光照、温度对黑鲷(♀)×真鲷(♂)杂交子代受精卵孵化效果的影响     

刘海林  张志勇  张志伟  许津  陈淑吟  贾超峰  祝斐  孟乾 《海洋科学》2018,42(5):108-115

为了研究不同光照强度、温度对黑鲷(Acantho pagrusschlegelii)(♀)×真鲷(Pagrosomus major)(♂)杂交F1代受精卵孵化效果及仔鱼存活的影响,作者采用试验生态学的方法比较不同温度(16、18、20、22、24、26℃)下杂交鲷受精卵的孵化率、畸形率、孵化时间、7日龄仔鱼的存活率;比较不同光照强度下(10、100、300、800、1500、4 000、10 000 lx)受精卵孵化率、畸形率、孵化时间;比较不同光照强度下(200、1 000、2 000、5 000、10 000、15 000、20 000 lx)7日龄仔鱼的存活率。结果表明:在盐度为22条件下,受精卵最高孵化率(34.00%)和最低畸形率(16.65%)的孵化温度为20℃;在16～26℃范围内,温度与孵化时间呈负相关,与7日龄仔鱼存活率也呈负相关。不同的光照强度对受精卵孵化率和孵化时间的影响不显著,孵化率为65.88%～71.88%;但大于800lx的光照会令畸形率上升(大于15.21%);另外,5000～10000lx的光照强度更适宜仔鱼生存,7日龄仔鱼存活率达到38%～40.75%。黑鲷(♀)×真鲷(♂)杂交子代最佳孵化温度为20℃,最适光照强度为5 000～10 000 lx。  相似文献   

基于概率积分法的采动坡体稳定性预测与分析          下载免费PDF全文

王猛  孙丽丽  薄怀志 《山东国土资源》2018,34(12)

地下采煤会引起地表沉降、变形,甚至引发山体、河堤滑坡等地质灾害。采动坡体的稳定性研究一直是采矿工程中实际关心的问题。该文首先介绍分析了概率积分法移动变形稳态、动态预测模型以及基于极限平衡理论的单滑面采动坡体稳定性预测模型,提出了使用概率积分法结合Knothe时间函数对采动坡体稳定性进行预测分析的方法,并使用C#及XML Schema语言编制了相关的计算程序。最后,结合一个工程实例对采动坡体稳定性和动态变化过程进行了预测与分析,通过实测数据验证了提出方法的可行性,得出了采动引起的坡体下沉是影响坡体稳定性的主要因素,并提出了在坡体拉伸阶段进行注浆加固的方法。  相似文献   

杭州湾中部实测波浪特性分析   总被引：1，自引：0，他引：1  

杨斌  杨忠良  叶钦  张俊彪  施伟勇 《海洋工程》2018,36(3):96-103

利用杭州湾中部一年实测波浪资料,分析该地区的波参数统计变化特性,采用最小二乘法拟合得出相关参数之间的关系式,并统计分析了频谱特性。结果表明:杭州湾中部以小浪和轻浪为主,在各月分布较为均匀,年平均周期为2.97 s;最大一次波浪过程为冷空气影响所致,影响强度大于台风莫拉克;常浪向分布在东北至东南向,其中又以小浪出现较多,对应的波周期以2~4 s为主;强浪向主要分布在西北和东北方向,对应的波周期主要分布在3~5 s;多数特征波参数之间相关关系较好;由谱分析得知风浪占多数,且以单峰为主。研究结果可为相关工程和理论研究提供基础资料。  相似文献   

基于高斯两步移动搜寻法的村镇避难场所可达性研究     

但文羽  肖映辉  胡周灵  詹庆明 《地球信息科学学报》2018,20(10):1412-1421

避难场所可达性是指避难场所与受灾居民之间的通达性,即灾害发生时,避难人员通过避难疏散通道到达避难场所的难易程度,是评价避难场所布局合理性的重要指标。本研究结合高斯两步移动搜寻法和网络分析法,从供需双向出发对村镇地区避难场所进行可达性分析。2种方法的结合,既充分考虑了需求点与设施点的相互作用,又充分考虑了设施点的吸引力随距离的衰减关系,并基于实际道路,以步行疏散时间作为搜索半径,降低了传统研究中因忽略供需间相互作用及实际距离而引起的可达性结果的误差。最后,以神农架松柏镇区为例,验证该方法的实际应用价值。结果表明,该方法能够有效测定村镇地区避难场所的空间可达性,同时,基于GIS软件可以直观地揭示研究区域内避难场所可达性空间分布差异。该方法可为制定科学的村镇防灾减灾规划提供方法支持。  相似文献   

中国大城市的城市组成对城市热岛强度的影响研究     

王美雅  徐涵秋 《地球信息科学学报》2018,20(12):1787-1798

城市的快速扩张诱发并加剧了城市热岛效应,对人类健康和生存发展提出严峻挑战,因此,探索城市组成对城市热岛的影响具有重要意义。本研究在传统城市热岛影响因子的基础上,重点分析城市组成与城市热岛的关系。以13个中国大城市为研究区,利用2015年夏季（6-8月）白天和夜间的MODIS LST数据计算城市热岛强度,并结合土地覆盖数据、人口、区位和气象数据,分析热岛强度和城市地表组成、地表空间格局、人口和区位4类因子的关系。研究结果表明：中国的13个大城市均存在不同程度的热岛效应,城市白天的热岛效应比夜间显著。影响城市白天热岛强度的主要因子为城市建筑用地和林地面积比例、城市建筑用地和林地平均斑块面积、城市建筑用地聚集度和人口密度。城市建筑用地和林地平均斑块面积、城市建筑用地聚集度和林地斑块密度是夜间热岛强度的主要影响因子。城市建筑用地面积和乡村林地面积的增加会导致城市热岛情况的加剧,而通过调节城市地表空间格局（减少平均建筑用地斑块面积和降低建筑用地斑块聚集度）可以更好地降低城市地表温度,减缓城市热岛效应。  相似文献   

Local level rainfall and temperature variability in drought-prone districts of rural Sidama,central rift valley region of Ethiopia     

Tafesse Matewos  Tewodros Tefera 《自然地理学》2020,41(1):36-53

ABSTRACT

The purpose of this study is to examine local level spatiotemporal rainfall and temperature variability in drought-prone districts of rural Sidama, Central Rift Valley region of Ethiopia. The study used 129 gridded monthly rainfall and temperature data of 32 years (1983–2014). The gridded rainfall and temperature records were encoded into GIS software and evaluated through different statistical and geospatial techniques. Mann-Kendal rank test and F distribution tests were used to test temporal and spatial statistical significance, respectively, of the data. The analysis revealed that Belg and Kiremt are the main rainfall seasons, constituting 81% of the annual rainfall. Although annual, Kiremt, and Belg rainfall amounts appear to have decreased over time, the decreasing trend is statistically significant only for Belg rainfall records. On the other hand, rainfall standard anomaly results indicated seven droughts of different magnitudes: one extreme, two severe, and four moderate. The study also revealed increasing temperature trends over the years under consideration that are statistically significant. The findings of this study on rainfall contradict other findings obtained around the study area. Thus, climate change adaptations need to focus on location-specific climate data analysis so that the intended adaptive interventions can be successful.  相似文献   

基于全球分布的地震观测数据估计0S0模态的特征频率及品质因子     

周丰森  王迪晋  旦增 《大地测量与地球动力学》2019,39(10):1013-1016

选取2011-03-11日本MW9.3地震后全球地震台站记录的约220 h波形数据，基于一定的判断准则，筛选出质量较高的448个垂向观测数据，采用频域AR方法对0S0模态的特征频率和品质因子进行估值，并以信噪比为权重进行加权平均，得到特征频率f=0.814 658 4±5.3×10-7，品质因子Q=5 586±12。该结果与已有研究成果相比精度更高，有助于约束现有地球介质密度和衰减模型，使其更接近真实地球。  相似文献   

A New Wavelet Method for Identification of Eddies and Assessment of Incidents on Islands of the Eastern Caribbean     

Jason D. Tambie  Madiha Farag-Miller  Keith Miller  Bheshem Ramlal  Michael Sutherland 《Marine Geodesy》2019,42(3):227-245

Using two dimensional continuous wavelet transforms, a novel method for identification of mesoscale eddies is presented to facilitate extraction of characteristics for area, amplitude, type, and location from maps of sea level anomalies. In comparison with the previously established growing method for eddy identification, it is found that the wavelet method identifies more than twice the number of eddies and is particularly better at resolving small eddies down to the 0.25 degree resolution of the data. Such research into eddy identification and tracking is significant to the assessment of eddies with potential to impact on coastlines of small islands. The method is applied to the identification of eddies on tracks towards islands of the Eastern Caribbean over 23?years. Spatial and temporal variation in rate of occurrence and magnitude is established. For Barbados there is an average of 9 anticyclonic incidents a year with maximum amplitude of typically 0.22?m in the dry seasons and 0.16?m in the wet seasons. Seasonal variation is reversed for the other islands with twice the number of anticyclonic incidents having maximum amplitudes of about 0.20?m annually.  相似文献   

Global method for stability analysis of anchored slopes     

Tan Zhang  Hong Zheng  Cong Sun 《国际地质力学数值与分析法杂志》2019,43(1):124-137

Based on the global method, an approach is proposed to consider the effect of anchor reinforcement on slope stability, where equilibrium conditions are formulated in terms of the whole slip body. Anchor pre-tension is assumed to be undertaken by the whole slip body instead of individual slices, causing internal force within slope more realistic. Meanwhile, the optimization model for locating the critical slip surface is of weak nonlinearity and easy to solve using the conventional optimization procedures. The effects of anchoring orientation and position are thoroughly investigated, and interesting results are obtained.  相似文献   

Fully coupled elastoplastic hydro-mechanical analysis of unsaturated porous media using a meshfree method     

Omid Ghaffaripour  Golnaz A. Esgandani  Arman Khoshghalb  Babak Shahbodaghkhan 《国际地质力学数值与分析法杂志》2019,43(11):1919-1955

This paper presents the first application of an advanced meshfree method, ie, the edge-based smoothed point interpolation method (ESPIM), in simulation of the coupled hydro-mechanical behaviour of unsaturated porous media. In the proposed technique, the problem domain is spatially discretised using a triangular background mesh, and the polynomial point interpolation method combined with a simple node selection scheme is adopted for creating nodal shape functions. Smoothing domains are formed on top of the background mesh, and a constant smoothed strain, created by applying the smoothing operation over the smoothing domains, is assigned to each smoothing domain. The deformation and flow models are developed based on the equilibrium equation of the mixture, and linear momentum and mass balance equations of the fluid phases, respectively. The effective stress approach is followed to account for the coupling between the flow and deformation models. Further coupling among the phases is captured through a hysteretic soil water retention model that evolves with changes in void ratio. An advanced elastoplastic constitutive model within the context of the bounding surface plasticity theory is employed for predicting the nonlinear behaviour of soil skeleton. Time discretisation is performed by adopting a three-point discretisation method with growing time steps to avoid temporal instabilities. A modified Newton-Raphson framework is designed for dealing with nonlinearities of the discretised system of equations. The performance of the numerical model is examined through a number of numerical examples. The state-of-the-art computational scheme developed is useful for simulation of geotechnical engineering problems involving unsaturated soils.  相似文献