The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts....The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.展开更多
Objective The rising prevalence of childhood obesity is closely associated with suboptimal dietary patterns.To address this public health concern,we conducted a comprehensive study to examine the association between c...Objective The rising prevalence of childhood obesity is closely associated with suboptimal dietary patterns.To address this public health concern,we conducted a comprehensive study to examine the association between coarse cereals consumption and body fat percentage(BFP)in Chinese children and adolescents.Methods The study included 48,305 children aged 6–17 years from 28 districts/counties in 14 provinces across seven regions of China(24,152 girls and 24,153 boys).BFP was examined using bioelectrical impedance analysis in the early morning.Coarse cereals consumption was assessed using a Food Frequency Questionnaire and categorized into three groups:0 g/1,000 kcal per day,0–10 g/1,000kcal per day,and>10 g/1,000 kcal per day(daily consumption of coarse cereals×1,000/total energy consumption).Quantile regression model was used to analyze the association between coarse cereals and BFP,adjusting for potential confounders such as age,pubertal development stage,urban/rural and regional factors,total daily dietary energy consumption,sedentary time,moderate-to-high physical activity,household income,parental education,and consumption of other foods.Results Boys aged 6–10,11–14,and 15–17 years had median daily coarse cereals consumptions of6.6 g,7.1 g,and 5.7 g,with BFP of 19.6%,19.5%,and 17.5%(all P<0.05).Girls in the same age groups showed consumption of 7.1 g,8.4 g,and 6.7 g,with BFP of 20.3%,26.4%,and 31.0%(all P<0.05).The quantile regression results for boys showed that daily consumption of coarse cereals was significantly correlated with their BFP in the 0.15,0.25,and 0.50 quartiles,with regression coefficients of-0.257,-0.221,and-0.330,respectively,after adjusting for potential confounders(P<0.05).For girls,there was a significant correlation with PBF at the 0.05,0.15,0.25,0.50,0.75,and 0.85 quartiles,with regression coefficients of-0.258,-0.366,-0.372,-0.431,-0.472,and-0.503(P<0.05 for all).Conclusions Coarse cereals consumption among Chinese children and adolescents remains relatively low.Higher consumption was inversely associated with BFP in children aged 6–17 years.Future interventional studies should assess how increased coarse cereals consumption prevents childhood obesity.展开更多
Overweight and obesity has been a major public health problem globally.It was estimated that more than 2.1 billion adults were affected by overweight or obese in 2021 worldwide,about one fifth of whom lived in China^(...Overweight and obesity has been a major public health problem globally.It was estimated that more than 2.1 billion adults were affected by overweight or obese in 2021 worldwide,about one fifth of whom lived in China^([1]).By 2050,the country is forecast to remain the one with the largest population of overweight and obese globally^([1]),if no effective strategies were applied on overweight/obesity control.展开更多
[Significance]In alignment with the national germplasm security strategy,current research efforts are accelerating the adoption of precision breeding in sheep.Within the whole-genome selection,accurate phenotyping of ...[Significance]In alignment with the national germplasm security strategy,current research efforts are accelerating the adoption of precision breeding in sheep.Within the whole-genome selection,accurate phenotyping of body morphometrics is critical for assessing growth performance and breeding value.Traditional manual measurements are inefficient,prone to human error,and may cause stress to sheep,limiting their suitability for precision sheep management.By summarizing the applications of sheep body size measurement technologies and analyzing their development directions,this paper provides theoretical references and practical guidance for the research and application of non contact sheep body size measurement.[Progress]This review synthesizes progress across three principal methodological paradigms:two-dimensional(2D)image-based techniques,three-dimensional(3D)point cloud-based approaches,and integrated 2D-3D fusion systems.2D methods,employing either handcrafted geometric features or deep learning-based keypoint detector algorithms,are cost-effective and operationally simple but sensitive to variation in imaging conditions and unable to capture critical circumference metrics.3D point-cloud approaches enable precise reconstruction of full animal morphology,supporting comprehensive body-size acquisition with higher accuracy,yet face challenges including high hardware costs,complex data workflows,and sensitivity to posture variability.Hybrid 2D-3D fusion systems combine semantic richness from RGB imagery with geometric completeness from point clouds.Having been effectively validated in other livestock specise,e.g.,cattle and pigs,these fusion systems have demonstrated excellent performance,providing important technical references and practical insights for sheep body size measurement.[Conclusions and Prospects]Firstly,future research should focus on constructing large-scale,high-quality datasets for sheep body size measurement that encompass diverse breeds,growth stages,and environmental conditions,thereby enhancing model robustness and generalization.Secondly,the development of lightweight artificial intelligence models is essential.Techniques such as model compression,quantization,and algorithmic optimization can substantially reduce computational complexity and storage requirements,facilitating deployment in resource-constrained environments.Thirdly,the 3D point cloud processing pipeline should be streamlined to improve the efficiency of data acquisition,filtering,registration,and segmentation,while promoting the integration of low-cost,high-resilience vision systems into practical farming scenarios.Fourthly,specific emphasis should be placed on improving the accuracy of curved-dimensional measurements,such as chest circumference,abdominal circumference,and shank circumference,through advances in pose standardization,refined 3D segmentation strategies,and multimodal data fusion.Finally,the cross-fertilization of sheep body size measurement technologies with analogous methods for other livestock species offers a promising pathway for mutual learning and collaborative innovation,accelerating the industrialization of automated sheep morphometric systems and supporting the development of intelligent,data-driven pasture management practices.展开更多
Objective:Hypertension is a serious public health concern that is influenced by a variety of body composition parameters.This study examines the associations between body composition metrics and blood pressure(BP)in a...Objective:Hypertension is a serious public health concern that is influenced by a variety of body composition parameters.This study examines the associations between body composition metrics and blood pressure(BP)in a rural population,specifically how variations in body fat distribution and other metrics affect systolic blood pressure(SBP)and diastolic blood pressure(DBP).Methods:A cross-sectional study of 226 participants examined the relationships between body composition metrics—such as total body fat,visceral fat,and body mass index(BMI)—and BP.Correlation and regression analyses were used to assess these relationships.Results:The study found substantial positive correlations between visceral fat and total body fat with both SBP and DBP.Visceral fat was strongly connected with both SBP(r=0.145,P=0.030)and DBP(r=0.331,P<0.01),while total body fat was significantly correlated with DBP(r=0.268,P<0.01)but not SBP.Body composition variables explained 12.8% of the variance in SBP(R^(2)=0.128,P=0.001)and 15.0% in DBP(R^(2)=0.150,P<0.001).Conclusions:The study found substantial connections between body composition,particularly visceral and subcutaneous fat and systolic and DBP.Higher levels of visceral fat were linked to elevate BP.Body composition accounted for a significant amount of BP fluctuation.展开更多
Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-...Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-mediated e–h recombination the dominant decay pathway.In this work,nonradiative e–h recombination within excitons in monolayer MoS_(2) is investigated using first-principles simulations that combine nonadiabatic molecular dynamics with GW and real-time Bethe–Salpeter equation(BSE)propagation.A two-step process is identified:rapid intervalley redistribution induced by exchange interaction,followed by slower phonon-assisted recombination facilitated by exciton binding.By selectively removing the screened Coulomb and exchange terms from the BSE Hamiltonian,their respective contributions are disentangled—exchange interaction is found to increase the number of accessible recombination pathways,while binding reduces the excitation energy and enhances nonradiative decay.A reduction in recombination lifetime by over an order of magnitude is observed due to the excitonic many-body effects.These findings provide microscopic insights for understanding and tuning exciton lifetimes in 2D transition-metal dichalcogenides.展开更多
Objective Previous studies link lower body mass index(BMI)with increased obsessive-compulsive disorder(OCD)risk,yet other body mass indicators may be more etioloically relevant.We dissected the causal association betw...Objective Previous studies link lower body mass index(BMI)with increased obsessive-compulsive disorder(OCD)risk,yet other body mass indicators may be more etioloically relevant.We dissected the causal association between body fat mass(FM)and OCD.Methods Summary statistics from genome-wide association studies of European ancestry were utilized to conduct two-sample Mendelian randomization analysis.Heterogeneity,horizontal pleiotropy,and sensitivity analyses were performed to assess the robustness.Results The inverse variance weighting method demonstrated that a genetically predicted decrease in FM was causally associated with an increased OCD risk[odds ratio(OR)=0.680,95%confidence interval(CI):0.528–0.875,P=0.003].Similar estimates were obtained using the weighted median approach(OR=0.633,95%CI:0.438–0.915,P=0.015).Each standard deviation increases in genetically predicted body fat percentage corresponded to a reduced OCD risk(OR=0.638,95%CI:0.455–0.896,P=0.009).The sensitivity analysis confirmed the robustness of these findings with no outlier instrument variables identified.Conclusion The negative causal association between FM and the risk of OCD suggests that the prevention or treatment of mental disorders should include not only the control of BMI but also fat distribution and body composition.展开更多
Background:Minimally invasive distal pancreatectomy(MIDP)is increasingly being used,although its oncologic safety for pancreatic ductal adenocarcinoma(PDAC)remains controversial.In Japan,MIDP for PDAC has limited endo...Background:Minimally invasive distal pancreatectomy(MIDP)is increasingly being used,although its oncologic safety for pancreatic ductal adenocarcinoma(PDAC)remains controversial.In Japan,MIDP for PDAC has limited endorsement due to insufficient data.This study aimed to compare the perioperative and long-term outcomes of open distal pancreatectomy(ODP)and MIDP for PDAC.Methods:We retrospectively analyzed patients with resectable pancreatic body and tail cancer treated with ODP or MIDP(laparoscopic or robotic)between January 2007 and July 2022.The surgical procedures(ODP and MIDP)were compared and the patient characteristics,perioperative outcomes,and long-term outcomes were analyzed.We also compared the outcomes of patients with neoadjuvant chemotherapy(NAC)and without NAC.Results:A total of 72 distal pancreatectomies were performed(37 ODPs and 35 MIDPs).In the upfront group,MIDP resulted in significantly less blood loss than ODP(P<0.01),despite similar operative time.There was no statistically significant difference in the 2-year recurrence-free survival(RFS)rates between ODP and MIDP(39.7%vs.57.8%,P=0.60)or in the overall survival(OS)rates(66.7%vs.74.1%,P=0.43).Similarly,in the NAC group,MIDP resulted in significantly less blood loss than ODP(P=0.01);ODP and MIDP had similar 2-year RFS rates(41.7%and 60.0%,P=0.75)and OS rates(50.0%and 70.0%,P=0.36).The interval from surgery to adjuvant chemotherapy initiation did not significantly differ between the ODP and MIDP subgroups in both the upfront group(P=0.13)and the NAC group(P=0.14).The incidence of recurrence was 64.8%for ODP and 42.8%for MIDP(P=0.06).Both procedures showed similar distributions of local and distant recurrence.Conclusions:MIDP caused less blood loss and had similar oncologic safety compared with ODP.MIDP could become a feasible,minimally invasive option with sufficient oncologic safety for pancreatic body and tail cancers.展开更多
Detecting biomarkers in body fluids by optical lateral flow immune assay(LFIA) technology provides rapid access to disease information for early diagnosis.LFIA is based on an antigen-antibody reaction and is rapidly b...Detecting biomarkers in body fluids by optical lateral flow immune assay(LFIA) technology provides rapid access to disease information for early diagnosis.LFIA is based on an antigen-antibody reaction and is rapidly becoming the preferred choice of physicians and patients for point-of-care testing due to its simplicity,cost-effectiveness,and rapid detection.Observing the optical signal change from the colloidal gold of the traditional LFIA strip has been widely applied for various biomarkers detection in body fluids.Despite the significant progress,rapid real-time detection of color changes in the colloidal gold by the naked eye still faces many limitations,such as large errors and the inability to quantify and accurately detect.New optical LFIA strip technology has emerged in recent years to extend its application scenarios for achieving quantitative detection such as fluorescence,afterglow,and chemiluminescence.Herein,we summarized the development of optical LFIA technology from single to hyphenated optical signals for biomarkers detection in body fluids from invasive and non-invasive sources.Moreover,the challenge and outlook of optical LFIA strip technology are highlighted to inspire the designing of next-generation diagnostic platforms.展开更多
Seabed mining operations have been found to induce significant movement and deformation in overlying rock strata,posing serious threats to mining safety.The presence of geological faults further complicates these defo...Seabed mining operations have been found to induce significant movement and deformation in overlying rock strata,posing serious threats to mining safety.The presence of geological faults further complicates these deformation patterns.This study utilized geophysical surveys and the continuum-based discrete element method(CDEM)to investigate how fault activity influences rock deformation and failure.The results demonstrate that:1)Acting in mechanically weak zones,faults exerted a pronounced barrier effect on deformation propagation and stress redistribution within the surrounding rock,leading to markedly divergent displacement patterns on either side of the fault plane.Comparative analyses between single-fault and double-fault models revealed an 18%−22%expansion of the damage zone under the latter,together with significantly intensified deformation and failure;2)The double-fault model exhibited a larger maximum cumulative vertical displacement and a spatial shift in the location of peak deformation,thereby posing a heightened threat to mine safety;3)Acting in an orebody substitute,backfill effectively constrained surrounding rock deformation,enhanced its load-bearing capacity,and delayed the overburden subsidence.Nevertheless,backfill only reduced the amplitude of deformation;it could not entirely prevent settlement.These findings provide essential theoretical insights and foundational knowledge for safer submarine mining practices.展开更多
Foreign body classification on coal conveyor belts is a critical component of intelligent coal mining systems.Previous approaches have primarily utilized convolutional neural networks(CNNs)to effectively integrate spa...Foreign body classification on coal conveyor belts is a critical component of intelligent coal mining systems.Previous approaches have primarily utilized convolutional neural networks(CNNs)to effectively integrate spatial and semantic information.However,the performance of CNN-based methods remains limited in classification accuracy,primarily due to insufficient exploration of local image characteristics.Unlike CNNs,Vision Transformer(ViT)captures discriminative features by modeling relationships between local image patches.However,such methods typically require a large number of training samples to perform effectively.In the context of foreign body classification on coal conveyor belts,the limited availability of training samples hinders the full exploitation of Vision Transformer’s(ViT)capabilities.To address this issue,we propose an efficient approach,termed Key Part-level Attention Vision Transformer(KPA-ViT),which incorporates key local information into the transformer architecture to enrich the training information.It comprises three main components:a key-point detection module,a key local mining module,and an attention module.To extract key local regions,a key-point detection strategy is first employed to identify the positions of key points.Subsequently,the key local mining module extracts the relevant local features based on these detected points.Finally,an attention module composed of self-attention and cross-attention blocks is introduced to integrate global and key part-level information,thereby enhancing the model’s ability to learn discriminative features.Compared to recent transformer-based frameworks—such as ViT,Swin-Transformer,and EfficientViT—the proposed KPA-ViT achieves performance improvements of 9.3%,6.6%,and 2.8%,respectively,on the CUMT-BelT dataset,demonstrating its effectiveness.展开更多
The Double Take column looks at a single topic from an African and Chinese perspective.This month,we explore how young people respond to the increasing focus on body weight management.As obesity rates climb,body weigh...The Double Take column looks at a single topic from an African and Chinese perspective.This month,we explore how young people respond to the increasing focus on body weight management.As obesity rates climb,body weight management has become a growing concern in China.The government is introducing targeted policies,hospitals are setting up dedicated clinics,and health experts are speaking out.But weight is no longer just a medical issue-it’s increas-ingly tied to identity,confidence,and social image.We examine the cultural forces shaping how young people in China and Africa approach weight-what drives their choices,how ideals are formed,and where health meets appearance in today’s shifting societies.展开更多
Background Depression is a common comorbidity in Parkinson's disease(PD)and Lewy body dementia(LBD).However,studies examining the rate of incident depression in the period preceding and following the diagnosis of ...Background Depression is a common comorbidity in Parkinson's disease(PD)and Lewy body dementia(LBD).However,studies examining the rate of incident depression in the period preceding and following the diagnosis of PD and LBD are lacki ng in the literature.Aims To quantify the incidence of depression in the period preceding and following the diagnosis of PD and LBD.Methods We conducted a retrospective case-control study.Specifically,we used Danish registers to identify all patients with a diagnosis of PD or LBD in the period from 2007 to 2019.These patients were matched by age,calendar year of diagnosis and sex with up to three patients diagnosed with rheumatoid arthritis(RA),chronic kidney disease(CKD)or osteoporosis,respectively.The outcome was incident depression.The incidence of depression was assessed for up to 10 years before and up to 10 years after the diagnosis of PD or LBD.Hazard rates of incident depression for patients with PD or LBD,both before and after diagnosis,were compared with those for patients with RA,CKD or osteoporosis using a Coxproportional hazards model.Results We identified 17711 patients with PD or LBD.Their median age was 74.98(68.10-80.85)years,and39.92%were females.These patients were matched to 19556,40842 and 47809 patients with RA,CKD and osteoporosis,respectively.From 7 to 8 years before diagnosis to 5 years after diagnosis,patients with PD and LBD consistently had higher hazard rates of incident depression than all comparator groups.Conclusions These findings are compatible with depression being an early manifestation of the neurodegenerative changes eventually leading to PD and LBD and imply that incident depression at a late age should raise awareness of potential PD and LBD.展开更多
Background:University students face significant challenges inmaintaining healthy physical activity(PA)and dietary habits,and they often fall short of global health recommendations.Psychological factors such as social ...Background:University students face significant challenges inmaintaining healthy physical activity(PA)and dietary habits,and they often fall short of global health recommendations.Psychological factors such as social physique anxiety,body image concerns,and self-objectification may act as barriers to PA engagement,influencing both mental and physical health.The present study constructed a structural equation model(SEM)to examine the relationship between body image-related psychological factors and resistance to PA in university students from southern Spain.Methods:A cross-sectional and correlational study was conducted with 519 university students(74%females,26%males;Mean age=21.14±3.26 years)from universities in Granada and Malaga(Spain).Data were collected between May and October 2024 via online questionnaires that assessed PA engagement,Mediterranean diet adherence,eating disorder symptoms,body image-related psychological factors(social physique anxiety,appearance control beliefs,body surveillance,body shame,and self-esteem),and sociodemographic characteristics.SEM was performed to analyze relationships and sex-based differences.Results:Social physique anxietywas positively associated with body shame,body surveillance,and eating disorders,and negatively associated with self-esteem,PA engagement,and appearance control beliefs(all p<0.001).Appearance control beliefs were positively related to self-esteem,body surveillance,and PA(all p<0.05).Body surveillance was negatively linked to PA and positively linked to body shame.Mediterranean diet adherence and eating disorders were positively associated with PA(all p<0.001).Sex-based differences were observed in the model.Conclusion:Body image-related psychological factors may act as barriers to PA among university students.Interventions should integrate mental health promotion and consider sex differences.展开更多
Body mass index(BMI),with its simple formula of weight divided by height squared,has become a cornerstone tool in global public health for assessing obesity and health risks.However,as populations aging and the demand...Body mass index(BMI),with its simple formula of weight divided by height squared,has become a cornerstone tool in global public health for assessing obesity and health risks.However,as populations aging and the demand for precise health evaluation grows,the limitations of this single metric have become increasingly apparent—it fails to distinguish between muscle and adipose tissue and cannot capture the complex relationship between inflammatory status and body composition.A recent study published in Biomedical and Environmental Sciences(BES)by Zhang et al.[1],which explores the association of white blood cell(WBC)count,platelet(PLT)count,and platelet-to-white blood cell ratio(PWR)with muscle mass among Chinese communitydwelling older adults,provides critical evidence for rethinking the role of BMI.Additionally,several studies published in BES,spanning from childhood nutrition to adult metabolism,further illuminate the complexity of health assessment[2−5].Building on these findings and integrating evidence from multiple Chinese population studies,this commentary revisits the historical context,utility,inherent limitations,and future directions of this classic indicator.展开更多
BACKGROUND:This study aims to explore the causal relationship of body weight,body mass index(BMI),and waist circumference (WC) with the risk of cardiac arrest (CA) using two-sample Mendelian randomization (MR).METHODS...BACKGROUND:This study aims to explore the causal relationship of body weight,body mass index(BMI),and waist circumference (WC) with the risk of cardiac arrest (CA) using two-sample Mendelian randomization (MR).METHODS:Data were summarized using genome-wide association studies (GWAS).Twosample MR analyses were performed using the inverse variance weighting (IVW) method,the weighted median method,and the MR-Egger analysis.Heterogeneity test and sensitivity analysis were performed using Cochran’s Q test and the leave-one-out method,respectively.The Steiger test was used to detect reverse causality.Bayesian model-averaged MR was used to identify the most influential risk factors.RESULTS:A total of 13 GWAS data were collected for BMI,body weight and WC.IVW analyses showed a positive correlation of body weight,BMI,and WC with CA (all OR>1 and P<0.05),with MR-Egger and weighted median methods confirming the IVW findings.No horizontal pleiotropy or heterogeneity was observed.Sensitivity analysis indicated that no single nucleotide polymorphism(SNP) caused significant changes in overall causality.Bayesian model-averaged MR was also used to rank causality based on marginal inclusion probability (MIP),and the corresponding modelaveraged causal estimate (MACE) were confirmed,which indicated that WC (GWAS ID:ukb-b-9405)was the highest-ranked risk factor (MIP=0.119,MACE=0.011);its posterior probability was 0.057.A total of 14 sex-specific GWAS data on weight,BMI,and WC were analyzed in relationship with CA,and the MR results showed no significant effects of sex-specific factors.CONCLUSION:Body weight,BMI,and WC are causally associated with an increased risk of CA,with WC identified as the most important risk factor.展开更多
The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and ce...The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.展开更多
Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car bo...Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.展开更多
文摘The concept of emissivity has been with the scientific and engineering world since Planck formulated his blackbody radiation law more than a century ago.Nevertheless,emissivity is an elusive concept even for ex⁃perts.It is a vague and fuzzy concept for the wider community of engineers.The importance of remote sensing of temperature by measuring IR radiation has been recognized in a wide range of industrial,medical,and environ⁃mental uses.One of the major sources of errors in IR radiometry is the emissivity of the surface being measured.In real experiments,emissivity may be influenced by many factors:surface texture,spectral properties,oxida⁃tion,and aging of surfaces.While commercial blackbodies are prevalent,the much-needed grey bodies with a known emissivity,are unavailable.This study describes how to achieve a calibrated and stable emissivity with a blackbody,a perforated screen,and a reliable and linear novel IR thermal sensor,18 dubbed TMOS.The Digital TMOS is now a low-cost commercial product,it requires low power,and it has a small form factor.The method⁃ology is based on two-color measurements,with two different optical filters,with selected wavelengths conform⁃ing to the grey body definition of the use case under study.With a photochemically etched perforated screen,the effective emissivity of the screen is simply the hole density area of the surface area that emits according to the blackbody temperature radiation.The concept is illustrated with ray tracing simulations,which demonstrate the approach.Measured results are reported.
基金supported by the Special Project of National Science and Technology Basic Resources Survey(Grant No.2017FY101100)。
文摘Objective The rising prevalence of childhood obesity is closely associated with suboptimal dietary patterns.To address this public health concern,we conducted a comprehensive study to examine the association between coarse cereals consumption and body fat percentage(BFP)in Chinese children and adolescents.Methods The study included 48,305 children aged 6–17 years from 28 districts/counties in 14 provinces across seven regions of China(24,152 girls and 24,153 boys).BFP was examined using bioelectrical impedance analysis in the early morning.Coarse cereals consumption was assessed using a Food Frequency Questionnaire and categorized into three groups:0 g/1,000 kcal per day,0–10 g/1,000kcal per day,and>10 g/1,000 kcal per day(daily consumption of coarse cereals×1,000/total energy consumption).Quantile regression model was used to analyze the association between coarse cereals and BFP,adjusting for potential confounders such as age,pubertal development stage,urban/rural and regional factors,total daily dietary energy consumption,sedentary time,moderate-to-high physical activity,household income,parental education,and consumption of other foods.Results Boys aged 6–10,11–14,and 15–17 years had median daily coarse cereals consumptions of6.6 g,7.1 g,and 5.7 g,with BFP of 19.6%,19.5%,and 17.5%(all P<0.05).Girls in the same age groups showed consumption of 7.1 g,8.4 g,and 6.7 g,with BFP of 20.3%,26.4%,and 31.0%(all P<0.05).The quantile regression results for boys showed that daily consumption of coarse cereals was significantly correlated with their BFP in the 0.15,0.25,and 0.50 quartiles,with regression coefficients of-0.257,-0.221,and-0.330,respectively,after adjusting for potential confounders(P<0.05).For girls,there was a significant correlation with PBF at the 0.05,0.15,0.25,0.50,0.75,and 0.85 quartiles,with regression coefficients of-0.258,-0.366,-0.372,-0.431,-0.472,and-0.503(P<0.05 for all).Conclusions Coarse cereals consumption among Chinese children and adolescents remains relatively low.Higher consumption was inversely associated with BFP in children aged 6–17 years.Future interventional studies should assess how increased coarse cereals consumption prevents childhood obesity.
文摘Overweight and obesity has been a major public health problem globally.It was estimated that more than 2.1 billion adults were affected by overweight or obese in 2021 worldwide,about one fifth of whom lived in China^([1]).By 2050,the country is forecast to remain the one with the largest population of overweight and obese globally^([1]),if no effective strategies were applied on overweight/obesity control.
文摘[Significance]In alignment with the national germplasm security strategy,current research efforts are accelerating the adoption of precision breeding in sheep.Within the whole-genome selection,accurate phenotyping of body morphometrics is critical for assessing growth performance and breeding value.Traditional manual measurements are inefficient,prone to human error,and may cause stress to sheep,limiting their suitability for precision sheep management.By summarizing the applications of sheep body size measurement technologies and analyzing their development directions,this paper provides theoretical references and practical guidance for the research and application of non contact sheep body size measurement.[Progress]This review synthesizes progress across three principal methodological paradigms:two-dimensional(2D)image-based techniques,three-dimensional(3D)point cloud-based approaches,and integrated 2D-3D fusion systems.2D methods,employing either handcrafted geometric features or deep learning-based keypoint detector algorithms,are cost-effective and operationally simple but sensitive to variation in imaging conditions and unable to capture critical circumference metrics.3D point-cloud approaches enable precise reconstruction of full animal morphology,supporting comprehensive body-size acquisition with higher accuracy,yet face challenges including high hardware costs,complex data workflows,and sensitivity to posture variability.Hybrid 2D-3D fusion systems combine semantic richness from RGB imagery with geometric completeness from point clouds.Having been effectively validated in other livestock specise,e.g.,cattle and pigs,these fusion systems have demonstrated excellent performance,providing important technical references and practical insights for sheep body size measurement.[Conclusions and Prospects]Firstly,future research should focus on constructing large-scale,high-quality datasets for sheep body size measurement that encompass diverse breeds,growth stages,and environmental conditions,thereby enhancing model robustness and generalization.Secondly,the development of lightweight artificial intelligence models is essential.Techniques such as model compression,quantization,and algorithmic optimization can substantially reduce computational complexity and storage requirements,facilitating deployment in resource-constrained environments.Thirdly,the 3D point cloud processing pipeline should be streamlined to improve the efficiency of data acquisition,filtering,registration,and segmentation,while promoting the integration of low-cost,high-resilience vision systems into practical farming scenarios.Fourthly,specific emphasis should be placed on improving the accuracy of curved-dimensional measurements,such as chest circumference,abdominal circumference,and shank circumference,through advances in pose standardization,refined 3D segmentation strategies,and multimodal data fusion.Finally,the cross-fertilization of sheep body size measurement technologies with analogous methods for other livestock species offers a promising pathway for mutual learning and collaborative innovation,accelerating the industrialization of automated sheep morphometric systems and supporting the development of intelligent,data-driven pasture management practices.
基金supported by Universitas Advent Indonesia(No.067/EKS-SU/V/24 and 389/KEPK-FIK.UNAI/EC/V/24)。
文摘Objective:Hypertension is a serious public health concern that is influenced by a variety of body composition parameters.This study examines the associations between body composition metrics and blood pressure(BP)in a rural population,specifically how variations in body fat distribution and other metrics affect systolic blood pressure(SBP)and diastolic blood pressure(DBP).Methods:A cross-sectional study of 226 participants examined the relationships between body composition metrics—such as total body fat,visceral fat,and body mass index(BMI)—and BP.Correlation and regression analyses were used to assess these relationships.Results:The study found substantial positive correlations between visceral fat and total body fat with both SBP and DBP.Visceral fat was strongly connected with both SBP(r=0.145,P=0.030)and DBP(r=0.331,P<0.01),while total body fat was significantly correlated with DBP(r=0.268,P<0.01)but not SBP.Body composition variables explained 12.8% of the variance in SBP(R^(2)=0.128,P=0.001)and 15.0% in DBP(R^(2)=0.150,P<0.001).Conclusions:The study found substantial connections between body composition,particularly visceral and subcutaneous fat and systolic and DBP.Higher levels of visceral fat were linked to elevate BP.Body composition accounted for a significant amount of BP fluctuation.
基金supported by the National Key Research and Development Program of China (Grant Nos.2024YFA1409800 for J.Z.and2024YFA1408603 for Q.Z.)the National Natural Science Foundation of China (Grant Nos.12125408,12334004for J.Z.,and 12174363 for Q.Z.)+1 种基金the Innovation Program for Quantum Science and Technology (Grant No.2021ZD0303306 for J.Z.)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0450101 for J.Z.)。
文摘Electron–hole(e–h)recombination is a fundamental process that governs energy dissipation and device efficiency in semiconductors.In two-dimensional(2D)materials,the formation of tightly bound excitons makes exciton-mediated e–h recombination the dominant decay pathway.In this work,nonradiative e–h recombination within excitons in monolayer MoS_(2) is investigated using first-principles simulations that combine nonadiabatic molecular dynamics with GW and real-time Bethe–Salpeter equation(BSE)propagation.A two-step process is identified:rapid intervalley redistribution induced by exchange interaction,followed by slower phonon-assisted recombination facilitated by exciton binding.By selectively removing the screened Coulomb and exchange terms from the BSE Hamiltonian,their respective contributions are disentangled—exchange interaction is found to increase the number of accessible recombination pathways,while binding reduces the excitation energy and enhances nonradiative decay.A reduction in recombination lifetime by over an order of magnitude is observed due to the excitonic many-body effects.These findings provide microscopic insights for understanding and tuning exciton lifetimes in 2D transition-metal dichalcogenides.
基金supported by the Yanzhao Gold Talent Project of Hebei Province(NO.HJZD202506)。
文摘Objective Previous studies link lower body mass index(BMI)with increased obsessive-compulsive disorder(OCD)risk,yet other body mass indicators may be more etioloically relevant.We dissected the causal association between body fat mass(FM)and OCD.Methods Summary statistics from genome-wide association studies of European ancestry were utilized to conduct two-sample Mendelian randomization analysis.Heterogeneity,horizontal pleiotropy,and sensitivity analyses were performed to assess the robustness.Results The inverse variance weighting method demonstrated that a genetically predicted decrease in FM was causally associated with an increased OCD risk[odds ratio(OR)=0.680,95%confidence interval(CI):0.528–0.875,P=0.003].Similar estimates were obtained using the weighted median approach(OR=0.633,95%CI:0.438–0.915,P=0.015).Each standard deviation increases in genetically predicted body fat percentage corresponded to a reduced OCD risk(OR=0.638,95%CI:0.455–0.896,P=0.009).The sensitivity analysis confirmed the robustness of these findings with no outlier instrument variables identified.Conclusion The negative causal association between FM and the risk of OCD suggests that the prevention or treatment of mental disorders should include not only the control of BMI but also fat distribution and body composition.
文摘Background:Minimally invasive distal pancreatectomy(MIDP)is increasingly being used,although its oncologic safety for pancreatic ductal adenocarcinoma(PDAC)remains controversial.In Japan,MIDP for PDAC has limited endorsement due to insufficient data.This study aimed to compare the perioperative and long-term outcomes of open distal pancreatectomy(ODP)and MIDP for PDAC.Methods:We retrospectively analyzed patients with resectable pancreatic body and tail cancer treated with ODP or MIDP(laparoscopic or robotic)between January 2007 and July 2022.The surgical procedures(ODP and MIDP)were compared and the patient characteristics,perioperative outcomes,and long-term outcomes were analyzed.We also compared the outcomes of patients with neoadjuvant chemotherapy(NAC)and without NAC.Results:A total of 72 distal pancreatectomies were performed(37 ODPs and 35 MIDPs).In the upfront group,MIDP resulted in significantly less blood loss than ODP(P<0.01),despite similar operative time.There was no statistically significant difference in the 2-year recurrence-free survival(RFS)rates between ODP and MIDP(39.7%vs.57.8%,P=0.60)or in the overall survival(OS)rates(66.7%vs.74.1%,P=0.43).Similarly,in the NAC group,MIDP resulted in significantly less blood loss than ODP(P=0.01);ODP and MIDP had similar 2-year RFS rates(41.7%and 60.0%,P=0.75)and OS rates(50.0%and 70.0%,P=0.36).The interval from surgery to adjuvant chemotherapy initiation did not significantly differ between the ODP and MIDP subgroups in both the upfront group(P=0.13)and the NAC group(P=0.14).The incidence of recurrence was 64.8%for ODP and 42.8%for MIDP(P=0.06).Both procedures showed similar distributions of local and distant recurrence.Conclusions:MIDP caused less blood loss and had similar oncologic safety compared with ODP.MIDP could become a feasible,minimally invasive option with sufficient oncologic safety for pancreatic body and tail cancers.
基金supported by the National Natural Science Foundation of China (Nos.22234005,22494632,22404081)the Natural Science Foundation of Jiangsu Province (Nos.BK20222015,BK20240534)。
文摘Detecting biomarkers in body fluids by optical lateral flow immune assay(LFIA) technology provides rapid access to disease information for early diagnosis.LFIA is based on an antigen-antibody reaction and is rapidly becoming the preferred choice of physicians and patients for point-of-care testing due to its simplicity,cost-effectiveness,and rapid detection.Observing the optical signal change from the colloidal gold of the traditional LFIA strip has been widely applied for various biomarkers detection in body fluids.Despite the significant progress,rapid real-time detection of color changes in the colloidal gold by the naked eye still faces many limitations,such as large errors and the inability to quantify and accurately detect.New optical LFIA strip technology has emerged in recent years to extend its application scenarios for achieving quantitative detection such as fluorescence,afterglow,and chemiluminescence.Herein,we summarized the development of optical LFIA technology from single to hyphenated optical signals for biomarkers detection in body fluids from invasive and non-invasive sources.Moreover,the challenge and outlook of optical LFIA strip technology are highlighted to inspire the designing of next-generation diagnostic platforms.
基金Project(42072305)supported by the National Natural Science Foundation of China。
文摘Seabed mining operations have been found to induce significant movement and deformation in overlying rock strata,posing serious threats to mining safety.The presence of geological faults further complicates these deformation patterns.This study utilized geophysical surveys and the continuum-based discrete element method(CDEM)to investigate how fault activity influences rock deformation and failure.The results demonstrate that:1)Acting in mechanically weak zones,faults exerted a pronounced barrier effect on deformation propagation and stress redistribution within the surrounding rock,leading to markedly divergent displacement patterns on either side of the fault plane.Comparative analyses between single-fault and double-fault models revealed an 18%−22%expansion of the damage zone under the latter,together with significantly intensified deformation and failure;2)The double-fault model exhibited a larger maximum cumulative vertical displacement and a spatial shift in the location of peak deformation,thereby posing a heightened threat to mine safety;3)Acting in an orebody substitute,backfill effectively constrained surrounding rock deformation,enhanced its load-bearing capacity,and delayed the overburden subsidence.Nevertheless,backfill only reduced the amplitude of deformation;it could not entirely prevent settlement.These findings provide essential theoretical insights and foundational knowledge for safer submarine mining practices.
基金funded by the National Key Research and Development Program of China(grant number 2023YFC2907600)the National Natural Science Foundation of China(grant number 52504132)Tiandi Science and Technology Co.,Ltd.Science and Technology Innovation Venture Capital Special Project(grant number 2023-TD-ZD011-004).
文摘Foreign body classification on coal conveyor belts is a critical component of intelligent coal mining systems.Previous approaches have primarily utilized convolutional neural networks(CNNs)to effectively integrate spatial and semantic information.However,the performance of CNN-based methods remains limited in classification accuracy,primarily due to insufficient exploration of local image characteristics.Unlike CNNs,Vision Transformer(ViT)captures discriminative features by modeling relationships between local image patches.However,such methods typically require a large number of training samples to perform effectively.In the context of foreign body classification on coal conveyor belts,the limited availability of training samples hinders the full exploitation of Vision Transformer’s(ViT)capabilities.To address this issue,we propose an efficient approach,termed Key Part-level Attention Vision Transformer(KPA-ViT),which incorporates key local information into the transformer architecture to enrich the training information.It comprises three main components:a key-point detection module,a key local mining module,and an attention module.To extract key local regions,a key-point detection strategy is first employed to identify the positions of key points.Subsequently,the key local mining module extracts the relevant local features based on these detected points.Finally,an attention module composed of self-attention and cross-attention blocks is introduced to integrate global and key part-level information,thereby enhancing the model’s ability to learn discriminative features.Compared to recent transformer-based frameworks—such as ViT,Swin-Transformer,and EfficientViT—the proposed KPA-ViT achieves performance improvements of 9.3%,6.6%,and 2.8%,respectively,on the CUMT-BelT dataset,demonstrating its effectiveness.
文摘The Double Take column looks at a single topic from an African and Chinese perspective.This month,we explore how young people respond to the increasing focus on body weight management.As obesity rates climb,body weight management has become a growing concern in China.The government is introducing targeted policies,hospitals are setting up dedicated clinics,and health experts are speaking out.But weight is no longer just a medical issue-it’s increas-ingly tied to identity,confidence,and social image.We examine the cultural forces shaping how young people in China and Africa approach weight-what drives their choices,how ideals are formed,and where health meets appearance in today’s shifting societies.
文摘Background Depression is a common comorbidity in Parkinson's disease(PD)and Lewy body dementia(LBD).However,studies examining the rate of incident depression in the period preceding and following the diagnosis of PD and LBD are lacki ng in the literature.Aims To quantify the incidence of depression in the period preceding and following the diagnosis of PD and LBD.Methods We conducted a retrospective case-control study.Specifically,we used Danish registers to identify all patients with a diagnosis of PD or LBD in the period from 2007 to 2019.These patients were matched by age,calendar year of diagnosis and sex with up to three patients diagnosed with rheumatoid arthritis(RA),chronic kidney disease(CKD)or osteoporosis,respectively.The outcome was incident depression.The incidence of depression was assessed for up to 10 years before and up to 10 years after the diagnosis of PD or LBD.Hazard rates of incident depression for patients with PD or LBD,both before and after diagnosis,were compared with those for patients with RA,CKD or osteoporosis using a Coxproportional hazards model.Results We identified 17711 patients with PD or LBD.Their median age was 74.98(68.10-80.85)years,and39.92%were females.These patients were matched to 19556,40842 and 47809 patients with RA,CKD and osteoporosis,respectively.From 7 to 8 years before diagnosis to 5 years after diagnosis,patients with PD and LBD consistently had higher hazard rates of incident depression than all comparator groups.Conclusions These findings are compatible with depression being an early manifestation of the neurodegenerative changes eventually leading to PD and LBD and imply that incident depression at a late age should raise awareness of potential PD and LBD.
基金financially supported by the Vice-Rector’s Office for Research and Transfer at the University of Granada(Grant Ref.PPJIB2023-084)Spanish Ministry of Universities(Grants Ref.FPU20/02739 and FPU20/01987)+1 种基金Maria de Maeztu Excellence Unit Program funded by the Ministry of Science,Innovation and Ministry of Universities attached to the State Research Agency(Grant Ref.CEX2023-001312-M/AEI/10.13039/501100011033)the Excellence Unit funded by the University of Granada(Grant Ref.UCE-PP2023-11/UGR.).
文摘Background:University students face significant challenges inmaintaining healthy physical activity(PA)and dietary habits,and they often fall short of global health recommendations.Psychological factors such as social physique anxiety,body image concerns,and self-objectification may act as barriers to PA engagement,influencing both mental and physical health.The present study constructed a structural equation model(SEM)to examine the relationship between body image-related psychological factors and resistance to PA in university students from southern Spain.Methods:A cross-sectional and correlational study was conducted with 519 university students(74%females,26%males;Mean age=21.14±3.26 years)from universities in Granada and Malaga(Spain).Data were collected between May and October 2024 via online questionnaires that assessed PA engagement,Mediterranean diet adherence,eating disorder symptoms,body image-related psychological factors(social physique anxiety,appearance control beliefs,body surveillance,body shame,and self-esteem),and sociodemographic characteristics.SEM was performed to analyze relationships and sex-based differences.Results:Social physique anxietywas positively associated with body shame,body surveillance,and eating disorders,and negatively associated with self-esteem,PA engagement,and appearance control beliefs(all p<0.001).Appearance control beliefs were positively related to self-esteem,body surveillance,and PA(all p<0.05).Body surveillance was negatively linked to PA and positively linked to body shame.Mediterranean diet adherence and eating disorders were positively associated with PA(all p<0.001).Sex-based differences were observed in the model.Conclusion:Body image-related psychological factors may act as barriers to PA among university students.Interventions should integrate mental health promotion and consider sex differences.
文摘Body mass index(BMI),with its simple formula of weight divided by height squared,has become a cornerstone tool in global public health for assessing obesity and health risks.However,as populations aging and the demand for precise health evaluation grows,the limitations of this single metric have become increasingly apparent—it fails to distinguish between muscle and adipose tissue and cannot capture the complex relationship between inflammatory status and body composition.A recent study published in Biomedical and Environmental Sciences(BES)by Zhang et al.[1],which explores the association of white blood cell(WBC)count,platelet(PLT)count,and platelet-to-white blood cell ratio(PWR)with muscle mass among Chinese communitydwelling older adults,provides critical evidence for rethinking the role of BMI.Additionally,several studies published in BES,spanning from childhood nutrition to adult metabolism,further illuminate the complexity of health assessment[2−5].Building on these findings and integrating evidence from multiple Chinese population studies,this commentary revisits the historical context,utility,inherent limitations,and future directions of this classic indicator.
基金This study is supported by the National Natural Science Foundation of China (No. 82072127)。
文摘BACKGROUND:This study aims to explore the causal relationship of body weight,body mass index(BMI),and waist circumference (WC) with the risk of cardiac arrest (CA) using two-sample Mendelian randomization (MR).METHODS:Data were summarized using genome-wide association studies (GWAS).Twosample MR analyses were performed using the inverse variance weighting (IVW) method,the weighted median method,and the MR-Egger analysis.Heterogeneity test and sensitivity analysis were performed using Cochran’s Q test and the leave-one-out method,respectively.The Steiger test was used to detect reverse causality.Bayesian model-averaged MR was used to identify the most influential risk factors.RESULTS:A total of 13 GWAS data were collected for BMI,body weight and WC.IVW analyses showed a positive correlation of body weight,BMI,and WC with CA (all OR>1 and P<0.05),with MR-Egger and weighted median methods confirming the IVW findings.No horizontal pleiotropy or heterogeneity was observed.Sensitivity analysis indicated that no single nucleotide polymorphism(SNP) caused significant changes in overall causality.Bayesian model-averaged MR was also used to rank causality based on marginal inclusion probability (MIP),and the corresponding modelaveraged causal estimate (MACE) were confirmed,which indicated that WC (GWAS ID:ukb-b-9405)was the highest-ranked risk factor (MIP=0.119,MACE=0.011);its posterior probability was 0.057.A total of 14 sex-specific GWAS data on weight,BMI,and WC were analyzed in relationship with CA,and the MR results showed no significant effects of sex-specific factors.CONCLUSION:Body weight,BMI,and WC are causally associated with an increased risk of CA,with WC identified as the most important risk factor.
基金funded by the National Natural Science Foundation of China(52474131)the National Natural Science Foundation of China(42467022)+1 种基金the Yunnan Major Scientific and Technological Projects(Grant No.202202AG050014)the Yunnan Fundamental Research Projects(NO.202101BE070001-038,202201AT070146).
文摘The strength of backfill body is a crucial parameter in backfilling mining,and the failure process of cemented backfill body is essentially an energy dissipation process.To investigate the effects of curing age and cement-sand ratio on the strength and energy consumption of backfill,whole tailings were used as aggregate to prepare slurry with mass concentration of 74%,and the slurry with cement-sand ratio of 1:4,1:6,1:8 and 1:12 was poured into backfill.Uniaxial compression tests were conducted on backfill body specimens that had been cured for 7 days,14 days,28 days,and 45 days.It aims at studying the compressive strength,damage,energy storage limit,energy dissipation,and crack propagation of the fill.The results show that when the cement-sand ratio is held constant,the strength of the backfill increases with curing age.Simultaneously,when the curing age is fixed,the strength is positively correlated with the cement-sand ratio.During uniaxial compression tests,it is observed that the pre-peak energy consumption,post-peak energy consumption,total energy consumption,and unit volume strain energy of the cemented backfill body exhibit exponential relationships with both curing age and cement-sand ratio.The energy storage limit of the backfill reflects its capacity to absorb energy prior to failure,while the relationship between damage and energy consumption provides an accurate depiction of its internal failure mechanisms at different stages.In the failure process of the cemented backfill body,primary cracks accompany secondary cracks,many microcracks initiate and propagate from the stress direction,and crack propagation consumes a significant amount of energy.This study on the strength,energy storage limit,and failure of the cemented backfill body can provide valuable insights for mine safety production.
基金Supported by National Natural Science Foundation of China(Grant No.U1934203)Research and Development Project of Science and Technology of China Railway Corporation(Grant No.P2023T002)。
文摘Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.
