Study of seismic behavior of PHC piles with partial normal-strength deformed bars     

Zhang Xizhi  Zhang Shaohua  Xu Shengbo  Niu Sixin 《地震工程与工程振动(英文版)》2020,19(2):307-320

Nine PHC piles with partial normal-strength deformed bars were prepared in present study, and cyclic loading tests were implemented to evaluate these piles’ seismic performance. The influence of the axial compression ratio and the amount of normal-strength deformed bars on failure modes, crack patterns, strength, stiffness, and ductility were examined. The test findings indicate that the change of axial compression ratio has a noticeable influence on the failure mode of PHC piles. A larger axial compression ratio results in a higher cracking bending resistance, ultimate bending resistance, and initial stiffness, but the propagation heights of flexural cracks decrease as the axial compression ratio increases. Furthermore, increasing the amount of normal-strength deformed bars causes a slight decrease in ductility. Finally, a calculation formula was proposed to predict the flexural capacity of PHC piles with partial normal-strength deformed bars.  相似文献   

基于误差分布估计的三峡水库入库洪水概率预报方法     

张俊  冯宝飞  牛文静  王乐  徐雨妮  田逸飞  严方家 《湖泊科学》2023,35(2):722-729

准确、及时的入库洪水预报,对三峡水库综合效益的发挥和长江流域水旱灾害防御、水资源利用、流域综合管理等具有重要作用。基于预报误差的最优分布估计和分布函数动态参数假定,提出了一种三峡水库入库洪水概率预报方法,并进行了洪水概率预报业务试验。结果表明:本文所提方法科学可行,计算快捷,使用方便,便于在实时作业预报中应用推广;概率预报结果较确定性预报结果,在水量预报、预警效果等方面均有所改善,1～5 d预见期预报的确定性系数提高0.1%～3.4%,水量误差减少0.1%～4.8%,可为三峡水库实时调度提供更可靠的预报信息;所提出的三峡水库入库洪水概率预报业务化产品,可提供更多风险信息,为三峡水库的科学调度,尤其是洪水资源化利用提供更好的优化决策支撑。  相似文献   

基于走航高频监测的水库冬季水体溶解甲烷浓度分布:以湖北西北口水库为例     

王雪竹  刘佳  牛凤霞  肖尚斌  陈敏 《湖泊科学》2021,33(5):1564-1573

水库是大气甲烷(CH4)的重要来源之一,但目前对水库(尤其是河道型水库)中溶解CH_4浓度及释放潜力的空间异质性的认识仍不足.为揭示河道型水库冬季溶解CH_4浓度的分布规律,于2020年1月在湖北宜昌黄柏河流域内西北口水库采用自主研发的新型快速水—气平衡装置(FaRAGE)连接便携式温室气体分析仪,开展了水体溶解CH4浓度的连续走航式监测及断面垂向监测.根据溶解CH4从库尾至库首的浓度变化可以将水库分为3段:距回水末端1 km内为快速降低段,溶解CH4浓度范围为0.117～0.233 μmol/L;1～6 km内为缓慢降低段,CH4浓度范围为0.055～0.117 μmol/L;6～13km范围内为浓度平稳段,CH4浓度范围为0.039～0.080 μmd/L.整体上,水库表层水体溶解CH_4浓度与表层水温、水深及距回水末端的距离呈显著负相关关系(r=-0.77、-0.89、-0.81;P0.01),与叶绿素a浓度、溶解氧浓度呈显著正相关性(r=0.95、0.97;P0.01).基于当月平均风速,采用薄边界层法估算了上述3段区域的DH_4扩散通量,分别为(0.023±0.004)、(0.012±0.003)、(0.007±0.001) mg/(m~2·h).西北口水库在冬季表现为向大气释放CH_4的"源",且由于溶解CH_4浓度分布不均而表现出较强的空间差异性.  相似文献   

Characteristics of rock fragments in different forest stony soil and its relationship with macropore characteristics in mountain area,northern China   总被引：1，自引：0，他引：1  

Chen Meng  Jian-zhi Niu  Zheng-cong Yin  Zi-teng Luo  Xing-na Lin  Jing-wei Jia 《山地科学学报》2018,15(3):519-531

Rock fragments have major effect on soil macropores and water movement. However, the characteristics of rock fragments and their relationship with macropore characteristics remain elusive in forest stony soils in northern mountainous area of China. The objectives of this study are to (1) use Industrial Computed Tomography (CT) scanning to quantitatively analyze rock fragment characteristics in intact soil columns in different forest lands and (2) identify the relationship between characteristics of rock fragments and that of the macropores. Intact soil columns that were 100 mm in diameter and 300 mm long were randomly taken from six local forest stony soils in Wuzuolou Forest Station in Miyun, Beijing. Industrial CT was used to scan all soil column samples, and then the scanned images were utilized to obtain the three-dimensional (3D) images of rock fragments and macropore structures. Next, the parameters of the rock fragments and macropore structure were measured, including the volume, diameter, surface area, and number of rock fragments, as well as the volume, diameter, surface area, length, angle, tortuosity and number of macropores. The results showed that no significant difference was found in soil rock fragments content in the 10-30 cm layer between mixed forest and pure forest, but in the 0-10 cm soil layer, the rock fragments in mixed forest were significantly less than in pure forest. The number density of macropores has significant negative correlation with the number of rock fragments in the 0-10 cm soil layer, whereas this correlation is not significant in 10-20 cm and 20-30 cm soil layers. The volume density of macropore was not correlated with the volume density of rock fragments, and there is no correlation between the density of macropore surface area and the density of rock fragment surface area. Industrial CT scanning combined with image processing technology can provide a better way to explore 3D distribution of rock fragments in soil. The content of rock fragments in soil is mainly determined by parent rocks. The surface soil (0-10 cm) of forest contains fewer rock fragments and more macropores, which may be caused by bioturbation, root systems, gravitational settling and faunal undermining.  相似文献   

The design and implementation of a ROACH2+GPU based correlator on the Tianlai dish array     

Chen-Hui Niu  Qun-Xiong Wang  David MacMahon  Feng-Quan Wu  Xue-Lei Chen  Ji-Xia Li  Hai-Jun Tian  Guillaume Shippee  Dan Werthimer  Xiao-Ping Zheng 《天文和天体物理学研究(英文版)》2019,(7)

A digital correlator is a crucial element in a modern radio telescope. In this paper, we describe a scalable design for the correlator system of the Tianlai pathfinder array, which is an experiment dedicated to testing key technologies for conducting a 21 cm intensity mapping survey. The correlator implements the FX design, which firstly performs a fast Fourier transform(FFT) including polyphase filter bank(PFB) computation using a Collaboration for Astronomy Signal Processing and Electronics Research(CASPER) Reconfigurable Open Architecture Computing Hardware-2(ROACH2) board, then computes cross-correlations by employing Graphics Processing Units(GPUs). The design has been tested both in laboratory and in actual observation.  相似文献   

桐柏——大别山主要构造热事件及40Ar/39Ar地质定年研究   总被引：23，自引：0，他引：23  

牛宝贵  富云莲  刘志刚  任纪舜  陈文 《地球学报》1994,15(Z1):20-34

桐柏——大别山是一条复合造山带。在其演化过程中曾经历了扬子旋回（1000Ma-761Ma）和加里东旋回（470Ma-401Ma）两个板块构造旋回的俯冲-碰撞造山作用，之后又经历了早、中华力西（357Ma-314Ma）的平移走滑和晚华力西（286Ma-261Ma）、印支期（224Ma-185Ma）、燕山期（130Ma-111Ma）逆掩或逆冲推覆的陆-陆叠覆造山作用。印支期的高压超高压变质岩系是在陆-陆叠覆造山作用下形成的。燕山期的造山不仅具显著的深层次构造岩浆作用特点，而且还伴随快速的隆升作用。  相似文献   

基于一致性标准的大城市多中心体系规划实施评估——以杭州为例   总被引：3，自引：3，他引：0  

丁亮  钮心毅  施澄 《地理科学》2020,40(2):211-219

基于一致性标准的2个方面——物质空间建设一致性和目标一致性,评估杭州核心建成区多中心体系的规划实施结果。研究发现多中心体系的物质空间建设较成功,现状已建成15个城市级中心,具有较显著的主、副、次3个规模等级,成功引导了空间结构由单主中心向两主多副转变。但是规划目标实现不理想,外围新建的公共中心集聚水平偏低,对传统中心地区过度集聚的公共活动的疏解作用有限,也没有成功优化居住和日常公共活动之间的空间关系。这主要是由于杭州是通过强有力的政策保障多中心体系建设,但经济活动仍倾向于向传统城市中心集聚;城市扩张速度过快导致居住外迁的居民还没有来得及调整居住和日常公共活动之间的空间关系。  相似文献   

Rockburst Risk Analysis During High-Hard Roof Breaking in Deep Mines     

Zhang  Qiming  Wang  Enyuan  Feng  Xiaojun  Niu  Yue  Ali  Muhammad  Lin  Song  Wang  Hao 《Natural Resources Research》2020,29(6):4085-4101

Natural Resources Research - Mining operations continue to advance to greater depths to address the demand and supply of coal. However, deep mining occurs in complex and dangerous environments...  相似文献   

河南省春季一次人工增雨作业效果分析   总被引：2，自引：1，他引：1  

牛淑贞  鲍向东  张一平  范学锋 《气象与环境科学》2007,30(4):24-29

利用河南省自动雨量站逐时降水资料、天气图资料及郑州新一代天气雷达产品,分析了2007年3月23日河南省飞机、高炮、火箭人工增雨作业效果,结果表明:飞机和高炮、火箭影响区1 h雨量增加0～4 mm,且作业时段内影响区维持较大降水.春季低槽、切变线天气过程,K指数在24 ℃左右、850 hPa θse在40 ℃左右时,850 hPa水汽通量散度在0～-16 g·s-1·cm-2·hPa-1之间的区域为最佳作业区;雷达反射率因子在30 dBz左右的降水发展阶段,作业效果明显.  相似文献   

沙地玉米水分利用效率日变化特征   总被引：1，自引：0，他引：1  

牛亚毅  李玉强  王旭洋  龚相文  杨欢 《中国沙漠》2019,39(1):142-148

以科尔沁沙地玉米农田生态系统为研究对象,利用涡度相关技术和便携式光合作用测定系统（LI-COR6400）同步观测玉米（郑单958）主要生育期（苗期、拔节期、抽穗期、灌浆期和成熟期）群体和叶片尺度瞬时CO₂交换及水汽交换速率,并分析其水分利用效率的日变化特征。结果表明：各生育期玉米群体尺度瞬时CO₂交换速率分别为-2.205、-26.113、-26.118、-8.201、-3.672 μmolCO₂·m^-2·s^-1,叶片尺度光合速率分别为27.57、59.55、24.38、22.03、20.09 μmolCO₂·m^-2·s^-1。各生育期群体水分利用效率（WUE_C）的日动态呈现“L”型,峰值出现在日出后（约06：00）,分别为0.025、0.039、0.088、0.058、0.191 gCO₂·g^-1H₂O,叶片尺度瞬时水分利用效率（WUE_L）的日动态呈“~”型,峰值出现在06：00—10：00,分别为0.029、0.041、0.017、0.019、0.024 gCO₂·g^-1H₂O。玉米各生育期群体及叶片尺度瞬时CO₂交换速率和水分利用效率均存在明显差异。  相似文献