To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been ...To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been proposed to develop the energy-dependent elastic scattering cross-sectional model. In this study, the Monte Carlo continuous energy code PSG2/Serpent was used to examine the difference between the constant cross-sectional model and the energy-dependent cross-sectional model during burnup. For the cases analyzed in this study,numerical simulations show that the multiplication coefficient was improved by hundreds pcm and ^(239)Pu concentration was improved by approximately 1–2% during burnup when the energy-dependent elastic scattering crosssectional model is considered.展开更多
Viewing gravitational energy-momentum PG<sup style='margin-left:-7px;'>μ as equal by observation, but different in essence from inertial energy-momentum PI<sup style='margin-left:-7px;'>μ...Viewing gravitational energy-momentum PG<sup style='margin-left:-7px;'>μ as equal by observation, but different in essence from inertial energy-momentum PI<sup style='margin-left:-7px;'>μ naturally leads to the gauge theory of volume-preserving diffeomorphisms of a four-dimensional inner space. To analyse scattering in this theory, the gauge field is coupled to two Dirac fields with different masses. Based on a generalized LSZ reduction formula the S-matrix element for scattering of two Dirac particles in the gravitational limit and the corresponding scattering cross-section are calculated to leading order in perturbation theory. Taking the non-relativistic limit for one of the initial particles in the rest frame of the other the Rutherford-like cross-section of a non-relativistic particle scattering off an infinitely heavy scatterer calculated quantum mechanically in Newtonian gravity is recovered. This provides a non-trivial test of the gauge field theory of volume-preserving diffeomorphisms as a quantum theory of gravity.展开更多
Objective:To assess prenatal Bisphenol A(BPA)exposure levels and explore their preliminary associations with maternal and fetal characteristics in a population from Northeastern Yunnan.Methods:A cross-sectional analys...Objective:To assess prenatal Bisphenol A(BPA)exposure levels and explore their preliminary associations with maternal and fetal characteristics in a population from Northeastern Yunnan.Methods:A cross-sectional analysis was performed using data and urine samples from 70 pregnant women in their third trimester recruited at Qujing Central Hospital.Urinary BPA was measured by HPLC-MS/MS.Participants were stratified into high and low BPA exposure groups based on the median concentration.Results:BPA was detected in all samples(100%)with a median concentration of 2.41μg/L(IQR:0.68-4.96).The high BPA exposure group(≥2.41μg/L)had a significantly higher proportion of gestational diabetes mellitus(GDM)(42.9%vs.17.1%,p=0.021)and a lower median fetal birth weight(3250 g vs.3450 g,p=0.048)compared to the low exposure group.Conclusion:This pilot study reveals ubiquitous BPA exposure in pregnant women from Northeastern Yunnan.The observed preliminary associations with GDM and reduced fetal birth weight warrant further investigation in larger,longitudinal studies.展开更多
By employing a full quantum theory of electron-photon scattering in intense laser fields,we calculate the angularresolved radiation rate of the fundamental wave in Thomson scattering.We investigate the dependence of r...By employing a full quantum theory of electron-photon scattering in intense laser fields,we calculate the angularresolved radiation rate of the fundamental wave in Thomson scattering.We investigate the dependence of radiation rate on Euler angles and elucidate the underlying physical mechanism.The figure-8 profile of the radiation rate within the polarization plane is validated,while its evolution with respect to laser intensity and electron momentum is illustrated.Our findings reveal that in lower-intensity laser fields and for slow electron motion,the angular-resolved radiation rate exhibits distinct dipole emission characteristics.However,significant changes are observed at high laser intensities and/or large electron momenta,leading to pronounced alterations in the angular-resolved radiation rate.Remarkably similar variation patterns can be achieved by proportionally adjusting both laser intensity and electron momentum.展开更多
Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentrat...Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentration,and forming defects are prone to occur during their extrusion.This study focuses on an Al-Zn-Mg-Cu ultra-high-strength aluminum alloy profile with a double-U,multi-cavity thin-walled structure.Firstly,hot compression experiments were conducted at temperatures of 350○C,400○C,and 450○C,with strain rates of 0.01 and 1.0 s^(−1),to investigate the plastic deformation behavior of the material.Subsequently,a 3D coupled thermo-mechanical extrusion simulation model was established using Deform-3D to systematically analyze the influence of die structure and process parameters on metal flow velocity,effective stress/strain,and temperature distribution.The simulation revealed significant velocity differences,stress concentration,and uneven temperature distribution.Key parameters,including mesh density,extrusion ratio,die fillet,and bearing length,were optimized through full-factorial experiments.This optimization,combined with a stepped flow-guiding die design,effectively improved the metal flow pattern during extrusion.Trial production based on both the initial and optimized parameters were carried out.A comparative analysis demonstrates that the optimized scheme results in a final profile whose cross-section matches the target design closely,with complete filling of complex features and no obvious forming defects.This research provides a valuable reference for the extrusion process optimization and die design of complex-section profiles made from ultra-high-strength aluminum alloys.展开更多
Objective This study aimed to determine the temporal trends in sleep duration among Chinese adults.Methods In this series of repeated nationally representative cross-sectional surveys(China Chronic Disease and Risk Fa...Objective This study aimed to determine the temporal trends in sleep duration among Chinese adults.Methods In this series of repeated nationally representative cross-sectional surveys(China Chronic Disease and Risk Factors Surveillance)conducted between 2010 and 2018,a total of 645,420 adult participants(97,741 in 2010;175,749 in 2013;187,777 in 2015;and 184,153 in 2018)were included in the trend analysis.Linear and logistic regression models were utilized to assess trends in sleep duration.Results In 2018,the estimated overall mean sleep duration among the Chinese adult population was7.58(SD,1.45)hours per day,with no significant trend from 2010.A significant increase in short sleep duration(≤6 hours)was observed in the total population,from 15.3%(95%CI:14.1%–16.5%)in 2010 to18.5%(95%CI:17.7%–19.3%)in 2018(P<0.001).Similarly,the trend in long sleep duration(>9 hours)was also significant,increasing in weighted prevalence from 7.2%(95%CI:6.3%–8.1%)in 2010 to 9.0%(95%CI:8.2%–9.9%)in 2018(P<0.001).Conclusion The prevalence of both short and long sleep durations significantly increased among Chinese adults from 2010 to 2018,highlighting the urgency of health initiatives to promote optimal sleep duration in China.展开更多
We investigated the impact of convexity and isoperimetric deficits on the accuracy of sectional area estimates of tree stems using traditional methods(caliper,tape,formulas based on stem diameter and circumference).In...We investigated the impact of convexity and isoperimetric deficits on the accuracy of sectional area estimates of tree stems using traditional methods(caliper,tape,formulas based on stem diameter and circumference).In two complementary experiments,the use of photographs to estimate cross-sectional areas was first validated,then the use of a caliper and diameter tape was computer-simulated.The results indicated that the photographic method offers high precision,with mean relative errors below 0.1%,minimal deviation,and no significant bias,and the traditional methods led to substantial and systematic errors,with deviations from circularity and convexity significantly increasing the errors in area estimation.展开更多
Based on Biot’s theory and considering the properties of a cavity,the boundary integral equations for the numerical simulation of wave scattering around a cavity with a circular cross-section embedded in saturated so...Based on Biot’s theory and considering the properties of a cavity,the boundary integral equations for the numerical simulation of wave scattering around a cavity with a circular cross-section embedded in saturated soil are obtained using integral transform methods.The Cauchy type singularity of the boundary integral equation is discussed.The effectiveness of the properties of soil mass and incident field on the dynamic stress concentration and pore pressure concentration around a cavity is analyzed.Our results are in good agreement with the existing solution.The numerical results of this work show that the dynamic stress concentration and pore pressure concentration are influenced by the degree of fluid–solid coupling as well as the pore compressibility and water permeability of saturated soil.With increased degree of fluid–solid coupling,the dynamic stress concentration improves from 1.87 to 3.42 and the scattering becomes more significant.With decreased index of soil mass compressibility,the dynamic stress concentration increases and its maximum reaches 3.67.The dynamic stress concentration increases from 1.64 to 3.49 and pore pressure concentration improves from 0.18 to 0.46 with decreased water permeability of saturated soil.展开更多
The purpose of this work is to determine the best analytical approximation of the differential cross-sections,used in Monte Carlo simulation,to study the electron and positron slowing down in solid targets in the ener...The purpose of this work is to determine the best analytical approximation of the differential cross-sections,used in Monte Carlo simulation,to study the electron and positron slowing down in solid targets in the energy range up to 10 keV.For this,our comparative study has been carried out on the angular distribution of the scattering angle,the elastic total and the first transport cross-sections which are the essential quantities used generally in both the electron and the positron transport studies by using either stochastic or deterministic methods.Indeed,the obtained results using the relativistic partial wave expansion method and the backscattering coefficient(BSC)experimental data are used as criteria to evaluate the used model.展开更多
Based on Tian et al. ＇s theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relations...Based on Tian et al. ＇s theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relationships between the calculated backscattering cross section and the environmental parameters, such as wind speeds, azimuthal angles and incidence angles, were studied. Compared with the traditional two-scale scattering model, the results are much more coincident with the observations under the condition of moderate incidence angles, which is very useful to make up for the two-scale model. To make the new calculation model to be used conveniently in the practice, its simplified form was proposed.展开更多
The pion-nucleus elastic scattering and reaction cross-section data at incident energies below, atop and above the Δ-resonance are analyzed using the full Klein-Gordon equation using an optical potential. Analytic fo...The pion-nucleus elastic scattering and reaction cross-section data at incident energies below, atop and above the Δ-resonance are analyzed using the full Klein-Gordon equation using an optical potential. Analytic forms of the potential are determined using the inverse scattering theory in those cases where phase shift analyses were available. The Coulomb effect is incorporated using Stricker’s prescription. Both elastic scattering data and the reaction cross sections between 120 and 400 MeV are well reproduced. Both real and imaginary parts of the potential are local. The potential points determined by the inverse scattering theory in the interior region at 230 MeV clearly establish that the real part is repulsive. This remains the case at higher incident energies. The real part turns repulsive above the resonance, whereas the imaginary part reflects the dominance of surface absorption, which is maximum near atop the Δ-resonance and then falling off at higher energies.展开更多
Objective The relationship between non-high-density lipoprotein(NHDL)cholesterol to high-density lipoprotein cholesterol(HDL-C)ratio(NHHR)and stoke remains unknown.This study aimed to evaluate the association between ...Objective The relationship between non-high-density lipoprotein(NHDL)cholesterol to high-density lipoprotein cholesterol(HDL-C)ratio(NHHR)and stoke remains unknown.This study aimed to evaluate the association between the adult NHHR and stroke occurrence in the United States of America(USA).Methods To clarify the relationship between the NHHR and stroke risk,this study used a multivariable logistic regression model and a restricted cubic spline(RCS)model to investigate the association between the NHHR and stroke,and data from the National Health and Nutrition Examination Survey(NHANES)from 2005 to 2018.Subgroup and sensitivity analyses were conducted to test the robustness of the results.Results This study included 29,928 adult participants,of which 1,165 participants had a history of stroke.Logistic regression analysis of variables demonstrated a positive association between NHHR and stroke(OR 1.24,95%CI:1.03-1.50,P=0.026).Compared with the lowest reference group of NHHR,participants in the second,third,and fourth quartile had a significantly increased risk of stroke after full adjustments(OR:1.35,95%CI:1.08-1.69)(OR:1.83,95%CI:1.42-2.36)(OR:2.04,95%CI:1.50-2.79).In the total population,a nonlinear dose-response relationship was observed between the NHHR and stroke risk(P non-linearity=0.002).This association remained significant in several subgroup analyses.Further investigation of the NHHR may enhance our understanding of stroke prevention and treatment.Conclusion Our findings suggest a positive correlation between the NHHR and an increased prevalence of stroke,potentially serving as a novel predictive factor for stroke.Timely intervention and management of the NHHR may effectively mitigate stroke occurrence.Prospective studies are required to validate this association and further explore the underlying biological mechanisms.展开更多
The umbilical,a key component in offshore energy extraction,plays a vital role in ensuring the stable operation of the entire production system.The extensive variety of cross-sectional components creates highly comple...The umbilical,a key component in offshore energy extraction,plays a vital role in ensuring the stable operation of the entire production system.The extensive variety of cross-sectional components creates highly complex layout combinations.Furthermore,due to constraints in component quantity and geometry within the cross-sectional layout,filler bodies must be incorporated to maintain cross-section performance.Conventional design approaches based on manual experience suffer from inefficiency,high variability,and difficulties in quantification.This paper presents a multi-level automatic filling optimization design method for umbilical cross-sectional layouts to address these limitations.Initially,the research establishes a multi-objective optimization model that considers compactness,balance,and wear resistance of the cross-section,employing an enhanced genetic algorithm to achieve a near-optimal layout.Subsequently,the study implements an image processing-based vacancy detection technique to accurately identify cross-sectional gaps.To manage the variability and diversity of these vacant regions,the research introduces a multi-level filling method that strategically selects and places filler bodies of varying dimensions,overcoming the constraints of uniform-size fillers.Additionally,the method incorporates a hierarchical strategy that subdivides the complex cross-section into multiple layers,enabling layer-by-layer optimization and filling.This approach reduces manufac-turing equipment requirements while ensuring practical production process feasibility.The methodology is validated through a specific umbilical case study.The results demonstrate improvements in compactness,balance,and wear resistance compared with the initial cross-section,offering novel insights and valuable references for filler design in umbilical cross-sections.展开更多
High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall...High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall.We propose an active polarized iterative optimization approach for high-resolution imaging through complex scattering media.By acquiring a series of sub-polarized images,we can capture the diverse pattern-illuminated images with various high-frequency component information caused by the Brownian motion of complex scattering materials,which are processed using the common-mode rejection of polarization characteristics to extract target information from scattering medium information.Following that,our computational reconstruction technique employs an iterative optimization algorithm that commences with patternilluminated Fourier ptychography for reconstructing the high-resolution scene.It is extremely important that our approach for high-resolution imaging through complex scattering media is not limited by priori information and optical memory effect.The proposed approach is suitable for not only dynamic but also static scattering media,which may find applications in the biomedicine field,such as skin abnormalities,non-invasive blood flow,and superficial tumors.展开更多
Objectives:This study aimed to classify young breast cancer patients into distinct ambivalence over emotional expression and to explore the factors influencingthe level of ambivalence over emotional expression.Methods...Objectives:This study aimed to classify young breast cancer patients into distinct ambivalence over emotional expression and to explore the factors influencingthe level of ambivalence over emotional expression.Methods:A total of 217 young breast cancer patients were enrolled from a tertiary Grade A oncology hospital in Tianjin,China,using the convenience sampling method.All participants completed the general questionnaire,Ambivalence over Emotion Expression Questionnaire(AEQ),and Family Adapt-Ability and Cohesion Evaluation Scales-Chinese Version(FACES-CV).We employed exploratory latent profileanalysis for ambivalence over emotional expression profilingand logistic regression analysis to identify the influentialfactors Results:The results of the latent profileanalysis supported the models of four latent profiles,which were definedas“low conflict-lowexpression reflection”(19.2%),“high conflict-high inhibition expression”(43.9%),“moderate conflict-highregret expression”(18.1%),and“moderate conflict-desire understand”(18.8%).Logistic regression revealed that family cohesion,marital status,residence,per capita monthly income,and cancer stage were the influencingfactors of ambivalence over emotional expression in young breast cancer patients(P<0.05)Conclusions:Levels of ambivalence over emotional expression ameast cancer patients with breast cancer were highly heterogeneous.Medical staff should provide psychological counseling and health education tailored to the unique characteristics of emotional expression ambivalence in different patient groups to promote healthy emotional expression among patients.展开更多
OBJECTIVE:To investigate the difference in gut microbiota between population with damp-heat constitution(DHC)and balanced constitution(BC).METHODS:A multi-centered cross-sectional casecontrol study was conducted,which...OBJECTIVE:To investigate the difference in gut microbiota between population with damp-heat constitution(DHC)and balanced constitution(BC).METHODS:A multi-centered cross-sectional casecontrol study was conducted,which included 249 participants with damp-heat constitution or balanced constitution.Baseline information of participants was collected,and stool samples were collected for gut microbiota analysis.Principal coordinate analysis,linear discriminant analysis effect size analysis,receiver operating characteristic,random forest model,and phylogenetic investigation of communities by reconstruction of unobserved states methods were used to reveal the relationship between gut microbiota and the damp-heat constitution.RESULTS:Compared to those in the BC group,the richness and diversity of the microbiota,specifically those of several short-chain fatty acid producing genera such as Barnesiella,Coprobacter,and Butyricimonas,were significantly decreased in the DHC group.Regarding biological functions,flavonoid biosynthesis,propanoate metabolism,and nucleotide sugar metabolism were suppressed,while arachidonic acid metabolism and glutathione metabolism were enriched in the DHC group.Finally,a classifier based on the microbiota was constructed to discriminate between the DHC and BC populations.CONCLUSION:The gut microbiota of the DHC population exhibits significantly reduced diversity and is closely related to inflammation,metabolic disorders,and liver steatosis,which is consistent with clinical observations,thus serving as a potential diagnostic tool for traditional Chinese medicine constitution discrimination.展开更多
Objective:Postpartum nutrition plays a critical role in maternal recovery and long-term health.However,the nutritional status of working mothers in the postpartum period remains understudied.This study aimed to assess...Objective:Postpartum nutrition plays a critical role in maternal recovery and long-term health.However,the nutritional status of working mothers in the postpartum period remains understudied.This study aimed to assess the dietary quality of postpartum women in urban Beijing,identify occupational-related factors influencing their diet,and explore potential interventions to improve maternal nutrition during the postpartum period.Methods:In this cross-sectional analysis,554 women one year after delivery were recruited from ten community health centers.Sociodemographic,occupational and postpartum care variables were collected via questionnaire.Dietary intake over the preceding year was assessed using a food frequency questionnaire.The modified dietary balance index for postpartum women were used for dietary quality assessment.Results:The study revealed severe dietary imbalances among postpartum women,characterized by excessive consumption of cereals,eggs,and meats,while their intake of vegetables,fruits,and dairy products was inadequate.According to dietary balance index for postpartum women,66.25%of mothers showed varying degrees of excessive intake.45.31%of mothers experienced varying levels of insufficient intake,with only 19.86%of participants having a relatively balanced diet.Occupational differences were observed,with women in the commercial employment group showing higher levels of excessive food intake.The analysis of influencing factors showed that family monthly income,maternity leave,and postpartum care significantly affected the dietary quality.Conclusions:Postpartum women in Beijing experience widespread dietary imbalances,with both excesses and deficiencies.Occupational context and related factors significantly shape diet quality.These findings highlight the need for targeted nutritional interventions tailored to the specific challenges of different occupational groups.展开更多
Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtain...Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.展开更多
To investigate the effects of the maximum principal stress direction(θ)and cross-section shape on the failure characteristics of sandstone,true-triaxial compression experiments were conducted using cubic samples with...To investigate the effects of the maximum principal stress direction(θ)and cross-section shape on the failure characteristics of sandstone,true-triaxial compression experiments were conducted using cubic samples with rectangular,circular,and D-shaped holes.Asθincreases from 0°to 60°in the rectangular hole,the left failure location shifts from the left corner to the left sidewall,the left corner,and then the floor,while the right failure location shifts from the right corner to the right sidewall,right roof corner,and then the roof.Furthermore,the initial failure vertical stress first decreases and then increases.In comparison,the failure severity in the rectangular hole decreases for variousθvalues as 30°>45°>60°>0°.With increasingθ,the fractal dimension(D)of rock slices first increases and then decreases.For the rectangular and D-shaped holes,whenθ=0°,30°,and 90°,D for the rectangular hole is less than that of the D-shaped hole.Whenθ=45°and 60°,D for the rectangular hole is greater than that of the D-shaped hole.Theoretical analysis indicates that the stress concentration at the rectangular and D-shaped corners is greater than the other areas.The failure location rotates with the rotation ofθ,and the failure occurs on the side with a high concentration of compressive stress,while the side with the tensile and compressive stresses remains relatively stable.Therefore,the fundamental reason for the rotation of failure location is the rotation of stress concentration,and the external influencing factor is the rotation ofθ.展开更多
We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)proc...We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)process.The coherent photon–phonon interaction where two optical modes couple to a Brillouin acoustic mode with a large decay rate provides an extra channel for the cooling of a Duffing mechanical oscillator.The squeezing degree and the robustness to the thermal noises of the Duffing mechanical mode can be enhanced greatly.When the Duffing nonlinearity is weak,the squeezing degree of the mechanical mode in the presence of BSBS can be improved by more than one order of magnitude compared with that in the absence of BSBS.Our scheme may be extended to other quantum systems to study novel quantum effects.展开更多
基金supported by the National Natural Science Foundation of China(Nos.11675057 and 11705195)the Hunan Provincial Education Department Project of China(No.15C1176)the General Financial Grant from the China Postdoctoral Science Foundation(No.2017M622697)
文摘To carry out accurate burnup calculations for a pebble-bed fluoride-salt-cooled high-temperature reactor,the energy-dependent cross-sectional model based on the Doppler broadening rejection correction method has been proposed to develop the energy-dependent elastic scattering cross-sectional model. In this study, the Monte Carlo continuous energy code PSG2/Serpent was used to examine the difference between the constant cross-sectional model and the energy-dependent cross-sectional model during burnup. For the cases analyzed in this study,numerical simulations show that the multiplication coefficient was improved by hundreds pcm and ^(239)Pu concentration was improved by approximately 1–2% during burnup when the energy-dependent elastic scattering crosssectional model is considered.
文摘Viewing gravitational energy-momentum PG<sup style='margin-left:-7px;'>μ as equal by observation, but different in essence from inertial energy-momentum PI<sup style='margin-left:-7px;'>μ naturally leads to the gauge theory of volume-preserving diffeomorphisms of a four-dimensional inner space. To analyse scattering in this theory, the gauge field is coupled to two Dirac fields with different masses. Based on a generalized LSZ reduction formula the S-matrix element for scattering of two Dirac particles in the gravitational limit and the corresponding scattering cross-section are calculated to leading order in perturbation theory. Taking the non-relativistic limit for one of the initial particles in the rest frame of the other the Rutherford-like cross-section of a non-relativistic particle scattering off an infinitely heavy scatterer calculated quantum mechanically in Newtonian gravity is recovered. This provides a non-trivial test of the gauge field theory of volume-preserving diffeomorphisms as a quantum theory of gravity.
文摘Objective:To assess prenatal Bisphenol A(BPA)exposure levels and explore their preliminary associations with maternal and fetal characteristics in a population from Northeastern Yunnan.Methods:A cross-sectional analysis was performed using data and urine samples from 70 pregnant women in their third trimester recruited at Qujing Central Hospital.Urinary BPA was measured by HPLC-MS/MS.Participants were stratified into high and low BPA exposure groups based on the median concentration.Results:BPA was detected in all samples(100%)with a median concentration of 2.41μg/L(IQR:0.68-4.96).The high BPA exposure group(≥2.41μg/L)had a significantly higher proportion of gestational diabetes mellitus(GDM)(42.9%vs.17.1%,p=0.021)and a lower median fetal birth weight(3250 g vs.3450 g,p=0.048)compared to the low exposure group.Conclusion:This pilot study reveals ubiquitous BPA exposure in pregnant women from Northeastern Yunnan.The observed preliminary associations with GDM and reduced fetal birth weight warrant further investigation in larger,longitudinal studies.
基金Project supported by the National Natural Science Foundation of China(Grant No.12074261)the Natural Science Foundation of Shanghai(Grant No.20ZR1441600)。
文摘By employing a full quantum theory of electron-photon scattering in intense laser fields,we calculate the angularresolved radiation rate of the fundamental wave in Thomson scattering.We investigate the dependence of radiation rate on Euler angles and elucidate the underlying physical mechanism.The figure-8 profile of the radiation rate within the polarization plane is validated,while its evolution with respect to laser intensity and electron momentum is illustrated.Our findings reveal that in lower-intensity laser fields and for slow electron motion,the angular-resolved radiation rate exhibits distinct dipole emission characteristics.However,significant changes are observed at high laser intensities and/or large electron momenta,leading to pronounced alterations in the angular-resolved radiation rate.Remarkably similar variation patterns can be achieved by proportionally adjusting both laser intensity and electron momentum.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB3710805).
文摘Ultra-high-strength aluminumalloy profile is an ideal choice for aerospace structuralmaterials due to its excellent specific strength and corrosion resistance.However,issues such as uneven metal flow,stress concentration,and forming defects are prone to occur during their extrusion.This study focuses on an Al-Zn-Mg-Cu ultra-high-strength aluminum alloy profile with a double-U,multi-cavity thin-walled structure.Firstly,hot compression experiments were conducted at temperatures of 350○C,400○C,and 450○C,with strain rates of 0.01 and 1.0 s^(−1),to investigate the plastic deformation behavior of the material.Subsequently,a 3D coupled thermo-mechanical extrusion simulation model was established using Deform-3D to systematically analyze the influence of die structure and process parameters on metal flow velocity,effective stress/strain,and temperature distribution.The simulation revealed significant velocity differences,stress concentration,and uneven temperature distribution.Key parameters,including mesh density,extrusion ratio,die fillet,and bearing length,were optimized through full-factorial experiments.This optimization,combined with a stepped flow-guiding die design,effectively improved the metal flow pattern during extrusion.Trial production based on both the initial and optimized parameters were carried out.A comparative analysis demonstrates that the optimized scheme results in a final profile whose cross-section matches the target design closely,with complete filling of complex features and no obvious forming defects.This research provides a valuable reference for the extrusion process optimization and die design of complex-section profiles made from ultra-high-strength aluminum alloys.
基金supported by the National Natural Science Foundation of China(82341245,82371491)the Chinese Central Government(Key Project of Public Health Program)the National Key Research and Development Program of China(2018YFC1311706,2018YFC1311702)。
文摘Objective This study aimed to determine the temporal trends in sleep duration among Chinese adults.Methods In this series of repeated nationally representative cross-sectional surveys(China Chronic Disease and Risk Factors Surveillance)conducted between 2010 and 2018,a total of 645,420 adult participants(97,741 in 2010;175,749 in 2013;187,777 in 2015;and 184,153 in 2018)were included in the trend analysis.Linear and logistic regression models were utilized to assess trends in sleep duration.Results In 2018,the estimated overall mean sleep duration among the Chinese adult population was7.58(SD,1.45)hours per day,with no significant trend from 2010.A significant increase in short sleep duration(≤6 hours)was observed in the total population,from 15.3%(95%CI:14.1%–16.5%)in 2010 to18.5%(95%CI:17.7%–19.3%)in 2018(P<0.001).Similarly,the trend in long sleep duration(>9 hours)was also significant,increasing in weighted prevalence from 7.2%(95%CI:6.3%–8.1%)in 2010 to 9.0%(95%CI:8.2%–9.9%)in 2018(P<0.001).Conclusion The prevalence of both short and long sleep durations significantly increased among Chinese adults from 2010 to 2018,highlighting the urgency of health initiatives to promote optimal sleep duration in China.
文摘We investigated the impact of convexity and isoperimetric deficits on the accuracy of sectional area estimates of tree stems using traditional methods(caliper,tape,formulas based on stem diameter and circumference).In two complementary experiments,the use of photographs to estimate cross-sectional areas was first validated,then the use of a caliper and diameter tape was computer-simulated.The results indicated that the photographic method offers high precision,with mean relative errors below 0.1%,minimal deviation,and no significant bias,and the traditional methods led to substantial and systematic errors,with deviations from circularity and convexity significantly increasing the errors in area estimation.
基金Projects(50969007,51269021) supported by the National Natural Science Foundation of ChinaProjects(20114BAB206012,20133ACB20006) supported by the Natural Science Foundation of Jiangxi Province of China
文摘Based on Biot’s theory and considering the properties of a cavity,the boundary integral equations for the numerical simulation of wave scattering around a cavity with a circular cross-section embedded in saturated soil are obtained using integral transform methods.The Cauchy type singularity of the boundary integral equation is discussed.The effectiveness of the properties of soil mass and incident field on the dynamic stress concentration and pore pressure concentration around a cavity is analyzed.Our results are in good agreement with the existing solution.The numerical results of this work show that the dynamic stress concentration and pore pressure concentration are influenced by the degree of fluid–solid coupling as well as the pore compressibility and water permeability of saturated soil.With increased degree of fluid–solid coupling,the dynamic stress concentration improves from 1.87 to 3.42 and the scattering becomes more significant.With decreased index of soil mass compressibility,the dynamic stress concentration increases and its maximum reaches 3.67.The dynamic stress concentration increases from 1.64 to 3.49 and pore pressure concentration improves from 0.18 to 0.46 with decreased water permeability of saturated soil.
文摘The purpose of this work is to determine the best analytical approximation of the differential cross-sections,used in Monte Carlo simulation,to study the electron and positron slowing down in solid targets in the energy range up to 10 keV.For this,our comparative study has been carried out on the angular distribution of the scattering angle,the elastic total and the first transport cross-sections which are the essential quantities used generally in both the electron and the positron transport studies by using either stochastic or deterministic methods.Indeed,the obtained results using the relativistic partial wave expansion method and the backscattering coefficient(BSC)experimental data are used as criteria to evaluate the used model.
文摘Based on Tian et al. ＇s theoretical model of microwave scattering, by using the wind wave spectrum suggested by Fung et al. , numerical results of polarized back-scattering were calculated. The quantitative relationships between the calculated backscattering cross section and the environmental parameters, such as wind speeds, azimuthal angles and incidence angles, were studied. Compared with the traditional two-scale scattering model, the results are much more coincident with the observations under the condition of moderate incidence angles, which is very useful to make up for the two-scale model. To make the new calculation model to be used conveniently in the practice, its simplified form was proposed.
文摘The pion-nucleus elastic scattering and reaction cross-section data at incident energies below, atop and above the Δ-resonance are analyzed using the full Klein-Gordon equation using an optical potential. Analytic forms of the potential are determined using the inverse scattering theory in those cases where phase shift analyses were available. The Coulomb effect is incorporated using Stricker’s prescription. Both elastic scattering data and the reaction cross sections between 120 and 400 MeV are well reproduced. Both real and imaginary parts of the potential are local. The potential points determined by the inverse scattering theory in the interior region at 230 MeV clearly establish that the real part is repulsive. This remains the case at higher incident energies. The real part turns repulsive above the resonance, whereas the imaginary part reflects the dominance of surface absorption, which is maximum near atop the Δ-resonance and then falling off at higher energies.
文摘Objective The relationship between non-high-density lipoprotein(NHDL)cholesterol to high-density lipoprotein cholesterol(HDL-C)ratio(NHHR)and stoke remains unknown.This study aimed to evaluate the association between the adult NHHR and stroke occurrence in the United States of America(USA).Methods To clarify the relationship between the NHHR and stroke risk,this study used a multivariable logistic regression model and a restricted cubic spline(RCS)model to investigate the association between the NHHR and stroke,and data from the National Health and Nutrition Examination Survey(NHANES)from 2005 to 2018.Subgroup and sensitivity analyses were conducted to test the robustness of the results.Results This study included 29,928 adult participants,of which 1,165 participants had a history of stroke.Logistic regression analysis of variables demonstrated a positive association between NHHR and stroke(OR 1.24,95%CI:1.03-1.50,P=0.026).Compared with the lowest reference group of NHHR,participants in the second,third,and fourth quartile had a significantly increased risk of stroke after full adjustments(OR:1.35,95%CI:1.08-1.69)(OR:1.83,95%CI:1.42-2.36)(OR:2.04,95%CI:1.50-2.79).In the total population,a nonlinear dose-response relationship was observed between the NHHR and stroke risk(P non-linearity=0.002).This association remained significant in several subgroup analyses.Further investigation of the NHHR may enhance our understanding of stroke prevention and treatment.Conclusion Our findings suggest a positive correlation between the NHHR and an increased prevalence of stroke,potentially serving as a novel predictive factor for stroke.Timely intervention and management of the NHHR may effectively mitigate stroke occurrence.Prospective studies are required to validate this association and further explore the underlying biological mechanisms.
基金financially supported by Guangdong Province Basic and Applied Basic Research Fund Project(Grant No.2022B1515250009)Liaoning Provincial Natural Science Foundation-Doctoral Research Start-up Fund Project(Grant No.2024-BSBA-05)+1 种基金Major Science and Technology Innovation Project in Shandong Province(Grant No.2024CXGC010803)the National Natural Science Foundation of China(Grant Nos.52271269 and 12302147).
文摘The umbilical,a key component in offshore energy extraction,plays a vital role in ensuring the stable operation of the entire production system.The extensive variety of cross-sectional components creates highly complex layout combinations.Furthermore,due to constraints in component quantity and geometry within the cross-sectional layout,filler bodies must be incorporated to maintain cross-section performance.Conventional design approaches based on manual experience suffer from inefficiency,high variability,and difficulties in quantification.This paper presents a multi-level automatic filling optimization design method for umbilical cross-sectional layouts to address these limitations.Initially,the research establishes a multi-objective optimization model that considers compactness,balance,and wear resistance of the cross-section,employing an enhanced genetic algorithm to achieve a near-optimal layout.Subsequently,the study implements an image processing-based vacancy detection technique to accurately identify cross-sectional gaps.To manage the variability and diversity of these vacant regions,the research introduces a multi-level filling method that strategically selects and places filler bodies of varying dimensions,overcoming the constraints of uniform-size fillers.Additionally,the method incorporates a hierarchical strategy that subdivides the complex cross-section into multiple layers,enabling layer-by-layer optimization and filling.This approach reduces manufac-turing equipment requirements while ensuring practical production process feasibility.The methodology is validated through a specific umbilical case study.The results demonstrate improvements in compactness,balance,and wear resistance compared with the initial cross-section,offering novel insights and valuable references for filler design in umbilical cross-sections.
基金supported by the National Natural Science Foundation of China(Grant Nos.62205259,62075175,62105254,and 62375212)the National Key Laboratory of Infrared Detection Technologies(Grant No.IRDT-23-06)+1 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.XJSJ24028,XJS222202,ZYTS24097,and ZYTS24095)the Open Research Fund of Beijing Key Laboratory of Advanced Optical Remote Sensing Technology.
文摘High-resolution seeing through complex scattering media such as turbid water,biological tissues,and mist is a significant challenge because the strong scattering scrambles the light paths and forms the scattering wall.We propose an active polarized iterative optimization approach for high-resolution imaging through complex scattering media.By acquiring a series of sub-polarized images,we can capture the diverse pattern-illuminated images with various high-frequency component information caused by the Brownian motion of complex scattering materials,which are processed using the common-mode rejection of polarization characteristics to extract target information from scattering medium information.Following that,our computational reconstruction technique employs an iterative optimization algorithm that commences with patternilluminated Fourier ptychography for reconstructing the high-resolution scene.It is extremely important that our approach for high-resolution imaging through complex scattering media is not limited by priori information and optical memory effect.The proposed approach is suitable for not only dynamic but also static scattering media,which may find applications in the biomedicine field,such as skin abnormalities,non-invasive blood flow,and superficial tumors.
基金funded by Tianjin Key Medical Discipline(Specialty)Construction Project,China(Grant No.TJYXZDXK-011A)Tianjin Medical University Cancer Institute&Hospital Nursing Special Fund Project(H2304)。
文摘Objectives:This study aimed to classify young breast cancer patients into distinct ambivalence over emotional expression and to explore the factors influencingthe level of ambivalence over emotional expression.Methods:A total of 217 young breast cancer patients were enrolled from a tertiary Grade A oncology hospital in Tianjin,China,using the convenience sampling method.All participants completed the general questionnaire,Ambivalence over Emotion Expression Questionnaire(AEQ),and Family Adapt-Ability and Cohesion Evaluation Scales-Chinese Version(FACES-CV).We employed exploratory latent profileanalysis for ambivalence over emotional expression profilingand logistic regression analysis to identify the influentialfactors Results:The results of the latent profileanalysis supported the models of four latent profiles,which were definedas“low conflict-lowexpression reflection”(19.2%),“high conflict-high inhibition expression”(43.9%),“moderate conflict-highregret expression”(18.1%),and“moderate conflict-desire understand”(18.8%).Logistic regression revealed that family cohesion,marital status,residence,per capita monthly income,and cancer stage were the influencingfactors of ambivalence over emotional expression in young breast cancer patients(P<0.05)Conclusions:Levels of ambivalence over emotional expression ameast cancer patients with breast cancer were highly heterogeneous.Medical staff should provide psychological counseling and health education tailored to the unique characteristics of emotional expression ambivalence in different patient groups to promote healthy emotional expression among patients.
基金National Nonprofit Institute Research Grant for the Institute of Basic Theory for Chinese Medicine,China Academy of Chinese Medical Sciences:Mechanism of Regulating Phlegm-Dampness Constitution to Prevent Metabolic Diseases based on Gut Microbiota-host DNA Methylation(No.YZ-202151)。
文摘OBJECTIVE:To investigate the difference in gut microbiota between population with damp-heat constitution(DHC)and balanced constitution(BC).METHODS:A multi-centered cross-sectional casecontrol study was conducted,which included 249 participants with damp-heat constitution or balanced constitution.Baseline information of participants was collected,and stool samples were collected for gut microbiota analysis.Principal coordinate analysis,linear discriminant analysis effect size analysis,receiver operating characteristic,random forest model,and phylogenetic investigation of communities by reconstruction of unobserved states methods were used to reveal the relationship between gut microbiota and the damp-heat constitution.RESULTS:Compared to those in the BC group,the richness and diversity of the microbiota,specifically those of several short-chain fatty acid producing genera such as Barnesiella,Coprobacter,and Butyricimonas,were significantly decreased in the DHC group.Regarding biological functions,flavonoid biosynthesis,propanoate metabolism,and nucleotide sugar metabolism were suppressed,while arachidonic acid metabolism and glutathione metabolism were enriched in the DHC group.Finally,a classifier based on the microbiota was constructed to discriminate between the DHC and BC populations.CONCLUSION:The gut microbiota of the DHC population exhibits significantly reduced diversity and is closely related to inflammation,metabolic disorders,and liver steatosis,which is consistent with clinical observations,thus serving as a potential diagnostic tool for traditional Chinese medicine constitution discrimination.
基金supported by an Innovation Fund for Medical Sciences of the Chinese Academy of Medical Sciences (Grant No.2019-I2M-2-007).
文摘Objective:Postpartum nutrition plays a critical role in maternal recovery and long-term health.However,the nutritional status of working mothers in the postpartum period remains understudied.This study aimed to assess the dietary quality of postpartum women in urban Beijing,identify occupational-related factors influencing their diet,and explore potential interventions to improve maternal nutrition during the postpartum period.Methods:In this cross-sectional analysis,554 women one year after delivery were recruited from ten community health centers.Sociodemographic,occupational and postpartum care variables were collected via questionnaire.Dietary intake over the preceding year was assessed using a food frequency questionnaire.The modified dietary balance index for postpartum women were used for dietary quality assessment.Results:The study revealed severe dietary imbalances among postpartum women,characterized by excessive consumption of cereals,eggs,and meats,while their intake of vegetables,fruits,and dairy products was inadequate.According to dietary balance index for postpartum women,66.25%of mothers showed varying degrees of excessive intake.45.31%of mothers experienced varying levels of insufficient intake,with only 19.86%of participants having a relatively balanced diet.Occupational differences were observed,with women in the commercial employment group showing higher levels of excessive food intake.The analysis of influencing factors showed that family monthly income,maternity leave,and postpartum care significantly affected the dietary quality.Conclusions:Postpartum women in Beijing experience widespread dietary imbalances,with both excesses and deficiencies.Occupational context and related factors significantly shape diet quality.These findings highlight the need for targeted nutritional interventions tailored to the specific challenges of different occupational groups.
基金supported by National Natural Science Foundation of China(12374358,91950207)Guangdong Basic and Applied Basic Research Foundation(2024A1515010420).
文摘Glucose molecules are of great significance being one of the most important molecules in metabolic chain.However,due to the small Raman scattering cross-section and weak/non-adsorption on bare metals,accurately obtaining their"fingerprint information"remains a huge obstacle.Herein,we developed a tip-enhanced Raman scattering(TERS)technique to address this challenge.Adopting an optical fiber radial vector mode internally illuminates the plasmonic fiber tip to effectively suppress the background noise while generating a strong electric-field enhanced tip hotspot.Furthermore,the tip hotspot approaching the glucose molecules was manipulated via the shear-force feedback to provide more freedom for selecting substrates.Consequently,our TERS technique achieves the visualization of all Raman modes of glucose molecules within spectral window of 400-3200 cm^(-1),which is not achievable through the far-field/surface-enhanced Raman,or the existing TERS techniques.Our TERS technique offers a powerful tool for accurately identifying Raman scattering of molecules,paving the way for biomolecular analysis.
基金supported by the National Natural Science Foundation of China (Grant Nos.52304227 and 52104133)Scientific and Technological Research Platform for Disaster Prevention and Control of Deep Coal Mining (Anhui University of Science and Technology) (Grant No.DPDCM2208).
文摘To investigate the effects of the maximum principal stress direction(θ)and cross-section shape on the failure characteristics of sandstone,true-triaxial compression experiments were conducted using cubic samples with rectangular,circular,and D-shaped holes.Asθincreases from 0°to 60°in the rectangular hole,the left failure location shifts from the left corner to the left sidewall,the left corner,and then the floor,while the right failure location shifts from the right corner to the right sidewall,right roof corner,and then the roof.Furthermore,the initial failure vertical stress first decreases and then increases.In comparison,the failure severity in the rectangular hole decreases for variousθvalues as 30°>45°>60°>0°.With increasingθ,the fractal dimension(D)of rock slices first increases and then decreases.For the rectangular and D-shaped holes,whenθ=0°,30°,and 90°,D for the rectangular hole is less than that of the D-shaped hole.Whenθ=45°and 60°,D for the rectangular hole is greater than that of the D-shaped hole.Theoretical analysis indicates that the stress concentration at the rectangular and D-shaped corners is greater than the other areas.The failure location rotates with the rotation ofθ,and the failure occurs on the side with a high concentration of compressive stress,while the side with the tensile and compressive stresses remains relatively stable.Therefore,the fundamental reason for the rotation of failure location is the rotation of stress concentration,and the external influencing factor is the rotation ofθ.
基金Project supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202400624)the Natural Science Foundation of Chongqing CSTC(Grant No.CSTB2022NSCQBHX0020)+3 种基金the China Electronics Technology Group Corporation 44th Research Institute(Grant No.6310001-2)the Project Grant“Noninvasive Sensing Measurement based on Terahertz Technology”from Province and MOE Collaborative Innovation Centre for New Generation Information Networking and Terminalsthe Key Research Program of CQUPT on Interdisciplinary and Emerging Field(A2018-01)the Venture&Innovation Support program for Chongqing Overseas Returnees Year 2022。
文摘We investigate theoretically the enhancement of mechanical squeezing in a multimode optomechanical system by introducing a coherent phonon–photon interaction via the backward stimulated Brillouin scattering(BSBS)process.The coherent photon–phonon interaction where two optical modes couple to a Brillouin acoustic mode with a large decay rate provides an extra channel for the cooling of a Duffing mechanical oscillator.The squeezing degree and the robustness to the thermal noises of the Duffing mechanical mode can be enhanced greatly.When the Duffing nonlinearity is weak,the squeezing degree of the mechanical mode in the presence of BSBS can be improved by more than one order of magnitude compared with that in the absence of BSBS.Our scheme may be extended to other quantum systems to study novel quantum effects.
