The Na I:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low ^(6)Li concentration.To achieve real-time n/γ discrimination,a zero-crossing time comparison algorithm based on t...The Na I:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low ^(6)Li concentration.To achieve real-time n/γ discrimination,a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was developed.The algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/γ discriminator based on a field-programmable gate array.The discriminator and Na I:Tl,^(6)Li detector were tested in a neutron-gamma mixed field produced by an ^(241)Am-Be neutron source to evaluate the performance of the algorithm.The figure of merits was measured as 2.88 at a sampling rate of 50 MHz,indicating that the discriminator with its embedded algorithm has a promising n/γ discrimination capability.Efficient discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.展开更多
At high count rates,pile-up events involving neutron and gamma signals result in inaccurate neutron counting and distortions in the energy spectrum.Additionally,a bipolar cusp-like pulse shaping algorithm based on an ...At high count rates,pile-up events involving neutron and gamma signals result in inaccurate neutron counting and distortions in the energy spectrum.Additionally,a bipolar cusp-like pulse shaping algorithm based on an unfolding synthesis technique was proposed.This algorithm exhibits a narrow pulse shape,and the parallel design of the dual algorithms enables the recovery of pile-up signal amplitudes while preserving the distinct characteristics of neutron and gamma signals.The simplicity of the algorithm facilitates real-time neutron/gamma discrimination on an FPGA,allowing the energy spectra to be updated with each incoming signal.Furthermore,the algorithm can be readily tailored to various experimental conditions by adjusting the decay time constants.Multi-objective optimization reduces the need for manual parameter tuning by rapidly identifying the optimal parameters.Testing with a^(241)Am-Be neutron source and a NaIL scintillator yielded a figure of merit(FoM)value of 2.11 and produced a clear energy spectrum even at high count rates.展开更多
We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chi...We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.展开更多
With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theor...With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theoretically derives the relationship between the formation density and inelastic gamma count rate to investigate the data-processing methods for deuterium–tritium(D–T)source neutron-gamma density logging while drilling.Then,algorithms for the net inelastic gamma count-rate extraction and neutron transport correction are studied using Monte Carlo simulations.A new method for fast-neutron effect identification and additional correction is proposed to improve the density-calculation accuracy of gas-filled and heavy-mineral formations.Finally,the effectiveness and accuracy of the proposed data-processing methods are verified based on simulated and measured data.The results show that the density-calculation accuracy of water-bearing conventional formations in simulated data is±0.02 g/cm^(3).The accuracy of gas-filled and heavy-mineral formations after the additional fast-neutron effect correction is±0.025 g/cm^(3).For the measured data from the actual tool,the algorithms perform well in the density calculation.The density results obtained using the processing algorithms are consistent with the density data provided by NeoScope.Therefore,the D–T source neutron-gamma density-logging algorithms proposed in this study can obtain relatively accurate data-processing results for a variety of formations.This study provides technical support for engineering applications and the development of logging tools for controllable-source neutron-density logging.展开更多
To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produce...To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produced by the tandem-accelerator in the China Institute of Atomic Energy was utilized.The proton beam was first transmitted through a 60.5μm aluminum foil and then impinged on a natural LiF target to produce neutron beam via^(7)Li(p,n)7Be reaction.The quasi-Gaussian energy distribution of protons in the LiF target resulted in neutron energy spectra that agreed with a Maxwellian energy distribution at kT=(22±2)keV,which was achieved by integrating neutrons detected within an emission angle of 65.0°±2.6°using a ^(6)Li glass detector positioned at 65°relative to the proton beam direction.The narrow angular spread of the Maxwelliandistributed neutron beam enables direct measurement of neutron capture cross-sections for most s-process nuclides,overcoming previous experimental limitations associated with broad angular distributions.展开更多
Shielding materials are critical for downhole pulsed neutron tool design because they directly influence the accuracy of formation measurements.A well-designed shield configuration ensures that the response of the too...Shielding materials are critical for downhole pulsed neutron tool design because they directly influence the accuracy of formation measurements.A well-designed shield configuration ensures that the response of the tool is maximally representative of the formation without being affected by the tool and borehole environment.This study investigated the effects of boron-containing materials on neutron and gamma detectors based on a newly designed logging-while-drilling tool that is currently undergoing manufacturing.As the boron content increased,the ability to absorb thermal neutrons increased significantly.Through simulation,it was proven that boron carbide(B_(4)C)can be used as an effective boron shielding material for thermal neutrons,and is therefore employed in this work.To shield against thermal neutrons migrating from the mud pipes,the optimal shielding thicknesses for the near-and far-neutron detectors were determined to be 5 and 4 mm.At a porosity of 25 p.u.,near-neutron sensitivity exhibited a 5.6%increase.Furthermore,to shield the capture gamma generated by thermal neutrons once they enter the tool from the mud pipe and formation,internal and external shields for the gamma detector were evaluated.The results show that the internal shield requires a boron content of 75%,whereas the external shield has a thickness of 14.2 mm thickness and a boron content of 25%to minimize the tool effect.展开更多
The multi-principal element characteristic of high-entropy alloys has revolutionized the conventional alloy design concept of single-principal element,endowing them with excellent mechanical properties.However,owing t...The multi-principal element characteristic of high-entropy alloys has revolutionized the conventional alloy design concept of single-principal element,endowing them with excellent mechanical properties.However,owing to this multi-principal element nature,high-entropy alloys exhibit complex deformation behavior dominated by alternating and coupled deformation mechanisms.Therefore,elucidating these intricate deformation mechanisms remains a key challenge in current research.Neutron diffraction(ND)techniques offer distinct advantages over traditional microscopic methods for characterizing such complex deformation behavior.The strong penetration capability of neutrons enables in-situ,real-time,and non-destructive detection of structural evolution in most centimeter-level bulk samples under complex environments,and ND allows precise characterization of lattice site occupations for light elements,such as C and O,and neighboring elements.This review discussed the principles of ND,experiment procedures,and data analysis.Combining with recent advances in the research about face-centered cubic high-entropy alloy,typical examples of using ND to investigate the deformation behavior were summarized,ultimately revealing deformation mechanisms dominated by dislocations,stacking faults,twinning,and phase transformations.展开更多
In recent years,there have been fewer missions to detect neutrons in low Earth orbits(LEO),and the data obtained have been extremely limited.Studying the distribution of the neutron energy spectrum in LEO satellites t...In recent years,there have been fewer missions to detect neutrons in low Earth orbits(LEO),and the data obtained have been extremely limited.Studying the distribution of the neutron energy spectrum in LEO satellites through detection can help solve three major scientific problems:the source of particles in the inner radiation belt,information on solar-accelerated particles,and the proportion of neutrons from different sources in near-Earth space.The detection efficiency and accuracy of neutrons are affected by charged and primary particles in the environment and secondary neutrons produced by the spacecraft itself,which has been a hot research topic.The neutron spectrometer developed in this study adopts two combinations of 15 silicon detectors in terms of detector type and arrangement,which are used for neutron detection via the nuclear reaction method and recoil proton method,respectively,in which a 27μm-thick^(6)LiF conversion layer is used for thermal neutron detection up to 0.4 eV and a 300μm-thick high-density polyethylene conversion layer is used for fast-neutron detection up to 14 MeV and below.The design of the detector set can also remove the influence of primary charged particles and secondary neutrons in the detection environment to a certain extent,thereby improving the accuracy of neutron detection.In this study,the neutron spectrometer hardware,firmware,software design,and basic performance of the front-end readout chip SKIROC2A were tested.The readout circuit of each channel baseline ADC code was less than 17;thus,the channel consistency was good.The RMS noise of the channel baseline was only 7.1 mV and exhibited good stability.The maximum number of events that could be processed per second is 75.The overall power consumption was 3 W,the weight was 792 g,and the volume was less than 1 dm^(3).Furthermore,the neutron spectrometer was tested for principle and detection efficiency using various neutron sources,such as ^(241)Am-Be neutron source,2.5 MeV neutron beam,and 14 MeV neutron beam,and the experiments were analyzed with corresponding simulations.The experimental data and simulation results were in good agreement and met the design requirements.The intrinsic detection efficiency of the probes used in the neutron spectrometer was 1.05%for 14 MeV fast neutrons.展开更多
Deep learning methods have achieved significant progress in solving partial differential equations.However,when applied to the widely used anisotropic scattering neutron transport equations in reactor engineering,thes...Deep learning methods have achieved significant progress in solving partial differential equations.However,when applied to the widely used anisotropic scattering neutron transport equations in reactor engineering,these encounter significant challenges.To address this issue,this study introduces a multi-antiderivative transformation alternating iterative deep learning method(M-AIM).This method transforms the integral terms of the scattering and fission sources in the transport equation into multiple antiderivative functions corresponding to the integrand,converts the differential-integral form of the transport equation into an exact differential equation,and establishes the necessary constraints for a unique solution.The M-AIM uses multiple deep neural networks to map the unknown angular flux density of transport equations and represents various forms of antiderivative functions.It constructs the corresponding weighted loss functions.By alternating iterative training with deep learning methods applied to these neural networks,the loss is reduced gradually.When the loss decreases to a preset minimum,the neural network approaches a numerical solution for both angular flux density and antiderivative functions.This paper presents a numerical verification of geometries such as flat plates and spheres.It verifies the validity of the theoretical framework and associated methods.The study contributes to the development of novel technical approaches for applying deep learning to solve anisotropic scattering neutron transport equations in reactor engineering.展开更多
The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was perf...The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was performed with a total measurement duration of approximately 1200 h.In the experiment,eight CLYC detectors and sixteen EJ309 liquid scintillation detectors were utilized,and the fission moment was tagged with the measured fissionγ-rays.The relative ratios of the energy spectra of the neutrons correlated with different energy neutrons to the^(252)Cf fission neutron energy spectra were obtained.The present results may be helpful for studying fission physics and nuclear technology applications.展开更多
The ultracold neutron(UCN)transport code,MCUCN,designed initially for simulating UCN transportation from a solid deuterium(SD_2)source and neutron electric dipole moment experiments,could not simulate UCN storage and ...The ultracold neutron(UCN)transport code,MCUCN,designed initially for simulating UCN transportation from a solid deuterium(SD_2)source and neutron electric dipole moment experiments,could not simulate UCN storage and transportation in a superfluid^(4)He(SFHe,He-Ⅱ)source accurately.This limitation arose from the absence of an^(4)He upscattering mechanism and the absorption of^(3)He.And the provided source energy distribution in MCUCN is different from that in SFHe source.This study introduced enhancements to MCUCN to address these constraints,explicitly incorporating the^(4)He upscattering effect,the absorption of^(3)He,the loss caused by impurities on converter wall,UCN source energy distribution in SFHe,and the transmission through negative optical potential.Additionally,a Python-based visualization code for intermediate states and results was developed.To validate these enhancements,we systematically compared the simulation results of the Lujan Center Mark3 UCN system by MCUCN and the improved MCUCN code(iMCUCN)with UCNtransport simulations.Additionally,we compared the results of the SUN1 system simulated by MCUCN and iMCUCN with measurement results.The study demonstrates that iMCUCN effectively simulates the storage and transportation of ultracold neutrons in He-Ⅱ.展开更多
The neutron diffusion equation plays a pivotal role in nuclear reactor analysis.Nevertheless,employing the physics-informed neural network(PINN)method for its solution entails certain limitations.Conventional PINN app...The neutron diffusion equation plays a pivotal role in nuclear reactor analysis.Nevertheless,employing the physics-informed neural network(PINN)method for its solution entails certain limitations.Conventional PINN approaches generally utilize a fully connected network(FCN)architecture that is susceptible to overfitting,training instability,and gradient vanishing as the network depth increases.These challenges result in accuracy bottlenecks in the solution.In response to these issues,the residual-based resample physics-informed neural network(R2-PINN)is proposed.It is an improved PINN architecture that replaces the FCN with a convolutional neural network with a shortcut(S-CNN).It incorporates skip connections to facilitate gradient propagation between network layers.Additionally,the incorporation of the residual adaptive resampling(RAR)mechanism dynamically increases the number of sampling points.This,in turn,enhances the spatial representation capabilities and overall predictive accuracy of the model.The experimental results illustrate that our approach significantly improves the convergence capability of the model and achieves high-precision predictions of the physical fields.Compared with conventional FCN-based PINN methods,R 2-PINN effectively overcomes the limitations inherent in current methods.Thus,it provides more accurate and robust solutions for neutron diffusion equations.展开更多
Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity ...Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity in PD and LID has frequently been reported in recent cross-sectional studies.We aimed to investigate the temporal features of beta and gamma activity in the hyper-direct pathway during the development of PD and LID in rats,as well as the regulatory role of the dopamine receptors DI(D1Rs)and DIII(D3Rs)in these disorders.We recorded motor behavior and electrophysiological data during the development of PD and LID,and after interventions with D1R and D3R antagonists and agonists.We demonstrated exaggerated beta-band activity in the PD state and excessive gamma-band activity during on-state dyskinesia.Subsequently,process-dependent increased beta activity correlated with bradykinesia during PD modeling,while process-dependent increased gamma activity correlated with dyskinesia under the cumulative effects of levodopa during on-state dyskinesia.Finally,both D1Rs and D3Rs were found to be involved in regulating dyskinesia and gamma activity.Dynamic oscillations are closely associated with motor behavior,and mapping dynamic oscillations may be associated with optimizing deep brain stimulation parameters and developing personalized neurotherapeutic targeting.Moreover,D1Rs and D3Rs may ameliorate dyskinesia by mediating gamma oscillations.展开更多
Accurate fission cross-sectional data for actinide nuclides are critical for nuclear energy,astrophysics,and defense applications.Traditional detectors,such as fission chambers,face limitations in achieving sub-3% unc...Accurate fission cross-sectional data for actinide nuclides are critical for nuclear energy,astrophysics,and defense applications.Traditional detectors,such as fission chambers,face limitations in achieving sub-3% uncertainty owing to particle identification challenges and dynamic range constraints.The time projection chamber(TPC)can record both the energy deposition dE/dx and the three-dimensional track of an event,providing the ability to identify particles and fission fragments.Based on this characteristic,we developed a novel TPC,INPC-TPC,featuring a symmetrical dual-chamber structure and gas electron multiplier(GEM)-based readout technology.The dual-chamber design isolates fission fragments and recoils protons,thereby reducing the dynamic range requirements of a single chamber,whereas the GEM ensures high spatial resolution and stable gain.Experiments conducted at the Chinese Spallation Neutron Source(CSNS)Back-n white neutron beamline validated the performance of the proposed detector.The INPC-TPC demonstrated effective fission fragment identification through particle energy-length correlation measurements and accurately measured the neutron beam spot size with a diameter relative error of<2%.The results highlight the capability of the system to achieve high-precision measurements of neutroninduced fission cross sections,particularly for ^(235)U and ^(238)U.展开更多
Amidst the growing global emphasis on nuclear safety,the integrity of nuclear reactor systems has garnered attention in the aftermath of consequential events.Moreover,the rapid development of artificial intelligence t...Amidst the growing global emphasis on nuclear safety,the integrity of nuclear reactor systems has garnered attention in the aftermath of consequential events.Moreover,the rapid development of artificial intelligence technology has provided immense opportunities to enhance the safety and economy of nuclear energy.However,data-driven deep learning techniques often lack interpretability,which hinders their applicability in the nuclear energy sector.To address this problem,this study proposes a hybrid data-driven and knowledge-driven artificial intelligence model based on physics-informed neural networks to accurately compute the neutron flux distribution inside a nuclear reactor core.Innovative techniques,such as regional decomposition,intelligent k_(eff)(effective multiplication factor)search,and k_(eff)inversion,have been introduced for the calculation.Furthermore,hyperparameters of the model are automatically optimized using a whale optimization algorithm.A series of computational examples are used to validate the proposed model,demonstrating its applicability,generality,and high accuracy in calculating the neutron flux within the nuclear reactor.The model offers a dependable strategy for computing the neutron flux distribution in nuclear reactors for advanced simulation techniques in the future,including reactor digital twinning.This approach is data-light,requires little to no training data,and still delivers remarkably precise output data.展开更多
The early developmental period is a critical window during which brain cells mature and contribute to both brain development and later life functions.Gamma-aminobutyric acid(GABA),recognized as a major neurotransmitte...The early developmental period is a critical window during which brain cells mature and contribute to both brain development and later life functions.Gamma-aminobutyric acid(GABA),recognized as a major neurotransmitter,plays a crucial role in coordinating synapse formation,neuronal proliferation,and migration during this time.展开更多
Internal leakage caused by wear in hydraulic spool valves represents a critical failure mode that threatens the performance of aircraft hydraulic systems and compromises flight safety.Due to complex operational loads ...Internal leakage caused by wear in hydraulic spool valves represents a critical failure mode that threatens the performance of aircraft hydraulic systems and compromises flight safety.Due to complex operational loads and time-varying material properties,the relationship between wear state and Remaining Useful Life(RUL)is nonlinear.Consequently,accurately modeling this wear remains a significant challenge,as existing research often neglects the coupled effects of material properties,stress conditions,and dynamic lubrication parameters.To address this issue,this study proposes a novel framework integrating physical mechanisms with stochastic processes to enhance wear degradation modelling and RUL prediction.First,a Physics-of-Failure(PoF)model is developed based on Archard's wear theory,which characterizes tribological behavior at the contact interface and accounts for the effects of lubrication and load conditions.Next,a Gamma process is introduced to model the degradation trajectory,with physical parameters guiding the specification of the time-scale function.A Bayesian expectation–maximization algorithm is employed to estimate and update the model parameters.Finally,a numerical simulation and case study on spool valves are conducted to demonstrate the effectiveness of the proposed model.The cross-validation results confirmed that the introduction of random effects effectively reduces the impact of uncertainty on physics-informed modeling.This study offers a systematic solution to RUL prediction for hydraulic systems.展开更多
Deep brain sti mulation(DBS)is a neuromodulation tool that involves the delivery of electrical impulses to specific brain regions through implanted electrodes.The principle behind DBS is to modulate dysfunctional neur...Deep brain sti mulation(DBS)is a neuromodulation tool that involves the delivery of electrical impulses to specific brain regions through implanted electrodes.The principle behind DBS is to modulate dysfunctional neural circuits without the need for permanent structural alterations to the brain.Initially developed as a treatment for movement disorders such as Parkinson's disease(PD),DBS has expanded to encompass various neurological and psychiatric disorders.展开更多
基金This work was supported by the National Natural Science Foundation of China(NSFC)(No.12075308).
文摘The Na I:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low ^(6)Li concentration.To achieve real-time n/γ discrimination,a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was developed.The algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/γ discriminator based on a field-programmable gate array.The discriminator and Na I:Tl,^(6)Li detector were tested in a neutron-gamma mixed field produced by an ^(241)Am-Be neutron source to evaluate the performance of the algorithm.The figure of merits was measured as 2.88 at a sampling rate of 50 MHz,indicating that the discriminator with its embedded algorithm has a promising n/γ discrimination capability.Efficient discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.
基金supported by the National Natural Science Foundation of China(NSFC)(No.12075308)。
文摘At high count rates,pile-up events involving neutron and gamma signals result in inaccurate neutron counting and distortions in the energy spectrum.Additionally,a bipolar cusp-like pulse shaping algorithm based on an unfolding synthesis technique was proposed.This algorithm exhibits a narrow pulse shape,and the parallel design of the dual algorithms enables the recovery of pile-up signal amplitudes while preserving the distinct characteristics of neutron and gamma signals.The simplicity of the algorithm facilitates real-time neutron/gamma discrimination on an FPGA,allowing the energy spectra to be updated with each incoming signal.Furthermore,the algorithm can be readily tailored to various experimental conditions by adjusting the decay time constants.Multi-objective optimization reduces the need for manual parameter tuning by rapidly identifying the optimal parameters.Testing with a^(241)Am-Be neutron source and a NaIL scintillator yielded a figure of merit(FoM)value of 2.11 and produced a clear energy spectrum even at high count rates.
文摘We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.
基金supported by the Natural Science Foundation of Shandong(ZR2022MD019)Technology Development Project of China Oilfield Services Limited(G2317A-0414T077)+3 种基金Science and Technology Project of China National O shore Oil Corporation(CNOOC-KJ GJHXJSGG YF 2022-01)Open Fund Project of CNPC Logging(CNLC2022-9C06)Fundamental Research Foundation for Central Universities(22CX01001A-2)China National Petroleum Corporation Scientific Research and Technology Development Project(2021DJ3801)。
文摘With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theoretically derives the relationship between the formation density and inelastic gamma count rate to investigate the data-processing methods for deuterium–tritium(D–T)source neutron-gamma density logging while drilling.Then,algorithms for the net inelastic gamma count-rate extraction and neutron transport correction are studied using Monte Carlo simulations.A new method for fast-neutron effect identification and additional correction is proposed to improve the density-calculation accuracy of gas-filled and heavy-mineral formations.Finally,the effectiveness and accuracy of the proposed data-processing methods are verified based on simulated and measured data.The results show that the density-calculation accuracy of water-bearing conventional formations in simulated data is±0.02 g/cm^(3).The accuracy of gas-filled and heavy-mineral formations after the additional fast-neutron effect correction is±0.025 g/cm^(3).For the measured data from the actual tool,the algorithms perform well in the density calculation.The density results obtained using the processing algorithms are consistent with the density data provided by NeoScope.Therefore,the D–T source neutron-gamma density-logging algorithms proposed in this study can obtain relatively accurate data-processing results for a variety of formations.This study provides technical support for engineering applications and the development of logging tools for controllable-source neutron-density logging.
基金National Natural Science Foundation of China(12125509,11961141003,12275361,U2267205,12175152,12175121)National Key Research and Development Project(2022YFA1602301)Continuous-support Basic Scientific Research Project。
文摘To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produced by the tandem-accelerator in the China Institute of Atomic Energy was utilized.The proton beam was first transmitted through a 60.5μm aluminum foil and then impinged on a natural LiF target to produce neutron beam via^(7)Li(p,n)7Be reaction.The quasi-Gaussian energy distribution of protons in the LiF target resulted in neutron energy spectra that agreed with a Maxwellian energy distribution at kT=(22±2)keV,which was achieved by integrating neutrons detected within an emission angle of 65.0°±2.6°using a ^(6)Li glass detector positioned at 65°relative to the proton beam direction.The narrow angular spread of the Maxwelliandistributed neutron beam enables direct measurement of neutron capture cross-sections for most s-process nuclides,overcoming previous experimental limitations associated with broad angular distributions.
基金supported by the Natural Science Foundation of China(Nos.U23B20151 and 52171253).
文摘Shielding materials are critical for downhole pulsed neutron tool design because they directly influence the accuracy of formation measurements.A well-designed shield configuration ensures that the response of the tool is maximally representative of the formation without being affected by the tool and borehole environment.This study investigated the effects of boron-containing materials on neutron and gamma detectors based on a newly designed logging-while-drilling tool that is currently undergoing manufacturing.As the boron content increased,the ability to absorb thermal neutrons increased significantly.Through simulation,it was proven that boron carbide(B_(4)C)can be used as an effective boron shielding material for thermal neutrons,and is therefore employed in this work.To shield against thermal neutrons migrating from the mud pipes,the optimal shielding thicknesses for the near-and far-neutron detectors were determined to be 5 and 4 mm.At a porosity of 25 p.u.,near-neutron sensitivity exhibited a 5.6%increase.Furthermore,to shield the capture gamma generated by thermal neutrons once they enter the tool from the mud pipe and formation,internal and external shields for the gamma detector were evaluated.The results show that the internal shield requires a boron content of 75%,whereas the external shield has a thickness of 14.2 mm thickness and a boron content of 25%to minimize the tool effect.
基金National Key R&D Program of China(2023YFB3711904,2022YFA1603801)National Natural Science Foundation of China(12404230,52471181,52301213,52130108,52471005)+2 种基金National Nature Science Foundation of Zhejiang Province(LY23E010002)Open Fund of the China Spallation Neutron Source,Songshan Lake Science City(KFKT2023B11)Guangdong Basic and Applied Basic Research Foundation(2022A1515110805,2024A1515010878)。
文摘The multi-principal element characteristic of high-entropy alloys has revolutionized the conventional alloy design concept of single-principal element,endowing them with excellent mechanical properties.However,owing to this multi-principal element nature,high-entropy alloys exhibit complex deformation behavior dominated by alternating and coupled deformation mechanisms.Therefore,elucidating these intricate deformation mechanisms remains a key challenge in current research.Neutron diffraction(ND)techniques offer distinct advantages over traditional microscopic methods for characterizing such complex deformation behavior.The strong penetration capability of neutrons enables in-situ,real-time,and non-destructive detection of structural evolution in most centimeter-level bulk samples under complex environments,and ND allows precise characterization of lattice site occupations for light elements,such as C and O,and neighboring elements.This review discussed the principles of ND,experiment procedures,and data analysis.Combining with recent advances in the research about face-centered cubic high-entropy alloy,typical examples of using ND to investigate the deformation behavior were summarized,ultimately revealing deformation mechanisms dominated by dislocations,stacking faults,twinning,and phase transformations.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.42225405 and U2106202)。
文摘In recent years,there have been fewer missions to detect neutrons in low Earth orbits(LEO),and the data obtained have been extremely limited.Studying the distribution of the neutron energy spectrum in LEO satellites through detection can help solve three major scientific problems:the source of particles in the inner radiation belt,information on solar-accelerated particles,and the proportion of neutrons from different sources in near-Earth space.The detection efficiency and accuracy of neutrons are affected by charged and primary particles in the environment and secondary neutrons produced by the spacecraft itself,which has been a hot research topic.The neutron spectrometer developed in this study adopts two combinations of 15 silicon detectors in terms of detector type and arrangement,which are used for neutron detection via the nuclear reaction method and recoil proton method,respectively,in which a 27μm-thick^(6)LiF conversion layer is used for thermal neutron detection up to 0.4 eV and a 300μm-thick high-density polyethylene conversion layer is used for fast-neutron detection up to 14 MeV and below.The design of the detector set can also remove the influence of primary charged particles and secondary neutrons in the detection environment to a certain extent,thereby improving the accuracy of neutron detection.In this study,the neutron spectrometer hardware,firmware,software design,and basic performance of the front-end readout chip SKIROC2A were tested.The readout circuit of each channel baseline ADC code was less than 17;thus,the channel consistency was good.The RMS noise of the channel baseline was only 7.1 mV and exhibited good stability.The maximum number of events that could be processed per second is 75.The overall power consumption was 3 W,the weight was 792 g,and the volume was less than 1 dm^(3).Furthermore,the neutron spectrometer was tested for principle and detection efficiency using various neutron sources,such as ^(241)Am-Be neutron source,2.5 MeV neutron beam,and 14 MeV neutron beam,and the experiments were analyzed with corresponding simulations.The experimental data and simulation results were in good agreement and met the design requirements.The intrinsic detection efficiency of the probes used in the neutron spectrometer was 1.05%for 14 MeV fast neutrons.
基金supported by the National Natural Science Foundation of China(No.12575189)。
文摘Deep learning methods have achieved significant progress in solving partial differential equations.However,when applied to the widely used anisotropic scattering neutron transport equations in reactor engineering,these encounter significant challenges.To address this issue,this study introduces a multi-antiderivative transformation alternating iterative deep learning method(M-AIM).This method transforms the integral terms of the scattering and fission sources in the transport equation into multiple antiderivative functions corresponding to the integrand,converts the differential-integral form of the transport equation into an exact differential equation,and establishes the necessary constraints for a unique solution.The M-AIM uses multiple deep neural networks to map the unknown angular flux density of transport equations and represents various forms of antiderivative functions.It constructs the corresponding weighted loss functions.By alternating iterative training with deep learning methods applied to these neural networks,the loss is reduced gradually.When the loss decreases to a preset minimum,the neural network approaches a numerical solution for both angular flux density and antiderivative functions.This paper presents a numerical verification of geometries such as flat plates and spheres.It verifies the validity of the theoretical framework and associated methods.The study contributes to the development of novel technical approaches for applying deep learning to solve anisotropic scattering neutron transport equations in reactor engineering.
基金supported by the National Natural Science Foundation of China(No.12105257)the Research and Development Fund(No.JMJJ202401)。
文摘The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was performed with a total measurement duration of approximately 1200 h.In the experiment,eight CLYC detectors and sixteen EJ309 liquid scintillation detectors were utilized,and the fission moment was tagged with the measured fissionγ-rays.The relative ratios of the energy spectra of the neutrons correlated with different energy neutrons to the^(252)Cf fission neutron energy spectra were obtained.The present results may be helpful for studying fission physics and nuclear technology applications.
基金the National Key R&D Program of China(No.2024YFE0110001)the National Natural Science Foundation of China(U1932219)the Mobility Programme endorsed by the Joint Committee of the Sino-German Center(M0728)。
文摘The ultracold neutron(UCN)transport code,MCUCN,designed initially for simulating UCN transportation from a solid deuterium(SD_2)source and neutron electric dipole moment experiments,could not simulate UCN storage and transportation in a superfluid^(4)He(SFHe,He-Ⅱ)source accurately.This limitation arose from the absence of an^(4)He upscattering mechanism and the absorption of^(3)He.And the provided source energy distribution in MCUCN is different from that in SFHe source.This study introduced enhancements to MCUCN to address these constraints,explicitly incorporating the^(4)He upscattering effect,the absorption of^(3)He,the loss caused by impurities on converter wall,UCN source energy distribution in SFHe,and the transmission through negative optical potential.Additionally,a Python-based visualization code for intermediate states and results was developed.To validate these enhancements,we systematically compared the simulation results of the Lujan Center Mark3 UCN system by MCUCN and the improved MCUCN code(iMCUCN)with UCNtransport simulations.Additionally,we compared the results of the SUN1 system simulated by MCUCN and iMCUCN with measurement results.The study demonstrates that iMCUCN effectively simulates the storage and transportation of ultracold neutrons in He-Ⅱ.
基金supported by the Science and Technology on Reactor System Design Technology Laboratory(No.LRSDT12023108)supported in part by the Chongqing Postdoctoral Science Foundation(No.cstc2021jcyj-bsh0252)+2 种基金the National Natural Science Foundation of China(No.12005030)Sichuan Province to unveil the list of marshal industry common technology research projects(No.23jBGOV0001)Special Program for Stabilizing Support to Basic Research of National Basic Research Institutes(No.WDZC-2023-05-03-05).
文摘The neutron diffusion equation plays a pivotal role in nuclear reactor analysis.Nevertheless,employing the physics-informed neural network(PINN)method for its solution entails certain limitations.Conventional PINN approaches generally utilize a fully connected network(FCN)architecture that is susceptible to overfitting,training instability,and gradient vanishing as the network depth increases.These challenges result in accuracy bottlenecks in the solution.In response to these issues,the residual-based resample physics-informed neural network(R2-PINN)is proposed.It is an improved PINN architecture that replaces the FCN with a convolutional neural network with a shortcut(S-CNN).It incorporates skip connections to facilitate gradient propagation between network layers.Additionally,the incorporation of the residual adaptive resampling(RAR)mechanism dynamically increases the number of sampling points.This,in turn,enhances the spatial representation capabilities and overall predictive accuracy of the model.The experimental results illustrate that our approach significantly improves the convergence capability of the model and achieves high-precision predictions of the physical fields.Compared with conventional FCN-based PINN methods,R 2-PINN effectively overcomes the limitations inherent in current methods.Thus,it provides more accurate and robust solutions for neutron diffusion equations.
基金supported by the Non-profit Central Research Institute Fund of the Chinese Academy of Medical Sciences(2020-PT310-01).
文摘Cortico-thalamic projections(the hyper-direct pathway)are implicated in levodopa-induced dyskinesia(LID),a challenging complication in the advanced stages of Parkinson’s disease(PD).Excessive beta and gamma activity in PD and LID has frequently been reported in recent cross-sectional studies.We aimed to investigate the temporal features of beta and gamma activity in the hyper-direct pathway during the development of PD and LID in rats,as well as the regulatory role of the dopamine receptors DI(D1Rs)and DIII(D3Rs)in these disorders.We recorded motor behavior and electrophysiological data during the development of PD and LID,and after interventions with D1R and D3R antagonists and agonists.We demonstrated exaggerated beta-band activity in the PD state and excessive gamma-band activity during on-state dyskinesia.Subsequently,process-dependent increased beta activity correlated with bradykinesia during PD modeling,while process-dependent increased gamma activity correlated with dyskinesia under the cumulative effects of levodopa during on-state dyskinesia.Finally,both D1Rs and D3Rs were found to be involved in regulating dyskinesia and gamma activity.Dynamic oscillations are closely associated with motor behavior,and mapping dynamic oscillations may be associated with optimizing deep brain stimulation parameters and developing personalized neurotherapeutic targeting.Moreover,D1Rs and D3Rs may ameliorate dyskinesia by mediating gamma oscillations.
基金supported by the auspices of the Youth Doctoral Talent Incubation Program of the Second Affiliated Hospital of Army Medical University(No.2024YQB060)。
文摘Accurate fission cross-sectional data for actinide nuclides are critical for nuclear energy,astrophysics,and defense applications.Traditional detectors,such as fission chambers,face limitations in achieving sub-3% uncertainty owing to particle identification challenges and dynamic range constraints.The time projection chamber(TPC)can record both the energy deposition dE/dx and the three-dimensional track of an event,providing the ability to identify particles and fission fragments.Based on this characteristic,we developed a novel TPC,INPC-TPC,featuring a symmetrical dual-chamber structure and gas electron multiplier(GEM)-based readout technology.The dual-chamber design isolates fission fragments and recoils protons,thereby reducing the dynamic range requirements of a single chamber,whereas the GEM ensures high spatial resolution and stable gain.Experiments conducted at the Chinese Spallation Neutron Source(CSNS)Back-n white neutron beamline validated the performance of the proposed detector.The INPC-TPC demonstrated effective fission fragment identification through particle energy-length correlation measurements and accurately measured the neutron beam spot size with a diameter relative error of<2%.The results highlight the capability of the system to achieve high-precision measurements of neutroninduced fission cross sections,particularly for ^(235)U and ^(238)U.
文摘Amidst the growing global emphasis on nuclear safety,the integrity of nuclear reactor systems has garnered attention in the aftermath of consequential events.Moreover,the rapid development of artificial intelligence technology has provided immense opportunities to enhance the safety and economy of nuclear energy.However,data-driven deep learning techniques often lack interpretability,which hinders their applicability in the nuclear energy sector.To address this problem,this study proposes a hybrid data-driven and knowledge-driven artificial intelligence model based on physics-informed neural networks to accurately compute the neutron flux distribution inside a nuclear reactor core.Innovative techniques,such as regional decomposition,intelligent k_(eff)(effective multiplication factor)search,and k_(eff)inversion,have been introduced for the calculation.Furthermore,hyperparameters of the model are automatically optimized using a whale optimization algorithm.A series of computational examples are used to validate the proposed model,demonstrating its applicability,generality,and high accuracy in calculating the neutron flux within the nuclear reactor.The model offers a dependable strategy for computing the neutron flux distribution in nuclear reactors for advanced simulation techniques in the future,including reactor digital twinning.This approach is data-light,requires little to no training data,and still delivers remarkably precise output data.
基金supported by the Center for Cognition and Sociality,Institute for Basic Science(IBS)(IBS-R001-D2)(to WK).
文摘The early developmental period is a critical window during which brain cells mature and contribute to both brain development and later life functions.Gamma-aminobutyric acid(GABA),recognized as a major neurotransmitter,plays a crucial role in coordinating synapse formation,neuronal proliferation,and migration during this time.
基金the financial support from the National Natural Science Foundation of China(Nos.U2233212,52375036,62303030 and 62403028)the Postdoctoral Fellowship Program of CPSF,China(Nos.GZC20242158 and GZC20233377)+1 种基金Open Fund of State Key Laboratory of Mechanical Transmission for Advanced Equipment,China(No.SKLMT-MSKFKT-202421)the Fundamental Research Funds for the Central Universities,China。
文摘Internal leakage caused by wear in hydraulic spool valves represents a critical failure mode that threatens the performance of aircraft hydraulic systems and compromises flight safety.Due to complex operational loads and time-varying material properties,the relationship between wear state and Remaining Useful Life(RUL)is nonlinear.Consequently,accurately modeling this wear remains a significant challenge,as existing research often neglects the coupled effects of material properties,stress conditions,and dynamic lubrication parameters.To address this issue,this study proposes a novel framework integrating physical mechanisms with stochastic processes to enhance wear degradation modelling and RUL prediction.First,a Physics-of-Failure(PoF)model is developed based on Archard's wear theory,which characterizes tribological behavior at the contact interface and accounts for the effects of lubrication and load conditions.Next,a Gamma process is introduced to model the degradation trajectory,with physical parameters guiding the specification of the time-scale function.A Bayesian expectation–maximization algorithm is employed to estimate and update the model parameters.Finally,a numerical simulation and case study on spool valves are conducted to demonstrate the effectiveness of the proposed model.The cross-validation results confirmed that the introduction of random effects effectively reduces the impact of uncertainty on physics-informed modeling.This study offers a systematic solution to RUL prediction for hydraulic systems.
文摘Deep brain sti mulation(DBS)is a neuromodulation tool that involves the delivery of electrical impulses to specific brain regions through implanted electrodes.The principle behind DBS is to modulate dysfunctional neural circuits without the need for permanent structural alterations to the brain.Initially developed as a treatment for movement disorders such as Parkinson's disease(PD),DBS has expanded to encompass various neurological and psychiatric disorders.
