We present new data on the^(63)Cu(γ,n)cross-section studied using a quasi-monochromatic and energy-tunableγbeam produced at the Shanghai Laser Electron Gamma Source to resolve the long-standing discrepancy between e...We present new data on the^(63)Cu(γ,n)cross-section studied using a quasi-monochromatic and energy-tunableγbeam produced at the Shanghai Laser Electron Gamma Source to resolve the long-standing discrepancy between existing measurements and evaluations of this cross-section.Using an unfolding iteration method,^(63)Cu(γ,n)data were obtained with an uncertainty of less than 4%,and the inconsistencies between the available experimental data were discussed.Theγ-ray strength function of^(63)Cu(γ,n)was successfully extracted as an experimental constraint.We further calculated the cross-section of the radiative neutron capture reaction^(62)Cu(n,γ)using the TALYS code.Our calculation method enables the extraction of(n,γ)cross-sections for unstable nuclides.展开更多
Reduction of the radar cross-section(RCS) is the key to stealth technology. To improve the RCS reduction effect of the designed checkerboard metasurface and overcome the limitation of thinlayer plasma in RCS reduction...Reduction of the radar cross-section(RCS) is the key to stealth technology. To improve the RCS reduction effect of the designed checkerboard metasurface and overcome the limitation of thinlayer plasma in RCS reduction technology, a double-layer-plasma-based metasurface—composed of a checkerboard metasurface, a double-layer plasma and an air gap between them—was investigated. Based on the principle of backscattering cancellation, we designed a checkerboard metasurface composed of different artificial magnetic conductor units;the checkerboard metasurface can reflect vertically incident electromagnetic(EM) waves in four different inclined directions to reduce the RCS. Full-wave simulations confirm that the doublelayer-plasma-based metasurface can improve the RCS reduction effect of the metasurface and the plasma. This is because in a band lower than the working band of the metasurface, the RCS reduction effect is mainly improved by the plasma layer. In the working band of the metasurface,impedance mismatching between the air gap and first plasma layer and between first and second plasma layers cause the scattered waves to become more dispersed, so the propagation path of the EM waves in the plasma becomes longer, increasing the absorption of the EM waves by the plasma. Thus, the RCS reduction effect is enhanced. The double-layer-plasma-based metasurface can be insensitive to the polarization of the incoming EM waves, and can also maintain a satisfactory RCS reduction band when the incident waves are oblique.展开更多
This paper investigates a wireless powered and backscattering enabled sensor network based on the non-linear energy harvesting model, where the power beacon(PB) delivers energy signals to wireless sensors to enable th...This paper investigates a wireless powered and backscattering enabled sensor network based on the non-linear energy harvesting model, where the power beacon(PB) delivers energy signals to wireless sensors to enable their passive backscattering and active transmission to the access point(AP). We propose an efficient time scheduling scheme for network performance enhancement, based on which each sensor can always harvest energy from the PB over the entire block except its time slots allocated for passive and active information delivery. Considering the PB and wireless sensors are from two selfish service providers, we use the Stackelberg game to model the energy interaction among them. To address the non-convexity of the leader-level problem, we propose to decompose the original problem into two subproblems and solve them iteratively in an alternating manner. Specifically, the successive convex approximation, semi-definite relaxation(SDR) and variable substitution techniques are applied to find a nearoptimal solution. To evaluate the performance loss caused by the interaction between two providers, we further investigate the social welfare maximization problem. Numerical results demonstrate that compared to the benchmark schemes, the proposed scheme can achieve up to 35.4% and 38.7% utility gain for the leader and the follower, respectively.展开更多
Interest has recently emerged in potential applications of(n,2n)reactions of unstable nuclei.Challenges have arisen because of the scarcity of experimental cross-sectional data.This study aims to predict the(n,2n)reac...Interest has recently emerged in potential applications of(n,2n)reactions of unstable nuclei.Challenges have arisen because of the scarcity of experimental cross-sectional data.This study aims to predict the(n,2n)reaction cross-section of long-lived fission products based on a tensor model.This tensor model is an extension of the collaborative filtering algorithm used for nuclear data.It is based on tensor decomposition and completion to predict(n,2n)reaction cross-sections;the corresponding EXFOR data are applied as training data.The reliability of the proposed tensor model was validated by comparing the calculations with data from EXFOR and different databases.Predictions were made for long-lived fission products such as^(60)Co,^(79)Se,^(93)Zr,^(107)P,^(126)Sn,and^(137)Cs,which provide a predicted energy range to effectively transmute long-lived fission products into shorter-lived or less radioactive isotopes.This method could be a powerful tool for completing(n,2n)reaction cross-sectional data and shows the possibility of selective transmutation of nuclear waste.展开更多
Based on the unified Hauser–Feshbach and exciton model,which can describe the particle emission processes between discrete energy levels with energy,angular momentum,and parity conservations,a statistical theory of l...Based on the unified Hauser–Feshbach and exciton model,which can describe the particle emission processes between discrete energy levels with energy,angular momentum,and parity conservations,a statistical theory of light nucleus reaction(STLN)is developed to calculate the double-differential cross-sections of the outgoing neutron and light charged particles for the proton-induced^(6) Li reaction.A significant difference is observed between the p+^(6) Li and p+^(7) Li reactions owing to the discrepancies in the energy-level structures of the targets.The reaction channels,including sequential and simultaneous emission processes,are analyzed in detail.Taking the double-differential cross-sections of the outgoing proton as an example,the influence of contaminations(such as^(1) H,^(7)Li,^(12)C,and^(16)O)on the target is identified in terms of the kinetic energy of the first emitted particles.The optical potential parameters of the proton are obtained by fitting the elastic scattering differential cross-sections.The calculated total double-differential cross-sections of the outgoing proton and deuteron at E_(p)=14 MeV agree well with the experimental data for different outgoing angles.Simultaneously,the mixed double differential cross-sections of^(3) He andαare in good agreement with the measurements.The agreement between the measured data and calculated results indicates that the two-body and three-body breakup reactions need to be considered,and the pre-equilibrium reaction mechanism dominates the reaction processes.Based on the STLN model,a PLUNF code for the p+^(6) Li reaction is developed to obtain an ENDF-6-formatted file of the double-differential cross-sections of the nucleon and light composite charged particles.展开更多
Based on the effective medium approximation theory of composites, the whitecap-covered sea surface is treated as a medium layer of dense seawater droplets and air. Two electromagnetic scattering models of randomly rou...Based on the effective medium approximation theory of composites, the whitecap-covered sea surface is treated as a medium layer of dense seawater droplets and air. Two electromagnetic scattering models of randomly rough surface are applied to the investigation of microwave backscattering of breaking waves driven by strong wind. The shapes of seawater droplets are considered by calculating the effective dielectric constant of the whitecap layer. The responses of seawater droplets shapes, such as sphere and ellipsoid, to the backscattering coefficient are discussed. Numerical results of the models are in good agreement with the experimental measurements of horizontally and vertically polarized backscattering at microwave frequency 13.9GHz and different incidence angles.展开更多
The elliptical cross-section ogive-nose projectile(ECOP) has recently attracted attention because it is well suited to the flattened shape of earth-penetrating weapons. However, the penetration performance of ECOPs ha...The elliptical cross-section ogive-nose projectile(ECOP) has recently attracted attention because it is well suited to the flattened shape of earth-penetrating weapons. However, the penetration performance of ECOPs has not been completely understood. The objective of this study was to investigate the penetration performance of ECOPs into concrete targets using a theoretical method. A general geometric model of ECOPs was introduced, and closed-form penetration equations were derived according to the dynamic cavity-expansion theory. The model was validated by comparing the predicted penetration depths with test data, and the maximum deviation was 15.8%. The increment in the penetration depth of the ECOP was evaluated using the proposed model, and the effect of the majoreminor axis ratio on the increment was examined. Additionally, the mechanism of the penetration-depth increment was investigated with respect to the caliber radius head, axial stress, and resistance.展开更多
Background:Since the trauma knowledge of trauma providers correlates with the outcomes of injured patients,this study aims to assess the socio-demographic characteristics and levels of trauma knowledge of trainees in ...Background:Since the trauma knowledge of trauma providers correlates with the outcomes of injured patients,this study aims to assess the socio-demographic characteristics and levels of trauma knowledge of trainees in the China trauma care training(CTCT)program in addition to their post-course test results to provide support for the development of trauma care training programs and trauma systems in China.Methods:A cross-sectional study was conducted by collecting demographic information,hospital-related information and trauma knowledge of the trainees from 19 regions in China.All participants were assessed by questionnaires collecting the socio-demographic data,the trauma care knowledge levels and the information of the hospitals.Results:There were 955 males(78.9%)and 256 females(21.1%)enrolled.Among them,854 were physicians(70.5%),357 were registered nurses(29.5%).In addition,64 of them also played an administrative role in the hospitals(5.3%).The score of the trainees who were members of the emergency department staff(72.59±14.13)was the highest among the scores of all the personnel surveyed,followed by those of the trainees from the intensive care unit(ICU)(71.17±12.72),trauma surgery department(67.26±13.81),orthopedics department(70.36±14.48),general surgery department(69.91±14.79)and other departments(69.93±16.91),P=0.031.The score of the professors(73.09±15.05)was higher than those of the associate professors(72.40±14.71),lecturers(70.07±14.25)and teaching assistants(67.58±15.16),P<0.0001.The score of the individuals who attended experts’trauma lectures(72.22±14.45)was higher than that of individuals who did not attend the lectures(69.33±15.17),P=0.001.The mean scores before and after the training were 71.02±14.82 and 84.24±13.77,respectively,P<0.001.The mean score of trauma knowledge after the training of trainees from different provinces and with different educational backgrounds was higher than that before the training,with a statistically significant difference(P<0.05).Conclusions:The level of trauma knowledge of trauma care providers was associated with their department,professional position and previous participation in related academic conferences.Trauma care experience and participation in academic lectures and training program including CTCT may effectively improve individuals’level of trauma knowledge.展开更多
A full aperture backscattering light diagnostic system （FABLDS） implemented on the Shen Guang-Ⅲ Prototype Laser Facility is described in the paper. FABLDS measures both stimulated brillouin scattering （SBS） and s...A full aperture backscattering light diagnostic system （FABLDS） implemented on the Shen Guang-Ⅲ Prototype Laser Facility is described in the paper. FABLDS measures both stimulated brillouin scattering （SBS） and stimulated Raman scattering （SRS） with a series of optical detectors. Energy sensors record the integrated energy, and streak cameras coupled with spectrometers measure the temporal spectrum of the backscattering light. This paper provides an overview of the FABLDS and detailed descriptions of the optical path. Special components, including off-axis parabolic mirror, spatial filter and optical light filters, are incorporated along the beam path for purifying the scattering light. Several hohlraum targets were employed, including C5H12 gas-filled targets and empty targets in the experiments. Results presented in the paper indicate that the fraction of backscatter light has been obviously shrinked when the laser is smoothed by continuous phase plates （CPP）.展开更多
The backscattering signal, which arises from the pulsed laser traveling through water, has limited the lidar system sensitivity and underwater target contrast. The transmitted optical carrier is modulated to be ultras...The backscattering signal, which arises from the pulsed laser traveling through water, has limited the lidar system sensitivity and underwater target contrast. The transmitted optical carrier is modulated to be ultrashort pulsed laser and it is effective to suppress the backscattering to adopt the coherent detection technology by identifying the modulation envelope. A nonstationary light field is formed in seawater by the ultrashort pulsed laser. The inherent relationship between the nonstationary light field formed by modulated lidar and the stationary light field formed by conventional lidar was discussed and the backscattering light model of the stationary light field for the ultrashort pulsed laser was proposed. The backscattering signal in modulated lidar system was processed and analyzed in the frequency domain on the basis of the model.展开更多
Objective To investigate whether ABO blood groups is associated with the severity of coronary artery disease(CAD). Methods Between January 2015 and December 2017, 1425 first diagnosed CAD patients confirmed by selecti...Objective To investigate whether ABO blood groups is associated with the severity of coronary artery disease(CAD). Methods Between January 2015 and December 2017, 1425 first diagnosed CAD patients confirmed by selective coronary angiography were recruited into this cross-sectional study, and their baseline characteristics, ABO blood groups, Gensini score were collected. Multiple linear regression analysis was performed to test the association between the severity of CAD and ABO blood groups. Results The Gensini score was significantly higher in the blood group A than in the non-A groups(41.2 ± 32 vs. 38 ± 27;P = 0.026). After adjusting for age, male, smoking, family history of CAD, hypertension, diabetes mellitus and hypercholesterolemia, multivariate linear regression indicated that blood group A was associated with the severity of CAD(β= 3.298, 95% CI: 0.91–6.505, P = 0.044). In diabetes group, A blood type was also associated with increased Gensini score(P = 0.02) after adjusting for age, male, family history of CAD, hypercholesterolemia, smoking and hypertension. Conclusion In this cross-sectional study, the data indicated that blood group A was an independent risk factor of severity of CAD in Chinese population and Chinese patients with type 2 diabetes.展开更多
Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadwa...Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadways. The experimental results show that the influence of blast load on adjacent roadway has a good relationship with the cross-section of roadway. The expansion distance of precrack existed in circular, arch-wall, rectangular roadway is respectively 1.76, 1.61 and 0 cm under blast load.At the same time, the direct-blast side of rectangular roadway has more obvious damage compared with circular and arch-wall roadway. It explains that plane reflects more stress wave than arc, so that it exerts more tensile failure in the direct-blast side, which leads to less stress wave diffracting to the precrack in the back-blast side. When the precrack extends, higher value dynamic stress intensity factor in circular roadway works longer than that of arch-wall roadway. Indirectly, it explains that plane's weakening function on stress wave is significantly stronger than arc. Stress wave brings about self-evident influence on the upper and bottom endpoints of the rectangular roadway, and it respectively extends 1.03, 2.06 cm along the line link direction of the center of the blasthole and the upper and bottom endpoints on the right wall.展开更多
Analyzing the mass of behind-armor debris (BAD) generated by Rolled Homogeneous Armor (RHA) subjected to normal penetration of variable cross-section Explosively Formed Projectile (EFP) is the purpose of this paper. S...Analyzing the mass of behind-armor debris (BAD) generated by Rolled Homogeneous Armor (RHA) subjected to normal penetration of variable cross-section Explosively Formed Projectile (EFP) is the purpose of this paper. So theoretical analysis, numerical simulation and experimental data are combined to analyze the influence of variable cross-section characteristic on the time history of crater radius. Moreover the relationships between time history of crater radius (as well as mass of BAD) and the thickness of RHA (from 30mm to 70 mm) and the impact velocity of EFP (1650 m/s to 1860 m/s) are also investigated. The results indicate that: 1) being compared to the variable cross-section characteristic is ignored, the theoretical time history of crater radius is in better agreement with the simulation results when the variable cross-section characteristic is considered;2) being compared to the other three conditions of plug, the theoretical mass of BAD is in the best agreement with the simulation results when the shape of plug is frustum of a cone and the angle between generatrix and bottom is 45- and the axial length of mushroom is considered.展开更多
Prediction models were proposed to estimate the reduced Townsend ionization coefficient and ionization cross-section.A shape function of the reduced Townsend ionization coefficient curves was derived from the ionizati...Prediction models were proposed to estimate the reduced Townsend ionization coefficient and ionization cross-section.A shape function of the reduced Townsend ionization coefficient curves was derived from the ionization collision probability model.The function had three parameters:the first ionization potential energy,A_(α),and B_(α).A_(α)and B_(α)were related to the molecule symmetry and size.The polarization of molecules could characterize the molecule symmetry.The multi-layer molecular cross-section(MMCS)was proposed to describe the contributions of electrons and molecule radius on different molecule surfaces to collisions.A prediction model of the ionization cross-section was also proposed based on Aα.The molecule parameters were calculated by the Becke3–Lee–Yang–Parr(B3LYP)method and the 6–311G**basis set.We used available data of 30 and 23 gases,respectively,to build the prediction models of reduced Townsend ionization coefficients and ionization cross-sections.The relationships between the molecular parameters Aαand Bαand the ionization cross-section were built up via nonlinear fittings.The determination coefficients R^(2)of Aα,Bα,and the ionization cross-section were 0.877,0.887,and 0.838,respectively.The results showed that the accuracy of models was positively correlated with the molecule symmetry and reduced electric field.This was mainly related to the accuracy of the MMCS model in predicting Aα.The MMCS model needed to be improved to describe the collision direction selectivity caused by the molecule asymmetry.Under a high reduced electric field,that error of Aαhad less influence on the prediction results.However,the prediction results for single atoms with high symmetry were poor.This may be due to the absolute error of the model close to single atoms’reduced Townsend ionization coefficients.The models could provide the basis for gas insulation prediction and discharge calculations,especially for symmetric molecules under a high electric field.展开更多
Out-of-plane microneedle structures are widely used in various applications such as transcutaneous drug delivery and neural signal recording for brain machine interface.This work presents a novel but simple method to ...Out-of-plane microneedle structures are widely used in various applications such as transcutaneous drug delivery and neural signal recording for brain machine interface.This work presents a novel but simple method to fabricate high-density silicon(Si)microneedle arrays with various heights and diverse cross-sectional shapes depending on photomask pattern designs.The proposed fabrication method is composed of a single photolithography and two subsequent deep reactive ion etching(DRIE)steps.First,a photoresist layer was patterned on a Si substrate to define areas to be etched,which will eventually determine the final location and shape of each individual microneedle.Then,the 1st DRIE step created deep trenches with a highly anisotropic etching of the Si substrate.Subsequently,the photoresist was removed for more isotropic etching;the 2nd DRIE isolated and sharpened microneedles from the predefined trench structures.Depending on diverse photomask designs,the 2nd DRIE formed arrays of microneedles that have various height distributions,as well as diverse cross-sectional shapes across the substrate.With these simple steps,high-aspect ratio microneedles were created in the high density of up to 625 microneedles mm^(-2)on a Si wafer.Insertion tests showed a small force as low as~172μN/microneedle is required for microneedle arrays to penetrate the dura mater of a mouse brain.To demonstrate a feasibility of drug delivery application,we also implemented silk microneedle arrays using molding processes.The fabrication method of the present study is expected to be broadly applicable to create microneedle structures for drug delivery,neuroprosthetic devices,and so on.展开更多
We have measured the cross-section ratios of helium induced by Cq＋ and Oq＋ （q = 1-4） in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method ...We have measured the cross-section ratios of helium induced by Cq＋ and Oq＋ （q = 1-4） in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections （SI, SC, SLSI, and DLSI）, total double-ionization cross-sections （DI, DC, TI, SLDI, and DLDI） and cross-sections of every process （SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI）, which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly.展开更多
To predict the soft error rate for applications, it is essential to study the energy dependence of the single-event-upset(SEU) cross-section. In this work, we present a direct measurement of the SEU cross-section with...To predict the soft error rate for applications, it is essential to study the energy dependence of the single-event-upset(SEU) cross-section. In this work, we present a direct measurement of the SEU cross-section with the Back-n white neutron source at the China Spallation Neutron Source. The measured cross section is consistent with the soft error data from the manufacturer and the result suggests that the threshold energy of the SEU is about 0.5 Me V, which confirms the statement in Iwashita’s report that the threshold energy for neutron soft error is much below that of the(n, α) cross-section of silicon.In addition, an index of the effective neutron energy is suggested to characterize the similarity between a spallation neutron beam and the standard atmospheric neutron environment.展开更多
Cross-sections of the(n,2n) reactions for neodymium(Nd) isotopes induced by 14 MeV neutrons were measured in this work by using the activation and relative methods. The measured cross-sections of the ^(150)Nd(n,2n)^(1...Cross-sections of the(n,2n) reactions for neodymium(Nd) isotopes induced by 14 MeV neutrons were measured in this work by using the activation and relative methods. The measured cross-sections of the ^(150)Nd(n,2n)^(149)Nd,^(148)Nd(n,2n)^(147)Nd, and ^(142)Nd(n,2 n)^(141)Nd reactions were 1854 ± 81, 1789 ± 119, and 1559 ± 98 mb, respectively, at a neutron energy of 14.2 ± 0.2 MeV,and 1485 ± 74, 1726 ± 85, and 1670 ± 119 mb, respectively, at 14.9 ± 0.2 MeV. The results were compared with the experimental values from the reported literature, with the evaluated data from the ENDF/B-VII.1, CENDL-3.1, and JENDL-4.0 libraries, and with the curves calculated by the Talys-1.8 code.展开更多
In this study,we present a new method for the indirect integration of beam charges in external beam proton-induced X-ray emission and proton-induced c-ray emission(PIXE–PIGE) analysis.We recorded proton spectra backs...In this study,we present a new method for the indirect integration of beam charges in external beam proton-induced X-ray emission and proton-induced c-ray emission(PIXE–PIGE) analysis.We recorded proton spectra backscattered by a Kapton film extraction window in different sample situations and under different beam currents.We also simulated backscattering spectra using the simulation of backscattering spectra program(SIMNRA).We determined that in a specific geometrical arrangement,different sample situations did not significantly affect factor C_Q(the ratio between integral backscattering proton counts and integral beam charges).We also studied the reproducibility and beam current dependence of factor C_Q.The statistic factor of C_Q was28.95 ± 0.6 kilo counts/l C,with a relative standard deviation of 2.0 %.Significantly,in external beam PIXE–PIGE analysis,we were able to calculate beam charge integration from the integral backscattering proton counts in an energy region.展开更多
Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly ...Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8＋δ （Bi2212） and YBa2Cu3O7-x （YBCO） along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the （100） plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a （110） surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.展开更多
基金supported by the National Key Research and Development Program(Nos.2023YFA1606901 and 2022YFA1602400)National Natural Science Foundation of China(Nos.U2230133,12275338,and 12388102)Open Fund of the CIAE Key Laboratory of Nuclear Data(No.JCKY2022201C152).
文摘We present new data on the^(63)Cu(γ,n)cross-section studied using a quasi-monochromatic and energy-tunableγbeam produced at the Shanghai Laser Electron Gamma Source to resolve the long-standing discrepancy between existing measurements and evaluations of this cross-section.Using an unfolding iteration method,^(63)Cu(γ,n)data were obtained with an uncertainty of less than 4%,and the inconsistencies between the available experimental data were discussed.Theγ-ray strength function of^(63)Cu(γ,n)was successfully extracted as an experimental constraint.We further calculated the cross-section of the radiative neutron capture reaction^(62)Cu(n,γ)using the TALYS code.Our calculation method enables the extraction of(n,γ)cross-sections for unstable nuclides.
基金supported in part by the China Postdoctoral Science Foundation (No. 2020M673341)in part by the Natural Science Basic Research Program of Shaanxi (No.2023-JC-YB-549)+1 种基金in part by National Natural Science Foundation of China (Nos. 62371375 and 62371372)Innovation Capability Support Program of Shaanxi (No. 2022TD-37)。
文摘Reduction of the radar cross-section(RCS) is the key to stealth technology. To improve the RCS reduction effect of the designed checkerboard metasurface and overcome the limitation of thinlayer plasma in RCS reduction technology, a double-layer-plasma-based metasurface—composed of a checkerboard metasurface, a double-layer plasma and an air gap between them—was investigated. Based on the principle of backscattering cancellation, we designed a checkerboard metasurface composed of different artificial magnetic conductor units;the checkerboard metasurface can reflect vertically incident electromagnetic(EM) waves in four different inclined directions to reduce the RCS. Full-wave simulations confirm that the doublelayer-plasma-based metasurface can improve the RCS reduction effect of the metasurface and the plasma. This is because in a band lower than the working band of the metasurface, the RCS reduction effect is mainly improved by the plasma layer. In the working band of the metasurface,impedance mismatching between the air gap and first plasma layer and between first and second plasma layers cause the scattered waves to become more dispersed, so the propagation path of the EM waves in the plasma becomes longer, increasing the absorption of the EM waves by the plasma. Thus, the RCS reduction effect is enhanced. The double-layer-plasma-based metasurface can be insensitive to the polarization of the incoming EM waves, and can also maintain a satisfactory RCS reduction band when the incident waves are oblique.
基金supported by National Natural Science Foundation of China(No.61901229 and No.62071242)the Project of Jiangsu Engineering Research Center of Novel Optical Fiber Technology and Communication Network(No.SDGC2234)+1 种基金the Open Research Project of Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology(No.NJUZDS2022-008)the Post-Doctoral Research Supporting Program of Jiangsu Province(No.SBH20).
文摘This paper investigates a wireless powered and backscattering enabled sensor network based on the non-linear energy harvesting model, where the power beacon(PB) delivers energy signals to wireless sensors to enable their passive backscattering and active transmission to the access point(AP). We propose an efficient time scheduling scheme for network performance enhancement, based on which each sensor can always harvest energy from the PB over the entire block except its time slots allocated for passive and active information delivery. Considering the PB and wireless sensors are from two selfish service providers, we use the Stackelberg game to model the energy interaction among them. To address the non-convexity of the leader-level problem, we propose to decompose the original problem into two subproblems and solve them iteratively in an alternating manner. Specifically, the successive convex approximation, semi-definite relaxation(SDR) and variable substitution techniques are applied to find a nearoptimal solution. To evaluate the performance loss caused by the interaction between two providers, we further investigate the social welfare maximization problem. Numerical results demonstrate that compared to the benchmark schemes, the proposed scheme can achieve up to 35.4% and 38.7% utility gain for the leader and the follower, respectively.
基金supported by the Key Laboratory of Nuclear Data foundation(No.JCKY2022201C157)。
文摘Interest has recently emerged in potential applications of(n,2n)reactions of unstable nuclei.Challenges have arisen because of the scarcity of experimental cross-sectional data.This study aims to predict the(n,2n)reaction cross-section of long-lived fission products based on a tensor model.This tensor model is an extension of the collaborative filtering algorithm used for nuclear data.It is based on tensor decomposition and completion to predict(n,2n)reaction cross-sections;the corresponding EXFOR data are applied as training data.The reliability of the proposed tensor model was validated by comparing the calculations with data from EXFOR and different databases.Predictions were made for long-lived fission products such as^(60)Co,^(79)Se,^(93)Zr,^(107)P,^(126)Sn,and^(137)Cs,which provide a predicted energy range to effectively transmute long-lived fission products into shorter-lived or less radioactive isotopes.This method could be a powerful tool for completing(n,2n)reaction cross-sectional data and shows the possibility of selective transmutation of nuclear waste.
基金supported by the National Natural Science Foundation of China(No.12065003)the Guangxi Key R&D Project(2023AB07029)+1 种基金the Scientific Research and Technology Development Project of Guilin(20210104-2)the Central Government Guides Local Scientific and Technological Development Funds of China(Guike ZY22096024)。
文摘Based on the unified Hauser–Feshbach and exciton model,which can describe the particle emission processes between discrete energy levels with energy,angular momentum,and parity conservations,a statistical theory of light nucleus reaction(STLN)is developed to calculate the double-differential cross-sections of the outgoing neutron and light charged particles for the proton-induced^(6) Li reaction.A significant difference is observed between the p+^(6) Li and p+^(7) Li reactions owing to the discrepancies in the energy-level structures of the targets.The reaction channels,including sequential and simultaneous emission processes,are analyzed in detail.Taking the double-differential cross-sections of the outgoing proton as an example,the influence of contaminations(such as^(1) H,^(7)Li,^(12)C,and^(16)O)on the target is identified in terms of the kinetic energy of the first emitted particles.The optical potential parameters of the proton are obtained by fitting the elastic scattering differential cross-sections.The calculated total double-differential cross-sections of the outgoing proton and deuteron at E_(p)=14 MeV agree well with the experimental data for different outgoing angles.Simultaneously,the mixed double differential cross-sections of^(3) He andαare in good agreement with the measurements.The agreement between the measured data and calculated results indicates that the two-body and three-body breakup reactions need to be considered,and the pre-equilibrium reaction mechanism dominates the reaction processes.Based on the STLN model,a PLUNF code for the p+^(6) Li reaction is developed to obtain an ENDF-6-formatted file of the double-differential cross-sections of the nucleon and light composite charged particles.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 40476062 and 10374026）.
文摘Based on the effective medium approximation theory of composites, the whitecap-covered sea surface is treated as a medium layer of dense seawater droplets and air. Two electromagnetic scattering models of randomly rough surface are applied to the investigation of microwave backscattering of breaking waves driven by strong wind. The shapes of seawater droplets are considered by calculating the effective dielectric constant of the whitecap layer. The responses of seawater droplets shapes, such as sphere and ellipsoid, to the backscattering coefficient are discussed. Numerical results of the models are in good agreement with the experimental measurements of horizontally and vertically polarized backscattering at microwave frequency 13.9GHz and different incidence angles.
基金supported by the National Natural Science Foundation of China (Nos. 11772269, 11802248, and 11872318)。
文摘The elliptical cross-section ogive-nose projectile(ECOP) has recently attracted attention because it is well suited to the flattened shape of earth-penetrating weapons. However, the penetration performance of ECOPs has not been completely understood. The objective of this study was to investigate the penetration performance of ECOPs into concrete targets using a theoretical method. A general geometric model of ECOPs was introduced, and closed-form penetration equations were derived according to the dynamic cavity-expansion theory. The model was validated by comparing the predicted penetration depths with test data, and the maximum deviation was 15.8%. The increment in the penetration depth of the ECOP was evaluated using the proposed model, and the effect of the majoreminor axis ratio on the increment was examined. Additionally, the mechanism of the penetration-depth increment was investigated with respect to the caliber radius head, axial stress, and resistance.
基金support by grants from the“Chongqing Science and Technology Benefiting project”(cstc2016kjhmpt1001)research project from the State Key Laboratory of Trauma,Burns and Combined Injury(SKLZZ201603)。
文摘Background:Since the trauma knowledge of trauma providers correlates with the outcomes of injured patients,this study aims to assess the socio-demographic characteristics and levels of trauma knowledge of trainees in the China trauma care training(CTCT)program in addition to their post-course test results to provide support for the development of trauma care training programs and trauma systems in China.Methods:A cross-sectional study was conducted by collecting demographic information,hospital-related information and trauma knowledge of the trainees from 19 regions in China.All participants were assessed by questionnaires collecting the socio-demographic data,the trauma care knowledge levels and the information of the hospitals.Results:There were 955 males(78.9%)and 256 females(21.1%)enrolled.Among them,854 were physicians(70.5%),357 were registered nurses(29.5%).In addition,64 of them also played an administrative role in the hospitals(5.3%).The score of the trainees who were members of the emergency department staff(72.59±14.13)was the highest among the scores of all the personnel surveyed,followed by those of the trainees from the intensive care unit(ICU)(71.17±12.72),trauma surgery department(67.26±13.81),orthopedics department(70.36±14.48),general surgery department(69.91±14.79)and other departments(69.93±16.91),P=0.031.The score of the professors(73.09±15.05)was higher than those of the associate professors(72.40±14.71),lecturers(70.07±14.25)and teaching assistants(67.58±15.16),P<0.0001.The score of the individuals who attended experts’trauma lectures(72.22±14.45)was higher than that of individuals who did not attend the lectures(69.33±15.17),P=0.001.The mean scores before and after the training were 71.02±14.82 and 84.24±13.77,respectively,P<0.001.The mean score of trauma knowledge after the training of trainees from different provinces and with different educational backgrounds was higher than that before the training,with a statistically significant difference(P<0.05).Conclusions:The level of trauma knowledge of trauma care providers was associated with their department,professional position and previous participation in related academic conferences.Trauma care experience and participation in academic lectures and training program including CTCT may effectively improve individuals’level of trauma knowledge.
文摘A full aperture backscattering light diagnostic system （FABLDS） implemented on the Shen Guang-Ⅲ Prototype Laser Facility is described in the paper. FABLDS measures both stimulated brillouin scattering （SBS） and stimulated Raman scattering （SRS） with a series of optical detectors. Energy sensors record the integrated energy, and streak cameras coupled with spectrometers measure the temporal spectrum of the backscattering light. This paper provides an overview of the FABLDS and detailed descriptions of the optical path. Special components, including off-axis parabolic mirror, spatial filter and optical light filters, are incorporated along the beam path for purifying the scattering light. Several hohlraum targets were employed, including C5H12 gas-filled targets and empty targets in the experiments. Results presented in the paper indicate that the fraction of backscatter light has been obviously shrinked when the laser is smoothed by continuous phase plates （CPP）.
文摘The backscattering signal, which arises from the pulsed laser traveling through water, has limited the lidar system sensitivity and underwater target contrast. The transmitted optical carrier is modulated to be ultrashort pulsed laser and it is effective to suppress the backscattering to adopt the coherent detection technology by identifying the modulation envelope. A nonstationary light field is formed in seawater by the ultrashort pulsed laser. The inherent relationship between the nonstationary light field formed by modulated lidar and the stationary light field formed by conventional lidar was discussed and the backscattering light model of the stationary light field for the ultrashort pulsed laser was proposed. The backscattering signal in modulated lidar system was processed and analyzed in the frequency domain on the basis of the model.
基金supported by grants from Clinical Vascular Grant in Chinese Physicians—VG
文摘Objective To investigate whether ABO blood groups is associated with the severity of coronary artery disease(CAD). Methods Between January 2015 and December 2017, 1425 first diagnosed CAD patients confirmed by selective coronary angiography were recruited into this cross-sectional study, and their baseline characteristics, ABO blood groups, Gensini score were collected. Multiple linear regression analysis was performed to test the association between the severity of CAD and ABO blood groups. Results The Gensini score was significantly higher in the blood group A than in the non-A groups(41.2 ± 32 vs. 38 ± 27;P = 0.026). After adjusting for age, male, smoking, family history of CAD, hypertension, diabetes mellitus and hypercholesterolemia, multivariate linear regression indicated that blood group A was associated with the severity of CAD(β= 3.298, 95% CI: 0.91–6.505, P = 0.044). In diabetes group, A blood type was also associated with increased Gensini score(P = 0.02) after adjusting for age, male, family history of CAD, hypercholesterolemia, smoking and hypertension. Conclusion In this cross-sectional study, the data indicated that blood group A was an independent risk factor of severity of CAD in Chinese population and Chinese patients with type 2 diabetes.
基金provided by the National Natural Science Foundation of China (Nos. 51274204 and 51134025)National Key Basic Research Program (No. 2010CB732002)The Ministry of Education Program for New Century Excellent Talents to Support Project of China (No. NCET-12-0965)
文摘Using digital laser dynamic caustics experimental system and conducting simulation experiment researched the influence rule of blasting excavation of a new roadway on neighboring existed different cross-section roadways. The experimental results show that the influence of blast load on adjacent roadway has a good relationship with the cross-section of roadway. The expansion distance of precrack existed in circular, arch-wall, rectangular roadway is respectively 1.76, 1.61 and 0 cm under blast load.At the same time, the direct-blast side of rectangular roadway has more obvious damage compared with circular and arch-wall roadway. It explains that plane reflects more stress wave than arc, so that it exerts more tensile failure in the direct-blast side, which leads to less stress wave diffracting to the precrack in the back-blast side. When the precrack extends, higher value dynamic stress intensity factor in circular roadway works longer than that of arch-wall roadway. Indirectly, it explains that plane's weakening function on stress wave is significantly stronger than arc. Stress wave brings about self-evident influence on the upper and bottom endpoints of the rectangular roadway, and it respectively extends 1.03, 2.06 cm along the line link direction of the center of the blasthole and the upper and bottom endpoints on the right wall.
基金financially supported by the National Natural Science Foundation of China(Grant No.11372136)
文摘Analyzing the mass of behind-armor debris (BAD) generated by Rolled Homogeneous Armor (RHA) subjected to normal penetration of variable cross-section Explosively Formed Projectile (EFP) is the purpose of this paper. So theoretical analysis, numerical simulation and experimental data are combined to analyze the influence of variable cross-section characteristic on the time history of crater radius. Moreover the relationships between time history of crater radius (as well as mass of BAD) and the thickness of RHA (from 30mm to 70 mm) and the impact velocity of EFP (1650 m/s to 1860 m/s) are also investigated. The results indicate that: 1) being compared to the variable cross-section characteristic is ignored, the theoretical time history of crater radius is in better agreement with the simulation results when the variable cross-section characteristic is considered;2) being compared to the other three conditions of plug, the theoretical mass of BAD is in the best agreement with the simulation results when the shape of plug is frustum of a cone and the angle between generatrix and bottom is 45- and the axial length of mushroom is considered.
基金supported by National Natural Science Foundation of China(No.U1966211)National Key R&D Program of China(No.2021YFB2401400)。
文摘Prediction models were proposed to estimate the reduced Townsend ionization coefficient and ionization cross-section.A shape function of the reduced Townsend ionization coefficient curves was derived from the ionization collision probability model.The function had three parameters:the first ionization potential energy,A_(α),and B_(α).A_(α)and B_(α)were related to the molecule symmetry and size.The polarization of molecules could characterize the molecule symmetry.The multi-layer molecular cross-section(MMCS)was proposed to describe the contributions of electrons and molecule radius on different molecule surfaces to collisions.A prediction model of the ionization cross-section was also proposed based on Aα.The molecule parameters were calculated by the Becke3–Lee–Yang–Parr(B3LYP)method and the 6–311G**basis set.We used available data of 30 and 23 gases,respectively,to build the prediction models of reduced Townsend ionization coefficients and ionization cross-sections.The relationships between the molecular parameters Aαand Bαand the ionization cross-section were built up via nonlinear fittings.The determination coefficients R^(2)of Aα,Bα,and the ionization cross-section were 0.877,0.887,and 0.838,respectively.The results showed that the accuracy of models was positively correlated with the molecule symmetry and reduced electric field.This was mainly related to the accuracy of the MMCS model in predicting Aα.The MMCS model needed to be improved to describe the collision direction selectivity caused by the molecule asymmetry.Under a high reduced electric field,that error of Aαhad less influence on the prediction results.However,the prediction results for single atoms with high symmetry were poor.This may be due to the absolute error of the model close to single atoms’reduced Townsend ionization coefficients.The models could provide the basis for gas insulation prediction and discharge calculations,especially for symmetric molecules under a high electric field.
基金This work was supported by KIST(Korea Institute of Science and Technology)institutional grants(2E30965,and 2V07360)the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(Nos.2020R1C1C1006065,2021M3F3A2A01037366)+1 种基金This work was also supported by the Korea Medical Device Development Fund grant funded by the Korea government(the Ministry of Science and ICT,the Ministry of Trade,Industry and Energy,the Ministry of Health&Welfarethe Ministry of Food and Drug Safety)(Project Number:9991006818,KMDF_PR_20200901_0145-2021).
文摘Out-of-plane microneedle structures are widely used in various applications such as transcutaneous drug delivery and neural signal recording for brain machine interface.This work presents a novel but simple method to fabricate high-density silicon(Si)microneedle arrays with various heights and diverse cross-sectional shapes depending on photomask pattern designs.The proposed fabrication method is composed of a single photolithography and two subsequent deep reactive ion etching(DRIE)steps.First,a photoresist layer was patterned on a Si substrate to define areas to be etched,which will eventually determine the final location and shape of each individual microneedle.Then,the 1st DRIE step created deep trenches with a highly anisotropic etching of the Si substrate.Subsequently,the photoresist was removed for more isotropic etching;the 2nd DRIE isolated and sharpened microneedles from the predefined trench structures.Depending on diverse photomask designs,the 2nd DRIE formed arrays of microneedles that have various height distributions,as well as diverse cross-sectional shapes across the substrate.With these simple steps,high-aspect ratio microneedles were created in the high density of up to 625 microneedles mm^(-2)on a Si wafer.Insertion tests showed a small force as low as~172μN/microneedle is required for microneedle arrays to penetrate the dura mater of a mouse brain.To demonstrate a feasibility of drug delivery application,we also implemented silk microneedle arrays using molding processes.The fabrication method of the present study is expected to be broadly applicable to create microneedle structures for drug delivery,neuroprosthetic devices,and so on.
基金Project supported by the National Natural Science Foundation of China(Grant No.10775063)
文摘We have measured the cross-section ratios of helium induced by Cq＋ and Oq＋ （q = 1-4） in an energy range from 20 keV/amu to 500 keV/amu, and obtained the two-dimensional spectra by employing the coincidence method combined with the MPA-3 data acquisition system. Hence, we obtain the ratios of total single-ionization cross-sections （SI, SC, SLSI, and DLSI）, total double-ionization cross-sections （DI, DC, TI, SLDI, and DLDI） and cross-sections of every process （SI, SC, SLSI, DLSI, DI, DC, TI, SLDI, and DLDI）, which induce the single-ionization and double-ionization, to the total cross sections respectively. The competitive relations between the reaction-channels and the experimental data law of each reaction-channel are revealed explicitly, and the qualitative explanations involved in those results are also presented accordingly.
基金supported by the National Natural Science Foundation of China (Grant Nos. 2032165 and 62004158)the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 52127817)+1 种基金the State Key Laboratory of Particle Detection and Electronics (Grant Nos. SKLPDE-ZZ-201801 and SKLPDE-ZZ-202008)the Special Funds for Science and Technology Innovation Strategy of Guangdong Province, China (Grant No. 2018A0303130030)。
文摘To predict the soft error rate for applications, it is essential to study the energy dependence of the single-event-upset(SEU) cross-section. In this work, we present a direct measurement of the SEU cross-section with the Back-n white neutron source at the China Spallation Neutron Source. The measured cross section is consistent with the soft error data from the manufacturer and the result suggests that the threshold energy of the SEU is about 0.5 Me V, which confirms the statement in Iwashita’s report that the threshold energy for neutron soft error is much below that of the(n, α) cross-section of silicon.In addition, an index of the effective neutron energy is suggested to characterize the similarity between a spallation neutron beam and the standard atmospheric neutron environment.
文摘Cross-sections of the(n,2n) reactions for neodymium(Nd) isotopes induced by 14 MeV neutrons were measured in this work by using the activation and relative methods. The measured cross-sections of the ^(150)Nd(n,2n)^(149)Nd,^(148)Nd(n,2n)^(147)Nd, and ^(142)Nd(n,2 n)^(141)Nd reactions were 1854 ± 81, 1789 ± 119, and 1559 ± 98 mb, respectively, at a neutron energy of 14.2 ± 0.2 MeV,and 1485 ± 74, 1726 ± 85, and 1670 ± 119 mb, respectively, at 14.9 ± 0.2 MeV. The results were compared with the experimental values from the reported literature, with the evaluated data from the ENDF/B-VII.1, CENDL-3.1, and JENDL-4.0 libraries, and with the curves calculated by the Talys-1.8 code.
基金supported by the Beijing Natural Science Funds(No.1142006)
文摘In this study,we present a new method for the indirect integration of beam charges in external beam proton-induced X-ray emission and proton-induced c-ray emission(PIXE–PIGE) analysis.We recorded proton spectra backscattered by a Kapton film extraction window in different sample situations and under different beam currents.We also simulated backscattering spectra using the simulation of backscattering spectra program(SIMNRA).We determined that in a specific geometrical arrangement,different sample situations did not significantly affect factor C_Q(the ratio between integral backscattering proton counts and integral beam charges).We also studied the reproducibility and beam current dependence of factor C_Q.The statistic factor of C_Q was28.95 ± 0.6 kilo counts/l C,with a relative standard deviation of 2.0 %.Significantly,in external beam PIXE–PIGE analysis,we were able to calculate beam charge integration from the integral backscattering proton counts in an energy region.
基金Supported by the National Natural Science Foundation of Chinathe National Key Research and Development Program of China under Grant No 2016YFA0300203
文摘Pairing in the cuprate high-temperature superconductors and its origin remain among the most enduring mysteries in condensed matter physics. With cross-sectional scanning tunneling microscopy/spectroscopy, we clearly reveal the spatial-dependence or inhomogeneity of the superconducting gap structure of Bi2Sr2CaCu2O8＋δ （Bi2212） and YBa2Cu3O7-x （YBCO） along their c-axes on a scale shorter than the interlayer spacing. By tunneling into the （100） plane of a Bi2212 single crystal and a YBCO film, we observe both U-shaped tunneling spectra with extended fiat zero-conductance bottoms, and V-shaped gap structures, in different regions of each sample. On the YBCO film, tunneling into a （110） surface only reveals a U-shaped gap without any zero-bias peak. Our analysis suggests that the U-shaped gap is likely a nodeless superconducting gap. The V-shaped gap has a very small amplitude, and is likely proximity-induced by regions having the larger U-shaped gap.
