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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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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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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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Preprocessing and Efficacy Analysis of Comprehensive Anti-Inflammatory Treatment for Lymphedema in Patients with Irritating Contact Dermatitis
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作者 Qiaoling Zhong Feng Liu +5 位作者 Huiting Zhang Liping Zhang Jinlan Li Lijuan Zhang Na Li Qinghua Luo 《Journal of Cosmetics, Dermatological Sciences and Applications》 2024年第2期188-199,共12页
Objective: To explore the pre-treatment and efficacy analysis of comprehensive anti-inflammatory treatment for lymphedema in patients with irritating contact dermatitis. Method: Convenience sampling method was used to... Objective: To explore the pre-treatment and efficacy analysis of comprehensive anti-inflammatory treatment for lymphedema in patients with irritating contact dermatitis. Method: Convenience sampling method was used to observe the skin of 160 patients with upper limb lymphedema admitted to the lymphedema outpatient department of our hospital. They were divided into an observation group (80 cases) and a control group (80 cases), and both groups received a course of comprehensive anti-inflammatory treatment (20 treatments). The control group received routine skin care;On the basis of the control group, the observation group received pre-treatment of the affected limb skin: Laofuzi herbal ointment was applied externally to the prone areas of irritating contact dermatitis (such as the upper arm, inner forearm, and cubital fossa). Result: The incidence of irritating contact dermatitis in the observation group was significantly lower than that in the control group (P 0.05). Patients in the observation group felt significantly better in terms of comfort, skin moisture, and itching relief after being wrapped with low elasticity bandages than those in the control group (P Conclusion: Preventive treatment can effectively reduce the incidence of irritating contact dermatitis, prolong the time of stress treatment, thereby increasing efficacy and improving patient compliance. 展开更多
关键词 Comprehensive Anti-Inflammatory Treatment Upper Limb Lymphedema Irritating contact Dermatitis effect
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考虑润滑与涂层影响的齿面接触法向刚度分形模型 被引量:1
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作者 王雪 刘晓鑫 马俐 《机床与液压》 北大核心 2025年第18期15-22,共8页
考虑润滑作用,建立包含固体刚度与液体刚度的齿面接触法向刚度模型。基于Hertz接触理论和分形理论,考虑微凸体弹塑性变形在内的4种变形机制,并引入齿面接触系数,建立齿面接触的法向固体刚度。利用固体接触载荷与刚度,求解液体接触油膜厚... 考虑润滑作用,建立包含固体刚度与液体刚度的齿面接触法向刚度模型。基于Hertz接触理论和分形理论,考虑微凸体弹塑性变形在内的4种变形机制,并引入齿面接触系数,建立齿面接触的法向固体刚度。利用固体接触载荷与刚度,求解液体接触油膜厚度,再通过超声波反射系数,建立包含微观分形形貌参数的润滑液体刚度模型。仿真分析润滑以及微观形貌参数对齿面法向接触刚度的影响,并通过4组包含涂层与未涂层齿轮试件的表面粗糙度获取接触面的微观分形参数,进而求解齿面法向接触刚度,分析涂层对齿轮承载性能的影响。最后将该模型与其他两个模型进行仿真对比,验证该模型的合理性。结果表明:有润滑作用和涂层技术的齿面法向刚度有明显提升,且齿面法向刚度随着分形维数、材料特性参数的增大而增大,随着分形尺度参数的增大而减小;所建立的模型与其他两个模型变化趋势与数量级一致,验证了模型的合理性,且所建模型考虑了润滑与弹塑性变形的作用,比其他模型更完整。 展开更多
关键词 齿面接触 法向刚度 分形模型 涂层齿面 润滑作用
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多市场接触与企业供应链战略——基于相互克制视角
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作者 邓新明 周强 刘新韬 《南开管理评论》 北大核心 2025年第7期101-113,共13页
本文试图以探讨多市场接触与企业供应链战略间的关系为切入点,将多市场接触的研究视角由竞争企业间扩展到竞争主体外的第三方,从而为企业在动态的竞争环境下如何采取理性有效的供应链战略提出建议。本文的研究结果如下:(1)多市场接触与... 本文试图以探讨多市场接触与企业供应链战略间的关系为切入点,将多市场接触的研究视角由竞争企业间扩展到竞争主体外的第三方,从而为企业在动态的竞争环境下如何采取理性有效的供应链战略提出建议。本文的研究结果如下:(1)多市场接触与强硬供应商战略之间正相关;(2)多市场接触与强硬经销商战略之间负相关;(3)供应商集中度会削弱多市场接触与强硬供应商战略之间的正向关系;(4)客户集中度会削弱多市场接触与强硬经销商战略之间的负向关系。具体而言,当多市场接触企业面对上游供应商时,竞争企业会选择对上游供应商实施强硬战略;但当面对下游客户时,竞争企业之间会展开激烈的竞争。同时,供应商集中程度越高,企业对供应商的竞争强度会减弱;客户集中程度越高,同类竞争企业间的竞争强度会减弱,但面对经销商的竞争强度会增加。本研究验证了相互克制理论在供应链领域的部分适用,丰富了多市场接触的相关理论研究,并拓展了供应链竞争问题的边界,将边界条件从二元组扩展到三元组,为供应链管理文献提供新的视角。研究对企业高层管理者具有重要启示,为其在多市场竞争环境下的供应链战略选择提供了参考。 展开更多
关键词 多市场接触 供应链战略 相互克制效应 供应商 经销商
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基于分形理论的滚珠丝杠副整体接触变形研究
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作者 杨飞 于亚维 +2 位作者 周长光 冯虎田 欧屹 《组合机床与自动化加工技术》 北大核心 2025年第3期170-176,共7页
目前,关于滚珠丝杠副承载特性研究主要考虑宏观接触变形阶段,忽略了初始微观接触变形。因此,构建了完整的滚珠丝杠副微观接-宏观接触变形模型,首先,基于微观接触力学理论构建了滚珠丝杠副微观接触模型;然后,基于Hertz接触理论、hornton... 目前,关于滚珠丝杠副承载特性研究主要考虑宏观接触变形阶段,忽略了初始微观接触变形。因此,构建了完整的滚珠丝杠副微观接-宏观接触变形模型,首先,基于微观接触力学理论构建了滚珠丝杠副微观接触模型;然后,基于Hertz接触理论、hornton弹塑性接触理论和屈服特性Mises准则,构建了宏观接触模型;结合修正后的有效承载滚珠个数,最终提出了一种滚珠丝杠副接触变形改进计算方法,并分析了分形维数D及分形尺度G对滚珠丝杠副接触变形的影响。实验结果表明,模型理论计算结果平均误差为4%以下。 展开更多
关键词 滚珠丝杠副 微观接触 宏观接触 有效滚珠数
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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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基于离散元法的块石填料摊铺层振动压实过程及效应研究
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作者 徐平 何嘉雄 +3 位作者 乔世范 董辉 陈宾 侯伟琦 《水资源与水工程学报》 北大核心 2025年第1期163-173,共11页
为了研究块石填料摊铺层在振动压实过程中的行为及其效应,采用离散元法进行了两种不同荷载工况下的振动碾压模拟试验:“慢速小激振力”和“快速大激振力”。通过对比分析这两种工况下块石填料的颗粒位移、应力响应、颗粒间空隙率变化以... 为了研究块石填料摊铺层在振动压实过程中的行为及其效应,采用离散元法进行了两种不同荷载工况下的振动碾压模拟试验:“慢速小激振力”和“快速大激振力”。通过对比分析这两种工况下块石填料的颗粒位移、应力响应、颗粒间空隙率变化以及压实过程,结果表明:增加碾压遍数显著增大了颗粒位移,并减少了颗粒间的空隙率;摊铺层表面沉降率与颗粒空隙率的变化值之间表现出强烈的线性相关性;压实能量的作用效应(包括颗粒位移、空隙率减少程度、峰值动应力和静土压力增量)随着摊铺层深度的增加而迅速减弱,压实能量主要沿竖直方向传播,摊铺层沿深度方向可分为主压实区、次压实区和弱影响区3个区域;大粒径块石填料颗粒的比例显著影响颗粒间的接触结构特征,从而影响压实效果和过程,块石填料的压实过程是由挤压压实效应、移动压实效应和填充压实效应共同作用引起的;在持续的振动碾压荷载作用下,颗粒间的接触结构特征和聚集状态从“单点接触”和“松散”状态逐渐演变为“多点接触”和“紧密”状态。研究成果可为工程实践提供重要的理论依据,有助于确定最适摊铺层厚度及优化压路机参数的选择。 展开更多
关键词 块石填料 振动碾压 压实效应 接触结构特征 压实过程 离散元模拟
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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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典型接触条件下双层螺旋曲杆束的弯曲特性
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作者 王荣辉 刘锡月 +2 位作者 赵勇霖 甄晓霞 张卓杰 《华南理工大学学报(自然科学版)》 北大核心 2025年第6期12-24,共13页
为研究双层螺旋曲杆束在拉-弯耦合作用下的力学行为及其内部钢丝协同工作机理,考虑丝间摩擦滑移,建立了层间接触、同步接触两类典型条件下的侧丝微段静力平衡关系并进行了解析推导,同步提出一种改进的半精细化有限元模型进行数值模拟和... 为研究双层螺旋曲杆束在拉-弯耦合作用下的力学行为及其内部钢丝协同工作机理,考虑丝间摩擦滑移,建立了层间接触、同步接触两类典型条件下的侧丝微段静力平衡关系并进行了解析推导,同步提出一种改进的半精细化有限元模型进行数值模拟和结果对比。由弯曲变形时侧丝所受剪切力的分布规律获得了两类接触条件下的丝间相对滑移方向,并在此基础上根据平衡方程推导得到侧丝滑移后的轴力限值;通过对各丝贡献的弯矩求和得到在拉-弯耦合作用下曲杆束各截面的弯矩-局部曲率关系式,并提出一种简化的弯矩-曲率均值关系式描述其整体弯曲行为。结果表明:由于侧丝沿曲杆束整体轴向周期旋转,相邻丝之间接触面有滑移驻点,且驻点两侧相对滑移方向相反;侧丝-侧丝、侧丝-芯丝接触面的滑移驻点、初始滑移位置不同;忽略内部滑移扩展过程,两类接触条件下双层螺旋曲杆束具有相同的弯矩-曲率均值关系式,函数图像呈双折线;半精细化有限元模型滑移前后的弯曲变形结果与解析值的相对误差小于4%,且提取的丝间相对滑移结果规律与分析结论相符。 展开更多
关键词 螺旋曲杆束 拉-弯耦合 丝间滑移 弯曲特性 接触条件 半精细化有限元模型
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井下应急封堵装置坐封过程的流固耦合效应
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作者 李劲松 王磊 +3 位作者 雷磊 殷志明 李中 黄小光 《石油机械》 北大核心 2025年第3期38-44,共7页
井下应急封堵装置是为应对海洋钻井过程中突发溢流和井涌事故而研发的应急设备。当井下出现溢流后,流体压力高、流速快,封堵装置在坐封钻套环空的过程中必定受到环空压力和流体流动的影响。为正确评估井下应急封堵装置的坐封效果,基于... 井下应急封堵装置是为应对海洋钻井过程中突发溢流和井涌事故而研发的应急设备。当井下出现溢流后,流体压力高、流速快,封堵装置在坐封钻套环空的过程中必定受到环空压力和流体流动的影响。为正确评估井下应急封堵装置的坐封效果,基于流固耦合方法,构建了井下应急封堵装置坐封的有限元分析模型,分析了流体流动和压力对坐封过程和坐封效果的影响。研究结果表明,坐封过程中,胶筒变形使胶筒与套管内壁环空通道变窄,导致流体流速与压力增大,增加了坐封难度。由于流体流动的影响,胶筒接触宽度减小,接触应力下降,坐封效果减弱。因此,在现场应用时,必须考虑井下高压流体的流动影响,优化井下应急封堵装置的坐封压力,以实现预定的坐封效果。研究结果可为油井现场应对突发事故提供参考解决方案。 展开更多
关键词 井下应急封堵装置 流固耦合 坐封效果 接触应力
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黑褐举腹蚁与红火蚁间的干扰竞争和机制 被引量:1
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作者 白卫辉 吴慧敏 +4 位作者 陈惠梅 陈立 陆永跃 许益镌 王磊 《环境昆虫学报》 北大核心 2025年第1期249-258,共10页
黑褐举腹蚁Crematogaster rogenhoferi是一种可以与重大入侵害虫红火蚁Solenopsis invicta共存的本地蚂蚁。为探究黑褐举腹蚁与红火蚁的竞争机制,本研究测定了二者在个体与群体水平上的竞争能力,并评价了黑褐举腹蚁毒液粗提物对红火蚁... 黑褐举腹蚁Crematogaster rogenhoferi是一种可以与重大入侵害虫红火蚁Solenopsis invicta共存的本地蚂蚁。为探究黑褐举腹蚁与红火蚁的竞争机制,本研究测定了二者在个体与群体水平上的竞争能力,并评价了黑褐举腹蚁毒液粗提物对红火蚁的触杀和驱避作用。一对一攻击试验结果表明:红火蚁大型、中型工蚁与黑褐举腹蚁工蚁组合的攻击指数分别为2.03和1.97;攻击指数在3级以上的攻击行为中,红火蚁主动攻击次数占总次数的85%以上,以物理攻击为主,黑褐举腹蚁大多数情况下为被动防御且全部以化学攻击应对。群体攻击试验结果表明,各处理组合中红火蚁的死亡率均高于黑褐举腹蚁;两者10∶10的组合中,红火蚁死亡率达到60%,而黑褐举腹蚁的仅为7%,后者群体竞争能力更强。而在黑褐举腹蚁尾部毒液分泌口封堵处理之后,在10∶10的群体竞争组合中其死亡率由6.67%提高至75.00%,说明毒液在其与红火蚁的竞争中起到重要作用。不同稀释浓度的黑褐举腹蚁毒液粗提物对红火蚁的致死率均会随着处理时间的增加而提高,浓度8%的毒液粗提物处理48 h后红火蚁死亡率超过85%。而且10%的黑褐举腹蚁毒液粗提物溶液对红火蚁的驱避率为81.67%,略微低于10%避蚊胺的驱避率91.67%,其他浓度的毒液粗提物的驱避效果均显著低于同浓度的避蚊胺。综上所述,黑褐举腹蚁的化学防御是其与红火蚁竞争的优势原因,而且其化学防御物质对红火蚁有较高的生物活性。 展开更多
关键词 红火蚁 黑褐举腹蚁 干扰竞争 生物活性 触杀毒性 驱避作用
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