according to soil samples around three coal-fired power plants.The predominant environmental variables affecting soil bacterial,archaeal and fungal communities were Mo-TN-TS,Cu-V-Mo,and organic matter(OM)-Mo,respectively.Certain soil microbial genera were closely related to multiple key factors associated with stacking coal and heavy metal deposition from power plants.This study provided useful insight into better understanding of the relationships between soil microbial communities and long-term disturbances from coal-fired power plants.

Novel polybenzimidazole/graphitic carbon nitride nanosheets composite membrane for the application of acid-alkaline amphoteric water electrolysis

It is a great challenge to develop membrane materials with high performance and long durability for acidalkaline amphoteric water electrolysis.Hence,the graphitic carbon nitride(g-C_(3)N_(4))nanosheets were compounded with the(2,2'-m-phenylene)-5,5'-benzimidazole(m-PBI)matrix for the preparation of m-PBI/g-C_(3)N_(4) composite membranes.The synthesis of g-C_(3)N_(4) nanosheets and m-PBI matrix have been confirmed by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscoy(TEM)and ^(1)H nuclear magnetic resonance spectra(^(1)H NMR),respectively.The fourier transform infrared spectroscopy(FT-IR)and SEM of the composite membranes showed the g-C_(3)N_(4) nanosheets were well dispersed in the m-PBI/g-C_(3)N_(4) composite membrane.The mechanical properties test exhibited the good mechanical strength,and the TGA curves of m-PBI showed the high thermal stability of composite membranes.Besides,the m-PBI/g-C_(3)N_(4) composite membrane showed excellent proton and hydroxide ion conductivity,which was higher than pure m-PBI and Nafion 115 membrane.The acid-alkaline amphoteric water electrolysis test showed m-PBI/1%g-C_(3)N_(4) composite membrane has the best performance with a current density of 800 mA cm^(-2) at cell voltage of 1.98 V at 20℃.It showed that m-PBI/g-C_(3)N_(4) composite membrane has a good application prospect for acid-alkaline amphoteric water electrolysis.

Non-destructive Testing Method for Crack Based on Diamond Nitrogen-vacancy Color Center

Magnetic field measurement plays an extremely important role in material science,electronic en-gineering,power system and even industrial fields.In particular,magnetic field measurement provides a safe and reliable tool for industrial non-destructive testing.The sensitivity of magnetic field measurement deter-mines the highest level of detection.The diamond nitrogen-vacancy(NV)color center is a new type of quan-tum sensor developed in recent years.The external magnetic field will cause Zeeman splitting of the ground state energy level of the diamond NV color center.Optical detection magnetic resonance(ODMR),using a mi-crowave source and a lock-in amplifier to detect the resonant frequency of the NV color center,and finally the change of the resonant frequency can accurately calculate the size of the external magnetic field and the sensi-tivity of the external magnetic field change.In the experiment,a diamond containing a high concentration of NV color centers is coupled with an optical fiber to realize the preparation of a magnetic field scanning probe.Then,the surface cracks of the magnetized iron plate weld are scanned,and the scanning results are drawn into a two-dimensional magnetic force distribution map,according to the magnetic field gradient change of the magnetic force distribution map,the position and size of the crack can be judged very accurately,which pro-vides a very effective diagnostic tool for industrial safety.

An Emerging Testing Method for Metallics Based on NV Center in the Diamond

Metal substance detection plays an extremely important role in daily life,industrial manufacturing and even industrial security.The traditional methods include optical detection,X-ray detection,microwave detection and ultrasonic detection.These methods,playing a vital role in the field of non-destructive testing,can not only judge the presence or absence of metal,but also accurately detect the type and size of metal defects.For microwave detection,the detection efficiency of metal materials is limited by the response sensitivity of the detector to microwaves.In recent years,scientists have discovered a quantum sensing system based on the diamond nitrogen-vacancy(NV)color center.The system obtains optical detection magnetic resonance(ODMR)fluorescence spectra under the combined action of a 532nm laser and a certain frequency band of microwaves,and the signal contrast changes significantly with the microwave power.Based on the NV color center quantum sensing system,this paper studies its application in the field of metal detection,and takes steel detection as an example to detect the size of steel bars according to the changes in the spectral line,providing a new method for non-destructive testing such as metal substance detection.

High-rate CH_(4)-to-C_(2)H_(6) photoconversion enabled by Au/ZnO porous nanosheets under oxygen-free system

Photocatalytic CH_(4) coupling into high-valued C_(2)H_(6) is highly attractive,whereas the photosynthetic rate,especially under oxygen-free system,is still unsatisfying.Here,we designed the negatively charged metal supported on metal oxide nanosheets to activate the inert C-H bond in CH_(4)and hence accelerate CH_(4) coupling performance.As an example,the synthetic Au/ZnO porous nanosheets exhibit the C_(2)H_(6) photosynthetic rate of 1,121.6μmol g^(-1)_(cat)h^(-1)and the CH_(4) conversion rate of 2,374.6μmol g^(-1)_(cat)h^(-1) under oxygen-free system,2 orders of magnitude higher than those of previously reported photocatalysts.By virtue of several in situ spectroscopic techniques,it is established that the generated Au^(δ-)and O^-species together polarized the C-H bond,while the Au^(δ-)and O^-species jointly stabilized the CH_(3) intermediates,which favored the coupling of CH_(3) intermediate to photosynthesize C_(2)H_(6) instead of overoxidation into CO_(x).Thus,the design of dual active species is beneficial for achieving high-efficient CH_(4)-to-C_(2)H_(6) photoconversion.

High-safety and high-voltage lithium metal batteries enabled by nonflammable diluted highly concentrated electrolyte

Lithium metal batteries(LMBs)show great promise for achieving energy densities over 400 Wh·kg^(-1).However,highly flammable organic electrolytes are a long-lasting problem that triggers safety hazards and hinders the commercial application of LMBs.Here,a nonflammable diluted highly concentrated electrolyte(DHCE)with ethoxy(pentafluoro)cyclotriphosphazene(PFPN)as a diluent is developed to simultaneously achieve high safety and cycling stability of high-voltage LMBs.The optimal DHCE not only ensures reversible Li deposition/dissolution behavior with a superior average Coulombic efficiency(CE)over 99.1%on lithium metal anode(LMA),but also suppresses side reactions and stress crack on the LiCoO_(2)(LCO)under high cut-off voltage.The newly developed DHCE exhibits high thermal stability,showing complete nonflammability and reduced heat generation between the electrolyte and delithiated LCO/cycled LMA.This work offers an opportunity for rational designing nonflammable electrolytes toward high-voltage and safe LMBs.

Regulated reaction pathway of CO_(2)photoreduction into CH_(4)by metal atom pair sites

The carbon dioxide(CO_(2))reduction process involves complex protonation,making the resulting product often unpredictable.To achieve the desired product,it is crucial to manipulate the reaction steps.Herein,we build the metal atom pair sites for selective CO_(2)photoreduction into methane.As a prototype,Ni atom pair sites loaded on the Mo S_(2)nanosheets were synthesized and verified by highresolution transmission electron microscopy(HRTEM),X-ray photoelectron spectroscopy(XPS)and X-rayabsorption near edge structure spectra(XANES).In-situ Fourier transform infrared spectroscopy(FTIR)monitors the*CHO group,a crucial intermediate in CH_(4)production,during CO_(2)photoreduction on the Ni-Mo S_(2)nanosheets,whereas this monitoring is not observed for the Mo S_(2)nanosheets.Also,theoretical calculations disclose that over the Ni-Mo S_(2)nanosheet slab,the formation energy of*CHO intermediates is determined to be lower(0.585 e V)than the desorption energy of*CO intermediates for CO production(0.64 e V),implying the higher selectivity of CH_(4)production.

Picotesla fiberized diamond-based AC magnetometer

Portable quantum sensors are crucial for developing practical quantum sensing and metrology applications.Fiberized nitrogen-vacancy(NV)centers in diamonds have emerged as one of the most promising candidates for compact quantum sensors.Nevertheless,due to the difficulty of coherently controlling the ensemble spin and noise suppression in a large volume,it often faces problems such as reduced sensitivity and narrowed bandwidth in integrated lensless applications.Here,we propose a fluorescence signal treatment method for NV spin ensemble manipulation by the exponential fitting of spin polarization processes,instead of integrating the photon emission.This enables spin state readout with a high signal-to-noise ratio and applies to the pulse sensing protocols for large-volume NV spins.Based on this,we further developed a fiberized diamond-based AC magnetometer.With an XY8-N dynamical decoupling pulse sequence,we demonstrated a T_(2)-limited sensitivity of 8pT/√Hz and T_(1)-limited frequency resolution of 90 Hz over a wide frequency band from 100 kHz to 3 MHz.This integrated diamond sensor leverages quantum coherence to achieve enhanced sensitivity in detecting AC magnetic fields,making it suitable for implementation in a compact and portable endoscopic sensor.

Calculation Model and Allocation Strategy of Network Usage Charge for Peer-to-peer and Community-based Energy Transaction Market

The emergence of prosumers in distribution systems has enabled competitive electricity markets to transition from traditional hierarchical structures to more decentralized models such as peer-to-peer(P2P)and community-based(CB)energy transaction markets.However,the network usage charge(NUC)that prosumers pay to the electric power utility for network services is not adjusted to suit these energy transactions,which causes a reduction in revenue streams of the utility.In this study,we propose an NUC calculation method for P2P and CB transactions to address holistically economic and technical issues in transactive energy markets and distribution system operations,respectively.Based on the Nash bargaining(NB)theory,we formulate an NB problem for P2P and CB transactions to solve the conflicts of interest among prosumers,where the problem is further decomposed into two convex subproblems of social welfare maximization and payment bargaining.We then build the NUC calculation model by coupling the NB model and AC optimal power flow model.We also employ the Shapley value to allocate the NUC to consumers fairly for the NUC model of CB transactions.Finally,numerical studies on IEEE 15-bus and 123-bus distribution systems demonstrate the effectiveness of the proposed NUC calculation method for P2P and CB transactions.

Atomically Precise Pd Species Accelerating CO_(2) Hydrodeoxygenation into CH_(4) with 100%Selectivity

High-rate CO_(2)-to-CH_(4)photoreduction with high selectivity is highly attractive,which is a win-win strategy for mitigating the greenhouse effect and the energy crisis.However,the poor photocatalytic activity and low product selectivity hinder the practical application.To precisely tailor the product selectivity and realize high-rate CO_(2)photoreduction,we design atomically precise Pd species supported on In_(2)O_(3)nanosheets.Taking the synthetic 1.30Pd/In_(2)O_(3)nanosheets as an example,the aberration-correction high-angle annular dark-field scanning transmission electron microscopy image displayed the Pd species atomically dispersed on the In_(2)O_(3)nanosheets.Raman spectra and X-ray photoelectron spectra established that the strong interaction between the Pd species and the In_(2)O_(3)substrate drove electron transfer from In to Pd species,resulting in electron-enriched Pd sites for CO_(2)activation.Synchrotronradiation photoemission spectroscopy demonstrated that the Pd species can tailor the conduction band edge of In_(2)O_(3)nanosheets to match the CO_(2)-to-CH_(4)pathway,instead of the CO_(2)-to-CO pathway,which theoretically accounts for the high CH_(4)selectivity.Moreover,in situ X-ray photoelectron spectroscopy unveiled that the catalytically active sites had a change from In species to Pd species over the 1.30Pd/In_(2)O_(3)nanosheets.In situ FTIR and EPR spectra reveal the atomically precise Pd species with rich electrons prefer to adsorb the electrophilic protons for accelerating the*COOH intermediates hydrogenation into CH_(4).Consequently,the 1.30Pd/In_(2)O_(3)nanosheets reached CO_(2)-to-CH_(4)photoconversion with 100%selectivity and 81.2μmol g^(−1)h^(−1)productivity.

Enclosure Fire-induced Temperature: Review and Model Modification for Horizontal Vented Space

Correlations of fire-induced temperature have been reviewed and revisited.The impact of XY factors,i.e.,the relative locations of the fire source and vent,on temperature models of ceiling-vented compartments could be reflected by the exponents of the two dimensionless terms which represent the ratio of the total energy to energy released through the ceiling vent,and the ratio of the energy lost through the walls to the energy released through the ceiling vent.For fires not located directly below the ceiling vent,the temperature rise was proportional to two thirds of the power of the heat release rate,while for fires immediately beneath this vent,the temperature rise was proportional to four thirds the power of the heat release rate,and was inversely proportional to one sixth the power of the ceiling vent size.