To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based sim...To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.展开更多
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
A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the re...A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the reference functions method to describe the solution to the depth-separated wave equation approximately using parabolic cylinder functions.The conditions for the validity of this approximation are also discussed.Furthermore,a formula that incorporates waveguide effects for the modal group velocity is derived,revealing that boundary effects at very low frequencies can have a significant impact on the propagation characteristics of even low-order normal modes.The present method not only offers improved accuracy compared to the classical WKB approximation and the uniform asymptotic approximation based on Airy functions,but also provides a wider range of depth applicability.Additionally,this method exhibits strong agreement with numerical methods and offers valuable physical insights.Finally,the method is applied to the study of very-low-frequency sound propagation in the South China Sea,leading to sound transmission loss predictions that closely align with experimental observations.展开更多
Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.Howev...Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.展开更多
Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are pr...Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are prepared with a solvent-free method at 25℃.The 99.8 wt% contents of Nano LLZO particles enable the Nano LLZO CSEs to maintain good thermal stability while exhibiting a wide electrochemical window of 5.0 V and a high Li~+ transfer number of 0.8.The mean modulus reaches 4376 MPa.Benefiting from the interfacial modulation,the Li|Li symmetric batteries based on the Nano LLZO CSEs show benign stability with lithium at the current densities of 0.1 mA cm^(-2),0.2 mA cm^(-2),and 0.5 mA cm^(-2).In addition,the Li|LiFePO_(4)(LFP) SSBs achieve favorable cycling performance:the specific capacity reaches128.1 mAh g^(-1) at 0.5 C rate,with a capacity retention of about 80% after 600 cycles.In the further tests of the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathodes with higher energy density,the Nano LLZO CSEs also demonstrate good compatibility:the specific capacities of NCM811-based SSBs reach 177.9 mAh g^(-1) at 0.5 C rate,while the capacity retention is over 96% after 150 cycles.Furthermore,the Li|LFP soft-pack SSBs verify the safety characteristics and the potential for application,which have a desirable prospect.展开更多
The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222...The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.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
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
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
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
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
An orthogonal 2D training image is constructed from the geological analysis results of well logs and sedimentary facies;the 2 D probabilities in three directions are obtained through linear pooling method and then agg...An orthogonal 2D training image is constructed from the geological analysis results of well logs and sedimentary facies;the 2 D probabilities in three directions are obtained through linear pooling method and then aggregated by the logarithmic linear pooling to determine the 3 D multi-point pattern probabilities at the unknown points,to realize the reconstruction of a 3 D model from 2D cross-section.To solve the problems of reducing pattern variability in the 2 D training image and increasing sampling uncertainty,an adaptive spatial sampling method is introduced,and an iterative simulation strategy is adopted,in which sample points from the region with higher reliability of the previous simulation results are extracted to be additional condition points in the following simulation to improve the pattern probability sampling stability.The comparison of lateral accretion layer conceptual models shows that the reconstructing algorithm using self-adaptive spatial sampling can improve the accuracy of pattern sampling and rationality of spatial structure characteristics,and accurately reflect the morphology and distribution pattern of the lateral accretion layer.Application of the method in reconstructing the meandering river reservoir of the Cretaceous McMurray Formation in Canada shows that the new method can accurately reproduce the shape,spatial distribution pattern and development features of complex lateral accretion layers in the meandering river reservoir under tide effect.The test by sparse wells shows that the simulation accuracy is above 85%,and the coincidence rate of interpretation and prediction results of newly drilled horizontal wells is up to 80%.展开更多
BACKGROUND Cognitive decline is common among older patients with cardiovascular disease(CVD) and can decrease their self-management abilities. However, the instruments for identifying mild cognitive impairment(MCI) ar...BACKGROUND Cognitive decline is common among older patients with cardiovascular disease(CVD) and can decrease their self-management abilities. However, the instruments for identifying mild cognitive impairment(MCI) are not always feasible in clinical practice. Therefore, this study evaluated whether MCI could be detected using the Japanese version of the Rapid Dementia Screening Test(RDST-J), which is a simple screening tool for identifying cognitive decline.METHODS This retrospective single-center study included patients who were ≥ 65 years old and hospitalized because of CVD.Patients with a pre-hospitalization diagnosis of dementia were excluded. Each patient's cognitive function had been measured at discharge using the RDST-J and the Japanese version of the Montreal Cognitive Assessment(Mo CA-J), which is a standard tool for MCI screening. The correlation between the two scores was evaluated using Spearman's rank correlation coefficient. Receiver operating characteristic(ROC) analysis was also to evaluate whether the RDST-J could identify MCI, which was defined as a Mo CA-J score of ≤ 25 points.RESULTS The study included 78 patients(mean age: 77.2 ± 8.9 years). The RDST-J and Mo CA-J scores were strongly correlated(r = 0.835, P < 0.001). The ROC analysis revealed that an RDST-J score of ≤ 9 points provided 75.4% sensitivity and 95.2% specificity for identifying MCI, with an area under the curve of 0.899(95% CI: 0.835-0.964). The same cut-off value was identified when excluding patients with a high probability of dementia(RDST-J score of ≤ 4 points).CONCLUSIONS The RDST-J may be a simple and effective tool for identifying MCI in older patients with CVD.展开更多
Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 Me V H^+was implanted in 6 H-SiC single crystals to investigate the effects of light ion i...Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 Me V H^+was implanted in 6 H-SiC single crystals to investigate the effects of light ion irradiation on SiC. Raman spectroscopy and scanning electronic microscopy(SEM) were carried out on crosssectional samples to reveal the in-depth damage states and dopant behavior. The most damaged region is a little shallower than that predicted by the SRIM procedure,owing to the uncertainty in SRIM simulations. Layered structures representing zones of varying damage after2 MeV H ion irradiation are clearly observed. Two bands are observed in SEM images, of which on band corresponds to the damage peak, while the other band at the end of the H ion-affected area is probably a result of H diffusion propelled by a hydrogen-rich layer during irradiation.A charge accumulation effect related with conductivity on the sample surfaces during SEM tests is observed in theH-implanted area. A model is proposed to explain these phenomena.展开更多
The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(R...The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.展开更多
In this study,the structural characters,antioxidant activities and bile acid-binding ability of sea buckthorn polysaccharides(HRPs)obtained by the commonly used hot water(HRP-W),pressurized hot water(HRP-H),ultrasonic...In this study,the structural characters,antioxidant activities and bile acid-binding ability of sea buckthorn polysaccharides(HRPs)obtained by the commonly used hot water(HRP-W),pressurized hot water(HRP-H),ultrasonic(HRP-U),acid(HRP-C)and alkali(HRP-A)assisted extraction methods were investigated.The results demonstrated that extraction methods had significant effects on extraction yield,monosaccharide composition,molecular weight,particle size,triple-helical structure,and surface morphology of HRPs except for the major linkage bands.Thermogravimetric analysis showed that HRP-U with filamentous reticular microstructure exhibited better thermal stability.The HRP-A with the lowest molecular weight and highest arabinose content possessed the best antioxidant activities.Moreover,the rheological analysis indicated that HRPs with higher galacturonic acid content and molecular weight showed higher viscosity and stronger crosslinking network(HRP-C,HRP-W and HRP-U),which exhibited stronger bile acid binding capacity.The present findings provide scientific evidence in the preparation technology of sea buckthorn polysaccharides with good antioxidant and bile acid binding capacity which are related to the structure affected by the extraction methods.展开更多
The selection and coordinated application of government innovation policies are crucial for guiding the direction of enterprise innovation and unleashing their innovation potential.However,due to the lengthy,voluminou...The selection and coordinated application of government innovation policies are crucial for guiding the direction of enterprise innovation and unleashing their innovation potential.However,due to the lengthy,voluminous,complex,and unstructured nature of regional innovation policy texts,traditional policy classification methods often overlook the reality that these texts cover multiple policy topics,leading to lack of objectivity.In contrast,topic mining technology can handle large-scale textual data,overcoming challenges such as the abundance of policy content and difficulty in classification.Although topic models can partition numerous policy texts into topics,they cannot analyze the interplay among policy topics and the impact of policy topic coordination on enterprise innovation in detail.Therefore,we propose a big data analysis scheme for policy coordination paths based on the latent Dirichlet allocation(LDA)model and the fuzzyset qualitative comparative analysis(fsQCA)method by combining topic models with qualitative comparative analysis.The LDA model was employed to derive the topic distribution of each document and the word distribution of each topic and enable automatic classi-fication through algorithms,providing reliable and objective textual classification results.Subsequently,the fsQCA method was used to analyze the coordination paths and dynamic characteristics.Finally,experimental analysis was conducted using innovation policy text data from 31 provincial-level administrative regions in China from 2012 to 2021 as research samples.The results suggest that the proposed method effectively partitions innovation policy topics and analyzes the policy configuration,driving enterprise innovation in different regions.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
Large cross-section tunnel construction induces ground surface settlements, potentially endangering both subterranean projects and nearby above-ground structures. A novel tunnel construction method, known as the suspe...Large cross-section tunnel construction induces ground surface settlements, potentially endangering both subterranean projects and nearby above-ground structures. A novel tunnel construction method, known as the suspension method,is introduced in this paper to mitigate surface settlement. The suspension method employs vertical tie rods to establish a structural connection between the initial tunnel support system and the surface steel beam, thereby exerting effective control settlements. To analyze the performance of the proposed method, systematic numerical simulations were conducted based on the practical engineering of Harbin Subway Line 3. The surface settlement and vault settlement characteristics during construction are investigated. The results show a gradual increment in both surface and vault settlement throughout the construction process, culminating in a stabilized state upon the completion of construction.In addition, compared to the double-side drift method and the Cross Diaphragm Method(CRD) method, the suspension method can obviously reduce the surface settlement and vault settlement. Moreover, the surface settlements and the axial force of tie rods were continuously monitored during the construction process at the trial tunnel block.These specific monitoring measurements are illustrated in comparison to numerical analysis results. The monitored results show great agreement with the numerical predictions, confirming the success of the project. This research can serve as a valuable practical reference for similar projects, offering insights and guidance for addressing ground surface settlements and enhancing construction safety in the domain of large cross-section tunneling.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52271317 and 52071149)the Fundamental Research Funds for the Central Universities(HUST:2019kfy XJJS007)。
文摘To address the problems of low accuracy by the CONWEP model and poor efficiency by the Coupled Eulerian-Lagrangian(CEL)method in predicting close-range air blast loads of cylindrical charges,a neural network-based simulation(NNS)method with higher accuracy and better efficiency was proposed.The NNS method consisted of three main steps.First,the parameters of blast loads,including the peak pressures and impulses of cylindrical charges with different aspect ratios(L/D)at different stand-off distances and incident angles were obtained by two-dimensional numerical simulations.Subsequently,incident shape factors of cylindrical charges with arbitrary aspect ratios were predicted by a neural network.Finally,reflected shape factors were derived and implemented into the subroutine of the ABAQUS code to modify the CONWEP model,including modifications of impulse and overpressure.The reliability of the proposed NNS method was verified by related experimental results.Remarkable accuracy improvement was acquired by the proposed NNS method compared with the unmodified CONWEP model.Moreover,huge efficiency superiority was obtained by the proposed NNS method compared with the CEL method.The proposed NNS method showed good accuracy when the scaled distance was greater than 0.2 m/kg^(1/3).It should be noted that there is no need to generate a new dataset again since the blast loads satisfy the similarity law,and the proposed NNS method can be directly used to simulate the blast loads generated by different cylindrical charges.The proposed NNS method with high efficiency and accuracy can be used as an effective method to analyze the dynamic response of structures under blast loads,and it has significant application prospects in designing protective structures.
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Project supported by the National Natural Science Foundation of China(Grant Nos.12174048 and 12204128)。
文摘A Wentzel-Kramers-Brillouin(WKB)method is introduced for obtaining a uniform asymptotic solution for underwater sound propagation at very low frequencies in deep ocean.The method utilizes a mode sum and employs the reference functions method to describe the solution to the depth-separated wave equation approximately using parabolic cylinder functions.The conditions for the validity of this approximation are also discussed.Furthermore,a formula that incorporates waveguide effects for the modal group velocity is derived,revealing that boundary effects at very low frequencies can have a significant impact on the propagation characteristics of even low-order normal modes.The present method not only offers improved accuracy compared to the classical WKB approximation and the uniform asymptotic approximation based on Airy functions,but also provides a wider range of depth applicability.Additionally,this method exhibits strong agreement with numerical methods and offers valuable physical insights.Finally,the method is applied to the study of very-low-frequency sound propagation in the South China Sea,leading to sound transmission loss predictions that closely align with experimental observations.
基金Supported by the National Natural Science Foundation of China(Nos.52222904 and 52309117)China Postdoctoral Science Foundation(Nos.2022TQ0168 and 2023M731895).
文摘Ocean energy has progressively gained considerable interest due to its sufficient potential to meet the world’s energy demand,and the blade is the core component in electricity generation from the ocean current.However,the widened hydraulic excitation frequency may satisfy the blade resonance due to the time variation in the velocity and angle of attack of the ocean current,even resulting in blade fatigue and destructively interfering with grid stability.A key parameter that determines the resonance amplitude of the blade is the hydrodynamic damping ratio(HDR).However,HDR is difficult to obtain due to the complex fluid-structure interaction(FSI).Therefore,a literature review was conducted on the hydrodynamic damping characteristics of blade-like structures.The experimental and simulation methods used to identify and obtain the HDR quantitatively were described,placing emphasis on the experimental processes and simulation setups.Moreover,the accuracy and efficiency of different simulation methods were compared,and the modal work approach was recommended.The effects of key typical parameters,including flow velocity,angle of attack,gap,rotational speed,and cavitation,on the HDR were then summarized,and the suggestions on operating conditions were presented from the perspective of increasing the HDR.Subsequently,considering multiple flow parameters,several theoretical derivations and semi-empirical prediction formulas for HDR were introduced,and the accuracy and application were discussed.Based on the shortcomings of the existing research,the direction of future research was finally determined.The current work offers a clear understanding of the HDR of blade-like structures,which could improve the evaluation accuracy of flow-induced vibration in the design stage.
基金supported by Science and Technology Project of China Southern Power Grid (SZKJXM20230049/090000KC23010038)。
文摘Solid-state batteries(SSBs) with high safety are promising for the energy fields,but the development has long been limited by machinability and interfacial problems.Hence,self-supporting,flexible Nano LLZO CSEs are prepared with a solvent-free method at 25℃.The 99.8 wt% contents of Nano LLZO particles enable the Nano LLZO CSEs to maintain good thermal stability while exhibiting a wide electrochemical window of 5.0 V and a high Li~+ transfer number of 0.8.The mean modulus reaches 4376 MPa.Benefiting from the interfacial modulation,the Li|Li symmetric batteries based on the Nano LLZO CSEs show benign stability with lithium at the current densities of 0.1 mA cm^(-2),0.2 mA cm^(-2),and 0.5 mA cm^(-2).In addition,the Li|LiFePO_(4)(LFP) SSBs achieve favorable cycling performance:the specific capacity reaches128.1 mAh g^(-1) at 0.5 C rate,with a capacity retention of about 80% after 600 cycles.In the further tests of the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) cathodes with higher energy density,the Nano LLZO CSEs also demonstrate good compatibility:the specific capacities of NCM811-based SSBs reach 177.9 mAh g^(-1) at 0.5 C rate,while the capacity retention is over 96% after 150 cycles.Furthermore,the Li|LFP soft-pack SSBs verify the safety characteristics and the potential for application,which have a desirable prospect.
基金supported by the National Natural Science Foundation of China(No.12075112)Natural Science Foundation of Hunan(No.2023JJ50121),Natural Science Foundation of Hunan Province(No.2023JJ50091)Key Projects of Hunan Provincial Department of Education(No.23A0516).
文摘The accumulation of^(222)Rn and^(220)Rn progeny in poorly ventilated environments poses the risk of natural radiation exposure to the public.A previous study indicated that satisfactory results in determining the^(222)Rn and^(220)Rn progeny concentrations by measuring the total alpha counts at five time intervals within 560 min should be expected only in the case of high progeny concentrations in air.To complete the measurement within a relatively short period and adapt it for simultaneous measurements at comparatively lower^(222)Rn and^(220)Rn progeny concentrations,a novel mathematical model was proposed based on the radioactive decay law.This model employs a nonlinear fitting method to distinguish nuclides with overlapping spectra by utilizing the alpha particle counts of non-overlapping spectra within consecutive measurement cycles to obtain the concentrations of^(222)Rn and^(220)Rn progeny in air.Several verification experiments were conducted using an alpha spectrometer.The experimental results demonstrate that the concentrations of^(222)Rn and^(220)Rn progeny calculated by the new method align more closely with the actual circumstances than those calculated by the total count method,and their relative uncertainties are all within±16%.Furthermore,the measurement time was reduced to 90 min,representing an acceleration of 84%.The improved capability of the new method in distinguishing alpha particles with similar energies emitted from ^(218)Po and^(212)Bi,both approximately 6 MeV,contributed to realizing more accurate results.The proposed method has the potential advantage of measuring relatively low concentrations of^(222)Rn and^(220)Rn progeny in air more quickly via air filtration.
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.
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.
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.
基金Supported by the China National Science and Technology Major Project(2017ZX05005-004-002,2016ZX05031-002-001)National Natural Science Foundation of China(41872138)Open Foundation of Top Disciplines in Yangtze University(2019KFJJ0818029)。
文摘An orthogonal 2D training image is constructed from the geological analysis results of well logs and sedimentary facies;the 2 D probabilities in three directions are obtained through linear pooling method and then aggregated by the logarithmic linear pooling to determine the 3 D multi-point pattern probabilities at the unknown points,to realize the reconstruction of a 3 D model from 2D cross-section.To solve the problems of reducing pattern variability in the 2 D training image and increasing sampling uncertainty,an adaptive spatial sampling method is introduced,and an iterative simulation strategy is adopted,in which sample points from the region with higher reliability of the previous simulation results are extracted to be additional condition points in the following simulation to improve the pattern probability sampling stability.The comparison of lateral accretion layer conceptual models shows that the reconstructing algorithm using self-adaptive spatial sampling can improve the accuracy of pattern sampling and rationality of spatial structure characteristics,and accurately reflect the morphology and distribution pattern of the lateral accretion layer.Application of the method in reconstructing the meandering river reservoir of the Cretaceous McMurray Formation in Canada shows that the new method can accurately reproduce the shape,spatial distribution pattern and development features of complex lateral accretion layers in the meandering river reservoir under tide effect.The test by sparse wells shows that the simulation accuracy is above 85%,and the coincidence rate of interpretation and prediction results of newly drilled horizontal wells is up to 80%.
文摘BACKGROUND Cognitive decline is common among older patients with cardiovascular disease(CVD) and can decrease their self-management abilities. However, the instruments for identifying mild cognitive impairment(MCI) are not always feasible in clinical practice. Therefore, this study evaluated whether MCI could be detected using the Japanese version of the Rapid Dementia Screening Test(RDST-J), which is a simple screening tool for identifying cognitive decline.METHODS This retrospective single-center study included patients who were ≥ 65 years old and hospitalized because of CVD.Patients with a pre-hospitalization diagnosis of dementia were excluded. Each patient's cognitive function had been measured at discharge using the RDST-J and the Japanese version of the Montreal Cognitive Assessment(Mo CA-J), which is a standard tool for MCI screening. The correlation between the two scores was evaluated using Spearman's rank correlation coefficient. Receiver operating characteristic(ROC) analysis was also to evaluate whether the RDST-J could identify MCI, which was defined as a Mo CA-J score of ≤ 25 points.RESULTS The study included 78 patients(mean age: 77.2 ± 8.9 years). The RDST-J and Mo CA-J scores were strongly correlated(r = 0.835, P < 0.001). The ROC analysis revealed that an RDST-J score of ≤ 9 points provided 75.4% sensitivity and 95.2% specificity for identifying MCI, with an area under the curve of 0.899(95% CI: 0.835-0.964). The same cut-off value was identified when excluding patients with a high probability of dementia(RDST-J score of ≤ 4 points).CONCLUSIONS The RDST-J may be a simple and effective tool for identifying MCI in older patients with CVD.
基金supported by the National Natural Science Foundation of China(Grant Nos.11705169,91426304 and 91226202)
文摘Cross-sectional investigation is an important method to study ion irradiation effects in the depth direction. In this study, 2 Me V H^+was implanted in 6 H-SiC single crystals to investigate the effects of light ion irradiation on SiC. Raman spectroscopy and scanning electronic microscopy(SEM) were carried out on crosssectional samples to reveal the in-depth damage states and dopant behavior. The most damaged region is a little shallower than that predicted by the SRIM procedure,owing to the uncertainty in SRIM simulations. Layered structures representing zones of varying damage after2 MeV H ion irradiation are clearly observed. Two bands are observed in SEM images, of which on band corresponds to the damage peak, while the other band at the end of the H ion-affected area is probably a result of H diffusion propelled by a hydrogen-rich layer during irradiation.A charge accumulation effect related with conductivity on the sample surfaces during SEM tests is observed in theH-implanted area. A model is proposed to explain these phenomena.
基金supported by the National Key Research and Development Program of China(No.2023YFC2907600)the National Natural Science Foundation of China(Nos.42077267,42277174 and 52074164)+2 种基金the Natural Science Foundation of Shandong Province,China(No.ZR2020JQ23)the Opening Project of State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology(No.KFJJ21-02Z)the Fundamental Research Funds for the Central Universities,China(No.2022JCCXSB03).
文摘The technology of drilling tests makes it possible to obtain the strength parameter of rock accurately in situ. In this paper, a new rock cutting analysis model that considers the influence of the rock crushing zone(RCZ) is built. The formula for an ultimate cutting force is established based on the limit equilibrium principle. The relationship between digital drilling parameters(DDP) and the c-φ parameter(DDP-cφ formula, where c refers to the cohesion and φ refers to the internal friction angle) is derived, and the response of drilling parameters and cutting ratio to the strength parameters is analyzed. The drillingbased measuring method for the c-φ parameter of rock is constructed. The laboratory verification test is then completed, and the difference in results between the drilling test and the compression test is less than 6%. On this basis, in-situ rock drilling tests in a traffic tunnel and a coal mine roadway are carried out, and the strength parameters of the surrounding rock are effectively tested. The average difference ratio of the results is less than 11%, which verifies the effectiveness of the proposed method for obtaining the strength parameters based on digital drilling. This study provides methodological support for field testing of rock strength parameters.
基金The Guangdong Basic and Applied Basic Research Foundation(2022A1515010730)National Natural Science Foundation of China(32001647)+2 种基金National Natural Science Foundation of China(31972022)Financial and moral assistance supported by the Guangdong Basic and Applied Basic Research Foundation(2019A1515011996)111 Project(B17018)。
文摘In this study,the structural characters,antioxidant activities and bile acid-binding ability of sea buckthorn polysaccharides(HRPs)obtained by the commonly used hot water(HRP-W),pressurized hot water(HRP-H),ultrasonic(HRP-U),acid(HRP-C)and alkali(HRP-A)assisted extraction methods were investigated.The results demonstrated that extraction methods had significant effects on extraction yield,monosaccharide composition,molecular weight,particle size,triple-helical structure,and surface morphology of HRPs except for the major linkage bands.Thermogravimetric analysis showed that HRP-U with filamentous reticular microstructure exhibited better thermal stability.The HRP-A with the lowest molecular weight and highest arabinose content possessed the best antioxidant activities.Moreover,the rheological analysis indicated that HRPs with higher galacturonic acid content and molecular weight showed higher viscosity and stronger crosslinking network(HRP-C,HRP-W and HRP-U),which exhibited stronger bile acid binding capacity.The present findings provide scientific evidence in the preparation technology of sea buckthorn polysaccharides with good antioxidant and bile acid binding capacity which are related to the structure affected by the extraction methods.
文摘The selection and coordinated application of government innovation policies are crucial for guiding the direction of enterprise innovation and unleashing their innovation potential.However,due to the lengthy,voluminous,complex,and unstructured nature of regional innovation policy texts,traditional policy classification methods often overlook the reality that these texts cover multiple policy topics,leading to lack of objectivity.In contrast,topic mining technology can handle large-scale textual data,overcoming challenges such as the abundance of policy content and difficulty in classification.Although topic models can partition numerous policy texts into topics,they cannot analyze the interplay among policy topics and the impact of policy topic coordination on enterprise innovation in detail.Therefore,we propose a big data analysis scheme for policy coordination paths based on the latent Dirichlet allocation(LDA)model and the fuzzyset qualitative comparative analysis(fsQCA)method by combining topic models with qualitative comparative analysis.The LDA model was employed to derive the topic distribution of each document and the word distribution of each topic and enable automatic classi-fication through algorithms,providing reliable and objective textual classification results.Subsequently,the fsQCA method was used to analyze the coordination paths and dynamic characteristics.Finally,experimental analysis was conducted using innovation policy text data from 31 provincial-level administrative regions in China from 2012 to 2021 as research samples.The results suggest that the proposed method effectively partitions innovation policy topics and analyzes the policy configuration,driving enterprise innovation in different regions.
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 the Fundamental Research Funds for the Central Universities(2023JBZD004)the National Natural Science Foundation of China(U2034204,52078031)the Science and Technology Development Project of cccC Harbin Metro Investment and Construction Co.,Ltd.(ZJHD-FW-2018-01-086).
文摘Large cross-section tunnel construction induces ground surface settlements, potentially endangering both subterranean projects and nearby above-ground structures. A novel tunnel construction method, known as the suspension method,is introduced in this paper to mitigate surface settlement. The suspension method employs vertical tie rods to establish a structural connection between the initial tunnel support system and the surface steel beam, thereby exerting effective control settlements. To analyze the performance of the proposed method, systematic numerical simulations were conducted based on the practical engineering of Harbin Subway Line 3. The surface settlement and vault settlement characteristics during construction are investigated. The results show a gradual increment in both surface and vault settlement throughout the construction process, culminating in a stabilized state upon the completion of construction.In addition, compared to the double-side drift method and the Cross Diaphragm Method(CRD) method, the suspension method can obviously reduce the surface settlement and vault settlement. Moreover, the surface settlements and the axial force of tie rods were continuously monitored during the construction process at the trial tunnel block.These specific monitoring measurements are illustrated in comparison to numerical analysis results. The monitored results show great agreement with the numerical predictions, confirming the success of the project. This research can serve as a valuable practical reference for similar projects, offering insights and guidance for addressing ground surface settlements and enhancing construction safety in the domain of large cross-section tunneling.
