期刊文献+
共找到11,571篇文章
< 1 2 250 >
每页显示 20 50 100
Bioengineered superoxide buffering extends lifespan via regulation of mitochondrial redox homeostasis and UPR^(mt) activation
1
作者 Chang Yuan Junying Zhang +4 位作者 Wei Yao Mingqin Qu Lingqiang Zhang Xiangming Wang Minmin Liang 《Nano Research》 2026年第1期765-779,共15页
Redox homeostasis is crucial for cellular function,and its disruption is associated with numerous diseases and age-related pathologies.Superoxide(·O_(2)-),a key reactive oxygen species(ROS),functions as a crucial... Redox homeostasis is crucial for cellular function,and its disruption is associated with numerous diseases and age-related pathologies.Superoxide(·O_(2)-),a key reactive oxygen species(ROS),functions as a crucial signaling molecule under normal physiological processes;however,both its excessive accumulation and deficiency can lead to significant detrimental effects on organismal health.Inspired by the natural enzyme superoxide dismutase(SOD),which alleviates oxidative stress by neutralizing excess free radicals and modulates intracellular ROS levels to activate anti-aging pathways,we bioengineered a novel"superoxide buffering formulation"(SOD Buffer)to precisely regulate mitochondrial superoxide levels.Using C.elegans as a model,we show that SOD Buffer reduces superoxide accumulation under oxidative stress(e.g.,UV exposure)and restores superoxide levels under its depletion(e.g.,post-MitoQ treatment),without affecting general ROS level.Mechanistically,SOD Buffer modulates superoxide levels to activate the mitochondrial unfolded protein response(UPR^(mt)),evidenced by the increased HSP-6 expression.This activation is mediated by the transcription regulators ATFS-1 and DVE-1,which govern mitochondrial stress responses.Functionally,SOD Buffer extends average lifespan by 36.98% and improves aging-related behaviors in C.elegans in a UPR^(mt) dependent manner.These findings highlight the therapeutic promise of targeted superoxide modulation to maintain mitochondrial health and promote longevity. 展开更多
关键词 superoxide buffering superoxide dismutase(SOD) redox homeostasis aging lifespan extension
原文传递
Effects of the buffer layer on the Casimir pressure of peptide films deposited on a substrate
2
作者 Dingding Lv Shuai Zhou +2 位作者 Kaipeng Liu Shiwei Dai Lixin Ge 《Chinese Physics B》 2025年第10期385-390,共6页
The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of... The Casimir pressure plays an important role in the adhesion stability of nanofilms at submicro scales.In this work,the Casimir pressure of peptide films deposited on a layered substrate is investigated.Three types of semi-infinite substrates,i.e.,silica,silicon and gold,are considered.The buffer layer between the peptide film and substrate consists of silicon or silica.The switching sign of the Casimir pressure can be controlled in a region ranging from about 130 nm to 1000 nm,depending on the thickness of the buffer layer and the substrate.The results suggest that the critical thickness of peptide films for Casimir equilibrium increases(or decreases)by increasing the thickness of the silicon(or silica)buffer film.The influences of wetting and electrolyte screening on the Casimir pressure are also investigated.Our finding provides a theoretical guide for the adhesion stability of peptide films in organic electronics. 展开更多
关键词 Casimir pressure buffer layer peptide films electrolyte screening
原文传递
Review of imaging buffers used in stochastic optical reconstruction microscopy
3
作者 Can Wang Zhe Sun Donghan Ma 《Chinese Chemical Letters》 2025年第9期56-63,共8页
Stochastic optical reconstruction microscopy(STORM),as a typical technique of single-molecule localization microscopy(SMLM),has overcome the diffraction limit by randomly switching fluorophores between fluorescent and... Stochastic optical reconstruction microscopy(STORM),as a typical technique of single-molecule localization microscopy(SMLM),has overcome the diffraction limit by randomly switching fluorophores between fluorescent and dark states,allowing for the precise localization of isolated emission patterns and the super-resolution reconstruction from millions of localized positions of single fluorophores.A critical factor influencing localization precision is the photo-switching behavior of fluorophores,which is affected by the imaging buffer.The imaging buffer typically comprises oxygen scavengers,photo-switching reagents,and refractive index regulators.Oxygen scavengers help prevent photobleaching,photo-switching reagents assist in facilitating the conversion of fluorophores,and refractive index regulators are used to adjust the refractive index of the solution.The synergistic interaction of these components promotes stable blinking of fluorophores,reduces irreversible photobleaching,and thereby ensures high-quality super-resolution imaging.This review provides a comprehensive overview of the essential compositions and functionalities of imaging buffers used in STORM,serving as a valuable resource for researchers seeking to select appropriate imaging buffers for their experiments. 展开更多
关键词 Single-molecule localization microscopy Stochastic optical reconstruction microscopy Photo-switching Photobleaching Imaging buffer
原文传递
Atmospheric‑pressure ion transfer in a gas flow device connected to the UniCell buffer gas cell for superheavy elements chemistry:simulation studies
4
作者 Yeqiang Wei Alexander Yakushev +2 位作者 Jochen Ballof Jörg Krier Christoph E.Düllmann 《Nuclear Science and Techniques》 2025年第10期87-97,共11页
Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing produc... Man-made superheavy elements(SHE)are produced as energetic recoils in complete-fusion reactions and need to be thermalized in a gas-filled chamber for chemical studies.The ever-shorter half-lives and decreasing production rates of the elements beyond Fl(atomic number Z=114)-the heaviest element chemically studied today-require the development of novel techniques for quantitative thermalization and fast extraction efficiency.The Universal high-density gas stopping Cell(UniCell),currently under construction,was proposed to achieve this.Within this work,we propose an Ion Transfer by Gas Flow(ITGF)device,which serves as a UniCell ejector to interface with a gas chromatography detector array for chemical studies.Detailed parameter optimizations,using gas dynamics and Monte Carlo ion-trajectory simulations,promise fast(within a few ms)and highly efficient(up to 100%)ion extraction across a wide mass range.These ions can then be transmitted quantitatively through the ITGF into the high-pressure environment needed for further chemical studies. 展开更多
关键词 Superheavy elements buffer gas cell Ion funnel Fast extraction ATMOSPHERIC-PRESSURE Chemical studies
在线阅读 下载PDF
Aluminum foam as buffer layer used in soft rock tunnel with large deformation
5
作者 WU Faquan MIAO Binxin +2 位作者 TIAN Yun ZHANG Fang ZHANG Chaoxuan 《Journal of Mountain Science》 2025年第1期324-336,共13页
The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such sof... The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress.Under such soft rock geological conditions,the large deformation of the surrounding rock can easily lead to the failure of supporting structures,including shotcrete cracks,spalling,and steel arch distortion.To improve the lining support performance during the large deformation of squeezed surrounding rock,this work selects aluminum foam with densities of 0.25 g/cm3,0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests.Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems,the strength,deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements.The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS,and the influence of the buffer layer setting on the lining support is analyzed.Compared with the conventional support scheme,the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining.The maximum and minimum principal stresses of the primary support are reduced by 13%and 15%,respectively.The maximum and minimum principal stresses of the secondary lining are reduced by 15%and 12%,respectively,and the displacement deformation of the secondary lining position is reduced by 15%.In summary,the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining,improve the stress safety of the support and reduce the deformation of the support. 展开更多
关键词 Soft rock tunnel Uniaxial confined compression Aluminum foam buffer layer Yielding support
原文传递
Multi-Level Subpopulation-Based Particle Swarm Optimization Algorithm for Hybrid Flow Shop Scheduling Problem with Limited Buffers
6
作者 Yuan Zou Chao Lu +1 位作者 Lvjiang Yin Xiaoyu Wen 《Computers, Materials & Continua》 2025年第8期2305-2330,共26页
The shop scheduling problem with limited buffers has broad applications in real-world production scenarios,so this research direction is of great practical significance.However,there is currently little research on th... The shop scheduling problem with limited buffers has broad applications in real-world production scenarios,so this research direction is of great practical significance.However,there is currently little research on the hybrid flow shop scheduling problem with limited buffers(LBHFSP).This paper deeply investigates the LBHFSP to optimize the goal of the total completion time.To better solve the LBHFSP,a multi-level subpopulation-based particle swarm optimization algorithm(MLPSO)is proposed,which is founded on the attributes of the LBHFSP and the shortcomings of the basic PSO(particle swarm optimization)algorithm.In MLPSO,firstly,considering the impact of the limited buffers on the process of subsequent operations,a specific circular decoding strategy is developed to accommodate the characteristics of limited buffers.Secondly,an initialization strategy based on blocking time is designed to enhance the quality and diversity of the initial population.Afterward,a multi-level subpopulation collaborative search is developed to prevent being trapped in a local optimum and improve the global exploration capability.Additionally,a local search strategy based on the first blocked job is designed to enhance the MLPSO algorithm’s exploitation capability.Lastly,numerous experiments are carried out to test the performance of the proposed MLPSO by comparing it with classical intelligent optimization and popular algorithms in recent years.The results confirm that the proposed MLPSO has an outstanding performance when compared to other algorithms when solving LBHFSP. 展开更多
关键词 Hybrid flow shop scheduling problem limited buffers PSO algorithm collaborative search blocking phenomenon
在线阅读 下载PDF
Tris-buffered efficacy:enhancing stability and reversibility of Zn anode by efficient modulation at Zn/electrolyte interface
7
作者 Yong-Jian Wang Su-Hong Li +3 位作者 Lin Li Jian-Yong Ren Ling-Di Shen Chao Lai 《Rare Metals》 2025年第2期925-937,共13页
Aqueous zinc-ion batteries(AZIBs)have developed rapidly in recent years but still face several challenges,including zinc dendrites growth,hydrogen evolution reaction,passivation and corrosion.The pH of the electrolyte... Aqueous zinc-ion batteries(AZIBs)have developed rapidly in recent years but still face several challenges,including zinc dendrites growth,hydrogen evolution reaction,passivation and corrosion.The pH of the electrolyte plays a crucial role in these processes,significantly impacting the stability and reversibility of Zn^(2+)deposition.Therefore,pH-buffer tris(hydroxymethyl)amino methane(tris)is chosen as a versatile electrolyte additive to address these issues.Tris can buffer electrolyte pH at Zn/electrolyte interface by protonated/deprotonated nature of amino group,optimize the coordination environment of zinc solvate ions by its strong interaction with zinc ions,and simultaneously create an in-situ stable solid electrolyte interface membrane on the zinc anode surface.These synergistic effects effectively restrain dendrite formation and side reactions,resulting in a highly stable and reversible Zn anode,thereby enhancing the electrochemical performance of AZIBs.The Zn||Zn battery with 0.15 wt%tris additives maintains stable cycling for 1500 h at 4 mA·cm^(−2) and 1120 h at 10 mA·cm^(−2).Furthermore,the Coulombic efficiency reaches~99.2%at 4 mA·cm^(−2)@1 mAh·cm^(−2).The Zn||NVO full batteries also demonstrated a stable specific capacity and exceptional capacity retention. 展开更多
关键词 Zn metal anode Hydrogen evolution reaction TRIS pH buffer Zn/electrolyte interface
原文传递
Long-term photocatalytic hydrogen peroxide production by hydroquinone-buffered covalent organic frameworks
8
作者 Chang Shu Xiaoju Yang +3 位作者 Peixuan Xie Xuan Yang Bien Tan Xiaoyan Wang 《Chinese Journal of Catalysis》 2025年第6期300-310,共11页
Photocatalytic hydrogen peroxide(H_(2)O_(2))production offers a sustainable route to convert water and oxygen into H_(2)O_(2)using solar energy.However,achieving long-term stability in photocatalysts remains a critica... Photocatalytic hydrogen peroxide(H_(2)O_(2))production offers a sustainable route to convert water and oxygen into H_(2)O_(2)using solar energy.However,achieving long-term stability in photocatalysts remains a critical challenge due to mismatched kinetics between oxygen reduction(ORR)and water oxidation(WOR),which leads to hole accumulation and oxidative degradation.Here,we report a redox-mediated strategy to address this bottleneck by designing a hydroquinone-embedded covalent organic framework(Tz-QH-COF)that enables reversible hole buffering and kinetic balance.The hydroquinone(QH)units act as dynamic hole reservoirs,capturing excess holes during ORR and converting to benzoquinone(Q),which is regenerated to QH via WOR,thereby preventing oxidative decomposition.This reversible QH/Q cycle,directly visualized through in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy,ensures unmatched stability,achieving continuous H_(2)O_(2) production for 528 h(22 d)with an accumulated yield of 18.6 mmol L^(–1)—the highest reported duration for organic photocatalysts.Density functional theory calculations reveal that the QH units exhibit a strong oxygen adsorption energy and favorable two-electron ORR/WOR pathways with low energy barriers.The synergy between experimental and theoretical insights elucidates a redox-mediated charge-balance mechanism,advancing the design of robust photocatalysts for solar-driven H_(2)O_(2) synthesis. 展开更多
关键词 Covalent organic frameworks Hole buffer Reversible redox chemistry Hydroquinone-quinone transformation Long-term photocatalytic hydrogen peroxide production
在线阅读 下载PDF
Construction of a Linear Engineering Visual Landscape Interference Model for the Buffer Zone of the Libo Heritage Site Based on the AHP-Fuzzy Comprehensive Evaluation Method:A Case Study of the Guiyang-Nanning High-Speed Railway
9
作者 WEI Wei MA Zhenrui XIAO Shizhen 《Journal of Landscape Research》 2025年第5期12-19,共8页
The buffer zone of a World Natural Heritage Site constitutes a critical element of the heritage site protection system.It not only functions as an ecological security barrier,but also significantly influences the visu... The buffer zone of a World Natural Heritage Site constitutes a critical element of the heritage site protection system.It not only functions as an ecological security barrier,but also significantly influences the visual integrity and aesthetic value of the core area’s landscape.Given the rapid development of transportation infrastructure,particularly the growing number of high-speed railways traversing ecologically sensitive regions,the scientific assessment of their impact on the landscape environment of heritage sites has emerged as a pivotal concern in heritage conservation and regional development.This study focused on the section of the Guiyang-Nanning High-Speed Railway that traverses the buffer zone of the Libo World Natural Heritage Site in Guizhou Province.Beginning with five primary indicators,including natural landscape and aesthetic value,geological geomorphology and Earth history value,biodiversity value,integrity and protection management,and impact on ecological environment,a visual landscape impact assessment system for high-speed railways was developed based on the analytic hierarchy process(AHP)and the fuzzy comprehensive evaluation method(FCE).Through expert scoring,hierarchical weight calculation,and fuzzy membership degree analysis,a comprehensive assessment was conducted on the landscape ecological quality,visual coordination,and aesthetic perception within the buffer zone following the construction of high-speed railways.The findings indicate that the construction of the Guiyang-Nanning High-Speed Railway generally harmonizes well with the landscape environment of the heritage site.The level of visual disturbance remains within an acceptable range and has not significantly damaged the overall aesthetic value or authenticity of the heritage site.Although the integrity of the landscape in certain local areas has experienced a slight decline due to the exposure of bridge and slope structures,the adverse effects have been effectively mitigated through engineering interventions such as vegetation restoration and color coordination.This study innovatively integrates the AHP with fuzzy mathematics methods to achieve a comprehensive evaluation that combines both qualitative and quantitative approaches.This integration provides a scientifically grounded analytical path and a practical technical framework for assessing the visual impact of linear infrastructure projects,such as high-speed railways,within the buffer zones of World Heritage Sites.The findings offer valuable insights for the protection of landscapes and the sustainable development of infrastructure in heritage sites. 展开更多
关键词 Heritage site buffer zone Analytic hierarchy process(AHP) Fuzzy comprehensive evaluation method(FCE)
在线阅读 下载PDF
Unveiling the orientation growth mechanism and solar-blind response performance of β-Ga_(2)O_(3)(100)film on SiC substrate with AlN buffer layer
10
作者 Jie Su Zixin Zhang +5 位作者 Liang Shi Liping Feng Fuchao He Jingjing Chang Jincheng Zhang Yue Hao 《Journal of Materials Science & Technology》 2025年第7期20-28,共9页
Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by... Optimizing the orientation of β-Ga_(2)O_(3) has emerged as an effective strategy to design high-performance β-Ga_(2)O_(3) device,but the orientation growth mechanism and approach have not been revealed yet.Herein,by employing AlN buffer layer,the highly preferred orientation of β-Ga_(2)O_(3)(100)film rather than(-201)film is realized on 4H-SiC substrate at low sputtering power and temperature.Because β-Ga_(2)O_(3)(100)film exhibits a slower growth speed than(-201)film,the former possesses the higher dangling bond density and the lower nucleation energy,and a large conversion barrier exists between these two ori-entations.Moreover,the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga_(2)O_(3)(100)film,which further reduces the nucleation energy and en-larges the conversion barrier.Meanwhile,the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga_(2)O_(3)(100)film.Consequently,the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22×10^(12) Jones and photo-to-dark current ratio of 1.11×10^(5),which are the highest among the reported β-Ga_(2)O_(3) solar-blind photodetector on the SiC substrate.Our results offer in-depth insights into the preferred orientation growth mechanism,and provide an effective way to design high-quality β-Ga_(2)O_(3)(100)orientation film and high-performance solar-blind photodetector. 展开更多
关键词 β-Ga_(2)O_(3)(100)film Orientation growth AlN buffer layer Solar-blind photodetector DFT calculation
原文传递
Enhancement of Cd-Free All-Dry-Processed Cu(In_(1-x),Ga_(x))Se_(2) Thin-Film Solar Cells by Simultaneous Adoption of an Enlarged Bandgap Absorber and Tunable Bandgap Zn_(1-x)Mg_(x)O Buffer
11
作者 Joo Hyung Park Yonghee Jo +6 位作者 Ara Cho Inyoung Jeong Jin Gi An Kihwan Kim Seung Kyu Ahn Donghyeop Shin Jun-Sik Cho 《Energy & Environmental Materials》 2025年第1期182-190,共9页
Attempts to remove environmentally harmful materials in mass production industries are always a major issue and draw attention if the substitution guarantees a chance to lower fabrication cost and to improve device pe... Attempts to remove environmentally harmful materials in mass production industries are always a major issue and draw attention if the substitution guarantees a chance to lower fabrication cost and to improve device performance,as in a wide bandgap Zn_(1-x)Mg_(x)O(ZMO)to replace the CdS buffer in Cu(In_(1-x),Ga_(x))Se_(2)(CIGSe)thin-film solar cell structure.ZMO is one of the candidates for the buffer material in CIGSe thin-film solar cells with a wide and controllable bandgap depending on the Mg content,which can be helpful in attaining a suitable conduction band offset.Hence,compared to the fixed and limited bandgap of a CdS buffer,a ZMO buffer may provide advantages in V_(oc) and J_(sc) based on its controllable and wide bandgap,even with a relatively wider bandgap CIGSe thin-film solar cell.In addition,to solve problems with the defect sites at the ZMO/CIGSe junction interface,a few-nanometer ZnS layer is employed for heterojunction interface passivation,forming a ZMO/ZnS buffer structure by atomic layer deposition(ALD).Finally,a Cd-free all-dry-processed CIGSe solar cell with a wider bandgap(1.25 eV)and ALD-grown buffer structure exhibited the best power conversion efficiency of 19.1%,which exhibited a higher performance than the CdS counterpart. 展开更多
关键词 atomic layer deposition conduction band offset engineering Cu(In_(1-x) Ga_(x))Se_(2)solar cell ZnMgO buffer ZnS heterojunction interface passivation
在线阅读 下载PDF
高密实石墨-膨润土块体的“两步压实”制备方法
12
作者 谈云志 赵凌晖 +2 位作者 张金生 祝雨 明华军 《岩土工程学报》 北大核心 2026年第1期217-224,共8页
膨润土和石墨细腻如粉,压成高密实大型块体,需要超大吨位的加载设备。为破解该难题,提出“两步压实”法,即先把细腻的粉粒压成高密实块体,再破碎成团;然后,团粒与粉粒再混合,以较低的荷载压成尺寸更大的高密实块体。研究表明,相较于用... 膨润土和石墨细腻如粉,压成高密实大型块体,需要超大吨位的加载设备。为破解该难题,提出“两步压实”法,即先把细腻的粉粒压成高密实块体,再破碎成团;然后,团粒与粉粒再混合,以较低的荷载压成尺寸更大的高密实块体。研究表明,相较于用纯粉粒膨润土直接压实,“两步压实”法可以实现用相同吨位压力机制备出更高密实度的块体,提升块体密度超4%。当目标干密度为1.93 g/cm3时,压实应力可减少4 MPa。压实过程中,团粒经历“重排、破碎、压密”的变化,当团粒含量在30%时,复压块体能更好地发挥压实力效益、具备更优的成型能力和均匀性。微观试验也表明:“两步压实法”能够减小复压块体中的孔径,提高块体的密实度。 展开更多
关键词 球状石墨 膨润土 压实 块体 缓冲层
原文传递
商业银行数字化转型与流动性缓冲顺周期性
13
作者 蒋海 朱云帆 《现代金融研究》 北大核心 2026年第1期46-59,共14页
本文以2010年至2021年我国167家商业银行为研究样本,检验了商业银行数字化转型对流动性缓冲顺周期性的影响。研究发现,流动性缓冲与经济周期负相关,呈现顺周期性。数字化转型通过降低流动性风险,挤出流动性缓冲;数字化转型通过动态调整... 本文以2010年至2021年我国167家商业银行为研究样本,检验了商业银行数字化转型对流动性缓冲顺周期性的影响。研究发现,流动性缓冲与经济周期负相关,呈现顺周期性。数字化转型通过降低流动性风险,挤出流动性缓冲;数字化转型通过动态调整银行的风险资产、提高风险管理前瞻性、分流零售存款,缓和流动性缓冲的顺周期性。战略和业务数字化转型是主要作用维度,数字化转型能够和金融监管发挥协同作用。流动性缓冲的顺周期性在高盈利、一级交易商、属地同业竞争高的银行中更显著;数字化转型对高盈利银行流动性缓冲的逆周期调节作用更显著,对属地同业竞争高的银行的流动性缓冲挤出作用更显著。 展开更多
关键词 数字化转型 流动性缓冲 经济周期 顺周期性
在线阅读 下载PDF
落石冲击荷载计算方法研究
14
作者 王玉锁 田四明 +5 位作者 杨竣翔 王明年 王伟 李传宝 赵状 肖鹏 《西南交通大学学报》 北大核心 2026年第1期21-30,共10页
为明晰落石冲击力与冲击荷载的关系,定义能反映落石、缓冲土层及结构间相互作用的综合反射系数(其值越大说明对结构的冲击效应越显著),提出基于波动理论的落石冲击荷载计算方法.通过落石冲击上覆缓冲土层拱形结构试验研究落石冲击荷载... 为明晰落石冲击力与冲击荷载的关系,定义能反映落石、缓冲土层及结构间相互作用的综合反射系数(其值越大说明对结构的冲击效应越显著),提出基于波动理论的落石冲击荷载计算方法.通过落石冲击上覆缓冲土层拱形结构试验研究落石冲击荷载的大小和分布特征,得到综合反射系数的取值和影响规律,并利用所提出的计算方法分析落石冲击荷载和落石冲击力的关系;进一步明确结构的落石冲击荷载在横剖面上呈对称抛物线分布,可由拱顶处最大冲击压力峰值和结构跨度控制的二次抛物线曲线方程表征.结果表明:在落石自由下落高度10 m及缓冲土层厚度2.0 m范围内,综合反射系数与缓冲土层厚度呈显著负相关性;缓冲土层厚度2.0 m时其受落石形状及下落高度影响较小,可取0.55;当厚度为1.0、0.5 m时,立方体落石的综合反射系数要大于球面体或锥体落石,且与落石下落高度呈正相关;结构所受落石冲击荷载的合力与落石对缓冲土层的冲击力与缓冲土层厚度和落石形状有关,当缓冲土层厚度为2.0 m时二者接近,前者稍小于后者,将落石冲击荷载合力等于落石冲击力对结构设计是偏于安全的,当缓冲土层厚度小于2.0 m时反之,且厚度越小相差的倍数越大;缓冲土层厚度1.0 m时,立方体落石冲击荷载合力较落石冲击力平均增大约20倍,而球顶锥体的增大约3倍,缓冲土层厚度0.5 m时,两种形状的落石冲击荷载合力较落石冲击力平均增大分别约30倍和10倍;相同条件下,立方体落石的冲击荷载合力大于球顶锥体的,且随落石下落高度增大或缓冲土层厚度减小,立方体与球顶锥体相差倍数越大. 展开更多
关键词 落石冲击荷载 缓冲土层 综合反射系数 落石冲击力
在线阅读 下载PDF
高温条件下膨润土缓冲层材料导热性能的热老化时间效应
15
作者 曾召田 林铭宇 +4 位作者 孙德安 邵捷昇 曹珊珊 赵长友 靳琳 《岩土力学》 北大核心 2026年第1期171-182,共12页
为探究高温条件下膨润土缓冲层材料导热性能的热老化时间效应,在100℃和200℃条件下分别对MX80膨润土粉末进行了0、15、30、60、90、120 d的热老化预处理,利用热探针法测定了预处理后膨润土压实试样的导热性能,并分析其热老化时效性;采... 为探究高温条件下膨润土缓冲层材料导热性能的热老化时间效应,在100℃和200℃条件下分别对MX80膨润土粉末进行了0、15、30、60、90、120 d的热老化预处理,利用热探针法测定了预处理后膨润土压实试样的导热性能,并分析其热老化时效性;采用粒度分析、X射线衍射和热重分析等微观试验,揭示出高温条件下MX80膨润土试样导热性能热老化时间效应的产生机制。试验结果表明:(1)高温(100、200℃)热老化预处理后膨润土试样的导热系数λ均随着热老化时间t的递增而降低,呈现出明显的热老化时间效应:0~15 d急剧降低,30 d后趋于稳定;相较于100℃,200℃条件下膨润土试样的热老化时间效应更显著。(2)高温(100、200℃)作用均会引起膨润土试样中各形态水逐渐脱附,结合水膜变薄,固体土颗粒粒径减小;此外,在200℃条件下,试样中的部分蒙脱石矿物转变为钠云母;上述微观特征演化呈现出与试样导热系数λ一致的热老化时效性。(3)膨润土材料导热性能热老化时间效应产生的本质原因在于:100℃条件下,随着热老化时间t的递增,温度作用导致膨润土中各形态水逐渐脱附,结合水膜变薄,颗粒粒径减小,固相体积减少,气相体积增加,但矿物成分未发生变化;而200℃条件下,随着热老化时间t的递增,上述温度作用进一步加剧,且高温引起了部分蒙脱石矿物转变为导热系数较低的钠云母。 展开更多
关键词 膨润土缓冲层 导热性能 热老化时效性 高温条件 微观机制
原文传递
环形弹簧-质量系统的变形及动态特性的数值研究
16
作者 霍银磊 冯一帆 《包装工程》 北大核心 2026年第1期261-269,共9页
目的基于数值方法研究环形弹簧缓冲器的非线性大变形特性,为其缓冲或隔振设计与应用提供理论参考。方法针对环形弹簧-质量组成的基本弹性系统,基于Euler-Bernoulli梁理论,以环形弹簧的半径及截面角为基本参数推导了弹簧的大变形控制方... 目的基于数值方法研究环形弹簧缓冲器的非线性大变形特性,为其缓冲或隔振设计与应用提供理论参考。方法针对环形弹簧-质量组成的基本弹性系统,基于Euler-Bernoulli梁理论,以环形弹簧的半径及截面角为基本参数推导了弹簧的大变形控制方程及质量的运动方程,考虑环形弹簧的大变形特性,给出环形弹簧平衡方程的边界条件。考虑系统运动方程与弹簧的平衡方程的动态耦合,利用两点边值问题的数值解法研究系统的非线性平衡问题、平衡点处的微幅振动特性及冲击响应特性。结果得到了系统的静态力-变形曲线、频率变化曲线以及冲击加速度变化曲线。环形弹簧-质量系统的力-变形曲线具有明显的分段非线性特性,两非线性阶段连续且在其节点处弹簧与支撑由点接触转变为线接触;系统基于平衡位置的小幅振动频率的突变及系统冲击加速度时程曲线的拐点进一步证明了系统的分段非线性特性;小幅振动频率存在较大的低频区,不同质量系统的冲击加速度响应具有明显的极小值。结论基于数值方法对环形弹簧缓冲器的非线性特性分析结果与相应试验测得的试验结果吻合性较好,证明了该数值计算方法的可靠性,相关结论可为其缓冲或隔振设计与应用提供指导。 展开更多
关键词 环形弹簧 大变形 低频隔振 缓冲性能
在线阅读 下载PDF
建成环境对网约车-地铁组合出行的非线性影响分析
17
作者 潘义勇 王聪伟 +1 位作者 宋文超 贾熙来 《重庆交通大学学报(自然科学版)》 北大核心 2026年第1期53-62,共10页
为探究建成环境对网约车-地铁组合出行需求的非线性影响,首先,基于网约车订单轨迹数据,识别、筛选出地铁站500 m缓冲区内接入、接出的网约车订单数据;其次,建立网约车-地铁组合出行聚集缓冲区,根据“5D”原则构建建成环境变量指标,并将... 为探究建成环境对网约车-地铁组合出行需求的非线性影响,首先,基于网约车订单轨迹数据,识别、筛选出地铁站500 m缓冲区内接入、接出的网约车订单数据;其次,建立网约车-地铁组合出行聚集缓冲区,根据“5D”原则构建建成环境变量指标,并将组合出行数据和变量数据对应至网格;最后,利用XGBoost模型分析建成环境对网约车-地铁组合出行的非线性影响,并识别出关键因素。研究结果表明:XGBoost模型的拟合效果整体优于选用的其他模型;到达市中心距离和人口密度是影响网约车-地铁组合出行的关键因素,它们的相对重要性在接入组合出行中超过45%,在接出组合出行中达到40%;建成环境对网约车-地铁不同组合出行模式的影响表现出显著的非线性特征,并展现出相应的阈值效应,到达市中心距离、人口密度和路网密度对组合出行表现出负向影响,商业设施对组合出行呈现出正向影响,金融设施的数量在16个时为关键阈值点,低于该值表现为正向影响,高于该值表现为负向影响,此外,不同时段公交站对组合出行表现出的非线性特征,表明网约车与城市公交之间具有复杂动态关系。 展开更多
关键词 交通工程 组合出行 XGBoost模型 非线性关系 建成环境 网约车聚集缓冲区
在线阅读 下载PDF
甘肃瓜州有机枸杞产地环境质量评价
18
作者 崔国忠 黄伟 +3 位作者 王晓桃 朱晓霞 杨娟 殷春 《安徽农学通报》 2026年第1期37-40,共4页
为科学评估有机枸杞产地环境是否符合有机生产标准,本研究基于监测数据,依据GB/T 19630—2019等国家标准,对甘肃省瓜州县有机枸杞产地土壤环境污染物、农田灌溉用水污染物、环境空气污染物和缓冲带设置合理性进行了全面评价。结果表明,... 为科学评估有机枸杞产地环境是否符合有机生产标准,本研究基于监测数据,依据GB/T 19630—2019等国家标准,对甘肃省瓜州县有机枸杞产地土壤环境污染物、农田灌溉用水污染物、环境空气污染物和缓冲带设置合理性进行了全面评价。结果表明,研究区土壤中汞、砷、铅、铬、铜、镍、锌含量均小于风险筛选值,滴滴涕(总量)、苯并[α]芘、六六六(总量)未检出;pH、水温等16项农田灌溉水质基本控制项目与大肠埃希氏菌、砷等37项生产用水补充分析项目均检测合格;研究区2022年和2023年PM_(10)、PM_(2.5)等6项环境空气污染物浓度均低于项目限值;研究区缓冲带设置30~50 m,未检出周边农作物的化学药剂和化肥投入物,检出砷、汞、铬含量微小。综合表明,有机枸杞试验示范园的选址位置、土壤污染物、农田灌溉水质基本控制项目、环境空气质量、缓冲带设置等指标整体良好,为开展有机枸杞生产提供可靠的产地环境保障。 展开更多
关键词 有机枸杞 土壤污染物 环境空气质量 缓冲带
在线阅读 下载PDF
Acid Buffering Capacity of Forest Litter from Some ImportantPlantation and Natural Forests in South China 被引量:6
19
作者 李志安 曹裕松 +2 位作者 邹碧 丁永祯 任海 《Acta Botanica Sinica》 CSCD 2003年第12期1398-1407,共10页
The role of forest litter as an acid-base buffering system was assessed by litter from plantation and natural forests in South China. Samples were either extracted with acid solutions or titrated with acid or base sol... The role of forest litter as an acid-base buffering system was assessed by litter from plantation and natural forests in South China. Samples were either extracted with acid solutions or titrated with acid or base solutions. Litter was found to be a strong acid-base buffering system. Two legume species, Acacia mangium Willd and A. auriculaiformis A. Cunn, had very high litter pH values of around 6, which was 2 pH units higher than that of the soil where they grew. Litter of all other plantation species had litter pH of around 4, similar to that of the soil. Both legume species have high potential to neutralize soil acidity and the litter layer could act to shield soil against acid rain. The current stand of two legume species was estimated to be able to raise rain acidity by 0.1 to 0.4 pH units. Inorganic ions did not fully explain the pH pattern of different litter extracts, but high sodium and low nitrate partly accounted for the high pH of the two legume species. Some natural forest species had extremely low pH. As a whole, the litter of the natural climax forest was the driving force of soil acidification. Although plant residues are strong acid-base buffering system and able to adjust acidity of environment, only a few species can be expected to make soil more acid or alkaline through this mechanism since most species have litter pH values similar to those of soil where they grow. 展开更多
关键词 acid-base buffer system inorganic ions acid rain forest litter legume species
在线阅读 下载PDF
Organic Photovoltaic Cells with Improved Performance Using Bathophenanthroline as a Buffer Layer 被引量:5
20
作者 王娜娜 于军胜 +1 位作者 林慧 蒋亚东 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2010年第1期84-88,I0002,共6页
The role of bathophenanthroline (Bphen) as a buffer layer inserted between fullerene (C60) and Ag cathode in organic photovoltaic (OPV) cell was discussed. By introducing Bphen as a buffer layer with thicknes fr... The role of bathophenanthroline (Bphen) as a buffer layer inserted between fullerene (C60) and Ag cathode in organic photovoltaic (OPV) cell was discussed. By introducing Bphen as a buffer layer with thicknes from 0 to 2.5 nm, the power conversion efficiency of the OPV cell based on copper phthalocyanine (CuPc) and C60 was increased from 0.87% to 2.25% under AM 1.5 solar illumination at an intensity of 100 mW/cm^2, which was higher than that of bathocuproine used as a buffer layer. The photocurrent-voltage characteristics showed that Bphen effectively improves electron transport through C60 layer into Ag electrode and leads to balance charge carrier transport capability. The influence of Bphen thickness on OPV cells was also investigated. Furthermore, the absorption spectrum shows that an additional Bphen layer enhances the light harvest capability of CuPc/C60. 展开更多
关键词 Organic photovoltaic cell buffer layer Bathophenanthroline Charge carrier transport
在线阅读 下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部