期刊文献+
共找到520篇文章
< 1 2 26 >
每页显示 20 50 100
No Degeneracy of the Ground State for the Impact Parameter Model
1
作者 Héctor C. Merino Juan Héctor Arredondo 《Applied Mathematics》 2011年第10期1191-1195,共5页
A time dependent Hamiltonian associated to the impact parameter model for the scattering of a light particle and two heavy ones is considered. Existence and non degeneracy of the ground state is shown.
关键词 impact PARAMETER Model Non DEGENERACY of the ground STATE
下载PDF
Pedestrian Countdown Signals: What Impact on Safe Crossing?
2
作者 Janusz Supernak Vinay Verma Iga Supernak 《Open Journal of Civil Engineering》 2013年第3期39-45,共7页
This paper examines safety impacts of a Pedestrian Countdown Signal (PCS) installed on a busy downtown intersection in San Diego, California. Crossing episodes of over 5000 pedestrians were videotaped and analyzed usi... This paper examines safety impacts of a Pedestrian Countdown Signal (PCS) installed on a busy downtown intersection in San Diego, California. Crossing episodes of over 5000 pedestrians were videotaped and analyzed using multivariate statistical methods. Details of timing of pedestrian crossing as well as information about vehicular traffic and signal timing were carefully coded for each pedestrian. Significant safety benefits of the PCS system were found on the long crossings over a street with high vehicular volumes: most pedestrians were able to effectively increase their walking speed to complete their crossing without committing the exit violation—even if they have already committed the entry violation. However, on the short crossing with light vehicular traffic, PCS was generally ineffective in preventing the entry violations from becoming exit violations. Over there, many pedestrians felt safe enough to walk over a short crossing with no apparent vehicular traffic in sight instead of waiting for a green signal. The length of crossing and volume of interfering vehicular traffic were consistently found the most significant variables affecting the crossing violation rates of different categories of pedestrians. Crossing violation rates were the highest for runners, bicyclists and older males. Crossing violation characteristics were found to be consistent over time. 展开更多
关键词 pedestrian SAFETY COUNTDOWN SIGNALS MULTIVARIATE Analysis SAFETY impacts
下载PDF
Impact of Pedestrian Traffic on Saturation Rate of Protected Left-Turn at Urban Intersections
3
作者 Yixin Chen Yulong He Xiaoduan Sun 《Open Journal of Applied Sciences》 2015年第1期22-31,共10页
Heavily congested intersections in metropolitan areas in China are facing unique problems due to high travel demand and a high degree of traffic law violations. Based on a study conducted by the authors of this paper,... Heavily congested intersections in metropolitan areas in China are facing unique problems due to high travel demand and a high degree of traffic law violations. Based on a study conducted by the authors of this paper, 93% of left-turn vehicles turning left in these areas were slowed in order to avoid conflict with pedestrians. Intertwined pedestrian and vehicular flows can significantly reduce the capacity of exclusive left-turn lane group through reducing saturation flow rate, which increases the congestion at intersections. This paper investigates how the saturation flow rate of exclusive left-turn lane group is affected by the characteristics of pedestrian flow. By analyzing the imagery data collected by video cameras installed at intersections, the research team is able to obtain the characteristics of both vehicular and pedestrian flows, such as speed and spatial locations. The average operating speed at the saturation flow rate with and without pedestrian traffic is used as a direct measurement to evaluate the effect of pedestrians. Based on the statistical analysis, the paper concludes that saturation flow rate is mainly affected by the position of pedestrian in the crosswalk (inside or outside of left-turn vehicle’s trajectory), and the distance between the vehicle and pedestrians. In general, when the distance is less than four meters, the smaller the distance between vehicle and pedestrians, the larger the impact. However, there is no significant impact when the distance is larger than four meters. To accurately quantify the effect, the degree of pedestrian-vehicle impact is defined in four levels. The results show that the difference in the saturation flow rate between the best and the worst level could be 15.7%, which clearly indicates how important it is to enforce pedestrian crossing behavior. 展开更多
关键词 impact of pedestrianS Exclusive LEFT-TURN Lane Speed of SATURATION FLOW SATURATION FLOW RATE
下载PDF
Virtual Reconstruction of Long Bone Fracture in Car-to-pedestrian Collisions Using Multi-body System and Finite Element Method 被引量:10
4
作者 HAN Yong YANG Jikuang MIZUNO Koji 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2011年第6期1045-1055,共11页
Lower limb injures are frequently observed in passenger car traffic accidents.Previous studies of the injuries focus on long bone fractures by using either cadaver component tests or simulations of the long bone kinem... Lower limb injures are frequently observed in passenger car traffic accidents.Previous studies of the injuries focus on long bone fractures by using either cadaver component tests or simulations of the long bone kinematics,which lack in-depth study on the fractures in stress analysis.This paper aims to investigate lower limb impact biomechanics in real-world car to pedestrian accidents and to predict fractures of long bones in term of stress parameter for femur,tibia,and fibula.For the above purposes,a 3D finite element(FE) model of human body lower limb(HBM-LL) is developed based on human anatomy.The model consists of the pelvis,femur,tibia,fibula,patella,foot bones,primary tendons,knee joint capsule,meniscus,and ligaments.The FE model is validated by comparing the results from a lateral impact between simulations and tests with cadaver lower limb specimens.Two real-world accidents are selected from an in-depth accident database with detailed information about the accident scene,car impact speed,damage to the car,and pedestrian injuries.Multi-body system(MBS) models are used to reconstruct the kinematics of the pedestrians in the two accidents and the impact conditions are calculated for initial impact velocity and orientations of the car and pedestrian during the collision.The FE model is used to perform injury reconstructions and predict the fractures by using physical parameters,such as von Mises stress of long bones.The calculated failure level of the long bones is correlated with the injury outcomes observed from the two accident cases.The reconstruction result shows that the HBM-LL FE model has acceptable biofidelity and can be applied to predict the risk of long bone fractures.This study provides an efficient methodology to investigate the long bone fracture suffered from vehicle traffic collisions. 展开更多
关键词 passenger car pedestrian accident lower limb FE model long bone fracture impact biomechanics
下载PDF
A modified Kelvin impact model for pounding simulation of base-isolated building with adjacent structures 被引量:13
5
作者 Ye Kun Li Li Zhu Hongping 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2009年第3期433-446,共14页
Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level bet... Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the baseisolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding under a limited seismic gap. 展开更多
关键词 structural pounding BASE-ISOLATION near-fault ground motions Kelvin impact model nonlinear damping
下载PDF
Influence of dynamic pressure on deep underground soft rock roadway support and its application 被引量:4
6
作者 Meng Qingbin Han Lijun +4 位作者 Chen Yanlong Fan Jiadong Wen Shengyong Yu Liyuan Li Hao 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2016年第5期903-912,共10页
Due to high ground stress and mining disturbance, the deformation and failure of deep soft rock roadway is serious, and invalidation of the anchor net-anchor cable supporting structure occurs. The failure characterist... Due to high ground stress and mining disturbance, the deformation and failure of deep soft rock roadway is serious, and invalidation of the anchor net-anchor cable supporting structure occurs. The failure characteristics of roadways revealed with the help of the ground pressure monitoring. Theoretical analysis was adopted to analyze the influence of mining disturbance on stress distribution in surrounding rock,and the change of stress was also calculated. Considering the change of stress in surrounding rock of bottom extraction roadway, the displacement, plastic zone and distribution law of principal stress difference under different support schemes were studied by means of FLAC3D. The supporting scheme of U-shaped steel was proposed for bottom extraction roadway that underwent mining disturbance. We carried out a similarity model test to verify the effect of support in dynamic pressure. Monitoring results demonstrated the change rules of deformation and stress of surrounding rock in different supporting schemes. The supporting scheme of U-shaped steel had an effective control on deformation of surrounding rock. The scheme was successfully applied in underground engineering practice, and achieved good technical and economic benefits. 展开更多
关键词 Deep soft rock roadway Dynamic pressure impact Similarity model test Combined support ground pressure monitoring
下载PDF
Performance of identical rockbolts tested on four dynamic testing rigs employing the direct impact method 被引量:1
7
作者 Charlie C.Li John Hadjigeorgiou +5 位作者 Peter Mikula Greig Knox Bradley Darlington Renee Royer Andrzej Pytlik Michael Hosp 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2021年第4期745-754,共10页
Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each... Impact drop tests are routinely used to examine the dynamic performance of rockbolts.Numerous impact tests have been carried out in the past decades on independently designed,constructed and operated testing rigs.Each laboratory has developed testing procedures;thus,the results are often reported in different ways by various laboratories.The inconsistency in testing procedures and reporting formats presents a challenge when comparing results from different laboratories.A series of impact tests of identical rockbolts was carried out using the direct impact method(i.e.the mass free-fall method)on the rigs in four laboratories in different countries.The purpose of these tests was to investigate the level of consistency in the results from the four rigs.Each rig demonstrated a high level of repeatability,but differences existed between the various rigs.The differences would suggest that there is noticeable equipment-dependent bias when test results obtained from different laboratories are compared.It was also observed that the energy dissipated for the plastic displacement of the bolt was smaller than the impact energy in the tests.The average impact load(AIL)and the ultimate plastic displacement(D)of the bolt describe the ultimate dynamic performance of the bolt.In the case where the bolt does not rupture,the specific plastic energy(SPE)is an appropriate parameter in describing the impact performance of the bolt.Two other relevant parameters are the first peak load(FPL)and the initial stiffness(K)of the bolt sample.The information from this test series will guide the formulation of standardised testing procedures for dynamic impact tests of rockbolts. 展开更多
关键词 Dynamic test Drop test impact test Rockbolt Rock reinforcement ground support
下载PDF
A Model for Capacity Considering the Interference by Pedestrian Traffic at Signal Intersections
8
作者 Yixin Chen Yulong He Xiaoduan Sun 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2016年第1期82-89,共8页
The capacity is impacted badly by pedestrians' violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow... The capacity is impacted badly by pedestrians' violation behavior at signal intersections. In order to quantify the impact,the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis,the timeheadway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians 'influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time,the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14%at the worst case( level I). The conclusions obtained in this paper are valuable for better management of the signal intersection. 展开更多
关键词 urban traffic capacity impact of pedestrians significant analysis
下载PDF
The Kaali Impact as Trigger of a Mega-Tsunami Event and Violent Seismotectonics in Sweden
9
作者 Nils-Axel Mö rner 《International Journal of Astronomy and Astrophysics》 2020年第3期235-246,共12页
A meteorite impacted the ground in Estonia forming the Kaali Crater dated at 1183 - 1162 BC. It set up a Baltic-wide mega-tsunami dated at 1171 absolute varve years BC. It also triggered violent seismotectonic effect ... A meteorite impacted the ground in Estonia forming the Kaali Crater dated at 1183 - 1162 BC. It set up a Baltic-wide mega-tsunami dated at 1171 absolute varve years BC. It also triggered violent seismotectonic effect in Sweden. Ancient legends testify of direct observations of the sky phenomena and personal experiences of the ground shaking and tsunami flooding, which makes the Kaali Crater the oldest impact event documented by humans. The Ragnar<span style="white-space:nowrap;">&#246;</span>k apocalypse is likely to lead its origin from the violent geodynamic activity along the Swedish east coast. 展开更多
关键词 Meteor impact in the Bronze Age The Kaali Crater ground Shaking Methane Venting Tectonics Baltic Mega-Tsunami Ancient Legends Ragnarök
下载PDF
车人碰撞中人地接触损伤仿真及防护方法鲁棒性分析
10
作者 邹铁方 刘志旗 +2 位作者 袁湘婷 曹太山 刘朱紫 《汽车工程》 EI CSCD 北大核心 2024年第3期509-519,共11页
人车事故中行人主要与车辆和地面接触而遭受损伤。此前已有大量研究在车辆接触阶段对多体行人模型进行了验证,但对地面接触阶段的验证较少。本文中评估了用于预测车辆撞击后行人运动和地面接触的4个PC-Crash行人模型。通过车辆和地面接... 人车事故中行人主要与车辆和地面接触而遭受损伤。此前已有大量研究在车辆接触阶段对多体行人模型进行了验证,但对地面接触阶段的验证较少。本文中评估了用于预测车辆撞击后行人运动和地面接触的4个PC-Crash行人模型。通过车辆和地面接触的HIC伤害与最近研究中的6个尸体实验数据对比显示,其中PC2014行人模型能很好地预测行人头部损伤,车辆和地面接触HIC的平均误差分别为6.07%和5.85%,数据说明PC2014行人模型可以用于再现人车碰撞事故以及开发未来地面接触伤害防护对策。控制制动防护方法鲁棒性研究显示,在3种行人姿态(奔跑、步行和应急)扰动下,HIC平均降低比例分别为63.2%、57.9%和67.8%,说明控制制动防护方法具有很好的抗行人姿态干扰能力。进一步分析不同姿态下的行人损伤发现,3种步态序列之间均有显著性差异,在应急步态下控制制动防护方法有着更好的抗行人姿态干扰能力;而在奔跑步态序列下,往往可以通过控制制动防护方法产生最低的头地碰撞损伤,表明在使用控制制动防护方法对行人进行保护时须考虑到不同姿态产生的影响,以进一步提高控制制动防护方法的地面伤防护效果。 展开更多
关键词 PC-Crash行人模型 车辆控制制动 行人地面伤 行人姿态扰动 鲁棒性
下载PDF
参数扰动对一种先前的车辆制动控制和防护方法的影响
11
作者 邹铁方 江碟 +1 位作者 周靖 袁湘婷 《汽车安全与节能学报》 CAS CSCD 北大核心 2024年第4期477-483,共7页
探究了作者早先提出的一种车辆制动控制防护方法在参数扰动下的防护效果。用MADYMO虚拟仿真软件,对4种形状的典型车头开展了仿真,分析了以下参数:人体头部与车体首次接触时间、制动系统协调时间、路面附着因数:扰动时,对该制动控制防护... 探究了作者早先提出的一种车辆制动控制防护方法在参数扰动下的防护效果。用MADYMO虚拟仿真软件,对4种形状的典型车头开展了仿真,分析了以下参数:人体头部与车体首次接触时间、制动系统协调时间、路面附着因数:扰动时,对该制动控制防护方法的影响。结果显示:在人体头部与车体首次接触时间时为80~100 ms时,对加权伤害费用(WIC)降幅的影响最显著,但不同车型下的参数敏感性排序存在差异。在路面附着因数扰动为0.45~0.80时,人车碰撞损伤未增加;但地面所致WIC降幅均大于零,可有效降低人地碰撞损伤。在制动系统协调时间参数扰动区间为80~350 ms时,该车辆制动控制防护方法仍然保持有效。 展开更多
关键词 人车碰撞事故 人地碰撞损伤 车辆制动控制 参数扰动 路面附着因数 制动系统协调时间
下载PDF
人车碰撞事故中人地碰撞损伤研究进展
12
作者 邹铁方 刘志旗 王丹琦 《长沙理工大学学报(自然科学版)》 CAS 2024年第3期116-133,共18页
为了解人车碰撞事故中人地碰撞损伤的研究进展,并对可行的人地碰撞损伤防护方法做出展望。本文从人车碰撞事故特征、人体损伤评价指标、人体损伤来源、人地碰撞损伤影响因素及人地碰撞损伤防护方法5个方面回顾了已有研究成果,并对已有... 为了解人车碰撞事故中人地碰撞损伤的研究进展,并对可行的人地碰撞损伤防护方法做出展望。本文从人车碰撞事故特征、人体损伤评价指标、人体损伤来源、人地碰撞损伤影响因素及人地碰撞损伤防护方法5个方面回顾了已有研究成果,并对已有研究中存在的问题进行讨论,就人地碰撞防护方法的发展作出展望。人地碰撞损伤研究仍然存在许多不成熟的地方,特别是人地碰撞损伤的致伤机理和影响因素方面仍须开展深入的研究。通过回顾现有的人地碰撞损伤防护技术指出,未来可从优化车辆前部形状、安装行人安全装置以及控制车辆制动等方面来降低行人损伤风险。大部分事故中碰撞速度为中低速,而在低车速下的人地碰撞损伤不容忽视,可通过控制车辆制动降低人地碰撞损伤。此外,人地碰撞损害评价指标仍存在不足。本文可为后续更好地开展人地碰撞损伤致伤机理及防护方法的研究提供参考。 展开更多
关键词 交通事故 人车事故特征 人地碰撞损伤 人体损伤来源 损伤影响因素 损伤防护方法
下载PDF
多胞圆管夹芯组合板落锤冲击试验及数值仿真
13
作者 吴丽丽 徐翔 +2 位作者 李远 王慧 李金鹏 《振动与冲击》 EI CSCD 北大核心 2024年第23期38-46,55,共10页
为了应对煤矿巷道冲击地压下支架结构破坏严重的问题,提出了一种多胞圆管夹芯组合板。该组合板可与煤矿巷道金属支架结合,通过溃缩变形吸能共同抵御冲击荷载。共设计了4个不同芯层厚度夹芯组合板试件的落锤冲击试验,并建立了有限元模型... 为了应对煤矿巷道冲击地压下支架结构破坏严重的问题,提出了一种多胞圆管夹芯组合板。该组合板可与煤矿巷道金属支架结合,通过溃缩变形吸能共同抵御冲击荷载。共设计了4个不同芯层厚度夹芯组合板试件的落锤冲击试验,并建立了有限元模型,基于试验验证了该数值模型,开展了多胞圆管夹芯组合板的冲击响应和吸能特性的参数分析。研究结果表明,冲击作用下,多胞圆管夹芯组合板面板呈现圆盘状凹陷,芯层胞体和十字肋发生了褶皱和下陷变形,各个腔室协同工作、相互支撑,并通过塑性变形吸能。同时底部冲击反力的峰值总是滞后且低于落锤冲击荷载峰值,在多次冲击条件下,该组合板也能展现出良好的吸能缓冲效果。多胞圆管夹芯组合板可吸收超过90.00%的冲击能量,其中65.00%以上能量由芯层结构吸收。芯层厚度从0.5 mm增加到2.0 mm,芯层部分吸收能量的占比增大了24.17%,相反面板吸能效率递减,减幅为17.17%,芯层厚度减小可降低峰值冲击荷载,芯层厚度为1.0 mm时吸能效果较好。面板厚度对吸能性能影响较小,建议其厚度选择与芯层厚度相近。冲击能量一定情况下,改变落锤质量和冲击速度对结构动力冲击性能和吸能效率的影响很小。 展开更多
关键词 落锤冲击试验 多胞圆管夹芯组合板 冲击地压 煤矿巷道 数值模拟
下载PDF
建筑底层架空对行人高度处风环境及污染物扩散影响的数值模拟
14
作者 谢海英 杨怡 张天霄 《能源研究与信息》 CAS 2024年第3期125-133,共9页
在规则建筑群内,考虑建筑底层的架空设计,利用realizable k-ε紊流模型数值模拟了6种工况下的风场和污染物浓度场,并采用时均风速比M_(VR)、风速面积占比A_(RSi)和无量纲浓度K等指标对行人高度处的风环境和污染物浓度进行了评价。建筑... 在规则建筑群内,考虑建筑底层的架空设计,利用realizable k-ε紊流模型数值模拟了6种工况下的风场和污染物浓度场,并采用时均风速比M_(VR)、风速面积占比A_(RSi)和无量纲浓度K等指标对行人高度处的风环境和污染物浓度进行了评价。建筑底层的架空设计能有效增加行人高度处的M_(VR),上游建筑的架空对M_(VR)的增加效果更显著。架空设计能减小低风速A_(RSi),增加中风速和中高风速A_(RSi),当建筑群中有2列及以上的建筑采用架空设计时,A_(RSi)的改善效果更好。当污染源位于建筑群上游地面时,架空设计对行人高度处的K分布影响不大,架空导致的回流使得污染物难以扩散至建筑群内,还会因其架空导致紧邻污染源的建筑迎风面行人高度处的K显著变小。 展开更多
关键词 底层架空 行人高度 风环境 污染物 数值模拟
下载PDF
近场地震动对我国RC框架结构地震响应影响分析
15
作者 张令心 王子铭 朱柏洁 《世界地震工程》 北大核心 2024年第4期39-50,共12页
近场地震常含有丰富的脉冲成分,其短时间内产生的冲击效应会对近场地区建筑结构造成严重破坏。钢筋混凝土(reinforced concrete,RC)框架结构在我国城镇地区应用较多,为此应开展近场地震动对我国框架结构地震响应影响研究。基于近期记录... 近场地震常含有丰富的脉冲成分,其短时间内产生的冲击效应会对近场地区建筑结构造成严重破坏。钢筋混凝土(reinforced concrete,RC)框架结构在我国城镇地区应用较多,为此应开展近场地震动对我国框架结构地震响应影响研究。基于近期记录较为完整的土耳其M 7.8级地震,筛选出近场脉冲型和非脉冲型两类地震动各2条作为输入,并对比分析了4条地震动加速度反应谱的形状特征;按8度设防设计并建立了4、7、10层三个不同周期的RC框架结构有限元分析模型,利用现有试验结果验证了该模型的准确性;采用非线性动力时程分析方法,通过比较地震加速度反应谱、结构层间位移角、结构耗能和梁、柱构件利用率等指标,从结构整体到构件层面综合分析了这两类地震动对框架结构地震响应的影响。研究结果表明:所选的脉冲型地震动加速度反应谱平台段较长且双峰和多峰特性明显,非脉冲型地震动加速度反应谱的单峰特性明显;在这两类地震动作用下,短周期结构整体响应以及梁、柱构件的破坏程度均与地震加速度反应谱值呈正相关性;而对于中和长周期结构,相比较非脉冲型地震动,脉冲型地震动作用下会造成加速度反应谱值小,而结构整体响应以及梁、柱构件的破坏程度较大的现象。因此,对该类结构进行抗震设计时应充分考虑近场地震动脉冲效应的影响。 展开更多
关键词 近场地震动 RC框架结构 地震响应影响分析 结构非线性分析 土耳其M 7.8地震
下载PDF
岩爆隧道冲击荷载作用特征及其计算方法
16
作者 罗勋 杨杰 +2 位作者 田红涛 刘大刚 王晓勇 《西南交通大学学报》 EI CSCD 北大核心 2024年第5期1095-1103,共9页
隧道中的硬脆围岩在高地应力情况下易发生岩爆,而目前国内针对岩爆隧道的支护结构设计主要采用工程类比法.为了量化作用在支护结构上的岩爆冲击荷载,从能量角度分析岩爆过程中的能量转化关系,利用动能定理及能量守恒原理计算冲击荷载,... 隧道中的硬脆围岩在高地应力情况下易发生岩爆,而目前国内针对岩爆隧道的支护结构设计主要采用工程类比法.为了量化作用在支护结构上的岩爆冲击荷载,从能量角度分析岩爆过程中的能量转化关系,利用动能定理及能量守恒原理计算冲击荷载,并结合隧道松散压力提出隧道发生岩爆时的荷载计算方法,同时探明洞径等不同因素对岩爆作用范围的影响规律;结合某高地应力隧道岩爆段对其合理性进行验证.研究结果表明:岩爆冲击荷载计算公式中,动荷因数与隧道支护所采用结构刚度正相关;在相同跨度与地应力条件下,圆形隧道的岩爆深度小于马蹄形隧道,岩爆横向范围大于马蹄形隧道;在相同洞形和地应力条件下,随着隧道跨度越大,岩爆深度与横向范围越大;在相同洞形和跨度条件下,地应力值越高,岩爆深度与横向范围越大;单线隧道Ⅱ级围岩岩爆荷载为12.02~337.75 kPa,单线隧道Ⅲ级围岩岩爆荷载为25.36~352.12 kPa,双线隧道Ⅱ级围岩岩爆荷载为8.54~288.55 kPa,双线隧道Ⅲ级围岩岩爆荷载为33.11~300.83 kPa. 展开更多
关键词 高地应力 岩爆隧道 能量法 冲击荷载
下载PDF
疫情影响下景区内旅游小企业组织韧性形成机制研究——以西江千户苗寨为例 被引量:1
17
作者 杨火木 李瑞 +1 位作者 郑超 谢梦月 《热带地理》 CSCD 北大核心 2024年第4期621-634,共14页
以西江千户苗寨景区内旅游小企业为研究对象,基于对西江千户苗寨的观察,通过实地调研与访谈收集原始材料,运用程序化扎根理论方法,抽象出疫情影响下景区内旅游小企业组织韧性的内在规律与形成机制。研究发现:1)组织能力和影响因素共同... 以西江千户苗寨景区内旅游小企业为研究对象,基于对西江千户苗寨的观察,通过实地调研与访谈收集原始材料,运用程序化扎根理论方法,抽象出疫情影响下景区内旅游小企业组织韧性的内在规律与形成机制。研究发现:1)组织能力和影响因素共同解释景区内旅游小企业组织韧性的由来和强弱,且从组织内外共同作用于韧性的形成和塑造;2)组织能力是旅游小企业组织韧性形成的内在逻辑与规律,即韧性组织具有观察环境、预判影响、危机应对和反思学习等基本能力;3)初始资源、社会资本和纾困措施等因素在景区内旅游小企业组织韧性形成中发挥重要作用,是其谋求组织生存、构建韧性潜力和塑造组织韧性的关键要素和重要手段。 展开更多
关键词 旅游小企业 组织韧性 程序化扎根理论 疫情影响 西江千户苗寨
下载PDF
城市地面塌陷灾害风险评估研究
18
作者 余满仓 吕敦玉 +3 位作者 孟舒然 张建羽 刘松波 王翠玲 《地质与勘探》 CAS CSCD 北大核心 2024年第1期63-75,共13页
随着城市化进程不断加快,城市地下空间安全问题引起广泛关注。本文以影响地下空间安全的典型灾害-地面塌陷为例,开展可能性风险评估研究,为降低地面塌陷灾害损失提供理论支撑。城市地面塌陷成因复杂,为了保证评价过程和结果的客观全面,... 随着城市化进程不断加快,城市地下空间安全问题引起广泛关注。本文以影响地下空间安全的典型灾害-地面塌陷为例,开展可能性风险评估研究,为降低地面塌陷灾害损失提供理论支撑。城市地面塌陷成因复杂,为了保证评价过程和结果的客观全面,通过调研对塌陷引发因素进行了总结,从管道因素、病害体因素、环境因素三个方面建立风险发生可能性评价指标体系,并使用AHP-熵权法-灰色关联法组合评价,建立地面塌陷风险评价模型。将该模型应用于郑州市典型地下空洞工程案例进行评估分析,结果表明:地面塌陷风险评价结果与实测结果相符,证明了评估模型的科学性,同时为城市地面塌陷预防提供了决策参考。 展开更多
关键词 城市地面塌陷 风险评价 影响因子 权重 灰色关联法 郑州市
下载PDF
基于OC&PGMF的弱监督行人检测方法
19
作者 曹鎏 徐巧玉 《计算机工程与设计》 北大核心 2024年第9期2725-2732,共8页
为解决弱监督行人检测训练过程中数据收敛到局部最优解和缺少回归能力问题,提出一种基于改进的在线学习与伪真值挖掘过滤算法的弱监督行人检测方法。采用WSDDN作为基础的弱监督检测器,通过优化OICR在线学习精细化策略,增加行人检测召回... 为解决弱监督行人检测训练过程中数据收敛到局部最优解和缺少回归能力问题,提出一种基于改进的在线学习与伪真值挖掘过滤算法的弱监督行人检测方法。采用WSDDN作为基础的弱监督检测器,通过优化OICR在线学习精细化策略,增加行人检测召回率并覆盖行人完整的位置,改善算法收敛到局部最优解的问题;基于邻域融合原理,通过设计伪真值挖掘过滤算法优化伪真值,进行全监督行人检测器训练,提高弱监督行人检测器的回归能力。实验结果表明,所提弱监督检测方法在VOC2007上实现了21.3%的mAP准确率,高于经典的弱监督行人检测方法(PCL)3.5%mAP准确率,验证了其有效性。 展开更多
关键词 行人检测 弱监督学习 在线学习 伪真值 挖掘过滤 局部最优解 回归能力
下载PDF
创业活动对高校毕业生职业发展的影响——基于扎根理论的研究
20
作者 高军德 乌恩夫 《山东高等教育》 2024年第3期39-46,90,共9页
对甘肃省7所高校不同专业的14位有在校创业经历的毕业生开展半结构化访谈,采用扎根理论的三级编码分析资料,考察大学生创业活动对职业发展的影响,发现大学生创业活动是个体追求实现创新价值的行动与创业机会、资源局限之间不断协调的动... 对甘肃省7所高校不同专业的14位有在校创业经历的毕业生开展半结构化访谈,采用扎根理论的三级编码分析资料,考察大学生创业活动对职业发展的影响,发现大学生创业活动是个体追求实现创新价值的行动与创业机会、资源局限之间不断协调的动态过程,个体在创业活动中逐步提升的职业素养对职业发展(就业、创业和学业)产生积极影响。具体表现在:创业活动有利于大学生在就业中积极求职、职场适应、工作革新和岗位晋升;有利于在创业中积累经验、建立基础、锻炼技能、洞察市场和应对逆境;有利于在学业中探索新知、学以致用、训练思维和跨科学习。研究对促进大学生职业发展和改进大学生创业教育具有借鉴意义。 展开更多
关键词 创业活动 职业发展 影响 扎根理论
下载PDF
上一页 1 2 26 下一页 到第
使用帮助 返回顶部