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Influence Predictions of Contact Effects on Mesh Stiffness of Face Gear Drives with Spur Gear 被引量:1
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作者 李政民卿 王晶 朱如鹏 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI CSCD 2015年第5期566-570,共5页
Mesh stiffness is one of important base parameters of face gear dynamic studies.However,a calculation solution of mesh stiffness of face gear drives is not to be constructed due to complex geometric flakes of face gea... Mesh stiffness is one of important base parameters of face gear dynamic studies.However,a calculation solution of mesh stiffness of face gear drives is not to be constructed due to complex geometric flakes of face gear teeth.Thus,a calculation solution of mesh stiffness of face gear drives with a spur gear,which is based on the proposed equivalent face gear teeth and Ishikawa model,is constructed,and the influence of contact effects on mesh stiffness of face gear drives is investigated.The results indicate the mesh stiffness of face gear drives is sensitive to contact effects under heavy loaded operating conditions,specially.These contributions will benefit to improve dynamic studies of face gear drives. 展开更多
关键词 face gear drive mesh stiffness contact effect equivalent tooth Ishikawa model
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Spontaneous Imbibition of Water and Determination of Effective Contact Angles in the Eagle Ford Shale Formation Using Neutron Imaging 被引量:1
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作者 Victoria H.DiStefano Michael C.Cheshire +11 位作者 Joanna McFarlane Lindsay M.Kolbus Richard E.Hale Edmund Perfect Hassina Z.Bilheux Louis J.Santodonato Daniel S.Hussey David L.Jacobson Jacob M.LaManna Philip R.Bingham Vitaliy Starchenko Lawrence M.Anovitz 《Journal of Earth Science》 SCIE CAS CSCD 2017年第5期874-887,共14页
Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extracti... Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extraction. Although modern analytical and computational models can capture fracture growth, there is a lack of experimental data on spontaneous imbibition and wettability in oil and gas reservoirs for the validation of further model development. In this work, we used neutron im- aging to measure the spontaneous imbibition of water into fractures of Eagle Ford shale with known geometries and fracture orientations. An analytical solution for a set of nonlinear second-order diffe- rential equations was applied to the measured imbibition data to determine effective contact angles. The analytical solution fit the measured imbibition data reasonably well and determined effective con- tact angles that were slightly higher than static contact angles due to effects of in-situ changes in veloci- ty, surface roughness, and heterogeneity of mineral surfaces on the fracture surface. Additionally, small fracture widths may have retarded imbibition and affected model fits, which suggests that aver- age fracture widths are not satisfactory for modeling imbibition in natural systems. 展开更多
关键词 spontaneous imbibition effective contact angle neutron imaging Eagle Ford shale rock fractures.
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Distinction between critical current effects and intrinsic anomalies in the point-contact Andreev reflection spectra of unconventional superconductors 被引量:1
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作者 Ge He Zhong-Xu Wei +12 位作者 Jérémy Brisbois Yan-Li Jia Yu-Long Huang Hua-Xue Zhou Shun-Li Ni Alejandro V Silhanek Lei Shan Bei-Yi Zhu Jie Yuan Xiao-Li Dong Fang Zhou Zhong-Xian Zhao Kui Jin 《Chinese Physics B》 SCIE EI CAS CSCD 2018年第4期451-459,共9页
In this work,we discuss the origin of several anomalies present in the point-contact Andreev reflection spectra of(Li1-xFex)OHFeSe,LiTi2O4,and La2-xCexCuO4.While these features are similar to those stemming from int... In this work,we discuss the origin of several anomalies present in the point-contact Andreev reflection spectra of(Li1-xFex)OHFeSe,LiTi2O4,and La2-xCexCuO4.While these features are similar to those stemming from intrinsic superconducting properties,such as Andreev reflection,electron-boson coupling,multigap superconductivity,d-wave and p-wave pairing symmetry,they cannot be accounted for by the modified Blonder–Tinkham–Klapwijk(BTK) model,but require to consider critical current effects arising from the junction geometry.Our results point to the importance of tracking the evolution of the dips and peaks in the differential conductance as a function of the bias voltage,in order to correctly deduce the properties of the superconducting state. 展开更多
关键词 critical current effect point-contact Andreev reflection unconventional superconductor
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Effects of Contact Resistance on Heat Transfer Behaviors of Fibrous Insulation 被引量:5
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作者 Zhao Shuyuan Zhang Boming Du Shanyi 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2009年第5期569-574,共6页
In this article, a numerical model combining conduction and radiation is developed based on two flux approximation to predict the heat transfer behavior of fibrous insulation used in thermal protection systems. Monte ... In this article, a numerical model combining conduction and radiation is developed based on two flux approximation to predict the heat transfer behavior of fibrous insulation used in thermal protection systems. Monte Carlo method is utilized to determine the modified radiative properties with experimentally measured transient external temperature as high as 1 000 K. It is found that the estimated radiative properties become time-independent after about t = 3 000 s. By comparing the predicted to the measured results in transient state, the contact resistance exerts significant influences upon the temperature distribution in the specimen. Results show that the averaged absolute deviation is 3.25% when contact resistance is neglected in heat transfer model, while 1.82% with no contact resistance. 展开更多
关键词 heat transfer Monte Carlo methods radiative properties effective thermal conductivity contact resistance
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Hunting down the ohmic contact of organic field-effect transistor
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作者 M Micjan M Novota +2 位作者 P Telek M Donoval M Weis 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第11期382-387,共6页
We report properties of contact resistances observed on pentacene organic field-effect transistors(OFET) with four different source/drain electrodes, namely, copper(Cu), gold(Au), silver(Ag), and germanium(Ge). The me... We report properties of contact resistances observed on pentacene organic field-effect transistors(OFET) with four different source/drain electrodes, namely, copper(Cu), gold(Au), silver(Ag), and germanium(Ge). The metals were selected to provide a wide range of energy barriers for charge injection, from blocking contact to smooth injection. All OFETs exhibited strong voltage dependence of the contact resistance, even for devices with smooth injection, which is in strong disagreement with the definition of ohmic contacts. A comparison with current crowding, resistive network, Fowler–Nordheim tunneling, and electric field enhanced thermionic injection(Schottky emission) pointed to importance of local electric fields and/or electrostatic field charges. 展开更多
关键词 organic FIELD-effect TRANSISTORS contact resistance CHARGE INJECTION
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Reiterated homogenization of a laminate with imperfect contact:gain-enhancement of effective properties
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作者 F.E.ALVAREZ-BORGES J.BRAVO-CASTILLERO +4 位作者 M.E.CRUZ R.GUINOVART-DIAZ L.D.PEREZ-FERNANDEZ R.RODRIGUEZ-RAMOS F.J.SABINA 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2018年第8期1119-1146,共28页
A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding ... A family of one-dimensional(1D) elliptic boundary-value problems with periodic and rapidly-oscillating piecewise-smooth coefficients is considered. The coefficients depend on the local or fast variables corresponding to two different structural scales. A finite number of imperfect contact conditions are analyzed at each of the scales. The reiterated homogenization method(RHM) is used to construct a formal asymptotic solution. The homogenized problem, the local problems, and the corresponding effective coefficients are obtained. A variational formulation is derived to obtain an estimate to prove the proximity between the solutions of the original problem and the homogenized problem. Numerical computations are used to illustrate both the convergence of the solutions and the gain of the effective properties of a three-scale heterogeneous 1D laminate with respect to their two-scale counterparts. The theoretical and practical ideas exposed here could be used to mathematically model multidimensional problems involving multiscale composite materials with imperfect contact at the interfaces. 展开更多
关键词 reiterated homogenization method(RHM) imperfect contact variational formulation effective coefficient gain
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Effect of Metal Contact and Rapid Thermal Annealing on Electrical Characteristics of Graphene Matrix
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作者 S, Fahad M. Ali +3 位作者 S. Ahmed S. Khan S. Alam S. Akhtar 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第10期65-69,共5页
Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order ... Development of graphene field effect transistors (GFETs) faces a serious challenge of graphene interface to the dielectric material. A single layer of intrinsic graphene has an average sheet resistance of the order of 1-5 kΩ/□. The intrinsic nature of graphene leads to higher contact resistance yielding into the outstanding properties of the material. We design a graphene matrix with minimized sheet resistance of 0.185 kΩ/□ with Ag contacts. The developed matrices on silicon substrates provide a variety of transistor design options for subsequent fabrication. The graphene layer is developed over 400 nm nickel in such a way as to analyze hypersensitive electrical properties of the interface for exfoliation. This work identifies potential of the design in the applicability of few-layer GFETs with less process steps with the help of analyzing the effect of metal contact and post-process anneMing on its electrical fabrication. 展开更多
关键词 effect of Metal contact and Rapid Thermal Annealing on Electrical Characteristics of Graphene Matrix
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Top contact organic field effect transistors fabricated using a photolithographic process
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作者 王宏 姬濯宇 +3 位作者 商立伟 刘兴华 彭应全 刘明 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第8期389-393,共5页
This paper proposes an effective method of fabricating top contact organic field effect transistors by using a pho- tolithographic process. The semiconductor layer is protected by a passivation layer. Through photolit... This paper proposes an effective method of fabricating top contact organic field effect transistors by using a pho- tolithographic process. The semiconductor layer is protected by a passivation layer. Through photolithographic and etching processes, parts of the passivation layer are etched off to form source/drain electrode patterns. Combined with conventional evaporation and lift-off techniques, organic field effect transistors with a top contact are fabricated suc- cessfully, whose properties are comparable to those prepared with the shadow mask method and one order of magnitude higher than the bottom contact devices fabricated by using a photolithographic process. 展开更多
关键词 organic field effect transistors top contact photolithographic
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Study of top and bottom contact resistance in one organic field-effect transistor
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作者 刘舸 刘明 +4 位作者 王宏 商立伟 姬濯宇 刘兴华 柳江 《Chinese Physics B》 SCIE EI CAS CSCD 2009年第8期3530-3534,共5页
This paper reports that the organic field-effect transistors with hybrid contact geometry were fabricated, in which the top electrodes and the bottom electrodes were combined in parallel resistances within one transis... This paper reports that the organic field-effect transistors with hybrid contact geometry were fabricated, in which the top electrodes and the bottom electrodes were combined in parallel resistances within one transistor. With the facility of the novel structure, the difference of contact resistance between the top contact geometry and the bottom contact geometry was studied. The hybrid contact devices showed similar characteristics with the top contact configuration devices, which provide helpful evidence on the lower contact resistance of the top contact configuration device. The origin of the different contact resistance between the top contact device and the bottom contact device was discussed. 展开更多
关键词 organic field-effect transistor top contact geometry bottom contact geometry hybrid contact geometry
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CONTACT ANALYSIS FOR FIBER-REINFORCED, DELAMINATED LAMINATES WITH KINEMATIC NONLINEARITY 被引量:7
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作者 Jianghong Xue Li Zi Hong Yuan Renhuai Liu 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2013年第4期388-402,共15页
A macro-micro analytical approach for the anti-penetrating contact problem at the interfaces of the delamination in symmetrically cross-plied,fiber-reinforced rectangular laminates is presented in this paper.The lamin... A macro-micro analytical approach for the anti-penetrating contact problem at the interfaces of the delamination in symmetrically cross-plied,fiber-reinforced rectangular laminates is presented in this paper.The laminate is simply supported and subjected to a uniform transverse load with a through-width delamination buried at the center position.A contact factor is defined to characterize the contact effect and determined using the micro-mechanics of composite material.By analyzing the kinematics of nonlinear deformation at the interfaces of the delamination,the contact force is derived.Asymptotic solutions from perturbation analysis are presented.It is found that the deformation of the laminate involves a global deflection and a local buckling.The antipenetrating contact effects are characterized by the local buckling and are intrinsic properties of the laminates,relying only on the geometries of the delamination and the material properties.Parametric analyses show that the location and size of the contact areas and the distribution of the contact force are hardly affected by the aspect ratio. 展开更多
关键词 rectangular laminate DELAMINATION contact effect perturbation approach nonlinear analysis
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一种高压油缸往复密封性能评估方法
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作者 高仕恒 索双富 +1 位作者 高建辉 王海平 《润滑与密封》 北大核心 2026年第3期173-180,共8页
高压油缸往复密封的接触应力是体现密封性能的关键指标,增加接触应力则会增强密封性能,但也会增加摩擦力从而降低密封寿命。为全面评估高压油缸V形往复密封的性能和寿命,通过ABAQUS软件对往复密封进行有限元仿真研究,建立V形组合密封有... 高压油缸往复密封的接触应力是体现密封性能的关键指标,增加接触应力则会增强密封性能,但也会增加摩擦力从而降低密封寿命。为全面评估高压油缸V形往复密封的性能和寿命,通过ABAQUS软件对往复密封进行有限元仿真研究,建立V形组合密封有限元模型,分析工况压力及结构因素对密封区域接触应力分布的影响。结果表明:随着工况压力的增加,接触应力峰值和接触宽度呈现规律性增加,且均匀系数也随之上升,这表明较高的工况压力会导致接触应力分布更加不均匀,从而增加局部磨损风险;结构参数如宽度、唇高、开口厚度及角度等对接触应力分布和密封性能有着显著影响,其中接触宽度和均匀系数与宽度和唇口夹角成正比关系,而与唇高、厚度、开口厚度及外夹角成反比关系;增加开口厚度虽会导致最大有效接触应力降低,但可显著提高接触宽度和均匀系数。通过总结接触应力分布的特点,提出均匀系数、最大有效接触应力和有效接触宽度3种评估指标,以弥补单一评估指标可能忽略的局部易磨损问题。研究结果为密封结构优化设计提供了新方法。 展开更多
关键词 往复密封 V形组合密封 均匀系数 最大有效接触应力 有效接触宽度
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Steigmann-Ogden表面效应对压电半平面无摩擦接触行为的影响
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作者 王洁 李孝宝 +1 位作者 詹春晓 徐洋 《力学学报》 北大核心 2026年第2期471-485,共15页
基于Steigmann-Ogden表面弹性理论与经典压电理论,建立了一个能够考虑包含表面残余应力、表面抗拉刚度和表面抗弯刚度在内完整表面力学效应影响的力电耦合接触力学模型.采用Fourier积分变换与Gauss-Chebyshev数值积分方法进行求解,获得... 基于Steigmann-Ogden表面弹性理论与经典压电理论,建立了一个能够考虑包含表面残余应力、表面抗拉刚度和表面抗弯刚度在内完整表面力学效应影响的力电耦合接触力学模型.采用Fourier积分变换与Gauss-Chebyshev数值积分方法进行求解,获得了刚性圆形压头作用下压电半平面结构的接触压力、接触应力和电位移的分布规律.系统分析了上述力电响应量对各表面力学模量以及压头尺寸的依赖规律和作用机制.研究发现,表面效应对压电半平面结构接触面的力电响应量分布具有显著影响.尤其值得指出的是,常被忽视的表面抗弯刚度在接触问题中也具有重要作用,其对法向接触应力的影响程度次于表面残余应力但强于表面抗拉刚度.此外,研究还表明接触力电响应具有明显的尺寸依赖性,当压头尺寸减小至0.1μm时,接触应力分布已显著偏离经典Hertz理论结果,且接触应力值随压头尺寸的减小而降低.本文研究结果对基于压电材料的电子器件性能表征与结构优化具有重要指导意义. 展开更多
关键词 Steigmann-Ogden 表面效应 接触力学 尺寸效应 压电半平面 力电耦合
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Potential Power of the Pyramidal Structure III: Discovery of Pyramid Effects with and without Seasonal Variation 被引量:4
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作者 Osamu Takagi Masamichi Sakamoto +2 位作者 Hideo Yoichi Kimiko Kawano Mikio Yamamoto 《Natural Science》 2020年第12期743-753,共11页
Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify the pyramid effects by the PS in... Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify the pyramid effects by the PS into the following two types. (i) The pyramid effects in which the PS converted the test subject’s unexplained energy to affect biosensors when the test subject entered the PS and meditated. (ii) The pyramid effects in which the potential power of the PS affect</span><span style="font-family:Verdana;">ed</span><span style="font-family:Verdana;"> biosensors if the test subject ha</span><span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> not been inside the PS for at least 20 days and the test subject’s unexplained energy was excluded. In this paper, we report new results regarding (ii). As a result of dividing a year according to the four seasons of winter, spring, summer, and autumn and analyzing the pyramid effect of each period, the following points were found. 1) There was a pyramid effect without seasonal variation. The pyramid effect on the lower and upper layers was different throughout the year for the biosensors placed at the PS apex in two layers, regardless of the season. 2) There was a pyramid effect with seasonal variation. The value of the psi index, which indicates the magnitude of the pyramid effect, changed as the seasons changed, while different pyramid effects were maintained on the lower and upper layers. Regarding the change in the pyramid effect depending on the season, the psi index in summer was larger than that in winter in both the lower and upper layers. From these results, we found that there are two types of potential power at the PS apex: seasonal potential power and non-seasonal potential power. 展开更多
关键词 PYRAMID Potential Power MEDITATION Non-contact effect Seasonal Variation Biosensor Cucumis sativus Gas Psi Index
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Potential Power of the Pyramidal Structure IV: Discovery of Entanglement Due to Pyramid Effects 被引量:4
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作者 Osamu Takagi Masamichi Sakamoto +1 位作者 Kimiko Kawano Mikio Yamamoto 《Natural Science》 2021年第7期258-272,共15页
Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify pyramid effects by the PS into t... Since October 2007, we have been conducting rigorous scientific research on the unexplained “power” of a pyramidal structure (PS). From our research results so far, we could classify pyramid effects by the PS into the following two types: (i) the pyramid effects due to the potential power of the PS and (ii) the pyramid effects due to the influence of the test subject meditating inside the PS. We have been using edible cucumber sections as the biosensors. The pyramid effect existence was clarified by measuring and analyzing the concentration of volatile components released from the biosensors. The biosensors were arranged as a pair: one member of the pair was placed at the PS apex and the other was placed at the calibration control point 8.0 m away from the PS. In this paper, we report a new discovery regarding the type (i) pyramid effects. We discovered a phenomenon considered to be entanglement between the biosensor pairs detecting the pyramid effects. In other words, the biosensors at the PS apex, which were affected by the potential power of the PS, affected the biosensors at the calibration control point. We also confirmed that the effects on the biosensors placed at the calibration control point were not due to the potential power of the PS. Furthermore, we showed that the magnitude of the effect of entanglement changed with the seasons. We expect that our research results will be widely accepted in the future and will become the foundation for a new research field in science, with a wide range of applications. 展开更多
关键词 PYRAMID Potential Power ENTANGLEMENT MEDITATION Non-contact effect Biosensor Cucumis sativus Gas Psi Index
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7种助剂对戊唑醇防治稻曲病的减量增效作用
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作者 李新怡 王佐乾 +7 位作者 郭晨晨 许婷 常向前 蔡旋 杨小林 张舒 吕亮 邓清超 《河南农业科学》 北大核心 2026年第2期89-97,共9页
为探究不同助剂对戊唑醇防治稻曲病的协同增效作用,选取纳米硅(NMG)、迈润(MR)、克欧森(KOS)、迈飞(MF)、犇牛(BN)、激健(JJ)、超牛(CN)7种新型助剂,首先通过接触角测定法量化分析添加助剂对戊唑醇减量后铺展性能的改善效果,进而采用温... 为探究不同助剂对戊唑醇防治稻曲病的协同增效作用,选取纳米硅(NMG)、迈润(MR)、克欧森(KOS)、迈飞(MF)、犇牛(BN)、激健(JJ)、超牛(CN)7种新型助剂,首先通过接触角测定法量化分析添加助剂对戊唑醇减量后铺展性能的改善效果,进而采用温室盆栽人工接种稻曲病菌+药剂喷施试验和自然条件下田间防控试验,综合评价戊唑醇减量添加助剂的协同防控效果。结果表明,戊唑醇减量50%复配各助剂后,药液在稻叶表面的接触角较不添加助剂显著降低,铺展性能显著提高。人工注射接种稻曲病菌条件下,戊唑醇减量50%添加7种助剂可使稻曲病抑制能力较单剂减量50%处理提高18.0%~71.3%,其中复配CN处理抑制效果最好,抑制率达85.5%。田间防控试验结果显示,戊唑醇减量30%添加助剂CN对稻曲病的防效最高,达87.1%,较戊唑醇减量30%处理极显著提升48.6%,与戊唑醇常规剂量单剂处理(86.6%)相当;此外,戊唑醇减量30%添加MF、JJ、MR、BN 4种助剂处理的防效与戊唑醇常规剂量单剂也无显著差异。可见,添加新型助剂可在稻曲病防控中实现杀菌剂减量增效,其中纳米载体CN助剂减量增效显著,为水稻病害绿色防控提供了依据。 展开更多
关键词 稻曲病 助剂 戊唑醇 接触角 减量增效 田间防效
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氨在流化床内的分解特性实验
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作者 郭子鹏 李建波 +3 位作者 赵梦佳 曹嘉 王泉海 卢啸风 《化工进展》 北大核心 2026年第2期789-798,共10页
氨(NH_(3))的分解是其燃烧过程中的关键步骤。本文在鼓泡流化床(bubbling fluidized bed,BFB)反应器中系统地研究了反应器温度(650~950℃)、流化数(0.83~2.50)、床层高度(0~25mm)、入口NH_(3)流量(0~500mL/min)和床料成分(SiO_(2)、Al_(... 氨(NH_(3))的分解是其燃烧过程中的关键步骤。本文在鼓泡流化床(bubbling fluidized bed,BFB)反应器中系统地研究了反应器温度(650~950℃)、流化数(0.83~2.50)、床层高度(0~25mm)、入口NH_(3)流量(0~500mL/min)和床料成分(SiO_(2)、Al_(2)O_(3)、CaO、Fe_(2)O_(3))对NH_(3)分解特性的影响,旨在揭示流化床操作参数对氨分解特性的影响。通过气相色谱仪检测尾气中H_(2)和N_(2)的浓度。研究表明,以SiO_(2)为床料时,NH_(3)的分解率在650℃时仅为0.26%~0.29%,但在950℃时显著提高至18.1%~25.3%,升高温度在很大程度上有助于促进NH_(3)的分解。当流化数从0.83增至2.5时,由于有效气固接触时间的变化,NH_(3)分解率呈先升高后降低的趋势;最高的NH_(3)分解率为20.66%,且出现在临界流化状态。此外,床料颗粒在增强NH_(3)分解率方面具有重要作用。增加反应器内床料高度,可促进NH_(3)分解。另外,床料成分对NH_(3)分解的促进效果从大到小依次为Fe_(2)O_(3)>CaO>Al_(2)O_(3)>SiO_(2),均高于不添加床料的空床工况。本文的研究结果有助于深化对NH_(3)分解的认识,为流化床NH_(3)燃烧过程的调控提供理论基础。 展开更多
关键词 鼓泡流化床 分解 NH_(3)分解率 有效气固接触时间
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保持架间隙对角接触球轴承气帘效应的影响
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作者 李朋华 邱明 +3 位作者 公平 庞晓旭 朱定康 刘佳奇 《航空动力学报》 北大核心 2026年第2期308-319,共12页
为了提高轴承喷射润滑方式下的润滑效率以及适用范围,研究高速角接触球轴承腔内气帘效应成因及影响因素,基于计算流体力学(computational fluid dynamics,CFD)的方法,构建轴承腔内单相流流场特性有限元分析模型,对不同引导/兜孔间隙以... 为了提高轴承喷射润滑方式下的润滑效率以及适用范围,研究高速角接触球轴承腔内气帘效应成因及影响因素,基于计算流体力学(computational fluid dynamics,CFD)的方法,构建轴承腔内单相流流场特性有限元分析模型,对不同引导/兜孔间隙以及转速下的轴承流场特性进行分析。以第二代涡识别技术中的Q准则为基础,提出了针对气帘效应的评价方法与评判标准;分析轴承腔内气帘形成机理,对比不同转速、引导间隙和兜孔间隙对气帘效应的影响;通过正交实验的方法分析影响气帘效应的主要因素。结果表明:轴承腔内气帘效应随着轴承转速的增加而加剧,增大引导间隙和兜孔间隙均能减弱气帘效应;转速对气帘效应的影响要远大于保持架间隙的变化;兜孔间隙相较于引导间隙对轴承气帘效应的影响程度要更加显著。 展开更多
关键词 角接触球轴承 气帘效应 引导间隙 兜孔间隙 涡识别
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Analytical modeling and approaches of multihelix cables incorporating with interwire mutual contacts
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作者 Zhichao ZHANG Xingzhe WANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第9期1633-1654,共22页
This study aims to develop an analytical model based on the curve beam theory to capture the mechanical response of a multihelix cable considering the internal contact displacements.Accordingly,a double-helix cable su... This study aims to develop an analytical model based on the curve beam theory to capture the mechanical response of a multihelix cable considering the internal contact displacements.Accordingly,a double-helix cable subjected to axial tension and torsion is analyzed,and both the line and point contacts between the neighboring wires and strands are considered via an equivalent homogenized approach.Then,the proposed theoretical model is extended to a hierarchical multihelix cable with mutual contact displacements by constructing a recursive relationship between the high-and low-level multihelix structures.The global tensile stiffness and torsional stiffness of the double-helix cable are successfully evaluated.The results are validated by a finite element(FE)model,and are found to be consistent with the findings of previous studies.It is shown that the contact deformations in multihelix cables significantly affect their equivalent mechanical stiffness,and the contact displacements are remarkably enhanced as the helix angles increase.This study provides insights into the interwire/interstrand mutual contact effects on global and local responses. 展开更多
关键词 wordshierarchical multihelix cable mutual contact effect mechanical response effective stiffness
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接触性学习及其教学促进
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作者 马永滔 吕鑫源 邓云辉 《当代教育科学》 北大核心 2026年第1期44-52,共9页
接触是学习发生的前提和基础,接触性学习是学生“打开”世界、进入世界、认识世界和改造世界的基本方式。接触性学习具有“境遇—具身—互动—表现”四维结构,是有效教学的必要条件,对于学生核心素养的培育至关重要。目前,接触性学习面... 接触是学习发生的前提和基础,接触性学习是学生“打开”世界、进入世界、认识世界和改造世界的基本方式。接触性学习具有“境遇—具身—互动—表现”四维结构,是有效教学的必要条件,对于学生核心素养的培育至关重要。目前,接触性学习面临接触情境抽离、接触时间稀缺、接触空间区隔的现实阻梗。为此,促进接触性学习的教学应创设感同身受的学习情境,深化具身接触;重拾教育节奏与留白,保障接触时间;构建开放融通的育人场域,重塑接触空间。 展开更多
关键词 接触性学习 有效教学 核心素养 教学促进
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弹性模量-温度效应对POM齿轮副啮合刚度的影响
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作者 胡波 邓启峰 +2 位作者 董建雄 汪红兵 尹来容 《湖南大学学报(自然科学版)》 北大核心 2026年第2期109-121,共13页
随着高强度工程塑料的出现,塑料齿轮开始广泛应用于动力传动,但其力学性能参数对温度非常敏感.为准确评估不同温度下聚甲醛(polyoxymethylene,POM)齿轮副的啮合刚度,提出了引入弹性模量-温度效应的塑料齿轮副时变啮合刚度计算方法.首先... 随着高强度工程塑料的出现,塑料齿轮开始广泛应用于动力传动,但其力学性能参数对温度非常敏感.为准确评估不同温度下聚甲醛(polyoxymethylene,POM)齿轮副的啮合刚度,提出了引入弹性模量-温度效应的塑料齿轮副时变啮合刚度计算方法.首先,结合齿轮脂润滑与对流换热理论,计算了齿轮的摩擦热流密度及对流换热系数,并通过温控拉伸试验获取了POM材料的弹性模量-温度曲线.随后,基于有限单元法构建了含弹性模量-温度效应的齿轮热弹接触模型,并与Blok闪温理论计算的温度对比,验证了其准确性.最后,基于该模型研究了POM圆柱直齿轮副啮合过程的温度场、应力场以及环境温度、转矩、转速对啮合刚度的影响.结果表明:弹性模量-温度效应对塑料齿轮副的稳态温度场影响甚小;但低温时可强化塑料齿轮的啮合刚度,高温也会明显弱化啮合刚度.因此,评估塑料齿轮刚度时,应当考虑温升及模量-温度效应的影响,以避免高估齿轮啮合刚度带来的设计风险. 展开更多
关键词 弹性模量-温度效应 时变啮合刚度 热弹接触模型 POM齿轮
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