New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the ligh...New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.展开更多
The present technical paper outlines the details of the controlled blasting techniques used to optimize blasting pattern for excavation of hard rock near the Bhira Earthen Dam in Maharashtra,India.In this connection,a...The present technical paper outlines the details of the controlled blasting techniques used to optimize blasting pattern for excavation of hard rock near the Bhira Earthen Dam in Maharashtra,India.In this connection,a series of experimental blasts were conducted by adjusting various blast design parameters at project site.The safe charge weight per delay was kept between 0.125 and 0.375 kg.The outcomes of these experimental blasts were analyzed to recommend optimized blasting patterns and methods for the overall excavation process during actual blasting operations.Blast design parameters,including the maximum quantity of explosive per delay,hole depth,burden and spacing between holes were optimized by using a site-specific attenuation equation,taking into account the proximity of the dam and tunnel from the blasting area.Peak particle velocity(PPV)level of 10 mm/s and 50 mm/s respectively were adopted as the safe vibration level for ensuring safety of the Bhira Earthen Dam and the nearby tunnel from the adverse effects of blast vibrations by analyzing the dominant frequency of ground vibrations observed and also by reviewing various international standards.Frequency of the ground vibrations observed on the dam and tunnel from majority of the blasts was found to be more than 10 Hz and 50 Hz respectively.During the entire period of blasting,the blast vibrations were recorded to be far lower than the safe vibration level set for these structures.Maximum Vibration level of about 0.8 mm/s and 35 mm/s were observed on dam and tunnel respectively which are far lower than the safe vibration level adopted for these structures.Hence,the entire excavation work was completed successfully and safely,without endangering the safety of dam or tunnel.展开更多
Myocardial perfusion imaging(MPI),which uses single-photon emission computed tomography(SPECT),is a well-known estimating tool for medical diagnosis,employing the classification of images to show situations in coronar...Myocardial perfusion imaging(MPI),which uses single-photon emission computed tomography(SPECT),is a well-known estimating tool for medical diagnosis,employing the classification of images to show situations in coronary artery disease(CAD).The automatic classification of SPECT images for different techniques has achieved near-optimal accuracy when using convolutional neural networks(CNNs).This paper uses a SPECT classification framework with three steps:1)Image denoising,2)Attenuation correction,and 3)Image classification.Image denoising is done by a U-Net architecture that ensures effective image denoising.Attenuation correction is implemented by a convolution neural network model that can remove the attenuation that affects the feature extraction process of classification.Finally,a novel multi-scale diluted convolution(MSDC)network is proposed.It merges the features extracted in different scales and makes the model learn the features more efficiently.Three scales of filters with size 3×3 are used to extract features.All three steps are compared with state-of-the-art methods.The proposed denoising architecture ensures a high-quality image with the highest peak signal-to-noise ratio(PSNR)value of 39.7.The proposed classification method is compared with the five different CNN models,and the proposed method ensures better classification with an accuracy of 96%,precision of 87%,sensitivity of 87%,specificity of 89%,and F1-score of 87%.To demonstrate the importance of preprocessing,the classification model was analyzed without denoising and attenuation correction.展开更多
In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile traj...In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.展开更多
BACKGROUND Hepatic steatosis,characterized by fat accumulation in hepatocytes,can result from metabolic dysfunction-associated steatotic liver disease(MASLD),infections,alcoholism,chemotherapy,and toxins.MASLD is diag...BACKGROUND Hepatic steatosis,characterized by fat accumulation in hepatocytes,can result from metabolic dysfunction-associated steatotic liver disease(MASLD),infections,alcoholism,chemotherapy,and toxins.MASLD is diagnosed via imaging or biopsy with metabolic criteria and may progress to metabolic dysfunction–asso-ciated steatohepatitis,potentially leading to fibrosis,cirrhosis,or cancer.The coexistence of hepatic steatosis with chronic hepatitis B(CHB)is mainly related to metabolic factors and increases mortality and cancer risks.As a noninvasive method,attenuation imaging(ATI)shows promise in quantifying liver fat,demonstrating strong correlation with liver biopsy.AIM To investigate the disparity of ATI for assessing biopsy-based hepatic steatosis in CHB patients and MASLD patients.METHODS The study enrolled 249 patients who underwent both ATI and liver biopsy,including 78 with CHB and 171 with MASLD.Hepatic steatosis was classified into grades S0 to S3 according to the proportion of fat cells present.Liver fibrosis was staged from 0 to 4 according to the meta-analysis of histological data in viral hepatitis scoring system.The diagnostic performance of attenuation coefficient(AC)values across different groups was compared for each grade of steatosis.Factors associated with the AC values were determined through linear regression analysis.A multivariate logistic regression model was established to predict≥S2 within the MASLD group.RESULTS In both the CHB and the MASLD groups,AC values increased significantly with higher steatosis grade(P<0.001).In the CHB group,the areas under the curve(AUCs)of AC for predicting steatosis grades≥S1,≥S2 and S3 were 0.918,0.960 and 0.987,respectively.In contrast,the MASLD group showed AUCs of 0.836,0.774,and 0.688 for the same steatosis grades.The diagnostic performance of AC for detecting≥S2 and S3 indicated significant differences between the two groups(both P<0.001).Multivariate linear regression analysis identified body mass index,trigly-cerides,and steatosis grade as significant factors for AC.When the steatosis grade is≥S2,it can progress to more serious liver conditions.A clinical model integrating blood biochemical parameters and AC was developed in the MASLD group to enhance the prediction of≥S2,achieving an AUC of 0.848.CONCLUSION The AC could effectively discriminate the degree of steatosis in both the CHB and MASLD groups.In the MASLD group,when combined with blood biochemical parameters,AC exhibited better predictive ability for moderate to severe steatosis.展开更多
Imagine a future where a single vaccine could protect you from a multitude of influenza strains,offering broad immunity with minimal risk.This vision is now closer to reality,thanks to a recent study that harnesses th...Imagine a future where a single vaccine could protect you from a multitude of influenza strains,offering broad immunity with minimal risk.This vision is now closer to reality,thanks to a recent study that harnesses the power of cellular proteins to create a new generation of live attenuated vaccines that outsmart flu’s relentless mutations.展开更多
The attenuation and anisotropy characteristics of real earth media give rise to amplitude loss and phase dispersion during seismic wave propagation.To address these effects on seismic imaging,viscoacoustic anisotropic...The attenuation and anisotropy characteristics of real earth media give rise to amplitude loss and phase dispersion during seismic wave propagation.To address these effects on seismic imaging,viscoacoustic anisotropic wave equations expressed by the fractional Laplacian have been derived.However,the huge computational expense associated with multiple Fast Fourier transforms for solving these wave equations makes them unsuitable for industrial applications,especially in three dimensions.Therefore,we first derived a cost-effective pure-viscoacoustic wave equation expressed by the memory-variable in tilted transversely isotropic(TTI)media,based on the standard linear solid model.The newly derived wave equation featuring decoupled amplitude dissipation and phase dispersion terms,can be easily solved using the finite-difference method(FDM).Computational efficiency analyses demonstrate that wavefields simulated by our newly derived wave equation are more efficient compared to the previous pure-viscoacoustic TTI wave equations.The decoupling characteristics of the phase dispersion and amplitude dissipation of the proposed wave equation are illustrated in numerical tests.Additionally,we extend the newly derived wave equation to implement Q-compensated reverse time migration(RTM)in attenuating TTI media.Synthetic examples and field data test demonstrate that the proposed Qcompensated TTI RTM effectively migrate the effects of anisotropy and attenuation,providing highquality imaging results.展开更多
In order to obtain a lower frequency band gap,this paper proposes a novel locally resonant meta-beam incorporating a softening nonlinear factor.An improved camroller structure is designed in this meta-beam to achieve ...In order to obtain a lower frequency band gap,this paper proposes a novel locally resonant meta-beam incorporating a softening nonlinear factor.An improved camroller structure is designed in this meta-beam to achieve the softening nonlinear stiffness of the local oscillators.Firstly,based on Hamilton's principle and the Galerkin method,the control equations for the coupled system are established.The theoretical band gap boundary is then derived with the modal analysis method.The theoretical results reveal that the band gap of the meta-beam shifts towards lower frequencies due to the presence of a softening nonlinear factor,distinguishing it from both linear metamaterials and those with hardening nonlinear characteristics.Then,the vibration attenuation characteristics of a finite size meta-beam are investigated through numerical calculation,and are verified by the theoretical results.Furthermore,parameter studies indicate that the reasonable design of the local oscillator parameters based on lightweight principles helps to achieve further broadband and efficient vibration reduction in the low-frequency region.Finally,a prototype of the meta-beam is fabricated and assembled,and the formations of the low-frequency band gap and the amplitude-induced band gap phenomenon are verified through experiments.展开更多
The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the ...The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the plasma sheath can be challenging.Obtaining the electron density of the plasma sheath is crucial for understanding and achieving plasma stealth of vehicles.In this work,the relationship between electromagnetic wave attenuation and electron density is deduced theoretically.The attenuation distribution along the propagation path is found to be proportional to the integral of the plasma electron density.This result is used to predict the electron density profile.Furthermore,the average electron density is obtained using a back-propagation neural network algorithm.Finally,the spatial distribution of the electron density can be determined from the average electron density and the normalized derivative of attenuation with respect to the propagation depth.Compared to traditional probe measurement methods,the proposed approach not only improves efficiency but also preserves the integrity of the plasma environment.展开更多
Amplitude dissipation and phase dispersion occur when seismic waves propagate in attenuated anisotropic media,affecting the quality of migration imaging.To compensate and correct for these effects,the fractional Lapla...Amplitude dissipation and phase dispersion occur when seismic waves propagate in attenuated anisotropic media,affecting the quality of migration imaging.To compensate and correct for these effects,the fractional Laplacian pure viscoacoustic wave equation capable of producing stable and noise-free wavefields has been proposed and implemented in the Q-compensated reverse time migration(RTM).In addition,the second-order Taylor series expansion is usually adopted in the hybrid finite-difference/pseudo-spectral(HFDPS)strategy to solve spatially variable fractional Laplacian.However,during forward modeling and Q-compensated RTM,this HFDPS strategy requires 11 and 17 fast Fourier transforms(FFTs)per time step,respectively,leading to computational inefficiency.To improve computational efficiency,we introduce two high-efficiency HFDPS numerical modeling strategies based on asymptotic approximation and algebraic methods.Through the two strategies,the number of FFTs decreased from 11 to 6 and 5 per time step during forward modeling,respectively.Numerical examples demonstrate that wavefields simulated using the new numerical modeling strategies are accurate and highly efficient.Finally,these strategies are employed for implementing high-efficiency and stable Q-compensated RTM techniques in tilted transversely isotropic media,reducing the number of FFTs from 17 to 9 and 8 per time step,respectively,significantly improving computational efficiency.Synthetic data examples illustrate the effectiveness of the proposed Q-compensated RTM scheme in compensating amplitude dissipation and correcting phase distortion.展开更多
In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formali...In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formalism and dual-variable and position(DVP)method,the general solution of the coupled fields for the Lamb wave is derived,and then the dispersion equation is obtained by the application of the boundary conditions.First,the influence of semiconducting properties on the dispersion behavior of the Lamb wave in a single-layer PSC plate is analyzed.Then,the propagation characteristics of the Lamb wave in a sandwich plate are investigated in detail.The numerical results show that the wave speed and attenuation depend on the stacking sequence,layer thickness,and initial carrier density,the Lamb wave can propagate without a cut-off frequency in both the homogeneous and multilayer PSC plates due to the semiconducting properties,and the Lamb wave without attenuation can be achieved by carefully selecting the semiconductor property in the upper and lower layers.These new features could be very helpful as theoretical guidance for the design and performance optimization of PSC devices.展开更多
Seismic wavefields propagate through three-dimensional(3D)space,and their precise characterization is crucial for understanding subsurface structures.Traditional 2D algorithms,due to their limitations,are insufficient...Seismic wavefields propagate through three-dimensional(3D)space,and their precise characterization is crucial for understanding subsurface structures.Traditional 2D algorithms,due to their limitations,are insufficient to fully represent three-dimensional wavefields.The classic 3D Radon transform algorithm assumes that the wavefield's propagation characteristics are consistent in all directions,which often does not hold true in complex underground media.To address this issue,we present an improved 3D three-parameter Radon algorithm that considers the wavefield variation with azimuth and provides a more accurate wavefield description.However,introducing new parameters to describe the azimuthal varia-tion also poses computational challenges.The new Radon transform operator involves five variables and cannot be simply decomposed into small matrices for efficient computation;instead,it requires large matrix multiplication and inversion operations,significantly increasing the computational load.To overcome this challenge,we have integrated the curvature and frequency parameters,simplifying all frequency operators to the same,thereby significantly improving computation efficiency.Furthermore,existing transform algorithms neglect the lateral variation of seismic amplitudes,leading to discrepancies between the estimated multiples and those in the data.To enhance the amplitude preservation of the algorithm,we employ orthogonal polynomial fitting to capture the amplitude spatial variation in 3D seismic data.Combining these improvements,we propose a fast,amplitude-preserving,3D three-parameter Radon transform algorithm.This algorithm not only enhances computational efficiency while maintaining the original wavefield characteristics,but also improves the representation of seismic data by increasing amplitude fidelity.We validated the algorithm in multiple attenuation using both synthetic and real seismic data.The results demonstrate that the new algorithm significantly improves both accuracy and computational efficiency,providing an effective tool for analyzing seismic wavefields in complex subsurface structures.展开更多
Multiphase flow in porous rock is of great importance in the application of many industrial processes,including reservoir delineation,enhanced oil recovery,and CO_(2) sequestration.However,previous research typically ...Multiphase flow in porous rock is of great importance in the application of many industrial processes,including reservoir delineation,enhanced oil recovery,and CO_(2) sequestration.However,previous research typically investigated the dispersive behaviors when rock saturated with single or two-phase fluids and conducted limited studies on three-phase immiscible fluids.This study investigated the seismic dispersion,attenuation,and reflection features of seismic waves in three-phase immiscible fluidsaturated porous rocks.First,we proposed the calculation formulas of effective fluid modulus and effective fluid viscosity of multiphase immiscible fluids by taking into account the capillary pressure,reservoir wettability,and relative permeability simultaneously.Then,we analysed the frequencydependent behaviors of three-phase immiscible fluid-saturated porous rock under different fluid proportion cases using the Chapman multi-scale model.Next,the seismic responses are analysed using a four-layer model.The results indicate that the relative permeability,capillary pressure parameter,and fluid proportions are all significantly affect dispersion and attenuation.Comparative analyses demonstrate that dispersion and attenuation can be observed within the frequency range of seismic exploration for a lower capillary parameter a3 and higher oil content.Seismic responses reveal that the reflection features,such as travel time,seismic amplitude,and waveform of the bottom reflections of saturated rock and their underlying reflections are significantly dependent on fluid proportions and capillary parameters.For validation,the numerical results are further verified using the log data and real seismic data.This numerical analysis helps to further understand the wave propagation characteristics for a porous rock saturated with multiphase immiscible fluids.展开更多
Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has bee...Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has been extensively studied,there is still no consensus on the correlation between acoustic attenuation coefficient and sediment physical properties.Predicting the acoustic attenuation coefficient remains a challenging issue in sedimentary acoustic research.In this study,we propose a prediction method for the acoustic attenuation coefficient using machine learning algorithms,specifically the random forest(RF),support vector machine(SVR),and convolutional neural network(CNN)algorithms.We utilized the acoustic attenuation coefficient and sediment particle size data from 52 stations as training parameters,with the particle size parameters as the input feature matrix,and measured acoustic attenuation as the training label to validate the attenuation prediction model.Our results indicate that the error of the attenuation prediction model is small.Among the three models,the RF model exhibited the lowest prediction error,with a mean squared error of 0.8232,mean absolute error of 0.6613,and root mean squared error of 0.9073.Additionally,when we applied the models to predict the data collected at different times in the same region,we found that the models developed in this study also demonstrated a certain level of reliability in real prediction scenarios.Our approach demonstrates that constructing a sediment acoustic characteristics model based on machine learning is feasible to a certain extent and offers a novel perspective for studying sediment acoustic properties.展开更多
This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ra...This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.展开更多
This study proposes a numerically efficient technique for computing the far-field scattered by a spherical target placed near the seabed.The bottom is supposed to be a homogeneous liquid attenuating half-space.The tra...This study proposes a numerically efficient technique for computing the far-field scattered by a spherical target placed near the seabed.The bottom is supposed to be a homogeneous liquid attenuating half-space.The transmitter and receiver are situated at different points of a homogeneous water half-space.The distances between the transmitter,receiver,and object of interest are assumed to be much larger than the acoustic wavelength in water.The scattered far-field is ascertained using Hackman and Sammelmann’s general approach.The arising scattering coefficients of a sphere are assessed using the steepest descent approach.The branch cut contribution is also considered.The obtained formulas for the form-function can be used for acoustically rigid or soft scatterers,as well as elastic targets or spherical elastic shells.Numerical simulations are conducted for an acoustically rigid sphere.Asymptotic expressions for the scattering coefficients allow a decrease in the number of summands in the formula for the target strength and a significant reduction in computational time.展开更多
Tungsten is considered the most promising plasma-facing material for fusion reactors with exceptional performance.Under certain conditions,activated tungsten dust can be generated through plasma–wall interactions and...Tungsten is considered the most promising plasma-facing material for fusion reactors with exceptional performance.Under certain conditions,activated tungsten dust can be generated through plasma–wall interactions and released into the atmosphere.Activated tungsten migrates downward in the soil after atmospheric deposition.However,effective methods for evaluating the environmental dose of gamma rays emitted by activated tungsten are still lacking.Consequently,a method for evaluating the air-absorbed dose rate of activated tungsten dust was proposed considering soil attenuation.Key parameters including the mass attenuation coefficient and energy absorption build-up factor were determined for the main gamma ray energies of radionuclides within the activated tungsten dust.Additionally,air-absorbed dose rates were calculated by assuming that radioactive sources were located at different soil depths and radii.It was found that a soil depth of 50 cm significantly attenuated the environmental dose by 99.9%,whereas the air-absorbed dose rates within the horizontal distance of 500 cm accounted for 91%of the total dose rate.Therefore,this study underscored the importance of soil attenuation in environmental dose assessments,which must be carefully re-examined for the safety analysis of fusion reactors.展开更多
The wave attenuation performance of a floating breakwater is important in engineering applications.On the basis of potential flow theory,the analytical and simplified solutions of the transmission coefficient of a flo...The wave attenuation performance of a floating breakwater is important in engineering applications.On the basis of potential flow theory,the analytical and simplified solutions of the transmission coefficient of a floating breakwater are deduced via velocity potential decompositions and eigenfunction expansions.The effects of the floating breakwater configuration,working sea state and motion response on the wave attenuation performance are described,facilitating a deeper investigation into the wave attenuation mechanism of the breakwater.The results indicate that the width and draft of the breakwater,incident wavelength,and motion response significantly affect the transmission coefficient of the breakwater.The wave passability rate,α1(α1=0.5−2B/L),is defined to qualitatively explain why long-period waves are difficult to control and attenuate.The radiation effect caused by the motion of the floating breakwater on the transmission coefficient is relatively complex,and the wave attenuation efficiency of the breakwater can be improved by optimizing the motion response.The incident wavelength and breakwater width are selected as the control parameters,and transmission coefficient charts of the floating breakwater for two-dimensional conditions are drawn,providing technical guidance for the configuration selection and design of the floating breakwater.展开更多
The Salmonella pathogenicity islands(SPIs) play crucial roles in the progression of Salmonella infection. In this study, we constructed an improved λ Red homologous recombination system to prepare single and triple d...The Salmonella pathogenicity islands(SPIs) play crucial roles in the progression of Salmonella infection. In this study, we constructed an improved λ Red homologous recombination system to prepare single and triple deletion mutants of 3 prominent SPIs(SPI-1, 2, and 3), aiming at the impact of deletion on morphology, carbon source metabolism, adhesion and invasion capacity, in vivo colonization, and immune efficacy in chicks. Our examination revealed that the surface of the single deletion mutants(SM6ΔSPI1, ΔSPI2, and ΔSPI3) exhibited a more rugged texture and appeared to be enveloped in a layer of transparent colloid, whereas the morphology of the triple deletion mutant(SM6ΔSPI1&2&3) remained unaltered when compared to the parent strain. The carbon metabolic spectrum of the SPI mutants underwent profound alterations, with a notable and statistically significant modification observed in 30 out of 95 carbon sources, primarily carbohydrates(17 out of 30). Furthermore, the adhesion capacity of the 4 mutants to Caco-2 cells was significantly reduced when compared to that of the parent strain. Moreover,the invasion capacity of mutants SM6ΔSPI1 and SM6ΔSPI1&2&3 exhibited a substantial decrease, while it was enhanced to varying degrees for SM6ΔSPI3 and SM6ΔSPI2. Importantly, none of the 4 mutants induced any clinical symptoms in the chicks. However, they did transiently colonize the spleen and liver. Notably, the SM6ΔSPI1&2&3mutant was rapidly cleared from both the spleen and liver within 8 days post-infection and no notable pathological changes were observed in the organs. Additionally, when challenged, the mutants immunized groups displayed a significant increase in antibody levels and alterations in the CD3+CD4+ and CD3+CD8+ subpopulations, and the levels of IL-4 and IFN-γ cytokines in the SM6ΔSPI1&2&3 immunized chicken serum surpassed those of other groups.In summary, the successful construction of the 4 SPI mutants lays the groundwork for further exploration into the pathogenic(including metabolic) mechanisms of SPIs and the development of safe and effective live attenuated Salmonella vaccines or carriers.展开更多
Using SiC nanowires(SiCNWs)as the substrate,reflux-annealing and electrodeposition-carbonization were sequentially applied to integrate SiC nanowires with magnetic Fe_(3)O_(4) nanoparticles and amorphous nitrogen-dope...Using SiC nanowires(SiCNWs)as the substrate,reflux-annealing and electrodeposition-carbonization were sequentially applied to integrate SiC nanowires with magnetic Fe_(3)O_(4) nanoparticles and amorphous nitrogen-doped carbon(NC)for the fabrication of SiCNWs@Fe_(3)O_(4)@NC nanocomposite.Comprehensive testing and characterization of this product provided valuable insights into the im-pact of structural and composition changes on its electromagnetic wave absorption performances.The optimized SiCNWs@Fe_(3)O_(4)@NC nanocomposite,which has 30wt%filler content and a corresponding thickness of 2.03 mm,demonstrates exceptional performance with the minimum reflection loss(RL_(min))of-53.69 dB at 11.04 GHz and effective absorption bandwidth(EAB)of 4.4 GHz.The synergistic effects of the enhanced nanocomposite on electromagnetic wave absorption were thoroughly elucidated using the theories of multiple scattering,polarization relaxation,hysteresis loss,and eddy current loss.Furthermore,a multicomponent electromagnetic wave attenu-ation model was established,providing valuable insight into the design of novel absorbing materials and the enhancement of their absorp-tion performances.This research demonstrated the significant potential of the SiCNWs@Fe_(3)O_(4)@NC nanocomposite as a highly efficient electromagnetic wave-absorbing material with potential applications in various fields,such as stealth technology and microwave absorption.展开更多
文摘New techniques for controlling the amplitudes of two orthogonal linearly polarized light are presented. One is based on adjusting the DC voltage into a Mach–Zehnder modulator（MZM） to alter the amplitude of the light traveling on the slow axis of a fiber into the modulator with little changes in the fast-axis light amplitude.Another is based on adjusting the input DC voltages of a dual-polarization MZM operating in the reverse direction, which enables independent control of the two input orthogonal linearly polarized light amplitudes.Experimental results demonstrate that more than 30 dB difference in slow-and fast-axis light power can be obtained by controlling an MZM input DC voltage, and over 24 dB independent power adjustment for light traveling on the slow and fast axes into a dual-polarization MZM.
文摘The present technical paper outlines the details of the controlled blasting techniques used to optimize blasting pattern for excavation of hard rock near the Bhira Earthen Dam in Maharashtra,India.In this connection,a series of experimental blasts were conducted by adjusting various blast design parameters at project site.The safe charge weight per delay was kept between 0.125 and 0.375 kg.The outcomes of these experimental blasts were analyzed to recommend optimized blasting patterns and methods for the overall excavation process during actual blasting operations.Blast design parameters,including the maximum quantity of explosive per delay,hole depth,burden and spacing between holes were optimized by using a site-specific attenuation equation,taking into account the proximity of the dam and tunnel from the blasting area.Peak particle velocity(PPV)level of 10 mm/s and 50 mm/s respectively were adopted as the safe vibration level for ensuring safety of the Bhira Earthen Dam and the nearby tunnel from the adverse effects of blast vibrations by analyzing the dominant frequency of ground vibrations observed and also by reviewing various international standards.Frequency of the ground vibrations observed on the dam and tunnel from majority of the blasts was found to be more than 10 Hz and 50 Hz respectively.During the entire period of blasting,the blast vibrations were recorded to be far lower than the safe vibration level set for these structures.Maximum Vibration level of about 0.8 mm/s and 35 mm/s were observed on dam and tunnel respectively which are far lower than the safe vibration level adopted for these structures.Hence,the entire excavation work was completed successfully and safely,without endangering the safety of dam or tunnel.
基金the Research Grant of Kwangwoon University in 2024.
文摘Myocardial perfusion imaging(MPI),which uses single-photon emission computed tomography(SPECT),is a well-known estimating tool for medical diagnosis,employing the classification of images to show situations in coronary artery disease(CAD).The automatic classification of SPECT images for different techniques has achieved near-optimal accuracy when using convolutional neural networks(CNNs).This paper uses a SPECT classification framework with three steps:1)Image denoising,2)Attenuation correction,and 3)Image classification.Image denoising is done by a U-Net architecture that ensures effective image denoising.Attenuation correction is implemented by a convolution neural network model that can remove the attenuation that affects the feature extraction process of classification.Finally,a novel multi-scale diluted convolution(MSDC)network is proposed.It merges the features extracted in different scales and makes the model learn the features more efficiently.Three scales of filters with size 3×3 are used to extract features.All three steps are compared with state-of-the-art methods.The proposed denoising architecture ensures a high-quality image with the highest peak signal-to-noise ratio(PSNR)value of 39.7.The proposed classification method is compared with the five different CNN models,and the proposed method ensures better classification with an accuracy of 96%,precision of 87%,sensitivity of 87%,specificity of 89%,and F1-score of 87%.To demonstrate the importance of preprocessing,the classification model was analyzed without denoising and attenuation correction.
文摘In this paper,the failure caused by HRAM loads which were generated by high-speed projectile penetration,and protection technology of the fluid-filled structure were explored.A bubble was preset on the projectile trajectory in a fluid-filled structure.Based on the reflection and transmission phenomena of pressure waves at the gas-liquid interface and the compressibility characteristics of gases,a numerical analysis was conducted on the influence of preset bubble on projectile penetration and structural failure characteristics.The results indicate that the secondary water-entry impact phenomenon occurs when a preset bubble exists on the projectile trajectory,leading to the secondary water entry impact loads.The rarefaction waves reflected on the surface of the preset bubble cause the attenuation ratio of the initial impact pressure peak to reach 68.8%and the total specific impulse attenuation ratio to reach 48.6%.Furthermore,the larger the bubble,the faster the projectile,and the more obvious the attenuation effect.Moreover,due to the compressibility of the bubble,the global deformation attenuation ratio of the front and rear walls can reach over 80%.However,the larger the bubble size,the faster the projectile velocity,the smaller the local deformation attenuation effect of the rear wall,and the more severe the failure at the perforation of the rear wall.
基金Supported by the National Natural Science Foundation of China,No.82202185and Shanghai Science and Technology Development Foundation,No.22Y11911500.
文摘BACKGROUND Hepatic steatosis,characterized by fat accumulation in hepatocytes,can result from metabolic dysfunction-associated steatotic liver disease(MASLD),infections,alcoholism,chemotherapy,and toxins.MASLD is diagnosed via imaging or biopsy with metabolic criteria and may progress to metabolic dysfunction–asso-ciated steatohepatitis,potentially leading to fibrosis,cirrhosis,or cancer.The coexistence of hepatic steatosis with chronic hepatitis B(CHB)is mainly related to metabolic factors and increases mortality and cancer risks.As a noninvasive method,attenuation imaging(ATI)shows promise in quantifying liver fat,demonstrating strong correlation with liver biopsy.AIM To investigate the disparity of ATI for assessing biopsy-based hepatic steatosis in CHB patients and MASLD patients.METHODS The study enrolled 249 patients who underwent both ATI and liver biopsy,including 78 with CHB and 171 with MASLD.Hepatic steatosis was classified into grades S0 to S3 according to the proportion of fat cells present.Liver fibrosis was staged from 0 to 4 according to the meta-analysis of histological data in viral hepatitis scoring system.The diagnostic performance of attenuation coefficient(AC)values across different groups was compared for each grade of steatosis.Factors associated with the AC values were determined through linear regression analysis.A multivariate logistic regression model was established to predict≥S2 within the MASLD group.RESULTS In both the CHB and the MASLD groups,AC values increased significantly with higher steatosis grade(P<0.001).In the CHB group,the areas under the curve(AUCs)of AC for predicting steatosis grades≥S1,≥S2 and S3 were 0.918,0.960 and 0.987,respectively.In contrast,the MASLD group showed AUCs of 0.836,0.774,and 0.688 for the same steatosis grades.The diagnostic performance of AC for detecting≥S2 and S3 indicated significant differences between the two groups(both P<0.001).Multivariate linear regression analysis identified body mass index,trigly-cerides,and steatosis grade as significant factors for AC.When the steatosis grade is≥S2,it can progress to more serious liver conditions.A clinical model integrating blood biochemical parameters and AC was developed in the MASLD group to enhance the prediction of≥S2,achieving an AUC of 0.848.CONCLUSION The AC could effectively discriminate the degree of steatosis in both the CHB and MASLD groups.In the MASLD group,when combined with blood biochemical parameters,AC exhibited better predictive ability for moderate to severe steatosis.
文摘Imagine a future where a single vaccine could protect you from a multitude of influenza strains,offering broad immunity with minimal risk.This vision is now closer to reality,thanks to a recent study that harnesses the power of cellular proteins to create a new generation of live attenuated vaccines that outsmart flu’s relentless mutations.
基金supported by the Marine S&T Fund of Shandong Province for Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2021QNLM020001)the Major Scientificand Technological Projects of Shandong Energy Group(No.SNKJ2022A06-R23)+1 种基金the National Natural Science Foundation of China(No.42374164)the basic theoretical research of seismic wave imaging technology in complex oilfield of Changqing Oilfield Company(No.2023-10502)。
文摘The attenuation and anisotropy characteristics of real earth media give rise to amplitude loss and phase dispersion during seismic wave propagation.To address these effects on seismic imaging,viscoacoustic anisotropic wave equations expressed by the fractional Laplacian have been derived.However,the huge computational expense associated with multiple Fast Fourier transforms for solving these wave equations makes them unsuitable for industrial applications,especially in three dimensions.Therefore,we first derived a cost-effective pure-viscoacoustic wave equation expressed by the memory-variable in tilted transversely isotropic(TTI)media,based on the standard linear solid model.The newly derived wave equation featuring decoupled amplitude dissipation and phase dispersion terms,can be easily solved using the finite-difference method(FDM).Computational efficiency analyses demonstrate that wavefields simulated by our newly derived wave equation are more efficient compared to the previous pure-viscoacoustic TTI wave equations.The decoupling characteristics of the phase dispersion and amplitude dissipation of the proposed wave equation are illustrated in numerical tests.Additionally,we extend the newly derived wave equation to implement Q-compensated reverse time migration(RTM)in attenuating TTI media.Synthetic examples and field data test demonstrate that the proposed Qcompensated TTI RTM effectively migrate the effects of anisotropy and attenuation,providing highquality imaging results.
基金supported by the National Natural Science Foundation of China(Nos.12172014,U224126412332001)。
文摘In order to obtain a lower frequency band gap,this paper proposes a novel locally resonant meta-beam incorporating a softening nonlinear factor.An improved camroller structure is designed in this meta-beam to achieve the softening nonlinear stiffness of the local oscillators.Firstly,based on Hamilton's principle and the Galerkin method,the control equations for the coupled system are established.The theoretical band gap boundary is then derived with the modal analysis method.The theoretical results reveal that the band gap of the meta-beam shifts towards lower frequencies due to the presence of a softening nonlinear factor,distinguishing it from both linear metamaterials and those with hardening nonlinear characteristics.Then,the vibration attenuation characteristics of a finite size meta-beam are investigated through numerical calculation,and are verified by the theoretical results.Furthermore,parameter studies indicate that the reasonable design of the local oscillator parameters based on lightweight principles helps to achieve further broadband and efficient vibration reduction in the low-frequency region.Finally,a prototype of the meta-beam is fabricated and assembled,and the formations of the low-frequency band gap and the amplitude-induced band gap phenomenon are verified through experiments.
基金Project supported by the Natural Science Foundation of Henan Province,China(Grant No.242300420634)the Cultivative Plan of Henan University of Technology(Grant No.2024PYJH035)+3 种基金the Research Foundation for Advanced Talents of Henan University of Technology(Grant Nos.2022BS067 and 2022BS068)the National Natural Science Foundation of China(Grant No.62301211)the Key Research and Development and Promotion Special Project(Science and Technology Research)in Henan Province,China(Grant No.232102211068)the Innovative Funds Plan of Henan University of Technology(Grant No.2022ZKCJ15)。
文摘The surface of a high-speed vehicle reentering the atmosphere is surrounded by plasma sheath.Due to the influence of the inhomogeneous flow field around the vehicle,understanding the electromagnetic properties of the plasma sheath can be challenging.Obtaining the electron density of the plasma sheath is crucial for understanding and achieving plasma stealth of vehicles.In this work,the relationship between electromagnetic wave attenuation and electron density is deduced theoretically.The attenuation distribution along the propagation path is found to be proportional to the integral of the plasma electron density.This result is used to predict the electron density profile.Furthermore,the average electron density is obtained using a back-propagation neural network algorithm.Finally,the spatial distribution of the electron density can be determined from the average electron density and the normalized derivative of attenuation with respect to the propagation depth.Compared to traditional probe measurement methods,the proposed approach not only improves efficiency but also preserves the integrity of the plasma environment.
基金support this research during the 14th Fiveyear Plan period under contract number 2021QNLM020001the Major Scientific and Technological Projects of Shandong Energy Group under contract number SNKJ2022A06-R23+2 种基金the National Natural Science Foundation of China under contract number 42374164the Funds for Creative Research Groups of China under contract number 41821002the basic theoretical research of seismic wave imaging technology in complex oilfield of Changqing Oilfield Company under contract number 2023e10502.
文摘Amplitude dissipation and phase dispersion occur when seismic waves propagate in attenuated anisotropic media,affecting the quality of migration imaging.To compensate and correct for these effects,the fractional Laplacian pure viscoacoustic wave equation capable of producing stable and noise-free wavefields has been proposed and implemented in the Q-compensated reverse time migration(RTM).In addition,the second-order Taylor series expansion is usually adopted in the hybrid finite-difference/pseudo-spectral(HFDPS)strategy to solve spatially variable fractional Laplacian.However,during forward modeling and Q-compensated RTM,this HFDPS strategy requires 11 and 17 fast Fourier transforms(FFTs)per time step,respectively,leading to computational inefficiency.To improve computational efficiency,we introduce two high-efficiency HFDPS numerical modeling strategies based on asymptotic approximation and algebraic methods.Through the two strategies,the number of FFTs decreased from 11 to 6 and 5 per time step during forward modeling,respectively.Numerical examples demonstrate that wavefields simulated using the new numerical modeling strategies are accurate and highly efficient.Finally,these strategies are employed for implementing high-efficiency and stable Q-compensated RTM techniques in tilted transversely isotropic media,reducing the number of FFTs from 17 to 9 and 8 per time step,respectively,significantly improving computational efficiency.Synthetic data examples illustrate the effectiveness of the proposed Q-compensated RTM scheme in compensating amplitude dissipation and correcting phase distortion.
基金Project supported by the National Natural Science Foundation of China(Nos.U21A20430 and 12302202)the Hebei Natural Science Foundation of China(No.A2023210040)+1 种基金the Science and Technology Project of Hebei Education Department of China(No.BJ2025005)the Hebei Provincial Department of Human Resources and Social Security of China(No.C20220324)。
文摘In this paper,we theoretically study the Lamb wave in a multilayered piezoelectric semiconductor(PSC)plate,where each layer is an n-type PSC with the symmetry of transverse isotropy.Based on the extended Stroh formalism and dual-variable and position(DVP)method,the general solution of the coupled fields for the Lamb wave is derived,and then the dispersion equation is obtained by the application of the boundary conditions.First,the influence of semiconducting properties on the dispersion behavior of the Lamb wave in a single-layer PSC plate is analyzed.Then,the propagation characteristics of the Lamb wave in a sandwich plate are investigated in detail.The numerical results show that the wave speed and attenuation depend on the stacking sequence,layer thickness,and initial carrier density,the Lamb wave can propagate without a cut-off frequency in both the homogeneous and multilayer PSC plates due to the semiconducting properties,and the Lamb wave without attenuation can be achieved by carefully selecting the semiconductor property in the upper and lower layers.These new features could be very helpful as theoretical guidance for the design and performance optimization of PSC devices.
基金supported in part by National Natural Science Foundation of China(NSFC)under grant 42274139in part by the R&D Department of China National Petroleum Corporation(Investigations on fundamental experiments and advanced theoretical methods in geophysical prospecting applications,2022DQ0604-03).
文摘Seismic wavefields propagate through three-dimensional(3D)space,and their precise characterization is crucial for understanding subsurface structures.Traditional 2D algorithms,due to their limitations,are insufficient to fully represent three-dimensional wavefields.The classic 3D Radon transform algorithm assumes that the wavefield's propagation characteristics are consistent in all directions,which often does not hold true in complex underground media.To address this issue,we present an improved 3D three-parameter Radon algorithm that considers the wavefield variation with azimuth and provides a more accurate wavefield description.However,introducing new parameters to describe the azimuthal varia-tion also poses computational challenges.The new Radon transform operator involves five variables and cannot be simply decomposed into small matrices for efficient computation;instead,it requires large matrix multiplication and inversion operations,significantly increasing the computational load.To overcome this challenge,we have integrated the curvature and frequency parameters,simplifying all frequency operators to the same,thereby significantly improving computation efficiency.Furthermore,existing transform algorithms neglect the lateral variation of seismic amplitudes,leading to discrepancies between the estimated multiples and those in the data.To enhance the amplitude preservation of the algorithm,we employ orthogonal polynomial fitting to capture the amplitude spatial variation in 3D seismic data.Combining these improvements,we propose a fast,amplitude-preserving,3D three-parameter Radon transform algorithm.This algorithm not only enhances computational efficiency while maintaining the original wavefield characteristics,but also improves the representation of seismic data by increasing amplitude fidelity.We validated the algorithm in multiple attenuation using both synthetic and real seismic data.The results demonstrate that the new algorithm significantly improves both accuracy and computational efficiency,providing an effective tool for analyzing seismic wavefields in complex subsurface structures.
基金supported in part by the National Natural Science Foundation of China under Grant 41874143 and Grant 42374163in part by the Key Program of Natural Science Foundation of Sichuan Province of China under Grant 2023NSFSC0019in part by the Central Funds Guiding the Local Science and Technology Development under Grant 2024ZYD0124.
文摘Multiphase flow in porous rock is of great importance in the application of many industrial processes,including reservoir delineation,enhanced oil recovery,and CO_(2) sequestration.However,previous research typically investigated the dispersive behaviors when rock saturated with single or two-phase fluids and conducted limited studies on three-phase immiscible fluids.This study investigated the seismic dispersion,attenuation,and reflection features of seismic waves in three-phase immiscible fluidsaturated porous rocks.First,we proposed the calculation formulas of effective fluid modulus and effective fluid viscosity of multiphase immiscible fluids by taking into account the capillary pressure,reservoir wettability,and relative permeability simultaneously.Then,we analysed the frequencydependent behaviors of three-phase immiscible fluid-saturated porous rock under different fluid proportion cases using the Chapman multi-scale model.Next,the seismic responses are analysed using a four-layer model.The results indicate that the relative permeability,capillary pressure parameter,and fluid proportions are all significantly affect dispersion and attenuation.Comparative analyses demonstrate that dispersion and attenuation can be observed within the frequency range of seismic exploration for a lower capillary parameter a3 and higher oil content.Seismic responses reveal that the reflection features,such as travel time,seismic amplitude,and waveform of the bottom reflections of saturated rock and their underlying reflections are significantly dependent on fluid proportions and capillary parameters.For validation,the numerical results are further verified using the log data and real seismic data.This numerical analysis helps to further understand the wave propagation characteristics for a porous rock saturated with multiphase immiscible fluids.
基金funded by the Basic Scientific Fund for National Public Research Institutes of China(No.2022 S01)the National Natural Science Foundation of China(Nos.42176191,42049902,and U22A2012)+5 种基金the Shandong Provincial Natural Science Foundation,China(No.ZR2022YQ40)the National Key R&D Program of China(No.2021YFF0501202)the Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(No.SML2023 SP232)the Fundamental Research Funds for the Central Universities,Sun Yat-sen University(No.241gqb006)Data acquisition and sample collections were supported by the National Natural Science Foundation of China Open Research Cruise(Cruise No.NORC2021-02+NORC2021301)funded by the Shiptime Sharing Project of the National Natural Science Foundation of China。
文摘Accurate acquisition and prediction of acoustic parameters of seabed sediments are crucial in marine sound propagation research.While the relationship between sound velocity and physical properties of sediment has been extensively studied,there is still no consensus on the correlation between acoustic attenuation coefficient and sediment physical properties.Predicting the acoustic attenuation coefficient remains a challenging issue in sedimentary acoustic research.In this study,we propose a prediction method for the acoustic attenuation coefficient using machine learning algorithms,specifically the random forest(RF),support vector machine(SVR),and convolutional neural network(CNN)algorithms.We utilized the acoustic attenuation coefficient and sediment particle size data from 52 stations as training parameters,with the particle size parameters as the input feature matrix,and measured acoustic attenuation as the training label to validate the attenuation prediction model.Our results indicate that the error of the attenuation prediction model is small.Among the three models,the RF model exhibited the lowest prediction error,with a mean squared error of 0.8232,mean absolute error of 0.6613,and root mean squared error of 0.9073.Additionally,when we applied the models to predict the data collected at different times in the same region,we found that the models developed in this study also demonstrated a certain level of reliability in real prediction scenarios.Our approach demonstrates that constructing a sediment acoustic characteristics model based on machine learning is feasible to a certain extent and offers a novel perspective for studying sediment acoustic properties.
文摘This research directly supported the author’s thesis work in partial fulfilment of Master of Science in biology from the University of North Texas(United States)from August 1996 to September 1997.Two sites at Lake Ray Roberts,Denton County,Texas(United States)were examined and contrasted for productivity.The site located in the pelagic zone exhibited a slight,thermal gradient with no stratification,and a slightly stratified clinograde oxygen profile which is typical for summer-stratified eutrophic lakes.The site located in the shallow,littoral zone exhibited high,increasing turbidity with depth,marked by shallow light attenuation through the water column.Temperature was constant at every depth in the littoral site,with a slight,clinograde oxygen profile,typical for shallow,littoral areas subject to wind-induced mixing.Volume estimations of chlorophyll-α shows a strong presence in the euphotic zone,indicating photosynthesis occurs until approximately 2.2 m below the surface.The shallow,littoral site showed the basic signs of higher productivity than the open,pelagic site.
基金Supported by the Ministry of Science and Higher Education of the Russian Federation as a part of World-class Research Center Program:Advanced Digital Technologies(contract No.075-15-2022-312 dated 20 April 2022).
文摘This study proposes a numerically efficient technique for computing the far-field scattered by a spherical target placed near the seabed.The bottom is supposed to be a homogeneous liquid attenuating half-space.The transmitter and receiver are situated at different points of a homogeneous water half-space.The distances between the transmitter,receiver,and object of interest are assumed to be much larger than the acoustic wavelength in water.The scattered far-field is ascertained using Hackman and Sammelmann’s general approach.The arising scattering coefficients of a sphere are assessed using the steepest descent approach.The branch cut contribution is also considered.The obtained formulas for the form-function can be used for acoustically rigid or soft scatterers,as well as elastic targets or spherical elastic shells.Numerical simulations are conducted for an acoustically rigid sphere.Asymptotic expressions for the scattering coefficients allow a decrease in the number of summands in the formula for the target strength and a significant reduction in computational time.
基金supported by the National Natural Science Foundation of China(No.12375314)。
文摘Tungsten is considered the most promising plasma-facing material for fusion reactors with exceptional performance.Under certain conditions,activated tungsten dust can be generated through plasma–wall interactions and released into the atmosphere.Activated tungsten migrates downward in the soil after atmospheric deposition.However,effective methods for evaluating the environmental dose of gamma rays emitted by activated tungsten are still lacking.Consequently,a method for evaluating the air-absorbed dose rate of activated tungsten dust was proposed considering soil attenuation.Key parameters including the mass attenuation coefficient and energy absorption build-up factor were determined for the main gamma ray energies of radionuclides within the activated tungsten dust.Additionally,air-absorbed dose rates were calculated by assuming that radioactive sources were located at different soil depths and radii.It was found that a soil depth of 50 cm significantly attenuated the environmental dose by 99.9%,whereas the air-absorbed dose rates within the horizontal distance of 500 cm accounted for 91%of the total dose rate.Therefore,this study underscored the importance of soil attenuation in environmental dose assessments,which must be carefully re-examined for the safety analysis of fusion reactors.
基金supported by the China National Funds for Distinguished Young Scientists(Grant No.52025112)the National Natural Science Foundation of China(Grant Nos.52331011 and 52301322)the Jiangsu Provincial Natural Science Foundation(Grant No.BK20220653).
文摘The wave attenuation performance of a floating breakwater is important in engineering applications.On the basis of potential flow theory,the analytical and simplified solutions of the transmission coefficient of a floating breakwater are deduced via velocity potential decompositions and eigenfunction expansions.The effects of the floating breakwater configuration,working sea state and motion response on the wave attenuation performance are described,facilitating a deeper investigation into the wave attenuation mechanism of the breakwater.The results indicate that the width and draft of the breakwater,incident wavelength,and motion response significantly affect the transmission coefficient of the breakwater.The wave passability rate,α1(α1=0.5−2B/L),is defined to qualitatively explain why long-period waves are difficult to control and attenuate.The radiation effect caused by the motion of the floating breakwater on the transmission coefficient is relatively complex,and the wave attenuation efficiency of the breakwater can be improved by optimizing the motion response.The incident wavelength and breakwater width are selected as the control parameters,and transmission coefficient charts of the floating breakwater for two-dimensional conditions are drawn,providing technical guidance for the configuration selection and design of the floating breakwater.
基金supported by the National KeyR&DProgramof China(2022YFF0710500)the National Natural Science Foundation of China(32172853 and 32373013)the Central Public-interest Scientific Institution Basal Research Fund,China(1610302022001).
文摘The Salmonella pathogenicity islands(SPIs) play crucial roles in the progression of Salmonella infection. In this study, we constructed an improved λ Red homologous recombination system to prepare single and triple deletion mutants of 3 prominent SPIs(SPI-1, 2, and 3), aiming at the impact of deletion on morphology, carbon source metabolism, adhesion and invasion capacity, in vivo colonization, and immune efficacy in chicks. Our examination revealed that the surface of the single deletion mutants(SM6ΔSPI1, ΔSPI2, and ΔSPI3) exhibited a more rugged texture and appeared to be enveloped in a layer of transparent colloid, whereas the morphology of the triple deletion mutant(SM6ΔSPI1&2&3) remained unaltered when compared to the parent strain. The carbon metabolic spectrum of the SPI mutants underwent profound alterations, with a notable and statistically significant modification observed in 30 out of 95 carbon sources, primarily carbohydrates(17 out of 30). Furthermore, the adhesion capacity of the 4 mutants to Caco-2 cells was significantly reduced when compared to that of the parent strain. Moreover,the invasion capacity of mutants SM6ΔSPI1 and SM6ΔSPI1&2&3 exhibited a substantial decrease, while it was enhanced to varying degrees for SM6ΔSPI3 and SM6ΔSPI2. Importantly, none of the 4 mutants induced any clinical symptoms in the chicks. However, they did transiently colonize the spleen and liver. Notably, the SM6ΔSPI1&2&3mutant was rapidly cleared from both the spleen and liver within 8 days post-infection and no notable pathological changes were observed in the organs. Additionally, when challenged, the mutants immunized groups displayed a significant increase in antibody levels and alterations in the CD3+CD4+ and CD3+CD8+ subpopulations, and the levels of IL-4 and IFN-γ cytokines in the SM6ΔSPI1&2&3 immunized chicken serum surpassed those of other groups.In summary, the successful construction of the 4 SPI mutants lays the groundwork for further exploration into the pathogenic(including metabolic) mechanisms of SPIs and the development of safe and effective live attenuated Salmonella vaccines or carriers.
基金supported by the National Natural Science Foundation of China(Nos. 52072196, 52002200, 52102106,52202262, 22379081, and 22379080)Major Basic Research Program of Natural Science Foundation of Shandong Province,China(No. ZR2020ZD09)+2 种基金Natural Science Foundation of Shandong Province,China(Nos. ZR2020QE063, ZR2022ME090, and ZR2023QE059)supported by the Visiting Scholar Fellowship Funding for Teachers in Shandong Province’s General Undergraduate Institutionsthe Visiting Research Fund for Teachers of Ordinary Undergraduate Universities of Shand ong Province
文摘Using SiC nanowires(SiCNWs)as the substrate,reflux-annealing and electrodeposition-carbonization were sequentially applied to integrate SiC nanowires with magnetic Fe_(3)O_(4) nanoparticles and amorphous nitrogen-doped carbon(NC)for the fabrication of SiCNWs@Fe_(3)O_(4)@NC nanocomposite.Comprehensive testing and characterization of this product provided valuable insights into the im-pact of structural and composition changes on its electromagnetic wave absorption performances.The optimized SiCNWs@Fe_(3)O_(4)@NC nanocomposite,which has 30wt%filler content and a corresponding thickness of 2.03 mm,demonstrates exceptional performance with the minimum reflection loss(RL_(min))of-53.69 dB at 11.04 GHz and effective absorption bandwidth(EAB)of 4.4 GHz.The synergistic effects of the enhanced nanocomposite on electromagnetic wave absorption were thoroughly elucidated using the theories of multiple scattering,polarization relaxation,hysteresis loss,and eddy current loss.Furthermore,a multicomponent electromagnetic wave attenu-ation model was established,providing valuable insight into the design of novel absorbing materials and the enhancement of their absorp-tion performances.This research demonstrated the significant potential of the SiCNWs@Fe_(3)O_(4)@NC nanocomposite as a highly efficient electromagnetic wave-absorbing material with potential applications in various fields,such as stealth technology and microwave absorption.
