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高层住宅中母子的行动特性 被引量:2
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作者 织田正昭 郭玲 《住宅科技》 北大核心 1991年第7期40-41,共2页
前言近年来,日本大城市及其近郊,高层住宅迅速发展。这是国土狭窄、地价高涨、人口向城市集中、家庭结构发生变化的必然结果。随着技术水平的提高,二十层至三十层的超高层住宅电开始出现。但是,高层住宅在日本的历史毕竟还很短,有关居... 前言近年来,日本大城市及其近郊,高层住宅迅速发展。这是国土狭窄、地价高涨、人口向城市集中、家庭结构发生变化的必然结果。随着技术水平的提高,二十层至三十层的超高层住宅电开始出现。但是,高层住宅在日本的历史毕竟还很短,有关居住者的生活和健康状况的调查还十分缺乏。为此,为了了解生活在高空的人们的感受,研究高层住宅存在的问题。 展开更多
关键词 住宅 高层 儿童 行动特性
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组织特徵、行动特性与竞争策略反应之研究
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作者 侯嘉政(Jia-Jeng Hou) 許凱萍(Kai-Ping Hsiu) 《金門技術學院學報》
本研究主要探讨行动者╱反应者之组织特徵、行动特性及竞争反应之间的关联性,并以国内电信业者竞争非常激烈的期间(1998~1999年),所蒐集的资料进行实证分析。研究结果发现,组织的规模对其所采行行动之攻击强度、可见性及类型具有... 本研究主要探讨行动者╱反应者之组织特徵、行动特性及竞争反应之间的关联性,并以国内电信业者竞争非常激烈的期间(1998~1999年),所蒐集的资料进行实证分析。研究结果发现,组织的规模对其所采行行动之攻击强度、可见性及类型具有显着影响,行动特性与竞争反应之关联性在行动电话系统产业中确实存在,若遭受对手竞争性行动的影响非常大,将会使得反应者更快、更积极地采取反击行为,但此反击行为与竞争性行动的相似程度将会很高;若面对之竞争性行动的广告出现次数非常高,亦会使得反应者更快、更积极地采取反击行为,且此反击行为与竞争性行动的相似程度亦会很高;另外所面对之竞争性行动的类型不同,亦会使得反应者所采取之反击行为的若干特性有所差异。本研究结论可提供厂商在采取某行动时,考量其可能引发之各种反应的依据,同时根据此讯息行动者在推测其行动所可能引发之反应行为的特性时,除须考量行动本身所可能造成竞争反应的差异外,更应视反应者的特徵而定,来预测其所可能采行之反应行为。 展开更多
关键词 組織特徵 行動特性 競爭反應
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从在线到离线:基于互联网的集体行动的形成及其影响因素 以反建X餐厨垃圾站运动为例 被引量:28
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作者 卜玉梅 《社会》 CSSCI 北大核心 2015年第5期168-195,共28页
本文以反对垃圾站选址的社区集体抗争为例,采用虚拟民族志方法,展现了业主利用互联网进行抗争的行动图景,揭示了基于互联网的集体行动从线上走向线下的过程和影响因素。研究发现,对于浅层行动,在线动员能够实现广泛的离线参与;对于深层... 本文以反对垃圾站选址的社区集体抗争为例,采用虚拟民族志方法,展现了业主利用互联网进行抗争的行动图景,揭示了基于互联网的集体行动从线上走向线下的过程和影响因素。研究发现,对于浅层行动,在线动员能够实现广泛的离线参与;对于深层行动,在政治弱控制、参与热情高涨的运动初期,在线动员效果较好,但在政治控制介入、行动力弱化的运动维持阶段,则需要通过离线的二次动员或现实网络及组织的生成来保证行动参与并支撑运动的持续性。文章指出,互联网的动员潜力、行动特性及运动历程综合影响着从在线到离线的转换,而控制因素产生的政治风险塑造着网络动员的方式和策略,型构着网民群体的行动逻辑,并最终呈现为对在线动员效果的约制。 展开更多
关键词 在线动员 离线集体行动 行动特性 运动历程 政治控制
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核心企业选择网络外部行动者的策略:行动者特性视角 被引量:4
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作者 刘锦英 《管理评论》 CSSCI 北大核心 2015年第7期177-186,共10页
随着技术创新复杂性的增强,以网络为平台寻求外部支持已成为企业技术创新战略的重要选择,而网络集成优势的发挥首先取决于核心企业能否选择到符合创新需要的外部行动者。基于行动者的关系特性、资源特性及空间特性,理论与案例分析相结合... 随着技术创新复杂性的增强,以网络为平台寻求外部支持已成为企业技术创新战略的重要选择,而网络集成优势的发挥首先取决于核心企业能否选择到符合创新需要的外部行动者。基于行动者的关系特性、资源特性及空间特性,理论与案例分析相结合,考察了创新网络中核心企业选择外部行动者的策略。研究显示,资源特性是核心企业选择外部行动者时必须考虑的前提条件;如果外部行动者不具备同样的资源特性,具有互补资源的行动者为核心企业极力选择的对象,而对关系特性及空间特性的考虑均在其次;如果外部行动者具备同样的资源特性,关系特性及空间特性就成为核心企业选择外部行动者时的重要约束条件。研究结果对核心企业正确选择外部行动者,全面理解创新与行动者特性之间的关系有重要启示。 展开更多
关键词 核心企业 创新网络 外部行动者选择 行动特性
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UNSTEADY AERODYNAMIC MODEL OF ISOLATED ROTORIN LARGE-AMPLITUDE MANEUVERS
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作者 徐进 高正 岳海龙 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2008年第1期1-10,共10页
To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A... To improve the rotor off-axis response prediction, aerodynamic models must include the wake distortion effects of the maneuvering rotor. And the crux of the matter is to obtain a precise wake curvature parameter KR. A Peters-He finite-state wake model is improved to incorporate the operating-state-dependent KR to embody maneuver-induced effects. The curvature parameter KR varies with rotor forward speed, thrust and maneuvering angular rate according to a smoking experiment. Moreover, aerodynamic force/moment experiment indicates that after a quasi-step angular input, both on-axis and off-axis rotor responses show that an overshoot and its amplitude increases with the pitching rate. The comparison between theoretical and experimental results shows that the operating-state-accurate curvature parameter must be adopted to obtain accurate aerodynamic forces/moments, especially for the off-axis response. Additionally, combined with a dynamic wake distortion model, the obtained correlation agrees well with experimental data. 展开更多
关键词 MANEUVERABILITY WAKES flight aerodynamics dynamic inflow off-axis response
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Influence of pavement frictional properties on braking distance 被引量:6
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作者 丛菱 黄晓明 《Journal of Southeast University(English Edition)》 EI CAS 2011年第2期210-212,共3页
In order to study the relationship between pavement friction management criteria and braking distance requirements of road geometric design, an approach for determining the braking distance considering pavement fricti... In order to study the relationship between pavement friction management criteria and braking distance requirements of road geometric design, an approach for determining the braking distance considering pavement frictional properties is proposed. A finite element model (FEM) of a rolling tire under steady state is established based on theoretical hydrodynamics and mechanics principles, in which factors, including tire type, water film thickness, pavement surface properties, and vehicle speed, are considered. With the FEM, braking distances under different operating conditions are calculated. Furthermore, the allowable water film thickness is determined by comparing braking distances calculated with friction management criteria and that required by road geometric design. The results show that the braking distance is affected by the above operating conditions. As a result, it is necessary to maintain consistency between geometric design braking distance requirements and pavement friction management to achieve safe road operations. 展开更多
关键词 pavement frictional properties braking distance operating conditions finite element simulation
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Start-up and Performance of a Novel Reactor----Jet Biogas Inter-loop Anaerobic Fluidized Bed 被引量:2
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作者 邓志毅 韦朝海 周秀峰 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2008年第1期143-150,共8页
A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed (JBILAFB), was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose w... A novel anaerobic reactor, jet biogas inter-loop anaerobic fluidized bed (JBILAFB), was designed and constructed. The start-up and performance of the reactor was investigated in the Process. of .artificial glucose wastewater treatment. With the wastewater recycle ratio of 2.5 : 1, the recycled wastewater with biogas could mix sludge and wastewater in the JBILAFB reactor completely. The start-up of the JBILAFB reactor could be completed in less than 70 d through maintenance of hydraulic retention time (HR^I") and stepwise increase of feed total organic carbon (TOC) concentration. After the start-up, with the volumetric TOC loadings of 14.3 kg·m ^-3·d^-1, the TOC removal ratio, the effluent pH, and the volatile fatty acids (VFA)/alkalinity of the JBILAFB reactor were more than 80%, close to 7.0 and less than 0.4, respectively. Moreover, CH4 was produced at more than 70% of the theoretical value, The reactor exhibited high stability under the condition of high volumetric TOC loading. Sludge granules in the JBILAFB reactor were developed during the start-up and their sizes were enlarged with the stepwise increase of volumetric TOC loadings from 0.8 kg.m^-3.d ^-1 to 14.3 kg.m^-3.d^-1. Granules, an offwhite color and a similar spherical shape, were mainly comprised of global-like bacteria. These had good methanogenic activity and settleability, which were formed probably through adhesion of the bacteria. Some inorganic metal compounds such as Fe, Ca, Mg, Al, etc. were advantageous to the formation of the granules. 展开更多
关键词 anaerobic reactor jet biogas inter-loop anaerobic fluidized bed wastewater treatment START-UP granule sludge
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Dynamic modeling of a parafoil system considering flap deflection 被引量:4
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作者 Tao Jin Sun Qinglin +1 位作者 Chen Zengqiang He Yingping 《Journal of Southeast University(English Edition)》 EI CAS 2017年第4期416-425,共10页
In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigi... In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system. 展开更多
关键词 parafoil system dynamic modeling and simulation fig h t chaacterstic airdrop experiment fap defection
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Nonlinear Dynamical Behavior in BS Evolution Model Based on Small-World Network Added with Mechanism of Preferential Connection
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作者 ZHANG Ying-Yue CHEN Tian-Lun 《Communications in Theoretical Physics》 SCIE CAS CSCD 2006年第3期493-498,共6页
In this paper, we introduce a modified small-world network added with new links with preferential connection instead of adding randomly, then we apply Bak-Sneppen (BS) evolution model on this network. Several dynami... In this paper, we introduce a modified small-world network added with new links with preferential connection instead of adding randomly, then we apply Bak-Sneppen (BS) evolution model on this network. Several dynamical character of the model such as the evolution graph, fo avalanche, the critical exponent D and T, and the distribution of mutation times of all the nodes, show particular behaviors different from those of the model based on the regular network and the small-world network. 展开更多
关键词 connectionpower-law behavior small-world network evolution model preferential
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Study on Lateral Aerodynamic Characteristics of Hypersonic Lifting-Configuration 被引量:1
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作者 Qing Gao Jianhua Li +1 位作者 Junbo Zhao Qian Li 《Journal of Energy and Power Engineering》 2014年第12期2053-2057,共5页
To have a deep understanding of the lateral stability of hypersonic lifting-configurations, wind-tunnel tests of roll static and dynamic stability for typical hypersonic lifting-configurations are carried out. The res... To have a deep understanding of the lateral stability of hypersonic lifting-configurations, wind-tunnel tests of roll static and dynamic stability for typical hypersonic lifting-configurations are carried out. The results show the roll is static unstable in small angles; the roll dynamic test curves present obvious non-linearity characteristics, and the model vibrates violently even When the angle of attack is small, which may be provoked by the non-symmetry transition from the small transverse flow around the nose of model. Subsequent research adopts longitudinal trips to generate symmetry transition at the fore-body of the model. As a result, the lateral stability of the aircrafts is apparently improved. The results show that the lateral stability of hypersonic aircrafts is very weak, and the main reason for this is lateral perturbation of flow over the nose, among which asymmetric transition weighs the most. Adoption of longitudinal trips could spur fixed transition of lateral flow, reduce the transition asymmetry of lateral flow, and strengthen the lateral stability of hypersonic aircrafts at the same time. 展开更多
关键词 Hypersonic lifting-configuration lateral stability wind-tunnel test asymmetric transition.
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Dynamic load sharing characteristics and sun gear radial orbits of double-row planetary gear train 被引量:5
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作者 盛冬平 朱如鹏 +2 位作者 靳广虎 陆凤霞 鲍和云 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第10期3806-3816,共11页
A new non-linear bending-torsional coupled model for double-row planetary gear set was proposed, and planet's eccentricity error, static transmission error, and time-varying meshing stiffness were taken into consi... A new non-linear bending-torsional coupled model for double-row planetary gear set was proposed, and planet's eccentricity error, static transmission error, and time-varying meshing stiffness were taken into consideration. The solution of differential governing equation of motion is determined by applying the Fourier series method. The behaviors of dynamic load sharing characteristics affected by the system parameters including gear eccentricities error, ring gear's supporting stiffness, planet's bearing stiffness, torsional stiffness of first stage carrier and input rotation rate were investigated qualitatively and systematically, and sun gear radial orbits at first and second stage were explored as well. Some theoretical results are summarized as guidelines for further research and design of double-row planetary gear train at last. 展开更多
关键词 double-row planetary gear load sharing time-varying stiffness torsional stiffness sun gear radial orbit
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Pedestrians Mobility on Public Sidewalks Evaluated by the IAAPE Method
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作者 Karla Conceicao Pereira Alcindo Neckel +8 位作者 Henrique Aniceto Kujawa Mauricio Kunz Grace Cardoso Lauro André Ribeiro Caliane Christie Oliveira de Almeida Silva Pamela Gnoatto Paola Pol Saraiva Juliana Frighetto Tales Goncalves Visentin 《Journal of Civil Engineering and Architecture》 2017年第8期789-799,共11页
This research aims to evaluate walkability as a strategy of urban mobility in relation to physical characteristics of accessibility and attractiveness from public sidewalks characteristics in the city of Passo Fundo/R... This research aims to evaluate walkability as a strategy of urban mobility in relation to physical characteristics of accessibility and attractiveness from public sidewalks characteristics in the city of Passo Fundo/RS-Brazil using the IAAPE (indicators of attraction and pedestrian accessibility) method. The concept of walkability corresponds to the simple act of walking in a pleasant way along the footpaths. Therefore, the IAAPE method was used, which considers aspects of connectivity, comfort, conviviality, coexistence, convenience, clarity and commitment in relation to the space evaluated. In this study, 40 adults, elderly, pregnant and wheelchair subjects were interviewed for evaluating the importance criteria on public sidewalks for a given type of user. In general, reduced sidewalk dimensions and obstacle presence are the main displacement hurdles in most of the cases analyzed. Thus, improvements are needed to avoid stress situations that arise from daily routine, to encourage physical activities, accessibility, and the emergence of meeting and leisure points. 展开更多
关键词 WALKABILITY MOBILITY public sidewalks IAAPE life quality.
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Finite Element Analysis of the Dynamic Behaviour of Transmission Line Conductors Using MATLAB
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作者 Evans E. Ojo Sergey Shindin 《Journal of Mechanics Engineering and Automation》 2014年第2期142-148,共7页
The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature... The dynamic behaviour of power line cables have been a source of interest to researchers ever since the phenomenon was first noticed in the 1920s. Conductor oscillation is mostly caused by the dynamic forces of nature such as wind loading. This imposes a periodic force on the conductors which is highly undesirable. It is therefore important for engineers to account for the possible effect of the wind loading when designing the power line. Investigations have shown that modeling the exact dynamic behaviour of a conductor is very difficult. Based on this fact, getting the exact analytical solution to conductor vibration is difficult, which is almost impossible, hence the numerical approximation becomes an option. This paper presents the developed finite element method used to analyse the dynamic behaviour of transmission line conductors. The developed FEM (finite element method) is implemented on MATLAB. The numerical analysis using MATLAB that is presented in this paper is used to simulate the response of the conductor when subjected to external loading in the time domain. The simulation is used to analyse the transverse vibration of the conductor. The formulation of the stiffness matrix and load vector is done and the results obtained are used to evaluate the conductor's internal energy dissipation. This finite element solution is compared with the results documented in literature. This numerical simulation is also used to investigate the effects of varying the axial tension on energy dissipation within the strands. Hence, this evolved in physically appropriate energy characterization process that can be used to evaluate the conductor self-damping with respect to line contact. 展开更多
关键词 Conductor mechanical vibration analytical model finite element method MATLAB software line contact stiffnessmatrix self-damping.
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The turbulent behavior of novel free triple-impinging jets with large jet spacing by means of particle image velocimetry 被引量:1
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作者 Jun Zhang Youzhi Liu Ying Luo 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第6期757-766,共10页
A novel reactor that achieves rapid liquid–liquid mixing via free triple-impinging jets(FTIJs) is developed to improve mixing efficiency at unequal flow rates for liquid–liquid reactions. The flow characteristics of... A novel reactor that achieves rapid liquid–liquid mixing via free triple-impinging jets(FTIJs) is developed to improve mixing efficiency at unequal flow rates for liquid–liquid reactions. The flow characteristics of FTIJs were investigated using particle image velocimetry(PIV). The instantaneous and mean velocities data at different Reynolds numbers(Re) were analyzed to provide insights into the velocity distributions in FTIJs. The effect of jet spacing on the stagnation points, instantaneous velocity, mean velocity, profiles of the x- and ycomponents of mean velocity, and turbulent kinetic energy(TKE) distributions of FTIJs were investigated at Re = 4100 with a volumetric flow rate ratio of 0.5. The characteristics of the turbulent flows are similar for all jet spacings tested. Two stagnation points are observed, which are independent of jet spacing and are not located in the center of the flow field. However, velocity and TKE distributions are strongly dependent on the jet spacing.Decreasing jet spacing increases the expansion angle and the values of TKE, leading to strong turbulence, improving momentum transfer and mixing efficiency in FTIJs. The present study shows that optimization of the operating parameters is helpful for designing FTIJs. 展开更多
关键词 Expansion angleFree triple-impinging jetsTurbulent kinetic energyPIV
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Epidemiological modeling of passive worm propagation on the P2P file-sharing network
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作者 Feng Chaosheng Qin Zhiguang +1 位作者 Laurissa Tokarchuk Muhammad Adeel 《High Technology Letters》 EI CAS 2011年第3期230-235,共6页
The peer-to-peer(P2P) file-sharing network as a vehicle of disseminating files has become very popular. The appearance of dozens of kinds of passive worms on this network has, however, made it unsecured. This proble... The peer-to-peer(P2P) file-sharing network as a vehicle of disseminating files has become very popular. The appearance of dozens of kinds of passive worms on this network has, however, made it unsecured. This problem has been paid attention and a few of models for passive worm propagation has been presented. Unfortunately, the dynamic properties of this network are ignored in these models. Given the fact, the characteristics of both this network and the passive worm are identified, and on this basis a new mathematical model of passive worm propagation on the P2P network is presented in applying epidemiology in this paper. Note that the dynamic properties of this network are considered in the presented model. The model has been validated by large scale simulation experiments, which demonstrates that the presented model may be used for analyzing the behaviors of passive worms and predicting the trend of their propagation. 展开更多
关键词 passive worms PROPAGATION modeling P2P networks FILE-SHARING simulation
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Stability of motion state and bifurcation properties of planetary gear train 被引量:2
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作者 李同杰 朱如鹏 +1 位作者 鲍和云 项昌乐 《Journal of Central South University》 SCIE EI CAS 2012年第6期1543-1547,共5页
A nonlinear lateral-torsional coupled vibration model of a planetary gear system was established by taking transmission errors,time varying meshing stiffness and multiple gear backlashes into account.The bifurcation d... A nonlinear lateral-torsional coupled vibration model of a planetary gear system was established by taking transmission errors,time varying meshing stiffness and multiple gear backlashes into account.The bifurcation diagram of the system's motion state with rotational speed of sun gear was conducted through four steps.As a bifurcation parameter,the effect of rotational speed on the bifurcation properties of the system was assessed.The study results reveal that periodic motion is the main motion state of planetary gear train in low speed region when ns<2 350 r/min,but chaos motion state is dominant in high speed region when ns>2 350 r/min,The way of periodic motion to chaos is doubling bifurcation.There are two kinds of unstable modes and nine unstable regions in the speed region when 1 000 r/min<ns<3 000 r/min. 展开更多
关键词 planetary gear train nonlinear dynamical model stability of motion state bifurcation properties
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Research on Behavior of Governing Gene/Epigene Networks as a Problem of Cellular Automata Identification
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作者 Rustem Tchuraev 《Journal of Life Sciences》 2012年第1期110-113,共4页
The aim of this work is to investigate the general functional properties of the intracellular governing gene/epigene networks. A body of mathematics used in automata and graphs theories is adequate for revealing the g... The aim of this work is to investigate the general functional properties of the intracellular governing gene/epigene networks. A body of mathematics used in automata and graphs theories is adequate for revealing the general dynamic properties of governing gene and epigene networks and provides a methodic basis for efficient analytical algorithms. The obtained results permit to reveal the properties of the characteristic function (transitions and outputs) of the cellular automata as models for the intracellular governing gene/epigene networks. 展开更多
关键词 Governing gene networks cellular automata and cell ensembles metastability.
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Some Dynamic and Combinatorial Properties of One Parameter Families of Unimodal Maps with Monotonicity
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作者 John Taylor 《Journal of Mathematics and System Science》 2013年第6期301-308,共8页
It is known that certain one parameter families of unimodal maps of the interval have a topological universality with regard to their dynamic behavior [ 1, 2]. As a parameter is smoothly increased, a fascinating varie... It is known that certain one parameter families of unimodal maps of the interval have a topological universality with regard to their dynamic behavior [ 1, 2]. As a parameter is smoothly increased, a fascinating variety of dynamic behaviors are produced. For some families the behaviors are monotonic in the parameter, while in others they are not [3]. The question is what sort of conditions on a one parameter family will ensure this monotonicity of the behavior with the parameter? The answer is unknown and will not be given here. What we do instead is to investigate certain geometric-dynamic-combinatorial consequences of assuming that the family has this monotonicity. Specifically, using tools of symbolic dynamics, state space is "course grained" with a finite alphabet. We decompose a non-invertible map into nonlinear but invertible pieces. From these invertible pieces, we form inverse maps via composition along words. Equations of motion are developed for both forward and inverse orbits (in both the variables of state space and the parameter), and an equation relating forward and inverse motions at fix-points is exhibited. Finally, we deduce a list of conditions, each of which is equivalent to monotone behavior. One of these conditions states that simple parity characteristics of words correspond to definite dynamics near fixed-points and vice versa. 展开更多
关键词 One parameter family unimodal map kneading theory connection equation.
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An Experimental Investigation on the Dynamic Behavior of Step Motor Drives
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作者 Paolo Righettini Roberto Strada Alberto Oldani Andrea Ginammi 《Journal of Mechanics Engineering and Automation》 2012年第7期431-440,共10页
Step motors, compared to other drive systems, are low-cost and easy to use devices. However, despite these undeniable advantages, they are characterized by some critical running conditions, due to the loss of synchron... Step motors, compared to other drive systems, are low-cost and easy to use devices. However, despite these undeniable advantages, they are characterized by some critical running conditions, due to the loss of synchronization between the stator's magnetic field and the rotor. In order to theoretically investigate such a behavior, several complex mathematical models have been developed, which require several parameters to be defined. For most step motors, such parameters cannot be easily drawn from their data-sheets; on the contrary, in this paper the authors refer to a simplified electro-mechanical model where the most of the parameters are known from data-sheets. The dependence between electrical and mechanical quantities can be investigated by an experimental point of view. At this aim, a specific novel test rig has been designed and developed for either static or dynamic characteristics measurement of small size step motors. In particular, the test rig allow to measure rotor's angular position, motor's torque, currents flowing in the motor's phases. The paper ends with the report of the results of several experimental tests, carried-out on a small-size motor in different running conditions, and with some preliminary remarks on the basis of the measures analysis. 展开更多
关键词 Step motor drives experimental investigation test-rig dynamic behavior electro-mechanical model
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Dynamic Characteristic of the Medium Span Concrete Footbridges
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作者 Marek Pafitak 《Journal of Civil Engineering and Architecture》 2014年第11期1445-1452,共8页
Concrete footbridges, due to their mass, stiffness and damping, are perceived as strucaires more resistant to vibration caused by dynamic action of the users. In order to verify the dynamic behaviour of concrete footb... Concrete footbridges, due to their mass, stiffness and damping, are perceived as strucaires more resistant to vibration caused by dynamic action of the users. In order to verify the dynamic behaviour of concrete footbridges, a series of field tests and numerical analyses have been carried out. In the paper, the results of the dynamic field tests of three medium span concrete footbridges with different structural systems (frame, beam and arch footbridges) and their dynamic characteristics (mass, stiffness and damping) are presented. The field tests were carried out for different types of vibration excitation caused by walking, running and jumping persons. Furthermore, the vibrational comfort criteria for footbridges are shortly described and verified for examined structures. The study were supplemented by numerical calculation of natural mode shapes and frequencies of the structures using the 3D FEA (finite element analysis) models with elastic supports elements in order to ensure the compatibility of the calculated and measured mode shapes of the footbridges. 展开更多
关键词 Footbridge vibrations concrete footbridges comfort criteria.
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