基于作物模型的河南省旱稻干旱风险评估     

薛昌颖 《气象与环境科学》2016,39(2):126-131

采用作物模型与数理统计相结合的方法,利用长期历史气象资料,以作物模型和地理信息系统技术为工具,系统分析了河南地区旱稻生育期水分盈亏情况。以模型模拟的雨养条件下实际蒸散量相对于潜在条件下的蒸散量(即需水量)的亏缺率,即水分亏缺指数,以雨养条件下产量相对于潜在产量的损失率(即灾损指数)作为产量灾损强度评价指标,从受旱程度和产量损失两个角度构建干旱风险评估模型,进行干旱风险评估。结果表明:河南省旱稻生育期集中在6—9月,水分亏缺最多的阶段为出苗—穗分化阶段,水分亏缺指数变化在0.50~0.60,其次是开花—成熟阶段和穗分化—开花阶段,水分亏缺指数变化在0.11~0.43;全生育期水分亏缺指数在0.36~0.50。出苗—穗分化阶段干旱发生的风险最大,其次是开花—成熟阶段,穗分化—开花阶段的最小。河南旱稻生育期干旱风险呈现为由东南向西北逐渐升高的分布,其中三门峡、济源西部一带风险最高,洛阳南部和南阳西北部一带最低,黄河以北大部地区和豫东、豫南地区风险居中。  相似文献   

1961-2013年东北三省玉米低温冷害频率的时空动态研究     

杨若子  周广胜 《气象科学》2016,36(3):311-318

基于东北三省1961-2013年气象数据,结合具有生物学意义的热量指数,利用SPSS聚类分析方法给出了东北三省低温冷害分类标准,并对低温冷害频率时空特征和年代际空间变化规律进行了分析。研究指出：东北三省玉米（轻、中、重度）低温冷害发生范围随时间呈减小-增大-减小变化趋势,1999年后东北三省出现低温冷害的范围显著减小,变化幅度均为中度> 重度> 轻度低温冷害。近10 a东北三省的轻度低温冷害仍时有发生,而中度和重度低温冷害发生较少。东北三省低温冷害频率呈由北向南呈减小趋势,轻、中、重度低温冷害频率高值区分别位于营口、哈尔滨和大兴安岭地区。各年代的重度低温冷害发生范围变化不大,中度与轻度低温冷害发生范围变化较大。研究结果可为东北三省低温冷害风险评估提供依据。  相似文献   

高水压顶管隧道管节修复装置的设计与应用          下载免费PDF全文

常喜平  贺建群  王乐  李贻浩 《探矿工程》2016,43(6):56-59

富春江顶管工程为例,介绍了一种可快速拆卸的用于深埋顶管隧道对管节局部破损进行修复的装置。装置结构简单、紧凑,易于在圆形截面的隧道中进行快速拼装。该装置最高耐水压力0.8 MPa,可对地下水位以下30~80 m顶管隧道中出现沿轴线长＜0.4 m环状破损的管节进行注浆修复。这种设计能够有效解决深埋顶管隧道小面积局部破损、小范围漏水涌砂等问题,为深埋顶管等方法构筑的圆形隧道提供应急修复保障。  相似文献   

Residual compressive strength of inclined steel tubular members with local corrosion     

《Applied Ocean Research》2016

In jacket-type offshore structures, corrosion damage affects the structural performance under compressive loading, which is created by the working and design loads of the main system. In this study, the effects of corrosion damage on the compressive structural behavior and strength of steel tubular members were investigated. Artificial corrosion damage was applied to the tubular specimens via mechanical processing and hand drilling to replicate the inclined nature of jacket-type offshore structures. The damage was applied to either half or all of the circumference of the specimens. The compressive failure modes of the artificially corroded tubular members were affected by the corrosion conditions. The compressive strengths were also affected by the level of corrosion. From the results of this study, the residual compressive strengths of corroded tubular steel members can be estimated based on the condition of the damaged sectional areas.  相似文献   

Fracture characteristics in Cretaceous platform and overlying ramp carbonates: An outcrop study from Maiella Mountain (central Italy)     

《Marine and Petroleum Geology》2016

This article focuses on field- and laboratory-based characterization of vertically persistent fractures that are part of oblique-slip normal fault zones and crosscut the Cretaceous platform and overlaying ramp carbonates outcropping at Maiella Mountain (central Italy). The achieved results show that: (i) fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones; (ii) joints and sheared joints composing the fault damage zones are taller, better connected and less spaced within the former rocks than in the ramp carbonates. The aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure. At Maiella Mountain, platform carbonates are, indeed, made up of overall stiffer (higher Uniaxial Compressive Strength values) and less porous rocks, due to more abundant intergranular void-filling cement and presence of matrix.In terms of hydrocarbon flow and recovery, geometric and dimensional attributes of fractures suggest that the well-connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow. In contrast, the relatively poorly connected and low-density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons.  相似文献   

抛锚撞击水下管汇的数值模拟研究     

娄敏  王艳红  明海芹 《海洋工程》2016,34(4):38-46

船舶抛锚撞击水下管汇会影响到管汇的正常作业,基于ANSYS/LS-DYNA动力学分析软件,建立锚-水下管汇-海床土体的三维有限元模型,对抛锚碰撞水下管汇的过程进行数值仿真。通过求解水下管汇受碰撞后的等效应力、应变的时间历程及受撞击部位的凹陷损伤深度,发现最大等效应力点出现在管汇与锚接触位置处,管汇的碰撞部位最终发生凹痕变形。同时讨论锚与管汇接触面的形状以及海床土体对水下管汇损伤程度的影响,当冲击能量相同时,锚与水下管汇的碰撞接触面积越小,水下管汇的损伤深度就越大;当锚与管汇接触的接触面积相同时,冲击能量越大,水下管汇的损伤变形越大。海床土体的剪切弹性模量对管汇的凹陷损伤深度以及最大等效应力影响与冲击能量有关,海床土体的内摩擦角对管汇的碰撞影响较小。  相似文献   

锈蚀钢筋在疲劳荷载作用下压磁场分布研究     

金伟良  周峥栋  毛江鸿  张军  崔磊  潘崇根 《海洋工程》2016,34(5):65-72

针对锈蚀钢筋的疲劳损伤与寿命评估中的难度大、精度低等问题,引入压磁检测技术,对锈蚀钢筋疲劳过程中的压磁场分布进行检测,从宏观与微观相结合的角度分析压磁场分布与疲劳损伤之间的联系。试验结果表明,锈蚀钢筋的压磁场分布能够反映疲劳损伤的演变规律,疲劳后期非线性特征加剧,锈蚀率及应力幅越大则变化越为明显,磁感强度值、磁场分布梯度、"反转"现象等均有助于进行疲劳损伤评价与寿命预测。研究结果可为压磁无损检测技术在钢筋混凝土结构中的应用提供依据。  相似文献   

Testing and modeling of the mechanical behavior of dolomite in the Wudongde hydropower plant     

J. C. Zhang  W. Y. Xu  H. L. Wang  Q. X. Meng 《Geomechanics and Geoengineering》2016,11(4):270-280

In order to understand the mechanical behaviours of the surrounding rocks in the underground caverns of the Wudongde hydropower plant, triaxial tests are performed on a type of dolomite. It is revealed that damage induced by crack development is the main factor controlling the nonlinear plastic deformation and failure behaviour of the dolomite in both pre- and post-peak regimes. Based on this understanding, a coupled elastoplastic damage model is developed for capturing the dolomite’s mechanical behaviours. In the model, the effects of plasticity and damage on rocks is described by introducing plastic hardening and damage softening commonly in the plastic yield surface. Which are both derived from a suitable Helmholtz free energy function. The model is used to simulate the triaxial tests. Comparisons between test results and the numerical modelling show that the developed model is capable of describing the macro mechanical behaviours of the Wudongde dolomite.  相似文献   

PM_2.5降尘对A549细胞线粒体氧化损伤的影响     

宋小芳  杨洁  霍婷婷  马骥  董发勤  马杰  王玉琳  邓建军 《岩石矿物学杂志》2018,37(6):985-992

将不同浓度PM_(2.5)降尘作用于A549细胞后,利用MTT法检测其存活率,W-G染色观察细胞形态,荧光探针法检测细胞ROS和MMP相对水平,以探讨PM_(2.5)降尘对A549细胞线粒体氧化损伤的影响及作用机制。结果显示,经12. 5μg/m L的PM_(2.5)降尘作用A549细胞3 h后,细胞存活率为(81. 77±6. 15)%,并随作用浓度及时间增加呈递减趋势。PM_(2.5)染毒后可观察到细胞形态不规则,胞膜溶解破坏,细胞微核出现。PM_(2.5)降尘作用于细胞24 h后,胞内ROS相对含量随暴露浓度增加呈递增趋势,细胞MMP相对水平随染毒浓度增加而降低,且胞内ROS和MMP两者间存在显著相关关系(R2=0. 878)。提示PM_(2.5)降尘处理A549细胞后可通过刺激ROS的产生,诱导细胞MMP下降,造成细胞线粒体氧化损伤。  相似文献   

煤渣改良土的抗冻能力及损伤特性研究     

张向东  任昆 《冰川冻土》2018,40(4):764-772

为研究煤渣改良土作为季节冻土区路基填料的抗冻能力,以不同煤渣掺量及不同养护龄期下的煤渣改良土为研究对象,利用GDS三轴试验系统开展了不同冻融次数下改良土的三轴压缩试验,获得了最佳的煤渣掺量及养护时间数据,提出冻融及加载综合影响下改良土的总损伤变量,并据此建立了损伤本构关系。结果表明：改良土的抗冻能力随着煤渣掺入量的增大出现先增强后减弱的变化趋势,随龄期的增长而逐渐增强。冻融循环对改良土物理力学性质的影响主要集中在前5次循环过程,超过5次后影响逐渐减弱。冻融加载总损伤变量能够较好地反映冻融及加载过程中改良土性质的劣化,据此建立的损伤本构关系具有一定的精度,可以为季节冻土区煤渣改良土路基工程提供参考。  相似文献