期刊文献+
共找到12篇文章
< 1 >
每页显示 20 50 100
软基中多向受荷大直径单桩桩土相互作用试验研究
1
作者 戴朴修 刘开富 +1 位作者 谢新宇 徐越栋 《浙江大学学报(工学版)》 EI CAS CSCD 北大核心 2024年第3期570-578,共9页
为了研究多向循环受荷大直径单桩的水平变形响应及桩土相互作用机理,开展多向受荷大直径单桩的1g大比尺模型试验,探讨不同竖向和水平循环荷载比下的桩侧受力及变形响应.试验结果表明,施加竖向循环荷载会增大桩身水平位移的发展速率;最... 为了研究多向循环受荷大直径单桩的水平变形响应及桩土相互作用机理,开展多向受荷大直径单桩的1g大比尺模型试验,探讨不同竖向和水平循环荷载比下的桩侧受力及变形响应.试验结果表明,施加竖向循环荷载会增大桩身水平位移的发展速率;最大弯矩出现在2.0倍桩径深度处,随着循环次数的增大,桩身弯矩表现出减小的趋势;在循环荷载作用下,最大土抗力所在的位置随着循环次数的增大逐渐从1.5倍桩径深度处向2.0倍桩径深度处移动,循环土体抗力-桩身水平变形(p-y)曲线的退化主要发生在表层土体;施加竖向循环荷载会增大桩土界面的初始刚度,但同时也会加速桩土体系的刚度退化.建议在海上风电大直径单桩的设计中,特别注意竖向循环荷载对长期循环荷载作用下桩身位移及桩土相互作用的不利影响. 展开更多
关键词 1g模型试验 大直径单桩 复杂荷载 P-Y曲线 桩土相互作用
下载PDF
Skeletal muscle as a molecular and cellular biomarker of disease progression in amyotrophic lateral sclerosis:a narrative review
2
作者 Peter H.King 《Neural Regeneration Research》 SCIE CAS CSCD 2024年第4期747-753,共7页
Amyotrophic lateral sclerosis is a fatal multisystemic neurodegenerative disease with motor neurons being a primary target.Although progressive weakness is a hallmark feature of amyotrophic lateral sclerosis,there is ... Amyotrophic lateral sclerosis is a fatal multisystemic neurodegenerative disease with motor neurons being a primary target.Although progressive weakness is a hallmark feature of amyotrophic lateral sclerosis,there is considerable heterogeneity,including clinical presentation,progression,and the underlying triggers for disease initiation.Based on longitudinal studies with families harboring amyotrophic lateral sclerosis-associated gene mutations,it has become apparent that overt disease is preceded by a prodromal phase,possibly in years,where compensatory mechanisms delay symptom onset.Since 85-90%of amyotrophic lateral sclerosis is sporadic,there is a strong need for identifying biomarkers that can detect this prodromal phase as motor neurons have limited capacity for regeneration.Current Food and Drug Administration-approved therapies work by slowing the degenerative process and are most effective early in the disease.Skeletal muscle,including the neuromuscular junction,manifests abnormalities at the earliest stages of the disease,before motor neuron loss,making it a promising source for identifying biomarkers of the prodromal phase.The accessibility of muscle through biopsy provides a lens into the distal motor system at earlier stages and in real time.The advent of“omics”technology has led to the identification of numerous dysregulated molecules in amyotrophic lateral sclerosis muscle,ranging from coding and non-coding RNAs to proteins and metabolites.This technology has opened the door for identifying biomarkers of disease activity and providing insight into disease mechanisms.A major challenge is correlating the myriad of dysregulated molecules with clinical or histological progression and understanding their relevance to presymptomatic phases of disease.There are two major goals of this review.The first is to summarize some of the biomarkers identified in human amyotrophic lateral sclerosis muscle that have a clinicopathological correlation with disease activity,evidence of a similar dysregulation in the SOD1G93A mouse during presymptomatic stages,and evidence of progressive change during disease progression.The second goal is to review the molecular pathways these biomarkers reflect and their potential role in mitigating or promoting disease progression,and as such,their potential as therapeutic targets in amyotrophic lateral sclerosis. 展开更多
关键词 amyotrophic lateral sclerosis biomarkers clinicopathological correlation disease progression muscle biomarkers neurogenic atrophy neuromuscular junction non-coding RNAs presymptomatic stages skeletal muscle SOD1g93A mouse model
下载PDF
FUNCTIONAL ANALYSIS METHOD FOR THE M/G/1 QUEUEING MODEL WITH OPTIONAL SECOND SERVICE 被引量:3
3
作者 艾尼.吾甫尔 艾合买提.卡斯木 《Acta Mathematica Scientia》 SCIE CSCD 2014年第4期1301-1330,共30页
By studying the spectral properties of the underlying operator corresponding to the M/G/1 queueing model with optional second service we obtain that the time-dependent solution of the model strongly converges to its s... By studying the spectral properties of the underlying operator corresponding to the M/G/1 queueing model with optional second service we obtain that the time-dependent solution of the model strongly converges to its steady-state solution. We also show that the time-dependent queueing size at the departure point converges to the corresponding steady-state queueing size at the departure point. 展开更多
关键词 M/G/1 queueing model with optional second service EIGENVALUE resolvent set
下载PDF
大比尺自升式平台插拔桩试验系统研制及验证 被引量:5
4
作者 高攀 段梦兰 +2 位作者 赵良美 宋林松 黎剑波 《中国海上油气》 CAS CSCD 北大核心 2016年第6期108-114,共7页
自升式平台顺利插拔桩对其安全作业具有至关重要的作用。根据插拔桩问题主要控制方程的相似,推导了1倍重力加速度模型主要物理量的相似系数,建立了主要由土池、加载装置、原位测量装置、冲桩系统和测量系统组成的大比尺自升式平台插拔... 自升式平台顺利插拔桩对其安全作业具有至关重要的作用。根据插拔桩问题主要控制方程的相似,推导了1倍重力加速度模型主要物理量的相似系数,建立了主要由土池、加载装置、原位测量装置、冲桩系统和测量系统组成的大比尺自升式平台插拔桩试验系统。该系统可以模拟自升式平台插桩、冲桩和拔桩,能够测量插拔桩深度和阻力,监测桩靴底部孔隙水压力的变化。运用该系统进行了初步插桩试验和边冲边拔的拔桩试验,将插拔桩阻力与规范和相关经验公式进行了对比,验证了系统的有效性和准确性,研究了桩靴底部孔压的分布规律以及孔压和插桩阻力的变化关系,证实了冲桩可以减小拔桩阻力的显著效果。本文研制的大比尺自升式平台插拔桩试验系统为进一步研究自升式钻井平台的插拔桩阻力和冲桩效果提供了基础,有利于保障自升式钻井平台的作业安全。 展开更多
关键词 大比尺 自升式平台 1倍重力加速度模型 插拔桩 冲桩 孔压监测
下载PDF
砂土中大直径单桩风机动力响应模型试验 被引量:2
5
作者 张陈蓉 田抒平 张纪蒙 《岩土工程学报》 EI CAS CSCD 北大核心 2022年第S02期16-19,共4页
采用电机伺服随机动力加载设备开展了一系列1g模型试验,研究砂土中大直径单桩基础的风机模型在风暴条件下的动力响应特性。试验结果表明:叶片风机模型,其位移响应极值相比集中质量风机模型大约偏小4%~8%。相比顶部集中质量模型5 Hz左右... 采用电机伺服随机动力加载设备开展了一系列1g模型试验,研究砂土中大直径单桩基础的风机模型在风暴条件下的动力响应特性。试验结果表明:叶片风机模型,其位移响应极值相比集中质量风机模型大约偏小4%~8%。相比顶部集中质量模型5 Hz左右的单共振峰值,叶片风机模型频响分布含4 Hz与6 Hz对应的2个固有频率共振峰值,分别为塔身固有频率与叶片塔筒耦合固有频率。风暴条件下随着平均风速的提高,风机位移响应极值呈现非线性增长的趋势。采用固定底端的风机模型相比单桩基础,其塔顶位移响应极值偏低约45%,固有频率偏高约11%;能量水平更高、高频分布更多的风谱,其对应风机动力响应极值更高,频域能量水平更高。 展开更多
关键词 海上风机 大直径单桩基础 动力响应 1g模型试验
下载PDF
Effect of Penetration Rates on the Piezocone Penetration Test in the Yellow River Delta Silt 被引量:1
6
作者 ZHANG Jiarui MENG Qingsheng +4 位作者 ZHANG Yan FENG Xiuli WEI Guanli SU Xiuting LIU Tao 《Journal of Ocean University of China》 SCIE CAS CSCD 2022年第2期361-374,共14页
Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate unde... Partial drainage often occurs during piezocone penetration testing on Yellow River Delta silt because of its intermediate physical and mechanical properties between those of sand and clay.Yet,there is no accurate understanding for the range of penetra-tion rates to trigger the partial drainage of silt soils.In order to fully investigate cone penetration rate effects under partial drainage condi-tions,indoor 1 g penetration model tests and numerical simulations of cavity expansion at variable penetration rates were carried out on the Yellow River Delta silt.The boundary effect of the model tests and the variation of key parameters at the different cavity ex-pansion rates were analyzed.The 1 g penetration model test results and numerical simulations results consistently indicated that the penetration rate to trigger the partially drainage of typical silt varied at least three orders of magnitude.The numerical simulations also provide the reference values for the penetration resistance corresponding to zero dilation and zero viscosity at any given normalized penetration rate for silt in Yellow River Delta.These geotechnical properties can be used for the design of offshore platforms in Yel-low River Delta,and the understanding of cone penetration rate effects under the partially drained conditions would provide some technical support for geohazard evaluation of offshore platforms. 展开更多
关键词 Yellow River Delta silt cone penetration rate effects 1g model simulation numerical analysis
下载PDF
钻井船插拔桩对邻近桩影响的模型试验 被引量:7
7
作者 田兆丰 王建华 范怡飞 《水利水运工程学报》 CSCD 北大核心 2018年第5期41-47,共7页
为评价黏土中钻井船插、拔桩对邻近桩基础的影响,开展了自由桩头条件下的1g模型试验,得出插、拔桩过程中所测量物理量数据变化规律,为后续离心模型试验提供了数据基础和试验方法。试验得到各物理量变化规律如下:插桩条件下,随着插桩深... 为评价黏土中钻井船插、拔桩对邻近桩基础的影响,开展了自由桩头条件下的1g模型试验,得出插、拔桩过程中所测量物理量数据变化规律,为后续离心模型试验提供了数据基础和试验方法。试验得到各物理量变化规律如下:插桩条件下,随着插桩深度的增加,邻近桩桩身最大弯矩产生的位置及最大土体水平位移产生的位置逐渐加深;拔桩条件下,最大桩身弯矩及最大土体位移值逐渐减小,但拔桩完成后桩身位移和土体位移都未恢复到初始桩状态;插桩初始阶段插桩阻力迅速增加,之后逐渐趋于稳定,拔桩初始阶段拔桩阻力迅速增加,随后进入相对稳定阶段,在桩靴距离土体表面约120 mm时,阻力突降为0。试验分析结果表明,土体位移变化直接导致桩身响应变化,两者存在一定正相关性。 展开更多
关键词 1g模型试验 自由桩头 桩靴 邻近桩 插桩 拔桩
下载PDF
砂土中大直径单桩水平循环加载模型试验研究 被引量:12
8
作者 张纪蒙 张陈蓉 张凯 《岩土力学》 EI CAS CSCD 北大核心 2021年第3期783-789,共7页
采用电机伺服水平循环加载设备开展了一系列1g模型试验,研究砂土中大直径单桩在水平循环荷载作用下的刚度和变形累积特性。试验结果表明,一次加卸载产生的残余位移约为峰值位移的80%;随着循环次数的增加,循环加载滞回曲线面积逐渐减小,... 采用电机伺服水平循环加载设备开展了一系列1g模型试验,研究砂土中大直径单桩在水平循环荷载作用下的刚度和变形累积特性。试验结果表明,一次加卸载产生的残余位移约为峰值位移的80%;随着循环次数的增加,循环加载滞回曲线面积逐渐减小,表明桩周土体行为从弹塑性向弹性阶段转变;滞回曲线割线刚度随着循环次数的增加,呈现先增后减的变化,为浅层桩周土体逐渐密实以及桩周土体抵抗由浅层向深层发展的趋势引起;桩顶累积位移随桩径增加而近似等幅减小,随埋深增加,位移的减小幅度也逐渐减小,表明了临界埋深的存在。在指数模型的基础上,在双对数坐标系中通过线性拟合给出了循环累积位移经验模型,发现增大桩径对于减小循环累积位移的效果要好于埋深。 展开更多
关键词 大直径单桩基础 水平循环加载 1g模型试验 累积位移
下载PDF
常重力模型实验在模拟断层错动中的应用 被引量:1
9
作者 沈超 薄景山 +3 位作者 李琪 王伟 张建毅 常晁瑜 《地震工程与工程振动》 CSCD 北大核心 2022年第1期122-131,共10页
断层错动是否会对工程造成影响是工程建设无法避开的问题,实验研究是解决这一问题的有效途径之一。常重力模型实验是指在自然环境1 g条件下的模型实验,被普遍应用在模拟不同类型断层错动产生的地表变形破裂研究中,并获得了较为丰富的研... 断层错动是否会对工程造成影响是工程建设无法避开的问题,实验研究是解决这一问题的有效途径之一。常重力模型实验是指在自然环境1 g条件下的模型实验,被普遍应用在模拟不同类型断层错动产生的地表变形破裂研究中,并获得了较为丰富的研究成果。文中系统地梳理了常重力模型实验在模拟断层上覆土体破裂研究方面的应用历史与现状,研究了不同因素对地表变形特征和破裂扩展规律的影响;分析了各类断层错动的实验结果以及对地下管线的影响;最终讨论了实验目前存在的问题和今后的研究方向,为关注并从事本领域研究的科技工作人员提供参考。 展开更多
关键词 常重力模型实验 断层错动 地表破裂 地下管线 破裂扩展
下载PDF
Time-dependent analysis for a queue modeled by an infinite system of partial differential equations 被引量:4
10
作者 GUPUR Geni 《Science China Mathematics》 SCIE 2012年第5期985-1004,共20页
By studying the spectrum of the underlying operator corresponding to the exhaustive-service M/G/1 queueing model with single vacations we prove that the time-dependent solution of the model strongly converges to its s... By studying the spectrum of the underlying operator corresponding to the exhaustive-service M/G/1 queueing model with single vacations we prove that the time-dependent solution of the model strongly converges to its steady-state solution. 展开更多
关键词 M/G/1 queueing model with single vacation resolvent set EIGENVALUE
原文传递
Displacement and force analyses of piles in the pile-caisson composite structure under eccentric inclined loading considering different stratum features
11
作者 Xiaoqing ZHAO Jinchang WANG +2 位作者 Panpan GUO Xiaonan GONG Yongle DUAN 《Frontiers of Structural and Civil Engineering》 SCIE EI CSCD 2023年第10期1517-1534,共18页
A novel anchorage for long-span suspension bridges,called pile-caisson composite structures,was recently proposed by the authors in an attempt to reduce the construction period and costs.This study aims to investigate... A novel anchorage for long-span suspension bridges,called pile-caisson composite structures,was recently proposed by the authors in an attempt to reduce the construction period and costs.This study aims to investigate the displacement and force behavior of piles in a pile-caisson composite structure under eccentric inclined loading considering different stratum features.To this end,both 1g model tests and three-dimensional numerical simulations were performed.Two groups of 1g model tests were used to validate the finite-element(FE)method.Parametric studies were then performed to investigate the effects of groundwater level,burial depth of the pile-caisson composite structure,and distribution of soil layers on the performance of the pile-caisson composite structure.The numerical analyses indicated that the influence of the groundwater level on the stability of the caisson was much greater than that of the piles.In addition,increasing the burial depth of the pile-caisson composite structure can assist in reducing the displacements and improving the stability of the pile-caisson composite structure.In addition,the distribution of soil layers can significantly affect the stability of the pile-caisson composite structure,especially the soil layer around the caisson. 展开更多
关键词 composite structure PILES foundation suspension bridge 1g model test finite-element analysis
原文传递
On First Returning Time and Last Exit Time of a Class of Markov Chain
12
作者 Hui Zeng ZHANG Min Zhi ZHAO Lei WANG 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2013年第2期331-344,共14页
Let {Xn} be a Markov chain with transition probability pij =: aj-(i-1)+,i,j ≥ 0, where aj=0 providedj 〈 0, a0 〉 0, a0+a1〈 1 and ∑∞n=0 an= 1. Let μ∑∞n=1nan. It is known that {Xn} is positive recurrent wh... Let {Xn} be a Markov chain with transition probability pij =: aj-(i-1)+,i,j ≥ 0, where aj=0 providedj 〈 0, a0 〉 0, a0+a1〈 1 and ∑∞n=0 an= 1. Let μ∑∞n=1nan. It is known that {Xn} is positive recurrent when μ 〈 1; is null recurrent when μ= 1; and is transient when μ 〉 1. In this paper, the integrability of the first returning time and the last exit time are discussed. Keywords Geom/G/1 queuing model, first returning time, last exit time, Markov chain 展开更多
关键词 Geom/G/1 queuing model first returning time last exit time Markov chain
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部