目的:系统评价培土生金中药联合西医常规疗法治疗支气管哮喘缓解期肺脾两虚证的疗效以及证据质量,为临床决策及疾病指南制订提供循证依据。方法:检索中国知网(CNKI)、万方数据库(Wangfang)、Pubmed、Web of Science等8大中英文数据库,由...目的:系统评价培土生金中药联合西医常规疗法治疗支气管哮喘缓解期肺脾两虚证的疗效以及证据质量,为临床决策及疾病指南制订提供循证依据。方法:检索中国知网(CNKI)、万方数据库(Wangfang)、Pubmed、Web of Science等8大中英文数据库,由2名研究者独立进行文献筛选、信息提取、偏倚风险评估及方法学质量评价,并对纳入研究的总有效率、中医证候积分、第一秒用力呼气容积(FEV1)、第一秒用力呼气容积/用力肺活量(FEV1/FVC)、哮喘控制测试(ACT)评分等结局指标进行Meta分析,最终依照GRADE评估证据质量。结果:共纳入14项研究,合计1263例患者。结果显示:(1)培土生金中药联合常规西医疗法可有效改善患者总有效率,降低患者中医证候积分,改善患者FEV1水平、FEV1/FVC及ACT评分。(2)总有效率证据质量较优,可信度高,其余指标证据质量较低,尚待更多高质量的研究支持以提升证据级别。结论:培土生金中药联合西医常规疗法治疗支气管哮喘缓解期肺脾两虚证优于单用西医常规治疗,且在总有效率上证据质量较高,具有一定的循证学意义。展开更多
Functionally graded cellular structures(FGCSs)have a multitude of applications to a wide range of industries.Utilising the ever-progressing technology of additive manufacturing(AM),FGCSs can be applied to control mate...Functionally graded cellular structures(FGCSs)have a multitude of applications to a wide range of industries.Utilising the ever-progressing technology of additive manufacturing(AM),FGCSs can be applied to control material grading and achieve the desired mechanical properties.The current study explores the design and optimisation of FGCSs for AM,with a focus on improving the compression and impact performance of below knee(BK)prosthetic limbs made of thermoplastic polyurethane(TPU).A multiscale research methodology integrating topology optimization(TO),finite element analysis(FEA),and design of experiments(Do E)was adopted to optimise lattice structures in terms of stiffness and lightweight properties.Two-unit cell designs were considered in the study:Schwarz P gyroid and body-centered cubic(BCC).Response surface methodology(RSM)was implemented to analyse the effect of minimum and maximum cell wall thickness,cell size,and unit cell type on the mechanical performance of TPU FGCS structures.The results indicated that a Schwarz P FGCS structure with cell size,minimum and maximum cell wall thickness of 6,0.9 and 2.8 mm,respectively,could be optimal for a compromise between performance and weight.In this optimized case,stiffness and volume fraction values of 684 N/mm and 0.64 were obtained,respectively.The study also presents a proof-of-concept design for a BK prosthetic damper,highlighting the potential of FGCSs to enhance patient comfort,reduce manufacturing costs,and enable personalised designs through 3D scanning and AM.The obtained results could be a step forward towards the incorporation of AM technologies in prosthetics,offering a pathway to lightweight,cost-effective,and functionally tailored solutions.展开更多
Thermomagnetic generation(TMG),a heat-to-electricity conversion technology based on the thermomagnetic effect,offers high reliability and broad adaptability to diverse heat sources.By exploiting the temperature-depend...Thermomagnetic generation(TMG),a heat-to-electricity conversion technology based on the thermomagnetic effect,offers high reliability and broad adaptability to diverse heat sources.By exploiting the temperature-dependent magnetization of thermomagnetic materials,TMG converts thermal energy into electrical energy through cyclic changes in magnetic flux based on Faraday's law.The performance of TMG systems is largely governed by the intrinsic properties of the working materials and the design of device architecture.Ideal TMG materials exhibit sharp and reversible magnetization transitions near the operating temperature,low thermal hysteresis,and high thermal conductivity.Device configurations can be broadly categorized into active and passive systems:active TMG devices rely on controlled thermal cycling and optimized magnetic circuits for enhanced output,whereas passive devices utilize self-actuated mechanical motion to generate electricity.In this topical review,we provide a comprehensive overview of recent advances in TMG materials and device configurations.Furthermore,we discuss future development trends and offer perspectives on experimental strategies to advance this field.展开更多
China's requisition-compensation balance strategy has dramatically reshaped cropland spatial patterns,drawing multidisciplinary research attention.However,existing studies predominantly emphasize horizontal distri...China's requisition-compensation balance strategy has dramatically reshaped cropland spatial patterns,drawing multidisciplinary research attention.However,existing studies predominantly emphasize horizontal distribution,overlooking the significant influence of slope gradient on cropland spatial patterns.This paper proposes a slope location quotient(SLQ)index that reflects the relative advantage of cropland distribution and explores the slope grade difference of cropland spatial patterns in China at the county scale.The analysis adopts 30-m resolution digital elevation model with land cover data,taking 2672 counties with cropland ratio>1%as study units.The temporal scope covers 1990 and 2020,with slope gradients categorized into five grades:0°~2°,2°~6°,6°~15°,15°~25°,and 25°~90°.Results show that:1)The inverse correlation between cropland area and slope gradient remained stable throughout the study period,with the variation in cropland area frequency across slope grades being less than 1%.2)The spatial patterns of SLQ in 1990 and 2020 both transited stepwise with slope gradient,while≤2°and>6°slopes exhibited opposing patterns.3)The mean absolute variation of SLQ during 1990-2020 increased with slope gradient(R2=0.926,p<0.01).Particularly for slope grades>15°,the mean absolute variation reached 0.26(for 15°~25°)and 0.43(for 25°~90°),respectively,and displayed a distinct southward-increasing and northwarddecreasing pattern.This study offers novel slopegradient perspectives for analyzing cropland spatial patterns.To enhance cropland protection benefits,reversing the steep cropland SLQ surge in southern China is recommended.展开更多
When micro/nano-scale gradient coatings are subject to large thermal gradients or high heat fluxes,the spatial size effect cannot be ignored.It is important to understand how the size effect influences the thermal fra...When micro/nano-scale gradient coatings are subject to large thermal gradients or high heat fluxes,the spatial size effect cannot be ignored.It is important to understand how the size effect influences the thermal fracture behavior of functionally graded coating/substrate structures.This study aims at analyzing the transient thermal fracture behavior of collinear interface cracks in functionally graded coating/substrate structures based on the nonlocal dual-phase-lag heat conduction model.By means of integral transform techniques,the mixed boundary problem is transformed into a set of singular integral equations,which are solved by the Chebyshev polynomials.The effects of the nonlocal parameter,coating thickness,crack spacing,and non-homogeneous parameters on the temperature and stress intensity factors(SIFs)are examined.The numerical results show that these parameters play an essential role in controlling the thermal fracture behavior of the structures,especially at micro/nano-scales.展开更多
We used hydrodynamic simulations and shock wave propagation theories to analyze the behavior of shock waves within Ti/Pt periodically modulated graded structures and their integration layers.The effects of the total n...We used hydrodynamic simulations and shock wave propagation theories to analyze the behavior of shock waves within Ti/Pt periodically modulated graded structures and their integration layers.The effects of the total number of periodic layers,the total thickness of graded materials and loading velocity on the integration layer thickness and behavior of pressure-strain rate were systematically investigated.The results reveal that,by adjusting the total number of periodically modulated layers,the total thickness of graded materials and loading velocity the pressure amplitudes of the reflected compressive and rarefaction waves at different interfaces of Ti/Pt periodically modulated graded materials can be precisely controlled.Furthermore,empirical structural design criteria for Ti/Pt periodically modulated graded materials are established.The thickness ratio variation between adjacent Ti/Pt layers in the periodic structure must exceed 0.32.After the collaborative design of the integration layer,Ti/Pt periodically modulated graded materials can achieve a controllable loading function with pressures ranging from 1.4 to 144 GPa and strain rates from 3.8×10^(4) to 1.7×10^(7) s^(–1).The outcomes of this research provide a theoretical and simulation basis for the optimized design of periodically modulated graded materials to be utilized in ramp compression experiments.展开更多
Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture ...Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture mechanics analysis.These two classes of problems respectively embody material non-uniformity and geometric discontinuity,thereby imposing more stringent requirements on numerical methods in terms of high-order field continuity and accurate defect representation.Based on the classical Kirchhoff-Love plate theory,a numerical manifold method(MLS-NMM)incorporating moving least squares(MLS)interpolation is developed for bending analysis of FGM plates and fracture simulation of homogeneous plates with defects.The method constructs an H^(2)-regular approximation with high-order continuous weighting functions and,combined with the separation of mathematical and physical covers,establishes a unified framework that accurately handles material gradients and cracks without mesh reconstruction.For the crack tip,a singular physical cover incorporating the Williams asymptotic field is introduced to achieve local enrichment,enabling the natural capture of displacement discontinuity and stress singularity.Stress intensity factors are extracted using the interaction integral method,and the dimensionless J-integral shows a maximum relative error below 1.2%compared with the reference solution.Numerical results indicate that MLS-NMM exhibits excellent convergence performance:using 676 mathematical nodes,the nondimensional central deflection of both FGM and homogeneous plates agrees with reference solutions with a maximum relative error below 0.81%,and no shear locking occurs.A systematic analysis reveals that for a simply supported on all four edges(SSSS)FGM square plate with a/h=10,the nondimensional central deflection increases by 212%as the gradient index nrises from 0 to 5.For a homogeneous plate containing a central crack with c/a=0.6,the nondimensional central deflection increases by approximately 46%compared with the intact plate.Under weak boundary constraints(e.g.,SFSF),the deformation is markedly amplified,with the deflection reaching more than three times that under strong constraints(SCSC).The proposed method provides an efficient,reconstruction-free numerical tool for high-accuracy bending and fracture analyses of FGM and cracked thin-plate structures.展开更多
To the Editor,Artificial intelligence(AI)usage has been increasing.Many fields have implemented the use of AI and Large LanguageModels(LLMs),especially in medicine.Furthermore,manypatients have increasingly been using...To the Editor,Artificial intelligence(AI)usage has been increasing.Many fields have implemented the use of AI and Large LanguageModels(LLMs),especially in medicine.Furthermore,manypatients have increasingly been using AI;often,they will prompt AI with questions before even stepping into a physi-cian's office.The question lies in whether the information produced by AI is reliable and if this information is concise and easy to read across all patient populations.展开更多
Sandwich functionally graded(FG)auxetic beams are extensively utilized in aerospace,automotive,and biomedical industries due to their excellent strength-toweight ratio,impact resistance,and tunable mechanical properti...Sandwich functionally graded(FG)auxetic beams are extensively utilized in aerospace,automotive,and biomedical industries due to their excellent strength-toweight ratio,impact resistance,and tunable mechanical properties.The integration of FG materials with auxetic structures enhances their adaptability in advanced engineering applications.However,understanding their dynamic behavior under external excitations is essential for optimal design and structural reliability.Nonlinear interactions in such structures pose significant challenges in vibration analysis,necessitating robust analytical methods.This study presents a closed-form solution for the nonlinear forced vibration analysis of sandwich FG auxetic beams,offering an accurate and efficient method for predicting their dynamic response.The beam consists of two FG face sheets with material properties varying through the thickness and a re-entrant honeycomb auxetic core with an adjustable Poisson's ratio.The governing nonlinear equations of motion are derived using the first-order shear deformation theory(FSDT),the modified Gibson model,and the von Kármán relations,formulated through Hamilton's principle.A closed-form solution is obtained via the Galerkin method and multiple-scale technique.The results demonstrate that FG layers enable control of the overweight and dynamic response amplitude,with positive power law indexes reducing weight.Comparisons with finite element results confirm the accuracy of the proposed formulation.展开更多
The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimiz...The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.展开更多
动物实验是生物医学研究中的重要手段,是连接基础研究与临床试验的桥梁。动物实验的系统评价/Meta分析(systematic review/meta-analysis,SRs/MAs)是整合动物实验证据的重要手段,能够促进成果向临床研究转化,降低转化风险,并推动基础研...动物实验是生物医学研究中的重要手段,是连接基础研究与临床试验的桥梁。动物实验的系统评价/Meta分析(systematic review/meta-analysis,SRs/MAs)是整合动物实验证据的重要手段,能够促进成果向临床研究转化,降低转化风险,并推动基础研究的资源整合。随着证据推荐分级的评估、制订与评价(grading of recommendations assessment,development and evaluation,GRADE)方法的不断发展,其在动物实验SRs/MAs中的应用受到了越来越多的关注。本文首先阐述了GRADE方法在动物实验SRs/MAs中的应用原理及具体应用类型,包括定性描述的系统评价、Meta分析及网状Meta分析;接着深入分析了GRADE方法在实际应用中的误用情况,主要包括未正确进行证据体分级、证据体分级不当、误用于定性系统评价、升降级过程记录与结果不一致,以及误用于提供推荐意见;此外,还全面探讨了GRADE方法在动物实验SRs/MAs中的证据确信度升降级因素,包括偏倚风险、间接性、不一致性、不精确性和发表偏倚对证据降级的影响,以及大效应量和跨物种一致性对证据升级的作用;最后,针对上述问题提出了改进策略,包括进一步研究与优化GRADE方法在动物实验SRs/MAs中的应用细节、制定符合动物实验研究特点的SRs/MAs报告规范,以及加强研究人员在GRADE方法上的专业培训等。本文旨在通过提升动物实验SRs/MAs的证据质量,增强其在临床决策中的可靠性,促进动物实验研究成果更高效地转化为临床实践。展开更多
目的:基于推荐分级的评估、制订和评价系统(grading of recommendations assessment,development and e valuation,GRADE)与整合证据链法(integrated evidence chain-based efficacy evaluation of traditional Chinese medicine,i EC-E...目的:基于推荐分级的评估、制订和评价系统(grading of recommendations assessment,development and e valuation,GRADE)与整合证据链法(integrated evidence chain-based efficacy evaluation of traditional Chinese medicine,i EC-Eff),评价电针治疗痛风性关节炎(gouty arthritis,GA)的证据质量。方法:计算机检索PubMed、Web of Science、Cochrane Library、Embase、中国知网、中文科技期刊数据库、万方医学期刊数据库、中国生物医学文献数据库等数据库,检索时限为建库至2025年4月,纳入电针治疗GA的随机对照试验(randomized controlled trial,RCT)、实验研究及临床经验文献,采用Cochrane偏倚风险工具以及针刺临床试验干预措施报告标准(standards for reportlng interventions in clinical trials of acupuncture,STRICTA)评估RCT质量,采用Stata 18软件进行Meta分析,采用GRADE工具对结局指标进行证据质量评级,通过i EC-Eff整合多维度证据。结果:GRADE评价中,单一电针干预血尿酸、疼痛视觉模拟评分(visual analogue scale,VAS)等指标证据为C级(低质量证据),针药结合降低血尿酸、改善炎症指标C反应蛋白(C-reactive protein,CRP)和红细胞沉降率(erythrocyte sedimentation reaction,ESR)为B级(中等质量证据),细胞因子等指标证据为C级(低质量证据)。i EC-Eff评价中,临床经验证据为B级,实验研究证据为A级,临床试验证据为B级,综合评定为BAB(中级证据)。GRADE与i EC-Eff评价体系差异源于前者对研究设计严谨性要求高,后者契合中医药整体模式。电针联合西药在降尿酸、抗炎方面具有优势,但需高质量RCT验证。结论:电针治疗GA可以改善关节红肿热痛症状、降低血尿酸水平、减轻关节炎症反应(如ESR、CRP等指标)等,证据质量较高,具有较好的临床应用前景。GRADE与i EC-Eff在电针治疗GA的证据评价方面各有优势,未来需将二者结合起来优化中医药疗效评价体系,推动电针治疗GA的循证医学证据积累与国际化认可。展开更多
应用推荐分级的评估、制订和评价(grading of recommendations assessment,development and evaluation,GRADE)系统与中药有效性评价整合证据链法(integrated evidence chain-based effectiveness evaluation of traditional Chinese me...应用推荐分级的评估、制订和评价(grading of recommendations assessment,development and evaluation,GRADE)系统与中药有效性评价整合证据链法(integrated evidence chain-based effectiveness evaluation of traditional Chinese medicine,Eff-iEC)对指南或专家共识推荐频次较高的12种治疗骨质疏松症的常用中成药进行了证据评价。结果显示,仙灵骨葆胶囊/片根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为BA+B^(+)(中级证据);金天格胶囊根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA+B(高级证据);骨疏康颗粒/胶囊根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为BA+B^(+)(中级证据);左归丸根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据);强骨胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA+B^(+)(高级证据);壮骨止痛胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为BA+B(中级证据);金匮肾气丸根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA+B(高级证据);全杜仲胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AD+B^(+)(低级证据);淫羊藿总黄酮胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AAB^(+)(高级证据);右归丸根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据);芪骨胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为BB^(+)B(中级证据);六味地黄丸根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据)。整体而言,Eff-iEC评价体系较GRADE系统能更全面地评价中医药的有效性证据,但仍有不够完善之处,制约其推广应用。在临床证据评价方面,Eff-iEC评价体系与GRADE系统均反映出当前中成药治疗骨质疏松症的临床研究质量普遍较低,未来尚需开展高质量临床试验,进一步验证临床疗效。展开更多
The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr mul...The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr multi-principal-element alloy(MPEA)binder,has been investigated by performing sliding wear tests and composition characterization.The results showed that compared with CC,FGCC had higher hardness,stronger fracture toughness,better wear performance,and similar TRS.FGCCs exhibited lower wear rates(3.44×10^(−7)–6.95×10^(−6)mm^(3)/(N m))and coefficients of friction(COFs)(0.27–0.39)than CCs from RT to 600℃due to mitigation of multiple risks caused by binder removal,fragmentation and pull-out of WC grains,high-temperature oxidation and softening.In the low-temperature wear stage,the MPEA binder underwent dynamic recrystallization(DRX)and twinning deformation before removing from the surface.The binder removal caused dislocation pile-ups and stacking faults(SFs)to form under high stress,resulting in fragmentation and pull-out of WC grains.The low-temperature wear was dominated by abrasive wear and adhesive wear,with a low wear rate and a high and unstable COF.In the high-temperature wear stage,initial pitting oxidation of WC grains generated many subgrain boundaries,reducing heat transfer and exacerbating oxidation,resulting in an oxide layer enriched with WO3,Mx Oy,and MWO4.High-temperature wear was dominated by oxidation wear and high-temperature softening,with a high wear rate and a low and smooth COF.The results from the present study do not only provide theoretical guidance for an understanding of the antiwear mechanism of WC-CoNiFeCr,but also a new approach for the preparation of cemented carbides with high wear resistance.展开更多
文摘目的:系统评价培土生金中药联合西医常规疗法治疗支气管哮喘缓解期肺脾两虚证的疗效以及证据质量,为临床决策及疾病指南制订提供循证依据。方法:检索中国知网(CNKI)、万方数据库(Wangfang)、Pubmed、Web of Science等8大中英文数据库,由2名研究者独立进行文献筛选、信息提取、偏倚风险评估及方法学质量评价,并对纳入研究的总有效率、中医证候积分、第一秒用力呼气容积(FEV1)、第一秒用力呼气容积/用力肺活量(FEV1/FVC)、哮喘控制测试(ACT)评分等结局指标进行Meta分析,最终依照GRADE评估证据质量。结果:共纳入14项研究,合计1263例患者。结果显示:(1)培土生金中药联合常规西医疗法可有效改善患者总有效率,降低患者中医证候积分,改善患者FEV1水平、FEV1/FVC及ACT评分。(2)总有效率证据质量较优,可信度高,其余指标证据质量较低,尚待更多高质量的研究支持以提升证据级别。结论:培土生金中药联合西医常规疗法治疗支气管哮喘缓解期肺脾两虚证优于单用西医常规治疗,且在总有效率上证据质量较高,具有一定的循证学意义。
基金financially supported and funded by the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University(IMSIU)(No.IMSIU-DDRSP2503)。
文摘Functionally graded cellular structures(FGCSs)have a multitude of applications to a wide range of industries.Utilising the ever-progressing technology of additive manufacturing(AM),FGCSs can be applied to control material grading and achieve the desired mechanical properties.The current study explores the design and optimisation of FGCSs for AM,with a focus on improving the compression and impact performance of below knee(BK)prosthetic limbs made of thermoplastic polyurethane(TPU).A multiscale research methodology integrating topology optimization(TO),finite element analysis(FEA),and design of experiments(Do E)was adopted to optimise lattice structures in terms of stiffness and lightweight properties.Two-unit cell designs were considered in the study:Schwarz P gyroid and body-centered cubic(BCC).Response surface methodology(RSM)was implemented to analyse the effect of minimum and maximum cell wall thickness,cell size,and unit cell type on the mechanical performance of TPU FGCS structures.The results indicated that a Schwarz P FGCS structure with cell size,minimum and maximum cell wall thickness of 6,0.9 and 2.8 mm,respectively,could be optimal for a compromise between performance and weight.In this optimized case,stiffness and volume fraction values of 684 N/mm and 0.64 were obtained,respectively.The study also presents a proof-of-concept design for a BK prosthetic damper,highlighting the potential of FGCSs to enhance patient comfort,reduce manufacturing costs,and enable personalised designs through 3D scanning and AM.The obtained results could be a step forward towards the incorporation of AM technologies in prosthetics,offering a pathway to lightweight,cost-effective,and functionally tailored solutions.
基金supported by the National Natural Science Foundation of China(Grant Nos.52171169 and 52101210)the National Key Research and Development Program of China(Grant No.2021YFB3501204)+3 种基金the State Key Laboratory for Advanced Metals and Materials(Grant No.2023-ZD01)USTB Concept Verification Funding Project(Grant No.GNYZ-2024-6)Fundamental Research Funds for the Central Universities(Grant No.FRF-TP-24-004A)USTB Research Center for International People-to-people Exchange in Science,Technology and Civilization(Grant Nos.2024KFZD001 and 2024KFYB004)。
文摘Thermomagnetic generation(TMG),a heat-to-electricity conversion technology based on the thermomagnetic effect,offers high reliability and broad adaptability to diverse heat sources.By exploiting the temperature-dependent magnetization of thermomagnetic materials,TMG converts thermal energy into electrical energy through cyclic changes in magnetic flux based on Faraday's law.The performance of TMG systems is largely governed by the intrinsic properties of the working materials and the design of device architecture.Ideal TMG materials exhibit sharp and reversible magnetization transitions near the operating temperature,low thermal hysteresis,and high thermal conductivity.Device configurations can be broadly categorized into active and passive systems:active TMG devices rely on controlled thermal cycling and optimized magnetic circuits for enhanced output,whereas passive devices utilize self-actuated mechanical motion to generate electricity.In this topical review,we provide a comprehensive overview of recent advances in TMG materials and device configurations.Furthermore,we discuss future development trends and offer perspectives on experimental strategies to advance this field.
基金supported by the project of the National Natural Science Foundation of China entitled“Distribution and change characteristics of construction land on slope gradient in mountainous cities of southern China”(No.41961039)。
文摘China's requisition-compensation balance strategy has dramatically reshaped cropland spatial patterns,drawing multidisciplinary research attention.However,existing studies predominantly emphasize horizontal distribution,overlooking the significant influence of slope gradient on cropland spatial patterns.This paper proposes a slope location quotient(SLQ)index that reflects the relative advantage of cropland distribution and explores the slope grade difference of cropland spatial patterns in China at the county scale.The analysis adopts 30-m resolution digital elevation model with land cover data,taking 2672 counties with cropland ratio>1%as study units.The temporal scope covers 1990 and 2020,with slope gradients categorized into five grades:0°~2°,2°~6°,6°~15°,15°~25°,and 25°~90°.Results show that:1)The inverse correlation between cropland area and slope gradient remained stable throughout the study period,with the variation in cropland area frequency across slope grades being less than 1%.2)The spatial patterns of SLQ in 1990 and 2020 both transited stepwise with slope gradient,while≤2°and>6°slopes exhibited opposing patterns.3)The mean absolute variation of SLQ during 1990-2020 increased with slope gradient(R2=0.926,p<0.01).Particularly for slope grades>15°,the mean absolute variation reached 0.26(for 15°~25°)and 0.43(for 25°~90°),respectively,and displayed a distinct southward-increasing and northwarddecreasing pattern.This study offers novel slopegradient perspectives for analyzing cropland spatial patterns.To enhance cropland protection benefits,reversing the steep cropland SLQ surge in southern China is recommended.
基金Project supported by the Natural Science Foundation of Shandong Province of China(No.ZR2024MA085)the Fundamental Research Funds for Central Universities of China(No.27RA2515008)。
文摘When micro/nano-scale gradient coatings are subject to large thermal gradients or high heat fluxes,the spatial size effect cannot be ignored.It is important to understand how the size effect influences the thermal fracture behavior of functionally graded coating/substrate structures.This study aims at analyzing the transient thermal fracture behavior of collinear interface cracks in functionally graded coating/substrate structures based on the nonlocal dual-phase-lag heat conduction model.By means of integral transform techniques,the mixed boundary problem is transformed into a set of singular integral equations,which are solved by the Chebyshev polynomials.The effects of the nonlocal parameter,coating thickness,crack spacing,and non-homogeneous parameters on the temperature and stress intensity factors(SIFs)are examined.The numerical results show that these parameters play an essential role in controlling the thermal fracture behavior of the structures,especially at micro/nano-scales.
基金Funded by the Guangdong Major Project of Basic and Applied Basic Research(No.2021B0301030001)the Foundation of National Key Laboratory of Shock Wave and Detonation Physics(No.JCKYS2022212004)。
文摘We used hydrodynamic simulations and shock wave propagation theories to analyze the behavior of shock waves within Ti/Pt periodically modulated graded structures and their integration layers.The effects of the total number of periodic layers,the total thickness of graded materials and loading velocity on the integration layer thickness and behavior of pressure-strain rate were systematically investigated.The results reveal that,by adjusting the total number of periodically modulated layers,the total thickness of graded materials and loading velocity the pressure amplitudes of the reflected compressive and rarefaction waves at different interfaces of Ti/Pt periodically modulated graded materials can be precisely controlled.Furthermore,empirical structural design criteria for Ti/Pt periodically modulated graded materials are established.The thickness ratio variation between adjacent Ti/Pt layers in the periodic structure must exceed 0.32.After the collaborative design of the integration layer,Ti/Pt periodically modulated graded materials can achieve a controllable loading function with pressures ranging from 1.4 to 144 GPa and strain rates from 3.8×10^(4) to 1.7×10^(7) s^(–1).The outcomes of this research provide a theoretical and simulation basis for the optimized design of periodically modulated graded materials to be utilized in ramp compression experiments.
基金supported by Beijing Natural Science Foundation(L233025)。
文摘Functionally graded material(FGM)plates are widely used in various engineering structures owing to their tailor-made mechanical properties,whereas cracked homogeneous plates constitute a canonical setting in fracture mechanics analysis.These two classes of problems respectively embody material non-uniformity and geometric discontinuity,thereby imposing more stringent requirements on numerical methods in terms of high-order field continuity and accurate defect representation.Based on the classical Kirchhoff-Love plate theory,a numerical manifold method(MLS-NMM)incorporating moving least squares(MLS)interpolation is developed for bending analysis of FGM plates and fracture simulation of homogeneous plates with defects.The method constructs an H^(2)-regular approximation with high-order continuous weighting functions and,combined with the separation of mathematical and physical covers,establishes a unified framework that accurately handles material gradients and cracks without mesh reconstruction.For the crack tip,a singular physical cover incorporating the Williams asymptotic field is introduced to achieve local enrichment,enabling the natural capture of displacement discontinuity and stress singularity.Stress intensity factors are extracted using the interaction integral method,and the dimensionless J-integral shows a maximum relative error below 1.2%compared with the reference solution.Numerical results indicate that MLS-NMM exhibits excellent convergence performance:using 676 mathematical nodes,the nondimensional central deflection of both FGM and homogeneous plates agrees with reference solutions with a maximum relative error below 0.81%,and no shear locking occurs.A systematic analysis reveals that for a simply supported on all four edges(SSSS)FGM square plate with a/h=10,the nondimensional central deflection increases by 212%as the gradient index nrises from 0 to 5.For a homogeneous plate containing a central crack with c/a=0.6,the nondimensional central deflection increases by approximately 46%compared with the intact plate.Under weak boundary constraints(e.g.,SFSF),the deformation is markedly amplified,with the deflection reaching more than three times that under strong constraints(SCSC).The proposed method provides an efficient,reconstruction-free numerical tool for high-accuracy bending and fracture analyses of FGM and cracked thin-plate structures.
文摘To the Editor,Artificial intelligence(AI)usage has been increasing.Many fields have implemented the use of AI and Large LanguageModels(LLMs),especially in medicine.Furthermore,manypatients have increasingly been using AI;often,they will prompt AI with questions before even stepping into a physi-cian's office.The question lies in whether the information produced by AI is reliable and if this information is concise and easy to read across all patient populations.
文摘Sandwich functionally graded(FG)auxetic beams are extensively utilized in aerospace,automotive,and biomedical industries due to their excellent strength-toweight ratio,impact resistance,and tunable mechanical properties.The integration of FG materials with auxetic structures enhances their adaptability in advanced engineering applications.However,understanding their dynamic behavior under external excitations is essential for optimal design and structural reliability.Nonlinear interactions in such structures pose significant challenges in vibration analysis,necessitating robust analytical methods.This study presents a closed-form solution for the nonlinear forced vibration analysis of sandwich FG auxetic beams,offering an accurate and efficient method for predicting their dynamic response.The beam consists of two FG face sheets with material properties varying through the thickness and a re-entrant honeycomb auxetic core with an adjustable Poisson's ratio.The governing nonlinear equations of motion are derived using the first-order shear deformation theory(FSDT),the modified Gibson model,and the von Kármán relations,formulated through Hamilton's principle.A closed-form solution is obtained via the Galerkin method and multiple-scale technique.The results demonstrate that FG layers enable control of the overweight and dynamic response amplitude,with positive power law indexes reducing weight.Comparisons with finite element results confirm the accuracy of the proposed formulation.
文摘The accurate mechanical analysis of thick-walled pressure vessel structures composed of advanced materials,such as hyperelastic and functionally graded materials(FGMs),is critical for ensuring their safety and optimizing their design.However,conventional numerical methods can face challenges with the non-linearities inherent in hyperelasticity and the complex spatial variations in FGMs.This paper presents a novel hybrid numerical approach combining Physics-Informed Neural Networks(PINNs)with Finite Element Method(FEM)derived data for the robust analysis of thick-walled,axisymmetric,heterogeneous,hyperelastic pressure vessels with elliptical geometries.A PINN framework incorporating neo-Hookean constitutive relations is developed in MATLAB.To enhance training efficiency and accuracy,the PINN’s loss function is augmented with displacement data obtained from high-fidelity FEM simulations performed in ANSYS.The methodology is rigorously validated by comparing PINN-predicted displacement and von Mises stress fields against ANSYS benchmarks for various scenarios of FGMconfigurations(with material properties varying according to a power law)subjected to internal and external pressurization.The results demonstrate excellent agreement between the proposed hybrid PINN-FEMapproach and conventional FEMsolutions across all test cases,accurately capturing complex deformation patterns and stress concentrations.This study highlights the potential of data-augmented PINNs as an effective and accurate computational tool for tackling complex solid mechanics problems involving non-linearmaterials and significant heterogeneity,offering a promising avenue for future research in engineering design and analysis.
文摘动物实验是生物医学研究中的重要手段,是连接基础研究与临床试验的桥梁。动物实验的系统评价/Meta分析(systematic review/meta-analysis,SRs/MAs)是整合动物实验证据的重要手段,能够促进成果向临床研究转化,降低转化风险,并推动基础研究的资源整合。随着证据推荐分级的评估、制订与评价(grading of recommendations assessment,development and evaluation,GRADE)方法的不断发展,其在动物实验SRs/MAs中的应用受到了越来越多的关注。本文首先阐述了GRADE方法在动物实验SRs/MAs中的应用原理及具体应用类型,包括定性描述的系统评价、Meta分析及网状Meta分析;接着深入分析了GRADE方法在实际应用中的误用情况,主要包括未正确进行证据体分级、证据体分级不当、误用于定性系统评价、升降级过程记录与结果不一致,以及误用于提供推荐意见;此外,还全面探讨了GRADE方法在动物实验SRs/MAs中的证据确信度升降级因素,包括偏倚风险、间接性、不一致性、不精确性和发表偏倚对证据降级的影响,以及大效应量和跨物种一致性对证据升级的作用;最后,针对上述问题提出了改进策略,包括进一步研究与优化GRADE方法在动物实验SRs/MAs中的应用细节、制定符合动物实验研究特点的SRs/MAs报告规范,以及加强研究人员在GRADE方法上的专业培训等。本文旨在通过提升动物实验SRs/MAs的证据质量,增强其在临床决策中的可靠性,促进动物实验研究成果更高效地转化为临床实践。
文摘目的:基于推荐分级的评估、制订和评价系统(grading of recommendations assessment,development and e valuation,GRADE)与整合证据链法(integrated evidence chain-based efficacy evaluation of traditional Chinese medicine,i EC-Eff),评价电针治疗痛风性关节炎(gouty arthritis,GA)的证据质量。方法:计算机检索PubMed、Web of Science、Cochrane Library、Embase、中国知网、中文科技期刊数据库、万方医学期刊数据库、中国生物医学文献数据库等数据库,检索时限为建库至2025年4月,纳入电针治疗GA的随机对照试验(randomized controlled trial,RCT)、实验研究及临床经验文献,采用Cochrane偏倚风险工具以及针刺临床试验干预措施报告标准(standards for reportlng interventions in clinical trials of acupuncture,STRICTA)评估RCT质量,采用Stata 18软件进行Meta分析,采用GRADE工具对结局指标进行证据质量评级,通过i EC-Eff整合多维度证据。结果:GRADE评价中,单一电针干预血尿酸、疼痛视觉模拟评分(visual analogue scale,VAS)等指标证据为C级(低质量证据),针药结合降低血尿酸、改善炎症指标C反应蛋白(C-reactive protein,CRP)和红细胞沉降率(erythrocyte sedimentation reaction,ESR)为B级(中等质量证据),细胞因子等指标证据为C级(低质量证据)。i EC-Eff评价中,临床经验证据为B级,实验研究证据为A级,临床试验证据为B级,综合评定为BAB(中级证据)。GRADE与i EC-Eff评价体系差异源于前者对研究设计严谨性要求高,后者契合中医药整体模式。电针联合西药在降尿酸、抗炎方面具有优势,但需高质量RCT验证。结论:电针治疗GA可以改善关节红肿热痛症状、降低血尿酸水平、减轻关节炎症反应(如ESR、CRP等指标)等,证据质量较高,具有较好的临床应用前景。GRADE与i EC-Eff在电针治疗GA的证据评价方面各有优势,未来需将二者结合起来优化中医药疗效评价体系,推动电针治疗GA的循证医学证据积累与国际化认可。
文摘应用推荐分级的评估、制订和评价(grading of recommendations assessment,development and evaluation,GRADE)系统与中药有效性评价整合证据链法(integrated evidence chain-based effectiveness evaluation of traditional Chinese medicine,Eff-iEC)对指南或专家共识推荐频次较高的12种治疗骨质疏松症的常用中成药进行了证据评价。结果显示,仙灵骨葆胶囊/片根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为BA+B^(+)(中级证据);金天格胶囊根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA+B(高级证据);骨疏康颗粒/胶囊根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为BA+B^(+)(中级证据);左归丸根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据);强骨胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA+B^(+)(高级证据);壮骨止痛胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为BA+B(中级证据);金匮肾气丸根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA+B(高级证据);全杜仲胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AD+B^(+)(低级证据);淫羊藿总黄酮胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AAB^(+)(高级证据);右归丸根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据);芪骨胶囊根据GRADE系统评价为D级(极低级证据),根据Eff-iEC体系评价为BB^(+)B(中级证据);六味地黄丸根据GRADE系统评价为C级(低级证据),根据Eff-iEC体系评价为AA^(++)B^(+)(高级证据)。整体而言,Eff-iEC评价体系较GRADE系统能更全面地评价中医药的有效性证据,但仍有不够完善之处,制约其推广应用。在临床证据评价方面,Eff-iEC评价体系与GRADE系统均反映出当前中成药治疗骨质疏松症的临床研究质量普遍较低,未来尚需开展高质量临床试验,进一步验证临床疗效。
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3701800)Special funding support for the Yuelu Mountain National University Science and Technology City“Ranking the Top of the List”Research Project:(Tunnel Boring Machine High-performance Long-life Cutting Tools)the State Key Laboratory of Powder Metallurgy,Central South University,Changsha,China.
文摘The good combination of mechanical and wear properties for cemented carbides is crucial.In this work,the wear behavior of functionally graded cemented carbide(FGCC)and non-graded cemented carbide(CC),with CoNiFeCr multi-principal-element alloy(MPEA)binder,has been investigated by performing sliding wear tests and composition characterization.The results showed that compared with CC,FGCC had higher hardness,stronger fracture toughness,better wear performance,and similar TRS.FGCCs exhibited lower wear rates(3.44×10^(−7)–6.95×10^(−6)mm^(3)/(N m))and coefficients of friction(COFs)(0.27–0.39)than CCs from RT to 600℃due to mitigation of multiple risks caused by binder removal,fragmentation and pull-out of WC grains,high-temperature oxidation and softening.In the low-temperature wear stage,the MPEA binder underwent dynamic recrystallization(DRX)and twinning deformation before removing from the surface.The binder removal caused dislocation pile-ups and stacking faults(SFs)to form under high stress,resulting in fragmentation and pull-out of WC grains.The low-temperature wear was dominated by abrasive wear and adhesive wear,with a low wear rate and a high and unstable COF.In the high-temperature wear stage,initial pitting oxidation of WC grains generated many subgrain boundaries,reducing heat transfer and exacerbating oxidation,resulting in an oxide layer enriched with WO3,Mx Oy,and MWO4.High-temperature wear was dominated by oxidation wear and high-temperature softening,with a high wear rate and a low and smooth COF.The results from the present study do not only provide theoretical guidance for an understanding of the antiwear mechanism of WC-CoNiFeCr,but also a new approach for the preparation of cemented carbides with high wear resistance.
